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Second Edition

P R I N C I P L E S O F

N E U R O P S Y C H O L O G Y

Eric A. Zillmer Drexel University

Mary V. Spiers Drexel University

William C. Culbertson Drexel University

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Principles of Neuropsychology, Second Edition Eric A. Zillmer, Mary V. Spiers, William C. Culbertson

http://www.thomsonrights.com

This book is dedicated to the memory of Carl R. Pacifico

Drexel Alumnus, Class of ’44

Friend, Mentor, Benefactor

E.A.Z.

This book is dedicated to my father.

His guidance as a psychologist and his personal struggle with Parkinson’s disease have brought some of my greatest lessons.

M.V.S.

This book is dedicated to

my wife and daughter, my greatest gifts.

W.C.C.

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B R I E F C O N T E N T S

Part One Introduction 1

Chapter 1 A History of Neuropsychology 3 Chapter 2 Methods of Investigating the Brain 32 Chapter 3 Neuropsychological Assessment and Diagnosis 62

Part Two The Functioning Brain 91

Chapter 4 Cells of Thought 93 Chapter 5 Functional Neuroanatomy 114 Chapter 6 Cerebral Specialization 154 Chapter 7 Somatosensory, Chemical, and Motor Systems 176 Chapter 8 Vision and Language 199 Chapter 9 Memory, Attention, Emotion, and Executive Functioning 224

Part Three Disorders of the Brain 267

Chapter 10 Developmental Disorders of Childhood 269 Chapter 11 Learning and Neuropsychiatric Disorders of Childhood 297 Chapter 12 Cerebrovascular Disorders and Tumors 339 Chapter 13 Traumatic Head Injury and Rehabilitation 369 Chapter 14 Normal Aging and Dementia: Alzheimer’s Disease 399 Chapter 15 Subcortical Dementias 423 Chapter 16 Alterations of Consciousness 443

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Part One I N T R O D U C T I O N 1

Chapter 1 A H i s t o r y o f N e u r o p s y c h o l o g y 3 Keep in Mind 4 Overview 4

The Brain in Antiquity: Early Hypotheses 5 Ancient Greek Perspectives 6 The Cell Doctrine 7 Anatomic Discoveries and the Role of the Spiritual Soul 8 Non-Western Attitudes 12

Localization Theory 13 Phrenology and Faculty Psychology 13 The Era of Cortical Localization 16 Critics of Cortical Localization 18

Localization versus Equipotentiality 20

Integrated Theories of Brain Function 20 Jackson’s Alternative Model 20 Luria’s Functional Model 21

Modern Neuropsychology 24

Emerging Research Areas in Neuropsychology 27 Forensic Neuropsychology 28 Sports Neuropsychology 28 Terrorism, Law Enforcement, and the Military 28

Summary 30 Critical Thinking Questions 30 Key Terms 30 Web Connections 30

Neuropsychology in Action

1.1 The Brain of a Nazi 15 1.2 Paul Broca: A Manner of Not Speaking 17 1.3 Sigmund Freud: The Neurologist 19 1.4 The Walter Freeman Lobotomies: Mind over Matter? 22

Chapter 2 M e t h o d s o f I n v e s t i g a t i n g t h e B r a i n 32 Keep in Mind 33 Overview 33

Neurohistology Techniques 34 Golgi Stain 34 Nissl Stain 34 Other Staining Techniques 35

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Radiologic Procedures 35 Skull X-Ray 36 Air Encephalography (Pneumoencephalography) 36 Computed Transaxial Tomography 36 Angiography 38 Sodium Amytal Injections (Wada Technique) 40

Electrophysiologic Procedures 40 Electroencephalography 40 Evoked Potential 44 Electrical Stimulation 45 Electromyography 47

Imaging of Brain Metabolism 47 Regional Cerebral Blood Flow 47 Single-Photon Emission Computed Tomography 48 Positron Emission Tomography 49

Magnetic Imaging Procedures 51 Magnetic Resonance Imaging 51 Magnetoencephalography 56

Cerebrospinal Fluid Studies: Lumbar Puncture 56

Behavioral Examinations 56 Neurologic Examination 56 Neuropsychological Evaluation 57

New Advances in Imaging Techniques: Mapping the Brain 57 Subtraction Procedures 57 Image Analysis and Quantification (Three-Dimensional) 57 Future Directions 58

Summary 60 Critical Thinking Questions 61 Key Terms 61 Web Connections 61

Neuropsychology in Action

2.1 Case Example of Brainstem Auditory-Evoked Response 46 2.2 Undergoing a Magnetic Resonance Imaging Procedure 52 2.3 New Frontiers in Functional Magnetic Resonance Imaging 54 2.4 Diagnostic Neuroimaging and Neuropsychology 59

Chapter 3 N e u r o p s y c h o l o g i c a l A s s e s s m e n t a n d D i a g n o s i s 62 Keep in Mind 63 Overview 63

General Considerations in Neuropsychological Testing 63 Why Testing? 64 Rationale of the Neuropsychological Examination 65 Appropriate Referrals for Neuropsychological Evaluation 66

Psychometric Issues in Neuropsychological Assessment 66 Reliability 67 Validity 67 False Positives and Base Rates 67

viii Contents

Neuropsychological Tests 68 Orientation (Arousal) 69 Sensation and Perception 70 Attention/Concentration 71 Motor Skills 72 Verbal Functions/Language 73 Visuospatial Organization 74 Memory 75 Judgment/Problem Solving 76 Neuropsychological Diagnosis 78 Describing Function, Adaptation, and Prognosis 79

Interpreting Neuropsychological Assessment Data 79 Approaches to Neuropsychological Interpretation 80 Assessing Level of Performance 84 Deficit Measurement 86 Lateralizing Signs 88 Pathognomonic Signs (Qualitative Observations) 88

Summary 89 Critical Thinking Questions 89 Key Terms 89 Web Connections 89

Neuropsychology in Action

3.1 Case Example: The Neuropsychology of Lyme Disease 86

Part Two T H E F U N C T I O N I N G B R A I N 91

Chapter 4 C e l l s o f T h o u g h t 93 Keep in Mind 94 Overview 94

Neurons and Glial Cells 94 Structure and Function of the Neuron 95 Glial Cells 99

Communication within a Neuron: The Neural Impulse 102 Resting Membrane Potential 102 Action Potential 102

Communication among Neurons 105 Structure of Synapses 105 Synaptic Transmission 105 Neurotransmitters 106

Regeneration of Neurons 110

Summary 112 Critical Thinking Questions 112 Key Terms 112 Web Connections 113

Neuropsychology in Action

4.1 Short-Circuiting Neurons: Multiple Sclerosis 98 4.2 Neuronal Firing: Clinical Examples 104

Contents ix

4.3 What Can We Learn from Songbirds? 109 4.4 Stem Cell Research: Science and Ethics 110

Chapter 5 F u n c t i o n a l N e u r o a n a t o m y 114 Keep in Mind 115 Overview 115

Anatomic and Functional Development of the Brain 116 Neurogenesis and Cellular Migration 116 Axon and Dendrite Development 117 Synaptogenesis 117 Myelination 117 Pruning 118 Regional Development 118 Lobular and Convolutional Development 118 Ventricular and Spinal Cord Development 119 Postnatal Development 120

Organization of the Nervous System 121

Peripheral Nervous System 122

Central Nervous System 122 Brain 122 Spinal Cord 123

Gross Anatomy: Protection and Sustenance of the Brain 124 Skull 125 Meninges 125 Ventricular System 127 Vascular System 131 Cerebral Arteries 132 Venous System 133

Principal Divisions of the Brain 133

Brainstem and Cerebellum 134 Lower Brainstem 137 Upper Brainstem: Diencephalon 141 Cerebellum 146

Telencephalon 147 Basal Ganglia 147 Limbic System 149 Corpus Callosum 151

Summary 152 Critical Thinking Questions 152 Key Terms 152 Web Connections 153

Chapter 6 C e r e b r a l S p e c i a l i z a t i o n 154 Keep in Mind 155 Overview 155

The Cerebral Hemispheres 155 Structure 155

x Contents

Function 159 Asymmetry, Lateralization, and Dominance 161

Hemispheric Anatomic and Functional Differences 163 Neuropsychological and Behavioral Cerebral Differences 166

Sex Differences and Hemispheric Specialization 167 Sexual Hormones 171

Summary 175 Critical Thinking Questions 175 Key Terms 175 Web Connections 175

Neuropsychology in Action

6.1 The Evolution of the Brain: A Focus on Brain Size 156 6.2 A Land Where Girls Rule in Math 172

Chapter 7 S o m a t o s e n s o r y , C h e m i c a l , a n d M o t o r S y s t e m s 176 Keep in Mind 177 Overview 177

Somatosensory Processing 178

Chemical Senses 184 Taste 184 Smell 187

Motor Systems 189 Cortical Motor Processing 189 The Cerebellum and Motor Processing 195 Subcortical Motor Processing 195

Summary 197 Critical Thinking Questions 197 Key Terms 197 Web Connections 198

Neuropsychology in Action

7.1 Synesthesia: Melded Sensory Integration 179 7.2 Phantoms of Feeling 184 7.3 Tourette Syndrome: Too Much Behavior 196

Chapter 8 V i s i o n a n d L a n g u a g e 199 Keep in Mind 200 Overview 200

Visual Processing 200 Primary Visual Processing 201 Higher Visual Processing: Object Recognition and Spatial Localization 204

Auditory and Language Processing 215 Primary Auditory Processing 215 Higher Auditory Processing: Speech and Language 215 Aphasia: A Breakdown of Language 219

Contents xi

Summary 221 Critical Thinking Questions 222 Key Terms 222 Web Connections 222

Neuropsychology in Action

8.1 Blindness: Helping Us See the Plasticity of the Brain 205 8.2 The Case of Jonathan 206 8.3 Case Study: Neglect 211

Chapter 9 M e m o r y , A t t e n t i o n , E m o t i o n , a n d E x e c u t i v e F u n c t i o n i n g 224 Keep in Mind 225 Overview 225

Memory Systems 225 A Framework for Conceptualizing Memory Systems 226 Long-Term Memory 227 Short-Term Memory and Working Memory 237

Attention 240 Subcortical Structures Influencing Attention 240 The Cerebral Cortex and Attention 241 Models of Attention 242

Executive Functioning 246 Development of Executive Functions 247 Frontal-Mediated Functions and Dysfunctions 252

Relation of Memory, Attention, and Executive Function 258

Neuropsychology of Emotional Processing 259 Brain Organization of Emotion 260

Summary 264 Critical Thinking Questions 264 Key Terms 265 Web Connections 265

Neuropsychology in Action

9.1 Amnesia: The Case of N.A. 227 9.2 Executive Function Tasks 248 9.3 The Case of Phineas Gage 255

Part Three D I S O R D E R S O F T H E B R A I N 267

Chapter 10 D e v e l o p m e n t a l D i s o r d e r s o f C h i l d h o o d 269 Keep in Mind 270 Overview 270

Vulnerability and Plasticity of the Developing Brain 270

Child and Adult Brain: Structural and Functional Differences 273

Specific Developmental Disorders 274 Abnormalities of Anatomic Development 274 Genetic and Chromosomal Disorders 281 Acquired Disorders 291

xii Contents

Summary 295 Critical Thinking Questions 295 Key Terms 295 Web Connections 295

Neuropsychology in Action

10.1 Principles of Assessment in Pediatric Neuropsychology 275

Chapter 11 L e a r n i n g a n d N e u r o p s y c h i a t r i c D i s o r d e r s o f C h i l d h o o d 297 Keep in Mind 298 Overview 298

Learning Disabilities 298 Verbal Learning Disability: Dyslexia 299 Nonverbal Learning Disability Syndrome 305

Pervasive Developmental Disorders 310 Autism 311

Disruptive Behavioral Disorders 322 Attention-Deficit/Hyperactivity Disorder 322

Tic Disorders 332 Gilles de la Tourette’s Syndrome 332

Summary 337 Critical Thinking Questions 337 Key Terms 338 Web Connections 338

Neuropsychology in Action

11.1 Genetics of Learning Disabilities 300 11.2 Case Study of an Adolescent with Asperger’s Syndrome 314 11.3 Case Study of a Child with an Attention-Deficit/Hyperactivity Disorder 327

Chapter 12 C e r e b r o v a s c u l a r D i s o r d e r s a n d Tu m o r s 339 Keep in Mind 340 Overview 340

Pathologic Process of Brain Damage 340 Brain Lesions 340 Anoxia and Hypoxia: Oxygen Deprivation to the Brain 341 Hydrocephalus 342

Overview of Cerebrovascular Disorders 342 Stroke Definition 343 Impairment of Blood Supply to the Brain 344

Types of Cerebrovascular Disorders 344 Transient Ischemic Attacks 344 Infarctions 345 Hemorrhage 346

Diagnosing Cerebrovascular Disease 347 Computed Transaxial Tomography 349 Angiography 349 Other Tests 349

Contents xiii

Treatment and Prognosis of Vascular Disorders 349 Factors Involved in Stroke Recovery 349 Medical Treatment 350 Preventing Stroke 350

Neuropsychological Deficits Associated with Stroke 351 Neuropsychological Risk Factors 351 Attention Deficits 352 Memory Problems 353 Deficits in Abstract Reasoning 353 Cognitive Deficits Associated with Right Brain Strokes 353 Cognitive Deficits Associated with Left Brain Damage 355 Anterior versus Posterior Strokes 356 Emotional and Behavioral Changes after a Stroke 356

Tumors of the Brain 357

Types of Intracranial Tumors 359 Infiltrating Tumors 359 Noninfiltrating Tumors 359 Childhood Tumors 361 Diagnosis of Brain Tumors 361 Treatment of Brain Tumors 362

Brain Tumors and Neuropsychology 363

Other Neurologic Disorders 363 Brain Abscess 363 Infections 363 Neurotoxins 365

Summary 367 Critical Thinking Questions 367 Key Terms 368 Web Connections 368

Neuropsychology in Action

12.1 Migraine Headache: A Vascular Disorder of the Brain 348 12.2 Case Example of a Left Stroke 354 12.3 Neuropsychology of Treatments for Individuals with Brain Tumors 364 12.4 Family and Child Adjustment to Cognitive Aspects of Cancer in Children 366

Chapter 13 T r a u m a t i c H e a d I n j u r y a n d R e h a b i l i t a t i o n 369 Keep in Mind 370 Overview 370

Traumatic Head Injury 370

Epidemiology of Traumatic Head Injury 371

Mechanism of Impact: Neuronal Shearing, Stretching, and Tearing 371 Penetrating Head Injury 373 Closed Head Injury 373 Assessing the Severity of Brain Injury 375

Complications of Moderate and Severe Brain Injury 376 Edema 376 Brain Herniation 376 Extradural and Subdural Hemorrhage 377

xiv Contents

Intracranial Bleeding 378 Skull Fractures 378 Post-traumatic Epilepsy 379

Mild Head Injury: “Concussions” 379 Sports-Related Concussions: A Neuropsychological Perspective 381 Postconcussional Syndrome 385

Treatment of Head Injuries 385 Neuropsychological Manifestations 386

Recovery, Rehabilitation, and Intervention of Traumatic Brain Injury 388

Adaptation and Recovery 388 Diaschisis 388 Brain Reorganization 389

Overview of the Rehabilitation Process 389 Admission to Rehabilitation Programs 390 Evaluation of Goals and Discharge Planning 393 Treatment Planning 394 Assessment of Everyday Activities 394

Treatment Methods for Neuropsychological Rehabilitation 395 Psychotherapy in Rehabilitation 395

Summary 397 Critical Thinking Questions 398 Key Terms 398 Web Connections 398

Neuropsychology in Action

13.1 Case Study: Penetrating Head Injury 374 13.2 Can a Concussion Change Your Life? 380 13.3 Consensual Sex after Traumatic Brain Injury: Sex as a Problem-Solving Task 386 13.4 It Is More Than a Black Box 396

Chapter 14 N o r m a l A g i n g a n d D e m e n t i a : A l z h e i m e r ’ s D i s e a s e 399 Keep in Mind 400 Overview 400

Normal Aging 400

Cognitive Changes Associated with Aging 401 Brain Changes Associated with Aging 404

Mild Cognitive Impairment 405 Summary 406

Defining Dementia 406 Diagnostic Criteria for Dementia 407 Subtypes and Classifications of Dementia 408

Alzheimer’s Disease 409 Diagnostic Problem of Alzheimer’s Disease 409 Neuropathology of Alzheimer’s Disease 411 Histologic Markers 411 Clinical Presentation and Neuropsychological Profile of Alzheimer’s Disease 413

Treatment 420

Contents xv

xvi Contents

Treatments for Cognitive Enhancement 420 Cognitive, Behavioral, and Psychiatric Symptom Control 421

Summary 421 Critical Thinking Questions 421 Key Terms 422 Web Connections 422

Neuropsychology in Action

14.1 The Discovery of Alzheimer’s Disease 410 14.2 Differentiating between Symptoms of Alzheimer’s Disease and Normal Aging 414

Chapter 15 S u b c o r t i c a l D e m e n t i a s 423 Keep in Mind 424 Overview 424

Parkinson’s Disease 424 Neuropathology of Parkinson’s Disease 424 Clinical Presentation and Neuropsychological Profile of Parkinson’s Disease 425 Treatments for Parkinson’s Disease 431

Huntington’s Disease 434 Neuropathology of Huntington’s Disease 434 Clinical Presentation and Neuropsychological Profile of Huntington’s Disease 435

Creutzfeldt–Jakob Disease 436 Neuropathology of Creutzfeldt–Jakob Disease 438 Clinical Presentation and Neuropsychological Profile of Creutzfeldt–Jakob Disease 439

Summary 441 Critical Thinking Questions 442 Key Terms 442 Web Connections 442

Neuropsychology in Action

15.1 Understanding Subcortical Dementia 426 15.2 Pallidotomy Surgery: A Case Report 432 15.3 Testing Fate: Would You Want to Know If You Were Going to Get

Huntington’s Disease? 435 15.4 Creutzfeldt–Jakob Disease and Mad Cow Disease: What’s the Connection? 438 15.5 The Neurologic Examination for Dementia 440

Chapter 16 A l t e r a t i o n s o f C o n s c i o u s n e s s 443 Keep in Mind 444 Overview 444

Understanding Consciousness 444 Mind and Brain 445 Anatomic Correlates of Consciousness 447

Rhythms of Consciousness 449

The Brain and Mind in Sleep 451 Sleep Architecture 451 Sleep Anatomy and Physiology 456 Reticular Activating System and Rapid Eye Movement Sleep 456 Functions of Rapid Eye Movement Sleep 459 Sleep Disorders 461

Runaway Brain: Seizure Disorders 463 Classification of Seizure Types 464 Neuroanatomy and Neurophysiology of Seizures 467 Neuropsychological Presentation 469 Treatment of Epilepsy 472

Summary 474 Critical Thinking Questions 474 Key Terms 474 Web Connections 475

Neuropsychology in Action

16.1 Self in the Mirror 446 16.2 The Case of the Last Coronation 450 16.3 Lucid Dreaming: A Paradox of Consciousness 453 16.4 Déjà Vu and Epilepsy 465 16.5 Epilepsy and the Case of the Sweeping Lady 468

References 477

Glossary 511

Answers to Critical Thinking Questions 539

Name Index 551

Subject Index 561

Contents xvii

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How can behavior make neuropsychological sense? That is the question we try to answer when we teach neuropsy- chology to our students. Like many teachers, we have had the experience of observing instructors and examining books on the topic of neuropsychology that presented the material in an esoteric manner removed from real-life sit- uations. Neuropsychology is an exciting and dynamic field that readily stimulates and inspires students and teachers alike. It was with this goal in mind that we have written a progressive and accessible text on the study of neuropsychology.

The goal of Principles of Neuropsychology was to write an undergraduate or beginning graduate-level psychology textbook that teaches brain function in a clear, interest- ing, and progressive manner. The guiding thesis of Prin- ciples of Neuropsychology is that all interactions in daily life, whether adaptive or maladaptive, can be explained neuropsychologically. Thus, the text challenges the reader to consider behavior from a broader biological perspec- tive. This, in turn, leads to the conceptualization of a more neuropsychologically oriented discipline within psy- chology. In this respect, the text covers the role of the brain in behavior as simple as a reflex and as complex as personality. Principles of Neuropsychology stresses the fol- lowing specific ideas:

1. An emphasis on human neuropsychology, experi- mental and clinical

Human neuropsychology is most appealing to psychology students, given that approximately half of all professional psychologists identify with a clinical or counseling spe- cialty. A major focus of Principles of Neuropsychology is to integrate the relatively new field of human clinical neu- ropsychology and compare it with what is known about the normal brain.

Rather than focus on a purely cognitive organization, which characterizes brain functioning and behavior ac- cording to specific aspects or components such as mem- ory, attention, or executive functioning, we chose to focus on disorders. Because neurologic disorders are multifaceted and usually involve overlapping and interacting cognitive

components, we believe it is most useful for aspiring prac- titioners and researchers to obtain a comprehensive view of each neurologic disorder with its multiple cognitive components.

2. An emphasis on integrating theory and research

The integration of theory with studies of neuroanatomic structure and functioning is central to a dynamic under- standing of neuropsychology. In this respect, Principles of Neuropsychology reviews general theories of brain function and specific theories of higher cortical functioning. A con- ceptual understanding of brain function is important be- cause it provides a foundation on which to base the study of complex behavioral syndromes as they correspond to brain regions and neuronal networks. Otherwise, nothing more than the memorization of brain anatomy and corre- sponding behavioral correlates is achieved, and an inte- grated understanding of neuropsychology remains out of reach.

3. An emphasis on behavioral function

We give special attention to presenting the function of specific neuroanatomic structures. Students often do not absorb the tremendous amount of information presented in similar texts because the material is presented in isola- tion, out of a psychological context. In this text, we pres- ent basic neurobiology as it relates specifically to behav- ior. Using such a functional approach facilitates both the absorption and comprehension of the material.

4. A focus on presenting real-life examples

To facilitate the reader’s understanding of complex mate- rial and to augment specific points, Principles of Neuropsy- chology includes numerous examples of clinical and nor- mal cases, procedures, and classic research findings at strategic places in the text. Like many other teachers, we find that didactic information is better understood when “real-life” situations are used. Many of the cases and proce- dures draw on our clinical and research experiences, which we accumulated in a variety of settings and services in- cluding state psychiatric hospitals, sleep centers, psychiatry

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departments, rehabilitation hospitals, and neurology and neurosurgery services. Throughout the text, we feature case examples and Neuropsychology in Action boxes, written by prominent neuropsychologists, that focus on interesting current issues related to brain functioning.

5. The presentation of didactic aids

Principles of Neuropsychology differs from other texts on the didactic dimension, because it uses unique aids to facilitate learning. These aids include an Instructor’s Manual, which provides outlines, class exercises, additional reference mate- rials, and didactic information; Web support, which in- cludes practice examinations, exercises, and additional refer- ence materials; more than 200 illustrations in the text; color illustrations; boldfaced Key Terms throughout the text, which are listed at the end of each chapter and again in the Glossary at the end of the text; a Keep in Mind section at the beginning of each chapter and Critical Thinking Ques- tions at the end of each chapter; and annotations on Web sites, called Web Connections, at the end of each chapter.

The companion Web sites for students and instructors have been updated and expanded for the new edition with a format that is easier to navigate. Now you will find chapter-by-chapter glossaries and interactive flash cards, plus videos and more practice exercises. To access these features and more, visit http://www.thomsonedu.com/ psychology/zillmer. For instructors, the Instructor’s Manual with Test Bank has been updated for the new edition and contains even more sample test items. Many of the figures and tables from the book are available for instructors as PowerPoint® electronic transparencies.

This second edition was revised related to the many suggestions that we have received. Specifically, the authors

have integrated the latest studies and research to give stu- dents the most up-to-date information in this dynamic and expanding field. Furthermore, this edition includes an increased emphasis on neuroscience coverage to pro- vide empirical data in support of the discussions of neu- ropsychology. Clinical examples throughout the text are updated in support of the new research in the developing field of neuropsychology. This second edition also pro- vides additional chapters and coverage on topics of So- matosensory, Chemical and Motor Systems, Vision and Language, and Memory, Attention, and Executive Func- tioning. A reorganization of the material now places as- sessment methods of the brain, both medical and psycho- logical, at the beginning of the text to introduce students to this area early in their studies.

In summary, the intent of Principles of Neuropsychology is to discuss brain functions, neurophysiology, and neu- roanatomy in an integrated and accessible format. An in- depth discussion on the relation among neuroscience, anatomy, and behavior is emphasized. Numerous exam- ples of clinical and real-life examples of neuropsychology are provided, as is a focus on relevant scientific and theo- retical contributions in the field of neuropsychology. Unique to the study of neuropsychology is an organiza- tion of the material from history, assessment, neu- roanatomy, to clinical assessment that makes intuitive and didactic sense. To facilitate a dynamic understanding of the field, the text emphasizes theory, functional process, case examples, and research, related to what has been learned about normal and neuropathological functioning. Approaching the field from this perspective challenges students to examine the field of neuropsychology as a framework for behavior.

xx Preface

http://www.thomsonedu.com

Dr. Eric A. Zillmer, a licensed Clinical Psychologist, received his Doctorate in Clinical Psychology from Florida Tech in 1984 and was subsequently awarded the Outstanding Alumnus Award in 1995. Dr. Zillmer completed internship training at Eastern Virginia Medical School and a postdoctoral fellowship in clinical neuropsychology at the University of Vir- ginia Medical School. A member of Drexel Univer- sity’s faculty since 1988, Dr. Zillmer is a Fellow of the College of Physicians of Philadelphia, the American Psychological Association, the Society for Personality Assessment, and the National Academy of Neuropsy- chology, for which he has also served as President. He has written extensively in the area of sports psychol- ogy, neuropsychology, and psychological assessment, having published more than 100 journal articles, book chapters, and books, and he is a frequent contributor to the local and national media on topics ranging from sports psychology, forensic psychology, to the psychology of terrorism. The Quest for the Nazi

Personality, published in 1995, has been summarized as the definitive psychological analysis of Third Reich war criminals. He is the coauthor of the d2 Test of Attention and the Tower of London test. Dr. Zillmer serves on the editorial boards of Journal of Personality Assessment and Archives of Clinical Neuropsychology. His most recent book is entitled Military Psychology— Clinical and Operational Applications (2006). Dr. Zillmer currently serves as the Director of Athletics at Drexel University.

Dr. Mary V. Spiers is Associate Professor of Psychol- ogy in the Department of Psychology at Drexel Uni- versity and is a licensed Clinical Psychologist specializing in Neuropsychology. She earned her Ph.D. in Clinical Psychology from the University of Alabama at Birmingham, where she specialized in medical psychology and neuropsychology. Dr. Spiers’s research and clinical expertise is in two areas. The first area is neuropsychological assessment with a focus on

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everyday problems of memory. She has developed tests to assess memory and cognitive problems in daily medication taking. Recently, she has focused on the development of ecologically valid spatial memory tests within a virtual reality environment. Dr. Spiers’s second area of focus relates to cognitive performance and strat- egy differences related to sex and gender. She leads the Women’s Cognitive Health Research Group at Drexel University, whose aim is to investigate variation in brain functioning through the influence of sex and gender, the menstrual cycle, genetics/handedness, experience, and culture. She regularly teaches Neuropsychology on both the undergraduate and graduate levels. In addition, she has taught a variety of graduate courses related to clini- cal assessment and memory, including Neuropsycholog- ical Assessment, Neuropsychological Case Analysis, and Models of Memory in Neuropsychology.

Dr. William C. Culbertson is in private practice as a Clinical Neuropsychologist who specializes in the

assessment and treatment of childhood and adolescent disorders, particularly those with attention-deficit/ hyperactivity disorder. He received his doctorate degree from Rutgers University and completed a postdoctoral fellowship in neuropsychology at Drexel University. Dr. Culbertson’s research interests are in the assess- ment of higher order problem-solving ability, specifi- cally as it relates to assessing frontal lobe damage, and executive functioning deficits. Dr. Culbertson has pub- lished in the field of neuropsychology (e.g., Assessment, Archives of Clinical Neuropsychology) and presented at professional conferences. He is an Associate Visiting Scholar at the University of Pennsylvania and has taught at Drexel University, both at the undergraduate and graduate level, including Counseling Psychology, Developmental Psychology, Cognitive Psychology, Theories of Personality, and various Seminars in Neuropsychology. He is a coauthor of the Tower of LondonDX, now in its second edition, which is a neuropsychological measure of executive function.

xxii About the Authors

This book could not have been written without the coop- eration, assistance, and support of numerous individuals. Many students, scholars, and friends listened to us, of- fered suggestions, and provided encouragement along the way. Many reviewers helped shape the book from begin- ning to end. We are most grateful to the following review- ers for their generous contributions to this second edition: Joan Ballard, SUNY Geneseo; Jody Bain, University of Victoria; Robert Deysach, University of South Carolina; Kenneth Green, California State University Long Beach; Julian Keenan, Montclair State University; Ann Marie Leonard-Zabel, Curry College; Jim Nelson, Valparaiso University; Elizabeth Seebach, Saint Mary’s University of Minnesota; Pamela Stuntz, Texas Christian University; Benjamin Walker, Georgetown University; Arthur Wing- field, Brandeis University; Nancy Zook, Purchase College SUNY. We would also like to thank those who con- tributed to the previous edition: Timothy Barth, Texas Christian University; Richard Bauer, Middle Tennessee State University; Gary Berntson, Ohio State University; Thomas Fikes, Westmont College; Michael R. Foy, Loyola Marymount University; Kenneth F. Green, California State University Long Beach; Gary Hanson, Francis Marion University; Barbara Knowlton, University of California Los Angeles; Paul Koch, St. Ambrose University; Mark McCourt, North Dakota State University; James Rose, University of Wyomong; Lawrence Ryan, Oregon State University; Bennett Schwartz, Florida International Uni- versity; Michael Selby, California Polytechnic Institute; Frank Webbe, Florida Institute of Technology; and finally, the many reviewers who did not wish to be named. We would also like to acknowledge those scholars who have contributed Neuropsychology in Action boxes to this text. All of them are prominent neuropsychologists who have, going beyond the call of duty, given valuable time to make Principles of Neuropsychology “come alive.”

Drexel University psychology students played an im- portant role in this project. They read initial chapters and provided feedback, were willing to use early versions of the manuscript as their textbook in class, and provided important research assistance. Simply put, this project could not have been accomplished without their diligent

efforts. Psychology undergraduate and graduate students who provided valuable research support on the first edi- tion included Barbara Holda, Priti Panchal, Dan Rosenberg, Holly Giordano, Stephanie Cosentino, Carrie Kennedy, Melissa Lamar, and Cate Price. Drexel University students in Dr. Spiers’s undergraduate and graduate neuropsychol- ogy classes provided valuable comments on both the structure and content of this second edition. Special thanks go to Karen Friedman, who coordinated reference updating in this second edition; to Heather McNiece, who coordinated the Key Terms and Glossary; and to Maiko Sakamoto, who assisted with the question bank.

Appreciation also goes to our colleagues Sepp Zihl and Karin Muenzel, both from the Ludwig-Maximilians University, Institute für Neuropsychologie, in Munich, Germany. Sepp and Karin allowed Dr. Zillmer to teach neuropsychology in an international forum. Our discus- sions on neuropsychology have been most stimulating and inspiring and have provided a springboard for many issues discussed in this text. We also want to acknowledge our col- leagues Mark Chelder and Joelle Efthimiou, who have as- sisted us in the development of the Assessment of Impair- ment Measure (AIM), which we have used extensively throughout the text to demonstrate the principles of neu- ropsychological assessment.

Our friend Carl Pacifico played a special role in this venture. He reminded us of how important it is to think about brain-behavior functioning within the context of evolution. Carl, ever the pragmatist, also shaped our thinking about the functional and applied aspects of neu- ropsychology. We especially welcomed the occasions when we discussed neuropsychology and its relation to culture, religion, and philosophy.

Special recognition goes to key administrators at Drexel University. Former Dean of the College of Arts and Sciences Thomas Canavan provided encouragement for our doctoral program in neuropsychology at Drexel and assistance for the successful APA accreditation process. Con- stantine “Taki” Papadakis, President of Drexel University, is acknowledged for revitalizing our university and, most importantly, making Drexel an exciting and fun place to teach and to do research.

A C K N OW L E D G M E N T S

xxiii

Our department faculty served as an important discus- sion group, “think tank,” and sounding board; whether it was around the copying machine, in the hallways, or over lunch, they allowed us to argue over the role of the brain and its relation to behavior. Thanks to Doug Porpora, David Kutzik, Tom Hewett, Elizabeth Petras, Arthur Shostak, Doug Chute, Lamia Barakat, and Anthony Glas- cock. Dorota Kozinska, at the University of Warsaw, Poland, taught us the three-dimensional imaging of brains and provided state-of-the-art brain electrical activity map- ping pictures. Erin D. Bigler, Professor of Psychology at Brigham Young University, and Frank Hillary, Assistant Professor at Penn State University, generously provided three-dimensional images of the brain. Frank Ruben C. Gur and his research group at the Department of Psychi- atry, University of Pennsylvania, allowed us to use cere- bral blood flow study pictures.

Any scholar with a family knows what it means to write a book and attempt to maintain a normal family life. Dr. Zillmer is grateful to his wife, Rochelle, and his

daughter, Kanya, for their support. Dr. Spiers thanks her husband, Sean, for his patience and understanding. Dr. Culbertson acknowledges his wife, Nancy, who provided countless hours of critical readings, tolerated his absences during those periods when he needed to write, and was unwavering in her support.

We cannot think of having had better editors for this project. We thank the production editor, Dan Fitzgerald, and the psychology editor, Erik Evans, assistant editor, Gina Kessler, and editorial assistant, Christina Ganim. They took our project seriously and forced us to focus on finishing a product of the highest quality. The assistance of many individuals has enabled us to publish this second edition. We are grateful to all of them and have benefited from their understanding, criticism, and advice. Thank you.

Eric A. Zillmer Mary V. Spiers

William C. Culbertson

xxiv Acknowledgments

S T R U C T U R E - F U N C T I O N R E L A T I O N S H I P S

1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 1

Cervical

Brain C2

C4 C5

T1 C8

L1 T12 T11 T10 T9 T8 T7 T6

T5 T4 T3

Thoracic

Lumbar

Sacral

c. 2 3 4 5

Sensory receptor

Dorsal root

Ventral root

Muscle

Parietal bone

Squamosal suture

Lambda

Occipital bone

Lambdoidal suture

External occipital protuberance

Temporal bone Asterion

External acoustic meatus

Mandible

Maxilla

Glabella

Sphenoid bone

Coronal suture

Frontal bone

Bregma Pterion

Nasion Nasal bone

Zygomatic bone

Lacrimal bone Ethmoid bone

Angle of mandible

Zygomatic archStyloid process

Mastoid process

(location of intervertebral disk)

spinal cord

ganglion nerve

meninges (protective coverings)vertebra

Anterior communicating artery

Anterior cerebral artery

Internal carotid artery Middle cerebral artery

Posterior communicating artery Posterior cerebral artery

Basilar artery Labyrinthine artery Vertebral artery

Anterior spinal artery

Posterior inferior cerebellar artery

Superior cerebellar artery

Pontine arteries

Anterior inferior cerebellar artery

Spinal Cord Anatomic features: Spinal nerves and internal organization of the spinal cord (gray and white matter) Function: Relays information to and from the brain; responsible for simple reflexive behavior

Skull Anatomic features: A fused connection of bony plates covering the brain Function: Protection of the brain

Meninges Anatomic features: Dura mater, arachnoid membrane, and pia mater Function: Protective covering of the central nervous system, location of venous drainage, and cerebrospinal fluid absorption

Vascular System Anatomic features: Arteries, veins, circle of Willis Function: Arteries: nourishment; supply of oxygen and nutrients Veins: carrying away waste products

(continued)

Third ventricle

Fourth ventricle

Lateral ventricles

Cerebral or Sylvanian aqueduct Central canal

of spinal cord

Ventricular System Anatomic features: Lateral (1st and 2nd), 3rd, and 4th ventricles, choroid plexus, cerebral aqueduct, and arachnoid granulations Function: Balancing intracranial pressure, cerebrospinal fluid production, and circulation

xxv

Thalamus Pineal gland

Tectum

Pons

Medulla

Tegmentum

Superior colliculus Inferior colliculus

Midbrain

Posterolateral view of brainstem

Optic nerve (Cranial nerve II)

Cranial nerve III Cranial nerve V

Cranial nerve VIII VII VI IX X

XI XII

Spinal nerve Spinal cord

Medulla

Cranial nerve IV

Midbrain

Pons Cerebellum

Lower Brainstem Anatomic features: Hindbrain: medulla oblongata (myelencephalon), pons (metencephalon) Midbrain: tectum and tegmentum, cranial nerves, reticular activating system Function: Relays information to and from the brain; responsible for simple reflexive behavior

Cranial Nerves Anatomic features: Located within the brainstem Function: Conducting specific motor and sensory information

Pulvinar nucleus

Dorsomedial nucleus

Ventral lateral nucleus

Ventral posteriolateral nucleus

Lateral geniculate body

Dorsal hypothalamus

Dorsomedial hypothalamus

Posterior hypothalamus

Paraventricular nucleus of hypothalamus

Anterior commissure Lateral hypothalamus (behind plane of view) Anterior hypothalamus Preoptic area

Supraoptic nucleus

Optic chiasm

Anterior pituitary

Mammillary body

Ventromedial hypothalamus

Posterior pituitary

Cortex

Reticular formation

Suprachiasmatic nucleus

Brainstem

Cerebellum

Reticular Formation Anatomic features: Neural network within the lower brainstem connecting the medulla and the midbrain Function: Nonspecific arousal and activation, sleep and wakefulness

Hypothalamus Anatomic features: Hypothalamic nuclei, major fiber systems, and third ventricle Function: Activates, controls, and integrates the peripheral autonomic mechanisms, endocrine activity, and somatic functions, including body temperature, food intake, and the development of secondary sexual characteristics

Thalamus Anatomic features: Thalamic nuclei and thalamocortical connections Functions: Complex relay station—major sensory and motor inputs to and from the ipsilateral cerebral hemisphere

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xxvi

Cerebellar cortex

Deep cerebellar nuclei Pontine

nuclei

Fourth ventricle

Globus pallidus (lateral part)

Caudate nucleus

Subthalamic nucleus

Substantia nigra

Putamen

Globus pallidus (medial part)

Thalamus

Corpus callosumFornix

Anterior nucleus of thalamus

Septum

Olfactory bulb

Mammillary body Amygdala

Hippocampus

Corpus callosum

Amygdala Involved in memory, emotion, and aggression

Hippocampus Involved in learning, memory, and emotion

Medulla Controls vital functions such as breathing and heart rate

Thalamus Switching station for sensory information; also involved in memory

Spinal cord Transmits signals between brain and rest of body

Cerebellum Controls coordinated movement; also involved in language and thinking

Hypothalamus Regulates basic biological functions, including hunger, thirst, temperature, and sexual arousal; also involved in emotion

Cerebral Hemispheres Anatomic features: Structures of the frontal, parietal, occipital, and temporal lobes Function: Higher cognitive functioning, cerebral specialization, and cortical localization

Cerebellum Anatomic features: Cerebellar cortex, cerebellar white matter, and glia Function: Coordination of movements, posture, antigravity, balance, and gait

Basal Ganglia Anatomic features: Structures of the caudate nucleus, putamen, globus pallidus, substantia nigra, and subthalamic nuclei Function: Important relay stations in motor behavior (such as the striato–pallido–thalamic loop); connections form part of the extrapyramidal motor system (including cerebral cortex, basal nuclei, thalamus, and midbrain) and coordinate stereotyped postural and reflexive motor activity

Limbic System Anatomic features: Structures of the amygdala, hippocampus, parahippocampal gyrus, cingulate gyrus, fornix, septum, and olfactory bulbs Function: Closely involved in the expression of emotional behavior and the integration of olfactory information with visceral and somatic information

Corpus Callosum Anatomic features: A large set of myelinated axons connecting the right and left cerebral hemispheres Function: Information exchange between the two hemispheres

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Part One

I N T R O D U C T I O N

Chapter 1 A History of Neuropsychology

Chapter 2 Methods of Investigating the Brain

Chapter 3 Neuropsychological Assessment and Diagnosis

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Chapter 1

A H I S TO RY O F N E U RO P S Y C H O L O G Y

I think, therefore I am. —René Descartes, Discourse on Method

There is no ghost in the machine. —Gilbert Ryle, The Concept of Mind

The Brain in Antiquity: Early Hypotheses Localization Theory Localization versus Equipotentiality Integrated Theories of Brain Function Modern Neuropsychology Emerging Research Areas in Neuropsychology

Neuropsychology in Action

1.1 The Brain of a Nazi 1.2 Paul Broca: A Manner of Not Speaking 1.3 Sigmund Freud: The Neurologist 1.4 The Walter Freeman Lobotomies: Mind over Matter?

Overview All the preceding questions concern the functions of the brain. The brain has evolved to play a particularly significant role in the human body, not only in sustaining life, but also in all thought, behavior, and reason- ing. It is the only organ completely enclosed by protective bony tissue, the skull, and it is the only organ that cannot be transplanted and still maintain the person’s self. But how exactly does brain tissue generate and constrain mental events?

Efforts to understand mind–body relationships and their relative contributions to health and well-being extend back at least to the philosophies of Plato, Descartes, and Kant. Like many other sciences, neuropsy- chology has evolved from related fields, most notably psychology, neurology, neuroscience, biology, and philosophy. Psychology is the study of behavior; specifically, it seeks to describe, explain, modify, and pre- dict human and animal behavior. Neuropsychology, a subspecialty of psychology, is the study of how com- plex properties of the brain allow behavior to occur. Neuropsychologists study relationships between brain functions and behavior; specifically, changes in thought and behavior that relate to the brain’s structural or cognitive integrity. Thus, neuropsychology is one way to study the brain by examining the behavior it pro- duces.

Humans read and write, compose music, and play sports. You would expect an organ that coordinates and mediates all activity to have a huge number of components. And, in fact, the brain contains billions of cells, or neurons, and an infinite number of possible connections among individual neurons, allowing us to exchange complex information. This amazing pattern of connections determines how and what the brain does. Understanding this network of neurons is the central focus of neuropsychology.

Neuropsychology has grown tremendously since the 1970s, and in the 1990s, it was the fastest grow- ing subspecialty within psychology. Neuropsychologists lead the study of brain–behavior relationships and are involved in the design and development of technologies to treat diseases of the brain. They are involved in patient care and research on the brain and work in universities, research institutes, medical and psychi- atric hospitals, correctional facilities, the armed forces, and private practice.

The study of neuropsychology currently is shaping our understanding of all behavior. But this has not always been true. Many previous ideas about how the brain functions did not derive from scientific evidence. In general, two doctrines have emerged. The first doctrine, vitalism, suggests that many behav- iors, such as thinking, are only partly controlled by mechanical or logical forces—they are also partially self- determined and are separate from chemical and physical determinants. Extreme proponents of vitalism argue that spirits or psychic phenomena account for much observable behavior. Sigmund Freud’s psycho- analysis would be a good example of this doctrine. The second doctrine, materialism, suggests that logical forces, such as matter in motion, determine brain–behavior functions. Materialism, in its simplest form, favors a mechanistic view of the brain (as a machine). Walter Freeman’s lobotomies embraced this idea. The history of neuropsychology is shaped by these two opposing principles.

This introductory chapter provides grounding in the historical, theoretical, and philosophical aspects of neuropsychology. By charting the work of noted scholars, this chapter traces the development of neuropsy- chology from antiquity to the present.

4 PART ONE | Introduction

K e e p i n M i n d

Does our brain constitute a major aspect of who we are?

Is the brain the source of all behavior?

Where do we go when our brain dies?

What is a soul?

The Brain in Antiquity: Early Hypotheses

Evidence from as long ago as the time of cave draw- ings shows that people have long been aware of brain-be- havior relationships. The earliest neuropsychological in- vestigations recognized how diseases and blows to the brain affect behavior. For example, trephination is an an- cient surgical operation that involves cutting, scraping, chiseling, or drilling a pluglike piece of bone from the skull. This procedure relieves pressure related to brain swelling. Archaeologists have recovered several thousand such skulls worldwide. Many who underwent trephina- tion clearly survived the operation, because many of the skulls show evidence of healing (new callus tissue); other skulls show no signs of healing, so the patients died dur- ing or shortly after the operation. In some cases, the same skull was trephined more than once. One recovered skull was found with seven boreholes, at least some of which were made on separate occasions.

Why did our ancestors perform trephination (Figure 1.1)? Did they have a reasonable understanding of the brain and its relationship to behavior? Did they use this proce- dure for medical reasons, such as trauma with swelling, or for other reasons? Did practitioners avoid certain areas of the brain because they knew that permanent behavioral problems or death were likely to follow?

Much debate focuses on the reason for trephinations. Researchers have suggested that some cases may have in- volved a medical reason, such as a skull fracture. Such in- juries presumably occurred during hand-to-hand fighting with stone-headed war clubs or perhaps as a result of a fall unconnected with warfare. On some skulls, however, trephi- nation was performed on intact crania with no sign of vio- lence. Thus, some investigators suggest that trephination was a “magical” form of healing, perhaps for displays of bizarre behaviors, including what we would now recognize as epilepsy or schizophrenia (Lisowski, 1967) (Figure 1.2).

Similar operations are important in modern neuro- surgery (Figure 1.3). Surgeons widely use two procedures. The first procedure, similar to the ancient Peruvian

CHAPTER 1 | A History of Neuropsychology 5

Figure 1.1 Trephination scene in Peru. (Image reprinted with permission from Department of Anthropology, National Museum of Natural History, Smithsonian Institution, Washington, D.C. Photo courtesy of the San Diego Museum of Man.)

technique of drilling a number of small holes, involves drilling a hole next to a depressed skull fracture to facili- tate the elevation and removal of depressed bone frag- ments. Incidentally, modern neurosurgeons still use man- ual drills, which allow them more control during the operation. The second surgical procedure drains internal bleeding after a blow to the head. With a special drill bit, the surgeon makes a hole over the site of the bleed. Then the surgeon screws a precisely machined bolt into the skull, allowing excessive blood to drain from within the cranium. This procedure reduces the intracranial pressure that is a major cause of death after a head injury (see Chapter 13).

That surgeons today use an ancient surgical technique that even modern doctors once thought controversial underscores that people have often misinterpreted the his- torical context in which ancient scientists proposed certain ideas about the brain or performed specific procedures. Most ideas about the brain make more sense when consid- ered within the societal and cultural context in which they were originally developed.

A N C I E N T G R E E K P E R S P E C T I V E S

Classical Greeks wrote the first accounts of brain–behavior relationships. Heraclitus, a philosopher of the sixth cen- tury B.C., called the mind an enormous space with boundaries that we could never reach. A group of schol- ars, including the geometer Pythagoras (about 580– 500 B.C.), was the first to suggest that the brain is at the center of human reasoning and plays a crucial role in the soul’s life. They described what is now called the brain hypothesis: the idea that the brain is the source of all behavior.

Hippocrates (460–377 B.C.), a Greek physician hon- ored as the founder of modern medicine (Figure 1.4), also believed the brain controls all senses and movements. He was the first to recognize that paralysis occurs on the side of the body opposite the side of a head injury, following the areas governed by the right and left hemispheres of the brain. Hippocrates suggested that pleasure, merri- ment, laughter, and amusement, as well as grief, pain, anxiety, and tears, all arise from the brain (Haeger, 1988). Furthermore, Hippocrates argued that epilepsy, once con- sidered the “sacred disease” (because people thought the patient was possessed by gods or spirits), is, in fact, no more divine or sacred than any other disease, but has spe- cific characteristics and a definite medical cause. These were bold propositions at a time when people thought behavior was mostly under divine control. Hippocrates and his associates could not, however, discuss exactly how such brain–behavior relationships arose, perhaps because it was then sacrilegious to dissect the human body, especially the brain.

Plato (420–347 B.C.) suggested in The Republic that the soul has three parts: appetite, reason, and temper. This may have served as the model for Freud’s psychoanalytic subdivision of the psyche into the id, ego, and superego (see later discussion). Plato believed the rational part of the tripartite soul lay in the brain, because it is the organ closest to the heavens. Plato also discussed the idea that health is related to harmony between body and mind. Thus, historians credit Plato as being the first to propose the concept of mental health.

6 PART ONE | Introduction

Figure 1.2 Adult male skull showing multiple trephina- tions by the scraping method. Evidence of inflammation indicates temporary survival. (Courtesy Mütter Museum, College of Physicians of Philadelphia.)

Figure 1.3 Modern trephination. A surgical hole is opened in the skull to relieve the intracranial pressure often associated with consequences of head trauma. (Courtesy Jeffrey T. Barth, PhD, University of Virginia.)

Not all ancient philosophers believed in the impor- tance of the brain to behavior. Aristotle (384–322 B.C.), a disciple of Plato, was a creative thinker in fields as var- ied as ethics, logic, psychology, poetry, and politics, and he founded comparative anatomy. Aristotle, however, er- roneously believed the heart to be the source of all mental processes. He reasoned that because the heart is warm and active, it is the locus of the soul. Aristotle argued that be- cause the brain is bloodless, it functions as a “radiator,” cooling hot blood that ascends from the heart. The influ- ence of Aristotle’s so-called cardiac hypothesis proposing the heart as the seat of such emotions as love and anger can still be seen in words such as heartbroken. Neverthe- less, Aristotle’s view of nature and his anatomic findings dominated medical thinking and methods for the next 500 years.

T H E C E L L D O C T R I N E

In Egypt, during the third and fourth centuries B.C., the so-called Alexandrian school reached its height. Well- known scientists worked in physiology and anatomy. They gained considerable knowledge of the nervous system and neuroanatomy from performing public dissections, which the Ptolemaic rulers encouraged. Reports exist of scientists actually vivisecting subjects—condemned criminals were at the scientists’ disposal. These dissections allowed scientists to notice different anatomic details, and they hypothesized that specific parts of the brain control different behaviors. Furthermore, they broke new ground by distinguishing between ascending (sensory) and descending (motor) nerves, and demonstrating that all nerves connect with the central nervous system.

An interesting development during this time was the erroneous suggestion that ventricular cavities within the brain control mental abilities and movement. The ven- tricular localization hypothesis postulated that mental as well as spiritual processes reside in the ventricular chambers of the brain. Indeed, gross dissection of the brain shows that the lateral ventricles are the most strik- ing features. Thus, brain autopsies might have led investi- gators to conclude that these cavities contain animal spir- its and are in large part responsible for mental faculties. This hypothesis subsequently became known as the cell doctrine (“cell” meaning a small compartment or ventri- cle), a notion that endured for 2000 years. Leonardo da Vinci (1452–1519), an Italian painter, sculptor, architect, and scientist, was a keen observer of anatomy. However, many of his early drawings were not guided by his keen scientific acumen, but instead by the inaccurate medieval conventions of his times. For example, Figure 1.5 shows one of his drawings based on a common, but inaccurate belief about spherical ventricles. According to the cell doc- trine, foremost was the cell of common sense, where peo- ple thought the soul resided and that connected to nerves leading to the eyes and ears.

Today, people know that the cell doctrine is entirely in- accurate. The ventricles are actually the anatomic site through which cerebrospinal fluid passes. This fluid pro- tects the brain and facilitates the disposal of waste material. It plays no role in thinking; in fact, a neurosurgeon friend of ours conceptualizes it poetically as “the urine of the brain.” The cell doctrine was scientifically important pre- cisely because it was in error, and thus presented an obsta- cle to further inquiry that people did not overcome until centuries later. However, it did focus the medical commu- nity on the brain and stimulated discussion of how behav- ior, thought processes, and brain anatomy may be related.

CHAPTER 1 | A History of Neuropsychology 7

Figure 1.4 Hippocrates suggested that all thoughts and emotions originated in the brain, not the heart, as Aristotle had believed. Here, the ancient Greek physician opens his book to one of his favorite axioms, “Life is short, and the art is long.” (© Snark/Art Resource, NY.)

Together with Hippocrates, Galen (A.D. 130–201), a Roman anatomist and physician, stands out as a supreme figure in ancient medicine (Figure 1.6). Galen was un- doubtedly the greatest physician of his time. By signifi- cantly advancing the anatomic knowledge of the brain, Galen distinguished himself as the first experimental physiologist and physician. He identified many of the major brain structures and described behavioral changes as a function of brain trauma. It was Galen’s misfortune, however, that during his life the Roman authorities for- bade autopsies. He therefore based much of his clinical knowledge on his experience as a surgeon appointed to treat gladiators; he remarked that war and gladiator games were the greatest school of surgery. Contemporary neu- ropsychologists have also made significant advances dur- ing periods of war, including World Wars I and II and the Korean and Vietnam conflicts, by studying the behavioral effects of wounds to the brain.

Galen suggested that the brain is a large clot of phlegm from which a pump forced the psychic pneuma out into the nerves. Perhaps he was comparing the brain to a major

technologic achievement of his time, the Roman system of aqueducts, which relied on hydraulic principles. Al- though Galen believed the frontal lobes (Figure 1.7) are the location of the soul, he supported the ventricular lo- calization hypothesis, describing in detail how he imag- ined human ventricles to look and function, based on his studies of the pig and the ox. Galen believed that all phys- ical function, including the brain, as well as the rest of the body, depends on the balance of bodily fluids or humors, specifically blood, mucus, and yellow and black bile, which he related to the four basic elements—air, water, fire, and earth, respectively. Given that people thought the agent that causes sickness resides in blood, doctors often bled patients as a curative procedure. Galen’s view of humors became so ingrained in Western thought that physicians barely elaborated on the role of the brain and other organs, which remained largely unquestioned for nearly the next thousand years. We still say “good humor” or “bad humor” to describe someone’s mental disposition. Terms such as melancholic (having frequent spells of sad- ness) and choleric (having a low threshold for angry out- bursts) also remain in our vocabulary (Figure 1.8).

A N A T O M I C D I S C O V E R I E S A N D T H E R O L E O F T H E S P I R I T U A L S O U L

During the thirteenth century, scientists began to take initial steps away from the ventricular theory. For exam- ple, Albertus Magnus, a German Dominican monk, the- orized that behavior results from a combination of brain structures that includes the cortex, midbrain, and cerebel- lum (Figure 1.9).

Not until scientific inquiry by Andreas Vesalius (1514–1564), however, were Galen’s anatomic mistakes corrected, particularly those related to the role of the ven- tricles and their effect on behavior. Galen had initially demonstrated the similar relative size of the ventricles in animals and humans, whereas Vesalius placed more em- phasis on the relatively larger overall brain mass of hu- mans as responsible for mediating mental processes. Through continual dissections and careful scientific ob- servations, Vesalius demonstrated that Galen’s views were inaccurate. Vesalius also pioneered the anatomic theater— a sort of performance dissection, where medical students and doctors could watch from a circular gallery. Despite a climate of political and religious restrictions, Vesalius per- formed the first systematic dissections of human beings in Europe. Clearly, many opposed and objected to his exper- imental predilections. After all, the church retained au- thority over the soul, which was not subject to direct investigation. But Vesalius proceeded to revolutionize

8 PART ONE | Introduction

Figure 1.5 Drawing by Leonardo da Vinci demonstrating, inaccurately, the placement of three spherical ventricles in accordance with the cell doctrine. (The Royal Collection © 2007, Her Majesty Queen Elizabeth II.)

medicine through precise drawings of human anatomy (Figure 1.10). For the first time, surgeons could see what they were dealing with.

By the seventeenth century, scientists were looking for a single component of the brain as the site of mental processes. René Descartes (1596–1650), for example, proposed a strict split or schism between mental processes and physical abilities. He hypothesized that the mind and body are separate, but interact with each other. Descartes theorized that mental processes reside in a small anatomic feature, the pineal gland. He reasoned that because the pineal gland lies in the center of the brain and is the only structure not composed of two symmetric halves, it was the logical seat for mental abilities. It is also close to the ventricular system; thus, the “flow of the spirits” might influence it. Today, the function of the pineal gland is something of a mystery and is perhaps related to light–dark cycles and the production of sleep-enhancing melatonin.

Descartes has had an important philosophic influence on the study of the brain, precisely because dualist thinking

CHAPTER 1 | A History of Neuropsychology 9

Figure 1.6 Galen learned from Hippocrates. Later, however, he was rather cynical about Hippocrates’s writings, stating that they “have faults, and lack essential distinctions his knowledge of certain topics is insuffi- cient, and he is often unclear as the old tend to be. In sum: he prepared the way, but I have made it passable” (Haeger, 1988, p. 59). (© Scala/Art Resource, NY.)

Occipital lobe

Figure 1.7 The lobes of the brain. (Adapted from Heller, K. W. [1996]. Understanding physical, sensory, and health impairments [p. 51, Figure 4.5]. Pacific Grove, CA: Brooks/Cole.)

10 PART ONE | Introduction

Figure 1.8 Ancient physicians took interest in humors, which served medieval notions of health and disease. (Clockwise) Excess black bile was responsible for a patient suffering from melancholy (depression); blood impassioned a lutist to play; phlegm is responsible for a slow response to a lover; and yellow bile results in anger. (Courtesy Zentralbibliothek Zürich.)

opposes the idea that we can explain psychological states and processes for physical phenomena. In fact, historians often call Descartes the founder of body–mind dualism. If he had been correct, it would be hopeless to search for an explanation of mental processes for brain states. How- ever, people have sometimes misunderstood Descartes. He proposed a concept of bodily movement, such as the eye blink, that reflected the mechanistic concepts of his time, such as the functioning of clockworks and water fountains (Figure 1.11). He generally believed the body to be a machine. Reflexes stem not from the intervention of the soul, but from nerves or message cables to and from the brain. Voluntary actions require a rational, nonmater- ial soul and the free exercise of will. The church, however, steadfastly endorsed the idea that animal spirits and vital forces are nonmaterial, and that all nervous activity re- quires such vital forces. Descartes, a devoted Catholic, barely remained respectable in the scientific community because of his constant warnings that he was probably in- correct. His work Treatise on Man (1664) (from which Fig- ure 1.11 is taken) was not published until 14 years after his death because he feared being charged with heresy.

By the seventeenth and eighteenth centuries, more pre- cise models of the brain became possible. This advance was related, in part, to the conviction that people could explain everything by mechanics. English anatomist Thomas Willis (1621–1675), best known for his work on blood cir- culation in the brain, theorized that all mental faculties re- side in the corpus striatum, a structure deep within the cerebral hemispheres. Others suggested that most mental faculties reside in the white matter of the cerebral hemi- spheres. Giovanni Lancisi (1654–1720), an Italian clini- cian who contributed greatly to our knowledge of the aneurysm (an abnormal, blood-filled ballooning of an artery in the brain), selected the corpus callosum, a band of fibers that joins the left and right cerebral hemispheres, as the seat of mental functions.

Early investigators were preoccupied with identify- ing the one precise part of the brain that was the seat of the mind, but they based their discussions primarily on speculation and, in fact, conducted relatively little ex- perimentation. Nevertheless, they were part of a move- ment that would become stronger in the centuries to come.

CHAPTER 1 | A History of Neuropsychology 11

Corpus callosum

Midbrain

Pons

Medulla oblongata

Spinal cord

Cortex

Skin

Cerebellum

Figure 1.9 Basic anatomy of the brain. (Reproduced from Heller, K. W. [1996]. Understanding physical, sensory, and health impairments [p. 50, Figure 4.4]. Pacific Grove: Brooks/Cole.)

N O N - W E S T E R N A T T I T U D E S

Although Western ideologies predominantly shaped the behavioral sciences, non-Western cultures also developed theories to explain behavior. Although some of these the- ories certainly must have involved the role of the brain, we know little about how advanced people such as the Egyptians and Eastern cultures approached the brain, be- cause we lack detailed written accounts.

Common to eastern Mediterranean and African cul- tures was the belief that a god or gods sent diseases. For example, Egyptians viewed life as a balance between in- ternal and external forces. As a result, they treated many mental disorders as integrating physical, psychic, and spir- itual factors (Freedman, Kaplan, & Sadock, 1978). They conceptualized the brain as different from the mind. As in Aristotelian theory, they considered the heart the cen- ter of mind, sensation, and consciousness. In India, one of the earliest and most important medical documents, the Atharva-Veda (700 B.C.), proposed that the soul is nonmaterial and immortal.

During the Middle Ages, Arab countries demonstrated a humanist attitude toward the mentally ill, partly because of the Muslim belief that God loves the insane person. Because of this, the same treatments were available for the rich and poor. The treatment of mental patients was hu- manist and emphasized diets, baths, and even musical concerts especially designed to soothe the patient.

Ancient Chinese medical texts also discussed psycho- logical concepts and psychiatric symptoms. For example, Chinese medical practitioners endorsed a mechanistic

12 PART ONE | Introduction

Figure 1.10 Vesalius’s drawings of the human brain. In his attempt to learn about anatomy, Vesalius initially depended on the work of others. Later, he wanted to see for himself, performing the first systematic dissections of human beings done in Europe. (National Library of Medi- cine.)

Figure 1.11 Seventeenth-century philosopher René Descartes’s illustration of the mechanistic view of how light transmits images to the retina, stimulating nerves in the arm to produce movement. Descartes proposed, erro- neously, that the mind interacts with the brain at the pineal gland. (National Library of Medicine.)

view of mental processes. They conceptualized many mental health disorders as illnesses or vascular disorders, as opposed to the prevailing European belief in demonic possession. The ancient Chinese medical textbook The Yellow Emperor’s Classic of Internal Medicine (ca. 1000 B.C.) includes references to dementia, convulsions, and violent behavior. Confucian writings reflected early Chi- nese philosophical thought in proposing that mental functions are not distinct from physical functions and do not reside in any part of the organism, although these writings give the heart special importance as a guide for the mind. Surgeons practiced trephination in eastern Mediterranean and North African countries as early as 4000 to 5000 B.C. There is no evidence of trephination in ancient Japan, China, or Egypt. Because contributions to the development of neuropsychology by non-Western scholars remain unknown, we are left to wonder whether there may have been great discoveries or, alternatively, many of the same fallacies that Western cultures endorsed about the role of the brain on behavior.

Localization Theory

P H R E N O L O G Y A N D F A C U L T Y P S Y C H O L O G Y

Not until the nineteenth century did modern neuropsy- chological theories on brain function begin to evolve. Thinkers formulated them, in part, from a need not only to recognize the brain as responsible for controlling be- havior, but more importantly, to demonstrate precisely how the brain organizes behavior. Early in the century, Austrian anatomist Franz Gall (1758–1828), borrowing perhaps from the concept of geography (the notion of borders, at a time when people were discovering and map- ping new continents), postulated that the brain consists of a number of separate organs, each responsible for a basic psychological trait such as courage, friendliness, or combativeness. Gall, a distinguished Viennese physician and teacher, suggested that mental faculties are innate and depend on the topical structures of the brain. His theory sought to describe differences in personality and cognitive traits by the size of individual brain areas. He hypothe- sized that the size of a given brain area is related to the amount of skill a person has in a certain field. Craniology is the study of cranial capacity in relation to brain size, which indicated intelligence.

Gall’s work, however, was severely limited by faculty psychology, the predominant psychological theory of that time, which held that such abilities as reading, writing, or intelligence were independent, indivisible faculties. Such

specific brain functions, therefore, were performed in iso- lation from functional systems in other parts of the brain. Gall also lacked statistical or methodologic theory that would have let him reliably measure the basic skills of in- terest to him. By assigning specific functions to particular places in the cerebral cortex, Gall formulated the basis of the localization theory of brain function (Table 1.1). Al- though Gall was wrong on most counts, he did help shape how we currently perceive brain–behavior relationships. For example, Gall correctly suggested that because their complexity is greatest in humans, the most intellectual parts of the brain are the frontal lobes. He also argued that the brain is the organ of the mind and functions are grouped within it.

From Gall’s basic theory of localization, the “science” of phrenology was born. This theory holds that if a given brain area is enlarged, then the corresponding area of the skull will also be enlarged. Conversely, a depression in the skull signals an underdeveloped area of the cortex. It is generally accurate that skull configurations closely follow brain configurations. Phrenology, in its most popular form, involves feeling the cranial bumps to ascertain which cerebral areas are largest (Figure 1.12). Sophisti- cated mechanical equipment was developed, such as the phrenology cap (Figure 1.13), to accurately identify bumps and indentations on the skull to make “precise” predictions about psychological strengths and weaknesses.

Although Gall made remarkable discoveries in neu- roanatomy, the theory of phrenology was entirely inaccu- rate. In Vienna and Paris, critics accused Gall of materialism

Selected “interpretations” corresponding to specific locations on the skull:

1. Amativeness: love between the sexes, desire to marry

2. Parental love: regard for offspring, pets, and so on

3. Friendship: adhesiveness, sociability, love of society

4. Inhabitiveness: love of home and country

5. Continuity: one thing at a time, consecutiveness

6. Combativeness: resistance, defense, courage, opposition

7. Destructiveness: executiveness, force, energy

8. Alimentiveness: appetite, hunger, love of eating

9. Acquisitiveness: accumulation, frugality, economy

10. Secretiveness: discretion, reserve, policy, management

Source: Wells, S. (1869). How to read character: New illustrated hand-book of phrenol- ogy and physiognomy (p. 35). New York: Fowler & Wells.

Table 1.1 Definition of the Organs

CHAPTER 1 | A History of Neuropsychology 13

and ultimately forced him to leave teaching. His student Johann Spurzheim (1776–1832) carried on his phrenol- ogy teachings, lecturing extensively on phrenology in the United States. As a result, phrenology societies sprang up in the United States, and the movement became increas- ingly popular. To this day, people sometimes make attri- butions about an individual solely from specific physical characteristics.

Gall also played an important role in developing de- terministic thought about the functions of the brain and the mind; but in the final analysis, his critics accused him of having made the most absurd theories about the facul- ties of human understanding. Phrenology in its simplistic form had followers who made sweeping statements about the brains and minds of men and women. Men, they sug- gested, have larger brain areas in the social region, with a predominance of pride, energy, and self-reliance, com- pared with women, whose brains reflect “inhabitiveness” (love of home) and a lack of firmness and self-esteem. Phrenologists also attempted cross-cultural comparisons, suggesting that the skulls of races and nations differ

widely in form (Neuropsychology in Action 1.1). Erro- neously, phrenologists (largely white individuals) sug- gested that the skulls of white people were superior, indi- cating great intellectual power and strong moral sentiment. The skulls from “less advanced races” did not fare as well, because those virtues were thought to be al- most invariably small in “savage” and “barbarous tribes” (Wells, 1869).

The promise of finding anatomic differences that could explain even complex social and intellectual be- haviors is, for some scientists, still quite tempting. Con- troversy exists whether the brains of murderers and ge- niuses are indistinguishable or different. Scientists in the former Soviet Union preserved and studied the brains of famous communists to identify their “intellectual supe- riority.” In the United States, Albert Einstein has been

14 PART ONE | Introduction

Figure 1.12 Phrenology head. Specific locations on the skull were thought to correspond to specific abilities. (National Library of Medicine.)

CHAPTER 1 | A History of Neuropsychology 15

Borrowing on ideas of Gall and Spurzheim, the Nazi propaganda leadership suggested that natural biological traits decide the total being of a person, and they challenged those who sought to explain personality on any basis other than a biological or racial one. Of course, the Nazis erred in refusing to recog- nize complex contributing environmental and social influences that also shape and deter- mine behavior and individual differences. But U.S. armed forces leadership was also invested in the same fallacy, trying to demonstrate that there may be something biologically wrong with the Nazis. For exam- ple, in 1945, the U.S. Army ordered a post- mortem autopsy of Robert Ley’s brain, a high-ranking Nazi Labor Front boss, after he had committed suicide while waiting to stand trial at the International Military Tribunal in Nuremberg. Allied doctors argued that deterioration in Ley’s frontal lobes as a result of an old head injury explained his criminal behavior, which included violent anti-Semitism. Army pathologists concluded that “the [brain] degeneration was of suffi- cient duration and degree to have impaired Dr. Ley’s mental and emotional faculties and could well account for his alleged aberra- tions in conduct and feelings” (“Dr. Robert Ley’s Brain,” 1946, p. 188).

That the U.S. Army and the American public had an investment in the pathology of Ley’s brain is ironic, because the Nazis

themselves expended much effort to demonstrate, through pseudomedical research using principles based on phrenol- ogy, that the skulls of Untermenschen (“subhumans”) were biologically inferior. In a morbid display of unethical medicine, Nazi doctors at concentration camps routinely sent postmortem specimens of the targeted groups to Berlin to exhibit and demonstrate inferiority (Lifton, 1986). In the same mode, the American public and media were in- vested in viewing the Nuremberg gang as biologically and psychologically abnormal. After World War II, British and U.S. psychia- trists went so far as to suggest that one could detect a Nazi by phrenology. They argued that Rudolf Hess, Hitler’s deputy, had specific anatomic features, including an “extreme primitive skull formation and misshapen ears,” that could serve as possi- ble warning signals in spotting future Nazis (Rees, 1948).

The neuropathologic evidence that Ley’s brain was abnormal actually turned out to be weak and undoubtedly distorted by the significant external pressure to find some- thing wrong with the Nazis at Nuremberg. Interestingly, after the execution of the 11 high-ranking Nazi leaders at Nuremberg, scientists asked to perform additional autopsies, particularly histologic studies of the Nazis’ brains (Zillmer, Harrower, Ritzler, & Archer, 1995). The authorities denied this

request, however, because the bodies were to be cremated at the Dachau concentration camp and the ashes disposed of secretly. Currently, the remains of Ley’s brain are kept at the U.S. Army Institute of Pathology in Washington, DC.

Although a variety of functional and organic disturbances may lead to aggression and violent behavior, most violence (e.g., domestic violence) is committed by people with no diagnosable brain impairment. Phrenology has always been a tempting theory, because it reduces complex racial views to simple physical observations. For example, when my mother studied physics at the University of Vienna during the early 1940s, the Nazi authorities did not have much interest in the study of individual differences. A required course during the Nazi occupation was Rassenkunde (Racial Theory), which replaced psychology and philosophy.

The final analysis of the Nazi data sug- gested that the Nazis could not plead “brain damage” in the court of universal justice. There was no specific biological or even psychological inclination found toward violence, aggression, or sadism. The Nazis were not deranged in a clinical sense. Crazy was not the answer. The Nazis came in a variety of stripes. Hitler’s men were more different from each other than they were alike (Kennedy & Zillmer, 2006).

N e u r o p s y c h o l o g y i n A c t i o n 1 . 1

T h e B r a i n o f a N a z i

by Eric A. Zillmer

preserved in storage for later analysis. Einstein’s brain, the focus of several studies, may be anatomically larger in strategic areas that may partly explain his uncommon ability for conceptual and multidimensional thinking (Witelson, Kigar, & Harvey, 1999). Most neuroscientists, however, agree that the idea of explaining a person’s per- sonality and abilities from neuroanatomic evidence is premature (Figure 1.14.)

Faculty psychology and discrete localization theory continued to develop for a century. Many factors were

erroneous and simplistic, but three major developments represented significant progress. First, scientists were re- luctant to accept a single part or component of the brain as responsible for all behavior, as had proponents of ear- lier theories. Second, they placed more emphasis on the role of the cortex, which until then had not been seen as functioning neural tissue but as relatively unimportant protective “bark” (“cortex” in Latin). Third, and perhaps most important, scientists focused on the brain for their study of behavior and the mind.

T H E E R A O F C O R T I C A L L O C A L I Z A T I O N

Before the nineteenth century, people knew little about the cortex of the brain. Almost completely unexplored as to their functions, cerebral convolutions were not consid- ered the least bit interesting. Scientific evidence support- ing a localization position was not available until 1861, when Paul Broca (1824–1880) announced to the med- ical community that motor speech was specifically located in the posterior, inferior region of the left frontal lobe. Before Broca’s time, what he called this “grotesquely shaped, fast-decaying, and unmanageable organ” had at- tracted few investigators (Schiller, 1982).

Broca’s accomplishments in his 56 years of life are im- pressive. Even nonhistorians know about his work in surgery, neuroanatomy, neurophysiology, and neuropathol- ogy. Broca, who was sympathetic to Charles Darwin’s con- cept of evolution by natural selection (On the Origin of Species, 1859), was also the founder of French anthropol- ogy. In fact, because of his stature in that field, he was one of the first to have been presented with a trephined skull recovered from a Peruvian burial site. Broca dismissed the evidence, however, as merely a “hole in the head,” because he was biased about “primitive” cultures and their ability for intellectual thought.

Broca’s landmark contribution was in understanding the origins of aphasia (Neuropsychology in Action 1.2). In Paris, he was a professor of surgery, but contributed most to advancing the field of brain anatomy. Broca presented two clinical cases to support his proposal for the locus of speech. Both individuals had fairly extensive injuries, in- volving lesions in the left posterior frontal lobe, correspond- ing paralyses on the right side, and motor speech deficits; but in other respects, they appeared to be intelligent and normal. From his investigations, Broca described the con- dition of aphasia (often called Broca’s aphasia or nonfluent aphasia), an inability to talk because the musculature of speech organs do not receive appropriate brain signals. Broca’s announcement, hailed by many as a major break- through, led to numerous investigations into the localiza- tion of other higher cognitive functions. Broca, of course, supported other localizationists by proposing that behavior, in this case, expressive speech, is controlled by a specific brain area. It was also one of the first discoveries of a sepa- ration of function between the left and right hemispheres of the brain. But most important, it was one of the first in- dications that specific brain functions exist in particular lo- cales in the brain. There is a connection, or so it seemed, between the anatomy of the brain and what the brain does.

Contemporary research methodology proposes that to attribute a precise cognitive function to a specific anatomic

16 PART ONE | Introduction

Figure 1.14 (a) Preserved brain of murderer John Wilson. In a widely publicized case in 1884, Wilson admitted to killing Anthony Daly in a fit of rage. Wilson attacked the former butcher with a cleaver to the forehead and then dismembered him. Phrenologists argued that murderers “generally have the forehead villainously low.” (b) Brain of Albert Einstein. Much controversy exists whether the physi- cist’s brain is in any way superior anatomically to the brain of a “normal” person. (a: Courtesy Mütter Museum, College of Physicians of Philadelphia; b: Reproduced from Witelson, S. F., Kigar, D. L., & Harvey, T. [1999]. The exceptional brain of Albert Einstein. Lancet, 353, 2149–2153, by permission.)

CHAPTER 1 | A History of Neuropsychology 17

Paul Broca identified a specific area on the convoluted surface of the human brain, approximately 1 cubic centimeter (cm3) in size, as the central organ for expressive speech. Broca’s famous discovery came at a time when he viewed the convolutions of the brain as distinct organs. The evidence for this, however, was particularly weak, and phrenology was receiving some criticism. Thus, it was not a coincidence that Broca made such a discovery. He had been search- ing for some time for a patient just like Monsieur Leborgne. In May 1861, Broca presented the brain of Leborgne, alias “Tan,” a 51-year-old man who had died the previ- ous day under Broca’s care:

“I found one morning on my service a dying patient who 21 years ago had lost the faculty of ar ticulate speech. I gathered his case history with the greatest care because it seemed to ser ve as a touchstone for the [localization] theory of my colleague. The patient died on April 17 [1861] at 11 A.M. The autopsy was performed as soon as possible, that is to say within 24 hours. The brain was shown a few hours later in the Société d’Anthropologie, then immediately put in alcohol.” (Schiller, 1982, pp. 177–178)

“The abolition of speech is a symptom of sufficient impor tance, that it seems useful to designate it by a special name.I have given it the name aphemia [the term was later changed to aphasia by a colleague of Broca’s, Professor Trousseau]. For what is missing in these patients is only the faculty to ar ticulate words.” (Schiller, 1982, pp. 180)

“Although I believe in the principle of local- ization, I have been and still am asking myself, within what limits may this principle apply? If it were demonstrated that the lesions, which abolish speech constantly, occupy the same convolution then one could hardly help admitting that this convolution is the seat of ar ticulated speech.” (Schiller, 1982, pp. 182)

Probably no other single preserved human brain has aroused more attention than the one Broca was describing. Some criticized the manner of its preservation (in an unorthodox vertical position) and the damage to the brain involving chronic and progressive softening of the second and third left frontal convolutions, as well as the specimen’s unavailability for examination (Figure 1.15). Broca responded to his critics, “I have refrained from studying the deeper parts (of the brain), in order not to destroy the specimen, which I thought should be deposited in the (Dupuytren) museum” (Schiller, 1982, p. 180).

Tan’s histor y has of ten been told, but his basic disease has never been satisfac- torily diagnosed. Broca’s acquaintance with this patient lasted barely a week. Neither the histor y nor the appearance and description of the brain allow a confi-

dent clinical and pathologic interpretation in modern terms. Leborgne had been epileptic since his youth and became aphasic at the age of 30. He showed progressive weakening on his right side since the age of 40, first in the arm. He became hemiplegic and was bedridden for 7 years. Leborgne deteriorated gradually, losing his intellect and vision, and finally died at 51 of cellulitis with gangrene of the paralyzed right leg. His early histor y of epilepsy arouses the suspicion that suc- cessive thrombotic infarcts might not have been the correct diagnosis, and that perhaps a form of degenerative disease may be more plausible. He was also known to have cursed when he was disturbed, which may also suggest that aphasia was the least of his problems (however, as we discuss in later chapters, cursing and grunts may be actually controlled by the right hemisphere, which does not domi- nate speech). In retrospect, Leborgne’s histor y suggests that many other symp- toms accompanied his aphasia. It now appears that Leborgne was a poor choice as the prototype for Broca’s aphasia. If Broca had had a statistical consultant, he would have been advised not to make such sweeping conclusions based on only one subject!

Just as Broca preser ved Leborgne’s brain for safekeeping, he would have been pleased to know that his own brain also has been stored in the Museum de l’Homme (Museum of Man) in Paris. There, deep in the museum in a remote, musty corner among abandoned cabinets and shelves hidden from the public, is a collec- tion of gray convoluted objects stored in formaldehyde. Among them is the brain of Paul Broca. If you look closely, you can detect the small region in the third convo- lution on the lef t frontal lobe of the cere- bral cor tex that made him famous—Broca’s Broca’s area!

N e u r o p s y c h o l o g y i n A c t i o n 1 . 2

P a u l B r o c a : A M a n n e r o f N o t S p e a k i n g

by Eric A. Zillmer

Figure 1.15 Leborgne’s brain. Note atrophy in Broca’s area. (Courtesy Museé Dupuytren.)

section of the brain, research must meet two conditions. The first condition, which Broca did demonstrate, is that destruction of a localized brain site impairs a specific func- tion, in this case, articulate speech. The second condition, which Broca did not demonstrate, relates to that damage to any other area of the brain—for example, the patient’s right frontal lobe—should not result in the same deficit. This second condition is called double dissociation (Teu- ber, 1950) and requires that “symptom A appear in lesions in one structure but not with those in another, and that symptom B appear with lesions of the other but not of the one” (Teuber, 1959, p. 187). Nevertheless, although Broca may not have followed the standards of modern science, to an important extent, articulate speech is, in fact, local- ized in and controlled by Broca’s area.

A decade after Broca’s discovery, Carl Wernicke (1848–1904) announced that the understanding of speech was located in the superior, posterior aspects of the tempo- ral lobe (Wilkins & Brody, 1970). Wernicke noted that no motor deficit accompanied a loss of speech comprehen- sion caused by damage in this area; only the ability to un- derstand speech was disrupted. That is, the patient was still able to talk, but his speech made no sense and sounded like some unknown foreign language. Such speech was called fluent aphasia (Geschwind, 1965). Although Wernicke, who like Broca has an area of the brain named after him (Figure 1.16), supported localizationists by lo- cating a specific area important for word comprehension, he also demonstrated that language is not strictly local- ized. Broca’s area, or expressive speech, is in the frontal

lobes, and Wernicke’s area, or receptive speech, is posterior to that, in the temporal lobe. As a result of Wernicke’s work, theories of strict localization have become less feasi- ble because speech is not located in one specific location of the cortex, but rather in two distinct cortical areas.

C R I T I C S O F C O R T I C A L L O C A L I Z A T I O N

Sigmund Freud (1856–1938) is best known as the founder of psychoanalysis. Yet Freud’s initial love was for investigating the secrets of the central nervous system (Neuropsychology in Action 1.3). Freud, who made sig- nificant discoveries in the area of brain-behavior relation- ships, never gained the respect that he deserved for his work as a neurologist. In Zur Auffassung der Aphasien (An Understanding of Aphasia) (1891), Freud criticizes Wernicke’s and Broca’s localization doctrine of aphasia. At the time of Freud’s publication, many neurologists con- fronted the task of explaining the many partial and mixed varieties of aphasias. We now know that aphasia comes in a variety of “flavors,” including the inability to speak spon- taneously, the inability to repeat words, the inability to read words yet being able to read letters, and so on. Wer- nicke proposed that for each different syndrome there was one corresponding specific lesion in the connections between Wernicke’s and Broca’s areas that would account for the disturbance. The more combinations of aphasic disturbances that he observed, however, the more compli- cated became Wernicke’s diagrams. To simplify Wernicke’s diagrams, Freud suggested that various aphasias could be explained by subcortical lesions in less localized associa- tion pathways. Freud pointed out, quite correctly, that the Broca and Wernicke centers are little more than nodal points in a general and complicated network of neurons. Freud proposed that Broca’s and Wernicke’s areas were not self-acting agencies and their significance was simply due to their anatomic location (in the former case, to the motor areas of the brain, and in the latter, to the entry of the fibers from the acoustic nuclei). Freud also described the distinction between the ability to recognize an object and the inability to name it, agnosia; this term remains in use today.

Is the whole greater than the sum of its parts? Clinical observation did not validate the idea that each skill is con- trolled by a circumscribed part of the brain. Localization- ists could not explain findings, reported by numerous physicians, that lesions in widely disparate parts of the brain, not one specific area, impaired the same skill. More- over, many patients with lesions in a specific brain area could still perform a skill assigned exclusively to that area.

Pierre Flourens (1794–1867) was the foremost early advocate of an alternative to localization theories (Krech,

18 PART ONE | Introduction

Temporal lobe

Frontal lobe Wernicke’s area

Parietal lobe

Broca’s area

Occipital lobe

Lateral sulcus

Figure 1.16 Broca’s area and Wernicke’s area. (Adapted from Heller, K. W. [1996]. Understanding physical, sensory, and health impairments [p. 52, Figure 4.7]. Pacific Grove, CA: Brooks/Cole.)

CHAPTER 1 | A History of Neuropsychology 19

Freud entered the University of Vienna in the autumn of 1873, at the early age of 17, and graduated with a medical degree in 1881. Considering an academic research career in physiology, he went to work in the laboratory of the Brücke Institute. There he enjoyed laboratory work and, initially, harbored an aversion to the clinical practice of medicine. Beset by financial difficulties, in May 1883, he began working under Meynert, a neuro- surgeon and psychiatrist, to gain additional practical experience. During this time, Freud came closer to disorders of the brain, but he restricted his laboratory work to dissecting the nervous system. At first, Freud investi- gated the cells of the spinal cord, the part of the nervous system that held his chief interest. For the next 2 years, he concen- trated on a specific area of the brainstem, the medulla, that resulted in three pub- lished articles. From October 1885 to February 1886, Freud visited Paris to study with the great neurologist Jean-Martin Charcot. Charcot was then at the zenith of his fame. No one, before or since, had so dominated the world of neurology, and for Freud to have been a pupil of his was a passport to distinction.

When Freud went to Paris, his anatomic interests were still more in his mind than

any ambition as a clinician. On his return to Vienna, he researched topics of visual field deficits, hemianopsia, in children and its localization. From correspondence, it is also known that in 1887 and 1888 Freud was working on a book on the anatomy of the brain, which he never finished (Jones, 1981). His next publication in 1891 was his first book Zur Auffassung der Aphasien (An Understanding of Aphasia). Freud thought this text the most valuable of his neurologic writings, although it proved not to be the one by which neurologic circles remembered his name. Despite Freud’s critical and speculative monograph on aphasia, which ultimately achieved accep- tance, he did not have much luck with his book. Of the 850 copies printed, only 257 had sold af ter 9 years, and Freud was paid only $62 in royalties (Jones, 1981). The neurologic community was not yet ready for his insights, and all historical writings on aphasia omit any reference to the book. Yet his neurologic achievements were remark- able, especially for a young student, and they illustrate his biological and genetic outlook.

In retrospect, Freud’s psychoanalytic model can be loosely related to brain processes. For example, Freud’s id, the

unconscious “beast in the basement” that operates on the pleasure principle, might have developed out of the reptilian brain, a product of presocial evolutionary history. Freud’s superego, our conscience, is an evolutionarily more recent invention, con- ceptualized within prefrontal lobe processes that are involved in forming such abstract concepts as morality, guilt, plan- ning, and inhibition. At this highest, most complex level of brain structure, a major function is to inhibit the spontaneous expression of the more biologically pro- grammed patterns of behavior that arise from lower and evolutionary older struc- tures of the brain such as the id. The ego, based on the reality principle, is perhaps related to complex brain processes in the “middle,” that is, the cor tex, excluding the prefrontal lobes (Wright, 1994). It is often difficult to trace threads between Freud’s subsequent focus on unobservable, in- trapsychic events and his early investiga- tion of the nervous system. He never did, however, venture too far away from his neurologic roots, as demonstrated in his work On Narcissism (1959), in which he suggested that all provisional ideas on psychology will one day be explained by organic substrates.

N e u r o p s y c h o l o g y i n A c t i o n 1 . 3

S i g m u n d F r e u d : T h e N e u r o l o g i s t

by Eric A. Zillmer

1962). Through an extensive number of experiments and logical arguments, Flourens attempted to disprove Gall’s localization theory. To support his beliefs, Flourens devel- oped the ablation experiment, in which removing any part of the brain in birds led to generalized disorders of behavior. From his experiments, he reached several gen- eral conclusions. Sensory input at an elementary level is localized, but the process of perception involves the whole brain. Loss of function depends on the extent of damage, not on the location. All cerebral material is equipoten- tial; that is, if sufficient cortical material is intact, the re- maining material will take over the functions of any miss- ing brain tissue. Flourens suggested that the brain operated in an integrated fashion, not in discrete faculties, and that mental functions depend on the brain functioning as a

whole. Thus, the size of the injury, rather than its loca- tion, determines the effects of brain injury.

Flourens, however, was criticized on a number of dif- ferent points. First, he used animals with brains so small that any ablation would invade more than one functional area. Second, he observed only motor behavior—that is, behaviors such as eating or wing flapping—whereas the localizationists were mostly interested in more complex faculties such as friendship or intellect. Flourens also er- roneously suggested that humans use only 10% of the brain, an idea that laypeople still commonly hold today. Despite these scientific problems, many accept Flourens as having refuted localization theory. Nevertheless, the work of Broca and other localization theorists was the pre- dominant view of brain–behavior relationships and was

in large part accepted by the scientific community. Con- sequently, few people supported Flourens’s work until the early 1900s, when equipotentialists again began to de- velop evidence and research to support their position.

Localization versus Equipotentiality

Pierre Marie (1906) challenged Broca’s findings by examining the preserved brains of the patients Broca had used to support his hypothesis of localization. Marie found that Leborgne had widespread damage, not a spe- cific lesion, as Broca had suggested. Marie attacked Broca’s theory, indicating that the patient could not speak be- cause the extensive lesion had caused a general loss of in- tellect, rather than a specific inability to speak. Other re- searchers soon expressed support for the equipotentiality position. In general, these researchers proposed that, al- though basic sensorimotor functions may be localized in the brain, higher cortical processes were too complex to confine to any one area.

Two important neuropsychological findings also challenged strict localization theory. In 1881 (cited by Blakemore, 1977), Hermann Munk (1839–1912) found that experimental lesions in the association cortex of a dog produced temporary mind-blindness: The animal could see objects but failed to recognize their significance (e.g., as objects of fear). In the experiment, Munk first had the dogs learn to associate the shape of a triangle with fear by pairing them together with an electric shock. After the dogs learned the association, Munk lesioned parts of the cortex that were not primarily involved with vision. Af- terward, the dogs could see the object but could not per- ceive the meaning of the stimuli to which they were con- ditioned before the surgery. In 1914, Joseph Babinski (1857–1932), the founder of neurology, introduced the term anosognosia, which means “no knowledge of the disease,” to describe an inability or refusal to recognize that one has a particular disease or disorder, thereby in- troducing the phenomenon of unawareness (Babinski & Joltran, 1924). Babinski observed patients who had le- sions, most often in the association cortex of the right hemisphere. These patients were capable of seeing and hearing, but denied that anything was wrong with them even when they had severe neurologic damage such as hemiplegia.

Karl Lashley (1890–1958), a student of the famous behaviorist John Watson, was a great exemplar of experi- mental neuropsychology and, according to Hebb (1983),

practically its founder. He was one of the first to combine behavioral sophistication in experiments with neurologic sophistication. Lashley become America’s most eminent early neuropsychologist, highly respected for his ingenu- ity in devising ways of disclosing the effects of brain oper- ations (Popplestone & McPherson, 1994). Although Lashley accepted the localization of basic sensory and motor skills, he supported equipotential views with ex- periments on rats similar to those of Flourens on birds (Lashley, 1929). Lashley found that impairment in maze running in the rat was directly related to the amount of cortex removed. He stated that the specific area removed made little difference. From his experiments, Lashley for- mulated his famous principle of mass action: The extent of behavioral impairments is directly proportional to the mass of the removed tissue. Lashley also emphasized the multipotentiality of brain tissue: Each part of the brain participates in more than one function (Teuber, Battersby, & Bender, 1960). Lashley believed that his results were highly compatible with a view that brain tissue is equi- potential and can be involved in tasks other than those assigned by the localizationists.

In one form or another, localization and equipoten- tiality have dominated U.S. psychology, although neither approach has enjoyed universal acceptance because nei- ther can encompass all the collected scientific data and clinical observations. Clinical observers of medical pa- tients with very small lesions have often reported marked behavioral deficits, even though the lesion may be micro- scopic. Thus, equipotentiality theory fails to account for the specific deficits often seen in the absence of general impairment in intellect, abstract attitude, perception, or other global ability.

Integrated Theories of Brain Function

J A C K S O N ’ S A L T E R N A T I V E M O D E L

Unable to accept either the localization or equipotential- ity models of brain function, psychologists and neurolo- gists have searched for other alternative models. The cre- ation of one such model has been credited to the English neurologist Hughlings Jackson (1835–1911), whose pri- mary work was written during the second half of the nine- teenth century, but was not published in the United States until the 1950s. Jackson, a London neurologist, devoted his research to the investigation of epileptic seizures and the study of connections between limb movements and

20 PART ONE | Introduction

specific areas in the brain. Jackson observed that higher mental functions are not unitary abilities, but consist of simpler and more basic skills. He suggested that one does not have a speech center; rather, one has the ability to combine certain basic skills, such as hearing, discrimina- tion of speech sounds, and fine-motor and kinesthetic control of the speech apparatus, to create more complex higher skills (Hebb, 1959). Consequently, the loss of speech can be traced to the loss of any one of a number of basic abilities or functional systems. It can be related to, for example, the loss of motor control, the loss of ade- quate feedback from the mouth and tongue, a defect in the understanding and use of the basic parts of speech, or the inability to decide to speak.

Thus, the loss of a specific area of the brain causes the loss or impairment of all higher skills dependent on that one area. Furthermore, a lesion that causes the loss of speech does not necessarily indicate that the brain area re- sponsible for speech has been found. Jackson proposed that localizing damage that destroys speech and localizing speech are two different things. Jackson also believed that behavior can exist on many different levels within the ner- vous system. Thus, a patient may be unable to repeat the word “no” when asked to repeat it, even though the pa- tient is capable of saying, in exasperation, “No, Doctor, I can’t say no!” (Luria, 1966). In the first instance, the pa- tient cannot say the word voluntarily. When the word is given as an automatic response, however, the patient is able to say it. The ability to say “no” exists as two separate skills: one voluntarily and one automatic. Each ability can be impaired independently of the other. Because of this, Jackson noted, behavior rarely is lost completely unless the damage to the brain is severe (Golden, Zillmer, & Spiers, 1992).

Jackson suggested that, given his observations, be- havior results from interactions among all the areas of the brain. Even the simplest motor movement requires the full cooperation of all the levels of the nervous sys- tem, from the peripheral nerves and the spinal cord to the cerebral hemispheres. In this regard, Jackson pointed toward a more holistic, nearly equipotential view of brain function. But Jackson also argued that each area within the nervous system had a specific function that contributed to the overall system. Thus, his views also had a localizationist flavor. In actuality, of course, Jack- son’s views were those of neither school but reflected an integration of significant empirical data. Jackson’s influ- ence can first be seen in British neurology of the early twentieth century, although many people overlooked the essential nature of what Jackson had proposed. They inter- preted his work as more supportive of an equipotentiality

view of higher mental functions than it actually was. Since World War II, many major theorists have pre- sented views compatible with Jackson’s. For example, Harlow (1952) concluded from his experimental mon- key studies that no cognitive ability is completely de- stroyed by any limited lesion, although there appears to be some localization, a view entirely consistent with Jackson’s beliefs. After reviewing much of the literature, Krech (1962) also reached two similar conclusions (Chapman & Wolff, 1959). First, no learning process or function depends entirely on any one area of the cortex. Second, each area within the brain plays an unequal role in different kinds of functions. These conclusions, although contrary to either the localization or equipo- tentiality views, were also in accordance with Jackson’s alternative approach.

L U R I A ’ S F U N C T I O N A L M O D E L

The most detailed adaptation of the principle first sug- gested by Jackson has appeared in the work of Russian neuropsychologist Alexander Luria (1902–1977). Luria was responsible for the most profound changes in our ap- proach to understanding the brain and the mind. Luria, who earned doctoral degrees in psychology, medicine, and education, was the most significant and productive neu- ropsychologist of his time, and during the 1960s, he raised the field to a level that could not have been imag- ined. Luria realized that a viable brain–behavior theory must not only explain data that fit both the localization and equipotentiality hypothesis but also must account for findings inconsistent with either theory. Luria—building on the work of his mentor and arguably the founder of cog- nitive psychology, Vygotsky (1965) as well as on Jackson’s alternative approach (Hebb, 1959)—conceived each area in the central nervous system as being involved in one of three basic functions, which Luria labeled units. The first unit, roughly defined as the brainstem and associated areas, regulates the arousal level of the brain and the main- tenance of proper muscle tone. The second unit, includ- ing posterior areas of the cortex, plays a key role in the re- ception, integration, and analysis of sensory information from both the internal and external environments. The third unit, the frontal and prefrontal lobes, is involved in planning, executing, and verifying behavior (Luria, 1964, 1966).

All behavior requires the interaction of those three basic functions. Consequently, all behavior reflects the brain op- erating as a whole. At the same time, each area within the brain has a specific role in forming behavior. The impor- tance of any one area depends on the behavior to be

CHAPTER 1 | A History of Neuropsychology 21

22 PART ONE | Introduction

Freeman saw his mission as severing the fibers of a sick mind. He believed that most psychiatric patients’ mental illnesses were related to “confused” neurologic processes, and that an appropriate surgical cut would free the patient of that confusion (Freeman & Watts, 1950). Over the span of 20 years, Freeman performed more than 3,500 lobot- omies across the United States and pio-

neered the transorbital lobotomy. Freeman recommended lobotomies for any patient who had been institutionalized for more than 2 years, regardless of the patient’s diagnosis or response to other therapy. The actual transorbital procedure consisted of initially anesthetizing the patient, typically achieved by electroconvulsive shock, with which the psychiatrist was familiar. Next, the patient’s

frontal lobes were pierced with an ice pick–like surgical instrument, a leukotome, inserted through the orbital cavity and passed through the orbital plate into the prefrontal region of the cortex, often “accom- panied by an audible crack” (El-Hai, 2005, p. 185). The psychiatrist swung the handle of the surgical instrument laterally and medi- ally, “windshield wiper fashion,” to sever the

N e u r o p s y c h o l o g y i n A c t i o n 1 . 4

T h e W a l t e r F r e e m a n L o b o t o m i e s : M i n d o v e r M a t t e r ?

by Eric A. Zillmer

Figure 1.17 (a) Dr. Freeman performing a lobotomy. According to Freeman, lobotomies should be performed in every patient if conservative therapy fails. (b) Lobotomy leukotome with Freeman’s name engraved at the handle. Freeman suggested that, even though the risk for infections was low, different leukotomes be used for the two frontal lobes because of hygienic reasons. (c) Electroconvulsive shock apparatus (ca. 1950s). Lobotomy patients were anesthetized using electroconvulsive shock to the brain. After an induced seizure, the patient was typically in a dazed and confused state, during which the lobotomy was performed. (a: © Bettmann/CORBIS; b, c: Courtesy Mütter Museum, College of Physicians of Philadelphia.)

CHAPTER 1 | A History of Neuropsychology 23

fibers at the base of the frontal lobe (Valen- stein, 1973). The complete procedure took less than 10 minutes and could be per- formed in an office by a psychiatrist and one assistant (Figure 1.17).

Between 1940 and 1954, approximately 40,000 to 50,000 psychiatric patients, most diagnosed as schizophrenic, underwent prefrontal orbital lobotomies in their doctors’ efforts to decrease inappropriate behavior whereas increasing ease of patient manage- ment. Although doctors claimed that many of these patients subjected to prefrontal loboto- mies were “cured,” some patients died and a large number showed dangerous side effects, including confusion, flat affect, impulsive-

ness, continued psychotic episodes, and deteriorated intellectual functioning (Glidden, Zillmer, & Barth, 1990). Furthermore, be- cause a major function of the frontal lobes is to inhibit behavior, many lobotomized pa- tients actually developed new symptoms (such as incontinence, inappropriate affect, violent behavior, and so forth). When I was a fellow in neuropsychology, I once evaluated an elderly schizophrenic woman. In reviewing the medical chart, I was surprised to learn that Freeman had operated on the same patient more than 30 years earlier. Freeman’s medical note was still in the patient’s medical chart, detailing the more gruesome aspects of this so-called treatment:

July 2, 1953 PRE-LOBOTOMY EXAMINATION: This patient looks quite a bit younger than her given age of 42. She stands with her head bowed and relatively little change of expression on her face. For the most part, she answers questions with a nod of her head, or a very silent yes, and even though conflicting state- ments are given, she nods just the same. At times she moves her lips in a way that suggests that she is continuously hallucinating. A story of a long psychotic illness with difficult behav- ior and brief furloughs since 1929 indicates that the problem is a very tough one. A pro- posal is made in this case to accompany the transorbital operation with an injection of 10cc. blood on each side into the inferior

(continued)Figure 1.17 (Cont.)

24 PART ONE | Introduction

external aspects of the lobe, in the hope of eliminating to some extent the hallucinatory activities. The outlook for her release from the hospital is not good, but it may be possible that she will be more effectively able to adjust on the ward.

July 2, 1953 OPERATIVE NOTE: This patient presents an exceptionally difficult problem: therefore, after a triple electroshock, the orbitoclasts were driven to a depth of 5 cm.

from the lid margin, parallel with the nose and 3 cm. from the midline. The instruments were pulled far laterally then brought back halfway and driven 2 cm. deeper. The handles were touched over the nose, then separated a total of 45 degrees and then elevated as firmly as possible. On the right side, the orbitoclast went through at an angle of about 60 degrees satisfactorily, but on the left side I met with such resistance that I was afraid for the instrument and replaced it with a new instru- ment, upon which I could apply the utmost in

two-handed traction. Finally, the orbital plate gave way, and a cut of something like 75 degrees was achieved on this side. Then I drew 10 cc. blood from the right arm and injected it into the outer lower portion of the frontal lobe on the left side, and a similar quantity on the left side. The patient was coming to by this time, and made known her displeasure by her rather excited praying. When the blood injection had been completed, however, she was apparently in good condition.

—Walter Freeman, M.D.

(continued)

performed. For example, picking up the receiver when the phone rings—a simple, well-practiced act—requires little arousal, planning, or evaluation. A more complex behav- ior, such as telling a caller what you will be doing next Tuesday evening, however, requires attention and arousal, as well as planning and evaluation. An injury that has lit- tle effect on the first behavior might be disastrous for the second, more complex one.

For each behavior, Luria formulated the concept of functional systems, which represent the pattern of inter- action among the various areas of the brain necessary to complete a behavior. Each area in the brain can operate only in conjunction with other areas of the brain. Fur- thermore, no area of the brain is singly responsible for any voluntary human behavior; thus, each area of the brain may play a specific role in many behaviors. As with the equipotentiality theory, Luria regards behavior as the re- sult of interaction among many areas of the brain. As with the localization theory, Luria assigns a specific role to each area of the brain. The multifunctional role of the brain is called pluripotentiality; any given area of the brain can be involved in relatively few or many behaviors.

Luria suggested that behavior results from several func- tions or systems of brain areas, rather than from unitary or discrete brain areas. A disruption at any stage is enough to immobilize a given functional system. For example, an individual without injury to what localizationists would call the “reading center” is unable to read if there is dam- age to any of a number of parts of the functional systems involved in reading. Each functional system, however, has some plasticity and can change spontaneously or through retraining. For example, sensory feedback is necessary for continually knowing the location of one’s fingers and arm to direct motor movement. A person who loses sensory feedback from the arm loses an important link in complet- ing fine-motor tasks. The functional system, however, can be altered by using visual feedback to locate the fingers of

the hand, something not previously needed. The patient can thus reestablish fine-motor skills, despite the disrup- tion of the old functional system. Luria’s concept of alter- native functional systems accounts for the ability of higher level brain skills to compensate for lower level skills in brain injury. This concept was demonstrated clearly in an interesting case of ours. At age 3 months, the patient had undergone a complete left hemispherectomy (removal of a hemisphere). When we saw him at age 7, not only could he walk, but he also spoke fluently. This was undoubtedly related to the plastic nature of the patient’s brain, in which the right side of the brain developed the organization nec- essary to execute behaviors, such as speech and control- ling the right side of the body.

Luria’s theories are particularly attractive and relevant to clinical neuropsychologists because they can account for most observations of patients with brain injuries. The the- ory also explains the observation that certain lesions gener- ally yield consistent deficits. In addition, through the con- cept of reorganization, Luria’s theory can account for individuals who recover from brain trauma. Finally, the the- ory suggests ways to establish rehabilitation and treatment programs for the brain-injured patient and provides a strong theoretical basis for understanding clinical neuropsychology.

Modern Neuropsychology

Herman Ebbinghaus (1850–1909) proposed that psychology has a long past but a short history. This is true for modern neuropsychology as well. Since Broca made his momentous discovery in the 1860s, a number of major achievements and influential concepts led to the evolution of neuropsychology as a discipline as we know it today. In 1933, Kleist published his monumental work on wartime brain injuries. Although his localization approach was ac- cepted in Germany, it was largely unknown outside that

country. In the United States and Britain, the findings and conclusions of Lashley, Marie, and Jackson set up a gen- eral antilocalization bias. In particular, the field of aphasia remained divided between the “holists” and “diagram makers” such as Wernicke (Benton, 1994). The birth of modern psychosurgery was in 1935, when Moniz and Lima first attempted to alleviate mental suffering by oper- ating on the human frontal lobes. The novelty of his con- cept and the “quality” of Moniz’s results earned him a con- troversial Nobel Prize in medicine in 1949. In the 1940s, the apparently favorable effects of the surgery on the ma- jority of severely disturbed patients led to its introduction in the United States by psychiatrist Walter Freeman and his surgical colleague James Watts. Currently, however, treating psychiatric patients with lobotomies is regarded as a step backward (Neuropsychology in Action 1.4).

Clinical neuropsychology originally emerged in the medical setting within traditional neurosurgery and neu- rology services. Early research was primarily concerned with the cortical functioning of patients with penetrating missile wounds or the diagnosis of neurologic disorders such as brain tumors or strokes. For example, a famous neurosurgeon who was advancing an understanding of the relationship between brain anatomy and behavior was Wilder Penfield (1891–1976). Penfield was educated at Princeton, Johns Hopkins, and Oxford universities and was the founder and director of the renowned Montreal Neurological Institute. He pioneered direct electrical stim- ulation of the brain during surgery by systematic mapping of the brain as a technique for finding damaged areas of the brain. He also used the services of psychologists as con- sultants to help him with the diagnosis of neurologic be- havioral conditions. In the 1930s, psychologists played a large role in diagnosing brain lesions, including stroke and tumor. For example, a friend and mentor of ours, Molly Harrower, a professor emeritus at the University of Florida and inventor of the Group Rorschach, was routinely asked in the 1930s to evaluate “organic patients.” In her autobi- ographical essay “Inkblots and Poems” (1991), she de- scribes how as a research fellow of noted neurologist Wilder Penfield at the Montreal Neurological Institute, she was asked to perform regular diagnostic workups using the Rorschach test: “I was assigned to examine all incom- ing patients suspected of tumor, with re-testing 14 days postoperatively” (Harrower, 1991, p. 141). Currently, neu- ropsychologists play a smaller role in diagnosing neuro- logic disorders but an important part in evaluating func- tional impairment, prognosis, and recovery.

In the late 1930s, neuropsychology engaged the inter- est of only a few neurologists, psychiatrists, and psycholo- gists. Neuropsychology was loosely organized, and no

journals reflected a focused interest in this area. But a number of scholars were working on issues that in time made decisively important contributions to the field and shaped neuropsychology as we know it today.

The first neuropsychology laboratory in the United States was founded in 1935 by Ward Halstead at the Uni- versity of Chicago. Halstead worked closely with neuro- surgery patients and developed assessment devices that dif- ferentiated between patients with and without brain damage (Figure 1.18). Together with Ralph Reitan, Halstead later developed the popular Halstead-Reitan Neuropsychologi- cal Battery, an empirical approach to assessing brain dam- age (Halstead, 1947; Reitan & Wolfson, 1993).

The term neuropsychology itself is of recent origin and was most likely first coined by Sir William Osler in 1913, when he used the word in an inaugural address for a new psychiatric clinic at Johns Hopkins Hospital in Baltimore, Maryland (Bruce, 1985). In 1936, Karl Lashley also used the term when he addressed the Boston Society of Psychi- atry and Neurology (Bruce, 1985). Hans-Leukas Teuber (1916–1977) is credited for first using the term in a na- tional forum during a presentation to the American Psy- chological Association in 1948, during which he described different aspects of brain–behavior relationships in war veterans with penetrating brain wounds (Teuber, 1950). Then, in 1949, Canadian Donald Hebb published his classic, The Organization of Behavior: A Neuropsychological Theory. Neuropsychology has enjoyed tremendous growth ever since. The study of neuropsychology has drawn infor- mation and knowledge from many disciplines, including anatomy, biology, physiology, biophysics, and even philos- ophy. Thus, many interdisciplinary professionals, including neurologists, neuropsychiatrists, linguists, neuroscientists, speech pathologists, and school psychologists, are inter- ested in the field of brain–behavior relationships and have contributed to its development.

Nevertheless, until the 1960s and Luria’s writings, there was no unifying theory of brain–behavior relationships. In fact, before the 1960s, few neuropsychology practitioners existed. Those that did were primarily researchers in what is now considered experimental neuropsychology.

Between 1960 and 1990 neuropsychology was charac- terized by a movement from the laboratory to the clinic and the establishment of distinct neuropsychological orga- nizations (e.g., The International Neuropsychological So- ciety in 1967; The National Academy of Neuropsychol- ogy in 1975; and the American Psychological Association, Division 40 of Clinical Neuropsychology, in 1980). This phase also marked the creation of many scientific journals that focused exclusively on advancing the science of neu- ropsychology (Table 1.2).

CHAPTER 1 | A History of Neuropsychology 25

Henry Hécaen (b. 1912) founded the journal Neu- ropsychologia. Hécaen, who earned his M.D. degree, made important contributions to brain–behavior relationships in health and disease. One of his discoveries, which earned him an enduring place in the history of neuropsychology,

26 PART ONE | Introduction

Figure 1.18 Ward C. Halstead is recording eye movements (summer, 1940). (Courtesy Archives of the History of American Psychology, David P. Boder Museum Collection, Encyclopaedia Britannica.)

Applied Neuropsychology

Archives of Clinical Neuropsychology

Behavioral Brain Research

Brain and Cognition

Cortex

Journal of Clinical and Experimental Neuropsychology

Neuropsychology

Neuropsychologia

Table 1.2 Major Neuropsychology Journals

was his demonstration of the functional properties of the right hemisphere. In the 1940s and 1950s, most scientists believed that the left hemisphere dominated the brain, be- cause it plays an important role in the mediation of lan- guage. Hécaen and his coworkers generated an irrefutable mass of evidence that the right, supposedly minor, hemi- sphere played a crucial role in mediating visuoperceptual and visuoconstructional processes. Much of Hécaen’s work was not translated into English from French until the 1970s (e.g., see Hécaen & Albert, 1978), and as recently as the early 1960s, scientists seldom discussed or researched issues regarding the role of the right cerebral hemisphere. The U.S. neuropsychologist Arthur Benton continued to explore the role of the right cerebral hemisphere in behavior (Benton, 1972). In the 1940s, Benton established one of the first neuropsychology laboratories in the Neurology Department at the University of Iowa School of Medicine, which still carries his name; he also supervised dissertations in the new field of neuropsychology and authored numerous books and neuropsychological testing instruments, including the Benton Visual Retention Test (BVRT).

Oliver Zangwill (b. 1913) founded neuropsychology in Great Britain. Zangwill, who received his M.A. from Cambridge University and saw no necessity to work for the Ph.D. degree, transformed into a clinical neuropsy- chologist while working in the Edinburgh Injury Unit of the British military services during World War II. There he was called on to evaluate hundreds of patients with traumatic brain lesions. Zangwill was also among the first investigators to show that hemispheric specialization for speech in left-handers did not conform to the then- accepted rule of right hemisphere dominance (Zangwill, 1960). He also contributed significantly to understanding of the nature of neuropsychological deficits associated with unilateral brain disease or injury.

Norman Geschwind (1926–1984) is another impor- tant neuropsychologist who helped to shape his profes- sion’s focus and development. Geschwind received his M.D. degree at Harvard and later single-handedly founded behavioral neurology. In 1958, he joined the staff of the neurologic service of the Boston Veterans Administration Hospital, where he made many significant contributions to neuropsychology. Among his contributions was his pro- posal that behavioral disturbances are based on the de- struction of specific brain pathways that he called discon- nections. He presented his idea in his now classic article “Disconnexion Syndromes in Animals and Man” (1965), which was largely responsible for reemphasizing the im- portant role of neuroanatomy in neuropsychology. Based on his faith that anatomy must play a central role for the description and operation of many complex mental func- tions, Geschwind set out to prove that the dominance of the left hemisphere for speech must have an anatomic basis. He and a young colleague set out to study the mor- phologic features of 100 brains and determined that, in- deed, there was a strong trend toward a larger auditory as- sociation cortex in the left hemisphere (Geschwind & Levitsky, 1968). This finding led to a continuing search for anatomic disparities that might be correlated with functional differences. His premature death at the age of 58 deprived behavioral neurology of its preeminent figure.

The most recent phase of modern neuropsychology, the 1990s to the present, has enjoyed unprecedented growth, and clinical neuropsychology has made impor- tant professional and theoretical contributions during the 1990s; in fact, the U.S. Congress recognized the 1990s as the “Decade of the Brain.” Muriel Lezak is one of sev- eral neuropsychologists who pioneered the assessment approach in clinical neuropsychology. Since the late 1980s, neuropsychological assessment has played a major role in the development of clinical neuropsychology. Neu- ropsychological evaluations have become an important procedure, allowing the generation of useful behavioral,

cognitive, and clinical information about diagnosis and the impact of a patient’s limitations on educational, so- cial, and vocational adjustment. In addition to the devel- opment of new testing methods to meet special needs in diagnostic evaluation, there has been a steady increase in the use of neuropsychological assessment techniques in neurology and psychiatry and an expansion of their scope of application into other fields such as education, be- havioral medicine, and gerontology. Lezak proposed that neuropsychological testing is clinically relevant and sug- gested a flexible approach to assessing the individual pa- tient. She also reminded those neuropsychologists who became interested in a rather narrow subspecialty within psychology that clinical neuropsychology is firmly rooted in clinical psychology. Her classic text Neuropsychological Assessment, originally published in 1976, is now in its fourth edition (Lezak, Howieson, & Loring, 2004).

The popularity of neuropsychology did not occur in iso- lation, but was directly related to developments in other fields, including clinical (e.g., behavioral neurology, biolog- ical psychiatry, and radiology) and experimental sciences (such as neurosciences and neurochemistry) (Table 1.3).

Emerging Research Areas in Neuropsychology

Many research areas of neuropsychology in which neuropsychologists and neuropsychology students can par- ticipate are emerging. Three such areas are at the forefront of

CHAPTER 1 | A History of Neuropsychology 27

Psychologists study behavior. Education includes an undergraduate degree in psychology and a doctoral degree (Ph.D. or Psy.D.) in an area of psychology.

Neuropsychologists are psychologists who study brain–behavior relation- ships. Education includes a doctoral degree in psychology and specialty (postdoctoral) training in neuropsychology.

Neurologists identify and treat clinical disorders of the nervous system, emphasizing the anatomic correlates of disease. Training includes a premed major at the college level, a doctoral degree from a medical school (M.D.), and residency training in neurology.

Neuropsychiatrists are medical doctors who have had residency training in psychiatry and are mostly concerned with the organic aspects of mental disorders, such as schizophrenia or bipolar disorder.

Neurosurgeons are medical doctors who have specialized in the surgery of nervous structures, including nerves, brain, and spinal cord.

Neuroscientists are researchers and/or teachers who have completed doctoral training in biology or related fields. They are primarily interested in the molecular composition and functioning of the nervous system.

Table 1.3 Professionals Who Study the Brain

applied neuropsychological science: forensic neuropsychol- ogy; sports neuropsychology; and the neuropsychology of terrorism, law enforcement, and the military (Zillmer, 2004).

F O R E N S I C N E U R O P S Y C H O L O G Y

Forensic assessment is one of the fastest growing areas in the field of clinical psychology, with an increasing num- ber of neuropsychologists presenting and/or evaluating assessment results in the courtroom setting. Because of the expertise of neuropsychologists in psychological as- sessment, they have been at the forefront of performing evaluations relative to the determination of damages in personal injury cases and assistance in criminal cases. Most often, these have included the bread and butter of forensic neuropsychology, an assessment of brain injury.

Neuropsychologists have become increasingly more in- volved in evaluating the emotional sequelae of injury, cus- tody evaluations, and the complex appraisal of deception and malingering in assessments performed in the forensic domain. In fact, it has become a common occurrence that a neuropsychologist is eventually confronted with some sort of forensic issue in his or her clinical work. Research in forensic neuropsychology is important because it pro- vides the practicing clinician with scientific data and a sci- entific process that allows neuropsychologists to pursue his or her work with increased precision. Also, as a scien- tist, the forensic expert must keep abreast of new scientific techniques and research in the field of neuropsychology. The sophistication of forensic neuropsychology attests to its emergent maturity (Zillmer, 2003a). Examples of emerg- ing research areas in forensic neuropsychology include the neuropsychology of comprehending an individual’s Miranda rights; the evaluation and detection of attempts to deceive or malinger in evaluations performed in the foren- sic domain; and the assessment of competency to stand trial, of criminal responsibility, and of insanity (Zillmer & Green, 2006).

S P O R T S N E U R O P S Y C H O L O G Y

Much attention has been given to the study of sports-related concussions, and great strides have been made in under- standing this health concern, including the cultivation of neuropsychological assessment tools to diagnose concus- sions and the refinement of recovery curves after injury. Concussion injuries are now thought of as significant neu- ropsychological events with real long-term consequences. Nevertheless, many issues related to the diagnosis, assess- ment, and management of concussions are akin to putting a complex puzzle together. What is the effect of age and sex in concussions? What neuropsychological tests are best suited for assessing concussions? What is the gold standard

for grading concussions? What return-to-play guidelines are most practical? Most often, the neuropsychologist’s role in the area of sports-related concussions is that of a consultant (Zillmer, 2003b).

Participation in competitive sports has increased world- wide, and sports-related concussions represent a signifi- cant potential health concern to all of those who partici- pate in contact sports. Given that there are approximately 300,000 sports-related concussions reported each year, the neuropsychologist’s role in testing for concussions for pur- poses of diagnosis and symptom resolution is one that our profession should embrace. Moreover, for those neuropsy- chologists who love sports, it provides a unique opportunity to merge one’s professional skills with one’s affinity for sports. The neuropsychologist’s training and expertise uniquely prepares him or her to play an important and re- warding role in this growing field. Examples of current research interests in this area include the return to play deci- sions after concussive injuries in sports (Zillmer, Schneider, Tinker, & Kaminaris, 2006), the neuropsychology of per- formance enhancement in competitive athletics, and the relationship between cognitive and personality factors re- lated to sports injury and rehabilitation.

T E R R O R I S M , L A W E N F O R C E M E N T , A N D T H E M I L I T A R Y

The surprise terrorist attacks against the United States and the devastating effects of hurricane Katrina have changed the collective psychology of our nation. Thus, there is an increased opportunity for the neuropsychology commu- nity to conduct behavioral research and consultation in law enforcement, disaster relief, and the armed forces.

Neuropsychologists have expertise that allows them to provide insight into the cognitive operations of terrorism; they can play an important role in using research in the cognitive sciences to assist in understanding the psychology of terrorism and the mindset of terrorists. In addition, neuropsychologists are in a unique position to study how the brain reacts in a crisis to investigate the opti- mal form of comprehending verbal information during a catastrophe, to examine the effects of anxiety among law-enforcement officials on their decision-making ability during a calamity, to understand the psychological im- pact of first responders, and to develop means for treating victims of terrorist attacks.

The most recent terrorism attacks and threats of chem- ical and biological warfare have also brought a new per- spective to the psychologist’s role in the military, in law enforcement (e.g., in the search for the Washington, D.C., sniper), and in the military’s role in enforcing peace (e.g., Iraq, Bosnia, and Korea). The armed forces can provide

28 PART ONE | Introduction

some real-life experience, responsibility, and exposure for military neuropsychologists that are seldom available for their civilian counterparts. For example, each operating U.S. Navy aircraft carrier has a “resident” psychologist onboard. Neuropsychologists are also deployed as part of combat stress units in Iraq, where they evaluate and man- age combat stress “on site.”

Neuropsychologists are experts in the science of human decision making, and we believe that neuropsy- chological science can be put to good use in counterter-

rorism endeavors, law enforcement, and the military. Ad- vancing neuropsychological science directly and indirectly in these areas benefits the security of our nation, as well as the discipline of neuropsychology. Research examples in- clude military fitness for duty evaluations, preparing mili- tary members for the demands of captivity, the neuropsy- chology of terrorists, the neuropsychological effects of weapons of mass destruction, and the assessment and se- lection of operational personnel for high-risk assignments (Kennedy & Zillmer, 2006).

CHAPTER 1 | A History of Neuropsychology 29

2000 B.C.: Early Brain Hypotheses

Peruvian and central European cultures practice trephination

Sixth to Fourth Centuries B.C.: Ancient Greek Influences

Heraclitus (sixth century B.C.): The mind is an unreachable, enormous space

Pythagoras (580–500 B.C.): The brain is the center of human reasoning

Hippocrates (460–377 B.C.): The brain controls all sense and movements

Plato (420–347 B.C.): The brain is the closest organ to the heavens

Aristotle (384–322 B.C.): The heart is the source of all mental processes

Third Century B.C. to Middle Ages: The Cell Doctrine

Alexandrian school (third to fourth century B.C.): Made advances in physiology and anatomy

Galen (Italian, A.D. 130–201): Suggested ventricular hypothesis and role of humors in health

Medieval and Renaissance Europe: Anatomic Discoveries and the Spiritual Soul

Albertus Magnus (German, ca. 1200): Deemphasized the role of the ventricles

Andreas Vesalius (Italian, 1514–1564): Corrected many historical mis- takes about brain anatomy

René Descartes (French, 1596–1650): Proposed a strict split between mental and physical processes

Thomas Willis (English, 1621–1675): Made contribution to understanding the brain’s vascular structure

Giovanni Lancisi (Italian, 1654–1720): Highlighted the role of the corpus callosum

Eighteenth and Nineteenth Centuries: Phrenology

Franz Gall (Austrian, 1758–1828): Personality is related to different sizes of specific brain areas

Johann Spurzheim (Austrian, 1776–1832): Intellectual capacity is related to brain size

Nineteenth-Century Europe: The Era of Cortical Localization

Paul Broca (French, 1824–1880): Motor speech is located in a small region of the left, frontal lobe.

Carl Wernicke (German, 1848–1904): Understanding of speech is located in the temporal lobe.

Nineteenth- and Twentieth-Century Critics of Cortical Localization

Sigmund Freud (Austrian, 1856–1938): Coined the term agnosia

Pierre Flourens (French, 1794–1867): Early advocate of an alternative tolocalization theories.

Hermann Munk (German, 1839–1912): Coined the term mind-blindness

Joseph Babinski (English, 1857–1932): Introduced the term anosognosia

Karl Lashley (American, 1890–1958): Formulated the principle of mass action in equipotentiality

Late Nineteenth- and Twentieth-Century Theories of Brain Function

Hughlings Jackson (English, 1835-1911): Claimed behavior exists on different levels in the nervous system

Alexander Luria (Russian, 1902–1977): Formulated the concept of functional systems of behavior.

Modern Neuropsychology

Karl Kleist (German, 1879–1960): Refined localization approach to neuropsychology

Wilder Penfield (Canadian, 1891–1976): Neurosurgeon who discovered direct electrical stimulation of the brain

Ward Halstead and Ralph Reitan (American, ca. 1940s): Pioneered neuropsychological testing

Donald Hebb (Canadian, 1904–1985): Published classic The Organiza- tion of Behavior

Henry Hécaen (French, ca. 1950s): Pioneered the role of the right hemi- sphere in neuropsychology

Arthur Benton (American, b. 1909): Continued to advance the role of the right hemisphere

Oliver Zangwill (British, ca. 1960s): Examined neuropsychology with traumatic brain injury

Norman Geschwind (American, 1926–1984): Founded behavioral neurology

Edith Kaplan (American, 1970s): Pioneered the process approach

Muriel Lezak (American, 1970s): Refined clinical assessment in neuropsy- chology

Table 1.4 Time Line of Significant Developments in Neuropsychology

30 PART ONE | Introduction

Summary Neuropsychology has had a particularly rich history (Table 1.4), and the future is promising as well. Philo- sophical thought, medical practice, and religious dogma have shaped human’s beliefs about the brain. Understanding “where we came from” and “where we are” shows how neuropsychology has evolved as a discipline. Furthermore, recognizing different viewpoints encourages the neuropsychology student to com- pare and contrast different theories. Knowledge of brain–behavior relationships is a developing science, rather than an absolute fact. In addition, we propose that neuropsychology is a paradigm of how to explain and research behavior, not just a body of knowledge. Neuropsychology is also not a separate area of re- search to be pursued in isolation from other models of psychology. It is distinct from physiology, however, because its direct concern is not with synapses but with behavior. In 1983, Donald Hebb suggested: “[The] neuropsychologist of the future must be a psychologist as well as a neurologist. The complexities of psy- chology and the complexities of neurology are the same complexities” (p. 7). We propose that neuropsy- chology is a natural part of psychology. We still know relatively little about the 3-pound organ that defines us, but many significant advances in recent years have brought the field to a new threshold of knowledge that has allowed researchers to identify many of the anatomic areas and functional systems within the brain that help determine behavior. The next chapter examines procedures for investigating the brain.

C r i t i c a l T h i n k i n g Q u e s t i o n s

How does localization brain theory differ from equipotentiality brain theory? What are the lasting contributions of each theory? Has the quest for the search of the organ of the soul been completed? Why is Luria’s functional model of the brain such an important step in understanding brain functions?

K e y Te r m s

Psychology Neuropsychology Neurons Vitalism Materialism Trephination Heraclitus Pythagoras Brain hypothesis Hippocrates Plato Aristotle Cardiac

hypothesis Ventricular localization

hypothesis

Cell doctrine da Vinci, Leonardo Galen Humors Magnus, Albertus Vesalius, Andreas Descartes, René Willis, Thomas Lancisi, Giovanni Atharva-Veda Gall, Franz Localization theory Phrenology Spurzheim, Johann Broca, Paul Aphasia

Double dissociation Wernicke, Carl Fluent aphasia Freud, Sigmund Agnosia Flourens, Pierre Ablation experiment Equipotential Munk, Hermann Mind-blindness Babinski, Joseph Anosognosia Lashley, Karl Mass action Jackson, Hughlings Luria, Alexander

Functional systems Pluripotentiality Penfield, Wilder Halstead–Reitan

Neuropsychological Battery Teuber, Hans-Leukas Hebb, Donald Hécaen, Henry Benton, Arthur Zangwill, Oliver Geschwind, Norman Lezak, Muriel

We b C o n n e c t i o n s

http://nanonline.org National Academy of Neuropsychology—The official home page of the National Academy of Neuropsychology (NAN). This site includes information on doctoral programs in neuropsychology, annual meetings, member- ship information, and more.

http://nanonline.org

CHAPTER 1 | A History of Neuropsychology 31

http://www.the-ins.org International Neuropsychological Society—The International Neuropsychological Society is a multidiscipli- nary organization dedicated to enhancing communication among the scientific disciplines that contributes to the understanding of brain-behavior relationships.

http://www.apa.org American Psychological Association—The official site of the American Psychological Association (APA) pro- vides links to student information, membership information, PsychNET, and career-planning information.

http://www.psychologicalscience.org American Psychological Society—The American Psychological Society is dedicated to the advancement of scientific psychology and its representation at the national level. The Society’s mission is to promote, pro- tect, and advance the interests of scientifically oriented psychology in research, application, teaching, and the improvement of human welfare.

http://www.the-ins.org

http://www.apa.org

http://www.psychologicalscience.org

Chapter 2

M E T H O D S O F I N V E S T I G AT I N G T H E B R A I N

The most important advancement in the clinical neurosciences is the imag- ing of the living human brain.

—Erin Bigler

The brain is the last and greatest biological frontier. —James Watts

Neurohistology Techniques Radiologic Procedures Electrophysiologic Procedures Imaging of Brain Metabolism Magnetic Imaging Procedures Cerebrospinal Fluid Studies: Lumbar Puncture Behavioral Examinations New Advances in Imaging Techniques: Mapping

the Brain

Neuropsychology in Action

2.1 Case Example of Brainstem Auditory-Evoked Response

2.2 Undergoing a Magnetic Resonance Imaging Procedure

2.3 New Frontiers in Functional Magnetic Resonance Imaging

2.4 Diagnostic Neuroimaging and Neuropsychology

CHAPTER 2 | Methods of Investigating the Brain 33

Overview The primary constraint in unlocking the secrets of the brain has been the limit of available techniques and examination procedures for investigating the brain. This was certainly true for early scientists, who struggled with how inaccessible the living brain is to direct visualization. Short of performing in vivo neurosurgical procedures or postmortem examinations immediately after death, early scientists simply could not examine the living brain. As a result, study of the brain was largely speculative and inferential, and researchers have made many errors (see Chapter 1). Because of such difficulties, many famous psychologists, including William James and B. F. Skinner, insisted that the brain is not the province of psychologists. They suggested that the brain is like a “black box”—researchers cannot study the brain itself, but can associate certain inputs with specific outputs of behavior.

Since the 1970s, an explosion in technology has allowed more precise examination of the brain. During the end of the nineteenth century, researchers developed staining techniques by which they could visualize neurons. In the early part of the twentieth century, X-ray technology and pneumoencephalography allowed scientists to visualize the skull and the ventricles. The brain, however, remained elusive. This all changed in the 1970s when researchers introduced computed transaxial tomography (CT), and then magnetic reso- nance imaging (MRI) in the mid-1980s. These two procedures, although crude in their initial stages of devel- opment, were soon refined so that visualizing specific and detailed brain structures became possible, in- cluding visualizing asymmetries in the living brain. At the same time, other technologies, including electroencephalography (EEG), single-photon emission computed tomography (SPECT), and positron emis- sion tomography (PET) advanced, allowing clinicians to view the brain from structural, metabolic, and elec- trophysiologic perspectives. For example, using PET, scientists can now measure, with three-dimensional (3-D) resolution, biochemical and physiologic processes in the human brain. More recently, the structural imaging of brain anatomy has been correlated with functional parameters of the brain, which created a new direction in brain research, namely, that of functional imaging.

These recent advances in neuroimaging dramatically changed how scientists investigate neural corre- lates of human behavior. These spectacular new developments are akin to changing filters in a camera, resulting in new and different images of the same picture. A “window to the brain” has opened, and so has our understanding of the brain.

This chapter summarizes the major technologic methods of examining the brain, and Chapter 3 exam- ines neuropsychological techniques of studying the brain. We discuss advantages and disadvantages for each procedure, particularly as they relate to understanding brain–behavior relationships and disease processes. This chapter provides the neuropsychology student with background on the various investiga- tional procedures he or she will likely encounter in the literature, research laboratory, or in clinical practice. Neuropsychologists should familiarize themselves with the basic information these techniques can provide. In fact, neuropsychologists play an important role in advancing this technology and are working side by side with radiologists and neurologists to unlock the secrets of the brain.

K e e p i n M i n d

What is the difference between a CT scan and an MRI?

What does an EEG measure?

What is functional imaging?

What is the difference between an invasive and a noninvasive procedure?

Are modern imaging techniques dangerous to the brain? Explain.

34 PART ONE | Introduction

Neurohistology Techniques

On visual inspection of brain tissue under a microscope, one can find order to the anatomic arrange- ment of neurons. For example, pyramidal cell bodies in the cerebral cortex and hippocampal tissue “line up” to process neural information. For neuroscientists, the key to understanding the structures that make up the brain lies in technology that facilitates visualization of differ- ent aspects of neural tissue. One of the first ways to study neural processes involves stains; stains are chemi- cals that attach to specific cell structures, thereby mak- ing it possible for researchers to examine the cells visu- ally and even count them. For more than a century, neuroscientists have developed several staining tech- niques to help visualize mapping fiber connections. Ini- tially, the light microscope, invented in the 1890s, gave birth to the pioneering works of Cajal (1937) and Brod- mann (1909) in cellular neuroanatomy. The introduc- tion of the powerful electron microscope in the 1950s made it possible to analyze in detail the synaptic con- tacts between individual neurons. Next, we outline this remarkable progress for several classic histologic tech- niques.

G O L G I S T A I N

One of the most remarkable developments in the neuro- sciences came with a discovery made by Camillo Golgi (1843–1926). Golgi, an Italian physician, discovered in the early 1870s that silver chromate stained dead neurons black. This remarkable breakthrough allowed, for the first time, visualization of individual neurons (Figure 2.1). The Golgi method enabled detailed study of cell process, often allowing a 3-D view of the cell and its processes. Practi- cally overnight, the basic building blocks of the nervous system became visible. More recently, researchers have even been able to stain single neurons in a Golgi-like fash- ion and visualize many of the different cells that make up the brain. Using this method, they found that Purkinje cells reside in the cerebellum and have a remarkably dif- ferentiated dendritic tree (see Chapter 4). The Golgi method also led to the classification of neurons based on the length of their axon. Golgi type I neurons, for exam- ple, have long axons that transfer information from one region of the brain to another. In contrast, Golgi type II neurons are those with short axons. The Golgi method has remained in use for more than 100 years to character- ize specific cell types in different regions of the nervous system.

N I S S L S T A I N

One drawback of the Golgi stain is that it provides little information about the number of neurons in a specific brain region, because it only affects a few neurons. It also permits a view only of neural tissue in silhouette and does not allow visualization of the inner structure of the neu- ron. In the 1880s, Franz Nissl (1860–1919), a German histologist, discovered that a simple dye will selectively stain cell bodies in neurons. As a result, researchers adapted several different stains, originally developed for dyeing cloth, for histologic purposes. Methylene blue, for example, is a neural stain that has an affinity for the inner structures of neural cell bodies. One of the most popular dyes is cresyl violet, a cell body stain that is not selective for neural cell bodies, but stains all central ner- vous system cells. Cresyl violet facilitates the differentia- tion of fiber bundles, which appear lighter, and nuclei, which appear darker. Using the Nissl stain technique,

Figure 2.1 Golgi-stained neurons at 400 � magnifica- tion. (Reproduced from Kalat, J. W. [1998]. Biological psy- chology, [6th ed., p. 104]. Pacific Grove, CA: Brooks/Cole, by permission. © Martin Rotker/Photo Researchers.)

scientists could then count the number of Nissl-stained dots that represented neurons in any area of the brain.

The Nissl method has become the classic microscopic method for studying the cell body and one of the most valu- able techniques for studying neurons in both normal and pathologic states. The Nissl stain outlines all cell bodies and selectively stains the nucleus but not the axon. Furthermore, Nissl patterns vary among different types of neurons. For example, motor neurons have larger Nissl bodies, and sen- sory neurons have smaller ones. The appearance of the Nissl substance also varies with cell activity; that is, Nissl bodies disintegrate when the axon of the neuron is injured.

O T H E R S T A I N I N G T E C H N I Q U E S

The Nissl and Golgi methods are selective in their affinity for specific characteristics of neurons. The Nissl method shows the cell body, specifically the cell nucleus. Thus, it maps cell density. The Golgi method is particularly useful for investigating the distribution of dendrites and axons in individual neurons, which appear pitch-black. Scientists have developed other staining procedures specifically for studying axons. For example, myelin staining selectively dyes the sheaths of myelinated axons. As a result, white matter, which consists of myelinated axons, is stained black, whereas other areas of the brain that consist primar- ily of cell bodies and nuclei are not (Figure 2.2).

Since the 1970s, researchers have introduced new tracing methods based on the principle of axonal trans- port to chart previously unexplored regions and circuits of the brain. For example, the horseradish peroxidase (HRP) method (HRP is an enzyme found in horseradish roots) was introduced. Researchers inject HRP into a re- gion of the nervous system, and surrounding cell bodies and axon terminals take it up. In neurons that have in- corporated HRP, axonal transport carries the enzyme to other interconnected cell bodies, where researchers can detect it with a simple staining procedure. Using the ax- onal transport technique, neuroscientists can study the tracing of pathways in the brain. Staining remains a vi- able method for studying the cellular function of the ner- vous system and helps neuroscientists in studying the specialized contacts among neurons and their complex and often puzzling arrangements. Table 2.1 summarizes the different staining techniques used in neuroscience.

Radiologic Procedures

From the initial X-ray of the head and the practically extinct air encephalogram to sophisticated CT, the rapid progress of radiology has made a significant impact on the

field of clinical neurology and neuropsychology. This sec- tion discusses the techniques involved in neuroradiology, with special emphasis on computed tomography and an- giography.

CHAPTER 2 | Methods of Investigating the Brain 35

Nissl stain: A dye that stains the cell body of the neuron; this method is particularly useful for detecting the distribution of cell bodies in specific regions of the brain

Golgi stain: A method of staining brain tissue that marks a few selected individual cells, differentiating the cell body, as well as its extensions

Myelin stain: Shows the myelin coating of axons, rendering it useful for mapping pathways in brain tissue

Horseradish peroxidase: Allows mapping of neuronal pathways using axonal transport mechanisms; this technique works in both directions, that is, from the axon back to the cell body, and vice versa

Table 2.1 Different Staining Techniques

Text not available due to copyright restrictions

36 PART ONE | Introduction

S K U L L X - R A Y

Physicist Wilhelm Conrad Röntgen (1845–1923) made a remarkable discovery that changed the science of medicine forever and earned him the 1901 Nobel Prize in physics. Röntgen (or Roentgen, to transliterate the German ö into English) quite serendipitously produced an invisible ray that, unlike heat or light waves, could pass through wood, metal, and other solid materials. This ray, also called the X-ray, created the field of radiology. The principle of X-ray technology is the generation of Roentgen rays, electromag- netic vibrations of very short wavelength that can penetrate biological tissue and can be detected on a photographic plate. At the basis of its medical application was the prin- ciple that the diagnostic rays travel through the body at different rates according to the density of organs. The re- sulting picture would show clear contrast between bones and, to a lesser degree, soft parts. Researchers discovered that X-rays pass easily though low-density tissue (water) but are absorbed by high-density tissue (bone). In addition, they found that the possible harmful effects of X-rays could destroy diseased tissue, a discovery that led to radiotherapy.

Diagnostic X-ray films are useful for clinical work on various parts of the body, because they demonstrate the presence and position of bones, fractures, and foreign bodies. A clinical disadvantage of X-ray films, specifically of the head, is that they are two-dimensional (2-D). Thus, positive diagnosis of a 3-D clinical pathology is difficult. Second, an X-ray film of the head shows little differentia- tion between brain structures and cerebrospinal fluid (CSF), making clinical use of this procedure ineffective, with the exception of large and vascularized brain tumors or massive bleeds. Furthermore, X-rays are potentially dangerous, because they are cumulatively absorbed by high-density tissue. Thus, X-ray exposure entails a minor risk. The advantage of X-raying the head is that it uses universally available technology, is inexpensive, and pro- vides good visualization of the skull. Thus, if there is the possibility of a skull fracture, X-ray technology remains a useful diagnostic tool (Figure 2.3).

A I R E N C E P H A L O G R A P H Y ( P N E U M O E N C E P H A L O G R A P H Y )

An air encephalogram, or pneumoencephalogram, is the radiographic visualization of the fluid-containing structures of the brain, the ventricles, and spinal column. It is similar to X-ray visualization, but it involves with- drawing CSF by lumbar puncture (see later); the CSF is then replaced with a gas such as air, oxygen, or helium. The gas rises and enters the ventricular system, specifi- cally the four interconnecting cavities of the brain. Once

the gas has filled the ventricles, a technician takes a stan- dard X-ray film of the head. Because the gas is of much lower density than the surrounding brain, the ventricles appear as a dark shadow on the X-ray film and clearly out- line the surrounding brain tissue. Using this approach, a clinician can make a clinical diagnosis. The air encephalo- gram represented an advance on the standard X-ray film because it allowed visualization of the ventricular system.

However, patients did not tolerate the procedure well. Attendants had to turn patients in various positions, often awkwardly, and invert them in 3-D space to advance the gas to a specific ventricle before the technician could take an X-ray film. Because gas had replaced the CSF, the cush- ioning aspects of the CSF had been compromised, which often resulted in excruciating headaches that could last for several days before the gas was reabsorbed. Today, the more modern CT scan has replaced both the traditional X-ray image and the pneumoencephalogram.

C O M P U T E D T R A N S A X I A L T O M O G R A P H Y

Computed transaxial tomography (CT) is based on the same principle as the X-ray examination. The medical community has widely embraced CT, making it the stan- dard technology for examining the brain.

H i s t o r y

CT scanning was invented in Great Britain in 1971 and introduced to the United States in 1972 (Haeger, 1988). Physicists developed the first model of transaxial

Figure 2.3 X-ray film of the head. (Courtesy Eric Zillmer.)

tomography in part by building on dramatic advances in computer technology. Since its development, CT tech- nology has progressed from detecting only gross brain fea- tures to visualizing highly refined structural features. Be- fore this technology, precise neuropathologic diagnosis was difficult.

T e c h n i q u e

After placing the patient’s head in the center of the CT scanner, the technician revolves an X-ray source around the head as detectors monitor the intensity of the X-ray beam passed through the brain. The technician does not take the images at a perfect horizontal perspective of the head. Rather, he or she slightly tilts the images at a 20-degree angle to avoid scanning the air-containing sinuses, which produce distortion because of the combination of low (air) and high (bone) density (Figure 2.4). The first (low- est) image selected is usually at the level of the foramen magnum, the base of the brain. Multiple sequential im- ages show the ventricles, basal ganglia, thalamus, and cere- bral cortex. Multiple transaxial images of the brain are ob- tained from many different angles. This requires a large apparatus or X-ray tube, which can rotate 360 degrees around the patient’s head (Figure 2.5). The detectors, which either rotate with the X-ray scanner or are placed in a circle around the patient, are more sensitive than the traditional X-ray film. For comparison, X-ray film can detect difference of 10% to 15% in the density of soft tissue, whereas CT can measure variations as small as 1%, often pinpointing density changes as small as 2 mm in diameter.

In contrast with the traditional X-ray visualization, in CT, the head is scanned using a very narrow beam. This al- lows for the segmentation of the brain into many different slices. Depending on the nature of the study, the slices of

CHAPTER 2 | Methods of Investigating the Brain 37

Figure 2.4 X-ray image of the head demonstrating the various “slices” of which the images are calculated. Note the absence of any differentiation of this patient’s brain using X-ray technology. The 20-degree angle of the cuts is implemented to avoid rays passing through the brain si- nuses at the front of the brain, which often causes distor- tion. (Courtesy Eric Zillmer.)

X– ra

y s ou

rce

X–r ay

de te ct or

a. b.

Figure 2.5 Computed transaxial tomography scanner. (a) The subject’s head is placed in the scanner, which is then subjected to a rotating source of X-rays that pass through the brain at various angles. (b) A computer con- structs the final image of the brain. (Reproduced from Kalat, J. W. [1998]. Biological psychology [6th ed., p. 106, Figure 4.28]. Pacific Grove, CA: Brooks/Cole, by permission. Photo by Dan McCoy/Rainbow.)

38 PART ONE | Introduction

the brain range from thin (2 mm) to thick (up to 13 mm). The information obtained by the CT scanner is entered into a computer, which then calculates, in 3-D space, cross sections of the brain within the plane of the horizontal X- ray beam and the available density information of the brain. From these data, the computer generates a picture of the brain that can be in any orientation (sagittal, hori- zontal, or coronal). The complicated calculations the com- puter performs use the mathematics for computing solid 3-D structures based on data from a 2-D source. In prin- ciple, the procedure is similar to examining any 3-D struc- ture (e.g., a soft drink can) from many different angles, and then drawing it from a different perspective.

I n t e r p r e t i n g t h e C o m p u t e d T r a n s a x i a l T o m o g r a p h y S c a n

The final product of CT technology is to produce a visu- alization of brain structures. This can take any form, in- cluding numbers or colors, but radiologists, not surpris- ingly, have favored an end result similar to the familiar X-ray film, with black-and-white shadings that reflect structure density. Accordingly, bone (high density) is white and CSF (low density) is dark. Dense collections of cell bodies, gray matter, and nuclei look darker. In con- trast, myelinated pathways or white matter look lighter. Neuroradiologists complete the interpretation of CT im- ages, which they relate to their examination of the general symmetry of the brain. Marked asymmetries of brain structures typically signal a pathologic process. Neurora- diologists also closely examine the scans for sites of ab- normal densities, both hypodensity (associated with low density and perhaps an old lesion) and hyperdensity (typ- ically signaling an abnormal density such as a tumor or a bleed). In this way, they examine the general distribution of white versus gray matter (Figure 2.6).

E n h a n c e d C o m p u t e d T r a n s a x i a l T o m o g r a p h y

Soon after the introduction of CT, researchers realized that the brain could be X-rayed more clearly by using a contrast material that would better absorb the rays. Thus, the enhanced CT scan, which involves intravenously in- jecting an iodinated contrast agent, shows more contrast of brain structures. In the intact cardiovascular system, the contrast agent does not enter the brain because it re- mains contained in the vascular system. But if there is a lesion, increased vascularization (as in an arteriovenous malformation or a tumor), or a defect in the blood–brain barrier, that area shows increased contrast.

The refinement of the CT scan has made available a new generation of brain images that previously were possible

only on autopsy. The CT scan has become a useful diag- nostic tool because alterations caused by pathologic processes or deformation of brain structures are easily vis- ible, even to the untrained eye. The routine availability of CT has also increased, almost overnight, the diagnosis of specific disorders. For example, small strokes, previously undetectable with X-ray technology, were all of a sudden easily diagnosed, which increased the prevalence of diag- nosed multi-infarct dementia.

A N G I O G R A P H Y

Angiography is the roentgenographic visualization (X-raying) of blood vessels in the brain after introducing contrast material into the arterial or venous bloodstream. Consistent and sufficient blood supply is essential for a healthy brain, and angiography has become a standard procedure for examining the integrity of the vascular sys- tem of the brain. Because the blood vessels of the brain reflect the surrounding brain tissue, angiography is a tech- nique based on the X-ray procedure of examining the brain through its vascular system. Angiography is particularly

Figure 2.6 Early-generation computed transaxial tomog- raphy scan (horizontal). (Courtesy Eric Zillmer.)

important in diagnosing structural abnormalities in the blood vessels themselves or in their arrangement. As a re- sult, angiography has become a useful tool in the early identification of aneurysms (a ballooning of an artery; see Chapter 12) and the subsequent prevention of stroke. To a lesser extent, clinicians can also identify other patholo- gies such as tumor, because they depend on increased vas- cularization or blood supply. Angiography also can detect shifts in cerebral arteries, which may indicate a mass- occupying lesion.

T e c h n i q u e

Femorocerebral angiography, developed in the mid- 1950s, introduces a catheter into the arterial system. Pre- viously, physicians injected the contrast material directly into an artery, such as the internal carotid artery, but it is safer to insert a catheter via the femoral artery. The spe- cialist passes the preshaped, semirigid catheter through a needle inserted in the femoral artery, and then guides it up the aorta to the aortic arch with the assistance of X-ray and television monitoring. The specialist can then place the catheter into any of the three major arteries arising from the aortic arch; the brachiocephalic artery, which leads to the common right carotid artery or the right ver- tebral artery; the left common artery, which leads to the left internal and external carotid artery; or the left subcla- vian artery, which connects to the left vertebral artery (see Chapter 12 for a more detailed discussion of the vascular

system of the brain). Using this technique, the specialist can position or “park” the catheter tip at various strategic places of blood supply to the brain, to examine anterior or posterior cerebral arteries. Next, an automatic injector sends an iodinated contrast agent through the catheter. At the same time, a technician takes rapid, serial X-ray films of the head over an 8- to 10-second interval in the frontal and lateral planes, providing visualization of the injected vessels and their complex intracranial branches.

Digital subtraction angiography, compared with con- ventional film angiography, is particularly effective in en- hancing visualization of blood vessels, including the mor- phologic and physiologic states of the arterial, capillary, and venous phases of the cerebral circulation (Figure 2.7). In this procedure, after the images of the contrast mate- rial have been acquired, the computer stores and subtracts the X-ray image of the brain. The resulting visualization of the vascular system is easily distinguished from that of brain tissue.

Intravenous angiography is somewhat more compli- cated than femorocerebral angiography; therefore, clini- cians do not use it as routinely. In intravenous angiogra- phy, the specialist inserts the catheter in the patient’s arm but must pass it through the heart, then the lungs, and then to the left side of the heart before it reaches the aortic arch. Thus, larger amounts of contrast medium must be used, which increases the patient’s risk for renal toxicity.

CHAPTER 2 | Methods of Investigating the Brain 39

a. b.

Figure 2.7 Examples of angiography: (a) normal lateral view angiogram; (b) arteriovenous malformation from coronal perspective; and (c) aneurysm from lateral perspective. (a: SPL/Custom Medical Stock Photo; b: English/Cus- tom Medical Stock Photo; c: English/Custom Medical Stock Photo.)

40 PART ONE | Introduction

C l i n i c a l U s e

Angiography allows, from the puncture of a single artery, the maximum radiographic detail for diagnosing intrac- erebral lesions. Angiography is an invasive procedure, yet it is relatively safe and well tolerated by the patient, who is awake but slightly sedated. The risk from the procedure is related to the possibility of the catheter loosening plaques in the arteries that may then separate and travel to a smaller location in the arterial system, where they can block the flow of blood, leading to an embolism. This is a concern in patients with arteriosclerotic vascular disease. Few patients are allergic to the contrast medium, but the procedure is contraindicated for these patients. In gen- eral, for initial diagnosis, clinicians prefer noninvasive techniques, including CT scan and ultrasound (see Chap- ter 12 for a description of ultrasound used to examine the carotid arteries). Angiography is, however, the most accu- rate diagnostic procedure for evaluating vascular anatomy and its abnormalities. Thus, it is particularly useful in di- agnosing cerebrovascular disorders.

S O D I U M A M Y T A L I N J E C T I O N S ( W A D A T E C H N I Q U E )

The Wada technique, named after its developer, is simi- lar to the angiogram in that the examiner places a catheter, typically in the left or right internal carotid artery. Then, a barbiturate sodium amytal is injected, which temporarily anesthetizes one hemisphere. Only one hemisphere is affected, even though vascular struc- tures connect the two hemispheres (Wada & Rasmussen, 1960). This difference relates to that the pressure gradi- ents along cerebral arteries in both hemispheres are the same; thus, there is no cross-filling (or crossover) of blood from one hemisphere to the other, except if there is a stroke or other damage to the vascular system. In this way, neuropsychologists can study the precise functions of one hemisphere while the other “sleeps” (see Chapter 16 for a detailed discussion of the Wada technique). Table 2.2 provides an overview of the radiologic proce- dures discussed in this section.

Electrophysiologic Procedures

E L E C T R O E N C E P H A L O G R A P H Y

One of the most widely used techniques in neurology is electroencephalography (EEG). The electroencephalo- gram is a recording of the electrical activity of nerve cells

of the brain through electrodes attached to various loca- tions on the scalp. The Austrian psychiatrist Hans Berger first discovered in 1924 that patterns of electrical activity can be recorded using metal electrodes placed on the human head (Brazier, 1959). Initially, Berger was inter- ested in finding physiologic evidence for telepathy, the scientifically unverified phenomenon of a mind commu- nicating with another by extrasensory means. Berger was, however, frustrated in his search to find support of men- tal telepathy, but he discovered that the electrical activity of the sleeping brain differed fundamentally from that of the awake brain. Researchers have used the resulting electroencephalogram (“electrical brain writing”) to inves- tigate distinct patterns of electrical activity in both the nor- mal and pathologic brain. Its potential use for identifying EEG correlates of behavior and personality have made it a popular research tool among behavioral scientists. Thus, EEG became the first dynamic way to measure brain function.

Skull X-ray: Two-dimensional representation of the head. Disadvantages include low resolution of brain anatomy; advantages include low cost, availability, and its use in the diagnosis of skull fractures, which are easily seen using this technique.

Air encephalography (pneumoencephalography): The radiographic visualiza- tion of the fluid-containing structures of the brain, which have been filled with gas. An improvement over the skull X-ray, but because of its invasive nature and side effects, it is not used in contemporary medicine.

Computed transaxial tomography (CT scan): CT renders an anatomic image of brain density based on multiple X-ray images of the brain. CT, which is readily available and can be used with almost anyone, provides a three- dimensional perspective of the brain with acceptable differentiation of brain structures. Its disadvantages include the use of penetrating radiation and that CT does not provide as much spatial resolution as does magnetic resonance imaging.

Enhanced CT: A CT scan that involves injecting a contrast agent to provide better visualization of brain structures, particularly bleeds. Disadvantages are it is invasive and some patients may not tolerate the contrast agent well.

Angiography: The roentgenographic visualization of blood vessels in the brain after introducing contrast material into the arterial or venous bloodstream. Angiography is the most useful technique for examining the blood supply to and from the brain. One disadvantage is that a catheter must be inserted into the patient’s bloodstream, which requires an invasive medical procedure.

Sodium amytal injections (Wada technique): The injection of sodium amytal temporarily anesthetizes one hemisphere. This is primarily a research technique. It is used clinically to determine the lateralization of language before temporal lobectomy is performed. It is a complicated medical proce- dure that requires placing an arterial catheter.

Table 2.2 Overview of Radiologic Procedures

T e c h n i q u e

To record an EEG, the technician places small metal elec- trodes, or leads, on the scalp and connects them via wires to the electroencephalograph machine (Figure 2.8), which amplifies the electrical potential of neurons recording their activity on moving paper, a polygraph. Previously, electrodes were small needles that were inserted just below the skin of the scalp. Modern electrodes used with con- ductive gel have proved to be just as effective. In princi- ple, each pair of electrodes can act as its own recording site, measuring the electrical activity of millions of neu- rons close to the scalp. The neuronal activity of deeper, subcortical structures is not easily evaluated using EEG. Also, surface electrodes are placed at electrically inactive sites on the head, such as the mastoid bone behind the ear (electrode placement A1 and A2), which act as ground leads. The EEG itself is generated primarily by neuronal activity immediately below the cortex. Pyramidal nerve cells, which have somewhat conical cell bodies, make up about 80% of neurons in that region and exist in all areas of the cerebral cortex. Thus, EEG is mostly a measure of cortical nerve cells of the pyramidal type.

The electrical signal of a neuron must penetrate through different tissues to reach the electrodes, including the meninges, CSF, blood, the skull, and the scalp, to be measured. The electrical contribution of each neuron is tiny, and it takes many thousands of neurons firing in con- cert to generate an electrical signal large enough for EEG to detect. Thus, the most easily visible EEG wave patterns depend on the synchronicity of millions of neurons.

In general, brain wave patterns are either rhythmic or arrhythmic. Neurons typically fire in a rhythmic or syn- chronous pattern, leading to alpha, beta, theta, and delta

waveforms. In epilepsy, however, many neurons fire at once, or in a burst or “spike” that corresponds with the amplitude that the EEG record shows. In principle, each electrode measures the summed signal of electrical activ- ity of groups of neuronal dendrites. EEG can be thought of as analogous to holding a microphone over New York City to estimate the traffic by measuring the amount of noise from automobiles. Thus, EEG is a diagnostic tool more sensitive to the “forest” than to the individual “tree.”

O v e r v i e w o f B r a i n W a v e A c t i v i t y

Brain wave activity may differ in polarity, shape, and fre- quency. The amplitude typically ranges from 5 to 100 mi- crovolts and is a measure of the signal strength of neural activity. The EEG records frequency of the waveforms from 1 to 100 Hz (signal frequency per second), meaning that neural activity oscillates in a particular frequency. The specific shape of the waveform also interests the electroen- cephalographer. For example, during light sleep, the EEG shows a characteristic spindle activity and vertex (V) waves. Researchers have established a system of dividing brain wave activity that is based on its frequency and am- plitude. To the neuropsychology student, frequency subdi- visions of the EEG may appear somewhat arbitrary, but in general, they correlate with distinct divisions of subjective experience of attention and arousal. Several different basic types have been established that vary according to whether a person is alert, wakeful, drowsy, or sleeping (Table 2.3).

CHAPTER 2 | Methods of Investigating the Brain 41

Figure 2.8 Electromechanical electroencephalographic recorder of the type used in the mid-1980s. (Courtesy Jeffrey T. Barth, University of Virginia.)

Gamma activity (35+ Hz) is a low-amplitude, fast-activity wave. Gamma rhythms are the fastest and are often associated with peak performance states and hyperarousal.

Beta is a low-amplitude, fast-activity wave with a frequency of more than 12 Hz. Beta is often divided into high beta (18–35 Hz), typically associated with a narrow focus, overarousal, and anxiety; mid-beta (15–18 Hz), often correlated with being active, alert, excited, or focused; and low beta (12–15 Hz), which has been associated with relaxed, external attention.

Alpha activity (8–12 Hz) is the predominant background activity in wakeful persons. Alpha is most often associated with quiet, passive, resting, but wakeful states.

Theta activity ranges from 4 to 7 Hz and is most indicative of drowsiness, deeply relaxed states, and inwardly focused states.

Delta activity is the slowest frequency (<0.5–4 Hz). High-voltage, slow- frequency delta waves are never present in a wakeful, healthy person, but mostly occur during non–rapid eye movement (nondream) deep stage 4 sleep.

Table 2.3 Brain States and Associated Subjective Experience

42 PART ONE | Introduction

The pursuit of a specific brain state is a goal in itself. Because alpha and theta waves are characteristic of a per- son being relaxed, isolation flotation tanks and relaxation audio cassette tapes, among other tools, have proved ef- fective in helping achieve such brain states. In athletics, researchers have demonstrated that peak performance is associated with specific cortical arousal levels (Van Raalte & Brewer, 1996). Alpha waves, in contrast, are incompat- ible with being alert and focused. Thus, it is advantageous for the competitive athlete to be in mid-beta rhythm when a difficult task is required, such as in ice hockey when the goalie faces a breakaway or in baseball when the batter steps to the home plate to face a pitch. During beta waves, the cortex is most actively engaged via complex sensory input and external processing. The activity rate of cortical neurons should be high, but also unsynchronized, because neurons may be involved in different aspects of complex neuropsychological tasks. During beta waves, neurons fire rapidly, but not in concert with each other. However, it is difficult to sustain beta rhythm for long pe- riods; thus, successful athletes are skilled in switching from alpha to beta rhythm and back “on command.”

S e i z u r e s a n d E l e c t r o e n c e p h a l o g r a p h y

Neurons can organize their rate of electrical activity in two fundamental ways. First, groups of neurons can fire in syn- chronized oscillations by taking cues from other cells, also known as pacemaker cells or k neurons (k for constant). Cor- tical neurons also take cues from other brain structures such as the thalamus, which can act as a powerful pacemaker, even when there is no external sensory input. For example, during non–rapid eye movement (NREM, or nondream sleep), the thalamus generates rhythmic, self-sustaining dis- charge patterns that prevent organized information from reaching the cortex. Thus, one’s brain is asleep, demonstrat- ing large, rhythmic delta waves. Second, neurons may fire in a consistent rhythmic pattern in response to collective behavior, such as a large group of people clapping in a syn- chronized way without a cheerleader being present.

Seizures are the most extreme form of synchronous brain activity, during which the whole brain (as in a grand mal seizure) or large portions of the brain (as in a partial seizure) fire with a defined and pronounced synchrony that never occurs during normal behavior (Figure 2.9).

Figure 2.9 Electroencephalogram example of spiking activity that accompanies epilepsy. (Courtesy Eric Zillmer.)

During seizures, most, if not all, cortical neurons partici- pate in excitation. Behavior is disrupted, and often con- sciousness is lost. Seizures themselves are best conceptual- ized as a symptom, not unlike a fever, and may be triggered by dozens of different causes. It is unlikely that seizures have one underlying cause. The lifetime preva- lence for a single seizure is high, approximately 10%. Drugs that block gamma-aminobutyric acid (GABA) re- ceptors increase the possibility of a seizure. GABA has strong inhibitory properties and plays a major role in the basic type of neuronal transmission that depends on rapid communication among neurons. Conversely, drugs that prolong the inhibitory action of GABA (barbiturates or benzodiazepines, e.g., Valium) suppress the possibility of seizures. The brain is potentially always close to having a seizure, because runaway excitation is possible given the redundant feedback circuitry of the brain and its delicate balance between inhibitory and excitatory potentials. Multiple seizures, however, are typical of a disorder known as epilepsy (see Chapter 16 for a detailed discus- sion of epilepsy).

In patients with intractable (incurable) epilepsy, one intervention is neurosurgery to remove, if possible, the precise site or origin of the pathologic electric discharge. In such cases, a more precise EEG measurement is needed, which can be obtained by placing electrodes di- rectly on the surface of the brain. This form of EEG, known as electrocorticography (ECoG), often is per- formed during temporal lobectomy surgery to isolate a precise location of brain pathology. In addition, a sur- geon can place depth electrodes in the brain close to the projected area of interest while the patient is awake and being monitored via 24-hour closed-circuit television. This is usually done to correlate seizure activity with EEG data. Depth electrodes and ECoG are invasive tech- niques and entail risks, including infection. These meth- ods are used only when the medical benefits greatly out- weigh the risks to the patient. Thus, surface scalp electrode placement is the first and least invasive electro- physiologic study of the brain. EEG is also relatively in- expensive compared with CT and MRI procedures and is readily available.

C l i n i c a l U s e o f E l e c t r o e n c e p h a l o g r a p h y

The primary referral for a clinical EEG is to help with di- agnosis of a seizure disorder, sleep disorder, level of coma, or presence of brain death. In fact, EEG is the primary tool in diagnosing epilepsy and can often pinpoint the type and location of seizure disorder. EEG is also useful in diagnosing sleep disorders, because specific sleep states

are associated with particular forms of electrical activity. The primary abnormality seen on EEG recordings is a slowing of activity, as well as the presence of epileptiform activity. For example, it is abnormal to find delta activity in a wakeful person. Typically, the slower the frequency in an awake patient, the more severe its abnormality. People with partial seizures often have EEG activity that slows to 3 Hz. Epileptiform EEG activity consists of sharp waves (spike-and-wave discharge), which indicate a seizure dis- order. EEG diagnosis of epilepsy, however, produces fre- quent type II errors (misses). Thus, a normal EEG may not indicate a normal brain.

Unfortunately, the EEG also demonstrates type I er- rors (false positive or false hits). That is, a mildly abnor- mal EEG may not necessarily reflect an abnormal brain unless the EEG indicates the specific profile of epilepsy, which, if present, has few false positives. Interpreting the EEG recording is something of an art because so many different variables are introduced. These variables include amplitude configuration of the polygraph, speed of recording paper, different electrode montages, a high in- cident of artifact caused by muscle movement that con- tributes to electrical activity, and inadequate electrical shielding of the examination room. Thus, different elec- troencephalographers often disagree on interpreting bor- derline abnormal EEGs, although they easily diagnose the more definite epileptic EEG patterns.

When a diagnostician suspects seizure disorder, several techniques can provoke epileptic discharges during the EEG recording, which is the absolute positive sign of epilepsy. These methods include administering an EEG during the patient’s sleep or when sleep deprived; that is, after the patient stays awake for one night, the diagnosti- cian administers the EEG in the morning. Other activa- tion techniques that provoke epileptic discharges during the EEG recording include hyperventilation and photic stimulation. The latter is the presentation of a strobe light, right in front of closed eyes, that is set at different fre- quencies to influence the base-rate activation pattern of occipital neurons. Diagnosticians also use serial EEGs and 24-hour EEG recordings to monitor brain wave patterns over time. Once epilepsy is identified, doctors most com- monly treat it with anticonvulsant medication to reduce spiking activity.

E l e c t r o e n c e p h a l o g r a p h y a n d N e u r o p s y c h o l o g y

EEG is a safe, painless, and relatively simple procedure. Its use in neuropsychology has been disappointing and limited historically by a lack of relationship between EEG parameters and behavior, specifically indices of higher

CHAPTER 2 | Methods of Investigating the Brain 43

44 PART ONE | Introduction

cortical functioning. In fact, complex EEG waveforms do not change much during different kinds of sensory input, but appear to be most sensitive to the general arousal level of the brain (Penfield & Jasper, 1954). This lack of con- vergence between EEG activity and behavior is probably caused by the fact that the EEG is a relatively nonspecific measure of the underlying brain activity. Thus, using the traditional eight-channel EEG, researchers have estab- lished only general relationships related to right versus left hemisphere differences, or to posterior and anterior re- gions of the cortex.

EEG does not give an account of what a person is thinking; rather, it tells us if the person is thinking. Over recent years, more sophisticated recording equip- ment and computer analysis have refined the EEG. In- vestigators have been using increased numbers of elec- trodes (64, 128, and even up to 256) placed over the patient’s entire head to correlate specific neural net- works involved in a particular neuropsychological task. Such enhanced EEGs have greatly improved signal quality and localization.

One invention that examines the more dynamic as- pects of electrophysiologic activity in the brain is brain electrical activity mapping (BEAM) (Duffy, 1989). CT shows the structure of brain tissue, and PET scans (see later) let researchers and clinicians examine the pattern of brain biochemistry and metabolism. BEAM, in contrast, uses computer technology to provide color-coded map- ping of the brain’s electrical activity in real time, that is, as quickly as it is occurring in the patient’s brain. In general, BEAM is nothing more than a way of enhancing the amount of information available on a standard EEG. Using an automated, integrated approach to EEG, the computer can calculate color-coded maps of electrical brain activity (Figure 2.10). Then it codes computed EEG parameters as topographic displays showing neuroelectric activity across the cortex while the patient is performing a neuropsychological task. BEAM is much more sensitive to electrical correlates of cognitive tasks than the tradi- tional EEG. Quantitative EEG analysis also has shown some promise in the diagnosis of clinical disorders such as dyslexia, a reading disorder.

Other improvements in EEG technology entail merg- ing the temporal resolution of EEG with the anatomic de- tail of MRI or the ability of PET to localize function. Such coregistration of different approaches to represent the functioning brain has resulted in multimodal approaches to neuroimaging, often providing new insights, as well as corroborating established findings. For example, schizo- phrenics show abnormal, less active BEAMs and PET scans (less metabolism) in the frontal regions of the brain.

E V O K E D P O T E N T I A L

A further electrophysiologic diagnostic test is evoked po- tential (EP; also called event-related potential [ERP] ). EP involves artificial stimulation of sensory fibers that, in turn, generate electrical activity along the central and pe- ripheral pathways, as well as the specific primary receptive areas in the brain. In contrast with EEG, EP is dependent on a stimulus and is most useful for assessing the integrity of the visual, auditory, and somatosensory pathways at specific regions of the brain. EEG technology can record the electrical activity in response to a stimulus or event. During the traditional EEG, the overall background ac- tivity of the cerebral cortex hides specific sensory stimuli. In EP, a computer makes it possible to visualize the changes in EEG responses to a specific stimulus (visual, auditory, or somatosensory), canceling out random elec- trical activity, but displaying electrical activity related to the potential evoked by the stimulus. The resulting EP consists of a series of positive and negative changes lasting for about 500 milliseconds after the stimulus ceases. The diagnostician analyzes the EP according to amplitude, la- tency, and the location of the specific brain region where the stimulus is processed.

B r a i n s t e m A u d i t o r y - E v o k e d R e s p o n s e

In brainstem auditory-evoked response (BAER), the ex- aminer presents clicks to each ear of the patient individu- ally via headphones. In response to the auditory stimulus, the auditory pathways generate an electrical signal along

Figure 2.10 Schizophrenic subject with history of seizures was examined by electroencephalography and magnetic resonance imaging (MRI) to observe extent of abnormal activity during a seizure (left). Color-coded brain electrical activity mapping (BEAM) presentation, with red indicating increased neuronal activity in the left frontal lobe (right). Results from BEAM superimposed over three- dimensional MRI cortex indicate abnormal discharge in left frontal lobe; note also widening sulci. See inside covers for color image. (Courtesy Dorota Kozinska, Ph.D., University of Warsaw, Warsaw, Poland.)

the central auditory pathways. EEG recording consists of five distinct waves that represent different latencies related to five nuclei groups where the auditory signal is being integrated. Although this delay is short, the examiner can measure and amplify it. Abnormal delays in responses, measured in milliseconds, often can pinpoint specific le- sions, but only along the pathways measured. The BAER can diagnose a malfunction of the auditory nerve at the cochlear nucleus, the superior olive, the lateral lemniscus, and the inferior colliculus (Figure 2.11).

In BAER, five characteristic waves are recorded. Wave I reflects activity of the vestibular nerve; wave II, the cochlear nucleus; wave III, the superior olivary complex; and waves IV and V, the pons or lower midbrain. Decreased ampli- tudes, the absence of a wave, or prolonged interwave laten- cies may point to abnormal brainstem responses.

Approximately 50% of patients with multiple sclerosis demonstrate a pathologic BAER typically at the level of the brainstem. BAER has also aided in diagnosing patients with acoustic neuromas (tumors). Research using EP indicates that schizophrenics, compared with healthy subjects, demonstrate an abnormality that may indicate a deficit in the “sensory gating” at the brainstem level, which may re- sult in impaired attention (Cullum et al., 1993). Research- ers can then confirm the finding using neuropsychological measures of attention, sustained concentration, and digit vigilance (e.g., digit cancelation). As with many of the other

imaging techniques featured in this chapter, there are inter- esting implications and a promising future in the interrela- tionships between neurophysiologic and neuropsychologi- cal indices of brain function. Neuropsychology in Action 2.1 reviews a case example using BAER technology.

V i s u a l - E v o k e d R e s p o n s e

Similar to the auditory-evoked response procedure, in visual-evoked response (VER), the examiner presents a vi- sual stimulus separately to each eye of the patient. An al- ternating light/dark reversing checkerboard pattern pro- vides the visual stimulus. EEG responses are recorded from electrodes over the parietal and occipital regions. One wave originates in the receptive visual cortex and is measured using EEG technology. A normal delay from the presentation of the visual stimulus to the registra- tion of the electrodes over the occipital cortex is about 100 milliseconds. Lesions along the visual nerve pathways result in abnormal delays, decreased amplitude of the recorded response, or both.

S o m a t o s e n s o r y - E v o k e d R e s p o n s e

In somatosensory-evoked response (SER), the examiner stimulates peripheral nerves via an electrode placed over the median nerve at the patient’s wrist. In addition, the examiner places three electrodes for purposes of measure- ment, with the first two measuring peripheral electrical activity of sensory pathways at the level of the patient’s arm and spinal cord. The third electrode is placed over the patient’s contralateral somatosensory cortex. Abnor- malities in amplitude or latencies at the first two points of measurement suggest peripheral nerve involvement. De- lays at the third wave suggest central sensory pathway in- volvement.

Figure 2.12 shows the graphic results of an SER exam- ination to evaluate somatosensory pathways in three dimensions. The technician delivers pulses transcuta- neously via a cup electrode to the median nerve at the patient’s wrist. He or she adjusts the intensity of the stim- ulus to determine a painless muscle twitch of the thumb. Collected data are then transmitted to a computer for analysis.

E L E C T R I C A L S T I M U L A T I O N

Historically, the electrical stimulation of nerve tissue is one of the oldest ways of investigating the living brain. Initially, scientists hoped that use of this technique could chart a precise map of the cortex that would outline, akin to phrenology, the behavioral and cognitive properties of the brain, specifically the topography of the cortex.

CHAPTER 2 | Methods of Investigating the Brain 45

Auditory cortex

Medial geniculate

+ + ––

Superior olive

Signal from right ear

Inferior colliculus Cochlear nucleus

Signal from left ear

Figure 2.11 Auditory pathways from receptors in the ear to the auditory cortex. Note the different nuclei along the pathways that form the basis for measuring integration delays, which can be measured and amplified using evoked potential and electroencephalographic technology. (Repro- duced from Kalat, J. W. [1998]. Biological psychology [6th ed., p. 184, Figure 7.6]. Pacific Grove, CA: Brooks/Cole, by permission.)

46 PART ONE | Introduction

Surprisingly, this technique, which has been largely con- fined to the primary and sensory areas of the cortex, has elicited few positive responses (the generation of a mea- surable behavior). However, scientists have found a great number of negative responses (disruption of function) as a result of electrical stimulation of the cortex.

For example, researchers easily demonstrated aphasia, a disruption of language functions, by numerous stimula- tions in different locations of the left hemisphere (Ojemann, 1980). More recently, neurologists have intro- duced electrical stimulation in the treatment of Parkin- son’s disease, based on the advances of stereotaxic opera- tions and knowledge of specific associations between electrical stimulation and subcortical regions of the brain. Obviously, because of its invasive nature, direct electrical stimulation of the brain is not a routine diagnostic proce- dure. Primarily, researchers use it experimentally in clinical cases for whom other interventions have not been suc- cessful. It can, however, provide great theoretical and clin- ical value in understanding the functions of the brain.

Figure 2.12 Sensory-evoked responses were averaged in a group of 10 healthy volunteers and superimposed onto the surface of a healthy brain. Images show electroencephalographic distribution of sensory-evoked potential to right median nerve, computed 18 milliseconds after stimulus presentation. See inside covers for color image. (Courtesy Dorota Kozinska, Ph.D., University of Warsaw, Warsaw, Poland.)

The patient is a 38-year-old man who was employed as a mechanic. Previously, he had worked as a tile layer for 6 months, during which he reported he was exposed to epoxy, alcohol, and other possibly toxic solvents.

Since then, he has reported dizziness and short-term memory loss. Physicians subse- quently diagnosed him with chronic solvent intoxication. An audiogram showed normal hearing bilaterally. An audiologist performed brainstem auditory-evoked response (BAER) testing. Specifically, the tester presented monaural click stimulation in each ear at 70 dB using click rates of 11.4 and 57.7 clicks/sec, with 2000 and 4000 repetitions, respectively. Absolute and interpeak latencies

in milliseconds at slow rate of 11.4 clicks/sec for waves I, III, and V were as follows: Note that the delays in milliseconds in- crease the further the signal is measured from its initial detection in the ear (e.g., at

nuclei I, the vestibular nerve, the latency is 1.5 milliseconds for the right ear; but at nuclei III, the superior olive, the signal was measured 3.9 milliseconds after it was intro- duced to the right ear). Also, note the symmetry between right and left auditory processing routes. BAER testing showed normal absolute and interpeak latencies at slow and fast rates in the right ear for waves I through III. Findings for the left ear demonstrated delayed absolute latencies for waves III and V at the fast and slow

rates. The audiologist measured interpeak delays at waves I to III for the slow and fast rates, and waves III to V and I to V for the fast rate. Interear absolute and interpeak latency differ- ences are within normal limits. Even though

there were minor variations among the brain wave recordings, the audiologist concluded that the test results suggested a normal BAER not consistent with brainstem dysfunction. Subsequent neuropsychological testing did show neuropsychological impairment on various tasks of new learning and memory. BAER, however, ruled out the possibility that those cognitive deficits were related to brain- stem impairment, and they were thus most likely related to cortical dysfunction.

N e u r o p s y c h o l o g y i n A c t i o n 2 . 1

C a s e E x a m p l e o f B r a i n s t e m A u d i t o r y - E v o k e d R e s p o n s e

by Eric A. Zillmer

I III V I–III III–V I–V

RIGHT 1.50 3.90 5.87 2.40 1.97 4.37

LEFT 1.60 4.14 6.10 2.54 1.87 4.42

E L E C T R O M Y O G R A P H Y

Electromyography (EMG) is the electrical analysis of muscles. In EMG, diagnosticians perform a nerve con- duction study of a specific muscle to diagnose neuromus- cular disorders. Patients undergoing EMG receive deep- needle stimulation of a muscle, which the technician measures electrophysiologically ventral (closer to the spinal cord) to the stimulation. The technician delivers an electrical potential to a muscle, using a wire inserted within a hollow needle. The electrical activity is amplified and displayed graphically via an oscilloscope. At the basis of EMG is that a relaxed muscle is electrically silent. Dur- ing voluntary contraction, muscle action potentials are present.

EMG is an important medical diagnostic technique that aids in diagnosing peripheral nerve damage, because it can isolate the dysfunction to a specific sensorimotor unit, including a motor or sensory neuron, neuromuscular transmission, or the muscle cell itself. The procedure also helps substantiate the presence of intact sensorimotor pathways—for example, when hysteria or malingering is suspected. If Sigmund Freud had had this diagnostic test available, he could have proved that Anna O., the patient of his first famous published case study, was truly hysteri- cal and did not suffer from a neuromuscular disorder as she complained. Anna O. actually was treated by Freud’s mentor Breuer, but Freud wrote up her case. Anna O.’s motor functioning was normal, even though she com- plained of partial paralysis. Freud suspected this normality anyway and concluded that Anna produced the paralysis of the arm hysterically, because of her unconscious wish to remain in the role of a patient and to receive daily visits by famous doctors. Nevertheless, using EMG technology, he could have diagnosed this much more efficiently, without needing to develop elaborate psychoanalytic theories.

A variation on the preceding techniques is recording an electric shock stimulus of a peripheral nerve and mea- suring the subsequent muscle contraction. This technique can test both motor and sensory nerves. Results assist in the differential diagnosis of muscle disease and peripheral nerve damage. For example, in carpal tunnel syndrome, a relatively common peripheral nerve disorder with accompa- nying sensory deficits in the first three digits and weakness of the thumb, there is a characteristic latency of muscle and nerve action potentials. Although most patients tolerate this procedure well, EMG is mildly uncomfortable be- cause pain accompanies the insertion of the needle into the muscle. Table 2.4 reviews the most popular electro- physiologic procedures currently in use.

Imaging of Brain Metabolism

Since the 1980s, researchers have developed tech- niques for analyzing the brain that focus on measuring para- meters of regional brain physiology. Such techniques are re- lated to the biological fact that neurons have an active metabolism that the cerebral blood supply provides. Specifi- cally, the delivery of oxygen and glucose to neurons depends on cerebral blood flow (CBF). If the metabolic needs of the active neurons are high, the rate of CBF is correspondingly higher. In this manner, neurologists can study regional blood flow while the patient is performing neuropsychological tasks. In contrast with CT, which provides a static represen- tation of brain structures, measuring regional blood flow pro- vides dynamic data on CBF and metabolic activity. The imaging of brain metabolism, therefore, permits a completely different approach to examining the brain.

R E G I O N A L C E R E B R A L B L O O D F L O W

Blood flow in the cerebral hemispheres varies with metab- olism and activity. It can be a sensitive index of the changes in cellular activity in response to cognitive tasks

Electroencephalography (EEG): EEG is one of the oldest brain-monitoring techniques. It measures the general electrical activity of the cortex. It is most useful in assessing, in real time, the overall arousal state in a person. Increased electrode placements and computer integration capabilities have resulted in high-resolution EEG and BEAM (brain electrical activity mapping), a promising assessment and research tool of the electrical activity of neu- rons.

Evoked potential (EP): EP, or event-related potential (ERP), is similar to EEG in that it assesses an electrical signal, but is related to a specific auditory (brainstem auditory-evoked response), visual (visual-evoked response), or sensory event (somatosensory-evoked response). Evoked potential assess- ment provides not an evaluation of general brain activity, but a millisecond- by-millisecond record of a specific sensory process.

Electrical stimulation: Researchers have used electrical stimulation of nerve tissue to empirically map pathways of the cortex. More recently, clinicians have introduced electrical stimulation in the treatment of Parkinson’s dis- ease. Direct electrical stimulation of the brain, an invasive medical proce- dure, is used only in those cases for whom other interventions or diagnostic procedures have not succeeded.

Electromyography (EMG): EMG is the electrical analysis of muscles, a diagnostic procedure useful in diagnosing peripheral nerve damage. The procedure, however, is uncomfortable because it requires insertion of a needle into the muscle.

Table 2.4 Electrophysiologic Procedures

CHAPTER 2 | Methods of Investigating the Brain 47

48 PART ONE | Introduction

(Andreasen, 1988). The amount of blood flowing through different regions of the brain can indicate the relative neural activity of that region. In the 1940s, researchers introduced a technique in which the patient inhaled ni- trous oxide (N2O), which circulates through the brain. Using this technique, scientists were able to measure total CBF per unit weight of brain per minute. The procedure, however, had disadvantages: It was invasive and could provide only a measure of overall CBF (Kety, 1979).

Lassen and Ingvar pioneered regional cerebral blood flow (rCBF) in living and awake subjects (Haeger, 1988). These researchers developed a special radioactive isotope known as xenon 133 (133Xe), which emits a low gamma radiation and stays in the bloodstream for approximately 15 minutes. Iso- topes are a form of chemical element with the same atomic number and position in the periodic table and nearly iden- tical chemical behavior, but with differing atomic mass numbers and different physical properties. Thus, isotopes are highly unstable. Initially, researchers injected this tracer intra-arterially into the bloodstream (via the internal carotid artery). The blood supply then carried the 133Xe to either hemisphere, over which researchers placed special scintilla- tion detectors that recorded the number of gamma rays the tracer emitted. In this manner, scientists could determine the rate of clearance of 133Xe from various regions of the brain. From this information, they could quantify the rCBF with considerable accuracy. CBF studies corroborate many brain–behavior relationships established in the literature

(Figure 2.13). Occipital areas are more involved when a subject examines moving stimuli, and auditory areas are involved when speech is initiated. The most interesting as- pects are anteroposterior comparisons of blood flow in the brain, rather than right–left differences. For example, the 133Xe technique reliably showed that the anterior brain regions have an increased rCBF in the resting subject (Gur et al., 1982).

One of the findings regarding rCBF relates to an ab- sence of measurable information in the deepest regions of the brain. Furthermore, the 133Xe technique can measure only one hemisphere at a time. In the 1970s, researchers developed a special noninvasive technique in which sub- jects inhaled an air-xenon mixture through a face mask. Using this technique, researchers can study both hemi- spheres at the same time. The amount of detail for mea- suring specific brain region blood flow depends on the number of detectors. Initially, this number was 8, then 16, and more recently, 254 detectors. A computer then analyzes the data and provides a color-coded visualization of the findings (Figure 2.14).

S I N G L E - P H O T O N E M I S S I O N C O M P U T E D T O M O G R A P H Y

A technique for the 3-D imaging of rCBF is single-photon emission computed tomography (SPECT). SPECT is similar to PET, which uses radionuclides, but unlike

Figure 2.13 Verbal encoding using positron emission tomography cerebral blood flow. Brain images show differences in regional blood flow between word encoding and averaged baseline for 23 healthy volunteers (top) and 23 patients with schizophrenia (bottom). Note activation in left and right prefrontal cortex for healthy volunteers and in right temporal and left occipital cortex for patients. Deactivation is visible in left precentral and occipital areas for healthy volunteers and in left precentral area for patients. The inability to activate prefrontal regions during encoding may underlie learning difficulties in patients with schizophrenia. See inside covers for color image. (Reproduced from Ragland, J. D., Gur, R. C., Raz, J., Schroeder, L., Smith, R. J., Alavi, A., et al. [2000]. Hemispheric activation of anterior and inferior prefrontal cortex during verbal encoding and recognition: A PET study of healthy volunteers. NeuroImage, 11, 624–633, by permission.)

CHAPTER 2 | Methods of Investigating the Brain 49

positron emission, SPECT does not require an expensive cyclotron (a device that can generate radioactive chemicals with a short half-life, also known as radioactive isotopes) for their production. Radiologists can label biochemicals of interest with a radioactive compound whose gamma rays can be picked up by detectors surrounding the brain. Using SPECT, it is possible to three-dimensionally image the distribution of a radioactively labeled contrast agent. As in CT, a computer analyzes the data and recon- structs a 3-D cross section of the emissions pattern. The tracer is injected intravenously and crosses into the brain tissue based on CBF. Using this technique, analysts can estimate CBF and blood volume. Researchers can study subjects undergoing SPECT while they are engaged in a neuropsychological task; however, the tracer has a long half-life, and it is difficult to keep a subject in the same mental state for a long period. A further limitation is that the tracer takes approximately 2 days to clear from the brain; thus, it is possible to obtain only a single ex- posure of the brain using SPECT. An advantage of SPECT is that it is relatively inexpensive (it is referred to as “the poor person’s PET”). A further advantage is that

individuals can be imaged while they are sleeping or se- dated, a useful option with young children or unmanage- able patients. Thus, imaging studies that require multiple conditions typically are investigated by using the more costly positron emission tomography (PET) technique.

P O S I T R O N E M I S S I O N T O M O G R A P H Y

Emission tomography is a new visualization technique that detects a diverse range of physiologic parameters, in- cluding glucose and oxygen metabolism, in addition to blood flow, by distributing a radioactively labeled sub- stance in any desired cross section of the head. The method of PET technology is intravenous injection of a radioactive tracer (specifically positron-emitting sub- stances) and subsequent scanning of the brain for radioac- tivity. In contrast with SPECT, the radioactive isotopes injected with the PET procedure have a short half-life and can attach to specific agents, such as glucose. Glucose, the body’s fuel, mixes with blood to reach the brain. As men- tioned earlier, the metabolism of the human brain varies in relation to its activity. The more active a specific area of the brain is, the more glucose it uses. Thus, the resting brain differs metabolically from the active brain. PET is the only procedure by which researchers can examine three-dimensionally the regional cerebral glucose use and oxygen metabolism in the living brain. PET analysts do not view the brain as a static structure, but investigate the dynamic properties of the brain (Raichle, 1983).

T e c h n i q u e

In the PET procedure, technicians administer radionu- clides intravenously that the subject’s brain tissue takes up. The radionuclei are unstable, because they have an ex- cess positive charge. When the radioactive tracer decays, it emits a positron that then travels a short distance (a few millimeters) before colliding with an electron. This colli- sion results in the emission of two photons traveling in opposite directions, generating energy that detectors around the scalp can measure (Figure 2.15). When two detectors calculate photon absorption at the same approx- imate time, the computer assumes they originate from the same collision and can then calculate the exact position showing neural “hotspots.” PET functions by calculating millions of counts from detectors and estimating their ori- gin. Using a subtraction technique, investigators can iso- late blood flow patterns related to specific mental tasks. Computed tomography allows researchers to calculate a count and the locations of these collisions (depending on the type of radionuclide used, such as carbon 11, nitro- gen 13, oxygen 15, or fluorine 18) to generate a visual

Figure 2.14 Topographic display of resting regional cerebral blood flow (rCBF) using an early system. Darker areas signal high rCBF; lighter areas suggest low rCBF. (Reproduced from Kalat, J. W. [1998]. Biological psychology [6th ed., p. 109, Figure 4.33]. Pacific Grove, CA: Brooks/Cole. Courtesy Karen Berman and Daniel Wein- berger, National Institute of Mental Health.)

50 PART ONE | Introduction

representation of radionuclide uptake. In this manner, re- searchers can obtain varied physiologic parameters, includ- ing glucose and oxygen metabolism, blood flow, and re- ceptor density of neurotransmitters for specific anatomic regions of interest (ROIs). For example, PET has shown different glucose uptake during various cognitive tasks (Figure 2.16). The major disadvantage of using PET clin- ically is the cost involved, principally related to the need for an expensive cyclotron, which can produce the short- lived radioactive isotopes. As a result, PET technology often is available only in large medical centers associated with research institutes.

P o s i t r o n E m i s s i o n T o m o g r a p h y a n d N e u r o p s y c h o l o g y

Can PET technology detect changes that occur during cognitive activity? Or are the changes in metabolic activity

Figure 2.15 An early version of a position emission tomogra- phy scanner in which detectors around the scalp measure energy caused by the emission of photons. (© Burt Glinn/Magnum.)

Resting state Music Cognitive

Visual Language Memory

Auditory Language and music Motor

Figure 2.16 Positron emission tomography images obtained during different cognitive tasks. Regions of highest metabolism are gray. (Reproduced from Kalat, J. W. [1998]. Biological psychology [6th ed., p. 108, Figure 4.31]. Pacific Grove, CA: Brooks/Cole. Courtesy E. Phelps and John C. Mazziota, UCLA School of Medicine.)

CHAPTER 2 | Methods of Investigating the Brain 51

too small to be detected? Measuring glucose metabolism rate is a more direct measure of neuron function than is CBF. New tracers with a shorter half-life (such as positron-labeled oxygen, O15) have led to investigations of neuropsychological functions using PET, often with remarkable findings. Researchers use O15, which readily crosses the blood–brain barrier, as a reference point for approximate blood intake of various regions in the brain. PET research demonstrates that the effects of cognitive effort on regional brain activity can be detected and measured (e.g., a verbal task corresponds to the left hemisphere and a spatial task to the right hemisphere). PET is also sensitive to individual differences, such as sex, that affect the direction and degree of hemispheric specialization for specific neuropsychological abilities. Thus, studies using imaging technology indicate that there is a relationship between brain activity and behavior, and that PET can detect these associations (Gur, Levy, & Gur, 1977).

A major finding using PET technology is that meta- bolic activity is suppressed in patients with a history of head trauma, brain tumors, and stroke, even though structural representation of the brain, using MRI or CT, suggests intact brain anatomy. Thus, metabolic imaging of the brain can lead to a clearer understanding of the functioning brain, specifically where the pathology is un- clear, as in schizophrenics or epileptics. Although PET re- mains primarily a research tool because of its cost, it has proved to be an important technique in measuring physi- ologic activity in the normal and damaged brain at rest or while engaging in behavior.

One of the most interesting research aspects of PET concerns subjects performing various mental activities. Experimenters have taken PET scans of female and male adult brains when subjects were either resting or solving a rotating figure problem, a rather difficult spatial puzzle (Gur et al., 1982). Female subjects not only scored lower than male subjects, but there was a sex difference on the PET results. Even though the PET scans were not differ- ent while subjects were resting, when subjects were solv- ing the rotating figure problem, male brains showed max- imum neural activity in the right frontal area, whereas female brains demonstrated maximum activity in the right parietotemporal lobe. This suggests that men out- perform women on the rotation problem, and that there may be a neural reason for this. There are, of course, tasks at which women outperform men. For example, women are generally faster on tests that require perceptual speed and score higher than men on a test of verbal fluency in which one must list as many words as one can that begin with the same letter (Lezak, Howieson, & Loring, 2004).

PET studies have generated much controversy regard- ing sex differences in the brain. Are there really functional differences in the brain that arise from being male or female? The most recent studies indicate there are. Some theorists suggest an evolutionary perspective by which sex differences in the brain might have come from different skills needed by early humans. Male individuals with good spatial skills, they argue, had an advantage in hunt- ing, and female individuals with good communication skills had an advantage in child rearing (Springer & Deutsch, 1993).

But researchers have not established whether sex dif- ferences are related to differences in socialization and learning experiences that are different for male and female individuals, or whether the brains of female and male in- dividuals are organized differently and, therefore, func- tion differently. This controversy is not easily decided, but PET may shed light on this puzzle. Table 2.5 reviews the most frequently used imaging techniques based on brain metabolism.

Magnetic Imaging Procedures

M A G N E T I C R E S O N A N C E I M A G I N G

Magnetic resonance imaging (MRI) is based on the work of Felix Bloch and Edward Purcell, who won the Nobel Prize in physics in 1952 for their development of a new method of nuclear magnetic precision measurement. This led to the medical application of this technology called MRI during the early 1970s. Whereas CT uses penetrating X-ray radiation and PET uses radioactive

Single-photon emission computed tomography (SPECT): SPECT measures blood flow, a correlate of brain activity. Because the radioactive tracer takes almost 2 days to be eliminated from the body, researchers cannot use SPECT to monitor the brain’s mental activity “moment to moment.”

Positron emission tomography (PET): PET tracks blood flow, which is associated with brain activity. It is primarily used to assess brain physiol- ogy, including glucose and oxygen metabolism, and the presence of specific neurotransmitters. The disadvantages of PET are that it is expen- sive, involves radiation, and renders low spatial resolution and data must be averaged over time (PET is not based on real time). The most promising use of PET has been its combined application with structural imaging techniques, which can provide a remarkable tool for mapping brain loca- tion and function.

Table 2.5 Imaging of Brain Metabolism

52 PART ONE | Introduction

“Eric, your brain looks OK!” announces Dr. Jonathan “Yoni” Nissanov, Research Professor of Biomedical Engineering and Science at Drexel University. It is 11:30 P.M., and I am lying in a magnetic resonance imaging (MRI) scanner at Drexel College of Medicine in Philadelphia. Yoni has reserved the million-dollar diagnostic tool for research he is conducting on functional imaging. I have agreed to be one of his test subjects. Because using the machine is expensive, research time is allotted only at night.

MRI is a relatively new diagnostic proce- dure that has been available for routine brain imaging only since the mid-1980s. Therefore, I am not surprised by the up-to-date, modern look of the facility, a space age–like control station. Yoni and his research assistant, who are operating the complex computerized machinery, greet me. My brain will be exposed to a strong magnetic field, so I must remove all metals that are on me, including my credit cards. The procedure is completely safe, I am being reassured. Yoni goes through his proto- col: “You don’t have a pacemaker? You don’t have an aneurysm clip? Is there any shrapnel in your head or metal plates in your skull?” Finally, Yoni asks, “You know the risks?” Yes, as a neuropsychologist I know them all too well. The risks relate to the possibility that I may find out something about my brain that I do not necessarily want to know. The MRI will produce textbook-quality anatomy pictures of my brain. Although the probability is small, there is the outside chance that the diagnostic procedure may reveal a tumor or some other abnormality of my brain. Just a month ago, one of my research colleagues learned that she had a malformation of her venous system in her brain. She was also one of Yoni’s re- search participants. I repress these thoughts as I enter the imaging suite. The layout of the MRI scanner consists of two rooms, which are connected via intercom. The first one is the control room, which features a rectangular window overseeing the second larger room, where an oversize, doughnut-shaped machine is placed. The control room has an assortment

of electronic gadgetry, the centerpiece being a large TV-type console that controls the imager and provides immediate visual feedback of the results. This is where Yoni and his assis- tant will remain during the procedure.

I lie on a stretcher-like surface, and at the push of a button I am whisked via electrical motors headfirst into the center of the large electromagnet. Yoni asked me earlier whether I was claustrophobic, and now I understand why. There is only about an inch of space around my head, which is placed approxi- mately 4 feet within the center of the imager.

The small confines of the MRI machine are a significant problem for patients who suffer from claustrophobia. I have been told that in the past such people were referred to the animal MRI at the Philadelphia Zoo, which can accommodate large animals, before “open” MRI was developed. I am grateful there is a small mirror positioned in an oblique angle right over my head, which gives me the illusion of space, because I can look out through the narrow opening toward my feet. I can see Yoni behind the window in the control room. “OK, we’re ready to start.” His voice reverberates through the intercom as a loud clicking noise begins.

For clinical diagnostic studies, the procedure takes about 15 minutes, during which the patient must remain as stationary as possible. But Yoni wants to go through a series of experiments during which I, on command, will clench my fists, right and left alternately, to see how the MRI machine detects functional activity in my brain. Yoni will then superimpose the functional MRI data, which reflect changes in blood oxy- genation in my motor cortex, over the struc- tural images of my brain. So I must keep my head still all the time. Yoni constantly re- minds me of this over the intercom. I’ve agreed to be in the imager for more than 90 minutes. Given the confines of the space and the incredibly loud, jackhammer-like, stac- cato noise, all of a sudden this does not seem like such a good idea, after all. The first task for Yoni is to establish a traditional MRI

study of my brain, a baseline. The loud clicks I hear are bombardments of radiofrequency (RF) on my brain, which has been placed under a high magnetic field. The radio fre- quencies realign the magnetic fields of billions of hydrogen protons in my brain. The MRI machine is tuned into the frequencies that the water molecules in my brain emit after the external RF stops. The deflection or realignment of this hydrogen map to the magnetic field can be detected, amplified, and recorded, and is the basis of the MRI process. Amazingly, I do not feel anything.

To be honest, I’ve thought about my MRI results for some time. As a neuropsychologist, I know that my personality, my intellect— essentially who I am—depends on the integrity of my brain. What if they find something wrong? Wouldn’t a small change in the organi- zation of my brain almost guarantee an altered sense of my reality? Haven’t I been acting rather eccentric lately? How would they break the news to me? Would a team of summoned doctors rush in to announce, “There is a problem with your brain”? I find myself wondering how much training in psychology physicians receive for sharing diagnostic test results with patients and their families.

After 15 minutes, Yoni steps into the imaging room to deliver his personal analysis of my brain. Although Yoni is a biomedical engineer, I am greatly relieved when he announces that my brain, on visual inspec- tion, looks “OK.” I have to remain in the increasingly uncomfortable same position for the next 75 minutes as Yoni goes through a series of studies. But now I am excited about the thought of actually seeing anatomic pictures of my brain for the first time. I can hardly wait until the procedure is over and Yoni shows me the coronal images on the control screen. Yes, everything is there, lateral ventricles, brainstem, cerebellum, and most importantly, my frontal lobes! I am a happy neuropsychologist as I leave the hospital at 1:30 A.M. with memory stick in hand, on which Yoni loaded an electronic copy of my brain images.

N e u r o p s y c h o l o g y i n A c t i o n 2 . 2

U n d e r g o i n g a M a g n e t i c R e s o n a n c e I m a g i n g P r o c e d u r e

by Eric A. Zillmer

CHAPTER 2 | Methods of Investigating the Brain 53

isotopes, MRI is based on a fundamentally different process, namely, that the hydrogen nucleus, which is present in high concentration in biological systems, generates alterations in a small magnetic field, which can be measured (Neuropsychology in Action 2.2). MRI provides pictures of anatomy superior to CT (Fig- ure 2.17), particularly for diagnosing underlying patho- logic disorders.

T e c h n i q u e

The principal technique involved in MRI is based on patterns similar to the pattern a magnet makes on sur- rounding metal flakes. The metal flakes align themselves according to the magnetic field. Similarly, when the head is subjected to a strong magnetic field, hydrogen pro- tons magnetize and align in the direction of the mag- netic field. A proton, which is an elementary particle present in all atomic nuclei, has a positive charge equal to the negative charge of an electron. A strong radio- frequency (RF) signal applied at a right angle to the magnetic field can alter the alignment of the hydrogen protons. This radio wave sets the aligned hydrogen atom oscillating. The RF specifically selects only aligned hy- drogen atoms; other atoms will not react. Once the RF ceases, the hydrogen “spins back” to its original

orientation as determined by the magnetic field, which remains active.

The emission of a small RF signal accompanies this deflection, or spin back to equilibrium. That is, the re- turn of the hydrogen atoms to their previous orientation generates a magnetic field, which researchers can am- plify, measure, and record. Computer analysis can then present a visualization of hydrogen density in various re- gions throughout the brain. Because water is present in most biological tissue, this procedure can generate a strikingly accurate picture of the brain, or any other anatomy.

The principle of MRI is that the hydrogen atom res- onates as a result of the combined effect of the radio waves and the magnetic field. This frequency is specific for a given nuclear species in a magnetic field and allows scientists to determine the origin of a given RF signal in space. For ex- ample, one measure of RF signal amplitude is hydrogen density. Thus, variation of number of protons returning the RF signal is unique for different biological molecules, in- cluding fat, brain tissue, bone, and blood. This variation contributes to the MRI contrast, allowing spatial detection of signal data in 3-D space. As a result, researchers can accu- rately calculate brain tissue densities and can generate a computer-constructed image, which is so spatially precise that it can visualize structures as small as 1 mm.

There is one more major determinant of signal ampli- tude, namely, the magnetic relaxation times, also known as T1 and T2. These are the time intervals necessary for a nucleus to magnetize when placed in a magnetic field and the delay before returning to its original equilibrium. Protons with short T1 values (solids) emit higher signal intensities and appear white on the MRI, whereas those with longer T1 values (fluids) appear dark. T2 measures the loss of the magnetic orientation (or spin) after RF perturbation. On T2-weighted images, nuclei with rela- tively long T2 values retain their signal strength, emit a higher intensity signal, and appear brighter. Sometimes, the difference in T1 and T2 values may provide addi- tional visual information, such as differentiating tumors and surrounding edema (swelling). More recently, 3-D images of the brain have been produced, based on MRI technology. MR images are used as a starting point, specifically, MRI pixels in the X-Y plane resolution of the subject’s original images. Using mathematic algorithms, a computer can generate a surface model of the scalp, as well as the brain. The algorithms assume that a rigid body transformation of objects can be matched. In this way, it is suitable to align MRI data sets into one whole object. The result is an exact model of the brain in three dimensions (Figure 2.18).

Figure 2.17 Normal magnetic resonance image (coronal view). Note the symmetry of the lateral ventricles and den- sity differences between white and gray matter in the cortex. (Courtesy Eric Zillmer.)

54 PART ONE | Introduction

Blood oxygen level dependent (BOLD) magnetic resonance imaging (MRI) has become synonymous with functional MRI (fMRI) and, largely because of its accessibil- ity, has grown to be the most widely used functional neuroimaging technique in the examination of human behavior. Put simply, fMRI is the measurement of blood flow in response to neural firing. The fMRI signal is based primarily on the ratio of oxyhemoglo- bin to deoxyhemoglobin expressed as a hemodynamic response function, and this signal is influenced by multiple factors including blood flow, blood volume, and vessel size. fMRI provides excellent spatial resolution (on the order of millimeters) and good temporal resolution (about 2000 milliseconds). It is important to emphasize that fMRI measures neither oxygen perfusion nor neural firing, but the hemodynamic response function that it does measure is reliable and well characterized.

Since the advent of fMRI, neuropsy- chology has been shaped and guided by noninvasive means of accessing informa- tion about the brain. Understanding brain and behavior relationships has profited greatly from continued MRI advancements, including novel sequences that provide information about the structural, neu- rometabolic, and functional status of the brain. The development of neuroimaging methods that integrate information about both structural and functional brain organi- zation in many ways has ser ved to empha- size the role of neuropsychology in the clinical and cognitive neurosciences. An impor tant reason for the integration of neuropsychology and neuroimaging is that information about brain status achieved through various imaging techniques is of ten difficult to interpret without a behav- ioral reference point; that is, the critical dependent variable is, and always has

been, human behavior. In functional imag- ing work, the role of the neuropsychologist is to provide exper tise for the cognitive, motor, or sensory paradigm development, as well as the out-of-the-scanner inter view and assessment. These assessment com- ponents are critical to linking information about the cerebral substrate to human behavior. For these reasons, the neuropsy- chologist has become an impor tant figure within many multidisciplinary teams using neuroimaging techniques to better under- stand the effect of pathophysiology on human behavior. Moreover, although many novel imaging techniques, such as fMRI, are only beginning to be used clinically, to date, the field of neuropsychology has played an impor tant role in the application and validation of these techniques in neurologically impaired samples (Figure 2.19).

N e u r o p s y c h o l o g y i n A c t i o n 2 . 3

N e w F r o n t i e r s i n F u n c t i o n a l M a g n e t i c R e s o n a n c e I m a g i n g

by Frank Hillary Ph.D., Pennsylvania State University

C l i n i c a l U s e

MRI of the central nervous system has provided behav- ioral scientists and neuroradiologists with revolutionary quality of brain images in all planes (coronal, sagittal, and horizontal). As a result, MRI has become an im- portant diagnostic tool for detecting disease processes. This usefulness is related to that MRI is sensitive to tissue alteration, including those seen in diseases associ- ated with demyelination (such as multiple sclerosis), hemorrhage (bleeding), and tumor. Because of its in- creased clinical use, MRI has become readily available, and mobile units have even been built that travel to remote hospitals.

MRI is a complex procedure based, in part, on molecu- lar physics and mathematics of imaging 3-D objects in space. The principles underlying MRI sound complicated, and they are. Its scientific basis lies in physics and com- puter science; thus, an exact understanding of the proce- dure is not necessary for the neuropsychology student. But

Figure 2.18 Three-dimensional geometric align- ment of scalp surface. See inside covers for color image. (Courtesy Dorota Kozinska, Ph.D., University of Warsaw, Warsaw, Poland.)

neuropsychologists are participating in the research using this technology because of their expertise in the functional aspects of neuroanatomic structures, their knowledge of neuropsychological tests, and their background in scien- tific methodology and design.

F u n c t i o n a l M a g n e t i c R e s o n a n c e I m a g i n g

Traditional MRI measures the frequencies of magneti- cally perturbed water molecules and provides a structural representation of the brain. More recent advances have focused on detecting frequencies emitted from other mol- ecular species associated with cerebral metabolism. Efforts have concentrated on reconstructing images from glucose metabolism and changes in blood oxygenation. A recent finding is that oxygenated blood has slightly different mag- netic properties that special-sequence MRI scans can de- tect. In this manner, researchers can measure motor activ- ity and neuropsychological tests. The data from functional MRI (fMRI) can then be superimposed (cross-sectioned

or co-registered) over the structural MRI for a precise mapping of structure and function. This combined use of MRI and fMRI may revolutionize the study of the acti- vated brain, because it can provide almost continuous real-time data on cerebral activity (Cohen, Noll, & Schneider, 1993).

The advantage of fMRI over SPECT, PET, and CT is that there is no radiation exposure. Therefore, fMRI is less invasive. However, scientists do not completely know the effects of exposure of the brain to high magnetic fields, which is higher in fMRI because molecules other than hydrogen are assessed. Furthermore, resolution of fMRI is better than in PET images, which are recon- structed from thousands of calculations averaged over 90 seconds, the half-life of the tracer. In contrast, fMRI can provide independent images every few seconds or as fre- quently as the RF is turned on and off. This capability gives investigators a better picture-by-picture account of the neural correlates involved in specific tasks (Neuropsy- chology in Action 2.3).

CHAPTER 2 | Methods of Investigating the Brain 55

Figure 2.19 Functional magnetic resonance imaging signal response (percentage change) from normal adult (a–c) and patient with severe traumatic brain injury (TBI) (d–f). (a, d) Motor response (i.e., finger tapping): note focal activation in healthy subject and disorganization activation in TBI patient. (b, e) Normal cerebral blood flow: note diminished cerebral blood flow in patient. (c, f) Corrected motor response based on baseline cerebral blood flow: note less organized activation in patient. See inside covers for color image. (Courtesy Frank Hillary, Ph.D., Pennsylvania State University.)

56 PART ONE | Introduction

M A G N E T O E N C E P H A L O G R A P H Y

Magnetoencephalography (MEG) involves measurement of changes in magnetic fields that are generated by under- lying electrical activity of active neurons. Neuronal activity generates not only electrical fields but also magnetic fields. When neurons fire, the magnetic changes result- ing from the electrical fields, which reflect neural activ- ity, can be measured. Recording the magnetic fields that accompany the electrical activity of neurons is known as MEG. MEG is the magnetic equivalent of EEG. The magnetic field of neurons is small, and it requires special superconducting coils, housed in elaborate magnetically shielded rooms, to detect and measure the weak magnetic fields. This specialized detector is called the superconduct- ing quantum interference device (SQUID), which is capa- ble of measuring tiny magnetic fields of the brain. MEG traditionally has used systems with one to seven SQUID sensors, although recent technology has made larger sensor arrays possible. The response of the brain to different stimuli, similar to the EP technique, results in measur- able alterations in the magnetic field. A computer then can calculate a 3-D location based on the source of the magnetic field in the brain. The physical location of the magnetic source can be improved by projecting the MEG onto MR images. MEG is more elaborate than EEG, but it can better localize the source of activity using isocon- tour maps of magnetic fields.

MEG is expensive and relies on complex technology; the SQUID is immersed in liquid helium to keep the sys- tem at a low temperature, which is necessary for super- conductivity. Currently, MEG is experimental and is not used for routine clinical diagnostic studies, although MEG is an added diagnostic tool in epilepsy, because it provides more accurate seizure diagnosis than EEG tech- nology (Hari, 1994). Table 2.6 reviews current magnetic imaging procedures.

Cerebrospinal Fluid Studies: Lumbar Puncture

The lumbar puncture, or spinal tap, is a medical technique to collect a sample of CSF surrounding the spinal cord for diagnostic study. The patient lies on his or her side in a fetal position, and the physician adminis- ters a local anesthetic. A long (3- to 3.5-inch) puncture needle is inserted perpendicular between the third and fourth (or fourth and fifth) lumbar vertebrae. The needle penetrates the dura and enters the spinal canal. Then the physician collects CSF and checks CSF pressure (normal

range � 100 mm). In some cases, the physician adminis- ters radiopaque material or medication through the nee- dle, in which case, the CSF withdrawn is equal to the volume of fluid introduced. At the end of the procedure, the physician withdraws the needle quickly. The lumbar puncture is a relatively easy and routine way by which to obtain a CSF sample. Yet, lumbar puncture is invasive and painful, requiring a local anesthetic, and infection is always a concern.

On visual inspection, normal CSF is colorless and does not coagulate. After a subarachnoid hemorrhage (for ex- ample), the CSF may be stained with blood. Technicians typically examine the CSF sample in a laboratory for cell count, glucose levels, and protein content to detect CSF abnormalities. The lumbar puncture is a useful diagnostic aid for a variety of neurologic conditions in which the CSF has been “contaminated,” including acute and suba- cute bacterial meningitis, viral infections, brain abscess or tumor, multiple sclerosis, and hemorrhage.

Behavioral Examinations

N E U R O L O G I C E X A M I N A T I O N

The neurologic examination is a routine, introductory eval- uation that a neurologist performs. A neurologist is a physi- cian who has specialized in evaluating and treating neuro- logic disorders. Although there are many variations, in principle, the neurologic examination involves a detailed his- tory of the patient’s medical history and a careful assessment of the patient’s reflexes, cranial nerve functioning, gross movements, muscle tone, and ability to perceive sensory

Magnetic resonance imaging (MRI): MRI can provide the most detailed images of brain structures. The obtained images are of excellent clarity, but individuals who have metal in their bodies are contraindicated for the procedure. Recent research focuses on the functional mapping of blood flow or oxygenation using MRI. The advantage of functional MRI over other functional procedures such as positron emission tomography is that it provides good spatial resolution and images in short time periods or “real time.”

Magnetoencephalography (MEG): MEG is the magnetic equivalent of electroencephalography, in which a computer can calculate a three- dimensional magnetic field of the brain. Superconducting quantum interfer- ence devices detect the small magnetic fields in the brain that are a marker of neural activity. A disadvantage of MEG is that it is expensive and not readily available for clinical applications.

Table 2.6 Magnetic Imaging Procedures

CHAPTER 2 | Methods of Investigating the Brain 57

neuropsychological techniques. In addition, no imaging tool yet developed can indicate how patients will adapt with a specific neurologic disorder, whether they will be able to work, or what quality of life they will have.

New Advances in Imaging Techniques: Mapping the Brain

S U B T R A C T I O N P R O C E D U R E S

Researchers often use the subtraction technique in imag- ing studies to isolate brain characteristics that are relevant during a specific neuropsychological task. In principle, the procedure uses two sets of data. The first set is obtained using the control condition. For example, to use PET in studying the neuronal aspects of a calculus task in the con- trol condition, researchers would ask subjects to recite numbers that have no meaningful relationship to each other. In the task condition, researchers obtain brain im- ages while subjects are performing calculus problems. The logic behind reciting numbers in the control task is that both tasks involve the neural mechanism of using num- bers, but only one condition uses numbers in a meaning- ful way. After researchers subtract the image of the noncal- culus condition from the second image they obtained during the calculus condition, the new picture should show brain regions involved in the mathematical effort of using numbers in meaningful relationship to each other.

I M A G E A N A L Y S I S A N D Q U A N T I F I C A T I O N ( T H R E E - D I M E N S I O N A L )

Recent advances in computer software have allowed 3-D computer reconstruction of specific brain structures. Be- cause of recent advances in calculating volumetric analy- sis of specific brain structures, scientists applied segmen- tation methods to construct 3-D images, to visualize a specific structure of the brain (such as ventricles) or a known pathology (such as hemorrhage). Such 3-D im- ages advance the understanding of pathologic conditions, as well as brain structures, because scientists can now vi- sualize the site of the lesion from any angle or perspective. The ventricular system is difficult to appreciate in a 2-D perspective, but in a 3-D model, it can be easily visual- ized. More recent quantitative imaging techniques have automated the evaluation of definable ROIs throughout the brain. Because normative data are not yet available, serial quantitative image examinations of individual cases have proved useful. The correlation between quantitative neuroimaging findings and neuropsychological indices of brain function has been only moderate.

stimuli. The neurologic examination typically includes a number of brief cognitive procedures. These include lan- guage function, memory (e.g., remembering digits or mem- ory for words), visuospatial function (drawing), attention (reverse counting), and mental status (i.e., an assessment of the patient’s understanding of where he or she is, what time it is, who he is, and why he is there). The neurologic exam- ination is not as detailed as a neuropsychological evalua- tion, because it is difficult to obtain an accurate compre- hensive assessment of higher cortical function during a brief examination. More recently, a special focus in neurology, on behavior and higher cortical function (behavioral neu- rology), has overlapped more with neuropsychology. In general, the domains previously held by neurologists and by neuropsychologists are getting much closer, and both disciplines have much to learn from each other.

N E U R O P S Y C H O L O G I C A L E V A L U A T I O N

Whereas neurologists are interested in changes in the ner- vous system that occur within the clinical context (such as lesions, disease, and trauma), neuropsychologists are primarily interested in higher cognitive functioning. Luria (1990) suggests that neuropsychology is the most com- plex and newest chapter in neurology, without which modern clinical neurology would be unable to exist and develop. The neuropsychological evaluation provides additional information about the patient’s health and is used, in conjunction with other pertinent information, for diagnosis, patient management, intervention, rehabil- itation, and discharge planning. Chapter 3 gives a detailed account of the role of the neuropsychological evaluation, its purpose, and its applications.

After reading this chapter, the student may wonder whether modern imaging technology will soon replace neu- ropsychology. We strongly suggest that imaging technolo- gies and neuropsychology are compatible. In fact, we are now in an era in which data from CT, for example, should be used routinely with neuropsychology information. Note that even though modern imaging technology has had spec- tacular success in depicting the brain’s anatomy, neuropsy- chological findings appear more sensitive to the progression of degenerative diseases than either CT or MRI. Modern imaging technology is most useful in concert with neuropsy- chological studies. For example, consider a CT scan that shows a large, marble-size tumor in the patient’s right pari- etal hemisphere. From a neurobehavioral view, we may make certain assumptions about what cognitive functions may be compromised, based on the CT data. Such assump- tions, however, would be only hypothetical, and one would need to assess the precise neurobehavioral sequelae using

58 PART ONE | Introduction

One procedure focuses on using volumetric MRI analyses to estimate brain volume and ventricle-to-brain ratio (VBR). A normal VBR is approximately 1.5%; that is, about 1.5% of a normal, healthy, adult brain is dedi- cated to CSF. Increased VBR has been particularly consis- tent in subjects after traumatic brain injury, who have much higher VBR ratios, up to 4% (Johnson, Bigler, Burr, & Blatter, 1994). This increase is related to brain atrophy after the injury to the brain, with a correspond- ing increase of its ventricular space.

Furthermore, researchers can now digitize and super- impose serial MRI sections to create a 3-D picture of the entire head or brain or specific brain structures. This cur- rent technology can use 3-D representation of any isolated brain structure (Bigler, 1996). Other methods, including SPECT, PET, quantitative EEG, and MEG, can also be used to generate 3-D images.

After establishing image analysis and quantification, the next step was to address the interfacing of different imaging technologies to further explore structure and function in brain-behavior relationships. For example, the high detail of MRI-based images of the brain can be superimposed over images derived from those obtained by PET. In this way, re- searchers can examine both structure and function simulta- neously. As technology develops further, it will be possible to increase the combination and integration of imaging techniques. Thus, one key focus in current imaging research is integrating multifaceted data to understand regional brain function. In this manner, topographic information from CT and MRI about the integrity of brain regions can com- plement information on regional brain physiologic activity derived from EEG, SPECT, and PET (Figure 2.20). How- ever, as with any research, neuropsychological theory is needed to guide explorations of how brain activity relates to behavior (Neuropsychology in Action 2.4).

F U T U R E D I R E C T I O N S

One of the greatest uncharted territories before the human species is the functional mapping of its own brain. Cartographers are scientists who use powerful technology to examine the living brain right through the skull. The task is formidable: 100 billion neurons with a seemingly infinite number of interconnections. The human brain is the most complex structure known in the entire universe. To make sense of this 3-pound “jungle” of cells, will it be enough to take pictures of the brain? Any new approach to brain mapping must move beyond simply visualizing structure. The challenge before the cartographers of the new millennium is to map function; that is, what brain structures do what, and when. It is true that neuropsy-

chologists have identified many regions that specialize in particular cognitive jobs, but they have gained much of this knowledge from people with brain pathology or in- jury. The new imaging technologies are capable of exam- ining the normal, healthy, functioning brain. We stand on the brink of learning how the living, normal brain per- forms sophisticated mental functions.

The most exciting use of neuroimaging, we propose, is in combination with neuropsychological procedures. That neuroimaging measures and neuropsychological studies depend on shared neuroanatomy needs to be studied fur- ther. Thus, it is likely that scientists will combine mea- sures of neurophysiology and neuropsychology to unlock the secrets of how the human brain functions. Further- more, imaging technologies will continue to be refined, with specific regard to the functional and structural as- pects of the brain. It will soon be possible to perform biochemical dissections on the human brain, to pinpoint the concentration of a neurotransmitter receptor within the brain of a living subject. It will be possible to examine the effects of treatment of diseases known to be associated with disturbances in neurotransmitters or its receptors (e.g., schizophrenia, Parkinson’s disease, and Huntington’s chorea).

New advances will also demonstrate brain activity from moment to moment in real time with precise localization.

Figure 2.20 Sensory-evoked response examina- tion with magnetic resonance imaging. With this technique, electrical activity and anatomic detail can be co-registered for clinical analysis. Image includes visualization of right frontal tumor. See inside covers for color image. (Courtesy Dorota Kozinska, Ph.D., University of Warsaw, Warsaw, Poland.)

CHAPTER 2 | Methods of Investigating the Brain 59

Contemporary neuroimaging represents a remarkable scientific breakthrough. Before the advent of computed transaxial tomogra- phy (CT) scanning around 1975, there was no way to visualize actual brain structure except

during neurosurgery or in cases in which skull trauma exposed the brain. In one technique, pneumoencephalography, techni- cians would remove cerebrospinal fluid (CSF) from the brain, replace it with air, and

take a standard X-ray image. But that method only outlined the ventricular system (internal cavity) of the brain and did not provide any actual direct image of brain tissue. Also, radioisotope scans would

N e u r o p s y c h o l o g y i n A c t i o n 2 . 4

D i a g n o s t i c N e u r o i m a g i n g a n d N e u r o p s y c h o l o g y

by Erin D. Bigler Ph.D., Professor of Psychology, Brigham Young University

Figure 2.21 Dr. Erin D. Bigler and imaging examples. (Courtesy Erin Bigler, Brigham Young University.) (continued)

60 PART ONE | Introduction

measure uptake of a radiopharmaceutical, but could not visualize actual tissue. Thus, in the early history of neurology and neuropsy- chology, the clinician had to rely on the powers of inference to make conclusions about underlying brain pathology and neuro- logic disorders, because the brain could not be viewed directly. Before the current state of neuroimaging, knowing the patient’s history, an in-depth knowledge of brain anatomy and pathology, and examining the patients on standard neurologic and neuropsychological tests allowed clinicians to make an inference about particular brain regions that might be involved (damaged) or what type of disease process might be present. All this changed radically with the advent of modern brain imaging techniques. The CT scan was the forerunner for the development of magnetic resonance imaging (MRI), which uses an entirely different technology. In scanning with CT technology, an X-ray beam passes through the head and various computer computations

create an index of tissue density. These tissue density values are then used to form an image of the brain on a gray scale. MRI uses radiofre- quency waves that permit a reconstruction of the brain, essentially mimicking gross anatomy. The beauty of MRI is that scientists can use it to acquire images of the brain in any plane and in any angle or orientation.

For example, the first set of images in Figure 2.21 (top right) are of my brain (that’s me, holding a brain, in the top left). Viewing my brain in the horizontal (axial) position, you can see that the brain is a symmetric organ; therefore, a view of one side should mirror the other side. In com- parison, just below my MRI scan is one from a patient who sustained severe traumatic brain injury (TBI) in a motor vehicle acci- dent, with penetrating damage to the frontal lobe. The lower left-hand quadrant shows the three-dimensional MRI recon- struction of the person’s head. You can see the residual scars about the face and nose and the indentation that is in the frontal

region where the rearview mirror stand penetrated the skull and brain. Looking at the horizontal (axial) view of this individ- ual’s brain in the bottom right-hand corner and applying the principle of symmetry, you can see the frontal (top) region of the brain, and on the right-hand side of the picture (the left side of the patient), a large area of degeneration in the frontal pole (areas in black). This indicates necrosis or wasting of the brain. From the neuropsychological standpoint, because the patient has pre- dominantly a frontal injury, you would expect difficulties with complex reasoning, decision making, change in temperament and personality, as well as alterations in memory functioning. In fact, the patient’s neuropsychological studies demonstrate such deficits. This is an excellent example of how brain imaging technology can inter- face with neuropsychological test findings to establish the most accurate and specific assessment of behavioral and cognitive changes in a patient with TBI.

The integration of different imaging technologies is only in its infancy. Scientists have yet to fully explore interrela- tionships among different neurodiagnostic procedures. The greatest potential of these tools may lie in assessing the neuropsychological functions during neurophysiologic

procedures. The tools that appear most valuable at this time are fMRI, MEG, quantitative EEG, PET, and SPECT. This direction will lead to a multidimensional and increasingly comprehensive approach to the functioning of the brain, bridging the gap between psychology and biology.

Summary The neuropsychology student may believe that the level of technology is so sophisticated that behavioral techniques add little to the overall information about a human being. This is true to some extent, particu- larly in the area of diagnosis. The presence of tumors, stroke, and hydrocephalus is most easily, efficiently, and accurately discerned by modern imaging techniques. However, some diagnoses are so subtle and dif- fuse that only comprehensive neuropsychological tests can identify them. Although the neuropsychologist’s role in diagnosis has shrunk, behavioral techniques still play a major role in diagnosing early stages of dementia or attention deficit disorder. Furthermore, sophisticated medical examination procedures cannot provide a functional assessment of an individual, and certainly not an understanding of the patient’s quality of life or perception thereof. A functional assessment is most effectively conducted by neuropsychologists using behavioral tools.

Moreover, remember that most of the outlined procedures provide a static picture of the brain, and that neuropsychological dysfunction may extend considerably beyond the pathology that modern imaging tech- niques uncover. No doubt the alphabet soup of new imaging technologies has become a powerful tool in the study of brain–behavior relationships. But will this new technology fulfill what the phrenologists were unable to do, that is, create a precise functional map of the brain? Probably not. Many constraints hinder the use of functional imaging in studying the human brain. For example, ultimately, the image rendered is not a direct representation of the mechanism involved in the mental activity, but some correlate. Furthermore, functional

(continued)

CHAPTER 2 | Methods of Investigating the Brain 61

imaging captures brief moments, most suitable for analyzing a neuroimage or process involved in sensorimotor operations or a specific neuropsychological task. But it is doubtful that imaging technology will ever be able to assess a thought or investigate personality.

One of the most exciting advances in the imaging of the living brain is the collaboration among differ- ent disciplines, including biomedical engineers, psychiatrists, neurologists, neurosurgeons, and neuropsy- chologists, to define and differentiate between the normal and the malfunctioning brain. We turn next to the developing brain and its often complex behavioral sequelae.

C r i t i c a l T h i n k i n g Q u e s t i o n s

What are the differences among electrical, magnetic, and metabolic technologies in imaging? Why is co-registration, that is, the use of multiple assessments using different technologies, an important advancement in neuropsychology? Which medical technology to examine your brain would you volunteer for? Why? Will neuropsychology be outdated by the increased use of sophisticated brain imaging technology? Why or why not?

K e y Te r m s

Golgi, Camillo Nissl, Franz Myelin staining Horseradish peroxidase (HRP) Röntgen, Wilhelm Conrad X-ray Air encephalogram, or

pneumoencephalogram

Computed transaxial tomography (CT)

Hypodensity Hyperdensity Enhanced CT Angiography Femorocerebral angiography Digital subtraction angiography

Wada technique Electroencephalography

(EEG) Electrocorticography (ECoG) Evoked potential (EP) Single-photon emission

computed tomography (SPECT)

Positron emission tomography (PET)

Magnetic resonance imaging (MRI)

Magnetoencephalography (MEG) Lumbar puncture Neurologic examination Neuropsychological evaluation

We b C o n n e c t i o n s

http://www.med.harvard.edu/AANLIB/home.html The Whole Brain Atlas—Harvard University site that provides neuroimaging primer and overview of brain anatomy and physiology, including images of CT, MRI, PET, MPEG movies, and SPECT. This site can be used as a general reference for exploring the latest in brain imaging. http://www.bic.mni.mcgill.ca Brain Web: Simulated Brain Database—Contains simulated brain MRI data based on two anatomic models. Full 3-D volumes have been simulated using a variety of slice thicknesses. Data are available for viewing in three orthogonal views.

http://www.med.harvard.edu

http://www.bic.mni.mcgill.ca

Chapter 3

N E U RO P S Y C H O L O G I C A L A S S E S S M E N T A N D D I A G N O S I S

The teacher is faced with the eternal dilemma, whether to present the clear, simple, but inaccurate fact, or the complex, confusing, presumptive truth.

—Karl Menninger

General Considerations in Neuropsychological Testing Psychometric Issues in Neuropsychological Assessment Neuropsychological Tests Interpreting Neuropsychological Assessment Data

Neuropsychology in Action

3.1 Case Example: The Neuropsychology of Lyme Disease

CHAPTER 3 | Neuropsychological Assessment and Diagnosis 63

Overview Jeanne was a passenger on a motorcycle with her husband when at an intersection a car ran a stop sign and hit them. Although her husband received only minor injuries, Jeanne was thrown about 5 feet. Luckily, she was wearing a helmet. However, Jeanne thinks she must have been knocked out, because she does not remember anything until the ambulance arrived. Emergency department personnel attended to her knee injury. She also had a terrible headache. Magnetic resonance imaging (MRI) did not detect any contusions or lesions. The hospital released Jeanne that day and told her to see her general practitioner if she had any more problems.

Jeanne recovered for a week at home, and then went back to her job as a medical records clerk. She also returned to school to enroll in coursework for a nursing degree. First, she noticed that she often forgot a client’s seven-digit medical record number between the time she looked at it and went next door to get the chart. Her grades also started slipping. Before the accident, she was earning As and Bs; but on her first biology test a month after the accident, she received a D. She also continued to have headaches, which she had not had before. Four months after her injury, after several visits to her general practitioner and a neu- rologist, neither of whom could find anything medically wrong with her, her practitioner referred her for a neuropsychological evaluation. The request was to evaluate Jeanne to determine whether she had suffered a brain injury as a result of her accident or if her symptoms might be a psychosomatic reaction, that is, related to increased stress in dealing with the accident and the aftermath.

What can neuropsychology offer Jeanne? Many people who have head injuries or suffer whiplash injuries in car accidents, sports injuries, or falls may have a brief lapse of consciousness. They may feel temporarily confused or disoriented. They may or may not go to a doctor or to the hospital, and if they do, they are usually released after a brief observation. Computed transaxial tomography (CT) or MRI results are quite likely to be negative for any small or microscopic contusions or lesions. Only after going home and trying to resume the normal tasks of working or going to school may someone such as Jeanne feel unable to concentrate or often forget things. The person may have other odd symptoms that he or she does not understand, such as becoming more easily frustrated or just not feeling “herself.” If these problems do not resolve and the person is persistent, or the physician perceptive, then the physician should make a referral for neuropsychological testing.

K e e p i n M i n d

What do clinical neuropsychologists do?

How is clinical neuropsychology distinguishable from clinical psychology or from neurology?

What makes a neuropsychological test reliable and valid?

What different roles do neuropsychologists play?

What individual differences influence neuropsychological test interpretation?

How can a neuropsychologist improve a patient’s quality of life?

General Considerations in Neuropsychological Testing

This chapter describes the most frequently used as- sessment techniques in neuropsychology and outlines the scientific and theoretical principles of neuropsychological measurement. We stress that clinical neuropsychologists

use a number of different methods to evaluate and treat individuals with brain dysfunction. Simply put, neu- ropsychologists are foremost clinical psychologists who have specialized in neuropsychological conceptualizations and methods. For neuropsychologists to understand the individual, they must view psychology as the expression of neuropsychology. From this perspective, neuropsychol- ogy is a broad field, and the neuropsychologist’s roles span

64 PART ONE | Introduction

the range from evaluation to rehabilitation to research. This provides flexibility for employment in diverse settings. Figure 3.1 outlines representative employment settings of clinical neuropsychologists. Almost half of all clinical neu- ropsychologists work in private practice, 24% in medical schools, 11% in rehabilitation hospitals, 5% in university settings, and 5% in Veterans Affairs (VA) medical centers. Other employment settings for clinical neuropsychologists include community mental health centers/clinics, school systems, military settings, and prisons/correctional facilities. Across all settings, the “average” clinical neuropsychologist devotes 63% of his or her professional time to neuropsy- chology, has approximately 12 years of experience in prac- ticing neuropsychology, is 45 years of age, and is predomi- nantly male (73%) (Gordon & Zillmer, 1997).

In private practice, the role of the neuropsychologist is perhaps the most varied and flexible, but also the most ambiguous, because the amount of time devoted to neu- ropsychology depends on the type of patient population. Thus, neuropsychologists in private practice may provide neuropsychological evaluation and diagnosis, as well as psychotherapy, family therapy, biofeedback, and other forms of traditional psychological services. Most often, clinical neuropsychologists in private practice are general- ists; that is, they have grounding in clinical psychology with expertise in clinical neuropsychology. Some private practitioners have teaching or clinical appointments in universities or medical schools and participate to some degree in teaching and research.

In medical schools and hospitals, and in VA medical centers, clinical neuropsychologists most frequently work in psychiatry and rehabilitation departments and, to a lesser extent, in neurology or neurosurgery departments.

The role of the neuropsychologist in the medical arena is typically neuropsychological diagnosis, evaluation, and intervention. The major difference compared with the private practice setting is the degree to which neuropsy- chologists participate in research. Particularly in medical schools, research plays an important role, and neuropsy- chologists are often important participants in multidisci- plinary research. In rehabilitation hospitals, neuropsychol- ogists are essential in interventions for and remediation of disabilities related to brain impairment. In the academic setting, neuropsychologists predominantly teach under- graduate students in psychology and graduate students in clinical psychology. Academic neuropsychologists typi- cally run active research programs. Clinical service deliv- ery may play a minor role. Neuropsychologists in univer- sity settings may treat patients in an integrated university neuropsychology clinic, or they may participate in a small private practice. Common to all employment settings is the emphasis on clinical diagnosis and evaluation, re- search, and rehabilitation and intervention. Figure 3.2 outlines the typical patient populations that clinical neu- ropsychologists serve. A combined total of more than 70% of the patients who neuropsychologists treat are re- habilitation, psychiatry, or neurology patients. To a lesser degree, neuropsychologists treat patients referred with learning disabilities, forensic issues, dementia, general medical conditions, and seizure disorders.

W H Y T E S T I N G ?

In the past, the interest in clinical neuropsychology, specifically in assessment, reflected a perceived need to expand the clinical understanding of behavior to include

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Medical school

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Rehab hospital

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Academia

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Figure 3.1 Distribution of neuropsychology practice, based on a survey of more than 2000 members of the National Academy of Neuropsychology. (Reproduced from Gordon, A., & Zillmer, E. A. [1997]. Integrating the MMPI and neuropsychology: A survey of NAN membership. Archives of Clinical Neuropsychology, 4, 325–326, by permission of Elsevier.)

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Figure 3.2 Types of patients treated by neuropsycholo- gists. (Reproduced from Gordon, A., & Zillmer, E. A. [1997]. Integrating the MMPI and neuropsychology: A survey of NAN membership. Archives of Clinical Neuropsychology, 4, 325–326, by permission of Elsevier.)

effects on human functioning caused by brain dysfunc- tion. As a result, evaluation of brain functioning through the development of neuropsychological testing has been a major contribution to psychology. Clinical neuropsychol- ogists, however, have often been—not undeservedly— pigeonholed as “brain damage testers” or reductionistic “lesion detectors.” But this notion is outdated. Clinical neuropsychology is a quickly evolving field in which the neuropsychologist can play several roles. One of those roles traditionally has been conducting psychological eval- uations of brain–behavior relationships. Understand that neuropsychologists gain expertise in neuropsychological assessment and diagnosis over years of study and clinical practice, which they usually pursue at predoctoral and postdoctoral levels. The purposes of administering psy- chological assessment instruments are to identify a pa- tient’s cognitive and behavioral strengths and weaknesses, to assist in the differential diagnosis of mental disorders, and to aid in treatment and discharge planning. Figure 3.3 reviews the neuropsychologist’s role in assessment and di- agnosis by summarizing the general purposes of neuropsy- chological assessments.

A majority (�50%) of all neuropsychological evalua- tions are diagnostic in purpose. In essence, the question to understand is whether there are indications of a decline in cognitive abilities and whether they suggest a specific diagnosis or neuropathologic condition. In many cases that involve obvious pathology (such as brain tumor and stroke), neuropsychological evaluations are a precursor or are complementary to more in-depth neurologic or neu- roimaging procedures that can establish the exact medical or neurologic diagnosis. In other cases (such as learning disabilities, attention deficit disorder, dementia, or minor

head injury), the medical diagnosis is much more obscure and cannot be verified precisely by medical imaging tech- niques. Neuropsychological evaluations play a major role in assessing such conditions, because the diagnosis often rests largely on behavioral symptoms. In some medical conditions (such as epilepsy, multiple sclerosis, and AIDS), neuropsychological assessments have only minor diagnostic value, but they are used for documenting the extent of cognitive strengths and weaknesses, to outline effective treatment strategies and appropriate placements for school or vocational settings. Thus, many neuropsy- chological evaluations are conducted with more descrip- tive purposes in mind. As a result, the neuropsychologist’s role has evolved from that of a strict diagnostician to pro- viding descriptions of cognitive functioning, current adaptation, and future prognosis.

R A T I O N A L E O F T H E N E U R O P S Y C H O L O G I C A L E X A M I N A T I O N

You cannot determine whether a certain function of the brain is impaired unless you test that function. The neu- ropsychological evaluation is an objective, comprehen- sive assessment of a wide range of cognitive and behav- ioral areas of functioning, which the neuropsychologist typically integrates with intellectual and personality as- sessments and evaluates within the context of CT and MRI scans. When based on a thorough description of abilities and deficits, neuropsychological testing leads to recommendations for rehabilitation and treatment. In using such tests, clinical neuropsychologists are interested principally in identifying, quantifying, and describing changes in behavior that relate to the cognitive integrity of the brain. Serial assessments can demonstrate gradual improvement or deterioration in mental status over time, allow better differentiation of cognitive deficits, and assist in treatment and disposition planning (Lezak, Howieson, & Loring, 2004). Thus, the neuropsychologist may ad- dress issues of cerebral lesion lateralization, localization, and progress. Neuropsychological evaluations can provide useful information about the impact of a patient’s limita- tion on his or her educational, social, or vocational adjust- ment. Because many patients with neurologic disorders, such as degenerative disease, cerebrovascular accidents, or multiple sclerosis, vary widely in the rate at which the ill- ness progresses or improves, the most meaningful way to equate patients for severity of illness is to assess their be- havior objectively, using neuropsychological procedures.

The neuropsychological evaluation has a number of ad- vantages that many standard neurodiagnostic techniques do not share; for example, it is noninvasive and provides

CHAPTER 3 | Neuropsychological Assessment and Diagnosis 65

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56%

Treatment implication

16%

Assess school/work

capacity

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Figure 3.3 Overview of the neuropsychologist’s role in assessment. (Reproduced from Gordon, A., & Zillmer, E. A. [1997]. Integrating the MMPI and neuropsychology: A survey of NAN membership. Archives of Clinical Neuropsychology, 4, 325–326, by permission of Elsevier.)

66 PART ONE | Introduction

descriptive information about the patient. Specific tests used in neuropsychological assessment batteries may vary, although most assessments include objective measures of intelligence, academic achievement, language function- ing, memory, new problem solving, abstract reasoning, constructional ability, motor speed, strength and coordi- nation, and personality functioning (Zillmer & Greene, 2006).

You can conceptualize neuropsychological assessment as a method of examining the brain by studying its be- havioral product. Because the subject matter of neuropsy- chological assessment is behavior, it relies on many of the same techniques and assumptions as traditional psycho- logical assessment. As with other psychological assess- ments, neuropsychological evaluations involve the inten- sive study of behavior by means of standardized tests that provide relatively sensitive indices of brain–behavior rela- tionships. Neuropsychological tests have been used on an empirical basis in various medical and psychiatric settings, are sensitive to the organic integrity of the cerebral hemi- spheres, and can often pinpoint specific neurologic or psy- chological deficits. Neuropsychological assessment has also become a useful tool for clinical service delivery and for research regarding the behavioral and cognitive aspects of medical disorders.

A P P R O P R I A T E R E F E R R A L S F O R N E U R O P S Y C H O L O G I C A L E V A L U A T I O N

Because a neuropsychological workup may take from 30 minutes to 8 hours of professional time, health practi- tioners should request consultations with some discrimi- nation for cost-effectiveness and utility. The interpreta- tion and diagnosis of the patient’s profile ultimately depends on the referral question, the neuropsychologist’s test selection, and the process by which the neuropsychol- ogist interprets the data. Referrals should specify exactly what questions or problems prompted the referral, what the referral source hopes to obtain from the consultation, and the purpose for which the referrer will use the infor- mation. The advanced student in neuropsychology often feels frustrated by the failure of medical professionals to give a clear referral question. Note, however, that generat- ing appropriate referral questions, as well as questions from the patient about the goals of the evaluation, is the responsibility of the neuropsychologist. Thus, it is often necessary to educate the professional community about the purpose and goals of a neuropsychological evaluation. Having the patients themselves ask specific questions about the goals of the evaluation (e.g., whether they can go back to work) often makes the evaluation process more

meaningful to patients, and typically motivates them to put forth a good effort.

In a medical setting, the neuropsychologist is most helpful to the treatment team as a neurobehavioral de- scriber of functional strengths and weaknesses, as well as a provider of neurodiagnosis. As mentioned earlier, such disorders as mild head injuries, early stages of Alzheimer’s dementia, or learning disabilities may show no symptoms beyond the cognitive dysfunction that formal neuropsy- chological testing assesses so well. Following is a listing of instances in which a neuropsychological consultation is generally useful:

Differential neurologic diagnosis

Acute versus static

Focal versus diffuse

Location of damage

Establishment of a baseline for neuropsychological performance from which future evaluations can assess improvement or deterioration

Descriptions of the effects of brain dysfunction on behavior

Determinations of disability levels for compensation in personal injury litigation

Evaluation of vocational potential

Assessment of environmental needs after discharge from hospital (disposition planning)

Development of remedial methods for rehabilitation of the individual brain-damaged patient

Measurement of residual abilities during rehabilitation

Patient management

Psychometric Issues in Neuropsychological Assessment

The success of psychological testing procedures to assess and select individuals to become officers and under- take special assignments in World War I was the impetus for some of the earliest recognition of psychology as a sci- entific field. Since then, the science of standardized clini- cal psychological testing has evolved to the point that there are now hundreds of psychological assessment instruments in use today. It is important for the neuropsychology stu- dent to understand the scientific principles of psychologi- cal measurement before examining neuropsychological assessment instruments in more detail.

Psychometrics, the science of measuring human traits or abilities, is concerned with the standardization of psy- chological and neuropsychological tests. A standardized test is a task or set of tasks administered under standard conditions and designed to assess some aspect of a person’s knowledge or skill. Standardized psychological tests typi- cally yield one or more objectively obtained quantitative scores, which permit systematic comparisons to be made among different groups of individuals regarding some psy- chological or cognitive concept. Most neuropsychologists agree that tests are rarely used alone and are not interpreted in a vacuum. Almost always, neuropsychological tests are only one of multiple components of information used to make important decisions about an individual. Neuropsy- chological assessment, therefore, depends on the complex interplay among the neuropsychologist, the patient, the context of the assessment, and the data from neuropsycho- logical testing.

R E L I A B I L I T Y

For any psychological test to be useful, it must be both reliable and valid. Reliability is the stability or depend- ability of a test score as reflected in its consistency on re- peated measurement of the same individual. A reliable test should produce similar findings on each administra- tion. If test scores show a great deal of variation when ad- ministered to the same individual on several occasions, the test scores are unreliable and there is concern about error. Interpretation of the scores becomes difficult. There are several different forms of reliability, including test- retest reliability, split-half reliability (the correlation be- tween two halves of the test), or internal consistency (the degree to which items of a scale measure the same thing, also known as Cronbach’s alpha). Thus, the concept of re- liability is not as simple as it first appears, and test devel- opers must present substantial detail when making claims of test reliability.

V A L I D I T Y

The validity of a test is the meaningfulness of specific in- ferences made from the test scores; that is, does the test really measure what it was intended to measure? If a test is unreliable, it cannot be valid. For example, if you take the same language test on three different days and obtain three different scores, it is easy to conclude that there is no consistency and, therefore, the test cannot possibly be used to predict anything about your language abilities. A reliable test is not necessarily a valid one. Let us say a test was purported to measure how well you make organized

extemporaneous speeches. The test requires you to generate as many words as you can in 1 minute. On three different days you took the test, and on three days you got a similar score. The test has high reliability. But is it telling us about your ability to make impromptu speeches? Not necessarily. An analysis of the test’s validity may show that it is primar- ily measuring your ability to search and retrieve words from memory. It may have little to do with your ability to put your thoughts together and come up with a good speech.

Although the concept of a test accomplishing its pur- pose is easy to grasp, applying this concept often results in confusion. Many tests that neuropsychologists use origi- nally were designed for purposes or diagnostic groups other than those for which they are used now. Rather than discuss validity in overgeneralized terms, scrutinize an eval- uation of a test’s validity in relation to the specific purpose and the specific population it is used in. That is, never con- sider a test generically “valid” or “invalid.” The question to ask is: “Is this test valid for this particular purpose?”

You can use several different strategies for determining validity. Construct validity focuses primarily on the test score as a measure of the abstract, psychological character- istic or construct of interest (such as memory, intelligence, impulsiveness, and so forth). Construct validity would be most important if you wanted a demonstration of the cog- nitive or functional abilities a test measures (e.g., visuo- spatial problem solving or perceptual-motor functioning).

Content validity pertains to the degree to which a sample of items or tasks makes conceptual sense or repre- sents some defined psychological domain. Various items of the test should correspond to the behavior the test is designed to measure or predict, such as measuring how fast someone can tap a finger, to assess upper extremity motor speed. Finally, criterion validity demonstrates that scores relate systematically to one or more outcome crite- ria, either now (concurrent validity) or in the future (pre- dictive validity). Criterion-related validity traditionally has been an area of prime concern in neuropsychology re- lated to the correct classification of diagnostic groups in- cluding brain-impaired, psychiatric, and normal individu- als. There is also the issue of whether the test is being used as a measure to describe current everyday functioning. Criterion-related predictive validity is important if a test is designed to predict decline or recovery of function or fu- ture behavior of any type (such as medication management or ability to drive a car).

F A L S E P O S I T I V E S A N D B A S E R A T E S

A false positive (also known as a type I error or false alarm) is a case in which a neuropsychological test erroneously

CHAPTER 3 | Neuropsychological Assessment and Diagnosis 67

68 PART ONE | Introduction

indicates a pathologic condition—such as “brain dam- age”—in an individual who is actually “normal.” In set- ting a cutoff score on neuropsychological tests, statisticians attend to the percentage of false rejects (or false positives), as well as to the percentages of successes and failures within the selected group. In most medical (life-threatening) situ- ations, statisticians set the cutoff point low enough to ex- clude all but a few false rejections (such as on tests that de- tect the presence of cancer). When the selection ratio is not externally imposed, the cutting score on a test can be set at a point yielding the maximum differentiation be- tween criterion groups. You do so, roughly, by comparing the distribution of test scores in the two criterion groups, including the relative seriousness of false rejections and ac- ceptances.

The validity resulting from the use of a test depends not only on the selection ratio but also on the base rate of the test. Base rate is the frequency with which a pathologic condition is diagnosed in the population tested. For example, if 10% of a psychiatric population of a hospital has organic brain damage, then 10% is the base rate of brain damage in this population. Although introducing any valid test improves predictive or diag- nostic accuracy, the improvement is greater when the base rates are closest to 50% (closest to chance). With extreme base rates found in rare pathologic conditions (e.g., �1%), an improvement with a neuropsychological test may be negligible. Under those conditions, the diag- nostic use of a neuropsychological test is unjustifiable when you take into account the cost of its administration and scoring. When the seriousness of a condition makes its diagnosis urgent, as in Alzheimer's disease (AD), neu- ropsychologists may often use tests of moderate validity in early stages of sequential decisions. Table 3.1 demonstrates a simple decision strategy for neuropsychological proce- dures. A single test is administered, and the decision to reject or accept a diagnosis is made with four possible outcomes.

Neuropsychological Tests

Table 3.2 reviews the most frequently used types of neuropsychological measures currently in practice. Dif- ferent types of tests have different goals and applications. Achievement tests measure how well a subject has prof- ited by learning and experience, compared with others. Typically, achievement is most influenced by past educa- tional attainment. Achievement tests are not designed to measure the individual’s future potential, which is typi- cally measured by aptitude tests. Behavioral-adaptive scales examine what an individual usually and habitually does, not what he or she can do. Neuropsychologists most frequently use such scales in evaluating the daily skills of individuals who are quite impaired (such as the mentally retarded or the severely brain injured). Intelligence tests are complex composite measures of verbal and perfor- mance abilities that are related, in part, to achievement (factual knowledge) and to aptitude (e.g., problem solv- ing). Neuropsychological tests traditionally have been defined as those measures that are sensitive indicators of brain damage. Today, scientists consider a measure to be a neuropsychological test if a change in brain function is systematically related to a change in test behavior. Most available neuropsychological tests, therefore, have a broader function (see later in this chapter for a more detailed description of these tests). Another area of psy- chological testing concerns the nonintellectual aspects of behavior. Tests designed for this purpose are com- monly known as personality tests—most often, measures of such characteristics as emotional states, interpersonal

Decision Positive (presence of pathology) Negative (absence of pathology)

CORRECT Valid acceptance (hit) Valid rejection (correct rejection)

INCORRECT False positive (false alarm, False negative type I error) (miss, type II error)

Table 3.1 Decision Making in Neuropsychological Assessment

Type of Test Characteristics Measured

Achievement Profit from past experience

Aptitude Profit from future training and educational experiences

Behavioral/adaptive Basic adaptive behaviors (e.g., self-care, communication, socialization)

Intelligence Ability to adapt to novel situations quickly

Neuropsychological Brain–behavior relationships

Personality Psychopathology and ability to adapt and cope with stress

Vocational Success in a specific occupation or profession

Table 3.2 Types of Tests Most Commonly Used by Psychologists

relations, and motivation. Finally, vocational inventories assess opinions and attitudes that indicate the individual’s interest in different fields of work or occupational settings.

Neuropsychologists generally recognize that there is considerable overlap among all types of psychological tests. For example, it is difficult to measure aptitude with- out measuring achievement, to measure vocational inter- est without measuring personality, or to measure intelli- gence without measuring neuropsychology. One way to deal with this overlap is to reduce the complexity to two basic neuropsychological constructs: “crystallized” and “fluid” functions. Psychologists consider crystallized functions to be most dependent on cultural factors and learning. In contrast, they believe fluid functions to be culture free and independent of learning. Problem-solving and abstract reasoning abilities are considered fluid, whereas spelling and factual knowledge are considered crystallized. Nevertheless, even this simple differentiation of psychological test properties is controversial. For exam- ple, much discussion concerns whether intelligence tests tap mostly crystallized or fluid forms of behavior. Actu- ally, it is nearly impossible to measure all aspects of a com- plex skill or group of skills with a single test. As a result, neuropsychologists prefer to administer a number of dif- ferent tests, known as a test battery, that address different areas of brain–behavior functioning. After all, testing be- havior, whether vocational or adaptive, is mediated by brain function. Thus, neuropsychologists use the preced- ing tests to some degree to evaluate specific questions about an individual. The neuropsychological interview is also an important part of the neuropsychological evalua- tion. The benefits of talking to the patient include an un- derstanding of the patient’s symptom presentation; the patient’s awareness of his or her symptoms; and a review of the patient’s educational, marital, social, and develop- mental histories.

The best way to understand the purpose of the neu- ropsychological assessment is to examine the evaluation process. Because neuropsychological assessment batteries typically evaluate a wide range of behaviors, they are con- sidered multidimensional in their approach to measuring higher cortical functions. Thus, the neuropsychological examination involves accurately evaluating multiple cog- nitive abilities (Table 3.3). The usual categories of the neuropsychological examination include the following functional areas, which are listed hierarchically; that is, higher cognitive functions depend to a large degree on in- tact lower functions, which are listed first:

Let us examine each of these areas in greater depth. For each neuropsychological domain, we present an example to elucidate the construct measured and the method used

to do so. In addition, we present examples of frequently used neuropsychological tests for each neuropsychological domain.

O R I E N T A T I O N ( A R O U S A L )

Brain impairment affects not only a person’s intellect or muscle movement but all other aspects of performance as well, including his or her level of consciousness. Patients who are lethargic or tired all the time tend to perform poorly compared with patients who have good energy. Lethargy is sometimes a symptom of brain damage and sometimes a symptom of depression. It is the psycholo- gist’s job to determine which factors are at work in a given case.

Alertness is the most basic aspect of cognition. Patients who cannot demonstrate adequate arousal may have difficulty participating in a neuropsychological evaluation and are, perhaps, unlikely to benefit from re- habilitation or psychological intervention. Orientation describes a patient’s basic awareness of himself or herself to the world around them. Specifically, in neuropsychol- ogy, orientation refers to an individual’s knowledge of who he or she is (orientation to person), what the date is (orientation to time), and where he or she is (orienta- tion to place). If a patient is fully oriented, the neu- ropsychologist will say that he or she is “oriented times three,” meaning that those three areas of awareness are intact.

N e u r o p s y c h o l o g i c a l I t e m s ( O r i e n t a t i o n )

The neuropsychological assessment typically involves the common evaluation of orientation in the three spheres; for example, “What is your full name?” (both first and last names are required) “Where do you live?” (specific town or city is required), or “How old are you?” In addi- tion, neuropsychologists may also ask additional ques- tions that relate to an individual’s ability to recall his or her specific whereabouts, the purpose of the hospitaliza- tion, and any part of his or her address: “What is the name of the place you are in now?” (a response indicating that the patient knows he or she is in a hospital is consid- ered correct) and “What town or city are you in now?” (any response indicating adequate orientation to the hos- pital’s location is scored). The following two examples are examples of the patient’s orientation to well-known cur- rent facts involving famous individuals: “Who is Presi- dent of the United States right now?” and “Who was pres- ident before him?”

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70 PART ONE | Introduction

N e u r o p s y c h o l o g i c a l T e s t s ( O r i e n t a t i o n )

To measure orientation, neuropsychologists frequently use the Galveston Orientation and Amnesia Test (GOAT) (Levin, O’Donnell, & Grossman, 1979). This short men- tal status examination assesses the extent and duration of confusion and amnesia after traumatic brain injury. Like the Glasgow Coma Scale (GCS; see Chapter 13), it was designed for repeated measurements and can be used sev- eral times a day and repeated over days or week as neces- sary. The GOAT yields a score from 0 to 100, with a sug- gested cutoff score of 75 or better indicating relatively intact orientation and the capacity of the patient to un- dergo formal neuropsychological testing. Both the GCS and the GOAT are simple to administer; therefore, the treatment team often uses them. Because these scales quan- tify level of patient arousal, researchers have frequently

used them in examining outcome of brain injuries that involve an alteration in consciousness.

S E N S A T I O N A N D P E R C E P T I O N

Sensation is the elementary process of a stimulus excit- ing a receptor and resulting in a detectable experience in any sensory modality; for example, “I hear something.” Perception depends on intact sensation and is the process of “knowing”; for example, “I hear music, it is Pearl Jam.” The perceptual process begins with arousal and orienta- tion, sensation is the second stage, and perception the third. In assessing sensation and perception, the neuropsy- chologist is interested in quickly and grossly evaluating the patient’s visual, auditory, and tactile functional levels. Screening for impaired sensation and perception yields im- portant information by ruling out the contributions of

Orientation Arousal Degree of confusion Disorientation Place Person Time Awareness of change/time

Sensation/Perception Recognition Familiarity of stimuli Relationship among features Visual acuity Auditory Taste/smell Tactile/proprioceptive Internal/environmental Awareness

Attention Span Selective attention Shifting Sustained attention Vigilance Neglect Fatigue

Motor Cerebral dominance Initiation and perseveration Manual dexterity

Graphomotor skills Balance Ambulation Motor speed Speech regulation Motor strength

Visuospatial Construction Route finding Spatial orientation Facial recognition

Language Skills Receptive speech (following directions, reading comprehension) Expressive speech (verbal fluency, naming, writing, math) Articulation (stuttering, stammering, articu- lation voice, fluency) Speech production (articulation fluency, voice) Syntax and grammar Aphasias: Broca’s, Wernicke’s, conduction, fluent, transcortical, subcortical

Memory Verbal Visual Immediate Short term Long term Recognition Encoding

Storage Retrieval Chunking Declarative Procedural

Abstract Reasoning/Conceptualization Comprehension Judgment Calculations Problem solving Organizational abilities Higher level reasoning Sequencing

Emotional/Psychological Distress Depression Attitude toward rehabilitation Motivation Locus of control Family relationships Group interaction One-to-one interaction Behavioral impulsivity Aggressive/confrontational

Activities of Daily Living Toileting Dressing Bathing Transferring Continence Feeding

Table 3.3 Common Areas of Neuropsychological Assessment Grouped Hierarchically by Function

dysfunctional visual or auditory sensation to test perfor- mance. In addition, discovering unilateral sensory deficits aids in diagnosis of lateralized brain injury. It is important to understand that neuropsychologists are in- terested in a more or less general assessment of a patient’s sensory functioning. Specialists, including audiologists (hearing) or optometrist (visual), perform diagnostic evaluations.

N e u r o p s y c h o l o g i c a l I t e m s ( S e n s a t i o n a n d P e r c e p t i o n )

Sample items of testing the sensory and perception do- main may include assessing the intactness of the patient’s left and right visual fields (see Chapter 8 for a description of visual field deficits). This is achieved by administering a visual field examination, common in a neurologic ex- amination. For this procedure, the examiner must sit fac- ing the patient, at a distance of approximately 3 to 4 feet, and ask, “I would like you to look straight at my nose. I am going to put my arms out like this, and I want you to tell me which finger I am moving. You can point to it if you like.” The examiner extends the index finger of each hand in a vertical fashion with arms spread out at shoul- der height and presents the stimuli by moving each finger slightly, waiting for the patient’s response between trials. Discrimination of similar auditory, verbal stimuli may be tested by the examiner saying, “I am going to say two words, and I want you to tell me whether I am saying the same word twice or two different words,” to assess audi- tory functioning:

house – house (same) people – peanut (different) bar – bar (same) first – thirst (different)

To assess the patient’s ability to sense or feel objects, the examiner may say, “I am going to place an object in one of your hands. I would like you to close your eyes, feel the object, and tell me what it is.” This procedure measures stereognosis, recognition of objects by touch.

N e u r o p s y c h o l o g i c a l T e s t s ( S e n s a t i o n a n d P e r c e p t i o n )

Some neuropsychologists have standardized their proce- dures for examining sensory and perceptual functioning and developed scoring systems as well. For example, part of the well-known and often used Halstead–Reitan Neu- ropsychological Battery includes a sensory-perceptual ex- amination that tests for finger agnosia, skin writing recog- nition, and sensory extinction in the tactile, auditory, and visual modalities (Reitan & Wolfson, 1993).

A T T E N T I O N / C O N C E N T R A T I O N

Attention is a critical requirement for learning. To remem- ber, you first have to pay attention. Some patients are in- capable of attending to their environment. Others may be able to attend to a learning task, but only for a limited amount of time. Still others may be able to attend to a task only if there are no distractions in the environment. Psy- chologists divide the concept of attention into separate categories such as sustained attention, paying attention to something over a prolonged period, and selective atten- tion, paying attention to more than one thing at a time.

N e u r o p s y c h o l o g i c a l I t e m s ( A t t e n t i o n / C o n c e n t r a t i o n )

Tasks requiring mental control involve simple, over- learned information, but also require the person to main- tain an adequate level of attention throughout the item. Errors in this area may indicate extreme fatigue or impair- ment in concentration skills. For example,

“Count from 1 to 20 as quickly as you can.” “Recite the days of the week backward beginning with

Sunday.” “Say the alphabet (A, B, C . . .) all the way through.” “Count by threes, beginning with 1 and adding 3 to each

number. For example, 1, 4, 7, and so on. (Stop when you reach 22.)”

Another form of attention in this cognitive skill area is attention span. Here, the examiner asks the patient to at- tend to various verbal stimuli, then repeat them. The stimuli become progressively more complex. In this man- ner, it is possible to evaluate a patient’s span of attention for unfamiliar combinations of stimuli.

“I am going to say some numbers, and after I finish, I would like you to repeat them.”

TRIAL 1 5 8 9

TRIAL 2 9 2 7 5

TRIAL 3 7 1 6 3 2

“Now I am going to say some more numbers; but this time when I finish, I want you to say them backward. For example, if I say 3 – 6, you say 6 – 3.”

TRIAL 1 5 8

TRIAL 2 2 6 1

Sustained attention is the ability to concentrate over a period of time. For example, you can assess verbal atten- tion with the following task: “Tap on the table when you hear me say the number 4”:

CHAPTER 3 | Neuropsychological Assessment and Diagnosis 71

72 PART ONE | Introduction

2 3 5 4 7 4 6 4 4 2

1 8 1 7 8 4 5 4 2 3

N e u r o p s y c h o l o g i c a l T e s t s ( A t t e n t i o n / C o n c e n t r a t i o n )

Standardized tests of attention include the Symbol Digit Modalities Test (SDMT) (Smith, 1982), which requires the respondent to fill in blank spaces with the number that is paired to the symbol above the blank space as quickly as possible for 90 seconds. The SDMT primarily assess complex scanning, visual tracking, and sustained attention. An interesting test of selective attention is the d2 Test of Attention (Brickenkamp & Zillmer, 1998). The d2 Test is a timed test of selective attention and is a standardized refinement of a visual cancelation test. It has been translated into four languages and is the most fre- quently used test of attention in Europe. In response to the discrimination of similar visual stimuli, the test mea- sures processing speed, rule compliance, and quality of performance, allowing estimation of individual attention and concentration performance (Figure 3.4). The test was originally developed in 1962 in Germany and Switzerland as an assessment tool for driving efficiency. Subjects who fail the d2 task tend to have difficulty concentrating, in- cluding difficulty in warding off distractions.

M O T O R S K I L L S

Neuropsychologists are interested in assessing a person’s ability to demonstrate motor control in the upper and lower extremities. Simple motor skills require little coordi- nation, whereas more complex items tap into higher motor processes. As items progress in difficulty, the patient must show more integration of cognitive skills to perform the task successfully. The following neuropsychological

procedures measure varied aspects of a patient’s motor functioning. The hierarchic nature of the item presenta- tion can yield clues to the patient’s limits in motor functioning.

Neuropsychological items (motor) that involve gross- motor movement assess one of the most basic cortically mediated motor responses such as a response to a single command; for example, “Raise your right hand,” or “Move your left leg.” You can evaluate motor speed from the pa- tient’s ability to “touch your thumb to your forefinger as quickly as you can,” and fine-motor ability can be evalu- ated from the command, “Touch your thumb to each fin- ger, one after the other.” These previous items assess the ability to perform a particular response; the following items tap the patient’s ability to perform and inhibit motor behavior: “If I clap once, you clap twice.” (Clap hands one time.) “Now, I clap twice, you clap once.” (Clap hands two times.) Neuropsychologists consider this a higher level cognitive process, because it requires the patient to shift between initiating and inhibiting behavior.

Neuropsychologists often examine graphomotor skills. The following items assess the ability to copy shapes with increasing degrees of difficulty. They involve the integration of visual perception (input) and a complex motor response (output). “Copy these designs. Take your time and do your best.” The patient’s drawings are scored related to the cor- rect shape, size, symmetry, and integration (Figure 3.5).

Motor apraxia items assess the intactness of common motor sequences. In general, the term apraxia refers to an inability to perform purposeful sequences of motor be- haviors. Although basic motor skills may be intact, the patient may be unable to perform even overlearned motor sequences. The form of apraxia assessed here is motor apraxia or ideomotor apraxia. Impairments in this area may stem from an inability to access a stored motor

Text not available due to copyright restrictions

sequence or an inability to relay that information to the motor association areas. An example to test this is, “Show me how you would make a telephone call from beginning to end.”

N e u r o p s y c h o l o g i c a l T e s t s ( M o t o r )

Examples of standardized motor tests include a measure of grip strength and finger-tapping speed, both from the Halstead–Reitan Neuropsychological Battery. Grip strength simply measures the patient’s ability to squeeze the dy- namometer (Figure 3.6) as hard as he or she can. The Finger Oscillation or Finger Tapping Test requires the patient to tap as rapidly as possible with the index finger

on a small lever attached to a mechanical counter (see Figure 3.6).

V E R B A L F U N C T I O N S / L A N G U A G E

Neuropsychologists screen for intactness of language. Ini- tial items test the patient’s ability to understand simple spoken language. More complicated areas of expressive language are then evaluated by assessing word repetition, naming, and word production.

N e u r o p s y c h o l o g i c a l I t e m s ( L a n g u a g e )

Receptive speech evaluates the patient’s ability to compre- hend simple spoken commands such as “Wave hello,” or a more difficult, three-step command: “Turn over the paper, hand me the pen, point to your mouth.” Expres- sive speech focuses on vocabulary knowledge and recog- nition of concepts and objects; for example, “Please tell me what the word happiness means.” Additional tests in- volve word and phrase repetition (“Repeat: ‘No if ’s, and’s, or but’s’”) and sentence generation (“Make up a sentence using the word vacation”). Deficits in verbal fluency and naming are also tested; for example, “Name all the ani- mals that you can think of as quickly as you can.” Visual naming can be evaluated by pointing to a picture and say- ing, “Tell me what this object is” (Figure 3.7).

You can evaluate writing by assessing the quality of writing at the word and sentence levels. You can also as- sess deficits in the motor component of writing (dys- graphia), simple reading (dyslexia), and spelling skills (spelling dyspraxia): “Please write down the name of this picture” (Figure 3.8).

CHAPTER 3 | Neuropsychological Assessment and Diagnosis 73

Example II

Example I

Figure 3.5 Visual integration examples. (Samples are from Zillmer, E. A., Chelder, M. J., & Efthimiou, J. [1995]. Assessment of Impairment [AIM] Measure. Philadelphia: Drexel University.)

Figure 3.6 The Finger Tapping and Strength of Grip tests. (Courtesy Jeffrey T. Barth, University of Virginia, Charlottesville, VA.)

Figure 3.7 Naming example #1. (Reproduced from Zillmer, E. A., Chelder, M. J., & Efthimiou, J. [1995]. Assessment of Impairment [AIM] Mea- sure. Philadelphia: Drexel University.)

74 PART ONE | Introduction

N e u r o p s y c h o l o g i c a l T e s t s ( L a n g u a g e )

Many standardized neuropsychological tests assess verbal and language functioning. A simple but effective test of auditory comprehension (receptive language) is the Token Test (e.g., see Boller & Vignolo, 1966). Almost every non- aphasic person who has completed fourth grade should pass this test in its entirety. The test consists of a number of commands (such as “Touch the small yellow circle.” or “Touch the green square and the blue circle.”) that relate to plastic tokens, which come in different shapes, sizes, and colors. This test is sensitive to disrupted linguistic processes that are central to aphasic disability.

The Controlled Oral Word Association (COWA) test (Benton & Hamsher, 1989) assesses the subject’s ability to use expressive speech. It measures verbal fluency by asking the subject to name as many words as possible that start with a specific letter. For example, within 60 seconds, an undergraduate or graduate student should be able to name 15 words that start with the letter R. In the COWA, ex- aminers administer three word-naming trials using the let- ters C, F, and L. These letters were selected by English word frequency. That is, words beginning with C have a relatively high frequency; the second letter, F, a somewhat lower frequency; and the third letter, L, a still lower fre- quency. Word fluency is a sensitive indicator of general brain dysfunction and expressive language dysfunction.

V I S U O S P A T I A L O R G A N I Z A T I O N

In the visuospatial domain, neuropsychologists assess var- ious aspects of processing. They ask the patient to per- form tasks of map skills, route finding, spatial integration and decoding, and facial recognition. The results of these neuropsychological tests can provide information about specific disorders of visuospatial organization.

N e u r o p s y c h o l o g i c a l I t e m s ( V i s u o s p a t i a l )

Neuropsychologists can evaluate spatial orientation with simple directional skills and mazes, and then proceed through clock drawing and motor-free constructional tasks: “If this were a compass on a map and you were fac- ing north, which direction would be behind you?” or “Draw the face of a clock, showing all the numbers, and set the hands to read 10 minutes after 11.” Testers may evaluate visuospatial processing by asking, “Which of these sets of lines makes up this figure at the top: A, B, or C?” (Figure 3.9).

Facial recognition is the patient’s ability to recognize a familiar face, as well as to compare similar faces and iden- tify facial affect. For example, the examiner may ask, “Show me ‘the happy face, the sad face, the angry face’” (Figure 3.10).

Visual sequencing also involves more integration and higher order processing. The person must comprehend the overall meaning of the activity, and then be able to correctly assemble the pictures to form the sequence of steps; for example, “This card has three pictures on it. If the pictures are put in the right order, they tell a story. Look carefully at the pictures, tell me the story, and point to the one you think comes first in the story. Now point to the one that would come second, and the picture that would finish the story” (Figure 3.11).

N e u r o p s y c h o l o g i c a l T e s t s ( V i s u a l - S p a t i a l )

The Bender Gestalt test consists of nine geometric de- signs, which the patient must reproduce exactly (Bender, 1938; Hutt, 1985). The “Bender,” as it is often called, is a popular measure of visuospatial construction. It measures

Figure 3.8 Naming exam- ple #2. (Reproduced from Zillmer, E. A., Chelder, M. J., & Efthimiou, J. [1995]. Assess- ment of Impairment [AIM] Measure. Philadelphia: Drexel University.)

a. b. c.

Figure 3.9 Visuospatial test item. (Reproduced from Zillmer, E. A., Chelder, M. J., & Efthimiou, J. [1995]. Assessment of Impairment [AIM] Measure. Philadelphia: Drexel University.)

a patient’s ability to organize visuospatial material and has been shown to be sensitive to changes in neuropsychologi- cal status, particularly visual-graphic disabilities. Rey (1941) and Osterrieth (1944) devised another drawing test to investigate perceptual organization. The Rey–Osterrieth Complex Figure Test presents the subject with an intri- cate figure to reproduce. For both the Bender and the Rey–Osterrieth tests, scoring systems have been devel- oped that evaluate specific copying errors.

M E M O R Y

You can look at memory in many ways. For example, as we noted earlier, to remember things, people must pay at- tention first. After paying attention, people must encode the information (do something meaningful with the in- formation such as rehearsing it) to put it into more per- manent storage. Once information is in storage, people must be able to retrieve the information as needed.

N e u r o p s y c h o l o g i c a l I t e m s ( M e m o r y )

Neuropsychologists assess general memory and new learn- ing skills in a variety of modalities. There are immediate and delayed memory tasks in both verbal and visual for- mats. Performance on free recall and recognition tasks can help identify different aspects of memory function and dysfunction. Multiple trials of a list learning task can as- sess immediate verbal memory. For example, the exam- iner presents the patient with five words, repeated over four trials regardless of the patient’s success on the item’s initial trials: “I’m going to say a list of five words. Please try to remember them, and repeat them when I finish: train, radio, apple, fork, chair.”

You can assess delayed verbal memory by asking the patient, at a later point during the examination (such as 30 minutes), to say whether each word had been included in the list: “I am going to read a list of words. Tell me which of these words were in the earlier list I asked you to

CHAPTER 3 | Neuropsychological Assessment and Diagnosis 75

Figure 3.10 Test of facial recognition. (Reproduced from Zillmer, E. A., Chelder, M. J., & Efthimiou, J. [1995]. Assessment of Impairment [AIM] Measure. Philadelphia: Drexel University.)

Figure 3.11 Example of picture arrangement. (Reproduced from Zillmer, E. A., Chelder, M. J., & Efthimiou, J. [1995]. Assessment of Impairment [AIM] Measure. Philadelphia: Drexel University.)

76 PART ONE | Introduction

recall several times: clock, apple, book, train, table, fork, sandwich, truck, radio, chair.”

Delayed visual memory assesses the patient’s ability to remember visual information the examiner presented ear- lier in the testing (an intermediate delay), as well as the ability to remember simple visual figures after a short delay. The examiner presents these items in a recognition format rather than a free recall format, so the patient chooses among similar stimuli, one of which is the cor- rect figure. “Earlier I asked you to copy four designs. Which of these designs was it?” (Figure 3.12).

You can assess contextual or logical memory, immedi- ate and delayed, by testing the patient’s free recall ability. The examiner presents a short story to the patient, testing memory for information presented in a specific contex- tual structure. After an interference item, the examiner again asks the patient to tell the story. Slashes separate each unit of information in the following example.

I am going to read to you a short story. When I finish, I want you to tell me as much of the story as you can remember. Try to remember it in the same words as I have used: “Joseph / Green / left his house / and headed for the subway. / He was on his way / to the supermarket. / He purchased / wine, / steak, / and ice cream. / Later that day / he had dinner / with his boss / from the office.” Now, tell me as much of the story as you can re- member.

A completely verbatim response is not necessary, be- cause neuropsychologists are mostly interested in whether the individual has formed a memory. For example, an ac- ceptable substitution for /steak/ is “meat” or “beef.”

N e u r o p s y c h o l o g i c a l T e s t s ( M e m o r y )

To provide thorough coverage of the varieties of memory disabilities, researchers have developed batteries of mem- ory tests. One of the memory assessment instruments most frequently used by neuropsychologists is the Wechsler Memory Scale (WMS; first introduced by Wechsler in 1945), which is now in its third revision (WMS-III). The WMS consist of seven subtests, which include personal and current information, orientation, mental control,

logical memory (which tests immediate recall of two ver- bal stories), digit span, visual reproduction (an immediate visual memory drawing task), and associate learning (which requires verbal retention). The WMS is sensitive to memory disorders and memory defects associated with aging.

J U D G M E N T / P R O B L E M S O L V I N G

A patient’s ability to use abstract reasoning relates, in part, to his or her capacity to understand concepts. In deter- mining a patient’s ability to use abstract reasoning, the neuropsychologist examines the patient’s ability to gener- alize from one situation to another. This skill is known as “transfer of learning.” For example, if a rehabilitation pa- tient can learn to transfer from the mat to the wheelchair with minimal assistance during physical therapy, one would normally expect the same patient to be able to gen- eralize that skill from the physical therapy wing of the hospital to the nursing wing. Otherwise, the patient’s learning is circumstantial.

Often, neuropsychologists are interested in evaluating insight specific to the patient’s capacity to realize the im- plications of his or her disorder. At times a patient pre- sents to a neuropsychologist, and says, “I’ll be fine as soon as I get home,” or “There is nothing wrong with me, I can drive a car.” Initially, the neuropsychologist will mea- sure his or her own evaluation against those by other team members. For example, if the patient has had a mild stroke and is hindered only by his or her own dislike of the hospital setting, it may be true that the patient will be “fine” on discharge. If the patient has experienced a mod- erate or more severe brain injury, the patient’s communi- cation may be evaluated as demonstrating lack of insight. One of the jobs of the neuropsychologist is to evaluate the insight that a patient has regarding the nature and the implications of his or her own disability.

N e u r o p s y c h o l o g i c a l I t e m s ( P r o b l e m S o l v i n g )

You can evaluate higher order cognitive functioning and abstract thinking skills by asking the patient to interpret proverbs, solve everyday problems, or perform mental arithmetic. For example, you can assess abstract reasoning by asking a patient to interpret a common proverb, scor- ing responses based on degree of abstraction. Proverb in- terpretations are a traditional feature of the neuropsycho- logical examination, assessing the ability to reason beyond the concrete level. For example, “What does this saying mean: ‘You can’t judge a book by its cover?’” An abstract answer may be, “Don’t judge a person by their looks”; a

Figure 3.12 Example of design copy test.

concrete answer may be, “You don’t know what is inside the book just by looking at its cover.”

A common way to assess concept formation is to use a similarities/differences paradigm or analogies. The follow- ing items involve the abstract categorization of objects and concepts. They assess whether the patient can determine the appropriate abstract links between the objects and dis- criminate form and function: “How are an eagle and a robin alike?” or “Please complete this sentence: ‘Banana is a fruit, cat is an animal. Father is a man, mother is a . . .’”

Problem-solving tasks tap the patient’s ability to for- mulate solutions to a common, everyday situation. Re- sponses can often demonstrate impulsivity and poor social judgment, as well as decreased functional independence or a need for supervision. “What should you do if you can’t keep an appointment?” Sometimes tests present absurdi- ties to evaluate reasoning skills, attention to abstract de- tails, and the ability to formulate an abstract verbal re- sponse: “What is strange about this sentence: ‘When the cook discovered that he had burned the meat, he put it in the refrigerator to fix it’?” or “What is funny or strange about this picture?” (Figure 3.13).

N e u r o p s y c h o l o g i c a l T e s t s ( P r o b l e m S o l v i n g )

Neuropsychologists have been creative in developing as- sessment procedures that evaluate executive abilities, and literally dozens of tests measure this neuropsychological domain. Only a few are mentioned here. The Trail Mak- ing Test B, part of the Halstead–Reitan Neuropsychologi- cal Battery, requires the participant to draw lines to con- nect consecutively numbered and lettered circles by alternating the two sequences (1 to A, A to 2, 2 to B, and so on). This timed task necessitates complex visual scan- ning, motor speed, mental flexibility, and attention.

The Wisconsin Card Sorting Test (WCST) (Berg, 1948; Heaton, Chelune, Talley, Kay, & Curtis, 1993) is widely used to study “abstract behavior” and “shifting sets.” The examiner gives the subject a pack of 64 cards on which are printed 1 to 4 symbols—triangle, star, cross, or circle, in red, green, yellow, or blue. No two cards are identical. The patient’s task is to place them one by one under four stimulus cards according to a principle that the patient must deduce from the pattern of the examiner’s responses to the patient’s placement of the cards. For ex- ample, if the principle is color, the correct placement of a red card is under one red triangle, regardless of the num- ber of symbols. Thus, the subject simply starts placing cards and the examiner tells him or her whether the place- ment is correct. After 10 cards have been placed correctly in a row, the examiner shifts the principle, indicating the shift only to the patient by the changed patterns of “right” and “wrong” statements. A poor performance on this test often suggests that the patient has trouble organizing his or her own behavior or has difficulty applying one set of rules to different situations. The WCST is a sensitive neu- ropsychological measure, particularly for injuries to the frontal lobes.

Culbertson and Zillmer (2005) designed the Tower of London–Drexel University (TOLdx) as a neuropsycholog- ical measure of executive planning and problem solving based on the original Tower of London (Shallice, 1982). The TOLdx measures executive planning that involves the ability to conceptualize change, respond objectively, gen- erate and select alternatives, and sustain attention (Lezak et al., 2004). The frontal lobes, in systematic interaction with other cortical and subcortical structures, support ex- ecutive planning. The TOLdx test materials include two identical tower structures (Figure 3.14), one for the sub- ject and one for the examiner to use. Each structure con- sists of three pegs of descending lengths and three colored beads that the patient can place on the pegs in different configurations or patterns. The examiner asks the subject to move the beads of his or her tower structure to match

CHAPTER 3 | Neuropsychological Assessment and Diagnosis 77

Figure 3.13 Example of a visual absurdity. (Repro- duced from Zillmer, E. A., Chelder, M. J., & Efthimiou, J. [1995]. Assessment of Impairment [AIM] Measure. Philadelphia: Drexel University.)

78 PART ONE | Introduction

bead configurations that the examiner presents. In solving the bead patterns, the subject must adhere to two strictly enforced problem-solving rules: Only move one bead at a time, and do not place more beads than fit on each peg. The examiner records number of moves, rule violations, and time the subject uses in solving the bead patterns. Interpret- ing the subject’s performance involves an analysis of both quantitative and qualitative variables. Empirical studies (Culbertson & Zillmer, 2005) show that the TOLdx is sen- sitive to a complex set of cognitive processes, including plan- ning computations, working memory, mental flexibility, attention allocation, and response inhibition.

S y m p t o m V a l i d i t y T e s t i n g i n F o r e n s i c N e u r o p s y c h o l o g y

Unlike traditional therapy clients, the potential monetary compensation associated with personal injury or insur- ance claims may motivate patients tested to exaggerate or distort their symptoms. For example, individuals suffer- ing from neuropsychological dysfunction as a result of trauma frequently report problems in attention and mem- ory. Therefore, neuropsychologists learn to assess for a client’s response bias. Psychologists have had a long and rich history of evaluating deception (e.g., polygraph proce- dures, assessing feigning of somatic symptoms). Through the use of their expertise in psychometrics and test theory, neuropsychologists have generated assessment procedures to measure symptom validity.

Although symptom validity tests are commonly referred to as malingering tests, malingering is just one possible

cause of invalid or biased performance. Test bias on the part of the client may range from outright malingering and conscious distortion of test performance to subtler, nonoptimal approaches to his or her performance, such as exaggeration. Thus, the neuropsychologist must also be expert in evaluating the test-taking approach and motiva- tion of each individual. In some instances, these biased test-taking approaches actually stem from the patient’s neurologic symptoms. For example, patients with right parieto-occipital stroke often have limited insight into their condition.

According to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) (American Psychiatric Association, 1994, p. 683), malingering is “the intentional production of false or grossly exaggerated phys- ical or psychological symptoms, motivated by external in- centives such as avoiding military duty, avoiding work, obtaining financial compensation, evading criminal pros- ecution, or obtaining drugs.” Thus, it has become a stan- dard procedure for neuropsychologists to perform an assessment of malingering when performing independent neuropsychological evaluations (Zillmer, 2004; Zillmer & Greene, 2006), for example, using the Test of Memory Malingering (TOMM) (Tombaugh, 1996, 2003).

N E U R O P S Y C H O L O G I C A L D I A G N O S I S

With the advent of modern medical diagnostic procedures (see Chapter 2), including single-photon emission com- puted tomography (SPECT), MRI, CT, positron emission tomography (PET), angiography, and evoked potential, using behavior-based assessments to diagnose organic- functional causative factors has become less essential. It has become less important for neuropsychologists and psychologists to act in the capacity of “lesion detectors” and more important to document the precise effects of brain dysfunction on behavior for purposes of remedia- tion and treatment (Zillmer & Perry, 1996). Nevertheless, clinical neuropsychologists continue to figure prominently in uncovering the behavioral syndromes that correspond to impaired brain regions and neuronal circuits and may play an important role in diagnosing neuropathologic conditions (e.g., see Goldman-Rakic & Friedman, 1991).

Medical teams still ask clinical neuropsychologists to aid in diagnosis, not merely confirming what might appear on PET or MRI images, but adding behavioral and descrip- tive information about a patient’s cognitive strengths and weaknesses. If a neurologist wants to know whether a pa- tient has had a left hemisphere stroke, a CT scan or an MRI can show this. Neuropsychological testing would be redundant and not as precise as sophisticated imaging

Figure 3.14 Administration of the Tower of London–Drexel University test, which evaluates frontal lobe functioning, that is, anticipatory-, pre-planning, and goal- oriented planning. (Courtesy Eric Zillmer.)

equipment for exactly locating the lesion within the brain. Imaging technology, however, does not provide informa- tion about how brain damage may affect behavior. Clini- cal neuropsychologists provide invaluable and unique diagnostic information in areas where behavioral infor- mation provides an important piece of the diagnostic puz- zle. Those areas include the diagnoses of mild head injury, attention-deficit/hyperactivity disorder, learning disabil- ity, or AD. Currently available imaging techniques are not sufficient to diagnose AD. Brain biopsy after death is the only certain method. Thus, Alzheimer’s dementia is a diag- nosis largely determined by behavioral methods. Through careful observation and history taking with the patient and family, the neuropsychologist documents the extent and probable progression of the behavioral deterioration. Then, through repeated evaluations spread out over time, the neuropsychologist charts the severity and course of the neuropsychological impairments. If the team can rule out all other medical causes of dementia, then the person can be diagnosed as having “possible” or “probable” AD. In fact, the diagnosis of most dementia subtypes requires close collaboration between neurologists and neuropsy- chologists (see Chapter 14).

Mild-to-moderate head injuries also present diagnostic issues that neuropsychology can help clarify. With many head injuries, particularly of the mild variety (such as con- cussion), it is not immediately evident whether the per- son has actually sustained a brain injury. In many cases, the diagnostic aim of the neuropsychological evaluation is to determine the presence and severity of brain injury. The diagnosis is made, not to answer the outdated ques- tion, “Is this patient ‘organic’?” but to answer the ques- tion, “Does this neuropsychological profile fit with what is known about the neuropsychological pattern of impair- ment after closed head injury?” CT and MRI may not show microscopic shearing, tearing, stretching, and bruis- ing of axons. Even if they did, you could not predict clear behavioral symptoms from looking at radiologic or imag- ing data. As in AD, behavioral testing largely determines the diagnosis and severity of brain damage after closed head injury. Thus, neuropsychologists play an important role in determining patterns of neuropsychological dys- function characteristic with a variety of central nervous system disorders. In addition, and to address the entire diagnostic picture, many neuropsychologists conduct comprehensive examinations of emotion and personality, to understand how the patient is adapting. For example, they not uncommonly diagnose depression or significant deficits in stress tolerance in patients who have experi- enced a head injury. The neuropsychologist’s diagnostic skills as a psychologist helps differentiate between the

impact of emotional/personality problems and brain dys- function.

Neuropsychological diagnosis remains an important component of the neuropsychologist’s role. However, di- agnosis usually is not the only question of interest when a patient seeks neuropsychological testing. The next section discusses certain other issues that practicing neuropsy- chologists address.

D E S C R I B I N G F U N C T I O N , A D A P T A T I O N , A N D P R O G N O S I S

Describing behavioral functioning—that is, a patient’s cog- nitive strengths and weaknesses—puts the “psychology” into neuropsychology. Psychology is the science of behav- ior; neuropsychology is the science of brain–behavior functioning. Although neuropsychology combines neuro- logic and psychological foci, the neurologic goal of de- tecting and classifying lesions dominated clinical neu- ropsychology through the 1970s. Since then, emphasis has shifted to a more behavioral focus, assessment of the human person, ranging from assessing cognitive abilities to evaluating quality-of-life indicators. In this approach, the goal as a clinical neuropsychologist is to describe brain–behavior functioning in such a manner as to accu- rately depict the current and future adaptive capabilities of the individual. Such information is important in evalu- ating the rehabilitation needs of a patient to facilitate adaptive functioning and prognosis, or in assessing the de- gree and type of assistance needed in the home and work environments. This chapter addresses these important is- sues in neuropsychological description, its similarities to and differences from generic psychological description, how it seeks to describe current adaptation in the real world, and how neuropsychologists use it to predict the course of recovery or decline of an individual.

Interpreting Neuropsychological Assessment Data

By now it should be obvious that the neuropsycho- logical examination is a complex undertaking. Not only are no two patients alike, but how neuropsychologists adminis- ter the tests and which tests they select often differ. In addi- tion, many procedures we have reviewed measure more than one functional domain, making it difficult to interpret the neuropsychological construct and cause underlying an impaired performance. This section presents an overview of interpretative guidelines for the neuropsychologist.

CHAPTER 3 | Neuropsychological Assessment and Diagnosis 79

80 PART ONE | Introduction

We provide quantitative and qualitative dimensions of neuropsychological performance, as well as case studies; elucidate neuropsychological diagnosis; and detail evalua- tion. Although this depends on the specific referral ques- tion, the clinical neuropsychologist is primarily interested in generating interpretive hypotheses about the patient and in answering specific questions about the test data, including the following:

Is there any cerebral impairment? Evidence of behavioral deficits? Behavioral changes caused by lesion? How severe is the injury? Is the injury medically significant? Does the injury impair the person’s ability to function in

his or her daily activities? Is the lesion progressive or static? Is the lesion diffuse or lateralized, or are there multiple

lesions? Is the impairment anterior or posterior? Can it be local-

ized? What is the most likely pathologic process? What is the

prognosis? What are the individual’s cognitive/behavioral strengths

and weaknesses, and how do they relate to daily living skills, treatment, and rehabilitation?

Do the neuropsychological deficits influence the patient’s quality of life?

What is the patient’s reaction to the injury and/or impair- ment?

A P P R O A C H E S T O N E U R O P S Y C H O L O G I C A L I N T E R P R E T A T I O N

Clinicians disagree somewhat in their approach to neu- ropsychological interpretation. These differences center on both practical and theoretical test issues and have be- come a source of debate. In making determinations re- garding the evolution of a specific assessment and inter- pretation approach, practical and theoretical issues are often intertwined. A typical example is test selection and time needed for completing the neuropsychological ex- amination. Neuropsychologists usually broaden informa- tion regarding a patient by administering a wider range of tests (such as memory, motor, learning, and language); they deepen information by administering a number of tests examining varying aspects of the same cognitive do- main (such as selective attention or sustained attention). They must balance these theoretical considerations against the practical reality of examination length. Many patients cannot tolerate long testing sessions because of

fatigue effects. Given the current climate in which man- aged health care reduces specialized services to patients, most clinicians are also concerned about cost-effectiveness in time spent on evaluating the patient.

The approaches presented here include the major strategies of neuropsychological assessment and interpre- tation from which numerous variations have developed. We discuss the pros and cons of each approach in regard to both theoretical and practical issues.

S t a n d a r d B a t t e r y A p p r o a c h

Halstead (1947) and Reitan (1966) pioneered the use of a standard battery approach of tests for identifying brain damage. First, Halstead and Reitan identified tests that were sensitive to the integrity of cortical functioning. Then they sought to incorporate the evaluation of all the major cognitive, sensory, motor, and perceptual skills that a neuropsychological examination should reflect. The purpose of the Halstead–Reitan Neuropsychological Bat- tery was to allow the development of various principles for inferring psychological deficit as applied to results ob- tained on individual subjects (Reitan & Wolfson, 1993). In this approach, the clinician gives the same tests to all patients, regardless of his or her impression of an individ- ual patient or the referral question. Typically, a technician administers the neuropsychological procedures, rather than a doctoral-level psychologist, because the tests are administered according to standardized rules of proce- dure, without variations. Using technicians allows more testing for the same cost, because the more expensive time of a doctoral-level neuropsychologist is not needed.

This standard battery approach has several advantages. First, it can ensure that all subjects are evaluated for all basic neuropsychological abilities. This makes it unlikely that the diagnosis could overlook a condition of impor- tance. Second, the neuropsychologist can use the data to identify objective patterns of scores that he or she can consider in diagnosing various neuropathologic condi- tions. Patterns within the data can help in diagnosing the probability of certain causes of brain dysfunction. Knowl- edge of causes can be useful in providing the patient, physician, or treatment team with tentative diagnoses, as well as in predicting the course of a disorder. Finally, the standard battery approach lends itself to the teaching of neuropsychological assessment and interpretation, because the beginning neuropsychology student need not make decisions about test selection, and the interpretation is objective and data driven. Finally, because the test instruc- tions, test selection, and test interpretation are all stan- dardized, this approach is particularly useful for empirical

studies and facilitates comparison across different research projects.

There are also drawbacks to the test battery approach. The time involved in testing any patient can be consider- able. Problems such as fatigue or loss of motivation may develop. The time involved forces the use of a testing tech- nician to ensure a reasonable cost and reasonable use of the neuropsychologist’s time. As a result, the neuropsy- chologist may have little contact with the patient outside of the interview and, thus, loses the opportunity to make a qualitative analysis of the patient’s behavior. Obtaining qualitative impressions of the patient’s appearance and be- havior often is important, however. For example, we once observed a neuropsychologist who used the standard bat- tery approach make an interesting misdiagnosis. This par- ticular neuropsychologist strictly favored the neuropsy- chological battery approach and therefore typically did not interview his patients. He claimed that the subjective pre- sentation of the case would “contaminate” his ability to make an objective interpretation. During a neuropsycho- logical examination of a patient, the neuropsychologist’s psychometrician indicated on her data summary sheet that the patient’s performance on the Finger Tapping test was zero. The neuropsychologist proceeded to interpret this score as “severe, right-sided, upper extremity motor slow- ing with possible corresponding left hemisphere cortical dysfunction.” But visual inspection of the patient would have made it obvious that the patient was not suffering from motor slowing and “brain damage”—instead, his right arm was amputated! The issue of using psychometri- cians to administer the neuropsychological tests remains controversial in contemporary neuropsychology.

The original choice of tests to include in the battery heavily influences standard batteries. The theoretical be- liefs of the person doing the choosing often bias the choice. A poorly chosen test battery, no matter how many times it is given, will continue to yield unsatisfactory re- sults. In different situations, alternate areas of assessment may be more effective in providing information. How- ever, because the user of a standard battery gives no addi- tional tests, he or she would never discover this. For ex- ample, the Halstead–Reitan Neuropsychological Battery does not include a memory test.

You can see a common problem of interpreting the empirical approach in composite tests that require the ex- aminee to have a number of cognitive skills. For example, the Hooper Visual Organization Test (Hooper, 1983) re- quires the subject to name or write more or less readily recognizable cut-up objects. The Hooper consists of 30 stimuli. The maximum score is 30, and a score below 20

typically indicates “organic brain pathology.” Because ex- aminers think the measure primarily measures perceptual integration, a function often associated with right hemi- sphere function, they often interpret low scores as percep- tual fragmentation most likely related to dysfunction of the right hemisphere. However, left hemisphere stroke pa- tients often make low scores on this test, not related to impaired perceptual functioning, but related to the pa- tient’s impairment in naming objects. Thus, critiques of the battery approach often suggest that understanding why a patient failed a task is as valuable as that the person failed (Luria, 1966). Such information, they argue, often can be more useful than test scores in making interven- tion and diagnostic decisions. Furthermore, opponents of the empirical approach argue that complex behavior can- not and should not be reduced to a single number or test score. For example, the Hooper demands include com- prehending the instruction; visually scanning the stimu- lus figure; mentally rotating the cut-up parts of the object to form a whole; and recognizing, naming, and articulat- ing the object, either in writing or orally. Thus, this seem- ingly simple task actually requires the person to integrate a number of neuropsychological processes to generate a correct response.

The standard battery method also fails to recognize that altering a test procedure is sometimes valuable in de- termining a specific deficit. A standard battery may not be appropriate for all patients, especially when there are peripheral deficits, such as injury to the limbs, a serious visual loss, or spinal cord injury. Such patients’ inability to complete a given test may reflect a peripheral motor or visual problem, rather than a dysfunction of the central nervous system. Consequently, data from such a patient on a standard battery may be useless for diagnosis, evalua- tion, and intervention. Finally, interpreting even a stan- dard battery requires considerable skill, knowledge, and experience. Nevertheless, as standard rules and norms de- velop, standard batteries are somewhat easier to interpret and to teach.

Although the criticisms of the battery approach are valid, many psychologists remain faithful to administer- ing a “core battery.” Approximately 55% of neuropsychol- ogists favor a flexible, modified battery approach, suggest- ing that the type of patient treated and the nature of the referral question play important roles in test selection.

P r o c e s s A p p r o a c h

The process approach to neuropsychological testing, often called the hypothesis approach, rests on the idea that the neuropsychologist should adapt each examination to

CHAPTER 3 | Neuropsychological Assessment and Diagnosis 81

82 PART ONE | Introduction

the individual patient. Rather than using a standard bat- tery of tests, the neuropsychologist selects the tests and procedures for each examination, using hypotheses he or she has made from impressions of the patient and from information available about the patient. As a re- sult, each examination may vary considerably from pa- tient to patient for length and test selection. The clini- cian may use standard tests, or may alter and adapt tests as he or she tries to form an opinion on the nature of the deficits (Christensen, 1979; Lezak et al., 2004). Al- tering tests to discover the patient’s strategies is a popu- lar method within the process approach to neuropsycho- logical assessment (e.g., see Milberg, Hebben, & Kaplan, 1986). Many conclusions reached in the examination follow the clinician’s qualitative interpretations of the test results and the patient’s behavior. The clinician also grounds the conclusions on his or her experience and knowledge of the clinical literature. The principal devel- opers of the process approach are Alexander Luria and Edith Kaplan.

The process approach has several advantages. First, it acknowledges the individual nature of the patient’s deficits and seeks to adapt the examination to this indi- viduality. Under the proper condition, such a technique can yield more precise measurements of a subject’s skill on a given ability than just the patient’s score on a given test. Second, the examination can concentrate on those areas the neuropsychologist sees as most important for the patient. It can ignore areas not important for the patient’s prognosis. Because the time for any examination is lim- ited, this enables the clinician to more thoroughly investi- gate significant areas.

Perhaps most important, the flexible/process approach emphasizes in what manner a patient fails or succeeds in a specific cognitive task. For example, a patient is unable to answer the question, “What is the capital of the United States?” Does this relate to the patient not understanding the question (speech comprehension), does it indicate an inability to answer verbally (expressive aphasia), or does the patient not know the answer (poor factual knowl- edge)? The standard battery approach does not allow a deviation from the standard instructions of the test, be- cause deviating would invalidate the results. If the patient is unable to answer the question, the process approach al- lows for further investigation. For example, the examiner can show the patient a multiple-choice card with the an- swer and several wrong alternatives. If the patient points to the correct answer, “Washington, D.C.,” the neu- ropsychologist would interpret this response as meaning that the patient knows this factual knowledge but cannot express this information either verbally or in writing.

Thus, the process approach lets the clinician concentrate on tasks related to the most important deficits that the patient exhibits.

The process approach also has several disadvantages. Because the content of the examination emphasizes areas that the clinician believes are important, the examination may selectively confirm the clinician’s opinion. Because the clinician may never test areas that he or she sees as ir- relevant, no one may realize that a deficit has been missed. Because the test’s focus is just on the patient and his or her expected problems, the data may be biased toward confirming the original hypothesis. Thus, many neu- ropsychologists believe this more subjective approach re- lies willy-nilly on clinical experience, hunches, colleagues’ anecdotes, intuition, common sense, folklore, and intro- spection (Meehl, 1973).

Using tests not standardized for a clinical population, or tests that have been adapted, also presents potentially serious problems. The interpretation of a test that has not been adequately standardized is always questionable. The clinician’s subjective impression of what a score should mean for a given patient may be quite wrong. A test that appears to measure one thing in a normal population may measure something entirely different in a brain-injured population. In each of these situations, the accuracy of the individual clinician’s judgment becomes the accuracy of the test. Thus, in the process approach, the opinion of the clinician is as good as his or her reputation. Currently, no measures of such accuracy exist, but probably this varies considerably among clinicians.

The use of different examinations and procedures for each patient precludes the experimental validation of in- dividual tests in applied clinical settings. It also precludes evaluation of the process as a whole, because conclusions do not come from test scores, but from the clinician’s judgments. Clinicians may, in such a situation, continue using an ineffective test because it appears to work. The process approach, therefore, does not lend itself to large- scale research, but often relies on case studies.

Structuring an examination on an individual basis may mean that it assesses only some of the basic functions me- diated by the brain. Rehabilitation and prognosis depend on the state of the brain as a whole; the lack of informa- tion on the entire brain can impede an intervention program or invalidate a prognosis. In practice, it is not unusual to see patients with secondary deficits that ap- pear unrelated to their primary referral problem and to the impression that the patient gives. For example, it is not unusual for a patient with a major stroke to have had smaller, secondary disorders of cerebral circulation. The deficits might have existed before the patient’s current

problem arose. Whatever the source of the deficits, the clinician must identify and consider them in making any recommendations for a client. Finally, the flexible/process approach is more difficult to teach to students, because few “rules” and “procedures” exist. Test selection, adapta- tion, and interpretation depend largely on extensive clini- cal experience. This approach is also time-consuming, be- cause the neuropsychologist, rather than a technician, must perform the evaluation. Table 3.4 reviews the ad- vantages and disadvantages of the standard battery and process approaches.

Paul Meehl, a preeminent psychodiagnostician and former president of the American Psychological Associa- tion, addressed the complex decision-making process in- volved in psychological assessment. In 1957, he wrote the now-classic essay entitled “When Shall We Use Our Heads Instead of the Formula?” (1973). With this question he examined the rationale for when to use more empirical (psychometric) compared with more clinical approaches (qualitative) to psychological assessment, interpretation, and diagnosis. By the term formula, Meehl implied the sci- entific, empirical, and data-driven approach to psychol- ogy, consistent with those neuropsychologists who favor the fixed battery approach. By “using our heads,” in con- trast, Meehl was referring to the more clinical, common- sense, approaches typically used by the process approach in neuropsychology. Meehl suggested that the two an- swers to his question—“Always” and “Never”—were equally unacceptable. He also proposed that it would be silly to answer, “We use both methods; they go hand in hand.” If the formula and your head invariably yield the

same predictions about an individual, you should use the less costly method, because the more costly one is not adding anything. If the methods do not always yield the same prediction—and most empirical studies show that they do not—then the psychologists cannot use both, be- cause they cannot predict in opposite ways for the same patient.

This discussion remains a central theme in any type of psychological assessment, although the empirical approach has been increasingly refined since Meehl wrote his fa- mous paper. Empirical and theoretic considerations sug- gest that the field of neuropsychology would be well ad- vised to continue to concentrate efforts on improving actuarial techniques, rather than to focus on calibrating each clinician for each of many different diagnostic prob- lems. In the meantime, neuropsychologists continue to make descriptions, interpretations, and predictions about human behavior. How should neuropsychologists be making interpretive decisions? Should they use the process approach, or should they follow the empirical, psychometric approach? Mostly, neuropsychologists will use their heads, because researchers have not developed adequate empirical batteries for every type of neuropsy- chological problem. In those cases in which there are good empirical approaches to neuropsychological problems (as in estimating intelligence), they should use an empirical approach. What if there is a case in which the formula disagrees with the clinical opinion of the process ap- proach? Which approach should neuropsychologists use then? Meehl, a staunch scientist, suggested that in such a situation, they should use their heads very, very seldom—

CHAPTER 3 | Neuropsychological Assessment and Diagnosis 83

Standard Battery Approach Process Approach

Same tests or “core battery” given to all Examination administered by a neuropsychologist Tests administered according to standardized rules Tests not administered in a standard way Interpretation based on standardized norms Conclusions based on clinical experience

Advantages Comprehensive evaluation of abilities Acknowledges the individuality of patient Objective interpretation based on normative data Examination focuses on most important deficits Facilitates teaching because of standard rules/norms Emphasizes how a task is failed or solved Useful for empirical studies Useful for clinical case studies

Disadvantages Time demanding and labor intensive Test procedure may be biased by clinician Tests only as good as standardization Opinion of the clinician is subjective Relatively inflexible approach to testing Difficult to teach, because it requires experience Scores may not reflect a single cognitive process Does not lend itself to large-scale research

Table 3.4 Summary and Comparison of Approaches to Neuropsychological Interpretation

84 PART ONE | Introduction

except, of course, if the issue is as clear as a broken leg or amputated arm.

Considerable controversy has raged about the preced- ing approaches to performing and interpreting a neuropsy- chological evaluation. Although there are certainly schools of thought about this, almost 50% of neuropsychologists report using parts of both approaches (Figure 3.15). That is, a majority of neuropsychologists use a modified bat- tery approach, in which they choose specific tests to an- swer a referral question. They may interpret some tests in an empirical fashion and other test behavior in a more qualitative way. Approximately 25% report that they strictly adhere to a standard/fixed battery approach or a process/qualitative approach.

We caution the neuropsychology student that diag- nostic and treatment decisions warrant integrating data drawn from a number of sources, including neuropsy- chological measures, pertinent neuromedical findings, and the patient’s developmental and medical histories. Neuropsychologists typically do not render diagnostic decisions based on a single neuropsychological mea- sure. Obviously, site, nature, and severity of the in- jury/disease process, premorbid personality, and a host of other moderating variables affect neuropsychological test performance. Interpreting the neuropsychological data requires a thorough understanding of neuropsy- chological principles, developmental findings, and psychopathology.

Interpretation of the neuropsychological protocol can then proceed through several levels of analysis, including the following:

Overall level of impairment

Pattern of impairment

Lateralizing and localizing signs Qualitative observations

Once interpretation proceeds through these levels, the neuropsychologist can then evaluate test data to deter- mine consistency with a patient’s known medical condi- tions and presenting diagnoses, as well as to predict func- tional abilities and limitations.

A S S E S S I N G L E V E L O F P E R F O R M A N C E

U s e o f N o r m s i n N e u r o p s y c h o l o g y

The use of norms in neuropsychology entails comparing an individual’s test scores and available normative data. This approach provides the neuropsychologist with infor- mation regarding an individual’s ability in comparison with others. This method compares the patient’s score on a test to an expected score, or norm. The method deter- mines the expected test score from the performance of a normative sample of patients and control subjects. Such norms may take into account such factors as age, sex, ed- ucation, and intelligence. Many neuropsychological tests have a cutoff score. A patient scoring worse than the cut- off score is labeled as impaired; a patient scoring better is labeled as within normal limits.

The selection of any specific cutoff point relates to fac- tors of test specificity and test sensitivity. When seeking to identify people whose cognitive abilities are abnormal (e.g., brain damage), neuropsychologists prefer a sensitive test. In such cases, they set the cutoff score so that as few errors as possible arise in classifying a disease entity. However, sensi- tive tests that rely on measuring impaired cognitive func- tioning may also include false-positive errors, for example, erroneously identifying psychiatric patients as brain dam- aged. Such a test is of little value to the neuropsychologist, who wants to delineate the precise nature of a patient’s deficits. Rather, the clinician needs tests that examine spe- cific aspects of neuropsychological functions; that is, tests that have high specificity. Such tests may assess more gen- eral areas of cognitive functioning, including sustained at- tention or immediate memory. But they may miss patients who have impairments outside of those specific areas of cog- nitive functions, which results in false-negative errors. Of course, tests that have high sensitivity and high specificity are most useful in neuropsychology. In reality, there is al- ways a tradeoff between aspects of how specific a procedure is versus its usefulness as a sensitive test. Thus, neuropsy- chologists often set cutoff scores at an intermediate point at which the chances of misclassifying either impaired perfor- mance or normal performance are about equal.

P e

rc e

n ta

g e

0 Modified/ extended

48%

Process/ qualitative

26%

Fixed battery/ psychometric

22%

Figure 3.15 Approaches to neuropsychological test interpretation. (Reproduced from Gordon, A., & Zillmer, E. A. [1997]. Integrating the MMPI and neuropsychology: A survey of NAN membership. Archives of Clinical Neuropsychology, 4, 325–326, by permission of Elsevier.)

S t a t i s t i c a l A p p r o a c h e s

When administering a battery of tests, it is important to be able to compare performance on tests that measure widely different skills. As you gain enough experience with a set of tests, this skill often becomes automatic. However, the easiest way to accomplish this task is to use standardized scores rather than raw scores. A raw score is a score that is presented in terms of the original test units. It is simply the number of items passed or points earned. A standard score, in contrast, is a derived score that uses as its unit the standard deviation of the population on which the developers standardized the test. Thus, a stan- dard score is a deviation score. A standard deviation re- lates to the variability or scatter of test scores. This pat- tern is known as a distribution of test scores. The normal probability distribution (also known as the bell-shaped curve) represents the frequency with which many human characteristics are dispersed over the population. For example, intelligence and spatial reasoning ability are dis- tributed in a manner that closely resembles the bell- shaped curve.

In the normal distribution, 68.2% of all cases fall be- tween �1 standard deviation (SD) from the mean, 95.4% of the cases fall between �2 SD from the mean, and 99.7% of the cases fall within �3 SD from the mean. The normal distribution is the basis for the scoring system on many standardized tests. For example, on the Scholastic Aptitude Test (SAT), the developers set the mean at 500 and the standard deviation at 100. Hence, SAT scores re- flect how many SDs above or below the mean a student scored. For example, a score of 700 means that you scored 2 SDs above the mean, exceeding approximately 97% of the population on which the test is normed. Thus, test scores that place examinees in the normal distribution can always be converted to percentile scores, which are often easier to interpret. A percentile score indicates the per- centage of people who score below the score you obtained. For example, if you score at the 60th percentile, 60% of the people who take the test scored below you, and the remaining 40% scored above you. Tables are available that permit transformation from any SD placement in a nor- mal distribution to a percentile score.

Neuropsychologists use a variety of standard scores. They determine standard scores by a mathematical for- mula that can convert raw scores from tests to a standard scale. For example, Table 3.5 lists commonly used stan- dardized scores in clinical neuropsychology.

Once you know the test score frequency of a neuropsy- chological measure, you can easily compute a standard score. For example, determine the standard score (SS) by first subtracting the mean score from a normative group

for a test from the person’s actual score. Divide the result by the SD of the scores in the normative sample. Multi- ply this result by 15 (the SD), and add 100 (the mean) to this answer. The formula for standard score is as follows:

SS � 100 � � 15.0

The standardized score approach to neuropsychologi- cal assessment has several advantages. First, all scores are roughly comparable. Second, you can make adjustments for such factors as age and education. You do this by de- termining normative means and SDs for different age or educational levels. You can then include the normative scores corresponding to a given person’s age or education. Of course, not all neuropsychological measures result in normal test distributions. Some distributions skew in one direction or another. Some neuropsychological tests, par- ticularly those that the process approach favors, are rela- tively “easy.” That is, most “intact” individuals would have few problems passing the test. For example, “On a plain piece of paper, draw a clock with all the numbers and the hands of the clock positioned at 10 minutes after 11.” Most individuals would pass this task, but patients with disturbances in visuospatial perception or planning ability may “fail.” Thus, the resulting test score distribution is dichotomous (pass/fail) and does not present a normal distribution. It is inappropriate to calculate standard scores from such a test distribution. A great pitfall of the statisti- cal approach to neuropsychological interpretation is that developers have transformed to standard scores many tests that are not normally distributed, thus providing inexact estimations of performance.

(Score obtained minus average normative score) ��

Standard deviation (normative sample)

CHAPTER 3 | Neuropsychological Assessment and Diagnosis 85

Name of Standardized Mean Standard Deviation Tests Used Score

Z-score 0 1 None

Sten score 5 1 16 personality factors

Scaled score 10 3 Wechsler subtests

T-score 50 10 Minnesota Multi- phasic Personality Inventory, many norms

Standard score (SS) 100 15 Wechsler Intelligent Quotient scores

Table 3.5 Examples of Different Standardized Scores

86 PART ONE | Introduction

David was an active, 66-year-old, right hand–dominant, married man who had com- pleted 11th grade before joining the U.S. Armed Forces. Before retiring, David was employed as a medical technician in a psychi- atric hospital. His wife, a nurse, was his super- visor. In August 1992, David began experienc- ing periods of blurred vision, headaches, nausea and “feeling ill all over, as if I was coming down with the flu.” The family doctor suspected a heart problem because David had a history of mild hypertension and angina beginning in 1987, but a 24-hour electrocar- diogram (EKG) monitor showed no heart malfunction. Over the next month, David experienced five similar episodes. Then, in September 1992, he awoke with numbness and weakness on the right side, as well as slurred speech, and was subsequently hospi- talized. Initial neurologic findings indicated that David was awake and alert with dysarthria and right hemiparesis. The examiner noted periods of paralysis, with the comment that the patient felt “locked in” when these occurred. Physicians at the hospital diagnosed him as having had a transient ischemic attack (TIA; see Chapter 12). After a 10-day course of treatment, the patient was sent home. Hospital records noted that he was “fully recovered” at this point.

MRI of the brain suggested prominence of the ventricular system and subarachnoid spaces consistent with moderate atrophy. The report also noted mild white matter changes on the periventricular region. CT and MRI films of the coronal (Figure 3.16) planes showed a subacute cerebellar infarct (stroke). CT scans

of the head, without intravenous contrast infusion, confirmed the atrophy and previ- ously visualized infarct in the left cerebellum. Repeat CT scan of the head without contrast 3 weeks later showed an additional new small infarction in the left thalamus (see Figure 3.16). Intracranial and neck angiogram sequences revealed no stenosis of the right or left carotid artery bifurcations. Taken together, radiologic data suggested moderate atrophy, postacute left cerebellar infarct, a small left thalamic infarct, and minimal thickening of the common, internal, and external carotid arteries. The radiologic studies did not indi- cate the presence of intracranial hemorrhage or any significant stenosis or plaque in the right or left carotid system. Electroencephalo- gram showed no definite focal or epilepto- genic features.

David continued to have episodes of nausea and blurred vision, and in October 1992, he was again hospitalized with right hemiparesis, dizziness, and slurred speech. Initial diagnosis was that he had suffered another TIA. He was experiencing projectile vomiting and had episodes of high fever and brief periods when he could move only one eye. He also had behavioral digressions during which he would not recognize anyone and would pull out his IV tubes and exhibit other strange behaviors until he had to be restrained to the bed. The medical staff was mystified as to the causes of David’s symptoms.

A few weeks into David’s treatment, the Centers for Disease Control and Prevention (CDC) notified the hospital that David had tested positive for Lyme disease. Puzzled by

the cause of David’s symptoms, his family doctor previously had taken a blood serol- ogy before the second hospitalization and forwarded samples to the CDC. David was given a course of treatment appropriate for

N e u r o p s y c h o l o g y i n A c t i o n 3 . 1

C a s e E x a m p l e : T h e N e u r o p s y c h o l o g y o f L y m e D i s e a s e

by Eric A. Zillmer

Figure 3.16 Horizontal computed axial tomography scan (top) showing infarction in left thalamus. Coronal magnetic resonance image (bottom) demonstrating subacute cerebellar infarct, as well as moderate atrophy. (Courtesy Eric Zillmer.)

D E F I C I T M E A S U R E M E N T

Deficit measurement, as an approach, is standardized and group oriented. It is useful for understanding general conditions and disease states. By comparing a person with “the norm,” you can determine statistically probable deficits. By examining a battery of tests, you can examine an individual’s pattern of strengths and weaknesses. You

can compare these with known, general profiles. But clin- icians are also concerned with the uniqueness and dy- namic qualities of each individual. The adaptive approach to neuropsychology mirrors developments in other areas of psychology. To paraphrase Howard Gardner, the Harvard psychologist, neuropsychologists should not be asking, “How smart is this person?” but “How is this person smart?” In clinical neuropsychology, the focus is not only

CHAPTER 3 | Neuropsychological Assessment and Diagnosis 87

both stroke and Lyme disease. As a result, David’s strange symptoms abated and have not returned, though the hemiparesis and dysarthria remain. The hospital physician did not agree that Lyme disease was re- sponsible for David’s symptoms. David was discharged to a rehabilitation hospital for continued care, where he was referred for neuropsychological testing to evaluate his cognitive status and his ability to participate in speech and physical therapies. Table 3.6 reviews the results of the neuropsychologi- cal battery.

David exhibited generalized deficits, with impaired performance across cognitive areas. His performance on the neuropsycho- logical tests indicated impaired attentional capacity, motor slowness, weakness in the nondominant upper extremity (the patient was unable to use his dominant hand), impaired fine-motor ability, left auditory suppressions, impaired visuoconstructional ability, deficient spatial memory, and poor executive functioning. David’s memory performance demonstrated slightly impaired verbal recall, moderately impaired visual recall, and moderately to severely impaired delayed recall for both verbal and visual material. His intellectual performance, as measured by the Wechsler Adult Intelligence Scale, Third Edition (WAIS-III), was in the Low Average range. David’s IQ scores indicated slightly higher verbal than performance ability, again partially because of his right hemiplegia, but also because of impaired perception of visual material, especially visual details. The visual impairment was further documented by his borderline perfor- mance on the Hooper Visual Organization Test. On the Wisconsin Card Sorting Task, David failed to complete any categories and used the maximum possible number of trials to complete the test. Results of clinical

personality testing (Minnesota Multiphasic Personality Inventory [MMPI]) did not indi- cate significant psychopathology or psycho- logical dysfunction. However, factors re- flected in the protocol did suggest susceptibility to developing psychological problems including denial, somatic concern, and tension. Individuals with similar profiles are often mildly dysphoric, pessimistic about the future, and difficult to engage in psycho- logical therapies because of their defensive- ness and lack of insight.

The neuropsychological evaluation did not shed any light on whether Lyme disease was the “culprit” for David’s medical problems (for a more detailed description of the clinical, radiologic, and neuropsychological manifes- tations of Lyme disease, see Bundick, Zillmer, Ives, & Beadle-Lindsay, 1995). David’s case analysis demonstrates that psychological and neuropsychological assessment may serve to aid in the more definitive diagnosis and improved intervention/rehabilitation of patients exhibiting complex symptoms.

Age, years 66 Sex Male Education, years 11 Occupation Retired medical technician

Intellectual functioning (WAIS-III) Verbal IQ 91 (31) Performance IQ 84 (28) Full Scale IQ 87 (27)

Abstract reasoning, cognitive efficiency, mental flexibility TMT A (seconds) 109 (26) TMT B (seconds) 255 (35) Wisconsin Card Sort (in perseveration errors) 65 (34)

Memory: WMS-R Logical Memory I 19 (36) Logical Memory II 5 (11)

Motor speed and coordination Finger Oscillation DH Not attempted Finger Oscillation NDH 31 (29) Grooved Pegboard (seconds) DH Not attempted Grooved Pegboard (seconds) NDH 154 (34)

Note: WAIS-III = Wechsler Adult Intelligence Scale, Third Edition; IQ = intelligence quotient; TMT = Trail Making Test; WMS-R = Wechsler Memory Scale–Revised; DH = dominant hand; NDH = nondominant hand.

T-scores in parentheses from Heaton, Grant, and Matthews (1991).

Table 3.6 Neuropsychological Profile of Patient with Lyme Disease

on the level of deficits and strengths to describe function- ing; for example, “How adapted (normal) is this person?” but also, “How does this person adapt to his or her con- dition?” Neuropsychologists should question what is lost in terms of understanding the brain if they do not con- sider the range and extent of individual adaptations to in- jury, tumor, and disease.

D i f f e r e n t i a l S c o r e A p p r o a c h

The deficit measurement approach compares a patient’s score on two tests. One test is theoretically highly sensi- tive to brain damage (e.g., a new problem-solving task); the second is theoretically insensitive to brain dysfunction (e.g., a measure of factual language). The insensitive test is supposed to reflect the individual’s ability before any

88 PART ONE | Introduction

brain injury occurred, whereas the sensitive test reflects the effects of brain damage. If the sensitive test score is significantly worse, the neuropsychologist assumes the difference is caused by a brain injury. In general, you com- bine two test scores to get a single score measuring their difference. You may accomplish this by simply subtract- ing or dividing one score by the other. Then analyze this single score by treating it as described in earlier in the As- sessing Level of Performance section.

P a t t e r n A n a l y s i s

A modification of the differential score approach is pat- tern analysis, which examines the relationships among the scores in a test battery. It seeks to recognize patterns consistent with specific injuries and particular neurologic processes and has value in identifying mild disorders that cause relatively little disturbance in level of performance. For example, in early stages of Alzheimer’s dementia, neu- ropsychologists would expect a deficit in memory func- tioning compared with performance on verbal tests, which may be relatively normal. If you plot all the neu- ropsychological data on a standardized norm worksheet, a profile of cognitive skills may emerge. You can then ob- serve the interrelationships among these differing cogni- tive skills areas. A basic method of pattern analysis in- volves observing strengths and weaknesses in the highest and lowest scores. You can evaluate cognitive strengths and weaknesses relative to the normative group by observ- ing which scores fall above, below, or within the average range. You can also determine strengths and weaknesses relative to the individual’s specific profile. Again, high and low scores are highlighted, but without regard for where they fall relative to the normative sample. Finally, you can integrate information about cognitive strengths and weak- nesses with therapeutic suggestions to family and the treatment team to improve the patient’s recovery.

The differential score method and pattern analysis have the advantage of recognizing that each individual starts at a different level of performance. Thus, it avoids error of misclassifying all people with low ability as “brain injured.” However, this approach has several po- tential sources of error. First, a sensitive test may fail to reflect the impairment present. Currently, no test is sen- sitive to all forms of brain dysfunction. Second, the brain injury may lower a score on an insensitive test. Be- cause all abilities depend on the brain, brain damage can affect all abilities. No test is fully insensitive to brain in- jury. Finally, relatively little is known about specific pat- terns of deficits that correlate with specific neurologic disorders, or how to set any cutoff points to identify those conditions.

L A T E R A L I Z I N G S I G N S

The two cerebral hemispheres control the contralateral sides of the body for most sensory and motor behaviors. If one side of the body performs significantly worse than the other, the opposite hemisphere may have been in- jured. Lateralizing signs are specific test results or behav- iors that suggest right or left cerebral hemisphere dys- function. This approach resembles the differential score approach in that one side of the body serves as the con- trol for the other. Generally, you subtract the scores from the two sides of the body to obtain a single difference score. You then treat this score as described in the level- of-performance approach. This approach may yield in- accurate conclusions, however, when an injury involves both hemispheres, or when an injury to the spinal cord is involved, because such injuries may also cause lateral- ized motor or sensory deficits or impair performance bilaterally.

P A T H O G N O M O N I C S I G N S ( Q U A L I T A T I V E O B S E R V A T I O N S )

Examining pathognomonic signs is a method that clini- cal neurologists commonly use. In the medical model, the clinical examination often assumes that specific, distinc- tive characteristics of a disease or pathologic condition can be detected. These signs or symptoms are often la- beled pathognomonic (derived from Greek meaning “fit to give judgment”), because often a specific diagnosis can be made from them. The medical model is a causal model in which specific signs stem either from a specific medical condition or from the disease itself. Thus, a standard med- ical examination is often a series of medical tests for pathognomonic signs. Once a disease has been diagnosed, it can be treated. This model has served the field of medi- cine rather well. For example, the model attempts to fit (pigeonhole) the available information from the medical examination into often rigid and inflexible diagnostic cri- teria. Also, if the signs from the medical examination do not precisely fit, or are contradictory, and if some symp- toms are transient, the model does not work well, because no substantive diagnosis can be established; thus, no treat- ment can be offered.

Pathognomonic signs occur rarely in normal individ- uals. In clinical neurology, this includes such signs as an eye that will not move from side to side. In neuropsy- chology, examples of pathognomonic signs include the rotation of a drawing or the failure to draw the left half of a figure. You can count the number of pathognomonic signs within a given test to get a summary number. You

CHAPTER 3 | Neuropsychological Assessment and Diagnosis 89

Summary The neuropsychological evaluation is a method of examining the brain by studying its behavioral product. As with other psychological assessments, neuropsychological evaluations involve the comprehensive study of behavior by means of standardized tests that are sensitive to brain–behavior relationships. In effect, the neuropsychological examination offers an understanding of the relationship between the structure and the function of the nervous system. Thus, the goal of the clinical neuropsychological examination is to be able to evaluate the full range of basic abilities represented in the brain. In practice, the neuropsychological assessment is multidimensional (concerned with evaluating many different aspects of neurofunctioning from basic to complex), reliable (stable across different situations and time), and valid (meaningful).

The neuropsychologist’s role in evaluation has evolved from a diagnostic emphasis to one in which current neuropsychological functioning is described and the individual’s adaptation to the unique demands of his or her environment is evaluated. The focus is on performance in the testing setting, as well as on a task analysis of the cognitive requirements of home and work. Neuropsychological testing profiles can aid in identifying general categories of neurologic disease and conditions. The purpose of the neuropsychological evaluation examines the individual’s strengths and weaknesses, ability to deal with stress, adaptation, and overall social and occupational functioning. It is in this latter, more descriptive role that neuropsychologists have made their most recent advances.

C r i t i c a l T h i n k i n g Q u e s t i o n s

Why are the concepts of reliability and validity so important in psychological and neuropsychological assessment? What kinds of questions and tests do neuropsychologists use in a neuropsychological evaluation? How are neuropsychology assessment procedures the same? How are they different? What sort of recommendations and treatments can neuropsychologists give to brain-impaired people that will be useful in their daily lives? How do the major two approaches (process and battery) to interpreting neuropsychological data differ?

K e y Te r m s

Neuropsychological evaluation Psychometrics Standardized test Reliability Validity Construct validity Content validity Criterion validity False positive

Base rate Achievement tests Behavioral-adaptive scales Intelligence tests Neuropsychological tests Personality tests Vocational inventories Crystallized functions Fluid functions

Orientation Sensation Perception Motor apraxia Ideomotor apraxia Malingering Interpretive hypotheses Standard battery approach Process approach

Normative data Cutoff score Specificity Sensitivity Normal distribution Deficit measurement Pattern analysis Pathognomonic signs

We b C o n n e c t i o n s

http://ericae.net ERIC Clearinghouse on Assessment and Evaluation—Extensive site on psychological and educational testing and assessment; includes test locator, frequently asked questions, search engine for ERIC, and many other links.

can treat this number as a level-of-performance score. In other cases, the simple presence of a particular pathog- nomonic sign is taken as an indication of brain damage.

See Neuropsychology in Action 3.1 for a case example related to the neuropsychological interpretation and diagnosis.

http://ericae.net

90 PART ONE | Introduction

http://www.unl.edu/buros Buros Institute of Mental Measurement—Home page of the Buros Mental Measurements Yearbook, tests in print, test reviews, and test locators.

http://www.mindtools.com/page12.html Psychometric Testing—Interactive page that lets you discover your learning style; provides “IQ test,” Myers–Briggs Personality Test(R), and other measures.

http://www.toldx.com More information on the Tower of London test.

http://www.sportsci.org/resource/stats/index.html A New View of Statistics—This site features a web-based book about the ins and outs of statistical proce- dures using simple sports analogies and common everyday problems. Within this site you can find concrete examples of simple statistical terms and validity and reliability procedures on interpretation discussed in this chapter.

http://www.unl.edu

http://www.mindtools.com

http://www.toldx.com

http://www.sportsci.org

Part Two

T H E F U N C T I O N I N G B R A I N

Chapter 4 Cells of Thought

Chapter 5 Functional Neuroanatomy

Chapter 6 Cerebral Specialization

Chapter 7 Somatosensory, Chemical, and Motor Systems

Chapter 8 Vision and Language

Chapter 9 Memory, Attention, Emotion, and Executive Functioning

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Chapter 4

C E L L S O F T H O U G H T

Immense numbers of individual units, the neurons, completely indepen- dent, simply in contact with each other, make up the nervous system.

—Santiago Cajal

An invitation is offered to cross a bridge as vast as the infinite space sur- rounding us and as small as the width of a neuron’s membrane. This is a journey into unknown territory, a voyage into the mind. To know the mind is to know the universe.

—Fred Alan Wolf

Neurons and Glial Cells Communication within a Neuron: The Neural Impulse Communication among Neurons Regeneration of Neurons

Neuropsychology in Action

4.1 Short-Circuiting Neurons: Multiple Sclerosis 4.2 Neuronal Firing: Clinical Examples 4.3 What Can We Learn from Songbirds? 4.4 Stem Cell Research: Science and Ethics

Overview Cells are the building blocks of all living organisms. Evolutionarily old, one-celled creatures such as the amoeba show elementary responses to sensation and have decision-making capabilities. In their universe of a droplet of water, amoebas can move about, locate food, and engulf it. They can differentiate light from dark and warmth from cold. This unicellular organism uses complex electrochemical processes, but has no nervous system and no brain. Moving up the evolutionary ladder, increased complexity of behavior corre- sponds with a more specialized nervous system, which is essential for speeded communication. The “jelly- fish,” for example, has a rudimentary nervous system, which allows coordinated movement, but still has no brain.

The human central nervous system (CNS) contains billions of interconnected cells. Of the two main types of cells, neurons alone account for about 100 billion cells, and estimates suggest that glial cells out- number neurons by 10 to 1. Considering there are approximately 6 billion people on earth, the number of cells in one human brain is more like the number of stars in the sky. The CNS is not connected in a simple, linear fashion, but in a densely packed tangle of interconnected networks. If 1 neuron connected only to 100 others, the emerging network would be staggering in its size and complexity. However, evidence sug- gests that the number of connections actually ranges from 1000 to 100,000, averaging about 10,000 per neuron (Beatty, 1995; Hubel, 1988). Cells of the CNS are specialized and interact with each other in a unique manner. Their processing systems require a great deal of energy and consume the most oxygen and glucose of any bodily system.

This chapter focuses on the essential building blocks of thought and behavior: neurons and glial cells. Neurons and glia are classes of cells that contain subtypes based on their structure and function. Neurons are considered the most important cells, and the basic electrical-chemical processes of neuronal communi- cation have been well described by scientists. Although glial cells traditionally have been described as hav- ing a supporting function for neurons, science now suggests that glial cells may have a larger role to play in thought and learning. The neuron can be studied as a universe unto itself, but neuropsychology is also focused on the effect of behavior related to neuronal disruption. Clinical problems such as multiple sclero- sis (MS) and spinal cord injury are the direct result of disease or injury at the neuronal level. The ability of the neuron to repair itself is intriguing because of the enormous implications for treatment.

94 PART TWO | The Functioning Brain

K e e p i n M i n d

How does the unicellular neuron differ from a one-celled creature?

What are the purposes of different cell types in the central nervous system?

How do neurons communicate?

Are damaged neurons able to regenerate?

Neurons and Glial Cells

The neuron differs from other cells in that it is spe- cialized for information processing. To some degree all functions that sustain life, as well as those that make us human, are coordinated and depend on the communica- tion of neurons. Neurons are anatomically independent;

they come very close to each other but do not touch. The nervous system thus consists of separate units rather than one continuous structure.

The neuron has often been studied by scientists with the idea that by studying the fundamental parts, a better understanding of the whole can be achieved. This reduc- tionistic view attempts to investigate complex phenomena

by dividing them into more easily understood compo- nents. Reductionists may describe their work as mapping the brain. Everything, they argue, exists at a particular lo- cation (Churchland, 1993). The neuron hypothesis is in accord with this viewpoint suggesting that (1) all neural function is reflected in behavior, and (2) all behavior has an underlying neural correlate (Pincus & Tucker, 1985). Reductionists argue that the healthy mature brain pro- duces the mind’s range of functions and experiences, which are perfectly correlated to precise biological phe- nomena. In other words, the reductionist viewpoint ar- gues that every human experience can be reduced to a physical phenomenon. Although reductionism is consid- ered outdated and oversimplified because it is not possi- ble to correlate behavior with individual neurons, some neuropsychologists study the relation of behavior to as- semblies of neurons and interconnected neural networks.

The structure of neurons is similar to that of other body cells in that they have a cell body that contains a nucleus, genes, cytoplasm, mitochondria, and other organelles nec- essary to conduct protein synthesis and energy production. However, neurons are quite different from other body cells in several ways. For example:

1. They possess specialized extensions, dendrites and axons, which allow for communication. Dendrites are treelike or feathery extensions that branch from the neuron into the immediate neighborhood of the cell body. The axon extends from the cell body to transmit information.

2. They possess specialized structures, particularly termi- nal buttons, which produce neurochemicals.

3. Neurons communicate through an electrochemical process.

The structure of neurons allows them to communicate with each other in an interesting way. Most body cells communicate with each other or the outside world through energy exchange and intercellular transport, using the cellular membrane. Neurons, however, commu- nicate with each other by axonal firing, which allows elec- trochemical transmission across the synapse, the tiny gap between two neurons. The process of such communica- tion releases chemical neurotransmitters, permitting highly sophisticated combinations of reactions that influ- ence downstream neuronal behavior.

Neurons also have properties of formation and regener- ation that differ from those of other body cells. In general, no new neurons form after birth (Cowan, 1990). In fact, during certain periods of development, massive pruning occurs as important neural connections form in response to learning and maturation. Excess neurons, which may

cause distracting associations, die off. An important ques- tion for brain science is to what extent neurons can re- generate once damaged. Neurons in the periphery can regenerate; for example, if surgeons reattach an ampu- tated finger, the finger may regain some mobility. Neu- rons in the spinal cord and brain do not heal sponta- neously. This is most evident in the complete severing of neurons in the spinal cord, which leads to paralysis. Re- cent findings, however, suggest that some regrowth may be possible. Research on reactivating damaged neurons is ongoing, so perhaps some day scientists will be able to re- verse spinal cord damage (Naugle, Cullum, & Bigler, 1998). Later in this section (see Regeneration of Neurons) we examine the question of neurogenesis, regeneration, and attempts to regain function after injury.

S T R U C T U R E A N D F U N C T I O N O F T H E N E U R O N

Neurons vary in shape and size, but have four common features (Figure 4.1):

1. A cell body with a nucleus 2. Dendrites 3. An axon 4. Terminal synaptic buttons

Neurons are specialized to exchange information, specifi- cally the reception, conduction, and transmission of elec- trochemical signals.

C e l l B o d y

The functioning and survival of the neuron depend on the integrity of the cell body that controls and maintains the neuronal structure. Because these cell bodies are gray, the term gray matter is used to describe areas of the brain that are dense in cell bodies, such as the cortex. The cell soma contains mitochondria, amino acids, and DNA, and it has the same properties of other cells in the body. Pro- tein synthesis cannot occur in the axon, so all axonal pro- teins come from the cell body.

D e n d r i t e s

Neurons generally receive chemical transmissions from one another through dendrites, feathery extensions that branch from the neuron into the immediate neighborhood of the cell body. There are often thousands of dendrites per neu- ron, and they differ in relation to the different functions of the neurons. The profuse branching of dendrites allows them to receive communication from a large number of ax- onal terminals across the synapse. The shapes of dendritic “trees” are often among the most characteristic morphologic

CHAPTER 4 | Cells of Thought 95

features of a neuron (Figure 4.2). For example, dendrites of Purkinje cells (see Figure 4.2a), which are found in all areas of the cerebellar cortex, are characteristically spread out in one plane and have thousands of dendritic spines. Many dendrites are covered with spines, or small knobs, that form the synaptic connection with communicating neurons. Dendrites are tiny, only visible under an electron microscope, and are usually shorter than the axon, but they can have up to thousands of synapses or contacts with other neurons. Neuroscientists estimate that the total possible connectivity among neurons in the human brain is approx- imately 1015, or 10,000,000,000,000,000—more numer- ous than the known stars in the universe (Beatty, 1995;

Williams & Herrup, 1988). Dendrites comprise most of the receptive surface of a neuron.

A x o n

The axon extends away from the cell body. Its primary func- tion is to transmit electrochemical information from the cell body to the synapse through microtubules along its length. Axons are anywhere from less than 1 millimeter (mm) in length to 1 meter (m) or more. Large motor neurons have long axons, some of them reaching from the lower end of the spinal cord to the foot muscles. Other neurons, includ- ing those that coordinate activity within a specific region of the CNS, have short axons. Unipolar axons proceed from

96 PART TWO | The Functioning Brain

Text not available due to copyright restrictions

one region in the CNS to another without branching. In bipolar or multipolar axons, the branching is elaborate.

Many axons are surrounded with a myelin sheath that increases the speed of axonal transmission (Beatty, 1995). This is especially important in longer neurons. Myelin is lipoprotein that wraps around the axon like the layers of an onion, giving neurons their characteristic white mat- ter appearance. The sheath begins at the first segment of the axon, where the nerve impulse or action potential begins. The myelin serves as an electric insulator that in- creases conduction velocity. The myelin sheath is formed

by glial cells, termed oligodendrocytes, in the CNS and by Schwann cells in the peripheral nervous system (PNS). The layers of the myelin wrap around the axon like layers of onion skin (Figure 4.3). Gaps called the nodes of Ranvier interrupt it at regular intervals (see Fig- ure 4.1). The projections of the surface membrane of each of those cells fan out and coil around the axon of neurons to form myelin sheaths. Because the nerve impulse jumps from node to node, the length of the myelin segment is of considerable importance. The longest axonal fibers, which can have a conduction velocity of up to 100 m/sec, may have myelin segments longer than 1 mm.

Myelination begins soon after birth and continues for many years. The development of the myelin sheath corre- sponds to behavior. Babies are unable to control their bladder and bowel functions: This is caused by insuffi- cient myelination of neurons; therefore, children cannot be toilet trained before about age 2 or 3. In adults, a breakdown of the myelin sheath is a consequence of MS (Neuropsychology in Action 4.1).

The speed of neuronal conduction is important in the adaptation of all species to potentially dangerous events in the environment. Given that, in some cases, the built-in conduction speed is not fast enough, the nervous system has evolved to process important sensory data at levels

CHAPTER 4 | Cells of Thought 97

Dendrites

Axon

Apical dendrite

Basilar dendrites

b. d.

Figure 4.2 Neurons of various shapes: (a) Purkinje cell; (b) sensory neurons; (c) pyramidal cell; (d) bipolar cell. (From Kalat, J. W. [2007]. Biological psychology [9th ed., p. 34, Figure 2.9]. Belmont, CA: Thomson Wadsworth.)

Figure 4.3 Cross section of a myelinated axon. (© Dennis Kunkel Microscopy, Inc.)

closer to their origin. The knee reflex is an example. The sensory information that you are about to fall is sent to your spinal cord, which relays it directly back with “instruc- tions” to extend your knee. This occurs without any higher cognitive processing. If the same sensory informa- tion traveled to the brain, the relay would take too long to process, which could result in a fall. Another example is the reflex arc in response to pain, such as a burn. The sensation is relayed to your spinal cord, which gives the appropriate response: “Withdraw finger!” The informa- tion also reaches your brain, of course, although somewhat later; it is then processed at that higher level: “Did I burn my finger?”

In large animals, such as dinosaurs, to compensate for the relatively long distances sensory and motor neurons have to travel, large dinosaurs had a small additional brain at the level of the pelvis. Presumably, the brain integrated many sensory and motor functions at this level so the di- nosaur could respond adaptively to the environment.

T e r m i n a l B u t t o n s

Near the end of the axon are branches with slightly en- larged ends called axonal terminals or terminal buttons. The site of interneuronal contact, where neurochemical information transmits from one neuron to another, is called a synapse (see later in this section for a detailed dis- cussion of synapses). The terminal button is the presy- naptic portion of the synapse, the place where electrical

nerve impulses cause the release of a neurotransmitter. This chemical in turn affects another neuron or muscle in either an excitatory or an inhibitory manner. Signals that travel along the axon are electrical, and the transfer of neurotransmitters across synapses, from one neuron to another, is chemical. Researchers can therefore study and analyze the brain through electrical means—for example, using the electroencephalograph, evoked potential, or electrical stimulation—or through biochemical or meta- bolic techniques such as positron emission tomography.

N e u r o n C l a s s i f i c a t i o n a n d T e r m i n o l o g y

Neurologists commonly classify neurons either by mor- phology (shape) or by function. The three principal classes of neurons are defined by the number of processes ema- nating from their cell bodies. Most are multipolar neu- rons, with more than two processes, or extensions from the cell body (see Figures 4.2a, c). One of these is the axon, and the others are dendrites extending from various parts of the cell body. Bipolar neurons have two processes (see Figure 4.2d ). Monopolar neurons have a single or unipo- lar process, and do not have dendrites originating directly from the cell body or soma (see Figure 4.2b). Neurons with short axons are called interneurons; they integrate neural activity within a specific brain region.

In classifying neurons by their function, motor neu- rons make muscles contract and change the activity of

98 PART TWO | The Functioning Brain

The destruction of the myelin sheath around the axon can result in significant and of ten striking behavioral changes, including blindness and paralysis. Such conditions are called demyelinating disor- ders, of which multiple sclerosis (MS) is the best known. MS is the most common neurologic illness in the United States, affecting 50 of every 100,000 young adults. Symptoms are most of ten first noticed between the ages of 20 and 40. Because MS is more frequent in cer tain geographic locations than in others (polar latitudes), an environmental agent may be implicated in the cause of the disease,

perhaps one related to a demyelinating slow virus or an autoimmune process (Ebers & Sadovnick, 1993).

Although the contracting factor of MS remains an enigma, the course of the dis- ease is known; it is related to the localized loss of myelin in the white matter of the brain and subsequent neuronal death. The loss of myelin initially results in “scrambled” electrical impulses, thus neuronal informa- tion slows or never reaches its target. The symptoms vary according to where the hardened patches, known as sclerotic plaques, lie in the brain and spinal cord, but most manifest visually (sudden unilateral

blindness), in the brainstem and cerebellum (wide-based gait, intention tremors), and in the spinal cord (spastic gait, loss of position sense, and paraplegia). Relapses are usually acute and persist for several weeks. Postmortem studies of MS patients have revealed hundreds of lesions smaller than 1.5 cm (Adams & Victor, 1993). Further- more, there is little potential for regrowth of myelin.

There is no known effective treatment or cure for MS. The prognosis is a gradual deterioration of the patient’s condition over many years. Death can result if the demyeli- nation affects vital centers of the brain.

N e u r o p s y c h o l o g y i n A c t i o n 4 . 1

S h o r t - C i r c u i t i n g N e u r o n s : M u l t i p l e S c l e r o s i s

by Eric A. Zillmer

glands; sensory neurons respond directly to changes in light, touch, temperature, odor, and so on. The majority of neurons are interneurons, or “between” neurons, be- cause they receive input from and send output to other neurons.

Neurons are organized in collective structures; that is, behavior arises from the firing of many neurons, not a single neuron. These bundles—large collections of neurons—are known as tracts, pathways, or fibers in the CNS and nerves in the PNS (Figure 4.4). The three major types of fibers all primarily consist of myelinated axons that appear as white matter:

1. Intracerebral (or association) fibers connect regions within one hemisphere.

2. Intercerebral (or commissural ) fibers connect struc- tures in the two hemispheres.

3. Projection fibers connect subcortical structures to the cortex and vice versa.

Anatomists often discuss pathways by the direction of the projection and the systems they connect (England & Wakely, 1991). For example, the corticostriatal pathway is where fibers connect cortical areas to the striatum. Like- wise, the hypothalamocerebellar tract projects from the hypothalamus to the cerebellum.

Aggregations of cell bodies—predominantly dendrites and terminal buttons—are grayish; their actual color in the living state is pink. As noted earlier, gray matter is typically found on the surface of the cerebral cortex, in the center of the spinal cord, and on large subcortical nuclei (e.g., in the thalamus). In the CNS, clusters of gray cell bodies are called nuclei (singular, nucleus), a term often used to des- ignate a group of nerve cells in direct relation to the fibers of a particular nerve. In the PNS, clusters of gray cell bod- ies are called ganglia (singular, ganglion). The presence of nuclei in the brain is important to neuropsychologists be- cause nuclei often signal strategic clusters of neuronal cell bodies. Vital integration of neuronal information may be occurring at a specific neuroanatomic location. Some functional roles have been attributed to certain nuclei. The precise role of any one nucleus is, however, difficult to delineate, because the dendrites and axons may extend for a considerable distance outside of the boundary of the nu- cleus. In addition, some nuclei consist of different neurons with different neurotransmitters from other neurons, which increases the complexity. In some cases, it may be more use- ful to conceptualize function according to neuronal regions or networks rather than by nuclei. Nevertheless, mapping and identifying specific nuclei in the brain continues to oc- cupy brain scientists.

G L I A L C E L L S

Glial cells (also known as neuroglia or glia) outnumber neurons by a factor of 10, but because of their small size (1/10 that of a neuron), they make up about 50% of the volume of the nervous system, with neurons comprising the other half. The term glia (derived from Greek gliok, meaning “nerve glue”) comes from an old notion that glial cells offer purely structural support to neurons. This is just part of the story; glia have more functions. Glial cells are often described as “servants” to neurons. They help support neurons by physically and chemically buffering them from each other, and they supply nutrients and oxy- gen to neurons to support their very high metabolic rate, because neurons cannot store their own nutrients. Some glial cells act as housekeepers, metabolizing and removing the carcasses of neurons destroyed by injury or disease, and as discussed earlier, certain glial cells form the protec- tive myelin sheath around axons. There is new evidence, however, that some glial cells (i.e., astrocytes) may func- tion more like “parents” than “servants” in directing and regulating neuronal behavior.

Glial cells are found throughout the CNS and PNS. The three main types of glial cells in the CNS are oligo- dendrocytes, microglia, and astrocytes. The primary

CHAPTER 4 | Cells of Thought 99

Figure 4.4 Bundles of myelinated neurons make up tracts, pathways, or fibers in the central nervous system and nerves in the peripheral nervous system. (© SPL/Photo Researchers, Inc.)

Figure 4.5 Glia cells of the central and peripheral nervous systems. Glia cells are of special interest to neurologists and neurosurgeons because they are the site of the principal tumors of the brain and spinal cord. (From Kalat, J. W. [2007]. Biological psychology [9th ed., p. 35, Figure 2.10]. Belmont, CA: Thomson Wadsworth. Photos: © Nancy Kedersha/UCLA/SPL/Photo Researchers.)

Microglia

Axon

Schwann cell

Schwann cell Oligodendrocyte

Astrocyte

corresponding cell in the PNS is the Schwann cell (Figure 4.5).

Of tumors that invade the brain, the most prevalent arise from glial cells and are termed gliomas. Unfortu- nately, gliomas are often relatively fast-growing tumors. Astrocytes respond to brain injury by swelling or prolifer- ating to fill a damaged space. With injury, astrocytes can also degenerate and form scar tissue.

As mentioned earlier, oligodendrocytes in the CNS and Schwann cells in the PNS are myelin-forming glia cells that envelope axons and neurons. These cells per- form a vital function in wrapping the nerve cell with a lipid layer of myelin and increasing the speed with which a neuron conducts its impulse along an axon. Schwann cells myelinate only a single segment of one cell, whereas oligodendrocytes may myelinate several segments of the same axon or several different axons.

Microglia are small cells within the CNS that undergo rapid proliferation in response to tissue destruction, mi- grating toward the site of injured or dead cells, where they act as scavengers and metabolize tissue debris.

Astrocytes are fibrous, star-shaped cells (derived from Latin astra, meaning “star”) with many small “feet” or processes that interpose themselves between neuronal cell bodies, dendrites, and the vasculature providing struc- tural support. The “servant,” or housekeeping, functions of astrocytes are well known. These functions include: (1) “border patrol” of the brain via the blood–brain bar- rier to protect neurons from potential pathogens trans- ported by the blood, (2) maintenance of local ionic and pH balance between groups of neurons, and (3) delivery of energy to neurons in the form of glucose and other metabolic substances.

The border patrol via the blood–brain barrier is ac- complished because blood vessels in the CNS have a lin- ing of tightly joined endothelial cells, which the “feet” of the tightly joined astrocytes hold in place (Figure 4.6). This wrapping of blood vessels keeps large molecules out and permits only restricted transfer of soluble material be- tween blood and brain. The blood–brain barrier allows water, gases, and small lipid-soluble substances to pass across. Certain substances (some drugs, for example) are totally barred from the brain, and other substances re- quire an active transport system across the blood–brain barrier.

Astrocytes help regulate the local intercellular ionic and pH balance. The receptor sites on the cellular mem- branes respond to ions such as calcium (Guthrie et al., 1999), and they restore the ion balance by removing excess ions after neuronal firing. Astrocytes also clear neu- rotransmitters released through synaptic firing and clean up intercellular metabolic waste.

Astrocytes also supply glucose to neurons through the blood–brain barrier. The “feet” of astrocytes, attached to capillaries and blood vessels throughout the brain, act as a suction system, drawing glucose up from the bloodstream via astrocytes and into neurons. Before being passed on, glucose is partially metabolized by astrocytes into a form usable by neurons.

100 PART TWO | The Functioning Brain

The most interesting role of astrocytes, however, may be their “parent” role. It recently has been suggested that astrocytes may play an important role in regulating and coordinating neuronal firing (see review by Nedergaard, Ransom, & Goldman, 2003). Astrocytes may act locally to help define not only structural but communication pathways among neurons. That is, according to this con- ceptualization, astrocytes are not just the support crew and the nurturers but the parental directors. Examples of this are seen in the ways that astrocytes can communicate among themselves and also affect neurons. They can, for example, release captured neurotransmitters and affect the synchronization of neurons. Astrocytes can also commu- nicate among themselves through neuron-independent signaling. Whereas neurons communicate through a com- bination of electrical impulse and chemical transmission, astrocytes rely on chemical signaling only. Their receptor sites respond to ions and specific neurotransmitters. Whereas the response time of electrical signaling in neu- rons is lightning fast, chemical responding through glial

cells may take 15 seconds or longer (Fields & Stevens- Graham, 2002). Because astrocytes can detect the ionic character of the intercellular space, particularly the synap- tic space between neurons, they are in a position to mod- ify the strength of connections between neurons and syn- chronize neuronal firing. For example, in animal models, it has been demonstrated that the synaptic connections between neurons can be strengthened through stimula- tion by adjacent astrocytes (see review by Nedergaard, Ransom, & Goldman, 2003). Therefore, astrocytes ap- pear to have a bigger role in learning and memory than previously thought (Fields & Stevens-Graham, 2002). Also, astrocytes participate in the formation of new neu- ronal synapses and help to specify the connections they make (Pfrieger & Barres, 1997). Finally, radial glial cells, a type of astrocyte, appear to aid in directing nervous sys- tem development (Lemke, 2001).

In summary, the role of astrocytes is emerging from one that was believed to be purely structural, to one of a servant role, to one that has an integrative and possibly

CHAPTER 4 | Cells of Thought 101

Cell membrane

Tight junction proteins

Cytoplasm

Basement membrane

Astrocyte foot processes

Capillary endothelial

cell Astrocyte

Tight junction

Capillary lumen

Red blood cell

Figure 4.6 Blood–brain barrier. (Courtesy Jim Perkins and Netter Images.)

directing role in the functioning of the nervous system. Interestingly, mammals have a greater percentage of glial cells in relation to neurons than creatures lower on the evolutionary scale. It is also interesting that Einstein’s brain, although having no greater density of neurons than other people, had a higher percentage of glial cells in areas of the brain related to higher cognition (Paterniti, 2000). This group of findings is leading brain scientists to pur- sue the study of glial cells to determine the manner in which they interact with and influence neurons.

Communication within a Neuron: The Neural Impulse

The message that travels along the axon from the cell body to the terminal buttons is electrical, but the neu- ron does not carry it down the axon the way an electrical wire conducts electricity. Rather, chemical alterations in the membrane of the axon result in exchanges of various ions between the axon and the fluid that surrounds it, producing an electrical current. This electrical signaling is the foundation of neuronal communication.

R E S T I N G M E M B R A N E P O T E N T I A L

As with all living cells, a cell membrane protects the neu- ron from other matter. Neurons show a resting potential or membrane potential when they are inactive; that is, they show a slight electrical imbalance between the inner and outer surfaces of the membrane caused by the separa- tion of electrically charged ions. Neural communication requires the passage of ions through tiny channels in the axon wall. Ions are atoms or molecules that have acquired an electrical charge by gaining or losing one or more elec- trons. Four ions are important: sodium (NA+), potassium (K+), calcium (Ca++), and chloride (Cl–). Electrophysio- logic equipment makes it possible to measure the electrical potentials (transmembrane potential) of axons. The inside of the axon is electrically negative with respect to the out- side of the neuron; thus, an electrical potential difference exists between the interior and exterior of the axon that is synonymous with the membrane potential. In the giant axon of the squid, this difference is approximately _70 mil- livolts (mV). An electrical imbalance can occur because the membrane of the axon is semipermeable to allow the flow of chemicals across the axonal membrane (Figure 4.7). Some molecules, including oxygen and water, flow through the membrane constantly, and other chemicals, such as potassium, chloride, and sodium, cross through

gates that control the rate of passage. When the neuron is not firing and the membrane is at rest, the sodium ions (Na+) are trapped outside of the neuron. The imbalance in an electrical charge maintains the cell in a state of tension, ready to fire rapidly in response to a stimulus.

The positively charged sodium ions are located in greater concentrations outside the neuron, even though the electrostatic field (negative charges inside the mem- brane) tends to attract them inside. The biological trans- port system that exchanges three sodium ions for every two potassium ions across the membrane of the axon is called the sodium–potassium pump. Many individual protein molecules in the membrane pump sodium out of the axon. This active transport system exchanges three sodium ions for every two potassium ions that push in, and it consumes considerable energy—up to 40% of the neuron’s metabolic resources. The concentration of potas- sium reflects an equilibrium of competing processes. The pump actively moves potassium into the neuron, expend- ing energy in the process. Concurrently, potassium ions flow passively from an area of greater concentration to an area of lesser concentration by the force of diffusion.

A C T I O N P O T E N T I A L

To generate a nerve impulse, a cell membrane must first depolarize. Depolarization begins when a sodium channel across the membrane briefly opens and sodium ions pass through it into the cell, reducing voltage. Depolarization occurs only when the membrane achieves a threshold of

102 PART TWO | The Functioning Brain

�

Action potential Relative refractory period

Absolute refractory period

Membrane

Na�

K� K�

Po te

nt ia

l ( m

ill iv

ol ts )

�40

�80

From the axon hillock

Toward the presynaptic terminal

Figure 4.7 During the resting state of the membrane, the unequal distributions of sodium (Na+) and potassium ions (K+) between the inside and the outside of the neuron produced a difference in voltage. (From Kalat, J. W. [1998]. Biological psychology [6th ed., p. 41, Figure 4.18]. Pacific Grove, CA: Brooks/Cole.)

at least 35 mV reduction of polarization toward zero. When this occurs, the membrane suddenly opens its sodium gates, permitting a rapid, massive, explosive flow of ions. When sodium enters the cell in this fashion, the neuron fires with an action potential. Subthreshold stim- ulation does not result in an action potential, but any stimulation beyond the threshold does. Thus, neurons fire in an all-or-none fashion. The force of the action poten- tial does not depend on the intensity of the stimulus ini- tiating it, and a neuron cannot send stronger action po- tentials down its axons. In fact, neurons fire more or less continuously, and the timing and sequences of impulses and pauses determine the message. Figure 4.8 illustrates the varying stages of an electrical potential across a neuron

membrane during electrical stimulation. The nerve im- pulse spreads down the axon as the voltage-controlled sodium channels open sequentially, like falling dominoes.

Neurons may be in different states of preparedness for firing. Some may be just a few millivolts below the critical voltage level, requiring little additional excitation to reach firing threshold. Others may need to overcome a larger voltage difference between the inside and the outside of the axon to generate an action potential. Once a neuron has fired, there is an associated recovery period when the neuron resists re-excitation and is incapable of firing. This refractory period lasts 1 or more milliseconds, during which the membrane cannot produce another action po- tential in response to stimulation of any intensity.

Neurons communicate through synapses. Chemical messages between neurons are carried by neurotransmit- ters and have one of two effects on the receiving neuron: excitation or inhibition. The inhibitory and excitatory properties of neurons on behavior are of special interest to neuropsychologists. The ability to sit quietly and read this book requires many functions, both excitatory and in- hibitory. It is common for patients with generalized brain trauma to have difficulties sitting still, concentrating, and reading for a prolonged period (Golden, Zillmer, & Spiers, 1992). Such problems are related to that many of the neu- ronal collections in the CNS, particularly those of the frontal lobe, serve to inhibit rather than excite behavior. This is of clinical importance because losing inhibitory neurons to trauma or disease may result in impulsivity and inappropriate behavior known as disinhibition.

It is the firing rate, not the magnitude of electrical ac- tivity of the neuron, that can change—that is, increase. For example, if inhibitory fiber collections increase their rate of firing, inhibition increases and behavior corre- spondingly decreases. This is why many traumas to the brain often cause both a loss of function, such as the in- ability to initiate behaviors, and disinhibition, which may include impulsiveness, hypersexuality, and inappropriate expression of emotions such as crying or silliness.

Communication among the cells of the brain is the basis of all behavior. Our previous discussion centered on how the individual neuron works. We now discuss how neurons communicate with each other. The anatomic location of this communication is known as the synapse. The synapse is the gap between the terminal button and the receptors of the next neuron.

The language of human neural communication is chem- ical. In fact, almost all mammalian synapses are chemical in nature, although researchers have found electrically trans- mitting synapses in invertebrates and lower vertebrates. The chemical messengers are called neurotransmitters. In simple

CHAPTER 4 | Cells of Thought 103

– 70

– 60

– 50

– 40

– 30

+ 30

– 20

– 10

Resulting electrical potential

1 ms

E le

ct ri

ca l p

o te

n ti

al (

in m

V )

+ 10

+ 20

+40

+50

1 ms

Rate of entry of sodium into neuron

Rate of exit of potassium from neuron

Time

Figure 4.8 Action potential. (From Kalat, J. W. [2007]. Biological psychology [9th ed., p. 43, Figure 2.16]. Belmont, CA: Thomson Wadsworth.)

terms, a chemical message transfers across the synapse from one neuron to another, where it influences the neuron or neurons to fire or not to fire. In reality, this particular ex- change is extremely complex, involving many different mol- ecules. The process is so intricate that a neuroscientist can easily dedicate an entire career to the study of one neuro- transmitter exchange. But human brains, and minds, are af- fected not only by internally produced chemical messengers but also by externally originating chemicals that find their way to the synapse. Such chemicals are known as

psychoactive drugs, and they include caffeine, cocaine, nico- tine, and alcohol, among many others.

Chemical transmission is very much at the center of human behavior and emotions. In fact, many of the most fascinating discoveries about the brain concern the chemi- cal nature of neuronal transmission. For example, research- ers have established that the large numbers of individual nerve cells or units in the nervous system are related to each other through synapses in a more or less continuous fash- ion, creating a network (Neuropsychology in Action 4.2).

104 PART TWO | The Functioning Brain

The influence of neuronal firing on behavior is easily seen in a variety of related clinical phenomena.

Seizures Seizures, which are unusual electrical events in the brain, have a wide range of causes, including trauma, tumors, and epilepsy. Seizures result from massive waves of synchronized nerve cell activation that may involve the entire brain. You can thus conceptualize them as “electrical storms.” Seizures may have dramatic behav- ioral manifestations, including uncontrolled muscle contractions, changes in perception, and alterations in mood and consciousness.

Drugs Certain drugs and poisons specifically alter the flow of sodium and potassium through the membrane. Most drugs act at the level of the synapse, but several substances directly influence the firing rate of the axon, changing the person’s perception or mood and, in some cases, causing death. For example, scorpion and black widow venoms overexcite the nervous system by keeping sodium channels open and closing potassium channels, causing prolonged depolarization that renders the neuron helpless to convey information. As a result, life-sustaining behavior may cease (e.g., breathing may stop), or there may be a lack of disinhibition (such as a continuous involuntary flexing of a

muscle or tic). Novocain, a topical anesthetic used by dentists, attaches itself to the sodium gates of the neuronal membrane and prevents sodium ions from entering. Consequently, the action potential is blocked and sensory nerve messages, including pain, cannot reach the brain because the neurons that typically convey this message cannot fire.

Chloroform decreases brain activity by promoting the flow of potassium ions out of the neuron. This reduces the number of sodium ions that spontaneously pass through the cell membrane and hyperpolarizes the neuronal membrane, which reduces the responsiveness of the nervous system. Tetrodotoxin (T T X), a poison found in the Japanese blowfish, directly blocks voltage-gated sodium channels. Lithium, a simple salt extracted from rock, is the most effective treatment for bipolar disor- der (manic-depressive illness), which is char- acterized by severe mood swings (Freedman, Kaplan, & Sadock, 1978). Lithium stabilizes mood most effectively during the manic stage. Its overall effect on brain activity is not clearly understood, but lithium is chemically similar to sodium and may partly take its place crossing the membrane.

Electroconvulsive Therapy Early in the twentieth century, a physician named Ladislaus von Meduna noted that psychotic patients who had epilepsy im- proved in mood immediately after each

epileptic attack. Reasoning that the electri- cal storm of neural activity in the brain somehow improved mental activity, Meduna applied a large amount of electricity to the skull of depressed patients, causing the collective firing of neurons—a seizure. Elec- troconvulsive therapy (ECT) sometimes improves severe forms of depression within a few days. Although researchers do not clearly understand the mechanism, cur- rently, clinicians use ECT when it is important to intervene quickly to prevent a patient from acting on suicidal thoughts.

Death When is a human considered dead? When the heart stops beating? Or when the lungs stop breathing? Because the brain is the Zentralorgan (German meaning “central organ”) that coordinates the beating of the heart and the breathing of the lungs, the clinical moment of death is precisely when the firing of the brain ceases. Thus, in most states, once an unconscious patient has been admitted to a hospital, the staff moni- tors brain electrical potential data with an electroencephalograph. As long as there is brain activity, the patient is considered alive. Interestingly, even after a brain has stopped generating action potentials, the brain mass itself can hold its own electrical charge for a short time. This can be measured by placing a dead brain slice on an apparatus that is sensitive to small electrical charges.

N e u r o p s y c h o l o g y i n A c t i o n 4 . 2

N e u r o n a l F i r i n g : C l i n i c a l E x a m p l e s

by Eric A. Zillmer

Communication among Neurons

S T R U C T U R E O F S Y N A P S E S

The presynaptic neuron delivers an action potential down its axon until it loses its myelin sheath and divides into many branches called buttons, or synaptic knobs. These buttons swell at the end to increase the area of contact with the postsynaptic neuron. The buttons themselves do not touch the postsynaptic cell, which is covered with myelin and surrounded by glia cells. Between the two neurons lies a small space known as the synaptic cleft or synaptic gap. This space is so tiny (about 200–300 Å) that it is observable only through an electron microscope.

Terminal buttons harbor oval structures called synaptic vesicles, which contain neurotransmitters. These vesicles are unique cellular structures that typically cluster close to the presynaptic membrane. Neurotransmitters are synthe- sized until they are delivered to the receptor sites on the postsynaptic neuron. There are numerous neurotransmitter

molecules, each shaped differently and with its own key fit to a specific receptor. This mechanism determines how the synaptic endings evoke excitation or inhibition in the postsynaptic neuron. Researchers have identified two major types of receptor sites (Beatty, 1995): the symmet- ric synapse, which appears to be involved in inhibitory functions, and the asymmetric synapse, which plays a role in excitatory processes. The anatomic location of the terminal button in relation to the postsynaptic mem- brane can vary. It may be on the dendrite, the soma, or the axon of the postsynaptic neuron.

S Y N A P T I C T R A N S M I S S I O N

The synapse includes the presynaptic membrane, the synaptic cleft, and the postsynaptic membrane. When the neural impulse from the presynaptic neuron reaches the button, the vesicles release a specific amount of a neu- rotransmitter (typically 1000–10,000 molecules) into the synaptic cleft (Figure 4.9).

CHAPTER 4 | Cells of Thought 105

Neurotransmitter binds to receptor

Postsynaptic neuron

Synaptic cleft

Presynaptic terminal

Vesicle

Glia cell

Transporter protein

Synthesis of smaller neurotransmitters such as acetylcholineTransport of peptide

neurotransmitter

Synthesis of peptide neurotransmitters and vesicles

Cell body

Action potential causes calcium to enter, releasing neurotransmitter

Reuptake of neuro- transmitter by transporter protein

Negative feedback sites respond to retrograde transmitter or to presynaptic cell’s own transmitter.

Postsynaptic cell releases retrograde transmitters that slow further release from presynaptic cell

Separation from receptors

Figure 4.9 Events in synaptic transmission. (From Kalat, J. W. [2007]. Biological psychology [9th ed., p. 59, Figure 3.8]. Belmont, CA: Thomson Wadsworth.)

Several scenarios are possible after the release of a neu- rotransmitter. The molecules may not fit a specific recep- tor site and, therefore, do not bind to the cell membrane. In this case, the neurotransmitter has no effect on a re- ceiving neuron, and no communication takes place. Or, neurotransmitters may be released in areas with no imme- diate postsynaptic receptors. In this case, the transmitter may diffuse over a wider area, affecting neurons far from the point of release. If the released neurotransmitter keys into the receptor site, it will bind to the cell membrane. Depending on the type of neurotransmitter, it will affect the ultimate firing or inhibition of the postsynaptic cell in one of two ways. Some neurotransmitters activate the postsynaptic receptors, which triggers an alteration in the ionic permeability of the cell membrane. Transmitters af- fecting the postsynaptic cell in this matter are considered to be rapid transmitters, because the onset of ionic action in the postsynaptic cell is fast, in the order of millisec- onds. Other neurotransmitters (e.g., serotonin) activate the postsynaptic receptor to transmit a chemical message through the cell membrane. The messenger, in turn, trig- gers a second messenger (intracellular molecule) that initi- ates a cascade of reactions within the postsynaptic cell. This intracellular activity produces a number of cellular changes, including an alteration in the ionic permeability of the postsynaptic membrane. Second-messenger transmis- sion is considered to be slow with regard to onset of post- synaptic activity; that is, onset can range from hundreds of milliseconds to seconds (Schwartz & Kandel, 1991; Preston, O’Neal, & Talaga, 1997). The ionic changes ini- tiated by the two forms of neurotransmitter actions are similar. If the alteration in the permeability of the cell re- sults in increased levels of Na+ and Cl– moving into the postsynaptic cell and smaller amounts of K+ moving out, the postsynaptic cell depolarizes. This depolarization, known as an excitatory postsynaptic potential (EPSP), increases the probability that the postsynaptic cell will reach its threshold. An EPSP makes it more likely that the membrane threshold will reach an action potential and that the postsynaptic neuron will fire.

During an inhibitory exchange, the presence of a neu- rotransmitter increases the permeability of the postsynap- tic membrane, particularly to K+. This results in an ionic current that hyperpolarizes the postsynaptic neuron. Thus, greater depolarization than normal is required to reach an action potential. This depolarization, called in- hibitory postsynaptic potential (IPSP), becomes less probable. Next, the synaptic vesicle either dissipates or is reabsorbed by the presynaptic membrane, which allows the recycling of neurotransmitters and completes the cycle. This summation of EPSPs and IPSPs, analogous to

yes/no messages, is the main principle of neural commu- nication. The nervous system is exceedingly complex, be- cause one single neuron may have many synaptic termi- nals on it that could influence the action potential of thousands of other neurons.

N E U R O T R A N S M I T T E R S

Neurotransmitters permit the exchange of information among neurons and between neurons and other cells. Neurotransmitter types (Table 4.1) are classified accord- ing to molecular size. For example, the biogenic amines and amino acids are small-molecule messengers, consisting of fewer than 10 carbon atoms, and the neuropeptides, which are larger molecules. Although smaller molecule neurotransmitters, such as acetylcholine (ACh), sero- tonin, and the catecholamines, have traditionally re- ceived the most scientific study, neuropeptides are more numerous in the brain, with more than 40 different neu- ropeptides currently identified (Kalat, 1998).

Just as each neurotransmitter has a specific shape, comparable with a key, each receptor site also has a spe- cific structure analogous to a lock. Thus, a specific neu- rotransmitter will attach itself only to a receptor with an appropriate fit. In some cases, a variety of neurotransmit- ters can adhere to a single type of receptor molecule: Many different keys may fit the same lock. At times, dif- ferent neurotransmitters may compete for the same re- ceptor molecule. For example, even though neurotrans- mitter A might have adhered to receptor Z at one time, in competition with neurotransmitter B, A may fail to

106 PART TWO | The Functioning Brain

Biogenic amines Acetylcholine (ACh) Serotonin (5-HT)

Catecholamines Dopamine (DA) Norepinephrine (NE) (noradrenalin) Epinephrine (EPI) (adrenalin)

Amino acids Gamma-aminobutyric acid (GABA) Glycine Glutamate Aspartate

Peptides Vasopressin Oxytocin Thyrotropin-releasing hormone (TRH) Corticotropin-releasing factor Substance P Tachykinins Cholecystokinin

Table 4.1 Neurotransmitters

activate because B fits better. This scenario may occur thousands of times even at the individual level of one neuron. Chemical transmission allows tremendous flexi- bility and refinement.

D i s t r i b u t i o n o f N e u r o t r a n s m i t t e r s

Many distinct neurotransmitter pathways define the brain chemically and anatomically. The tracing of neuronal pathways along neurotransmitter systems has been at the center of the neurosciences since the development of modern staining methods. Investigations show that neu- rotransmitters are both localized to specific regions and widely dispersed in the brain. The pathways of the cate- cholamine transmitters such as dopamine (DA) and nor- epinephrine are relatively specific in their targeting of brain regions, whereas other transmitters (e.g., glutamate) are widely distributed throughout the brain.

Acetylcholine—In the early 1900s, ACh (or choline) was the first neurotransmitter to be identified; researchers discov- ered that it stimulates the parasympathetic nervous sys- tem. It plays a prominent role in the PNS, influencing motor control, and in autonomic nervous system func- tioning. ACh also is a predominant neurotransmitter at the neuromuscular junction, stimulating muscular con- traction. In the CNS and brain, ACh affects a wide be- havioral repertoire. One of its most important functions might be to influence alertness, attention, and memory.

ACh has a simple chemical structure, but its method of action is complicated and is yet to be fully understood. One component necessary for synthesizing ACh is choline, which is supplied by foods such as liver, kidneys, egg yolks, seeds, and many vegetables and legumes. It is synthesized in the liver and recycled in the brain. Choline easily crosses the blood–brain barrier. There is evidence that shows an influx of choline in the brain after eating and an outflow when plasma choline levels are lower, that is, between meals (see Feldman, Meyer, & Quenzer, 1997). Like other neurotransmitters, ACh binds to a variety of postsynaptic receptor subtypes. The two main subtypes of ACh are muscarinic choline and nicotinic choline, named after the bitter botanical alkaloids that stimulate the receptors (muscarine from the fly agaric mushroom, Amanita mus- caria, and nicotine from tobacco, Nicotiana tabacum). The implication is that the action of ACh may differ from one receptor subtype to another. Nicotinic receptor binding creates an excitatory response, whereas muscarinic re- sponses may be either excitatory or inhibitory. Therefore, in the PNS, for example, glands and muscles may be either excited or inhibited, depending on the subtype of ACh

receptor. Certain drugs act on nicotinic receptors, and oth- ers are specific to muscarinic receptors.

As in the PNS, distribution of ACh is widespread in the brain, where it has many possible behavioral functions. First, cholinergic (ACh) neurons in the striatum, a collection of brain structures named after their striped or striated appear- ance, influence motor system functioning. Degeneration of striatal neurons is associated with Huntington’s disease.

Second, ACh functions in arousal and in the sleep/ wake cycle. The reticular activating system is a network of neurons that arises from the brainstem and projects throughout the cortex. One of its primary functions is to regulate brain activation. For example, Sitaram, Moore, and Gillin (1978) report that an ACh antagonist such as scopolamine extends the normal interval (about 45 min- utes) between rapid eye movement (REM) sleep. Al- though many neurotransmitter systems are involved in the sleep cycle, ACh appears to play a role in activating the cortex. Increased levels of ACh in the brainstem and basal forebrain are associated with increased cortical arousal and wakefulness. Researchers can elicit REM sleep, which is characterized by increased cortical activity, by activating muscarinic ACh receptors.

Third, a major cholinergic system thought to influ- ence attention, memory, and learning emerges from the basal forebrain and projects throughout the cortex and to structures important for consolidating memory, such as the hippocampus. An important cholinergic nucleus in the basal forebrain is the nucleus basalis of Meynert (named after its discoverer). Its degeneration as a factor in Alzheimer’s disease became evident when researchers found that patients with this disorder had measurably lower than normal levels of ACh in their brains. Alzheimer’s disease is associated with severe memory dysfunction, and this obser- vation led researchers to wonder whether ACh plays a role in memory functioning. Scopolamine, a drug that blocks ACh at muscarinic receptor sites, causes deficits in encod- ing and consolidation into long-term memory (see Polster, 1993). Surgical patients given scopolamine often have amnesia for the events before surgery. These findings led to the development of drugs that serve as ACh agonists binding to the same receptors as ACh and in- creasing ACh levels for use in clinical trials with patients with Alzheimer’s disease. However, this intervention was largely disappointing, perhaps in part because Alzheimer’s disease involves much more than one neurotransmit- ter system. It is also possible that ACh has a less direct influence on memory, and instead functions to main- tain a higher level of cortical alertness and attention that may be a necessary precursor to adequate memory functioning.

CHAPTER 4 | Cells of Thought 107

Serotonin—Serotonin is widely distributed throughout the brain, but the serotonin system originates in a small area of the brainstem called the nuclei of the raphe. The raphe nuclei consist of a collection of neurons through- out the midline of the brainstem. The serotonin pathways of the raphe nuclei branch out toward the cerebellum. Those pathways in the medulla oblongata project toward the spinal cord, and axons of the cells in the rostral group of the nuclei branch out to the forebrain. Ascending fibers of serotonergic neurons project to the limbic sys- tem, a major collection of subcortical structures involved in the modulations of mood and emotion. Destroying the raphe nuclei leads to insomnia, and serotonin plays a major role in the sleep/wake cycle. Low levels of serotonin are also associated with severe depression. Several studies have demonstrated that depressed individuals are more likely to commit suicide if they have unusually low levels of serotonin being produced and released in the brain (Roy, De Jong, & Linnoila, 1989; Träskmann, Asberg, Bertilsson, & Sjöstrand, 1981). Alterations in serotonin also accompany violent and aggressive behavior in ani- mals (Brown & Linnoila, 1990) and in humans (Elliott, 1992).

Norepinephrine—Norepinephrine (NE) forms predomi- nantly among neurons and their nuclei in a brainstem site named the locus ceruleus (the “blue place”), located below the wall of the fourth ventricle. NE pathways innervate many areas in the forebrain, the cerebellum, and the spinal cord. Its functions are complex and widespread. Research suggests that NE is important in regulating mood, hor- mones (via the hypothalamus), cerebral blood flow, and motor behavior. Similar to DA, NE plays a role in arousal and attentional regulation (specifically, the focusing of at- tention), as well as other cognitive operations such as mem- ory and speed of information processing. NE is implicated in clinical disorders involving depression, anxiety, and inat- tention (Stahl, 2000). Researchers have also found that stressful situations can increase the production and release of NE in the hypothalamus in rats (Cenci, Kalen, Mandel, & Bjoerklund, 1992).

Dopamine—DA is an important neurotransmitter that has been implicated in a number of clinical disorders. Three relatively distinct brain dopaminergic pathways are impli- cated in neuropsychological functioning (Figure 4.10). The first pathway, the mesolimbic pathway, projects from the ventral tegmental area of the brainstem to the nucleus ac- cumbens (basal ganglia), other limbic areas of the brain, and prefrontal cortex. This pathway is associated with the experience of pleasurable sensations, including euphoria

with the abuse of certain drugs, and the positive symptoms (e.g., hallucinations and delusions) of schizophrenia. Most antipsychotic drugs that target the positive symptoms of schizophrenia operate to block DA receptors. The second pathway, the mesocortical DA pathway, also originates in the ventral tegmental regions of the brainstem, but trans- verses to the frontal cortex and limbic regions. This path- way has been implicated in the pathogenesis of the nega- tive symptoms of schizophrenia and the mediation of a number of cognitive functions (verbal fluency, serial learning, attention regulation, and regulation of behavior based on social cues) (Stahl, 2000). The third DA path- way, mesostriatal, projects from the substantia nigra of the brainstem to the caudate nucleus and putamen of the basal ganglia. This pathway is involved in the regulation of voluntary motor functions and initiation of behavior in response to environmental stimuli (Feifel, 1999). De- creased DA activity in the pathway is associated with motor symptoms such as rigidity, loss or slowing of move- ment, and tremors. In contrast, excessive DA in the sys- tem appears to prompt motor tics, chorea, and other motor behavior disruptions. Two subcortical disorders implicated in the overactivity and underactivity of the ni- grostriatal pathways are, respectively, Parkinson’s and Huntington’s diseases.

Amino Acids—Amino acids are the building blocks of pro- tein and are present in every cell in the body. In the brain,

108 PART TWO | The Functioning Brain

Basal ganglia

Prefrontal cortex

Mesostriatal system

Substantia nigra

Ventral tegmental area

Mesolimbocortical system

Figure 4.10 Dopamine pathways. (From Kalat, J. W. [2007]. Biological psychology [9th ed., p. 479, Figure 15.20]. Belmont, CA: Thomson Wadsworth.)

amino acids are involved in the basic neuronal transmis- sion that depends on rapid communication among neu- rons. Of the more than 20 amino acids, the most common are gamma-aminobutyric acid (GABA), which has strong inhibitory properties, and glutamate, an excitatory neurotransmitter. In fact, GABA is so common in the CNS that researchers believe one third of all synapses are receptive to it. Glutamate also occurs in high concentra- tion throughout the nervous system and is the major ex- citatory neurotransmitter. The most prominent GABAer- gic projection system consists of the inhibitory Purkinje cells that extend into the deep portions of the cerebellar nuclei. Some of the major projecting systems of the basal ganglia that are also inhibitory are the striatum, globus pallidus, and substantia nigra. The inability of patients with Huntington’s disease to control their own motor be- havior perhaps relates to the loss of inhibitory GABAergic neurons in the basal ganglia.

Peptides—Peptides are short chains of amino acids; scien- tists have identified more than 60 peptides. High levels of peptides are present in the hypothalamus and the amyg- dala, and to a much lesser extent, in the cortex, the thala- mus, and the cerebellum. Naturally produced peptides with opiate properties are called endorphins. Endorphins have received much scientific attention for their analgesic effects and their possible role in a pain-inhibiting neu- ronal system. Psychologists have always been interested in new procedures to alter the perception of pain, and re- search suggests that acupuncture and electrical stimula- tion of the brainstem arouse the pain-inhibiting endor- phin system. The nervous system has specific receptor sites that bind the drug morphine and related opiate com- pounds. The presence of opiate receptors suggests that the brain itself can create opiate neurotransmitters, perhaps to produce a natural high after prolonged physical stress or in the event of a catastrophic injury. Endorphins that

CHAPTER 4 | Cells of Thought 109

Can the adult brain form new neurons? The common wisdom has been that at birth the brain has all the neurons it will ever possess. In fact, the brain goes through a necessary process of pruning neurons as learning strengthens certain neural associations and others become unnecessary. There is evi- dence in some species of songbirds, how- ever, that new brain cells form in conjunction with seasonal changes in mating songs. Researchers Ball and Hulse (1998) have reviewed this literature and report intriguing findings. Male canaries and sparrows, some of the most studied songbirds, have complex mating songs that show seasonal variation, being most prominent in spring. Neurobiolo- gists have precisely mapped the vocal system of these songbirds and have found a consistent structure–function relation be- tween specific nuclei and singing behavior.

For example, the high vocal center (HVC) is responsible for vocal production, and the robust nucleus of the archistriatum (RA) aids in coordinating respiration with singing. Within this circuit of nuclei are neurorecep-

tors that are specific for sex hormones, such as androgens and estrogens. Receptors for these steroid sex hormones are not present in the vocal control circuitry of birds that are not songbirds. The complexity of song pro- duction differs in male and female song- birds, with males singing more songs and more complex songs. Researchers think this greater production in males serves as a mating function, to attract females and establish territory. This sex difference in singing behavior corresponds to structural differences in the vocal control systems of males and females. Specifically, in male songbirds, the HVC and RA are larger and contain more hormonal receptor nuclei. These differences aroused the curiosity of researchers. Male song production is sea- sonal, so might there be seasonal changes in the brains of males?

In fact, there were. In male canaries, the HVC had increased in size by nearly 100% in the spring compared with the fall! The RA had increased by a factor of about 75% (Nottebohm, 1981). The next question was,

“What was causing this increase?” Was the size or volume of existing neurons changing? For example, might new dendritic connec- tions form during this time? Or were new neurons developing? Evidence showed that the nuclei that control singing increase in volume when the blood levels of testos- terone rise. New staining techniques involv- ing a traceable radioactive tag of newly forming cells indicated that new neurons formed in the ventricles of canaries and migrated to the vocal control system, specifi- cally the HVC and RA (Goldman & Nottebohm, 1983). This was an astonishing finding. Further evidence indicates that adults of other species also generate new neurons, and that this co-occurs with learning. Such research has exciting implications for the study of human language. Will the findings of neurogenesis in adult canaries generalize to human language or other types of learning? And if new neurons can be formed, what is the implication for rehabilitation from brain injury and for lifetime adult learning programs?

N e u r o p s y c h o l o g y i n A c t i o n 4 . 3

W h a t C a n W e L e a r n f r o m S o n g b i r d s ?

by Mary V. Spiers

originate in the brainstem may interfere with pain im- pulses via their action on the spinal cord.

Regeneration of Neurons

To what extent a patient recovers from an injury to the PNS or CNS pathways depends largely on the regen- erative capacity of the damaged neurons. The capacity for regeneration in the PNS is actually quite good; useful function can often be restored with surgical nerve repair. Surgeons have reattached fingers and even complete limbs, and much sensory and motor function has been restored (Neuropsychology in Action 4.3).

The regeneration of neurons in the CNS is more com- plex. Once damaged, neurons do not heal spontaneously after the developmental period. Generally speaking, hu- mans are born with as many neurons as they will ever have, although new research has suggested that adult hu- mans do generate new neurons from some stem cells in various parts of the brain. This fact is related, in part, to the structure of the CNS, which is infinitely more com- plicated than that of the PNS. As a result, the CNS has

little of the spontaneous cellular regeneration required to reconnect a damaged axon to its normal target. Most often, the projections of such neurons, as well as the tar- gets of other neurons, are lost. Later chapters discuss why the brain can compensate when neurons are lost and also how neuronal plasticity and the reconfiguration of func- tional systems are important to the developing brain. Re- cently, a flurry of research activity has focused on estab- lishing procedures that facilitate neuronal growth through stem cell research (Neuropsychology in Action 4.4) or by attempting to coax injured neurons into regrowing.

Injuries and diseases that result in neuronal loss or degen- eration are a major health concern and can significantly af- fect the quality of life in individuals with CNS disorders. For example, more than 100,000 people in the United States have paraplegia or quadriplegia, a disabling condition that results from severed neurons in the spinal cord. Head in- juries—in which axonal shearing, a form of stretching caused by physical forces, is common—affect about 3 million peo- ple. Stroke, which is neuronal cell death due to insufficient oxygen, affects about 2 million people; degenerative condi- tions such as Alzheimer’s, Parkinson’s, and Huntington’s diseases burden millions more. It is thus important for

110 PART TWO | The Functioning Brain

As scientific inquiry has evolved, so too have ethical dilemmas. Nowhere is this illustrated more prominently than in the area of stem cell research. Stem cells are undifferentiated cells; they do not yet have either an identi- fied or specialized function. They eventually differentiate into the building blocks of tissues and organs. Another unique charac- teristic of stem cells that distinguishes them is their ability to proliferate or replicate themselves for long periods.

Stem cells used for research typically are either embryonic or adult stem cells (Com- mittee on the Biological and Biomedical Applications of Stem Cell Research, 2002, p. 13). Embryos usually come as a donated by-product of in vitro fertilization (National Institutes of Health, 2002). Embryonic stem cells can be stimulated to differentiate into specific cell types such as heart muscle

cells, blood cells, or nerve cells. Stimulation includes changing “the chemical composi- tion of the culture medium,” altering “the surface of the culture dish,” or modifying “the cells by inserting specific genes” (National Institutes of Health, 2002). The goal of such procedures is the future ability to produce, on demand, specialized cells that can be used as a treatment for certain diseases where there is degeneration or destruction of cells.

Adult stem cells have been located in “bone marrow, peripheral blood, brain, spinal cord, dental pulp, blood vessels, skeletal muscle, epithelia of the skin and digestive system, cornea, retina, liver, and pancreas” (Department of Health and Human Services, 2001). It was not until the 1990s that scientists discovered that the brain contains stem cells. These stem cells

are able to generate the brain’s major cell types: astrocytes and oligodendrocytes, which are nonneuronal glial cells, and neurons. Stem cells in adults have been identified in the subventricular zone of the telencephalon (Alvarez-Buylla & Garcia- Verdugo, 2002) and in the dentate gyrus of the hippocampus (Gould & Gross, 2002; Song et al., 2002); these cells were demon- strated to differentiate into any type of nervous tissue cell (Alvarez-Buylla & Lois, 1995; Gage, 2000; Weiss et al., 1996).

The pluripotency, or plasticity, of embry- onic cells has been one of the touted advan- tages of embryonic stem cells compared with adult stem cells. However, recent re- search supports that at least some adult stem cells may also demonstrate this pluripotency, with the possibility that further research will uncover other adult stem cells

N e u r o p s y c h o l o g y i n A c t i o n 4 . 4

S t e m C e l l R e s e a r c h : S c i e n c e a n d E t h i c s

by Meghan L. Butryn, Danielle Kerns, and Heather W. Murray

neuropsychologists to understand the life cycle of a neuron and what happens when it becomes damaged or diseased.

Some immediate recovery of function can be observed after traumatic or vascular lesions to the CNS. A lesion is any pathologic or traumatic discontinuity of tissue result- ing in the loss of neurons. Interestingly, recovery is related

to a reduction of swelling in surrounding brain or spinal cord tissue, not to a spontaneous healing of neurons. A process called collateral sprouting, which occurs in nearby intact neurons, may also facilitate functional reorganization (Figure 4.11). Researchers have made great advances in stimulating the growth responses with which the CNS

CHAPTER 4 | Cells of Thought 111

that are multipotent. A second key difference is related to the ease of growth in cultures, with embryonic stem cells being more easily grown. Researchers are attempting to deter- mine why embryonic stem cells proliferate for a year or more in the laboratory without differentiating, whereas most adult stem cells appear to have a more limited capacity for doing so (Carpenter, Mattson, & Rao, 2003). Finally, the ability to use an individ- ual’s own adult stem cells eliminates the risk for rejection by the immune system.

If scientists can direct the differentiation of stem cells into specific cell types, they may be able to treat many diseases and injuries. Patients who have conditions in which destruction of cells occurs within a defined area, such as stroke or spinal cord injury, may be candidates for transplanta- tion. Patients with diffuse conditions such as Alzheimer’s disease, where neurochemical destruction of many types of cells occurs, may be more difficult to treat with stem cell transplantation because many different types of neurons would need to be replaced in many different locations (Armstrong, Watts, Svendsen, Dunnett, & Rosser, 2000).

Similarly, replacement of entire circuits, which would likely be necessary to treat conditions such as Huntington’s disease, may prove to be more difficult. Cell-specific conditions, such as amyotrophic lateral sclerosis (ALS) and Parkinson’s disease, where destruction is limited to certain tracts of cells, and demyelinating conditions, such as MS, are also considered candidates for advanced research in stem cell transplanta- tion. Other conditions that eventually might be treated with stem cell transplantation include Purkinje cell degeneration and vision and hearing loss.

ALS, also known as Lou Gehrig’s disease, is a progressive disease that degenerates cholinergic motor neurons in the brain and spinal cord. As the disease progresses, patients with ALS eventually become para- lyzed and, on average, die 5 years after onset. In a study conducted by Kerr and colleagues (2003), rats were exposed to the Sindbis virus, which destroys motor neurons and causes paralysis in a way that mimics ALS. These researchers selected embryonic stem cells that were barely differentiated and that had two molecular markers of motor cells and

injected them into the spinal cords of these rats. Three months after transplantation, treated rats had regained movement in their hind limbs, including the ability to walk, whereas untreated rats remained paralyzed. The transplanted stem cells migrated through- out the spinal cord and further developed molecular markers of motor neurons.

In addition to typical ethical issues of research, stem cell research involves proce- dures that are controversial, particularly regarding use of embryonic stem cells. The heart of the stem cell research debate is based on the definition of life. There is a push to develop less controversial alterna- tive treatments to replace embryonic stem cell transplantation. But the lack of plastic- ity of adult stem cells in comparison with embryonic stem cells leads some research- ers to suggest that advancements in stem cell research will come largely from further investigation of embryonic stem cells. Limiting research with embryonic cells, it is believed, will only slow the progression of learning about the development of increased plasticity of adult stem cells (Civin, 2002).

At first

Axon 2

Dendrites

Cell body

Axon 1

Loss of an axon Sprouting to fill vacant synapse

Collateral sprouting

Axon injured, degenerates

Figure 4.11 Example of collateral sprouting. (From Kalat, J. W. [2007]. Biological psychology [9th ed., p. 141, Figure 5.16]. Belmont, CA: Thomson Wadsworth.)

typically reacts to trauma, replacing tissue lost to injury or disease with neuronal transplants and developing assess- ment, prosthesis, and cognitive rehabilitation techniques for disrupted functional systems. One major finding by

neuropsychologists has been that an active training rehabil- itation program facilitates recovery of function. It is within this area of assessment and intervention that clinical neu- ropsychologists have made some of their greatest advances.

112 PART TWO | The Functioning Brain

Summary This chapter discusses the structure and function of the important “cells of thought.” Each of these classes of cells contain subtypes that are specialized for different types of information processing. Although scien- tists know most about the electrochemical processes of neurons, the chemical processes of glial cells are gaining more attention for their role in cognitive functioning. At its most fundamental level, all human be- havior originates from the basic processes mediated by the structural interconnections and the chemical influences of neurons and glial cells with each other. Clinical disorders of neurons include diseases or con- ditions that physically damage the neuron or disrupt communication. In this chapter, we discuss multiple sclerosis and introduce disorders that will be examined in more depth in later chapters, such as epilepsy and spinal cord injury. Research related to the mechanisms of structural neuronal repair as well as a better understanding of the chemical interplay of these cells is helping to inform treatment.

C r i t i c a l T h i n k i n g Q u e s t i o n s

Will it be possible one day to “map” the circuits of the human brain? Actor Christopher Reeve suffered a severe spinal cord injury and died without fulfilling his pledge to walk again. What is the outlook for other people with paralysis caused by spinal cord injury? Is it possible for a drug to be effective if it does not activate a naturally occurring brain chemical receptor? What scientific and ethical questions will need to be resolved for research into neuronal repair and neurogenesis to be successful?

K e y Te r m s

Dendrites Axon Terminal buttons Synapse Neurotransmitter Pruning Gray matter Purkinje cells Dendritic spines Myelin sheath White matter Action potential Glia Oligodendrocytes Schwann cells Nodes of Ranvier Multipolar neurons Bipolar neurons Monopolar neurons

Interneurons Motor neurons Sensory neurons Tracts Pathways Fibers Nerves Intracerebral fibers Intercerebral fibers Projection fibers Nuclei Ganglia Microglia Astrocytes Gliomas Blood–brain barrier Resting potential Membrane potential Ions

Sodium–potassium pump Refractory period Disinhibition Seizures Electroconvulsive therapy (ECT) Electroencephalograph Synaptic knobs Synaptic vesicles Receptor sites Excitatory postsynaptic potential

(EPSP) Inhibitory postsynaptic potential

(IPSP) Acetylcholine (ACh) Serotonin Catecholamines Dopamine Muscarinic choline Nicotinic choline

Striatum Reticular activating system Basal forebrain Hippocampus Nucleus basalis of Meynert Nuclei of the raphe Norepinephrine Locus ceruleus Substantia nigra Amino acids Gamma-aminobutyric acid

(GABA) Glutamate Peptides Endorphins Stem cells Amyotrophic lateral sclerosis

(ALS)

We b C o n n e c t i o n s

http://psych.hanover.edu/Krantz/neurotut.html Basic Neural Processes Tutorials A good tutorial on the basics of neural processing. Includes a glossary of terms and quizzes on the structure of the neuron and the brain.

http://www.neuroguide.com Neurosciences on the Internet A searchable page that provides links to sites in neuroscience.

CHAPTER 4 | Cells of Thought 113

http://psych.hanover.edu

http://www.neuroguide.com

Chapter 5

F U N C T I O N A L N E U ROA N ATO M Y

Anatomy is for physiology what geography is for the historian: It describes the scene of action.

—Jean Fernel

The Brain—is wider than the sky— For—put them side by side— The one the other will contain With ease—and You—beside—

—Emily Dickinson

Anatomic and Functional Development of the Brain Organization of the Nervous System Peripheral Nervous System Central Nervous System Gross Anatomy: Protection and Sustenance of the Brain Principal Divisions of the Brain Brainstem and Cerebellum Telencephalon

CHAPTER 5 | Functional Neuroanatomy 115

Overview Neuroanatomy is best understood within a conceptual framework of structure–function relationships. In neuropsychology, a primary goal is to understand the psychological functions and systems of the brain. Rather than memorizing structures for structure’s sake, a more meaningful picture emerges from knowing how the subdivisions of the brain are related, and what roles they play in initiating and regulating behavior. Neuroanatomy and neuroscience texts present slightly different variations of organization within the major subdivisions of the brain. Some authors focus on morphology as the organizing scheme, some on physiol- ogy, and some on embryonic and fetal development. Despite the daunting array of structures, the basic logic of neuroanatomy is straightforward. The organization presented in this chapter shows the relationships between the often-confusing terms and groupings. This goal is accomplished by using the foundation of the developing brain within the context of evolution, which provides a useful picture of functioning from basic to more complex behaviors.

This chapter discusses individual structures and terminology, shows their location in the brain, and gives a brief overview of function. The material covered here is not a detailed review of the content often covered in courses on neuroscience or sensory motor systems, but rather constitutes an illustrated account of the functional anatomy of the major components of the nervous system. With the foundation of the gross anatomy and functioning this chapter presents, you can appreciate the normal and abnormal phenomena associated with brain dysfunction. The structures are the important topographical features on which the various processing systems of the brain depend. This chapter is a stepping-stone for subsequent chapters related to functional systems and, indeed, for the entire book. We develop these structures further as we examine functional brain systems and neuropsychological disorders.

To set the stage for our discussion of the functional neuroanatomy of the brain, we discuss the prena- tal and postnatal development of the human brain. The gestation of the brain is a significant developmen- tal period when you consider that the rate of neuronal development is estimated at 250,000 neurons per minute, for a total, at birth, in excess of 100 billion (Cowan, 1979; Papalia & Olds, 1995). Despite this astonishing rate of early brain development, the process is both orderly and systematic. That is, the brain develops in accordance with genetically predetermined templates or “blueprints” that guide the unfolding of structure and function. The developmental process does not stop and wait for better conditions such as optimal maternal health and nutrition, nor does it reverse direction to repeat developmental stages that are compromised by insults engendered by trauma, drugs, or environmental toxins. Accordingly, it is not surprising that negative events during gestation account for a significant number of childhood neurologic disorders.

The first section presents an overview of the anatomic development of the brain, followed by a presenta- tion of the major components of the nervous system. We also introduce the necessary terminology for a common orientation to the geographical locations of structures. Next, we present structural features that protect and sustain the brain. Finally, we discuss principal divisions of the brain, from lower, evolutionarily older structures to higher order structures.

K e e p i n M i n d

What are the stages and processes of anatomic development?

How are the subsystems of the brain organized?

How does the brain protect and nourish itself?

Does brain structure follow brain function?

What are the major divisions of the brain?

Anatomic and Functional Development of the Brain

Beginning as a hollow tube, the brain develops steadily through temporally distinct stages to its final anatomic and functional state of well-delineated cellular layers and regions. The development of the central ner- vous system (CNS) is orderly and systematic, generally unfolding from head (cephalic) to tail (caudal), from near (proximal) to far (distal), and from inferior (subcortical) to dorsal (cortical). The earliest stage, neurogenesis, in- volves the proliferation of neurons of the neural tube and the migration of these cells to predetermined locations. This stage is primarily genetically determined, although environ- mental influences can have an impact on this process. Sub- sequent stages include the growth of axons and dendrites, formation of synaptic junctures, myelination of axons, and synaptic reorganization involving strengthening or loss of synaptic connections. The latter stages complete much of their maturation during postnatal development. In gen- eral, prenatal development is primarily concerned with the formation of the CNS, whereas postnatal development in- volves the increasing emergence of functionality.

N E U R O G E N E S I S A N D C E L L U L A R M I G R A T I O N

Both the CNS and peripheral nervous system (PNS) de- velop from the outer ectoderm layer of the fertilized egg at approximately 18 days after conception. Ectodermal tissue (neural plate) rises, then subsequently folds and fuses at approximately the fourth week to form the neural tube (Figure 5.1). The cavity of the neural tube gives rise to the ventricular system of the CNS, and the cells lining the wall of the neural tube, termed precursor or progenitor cells, create the neurons and glial cells (astrocytes, oligoden- drocytes, and microglia) of the brain (Martin & Jessell, 1991). Developing cells do not proliferate at the same rate along the expanding neural tube. The timing and location of these cells are genetically predetermined and relate to their final placement and function in the mature brain. Once the proliferation of a specified group of neurons is complete, the migratory process commences and the cells move outward toward their genetically determined desti- nation in temporally different waves. As the cells reach their destination, they begin to develop the characteristics of the cell types that are intrinsic to that particular brain region (Kolb & Fantie, 1997). The process of increasing regional specialization of cells is referred to as differentia- tion. The migrating cells do not differentiate at the same

rate; for example, the cells destined for the hippocampus differentiate at a faster rate than the cells of the cortex (Monk, Webb, & Nelson, 2001).

The open ends of the neural tube close at approxi- mately the 26th day of gestation, with the anterior end subsequently creating the brain, and the posterior end forming the spinal cord. The process of forming and clos- ing the neural tube is called neurulation. Failure of the neural tube to close during development can cause a num- ber of developmental disorders. For example, neuroscien- tists believe that spina bifida, a congenital developmental disorder characterized by an opening in the spinal cord, results from a disruption of the proliferation rate of neural cells or from the failure of these cells to differentiate prop- erly in the neural tube. In contrast, when the anterior end

116 PART TWO | The Functioning Brain

Figure 5.1 Formation and closure of the neural tube. (a) Start of neurulation, two cross-sectional views. (b) Late stage of neurulation, showing the anterior and posterior closing. (From Lemire, R. J., Loeser, J. D., Leech, R. W., & Alvord, E. C. [1975]. Normal and abnormal develop- ment of the human nervous system. Philadelphia: Lippincott Williams & Wilkins, by permission.)

of the tube fails to close, the brain fails to develop anatomically, producing a condition termed anen- cephaly. In this condition, the brain is a vascular mass and the infant does not survive.

The development of the cortex, corticogenesis, be- gins in the sixth to seventh embryonic week. The rapidly proliferating cells along the wall of the neural tube mi- grate outward at different predetermined times. The neu- rons migrate in sheets (laminae) along nonneuronal (glial) fibers that span the cortical wall. Ultimately, these neu- ronal sheets constitute the six laminated layers of the cor- tex and the subcortical nuclei. The inner layer forms first, followed by the development of the outer layers of the cortex. Each successive generation of migrating cells passes through the previously developed neuronal cells. Thus, the cortex develops from inside out, with migra- tion beginning earlier for the more anterior and lateral areas of the cortex (Rakic & Lombroso, 1998). By the 18th week of gestation, virtually all cortical neurons have reached their designated locations and cell proliferation ceases. The exceptions are the cells of the hippocampus and cerebellum that continue to proliferate after birth (Anderson, Anderson, Northam, Jacobs, & Catroppa, 2001). After migration, many of the glia cells transform into astrocytes, whereas others merely disappear (Monk et al., 2001).

Disruption in the migratory process can result in sig- nificant and extensive malformations of the developing brain. For instance, abnormalities of cell migration can produce developmental anomalies of the corpus callosum and other subcortical structures. Similarly, disruption of cell migration during the first trimester of development is associated with malformations of the cerebral cortex. An example is the condition of agyria, or lissencephaly, a disorder that occurs during the 11th to 13th weeks of ges- tation and involves the underdevelopment of the cortical gyri (Hynd, Morgan, & Vaughn, 1997). Severe neuro- logic problems accompany this condition, such as severe mental retardation, motor retardation, seizures, and re- duced muscle tone. Most infants with agyria do not sur- vive beyond 2 years of age.

A X O N A N D D E N D R I T E D E V E L O P M E N T

As the neurons migrate along the glial fibers, axons begin to form rapidly and travel to other neurons of the brain, allowing for cortical–cortical, cortical–subcortical, and interhemispheric communication. The intercommunica- tions afforded by axonal connections are crucial to the in- tegrative functioning of the brain. As the migrating neu- ronal cells reach their designated positions, dendrites

begin to sprout in a process called arborization. Subse- quently, little extensions called dendritic spines begin to extend out from the dendrites. The dendrites and den- dritic spines create synapses for gathering information to transmit to the neuron. Dendritic growth begins prena- tally and proceeds slowly, with the majority of arboriza- tion and spine growth actually occurring postnatally. The most intensive period of dendritic growth occurs from birth to approximately 18 months of age.

The development of the dendrites and dendritic spines is highly sensitive to the effects of environmental stimula- tion. This sensitivity fosters the growth and differentia- tion of the brain; yet, it increases its vulnerability to dam- age. An example of this vulnerability is the discovery, for certain groups of mentally retarded children, of abnor- malities of the dendritic spines that are not attributable to genetic factors. In these cases, neuroscientists suspect some form of environmental insult as having produced the anomaly.

S Y N A P T O G E N E S I S

Paralleling the growth of the axons and dendrites of the brain is the formation of synapses, that is, synaptogene- sis. Synaptogenesis begins during the second trimester as neuronal migration approaches completion. Thus, at the 28th gestational week, synaptic density is low in all cortical regions, particularly the prefrontal cortex. Whereas the occipital lobe begins developing before birth and rapidly achieves near adult-level synaptic den- sity between ages 2 and 4, the more slowly developing prefrontal cortex does not reach adult levels until late adolescence or adulthood. Likewise, the synaptic devel- opment of the motor speech cortex (Broca’s area) follows a slow trajectory paralleling that of the prefrontal cortex (Huttenlocher & Dabholkar, 1997). Regional increases in synaptic density accompany the emergence of function. For example, a rapid increase in synaptic density of the frontal lobes during the latter part of the first year of life correlates with the emergence of rudimentary executive functions.

M Y E L I N A T I O N

As cellular migration nears completion, oligodendrocytes begin to encircle the axons, providing a protective white insular sheath called myelin (see discussion in Chapter 4). The process of myelination begins in the spinal cord, pro- ceeds through the subcortical regions, and finally com- pletes the cortical circuitry. The cortical regions myelinate at different times, beginning in the posterior regions of

CHAPTER 5 | Functional Neuroanatomy 117

the brain and moving in an anterior direction, with the parietal and frontal lobes completing the process last. The myelination of the latter two regions begins after birth, and in the case of the frontal regions, continues into ado- lescence and adulthood. The significant increase in brain weight in the postnatal years is primarily a function of the brain’s increased myelination. Furthermore, the myelina- tion of regional circuitry generally correlates with the emergence of function. Thus, similar to synaptic density, myelination is a “marker” of increasing functional matu- rity of brain circuitry. For example, myelination of the optic nerve begins at birth and is completed by the third month, consistent with the emergence of vision.

P R U N I N G

During the early months of neurodevelopment, the neu- rons and synaptic processes of the brain are initially over- produced. Researchers believe that the synaptic connec- tivity of the neurons is not completely genetically preprogrammed, and many of the initial connections may be random, unnecessary, or poor. Subsequent develop- ment eliminates, or prunes, large numbers of neurons, with the process often beginning at the sites of the den- dritic spines. Pruning does not appear to be random, but rather to be a purposeful sculpting of the brain; that is, synaptic connections that are strengthened through sen- sory input and motor activity are spared. In contrast, pruning eliminates weakly reinforced or redundant con- nections, thus promoting neural efficiency. Economy in structure and function appears to be an overarching prin- ciple of evolutionary development. This process is exem- plified by the development of speech and language spe- cific to one’s culture. At birth, the infant is sensitive to the range of sounds that are evident in all languages. However, the reinforcement of speech sounds unique to one’s culture results in the loss of sensitivity to sounds not evident in the language. Neuroscientists speculate that neurons and synaptic processes representing the under- stimulated sounds are pruned. Functionally, this pruning potentially accounts for the greater difficulty encountered in learning a second language at an older age as opposed to at an earlier age.

Pruning is primarily a postnatal process, eliminating 40% of the cortical neurons of the brain during child- hood. The remaining neurons are eliminated during ado- lescence, and possibly into early adulthood. The observed reduction in cortical gray matter during adolescence is be- lieved related to synaptic pruning (Gogtay, Giedd, Lusk, Hayashi, Greenstein, Vaituzis, et al., 2004). Pruning of brain regions proceeds at different times and rates. Thus,

reduction of the synapses in the visual cortex begins at 1 year of age and is completed by age 12, whereas pruning of the prefrontal region proceeds from 5 to 16 years of age (Pfefferbaum, Mathalon, Sullivan, Rawles, Zipursky, & Lim, 1994).

R E G I O N A L D E V E L O P M E N T

As noted earlier, the anterior, cranial end of the neural tube expands to form the brain, and the posterior end evolves to form the spinal cord. Before neurulation is complete, three vesicles (dilations or expansions) develop at the anterior end. These vesicles subsequently form the forebrain (prosencephalon), midbrain (mesencephalon), and hindbrain (rhombencephalon). In the fifth week of development, the forebrain and hindbrain each subdivide, whereas the third vesicle, the midbrain, maintains its re- gional structure. The division of the prosencephalon results in the formation of the telencephalon and diencephalon. The rhombencephalon subdivides to form the meten- cephalon and myelencephalon. These regions, in turn, give rise to the cortical and subcortical structures of the brain. The five subdivisions, in combination with the ven- tricular system and spinal cord, constitute the seven major divisions of the CNS. Figure 5.2 presents the regional development of the brain.

L O B U L A R A N D C O N V O L U T I O N A L D E V E L O P M E N T

As the cerebral cortex moves forward in development, it first expands anteriorly to form the frontal lobes, then dorsally to form the parietal lobes, and finally, posteriorly and inferiorly to form the temporal and occipital lobes. The posterior and inferior expansion pushes the cortex into a C-shape. As a result, this C form also shapes many of the underlying structures, including the lateral ventri- cles, the head of the caudate of the basal ganglia, the hip- pocampus and fornix, and the cingulate and parahip- pocampal gyri (Martin & Jessell, 1991).

In the initial stages of prenatal development, the brain surface is smooth, lacking both gyri and sulci. The gyri and sulci patterns of the cortex form after neuronal migration, and they reflect the processes of neuronal specialization, dendritic arborization, synaptic formation, and pruning.

The major sulci dividing the cerebral lobes appear first, whereas the gyri within the individual lobes emerge later. At approximately 14 weeks gestation, the longitudinal fis- sure dividing the two cerebral hemispheres and the Syl- vian (lateral) fissure demarcating the border of the pari- etal and frontal lobes are visible. Gyrification continues in

118 PART TWO | The Functioning Brain

an orderly and symmetric fashion through gestation, and by birth, the gyral patterns of the adult are present (Hynd & Hiemenz, 1997). Table 5.1 details this progression.

The formation of the gyri signals that intracortical con- nections are established. Although the gyri and sulci pat-

terns of each person differ slightly, unusual or extreme al- terations suggest deviations in cortical connections and potential cognitive and behavioral deficits (Hynd & Hiemenz, 1997). For example, an insult to the brain (such as intrauterine infection) during the fifth and sixth month of gestation can produce polymicrogyria, a condition characterized by the development of small, densely packed gyri. This anomaly is associated with learning disabilities, mental retardation, and epilepsy (Hynd et al., 1997).

V E N T R I C U L A R A N D S P I N A L C O R D D E V E L O P M E N T

As the CNS matures, the cavities within the cerebral vesi- cles of the neural tube subsequently form the ventricular system and the central canal of the spinal cord. The cavi- ties of cerebral vesicles differentiate into (1) the two lat- eral ventricles, formerly called the first and second ven- tricles of the forebrain; (2) the narrow cerebral aqueduct, or aqueduct of Sylvius, of the midbrain; and (3) the fourth ventricle of the hindbrain (Martin & Jessell, 1991). The transformation of the ventricles into their characteristic C-shape begins at approximately 3 months. Cerebrospinal fluid (CSF) is produced in the ventricles,

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Text not available due to copyright restrictions

cushions the brain and spinal cord within the skull and vertebral column, and removes waste products from the brain.

The spinal cord does not divide; rather, it segments during development. These units correspond to the cervi- cal, thoracic, lumbar, sacral, and coccygeal levels of the mature spinal cord. Throughout early prenatal develop- ment, the spinal cord grows at the same rate as the verte- bral column and occupies the entire length of the verte- bral canal (space within the vertebral column). Later in development, the growth of the vertebral column exceeds that of the spinal cord. At birth, the caudal end of the spinal cord extends only to the lumbar vertebra (Martin, 1996).

P O S T N A T A L D E V E L O P M E N T

During the last 3 months of prenatal life and the first 2 years of postnatal development, the brain changes rapidly. At birth, a baby’s brain is one-fourth the weight of its final adult weight of approximately 1300 to 1500 grams (Majovski, 1997). By age 2, the brain has achieved three fourths of its eventual adult weight and the cortical surface area of the hemispheres has doubled. During this rapid growth period, significant synaptic and dendritic interconnec- tions form, and pruning and myelination are occurring. Other maturational processes are also evident during this period, including increases in neurotransmitters and re- lated biochemical agents and changes in electroencephalo- graphic wave patterns.

Positron emission tomography (PET) studies of in- fants are providing insights into the early postnatal de- velopment of the brain. Glucose is a primary energy source of the brain, and the rate at which glucose is used (metabolized) in various brain regions provides a mea- sure of the activation of these regions. PET imaging can capture the glucose metabolism of brain structures. Moreover, the pattern of glucose metabolism of brain regions correlates with the behavioral, neurophysiologic, and neuroanatomic maturation of the brain (Chugani, Muller, & Chugani, 1996). In the newborn (5 weeks), four brain regions show the highest rate of glucose uti- lization. These areas include the sensorimotor cortex, thalamus, brainstem, and cerebellum. In contrast, glu- cose utilization is generally at low levels in other regions of the cortex and basal ganglia. This pattern of regional utilization indicates that the phylogenetically older brain structures (primarily subcortical) are rapidly developing, consistent with the reflexive and limited behavioral repertoire of the newborn. Cortical functions are at a rudimentary level and are limited to the primary sen-

sory and motor areas. As the infant begins to demon- strate more coordinated visuomotor movements during the second to third month, increases in glucose metabo- lism are evident in the parietal, temporal, primary visual cortical regions, basal ganglia, and cerebellum. Primitive neural reflexes become less prominent as subcortical and cortical regions integrate. Between 6 and 8 months, the frontal and association cortices increase in activation. This increase correlates with the emergence of more ad- vanced cognitive behaviors. For example, by the eighth month, the infant is able to perform the delayed re- sponse task, a rudimentary measure of working memory (see Chapter 9). Continued changes in regional metabo- lism and associated behavioral maturation are evident through childhood.

Total brain volume does not significantly increase after 5 years of age. This stability of total brain volume belies the progressive and regressive growth of white and gray matter; that is, white matter volume increases are offset by decreases in gray matter volume. White matter in- creases are evident throughout childhood into adulthood, although the growth varies across and within different brain regions. Cortical and subcortical gray matter ini- tially increases, with peak volumes being achieved at dif- ferent temporal points. For example, the peak in gray matter volume for the parietal lobes is between 10 and 11 years of age, the temporal lobes by 16 years of age, and the frontal lobes by 11 to 12 years of age (Casey, Giedd, & Thomas, 2000; Giedd, 2004). Progressive loss of gray matter occurs after these peaks. This loss of gray matter volume reflects the developmental processes of pruning and cell death of neurons and glial cells. Among the last maturing cortical regions, as evidenced in achievement of adult gray-to-white matter volumes, is the dorsolateral prefrontal cortex. The relatively late maturation of the dor- solateral prefrontal cortex is consistent with the protracted development of higher order or “executive” cognitive, emotional, and social processes and functions. The in- crease in white matter significantly enhances the speed of neural transmission, whereas the reduction in gray matter represents a form of neural “streamlining” to support com- plex and efficient processing. Developmentally, the matu- ration of gray and white matter parallels the emergences of ever increasing cognitive, affective, and social behaviors. That is, brain regions associated with primary sensory and motor functions mature first, followed by regions support- ive of higher order integrative (e.g., association brain areas) and executive functions (Gogtay et al., 2004).

This discussion of the anatomic development of the brain completes our first step. We now examine the orga- nization and function of the nervous system.

120 PART TWO | The Functioning Brain

Organization of the Nervous System

The nervous system is customarily divided into two parts: the PNS and the CNS (Figure 5.3 and Table 5.2). This division stems from the different properties and functions of neurons and systems within the two systems. Chapter 4 discusses neuronal differences, specifically the special properties of neurons within the CNS; this chap- ter discusses functional differences. The PNS includes all the portions of the nervous system outside the CNS. The PNS consists of the somatic nervous system (SNS), which interacts with the external environment, and the autonomic nervous system (ANS), which participates in regulating the body’s internal environment. The ANS has two divisions: the sympathetic and parasympathetic nervous systems. The PNS and the CNS are in constant communication with each other.

The CNS includes the brain and spinal cord. It com- municates with the PNS by exchanging sensory and motor information via the spinal nerves and cranial nerves. You can imagine the spinal cord as a cable carry-

ing bundles of spinal nerves from the body up to higher processing areas in the brain. It serves as the CNS con- duit of the majority of sensory and motor information to and from the body. The cranial nerves also carry very spe- cific sensory and motor information directly to the brain, bypassing the spinal cord.

CHAPTER 5 | Functional Neuroanatomy 121

Peripheral Nervous System (PNS)

Corpus callosum

Cerebral cortex

Cerebellum

Thalamus Hypothalamus Pituitary gland

Pons Medulla

Brain Spinal cord

Central Nervous System (CNS)

Figure 5.3 Human nervous system. (From Kalat, J. W. [2007]. Biological psychology [9th ed., p. 82, Figure 4.1]. Belmont, CA: Thomson Wadsworth.)

1. Central nervous system (CNS) Brain Spinal cord

2. Peripheral nervous system (PNS) Somatic nervous system

Cranial nerves Spinal nerves

Autonomic nervous system (ANS) Sympathetic Parasympathetic

Table 5.2 Principal Divisions of the Nervous System

Peripheral Nervous System

In principle, all components of the PNS inform the CNS about events in the environment and transmit com- mands from the CNS to the body. The somatic nervous system consists of afferent nerves or sensory nerves that convey messages from the sense organs to the CNS (in- coming) and efferent nerves that carry motor signals from the CNS to muscles (outgoing). Most nerves of the somatic nervous system project at regular intervals to the spinal cord via the spinal nerves, except for 12 pairs of cranial nerves, which synapse directly with the brain.

The function of the ANS is the neural control of in- ternal organs (e.g., heart and intestines). The ANS con- sists of both peripheral and central parts and includes a sympathetic division that is involved in activities that ex- pend bodily energy. This expenditure most often occurs in response to, or anticipation of, a stressful event. A sim- plified summary of the role of sympathetic activation is that it prepares the body for action based on the “fight- or-flight” principle. Sympathetic activity mobilizes the energy necessary for psychological arousal. It includes an increase in blood flow, blood pressure, heart rate, and sweating, and a decrease in digestion and sexual arousal.

The parasympathetic division of the ANS acts to con- serve energy and is typically associated with relaxation. It increases the body’s supply of stored energy and facilitates digestion and gastric and intestinal motility. Most auto- nomic organs receive both sympathetic and parasympa- thetic input and are influenced by the relative level of sympathetic and parasympathetic activity. For many bod- ily functions, the sympathetic and parasympathetic divi- sions act in opposite directions. You can think of the two branches of the ANS as balancing each other, like two sides of a scale. People generally consider the functions of the ANS automatic, not under voluntary control. The view that the response of the ANS to stress is not under voluntary control provided the basis for the development of the lie detector test. However, biofeedback, medita- tion, hypnosis, and other forms of stress management have shown that these functions are not as “automatic” as once thought, although some controversy has focused on the degree to which humans can control them (Zillmer & Wickramaserkera, 1987).

Although it is useful to divide the nervous system as outlined above, real functional anatomic circuits and sys- tems pay little heed to these boundaries. For example, many nerve cells described as part of the PNS have their cells of origin or terminal branches actually situated in the CNS. Consider the divisions within the nervous system as

somewhat flexible; they follow the organizational need to separate complex phenomena into discrete and less com- plex units.

Central Nervous System

The brain and spinal cord form a continuous com- munication system of the CNS. The CNS has several unique features. First, as discussed earlier, CNS neurons have some properties that differ from PNS neurons in that, for example, they do not show similar properties of regeneration. Second, you can recognize the importance of the CNS by the extra protection the body provides it. Structurally, it is located within the bony cavities of the skull and spine. Coverings called the meninges protect it, and it is surrounded by and floats in the protective CSF. The CNS, and especially the brain, is the most well-nourished area of the body, being supplied with an intricate system of arteries designed with “backup” systems. The body gives it priority in receiving nutrients and oxygen, and at the same time, gives it more protection, through the blood–brain barrier, from potentially harmful substances circulating in the body.

B R A I N

Anatomically, the brain is continuous with the spinal cord, from which it emerges. From an exterior view, the brain appears to be one organ with a left and a right hemi- sphere. It actually consists of several divisions with many identifiable structures.

How the brain is organized into subsystems that ulti- mately result in human behavior is a challenging ques- tion, one on which the rest of this text focuses. Consider that the brain occupies a relatively small space of about 1000 to 1500 cm3, roughly the size of a cantaloupe. Within this space functions an incredible array of differ- ent types of cells. There is also an almost infinite number of possible connections that make up exceedingly com- plex networks. From this complexity a sense of order and organization emerges that supports basic life, behavior, and consciousness. The human brain represents the most advanced stage of this integration.

A n a t o m i c T e r m s o f R e l a t i o n s h i p

Because the brain is a three-dimensional structure, neu- ropsychologists use a number of terms that describe spe- cific parts, planes, and directions. Unfortunately, the ter- minology is complex and not entirely standardized. This

122 PART TWO | The Functioning Brain

is related, in part, to the fact that we still use nomencla- ture proposed in Latin or Greek more than a century ago. In some instances, anatomists disagree about the bound- aries of a specific brain structure; thus, several terms may describe overlapping brain regions. Early anatomists used names to describe structures simply because they re- minded them of something else. For example, the outer part of the brain was named cortex, meaning “bark,” because it is a thin mantle or covering for the brain. Thus, whenever we use the original meaning of the names of brain structures to help the reader form association about the nomenclature, we also provide precise anatomic terms to clear up any re- sulting confusion. Additionally, these precise anatomic terms will enable the reader to accurately communicate about the geography and topology of the brain.

Descriptions usually divide the brain into one of the three main planes (using the x-, y-, and z-axes). Table 5.3 lists terms that describe the planes and orientation of brain anatomy.

S P I N A L C O R D

Overview

Gross anatomic features: spinal nerves, internal organi- zation of the spinal cord (gray and white matter)

Function: relays information to and from the brain, responsible for simple reflexive behavior

S t r u c t u r e

The spinal cord is continuous with the brain and extends downward along the back for about 46 cm. Like the brain, it is protected by bone, meninges, and CSF. The spinal cord is physically housed in the spinal column, which consists of alternating bony vertebrae and interver- tebral disks made up of cartilage that absorb mechanical shocks sustained to the spinal column. The spinal cord it- self is considerably smaller than the vertebral canal and the meninges. Fat, CSF, and veins combine to protect against contact with bony surroundings.

The spinal nerves consist of both sensory and motor neu- rons. At each of the 30 levels of the spinal cord, a pair of in- coming (afferent) dorsal root fibers signals incoming sen- sory information and a pair of outgoing (efferent) ventral root fibers controls motor nerves and muscles (Figure 5.4). These nerves conduct information related to both the so- matic and autonomic nervous systems in the periphery. In the spinal cord, white matter (myelinated axons) makes up the outside of the cord, whereas gray matter (cell bodies) is located on the interior. Each area of the spinal cord corre- sponds to a specific body location and controls sensation

and movement of the associated body area: skin, mus- cle, and internal organs. There are 1 coccyx, 5 sacral (S), 5 lumbar (L), 12 thoracic (T), and 8 cervical (C) spinal cord levels. The spinal nerves form ringlike innervations around the trunk of the body at each level of the spinal cord. The innervations of the limbs are extensions of the body rings. For example, the nerves to the arms and hands are extensions of C-6, C-7, and C-8 innervations from the trunk.

F u n c t i o n

The spinal cord relays somatosensory information from the trunk and limbs to the brain. The cord also relays sim- ple motor messages from the brain to the trunk and limbs.

CHAPTER 5 | Functional Neuroanatomy 123

Planes bisecting the brain:

Horizontal plane—plane (x-axis) that shows the brain as seen from above or parallel to the ground.

Coronal plane—plane (y-axis) that shows the brain as seen from the front (frontal section). Typically, this plane is viewed from behind to provide consistency for right and left directions of the brain and the picture.

Sagittal plane—plane (z-axis) that shows the brain as seen from the side or perpendicular to the ground, bisecting the brain into right and left halves (derived from Latin sagitta, meaning “arrow”).

Directional terms: Most often, directions in the human nervous system are related to the orientation of the spinal cord.

Anterior: toward the front or front end

Posterior: toward the back or tail

Inferior: toward the bottom, or below

Superior: toward the top or above

Medial: toward the middle/midline, away from the side

Lateral: toward the side, away from the midline

Rostral: toward the head

Caudal: toward the rear away from the head

Proximal: near the trunk or center, close to the origin of attachment

Distal: away from the center, toward the periphery, away from the origin of attachment

Dorsal: toward the back; the top of the brain is dorsal in humans

Ventral: toward the belly; the bottom of the brain is ventral in humans

Ipsilateral: on the same side

Contralateral: on the opposite side

Table 5.3 Planes of the Brain and Directions of Orientation to the Central Nervous System

It does some integration of information that involves basic reflexive behavior. Spinal cord lesions can result in motor and sensory impairment. Although neuropsychologist often place greater emphasis in their evaluations on whether sensory or motor impairments relate to brain le- sions, similar symptoms may also reflect spinal cord or even peripheral nerve damage. A thorough neurologic evaluation in combination with a comprehensive neu- ropsychological evaluation often clarifies the location of the dysfunction. Spinal cord injuries frequently occur with brain injury caused by whiplash, which may go unnoticed until after the trauma of paralysis has been stabilized.

Gross Anatomy: Protection and Sustenance of the Brain

The body affords extra protection and sustenance to the CNS because of its special status. The structural and physiologic protections extend to the spinal cord and the brain, although the focus is on the brain. Structurally, bone provides a type of “armor” to surround both the brain and spinal cord. In most cases, the skull holds the brain snugly and physically protects it from injury. However, as in closed head injury (see Chapter 13), the gelatinous

124 PART TWO | The Functioning Brain

1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 9

10 11 12 1 2 3 4 5 1

Cervical

Brain C2

C4 C5

T1 C8

L1 T12 T11 T10 T9 T8 T7 T6

T5 T4 T3

Thoracic

Lumbar

Sacral

2 3 4 5

Sensory receptor

Dorsal root

Ventral root

Muscle

Figure 5.4 Spinal nerves and areas of body innervation. (a) The body segments of spinal innervation are segmented in rings around the body. (b) The divisions of the 30 segments of the spinal cord. (c) Cross section through a segment of the spinal cord showing sensory input through the dorsal root and motor output through the ventral root. (Adapted from Kolb, B., & Wishaw, I. Q. [1996]. Fundamentals of human neuropsychology [4th ed., p. 46, Figure 3.3]. New York: W. H. Freeman and Company, by permission of Worth Publishers.)

brain may accelerate and scrape against the bony projec- tions of the skull. It is important to understand the skull–brain relationship to understand how the brain may be vulnerable to skull-related damage. Under the hard protection of bone, protective membranes called meninges form a flexible structural but semipermeable protective pad that completely surrounds the brain and spinal cord. The covering of the meninges forms another layer of pro- tection. However, certain types of tumors called menin- giomas may form here and impact on the brain. The CSF circulates around and throughout the CNS via the ven- tricular system, which provides not only an additional structural fluid cushion but also physiologic protection through its immunologic functions and its ability to act as a “waste disposal” system. The unique vascular system of the brain not only supplies nutrients to the energy- demanding brain but also adds a layer of protection through the blood–brain barrier. The blood–brain barrier (see dis- cussion in Chapter 4) is formed by tightly formed endothe- lial cells in the walls of the capillaries of the brain, held in place by astrocytes that prevent the passage of certain sub- stances into the brain.

S K U L L

Overview

Gross anatomic features: fused connection of bony plates covering the brain

Function: protection of the brain

S t r u c t u r e

The skull consists of the frontal bone (in some individu- als, the frontal bone develops in two parts), two parietal bones, two temporal bones, the occipital bone, and the sphenoid bone (Figure 5.5). The cerebral lobes derive their names from the cranial plates of the skull, whose corresponding outline they generally follow. This has led to an imprecise nomenclature of the cortex because the external aspects of the skull are easily differentiated, un- like those of the cortical lobes. The skull provides grooves for blood vessels in the roof (calvaria) of the cranium, con- spicuous ridges in the base of the skull, known as fossae, that hold the brain in place, and more or less symmetric orifices or foramina in the base of the skull that provide passage for nerves and blood vessels. The largest of these orifices is the foramen magnum, which provides a large median opening in the occipital bone for the spinal cord to pass through to the brainstem.

In the newborn, the skull is a relatively large part of its body, accommodating the disproportionally large brain.

At birth, the brain is approximately 25% of its adult size, weighing about 500 grams, but will reach about 75% of its mature size by its first year of maturation. Facilitating this rapid development of the brain, the bony plates that comprise the skull are not fused as they are in later years, but are separated by membranous, soft tissue. In the new- born, the membranous gaps are largest at the corners of the parietal bone. These soft openings are labeled fontanelles (“small fountains”) and may fluctuate with changes in intracranial pressure. The largest of these open- ings is the anterior fontanelle, located at the top of the head between the frontal and parietal bones. It does not fully close until 2 years after birth.

F u n c t i o n

The skull completely encases the brain, protecting it from external influences. Although normally the shell of the skull is an asset, in some instances, it can actually be a liability. The fact that the skull is rigid can become life threatening when the internal pressure of a swelling, in- jured brain cannot be released. Because the skull is not smooth on the interior, but rather consists of bony pro- jections designed to hold the brain in place, injury to the areas around the bony projections of the frontal and tem- poral lobes is common with whiplash and other head in- juries, which cause the gelatinous brain to reverberate in the skull. The skull varies in thickness; particularly, the areas around the temporal and sphenoid bones are rela- tively thin and are easily fractured by a blow to the side of the head. Fractures to the base of the skull can lead to serious damage of the brain related to shearing of the cra- nial nerves, leakage of the CSF from the nose, and bleed- ing from the auditory canal.

M E N I N G E S

Overview

Gross anatomic features: dura mater, arachnoid mem- brane, pia mater

Function: protective covering of the CNS, location of venous drainage and CSF absorption

S t r u c t u r e

The brain and spinal cord are the only human structures completely enclosed in protective bone. In addition, they are covered by the meninges, a set of thin membranes that hold the brain and spinal cord in place and act as a protec- tive buffer. The meninges of the CNS consist of three meningeal membranes and completely surround the brain and the spinal cord. Inner to outer they can be remembered

CHAPTER 5 | Functional Neuroanatomy 125

126 PART TWO | The Functioning Brain

Figure 5.5 Lateral (a) and basal (b) views of the skull. (From Chusid, J. G. [1982]. Correlative neuroanatomy & functional neurology [p. 256, Figure 19.3; p. 257, Figure 19.4]. New York: Appleton & Lange, by permission of the McGraw-Hill Companies.)

with the mnemonic PAD: pia mater, arachnoid mem- brane, and dura mater (or simply dura) (Figure 5.6). The thin pia mater (derived from Latin meaning “pious mother”) directly adheres to the surface of the CNS, fol- lowing its contours closely. The arachnoid membrane (spider web–like membrane) overlies the subarachnoid space, which contains CSF. The dura mater (derived from Latin meaning “tough mother”) is a dense, inelastic, double-layered membrane that adheres to the inner sur- face of the skull. The meningeal veins are in the outer por- tion of the dura. The space between the two dural layers is the epidural space. The space between the dura and the arachnoid is the subdural space. Cerebral veins cross- ing the subdural space have little supporting structure

and, therefore, are most vulnerable to injury and bleeding as a result of trauma (e.g., subdural hematoma).

F u n c t i o n

The meninges provide a protective covering by encasing the brain and spinal cord. They have no function in cog- nitive activity, but are of importance to neuropsycholo- gists because of clinical complications during injury. For example, a head trauma frequently tears large blood ves- sels in the subarachnoid space. In addition, the meninges are susceptible to inflammation, usually by bacterial in- fection, resulting in meningitis. Meningitis can be caused by both bacteria and viral infection. The disease is dan- gerous because it can progress quickly, within 24 hours,

from a respiratory illness with fever, headache, and a stiff neck to changes in consciousness, including stupor, coma, and death.

V E N T R I C U L A R S Y S T E M

Overview

Gross anatomic features: lateral (first and second), third, and fourth ventricles; choroid plexus; cerebral aqueduct; arachnoid granulations

Function: intracranial pressure, CSF production and circulation

S t r u c t u r e

Within the brain are four interconnected, fluid-filled cav- ities known as the ventricles (Figure 5.7). There are two lateral ventricles, one in each hemisphere, the third ven- tricle, and the fourth ventricle. The lateral ventricles are the largest and are seen easily in many types of brain imag- ing, because they occupy what appears to be a large hol- low in each hemisphere. They are connected by a small opening, the interventricular foramen or foramen of Monro, to the third ventricle, which is situated between the two lateral ventricles at the level of the thalamus and the hy- pothalamus. The third ventricle has a single opening that leads downward through a narrow channel known as the

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Figure 5.5 (continued)

cerebral aqueduct (or aqueduct of Sylvius), connect- ing it to the fourth ventricle. The cerebral aqueduct passes through the midbrain and expands into the fourth ventricle, which lies in the brainstem, just beneath, and anterior to, the cerebellum. Early anatomists such as Leonardo da Vinci were fascinated by the ventricles, which were believed to contain the spirit (Figure 5.8).

Within these ventricles the choroid plexus tissue se- cretes CSF, which flows from the upper to the lower ventri- cles. The choroid plexus is a highly vascularized network of small blood vessels that protrude into the ventricles from the lining of the pia mater. It continually produces CSF. The CSF circulates through the ventricles and around the spinal cord and brain. In humans, approximately 450 ml

128 PART TWO | The Functioning Brain

Figure 5.6 The meninges. (top left) Midsagittal view of the three layers of the meninges. (right) Panels are enlarged to show the details of the meninges. (From Purves, D., Augustine, G. J., Fitzpatrick, D., Katz, L. C., LaMantia, A., McNamara, J. O., & William, S. M. [Eds.]. [2001]. Neuroscience [2nd ed., p. 34, Figure 1.18]. Sunderland, MA: Sinauer Associates, by permission.)

CSF (somewhat more than a 12-ounce soft drink can) is produced every day, mostly by the choroid plexus in the lateral ventricles. Then, after flowing through the inter- ventricular foramen of Monro, CSF volume is increased by fluid produced in the third ventricle.

The fourth ventricle has three openings in its mem- branous roof, the foramen of Magendie and two lateral foramina of Luschka, that allow the CSF to flow outside the brain and recirculate. The cycle is completed via the continuous reabsorption of CSF from the subarachnoid space between the arachnoid and the pia mater. From the expansions of the subarachnoid space called cisterns, most of the CSF moves upward along pressure gradients to a large sinus called the superior sagittal sinus and is reabsorbed into the blood system into larger blood-filled spaces. Within the subarachnoid space are also small pockets of veins, termed arachnoid villi or granulations (see Figure 5.6). These cauliflower-like projections serve as pathways for the CSF to be absorbed and re-enter the ve- nous circulation. The fluid recirculates every 6 to 7 hours.

The ventricular system not only boasts some of the most exotic terms of the brain but is also important to any study of brain anatomy. The reason for this is that the brain shapes the ventricular system; thus, any changes in the anatomy of the brain can distort the ventricular sys- tem. The location of the fourth ventricle, for example, near the cerebellum, is important for neuroradiology.

When neuroradiologists view two-dimensional pictures of the brain, locating any of the four ventricles helps pre- cisely locate the brain image, because the structure of the surrounding brain defines the ventricles. If brain tissue is distorted, ventricle size and shape are usually distorted.

F u n c t i o n

The ventricles and the CSF are involved in two principal processes. First, CSF protects the brain and the spinal cord by acting as a buffer. The ventricles of the brain, the central canal of the spinal cord, and the subarachnoid spaces all contain CSF with a normal intracranial pressure of 0 to 15 torr (1 torr � pressure necessary to support a column of mercury 1 mm high). The CSF thus floats the CNS like a buoy and protects the brain by acting as a liq- uid buffer or cushion to absorb internal and external forces. This is easily appreciated in patients who had some of their CSF drained as part of the now outdated X-ray diagnostic procedure known as pneumoencephalography (see Chapter 2). These patients experienced severe headaches and stabbing pain with any head movement because of in- jected air and less support to the brain.

The second function of CSF is in disposing of waste products from the brain, which are thus absorbed via cis- terns into the venous vascular system. Chapter 1 notes that medieval scientists attributed significant mental and spiri- tual processes to the presence of CSF within the ventricular

CHAPTER 5 | Functional Neuroanatomy 129

Figure 5.7 Ventricular system (lateral view, left panel). (right) Panels show the locations of the foramina of Luschka and Magendie in the fourth ventricle viewed from the ventral (top) and lateral surfaces (bottom). (From J. H. Martin, Neuroanatomy: Text and Atlas, 2nd ed., 1996, p. 19, Figure 1.10. Reproduced by permission of the McGraw-Hill Companies.)

chambers of the brain. This theory became known as the ventricular localization hypothesis and later formed the basis for the cell doctrine. On gross dissection of the brain, the lateral ventricles are the most striking features; thus, this theory, although wrong, persisted robustly.

The ventricles have no direct role in cognitive func- tion. However, abnormal intracranial ventricular pressure (>15 torr) may lead to general cognitive deficits. A se- quence of events can occur in which the ventricles become enlarged with fluid, occupying greater space than usual. This results in brain swelling and an increase in intracra- nial pressure. The squeezing or displacing of brain tissue, in turn, leads to changes in behavior and cognition. This expansion of the ventricles accompanied by increased in- tracranial pressure results in a medical condition called hydrocephalus, which may be caused by an imbalance in the rate of CSF production or absorption, or by blockage (such as by a tumor) of the circulation. The skull itself

may actually swell. If hydrocephalus occurs in childhood before the cranial bones have closed, the skull may en- large to enormous size (Figure 5.9). Acute hydrocephalus can be life threatening. Because the fused plates of the skull cannot accommodate the additional space, untreated hydrocephalus among adults and older children results in chronic dilation of the ventricles and a thinning of the cortex. A variant of hydrocephalus in adulthood, particu- larly the elderly, is normal-pressure hydrocephalus (NPH), characterized by the presence of normal levels of intracranial CSF. The term may actually be a misnomer insofar as research (Vanneste, 2000) suggests that there appears to be an initial stage of increased CSF pressure with a subsequent enlargement of the ventricles. As the ventricles expand, the CSF pressure returns to upper nor- mal to normal levels. However, there may be further tran- sient episodes of increased intraventricular pressure. It is believed that the mechanism of action that produces the

130 PART TWO | The Functioning Brain

Figure 5.8 Although many of Leonardo da Vinci’s (1452–1519) early brain anatomy drawings were inaccurate, he later became a keen observer of neuroanatomy. For this drawing, which presented an anatomic breakthrough, he poured melted wax into the ventricles of an ox, then cut away the brain tissues to determine the true shape of the ventricles. (The Royal Collection © 2007, Her Majesty Queen Elizabeth II.)

expansion of the ventricles is a reduction in CSF absorp- tion at the arachnoid villi (see Figure 5.6), resulting in an abnormal increase in intracranial CSF pressure. However, the validity of this mechanism of action has been chal- lenged, and alternative mechanisms have been proposed (Vanneste, 2000). Events that often precede the develop- ment of NPH include subarachnoid hemorrhage, menin- gitis, and head injury, although the cause in other cases is frequently unknown. Regardless of the originating cause, a triad of progressive neuropsychological signs alerts the clinician to possible NPH (Verrees & Selman, 2004). Walking difficulties and postural imbalance is usually the first sign of the disorder. Later, dementia and urinary in- continence develop. With treatment, particularly early treatment, these symptoms can be reversed or reduced.

Because the subarachnoid space extends down toward a small central channel that runs the length of the spinal cord, it is possible to collect a small sample of CSF at the level of the lower back by tapping into the subarachnoid cisterns of the lower lumbar vertebrae. This can be done without damaging the integrity of the spinal cord using an invasive diagnostic procedure known as a lumbar puncture or “spinal tap” (see Chapter 2). The CSF sample can then be examined under the microscope for the ab- normal presence of blood, infection, or cancerous cells.

V A S C U L A R S Y S T E M

Overview

Gross anatomic features: arteries (Table 5.4), veins, circle of Willis

Function: Arteries: nourishment: supply of oxygen, nutrients Veins: carrying away of waste products

To function properly, the brain must receive adequate oxygen and many nutrients (such as glucose) from the blood vessels. If a blood vessel is obstructed or bursts, the brain cells supplied by that vessel cannot function prop- erly and begin to die. When brain cells do not function, neither do the parts of the body controlled by those neu- rons or other related parts of the brain to which the dam- aged neurons project (targets). Becoming familiar with the blood supply of the brain can make important vascu- lar disorders such as stroke more understandable.

A r t e r i e s T h a t S u p p l y t h e B r a i n

All major cerebral arteries and the meninges are supplied by four large arteries to the brain. They are the right and left internal carotid arteries, as well as the two vertebral arteries (Figure 5.10 and Table 5.4). These vessels origi- nate directly or indirectly from branches of the aortic arch, which arises from the left ventricle of the heart. The internal carotid arteries supply the anterior portions of the brain, and the vertebral arteries supply the posterior portion.

The two vertebral arteries join together at the level of the brainstem to form the basilar artery. The basilar artery divides into the left and right posterior cerebral arteries. This vertebrobasilar system provides approxi- mately 20% of the total cerebral blood circulation mostly to the posterior portions of the brain, and a correspond- ing 20% of all cerebrovascular accidents (CVAs), or strokes, are restricted to this territory.

C i r c l e o f W i l l i s

The cross-brain connections from both the internal carotid and basilar systems form a remarkable vascular structure near the base of the brain, the circle of Willis (Figure 5.11), named after its discoverer, English anatomist and physician Thomas Willis (1621–1675). The circle is formed by the anterior cerebral branches of the internal carotid artery and its connections, the anterior communicating artery, the posterior communicating artery, and the posterior cerebral branches of the basilar artery. The circle of Willis is the most important intracranial

CHAPTER 5 | Functional Neuroanatomy 131

Figure 5.9 Skull of a child with severe hydrocephalus. Note the enlarged fontanelle. (Mütter Museum, College of Physicians of Philadelphia.)

collateral blood supply, and it allows a certain degree of redundancy among blood vessels and blood supply to the various areas of the brain.

C E R E B R A L A R T E R I E S

The internal carotid artery on each side of the body di- vides into the anterior cerebral artery (which supplies the anterior paramedian cerebral hemisphere) and the larger middle cerebral artery (which supplies the lateral hemisphere and most of the basal ganglia). Figure 5.12 shows the areas of the brain served by each of the three cerebral arteries. The left and right anterior cerebral arter- ies are connected by the anterior communicating artery. The posterior communicating arteries arise from the in- ternal carotid arteries and connect the middle and poste- rior cerebral arteries. The major cerebral arteries have mul- tiple cortical branches (these branches are not discussed in

detail here). Disrupting blood supply to any of the cere- bral arteries or its branches may cause relative uniform and characteristic symptoms related to each brain area served by the artery. Of the major arteries that supply the brain, blockage of the carotid arteries most often results in a stroke affecting the middle cerebral artery. The ante- rior cerebral artery is not as commonly involved in stroke because the anterior communicating artery can supply blood.

In the normally functioning brain, there is little arter- ial crossover from one hemisphere of the brain to the other, or between anterior and posterior arteries. In the event of a stroke to a major artery, other intact blood ves- sels can take over for injured blood vessels. For example, if the basilar artery is occluded, shutting off blood supply to the posterior communicating artery, the internal carotid arteries may provide blood to posterior circulation via the posterior communicating artery. However, there is

132 PART TWO | The Functioning Brain

Figure 5.10 Major arteries to the brain. The cerebral arteries are seen from the base of the brain. The left half of the cerebellum and the tip of the left temporal lobe have been removed. (From Burt, A. M. [1993]. Textbook of neuroanatomy [p. 179, Figure 9.8]. Philadelphia: W.B. Saunders.)

much individual variation in the circle of Willis; parts of the system may actually be missing in some people (e.g., in 15% of normal brains, the posterior cerebral artery is a direct extension of the posterior communicat- ing artery).

V E N O U S S Y S T E M

The veins are located in the outer portion of the dura and pass blood through vessels back to the heart. Venous drainage starts with the superficial cerebral veins, which originate in the brain substance within the pia mater and empty into the superior sagittal and transverse sinuses, the deep veins of the brain, and the straight sinus, which connects to the internal jugular vein. As noted earlier in the discussion of the ventricular system, the subarachnoid space contains pockets of veins called arachnoid granula- tions that serve as pathways for the subarachnoid CSF to be absorbed and re-enter the venous circulation. Arachnoid

granulations first appear in childhood, around age 7, and increase in size and number during adulthood. Unlike the arterial blood supply, the venous system of the brain does not have a right and left system. Thus, there is free circu- lation within the venous system, which may facilitate the spread of infectious agents from one hemisphere to the other. Chapter 12 gives a detailed description of vascular disorders.

Principal Divisions of the Brain

The brain can be subdivided into three major divi- sions based on the development of the human embryo (see earlier). As the embryo’s neural tube closes, it begins to differentiate into three bulges. The topmost becomes the forebrain (prosencephalon), the middle is the midbrain (mesencephalon), and the third is the hindbrain (rhomben- cephalon). The remainder of the neural tube develops into

CHAPTER 5 | Functional Neuroanatomy 133

Artery Origin Distribution

Basilar Junction of right and left vertebral arteries Brainstem, internal ear, cerebellum, posterior cerebrum

Carotid, common Brachiocephalic (right), aorta (left) Internal and external carotid

Carotid, external Common carotid artery Neck, face, skull

Carotid, internal Common carotid artery Middle ear, brain, choroid plexus of lateral ventricles

Cerebellar, inferior anterior Basilar artery Lower anterior cerebellum, inner ear

Cerebellar, inferior posterior Vertebral artery Lower part of cerebellum, medulla, choroid plexus of fourth ventricle

Cerebellar, superior Basilar artery Upper part of cerebellum, midbrain, pineal body, choroid plexus of third ventricle

Cerebral, anterior Internal carotid artery Orbital, frontal, and parietal cortex, corpus callo- sum, diencephalon, corpus striatum, internal capsule, choroids plexus of lateral ventricles

Cerebral, middle Internal carotid artery Orbital, frontal, parietal and temporal cortex, corpus striatum, internal capsule

Cerebral, posterior Basilar artery Occipital and temporal lobes, basal ganglia, choroid plexus of lateral ventricles, thalamus, midbrain

Ophthalmic Internal carotid artery Eye, orbit, facial structures

Spinal, anterior Vertebral artery Spinal cord

Spinal, posterior Vertebral artery Spinal cord

Vertebral Subclavian artery, which arises from Neck muscles, vertebrae, spinal cord, brachiocephalic (right), aorta (left) cerebellum, cortex

Table 5.4 Arteries to the Brain

the spinal cord. The three major subdivisions of the brain further differentiate into five subdivisions: (1) telen- cephalon, (2) diencephalon, (3) mesencephalon, (4) me- tencephalon, and (5) myelencephalon. This framework organizes the study of the primary structures evident in the adult. Table 5.5 and Figure 5.13 depict the relation- ships among the principal anatomic divisions, subdivi- sions, and major structures of the brain.

Traditionally, neuropsychologists focus on the brain areas of complex processing within the telencephalon, pri- marily the cerebrum. In fact, the major structures of the telencephalon, including the cerebrum, basal ganglia, and basal forebrain, comprise about 85% of the brain’s weight (Burt, 1993). Therefore, although this is only one subdivision of the brain, it covers much area and is of great importance in understanding higher cognitive abili- ties. Consequently, a common manner of dividing the brain is to differentiate between the telencephalon and the brainstem. The brainstem includes all the subdivisions below the telencephalon (diencephalon, mesencephalon, metencephalon, and myelencephalon), except for the cerebellum, and mediates many primary regulatory processes of the body. We begin by discussing the major

structures of the brainstem and cerebellum, and then move to the telencephalon.

Brainstem and Cerebellum

The brainstem and the cerebellum, in terms of evo- lution, form the most primitive area of the brain. The cerebellum, which looks like a “little brain,” connects to the dorsal aspect of the brainstem. Figure 5.14 shows the brainstem and cerebellum in relation to the entire brain.

The brainstem extends from the spinal cord and com- prises about 4.4% of the total weight of the adult brain; the cerebellum makes up about 10.5% (Burt, 1993). The four parts of the brainstem include the medulla oblon- gata (myelencephalon), the pons (metencephalon), the structures of the midbrain (tectum and tegmentum), and the structures of the diencephalon (thalamus and hypothal- amus). Although the brainstem and cerebellum account for relatively smaller areas of the brain and function more prim- itively than the telencephalon, these areas consist of a num- ber of different structures relevant to understanding the basics of brain functioning. We first discuss the structures

134 PART TWO | The Functioning Brain

Anterior communicating artery

Anterior cerebral artery

Opthalmic artery

Internal carotid artery

Middle cerebral artery

Posteromedial and thalamoperforating arteries

Anterolateral arteries

Anteromedial and medial striate arteries

Lateral striate arteries

Thalamogeniculate arteries

Basilar artery Pontine rami

Superior cerebellar artery

Posterior cerebral artery

Posterior communicating artery

Anterior choroidal artery

CHAPTER 5 | Functional Neuroanatomy 135

Figure 5.12 Blood supply to the cortex. Major arteries and areas of cortical profusion. (a) A lateral view shows the middle cerebral artery and its branches. (b) The course of the anterior and posterior cerebral arteries in midsagittal view. (From J.G. Chusid, Correlative Neuroanatomy & Functional Neurology, NY: Appleton & Lange, 1982, p. 50, Figure 1-54. Reproduced by permission of the McGraw-Hill Companies.)

136 PART TWO | The Functioning Brain

Basal ganglia

Spinal cord

Medulla

Lower brainstem

Cerebellum

Pons

Midbrain

Diencephalon

Cerebral cortex

Cervical

Thoracic

Lumbar

Sacral

Hindbrain

Midbrain

Forebrain

Figure 5.13 The three divisions of the brain. (From Banich, M. T., Neuropsychology: The Neural Basis of Mental Function, p. 13, Figure 1.7. Copyright © 1997 by Houghton Mifflin. Adapted with permission.)

Major Division

Forebrain (prosencephalon)

Midbrain (mesencephalon)

Hindbrain (rhombencephalon)

Subdivisions

Telencephalon (endbrain)

Diencephalon (between brain)

Mesencephalon (midbrain)

Metencephalon

Myelencephalon

Structures

Cerebral cortex Basal ganglia Basal forebrain Hippocampal complex Corpus callosum

Epithalamus Thalamus Hypothalamus

Tectum Tegmentum

Pons Cerebellum

Medulla oblongata

Cavity

Lateral ventricles

Third ventricle

Cerebral aqueduct

Fourth ventricle

Table 5.5 Principal Anatomic Divisions of the Brain

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CHAPTER 5 | Functional Neuroanatomy 137

Cingulate gyrus

Frontal lobe

Corpus callosum

Tissue dividing lateral ventricles

Cerebral cortex Parietal lobe

Occipital lobe

Superior and inferior colliculi

Midbrain

Cerebellum

Central canal of spinal cord

Thalamus

Nucleus accumbens

Hypothalamus

Pituitary gland

Pons

Medulla

Spinal cord

Figure 5.14 Human brain in midline and brainstem. (From Kalat, J. W. [2007]. Biological psychology [9th ed., Figure 4.10]. Belmont, CA: Thomson Wadsworth.)

of the lower brainstem (medulla, pons, and midbrain), then the upper brainstem (diencephalon), and finish by considering the cerebellum.

L O W E R B R A I N S T E M

Overview

Gross anatomic features: Hindbrain: medulla oblongata (myelencephalon), pons (metencephalon) Midbrain: tectum and tegmentum Cranial nerves Reticular activating system

Function: relay information to and from the brain; responsible for simple reflexive behavior

S t r u c t u r e

The lower brainstem resembles a road system of neural interconnections. In it, large tracts ferry information be- tween telencephalon and spinal cord and between cere- bellum and brainstem. It also contains smaller groups of nerves such as the cranial nerves, specialized nuclei, and

the network of the reticular activating system (RAS). The medulla oblongata, pons, and midbrain structures are old structures, from an evolutionary perspective. In- terestingly, they are relatively uniform in shape and organi- zation over the range from evolutionarily less complex species such as fish to more complex humans (Figure 5.15). However, the size of the pons appears to increase in pro- portion to the degree of neocortical organization across species (Burt, 1993). The medulla is immediately supe- rior to the spinal cord and forms an intermediary zone between the elementary neuronal configuration of the spinal column and the complex neural organization of the brain. It contains myelinated tracts that carry motor and sensory information between the brain and spinal cord, where the tracts decussate, switching transmission of in- formation from one side of the body to the contralateral side of the brain. From this point upward, the left side of the brain controls the right side of the body and vice versa. The pons (“bridge”) resembles two bulbs immediately su- perior and anterior to the medulla and inferior to the mid- brain. The cerebellum connects to its posterior aspect, and information from the cerebellum funnels through the pons by way of large tracts termed cerebellar peduncles (see Figure 5.22 in Cerebellum section).

The midbrain lies between the cerebrum and the pons and is the smallest portion of the brainstem. It merges anteriorly with the hypothalamus and thalamus. Although its beginning and end are not well outlined, it can be divided into the tectum (“roof ”) and the tegmentum (“covering”). Within the roof of the tectum are four small elevations, a pair of inferior colliculi, and above these, a pair of superior colliculi. The tegmen- tum surrounds the tiny cerebral aqueduct, which con- nects the third and fourth ventricles. The lower brain- stem contains many important nuclear groups, including the cranial nerves and important pathways connecting the spinal cord and cerebellum with the telencephalon. The major motor and sensory tracts to and from the cerebral hemispheres all pass through the lower brain- stem. The lower brainstem also contains a network of neurons known as the RAS, or reticular formation (the cranial nerves and the RAS are discussed separately later in this section).

F u n c t i o n

The lower brainstem serves several functions in addition to conducting information from spinal cord to brain. This complex system with many different nuclei and ascend- ing and descending connections plays a crucial role in re- flexive functions necessary for life, as well as in arousal

level, auditory processing, visually guided movements, and the control of movement. The medulla mediates vital functions such as respiration, blood pressure and heart rate, and basic muscle tone. Damage to this area can interrupt motor and sensory pathways and threaten life itself. The pons serves as a major juncture for infor- mation passing between the structures of the spinal cord, brain, cerebellum, and some of the cranial nerves. It also plays a role in balance, vision, and auditory processing.

Together with the midbrain, structures of the lower brainstem play an important role in orientating to visual and auditory information. The superior colliculi contain important reflex centers for visual information and con- tain some retinal fibers via the optic tracts and the visual cortex. The inferior colliculi serve as an important relay center for the auditory pathway. Interestingly, compared with humans, bats have proportionally enlarged inferior colliculi. This is related to their sonar-like system, which allows them to receive echoes, and thus determine struc- tures in space. Tracts originating in the colliculi connect to established motor nerve cells and influence the move- ment of the neck and head in response to visual and audi- tory information.

C r a n i a l N e r v e s : S t r u c t u r e a n d F u n c t i o n

Overview

Gross anatomic features: located within the brainstem

Function: conduit of specific motor and sensory infor- mation

The lower brainstem is also the site of origin of 10 of the 12 cranial nerves. These nerves, which are directly con- nected to the brain, carry information to muscles or sen- sory information back to the brain. The cranial nerves were originally numbered by Galen, and each one also has a name associated with it. Cranial nerves I through IV arise from nuclei in the midbrain and forebrain, and nerves V through XII originate from the medulla and pons in the hindbrain (Figure 5.16).

The cranial nerves integrate sensory information and motor output. Table 5.6 lists the individual cranial nerves and their functions. These nerves are very old from an evolutionary point of view. Some aspects of facial emo- tional expressions are also organized at this level, suggest- ing that our basic facial expressions are ancient and con- sistent across all human cultures. Because cranial nerves have more or less specific sensory or motor responsibili- ties, neurologists often test them during a clinical exami- nation. For example, difficulties with eye tracking or numbness on one side of the face are clear symptoms of dysfunction with a cranial nerve.

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Thalamus Pineal gland

Tectum

Pons

Medulla

Tegmentum

Superior colliculus

Inferior colliculus

Midbrain

Posterolateral view of brainstem

Figure 5.15 Brainstem structures. (From Kalat, J. W. [2007]. Biological psychology [9th ed., p. 88, Figure 4.8]. Belmont, CA: Thomson Wadsworth.)

R e t i c u l a r F o r m a t i o n Overview

Gross anatomic features: a neural network located within the lower brainstem transversing between the medullae to the midbrain

Function: nonspecific arousal and activation, sleep and wakefulness

Structure—The reticular formation is, evolutionarily, one of the oldest systems in the nervous system (Figure 5.17). The brains of primitive vertebrates are almost exclusively made

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Optic nerve (Cranial nerve II)

Cranial nerve III

Cranial nerve V

Cranial nerve VIII VII VI IX X XI XII

Spinal nerve Spinal cord

Medulla

Cranial nerve IV

Midbrain

Pons

Cerebellum

Figure 5.16 The 12 cranial nerves. (From Kalat, J. W. [2007]. Biological psychology [9th ed., p. 89, Figure 4.9]. Belmont, CA: Thomson Wadsworth.)

Number Name Function

I Olfactory Sensory: smell

II Optic Sensory: vision

III Oculomotor Sensory: eye muscle; motor: eye movement, pupil constrictions

IV Trochlear Sensory: eye muscle; motor: eye movement

V Trigeminal Sensory: skin of face, nose and mouth; motor: chewing and swallowing

VI Abducens Sensory: sensation from eye muscles; motor: eye movement

VII Facial Sensory: taste; motor: facial expression, crying

VIII Statoacoustic Sensory: hearing, equilibrium

IX Glossopharyngeal Sensory: taste; motor: swallowing

X Vagus Sensory: taste, sensation from neck; motor: control of larynx, parasympathetic nerves to heart and viscera

XI Accessory Motor: movements of shoulder and head

XII Hypoglossal Sensory: tongue; motor: movement of tongue

Table 5.6 Cranial Nerves

up of a reticular or “netlike” formation. Humans retained the reticular formation over the course of evolution, as the more organized parts of the nervous system appeared. The formation has a diffuse arrangement of both ascending and descending neurons that form a system of networks (hence “reticular”). The network interacts with all major neural tracks of the brain. The reticular formation is not a singular set of nuclei, but rather consists of many clusters of nerve cells (Lezak, Howieson, & Loring, 2004).

Function—The reticular system is the starting point for the brain’s vital activity. Life-sustaining nuclei and widespread connections here lead to the cerebral cortex. The reticular formation plays a role in nonspecific arousal, cortical activa- tion and tone, and regulating sleep and wakefulness. Be- cause of the system’s role in arousal, it is often called the reticular activating system (RAS), which may be stimulated by outside, environmental events or by internal events. The reticular system forms the basis of Unit 1 in Luria’s concep- tion of the brain (Units 2 and 3 reside in the cerebral hemi- spheres; see Chapter 1). Defects in the reticular system can lead to a variety of problems. The major deficit, seen in many neurologic disorders, is a change in the level of con- sciousness, ranging from sleepiness to coma. The role of the RAS in sleep and wakefulness is discussed in Chapter 16.

As mentioned in the earlier discussion of the medulla, the medullary levels of the reticular formation contain important respiratory and cardiovascular centers. Injury to these areas can result in death due to impaired respi- ratory rate, heart rate, and blood pressure. Thus, low- level RAS injuries (or high-level spinal cord injuries; e.g., C-1, C-2, and C-3) may result in respiratory deficits. One such example is that of actor Christopher Reeves, who fractured his neck at the C-2 level while horse jumping. Not only was he paralyzed after the accident, he also required an artificial respirator because part of his brainstem, and specifically the reticular formation, was injured.

In addition to the task of arousal, the RAS is also re- sponsible for selective attention. The system must decide what information to let pass on its way to the cortex and what information to filter. This is an important function because there is generally too much competing informa- tion at any one point in time for the brain to analyze it all. Thus, a further deficit or injury to this structure is one of filtering. Such a deficit can be related to RAS injuries that occur at or near birth. In these cases, the ability of the brain to filter information is either increased or de- creased to an abnormal level. In the case of decreased fil- tering, the child is stimulus bound, easily distractible, and

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Cortex

Reticular formation

Suprachiasmatic nucleus

Brain stem

Cerebellum

Figure 5.17 Reticular formation. (From Goldstein, E. B. [1994]. Psychology [p. 188, Figure 5.8]. Pacific Grove, CA: Brooks/Cole.)

more pliable in low-stimulus sensory environments. In the case of increased filtering skills, the child shows symp- toms of sensory deprivation. This can result in a complete withdrawal from the external world, similar to the deficit seen in some autistic children.

In general, the brainstem, and the RAS in particular, plays a major and vital role in regulating wakefulness and in mediating and filtering ascending and descending sensory and motor information. As such, the brainstem constitutes the starting point of the brain’s analysis of in- formation. Disruption of the brainstem, specifically of the RAS, affects the level of arousal, orientation, and general awareness of one’s surroundings. Neuropsychologists are interested in the often profound symptoms associated with dysfunction of these areas. Neuropsychologists can system- atically assess general arousal when it is important to mon- itor the progress of people who are recovering from RAS injuries. Individuals with acute brainstem injuries may be placed in inpatient medical care, because such patients may be in a stupor or coma, and thus dependent on exter- nal life support.

U P P E R B R A I N S T E M : D I E N C E P H A L O N

The diencephalon (also known as the interbrain or “between brain”) is located at the head of the brainstem connecting the cortex with lower structures of the brain. The dien- cephalon is part of the larger forebrain, and its evolution has paralleled that of the cortex. The diencephalon consists of two prominent brain structures, the thalamus and the hy- pothalamus, which contain many nuclei that are of interest to neuropsychologists because of their functions in regulat- ing behavior. Phylogenetically, the thalamus consists of an- cient nuclei that may have originally reacted reflexively to pleasant and unpleasant environmental stimuli before the cerebral cortex evolved. The hypothalamus, part of the lim- bic system, is considered instrumental in controlling the au- tonomic system. This system regulates emotional responses and other functions such as thirst, appetite, digestion, sleep, temperature of the body, sexual drive, heart rate, and smooth muscles of the internal organs.

H y p o t h a l a m u s

Overview

Gross anatomic features: structure of the hypothalamus, hypothalamic nuclei, major fiber systems, third ventricle

Function: activates, controls, and integrates the pe- ripheral autonomic mechanisms, endocrine activity, and somatic functions, including body temperature, food intake, and development of secondary sexual characteristics

Structure—The hypothalamus is the portion of the dien- cephalon that forms the floor and part of the lateral wall of the third ventricle. Anatomically, it is defined by the optic chiasm rostrally and the mamillary bodies caudally. The boundaries of the hypothalamus are easily de- scribed, but it does not form a well-circumscribed re- gion and extends into surrounding parts. The hypothal- amus itself is small by weight (pea size, about 4 grams in adults), but contains a grouping of small and complex nuclei located at the junction of the midbrain and the thalamus (close to the roof of the mouth). Within the hypothalamus lie at least a dozen identifiable cell clus- ters named the hypothalamic nuclei (Figure 5.18). The exact number depends on how the clusters are orga- nized, but is similar in most vertebrates, suggesting that little has changed over time and across species. Origi- nally thought of as “a trifling part of the human brain,” the hypothalamic nuclei have become known over the past half century as an important collection of nuclei, “the brain within the brain.” The hypothalamus plays an important role in regulating, activating, and integrat- ing peripheral autonomic processes, endocrine activity, and somatic functions.

In general, the hypothalamus has three longitudinal zones: lateral, medial, and periventricular. The medial as- pects of the hypothalamus have rich connections with the thalamus. The lateral nuclei have efferent and afferent connections to and from regions outside the hypothala- mus, including brainstem fiber systems and preoptic and olfactory areas. In addition, the hypothalamus is an inter- action center for several neurotransmitter substances. The hypothalamus, therefore, is a complex diencephalic struc- ture in terms of its communicating neurotransmitters and dendritic and axonal interconnectedness.

Function—The hypothalamus is interconnected to the ad- jacent “master gland” of the brain, the pituitary (also known as hypophysis). The hypothalamus regulates the endocrine activity of the pituitary, both directly and in- directly (Kupfermann, 1991). The direct route involves the transport of hormones via axons from hypothalamic neurons extending downward to the posterior region of the pituitary. These axonal bundles constitute, in part, the pituitary stalk. Stimulation of these cells results in the re- lease of the hormones by the pituitary directly into the bloodstream. The direct route controls the release of the antidiuretic hormones and oxytocin, which are actually produced by the hypothalamus, but are stored in the pi- tuitary gland. The antidiuretic hormones are involved in homeostatic regulation, and oxytocin influences uterine contractions at birth and lactation. The indirect track

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involves the transport of releasing and inhibitory hor- mones via the vascular-capillary system interconnecting the hypothalamus and the anterior region of the pituitary. These regulating hormones signal the pituitary to release (or inhibit) a variety of hormones into the bloodstream. These hormones, in turn, regulate en- docrine glands and body organs throughout the body. For example, the corticotropin-releasing hormone signals the release of adrenocorticotropic hormone (ACTH) in response to stress and pain. ACTH, in turn, stimulates the release of cortisol and other hormones by the adrenal cortex as part of the body’s autonomic response to stress.

Thus, the hypothalamus, through its interactions with the pituitary and other brain structures and systems, is es- sential for body homeostasis, physical growth, sexual di-

morphism, reproductive activities, and response to stress. The regulation of body temperature, food intake, and de- velopment of secondary sex characteristics are also impor- tant functions of the hypothalamus. Furthermore, the hy- pothalamus plays a role in digestion, sexual arousal, and circulation. It also influences thirst, hunger, and circadian rhythms (Victor & Ropper, 2001).

Many pathologic processes can influence the func- tion of the hypothalamus. Of these, tumors are the most frequent, including hypothalamic tumors and the more frequent tumors of the pituitary (see Chapter 12). Disturbances of the medial aspects of the hypothalamus (the ventromedial nucleus) may lead to severe behav- ioral disorders, because these nuclei have important connections with the frontal cortex and the amygdaloid complex.

142 PART TWO | The Functioning Brain

Anterior commissure

Hypothalamus

Pituitary

Dorsal hypothalamus

Dorsomedial hypothalamus

Posterior hypothalamus

Ventromedial hypothalamus

Posterior pituitary

Paraventricular nucleus of hypothalamus

Anterior commissure

Lateral hypothalamus (behind plane of view)

Anterior hypothalamus

Preoptic area

Suprachiasmatic nucleus

Optic chiasm

Anterior pituitary

Mamillary body

Arcuate nucleus

Pituitary stalk

Figure 5.18 Hypothalamus and pituitary. (From Kalat, J. W. [2007]. Biological psychology [9th ed., p. 300, Figure 10.5]. Belmont, CA: Thomson Wadsworth.)

T h a l a m u s

Overview

Gross anatomic features: structure of the thalamus, its nuclei, and thalamocortical connections

Function: complex relay station, handling major sen- sory and motor inputs to and from the ipsilateral cerebral hemisphere

Structure—The thalamus consists of two symmetric large nuclei embedded in the cerebral white matter toward the base of the cerebral hemispheres superior to the hypo- thalamus (derived from Greek hypo, meaning “beneath”). Each cerebral hemisphere contains half of the thalamus (Figure 5.19). Each half is a relatively large (about 4 cm in length), ovoid, gray mass that sits partially within the hollow made by the internal capsule and helps form the lateral walls of the third ventricle. The word thalamus means “bridal chamber,” a name that reflects the deep, hidden, and secure location of the thalamus within the two hemispheres. On dissection of the brain, the rela- tively well-defined thalamus is easily visible because of its grayish color, signaling the presence of many nerve endings.

Cortical and thalamic functions are significantly inter- related. The thalamic nuclei consist primarily of gray mat- ter and are connected extensively with most other parts of

the CNS. For example, many pathways that carry infor- mation from the brainstem to the cortex relay their infor- mation through the thalamic nuclei before reaching the cortex. Thus, the thalamus plays a central role in process- ing most information that reaches the cortex. The thala- mic nuclei are relatively well-defined geographic areas that can be divided into groups, based on their geographic lo- cation within the thalamus and their specific function. Some major nuclei of the thalamus are the pulvinar nu- cleus (PN), ventral posterolateral (VPL), ventral postero- medial (VPM), medial geniculate (MG), lateral genicu- late (LG), ventral lateral (VL), and dorsal medial (DM).

In addition to receiving ascending input, all thalamic nuclei receive descending input from the cerebral hemi- spheres, principally from the cortical regions to which they project. As such, the thalamus plays a key role in pro- viding a complex “relay station” for all sensory systems, except for olfaction, that project to the cerebral hemi- spheres. The thalamus and the hypothalamus together make up an important part of the activities of the limbic system (see later in this chapter for a more detailed de- scription). Figure 5.20 shows the relation of the thalamus and hypothalamus to other brain structures.

Function—As the gateway to the cortex, the thalamus serves as the major pathway for primary sensory and motor im- pulses to and from the cerebral hemispheres. The one ex- ception is olfactory sensory information (cranial nerve I),

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Cingulate gyrus

Thalamus

Hypothalamus

Mamillary body

Hippocampus

Amygdala

Olfactory bulb

Figure 5.19 The thalamus. (From Kalat, J. W. [2007]. Biological psychology [9th ed., p. 91, Figure 4.12]. Belmont, CA: Thomson Wadsworth.)

which bypasses the thalamus and progresses directly from olfactory receptors to olfactory bulbs to the cerebral cor- tex. Other neuronal fibers that do not pass through the thalamus are those that are involved in arousal.

The thalamus is analogous to the concept of a large, busy, commuter train station. It makes preliminary classi- fications, integrates information, and “sends” it on to the cortex for further processing. Specifically, each half of the thalamus sends information to, and receives information from, the cerebral hemisphere on the same (ipsilateral) side of the brain. In this fashion, the descending projec- tions serve as a two-way system between each cortical re- gion and the corresponding thalamic nuclei.

The nuclei of the thalamus can be divided into two groups by their structure, connections, and function. The first group includes nonspecific nuclei, which are located primarily toward the median portion of the thalamus. These nuclei project widely to other brain structures, in- cluding other thalamic areas, and to the cortex, particu- larly its frontal regions. They receive input from the spinal

cord and the reticular formation and appear to play a role in monitoring the overall excitability of neurons in the cortex and the thalamus.

The second group of thalamic nuclei is referred to as specific nuclei, which are involved in sensory and motor processing (Figure 5.21). Specific nuclei project to re- stricted regions of the cortex. For example, specific sen- sory nuclei include the VPL and VPM (not shown) nu- clei, which receive input from somatosensory relay neurons and project directly to the primary and secondary somatosensory cortex. The LG body receives input from the optic tract and projects to the primary visual area in the occipital cortex. The MG body receives input from the auditory relay nuclei and projects to the primary audi- tory cortex in the temporal lobe. Specific nuclei of the thalamus that are involved in controlling motor activity include the VL and ventral intermedial (VI; not shown) nuclei, which receive input from the cerebellum. The lat- eral portion of the ventral anterior (VA) nucleus receives ascending fiber tracts from the basal ganglia, which are

144 PART TWO | The Functioning Brain

Amygdala Involved in memory, emotion, and aggression

Hippocampus Involved in learning, memory, and emotion

Medulla Controls vital functions such as breathing and heart rate

Thalamus Switching station for sensory information; also involved in memory

Spinal cord Transmits signals between brain and rest of body

Cerebellum Controls coordinated movement; also involved in language and thinking

Hypothalamus Regulates basic biological functions, including hunger, thirst, temperature, and sexual arousal; also involved in emotion.

Figure 5.20 Subcortical structures of the brain. (From Goldstein, E. B. [1994]. Psychology [p. 89, Figure 3.8d]. Pacific Grove, CA: Brooks/Cole.)

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Figure 5.21 Thalamocortical radiations. (a) Principal thalamocortical projections. (b) Relation of cortical areas to thalamic nuclei. (a: From J. G. Chusid, Correlative Neuroanatomy & Functional Neurology, NY: Appleton & Lange, 1982, p. 19, Figure 1.10 and p. 20, Figure 1.21. Reproduced by permission of the McGraw-Hill Companies; b: reproduced with permission from original drawings by Frank H. Netter, MD; first appeared in Ciba Clinical Sym- posia. Copyright ©1950, Ciba Pharmaceutical Co.)

involved in regulating motor behavior. All three thalamic nuclei (VL, VI, and VA) project to the precentral motor areas of the cortex. Finally, the DM nucleus has many connections to the limbic system, which regulates emo- tional activity. In addition, the DM nucleus is one of the thalamic nuclei involved in memory. This list of thalamic nuclei provides only an overview of the neuropsychologi- cal function, because the connections of the thalamus are extremely complicated and an understanding of them all lies beyond the scope of this text.

Lesions, particularly vascular accidents, and to some extent tumors, have been most often associated with the thalamic syndrome, marked deficits in gross areas of sen- sory or motor function. For example, lesions of the left thalamus have been implicated with depressed scores on cognitive-verbal tasks (Vilkki & Laitinen, 1974; Zillmer, Fowler, Waechtler, Harris, & Khan, 1992). Lesions of the right thalamus have been associated with defects in spa- tial ability (Bundick, Zillmer, Ives, & Beadle-Linsay, 1995; Jurko & Andy, 1973), facial recognition (Vilkki & Laitinen, 1974), and the perception of music (Roeser & Daly, 1974). Consequently, many sequelae of thalamic injury are those you might expect from the interruption of essential relay elements in pathways to and from the

cerebral hemispheres. In some thalamic lesions, the symp- toms are short lived, indicating that alternative pathways are quickly formed.

C E R E B E L L U M

Overview

Gross anatomic features: cerebellar cortex, cerebellar white matter, and glia

Function: coordination of movements, posture, anti- gravity movements, balance, and gait

S t r u c t u r e

The cerebellum (derived from Latin meaning “little brain”), surprisingly, contains nearly 50% of the neurons of the brain, even though it makes up only 10% of its weight. On visual inspection, the cerebellum is a spectac- ular brain structure because of its clearly defined mor- phology and symmetry (Figure 5.22). The cerebellar cor- tex is heavily infolded, and the numerous parallel sulci give it a layered appearance. The cerebellum also has several deep fissures dividing each cerebellar hemisphere into sep- arate lobes. Its histologic structure, however, is relatively

146 PART TWO | The Functioning Brain

Figure 5.22 Structure of the cerebellum. (a) Dorsal view of the left cerebellar hemisphere with the right hemisphere removed to reveal the cerebellar peduncles. (b) Flattened view of the cerebellar surface showing the three major subdivisions and vermis. (From Purves, D., Augustine, G. J., Fitzpatrick, D., Katz, L. C., LaMantia, A., McNamara, J. O., & William, S. M. [Eds.]. [2001]. Neuroscience [2nd ed., p. 410, Figure 19.1]. Sunderland, MA: Sinauer Associates, by permission.)

simple compared with that of the cortex. The neurons ap- pear to be organized in repeating patterns. The cerebel- lum is located posteriorly and superiorly to the pons and medulla, just inferior to the posterior portion of the cere- bral hemispheres. The cerebellum is attached to the brain- stem at the level of the pons (“bridge”) via the cerebellar peduncles and consists of two large oval hemispheres con- nected by a single median portion, termed the vermis (de- rived from Latin meaning “worm”).

F u n c t i o n

The cerebellum is phylogenetically old and may have been the first brain structure to specialize in coordinating motor and sensory information. Observing patients with cerebellar disease makes clear the importance of this cen- ter for coordinating movement and postural adjustments. The cerebellum is heavily involved in basic processes nec- essary for general motor behavior, as well as in coordinat- ing movements. The oldest areas of the cerebellum are concerned with keeping the body oriented in space mo- torically. The cerebellum also helps control muscles keep- ing the body upright despite the pull of gravity and mon- itors background muscle tone involved in voluntary movement.

Lesions of the cerebellum, depending on location, may cause a variety of disorders, including deterioration of co- ordinated movement, irregular and jerky movements, in- tention tremor when attempting to complete a voluntary task, static tremor when resting, impairment of alternat- ing movements, impairment in balance, disturbances of gait, and uncontrolled nystagmic movements of the eyes. Evidence exists that people born without a cerebellum can function completely normally, because other brain struc- tures have adapted to take over its functions. Neuropsy- chologists often erroneously ignore the cerebellum because no obvious cognitive properties have been associ- ated with lesions of the cerebellum. However, it now ap- pears that the cerebellum stores memories for simple learned motor responses and is involved in attentional shifting, as well as other cognitive functions (Diamond, 2000).

Telencephalon

The telencephalon, or endbrain, consists of the two cerebral hemispheres connected by a massive bundle of fibers, the corpus callosum. The outer layer of the cortex consists primarily of cell bodies (gray matter) and affects thinking, memory, and voluntary behavior, as well as the regulation of motor behavior. Within each hemisphere is

a lateral ventricle and a collection of several large nuclei known as the basal ganglia, which contain the cell bodies of motor control neurons. The basal forebrain is also rec- ognized as a prominent division of the subcortical (below the cortex) aspect of the cerebrum. This area, sur- rounding the inferior tip of the frontal horn, is strongly interconnected with limbic structures, and some re- searchers (e.g., Crosson, 1992) consider it part of the limbic system.

B A S A L G A N G L I A

The basal ganglia, also called the basal nuclei, are a col- lection of deep nuclei of the telencephalon (basal means “lowest level”; Figure 5.23) The basal ganglia communi- cate with motor regions in the cortex via the thalamus. With their complex interconnections and efferent out- puts and afferent inputs, the basal ganglia participate in the control of higher order movement, particularly in starting or initiating movement.

Overview

Gross anatomic features: structures of the caudate nu- cleus, putamen, globus pallidus, substantia nigra, and subthalamic nuclei

Function: important as relay stations in motor behav- ior (e.g., the striato-pallido-thalamic loop), coordi- nating stereotyped postural and reflexive motor activity, and supporting higher order cognitive func- tions

S t r u c t u r e

Embedded deep within the cortex lies a group of symmet- ric subcortical gray matter structures known collectively as the basal ganglia. They partially surround the thalamus and are themselves enclosed by the cerebral cortex and cerebral white matter. They have sensory projections to the cerebral hemispheres, interconnections between parts of the cortex, and outflow from the cerebral cortex to other nervous system structures. Neuropsychologists most often conceptualize the basal ganglia within the context of the motor system and, thus, typically exclude the amygdala (located at the tail of the caudate nucleus) and a large part of the thalamus. However, the substantia nigra and the subthalamic nucleus have important motor functions and are usually included as part of the basal ganglia.

The two major structures of the basal ganglia are the caudate nucleus and the putamen, with the adjacent me- dial and lateral globus pallidus. In general, these structures

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connect with the cortex, via the thalamus, the reticular formation, and the midbrain, but to a lesser degree with the spinal cord. The caudate nucleus connects to the puta- men via the anterior limb of the internal capsule. This conglomeration is so difficult to identify as separate struc- tures that it is usually referred to as the striatum because of its striped or striated appearance.

The precise circuitry of the basal nuclei is not fully un- derstood, but researchers think they act as a relay station between the cerebral cortex via the thalamus. The major output from the basal ganglia targets the thalamus.

One major pathway between different structures com- prising the basal ganglia is the striato-pallido-thalamic loop. This communication loop greatly interests neuropsy- chologists because it provides a mechanism for processing and integrating information from different regions of the brain before cortical processing. The input side of the basal ganglia, the striatum, receives information (descend- ing connections) from separate sources, including the motor system, sensory and higher integrative areas of the cortex, the language centers of Broca’s and Wernicke’s areas, the thalamic nuclei, and the substantia nigra. The striatum, in turn, projects to the globus pallidus, which directly projects to the motor areas of the thalamus. The substantia nigra plays an important role in basal ganglia function via the dopaminergic nigrostriatal system. Its links

to the globus pallidus, and the thalamus can influence motor behavior, which is organized by the cortex.

F u n c t i o n

Researchers think the primary activity of the basal ganglia regulates voluntary movements, specifically related to planning and initiating motor behavior. The basal gan- glia, together with the red nucleus and substantia nigra of the midbrain and the cerebellum, form what has clinically been termed the extrapyramidal motor system, which is responsible for stereotyped postural and reflexive motor activity. The system also acts to keep individual muscles ready to respond. The other major motor system, the pyramidal system, originates in the cerebral cortex.

Two general theories of the role of the basal ganglia have been advanced. One suggests that the basal ganglia are mostly integrative in nature and receive input from vi- sual centers, from the balance centers of the brain, and from the muscles and joints of the body. An alternative hypothesis assigns less importance to the basal nuclei, sug- gesting they are, more or less, a relay station with few in- tegrative properties (Noback & Demarest, 1975). The basal ganglia may also play a role in language, specifically motor planning and programming for speech, and per- haps even functions associated with attention and alerting before a motor response. Increasingly, research suggests

148 PART TWO | The Functioning Brain

Globus pallidus (lateral part)

Caudate nucleus

Subthalamic nucleus

Substantia nigra

Putamen

Globus pallidus (medial part)

Thalamus

Figure 5.23 Basal ganglia within the cortex. (From Kalat, J. W. [2007]. Biological psychology [9th ed., p. 251, Figure 8.16]. Belmont, CA: Thomson Wadsworth.)

that the basal ganglia, via their interconnections with the frontal lobes, participate in the generation, inhibition, and execution of higher order behaviors (Lichter & Cum- mings, 2001). For instance, damage to the caudate nu- cleus of the basal ganglia can impair cognitive or mental flexibility, a finding also evident with prefrontal damage.

Most understanding regarding the function of basal ganglia is gained from knowledge of movement disorders associated with basal ganglia dysfunction. Such abnor- malities, which also include disorders of the cerebellum, have been labeled extrapyramidal and are characterized by atypical movements and changes in muscle tone. In con- trast, pyramidal symptoms involve upper motor neuron disorders of the cortex and are more often associated with a loss of voluntary movement, including paralysis. Two relatively common basal ganglia disorders are Parkinson’s disease and Huntington’s disease (see Chapter 15).

Extrapyramidal symptoms also have been observed in schizophrenics who are treated with antipsychotic drugs. Those drugs, including Thorazine (chlorpromazine), Stelazine (trifluoperazine), and Haldol (haloperidol), block dopamine transmission. Although this reduces psychotic behavior and hallucinations, it has the side ef- fect of Parkinson-like symptoms, including writhing movements of the mouth, face, and tongue. This neuro- logic presentation in schizophrenics who develop such symptoms is known as tardive dyskinesia and is irre- versible. In general, the overall connections and func- tions of the basal ganglia are not fully understood, al- though the principal function of this formation is associated with motor behavior, specifically organizing ease and flow of movement.

L I M B I C S Y S T E M

The anatomic term limbic (derived from the Latin word limbus, meaning “border”) was first coined by Paul Broca (Schiller, 1982). Broca noticed that a ring of cortical tis- sue forms a border around the brainstem and medial as- pects of the brain. Broca thought “le grand lobe limbique” was primarily involved with olfaction, because of its in- terconnections with the evolutionarily older rhinen- cephalon, or “smell brain.” In 1937, James Papez sug- gested the presence of a more precise circuit or “limbic system,” which he proposed was significantly involved in mediating emotional behavior. Indeed, proposing that a set of brain structures might be primarily involved in pro- cessing emotions was a bold statement at the time. Since then, however, the limbic system has received much at- tention for its major role in the expression of emotions, as well as in olfaction, learning, and memory.

Overview

Gross anatomic features: structures of the amygdala, hippocampus, parahippocampal gyrus, cingulate gyrus, fornix, septum, and olfactory bulbs

Function: the limbic system is closely involved in the expression of emotional behavior and the integration of olfactory information with visceral and somatic information

S t r u c t u r e

Broca defined the limbic lobe to include those structures on the medial and basal surfaces of the cerebral hemi- spheres. Because the limbic lobe is most developed in mammals, it is also known as the mammalian brain. In fact, in some primitive animals, such as the crocodile, the entire forebrain is limbic brain (the limbic cortex is part of the forebrain that developed first in evolution). The primary structures of the lobe include the medial cortex surrounding the corpus callosum, termed the cingulate gyrus (see Figure 5.14), and the medial cortex of the tem- poral lobes, or the parahippocampal gyrus, and the hip- pocampal formation (hippocampus, dentate gyrus, and subiculum; see Figure 9.2). The structures of the limbic system are often debated, but usually also include the fornix, some brainstem areas, particularly the mammil- lary bodies of the hypothalamus, specific basal forebrain structures, including the amygdala (“almond” because of its shape), and the septum (Figure 5.24). Several anatomic circuits have been described that include limbic system structures. The most likely role of the basolateral circuit, which centers around the amygdala, is in emo- tional processing. The Papez circuit, which centers around the hippocampus, is perhaps the most well-known loop. We further discuss these functional systems in Chapter 9.

F u n c t i o n

The limbic system is a most complex but important set of brain structures that has fascinated anatomists, neurolo- gists, and neuroscientists for more than 50 years. The lim- bic system is a bit misnamed because there is no one-to- one structure–function relationship, as is evident in many sensory systems that are discussed in Chapter 7. The role of the limbic system in emotions and memory has gener- ated a great deal of interest in neuropsychology. Extensive research has been conducted on several components of the highly interconnected limbic system. However, be- cause of the interconnectivity of the system, it is often dif- ficult to discern structure–function relationships. For ex- ample, the amygdala and hippocampus have specific

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connections with other brain structures and also have been studied as separate entities. The activities of the lim- bic system in memory consolidation, emotional behavior, and olfactory processing are topics on which we further elaborate in Chapters 7 and 9.

The limbic system is closely related to the hypothala- mus, which researchers have singled out as the main brain structure for integrating and organizing autonomic processes related to the emotional expression of behavior. In humans, limbic system dysfunction has been associ- ated with a variety of abnormalities, including emotional and behavioral problems (Glaser & Pincus, 1969) and sexual dysfunction (Rosenblum, 1974).

The hippocampal formation has been specifically asso- ciated with memory acquisition (Douglas & Pribram, 1966; Penfield & Milner, 1958; Scoville & Milner, 1957). The primary defect, seen after bilateral injury of the hip- pocampus, involves difficulty in learning new informa- tion. Such patients find themselves unable to retain newly learned information, although immediate and old memo- ries remain relatively intact (Luria, 1971; Milner, 1968).

These effects on memory functioning are less profound when only one hippocampal gyrus is affected (McLardy, 1970). Lesions of the left hippocampal gyrus may cause problems with verbal memory (Russell & Espir, 1961), whereas lesions of the right hippocampal gyrus may cause greater impairment in spatial memory, including maze learning (Corkin, 1965).

The amygdala has ascending and descending connec- tions with the cerebral hemispheres, the thalamus, the hippocampus, and even the spinal cord. The amygdala plays a specific role in fear conditioning and in impacting the strength of stored memory (LeDoux, 1994). The amygdala is discussed in greater detail in Chapter 9.

Numerous psychological disorders are characterized by emotional disturbances, and the limbic system has been implicated in many of them. Extreme violence in patients who exhibit rage attacks and frequent aggressive behavior can follow damage to the amygdala and its connections. In fact, removal of the amygdala (amygdalotomy) has been performed on extremely violent and aggressive patients in an attempt to stem rage reactions. Balasubramanian and

150 PART TWO | The Functioning Brain

Corpus callosumFornix

Anterior nucleus of thalamus

Septum

Olfactory bulb

Mammillary body

Amygdala

Hippocampus

Figure 5.24 Limbic system with cortical area removed. (From Heller, K. W. [1996]. Understanding physical, sensory, and health impairments [p. 54, Figure 4.9]. Pacific Grove, CA: Brooks/Cole.)

Ranamurthi (1970) have reported 100 cases of bilateral destruction of the amygdala in patients with behavior dis- orders.

Another clinical disorder associated with memory function of the limbic system is Wernicke-Korsakoff ’s syndrome. This is typically observed in severe alcoholics who show multiple nutritional deficiencies because they have essentially replaced solid food with alcohol. Such pa- tients may develop a confusional state over time, as well as severe motor and new learning difficulties. This syn- drome is related to vitamin B1 (thiamine) deficiency.

Despite the limbic system’s popularity among research- ers, the complexity of the system’s connections, internally as well as to other areas outside of the system, and the dis- agreement as to what brain structures should be included in the limbic system, it still puzzles modern neuropsy- chologists. In fact, some scientists suggest that neuropsy- chology needs to move away from the concept of the larger “system” of the limbic structures and should define them in more precise individual terms.

C O R P U S C A L L O S U M

Overview

Gross anatomic features: a large set of myelinated axons connecting the right and left cerebral hemispheres

Function: information exchange between the two hemispheres

S t r u c t u r e

The most prominent bundle of axons in the brain is a col- lection of intercerebral fibers known as the corpus callo- sum, an arched mass composed almost exclusively of myelinated axon bundles or white matter. The corpus cal- losum lies in the depths of the space between the two hemispheres called the longitudinal fissure and lies im- mediately inferior to the cingulum, a major intracerebral fiber within the cingulate gyrus (Figure 5.25).

F u n c t i o n

In the normal brain, information that enters one hemi- sphere crosses to the opposite side almost instantaneously (about 7–13 milliseconds). This happens via the corpus callosum, but also through smaller intercerebral fibers, the anterior commissure and hippocampal commis- sure. Because of the corpus callosum, both hemispheres share information, even though initially only one hemi- sphere may have received the information. The corpus callosum enables most communication and exchange of information between left and right hemispheres (Springer & Deutsch, 1993; Sperry, 1958).

An interesting problem for the brain arises if the corpus callosum is severed. This is intriguing to neuropsycholo- gists, because now information presented to only one side of the body (or brain) is not shared with the other hemi- sphere. In very young children, cutting the corpus callo- sum has little apparent effect, because the brain develops alternative pathways to help compensate for the loss. In the adult brain, however, neural pathways have already developed. If the corpus callosum is severed surgically, which is sometimes done as a medical procedure to arrest the spread of seizures between hemispheres, the process- ing of some sensory information is confined to only one hemisphere. The study of such individuals, also known as

CHAPTER 5 | Functional Neuroanatomy 151

Corpus callosum

Cingulate gyrus

Figure 5.25 Corpus callosum. (From Kalat, J. W. [2007]. Biologi- cal psychology [9th ed., p. 418, Figure 14.2]. Belmont, CA: Thomson Wadsworth.)

split-brain patients, has helped provide extensive and in- teresting data on the independent functioning of the two cerebral hemispheres (Gazzaniga, 1966; Geschwind, 1965; Zaidel & Sperry, 1973). Researchers have learned from such cases that each hemisphere can function and

process information in isolation. The idea that the brain might be composed of two independently functioning brain halves, perhaps even having two personalities or sep- arate minds, is a question we explore in our later discus- sion of consciousness (see Chapter 16).

152 PART TWO | The Functioning Brain

Summary This chapter reviews the development, major structures, and functions of the brain. This anatomy lesson is important for a variety of reasons. It is important to understand the functional aspects of the brain as they relate to brain anatomy. Knowledge of brain structures, in and of itself, is not very useful to neuropsycholo- gists. This is most interestingly demonstrated when students with little neuropsychological knowledge dis- sect a brain. They proceed in a most rapid manner with the dissection, naming each structure they are able to detect as they go along. Once finished, they are typically perplexed with the mess they have made and how little they have learned. They often ask, “Where has the brain gone?” Novices look at the brain as an anatomic object; neuropsychologists examine it as a functioning organ of interconnected systems.

This chapter serves as an overview of the basic neuroanatomic structures and functions of the CNS. However, it is typically the more integrated behaviors that interest neuropsychologists. Therefore, it is neces- sary to move from discussions of groupings of structures based on ontogeny to the idea of pluripotentiality of structures within functional systems. This concept, first introduced in Chapter 1, often transverses group- ings based on migration of structures during brain development. It is to the systemic organization of regions of the cerebral hemispheres in support of behavior, particularly those involving higher order mental func- tions that we now turn.

C r i t i c a l T h i n k i n g Q u e s t i o n s

Why is an understanding of the stages and processes of brain development important to the neuropsychologist? If a child was born without the telencephalon region of the brain, would the child be able to orient to visual and auditory stimuli, perform reflexive movements, and sit up? Explain why or why not. To what extent can behavioral functions be localized to specific brain structures? What level of brain mapping is most useful to the neuropsychologist?

K e y Te r m s

Central nervous system (CNS) Neurogenesis Peripheral nervous system

(PNS) Neural tube Precursor or progenitor cells Glial cells Oligodendrocytes Microglia Migratory process Differentiation process Neurulation Spina bifida Anencephaly Corticogenesis

Agyria or lissencephaly Axons Dendrites Arborization Dendritic spines Synaptogenesis Prefrontal cortex Myelin Pruning Visual cortex Forebrain (prosencephalon) Midbrain (mesencephalon) Hindbrain (rhombencephalon) Telencephalon Diencephalon

Metencephalon Myelencephalon Gyrus (gyri) Sulcus (sulci) Sylvian (lateral) fissure Polymicrogyria Cerebrospinal fluid (CSF) Vertebral column Somatic nervous system (SNS) Autonomic nervous system

(ANS) Sympathetic nervous system Parasympathetic nervous

system Brain

Spinal cord Cranial nerves Afferent nerves Efferent nerves Meninges Horizontal plane Coronal plane Sagittal plane Anterior Posterior Inferior Superior Medial Lateral Rostral

Caudal Proximal Distal Dorsal Ventral Ipsilateral Contralateral Meningiomas Ventricular system Vascular system Fossae Foramina Foramen magnum Fontanelle Pia mater Arachnoid membrane Subarachnoid space Dura mater Epidural space Subdural space Subdural hematoma Meningitis Ventricles Interventricular foramen or

foramen of Monro

Cerebral aqueduct or aqueduct of Sylvius

Choroid plexus Foramen of Magendie Foramina of Luschka Cisterns Superior sagittal sinus Arachnoid villi or granulations Hydrocephalus Normal-pressure hydrocephalus

(NPH) Internal carotid arteries Vertebral arteries Aortic arch Basilar artery Posterior cerebral arteries Cerebrovascular accident (CVA) Circle of Willis Anterior cerebral artery Middle cerebral artery Anterior communicating artery Posterior communicating

arteries Cerebrum Basal forebrain

Cerebellum Brainstem Medulla oblongata Pons Reticular activating system

(RAS) Decussate Cerebellar peduncles Tectum Tegmentum Inferior colliculi Superior colliculi Thalamus Hypothalamus Pituitary stalk Adrenocorticotropic hormone

(ACTH) Vermis Basal ganglia Basal nuclei Subthalamic nucleus Caudate nucleus Putamen Globus pallidus Striatum

Substantia nigra Extrapyramidal motor system Pyramidal motor system Tardive dyskinesia Rhinencephalon Cingulate gyrus Parahippocampal gyrus Hippocampal formation Limbic system Fornix Mammillary bodies Amygdala Septum Basolateral circuit Papez circuit Wernicke-Korsakoff’s

syndrome Corpus callosum Longitudinal fissure Cingulum Anterior commissure Hippocampal commissure

CHAPTER 5 | Functional Neuroanatomy 153

We b C o n n e c t i o n s

http://www.meddean.luc.edu/lumen/MedEd/GrossAnatomy/h_n/cn/cn1/mainframe.htm The Cranial Nerves This site provides excellent discussion of the cranial nerves.

http://www.neuropat.dote.hu Neuroanatomy This page features links to a number of resources in neuroanatomy.

http://www.meddean.luc.edu

http://www.neuropat.dote.hu

Chapter 6

C E R E B R A L S P E C I A L I Z AT I O N

Men are from Mars, and Women are from Venus. —John Gray

The Cerebral Hemispheres Hemispheric Anatomic and Functional Differences Sex Differences and Hemispheric Specialization

Neuropsychology in Action

6.1 The Evolution of the Brain: A Focus on Brain Size 6.2 A Land Where Girls Rule in Math

Overview This chapter focuses on the cerebral cortex with regard to structure, function, lateralization, and sex differ- ences. Our discussion of the cortex provides a foundation for subsequent chapters that explore the func- tional systems of the brain that support complex behavior such as language, memory, and emotions. The cortical regions of the brain can be defined in a number of ways, although the most frequently used nomen- clature involves the divisions of the cortex into four lobes (occipital, temporal, parietal, and frontal). Although there is greater correspondence between region and primary sensory functions of the posterior regions of the brain, higher order cognitive, emotional, and social functions are not specifically localized to a particular lobe. Rather, multiple pathways and regions underpin functions, particularly those that involve complex behavior.

The human brain is composed of two hemispheres that interact in the support of behavior. The hemi- spheres differ regarding structure and function, with certain human attributes being lateralized to either the left or right hemisphere. However, the lateralization of a function to one hemisphere does not mean that the other hemisphere is uninvolved in the support of the function. For example, speech and language are gener- ally lateralized to the left hemisphere in most people (both right- and left-handed individuals), but the right hemisphere is also intimately involved in speech and language functions.

It is generally recognized that each person’s brain is different from the brain of every other person. Putative cognitive and behavioral differences of male and female individuals have led to neuropsychological investigations to determine whether structural and functional differences exist between the brains of the two sexes. Significant attention has focused on the role of sex hormones in the organization and activation of the brain. You will soon realize that the relation of sex hormones to behavior is complex and not fully understood.

CHAPTER 6 | Cerebral Specialization 155

The Cerebral Hemispheres

Overview

Gross anatomic features: structures of the frontal, pari- etal, occipital, and temporal lobes

Function: higher cognitive functioning, cerebral spe- cialization, and cortical localization

The cerebral hemispheres represent the most recently evolved brain structure in humans, although they are ap- proximately 1 to 3 million years old (see Neuropsychology

in Action 6.1). The complexity of the interhemispheric and intrahemispheric connections reflects this degree of evolution, which allows humans to use such abstract con- cepts as symbols, language, and art.

S T R U C T U R E

The largest part of the brain consists of the cerebrum, or the right and left cerebral hemispheres. The two hemi- spheres form a half globe with a flat basal surface. The hemispheres are separated by a deep midline cleft, the longitudinal fissure, and are connected via the corpus

K e e p i n M i n d

What is the relation of brain size to function?

Is there a one-to-one relationship between cerebral regions and function?

Why are the concepts of laterality, dominance, and asymmetry important in understanding brain–behavior functions?

Do sex differences exist in brain organization and activation? What are the implications of these differences?

How do you account for the presumed sex difference in mental rotation and verbal fluency?

156 PART TWO | The Functioning Brain

To understand the functioning brain, place it within the context of evolution. Two to three million years ago, humans living in East Africa were making stone tools, perhaps building simple dwellings. Their brains would, in the course of a spectacular evolution, eventually enlarge to the size and complexity of today. Humans could not possibly perform the numerous and complex behaviors that they do without brain mechanisms that have evolved over hundreds of thousands of years. Evolutionary psychology offers a coherent theory that may begin to explain the strategic differences and similarities in the structures and functions of the brain.

Central to the concept of evolution was Charles Darwin’s (1809–1882) text On the Origin of Species (1859). His historic 1835 trip to the Galápagos Islands laid the foun- dation of his theory of biological evolution, even though he stayed for only 5 weeks. Darwin suggested that the mechanism for explaining how species evolve from existing forms is a process based on natural selec- tion. He identified the process of natural selection as the mechanism underlying the evolution of all organisms. He reasoned that some individuals were better able to survive and reproduce than others, and that the characteristics that made these species more successful could then be transmitted to the next generation. Perhaps the most significant legacy of evolution is a powerful brain that has evolved to a degree allowing humans to learn from experiences.

Basic human psychological mechanisms related to brain processes are likely to be species specific. For example, most or all humans share certain psychological

processes, including fear of darkness; characteristic emotions such as anger, love, and humor; weapon making; sexual attrac- tion; and probably hundreds more (Wright, 1994). People often call these processes human nature, but they must be related to brain processes. One reason most humans share many psychological mechanisms relates to that natural selection tends to impose relative uniformity in complex adap- tive designs, such as the brain. Thus, central to any theory on brain evolution is that certain aspects of the CNS remain stable, whereas others must adapt over time. This is most readily apparent at the level of human physiology and anatomy: All people have two arms, a heart, and a brain; that is, they do not vary in possessing basic physiologic mechanisms. According to evolutionary psychology, however, the brain must contain a large number of specialized psychological mechanisms; each designed to solve a different or related adaptive problem. Thus, individuals also differ, and fundamental individual differences must be central to any comprehensive brain theory.

One way that the human brain differs, compared with other species, is its size, particularly the size of the neocortex. For example, a general principle of neural orga- nization indicates that the size and complex- ity of a structure is related to its functional importance of the structure. The brain, through the meninges, is firmly attached to the skull. Anthropologists measure the internal volume of skulls, which is easily preserved over time, to estimate the weight of the brain. Using this technique, re- searchers estimated the brains of our

earliest ancestors, dated approximately 5 million years ago, to be relatively small, about 400 cm3 (Changeux & Chavaillon, 1995). Anthropologic evidence suggests that approximately 3 million years ago the anatomic organization of the CNS and its associated functions evolved at a spectacu- lar rate. Although the human brain was always relatively large in proportion to the body, and presented a modern organization, the relative size of the brain rapidly increased in size. About 1 million years ago, the occipital lobes began to develop, fol- lowed by the frontal, parietal, and temporal lobes. This new biological foundation en- abled increased memory capacity, more frequent and specific spoken communica- tion (language), a more elaborate social life, and a more extensive exploration of the environment. Humans no longer depended on gathering rocks, carcasses, and vegeta- bles, but became proficient in animal cap- ture. This evolution in the structural complex- ity and performance of the brain corresponded directly with the formation and development of diverse cultures.

Neanderthals are thought to have inhab- ited Europe and the Middle East as early as 100,000 years ago. It is not clear exactly how similar they were to us, but they certainly had an elaborate tool-using culture that included ritual burial (Changeux & Chavaillon, 1995). About 100,000 years ago, the growth in brain size started to level off, probably related to the fact that the female pelvis, and the size of the skull that can fit through it, had not kept pace with the evolution of the brain. This has made for a remarkable state of affairs as it relates to brain development in humans. At birth, the

N e u r o p s y c h o l o g y i n A c t i o n 6 . 1

T h e E v o l u t i o n o f t h e B r a i n : A F o c u s o n B r a i n S i z e

by Eric A. Zillmer

callosum. The surface of each hemisphere folds in on it- self in many places, creating grooves along the surface re- ferred to as sulci (singular, sulcus). Very deep grooves are termed fissures. The irregularly shaped ridges between sulci are known as gyri (singular, gyrus). No two brains are exactly identical in the size or the shape of their gyri,

although the general gyral pattern is consistent enough to locate major landmarks. The morphology of the brain’s gyri can be thought of as somewhat related to the idea of a face, where the features such as the nose, eyes, and mouth are generally localizable but vary in shape accord- ing to the person. Perhaps, more like a fingerprint, each

person has his or her own “brain print.” So much varia- tion is evident between the brains of people that research- ers conducting imaging and histologic analyses must com- pensate for interindividual variability by standardizing and transforming formulas, rather than by comparing brains directly (Mai, Assheuer, & Paxinos, 1997). Figure 6.1 pre- sents general gyral and sulcal features.

The surface of the cerebral hemispheres is covered by gray matter. As described in Chapter 4, the gray areas of the central nervous system (CNS) consist mainly of cell bodies of neurons that serve as the brain’s functional units. Underlying the cortex is white matter that links structures within the cerebral hemispheres and the CNS as a whole. The size, shape, and distribution of the cells and fibers vary

CHAPTER 6 | Cerebral Specialization 157

brain is approximately 1/4 its eventual size, compared with the rest of the body, which is 1/20 its eventual size. Then, over the next 20 years of a human’s life, the brain matures at an amazing rate, developing billions of connections and supporting cells. At age 16, it reaches a level of behavioral control and conscious realm (maturity) that the owner of the brain is allowed to drive himself or herself around in an automobile. At age 18, the brain is allowed to render an opinion, a vote, affect- ing other brains (through culture and society).

The basic brain structures are similar for all mammals, although brain size may vary considerably among different species. One of the many fascinating aspects of how humans have evolved as a species is related to this extreme and unprecedented growth of the human brain, the cerebral cortex, and specifically the prefrontal cortex, which Luria named the “organ of civilization.” To many students, the size of an organism’s brain may seem intuitively related to the intellectual properties of a species. Cer- tainly, if you compare animals with humans, there is a relation between brain size and intelligence. Aristotle commented on that humans had proportionally the largest brains of all animals.

Consider, for example, that gorillas, although physically larger than humans, only have about one fourth of the brain size. In humans, the average adult brain size is about 1300 cubic centimeters (cm3) and weighs about 1500 grams. But a blue whale’s brain weighs 6000 grams, and an African elephant’s brain 5700 grams. If, however, brain size is held constant as it relates to body size, humans compare very well. The brain of a whale accounts for only 1/10,000 of its body weight, the elephant’s brain 1/600, and the human brain 1/40. Thus, if the range of brain size with body size is held constant, the human brain is 21,000 times larger and the neocortex is 142,000 times larger than that of the shrew, a very

small, mouselike mammal. This means that if a shrew were the size of a human, its brain would weigh only 46 grams. The body/brain weight formula, however, does not work well with all small animals. For example, the ferret’s brain makes up 1/12 of its body weight. In fact, the best ratio appears to be between an organism’s body surface (not body weight) and brain size. Certainly, it is logical to assume that the surface of the body, through which the organism has contact with the environment, is more di- rectly related to brain function than is the total weight in bones and blood. When body surface is taken into consideration, the human comes in first among all vertebrates, with the chimpanzee and the dolphin follow- ing second and third (Changeux & Chavail- lon, 1995).

Large brains are not necessarily more efficient or effective; in fact, absolute brain weight has no significance in itself. It may require a larger brain more time to process information than a smaller one. There are even differences in brain size among hu- mans. Big people tend to have larger brains than smaller people. This does not imply that men, who are, on average, taller and heavier than women, are smarter. After correcting for body size, men and women have brains of approximately equal size.

The size of a brain has been an object of debate and controversy for many centuries. Broca, for one, argued that the size of the brains of human races had to account for something (1861). He proposed that “in general, the brain is larger in mature adults than in the elderly, in men than in women, in eminent men than in men of mediocre talent, in superior races than in inferior races . . . . There is a remarkable relationship between the development of intelligence and the volume of the brain” (1861, pp. 188, 304). As evidence, Broca offered findings that 51 unskilled workers had an average brain weight of 1365 grams, compared with the

brain weight of 24 skilled workers, which was an average of 1420 grams. Any student of statistics knows that this finding may not be statistically significant, given the large variation of brain weights in humans and, presumably, in Broca’s sample as well. Furthermore, it is entirely possible that the unskilled workers were malnourished and, therefore, were smaller in stature than the skilled workers. In any case, Broca’s data have not been confirmed by more recent studies, suggesting that his findings were due to chance. Nevertheless, Broca went to great lengths to “prove” his theory. One has to wonder what Gall himself must have thought of this—his brain measured “only” 1100 grams.

The measurement (or mismeasurement) of human intellectual properties according to brain size has been described by the evolu- tionary biologist Stephen J. Gould in The Mismeasure of Man (1981), in which he presented a fascinating historical account of phrenology and other pseudoscientific expla- nations of the size of the human brain and its relation to intelligence. What Broca and others did not realize was that body size, as well as many other factors, relates to the complexity of the brain and the nervous systems of humans and other species. In fact, the complexity of the brain depends on many dimensions in addition to brain size, including connectivity, cell density, cell morphology, neurotransmitter complements, and perhaps the most important variable, the rate and duration of neuronal sprouting. Among hu- mans, no brain size–intelligence relation exists.

The brain of Albert Einstein, the Nobel Prize–winning physicist, underwent autopsy after his death on April 18, 1955. Gall and Broca would have been surprised to learn that the Princeton professor’s brain was basically normal in appearance and of average size, although there were structural differences in the parietal lobe.

158 PART TWO | The Functioning Brain

from place to place within the cerebral cortex. In princi- ple, there are many connections within the cortex itself, both horizontal and vertical, as well as to subcortical areas.

The frontal, parietal, temporal, and occipital lobes (Figure 6.2) are the four major divisions of each hemisphere. The frontal and parietal lobes are separated from the temporal lobe by the lateral fissure. The frontal and parietal lobes are separated by the central sulcus. The parietal and occipital lobes are separated by the parietal–occipital fissure and its imaginary extension across the lateral surface of the hemisphere to the occipi- tal notch. The division and naming of the cortex into four lobes is quite arbitrary and is related to the names of the cranial plates that provide protective covering just su- perior to the lobes.

Another way of referring to the topography of the brain is related to the architectural arrangement of neu- rons in different regions throughout the brain. Brodmann (1909) divided the cortical surface according to these dif- ferences and showed that the anatomic organization of the cortex is similar in all mammals. He divided the brain into 52 sections, which are now referred to as Brodmann’s areas (Figure 6.3). Correspondence between architectural regions and functional regions is, however, not precise. In fact, Brodmann’s cytoarchitectural scheme is now considered questionable. For example, in humans, the cerebral cortex is much more developed than Brodmann’s map suggests. In particular, the Brodmann system did not do justice to the degree of complexity of the brain’s interhemispheric and intrahemispheric connections. Nevertheless, it is still

Figure 6.1 Major gyri and sulci of the cerebral hemispheres. (a) Lateral and (b) medial views of gyri; (c) lateral and (d) medial views of sulci. (Adapted from Kolb, B., & Wishaw, I. Q. [1996]. Fundamentals of human neuropsychology [4th ed., p. 51, Figure 3.5]. New York: W. H. Freeman and Company, by permission of Worth Publishers.)

Central Central

Cingulate

Corpus callosum

Postcentral

Precentral

Paracentral

Superior frontal

Superior parietal lobule

Super marginal

Inferior parietal lobule

Superior frontal

Inferior frontal

Inferior temporal

Occipitotemporal

Parolfactory

Gyrus rectus

Middle frontal

Middle temporal

Middle temporal Inferior temporal

Superior temporal

a. b.

c. d.

Lateral fissure

Lateral occipital

Collateral

Calcarine

Callosal

Sub- callosal

Parieto- occipital

Parahippocampal

Lingula

Cuneus

Precuneus

Uncus

Angular

Opercular

Triangular Orbital

used widely for referring to particular parts of the cortex and is certainly more sophisticated than gross descrip- tions of the cerebral lobes. The publication of Brod- mann’s famous map of the human cortex in 1909 was in- strumental in clarifying the confusion that existed until then. Using Brodmann’s system, for example, Broca’s area is called area 44.

F U N C T I O N

Because the cerebral hemispheres are responsible for the “higher mental functions” of humans, it is not surprising that neuropsychologists have shown particular interest in these structures. In essence, the cerebral cortex is what

makes us uniquely human. The cerebral cortex orga- nizes higher cognitive functions related to the following operations: (1) analyzing input, or processing of elemen- tary sensory information such as touch, sound, or vision; (2) sorting, organizing, integrating, synthesizing, storing, or otherwise using the information; and (3) directing out- put through motor processing, which can range from ac- tivities such as walking to speaking.

The greatest one-to-one correspondences between structure and function within the cortex are in the areas of primary sensory input and primary motor output. For example, the somatosensory cortex, which occupies the anterior aspect of the parietal lobes, is responsible for re- ceiving primary tactile sensation from the body, and the

CHAPTER 6 | Cerebral Specialization 159

Figure 6.2 Lobes of the cerebral cortex. Four views of the frontal, temporal, occipital, and parietal lobes of the brain. (Adapted from Kolb, B., & Wishaw, I. Q. [1996]. Fundamentals of human neuropsychology [4th ed., p. 52, Figure 3.6]. New York: W. H. Freeman and Company, by permission of Worth Publishers.)

Frontal

Lateral fissure

a. Lateral b. Medial

c. Dorsal d. Ventral

Frontal

Central sulcus

ParietalParietal

Occipital

Temporal

Parietal

Frontal

Longitudinal fissure

Central sulcus

160 PART TWO | The Functioning Brain

primary motor cortex of the frontal lobe is concerned with initiating, activating, and performing motor activity. As a general rule, within the cortex, sensory processing occurs in the posterior aspects (the temporal, parietal, and occipital lobes), whereas motor processing is controlled primarily by the anterior aspects (frontal lobes).

The four lobes of the brain are associated with varied and identifiable functions in the primary sensory and association cortical areas. For example, in addition to the primary somatosensory and motor cortexes, elemen- tary visual processing is associated with the occipital lobe, whereas the temporal lobes are concerned with re- ceiving and interpreting auditory information. The in- terconnections of the auditory (temporal), somatosen- sory (parietal), and visual (occipital) segments of the

lobes combine to form complex, highly integrated areas of the cortex called association or polymodal areas. When one cortical area is activated by a stimulus, other areas also respond. This is caused by the rapid activity along a large number of precisely organized, reciprocally acting association pathways, which ensures coordination of sensory input and motor activity, as well as regulation of higher cognitive functions. For example, occipital input via the occipito-temporal pathway (the “what” pathway) to the inferior temporal region is integrated to support the function of object recognition and percep- tion, whereas occipital input to the posterior parietal lobe via the occipito-parietal pathway (the “where” path- way) is processed for the support of spatial perception. Pathways from the temporal and parietal lobes to the frontal motor regions serve to orchestrate the motor movements related to visual object and spatial percep- tion. Some of these neuronal pathways are short (intrac- erebral fibers), linking neighboring areas within the gray area, and others are long bundles, passing through the white matter connecting different lobes (intercerebral fibers).

The frontal lobe contains the motor cortex and also houses the prefrontal cortex. This area is akin to a con- ductor or executive of the brain—organizing, control- ling, and managing behavior, and making high-level de- cisions about socially appropriate behavior; that is, when to act and when not to act. The prefrontal cortex makes it possible to perceive, even anticipate, the consequences of your brain’s behaviors. It is very much responsible for the many aspects of what makes you unique—your per- sonality and your conscience. Obviously, for such a suprasystem to function, it must have many connections to practically every major cortical and subcortical region of the brain. It must constantly be informed about events, both inside and outside the body, and it must overlap with important motor areas to immediately ex- press and change the environment through behavior. Al- though there is not a one-to-one correspondence between a specific region and functions of the prefrontal lobes, cer- tain divisions appear to make relatively distinct contribu- tions to complex behavior. These divisions include the dor- solateral, orbital, and medial (anterior cingulate) regions (Figure 6.4). The dorsolateral prefrontal lobe is associated with higher order or executive function, the orbital region is intimately involved with the modulation of emotional- social behavior, and the anterior cingulate is central to mo- tivational behavior.

As can be seen, whereas sensory-perceptual and motor processing are more easily associated with certain lobes, higher mental functions such as executive functions,

Figure 6.3 Brodmann’s map of the human cortex. This map is based on hypothesized cytoarchitectural differences between brain areas. Dashed lines refer to less distinct borders. (a) Lateral view; (b) midsagittal view. (Adapted from Kolb, B., & Wishaw, I. Q. [1996]. Fundamentals of human neuropsychology [4th ed., p. 55, Figure 3.3]. New York: W. H. Freeman and Company, by permission of Worth Publishers.)

10 46 45

47 11

1819

8 6

27 25

34 35

3033 32

29 26

4 3 12

5 7

8 6

43 41

40 39

2138 37 19

20 a.

7 53

1 2

22 52

language rule learning, memory, emotion, and social cogni- tion rely on integrative functions and cross-sensory modal- ities. These functions do not wholly reside within the boundaries of a single lobe. For example, although encod- ing new information into memory is often associated with the temporal lobes, memory can best be conceptualized as a processing system spanning the limbic system structures, as well as aspects of the frontal, temporal, and parietal lobes. Likewise, reading is an exceptionally complex func- tion that requires the systemic contributions of the occipital, temporal, parietal, and frontal regions, as well as subcortical regions such as the thalamus and basal ganglia. Aspects of higher mental processing such as memory, executive func- tioning, emotional processing, language, and consciousness are discussed as systems in subsequent chapters.

In general, damage to primary receptive areas produces identifiable deficits, whereas lesions in nonspecific or as- sociation areas of the cortex may produce a deficit far beyond the functional identity of that particular area, be- cause the complex interconnections beneath that cortical region may also be damaged. For example, lesions of the somatosensory cortex may cause contralateral paralysis and loss of sensory reception. In contrast, lesions of the parietal-temporal-occipital association area often result in a more complex neuropsychological deficit, such as an in- ability to understand the numeric value of numerals even though the person is able to read them. Damage to the prefrontal area often produces deficits in concentration, ability to solve new problems, planning, and judgment.

A S Y M M E T R Y , L A T E R A L I Z A T I O N , A N D D O M I N A N C E

Well-known differences in hemispheric functioning exist. This phenomenon has become so popularized, in fact, that many have taken to differentiating people according to the notion of being “right-brained” or “left-brained.” Later in this chapter, we discuss the lateralization of hemi- spheric functions to determine whether this popular no- tion is, in fact, supported.

Much of what has been discovered about lateralization of function has come from the study of brains by one of four methods. In the first instance, destroying cortical tis- sue creates a situation similar to that which Broca encoun- tered, whereby location of a function is inferred if dam- age to a particular area results in loss of that function. The second line of evidence has come from split-brain patients who have undergone the surgical separation of the corpus callosum, leaving the two hemispheres largely unable to communicate with each other. Third, epilepsy patients being considered for surgery typically submit to anesthe- sia of one cortical hemisphere at a time in a procedure called the Wada test. While one hemisphere is “uncon- scious,” neurologists test the functional abilities of the op- posite conscious hemisphere in isolation. Finally, neuro- surgeons also electrically stimulate specific cortical areas to delineate boundaries of function before removing brain tissue. These methods have provided valuable converging evidence regarding general brain function and lateraliza- tion. However, all these methods seek to measure brain functioning in an “unnatural state.” Can it be assumed from measuring the function of an isolated portion of the brain that functioning will remain the same within the context of whole-brain function? In addition, the patients being assessed typically have a brain disorder of some type. Dysfunctioning brains, particularly if the disorder

CHAPTER 6 | Cerebral Specialization 161

Figure 6.4 The prefrontal dorsolateral, orbital, and anterior cingulate regions in relation to other cortical brain areas. (top to bottom) Lateral (left hemisphere) and mesial views. (Adapted from John L. Bradshaw, 2001, Developmental Disorders of the Frontostri- atal System, Philadelphia, PA: Psychology Press, p. 21, Figure 2.2. Reprinted by permission of Routledge/Taylor & Francis Group, LLC.)

Orbitofrontal cortex

Anterior cingulate

Orbitofrontal cortex

Supplementary motor area

Sylvian fissure

Corpus callosum

Orbitofrontal cortex

Lateral premotor area

Primary motor cortex

Central sulcus

Dorsolateral prefontal

cortex

Somatosensory cortex

Inferior parietal lobule

Cerebellum

162 PART TWO | The Functioning Brain

has existed over a long period, may not behave the same way as intact brains. Now, through newer, noninvasive methods of brain imaging, such as positron emission to- mography (PET), functional magnetic resonance imaging (fMRI), and single-photon emission computed tomogra- phy (SPECT), which show the dynamic workings of the brain (see Chapter 2), researchers can test normal subjects and pinpoint the centers of greatest brain activity for any one type of task. In addition, two innovative neuroimag- ing techniques, magnetic resonance spectroscopy (MRS) and diffusion tensor imaging (DTI), allow for even “finer” analysis of brain functioning. MRS provides visualization of the neurochemical activity of brain material, whereas the DTI maps the axonal connectivity of brain regions (Nordahl & Salo, 2004). These latter two techniques should further increase our understanding of hemispheric and regional brain functioning.

The term hemispheric asymmetry refers to the differen- tiation in morphology and physiology of the brain between the right and left hemispheres. The terms lateralization and dominance refer to the differences in functional spe- cialization between the two hemispheres.

Probably the function most associated with laterality is speech. Paul Broca first determined that damage to the frontal operculum of the left hemisphere resulted in loss of speech (aphasia), whereas the right hemisphere ap- peared to play little or no role in language processing. Before Broca’s seminal finding, it was widely believed that the two hemispheres were redundant in function. Broca’s discovery led to the proposition that speech and language were properties of the left hemisphere. To say speech and language are lateralized to the left hemisphere denotes a functional dominance of the left hemisphere over the right hemisphere for language processing. Dominance does not mean that one hemisphere has complete or total responsibility for a function, but rather plays a primary or major role in the support of a function. For example, although there is significant empirical support for the lat- eralization of language to the left hemisphere (for most people), research has demonstrated that the right hemi- sphere is, in fact, able to perform a limited number of language functions such as understanding and processing of rudimentary linguistic contents. It is unable, however, to process complex linguistic information, and only rarely is able to communicate via speech. In addition, as discussed later, the right hemisphere plays a major and complemen- tary role in regulating the nonverbal aspects of speech and language.

Because of the decussation of the sensory and motor tracks from the brain to the spinal cord, the right hemi- sphere shows greater involvement in the control of the

left hand, whereas the left hemisphere is associated with modulation of the right hand. Broca (1861) proposed that a person’s preferred handedness was opposite from the hemisphere specialized for language. Although the concept of preferred handedness appears simple to as- certain, there continues to be disagreement over the def- inition of the concept. For example, some researchers have defined preferred handedness based on the hand the individual uses to write, whereas others prefer to look to the hand the person uses across a number of ac- tivities to determine preference. The latter definition lends to representing handedness as a differential vari- able that ranges on a bipolar continuum, with one ex- treme indicating complete right-handedness and the other extreme complete left-handedness. The midpoint of the continuum would reflect mixed-handedness (am- bidexterity). Finally, preferred handedness has been de- fined by the relative efficiency or speed of the hands. The latter definition shifts the emphasis from “preference” to “proficiency” of hand use.

Consistent with Broca’s proposition, subsequent research demonstrates that the relation of preferred handedness to hemispheric lateralization is partially accurate when later- alization of right-handed individuals is considered. For example, an MRI study (Springer et al., 1999) of 100 healthy right-handed participants (48% female, 52% male) reported that 94% were left hemisphere dominant for language, whereas 6% showed bilateral, roughly sym- metric language representation. None of the healthy par- ticipants were found to be right hemisphere dominant. In another study (Knecht, Dräger, Deppe, Bobe, Lohmann, Flöel, et al., 2000) of 188 healthy right-handed participants (59% female, 41% male), left language lateralization was identified in 92.5% of the participants, whereas 7.5% demonstrated right hemisphere lateralization.

Left-handed individuals are also likely to show left hemisphere lateralization for language, although to a lesser extent than right-handed individuals. Szaflarski et al. (2002) selected 50 healthy left-handed and ambidextrous participants for fMRI study. Predominately left hemi- sphere lateralization was found in 78% of the individuals, whereas 8% were predominantly right hemisphere lateral- ized, and 14% showed symmetric lateralization. In a larger study (Knecht, Dräger, Deppe, Bobe, Lohmann, Flöel, et al., 2000) with 326 healthy participants (198 females, 128 males), handedness was determined by the Edinburgh Inventory (Oldfield, 1971), a self-rating scale. This mea- sure allows for a rating of handedness ranging from strong left-handedness to strong right-handedness. Seven groups were identified based on the Edinburgh Inventory. The determination of language laterality was made by having

the participants perform word generation tasks while un- dergoing Doppler ultrasonography (fTCD). Overall re- sults demonstrated a linear relation: the greater the right- handedness, the higher the incidence of left hemisphere language dominance, and vice versa. In extreme left-han- ders, the incidence of right hemisphere dominance was 27% compared with 4% for extreme right-handers with right hemisphere speech. The intermediate groups showed decreasing right hemisphere lateralization as the degree of right-handedness increased.

Initially, it was believed that “atypical” lateralization, particularly for right-handed people, was potentially an abnormal sign indicative of brain pathology or perturba- tions of brain organization. Support was drawn for this view from the finding that a significant number of indi- viduals with brain abnormalities (e.g., epilepsy) demon- strated atypical lateralization. Yet, this assumption has been challenged by empirical findings demonstrating that a significant proportion of healthy individuals also show atypical language specialization without neuropsychologi- cal impairments (Hartlage & Gage, 1997). When there is a family history of left-handedness, the likelihood that left-handedness of offspring will be associated with brain pathology is significantly reduced.

In summary, empirical and clinical studies suggest that speech is generally lateralized to the left hemisphere for right-handed individuals (about 95%). Although the ma- jority of left-handed individuals also show left hemisphere specialization for speech (about 70%), the incidence of bilateral or right hemisphere lateralization is greater in left-handed individuals.

Hemispheric Anatomic and Functional Differences

Although some structural differences between the hemispheres are known to correspond to functional dif- ferences in behavior, the relation between structure and function has not been fully determined. Table 6.1 out- lines the differences in morphology between the two hemispheres. Figure 6.5 depicts some of the major hemi- spheric differences in structure.

Gross inspection of the two hemispheres of the brain reveals a number of differences. If you first look at the en- tire brain from the top down, it appears askew. This is be- cause the right hemisphere often protrudes anteriorly from the frontal lobes, and the left hemisphere protrudes posteriorly from the parietal-occipital area. Turning the brain to the lateral surface of the cerebral hemispheres,

the Sylvian fissure (which is normally the large fissure separating the frontal from the temporal and parietal lobes) is steeper in the right hemisphere than in the left. This results in a larger parietal and temporal area within the right hemisphere. It is reasonable to speculate that this allows higher level integration of visual, auditory, and pro- prioceptive information in the more spatially oriented right hemisphere. From an anterior view, the frontal op- erculum (Broca’s area) of the right hemisphere has a larger surface area, whereas the surface area of the left hemi- sphere is more pronounced in the subcortical area. This may reflect differences in the language production abili- ties between the two hemispheres. If you remove the top half of the brain, allowing a view of the horizontal sec- tioning of the two hemispheres (see Figure 6.5), you can easily examine the area of the temporal lobes. Within the superior temporal lobes is Heschl’s gyrus, and posterior to that is the planum temporale. The Heschl’s gyrus (also known as the primary auditory cortex) of the right hemi- sphere is often larger than that of the left hemisphere, since it frequently consists of two gyri. In the left hemi- sphere, the planum temporale is larger than that of the right hemisphere. The structural differences here may ac- count for the functional differences in auditory process- ing between the two hemispheres: Heschl’s gyrus may have greater functional responsibility for the nonspeech aspects of language (pitch, tone, melody) and musical processing, whereas the planum temporale plays a larger role in speech comprehension. In addition to visible struc- tural differences, there are also differences in neuronal ar- chitecture and neurochemistry, dependent on the side of the brain.

CHAPTER 6 | Cerebral Specialization 163

Morphology Left Hemisphere Right Hemisphere

Size Greater density Larger and heavier

Lobes Parieto-occipital Frontal protuberance protuberance

Frontal Frontal operculum Frontal operculum larger subcortical larger surface

Temporal Larger planum temporale Larger Heschl’s gyrus (often 2)

Parietal Larger area

Sylvian fissure Longer and more Steeper slope horizontal slope

Table 6.1 Anatomic and Physiologic Brain Asymmetries

164 PART TWO | The Functioning Brain

The gray and white matter composition of the two hemispheres provides clues to the type of processing as- sociated with each hemisphere. The right hemisphere is heavier and contains more white matter than the left hemisphere. In contrast, the left hemisphere is composed of greater gray matter and more modality-specific sen- sory cortices. The composition of the left hemisphere suggests that it is more suited for single-modality and in- traregion or within-region processing. A greater conver- gence of sensory regions is evident in the right hemi- sphere, signaling an increased representation of association regions. The increased association regions of the right hemisphere allows for multimodal and inter- regional processing (e.g., the association of the visual rep- resentation of an apple with its tactile representation). Because of these anatomic differences, it is hypothesized that the left hemisphere is better suited for processing in- formation that is linear, sequential, rule-governed, or conforms to specific codes, such as language. In contrast, the right hemisphere appears more suited for holistic or

global processing of information; for example, determin- ing the orientation of one’s body in space (propriocep- tive) or the spatial configuration and orientation of objects requires holistic or simultaneous processing of representative sensory input.

Empirical and theoretic efforts to associate hemi- spheric dominance to function have focused primarily on the content to be processed or the mental operation to be performed. Thus, differences in hemispheric domi- nance are generally associated with the type of content (e.g., verbal versus visuospatial), characteristics of the content (e.g., abstract versus concrete), or the mental functions recruited (e.g., analytic versus holistic opera- tions). Based on a review of approximately 1000 studies of cerebral lateralization, Dean and Reynolds (1997) have summarized the functions and contents that are considered to show lateralization (Table 6.2). However, none of these characterizations of hemispheric domi- nance fully accounts for the functioning of the hemi- spheres. For example, Gazzaniga’s (2000) research with

Figure 6.5 Brain hemisphere asymmetries. (a) The sylvian fissure on the right (bottom) has a steeper slope than on the left. (b) View cutting through the top portion of the brain at the level of the temporal lobes. (Adapted from Kolb, B., & Wishaw, I. Q. [1996]. Fundamentals of human neuropsychology [4th ed., p. 181, Figure 9.1]. New York: W. H. Freeman and Company, by permission of Worth Publishers.)

b. a.

Sylvian fissure

Heschl's gyrus

Planum temporale

Heschl's gyri

split-brain individuals demonstrates that the processing of certain inputs (contents) shows greater association with one or the other hemisphere; yet, the hemispheres also differ in their processing orientation. The right hemisphere appears to show superiority to the left in “veridical processing” (accuracy of information represen- tation), whereas the left tends to process information from an elaborative or explanatory perspective (interpre- tation and hypothesis generating), regardless of whether the content is verbal, facial, or abstract-figural.

There is a tendency to view the operations of the hemi- spheres as “either/or,” rather than as overlapping or com- plementary operations. The involvement of the hemi- spheres in the processing of language exemplifies this mutual functioning. As discussed earlier, language is consid- ered lateralized to the left hemisphere; however, neuroimag- ing studies (Vouloumanos, Kiehl, Werker, & Liddle, 2001) indicate that both hemispheres generally activate when lan- guage is processed, suggesting that complementary opera- tions are necessary to support the comprehension and expression of language. Furthermore, individual differences in lateralization of functions are frequently encountered,

which argues against the rigid mapping of specific func- tions or processes to either the left or right hemisphere.

As you are aware, the brain is composed of two hemi- spheres that are interconnected by major pathways (e.g., corpus callosum). What factors would account for the lat- eralization of brain functions, and what are the advan- tages of hemispheric specialization? Although definitive answers to these questions are not evident, several related speculations have emerged. First, the efficiency and speed of processing would be improved if a hemisphere was spe- cialized for processing. For example, speech involves the rapid sequencing of complex motor commands that may be better served by a single hemisphere, rather than by two hemispheres that are spatially and temporally sepa- rate. In essence, keeping functions “within house” would have an advantage over the “between-house” processing of two hemispheres. Of course, lateralization of a func- tion poses a significant disadvantage when the designated hemisphere is damaged. The degree of loss would be greater after unilateral damage to the hemisphere support- ing the function than if the function was represented asymmetrically. With asymmetric representation, the un- damaged hemisphere continues to provide some degree of support of the function.

A second, although a variant of the previous proposal, relates to the differences in the manner and mode of pro- cessing of the left and right hemispheres. These differ- ences could lead to competition or conflict if the two hemispheres shared equally in control of processing. Sup- port for this view is provided by neuroimaging studies of chronic stutters that show the presence of bilateral hemi- spheric activation associated with speech. Training for the amelioration of stuttering appears to be associated with increased left dominance for speech (Fox et al., 1996).

Third, lateralization of one set of functions within a hemisphere frees the other hemisphere to specialize in a different set of functions. Gazzaniga (2000) notes that, as humans have evolved, the need for greater cortical space has increased. Lateralization of functions to sepa- rate hemispheres provides the needed cortical space and also reduces redundancy of cortical regions. The pres- ence of the corpus callosum enables the lateralized brain functions to contribute to the entire cognitive system. The importance of adequate cortical space to support function is illustrated by the neuropsychological perfor- mance of young children who have undergone the re- moval of the left hemisphere (hemispherectomy). Some of these children are able to develop right hemisphere lan- guage. Yet, there appears to be a cost to the reorganization, as evidenced in the disruption of functions considered

CHAPTER 6 | Cerebral Specialization 165

Modes/Contents: Modes/Contents: Right Hemisphere Left Hemisphere

Simultaneous Sequential

Holistic Temporal

Global Local

Visual/Nonverbal Verbal analytic

Spatial reasoning Speech lateralization/verbal abilities

Depth perception Calculation/arithmetic

Melodic perception Abstract verbal thought

Tactile perception Writing (composition)

Haptic perception Complex motor functions

Nonverbal sound recognition Body orientation

Motor integration Vigilance

Visual constructive performance Verbal paired-associates

Pattern recognition Short-term verbal recall

Nonverbal memory Abstract and concrete words

Face recognition Verbal mediation

Complex motor functions

Table 6.2 Lateralized Functions of the Left and Right Hemispheres

166 PART TWO | The Functioning Brain

lateralized to the right hemisphere, namely, spatial pro- cessing. It has been hypothesized that the transfer of language to the right hemisphere “crowds out” certain spatial functions (Anderson, Northam, Hendy, & Wrennall, 2001).

N E U R O P S Y C H O L O G I C A L A N D B E H A V I O R A L C E R E B R A L D I F F E R E N C E S

To understand the difference in styles between right and left hemisphere processing, consider how you would ap- proach the following tasks: When asking for directions, do you prefer verbal instructions directing you to go three blocks to the first stop sign, then turn left and proceed three blocks, then take a right, and so on, or do you pre- fer a spatial map with directions marked on it? When you complete a puzzle, do you attempt to match individual features or concentrate on the overall gestalt? When learn- ing or listening to music, are you more attuned to the rhythm or the melody? In math, are you more adept with mathematical calculations and algebra or with geometry? In each of these cases, the first preference corresponds to the verbal-sequential processing typically associated with the left hemisphere, and the second to right hemisphere spatial-holistic processing. The stereotype of “left- brained” or “right-brained” individuals has resulted from the oversimplified notion that one set of hemispheric skills will become dominant in a particular person. Per- haps you feel you use one style more than another. But in a normally functioning brain, all capabilities are used to some degree, although they may be developed to different degrees. Sometimes the contributions of various hemi- spheric abilities are not even noticed until their loss is made evident through brain damage or disease. When neuropsychologists discuss lateralization and dominance, the reference is to the division of labor for a particular skill in the brain, rather than the dominance of “brain traits” in any one person.

A number of behavioral differences are evident in the functioning of the two hemispheres. The correspondence between structural asymmetries and functional lateraliza- tion depends, in some measure, on the complexity of the behavior. The more simple primary sensory and motor functions show specific patterns of representation in each hemisphere. In general, except for smell and taste, sen- sory processing is funneled from the site of the sensory stimulation to the contralateral, or opposite, hemisphere. For example, the somatosensory strip of the parietal lobe of the left hemisphere processes objects placed in the right hand. The primary occipital cortices of the left and right hemispheres are involved in the processing of informa-

tion in the right and left visual fields, respectively. These two senses are completely crossed, because the neural tracts project only to one hemisphere, opposite from the body site of stimulation. Audition is only partially crossed. The left hemisphere processes the majority of in- formation presented to the right ear, whereas the right hemisphere processes a smaller portion of this auditory input. Olfactory information, which evolutionarily repre- sents a more primitive sense, projects to the same (ipsilat- eral) hemisphere from each nostril; the right nostril is processed via the right olfactory bulb. Similarly, each hemisphere receives taste sensations from its respective side (ipsilateral) of the tongue. On the output side, the primary motor strip of the contralateral hemisphere con- trols primary motor processing. Thus, for instance, the motor strip of the left hemisphere controls motor move- ments of the right hand.

Higher order processing is, by definition, integrative in nature, involving multiple mental computations. Depending on the nature of the integration required, more or fewer brain areas are involved. Some may reside in the domain of a single hemisphere, and some may re- quire both sides of the cortex. Although neuropsychologists recognize the integrative nature of higher order skills, some abilities demonstrate greater lateralization than oth- ers. As a general way of conceptualizing the differences between the hemispheres, the side that is dominant for verbal abilities (often the left) is usually more proficient in speech production and understanding. It is facile in manipulating the symbols of language, such as letters, words, and numbers. Both hemispheres are comparable in processing sound, with the left hemisphere (temporal region) responding selectively to meaningful language (Giraud & Price, 2001). Of interest, neuroimaging (PET) shows that communicative signing by congenitally and profoundly deaf individuals recruits similar left hemi- sphere regions (left inferior and middle frontal, and supe- rior temporal gyrus) as individuals with normal hearing when processing language (Petitto et al., 2000).

The right hemisphere is more adept at processing the melodic, or prosodic, aspects of sound. Furthermore, the right hemisphere holds the advantage for visuospatial transformations, analysis of complex visual patterns, and emotional processing. Regarding emotional processing, the right hemisphere is thought to be more adept at read- ing emotions when expressed as gestures, tonal inflections, and facial expressions. When the right hemisphere is dam- aged, patients often speak in a monotone, fail to under- stand the emotional expressions of others, miss the gist of conversations, have problems expressing emotions nonver- bally and verbally, and are limited in their understanding

of humor and sarcasm (Beeman & Chiarello, 1998; Heil- man, 2002; Meyers, 1999). Moreover, the right hemi- sphere, particularly the prefrontal cortex, exhibits prefer- ential control of attentional functions such as arousal, sustained and selective attention, response inhibition, and self-monitoring. Although the left hemisphere is less in- volved in attentional functions, it does play a significant role in divided attention (Anderson, Jacobs, & Harvey, 2005).

Sex Differences and Hemispheric Specialization

Virtually every discipline of behavior has investigated the two sexes in an effort to identify and determine the origin and nature of putative behavioral and psychologi- cal differences. Neuropsychology and related professions have joined these efforts from the perspective of deter- mining whether the sexes show brain-behavior differ- ences. Although significant neuropsychological literature exists concerning sex differences, these empirical studies are inconsistent and often contradictory, precluding un- equivocal conclusions. A number of morphologic (weight, volume, size, and composition) and functional differences have been identified through neuroimaging, electrophysi- ologic measures, and autopsy. Examples of structural and functional studies are presented in Tables 6.3 and 6.4, re- spectively. The most consistent findings relate to hemi- spheric differences, particularly in the morphology and ac- tivation of left temporal regions associated with language, as well as the anterior cingulate, corpus callosum, and gray/white matter ratios. However, not all studies have identified significant or similar differences (Sommer, Aleman, Bouma, & Kahn, 2004). For example, as presented in Table 6.3, Good et al. (2001) found that healthy male participants presented greater leftward asymmetry of the planum temporale than healthy female participants, whereas the opposite finding was evident in a study by Knaus, Bollich, Corey, Lemen, & Foundas (2004). Method- ologic differences and weaknesses likely contribute to the inconsistencies in findings. The identification and con- trol of moderating variables (age, handedness, hormonal levels, task type, method of administration, and so forth) and improved standardization of and advances in neu- roimaging and related techniques should help determine whether, and under what circumstances, the brains of fe- male and male individuals differ.

It has been proposed that men are more likely to show strongly lateralized speech functions, whereas women are more likely to demonstrate bilateral or right representa- tion of speech. This came to light when researchers noticed

that, after suffering a left hemisphere stroke, women were less likely to suffer the language impairment seen in men (see Levy & Heller, 1992). Support for this proposition is provided by an fMRI study (Shaywitz et al., 1995) of men and women while performing a rhyming task. Brain acti- vation during the rhyming task was found to be more bi- lateral in women than men. Specifically, males demon- strated activation of the left lateralized inferior frontal gyrus, whereas females exhibited bilateral activation in this brain region. Similarly, a study (Saucier & Elias, 2001) of the relation of hand gestures to speech revealed that males made significantly more hand gestures with the right hand when speaking, yet when listening to conver- sation, demonstrated an increase in gesturing with the left hand. Females, in contrast, did not demonstrate asymme- tries in gesturing during either speech or listening. These findings suggest that males are more functionally lateral- ized in speech than females. However, several subsequent investigations have challenged these findings. Frost and colleagues (1999) determined that males and females did not differ in their activation patterns in an fMRI study involving the performance of a language comprehension task. Similarly, Knecht and colleagues (2000a) presented a word fluency task to 188 healthy right-handed male and female participants while undergoing fTCD. The perfor- mance of the two groups did not differ in word fluency performance. Of importance, the distribution of language lateralization was equivalent for males and females. Fi- nally, a recent study (Boles, 2005) of the relation of sex to performance on measures of lateralized cerebral functions demonstrates several significant differences, but these dif- ferences were small, accounting for less than 9% of shared variance (commonality of measurement). The investiga- tor concludes that sex differences on measures of laterality are so small as to preclude the use of these measures for clinical prediction.

Empirical investigations reveal that females show su- periority in language abilities, whereas males demonstrate greater proficiency in visuospatial skills (Gur et al., 1999; Voyer, Voyer, & Bryden, 1995). Before reviewing this issue, however, several caveats are in order. First, the supe- riority of the respective sexes with regard to verbal and vi- suospatial skills does not pertain to all forms of verbal or visuospatial tasks. Second, the differences in performance reflect group data and are not large in magnitude. In fact, there is substantial overlap in the performance of the two groups. Based on a recent review of studies of sex differences, Hyde (2005) concludes that the research indicates that the sexes are significantly more alike than different. Specifically, the differences between the sexes across multiple domains (cognitive, memory, motor, social, and personality) were, at

CHAPTER 6 | Cerebral Specialization 167

168 PART TWO | The Functioning Brain

best, small in approximately 80% of the studies reviewed. Third, sex differences may relate more to differences in sociocultural expectations, socialization, and experiential history than to neurobiological factors.

Differences in cognitive performance favoring female individuals include verbal fluency and perceptual speed (Halpern, 1992; Kimura, 1999), delayed verbal memory and retrieval efficiency (Drake et al., 2000), mathematic computation (Eals & Silverman, 1994; James & Kimura, 1997), episodic olfactory memory (Öberg, Larsson, & Bäckman, 2002), and fine-motor dexterity (Agnew, Bolla- Wison, Kawas, & Bleecker, 1988). Females further excel in one form of spatial memory that involves the encoding and

retrieval of object location. However, the latter superiority has been related to the greater verbal facility of females, rather than to their spatial ability (Postma, Izendoorn, & De Haan, 1998). Conversely, males show an advantage with tasks that involve mental rotation and spatial per- ception (Burton, Henninger, & Hafetz, 2005; Siegel- Hinson & McKeever, 2002), mathematic aptitude, map reading, aiming at and tracking objects, geographic knowl- edge (Kolb & Whishaw, 1996), and three-dimensional maze performance (Grön et al., 2000; Kimura, 1999; Roberts & Bell, 2003). Voyer et al. (1995) performed a meta-analysis of 286 empirical studies that involved spatial abilities and sex differences. The findings of the analysis

Table 6.3 Comparisons of Female and Male Brain Structures

Sex Investigations

Female Smaller overall brain size (Kolb & Whishaw, 1996)

Higher percentage of overall gray matter; distribution of white matter and cerebrospinal fluid (CSF) symmetric for the hemispheres (Gur et al., 1999)

Increased gray matter volume adjacent to the depths of both central sulci and in the left superior temporal sulci, right Heschl’s gyrus and planum temporale, right inferior frontal and frontomarginal gyri, and cingulate gyrus (Good et al., 2001)

Leftward asymmetry of the planum temporale (Knaus et al., 2004)

Greater density of neuronal material in the left planum temporale (Witelson, Glezer, & Kigar, 1995)

Larger volume of gray matter in the dorsolateral prefrontal cortex and superior temporal gyrus (Schlaepfer et al., 1995)

Greater cingulate sulcus volume (Paus et al., 1996)

Proportionally larger Broca and Wernicke areas (Harasty, Double, Halliday, Kril, & McRitchie, 1997)

Larger isthmus of the corpus callosum (Steinmetz et al., 1992)

Larger corpus callosum (Dubb, Gur, Avants, & Gee, 2003; Steinmetz et al., 1995)

Larger splenium of the corpus callosum with increasing size with age (Dubb et al., 2003)

Increased volume of the hippocam- pus across childhood and adoles- cent development (Giedd, Castel- lanos, Rajapakse, Vaituzis, & Rapoport, 1997)

Male Higher percentage of overall white matter and CSF; higher percentage of gray matter in left hemisphere, white matter symmetric, and greater percentage of CSF in the right hemisphere (Gur et al., 1999)

Increased leftward asymmetry in the Heschl’s gyrus and planum temporale; greater gray matter volume, bilaterally in the mesial temporal lobes, entorhinal and perirhinal cortex, and anterior lobes of the cerebellum (Good et al., 2001)

Symmetry of the planum temporale (Knaus et al., 2004)

Thicker cortex, higher neuronal density, and increased neurons in the left temporal lobe (Rabinowics, Dean, Petetot, & de Courten- Meyers, 1999)

Greater hippocampal dendritic reduction in male rats with aging (Markham, McKian, Stroup, & Juraska, 2004)

Greater paracingulate sulcus volume (Paus et al., 1996)

Greater asymmetry (L > R) of the anterior cingulate due to increased fissurization (Yücel et al., 2001)

Larger genu and decreasing genu size with age (Dubb et al., 2003)

Increased volume of the lateral ventricles and amygdala across childhood and adolescent develop- ment (Giedd et al., 1997)

Longer corpus callosum and decrease in width of the trunk and genu of corpus callosum with age (Suganthy et al., 2003)

were as follows: males showed significantly greater profi- ciency relative to the performance of females with tasks that involve mental rotation (ability to mentally rotate two- or three-dimensional figures quickly and accurately) and spatial perception (ability to determine spatial rela- tions despite the presence of distracting information). Further analysis demonstrated that sex differences gener- ally did not emerge until after 13 years of age, and the magnitude of sex differences in mental rotation and spa- tial perception increased with age. Of significance, sex dif- ferences were evident on only certain measures of mental rotation and spatial perception, suggesting that (1) spatial

ability is not a unitary concept, but rather represents a group of relatively distinct component skills; and (2) males do not demonstrate an advantage across all tasks that in- volve spatial abilities.

A number of studies have endeavored to determine whether men and women recruit different brain circuitry during spatial processing (Voyer et al., 1995). Illustrating this research is a neuroimaging (fMRI) study by Grön and colleagues (2000) that determined a significant overlap in the neural circuitry activated while performing mazes, with exclusive activation in the left parahippocampal gyrus and left hippocampus proper for males, and in the left superior

CHAPTER 6 | Cerebral Specialization 169

Table 6.4 Neuroimaging and Electrophysiologic Comparisons of Male and Female Brains

Sex Investigations

Female fMRI: Bilateral activation of the inferior frontal gyrus (rhyming task) (Shaywitz et al., 1995)

MRI: Bilateral activation of the superior and middle temporal gyri (linguistic listening) (Kansaku, Yamaura, & Kitazawa, 2000)

fMRI: Greater activation of the left superior frontal gyrus and the right medial frontal gyrus, and right prefrontal cortex, right inferior and superior parietal lobe (mazes) (Grön, Wunderlich, Spitzer, Tomczak, & Riepe, 2000)

fMRI: Greater activation of the left ventral premotor cortex (hands mental rotation) (Seurinck, Vinger- hoets, de Lange, & Achten, 2004)

PET: Greater activation of the right inferior frontal gyrus and right precentral cortex (concrete nam- ing/face orientation) (Grabowski, Damasio, Eichhorn, & Tranel, 2003)

fMRI: Predominately left-sided activation (visual discrimination and construction tasks) (Georgopoulos et al., 2001)

EEG: Greater right parietal activa- tion than left (two-dimensional mental rotation); greater right parietal activation than left (three- dimensional mental rotation) (Roberts & Bell, 2003)

PET: Enhanced activation of the left amygdala (emotional memory) (Cahill et al., 2001)

PET: Symmetric dorsal premotor activation (tactile discrimination) (Sadato, Ibañez, Deiber, & Hallett, 2000)

fMRI: Greater in the orbitofrontal lobe in response to both happy and sad, relative to neutral, faces (Amin, Constable, & Canli, 2005)

Male fMRI: Activation of the left lateral- ized inferior frontal gyrus (rhyming task) (Shaywitz et al., 1995)

MRI: Left activation of the superior and middle temporal gyri (linguistic listening) (Kansaku et al., 2000)

fMRI: Greater activation of the left parahippocampal gyrus and left hippocampus proper and right hippocampal gyrus and left poste- rior cingulate (mazes) (Grön et al., 2000)

fMRI: Greater activation of the lingual gyrus (hands mental rota- tion) (Seurinck, et al., 2004)

PET: Greater activation of left inferotemporal regions and other left hemisphere regions (concrete naming/face orientation) (Grabowski et al., 2003)

fMRI: Primarily right hemisphere activation (visual discrimination and construction tasks) (Georgopoulos et al., 2001)

fTCD: Comparable hemispheric activation to females (word fluency task) (Knecht, Deppe, Dräger, Bobe, Lohmann, Flöel, et al., 2000)

EEG: Greater left parietal activation than right activation (two- dimensional mental rotation); greater right parietal activation than left (three-dimensional mental rotation) (Roberts & Bell, 2003)

PET: Enhanced activation of the right amygdala (emotional memory) (Cahill et al., 2001)

fMRI: Greater activation in bilateral parietal to fearful, relative to neutral, faces (Amin et al., 2005)

fMRI: Comparable hemispheric activation to males (language comprehension task) (Frost et al., 1999)

Note: fMRI = functional magnetic resonance imaging; PET = positron emission tomography; fTCD = Doppler-ultrasonography; EEG = electroencephalography.

170 PART TWO | The Functioning Brain

frontal gyrus and the right medial frontal gyrus for females. In addition, males showed greater activation of the right hippocampal gyrus and left posterior cingulate, as com- pared to females who demonstrated increased activity of the right prefrontal cortex, right inferior and superior pari- etal lobe. Finally, males were more proficient than females in solving the mazes. While males and females appear to use different neural circuitry during maze performance, this does not rule out the possibility that other factors (for ex- ample, experiential history with spatial activities) may ac- count for the greater facility of males in maze performance.

A variety of explanations for the sex differences in spa- tial processing, particularly mental rotation, have been pro- posed. One explanation, consistent with our discussion, relates the male advantage in spatial processing to the greater specialization of this function to the right hemi- sphere. A second proposal is that men have more experi- ence in spatial processing by virtue of socialization and role expectations. In a relatively recent lateralized tachistoscopic study (Siegal-Hinson & McKeever, 2002), males were found to be more right hemisphere specialized (left visual field superiority) and to have greater previous spatial activ- ity experience than females. The magnitude of right hemi- sphere specialization correlated significantly and positively with mental rotation ability. Further analysis determined that sex differences in spatial ability were primarily related to right hemisphere specialization, and experiences with spatial activity were of only secondary importance. Thus, experience with spatial activities was not supported as a pri- mary determinant of the difference in performance of the sexes. However, other lateralized tachistoscopic studies have not identified male-related visual field superiority in spatial processing (Siegal-Hinson & McKeever, 2002), highlight- ing the current contradictions in this area of study.

Women have been found to work more carefully than men when performing mental rotation tasks, suggesting that time may be a factor influencing overall performance (Voyer, 1997). Yet, when females and males were presented a mental rotation task without time constraints (Voyer, Rodgers, & McCormick, 2004), males once again showed an overall advantage in performance. Thus, behavioral style (careful, time-consuming approach) did not account for the difference in mental rotation performance. Spatial experiences and stylistic approach are but two of several factors that could account for sex differences in spatial per- formance. A multitude of social and cultural influences shape and maintain sex differences. Unfortunately, the ul- timate impact of these sociocultural influences on sex are complex, often subtle, and not fully understood.

Adding to the complexity of determining whether sex differences exist in neuropsychological functioning is the

realization that task variations can prompt the recruit- ment of different neural circuits. For example, mental ro- tation of two-dimensional figures appears to recruit more right parietal activation than left activation for females. The opposite pattern (left > right parietal activation) is evident for males. Yet, with three-dimensional figures, greater right parietal activation is evident for both males and females (Roberts & Bell, 2003). Further exemplify- ing the effects of task differences on level of performance and recruited neural processes is a recent fMRI study (Seurinck, Vingerhoets, de Lange, & Achten, 2004) that compares the performance of male and female healthy volunteers in the mental rotation of tasks that involve hands and tools. The neuroimaging findings of the par- ticipants with comparable levels of mental rotation per- formance demonstrated that both sexes activated a com- mon neural substrate (superior parietal lobe, dorsolateral premotor cortex, and extrastriate occipital regions). How- ever, activation differences were evident in the mental ro- tation of hands, with females showing greater involvement of the left ventral premotor cortex and males demonstrat- ing greater activation of the lingual gyrus. These, as well as other studies, demonstrate the effects that task varia- tions might have on neuropsychological performance both across and between the sexes. Moreover, task varia- tions may contribute to the failure of investigators to repli- cate results and likely account for contradictory findings.

Although a number of studies report that females show greater facility with verbal skills, particularly verbal flu- ency, conflicting studies are also evident. Similar to the findings with spatial tasks, different verbal tasks may re- cruit different neural substrates for males and females. For example, men and women were asked to name concrete aspects of visually presented objects and perform a face ori- entation decision task while undergoing PET (Grabowski et al., 2003). Males showed greater activation of the left inferotemporal and other left hemisphere regions than females. In contrast, females demonstrated greater activa- tion of the right inferior frontal gyrus and right precen- tral cortex, as compared to males who evidenced less acti- vation or actual deactivation of these regions. These differences suggest that men and women use different strategies in processing similar contents.

Increasingly, empirical efforts to control variables that may account for differences in sex-related neuropsycholog- ical performance are evident, as illustrated in Georgopou- los and colleagues’ (2001) study. Men and women were presented two visual tasks: one task required visual discrim- ination and another required visual object construction. The same visual stimuli were used for both tasks, thus re- ducing the likelihood that task differences accounted for

performance. The visual discrimination task required the participants to judge whether pairs of square fragments were the same or different, whereas the visual object con- struction task required a determination of whether square fragments, when visually assembled and related, would make a “perfect square.” Blood oxygen level–dependent (BOLD) fMRI did not show differences in left versus right hemispheric activation for the sexes when performing the visual discrimination task. However, the sexes did differ with respect to the visual object construction task, with fe- males showing predominately left-sided activation, and males exhibiting both left and right hemisphere activation. The finding of increased right hemisphere activation was specific to the performance of men. The difference in per- formance between males and females could not be attrib- uted to the features of the task employed, and thus reflected the cognitive operations recruited. That is, the two sexes appeared to utilize different cognitive strategies to solve the visual constructive tasks.

Sex differences have also been presented for emotional- ity. Wager, Phan, Liberzon, and Taylor (2003) conducted a meta-analysis of 65 neuroimaging studies related to sex, emotions, lateralization, and other relevant variables. These results indicate that the relationship between sex, brain activation, and emotional responses is much more complex than originally believed. Both sexes showed simi- lar lateralized activation patterns for emotion, although men showed these patterns to a greater degree. Differences in neural activation by sex were most evident at the re- gional, rather than the hemispheric, level. At the regional level, the sexes recruited relatively distinct but overlapping areas, with some regions lateralized left and others right. When processing emotions, males activated the left infe- rior frontal cortex and posterior cortex, and females more reliably involved the midline limbic regions, including the subcallosal anterior cingulate, thalamus, midbrain, and cerebellum. Moreover, females showed left involvement in regions surrounding the amygdala (sublenticular nuclei), and males activated right-sided regions near the hippocam- pus. Based on these findings, Wager and colleagues specu- late that males may be more biased toward processing the sensory aspects of emotional stimuli with regard to action, whereas females direct more attention to the subjective ex- perience of emotion or, alternatively, show greater overt response to emotion. Finally, whether these regional and lateralized sex differences relate to actual or meaningful behavioral differences awaits further study.

The impact of sociocultural opportunities, resources, expectations, and attitudes regarding sex differences cannot be underestimated. For example, greater facility with math- ematics has been attributed to males relative to females.

Although some have maintained that this greater facility is sex determined, Neuropsychology in Action 6.2 clearly challenges this supposition.

In summary, there are indications that females show an advantage in verbal abilities, while males tend to demonstrate superiority in visuospatial ability, particu- larly related to mental rotation tasks. However, these dif- ferences are not uniformly supported, and sex differences may be a consequence of sociocultural rather than neuro- biological influences, or the interaction of these factors. Finally, differences in emotional processing are evident for males and females that do not conform to a simple left or right hemispheric specialization.

S E X U A L H O R M O N E S

Because of the pervasive effects of sex hormones on devel- opment and functioning, investigations have sought to determine whether hormonal influences relate to sex dif- ferences in neuropsychological functioning. Much of this focus has been on the reproductive hormones (androgen and ovarian). An androgen hormone refers to any steroid hormone with a “masculinizing” effect. Up to 95% of an- drogens are produced by the testes. The principal func- tions of the androgen hormones include the masculiniza- tion of the fetus, production of sperm, and development of secondary sexual characteristics. The ovarian hormones (estrogens and progestins) are primarily secreted by the ovaries. These hormones are responsible for the in utero “feminization” of the brain, regulation of the ovarian- reproductive cycle, secondary sexual characteristics, and menopause. Sex hormones are believed to have both an organizing and activating effect. The organization effect relates to the effects of early exposure to hormones during prenatal development, whereas the activation effect refers to the effects of hormones during later development; that is, prenatal exposure to hormones organizes the way be- havior is activated by hormones later in development. The masculinization and feminization of the prenatal brain exemplifies the organizing effects of sex hormones, while the physical and psychological changes associated with puberty and menstruation illustrate the activating effects. Notably, male and female hormones are not restricted to either sex in that both sexes produce androgen and ovarian hormones. Sex differences are evident in the hormonal- induced organization of the brain and the ratio of male- to-female circulating hormones in the respective sexes.

Efforts to determine whether reproductive hormones account for visuospatial sex differences have involved studies of healthy individuals, individuals with develop- mental abnormalities affecting hormone levels, and those

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172 PART TWO | The Functioning Brain

with surgically induced or naturally occurring reductions in hormone levels (Erlanger, Kutner, & Jacobs, 1999). Stud- ies of healthy subjects show a possible inverted U-shaped curve regarding the effects of androgens on spatial perfor- mance (Moffat & Hampson, 1996); that is, a positive

correlation is evident between testosterone levels and spa- tial task performance for females, but a negative correla- tion exists for males. Thus, males with elevated levels of testosterone exhibit poorer spatial performance, whereas females with increased levels demonstrate enhanced

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spatial performance. Additional investigations with healthy participants indicate that average, not extreme, levels of testosterone relate to optimal spatial perfor- mance; that is, high levels of testosterone for males and low levels for females are each associated with reduced spatial performance (McCormick & Teillon, 2001). Simi- larly, transsexuals undergoing cross-sex hormonal treat- ment also demonstrate differences in spatial performance. Individuals moving from a male to female gender demon- strate decreased spatial performance when administered antiandrogens and estrogen, whereas those moving from a female to male gender demonstrate improved spatial performance when treated with testosterone supplements (van Goozen, 1994; van Goozen, Cohen-Kettenis, Gooren, Frijda, & Van de Poll, 1995). Overall, these find- ings suggest that increased levels of male androgens en- hance the spatial performance of females, but have a “de- masculinizing” effect on male spatial performance. Notably, however, male androgens are not the only hormones that effect spatial performance. For example, higher levels of estrogen are associated with poorer spatial performance (Jones, Braithwaite, & Healy, 2003). Young women regu- larly taking oral contraceptives have near postmenopausal levels of estradiol and also perform more poorly on some spatial tasks than women not taking oral contraceptives (Mohn, Spiers, & Sakamoto, 2005).

The circulating levels of both male and female hormones warrant consideration when sex differences are the subject of investigation. For example, one study (Drake et al., 2000) demonstrated that sex hormones may affect cognitive abilities in a differential manner. In this study, the estro- gen, progesterone, androstenedione (natural hormone that is a direct precursor to testosterone), and testosterone circulating levels of healthy elderly women were compared with measures of neurocognitive functioning. The results showed that high levels of estrogen were associated with better delayed verbal memory and retrieval, whereas low levels were correlated with better immediate and delayed visual memory. Interestingly, testosterone levels were pos- itively associated with verbal fluency, but levels of proges- terone and androstenedione did not have any relationship to cognitive performance.

In addition, circulating levels of female hormones may interact with brain organization. For example, as dis- cussed earlier, right-handers are largely considered left hemisphere dominant for speech; however, sex may influ- ence bilateral expression of speech or other abilities. It may also be that other brain organizing factors, such as degree of left-handedness in the family, termed familial sinistrality, may interact with the sexual organization of the brain. It has been suggested that right-handed women

with left-handed relatives (that is, familial sinistrals [FS�] women) may have shifted brain organization away from the “female” preference for high reliance on verbal strate- gies and toward more male strategies (Annett, 1985, 2002). This has been supported in investigations of spa- tial performance on the Rey Complex Figure test (Rey, 1941, translated by Corwin & Bylsma, 1993), where fa- milial sinistrality accounted for performance and strategy regardless of academic major, with FS� women perform- ing as well or better than men (D’Andrea & Spiers, 2005a, 2005b). These investigators also report that across a range of spatial, verbal, and speeded motor tasks, famil- ial sinistrality interacted with the menstrual cycle such that FS� women performed better on all tasks during menses when ovarian hormone levels were low, whereas women without the hypothesized shift (FS� women) performed better on all tasks close to ovulation when ovarian levels were high (D’Andrea & Spiers, 2005a)

These various findings highlight the complexity of the relation of sex hormones to the performance of the sexes. Increasingly, we are realizing that the variables that inter- act with sex hormones and gender are multiple and not fully understood. Illustrating this issue is a relatively re- cent investigation (van Goozen, Gooren, Slabbekoorn, Sanders, & Cohen-Kettenis, 2002) in which individuals undergoing transsexual hormonal treatment did not demonstrate the predicted shift in spatial performance. Previous studies have frequently used “mixed” transsexual groups composed of right- and left-handed transsexuals who were either homosexual or heterosexual. In van Goozen and colleagues’ study, the spatial performance of only right-handed, homosexual transsexuals was con- trasted with the performance of heterosexual participants. The transitioning transsexuals were treated with the ap- propriate sex hormone supplements and pretested and post-tested with a battery of spatial measures. Post-testing was undertaken 3 months after the sex hormone treat- ment. Results regarding levels of pretest and post-test spa- tial performance were as follows: heterosexual male con- trol participants showed a higher level of performance than homosexual males transitioning to female gender, who, in turn, demonstrated greater proficiency than ho- mosexual females transitioning to male gender. Hetero- sexual female control participants achieved significantly lower scores than the previous three groups. Pretesting to post-testing did not demonstrate a significant effect of sex hormone treatment on spatial performance. The authors speculate that the failure to find the predicted effect may have been due to the unique composition of the transsex- ual group. They note that previous investigations have suggested that homosexual transsexuals are biologically

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174 PART TWO | The Functioning Brain

more similar to their desired sex, and their spatial perfor- mance tends to be similar to the opposite sex. Accord- ingly, their level of spatial performance would more closely approximate the opposite sex before sex hormone treatment; thus, the degree or magnitude of possible change in performance would be limited (“ceiling effect”) after the introduction of sex hormones. Second, the au- thors report that left-handed individuals are more sensi- tive to neuroendocrinologic interventions, and the omis- sion of this group may have accounted for the failure to find an activating effect of sex hormone treatment. Al- though replication and expansion of this study is war- ranted, it serves to capture the difficulty of disentangling the effects of sex hormones on gender performance.

Investigations of individuals with developmental disor- ders that affect reproductive hormones have identified simi- lar relations between androgen levels and visuospatial per- formance. For example, individuals with congenital adrenal hyperplasia (CAH; an endocrine disorder of prenatal origin characterized by excessively high levels of androgen hor- mones) have been the subject of research. Hampson and col- leagues (1998) compared the visuospatial performance of preadolescent girls with CAH to unaffected control partici- pants and found that the visuospatial performance of the CAH group was significantly higher. In the same study, boys with CAH hyperplasia showed lower visuospatial proficiency relative to the performance of unaffected control boys. In a similar vein, individuals with androgen insensitivity (ge- netic males who produce androgens but whose androgen re- ceptors are not responsive to the hormone) demonstrate lower performance relative to verbal intelligence when con- trasted with male and female control participants (Imperato- McGinley, Pichardo, Gautier, Voyer, & Bryden, 1991). The measure of performance intelligence involved tasks requir- ing visual, visuospatial, and visuomotor abilities.

For verbal abilities, a number of studies demonstrate that women, during the high-estrogen phase of their men- strual cycle, demonstrate enhanced cognitive skills in color naming and color reading, mental flexibility, and paired- associate learning (see Erlanger et al., 1999 for review). A comparison (Phillips & Sherwin, 1992) of the cognitive per- formance of women before and after hysterectomies who received either an estrogen supplement or a placebo revealed that the women who maintained their presurgical estrogen levels demonstrated comparable memory recall (paragraph recall). In contrast, those in the postsurgery placebo group exhibited a significant decline in memory performance. A similar decrement in memory performance has been docu- mented in women who have been administered estrogen- suppressing agents (Sherwin & Tulandi, 1996). Shaywitz and associates (1999) investigated the fMRI activation pat-

terns of postmenopausal females when tested with tasks of verbal and nonverbal memory. One group was treated for 21 days with estrogen, and the second group received a placebo. The estrogen-treated group showed greater left hemisphere activation during encoding and increased acti- vation in the right frontal superior frontal gyrus during re- trieval. Increased activation of the inferior parietal lobe was evident during storage of verbal information, and deceased activation of the inferior parietal lobe was observed during the storage of nonverbal information. Interestingly, the two groups, despite their differences in regional activation, per- formed in a comparable manner on the measures of verbal and nonverbal memory. A number of studies (see Cameron’s [2001] review) have failed to support the enhancing effects of hormone replacement therapy on cognitive performance. The mixed results suggest that certain hormone regimens may have an enhancing (although subtle) effect on specific cognitive and memory processes.

Cognitive concerns are frequently voiced by women going through menopause. When the ovaries stop produc- ing estrogen, only estrone (a weaker sex hormone produced by the adrenal glands) remains. Initially, it was believed that the risk for stroke, heart disease, vascular dementia, and os- teoporosis were associated with decreased estrogen produc- tion. Although estrogen augmentation has been associated with improved cognitive performance in menopausal women, particularly in the area of verbal memory, other studies have provided contradictory results. A meta-analysis of studies (Yaffe, Sawaya, Lieberburg, & Grady, 1998) sug- gests that improved cognitive performance is evident only in women receiving estrogen therapy who were recently menopausal. More disturbing have been recent large-scale studies (Nelson, Humphrey, Nygren, Teutsch, & Allan, 2002; Shumaker et al., 2003, 2004; Wassertheil-Smoller et al., 2003) demonstrating that estrogen therapy for post- menopausal females may increase the risk for stroke, throm- boembolic events, breast cancer (with 5 or more years of use), and cholecystitis (inflammation of the gall bladder). An increased risk for dementia appears to be evident for women 65 years or older (Espeland et al., 2004). Related to the latter finding, a recent study (Erickson et al., 2005) of elderly women who were maintained on estrogen treatment for up to 10 years demonstrated spared gray matter in the frontal cortex and increased performance on measures of executive function. In contrast, elderly women who contin- ued estrogen treatment beyond 10 years exhibited increased prefrontal deterioration and a greater rate of decline on the measures of executive function. Currently, the increases in physical and cognitive risk associated with prolonged estro- gen therapy in postmenopausal women appear to over-ride the modest gains initially evident in cognitive functioning.

CHAPTER 6 | Cerebral Specialization 175

Cerebral hemispheres Fissures Frontal lobes Parietal lobes Temporal lobes Occipital lobes Lateral fissure Central sulcus

Occipital notch Brodmann’s areas Somatosensory cortex Primary motor cortex Association or polymodal areas Wada test Hemispheric asymmetry Lateralization

Dominance Doppler ultrasonography

(fTCD) Sylvian fissure Heschl’s gyrus Planum temporale Meta-analysis Mental rotation

Spatial perception Subcallosal anterior cingulate Sublenticular nuclei Androgen hormone Familial sinistrality Congenital adrenal

hyperplasia Androgen insensitivity

the participants. Notably, similar neural substrates are often implicated in the cognitive processing of the sexes, and identified differences are often more of de- gree than type. In addition, differences in activated or recruited neural substrates do not necessarily translate into observable or meaningful differences in cognitive performance.

Overall, sex hormones appear to have an organizing and activating effect on brain development and func- tioning. Studies of varied gender groups show that sex hormones have either an enhancing or depressing effect on cognitive performance depending on such factors as the levels of circulating hormones, the specific sex hor- mone manipulated, type of task introduced, and age of

Summary In this chapter, we examined the major structures and functions of the cortex, setting the stage for examining the systematic interaction of brain regions (cortical and subcortical) that support the complex behaviors that are presented in subsequent chapters. Hemispheric differences exist, but they are not consistent with the simple notion that people are either “right-brained” or “left-brained” in their behavior. Generally, the brain functions as a cohesive whole with interconnected pathways and regions performing both distinct and overlapping functions. However, certain functions, such as speech, tend to be lateralized to one hemisphere or the other. Lateralization does not imply that the other hemisphere is not providing a complementary function. For example, the left hemisphere is generally specialized for verbal speech, whereas the right hemisphere plays an equally important role in providing the prosodic aspects to speech.

Sex differences in the performance of neuropsychological tasks are evident, although the sexes over- lap in their performance and the actual differences are small. Morphologic and functional brain differences have been identified; however, there is a lack of empirical consensus. Because of the organizing and acti- vating influence of sex hormones, the relation of these hormones to neuropsychological performance has been the subject of considerable investigation. Androgens appear to have an enhancing effect on visuospa- tial performance, whereas the bolstering effect of estrogen on verbal performance has received less sup- port. Certainly, the relation of sex hormones to neuropsychological performance is complex, and additional studies are warranted to identify the factors that mediate this relation.

C r i t i c a l T h i n k i n g Q u e s t i o n s

How would you explain the functional differences between the right and left hemispheres? Are there adaptive reasons why the cerebral hemispheres would gravitate toward either a bilateral or asymmetric organi- zation? Explain. What ecologic or evolutionary factors could account for the advantage of males in visuospatial abilities?

K e y Te r m s

We b C o n n e c t i o n s

Neuroanatomy

http://www.med.harvard.edu/AANLIB/hms1.html

http://www.med.harvard.edu

Chapter 7

S O M ATO S E N S O RY, C H E M I C A L , A N D M OTO R S Y S T E M S

[W]e naturally came into conflict both with the naive mechanistic ideas of localization, in which mental functions are consigned to rigidly demarcated areas of the brain, and with the idealistic concept that the higher mental processes stand quite apart from the biological functions of the brain or result from the indivisible activity of the “brain as a whole.”

—Alexander Luria

Somatosensory Processing Chemical Senses Motor Systems

Neuropsychology in Action

7.1 Synesthesia: Melded Sensory Integration 7.2 Phantoms of Feeling 7.3 Tourette Syndrome: Too Much Behavior

CHAPTER 7 | Somatosensory, Chemical, and Motor Systems 177

K e e p i n M i n d

How does the brain map incoming sensory information?

Is sensory information processed in the same manner by each system?

What happens when brain alteration causes malfunctions of ordinary experiences of perception?

Overview A functional system is a circumscribed area of behavior that corresponds to a specific neuroanatomic path- way or network of pathways. Some systems are well defined and traceable, and others remain incompletely mapped. The sensory systems are among the most well delineated.

At times tracing systems through the brain may appear mechanistic, like the “leg bone connected to the thigh bone” routine. Scientists have gained their current understanding of the brain by identifying indi- vidual functions and attempting to map them to structure hierarchically, from lower to higher order func- tions. However, many structures participate in multiple functions. A complex internetworking of functions is evident in the progression from the sensory and motor systems to higher functional systems where the work involves anatomic networks that are sometimes widely dispersed throughout the brain.

The brain is a dynamic biological network, but a small lesion in a strategic location can have devastat- ing effects on the system. It is therefore impossible to gain a thorough understanding of sensory and motor systems by studying only intact brains. Russian psychologist Alexander Luria, whose pioneering work made possible our understanding of functional brain systems, has argued that although higher mental functions may be disturbed by a lesion in any of the many different links of the system, they are disturbed differently by lesions in different links (Luria, 1966). Luria’s research profited greatly from his keen observations of neuro- logic patients. He noticed that anatomically different lesions were possible within the same behavioral syn- drome. He also noticed that a lesion in one area could affect a number of different behaviors.

The functional systems we focus on in this chapter may be broadly categorized as arising from sensory input and resulting in motor output. This chapter focuses on the somatosensory and motor systems, as well as the chemical senses of taste and smell. In the next chapter, we examine the visual and auditory systems. We concentrate on how each system operates at the level of central brain mechanisms. Most sensory sys- tems are anatomically mapped to specific cortical areas devoted to primary sensory processing, which provide information that is then routed to secondary processing areas where it is “perceived” and meaning is attached. All sensory systems except smell follow a pathway through the thalamus, where they are di- rected to primary and secondary cortical processing areas (Figure 7.1). This chapter examines how each system functions at the level of the brain, and what can happen when behavior goes awry because of injury or disease. In general, we discuss disorders that illustrate a specific breakdown of a system rather than broad-based disorders. Also, the odd phenomenon of synesthesia is presented as an interesting possible evolutionary mutation (Neuropsychology in Action 7.1). (We discuss disorders that involve multiple systems in later chapters.)

Sensation is the body’s window to the world. The range of what humans can detect is unique to our species and becomes the raw material of our perceptions and the stuff of our experiences. Information comes in fragments and requires the central processor of the brain to literally “make sense” of the outside environment. Sensation begins with

the process of transduction (derived from the Latin trans- ducere, meaning to “lead across”). An environmental stim- ulus activates a specific receptor cell, creating energy, which is transduced into an electrical stimulus that is then carried to neurons for the brain to process. (Receptor cells are not technically neurons, although they do synapse with

178 PART TWO | The Functioning Brain

neurons.) Sensory receptor cells throughout the body de- tect numerous stimuli, including sight, sound, pressure, pain, chemical irritation, smell, and taste, to name a few. We hear with our ears and see with our eyes, but if pho- toreceptor cells were on our hands, we would see with our fingers. Some sensory systems are complex. For example, taste uses multiple transduction processes to detect subtle differences of flavor. The visual system uses two primary types (rods and cones), and the auditory system uses a single basic mechanism.

The hour is striking so close above me, so clear and sharp, that all my senses ring with it. I feel it now; there’s a power in me to grasp and give shape to my world. I know that nothing has ever been real without my beholding it. All becoming has needed me. My looking ripens things and they come toward me, to meet and be met.

—Rainer Maria Rilke

Agnosia, the inability to recognize the form and/or func- tion of objects and people, occurs in every sensory domain. For example, tactile agnosia, also called astereognosis, is an inability to recognize objects by touch; for instance, failing to recognize a quarter or a pen held in the hand. Agnosia is possible in every sensory domain and can sometimes result in odd behavior. In his popular book of

neurologic tales, The Man Who Mistook His Wife for a Hat (1987), Oliver Sacks tells the story of a music professor who, coming upon his wife standing next to a coat rack, tried to lift her head instead of his hat. He no longer “knew” people or objects visually, but relied on distinctive voice characteristics and his other senses for identification.

Agnosia is not a single sensory phenomenon. It may strike any sensory domain, but the most commonly stud- ied instances affect the somatosensory visual and auditory senses. Olfactory and taste agnosias have not been re- searched extensively. Agnosias, in general, are relatively rare, but they have received considerable attention in the neuropsychological literature, perhaps because they so strikingly alter consciousness.

Somatosensory Processing

The somatosensory system includes two types of sensory stimulation, external and internal. This system can monitor sensations such as cold and heat, whether the sen- sation comes from handling an ice cube or from a fever. Thus, the system processes external stimulation of touch (pressure, shape, texture, heat) in recognizing objects by feel and is also concerned with the position of the body in extrapersonal space, termed proprioception. Sensory dys- functions that result in proprioceptive disorders of altered sense of bodily sensation or bodily position are of great in- terest to neuropsychology.

Figure 7.1 Primary sensory and motor cortexes. In general, primary sensory processing lies posterior to the central sulcus, and primary motor processing is anterior. The chemical senses of olfaction and taste are the exception. The primary gustatory cortex cannot be seen from this view. (Adapted from Banich, M. T. [1997]. Neuropsychology: The neural bases of mental function [p. 25, Figure 4.1]. Boston: Houghton Mifflin Company, by permission.)

Central sulcus Primary

motor cortex

Frontal lobeParietal lobe

Temporal lobe

Occipital lobe

Primary somatosensory

cortex

Primary olfactory cortex (mostly

hidden from view)

Primary auditory cortex (mostly

hidden from view)

Primary visual cortex

(mostly hidden from view)

CHAPTER 7 | Somatosensory, Chemical, and Motor Systems 179

One of the more exotic and seemingly rare (reported by 1 in 500,000) alterations in sensory processing is the “cross-wiring” of senses called synesthesia. One woman reported that tasting lemon is like “points pressing against the face,” and spearmint feels like “cool glass columns.” The most reported form of synesthesia is “audition colorée,” or colored hearing, described vividly by the synesthete poet Arthur Rimbaud in his poem “Les Voyelles” (“The Vowels”).

Probably the most completely described case of synesthesia was “S,” reported by Luria in his book The Mind of a Mnemonist (1968). Every sound, including tones, words, music, voices, and other noises, summoned up a vivid visual image. One tone could be a “velvet cord with fibers jutting out on all sides,” whereas another tone conjured up a strip, the color of “old tarnished silver.” The sound of a voice could be “crumbly and yellow” or like a “flame with fibers.” Seeing sounds could often be so attention grabbing that “S” could not follow the content of what people were saying to him unless they spoke very slowly.

The melding of sensory perceptions appears unique to each person, but the underlying neural processes may be quite similar. Neurologist Richard Cytowic (1993) has suggested that the source of synesthe- sia emanates from the most primitive reaches of the brain, specifically the limbic system. In his early studies, Cytowic used xenon inhalation to study the dynamic blood flow activity within the brain of synesthetes in mid audition colorée. Contrary to his initial expectations, neural activity in the cortex did not increase, but actually de- creased an average of 18%. Surprisingly, it was the limbic system that “lit up.” Cytowic

hypothesizes that the neocortex “turns off” during synesthetic processing whereas a more ancient, fundamental processing system takes over. Finding limbic system involvement seems congruent in light of the way Luria’s patient S describes his own experiences:

S: I recognize a word not only by the images it evokes, but by a whole complex of feelings that image arouses. It’s hard to express . . . . Usually I experience a word’s taste and weight, and I don’t have to make an effort to remember it— the word seems to recall itself. But it’s difficult to describe. What I sense is something oily slipping through my hand . . . or I’m aware of a slight tickling in my left hand caused by a mass of tiny, lightweight points. When that happens I simply remember, without having to make the attempt. (Luria, 1968, p. 28)

Mood and memory are intimately linked through the limbic system. In the case of S, auditory and visual sensation also appear linked to this system. The final effect was effortless and seemingly unlimited memory capacity. A sound, once experienced, would always recall an image. S went on to use this strange gift as a professional performer of feats of memory, astounding audiences throughout Russia.

Many viewed synesthesia as an abnormal medical oddity. It is different from other “disor- ders” in that it is not an effect of acquired brain damage. This cross-wiring appears to be “hardwired” since birth. If, as Cytowic sug- gests, synesthesia is an evolutionarily more primitive form of processing sensory experi- ence, there may be remnants of synesthesia in many of us. Do you ever feel blue?

N e u r o p s y c h o l o g y i n A c t i o n 7 . 1

S y n e s t h e s i a : M e l d e d S e n s o r y I n t e g r a t i o n

by Mary Spiers

Vowels

A black, E white, I red, U green, O blue: vowels, One day I will tell you latent birth. A, black hairy corset of shining flies Which buzz around cruel stench,

Gulfs of darkness; E whiteness of vapors and tents, Lances of proud glaciers, white kings, quivering of flowers; I, purples, spit blood, laughter of beautiful lips In anger or penitent drunkenness;

U cycles, divine vibrations of green seas, Peace of pastures scattered with animals, peace of the wrinkles which alchemy prints on heavy studious brows;

O supreme Clarion full of strange stridor, Silences crossed by worlds and angels: O, the Omega, violet beam from HIS eyes!

—Arthur Rimbaud

The somatosensory system contains a conglomeration of receptor types and sensory information. Receptors on the skin are attuned to external sensations such as the pres- sure of a hand, a blast of wind, the pricking of a finger, the vibrational frequency of touch, the burn of a hot

stove, and the itching of poison ivy. Somatosensory recep- tors are also spread internally throughout the body to monitor the stretching of the stomach during eating and di- gestion, the pain of muscle aches, and the spatial position of arms and legs, to name a few examples. The receptor types

180 PART TWO | The Functioning Brain

and systems discussed in this section range over widely vary- ing areas of function, from mechanical and chemical moni- toring to damage and body position monitoring.

The somatosensory system begins at the level of recep- tors, of which five types are found on the skin and throughout the body. Mechanical receptors transduce en- ergy from touch, vibration, and the stretching and bend- ing of skin, muscle, internal organs, and blood vessels. A detailed discussion of subtypes is not necessary, but at least five different types of mechanical receptors exist. For ex-

ample, hair follicle receptors sense breezes or a brush of fern across the skin. They are essential to animals such as cats and mice in their whisker navigational system. Chemoreceptors respond to various chemicals on the sur- face of the skin and mucous membranes. They range from detecting level of stomach acidity to skin irritations. Smell and taste are special examples of chemoreception that we discuss separately. Thermoreceptors detect heat and cold. Nocioceptors (derived from the Latin nocere, meaning “to hurt”) serve as monitors to alert the brain to damage or

Figure 7.2 The two primary somatosensory pathways. (a) The ascending spinal-thalamic tract carries pain and temperature information. (b) The dorsal column medial lemniscal pathway carries touch and proprioceptive information. (Modified from Bear, M. F., Connors, B. W., & Paradiso, M. A. [1996]. Neuroscience: Exploring the brain [p. 327, Figure 12.15; p. 328, Figure 12.16]. Baltimore: Williams & Wilkins, by permission.)

1 3

1a.

Large dorsal root axons

Dorsal column

Medial lemniscus

Dorsal column nuclei

Spinal cord

Primary somatosensory cortex (S1)

Thalamus (VP nucleus)

Medulla

CHAPTER 7 | Somatosensory, Chemical, and Motor Systems 181

threat of damage. They can be mechanical or chemical, but are specifically activated by potentially damaging stim- ulation such as heat or cold, painful pressure or pricking, or chemical damage such as exposure to noxious chemi- cals. They are present throughout the body, but they are noticeably absent in the brain. This is how some types of brain surgery and brain mapping can be done while the patient is conscious and alert. Proprioceptors (derived from the Latin proprius, meaning “one’s own”) on skeletal muscles detect movement via degree of stretch, angle, and relative position of limbs. Proprioceptors on the hands help identify the shapes of objects via touch.

These somatosensory receptors synapse with neurons into two primary pathways that transmit information from the spinal cord to the thalamus (Figure 7.2). In each case, sensory information travels to the contralateral hemisphere from the point of origin. The first pathway, the ascending spinal-thalamic tract, carries sensory in- formation related to pain and temperature and runs par- allel to the spinal cord. It synapses over a wide region of the thalamus, and then to the somatosensory cortex. The second pathway is the dorsal column medial lemniscal pathway, which carries information pertaining to touch and vibration. It is so named because it is routed up the

Figure 7.2 (Continued)

Primary somatosensory cortex (S1)

Thalamus (intralaminar and VP nuclei)

Dorsal columnSmall dorsal

root axons

Spinal cord

Spinothalamic tract

Medulla

182 PART TWO | The Functioning Brain

dorsal aspects of the spinal cord to a white matter tract termed the medial lemniscus, which courses through the contralateral side of the brainstem through the medulla, pons, and midbrain, and then up through the thalamus (ventral posterior nucleus) and on to the primary so- matosensory cortex. All stimulation of the face is on a sep- arate system through the large trigeminal nerve (cranial nerve V), which enters the brain through the pons.

The primary somatosensory cortex lies in the parietal lobe immediately posterior to the central sulcus on the post central gyrus (Brodmann’s areas 1, 2, and 3; Figure 7.3). It is somatopically organized; that is, the distorted figure of the sensory homunculus mapped onto the primary so- matosensory cortex represents the relative importance and distribution of touch in various areas of the body, rather than the actual size of the body part. Notice that the thumb,

Figure 7.3 The homunculi from the primary motor and somatosensory cor- texes. (Adapted from Kalat, J. W. [1998]. Biological psychology [6th ed., pp. 96, 227]. Pacific Grove, CA: Brooks/Cole.)

Premotor cortex

Supplementary motor cortex

Prefrontal cortex

Primary motor cortex

Primary somatosensory cortex (Brodmann's Areas 1,2,3)

Parietal cortex

Central fissure

Secondary somatosensory cortex (Brodmann’s areas, 5, 7)

Toes

Primary motor cortex

H ip

Knee

Trunk

Shoulder

A rmElbowW

ristHandFingersThumbNeckBrowEye Face

Lips

Jaw

Tongue

Swall owing

Intr a-a

bdo min

alPh aryn

x Tongu

Genitals

Primary somatosensory cortex

Jaw H

Leg Gums Teeth

Lips

Face

Nose

Eye

Thumb

Fingers

Hand Forearm

Elbow Arm

H ead

N eck

Trunk

Astereognosis/tactile agnosia: inability to recognize an object by touch

Finger agnosia: inability to recognize or orient to one’s own fingers

Paresthesia: spontaneous crawling, burning, or “pins and needles” sensation

Peripheral neuropathy: peripheral nervous system dysfunction causing sensory loss (for example, in diabetes)

Phantom limb pain: a feeling of pain in a nonexistent limb

Proprioceptive disorder: loss of body position sense

Tactile extinction/suppression/inattention: suppression of touch sensation on one side of body

Table 7.1 Examples of Somatosensory Dysfunction

fingers, and face represent proportionately the largest areas. These are the areas of most sensitive and discriminating sensation in the body, having the largest proportion of touch receptors. The somatosensory system is organized contralaterally, with the left hemisphere processing tactile sensation from the right side of the body and vice versa. The work documenting the close correspondence of sensation to cortical mapping in the primary somatosensory cortex began in the early days of neurosurgery. In the 1940s, Wilder Penfield, a noted neurosurgeon at the Montreal Neurological Institute, started to use electrical stimulation to explore the functions of the cortex in patients undergo- ing neurosurgery for the relief of epilepsy. Applying electri- cal stimuli to different cortical areas in more than 1000 fully conscious patients, Penfield mapped motor, sensory, lan- guage, and memory functions (Figure 7.4).

From the primary somatosensory cortex, sensory infor- mation is then integrated at the next level in the secondary somatosensory cortex, which is immediately posterior (Brodmann’s areas 5, 7). There, the individual properties of tactile stimuli such as shape, weight, and texture are com- bined to form the perception of single and whole percepts such as “pencil,” “coin,” or “key” that can be recognized by feel. Damage to this area may result in astereognosia, even though the person may readily recognize objects by sight. In this case, elementary powers of sensation are intact, but the person cannot recognize things placed in the hand con- tralateral to the lesion. Neuropsychologists usually test for

this problem by blindfolding the patient, placing an object in the hand, and asking the person to recognize and name it by touch only. Damage interrupting higher level so- matosensory integration in the parietal area, particularly the right parietal lobe, may result in a problem variously referred to as tactile suppression, tactile extinction, or tactile inattention. In this instance of right parietal damage, a per- son does not report the sensation of touch on the left hand (that is, left-sided suppression) when the left and right hands are touched simultaneously, although he or she may accurately report a left-sided touch when that hand is touched in isolation. In this case, the problem involves sort- ing out competing tactile sensations. Left-sided touch is sup- pressed or extinguished when there is competing sensation from both sides of the body. Part of the Halstead–Reitan Neuropsychological Battery includes a sensory-perceptual examination that tests for finger agnosia, skin writing recog- nition, and sensory extinction in the tactile, auditory, and visual modalities (Reitan & Wolfson, 1993). Table 7.1 lists examples of somatosensory disorders.

Disorders of proprioception represent the second type of tactile disorder in that the sensory problem is one of recog- nizing the relative position of your own body in space, rather than the recognition of objects external to yourself. This is a problem of tactile integration, which is usually compro- mised by parietal lobe dysfunction. Because proprioceptors record from the stretching of muscle, what you are receiving as sensory information is feedback from your own motor movements. This sensory information then is available to feed back to fine-tune body movement. Normally, a combi- nation of vision, the vestibular organs, and the propriocep- tive sense supplies a kinesthetic sense of your physical body. Proprioception, like most elementary sensations, is so basic and automatic that you take it completely for granted unless it is disrupted or absent. Imagine, however, having no sense of where your hands and legs are, or even of your

CHAPTER 7 | Somatosensory, Chemical, and Motor Systems 183

Image not available due to copyright restrictions

184 PART TWO | The Functioning Brain

posture if your eyes are closed. In Oliver Sacks’s case of the “Disembodied Lady” (Sacks, 1987), a young woman of 37, suffering a sensory neuritis, had the feeling of “losing” parts of her body if she could not see them; that is, she experi- enced the feeling of total disembodiment. Having no nat- ural posture, her movements became a caricature of types, such as a dancer’s pose. Quite the opposite problem is ex- pressed in phantom limb pain. People with no external sen- sation entering the brain still have the curious experience of pain or other sensation. Neuropsychology in Action 7.2 ex- plores this odd phenomenon.

Chemical Senses

Taste and smell evolutionarily are the oldest sensory systems. They work in concert, and to most people, they appear indistinguishable until a cold or other sinus condi- tion congests and diminishes the sense of smell. People are likely to report that food does not “taste” so good or have as much flavor as usual, when it is actually blocked smell that

is affecting the pleasurability of food. It is easy to experience this condition by just holding your nose and sampling dif- ferent foods to see what “tastes” you actually experience. Taste and smell are also the least studied of the senses within neuropsychology and neuroscience. This neglect may be due, in part, to that other senses such as vision and audition are well developed in humans, and thus have overshadowed the chemical senses. The idea that the senses of taste and smell may be vestigial and no longer of any real adaptive use to modern humans has also probably contributed to the lack of interest. However, these chemical senses are enjoying a surge of research attention that is pointing to connections with emotional behavior, hormones, immunology, and identification of neurologic disease states.

T A S T E

The tongue contains numerous papillae or bumps on which lie from one to several hundred taste buds consist- ing of between 50 and 150 taste receptor cells. The bun- dles of receptor cells resemble onions, with the cilia at the tips of the cells protruding into the surface of the pore.

Phantoms are the experience of external sensory experience in the absence of avail- able sensory input. This sounds strikingly like a hallucination. And perhaps had it not been for the widespread occurrence of phantoms felt by what are considered otherwise “ratio- nal” people, phantoms might have been considered psychosomatic experiences at best and psychotic episodes at worst. People most commonly think of phantoms in respect to phantom limb pain after amputation, but they can and do exist in any sensory modal- ity. The interesting questions here are, How are phantoms experienced, and what are their causes? Finally, understanding phan- toms may also provide some clues to under- standing certain aspects of brain plasticity and reorganization.

Phantom limbs and phantom limb pain are most commonly associated with ampu- tations. The amputee may feel a lost arm, feel that it swings in coordination with the

other arm while walking, or experience it sticking out so much as to necessitate maneuvering through doors sideways. All the while, objective reality is shouting that it is not there. Cold, heat, pressure, itching, tickling, and sweat can all be experienced in the missing limb. Because as many as 70% of amputees experience pain in the ampu- tated part, psychologists specializing in pain management are striving to understand causes and formulate treatments for this problem.

Phantoms may also be experienced in situations other than amputation and in senses other than tactile. Children born without limbs, people who have suffered paralysis after a spinal cord injury, and even women in labor who have had spinal anes- thesia have also “felt” the presence of a limb. Some congenital amputees have reported being able to move nonexistent fingers or to experience the phantom emerge

and disappear from consciousness. Phan- tom seeing and hearing can occur in the complete or partial absence of vision and audition. Auditory phantoms may be passed off as tinnitus, or ringing in the ears, but some people hear voices or music. Visual phantoms can also range from flashes of light and color to fully formed images of people and objects. In both cases, and perhaps a differentiating factor between these types of “hallucinations” and those experienced by schizophrenics, phantoms are quickly judged as separate from normal sensory-perceptual reality.

How can phantoms be described neuro- logically? Scientists know that phantoms emanate from central brain mechanisms rather than purely peripheral ones, although the exact mechanism for the production of phantoms is still a matter of some specula- tion. In the case of phantom limbs, amputa- tions leave exposed nerve endings that heal

N e u r o p s y c h o l o g y i n A c t i o n 7 . 2

P h a n t o m s o f F e e l i n g

by Mary Spiers

CHAPTER 7 | Somatosensory, Chemical, and Motor Systems 185

Taste receptors are not neurons, but respond to the chem- ical qualities in food dissolved in saliva as they wash over the tips of the receptors. In the course of eating, taste re- ceptors endure extremes of temperature, spicy food, and other chemical substances, which may cause damage. Per- haps because of this, taste receptors quickly wear out and are replaced on a cycle of about 10 days.

The traditional theory about how taste functions, presented in most general psychology textbooks, describes the ability of the tongue to discriminate four primary taste sensations: sweet, salty, sour, and bitter. This schema is based on specific taste bud receptor ability to detect the chemicals associated with each taste. For example, certain receptors are attuned to sodium chloride (NaCl) and other salty chemicals, and likewise for the remaining pri- mary taste sensations. Some researchers have suggested a fifth taste, umami (derived from the Japanese, meaning “delicious”). Deliciousness is operationally defined by the activation of L-glutamate receptors that are attuned to glutamate-triggering substances such as monosodium glu- tamate (MSG). The primary tastes theory implies that, in

any mixture, individual taste sensations, such as saltiness, are identified by specific saltiness receptor types and trans- mitted to the brain along dedicated pathways, where they are analyzed and labeled as salty. According to this theory, taste receptors of different types are grouped in various areas of the tongue; the tip is specific for sweetness and saltiness, the sides detect sourness, and the back is most sensitive to bitterness.

The competing pattern theory suggests that taste is best thought of as a pattern of sensation in which individ- ual receptors can process information about more than one taste type. There is strong evidence that individual taste fibers are not exclusive to one taste sensation, al- though they may roughly focus on one type (Smith & Vogt, 1997). The suggestion from the pattern theory is that the experience of any particular taste, such as salti- ness, is carried to the brain, because the fibers are acti- vated to respond mostly to saltiness of the substance in the mixture. The implication is that taste receptors may have multiple potentiality, rather than being dedicated to respond to a specific chemical.

as nodules called neuromas. Neuromas continue to generate neural impulses. For this reason, initial treatments focus on severing communication between the pe- ripheral sensory input and the spinal cord. However, this does not obliterate phantoms. Consequently, as an attempted treatment, surgeons have blocked or cut spinal nerves, and then central pathways feeding the somatosensory cortex from the sensory relay station of the thalamus. But phantoms still exist. Traditional painkilling drugs are also largely ineffective, because phantom pain does not seem to arise from the same pain system.

From where in the brain do phantoms arise? Recent work in this area has led to rethinking about the supposed lack of plasticity of adult brains. A logical place to start is to understand what happens in the somatosensory strip when the corresponding sensory area on the body ceases to provide input. Researchers have done deep-brain electrode recordings on monkeys with an amputated finger. Surprisingly, sensory input from adjacent fingers remapped itself onto the somatosensory cortex so that it invaded the area previously serving the amputated finger. This remapping occurred within weeks of the amputation. Neuroscientist Timothy

Pons demonstrated this sensory strip en- croachment in monkeys who had had their sensory nerves cut more than 12 years earlier. In this case, massive territorial invasion was seen; in one case, a hand and arm were now mapped onto the face. Recall that we made the point earlier that neurons, once severed, are for all practical purposes dead and unable to regenerate; only par- tially severed axons can resprout. At least, this has been the common wisdom. Also, no brain reorganization is expected after a cer tain critical period of development. However, in the case of phantoms, there is no damage to neurons in the brain; all the damage is peripheral. Somehow, healthy neurons are reorganizing themselves to take over an area of the brain that the body is no longer using. It is reasonable to expect that healthy brain neurons may more easily reorganize themselves than damaged ones. However, the mechanism by which this is done is still a mystery. One aspect that has puzzled scientists working on this problem is that if neurons were reorganizing them- selves on the homunculus of the somatosensory strip itself, their growth would have to cover long distances. This mechanism seems unlikely, given that adult neurons can sprout over only shor t dis-

tances. One possible explanation is that instead of reorganization at the level of the somatosensory cortex, reorganization is occurring within the relay station of the thalamus, where all sensory inputs from touch, vision, and audition funnel through in a tight space. An axon merely has to reach across a narrow stream to remap a finger to the face or to even to the back. Odd as it may seem, this phenomenon is now being demonstrated in human amputees. Ramachandran (Ramachandran, Rogers-Ramachandran, & Steward, 1992) tested a teenager who had recently lost his left arm in an auto accident. As the boy sat blindfolded, Ramachandran touched various par ts of his body with a cotton swab. When he stimulated various areas of his lip and lower face, the boy felt his missing thumb and fingers tingle. Sensa- tions from his hand were now remapped onto his face. Because acupuncture has helped some people with phantom limb pain, it seems reasonable to speculate that knowledge of remapping may dampen pain if massage, acupuncture, or other means can be applied to the newly remapped areas of the body. In the case of this boy, odd as it may seem, face massage may alleviate left arm and hand pain.

186 PART TWO | The Functioning Brain

Taste receptor cells synapse with sensory neurons that carry information via cranial nerves VII, IX, and X to the medulla of the brainstem (specifically the nucleus of the solitary tract), where they are relayed via the thalamus (ventral posterior medial nucleus) to the primary gusta- tory cortex (Figure 7.5). Additional projections run from the thalamus directly to the somatosensory cortex amyg- dala, hypothalamus, and orbital prefrontal cortex. The hypothalamus may code for pleasurability of food, be- cause it contains neurons that respond specifically to sweetness of food (Rolls, 1986).

The function of taste appears to be drawing us to cer- tain basic substances that the body needs and repelling us from potentially harmful chemicals. Certain receptors are attuned to sweet and salty foods, which the brain codes as pleasurable. Before the days of candy and salty fast foods, being drawn to sweet foods such as fruit provided needed nutrition. Salt contains the body’s necessary sodium. It is also adaptive to be repelled by bitter foods, which might be poisonous, and by sour foods, which might be spoiled.

Disorders of taste are rare in comparison with disor- ders of smell, although as mentioned earlier, people may

Figure 7.5 From taste buds to taste pathways in the brain. (Adapted from Kalat, J. W. [2004]. Biological psychology [8th ed., p. 210, Figure 7.18a, p. 212 Figure 7.19]. Belmont, CA: Wadsworth/Thomson Learning.)

From taste buds on tongue

Nucleus of tractus solitarius

Somatosensory cortex

Ventral posteromedial thalamus

Hypothalamus

Orbital prefrontal cortex

Amygdala

Corpus callosum

Primary gustatory cortex

Foliate papilla

Taste bud close-up

Vallate (or circumvallate) papilla

Fungiform papilla

Taste buds

report disorders of smell as disorders of taste because the two systems interact in flavor perception. Taste disorders may range from a diminished sense of taste (hypogeusia) to a complete loss of taste (ageusia). Table 7.2 summarizes taste disorders. Phantogeusia is the experience of a taste “phantom” or hallucinatory taste. Taste phantoms often coincide with other disorders of taste. Most disorders of taste appear to be caused by a problem in the central per- ception of taste, rather than a problem at the level of the taste buds. For example, one of the more common reasons for taste distortion is medication usage. Other causes of taste dysfunction include head injury, upper respiratory infection, and in the case of phantogeusia, sometimes damage to the “taste nerve,” the chorda tympani (cranial nerve VII) if it is injured during ear or dental surgery (see Cowart et al., 1997).

S M E L L

Amble through a field on a summer afternoon, and the air is fragrant with smells of wildflowers, grasses, and aro- matic herbs. Inhale and microscopic molecules of scent wafting through the air are gradually taken in by your rel- atively slow olfactory detection system. The aromas you detect and identify are, in part, a function of the ability of the odorant to dissolve in the moist mucous lining of the nose, but are also affected by age, sex, health, and brain injury.

Smell is the least understood sensory system, perhaps because scientists have considered it of little adaptive value to humans. Certainly, it is the oldest sensory system evolu- tionarily, and it appears much more crucial to animals such as bloodhounds and snakes, which are lower on the phylo- genetic scale. What function does scent serve for humans? Is it a vestigial sense? Many people appear to function well in their lives having completely lost their sense of smell. However, the perfume industry is booming and aromather- apy is becoming a popular naturopathic approach to mood enhancement. This section examines the unique neu- roanatomy of the primary olfactory system. Unlike other systems, olfactory neurons have regenerative qualities when

damaged. Finally, we also reflect on the potential implica- tions of links among mood, memory, and olfaction.

Inhalation (but actually just a sufficient sniff is needed) sends molecules of scent traveling up to the roof of the nasal cavity. These odorants dissolve in the olfactory ep- ithelium, a fine mucous lining consisting of odorant- binding proteins (OBPs), antibodies, and enzymes. Mucus is being continually produced; thus, the entire ep- ithelium is replaced about every 10 minutes. Scent mole- cules bound to OBPs activate the fine, hairlike cilia of ol- factory neurons waving within the olfactory epithelium. Researchers have discovered at least 500 to 1000 OBP genes that appear to be coded for different odorants. In humans, the epithelium is small, about half the size of a postage stamp (5–10 cm2). Dogs, with their keen sense of smell, have an epithelium easily 10 times that of humans (100 cm2), with 100 times the neurons per square cen- timeter. Olfactory neurons in the epithelium synapse with the right or left olfactory bulb through the thin cribri- form plate of the skull, where the central olfactory path- way (cranial nerve I) originates. So whereas three cranial nerves subserve taste, smell has only one pathway.

The olfactory system is unique in several ways. Note that we have considered receptors when discussing other sensory systems. These receptors then synapse with den- drites of neurons. This is not the case with the olfactory system. The neurons themselves are directly exposed to the environment. The health of the epithelial layer, where the dangling neurons lie, is crucial because some viruses, such as rabies, take advantage of this direct route to the brain. This system is also interesting in that con- trary to the notion that new neural cells do not form in adults, the olfactory neurons compose a uniquely “plas- tic” system, continuing to reproduce and replace them- selves every 1 to 2 months throughout adulthood. The olfactory neurons, however, are susceptible to traumatic injury because they dangle through a opening in the skull, the cribriform plate. A blow to the head can easily sever these neurons. Although the neurons do regrow, they do not always reconnect with the olfactory bulbs (Figure 7.6).

The olfactory bulbs contain complex circuitry; the two bulbs even communicate with each other. Although the mechanism is not completely understood, microelectrode recordings show that various aromas produce identifiable spatial maps on the bulbs, and these mosaics may change even during the sniffing of an odorant. The plasticity of the system has suggested to scientists that experience with smell can easily modify the representational pattern of stimulation on the olfactory bulb. The map on the bulb projects to the areas of the brain that process and encode

CHAPTER 7 | Somatosensory, Chemical, and Motor Systems 187

Ageusia: inability to recognize tastes

Dysgeusia: distorted taste sensation

Phantogeusia: experience of a phantom or hallucinatory taste

Hypogeusia: diminished taste sensitivity

Table 7.2 Disorders of Taste

188 PART TWO | The Functioning Brain

the scent. It appears that specific odors code specific pat- terns. It is unclear whether these coded representations are invariant, in other words, always stimulating the same brain areas, or whether learning can also feed back to modify scent maps when the same scent is later reintroduced.

Figure 7.6 Olfactory system. (a) Odorants are taken up via the olfactory neurons. (b) Close-up of olfactory neurons, which protrude through the cribriform plate. (From Kalat, J. W. [1998]. Biological psychology [6th ed., p. 205, Figure 7.22]. Pacific Grove, CA: Brooks/Cole.)

Olfactory bulb

Olfactory nerve axons

Olfactory epithelium

Olfactory Neurons receptor cell

Supporting cell

Olfactory cilia (dendrites)

Olfactory nerve

Cribriform plate

Another unique aspect of olfaction is its pattern of pro- jection into the brain. All other sensory systems first pass through the thalamus and then into the neocortex. How- ever, the primary projections of the olfactory system inner- vate the limbic system directly through the amygdala and hippocampal formation. Olfactory information projects

CHAPTER 7 | Somatosensory, Chemical, and Motor Systems 189

into these primitive areas of the brain before passing through the relay station of the thalamus, and then into the frontal cortex and onto other areas of the neocortex. Because of this connection, the effect of scent on emotion and mood is instantaneous and is most intensely processed preconsciously. Secondarily, scientists believe that parallel thalamic projections to the frontal lobes are responsible for conscious recognition of scent. The cortex can then elabo- rate and refine the perception of aroma. The hippocampus, although not a memory storage center, is responsible for processing and coding memories before they are stored in the neocortex. Together with the amygdala, these limbic system structures appear to be responsible for coding much of the emotional tone of memories. This neural pattern of projection into the brain reflects the ancient evolution of olfaction. Considering this brain anatomy, it is no wonder that smell is so strongly tied to emotional memory.

In the early part of the nineteenth century, Freud sug- gested that disorders of smell and specific psychological dysfunctions may be connected (for types of olfactory dys- function, see Table 7.3). This idea remained largely unex- amined until a relatively recent resurgence of interest in olfaction occurred as it relates to certain brain diseases such as Alzheimer’s disease, Parkinson’s disease, and schizophre- nia. For some time, people have observed that decreased ability to smell (hyposmia) is associated with aging, and that both loss and distortion of smell (dysosmia) are asso- ciated with depression. With aging, the ability to perceive sour or bitter odors appears to diminish first, whereas the ability to detect pleasant smells such as sweetness may per- sist well into old age. Interestingly, recent work has shown that diminution of olfactory ability is an early sign of dis- eases of accelerated aging, such as Alzheimer’s disease and Parkinson’s disease (for example, see Doty, 1990). Also, schizophrenics often have a distorted sense of smell. Clini- cal neuropsychologists are now using scratch-and-sniff tests of odor identification and odor recognition thresh- old, such as the University of Pennsylvania Smell Identifi- cation Test (UPSIT) (Doty, Shaman, & Dann, 1984), to test for the presence of olfactory dysfunction in cases where clinicians suspect these diseases.

Partial or complete loss of smell is also a common oc- currence after traumatic injury to the brain. As noted ear- lier, because the olfactory neurons dangle through the cribriform plate, they are easily damaged or sheared off by sudden movements of the brain in relation to the skull. Even though olfactory neurons can regenerate, they often do not reconnect to the olfactory bulbs because they are blocked by scar tissue.

Motor Systems

The sensory systems provide a window to the world, and the motor systems, in turn, provide the means of acting on the world. Whereas control of sensory sys- tems occurs in posterior brain regions, the cortical con- trol of movement is largely anterior. Movement takes sev- eral forms, including reflex actions, automatic repetitive actions such as walking, semivoluntary actions such as yawning, and voluntary actions such as deciding to pick up an object (Bradshaw & Mattingly, 1995).

Traditionally, scientists thought the motor system was organized hierarchically. Whereas sensory process- ing is thought to proceed in a bottom-up fashion, motor processing would follow a reverse path in a top- down manner. Sensory-perceptual processes build up from fragments analyzed in primary processing areas and are synthesized in secondary and higher order cor- texes. Then information that directs motor processing comes into the system in the form of highly integrated sensory information from the sensory association areas, such as the parietal lobes, and the subcortical structures of the basal ganglia and the cerebellum. In addition, internally generated motivation for action also directs movement. The system then directs this infor- mation to areas of secondary motor planning and pro- gramming before sending it to the primary motor cor- tex. According to this hierarchy theory, the primary motor cortex sits at the top and funnels all information about movement to the body. However, a competing theory suggests that the system works in a parallel pro- cessing mode, with several motor processing circuits working in coordination with the primary motor cortex (Haines, 1997).

C O R T I C A L M O T O R P R O C E S S I N G

Several cortical areas of the motor system are involved in motor processing (Figure 7.7). The first of these is the pri- mary motor cortex. The next three motor areas are often referred to as the secondary motor cortex and include the

Anosmia: total loss of smell

Dysosmia: distorted smell sensation

Phantosmia: experience of a phantom or hallucinatory smell

Hyposmia: diminished taste sensation

Table 7.3 Disorders of Smell

190 PART TWO | The Functioning Brain

supplementary motor area, the premotor area (PMA, or premotor cortex), and the cingulate motor area (CMA or cingulate motor cortex). Finally, areas of the parietal lobes and the dorsolateral prefrontal cortex are areas of premotor planning.

The role of the primary motor cortex is to manage the fine details required to perform movement. The pri- mary motor cortex lies in the precentral gyrus, or motor strip of the frontal lobes, just anterior to the central sul- cus and the somatosensory strip. Neuronal input em- anates from the secondary motor areas and from the so- matosensory cortex. Neuronal output travels through the internal capsule, and on to descending tracts of the spinal cord, and ultimately to the muscles of the body. The pri- mary motor cortex, like the somatosensory cortex, is so- matopically (or topographically) mapped as a homuncu- lus and allots area according to its degree of motor innervation (see Figure 7.3). If the primary motor cortex is stimulated directly, typically through microstimulation in the course of neurosurgery, corresponding muscles in the body move. For example, stimulating the thumb

causes the thumb to twitch or jerk. If the motor ho- munculus is compared with the sensory homunculus, it is evident that there are many similarities in the cortical mapping for motor control and sensory processing of movement. For example, the acute sense of touch on the fingers is also related to fine finger dexterity. However, some areas have proportionately more motor control abil- ities, or vice versa, so the maps appear somewhat differ- ent. The motor cortex, like the somatosensory cortex, controls the contralateral side of the body. Damage or dis- ease of the motor cortex results in hemiplegia, or the loss of voluntary movement, to the opposite side of the body. Hemiplegia is often a hallmark of stroke to the middle cerebral artery. So, for example, a common occurrence is to have a patient present with right-sided hemiplegia and difficulty speaking due to a left-hemisphere stroke.

The primary motor cortex and the somatosensory cor- tex are in reciprocal communication with each other through a reflex circuit. The primary motor cortex re- ceives feedback from the somatosensory cortex about the effect of movement just initiated. So when your thumb

Text not available due to copyright restrictions

moves across the page to turn it, the sensation of the con- tact of the thumb on paper is immediately sent to the so- matosensory cortex and informs the primary motor cortex of the effect of its movement.

Each area of the secondary motor cortex has a slightly different role. The supplementary motor area (SMA, also supplementary motor cortex, or medial premotor cortex) functions in organization and sequen- tial timing of movement. The internal intention to move is also a function of this area. The SMA lies on the dorsal and medial portion of each frontal lobe (in Brodmann’s area 6). It is posterior to the prefrontal cortex and ante- rior to the primary motor cortex. The SMA receives input from the parietal lobes (posterior parietal associa- tion area), the somatosensory strip, the secondary somatosensory areas, and subcortically from the basal ganglia and the cerebellum. It also interconnects with the PMA. The SMA outputs to the primary motor cortex in both the ipsilateral and contralateral hemisphere. It also outputs back to the basal ganglia and the cerebellum (Bradshaw & Mattingly, 1995). It functions specifically as a planner of motor sequences. Like the primary motor cortex, it is also somatopically mapped to the muscula- ture in the body; however, the mapping is not as tightly organized. Electrical microstimulation of the SMA elicits the urge to make a movement, or the feeling of anticipa- tion of a movement (Bradshaw & Mattingly, 1995). Stimulation may also elicit muscle movement. But in- stead of the single-muscle flexion of the primary motor cortex, this stimulation activates groups of muscles and a sequence of movement, and it can activate bilateral movement (Haines, 1997).

Experiments with humans show a dissociation, or separation, between the functional contributions of the primary motor cortex and the SMA. In an early method of studying areas of brain activity, researchers injected ra- dioactive xenon into the bloodstream. In this way, they could measure increased areas of brain blood flow, and thus brain neuronal activity, as they were occurring. When the researchers asked volunteers to make random finger movements, the primary motor cortex “lit up,” but the SMA remained relatively silent. When the experi- menters asked volunteers to make a sequence of move- ments with their fingers, such as drumming their fingers in a certain order, both the primary motor cortex and the SMA were active. Finally, when they asked the partici- pants to only imagine and rehearse the movements in their minds, without doing anything, only the SMA was active (Roland, Larsen, Lassen, & Skinholf, 1980). This offered strong evidence for the planning role of the SMA in sequential motor activities.

The PMA also plays a role in motor planning and sequencing and movement readiness. The PMA lies next to the SMA in Brodmann’s area 6 of the frontal lobes. Whereas the SMA is more medial, the PMA is more lateral. The PMA receives neuronal input from some of the same general areas as does the SMA, but from slightly different places. For example, the PMA receives parietal input from posterior parietal areas, rather than parietal association cortex. The PMA re- ceives input from the secondary somatosensory areas, rather than from both the primary and secondary so- matosensory areas, and receives more cerebellar input. As stated earlier, it is also reciprocally interconnected with the SMA and projects to the primary motor cortex and the reticular formation (Haines, 1997). The PMA is also somatopically organized. In a general way, the PMA performs similar premotor planning functions as the SMA, such as the sequencing, timing, and proper initiation of voluntary movement, but it may function more in externally cued readiness for action, whereas the SMA provides more of an internal readiness cue (Brad- shaw & Mattingly, 1995). For example, when runners line up for a race and hear the official say, “On your mark . . . Get set . . . Go,” their PMA is most active be- tween “Get set” and “Go.” Studies with monkeys also indicate that the PMA is most active during this inter- val between cue and go (see Haines, 1997).

Less is known about the functioning of the third structure of the secondary motor cortex, the CMA, al- though it likely plays a role in the emotional and moti- vational impetus for movement. The CMA is a medial infolding of the frontal area of the cingulate gyrus. Re- call that the cingulate gyrus plays a role in the limbic system. The CMA lies next to the cingulate gyrus. The CMA is organized somatopically in relation to the spinal cord. It projects both to the spinal cord and to the primary motor area. Damage to the CMA results in a lack of spontaneous motor activity (Bradshaw & Mattingly, 1995). This apparent apathy is neurologic in origin and not necessarily caused by a depressive state. People may be able to say what they can do or should do, but often do not translate this into action. Together with the SMA, the anterior cingulate also appears to play a role in the semantic premotor processing, or initiation, of speech.

Two additional cortical areas contribute to motor pro- cessing: the posterior parietal lobes and the dorsolateral prefrontal cortex. The posterior areas of the parietal lobes (Brodmann’s areas 5 and 7) are important in coordinating spatial mapping with motor programming. These association areas receive input from the somatosensory cortex, the

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192 PART TWO | The Functioning Brain

vestibular system, and the visual system. Integrated sensory information travels to the supplementary and premotor cortexes regarding the relative spatial position of the body and objects in space.

Much initiation for motor behavior and executive programming for movement originates in the higher as- sociation area of the dorsolateral prefrontal cortex. This area lies, functionally, in the prefrontal cortex, which is responsible for orchestrating and organizing many brain functions. The dorsolateral prefrontal cortex is not a “movement center” in and of itself, but it is in- strumental in deploying movement. Much input to this area comes from the subcortical motor centers of the basal ganglia.

T e s t i n g M o t o r F u n c t i o n i n g

Neuropsychologists are interested in assessing both sim- ple and complex motor programming. Simple motor skills require little coordination, whereas more complex items tap into higher motor and cortical processes. Items involving gross-motor movement assess one of the most basic cortically mediated motor responses, such as a re- sponse to a single command: “Raise your right hand,” or “Move your left leg.” Motor speed can be qualitatively evaluated by asking someone to “Touch your thumb to your forefinger as quickly as you can,” and fine-motor ability can be evaluated from asking, “Touch your thumb to each finger, one after the other.” Examples of standard- ized motor tests include a measure of grip strength and finger-tapping speed, both from the Halstead–Reitan Neuropsychological Battery. The strength of grip test sim- ply measures a person’s ability to squeeze a hand dy- namometer (Figure 7.8) as hard as possible. The Finger Oscillation or Finger Tapping Test requires a person to

tap as rapidly as possible with the index finger on a small lever attached to a mechanical counter, alternating trials between the dominant and nondominant hand. It is generally expected that one’s dominant hand would be both stronger and faster than the nondominant hand by about 10%.

Male individuals generally perform better on pure speed tests, whereas female individuals tend to show bet- ter performance on coordinated motor speed tests such as various pegboard tests that require one to insert, as quickly as possible, round or grooved pegs into slots with the dominant and nondominant hands (Figure 7.9).

Other motor tests integrate higher level cognitive pro- cessing, because they may, for example, require a person to shift between initiating and inhibiting behaviors (for

Figure 7.8 The Finger Tapping Test and Strength of Grip Test. (Courtesy Jeffrey T. Barth, University of Virginia, Charlottesville, VA.)

Figure 7.9 Neuropsychological tests of speeded motor coordination: (a) Grooved Pegboard Test; (b) Purdue Pegboard Test. (C/O Lafayette Instrument Company, Inc.)

D i s o r d e r s o f C o m p l e x M o t o r P r o c e s s i n g

A number of movement disorders may occur as a result of brain damage or disease. If the primary motor area in one hemisphere is damaged by stroke or injury, hemi- plegia often results. Disorders of motor processing that go beyond the primary motor cortex can be classified under two main types: disorders of when to act and dis- orders of how to act. For example, the motor system in- structs when to start and stop various behaviors. Akine- sia is a difficulty in initiating and maintaining behavior. Patients with akinesia may be extremely slow to start or perform a movement, may become rapidly fatigued when performing repetitive movements, or may have problems in performing simultaneous or sequential movements. If a person continues in the same behavior, or constantly selects it in the presence of other choices, this is termed motor perseveration, another problem of when to act. In addition, if a person behaves inappropri- ately, displaying a motor response when it is unwanted, this is termed defective response inhibition. These ex- amples of disorders of when to act can arise from a vari- ety of cortical and subcortical lesions and disorders. For example, patients with Parkinson’s disease show classic deficits in motor initiation and motor perseveration. People with this affliction often display a slow, shuffling

example, “If I clap once, you clap twice.” [Clap hands one time.] “Now, I clap twice, you clap once.” [Clap hands two times.]). Neuropsychologists often examine grapho- motor skills. The following items assess the ability to copy shapes with increasing degrees of difficulty. They involve the integration of visuoperception (input) and a complex motor response (output).

Apraxia/dyspraxia: an inability or disability in performing voluntary actions

Akinesia: difficulty initiating and maintaining movement

Dyskinesia: uncontrolled involuntary movement

Chorea: involuntary, jerky, writhing, undulating “puppet-like” movements

Defective response inhibition: the inability to inhibit or an inappropriate motor response.

Hemiplegia: loss of voluntary movement to one half of the body contralateral to the affected motor strip

Motor perseveration: an inability to stop a behavior or series of behaviors

Tremor: involuntary shaking, usually of a limb; tremors may be resting or occur with intentional movement

Table 7.4 Examples of Motor Dysfunction

Example II

Example I

gate when they walk and may “freeze” and be unable to move or back up when they enter a closet. People with Huntington’s chorea often show jerky, undulating, “pup- pet-like” movements of their limbs and grimacing, writhing movements of their faces. (Parkinson’s and Hunt- ington’s disease are discussed at length in Chapter 15.) Some examples of clinical motor dysfunction are de- scribed in Table 7.4.

Apraxia is the main type of disorder under the cate- gory of problems of how to act. Strictly defined, apraxia implies an absence of action, but neuropsychologists most often use it to describe a variety of missing or inappropri- ate actions that cannot be clearly attributed to primary motor or sensory deficits, or lack of comprehension, at- tention, or motivation. Thus, the term apraxia refers to an inability to perform voluntary actions despite an ade- quate degree of motor strength and control. The adjective “voluntary” is key to understanding this disorder. A pa- tient may be able to spontaneously don a jacket, for in- stance, but be unable to do so on command. Therefore, family members who ask a patient to do something may perceive him or her as being oppositional or stubborn when, in fact, he or she does not control the skills required to perform the action. A typical type of task that is given if apraxia is suspected is to ask a patient to pantomime a goal-directed action or series of actions. For example, a person may be asked, “Show me how you would use a key to open a door.” Depending on the type of apraxia, a pa- tient may “misperform” this action in several ways.

There are several subtypes of apraxia, depending on a number of behavioral variables affecting movement and movement initiation. The types discussed in this chapter—limb-kinetic, ideomotor, conceptual, and

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Figure 7.10 Two views of the cerebellum: (a) lateral view and (b) cutaway medial view. (Courtesy Mark DeSantis.)

Figure 7.11 Basal ganglia. (Modified from Bear, M. F., Connors, B.W., & Paradiso M. A. [2001]. Neuroscience: Exploring the brain [2nd ed., p. 389, Figure 14.11]. Baltimore, MD: Lippincott Williams & Wilkins, by permission.)

VL nucleus of thalamuc

Caudatse nucleus

Putamen

Striatum

Globus palidus

Subthalamic nucleus

Substantia nigra

CHAPTER 7 | Somatosensory, Chemical, and Motor Systems 195

dissociation (formerly ideational) apraxia—are the most frequently described.

People with limb-kinetic apraxia (also ideokinetic) appear clumsy and have poor motor control. In attempt- ing to show how a key would be used, limb-kinetic apraxics may make large grasping motions, rather than fine thumb-to-forefinger movements. Because limb- kinetic apraxia is defined as a problem in executing pre- cise, independent, or coordinated finger movements, people with this disorder are also likely to perform quite poorly on the finger-tapping (see Figure 7.8) and pegboard tests (see Figure 7.9). The theories regarding the brain areas implicated in limb-kinetic apraxia in- volve the corticospinal tract, basal ganglia, and the pre- motor cortex, as well as a larger frontoparietal circuit of motor control. A progression of gross- to fine-motor control can be observed with the myelinization of the corticospinal tract during development. As the corti- cospinal tract matures, children first grasp with the en- tire hand before being able to execute independent and coordinated finger movements. However, limb-kinetic apraxia goes beyond a corticospinal or basal ganglia deficit and involves aspects of grasping and fine-motor manipulation involved with the larger frontoparietal cir- cuit (Leiguarda, Merello, Nouzeilles, Balej, Rivero, & Nogues, 2003).

Ideomotor apraxia involves difficulties in the execu- tion of the idea of a movement, even though the knowl- edge of the action is preserved. For example, in response to a request to pantomime use of a key, the person may mistakenly use the index finger as the key (body part as tool error) or turn the whole arm in an unnatural fashion (movement orientation error). However, someone with ideomotor apraxia may be able to use a key correctly if it is put in the hand and should recognize the correct ges- ture if it is performed by someone else, or if given a choice, can match tools with correct actions. Lesions to the left parietal lobes are commonly associated with ideo- motor apraxia of either hand. It is believed that the left parietal lobes have a special role in programming purpose- ful, skilled movements, especially in those who are left hemisphere dominant for language (Meador, Loring, Lee, Nichols, & Heilman, 1999).

With conceptual apraxia, in contrast, the knowledge of the action has been lost. For example, when asked to gesture how to use the key, the person may perform any number of vague movements. When given a key, he or she may try to use it as a pen or a toothbrush and, in ad- dition, may not be able to pick out the correct gesture if shown by someone else. Conceptual apraxia is not associ- ated with damage to any one area, but is related to wider

loss of semantic knowledge of tools and actions. This problem may be seen in the early stages of dementia, such as Alzheimer’s disease.

Dissociation apraxia (formerly ideational apraxia) in- volves impairment in an action sequence. This type of apraxia can be witnessed in a multistage request such as, “Show me how you would pour and serve tea.” Actions may be performed out of order, although the individual actions themselves are correct. Disorders of an action se- quence may be caused by executive or frontal lobe dys- function and a possible dissociation of action programs from language.

In summary, the apraxias, as disorders of the how sys- tem of motor control, represent problems with the men- tal representation of actions. Although we present apraxia subtypes as independent entities, different types can occur together in the same person. The apraxias repre- sent the most common type of motor problems treated by neuropsychologists, because they can occur due to a wide variety of cerebrovascular disorders (i.e., strokes), as well as with tumors or disease states, and the disability they produce interferes with many complex actions of daily life requiring higher cortical functioning.

T H E C E R E B E L L U M A N D M O T O R P R O C E S S I N G

The cerebellum permits seamless coordination and uncon- scious flow of movement. It coordinates reflex action and voluntary movement, is concerned with the timing of movement, and can differentiate movement frequency at a rate of 1/1000 of a second. The cerebellum aids in main- taining posture, balance, and muscle tone. It is also impli- cated in sequential aspects of motor learning, such as the steps required to learn to play the piano. The cerebellum is located posterior to the brainstem and inferior to the te- lencephalon (Figure 7.10) and reciprocally connects to the cortical sensory and motor systems, resulting in a constant feedback loop coordinating the two areas. Cerebellar motor disorders are most often caused by structural dam- age caused by trauma or stroke. They are characterized by irregular, jerky, and poorly coordinated movement. Mus- cle tone and strength, as well as motor resistance, may also decrease. Finally, in contrast with the resting tremor seen in Parkinson’s disease patients, cerebellar patients show an intention tremor.

S U B C O R T I C A L M O T O R P R O C E S S I N G

Cortical motor processing is largely concerned with volun- tary, conscious movement, whereas subcortical structures,

196 PART TWO | The Functioning Brain

namely, the basal ganglia and the cerebellum, function in a more automatic manner to regulate movement. The func- tion of the basal ganglia in movement largely controls the fluidity of overlearned and “semiautomatic” motor pro- grams (Bradshaw & Mattingly, 1995). The basal ganglia reciprocally connect to the PMA and the SMA via the thal- amus. Also, an important brain circuit responsible for per- ceptual-motor learning and adaptation centers on the basal ganglia. Specifically, this circuit includes the caudate nu- cleus, putamen, and globus pallidus. The nuclei of the stri- atal complex (caudate and putamen) receive projected in- formation from cortical sensory areas. From the striatum, information then funnels through the globus pallidus, and

then on to the thalamus, where it projects to the premotor and prefrontal areas (Mishkin, Malamut, & Bachevalier, 1984) (Figure 7.11).

Some well-known motor disorders are associated with neurochemical abnormalities that affect the basal ganglia— Tourette syndrome is one of these (Neuropsychology in Action 7.3) as well as Parkinson’s disease, which specifically targets the substantia nigra, and Huntington’s disease, which attacks the caudate nucleus. Although these two dis- orders attack structures within centimeters of each other, you can easily distinguish these motor disorders. You can recognize Parkinson’s disease by its resting tremor and diffi- culty in initiating movement, whereas Huntington’s disease

George was a patient I saw for neuropsycho- logical evaluation. I knew that George, a 29-year-old left-handed man, was diag- nosed with Gilles de la Tourette syndrome (TS), but I was not prepared for his odd behavior during my administration of the Category test. The Category test measures planning and reasoning. I asked George to match a stimulus to one of four targets. In essence, George had to figure out which abstract category the stimulus fit best. My responsibility was to present each stimulus figure, tell George whether he was correct, tell him when the category changed, and keep score. In total, more than 200 stimuli cards were presented, which fall into 7 categories. The first stimulus card was easy, and I told George his response, “two,” was correct. As soon as I did so, he made a peculiar gesture, a kissing motion, in which he looked directly at me, raised his eyebrows, and shaped his mouth as if “blowing” me a kiss. If this were not odd enough, I was dumbstruck with George’s behavior when I told him he had made an error. He made an obscene gesture commonly known as “flipping the bird”!

And so it went for the entire examination. When George was correct, he blew me a kiss, and when he made an error, he “gave me the finger.” Like many neuropsychological tests, this one is staggered, so it becomes more

and more difficult. This resulted in George making more errors toward the end, a total of 53. Midway through the examination, I decided to continue with the test, but I did ask George after the evaluation whether he knew he was engaging in these behaviors and if he was somehow angry with me. He informed me that he was aware of what he did, but that it seemed uncontrollable; “I just had to do it,” he explained. He also told me that he was not angry with me and, in fact, enjoyed the testing and my company.

TS is a rare and fascinating disorder that has puzzled scientists for more than a century. TS occurs in less than 1% of the population. Symptoms include facial and bodily tics, usually progressing from the head to the torso and extremities, as well as repetitive verbal utterances, including copro- lalia (uncontrollable cursing) in approxi- mately 50% of the cases (Newman, Barth, & Zillmer, 1986). Onset of the disorder is typically before age 10; symptoms vary in intensity over time and may be exacerbated by stress. Most individuals with TS are male and left-handed.

The specific cause of TS is unknown, but the prevailing view is that there is a neuro- logic basis for the disorder, possibly involving subcortical structures that are responsible for motor coordination (Devinsky, 1983;

Bornstein, King, & Carroll, 1983). This view is supported by findings of a high incidence of motor asymmetries on clinical neurologic examinations and abnormal electroen- cephalographic and computed tomography scans (Newman, Barth, & Zillmer, 1986). However, no consistent or focalized neuro- logic deficits have emerged.

George, adopted in infancy, first dis- played bizarre motor symptoms—jerking of his shoulders—at age 2. Later, he developed short barking sounds, repetitive movements of his facial muscles and arms, and finally, loud shouting of profanities. The bouts of impulsive and sometimes assaultive behav- ior became so difficult to manage in the classroom that George was taken out of school in the third grade. Subsequently, he was in and out of psychiatric institutions most of his life. He was in a state psychiatric facility when I evaluated him. He had been hospitalized because he threw a brick at a passing car and chased it with an ax. Some- how, he thought that passengers in the car were teasing him. Like George, many pa- tients with TS display peculiar motor symp- toms and psychiatric symptoms, including depression and impulsivity. Medications often help patients with TS so that, in most cases, they can lead a productive and symptom-free life.

N e u r o p s y c h o l o g y i n A c t i o n 7 . 3

T o u r e t t e S y n d r o m e : T o o M u c h B e h a v i o r

by Eric Zillmer

CHAPTER 7 | Somatosensory, Chemical, and Motor Systems 197

Summary The primary sensory areas receive afferent input through the relay station of the thalamus, except for olfac- tion, which receives input directly from the olfactory bulbs. In some sensory systems, such as touch and taste, primary sensory reception is completely crossed, coming entirely from the contralateral side of the body. In vision, the contralateral hemispace sends input to each hemisphere. In audition, information trav- els bilaterally. Olfaction has ipsilateral projection to the primary olfactory cortex.

Each sensory system has a primary receiving area in the cortex. In general, sensory information is represented in detailed one-to-one or pattern mapping onto the corresponding primary cortex. In vi- sion, audition, and touch, these are, respectively, the retinotopic, tonotopic, and somatotopic maps. The primary mapping for the chemical senses is less well understood but likely occurs in a similar manner.

From the primary sensory cortices, where information is first labeled, it is then sorted and relayed to the secondary sensory processing areas. These areas are generally contiguous to the primary sensory areas. They receive preprocessed sensory information through reciprocal connections with primary areas. They do not receive sensory information directly. Secondary areas may process only specific qualities of sensory information in a parallel manner. In other systems, a distributed “maplike” representation may remain. As processing moves into tertiary or association areas, dense reciprocal interconnections both within and between sensory modalities are evident.

The motor system involves both cortical and subcortical areas of processing. The general stream of processing moves from subcortical and secondary motor areas to the primary motor area to output; how- ever, there are many reciprocal interconnections. Some of the coordination and planning of movement occurs in the subcortical areas of the cerebellum and the basal ganglia. The three secondary cortical motor areas add fine planning, sequencing, and motivational aspects. The primary motor cortex, or motor ho- munculus, is responsible for managing the fine details of movement.

It would be difficult to imagine the behavioral oddities that disorders of specific sensory and motor systems present had not nature and odd twists of fate actually presented them. These include descriptions of sensory phantoms, distortions of chemical senses, and the odd disorder of “miswired” sensation termed synesthesia. Although these disorders can be connected to specific sensory modalities, it is at once evident that most afflictions do not stay within the bounds of a single system.

C r i t i c a l T h i n k i n g Q u e s t i o n s

In what ways do the study of sensory-perceptual and motor disorders inform us about intact brain functioning? In what instances might the study of damaged brains lead us astray? Do conditions such as phantoms, neglect, and synesthesia represent altered states of consciousness? Explain. Does intact motor processing require intact sensory-perceptual processing? Explain.

patients show characteristic puppet-like jerking and gri- macing choreic movements. The motor difficulties in these patients are prominent but exist within a larger constella- tion of symptoms. We discuss these two disorders and their

specific motor impairments at length in conjunction with the discussion of subcortical dementia in Chapter 15. Tourette syndrome also is thought to affect the basal gan- glia as well as other cortical structures.

K e y Te r m s

Transduction Receptor cell Agnosia Tactile agnosia or Astereognosis

Somatosensory system Proprioception Mechanical receptors Chemoreceptors

Thermoreceptors Nocioceptors Proprioceptors Ascending spinal-thalamic tract

Dorsal column medial lemniscal pathway

Medial lemniscus Somatopic organization

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Kinesthetic sense Finger agnosia Paresthesia Peripheral neuropathy Phantom limb pain Proprioceptive disorder Tactile extinction/

suppression/ inattention

Papillae Ageusia

Dysgeusia Phantogeusia Hypogeusia Anosmia Dysosmia Phantosmia Hyposmia Sensory association

areas Premotor cortex or premotor

area (PMA)

Cingulate motor area (CMA) or cingulate motor cortex

Primary motor cortex Hemiplegia Secondary motor cortex Supplementary motor area

(SMA) or supplementary motor cortex, medial premotor cortex

Dissociation Dorsolateral prefrontal cortex

Akinesia Motor perseveration Defective response

inhibition Apraxia Limb-kinetic apraxia Ideomotor apraxia Conceptual apraxia Dissociation apraxia Tremor Striatal complex

We b C o n n e c t i o n s

http://www.ninds.nih.gov/disorders/chronic_pain/detail_chronic_pain.htm The National Institute of Neurological Disorders and Stroke site on Pain: Hope through research.

http://www.pbs.org/safarchive/3_ask/archive/qna/3294_peppers.html Linda Bartoshuk of Yale University discusses her research on supertasters.

http://www.cf.ac.uk/biosi/staff/jacob/teaching/sensory/olfact1.html Tutorials on smell and what’s new in olfaction research.

http://www.ninds.nih.gov

http://www.pbs.org

http://www.cf.ac.uk

Chapter 8

V I S I O N A N D L A N G U A G E

I am part of all that I have seen. —Alfred Lord Tennyson

It is not often that we use language correctly; usually we use it incorrectly, though we understand each others meaning.

—St. Augustine

Visual Processing Auditory and Language Processing

Neuropsychology in Action

8.1 Blindness: Helping Us See the Plasticity of the Brain

8.2 The Case of Jonathan 8.3 Case Study: Neglect

Overview The human visual and auditory systems cover more cortical area outside of their primary sites of processing than the sensory systems discussed in Chapter 7. Humans rely greatly on vision and hearing, and the areas of the cortex devoted to each reflect this. In the areas of visual and auditory processing, we progress to higher order functions such as visual object recognition, visuospatial processing, and speech and language that require an understanding beyond primary processing based on mapping of functions. This chapter discusses vision and audition from primary processing to higher integrative functions of vision and hearing. We also discuss representative disorders that can occur at each level of processing. As in Chapter 7, these include agnosias, or in the case of language, aphasias. In the visual system, we also take an in-depth look at the disorder of neglect as an example of a visuospatial problem, but also one that involves aspects of attention and consciousness.

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K e e p i n M i n d

Does vision operate as a bottom-up or top-down process?

What would it be like to no longer be able to recognize your friends by their faces?

What is the difference between primary auditory and visual processing and higher order processing?

Visual Processing

Vision is one of our most important senses. In ad- dition to the occipital cortex, major portions of the tem- poral and parietal lobes are devoted to visual processing. Areas of the frontal lobes are involved in eye movement and higher processing of visuospatial working memory. The large areas devoted to vision reflect the human re- liance on sight and visual processing. Visual information processing is also the most complex and best understood sensory systems of the brain. However, for all of the at- tention, there are still debates about how vision works.

No one “master processor” integrates all visual infor- mation into perceptible form. Recognition of surround- ings, people, faces, and objects, though seemingly instan- taneous, is the culmination of separate but locally connected visual-perceptual processes. As a prerequisite to recognizing a friend walking through a crowd, you must first have the necessary visual acuity, as well as adequate color and form perception. Visual acuity speaks to the abil- ity to perceive light, contrast between light and dark, re- solve a target, and have adequate visual fields. Receptors for form interpret shapes such as roundness or squareness, as well as orientation of lines to each other. Qualities of texture and color such as feathery and blue are processed

by yet other primary visual areas. Although somewhat overgeneralized, at a higher perceptual level, the ventral visual pathway to the temporal lobes serves as the “what” system largely responsible for object and face recognition. The dorsal pathway to the parietal lobes, or the “where” system, is specialized for spatial location. In building a vi- sual percept, some of these processes operate in sequence, and others may operate in parallel. Although we discuss visual processing as a “bottom-up” process of analyzing rudimentary or local bits of information that are built up into coherent percepts, the issue of degree of impact of “top-down” or perceptual-driven processing on vision is an area of debate (Grill-Spector & Malach, 2004).

As complicated as this general characterization may be, the human visual system is actually much more so- phisticated. In daily life you see under extremely “messy” visual conditions, through haze, from different perspec- tives, and from varying distances. Amazingly, visual per- ception of a tree stays constant, even though sometimes you may see it through a fog, sometimes in the shade, partially obscured, from the north, from a distance, or from under- neath. Each time the image of the tree makes a different impression on your retina; yet, your brain’s perception of “tree” remains constant. Obviously, you do not simply match templates for a particular tree—there would be so

many as to soon overload the system. The visual-perceptual system must be highly flexible and sophisticated to ac- commodate a constantly changing visual landscape.

P R I M A R Y V I S U A L P R O C E S S I N G

In a general way, the eye functions as a type of camera, map- ping visual images on the retina and transmitting the in- verted “picture” to a corresponding “retinotopic” map to the primary visual processing area of the cortex. But the eye is much more dynamic and complex in operation; it can con- stantly adjust focus and adapt to changing visual conditions, as well as extract information about images. The visual sys- tem operates via two types of photoreceptor cells. The rods and cones transduce the electromagnetic wavelengths of light energy and extract properties of objects. Cones, which detect wavelengths of color, are fewer, and center in the mid- dle of the retina. The more numerous rods surround the cones and are attuned to the shades of gray we experience in low-light and nighttime conditions. Visual stimuli from the right side of space (that is, right visual field) activate recep- tors on the left side of each retina, and information from the left visual field activates right-sided receptors.

Visual information leaves the eye through the optic nerve’s bundle of axons. The retina sends projections to at least 10 brain areas. Some of these areas, such as the pineal gland and the superchiasmic nucleus, are important in regulating long biological rhythms such as migration in birds and the circa-

dian rhythms of sleep and wakefulness. Others are involved in controlling eye movement. A small proportion of neurons from the optic tract synapse with the hypothalamus, and a proportion (10%) synapse with the superior colliculus in the midbrain tectum. However, the primary route, consisting of the largest number of axons, funnels information along the visual pathway to the occipital cortex (Figure 8.1). The route leaving the eye follows the optic nerve to the optic chiasm on the ventral surface of the brain, just anterior to the pituitary gland. There, information from both eyes joins and partially decussates (crosses over to the contralateral side). From then on, the left hemisphere processes information from the right visual field, and vice versa. In addition, information from the visual fields also reverses top to bottom. The lower portion of the visual field is now on top, close to the parietal lobes, and the upper portion is on the bottom, next to the temporal lobes. The optic tracts synapse with the thalamus in the dor- sal portion at the lateral geniculate nucleus, then project to the occipital lobes.

Disorders of the visual system, along the pathway from the retina to the occipital lobes, depend on where along the pathway a lesion occurs. Because the pathway is topo- graphically oriented, observing visual abilities gives a good clue to lesion location. Figure 8.2 shows a number of vari- ants of visual difficulties, or anopias, possible with lesions to the optic pathways. If a lesion occurs anterior to the optic chiasm, effectively cutting off the visual input from one eye, the effect is blindness in one eye. Both visual

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Figure 8.1 Visual pathways. The primary visual pathway partially crosses over at the optic chiasm. From there it routes through the thalamus to the primary visual cortex. (Reproduced from Kalat, J. W. [1998]. Biological psychology [6th ed., p. 174, Figure 6.6]. Pacific Grove, CA: Brooks/Cole.)

Retina

Lateral geniculate nucleus of thalamus

Optic nerve

Optic chiasm

Superior colliculus

Primary visual cortex (occipital lobe)

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Figure 8.2 Visual field defects. Numbers indicate interruptions of visual pathways and their corresponding behavioral effects. In lesion 4, only the ventral temporal lobe fibers have been sev- ered. In lesion 5, only the dorsal parietal lobe fibers have been severed. (Reproduced from Peele, T. L. [1977]. The neuroanatomical basis for clinical neurology [3rd ed.]. New York: McGraw-Hill, by permission.)

Left visual field Right visual field

Left visual field right visual field Left visual field right visual field

fields with full peripheral vision remain in the other eye. If, however, the optic nerve is cut posterior to the optic chiasm, the relay for one visual field in both eyes is de- stroyed. This condition is technically termed homony- mous (same-sided) hemianopia (half blindness), and refers to partial blindness on the same side, or visual field, of each eye. The partial blindness is not related to a mal- function of the eye, but to the neural connection to the occipital lobes. This problem is also attributed to unilat- eral damage to the right or left occipital lobes. Often right- or left-homonymous hemianopia occurs as a result of hemorrhage, tumor, or trauma. The result of this con- dition can be quite hazardous. For instance, a person at- tempting to maneuver across a busy highway may not see traffic on the left side of his or her visual space. This con- dition is often compounded by other problems, for exam- ple, muscle weaknesses of the eyes that prevents a syn- chronized movement of the eyes across space.

Visual information reaches the occipital lobes after it has undergone early-stage processing at the level of the eye and as it passes through the thalamus. Early visual processing at the level of the occipital lobes corresponds

to retinotopic areas that researchers have attempted to map out according to functional areas (generally labeled V1-V8). Although some functional areas are well under- stood, controversy remains for others. Areas V1-V3 ap- pear to be best understood. Area V1 (visual area 1, for- merly Brodmann’s area 17) is also known as the striate cortex, because of its striated or banded appearance. It lies in the most posterior aspect of the occipital lobes, but a major portion of it extends onto the medial portion of each hemisphere. Functionally, this area is the primary vi- sual cortex (Figure 8.3). The secondary association, or prestriate cortex, is contiguous and corresponds to func- tional visual areas V2 through V5. On the surface of the cortex these areas form donut-like rings around area V1. The responsibility for elementary visual interpretation lies in these visual areas, which process primary features of vi- sual information such as light wavelength, line orienta- tion, and features of shape. These represent the building blocks of the eventual composite image.

Area V1 contains the retinotopic map, which maintains the same topographic relations among visual elements as they are mapped on the retina. The primary purpose of this

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Figure 8.3 Cortical visual processing. Information relays from the thalamus to the primary visual cortex (Area V1). Visual information passes to the secondary areas of visual processing (V1–V8) where aspects of color, form, and motion are processed. From there it is analyzed in parallel streams through the ventral temporal (“What”) and the dorsal parietal areas (“Where”). (Modified from Carlson, N., & Buskist, W. [1994]. The science of behavior [5th ed., p. 201]. Boston: Allyn & Bacon.)

Occipital lobe

MT/V5

V3A

V4v

Cerebellum Second level (what) processing in temporal lobe

Optic nerve

Thalamus

Part of thalamus that receives visual information Second level (where) processing

in parietal lobe

Eye

area is to assemble and relay information to prestriate areas. In a reciprocal fashion, V1 also receives back pro- jections from information processed by these visual areas within the occipital lobes and continues to play a role in maintaining spatial orientation between local bits of in- formation. Area V2, which is closely related to V1, is also a visual preprocessing area, assembling and mapping in- formation. Damage to area V1 causes cortical blindness, or hemianopia, in the opposite visual field. If area V1 is damaged in both hemispheres, complete blindness will occur. However, people with cortical blindness are some- times able to indicate that a stimulus is present, that it has moved, or that it is in a certain location, even though they have no conscious ability to “see” in the conventional sense. This phenomenon is termed blindsight. Why does this happen? Although explanations are not definitive, part of the explanation may lie in that V1 may not be completely damaged or that some visual information, per- taining to motion, for example, may be processed outside of the striate (V1) cortex. However, the information is processed largely in an automatic or preconscious man- ner. No reports exist on the effect of damage to V2 alone. If V2 is damaged, V1 is also likely involved, because V2 encircles V1 like a donut. Blindness, in general, raises interesting questions about the plasticity of the brain. Neuropsychology in Action 8.1 examines what may happen to the occipital cortex in the absence of visual stimulation. As we discussed in Chapter 7, with phan- tom limb, the brain may reorganize itself in interesting ways.

The remaining functional visual areas in the occipi- tal lobes (areas V3-V8) are organized into four parallel systems with reciprocal integration (Zeki, 1992). The four systems include motion, color, dynamic form (without color), and color plus dynamic form or shape. Area V3 appears specialized for dynamic form, or recog- nition of moving shapes, but does not code aspects of color. It has been postulated that area V4 is selective for the electromagnetic wavelengths of color, some aspects of line orientation, and form (color-and-form area). Area V5 (also called area MT) lies on the occipitopari- etal juncture and receives input from a number of vi- sual cortical areas. It contains visual motion detector cells that are specialized to respond to direction of mo- tion. Columns of cells within the layers of the cortex are responsive to different directions. Damage that tar- gets individual components of these secondary proces- sors leads to specific deficits in visual behavior. For ex- ample, damage to V4 has resulted in achromatopsia, the complete loss of ability to detect color. People with this malady live in a black-and-white world. One man,

a successful painter of abstract art, experienced this as different from watching black-and-white TV (Neu- ropsychology in Action 8.2). V4 and V8 are contiguous to each other, and some have also attributed color pro- cessing to area V8. Lesions to area V5 result in a very different problem, akinetopsia, or the specific inability to identify objects in motion (Zihl, 1995). Damage to areas V3-V5 can result in a general inability to perceive form. In this situation, patients may be able to make a perfect copy of a drawing, but are totally unable to un- derstand that the connection of lines corresponds to a specific shape or object.

In summary, the occipital cortex processes elementary aspects of vision. Although the functional types of pro- cessing are known, and some areas are mapped by cur- rently understood functional location, elementary visual processing is still not completely understood. Some would suggest that visual processing, including color, proceeds in streams of processing that work in parallel fashion, rather than in localized or circumscribed structure- function maps. The next section further discusses the con- cept of processing streams.

H I G H E R V I S U A L P R O C E S S I N G : O B J E C T R E C O G N I T I O N A N D S P A T I A L L O C A L I Z A T I O N

Neuroscientists have identified at least 20 areas of sec- ondary or higher visual processing. However, for the pur- poses of this discussion, we focus on the following topics: (1) how visual elements are integrated so that the viewer appreciates the pieces of vision as a coherent whole, or object; and (2) how objects are localized within a spatial framework. These two streams of visual processing are dif- ferentiated neuroanatomically, and they are often referred to as the “what” system, or ventral processing stream, of object recognition, in contrast with the “where” system, or dorsal processing stream, of object localization (Mishkin, Ungerleider, & Macko, 1983) (see Figure 8.3). The two anatomically distinct areas of the ventral and dorsal streams are probably coordinated through the thal- amus (Petersen, Robinson, & Morris, 1987). In the first part of this section, we discuss the behavioral functions associated with object recognition and object localization and give an overview of the ventral and dorsal processing streams.

One of the best ways to understand the differences be- tween the two systems is to examine the types of disor- ders that occur if each system is damaged. The disorders evident at this higher level of visual processing and per- ceptual integration involve the interaction of vision with

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CHAPTER 8 | Vision and Language 205

Does the brain’s “visual” cortex lie dormant in the absence of visual input? Esref Armagan, a renowned Turkish painter, has been blind from birth. He impresses audi- ences all over the world with his realistic representations of objects and landscapes, complete with color, shadow, and perspec- tive. Although visual input has never reached his brain, Mr. Armagan’s occipital cortex has not atrophied, shrunk, disappeared, or even simply remained inactive over his 52 years without vision. In fact, research conducted at Beth Israel Deaconess Medical Center in Boston shows that while drawing objects that he had previously explored tactilely, his visual cortex becomes activated as if he were seeing. Current research on neuroplasticity is helping us to understand how we can explain “visual” cortex activation in a man who has never seen with his eyes.

Traditionally thought to handle only vision, research now suggests the occipital cortex can take on other duties ranging from so- matosensory processing to verbal memory. In blind individuals, the occipital cortex is able to reorganize to accept nonvisual sensorimotor information. In an experiment using positron emission tomography scanning, occipital lobe activation was measured during tactile dis- crimination tasks in sighted subjects and in Braille readers blinded in early life. Blind volunteers showed activation of primary and secondary visual cortical areas during tactile tasks, whereas sighted control subjects actually showed reduced levels of regional cerebral blood flow in the visual cortex (Sadato, Ibañez, Deiber, & Hallett, 1996).

Further research suggests that disrupting the functioning of the occipital areas during tactile tasks leads to corresponding behavioral disruption in blind individuals. In a study conducted by Dr. Leonardo Cohen, early-blind and sighted volunteers read tactile symbols (Braille and embossed Roman letters, respectively) while transcra- nial magnetic stimulation (TMS) was applied to different scalp positions, transiently

disrupting the functioning of the correspond- ing cortical areas. In blind volunteers, TMS delivered over midoccipital regions resulted in increased errors in Braille reading as well as subjective accounts of distorted so- matosensory perceptions. They reported missing dots, faded dots, extra dots, and dots that did not make sense. In contrast, midoccipital stimulation in sighted subjects did not produce significant effects on identi- fication of embossed Roman letters or reports of abnormal perception of letters (Cohen, et al., 1997). This research suggests that the occipital or “visual” cortex is not only active during the processing of somatosen- sory stimulation but is functionally relevant during Braille reading for blind individuals.

Can neural plasticity also partially ex- plain the widely recognized superior verbal memory abilities in the blind? A functional magnetic resonance imaging study con- ducted by Dr. Amir Amedi found occipital lobe activation during both verbal memory tasks and verb generation tasks in congeni- tally blind volunteers. During the same tasks, the extensive occipital activation was not observed in sighted volunteers. The results of this study suggest that, in the case of visual deprivation due to congenital blindness, the occipital lobe becomes involved during tasks that require verbal memory and may be related to the superior verbal memory skills reported in the blind. In fact, a functional role for the occipital cortex in verbal memory tasks is suggested by Amedi, as early visual cortex activity was correlated with verbal- memory scores (Amedi, 2003).

A growing body of evidence now con- tributes to the notion that brain regions traditionally associated with one sensory modality also participate in the processing of other senses. In this way, the occipital cortex may be viewed as being “metamodal,” meaning that it is capable of adapting and changing in order to process information regardless of the sensory modality it receives. The occipital cortex may have evolved to

become the “visual cortex” simply because this region of the brain may be best suited for the processing of information supplied by vision; it may have qualities that provide it with strengths in processing spatial informa- tion using retinal visual information (Pascual-Leone & Hamilton, 2001). Because of neural plasticity, in the event of loss of visual input, the brain is able to adjust by recruiting the occipital cortex for use in another capacity, or by unmasking pathways that may already be present in the blind and sighted alike (Pascual-Leone & Hamilton, 2001).

From this collection of studies that suggest the “visual cortex” plays a role in tactile Braille reading and verbal memory in the blind, we now know that the human brain is capable of reorganizing itself and readily adjusts through adaptive recruitment of the occipital cortex. Advances in the under- standing of this neuroplasticity have implica- tions for the development of visual prosthe- sis aimed at restoring vision in the blind. Historic accounts of attempts at the restora- tion of vision have been largely unsuccessful, with some ending in depression and wishes to become blind again, presumably because of the reorganization that takes place in the cortex (von Senden, 1960). For example, when vision has been restored in patients, many have exhibited difficulties with depth perception, causing incapacitating fears of everyday activities such as crossing the street because of the inability to judge the proximity of oncoming cars. Despite cutting edge technology, restoration of functional vision through visual prosthesis without regard to the way blindness affects the brain is not likely to result in meaningful visual perception (Merabet, et al., 2005). Indeed, success in developing technology that will allow blind individuals to see will depend on the understanding of the neuroplasticity of the human brain and our ability to success- fully communicate with the brain that has adjusted to blindness and that is readjusting to sight once again (Merabet, et al., 2005).

N e u r o p s y c h o l o g y i n A c t i o n 8 . 1

B l i n d n e s s : H e l p i n g U s S e e t h e P l a s t i c i t y o f t h e B r a i n

by Erin Abrigo

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Text not available due to copyright restrictions

other sensory-perceptual and higher order systems such as attention, memory, and consciousness. The problem of visual object recognition is best illustrated by the visual agnosias, and the problem of spatial location can be con- sidered by examining neglect.

T h e “ W h a t ” a n d “ W h e r e ” S y s t e m s o f V i s u a l P r o c e s s i n g

The ventral processing stream is perceptually specialized for higher aspects of visual object recognition. It helps con- nect the visual perception of shape and form with the rep- resentation of that object’s meaning. The ventral process- ing stream contains interconnected regions from the occipital lobes to the temporal lobes. The visual processing stream of the left hemisphere is more specific to recogniz- ing symbolic objects such as letters and numbers. The left ventral occipital lobe shows increased blood flow when people process strings of letters (Snyder, Petersen, Fox, & Raichle, 1989). The right ventral system is more specific to the global recognition of objects and faces. Damage to this system can result in visual agnosia. The next section provides an in-depth discussion of the subtypes of visual agnosia (apperceptive and associate agnosia).

The dorsal processing stream is essential for visually localizing objects in space and for appreciating the rela- tive relation of those objects to each other. Through reci- procal feedback to the motor system, this “where” system also helps in planning and coordinating motor move- ments. This stream of integrated structures connects the occipital to the parietal lobes. Disorders of this system contribute to right–left discrimination problems, con- structional apraxia, and neglect.

Directional impairment, a form of spatial relations con- fusion, is usually referred to as a right–left discrimination problem. Patients with this kind of difficulty routinely get lost if left on their own, particularly in a new environment. An inability to perform voluntary actions, termed con- structional apraxia, is the inability to perform actions that require three-dimensional movement, such as building a tower from blocks. (Apraxia is discussed in Chapter 7.)

D i s o r d e r s o f t h e “ W h a t ” S y s t e m : A p p e r c e p t i v e a n d A s s o c i a t i v e V i s u a l A g n o s i a

Agnosia is derived from the Greek, gnosis, meaning “ab- sence of knowing” and can occur in any sensory domain. In the modality of vision, people with visual object ag- nosia may fail to recognize objects at all, or in milder cases, confuse objects that they observe from different an- gles or in different lighting conditions. The term

prosopagnosia refers to the special case of inability to rec- ognize people by their faces, even though the person can often recognize people by other means such as gait or tone of voice. People with visual agnosias can see. The disorder is less a pure sensory disorder than a higher perceptual disorder of “knowing.” In The Man Who Mistook His Wife for a Hat, Oliver Sacks describes the affliction of Dr. P, a music teacher who can no longer recognize objects or peo- ple by sight. Presented with a red rose, Dr. P “took it like a botanist or morphologist given a specimen, not like a person given a flower. ‘About six inches in length,’ he commented. ‘A convoluted red form with a linear green attachment.’” Dr. P was completely unable to name what he had in his hand until it was suggested to him to smell it. “‘Beautiful!’ he exclaimed. ‘An early rose. What a heav- enly smell!’ He started to hum [the German tune] “Die Rose, die Lilie. . . .” (Sacks, 1987, pp. 13–14). Dr. P’s af- fliction was that he was visually unaware of the totality or gestalt of objects. He could see and identify form and color but could not combine these aspects into a higher sense of meaning that is a rose. His only visual reality was a mechanistic identification of features. This is typi- cal of how visual agnosia primarily involves the processes necessary for object recognition or object meaning while leaving intact elementary visual processes. Also, Dr. P’s ag- nosia, as is usually the case, was modality specific. Although his visual knowing was impaired, a higher sense of know- ing was available through sense of smell. Dr. P also had no problem in recognizing people by their voices.

Cognitive neuropsychologists often differentiate be- tween apperceptive visual agnosia and associative vi- sual agnosia. The essential difficulty in apperceptive vi- sual agnosia is object perception, or the inability to combine the individual aspects of visual information such as line, shape, color, and form together to form a “whole” percept. They seem to see in bits and pieces, like the proverbial blind men feeling the elephant. Their brains are not synthesizing the entire picture. Associative visual agnosics have difficulty to varying degrees in assigning meaning to an object. Even though they can, for instance, recognize differences in form between pictures of a pair of scissors and a paper punch by matching the scissors to a like pair in a display of office objects (with which an ap- perceptive agnosic would have difficulty), they have lost the link between the visual percept and the semantic meaning. In both cases, if shown a pair of scissors, neither the apperceptive nor the associative agnosic can correctly name “scissors.” But although the associative agnosic can pick out a pair of scissors, she or he shows difficulties not only in naming but in explaining or demonstrating the use for scissors.

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This distinction provides a useful conceptual frame- work and is used here; but in practice, the line between apperceptive and associative agnosias becomes cloudy, partly because the brain damage likely to cause these problems is often widespread and overlapping.

Apperceptive Agnosia—At first glance, those individuals, like Dr. P., with the apperceptive form of object agnosia may be thought blind, because they tend to take no apparent notice of objects and people in their vicinity. But on closer examination, their sensory functions are clearly intact. Many people with this condition are aware that they can indeed see, but they have a problem correctly perceiving things. Curiously, others with apperceptive agnosia are strangely unaware of their condition. Only watching for a period of time might you catch them stepping over or avoid- ing objects. Awareness in this case is not an either/or phe- nomenon. Apperceptive agnosics may appear to disregard or show no concern for their problem until neuropsycho- logical testing reveals it to them. For example, visual recog- nition tasks of the type shown in Figure 8.4, in which an object must be identified from fragments, is embedded, or is at an odd angle, are notoriously difficult. Apperceptive agnosics also have difficulty copying objects. Because they only “see” pieces, their drawings are likely to appear as a set of unconnected fragments focusing on the details rather than on the entire gestalt of the object.

The most common site of damage in apperceptive ag- nosia is the parieto-occipital area of the right hemisphere. Sudden insults to the brain are the most common cause, often from carbon monoxide poisoning, mercury intoxi- cation, cardiac arrest, or stroke. In these cases, appercep- tive agnosia does not usually occur in isolation without other visuospatial impairment, because these brain insults are likely to affect large areas of the cortex. Some cases of apperceptive agnosia are caused by bilateral cortical atro- phy. If both hemispheres are involved, then the patient may have Balint’s syndrome, which includes visual ag- nosia together with other visuospatial difficulties such as misreaching and left-sided neglect.

Associative Agnosia—Associative agnosia is differentiated behaviorally from apperceptive agnosia in that the pri- mary difficulty is a loss of knowledge of the semantic meaning of objects. Conceptually, the person can “recog- nize” objects at a perceptual level by picking them out, or correctly copying them, but perception breaks down at a higher level of meaning. For example, some people have little apperceptive difficulty and can draw or copy pictures of objects in great detail but cannot name them (for example, see Rubens & Benson, 1971). As Figure 8.5

shows, after making an accurate rendition of a bird, the patient tentatively guessed it could be a “beach stump.” This represents a pure form of associative agnosia, but many other patients also show aspects of apperceptive ag- nosia. For example, they may copy objects inconsistently, sometimes drawing them accurately and at other times making perceptual mistakes. However, whereas the per- ceptual mistakes of the apperceptive agnosic are likely to show inability to recognize the whole, the perceptual mistakes of the associative agnosic may show problems of either recognition of the whole or of the details of an object.

The research on the neurocorrelates of associative ag- nosia is confusing. A lateralized left hemisphere parieto- occipital lesion may be enough to cause an associative ag- nosia, although it can also occur in the presence of a unilateral right occipital lesion. Indeed, a number of struc- tural areas may produce associative agnosia. Farah (1990) suggests the variety of sites that produce associative ag- nosia may lead to heterogeneous perceptual impairments. Because assigning meaning is such a high-level cortical process, different lesion sites producing a similar effect also speaks to the complexity of the perceptual-meaning system. We would venture, as have others, that, in gen- eral, the left hemisphere assigns meaning, whereas the right hemisphere governs the global aspects of perceptual integration.

As stated earlier, many patients show both appercep- tive and associative aspects to their visual agnosia. For ex- ample, one artist who experienced a stroke resulting in bi- lateral medial occipital damage could name some objects but not others. Those he could name he could also draw well. But those he did not recognize, he could only mech- anistically copy, feature by feature, first a square, then a circle, then connecting lines, without any inkling of what they represented (Wapner, Judd, & Gardner, 1978). In summary, the differentiation between apperceptive and associative agnosia is useful for descriptive and conceptual understanding, but it does not correspond to strict anatomic correlates that can be readily differentiated or dissociated.

D i s o r d e r o f t h e “ W h e r e ” S y s t e m : N e g l e c t

Certain types of brain damage can alter body experience. Damage to the right parieto-occipital or inferior parietal area is the most common site of damage for an odd type of inattention termed unilateral neglect, or simply ne- glect. (Unilateral spatial neglect has other aliases, such as contralesional neglect, hemineglect, visuospatial or hemispa- tial agnosia, and visuospatial or hemispatial inattention.)

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Figure 8.4 Tests for apperceptive agnosia. Apperceptive agnosics have difficulty recognizing (a) fragmented objects, (b) entangled object, and (c) objects seen from unusual views. (Modified from Bradshaw, J. L., & Mattingly, J. B. [1995]. Clinical neuropsychology: Behavioral and brain science. San Diego: Academic Press, by permission.)

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People with neglect lose conscious awareness of an aspect of spatial or personal space despite adequately function- ing sensory and motor systems. Behaviorally, this prob- lem may first look like the result of a right hemisphere stroke or lesion affecting the motor and somatosensory strips on the contralesional side. The left limbs may ap- pear useless and hang limply. On closer examination, the arm or leg can clearly move and feel touch or pain—they are simply being ignored by the conscious mind. This fail- ure of awareness extends beyond the body to the entire left hemispace from the perspective of the afflicted person. It

is not unusual for people with neglect to collide with ob- jects and people on their left sides. Also, when reading, they may leave out the left side of words or pages. Their copied drawings focus on the right side of pictures. In one respect, neglect can be thought of as a forgetting or lack of con- scious attention to the left side; but even more so, it is as if awareness is being pulled to the right. When trying to nav- igate, neglect patients frequently veer rightward and end up traveling in circles. The case study in Neuropsychol- ogy in Action 8.3 gives an in-depth illustration of the behavioral manifestations of unilateral neglect. Although

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not in this case, many people with neglect think that the left-sided part of their body does not belong to them. Protesting that it belongs to someone else, they may fail to dress half of the body, put makeup on only one side of the face, or simply treat the neglected parts as objects with no personal meaning. What mechanisms disable body and spatial awareness? We will return to this question after considering the neuropathologic and clinical presentation of neglect.

Neuropathology of Neglect—The classic picture of unilateral neglect that we have been discussing is most likely to occur with lesions in the right inferior parietal lobe or generally in the posterior regions of the cortex. As men- tioned earlier, neglect cannot be solely attributed to sensory processing deficits, implying that lesions in the somatosen- sory strip are not enough to produce neglect. Neglect can

also appear with other right hemisphere lesions, and much less frequently, with left hemisphere lesions. Other right hemisphere locations reported to produce neglect include a variety of subcortical structures, the majority of which implicate the thalamus.

Classic neglect produces an abrupt alteration of con- sciousness most commonly occurring as a result of a right parietal stroke, but sometimes coinciding with a trau- matic brain injury. In any case, the manifestation is typi- cally sudden and rarely seen in slow-growing tumors or disease processes. Temporary and reversible neglect may also occur in conjunction with seizures, electroconvulsive therapy, and intracarotid sodium amytal testing (Wada testing) (see Bradshaw & Mattingly, 1995). Neglect may also stand out against the background of widespread right hemisphere damage. In this instance, there are accompany- ing motor, sensory, or attentional problems. For example, a

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One of the first cases of pure spatial ne- glect was published by Paterson and Zang- will in 1944. Their patient was a healthy 39- year-old right-handed man who, because of an explosion, was hit by a projectile steel nut that penetrated his skull in the right parietal occipital area. “Stereoscopic X- rays of the skull (28.9.43) showed a metal- lic foreign body consisting of a hexagonal nut about 1 in. in diameter with a shor t length of screw-headed bolt projecting from its upper lateral surface” (Paterson & Zangwill, 1944, pp. 335–336). “The upper borders of the supramarginal and angular gyri on the right side were damaged on the surface and their deeper connection inter- rupted by the in-driven bone fragments to a depth of just over 1 in. The lesion was circumscribed and there was minimal contusional damage” (p. 337). The resul- tant difficulties, as you would expect, were largely confined to spatial and visual- perceptual functions. This man could perceptually recognize objects, identify colors, and discriminate right and left. He

also had no problems in spatial depth perception and size constancy. But the patient himself aler ted his doctors that he was having trouble finding his way through the hallways on the way to the bathroom and was having trouble reading the time. He said he had to read each hand of the clock separately and then figure out the time. Staff observed him to collide “with objects on his left which he had clearly perceived a few moments before. He was liable at table to knock over dishes on his left-hand side and occasionally missed food on the left of his plate. He commonly failed to attend to the left-hand page in turning the pages of a book and reading lines of disconnected words commonly omitted the first word or two” (Paterson & Zangwill, 1944, p. 339). On neuropsychological testing, when asked to draw, his figures showed a “piecemeal perception” typical of right hemisphere spatial problems. Interestingly, he could slowly recognize objects placed in his left visual field, but if two designs were pre- sented simultaneously to the right and left

visual fields, he did not acknowledge the left-sided design. In setting the time on a clock, he often transposed the minute hand from the left- to the right-hand side. In a pointing task, the authors arranged objects around the patient in a semicircle. “He was instructed to point to each object in turn. With eyes open no errors were made. With his eyes closed, on the other hand, there was at once a general shift toward the right-hand side. Thus when asked to point to the object on his extreme left the patient often pointed straight ahead” (Paterson & Zangwill, 1944, p. 339). Unlike other cases of neglect, this man did not neglect the left side of his own body, only his extrapersonal space.

This case presents an interesting prob- lem of consciousness. How can this loss of awareness be explained? On one level, the patient was aware that he now disregarded the left side of space. This shows some insight into his problem. But on another level, no force of will could coax a full know- ing of his left-sided spatial world.

N e u r o p s y c h o l o g y i n A c t i o n 8 . 3

C a s e S t u d y : N e g l e c t

by Mary Spiers

variety of neglect-type problems are associated with motor weakness. In these cases, awareness of left-sided stimuli may be less impaired, but neglect-type symptoms become evident with the inability to perform or sustain motor acts on the side contralateral to the lesion (see Heilman, Watson, & Valenstein, 1993). If we include all the sub- types and derivations, we can best conceptualize neglect as a syndrome or general classification for a number of re- lated problems. However, we restrict this discussion to classical unilateral spatial neglect, caused by right hemi- sphere damage, which is the best example of the neglect phenomenon.

Clinical Presentation—In clinically evaluating cases of uni- lateral neglect, neuropsychologists must disentangle the contributions of spatial, motor, and attentional factors. This can only be done in a relative fashion, because each of these systems contributes a portion to a sense of body and spatial consciousness. For example, although investi- gators agree that a functioning attentional system is cru- cial to spatial awareness, unilateral neglect and severe inattention can be differentiated. With both problems there can be a failure to detect an object, such as an apple, that is placed in the left visual field. However, the inat- tentive person becomes aware of the apple if forced to orient to it, whereas the person with neglect may con- tinue to insist that nothing is there. Neglect is also disso- ciable from visual field defects such as hemianopia, in which the person visually explores the left side of space (Hornak, 1992). Neglect may look similar to visual prob- lems, but it is actually a problem at a much higher level of integration.

Because neglect is so obviously out of the range of or- dinary experience, measures to test for it do not rely on norms, but rather on pathognomic signs. For example, we do not expect neglect to be evenly distributed in the population in the form of a bell-shaped curve, with only a few of us having no neglect, many of us having moder- ate neglect, and a few of us having profound neglect. In- stead, we expect all people with normally functioning brains to be free of neglect. Therefore, the detection of neglect and neglect-like symptoms is fairly straightfor- ward by observing performance on tasks such as drawings and line bisection tasks. Figure 8.6 shows several clinical examples of neuropsychological tasks performed by peo- ple with neglect. Notice that in the drawings the left side of the picture may be left out, sparse, or grossly distorted. In the line bisection and line cancellation tasks, the mid- point shifts to the right, leaving the left side of the line or the page empty.

It is clear that unilateral neglect patients do not con- sciously acknowledge stimuli in the left side of space. But does perception or a tacit recognition at an unconscious level exist? Clinical investigations suggest that it does. In an interesting series of studies, Vallar and his colleagues (Vallar, Sandroni, Rusconi, & Barbieri, 1991) tested au- tonomic responses such as galvanic skin conductance and brain response via evoked potentials. In each case, the pa- tients with unilateral left-sided neglect failed to con- sciously recognize the presence of a stimulus presented to the right side, although autonomic testing demonstrated the patients were processing the stimulus implicitly at a preconscious level, without reaching awareness. Some clinical studies also suggest that people with neglect may implicitly process at a higher level, indicating acknowl- edgment of meaning or semantic awareness. In one of the first case studies to suggest implicit awareness in neglect, Marshall and Halligan (1988) gave their patient two pic- tures of a house, identical except for that in one the left side of the house was obviously burning. The patient did not acknowledge any discrepancies between the two houses when asked to describe the pictures, nor did she say they were different when forced to make a same– different choice. Curiously, however, when asked which house she would prefer to live in, she consistently chose the picture of the house that was not burning, although she could not explain or give reasons for her choice. It is as though, from her perspective, the only explanation she could give relied on an intuitive sense. Although not all neglect patients show this preservation of semantic knowl- edge (some actually chose the burning house; see Bisiach & Rusconi, 1990), studies using a variety of methodolo- gies confirm that higher order processing of various types is possible in some patients with neglect (see Bradshaw & Mattingly, 1995).

Interestingly, the behavior of left unilateral neglect usually resolves somewhat over time if the damaged area remains stable. Afflicted people gradually begin to ac- knowledge stimuli on the left side of their bodily space. Tests of tactile recognition, in which the researcher touches one hand or the other while the patient is blindfolded, show that he or she is recognizing both hands. However, when both hands are touched at the same time in a specific test of double simultaneous stim- ulation, residual neglect is often evident in that the pa- tient again suppresses or extinguishes perception of the left hand.

Neglect, as can be imagined, is notoriously difficult to treat in the beginning stages. Patients who do not ac- knowledge their problem and who may believe their left

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side does not even belong to them are not motivated to pay attention to their left side. Rehabilitation methods often try to direct attention to the neglected side. Thera- pists may use various methods such as forcing attention to the left side via gradual movement of objects to the left, or even through the use of prism glasses. These methods do meet with some success, but often do not generalize to daily life.

Theories of Neglect—Two primary issues exist in conceptual- izing neglect. The first issue is understanding the asym- metric presentation of neglect between the two hemi- spheres. Why is neglect more prevalent with right hemisphere lesions? Any theory of neglect must explain why the overwhelming majority of cases show left-sided neglect, and why right-sided neglect is so rare. The second issue relates to the higher order or “conscious” processing

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problem that is neglect. If neglect is thought of as a net- work problem rather than as a dysfunction of an individ- ual system, it is easier to make sense of the variety of le- sion sites that may produce neglect.

Research has established that the right hemisphere is more specialized for global spatial processing, whereas the left hemisphere has a propensity for decoding spe- cific spatial features. Because the right hemisphere, and particularly the right parietal lobe, plays a role in under- standing the gestalt or totality of space, disruptions there are more likely to upset global spatial awareness. Also, the right hemisphere plays a larger role in arousal and at- tentional levels, which are prime factors in many explana- tory models of neglect. However, each of these problems can occur in isolation without the patient losing con- sciousness of the left side of space. As with the man de- scribed in Neuropsychology in Action 8.3, no force of will could coax a “knowing” of his spatial world on the left. Interestingly, it appears that patients may shift their “spatial axis” to the right so that midline is pulled or repositioned within the right side of space relative to the body (Mattingly, 1996). Marcel Kinsbourne (1993) has postulated that this strong rightward orientation is less a function of right hemisphere dysfunction per se than a release of inhibition that lets the left hemisphere assert dominance in the presence of a now weakened right hemisphere. Perhaps some of the prime areas damaged, rendering the right hemisphere spatially ineffective, are locations within the right parietal lobe having to do with personal spatial frames of reference. Body position with respect to space is always egocentric, although peo- ple may have multiple frames with respect to bodies, heads, or position in relation to environment. Animal studies support the contention that there are distinct neuronal centers for these spatial frames within the right parietal cortex (for example, see Anderson, Snyder, Li, & Stricanne, 1993).

Do these findings explain why the midline shift in neglect is nearly always to the right? Bradshaw and Mattingly (1995) suggest that each hemisphere plays a specific role in spatial body position processing. The left hemisphere focuses on features and is strongly right- ward oriented. The right hemisphere takes a “global view.” Normally, the two hemispheres hold each other in balance, but when certain spatial positioning aspects of the right hemisphere are damaged, the left hemi- sphere becomes overbearing, forcing a reorientation to the right side of space. According to this view, damage to the left parietal lobe produces no corresponding left- ward shift because the spatial concerns of the left hemi- sphere are more feature oriented and language focused,

resulting in a “no specialized spatial position” sense within the left parietal lobes. If right neglect does occur, they suggest, together with other investigators (such as Ogden, 1985), that the focus of the left hemisphere le- sion would be anterior to the parietal lobes. Unfortu- nately, partly because of the rarity of occurrence, no re- search has explained the mechanisms of right-sided neglect.

Understanding neglect is not only a problem of dom- inance and asymmetry, it is also an issue of conceptualiz- ing the problem as a higher order network processing phenomenon. That unilateral neglect can occur with other nonparietal foci of damage is partial testament to this claim. We mentioned earlier that the region of the right inferior parietal lobe is the area most commonly damaged in cases of left unilateral neglect. As in other dis- orders discussed throughout this book, however, absence of function associated with a lesion does not necessarily imply that the lesioned area “contains” the function. Just as the hippocampus does not “contain” or store memory but is one of the most crucial links in memory processing and consolidation, the right inferior parietal lobe does not in itself contain “body mindfulness” but may be a crucial link. Neuroanatomically, left unilateral neglect also oc- curs with damage to a variety of subcortical structures, most notably the thalamus (see Bradshaw & Mattingly, 1995). It is reasonable to speculate that neglect results from a disconnection in higher order processing that in- volves the coordination of many second-order systems, such as visual processing, attention, memory, and possi- bly other systems.

A number of theories attempt to provide models for unilateral neglect. They are beyond the scope of this overview, and excellent reviews exist elsewhere (for ex- ample, see Bradshaw & Mattingly, 1995). Most models describe the process of body and hemispace cognition as including visual-perceptual processes, attention, and motor action. Mesulam’s neural network model (for ex- ample, see Mesulam, 1985, 1990) is closely tied to neu- roanatomic functioning. He identifies three major func- tional areas that must interact for the body–space system to work normally. Each of these areas corre- sponds to a cortical site. The parietal lobes control per- ceptual processing, the premotor and prefrontal cor- tices mediate exploratory-motor behavior, and the cingulate gyrus directs motivation. In turn, subcortical structures probably coordinate the orchestration of all three areas. The reticular formation directs arousal, and the thalamus (particularly the pulvinar of the thalamus) is postulated to focus and guide attention between spa- tial locations.

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Summar y—The visual processing system reflects both the complexity and the reliance of humans on our visual sense. We discussed both features and streams of visual processing. The primary visual system, which serves as a “feature analyzer,” builds to the higher order systems of object recognition and spatial localization. Disorders such as visual agnosia and neglect provide good examples of how each of these systems may malfunction. However, with vision, there is much reciprocal networking between parallel systems, so what appears hierarchical may not be entirely so. What is discussed in a bottom-up fashion may also be affected by top-down processing. Currently, brain science has uncovered much of the structure and many of the functions of the visual road map through the brain. However, much work needs to be done in understanding how the brain accommodates to varying visual experi- ences that represent the same precept. With an expansion of functional imaging techniques, a better understanding of high-level integration of the fragmentary components of visual processing is occurring, especially in visual disor- ders, in which integration may be a product of systems beyond the visual system.

Auditory and Language Processing

The human auditory system is a crucial sensory sys- tem, because it is the pathway to language, a uniquely human development. This section examines the brain’s control of auditory processing, speech, and language by exploring the brain structures believed to be principal in language functioning. Because no animal models of lan- guage exist, much knowledge of the neuropsychology of language links closely to knowledge about the behavioral effects of aphasia subtypes. Reliance on brain-damaged patients to delineate systems can be tricky because lesions may not indicate site of damage, and many aphasics are stroke patients with a fairly wide area of damage.

P R I M A R Y A U D I T O R Y P R O C E S S I N G

Humans can detect a wide range of sound from the 30-Hz to the 20,000-Hz range. Difficulties in detecting the fea- tures of sound, such as how long a vowel versus a conso- nant sound might resonate, can result in higher level language disturbance. One theory of autism considers the idea that autistic people may not be tuned in to the frequency of human speech, but instead have a propen- sity for lower frequency environmental sounds such as

those made by machines. If human speech is an aversive and even fear-producing noise, then there would be a withdrawal from the sound of human speech. Many dif- ficulties can emerge if the primary building blocks of sound detection and recognition are not intact.

The auditory system contains mechanical receptors de- signed to detect sound frequency. These hairlike receptors are located in the fluid of the long, coiled, snail-like cochlea of the inner ear. As the mechanical mechanisms of the middle ear respond to external sound waves, they cause vibrations in the fluid of the inner ear, thus vibrating the hairs of the auditory receptors. These receptors synapse with the auditory nerve. The auditory nerve from each ear projects ipsilaterally to the cochlear nuclei of the medulla. From there, each pathway branches to project auditory information to both the ipsilateral and contralat- eral superior olivary nuclei of the medulla. In this way, the auditory system differs from the visual system in that each hemisphere receives input from both ears, resulting in bilateral representation of sound. This may help the person localize sound in space. The auditory pathways then course through the lower brainstem and ascend through the thalamus, where they are projected to the pri- mary auditory cortex (Figure 8.7).

The primary auditory cortex of each hemisphere lies deep within the temporal lobe, largely on the medial as- pect of the superior temporal gyrus, within the valley of the lateral fissure. This area is commonly termed Heschl’s gyrus and corresponds to Brodmann’s area 41. Heschl’s area is often larger in the right hemisphere, sometimes consisting of two gyri to the left’s one gyrus. This corti- cal area processes the “fragments” of sound, much as the visual system processes individual visual stimuli. The primary auditory cortex is organized into frequency- specific bands that parallel the layout of auditory frequency ranges mapped on the cochlea (see Figure 8.7). In this way, a tonotopic map projects onto the audi- tory cortex, similar to the retinotopic map of the visual system. Because the cortical bands can respond to multiple frequencies, there is no strict one-to-one correspondence; rather, some bands are more attuned to certain frequencies than others. The primary auditory cortex processes several elements of sound. In addition to frequency, the features of sound include loudness, timbre, duration, and change.

H I G H E R A U D I T O R Y P R O C E S S I N G : S P E E C H A N D L A N G U A G E

Speaking requires the ability to differentiate between speech sounds, or phonemes, such as vowels and consonants. For

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example, in French, the brain must hear the fine distinc- tions between the pronunciations of tu and tous, the sounds of which are not differentiated in English and only heard as too. Vowels have a slightly different frequency from consonants, and different consonants are differenti- ated from each other. Speech also requires the ability to

produce intelligible speech output. Learning a language, as anyone who has tried to master a second language knows, involves much more than being able to understand and articulate words in a spoken fashion. Language also re- quires putting meaning to word fragments (morphemes), words, and groups of words (semantics). Another major

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Figure 8.7 Pathway from the ear to the primary auditory cortex. (a) Each ear projects to the ipsilateral cochlea, and then projects to the primary auditory cortex in both hemispheres. (b) The primary auditory cortex is organized according to a tonotopic frequency map. ([a] Reproduced from Kalat, J. W. [1998]. Biological psychology [6th ed., p. 184, Figure 7.6]. Pacific Grove, CA: Brooks/Cole, by permission; [b] modified from Bear, M. F., Connors, B. W., & Paradiso, M. A. [1996]. Neuroscience: Exploring the brain [p. 303, Figure 11.28]. Baltimore: Williams & Wilkins.)

Auditory cortex

Medial geniculate

+ + ––

Superior olive

Signal from right ear

Inferior colliculus

Cochlear nucleus

Signal from left ear

a. Primary auditory cortex

Primary auditory cortex

Secondary auditory cortex

requirement of language is knowledge of its syntax or grammatical rules. This requires learning information regarding subject–verb agreement (for example, “girls run”), how to use articles and propositions (for example, the, to, but, if, and ), and how to put strings of words to- gether to make meaningful sentences.

After the primary auditory cortex processes sound fea- tures, they are integrated into understandable speech sounds in the secondary auditory processing area com- monly known as Wernicke’s area. Wernicke’s area lies on the posterior aspect of the superior temporal gyrus (see Figures 8.7 and 8.8). It includes the secondary auditory cor- tex and does not technically involve the adjacent primary auditory cortex (Heschl’s gyrus). The secondary auditory processing area serves to connect sound from the primary auditory areas to word meaning stored in the cortex. This is an intermediate step to the full understanding of lan- guage. Additional cortical processing areas are required to integrate the comprehension of individual words into grammatically correct phrases and sentences, and to link spoken words with the written symbols of language nec- essary for reading comprehension. The supramarginal and angular gyri of the inferior parietal lobes are contiguous

to Wernicke’s area, and the two are closely integrated. These higher association areas serve to bring together vi- sual and spatial information from the occipital and pari- etal lobes with auditory information. The angular gyrus plays a role in reading comprehension by matching words and word sounds (phonemes such as the sound of /ba/) to written symbols of language (graphemes such as b).

Damage to the left hemisphere auditory processing areas results in the partial or total inability to decipher spo- ken words. This condition is known as receptive aphasia, or Wernicke’s aphasia. However, people with receptive aphasia can often still recognize the emotional tone of lan- guage, because the speaker’s intent, such as anger, sarcasm, or humor, is processed as voice intonation. Conversely, right hemisphere damage has the opposite effect: The pa- tient accepts words at face value but loses the nuances of jokes and emotional intention. Another hallmark of right hemisphere damage is impaired harmonic and melodic ability. The ability to appreciate musical tunes may be completely eliminated. As an example of a problem with recognition of environmental sounds, one patient with a right hemisphere auditory processing deficit repeatedly had to have starters replaced in her car. She could no

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Figure 8.8 Major cortical language areas. In most people, the left frontal operculum, or Broca’s area, is specialized for speech production, whereas Wernicke’s area is specialized for speech comprehension. (Reproduced from Kalat, J. W. [1998]. Biological psychology [6th ed., p. 390, Figure 14.13]. Pacific Grove, CA: Brooks/Cole.)

Broca’s area

Sylvian or lateral fissure

Wernicke’s area

Visual cortex

Supermarginal gyrus

Angular gyrus

longer discriminate the difference in sound between the sound of the starter engaging and the sound of the engine turning over. Speech understanding, therefore, conveys word analysis, as well as emotional intentions, through tone of voice, pitch, intensity, and rhythm.

Expressive speech links to the frontal operculum (Broca’s area), located in the left frontal lobe on the poste- rior portion of the third frontal gyrus (the inferior frontal gyrus). This area is adjacent to the facial area of the motor cortex. The inferior frontal gyrus is a premotor area of the frontal lobes, and thus is concerned with aspects of speech planning before output coordinated by the nearby motor strip. In addition to mediating the fluency of speech, Broca’s area plays a role in the grammatical and syntacti- cal arrangement of words. Wernicke’s and Broca’s areas are linked by a band of white matter fibers called the ar- cuate fasciculus. This allows for close communication be- tween the two areas in expressive output. Words, whether from external sources or from the self, are picked out for meaning in Wernicke’s area, and in parallel, the syntax of the phrase is constructed in Broca’s area. This is possible because the arcuate fasciculus permits reciprocal interac- tion between the two areas (Yeterian & Van Hoesen, 1978). This interaction also makes logical sense, because syntax depends on the words used and the words selected also de- pend on the emerging syntax of the sentence (Bradshaw & Mattingly, 1995).

The basal ganglia and the thalamus have also been im- plicated in language functioning via their participation in a cortico-striato-pallido-thalamo-cortical loop (see Crosson, 1992). This loop, or perhaps set of loops, con- nects the language centers of the cortex to the putamen and caudate nucleus of the striatum, to the globus pallidus, to specific nuclei in the thalamus, and back to the cortical language centers. The current thinking regarding the func- tion of these loops is that they play a role in regulating lan- guage; this role involves initiating language production more than constructing speech content (Crosson, 1992).

One hemisphere, usually the left, is dominant for speech. This means that the left cerebral cortex prefer- entially processes speech sounds, whereas the right processes nonspeech sounds. Not surprisingly, the func- tional dominance of the left hemisphere for speech cor- responds to preferential treatment for speech sound pro- cessing in the larger planum temporale of the left hemisphere. After analysis of sound features, secondary auditory information, such as phonemes, is integrated in the planum temporale, in the temporal area adjacent to the primary auditory cortex (Brodmann’s area 42). Although sound from each ear projects bilaterally, there

is an opposite hemisphere advantage; in this case, the left hemisphere preferentially processes sound from the right ear. Because the left hemisphere shows a preference for analyzing speech in most people, speech sounds processed through the right ear will be understood faster and more accurately than speech sounds processed through the left ear.

The left hemisphere also has a propensity for rhythm of both speech and music as it codes for the sequence of sounds. To check your left hemisphere dominance for rhythm, try keeping a metronome-like beat with your left hand and beat out the rhythm of a familiar tune, such as Jingle Bells, with your right hand. Most people find this easy if their left hemisphere, which controls their right hand, is dominant for rhythm. After doing this, try reversing what each hand is doing (right keeps the beat, and left taps out the rhythm) and see if you have more or less difficulty. The secondary auditory cortex of the right hemisphere, by contrast, is specific for aspects of tonality, including the melody of music and the intonation of speech, which is commonly referred to as speech prosody. The right hemisphere is adept at recognizing the relation between simultaneous sounds, such as the harmony of chords, or the musical interval between notes. It also shows an advantage for recognizing nonspeech or environ- mental sounds such as those made by machines and cars, as well as animals, birds, the pounding ocean surf, or a bab- bling creek.

The brain’s asymmetry for language processing and production is an extension of speech processing. The left hemisphere specializes in processing word sounds, or morphemes; semantics; and the grammatical rules of language. The right hemisphere, long thought to be “mute,” plays a role in the emotional intention of both vocalization and understanding. The right hemisphere may have no speech or understanding of grammatical rules; however, a number of people, and more women than men, have some bilateral representation of speech. The right hemisphere is nonetheless capable of consider- able comprehension and expression. Although frank aphasia is rare after right hemisphere strokes, there can be linguistic impairments. These include a deficit in com- prehending tone and voice, producing similar emotional tone, and understanding metaphors and jokes. We once examined a male adult patient who had undergone a com- plete left hemispherectomy. Although he was severely aphasic, he could communicate somewhat using “grunts.” He was also able to curse, possibly because such commu- nication is more emotional in nature and, therefore, partly controlled by the right hemisphere.

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In summary, the complexity of speech and language necessitates specific brain systems, which in most people are lateralized. Beyond the discrete cortical components controlling auditory reception (auditory cortices and Wernicke’s area) and auditory speech production (Broca’s area and motor cortex), language requires thought and, therefore, extensive interconnections to higher order planning and memory centers. The supramarginal gyrus and the angular gyrus of the parietal lobes are also im- portant to integrating verbal aspects of language with the visual symbolic components involved in reading. Subcortical neural connections, including portions of the basal ganglia and the thalamus, also play a role in lan- guage. Finally, cerebral lateralization exists for various lan- guage functions.

A P H A S I A : A B R E A K D O W N O F L A N G U A G E

Aphasia is a disturbance of language usage or comprehen- sion. It may impair the power to speak, write, read, gesture, or to comprehend spoken, written, or gestured language. Aphasia is a disturbance connecting speaking to thinking, and thus is differentiated from purely mechanical disor- ders of speech such as dysarthria or speech apraxia caused by paralysis or incoordination of the musculature of the mouth or vocal apparatus. Aphasic disorders also do not include pure mutism, that is, disturbances of lan- guage caused by severe intellectual impairment or loss of sensory input (such as deafness or inability to see words). Aphasias are most frequently caused by vascular disorders such as stroke or by tumor or brain trauma. Although cor- tical damage to the frontal and temporal areas of the left hemisphere causes most aphasias, damage to subcortical

structures of the basal ganglia (specifically the corpus striatum) and the thalamus has also produced aphasia.

The two major types of aphasia are commonly referred to as Broca’s aphasia and Wernicke’s aphasia. Other classi- fications, subtypes, and combinations exist that may con- tain slightly different features or a mixture of some fea- tures of these two types (see Table 8.1). In seeing aphasia patients, it is quickly evident that few patients fit neatly into one classification or the other. This is not surprising, because brain lesions and preexisting brain anatomy for language varies among individuals, most notably between men and women. Many clinicians find it most useful to describe the features of the aphasia in behavioral terms, describing aphasia according to degree of fluency and the nature of the expressive and receptive problems involved. Fluent aphasia is characterized by fluent spontaneous speech with normal articulation and rhythm, or fluency in the repetition of words, phrases, or sentences. Nonflu- ent aphasia is difficulty in the flow of articulation, so that speech becomes broken or halting. Expressive aphasia is a disorder of speech output. Receptive aphasia implies a difficulty in auditory comprehension.

Often, patients experience not only a loss of spoken lan- guage but also a loss of written language and reading com- prehension. Writing is one of the most complex language abilities. If it is disturbed as a result of impairment of the limb to produce letters and words, the disturbance is not thought to be a disorder of language. Rather, words, letters, or numbers may appear foreign or incomprehensible be- cause of an inability to recall the form of letters. Attempts at writing may be filled with real or imagined letters that make no sense to others. With time and training, the per- son may be able to understand simple written language (for

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Type of Aphasia Fluency, Content Repetition of Speech Comprehension of Speech Reading and Writing

Broca’s Confluent, agrammatical Impaired Normal Agrammatical, misspelling

Wernicke’s Normal, word salad Abnormal Poor Inaccuracies

Conduction Normal fluency, phonemic errors Abnormal Relatively intact Abnormal

Transcortical motor Halting Fluent Normal Reading normal, writing impaired

Transcortical sensory Normal Normal Poor Inaccuracies

Anomic Normal fluency, Normal Normal Normal word-finding errors

Global Abnormal Abnormal Abnormal Abnormal

Table 8.1 Aphasia Types

example, single words such as bath or food ) but not more complex written language, such as sentences or para- graphs. The extent of the recovery in this and other areas largely depends on the degree of damage. Because reading comprehension is based on prior mastery of auditory lan- guage, deficits in reading (alexia) often accompany deficits in auditory comprehension. As with auditory defects, im- pairment in visual comprehension may involve a deficit in recognizing individual letters or words as being letters or words, or an impairment in attaching the correct meaning to the symbols written on a page. Deficits in writing are most often associated with lesions to the an- gular gyrus, a cortical association area that provides cross- modal integration of visual, tactile, and verbal informa- tion. Reading deficits (alexia) are frequently related to lesions of the left fusiform and lingual areas.

B r o c a ’ s A p h a s i a

Broca’s aphasia is an expressive, nonfluent aphasia charac- terized by difficulties in speech production but relatively adequate auditory verbal comprehension, as evidenced by the ability to follow spoken commands (such as, “Point to the cup”). Many forms of disorders of production exist, which can range from an inability to form words to an in- ability to place words together to form a spoken or writ- ten sentence. In simple expressive aphasia, the person knows what he or she wants to say but cannot find the words to say it. It is like continually experiencing a situa- tion in which the word or words are on the tip of the tongue but are not quite connected to thought.

In mild cases of anomia, or word-finding difficulties, only a word or two here and there is lost, and the commu- nication can proceed quite normally. In more severe cases, most or all words can be lost. This problem in word find- ing is one that virtually all expressive aphasics suffer. Even when the person produces words, he or she takes longer than normal to do so. Difficulty in finding a word often results in the person’s deliberately “talking around” a word that approximates the intended idea when he or she can- not find the intended word. For example, an aphasic might say, “I looked through that long pipe thing at the stars” (that is, a telescope). Aphasics may also make phonetic or like-sounding errors, such as “I looked through that tele- phone at the stars,” or semantic meaning–related errors, such as “I looked through that barometer at the stars.”

Another problem experienced by many Broca’s apha- sics is one of articulation, or the ability to form phonetic sounds of vowels and consonants, which then are placed in different combinations to form words and sentences. People with severe deficits in articulating words often can- not produce simple sounds, even by imitation. If the

deficit in articulation is related to a motor impairment of the mouth, tongue, larynx, or pharynx, then it is not aphasia. The aphasic impairment is marked by the per- son’s confusion or deficit in choosing the desired sound from all those available in his or her repertoire. This some- times results in unintended strange-sounding syllables, words, or phrases (phonemic paraphasias) during the ef- fort to speak, or in noises being produced rather than lan- guage. Those with Broca’s aphasia may also show poor pronunciation and inappropriate speech rhythm, mani- fested by dysarthria, stuttering, and effortful speech.

Broca’s aphasia most commonly occurs with lesions to the frontal operculum, but typically also includes lesions to the motor cortex (precentral gyrus or motor strip) and underlying white matter and subcortical structures of the basal ganglia. Aphasia appears to resolve quickly if the frontal operculum is the only structure involved, but it tends to be more persistent the more surrounding struc- tures are damaged (Bradshaw & Mattingly, 1995).

W e r n i c k e ’ s A p h a s i a

Wernicke’s aphasia is a receptive, fluent aphasia. This im- plies reduced comprehension of spoken language with the continued ability to produce speech. If you stop to imagine this odd situation, you can see that Wernicke’s aphasics, in addition to not understanding what others say, may not be able to understand what they themselves are saying. This problem contributes to speaking in the form of a word salad of unconnected words and word sounds. This feature of Wernicke’s aphasia is a deficit in putting words together in proper grammatical and syn- tactical form. This condition, more formally known as paragrammatism or extended paraphasia, refers to run- ning speech that is logically incoherent, often sounding like an exotic foreign language. That is, the speech of a person with Wernicke’s aphasia flows forth without hesi- tation and has appropriate intonation. Appropriate social interaction, such as speaking in turn and gesturing ap- propriately, remains intact. However, the words and phrases spoken are meaningless. Wernicke’s aphasics usu- ally do not realize their spoken language is meaningless to others (anosognosia for speech). It is as if they know exactly what is to be communicated, but their delivery is incoherent.

In mild cases of Wernicke’s aphasia, only a word or two here and there sounds garbled or incomprehensible. In this case, communication can generally proceed because the person is able to grasp the essence of the intention based on the context within which the communication takes place. With moderate disability, the patient can under- stand part, but not all, of the communication. In severe

220 PART TWO | The Functioning Brain

CHAPTER 8 | Vision and Language 221

cases, the patient may experience most or all speech as if it were nonsense syllables or a foreign language. It is not un- common for others to misattribute behavior problems to people with receptive aphasia. Sometimes noncompliance is actually caused by the fact that the patient has misun- derstood the communication in the first place. Thus, a pa- tient may act as though a word was not heard at all (so- called word deafness) or as though only fragments of the word were heard. The most common defect, however, lies not in failing to recognize that a word was spoken, but rather in failing to attach meaning to the word. In some aphasics, comprehension of individual words is intact, but grammatical constructions are not.

Damage in Wernicke’s aphasia includes the secondary auditory cortex (Wernicke’s area) and some involvement of surrounding structures. These often include the supra- marginal and angular gyri and portions of the middle temporal gyrus.

O t h e r A p h a s i a S u b t y p e s

The classification of aphasias into receptive and expressive is a useful didactic tool, but many people with left hemisphere lesions have a combination of both symptoms, because of damage to the left middle cerebral artery, which serves both expressive and receptive areas. This section briefly reviews the symptoms of the various subtypes of aphasia beyond the more common Broca’s and Wernicke’s aphasias. Table 8.1 summarizes the behavioral features of the aphasias.

Conduction Aphasia—The behavioral hallmark of conduction aphasia is a problem in repeating what others say. This problem, obviously, may not become apparent except on formal testing. In ordinary conversation, expressive speech is fluent but marked with phonemic paraphasias, or er- rors of word usage of similar-sounding words (such as using the word bark for tarp). Comprehension is relatively well preserved but may suffer from minor errors. Reading aloud and writing are frequently impaired. Neuroanatom- ically, conduction aphasia is a result of separation of Broca’s area from Wernicke’s area by damage of the arcuate fasci- culus, the connecting white matter fibers between the two areas. The damage may also include lesions to the poste- rior portions of the lateral fissure responsible for aspects of

reading and writing, specifically the supramarginal and an- gular gyri.

Transcortical Motor Aphasia—Clinicians can recognize transcor- tical motor aphasia by the patient’s halting, nonfluent spontaneous speech; oddly, however, speech becomes flu- ent if the person merely repeats what another says. In many respects, except for the differences in repetition abil- ity, this deficit resembles Broca’s aphasia. Speech compre- hension is unimpaired and writing may also suffer. Read- ing comprehension, however, is generally intact. Lesions to the area anterior or superior to Broca’s area are associ- ated with this aphasia type.

Transcortical Sensory Aphasia—Severe speech comprehension deficit marks transcortical sensory aphasia. Interestingly, de- spite being unable to comprehend speech, such aphasics can adequately repeat phrases and sentences presented to them. Lesions in the angular gyrus are the most likely culprits for this aphasia; thus, reading and writing are also affected.

Anomic Aphasia—A problem in word finding, or anomia, is the primary, and often only, difficulty in anomic aphasia. This aphasia is a frequent result of widespread brain im- pairment caused by conditions such as traumatic brain injury and dementias such as Alzheimer’s disease. As peo- ple age, an annoying concomitant often reported is a dif- ficulty in remembering people’s names or being unable to retrieve a word that is just on the “tip of the tongue.” The act of “word finding” seems to be one of the most easily affected aspects of expressive language. Witness even the problem of being “speechless” with anxiety. It is difficult, therefore, to distinguish what might be a temporary word- finding difficulty and a true aphasia.

Global Aphasia—Global aphasia is the most devastating of the aphasia subtypes because of its profound effect across all areas of speech functioning. There is marked disability in speech production, as well as speech comprehension. Reading, writing, and repetition are also impaired. This aphasia is caused by a massive lesion encompassing major portions of the left hemisphere.

Summary The visual and auditory systems are two of the most important sensory systems for humans. Visual pro- cessing covers a wide cortical area beyond the occipital lobes when the meaning of visual material is considered. Likewise, auditory processing, because it also includes understanding and expression of the

222 PART TWO | The Functioning Brain

meaning of language, spreads out in a web that encompasses large portions of the cortex. One can con- ceptualize sensory-perceptual processing as a bottom-up process of sensory logic, because in each do- main the brain seeks to make “sense” of incoming information. But, it is becoming more evident that we impose perceptions on sensory information from the top down as well. A fundamental question of con- sciousness is how the brain constructs perceptions of integrated wholes, such as an orange, for which you integrate the visual features with the smell and taste. Brain scientists are beginning to ask how the dis- parate local elements bind to form a unified experience. This is referred to as “the binding problem of consciousness.”

A question related to the binding problem concerns how the brain accesses meaning. Some argue that meaning is specific within each sensory system. In other words, there exists a specific visual mean- ing, auditory meaning, or even olfactory meaning. If this meaning is lost, as in various sensory agnosias, the ability to access it through another sensory modality would be impossible. In discussing the senses, it is quickly evident that basic sensory perception is anatomically and functionally distinct. However, meaning lost in one sensory modality can often be accessed through another. Exactly how an integrated sense of meaning emerges remains unclear. Local interconnections may exist between sen- sory cortices or some sort of central integrative multimodal processor that allows multiple access from the sensory systems. Chapter 16 evaluates the problems of binding and how the mind constructs meaning. Neuropsychology and neuroscience are still wrestling with the larger questions of how this system operates. Functionally, however, knowing that sensory-perceptual agnosias are modality specific lets rehabilitation professionals seek alternative “routes” for accessing meaning when one system is damaged.

C r i t i c a l T h i n k i n g Q u e s t i o n s

What does the neuropsychology of sensory-perceptual processing have to contribute to the idea that there is an objective reality related to object perception? How might it be possible to imagine or conjure up images in a sensory domains despite a lack of sensory input? Can one be “conscious” in one sensory domain but not in another?

K e y Te r m s

Decussating Anopia Homonymous Hemianopia Striate cortex Secondary association or

Prestriate cortex Blindsight Achromatopsia

Akinetopsia Visual agnosias Visual object agnosia Prosopagnosia Apperceptive visual agnosia Associative visual agnosia Balint’s syndrome Tonotopic map Wernicke’s area

Receptive aphasia or Wernicke’s aphasia

Frontal operculum Aphasia Dysarthria Speech apraxia Fluent aphasia Nonfluent aphasia Expressive aphasia

Anomia Articulation Word salad Paragrammatism or extended

paraphasia Phonemic paraphasias

We b C o n n e c t i o n s

http://serendip.brynmawr.edu/bb See the exhibits related to vision: blindsight, blind spot, and tricks of the eye.

http://neuro.caltech.edu/~seckel Home page of illusions, perception, and cognitive science.

http://serendip.brynmawr.edu

http://neuro.caltech.edu

http://www.eyetricks.com This site includes tons of optical illusion galleries, three-dimensional images, and brainteasers.

http://www.aphasia.org This site provides information on aphasia from the National Aphasia Association.

http://www.nidcd.nih.gov/health/voice/adultaphasia.asp This site provides information on aphasia from the National Institute on Deafness and Other Communica- tion Disorders.

CHAPTER 8 | Vision and Language 223

http://www.eyetricks.com

http://www.aphasia.org

http://www.nidcd.nih.gov

Chapter 9

M E M O RY, AT T E N T I O N , E M OT I O N , A N D E X E C U T I V E F U N C T I O N I N G

It is abundantly obvious here that for longer than we can tell, the truth is immeasurably greater than all the tiny fragments we have so far been able to discover.

—Attributed to Pavlov by Luria (1947)

Everything should be made as simple as possible, but not simpler. —Attributed to Albert Einstein

Memory Systems Attention Executive Functioning Relation of Memory, Attention, and Executive Function Neuropsychology of Emotional Processing

Neuropsychology in Action

9.1 Amnesia: The Case of N.A. 9.2 Executive Function Tasks 9.3 The Case of Phineas Gage

CHAPTER 9 | Memory, Attention, Emotion, and Executive Functioning 225

Overview This chapter is devoted to higher functional systems that are not specific for sensory modalities. Language and visual perception (see discussion in Chapter 8) are also considered higher functional systems because their full expression depends on additional functional systems such as memory, attention, and executive functioning. However, language and visual perception emerge from sensory-perceptual systems; thus, it is easier to follow their progression when they are discussed with these systems. The sensory and motor systems represent the building blocks on which other systems are constructed and the raw material from which other systems draw; they are the most straightforward and best mapped systems. The systems we discuss in this chapter are integrated with the sensory-perceptual and motor systems but do not depend on any one modality. We refer to the systems here as higher order systems because, evolutionarily, the expres- sion in humans is complex and highly integrated. Most of these systems can be thought of as background management systems. Their functions are important for learning, organizing, setting priorities, planning, self-reflection, and self-regulation.

The systems discussed in this chapter include the classic systems or modules of cognitive neuropsy- chology, namely memory, attention, and executive functioning. In addition, we consider the brain and mind expressions of emotional processing. For each system, we discuss the conceptual organization of the sys- tem, as well as known structure–function relations.

K e e p i n M i n d

What integrative and management functions do higher systems serve?

If short-term memory is impaired, can information be learned and consolidated into storage?

What are the similarities and differences of the models of attention?

Is there a cognitive function that could be considered the highest function?

What effects on behavior do disorders of “management” and “executive” functions have?

Memory Systems

Memory forms the basis of experience and percep- tions of self. It is dynamic and malleable. It allows people to travel back in time. How you see yourself, to a large degree, is a product of the experiences of your life, the lessons you have learned, and what you remember as being important. Even what you tell yourself to remem- ber to do in the future must incorporate memory. Mem- ory pervades most aspects of human experience. Stories of your personal and cultural past are stored in memory; thus, it is a necessary foundation of social communica- tion. This section examines the various components of memory and what can happen when aspects of the mem- ory system malfunction.

When memory is working fluidly, there is little need to notice it. But consider the question from a neuropsy-

chological perspective: What do you lose if you lose your memory? One patient we evaluated, a man in his 70s with Alzheimer’s disease, could not remember that his wife had died 2 years earlier. All his memories were still of her being there. Every time someone mentioned that his wife was dead, he relived the grieving experience. It is scary to imagine waking up and not knowing who you are, who your friends are, and what has happened in your life. Consider also what it might be like if you could not en- code new information, if you could not remember what someone said 10 minutes ago, or if you could not register the information you needed to take a test or learn a new skill.

Memory is an umbrella concept, and it is impossible to say categorically that someone has an overall good or bad memory. It is simply not a single system. Memory is parceled into subsystems based on ideas of storage and

226 PART TWO | The Functioning Brain

processing. Neuropsychologists ask how the brain stores in- formation over the long term and how it encodes, orga- nizes, and then retrieves information from memory. In many disorders neuropsychologists treat on a daily basis, memory processing is at issue because memory is a “fragile” system, affected by many disorders, including most of the dementias, such as Alzheimer’s disease, toxic conditions, loss of oxygen, and head injury.

Scientific understanding of normal memory process- ing in the brain has profited greatly from the study of peo- ple afflicted with various memory disorders, especially types of amnesia. However, the term amnesia can refer to more than one type of condition. The “soap opera” ver- sion of amnesia occurs when one of the characters gets hit on the head and promptly forgets who she or he is and all the specific episodes of her or his life. This character in- variably wanders off to make a new life, including the development of a new identity. Perhaps, after a time, a startling event occurs (possibly another blow to the head) and the character’s prior memory and identity floods back. This type of memory deficit is reminiscent of a psy- chiatric dissociative state caused by severe emotional trauma, but it is not what occurs with neurologic injury or disease.

Because neurologic patients acquire their memory problems in conjunction with a brain injury or disease, it is important to have terminology that marks the nature of the patient’s memory before the event and the effect on memory after the event. Anterograde amnesia is the loss of the ability to encode and learn new information after a defined event (such as head injury, lesion, or disease onset). Retrograde amnesia is the loss of old memories from before an event or illness. For example, one of our patients, L.S., experienced a head injury as a result of a car accident and had moderate anterograde amnesia and mild retrograde amnesia. She had no memory of the car accident and only vaguely remembered the paramedics. She did remember being in the hospital emergency room. After the accident, she had difficulty learning new infor- mation (anterograde amnesia). She often forgot her physi- cian’s name, and when she returned to college, she found it hard to study and perform well on history tests for which she had to recall facts and dates. Her mild retro- grade amnesia is evidenced by her memory for driving out of the grocery store parking lot, which was about five blocks from the accident. However, she remembered noth- ing else of the short time preceding the accident. Amnesias of this type are common in closed head injury (this con- dition is described further in Chapter 13). In general, anterograde (or a combination of anterograde-retrograde) amnesia is evident with brain injury. However, there are

instances of retrograde amnesia with relatively spared an- terograde learning and memory (Levine et al., 1998). Amnesia can be caused by a number of different prob- lems and can take several forms. An example of a circum- scribed lesion causing amnesia is the classic case of N.A. (Neuropsychology in Action 9.1).

A F R A M E W O R K F O R C O N C E P T U A L I Z I N G M E M O R Y S Y S T E M S

Psychology textbooks typically describe memory as hav- ing three main divisions: sensory memory, short-term memory (STM), and long-term memory (LTM). Sen- sory memory is fleeting, lasting only milliseconds, but its capacity is essentially unlimited in what may be taken in. STM is of limited capacity (7 � 2 bits of information) and degrades quickly over a matter of seconds if informa- tion is not held via a means such as rehearsal, or trans- ferred to LTM. LTM, theoretically, is of unlimited capac- ity and is relatively permanent except for models that suggest that loss of information through forgetting is pos- sible. Neuropsychologists are most concerned with LTM and its disorders because these are the problems most evi- denced by patients. Often, STM, as measured by neu- ropsychological tasks, is intact even when there are deficits in LTM, although isolated disorders of STM exist. Neu- ropsychological conceptualizations of memory generally do not consider sensory memory; rather, it is thought of as a component of sensory processing.

Neuropsychology concerns itself with understanding how memory systems work in correspondence with known brain functioning. An important question con- cerns the possible existence of anatomically separate sys- tems in the brain for such concepts as STM, LTM, explicit-implicit memory, and episodic-semantic mem- ory. One way in which researchers can support the idea of separate structures is by showing a double dissociation between behaviors. Research can demonstrate strong evi- dence for different systems if a lesion in an area of the brain affects one system (LTM) but not the other (STM). Evidence is even stronger if researchers can show that a different lesion results in the opposite dissociation (affects STM but not LTM). This section focuses on conceptualizations of LTM and short-term working memory. We explore evidence for different memory sub- systems, a division between STM and LTM, and between possible divisions of LTM such as separate declarative/ex- plicit versus procedural/implicit systems. As we explore each subsystem, we also discuss disorders that affect that system.

L O N G - T E R M M E M O R Y

A problem that is inherently confusing in studying mem- ory is the multiple terms scientists use to describe the pos- sible subcomponents of LTM. Cognitive psychologists, neuropsychologists, neurologists, and the lay public use various, and sometimes conflicting, terms. For example, when referring to LTM, the lay public often thinks of the ability to remember information from the distant past. However, neuropsychologists are referring to the specific ability to register information (encode), organize the in- formation in a meaningful way (storage), and recall or rec- ognize the information when needed (retrieval). Accord- ing to this definition, LTM is the ability to learn and retain new information. Remote memory, by contrast, concerns memory for long-past events.

Various theoretical conceptualizations parcel LTM into subsystems (Figure 9.1). Squire (Squire & Cohen, 1984; Squire & Butters, 1992) and other investigators advocate for a structural–functional difference between declarative and nondeclarative memory.

Declarative memory is explicit and accessible to con- scious awareness. Nondeclarative memory is usually im- plicit, and a person demonstrates it via performance. Squire and Butters (1992) maintain that the domain of nondeclarative or procedural memory is that of rules and procedures, rather than information that can be verbal- ized, although nondeclarative memory has not been clearly operationally defined and often includes a hodge- podge of tasks such as motor skills learning, mirror read- ing, and verbal priming. Schacter (1987) differentiates between explicit and implicit memories. Recall or

CHAPTER 9 | Memory, Attention, Emotion, and Executive Functioning 227

In 1960, N.A. was 22 years old and was a member of the U.S. Air Force. One day while working on a model airplane, he suffered an accident that would affect him for the rest of his life. His roommate, apparently in a playful mood, took a miniature fencing foil from the wall, tapped N.A. from behind, and as he turned around, thrust it forward. Unfortu- nately for N.A., the tiny foil penetrated the cribriform plate at the top of his nasal cavity and entered his brain. The foil pierced his third cranial nerve, but more important, it made a small lesion in the left dorsomedial nucleus of the thalamus. It was quickly discovered that N.A. was amnesic (retro- grade) for the past 2 years. In addition, this minute injury left him with a devastating impairment in his ability to register new verbal memories (anterograde amnesia).

In meeting him, the casual observer may not initially suspect there is anything wrong. N.A.’s intelligence quotient (IQ) is in the high average range and he exhibits good social skills. Furthermore, he is friendly, polite, and has a good sense of humor. But after talking with him for a few minutes, it becomes apparent that he does not remember details

of just a few minutes ago. If he is distracted by a passing thought or a passing car, the thread of conversation is lost. He has little recollection of the day’s events. If you meet again the next day, he probably will not remember you or what transpired in your previous meeting with him.

N.A. likes to keep his room exactly the same at all times and spends much time obsessively arranging things. He becomes upset at his mother if she moves the tele- phone or one of his model airplanes. He likes things exactly the same so he has a better chance of finding them. Only after a long period and much repetition does he remem- ber something. If N.A. saw you every day, after a period of time he might recognize you, but still might not know your name. He has only a sketchy memory of events that have tran- spired since 1960. For example, he has a vague idea that Watergate was a political scandal in “Washington or Florida” but recalls no other details. Because N.A.’s injury is in the left dorsomedial nucleus, he shows more verbal than visual memory deficits. Interest- ingly, when he had to learn a new route from his house to the Veterans Administration

hospital for therapy, even after 4 years he was unable to form a spatial map. He found his way much like an adult returning to a child- hood neighborhood after years of absence. As pieces of the visual scenery popped up before him, he decided if the landmark looked familiar and turned accordingly. This haphaz- ard approach of seeing things sometimes required him to back up or retrace his steps until something looked familiar.

N.A. recognizes that he has memory problems and is not confused. He knows who he is and where he is, but may not know the day or year. As would be suspected, he has little social life. In a sense, he remains stuck in time. Most of his memories are from the 1950s. When he fantasizes, he thinks of Betty Grable. He does not know of the people or events since then. However, N.A. remains optimistic about his situation and rarely uses notes because he wants to work on his memory.

This case demonstrates that even a very small lesion, strategically placed, can cause a devastating problem of memory. Kaushall, Zetin, and Squire (1981) have reported the complete case of N.A.

N e u r o p s y c h o l o g y i n A c t i o n 9 . 1

A m n e s i a : T h e C a s e o f N . A .

by Mary Spiers

228 PART TWO | The Functioning Brain

recognition, through verbal or nonverbal means, directly indicates explicit memories. Conscious awareness is usu- ally implied, as is intention to remember. People demon- strate implicit memory by means in which conscious awareness is not always necessary, such as implicit prim- ing, skill learning, and conditioning. Yet another possible distinction within LTM is between semantic and episodic memory. Researchers consider both of these to be forms of explicit or declarative memory. Tulving (1972) intro- duced the distinction between an episodic memory, which refers to individual episodes, usually autobiograph- ical, that have specific spatial and temporal tags in mem- ory, and semantic memory, which refers to memory for information and facts that have no specific time tag refer- ence. For example, remembering the details and events of your first date involves episodic memory, whereas remem- bering the definition of a word relates to semantic mem- ory. With semantic memory, the context in which the memory was encoded is generally not present. Thus, most of us do not remember the specific setting and people in- volved when we learned the name of the first president of the United States.

The most neuroanatomically defensible division be- tween LTM systems is that of declarative/explicit and

nondeclarative memory systems. Some also use the terms declarative versus procedural or explicit versus implicit in a nearly synonymous manner. There is much debate over the existence of separate episodic and semantic systems; in fact, although researchers first described these two sys- tems as clearly distinguishable conceptually, they now con- sider the systems to overlap with other memory concepts.

D e c l a r a t i v e M e m o r y

One of the first questions that come to mind when peo- ple begin thinking about memory is, “Where is memory stored in the brain?” This often implies the search for a “center” for memory storage in the brain. It also implies that if this center is removed, then all memory is removed. This would be like erasing the entire hard disk of a com- puter. (Please note that the brain does not operate like a computer; in fact, brains build computers!) If all remote memory were removed from the brain, a person would be unable to remember his or her language, facts, episodes, names of people, or any other information previously encoded. From studies of brain-injured individuals, we know that this does not happen. People may lose pieces of remote memory, but their brains are not “erased.” There is no one memory storage center. Rather, most neuropsychologists

Figure 9.1 Long-term memory (LTM) taxonomy. Theories of anatomically separate LTM stores have included the noted distinctions. (From Weiten, W. [1998]. Psychol- ogy: Themes and variations [p. 291, Figure 7.28]. Pacific Grove, CA: Brooks/Cole.)

Memory

Declarative memory system (factual information, explicit memories)

Nondeclarative/Procedural memory system (actions, perceptual-motor skills, conditioned reflexes, implicit memories)

Example: Riding a bicycle

Semantic memory system (general knowledge, stored undated)

Example: Lincoln gave Gettysburg Address

Episodic memory system (dated recollections of personal experiences)

Example: First kiss

think of memory as being ultimately stored in the area where it was first processed (for example, see Squire, 1987). This would imply, for example, that auditory memories are stored in primary, secondary, or auditory association areas, and likewise for other functional systems.

The function of the declarative memory system is to process information in such a way as to tag it or consoli- date it for storage in the brain. According to this model, when new declarative learning is occurring, information from various cortical areas funnels into the structures responsible for declarative memory. After it is processed, re- turn neural pathways transmit information back to specific cortical areas.

Declarative Model of Encoding and Retrieval—Tulving and coworkers (1994), based on neuroimaging studies of healthy individuals, developed a model of memory en- coding and retrieval, Hemispheric-Encoding-Retrieval- Asymmetry (HERA). The model proposes that the pre- frontal (dorsolateral) region of the left hemisphere is primarily involved in episodic encoding, whereas the prefrontal area of the right hemisphere is prominently activated for retrieval of episodic information. Subse- quently, a comprehensive review of 275 positron emis- sion tomography (PET) and functional magnetic reso- nance imaging (fMRI) studies by Cabeza and Nyberg (2000) provided partial support for the model. Analysis of these neuroimaging studies showed that the left pre- frontal region activated in verbal episodic encoding while retrieval of episodic information was right-later- alized (prefrontal region) for both verbal and nonverbal contents. In contradiction with the prediction based on the HERA model, encoding of nonverbal information yielded bilateral and right-lateral prefrontal activation. Other regions activated during episodic retrieval in- cluded temporomedial, parietal, medial parietotempo- ral, temporal, occipital, and cerebellar areas, highlight- ing the multiplicity of regions and circuitry involved in memory retrieval. Unlike episodic retrieval, the recall of semantic information is dependent on the left pre- frontal area for both verbal and nonverbal information (Cabeza & Nyberg, 2000). Similar to episodic retrieval, other brain regions are involved in semantic retrieval including temporal, anterior cingulate, and cerebellar regions.

Declarative Consolidation—Three major interconnected con- stellations of brain structures play a role in consolidating information into LTM. The first memory centers around the medial temporal lobes, the second around the dien- cephalon, and the third in the basal forebrain.

The medial temporal structures, which are important for long-term declarative memory, center around the hip- pocampus and medial temporal lobe. The well-documented case of H.M. (Milner, Corkin, & Teuber, 1968; Scoville, 1968) best exemplifies what occurs when these structures are damaged. In 1953, at the age of 27 years, H.M. un- derwent brain surgery to reduce intractable seizures. The surgery involved bilateral removal of the hippocampus and portions of the surrounding area, which included the hippocampal formation (Figure 9.2). The hippocampal formation, or hippocampal complex, includes the hip- pocampus, the dentate gyrus, and the subiculum. In cross section, the hippocampus has a distinctive “sea horse” shape. Information funnels into the hippocampus via the entorhinal cortex. In addition, the perirhinal and parahip- pocampal cortexes adjacent to the hippocampal forma- tion are believed to have a role in memory. At the time of H.M.’s surgery little was known regarding the effects of such surgery on memory. After the surgery, despite the preservation of above-average intelligence, he was pro- foundly amnesic for new learning (anterograde amnesia), both episodic and semantic. He was able to recall old memories and facts, but new learning was no longer pos- sible. STM was preserved in that he could retain new in- formation for a few minutes. However, this information could not be consolidated into long-term storage. If he met someone and then the person left, he would not have any memory of the meeting a few minutes later. As a re- sult, if he met the person again, it was as if they had met for the first time. H.M.’s amnesia was even more pro- found than N.A.’s, in that he also had difficulty learning new visuospatial information.

The preservation of old memories with medial tempo- ral damage suggests that memories are not stored in the hippocampus; rather, this structure appears to be involved in the movement of new information into long-term stor- age. PET and fMRI studies (Cabeza & Nyberg, 2000) show that the left medial temporal region activates during the encoding of verbal material, whereas bilateral activa- tion is evident for processing of nonverbal contents. Dam- age to the hippocampus can significantly disrupt declara- tive memory, but the extension of damage to the entorhinal and parahippocampal regions produces even more severe and long-lasting amnesia.

The specific functions of the regions of the medial temporal lobe are not fully known, but research suggests that they make differential contributions to memory. For example, the visual association cortex shows significant projections to the perirhinal cortex, whereas the parietal cortex projects to the parahippocampal cortex. These struc- tures appear to play specific roles in visual recognition and

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Figure 9.2 The hippocampal complex. (a) The hippocampal complex is located on the medial surface of the temporal lobe. (b) A coronal section shows the hippocampus as a deep infolding of the temporal lobe. (c) A close- up shows the structures in relation. The hippocampus consists of four parts (CA1-CA4). The pathway to the hip- pocampus from the cortex leads through the entorhinal cortex. ([b] Adapted from Pinel, P. J., & Edwards, M. [1998]. A colorful introduction to the anatomy of the human brain [p. 169, Figure 10.1]. Boston: Allyn & Bacon, by permission; [c] adapted from Burt, A. M. [1988]. Textbook of neuroanatomy [p. 488, Figure 20.7]. Philadelphia: W.B. Saunders, by permission.)

Temporal lobe

Lateral tissue

Dentate gyrus

Subiculum

Entorhinal cortex

Third ventricle

Coronal section of left temporal lobe

Amygdala

Cingulate gyrus

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Mammillary body

Fornix

Neocortex

CA3

CA4 CA2

CA1

spatial memory, respectively (Squire & Knowlton, 2000). The hippocampus appears to have a special role in memory tasks that require the relating or combining of information from different cortical sources, such as the relation of spe- cific objects or events in time and space.

The structures of the diencephalon involved in mem- ory center around specific nuclei of the thalamus and the mammillary bodies of the hypothalamus (Figure 9.3). The thalamus consists of several nuclei, with the dorsal medial nucleus of the thalamus the most often implicated in memory disorders. Although the dorsal medial nucleus is involved in memory consolidation, there are sugges- tions that it may also assist in the initiation and monitor- ing of conscious retrieval of episodic memories (Wenk, 2004). Damage to the dorsal medial nucleus is often im- plicated in Korsakoff ’s syndrome and in some cases of spe- cific amnesia, such as N.A.’s case (see Neuropsychology in Action 9.1). Korsakoff ’s syndrome is a consequence of chronic alcoholism associated with vitamin deficiency (thiamine). As a result, degeneration of the thalamic dor- somedial nucleus and the mammillary bodies occurs. Patients with Korsakoff ’s syndrome exhibit significant an- terograde and retrograde amnesia, although certain forms of nondeclarative memory (for example, procedural mem- ory) are preserved. Moreover, there are cases of damage specific to the diencephalon region resulting in amnesia, such as N.A.’s case (see Neuropsychology in Action 9.1).

The basal forebrain is the third area implicated in long- term declarative memory processing. As described in Chapter 5, this area is a subcortical part of the telen- cephalon surrounding the inferior tip of the frontal horn and is strongly interconnected with limbic structures; some neuroscientists consider it part of the limbic system (for ex- ample, see Crosson, 1992). The basal forebrain represents a major source of cholinergic output to the cortex. Some in- vestigators have suggested that extensive damage of basal forebrain structures may be needed to affect memory (Zola- Morgan & Squire, 1993); thus, looking at the contribu- tions of an individual nucleus to memory is probably not as profitable as regarding the system as a network. Because of its location surrounding the inferior tip of the frontal horn and that the inferior communicating artery perfuses this area, stroke easily affects the basal forebrain. This area is important to memory not only for the nuclei within but for the fibers that traverse the area. The basal forebrain also contains numerous connections to the mediotemporal area.

The basal forebrain structures implicated in memory include the nucleus basalis of Meynert, the medial septal nucleus, the nucleus of the diagonal band of Broca, and the substantia innominata (Figure 9.4). The nucleus basalis of Meynert includes a group of large neurons in-

terspersed within the substantia innominata. The substan- tia innominata is a gray and white matter area that sepa- rates the globus pallidus from the inferior surface of the forebrain. It interconnects with the frontal, parietal, and temporal cortexes. An important tract coursing through the substantial innominata is the ventral amygdalofugal pathway, which connects the amygdala to the dorsal me- dial nucleus of the thalamus. The medial septal nucleus lies at the precommissural end of the fornix and projects to the hippocampus through the fornix. It most likely af- fects memory when damage disrupts information flow to the hippocampus. The nucleus of the diagonal band of Broca is a white matter and cell body area located near the nucleus basalis. It also projects to the hippocampus through the fornix. Researchers think these structures are important cholinergic memory structures.

The major declarative memory system is the Papez cir- cuit. Papez originally proposed that this looping pathway was specific for emotional processing. He noticed that the clinical presentation of intense emotional symptoms in animals with rabies (derived from Latin meaning “rage”) was associated with lesions in several limbic system struc- tures, specifically the hippocampus. Today, researchers know this loop has more to do with consolidating infor- mation in memory than as a primary emotional proces- sor. Information from the cortex and higher cortical asso- ciation areas enters the circuit through the cingulate gyrus, moves to the parahippocampal gyrus, and then into the hippocampus through the hippocampal formation. The major output system of the hippocampal formation is the fornix. It contains nearly 1 million fibers and is comparable in size with the optic tract (Nauta & Feirtag, 1986). The fornix rises out of the hippocampal complex and arches anteriorly under the corpus callosum. The fornix relays information to the mammillary bodies (specifically the medial mammillary nucleus) of the hypo- thalamus. From there information is projected to the ante- rior nucleus of the thalamus along the mamillo-thalamic tract, from where it then goes to the cingulate gyrus to complete the circuit. Figures 9.2 and 9.5a show the anatomic location of the structures, and Figure 9.5b pre- sents a schematic of the loop.

It is readily apparent by examining amnesia cases such as H.M. and N.A. that a break in the memory consolida- tion circuit can disrupt memory in a manner similar to di- rect removal of the hippocampus, which neurologists typi- cally consider the most crucial structure in the system.

N o n d e c l a r a t i v e M e m o r y

The term nondeclarative memory does not refer to a discrete memory system as much as it acknowledges that some

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memory functions operate outside the limbic circuitry of explicit or declarative memory. Researchers have variously referred to the opposite of limbic circuitry–based memory as “habit memory” (Mishkin, Malamut, & Bachevalier, 1984), “procedural memory” (Cohen, 1984), and “im- plicit memory” (Graf & Schacter, 1985). The variety of memory functions this term encompasses most likely re- flects a collection of different abilities, not necessarily mu- tually exclusive, and perhaps dependent on different pro- cessing systems. For example, implicit memory implies influence by prior experience without conscious aware- ness of the event. Procedural learning concerns the learn- ing of procedures, rules, or skills manifested through per- formance rather than verbalization, although conscious awareness may aid procedural learning. Because these

terms do not by themselves encompass the entire range of nondeclarative memory, researchers prefer the less specific term (see Squire, 1994). Neurologists also know that a single lesion cannot erase all nondeclarative memory, as it may for declarative new learning. Although it is premature to present a neuroanatomic classification scheme, scien- tists can describe some aspects of nondeclarative memory with respect to brain structures, particularly subcortical basal ganglia areas.

Researchers observing H.M. noticed that despite se- vere amnesia for declarative information, H.M. improved with practice on certain perceptual motor tasks (Milner et al., 1968; Scoville, 1968). He was learning, with prac- tice, without conscious recognition of this learning. If his amnesia had been total, examiners would have expected

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that each presentation of the task would be performed as if it were brand new. One area of nondeclarative memory involves perceptual motor adaptation and skills acquisition. Many amnesiacs, such as H.M., show a normal learning curve as they practice the pursuit rotor and reverse mirror- reading tasks. The pursuit rotor requires the examinee to keep a stylus on a spinning disk, much like having to hold a place on a record on a turntable. Reverse mirror reading requires an individual to trace a maze while looking at it through a mirror. Perceptually, amnesiacs also show nor- mal adaptive behavior when wearing visual prisms. Be- cause prisms distort visual input, simple acts such as reaching for an object are misdirected at first. The visual motor system must quickly learn to “retune” the system so that it again correctly targets reaching according to the new visual information. Interestingly, amnesiacs can do this performance learning and adaptation despite severe declarative amnesia. However, amnesiacs do not show normal nondeclarative skill learning for all tasks. For example, investigations (Gabrieli, Keane, & Corkin, 1987; Xu & Corkin, 2001) of H.M.’s performance on a complex, nondeclarative, problem-solving task (Tower of Hanoi) did not find evidence of consistent improvement across learning trials or mastery of the task.

Further support for a nondeclarative memory system is provided by the differential performance of patients with amnesia, Huntington’s disease, and Parkinson’s dis- ease on a measure of serial reaction-time skill learning (Schacter & Curran, 2000). The patients were required to press one of four keys when illumination occurred above a key. The patient groups were not aware that there was a repeating sequence of illumination; yet, across learning trials, the patients with amnesia demon- strated improved performance as evidenced in decreased key press reaction times. In contrast, patients with Huntington’s and Parkinson’s diseases showed impaired learning. Subcortical striatal pathology is central to both Huntington’s and Parkinson’s diseases, suggesting the involvement of this region in serial reaction-time learning. Functional imaging studies have confirmed that serial reaction-time skill learning is supported by the striatal region and circuitry. Other regions that exhibit learning-related changes during serial reaction-time skill learning primarily involve the neocortex (primary motor, supplementary motor, premotor, parietal and occipital cor- tices). These changes suggest that serial reaction-time learning involves changes in perceptual and motor areas supporting visually guided movements (Schacter & Curran, 2000).

Researchers also noticed that severely amnesic patients with Korsakoff ’s syndrome showed a phenomenon known

as implicit priming. For example, in the word stem com- pletion priming paradigm, a list of words is first presented (for example, church, parachute, clarinet, and so on). Be- cause of the severe amnesia, the person’s memory is poor when examiners demand recall in a declarative task. Ex- aminers then give patients three-letter word stems (for ex- ample, chu____, par____, cla_____) and ask them to make a word by completing the stems. “Primed” patients with Korsakoff ’s syndrome were more likely to complete the stem with a word they had already seen than were un- primed examinees, despite the same level of declarative amnesia for the words. Perceptual priming also appears in the quicker recognition of fragmented objects (such as those presented in Chapter 8 for testing apperceptive ag- nosics) or of words (see Figure 9.6 for examples of prim- ing stimuli). Similar to patients with Korsakoff ’s syn- drome, amnesic patients with damage to medial and diencephalic brain areas often show unimpaired implicit perceptual priming.

Perceptually based implicit priming is associated with decreased activity of the posterior neocortex. It has been theorized that the decreased activation of the posterior neo- cortex reflects a reduction in neural resources needed to process the content when it recurs, because a visual trace remains from the original presentation of the material (Squire & Knowlton, 2000). Notably, implicit priming is

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Figure 9.6 Amnesiacs who have deficient declarative memory may still have intact implicit memory as they demonstrate by quickly recognizing fragments of previously presented words. (Reproduced from McCarthy, R. A., & Warrington, E. K. [1990]. Cogni- tive neuropsychology [p. 302, Figure 14.3]. San Diego: Academic Press, by permission.)

236 PART TWO | The Functioning Brain

not synonymous with recognition memory (identification of target stimuli when presented with other nontarget stim- uli). Recognition memory appears to involve the encoding of phonetic or semantic declarative information, whereas priming depends on the visual features of the presented con- tent. In addition, different brain systems are believed to sup- port the two types of memory. An example of recognition memory would be asking a person to memorize a list of words, and then presenting the words, at a later time, ran- domly interspersed with other nonpresented words. The per- son is then asked to identify the words initially learned. Identification of the words originally learned provides a mea- sure of recognition memory. Case studies show that patients with lesions of the visual extrastriate region demonstrate deficits of visual perceptual priming but intact recognition memory. Patients with amnesia show the opposite pattern.

Another form of implicit learning is that of “artificial grammar.” Individuals are presented seemingly random strings of consonants without awareness that the organi- zation of these strings reflects a complex set of rules. The individuals are then informed that the consonant strings were generated in accordance with a set of rules. After this explanation, they are exposed to a list of grammatical and nongrammatical consonant strings and are asked to judge which strings were formed by the same set of rules. Pa- tients with amnesia perform the task as well as healthy par- ticipants, even though they have no memory for the conso- nant strings used during the training. In addition, patients with basal ganglia disease (for example, Parkinson’s disease) are also able to perform artificial grammar tasks, indicat- ing that striatal pathology is not involved in this form of memory. Research suggests that the posterior neocortex may support the performance of artificial grammar tasks, leading some investigators to pose that this type of learning may reflect priming or perceptual processing (Schacter & Curran, 2000; Squire & Knowlton, 2000).

The simplest form of nondeclarative memory involves classic or associative learning. This type of memory is evo- lutionarily much older and generally operates on the basis of learned associations. Researchers can demonstrate that even animals whose hippocampus has been removed can learn simple stimulus–response associations. For example, planaria can learn a light–shock pairing and recoil from the light when they subsequently encounter it alone. This suggests that some basic and primitive aspects of associa- tive conditioning are operating. Human amnesiacs pro- duced corroborating evidence for this associative learn- ing. Amnesiacs who meet a doctor on one occasion do not remember the doctor’s name on the next meeting. But, amnesiacs who have been pin-pricked by their doc- tor while shaking hands during their first meeting, often

withdraw their hand when the doctor extends his or her hand at a second meeting even though they may not con- sciously recall the association between shaking hands with the doctor and being pricked by a pin.

Whether the same brain circuitry governs all aspects of nondeclarative memory is not fully understood. How- ever, evidence suggests that structures supporting nonde- clarative memory are probably evolutionarily and onto- logically older and more primitive. We stated earlier that even simple animals without a hippocampal system can learn associative information. Also, preverbal babies show perceptual-motor learning. Infants between 2 and 5 months of age quickly learn that they can kick to move a mobile attached to one leg (Rovee-Collier, 1993). Many brain structures involved in movement, including the cerebellum, the basal ganglia, and the motor strip, are implicated in motor learning. The cerebellum aids in sequential motor learning such as the steps required in learning the piano. The basal ganglion is an important brain circuit responsible for perceptual-motor learning and adaptation (Figure 9.7). We discuss this circuit in

Figure 9.7 (a) The circuitry of nondeclarative perceptual- motor learning. (b) Schematic of information flow from the neocortex through the basal ganglia to the premotor cortex. (Adapted from Petri, H. L., & Mishkin, M. [1994]. Behaviorism, cogni- tivism and the neuropsychology of memory. American Scientist 82, 30–37, by permission.)

Premotor cortex

Basal ganglia

Frontal Temporal

Occipital

Parietal

Thalamus

Substantia nigra

Ventral thalamusBasal ganglia

Premotor cortexNeocortex

A moment in time. In the case of amnesiacs such as H.M. and N.A., this is everything they had. But healthy people also travel from moment to moment in a “presence- chamber” of the mind, using this workspace to assemble information for storage and to connect and reconnect in- formation retrieved from LTM, to solve problems or to make new associations. The difference is that N.A. could no longer connect moments and store aspects of the pres- ent as new memory in LTM. The limited capacity and short time frame of STM does not accommodate more than a few thoughts, ideas, or bits of information at a time. As new bits arrive, they may take the place of others or simply degrade. If there is no linkage between STM and LTM, STM floats as an island with only a small area of possible habitation.

Researchers interested in memory have debated the question of the relation of STM to LTM. Cognitive tasks il- lustrate that the two appear to measure different areas of memory. STM is a limited-capacity, rapid-access, input- and-retrieval system analogous to computer RAM (random- access memory). LTM has unlimited capacity but with a restricted rate of input and retrieval much like ROM (read-only memory). The two systems are also coded dif- ferently. STM uses phonologic coding, relying on an acoustic code, whereas LTM heavily uses semantic cod- ing, or the associative meaning value of information to be remembered (for review, see Baddeley, 1986). Even though the two seemingly measure different aspects of memory functioning, a unitary view of memory function- ing would argue that LTM depends on STM. That is, these two systems are viewed as two components of one system linked in a serial fashion; thus, information enter- ing LTM must inevitably flow through STM. In contrast, a separate system view would argue that LTM and STM are dissociated, so someone could have an LTM deficit with intact STM, whereas another person could have an STM deficit but maintain adequate LTM. Patients with amnesia with severe LTM deficits often show intact STM. On formal testing, they can repeat increasingly longer se- ries of digits and perform well on other tasks presumed to test STM. However, other patients have a specific STM deficit with preserved LTM. This is some of the most con- vincing evidence that STM and LTM are anatomically separate.

Patients with a pure STM deficit are rare. However, re- searchers have reported cases with exactly this problem (for example, see Shallice & Warrington, 1970; Basso, Spinnler, Vallar, & Zanobio, 1982). Shallice and Warrington (1970) reported the case of K.F., a patient who suffered a left pos- terior temporal lesion that left him with a greatly reduced STM capacity for verbal information. He had a profound

CHAPTER 9 | Memory, Attention, Emotion, and Executive Functioning 237

Chapter 7 (see the section “Subcortical Motor Process- ing”). Specifically, this circuit includes the caudate nu- cleus, putamen, and globus pallidus. The nuclei of the striatum (caudate and putamen) receive projected infor- mation from cortical sensory areas. From the striatum, information then funnels through the globus pallidus, and then on to the thalamus, where it projects to the pre- motor and prefrontal areas (see Figure 7.11) (Mishkin, Malamut, Bachevalier, 1984). Behaviorally, Huntington’s disease best portrays the effect of caudate nucleus dys- function of the basal ganglia. Huntington’s disease devel- ops as a progressive subcortical dementia (see Chapter 15 for a thorough description), but caudate nucleus degen- eration is the hallmark of Huntington’s disease and is one of the first structural changes that computed tomogra- phy scans identify. The atrophic imaging change appears at the onset of the choreiform movement disorder. The effect of this change appears to target perceptual-motor learning tasks. In a series of studies spearheaded by Nel- son Butters (for review, see Squire & Butters, 1992), pa- tients with Huntington’s disease showed a dissociation in performance from patients with Korsakoff ’s syndrome, amnesia, and Alzheimer’s disease. On declarative verbal memory tasks, patients with Huntington’s disease per- formed relatively better than patients with Korsakoff ’s syndrome and Alzheimer’s disease. However, on motor learning tasks, the two cortically impaired groups out- performed the patients with Huntington’s disease. This double dissociation in functioning prompted the initial suggestion for separate cortical and subcortical memory structures. Since that time, animal studies and imaging studies with healthy participants performing motor learning tasks have added evidence for the role of the basal ganglia in implicit memory.

S H O R T - T E R M M E M O R Y A N D W O R K I N G M E M O R Y

There seems to be a presence-chamber in my mind where full consciousness holds court, and where two or three ideas are at the same time in audience, and an ante-chamber full of more of less allied ideas, which is situated just beyond the full ken of consciousness. Out of this ante-chamber the ideas most nearly allied to those in the presence chamber appear to be summoned in a mechanically logical way, and to have their turn of audience.

—Francis Galton (1883)

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STM deficit, having a digit span length of about two, rather than the usual seven bits of information. He also demonstrated conduction aphasia whereby he could not repeat sentences. Surprisingly, K.F. showed a normal ver- bal learning curve with practice, indicating intact storage of information in LTM. It is difficult to reconcile K.F.’s performance with theories posing that verbal STM and LTM use the same anatomic structure, but in different ways. K.F.’s performance also challenges models that seri- ally link STM and LTM and, conversely, provides sup- port for models that postulate that verbal STM and LTM are separate or parallel systems.

The notion of STM as a component of LTM has grad- ually given way to ideas that now refer to working mem- ory (Baddeley, 1986) as a distinct system encompassing some of the capacity limitations of STM, but that is a dy- namic system also influencing aspects of attention and ex- ecutive functioning. Several distinctions differentiate STM (sometimes called short-term span) from working mem- ory. First, a cognitive (mental) representation of informa- tion is held “on line” in temporary store (similar to STM). Second, the cognitive representations are subjected to some form of mental manipulation or transformation. Third, attentional and inhibitory control is necessary for the protection of the on-line cognitive representations, manipulations, and transformations from external or in- ternal inference. Fourth, the cognitive manipulations or computations often involve using information drawn from long-term storage. To understand working memory, con- sider the following: You are presented a multiplication problem to solve mentally such as multiplying 234 by 354. When performing this problem, you will hold a mental representation of the problem in short-term storage. As you maintain this mental representation while performing the necessary computations to solve the problem, you will need to intensely concentrate and, at the same time, block out any internal or external stimuli that could disrupt your focus. Simultaneously, you will draw from LTM the ap- propriate multiplication facts and the mathematical opera- tions needed to solve the problem. Because of the dynamic and effortful cognitive processes involved in working memory, Moscovitch and Winocur (2002) believe that it would be more aptly named “working-with-memory.”

Alan Baddeley’s (2001, 2002) seminal research and the- orization has substantially enhanced our understanding of working memory. Working memory is integral to a wide range of cognitive tasks from reading to math to problem solving. Baddeley initially conceptualized working mem- ory as involving three components (Figure 9.8). The cen- tral executive is an attention-controlling system; it super- vises and coordinates slave systems and is the proposed

deficit in Alzheimer’s disease. The attention-controlling functions of the central executive system involve focusing, shifting, and dividing attention and interfacing with LTM. There are also two modality-specific “slave” systems. The articulatory phonologic loop stores speech-based infor- mation and is important in the acquisition of vocabulary. The visuospatial sketch pad manipulates visual and spa- tial images. Recently, Baddeley (2000, 2002) extended the model to include a fourth component, the episodic buffer (see Figure 9.8). The episodic buffer is a temporary and limited capacity storage system whose posited function is to hold and integrate information of different modalities (for example, visual and auditory) through linkage with LTM. The central executive controls this buffer and uses conscious awareness as a primary retrieval strategy. For ex- ample, if you are asked to recall a series of numbers pre- sented in word form, and you are able to categorize the numbers into meaningful groups based on associations in long-term storage, memory recall will be enhanced. Thus, if numbers are visually presented in word form—fourteen, ninety-two, nineteen, forty-one—and you draw from LTM the numeric representation of historically significant dates and group the numbers as 1492 (Columbus discov- ers America) and 1941 (beginning of the World War II), you have integrated verbal and visual information through linkage with associative information held in LTM.

Neuropsychologically, the phonologic loop and the vi- suospatial sketch pad link to lateralized modalities in the brain and to frontal lobe executive processes. The phono- logic loop involves auditory-verbal processing and de- pends on language-based left hemisphere processes. Like- wise, the visuospatial sketch pad is associated with the

Figure 9.8 A simplified representation of Baddeley’s working memory model. (Adapted from Baddeley, A. [2002]. Fractionating the central executive. In D. T. Stuss & R. T. Knight [Eds.], Principles of frontal lobe functioning [p. 256, Figure 16.4]. New York: Oxford Univer- sity Press, by permission.)

Visuo-spatial sketch-pad

Visual semantics

Central Executive

Episodic Buffer

Episodic long-term memory

Phonological loop

Language

right hemisphere. The neural substrates that support the episodic buffer remain to be identified, although frontal architecture is believed to play a crucial role (Baddeley, 2002). Goldman-Rakic’s (1988) groundbreaking work in primate models of working memory points to the dorsolat- eral prefrontal cortex as the area that holds information “on

line” while it is processed. In these studies, Goldman-Rakic tested monkeys’ abilities to recall the position of food in one of two food wells after a short delay of several sec- onds. Figure 9.9 shows the general paradigm of the study. Simultaneous recordings from neurons in the dorsolat- eral prefrontal area continued to fire during the delay

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240 PART TWO | The Functioning Brain

until the action of food selection was completed. Since Goldman-Rakic’s work, PET and fMRI studies have sup- plied confirmation in humans that the prefrontal cortex activates during working memory tasks (Jonides et al., 1993; Smith, Marshuetz, & Geva, 2002). For example, based on neuroimaging research, Petrides (1998) has iden- tified two areas of the prefrontal cortex that are involved in support of working memory. The first area, the ventro- lateral prefrontal cortex (Brodmann’s areas 45 and 47/12), activates when dynamic (strategic) retrieval of informa- tion from posterior brain regions is required; that is, when there is a conscious effort to retrieve specific information in accordance with the individual’s intentions and plans. Thus, the ventrolateral cortex is actively involved in the selection, comparison, and judgment of information held in memory. In contrast, the mid-dorsolateral frontal cor- tex (Brodmann’s areas 46 and 9) activates when informa- tion is to be maintained on line for the purpose of moni- toring and manipulation. Jointly, these two areas provide the foundation for higher order processes involved in the planning and organization of behavior.

The move from conceptualizing STM as a storage ca- pacity system to that of working memory as a dynamic, integrated system entailing both lower and higher order processes highlights the interrelated nature of brain sys- tems. Other memory processes such as prospective mem- ory (the memory for future intention), temporal memory (memory for information in time order), and source mem- ory (memory for context) also rely on frontal lobe and ex- ecutive functioning processes. The next section discusses attention, a major higher function that is essential to the efficiency of mental processing.

Attention

Everyone knows what attention is. It is the taking possession of the mind in clear and vivid form of one out of what seem several simultaneous objects or trains of thought.

—William James (1890)

Moving about the world, people confront a flood of infor- mation that the nervous system cannot treat equally. Your brain must target or “spotlight” specific material to process and tune out the irrelevant information. For example, when you stop to talk to a friend in a hallway, you may hear com- peting sounds of others talking and people walking down the corridor. You may also be preoccupied by your own

inner thoughts. Nonetheless, if you “pay attention,” you can orient to a small sample of the incoming information and ignore most of the other input. In this way, attention operates as a gateway for information processing. Atten- tion allows orienting to, selecting, and maintaining focus on information to make it available for cortical processing.

The neuropsychology of attention historically has been a confusing subject because there are so many sub- sets of attentional processing and many possible defini- tions of attention. The term attention can refer to a general level of alertness or vigilance; a general state of arousal; orientation versus habituation to stimuli; the ability to focus, divide, or sustain mental effort; the ability to target processing within a specific sensory arena (such as visual attention or auditory attention); or a measure of capacity. Researchers have also asked whether attention implies a general state of cortical tone or energy, or functions as a network or set of specific structures or networks within the brain. Attentional processing does not imply a unified system, and most researchers now view it as a multifac- eted concept that implies multiple behavioral states and cortical processes that various subsets of cerebral struc- tures control.

In many types of brain dysfunction, efficiency of the brain to process information diminishes. Sometimes peo- ple cannot sustain attention to one particular stimulus for longer periods or cannot select information (selective at- tention) from competing sources. This impairment may be minimally present and detected only through formal neuropsychological testing, or may be profound and easily noticeable by any observer.

Neuropsychological theories of attentional processing (for example, see Mesulam, 1981; Posner & Petersen, 1990) usually consider the role of the reticular activating system (RAS) in cortical arousal, subcortical and limbic system structures (particularly the cingulate gyrus) in reg- ulation of information to be attended to, the posterior parietal lobe system in focusing conscious attention, and the frontal lobes in directing attentional resources. They also give the right hemisphere prominence as an atten- tional processor. Theorists have not yet worked out any one-to-one correspondence between levels of attentional behavior and brain structures or networks. Rather, they can describe general subsets of brain systems related to at- tentional functioning.

S U B C O R T I C A L S T R U C T U R E S I N F L U E N C I N G A T T E N T I O N

The RAS regulates the level of cortical activation or arousal—a necessary first step in attentional processing.

With its genesis in the midbrain and its ability to project to large cortical areas, the RAS sets a general cortical tone. Researchers can observe and categorize this arousal into brain wave types (beta, alpha, theta, and delta) by their frequency as measured by an electroencephalograph (EEG). In a general way, sensory input “charges” the RAS. If the brainstem is processing sensory input, the RAS maintains high cortical activation. However, lack of sen- sory input does not necessarily make one drowsy. In fact, even with constant sensory input there can be habitua- tion. Those who live on a noisy street grow accustomed to the sound, but a sudden silence will cause the brain to orient to the change in sound patterning. Daily bio- rhythms of 90 minutes of relatively higher and lower alertness also cycle throughout the day, and circadian rhythms control the sleep/wake cycle through the RAS. We discuss these changing levels of cortical tone further in our discussion of sleep (see Chapter 16). If a person is awake and alert, general level of arousal is more of a back- ground issue than a central one in the neuropsychology of attentional processing. However, the RAS also plays a role in anticipatory responding. Researchers have hypoth- esized that the RAS may send a preparatory signal to the cortex to alert it to receive stimuli, and thus put it in a heightened state of readiness to receive. Lesions to the RAS can result in lowered alertness or coma. Chapter 13 discusses coma in greater detail.

Neuroscientists are also identifying the role of other subcortical structures in attention. Although the precise functions that these structures play in attentional func- tioning remains to be specified, several interpretations have been posed. Moreover, these regions do not operate in iso- lation from one another or from other subcortical and cor- tical structures. For example, support of sustained atten- tion is ascribed to the right fronto-parietal-thalamic neural network (Sarter, Givens, & Bruno, 2001). With regard to selective visual attention, the thalamus, basal ganglia, and superior and inferior colliculi play a supporting role. The thalamus receives activation from the reticular formation and projects this arousal to the cortex. Moreover, the thal- amus serves to select and relay information from subcorti- cal regions to the cortex and, conversely, conveys cortical neural signals to subcortical regions. Through its gating function, it is in position to influence the selectivity of at- tention (Cohen, 1993). The superior colliculus of the mid- brain plays a role in the reflexive movement of the eyes and head when orientating to visual stimuli, whereas the infe- rior colliculus is implicated when orientating to auditory stimuli. Researchers have historically attributed motor functions to the basal ganglia, but increasingly are recog- nizing their role in cognitive operations. Posner and

DiGirolamo (1998) pose that the basal ganglia is involved in shifting or switching sets, and thus is a component of the act of orienting to stimuli.

T H E C E R E B R A L C O R T E X A N D A T T E N T I O N

The attentional issues of most interest to human neu- ropsychology generally concern the higher levels of atten- tional processing coordinated by the cerebrum, including focused attention, the ability to alternate and divide at- tentional processes, and the ability to sustain attention. Focused attention is the ability to respond and pick out the important elements or “figure” of attention from the “ground” or background of external and internal stimula- tion. Focused attention also implies a measure of concen- tration or effortful processing. A basketball player who can concentrate on making a free throw, while tuning out the crowd, is a good example of high focus. However, even the most ordinary event of noticing requires cogni- tive focus. People are frequently called on to alternate and divide attention in the course of daily activities. For ex- ample, a receptionist who must switch back and forth be- tween answering the phone and talking with customers must use alternating attention while mentally holding a place to return to the other activity. Divided attention requires partialing out attentional resources at the same time rather than switching back and forth, however quickly. A good example is driving a car, listening to a radio, and talking with a passenger. Researchers have de- bated whether divided attention is, in fact, possible, or whether people just manage to shift their attention quickly between different stimuli. However, evidence in- dicates that people can divide attention to some degree. Sustained attention is the ability to maintain an effortful response over time. It is related to the ability to persist and sustain a level of vigilance. People who work as air traffic controllers or on assembly-line jobs must have ex- cellent abilities for sustaining attention.

Attention can be further characterized by task or in- formation-processing demands. Tasks that are routinely processed or overlearned can be performed automatically with minimal conscious thought. Automatic processing places minimal demands on attentional resources, and since processing demands are low, other tasks can be per- formed concurrently. In contrast, new, unfamiliar, or con- flicting tasks require the conscious deployment of mental operations. Controlled processing involves the execution of mental operations in a linear or serial manner with a significant allocation of attentional resources. Parallel pro- cessing of additional tasks is generally not possible (Cohen, Aston-Jones, & Gilzenrat, 2004). An experienced driver

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242 PART TWO | The Functioning Brain

does not need to attend to the mechanics of driving while conversing with a passenger, because eye, hand, and foot movement associated with driving are well-practiced or “habitual.” A person driving for the first time must com- mit considerable attention to the mechanics of driving and will find conversing with a passenger to be not only difficult but highly disruptive.

The disruption of attention is a common complaint of patients who have a variety of disorders. Table 9.1 provides a partial listing of disorders that include attentional dys- function as a prominent component of the symptom pat- tern. The range of disorders illustrates that attentional dysfunction is easily compromised by neurologic, meta- bolic, and psychiatric disorders. Fatigue, or inability to sustain attention to an activity, frequently appears across a number of more generalized neuropsychological disor- ders. Patients with neurologic disease, as well as patients who have suffered focal or generalized brain insults, often describe mentally wearing out when engaged in tasks that require persistent effortful attention. People with affective disorders frequently report attention and concentration problems. Depressed people often describe drifting off or “spacing out,” so that even when driving they may miss an exit. Mania is associated with concentration problems of another sort. Manic people may become so energetic with a relentless “flight of ideas” passing through their minds that they cannot accomplish anything, because they cannot concentrate on one thing at a time.

Attentional deficits are also a common concomitant of schizophrenia. These include perseveration of thought

and action, inability to disengage attention, problems in sustained attention or vigilance, distractibility, and an al- most random tendency to orient to both external and in- ternal stimuli. This set of deficits may cause the loose as- sociations in thought processes that schizophrenics commonly show. Close to half of schizophrenics show no galvanic skin conductance response (SCR), which is ordi- narily considered an orienting response to novel sensory stimuli (Dawson & Nuechterlein, 1984). Neuropsychol- ogists call this subgroup of schizophrenics electrodermal nonresponders. Nonresponders are more likely to show the negative symptoms of schizophrenia including apathy, emotional and social withdrawal, and blunted affect. Nonresponders are also more likely to have cortical atro- phy than schizophrenic galvanic skin responders. Interest- ingly, the failure of a psychophysiological skin conduc- tance orienting response to sensory stimulation comes against a background of chronic elevation of autonomic responses, which implies a generalized hyperarousal in this subgroup. Some investigators suggest (see Cohen, 1993, for review) that the attention deficit in schizophre- nia may be a primary cognitive dysfunction.

M O D E L S O F A T T E N T I O N

A myriad of models have been developed to conceptual- ize attentional functioning. Each model represents a dif- ferent theoretical orientation, type of attention, method of study, and degree of empirical verification. We present the individual models that Mesulam, Posner, and Mirsky developed in order to provide familiarity with neuropsy- chological conceptualizations of attentional functioning.

M e s u l a m ’ s M o d e l o f S p a t i a l A t t e n t i o n

Mesulam (2000) presents a model of selective, spatial at- tention that has enhanced our understanding of neu- ropsychological manifestations of patients exhibiting symptoms of attentional neglect. Based on clinical and em- pirical research, Mesulam poses that a neural network in- volving the frontal, parietal, and cingulate cortices supports spatial attention to the extrapersonal world (Figure 9.10). Each of these regions makes a differential contribution to spatial attention. The parietal region generates an internal spatial representation (sensory map) of the extrapersonal environment, whereas the cingulate cortex assigns and regulates motivational and emotional significance to ex- trapersonal elements (Gitelman et al., 1999; Kim et al., 1999). The frontal cortex, particularly the frontal eye fields (Brodmann’s area 8) and surrounding areas, modu- lates and coordinates motor programs for exploration,

Attention-deficit/hyperactivity disorder

Neurologic disease Multiple sclerosis Alzheimer’s disease Parkinson’s disease

Head trauma

Seizure disorders

Metabolic disorder Hypoglycemic encephalopathy Hyperthyroidism

Psychiatric disorders Depression Mania Schizophrenia

Right hemisphere stroke: unilateral neglect

Table 9.1 Disorders That Show Prominent Attentional Dysfunction

scanning, foveating, fixating, and manipulating (reach- ing) extrapersonal stimuli. Spatial attention requires the integrity of these three cortical areas, as well as their inter- connections with one another and with subcortical regions in the thalamus and striatum. The model thus conceptualizes spatial attention in terms of sensory repre- sentation, motivational importance and expectancy, and motor response.

Recently, Mesulam’s model (Nobre, Coull, Maquet, Frith, Vandenberghe, & Mesulam, 2004) was extended to spatial attention to information held within working memory. Research participants underwent neuroimaging (fMRI) while performing a spatial working memory task and a spatial orientation task. The former task required the orientation of attention to internalized representa- tions of previously encoded stimuli, and the latter re- quired attentional orientation to extrapersonal stimuli. Neuroimaging demonstrated that both tasks recruited overlapping networks involving the occipital, parietal, and frontal cortices. While both spatial tasks activated the su- perior parietal lobe, only the right inferior parietal cortex was selectively activated during extrapersonal attentional orienting. With regard to the frontal lobes, orienting to extrapersonal stimuli activated the premotor and dorsal prefrontal cortex, while more anterior prefrontal regions

were selectively engaged in orienting attention to inter- nally represented stimuli. Previous research has associated these anterior prefontal regions with working memory operations. Overall, the findings suggest that overlap- ping neural networks are involved in orienting attention to external and internal spatial representations.

Lesions in any of the neural components supporting spatial attention can lead to hemispatial neglect, that is, a failure to attend to the contralateral visual field. Hemis- patial neglect generally relates to right rather than left hemisphere injury, suggesting hemispheric asymmetry in the support of spatial attention. The right hemisphere ap- pears specialized for control of spatial attention across the visual field, whereas the left hemisphere’s control is pri- marily limited to the contralateral right side visual field.

P o s n e r ’ s A n t e r i o r a n d P o s t e r i o r A t t e n t i o n M o d e l

Michael Posner presents a model of attention from the per- spective of cognitive psychology and neuroscience. He poses that attention can be defined by three major func- tions: (1) orienting to events, particularly to locations in vi- sual space; (2) achieving and maintaining a vigilant or alert state; and (3) orchestrating voluntary actions (Fernandez- Duque & Posner, 2001). Each attentional function is, in turn, supported by separate neural networks, namely, ori- enting, vigilance, and executive networks (Table 9.2). Moreover, these attention-neural networks operate inter- actively with each other and other cortical and subcortical regions.

CHAPTER 9 | Memory, Attention, Emotion, and Executive Functioning 243

Figure 9.10 A theoretical schematic of the attentional sys- tem. (From Mesulam, M. M. [1985]. Principles of behavioral neurol- ogy. Philadelphia: E. A. Davis; reprinted from Cohen, R. A. [1993]. The neuropsychology of attention [p. 334, Figure 14.2]. Reprinted by kind permission of Springer Science and Business Media.)

Attention Networks Functions Neural Correlates

Posterior Orienting to stimuli orienting system

Disengage attention Temporoparietal, superior from a stimuli temporal, superior

parietal

Move to a stimuli Superior colliculus Engage new stimuli Thalamus

Vigilance attention Achieving and Right frontoparietal system maintaining an

alert state

Anterior or executive Orchestrating Anterior cingulate, attention system voluntary actions lateral and orbitofrontal

prefrontal cortex, basal ganglia, thalamus

Table 9.2 Posner’s Attention Networks

244 PART TWO | The Functioning Brain

When visually orienting to an event in the environ- ment, three basic cognitive operations—disengage, move, and engage—activate. Attention is first disengaged from the current event of focus and then moved to the new point of focus, where attentional resources are engaged. The operations of disengage, move, and engage are linked to the parietal, midbrain, and thalamic region, respec- tively. Accordingly, the visual orienting system is termed the posterior attention system. This system plays a role in conscious attention to portions of your visuospatial field and directs the attention of your eyes to a point in space. The posterior parietal lobe mediates conscious at- tention to spatial targets, the midbrain superior colliculus plays a role in moving the eyes from one position to an- other, and the pulvinar of the thalamus helps select and filter important sensory information for processing. The orienting system is also activated in covert orientation. Covert orientation refers to the spatial engagement of at- tention to a target without moving the eyes or the head. For example, if you fixate your eyes on an object, you can also attend to a peripherally located object without mov- ing your eyes or head.

Posner initially ascribed the disengage function to the superior parietal lobe. However, lesion studies showed that disruption of the disengage function was often associated

with lesions in the temporoparietal junction or superior temporal lobe. This difference was resolved by the discov- ery that lesions of the temporoparietal junction or supe- rior temporal regions impair the ability to disengage from a stimulus, and then shift attention to a new or novel stimulus (Posner & Fan, in press). In contrast, lesions of the superior parietal lobe disrupt voluntary shifts of at- tention following a cue or when searching a visual target.

There are indications that the orienting system is mod- ulated, in part, by the cholinergic neurotransmitter ACh (acetylcholine). ACh is produced by the nucleus basalis of the brain forebrain and innervates many cortical areas, in- cluding the parietal lobes. Research with primates shows that lesions of the nucleus basalis disrupt the disengage- ment of attention from an ipsilesional cue to engage a tar- get contralateral to the side of the lesion (Fernandez- Duque & Posner, 2001).

Patients with lesions to the right posterior orienting system frequently fail to attend to the opposite visual field, a condition referred to as hemispatial neglect. As discussed previously, hemispatial neglect is not a sensory deficit to visual input, but rather a failure to attend to half of the visual field (Figure 9.11). Posner (Posner & Petersen, 1990) describes this as a problem of engaging, moving, and disengaging focus to objects in the contralateral field

Figure 9.11 A case of hemispatial inattention. (From Honoré Daumier, M. [1858]. Babinet prevenu par sa portiere de la visite de la comete. Le Charivari. Courtesy of Museum of Fine Arts, Boston, MA. Reprinted from Cohen, R. A. [1993]. The neuropsychology of attention [frontispiece]. New York: Plenum Press, by permission.)

of vision. In this view, the system does not direct the eyes and the brain to engage the left side of space, or to disen- gage attention from the right side of space.

The vigilance attention system mobilizes and sus- tains alertness for processing high-priority targets and is important to attentional functioning. For example, if you were involved in an aerial search for survivors of a boating accident, you would have to maintain a high level of alertness and preparedness to identify a survivor in the expanse of the ocean. In addition, you would need to avoid processing irrelevant information (external or internal) to avoid distraction. The neural network sup- porting the vigilance system includes the right frontal and parietal regions of the brain. The neurotransmitter norepinephrine, produced by the locus ceruleus of the mid- brain, is implicated in achieving an alert state and main- taining attention over time (Fan, McCandliss, Sommer, Raz, & Posner 2002).

The anterior or executive attention system controls and coordinates other brain regions in the execution of voluntary attention. A hierarchy exists for attentional pro- cessing, with the anterior system passing control to the posterior system as needed. The executive attention sys- tem orchestrates higher order cognitive functions such as task switching, inhibitory control, conflict resolution, error detection, attentional resource allocation, planning, and the processing of novel stimuli. A number of cortical and subcortical substrates support the executive attention network, although Posner has focused much of his re- search and theorization on the anterior cingulate and lat- eral prefrontal cortex (Posner & DiGirolamo, 1998). One of the primary functions of the anterior cingulate relates to the monitoring and resolution of conflict between op- erations occurring in different brain areas (Posner & Fan, in press). For example, if an overlearned (automatic) re- sponse to a stimulus is to be inhibited in favor of a less salient response, the anterior cingulate provides the top- down control necessary to initiate the operations of inhi- bition and response selection. Similarly, the anterior cin- gulate activates when a task requires error detection. Thus, if you were proofreading a recent paper that you had pre- pared for a class, the anterior cingulate would be active with regard to identifying errors in the text.

Often, the lateral prefrontal cortex and anterior cingu- late are jointly activated, depending on the nature of the presented demand or task. The involvement of the lateral prefrontal cortex in the executive attention system relates to its role in holding mental representations of specific in- formation in temporary memory. This set of cognitive op- erations is consistent with the definition of working mem- ory. The Stroop test (1935) illustrates the roles of the

anterior cingulate and lateral prefrontal cortex in execu- tive attention. One of the trials of the Stroop test presents the examinee with the words red, green, and blue printed in an incongruous color. For example, the word red is printed in green type. Reading is an overlearned (auto- matic) behavior for most adults, and when written text is presented, decoding occurs quickly and automatically. In contrast, naming the color of objects is a less rapid and automatic process. When the words red, green, and blue are presented in incongruous color, reading the word is the salient response. If you are asked not to read the words, but to name the incongruous color of the printed words, significant conflict is produced. The anterior cin- gulate activates, as discussed earlier, to provide the top- down inhibitory control and response selection. The lat- eral prefrontal region holds the mental representation of the “rule” (“Name the color, don’t read the word.”) in working memory to guide the process.

Although norepinephrine and ACh are implicated in the support of the alerting and orientating systems, re- spectively, dopamine is considered the primary neural modulator of the executive or anterior attention system (Fernandez-Duque & Posner, 2001). Disorders that in- volve disruption of dopaminergic modulation (for exam- ple, schizophrenia) frequently demonstrate dysfunctions of executive attention. Furthermore, administration of a dopamine agonist to patients with lesions of the frontal lobes improves performance on measures of executive function (McDowell, Whyte, & D’Esposito, 1998).

M i r s k y ’ s E l e m e n t s o f A t t e n t i o n M o d e l

Allen Mirsky (National Institute of Mental Health, Bethesda, MD) developed a neuropsychological model that identifies the possible elements of attention and re- lates these elements to neuropsychological measures and the underlying neural systems. Mirsky (1996) proposed that there were three elements of attention: focus-execute, sustain, and shift. A battery of neuropsychological mea- sures considered sensitive to attentional functioning was compiled (Table 9.3) and administered to adult neuropsy- chiatric patients and healthy control participants. The test data revealed four factors, three of which corresponded with the elements of attention proposed by Mirsky, and an additional element that was labeled encode. Subse- quently, the battery was extended to healthy children with measures appropriate to the younger age-group. Once again, four factors were identified, each similar to the ele- ments of attention identified in the adult studies.

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246 PART TWO | The Functioning Brain

The four elements of attention, and their hypothesized supportive neural substrates, are presented in Table 9.3. In brief, the four elements are described as follows:

1. Focus-execute attention involves selective attention and rapid perceptual-motor output.

2. Shifting attention describes the ability to move or change attentional focus in a flexible and adaptive manner.

3. Sustained attention pertains to the attention func- tion of vigilance.

4. Encode attention specifies the capacity to briefly maintain information in memory (that is, “on line”) while performing other related computations or actions.

Recently, a fifth component of attention, stable, was identified, and represents the consistency of attentional effort. The five elements of attention are believed to be supported by relatively distinct neuroanatomic regions (see Table 9.3) that interconnect to form an attention sys- tem. The distribution of the attention system throughout the brain is widespread. Accordingly, the attention system is quite vulnerable to disruption when brain injury is sus- tained; yet, it is also resilient. A specific attention func- tion may be compromised by injury, but undamaged neural regions can provide some degree of compensation.

Mirsky’s model has enhanced our understanding of the potential difference in attentional regulation of various clinical groups. Chapter 11 discusses the application of Mirsky’s model to the investigation of the attentional pro- cessing of children with attention-deficit/hyperactivity disorder (ADHD).

The attention systems and structures presented here are skewed toward visual attentional processing because this is the best understood and most widely studied sensory processing system in relation to attention. Interestingly, studies of auditory spatial attention, similar to visuospa- tial attention, have been found to recruit the parietal cor- tex (Kim et al., 1999). There is agreement that, at a corti- cal level, the right hemisphere, particularly the parietal and frontal regions, plays a central role in attentional con- trol. Subcortically, the anterior cingulate, thalamus, colli- culi, and basal ganglia contribute to attentional function- ing. These cortical and subcortical regions do not operate independently, but rather perform their functions via in- terconnecting neural systems.

Executive Functioning

Compared with all other areas of the cortex, the pre- frontal lobes are unique in organization and function. For more than a century, controversy, confusion, and specula- tion have existed over the function(s) of the frontal lobes. Speculation has included conceptualizations of the frontal lobes as structures that are “silent” (having limited func- tion), support a singular or global function (for example, abstract thinking), or underpin different classes of behav- iors (for example, impulse control, judgment, creativity, emotional regulation, and moral judgment). The functions of the temporal, parietal, and occipital lobes follow straight- forward principles of organization built around sensory sys- tem processing. In contrast, frontal lobe pathology does not

Subject Group Factor 1: Focus-Execute Factor 2: Shift Factor 3/5: Sustain/Stable Factor 4: Encode

Adult WAIS-R Digit Symbol, WCST CPT WAIS-R Digit Span Stroop test, Letter and Arithmetic Cancellation, and TMT-A and -B

Child WISC-R Coding and WCST CPT WISC-R Digit Span Digit Cancellation and Arithmetic

Supporting substrata Focus: Inferior parietal and Prefrontal cortex Rostral midbrain structures Hippocampus and superior temporal cortexes and brainstem amygdala Execute: Inferior parietal and corpus striatum

Note: WAIS-R � Wechsler Adult Intelligence Scale-Revised (Wechsler, 1981); Stroop Test (Stroop, 1935); Letter Cancellation � Letter Cancellation Test (Talland, 1965); TMT-A and -B � Trail Making Test Parts A and B (Reitan & Davison, 1974); WCST � Wisconsin Card Sorting Test (Grant & Berg, 1948); CPT � Continuous Performance Test (Rosvold, Mirsky, Sarason, Bransome, & Beck, 1956); WISC-R � Wechsler Intelligence Scale for Children-Revised (Wechsler, 1974); Digit Cancellation (Mirsky, 1995).

Source: Adapted from Mirsky (1995, 1996).

Table 9.3 Mirsky’s Elements of Attention

CHAPTER 9 | Memory, Attention, Emotion, and Executive Functioning 247

result in primary disorders of sensation or perception, motor disability, memory, or language. Rather, the frontal lobes, by virtue of their interconnections with almost all other brain regions—including the brainstem; occipital, temporal and parietal lobes; limbic regions; and subcortical areas— serve to guide, direct, integrate, and monitor goal-directed behavior (Anderson, 2002; Anderson, Levin, & Jacobs, 2002). If the brain is a symphony, the frontal lobes act as the conductor—guiding, coordinating, and directing the separate sections of the orchestra to produce a harmonious and integrated musical performance.

The terms frontal lobe functioning and executive func- tioning are often used interchangeably. Although the terms overlap, the former suggests that presented behaviors are directly linked to the frontal lobes, whereas the latter con- notes a class of behavioral manifestations that may be di- rectly or indirectly related to frontal lobe functioning. Be- cause of the significant afferent and efferent connectivity of the frontal lobes with other brain regions, disruption to any one these connecting systems can produce pathologic behaviors similar to those caused by direct frontal damage. For example, lesions to the caudate nucleus of the basal ganglia can result in pathologic behaviors similar to those seen with dorsolateral prefrontal damage. Although the term executive functioning does not denote a specific anatomic basis for behavior, it does implicate the frontal cortex and its interconnective neural circuitry. Both terms converge in the conceptualization of cortical functions that relate to the directing, controlling, and managing of be- havior, that is, higher order supervisory brain computa- tions. Functions attributed to the executive system include planning, flexible problem solving, working memory, at- tentional allocation, inhibition, and at the highest levels, the self-monitoring and self-assessment of behavior. Clearly, executive functioning refers to sets of higher order behavior, rather than a single type of behavior. Likewise, executive functioning is not limited to cognitive processes, but is intimately involved in emotional and social behav- ioral regulation. In fact, lesions of the prefrontal regions, and associated subcortical regions linked to emotional and social functioning, can produce some of the most devastat- ing impairments. Executive functioning impairments be- come more evident in the most complex aspects of human conscious activity, or those activities of higher problem solving, reasoning, abstraction, critical self-awareness, and social interaction that make us human.

D E V E L O P M E N T O F E X E C U T I V E F U N C T I O N S

The maturation of executive functions is crucial to psy- chological adaptation and adjustment across the life span

(Eslinger, Biddle, & Grattan, 1997). Initially, our under- standing of the development of executive functions lagged behind that of the maturation of other cortically sup- ported functions such as intelligence. As discussed earlier, the lag was partially related to the belief in neuropsychol- ogy that prefrontal functions did not begin to emerge until late childhood or early adolescence. Although this belief delayed the initiation of active study and research of childhood executive functions, significant progress has been evident since the early 1980s. Accordingly, we pre- view here some of the advances in our understanding of the development of executive functions.

Empirical studies (Levin et al., 1991; Welsh, Pennington, & Groisser, 1991) suggest that basic executive functions develop early in life and follow a protracted, multistep trajectory to maturity in adulthood. The early appearance of rudimentary executive functions and the later develop- ment of more complex functions, such as abstract reason- ing and judgment, parallel the lengthy development of the prefrontal cortex. Interestingly, the emergence of rudi- mentary executive functions correlates with the periods of maximum synaptic density of the frontal lobes. However, more complex functions continue to evolve long after maximum synaptic density is reached, and reflect a host of other developmental advances such as synaptic pruning and sculpting, axonal myelination, and neuro- chemical and neurophysiologic changes.

Important advances in understanding the development of executive functions are due to the remarkable investi- gations of Goldman-Rakic (1987a,b), Diamond (1991), and others. Goldman-Rakic has studied the relation of prefrontal development to the emergence of the cognitive operation of object permanence, that is, the capacity to store in memory a representation of an object that is re- moved from view for the purpose of guiding future be- havior. Using a delayed response task (see Figure 9.9), the experimenter required rhesus monkeys to maintain in memory the spatial location or features of an object over delays ranging from 0 to 10 seconds. By the age of 2 to 4 months, the rhesus monkeys could perform the memory tasks at delay intervals of 2 to 5 seconds. During this 2- to 4-month period, researchers observed maximum synaptic density in the prefrontal lobes of the rhesus monkeys. The corresponding period of synaptic density in the human in- fant occurs between 8 and 24 months (Huttenlocher, 1990). The latter time interval also correlates with the infant’s abil- ity to perform a delayed response task (Neuropsychology in Action 9.2), suggesting that the executive function of working memory has emerged.

Diamond (1991) conducted a series of infant studies that have helped clarify the development of executive

248 PART TWO | The Functioning Brain

Diamond (1991) has adapted a number of tasks that Jean Piaget initially used in studying cognitive development to inves- tigate executive functions. In her study of infants, Diamond endeavored to relate the development of executive functions to the maturation of the underlying frontal circuitry.

Contiguous Object Task The contiguous object task involves the use of a transparent box that is open at the top (Figure 9.12). The experimenter places a toy block behind the wall of the box and prompts the infant to pick up the toy block. Infants of 7 months can reach the block behind the wall if a single straight movement is required (frame A). However, if the placement of the block necessitates a two-directional reach (two sequential movements), the infant cannot accomplish these movements until approximately 10 months (frame B). Also, at younger than 10 months, the infant cannot inhibit the reflexive grasping of the edge of the box when his or her hand comes in contact with it.

Hidden Object Piaget noted that the infant 5 to 7 months old would not reach or search for an object hidden from view; that is, “out of sight, out of mind.” The hidden object task involves showing the

infant a toy, and then covering it with a blanket or placing a screen in front of it to block the child’s view (Figure 9.13). Diamond’s research suggests that the 5- to 7-month-old infant does, in fact, realize that the object is hidden, but cannot demonstrate this knowledge by executing a motor response. That is, the infant is unable to organize and execute a means–end action sequence such as removing the blanket from the hidden object. However, by 7.5 to 8 months old, the infant is capable of executing the necessary action sequence.

A not B (Delayed Response Task) The A not B task involves placing two “wells” in front of the infant (Figure 9.14) in which a toy can be hidden. The infant observes the researcher hide a toy in one of the wells, and then after a short period (2–5 seconds) is allowed to reach for the toy. Then the re- searcher hides the toy in the opposite well, and after a delay again allows the infant to reach for the toy. An infant younger than 8 months will reach for the well that con- tained the previously retrieved toy, even

N e u r o p s y c h o l o g y i n A c t i o n 9 . 2

E x e c u t i v e F u n c t i o n T a s k s

by William C. Culbertson

Figure 9.12 Contiguous object task. (a) Single, straight-line reach for the block. (b) Two-directional reach- ing movement for the block. (Reproduced from Diamond A., & Gilbert, J. [1989]. Development as progressive inhibitory control of action: Retrieval of a contiguous object. Cognitive Development, 12, 223–249. Presented by Diamond, A. [1991]. Neuropsychological insights into the meaning of object concept development. In S. Carey & R. Gelman [Eds.], The epigenesis of mind: Essays on biology and cognition [p. 72, Figure 3.2]. Hillsdale, NJ: Erlbaum, by permission.)

Figure 9.13 Hidden object task. (a) The infant is gazing at a toy. (b) The toy is shielded by a screen and the infant does not search or reach for the object. (Courtesy Rutgers University)

CHAPTER 9 | Memory, Attention, Emotion, and Executive Functioning 249

though he or she has seen the researcher place the toy in the opposite well.

In Figure 9.14, the infant has already successfully retrieved the toy from the well to the viewer’s right. The researcher then placed the toy in the opposite well. In the first two frames (top left and right), the infant is look-

ing at the well containing the toy. However, when allowed to reach for the toy, the infant uncovers the well that contained the toy on the previous trial (bottom left and right). Success on this task requires the emergence of working memory capability and the ability to inhibit a previously reinforced response.

Detour Reaching Task In the detour reaching task, the experimenter requires the infant to detour around a barrier to reach and retrieve an object. The task involves a small transparent box that the experimenter places in front of the infant with one of its sides open (Figure 9.15). If they can see the toy through an open side, infants 6.5 to 7 months of age will reach in to retrieve a toy. However, if the experimenter places the toy directly in the child’s view, but behind a closed side, the infant repeatedly and unsuc- cessfully tries to reach through the closed side. The infant is unable to inhibit reaching straight for the toy. Also, the infant is unable to raise the box with one hand and reach at the same time with the other hand. In Figure 9.15, the child has lifted the box and is establishing a direct line of sight to the toy. As one hand moves down to reach into the box (second frame), the other hand holding the box also moves down. At this point (third frame), the toy is in the child’s direct line of sight through the top of the box. The child withdraws her hand from the opening and tries, unsuccessfully, to reach for the toy through the closed top of the box. Between 8 and 12 months, the child develops the ability to look through one side of the box while reaching through another side. Similarly, the child can raise the box with one hand, and simultaneously reaching in with the other.

Figure 9.14 A not B task. (top) The infant is gazing at the toy in the well. In the following frames, the infant continues to gaze at the well holding the toy, yet lifts the cover from the well that contained the toy on the previous trial. (Reproduced from Diamond, A. [1991]. Neuropsychological insights into the meaning of object concept development. In S. Carey & R. Gelman [Eds.], The epigenesis of mind: Essays on biology and cognition [p. 86, Figure 3.4]. Mahwah, NJ: Lawrence Erlbaum Associates, by permission.)

Figure 9.15 Detour reaching task. (a) The child has lifted the box and is looking in at a toy. (b) As the child begins to reach for the toy, the box lowers. The toy is now in the child’s line of sight through the top of the box. (c) The child removes the hand from the box and tries to reach for the toy through the top of the box. (Society for Research in Child Development Abstracts, 3, 78, as presented in Diamond, A. [1991]. Neuropsychological insights into the mean- ing of object concept development. In S. Carey & R. Gelman [Eds.], The epigenesis of mind: Essays on biology and cognition [p. 90, Figure 3.5]. Mahwah, NJ: Lawrence Erlbaum Associates, by permission.)

a. b. c.

250 PART TWO | The Functioning Brain

Figure 9.16 Tower of London-Drexel University (TOLDX) test: start and goal positions. (Reproduced from Culbertson, W. C., & Zillmer, E. A. [1998]. The Tower of London: A standardized approach to assessing executive functioning in children. Archives of Clinical Neu- ropsychology, 13, 289. Copyright © 1998 Elsevier Science, Ltd. Reprinted with permission of the authors and the publisher.)

inhibitory control and other functions as they relate to the maturation of the frontal cortex. She presented in- fants from 5 to 12 months old with tasks involving de- tour reaching, contiguous objects, hidden objects, and de- layed response (A not B task) to determine the emergence of frontal functions (see Neuropsychology in Action 9.2). Her findings demonstrated that the ability to inhibit re- flexive reactions to contact (elicitation of the grasp reflex when touching an object) and to combine two or more actions into a behavioral sequence develops between the 5th and 9th months of life. These two functions are con- tingent on the maturation of the supplementary motor cortex (SMC) of the frontal lobes.

Between 8 and 12 months of age, an infant develops the ability to inhibit a response that is primed for release, and to relate information over time delays and spatial sep- aration. The infant’s successful performance of the de- layed response task (A not B) and the detour reaching task, respectively, reflects the development of the ability to relate information across time and space. The perfor- mance of these tasks requires inhibitory control and work- ing memory capabilities, functions that the dorsolateral pre- frontal cortex support (Goldman-Rakic, 1987b). Finally, the ability of the infant to simultaneously coordinate two different movements emerges between 8 and 12 months of age. That is, the infant can execute an action with one hand and simultaneously perform a different action with the other. These hand movements require both coordina- tion and inhibition of movements. That is, the action of each hand must coordinate with the other, but each is inhibited from performing the same movement as the other. This complex set of actions requires the matura- tion of the corpus callosum that joins the SMC areas of each hemisphere. The interhemispheric communication of the SMC regions is necessary for coordinating bilat- eral actions.

Other researchers (Denckla, 1996; Pennington, 1997b) have also made notable contributions to the identification of emerging childhood executive functions. For example, Welsh and coworkers (1991) have traced the development of executive functions in healthy children, ages 3 to 12, and young adults. The investigators determined that sub- jects achieved adult-like performance at three different age levels: 6 years old, 10 years old, and during adoles- cence. Simple functions, such as visual search (searching an array of stimuli for targets), emerge early, followed by the more complex inhibitory skills, and finally, the most advanced abilities as demonstrated in complex planning. Age-related changes in the development of the executive functions of working memory, inhibition, and cognitive flexibility have been identified for healthy preschool

(Espy, Kaufmann, Glisky, & McDiarmid, 2001) and ele- mentary school (Archibald & Kerns, 1999) children. There are suggestions that some executive functions un- fold in a gradually progressive manner, whereas others move toward maturity in a stepwise, or staged fashion. Furthermore, executive function performance does not appear to correlate significantly with intelligence, sup- porting the proposition that these two cognitive con- structs are relatively independent from each other.

Similarly, Culbertson and Zillmer (1998a, 1998b, 2005) used the Tower of London-Drexel University (TOLDX) test to assess age-related changes in the executive planning of healthy children and children with ADHD. Executive planning, as assessed by the TOLDX, involves the develop- ment of a “mental template” to guide the sequential move- ment of colored beads across three pegs to match a pattern presented on the examiner’s model (Figure 9.16). The ex- aminer asks the child to replicate a series of bead patterns of increasing difficulty while adhering to specific problem- solving rules. The goal is to solve each pattern in a mini- mum number of moves without violating the rules. Chil- dren who fail to plan, or plan superficially, require additional moves to reproduce the target patterns.

Culbertson and Zillmer selected children with ADHD for study in an effort to determine whether deficits in ex- ecutive planning were associated with the disorder (see Chapter 11 for a discussion of ADHD). The researchers hypothesized that the ADHD children would perform less efficiently on the TOLDX. Figure 9.17shows the TOLDX total move scores of the two groups of children.

Noteworthy is the steady improvement in executive planning from 7 to 12 years of age, with the healthy and ADHD children groups showing a parallel trajectory. However, the children with ADHD, as predicted, per- formed in a significantly less efficient manner than the healthy children. The poorer TOLDX performance of ADHD children is consistent with emerging research (Pennington, 1997b) suggesting that the disorder is de- velopmental in origin and potentially a consequence of impaired executive functions. Further analysis of the chil-

dren’s TOLDX performance showed the following results for the younger children, both healthy and those with ADHD: (1) spent less time planning before attempting to solve the bead patterns, (2) solved fewer bead patterns in a minimum number of moves, and (3) violated a greater number of problem-solving rules than the older healthy and ADHD children. Clearly, the maturation of executive planning involves the advance of a number of component cognitive skills.

Recently, Anderson (2002) reviewed factor analytic stud- ies pertinent to the development of executive functioning of childhood and adolescent populations. Despite differ- ences in executive measures used, participants sampled, and ages represented, similar executive factors were iden- tified to include planning, impulse control, concept rea- soning, and response speed. Integrating these findings with the recent conceptualizations of executive function- ing reported by Alexander and Stuss (2000), Anderson proposed four developmentally sensitive executive func- tion domains: attention control (selective attention, in- hibitory control, sustained attention, and monitoring of executed plans), information processing (fluency, effi- ciency, and speed of output), cognitive flexibility (shifting between response sets, profiting from mistakes, develop- ing alternative strategies, dividing attention, and multi- tasking), and goal setting (planning, organization, con- ceptual reasoning, and strategic problem-solving). Using this framework, a developmental trajectory of executive functions is proposed (Figure 9.18). Attention control un- dergoes significant maturation during infancy and early childhood, with adult levels of functioning reached by

CHAPTER 9 | Memory, Attention, Emotion, and Executive Functioning 251

Figure 9.17 Mean Tower of London-Drexel University (TOLDX) test total move score by age level for attention-deficit/hyperactiv- ity disorder (ADHD) and normal control (NC) children. (Reproduced from Culbertson, W. C., & Zillmer, E. A. [1998]. The Tower of London: A standardized approach to assessing executive functioning in children. Archives of Clinical Neuropsychology, 13, 291. Copyright © 1998 Elsevier Science, Ltd. Reprinted with permission of the authors and the publisher.)

Text not available due to copyright restrictions

252 PART TWO | The Functioning Brain

middle childhood. Despite somewhat different trajecto- ries, information processing, cognitive flexibility, and goal-setting functions achieve maturation by the end of middle childhood. However, developmental refinement continues into mid-adolescence and early adulthood.

A more recent meta-analysis of relevant studies of ex- ecutive/frontal development (Romine & Reynolds, 2005) reported that abilities such as planning, verbal fluency, and inhibition of perseveration demonstrated pronounced increases between 5 and 8 years of age. Developmental increases were evident across all executive functions be- tween 8 and 11 years of age. Small incremental changes were noted between 11 and 14 years of age for the inhibi- tion of perseveration and set maintenance. Planning and verbal fluency functions continue to develop throughout adolescence and into early adulthood. The two reviewed meta-analyses indicate that executive functions reach ma- turity at different points during development. It should be remembered that the development of executive functions is, in part, contingent on the maturation of other brain regions and neural systems that support attention, lan- guage, emotions, and memory.

Research has also focused on the relation between the development of emotional regulation and maturation of the frontal region. Bell and Fox (1994) have found that changes in EEG activation associated with emotional ex- pression appear early in infant development. When a stranger approached, 10-month-old infants exhibited right frontal EEG activation, but the opposite pattern was evident when the mother approached—that is, greater left frontal activation. Similarly, infants who appeared sad or distressed, as assessed by facial expressions, showed greater right frontal activation, whereas those expressing joy demonstrated greater left frontal activation. Of impor- tance was the finding that comparable frontal EEG acti- vation patterns continue to be evident in childhood and adulthood (Davidson, 1994).

Case studies of children who sustained damage to the frontal cortex provide further insight into frontal lobe de- velopment and the regulation of emotional, moral, and social behavior. In a review of cases with varying ages of lesion onset (ranging from prenatal to age 16), Eslinger and colleagues (1997, 2004) found that the children demonstrated impairments in emotional regulation and interpersonal relations, regardless of the age at which the damage occurred. Both immediate and delayed deficits were observed, suggesting that the development of socioe- motional regulatory control was ongoing. The progressive emergence of delayed deficits indicated that the damaged frontal system could not negotiate the increasing cogni- tive, social, and emotional demands of adolescence and

adulthood. For example, a boy who suffered damage to his right frontal lobe at age 3 appeared to recover fully, al- though the mother did note alterations in his personality after the insult. During his early school years, he demon- strated problems in visuospatial performance, attentional focus, impulse control, and establishing friendships. By adolescence, he exhibited limited facial expressions and modulation of voice, interrupted the conversation of oth- ers, had not developed friendships or dated, and often failed to understand the gist of intended communications. His social deficits reflected an inability to empathize or reciprocate emotionally with others, to understand social cues and the pragmatics of language, and to accurately evaluate his own social strengths and weaknesses.

F R O N T A L - M E D I A T E D F U N C T I O N S A N D D Y S F U N C T I O N S

There is increasing evidence that the frontal lobes, inter- acting with cortical and subcortical circuitry, support relatively distinct but overlapping functions. Five pri- mary circuits have been identified—although evolving research suggests that there may be at least two addi- tional circuits (Middleton & Strick, 2001). These cir- cuits project from different regions of the frontal lobes to designated regions of the basal ganglia and return via specific thalamic nuclei. The five neural circuits (Saint- Cyr, Bronstein, & Cummings, 2002) and their cortical origination are skeletomotor (motor and premotor re- gions and parietal somatosensory cortex), oculomotor (frontal and supplementary eye fields), dorsolateral pre- frontal (dorsolateral prefrontal cortex), orbitofrontal (consists of two subcircuits that originate in the lateral and medial frontal cortex), and anterior cingulate (ante- rior cingulate cortex).

We focus on the three circuits that are often implicated in neuropsychological and neuropsychiatric disorders. However, before we begin, several caveats are in order. The frontal lobes are, as previously discussed, richly inter- connected with other cortical and subcortical regions of the brain. Thus, the student should not consider the func- tions attributed to the frontal circuits to be solely local- ized or mediated by a specified region or circuit. The find- ing that damage to different regions of a circuit can produce executive dysfunction comparable with that evi- dent when the frontal lobes are directly involved speaks to this caution. It is probably more accurate to describe the different frontal circuits as contributors, often major, to the mediation of certain types or forms of behavior. Sec- ond, a review of relevant studies shows that differential processing biases for content (for example, verbal versus

nonverbal), modality, and types of mental operations are ascribed to left versus right frontal architecture. However, there are notable exceptions to the putative specificity of right versus left prefrontal systems. For example, verbal semantic retrieval and episodic encoding activates the left prefrontal region, whereas episodic retrieval instigates right prefrontal computations (Cabeza & Nyberg, 2000). Moreover, it is not unusual to find bilateral activation of the frontal cortex for a given task, suggesting complemen- tary processing. Thus, care needs to be exercised when as- suming a one-to-one correspondence between task con- tent, input-output modality, or mental process recruited and the implicated anterior laterality (left versus right). Third, despite significant research and study, we do not fully understand the functions of the frontal systems, nor do researchers and clinicians agree on the functions that are associated with the different frontal circuits or regions.

D o r s o l a t e r a l C i r c u i t

The first circuit, dorsolateral prefrontal, is involved in higher order cognitive operations. Often, this circuit is la- beled the “executive” circuit; however, with our realiza- tion that executive functioning is implicated in the medi- ation of emotional, motivational, and social behavior, we consider the functions of each of the three circuits to be executive in nature. A sample of functions attributed to the dorsolateral circuit includes working memory, cogni- tive flexibility, maintenance of behavioral sets, selective and sustained attention, generation of strategic and diver- gent responses, verbal and nonverbal fluency, planning and organization, inhibitory control, abstract reasoning, mem- ory search and retrieval, temporal-spatial “tagging” (bind- ing time and spatial context to episodes), self-monitoring, insight, and judgment. Furthermore, the dorsolateral circuit participates in emotional-motivational behavior, such that damage to the region may precipitate depres- sive symptoms, although these symptoms are more fre- quently associated with damage to the ventromedial pre- frontal region. The depressive symptoms associated with the dorsolateral prefrontal cortex are characterized by decreased initiative, apathy, indifference, psychomotor re- tardation, and social uneasiness (Anderson & Tranel, 2002). This depressive presentation differs from clinical depression by the absence of vegetative functions, nega- tive cognition, and dysphoria. Some patients with dor- solateral damage demonstrate a decreased capacity to empathize with others, although this impairment is more frequently associated with disruption of the or- bitofrontal circuit (Anderson & Tranel, 2002). The dor- solateral and orbital circuits may play complementary roles in empathic processing, with the former mediating

the cognitive aspects of empathy, and the latter mediat- ing the emotional elements (Eslinger, 1998).

Luria (1990) gives an example of the cognitive diffi- culties of Patient U, who suffered from a progressive frontal lobe tumor:

Patient U is presented the problem: One ABC book and one pen cost 37 cents. One ABC book and two pens cost 49 cents. How much do one ABC book and one pen cost separately?

The patient repeats the problem correctly but does not begin to solve it.

(Dr. Luria): What should you do to solve the problem? (U): “37 and 49. . . . then it’s 86 all in all. . . .” (Dr. Luria): What did you add them for? (U): “To learn how much they paid all in all.” (Dr. Luria): What should you do next? (U): “Next. . . . I don’t know what next. . . . There is nothing else. . . .”

In order to draw the patient’s attention to the final question and help him distinguish the main solution elements, the statement is presented in writing in the form of the following equations:

One ABC book � one pen � 37 cents One ABC book � two pens � 49 cents

(Dr. Luria): How much do one ABC book and one pen cost sepa- rately?

Patient U reads the equation, draws a line underneath and writes down the result of simple summation:

“Two ABC books + three pens = 86 cents” saying, “I’ve learned how many pens and ABC books, how much everything costs.”

It is evident that our attempt to show the difference between the two equations and to prompt the proper logical sequence ended in failure. . . . [T]he investigator gives him the initial element of the respective logical chain.

(Dr. Luria): First 37 cents were spent, then 49 cents. What is the difference accounted for? (U): “It is accounted for by one pen! Then, 49 – 37 = 1 pen.” (Dr. Luria): What should you learn? (U): “How much do an ABC book and a pen cost separately.” (Dr. Luria): So? (U): So, a pen costs 12 cents. Now an ABC book. . . . 49 – 24 = 25 cents. One ABC book costs 25 cents. (Luria, 1990, pp. 106–107)

In the above example, Patient U knows the arithmetic operations necessary to solve problems but cannot discern the important aspects of the problem without external structure. In fact, at first, he cannot initiate any response. His first, rather impulsive response is simply to sum the numbers. He rigidly adheres to this strategy and is too cog- nitively inflexible to think of other possibilities. However,

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254 PART TWO | The Functioning Brain

when he is guided, when the interviewer provides the im- portant aspects of the problem for him, he can arrive at the correct answer. According to Stuss and Benson (1986), Patient U’s primary programs for math algorithms are in- tact, and they act in a fairly automatic or stereotyped man- ner. Unless organized by higher order executive functions, problem-solving behavior becomes chaotic—sometimes failing to initiate, sometimes having no logical sequence, or sometimes perseverating on the first problem-solving strategy that comes to mind.

Joaquin Fuster (2002, 1997) has developed a theory of prefrontal functioning that focuses significantly on the role of the dorsolateral cortex. He poses that the overar- ching function of the prefrontal architecture is the tem- poral organization of behavior, that is, the development and implementation of action sequences across time. Temporal organization of behavior extends to all volun- tary behavior including skeletal, ocular, speech, and inter- nal cognitive processes such as logical reasoning (Fuster, Van Hoesen, Morecraft, & Semendeferi, 2000). Four cog- nitive processes support the temporal organization of be- havior: attention, working memory, preparatory set, and monitoring. These four cognitive processes are based on the functional cooperation of the prefrontal cortex and the subcortical and other cortical structures and circuits.

Attentional control relates to the cooperative activa- tion of the dorsolateral (selective, sustain, and orient- ing of attention), anterior cingulate (motivation and drive aspects of attention), and orbital (inhibitory control and filtering) cortices.

Working memory encompasses the processes dedi- cated to the maintenance and manipulation of infor- mation held in short-term storage to guide behavior. This function is supported by the dorsolateral pre- frontal areas. Working memory provides a retrospec- tive function in temporal organization. Its retrospec- tive function relates to the temporary retention of mental representations of environmental (sensory) information pertinent to goal-directed behavior. For example, you need to hold “on line” the instructions for a test if you are to perform it correctly. The tem- poral organization of behavior requires both retrospec- tive memory and the preparation for action.

Preparatory motor set involves the preparation, tim- ing, and instigation of relevant goal-directed motor behaviors. Once again, the dorsolateral cortex is impli- cated in the support of this function. Patients with frontal lateral lesions often demonstrate deficits in plan- ning due to a failure to prepare for or to initiate a series of actions to achieve a goal. In essence, preparatory set

can be viewed as a failure in prospective memory, or memory for future action.

Response monitoring determines whether current goal-directed behaviors should be maintained or mod- ified. This is important since sensory processing and motor output operate across time, and environmental changes may occur that warrant alterations in goal- directed behaviors. Both the dorsolateral cortex and the anterior cingulate are implicated in the support of response monitoring.

These four functions support the diverse cognitive func- tions attributed to the dorsolateral prefrontal cortex. No- tably, Fuster recognizes that the dorsolateral cortex func- tions in concert with other cortical and subcortical circuitry in the support of behavior.

O r b i t o f r o n t a l ( L a t e r a l a n d M e d i a l ) C i r c u i t

The orbitofrontal circuit is involved in the mediation of emotional and social responses. Initially, neuropsycholo- gists considered inhibitory processes as a primary func- tion of the orbitofrontal cortex. Converging research has altered this notion in that each region of the prefrontal cortex plays a role in behavioral inhibition (Roberts, Robbins, & Weiskrantz, 1998). However, the inhibitory processes of the orbitofrontal circuit are relatively specific to the regulation of emotional and social behavior.

Impulsive, poorly modulated, and contextually inap- propriate behavior results when orbitofrontal inhibitory functioning is impaired. For instance, one of our patients, a man in his 50s, provides a classic example of impulsivity after a frontal lobe injury. Before his injury, T.J. was a suc- cessful businessman who traveled around the region mak- ing sales calls. One day, after the injury, he was to arrive at our office within a major medical center at 9 A.M. He drove around the parking garage trying to find a parking space. Unsuccessful in finding an empty spot, he became frustrated. Finally, he was stuck behind a car whose driver was waiting for someone else to back out. Impulsively, T.J. rammed the car ahead of him. Relating this story, T.J. expressed dismay at himself for acting in a way he felt was wrong. Yet, he felt that at the moment, he just could not help himself.

Patients with orbitofrontal damage can show a range of negative or poorly modulated emotionality. Often, irri- table, angry, depressive, or manic-like emotions are prominent. Paradoxically, some patients exhibit a blunt- ing or dampening of affective responsivity and reduced initiative. Accompanying characteristics of social disinhi- bition may include crude, coarse, and tactless behaviors.

There is often a disregard for rules of social decorum and restraint; an excessive involvement in pleasure seeking; a minimal tolerance for frustration; a lack of sensitivity to future outcomes, both positive and negative (Bechara, Tranel, & Damasio, 2000); and a diminished or lost ca- pacity to empathize with others (Chow & Cummings, 1999; Lichter & Cummings, 2001). Consequently, pa- tients with orbitofrontal damage are prone to make poor, and sometimes disastrous, life decisions (poorly conceived business ventures). Moreover, antisocial actions may re- sult and lead to criminal or legal difficulties (Zald & Kim,

2001). As in the tragic case of Phineas Gage (Neuropsy- chology in Action 9.3), family members and friends often report that the “personality” of the patient, subsequent to orbitofrontal damage, has undergone significant change.

As you read the description of behaviors associated with orbital frontal damage, you might have noted the similarity between many of the behaviors associated with orbitofrontal damage and those exhibited by individuals with the diagnosis of “psychopath or sociopath” (cur- rently, the diagnoses of psychopath and sociopath have been replaced by the diagnosis of antisocial personality

CHAPTER 9 | Memory, Attention, Emotion, and Executive Functioning 255

In 1848, Phineas Gage was a 25-year-old foreman employed by the Rutland and Burlington Railroad. On an autumn day in Vermont, he and his crew were blasting through a rocky section when an accidental explosion sent a long metal bar, a tamping iron, shooting through his head. The pointed end of the rod entered under his left cheek and exited near the top middle of his skull, near the coronal and sagittal sutures. The rod was launched with such force that it landed 30 meters away from him. Amazingly, although Gage was knocked flat, he was able to get up and walk to the ox cart on which he sat while being driven into town. During the ride he chatted and made an entry into his logbook. Because he survived such a freak- ish accident, the case of Phineas Gage is arguably one of the most famous in the early history of neuropsychology.

Before the accident, Gage was seen as well balanced emotionally and mentally, healthy and active. Immediately after the accident, he fought postinjury infection to recover physically. He could walk and con- verse, recognized his friends and family, and appeared rational. To some he seemed fully recovered. But changes in his behavior soon emerged. His physicians noted, “Remembers passing and past events correctly, as well as before the injury. Intellectual manifestations feeble, being exceedingly capricious and childish, but with a will as indomitable as

ever; is particularly obstinate; will not yield to restraint when it conflicts with his desires” (Harlow, 1868, cited in Macmillan, 1996, p. 246). As time went on, this behavior did not abate but endured. Six months later, his physician, John Martin Harlow, summarized his condition:

The equilibrium or balance, so to speak, between his intellectual faculties and his animal propensities, seems to have been destroyed. He is fitful, irreverent, indulging at times in the grossest profanity (which was not previously his custom), manifesting but little deference for his fellows, impatient of restraint or advice when it conflicts with his desires, at times pertinaciously obstinate, yet capricious and vacillating, devising many plans of future operation, which are no sooner arranged than they are abandoned in turn for others appear- ing more feasible. A child in his intellectual capacity and manifestations, he has the animal passions of a strong man. Previous to his injury, although untrained in the schools, he possessed a well-balanced mind, and was looked upon by those who knew him as a shrewd, smar t businessman, very energetic and persistent in executing all his plans of operation. In this regard his mind was radically changed so decidedly that his friends and acquaintances said he was “no longer Gage.” (Harlow, 1868, cited in Macmillan, 1996, p. 247)

Gage cer tainly suffered extensive damage to his lef t frontal lobe and probably also suffered damage to his right frontal lobe. Damasio and colleagues (Damasio, Grabowski, Frank, Galaburda, & Damasio, 1994) have attempted to reconstruct the trajectory and site of damage based on three-dimensional computer modeling of the brain and skull. Their best estimate is that the tamping rod impacted “the ante- rior half of the orbital frontal cor tex . . . the polar and anterior mesial frontal cortices . . . and the anterior-most sector of the anterior cingulate gyrus” (p. 1104). Some right hemisphere damage was also implicated. It is interesting that Harlow implied Gage could no longer “execute” his plans. Many behaviors Gage exhibited are characteristic of people who have problems of executive functioning. Although his basic abilities to process information were intact, he showed low frustration tolerance and impulse control and a loss of ability to structure and follow through on plans—so much so, in fact, that he was seen as a changed person.

Source: The historical references for this case were summarized from Macmillan, M. (1996). Phineas Gage: A case for all reasons. In C. Code, C. Wallesch, Y. Joanette, & A. R. Lecours (Eds.), Classic cases in neuropsychology (pp. 243–262). Sussex, United Kingdom: Psychology Press, by permission.

N e u r o p s y c h o l o g y i n A c t i o n 9 . 3

T h e C a s e o f P h i n e a s G a g e

by Mary Spiers

256 PART TWO | The Functioning Brain

disorder (Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition [DSM IV], 1994). In fact, the similarity between the two conditions prompted the la- beling of the orbitofrontal behavioral syndrome as “pseudopsychopathic” or “acquired sociopathy” (Blumer & Benson, 1975; Damasio, Tranel, & Damasio, 1990). Unlike the true psychopath or sociopath, the pa- tient with orbitofrontal damage experiences remorse for inappropriate actions (Knight & Stuss, 2002) and does not demonstrate the intentional viciousness or planning with regard to committing antisocial acts (Zald & Kim, 2001).

With large lesions, particularly bilateral to the or- bitofrontal region, stimulus-bound behaviors or environ- mental dependency syndrome may be evident. Stimulus- bound behaviors or environmental dependency syndrome subsume a group of actions (utilization behavior, imita- tion behavior, grasp reflex, and manual groping; Archibald, Mateer, & Kerns, 2001) that are emitted with- out voluntary intent as the result of the loss of frontally mediated inhibitory control. This loss of inhibitory con- trol enables external stimuli to directly trigger thoughts and actions. For example, utilization behavior relates to use of a presented object without intent or regard for the context. Thus, if pajamas are presented to a patient with orbitofrontal damage, she or he may undress and slip into the garment, although the act is not “willed” or appropri- ate to the setting (for example, disrobing in the presence of others).

Several theoretical explanations have been posed to ac- count for the social deficits associated with orbitofrontal damage. First, the orbitofrontal circuit is intimately in- volved in the support of the capacity to empathize with others. The diminishment or loss of the capacity for em- pathy appears to preclude an emotional appreciation of others, an essential prerequisite of social sensitivity and reciprocal interactions. Second, Damasio and colleagues (Damasio, 1994, 1998; Bechara, Tranel, & Damasio, 2000, 2002) hypothesize that the orbitofrontal cortex (ventromedial) participates in the attachment of auto- nomic “tags” to events that, in turn, bias response selec- tion. These autonomic tags are termed somatic markers and represent “gut” reactions that covertly or overtly influ- ence behavior. Specifically, somatic markers are visceral- autonomic signals as to the valence (desirability or unde- sirability) of choices or decisions learned through previous experiences with similar or related events. They assist in decision making by rapidly tagging those options that have been associated with positive outcomes, and they eliminate those alternatives that are likely to be associated with negative outcomes. They are particularly influential

when a presenting issue is novel or when uncertainty ex- ists as to the immediate or long-term consequences of available decision or judgment options. In real-life situa- tions, we frequently encounter decision-making demands in which the presenting situation is unfamiliar and/or un- certainty exists regarding which responses will or will not bring about desired consequences. In such situations, we rely on a conflation of past knowledge, cognitive abilities, and intuition (hunch, “a sense,” or “best guess”). The lat- ter reflects a conscious awareness of somatic biasing, al- though such effects need not be conscious. Support for the somatic marker hypothesis is evident in studies (Bechara, Tranel, Damasio, & Damasio, 1996; Bechara et al., 2000) showing that patients with bilateral or- bitofrontal damage (ventromedial) do not generate an SCR (indexing autonomic activity) when viewing emo- tionally arousing stimuli (pictures). Similarly, these pa- tients are able to recall these emotionally arousing images, but do so without the concomitant autonomic response. The latter suggests a disruption of the coupling of mem- ory content and somatosensory states. These patients are not emotionless and are capable of evoking simple so- matic states in response to emotional stimuli. However, their ability to generate and couple complex somatic states to events necessary for the guidance and constraint of de- cision making and judgment is impaired.

Third, Rolls’s (1998, 2002) research with nonhuman primates and humans suggests that the orbitofrontal cor- tex is specialized for rapidly altering behavior in response to changing reinforcement contingencies (reward, nonre- ward, and punishment). The alteration of behavior in re- sponse to changing reinforcing consequences is not restricted to motor actions, but also pertains to emotional and social behavior. The orbitofrontal cortex is uniquely suited for its involvement in emotional-social processing because of its significant anatomic connections (direct and indirect) with the primary and association sensory cor- tices and limbic regions. Thus, the orbitofrontal cortex plays a crucial role in rapidly learning, modifying, and re- learning behavioral responses to changing contextual sig- nals, particularly those of a social nature. Rolls (2002) views emotions as a form of response elicited by reinforc- ing contingencies. In social situations, reinforcing contin- gencies are continually being exchanged and updated based on the presentation of interpersonal stimuli and the association of these stimuli with reward and punishment. As a function of this exchange, preexisting responses are maintained, altered, or extinguished, and new re- sponses are learned. With orbitofrontal damage, the capacity to rapidly alter and learn emotional and re- lated responses in the face of changing contingencies is

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impaired. Consequently, emotional and social behaviors lack contextual regulation as evidenced by in impulsive, rigid, or inappropriate responses.

Interestingly, individuals with orbitofrontal (ventro- medial) lesions can demonstrate a relatively unimpaired neuropsychological profile when administered traditional measures of executive functioning, perception, intelli- gence, memory, and language. Paradoxically, their social, vocational, and economic lives are often in shambles. The case of EVR (Barrash, Tranel, & Anderson, 2000) por- trays the consequences of such damage.

At age 35, EVR underwent resection of a bilateral orbitofrontal meningioma. To achieve complete removal, orbital and lower mesial frontal cortices were excised along with the tumor. Profound personality changes ensued. Although his marriage had previously been stable, he divorced his wife of many years and quickly entered into a second, short-lived marriage. Whereas formerly he had had a keen business sense with con- siderable financial success, postsurgically he entered into a series of disastrous business ventures over a brief period of time. He had been a respected community leader, but since the tumor resection he has never been able to maintain employment and now lives in a sheltered environment. Despite generally superior intellect, memory, and social knowledge by formal neuropsy- chological assessment, in real life he manifests severe defects in decision making, ability to judge the character of others, and in his abilities to plan activities on a daily basis and into the future. (p. 356)

The finding that traditional executive measures fail to identify the deficits of patients such as EVR has prompted the development of measures that are potentially more sensitive to dysfunctions associated with orbital damage. Illustrating this advancement is the “gambling task” that Bechara and colleagues (2002) developed. The measure provides a facsimile of decision-making in real life with regard to the weighting of potential rewards and punish- ments and the uncertainty of outcomes. The gambling task consists of four decks of cards (A, B, C, and D). The patient can select from any deck, and with each selection receives a reward (accrual of money) or penalty (loss of money). Two of the decks are “disadvantageous” because they provide large rewards, but periodically assign unpre- dictably large penalties. Continued selection from the dis- advantageous decks culminates in a net loss. The two ad- vantageous decks provide smaller rewards and penalties and, if repeatedly selected, result in a net gain. Healthy subjects, over time, show a response pattern beginning with a random selection from the four decks to a prefer- ence for the two advantageous decks. In contrast, the pa- tients with ventromedial lesions did not develop this pref- erence pattern and, in fact, were more likely to choose the

high-risk decks. Moreover, the SCRs of the healthy and ventromedial subjects were monitored during the perfor- mance of the gambling task. Initially, the healthy subjects generated SCRs as they won or lost money. Subsequently, as they gained experience with the decks, they began to generate SCRs before the selection of any of the cards. These SCRs were more pronounced before picking a card from a disadvantageous relative to an advantageous deck. In contrast, the patients with ventromedial damage did not generate SCRs before selecting cards and continued to show a preference for the disadvantageous decks. These findings suggest that decision making is guided by somatic signals that are generated in anticipation of fu- ture consequences. With damage, insensitivity to the fu- ture consequences of behavior often results (Wagar & Thagard, 2004).

A n t e r i o r C i n g u l a t e C i r c u i t

The anterior cingulate is a relatively large neural substrate with widely distributed interconnections to other cortical and subcortical regions, implicating its functional in- volvement in neural circuits that support behavior. Not surprisingly, it is implicated in both cognitive and affec- tive/motivational processing (Devinsky, Morrell, & Vogt, 1995). The anterior cingulated is believed to support a number of overlapping functions, including response monitoring, error detection, conflict resolution (incom- patible competing responses), inhibition when prepotent (primed) responses are to be overcome, selective and di- vided attention, and motivation or drive behavior. De- bate continues over whether the major role of the anterior cingulate relates to the monitoring or regulation of neural processing. Neuroimaging and event-related potential studies (Barch, Braver, Sabb, & Noll, 2000; Van Veen & Carter, 2002) show involvement of the anterior cingulate when (1) competing responses vie for release; (2) an error occurs in performance; or (3) a presented task is difficult, novel, complex or ambiguous. Moreover, its activation often precedes or co-occurs with the activation of other neural substrates. This latter activation pattern suggests that the anterior cingulate may monitor and coordinate the engagement or amplification of control by other neural systems. The purpose of this engagement or ampli- fication of control is to ensure efficient or optimal goal- directed performance (MacDonald, Cohen, Stenger, & Carter, 2000; Miller & Cohen, 2001).

The proximity and interconnectivity of the anterior cingulate and orbitofrontal regions suggests that they may interact in support of executive functioning. Ullsperger and von Cramon (2004) pose that both are implicated in

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monitoring and decision-making behavior. The two re- gions appear to play complementary roles, with the ros- tral anterior cingulate implicated in monitoring self- generated actions and in signaling the need to quickly alter neural processes to ensure optimal goal-directed motor performance, whereas the orbitofrontal cortex monitors the outcome of goal-directed actions by external consequences. The external consequence of action is, in turn, used to guide future decision making. Thus, the an- terior cingulate appears to be involved in the monitoring and alteration of ongoing actions, and the orbitofrontal cortex monitors the external consequences of these ac- tions to guide future actions.

Although the role of the anterior cingulate in response inhibition is often stressed, it appears also to play an im- portant part in the initiation of behavior. For example, when confronted with conflicting response options, the anterior cingulate participates in both the suppression of inappropriate responses and the initiation of appropriate ones (Cabeza & Nyberg, 2000). Its role in initiating be- havior is further indexed by its activation when an indi- vidual is confronted with tasks that require semantic gen- eration, episodic memory retrieval, and working memory. In addition, evidence exists that the anterior cingulate may be selectively activated when an individual’s move- ments are “willed” (volitional), as contrasted with actions that are determined by external stimuli. The effects of bi- lateral anterior cingulate damage dramatically illustrate the role of the anterior cingulate in behavioral initiation. With bilateral anterior lesions, the patient may experi- ence “akinetic mutism” or “abulia.” Akinetic mutism refers to a syndrome involving profound apathy, reduced or absent verbal or motor behavior, a sense of psychologi- cal “emptiness,” reduced response to novelty, and indif- ference to pain, hunger, or thirst. Abulia refers to a simi- lar, although less severe syndrome of apathy, indifference, and minimally spontaneous verbal and motor activity (Lichter & Cummings, 2001). Damage to the orbital frontal cortex has also been associated with akinetic mutism; however, research (Bechara, Tranel, & Damasio, 2002) suggests that the damage has to extend into regions of the anterior cingulate and/or basal forebrain for the syndrome to be evident. Duffy and Campbell (2001) de- scribe the following case of akinetic mutism:

One patient, after a gunshot wound to both frontal lobes, was essentially inert when left alone. When questioned, he related an awareness of personality change. He denied boredom and de- scribed it as a “loss of motivation” in that he entertained numer- ous ideas for activities but felt no impetus to act on them. His facial expression was one of casual indifference, and he would often respond with simple gestures instead of speaking. (p. 118)

Clearly, this patient portrays the amotivational state that characterizes akinetic mutism.

Relation of Memory, Attention, and Executive Function

Memory, attention, and executive function repre- sent relatively distinct processes, although in some cases, there is disagreement whether a particular attentional or memory process is better classified as an executive func- tion (for example, working memory). Clearly, these processes are inter-related, but specifying the exact nature of this inter-relation is hindered by our limited under- standing of these domains, divergent definitions and con- ceptualizations, and varied theoretical perspectives. When experts from the fields of memory, attention, and execu- tive function were asked to specify the behaviors denoted by the term executive function, no less than 33 different terms were generated with only 40% agreement for 6 of the terms (self-regulation, sequencing of behavior, flexi- bility, response inhibition, planning and organization; Eslinger, 1996). Nonetheless, there is some agreement that executive functions represent overarching controlling, organizing, integrating, and supervising computations. Attention and memory processes are subject to varying degrees of executive orchestration depending on the na- ture and type of attention and memory processes in- volved. From a neuroanatomic perspective, memory, at- tention, and executive functions are served by relatively distinct, yet interconnected and overlapping, neural sys- tems. Neuroimaging investigations demonstrate that dif- ferent neural systems support executive, attention, and memory functions; yet, these neural systems coactivate in the performance of many executive, attentional, and memory tasks, indicating shared or distributed process- ing. Furthermore, the inter-relation of these functions is evident when one realizes that executive functions would be of little value if memory systems did not operate to register, store, and enable the retrieval of life experiences and knowledge, and if attentional systems did not support the processing of relevant or critical environmental and body events. Jointly, attention, memory and executive functions play a central role in thinking, reasoning, prob- lem solving, language, and emotional and social behavior. Finally, human experience involves the capacity to repre- sent and relate past, present, and future events. Attentional systems are necessary for the processing of relevant ongo- ing and novel events, memory systems for the symbolic maintenance of these experiences over time, and executive

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functions for the generation, guidance, and evaluation of behavior necessary to attain future goals (Eslinger, 1996).

As you reviewed the effects of damage to the atten- tional, memory, and executive systems, you likely realized that there is typically either a direct or indirect disruption of emotional functioning. A review of Phineas Gage’s case (see Neuropsychology in Action 9.3) clearly portrays the profound disruption to emotional regulation, arousal, and style that damage to the brain can engender. It is emotion that gives direction, drive, and value to our personal and social behavior. Emotions intimately affect that which we attend to, remember, and strive to achieve (goals). It is to this fundamental aspect of human behavior that we now turn.

Neuropsychology of Emotional Processing

Brain processing of emotion is an area that neu- ropsychology has largely ignored until recently. This ne- glect is partly a holdover from philosophical traditions of rational empiricism and from conceptualizations of the body and brain as being machine-like. People saw emo- tions as peripheral to understanding cognition, as being of a lower order of evolutionary development, perhaps even vestigial. In other words, humans had evolved to be- come rational, logical beings somehow above emotion. Moreover, it is difficult to study subjective feeling states. Such research is not straightforward, as is presenting a vi- sual or auditory stimulus and recording activation of cor- responding brain regions. Also, animal models can pro- vide only limited information, because they cannot verbalize their feelings, and researchers must rely on motor behaviors to infer the expression of emotions as rage and fear. The emotional repertoire of humans is enor- mous, subtle, and much more complicated than a re- sponse to external threats to physical safety, such as em- bodied in the fight-or-flight response.

Today, science views emotions as necessary for higher evolutionary adaptation. In the television show Star Trek (and its spinoffs), the ultralogical characters Mr. Spock, Data, and Seven of Nine show that being human entails having “emotional equipment.” People who are out of touch with emotions and who have autistic-like qualities— like Temple Grandin, who describes herself as an “anthro- pologist on Mars” in Oliver Sacks’ book of the same name (1995)—have expressed a sense of alienation from other humans on these grounds. Humans live in a social context where self-understanding and social skills are

some of the most crucial factors in determining success in society. Witness the surging interest in “emotional intelli- gence,” which stresses the ability to understand mood and emotion in self and others, to understand self and one’s own character, and then to act effectively on that knowl- edge. Researchers suggest that emotional intelligence ac- counts for just as much or more variance in determining success in life as traditionally measured general cognitive intelligence.

One of the more interesting questions related to un- derstanding emotions is to ask whether emotional pro- cessing is a type of cognitive processing that the cortex initiates, or whether emotion emerges without conscious thinking, and only secondarily becomes labeled. This di- chotomy is a variation on an old debate emanating from the early twentieth century. The James–Lange theory of emotion, promoted by American psychologist William James and Danish psychologist Carl Lange (Lange, 1922), postulates that people consciously experience emotion as a reaction to physical sensory experience. That is, we feel fear because our hearts are racing; we are sad because we are crying. Although others saw this as an overstatement, the James–Lange theory does insist that sensory and cog- nitive experiences were intimately entwined and insepa- rable from each other. In other words, if all the physical sensations of fear disappeared, so would the cognitive experience of fear. The opposing theory of the time was the Cannon–Bard theory (Cannon, 1927). Walter Cannon, and later Philip Bard, argued that the conscious emotional experience is separate from bodily sensation or expression. Although today most scientists agree that cognitive experience of emotion corresponds to sensory experience, much variation exists among types of emo- tion, emotional intensity, and individual variation.

Joseph LeDoux (1992, 1996) describes emotion as a subjective state of awareness and suggests that only be- cause people have a cortex can they label emotion and think about it, rather than just react to it as other animals might. Someone walking along in a forest might be star- tled by something that looks like a snake. It is adaptive if the mind signals the body in an immediate response of danger. Some scientists suggest that certain emotional re- sponses, such as reactions to certain movements and noise, may be genetically “hardwired” as a protective mechanism. According to LeDoux (1996), after that ini- tial lower order automatic processing, the cortex receives and further processes the information, perceiving the ob- ject as a snake or a stick, weighing options, and direct- ing the body to take further action. The competing view argues that the person must first recognize something cog- nitively as a threat for the emotion to develop. LeDoux

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and others have amassed convincing research suggesting that basic fear conditioning can occur without a cortex. Some animals with their cortex removed still show basic fear responses. In this scenario, thought does not neces- sarily precede emotion. However, in addition to subcorti- cally initiated emotion, is it also possible to initiate an emotional response just by thinking? Certainly the expe- rience of most people would confirm this. Considering an upcoming speech, thinking about running into a snake, feeling socially embarrassed, or anticipating a joy- ful reunion can all produce emotional responses in the body separate from immediate external threats or joys. This section examines both subcortical and cortical con- tributions to emotional behavior.

B R A I N O R G A N I Z A T I O N O F E M O T I O N

Emotions involve complex physiological, cognitive, and motor (action) processes that are supported by multiple cortical-subcortical architectures and circuitries. Different and overlapping interconnected regions are involved in processing varied emotions, a clear indication that there is not a single “emotional system.” Yet, these subsystems are collectively referred to as the “limbic system” of the brain. The Papez’s circuit (see Figure 9.5) was initially proposed as the supporting system of emotional processing. Subse- quently, MacLean (1949, 1952) extended the system to include the amygdala, orbital prefrontal cortex, and re- gions of the striatum. Advances in neuroscience do not fully support these earlier conceptualizations of the lim- bic system because we now realize that the hippocampus is more intimately involved in nonemotional memory processing, whereas the amygdala and related structures play a greater role in emotional processing. The two re- gions work in a complementary manner depending on the event being processed. For example, patients with dam- age to the amygdala without co-occurring hippocampal damage do not demonstrate a learned fear response to a con- ditioned stimulus. However, the patients are able to recall that the conditioned stimulus was associated with an un- conditioned stimulus during training. In contrast, patients with the opposite lesion profile (damaged hippocampus � preserved amygdala) exhibit a fear response to the condi- tioned stimulus without memory of the conditioned and unconditioned pairing (Armony & LeDoux, 2000). Thus, one region appears to underpin the learning of the declarative content (context), whereas the other supports the emotional learning associated with the event.

Investigations of the effects of emotion on memory re- tention provide further evidence of the complementary relation of the hippocampus and amygdala. Studies

(Cahill & McGaugh, 1998; McGaugh, 2004) of animals and humans show that the degree of activation of the amyg- dala during encoding of emotionally arousing material (positive or negative) correlates significantly with subse- quent recall of the material. That is, as amygdala/emotional arousal increases, the retention of declarative information improves. It has been hypothesized that the amygdala enhances the consolidating processes of the hippocam- pus, and thus strengthens the retention of the declarative learning. However, there is a limit to this enhancing ef- fect. With excessive or chronic emotion, memory reten- tion can actually be impaired. High levels of adrenocorti- cal hormones released during stress may account for this impairing effect.

P r i m a r y E m o t i o n s

Primary emotions are automatic, preorganized, arise from sensory experience, and are processed through the limbic system before or parallel to being recognized consciously. Emotions such as fear, disgust, surprise, anger, and joy appear to be universal, because people express and recog- nize them across all cultures of the world. Damasio (1994) suggests that these emotions are innate and primarily con- trolled by the amygdala and anterior cingulate of the lim- bic system. As we have discussed, sensory information first funnels through the thalamus, is relayed to the cortex, and then travels to the subcortical limbic system. Because of this anatomy, the general consensus was that conscious perception of an emotion preceded emotional limbic re- sponse. But LeDoux, who has studied fear conditioning, has suggested that projections from the thalamus to the amygdala provide a “shortcut” allowing the amygdala to process information directly, bypassing the cortical loop. This allows for an immediate, automatic, preconscious, and unconscious emotional response.

Fear is a well-researched primary emotion. In the hope that the knowledge of fearful emotions can aid in treat- ing secondary emotions, such as human anxiety and post-traumatic stress disorders, Joseph LeDoux, who has done extensive work in the area of fear conditioning with animals, has studied how primary fear interacts with memory. The neuroanatomy of the primary conditioned- fear response centers on the amygdala. Fearful behaviors are easily conditioned to a tone via shock, trauma, or loud noise. Researchers have long known that severing connections between the subcortical areas of the brain and the cortex does not eliminate the conditioned-fear re- sponse. Therefore, the learning and maintenance of fear conditioning must occur in the subcortical structures. Re- searchers then demonstrated that lesioning the amygdala in certain places did interfere with fear conditioning.

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Most notably, if they destroyed the central nucleus of the amygdala, animals no longer showed an autonomic fear response when presented with a tone (which previously had been associated with shock). The expected increase in heart rate, respiration, and vasodilation did not occur. LeDoux concluded that the cortex is not necessary to condition fear, but the amygdala is crucial. He then showed that the sensory information reaches the amygdala via two routes. The first or direct route (thalamo-amygdala circuit) sends sensory information to the thalamus, which, in turn, transmits it to the amygdala. The second or indirect route (thalamo-cortico-amygdala), involves the transmission of sensory information to the thalamus and then to the cortex. After cortical processing, the in- formation is returned to the thalamus, which directs it to the amygdala. The more direct route allows for rapid, although relatively imprecise, appraisal of the threat po- tential of a sensory event. The indirect route is slower but provides a more detailed representation of the event (Armony & LeDoux, 2000). Once the input is processed by the amygdala, it is transmitted via the central nucleus to various brain regions that instantiate autonomic, at- tentional, perceptual, cognitive, and behavioral response (Figure 9.19).

As noted earlier, primary emotions are processed without conscious awareness. This does not mean that processing of the emotional stimuli is not ultimately re- alized at a cortical level. Rather, the emotional state can

Figure 9.19 The amygdala and fear conditioning. (a) A lateral view showing the amygdala through the temporal lobes. (b) A coronal section showing the amygdala. (c) A close-up of the nuclei of the amygdala showing the pathways of the conditioned fear response to emotional auditory stimuli. ([a, b] Reproduced from Bear, M. F., Connors, B. W., & Paradiso, M. A. [1996]. Neuroscience: Exploring the brain [pp. 444, Figure 16.5]. Philadelphia: Lippin- cott Williams & Wilkins, by permission; [c] reproduced from Bear, M. F., Connors, B. W., & Paradiso, M. A. [1996]. Neuro- science: Exploring the brain [pp. 445, Figure 16.6]. Philadelphia: Lippincott Williams & Wilkins, by permission.)

Lateral view

Amygdala Hippocampus

Lateral ventricle

Hypothalamus AmygdalaThird

ventricle

Thalamus

Neocortex

Central nucleus

Amygdala

Basolateral nuclei

Emotional experience

Autonomic response

Behavioral reaction

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be triggered before there is conscious awareness. Support has been provided for the involvement of the amygdala in the unconscious mediation of learned emotional re- sponses. For example, Morris, Ohman, & Dolan (1998) presented healthy participants with two angry faces, one face (CS�) paired with a noxious stimuli (unconditioned stimulus, white-noise burst), and the other face (CS�) displayed without aversive stimulus pairing. After the conditioning training, the faces were presented to the par- ticipants either masked or unmasked. Masking enables a stimulus to be processed, but without conscious aware- ness of the stimulus. The participants were instructed to press a button if they saw an angry face. None of the par- ticipants reported perceiving the masked faces, whereas all identified the unmasked faces. A measure of emotional evocation (skin conductance) revealed that the CS� face produced a significantly greater emotional response than the CS� face for both the masked and unmasked condi- tions. Moreover, PET neuroimaging showed significantly greater activation of the amygdala for the presentation of the CS� face relative to the CS� face, regardless of whether it was masked or unmasked. That is, fear learn- ing was evident with and without conscious awareness. Interestingly, the right amygdala showed greater activa- tion to the masked CS� face, while the activation of the left amygdala was enhanced for the unmasked CS� face. This finding suggests greater involvement of right hemi- sphere regions in unconscious emotional facial process- ing, whereas left hemisphere regions appear preferentially involved in conscious or cortically mediated emotional processing.

Damage to the amygdala can adversely impact on cor- tical processing of emotions. In essence, it leaves higher cortical processing bereft of important input. Exemplify- ing this negative impact is a study (Adolphs, Tranel, & Damasio, 1998) of patients with complete bilateral amyg- dala damage. These patients were presented facial pictures and asked to rate the degree of positive/negative emotions represented by each face and the degree of approachabil- ity and trustworthiness of the person represented by the face. When contrasted to patients without lesions of the amygdala, the patients with bilateral amygdala damage rated the faces as expressing more positive emotions and as more approachable and trustworthy. This positive bias was particularly evident for faces considered to be most negative. The investigators pose that the positive bias re- lated to the role of the amygdala in processing threaten- ing and aversive stimuli. The loss of this input to cortical regions resulted in a shift to more positive ratings and in- creased approachability/trustworthy judgments by the bi- lateral amygdala group.

Fear learning is not limited to subcortical amygdala action (direct sensory conditioning). For example, one can learn to fear a wild animal, such as a lion, without ex- periencing an attack by the animal. Support for involve- ment of the amygdala in fear learning without experienc- ing a noxious event is provided by Phelps and colleagues (2001), as well as other investigators. In Phelps’ study, participants were informed that the presentation of a spe- cific stimulus (blue square) would be associated with a shock, whereas a second stimulus (yellow square) would not. Neither stimulus was ever paired with a shock. Yet, when the shock-specific stimulus was presented, there was significant activation of the amygdala, insular cortex, an- terior cingulate, premotor cortex, and striatum. A mea- sure of fear evocation (skin conductance) confirmed a fear response with the specified stimuli. The investigators pose that the insular cortex was central to the transfer of a cor- tical representation to the amygdala. Thus, fear learning was produced by an imagined or anticipated cognitive representation without actual contact with a negative sen- sory event. Clearly, fear learning can involve both subcor- tical and cortical processes.

S e c o n d a r y E m o t i o n s

Secondary emotions require higher cortical processing, and according to Damasio (1994), this processing is or- chestrated by the prefrontal cortical networks. There is also a hemispheric asymmetry to higher emotional pro- cessing. People acquire secondary emotions through learning and experience. The perception of these states is highly personal and individual. Social emotions such as embarrassment, pride, shame, and anxiety are highly de- pendent on learning and interact with one’s cognitive perception of the social environment as it pertains to oneself. Secondary emotions do not necessarily imply a separate “feeling” experience in the body. The feeling of emotional experience remains linked through the limbic system. The difference is that secondary emotions are generated through higher cortical processes and arrive at the limbic system over a different route from that taken by primary emotions generated through sensory experi- ence. Once in the limbic system, the brain processes the experience of primary and secondary emotions in a simi- lar manner.

Secondary, or social, emotions mediated by the cere- bral hemispheres show lateralization of functioning. If a face is considered closely, you soon see that it is not sym- metric. In 1902, before the days of computer morphing, the German scientist Hallervorden (cited in Borod, Hay- wood, & Koff, 1997) cut pictures of faces in half at the midline. Taking the left half, he recreated the whole face

by using the original and its mirror image. He did the same with the right half. Among other descriptors, he saw right-sided faces as more “lucid,” “sensible,” and “ac- tive,” and left-sided faces as more “perceptive” and “af- fective.” Because the right hemisphere controls the left side of the lower face, and vice versa, lateralized facial dif- ferences in emotion basically reflect the activity of the contralateral hemisphere. The general consensus across subsequent studies confirms some of the early observa- tions in that the left side of the face (left hemiface) is more emotionally expressive than the right hemiface. In general, the right hemisphere seems to be dominant for emotional expression (for a review of the literature, see Borod, Haywood, & Koff, 1997). The picture, however, is not completely cut and dry. Faces have an amazingly complex ability for emotional expression. The amount of space devoted to facial control on the motor homuncu- lus attests to this. Just in variations of smiles, there may be more than 18 different types. Psychologist Paul Ekman has described the cocktail party smile, the smile of relief, and the miserable smile, to name just a few. Some theorize that each hemisphere may be specifically attuned to emotional type. Perhaps positive emotions emanate from the left hemisphere and negative emotions from the right (for review, see Borod, Haywood, & Koff, 1997). The structure–function picture for emotion is complex, but many neuroanatomic theorists continue to assert that the right hemisphere plays the major integra- tive role in emotional processing. People with right hemi- sphere damage caused by stroke are usually less accurate at producing emotions compared to those with left-sided damage or healthy control individuals (Borod, 1993).

Observations of neurologically impaired patients have provided clues to an interesting issue in emotional pro- cessing, the anatomic differences between spontaneous and posed smiles. Posed facial expression appears largely controlled by contralateral cortical structures in the motor cortex. Spontaneous smiles and laughter, however, appear to be largely a function of subcortical limbic system struc- tures, including the cingulate gyrus, thalamus, and some structures of the basal ganglia (such as the globus pal- lidus). Left hemisphere stroke patients, with damage to the left motor cortex, have difficulty smiling for the cam- era because their facial muscles malfunction in response to the brain command to produce a willful or social smile. The smile pulls to the left. A quite different picture emerges if the person laughs spontaneously. The smile ap- pears natural. The limbic system and other subcortical structures, including the basal ganglia, control the spon- taneous smile (Figure 9.20). In any person, an observer can easily see a difference between these two types of

smiles. The true smile of enjoyment activates the orbicu- laris oculi muscles around the eyes; a fake smile does not. Another way of describing this is that smiling eyes show an activated limbic system. People with subcortical disor- ders, such as Parkinson’s disease, show the opposite prob- lem of stroke patients. Although they can show willful emotion, much of their spontaneous emotion is damp- ened by a “masklike” face.

An area of research that has increased our understand- ing of cortical involvement in emotionality centers on the consequences of frontal damage. As reviewed earlier, dam- age to the frontal cortical system can result in a wide range of emotional and behavioral dysfunctions. Some speci- ficity in the type of emotional dysregulation produced can be traced to whether the dorsolateral, orbital, or medial frontal region is preferentially damaged. In addition, cer- tain regions of frontal damage leave cognitive processes relatively unimpaired, as verified by neuropsychological assessment, but result in significant social and emotional deficits. This pattern is often evident in patients who have experienced damage to the ventral and medial prefrontal cortices. Studies of the ventromedial cortex indicate that this region is implicated in emotional decision making (O’Doherty, Kringelbach, Rolls, Hornak, & Andrews, 2001), recognition of emotions as represented in voice

CHAPTER 9 | Memory, Attention, Emotion, and Executive Functioning 263

Image not available due to copyright restrictions

264 PART TWO | The Functioning Brain

and facial expressions (Hornak, Rolls, & Wade, 1996), and processing of fear and anger (Blair, Morris, Frith, Perrett, & Dolan, 1999; Vuilleumier, Armony, Driver, & Dolan, 2001). Anatomically, the ventromedial prefrontal cortex is interconnected with the hypothalamus, brainstem, amygdala, ventral striatum, and basal forebrain. These re- gions have been implicated in the mediation of attention, memory, and other cognitive functions in the processing of emotions.

Recently, an investigation (Kawasaki et al., 2005) sought to determine whether the ventromedial prefrontal cortex was involved in the processing of different cate- gories of emotions. Electrophysiologic monitoring via implanted electrodes allows for the assessment of neu- ronal responsiveness. However, because of ethical con- straints, this method is generally not condoned for use with healthy individuals. Therefore, the investigators identified patients with epilepsy who had electrodes im- planted in the ventromedial prefrontal cortex to monitor their epilepsy. The epileptic foci of these patients did not involve the ventromedial prefrontal region. The patients were presented emotional scenes of different emotional valence and arousal. Three categories of scenes (pleasant, aversive, and neutral) of high and low levels of emotional arousal were used. More than 200 neurons in the left and

right ventromedial prefrontal regions were monitored. Results of the study showed that approximately 60 neu- rons in the left and right ventromedial prefrontal cortices participated in encoding the emotional significance of the visual scenes. These neurons were selective for pleas- ant and aversive scenes, with the largest number being responsive to the aversive scenes. The investigators hy- pothesize that the ventromedial prefrontal cortex, in co- ordination with other interconnected cortical-subcortical regions, participates in associating visual stimuli with emotion and with the recognition (awareness) of this emotion.

Emotional dysfunction often appears in conjunction with neurologic disorders, sometimes as normal reaction to loss of function, and sometimes as a direct result of brain dysfunction. For example, depression is a common reaction to a life-altering injury or disease, but depression is also common in people with cortical dysfunction and some subcortical disorders such as Parkinson’s disease. As discussed earlier, a frontal executive system called amoti- vational syndrome often appears behaviorally as indiffer- ence, apathy, or depression. On the other side of the emo- tional spectrum, euphoria or inappropriate labile emotional responses can occur with frontal and subcorti- cal syndromes.

Summary The systems presented in this chapter represent the highest level of brain integration. They depend on the input of processed sensory information and, to a large extent, manage, organize, manipulate, and store this information for further use. Many of the processes of these systems operate automatically or unconsciously without apparent verbal awareness. Subcortical brain regions control many “unconscious” processes. The more explicit and, therefore, more seemingly conscious aspects of higher order processing are represented in the cortical areas, most notably the frontal lobes. Cortical functions mediate our interactions with the external environment and support those behaviors that we consider to be “willed” or volitional.

This chapter, as well as the previous chapters, provides the foundation for the clinical issues and disor- ders presented later in this book. Whereas here we have considered functions and disorders by subsystem, we next examine cases of disorders that cut across functional areas.

C r i t i c a l T h i n k i n g Q u e s t i o n s

Do the higher cognitive functions discussed in this chapter represent more intelligent thought processes than those func- tions discussed in previous chapters? Explain. The memory, attention, and executive function systems interact. How would you explain this interaction? Do disorders of executive functioning represent a greater disability for humans than sensory-perceptual and motor disor- ders? Why or why not? Do emotions represent a higher cognitive function or a lower basic function? Explain. Are there advantages to multiple brain memory systems as contrasted to a single memory system?

CHAPTER 9 | Memory, Attention, Emotion, and Executive Functioning 265

Anterograde amnesia Retrograde amnesia Short-term memory (STM) Long-term memory (LTM) Remote memory Declarative memory Nondeclarative memory Procedural memory Explicit memory Implicit memory Episodic memory

Semantic memory Implicit priming Working memory Central executive Articulatory phonologic

loop Visuospatial sketch pad Episodic buffer Focused attention Alternating attention Divided attention

Hemispatial neglect Posterior attention system Vigilance attention system Anterior or executive attention

system Focus-execute attention Shifting attention Sustained attention Encode attention Stable attention Object permanence

Executive planning Pseudopsychopathy Acquired psychopathy Environmental dependency

syndrome (stimulus-bound) Utilization behavior Somatic markers Akinetic mutism Abulia James–Lange theory Cannon–Bard theory

We b C o n n e c t i o n s

http://www.lycaeum.org/drugs/other/brain Mind-Body—great source for links to topics related to theories of the mind.

http://www.nimh.nih.gov/events/prfmri2.htm Working Memory—site provides graphics for three-dimensional MRI reconstruction of the subject’s brain, including parietal and frontal areas, while holding a series of letters in working memory.

http://www.exploratorium.edu/memory/index.html Memory Web Site—features online exhibits and articles and lectures on memory. Page also shows demon- stration of memory for common objects such as a penny. The page asks the user to click on the penny that actually looks like one.

K e y Te r m s

http://www.lycaeum.org

http://www.nimh.nih.gov

http://www.exploratorium.edu

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Part Three

D I S O R D E R S O F T H E B R A I N

Chapter 10 Developmental Disorders of Childhood

Chapter 11 Learning and Neuropsychiatric Disorders of Childhood

Chapter 12 Cerebrovascular Disorders and Tumors

Chapter 13 Traumatic Head Injury and Rehabilitation

Chapter 14 Normal Aging and Dementia: Alzheimer’s Disease

Chapter 15 Subcortical Dementias

Chapter 16 Alterations of Consciousness

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Chapter 10

D E V E L O P M E N TA L D I S O R D E R S O F C H I L D H O O D

Sometimes even to live is an act of courage. —Seneca (died a.d. 65), Letters to Lucilius

Vulnerability and Plasticity of the Developing Brain Child and Adult Brain: Structural and Functional

Differences Specific Developmental Disorders

Neuropsychology in Action

10.1 Principles of Assessment in Pediatric Neuropsychology

or diffuse, and can result in minimal to complete loss of function. Examples of potential teratogens are general dis- eases (such as rubella, influenza, and mumps), sexually transmitted diseases (such as syphilis, AIDS, and genital herpes), drugs (such as alcohol, cocaine, barbiturates, and vaccines), environmental toxins (such as mercury, carbon monoxide, lead, and polychlorinated biphenyls [PCB]), and radiation (such as from x-rays and exposure to ra- dioactive materials).

The precise impact of the teratogen on the unborn fetus varies with the nature of the insult and its proximity to a particular period of rapid brain growth, the genetic makeup of the child/mother, the quality of the intrauter- ine environment, and the “dosage” and extent of exposure (Spreen, Risser, & Edgell, 1995). The prenatal brain ap- pears most vulnerable to morphologic damage during early organogenesis (weeks 2–8). Resultant malformations are often so severe that the embryo is spontaneously aborted or presents at birth with conditions incompatible with life (Anderson, Northam, Hendy, & Wrennall, 2001). Although the probability of massive malformations de- creases during later periods of gestation, the brain continues

270 PART THREE | Disorders of the Brain

K e e p i n M i n d

What differences in the impact of brain injury are there for children compared with adults?

Is the brain of a child merely a small replica of the adult brain, differing only in size, or do the two brains differ in significant ways?

How do children with Turner’s syndrome differ from children with Williams syndrome?

Can children with fetal alcohol syndrome outgrow their cognitive deficits?

Overview This chapter focuses on childhood developmental disorders that result from genetic and chromosomal alteration, and early environmental insults. Although these disorders can be traced to disruption of early brain development, the effects of the disruption persist throughout childhood, adolescence, and adulthood. We first discuss the vulnerability and plasticity of the young brain, then compare the child and the adult brain. These topics are particularly significant in evaluating and predicting the immediate and long-term effects of brain insult or injury. Next, we examine a number of developmental disorders to highlight the often disabling consequences of anomalies in brain development. The disorders reviewed include hydro- cephalus (HC), Turner’s syndrome (TS), Williams syndrome (WS), and fetal alcohol syndrome (FAS). We dis- cuss these developmental disorders for prevalence and manifestations, pathogenesis and neuropsychologi- cal assessment, and current interventions to halt or ameliorate the negative effects of early neural disruption.

Vulnerability and Plasticity of the Developing Brain

The brain may fail to develop structurally and func- tionally as a consequence of inborn (genetic and chromo- somal) anomalies and environmental insults. Brain disor- ders, such as phenylketonuria (PKU), a genetic metabolic disorder, can be inherited or result from alterations of cel- lular material, as evident in TS. Environmental causes re- late to damaging agents (such as alcohol) that preclude, alter, or halt natural brain development. The degree to which a brain can recover from damage is complex and not fully understood. Neuroscientists do know, however, that the plasticity of the brain allows for recovery of func- tion under certain conditions.

Teratogens are agents that, if introduced or present during certain periods of prenatal development, can pro- duce central nervous system defects. The defects can include agenesis, the failure of an organ to develop, or dys- genesis, the abnormal development of an organ. Further- more, the damaging effects of the teratogens can be focal

to be vulnerable to damage throughout pregnancy (Fig- ure 10.1). For example, disruption of cell migration (16–20 weeks) is associated with polymicrogyria, whereas porencephaly relates to perturbations at a later point (5–7 months) of gestation. Damage during later gestational periods of cell proliferation and growth often results in disruption that is more limited to specific cellu- lar layers, structures, or circuitry. However, generalized brain dysfunction may also occur depending on the na- ture of the insult. Cortical cellular migration, myelina- tion, dendritic arborization, and synaptogenesis continue for significant periods after birth. Damage during these periods can also lead to differential impairment of cogni- tive and behavioral functions.

To exemplify the hazards of prenatal exposure to tox- ins, we will review one of the heavy metals that is rela- tively well studied, and the impairing effects of which are increasingly being identified. Inorganic lead may be one

of the most widespread neurotoxins in the world due to its presence in gasoline, paint, and industrial plants. For- tunately, there has been a significant decrease in reported lead blood levels in the United States due to the elimina- tion of lead from gasoline and the banning of lead from interior house paints. Specifically, the average lead blood level of U.S. residents has decreased from an average of 15 µg/dL (micrograms per deciliter) to 2 µg/dL since the mid-1990s (Canfield, Gendle, & Cory-Slechta, 2004). Children continue to be exposed to lead through both older and substandard homes painted with lead-based paint, contaminated soil, and water (lead pipes) (Nigg, 2006). Currently, the major source of exposure for preg- nant women is the industrial/work setting.

Of significance, cross-sectional and longitudinal stud- ies have shown that the injurious effects of lead exposure may occur at lower levels than previously deemed safe. As a result, there has been a decrease in blood lead levels

CHAPTER 10 | Developmental Disorders of Childhood 271

Figure 10.1 Gestational periods that developing organs or structures are most susceptible to teratogenic effects. The dark bands indicate the most sensitive periods, whereas the light bands specify periods when each organ or structure is less sensitive to teratogens, although damage may still occur. (Reproduced from Moore, K., & Persaud, T. [1993]. Before we are born: Essentials of embryology and birth defects [4th ed., p. 130]. Philadelphia: WB Saunders.)

• Indicates common site of action of teratogenUsually not susceptible to teratogens

Period of dividing zygote, implantation

Heart

Eye Eye

Ear

Ear Brain

Palate External genitalsArm Leg

TeethHeart

Central nervous system

1 2 3 4 5 6 7 8 9 16 20–36 38

Embryonic period (in weeks)

Prenatal death Major structural abnormalities Physiological defects and minor structural abnormalities

Fetal period (in weeks)—full term

External genitals

Teeth

Legs

Arms

Central nervous system

Heart

Palate

Ear

Eyes

considered nonhazardous by the Centers for Disease Con- trol and Prevention and the World Health Organization. Before 1991, the safe blood lead level threshold was ≤25 µg/dL, whereas the current standard is ≤10 µg/dL. Yet, there is growing evidence that even this blood level threshold may be too high, as evident in the finding of cognitive and behavioral impairments after blood lead lev- els of ≤10 µg/dL, leading some investigators (Canfield, Henderson, Cory-Slechta, Cox, Jusko, & Lanphear, 2003) to propose that an even lower standard is war- ranted. At higher levels, there is clearer evidence regard- ing the negative impact of lead exposure on intellectual functioning; however, the findings for the negative effects of lower levels of exposure on intelligence are less defini- tive. That is, not all studies (for review, see Kaufman, 2001) report a decrease in intellectual performance at lower levels of exposure, and many report only small re- ductions, and often these reductions are related more to postnatal relative to prenatal lead exposure (Koller, Brown, Spurgeon, & Levy, 2004). Notably, many of these studies fail to control for potential confounding factors (namely, mother’s intelligence quotient [IQ], education level, socioeconomic level, prenatal care, and use of other sub- stances) that could account for lower IQ scores.

Recent longitudinal and cross-sectional studies of chil- dren exposed to prenatal lead that have controlled for potentially confounding variables report a reduction in intellectual performance. For example, Schnass and col- leagues (2006) observed children with prenatal lead expo- sure (pregnant mothers’ average blood lead levels were 8 µg/dL) through their first 10 years of life. The average lead blood level for the children during their 1st to 5th years of life was 9.8 µg/dL, and the level was 6.2 µg/dL when the children were 6 to 10 years of age. The investi- gators determined that lead exposure at approximately 28 weeks gestation was negatively related to intellectual performance. That is, the higher the maternal blood lead level, the lower the child’s assessed postnatal intelligence. A dose–response analysis indicated that the most signifi- cant impact on intelligence occurred within the first few micrograms of blood lead levels. The investigators con- cluded that prenatal lead exposure has a lasting and nega- tive impact on intellectual development.

Similarly, in an earlier well-controlled study (Ris, Dietrich, Succop, Berger, & Bornschein, 2004) of chil- dren exposed to prenatal lead, the effects on specific cog- nitive and motor skills were examined. Neurocognitive assessments during childhood showed that the children demonstrated deficits in attentional control, fine-motor speed and dexterity, and visuoconstructive abilities. More alarming was the finding that the children’s deficits in

attentional control and visuoconstructive skills continued to be evident when they were assessed as adolescents.

Empirical studies with animals suggest that lead expo- sure disrupts the mesocorticolimbic dopamine and gluta- mate neurotransmitter brain receptors, particularly those receptors in the nucleus accumbens of the basal ganglia. Other structures that have been implicated are the frontal cortex, hippocampus, amygdala, and cerebellum (Ris et al., 2004). However, the precise disruption of brain structure and function remains to be clarified.

Dangers to the developing brain are not limited to pre- natal teratogens. Potential dangers also threaten the peri- natal process of birth, including anoxia, medications in- troduced during labor and delivery, and mechanical injury to the skull and brain caused by trauma during de- livery. Intracranial hemorrhage and tissue damage are rec- ognized results of mechanical injury associated with the birthing process (Spreen, Risser, & Edgell, 1995). Babies of low birth weight are at particular risk for central ner- vous system damage. Furthermore, a wide range of poten- tial dangers threaten postnatal development. Traumatic head injury, toxins, radiation, malnutrition, tumors, infec- tions, and stroke all can cause significant injury to the de- veloping brain. Yet, there is resilience to the damaged brain related, in part, to protective factors such as a responsive, nurturing, and stimulating postnatal environment.

The term plasticity refers to the enduring changes in neural activity that accompany learning, or the recovery of behavioral functioning after brain injury or disease (Frackowiak, 1996). Neuroscientists hypothesize that the brain’s plasticity is greatest during developmental periods when synaptic density is highest; that is, when excessive numbers of synapses exist, many of which have not com- mitted to function. These periods of maximum synaptic density differ across cortical regions due to differential rates of neuromaturation. For example, the window of plasticity for the visual cortex is smaller than for the pre- frontal cortex. In the former case, synaptic density extends until 5 years of age, whereas in the latter case, maximum density extends into late childhood (Huttenlocher, 1999; Huttenlocher & Dabholkar, 1997).

Initially, neuroscientists believed that the likelihood of recovery from a brain insult was greater if the injury oc- curred earlier rather than later in development. They later named this principle the Kennard principle in honor of its originator, Margaret Kennard (Kolb, Gibb, & Gorny, 2000). The Kennard principle suggests that the immature brain is more plastic than the mature brain. Some forms of insult do appear to follow this principle; for example, chil- dren with early focal brain injury often demonstrate milder and less extensive cognitive and emotional impairments

272 PART THREE | Disorders of the Brain

than adults with comparable lesions (Anderson, Northam, Hendy, Wrennall, 2001). However, the opposite effect is also evident. That is, earlier brain lesions, particularly if generalized, can have a pervasive impact on developing functions. In some cases, the early injury may initially ap- pear to have minimal effect if the cognitive or behavioral functions that the damaged region subserves do not emerge until a later point in development. As this devel- opment point is reached, significant functional impair- ments emerge. For example, the effects of early damage to the auditory cortex may not be fully evident until language skills fail to develop.

Some authors have proposed (Anderson, Northam, Hendy, Wrennall, 2001; Kolb, 1995) that the effect a lesion has on the developing brain varies with the age at insult. Lesions occurring before age 1, including prenatal development, typically correlate with more global and lasting impairment than later injuries. Some degree of neural reorganization and sparing of function is possible with lesions occurring between 1 and 5 years of age, de- pending on the nature, severity, and region of damage. During this period, most cortical regions reach maximum synaptic-dendritic density. Finally, injuries after age 5 gen- erally predict minimal recovery of function. Thus, there appears to be a “window” for optimum recovery extend- ing from the toddler through the preschool years. How- ever, not all studies support this set of generalities. For ex- ample, Bates (1999), in a review of studies, concluded that worse outcomes were associated with damage occur- ring between 5 and 12 years of age as contrasted with in- jury during the prenatal period and subsequent early childhood years. Clearly, a simple linear association be- tween age of damage and cognitive and behavioral out- comes does not exist.

Child and Adult Brain: Structural and Functional Differences

Neuroscientists are learning more and more about the maturation of the central nervous system. An impor- tant realization is that the child’s brain differs in many significant ways from the adult brain. This section dis- cusses several of these differences to clarify this basic, though often forgotten, principle of the relation between brain and behavior.

The brain of the adult is anatomically, physiologi- cally, and functionally mature, whereas that of the child is still developing. Accordingly, the effects of lesions to the immature and mature brain differ significantly. In the

former case, injuries disrupt the acquisition of develop- mental abilities; in the latter case, previously acquired abilities break down (Eslinger, Biddle, & Grattan, 1997). With the achievement of brain maturity, greater stability and predictability of behavior is evident. In comparison, the cognitive and behavioral functions of the developing brain can vary dramatically. This variability depends on the current developmental stage and on the nature and quality of the child’s social-psychological-physical environment.

With lesions of the mature brain, assessing the degree of functional loss and potential for recovery often involves examining the adult’s premorbid history. Young children have an obviously abbreviated history from which to draw variables necessary for prediction. Likewise, the young child has not developed a host of higher order functions such as reading and writing, thus severely hindering ef- forts to determine which functions are spared or compro- mised, both in the present and in the future.

Many pathologic signs of adult brain injury are devel- opmentally appropriate if the developing child exhibits them (Bernstein & Waber, 1997). For example, the prim- itive neural reflexes of the infant are obviously normal, but in adulthood, they are signs of frontal lobe or related neural damage. Likewise, early childhood damage to one cortical region may impact the development of other brain regions—a phenomenon not consistently observed with adult injury. For example, Eslinger and coworkers (1997) report that childhood lesions to the left prefrontal cortex can disrupt development of the right prefrontal re- gions, an effect these researchers did not observe with comparable damage to the mature brain.

One of the most striking examples of how the child’s brain contrasts with that of the adult’s is the differing re- sponse to lesions in the language areas of the left hemi- sphere. Young children who experience such injury rarely show aphasia. Moreover, most children with early left hemisphere damage acquire language abilities within the lower end of the average range (Stiles, 2000). In contrast, adults subject to similar lesions show a high prevalence of aphasic disorders and recovery is often less robust. Inves- tigators initially attributed the difference to the brain’s plasticity, and they posed that language transferred to the opposite hemisphere. However, the transfer of language to the right hemisphere is at a cost due to the finding that many of the affected children show visuospatial deficits and significant declines in intellectual performance. Re- searchers attributed the functional loss to a “crowding” effect. That is, language “crowds” into right hemisphere at the expense of other cognitive functions.

The posing of a transfer and crowding effect to account for the differences in language functioning of childhood

CHAPTER 10 | Developmental Disorders of Childhood 273

versus adulthood damage is being challenged. Emerging research suggests that the relationship between early hemispheric damage and language performance differs for young children as compared to adults with similar injury. In a series of studies (Bates & Roe, 2001; Stiles, 2000; Stiles, Bates, Thal, Trauner, & Reilly, 1998), the language development of children with either early left or right uni- lateral damage was examined. During the initial assess- ment, when the children were between 10 and 17 months of age, the majority of children were delayed in early lan- guage acquisition. Noteworthy was the finding that re- ceptive language deficits were more common in the chil- dren with right hemisphere rather than with left hemisphere injury. Furthermore, children with damage specific to the left temporal injury were delayed in word production, but they performed within the normal range on measures of comprehension and gestures. This profile is the opposite of adults with left posterior injury, in whom language pro- duction is spared whereas comprehension is impaired. In contrast, children with right hemisphere damage demon- strated visuoconstructive and emotional comprehension and expression deficits similar to those demonstrated by adults with comparable damage. These findings suggest that language acquisition is supported by widely distrib- uted brain regions of both hemispheres, and thus allows for the development of alternative pathways for neural me- diation of language. In contrast, there is greater neural specificity to the regions supporting spatial and affective processes. Accordingly, the visual constructive and emo- tional deficits associated with injury during early childhood are more likely to be similar to those demonstrated by adults (Stiles, 2000). With age and commitment of brain regions and circuitry to language and other abilities, the brain is less able to reorganize and redistribute functions to accommodate to injury. However, brain plasticity is evi- dent in adulthood, although greatly constrained.

The impact of adult injury is generally apparent soon after the lesion occurs, whereas the effects of injury to the immature brain are less straightforward. Studies of pri- mates suggest that early lesions to the prefrontal and tem- poral cortexes can produce both immediate and delayed presentation of impairments. Goldman-Rakic (1987a,b) conducted a series of studies to investigate the effects of damage to the prefrontal cortex. Lesions in the prefrontal dorsolateral region of the brain of mature monkeys impaired performance on a delayed response task (see Figure 9.9), whereas infant monkeys with comparable lesions did not show immediate impairment. However, as the infant monkeys matured, a significant deficit emerged in delayed response performance. In contrast, lesions of the pre- frontal orbital cortex produced delayed response deficits

regardless of age at injury. Thus, age and region of pre- frontal cortex damage interacted to determine immediate or delayed impairment.

Similarly, case studies of children (Eslinger et al., 1997; Tranel & Eslinger, 2000) with early prefrontal damage suggest that immediate and delayed impairments of cog- nitive and socioemotional executive functions can result. The emerging deficits in adolescence and early adulthood appear most prominent in the development and regula- tion of socioemotional behaviors such as social awareness, interpersonal sensitivity, perspective taking, friendship skills, and close emotional relationships. These emerging deficits appear more disruptive to adjustment than similar deficits that occur in adulthood. The relation of immedi- ate and late-appearing deficits of age, affected hemisphere, specific cortical region of damage, and other mediating variables remains unclear and warrant further study.

Our discussion of the vulnerability and plasticity of the brain, as well as its difference from the adult brain, serves as a basic framework for understanding the neu- ropsychological assessment of childhood disorders. William Culbertson presents a case study of the effects of an early frontal tumor and its subsequent cognitive im- pact (Neuropsychology in Action 10.1).

Specific Developmental Disorders

This section reviews several groups of neurodevelop- mental disorders that neuropsychologists frequently treat. These include abnormalities of anatomic development, ge- netic and chromosomal disorders, and acquired cerebral in- sults and diseases. We discuss a sample disorder from each of these groups to acquaint the student with the clinical pre- sentation, neuropsychological pathogenesis, and treatment of the disorder. The first disorder, HC, frequently co-occurs with many other disorders of anatomic malformation. Next, TS is one of the most commonly seen chromosomal disor- ders. We follow with a discussion of WS, a unique genetic disorder that continues to spawn research because of its neu- rocognitive profile. Finally, FAS is a relatively common and destructive disorder. Of the four disorders developmental disorders, FAS is completely preventable.

A B N O R M A L I T I E S O F A N A T O M I C D E V E L O P M E N T

Many conditions exist that reflect anomalies of neurodevel- opment. Hynd, Morgan, and Vaughn (1997) divide these disorders into five groups (Table 10.1). Each category reflects a malformation of brain tissue with concurrent disruption

274 PART THREE | Disorders of the Brain

CHAPTER 10 | Developmental Disorders of Childhood 275

Case Presentation S.B. is an 8-year-old girl who was referred for neuropsychological evaluation after neuro- surgical removal of a right frontal tumor. The evaluation was sought to determine her current levels of cognitive functioning, establish a baseline for monitoring her recovery, and provide appropriate educa- tional and management recommendations. The referral for evaluation was made 2 months after surgery.

During second grade, S.B. began to complain of headaches. These headaches became increasingly frequent and intense. Initial medical consultations did not identify the basis for her headaches. Subsequently, her academic skill levels began to decline. Her headaches failed to abate and were accompanied by vomiting. She experienced at least one night seizure. She was referred for neuroimaging (magnetic resonance imaging and computed axial tomography). The neuroimaging studies showed a massive (7 � 5 � 6 cm) nonfiltrating right frontal lobe tumor. Subsequently, S.B. underwent neurosurgery for the excision of the tumor. Her postsurgical recovery was uneventful, and neither adjunctive radiation nor chemotherapy was recommended.

Since the surgery, S.B. has continued to experience headaches, although these are less frequent and intense than in the past. She fatigues quickly, appears to sleep more, and seems to struggle with sustaining attention to tasks. Her parents have wit- nessed no major sensory, motor, or cognitive alterations since her release from the hospi- tal. Similarly, no major changes or alter- ations in personality or social interactions have been observed. She continues to be viewed by her parents as an active, ener- getic, and socially adept child.

Before the tumor, S.B.’s developmental and medical history was unremarkable. She was an average student who was well liked by her teachers and peers. At the time of the evaluation, S.B. had returned to school on a

reduced day schedule and was making steady but slow academic progress. Her teacher reported inattentiveness, impulsivity, disorganization, and high levels of minor motor activity as areas of concern.

Behavior Observed During Assessment S.B. is a dark-haired, well-developed child who was appropriately attired in contempo- rary garb for the assessment. Her surgical scar was clearly evident in the anterior region of her skull. She did not appear to be con- cerned by the visibility of the scar to others. She related in a friendly, talkative, and spontaneous manner. Her verbal responses tended to be overly detailed, poorly orga- nized, and often tangential in nature. How- ever, her thinking was reality oriented, and emotional responses were appropriate to the evaluative context. She was prone to fatigue quickly and to report that she was develop- ing (or had developed) a headache. Accord- ingly, a number of relatively short sessions were required to complete the assessment.

S.B. was motorically active across assessment sessions. This activity included fidgety and restless behaviors and actions such as fiddling with her hair, the zipper on her jacket, objects on the desk, and a piece of thread pulled from her shir t. It was not uncommon for her to sing or hum as she worked on tasks. She was quick to reach out and manipulate test materials as they were placed in front of her. Similarly, she would often try to initiate her performance of the assessment tasks before the exam- iner could complete the directions for the tasks.

When presented with new or difficult tasks, S.B. was prone to state, “I won’t be able to do this,” or to seek assistance. Her sense of self-efficacy appeared limited, as evident in frequent requests for feedback on the adequacy of her performance (such as, “How many did I get right?” “Did I miss any?”). Her tolerance for frustration was

limited, and support and coaxing was often necessary to maintain her comfort and performance.

S.B. did not consistently monitor the accuracy of her performance, resulting in needless errors. She encountered difficulty with drawing/copying tasks due, in part, to a quick and uncritical approach. Her pencil grasp (right hand) was unusual in that the barrel of the pencil rested on her ring finger.

Neuropsychological Assessment S.B.’s teacher completed rating scales pertinent to her observations of S.B.’s in- class behavior. The teacher provided ele- vated ratings (clinical range) on subscales sensitive to deficits in working memory, planning and organization, organization of materials, and self-monitoring. The parents also completed rating scales related to their observations of S.B.’s behavior. Their ratings showed clinical elevations on subscales assessing inattention, hyperactivity, rest- less-impulsive behaviors, psychosomatic complaints, and poor organization of materi- als. Borderline clinical ratings were pre- sented for problems with inhibition, working memory, planning and organization, and self-monitoring.

S.B.’s intelligence was determined to be within the average range, with a nonsignifi- cant discrepancy between verbal and perfor- mance intelligence. Her verbal subtest scores fell within the average range without any significant individual strengths or weak- nesses. In contrast, her performance subtest scores ranged from significantly below average to above average. Her above-average performance was evident on a subtest assessing her ability to determine the appro- priate sequence of social stimuli. Below- average performance was demonstrated on subtests assessing visual attention to details and visuoconstructive abilities (block design construction and puzzle assembly). Her achievement in reading, mathematics, and

N e u r o p s y c h o l o g y i n A c t i o n 1 0 . 1

P r i n c i p l e s o f A s s e s s m e n t i n P e d i a t r i c N e u r o p s y c h o l o g y

by William C. Culbertson

(continued)

276 PART THREE | Disorders of the Brain

of function. Several of these malformations are incompat- ible with life (for example, anencephaly and hydranen- cephaly), whereas others do not necessarily compro- mise the child’s survival, but do significantly impair or alter neuropsychological functioning. In many cases, a given disorder may have multiple causes; in others, the pathogenesis is quite specific. However, the origin of most of the disorders is undetermined.

The extensiveness and severity of damage to the devel- oping brain tends to reduce life expectancy of children with anatomic brain malformations. Surviving children show a high rate of mental retardation, speech and lan- guage delays, learning disabilities, motor impairments, physical anomalies, and epilepsy. Children with severe and global neuropsychological deficits often require life- long supervision and assistance. We turn first to HC, a relatively frequent anomaly of the brain that can result in minimal to severe neuropsychological deficits.

H y d r o c e p h a l u s

Clinical Presentation and Incidence—Hydrocephalus (HC) can occur during any developmental period and seriously damages the developing brain, disrupting both subcorti- cal and cortical functions. This condition results from an excessive accumulation of cerebrospinal fluid (CSF) in the brain’s ventricles (Figure 10.2). The increased volume of CSF produces a concomitant increase in intracranial pres- sure and expansion of the ventricles. As the ventricles ex- pand, cerebral tissue is compromised and the cranium dis- torts. If untreated, the child may die or suffer severe mental retardation. The actual incidence of HC is un- known because it is frequently associated with other con- genital disorders. However, it is estimated that 27 per 100,000 newborns suffer from the condition (Kolb & Whishaw, 1996). The incidence of HC of mixed causes appears to be greater for boys (62%) than girls.

spelling was found to be consistent with her assessed level of intelligence.

S.B.’s working memory for verbal con- tents (mental arithmetic, repeating digits backward) was age appropriate. Similarly, when learning a list of words across repeated trials, she demonstrated an age-appropriate learning curve and unimpaired memory recall. However, the introduction of an alternative list of words for learning revealed interference from the originally encoded list (words from the first list intruding into her recall of the second list of words). Although her verbal fluency (letter and semantic) performance was within the average range, her design fluency performance fell within the impaired range.

Deficits were also evident when judging the spatial orientation of lines, imitating sequences of movement in space, drawing familiar objects (for example, bicycle), and copying developmental visuomotor forms. Furthermore, she demonstrated an impaired level of performance when rapidly shifting between numbers and letters. Her fine-motor dexterity with her dominant and nondomi- nant hand was below age expectancy, with significant impairment evident for her non- dominant left hand.

S.B.’s performance on measures of sustained attention demonstrated poor attentional and inhibitory control. Although she demonstrated age-appropriate perfor- mance on an executive task assessing ab- stract abilities and cognitive flexibility, she significantly faltered on a second measure assessing executive planning and problem solving.

Commentary The impact of a major tumor on the develop- ing brain can result in a myriad of cognitive, emotional, and social deficits/excesses. Factors mediating the effects of the tumor are the child’s stage of development, nature and extent of the insult, cognitive resources (for example, intelligence), form of postsurgi- cal treatment (radiation and/or chemother- apy), and the availability and quality of supportive services. Despite the multiplicity of outcomes, a number of sequelae are associated with right anterior damage, including poorly organized narrative dis- course, inattention/distractibility, disruption of working memory, disinhibition, visual construction skill deficits, limited nonverbal fluency, and impaired monitoring. Moreover, memory disruption secondary to inattention and interference effects is frequently evi-

dent. Executive planning and problem solving can be markedly impaired. In con- trast, cognitive functions associated with left frontal circuitry can be relatively well pre- served. S.B.’s pattern of neuropsychological performance is consistent with compro- mised cognitive functions supported by right anterior brain circuitry.

S.B.’s neuropsychological strengths and weaknesses were presented to the parents. It was stressed that it was too early in her recovery to determine precisely which deficits would persist or resolve, but her progress should be monitored carefully, particularly because the impact of anterior damage is often not fully evident until adolescence. Recommendations were developed to aid school personnel in provid- ing appropriate educational modifications and interventions. An evaluation by a physi- cal therapist was recommended. The par- ents were further advised that if S.B.’s inattention, impulsivity, and minor motor activity did not improve over time, they should consult with her neurologist to determine the feasibility of introducing psychostimulant medication. Supportive group therapy/counseling with children who had undergone treatment for brain tumors was recommended.

(continued)

CHAPTER 10 | Developmental Disorders of Childhood 277

Neuropathogenesis—HC is a disorder that occurs secondary to other pathologic events or processes. This pathogenesis can be of prenatal, perinatal, or postnatal origin. Congenital (prenatal) disorders such as spina bifida, Dandy–Walker malformation, Arnold–Chiari malformation, and stenosis of the aqueduct of Sylvius often result in HC (see Table 10.1). Of these congenital disorders, spina bifida is most fre- quently associated with HC (Mataró, Junqué, Poca, & Sahuquillo, 2001). The most common cause of perinatal and postnatal HC is intraventricular hemorrhage (IVH), a condition that occurs in premature infants (see later). Other causes of HC, both prenatal and postnatal, include infections (meningitis and encephalitis), vascular abnor- malities, tumors, cysts, traumatic brain injury, and other disease processes (Erickson, Baron, & Fantie, 2001; Fletcher et al., 1996).

Physiological Dynamics—Any one of three underlying causes can produce an abnormal increase in the volume of ven- tricular CSF. These causative factors include oversecretion of CSF, obstruction of CSF passages, and impaired ab- sorption of CSF (Greenberg, Aminoff, & Simon, 2002; Fletcher et al., 1996). Oversecretion of CSF is rare and is generally a consequence of a secreting tumor of the choroid plexus, the primary producer of CSF in the lat- eral ventricles.

The second cause of HC occurs within the ventricu- lar system and involves obstruction of the CSF pathways as a result of congenital malformation, tumors, or scar- ring. HC of this etiology is termed obstructive or non- communicating HC (Brookshire, Fletcher, Bohan, Landry, Davidson, & Francis, 1995; Marino, Fine, & McMillan, 2004). The aqueduct of Sylvius, also called the cerebral aqueduct of the third ventricle, is the most commonly obstructed ventricular pathway, because of its long, narrow structure. Conditions obstructing the aque- duct of Sylvius include: (1) congenital narrowing (steno- sis) of the aqueduct; (2) a thin membrane lying on the aqueduct; (3) constriction of the aqueduct by pressure from an adjoining tumor; and (4) herniation of the cere- bellum and displacement of the fourth ventricle, as in Arnold–Chiari malformation (Hynd et al., 1997). How- ever, the pathogenesis of obstructive or noncommunicating HC may be idiopathic (unknown), and research findings suggest that different familial forms may exist (Hynd & Willis, 1988).

The third form of HC results from disrupted reabsorp- tion of CSF into the bloodstream caused by obstruction in the basal subarachnoid cisterns or in the arachnoid villi (Fletcher et al., 1996; Marino et al., 2004; see Figure 10.2).

When spina bifida is excluded, the most common cause of HC in early development is IVH, a condition that, until relatively recently, occurred in 40% to 50% of pre- mature infants with birth weights less than 1800 g (Mataró et al., 2001; Willis, 1993). Recent medical ad- vances have reduced the incidence of IVH to 20% for pre- mature infants (Fletcher, Dennis, & Northrup, 2000). IVH is a result of breathing problems or pressure on the brain during the delivery process causing vessels in the germinal matrix (area around the ventricles) to rupture and bleed into the ventricles. Blood and cellular debris clog the arachnoid villa (which is responsible for reabsorbing CSF into the bloodstream) and CSF volume and pressure increase, although its outward flow into the spinal canal is not blocked. HC of this form is known as nonobstruc- tive or communicating HC.

Obstructive or noncommunicating HC is a congeni- tal disorder that develops early in gestation and is associ- ated with an ever-expanding impact on subsequent brain development. In contrast, nonobstructive or communi- cating HC is primarily a consequence of perinatal and postnatal insults to a brain that heretofore had developed normally.

Impact of Hydrocephalus on the Developing Brain—If unchecked, HC has a devastating impact on the developing brain and skull (Figure 10.3). As CSF volume increases, the ventri- cles progressively enlarge in a posterior to anterior direc- tion with corresponding disruption of brain anatomy and function. The ventricle lining suffers focal damage, cere- bral blood vessels distort and become dysfunctional, neu- rons are injured, and the concentration of neurotrans- mitters and cerebral fluid alters (Del Bigio, 2004; Dennis & Barnes, 1994). Increasing pressure extensively damages the underlying white matter of the brain. Specifically, the corpus callosum stretches and thins (hy- poplasia), midline projection fibers that connect the hemispheres to the diencephalon and caudal regions stretch and distort, the internal capsule (fanlike white fibers separating regions of the basal ganglia and dorsal thalamus) displaces, and the periventricular white mat- ter (white matter adjacent to the lateral ventricles) is damaged (Dennis & Barnes, 1994; Ewing-Cobbs, Barnes, & Fletcher, 2003). Furthermore, the cortical mantle thins, often damaging the cerebral cortex and compromising cognitive functions. Because of the posterior-to-anterior progression of HC, the cognitive and motor functions supported by the posterior cortical regions, cerebellum, and midbrain structures with their connecting white matter tracks are most compromised

additional surgeries during the child’s life. Each surgery increases the risk for ventriculitis, or infection of the ven- tricles. Furthermore, introducing the shunt involves caus- ing a lesion to the brain, generally of the parietal lobe of the right hemisphere. The shunt track can irritate the sur- rounding brain tissue and increase the potential for seizures (Willis, 1993).

Although cognitive, motor, and sensory (visual) im- pairments frequently associate with HC, the precise symptom presentation is highly individualistic. The pe- riod of developmental onset, the presence of other con- genital disorders and anomalies, surgery to introduce or adjust a shunt, and the nature of the child’s environmen- tal context are several variables that affect the array, sever- ity, and form of symptoms the child will experience.

278 PART THREE | Disorders of the Brain

Malformation Description Clinical Manifestations

Abnormalities of bulk growth

Micrencephaly Subnormal brain size associated with abnormally Size of face near normal; folded scalp, possible small head (<2 SD below mean for age and gender) epilepsy, and most typically intellectual retardation

Megalencephaly Abnormally large brain from overproduction of Associated with mental subnormality, normality, cerebral parenchyma. Males > females or (hypothetically) giftedness. Epilepsy may occur.

Dysplasias of cerebral hemispheres

Holoprosencephaly Two hemispheres fail to develop. A large fluid-filled Faciocerebral dysplasias, cebocephaly, apnea cavity results. No interhemispheric fissure present. spells, severe mental retardation, hypotelorism, 1:13,000 live births and other systemic deformities. Usually incom-

patible with life.

Agenesis of the corpus callosum Complete or partial failure of the corpus callosum Occasionally asymptomatic or found in associa- to develop. Males > females tion with spina bifida, facial and ocular deformities, micren-

cephaly, and hydrocephalus. Epilepsy and mental retardation may occur.

Malformations of the cerebral cortex

Agyria/pachygyria Smooth lissencephalic surface of brain. Few Commonly found in association with agenesis of coarse gyri may be present corpus callosum, micrencephaly, epilepsy, severe mental

retardation, and early death

Polymicrogyria Development of many small gyri. Microscopically, Found in association with learning disabilities they may form an overlapping folded cortex (dyslexia), severe mental retardation, and epilepsy. Also appear

asymptomatically

Focal dysplasia Focal abnormalities in the cortical architecture Reported in cases of epilepsy and learning dis- usually consisting of disordered cells and layering abilities (dyslexia) of cortex

Malformations associated with congenital hydrocephalus

Dandy-Walker malformation Malformation of the cerebellum associated with a Hydrocephalus, agenesis of the corpus callosum, dilation of the fourth ventricle. Males > females Klippel-Feil and DeLange syndromes, and severe psychomotor

retardation

Table 10.1 Anatomic Disorders

(Mataró et al., 2001). As a result, children with HC fre- quently exhibit deficits in nonverbal (especially visu- ospatial) and motor performance.

As the ventricles continue to distend, the cerebral hemispheres mold into a balloon shape. Because sutures in the cranium of the fetus and infant have not yet fused, increasing pressure enlarges the skull to accommodate the increased CSF volume. Once the sutures close, however, cranial volume is invariant, and the HC develops further at the expense of brain tissue (Rowland, Fink, & Rubin, 1991).

Most children with symptoms of HC receive a shunt (see Figure 10.3). This medical procedure drains excessive CSF away from the ventricular system into the stomach. A shunt that fails, or needs adjustment, may necessitate

Neuropsychological Assessment—Neuropsychological assess- ment of the child with HC focuses on clarifying both spared and compromised functions. The extent and de- gree of impaired or spared cognitive functions differ for each child. In general, greater overall impairment of higher order cognitive abilities accompanies more ad- vanced cases of HC. However, interaction of HC with other moderating variables, such as age, intelligence, and socioeconomic status, potentially can lead to differential effects on cognitive functioning.

Before widespread use of the shunt, only a fourth of untreated HC children survived to adulthood, and many survivors were profoundly retarded (Hynd, Morgan, & Vaughn, 1997). In contrast, the cognitive performance of early shunted children is significantly higher, span- ning the range of abilities from below to above average

CHAPTER 10 | Developmental Disorders of Childhood 279

(Willis, 1993). Some investigators suggest that children with HC uncomplicated by other structural disruptions (such as multiple shunt operations or Arnold–Chiari malformation) are likely to demonstrate less impairment of overall cognitive ability (Erickson, Baron, & Fantie, 2001). Yet, even in cases of relatively preserved overall intelligence, children with shunted HC frequently demonstrate deficits in visual-perceptual, visuospatial, motor (fine and gross), and memory performance (Ewing-Cobbs, Barnes, & Fletcher, 2003; Scott et al., 1998). The deficits in the visual-perceptual, visuospa- tial, and visuomotor domains are related to the disrup- tion of the posterior cortical regions, cerebellum, corpus callosum, and other white matter pathways, whereas poor motor skills are believed to be a consequence of damage to the cerebellum, basal ganglia, motor strip,

Malformation Description Clinical Manifestations

Malformations associated with congenital hydrocephalus (continued)

Arnold-Chiari malformation Congenital deformation of the brainstem and Congenital hydrocephalus, spina bifida, and cerebellum severe psychomotor retardation

Stenosis of the aqueduct of Sylvius Obstruction of the aqueduct and CSF circulation Often insidious onset of symptoms associated with hydro- cephalus. Shunted children may suffer learning/behavioral problems. Nonverbal IQ < verbal IQ

Abnormalities of the neural tube and fusion defects

Spina bifida occulta Usually asymptomatic lesion discovered incidentally Can be associated with lipoma, dermal sinuses, and dimples

Spina bifida cystica Spinal defect that includes a cyst-like sac that Hydrocephalus a frequent complication. Cognitive may or may not contain the spinal cord deficits related to extent of hydrocephalus. Arnold-Chiari

malformation not uncommon

Cranium bifidum and encephalocele Fusion defects of skull referred to as cranium Many associated difficulties with hydrocephalus bifidum; myelomeningoceles or meningoceles including ataxia, cerebral palsy, epilepsy, and on the skull are referred to as encephaloceles. mental retardation Males < females

Anencephaly Vault of skull absent and brain represented by Condition incompatible with life vascular mass. Face is grossly normal. 1 male: 4 female

Hydranencephaly Cerebral hemispheres replaced by cystic sacs Difficult initially to distinguish from hydrocephalus. containing CSF Hypnoatremia, eye movement disturbances, and death

Porencephaly Large cystic lesion develops on the brain. May Occasionally asymptomatic but typically associ- occur bilaterally or unilaterally ated with mental retardation, epilepsy, and other neurodevel-

opmental malformations

Source: Modified and updated from Hynd, G., Morgan, A., & Vaughn, M. (1997). Neurodevelopmental anomalies and malformations. In C. Reynolds & E. Fletcher-Janzen (Eds.), Handbook of clinical child neuropsychology (2nd ed., p. 45). New York: Plenum Publishing Corporation. Reprinted by kind permission of Springer Science and Business Media.

280 PART THREE | Disorders of the Brain

and connecting white matter pathways (Erickson, Baron, & Fantie, 2001).

The memory deficits associated with HC include poor recall of both verbal and nonverbal contents. However, de- bate continues over which memory processes (encoding, retrieval, or consolidation) are impaired (Erickson, Baron, & Fantie, 2001). A singular profile of strengths and deficits associated with HC is not likely to be identified because of the multiple and widely distributed neurosubstrates that support memory processes. Rather, different memory profiles will likely be identified that reflect the specific neural memory systems that are impacted, the severity of damage, the stage of brain development at the onset of the disorder, and a host of other mediating variables.

HC may also affect the development of other important cognitive abilities and skills. For example, children with HC tend to demonstrate age-appropriate word recognition, but markedly lower reading comprehension, math computation and problem solving, and writing skills. Even HC children of average to above-average intelligence are likely to demon- strate this disparity (Dennis & Barnes, 1994; Ewing-Cobbs, Barnes, & Fletcher, 2003). Similarly, HC children often ex- hibit relative strengths in speech and language production. Yet, even though their language is fluent and well structured, 28% to 41% of the children exhibit an atypical communi- cation style termed “cocktail party syndrome” (CPS) (Mataró et al., 2001). This communication style is charac- terized by excessive verbiage that lacks clarity, organization, and relevance—a form of speech that resembles the “fluent, but empty” speech patterns associated with receptive apha- sia, a communication disorder that involves impaired

Figure 10.3 Computed tomography (CT) images of child with hydrocephalus. (A) Child at 3 months of age with unshunted hydrocephalus. Note the significantly enlarged ventricles. (B) The same child at 4 years 8 months with shunt in left hemisphere (white line, bottom right). (Reproduced from Anderson, V., Northam, E., Hendy, J., & Wrennall, J. [2001]. Developmental neuropsychology: A clinical approach [p. 193, Figure 6.4]. Philadelphia: Taylor & Francis, by permission.)

Text not available due to copyright restrictions

language comprehension. Interestingly, deficits related to understanding and expressing abstract language are associ- ated with HC and are believed to contribute potentially to the development of CPS. On a more positive note, many children who demonstrate CPS develop a more appropriate communication style with increasing age.

A particularly interesting finding concerns the relation of cognitive functioning to early- and late-occurring HC. Children with prenatal obstructive HC are prone to ex- hibit average verbal and language abilities, but below- average visuospatial and visuomotor abilities. This profile is similar to that of the nonverbal learning disability syn- drome (see discussion in Chapter 11). In contrast, chil- dren with HC resulting from perinatal and postnatal in- sults (such as IVH) are more likely to show comparable verbal and performance abilities, although both generally fall within the low-average range (Willis, 1993).

The integrity of the executive functions of children with HC has received less empirical attention than other cognitive domains. Executive functions refer to a wide range of higher order mental processes related to the generation, integration, control, and evaluation of goal-directed be- haviors that are supported by the frontal and frontal- cortical-subcortical networks of the brain (see Chapter 9). Preliminary studies of executive performance in children with HC have identified executive deficits of attentional allocation and control, concept formation, planning, cog- nitive flexibility, response inhibition, and self-regulation (Fletcher, Dennis, & Northrup, 2000; Willis, 1993).

Importantly, poor executive performance by children with HC does not necessarily implicate damage or dis- ruption in the frontal cortex. For instance, in a recent study (Anderson, Anderson, Northam, Jacobs, & Mikiewicz, 2002), the executive performance of children with HC, PKU, and frontal focal lesion and healthy con- trol children was examined. Both the HC and frontal le- sion groups performed poorly, relative to the healthy con- trol children, on an executive measure sensitive to visuocontructive, planning, and organization skills (Rey Complex Figure; Rey, 1941, translated by Corwin & Bylsma, 1993). These findings leave unanswered the ex- tent to which the poor executive performance of the HC group related to visuospatial, motor, or executive plan- ning/organizational deficits, or some combination of these deficits. Because of the posterior-to-anterior pro- gression of damage associated with HC, posterior cortical and subcortical structures, as well as white matter path- ways, are generally disrupted before the frontal structures. This posterior disruption can, in turn, result in the trans- mission of distorted or incomplete visuospatial and/or motor input to the frontal system. Thus, the poor perfor-

mance of the HC group could reflect an “executive deficit” engendered by anomalies of nonfrontal structures and pathways, rather than actual damage to the frontal lobes. Additional empirical study is needed to clarify the specific contributions of different neurosubstrates to the executive deficits of children and adolescents with HC.

Treatment—The prognosis for children with HC was dire before the development of shunting. However, the advent of shunting has markedly increased the number of chil- dren who both survive and escape the significant destruc- tion of their cognitive functioning. Children with HC uncomplicated by the presence of other anomalies who receive early shunting often exhibit few, if any, cognitive impairments. Ultrasonography, a procedure that uses sound waves to image internal structures, enables medical personnel to identify HC in utero. This procedure allows for measurement of the ventricular expansion that pre- cedes the later enlargement of the cranium. From birth until age 2, HC is fairly easy to diagnose because the cra- nium quickly enlarges, developmental delays are evident, and eye movement abnormalities are present (Hynd, Morgan, & Vaughn, 1997).

G E N E T I C A N D C H R O M O S O M A L D I S O R D E R S

This section explores genetic and chromosomal disorders. Advances in the study of genetics, such as the mapping of the human genome, are accelerating at an exponential rate. More than 100 genetic and chromosomal disorders have been identified that, if untreated, can produce significant neuropsychological and physical deficits (see Table 10.2 for examples). A multitude of factors can disrupt the genetic blueprint that defines the developing child. Genetic disor- ders can be a consequence of single-gene, chromosomal, parental imprinting, or molecular cytogenic anomalies. A discussion of the disorders associated with each of these genetic abnormalities is beyond the scope of this chapter. Accordingly, we focus on neurodevelopmental disorders associated with chromosomal abnormalities.

Chromosomal disorders are a consequence of the mal- formation, deletion, addition, and/or dislocation of chro- mosomal material during the development of the oocyte or spermatocyte, or during conception and germination of the egg (Marino, Fine, & McMillan, 2004; Spreen, Rissell, & Edgell, 1995). As a result, a genetic defect oc- curs even though the family history is negative for the disorder. However, there are some families who have a his- tory of chromosomal disorders, suggesting direct genetic transmission from the parent to the offspring.

CHAPTER 10 | Developmental Disorders of Childhood 281

Chromosomal abnormalities can affect either autosomes or sex chromosomes. Autosomal abnormalities generally produce more severe birth defects than sex chromosome dis- turbances. More than 50% of first-trimester miscarriages are due to chromosomal defects. In addition, congenital and cognitive deficits are frequently a consequence of this class of genetic disorder (Marino, Fine, & McMillan, 2004). We discuss two chromosomal disorders: TS and WS. TS is the consequence of a missing or abnormal X sex chromosome, whereas WS is produced by a submicroscopic deletion on autosome 7. Studies of these two disorders have significantly advanced our understanding of the neuropsychological ef- fects of disturbances to the developing brain.

T u r n e r ’ s S y n d r o m e

Background and Clinical Presentation—In 1938, Turner pre- sented a syndrome characterized by a failure to develop secondary sexual characteristics, short stature, webbed neck, and cubitus valgus (an increased carrying angle at the elbow). The disorder was subsequently named Turner’s syndrome (TS). A previous case of the disorder had also been reported by Otto Ullrich (1930); therefore, the syndrome is occasionally known as Ullrich–Turner syndrome. TS was recognized as a chromosomal disorder affecting female individuals in 1959, when Charles Ford and colleagues identified a missing X on the 45th chro- mosome. The karyotype—a visual representation of the configuration of a chromosome—is designated as 45,XO,

although there are other variations (see Web Connections section later in this chapter).

Consistent with Turner’s earlier description of the dis- order, an essential characteristic of TS is gonadal dysgene- sis, as evident in either the absence of the ovaries or the presence of vestigial ovarian streaks. Short stature is an- other distinguishing characteristic, with achieved height often falling between 4 feet 6 inches and 4 feet 10 inches (Powell & Schulte, 1999). Physicians often identify in- fants with TS at birth due to characteristic edema of the hands and feet and loose skin folds at the nape of the neck. In childhood, physicians observe webbing of the neck, low-set ears, shield chest, deformed nails, cardiac and kidney malformations, and other features. Table 10.3

282 PART THREE | Disorders of the Brain

Genetic Chromosomal

Adrenoleukodystrophy Angelman’s syndrome

Friedreich’s ataxia Cornelia de Lange’s syndrome

Galactosemia Down’s syndrome

Hyperphenylalaninemia Fragile X syndrome

Krabbe’s disease Klinefelter’s syndrome

Lafora’s disease Prader-Willi syndrome

Lesch-Nyhan disease Sotos’ syndrome

Mucopolysaccharidosis Trisomy X syndrome

Phenylketonuria Tuberous sclerosis complex

Turner’s syndrome

Williams syndrome

Source: Harris, J. C. (1995). Developmental neuropsychiatry, vol. II: Assessment, diagnosis, and treatment of developmental disorders. New York: Oxford University Press, by permission.

Table 10.2 Genetic and Chromosomal Disorders

Anatomic Abnormalities

Short stature

Webbed neck

Cubitus valgus

Broad chest

Prepubertal ovarian failure

Growth

Decreased mean birth weight

Lack of pubertal growth spurt

Skeletal

Curvature of the spine

Genu valgum (knock-knee)

Wrist deformity

Short hand and feet bones

Craniofacial

Premature closure of the skull sutures

Small jaw

Strabismus (cross-eyes)

Inner ear defects

Malrotation of ears

High arched palate

Cardiovascular

Aortic narrowing

Mitral valve prolapse

Septal defect (defect of the wall separating chambers of the heart)

Partial anomalous venous blood return

Renal

Horseshoe kidney (abnormal tissue connecting the kidneys) or ptotic kidney (abnormal location in the pelvis)

Unilateral failure to develop or underdeveloped kidney

Unilateral double ureter

Lymphatic

Dilation of the lymph vessels

Congenital swelling of the hands/feet

Hair and Skin

Low posterior hairline

Multiple moles

Finger/toenail deformities

Source: White, B. J. (1994). The Turner syndrome: Origin, cytogenetic variants, and factors influencing the phenotype. In S. H. Broman & J. Grafman (Eds.), Atypical cognitive deficits in developmental disorders (p. 185). Mahwah, NJ: Lawrence Erlbaum, by permission.)

Table 10.3 Physical and Medical Problems of Turner’s Syndrome

presents a sample of the physical characteristics and med- ical problems associated with TS. A distinctive cognitive profile for TS has been proposed and is discussed later in this section (see Neuropsychological Assessment).

Incidence and Comorbidity—TS is one of the most common chromosomal disorders, with an estimated female inci- dence rate of 1 in 2500 to 5000 births (Berch & Bender, 2000). Researchers believe it occurs at conception, and 99% of the affected fetuses spontaneously abort. The life expectancy of individuals born with TS is not affected, al- though a number of physical conditions accompany the disorder (see Table 10.3).

Frequent comorbid conditions of TS are learning dis- abilities and early symptoms of an attention-deficit/hyper- activity disorder (ADHD). Also, some researchers have suggested that female individuals with TS are prone to de- pression, feelings of inadequacy, difficulty in concentrat- ing, poor peer relationships, and anxiety over sexuality and relationships with male individuals. The factors that ac- count for these difficulties are unclear, but the small stature and sexual limitations of the individual with TS likely con- tribute to social difficulties and negative emotionality.

Chromosomal Defect and Turner’s Syndrome—TS is the result of an anomaly of the female sex chromosome. The XX chro- mosome defines the developing embryo as female. In TS, the second X is either missing (monosomy X or 45,XO) or otherwise abnormal in formation or location. A wide vari- ety of karyotypes appear in liveborn TS children, with 45,XO evident in approximately 50% of the cases. Isochromosome, the duplication of one arm of the X chro- mosome with the loss of the other arm, constitutes 10% to 20% of cases. Mosaic karyotypes appear in 30% to 35% of children with TS (Temple, Carney, & Mullarkey, 1996). The mosaic karyotypes are characterized by the presence of normal chromosomes in some cells (46,XX) and abnormal chromosomes in others (Temple & Marriott, 1998). The mosaic karyotype, 45,X/46,XX, is associated with milder and less pervasive anomalies than the other karyotypes.

At birth, these children exhibit few distinguishing fea- tures, and short stature may be the first presenting symp- tom. In contrast, the small X-ring karyotype appears to increase the risk for mental retardation, smaller head size, and greater growth-related retardation than the other TS karyotypes. Note, however, that the TS physical pheno- type occasionally appears in children with apparently nor- mal karyotypes.

Neuropathogenesis—Neuroimaging studies provide support for right hemisphere (particularly posterior region)

involvement in the pathogenesis of TS. In an earlier mag- netic resonance imaging (MRI) study of TS and healthy control children, Reiss and coworkers (1995) determined that the ratios of gray to white matter for the right tem- poral and parietal areas were significantly lower for the participants with TS. In a more recent study (Brown et al., 2002) of children and adolescents with TS, MRI showed bilateral decreases in parietal gray and occipital white mat- ter and increased cerebellar gray matter. Moreover, a positron emission tomography (PET) study (Elliott, Watkins, Messa, Lippe, & Chugani, 1996) of children with TS demonstrated significant bilateral parietal region hypometabolism (reduced metabolism) relative to a healthy control group. The researchers also observed a trend toward hypometabolic activity of the occipital re- gion. They hypothesized that the visuospatial and mathe- matic deficits associated with TS stemmed from parieto- occipital hypoactivation. Other regional differences in brain volume or neuroactivation of patients with TS have been identified in the hippocampus, lenticular nucleus, thalamus, temporal cortex, and insula (Murphy et al., 1993, 1997). However, reduced tissue volume or atypical activation patterns for parietal and parieto-occipital areas are the most consistent findings across neuroimaging studies.

Although posterior brain regions have received the greatest empirical attention, increasing attention has fo- cused on the frontal system as it relates to executive per- formance associated with TS. Neuropsychological studies have shown that individuals with TS demonstrate deficits in verbal fluency, planning and organization, impulsive regulation, strategic memory organization, cognitive flex- ibility, and attentional control (Buchanan, Pavlovic, & Rovet, 1998; Romans, Roeltgen, Kushner, & Ross, 1997; Temple, Carney, & Mullarkey, 1996). Haberecht and col- leagues (2001) subjected children and adolescents with TS and healthy control participants to function MRI (fMRI) while performing an executive function task, namely, a visuospatial working memory task. The chil- dren and adolescents with TS showed poorer perfor- mance than healthy control participants on the visuospa- tial working memory task. Moreover, fMRI showed significant bilateral hypoactivation (relative to healthy con- trol participants) of the dorsolateral prefrontal cortex, cau- date, and inferior parietal cortex while performing the working memory task. The authors hypothesized that the working memory deficits of TS relate to disruption of the frontal-striatal and frontal-parietal executive circuits.

In a more recent study (Tamm, Menon, & Reiss, 2003), children and adolescents with TS and healthy vol- unteers underwent fMRI while performing a measure of

CHAPTER 10 | Developmental Disorders of Childhood 283

executive inhibitory control. The TS and healthy groups did not, contrary to prediction, differ in their inhibitory performance. Yet, the TS group was found to show acti- vation of additional regions of the superior and middle prefrontal cortices not demonstrated by the healthy con- trol group. The authors conclude that patients with TS demonstrate altered (possibly compensatory) prefrontal cortical functioning with regard to response inhibition. Overall, neuroimaging studies have contributed to our understanding of the brain-behavior relations of TS, but much remains to be discovered.

Neuropsychological Assessment—Originally, it was believed that mental retardation was a common concomitant of TS. However, ongoing studies (Powell & Schulte, 1999) have demonstrated that the intellectual functioning of children with TS is generally within the low-average to average range. A smaller proportion of children fall within the below- or above-average range of intelligence (Swillen et al., 1993). Often, verbal intelligence exceeds performance in- telligence. That is, children with TS, when performing in- tellectual measures such as the Wechsler scales (1997, 2002, 2003), tend to achieve higher scores on verbal lan- guage–related scales (for example, vocabulary) as con- trasted with performance scales (for example, block de- sign) that assess visual-perceptual and visuomotor abilities.

Several researchers have suggested that children with TS demonstrate a relatively distinct neurocognitive pro- file. The profile is characterized by intact verbal abilities in contrast with deficits in visuospatial, visuomotor, and arithmetic performance (Romans et al., 1997; Temple & Marriott, 1998). Table 10.4 summarizes the types of visu- ospatial and visuomotor deficits identified. Note that these deficits are generally associated with right parietal or dif- fuse right hemisphere dysfunction. Several investigators have drawn a parallel between the neurocognitive profile of TS and that of the nonverbal learning disability syndrome (see discussion of the NVLD syndrome in Chapter 11). Alternatively, Pennington and Smith (1983) contend that the performance of individuals with TS suggests diffuse brain injury, rather than injury specific to either the right or left hemisphere. Increasingly, investigators are realizing that children with TS are at greater risk for the development of specific neurocognitive deficit patterns (such as preserved verbal abilities and visuospatial weaknesses), but these deficits are not universal for all children with TS.

Developmental Course—The incidence of prematurity for children with TS (45,XO) is high, with more than 25% of the infants born 2 to 4 weeks early, and approximately

30% born more than 4 weeks before their due dates (Harris, 1995). The body length of the infant at birth is below average. Measures (blood assays) of gonadotropins assist in diagnosing the disorder. In the female individual, gonadotropins are hormones that stimulate the functions of the ovaries. The majority of children with TS are diag- nosed before school age.

During the preschool years, children with TS are de- scribed as immature, overactive, distractible, and having difficulty sustaining attention. With increasing age, activ- ity appears to slow, and many children with TS later be- come normally active or hypoactive. Young children with TS do not exhibit behavioral problems and are gen- erally accepted by and involved with peers. However, by school age, the peer interactions of many children with TS lessen and involvement in solitary activities increases. Temperamentally, children affected with TS tend to be compliant, unassertive, and conforming in their interac- tions with caretakers and peers. Peer interactions, how- ever, continue to decline during the elementary and mid- dle school years, and many youngsters with TS report feelings of loneliness and alienation (Powell & Schulte, 1999; Swillen et al., 1993). With the onset of adolescence, teenagers with TS date less frequently and are involved in fewer romantic and sexual relationships than their peers. Some investigators suggest that they may not be profi- cient at reading social cues, which negatively affects their efforts to relate to peers. Growth retardation, physical anomalies (such as webbing of the neck), medical prob- lems, social difficulties, and an awareness of their sexual difference likely contribute to diminished self-esteem

284 PART THREE | Disorders of the Brain

Dysfunctions of:

Arithmetic

Design copying

Directional sense

Extrapersonal space

Left–right discrimination

Maze performance

Mental rotation

Motor learning

Part–whole perception

Route finding

Spatial reasoning

Visual discrimination

Spatial working memory

Visual sequencing

Visual-motor integration

Visual memory

Source: Buchanan, L., Pavolic, J., & Rovet, J. (1998). A reexamination of the visuospa- tial deficit in Tuner syndrome: Contributions of working memory. Developmental neuropsychology (pp. 341–367). Mahwah, NJ: Lawrence Erlbaum, by permission.)

Table 10.4 Visuospatial and Visuomotor Deficits Associated with Turner’s Syndrome

(Bender, Linden, & Robinson, 1994). In light of these factors, it is not surprising that teenagers with TS are at risk for development of anxiety, insecurity, and depres- sion. Despite deficits in the visuospatial and visuomotor areas, most children affected by the disorder (90%) at- tend regular school programs, although they may need re- medial interventions. Moreover, because of the physical problems associated with the condition (see Table 10.3), individuals with TS often need ongoing medical moni- toring and services. On a more encouraging note, TS does not preclude the establishment of stable personal relation- ships, marriage, or gainful employment.

Treatment—It is essential that adolescents with TS receive es- trogen therapy because of their gonadal dysgenesis. With- out proper medical interventions, youngsters with the dis- order do not mature sexually, which can cause significant distress. Furthermore, the short stature associated with TS often requires growth hormone therapy. Psychological or counseling services may be needed, because the risk for teasing and lack of peer acceptance appears high for chil- dren with TS (Powell & Schulte, 1999; Rovet, 1993). Chil- dren and adolescents with TS who demonstrate inatten- tion, impulsivity, and hyperactivity encounter significant difficulties within the classroom. Specialized educational interventions and, in many cases, the introduction of psy- chostimulant medications may assist the student. In addi- tion, spatial, executive, and academic weaknesses (mathe- matics) must be addressed to ensure appropriate academic progress. Chapter 11 explores additional educational rec- ommendations relevant to the needs of the child with TS (see the Nonverbal Learning Disability Syndrome section).

W i l l i a m s S y n d r o m e

WS is an intriguing and enigmatic disorder. The disorder is characterized by physical abnormalities and low intellectual functioning, yet presents an uneven cognitive profile of rel- atively preserved strengths and distinct weaknesses. Our understanding of the disorder is rapidly increasing due to the surge in significant research since the mid-1980s.

Background and Incidence—In 1961, Williams, Barratt-Boyes, and Lowe described a neurodevelopmental disorder charac- terized by unusual facial features, cardiovascular defect, hy- percalcemia, and mental retardation that subsequently was designated as Williams syndrome (WS). The disorder is also referred to as Williams–Beuren syndrome because of the contributions of Beuren and colleagues (1964) to the understanding of the medical features of WS. Advances in genetics and molecular biology reveal that WS is associated

with a submicroscopic genetic deletion on chromosome 7 (band q11.23). WS equally affects male and female indi- viduals and does not appear to be overly represented in any specific ethnic groups. The disorder is relatively rare and occurs at an estimated incidence rate of 1 per 20,000 to 50,000 live births (Dykens, 2003; Karmiloff-Smith, 1997).

Clinical Presentation—WS is a unique neurodevelopmental disorder characterized by a recognizable pattern of dys- morphic facial features, cardiovascular and physical ab- normalities, mental retardation, specific cognitive profile, and distinct personality.

Table 10.5 presents a number of the physical and medical features associated with WS (Morris & Mervis,

CHAPTER 10 | Developmental Disorders of Childhood 285

Visual and Ocular Gastrointestinal Renal

Stellate or lacy iris Infant feeding Kidney structural

Hyperopia (farsighted) difficulties abnormalities

Abnormal binocular Colic Renal artery stenosis

vision Vomiting Recurrent bladder

Strabismus Failure to thrive infections

Constipation Enuresis

Auditory/Voice Chronic abdominal pain Urinary frequency

Chronic otitis media Umbilical and inguinal

Sound hypersensitivity hernias Dental

(hyperacusis) Obesity (adult) Small, widely spaced

Hoarse, low pitched teeth

Musculoskeletal Malocclusion

Enamel hypoplasia Cardiovascular Hyperextensible joints

Supravalvar pulmonic Muscle hypotonia

stenosis Nocturnal leg pains

Peripheral pulmonic Compensatory posture stenosis

Kyphosis, lordosis, Generalized arteriopathy and scoliosis

Hypertension Joint contractors

Stiff, awkward gait

Metabolism/Growth Muscle hypertonia (Adult)

Hypercalcemia

Precocious puberty

Short stature

Table 10.5 Physical and Medical Conditions Associated with Williams Syndrome

1999). The distinctive facial dysmorphia of the child with WS (Figure 10.4) has been called “elfin” due to a broad brow, puffy eyes, a stellate or lacy iris pattern, a small upturned nose, a broad nasal bridge, full cheeks, a wide mouth, prominent lips and ears, and small, widely spaced teeth. As the child ages, the face narrows, the nose tip broadens, and asymmetry of facial features is common.

Cardiovascular anomalies, particularly supravalvar aortic stenosis (SVAS), are common. SVAS refers to the abnormal narrowing of the walls of the aorta, potentially leading to cardiac pathology. Approximately 65% to 75% of children and adults with WS are afflicted with SVAS (Morris & Mervis, 1999). Although aortic stenosis is of significant concern, other arterial systems (for example, renal) are also affected. Because of the generalized arteri- opathology associated with WS, ongoing medical moni- toring and treatment are warranted.

During infancy and childhood, the hypercalcemia (ex- cessive calcium in the blood) of WS contributes to feeding disturbances, vomiting, failure to thrive, constipation, and chronic abdominal pain. Individuals with WS are highly sen- sitive to sounds (hyperacusis), and young children demon- strate an exaggerated startle response to noise (Hagerman, 1999). Similarly, older individuals with WS are often aware of sounds that others fail to detect and complain that cer- tain sounds produce a sense of apprehension. Children with WS are prone to distractibility and hyperactivity, and

the extent to which hyperacusis contributes to these dis- turbances remains unclear.

Young children with WS exhibit hypotonia, whereas older children and adults have problems with hyperto- nia. Joint instability and joint contractures adversely af- fect fine- and gross-motor movements. Due to poor mus- cle tone and joint anomalies, children with WS demonstrate delays in motor development; a stiff, awk- ward gait; and abnormal posture.

Genetic Defect and Williams Syndrome—The microdeletion of chromosome 7q11.23 can be transmitted by either par- ent, and the resulting physical and cognitive features of the disorder vary depending on the size of the deletion (Morris & Mervis, 1999). Seventeen genes have been identified in the 7q11.23 region that potentially relate to WS. The specific genes deleted and size of the deletions are believed to affect the particular constellation of fea- tures that can be exhibited by individuals with WS. Sev- eral of these 17 contiguous genes are associated with spe- cific features of the WS phenotype. Of these genes, deletion of the elastin (ELN) gene has received the great- est support as pathogenic to WS (Schultz, Grelotti, & Pober, 2001). ELN is an important connective tissue pro- tein found in the skin, ligaments, organ walls, and walls of arteries. The ELN deletion is believed to account for a number of the physical anomalies associated with WS (see Table 10.5), particularly those related to the cardiovascu- lar system. Currently, the chromosomal test fluorescent in situ hybridization (FISH) is the primary tool for de- termining whether an individual is afflicted with WS. Using this technique, 97% to 100% of individuals with WS demonstrate the deletion of the ELN gene (Morris & Mervis, 1999).

The second identified gene, LIM-Kinase (LIMK1), is a protein kinase that appears important in axon guid- ance during brain development (Osborne & Pober, 2001). It is hypothesized that deletion in the LIMK1 gene is associated with the significant visuospatial and visuospatial construction deficits demonstrated by indi- viduals with WS. A third implicated gene, syntaxin 1A (STX1A), is a protein found in the membrane of cells, particularly neurons, and is necessary for neurotransmit- ter release. Hyperactivity and other behavioral problems of individuals with WS are hypothesized to relate to the deletion of this gene. Finally, the deletion of three other genes—GTF2I (general transcription factor 2-I), GTF2IRD1 (general transcription factor 2-I repeat do- main containing protein 1), and CYLN2 (cytoplasmic linker 2)—may be associated with the mental retardation associated with WS. GTF2I and GTF2IRD1 are believed

286 PART THREE | Disorders of the Brain

Figure 10.4 The distinctive facial features of a 7-year-old child with Williams syndrome (right) and her normally develop- ing 4-year-old sister (left). (Reproduced from Morris, C. A., & Mervis, C. B. [1999]. Williams syndrome. In S. Goldstein & C. R. Reynolds [Eds.], Handbook of neurodevelopmental and genetic disorders in children [p. 558, Figure 24.2]. New York: Guilford Press, by permission.)

to be involved in the regulation of gene expression, and CYLN2 is thought to perform linkage functions within the neurons (Osborne & Pober, 2001). Notably, the dis- cussed linkage of individual gene deletions to the specific features of WS awaits future research for verification. Likewise, little currently is known of the functions of the remaining genes located at 7q.11.23 with regard to the WS phenotype.

Anatomic Brain Anomalies—Neuroimaging studies (Reiss et al., 2000; Schultz, Grelotti, & Pober, 2001) have reported a reduction in the overall brain volume of individuals with WS, although regional brain reductions were not uni- form, with preserved volume of the temporal-limbic structures, cerebellum, and gray matter noted. Further- more, Reiss and associates (2000) found that the de- creased volume was primarily in the white matter, al- though there was significant loss of gray matter evident in the right occipital lobe. There were also indications of greater posterior (occipitoparietal) than anterior volume loss. These anatomic differences are consistent with the cognitive profile of relatively preserved language and im- paired visuospatial abilities demonstrated by individuals with WS.

Likewise, cytoarchitectonic studies of individuals with WS have shown abnormal auditory cell packing density and neuronal size in the temporal lobe (Brodmann’s area 41), suggesting hyperconnectivity of the auditory cortex (Galaburda & Bellugi, 2000; Holiger, McMenamin, Sherman, & Galaburda, 2001). This finding may be re- lated to the relatively spared auditory functions (lan- guage and music) and unusual reactions to auditory stimuli such as hyperacusis (Levitin, Cole, Chiles, Lai, Lincoln, & Bellugi, 2004).

Neuropsychological Profile—The neuropsychological profile associated with WS includes a unique constellation of abilities, skills, and interests. This profile includes intel- lectual impairment, relatively preserved language skills, increased attention to facial processing, visuoconstructive skill weaknesses, significant interest and relative profi- ciency in music, and high levels of sociability.

General Intellectual Performance and Language Abilities— Individuals with WS frequently demonstrate mild-to- moderate mental retardation; there is appreciable variabil- ity in intellectual performance, with cognitive scores ranging from significantly below average to low average (Robinson, Mervis, & Robinson, 2003). Particular weak- nesses are often evident in higher order conceptual reason- ing and problem solving (Levitin et al., 2004). Generally,

measures of verbal intelligence reveal higher levels of func- tioning than measures of nonverbal intelligence, particu- larly if visuospatial abilities are assessed.

Language skills are consistently reported to be an area of relative strength for individuals with WS. Particular verbal strengths are evident in vocabulary development, phonologic processing, auditory short-term memory, au- ditory working memory, and verbal fluency (Robinson et al., 2003; Volterra, Caselli, Capirci, Tonucci, & Vicari, 2003). In the normal population, language and global intelligence are generally highly correlated with each other. Yet, the language abilities of individuals with WS are often more advanced than would be predicted by their cognitive ability performance. Increasingly, however, research shows that certain aspects of the lan- guage development associated with WS are far from nor- mal. Specifically, anomalies in the development of se- mantics, complex syntax, grammar, pragmatic language (Laws & Bishop, 2004), and comprehension of nonlit- eral language (Sullivan, Winner, & Tager-Flusberg, 2003) are evident. Furthermore, indications exist that the precursors of language, as well as formal language, develop later and in different ways in children with WS relative to healthy children. For example, the precursor to naming objects is referential pointing; yet, Mervis and Bertrand (1997) found that naming precedes referential pointing for young children with WS. Moreover, joint attention, another precursor of normal language devel- opment, is significantly reduced in toddlers with WS compared with healthy peers of comparable mental and chronologic age (Karmiloff-Smith, Brown, Grice, & Paterson, 2003). The emergence of formal language in children with WS is delayed approximately 2 years as contrasted with healthy children of a similar age (Morris & Mervis, 1999). Furthermore, the onset of novel two- word combinations is even more delayed, ranging from 26 to 50 months of age. However, once language emerges, it develops at an increasing rate, often more rapidly than in children with other neurodevelopmental disorders such as Down’s syndrome (Mervis & Robinson, 2000). The language of adolescents and adults with WS continues to be an area of relative strength, although language attainment is not comparable with that of healthy adolescents and adults.

A number of studies have indicated that children with WS differ in the manner in which they acquire language. For example, a series of recent studies (Robinson, Mervis, & Robinson, 2003; Volerra et al., 2003) has determined that children with WS rely more heavily on auditory working memory and short-term phonologic memory in language acquisition, particularly grammar, than typically

CHAPTER 10 | Developmental Disorders of Childhood 287

developing children. Similarly, children with WS, relative to matched control children, show greater proficiency in encoding language via phonologic relative to linguistic- semantic features. Overall, these findings suggest that lan- guage, although a relative strength for children with WS, is less advanced than typically developing children of the same age and is possibly acquired by different cognitive processes.

Facial Processing—The facial processing abilities are rec- ognized as another unique aspect of the cognitive pro- file associated with WS. Children with WS spend an in- ordinate amount of time focusing on the faces of others. For example, in a relatively recent study (Mervis et al., 2003), infants and toddlers (8–43 months old) with WS demonstrated greater attention to and focus on the face of others relative to that of healthy children. More- over, normal to near-normal performance has been re- ported (Deruelle, Mancini, Livet, Casse-Perrot, & de Schonen, 1999; Karmiloff-Smith, 1998) for individuals with WS on standardized measures of facial recognition (for example, Benton Facial Recognition Test; Benton, Hamsher, Varney, & Spreen, 1983). Yet, facial recogni- tion appears to be accomplished by different cognitive processes for WS relative to healthy control individuals. Specifically, typically developing children focus more on the configuration of facial features for recognition, whereas those with WS rely primarily on the features of the face for identification (Karmiloff-Smith et al., 2003).

Visuoconstructive Skills—Despite a relative strength in fa- cial processing, visuoconstructive abilities are generally significantly impaired relative to the global intellectual ability of individuals with WS. Two areas of visuocon- structive, drawing and replication of block patterns, have been examined extensively. The performance of in- dividuals with WS in drawing or copying geometric or familiar forms (for example, a person) is significantly poorer than that of healthy children (matched for chronologic or mental age) or children with Down’s syn- drome (matched for chronologic and mental age) (Klein & Mervis, 1999; Morris & Mervis, 1999). The draw- ings of children and adolescents with WS are often un- recognizable (Figure 10.5), with the components or parts of the drawn object scattered over the page and un- connected. Thus, the drawings reveal deficits in global or- ganization and spatial integration. Interestingly, the draw- ings of children and adolescents with Down’s syndrome are recognizable, although simplified (see Figure 10.5). That is, the global organization and integration of the

drawings of the children with Down’s syndrome are rel- atively preserved.

Similarly, the ability of children and adolescents with WS to replicate structures (for example, a tower) or geo- metric designs with blocks is poorer than that of matched control participants. That is, the performance of children and adolescents with WS is often below that of healthy children matched for mental age, children with mental retardation of mixed etiology, and children with Down’s syndrome. The WS groups struggle with maintaining the overall organization or configuration of the block structures/designs, whereas the other matched groups demonstrated significantly less difficulty in spatial- motor organization (Farran & Jarrold, 2003; Morris & Mervis, 1999).

288 PART THREE | Disorders of the Brain

Figure 10.5 Drawings of an elephant by an adolescent with Williams syndrome (WS; top) and an adolescent with Down’s syndrome (DS; bottom). (Reproduced from Temple, C. [1997]. Developmental cognitive neuropsychology [p. 154, Figure 4.6]. Philadelphia: Psychology Press Ltd., by permission.)

Visuoconstructive tasks require that visuospatial infor- mation be processed and transmitted to the frontal sys- tem for action. Although the spatial deficits of WS have been associated with disturbances of the posterior regions of the brain, the impact of the disorder on the executive action system and interconnecting pathways remains to be elucidated. For example, Atkinson and associates (2003) presented a WS and a healthy control group of children with three executive measures sensitive to the in- hibition of a prepotent response—holding in abeyance a response that is primed for release. The children with WS, in contrast with the healthy children, showed a dimin- ished ability to inhibit a prepotent spatially directed re- sponse. Yet, the two groups demonstrated comparable performance related to inhibiting a pictorial-verbal (non- spatial) response. Although executive dysfunction is sug- gested, the basis of the deficit remains unanswered. As the authors correctly conclude, the inhibitory deficit may re- late to a disturbance of the dorsolateral frontal region, parietal region, and/or interconnecting pathways of the two systems.

A potentially confounding factor in the studies of the visuospatial processing of individuals with WS is pre- sented in Table 10.5. Children with WS frequently expe- rience visual sensory deficits such as binocular disorders, poor visual refraction, and decreased visual acuity. Thus, the visual sensory deficits associated with WS may ac- count for, or contribute to, poor visuoconstructive per- formance. To test this possible confound, Atkinson and colleagues (2003) have investigated the relation of visual sensory deficits to visuospatial and visuoconstructive per- formance. Approximately 50% of the children and ado- lescents sampled for study exhibited some form of visual sensory deficit. The children and adolescents were admin- istered a battery of tests sensitive to visuospatial and visuoconstructive abilities. The results demonstrated a neg- ligible relation between the occurrence of visual sensory deficits and severity of spatial deficits. Accordingly, the vi- suospatial and visuoconstructive deficits associated with WS do not appear to relate to visual sensory impairments.

As discussed previously, individuals with WS demon- strate a local rather than global bias in face processing. A similar processing bias is proposed to account for, at least in part, the visuoconstructive deficits associated with WS. However, Farran and Jarrold (2003), based on a review of research of visual-perceptual and visuoconstructive per- formance of individuals with WS, conclude that individ- uals with WS are capable of global processing depending on the nature of the task introduced. Specifically, individ- uals with WS show a global processing style on tasks of visual perception, but rely on a local processing approach

with tasks requiring visuoconstruction. That is, they rely on local processing when task performance involves the manipulation and construction of spatial elements. If the elements of the task are spatially invariant, and mental- motor manipulation is not required, they are able to use a global processing approach. Unfortunately, this interpre- tation does not account for the local preference of indi- viduals with WS in facial processing.

Dorsal versus Ventral Processing—Because of the significant deficits in visuospatial relative to facial processing, neu- roscientists and neuropsychologists have sought to de- termine whether the disparity represents a dissociation between the ventral and dorsal streams of visual process- ing. The ventral stream (“what” processing; see Chapter 8) conveys visual object and face recognition to the tempo- ral lobes, whereas the dorsal stream (“where” processing) carries information to the parietal lobes necessary for the processing of spatial relations. Using tasks sensitive to ventral and dorsal processing, investigations (Atkinson et al., 1997, 2003) have shown that WS is generally as- sociated with deficits in dorsal relative to ventral pro- cessing, although a number children and adolescents with WS show equally poor performance on both types of tasks. Thus, there appears to be a subgroup of individ- uals with WS who demonstrate deficits in processing tasks supported by the dorsal stream, and another group who show deficits consistent with dorsal and ventral stream disruption.

Recently, a National Institute of Mental Health (NIMH)–sponsored study (Meyer-Lindenberg et al., 2004) investigated the dorsal and ventral stream activa- tion of individuals with WS of normal intelligence. WS and control participants underwent neuroimaging (fMRI and MRI) while performing visual tasks requiring dorsal or ventral stream activation. The performance of the WS group with dorsal stream items showed isolated hypoacti- vation in the parietal portion of the dorsal stream. Control and WS participants did not differ in activation when processing ventral stream items. Furthermore, structural MRI revealed a reduction in gray matter volume in an area immediately adjacent to the parieto-occipital intra- parietal sulcus for only the WS group (Figure 10.6). Analysis determined that the hypoactivation of the dorsal stream could be attributed to impaired input from this isolated region. Clearly, the findings of the neuroimaging study are consistent with the deficits of individuals with WS on measures of visuospatial processing.

Musicality and Williams Syndrome—WS is associated with en- hanced interest, involvement, and proficiency in music.

CHAPTER 10 | Developmental Disorders of Childhood 289

Those with WS are as proficient at reproducing music, show comparable levels of achievement in music, and spon- taneously produce rhythmic sequences as often as typically developing individuals of the same age. Furthermore, indi- viduals with WS are more musical than Down’s syndrome and autistic individuals. Specifically, individuals with WS spend more time listening to music, show more interest in music-related activities, are more accurate in their repro- ductions of music, and play original music and rhythms more frequently those with other neurodevelopmental disorders (such as Down’s syndrome and autism). Fur- thermore, individuals with WS demonstrate a greater emotional response to music than other groups. For ex- ample, one child with WS began to weep with she heard a couple of notes played at a Mozart concert. The girl’s re- action was so strong that she had to leave the concert. When she tried to return, she once again began to weep. She later noted, “There are two kinds of Mozart: the kind that hurts and the kind that does not hurt” (Levitin et al., 2004, p. 238).

Sociability and Emotionality—Children and adolescents with WS are characterized as highly sociable, interpersonally sensitive, and empathetic. They tend to be overly happy and friendly, yet are also prone to irritability (which ap- pears to abate with age) and moodiness. They are known to approach and speak indiscriminately with others and

to be excitable, restless, and inattentive. In addition, they experience high levels of anxiety, worry, fearfulness, and somatic complaints. They are significantly more anxious than children with other neurodevelopmental disorders (for example, Down’s syndrome) (Morris & Mervis, 1999), mental retardation of mixed etiology, and healthy developing children (Dykens, 2003). Although they are proficient at understanding the feel- ings of others, they find it difficult to recognize their own fears (Lai, 1998). Interestingly, in contrast with healthy children, they do not show an age-related reduc- tion in their fears.

Despite their social interest and affability, children and adolescents with WS are not fully accepted by peers because of their indiscriminate approach to others, im- maturity, and communication differences. The basis of their overfriendliness and sociability is unclear, but it is believed that their extreme focus on the faces of others may play a role in shaping these characteristics (Mervis et al., 2003). In a recent study (Meyer-Lindenberg et al., 2005), the amygdala activation of individuals with WS and healthy control participants was investigated. The participants underwent fMRI while processing faces portraying threatening feelings (anger and fear) and threatening scenes (for example, burning building). The amygdala is implicated in the support of a number of emotion-related functions, including the monitoring of environmental events for danger. For healthy control participants, the amygdala showed greater activation when processing threatening faces than threatening scenes. The participants with WS showed the opposite pattern of greater activation for threatening scenes rela- tive to faces. The investigators hypothesize that the un- deractivation of the amygdala to threatening faces may account for the diminished fear of strangers and social disinhibition demonstrated by individuals with WS. That is, the decreased activation may indicate an atten- uation of normal social fear or apprehension. In con- trast, the greater activation of the amygdala to threaten- ing scenes may underpin their high rates of nonsocial anxiety, worry, and fears.

Treatment—The first few months of the infant’s life can be quite trying for the parents and the infant. Infants with WS often feed poorly, vomit frequently, experience reflux, and fail to thrive. Hypercalcemia contributes to these gas- trointestinal disturbances, requiring medical attention and dietary restrictions. When a child is identified with WS, a comprehensive examination should be undertaken due to the increased probability of medical complications, particularly cardiovascular disease.

290 PART THREE | Disorders of the Brain

Figure 10.6 A three-dimensional magnetic resonance image rendering of the white matter of individuals with Williams syn- drome. A small anomaly (A) of the occipitoparietal region that may disrupt the “downstream” activation of the “where” dorsal stream. The regional activation of the dorsal stream is evident in visuospatial processing of location (B) and construction (C). D represents regional overlap. (Karen Berman, M.D./NIMH.)

C D

Motor delays, muscle weakness, and hip contractures become increasingly evident as the child moves into his or her toddler/preschool years. Orthopedic and physical/oc- cupational services are often needed to address these prob- lems. Although verbal skills are an area of relative strength for children with WS, the precursors to formal language, and the emergence of formal language itself, are delayed or disturbed, warranting speech and language interventions.

The hyperacusis associated with WS may be a signifi- cant problem for the child. Accordingly, environmental modifications to reduce or alleviate the occurrence of loud and disturbing noises are needed. For example, the child might be removed from the classroom in advance of a fire drill and placed in a room where the sound of the fire alarm is muffled or be allowed to use ear plugs or ear phones. Interestingly, as discussed earlier, individuals with WS often enjoy and show relative proficiency in the area of music (Hopyan, Dennis, Weksberg, & Cytrynbaum, 2001).

During the preschool and elementary school years, the child often warrants special or remedial educational ser- vices because of general cognitive delays. These children frequently demonstrate greater success in reading and spelling relative to math and handwriting. The academic interventions used for children with nonverbal learning disability syndrome (see Treatment of Nonverbal Learning Disability Syndrome in Chapter 11) are generally recom- mended for children or adolescents with WS (Hagerman, 1999). Behavioral modification techniques and psychos- timulant medication may be warranted to address poor attentional focus, distractibility, and impulsivity. Social skills training is important to facilitate social acceptance by peers because of their overfriendliness and indiscrimi- nate approaching of others. The child or adolescent may need to learn verbal self-protective skills to cope with teas- ing or abuse by peers.

As discussed earlier, individuals with WS often experi- ence disruptive anxiety, depression, and other psychiatric issues. They can profit from psychotherapy due, in part, to their verbal strengths. Often, medications addressing anxiety or depression are needed to augment treatment; however, careful monitoring by medical professionals is imperative for those individuals with cardiovascular dis- ease or other significant medical issues.

A C Q U I R E D D I S O R D E R S

The number of agents, events, and processes that can po- tentially injure the prenatal and postnatal brain is stagger- ing. Environmental toxins, radiation, infections, anoxia, malnutrition, tumors, and traumatic head injuries can

result in anomalies of the developing brain. Of these agents, traumatic head injuries, such as concussions, lac- erations, and contusions, are the cause of most brain damage in children and adolescents. Regardless of the nature of the insult, a one-to-one relation between brain disturbance and behavior is not evident. The prediction of functional outcomes is contingent on a host of factors including: (1) age at which the lesion is incurred; (2) type, severity, and status (static or progressive) of the lesion; (3) premorbid personality and intelligence of the child; (4) quality and timeliness of medical attention; and (5) acces- sibility of acute and long-term services.

FAS is a specific condition that reflects the devastating effects of prenatal exposure to alcohol. Initially, it was sus- pected that impairments associated with FAS were re- stricted to mothers who chronically abused alcohol or were “binge” drinkers. Increasingly, it is being realized that the prenatal embryo/fetus is at risk even with social drinking.

F e t a l A l c o h o l S y n d r o m e

Clinical Features—Fetal alcohol syndrome (FAS) is a long- lasting and debilitating disorder recognized in the medical and neuropsychological fields since the early 1970s. Lemoine, Harrowsseau, Borteryu, and Menuet (1968) are credited with being the first to describe the effects of alco- hol on a group of children with alcoholic parents. Jones, Smith, Ulleland, and Streissguth (1973) later identified the anomalies and characteristics that have come to define FAS.

Children with FAS frequently exhibit intrauterine growth retardation; characteristic facial features of widely spaced eyes, shortened length of eyelids, elongated midface, flattened nose, underdeveloped upper lip (Figure 10.7), and deficits associated with central nervous system involve- ment (Streissguth, 1997). Central nervous system deficits include microcephaly (abnormally small head), infantile irritability, seizures, tremors, poor coordination, poor ha- bituation (difficulty in tuning out repeating stimuli), and reduced muscle tone. In addition, below-average intelli- gence, inattention, hyperactivity, learning disabilities, and poor behavioral regulation commonly characterize chil- dren with FAS (Mattson, Riley, Gramling, Delis, & Jones, 1998; Kerns, Don, Mateer, & Streissguth, 1997). Although FAS is one of the most well-known causes of mental re- tardation, not all children affected with it are retarded. Table 10.6 presents frequently identified physical and medical characteristics associated with FAS.

Children who are exposed to alcohol in utero, but who fail to exhibit growth deficits or other physical abnormali- ties of FAS, may still show functional impairments similar

CHAPTER 10 | Developmental Disorders of Childhood 291

to those of FAS. That is, the exposed children may mani- fest sensory and sensorimotor impairments, speech and language delays, cognitive and learning weaknesses, and regulatory deficits such as inattention, impulsivity, and hyperactivity (Jacobson, Jacobson, Sokol, Martier, & Ager, 1993). These features are called fetal alcohol ef- fects (FAE) or alcohol-related neurodevelopmental dis- abilities (ARND).

Incidence—Estimates of the incidence rate of FAS in the gen- eral population range from 1 to 3 per 1000 live births. Re- searchers consider the incidence significantly higher, possi- bly two to three times greater, if children with FAE are included (Streissguth & Connor, 2001). The incidences of FAS and FAE among alcoholic mothers (chronic users) are markedly greater, with estimates of 25 per 1000 and 90 per 1000, respectively (Jenkins & Culbertson, 1996).

Neuropathogenesis—FAS is a consequence of alcohol use by the pregnant mother during the baby’s prenatal develop- ment. The relation of the teratogenic effects of prenatal alcohol exposure to intake (amount, frequency, and drinking patterns), period of brain development, and ma- ternal health/lifestyle variables during pregnancy remains poorly understood.

The teratogenic effects of alcohol, as revealed in ani- mal and human studies, suggest a continuum of negative effects determined, in part, by a dose–response relation, that is, increasing amount and frequency of alcohol inges- tion correlates with greater injurious effects (Korkman,

292 PART THREE | Disorders of the Brain

Figure 10.7 The facial features of the developing FAS child (a–c): Unique features are the widely spaced eyes, shortened length of eyelids, low nasal bridge, short and flattened nose, elongated midface, and thin upper lip. ([a, b] Reproduced from Hanson, J. W., Jones, K. L., & Smith, D. W. [1976]. Fetal alcohol syndrome: Experience with 41 patients. Journal of the American Medical Association, 235[14], 1459, by permission of the American Medical Associa- tion; [c] reproduced from Streissguth, A. [1997]. Fetal alcohol syndrome [p. 53]. Baltimore: Paul Brookes, by permission.)

Kettunen, & Autti-Rämö, 2003). The children of moth- ers who consumed relatively low levels of alcohol are less likely to exhibit either physical or structural stigmata, but they may still experience behavioral disturbances, social maladjustment, and cognitive deficits (Mattson et al., 1998). At the most severe end of the continuum, charac- terized by excessive alcohol abuse, there is a significantly greater risk for the development of the full-blown FAS.

Although the risk to the developing embryo/fetus is much greater for pregnant mothers who chronically abuse alcohol or frequently “binge” (multiple drinks consumed in a relatively short period), the point in brain gestation that alcohol is introduced appears to have a differentially damaging impact. Alcohol exposure appears to cause greater damage to the developing brain during the early months of gestation (first trimester). However, the great- est disruption occurs when the exposure spans the entire pregnancy (Carmichael Olson et al., 1997). There are in- dications that the introduction of alcohol during the stage of brain neurogenesis (weeks 6–18th week) may disturb cortical cell migration, resulting in global cognitive deficits, whereas later prenatal exposure produces cogni- tive deficits that are more circumscribed in nature. Fra- ternal twin studies suggest that genetic factors may play a role in determining the vulnerability of the embryo/fetus to FAS. That is, maternal alcohol use can significantly affect one twin more than the other twin, despite their sharing the same prenatal environment. Other factors, such as the mother’s health, psychiatric status, and lifestyle (for example, cigarette smoking and abuse of

CHAPTER 10 | Developmental Disorders of Childhood 293

other substances) and how efficiently she metabolizes al- cohol appear related to the risk for development of FAS/FEA (Streissguth & Connor, 2001).

An often neglected but important factor mediating the phenotypic expression of FAS/FEA is the postnatal social environment (particularly the home) of the child. The FAS/FEA child is often raised by a mother who is coping with the stresses of alcoholism and the demands of parent- ing a child. Children of alcoholics are subject to high levels of neglect, abuse, inconsistent parenting, and out-of-home placements. The extent to which adverse environmental events shape and exacerbate the cognitive-emotional-

behavioral disturbances of the child with FAS/FEA remains poorly understood (Streissguth & Connor, 2001).

Originally, researchers thought more severe neuropsy- chological deficits were specific to FAS. However, increas- ing evidence indicates that children, adolescents, and adults with FAE can display comparable functional deficits (Connor, Sampson, Bookstein, Barr, & Streissguth, 2000; Korkman et al., 2003). In one study (Mattson et al., 1998), for example, children with FAS and FAE underwent a com- prehensive neuropsychological evaluation. The assessment results showed that both groups, relative to healthy control children, demonstrated impairment in language skills, ver- bal learning and memory, academic performance, fine- motor speed, and visuomotor integration skills. Of signifi- cance was the finding that children with FAE showed a pattern of deficits comparable with those of FAS children, except in the areas of visuomotor integration and nonver- bal concept formation. In a more recent study of adults with FAS and FEA (Connor et al., 2000), both the FAS and FEA groups were found to be significantly impaired on a number of measures of executive function. Thus, indi- viduals with a history of prenatal alcohol exposure are likely to demonstrate significant neuropsychological deficits, even though they appear physically normal.

Investigators have identified a number of neu- roanatomic alterations in the brains of FAS/FEA children that reflect the destructive impact of alcohol on the devel- oping brain. Specifically, children with the disorder pres- ent with dysgenesis or agenesis of the corpus callosum, hippocampal damage, reduced basal ganglia volume, cere- bellar anomalies, expanded ventricles, and reduction in white matter (Archibald, Mateer, & Kerns, 2001; Kaemingk & Paquette, 1999; Streissguth & Connor, 2001). The high proportion of FAS children with microcephaly indicates that brain size is reduced. Wass and colleagues (2001) stud- ied living fetuses exposed to alcohol with ultrasound sonography and identified a reduction in size of the frontal cortex. Executive dysfunctions (Kaemingk & Paquette, 1999) consistent with disturbances of the frontal circuitry have been identified. Similarly, studies of animals exposed to prenatal alcohol report a wide range of brain anomalies, including reduction in brain weight and volume, and structural disturbances or loss of neurons, dendritic spines, and subcortical and cortical white matter circuitry (Chen, Maier, Parnell, & West, 2004).

Neuropsychological Assessment—Children with FAS/FEA ex- hibit a broad spectrum of neuropsychological deficits. In addition to mental retardation, common FAS/FEA deficits are evident in attentional regulation, response in- hibition, complex problem solving, spatial and object

Growth

Decreased fat tissue

Prenatal and postnatal growth deficiency

Cardiac

Atrial septal defect (defect in the wall between the atria)

Ventricular septal defect (defect of wall between the ventricles)

Craniofacial

Abnormally small jaw in adoles- cence

Microcephaly (abnormally small head)

Ptosis (droopy eyelid)

Short upturned nose

Shortened eyelid length

Underdeveloped lip features

Underdeveloped upper jaw

Skeletal

Altered palm crease patterns

Cervical spine abnormalities

Foot position defects

Joint alterations

Skeletal (continued)

Pectus excavatum (abnormally depressed sternum)

Tapering terminal fingers, deformi- ties of finger/toenails

Union of the radius and ulnar bones

Other

Abnormal thoracic cage

Abnormally small eyes

Anomaly of the sex organs

Cleft lip and/or cleft palate

Dental malocclusion

Epicanthal folds

Excessive hair in infancy

Hearing loss, protuberant ears

Hernias of diaphragm, umbilicus, or groin

Myopia, strabismus (cross-eyes)

Renal deformity

Small teeth with faulty enamel

Strawberry hemangiomata (blood- filled birthmarks or benign tumors of small blood vessels)

Source: Harris, J. C. (1995). Developmental neuropsychiatry, vol. II: Assessment, diagnosis, and treatment of developmental disorders (p. 362, Table 12.1-1). New York: Oxford University Press, by permission.)

Table 10.6 Physical and Medical Conditions Associated with Fetal Alcohol Syndrome

memory, language skills, verbal learning and memory, speed of information processing, consistency of task per- formance, cognitive flexibility, planning, and academic performance (Korkman, Kirk, & Kemp, 1998; Mattson, Riley, Delis, Stern, & Jones, 1996; Streissguth, Barr, Bookstein, Sampson, & Carmichael Olson, 1999). Fur- thermore, the array of deficits that accompany FAS/FEA often exceeds what would be predicted based on level of intelligence, suggesting that limited cognitive ability is not the sole basis for these impairments (Kerns et al., 1997). Thus, multiple cognitive domains of functioning are vulnerable to in utero alcohol exposure including in- tellect, language, learning and memory, and executive functions (Lee, Mattson, & Riley, 2004).

Interestingly, the ratings of parents and teachers sug- gest that the primary behavioral difficulties of children with FAS/FEA relate to attention deficits and social prob- lems (Streissguth & Connor, 2001). Empirical support for the observations of parents and teachers regarding the poor attentional regulation associated with FAS/FEA is growing (Lee, Mattson, & Riley, 2004; Mattson, Lang, & Calarco, 2002). Moreover, there are indications that poor attention may be a more sensitive marker of prenatal al- cohol exposure than either low global intelligence or fa- cial stigmata (Mattson & Riley, 2000).

The myriad of behavioral, adaptive, and neuropsycho- logical characteristics of the child with FAS/FEA signals the need for a multidisciplinary approach to assessment. Clearly, a comprehensive neuropsychological evaluation is needed to identify and interpret the cognitive, behavioral, and adaptive dysfunctions that characterize the child. Be- cause of the increased risk for cardiac, skeletal, and other physical conditions (see Table 10.6), a medical consulta- tion is certainly warranted. Finally, contingent on the child’s presenting issues, the evaluative services of a speech and lan- guage pathologist, educational specialist, social worker, and occupational/physical therapist may be warranted.

Developmental Course—Longitudinal studies (Streissguth, 1997) have revealed that the cognitive, behavioral, and adaptive deficits of FAS/FEA children do not fully resolve with age. Thus, the negative effects of intrauterine expo- sure to alcohol generally endure. Infants with FAS/FEA often present with low birth weight, feeding and sleep dis- turbances, poor habituation, and high levels of irritability (Jenkins & Culbertson, 1996). By 4 years of age, deficits appear in gross- and fine-motor skills, attention, memory, academic achievement, and reaction time. In addition, enuresis (age-inappropriate bedwetting) and communi- cation disorders are quite frequent. By elementary school age, attention-deficit/hyperactivity disorder (ADHD)

symptoms of inattention, impulsivity, and hyperactivity, coupled with poor organization, communication deficits, behavioral problems, and disturbances of basic functions (sleeping, eating, and elimination) disrupt the adaptive ef- forts of FAS children (Steinhausen, Willms, & Spohr, 1993). Cognitive deficits, microcephaly, small physical stature, and poor socialization skills often interfere with peer acceptance. Children affected by FAS/FEA with significant intellectual and learning deficits are often identified in their preschool or elementary years and provided with early special educa- tion services.

With the advent of adolescence, communication dis- orders and disturbances of basic functions decline, al- though other cognitive and behavioral deficits persist. Re- ports that teenagers with FAS/FEA tend to manifest high rates of antisocial behaviors and substance abuse are of considerable concern. Unfortunately, the multiple cogni- tive, behavioral, and adaptive deficits of FAS/FEA appear to continue into adulthood.

Treatment—It goes without saying that the best form of treatment for an acquired disorder is prevention. Avoid- ing or significantly reducing alcohol consumption during pregnancy eliminates or reduces the risk for FAS/FEA to the unborn child. Although public awareness discourages many mothers from drinking during pregnancy, the alco- holic mother is of special concern. The physician, or other personnel who encounter a pregnant women who abuses alcohol, should immediately apprise her of the risk to the fetus. In addition, the mother should be informed that emerging research indicates that children of mothers who appreciably reduce or cease drinking during the first or second trimester are at a reduced risk for development of FEA/FAS (Korkman et al., 2003). A referral to persons or agencies that can assist the mother in altering her drink- ing behavior is a priority. Furthermore, the finding that FAS/FEA children often experience high levels of neglect, abuse, inconsistent parenting, and out-of-home place- ments should prompt an assessment of the family’s need for therapeutic, social, and economic assistance.

Children with FAS/FEA who are mentally retarded generally require specialized educational services either within the public schools or in a residential setting, de- pending on the severity of retardation and particular learn- ing needs of the child. Higher functioning children af- fected by FAS/FEA, despite average or above-average intelligence, may also need supplemental or specialized ed- ucational services due to specific cognitive and achieve- ment weaknesses (Kerns et al., 1997). Furthermore, chil- dren with FAS/FEA with communication deficits should have appropriate speech and language therapy. Behavioral

294 PART THREE | Disorders of the Brain

Phenylketonuria (PKU)

Teratogens Agenesis Dysgenesis Polymicrogyria Porencephaly Kennard principle Anencephaly Hydranencephaly Hydrocephalus (HC) Spina bifida Intraventricular hemorrhage

(IVH)

Obstructive or noncommunicating hydrocephalus

Nonobstructive or communicating hydrocephalus

Shunt “Cocktail party syndrome” (CPS) Ultrasonography Single-gene disorders Chromosomal disorders Parental imprinting disorders Molecular cytogenic anomalies Autosomes

Sex chromosomes Cubitus valgus Turner’s syndrome (TS) Karyotype Vestigial ovarian streaks Isochromosome Mosaic karyotypes Inhibitory control Gonadotropins Williams syndrome (WS) Supravalvar aortic stenosis

(SVAS) Hypercalcemia Hyperacusis

Hypotonia Hypertonia Joint contractures Elastin Fluorescent in situ hybridization

(FISH) Down’s syndrome Fetal alcohol syndrome (FAS) Microcephaly Fetal alcohol effects (FAE) or

alcohol-related neurodevelopmental disabilities (ARND)

Enuresis

management systems are often needed within the home and school, particularly if the child also displays symp- toms of ADHD. Medications can be introduced to help regulate the child’s ADHD, particularly if the symptoms of inattention, impulsivity, and hyperactivity significantly

disrupt the child’s learning, family, and peer relationships. Social skills training may help improve peer acceptance. The aforementioned interventions must be continued into adolescence and modified in accordance with the changing learning and behavioral needs of the teenager.

CHAPTER 10 | Developmental Disorders of Childhood 295

Summary The developing brain is vulnerable to a myriad of insults that can lead to damage and dysfunction. Yet, a degree of plasticity allows limited compensation, or return of function, after cerebral insults. However, the dynamics of this recovery process remain poorly understood. The clinical presentation, neuropathogenesis, neuropsychological assessment, and treatment of HC, TS, WS, and FAS illustrate the complex brain– behavior relations that define each of these neurodevelopmental disorders.

C r i t i c a l T h i n k i n g Q u e s t i o n s

In light of the devastating effects of many of the genetic and chromosomal disorders, do you think that potential parents should seek genetic counseling before having children? Explain. In recent years, an increasing number of teratogens have been identified in the environment. Are our children at greater risk for brain anomalies than children of earlier generations? Why or why not? What steps can be taken to prevent FAS? What do the neuropsychological profiles associated with TS and WS tell us about the organization of the brain?

K e y Te r m s

We b C o n n e c t i o n s

http://www.patientcenters.com/hydrocephalus Hydrocephalus Center—provides information about hydrocephalus and its treatment.

http://gslc.genetics.utah.edu/units/disorders/karyotype Genetic Science Center at the University of Utah—presents karyotypes for a number of genetic disorders including TS and WS.

http://www.patientcenters.com

http://gslc.genetics.utah.edu

http://www.turner-syndrome-us.org Turner’s Syndrome Society of the United States—facts and information on TS.

http://www.williams-syndrome.org Williams Syndrome Association—provides information on the identification and treatment of individuals with WS.

http://www.nofas.org National Organization of Fetal Alcohol Syndrome—page dedicated to raising the public awareness of FAS; includes definition and strategies for working with children with FAS.

296 PART THREE | Disorders of the Brain

http://www.turner-syndrome-us.org

http://www.williams-syndrome.org

http://www.nofas.org

Chapter 11

L E A R N I N G A N D N E U RO P S Y C H I AT R I C D I S O R D E R S O F C H I L D H O O D

Youth, even in its sorrow, always has a brilliancy of its own. —Victor Hugo, Les Miserables (1862)

Learning Disabilities Pervasive Developmental Disorders Disruptive Behavioral Disorders Tic Disorders

Neuropsychology in Action

11.1 Genetics of Learning Disabilities 11.2 Case Study of an Adolescent with Asperger’s

Syndrome 11.3 Case Study of a Child with an

Attention-Deficit/Hyperactivity Disorder

Overview This chapter discusses learning, pervasive developmental, disruptive behavioral, and tic disorders of child- hood. These four classes of disorders can significantly disrupt a child’s developmental progression and adaption and often coexist with other conditions that further compromise the child’s functioning. Although the pervasive developmental disorders occur less frequently, the impact of these conditions is profound, generally precluding self-sufficiency and independence and necessitating lifelong supervision.

The developmental disorders reviewed in Chapter 10 are often considered biological rather than psy- chological in origin because prominent anatomic brain defects and physical anomalies often accompany the disorders. Moreover, the cause of these disorders is generally traceable to genetic/chromosomal de- fects or prenatal disruption. In contrast, the causes of childhood learning and neuropsychiatric disorders are not as easily linked to congenital anomalies. Accordingly, theorists have often proposed psychological factors as determinants of these disorders. However, ongoing research and advances in neuroimaging are providing evidence that brain disturbances may, in fact, play a prominent role in the etiology of both learning and neuropsychiatric disorders.

This chapter examines, in detail, specific disorders that represent learning, pervasive developmental, disruptive behavioral, and tic disorders. The first disorder, dyslexia, has received considerable attention because of the importance of reading skills in our technologically advanced society. The second disorder, nonverbal learning disability syndrome (NVLD), reflects a major contribution of neuropsychology to the study of learning disabilities. Byron Rourke (1989), through his extensive research, has identified a specific pat- tern of neurocognitive assets and deficits that differentiates the NVLD from reading disabilities. The third disorder, autism, is a pervasive developmental disorder that has attracted a voluminous body of research. Despite this research, the cause and brain–behavior relations of autism remain poorly understood. We then review attention-deficit/hyperactivity disorder (ADHD), one of the most prevalent childhood disruptive behav- ioral disorders, comprising about 50% of the population of child psychiatric clinics (Cantwell, 1996). Similar to autism, ADHD is the focus of considerable research that transverses diverse fields of study. Neuropsy- chology and related fields have identified a number of brain–behavior relations of ADHD that are enhancing our understanding of the pathogenesis of this disorder. Finally, we examine Gilles de la Tourette disorder, a childhood tic disorder, that waxes and wanes in severity and presentation over time.

7% and 15% of the school population (Gaddes & Edgell, 1993) and are one of the largest childhood groups referred for neuropsychological services (Culbertson & Edmonds, 1996). Controversy persists regarding the definition, diag- nosis, etiology, and remediation of learning disabilities.

298 PART THREE | Disorders of the Brain

K e e p i n M i n d

What are the specific neurocognitive assets and deficits of children with verbal and nonverbal learning disabilities?

Can a nonverbal learning disability directly disrupt a child’s socioemotional adjustment?

Is Asperger’s syndrome a separate disorder, or merely high-functioning autism?

What treatment interventions are effective for children with attention-deficit/hyperactivity disorder (ADHD)?

Why is there such a high rate of comorbidity among ADHD, Gilles de la Tourette’s syndrome, and obsessive-compulsive disorder?

Learning Disabilities

Learning disabilities adversely affect the ability of the child to communicate and meet the challenges of educa- tion. Children with learning disabilities constitute between

Generally, professionals define learning disabilities as impairments of one or more academic skills that cannot be accounted for by sensory or motor deficits; mental retarda- tion; emotional disturbance; or environmental, cultural, or economic disadvantage (Hooper, Willis, & Stone, 1996). Common learning disabilities involve impairment of reading (dyslexia), arithmetic (dyscalculia), and written expression (dysgraphia).

Verbal learning disabilities, such as dyslexia, have re- ceived significantly more research and theoretical attention than the NVLD, which focuses on deficits in mathematics. We discuss dyslexia to help clarify, by contrast, the NVLD. An expanded coverage of the NVLD follows. This empha- sis acknowledges the greater disruptiveness of the NVLD to the child and the availability of a specific neuropsycho- logical model to guide identification and treatment of the disorder (James & Selz, 1997).

V E R B A L L E A R N I N G D I S A B I L I T Y : D Y S L E X I A

Dyslexia may be acquired by insult to a previously nor- mal functioning brain or be developmental in origin. With acquired dyslexia (often referred to as alexia), the patient, before brain insult, possessed reading skills. How- ever, after the insult, this ability is partially or fully lost.

In contrast, developmental dyslexia characterizes a lim- itation in the ability to acquire reading skills. Historically, the diagnosis of dyslexia has involved evidence of a signif- icant discrepancy between the child’s current reading achievement and grade level or intelligence. The discrep- ancy models that contrast reading to grade level or intelli- gence are currently under challenge, and alternative crite- ria for classification are being proposed (Siegel, 2003; Van den Broeck, 2002).

Dyslexia is a prevalent disorder, as evident in the finding that approximately 4% to 9% of school-age children are af- fected, with boys outnumbering girls 3 to 2 (Culbertson & Edmonds, 1996; Pliszka, 2003; Rumsey, 1996a). Similar to other developmental disorders, dyslexia tends to run in families, suggesting a genetic etiology. As Bruce Penning- ton reports in his discussion of the genetics of learning disabilities (Neuropsychology in Action 11.1), a child with parents affected with dyslexia is eight times more likely to exhibit the disorder than children of parents who are not reading disabled.

V i s u a l P r o c e s s i n g M o d e l o f D y s l e x i a

Despite a long history of research and investigation, the study of dyslexia continues to be fraught with divergent diagnostic criteria, putative classifications, and a myriad

of theoretical explanations. However, a review of the re- search and theoretical models demonstrates increasing convergence on two basic subtypes. The first subtype en- compasses children with significant reading deficits caused by possible visual and visual-perceptual anomalies, whereas the second relates to children whose reading im- pairment stems from auditory-language dysfunction. Re- flecting this division are two forms of dyslexia: “surface” and “deep.” Surface dyslexia refers to impaired whole- word reading and an unimpaired ability to sound out words, whereas deep dyslexia involves intact whole-word reading and impaired ability to sound out words. The for- mer suggests an impairment of orthographic skills, and the latter, an impairment of phonologic skills.

In studies of the visual domain, researchers have exam- ined eye movements and speed of visual processing (Eden, Stein, Wood, & Wood, 1995; Stein, 2001). Specifically, reading-disabled children and adults show slower flicker fusion rates when presented images of low spatial density and contrast (brightness). Flicker fusion rate is the speed at which two separate visual images fuse into a single image when rapidly presented. The magnocellular visual system controls the processing of this form of visual input, prompting the magnocellular-deficit theory of dyslexia.

The magnocellular-deficit theory centers on the two visual pathways of the human visual system, namely, the magnocellular and parvocellular pathways. Each of these pathways processes information from the retina and, in turn, transfers the information to the visual cortex for fur- ther processing (Figure 11.1). The magnocellular visual system consists of large cells that are located in the infe- rior region of the lateral geniculate bodies and are highly sensitive to movement, rapid stimulus change, low con- trast, and spatial location. The parvocellular visual sys- tem involves smaller cells that are located dorsally in the lateral geniculate bodies and are responsive to stationary objects, color, high contrast, and fine spatial details (Birch & Chase, 2004; Skottun & Parke, 1999). The former sys- tem is activated during rapid saccadic eye movements, whereas the latter system is stimulated during eye fixation and is involved extensively in discriminating and identify- ing printed/written symbols. In reading, the individual makes a series of brief fixations, separated by saccadic eye movements. Neuroscientists hypothesize that the magno- cellular visual system inhibits the parvocellular system at the time of each saccade, ensuring that the previous eye fixation image is terminated. In dyslexia, the magnocellu- lar visual system may fail to appropriately inhibit the par- vocellular system, resulting in a prolonged afterimage that interferes with reading; that is, letters seen in one fixation blur into the next fixation.

CHAPTER 11 | Learning and Neuropsychiatric Disorders of Childhood 299

300 PART THREE | Disorders of the Brain

When I finished graduate school in clinical psychology in 1977, considerable controversy existed about the validity of the construct of learning disabilities. Some claimed the construct was a middle-class myth to excuse the poor performance of some children. Another possibility, offered by the psychoan- alytic paradigm that dominated clinical work at that time, reduced learning problems to largely unconscious motivational problems. One of my supervisors only half-jokingly interpreted problems with addition as repre- senting conflicts over oral issues, problems with subtraction as representing castration anxiety, and so on. Partly because I had minored in cognitive development in gradu- ate school, I was quite curious about whether learning disabilities existed, and if they did, how to understand and treat them.

Serendipity played a major role in focus- ing my curiosity. My first job after graduate school was to help with a longitudinal study of children with abnormal sex chromosome numbers (the 45X, 47XXX, 47XXY, and 47XYY karyotypes) initiated by Dr. Arthur Robinson, a pediatric geneticist. These children had been observed since birth, and they were now of school age. It soon became clear that these children had higher rates of learning disabilities than either their siblings or children with abnormal numbers of sex chromosomes in only some of their cell lines (mosaics). Most interestingly, the type of learning disability a child exhibited was largely karyotype specific. These children provided strong evidence that some learning disabilities were influenced by genetic factors, and that different genetic factors affected different aspects of cognitive development and academic skill.

Suddenly, a whole new vista opened on the question of how valid the construct of learning disabilities was. The fact of differen- tial genetic cause for at least some learning disabilities convinced me of their validity, and also gripped me with an intense curiosity to

understand in detail how the genetic alter- ation lead to the alteration in cognitive development. It was clear to me that one of the missing links in this causal chain was the brain, and so I set out to learn all that I could about neuropsychology, as well as genetics. My new question was, How do the genetic alterations change brain development to cause specific changes in cognitive develop- ment? I also wondered whether genetic influences on learning disabilities were rare and limited to infrequent syndromes, such as abnormalities in sex chromosome number, or if they played a substantial role in learning disabilities that currently had no known cause.

An opportunity to answer this second question soon presented itself. Herbert Labs and Shelley Smith, both medical geneticists, invited me to help with their study of familial dyslexia by helping to define its cognitive phenotype. They had taken quite seriously Hallgren’s (1950) classic study, which had demonstrated a possible dominant gene influence on dyslexia, and were studying genetic linkage in extended families with dyslexia to find such genes. In 1983, we published an article in Science that pre- sented evidence for a gene influencing dyslexia located near the centromere of chromosome 15. That same year, Shelley Smith and I published in Child Development a review of what was then known about genetic influences on learning disabilities and speech and language disorders. Subse- quently, I published a number of articles on the cognitive phenotype in familial dyslexia, finding that it was characterized by dyspho- netic spelling errors and an underlying deficit in phoneme awareness.

It eventually became clear that a large proportion of the children who present clinically with dyslexia have affected rela- tives, and that the recurrence rate among first-degree relatives is quite high, about 35% to 45%. This means that if a parent is dyslexic, the risk for having a dyslexic child is

about eight times greater than the risk in the general population. Thus, genetic influences on learning disabilities are not rare, but instead account for a substantial portion of the etiology of the most common learning disability, dyslexia.

The search for genes that influence dyslexia has continued. Shelley and I soon joined forces with John DeFries and col- leagues at the Institute for Behavioral Genet- ics in Boulder, Colorado, who had indepen- dently conducted important family and twin studies of dyslexia. Together, we eventually identified the approximate location of a second gene that influences dyslexia, this time on the short arm of chromosome 6. Cardon and colleagues reported this discov- ery in Science in 1994. Three years later, a separate team at Yale and Bowman Gray medical schools essentially replicated both our linkage results, those on 15 and 6, in an independent sample of families with dyslexia (Grigorenko et al., 1997). Taken together, these findings are essentially the first repli- cated genetic linkage results for a complex behavioral disorder.

Therefore, some, but not all, of the questions I began with have been answered. Learning disabilities exist in much the same way that other complex medical phenotypes (such as obesity or heart disease) exist. There are genetic influences on them and a substantial portion (about 50% according to twin studies) of the variance in the most common learning disability, dyslexia, is attributable to genes. The approximate locations of two of these genes influencing dyslexia are now known. Other disorders have shown us that understanding genetic mechanisms can illuminate the brain mech- anisms underlying learning disabilities. The challenge for the future (and for future developmental neuropsychologists) is to better understand both genetic and brain mechanisms in dyslexia and other learning disorders.

N e u r o p s y c h o l o g y i n A c t i o n 1 1 . 1

G e n e t i c s o f L e a r n i n g D i s a b i l i t i e s

by Bruce Pennington Ph.D., Department of Psychology, Director of Developmental Cognitive Neuroscience Program, University of Denver, Denver, CO

Initial support for anomalies of the magnocellular sys- tem in dyslexic persons stems from investigations (Galaburda & Livingstone, 1993) of the lateral geniculate bodies of normal-reading and reading-disabled adults. Brain autopsies revealed that the parvocellular cells of the two groups were similar, but the magnocellular cell bod- ies were generally smaller and more variable in size and shape in the dyslexic group. The investigators propose that the structural differences in magnocellular cells are consistent with slower visual processing.

In a more recent study (Demb, Boynton, Best, & Heeger, 1998) of young adults with a history of dyslexia, tasks were presented that required the visual detection of

moving stimuli. Dyslexic and healthy adults underwent functional magnetic resonance imaging (fMRI) while performing the tasks. The fMRI showed less activation in the magnocellular pathway of the individuals with dyslexia relative to control participants. Furthermore, magnocellular-occipital areas of activation correlated sig- nificantly with reading speed, which is supportive of a re- lation between magnocellular deficits and reading perfor- mance. Although dyslexia may be causally related to the disruption of magnocellular-parvocellular visual process- ing, it may also represent a more generalized deficit in rapid temporal processing.

P h o n o l o g i c M o d e l o f D y s l e x i a

Although dyslexia as a consequence of underlying deficits in visual processing has received attention, impairment in phonologic processing as the central feature of the disor- der has received greater support (Swanson, Mink, & Bocian, 1999). The term phonologic processing refers to the application of rules for translating letters and letter se- quences into their corresponding speech–sound equiva- lents. This processing is supported by phonologic aware- ness, the awareness of and ability to differentiate between individual phonemes, or speech sounds (Rumsey, 1996a). Children with dyslexia exhibit deficits in translating letter strings into word sounds, also called word decoding. Deficits in this process cause reading to be slow and nonautomatic, disrupting efforts to identify and compre- hend presented words (Pennington, 1991). The word recognition deficits of the child with dyslexia are most ev- ident when he or she must read novel or unfamiliar words, that is, when the determination of letter–sound associa- tions is most critical. Moreover, children with dyslexia often have problems spelling because they are unable to efficiently translate the phonologic representation of a word to its visual configuration, a process that is the con- verse of reading. Despite these deficits, children with dyslexia frequently demonstrate preserved “listening com- prehension” when someone reads material to them. Fur- thermore, higher order cognitive functions such as gen- eral intelligence and reasoning, vocabulary, and syntax are typically unimpaired (Shaywitz & Shaywitz, 2005).

Early deficits in phonologic processing are predictive of later reading achievement, and interventions to reme- diate phonologic skill weaknesses facilitate the acquisition of reading skills (Shaywitz & Shaywitz, 1999). Individu- als with severe phonologic deficits continue to show read- ing deficits into adolescence and adulthood, suggesting that reading deficits are often a lifelong problem. Interest- ingly, adults who were dyslexic as children, but who show good reading outcomes in adulthood, continue to exhibit

CHAPTER 11 | Learning and Neuropsychiatric Disorders of Childhood 301

Figure 11.1 Magnocellular and parvocellular visual systems. The ventral magnocellular pathways are designated 1–2, and the dorsal parvocellular pathways are indicated by 3–6. (Adapted from Mason, C., & Kandel, E. [1991]. Central visual pathways. In E. Kandel, J. Schwartz, & T. Jessell [Eds.], Principles of neural science [3rd ed., p. 425, Figure 29-6]. New York: Elsevier Science, by permission of the McGraw-Hill Companies.)

phonologic deficits and a slow reading rate. For example, they continue to experience significant decoding deficits when required to read or spell nonwords, such as yite. Re- searchers believe their improvement in reading reflects a compensatory expansion of their sight vocabulary.

Deficits in phonologic processing are often accompa- nied by a second deficit, naming speed. Reduced naming speed is commonly evident in dyslexic populations. Naming speed refers to the rate of retrieval of names for letters, digits, colors, and objects (Catts, Gillispie, Leonard, Kail, & Miller, 2002). Although debate contin- ues as to whether naming speed is independent of phono- logic awareness or a generalized deficit of cognitive pro- cessing, there are indications that naming speed is a precursor to reading fluency. The identification of two pri- mary deficits associated with disabled reading has led to the double-deficit hypothesis. The double-deficit hypoth- esis poses that reading disabilities can result from deficits in either phonologic processing or naming speed. How- ever, children with both deficits are at the greatest risk for reading impairment (Schatschneider, Carlson, Francis, Foorman, & Fletcher, 2002; Waber, Forbes, Wolff, & Weiler, 2004).

In addition to phonologic and naming speed deficits, some children with dyslexia also demonstrate limitations in working memory (a form of short-term memory in which information is both maintained and manipulated). As discussed earlier (see Chapter 9), working memory can be conceptualized as a higher order central executive sys- tem that interacts with and regulates two “slave systems,” the articulatory phonologic loop and the visuospatial sketchpad (Baddeley & Hitch, 1994). The articulatory phonologic loop is a temporary buffer for maintaining and manipulating auditory and verbal information, whereas the visuospatial sketchpad provides the same functions for visual and visuospatial information.

All three working memory components support read- ing performance, but disruption of the central executive system and phonologic loop are more strongly related to reading disabilities. Support for the involvement of the executive system is provided by studies of the memory performance of children with dyslexia. When performing measures of auditory and verbal working memory (sub- served by the phonologic loop), children with dyslexia show significantly poorer performance than unimpaired readers (Kibby, Marks, Morgan, & Long, 2004). They also demonstrate deficits when performing tasks that as- sess temporal order memory (memory for the sequence of events across time). Temporal order memory involves higher order cognitive processes supported by the execu- tive system (Howes, Bigler, Burlingame, & Lawson,

2003). Further support for the involvement of the execu- tive system includes the finding that under conditions of high-processing demands, such as attempting to recall and manipulate complex information, children with dyslexia demonstrate poorer memory for both verbal and visual in- formation than unimpaired readers (Swanson & Sachse- Lee, 2001). That is, the executive system fails to effec- tively allot attentional resources to coordinate the two slave systems when confronted with high-processing de- mands. Despite these findings, it remains unclear whether working memory deficits are central or contributory to the etiology of dyslexia.

N e u r o p a t h o g e n e s i s o f D y s l e x i a

The genetics of dyslexia is an area of significant study. Twin studies demonstrate that reading deficits are highly herita- ble (h2 � 0.81), with a concordance rate of 83% for iden- tical twins (Alarcón, Pennington, Filipek, & DeFries, 2000). Genetic studies have identified a linkage between reading disorders and genes on chromosomes 6 and 15. The heritability rate of phonologic processing is higher than that of sight-reading, suggesting a greater genetic basis for the former (Grigorenko et al., 1997). Although other genes are the focus of study, research investigations have most consistently replicated the link between chro- mosome 6 and reading disabilities (Wood & Grig- orenko, 2001).

The primary emphasis of neuropsychological research concerning dyslexia has focused on the language cortex of the left hemisphere of right-handed individuals. The planum temporale of the left posterior temporal lobe (Figure 11.2) is one of the neural regions specifically im- plicated in phonologic processing (Hynd & Hiemenz, 1997; Morgan & Hynd, 1998). For most people, the planum temporales of the left and right hemispheres are asymmetric, with the left planum temporale being larger than the right (L � R). Neuroimaging shows that indi- viduals with dyslexia often exhibit left-right planum tem- porale symmetry (L � R), or reversed normal asymmetry (R � L). However, the precise relation of atypical sym- metry to dyslexia awaits clarification.

Regional anomalies of the brains of dyslexic individu- als are also associated with differences in brain activation as revealed by cerebral blood flow. For example, a positron emission tomography (PET) study by Rumsey and col- leagues (1992) reported less activation of the left poste- rior temporal and temporoparietal cortices of individuals with dyslexia relative to normal-reading control individu- als when performing a task sensitive to phonologic aware- ness, namely, rhyme detection. A related PET study (Flowers, Wood, & Naylor, 1991) of dyslexic and normally

302 PART THREE | Disorders of the Brain

reading children found that the rate of cerebral blood flow to both the Wernicke’s area (region surrounding the planum temporale) and angular gyrus related to reading performance.

Further evidence for disruption of the temporal and temporoparietal regions is provided by postmortem in- vestigations of the brains of dyslexic individuals. Post- mortem studies revealed neuronal ectopias (small loci of abnormally placed neurons, sometimes referred to as “brain warts”) and cytoarchitectonic dysplasia (focal pathologic changes of cortical architecture) of the left plenum temporale, suggesting abnormal neural develop- ment, most likely between the 5th and 7th month of fetal gestation (Hynd & Hiemenz, 1997). During this period, the gyri are rapidly forming, suggesting that the origin of developmental dyslexia, whether genetically determined or a consequence of an insult, can be traced to a specific period of fetal development. However, not all studies have replicated the finding of atypical planum temporale de- velopment (Filipek, 1996; Rumsey, 1998), suggesting that other neural regions/systems may be involved in the etiol- ogy of dyslexia.

Greater specification of the neural substrates that sup- port phonologic processing is emerging (Horwitz, Rumsey, & Donohue, 1998; Pugh et al., 2000). PET studies of re- gional cerebral blood flow activation demonstrate that re- gions of the left angular gyrus, superior and middle tem- poral gyri (part of Wernicke’s area), inferior frontal cortex (near Broca’s area), and extrastriate and striate cortex (occipital) activate when individuals without dyslexia read irregular words (reading that requires orthographic famil- iarity) and pseudowords (reading that requires the use of phonologic rules). The activation of these regions signifi- cantly correlates, suggesting a functional network support- ive of reading. In contrast, individuals with dyslexia demonstrate reduced activation across the functional network, and the left angular gyrus fails to significantly correlate with the activation patterns of the other reading- related regions. The latter finding prompted the investi- gators to conclude that the left angular gyrus of individu- als with dyslexia is functionally disconnected from the other regions of the network. Insofar as the angular gyrus is involved in the cross-modal transformation of visual (written) information into linguistic representations, the disconnection would limit or distort input to the other regions of the left hemisphere necessary for reading- related processing. Whether the functional disconnect is the result of anomalies in the white matter interconnect- ing pathways that link the left angular gyrus with the other reading-related regions of the left hemisphere, functional anomalies specific to the angular gyrus, or some other un- known set of factors remains to be determined.

In a particularly well-designed study, Shaywitz and col- leagues (1998) endeavored to identify the neural sub- strates that correlated with reading performance. Hierar- chically arranged orthographic and phonologic tasks, progressing from simple to complex, were presented to adolescents and adults with dyslexia and participants without dyslexia while undergoing fMRI. The progres- sion and type of tasks presented were as follows: (1) judg- ment of line orientation (visuospatial processing without orthographic demands); (2) lowercase and uppercase letter discrimination (orthographic processing without phono- logic demands); (3) single-letter rhyming (orthographic to phonologic coding and analysis); (4) nonword rhyming (complex orthographic to phonologic coding and analy- sis); and (5) semantic categorization (orthographic, phonologic, and semantic analysis). As the presented tasks progressed from lowercase and uppercase discrimination through nonword rhyming, unimpaired readers mani- fested increasing and systematic activation of the left pos- terior superior temporal gyrus, angular gyrus (parietal), and extrastriate and striate cortices (occipital), whereas

CHAPTER 11 | Learning and Neuropsychiatric Disorders of Childhood 303

Images not available due to copyright restrictions

individuals with dyslexia did not demonstrate this pro- gressive activation. The dyslexic group showed greater ac- tivation of the right inferior frontal gyrus as phonologic de- mands became more complex. This increased activation of the right anterior regions suggests that individuals with dyslexia rely on alternative or “spared” circuitry to process reading contents. Thus, individuals with dyslexia demon- strated decreased activation of posterior brain regions that encompassed both visual and language areas, and an in- creased activation of anterior brain regions. This activa- tion profile may provide a neural “marker” for identifying individuals with dyslexia.

Shaywitz and associates (2002) extended their study to dyslexic and non–reading-impaired children and adoles- cents. The participants underwent fMRI while perform- ing the previously discussed hierarchically arranged or- thographic and phonologic tasks. The regional activation patterns of the children and adolescents with dyslexia dif- fered from those of the nonimpaired readers. Further- more, the regional activation patterns paralleled those identified in Shaywitz and colleagues’ (1998) earlier study. Based on the findings of these two studies and sub- sequent investigations (Shaywitz et al., 2003; Shaywitz & Shaywitz, 2005), three reading-related systems were posed. Two of these systems involve the left posterior re- gion, and the third involves the left anterior region of the brain. The first system, located in the left dorsal pari- etotemporal area (angular gyrus and posterior portions of the superior temporal gyrus), is believed to support the mapping of visual print to its phonologic representation. This word analysis system operates on individual units of words (for example, phonemes), requires attentional allo- cation, and processes information slowly. The second sys- tem encompasses the left ventral occipitotemporal region (portions of the middle occipital and middle temporal gyrus) and operates on the whole word (visual word recognition). This visual word system requires minimal attentional allocation and serves the automatic and rapid recognition of words. The final system is localized in the left inferior frontal region of the brain (Broca’s area) and is implicated in articulation, silent reading, and naming. Disruptions of the two posterior systems are the primary determinants of dyslexia.

Two other neural regions, the corpus callosum and frontal cortex, have received attention in the study of dyslexia. Investigative studies of the structural integrity of the corpus callosum of dyslexic groups have produced contradictory findings. Specifically, studies of the anterior (genu) and posterior (splenium) areas of the corpus callo- sum of individuals with dyslexia and individuals with pre- served reading skills have not shown consistent structural

differences in these regions (Hynd et al., 1995; Larsen, Hoien, & Odegaard, 1992). Causal explanations for the relation of the corpus callosum to dyslexia, when struc- tural differences are identified, center on increased or de- creased interhemispheric communication or inappropriate inhibition of one hemisphere by the other. Neuroscientist believe that these conditions disrupt the flow and integra- tion of information between the two hemispheres that is necessary for reading.

The frontal cortex has also received attention, with re- searchers observing tentative differences between profi- cient and disabled readers. Children with either dyslexia or ADHD presented bilaterally smaller frontal cortices than a group of healthy children (Hynd, Semrud-Clikeman, Lorys, Novey, & Eliopulos, 1990). Moreover, the chil- dren with dyslexia differed from the other two compari- son groups by exhibiting greater symmetry of the anterior region because of the smaller width of the right frontal lobe (R � L). Similarly, in a more recent pilot study (Semrud-Clikeman, Hooper, Hynd, Hern, Presley, & Watson, 1996), the smaller width of the right anterior frontal cortex was one of several anatomic variables that discriminated among dyslexic, ADHD, and healthy con- trol children. The functional relation of the anatomic dif- ference of the frontal lobe to dyslexia is unclear. However, the frontal lobes mediate a number of executive functions, such as mental shifting, allocation of attention, and work- ing memory, that are crucial to reading (James & Selz, 1997). Support for a relation between executive dysfunc- tion and dyslexia is emerging. For instance, in one study (Helland & Asbjørnsen, 2000), children with dyslexia showed deficits on measures of attentional flexibility and shifting relative to the performance of healthy control children.

In summary, reading is an exceptionally complex process that requires letter identification, phonologic and orthographic skills, naming speed, sequencing skills, at- tention, mental flexibility, and working memory. Further- more, the lexicon stores (our “internal dictionaries”) must be accessed to determine the meaning of words and to comprehend what is being read. These myriad functions require the support of multiple brain systems, with the left posterior regions serving a central role in skilled reading.

The next section explores NVLD. Children exhibiting NVLD potentially manifest distinctly different neuropsy- chological profiles from those with verbal learning dis- abilities. Whereas verbal learning disabilities are generally attributed to left hemisphere dysfunction and are impli- cated in reading disturbances, NVLD is attributed to right hemisphere dysfunction and is associated with deficits in mathematics (dyscalculia).

304 PART THREE | Disorders of the Brain

N O N V E R B A L L E A R N I N G D I S A B I L I T Y S Y N D R O M E

C l i n i c a l P r e s e n t a t i o n a n d P r e v a l e n c e

The concept of NVLD as a neuropsychological disorder has emerged from the ongoing investigations of Byron Rourke, who has attempted to identify the neurocogni- tive, psychosocial, and adaptive characteristics of children with learning disabilities. His investigative efforts revealed two basic subtypes of learning disability: one labeled R-S, for reading and spelling disability, and the other NVLD, for nonverbal learning disability syndrome. R-S children demonstrate weak psycholinguistic skills with relatively preserved skills in visual-perceptual, tactile-perceptual, psychomotor, and nonverbal/novel problem solving (Table 11.1). Reading and spelling skills are poor, with greater competency evident in mechanical arithmetic, al- though their performance is still below age expectancy. Rourke (1993) hypothesizes that the neuropsychological deficits of the R-S group are associated with left hemi- sphere dysfunctions.

In contrast, children in the NVLD group present es- sentially the opposite pattern of strengths and deficits as the R-S group (Table 11.2). That is, the NVLD group show relatively poor skills in visual-perceptual, tactile- perceptual, psychomotor, and nonverbal/novel problem- solving skills coupled with strengths in the psycholinguis- tic domain. They manifest major academic weaknesses in basic arithmetic but demonstrate preserved linguistic skills such as sight word reading (Harnadek & Rourke, 1994). Both groups exhibit comparable deficits in actual arithmetic achievement; however, Rourke (1993) attrib- utes the poor performance of the R-S group to verbal deficits, and the low performance of the children with NVLD to weaknesses in visual-perceptual and nonverbal reasoning.

Researchers estimate the prevalence rate of NVLD within clinic populations at 5% to 10% (Rourke, 1989). Furthermore, NVLD represents between 0.1% and 1.0% of the entire learning disability population, with an over- all male-to-female ratio of approximately 1.2 to 1.0 (Pennington, 1991).

N e u r o p s y c h o l o g i c a l P a t h o g e n e s i s

Rourke (1993) considers that NVLD reflects right hemi- sphere (particularly posterior) damage, or dysfunction, whereas R-S deficits more closely reflect problems in the left, language-dominant, hemisphere system. Rourke has adopted Goldberg and Costa’s (1981) theorization of

CHAPTER 11 | Learning and Neuropsychiatric Disorders of Childhood 305

Neuropsychological Assets Neuropsychological Deficits

Primary assets Primary deficits

Motor and psychomotor Auditory perception

Novel material

Tactile perception

Visual perception

Secondary assets Secondary deficits

Tactile attention Auditory attention

Visual attention Verbal attention

Tertiary assets Tertiary deficits

Concept formation Auditory memory

Problem solving Verbal memory

Tactile memory

Visual memory

Verbal assets Verbal deficits

Pragmatics Phonology

Prosody Verbal association

Semantic > phonology content Verbal output (volume)

Verbal associations function Verbal reception

Verbal repetition

Verbal storage

Academic assets Academic deficits

Reading comprehension (late) Comprehension (early)

Mathematics Graphomotor

Reading Mechanical arithmetic

Science Reading

Spelling

Verbatim memory

Word decoding

Socioemotional/adaptive assets Socioemotional/ adaptive deficits

Activity level Undetermined

Adaptive to novelty

Emotional stability

Social competence

Source: Rourke, B., & Fuerst, D. (1996). Psychosocial dimensions learning disabilities subtypes. Assessment, 3, p. 281, by permission.

Table 11.1 Core and Clinical Features of the Reading and Spelling Group

brain functioning in conceptualizing the neuropathogen- esis of NVLD. Goldberg and Costa propose that the right hemisphere, relative to the left, is more diffusely orga- nized, has more association regions, and shows greater specialization for inter-regional integration of informa- tion. Because of its capacity to integrate input from mul- tiple brain regions, the right hemisphere is more adept at processing complex, novel, or ambiguous informa- tion. In contrast, the left hemisphere is more focally or- ganized, presents greater modality-specific cortical re- gions, and shows greater specialization for intraregional integration of input. The specialization of the left hemi- sphere is hypothesized to relate to the routine application of previously acquired cognitive strategies. The two hemi- spheres complement each other, with the right hemi- sphere showing prominence in establishing new rules, rou- tines, or strategies, and the left storing and applying these newly established computations in similar situations or with comparable tasks in the future (Fisher, DeLuca, & Rourke, 1997).

Rourke (1995) maintains that the primary deficits of tactile-perceptual, visual-perceptual, and psychomotor abilities of NVLD are consistent with damage or dysfunc- tion of right hemisphere inter-regional integration, whereas assets of auditory-perceptual and verbal skills sug- gest a relatively intact left hemisphere. He also views deficits such as poor problem solving in novel situations, or in the face of complexity, weaknesses in conceptual thinking, and impaired socioemotional skills as emanat- ing from right hemisphere involvement.

Rourke suggests that, although right hemisphere dam- age is sufficient to produce NVLD, it is the destruction of the white matter (myelinated circuitry) required for inter- regional integration that is necessary for producing the dis- order. That is, the development of NVLD can be caused by damage to white fibers (1) accessing the right hemi- sphere, (2) connecting cortical regions within the right hemisphere, or (3) linking cortical to subcortical regions within the right hemisphere (Rourke, 1995). Interest- ingly, Rourke hypothesizes that damage to these different communicating fibers accompanies diverse disorders in association with NVLD. For example, early damage to the association fibers of the right and left hemispheres could potentially cause both the primary features of NVLD and the global linguistic deficiencies that charac- terize autism.

Although Rourke emphasizes the posterior right hemi- sphere as playing an important role in the pathogenesis of NVLD, he proposes that the anterior brain regions may also be involved. For example, children with NVLD per- formed in a less efficient manner than children with

306 PART THREE | Disorders of the Brain

Neuropsychological Assets Neuropsychological Deficits

Primary assets Primary deficits

Auditory perception Complex psychomotor

Rote material Novel material

Simple motor Tactile perception

Visual perception

Secondary assets Secondary deficits

Auditory attention Exploratory behavior

Verbal attention Tactile attention

Visual attention

Tertiary assets Tertiary deficits

Auditory memory Concept formation

Verbal memory Problem solving

Tactile memory

Visual memory

Verbal assets Verbal deficits

Phonology Oral-motor praxis

Verbal association Phonology � semantics content

Verbal output Pragmatics function

Verbal reception Prosody

Verbal repetition

Verbal storage

Academic assets Academic deficits

Graphomotor (late) Graphomotor (early)

Spelling Mechanical arithmetic

Verbatim memory Reading comprehension

Word decoding Science

Socioemotional/adaptive assets Socioemotional/adaptive deficits

Undetermined Activity level

Adaptive to novelty

Emotional stability

Social competence

Source: Rourke, B., & Fuerst, D. (1996). Psychosocial dimensions learning disabilities subtypes. Assessment, 3, p. 281, by permission.

Table 11.2 Core and Clinical Features of Nonverbal Learning Disability Syndrome

verbal learning disabilities when presented tasks requiring higher order mental operations such as conceptual think- ing and mental flexibility (Fisher, DeLuca, & Rourke, 1997). Moreover, Rourke (1995) indicates that the frontal system is necessary for (1) integrating lower level systems (such as sensorimotor) to formulate higher order levels of abstraction; (2) responding to novelty and complexity; and (3) metacognition, that is, the ability to understand the operation of one’s own cognitive processes. Rourke believes that damage to the interconnecting white matter tracks between the frontal lobes and the posterior regions of the right hemisphere contributes to the deficits of higher order cognition evident in NVLD.

Many disorders and brain insults accompany NVLD, spanning genetic, chromosomal, structural, and environ- mental anomalies. Table 11.3 presents a partial list of im- plicated disorders. Although these disorders and insults represent a varied and seemingly dissimilar set of causative factors, clinical presentations, and developmental courses, Rourke and Del Dotto (1994) suggest that each shares a common pathway to NVLD, namely, dysfunction of the

white matter of the brain. These disorders represent a spectrum of neurodevelopmental conditions that vary in the severity of expression of NVLD, ranging from disor- ders that present virtually all the assets and deficits of NVLD (such as hydrocephalus and Asperger’s syndrome), to those that display a majority of the assets and deficits (such as fetal alcohol syndrome and Turner’s syndrome), and finally, to those that exhibit only a subset of the assets and deficits of the NVLD (such as autism). Thus, varying numbers of assets and deficits of NVLD are comorbid manifestations of these disorders caused by damage to the white matter (Rourke, 1995).

N e u r o p s y c h o l o g i c a l A s s e s s m e n t

Harnadek and Rourke (1994) attempted to identify the primary neuropsychological deficits of the NVLD and R-S groups. The neuropsychological test data of three groups, NVLD, R-S, and healthy control children, was subjected to statistical analysis to determine the most dis- criminating measures for classifying the children into their respective groups. Two sets of tests statistically dif- ferentiated the NVLD, R-S, and healthy control groups. The first set of measures assessed visuospatial organiza- tion, tactile-perceptual, and psychomotor skills, and the second, academic (reading) and auditory-perceptual skills. The measures of visuospatial-tactile-psychomotor skills contributed significantly to the discrimination of the NVLD group from the R-S and healthy control groups, whereas the academic-auditory skill measures differenti- ated the R-S from the NVLD and healthy control groups. These two sets of measures accurately classified the chil- dren in their respective groups at an overall classification rate of 98%. Recently, using a larger sample of children with NVLD or reading/spelling deficits, the two sets of measures once again accurately classified children with R-S and NVLD into their respective groups (Pelletier, Ahmad, & Rourke, 2001).

As noted earlier, children with NVLD frequently ex- hibit arithmetic deficits. Rourke and Conway (1997) hy- pothesize that during the initial learning of arithmetic skills in childhood, the novel, visuospatial, and concep- tual nature of the content recruit mainly right hemi- spheric systems. Once these skills are learned, however, they shift to the left hemisphere because of its greater fa- cility in processing and retrieving automatic information (Dool, Stelmack, & Rourke, 1993).

Examining the mathematics performance of children with NVLD, researchers have identified seven overlapping errors (Rourke, 1993): (1) errors in spatial organization, (2) misreading or omitting required mathematic symbols, (3) failure to apply or misapplication of mathematic

CHAPTER 11 | Learning and Neuropsychiatric Disorders of Childhood 307

Asperger’s syndrome

Autism

Callosal agenesis (absence of the corpus callosum)

Congenital hypothyroidism

Cranial irradiation

Fetal alcohol syndrome

Hydrocephalus

Insulin-dependent diabetes mellitus

Intracranial tumors

Metachromatic leukodystrophy (genetic metabolic disorder)

Myelomeningocele (neural tube defect)

Sotos syndrome (growth disorder)

Traumatic brain injury

Triple X syndrome (genetic neurodevelopmental disorder)

Turner’s syndrome

Williams syndrome (genetic neurodevelopmental disorder)

Source: Adapted from Tsatsanis, K., & Rourke, B. (1995). Conclusions and future directions. In B. Rourke (Ed.), Syndrome of nonverbal learning disabilities: Neurodevel- opmental manifestations (p. 486), New York: The Guilford Press, by permission.

Table 11.3 Brain Disorders and Insults Associated with Nonverbal Learning Disability Syndrome

procedures, (4) poorly formed or spaced numbers, (5) fail- ure to remember number facts or arithmetic rules, (6) dif- ficulties shifting from one set of arithmetic operations to another, and (7) poor arithmetic judgment and reason- ing. The latter error involves production of unreasonable solutions, or failure to generalize solutions, strategies, or plans for new or different arithmetic problems. Although children with other forms of learning and neuropsycho- logical deficits can show errors involving spatial and re- trieval deficits, several of the errors, particularly those due to poor judgment and reasoning, discriminate children with NVLD from other learning-disabled children. Er- rors in cognitive shifting, judgment, and reasoning po- tentially implicate deficits in executive function.

S o c i o e m o t i o n a l C h a r a c t e r i s t i c s

A broad set of adaptive and socioemotional disturbances accompany NVLD. Rourke believes these deficits are a direct consequence of the core deficits of the disorder (see Table 11.2). Of these deficits, the most prominent lie in the communication and interactional domains. The com- munication deficits appear in both verbal and nonverbal behaviors. At the verbal level, children and adolescents with NVLD tend to talk excessively, present tangential contents, and show a poor understanding of the pragmat- ics of language, that is, the emotional and social content of a message. Moreover, they find it difficult to understand the nonverbal behavior of others and to convey informa- tion through their own nonverbal behaviors (Rourke, Bakker, Fisk, & Strang, 1983).

Regarding social behavior, deficits in social sensitivity, interactional skills, social problem solving, and judgment seriously hinder the efforts of individuals with NVLD to relate to others. They are prone to misread or fail to ap- preciate the social intents, perspectives, or feelings of oth- ers. In addition, they do not accurately assess social cause- and-effect relations (Rourke & Fuerst, 1996). Social problem solving of children with NVLD is particularly compromised in new, changing, or complex social situa- tions, often resulting in rigid or stereotypic responses that are inappropriate to the demands of the situation. Because of poor social judgment, caretakers and peers view the in- dividual with NVLD as lacking in common sense. Fre- quently, the child or adolescent encounters difficulties generalizing social skills learned in one situation to an- other, even though the new situation is similar to the orig- inal learning context. Social conventions, such as main- taining eye contact and appropriate social distance, are often violated. Finally, the poor psychomotor skills and clumsiness of children with NVLD can elicit teasing and taunting from peers.

Although prone to acting-out behaviors and symptoms of ADHD while young (Voeller, 1996), children with NVLD tend to become shy and withdrawn with increas- ing age. Assessment by their mothers reveals that children with NVLD often present internalizing symptoms such as anxiety, depression, withdrawal, and poor social skills. Whether this is a direct response to their failures within the social sphere is unclear, although it is likely that social failings contribute to the emotional distress of children and adolescents with NVLD. The finding that children with NVLD exhibit increasing and more severe internal- izing psychopathology (anxiety, depression, emotional la- bility, social isolation, and withdrawal) with age is of con- cern (Pelletier et al., 2001). In contrast, children with R-S deficits are less likely to demonstrate increased internalizing or externalizing (acting-out patterns) with advancing age.

N e u r o p s y c h o l o g i c a l M o d e l

Rourke’s model of learning disability, with regard to sub- types such as NVLD and R-S, is summarized as follows:

Subtypes of LD [learning disabilities] are manifestations of distinct profiles of neuropsychological assets and deficits; the subtypes of LD may lead to specific problems in academic functioning, psychosocial functioning, or both; and, the rela- tionship between profiles of neuropsychological assets and deficits, LD, and academic and social learning deficits can be understood fully only within a neurodevelopmental framework that takes into consideration the changing nature of the acade- mic, psychosocial, and vocational demands that humans in a particular society confront. (Rourke & Fuerst, 1996, p. 278)

A hierarchical organization is evident, with primary neurocognitive assets and deficits leading to predictable and differential patterns of neuropsychological function- ing (secondary, tertiary, and linguistic) that, in turn, di- rectly affect academic, socioemotional, and adaptive func- tioning (see Tables 11.1 and 11.2). Thus, the adequacy of the child’s sensorimotor development sets the stage for subsequent levels of cognitive development. The young child experiences the world through touch, movement, and vision. Contacting and exploring the environment through the basic sensory modalities fosters the develop- ment of increasingly complex and higher level mental structures. The early deficits of the child with NVLD in the tactile-perceptual, visual-perceptual, and psychomotor domains limit sensorimotor learning; and thus, hinder the formation of the basic building blocks necessary for the de- velopment of more advanced mental structures. Rourke and others believe these early limitations bias the later develop- ment of conceptual thinking, creative problem solving, com- munication skills, and socioemotional interactions. As the child moves into adolescence and developmental tasks

308 PART THREE | Disorders of the Brain

become increasingly complex, the functional deficits be- come more apparent. Unfortunately, the impairments of the adult are even more pronounced, as evident in the common finding of marginal adaptive success across be- havioral domains.

Little (1993) indicates that the primary deficits and as- sets of NVLD are a robust finding in the studies of learn- ing disabilities. However, support for the socioemotional aspects of the disorder is less compelling. For example, Guy (1996) failed to find a greater prevalence of internal- izing psychopathology in children with NVLD relative to healthy control children and children with verbal learning disabilities.

D e v e l o p m e n t a l C o u r s e

The developmental course of NVLD is somewhat simi- lar to the natural history reported for Turner’s syndrome and higher functioning autistic/Asperger’s syndrome children (see Pervasive Developmental Disorders section later in this chapter). For the NVLD infant/toddler, ex- ploratory behavior and motor skills lag behind language development. With increasing age, delays hinder the devel- opment of self-help skills, and the child tends to depend too much on caretakers. Increasingly, the child encoun- ters difficulties in the social domain, with playmates being either younger or older than the child with NVLD.

In the elementary years, children with NVLD are prone to act out, respond impulsively, exhibit hyperactivity, and encounter problems in sustaining attention (Rourke, Fisk, & Strang, 1986). Despite relatively advanced verbal skills, their communication patterns (both verbal and nonverbal) are often inappropriate. Misperceptions of social situations impair social problem solving and judgment, and poor social skills compromise efforts to relate successfully with peers. The child develops few, if any, close friendships, and during adolescence, peers often avoid teenagers with NVLD. Increasingly, teenagers with NVLD become socially withdrawn and isolated and show internalizing symptoms of anxiety and depression. Developmental patterns for adults with NVLD await clarification. Unfortunately, NVLD adults show elevated rates of psychopathology, and their risk for depression and suicidal behavior appears to be great.

T r e a t m e n t

Because of the communication and social deficits often associated with NVLD, the child needs help developing verbal and nonverbal communication skills, basic social skills (such as greeting), and more advanced social skills (social awareness, friendship skills, and social problem solving). Early and ongoing interventions focused on the

development of communication and social skills may im- prove the child’s acceptance by peers. The young child with NVLD who exhibits ADHD symptoms may benefit from increased structuring of home and school activities, and the introduction of psychostimulant or related med- ications. Furthermore, parents can profit from learning management techniques to foster greater self-help skills and independence by the child.

Children with NVLD are at risk for development of psychological difficulties. Parents and professionals should be aware of this risk and prepare to provide early interven- tions if psychological problems arise. They should pay par- ticular attention to the NVLD youngster with depressive symptoms that might signal an increased risk for suicide.

Rourke and Del Dotto (1994) have developed a com- prehensive intervention program for children and adoles- cents with NVLD. The program actively involves the caretakers from its inception. A set of general principles organizes and guides treatment, with each program re- quiring individualization to accommodate the strengths and deficits of each child. Initially, the program provides the caretakers with information that helps them under- stand the nature and extent of the child’s disorder and de- velop realistic expectations. Then the program provides interventions that will help the child (1) understand, learn, and generalize cognitive and social problem-solving strategies; (2) develop necessary communication skills; (3) engage and interact appropriately with others; (4) explore and experience his or her environment; (5) use available aids (such as a digital watch for learning time concepts); and (6) gain a realistic view of his or her strengths and weaknesses.

School-age children with NVLD are at risk for acade- mic difficulties, particularly if spatial reasoning or execu- tive deficits are severe. Academic subjects that can be par- ticularly challenging to children with NVLD include handwriting and mathematics. Since it is highly unlikely that children with NVLD will outgrow these deficits, pro- grams should be directed toward helping them develop compensatory skills and strategies. For example, children with NVLD often struggle with writing because of spatial and motor deficits. Accordingly, parents and professionals should encourage them, at an early age, to develop word- processing skills. Similarly, adolescents with NVLD need help in developing realistic academic and career goals in light of their individual strengths and visuospatial and mathematic weaknesses.

E v o l u t i o n

NVLD, similar to other syndromes, is an evolving disorder. That is, the validity and clinical utility of the disorder is being evaluated based upon ongoing clinical investigations

CHAPTER 11 | Learning and Neuropsychiatric Disorders of Childhood 309

and research. This process is clarifying the major tenets, as well as prompting the modification of defining features, diagnostic criteria, and specification of differences from other disorders. For example, research is suggesting that children with NVLD do not necessarily exhibit deficits in the area of math calculation but rather in the visuospatial aspects of calculation. Venneri, Cornoldi, & Caruit (2003) determined that children with NVLD show knowledge of math facts and an understanding of calcula- tions similar to that of healthy control children. In con- trast, they made significantly more errors in the execution of written calculations, particularly when regrouping (“borrowing” or “carrying”) was involved. In addition, children with NVLD demonstrated significantly poorer performance on measures of visuospatial skills and visu- ospatial working memory than healthy control children. The authors hypothesize that the poorer performance of the children with NVLD relates to visuospatial skill deficits, including visuospatial working memory weak- nesses. Forrest (2004) has recently determined that chil- dren with NVLD were proficient in math operations (concepts and application) that allowed for the applica- tion of verbal abilities, but they faltered when confronted with mechanical arithmetic. The latter involved solving written calculations (for example, 3 � 9 � 12), that is, problems that place greater demands on visual perceptual processing. Likewise, the author determined that visual- perceptual deficits were not generalized across all forms of visual and visuomotor tasks; rather, they appeared specific to the location of objects in space (spatial). Interestingly, children with NVLD did not demonstrate a greater preva- lence of internalizing psychopathology (namely, depres- sion or anxiety) than children with verbal disabilities and healthy control youngsters. This finding conflicts with an earlier study (Carey, Barakat, Foley, Gyato, & Phillips, 2001) of children treated for brain tumors who, upon as- sessment, demonstrated a profile consistent with NVLD including internalizing behavioral problems and social deficits. The children that participated in these two studies (Forrest, 2004; Carey et al., 2001) represent significantly different clinical populations, and further investigations are needed to determine under what conditions children with NVLD do or do not exhibit internalizing psychopathology.

Pervasive Developmental Disorders

Pervasive developmental disorders encompass a set of severe neuropsychological deficits that are evident early in childhood and have a poor prognosis for achieving normal

adaptive functioning. To varying degrees, each of the per- vasive developmental disorders involves impairment in one or more of the following domains of development: social interactions, verbal and nonverbal language, range of interests and activities, and flexibility of behavior. The behaviors manifested in these domains are age inappro- priate and are disproportionate to the child’s intelligence and age, even though mental retardation is frequently a correlate of the disorders. Researchers hypothesize that a myriad of central nervous system abnormalities play roles in the etiology of the pervasive developmental disorders. However, in many cases, the origin of the disorder re- mains unknown. Table 11.4 summarizes the primary per- vasive developmental disorders and their associated be- havioral features.

310 PART THREE | Disorders of the Brain

Autistic Disorder

Impairment or delays in the domains of social interactions and communica- tions (including symbolic and imitative play), and repetitive and stereotyped patterns of behavior, interests, and activities, with age of onset evident before age 3.

Asperger’s Disorder

Symptom presentation similar to autism with regard to delays in developing age-appropriate social interactions and repetitive and stereotyped patterns of behavior, interests, and activities. Unlike autism, few significant develop- mental delays in language, cognitive, adaptive (other than social), self-help, and exploratory behaviors are evident.

Rett’s Disorder

Initial normal psychomotor development with normal head circumference. Between 5 and 48 months, head growth decelerates, accompanied by the loss of acquired hand motor movements, diminished social interest, emer- gence of poorly coordinated gait or trunk movements, and severely impaired language development with psychomotor retardation. Present only in female children.

Childhood Disintegrative Disorder

Normal development across behavioral domains is evident until 2 years of age or later. Previously acquired skills deteriorate in two or more of the following domains: language, social or adaptive behaviors, elimination control, play, or motor skills. The emergence of autistic-like symptoms in social relatedness, communication, and repetitive and stereotypic behavior is evident. The loss of skills can plateau or continue to decline if accompa- nied by a degenerative neurologic disorder. Present in male and female children, with greater prevalence in male children.

Table 11.4 Distinguishing Features of Pervasive Developmental Disorders

A U T I S M

B a c k g r o u n d a n d C l i n i c a l P r e s e n t a t i o n

Leo Kanner and Hans Asperger are credited with the identification, first theoretical conceptualizations, and la- beling of the developmental disorder autism (Frith, 1989). Autism entails severe impairments in social relat- edness and language development, and the presentation of unusual, repetitive, and/or stereotypic patterns of be- havior. Kanner, working in Baltimore, and Asperger, working in Vienna, each studied a group of disturbed children for whom there was little recognition, much less understanding. Independently, each published their clas- sic articles (Asperger, 1944/1991; Kanner, 1943) without consultation or reported awareness of the other. Remark- ably, both used the term autistic in characterizing the dis- order. Asperger’s work, largely ignored until recent years, is often associated with a higher functioning level or subtype of autism, Asperger’s syndrome, in which near- normal to normal functioning is evident in several behav- ioral domains (Frith, 1991).

The first area of disturbance in autism, impairment in the ability to relate to others, particularly with regard to understanding and entering into reciprocal social relation- ships, is the cardinal symptom of the disorder. Kanner (1943) referred to this dramatic aspect of behavior as “autistic aloneness,” a psychological state of profound separation and disconnection from other people. At a be- havioral level, the child with autism exhibits this social disconnection by displaying the following characteristics: (1) a limited awareness of, or interest in, the desires, needs, distress, or presence of others; (2) an emotional remoteness or aloofness; (3) a failure to share activities, pleasures, and achievements with others; (4) a lack of understanding of social convention; (5) an impairment in social perspective and empathetic role taking; (6) a restricted repertoire of so- cial skills, such as greeting behavior; and (7) awkward or stereotypic responses to others (Bailey, Phillips, & Rutter, 1996). Moreover, children with autism often show deficits in joint attention (reciprocal attention between the child and another), poor conversational skills, lack of eye con- tact, unusual body postures or gestures, and inappropri- ate facial expressions (Charman, 1997; Tanguay, 2000).

The second core characteristic of autistic behavior, deficits in communication, appears as impairments of lan- guage expression and comprehension. Spoken language may be delayed in onset or fail to develop altogether, and the child makes little effort to compensate through non- verbal behaviors such as gestures or facial expressions. When language is used, the child may restrict it to the

repetitive use of stereotypic or idiosyncratic content. Caretakers see deficits in the understanding and use of pragmatics of language (Rumsey, 1996b) and deviant forms of language such as echolalia (repeating the words or phrases of others), pronoun reversal, and neologisms (invention of words). The ability to understand language is often impaired and is limited to the comprehension of simple, literal contents.

The ability to initiate and enter into symbolic, pre- tend, or imitative play is minimally developed (McDo- nough, Stahmer, Schreibman, & Thompson, 1997). Ini- tially, the child shows little interest in toys, suggesting delayed or poor comprehension of the symbolic meaning of toys (Rutherford & Rogers, 2003). As interest devel- ops, the child manipulates toys repetitively as objects without symbolic or imaginative connotations. Insofar as pretend play is considered necessary for the development of social and communication skills, it is diagnostically significant that the child with autism rarely partakes in complex, imaginative, or cooperative play.

The third core feature of autism relates to one or more of the following unusual behavioral patterns: (1) preoccu- pation with specific areas of interest, objects, or qualities of objects; (2) demands for environmental or behavioral sameness; and (3) stereotypic body movements or abnor- malities of posture (American Psychiatric Association [APA], 1994).

A fascination with and abnormal focus on areas of in- terest (such as geography), objects (fans, vacuum cleaners, and so on), parts of objects (such as buttons), movement of objects (such as spinning toys), or activities (such as drawing) can dominate the child’s daily pursuits. More- over, the child may demand the maintenance of constancy (for example, the child’s room cannot be altered), order (toys must be lined up in a certain manner), or routine (the child must always walk the same route to the play- ground). Interference or disturbance of the child’s in- volvement in areas of interest or the child’s efforts to maintain constancy can prompt a range of responses from irritation, to overwhelming anxiety, to thunderous rage. Finally, disturbances of motility can encompass a wide range of movements such as rocking, spinning, twisting, or hand flapping. A variety of unusual postural move- ments may also be evident, such as a tendency to walk on tiptoe, holding the hands in an awkward manner, and walking without moving the arms.

D e m o g r a p h i c a n d C o m o r b i d C o n d i t i o n s

Researchers estimate the prevalence rate of autism at 10 affected children per 10,000, whereas the prevalence rate

CHAPTER 11 | Learning and Neuropsychiatric Disorders of Childhood 311

for Asperger’s syndrome is 2 to 2.5 per 10,000 (Fombonne, 2001, 2003a). Males outnumber females with autism by a 2:1 to 6:1 ratio.

Concern exists that the prevalence of pervasive devel- opmental disorders, particularly autism, is increasing at an alarming rate. A review of relevant epidemiologic stud- ies reports an increase in prevalence from 4.4 per 10,000 for the years 1966 through 1991 to 12.7 per 10,000 for the years 1992 through 2001 (Fombonne, 2003a). An ex- amination of the studies suggests that the increase may be spurious. Specifically, the increase may relate to the fol- lowing factors: (1) changes and broadening of the diag- nostic criteria for autism (for example, APA, 1994); (2) different methods used to identify individuals with autism; (3) increased focus and emphasis on identifica- tion, especially for the very young; (4) increased referrals for services and interventions; and (5) diagnostic substi- tution (Fombonne, 2003a,b; Volkmar, Lord, Bailey, Schultz, & Klin, 2004). Concerning diagnostic substitu- tion, a study (Fombonne, 2003b) of the prevalence rate of autism in the state of California showed an increase from 5.8 to14.9 per 10,000 for the years 1987 to 1994, whereas the number of children diagnosed as mentally re- tarded during this same period decreased from 28.8 to 19.5 per 10,000. The change in the two prevalence rates suggests that greater numbers of individuals who, in ear- lier years, would have been classified as mentally re- tarded were being identified as autistic. There is a dearth of well-developed and comprehensive epidemiologic studies concerning the incidence and prevalence rates for autism, and we await the development and results of fu- ture studies to determine whether the rates of autism are actually increasing.

Many children with autism (approximately 70%) function within the retarded range of intelligence, as ev- ident in intelligence quotient (IQ) scores below 70 (Fombonne, 2003a). Interestingly, the ratio of male to fe- male individuals with autism is largest for those of nor- mal intelligence, but is approximately 2 : 1 (male/female) for those individuals with autism who are mentally re- tarded. An inverse relation exists between IQ and severity of autistic symptoms. That is, the higher the level of in- telligence, the less severe the autistic symptoms. Circum- scribed abilities and skills of exceptional levels (such as hyperlexia, or early acquisition of reading skills without comprehension) may appear within the context of severe mental retardation. The rate of savant skills—that is, ex- traordinarily developed skills within the context of limited cognitive capability—in autism is estimated to be 10 times that of the normal population (Waterhouse, Fein, & Modahl, 1996). The risk for seizure disorders is high in

autistic groups, with a mean rate across studies of 16.8% and even higher for autistic children with IQs less than 50 (Fombonne, 2001; Fein, Joy, Green, & Waterhouse, 1996).

H i g h - F u n c t i o n i n g A u t i s m o r A s p e r g e r ’ s S y n d r o m e ?

Currently, controversy exists over whether the two pri- mary representatives of pervasive developmental disor- ders, autism and Asperger’s syndrome, are separate disor- ders, overlapping subtypes, or one disorder with Asperger’s syndrome representing individuals with autism who are higher functioning, both cognitively and adap- tively. Before considering this controversy, we review the symptom presentation of Asperger’s syndrome.

The term Asperger’s syndrome refers to a group of chil- dren, adolescents, or adults who exhibit autistic-like symptoms but do not strictly fulfill the autism criteria. The criteria for autism and Asperger’s syndrome of the American Psychiatric Association (1994) show a signifi- cant overlap in symptoms related to impairments in so- cial interactions and preoccupations with narrow, repeti- tive, and stereotypic patterns of behavior, interests, and activities. Despite this overlap, the APA proposes several differences. Specifically, children with autistic-like behav- ior are not to receive the diagnosis of Asperger’s syndrome if they exhibit the following characteristics: (1) significant impairment in verbal and nonverbal communication skills, (2) a lack of developmentally appropriate symbolic or imaginative play, (3) delayed language development or absence of language, (4) cognitive deficits, (5) impairment in self-help and adaptive skills (excluding those involving social interactions), and (6) limited or absent exploratory curiosity (Bailey et al., 1996). These exclusionary crite- ria are consistent with Asperger’s original behavioral de- scription of children exhibiting the disorder. That is, these children display poor social skills, odd and eccen- tric behaviors, and restrictive patterns of interests and ac- tivities, without significant delays in cognitive or language abilities.

Research studies (Eisenmajer et al., 1996; Volkmar et al., 2004) have sought to further clarify the differences be- tween Asperger’s syndrome and autism. Children diag- nosed as exhibiting Asperger’s syndrome, as contrasted with autism, show a greater (1) desire for social contact and friendship; (2) willingness to participate in play with other children centered on their special interest, such as dinosaurs; (3) likelihood of normal onset of language de- velopment and an absence of echolalia and pronoun re- versal; (4) use of odd words of speech, pedantic speech, and one-sided, repetitive conversations; (5) tendency to

312 PART THREE | Disorders of the Brain

pursue narrow and limited areas of interest, such as pre- occupation with clocks; and (6) likelihood of being inattentive, impulsive, and overactive. However, these differential characteristics have been challenged in re- cent studies (Macintosh & Dissanayake, 2004; Mayes & Calhoun, 2001).

The separation of the two disorders poses several chal- lenges. First, varied definitions and differential selection criteria artificially blur the boundaries between the two disorders, hindering efforts to identify commonalities and differences in cognition and behavior, etiology, and re- sponsiveness to differential treatments. In addition to the major diagnostic criteria of the DSM-IV (APA, 1994) and International Classification of Diseases (ICD-10; World Health Organization, 1992), no less than five other widely publicized definitions of Asperger’s syndrome exist (Volkmar & Klin, 2000). Each definition leads to differ- ences in selection criteria, areas of study, and research re- sults, thus hindering efforts to determine whether the two disorders are independent of one another.

Second, the reported difference between autism and Asperger’s syndrome may reflect the level of intellectual or language development of the two disorders. By defini- tion, one criterion for differentiating Asperger’s syndrome from autism is the relative absence of language and cogni- tive impairment in Asperger’s syndrome. Thus, children with Asperger’s syndrome may simply be brighter chil- dren with autism who show fewer language deficits.

Third, a number of studies are flawed by the failure of the investigators to use outcome measures that are inde- pendent of those used for the selection of the partici- pants. For instance, it is certainly appropriate for re- searchers who are interested in identifying the differential characteristics of Asperger’s syndrome and high-function- ing autism to use a measure of motor functioning to form the two groups. As a result of this selection criterion, one group would consist of children who exhibit motor deficits and the other group would include children who did not. However, in the formal study of the two groups, it would then be inappropriate to assess them with motor measures in an effort to determine whether motor deficits differentiated between the groups. The circular- ity of this approach is evident, because the groups were originally selected based on their differences in motor functioning.

Fourth, young, higher functioning children with autism frequently exhibit behaviors consistent with Kanner’s char- acterization of autism. However, with maturity, they often show fewer differences in symptom presentation from indi- viduals with Asperger’s syndrome (Howlin, 2003; Volkmar et al., 2004). Accordingly, Asperger’s syndrome may

merely reflect the changing presentation, over time, of higher functioning individuals with autism.

The case study of Tom Z. familiarizes the student with Asperger’s syndrome (Neuropsychology in Action 11.2). The study details the symptoms, evaluative data, and fam- ily history of Tom Z., as well as some rather surprising neuroimaging findings.

N e u r o p s y c h o l o g i c a l P a t h o g e n e s i s

Various researchers attribute the development of autism to a host of causative factors. There are indications that the disorder is either familial or genetic in origin; how- ever, the finding of high rates of perinatal complications in the history of children with autism also implicates en- vironmental factors. Some evidence exists for an autistic diathesis, that is, a genetically mediated vulnerability for autism that interacts with an early environmental insult to produce the disorder (Pennington, 2002). However, a definitive number of environmental risk factors for the development of autism have not been identified. For in- stances, there is public concern that the combined measles-mumps-rubella (MMR) immunization (or sub- stances used as a preservative of the active immune agents) places children at risk for autism. Empirical studies, to date, have not supported a relation between autism and immunizations (Fombonne, 2003b). For instance, in Yokohama, Japan, the combined MMR immunization was withdrawn beginning in 1988 with no child receiving the vaccine as of 1993 or thereafter. Single immunizations for each of these diseases continued to be administered. The cumulative incidence of autism increased significantly be- tween 1988 and 1993, with the highest increase evident in 1993 (Honda, Shimizu, & Rutter, 2005). The findings in- dicate that the increased incidence of autism was unrelated to the MMR vaccination. Unfortunately, the public con- cern over a possible relation between the MMR immuniza- tion and autism has prompted some parents to withhold MMR inoculations from their children. Clearly, such a decision increases the risk for the children to contract one or more of these diseases.

Support for a familial/genetic component of autism is the finding of relatively high rates of the disorder in the siblings of children with autism. The rate is approximately 3% to 6%, which is 25 to 50 times greater than the inci- dence in the normal population (Fombonne, Bolton, Prior, Jordon, & Rutter, 1997; Sutcliffe & Nurmi, 2003). Heritability studies of identical twins reveal co-occurrence rates of 60% to 92%, whereas rates for fraternal twins range from 0% to 10% (Tanguay, 2000). The substantial

CHAPTER 11 | Learning and Neuropsychiatric Disorders of Childhood 313

314 PART THREE | Disorders of the Brain

N e u r o p s y c h o l o g y i n A c t i o n 1 1 . 2

C a s e S t u d y o f a n A d o l e s c e n t w i t h A s p e r g e r ’ s S y n d r o m e

Tom Z. is a tall, stocky 15-year-old male adolescent. He was born after an uncompli- cated pregnancy, and subsequent develop- mental milestones were achieved within normal limits. Tom talked before he walked. He taught himself to read by age 3 and was reading adult-level books by age 4. By the age of 2.5 years, he had atypical interests that were pursued to the exclusion of other activities. Over the years, these interests have included stop signs, arrows, storm drains, windmills, clocks, mathematics, and computers.

In nursery school, he had poor peer relations, talked incessantly about topics of interest only to himself, failed to listen to the comments of others, and was often opposi- tional and impulsive. A clumsy and poorly coordinated child, he often seemed markedly odd. A preschool psychological assessment recommended special educa- tion placement, and the parents tried various programs with limited success. They finally moved him to homebound education. De- spite precocious academic achievements, Tom continued to have significant problems with social interaction and in controlling his behavior.

At his first formal evaluation, when he was 9.5 years old, Tom had no friends, poor interpersonal skills, and signs of depression. His fascination with clocks pervaded all conversation. His poor social judgment was clearly evident, particularly in his description of interactions with peers. He showed limited nonverbal social behaviors, such as ges- tures, facial grimaces, emphasis of voice, and nonliteral communications. Interest- ingly, Tom’s father had a history of similar problems. For example, Mr. Z. carried a small notebook to write down the names of impor- tant people he met because, “I can never remember people’s faces; I can only remem- ber names when I write them down.”

Tom was evaluated again when he was 12 years old. He continued to show a markedly eccentric social style and engaged in one-sided conversations about computers

and mathematic concepts in a loud, poorly modulated voice. His limited awareness of social conventions was evident in his one- sided conversational style, his tendency to belch and pass gas in public, and his use of graphic expletives without apparent intention to shock others. He was preoccupied with the subject of girlfriends and his sexual needs.

Tom’s clinical presentation and assess- ment results were extreme in many respects. There was a significant discrepancy between his Wechsler Intelligence Scale for Children–Third Edition (WISC-III; Wechsler, 1991) verbal and performance abilities (Verbal IQ � 139; Performance IQ � 127). He had superior scores in verbal reasoning, except for tasks involving social comprehen- sion. Although able to describe social demands, he could not translate this knowledge into appropriate conduct. He also exhibited significant deficits in visuomotor skills, speed of processing, and motor functioning. Moreover, a large difference existed between his superior intelligence score and his ratings on a measure of adap- tive skills. His adaptive rating score was significantly below average, indicating severe deficits in meeting the demands of everyday life.

Neuroimaging Father and son underwent magnetic resonance imaging (MRI) of the brain. The father’s sagittal brain images showed a large V-shaped wedge of missing tissue in the dorsolateral frontal region of the brain (Figure 11.3a). This region of tissue loss appeared in the same location of both hemispheres, but was somewhat larger in the left. Given the absence of a history of trauma, the tissue loss likely represented an area of focal dysmorphology of unknown origin.

Tom showed a similar but noticeably smaller region of structural anomalies in exactly the same area of both hemispheres. His abnormality, however, was somewhat

larger on the right, the reverse of the father’s (see Figure 11.3b). In addition, he showed decreased tissue in the anteromesial region of the left temporal lobe (see Figure 11.3c). The similarity of abnormalities in Mr. Z. and Tom indicated potential familial transmission.

Discussion of Magnetic Resonance Imaging and Psychological Testing A three-dimensional rendering of the father’s brain showed his neurodevelopmental abnormality to be in the region of the middle frontal gyrus (see Figure 11.3d). The deficit was a recessed area of absent tissue. Fur- thermore, the three-dimensional image showed an abnormality that did not appear on the two-dimensional images: both right and left frontal lobes showed an abnormal pattern of gyri and sulci. Normally, the frontal lobe consists of three prominent horizontal gyri (the superior, middle, and inferior gyri) that run in parallel from anterior to posterior. Although the father’s superior frontal gyrus appeared normal, the middle frontal gyri were vertical in both hemispheres. This aberrant pattern of surface structure may have originated from an abnormal prenatal developmental process.

Because of movement artifacts, a clear three-dimensional representation of Tom’s brain was not possible. However, researchers reconstructed coronal images by computer methods to evaluate his left temporal lobe abnormality. The images showed a large region of missing tissue and also an asymmetry of the lateral ventricles.

Any single case report must be inter- preted with caution, yet it is of interest that Tom’s neuropsychological deficits are under- standable in light of his brain abnormalities and other studies of individuals with autism, Asperger’s syndrome, and similar disorders (for example, see Piven et al., 1990). As described earlier, Tom’s psychological testing demonstrated significantly higher WISC-III Verbal IQ relative to Performance IQ. Consistent with his greater nonverbal difficul- ties, Tom’s frontal lobe abnormalities were

CHAPTER 11 | Learning and Neuropsychiatric Disorders of Childhood 315

more prominent on the right than the left side. The right hemisphere is also more prominently involved than the left hemisphere in regulating language prosody and pragmatics (Kolb &

Whishaw, 1990), two areas in which Tom performed poorly. Moreover, the volume of his left hemisphere was somewhat larger than that of the right. In a study published several years

ago, Willerman, Schultz, Rutledge, & Bigler (1992) found that a larger left than right hemisphere predicted a higher Verbal IQ than Performance IQ in male individuals.

(continued)

Images not available due to copyright restrictions

co-occurrence rates for identical twins suggest that genetic factors play a significant role in the etiology of autism. Genetic research has implicated at least 20 genes as con- tributing to autism risk. Of these implicated genes, anom- alies of chromosome 15q11-q13 have been frequently replicated across studies (Nurmi et al., 2003; Sutcliff & Nurmi, 2003).

The neural substrates considered to produce autism are numerous, but none has received unanimous support. Anatomic abnormalities, hypothesized or identified in autistic samples, have included most cortical and subcor- tical regions of the brain. In addition, empirical studies reveal differences in neurochemical systems, brain vol- ume, proportion of white-to-gray matter, neuronal me- tabolism, and cellular migratory patterns of the cortex, prefrontal cortex, cerebellum, and limbic system (hip- pocampus, amygdala, and other limbic nuclei).

Studies have implicated abnormalities involving neu- rotransmitters as pathogenic of autism, with serotonin re- ceiving the most attention. Serotonin (5-HT) is involved in regulating a number of brain functions, including learning, memory, sleep, pain responsiveness, mood, and inhibitory processes. In addition, there are indications that excessive 5-HT can disrupt social affiliation and at- tachment. Children with autism show 25% to 50% in- crease in serotonin (hyperserotonemia), although the precise role of 5-HT in the production of autistic symp- toms is unclear. Even more troublesome are studies show- ing that elevated levels of serotonin are not specific to autism, with other disorders such as mental retardation also exhibiting hyperserotonemia (Anderson, 2002; Fein et al., 1996).

Converging evidence indicates that a large proportion of children with autism (14–30%) have a greater head circumference than healthy control children. Brain size is also larger (approximately 10%) in autistic populations (Volkmar et al., 2004). Of importance is the finding of small brain size at birth, followed by two periods of ac- celerated growth occurring at 1 to 2 months and 6 to 14 months of age. Subsequently, brain size in autism reaches its maximum growth by ages 4 to 5 years and

thereafter begins to gradually decline. By adolescence and adulthood, brain size is similar to that of healthy adults (Courchesne, Carper, & Akshoomoff, 2003). Although the underlying neurobiological factors accounting for this developmental pattern are unknown, this growth profile may provide an early warning signal for the risk for autism. However, head or brain size enlargement may not have a direct causative role in autism insofar as there is lit- tle relation between head/brain size and specific autistic symptoms. In addition, other clinical populations show increased head/brain size, specifically fragile X syndrome and tuberous sclerosis (Tanquay, 2000).

A second area of convergence relates to the finding of atypical white-to-gray brain matter ratios in autistic pop- ulations (Schultz, Romanksi, & Tsatsanis, 2000). Al- though the pathogenic relation of disproportionate white- to-gray matter to autism remains to be clarified, it is hypothesized that it represents a disruption of the brain’s interconnectivity (Volkmar et al., 2004). In turn, integra- tive brain functions are impaired. Interestingly, there is also speculation that the atypical white-to-gray matter may result in modularity of brain functions. Modularity relates to brain functions that are specific to relatively sep- arate and independent brain regions or circuits. The high rate of savant capabilities in cognitively impaired autistic groups is consistent with a modular organization—that is, a set of neurally distinct, preserved, and self-contained mental functions.

Historically, the cerebellum has been thought to medi- ate motor behavior. Increasingly, clinical and research studies are reporting that the cerebellum is involved in a number of cognitive operations including attentional be- havior, classical conditioning, and executive functions. Structural and functional abnormalities of the cerebellum in autistic populations are evident. For instance, studies have identified hyperplasia or hypoplasia of the cerebellar vermis lobules (Courchesne, Townsend, & Saitoh, 1994; Filipek, 1995). Malformation of the cerebellar vermis lob- ules is believed to cause a disruption of attentional shift- ing and possibly other cognitive processes often evident in autism. However, subsequent studies of cerebellar

316 PART THREE | Disorders of the Brain

(continued) The frontal lobe findings may clarify Tom’s motor difficulties and conceptual inflexibility. The structural abnormality was at the juncture of the primary motor strip, premotor area, and dorsolateral convexity, thus potentially affect-

ing the functions mediated by each of these regions. The dorsolateral prefrontal cortex is known to be involved in the executive functions of working memory and shielding of cognitive operations from disruption by unwanted distractions (Goldman-Rakic, 1987a).

Source: Adapted from Volkmar, F. R., Klin, A., Schultz, R., Bronen, R., Marans, W. D., Sparrow, S., et al. (1996). Asperger’s syndrome. Journal of the American Academy of Child and Adolescent Psychiatry, 35, 118–123.

structure have produced negative results (Schultz et al., 2000). Furthermore, cerebellar anomalies are not specific to autism, as evident in similar malformations in the brains of mentally retarded populations.

The temporal and limbic system structures, including the amygdala, hippocampus, and entorhinal cortex, ap- pear to play a major role in mediating human socioemo- tional behavior. Studies of the temporal lobe-limbic sys- tem of autistic populations reveal volumetric reductions, hypofunctional activity, and abnormalities in neuronal size and density (Schultz et al., 2000). The important findings of atypical facial processing in autistic groups are of particular interest. Orienting to and focusing on the faces of others initially occurs in early infancy and is an important precursor of healthy emotional and social de- velopment. Children with autism show a lack of interest in human faces and, in contrast, a preferential interest in objects as early as the first year of life.

The medial temporal-limbic system is intimately in- volved in facial and emotional processing. The fusiform and inferior temporal gyri (and possibly the lateral occipi- tal gyrus and parahippocampal gyrus) are preferentially involved in facial and object processing, respectively. Be- cause of its activation in facial processing, an area in the middle region of the fusiform gyrus is referred to as the fusiform face area (FFA). At least seven different studies of children, adolescents, and adults with autism (Piggot et al., 2004; Schultz et al., 2003; Wang, Dapretto, Hariri, Sigman, & Bookheimer, 2004) show reduced activation of the FFA to images of human faces. For instance, Schultz and associates (2000) have investigated the fMRI activation patterns of autistic (autistic and Asperger’s syn- drome) and healthy young adults of normal intelligence when performing facial and object discrimination tasks. The study revealed that subjects with autism demon- strated decreased activation in the FFA and increased ac- tivation of the inferior temporal gyrus when performing the facial discrimination task. In contrast, the healthy control participants showed significant activation of the FFA and decreased activation of the inferior temporal lobe. Both healthy control participants and those with autism activated the inferior temporal gyrus when view- ing objects. Likewise, autistic groups have been found to show reduced activation in the FFA when required to match emotional facial expressions or identify mental states based on facial details (Piggot et al., 2004; Schultz et al., 2003). Overall, these studies indicate that autism is associated with atypical activation of a brain region re- lated to a basic building block of socioemotional behav- ior, namely, facial processing. A failure to attend to the faces of significant others, and people in general, disrupts

normal socioemotional learning during development and potentially contributes to the significant social disinterest and atypical interaction patterns that characterize autistic groups.

There are indications that the FFA may have an even broader role in the mediation of socioemotional behavior. In an ingenious experiment, Klin (2000) used a task, the Social Attribution Task, to assess the social cognitions of young adults with autism. The Social Attribution Task in- volves the presentation of systematic movements of geo- metric shapes that, when viewed by healthy individuals, are imbued with social meaning. In contrast, individuals with autism do not impose social meaning on these movements; instead, they describe the physical features of the stimuli. In a recent fMRI study (Schultz et al., 2003), healthy con- trol participants were presented the Social Attribution Task, a face perception task, and control tasks. Of impor- tance to our discussion is the finding of marked activa- tion of the FFA for both the Social Attribution Task and face perception tasks, but not for the control tasks. The authors conclude that the FFA appears to have an impor- tant role in social attribution and judgment. However, the FFA is but one functional component of the limbic system, and attention by neuroscientists has also focused on other limbic structures, such as the amygdala.

The amygdala is richly interconnected with the tem- poral cortex and other cortical and subcortical regions. It is involved in emotional arousal, appraising the behav- ioral significance of environmental stimuli, attributing emotional valence to stimuli, and emotional learning (Schultz et al., 2003). Animal research demonstrates that damage to the limbic system, including the amygdala, can produce autistic-like behaviors (Bachevalier, 1994). In addition, atypical neuroactivation of the amygdala is ap- parent in autistic groups when processing facial (Wang et al., 2004; Sparks et al., 2002) and theory of mind tasks (Baron-Cohen, O’Riordan, Stone, Jones, & Plaisted, 1999).

Evidence also exists of anomalies in frontal lobe func- tioning associated with autism. Neuroimaging studies show atypical activation of the orbital and medial pre- frontal cortices and anterior cingulate in individuals with autism (Schultz et al., 2000). Because of the rich inter- connections of the frontal regions with limbic and other brain structures, the frontal cortices are in a position to integrate and regulate the internal and external inputs necessary for socioemotional behavior.

Increasingly, research and clinical work with autism and other populations has led to the theorization of a so- cial brain network. Interconnected orbital and medial pre- frontal cortices, anterior cingulate, amygdala, superior

CHAPTER 11 | Learning and Neuropsychiatric Disorders of Childhood 317

temporal sulcus, and FFA are believed to underpin the so- cial brain. It is hypothesized that the orbital and medial prefrontal cortices play a role in integrating and regulat- ing affective and cognitive processes, whereas the dorso- medial prefrontal cortex and cingulate support social cog- nition (thinking about the thoughts, feelings, and intentions of others and social judgment). The amygdala appears to be involved in modulating and interpreting the emotional significance of stimuli and in assisting the cor- tex with the integration of emotion and cognition for evaluation and action by the frontal lobes. The superior temporal sulcus supports facial expressions, social ges- tures, eye gaze, and facial recognition, while the FFA as- sists in facial discrimination and social attribution. To- gether, the latter two structures support the perception of social behavior (Schultz et al., 2000, 2003). Damage to different aspects of this distributed social brain network may account for the heterogeneity of cognitive, emo- tional, and social deficits of autistic populations. Obvi- ously, the social brain network warrants additional empir- ical verification and possible expansion to include other limbic structures.

N e u r o p s y c h o l o g i c a l A s s e s s m e n t

The diagnosis of autism requires a careful review of the child’s developmental history and observations of the child with family members, teachers, and peers. In addi- tion, a complete medical evaluation and review of perti- nent medical records should be standard practice because of the potential presence of genetic and chromosomal ab- normalities, the high likelihood of co-occurring medical conditions (such as seizures), and the association of autism with other neurodevelopmental disorders. More- over, assessments by other disciplines (such as speech and language) are often needed to augment the evaluation.

The neuropsychological evaluation of the child with autism should involve a comprehensive assessment of cog- nitive and related behaviors. The selection of measures depends heavily on the unique presentation of the child. For example, the evaluation and selection of measures may be quite different for the child who has not devel- oped language than for the child who has rudimentary language. Currently, the Autism Diagnostic Interview- Revised (Rutter, Le Couteur, & Lord, 2003) and Autism Diagnostic Observation Schedule (Lord et al., 2000) are two well-standardized measures that are considered the “gold standards” for the assessment of autism.

Cognitive Profiles—It was initially proposed that children with Asperger’s syndrome and autism demonstrated dif- ferential cognitive patterns (Ehlers et al., 1997; Minshew,

1997). The Asperger’s syndrome profile involves greater facility in verbal relative to visuospatial or visuomotor problem solving. This cognitive profile is consistent with that demonstrated by children with NVLD (Rourke & Conway, 1997; see Nonverbal Learning Disability section earlier in this chapter). The autism cognitive profile is the converse of the Asperger’s syndrome profile. That is, chil- dren with autism demonstrate relative strengths in visual- perceptual and visuospatial as contrasted with verbal problem solving. The majority of subsequent studies (Macintosh & Dissanayake, 2004) are not supportive of these differential cognitive profiles. In fact, several of these studies have found no differences between the two groups, whereas others have shown the opposite cognitive pro- files, with autistic groups showing relatively advanced ver- bal relative to visuospatial and visual-perceptual abilities.

Although differential profiles for autism and Asperger’s syndrome are not fully supported, they do highlight the variability of performance that may be encountered in the neuropsychological assessment of this group, particularly as contrasted with mentally retarded populations where a more uniform suppression of cognitive abilities is often evident. However, individuals with autism often demon- strate poor performance on tasks that require higher level conceptual processes such as reasoning, inferring, inte- grating, and abstracting (Minshew, 1997). This deficit cuts across the domains of cognition involving language, memory, executive functions, and academic performance. In addition, individuals with autism tend to be more de- tail oriented and have difficulty with (1) integrating parts into wholes, (2) identifying central elements or themes, (3) differentiating between relevant and irrelevant infor- mation, and (4) determining meaning (Ozonoff, 2001). Their thinking is often literal and concrete. The high rate of hyperlexia in autism exemplifies this disparity. The autistic child with hyperlexia learns to read (decode) early but is impaired in comprehending the reading material. Interestingly, the cognitive and learning profile of autism is the converse of learning disabilities such as dyslexia. The dyslexic child cannot decode words but shows pre- served listening comprehension when another person reads the material aloud. In summary, deficits in higher order thinking processes are evident across the autistic spectrum, including those individuals who are higher- functioning.

Executive Function—Similarities in the behaviors of individ- uals with autism and patients with prefrontal damage have prompted speculation that executive dysfunction may be of causative significance in autism. Empirical ef- forts to determine the validity of this speculation, and to

318 PART THREE | Disorders of the Brain

identify differential patterns of executive performance, are growing.

Consistent with this line of investigation, Hughes, Russell, and Robbins (1994) have determined that chil- dren with autism perform in an inferior and differential manner on executive measures compared with healthy control children. Specifically, the autistic group exhibited poorer complex planning and mental shifting perfor- mance and also a unique type of executive deficit termed “stuck in set” perseveration. The researchers interpreted the concept of “stuck in set” perseveration as a failure to disengage the current attentional focus from ongoing cog- nitive operations (Ciesielski & Harris, 1997). Such disen- gagement is necessary if the person is to shift attentional focus to a new set of demands, activities, or goals.

The most robust executive deficit associated with autism is that of higher order planning (Ozonoff, 2001). Executive planning involves complex, means–end prob- lem solving to achieve a behavioral goal and is supported by a number of component processes to include working memory, mental flexibility, response inhibition (the abil- ity to delay a response), and the ability to project ahead in time. Research using tower tasks (Tower of London/ Hanoi) to assess executive planning consistently shows poorer performance by autistic groups (both high- and low-functioning) relative to healthy and other clinical groups (Pennington & Ozonoff, 1996). A set of studies by Ozonoff and others (Ozonoff & Jensen, 1999; Ozonoff & Strayer, 2001) revealed distinct executive profiles for autis- tic, Gilles de la Tourette’s syndrome, and ADHD groups. Specifically, autistic groups showed impaired planning and mental flexibility, whereas ADHD groups exhibited defi- ciencies in response inhibition. The Gilles de la Tourette’s syndrome and healthy control groups did not differ in their performance across executive function tasks.

Ozonoff (2001) calls attention to the importance of subtle or overlooked factors that may affect the perfor- mance of individuals with autism. For instance, when ex- amining studies of executive performance, particularly those that involved tower tasks, the performance of autis- tic groups varied from impaired to unimpaired. She dis- covered that most of the studies reporting unimpaired or improved executive performance involved computerized administration of the executive measures. In contrast, im- paired performance was more likely to be evident when the measures were presented in a face-to-face format. Sub- sequent investigations indicated that the issue is much more subtle than type of test administration. The impor- tant variable appears to be the mode of feedback, human versus nonhuman. Individuals with autism appear to show poorer performance when feedback is presented

within a verbal, social-interactive, as contrasted to an im- personal, computer-generated context.

Social Cognition—Converging evidence is revealing that autism is associated with deficits in social cognition. Social cognition encompasses a diverse set of processes such as fa- cial perception, social orientation, joint attention, imita- tion, and theory of mind (TOM). We have reviewed facial processing in autism (see Neuropathogenesis earlier in this chapter). Deficits in social orientation (interest in and pref- erence for human contact over objects) and joint attention (sharing a common focus of attention with another) are ev- ident in autistic children. Likewise, imitation of others is a key component of social learning. Research reports that children with autism often do not imitate the actions of significant others and peers (Pennington, 2002).

TOM has received considerable empirical and theoret- ical attention. TOM, or “mentalism,” refers to the ability to represent or infer mental states such as the beliefs, mo- tives, and intentions of others. This ability enables people to make attributions, to reason about mental states, and to understand and predict the behavior of others (Rowe, Bullock, Polkey, & Morris, 2001). It is posed to be in- volved in or support the social behaviors of perspective- taking, “mind-reading,” empathy, and the detection of de- ception, irony, humor, and faux pas (Baron-Cohen et al., 1999; Lawson, Baron-Cohen, & Wheelwright, 2004). An example of TOM would be observing a person and infer- ring what the person is “thinking” or predicting how the person would respond. This example portrays a first-order TOM. Higher levels of TOM are also evident. A second- order TOM would involve representing or inferring one person’s mental state about another person’s mental state (“Bill thinks that Mary believes that Joe believes . . .”). Young children are capable of performing first-order tasks, whereas success with second-order TOM tasks is not achieved until a later age, depending on the com- plexity and difficulty of the task presented. Unimpaired TOM processing is viewed as central to the develop- ment of appropriate interpersonal and communication patterns.

Investigations reveal deficits in TOM for autistic groups relative to healthy control participants (Jarrold, Butler, Cottington, & Jimenez, 2000; Ozonoff & Griffith, 2000; Rutherford & Rogers, 2003). Suggestions have been made that TOM performance is supported, in part, by the or- bital prefrontal cortex (Baron-Cohen, Ring, Bullmore, Wheelwright, Ashwin, & Williams, 2000), a region impli- cated in higher order socioemotional regulation. A num- ber of imaging studies have also demonstrated a relation between TOM performance and the medial prefrontal

CHAPTER 11 | Learning and Neuropsychiatric Disorders of Childhood 319

cortex activation (Shallice, 2001). In a relatively recent in- vestigation (Stuss, Gallup, & Alexander, 2001), patients with lesions of the frontal and nonfrontal cortices were presented with measures of TOM. In contrasting the per- formance of the different lesion groups, significantly poorer TOM performance was associated right and bilat- eral frontal lesions, particularly lesions of the right medial prefrontal cortex.

Although TOM has enhanced our understanding of autism, it has received its share of criticism. For example, TOM deficits are evident in other clinical groups, indi- cating a lack of specificity to autism (Pennington, 2002). Furthermore, TOM performance is related to verbal abil- ity and general cognitive level which undermines its util- ity as a specific index of social cognition. Finally, TOM has been variously defined as a cognitive, language, emo- tional, or social construct, leading to confusion as to what processes are actually encompassed by the theory. There- fore, we await further theoretical developments and re- search to clarify the meaning, boundaries, and utility of TOM.

Although psychological constructs such as executive function and social cognition have enabled us to charac- terize and predict certain autistic behaviors, they lack the theoretical breadth necessary to account for the diverse communication, language, and social behaviors associ- ated with the disorder. We next turn to a theoretical model that endeavors to provide a comprehensive neuro- functional model of autism.

C o m p r e h e n s i v e N e u r o f u n c t i o n a l M o d e l

Multiple theories and models are available to account for the behavioral manifestations, core deficits, and cause of autism. These conceptualizations focus on impairments of attention (shifting and selective), TOM, social attach- ment, socioemotional perception, memory, language, and executive function (Fein et al., 1996). The majority of these theoretical efforts are rather narrow with regard to the specific autistic behavior that is interpreted or pre- dicted. Accordingly, most fail to account for the multiple behavioral manifestations and proposed neural impair- ments of autism.

Waterhouse and coworkers (1996) propose a compre- hensive model to account for the heterogeneity of symp- toms and causes of autism. The comprehensive model rests on a series of assumptions relating human social be- havior to brain functioning. It proposes four neurofunc- tional impairments that, in interaction, account for the social and related behavioral disruptions of autism:

1. Canalesthesia involves the fragmented processing of incoming information from the different sensory modalities. Because of this fragmentation, sensory in- formation in consciousness, working memory, and de- clarative memory fails to integrate properly, resulting in distorted representations of the information.

2. Impaired affective assignment is the disrupted link- ing of appropriate emotional meaning or significance to novel and social stimuli. This disruption impairs appropriate responses to new situations and the social actions of others.

3. Asociality is a profound disturbance of normal social attachment and interdependence with others. Social interest and bonding motivation are minimal or lack- ing altogether.

4. Extended selective attention is an overextended at- tentional focus and inordinate delay in shifting atten- tion, resulting in a variety of inappropriate responses such as hypersensitivity to sensory input and persever- ative behaviors.

Waterhouse and coworkers (1996) link each of the aforementioned neurofunctional impairments to rela- tively distinct neural regions and circuitry. That is, dys- function of the hippocampus and amygdala of the tem- poral lobes produces canalesthesia and the impaired assignment of affective significance, respectively. Asocial- ity relates to the aberrant functioning of three interrelated neurochemical systems: oxytocin and vasopressin neuropep- tide, endogenous opiate, and serotonin. Finally, the re- searchers consider extended selective attention to relate to a disruption of the temporal and parietal association areas. Although each of these supporting neural regions and cir- cuitry links to specific broad functions, they interact and overlap to produce the deficits that the child with autism displays. Interestingly, Waterhouse and coworkers view brainstem, cerebellum, and frontal lobe damage—all of which other researchers and theorists have considered of eti- ologic significance in autism—as only secondary causes or by-products of aberrant input from other neural systems.

An impressive body of supporting research based on neuroimaging, electrophysiology, neuropathology, and animal studies supports the four neurofunctional impair- ments as pathogenic of autism. An individual with autism can present all four of these impairments. However, some individuals present three or fewer impaired neurofunc- tional systems. In such cases, the number and form of the symptoms exhibited relate to damage to the individual system or group of systems. For example, if damage is re- stricted to the oxytocin-opiate system, the model predicts that most of the autistic symptoms will be absent, except

320 PART THREE | Disorders of the Brain

for those behaviors associated with disrupted social at- tachment and lack of affiliation with others. Although the validity and utility of the comprehensive model re- quires further empirical verification, it represents a bold effort to integrate the theories and empirical findings of autism.

D e v e l o p m e n t a l C o u r s e

Autism is a chronic, lifelong disorder that parents and pro- fessionals generally detect before the child reaches age 3. A number of distinguishing characteristics appear as the child with autism develops, although individual differ- ences are evident. In infancy, the baby with autism may be passive and unresponsive to being held and cuddled. Social or interactive behaviors directed to the infant by caretakers often fail to elicit recognition or interest.

As the child with autism moves into the toddler and preschool years, the onset of speech and language is often delayed or may fail to develop altogether. Moreover, as language develops, echolalia, reversed pronouns, and ne- ologisms may emerge. Self-help skills lag in development. The child with autism is less likely than healthy children to imitate the gestures or vocalizations of adults (Sigman, 1994; Tanguay, 2000) and has only a limited desire or ability to communicate with others.

The play of the child with autism lacks sophistication in both structured and unstructured situations. The de- velopmental stages of parallel and cooperative play are de- layed or not attained at all. Stereotypic motor behaviors, unusual interests or preoccupations, demands for order and sameness, and other peculiar behaviors may domi- nate the child’s daily activities. Unusual reactions, such as hypersensitivity to specific environmental stimuli (such as noise) or advanced abilities or skills (such as hyperlexia), may also be apparent.

During the toddler and early preschool years, the par- ents begin to realize their child is not developing appropri- ately. Professional services are typically sought, and the child is involved in a series of medical, psychological, speech, language, and related evaluations. At this point, there is a rendering of the diagnosis of autism for the first time, and comorbid conditions, such as mental retar- dation, are identified. Subsequently, the parents often enter the child into a preschool special education or treat- ment program with supportive services.

Autistic behavioral excesses and deficits continue to be evident during the child’s elementary school years. How- ever, as discussed earlier, improvement across behavioral domains begin to be evident with increasing age, particu- larly for the higher functioning child with autism. Despite

this improvement, the child remains developmentally de- layed and continues to exhibit unusual behavioral pat- terns. Many of these children cannot enter a normal edu- cational program. Academic achievement is variable and poor, particularly if cognitive or intellectual deficits are pronounced. Peer interactions are minimal, and most children with autism never develop a close friendship.

Continued improvement may be evident with the ad- vent of adolescence, particularly for the higher function- ing child with autism. However, most individuals with autism continue to exhibit deficits in one or more of the core impairment areas, and unfortunately, some teenagers with autism regress (Piven, Harper, Palmer, & Arndt, 1996). Low-functioning adolescents with autism often need continued training in the more basic life skills and placement in a program, such as a sheltered workshop, that emphasizes the development of rudimentary voca- tional skills. Higher functioning teenagers with autism, despite relative success in academics, lack social accep- tance by peers because of their ongoing deficits in social- ization and communication and their unusual interests and patterns of behavior.

Approximately 80% of individuals with autism are un- able to move fully into the workforce, and up to half re- quire lifelong residential care (Pennington, 1991). Others can function effectively in a sheltered workshop or higher level of employment if the work environment is support- ive. Higher functioning individuals may be capable of life in a group home or other assisted living program in the community. Only about one-third are able to live inde- pendently.

T r e a t m e n t

Currently, the most significant treatments for autism and other pervasive developmental disorders include behav- ioral interventions, special education, and occasionally, pharmacotherapy. Despite early intervention and applica- tion of currently available treatment options, autistic and related disorders generally do not fully resolve.

Caretakers generally use behavior modification as an intervention in an autistic child’s comprehensive treat- ment program. Several investigators consider behavior modification one of the more effective treatment options for children with autism. Generally, the use of behavioral interventions involves a functional analysis of targeted be- haviors to determine the relation of environmental an- tecedents and consequences to the child’s behavior. Using this analysis, psychologists develop a behavioral plan to generate behaviors (such as social skills), strengthen appro- priate actions (such as increased eye contact), and reduce

CHAPTER 11 | Learning and Neuropsychiatric Disorders of Childhood 321

or eliminate maladaptive behaviors (such as aggression or self-injury). Caretakers use both rewarding and aversive behavior interventions to bring about desired change. Positive reinforcement and token systems are two exam- ples of rewarding interventions used to produce or strengthen target behaviors. Aversive behavioral tech- niques incorporate the use of corrective feedback, time- out, response cost, and overcorrection to reduce inappro- priate behaviors. Response cost involves the loss of a reinforcer contingent on the child demonstrating an in- appropriate behavior, whereas overcorrection involves having the child practice a positive response that is in- compatible with an inappropriate behavior. Overcorrec- tion is particularly effective in reducing self-stimulating behaviors, such as repetitive mouthing of objects.

Insofar as deficits in language and communication skills are often dramatic, initial treatment efforts focused on increasing language acquisition and production. That is, the interventions centered on prompting speech and reinforcing the child’s verbalizations. Although verbaliza- tions increased, the child’s actual ability to communicate did not necessarily improve. The realization that verbal production does not equate with communication has prompted a shift in treatment focus to increasing the child’s spontaneous, communicative language. Moreover, social skills training is receiving increased attention as a treatment modality. These interventions target one of the central deficits of autism, the impaired ability to relate to others. Finally, some children with autism benefit from pharmacologic interventions to reduce self-injurious behav- iors, hyperactivity, ritualistic behaviors, and aggressiveness. However, a number of the medications (such as haloperi- dol [Haldol]) require careful monitoring for potentially serious side effects. The advent of atypical antipsychotic medications (for example, risperidone [Risperdal]) is receiving support for treating severe behavioral distur- bances, significant agitation, and self-injurious or stereotypic behaviors (McDougle et al., 2000). Simi- larly, selective serotonin reuptake inhibitors (for exam- ple, fluoxetine hydrochloride [Prozac]) are efficacious in treating compulsive, stereotypic behaviors and aggression.

In summary, children with autism frequently require special educational services tailored to their individual learning, social, and adaptive needs. In addition to acade- mic and daily living skills, many require ancillary services such as speech, language, and physical therapy. Vocational training and supervised job placement, often in a shel- tered workshop environment, provide meaningful em- ployment and the opportunity for social and recreational activities for individuals with autism.

Disruptive Behavioral Disorders

The APA (1994) currently classifies disruptive or ex- ternalizing behavioral disorders as psychiatric disorders. These disorders feature a variety of poorly controlled or acting-out behaviors that are developmentally inappropriate or violate societal dictates for acceptable behavior. The three primary representatives of this category are ADHD, opposi- tional defiant disorder (ODD), and conduct disorder (CD). As a developmental disorder, ADHD has generated an enor- mous number of theoretical and empirical studies since the mid-1980s. It is to this disorder, the most prevalent of child- hood disruptive disorders, that we turn our attention next.

A T T E N T I O N - D E F I C I T/H Y P E R A C T I V I T Y D I S O R D E R

C l i n i c a l B a c k g r o u n d a n d P r e s e n t a t i o n

The clinical manifestations of children exhibiting an attention-deficit/hyperactivity disorder (ADHD) are variable, although clinicians generally agree that the core symptom patterns include age-inappropriate inattention, impulsivity, and hyperactivity. These symptom patterns are chronic, cross situational in presentation, and devel- opmental in origin (APA, 1994). Thus, the behavioral symptoms of ADHD are not transient in presentation and generally continue into adolescence and adulthood. Furthermore, these symptoms are typically observed be- fore school age and across multiple contexts such as home, school, and the community.

Since its inception in 1980, the diagnosis of ADHD has undergone several revisions (Table 11.5). These revi- sions involve introducing different diagnostic models, changing exclusionary criteria, and delineating specific subtypes. Despite these modifications, the diagnosis re- tains the core symptoms of inattention, impulsivity, and hyperactivity, although the combinations, relations, and definitions of these symptom patterns have altered.

D e m o g r a p h i c a n d C o m o r b i d C o n d i t i o n s

Currently, ADHD accounts for a third to half of all child- hood referrals for psychological services (Richters et al., 1995). Prevalence rates of 3% to 9% for childhood popula- tions are commonly cited (Spencer, 2002). The breakdown of ADHD figures by sex reveals that boys, compared with girls, are more frequently diagnosed as exhibiting ADHD, with cited ratios ranging from 3 : 1 to 9 : 1 (Pennington, 1997a). However, some researchers suggest that girls are

322 PART THREE | Disorders of the Brain

DSM Symptom Presentation

DSM-III (1980)

Attention-deficit with Inattention, impulsivity, hyperactivity and hyperactivity

Attention-deficit without Inattention and impulsivity hyperactivity

DSM-III-R (1987)

Attention-deficit/ Inattention, impulsivity, hyperactivity disorder and hyperactivity

Undifferentiated attention Inattention deficit disorder

DSM-IV (1994)

Attention-deficit/hyperactivity Inattention, impulsivity, disorder—combined type and hyperactivity

Attention-deficit/hyperactivity Inattention disorder—inattentive type

Attention-deficit/hyperactivity Impulsivity and hyperactivity disorder—impulsive-hyperactive type

DSM-III � Diagnostic and Statistical Manual of Mental Disorders, Third Edition; DSM-III-R � Diagnostic and Statistical Manual of Mental Disorders, Third Edition, Revised; DSM-IV � Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition. Reprinted with permission from the Diagnostic and Statistical Manual of Mental Disorders, Four th Edition. Text Revision, Copyright 2000, American Psychiatric Association.

under-represented, partly because of the greater likelihood that boys will present with higher levels of overactivity and aggressive behaviors that quickly draw the attention of caretakers. Although a childhood disorder, 30% to 60% of diagnosed children continue to exhibit symptoms of ADHD in adulthood (Sheppard, Bradshaw, Purcell, & Pantelis, 1999). Currently, increased focus has been on the identification and treatment of adults with ADHD.

There is a growing recognition that ADHD frequently coexists with other psychiatric and psychological disor- ders. ODD and CD are the most prevalent comorbid con- ditions of ADHD, with reported rates of occurrence rang- ing from 40% to 65% (Barkley, 1990; Wilens et al., 2002). ODD is characterized by chronic, age-inappropriate, angry mood and resistant, stubborn behaviors, and CD involves the repeated violations of the rights of others or of societal norms. Assaultive behaviors and illicit drug use are examples of the types of violations CD children ex- hibit. The basis for the high rates of comorbidity of ODD/CD with ADHD is unclear. However, evidence suggests that social factors such as family sociopathy,

rather than genetic determinants, are contributors to the pathogenesis of these disorders.

ADHD also covaries with anxiety and depressive dis- orders at rates ranging from 18% to 51%, depending on the childhood population sampled for study (Eiraldi, Power, & Nezu, 1997; Jensen, Martin, & Cantwell, 1997; Wilens et al., 2002). Estimates of the rate of comorbidity of ADHD and Gilles de la Tourette disorder range from 25% to 50% (Cirino, Chapieski, & Massman, 2000). Fi- nally, from 15% to 20% of children with ADHD also ex- hibit learning disabilities (Richters et al., 1995). The high rates of comorbidity have led to speculation that ADHD is one disorder within a spectrum of related disorders.

N e u r o p s y c h o l o g i c a l P a t h o g e n e s i s

Neuropsychologists consider ADHD a neurobiologically based developmental disorder that responds to specific types of environmental and pharmacologic interventions. However, the etiology of ADHD is currently unknown. We review areas of investigation that are expanding our knowledge of the pathogenesis and symptoms of ADHD.

Familial and Genetic Influence—Accumulating evidence suggests that ADHD is a familial disorder, possibly inheritable. The familial nature of the disorder is clear from the elevated rates of ADHD in first- and second-degree relatives. The presence of familial ADHD does not necessarily signal that the disor- der is genetically determined because little is known of the psychosocial environmental transmission of ADHD across generations. The finding of significant parental discord and psychopathology in families of children with ADHD sug- gests that environmental factors may be of causative signifi- cance. However, the high rate of concordance of ADHD for identical twins and the discovery of a potential linkage be- tween ADHD and genetic markers tips the balance in the direction of a genetic component as the primary determi- nant of the disorder. Regarding the latter, researchers have linked a thyroid gene to a narrow subgroup of children with ADHD (Hauser et al., 1993) and have also identified a rela- tion between ADHD and a number of gene variants.

The D4 receptor gene on chromosome 11 has been implicated in the etiology of ADHD (Holmes et al., 2000; Smalley et al., 1998). One variant of the D4 gene, the 7-repeat allele (a segment of the DNA is repeated seven times), has been associated with the personality trait of “novelty seeking” or “thrill seeking,” a characteristic often evident in children with ADHD. Several studies have found that children with ADHD are more likely to have the 7-repeat allele than healthy children. However, only 25% to 30% of children with ADHD carry the 7-repeat

CHAPTER 11 | Learning and Neuropsychiatric Disorders of Childhood 323

Table 11.5 Changing Attention-Deficit/ Hyperactivity Disorder Criteria

allele, indicating that the gene is neither necessary nor suf- ficient to produce the disorder (Barr, 2001; Pliszka, 2003).

The dopamine transporter gene (DAT1), located on chromosome 5, governs the reuptake of dopamine into the neuron. The presence of one variant of the DAT1, 10-repeat (segment of DNA repeated 10 times) allele, is as- sociated with greater risk for ADHD (Daly, Hawi, Fitzger- ald, & Gill, 1999; Waldman et al., 1998). The genetic re- search with “knockout” mice that examines the relation of the DAT1 gene to behavior is of interest. Knockout mice are bred without selected genes to study the effects of muta- tions and other genetic alterations. Investigations of knock- out mice without the (DAT1) gene reveal that the animals demonstrate hyperactivity, poor spatial performance, and other behaviors suggestive of disrupted inhibitory control. When administered a psychostimulant medication (for ex- ample, methylphenidate [Ritalin]), the mice showed a calm- ing response, similar to that evident with medicated chil- dren with ADHD (Gainetdinov & Caron, 2001).

Other genes implicated in ADHD are the dopamine receptor D5, catechol O-methyltransferase (COMT; codes for the enzyme that catalyzes the breakdown of dopamine and norepinephrine), and monoamine oxi- dase (MAO; codes for the enzyme that breaks down dopamine and norepinephrine after reuptake into the neuron). However, there are both confirmatory and con- tradictory studies regarding the association of the dopamine receptor (D5 ), COMT, MAO, and other genes with ADHD (Pliszka, 2003), indicating the need for further research to clarify and expand our knowledge of the role of genetics in the pathogenesis of ADHD.

Neural Substrates—Numerous neural substrates have been implicated in the etiology and neuropsychological man- ifestations of ADHD, including most major cortical and subcortical systems, regions, and axes of the brain. Currently, four cortical-subcortical brain regions are the focus of study. The first relates to possible abnormali- ties in the structure of the corpus callosum. Such anom- alies are believed to disrupt the transmission of impulses between the cerebral hemispheres, thereby interfering with the communication necessary for integrated be- havioral control. However, neuroimaging studies of the genu (anterior portion) and splenium (posterior por- tion) of the corpus callosum of children with ADHD have produced inconsistent results, with subjects dis- playing anatomic differences in both regions, in only one region, or in neither region, relative to healthy con- trol children (Hynd, Semrud-Clikeman, Lorys, Novey, & Eliopulos, 1991; Giedd et al., 1994; Semrud- Clikeman et al., 1994).

The second neural substrate considered of pathologic significance for ADHD is the frontal lobes. The parallel between the symptom patterns of patients with acquired frontal lobe damage and those of children with ADHD has fostered speculation that disruption of the frontal lobes may contribute to the etiology of the latter disorder (Bensen, 1991). Neuroimaging investigations have pro- vided some support for this speculation. The majority of these investigations (Castellanos et al., 1994; Filipek, Semrud-Clikeman, Steingard, Renshaw, Kennedy, & Biederman, 1997; Hynd et al., 1990) have found a lack of normal asymmetry (R � L) in the frontal lobes of chil- dren exhibiting ADHD, with the right prefrontal region being anatomically smaller and, therefore, symmetric with the left prefrontal lobe (R � L). In addition, there are in- dications that both left and right frontal lobes may be smaller for groups with ADHD relative to those without the disorder (Sowell et al., 2004). The frontal lobes con- tribute to the control of attentional functioning, and the finding of atypical symmetry and volume suggests a relation to ADHD. However, studies have not always replicated these findings of structural differences, nor have they deter- mined that differences in symmetry of the prefrontal lobes are specific to ADHD. For example, Hynd and colleagues (1990) have also identified atypical symmetry (R = L) of the prefrontal lobes in children exhibiting dyslexia.

Studies of cerebral blood flow within the frontal lobes have revealed differences between individuals with ADHD and healthy volunteers. Zametkin and coworkers (1990), in a PET study of adults with ADHD, discovered that the participants exhibited hypofrontality in glucose use/cere- bral blood flow. Hypofrontality can reflect a disruption in executive inhibitory control of behavior. However, subsequent studies of children and adolescents with ADHD have not consistently replicated these findings, particularly when contrasting male and female adoles- cents (Ernst, Cohen, Liebenauer, Jons, & Zametkin, 1997; Ernst, Liebenauer, Jons, & Zametkin, 1994; Zametkin et al., 1993).

Recently, a preliminary proton magnetic resonance spectroscopy (1H-MRS) and MRI study (Yeo et al., 2003) of children with ADHD and healthy control children ex- amined the relation of neurometabolite concentration, frontal volume, and attentional performance. For healthy control children, a significant relation between neu- rometabolite concentration, frontal volume, and atten- tional performance was not evident; however, a signifi- cant relation was evident for those children with ADHD. Specifically, concentration levels of Cre (sum of intracel- lular creatine and phosphocreatine indexing cellular energy metabolism) and N-acetylaspartate (a marker of neuronal

324 PART THREE | Disorders of the Brain

viability) correlated with right dorsolateral volume and poorer performance on a measure of sustained attention for children with ADHD. These findings contribute to the growing body of evidence that ADHD is associated with atypical neurobiology at the cellular level. Clearly, further investigations are needed to verify the findings of this study and to clarify the relation of atypical metabolic activity to attentional functioning, and possibly other cognitive processes associated with ADHD.

The third focus of study asks, “How significant is dis- ruption of the frontal-basal ganglia circuitry to the cause of ADHD?” The basal ganglia are subcortical nuclei em- bedded below the frontal lobes. The prefrontal lobes send projections to the basal ganglia (caudate, putamen, globus pallidus, and nucleus accumbens) that, in turn, direct pro- jections back to the prefrontal lobes via thalamic nuclei, forming neural circuits. Figure 11.4 portrays the frontal- basal ganglia circuitry involved in mediating higher order behavior. These frontostriatal pathways have been the focus of attention in the study of ADHD.

Early investigations suggest that the basal ganglia are primarily involved in motor control (Denckla & Reiss, 1997). Increasingly, investigators are realizing that the basal ganglia may play a role in cognitive func- tioning, although the precise nature of this role remains unclear. Neuroscientists have posed many and varied speculations as to the cognitive role of the basal ganglia, with most suggesting an inhibitory function that parallels or serves to augment executive control of the frontal lobes.

Neuroimaging of the frontostriatal circuitry of chil- dren with ADHD has identified decreased cerebral blood flow or other abnormalities of metabolism in sev- eral of the basal ganglia nuclei (Castellanos, 1997; Zang et al., 2005). For instance, adolescent boys with ADHD were scanned (fMRI) while performing a measure of re- sponse inhibition. Relative to healthy control partici- pants, the ADHD group showed less brain activation of the right inferior frontal lobe and left caudate nucleus in performing the inhibitory measure (Rubia et al., 1999). Different striatal nuclei have been associated with decreased activation, with most being specific to the right hemisphere. Similarly, there is evidence of a reduction in the size of basal ganglia nuclei in individu- als with ADHD (Aylward, Reiss, Reader, Singer, Brown, & Denckla, 1996; Faraone & Biederman, 2004). Unfortunately, inconsistent findings exist regard- ing whether volumetric differences are specific to the right or left hemisphere (Casey et al., 1997; Castellanos et al., 1994, 1996; Hynd et al., 1993) or whether hy- poactivation or hyperactivation of frontostriatal struc- tures characterize children with ADHD (Schultz et al., 2005). Finally, psychostimulant medication known to significantly reduce the core symptoms of ADHD can increase, or normalize the blood perfusion of the basal ganglia (Teicher, Polcari, Anderson, Andersen, Glod, & Renshaw, 1996), providing additional evi- dence for the involvement of these nuclei in the etiol- ogy of ADHD.

Finally, morphologic differences in the cerebellum are implicated in the pathogenesis of ADHD. Structural neu- roimaging reveals smaller volume of the cerebellar hemi- spheres, particularly the posterior vermis lobules, for children with ADHD (Hill, Yeo, Campbell, Blaine, Vigil, & Brooks, 2003). However, the specific lobules or the proportion of volume found to be reduced differs across studies (Castellanos et al., 2001; Mostofsky, Reiss, Lockhart, & Denckla, 1998). It has been speculated that the cerebel- lum supports motor control, inhibition, temporal pro- cessing, attention, and executive functions (Giedd, Blumenthal, Mollowy, & Castellanos, 2001; Halpern & Schulz, 2006).

Overall, support is growing for anomalies in the frontal-striatal-cerebellar regions and circuitry in the pathogenesis of ADHD. Although the frontostriatal cir- cuits are implicated in the inhibition, selection, initia- tion, and execution of complex motor and cognitive re- sponses, and cerebellar circuits provide ongoing guidance of activated programs (Giedd et al., 2001), the precise role of these neurosubstrates in ADHD remains to be specified.

CHAPTER 11 | Learning and Neuropsychiatric Disorders of Childhood 325

Figure 11.4 Three of the frontal-basal ganglia circuits involved in the mediation of higher order behavior. MD = mediodorsal; VA = ventral anterior. (From D. G. Lichter and J. L. Cummings, “Introduction and Overview,” in D. G. Lichter and J. L. Cummings, eds., Frontal-subcortical Circuits in Psychiatric and Neurological Disorders, New York: The Guilford Press, 2001, p. 6, Figure 1. 2. Reprinted by permission of the American Medical Association.)

Thalamus (VA and MD)

Globus Pallidus (Lateral

Dorsomedial)

Caudate (Dorsolateral)

Dorsolateral Prefrontal Cortex

Thalamus (MD)

Globus Pallidus (Rostrolateral)

Nucleus Accumbens

Anterior Cingulate Cortex

Thalamus (VA and MD)

Globus Pallidus (Medial

Dorsomedial)

Caudate (Ventromedial)

Lateral Orbitofrontal

Cortex

N e u r o p s y c h o l o g i c a l A s s e s s m e n t

The heterogeneity of children diagnosed with ADHD; the failure to delineate sensitive, specific, and verifiable neuropsychological markers of the disorder; and the in- ability to identify the underlying pathogenesis of the dis- order have hampered assessment. This state of affairs has resulted in a diagnosis by exclusion. That is, clinicians must first rule out all other disorders that could account for the child’s inattentive, impulsive, and overactive be- haviors before they can diagnose ADHD. This process be- comes even more muddled when the child identified as ADHD exhibits comorbid psychological disorders such as ODD.

An assessment to determine whether a child is display- ing ADHD warrants the integration of information drawn from developmental data and school records; sys- tematic interviews with the parent, child, and other sig- nificant adults; behavioral observations and rating scales completed by the parent, teacher, and child; and a com- prehensive battery of neuropsychological measures. Often, a team approach enables professionals from a vari- ety of disciplines (for example, neuropsychologist, physi- cian, social worker, and educators) to answer specific questions concerning the child’s functioning.

Executive Function—The current focus on frontostriatal dys- function as a cause of ADHD has prompted efforts to as- sess the executive functions attributable to these neural circuits. Investigators have found that children with ADHD perform in a differential manner on measures of executive function (see Chapter 9). Pennington and Ozonoff (1996) have reviewed 18 studies that sought to assess the executive functions of children with ADHD. Table 11.6 lists the executive measures that most markedly and consistently differentiated children exhibit- ing ADHD from healthy control children. Of these mea- sures, the Tower of Hanoi (TOH) was the most sensitive to ADHD. The TOH is a complex measure that assesses exec- utive planning, working memory, and inhibitory control.

Researchers report executive deficits for a variety of disorders, including Turner’s syndrome, fragile X, autism, phenylketonuria (PKU, a genetic metabolic disorder), and Gilles de la Tourette’s syndrome. Thus, impairment of ex- ecutive performance may be a common impairment of developmental disorders. This does not, however, rule out the possibility that a specific executive function (such as cognitive flexibility) or set of executive functions (such as planning and working memory) may be unique to ADHD. Several investigators (Barkley, 1998; Pennington, 1997b) have proposed that a deficit of inhibitory control may be central to ADHD.

To familiarize the student with the neuropsychological assessment of ADHD, Neuropsychology in Action 11.3 provides a case study. As will soon become evident, the case study demonstrates significant impairments in several executive functions that have been implicated in ADHD.

N e u r o p s y c h o l o g i c a l M o d e l s

Several neuropsychological models of attentional func- tioning have evolved that are relevant to the understand- ing and treatment of ADHD. The following sections pro- vide brief reviews of the representative models of Allan Mirsky (1995, 1996), Michael Posner (1992; Fernandez- Duque & Posner, 2001), and Russell Barkley (1997a, 1997b, 1997c).

Mirsky’s Model and Attention-Deficit/Hyperactivity Disorder—As discussed in Chapter 9, Allen Mirsky (National Institute of Mental Health, Bethesda, MD) provides an empirically derived neuropsychological model that identifies five el- ements of attention, and he relates these elements to neuropsychological measures and underlying neural sys- tems. The five elements of attention are focus-execute (se- lective attention and rapid perceptual-motor output),

326 PART THREE | Disorders of the Brain

Measures Consistency† Average d

WCST perseverations 4/10 0.45

TMT B time 4/6 0.75

MFFT

_Time 4/6 0.44

_Errors 5/5 0.87

Stroop Test time 4/5 0.69

Mazes 3/4 0.43

TOH 3/3 1.08

Motor inhibition tasks 6/6 0.85

†Number of studies finding a significant group difference divided by the number of studies using the measure.

WCST = Wisconsin Card Sorting Test (Heaton, 1981); TMT B = Trail Making Test B (Reitan & Davison, 1974); MFFT = Matching Familiar Figure Test (Kagan, 1964); Stroop Test (Golden, 1978); TOH = Tower of Hanoi (Welsh, 1991).

Source: Pennington, B., & Ozonoff, S. (1996). Executive functions and developmental psychopathology. Journal of Child Psychology & Psychiatry, 37, 63, by permission of Cambridge University Press.

Table 11.6 Consistency of Differences and Average Effect Size of Executive Measures in Attention- Deficit/ Hyperactivity Disorder

shift (attentional flexibility), sustain (vigilance and persis- tence of attention), encode (working memory), and stable (consistence of attentional effort). The five components constitute an attentional system that is widely distributed throughout the brain. Accordingly, the system is quite vulnerable to disruption after brain injury; yet, it is also resilient. A specific attentional function may be compro- mised by injury, but undamaged neural regions may pro- vide some degree of compensation.

Support for the utility of the model for identifying and understanding the attentional processing of children with ADHD is emerging. In an early study (Lowther & Wasserman, 1994), a battery of attentional measures se- lected to represent each element of attention was adminis- tered to children with ADHD and healthy control chil- dren. Each element of attention differentiated ADHD and healthy children and correctly predicted group membership

with 91% accuracy. Recently, Kunin-Batson and associ- ates (2002), in a double-blind, placebo–control study of children, determined that the introduction of psychos- timulant medication significantly augmented the “sus- tain” and “stable” components of attentional functioning, but not the “focus-execute” or “encode” elements of at- tention. Measures of the “shift” attentional component were not included for study in the investigation. Finally, as reviewed later, clinical childhood groups demonstrate differential patterns of performance on measures sensitive to Mirsky’s components of attention and the attentional processes that Michael Posner poses.

Posner’s Model and Attention-Deficit/Hyperactivity Disorder—As discussed in Chapter 9, Michael Posner has developed a model of attention from the perspective of cognitive psy- chology and neuroscience. He hypothesizes that ADHD

CHAPTER 11 | Learning and Neuropsychiatric Disorders of Childhood 327

B.C. is a 10-year-old boy with a history of school and home difficulties. His parents and regular class teacher were concerned about his inconsistent academic perfor- mance and poor behavioral control. The teacher reported that B.C. frequently failed to complete his assignments, appeared distracted, failed to follow directions, and rarely checked his work. Furthermore, he was prone to call out in class, leave his seat, walk about the room, and squirm when required to remain seated. Despite his classroom difficulties, his group achievement test scores demonstrated average to above- average skill development.

At home, he was “always on the go,” could not sit quietly unless playing with building blocks, and rushed when complet- ing chores or homework. It was difficult for B.C. to initiate or focus on his homework unless a parent sat with him to guide his efforts. His ability to plan and organize activities (for example, picking up his toys, organizing game activities with friends, and so forth) was described as very poor. Despite his behavioral difficulties, he was character-

ized as a gentle child who was rarely aggres- sive or noncompliant.

Neuropsychological Findings Behavioral rating scales were completed by the teacher and parents regarding B.C.’s behavior. These ratings showed very high rates of inattention, impulsivity, and hyperactivity. Formal neuropsychological results revealed that B.C. was functioning within the average range of intelligence. Verbal and performance intelligence were both comparably developed in the average range. Relative weaknesses were evident on subtests sensitive to atten- tional weaknesses. His memory performance was age appropriate. However, he demon- strated very poor sustained attention and high rates of impulsivity on auditory and visual measures of continuous performance. Relat- edly, he performed poorly on measures sensitive to selective attention and response inhibition, goal persistence and impulse control, and cognitive flexibility.

B.C. manifested very poor executive planning on the Tower of London-Drexel University test (TOLDX) (Culbertson & Zillmer,

1998a, 1998b, 2005) relative to the perfor- mance of his peers. His planning attempts were quick, without adequate forethought or reflection. From a qualitative perspective, his problem-solving approach was impulsive, rigid, and comparable with that of a much younger child.

The integration of the developmental, rating, and neuropsychological findings supported the diagnosis of an attention- deficit/hyperactivity disorder–combined type. The neuropsychologist developed behavioral interventions with B.C.’s teacher and family. These interventions focused on B.C.’s inat- tention, impulsivity, hyperactivity, and plan- ning deficits. Although he was responsive to behavioral interventions, his behavioral disinhibition remained high. Accordingly, the neuropsychologist sought a medical consul- tation to determine the feasibility of stimulant therapy. Stimulant medication was intro- duced and gradually titrated to therapeutic levels. A significant additive effect (behav- ioral interventions and medication) was evident, with attention, impulse, and activity control showing marked improvement.

N e u r o p s y c h o l o g y i n A c t i o n 1 1 . 3

C a s e S t u d y o f a C h i l d w i t h a n A t t e n t i o n - D e f i c i t / H y p e r a c t i v i t y D i s o r d e r

by William C. Culbertson

may result from disruption of the vigilance attention system, insofar as children with ADHD are impaired in their abil- ity to maintain attention over time. The study revealed that children with ADHD showed deficits, relative to healthy control children, on measures sensitive to the functioning of the vigilance and anterior attention system (Pearson, Yaffee, Loveland, & Norton, 1995; Swanson et al., 1991). Thus, disruption of both the vigilance and anterior attentional sys- tems may play a key role in the etiology of ADHD.

The utility of Posner’s model was recently examined in a study (Brewer, Fletcher, Hiscock, & Davidson, 2001) of three groups of children (ADHD, congenital hydro- cephalus, and healthy control children). The children were presented with measures sensitive to attentional focus, maintenance, and shifting. Furthermore, the mea- sures allowed for the separation of the disengage, move, and engage processes of Posner’s model of attention. Rel- ative to the control group, the children with hydro- cephalus demonstrated deficits in focusing and shifting attention, whereas the children with ADHD were im- paired in sustaining and shifting attention. The difficul- ties of the hydrocephalus groups with focusing and shift- ing attention were related to impairments of disengaging and moving the focus of their attention. These impair- ments are consistent with disruption of the posterior at- tention system. In contrast, the shifting difficulties of the ADHD group reflected preservative errors consistent with anterior system involvement. Likewise, poor sustained at- tention implicates impairment of the vigilance and anterior systems. The findings of greater posterior versus anterior attentional dysfunction in the congenital hydrocephalus and ADHD groups correlate with the neuroanatomic and neurofunctional differences identified for the two groups.

Recently, Swanson and colleagues (2000) have pro- posed a tentative model linking the symptoms of ADHD delineated in the DSM-IV (APA, 1994) to the cognitive processes and neural circuits that Posner pro- posed (Table 11.7). Different symptoms of inattention reflect disruptions to the alerting and orienting processes supported primarily by the right frontal and posterior parietal neural networks. Alerting symptoms relate to deficits in persistence of attention (sustained) and vigi- lance, whereas orienting symptoms define deficits of se- lective attention. The hyperactivity-impulsive symptoms are linked to perturbations of the executive control processes underpinned by the anterior cingulate region of the brain. Although the neural circuits are relatively dis- tinct, they interact and overlap in their support of the complex behavioral manifestations associated with ADHD. When considering the distribution of the neural

networks implicated in ADHD, damage within or be- tween networks could produce variability in the symp- tom presentation of children with the disorder. In fact, significant variability exists in the symptoms demon- strated by children with ADHD, and the proposed model may help clarify and further specify the behav- ioral manifestations of this disorder. We await the clinical and empirical application of the model.

Barkley’s Model of Attention-Def icit/Hyperactivity Disor der— Russell Barkley (1997a,b,c) proposes a three-tiered execu- tive model of ADHD (Figure 11.5). The first tier, behav- ioral inhibition, is central to the model. Behavioral inhibition involves three inter-related processes: (1) the in- hibition of a prepotent response, (2) stopping an ongoing response, and (3) protecting an ongoing mental operation from disruption by competing external or internal events (interference control). These inhibitory processes are nec- essary for the effective operation of the four executive func- tions of tier 2: working memory; internalization of speech; regulation of arousal, emotions, and motivation; and re- constitution (recombining behavioral elements to create

328 PART THREE | Disorders of the Brain

Symptom Domains Cognitive Processes Neural Networks

Inattentive Alerting Frontal

Difficulty sustaining attention Right frontal cortex

Fails to finish Right posterior parietal

Avoids sustained efforts Locus ceruleus

Inattentive Orienting Posterior Parietal

Distracted by stimuli Bilateral parietal

Does not appear to listen Superior colliculus

Fails to pay close attention Thalamus

Hyperactive-Impulsive Executive control Anterior cingulate

Blurts out answers Anterior cingulate

Interrupts or intrudes Left lateral frontal

Cannot wait Basal ganglia

Source: Adapted from Swanson, J., Posner, M., Cantwell, D., Wigal, S., Crinella, F., Filipek, P., Emerson, J., Tuciker, D., & Nalcioglu, O. (2000). Attention-deficit/ hyperactivity disorder: Symptom domains, cognitive processes and neural networks. In R. Parasuraman (Ed.), The attentive brain (p. 455, Table 20.2). Cambridge, MA: The MIT Press, by permission.

Table 11.7 Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Attention-Deficit/ Hyperactivity Disorder Symptoms, Cognitive Processes, and Neural Networks

new behaviors). Tier 2 functions, in turn, affect the con- trol, organization, and flexibility of the behavioral output of tier 3. Although the brain as a whole supports these processes, the prefrontal and frontal cortices are primarily responsible for the inhibitory and executive processes.

When inhibitory and executive processes are intact, the child develops the capacity to regulate behavior by using internal representations of events in thought and image. These internal representations enable the child to link past learning and experience with both present de- mands and future consequences of actions. Furthermore, the capacity to internally manipulate and guide behavior via internal representations allows for the regulation of emotion and motivation and the generation of new be- havioral patterns to augment goal-oriented behavior, par- ticularly when something thwarts intended actions. In ADHD, impaired inhibitory control processes disrupt the operation of the executive processes. The cascading effect of this impairment results in a host of behavioral excesses

and deficits, including poor impulse control, inattention, and hyperactivity.

Barkley’s model continues to spawn studies of in- hibitory control and executive function as they relate to ADHD. Support is amply evident for poor inhibitory control and executive functions deficits in ADHD popu- lations (Nigg, 2001; Purvis & Tannock, 2000), although the verification is stronger for inhibitory weaknesses than executive dysfunctions. Varieties of methodologic issues cloud recent efforts to determine the factors that account for differences in findings. A primary problem is the se- lection of developmentally appropriate tasks to assess ex- ecutive functions. Executive functions emerge at different points in childhood, continue to develop in a multistep manner, and reach final maturity in adolescence or early adulthood. Thus, the assessment of a specific executive skill requires a measure sensitive to the stage/level of mat- uration of that particular skill. For example, the ability to inhibit a motor response is more fully developed than

CHAPTER 11 | Learning and Neuropsychiatric Disorders of Childhood 329

Text not available due to copyright restrictions

interference control (shielding a cognitive operation from distracting, nonrelevant intrusions) during the early child- hood years. Interference control has a more contracted developmental trajectory that continues through the upper elementary years. Accordingly, comparing the per- formance of healthy preschool children with a group of children with ADHD on a measure of interference con- trol will likely show minimal differences, because neither group fully possesses the executive skills to perform the measure.

Recently, Berlin, Bohlin, Nyberg, and Janols (2004) presented children with ADHD and healthy control chil- dren (age 7–10 years) with a battery of developmentally appropriate measures of inhibitory control and executive function. The measures were selected to target the execu- tive domains articulated in Barkley’s model. The results revealed that the children with ADHD performed signifi- cantly poorer across the measures of inhibitory control and executive function, except for one, reconstitution. More importantly, when the measures that differentiated the two groups were combined for prediction (logistic regression), 86% of the children were correctly classified into their diagnostic groups. The sensitivity (probability that a child with ADHD would be correctly classified) and specificity (probability that a healthy child would be cor- rectly classified) rates were 81% and 88%, respectively. In addition, inhibition, working memory, and self-regulation were determined to be distinct predictors of group mem- bership. The latter finding indicates that the three execu- tive functions were each assessing a relatively unique set of abilities. Overall, the findings of the study are support- ive of Barkley’s model, but suggest that it be reduced to three major components: inhibition, working memory, and self-regulation.

D e v e l o p m e n t a l C o u r s e

As a developmental disorder, ADHD is evident early in childhood and, with maturation, shows changing symp- tom manifestations. In infancy, children displaying ADHD tend to be highly active, overly responsive to stim- ulation, quick to anger, and show low adaptability to change. During the toddler and preschooler years, chil- dren with ADHD are constantly “on the go,” seem “dri- ven by a motor,” continually manipulate objects, and shift across activities. Moreover, they constantly run and climb, often without apparent consideration for the consequences of their actions. Preschoolers exhibiting ADHD are at risk for accidental injury due to their inattention, impulsivity, and high activity levels. One 3-year-old, for example, was so inattentive and hyperactive that he ran into walls, doors, and other stationary objects on a daily basis!

In a preschool setting, children with ADHD often find it difficult to remain seated, fail to listen to or follow di- rections, become too excited when stimulated, and talk loudly and incessantly. Peers describe classmates with ADHD as bossy, uncooperative, and intrusive into their activities and games. The parents may be asked to remove their child from the preschool program if the child is also highly oppositional or aggressive. The traditional elemen- tary school environment is referred to as the “showplace” for ADHD. The demands of school highlight the regula- tory deficits of children with ADHD. Specifically, the fol- lowing school requirements all tax the controlling efforts of children displaying ADHD: (1) attention to work that can be boring, tedious, and effortful; (2) organization of assign- ments and belongings; (3) completion of work without rushing; (4) remaining seated for long periods; (5) adher- ence to multiple classroom rules; (6) reflection before re- sponding; (7) refraining from talking unless permitted; and (8) cooperation with others. It is during the elemen- tary school years that children with ADHD begin to avoid homework assignments, which inevitably leads to signifi- cant conflict with teachers and parents. Furthermore, peers often begin to move away from these children, find- ing their impulsivity, hyperactivity, and inattention to rules of behavior difficult to tolerate.

As children with ADHD enter middle and high school, their inability to meet the expectations for greater independence in managing the academic demands of multiple teachers leads to an ever-increasing sense of fail- ure and frustration. Perplexed, if not angry, teachers and parents continually confront these adolescents over their failure to live up to expected levels of academic perfor- mance. The normal adolescent strivings for independence and self-direction fuel resistance to parental offers of assistance or attempts to provide structure to the teenager’s studying and homework habits. Ongoing rejec- tion by peers, particularly if the adolescent is aggressive, often results in the teenager gravitating toward peers who are experiencing similar difficulties. Cumulatively, these negative experiences diminish the adolescent’s self-esteem and contribute to a growing realization that future educa- tional and vocational aspirations may be unattainable.

As adolescents who exhibit ADHD move into adult- hood, some show greater regulatory control and a related reduction or resolution of core symptoms of inattention, impulsivity, and hyperactivity. Unfortunately, a signifi- cant number of the adolescents (Weiss & Hechtman, 1993) continue to manifest the core or residual symptoms as they enter adulthood. Early failings in school, rejection by peers, and disappointed family members evolve into problems related to achieving success in work, marriage,

330 PART THREE | Disorders of the Brain

and family life. Not surprisingly, investigators report high rates of mood disorders, alcoholism, substance abuse, and antisocial personality disorders among adults with ADHD (Barkley, 1998). Adults with ADHD are gener- ally gainfully employed and self-sufficient, although they tend to have poorer work records and lower vocational status than their adult peers without ADHD. Clearly, many children and adolescents manifesting ADHD con- tinue to encounter adjustment difficulties in adulthood.

T r e a t m e n t

The treatment of children with ADHD warrants a com- prehensive, multimodal approach due to the multiplicity of deficits and difficulties that these children present. Each child presents a unique set of strengths and weak- nesses and, accordingly, warrants an individual treatment plan tailored to his or her individual needs. When target- ing the ADHD child’s needs, the core symptoms of inat- tention, impulsivity, and hyperactivity serve as the pri- mary point of intervention. These core symptoms, as they are manifested across contexts (family, educational, and social), expand and alter the specific treatment com- ponents. The presence of comorbid conditions (such as depression) further modifies the treatment interventions appropriate for the child. Typically, caretakers and teach- ers are involved in the process of implementing treatment interventions because of their key roles in engender- ing, exacerbating, or attenuating the child’s presenting symptoms.

The two primary and most successful interventions with ADHD are behavioral management and psy- chopharmacology. Behavioral management involves using learning principles to develop interventions to facilitate or inhibit behavior. Externally imposed interventions, such as token systems or response costs, appear more ef- fective for managing the child’s impulsivity, inattention, or overactivity than cognitive-behavioral interventions that focus on the child developing internal verbal self- control (Barkley, 1998).

Psychologists mold behavioral interventions to the spe- cific needs of the child in the home, school, and commu- nity. Such interventions frequently lead to significant pos- itive change in targeted ADHD core symptoms and coexisting emotional-behavioral difficulties. Unfortu- nately, this improvement in behavioral control does not often generalize beyond the specific context for which the interventions were developed. For example, the improve- ment in impulse control brought about by behavioral in- terventions in a classroom may not transfer to the home and community unless psychologists develop additional behavioral interventions for these contexts. A serious lim-

itation of behavioral management interventions is the rapid reappearance of the child’s core ADHD symptoms when the behavioral systems are faded out. In addition, it is difficult to implement behavioral management systems for older children and adolescents because they naturally resist external structuring and control.

Various psychopharmacologic interventions currently are available for treating ADHD. The psychostimulant medica- tions (namely, methylphenidate [Ritalin], methylphenidate hydrochloride [Concerta], amphetamine [Adderall], and dextroamphetamine sulfate [Dexedrine] are the most fre- quently prescribed medications for ADHD. If the child is presenting other comorbid disorders, the physician may introduce additional medications in combination with the psychostimulants. For example, a depressed child with ADHD may need an antidepressant medica- tion in conjunction with a psychostimulant medication. A relatively recent addition to the medication armamen- tarium of the physician is atomoxetine (Strattera). Atom- oxetine is a nonstimulant medication (norepinephrine reuptake inhibitor) that has been determined to signifi- cantly reduce the symptoms of ADHD (Weiss et al., 2005). It is a viable treatment option for children who are nonresponsive to or unable to tolerate psychostim- ulant medications.

Several factors prompt the use of medication. As noted earlier, behavioral improvement often does not generalize beyond the setting in which the training occurs. More- over, behavioral interventions may not fully manage the more seriously involved children who exhibit moderate to high levels of core symptoms. Finally, parents and educa- tors often find it difficult to use and maintain behavioral interventions unless the psychologist who develops the interventions closely supervises and supports them.

The behavioral improvements exhibited by children treated with psychostimulant medications can range from slight to dramatic. Psychostimulant medications have en- abled children with ADHD to remain in the regular class- room due to the substantial improvement in their behavioral control and academic achievement. Negative parent–child interactions frequently decline as a consequence of the child’s new ability to complete homework, follow home rules, and behave appropriately in public settings. Peers can often identify when a child is medicated because of notice- ably improved behavioral control, although it is unclear whether the medications actually contribute to increased peer acceptance. Interestingly, despite the widespread use and effectiveness of psychostimulant medications, neuro- scientists do not completely understand the neurochemical actions of the drugs. Researchers have proposed a number of hypothesized actions, most implicating the impact of

CHAPTER 11 | Learning and Neuropsychiatric Disorders of Childhood 331

psychostimulant medication on the brain’s neurotrans- mitters, specifically dopamine and norepinephrine, result- ing in increased inhibitory control across cognitive and behavioral systems.

Despite the positive effects of psychostimulant med- ications, these drugs also have several limitations: (1) side effects are common, such as temporary appetite suppres- sion and sleep disruption; (2) the therapeutic effective- ness of the medications vary from child to child; (3) the child may show a brief intensification of core symptoms at the end of the last daily dose (“rebound effect”); (4) children often resist compliance with the medication regimen; (5) the medications have minimal effect on cer- tain problems (such as learning disabilities); and (6) the medications do not “cure” the disorder. Regarding the lat- ter limitation, the core symptoms re-emerge when the child is not medicated.

We now discuss Gilles de la Tourette’s disorder, a tic disorder that can be baffling to observers and distressing to the affected child or adolescent. Unfortunately, Gilles de la Tourette’s disorder frequently co-occurs with ADHD and obsessive-compulsive disorder.

Tic Disorders

Motor and/or vocal tics can be transient, episodic, or chronic. Tics are particularly intriguing to neuroscientists insofar as they appear to represent a type of behavior that is both voluntary and involuntary with regard to expression. Whether a tic condition constitutes a “disorder” depends on a number of factors such as chronicity; disturbance to acad- emic, social, or work performance; or degree of subjective distress. The most serious tic disorder is that of Gilles de la Tourette’s syndrome, which involves the presentation of both motor and vocal tics.

G I L L E S D E L A T O U R E T T E ’ S S Y N D R O M E

B a c k g r o u n d a n d C l i n i c a l P r e s e n t a t i o n

Gilles de la Tourette was a brilliant neurologist who stud- ied with Charcot at the Parisian Hôpital de la Saltpêtrière during the latter part of the seventeenth century. Because of his work, the disorder of multiple motor and vocal tics, Gilles de la Tourette’s syndrome (GTS), bears his name. Unfortunately, Gilles de la Tourette’s professional contri- butions were overshadowed by a series of tragedies during his life. He suffered gunshot wounds inflicted by a

psychiatric patient, struggled with bouts of depression and mania in later life, and is believed to have died of syphilis (Bradshaw, 2001).

GTS is a developmental disorder that exemplifies the hazy boundary between neurology and psychiatry. Ini- tially, GTS was viewed as a psychiatric disorder and, con- sistent with the early development of psychiatry, consid- ered amendable to psychoanalytic interpretation and therapeutic interventions (Cohen & Leckman, 1994). The APA (DSM IV, 1994) lists it as a “mental disorder,” despite advances in the neurosciences and related fields elucidating the neuropathogenesis of the disorder. More accurately, GTS appears to be a product of a complex and only partially understood interplay of genetic, neurophys- iologic, and psychological factors.

Tics refer to repetitive, stereotypic, nonrhythmic, and reoccurring motor movements or vocal responses of brief duration (≤1 second). Tics are fragments of normal motor/vocal behavior that are semivoluntary in expression. They occupy an intermediate point on the continuum of motor behavior, with one end represented by involuntary movements (for example, resting tremor associated with Parkinson’s disease) and the other end characterized by volitional, deliberate, and purposeful actions. The semi- voluntary nature of tics relates to the fact that they can be temporarily either suppressed or expressed in an altered or concealed manner (for example, integrating the tic into a series of voluntary movements). An example of a semi- voluntary behavior that we all experience is yawning. The urge to yawn can be temporarily suppressed or concealed (namely, covering one’s mouth), but if we are truly tired, it will ultimately emerge. Similarly, the tic is often pre- ceded by an urge or sensation (premonitory urge/sensa- tion) that can be suppressed, but this produces tension and discomfort that, in turn, compels the release of the move- ment or vocalization. Furthermore, the release of the movement/vocalization provides short-term relief from the tension and discomfort. Unfortunately, the relief is followed by renewed tension and discomfort, producing a cycle of repeated tic behaviors.

Tics are classified as simple or complex. Table 11.8 pre- sents examples of each. Simple tics appear more reflexive, whereas complex tics appear more purposeful and coordi- nated. In extreme cases, motor or speech actions are per- formed compulsively.

Developmentally, tics are evident in healthy developing children, but resolve over time. Tic disorders are classified as transient, chronic, and GTS. A transient tic disorder refers to motor and/or vocal tics that are exhibited from 1 to 12 months. A chronic disorder relates to the presentation of motor or vocal tics for a period greater than 12 months.

332 PART THREE | Disorders of the Brain

Finally, GTS encompasses the expression of motor and vocal tics for a period exceeding 12 months. The tics asso- ciated with GTS are also required to cause significant dis- tress or interfere with the child’s or adolescent’s adjustment to home, school, or community.

The onset of GTS can be gradual or rapid, with initial motor tics involving the head and face, and later showing a caudal progression. The motor and vocal tics of GTS fluctuate (“wax and wane”) in their nature, location, fre- quency, severity, and duration of presentation. Thus, it is a condition that tends to be intermittent in its expres- sion—periods of tic behaviors that abate, only to reoccur at another point in time—through childhood and ado- lescence. The average age of onset is 7 years of age, al- though cases are known to occur both earlier and later than this age.

Tics tend to exacerbate with the onset of adolescence, but generally lessen or resolve by adulthood (Figure 11.6). Unfortunately, the public media often presents copro- praxia (obscene gestures) and coprolalia (obscene or inap- propriate speech) as representative of GTS. In fact, these extreme behaviors are relatively rare, occurring in less than 10% of the cases (APA, 1994).

Tic behaviors are exacerbated by stress, boredom, and excitement. Conversely, they tend to diminish when the child is relaxed, intensely focused on an activity, or emo- tionally calm. Interestingly, tics significantly abate when the child is asleep.

P r e v a l e n c e

The prevalence of GTS for school-age children is esti- mated to be 1 to 8 per 1000 children (Costello et al., 1996;

Hornsey, Banerjee, Zeitlin, & Robertson, 2001). Boys are affected at a higher rate than girls, with estimated ratios ranging from l.8 to 8 boys to 0 to 6.6 girls (Leckman, Peterson, Anderson, Arsten, Pauls, & Cohen, 1997). A generally accepted estimate is a 4 : 1 ratio of boys to girls. GTS does not appear to have a disproportional affect on any specific racial or ethnic group.

CHAPTER 11 | Learning and Neuropsychiatric Disorders of Childhood 333

Simple Motor Complex Motor Simple Vocal Complex Vocal

Blinking Jumping Throat clearing Repeating others’ speech

Facial twitches Touching others Sniffing Repeating one’s own words

Head or arm jerk Smelling Snorting Obscene words

Shoulder shrugs Facial expressions Yelping

Foot stomping Hand or head gestures Barking

Squatting Clicks

Twirling Grunts

Spinning in a circle Speech fragments

Imitating others’ behaviors Phrases

Obscene gestures Humming

Table 11.8 Simple and Complex Motor and Vocal Tics

Figure 11.6 Plot of mean tic severity for ages 2 to 18 years. Tic severity reaches its highest point between 10 and 12 years of age and begins to decline thereafter. (Reproduced from Leckman, J., Peterson, B., Schultz, R., & Cohen, D. [2001]. Tics: When habit- forming neural systems form habits of their own. In C. Nelson & M. Luciana [Eds.], Handbook of developmental cognitive neuroscience [p. 557, Figure 35.5]. Cambridge, MA: The MIT Press, by permission.)

0 5 10 15

Re la

tiv e

TI C

S ev

er ity

(A RR

TS )

Age (yrs)

Actual Means Estimated Means

C o m o r b i d C o n d i t i o n s

Individuals with GTS often experience anxiety, depression, and aggression. Aggression can range from oppositional re- sponses to overt acting-out behavior. However, the two major conditions most likely to co-occur with GTS are obsessive-compulsive disorder (OCD) and ADHD. OCD is estimated to occur in approximately 30% to 60% of individuals with GTS, whereas 25% to 50% of children and adolescents with GTS exhibit a co-occurring ADHD (Cirino, Chapieski, & Massman, 2000; Leckman et al., 1997).

Obsessions are repetitive, intrusive, unwanted, and often inappropriate thoughts or images. Obsessive thoughts/ images typically relate to themes of aggression, sexuality, contamination, cataclysmic events, symmetry, and exact- ness. Often, obsessions prompt compulsions that are thoughts or actions to resist, suppress, or neutralize the ob- sessions. Compulsive behaviors are many and varied, fre- quently involving checking, counting, ordering, washing, seeking reassurance, and ritualistic behaviors (Bradshaw, 2001). Unfortunately, the anxiety reduction produced by compulsions is short-lived. Obsessive thoughts/images re- occur and prompt, once again, the compulsive behaviors.

When GTS and OCD co-occur, it can be difficult to differentiate complex motor tics from compulsive behav- iors. The two disorders can sometimes be differentiated by the dynamics of the two conditions. The sequence of events in GTS is as follows: a premonitory urge or sensa- tion (sensorimotor prompting), followed by the release of the tic behavior and momentary relief of the tension and press associated with the premonitory urge/sensation. In contrast, OCD involves an unwanted image or thought (cognitive prompting) that engenders anxiety and distress. The compulsive behavior serves to alleviate the anxiety associated with the obsessive thought/image.

As we have discussed, ADHD relates to the manifesta- tion of age-inappropriate inattention, impulsivity, and hyperactivity. The comorbidity of ADHD, OCD, and GTS is highly disruptive to the child or adolescent’s acad- emic performance, social acceptance, and self-valuing. A number of interpretations have been posed to account for the comorbidity of OCD and ADHD with GTS. Of sig- nificance, however, are research findings indicating that all three disorders appear to relate to perturbations of the frontostriatal brain systems.

N e u r o p s y c h o l o g i c a l P a t h o g e n e s i s

GTS is one of the most familial of the neuropsychiatric disorders and appears to be transmitted via autosomal dominant genes with incomplete penetrance (incomplete expression in affected individuals) (Bradshaw, 2001;

Pennington, 2002). With monozygotic twins, the rate of concordance for GTS is 50% to 56%, and it increases to 77% to 94% when GTS and chronic tic disorders are combined. The concordance rate for dizygotic twins is 8% to 18%, but increases to only 23% when combined with chronic tic disorder (Leckman et al., 1997; Leckman & Cohen, 1996; Pennington, 2002). The dopamine D2 A1 allele and dopamine D3 and D4 receptor genes and chromosomal abnormalities (8, 18, and 22) have also been implicated (Alsobrook & Pauls, 1999; Bradshaw, 2001; Casey, Tottenham, & Fossella, 2002).

Alterations of neurotransmitters intrinsic to the frontos- triatal pathways have been posed as pathogenic to GTS (Bradshaw, 2001; Sheppard et al., 1999). The cate- cholamines (dopaminergic, serotonergic, and noradrenergic systems) have received the greatest attention. Of these trans- mitters, dopamine appears to play the crucial role in GTS. In part, this is based on the effects of medications that either inhibit or facilitate dopamine activity. Dopamine (D2) re- ceptor antagonists such as haloperidol (Haldol) reduce motor and vocal tics. In contrast, dopamine agonists such as central nervous system stimulants (for example, methylphenidate [Ritalin]) can exacerbate motor and vocal tics. It is unclear whether striatal D2 receptors are hypersensitive to dopamine or whether there is a dopaminergic hyperinnervation of the striatum (Leckman et al., 1997). The effectiveness of cloni- dine (Catapres) and guanfacine (Tenex) ( 2 noradrenergic receptor agonists) in the treatment of the symptoms of both GTS and ADHD further suggests a role of noradrenalin in the modulating cortico-striatal-thalamo-cortical pathways. Support for the role of serotonin in the cause of GTS is lim- ited, although there is significant evidence for its role in OCD (Pennington, 2002). Currently, the role of other central neurotransmitters in the pathogenesis of GTS awaits clarification.

Since the mid-1990s, ongoing research has focused on the role of environmental factors that place a child at risk for the development of tic disorders. Extensive research has been directed toward determining whether there is a risk for the development of tic disorders as part of an autoimmune response. Clinical findings of a temporal relation between -hemolytic streptococci and the onset or exacerbation of tic disorders and/or OCD provided the impetus for this re- search. The National Institute of Mental Health labeled this disorder pediatric autoimmune neuropsychiatric disorders asso- ciated with streptococcal infections (PANDAS). Pathogeni- cally, it is hypothesized that the human body’s antibodies targeting the streptococci also cross-react with the basal gan- glia, with resulting damage and production of tics and OCD behaviors. A number of studies have supported dif- ferences between increased levels of antistreptococcal anti- bodies for GTS relative to control groups; however, others

334 PART THREE | Disorders of the Brain

have not (Hoekstra, Kallenber, Korf, & Minderaa, 2002). Moreover, the mechanism of action of antistreptococcal an- tibodies with regard to the development or exacerbation of tics remains to be elucidated. Insofar as streptococcal in- fections are common among children and most do not de- velop tics and/or OCD, additional investigations are needed to determine what factors account for the development of tics and/or compulsions in a select few individuals.

Structural and functional neuroimaging studies have re- ported alterations of brain structure and metabolic activa- tion patterns associated with GTS. A consistent finding across studies is reduced volume or atypical asymmetries of the caudate, putamen, and globus pallidus of the basal gan- glia (Peterson et al., 2003; Sheppard et al., 1999). Altered activations of the prefrontal cortex (lateral orbitofrontal and anterior cingulate), motor cortex, somatosensory associa- tion areas, and thalamus have also been reported (Jeffries, Schooler, Schoenbach, Herscovitch, Chase, & Braun, 2002). Jointly, the neuroimaging studies provide growing evidence for the role of the frontostriatal pathways in the pathogenesis of GTS (Singer & Minzer, 2003). The motor and vocal tics of GTS are hypothesized to relate to disinhi- bition (possibly because of hypersensitivity of dopamine re- ceptors or hyperinnervation of the striatum) of the frontal motor-striatal circuit, particularly at the level of the caudate, resulting in the release of motor programs. Notably, the frontal motor circuit includes projections from the so- matosensory cortex, implicating its potential role in the gen- eration of premonitory urges. Hypoactivation at the level of the lateral orbitofrontal and anterior cingulated cortex sug- gests a disruption of top-down voluntary control.

While there are indications of hyperactivation and hy- poactivation of different frontostriatal circuits in OCD and ADHD, the interactive pathogenic role of the circuits in co- occurring GTS, OCD, and ADHD is not well understood. The comorbidity of the three disorders implicates some level or degree of dysfunction across the major frontostriatal cir- cuits; however, we await research findings explicating the nature and cause of this dysfunction.

N e u r o p s y c h o l o g i c a l A s s e s s m e n t

Because of the putative role of disinhibition in the expres- sion of motor and vocal tics, studies of inhibitory control have been undertaken. The evidence from these studies has been inconsistent in supporting inhibitory weaknesses as specific to GTS (Channon, Pratt, & Robertson, 2003). Similarly, little evidence exists of deficits in executive functions supported by the dorsolateral prefrontal cortex, such as planning, rule finding, and set shifting (Ozonoff & Jensen, 1999). Lateral frontal regions are believed to contribute to strategic, working, and procedural memory

processes, and at least one study (Stebbins, Singh, Weiner, Wilson, Goetz, & Gabrieli, 1995) has identified weak- nesses in this domain for adults with GTS participants.

Deficits related to visual-construction, visuomotor inte- gration, and motor performance are frequently evident in children and adults with GTS, possibly reflecting disrup- tion of the motor-striatal pathway (Leckman, Peterson, Schultz, & Cohen, 2001). Unfortunately, many of these studies have not controlled for the high frequency of co- morbid conditions that accompany GTS, potentially con- tributing to conflicting and equivocal results. However, se- lected studies controlling for comorbidity and GTS are available. For example, Silverstein, Como, Palumbo, West, and Osborn (1995) found that the poor attentional perfor- mance of adults with GTS is related to the presence of ADHD and OCD, and not a unique deficit associated with GTS. In a more recent study, Channon and colleagues (2003) compared GTS, GTS � ADHD, GTS � OCD, and healthy control children and adolescents on measures of executive functioning, memory, and learning. Children and adolescents with only GTS differed from the healthy control youngsters on one measure of response initiation, whereas the GTS � ADHD group demonstrated deficits on several measures of executive function assessing response inhibition, strategy generation, and multitasking. Further- more, the GTS � OCD group did not differ in their exec- utive performance from the healthy control group. Finally, none of the clinical groups differed from healthy control individuals in memory or learning performance.

Casey and colleagues (2002) have extensively studied the frontostriatal regions and circuitry of children with de- velopmental disorders and healthy children. Reflecting this ongoing research has been the development of a model of cognitive control. One critical aspect of cognitive control is the ability to suppress or override competing attentional and behavioral responses to resolve conflict. The inhibi- tion of three forms of cognitive-motor processing (stimu- lus selection, response selection, and response execution) was studied with healthy control and clinic groups (chil- dren with GTS, ADHD, childhood onset schizophrenia, and Sydenham’s chorea). The Sydenham’s chorea group was selected because of the high rate of OCD (75%) asso- ciated with the disorder. The intent of the studies was to determine whether the separate disorders demonstrated different cognitive control deficits.

The children were administered a battery of tasks that assessed the three cognitive control processes. The stimulus selection task requires the inhibition of attention to visual features previously viewed in order to attend to a new fea- ture. The response selection task involved the learning of a series of responses to specific stimuli, and then the produc- tion of a different (incompatible) set of responses to the

CHAPTER 11 | Learning and Neuropsychiatric Disorders of Childhood 335

same stimuli. In the latter condition, the child was faced with inhibiting the first learned response set in order to se- lect and generate the second response set. In contrast, the third task, response execution, involved the creation of a prepotent response through the frequent association of the response with a specific stimuli and then periodically requir- ing the inhibition of the response to a different stimuli. Rel- ative to healthy children, the GTS group demonstrated sig- nificantly poorer performance in response-execution, whereas the ADHD group showed deficits in stimulus se- lection and response-execution. Furthermore, the childhood schizophrenic group was impaired in stimulus-selection, and the Sydenham’s chorea (OCD) group showed deficits in response-selection. Mapping of these cognitive processes to the neural circuits is incomplete, although there are indica- tions that the right prefrontal cortex is primarily involved in stimulus-selection, the right orbital/anterior cingulate cir- cuits are related to response execution, and the basal ganglia-thalamocortical circuits, at the level of the caudate, underpin response selection. Confirmation of these findings should increase our neuropsychological understanding of GTS and other disorders and provide differential informa- tion to aid diagnosis and treatment.

T r e a t m e n t a n d D e v e l o p m e n t a l C o u r s e

The two primary treatment interventions for GTS are be- havioral modification and pharmacologic therapy. A wide range of behavioral interventions has been applied to GTS with varying degrees of success. The techniques that have been introduced in the treatment of GTS include: (1) massed practice (rapid and repeated voluntary produc- tion of a tic); (2) operant conditioning (providing reinforce- ment for tic-free periods); (3) anxiety management training (for example, training in muscle relaxation for use in anxiety- engendering situations); (4) exposure plus response preven- tion (stimuli or conditions are presented that increase the likelihood of premonitory urge, and the child is not allowed to release the tic); and (5) habit reversal (performing a com- peting and incompatible physical response contingent on the urge to perform the tic). Of these techniques, habit re- versal has received the greatest support as an efficacious treat- ment (Piacentini & Chang, 2001). Although each of these techniques can lead to tic reduction, the treatment effects often fail to generalize to other situations and are frequently short-lived.

The medications used for GTS treatment are generally dopamine antagonists, such as the neuroleptic haloperi- dol (Haldol), which are effective in the treatment of the disorder. Unfortunately, the use of typical neuroleptics can result in a number of undesirable and sometimes se-

vere side effects. These side effects range from cognitive slowing to Parkinsonian-like motor disturbances. The use of the newer atypical antipsychotic medications such as risperidone (Risperdal) reduces the likelihood of side ef- fects, but their efficacy has not been fully established. Re- cently, there has been interest in the dopamine antagonist metoclopramide, which has been found to be effective in tic reduction without significant neuroleptic-like adverse side effects (Nicolson, Craven-Thuss, Smith, McKinlay, & Castellanos, 2005). However, further studies are war- ranted to assess its efficacy and safety over long periods of use. Clonidine (Catapres) and guanfacine (Tenex) are 2 agonists and have been used with varying success in re- ducing tic behaviors. The precise mechanism of action of 2 agonists is unknown, although there are indications that dopamine utilization is increased in the frontal re- gions of the brain (Pennington, 2002).

The child or adolescent with GTS and comorbid OCD often requires the introduction of behavioral and cognitive behavioral interventions that target tic behaviors and dis- ruptive obsessions and compulsions. Often, these tech- niques are insufficient, and medication is introduced. Clomipramine (Anafranil), a tricyclic antidepressant, is ef- ficacious for the treatment of OCD. However, because of the potential for significant side effects associated with Anafranil, selective serotonin reuptake inhibitors (SSRIs) are currently the first line of pharmacologic intervention. Paroxetine (Paxil) is an SSRI that has been determined to be helpful in reducing intrusive ideations and compulsive behaviors for both children and adults. Importantly, SSRIs do not typically exacerbate motor or vocal tics.

A particularly difficult presentation is the child with GTS and ADHD. The psychostimulants, although effec- tive for treating ADHD, can exacerbate the motor and vocal tics associated with GTS. However, not all children who receive a psychostimulant medication experience ac- celeration of tic behaviors. For the child who is unable to tolerate a psychostimulant, clonidine or guanfacine may be introduced to reduce tics, as well as the hyperactivity and impulsivity associated with ADHD. However, the 2 ago- nists are not always effective in the treatment of GTS or ADHD. In addition, the child medicated with a 2 ago- nist warrants careful monitoring because of the potential for adverse cardiac effects. Recently, atomoxetine (Strattera) was approved for the treatment of ADHD. Atomoxetine is a noradrenaline reuptake inhibitor that, in addition to re- ducing ADHD symptoms, does not appear to exacerbate co-occurring motor and vocal tics. In more severe cases of GTS with co-occurring OCD and/or ADHD, a combina- tion of medications is often needed to reduce disruptive symptoms.

336 PART THREE | Disorders of the Brain

Neuropsychological strengths and weaknesses warrant consideration when mapping out the child’s educational curriculum. The teacher and classmates of the child with GTS can profit from a discussion with the neuropsychol- ogist or other informed person concerning what tic be- haviors are and are not, the intermittent expression and possible increasing severity of tic behaviors, and what they are to do or not to do when the child is exhibiting tic be- haviors. This information is important for increasing their understanding of GTS, disabusing misinterpretations, and reducing negative responses to the afflicted child. In- terventions to help the teacher and child to cope with tics within the classroom are important. For example, the teacher may need to allow the child to leave the classroom and go to the nurse’s office if a significant exacerbation of tic behavior occurs. While in the nurse’s office, the child can be helped to initiate any techniques that have been found to be effective in reducing his or her tics. Seating the child in the front row of the class can reduce the de- tection of tics by classmates, because the majority of them

will be seated behind the child. Most important, the teacher and educational staff need to be alert and inter- vene quickly if they observe teasing or taunting of the child by peers.

Adolescence can be a difficult period of development for a healthy teenager. The motor and vocal tics of GTS, cou- pled with ADHD and/or OCD comorbidity, can be disrup- tive to the adolescent’s efforts to affiliate with peers, initiate dating relationships, develop a positive body image, and es- tablish a healthy self-identity. Fortunately, as discussed ear- lier, motor and vocal tics of GTS begin to attenuate or re- solve during adolescence and early adulthood. Most adolescents with GTS graduate from high school and demonstrate appropriate adaptation to their disorder. In cases when GTS symptoms do not reduce, or even exacerbate, so- cial, vocational, and emotional adjustment in adulthood may be compromised (Brown & Ivers, 1999). Hopefully, future pharmacological advances and refinements will identify med- ications that will effectively address vocal and motor tics at all age levels while producing fewer negative side effects.

CHAPTER 11 | Learning and Neuropsychiatric Disorders of Childhood 337

Summary Several developmental disorders currently are the focus of extensive research by neuropsychology and other disciplines. The neuropsychological identification of the potential brain and behavior correlates of dyslexia and NVLD have enhanced our understanding of learning disabilities. Although most theorization and research has focused on disorders of reading and mathematics, other forms of learning disabilities, such as dysgraphia, await investigation. Autism has a profound and often global impact on the cognitive and behavioral development of a child. Advances have been made in the understanding of the neuropatho- genesis, neuropsychological assessment, neuropsychological models, developmental course, and treatment of autism. However, the cause of autism remains elusive, and treatment interventions often fail to signifi- cantly alter the symptoms of the disorder. ADHD is one of the most studied childhood disorders of our time. Researchers have redefined and relabeled the disorder, spawned numerous hypotheses and theories, and generated multiple interventions. Unfortunately, the etiology of ADHD remains unknown; the interplay of mediating variables such as the child’s personality, environmental effects, and presence of comorbid disor- ders is also poorly understood; and the current treatment options are limited and often ineffective. Although the entrance of neuropsychology into the study of ADHD is relatively recent, optimism remains high that its contribution will provide new and much needed direction to the study and understanding of the disorder. Finally, GTS is a significantly disruptive and potentially embarrassing disorder that falls on the boundary of voluntary-involuntary behavior. The high frequency of comorbidity of other disorders with GTS highlights the diverse effects of frontostriatal dysfunction.

C r i t i c a l T h i n k i n g Q u e s t i o n s

Why are the symptoms of NVLD and ADHD so often displayed by children exhibiting a wide range of developmental disorders? Can a child with autism or Asperger’s syndrome develop normal social awareness and attachment? If so, how would this be accomplished? How would you respond to the comment, “ADHD does not exist, it is merely a diagnosis to excuse lazy and undisciplined children?”

Dyslexia Dyscalculia Dysgraphia Surface dyslexia Deep dyslexia Flicker fusion rate Magnocellular visual system Parvocellular visual system Saccadic eye movements Phonologic awareness Double-deficit hypothesis Planum temporale Neuronal Ectopias

Cytoarchitectonic dysplasia

Lexicon store Metacognition Pragmatics of language Autism Asperger’s syndrome Autistic aloneness Joint attention Echolalia Neologism Hyperlexia Savant skills

Hyperserotonemia Fragile X “Stuck in set” perseveration Executive planning Response inhibition Theory of mind Canalesthesia Impaired affective

assignment Asociality Extended selective

attention Response cost

Overcorrection Attention-deficit/hyperactivity

disorder (ADHD) Disengage attention Move attention Engage attention Prepotent response Interference control Gilles de la Tourette’s syndrome

(GTS) Obsessive-compulsive

disorder (OCD) Sydenham’s chorea

We b C o n n e c t i o n s

http://www.bda-dyslexia.org.uk Dyslexia—provides a large collection of references on dyslexia.

http://www.cognitivedesigns.com Cognitive Designs—provides educational and clinical tools to teach and treat children with autism or other developmental learning disorders.

http://www.mentalhealth.com/dis/p20-ch06.html Autistic Disorder—comprehensive site that provides descriptions, treatments, research references, books, magazine articles, and various links concerning autism.

http://www.mentalhealth.com/fr20.html Attention-Deficit Hyperactivity Disorder—provides a comprehensive overview of ADHD: a review of descrip- tions, treatment options, books, and magazine articles.

http://www.mentalhealth.com/dis/p20-ch02.html Conduct Disorder—provides a complete listing of materials on CD; links are provided and reviews of treat- ments, books, and magazine articles.

http://www.mentalhealth.com/dis/p20-ch05.html Oppositional Defiant Disorder—provides a complete listing of materials on oppositional defiant disorder; links are provided and reviews of treatments, books, and magazine articles.

http://www.tsa-usa.org Tourette Syndrome Association—provides parents and professions with information related to the identification, treatment, and education of individuals with Tourette’s syndrome.

338 PART THREE | Disorders of the Brain

As our understanding of the neural correlates of learning and neuropsychiatric disorders expands, what impact will this have on traditional psychological and educational treatment? Does the finding that the symptoms of GTS often attenuate or resolve in later adolescences or early adulthood support a conceptualization of the disorder as a developmental lag? How do you account for individuals who do not show such improvement and struggle with GTS as a lifelong disorder?

K e y Te r m s

http://www.bda-dyslexia.org.uk

http://www.cognitivedesigns.com

http://www.mentalhealth.com

http://www.tsa-usa.org

Chapter 12

C E R E B RO VA S C U L A R D I S O R D E R S A N D T U M O R S

In whatsoever house I enter, I will enter to help the sick. —Hippocrates (460–377 B.C.)

Pathologic Process of Brain Damage Overview of Cerebrovascular Disorders Types of Cerebrovascular Disorders Diagnosing Cerebrovascular Disease Treatment and Prognosis of Vascular Disorders Neuropsychological Deficits Associated with Stroke Tumors of the Brain Types of Intracranial Tumors Brain Tumors and Neuropsychology Other Neurologic Disorders

Neuropsychology in Action

12.1 Migraine Headache: A Vascular Disorder of the Brain

12.2 Case Example of a Left Stroke 12.3 Neuropsychology of Treatments for Individuals

with Brain Tumors 12.4 Family and Child Adjustment to Cognitive Aspects

of Cancer in Children

340 PART THREE | Disorders of the Brain

B R A I N L E S I O N S

What are lesions, and what effects do they have on the brain? Brain lesions (derived from Latin laesio, meaning “to hurt”) are any pathologic or traumatic discontinuity of brain tissue. Lesions result in “holes” or “cavities” in the brain and almost always entail loss of function. De- pending on their size and location, lesions result in minor or major behavioral effects. Lesions may be caused by traumas, such as punctures from bullet wounds, frag- ments of skull fractures, or other foreign objects entering the brain. Other events that cause lesions include CVAs, surgical removal of tumors, or diseases such as multiple sclerosis or Creutzfeldt–Jacob disease.

Neurons that are completely severed often degener- ate. The tissue that surrounds the lesion shrinks and dies

K e e p i n M i n d

What is a stroke?

How long can the human brain function without oxygen?

How is the brain supplied with blood?

What are the lasting neuropsychological deficits after stroke?

What happens when a tumor grows in the brain?

Overview The normal functioning central nervous system (CNS) can be affected by a number of neurologic disorders and diseases. Some will result in similar types of damage, and some will be vastly different. Some result in focal effects, others result in diffuse damage. Physicians expect some, if not complete, recovery after many types of brain damage, such as mild head injuries. Other types of brain diseases are more severe and may result in lasting impairment, as is often the case in stroke, or may be even fatal, as is Alzheimer’s disease, with which there is an inevitable decline in health culminating in death. Thus, brain disorders may have a wide-ranging impact on a person’s well-being. Often, significant neuropsychological deficits exist that result in marked disabilities, alterations in personality, and a decline in quality of life.

This chapter discusses the most common neurologic problems and neuropsychological sequelae that are associated with cerebrovascular accidents (CVAs) and tumors. Chapter 13 discusses the impact on the brain and its recovery related to head injury. Chapters 14 and 15 present degenerative disorders, which are good examples of diffuse and generalized involvement of brain pathology. Chapter 16 reviews disorders of consciousness, in which the typical clinical picture is also more generalized, with many behavioral adaptive skills possibly affected.

For each disorder, we examine neuropathology, neuropsychological sequelae, appropriate treatments, and case examples of patients we have treated. We present the information within a neuropsychological perspective; that is, we describe the disorders with particular relevance to the relations among brain anatomy, biological processes of the brain, and their behavioral product.

Pathologic Process of Brain Damage

This section reviews examples of brain damage and their mechanisms of action within the brain. These exam- ples are not necessarily mutually exclusive, and many con- ditions may result in more than one problem. They also are not totally inclusive, but are meant to provide an overview of some of the more common terms and condi- tions you will encounter as you read about various pathologies throughout this book. Although some exam- ples result in specific behavioral effects, many terms, such as “lesion,” are more generic, and their behavioral effects often depend on the specific location and extent of dam- age within the brain.

within hours. Cerebrospinal fluid (CSF) then fills the cavity. With time, surrounding brain tissue may collapse the cavity, which may concomitantly distort other areas of the brain or ventricles, depending on the size of the lesion (Figure 12.1). Any dead neuronal debris is en- gulfed by the brain’s micro “cleaning machines,” the phagocytes, which are forms of glial cells (see Chapter 4). As a result, glial cells may be all that remains in the cav- ity of the lesion where neurons were once active. This obviously results in a blockage or interruption of neural transmission.

A N O X I A A N D H Y P O X I A : O X Y G E N D E P R I V A T I O N T O T H E B R A I N

Most readers will know that reduced flow of oxygen to the brain is dangerous. CVAs or strokes imply by defini- tion a disruption or stoppage of blood to the brain. Strokes almost always result in neuronal loss or degenera- tion. Neurons need oxygen to break down glucose into carbon dioxide and water. Furthermore, the brain has no reservoir of glucose or oxygen. Thus, the brain depends on a constant and immediate supply. An elaborate blood system carries oxygen and important nutrients to the brain. Although weighing less than 3 pounds, the brain is

rather demanding, requiring more than 20% of the body’s oxygen to keep functioning effectively. As a result, the brain is particularly vulnerable to oxygen depletion.

If a neuron lacks oxygen for some time, the neuron will die. This necrosis, or neuronal cell death, is a direct result of a crucial interference with the cellular metabo- lism of the neuron. A complete absence of oxygen supply to the brain is anoxia. The most common causes of anoxia are cardiopulmonary failures associated with heart attacks, complications of anesthesia, accidents such as near-drowning episodes, or other severe traumas to the brain, such as are often seen in gunshot wounds to the head. In these cases, where there may be respiratory or cardiac arrest, permanent brain damage follows unless oxygen is restored quickly. Most anoxic episodes appear to result in damage to subcortical and limbic areas, the frontal lobes, and the cerebellum.

In contrast, hypoxia describes a reduced, but not complete, oxygenation of brain. Hypoxia typically en- tails not cell death, but some possible interference in the functioning of the neuron. In general, 4 to 6 minutes of anoxia may cause necrosis, although this is highly variable and depends on individual and environmental characteristics. Hypoxia can occur at high altitude, dur- ing acute cardiac crisis, during the aftermath of open- heart surgery, and during exertion in deep-sea divers. It may also be seen in carbon monoxide poisoning, may accompany sleep in the aging brain, and is present in people with chronic obstructive pulmonary disease re- lated to chronic, intermittent lowered oxygen saturation in the blood.

A growing body of literature suggests that individuals who are otherwise healthy and who experience mild- to-moderate hypoxia may demonstrate significant diffi- culties in concentration, short-term memory, new learn- ing, and judgment. At extreme altitude—that is, more than 22,000 feet—hypoxia can impair a human’s cogni- tive function, including motor speed, judgment, verbal fluency, learning, and short-term memory. Severe hypoxia produces more dramatic deficits, often resulting in irre- versible brain damage. However, under specific environ- mental conditions (such as cold water submersion), chil- dren may recover completely from acute hypoxia, even if it has lasted as long as 20 minutes. The reasons for this are unclear, but are probably related to young age and the poorly understood effects of cold-water submersion on brain metabolism.

Hypoxia can occur at high altitudes. For example, climbers refer to elevations above 25,000 feet as the “death zone,” because of the low oxygen level in the air (Krakauer, 1997). The air is so thin that even

CHAPTER 12 | Cerebrovascular Disorders and Tumors 341

Figure 12.1 Sagittal magnetic resonance imaging of brain with small stroke in the superior portion of the cerebellum (bottom). Significant atrophy is associated with increased size of the lateral ventricles and intracranial space (top). See inside covers for color image. (Courtesy Eric Zillmer.)

conditioned climbers may become hypoxic. In fact, if one were to “pluck” a person from sea level and drop him or her on Mount Everest, which has an elevation of 29,028 feet, death by anoxia would occur within min- utes. Even when adapted to extreme elevations, many climbers must use supplemental oxygen. Nevertheless, at such high altitudes, one becomes careless, sluggish, and fatigued. To conserve oxygen, the brain may dimin- ish oxygen supply to more distal parts of the body, in- creasing the risk for frostbite and hypothermia, and sometimes edema of the brain and death. Recent neu- ropsychological studies conducted on the ascent and the summit of Mount Everest clearly indicate hypoxia in climbers and a related dysfunction in memory and con- centration (for example, see Virues-Ortega, Buela-Casal, Garrido, & Alcazar, 2004).

Medical conditions can also affect oxygen uptake. For example, chronic obstructive pulmonary disease is a dis- order in which the lung has lost its capacity to efficiently exchange oxygen with white blood cells. Sleep apnea (derived from Greek apnoia, meaning “negative breath- ing”) is a good example of chronic hypoxia during sleep. Breathing is disturbed throughout the night and often completely stops for periods as long as a minute. These hypoxic episodes often occur with more severity during rapid eye movement (REM) sleep, because the volun- tary muscles that assist in breathing are paralyzed during dream sleep. Under normal circumstances, blood is 95% oxygenated, but in sleep apnea patients, this can de- crease to 50% and less. Consequently, people with sleep apnea often report morning headaches, poor attention and concentration and, of course, sleepiness during the day (Zillmer, Ware, Rose, & Maximin, 1988). It is un- clear whether the effects of hypoxia reverse with in- creased oxygen saturation in the blood. To some extent, they appear to, because patients often completely recover. Reversibility is likely related to the length of deprivation.

H Y D R O C E P H A L U S

Hydrocephalus is a condition in which the ventricles en- large abnormally, because of increased CSF production, decreased CSF absorption, or a blockage of CSF flow through the ventricles. There are several medical reasons why this occurs. You may recall from Chapter 5 that the ventricles produce and circulate CSF through and around the brain and spinal cord. Spinal fluid and waste products are then reabsorbed, in part by the ventricles. The pres- ence of blood or blood products mixing with the CSF,

perhaps as a result of hemorrhage or infection, may inter- fere with reabsorption. This condition is called commu- nicating hydrocephalus. Finally, blockage of the circula- tion of CSF is termed obstructive hydrocephalus. In young children, obstructive hydrocephalus is often caused by a congenital narrowing or stenosis of the aqueduct of Sylvius between the third and fourth ventricles. In adults, obstructive hydrocephalus is most likely caused by brain tumors protruding into the ventricles.

Damage to the brain caused by hydrocephalus results from the pressure of squeezing parts of the brain against an immovable skull. If not corrected quickly, intense pressure can cut off the blood supply and result in cell death. Behaviorally, hydrocephalus results in symptoms of increased cranial pressure, such as sleepiness, severe headache, and nausea. Hydrocephalus is usually an acute condition, but physicians can reverse it by releasing the pressure; they surgically insert a tube to shunt the CSF into the peritoneal cavity of the body—the potential space around the lining of the abdominal and pelvic walls. If not treated quickly, progressive hydrocephalus can be life threatening, because it impinges on vital brainstem func- tions such as respiration and arousal.

Overview of Cerebrovascular Disorders

Bubbeh had to die, as you and I will one day have to die. Just as I had witnessed the decline of my grandmother’s life force, I was present when it gave the first signal of its finality. It was early on an ordinary morning; Bubbeh and I were doing ordi- nary things. Having finished breakfast a few minutes before, I was still hunched over the sports section of the Daily News when I became aware that there was something very strange in the way Bubbeh was trying to wipe clean the surface of the kitchen table. Even though we had long since realized that such household tasks were beyond her, she had never quite given up trying, and seemed oblivious to the fact that one or another of us always repeated the work after she laboriously shuffled out of the room. But when I looked up from the tabloid, I saw that her wide circular strokes were even more ineffectual than usual. Her sweeping hand had become aimless, as though acting on its own with no plan or direction. The circles ceased to be circles and soon became mere languid, useless drags of the moist cloth that was barely held in her flaccid hand, adrift on the table without purpose or weight. Her face was turned straight ahead. She seemed to be looking at something outside the window behind my chair instead of at the table in front of her. Her unseeing eyes had the dullness of oblivion; her face was expres- sionless. Even the most impassive of faces betrays something,

342 PART THREE | Disorders of the Brain

but I knew at that instant of absolute blankness that I had lost my grandmother. I shouted, “Bubbeh, Bubbeh!” but it made no difference. She was beyond hearing me. The cloth slipped from her hand and she crumpled soundlessly to the floor.

I bounded to her side and called her name again, but my shout- ing was as futile as my attempts to comprehend what was happening. Somehow, and I remember not a moment of it, I gathered her up and staggered to the room we shared. I laid her down in my bed. Her breathing was stertorous and loud. It blew in long, forceful blasts from only one corner of her mouth, and it flapped her cheek out like a buffeted wet sail each time she exhaled from that noisy bellows somewhere down deep in her throat. I can’t recall which side it was, but one entire half of her face seemed toneless and flaccid. I rushed to the phone and called a doctor whose office was not far away. Then I contacted my aunt Rose at the Seventh Avenue dress factory where she worked. Rose got there before the doctor could free himself from a waiting room filled with early- morning patients, but we knew there was nothing he could do anyway. When he arrived, he told us Bubbeh had suffered a stroke, and wouldn’t live more than a few days. She outsmarted the doctor and hung on for the next 14 nights. (Nuland, 1993, p. 58–59)

Cerebrovascular disease is reported to be the most common cause of neurologic disability in the Western world, the second leading cause of death among the old- est old (age �85), and the third most common cause of death in the developed countries of the world. Only can- cer and heart attacks affect more people. Strokes are a major health concern in the United States, and they can significantly affect the quality of life of those afflicted, as well as their families.

In the United States, stroke affects approximately 500,000 people each year, and it is the major cause of dis- ability among adults. The death rate associated with strokes is approximately 5%, corresponding to approxi- mately 150,000 deaths each year in the United States. An- other 150,000 people are left with permanent severe dis- ability. Individuals suffering from a cerebrovascular disorder place a significant financial and emotional burden on the families who take care of their loved ones. The estimated public health costs related to stroke amount to billions of dollars per year and are expected to accelerate steadily as advances in emergency medicine allow more stroke victims to survive.

The average age of a stroke victim is approximately 70 years (see Zillmer, Fowler, Waechtler, Harris, & Khan, 1992). As the population of the United States is growing, life expectancy is likewise increasing. Today, people are living longer and into the age-groups that are more at risk for CVAs. In fact, gerontologists have called the over 65

age-group the fastest-growing segment of the U.S. popu- lation. This increase in the elderly population greatly swells the number of those at risk for strokes, creating a situation in which more people in the population will ac- tually be suffering from CVAs.

S T R O K E D E F I N I T I O N

The term stroke itself is not clearly defined and is not a precise medical term. A more technical term for stroke is cerebrovascular accident (CVA), which describes a het- erogeneous group of vascular disorders that result in brain injury. The brain’s blood vessels are damaged, which can decrease blood flow within and to the brain. In simple terms, stroke “suffocates” brain tissue and often produces an area of dead or dying brain tissue. A stroke always oc- curs in the brain and is the most common type of cere- brovascular disease. Thus, CVA or stroke is a common label assigned to clinical syndromes that are caused by blockage in blood supply or by bleeding in the brain. Stroke can result from a wide variety of different vascular diseases, but not all vascular disorders produce stroke. Al- though the onset of symptoms is rapid (hence the term stroke), the full development of the clinical picture may take an appreciable time, sometimes hours, depending on the rate of the bleed and its final cessation (Bannister, 1992).

In the past, people have conceptualized stroke as a “fait accompli”; That is, once it occurred, little could be done. Recent medical technology, however, has made advances in treating the stroke patient immediately; therefore, early diagnosis and intervention have become a high priority. Physicians now treat stroke as a “brain attack,” a medical emergency similar to a heart attack. Stroke can produce an array of disorders of great complexity. Most strokes occur, or are localized, in only one of the cerebral hemi- spheres, although in some instances, multiple strokes or one major subcortical stroke affects the entire brain. In general, the deficits directly relate to the location or the hemisphere where the stroke occurs.

Neuropsychologists play a crucial role in CVA diagno- sis and rehabilitation. They are at the forefront in many significant advances in long-term treatment and rehabili- tation of stroke patients. In addition, neuropsychologists conduct research on CVA survivors because it provides them with clinical data by which to examine localized le- sions, propose strategies for intervention and rehabilita- tion, and indirectly develop knowledge of the function- ing intact brain (Naugle, Cullum, & Bigler, 1998).

CHAPTER 12 | Cerebrovascular Disorders and Tumors 343

I M P A I R M E N T O F B L O O D S U P P L Y T O T H E B R A I N

The clinical presentation of a patient after stroke reflects the damage to the anatomic structures of the brain. Dis- ruption of major arteries can cause characteristic symp- toms according to the area of the brain that artery serves (the vascular system of the brain is reviewed in Chapter 5). For example, the symptoms of a right hemisphere stroke are quite different from those of a left hemisphere CVA. Almost always behavior is disrupted, and thus physi- cians often consult neuropsychologists to evaluate stroke patients. The following three related neuropsy- chological events often occur after a stroke, all of which interfere with normal brain functioning. Victims may have to contend with these three serious consequences of stroke:

1. Disrupted blood supply decreases oxygenation, as in hypoxia or anoxia, of the involved brain tissue.

2. Related to bleeding (or hemorrhage), a space-occupying mass or pocket of blood often develops, which may press on nearby brain structures, affecting their in- tegrity. As a result, intracranial pressure (ICP) may suddenly increase.

3. When blood spills out of the artery and into brain plasma, many toxins in the blood can interfere with normal brain metabolism. In an intact vascular sys- tem, the blood–brain barrier (BBB) protects the sur- rounding tissue from any toxic properties contained in blood, but exposed blood outside of the artery irritates brain tissue.

Types of Cerebrovascular Disorders

To effectively rehabilitate the patient and provide appropriate guidance to the family and patient, neuropsy- chologists differentiate among three different types and mechanisms of stroke:

1. “Temporary” strokes arise from insufficient blood sup- ply to an area of the brain. These events, collectively called ischemia, often manifest in short-lasting attacks that cause only transient deficits.

2. Blockage of an artery causes a more severe loss of blood supply. This infarction often results in more lasting neuropsychological deficits.

3. The third type of stroke is related to bleeding and to displacement of the brain that arises from a hemor-

rhage. Hemorrhages are the most severe form of stroke and often cause permanent brain damage or death.

Each cerebrovascular event is described in more detail in the following paragraphs.

T R A N S I E N T I S C H E M I C A T T A C K S

Neuropsychologists call an acute, focal (localized) neuro- logic deficit, evidenced by a transient loss of function, a transient ischemic attack (TIA). Recovery should occur within 24 hours, but is often complete within a much shorter time, often minutes. The attacks vary from infre- quent (that is, less than one a month) to very frequent (that is, several times a day).

Rudolf Virchow, a German physician and the founder of German medicine, coined the term ischemia (derived from Greek ischein, meaning “to hold in check,” and haima, meaning “blood”); literally, ischemia means “a holding in check of the flow of blood” to refer to the tem- porary disruption of blood flow. Deficits from TIAs heal gradually, and the patient most often returns to normal neurologic and neuropsychological functioning. An im- portant assumption in a TIA is that no actual damage to any neurons has occurred, just a temporary insufficiency of oxygen supply (Powers, 1990).

TIAs most commonly involve the internal carotid, middle cerebral, or the vertebral-basilar arteries. Clini- cally, neuropsychologists divide the deficits into the ante- rior circulation involving the carotid system and those affecting the posterior circulation involving the vertebral- basilar system. If the ischemic attack affects anterior cir- culation, the deficits manifested will most likely relate to brief clumsiness or weakness of a limb, dysarthria, or aphasia. If the attack affects the posterior circulation, deficits may include dizziness, neglect, double vision, and numbness or weakness of the extremities. Individu- als suffering from TIAs rarely lose consciousness com- pletely, and as mentioned earlier, cognitive and physical functioning usually return to normal once the attack has ceased.

Because one of the first “signs” of stroke is TIAs, their occurrence should be taken seriously. People suffering from TIAs have a 20% to 35% greater risk for stroke than do unaffected individuals, and they go on to suffer obvi- ous infarction (see later). Little research has been con- ducted, however, to determine which individuals suffer- ing from TIAs go on to experience development of the more severe infarctions. Another third continue to have TIAs without any permanent disability, and the remainder

344 PART THREE | Disorders of the Brain

have attacks that cease spontaneously. Two-thirds of those suffering from TIAs are male or hypertensive, or both (Powers, 1990). A neurologist or neuropsychologist easily recognizes symptoms of a TIA (Table 12.1). Unfortu- nately, the person suffering the TIA, because of confusion or an impaired capacity to use judgment, often does not recognize the symptoms resulting from a TIA. In other cases, the TIA symptoms are so peculiar and vague that clinicians find them difficult to establish, because of their waxing-and-waning, transient nature. This is particularly frustrating to the patient, who may be inadvertently re- ferred to a psychiatrist or psychologist because his or her presentation does not appear to fit any established med- ical categories or because physicians can find nothing physically wrong.

I N F A R C T I O N S

When ischemia is severe enough to kill the nerve cell, neurologists consider the neuron infarcted. Infarctions re- sult from an inadequate blood supply to an area of the brain, causing tissue death or necrosis from the lack of oxygen. This event most often relates to obstruction of the local vascular circulation by blockage or occlusion of a vessel, stopping blood flow. Occlusions are typically caused by either a blood clot or a fatty deposit lodged in a vessel. The area of the brain in which this occlusion oc- curs depends on clot size. Occlusion can happen to the brain as a whole, as in severe heart failure; in one of the major arteries or their branches supplying blood to the brain; or in a small capillary. Cerebral infarction is most likely the result of a thrombotic or an embolic vas- cular occlusion in blood flow. We discuss both ischemic events in more detail in the following paragraphs.

T h r o m b o s i s

Thrombosis is the formation of a blood clot or thrombus (derived from Greek meaning “clot”) within the blood vessel. A thrombosis at the heart is a heart attack. A thrombosis in the brain is a stroke. The most common basic neuropathologic process in infarction is that of ath- erosclerosis. In atherosclerosis, irregularly distributed yel- low fatty plaques are present in large- and medium-size arteries. Fat deposits build up along blood vessel walls, re- ducing the size of the cerebral artery. In atherosclerosis, the blood clot lodging in the vessel reduces or completely blocks blood flow through the vessel. Thus, atherosclerosis often precipitates infarction due to occlusion. Atheroscle- rosis is not a uniform process throughout the cardiovas- cular system; it can affect certain parts of the arterial sys- tem more than others. The most common location for atherosclerosis is at the bifurcation of arteries (the point where the division occurs), specifically at the common carotid artery. This condition is progressive, variable, and difficult to predict, although it tends to become worse as a person grows older. Atherosclerosis restricts blood supply to the brain and results in inadequate oxygenation of brain tissue. This produces a general decline in neuropsychologi- cal abilities of a diffuse nature. TIAs often, but not always, precede stroke that results from cerebral thrombosis.

The pathologic process underlying a thrombosis in- volves platelets. Platelets are disk-shaped cells found in the blood of all mammals. They are important for their role in blood coagulation and are produced in large num- bers in the bone marrow. From there, they are released into the bloodstream, where they circulate for approxi- mately 10 days. While circulating, these cells do not ad- here to each other or to the wall of a blood vessel. When the endothelium, the layer of epithelial cells that line the blood vessels, is breached, however, the blood-clotting properties of the platelets activate. That is, they change shape and stick to the vessel wall, each other, and red blood cells. If this occurs pathologically—that is, in a nor- mal vessel—it leads to a thrombosis, ultimately occluding the vessel. Aspirin is an important antithrombotic agent.

The middle cerebral artery on the left side is the most commonly reported site for an occlusion. Research has shown that blood clot formation most frequently stems from abnormality within the vessel wall and less fre- quently from an abnormality of the blood itself (Brown, Baird, & Shatz, 1986). If a thrombus forms and blocks the flow of blood to the brain, a cerebral infarction oc- curs. The area of the brain in which this occlusion occurs depends on the size of the blood clot. If it is large, it may lodge in one of the major arteries; if smaller, it will lodge

CHAPTER 12 | Cerebrovascular Disorders and Tumors 345

Sudden tingling or numbness on one side of the face

Confusion as to time, place, or person

Loss or impairment of speech for understanding and/or communicating

Sudden slurring of speech, dizziness

Visual disturbances such as blurring or double vision

Other cognitive changes such as difficulty reading, writing, or thinking

Weakness on one side of the body (arm or leg)

Table 12.1 Symptoms of a Transient Ischemic Attack

in a branch of the major arteries. The effects of occlusions in small and large vessels differ. People with long-standing hypertension and diabetes often have occlusions of small vessels, called lacunar infarctions (derived from Latin lacuna, meaning “hole”), because the infarctions are gen- erally small and round. Patients with lacunar infarctions frequently have multiple small lesions. Because the lesions are small and typically deep in the brain (Figure 12.2), they produce not disturbed alertness, headache, or elec- troencephalographic changes, but usually pure motor and sensory deficits. The disease course is often fluctuating or stepwise.

E m b o l i s m

The term embolism (derived from Greek embolos, mean- ing “plug” or “wedge”) refers to a blood clot that has trav- eled from one part of the body to another. Sometimes a piece of plaque originally formed in the heart can “break” off into the blood circulation and travel to the brain. If the blockage is not relieved rapidly, the brain area served by that artery dies of infarction. Embolism are often (up to 33%) associated with a condition known as atrial fib- rillation, an arrhythmia of the heart. Research has re- cently established that cardiac surgery (such as valve re- placement) may potentially contribute to cerebral emboli. When a traveling blood clot or embolism lodges in a dis- tal intracranial branch of a blood vessel, it may block blood flow to specific parts of the brain, so a cerebral in- farction occurs. At younger ages, embolic strokes are more prevalent than thrombotic strokes and are more likely to involve the anterior areas of the brain. Embolisms develop suddenly, often without immediate warning. Most often the patient is awake and active (Toole, 1990).

H E M O R R H A G E

Hemorrhage (derived from Greek haima, meaning “blood,” and regnynai, meaning “to burst forth”) results from rupture of a blood vessel causing heavy spilling of blood into cerebral tissue. The large accumulation of blood within tissue is called a hematoma. Onset of cere- bral hemorrhage is abrupt and usually occurs during wak- ing hours, presumably because the person is more active and thus has a higher blood pressure. Although the sever- ity may vary from a small, symptomless bleed to massive hemorrhage leading to sudden death, prognosis for cere- bral hemorrhage is usually poor, especially if the patient is unconscious for more than 48 hours. A hemorrhage usu- ally occurs when a weak spot in a blood vessel, called an aneurysm, ruptures. Such hemorrhages are usually mas- sive, cause the most severe damage structurally, and often result in death. A large, space-occupying bleed may dis- charge itself through the ventricles and can be detected using a spinal tap. Often alterations in consciousness ac- company hemorrhages, ranging from disorientation to coma. Severe motor and sensory deficits are also usually present, although the degree of deficits depends on the speed and extent of the bleed. Hemorrhages occur most commonly in brain regions that are susceptible to the presence of aneurysms. Those include the putamen (50%), cerebral white matter (16%), thalamus (12%), pons (8%), cerebellum (8%), and caudate nucleus (6%) (Barnett, Mohr, Stein, Yatsu, 1986). There are two kinds of hemorrhagic strokes: intracerebral and subarachnoid.

I n t r a c e r e b r a l H e m o r r h a g e

Intracerebral means “within the cerebrum,” or within the brain. In this type of hemorrhage, a defective artery bursts and floods the surrounding brain tissue with blood. Intracerebral hemorrhages most often accompany hyper- tension and result in deficits localized to either the left or right hemisphere. Medical and neuropsychological prob- lems resulting from an intracerebral hemorrhage occur not only because of the disruption of blood flow that would normally reach the brain tissue from the intact artery, but also because of increased ICP on the brain tis- sue from the increased amount of blood flow into the skull. Large hemorrhages not only destroy brain tissue, particularly if the bleed continues, but also displace vital brain centers, which may prove fatal. Less serious hemor- rhages may disrupt the integrity of adjacent brain tissue without destroying it and produce highly localized symp- toms. When the bleeding does cease, there is usually no recurrence from the same site, a situation unlike that of a bleed resulting from an aneurysm.

346 PART THREE | Disorders of the Brain

Figure 12.2 Lacunar infarcts of the thalamus as seen on computed transaxial tomography scan. (Courtesy Eric Zillmer.)

S u b a r a c h n o i d H e m o r r h a g e

A subarachnoid hemorrhage occurs when a blood vessel on the surface of the brain bursts and blood flows into the subarachnoid space, the small cavity that surrounds the brain. As with intracerebral hemorrhages, a major prob- lem that can occur from this type of stroke is increased pressure on the brain. The extent of dysfunction seen with subarachnoid hemorrhages depends, in part, on how much pressure is exerted on the brain. Acute symptoms include sudden headache, vomiting, and a possible inter- ruption of consciousness. Because of the diffuse effects on the brain, localized symptoms, such as paralysis, typically are not present during a subarachnoid hemorrhage.

A n e u r y s m s

Aneurysms represent weak areas in the walls of an artery that cause the vessel to balloon. These localized dilations of blood vessels may be of congenital origin, but are also pres- ent after trauma, infection, and arteriosclerosis. Aneurysms can produce more significant disorders when they begin to hemorrhage and are a major cause of stroke-related mortal- ity and disability. Aneurysm bleeds range from minor to a complete rupture resulting in a hemorrhage, as described earlier. Approximately 50% of aneurysms occur in the middle cerebral artery and are most likely inherited or re- lated to a pathologic process that weakens arterial walls. Many vascular anomalies remain undetected only to begin causing problems when they rupture because of such fac- tors as high blood pressure. The base rate for adults is 4%; and among those who have aneurysms, 20% have multi- ple ones. Aneurysms, which expand with time, are most often less than 6 to 7 mm in diameter, with giant aneurysms expanding to 2.5 cm. It is relatively rare that small aneurysms rupture (Bannister, 1992).

A r t e r i o v e n o u s M a l f o r m a t i o n s

Arteriovenous malformations (AVMs) represent direct and essentially useless communications between arteries and veins without an intervening capillary network. AVMs are typically congenital collections of abnormal vessels that result in abnormal blood flow. Because they are inherently weak, AVMs may lead to stroke or to inad- equate distribution of blood in the regions surrounding the vessels. Rupture of AVMs may produce intracerebral and subarachnoid bleeding. Like aneurysms, AVMs have a tendency for recurrent bleeding. The clinical symptoms of AVMs can include headache, which is similar to mi- graine in that it is related to the dilation of vessels, or other more vague cognitive complaints (Neuropsychol- ogy in Action 12.1). Often, AVMs have no identifiable clinical consequence and many individuals are not aware

they have the condition. The most serious complication of AVMs is bleeding, typically at a very slow rate. Table 12.2 summarizes the various types of cerebrovascular disorders reviewed in this chapter.

Diagnosing Cerebrovascular Disease

Because of their sudden onset, infarctions are rela- tively easy to differentiate from other focal neurologic dis- orders such as tumors. Gradual obstruction of one vessel, however, may not produce an infarction at all. Because the occlusion develops over a long period, its eventual course into full occlusion may have few or mild effects, because alternative blood sources for the affected brain tissues may have formed over time. The major diagnostic task in differentiating stroke from other neurologic con- ditions is to exclude other causes of lesions that produce similar clinical pictures or cause a bleed. A precise diagnosis

CHAPTER 12 | Cerebrovascular Disorders and Tumors 347

Arteriovenous malformation—arteriovenous malformations (AVMs) represent abnormal, often redundant vessels that cause abnormal blood flow. Because they have inherently weak vessel walls, AVMs may lead to slow bleeding or inadequate distribution of blood in the regions surrounding the vessels.

Embolism—a type of artery occlusion in which the clot forms in one area of the body and travels through the arterial system to another area, in this case, the brain, where the clot becomes lodged and obstructs cranial blood flow. Approximately 14% of all CVAs are caused by an embolus.

Hemorrhage—means bleeding, or literally, the escape of blood from the vessels. It is the most severe form of cerebrovascular accident (CVA), charac- terized by the rupturing of a blood vessel. Hemorrhages account for approxi- mately 10% of all strokes. Most hemorrhages stem from increased blood pressure and the presence of abnormal formations of blood vessels, includ- ing aneurysms.

Migraine stroke—a rare type of stroke caused by severe transient ischemic attacks (TIAs), typically associated with classic migraine.

Thrombosis—a type of occlusion in which a clot or thrombus forms in an artery and obstructs blood flow at the site of its formation. This is the most common form of stroke and accounts for approximately 65% of all CVAs.

Transient ischemic attack—a temporary (transient) lack of oxygen (ischemia) to the brain. This temporary lack of oxygen can cause a time-limited set of neuropsychological deficits. TIAs technically are not considered a stroke, because neuronal death does not occur.

Table 12.2 Summary of Different Types of Vascular Disorders

348 PART THREE | Disorders of the Brain

Although the primary symptom of migraine is a seemingly subjective and excruciating headache, migraine is, in fact, a neurologic disorder of the brain’s vascular structure. Symptoms consist of a moderate to severe lateralized, “throbbing” headache, typically behind the eye, associated nausea, and an increased sensitivity to light, odors, and sounds. Often, a family history shows similar headaches, but the diagnosis is indicated only if no evidence of other organic disease, such as tumor or stroke, could account for the symptoms. Migraines are common: 24 million or 1 of every 11 people in the United States suffer from migraine (Lezak, Howieson, & Loring, 2004). Migraines are more prevalent among women than men (by a 3:1 ratio) and occur most often between ages 30 and 45. The typical frequency of migraine is intermittent (about 2–5 per month), and an attack lasts between 4 and 72 hours. A migraine attack can incapacitate the victim, so high labor costs arise from decreased work productivity and increased absenteeism. About 20% of migraine suffer- ers experience an aura, a neurologic event that occurs before the onset of pain and is most likely caused by a TIA. The aura pre- sents usually as a visual symptom including flashing lights, zigzag lines, or blurred or partial loss of vision. Other neurologic symptoms may also be present during an aura, including increased numbness of the skin (especially in the arms), difficulties in motor coordination, and symptoms of aphasia.

The trigeminal nerve, a large cranial nerve with three branches, has been impli- cated in migraine. The trigeminal nerve conveys sensory information including pain, touch, and temperature from most of the face and the scalp. A proposed mechanism for migraine implicates the sensory “pain” fibers of the trigeminal nerve that surround the cranial arteries that supply blood to the

meninges. In people with migraine, these nerve fibers sometimes release chemicals known as peptides. As a result, blood ves- sels become inflamed, and cranial blood flow changes, first abnormally constricting and then dilating.

Migraine auras occur during the constric- tion phase. This is such a common event among migraine sufferers that many patients notice this as a first sign of the oncoming migraine. During the subsequent dilation, patients experience the symptoms of the migraine attack. Swollen blood vessels stimulate surrounding nerve fibers to relay impulses to the brain, where they are per- ceived as pain. The accompanying severe nausea perhaps relates to a compromise in the blood–brain barrier, which, in turn, allows toxins naturally present in the blood to enter into brain tissue. The neurotransmitter serotonin plays a major role in migraine (Figure 12.3). During migraine attacks,

serotonin levels decrease and medications or substances that deplete serotonin (such as chocolate or the food additive MSG) often trigger a migraine. Conversely, administering a serotonin agonist (such as sumatriptan succinate [Imitrex]) often relieves the headache.

Although many individuals with migraines experience development of transient ischemic attacks (TIAs), few go on to suffer from a cerebrovascular accident (CVA). Although rare, migraine strokes do occur and seem to account for a small proportion of CVAs in people younger than 40 years, particularly female individuals. Medical research has demonstrated that individuals suffering from migraines are actually at less risk for stroke than the general population (Bannister, 1992). This is because the migraine patient’s cardiovascular system is inherently flexible, which allows the constriction and dilation of arteries in the first place (Walton, 1994).

N e u r o p s y c h o l o g y i n A c t i o n 1 2 . 1

M i g r a i n e H e a d a c h e : A V a s c u l a r D i s o r d e r o f t h e B r a i n

by Eric A. Zillmer

is important to the medical team, as well as the neuropsy- chologist, to plan an appropriate rehabilitation program for the stroke patient. The following sections review diag- nostic procedures that are used to document stroke.

C O M P U T E D T R A N S A X I A L T O M O G R A P H Y

Computed transaxial tomography (CT) is a powerful, al- most risk-free technique for imaging the structure of the brain (see Chapter 2). The CT scan often provides the first evaluation in diagnosing stroke, particularly in dif- ferentiating between hemorrhagic and nonhemorrhagic stroke. On CT scans, hemorrhages appear initially as round, well-circumscribed lesions of uniform high den- sity. Over time, the circumference of the lesions becomes more irregular and the lesion less dense. CT scans provide information not only about the location of a hemorrhage, but also size, possible edema (swelling), displacement of other brain structures, and presence of blood in the ven- tricular system. Tumors, which appear on CT with a dif- ferent density, are easily differentiated. Contrast-enhanced CT typically does not increase detection of hemorrhages. TIAs are less easily monitored on CT because of their small size.

A N G I O G R A P H Y

Angiography represents the most accurate diagnostic pro- cedure for vascular disorders. Angiography can also pro- vide an evaluation of collateral vessel potential and a diag- nosis of coexisting neurologic problems. Angiography is an invasive diagnostic procedure that entails some risk (see Chapter 2). Therefore, it is usually reserved as the final diagnostic test for stroke, and CT typically precedes angiography. The two most common routes for angiogra- phy are via the venous and arterial systems (see review in Chapter 2). Arterial angiography is more popular in diag- nosing stroke, because it provides precise images of cere- bral arteries. This is because the specialist can pass the catheter, which injects the contrast medium, up the aortic arch and selectively place it into the carotid or vertebral arteries. Angiography can also show whether the obstruct- ing lesion is significantly impairing carotid blood flow and whether the lesion can be removed surgically. Precise diagnosis of cerebral aneurysms, AVM, artery occlusion, and stenosis (narrowing of an artery) are all possible using angiography.

O T H E R T E S T S

An alternative to angiography and imaging are noninva- sive tests, typically targeted at detecting anatomic and

physiologic information of the common and internal ar- teries. These devices, which use ultrasonic waves, func- tion on the principle that extensive lesions to the carotid arteries may produce distorted sound-wave feedback. In addition, pulse-wave Doppler imaging systems may be sensitive to blood flow velocity. In most cases, a conclu- sive diagnosis is not made; rather, noninvasive devices for carotid blood flow serve to screen for subsequent referral to the more invasive angiogram. CSF analysis using a lumbar puncture is also of value in ruling out or confirm- ing a subarachnoid hemorrhage not seen on CT.

Treatment and Prognosis of Vascular Disorders

F A C T O R S I N V O L V E D I N S T R O K E R E C O V E R Y

Once an individual has had a stroke, the type of damage or lesion and associated neuropsychological symptoms de- pend on a number of medical and neuroanatomic factors. These include the extent of the lesion, the general health of the cerebrovascular system, the presence of collateral circulation in the brain, and the location of the lesion. These factors influence the extent and nature of associ- ated cognitive symptoms, as well as the possibility and prognosis for recovery and extent of rehabilitation.

S i z e o f B l o o d V e s s e l

If a small blood vessel (such as a capillary) is interrupted, the effects are more limited than the often devastating consequences of damage to a large vessel, such as the in- ternal carotid artery or other cerebral arteries. Strokes of these large arteries can result in lesions that include large portions of the brain and produce serious behavioral deficits, coma, and even death.

R e m a i n i n g I n t a c t V e s s e l s

If a CVA occurs in one restricted portion of the brain, the prognosis may be rather good, because healthy blood ves- sels in surrounding brain tissue often can supply blood to at least some of the deprived areas. In addition, the pres- ence of collateral blood vessels allows redundant blood supply to take more than one route to a given region. The term collateral is used to describe redundant blood flow present in the vascular network after occlusion of an artery. If one vessel is blocked, a given region may be spared an infarct because the blood has an alternative route to the affected brain area. Conversely, if a stroke oc- curs in a region surrounded by weak or diseased vessels

CHAPTER 12 | Cerebrovascular Disorders and Tumors 349

(as in arteriosclerosis), the effects may be much more seri- ous, because there is no possibility of compensating. The surrounding weak zones may also be at an increased risk for stroke.

This communication between blood vessels by collat- eral channels is also known as anastomosis and provides an important defense against stroke. The properties of collateral communication that provides a sufficient blood supply to obstructed areas vary considerably among indi- viduals. Thus, damage to the same vessel in different peo- ple can produce symptoms that vary considerably. Anas- tomosis can provide some relief to blood-depleted brain areas, particularly if the primary vessel affected is gradu- ally blocked, rather than rapidly occluded.

P r e m o r b i d F a c t o r s

The presence of previous strokes is a strong predictor of disability. A small stroke in an otherwise healthy brain will, in the long run, have a good prognosis for substan- tial recovery of function. However, the effects of an addi- tional lesion most often are cumulative. As a result, de- struction of a functional zone of brain tissue may produce serious consequences for the patient.

L o c a t i o n

The location of brain tissue involved in a vascular disor- der has neuropsychological significance. A lesion in the temporal lobe can produce a deficit in understanding speech; a stroke in the hippocampus can cause memory deficits; and a lesion in the brainstem can trigger heart failure, resulting in death. Thus, behavioral symptoms of vascular disorder are important clues to the neuropsychol- ogist for locating the area of brain damage and assessing the extent of damage.

M E D I C A L T R E A T M E N T

The initial treatment of the stroke patient involves med- ical stabilization and control of bleeding, if necessary through surgery. Common medications include anticoag- ulants to dissolve blood clots or prevent clotting, vasodila- tors to dilate or expand vessels, and blood pressure med- ication and steroids to control cerebral edema. Surgeons have developed interventions to reduce the risk for bleed- ing for some aneurysms by “clipping” them (Figure 12.4). Other surgical procedures are used in the case of hemor- rhages when it may be necessary to operate to relieve the pressure of the blood from the ruptured vessel on the rest of the brain. Small hemorrhages typically are not treated surgically, but rather are controlled by altering the pa- tient’s blood pressure.

Physicians typically treat infarctions by intravenously administering heparin (a potent anticoagulant agent), but only if diagnosis rules out a mass lesion from a trauma or hemorrhage (either intracerebral or subarachnoid). Ad- ministering an anticoagulant agent to a patient with a he- morrhage can be fatal; therefore, establishing a precise dif- ferential diagnosis is important. In medium-size bleeds, surgical draining is often effective, although this tech- nique may leave a surgical hole in the brain that may later entail neuropsychological deficits. Other ways to decom- press the brain include artificial hyperventilation, corti- costeroids, and diuretics. In most cases, physicians artifi- cially lower the blood pressure. Treatment for TIA symptoms, which is more difficult because the symptoms are ambiguous, is often restricted to pharmacologic inter- vention with anticoagulants. An obvious danger in using anticoagulants is the inherent risk for an uncontrolled bleed.

AVMs are often surgically removed or are embolized artificially. In the latter technique, the surgeon delivers an agent that blocks the blood vessel close to the lesion, in some cases permanently. The embolization agent is a sponge, ball, coil, or balloon and entails certain risks. This delicate technique uses highly selective catheterization procedures and close radiographic monitoring. The rea- son for this care is that the delivery system must advance as close to the lesion as is possible; otherwise, healthy ar- teries may be embolized, or the embolus may migrate to the lung or heart.

P R E V E N T I N G S T R O K E

Many people who have had a stroke say that it “struck out of nowhere”—there seemed to be no obvious warning. Typically, a stroke that occurs spontaneously results from an embolism or a hemorrhage. That one can have a stroke with little or no warning testifies to the importance of iden- tifying the many risk factors associated with stroke. The most prominent risk factor is a history of stroke. In fact, as mentioned earlier, stroke recurrence is an important con- tributor to disability. In addition, common demographic

350 PART THREE | Disorders of the Brain

Figure 12.4 Aneurysm clip (approximate size � 6 mm). (Courtesy Eric Zillmer.)

factors predispose an individual to cerebrovascular dis- ease, including:

Heredity (cardiovascular disease in one’s family) Sex (men are at greater risk for stroke than women, a risk

related to their higher incidence of heart disease and hypertension)

Ethnicity (African Americans have one of the highest stroke rates, 40% greater among women and 10% greater among men)

Lifestyle indices also affect the probability of cardio- vascular disease. A well-known risk factor of CVA is hy- pertension. Elevated blood pressure means that the force of the blood against the walls of the arteries is too high. As a result, over time the arteries become weakened and can burst. If this happens in the brain, it results in a cere- bral hemorrhage. High blood pressure can also increase the force of the blood against the artery walls and break off some plaque along those walls, which then travels as an embolus through the bloodstream until it clogs a narrower vessel. The dangerous part of hypertension is that most people do not feel it, and thus do not seek medical help.

Other risk factors for stroke are diabetes and high cho- lesterol. Individuals with diabetes run a greater risk for stroke. Vascular diseases are most often related to prob- lems in artery linings, which become hardened by de- posits of cholesterol, fat, calcium, and other materials such as fibrin, a substance that encourages clot formation. Fat causes plaque to build up along the lining of blood vessels, which can break off and lead to embolic stroke or can become so built up that thrombotic stroke can occur. Because smoking is a vasoconstrictor, it is an additional risk factor for stroke. Smoking a cigarette constricts an al- ready too-narrow blood vessel.

Small amounts of alcohol may actually thin blood and can serve the same purpose as one aspirin per day. Also, some evidence suggests that a glass of wine with dinner reduced cholesterol. Alcohol becomes a risk factor when consumed in large quantities. Excessive consumption contributes to high blood pressure and may result in ataxia (poor balance), which is often already a problem after a stroke. Also, alcohol is a sedating drug and may not interact well with other drugs. Finally, obesity con- tributes to the onset and maintenance of diabetes, hyper- tension, heart disease, and high cholesterol. Obesity is medically defined as being 25% over your ideal weight. Approximately 26% of men and 30% of women in the United States are overweight. Cardiovascular complica- tions in obesity are related to the high correlation between being overweight and hypertension, a precursor of coro- nary heart disease.

Neuropsychological Deficits Associated with Stroke

Significant functional and cognitive impairments are often the result of stroke. These deficits can seriously impair the patient’s ability to function independently and are often incapacitating and serious enough to lead to hos- pitalization in a rehabilitation facility. Typically, long-term hospitalization occurs because the patient is exhibiting symptoms of inattentiveness, apraxia, communication difficulties, apathy, or general intellectual impairment.

Many factors influence cognitive changes as a result of stroke. These factors include the patient’s age, interval be- tween the stroke onset and time of rehabilitation, nature of the stroke (infarction or hemorrhage), and size and lo- cation of lesion (such as right or left brain, anterior or posterior). The patient’s medical history is important, par- ticularly as it relates to the presence of previous strokes (such as lacunar strokes), prior CNS trauma or disease, and premorbid level of functioning. Many stroke-related cognitive deficits may resolve over time, sometimes im- mediately after the stroke. For example, the more local- ized the effects, the more positive the prognosis. But resid- ual deficits may remain that require an evaluation of cognitive abilities and subsequent rehabilitation (Brown, Baird, & Shatz, 1986).

Because of their complexity and variability from pa- tient to patient, the cognitive deficits associated with stroke are not easily classified into simple categories. For didactic purposes, neuropsychologists correlate cognitive deficits with the specific type of stroke. Correlating the location of an anatomic lesion with the stroke patient’s cognitive impairments has been only modestly successful. Thus, the neuropsychology student should be careful not to rigidly adhere to specific patterns of deficits and recov- ery, but instead should realize that the disease course in individual patients varies greatly (Weimar et al., 2002).

N E U R O P S Y C H O L O G I C A L R I S K F A C T O R S

Several important principles govern the properties of neu- ronal processes that are particularly relevant to under- standing the neuropsychology of cerebrovascular disor- ders. These principes are explained in the following paragraphs.

N e c r o s i s

Neurons that have died as a result of necrosis do not spon- taneously regenerate. In most instances, lost neurons in the CNS are incapable of healing after the developmental

CHAPTER 12 | Cerebrovascular Disorders and Tumors 351

period (see Chapter 4). Thus, no cellular regeneration of the neuron or regrowth of damaged neurons to their nor- mal target occurs. Neurons lost as a result of stroke are not replaced. Fortunately, functional losses entailed by these structural losses are not necessarily permanent, be- cause the brain has redundant pathways for supplying blood to various areas. Specifically, redundant blood sup- ply in the brain may minimize neuronal death because there is sufficient blood supply to brain areas that have been damaged. Also, the process of rehabilitation allows some compensation of functional losses with behaviors that have been left relatively intact. Rehabilitation may alleviate enough disruption caused by stroke that the vic- tim regains some or nearly all of his or her premorbid level of functioning. In fact, neuropsychologists have made sig- nificant headway recently in developing assessment, pros- thesis, and cognitive rehabilitation techniques to com- pensate for disrupted functional brain systems. In addition, neuroscientists are making some progress in designing drugs that facilitate the regrowth of injured neurons.

D i s i n h i b i t i o n

An important principle of neuronal processes relevant to understanding the neuropathology of stroke relates to the capacity for inhibiting behavior after a stroke. As dis- cussed in previous chapters, many of the neuronal collec- tions, particularly in the frontal lobe, serve to inhibit rather than initiate behavior. This is important because losing inhibitory neurons to stroke may actually result in an inappropriate increase in behavior or disinhibition, and often causes striking behavioral and personality changes in stroke victims. Damage to an excitatory col- lection of fibers, of course, results in losing some func- tion. This is why many traumas to the brain, including stroke, often show both loss of function (such as aphasia and the inability to speak) and disinhibition (increased likelihood of inappropriate behavior) including impul- siveness, hypersexuality, and inappropriate feelings. This was made painfully clear when a colleague of ours was leading a stroke support group. All members of the sup- port group had sustained a stroke, and many had signifi- cant related cognitive deficits. Almost all members demonstrated poor judgment and disinhibition when it came to operating an automobile, and they spent much time in the group discussing this. Nevertheless, they in- sisted on continuing to drive and drive poorly; in fact, many accidents happened in the parking lot before and after group meetings. When group participants returned from trips, they would discuss and bring along pictures of their recent accidents. They described these crashes with

some bravado, reflecting poor insight and a general lack of awareness of the dangers. This is a typical example of disinhibition because victims do not inhibit high-risk be- havior, as they may have done premorbidly, that is, before the stroke. The incapacity to drive after a stroke is one of the most sensitive issues facing health care workers, stroke victims, and their families.

D i s c o n n e c t i o n S y n d r o m e

Because the substructures of the brain connect so intri- cately, observed deficits in a stroke patient may not neces- sarily correspond to the lobe or site where the stroke oc- curred. For example, a stroke in the visual area of the cortex (occipital lobe) ordinarily results in some form of visual impairment. In addition, however, these visual deficits may also disturb motor behavior or gait. Further- more, a stroke may disrupt important pathways of neu- rons that project to other centers of the brain. This is a common problem when strokes occur near subcortical structures such as the striatum, a common stroke site. Such a stroke commonly results in higher order cognitive deficits, because injury has severed projections to the cortex. This problem is called disconnection syndrome, because impor- tant pathways in the brain have been “disconnected.”

A T T E N T I O N D E F I C I T S

Many types of brain dysfunction typically reduce effi- ciency of the brain in processing information. This is cer- tainly true for CVA. In milder cases, stroke victims can- not sustain their attention to one particular stimulus for long periods or select information from competing sources (selective attention). This impairment may be minimally present and detectable only with formal neu- ropsychological testing, or it may be profound and easily noticeable by any observer. Sometimes cognitive changes in stroke patients are so pervasive that the patient is con- siderably confused and disoriented as to time, place, and person. Deficits of arousal typically relate to damage of the patient’s frontal lobe circuitry or the brainstem region. In contrast, deficits in attention may relate to local or global brain damage.

M o t o r a n d S e n s o r y I m p a i r m e n t

General behavioral slowing and a reduction of psychomo- tor activity can be dominant characteristics of stroke. Both the right and left hemispheres are associated with changes in motor and sensory functioning from stroke. Such changes can be as benign as mild motor slowing or as debilitating as complete paralysis, particularly if the le- sions are in the thalamic area or the motor and premotor

352 PART THREE | Disorders of the Brain

areas of the frontal lobes. Motor deficits of the right brain resemble those of the left brain. Right hemisphere stroke motor deficiencies, however, are generally less severe, be- cause the nondominant left hand is not as important for skilled tasks.

Severe motor deficits are often apparent without for- mal testing and may involve impairment in motor speed, strength, steadiness, and fine-motor coordination. Even mild deficits may significantly reduce the efficiency on highly demanding manual tasks, interfere with self-care or light housework, deteriorate handwriting skills, and slow reaction times, which may require the victim to give up driving. Diminished sensory functioning is most likely in areas of visual acuity, visual field perception, and hearing.

M E M O R Y P R O B L E M S

Stroke survivors commonly report that their memory is not as good as it was before the stroke, and on occasion, they may not recall a person’s name, even when they know that person well. Many stroke patients exhibit intact memory for old learning, but not always for new learn- ing. That is, they can remember events that happened years ago, but may be unable to remember what they had for lunch today. Unless the lesion is extensive, CVAs do not typically cause loss of primary, immediate, or long- term memory, but are most pronounced in the area of short-term memory. This most likely relates to the stroke patient’s decreased capacity to organize and process large amounts of information (“chunking”) in a fashion that lends itself to easier memory storage or retrieval. Not un- commonly, these patients recall only a small amount of new material 30 minutes after it is presented to them.

Patients that have stroke-related hippocampal damage experience significant memory difficulties, may require repetition of new information, and may show significant problems with forgetfulness associated with a variety of everyday tasks. Such patients have frequent difficulty re- calling details of recent experiences, tend to misplace things, fail to follow through on new obligations, and tend to get lost more easily in unfamiliar areas.

Stroke patients with the most severe memory deficits are virtually unable to retain any information, particu- larly if their attention has been directed elsewhere. Such individuals also cannot profit from repeated exposures to stimuli. They need substantial assistance in daily living and characteristically cannot take care of themselves, be- cause they may create fire hazards at home and cannot manage financial affairs or keep track of scheduled activi- ties. For such patients, it helps to create an environment where important objects are kept in the same place, the

same daily routines are maintained, and instructions are verbalized in the same sequence. A major concern related to memory impairment is the stroke patient’s ability to manage his or her own medication schedule.

D E F I C I T S I N A B S T R A C T R E A S O N I N G

Impaired judgment, loss of insight, and diminished ca- pacity for abstract and complex thinking are common cognitive changes among stroke victims, particularly if anterior aspects of cortical areas are involved. People with mildly impaired abstract reasoning and new concept for- mation can often use their past accumulated knowledge to exercise reasonable judgment for routine daily activi- ties. Those who show more serious cognitive decline often encounter difficulties with tasks that require complex planning or organization and with novel situations. Such patients cannot assess new situations accurately and demonstrate poor judgment, with serious consequences to themselves or others.

C O G N I T I V E D E F I C I T S A S S O C I A T E D W I T H R I G H T B R A I N S T R O K E S

Researchers have directed much research attention toward distinguishing the cognitive deficits between left versus right hemisphere brain damage. In general, patients with left-sided brain damaged show markedly impaired lan- guage comprehension and communication, and stroke pa- tients with damage to the right hemisphere exhibit signifi- cantly more impairment in ability to process and execute behaviors that require visual-perceptual ability (Lezak, Howieson, & Loring, 2004; Reitan & Wolfson, 1993).

Deficits that affect the right cerebral artery involve areas responsible for spatial, rhythmic, and nonverbal pro- cessing. Right hemisphere symptoms, although serious in the patient’s overall functioning, can be less striking in the acute phase, particularly if they do not involve motor dys- function. Right brain damage occurs as a consequence of right-sided CVAs and is often associated with contralateral motor and sensory impairment. Patients with right-sided brain injury present a variety of symptoms that pose a par- ticular challenge to the neuropsychologist. First, the deficits often found among patients with right hemi- sphere brain damage are not as striking initially as the deficits observed among patients with left hemisphere brain damage, in which case the patient is often aphasic. Second, many patients with right-sided brain damage dis- play a range of emotions from indifference to euphoria. This is in contrast with the depression often observed among patients with left hemisphere brain damage.

CHAPTER 12 | Cerebrovascular Disorders and Tumors 353

Therefore, it is easy to assume that the deficits from right brain damage are not as serious as those from left brain damage. However, this is not true, because both types of problems can be highly disruptive to patient and family alike, often even exceeding the problems associated with left hemisphere CVAs.

For example, research has shown consistently that pa- tients with right hemisphere stroke remain longer in re- habilitation facilities than do patients with left hemi- sphere strokes (Zillmer et al., 1992). This difference is related to the pervasive deficits that patients with right hemisphere damage present in visuospatial abilities and the extended rehabilitation required for dressing, ambu- lating, and other self-care behaviors.

Right hemisphere stroke patients are not diagnosed as rapidly as are left hemisphere stroke patients. This is prob- ably related to the difficulty that left hemisphere stroke patients display in using language—an obvious symptom that helps a family member identify that something is “wrong” with their loved one. In contrast, patients with right-sided brain damage often use language fluently. Thus, on the surface, they “sound” okay. Furthermore,

patients with right-sided brain damage tend to be un- aware of their problems. Such patients often deny that there is anything wrong with them. As a result, patients may be blamed for being “rude,” “disruptive,” or “inap- propriate,” when they are actually exhibiting symptoms of right brain injury, including impulsivity, verbosity, inat- tention, and poor judgment. Thus, although neuropsy- chological deficits in patients with right hemisphere stroke may be more subtle, they are equally and sometimes more functionally disabling than the more obvious language im- pairments typically associated with left hemisphere stroke.

V i s u o s p a t i a l D e f i c i t s

Deficits in right hemisphere stroke patients almost always include visuospatial deficits—that is, the patient’s capac- ity to accurately perceive his or her surrounding world in its completeness. Neuropsychologists report that visu- ospatial deficits occur particularly after right hemisphere stroke and include both visual-perceptual and visual- constructional abilities. Patients with problems in spatial relations have difficulty estimating the distance between different objects, as well as between themselves and other

354 PART THREE | Disorders of the Brain

The patient is a 32-year-old, married, right- handed woman with 12 years of education. She worked as a manager for a fast food restaurant and lived with her husband and two young children in a two-story house. One month before my evaluation, she sustained a sudden onset of aphasia, right-sided weak- ness, and headache. Computed transaxial tomography (CT) scan showed an infarction in the area of the left cerebral hemisphere. A carotid angiogram showed an occluded internal carotid artery. Medical history was unremarkable.

I tested her neuropsychologically 1 month after the stroke. In my clinical interview with the patient, her speech was marked by paraphasias (the substitution of wrong words or phrases) and verbal perse- verative tendencies (unnecessary repeat- ing), which are signature symptoms for a left hemisphere stroke. She was oriented to person and could state her name, age, and

date of birth. She was somewhat oriented to place; that is, she knew she was in a rehabili- tation hospital but could not give its name or location. She could write the correct date, but could not recall the current or last presi- dent. She showed a significant sensory and motor deficit on her dominant right side. She could not feel light touch on her right hand with single or double simultaneous stimula- tion. On verbal tasks, she was able to per- form automatic tasks such as counting from 1 to 20 and reciting the alphabet, but she could not perform any other tasks that required voluntary and purposeful speech. The patient’s gross- and fine-motor ability and speed were intact on her nonaffected left side. However, on her dominant right side, she showed a marked hemiparalysis and could not voluntarily move her right shoulder, arm, hand, or fingers. She did not show any evidence of motor apraxia and could copy simple designs adequately with

her nondominant hand, suggesting intact right hemisphere functioning.

As expected, her verbal functions were severely impaired, consistent with the loca- tion of her cerebrovascular accident (CVA) in the distribution of the left middle cerebral artery. Receptive language skills were mod- erately impaired, as she could follow only one-step commands without difficulty. She became easily confused with two-step commands. Expressive speech was severely impaired. On the word fluency item, which requires the individual to name as many animals as possible in 30 seconds, she was able to name only one and perseverated with the word baseball, which was an incorrect response to a previous item. She was able to correctly repeat words and phrases after the examiner, but was unable to initiate a correct response on her own. She also demon- strated alexia and agraphia for written language.

N e u r o p s y c h o l o g y i n A c t i o n 1 2 . 2

C a s e E x a m p l e o f a L e f t S t r o k e

by Eric A. Zillmer

people or things. Common examples of mistakes that pa- tients make with this kind of disturbance include knock- ing items off a table when dusting, misplacing items on tables so that they are no longer centered or are in danger of falling off, and misjudging steps or thresholds, which puts them in danger of falling.

Obviously, patients with spatial relations disturbance may have difficulty driving a car, and they may often need help in other areas of their lives such as stair climbing and activities of daily life such as dressing, bathing, toileting, and eating. It is in unfamiliar environments and in novel situations that driving is difficult for these patients. In case of marginal impairment, it may be helpful to limit patients to driving only in their own neighborhoods. In difficult cases, a neuropsychological evaluation can aid in making this decision. Motor impersistence is also a com- mon sign—the stroke patient cannot persist with a motor response for any length of time (such as keeping eyes closed or holding arms over the head). Often, others may perceive the patient as being oppositional or stubborn, when, in fact, he or she is not in control of the skills re- quired to perform the action.

C O G N I T I V E D E F I C I T S A S S O C I A T E D W I T H L E F T B R A I N D A M A G E

In general, cognitive profiles are most robust when associ- ated with damage of the left versus the right brain hemi- sphere. For example, the middle cerebral arteries serve major sensory and motor areas; thus, significant motor and sensory deficits often affect the side contralateral to the stroke. One of the most common infarctions is that of the left middle cerebral artery, in which deposits have traveled up from the heart and then blocked the middle cerebral artery. Disorders of the left middle cerebral artery most often involve cortical areas of the brain responsible for both expressive and receptive speech. Thus, one of the most dramatic symptoms of a left middle cerebral artery stroke is the impairment in speaking or understanding speech, or both. Deficits also include severe motor and tactile symp- toms on the contralateral right body side in addition to ex- pressive aphasia (Neuropsychology in Action 12.2).

Understanding and being understood by others is the goal of most human interactions. When a stroke dam- ages that part of the brain that controls language and

CHAPTER 12 | Cerebrovascular Disorders and Tumors 355

The patient’s visuospatial functions were basically intact. Figure–ground distinctions, spatial manipulation, visual sequencing, facial recognition, and spatial orientation all tested within normal limits. Her visual mem- ory appeared to be within normal limits for both immediate and delayed recall proce- dures. However, verbal memory was severely impaired secondary to her receptive and expressive aphasia. She was able to correctly repeat a list of five words for four separate trials. However, on the recognition task (2 minutes later), she could identify only two words and made five false positive responses.

Her judgment/problem solving appeared moderately impaired secondary to her receptive and expressive aphasia. Yet, she did demonstrate some reasoning skills on the purely visual problem-solving items such as the visual analogies. She showed a moderate degree of psychological distress.

Overall, she showed a moderate degree of cognitive impairment for left hemisphere functions, which was consistent with the site of her CVA. Interestingly, on casual observa- tion, she looked more impaired than she was on testing, given that laypeople almost always evaluate a person’s cognitive status based on the vocabulary they use.

I retested the client 1 month later after she had completed her inpatient rehabilita- tion program. Overall, she showed significant improvement in orientation, verbal functions, memory, judgment/problem solving, psycho- logical distress, and activities of daily living skills. The client correctly responded verbally to all the orientation questions except for one, which asked what town the hospital was located in. Verbal functions improved dra- matically. The client showed good receptive speech in that she was now able to follow two-step commands easily. Verbal fluency remained limited but still showed a dramatic improvement. On the animal fluency item, she went from zero to five words and could now read and write sentences to dictation. Memory functions showed a significant improvement in her verbal memory, because she could now encode verbal information and retrieve it spontaneously. Judgment/problem solving showed some problems with concrete thinking, but generally good common sense, reasoning, and judgment. The reported amount of psychological distress experienced by this young woman decreased significantly, and she showed remarkable increase in her level of independent functioning in her activi- ties of daily living.

In summary, neuropsychological testing proved a valuable technique in tracking this young woman’s recovery from stroke during the acute stage of recovery. It was also effective in demonstrating the breadth of improvement this client made in cognitive, psychological, and physical skills, as well as documenting the residual areas of impair- ment in verbal functioning and verbal mem- ory. A follow-up evaluation as an outpatient 12 months after stroke was recommended. The neuropsychology student should note that the precise extent of this patient’s deficits and partial recovery is not obvious even to health care workers and the immedi- ate family. That is why neuropsychological testing can be so important, not only in quantifying cognitive abilities but also in setting realistic expectations for recovery and rehabilitation. In this case, the family was focusing primarily on the patient’s residual impairment in memory and lan- guage. In charting the patient’s remarkable recovery, I was able to help the family re- frame their perceptions of the perceived strengths and weaknesses, thus helping them also cope with this potentially devas- tating disease.

communication, the effects can devastate both patient and family. Several types of communication problems can occur with stroke, and neuropsychologists play an impor- tant role in diagnosing and rehabilitating specific forms of communication problems in stroke survivors. Many patients also have apraxia, a loss of voluntary movement that makes it difficult or impossible for patients to use gestures to communicate their needs. The presence of apraxia is the main reason why speech pathologists do not routinely attempt to teach aphasic patients sign language to compensate for spoken language difficulties.

Often, patients lose not only spoken language but written language as well. Writing is one of the most com- plex of language abilities. If writing is disturbed by im- pairment to the limb that produces letters and words, neuropsychologists do not consider that a disorder of lan- guage. Rather, in written language deficits, words, let- ters, or numbers may appear foreign or incomprehensi- ble because the person cannot recall the form of letters. His or her attempts to write may be filled with real or imagined letters that make no sense to others. With time and training, the person may be able to understand simple written language—for example, single words such as bath or food—but still be unable to compre- hend more complex written language such as sentences or paragraphs.

Many so-called behavioral problems seen with stroke patients with aphasia occur because of receptive aphasia. In moderate cases, the patient can understand part but not all of the communication. Sometimes patients’ appar- ent noncompliance is actually caused by their misunder- standing the communication. Thus, a patient may act as though he or she had not heard a word at all (so-called word deafness) or as though he or she had heard only frag- ments of the word. The most common defect lies not in failing to recognize that someone spoke a word, but in failing to attach meaning to the word. Some patients with aphasia comprehend individual words, but not certain grammatical constructions.

Often, stroke patients with visual disorders have considerable difficulty reading because they are blind to certain visual fields. This problem is not related to re- ceptive aphasia; rather, the patients cannot see the word—if they could, they would read it correctly—or are unaware of additional words that need to be read, as in unilateral inattention. The classification of aphasias into receptive and expressive is a useful didactic tool, but in reality, most left hemisphere stroke patients have a combination of both aphasia types, because the left mid- dle cerebral artery serves both expressive and receptive areas.

A N T E R I O R V E R S U S P O S T E R I O R S T R O K E S

Disorders of the anterior cerebral artery may cause motor or sensory impairment involving the leg. Because the an- terior cerebral arteries serve the prefrontal lobes, deficits consistent with a prefrontal syndrome, including disinhi- bition and dysfunction of executive skills, are also charac- teristic. Strokes in the posterior cerebral artery are less common and typically cause visual field loss and sensory loss of one side. Basilar artery disorders may have a simi- lar effect as posterior cerebral arteries stroke if the poste- rior communicating artery provides insufficient blood supply. Those include blood flow disruption of the brain- stem, including cranial nerve involvement, the cerebel- lum (see Figure 12.1 for an example of a cerebellar stroke), and the occipital lobes.

E M O T I O N A L A N D B E H A V I O R A L C H A N G E S A F T E R A S T R O K E

After a stroke, it is common for patients to respond dif- ferently to people and events in terms of their emotional reactions. This relates, in part, to the experience of signif- icant stress in the patient’s life, but also to that the in- tegrity of the brain has been compromised.

D e p r e s s i o n

Depression is a common and not surprising reaction to stroke. Depression may be indicated if patients feel over- whelmed with sadness, believe they have failed completely, blame themselves for their problems, and often feel like crying. Poor sleep, decreased appetite, low self-esteem, and reduced efficiency are present as well. Whenever people experience loss, depression is a natural response. Depres- sion is most likely to occur among patients with right- sided weakness and corresponding left hemisphere stroke. Often, a patient does not show signs of depression until 6 to 12 months after a stroke, when the scope of the loss has sunk in and there is time to think about how life has changed. Research and experience tells us that depression is best treated with a combination of psychotherapy and antidepressant medication.

A p a t h y

Apathy, or indifference, involves lack of emotions. The person is not sad or happy. In fact, the person may not appear to have any emotions. The voice sounds monot- one, the face lacks expression, and if you ask the patient what he or she feels, the answer will be neutral, or without affective tone. On occasion, patients who lack vocal and fa- cial expression nevertheless report that they feel depressed,

356 PART THREE | Disorders of the Brain

afraid, or angry. Both depression and apathy are quite common after a stroke, especially after anterior medial damage. This is related, in part, to the loss of function that can accompany stroke, but also to reduced brain efficiency after such trauma. Thus, part of the depression or apathy in a stroke patient is related to the stroke itself. In this sense, the depression is more biological than psychological.

E u p h o r i a

Euphoria is an overriding positive emotional response that is “too happy” given the circumstances. Euphoric people are not sad, indifferent, or apathetic; in fact, they are full of ideas and energy. Patients with euphoria seem posi- tively happy about or despite their condition. Euphoria goes beyond a capacity to overcome obstacles—it is as if no obstacles existed. Apathy and euphoria are especially common among patients with left-sided weakness—that is, those suffering from right hemisphere stroke.

I m p u l s i v e E m o t i o n a l a n d B e h a v i o r a l D i s p l a y s

An impulsive emotional response is one that appears to come without warning. Patients who have labile emotions will cry or laugh in response to events or phrases that oth- ers around them might find only mildly arousing. For ex- ample, most people respond to the National Anthem be- fore a baseball game with a smile. The stroke patient may respond with seemingly uncontrolled tearfulness or laugh- ter. Labile emotional responses usually embarrass the pa- tient and upset the family members. As a consequence, family members often avoid talking about important fam- ily topics, lest the discussion “upset” the patient. It is im- portant to remember that labile emotional responses are a physiological and not an emotional response to a stroke. In fact, patients often cry in response to happy events—as when a therapist compliments them.

Impulsivity of behavior also affects a person’s ability to stop motor actions. For example, a stroke survivor may automatically stand up and begin to walk on legs that cannot support him or her. This is dangerous to the well- being of the stroke patient, and therapists spend much time in rehabilitation helping the patient to inhibit dan- gerous or inappropriate behaviors.

L a c k o f I n i t i a t i o n

On the other end of the spectrum, strokes can also impair a person’s ability to initiate (or start) a behavior (akine- sia). For example, the person may be hungry, and food may be sitting there ready to be consumed, but the per- son fails to bring the food to his or her mouth. In the ex- treme, the person may fail to chew once food has been

placed in his or her mouth. The inability to initiate be- havior may appear in the person’s verbal responses. For example, it may take a long time to answer questions. A difficulty related to problems initiating actions is the per- severation of behavior. Perseveration is the inability to stop behaviors once they have started. A patient may per- form a motor movement over and over again, unable to stop it. Motor rigidity, perseveration, motor impersis- tence, and disinhibition are common problems in stroke patients and generally improve with rehabilitation.

P o o r J u d g m e n t

Many stroke victims demonstrate poor judgment, espe- cially with prefrontal cortical damage. Ironically, many such patients often can verbalize the appropriate actions they “should take,” but cannot follow through with those actions. For example, individuals with a spatial problem may be able to verbalize the steps in preparing a cup of coffee, but nevertheless continue to let coffee overflow when pouring a cup. It is as if their words and actions were not related. The brain trauma has impaired their ability to monitor their own behaviors and to understand the consequences of their own actions.

Tumors of the Brain

When I was in graduate school my aunt (EAZ) was diagnosed with a brain tumor. The MRI suggested that it was consistent in size and appearance with a malignant tumor. A decision was made to operate and remove as much of the tumor as was possible. Because the tumor was the size of a baseball it had already displaced and in- vaded healthy brain tissue. As a result, my aunt’s speech was severely impaired and she complained of headaches and dizziness. The brain surgery would immediately re- lieve many of my aunt’s symptoms and would allow for a biopsy to classify the exact type of tumor cell.

To reach such a tumor, a team of specialists first drill a series of holes into the patient’s skull, not unlike the burr holes used in the ancient procedure of trephination (re- viewed in Chapter 1). Then the surgeon connects the holes with a surgical jigsaw. After he or she lifts the oval- shaped piece of skull the dura mater is exposed, a thick membrane that protects the brain and spinal cord. My aunt’s tumor was inside of the brain tissue and thus the neurosurgeon had to proceed through healthy brain tis- sue to reach the tumor. The neurosurgeon had to navi- gate carefully, dividing the tumor from the normal brain, cauterizing severed blood vessels along the way. Gradually

CHAPTER 12 | Cerebrovascular Disorders and Tumors 357

the tumor was cut, actually siphoned, away from my aunt’s brain and extracted. A lab autopsy verified the ini- tial diagnosis: a malignant glioma, a fast-growing and dangerous tumor (discussed later). By the following day, she would be walking the halls and feeling much better. Her long-term prognosis was poor, however, since re- search clearly demonstrated that similar patients only live 6 to 12 months, even after a successful operation. No matter how careful the surgeon cuts out the malignant tumor, the few stray cancer cells that are inevitably left behind will begin to grow again. My aunt’s death sentence had been postponed, perhaps by a year.

The term tumor refers to a morbid enlargement or new growth of tissue in which cell multiplication is un- controlled and progressive. Tumors are also called neo- plasms, which means “new tissue.” The new cell growth resembles cells already normally present in the body. This growth is, however, often arranged in disorganized ways, does not serve any functional purpose, and often grows at the expense of surrounding intact tissue. Brain tumors make up approximately 5% of all cancers and appear in approximately 2% of all autopsies. Because cancer is the second most frequent cause of death, the actual number of victims with brain tumors is actually quite high. Brain tumors can occur at any age, but are most common in early and middle adulthood (Golden, Zillmer, & Spiers, 1992).

Brain tumors can be conceptualized according to two principal forms:

1. Infiltrative tumors—take over (or infiltrate) neigh- boring areas of the brain and destroy its tissue

2. Noninfiltrative tumors—are encapsulated and differ- entiated (easily distinguished from brain tissue), but cause dysfunction by compressing surrounding brain tissue

Tumors can be further classified according to two addi- tional descriptors:

1. Malignant—indicates that the properties of the tumor cells invade other tissue and are likely to regrow or spread

2. Benign—describes cell growth that is usually sur- rounded by a fibrous capsule, is typically noninfiltra- tive (noninvasive), and will not spread

The primary feature of malignant tumors is that they are much more likely to reappear after surgical interven- tion. Because they are infiltrative, it is difficult to completely remove malignant tumors surgically. Malignant tumors may also “travel” to other organs in the body through the blood- stream. This form of spreading is called metastasis.

Metastatic brain tumors typically originate from primary sites other than the brain, most frequently the lung or the breast. Even benign tumors, however, are troublesome if they occur in the brain. This is because the skull completely encloses the brain, and any mass-producing lesion displaces healthy brain tissue. You may already realize that nerve cells are not likely to cause brain tumors, because neurons do not grow or heal spontaneously. This is correct. Tumors of the brain arise mostly from the supporting cells of the brain. As a result, neurons are only indirectly affected. Neuromas are tumors or new growths that are largely made up of nerve cells and nerve fibers.

One method of evaluating the malignant features of a brain tumor is to grade them from slow-growing neo- plasms to rapidly growing tumors. The grade of a tumor is determined by its malignancy, the tendency of a tumor to grow at a fast rate, causing severe destruction of brain tissue and eventually death. Grading is from 1 to 4, with a Grade 1 tumor representing a slow-growing tumor accom- panied by few neuropsychological deficits. Grades 2 and 3 represent intermediate rates of growth and neuropsycho- logical dysfunction. Grade 4 tumors grow fast and typi- cally have a poor prognosis for recovery. Table 12.3 reviews the different characteristics of brain tumors. Neurological and neuropsychological dysfunction results from the inva- sion and destruction of brain tissue by the tumor. Secondary effects include increased ICP and cerebral swelling (edema), which displace and compress brain

358 PART THREE | Disorders of the Brain

1. Characteristics of brain tumors Atypical, uncontrolled growth of cells Cells do not serve functional purpose Tumor grows at the expense of healthy cells

2. Infiltrating tumors Take over and “invade” neighboring areas of the brain and destroy surrounding tissue

3. Noninfiltrating tumors Encapsulated, well differentiated, and noninvasive

4. Malignant Indicates that the properties of the tumor cells invade other tissue and that there is a propensity for regrowth

5. Benign Describes abnormal cell growth that is usually surrounded by a fibrous capsule and is noninfiltrative; a much smaller probability for regrowth

6. Grading A classification system of tumor growth; grading is in order of increasing malignancy from Grades 1 to 4, depending on cell type.

Table 12.3 Characteristics of Intracranial Tumors

tissue, cranial nerves, the cerebral vascular structure, and the CSF system.

Types of Intracranial Tumors

I N F I L T R A T I N G T U M O R S

As mentioned earlier, infiltrative tumors are not clearly differentiated from surrounding brain tissue. The most common infiltrative tumors are gliomas, which make up approximately 40% to 50% of all brain tumors. Gliomas are relatively fast-growing tumors that arise from support- ing glial cells (Figures 12.5 and 12.6). Any type of glial cells can form a tumor, including gliomas (arising from neuroglial cells), astrocytomas (which are formed from astrocyte cells), and oligodendrogliomas (composed of oligodendrocyte cells). A particularly destructive and fatal glioma is the glioblastoma multiforme (GBM), which generally arises after middle age and is most often con- fined to one hemisphere. A GBM is typically a large, Grade 4 tumor that grows rapidly, with symptoms arising within several weeks. Surgical removal is often incomplete because of the highly infiltrative and malignant character- istics of these tumors. Thus, regrowth and eventual death are common within 6 to 12 months after surgery, even after aggressive radiation therapy. Astrocytomas are infiltrative tumors of astrocytes, a type of glial cell. Astrocytomas grow

more slowly than GBMs; thus, they have a somewhat bet- ter prognosis. Gliomas of the brainstem are typically as- trocytomas and often affect cranial nerves V, VI, VII, and X. Finally, an oligodendroglioma is a rare, slowly grow- ing tumor that affects primarily young adults.

N O N I N F I L T R A T I N G T U M O R S

M e n i n g i o m a s

The most common noninfiltrative tumors are the menin- giomas, which represent approximately 15% of all brain tumors. Meningiomas are highly encapsulated benign tu- mors that arise from the arachnoid layer of the meninges. Their incidence increases with age, and they are more fre- quent in women than in men (by a 2 :1 ratio). Menin- giomas grow slowly and can become rather large before the gradually increasing pressure on the brain and dis- placement of surrounding healthy brain tissue cause symptoms. Technically, a meningioma is not a brain tumor, because the growth is in the brain’s covering, out- side the brain. This is why we refer to all tumors discussed in this chapter as intracranial (within the skull) rather than as brain tumors. With meningiomas, brain tissue is not destroyed, but neuropsychological impairments may appear because the space-occupying mass puts physical pressure on the cortex, especially in large meningiomas. Because meningiomas grow over many years, the brain can often accommodate the size of the tumor. Thus, focal

CHAPTER 12 | Cerebrovascular Disorders and Tumors 359

Figure 12.5 Magnetic resonance imaging (MRI) examination of a patient with a cerebral glioma. The patient had suffered from increasing headaches for 6 weeks, memory impairment, and increasing paresis of the left side. Walking remained undamaged. MRI examination indicated a tumor 65 � 56 � 69 mm in size in the right frontal lobe. The tumor displaced the anterior part of the right lateral ventricle and moved a part of the corpus callosum to the left. (Courtesy Dorota Kozinska, University of Warsaw, Warsaw, Poland.)

Figure 12.6 Injected magnetic resonance imaging–visible dye amplifies boundaries of right frontal tumor, a glioma, in relation to cortex and scalp surfaces. See inside covers for color image. (Courtesy Dorota Kozinska, University of Warsaw, Warsaw, Poland.)

or severe deficits usually do not accompany this type of tumor. Because the brain adapts to the slowly growing meningiomas, tumors in the frontal area may grow rela- tively large before ICP produces behavioral symptoms. Therefore, meningiomas often cause no symptoms and re- main undiagnosed, only to be discovered later on autopsy.

The neurosurgeon finds meningiomas relatively easy to remove because they are encapsulated outside the brain. Removal can, however, become complicated if the tumor is difficult to access, as when the lesion is in the in- trahemispheric fissure or the inferior parts of the brain. Meningiomas arising from the optic nerve sheath may be particularly difficult or impossible to remove, because they almost envelop the optic nerve. Nevertheless, be- cause they are encapsulated and benign, meningiomas offer the best prognosis for complete recovery of any of the brain tumors.

M e t a s t a t i c T u m o r

A malignant but encapsulated tumor is a metastatic tumor. Metastasis is a medical term for the transfer of dis- ease from one organ or part not directly connected with it. The capacity to metastasize is a characteristic of all ma- lignant tumors. Metastatic tumors arise secondarily to cancerous tumors, which have their primary site in other parts of the body, such as the lungs, breasts, or lymph sys- tem. The secondary growths arise because cancer cells from the primary neoplasm detach. The bloodstream can carry the cells to the brain, where they multiply. This is why early diagnosis in cancer is so important: to keep tumor tissue from “metastasizing.” Metastatic brain tu- mors typically have multiple sites and represent up to 40% of all brain tumors seen in elderly adults. They gen- erally grow fast and typically occur at the junction of gray and white matter, close to the cortex surface, although they can grow at any location in the brain. Metastatic brain tumors in adults arise most frequently from bron- chogenic carcinoma (lung cancer), adenocarcinoma of the breast (breast cancer), and malignant melanoma (skin cancer).

A typical clinical picture in metastatic tumor is the di- agnosis of an elderly man with lung cancer related to a long history of cigarette smoking. Examination of the pa- tient’s lymph nodes shows evidence of a tumor. Twelve weeks later, the patient develops a gait disturbance. Neu- ropsychological evaluation shows that the patient is cog- nitively intact but has motor slowing on the left side, an intention tremor, and difficulty walking in a straight line. Diagnostic imaging shows a metastatic tumor in the left

hemisphere of the cerebellum (recall that cerebellar deficits involve the ipsilateral arm and leg). Despite inten- sive chemotherapy and radiation therapy, the patient dies. The prognosis in metastatic brain cancer is typically poor because cancer invades multiple organs and produces multiple growths in the brain. Neurosurgeons usually do not consider extracting metastatic tumors if multiple sites are present. But as with any disease, there are exceptions, and disease progress is often difficult to predict. For example, U.S. cyclist Lance Armstrong was diagnosed with testicular cancer. His cancer metastasized to his lungs and his brain, spawning multiple tumors. After surgery, Armstrong made a remarkable recovery and has not only stayed cancer free, but went on to win the month-long Tour de France, the most grueling bicycle race in the world, a record seven times.

A c o u s t i c N e u r o m a

Acoustic neuromas are progressively enlarging, benign tumors within the auditory canal arising from Schwann cells of cranial nerve VIII, the auditory vestibular nerve, which sends sensory hearing and equilibrium information to the brain. Initial symptoms include ringing in the ears (tinnitus), followed by partial deafness, such as in distin- guishing speech sounds and rhythmic patterns. Acoustic neuromas typically begin to grow in the internal auditory canal and then grow medially. They affect the cranial nerves V (the trigeminal nerve, which provides sensory in- formation of the face and motor control for chewing and swallowing) and VII (the facial nerve, which provides sen- sory information from the tongue and motor control of facial expressions and crying). As a result, the patient may lose his or her sense of hearing, followed by reports of a loss of taste on one side. Physicians often consult audiolo- gists in diagnosing acoustic neuromas.

P i t u i t a r y T u m o r s

The classification and neuropathology of pituitary tu- mors is complex because of the relation of the pituitary gland to the chemistry of the nervous and endocrine sys- tems. Scientists traditionally divide pituitary tumors into functioning and nonfunctioning adenomas. Pituitary adenomas are benign neoplasms of the pituitary gland. Nonfunctioning adenomas produce symptoms caused by pressure on the pituitary and adjacent structures. As the tumor grows out of the sella—the bony capsule that holds the pituitary—headaches are common. Visual field deficits may also occur due to compression of the optic

360 PART THREE | Disorders of the Brain

chiasm (bitemporal hemianopsia). Hypothalamic com- pression usually causes diabetes insipidus.

Functioning pituitary tumors play an “uninvited” role in the operation of the pituitary gland, often affecting the release of the gland’s hormones. Functioning tumors of the pituitary gland include the acidophilic adenoma, a tumor usually found in the anterior lobe of the gland. The acidophilic adenoma provokes excessive secretion of growth hormones, often resulting in giantism, a condi- tion featuring enlarged jaw, nose, tongue, hands, and feet. The chromophobic adenoma also appears in the ante- rior aspects of the pituitary gland and often produces hy- perpituitarism or hypopituitarism. Basophilic adenomas also occur in the anterior lobe of the pituitary gland, but cause excessive secretion of adrenocorticotropic hormone (ACTH), which can cause Cushing’s syndrome. This syndrome, named after Boston surgeon Harvey Cushing (1869–1939), is a severe systemic illness most often seen in female individuals that includes neurologic symptoms and changes in bone structure, hypertension, and dia- betes. The ACTH-secreting tumor is the most serious condition encountered by any of the pituitary tumors and can necessitate complete removal of the tumor, including the pituitary gland.

C H I L D H O O D T U M O R S

Childhood tumors are less frequent than brain tumors in adults. The most frequent is the medulloblastoma, a rapidly growing and malignant tumor located in the infe- rior vermis close to the exit of CSF from the fourth ven- tricle. This type of tumor accounts for about two thirds of all tumors in children and causes increased ICP due to obstructive hydrocephalus. Early symptoms include vom- iting and headache. Other common childhood tumors are cerebellar astrocytomas, gliomas of the brainstem and optic nerve, and pinealomas. Pineal tumors are most common in prepubescent boys. The tumor often com- presses the aqueduct of Sylvius, causing hydrocephalus, papilledema, and other signs of ICP. Table 12.4 summa- rizes the different types and features of brain tumors.

D I A G N O S I S O F B R A I N T U M O R S

The overall incidence of brain tumors for male and fe- male individuals is about equal, but cerebellar medul- loblastomas and GBM are more common in male indi- viduals, and meningiomas are more frequent in female individuals. The overall frequency of various types of in- tracranial tumors is approximately 45% for gliomas, 15%

for pituitary adenomas, 15% for meningiomas, 15% for metastatic brain tumors, and 10% for other types.

Early behavioral symptoms in the diagnosis of tumor include a sudden onset of headaches, nausea, loss of cog- nitive function, or seizures. The ICP triad often accom- panies the growth of brain tumors and includes:

1. Headache 2. Nausea and vomiting 3. A positive papilledema, a swelling of the optic disk in

the eye

Of course, not every patient reporting a headache has a brain tumor, but headache often accompanies brain tumor because of the enlarging tumor mass.

The introduction of the CT scan and the more recent magnetic resonance imaging (MRI) has literally revolu- tionized diagnosis of tumors. High-resolution CT can vi- sualize even tiny tumors. Three-dimensional reconstruc- tion can often demonstrate the intimate relations of the

CHAPTER 12 | Cerebrovascular Disorders and Tumors 361

Acoustic neuroma—a benign tumor growing from the sheath of the acoustic nerve at the cerebellopontine angle

Gliomas—a tumor composed of tissue representing neuroglia; the term glioma is often used to describe all primary, intrinsic neoplasms of the brain and the spinal cord

Glioblastoma—Malignant forms of astrocytoma

Glioblastoma multiforme—an astrocytoma of Grade 3 or 4, a rapidly growing tumor usually confined to one cerebral hemisphere and composed of a mixture of spongioblasts, astroblasts, and astrocytes

Astrocytoma—a malignant tumor composed primarily of astrocytes

Ependymal glioma—a bulky, solid, firm vascular tumor of the fourth ventricle

Oligodendroglioma—a neoplasm derived from and composed of oligoden- drocytes

Optic glioma—a slowly growing glioma of the optic nerve or optic chiasm, associated with visual loss and loss of ocular movement

Meningioma—a typically benign tumor arising from arachnoid cells; produces neuropsychological deficits by exerting pressure on surrounding brain substances or cranial nerves

Metastatic tumor—a growth of a tumor, often multiple, distant from the site primarily involved in the morbid process

Pituitary adenoma—a tumor of the pituitary gland; pituitary adenomas are often classified as functioning (changing the secretion of the pituitary gland) and nonfunctioning (benign)

Pinealoma—a tumor of the pineal body

Table 12.4 Types of Brain Tumors

tumor to its surrounding brain structure, facilitating precise removal of the tumor by surgeons. Today, neurol- ogists most efficiently diagnose brain tumor using CT or MRI, which often provides the definitive diagnosis (see Chapter 2 for a comprehensive review of medical diag- nostic procedures). Neurologists have used functional MRI (fMRI) to differentiate brain tissue from tumor tis- sue, as well as to identify areas of the brain that are partic- ularly vital for cognitive functions. This is often impor- tant, because using fMRI neurologists can identify a safe corridor through the brain into the tumor, which the surgeon can then use. In addition, fMRI can help differentiate whether the cancer itself contains vital brain tissue. Somatosensory-evoked responses and di- rect stimulation of the brain can also help separate im- portant brain tissue from brain tumor tissue. Neurolo- gists often use plain X-ray films in diagnosing and planning surgery to remove meningiomas, because this type of tumor can erode the skull in a high percentage of patients, as shown in radiographic changes on skull X-ray films.

Angiography occasionally can be useful in tumor diag- nosis to identify which primary branches of the cardiovas- cular system supply the tumor with its blood supply. Mod- ern imaging is most effective in diagnosing the presence of a tumor, but not in diagnosing its type. Histologic exami- nation via brain biopsy is necessary to precisely diagnose the type of tumor and to select the most appropriate inter- vention. Neurologists most frequently do this using CT- guided stereotaxic biopsy, which interfaces stereotactic frames that fasten to the patient’s head with steel pins. A biopsy needle is affixed to the frame, which the neurosur- geon can move with precision in all three dimensions. Using this procedure and with the patient under local anesthesia, the neurosurgeon can take a brain specimen through a burr hole. Subsequent laboratory examination can then provide the exact diagnosis of the tumor.

T R E A T M E N T O F B R A I N T U M O R S

The preferred treatment for brain tumors is total surgical excision of the tumor whenever possible. The prognosis for recovery after removing a brain tumor depends on two primary factors, the location and type of tumor. For ex- ample, a relatively simple surgical excision may involve a well-differentiated tumor, such as a meningioma, particu- larly if the tumor is in an easily accessible location (as in superior aspects of the cortex). If the tumor is malignant, local radiation therapy typically follows surgical removal to prevent regrowth. If the tumor is inaccessible, for

example, in the region of the thalamus or brainstem, radi- ation therapy is the primary intervention. A fast-growing glioblastoma in a nonresectable location is often fatal within 12 months. Thus, the prognosis for GBMs is not good, but combined treatments have a small success rate. For tumors that are difficult to access, located at the base of the skull or covering the superior sagittal sinus, the neurosurgeon often uses a sophisticated operating micro- scope or a laser.

Chemotherapy for brain tumors is playing an increas- ingly important role in the battle against cancer. Chemotherapy is most effective in tumors that have a high growth fraction; that is, tumors that are actively di- viding and producing DNA. When a tumor is young, most of its cells are making DNA. When antitumor drugs reach tumor cells in the phases of cell cycling, the cells die. As the tumor ages, growth fraction decreases and drug sensitivity declines. Thus, the most effective form of chemotherapy is when the tumor is young and 100% of its cells are in the growth fraction—this again emphasizes the importance of early diagnosis. However, the BBB, which protects the brain from foreign substances, compli- cates chemotherapy for brain tumors. The BBB prevents cancer-killing drugs from entering brain tissue via the bloodstream. Thus, antitumor drugs targeting brain tu- mors are limited to agents easily transported across the BBB—typically, very lipid-soluble substances. In recent years, however, researchers have discovered that some chemicals (such as the bradykinin agonist, RMP-7) are highly effective in opening the BBB by making capillary walls “leaky.” As a result, chemotherapy drugs can act di- rectly on the tumors, increasing their effectiveness as much as 10-fold.

Medicine will only achieve a cure in the fight against brain tumors, however, when it can enlist the patient’s own immune system to attack the cancer. Tumors pro- duce a chemical that tricks the immune system into ig- noring them. Recent genetic engineering research in an- imals has shown some promise in discovering substances that turn off the ability of the tumor cells to produce their own vaccine. The tumor cells then become imme- diate targets of the immune system, which destroys them.

Treating brain tumors is not only complicated from a scientific perspective, it also takes a psychological toll on the patient, as well as the patient’s family. As a re- sult, psychologists also play an important role in coun- seling patients undergoing cancer treatment or in hos- pice centers—health care centers that provide medical and emotional support for the terminally ill and their families.

362 PART THREE | Disorders of the Brain

Brain Tumors and Neuropsychology

The neuropsychological manifestations of brain tu- mors depend on the location, size, and grade of the tumor, rather than on its histologic type. Smaller tumors near primary motor areas may cause seizures and loss of motor function, whereas deeper intracranial tumors may grow rather large before focal clinical symptoms appear. Evaluations also find a general decline in adaptive areas, as well as in overall cognitive functioning, because the tumor displaces neighboring areas. The neuropsychologi- cal deficits of a GBM are profound. The destruction of whichever cerebral hemisphere is involved is severe and nearly complete. In the acute stages of GBM, neuropsy- chological evaluation typically is not undertaken, because the deficits are so severe and the overall medical condition of the patient is of foremost concern. Patients with astro- cytomas may have longer histories of increasing problems, because of the slow growth of these neoplasms. Oligoden- drogliomas typically produce few neuropsychological ef- fects because they grow so slowly.

Focal neuropsychological symptoms of brain tumors stem from localized destruction, compression of nervous tissue, or altered endocrine function. Tumors in the frontal lobes are most commonly meningiomas and gliomas. They can produce both localized and generalized cognitive deficits, including expressive aphasia (if located in the dominant hemisphere) or difficulties smelling (anosmia) related to a meningioma at the base of the frontal lobe. Inattention and changes in motivation com- monly accompany tumors that affect both frontal hemi- spheres. Parietal lobe tumors may contralaterally impair sensory modalities, stereognosis, contralateral homony- mous hemianopsia, and apraxia. Speech disturbances, agraphia, and finger agnosia may appear if the left hemi- sphere is involved, and neglect is characteristic of patents whose right hemisphere is affected.

Temporal lobe tumors may produce mixed expressive and receptive aphasia of the dominant temporal lobe. Nondominant temporal tumors often do not have “obvi- ous” cognitive signs. Tumors deep in the temporal lobe may cause contralateral hemianopsia. Occipital lobe tu- mors most often entail visual deficits, typically a contralat- eral quadrant defect in the visual field or a hemianopia with sparing of the macula. Subcortical tumors that in- volve the internal capsule produce contralateral hemiple- gia. Thalamic tumors produce contralateral sensory im- pairment. Basal ganglionic tumors often result in tremors. All brain tumors may produce seizures, which may be

preceded by an aura that may indicate the location of the tumor.

Metastatic tumors are often associated with neuropsy- chological test results indicating focal areas of deficits. Skills that the tumor does not affect may be relatively in- tact. Later stages of metastatic tumors with numerous sites and sizes may produce a diffuse loss of most neuropsy- chological abilities. Acoustic neuromas typically do not entail severe cognitive loss, but rather a hearing impair- ment. A meningioma produces its behavioral effects by compressing the brain. Meningiomas near the optic nerve result in visual disturbances and are difficult to remove because of their location. Pituitary tumors also produce visual field defects because of the close relation between the optic chiasm and the pituitary gland.

Neuropsychological evaluations have proved most use- ful in establishing a cognitive baseline before neurosurgery and in evaluating outcomes of patients after surgery. As mentioned earlier, neuropsychologists also provide coun- seling and education to patients with brain tumor and their families. More recent research has focused on the neuropsychological implications of radiation therapy (Neuropsychology in Action 12.3).

Other Neurologic Disorders

B R A I N A B S C E S S

Brain abscesses are similar to tumors, both in appearance and on visualization using imaging. Compared with a tumor, however, a brain abscess arises from an infection spreading to the brain or originating in the brain. Ab- scesses begin as an area of generalized inflammation and progress to a “walled off,” localized pocket of pus within the brain. The abscess can gradually expand, destroying and compressing brain tissue as it grows. Compared with brain tumors, however, imaging typically shows an empty center within the abscess, differentiating it from a tumor, which appears more “solid.” In addition, the patient typi- cally presents with a history of prior infection.

I N F E C T I O N S

Infections and infectious diseases tend to attack specific brain structures depending on the type. At least 20 different types of infections affect the brain. Many are obscure and rare. Among the well studied are meningitis, herpes en- cephalitis, and human immunodeficiency virus (HIV).

CHAPTER 12 | Cerebrovascular Disorders and Tumors 363

Meningitis is a bacterial or viral infection of the meninges that provide the protective covering of the brain. Menin- gitis can also be a result of brain surgery (there is an up to 5% incidence rate); physicians routinely administer an- tibiotics to patients who have undergone intracranial pro- cedures to prevent such infections. Interestingly, such in- fections acquired during brain surgery vary, not only from hospital to hospital depending on the thoroughness of sterilization of the operating room but also among oper- ating rooms within a single hospital. Such data are, how- ever, not commonly published for the consumer, for

obvious reasons. Herpes encephalitis (not to be confused with genital herpes) aggressively attacks the medial tem- poral and orbital frontal areas. This appears to destroy much of the limbic system, especially the hippocampus. The result is a near total inability to learn new informa- tion (anterograde amnesia). The HIV/AIDS virus has wider effects on the brain, because it progressively de- stroys the immune system. The virus itself may have di- rect consequences for the brain, but it also opens the brain to opportunistic infections and other diseases that can at- tack the brain.

364 PART THREE | Disorders of the Brain

Effective brain tumor treatment is always a compromise, involving the protection of healthy cells and the destruction of aggres- sive cancer cells that have infiltrated healthy tissue. Treatment choices are complex and should involve input from a team of onco- logic professionals, including neurosurgeon, oncologist–hematologist, radiation therapist, neuroradiologist, neurologist, and neuropsy- chologist. Surgical interventions range from biopsy, or the removal of enough tissue for microscopic determination of histologic type and pathologic grade of tumor cells, to the resection of 100% of tumor tissue as a method of preventing tumor regrowth. Brain surgery may also involve Wada testing or functional magnetic resonance imaging (see Chapter 2), with the aid of the neuropsychol- ogist in determining hemispheric dominance of movement and language, and help from the neuroradiologist in outlining blood flow patterns in the brain. Specialists also may use brain mapping to localize function and preclude resection of brain tissue crucial for language or memory.

Besides surgical treatments for brain tumors, medical professionals often give radiation therapy and chemotherapy, either alone or in combination. The most common method of radiotherapy involves external photon beam radiation; with this method,

technicians administer a total dose of radia- tion in fractions over a period of about 6 weeks, 5 days a week. If the treatment is to prevent metastasis or the seeding of tumor cells by blood- or lymph-based cancer, then radiation may include the whole brain. However, to shrink or prevent the spread of a primary tumor, radiation is focused on just parts of the brain. The best current alterna- tive therapies include conformal and stereo- tactic radiotherapy, surgical placement of chemotherapy wafers in the tumor bed, and gene therapy.

The natural history of radiotherapy effects is not well understood. Experimental animal studies demonstrate brain damage or decreased cell density from radiotherapy. Several studies in humans have associated damage to the brain’s white matter with delayed radiation effects (Corn et al., 1994). In addition, chemotherapy interacts with radiotherapy to exacerbate radiation dam- age. Although studies of children and several retrospective studies have found alarming effects of radiation injury, some studies of adults have not. The methodology used is often the source of the discrepancies. For example, retrospective studies find abnor- mally high rates of white matter damage, low IQ, memory impairment, and even dementia in both adults and children from 3 months to

many years after irradiation (DeAngelis, Delattre, & Posner, 1989). A late effect, up to 20 years after treatment, may result in an atherosclerotic-like disorder if carotid arter- ies were irradiated. Conclusions are con- founded when patients are tested at irregular time periods, only brief neuropsychological evaluations are conducted, or no baseline neuropsychological testing (before treat- ment) is ordered.

Memory deficits have been implicated as the most frequent and severe delayed effect of radiation therapy. Researchers consider the early delayed effects, occurring 2 to 3 months after completion of radiation treatment, to be mild and temporary. The late delayed effects of radiation therapy are more severe, may progress, and are irre- versible. We compared longitudinal research on patients who received radiation therapy with patients with similar tumor types but who did not have radiotherapy. Patients with low-grade, cortical, primary brain tumors often have long life expectancies and rela- tively few cognitive deficits. Neuropsycholo- gists give these patients a repeatable, comprehensive battery of tests that includes many sensitive measures of attention and memory processes. Evaluations occur just before irradiation, and then at 3-, 6-, and 12-month intervals. Thus far we have learned

N e u r o p s y c h o l o g y i n A c t i o n 1 2 . 3

N e u r o p s y c h o l o g y o f T r e a t m e n t s f o r I n d i v i d u a l s w i t h B r a i n T u m o r s

by Carol L. Armstrong Ph.D., Department of Neurology, University of Pennsylvania and the Joseph Stokes Research Institute, Children’s Hospital of Philadelphia, Philadelphia, PA

N E U R O T O X I N S

Neurotoxins include any substances that are poisonous to the brain (Lezak, 1995). These may include drugs, alco- hol, solvents, fuels, pesticides, and metals such as lead or mercury. Many substances can be toxic to the brain in high doses, whereas they may not be toxic in low doses. Many prescription drugs fall into this category, for exam- ple, lithium, which is used to treat bipolar affective disor- der (manic depression).

Many heavy metals, such as lead or mercury, can be extremely damaging to the body and the CNS, even in low dosages (Zillmer, Lucci, Barth, Peake, & Spyker,

1986; Zillmer, 1995). Although not many people come in contact with heavy metals, the general population may be exposed to some toxins routinely or by accident. For example, more than half a million accidental poisonings from pesticides are reported each year worldwide. One common group of pesticides are chlorinated hydrocarbon insecticides (for example, chlordane, heptachlor, and lin- dane), which people use extensively to combat household pests such as flies, cockroaches, fleas, termites, and mos- quitoes, as well as agricultural crop enemies. Because chlordane maintains its effects for approximately 15 or more years after application, it offers an economically

CHAPTER 12 | Cerebrovascular Disorders and Tumors 365

that robust patterns of neurocognitive change appear during the first year after radiotherapy (Figure 12.7). Visual-percep- tual memory learning and recall are impaired at baseline but improve steadily over 1 year. Verbal-semantic retrieval is often not af- fected at baseline, but declines at the early delayed phase. Researchers think the early delayed phase of radiation damage is caused by interruption of myelin synthesis, which stems from inhibition of glial mitosis. Thus, verbal-semantic retrieval appears sensitive to the damaging effects of radio- therapy and may be sensitive to the more crucial late delayed phase of irradiation. The initial impairment and improvement in visual

memory may represent recovery from surgi- cal injury to the hippocampal memory system.

We discovered that radiation selectively impairs verbal-semantic memory signifi- cantly more than motor control, visual and auditory attention, visual and auditory working memory, visual long-term memory, language, visuospatial perception, process- ing speed, and reasoning. Why would re- trieval be so sensitive to radiation? Retrieval, the end point of remembering, depends on reconstructive processes in which the system associates the contents of current con- sciousness with information stored in perma- nent memory. Several other cognitive

processes theoretically could account for the patient’s failure to retrieve words from long- term memory, including failure of selective attention, working memory deficit, slowed processing speed, and failure to regenerate the attributes of the target. However, we found that none of these related cognitive processes explained the retrieval impair- ment. We are pursuing the questions of whether the rate of reconstruction of current memory or the recall of novel arrangements of memory attributes predicts the retrieval deficit, and how these processes correspond with regions of the brain’s white matter.

Neuropsychological findings have influenced the treatment of brain tumors. Neuro-oncologists have become more selective about the doses and timing of radiotherapy. Radiation oncologists may advise patients about the early delayed effects on memory. Patients are more likely to receive referrals for rehabilitative thera- pies, and neuropsychologists are more cautious when recommending return to work. Neuro-oncology researchers are investigating other potential damaging effects on the brain, such as the possible association with Alzheimer’s-like neural changes in gray matter. Researchers are also aiming studies at developing pharmacologic treatments to block the damaging effects of radiotherapy and at identifying chromosomal markers of beneficial sensitivity to cancer treatments. Neuropsychologists can play an important role in helping to understand the psychological (Neuropsychology in Action 12.4) and the cognitive changes associated with brain tumor treatment.

Figure 12.7 Double dissociation of patient’s word and figure retrieval after delay at baseline and at point of early delayed phase of radiotherapy. (Reproduced from Armstrong, C., Corn, B., Ruffer, J., Pruitt, A., Mollman, J., & Phillips, P. [2000]. Radiotherapeutic effects on brain function: Double dissociation of memory systems. Neuropsychiatry, Neuropsychology, and Behavioral Neurology, 13, 100–111, by permission.)

Baseline – 2.0

0.5

3 months post-baseline

Time since initiation of radiotherapy

Z s

c o

0.0

– 0.5

– 1.0

– 1.5 Word retrieval

Figure retrieval

366 PART THREE | Disorders of the Brain

Lisa, a 21-year-old woman, was referred to a consulting psychologist by her pediatric oncologist because of depressed mood, behavioral manifestations of seizures with no associated neurologic changes, and family conflict. When she was 10 years old, Lisa was treated for acute nonlymphoblastic leukemia through bone marrow transplant, which included high-dose, whole-body radiation. Sequelae of the cancer and its treatment included apparent seizures (par- ticularly when stressed); cognitive deficits associated with cranial radiation, including limitations in general intellectual functioning; and a pattern of deficits associated with nonverbal learning disability (Carey, Barakat, Foley, Gyato, & Phillips, 2001), cataracts, and infertility. At the time of referral, Lisa lived with her parents and her younger brother. Although a high school graduate, she was not employed and spent most of her time alone at home. Although her parents were caring and protective, they did not encourage Lisa to branch out of the home, because they feared she would have a seizure in a public place, were uncertain of her capabilities, and viewed the cancer and its consequences as severe and insurmount- able. Despite her current situation, Lisa hoped to go to college, get married, and have children.

The complexities of Lisa’s medical condi- tion placed a considerable burden on the family as a whole. The role of the patient’s cognitive factors in family functioning is complex; some detrimental effects may appear, but some families can cope with these problems (Carlson-Green, Morris, & Krawiecki, 1995). A key to understanding the relations among cognitive aspects of childhood cancer, child adjustment, and family functioning may be child and parent perceptions or appraisals of the impact of the illness. A series of studies on childhood cancer survivors and their parents consis- tently relate perception of life threat associ-

ated with cancer, and its treatment in the past and present, and appraisals of treat- ment intensity to child, parent, and family adjustment (Barakat, Kazak, Meadows, Casey, Meeske, & Stuber, 1997; Foley, Barakat, Herman-Liu, Radcliffe, & Molloy, 2000). However, objectively rated intensity of the treatment, severity of medical late effects, and history of cranial radiation treatment are not consistently associated with adjustment in children treated for cancer.

These findings provide strong evidence for the importance of child and parent subjective appraisals or perceptions of cognitive limitations in understanding child and family functioning after cancer diagnosis and treatment. Importantly, preventive interventions can modify child and parent appraisals of cognitive limitations and the impact of the illness, to improve long-term family adaptation (Barakat & Kazak, 1999). It is essential to work with families from the point of cancer diagnosis to provide a realis- tic but optimistic framework for understand- ing children’s capabilities and needs. The intervention must consider the child’s ability to comprehend this information, given cognitive limitations.

Such interventions must also take into account developmental process in families. As the children grow older, families must reassess and reintegrate the meaning of cognitive limitations for their child and family. For example, as children enter formal schooling, families must balance the need to address potential learning problems with the need for children to engage in routine activi- ties with peers. As children reach adoles- cence and strive for autonomy, families must be able to set realistic goals with their chil- dren while allowing them to achieve inde- pendence in functioning. On the flip side, children and adolescents should gain guid- ance in choosing academic, vocational, and social goals that they can attain.

In addition to addressing perceptions, it is necessary to foster positive changes in family interactions (such as interactions around homework, rules in the home, and peer relationships) to promote children’s competencies and, in turn, improve function- ing. In relation to this, frequent communica- tion among other systems, such as the school, religious community, or medical treatment team, decreases conflicting infor- mation provided to families and improves coordination of support. For instance, the child, parents, and teachers may coopera- tively develop and implement a plan aimed at homework completion that provides structure and builds on the child’s cognitive strengths.

Finally, improving parent resources and coping helps improve the functioning of fami- lies dealing with the long-term strains and medical sequelae of cancer treatment, includ- ing cognitive changes. Family-to-family con- tact and support through multiple-family groups is an integral part of bolstering chil- dren’s and their parents’ resources. Families learn from one another which coping strategies most facilitate healthy family development as the childhood cancer survivor moves into adulthood.

After complete neurologic and psycho- logical evaluations, Lisa was diagnosed with grand mal seizures, as well as unexplained seizure activity, and major depression with dissociative features. Treatment entailed achieving a therapeutic dose of medication for her seizures and individual and family therapy. The goal of family therapy was to help Lisa and her parents realistically assess her skills and recognize her potential. Ini- tially, through increasing her responsibility in the home, trips to the mall (where she was free to shop on her own), and engagement in hobbies, Lisa’s sense of competence im- proved. Her parents’ perceptions of her abilities became more optimistic, and their appraisals of her illness severity lightened. Lisa and her parents began to focus on

N e u r o p s y c h o l o g y i n A c t i o n 1 2 . 4

F a m i l y a n d C h i l d A d j u s t m e n t t o C o g n i t i v e A s p e c t s o f C a n c e r i n C h i l d r e n

by Lamia P. Barakat Ph.D., Associate Professor of Psychology, Department of Psychology, Drexel University, Philadelphia, PA

appealing long-term treatment against termites. Chlor- dane is readily absorbed through the gastrointestinal tract, respiratory tract, or unbroken skin, and it is stored in body fat. Once absorbed, chlordane is an axon poi- son, which disturbs the normal action of the sodium- potassium adenosinetriphosphatase (ATPase) pump, interfering with the transmission of nerve impulses. Be- cause of its chemical stability, chlordane can be detected in approximately 70% of U.S. homes today and ranks among the most ubiquitous neurotoxic materials being released into the ecosystem (Zillmer, Montenegro, Wiser, Barth, & Spyker, 1996).

In general, toxic effects on the brain cannot be described in simple terms, because the mechanisms of action are so varied. Most common are cognitive deficits ranging from mild to severe on tasks that require speeded processing, problem solving, and delayed memory. Somatization, hys- terical features, and depression often dominate the clini- cal picture. Thus, the medical profession increasingly recognizes that chemicals can have significant neuropsy- chological effects (Hartman, 1995), and that neuropsychol- ogy offers promise in increasing knowledge of the effects of toxins on the human CNS, describing specific patterns of performance, and monitoring the course of treatment.

CHAPTER 12 | Cerebrovascular Disorders and Tumors 367

increasing Lisa’s independent functioning. She successfully entered a vocational reha- bilitation program and made plans for a clerical position in the future. She began to make friends and to attend social functions

through her rehabilitation program. Lisa made a number of overnight visits with siblings, and her parents took a long-needed vacation without their daughter. Concur- rently, counselors gently guided Lisa through

cognitive interventions to understand and come to terms with her limitations, particu- larly those relevant to her hopes for a college education and children. Lisa’s seizures and depression remitted.

Summary In general, damage to the brain may result from either primary or secondary damage and may have either acute or long-term effects. In addition to damage within the immediate area, there may also be damage to more distal areas because of disconnected neuronal pathways. The diagnosis of primary damage relates to the initial injury or insult to the brain. If axons are completely severed or destroyed, the damage is often permanent and that tissue is lost. Secondary brain damage, in contrast, may result in either permanent or temporary damage. Secondary damage is caused by the aftereffects of the primary injury. Hemorrhage or bleeding causes oxygen deprivation and can lead to cell death known as necrosis. Edema, or “brain swelling,” hemorrhage, and infection may all cause increased cranial pressure. This pressure in the nonex- panding skull may effectively “cut off” areas of brain functions. If these secondary effects can be controlled quickly, the damage and functional effects may reverse in the acute stages of recovery. What is considered primary damage in one situation may be secondary damage in another. For example, a head injury (see discussion in Chapter 13) may cause primary axonal severing, destruction of brain tissue, and secondary swelling and hemorrhaging. The primary damage of a stroke may be caused by a hemorrhage, but there may still be secondary swelling and ICP. Sudden traumas such as stroke tend to have more striking and noticeable behavioral effects than slowly emerging processes. The most frequently encountered cerebro- vascular disorders may, at times, produce multiple cognitive disabilities; yet, often such dysfunction is rela- tively localized for the anatomic area involved, as well as the corresponding neuropsychological sequelae. However, more general neuropsychological disabilities are possible when, for example, larger areas of the brain are infarcted. Brain tumors affect a significant proportion of the population and may lead to many debilitating conditions. Neuropsychologists are at the forefront in researching cerebrovascular and tumor treatment and rehabilitation. In Chapter 13, we discuss other neurologic disorders of the brain, specifically the neuropsychological consequences and rehabilitation of traumatic head injuries.

C r i t i c a l T h i n k i n g Q u e s t i o n s

What are the neurologic, behavioral, and emotional symptoms of a stroke? What are the major forms of treatment for stroke? Why do some stroke victims downplay their illness, whereas others go into a deep depression?

Lesions Necrosis Anoxia Hypoxia Sleep apnea Hydrocephalus Communicating hydrocephalus Obstructive hydrocephalus Stroke Cerebrovascular accident (CVA) Intracranial pressure (ICP) Infarction Hemorrhage Transient ischemic attack (TIA) Ischemia Thrombosis

Atherosclerosis Platelets Endothelium Embolism Atrial fibrillation Hematoma Intracerebral Subarachnoid hemorrhage Aneurysms Arteriovenous malformations

(AVMs) Aura Migraine stroke Stenosis Collateral blood vessel Anastomosis

Tumor Neoplasm Infiltrative tumors Noninfiltrative tumors Malignant tumors Benign tumors Metastasis Neuromas Grade of tumor Gliomas Glioblastoma multiforme (GBM) Astrocytomas Oligodendroglioma Meningiomas Metastatic tumors Acoustic neuromas

Pituitary tumors Functioning adenomas Nonfunctioning adenomas Pituitary adenoma Acidophilic adenoma Chromophobic adenoma Basophilic adenoma Cushing’s syndrome Medulloblastoma Pinealoma Optic glioma Brain abscess Meningitis Herpes encephalitis Human immunodeficiency virus

(HIV)

We b C o n n e c t i o n s

http://www.med.harvard.edu/AANLIB/home.html Harvard Medical School: CVA Facts—This site for the Whole Brain Atlas has an excellent section of images demonstrating various types of CVAs discussed in our text. A great way to visualize the extent of damage different types of CVAs may manifest. Also shows MRI and single-photon emission computed tomography images of various neoplastic diseases, including glioma, metastatic tumors, and meningioma.

http://neurosurgery.mgh.harvard.edu Brain Aneurysm and AVM Center—Links you to the Harvard Brain Aneurysm and AVM Center at Mass Gen- eral, where you can find discussions of the latest treatment for these and other cerebrovascular disorders.

http://www.stanford.edu/group/neurology/stroke Stroke Awareness—Stanford Medical Center’s site for stroke awareness and treatment information.

http://www.ninds.nih.gov National Institute on Neurological Disorders and Stroke—An excellent site for the most up-to-date informa- tion on CVAs and related disorders. Internal search engines allow you to be as specific as you would like in obtaining information.

Describe the most common neuropsychological deficits associated with stroke. Would you want to know what type of cell a tumor arises from if one of your family members had brain cancer? Why? Should physicians routinely inform their patients of such medical details? What is the neuropsychologist’s role in diagnosing and treating patients with brain tumors? What is his or her role with the patient’s family? How do children who have brain tumors react differently to their disease from the way adults do? How do their families react?

K e y Te r m s

368 PART THREE | Disorders of the Brain

http://www.med.harvard.edu

http://neurosurgery.mgh.harvard.edu

http://www.stanford.edu

http://www.ninds.nih.gov

Chapter 13

T R A U M AT I C H E A D I N J U RY A N D R E H A B I L I TAT I O N

If you want to understand God, you study the anatomy of the brain. —Keith Black (neurosurgeon)

Traumatic Head Injury Epidemiology of Traumatic Head Injury Mechanism of Impact: Neuronal Shearing, Stretching,

and Tearing Complications of Moderate and Severe Brain Injury Mild Head Injury: “Concussions” Treatment of Head Injuries Recovery, Rehabilitation, and Intervention of Traumatic

Brain Injury Adaptation and Recovery Overview of the Rehabilitation Process Treatment Methods for Neuropsychological

Rehabilitation

Neuropsychology in Action

13.1 Case Study: Penetrating Head Injury 13.2 Can a Concussion Change Your Life? 13.3 Consensual Sex after Traumatic Brain Injury:

Sex as a Problem-Solving Task 13.4 It Is More Than a Black Box

370 PART THREE | Disorders of the Brain

Traumatic Head Injury

The Kennedy clan (that is, President John F. Kennedy’s family) engage in an annual family ritual dur- ing their skiing vacation in Aspen, Colorado. The Kennedy clan and friends gather at a mountaintop bar, waiting until the lifts shut down at about 4 P.M. Then, with few other skiers on the trails, they play football down the slope, with skis but no poles. A cross between Frisbee and touch football, “ski football” is an old Kennedy pas- time. They divide into two teams and start tossing a makeshift football through the thin mountain air toward

a goal, typically a trail marker. The rules of the game de- mand that a player must pass the ball to a teammate within 10 seconds or turn the ball over. This seems like a lot of fun, but inherent in skiing, as is true for most sports, is risk in the form of speed. Sports, in fact, account for 17% of all head injuries, second only to motor vehicle accidents (MVAs). The most dangerous sports are eques- trian events, gymnastics, and cheerleading. Among inter- collegiate sports, gymnastics, football, lacrosse, and ice hockey are the most likely to lead to head injuries. Skiing is actually a relatively safe sport—there is less than 1 death per 1 million skied days. But that New Year’s Eve afternoon

K e e p i n M i n d

Do different injuries to the brain have similar effects on the brain, or should we expect a variety of effects?

What is the difference between a penetrating and a closed head injury?

What role do neuropsychologists play in the diagnosis and treatment of head injuries?

How do rehabilitation programs further the process of recovery and adaptation with traumatic brain injury?

What is the specific role of the neuropsychologist on the rehabilitation team?

Overview Neurologists commonly differentiate neurologic disorders of the brain by whether they have a particular focus or site, or are more generalized, affecting the brain as a whole. There are, however, many exceptions to this simple classification paradigm. As discussed in Chapter 12, a stroke or a bleed in the brain is a focal disorder because the damage occurred at a specific location. In contrast, many small bleeds or very large hemorrhages often present a diffuse clinical picture. Similarly, a single brain tumor may represent a precise focal deficit, whereas a large tumor or multiple small tumors of the brain may leave the patient with more wide-reaching deficits, which typically entail diffuse neuropsychological deficits. For the most part, neu- ropsychologists consider tumors to be focal disorders of the brain, because most often they entail more or less circumscribed brain damage.

In contrast, diffuse disorders most often involve dysfunction of the entire brain and most frequently appear in closed head injuries (CHIs), toxic conditions, and degenerative disorders. This classification para- digm is not entirely accurate, but it helps the neuropsychologist make an overall determination of the sever- ity and extent of possible dysfunction. In a car accident, the rotational forces on the head often result in blunt trauma to the brain, and thus cause diffuse damage. In contrast, a gunshot wound to the head may present a relatively localized but devastating trauma to the brain and may have more localized deficits. Therefore, keep in mind that this categorization is not a hard-and-fast rule. In principle, focal disorders may interrupt a small area of brain functioning, whereas other areas of the brain remain relatively intact. Some- times the loss of brain tissue is so small that it may not be noticeable except with sophisticated neuropsy- chological testing or advanced imaging techniques.

This chapter discusses the more diffuse traumas of the brain related to head injury. Finally, less frequently encountered neurologic disorders are discussed, including brain abscesses, infections, and neurotoxins.

the conditions were getting worse, the slopes were slick and icy, and the sun was setting behind the mountains, making it hard to see in the shadows and flat light. On the quintessential “last run” on the last day of the year, Michael L. Kennedy, the 39-year-old son of Ethel and the late Senator Robert, turned his head to catch the ball. He hit a fir tree headfirst on the left side of the trail. Yes, it was reckless to ski while playing a daring game of moun- tainside football. The ski patrol had warned against it. Tossing a makeshift football back and forth may have dis- tracted Kennedy just enough that he was not able to stop or swerve before striking the tree. According to eyewit- nesses, Kennedy—a good skier—first struck the tree with a tip of his ski, which caused him to catapult slightly and slam his head directly into its trunk without slowing down. With his three youngest children watching in hor- ror, Michael Kennedy died of a severe head injury to the back of his fractured skull. His injury must have damaged his brainstem, because his sister Rory, who was the first to his side, noticed no pulse or breathing. The medulla ob- longata, a part of the lower brainstem, mediates vital func- tions necessary for life such as respiration, blood pressure, heart rate, and basic muscle tone. Damage to the medulla can interrupt motor and sensory pathways, as well as threaten life itself. The death, ruled accidental, adds yet another tragedy to America’s most famous clan.

Would a helmet have saved his life? Those who survive head injuries often sustain significant brain damage, which can change them for a lifetime, both physically and emotionally. This can result in a markedly altered lifestyle for the survivor, those who take care of him or her, the family, and loved ones.

Epidemiology of Traumatic Head Injury

Human brains have evolved over hundreds of thou- sands of years, but only recently have people invented tech- nology, both recreational and occupational, that has put brains in motion, often at high speeds. The skull and the dura mater protect the brain well, but they are no match for the physical forces unleashed on the brain during a head injury, which often can result in brain damage. Head in- juries do not occur in isolation, and additional injuries are common; thus, most cases require additional medical at- tention to other seriously traumatized parts of the body, complicating the overall prognosis and intervention.

Accidents are the leading cause of death in people ages 1 to 30. In the 1970s, the medical profession first recognized

head injuries, particularly those related to MVAs, as a na- tional epidemic. Researchers estimate that 500,000 peo- ple suffer brain injury every year. A majority of those are in the mild range, but millions of people in the United States are surviving and living with a moderate to severe brain trauma (Zillmer, Schneider, Tinker, & Kaminaris, 2006). After MVAs, the causes of head injuries are, in order, sports injuries, falls, violence, and industrial acci- dents. In individuals younger than 45 years, head injuries cause more deaths and disability every year than any other neurologic illness. Those most at risk are young, under age 30, single, and male. The male/female ratio may be as high as 4:1. Young adults between ages 15 and 24, fol- lowed by children and adolescents aged 5 to 14, are at greatest risk for traumatic brain injury (TBI). But no one is immune. Studies implicate alcohol in one third to half of all traumatic head injuries. In fact, head injuries are such a significant health problem among developed coun- tries that they play a role in approximately half of all deaths related to trauma (Rimel, Giordani, Barth, Boll, & Jane, 1981).

Most often head injuries show no visible physical “scars.” However, significant changes in behavior and emotion follow head injuries, often most noticeable by people close to the victim. As recently as the mid-1980s, hospitals typically discharged survivors of head injuries, after recovering medically, without consideration of whether they had recovered cognitively or emotionally. Neuropsychologists now know that even mild head in- juries may entail a variety of learning and mood disorders. Head injuries also place a financial burden on society. On average, each brain injury costs more than $100,000 in acute medical care and rehabilitation. Neuropsychologists play an important role in assessing survivors and in pro- viding rehabilitation. Because of the complexities of brain functions and the sequelae of TBI, the neuropsychology student must understand the pathophysiologic aspects of head trauma, as well as their neuropsychological correlates.

Mechanism of Impact: Neuronal Shearing, Stretching, and Tearing

Bumps to the head are something everyone has en- dured. But when does a “bump” become a TBI? The patho- mechanism of head injuries relates to the physical forces placed on the neuron, specifically the axon and cell body (Figure 13.1). Neurologists have described these forces as shear and straining effects at the neuron level. The axon in particular can take only a certain amount of physical

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stress; the tensile strength of the axon is its resistance to longitudinal stress, measured by the minimal amount of stress required to rupture the axon. Brain trauma may de- form, stretch, and compress the brain and its tissue, ex- ceeding normal tissue’s extendibility, particularly along the axon. These forces may tear the axon, and once dam- aged, the axon may degenerate back to the cell body, which may lead to cell death. This process is called retro- grade degeneration. Conversely, the tear or rupture of a cell body can lead to the axon fiber degenerating, called anterograde degeneration. Because the neuron dies, the now-damaged axon is not activated by the postsynaptic axon. This may lead to a “domino effect,” that is, meta- bolic changes in the postsynaptic neuron and possible cell death. The shearing effect on axons is most noticeable at the junction of gray and white matter regions of the brain (Naugle, Cullum, & Bigler, 1998). Recent advances in understanding of neuronal changes in the brain have im- proved knowledge of the microanatomic changes related to TBI. This knowledge has confirmed the long-assumed idea that during brain trauma, real physical changes at the cellular level may have associated cognitive deficits.

These types of degeneration most likely result from rapid acceleration and deceleration that shake the “Jell- O–like” brain within the cranial cavity. The types of trau- mas most likely to cause such shaking are CHIs, in which the head impacts another object or is suddenly thrown back in whiplash. Only neurons that are not completely severed may “resprout” axonal projections. Shearing, tear- ing, and stretching may result in axonal sprouting, or new growth from the damaged neurons. Perhaps these new connections will bypass damaged areas and restore func- tion. New axonal sprouting, however, is not always bene- ficial. Neurons may also form unwanted connections, re- sulting in behavioral disturbances. Apparently, much axonal activity occurs in the area of the neuronal injury. There may be not only axonal sprouting from damaged neurons but also collateral sprouting from nearby intact neurons.

Damage to the brain itself results either from an object penetrating the skull or from rapid acceleration or decel- eration of the brain. Thus, it is useful to divide the mech- anisms of impact according to two major classifications of head injuries:

Figure 13.1 Magnetic resonance imaging (MRI) of a 12-year-old who sustained a traumatic brain injury (TBI). The MRI scans demon- strate frontal contusions and atrophy with associated enlarged ventricles, compared with the MRI of the noninjured twin. The three- dimensional representation of the brain shows the increased lateral ventricles in the TBI survivor. See inside covers for color image. (Courtesy Erin Bigler, Ph.D., Brigham Young University, Provo, UT.)

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1. Head injuries associated with a penetrating mecha- nism, called penetrating head injury

2. Closed head injuries (CHIs), associated with a blow to the head, but not penetrating the skull

P E N E T R A T I N G H E A D I N J U R Y

A penetrating head injury occurs when a small object has lodged in the brain, such as a knife, scissors, or a bullet from a gun. Penetrating head injuries are extremely dan- gerous to the cortical integrity of the brain because of two factors. The first factor is the location and extent of the damage. For example, a gunshot wound to the brainstem is almost always fatal. Conversely, damage to a cortical as- sociation area may entail “less” damage. The second fac- tor is the complications typically associated with pene- trating head injuries, which include infection and hemorrhaging.

Although most gunshot wounds to the head result in fatal brain damage, survivors almost always receive a neu- ropsychological evaluation to outline the deficits and residual strengths associated with the injury. We have consulted on many cases in which patients with seem- ingly fatal penetrating head injuries have survived, al- though with neuropsychological deficits (Neuropsychology in Action 13.1).

Penetrating head injuries can greatly damage the brain, which is often incompatible with sustaining life. A large- caliber gunshot wound to the brain usually causes death, because there is significant tearing of blood vessels and destruction of brain tissue along the bullet’s path through the brain. Small-caliber gunshot wounds can also be fatal, because they can “bounce” within the skull, fatally dam- aging a strategic area of the brain.

Self-inflicted gunshot wounds to the head are the pri- mary way men commit suicide, followed by jumping off high buildings and hanging. There are more than 25,000 suicides in the United States every year, with a majority being from gunshot wounds.

People who survive penetrating head injuries are often disabled for life. A well-documented case is James Brady, who was President Ronald Reagan’s press attaché. During an assassination attempt by John Hinckley, Jr., Brady was struck by bullets to his right frontal lobe. Hinckley used “killer bullets,” which, on impact, explode into hundreds of fragments. Surgeons completely removed Brady’s right frontal lobe, which was seriously damaged. Hinckley, a paranoid schizophrenic, later used the insanity defense to avoid prison; he is currently hospitalized in St. Elizabeth’s Hospital in Washington, DC. Brady was left hemiplegic on the left side of his body and has many other, more subtle,

neuropsychological symptoms. He and his wife have been the primary political forces behind the Brady Bill, which seeks to control handgun purchases by former mental pa- tients and people with a criminal record. Countries that monitor gun purchases have shown dramatic success in reducing gun-related deaths and injuries. For example, in Norway, a small, northern European country of approxi- mately 5 million people, less than 10 deaths a year are at- tributed to gunshot wounds to the head. The latest statis- tics from the U.S. Department of Justice report that of all homicides perpetrated in the United States in 1998, 52% or 14,000 were committed with handguns.

C L O S E D H E A D I N J U R Y

Closed head traumas have many different causes, but common to all is that the brain undergoes either marked acceleration or deceleration, or both. In acceleration, the brain experiences a significant physical force that propels it quickly from stationary to moving. Examples are the brain being hit by a moving object such as a baseball bat or a car, or a passenger in a rocket accelerating very fast. In deceleration, the brain is already in motion, traveling at a certain speed, and then stops abruptly, sometimes in- stantaneously. Examples include most MVAs and the ski- ing accident described earlier. The kinetic potential—that is, the physical forces acting on the brain—can be ex- pressed mathematically for both types of injuries.

Let us first start with acceleration injuries. You can measure acceleration by noting the time elapsed from the start of acceleration and multiplying it by the acceleration of gravity, or g � 9.8 m/sec2, and time, according to the following formula: velocity (v) � the product of accelera- tion (g) and time (t) or v � gt. For example, think of your- self jumping off a 3-meter-high diving board. There are two ways you could get hurt. The first is related to acceler- ation from the forces (in this case, from gravity) that your brain is experiencing during the period of free fall. In mathematical terms, you can calculate this using the pre- ceding formula. Thus, maximum impact velocity (v) for a 3-meter board would be 12.94 m/sec, corresponding to approximately 29 mph maximum impact speed (depend- ing how high you jump off the board; see Zillmer, 2003c).

The second type of injury you could receive is related to how fast your kinetic energy that you have acquired (29 miles/hour), as a result of the free-fall deceleration, is absorbed by your body and brain. For example, you may have performed a jump in which you landed flat on your stomach. In this case, you decelerate much more quickly than you would if you entered the water feetfirst. You can calculate deceleration (a) by dividing velocity over time

374 PART THREE | Disorders of the Brain

This case concerns a patient I treated in a trauma intensive care unit (ICU). The client was a 25-year-old, right-handed, unem- ployed, single mother with a 12th-grade education. She was suffering from severe depression when she shot herself in the forehead with a small .32-caliber pistol. She was right-handed and held the pistol to her right temple, an inch above her right eye. With her two young children in the home, she then pulled the trigger. The bullet pierced her right frontal skull, sending fragments of bone into her right frontal and parietal lobe. The bullet itself, sterilized by the heat from the acceleration from the gun barrel, came to rest in the left frontal lobe (Figure 13.2). Damage to her brain was confined to her frontal lobes. She did not injure subcortical structures and motor areas of the frontal lobes, and no vital arteries or veins were severed. In a way, she lobotomized herself, and surprisingly, she was actually conscious and responsive when she arrived in the emergency department!

She underwent a right frontal craniotomy for debridement of the gunshot because the bone and skin fragments presented a risk for infection. Surgeons inserted a metal plate in her right skull to repair the damage where the bullet had entered. The bullet itself was too deeply lodged in the brain to be removed. The neurosurgeon decided not to extract the bullet, because doing so would have required cutting through intact brain tissue to reach the bullet. The bullet remained in her brain.

I conducted a neuropsychological evalu- ation while the client was still in the trauma ICU, 3 days after trauma. It was not possible to administer a complete neuropsychological examination of the patient because of her level of fatigue and poor endurance. The results from the screening showed that she was alert and oriented to person, place, and time. She was aware that her speed of processing was extremely slow and kept asking, “Why am I taking so long to respond to these questions?” Attention was mildly

impaired. She could repeat up to 5 digits forward and could do automatism, such as counting from 1 to 20 and reciting the alphabet. On tasks requiring more sustained attention/concentration, however, she showed moderate problems, because she could repeat only up to two digits backward and made errors adding serial threes.

Her motor functions showed decreased motor speed and motor-sequencing prob- lems on the nondominant left hand. Visu- ospatial functions showed mild problems in spatial orientation and a left visual neglect syndrome. Copying of designs showed a neglect of the left visual space. For example, her drawing of a clock was missing the numbers from 6 to 10 on the left side. Receptive speech was adequate: She could follow two-step commands, but her process- ing speed was very slow. Expressive speech showed markedly decreased fluency. Imme- diate visual and verbal memory were ade- quate. On delayed recall, however, she showed mild-to-moderate short-term mem- ory problems. Her overall abstract reasoning and planning were significantly impaired.

I include this evaluation here to demonstrate the neuropsy- chologist’s role in a critical care setting, as well as to document the neuropsychological func- tioning of a gunshot victim. In making this neuropsychological evaluation, I established some cognitive impairment and identified this client as a poten- tial rehabilitation patient. The relatively mild degree of impair- ment, given the nature of the trauma, suggests that the integration centers of the brain were spared from damage. It could have been a lot worse neuropsychologically and med- ically, although the patient contin- ued to struggle with depression.

Another account of penetrating gunshot wound from our clinical experience concerns a depressed man who tried to kill himself by using a shotgun. He placed the shotgun underneath his chin, pointing the gun straight up, and pulled the trigger. The blast removed his chin, nose, mouth, and most of the prefrontal cortex. The suicide attempt also left him blind. But vital areas of the brain, including the brainstem, hypothala- mus, and subcortical structures, remained intact, and the patient survived. Interest- ingly, the patient had inadvertently given himself a prefrontal lobotomy. His depres- sion was not present anymore, but he had many cognitive deficits and a bad temper.

In another, final example, during a prison fight, one inmate plunged a pair of scissors into another inmate’s brain, straight down the parietal cortex. The scissors missed the superior sagittal sinus and must have been short enough to avoid penetrating subcortical areas. The prisoner walked into the emer- gency department with the scissors still implanted in the skull—only the handles showed!

N e u r o p s y c h o l o g y i n A c t i o n 1 3 . 1

C a s e S t u d y : P e n e t r a t i n g H e a d I n j u r y

by Eric A. Zillmer

Figure 13.2 Computed transaxial tomography (CT) scan of .32-caliber bullet gunshot wound. CT scan shows that the gunshot was to the right frontal area with bone fragments in the right frontal lobe. (Courtesy Eric Zillmer.)

(a � v/t). You have already calculated the velocity, so all you need to establish is the time it takes to decelerate. If that time period is instantaneous—if you were to hit the asphalt rather than the water—the deceleration would be high and injury likely. If, however, it takes the diver 1 or 2 seconds to decelerate, then the forces are much less. The time of deceleration is an important variable in the decel- eration equation. If very short, it corresponds to higher deceleration. This is why downhill skiing or race car crashes that take a “considerable” amount of time, al- though horrific to the observer, are actually safer, because the brain is decelerating more slowly.

Using the preceding formula, a springboard diver expe- riences approximately a corresponding deceleration of 16.28 m/sec2 or approximately 2 g when jumping off a 3- meter board. If you were to hit asphalt from the same height, the approximate deceleration expressed in mathe- matical terms would be more than 50 g! In their cars, race car drivers at the Indy 500 carry G-meters, which can cor- roborate the amount of gravity forces the driver experi- ences during a crash. In one crash during practice, a driver hit the retaining wall almost head-on. The G-meter indi- cated a force of 87 g, incompatible with sustaining life. Be- cause car racing is dangerous and drivers are at risk for CHIs, Indy race car drivers undergo preseason neuropsy- chological testing to establish a baseline in cognitive abili- ties if injuries occur during the season. This is also the case for the National Hockey League (NHL), which has started baseline neuropsychological testing for all its players to evaluate the effects of mild CHIs (also called concussions), which have cut short some of the players’ careers.

In CHIs, the physical forces acting on the brain tissue may occur at the point of impact (an impact injury) or its opposite pole, because the brain “tears” away from the skull (countercoup injury). Diffuse injury is also com- mon and most likely to occur at the frontal lobes and tem- poral poles, because of the uneven, “sandpaper-like” sur- face of the tentorial plates that hold those brain structures in place. The physical forces may shear, tear, and rupture nerves, blood vessels, and the covering of the brain. In se- vere head injury, those forces are so strong that they re- duce the brain to a bloody, swollen pulp. As a result, there may be severe complications associated with neuronal dis- ruption, ischemia, hemorrhaging, and edema.

A S S E S S I N G T H E S E V E R I T Y O F B R A I N I N J U R Y

The severity of a traumatic head injury has been most often associated with corresponding scores on the Glasgow Coma Scale (GCS) (Teasdale & Jennett, 1974). This mea-

sure gives the head injury trauma team a rapid, reliable measure of coma depth by assessing separate symptoms, in- cluding language, consciousness, and motor domains. Neu- ropsychologists generally accept the GCS as the standard measure for determining severity of injury in patients with compromised consciousness, from the mildest confusional state (scores �13) to deep coma (scores �5; Table 13.1). Medically, coma is defined as a score of 8 or less, which cor- responds to a severe head injury. Thus, the standard defini- tion of coma is that a patient cannot open his or her eyes, make any recognizable sounds, and follow any commands (Levin, Benton, & Grossman, 1982). Depth of coma, to- gether with post-traumatic amnesia (PTA; described later in this chapter), is a reliable measure of the overall level of brain damage and prognosis. The GCS has proved a good outcome measure after coma, with scores greater than 8 in- dicating a good recovery. Greater mortality is typically as- sociated with scores less than 7.

Coma is not the same as “being asleep.” In fact, elec- troencephalographic (EEG) monitoring shows that a co- matose patient has sleep–awake cycles even while in coma. Coma is directly associated with an injury to those areas of the brain, typically the lower brainstem and reticular activating system (RAS), that are involved in brain arousal. Although it is not clear what precisely causes coma, researchers believe it is related to RAS damage. In animal experiments, researchers found that a linear accel- eration blow did not result in coma, but when the head was free to move in a rotational plane, as in injuries from MVAs, coma did appear. Coma is also not a binary phe- nomenon: It is incorrect to conceptualize the patient as either in a coma or not. Rather, coma falls along a contin- uum. That is, patients can be in a deep coma or in a light, shallow coma, or somewhere in between. Alternatively, head injury survivors may not be in a coma at all, but may be confused and disoriented. When patients recover from coma, they do not “suddenly awake” from it. Rather, they slowly progress from deeper stages to more shallow stages of coma. In this respect, the GCS has been a useful tool for monitoring recovery of comatose patients. Limitations of the GCS are twofold: First, incorrect assessment is pos- sible because of confounding factors including eye swelling that prohibits assessment of eye opening and the presence of an endotracheal tube and the use of drugs (such as barbiturates or anticonvulsants), both of which can prevent verbal response. The second limitation relates to that a small lesion to the brainstem can cause coma, al- though most of the brain is not injured. In such a case, the coma, although serious and potentially life threaten- ing, is not a good indicator of overall brain damage, be- cause the cortex, for example, may be entirely intact.

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Research has demonstrated a relation between the severity of a head injury, defined by the GCS, and neu- ropsychological outcome. The most severe injuries entail the most substantial neuropsychological deficits (Levin et al., 1982). Although initial severity of GCS is an im- portant prognostic indicator for the patient’s survival, other indicators, such as number of days to reach a GCS of 15, have also been associated with long-term neuropsy- chological outcome.

Complications of Moderate and Severe Brain Injury

The major complications of moderate and severe CHIs are edema of the brain and associated brain hernia- tion, intracranial bleeding, and skull fractures. We de- scribe each of these processes next because they are im- portant variables for a positive neuropsychological outcome.

E D E M A

Edema of the brain refers to swelling. Just as swelling fol- lows a bruise to a leg, the brain swells as a result of trauma. The problem with brain edema is that there is no space for the brain to swell into. As a result, internal pressure of the brain increases, often dramatically. Therefore, the trauma team almost routinely places an intracranial mon- itoring catheter into the ventricles or the subarachnoid space to monitor intracranial pressure (ICP). ICP can cause diffuse damage to the brain. In fact, in moderate and severe head injuries, severe and uncontrollable ICP is the main cause of death.

B R A I N H E R N I A T I O N

Besides head injury, other pathologic processes occur in the brain, including hemorrhages, tumors, or infections, which may displace and deform the brain. This process, called brain herniation, is associated with increasing ICP often related to the presence of a large pocket of blood (also called a hematoma). In more than 75% of se- vere CHI cases, there is an associated ICP of greater than 20 mm Hg (or Torr; normal is 0–15 mm Hg). Such a high ICP often results from an intracranial hematoma and a generalized swelling of the brain. These displace the brain downward. This transtentorial herniation is character- ized by downward displacement of the parahippocampal gyrus and uncus of one or both temporal lobes through

Dimension Score Description

Eye opening (E)

Spontaneously 4 Eyes are open; scored without reference to awareness

To speech 3 Eyes are open to speech or shut (“Open eyes.”) without implying a response to a direct

command

To pain 2 Eyes are open with painful stimulus to limbs or chest

Not at all 1 No eye opening, not attributed to ocular swelling

Best verbal response (V) (“What year is it?”)

Oriented 5 Aware of self, environment, time, and situation

Confused 4 Attention is adequate and patient is responsive, but responses suggest disorientation and confusion

Inappropriate 3 Understandable articulation, but speech is used in a nonconversational manner or conversation is not sustained

Incomprehensible 2 Verbal responses (moaning), but without recognizable words

None 1

Best motor response (M) (“Show me two fingers.”)

Obeys commands 6 Follows simple verbal directions

Localizes pain (by touch) 5 Moves limbs to attempt to escape painful stimuli

Withdraws from pain 4 Normal flexor response

Abnormal flexor 3 “Decorticate”: abnormal adduction response of shoulder

Extensor response 2 “Decerebrate”: internal rotation of shoulder

None 1 Flaccid

Glasgow Coma Scale score (E + V + M) = 3–15

Source: Adapted from Teasdale, G., & Jennett, B. (1974). Assessment of coma and impaired consciousness. Lancet, 2, 81–84.

Table 13.1 Glasgow Coma Scale

the tentorial hiatus. There is only one large opening in the skull, the foramen magnum, which is the normal anatomic site of the lower brainstem. Brain herniation can place extreme pressure on the lower brainstem, typi- cally cutting off the cranial nerve III (the oculomotor nerve) and compromising the integrity of the brainstem. The cranial nerve symptom causes initial constriction, fol- lowed by dilation of the pupil on the herniation side. Fur- thermore, the patient may lose motor functions on the same side as the herniation. Compression of the posterior cerebral artery may obstruct blood circulation and even- tually cause necrosis. In the herniation syndrome, con- sciousness deteriorates to a state of deep coma within minutes to hours. If left untreated, the patient goes into a coma and dies of respiratory failure because the brain cen- ters, among them the medulla oblongata, have been dam- aged and life-sustaining functions cease to operate.

Because edema thus progresses to brain herniation, controlling ICP is the main medical issue in acute CHI. Medical trauma personnel carefully monitor ICP, and if it is elevated, they treat it, often aggressively. Reducing the patient’s blood pressure medically or by hyperventilation is often enough to stabilize ICP. In extreme cases, the trauma staff artificially places the patient in a coma. Of course, he or she is already in a coma related to the brain injury, but a pharmacologically induced coma addition- ally reduces brain metabolism, and hence swelling. A last resort in controlling ICP is evacuation (surgical removal) of a lobe, such as the right frontal lobe, to make room for the brain to swell into. This happened to one of our pa- tients, Frank, a 22-year-old college student. One night he joined a friend to travel by car to a questionable location of the city to buy marijuana. The drug dealers mistook Frank for someone else who, the night before, either did not pay for drugs or started an altercation. His attackers were never caught. They pulled Frank from the car, beat him up with a baseball bat, and left him for dead. Mirac- ulously, he survived, but with a severe CHI and in a coma. His ICP was so severe that he would have not lived had not the neurosurgeons removed his right frontal lobe, al- though there was no specific injury to that lobe. They simply removed it because Frank’s brain needed the addi- tional space to expand. Frank has now been through 10 years of rehabilitation. He has severe cognitive deficits and needs supervision 24 hours a day. His life has changed dramatically. He has had to learn all over again how to walk and talk. The rehabilitation hospital where Frank now lives has built a special room for him with soft padded walls, because of his uncontrollable temper. To his parents he is a completely different person from who he was before the assault. His parents deal with the situa-

tion as if their son had died that night and as if the new Frank were their new son.

E X T R A D U R A L A N D S U B D U R A L H E M O R R H A G E

As a result of a head injury, cerebral blood vessels may te- ar, producing pools of blood within and between the meninges. Subdural and extradural bleeding frequently complicate head injuries and are medically significant. A subdural hematoma, in particular, may be associated with trivial bleeding only to cause problems weeks after the injury (Figure 13.3). Acute subdural or intracerebral bleeds most often appear in severe head injury. Together with brain edema, they are present in most fatal cases. The classic symptom in the subdural is an initial period of un- consciousness, but because the dura adheres tightly to the skull, the bleeding delays and a prolonged interval occurs during which the patient is conscious and functioning more or less normally. Once the bleed enlarges, it pushes the brain laterally and downward, causing brain hernia- tion. As the hematoma enlarges, level of consciousness deteriorates quickly. This sequence of events is very dan- gerous, because the patient appears to have recovered from the trauma to the head, only to deteriorate once more quickly—and often fatally.

The frequent subdural hematoma corresponds to a bleed between the dura and the arachnoid space. A sub- dural hematoma is most likely caused by an acute venous hemorrhage related to rupture of a cortical vein, such as the superior sagittal sinus. Subdural bleeding typically oc- curs over the outward surfaces of the frontal and parietal lobes. Subdural hematomas are medical emergencies and typically develop within 1 week after the injury (if the bleed is slow) to as quickly as within 1 hour. Skull frac- tures (of which MVAs are the most frequent cause) cause more than half of all subdurals. Alcohol is a major cata- lyst, because of its anticoagulant properties in blood. Left untreated, the brain pressure increases to such a degree that the brain herniates, ultimately resulting in death. Symptoms of subdural hematoma include contralateral hemiparesis, ipsilateral pupil dilation, and changes in level of consciousness. Radiologists can easily make the diagno- sis using computed transaxial tomographic (CT) imaging.

The less frequent extradural hematoma is a bleed that occurs between the skull and the dura. Bleeding of the large middle meningeal artery most often causes an extradural hematoma. An epidural hematoma repre- sents a bleed between the meninges and the skull and is less common only occurring in 1% to 3% of major CHIs. The cause of an epidural is most often related to

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the rupture of an artery, but in some cases, an epidural develops as a result of injury to a meningeal vein or to the dural sinus.

Surgeons treat an epidural or subdural hematoma by drilling one or more burr holes over the parieto-occipital and temporal regions. This drains the pocket of blood and is the most rapid and effective intervention. In essence, the hematoma drains through a shunt placed within the bleed. Drainage needs to occur as quickly as possible once the hematoma has been diagnosed, and before the blood coagulates, which would have to be removed by neuro- surgery. If such intervention occurs in a timely manner, the outcome of the subdural or epidural hematoma is gen- erally good, with few, if any, cognitive deficits.

I N T R A C R A N I A L B L E E D I N G

“Space-occupying clots” appear in about 15% of fatal head injuries. Most frequent are microscopic hemor- rhages, commonly formed by shearing forces that tear blood vessels in subcortical white matter, the corpus callo- sum, and the orbital surfaces of the frontal and temporal lobes. Focal lesions do not occur as frequently, but appear as contusions and intracranial hematoma (a collection of

blood, typically clotted). Technically, epidural and sub- dural hematomas are not intracerebral hematomas, in which the bleed is intracranial—that is, within the brain. Epidural and subdural bleeds are actually outside the brain. Intracerebral hematomas are more difficult to treat than epidural and subdural hematomas and may require emergency neurosurgery.

S K U L L F R A C T U R E S

Examiners find skull fractures in approximately 75% to 90% of all patients with intracranial or epidural hematoma. Two different types of skull fractures exist. The first is the relatively benign linear fracture, which results in a rather distinct, straight line. The second is the more com- plicated depressed skull fracture, in which the impact has often driven fragments of the skull into the underly- ing dura and brain. Location is another important vari- able. Fractures to the base of the skull are difficult to de- tect in X-ray films and often entail more damage than do the simple linear fractures. Although the brain can be se- verely damaged without any skull damage, the presence of a skull fracture always creates the possibility of infection, cerebrospinal fluid leaks, and bleeding. Skull fractures may

Figure 13.3 Images obtained from a 42-year-old man, 4 years status after work- related landscaping accident where a branch from a tree struck the left posterior portion of his skull. His initial Glasgow Coma Scale was 3, and his duration of loss of consciousness was greater than 2 weeks. The left image is a magnetic resonance imaging (MRI) scan showing significant neuronal loss secondary to massive subdural hematoma. Right image is an MRI scan with cerebral blood flow (CBF) superimposed. Numbers (5.7 ml/100 compared with 8.9 m/ml) reflect lower average CBF in le- sioned brain area. See inside covers for color image. (Courtesy Frank Hillary, Ph.D., Pennsylvania State University.)

also rupture meningeal arteries or large venous sinuses, resulting in epidural and subdural hematomas.

The relation between skull fractures and neuropsycho- logical functioning has been debated. Clearly, for the skull to fracture a significant force must have acted on the cra- nial plates. This force may have transferred to the brain, making actual brain damage more likely. The physics of skull fractures are complicated. In a skull fracture, the skull itself may have absorbed much, if not most, of the kinetic energy, thereby protecting the brain from damage. This is analogous to falling off a bicycle while wearing a helmet. The helmet absorbs much of the physical force, which transferred to the physical structure of the helmet (often destroying it), thereby protecting the head and the brain. For these reasons, skull fractures may not be di- rectly related to specific levels of neuropsychological dys- function. However, brain damage is more likely in skull fractures because the initial forces that fractured the skull must have been high, increasing the likelihood of brain damage.

P O S T - T R A U M A T I C E P I L E P S Y

Seizures are a major complication after head injury. Post- traumatic epilepsy follows about 10% of severe closed head wounds and 40% of penetrating head injuries. The causes of the seizures relate to the presence of scar tissue, specifically alterations in neuronal membrane function and its structure. Neurologists consider seizures stemming from a head injury secondary, because they result from a known pathologic lesion. It is difficult to predict which head injury survivor may experience development of seizures, because onset can be delayed as much as 2 years after the trauma. Risk factors that increase the likelihood of for development of post-traumatic seizures include penetrating type head injury, severity of brain damage, prolonged periods of coma, PTA (described later in this chapter), inflammation associated with the wound, and residual neurologic symptoms. Seizures are such a fre- quent complication of head injury that patients receive anticonvulsant medication prophylactically (routinely) to control even the possibility of seizures.

Mild Head Injury: “Concussions”

The concept of a mild head injury is relatively re- cent. In the early 1980s, one of our mentors, Jeffrey T. Barth from the University of Virginia Medical School, was curious about what happens to patients who report

to the emergency department for a head injury complain- ing of a concussion. These patients typically have had no or a short loss of consciousness, followed by prompt re- covery without any localizing neurologic signs. They ex- hibit few immediate cognitive or physical complaints be- yond a headache, feeling dizzy, and vague memory problems. Together with a team of neurosurgeons and neurologists, Barth examined hundreds of patients who were turned away from the emergency department, usu- ally with no referral follow-up, because their injury was not thought to be severe enough to hospitalize the pa- tient. The assumption was that there were no long-term problems. In the early 1980s, concussions were not con- sidered a medical emergency.

Perhaps this indifference relates to how society deals with mild head trauma. For example, in athletics, con- cussions are often tolerated with some bravado: “I was hit in the head and didn’t know the score of the football game.” In fact, television football announcers recount how “amusing” it was to have someone knocked out, only to return to the opponent’s sideline rather than his own. They recall with great humor how a teammate, after being knocked out, proceeded to run with the foot- ball in the wrong direction. Similarly, the symptoms of “seeing stars” has not been thought of as a neurologic symptom in this society, although it clearly is, but as a relatively benign, perhaps comic, event. In fact, many comic strips use “stars” to characterize transient confu- sion (Figure 13.4).

Until recently, researchers have not studied and un- derstood the medical, neurologic, and psychological manifestations of mild head injuries. Since the early 1990s, an appreciation for milder forms of injuries to the head has appeared in the scientific literature. Mild head in- juries often entail dizziness, fatigue, or headaches, with no loss or only brief loss of consciousness (Levin, Eisenberg, & Benton, 1989). The traditional literature often calls this type of head injury a “concussion.” However, neu- ropsychologists now treat mild head injury as a signifi- cant medical event that has real, even long-term, conse- quences (Neuropsychology in Action 13.2). This finding is related not only to clinical evidence, in which patients have described physical and cognitive symptoms, but also to experimental evidence. Research studies have demon- strated that earlier studies using only the light micro- scope were incorrect in finding no reliable association between mild head injury and pathologic lesions in the brain. Recent animal research, using histologic staining techniques, shows that neurons exposed to forces consis- tent with a mild head injury are damaged and die (Barth et al., 1983).

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380 PART THREE | Disorders of the Brain

Three important findings have emerged from this body of research that are important to mild head injuries:

1. Mild head injuries usually go medically unnoticed. The medical community does not widely recognize the often debilitating sequelae of such injuries.

2. During mild head injury, the physical energy trans- ferred to the brain is related to linear and rotational mechanical forces associated with the sudden accelera- tion, deceleration, or both. These forces can result in shearing or stretching, and even in necrosis (cell death)

of neurons, which are the central building blocks of the central nervous system (for example, see Levin et al., 1982).

3. Head injuries, including the mild variety, are cumula- tive in effect. For example, Gronwall and Wrightson (1975) conducted one of the first investigations to es- tablish that after a second concussion the capacity of adults to process information declined significantly. Thus, repeated blows to the head, such as those occur- ring in boxing and football, are especially dangerous to the athlete’s health.

After attending a research meeting in Vail, Colorado, on traumatic brain injuries, my colleague, a 42-year-old neurosurgeon, decided to hit the ski slopes. While descend- ing a modest incline, he lost his balance and fell, striking his head. He was immediately knocked unconscious for a period of only 10 to 15 seconds. On awakening, he experi- enced confusion that cleared within minutes, with the exception of a modest vertigo that persisted but did not interfere with his ability to ski down the mountain. Because my mentor and friend, who is a renowned spe- cialist in brain trauma, continued to ski that day, I thought this concussion had had no effect on him. However, on returning home, he did report that he was a bit more dis- tractible and that his memory was flawed, for example, when remembering the location of his Dictaphone, briefcase, and keys. He also noticed that when talking with colleagues and residents, he could no longer quickly recall references to articles. His speed of information processing was not affected, nor was his skill and judgment as a neurosur- geon; however, he did fatigue more quickly than before.

What exactly is a concussion? The term concussion refers to an injury to the brain, resulting either from a collision between the head and an object or from a rapid, forceful acceleration and deceleration. Neuropsy-

chologists typically diagnose a brain injury when the consequences include one or more of the following: (1) an alteration or loss of consciousness, (2) a loss of memory for the events immediately before and after the injury, and (3) neurologic symptoms. The degree of injury can vary significantly, from a mild concussion to death. The terms concus- sion and mild traumatic brain injury (TBI) frequently are used as synonyms, although I focus here on mild TBI. What features sepa- rate a mild from a moderate brain injury? Medical professionals generally accept that a “mild” rating should not involve a loss of consciousness that exceeds 30 minutes; in addition, memory loss for events after the trauma should not exceed 24 hours, and the neurologic symptoms should not lead to a deterioration of the patient’s Glasgow Coma Scale (GCS) score to less than 13.

How many of us have sustained a mild TBI? Neurologists classify approximately two thirds of all brain injuries as mild. In the United States alone, researchers estimate that approximately 1,300,000 people sustain a mild TBI each year. Approximately half are the result of motor vehicle accidents, and the rest involve assaults, falls, or sports- related injuries (such as in skiing, boxing, football, horseback riding, and ice hockey). What happens to the brain during mild TBI? Currently, the best data are derived from

studies of concussed animals or from hu- mans who, in addition to having concussions, died of other medical complications such as chest wounds. Particularly because of rota- tional forces, brain cells tear, and this shear- ing of axons most often occurs in subcortical and frontotemporal regions. Because impact to the brain from the outside can vary so significantly, tearing and shearing of cells can also vary among individuals. However, post- mortem examinations of concussed brains have provided evidence of microscopic changes, which can no doubt lead to neuro- physiological and neurochemical alterations.

What typical difficulties do patients encounter? By evaluating patients in the first phases after a mild TBI, researchers have documented frequent impairments on neuropsychological tests of sustained attention, memory, and learning, and mea- sures that capture speed of information processing. Most mild TBI survivors enjoy a favorable recovery in the 3 to 6 months after the injury. That is, these patients improve up to a level that is not statistically below that of a control group. One study even found a way to test patients before and after a mild TBI. Before the playing season, researchers tested college football players who had never sustained a brain injury and did follow-up testing on those who later sustained a mild TBI. This retesting showed an initial decline

N e u r o p s y c h o l o g y i n A c t i o n 1 3 . 2

C a n a C o n c u s s i o n C h a n g e Y o u r L i f e ?

by Ronald M. Ruff Ph.D., Director of Neurobehavioral Rehabilitation, St. Mary’s Medical Center; Associate Adjunct Professor, Department of Neurosurgery and Psychiatry, University of California at San Francisco, San Francisco, CA

S P O R T S - R E L A T E D C O N C U S S I O N S : A N E U R O P S Y C H O L O G I C A L P E R S P E C T I V E

Competitive sports participation has increased world- wide. Sports-related concussions represent a significant potential health concern to those who participate in con- tact sports. In the United States alone, it is estimated that approximately 1.3 million individuals sustain a mild TBI each year, approximately half of which result from MVAs. After MVAs, the causes of head injuries are, in order,

sports injuries, falls, violence, and industrial accidents. Thus, a high number of athletes are at risk for concus- sion, approximately 2% to 10% (Ruchinskas, Francis, & Barth, 1997), representing more than 300,000 sports- related head injuries annually (Moser & Schatz, 2002).

It has been recognized only recently that concussive in- juries present a significant neuropsychological event (Zillmer, 2003b). As a result, increasing emphasis has been in providing protection to athletes. Those forms of pro- tection include rule changes to minimize concussion-type

CHAPTER 13 | Traumatic Head Injury and Rehabilitation 381

on neuropsychological testing, with a posi- tive recovery in the subsequent weeks. However, a large body of literature has unequivocally demonstrated that not all mild TBI patients enjoy a favorable recovery. A minority continue to have not only persistent cognitive problems but also physical prob- lems, which typically include headache, vertigo, dizziness, energy loss, and in some cases, a heightened sensitivity to noise, light, alcohol, or medications. Emotional reactions commonly include irritability, elevated anxiety, or depressive symptoms. These cognitive and physical problems can, in turn, lead to emotional, psychosocial, and vocational changes. Neuropsychologists use the term postconcussive disorder for such cases. In the literature, researchers have estimated that postconcussive disorders occur in 10% to 20% of all mild TBI cases (130,000–260,000 cases each year in the United States). Over the years, the impor- tance of a careful neuropsychological evalu- ation of patients with mild TBI has become more and more recognized.

What is the neuropsychologist’s role in evaluating mild TBI? The objective tools that physicians tend to rely on for diagnosing brain injuries include computed transaxial tomography (CT) and magnetic resonance imaging (MRI). However, for mild TBI, these neuroimaging techniques lack sufficient sensitivity to visualize microscopic changes. Thus, CT and MRI scans are, as a rule, “nor- mal” in most mild TBI cases. Although the newer dynamic neuroimaging techniques such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT) scans have demon- strated greater sensitivity in case studies,

more research is required to determine whether these newer techniques can objec- tify mild TBI conclusively. Because objective tools cannot yet reliably evaluate the poten- tial brain damage involved in mild TBI, medical teams frequently assign to neu- ropsychologists, using subjective tools, the task of providing answers. Using psychomet- ric tests, neuropsychologists are uniquely qualified to delineate the upper thresholds of cognitive functioning. Based on a pattern analysis across a neurocognitive test battery together with a psychodiagnostic evaluation, neuropsychologists can reach a diagnosis to determine the extent to which brain damage has contributed to the postconcussive disorder. The three key challenges for making a differential diagnosis are: (1) estimating preinjury functioning levels, (2) evaluating comorbid factors, and (3) exploring interac- tions among the postinjury problems. Esti- mating preinjury functioning is paramount for capturing not only “deficits” but also any decline in functioning.

To illustrate, let us return to the earlier- mentioned neurosurgeon who struck his head while skiing. Many neuropsychologists use an impairment index that largely represents a common notion that a deficit is defined by a score that falls two standard deviations below the mean. However, this notion may lead to false negatives. For example, a 50% decrease in performance in an individual whose preinjury functioning levels were at the 95th percentile will result in a postinjury performance at the 45th percentile. This neurosurgeon commented, with respect to the challenges neuropsychologists face:

Perceptions of a disease by one who has not had the disease as a patient tend to be

modestly inaccurate. Recovery from a head injury appears to be a long process, one requiring innumerable strategies for compen- sation. Neurocognitive testing will indicate part of the story, only if the results are abnor- mal; it leaves something to be desired in predicting levels of performance for those who are adequate competitors in a modern society. (Marshall & Ruff, 1989, p. 278).

In addition to capturing a relative loss based on a comparison with the patient’s estimated preinjury functioning levels, it is also crucial that the neuropsychologist become aware of preexisting medical risk factors (history of alcohol or substance abuse; prior concussion), as well as cogni- tive risk factors (preexisting learning disabili- ties) and emotional risk factors (such as hysteria, somatization, and secondary gain). Concurrent medical injuries are common in mild TBI cases, including neck, shoulder, and rib fractures, which can result in a pain syndrome. Excessive pain can interfere with sleep, and it always results in emotional reactions that can, in turn, affect neurocog- nitive functioning. More systematic research is called for to evaluate mild TBI cases with and without comorbid medical injuries. Finally, the interactions among postinjury problems require careful analysis. Postcon- cussive syndromes derail some patients from their vocations as a result of a combina- tion of factors (such as headaches, vertigo, attentional difficulties, and mood changes). All of us who work in this field believe that we must stress prevention. The mandatory introduction of helmets, safety belts, and airbags has reduced TBI rates. Be careful: A concussion has the potential to change your life!

382 PART THREE | Disorders of the Brain

injuries, as well as equipment changes, including improved helmets, mouth guards, and other face and head protection to reduce the transfer of kinetic energy to the head during an athletic contest (Figure 13.5). In the area of brain- behavior research, a concomitant focus has been on under- standing the neuropsychological manifestations of sports- related concussions. Neuropsychologists have directed their

attention to defining and grading concussions, as well as to understanding the neurometabolic changes associated with concussions. In the area of clinical neuropsychology, ad- vancements have been made for concussion assessment and diagnosis, as well as concussion management, rehabilita- tion, and return to play decisions. Accordingly, neuropsy- chologists have become an integral part of the sports medi- cine team involved in the care of athletes with sports-related concussions. Today, neuropsychologists are playing a lead- ing role in the clinical and scientific aspects of sports-re- lated concussions.

T h e T w e n t i e t h C e n t u r y : A R e v o l u t i o n o f S c i e n c e a n d S p o r t s

The history of sports-related concussions is long, but its past has been short. In the early part of the twentieth century, the frequent nature of collisions between foot- ball players called into question the safety of the sport and highlighted an awareness of head injuries in sports. Football helmets were not available until 1896, and be- cause of the physical properties of the helmets them- selves, as well as the nature of play, they were not effec- tive in the protection of athletes (Cantu & Mueller, 2003). In fact, the 1905 college season ended with much protest over the brutality of football. On October 9, 1905, midseason, President Roosevelt met with repre- sentatives from Harvard, Yale, and Princeton to discuss making football less dangerous, in an effort to ulti- mately save the sport. Football was being publicly de- nounced as brutal and inappropriate for young men after the Chicago Tribune published an injury report

Figure 13.5 Many sports have the potential for physical contact and collision. Sport is clearly a breeding ground for physi- cal injury. (Courtesy Drexel University, Philadelphia, PA, 2003, by permission.)

Image not available due to copyright restrictions

listing 18 deaths and 159 serious injuries (Stewart, 1995). Led by Henry M. MacCracken, the chancellor of New York University, the parties responsible for football rules agreed to change the game. As a result, the Inter- collegiate Athletic Association was established, which would later become the National Collegiate Athletic As- sociation (NCAA), the current governing body for in- tercollegiate sports. The rule changes included outlaw- ing the “flying wedge” (Figure 13.6), one of football’s most violent offensive formations, during which a group of lead offensive tacklers would provide protection for the ball carrier. Overall, the consequences of head in- juries in football were the primary force underlying the creation of the NCAA, which was established initially to ensure the welfare of the student–athlete.

T h e 1 9 8 0 s V i r g i n i a F o o t b a l l S t u d i e s

Clinical and epidemiologic studies of mild head injury in the 1980s reported neuropsychological deficits in new and rapid problem solving, attention and concentration, and memory, which lasted up to 3 months after trauma (Barth, Macciocchi, Boll, Giordani, Jane, & Rimel, 1983; Rimel et al., 1981). At about the same time, Gennarelli (1983) and Ommaya (Ommaya & Gennarelli, 1974) were performing primate studies to evaluate the histologic effects of mild acceleration/deceleration during head trauma. They documented visible axonal shearing and straining in the brainstem in experimentally induced mild

head injury. By the 1980s, there appeared to be a growing consensus that mild head injury was not as innocuous as previously thought. Still, recovery curves lacked defini- tion and individual vulnerability of mild head injuries were not well understood. Research was needed that would control preexisting factors and assess neurocogni- tive functions in a laboratory setting before and after the administration of a controlled mild head injury to a human subject. In this way, the individual would act as his or her own control.

Within this context, Jeff Barth and his colleague at the University of Virginia (UVA) designed one of the most creative experiments in neuropsychology. They ap- proached college football players as the practical solu- tion to this research problem. Football players were at risk to experience an acceleration/deceleration mild head injury similar to the type of linear of rotational brain trauma experienced in MVAs within a natural yet controlled environment. The first landmark sports-related concussion study therefore focused on the UVA foot- ball team. These early football studies suggested that young, bright, healthy, and well-motivated student– athletes, who experience mild, uncomplicated head trauma without loss of consciousness did demonstrate neuropsychological decline in areas of information problem solving and attention, but would likely follow a rapid recovery curve and have no lasting disability (Barth et al, 1989).

Interestingly, these investigators at UVA also consulted with professional football teams hoping to extend these findings beyond the college arena. But they found little interest in allowing scientists to study the potentially neg- ative effects of concussion, which were presumed to occur (Jeffrey Barth, personal communication, January 10, 2004). A decade later, however, Mark Lovell and his col- leagues again spearheaded a movement aimed at imple- menting a program designed to educate and protect pro- fessional athletes. The Pittsburgh Sports Concussion Program initiated pilot baseline and postconcussive neuropsychological testing of the Pittsburgh Steelers play- ers in the late 1980s through early 1990s. This program successfully broke down many of the barriers regarding professional football players’ acknowledgment and accep- tance of concussive injuries, and in combination with the NFL Players Association’s growing concerns over career- ending injuries related to multiple concussions (for exam- ple, Troy Aikman and Steve Young), has now led to league- wide programs in both the National Football League (NFL; 1993) and NHL (1996) (Mark Lovell, personal communication, November 23, 2004; Pellman, Lovell, Viano, et al., 2004).

CHAPTER 13 | Traumatic Head Injury and Rehabilitation 383

Figure 13.6 A bronze statue of the flying football wedge as seen at the NCAA museum in Indianapolis. The flying wedge revolutionized the game but also led to numerous injuries and even deaths on the field. (Courtesy NCAA Hall of Champions, Indi- anapolis, IN.)

384 PART THREE | Disorders of the Brain

T w e n t y - F i r s t C e n t u r y a n d t h e R e f i n e m e n t o f S p o r t s N e u r o p s y c h o l o g y

Besides the advances that have been made in the neuro- scientific and neuropsychological community, experts on the psychology of sports injuries have made significant advances in how concussion injuries can be treated and conceptualized. Even though an injury is essentially a neg- ative experience, some unexpected benefits have been noted; for example, the challenge in response to injury to reorder one’s life and lifestyle, to develop creative solu- tions in overcoming physical and mental deficits, and to forge new and meaningful relationships with others (Pargman, 1999). Thus, a renewed focus on the concept of injury prevention and a multidisciplinary approach to the rehabilitation of injured athletes has been made, which includes psychological intervention, as well as med- ical, mechanical, and social factors. This newly conceptu- alized multimodal approach appears especially appropri- ate in the context of making return-to-play decisions with concussed athletes in view of the emergence of neuropsy- chology in sports medicine (Echemendia & Cantu, 2003). In addition, neuropsychological profiles of ath- letes may help us understand their specific strengths and weaknesses and how they may cope with sports-related concussions. As scientists and researchers provided in- creasing evidence for an organic basis to the clinical symp- toms of concussion, it became evident that the clinical picture reflects a dynamic state of affairs in which physi- cal, personal, social, competitive, and economic factors contributed in varying degrees (Zillmer 2003b).

Contemporary sports-related concussion research is akin to putting a complex puzzle together: What is the ef- fect of age and sex in concussions? What is the epidemiol- ogy of the sports-related concussion injuries and how they differ by sport and sex (Figure 13.7). What neuropsycho- logical tests are best suited to assess concussions? What is the gold standard for grading concussions? Who is most susceptible to sports-related concussion? What return-to- play guidelines are most practical?

We believe neuropsychologists play, and will continue to play, an important role in assembling this complex puz- zle. In the absence of any detectable abnormalities on tra- ditional magnetic resonance imaging (MRI) scans for cases with concussion (Bigler & Snyder, 1995), the objec- tive nature of neuropsychological testing has become a re- liable and valid approach to measuring cognitive impair- ment and symptom resolution for mild TBI. The future of sports-related mild head injury research is expanding and will be best served by prospective neuropsychological study of athletes at high risk for multiple concussions. Bet-

ter protective equipment and devises, rule changes, and pooling of information into a comprehensive concussion data bank to better define safe return-to-play criteria should be the focus of sports medicine in the new millennium.

Future directions in the assessment and management of sports-related concussion include: increased research on prevalence rates and effects of concussions for female and young athletes, educating parents of youth athletes and family physicians on the importance of baseline and postconcussion cognitive assessments, and further valida- tion of computerized assessment measures. Despite a paucity of research on female and youth athletes, there is evidence that female athletes are at greater risk for injury than male athletes, and that concussions may affect chil- dren and young adolescents differently than older adoles- cents and adults. Sideline, baseline, and postconcussion assessments have become prevalent in documenting prein- jury and postinjury performance, recovery rates, and return-to-play decisions. New computerized assessment procedures are growing in popularity and are used in the NFL, NHL, NASCAR, and Formula 1.

The role of the neuropsychologist in the assessment of concussions for purposes of diagnosis and symptom resolution is one that our profession should embrace. Moreover, for those neuropsychologists who love sports, it provides a unique opportunity to merge one’s profes- sional skills with one’s affinity for sports. Most often the

Figure 13.7 Female athletes are consistently found to be at higher risk for sustaining concussions than male athletes across all sports and all ages (Covassin, Swanik, & Sachs, 2003). Pic- tured are two college lacrosse players. In collegiate lacrosse men wear helmets, whereas women do not, which has initiated a debate regarding the use of head protection in the sport. (Courtesy Drexel University, Philadelphia, PA.)

role of the neuropsychologist in the area of sports-related concussions will be that of a consultant and a researcher. In addition to being an expert in the neuropsychological assessment of concussions, the neuropsychologist must understand the culture and epidemiology of the injuries of the athletic arena and of various sports they may be asked to cover. We believe that the neuropsychologists’ training and expertise uniquely prepares him or her to play an important and rewarding role in this growing field in the future (Zillmer, Schneider, Tinker, & Kaminaris, 2006).

P O S T C O N C U S S I O N A L S Y N D R O M E

Medical personnel often call the behavioral and cognitive sequelae of mild head injury “postconcussional syn- drome.” These sequelae range over a variety of somatic and neuropsychological symptoms, including headache, irritability, dizziness, lack of concentration, and impaired memory. Researchers have documented the symptoms of mild head injury most frequently with MVAs. However, analogous situations with acceleration/deceleration of the head arise in the context of competitive sports. Many sports involve speed and the potential for collision. In fact, as mentioned earlier, 17% of all head injuries are sports related.

For example, research with football players suggests that many effects of sports-related collisions (such as tack- ling) that were originally thought to be relatively benign, actually have measurable neuropsychological conse- quences in college athletes. These collisions may not only diminish the performance of players on the field but can also compromise their health off the field. Full apprecia- tion of impact injuries has only recently developed as many NFL quarterbacks have reported the negative ef- fects of repeatedly being hit in the head. Frequent head impact places them at risk for losing consciousness even when experiencing relatively minor concussive forces to the head. In some cases, this has resulted in cognitive changes, including excessive dizziness and difficulty in concentrating. Several players were forced to retire, and rules were changed, disallowing tackling with the helmet or “spearing” to the opposing player’s head.

Researchers have studied the neurologic aspects of pro- fessional boxing in more detail; these aspects are easily ap- preciated by the public because of the knockout (KO), which is a neurologic event synonymous with cerebral con- tusion. Only recently have researchers examined the neu- rologic aspects of amateur boxing, where duration of fights, rules, and protective devices differ from profes- sional boxing. Other less obvious sports-related neurologic

effects appear in soccer players who frequently head the ball. Findings indicate more EEG abnormalities among professional players (Tysvaer, Storli, & Bachen, 1989) and the presence of neuropsychological deficits among college players (Witol & Webbe, 1993). That football and soccer can involve potential mechanical forces to the head that can cause injury seems disturbing, particularly at the non- professional, “recreational” level. At that level, many ele- mentary school, high school, and college players are par- ticularly vulnerable to the developmental delays related to such head injuries (Levin et al., 1982).

Treatment of Head Injuries

An acute TBI often entails severe neurologic im- pairment. In severe head injuries, the patient is comatose when the medical emergency unit arrives. The initial management of severe head injury follows the ABC as- sessment (airway, breathing, and circulatory status); the medics establish a respiratory airway, often freeing the pharynx from blood and other obstructions. If they do not establish an airway, anoxia will result, adding to the physical injuries of the brain. After a clear airway has been established, medics assess the patient’s breathing. Then the team establishes regular breathing, if necessary, artifi- cially, with sufficient oxygen, because hypoxia is common in head injuries. Alterations in breathing may be related to brainstem dysfunction. Medics then evaluate circula- tory status by examining blood gases and blood pressure. They initiate intravenous infusion, including blood re- placement. Then, once the patient has been medically sta- bilized, they obtain diagnostic imaging using CT and MRI. Next, a neurologist conducts an evaluation to as- certain the level of consciousness and presence of neuro- logic symptoms. If the patient remains in a coma, the team may hospitalize him or her in a neuro-intensive care unit, which has a specialized environment that facilitates care of comatose patients.

As mentioned earlier, intracranial monitoring is the cornerstone of medical therapy. If ICP remains normal, the patient undergoes intensive supportive care. If ICP is elevated, medical personnel use aggressive measures to reduce it. These include controlled ventilation, which de- creases cerebral blood volume and constricts cerebral ves- sels, thus reducing ICP. Steroid therapy may prevent in- tracerebral edema. Patients are typically temperature controlled with heating/cooling blankets, because ele- vated body temperature increases metabolic rate and hy- pothermia leads to other medical complications. Some- times medical personnel administer diuretics to reduce

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386 PART THREE | Disorders of the Brain

John, age 24, and Theresa, age 22, are two adults with traumatic brain injuries (TBIs). John suffered a head injury at age 17 in a motorcycle accident. At age 20, Theresa suffered a head injury when a drunk driver struck her car as she waited at a red light. As a result of their injuries, John and Theresa currently live in a community-based rehabili- tation facility.

John experiences hemiplegia, difficulty in planning for future events, and memory and attention deficits. Theresa experiences seizures, as well as severe speech and memory deficits. John and Theresa enjoy each other’s company and often attend community events together. More recently, John and Theresa have become interested in a physically intimate relationship.

The last issue is a concern for the agency that provides their rehabilitative services. With their specific cognitive deficits, can John and Theresa consent to have sex? Can

they each make an informed decision using information on sexual conduct, diseases, and pregnancy? Is either at a high risk for being victimized because of an inability to adequately protect himself or herself from unwanted sexual advances? To explore the answers to these questions, the issues of TBI and sexuality must be considered.

After a head injury, the often-ambiguous rules and rituals pertaining to sex can be- come even more difficult. Adverse effects of TBI on sexuality range from sensorimotor deficits and bowel and bladder dysfunction, to changes in sex drive and various male and female genital sexual dysfunctions. In addi- tion to the neurologic, physical, and emo- tional effects on sexuality are cognitive changes associated with TBI. Cognitive changes can affect sexuality in a variety of ways, including impairment of the ability to make safe choices regarding sexual behav- ior. The individual can be physically able to

engage in a sexual relationship, and even be interested in pursuing one, but at the same time be cognitively incapable of consenting. An inability to make decisions can result in victimization, unwanted pregnancies, and diseases.

One hallmark of a moderate-to-severe TBI can be the loss of the ability to make complex decisions requiring judgment, insight, preplanning, reasoning, organiza- tion, and impulse control. Clearly, such cognitive deficits can impair the ability to consent to sex. When this issue arises, the neuropsychologist serves two main roles. First, the neuropsychologist, together with formal testing of cognitive and functional strengths and weaknesses, can assess an individual’s capacity to consent to sex. Second, the neuropsychologist can recom- mend rehabilitative and educational strate- gies that are specially geared to a person’s functioning level and cognitive abilities and

N e u r o p s y c h o l o g y i n A c t i o n 1 3 . 3

C o n s e n s u a l S e x a f t e r T r a u m a t i c B r a i n I n j u r y : S e x a s a P r o b l e m - S o l v i n g T a s k

by Carrie H. Kennedy Ph.D., Lieutenant Commander, Navy Neuropsychology Fellow, University of Virginia, Charlottesville, VA

the ICP. If these measures do not control ICP, the prog- nosis is typically poor, and more aggressive measures are taken, such as inducing barbiturate coma and surgery. Administering a large dosage of barbiturates decreases the cerebral metabolic rate and constricts cerebral vessels. Inducing barbiturate coma is controversial, because it may contribute to additional neuropsychological seque- lae. A final measure is to remove part of the brain to make space available.

N E U R O P S Y C H O L O G I C A L M A N I F E S T A T I O N S

Neuropsychological sequelae, of course, are prominently associated with TBI. They range from patient reports of memory difficulty to problems with attention and con- centration, as well as alterations in mood. Neuropsychol- ogists play an important role in objectively assessing residual ability after mild, moderate, and even severe head injuries, once the patient has been medically stabi- lized and is no longer in a coma or in acute medical care.

In addition to the cognitive effects of brain injury, per- sonality changes from frontal lobe damage may affect the patient’s well-being and quality of life (Neuropsychology in Action 13.3). Neuropsychologists routinely test head injury survivors, because unless tested, cognitive deficits, especially memory, may at first go unnoticed, but cause problems later when the patient returns home or to work. Most recovery after severe head injury occurs within the first 6 months, with smaller adjustments continuing for perhaps as long as 2 years. In the past, rehabilitation ex- perts have waited until the “natural” healing cycle has finished before initiating rehabilitation. More recent thinking has proved that rehabilitation is most effective when started as early as medically possible (Levin et al., 1989).

A n t e r o g r a d e a n d R e t r o g r a d e A m n e s i a

Memory problems constitute a major deficit for people who have sustained traumatic head injuries and are of

special interest to neuropsychologists. In fact, head in- jury experts grade the severity of a head injury partly on the patient’s memory surrounding the accident. Such memory problems are called post-traumatic amnesia (PTA). Retrograde amnesia is the loss of memory for the interval preceding the injury. Conversely, antero- grade amnesia is the loss of memory for events after trauma or disease onset. Although the patient may have residual short-term memory impairment from the head injury, as well as other cognitive deficits, neuropsycholo- gists have established retrograde and anterograde amne- sia as a relatively robust measure of the severity of trauma and its associated cognitive symptoms. Because cortical and subcortical structures mediate memory, PTA has proved a better overall indicator of brain damage than length and depth of coma, which may relate to isolated damage of the brainstem. Neuropsychologists consider these types of amnesia to relate mostly to anterior tem- poral lesions, an anatomic area particularly vulnerable to head injuries, because of the bony features surrounding this area of the brain.

N e u r o p s y c h o l o g i c a l E v a l u a t i o n Often other medical personnel ask neuropsychologists to evaluate head-injured patients at their bedside, close to the time of their accident, while they are still hospitalized (see Neuropsychology in Action 13.1). This examination is typically brief and serves to assess whether the patient can tolerate more formal, longer testing. It also establishes a baseline of overall cognitive abilities for future compar- isons. An example of such a neuropsychology consult is as follows:

Neuropsychology Note. Results from brief neuropsychological procedure, post-MVA with LOC (loss of consciousness) 30 min, revealed a 33 yowm (year-old white male) who was ori- ented � 3 (to self, time, and place) and attentive/cooperative with the exam. The patient was able to follow simple com- mands involving two-step learning. Memory appeared within normal limits (WNL) for immediate and short-term verbal/vi- sual material. Expressive/receptive speech were also WNL. No sensory deficits including astereognosis, finger agnosia, neglect, right–left confusion, or hemianopsia, were observed. The patient did manifest a bilateral resting hand tremor as well as motor

CHAPTER 13 | Traumatic Head Injury and Rehabilitation 387

strengths. In this way, neuropsychologists can optimize the decision making and safety of TBI survivors, whereas facilitating the return of an important aspect of quality of life, that of sexual intimacy.

Using an instrument such as the Sexual Consent and Education Assessment (SCEA; see Kennedy, 1999), neuropsychologists make a capacity determination based on prescribed legal criteria for consent. Legal criteria for sexual consent vary from state to state, but a consensus of psychologists is that individuals must have knowledge of sexual conduct, knowledge of the conse- quences of sexual activity, and basic safety skills to be deemed capable of consenting (Kennedy & Niederbuhl, 2001). Although, taken together, these criteria determine the capacity of any given individual, each crite- rion is also a separate entity directly related to cognitive abilities that neuropsychologists can measure.

The first two criteria for capacity for sexual consent, regarding the nature of sexual conduct and consequences of sexual activity, are a function of crystallized intelli- gence (knowledge that has been acquired over the years) in most adults. That is, individuals who have had previous sexuality

education, sexual experience, or both are more likely to retain general knowledge and information regarding sexuality. Later, such adults who have experienced a TBI typically have little difficulty communicating their understanding of the nature of sexual con- duct and the various consequences of sexual activity. However, individuals who have not yet obtained general knowledge about sexuality must learn it for the first time. After TBI, attentional, memory, and executive function deficits significantly hinder new learning and can make a task such as learn- ing basic sexual knowledge daunting.

The third criterion, however, basic safety skills, appears to be the most significant hurdle for individuals with moderate to severe head injuries. This particular neu- ropsychological task appears to be an executive decision that involves a complex string of decision making, reasoning, judg- ment, and planning. Preliminary findings suggest that neuropsychological tasks that assess those abilities, such as the Tower of London–Drexel University (Culbertson & Zillmer, 2005), the Modified Wisconsin Card Sorting Test, and word fluency are able to correctly classify cognitively impaired individ- uals who are and are not capable of consent-

ing to sexual activity (Kennedy, 2003). Additional research will provide further information regarding sexual consent and related neuropsychological requirements. In turn, investigation of these questions will also provide the basis for developing more effec- tive rehabilitative strategies to help people with neurologic damage in regaining impor- tant parts of their lives, not least of which will be sexual intimacy. This leads us back to our original questions about John and Theresa.

John and Theresa were both tested using the SCEA and a neuropsychological battery. Theresa easily passed all aspects of the assessment, whereas John showed signifi- cant difficulty with the concepts of sexually transmitted diseases and protection against them. John was declared not capable of giving consent until he could successfully complete an educational program dealing specifically with diseases and methods of protection. The educational program, which John completed, included methods of learning that were optimal for John given his neuropsychological test findings. Subse- quently, the rehabilitation facility worked with John and Theresa about establishing privacy, and their subjective quality of life is vastly improved.

388 PART THREE | Disorders of the Brain

incoordination, and difficulty in initiating specific motor move- ments. Perseveration of motor behavior was also apparent. Additional frontal lobe signs included poor reasoning ability and judgment.

Results are consistent with mild to moderate head injury and bilateral frontal lesions as seen on MRI from revealing contu- sions in the inferior frontal regions. Psychologically, the pa- tient appears very distressed and depressed about his hospital- ization and MVA, with suicidal thoughts present (but no specific plan). No other psychiatric symptoms were noted (hallucinations, delusions). Patient should be placed on sui- cide watch. Psychiatric consult should be ordered, and reloca- tion to psychiatric ward should be considered to better man- age suicide threats when the patient is medically stable. Other recommendations include comprehensive neuropsychological and psychological evaluation within the next four weeks to identify functional strengths and weaknesses. Cognitive resid- ual effects that may hinder this patient’s ability to return to his previous employment as a manager include his ability to function independently in life, and his need for outpatient psychotherapy. This testing can be done on an inpatient or outpatient basis and should be repeated over a 6- to 9-month period to monitor his recovery. Once he is discharged I also recommend that he join our head injury group meetings, designed for individuals and families with histories of head injuries. Signed: Dr. Eric A. Zillmer, Neuropsychologist

In general, the long-term neuropsychological effects of head trauma may vary considerably and depend on the strength of the trauma and the medical condition of the patient with the head injury. Not all head traumas pro- duce significant neuropsychological deficits. Others cause permanent and severe deficits. In general, neuropsycholo- gists consider CHIs a diffuse disorder of the brain, be- cause they may affect many different areas of the brain. Thus, differences in neuropsychological presentation in a head-injured protocol typically relate to the patient’s level of overall deficits.

Recovery, Rehabilitation, and Intervention of Traumatic Brain Injury

What is the potential for the human brain to re- cover or adapt after brain injury? First, insult to the brain can result in different effects depending on the site and mechanism of damage. What is remarkable, however, is the brain’s amazing ability to try to adapt to damage. If damage does not totally destroy neurons, the brain

attempts to restore functioning. If the injury was caused by shock or some other temporary mechanism, diaschisis may serve to “unmask” functioning neuronal systems. When neurons are damaged through processes such as tear- ing and shearing, they may reorganize through axonal re- sprouting, collateral sprouting, or developing supersensitiv- ities to neurotransmitters. When neuronal damage is complete, depending to a large degree on plasticity, the brain may sometimes be able to substitute other function- ing neurons or neuronal systems or rely on some redun- dancy to take over. The neuropsychologist should con- sider the following factors when evaluating influences on recovery:

1. Location and extent of damage 2. Duration of time since injury 3. Age (brain plasticity) 4. Premorbid intellectual level 5. Premorbid personality characteristics 6. Premorbid functional level 7. Medical health 8. Emotional health 9. Support system

10. Type of treatment

Behind most theories of neuropsychological recovery and rehabilitation lies the premise that if functions are not completely ablated, there is a chance that they can be restored through the ability of the brain to heal and adapt. To what degree functions may spontaneously re- cover versus needing aid via neuropsychological rehabil- itation techniques remains unresolved. There is no doubt that some spontaneous recovery can occur, but how much does targeted training also help to restore function? What if a function is completely lost? In this case, most neurobehavioral rehabilitation focuses on substitution, or the use of other behavioral strategies or devices to “work around” the problem or serve as an ex- ternal prosthetic device to help take the place of the lost function.

Adaptation and Recovery

D I A S C H I S I S

Diaschisis (first described by von Monakow, 1911) refers to an unmasking of function after temporary neuronal disruption. Monakow’s theory of diaschisis (derived from Greek schizein, meaning “to split”) described the loss of function caused by cerebral lesions in areas that are remote

from the lesion, but that are neuronally connected to it. A depression in neuronal functioning can occur due to neu- ronal shock, intercranial pressure, edema, metabolic changes, or any condition that reduces blood flow. This transience of function inhibition implies that the neu- ronal systems have not been permanently damaged. Therefore, diaschisis differs from restitution in that it is a passive process of uncovering working systems rather than an active process of repairing damaged systems. As the condition causing the dysfunction is removed, the behav- ioral function re-emerges.

Researchers have proposed that diaschisis represents an imbalance between excitatory and inhibitory mechanisms (Poppel & von Steinbuchel, 1992). An interesting demon- stration in animals (Poppel & Richards, 1974) provides an example. If the right occipital lobe is damaged, blindness in the left visual field results; however, if the left superior colliculus is destroyed, sight is restored. How is this so? Apparently, the colliculi of each hemisphere serve to in- hibit each other while each occipital lobe excites its ipsilat- eral colliculus. Thus, in the normal brain, all is balanced. However, when the right occipital lobe is damaged, the right superior colliculus, which no longer is receiving input from its occipital lobe, cannot moderate the left superior colliculus. In fact, the right becomes overinhibited by the relative overactivity of the left. If the inhibitory input of the left is removed, the right becomes functional again and some sight is restored. This complicated interplay between excitatory and inhibitory functions repeats itself over and over again with different functional systems of the brain. According to the theory of diaschisis, this imbalance be- tween excitation and inhibition resolves spontaneously.

B R A I N R E O R G A N I Z A T I O N

Reorganization of brain function after injury has much to do with the plasticity of the brain. Plasticity, the behav- ioral or neural ability to reorganize after brain injury, ap- pears to be one of the more important factors contribut- ing to the speed and level of final recovery. Most research on plasticity has tested animals, leaving the relation be- tween neuronal reorganization and behavioral organiza- tion unclear in humans. Immature nervous systems are much more plastic than those of adults; children show less behavioral effect and recover faster from brain injury. Some have suggested that recovery from aphasia in pre- pubescent children may be caused by the adaptability of the short-axon Golgi type II cells (Hirsch & Jacobson, 1974; Kertesz & Gold, 2003). Whereas the long axon neu- rons of the brain appear to be preprogrammed genetically

for certain functions, the more flexible Golgi type II cells appear to maintain flexibility until the onset of hormonal changes associated with puberty.

A x o n a l a n d C o l l a t e r a l S p r o u t i n g

One way in which the brain reorganizes is through the re- growth of neurons that have been only partially damaged. As mentioned in Chapter 4, unlike axons in the periph- eral nervous system, those in the central nervous system are not known to regenerate after total severing. However, axons that have been sheared may resprout, and collateral sprouting can occur from nearby intact neurons. Younger organisms appear to have the greatest potential for axonal regrowth. Theoretically, sprouting could replace the lost function. Although researchers have documented that ax- onal and collateral sprouting does occur, they do not yet know whether the “reconnections” rebuild the previous function. Excessive sprouting may even hinder behavioral functioning.

D e n e r v a t i o n S u p e r s e n s i t i v i t y

If an area of the brain is lesioned, any remaining neurons in that area may become hypersensitive to the neurotrans- mitters that act on them. The mechanism appears to act via a proliferation of postsynaptic receptor sites. This may result in a greater excitatory or inhibitory potential, de- pending on the type of neuron.

Overview of the Rehabilitation Process

Rehabilitation seeks to retrain and re-educate peo- ple with disabling injuries, to improve level of daily func- tioning. The philosophy of a rehabilitation center is very different from that of an acute care hospital. In the early stages after an injury or trauma, the hospital’s goal is to medically stabilize the patient. The hospital provides care for the patient and does not require the patient to be ac- tive in treatment. Rehabilitation centers expect the pa- tient and family to take a more active role in retraining, and to become partners in treatment planning. Rehabili- tation settings also use rehabilitation teams of specialists who work together in setting goals and implementing treatment. This section considers the various specialties in more detail. Traditionally, rehabilitation treatment was set up over a period of weeks to months on an inpatient unit, then followed periodically on an outpatient unit. With the advent of managed care, inpatient rehabilitation has

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390 PART THREE | Disorders of the Brain

shortened, outpatient rehabilitation has lengthened, and the role of the neuropsychologist has evolved to meet new demands for services. The final goal of rehabilitation is to reintegrate people back into the community at the high- est level of functioning possible.

Rehabilitation psychology, like neuropsychology, is a distinct specialty area within psychology. Practicing re- habilitation psychologists may treat people who have suffered non-neurologic problems such as burns, chronic pain, amputation, or blindness, as well as neu- rologic brain and spinal cord injuries and trauma. The focus is on applying psychological principles to recov- ery and adjustment to disability. More specifically, for the psychologist working with brain disorders, neu- ropsychological rehabilitation—or brain injury rehabil- itation, as it is more commonly known—represents the intersection of neuropsychology and rehabilitation. As such, the focus is on the process of recovery, adjust- ment, and rehabilitation of brain disorders. The condi- tions most often seen on brain injury units of rehabilitation hospitals include TBI caused by head injuries from ac- cidents and falls and cerebrovascular accidents (CVAs). Less often, rehabilitation units treat patients recovering from brain tumor or brain disease. With the increasing survival rate of heart attack victims, rehabilitation cen- ters are experiencing a greater influx of anoxic/hypoxic injuries resulting from loss of oxygen to the brain be- fore resuscitation.

Rehabilitation hospitals are specialty hospitals, which admit patients who fit a restricted group of diagnoses, such as TBI. Length of inpatient stay varies but has short- ened dramatically since the advent of managed care. As inpatient stays shortened, the focus of treatment evolved to include a greater emphasis on outpatient treatment within a person’s home, social, and occupational settings.

There are about 1600 TBI treatment programs in the United States (National Directory of Head Injury Ser- vices, 1992). A large proportion of neuropsychologists work in rehabilitation settings where they apply knowl- edge of brain–behavior relations and neuropsychological evaluation to the process of recovery and community reintegration. A challenge for neuropsychologists work- ing in these settings is to translate the patient’s level of functioning to appropriate treatments regarding daily life, since rehabilitation neuropsychologists spend the majority of their time treating the patient and family. Those involved in research constantly wrestle with the issue of ecologic validity—that is, with developing means of evaluation and treatment specific to common issues of rehabilitation such as driving, cooking, and return to work.

A D M I S S I O N T O R E H A B I L I T A T I O N P R O G R A M S

Although most neuropsychologists in rehabilitation work in specialty rehabilitation hospitals or treatment programs that focus primarily on treatment, others work in large, acute-care hospitals that have rehabilitation units and focus on early evaluation before transfer to a specialized facility. Brain injury specialists working in acute-care hos- pitals get the earliest view of a person’s functioning, per- haps while emerging from coma or recovering from brain surgery. They conduct the first evaluations of alertness, attention, sensorimotor, and cognitive skills over the course of the first few days and weeks of recovery before being transferred to a longer term rehabilitation hospital. The GCS (see earlier) is a good example of a measure used early in the process of recovery from head injury. Also, acute care rehabilitation neuropsychologists conduct pre- operative and postoperative assessments to document the level of change in cognitive functioning. These first neu- ropsychological evaluations can serve as a valuable baseline and predictor of future level of recovery. Therefore, neu- ropsychological evaluation becomes a valuable part of the prescreening process. Neuropsychologists design the pre- screening process for entry into a rehabilitation program to select patients whom they consider to have potential for treatment success and enough social support for postreha- bilitative care. In fact, admission to a rehabilitation program in itself suggests the absence of a medical life-threatening crisis and the potential for further recovery.

The rehabilitation hospital is the primary setting for learning the skills to return to a home setting. If rehabili- tation facilities did not exist, a large proportion of patients with brain-damage would go directly from the acute-care hospital to a skilled nursing facility. This is because most patients admitted to rehabilitation hospitals cannot care for themselves and may still be in a state of significant cognitive confusion, and their families do not yet under- stand the condition and the caretaking responsibilities. The rehabilitation hospital is an opportunity to take ad- vantage of the skills of others and to practice practical skills with professional supervision. Therefore, it is quite normal for patients to spend some time getting used to the functioning and philosophy of a rehabilitation unit. The “team” approach is also a new concept for most peo- ple accustomed to acute-care hospitals.

As patients move from the acute-care hospital to a re- habilitation program, they must make the transition from the hospital environment to the rehabilitation environ- ment. Rehabilitation patients need time to orient to the philosophy of empowerment that rehabilitation programs

advocate. The team teaches the means to maximize inde- pendence both for survivor and family caretaker. The goal for a patient is not to live in the rehabilitation hospital, but to get back to community life. Thus, patients in a re- habilitation hospital are not relegated to the traditional “sick” role or to a self-perception that earlier experiences in other acute-care medical units might have shaped.

A newly admitted patient must adapt to many factors in the rehabilitation environment, such as structured re- habilitation programs and new expectations. In addition, the sheer variety of patients of different ages recovering from myriad disorders can be overwhelming. Depending on the size of the facility and the extent of services, there are often separate units for orthopedic and brain injury patients, although sometimes the patients are mixed to- gether. Where brain injury is involved, there is usually a preponderance of young men in their teens and 20s re- covering from head injuries, gunshot wounds, or spinal cord injury. Elderly heart attack and stroke victims are also present, as well as tumor surgery patients. The pa- tients with brain injury can be expected to have signifi- cant cognitive compromise, often still involving confu- sion and PTA, as they arrive at a rehabilitation facility.

T h e R e h a b i l i t a t i o n T e a m : G o a l S e t t i n g , T r e a t m e n t , a n d E v a l u a t i o n

Once a patient is accepted for admission, the typical proto- col assigns him or her to a rehabilitation team. Teams usu- ally consist of specialists in rehabilitation nursing, social ser- vices, psychology/neuropsychology, physiatry, speech therapy, occupational therapy, physical therapy, and thera- peutic recreation. Treatment teams are often directed by the physiatrist, but may also be directed by psychologists or speech therapists. A “physiatrist” is a physician who special- izes in physical medicine and rehabilitation. Other related specialists may also become involved, including specialists in audiology, nutrition, orthotics, optometrics, and den- tistry. A variety of medical specialists are also available to pa- tients, such as internists, urologists, cardiologists, ophthal- mologists, and pediatricians. These teams generally follow a multidisciplinary or transdisciplinary approach in which each discipline works together in a coordinated fashion to achieve specific treatment goals. More and more patients and their families are becoming integral members of their own treatment teams. This approach includes them in all areas of treatment planning and evaluation of progress.

Initial treatment planning routinely puts patients on a schedule of daily “therapies”; for example, 1 hour each of physical therapy, occupational therapy, and speech therapy. As noted earlier, patients who cannot endure this daily

training are generally not considered ready for compre- hensive rehabilitation and may be sent to a continuing care center until they are more able. Beyond the minimum re- habilitation requirement, many rehabilitation hospitals provide additional rehabilitation hours, which consist of whatever the patient needs most. Next, we explore the in- dividual contributions of neuropsychology, physical ther- apy, occupational therapy, speech therapy, and recreational therapy in greater detail. Although we discuss these as sep- arate disciplines, as a treatment team works together over a period of time, a degree of “cross-training” often occurs. In some rehabilitation hospitals, the lines between disci- plines become totally blurred as each person is referred to as a “brain injury therapist,” although their individual con- tributions may be somewhat different.

N e u r o p s y c h o l o g y

Neuropsychologists are active in the rehabilitation process from admission to discharge. As mentioned earlier, neu- ropsychologists on rehabilitation units of acute-care or comprehensive hospitals may provide baseline evaluations that help determine an individual’s capability to partici- pate in a rehabilitation program. On a patient’s admission to a rehabilitation unit, a neuropsychologist may conduct a formal evaluation. He or she may also evaluate func- tional neuropsychological skills such as meal planning and preparation, ability to plan and self-administer medica- tion, driving, or work-related tasks. The recommenda- tions generated specifically aim at helping the treatment team form workable goals and objectives given an indi- vidual’s pattern of cognitive and emotional strengths and weaknesses. These evaluations necessarily focus on the functional level of the individual and serve as a baseline to document impairment. Notice that the focus of this evalu- ation is not only on the pattern of deficits exhibited but on the strengths that may aid the person in compensating for losses in other areas. During treatment planning, it is the neuropsychologist’s role to discuss specific recommen- dations with the team regarding potential remediation strategies. For example, would memory log training be likely to be successful? How will the person’s level of frus- tration tolerance impact his or her ability to participate in various therapies? How feasible is this training, given the cognitive demands of the patient’s home environment?

During the treatment process, the neuropsychologist continues to assess progress toward goals of daily living in conjunction with other team members. Neuropsychologists take part in individual patient counseling surrounding is- sues of loss and cognitive readjustment. Family education and counseling regarding the effects of brain damage on be- havior and strategies to cope with cognitive and behavioral

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392 PART THREE | Disorders of the Brain

deficits are also quite important to support the patient in return to the community. Finally, the neuropsychologist often coordinates compensatory strategies across settings from rehabilitation, home, community, work, and school. We discuss the neuropsychologist’s assessment and rehabili- tation methods in greater depth later in this chapter.

P h y s i c a l T h e r a p y

Physical therapists (PTs) focus on motor control with the aim of improving physical functioning to the highest de- gree possible. PTs evaluate each patient on admission to as- sess performance of functional activities related to strength, balance, coordination, physical endurance, and range of motion. The evaluation also considers the neurologic status of the motor systems. For example, PTs evaluate activities such as rolling, standing, sitting, transferring, using a wheelchair, and walking. PTs develop and individualize treatment programs for each patient according to specific strengths and weaknesses. For example, treatment programs for those with motor disability, weakness, or paralysis may consist of the following activities: mat activities, develop- mental sequences, balance training, hydro/pool therapy, strengthening exercises, transfer and wheelchair training, walking, and use of adaptive equipment. PTs accomplish goals by teaching such activities as wheelchair management and wheelchair propulsion. They instruct patients how to transfer from their wheelchairs, bed, toilet, and car. To walk again may be a major goal. PTs determine when a patient has sufficient strength, muscle control, and balance to at- tempt walking, and they assess the need for assistive devices such as walkers, canes, crutches, braces, or splints.

O c c u p a t i o n a l T h e r a p y

The term occupational therapy is confusing to some peo- ple who think that the training is specific to individuals who have an “occupation” and want to go back to work. This is not the only goal of occupational therapy. Occu- pational therapy is concerned with self-care activities such as grooming, bathing, dressing, and feeding, commonly called activities of daily living (ADLs). Occupational ther- apists (OTs) also focus on work activities ranging from home management, meal preparation, money manage- ment, household chores, and activities involved with oc- cupations as well as avocations (that is, hobbies).

The OT evaluates and treats the performance compo- nents that are necessary for functioning in ADLs, work, and leisure. The performance components include many aspects of human functioning. Of great importance to the OT is an assessment of sensory and perceptual-motor functioning. The use of muscles to bend, move, and perform purposive action (praxis) lies within the domain of occupational

therapy. Finally, issues of thinking, remembering, and prob- lem solving for daily life hold special importance for the OT.

Several ways exist to distinguish the difference in spe- cialization between PT and OT. Both are concerned with muscle strength and coordination. However, in many hos- pitals, PTs work primarily on the lower extremities (all muscles below the waist), and OTs work primarily on the upper extremities (everything above the waist). In those hospitals that do not distinguish between upper and lower extremity strength, the difference between PTs and OTs is usually broadly defined by strength (PT) and function (OT). In regard to the latter definition, for example, a stroke survivor may be able to walk with strength and en- durance. That same patient, however, may not be able to judge distances, determine left from right, or near from far. As a consequence, walking per se adds little to the pa- tient’s independence, because walking is not safe. The OT takes on the job of applying strength gained from PT to using that strength within everyday types of activities. For example, an occupational therapy session may focus on teaching the patient to discriminate between things that are close and things that are far away (as in depth perception training) or things seen to the right versus things seen to the left (as in left neglect training). This therapy is referred to as perceptual retraining, or perceptual remediation.

Another area of occupational therapy concerns among brain injury survivors is apraxia. Stroke victims often show this lack of purposive action. In practical terms, the OT will refer to, for instance, “dressing apraxia,” indicating that the patient cannot dress on command, or “on purpose.” This form differs somewhat from stroke patients who fail to dress one side of their bodies because of neglect. If you say to a stroke victim, “Let’s go outside,” she may automat- ically put on the sweater that is nearby. However, if you say, “Put on your sweater so we can go outside,” she may either simply go outside without regard for the sweater or may sit there and fumble with the sweater because she can no longer put it on. OTs try to use activities to meet goals; thus, in this case, the actions chosen will have the purpose or function of overcoming dressing apraxia.

S p e e c h T h e r a p y

Speech therapists provide therapy for patients experienc- ing a range of communication difficulties. These may in- clude mechanical speech difficulties involving speech pro- duction, expressive language, hearing and understanding speech, reading, writing, and the social use of language. Speech therapists specifically trace communication prob- lems from the basic level of auditory acuity and speech production to higher level skills of communication and linguistic integration.

The ultimate goal is to design interventions to aid in speech production and understanding and to facilitate communication. This may be accomplished through prac- tice and retraining or with prosthetics aimed at assisting communication through artificial means.

The speech problems most commonly treated deal with articulatory difficulties, or dysarthrias, caused by improper muscle control of tongue, lips, or cheeks for pronouncing words. If either the left or right hemisphere is damaged, people with damage to the section of the motor strip controlling speech production will have con- tralateral impairment. Thus, half of the lips, cheeks, and tongue muscles used to articulate words may be weak- ened. Although it is not caused by a similar mechanism, if you have ever experienced slurred speech after a visit to a dentist who used Novocain, you will readily sympathize with the problems stroke survivors face in articulating speech. In the extreme case, such speech may sound gar- bled or unintelligible.

Neuropsychologists often design higher order language and communicative evaluations to assess the presence and degree of aphasia, alexia, or agraphia. Speech therapists may specialize in evaluations to categorize aphasias (such as expressive, receptive, transcortical, and global), and to understand the nature of reading and writing difficulties such as alexia and agraphia. At this level the interest is in cognitive-linguistic integration.

T h e r a p e u t i c R e c r e a t i o n

Therapeutic recreation emphasizes the importance of recreational and leisure time activities. These activities serve a purpose beyond being just fun. For instance, pa- tients are encouraged to use skills learned in physical or occupational therapy in completing craft projects. This helps in the “transfer” of learning. Therapeutic recreation also allows patients to begin socializing with each other in a structured but less formal atmosphere than that afforded in other therapy settings.

At some facilities, the therapeutic recreational specialist takes patients on community outings. Community out- ings allow patients to practice their skills in real-life set- tings, among nonhospital people. This can help patients on the first important step in their transition from the hos- pital setting back to their home, friends, and family. The skills addressed in community outings may include:

1. Mobility: ramps, elevators, curbs, doorways, obstacles, transfers, and so on

2. Daily living skills: money management, safety aware- ness, personal energy pacing, nutritional awareness, and problem solving

E V A L U A T I O N O F G O A L S A N D D I S C H A R G E P L A N N I N G

The rehabilitation team begins planning discharge from the hospital and outpatient rehabilitation from day 1. This idea sometimes confuses patients and families, who believe they cannot make discharge plans until they ab- solutely know the final functioning level of the brain in- jury survivor. It is often difficult to realize that no one can guarantee the exact level of functioning a person will at- tain by the end of a rehabilitation program. However, re- habilitation teams are in the business of estimating rea- sonable goals and can give a solid ballpark estimate of function level. Once this expected level of functioning is determined, then everyone can make appropriate plans for what will happen after the hospital stay.

Many brain injury survivors living at home before the injury choose to consider returning home after rehabili- tation. As they contemplate this option, everyone must consider the feasibility of living at home safely and hap- pily. The treatment team, patient, and family must con- sider the functional requirements of a person’s current living situation and his or her resources to cope with that environment.

Increasingly, rehabilitation programs are incorporating shorter inpatient stays and longer outpatient treatment into their programs. Some impetus for this, of course, is due to the financial pressures of managed care. However, there is also a move to integrate people into the commu- nity as soon as possible. We return to a discussion of com- munity integration programs, with the example of job coaching, later in this chapter. Next, we turn to an in- depth look at the methods that neuropsychologists use in rehabilitation settings.

In summary, the philosophy of treatment in a rehabili- tation hospital requires that patients and families be ac- tive in rehabilitation. They are “trained” by multidiscipli- nary teams, which typically consist of specialists in areas of neuropsychology, as well as physical therapy, occupa- tional therapy, speech therapy, and therapeutic recreation. Each area contributes a unique expertise related to brain- behavior functioning. PTs focus on the motor system, OTs are concerned with applying motor functioning to daily life tasks and with other functional tasks of daily liv- ing, speech therapists evaluate and facilitate improvement in all aspects of communication, and therapeutic recre- ation specialists focus on leisure activities and on practic- ing skills in the community. Neuropsychologists provide initial and ongoing evaluation, as well as treatment for cognition, mood, and behavior disorders. The training done by each team member necessarily focuses on parallel

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tracks: The first is to work directly with the patient to try to restore function or compensate for lost function, and the second is to work with caregivers and family to ensure that treatment will continue after rehabilitation ends. During outpatient treatment, where community reentry is the focus, the focus of the team turns to providing bridges to employment or other vocational endeavors. The next sec- tions take an in-depth look at the role of neuropsycholo- gists in rehabilitation settings—first the role in assess- ment, then the role in treatment.

T R E A T M E N T P L A N N I N G

Successful treatment rests on appropriate evaluation. As- sessments need to answer questions related to the possi- bilities of success in treatment and in returning to the “real world.” What is the pattern of strengths and weak- nesses according to the functional areas of verbal process- ing, visuospatial processing, and so forth? Will the person be able to absorb the purpose of therapy and remember instructions? Does the patient appreciate the need for therapy? When deficits appear, what exactly is the nature of the problem? For example, in language, are there more expressive or receptive difficulties? How severe is the prob- lem? Are there residual abilities that indicate the deficit can be strengthened through practice? Are there other areas of strength that can be trained to compensate or sub- stitute for the problem? What is the likelihood that this person will be able to return home, return to work, return to independent functioning? These questions, in addition to describing patterns of neuropsychological functioning, definitely require predictions. This forces the neuropsy- chologist to consider not only current level of function- ing but also the accumulated research and clinical knowl- edge regarding the probability and time course of recovery for the particular problem. Recovery depends on numer- ous factors: pattern of impairment, treatment program, degree of spontaneous recovery, physical and emotional state of the person, family support, and several other fac- tors. Prediction becomes quite a challenging task.

A S S E S S M E N T O F E V E R Y D A Y A C T I V I T I E S

Real-world tasks such as driving, cooking, balancing a checkbook, taking medication, or navigating an unfamil- iar route require numerous cognitive components. Neu- ropsychological assessment often attempts to isolate the effects of functional areas such as divided attention, re- ceptive language, or memory encoding. Although this is helpful in understanding the pattern of neuropsychologi- cal strengths and weaknesses, the “whole” of a process

such as preparing a meal may be more than the sum of its generic cognitive “parts.” Cooking certainly requires sus- tained attention, the ability to read and follow recipes, the ability to organize preparation of different dishes so they are finished at the same time, the necessity to moni- tor time so the cake will not burn, and of course, basic vi- suospatial abilities. A problem in any one of these areas may lead to a dining disaster. But does the presence of basic skills ensure competence in cooking? A neuropsy- chological assessment that measures attention, reading, organization, and time monitoring may reveal deficits that pose problems for independent meal preparation. But if no problems are found, does this mean the person can prepare meals independently? Not necessarily. First of all, tests of general functional areas such as attention and memory may be too nonspecific to shed light on the exact neuropsychological requirements that make up successful meal preparation. Does a general test of organizational ability adequately predict organization of meals? This is a question of ecologic validity. Second, even if we can iden- tify the basic cognitive components involved, do the de- mands of combining and integrating these components into fluid action somehow change the nature of the task?

To deal with these issues, neuropsychologists who de- velop “ecologically valid” measures can take one of two approaches, and may take both. First, they may attempt a task analysis. This involves identifying all the relevant spe- cific neuropsychological requirements of the task. Then they must devise tasks that measure components. The idea is that if any deficits appear there is a strong likelihood that the person cannot perform the task. The advantage of this method is that it may use paper-and-pencil mea- sures and small, portable tasks to simulate the cognitive components. These tests can also be standardized using large populations. If the patient performs specific aspects of the test poorly, that pinpoints the deficits, which can be targeted for rehabilitation. The disadvantage is that this analytic approach may not totally capture the require- ments of the whole task. The second method is to actu- ally do the task or closely simulate it. Many rehabilitation hospitals use driving simulators to test driving skills. They may also build kitchens or apartments to directly test the functional skills of meal preparation or laundry, for exam- ple. If tasks can be recreated in a controlled environment, then the huge advantage is that they come closest to mim- icking real life. Then performance on the task as an inte- grated whole can be assessed. Of course, the primary dis- advantage is the initial expense of installing an entire working kitchen or a driving simulator. In addition, un- less the key cognitive components of the task can be teased apart, doing poorly on a meal preparation task, for

example, may not yield much information on how to in- tervene in training. Finally, because each kitchen is differ- ent, and the components of meal preparation may differ on any given day, success does not automatically translate into success at home.

Treatment Methods for Neuropsychological Rehabilitation

Neuropsychologists use two primary approaches to brain injury rehabilitation that hearken back to our ear- lier discussion of restitution versus substitution of func- tioning: (1) approaches that stress retraining of an im- paired skill, such as attention or memory; and (2) those that focus on searching for adaptations to the person’s en- vironment in the context in which the person will use them (Diller, 1994).

The first approach is cognitive remediation, or cogni- tive retraining. In this case, for example, computers may be used to provide practice exercises to attempt to strengthen memory or attention. In many instances, the underlying hope is that the brain may be able to rebuild axonal connections through retraining; that is, restitu- tion. Approaches to cognitive remediation, however, do not necessitate proving structural changes to achieve func- tional success. For those functions that appear lost, cogni- tive remediation may focus on finding adaptive means, or “work-arounds,” for lost memory or lost expressive speech, for example. In other words, the idea is to find compensatory strategies for the lost process. Cognitive re- mediation approaches are usually practiced in a labora- tory setting. They vary a great deal in the degree to which they seek to simulate real-life situations and in which sit- uations they might generalize.

Cognitive retraining rests on theories of learning and pedagogy. Learning or relearning a skill or behavior is a building process that depends on an adequate base for es- tablishing higher order skills. If the aim is restitution, some neuronal functioning must be left. Whyte (1986) provides a useful hierarchical conceptualization for train- ing. Basic mental activities such as focused attention or au- ditory processing represent the first level of cognitive oper- ations. Cognitive processes, the next step, are combinations of cognitive operations. Flexible problem solving and word fluency are two examples. A skill such as performing men- tal arithmetic or writing requires coordination of cognitive processes. Even more complex are metaskills that require the ability to sequence skills together, or to apply old skills

to new situations. Finally, global functions such as work- ing, driving, or managing a household are the most com- plex and integrative activities that depend on the integrity of the lower functions. The idea is to train in sequence from lower to higher order operations.

Context-driven approaches (Diller, 1994) emphasize treatments that either involve actually training the person in his or her home or work environment or are specifically tailored to the person’s future needs outside the hospital, even though he or she may practice them in the rehabilita- tion hospital. This is a relatively newer area of rehabilita- tion than is cognitive retraining. After it became evident that many people with brain injury fail to generalize or translate what they have learned in the laboratory environ- ment to their own home or work environment, neuropsy- chologists recognized the need to train specific skills rele- vant to an individual’s environment. Some of the approaches that train “in place” include the use of job coaches and supported employment, driver training, fam- ily training to aid in the home, or computers to assist sched- uling or memory. Patients can also practice additional rele- vant skills for daily life in group therapy situations, in which groups of individuals with similar impairments may concentrate on social, orientation, or organizational skills (to name a few). Although, in some cases, the planners of training in the context where the skills will be used may hope to restore function, usually the aim is compensatory.

Review of various treatment approaches makes ap- parent that practical, “ecologically valid,” or contextual approaches to rehabilitation are increasingly the focus of many treatment programs. However, currently, there re- mains little outcome research to demonstrate their effec- tiveness. The largest number of studies has focused on such cognitive mediation efforts as documenting im- provements in deficits such as attention or memory (Diller, 1994). Also, most approaches to rehabilitation combine deficit retraining and contextual methods in a more eclectic model. However, unless the neuropsycholo- gist takes a conceptual approach toward the rehabilitation program, a combination of methods may be criticized for its resemblance to a shotgun approach to treatment (throw everything at the problem and see if something hits).

P S Y C H O T H E R A P Y I N R E H A B I L I T A T I O N

Neuropsychological rehabilitation is concerned not only with rehabilitating cognition but also with personality, emotion, and awareness. Of course, the brain is also the mediator of these functions. Altered self-awareness and personality after brain injury may, in fact, represent some of the most complicated and higher order brain processes

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396 PART THREE | Disorders of the Brain

that a neuropsychologist and rehabilitation team at- tempts to treat (for a case discussion, see Neuropsychol- ogy in Action 13.4). Psychotherapy can aid by discussing frustrations in progress and providing motivational strategies. But more importantly, and more profoundly, individuals with brain damage who have suffered more than mild impairment often report they no longer feel “normal” and have to go through a readjustment process to adapt to their new level of functioning. Those who have suffered brain injuries report that their social life has declined (Elsass & Kinsella, 1987) and rank loneli- ness as their most frequent complaint (Thomsen, 1974). Relatives and significant others often describe a “person- ality change” (Jennett & Teasdale, 1981). Poor social in- teraction is evident in ratings of close others and direct behavioral observations (Newton & Johnson, 1985). These losses are perhaps the most tragic and far-reaching aspects of brain injury.

Frontal lobe damage, as we discussed earlier in this book, is a common result of moderate to severe head in-

jury due to bony skull projections and shearing. Frontal lobe damage is typically suspect when certain qualities of psychosocial functioning are observed after injury. Among the difficulties co-occurring with frontal lobe injury are impulsivity, disinhibition, lack of initiation, rigidity, loss of abstract attitude, poor social judgment, and loss of per- sonal and social awareness (Lezak, Howieson, & Loring, 2004). Prigatano (1992; also see Prigatano, 1999) argues that self-awareness requires the highest integration of “thought” and “feeling” areas of the brain, combining in- puts from sensorimotor, limbic, and paralimbic areas. The common perception that people with CHIs have an “ego- centric” or “unempathic” attitude is usually attributed to various manifestations of these and frontal lobe difficul- ties. The specific inability to see a situation from another’s viewpoint may be one of the cognitive dysfunctions un- derlying apparent egocentric or unempathic behavior. This skill, labeled cognitive perspective taking, varies among moderately to severely injured people (Spiers, Pouk, & Santoro, 1994; Santoro & Spiers, 1994). The

N e u r o p s y c h o l o g y i n A c t i o n 1 3 . 4

I t I s M o r e T h a n a B l a c k B o x

Cecil R. Reynolds Ph.D., Department of Educational Psychology, Texas A&M University, College Station, TX

A popular means of treating disorders of learning and behavior in children is behav- ioral therapy and derivative approaches that capitalize on changing behavior by imple- menting specific reinforcement programs. Clinically, this approach derived from work by the Russian physiologist Ivan Pavlov on classical conditioning (known sometimes as Pavlovian conditioning) and the American psychologist B. F. Skinner, who developed theories of operant conditioning (Skinnerian conditioning). Pavlov is best known for teaching, quite by accident, a dog to salivate on hearing the sound of a bell. Skinner taught rats to press levers for food and pigeons to peck keys to be fed. Early clini- cians such as Joseph Wolpe were able to take these phenomena and translate them into methods to cause humans to alter their behavior by altering the so-called reinforce- ment systems they believe control a specific person’s behavior.

As behavioral approaches to treating disorders of learning and behavior grew in

schools and clinics around the world, peak- ing in the late 1970s, understanding brain functioning faded into the background. Skinner and other radical proponents of behavior therapies argued that what went on in the brain was irrelevant. Only input and output were important, and people need not understand the brain’s function further; it was treated as a black box, a euphemism for a space in which some transformation may occur through processes not understood but also that are irrelevant to the understanding of behavior and learning. As late as 1977, I had a professor in graduate school, teaching a course in learning, make the pronounce- ment in class that “the brain has nothing to do with learning; learning is all accomplished through change or continuance of reinforce- ment paradigms.” Such views were not uncommon.

Behavioral approaches to the manage- ment and alteration of behavior in children with developmental disorders are often, but far from always, effective. And as it turns out,

brain systems are crucial in mediating reinforcement schedules and learning. Let me provide an example. At age 11, Deanna attended a program for gifted and talented children at her local public school, with a measured IQ in excess of 130. She played piano and had won a trophy as star player of her soccer team a year earlier. In spring of that year, Deanna was riding in the passen- ger seat of her dad’s car when a drunk driver ran a stop sign, striking the car at Deanna’s door. She suffered many injuries, including a broken pelvic bone and numerous cuts and bruises. Most devastating, however, was her head injury. Deanna had suffered a massive right frontal lobe injury, producing a large subdural hematoma that was evacuated in neurosurgery. Her cerebral bleeding ex- tended through the right superior parietal areas, and much microscopic shearing and tearing of neurons occurred throughout her brain. She spent 11 days in a deep coma, and her parents were warned that she might not even recognize them if she came out of

CHAPTER 13 | Traumatic Head Injury and Rehabilitation 397

general ability to recognize and appreciate one’s own func- tional and cognitive changes also varies over individuals and time since injury. However, those who have greater awareness of their dysfunction typically show higher lev- els of emotional distress (Nockleby & Deaton, 1987).

Psychotherapy in the rehabilitation setting often targets these neuropsychology-based issues of self-awareness, ego- centricity, and empathy. Psychotherapy can be useful not only to aid coping and adjustment but also for practical rea-

sons. Difficulty in psychosocial functioning and poor self- awareness is one of the prime reasons for poor vocational outcomes. If therapy targeting affective issues is provided, another 20% to 30% of patients may become productive workers (Prigatano, 1992). Beh-Yishay and Prigatano (1990) found that three factors largely predicted vocational outcome: involvement with others, ability to regulate affect, and acceptance of cognitive limitations. All three of these factors are mainly influenced by psychotherapy.

Summary Neuropsychologists play an important role in evaluating the cognitive profile of patients who have suffered from a TBI and are actively involved in the rehabilitation for these conditions. Neuropsychologists are most interested in how such conditions result in specific neuropsychological deficits and disabilities in adaptive behaviors. Research in this area not only improves the patient’s care but also provides new knowledge on the normal functioning brain. Rehabilitation is clearly becoming one of the major areas of practice for neuropsy- chology. The rehabilitation process is complex and depends on many mechanisms, including biological,

the coma at all. Deanna did revive and had a miraculous recovery.

After 6 months in a rehabilitation hospi- tal, Deanna returned to school. Over the next 2 years, additional cognitive recovery was evident. Her IQ, measured in the 60s (men- tally deficient) 6 months after injury, gradu- ally increased to nearly 100 (average), and her academic skills in reading, writing, and arithmetic came to grade level. A far cry from their prior, or premorbid, status, but all in all, a positive outcome. However, this once popular, socially adept young girl was now ostracized by her peers due to her now obnoxious behavioral patterns.

She had few social skills and just did not appear to know how to interact positively with others. She was extremely impulsive, as she acted most often without thought, was constantly reaching out to touch whomever she talked to, and had no clear sense of personal space. Her social judgment was severely impaired, and she often blurted inappropriate and embarrassing comments to others. Deanna came to my attention after a consult request from the University Clinic, where a doctoral student had been working with the family for more than a year to de- velop a behavioral treatment plan to change these many socially inappropriate behaviors. Such problems are common among patients

of all ages with frontal lobe damage, espe- cially prefrontal and orbitomedial damage, all of which were present in this case. The early images of her brain injury, taken via magnetic resonance imaging (MRI) in the first few weeks and months after her injury, docu- mented these lesions well. However, Deanna appeared resistant to behavioral intervention.

After a careful review of her case, another MRI scan was requested and obtained, now more than 30 months after injury. The new images showed an injury that had not ap- peared before. Deanna had a lesion and scar tissue on the posterior portion of her hip- pocampus just above the fourth ventricle of the brain. The importance of such a lesion may not be immediately obvious; however, the hippocampus is a component of the limbic system and is crucial to memory functions. These brain systems, the fron- tolimbic system and particularly the hip- pocampus, are significantly involved in learning reinforcement systems. Individuals with posterior hippocampal damage are especially resistant to reinforcement sched- ules that are anything less than a one-to-one ratio reinforcement schedule.

The mediation systems that allow rein- forcement to be recalled and to mediate learning had been irreparably damaged in Deanna. Despite the protestations of the

devotees of Skinnerian conditioning, the brain does matter! Behavior therapies can be effective in treating TBI and developmentally disordered children with behavior problems, even with frontal lobe systems that are impaired. However, once limbic system and specifically hippocampal functions are also damaged, such interventions fail.

With this knowledge and evidence, Deanna’s insurance carrier was persuaded to fund a different, more intensive interven- tion. An in vivo therapeutic approach was devised in which a therapist went with Deanna to local shopping malls for several hours several times a week. Deanna’s behav- ior was constantly monitored and redirected in this setting by a therapist, who also de- vised a set of verbal cues and self-talk strategies. In doing so, we took advantage of her stronger verbal skills, given that most of her injuries were in the right hemisphere, as Deanna learned social skills in real-life settings, in vivo, or “on the job,” so to speak. Being a teenager is a tough job; being a teenager with frontal lobe injury who does not respond to changes in the reward-and- punishment systems of life is nearly impossi- ble. Deanna did graduate from high school, a year late, and is now employed in a clerical assistant position at a university library. She still hopes to attend college.

398 PART THREE | Disorders of the Brain

Tensile strength Retrograde degeneration Anterograde degeneration Penetrating head injury Closed head injury Acceleration Deceleration Impact injury

Countercoup injury Glasgow Coma Scale

(GCS) Coma Edema Intracranial pressure (ICP) Brain herniation Transtentorial herniation

Subdural hematoma Extradural hematoma Epidural hematoma Post-traumatic amnesia

(PTA) Retrograde amnesia Anterograde amnesia Substitution

Diaschisis Restitution Plasticity Physical therapist Occupational therapy Speech therapist Dysarthria Therapeutic recreation

personal, and environmental factors. The assessment and evaluative methods used necessarily focus on functional or “real-life” tasks of daily living. Treatment requires that patients and families be active in reha- bilitation and work as “trainees” of the team. In rehabilitation, assessment is an ongoing process, monitor- ing the progress of treatment and aiding decision making regarding the effectiveness of interventions and the prognosis for long-term outcome.

The methods of treatment currently being developed by neuropsychologists provide exciting and cre- ative ways to help ameliorate dysfunction of individuals with brain impairments. With specialized knowledge of the brain and behavior, as well as technical advances, neuropsychologists are uniquely positioned to guide individuals and their families to their highest potential for recovery and functioning. Chapters 14, 15, and 16 focus on the relation between diffuse neuropsychological deficits and dementing conditions such as encountered in Alzheimer’s disease and disorders of consciousness.

C r i t i c a l T h i n k i n g Q u e s t i o n s

Can a head injury change a person’s life? What is the potential for the human brain to adapt and recover after brain injury? What are the challenges for rehabilitation in the twenty-first century?

K e y Te r m s

We b C o n n e c t i o n s

http://www.tbilaw.com Brain Injury Information Page—provides information about brain injury, concussion, and head injury.

http://www.neuropsychologycentral.com Neuropsychology Central—a great site that keeps you up to date on the latest in neuropsychological links and resources. Internal search engine allows you to determine what topic you would like to focus on and provides you with detailed summaries of each link that has been found. Provides links to neuropsychologi- cal assessment, forensics, treatment, and other related areas.

http://www.tbims.org Traumatic Brain Injury (TBI) Model Systems—learn about TBI’s National Database, the diagnosis of TBI, the Center for Outcome Measures, and more.

http://www.healthpsych.com Health Psychology and Rehabilitation Web Site—comprehensive site that provides information on health and rehabilitation psychology.

http://www.neuro.pmr.vcu.edu National Resource Center for Traumatic Brain Injury (TBI)—guide for TBI survivors; tips on rehabilitation and on living and working productively with TBI.

http://www.tbilaw.com

http://www.neuropsychologycentral.com

http://www.tbims.org

http://www.healthpsych.com

http://www.neuro.pmr.vcu.edu

Chapter 14

N O R M A L A G I N G A N D D E M E N T I A : A L Z H E I M E R ’ S D I S E A S E

In one’s youth every person and every event appear to be unique. With age one becomes much more aware that similar events recur. Later on one is less often delighted or surprised, but also less disappointed than in earlier years.

—Albert Einstein

Normal Aging Mild Cognitive Impairment Defining Dementia Alzheimer’s Disease Treatment

Neuropsychology in Action

14.1 The Discovery of Alzheimer’s Disease 14.2 Differentiating between Symptoms of Alzheimer’s

Disease and Normal Aging

Normal Aging

Defining “normal aging” is a challenge. Stereotypes and concerns abound as people face getting older. So- cially, we may fear becoming isolated with adjustment to

retirement and death of friends or a spouse. Physically, age brings the threat of increased ailments and chronic illness. Cognitively, the possibility of memory problems, mental slowing, and dementia looms. These concerns are often amplified by myths of aging, painting people older

400 PART THREE | Disorders of the Brain

Overview Elderly adults are the fastest growing segment of the U.S. population. In 1900, 4% of the population was older than 65. As of the 2000 census, this number has mushroomed to 12.4%, or 34.9 million people. In the year 2030, estimates suggest 20% of the population will be older than 65, constituting approximately 70 million people (Administration on Aging, 2000). The 85-and-older group is expected to double its current size. This trend toward an aging population is found throughout Western industrialized countries. These numbers reflect increased life expectancy and medical advances. However, diseases of aging become a great concern.

Tremendous research effort is focused on understanding the neurologic conditions that target older people. Among these conditions are a group of disorders, collectively known as the dementias, that cause global declines in cognitive and behavioral functioning. They have no one cause, and most causative factors are still not fully understood. Moreover, many dementias have no known cure. Dementia is often progres- sive, eventually affecting numerous higher mental facilities. It is often considered a “thief of the mind,” first robbing one aspect of cognition such as memory, communication ability, or visuospatial skills, but then returning to steal other aspects of mental functioning.

With a top-heavy population of aging baby boomers, the problem of identifying dementia and providing medical and psychological services to patients and families is becoming increasingly important. About 10% of Americans older than 65 live in specialized settings (such as residential care facilities or assisted living), and more than 1 million live in nursing homes. Older people account for more than 40% of hospitalization days in acute-care hospitals. They buy 25% of all prescription drugs and use 30% of the total health budget. Clinical neuropsychologists contribute valuable assessment skills to distinguish normal aging from demen- tia. They also play an important role in health care decision making, helping match level of care to an older patient’s actual needs.

This chapter examines the differences among normal aging, mild cognitive impairment (MCI), and dementia, and addresses questions regarding the aging brain and neuropsychological functioning. For example, is there an inevitable cognitive decline with age? This question can be addressed by considering the neuropsychological profiles of both healthy older adults and those with dementia. We examine demen- tias in both this and the next chapter. This chapter presents an in-depth evaluation of the most common de- mentia syndrome: Alzheimer’s disease (AD). This cortical dementia is examined from a neuropathologic, neu- ropsychological, and behavioral perspective. Chapter 15 presents the subcortical dementias of Parkinson’s disease, Huntington’s disease, and Creutzfeldt–Jakob disease.

K e e p i n M i n d

Is dementia inevitable? How does healthy “normal” aging differ from dementia?

Are dementia and Alzheimer’s disease synonymous?

Does Alzheimer’s disease selectively affect “memory” structures of the brain?

Why is Alzheimer’s disease so difficult to diagnose?

than 65 as unattractive, dull, sickly, and unproductive (Dychtwald & Flower, 1989). Stereotypes of aging, how- ever, can be shattered by examples of highly functioning people. From rock performers such as Tina Turner to renowned scientists like Ruth Patrick (Figure 14.1), we witness the great range of physical, social, and mental ability of people older than 65 and ask, What can we learn from those who age well?

One of the challenges for brain scientists is that the range of cognitive variation for people older than 65 is wide compared with people in their 20s, 30s, 40s, and 50s. Some of this increased variation is due to the inci- dence of brain diseases of aging, such as the dementias or strokes, and some of this may be due to “age-related” de- clines in cognition that affect people differentially as they age. A large part of what clinical neuropsychologists are asked to do is to aid in determining the difference between normal cognitive declines due to the aging brain and brain diseases. Inherent in this is whether problems such as forgetting of names can be considered “normal age- related” or as the harbinger of AD. Scientists have won- dered whether age-related declines in cognition will inevitably lead to dementia (that is, is normal aging and de- mentia on a continuum?) or whether there is a qualitative difference between a disease state and the aging brain. This issue is explored within this chapter and in Chapter 15.

This section reviews both cognitive and brain changes associated with normal aging in humans. By considering both cross-sectional and longitudinal studies, as well as studies that compare normal aging with dementia, a pic- ture of normal aging, cognition, and the brain emerges.

C O G N I T I V E C H A N G E S A S S O C I A T E D W I T H A G I N G

Why is there such a range of functioning in people older than 65? Does everyone lose some cognitive functions even if they do not have degenerative brain disease? Is cog- nitive decline uniform, or are certain areas more likely to decline than others? What is the trajectory of cognitive decline? Finally, are there protective factors against cogni- tive decline and disease?

Numerous examples exist of people who stay active and working in their fields well past the age of retirement. Whether a scientist, a musician, or a mechanic, these peo- ple have developed an expertise and an accumulated body of knowledge related to their work. In fact, all people are likely to develop areas of expertise over their lifetimes re- lated to work, hobbies, or talents. This crystallized intel- ligence consists of stored knowledge and habitual ways of acting or solving problems built up over a lifetime. By re- hearsal, practice, and use, certain domains of knowledge become strengthened and are more easily accessible and perhaps less subject to decay. Verbal scales of intelligence tests typically measure general crystallized intelligence not related to a specific work domain. They measure factual knowledge, such as vocabulary definitions, or general information learned in school. Crystallized intelligence represents an accumulation of acquired skills and general

CHAPTER 14 | Normal Aging and Dementia: Alzheimer’s Disease 401

Figure 14.1 (a) Tina Turner, one of the world’s most success- ful female rock artist, performs at age 65. (b) Dr. Ruth Patrick, one of the world’s leading biologists, is still active at age 94. ([a] © Heinz Award photo/Lynn Keith; [b] REUTERS/Alexandra Beier.)

information and is more related to formal education or di- verse social experiences. Research using the Wechsler Adult Intelligence Scales (WAIS-R) suggests that levels of crys- tallized intelligence show only slight changes as we age (Kaufman, Reynolds, & McLean, 1989). It has also been theorized that higher levels of crystallized intelligence or general knowledge may provide a protective factor, or “functional reserve” (in this case, a “cognitive reserve”), against dementia that allows the brain to compensate in the presence of declines presented by aging or disease.

Two series of studies lend credence to the idea that a protective cognitive reserve may start early in life. The first of these is provided by the longitudinal study of aging and AD called the Nun Study. David Snowdon of the University of Kentucky has followed 678 Roman Catholic sisters who agreed to regular cognitive and medical assess- ments and brain donation at death. Snowdon and his col- leagues seek to shed light on the factors that lead to in- creased longevity, as well as on the determinants of AD and other brain disorders such as stroke. What is unique about this research is the availability of records from young adulthood and throughout the time each nun resided in the convent. In one study, Snowdon and col- leagues (1999) examined the linguistic complexity of au- tobiographies written as the nuns entered the convent be- tween ages 18 and 32. Women who scored lower on “idea density” (that is, the number of different ideas discussed) early in life also showed lower cognitive functioning after age 75. Also, autopsies of a small sample of nuns indi- cated that the women who had brain markers of AD showed lower “idea complexity” as young women than those who did not have brain pathology.

Snowdon’s studies used “idea density” as a proxy for intelligence, but researchers from Scotland (Whalley, Starr, Athawes, Hunter, Pattie, & Deary, 2000) were able to actually assess the relation between a standardized gen- eral intelligence test, administered at age 11, and signs of dementia more than 50 years later. Children who had higher mental ability were less likely to have dementia when they were located again at age 72. Interestingly, there was no relation between mental ability and decline for those who had been diagnosed with an early-onset (be- fore age 65) dementia. Early-onset dementias, as discussed later, may be caused by disease processes that are different than late-life cognitive decline.

Both the Nun studies and the Scottish studies show a correlational link between early intelligence and the health of the aging brain. One possible explanation is that a “cog- nitive reserve” serves as a reservoir to resist the effects of aging. If this is so, it is not yet known whether cognitive re- serve is, for example, a reflection of having more neurons and glial cells in crucial areas or the result of wider or more

efficient semantic networks. In addition, the positive corre- lation between intelligence and the aging brain may be re- lated to other factors associated with longevity. Those with higher intelligence may be more likely to seek and follow health information, have higher paying jobs, adhere to a better diet, and have better access to health care.

Even people who show little signs of cognitive decline, however, are likely to notice changes in fluid intelligence. Areas of fluid intelligence involve novel reasoning and the efficiency of solving new problems or responding to ab- stract ideas. Fluid intelligence has also been conceptualized as a measure of adaptability. Fluid intelligence is most directly related to the influences of changing biological fac- tors and is relatively unaffected by higher levels of experi- ence or education. The most reliable declines in cognition show up in three areas of intellectual activity, all of which are considered fluid markers of intelligence: (1) processing speed, (2) abstract and complex new problem solving, and (3) memory and new learning.

Tests of fluid intelligence (for example, Wechsler’s Digit Symbol and Block Design) generally require both novel processing and the ability to complete a task quickly. Studies of aging suggest that performance on tests of this type declines across the life span (Salthouse, 1991). Behavioral slowing also occurs and may partly contribute to poorer performance on a number of tests of fluid intel- ligence where speed is a factor, but age-related decline is still observed on novel problem-solving tasks even in the absence of speed demands.

Studies of aging suggest that older people are more likely to have more difficulties in many aspects of memory. Early research in aging and memory suggested that the main problem for older people was information retrieval. Poorer performance occurs with free recall, compared with recog- nition, with less contextualized information, and when more effort is involved. However, new learning may also be difficult because of problems in encoding, particularly with intentional encoding. In fact, some of the retrieval issues relating to poorly remembered contextual information may be due, in part, to poor encoding of context at the outset. Once information is encoded, however, healthy older adults seem to show similar semantic storage in long-term memory as younger adults. Semantic storage can be con- ceptualized as drawing more heavily on crystallized intelli- gence and knowledge structures (Bäckman, Small, Wahlin, & Larsson, 2000). There also appears to be little effect of aging on procedural and implicit memory tasks, although these may be performed more slowly.

It has been predicted that older adults would perform more poorly on prospective memory tasks because of a high degree of self-initiation required in remembering to do something in the future (for example, McDaniel &

402 PART THREE | Disorders of the Brain

Einstein, 2000). However, because prospective memory requires both remembering “what” is to be done and “when,” it appears that older people have more trouble with the “what” or content that may have more to do with basic encoding, storage, and retrieval mechanisms in ret- rospective memory (for review, see Henry, MacLeod, Phillips, & Crawford, 2004). Although older people may perform more poorly on laboratory prospective memory tasks, they do much better on real-life tasks, such as keep- ing appointments or remembering to post mail or return phone calls; tasks for which motivation may be different or external reminder aids may come into play (for review, see Henry et al., 2004).

A number of researchers suggest that working memory (WM) capacity declines with age. Interestingly, short- term memory, or the ability to recall strings of digits, does not appear to decline with age. However, this is a more passive task than WM, where information must not only be held but also manipulated and processed in a more complex manner.

How stable is cognitive functioning among those 75, 85, or older? Does the pattern look the same as one contin- ues to get older? Do initial losses of function stabilize, is there a gradual decline, or is there an acceleration of loss in some areas of functioning? In a review of studies of longi- tudinal aging, it appears that the pattern of preserved crys- tallized intelligence over fluid intelligence does not hold in those adults older than 75 (Bäckman et al., 2000), and all intellectual abilities show a decline in group studies.

However, a series of interesting studies conducted in Sweden document the neuropsychological performance of the oldest segment of the population. In one study, re- searchers gave neuropsychological tests twice, 2 years apart, to more than 300 people between the ages of 84 and 90 (Johansson, 1991). This study of the oldest old (84–90 years old) found surprising stability in neuropsy- chological functioning between the first and second test sessions. Researchers expected that functioning of people at this advanced age would decline over 2 years. However, two thirds of the sample (66%) remained at the same cog- nitive level, whereas 31% declined (Johansson, Zarit, & Berg, 1992). Almost half (42%) remained in the normal range of functioning during the 2-year time period. This finding was surprising not only in that a large portion of the sample showed stability of cognitive function over time but also that a significant portion of quite elderly adults still had “normal” cognitive function.

Johansson and his colleagues (Johansson, 1991) sug- gest that cognitive changes were more related to terminal decline, or proximity to death, than to chronologic age. Among other neuropsychological tests, these examiners administered the digit span task, at regular intervals, to

normally aging Swedes older than 70. This requires re- peating increasingly longer series of digits either in se- quential or reverse order, respectively, until the testee misses them. For the 70- to 88-year-olds studied over time, Johansson examined two groups: those who died before age 85 and those still living. Those alive at age 85 showed a consistent performance as they aged; those who died before age 85 started showing a drop in backward digit span by age 75 and marked declines in both forward and backward span lengths by age 79.

What then is the secret of people who are active and productive well into their later years? In recent years, much focus has been on what can be termed the “use it or lose it” hypothesis. This idea suggests that by keep- ing mentally active, or by increasing mental exercise, older people may be able to stave off mental decline and diseases of aging. The question is, does mental exercise, such as doing crossword puzzles, starting a new hobby, or memory training help to slow or reverse the affects of aging? This hypothesis has also been called the differential-preservation hypothesis (Salthouse, Babcock, Skovronek, Mitchell, & Palmon, 1990) because it is as- sumed that the large age differences in cognitive function- ing seen in the oldest adults are due to differences in their current levels of mental activity and mental exercise. This is in contrast with the preserved-differentiation hypothesis (Salthouse et al., 1990) that is more in line with the idea of “cognitive reserve” discussed earlier in this section. In other words, it may be that the range of cognitive differ- ences found among older people are because those who showed higher cognitive ability to begin with continue to show this pattern as they age. In a recent review and com- mentary on this issue, Salthouse (2006) suggests that the research on “mental exercise” or training as a strategy has not yet demonstrated convincing results. For example, re- search focused on training people on various cognitive tasks, although showing some immediate benefits in tar- geted task performance, has not shown to be generaliz- able to other tasks, often in the same cognitive domain. Also, the effects of training are not convincingly sustained over time compared with those who were not trained. Therefore, although there is much optimism in the popu- lar press about our potential ability to stave off the gen- eral effects of aging through mental exercise, this idea does not yet appear to be supported.

Although the mechanisms are not yet known, people who continue to be active well into their 70s, 80s, and 90s may be the best at resisting both declines in fluid and crystallized intelligence. They may have started out with a higher level of crystallized intelligence, and thus are pro- vided with a certain degree of cognitive reserve. They may have learned a great deal in their life, which also provides

CHAPTER 14 | Normal Aging and Dementia: Alzheimer’s Disease 403

them with strong crystallized semantic networks. Although aspects of fluid intelligence such as speed and flexibility of thought may decline, many older people do maintain an active and independent lifestyle well into their later years.

B R A I N C H A N G E S A S S O C I A T E D W I T H A G I N G

Variation in functional abilities with aging is a clue that the brain may not decline in a uniform manner. But how does it age, and when is change noticeable? By reviewing both global (structural and neuronal) and regional brain changes affected by aging, as well as considering the tra- jectory of decline and factors that impact brain aging, a picture emerges of how the brain changes as people grow older.

The aging brain undergoes visually apparent gross structural changes such as diminution in size and weight, flattening of the cortical surface, and expansion of the cerebral ventricles. The loss of weight and volume occurs in a general linear trajectory (for review, see Raz, 2000). One of the first recognizable global indexes of brain health or shrinkage is widening of the ventricles. If the brain loses volume in any area, the ventricles reflect this. How- ever, this gross marker does not necessarily imply that the brain loses volume equally across all areas.

Concomitant changes occur at the neuroanatomic and biochemical levels. Neurons undergo significant struc- tural changes with aging. Aging cells may shrink and die, lose some of their dendritic processes, and develop a yel- lowish brown pigment that accumulates in cells of the cortex and cerebellum and may have to do with “wear and tear” (Bourne, 1973; Kemper, 1994). Observations of cortical thinning may have led to one of the myths of human neurobiology, namely, that throughout adulthood people lose a great number of neurons from their brains each day. Better measurement methods indicate that this is exaggerated, and that much cortical thinning may be due to neuronal shrinkage rather than loss (for review, see Haug, 1985). Although some markers of neuronal abnor- malities such as neurofibrillary tangles and senile plaques (see Figures 14.6 and 14.7) are hallmarks of AD and other dementias, they also occur in older people with- out frank evidence of cognitive dysfunction.

Images of aging brains often show white matter abnor- malities indicating attenuation of myelin around the axons of neurons. This observation has led a number of researchers to question whether white matter (that is, myelinated axons) or gray matter (that is, cell bodies) may succumb more quickly to the aging process. Cerebrovascu- lar disease and hypertension, both more common in older

adults, are associated with white matter abnormalities (for example, Strassburger et al., 1997), but these comorbid problems of aging do not appear to fully explain white matter aging. In an analysis of studies across the life span, gray matter suffers a linear decline from infancy through old age, whereas white matter shows an inverted U- shaped function with increasing white matter into young to middle adulthood, followed by a plateau and then a decline into old age (for review, see Raz, 2005).

The brain shows differential changes with aging. Al- though some brain areas appear more vulnerable to the effects of aging, there are islands of relative preservation. The hippocampus, the frontal lobes, and specific associa- tion areas of the temporal and parietal lobes are more vul- nerable, whereas the occipital and somatosensory cortices are relatively preserved. The frontal cortex is one of the cortical areas most affected by aging. The most likely set of age-related neuronal changes specifically affects the pre- frontal cortex (Esiri, 1994). Neuronal loss in this area may account for some of the fluid intelligence changes in cog- nitive functions occurring in older people.

Because cognitive functioning varies widely among older people, it is also reasonable to assume that there is a range of individual variability in physical brain changes. When as- sessing the degree of cortical atrophy caused by advancing age, gross inspection of the brain demonstrates wide varia- tion (Figure 14.2). In the Swedish study (Johansson, 1991), 85% of elderly adults’ brains appeared to have little to no evidence of cerebral atrophy. However, all did show some neuropathologic markers usually associated with dementia, including signs of ischemia (that is, insufficient blood sup- ply), neurofibrillary tangles, and senile plaque formations. In individuals older than 85, gray matter atrophy is often apparent on computed transaxial tomography (CT) in both demented and nondemented people. White matter attenua- tion (thinning of the white matter) relates to cognitive changes associated with fluid intelligence, such as slowed speed of behavior, poorer spatial ability, poorer arithmetic, and memory recognition skills (Johansson, 1991).

Genetic and environmental factors also play a role in an individual’s vulnerability to brain aging. A variety of genetic factors have been implicated in the dementias dis- cussed in this and the next chapter. Some of these genetic factors may also prove to accelerate the aging process in people who do not develop a full-blown dementia. For example, a specific allele of apolipoprotein E (that is, ApoE4) has been implicated in some forms of AD. How- ever, ApoE4 may also be implicated in general problems of white matter maintenance through its action on the cholesterol system of the fatty oligodendrocytes that make up the myelin sheath and through a disruption in the

404 PART THREE | Disorders of the Brain

maintenance of intracellular calcium balance (Masliah, Mallory, Veinbergs, Miller, & Samuel, 1996; Raz, 2000).

It is generally accepted that prolonged stress has nega- tive effects on health. However, studies of stress and aging suggest that stress may age both immune and brain cells. Immune cells contain chromosomes with end caps termed telomeres. Telomeres shorten as cells reproduce and are a measure of the life of the cell. In a study of women who were continually under high stress levels because of caring for chronically ill children, it was found that their telom- eres had undergone the equivalent of 10 more years of aging as compared with women who were living less stress- ful lives (Epel et al., 2004). Stress also appears to affect cer- tain brain areas. For example, people who have high basal cortisol levels (a biochemical marker of stress) show reduced hippocampal volumes over time (Lupien et al., 1998).

Whereas stress may negatively impact the brain and cognition, aerobic activity appears to enhance it. Older people who engage in regular aerobic activity perform bet- ter than sedentary people on a wide range of cognitive tasks (for review, see Colcombe & Kramer, 2003). In di- rect measures of brain density, it has also been reported that exercising older adults showed reduced loss of gray matter in frontal, temporal, and parietal areas, as well as less reduction in white matter tracts in both anterior and posterior brain areas (Colcombe et al., 2003).

Mild Cognitive Impairment

People who show more than age-related cognitive de- cline, but do not meet the criteria for dementia, have been the focus of active research interest in recent years. The term mild cognitive impairment (MCI), although somewhat controversial and nonspecific, has come to imply an inter- mediary, and perhaps transitional, stage between normal aging and dementia. The use of this term has been some- what controversial because it may be used in an overgeneral- ized fashion to refer to any number of cognitive changes, but it can be useful if it is well defined. Research also sug- gests that the presence of MCI is a risk factor for dementia.

Theoretically, MCI can affect many areas of cognition, but most research has focused on memory, or the MCI- amnestic type. This criterion identifies memory impair- ment (for example, Petersen et al., 1999) as the primary cognitive abnormality. In comparison with age-matched control participants, those with MCI-amnesia show deficits in both encoding and retrieval (Bennett et al., 2002; Wang & Zhou, 2002). In comparison with indi- viduals with AD, those with MCI show similar memory deficits but do not show the same level of decline in other areas of cognition (Petersen et al., 1999). Following the initial focus on the MCI-amnestic group, other non- amnestic MCI subtypes have been identified based on

CHAPTER 14 | Normal Aging and Dementia: Alzheimer’s Disease 405

Figure 14.2 Normal brain (left) and brain showing widespread cortical atrophy (right). Note the thinner gyri, wider sulci, and widen- ing of the interhemispheric fissure on the right. Cortical atrophy indicates loss of neuronal connections but not necessarily clinical dementia. (Reproduced from Bigler, E. D. [1987]. The clinical significance of cerebral atrophy in dementia. Archives of Clinical Neuropsychology, 2, 178, by permission. Copyright © 2000 Elsevier Science.)

other variations in cognitive decline (Petersen, 2004, 2005). Imaging studies also suggest that this MCI group shows hippocampal and brain atrophy that is worse than would be expected in normal aging but is not as marked as that seen in AD (Jack et al., 2000, 2004, 2005).

A major reason for targeting those with MCI is to de- termine their risk for progressing to AD or another de- mentia. Indeed, longitudinal research has suggested that the MCI-amnestic group is at a greater risk for develop- ment of a dementia at an accelerated rate (Bennett et al., 2002; Daly et al., 2000; Flicker, Ferris, & Reisberg, 1991; Ganguli, Dodge, Shen, & DeKosky, 2004; Lopez et al., 2003). Through the identification of this group, at a high risk for dementia, therapeutic interventions can poten- tially be started earlier and biomarkers for various types of dementias can be studied.

S U M M A R Y

The findings from various researchers in aging and cogni- tion suggest that both crystallized and fluid intelligence are important for successful functioning in advanced age. Ability, level of education, and knowledge gained early in life appear to provide some buffer against later brain dis- orders. Not everyone ages cognitively at the same rate, and many people retain high abilities into advanced age. Some individuals may suffer devastating effects, both physical and cognitive, whereas others suffer relatively few effects. Therefore, among groups of older people, age is not the only, or best, predictor of cognitive decline or mortality. The process of aging increases the probability of cognitive problems. Aging also results in brain and neu- ronal changes, but physical changes do not by themselves always differentiate between normal aging and dementia because of a wide range of individual differences and dif- ferences in functional cognitive reserve. Different mea- sures of functional capacity may well be the key to identi- fying those at greatest risk for cognitive impairment. Advanced imaging methods correlated with neuropsycho- logical functioning hold promise for more precisely relat- ing structure to function. This will also aid in identifying people at greatest risk for development of dementia, such as those with MCI, and in ultimately answering the fol- lowing question: What is the difference between normal aging and dementia?

Defining Dementia

With public and scientific attention focused on de- mentia, one might expect general agreement when refer- ring to dementia and subtypes of dementia such as AD. Given the cornucopia of terms used to refer to dementia

and subtypes of dementia, however (Table 14.1), there can be confusion. Professionals and laypeople alike may confuse dementia—the behavioral syndrome—with one particular condition, such as AD. Patients and families often label de- menting conditions as “hardening of the arteries,” “senility,” or “old-timers’ disease,” which often reflects a perception that the problem is inevitable in aging. In the most generic sense, dementia refers to a behavioral syndrome, and not one disease or cause. It denotes conditions that may have a variety of causes. Some dementias may be treatable, and oth- ers may not be treatable. Some stem from disease processes that inevitably become worse, and some from toxic expo- sure or injury, resulting in a behavioral decline that plateaus.

The dementia syndrome is a cluster of behavioral symptoms that may or may not point to a disease, but de- mentia is not a disease entity in and of itself. The various subcategories of dementia usually relate to the suspected disease, cause, or primary site of damage (for example, cortical versus subcortical). Researchers have found well over 50 causes of dementia (see Table 14.1). Among the

406 PART THREE | Disorders of the Brain

Progressive Dementias

Cortical dementias Alzheimer’s disease Motor neuron disease Pick’s disease Progressive aphasia Wilson’s disease

Subcortical dementias Huntington’s disease Parkinson’s disease Progressive supranuclear palsy AIDS dementia Creutzfeldt–Jakob disease

Mixed dementias Lewy body dementia Vascular dementias Binswanger’s disease

Potentially Static Dementias

Toxic conditions Alcoholic dementia Heavy metal poisoning (such as

lead and mercury)

Infectious conditions Herpes encephalitis

Miscellaneous conditions Tumor Normal pressure hydrocephalus Trauma

Potentially Reversible Dementias

Systemic illness Severe anemia Uremia

Deficiency states B12 deficiency

Endocrine disorders Addison’s disease Thyroid disorders

Drug toxicity Anticholinergics Antipsychotics

Table 14.1 Representative Causes of Dementia

most well known are the degenerative dementias caused by a progressive and unrelenting disease process such as AD or Parkinson’s disease. Neurologists traditionally have categorized these disease processes as cortical, subcortical, or mixed, depending on the degree to which they affect gray or white matter areas of the brain. Vascular, infectious, and toxic conditions, as well as a variety of other brain conditions, may also result in dementia.

Some of these conditions are progressive, whereas oth- ers, such as the dementia resulting from herpes encephali- tis, may be static, rarely worsening over time. Although most dementing conditions encountered by neuropsychol- ogists represent persistent or progressive states, or both, re- searchers have also documented “reversible” or temporary dementias. Reduced metabolic efficiency accompanies aging, making older adults especially susceptible to condi- tions and substances that they might have tolerated when younger. For example, symptoms of dementia can stem from adverse reactions to medications (such as sedative- hypnotics and anticholinergic drugs), nutritional disor- ders (such as thiamine deficiency and pernicious anemia), metabolic disorders (hypoglycemia, hypercalcemia, kidney failure), psychiatric disorders (severe mood disorders, psy- chosis), and other conditions such as anesthesia or surgery. However, when these conditions are treated, the dementia is usually reversible and the patient returns to baseline.

D I A G N O S T I C C R I T E R I A F O R D E M E N T I A

No one set of criteria represents definitive agreement re- garding the diagnosis of dementia. Somewhat varying di- agnostic standards are described in the Diagnostic and Sta- tistical Manual (4th ed., revised; DSM-IV-R) and by the National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer’s Disease and Related Dis- orders Association (NINCDS-ADRDA) (McKhann et al., 1984) (Table 14.2). However, experts agree about some of the major features of dementia. The first is that dementia results in a loss of cognitive or intellectual function. This fea- ture implies a decline that is acquired and unusual. It is acquired because people born with impaired intellectual function, having developmental disorders such as mental retardation, do not have dementia simply by virtue of poor intellect, although they too can experience develop- ment of dementia. The loss of cognitive or intellectual functioning must also be unusual or outside of the realm of what would be expected with normal aging. As we have discussed, aging may bring about some cognitive decline, particularly in memory and areas of fluid intelligence. But the decline associated with dementia represents a marked change from previous levels of intellectual and memory abil- ity. Although the most well known subtypes of dementia

have a predilection for the elderly and result in progres- sive deterioration, this broad definition of dementia could hypothetically refer to the sudden loss of intellectual func- tion from head injury in a 17-year-old.

Although patterns of impairment may differ, the second area of diagnostic agreement in dementia involves multiple areas of cognitive impairment. The abilities impaired in de- mentia may represent all cognitive functions or may pres- ent different patterns of neuropsychological disability. Both sets of criteria for dementia identify memory impairment as a prominent and necessary feature. However, it is the multiple and often diffuse cognitive decline that character- izes dementia. It is not uncommon to see impairment in abstract thinking and problem solving, impaired judgment, and other problems of higher cortical functioning.

In summary, the term dementia in its broadest sense refers to a group of conditions and diseases that share some similar neuropsychological and behavioral symp- toms, although the underlying causes may vary widely. The prime identifying feature is a decline in multiple areas of cognitive functioning, including memory. Beyond this initial definition of dementia, however, lies what is probably most important in working with patients with dementia— an understanding of the different neuropsychological pre- sentations of dementia subtypes.

CHAPTER 14 | Normal Aging and Dementia: Alzheimer’s Disease 407

Criteria DSM-IV-R NINCDS-ADRDA

Memory impairment R R

Impairment of additional area of R D cognition (such as language, construction, praxis, or executive functioning)

Confirmed on mental status tests NS R

Impaired/decline in social or R NS occupational function

State of consciousness unclouded R R

Evidence of specific organic factor R NS etiologically related to the disorder or absence of conditions other than organic mental syndrome

Note: DSM-IV-R = Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Revised; NINCDS-ADRDA = National Institute of Neurological and Communica- tive Disorders and Stroke-Alzheimer’s Disease and Related Disorders Association; R = required; D = desirable but not required; NS = not specified.

Source: Adapted from Rebok, G. W., & Folstein, M. F. (1993). Dementia. Journal of Neuropsychiatry and Clinical Neurosciences, 5, 265–276; and Katzman, R., Lasker, B., & Bernstein, N. (1988). Advances in the diagnosis of dementia: Accuracy of diagnosis and consequences of misdiagnosis of disorders causing dementia. In R. D. Terry (Ed.), Aging and the brain (Vol. 32, pp. 17–61). New York: Raven Press.

Table 14.2 Diagnostic Criteria for Dementia

S U B T Y P E S A N D C L A S S I F I C A T I O N S O F D E M E N T I A

C o r t i c a l v e r s u s S u b c o r t i c a l

Traditionally, the primary demarcation among subtypes of dementia has followed the attempt to distinguish be- tween cortical and subcortical dementias. Cortical de- mentias primarily affect, or start out by affecting the cere- bral cortex, or gray matter. AD is typically included within this category. With subcortical dementias, the disease state predominantly affects the white matter, or neuronal connections between cortical areas, and gray matter structures below the cortex. The term subcortical was first used to describe the neuropathology and accom- panying pattern of cognitive deficits associated with pro- gressive supranuclear palsy (Albert, Feldman, & Willis, 1974). Since that time, it has expanded to include Hunt- ington’s and Parkinson’s diseases and may also refer to dis- eases such as acquired immune deficiency syndrome (AIDS)–related dementia and some depressions. The dif- ficulty with this differentiation, both neuroanatomically and behaviorally, is that these disorders do not conform to strict cortical–subcortical boundaries in the brain. For example, AD typically causes significant cortical neuronal loss and atrophy, but also specifically attacks the hip- pocampus, a subcortical limbic system structure. In con- trast, diagnosticians usually identify Parkinson’s disease by the subcortical structure that it targets, the substantia nigra, although evidence suggests that it also affects some higher cortical functions such as executive functioning. Even when evidence indicates that a disease targets only subcortical structures, “cortical” effects may appear be- cause of the disconnection of neural pathways in the white matter that connect the gray matter areas. Although we use the terms cortical and subcortical dementia as gen- eral categories, you must loosely interpret them to imply a major or primary area of damage rather than an exclu- sive area of damage.

S t a t i c v e r s u s P r o g r e s s i v e

All dementias that result from a disease process are pro- gressive. Diseases such as AD, Pick’s, Huntington’s, or Creutzfeldt–Jakob inevitably follow a continuous cogni- tive and behavioral decline. Other conditions, however, may cause a static or steady-state cognitive disorder. A neurotoxic substance (such as lead or alcohol) or infec- tion (such as herpes encephalitis) continues to cause brain damage as long as it is present. But when the condition is arrested, the resultant dementia usually plateaus.

Both static and progressive dementias can begin with a sudden change of functioning, over days or weeks, or a

more insidious or gradual onset, over the course of months or years. Lead poisoning may impact the brain for a period of years before obvious impairment appears. Herpes encephalitis, in contrast, is an acute infectious condition with sudden and dramatic effects on the brain. Progressive dementias can also vary in their course. The progression, as in the case of AD, is gradual. However, there may be long periods during which the decline plateaus. Vascular dementias often produce a stepwise progression, as multiple infarcts (multi-infarct demen- tia) or strokes occur at different times. Only repeated neuropsychological testing and keen observation by the neuropsychologist, patient, or family can demonstrate the progression of the dementia.

R e v e r s i b l e v e r s u s I r r e v e r s i b l e

Researchers have focused primarily on irreversible and progressive dementias. However, clinicians are likely to see a variety of patients with dementia-like symptoms that may remit with time. Part of the diagnostic problem with the so-called reversible dementias is that these peo- ple may actually have delirium rather than dementia. Delirium does not signal dementia, but rather is a tran- sient cognitive problem associated with an acute confu- sional state. Typically, individuals with delirium have poor attention, disorganized thinking, perceptual disrup- tion, disorientation, memory impairment, and an altered state of consciousness. Because delirium and dementia share memory impairment and disorientation, they can be easily confused. However, with delirium, the symp- toms develop over a period of days or hours and are caused by specific organic problems such as overmedica- tion or an acute or worsening medical condition. Many medical problems listed in Table 14.1 as potentially re- versible dementias cause delirium. Moreover, it is not un- common for patients with dementia to experience devel- opment of delirium. For example, a person might be admitted to the hospital to have surgery or to be treated for an acute medical condition. Perhaps an already re- duced cognitive capacity causes vulnerability to the cog- nitive effects of general metabolic dysfunction. People who become delirious for short periods and then recover should not be diagnosed with dementia, even a reversible one. One difference in presentation is that people with dementia, other than in the late stages, are alert and can respond to what is going on around them. People with delirium are grossly confused and disoriented to their surroundings. A true “reversible dementia” should meet the behavioral criteria for dementia discussed earlier; that is, the individual must show dementia in the absence of a delusional state.

408 PART THREE | Disorders of the Brain

Research continues on the question of reversibility. Several possibilities exist. For example, anticholinergic drugs impair memory functioning. Perhaps, reduced cog- nitive functioning caused by large doses of a medication can, indeed, permanently reverse when the person stops taking the medication. Or perhaps, dementia symptoms stemming from overmedication indicate the early stages of dementia in an already compromised brain, so that dis- continuing the drug only temporarily increases cognitive functioning.

The remainder of this chapter focuses on AD. This represents the most scrutinized and researched dementia. We focus on the epidemiology of AD, diagnostic issues, clinical presentation, and neuropsychological profile and treatment.

Alzheimer’s Disease

Alzheimer’s disease (AD), named after its discov- erer, Alois Alzheimer (Neuropsychology in Action 14.1), is a progressive cortical dementia that is irreversible and thus results in an inevitable decline. It is the most devas- tating and prevalent of the dementias, representing the eighth leading cause of death overall for people older than 65 (Hoyert & Rosenberg, 1997) and more than 50% of diagnosed dementia cases (Kay, 1995). The number of new cases of AD increases with age from 1% of the popu- lation aged 65 to 75 years to 6% to 8% of adults older than 85. The rate of survival varies widely between 2 and 20 years with a median survival rate of between 3 and 4 years after diagnosis (Helmer et al., 2001; Wolfson et al., 2001). The prevalence, or number of people living with AD at any one time, increases with age and survival rate. It is estimated that between 10% and 30% of people around the world older than 85 have AD (for example, Bowirrat, Treves, Friedland, & Korczyn, 2001; Gurland et al., 1999; Stevens et al., 2002; Wang et al., 2000). Based on the 2000 census, it is estimated that between 3 and 4 million people older than 65 have AD (Mayeux, 2003).

There appears to be no single cause for AD, and in most cases, the causative factor remains unknown. AD is linked to increased age, which has led some to speculate that it is a disease of “accelerated aging”—implying that if we all lived long enough, AD would be inevitable. Over a lifetime, women are about twice as likely to experience development of dementia or AD as men (Seshadri et al., 1997), but this may be partly accounted for by that women have a longer life expectancy (Mayeux, 2003). People with more education appear less likely to experi-

ence development of AD, but again, this is probably a marker of larger cognitive reserves acting as a buffer be- tween neuropathology and disease manifestation.

AD does not have a clearly identified genetic compo- nent in most cases. A variation exists that is autosomal dominant, meaning the family pedigree shows about 50% of the family members as having AD, but this type proba- bly affects less than 150 families worldwide. The most likely chromosomal culprits in genetically established AD appear to be chromosomes, 1, 14, and 21. Interestingly, people born with Down’s syndrome, or trisomy 21 (named because the disorder results from an abnormality on chromosome 21), inevitably develop a dementia, usu- ally by age 40. The associated brain changes corresponding to AD (neurofibrillary tangles and senile plaques) appear years before clinical diagnosis. In summary, although the biomedical research searching for causes and markers of the disease appears promising, scientists still know little about the actual causes of AD.

D I A G N O S T I C P R O B L E M O F A L Z H E I M E R ’ S D I S E A S E

A definitive diagnosis of AD requires the behavioral pres- ence of dementia and the identification of neuropatho- logic markers of AD. No single medical test, imaging pro- cedure, or behavioral test can positively identify AD (for example, Mayeux, 2003), short of a brain biopsy showing the characteristic neurofibrillary tangles and neuritic plaques, which are most predominant in the hippocam- pus and cortical association areas. Because biopsy is not a procedure to which most people would submit, a defini- tive diagnosis cannot be made until autopsy. AD is diffi- cult to diagnosis because there are other dementias that have may have similar symptoms, especially in the later stages of the disease. In diagnostic accuracy studies, where physicians have to choose the correct diagnosis among several types of dementias, AD disease tends to be over- diagnosed, meaning that other progressive dementias may be misdiagnosed as AD (Lopez et al., 1999). A recent Chi- nese study that analyzed both the clinical features and brain markers of various dementias at autopsy found that the agreement rate between clinical diagnosis of dementia and pathologic findings was 64.5% of cases (Wang, Zhu, Gui & Li, 2003). Concordance between clinical and bio- logical findings was strongest for vascular dementias (66.7%) and less strong for degenerative dementias (40%).

The clinical diagnosis of AD depends largely on evi- dence related to behavioral and neuropsychological profiles

CHAPTER 14 | Normal Aging and Dementia: Alzheimer’s Disease 409

and on ruling out all other identifiable causes of de- mentia, such as those listed in Table 14.1. The clinical diagnoses of “probable” and “possible” AD reflect, in large measure, the certainty with which other causes of

dementia can be excluded. This chapter also refers to probable AD as “senile dementia of the Alzheimer’s type” (SDAT), to reflect the probable nature of the di- agnosis.

410 PART THREE | Disorders of the Brain

A piece of neuropsychology history puts to rest doubts about Auguste D., the first case of Alzheimer’s disease (AD) ever described. After having gone missing for nearly 90 years, Alois Alzheimer’s blue cardboard file was found by psychiatrists in the archives of the University of Frankfurt, Germany, in 1996. Among the 32 sheets were Alzheimer’s handwritten interview notes, samples of Auguste D.’s “amnestic writing disorder,” and a report of the course of the disease. Alzheimer’s first notes are as follows:

Nov. 26, 1901

She sits on the bed with a helpless expression. What is your name? Auguste. Last name? Auguste. What is your husband’s name? Auguste, I think. Your husband? Ah, my husband. She looks as if she didn’t under- stand the question. . . .

What is this? I show her a pencil. A pen. A purse and a key, diary, cigar are identified correctly. At lunch she eats cauliflower and pork. Asked what she is eating, she answers spinach. . . .

When objects are shown to her, she does not remember after a short time which objects have been shown. In between she always speaks about twins. When she is asked to write, she holds the book in such a way that one has the impression that she has a loss in the right visual field. Asked to write Auguste D, she tries to write Mrs. and forgets the rest. It is necessary to repeat every word. (Maurer, Volk, & Gerbaldo, 1997, p. 1547)

Dementia had been described before, with terms such as paralytic dementia, athero- sclerotic dementia, and senile dementia. What made Auguste so unusual was that she was so young, only 51. After 4 1/2 years,

Auguste died. When Alzheimer published his description of this case (1907, 1987), he had examined her brain and could describe the unique histologic findings of neurofibril- lary tangles: “The nucleus and the cell have fallen apart and only a tangled bundle of fibrils points to the place in which there was once a ganglion cell” (Alzheimer, 1907, 1987). He had even drawn pictures of Auguste D.’s neurofibrillary tangles (Figure 14.3). To Alzheimer, this represented a new entity of “presenile dementia.” In 1910, Kraepelin included the new syndrome of Alzheimerische Krankheit (Alzheimer’s disease) in his famous textbook of psychiatry.

A controversy erupted after their discovery of Alzheimer’s file because the original au- topsy findings also indicated that Auguste D.

had arteriosclerosis in smaller blood vessels, a fact that today is a criterion excluding pure AD. Other scientists argued that she may have had a metabolic disorder. Finding Auguste D.’s brain would be the only way to resolve whether she had what we now recog- nize as AD. After a 2-year search, yet another group of German researchers found more than 250 slides of Auguste’s brain in the basement of the University of Munich. Ger- man researchers have been able to confirm the two classic signs of AD in the brain of Auguste D.: neurofibrillary tangles and amyloid, or senile, plaques. This puts to rest the notion that Auguste D. might have had a disease process other than AD. However, whether she had a coexisting vascular prob- lem is likely to fuel debates for some time.

N e u r o p s y c h o l o g y i n A c t i o n 1 4 . 1

T h e D i s c o v e r y o f A l z h e i m e r ’ s D i s e a s e

by Mary V. Spiers

Figure 14.3 Alzheimer’s drawings of neurofibrillary tangles from the brain of Auguste D. (From K. Maurer, S. Volk, & H. Gerbaldo, “August D. and Alzheimer’s Disease,” The Lancet, 1997, 349, Figure 5, p. 1549. Reprinted by permission of Elsevier.)

N E U R O P A T H O L O G Y O F A L Z H E I M E R ’ S D I S E A S E

M a j o r B r a i n S t r u c t u r e s A f f e c t e d b y A l z h e i m e r ’ s D i s e a s e

Two interesting facts exist regarding the neuropathology and pathophysiology of AD. First, the disease targets spe- cific regions of the brain. Second, disease-targeted struc- tures sustain neuronal loss and atrophy. Although AD is a “cortical dementia,” because major areas of the cerebral cortex show brain shrinkage, this disease does not respect cortical boundaries. It greatly affects major subcortical limbic system structures such as the hippocampus and amygdala. Most pathologic changes occur in the cortical temporoparietal association areas and the subcortical lim- bic cortexes. Specifically, the disease destroys the major pathways to and from the hippocampus, cutting off di- rect connections to association cortices.

Gross postmortem inspection of the brain often finds cortical atrophy. In Figure 14.4, the most marked atrophy is in the frontal, temporal, and parietal areas. The gyri are thinned, and the sulci are noticeably widened. Researchers estimate that in AD about half of the large neurons deteri- orate (Terry, Peck, deTeresa, Schecter, & Horoupian, 1981), resulting in a loss of volume. Specifically, these neurons lose dendritic arborization, or branching. The ventricles also enlarge, because of cortical thinning (Fig- ure 14.5). Although dementia severity increases with in- creased cell death, longitudinal comparisons of global cerebral atrophy with dementia severity do not reliably indicate dementia (Bigler, 1987; Johansson, 1991).

A closer look at specific structures reveals that they sus- tain massive cell loss. In fact, SDAT appears to follow structural borders. Chief among these are the parietal and temporal cortices, the hippocampus and the structures lead- ing to it (entorhinal cortex and the perforant neural path), the amygdala, and specific nuclei of the thalamus (Van Hoesn & Damasio, 1987). In addition, certain subcortical

frontal areas are implicated, such as the nucleus basalis of Meynert and the olfactory areas. Noticeably spared are the primary motor and sensory areas (tactile, auditory, vi- sual) and the basal ganglia. The affected structures corre- spond to areas of higher cognitive functioning and mem- ory, leaving relatively untouched more basic sensory and motor abilities.

H I S T O L O G I C M A R K E R S

The two neuropathologic findings that Alzheimer (1907, 1987) identified, still considered the primary markers of the disease, are neurofibrillary tangles and neuritic, or se- nile, plaques. These are evident by microscopic inspec- tion of brain tissue obtained at autopsy. Neurofibrillary tangles resemble entwined and twisted pairs of rope within the cytoplasm of swollen cell bodies (see Figures 14.3 and 14.6). Tangles consist of proteins, termed tau proteins, that are believed to accumulate as a result of ab- normal phosphorylation. The excessive collection creates tangles that are dispersed throughout the brain but dis- proportionately in the areas just listed, including the tem- poroparietal areas and the hippocampal complex. The specificity of structural deterioration in AD extends to the cellular layers of the cortex. For example, within the six- layered isocortex of the cortical association areas, tangles and plaques devastate layers 3 and 5, whereas other layers are relatively spared (Van Hoesn & Damasio, 1987).

Alzheimer described neuritic plaques as “clump-like deposits in the neuropil.” They are round aggregates of “cellular trash” that have a particular affinity for the re- gions where the majority of synapses lie (the neuropil).

CHAPTER 14 | Normal Aging and Dementia: Alzheimer’s Disease 411

Images not available due to copyright restrictions

Image not available due to copyright restrictions

The synapses eventually disintegrate, leaving holes and neurites (that is, pieces of axons and dendrites) where there were once active connections (Figure 14.7). Plaques are likely to concentrate in the frontal and temporal re- gions (Zubenko, Moossy, Martinez, Rao, Kopp, & Hanin, 1989) and are numerous around the hippocampal formation. As we discussed earlier, tangles and plaques are not specific to AD. They also appear in normally aging individuals without evidence of dementia, as well as in other degenerative diseases. It is the pattern and quantity of these markers that defines AD.

An exciting recent discovery is that the substance of neuritic plaques and tangles may lead to hypotheses re- garding possible causes of and treatments for AD. The neuritic plaques found in AD contain an amino acid pep- tide protein core termed beta-amyloid (�-amyloid). As

a result, these neuritic plaques are also called amyloid plaques. Bradshaw and Mattingly (1995) review several possibilities for how β-amyloid may operate. First, it is coded on chromosome 21, the same chromosome respon- sible for Down’s syndrome. The behavioral significance of this is that if they live past 30 years, people with Down’s syndrome often show AD-like dementia symp- toms. Therefore, chromosome 21 may be responsible for both problems. Second, there is debate on the function of β-amyloid. Is it a cause of the disease, a by-product of the disease, a “protective reactant,” or an autoimmune response?

As we discussed earlier in this chapter, genetic research has focused on the protein ApoE4, which may be associ- ated with both WM aging and AD. This additional pro- tein in plaques and tangles has been studied for its impor- tance in AD. ApoE4 is one of four possible variants, or alleles, of the protein ApoE. Seventy-five percent of peo- ple in the population have the ApoE3 variant (Corder et al., 1993), but risk for development of AD increases to 90% if a person inherits the ApoE4 variant from both parents. In addition, a double set of ApoE4 alleles also re- duces the mean age of onset. ApoE4 is responsible for fer- rying cholesterol into the brain; however, researchers are currently investigating how this protein may operate in AD. It appears on yet another chromosome, chromosome 19, which binds with β-amyloid in cerebrospinal fluid. The exact mechanism for this binding process is not yet known; however, researchers hypothesize that ApoE4 may not be the direct or sole cause of the disease (see Bradshaw & Mattingly, 1995); rather, the protective factors that ApoE2 or ApoE3 provide may be lost. However, there is not yet consensus whether it can serve as a specific or sen- sitive marker of the disease (Mayeux et al., 1998), and there are no genetic markers of AD that have yet been es- tablished for diagnostic purposes (Knopman et al., 2001). Researchers have also examined the CSF of patients with potential AD to examine potential β-amyloid deficiencies or the presence of tau proteins in cerebrospinal fluid. Al- though a combination of some of these biomarkers holds promise in aiding diagnosis, that some biomarkers are sensitive to more than one condition precludes their rou- tine use in determining the diagnosis of AD (Knopman et al., 2001).

N e u r o t r a n s m i t t e r S y s t e m s A l t e r e d b y A l z h e i m e r ’ s D i s e a s e

AD may impact multiple neurotransmitter systems. However, the most consistent evidence of a neurotrans- mitter with a direct effect on memory processes in AD is acetylcholine (ACh).

412 PART THREE | Disorders of the Brain

Image not available due to copyright restrictions

In the brain, ACh is synthesized in a group of neurons called the basal forebrain cholinergic complex (BFCC). The cell bodies of these neurons lie in the basal forebrain struc- tures of the nucleus basalis of Meynert, the diagonal band of Broca’s area, and the globus pallidus. These axons proj- ect to the hippocampus and the cerebral cortex, primarily the frontal and temporal cortexes. The BFCC is a subcor- tical component of the limbic system and the major source of choline for the hippocampus and cortex (Coyle, 1985). Researchers have long known that ACh plays a role in memory. Drachman (1977) demonstrated that block- age of receptors causes memory loss even in young adults. In AD, the devastation of the BFCC neurons profoundly depresses brain levels of ACh, perhaps as much as 60% to 90% (Terry & Davies, 1980; Bowen, Benton, Spillane, Smith, & Allen, 1982).

Some of the other neurotransmitters implicated in AD are the catecholamines, the amino acid glutamate, and the neuropeptides somatostatin and corticotrophin. How- ever, at this juncture, none of these neurotransmitters ap- pears to play a clear role in AD. Researchers have reported that all are reduced in AD, but their reduction may be secondary to the disease process. For example, general stress also reduces somatostatin. As you might imagine, research in this area is progressing quickly because of the push to find appropriate pharmacologic treatments.

N e u r o i m a g i n g i n A l z h e i m e r ’ s D i s e a s e

Gross neuroimaging of the brain in patients with AD may indicate cerebral atrophy on CT or magnetic resonance imaging (MRI). The electroencephalograms of patients with AD are likely to show generalized slowing (LaRue, 1992). Degree of atrophy or slowing taken in isolation is not reliably associated with degree of neuropsychological impairment (for example, see Bigler, 1987), but the de- gree of ventricular enlargement seen over time as the cor- tex atrophies accompanies increasing cognitive impair- ment (Burns, Jacoby, & Levy, 1991) but is only a gross index of general brain health. Special imaging procedures demonstrate the enlarged hippocampal fissure that results from neuronal loss, tangles, and plaques that begin early in the disease process. Also characteristic of AD is a pat- tern of metabolic or vascular insufficiency, or both, seen in the temporoparietal area, which shows up on positron emission tomography (PET) and single-photon emission computed tomography (SPECT) scans. This hypometab- olism can be either unilateral or bilateral and depends on factors such as severity of illness, sex, and age at onset (for review, see Forstl & Hentschel, 1994).

CTs and MRIs are primarily useful, not to confirm a diagnosis of AD, but to rule out other conditions such as tumor or vascular causes of dementia seen as multiple small strokes or ischemic attacks. However, promising new methods of analyzing volume and ratio of specific structures through structural imaging may help confirm diagnosis of AD. PET and SPECT scans appear most sen- sitive for detecting the characteristic patterns of SDAT. These imaging measures are then correlated with neu- ropsychological measures to provide a dynamic picture of the disease process.

C L I N I C A L P R E S E N T A T I O N A N D N E U R O P S Y C H O L O G I C A L P R O F I L E O F A L Z H E I M E R ’ S D I S E A S E

The clinical presentation of patients with AD can vary, but many share characteristic patterns (Neuropsychology in Action 14.2). The most consistent deficits across pa- tients with autopsy-documented AD are memory and flu- ent anomic aphasia (for example, see Price et al., 1993). Visuospatial difficulties are also characteristic. These deficits correspond with neuroimaging studies showing patterns of hypometabolism in limbic and association areas in early stages of the disease. In this classic presenta- tion, some frontal areas of the brain appear relatively spared. This also corresponds with neuropsychological testing and clinical observation indicating that, despite severe memory impairment, many patients with AD re- tain an appropriate “social facade,” do not have a Broca- type (nonfluent) aphasia, and retain normal strength and simple motor speed until the end stages of the disease. However, the impairments progress over time, gradually affecting all higher mental functions of the brain. What follows is a description of the neuropsychological and be- havioral performance, according to functional area, typi- cal of those with the SDAT variant. Because memory dys- function is the hallmark of AD, we devote more discussion to this problem than to the other functional areas.

M e m o r y

AD globally and profoundly impairs memory. New de- clarative learning problems at all levels (encoding, stor- age, and retrieval) and retention over time are usually no- ticed first. In addition, structures of the brain that hold previously well-learned semantic knowledge information in organized associational frameworks begin to deterio- rate. Finally, short-term memory span, names of family members, and familiar stories fragment. The only type of learning that appears to persist lies outside the corticolim- bic system, with certain types of nondeclarative learning.

CHAPTER 14 | Normal Aging and Dementia: Alzheimer’s Disease 413

414 PART THREE | Disorders of the Brain

Although memory impairment is the hall- mark of Alzheimer’s disease (AD), those older than 65 (the time of life when AD is most likely to manifest) often decline in memory ability. The key is to differentiate between general complaints of forgetfulness and lowered cognitive functioning that accompany normal aging and cognitive indicators of incipient dementia. Consider the following two scenarios, which are compilations of cases seen by the authors.

Case 1: Mrs. C

Mrs. C is a 90-year-old woman from a small midwestern town who has lived by herself for the past 10 years since her husband died. She is active in her church and volunteers at a local thrif t shop. At home she spends most of her time reading, keeping up with corre- spondence to family and friends, and talking with neighbors on the phone. She drove her car until a year ago, when af ter increasing restrictions on night driving due to failing eyesight, she agreed with her physician that she should give it up. She tells her family that her memory is quite poor. She can read through a whole book, but says if she picked it up again it would be “just like reading a new book.” She watches the news daily and is interested in following the elections and candidates for office. Mrs. C has a definite opinion regarding who she likes, although she does not remember many of the details of current events and says the news “goes in one ear and out the other.” However, she does remember major life events, if asked about them by her children. She can recount episodes from her teens and 20s quite well and tells old family stories from her child- hood with incredible detail and animation. For the first time in her life she has had to star t taking several prescription medicines for hear t problems. At first she needed nearly constant prompting to remember to take her three daily doses at the right times. However, over the course of 2 to 3 months,

she learned her medication routine. She always remembered to take her pills when she got up and before bed, but frequently forgot the 11 A.M. pill.

Case 2: Mrs. R

Mrs. R is a 75-year-old woman who is married and lives with her husband. Mr. and Mrs. R have always had an active social life, getting together with friends quite often to go dancing or play bridge in their retirement community. Within the past several years, Mr. R has noticed that his wife does not seem to be paying attention when they play bridge anymore. She has made wrong bids and makes mistakes keeping score. She usually makes a joke about these things, saying to her friend, “Lucy, you’re just trying to distract me so you’ll win.” Everyone has a big laugh, which seems to just egg her on. Mrs. R particularly likes to tell stories of when she was young, and she has a lot of them to entertain everyone. When the conversation turns to the day’s news, Mrs. R seems to have little comment on current events, although she and her husband have always watched the news together every night. She seems to get news stories mixed up. Mrs. R says she just does not have too much use for the news and that “it goes in one ear and out the other.” A new couple has joined their dancing club, and much to Mr. R’s embarrassment, Mrs. R keeps reintroducing herself to them even after 4 months. After a while it became comical, and Mrs. R says she does it on purpose for a joke. Mrs. R has taken medication for the past 15 years and has always managed well. But now her husband feels like he must remind her to take her pills because he noticed she often does not put it out by her plate as she used to do. She resents being reminded and says accusingly, “I put it out. Are you sure you didn’t just take it and put it away when you cleared the table?” This behavior is upsetting to Mr. R, but the thing that bothers him most is that his wife, who had been a good cook, is now very

disorganized in the kitchen. After he noticed that a cake tasted salty, he watched her as she prepared other things. She often added ingredients twice or totally left out essentials of her recipes.

Both Mrs. C and Mrs. R have trouble remembering in areas in which they were previously more able, and they appear to have declined from their own former levels of ability. In some respects, both show a similar pattern of memory loss in that remote memory, or information learned many years ago, such as stories from child- hood or facts related to work or home persist remarkably well in comparison with new learning. Difficulty remembering what the news commentator said or learning a new medication routine or a new name presents more of a problem in both cases. These similarities between normal aging and dementia can prompt dread in people who see themselves as less able to rely on their powers of memory. However, these two cases have several notable differences. First, Mrs. C appears to have some insight into her memory difficulties, whereas Mrs. R rationalizes, jokes, and blames others for her poor memory. Second, Mrs. C learns and retains some new things, even though the learning may take longer.

Mrs. R, in contrast, not only is showing difficulty learning new things but appears to be losing her ability to perform previously well-learned tasks, such as cueing herself to take her own medication or to cook. Finally, there is a suggestion that Mrs. R’s problems seem more pervasive, in that she may also have problems in concentration, attention, calculation skills, and name finding. Mrs. R’s memory difficulties are characteristic of dementia, possibly AD, and may appear paradoxic to patients’ families, who can see that their family member is socially appropri- ate and retains remote and overlearned information quite well. It is easy to discount the importance of cognitive problems.

N e u r o p s y c h o l o g y i n A c t i o n 1 4 . 2

D i f f e r e n t i a t i n g b e t w e e n S y m p t o m s o f A l z h e i m e r ’ s D i s e a s e a n d N o r m a l A g i n g

by Mary V. Spiers

Long-Term Declarative Memor y—As in other conditions that produce “amnesia,” SDAT results in profound difficulties in learning new declarative information. As discussed in Chapter 9, declarative memory can be loosely divided into episodic and semantic memory; people with SDAT have deficits in both. One of the first and most promi- nent symptoms of AD is a deficit in new declarative learn- ing (sometimes termed anterograde amnesia to differenti- ate it from retrograde amnesia [deficit in remote recall]). On neuropsychological testing, patients with SDAT in the mild to moderate stages of the disease typically show marked impairment on both verbal and visual learning tasks, although the progression may begin with one area being of greater deficit. Performance on list learning over trials usually does not progress much beyond an immedi- ate memory span length. That is, if a person has a mem- ory span of four or five items, five attempts to learn a nine-word list often reveals a flat learning curve begin- ning with recall of four to five items and ending with re- call of four to five items. Verbal recall of stories and word lists shows a large number of perseveration and intrusion errors (among others, see Butters et al., 1988). For exam- ple, the person may repeat words from the same list as if recalling them for the first time or may recall one aspect of a design that is presented, such as a dot in a box as five or six dots in a box. The person may recall specific events or stimuli across situations, intruding elements from one story into another story or remembering elements of one design as part of another. Although all people with classi- cal amnesia show profound difficulties in new learning, this repeating and confusion of memory differs from most other amnestic dysfunctions that the corticolimbic circuit causes. Intrusions and perseverations are most common in two conditions, AD and Korsakoff ’s amnesia, which also involve similar patterns of frontal lobe involvement. Butters (for example, see Butters et al., 1988) hypothe- sizes that the similar pattern of intrusion and persevera- tion errors in SDAT and alcoholic Korsakoff ’s amnesia may be caused by a significant loss of cholinergic neurons in the basal forebrain area.

Although many healthy elderly people may forget, they can often remember lost thoughts with the help of retrieval cues. This facilitation of memory by retrieval cues also characterizes Huntington’s disease, but the memory problem in AD is more global and profound. People with AD show impairment in encoding, consolidation, and re- trieval. The constellation of memory deficits in AD greatly hinders retrieval because it depends on proper en- coding, organization, and consolidation of material to be remembered. Thus, retrieval cues will not aid AD pa- tients’ recall of information, suggesting that encoding and

consolidation have not occurred. Besides that patients with SDAT show flat learning curves (demonstrating lit- tle to no ability to profit from practice), any information that the patient may have remembered immediately after presentation quickly disappears. As the disease progresses, information is lost faster and faster. Although many peo- ple benefit from practice over days and weeks, patients with SDAT do not appear to show this consolidation of declarative learning.

Breakdown of Semantic Knowledge—People afflicted with AD have another fundamental problem of memory, which pervades the entire organization of knowledge. As dis- cussed earlier in this book, the brain stores information at the site where it was first processed. That is, most visu- ospatial information is stored in the posterior areas of the cortex, primarily the parietal and posterior temporal lobes. Auditory information is stored in the temporal lobes, and so on. The dominant theory of memory con- solidation, simply put, is that the hippocampus, which has afferent and efferent projections to most areas of the cortex receives to-be-remembered information, codes it for storage, and sends it back to the original processing site (Squire, 1987). Researchers believe memory for infor- mation and facts is not stored as separate and complete units (for example, all information about robins stored in one node). Rather, they hypothesize that the brain con- tains associations of meaning, “semantic networks,” whose individual nodes may contain pieces of informa- tion or attributes, such as “bird,” “wings,” “small,” and “red breast,” which when activated as a pattern lead to the recognition of “robin.”

Most amnestic patients, although they cannot encode new information, have an intact semantic organizational network for information. In AD, the memory disorder is much more pervasive, involving a progressive disintegra- tion of this associational network, eventually even for old learned information. The evidence for this loss of knowl- edge through semantic degradation rests on several find- ings. First, neuropsychologists noticed that patients with AD do not organize new information semantically as they are attempting to learn it. Thus, if presented with word lists that have inherent semantic categories, such as fruits, vegetables, and items of clothing, most people learn and recall information within semantic categories, clustering the information together. This “semantic clustering” is deficient or nonexistent among patients with AD, who instead show a serial ordering or primacy/recency effect. Second, patients with AD appear to lose conceptual knowledge. Fluency tasks often reveal an interesting pattern. Asked to name as many animals as possible in

CHAPTER 14 | Normal Aging and Dementia: Alzheimer’s Disease 415

60 seconds, people with AD often can retrieve superordi- nate and high-frequency category exemplars such as cat or bird, but show difficulty retrieving subordinate cate- gory exemplars such as leopard or robin. This degrada- tion appears to be more than just a problem in retrieving semantic information from long-term memory. This degradation has been shown to be consistent across tasks, so that the patient may also have difficulty in defining “robin” or naming a picture of a robin (Hodges, Salmon, & Butters, 1991). These difficulties represent neu- ropathologic changes of higher order intermodal associa- tion cortices strongly involved in semantic networking (for example, posterotemporal, inferior parietal), rather than classical language problems associated with the frontal operculum (Broca’s area), superior temporal gyrus, or supramarginal gyrus. As the disease progresses, these connected memories or knowledge structures appear to break down to such a degree that even the identity and association of family members eventually become con- fused in the patient’s mind.

In this discussion of memory in AD, we have focused primarily on the encoding, storage, and retrieval processes of declarative long-term memory. These are undoubtedly the areas of the most recognizable and profound memory difficulty. Two areas of memory that appear less affected by AD are short-term memory span and nondeclarative long-term memory.

Relatively Spared Memor y Systems—On short-term memory tasks such as length of digit span forward, patients with AD perform relatively well in the early stages of the dis- ease. In later stages, short-term memory retention declines. However, if the examiner looks closely at short-term mem- ory capacity, or WM, it is typically compromised.

Patients with AD perform relatively well on some non- declarative memory tasks. Separate nondeclarative mem- ory systems exist outside of the subcortical limbic system. The workings of these systems for the most part appear implicit, or outside consciousness. Learning skills with a large motor and practice component, such as riding a bike or typing, or learning psychomotor tests, such as pursuit rotor or mirror tracing, appear to be part of a motor skills learning system. It is not yet clear whether other systems controlling classically conditioned re- sponses and priming represent yet other nondeclarative memory networks, or if they are subcomponents of a single nondeclarative network.

People with AD show normal performance on some nondeclarative tasks and impairment on others. Soliveri (Soliveri, Brown, Jahanshahi, & Marsden, 1992) describes the pattern of nondeclarative memory performance in

various neurologically impaired groups. Most people with AD perform well on motor learning tasks that researchers think represent an unimpaired striatal system. However, the picture is different with priming tasks. The method- ology of priming, discussed in Chapter 9 with the discus- sion of memory, assumes that previous exposure to an item will facilitate its future processing. Word stem com- pletion priming tasks typically first present a list of words, such as there, church, and leaf. Later, they present three- letter stems such as the___, chu___ and lea__. Typically amnestics—even though they have not been able to demonstrate learning of the words through declarative means, namely, spontaneous recall—are likely to produce the targeted words on word stem completion tasks. Peo- ple with AD usually cannot perform these tasks well. In- terestingly, on perceptual priming tasks that present com- plete and incomplete figures, patients with AD appear to perform better in some instances. Because of this pattern, researchers suggest that patients with AD confront a spe- cific difficulty in implicit verbal priming whereas main- taining nondeclarative learning abilities in perceptual priming and in attaining motor skills. Why would this be so? Verbal implicit priming tasks are probably another pointer to the AD breakdown of the semantic network. Motor skill learning is intact because it is controlled by the striatum, which is relatively unaffected in AD. Per- ceptual priming appears to point to a relatively more in- tact visual object recognition system, which may not be affected until late in the disease process.

L a n g u a g e / S p e e c h

Patients with AD do show language problems, but these cannot be neatly characterized with other classic aphasias. In fact, the aphasia progressively worsens both in degree and type. Early in the disease process, AD patients show an anomic aphasia, characterized chiefly by word-finding and naming difficulties (Cummings, Benson, Hill, & Read, 1985). A confrontation naming test (such as the Boston Naming Test), in which the person must retrieve the exact name of an item from line drawings, often re- sults in semantic and circumlocution (talking around) er- rors. A patient with AD is more likely to say “tool” for “hammer” or “some type of musical instrument” for “har- monica,” indicating that he or she recognizes the seman- tic category but can retrieve only the general category or the wrong exemplar from the same category (for example, see Hodges, Salmon, & Butters, 1991). This type of anomia, together with the difficulty in semantic fluency tasks discussed earlier, suggests a semantic anomic apha- sia. As the dementia progresses, language problems be- come more profound. Comprehension problems begin to

416 PART THREE | Disorders of the Brain

appear, followed by problems in repeating information, and last, declines in fluent conversational output may ap- pear that resemble a global aphasia (Zec, 1993; Cummings et al., 1985).

V i s u o s p a t i a l F u n c t i o n i n g

Visuospatial problems crop up by the middle stages of AD, if not before. Mr. T, a 70-year-old retired salesman and a patient of ours, came in for neuropsychological eval- uation at the request of his wife and neurologist. When they moved to a new retirement community in Florida, Mr. T’s wife noticed a change. He started getting lost while driving in the neighborhood, sometimes ending up at the other end of town; embarrassed and angry, he would have to call his wife. Even though they had been there for nearly a month, he kept losing his way and blamed it on that “all those tract houses built in the 60s look alike.” Accompanied by his wife, Mr. T could follow the correct route; however, Mrs. T was a bit nervous about riding with her husband. She reported he had a tendency to drift to the left, and on several occasions she had to shout at him to avoid hitting another car. What was most disconcerting to Mrs. T, however, was that Mr. T seemed disoriented in his own home, often heading out to the kitchen to use the bathroom.

The problems Mr. T is showing demonstrate two things. First, he has marked visuospatial impairments in his daily life. Most obviously, he cannot orient himself in his environment, either in the neighborhood or at home. He does not have good spatial sense when he is driving. He veers to the left and appears to have lost his “inner compass.” Second, moving to a new residence may un- mask a condition that was not evident in a more familiar environment. Mr. T did not have a stroke or some other neurologic event that occurred suddenly. His wife dis- covered his spatial problems when they moved. Although Mr. T would still have been able to function in his old home, as his dementia progressed, it would have been only a matter of time before he was getting lost in his old, familiar neighborhood and becoming disoriented in his home of 15 years.

On neuropsychological examination, patients with AD usually show poor performance on a number of visuospa- tial measures. As in the other functional domains, the de- gree of impairment corresponds to the stage of dementia. Tests of line orientation (for example, the Benton Judgment of Line Orientation Test), spatial construction tasks (such as the WAIS-R Block Design), copying (such as the Rey–Osterreith Complex Figure Test, Bender Gestalt), drawing (such as the Clock Drawing Test), and visual in- tegration (such as the Hooper Visual Organization Test)

are the most likely to be affected (for review, see Zec, 1993). Complex tasks such as the Rey–Osterreith appear more sensitive to impairment in the early stages of the dis- ease than are simple drawing tasks. Figure 14.8 shows drawing performance in a patient with autopsy-confirmed AD. The patient made these drawings in the early stages of the disease. The more complex Rey figure is somewhat impaired even on the copy. As the dementia progresses, copying designs also becomes distorted.

G e n e r a l I n t e l l e c t u a l F u n c t i o n i n g

Experts often say that AD, like other dementias, results in a “decline in general cognitive functioning.” However, as noted earlier, all functions do not decline at the same rate; thus, it is more useful to consider the subcomponents of measures of global intellectual functioning. We focus here on verbally mediated tasks of abstract reasoning, judgment, crystallized intelligence, and speed of cognitive processing.

The ability to abstract a higher order construct is often impaired in even mild SDAT (Zec, 1993). Verbally, the patient may be unable to say how two objects or concepts are alike, such as a phone and a radio (for example, on the WAIS-R Similarities Test). Visually, the person may be unable to state a common principle that relates multiple figures (for example, on the Category Test or the Ravens Progressive Matrices). This deficit is a problem in concep- tualization and abstract reasoning. Thus, people with AD do poorly on a number of tasks that require reasoning and problem solving.

CHAPTER 14 | Normal Aging and Dementia: Alzheimer’s Disease 417

Figure 14.8 Drawing and memory performance on a modified Rey–Osterreith figure drawn by a patient with Alzheimer’s disease (AD) and a normal elderly adult: (a) AD copy, (b) AD immediate recall, (c) normal control copy, and (d) normal control immediate recall. (Courtesy David Libon, Ph.D.)

Crystallized intelligence (see earlier discussion) refers to accumulated knowledge over the life span. Often, neu- ropsychologists measure this via tests of vocabulary knowledge (for example, WAIS-R Vocabulary) or over- learned information. For example, someone who has lived in the United States for several years should know in what month Memorial Day falls. However, few formal tests measure specific areas of expertise that may accumulate from a person’s line of employment. This knowledge store is one of the few areas that remain preserved until the later stages of the disease.

Although patients with SDAT are slower on speeded complex tasks (for review, see Zec, 1993), they do not ex- hibit the bradyphrenia, or extremely slow information processing speed characteristic of patients with subcorti- cal dementias.

E x e c u t i v e F u n c t i o n i n g

Although deficits are subtle early on, difficulties in execu- tive control are evident to caregivers. For example, in an at- tempt to compensate for memory loss, a person may keep notes. But without an adequate executive strategy, increased disorganization may show up in notes found in various places around the house and in tasks started but left un- finished. Family members often notice perseveration of thought because the person tells stories over and over or asks questions repeatedly. The person may be less flexible than before. Many apparent “personality” changes may actually stem from frontal impairment. Repeated behaviors, such as checking and rechecking, may emerge from the combined effect of a poor memory and increased perseveration.

An interesting aspect of dysfunctional executive ability is that many patients with AD appear to lose metacogni- tive awareness, or the inability to self-monitor their own behavior and performance. Many clinicians describe pa- tients with AD as having little insight into their own deficits. Often, they appear generally unaware or uncon- cerned about the magnitude or consequences of their deficits. Is this psychological response understandable as a defense mechanism against the devastating effects of the disease? Not in the typical sense. Many patients with AD appear truly unaware of their difficulties, and consistently overestimate their abilities to accomplish things.

Problems in the ability to organize, plan, and use ap- propriate strategies for problem solving in patients with AD often appear on tests designed for evaluating strategic processing (such as Tower of London or Tower of Hanoi) and qualitatively on tests designed for other purposes such as visuospatial problem solving (such as the Block Design Test of WAIS-R). Intrusions and perseverations often show up on memory tests. Perseveration is evident as an

418 PART THREE | Disorders of the Brain

inability to shift sets on tests that require flexible problem solving (for example, Wisconsin Card Sorting Test or Trails Making Test B).

O r i e n t a t i o n , A t t e n t i o n , a n d L e v e l o f C o n s c i o u s n e s s

AD is not an altered state of consciousness, such as delir- ium. General orientation and selective attention persist until late in the course of the disease. However, more complex forms of attention such as divided and alternat- ing attention decline from the early stages. Orientation for person, time, and place is generally intact until the moderate to severe stages of AD.

M o t o r a n d S e n s o r y F u n c t i o n

In relation to other areas of functioning, motor and sen- sory abilities are relatively preserved throughout the course of AD. Simple motor speed and strength persist until late in the course of the dementia. However, more complex motor behavior, which may involve coordina- tion or skilled movement, declines earlier.

The disease process appears to spare sensory function- ing—that is, visual, auditory, and tactile acuity. Olfaction is the only primary sensory area affected; sense of smell is compromised even in the mild stages of the disease (Jones & Richardson, 1990). Many patients with AD report vi- sual disturbances such as difficulty in reading, interpret- ing pictures, and recognizing familiar people. Although ophthalmologists often find good acuity and full visual fields, neuropsychological testing often reveals visual- perceptual and visuospatial deficits, which may cause the self-reported visual disturbances.

M o o d , E m o t i o n , P e r s o n a l i t y , a n d I n s i g h t

As with Alzheimer’s (1907, 1987) famous patient, clini- cians may first refer people for psychiatric symptoms. In some cases, these symptoms stem from the cognitive diffi- culties that accompany AD, but in other cases, the symp- toms, such as depression, may represent an additional dis- order. Suspiciousness of others and frank paranoid delusions can manifest memory dysfunction. One 70- year-old woman tearfully related that her husband had begun accusing her of stealing his glasses and other per- sonal items. After 50 years of marriage, he also accused her of having an affair. On questioning, it became apparent that he was accusing her of taking things he was misplac- ing. Because of his impaired time estimation, not uncom- mon in AD, 5 minutes could seem like an hour, or an hour like 5 minutes. So when she went to the grocery store on a quick errand, it seemed like an eternity to him.

He had little insight into his memory difficulties, and in trying to make sense of a frustrating situation, he exter- nalized the problem and blamed his wife.

Symptoms that herald a significant about-face in per- sonality usually raise a red flag for family members. Such patients are most likely to be seen by mental health pro- fessionals. However, psychiatric symptoms that are exacer- bations of premorbid personality styles make recognizing change extremely difficult. A woman always considered impulsive and distractible, flighty or disorganized, may at first appear simply eccentric when she begins to lose track of daily memories. When attempting to deal with mem- ory loss, the person is likely to carry on with coping styles and defense mechanisms characteristic of earlier times. As memory becomes less reliable, a person concerned with order, timeliness, or organization may obsessively check dates, doctor’s appointments, medications, memos, and lists.

Depression and Dementia—A common problem in making a differential diagnosis of behavioral disturbances among the elderly is to distinguish psychological depression from global loss of intellectual function. The most effective way to make these diagnostic determinations is to obtain for- mal psychometric testing from a neuropsychologist, who can describe the patient’s cognitive functioning in detail, recognize normal and abnormal patterns of performance, and establish a baseline of performance against which to measure any changes over time. In addition, more subjec- tive guidelines may include the depressed patient’s ten- dency to exaggerate memory problems when compared with the demented patient’s tendency to deny or mini- mize them. It is important to query for information re- garding any situational/environmental life crisis that might have precipitated a depressive reaction, but that would not be expected to trigger a dementia process. Be- cause some elderly patients are heavily medicated, it is also important to review all prescriptions to determine whether any, alone or in combination, interfere with op- timal cognitive functioning. Of course, depression may also coexist with a cognitive disorder. Approximately 40% of people with AD may also suffer from depression or symptoms of depression, although major depressive episodes are relatively rare (Cummings, 1994).

A common differential diagnostic issue with which consulting neuropsychologists deal is the referral to dis- tinguish between depression and dementia in elderly pa- tients. Following is a possible scenario:

When asked about her husband’s behavior during an initial interview, Mrs. S related that her husband no longer appears interested in his daily activities and hobbies.

CHAPTER 14 | Normal Aging and Dementia: Alzheimer’s Disease 419

He used to tinker with their cars and had a hobby of building wooden clocks. He has gradually given both of these up over the past year and a half and says he is no longer interested in them. He spends much more of his day sleeping than he used to, although he is up a lot at night. He has also lost weight and doesn’t seem to have a strong interest in eating. In fact, says his wife, Mr. S does- n’t seem to have a strong interest in anything. “If it wasn’t for me,” she says, “he’d probably spend his whole day sit- ting in his chair. I try to give him things to do, like cross- word puzzles or little things to fix, but when I come back, he hasn’t gotten anywhere. We don’t see our friends any- more because he just doesn’t seem to have much to say.” Mr. S agreed that he had given up most of his former hob- bies, saying he just wasn’t interested in them anymore, al- though he wasn’t sure why. He didn’t admit to feeling par- ticularly sad or discouraged about these or any other events. Largely, he appeared to be apathetic, not particularly moved in any direction either to be excited and motivated to ac- complish things, or to be despondent about his situation. Although he didn’t seem to display internal motivation, Mrs. S did say that her husband would accompany her on outings when she planned them. Recently, they had gone to New England on a four-day chartered bus trip with members of their church. Mr. S went along on all the ac- tivities and did not spend time sleeping during the day.

At first glance, Mr. S appears to suffer from symptoms suggestive of depression: He has lost interest in previously enjoyable hobbies and activities, and his eating and sleep- ing habits have changed. Curiously, however, he does not admit to depressed mood or show other subjective or af- fective signs of depression. He also will become involved in some activities. At this point, three possibilities need to be considered: (1) Mr. S may have primary depression, (2) a dementing process may explain Mr. S’s depressive symptoms, or (3) Mr. S may have both progressive de- mentia and depression. Further discussion of depressive symptoms and testing for depression may show motiva- tional and affective difficulties, perhaps a reaction to a more sedentary lifestyle after retirement, or problems re- lated to his current life situation over the past several years. Chronic medical problems, if they exist, are likely to result in decreased energy, a loss of vitality, and de- pressed mood. However, it is also possible that these symptoms may be largely explained by dementia. Mr. S may have given up former hobbies such as clock building because he no longer has adequate visuospatial functioning or the organizational and planning abilities to successfully approach novel or complex problems. He also may suffer from “cognitive inertia.” If this is the case, what appears to be poor motivation may be an inability to structure

and organize in such a manner as to accomplish tasks. Al- though at first only complex projects may be affected, later in the disease, even straightforward tasks such as washing dishes or taking out the garbage may be difficult to begin, because the affected person does not know where to start. Other possibilities to consider, consistent with AD, are that he may have little insight into his diffi- culties and thus may appear vague and somewhat de- tached when speaking about himself. Certainly, further interviewing and testing concerning memory and other cognitive problems are warranted. The primary objective here is not to differentiate between dementia and depres- sion based on a brief description of Mr. S’s difficulties. Rather, the point is to consider that, especially when psy- chiatric symptoms present themselves for the first time in older patients, these may signal underlying cognitive problems. Although changes in personality and mood occur with some frequency in AD, they are not necessary or particular to this disease.

Treatment

No currently available treatments can reverse, halt, or slow the progression of AD. We simply do not yet know enough about the neurophysiology and causes of the disease to develop medical treatments tailored to at- tack the underlying mechanisms. What, then, does treat- ment focus on? First, there is a big push for psychophar- macologic investigators to develop drugs that will enhance cognitive functioning. Many drugs are in the experimen- tal stages, and a few have made it to market. Most target the cholinergic system, and therefore memory. Second, both pharmacologic and behavioral interventions are aimed at ameliorating psychiatric symptoms and excess disability (that is, additional cognitive and psychiatric im- pairment not directly attributable to the disease). With each of these treatments, the goal is to improve quality of life for both the AD sufferers and their caregivers. This section provides an overview of psychopharmacologic and behavioral approaches to intervention.

T R E A T M E N T S F O R C O G N I T I V E E N H A N C E M E N T

As discussed earlier, ACh is the neurotransmitter system that holds the most promising physiological link to AD. Many drugs that target the cholinergic system seek to increase its production or action and, therefore, to com- pensate for the impaired cholinergic production in the basal forebrain, including the nucleus basalis. Researchers have tried varied approaches to augment levels of brain

ACh. One approach is to increase the availability of ACh precursors such as choline. Because large quantities of choline are found in lecithin, a substance contained in foods such as egg whites and chocolate, researchers once thought that by increasing dietary choline, they might also elevate brain levels of ACh. However, no clear im- provements in memory have materialized from this or other approaches. Other pharmacologic approaches have attempted to target the synaptic transmission itself. One method increases ACh by blocking its breakdown by in- hibiting acetylcholinesterase. Other methods strive to di- rectly increase the output of ACh or stimulate the post- synaptic cholinergic (muscarinic) receptors to increase firing. Physostigmine (Synapton) was one of the first cholinergic augmenting drugs that clinical trials tested with AD patients in the mid-1980s. Although some studies sug- gested improvement, this gain appeared minimal in light of overall declining functioning. But there is some indica- tion that longer term use may result in more gain (for re- view, see Ashford & Zec, 1993). In the mid-1990s, tacrine (Cognex), which is a long-acting acetylcholinesterase in- hibitor, received a flurry of attention. It appeared to show some positive effects, but also resulted in a side effect of liver toxicity. To date, no fewer than 10 drugs have been designed specifically to enhance cholinergic activity in the brain. At this point, however, the search is still on to find the right combination of noticeable memory enhancement coupled with tolerable side effects.

Alternative experimental approaches aimed at under- standing the pathophysiology of AD hold the promise of future therapeutic benefit. Nerve growth factor (NGF) is a method being researched to increase cholinergic neuronal functioning. NGF is part of a family of neurotrophins, or neuron-feeding nutrients, that researchers have long known sustain neural viability in the autonomic nervous system. The cholinergic system neurons in the basal fore- brain also have specific receptors for NGF. In animals, an- tibodies to NGF result in neuronal shriveling and death. Also in animals, introducing NGF appears to increase ACh functioning and learning and memory behavior in those with lesioned brains. NGF may prove therapeutic in AD if it can sustain life and promote growth of surviving cholinergic neurons. Methods suggested include intraven- tricular infusion of NGF through a pump (Olson, 1990), attachment of NGF to a gene that can specifically target the ACh system through a retrovirus, and direct neural im- plants of tissue with active NGF (Dunnet, 1991).

A pharmacologic treatment to halt or reverse the mem- ory and cognitive loss suffered in AD is likely to emerge as our understanding of the underlying pathophysiol- ogy develops. Probably this will involve a multifaceted

420 PART THREE | Disorders of the Brain

CHAPTER 14 | Normal Aging and Dementia: Alzheimer’s Disease 421

approach to treatment, because large areas of the brain are affected. The treatments reviewed here primarily tar- get the most common and prominent symptom of new learning. A truly effective solution will have to conquer the pervasive cognitive decline.

C O G N I T I V E , B E H A V I O R A L , A N D P S Y C H I A T R I C S Y M P T O M C O N T R O L

The other avenue of treatment for AD aims at symptom control. Behavioral, psychiatric, and cognitive difficulties can emerge either associated with the progression of the disease itself or attributable to processes above and be- yond those symptoms that can be explained by the dis- ease itself—a condition termed excess disability. Attempts to manage these symptoms use either pharmacologic or behavioral tools.

Common behavioral and affective symptoms associ- ated with dementia include depression, insomnia, perse- cutory ideation, hallucinations, apathy, agitation, irritabil- ity, and purposeless or inappropriate activity patterns. Minor tranquilizers or antidepressants may aid depression and insomnia, but pharmacologic treatment of psychotic symptoms such as delusions or hallucinations may cause serious unwanted side effects. Neuroleptics may further

impair cognition, increase agitation, and cause other un- wanted motor symptoms.

Patients with AD are also susceptible to illness and conditions associated with aging such as respiratory or urinary tract infections and hearing and vision problems. The associated behavioral problems associated with this “excess disability” can include decreased or increased ac- tivity levels, delirium, or hallucinations. In the case of ill- ness, when the condition resolves the behavioral problem likewise should subside. Visual or hearing problems may also amplify hallucinations or sensory illusions.

Because of the severe memory deficit, behavioral man- agement strategies based on learning and responding to reinforcement paradigms can easily prove futile. Instead, most management strategies seek to restructure the envi- ronment to ensure safety, provide appropriate stimula- tion, and redirect inappropriate behavior. As the disease progresses, the person needs more constant supervision. Many nursing homes have specially designated Alzheimer’s units because of the difficulties of behavioral manage- ment. If a patient is living at home, the burden on care- givers can be enormous. Respite care in the form of de- mentia “day care” programs serves the purpose of providing appropriate activity and behavioral management, as well as a needed break for caregivers.

Summary Psychological studies of the elderly have established that aging itself does not necessarily cause dementia. Instead, aging produces predictable changes in patterns of abilities in crystallized and fluid intelligence. Healthy and active individuals in their 60s, 70s, and 80s do not necessarily differ substantially from their past level of functioning in the level of their crystallized cognitive skills or abilities. Relatively stable skills include well-learned verbal abilities such as reading, writing, and speaking; simple arithmetic ability; and immediate and long-term memory. In contrast, fluid intelligence, including short-term memory, abstract and novel problem solving, and behavioral slowing are examples of types of functioning that normal aging may compromise. Health care costs, the aging of the U.S. population, and a renewed concern for well-being of older people have hastened inquiries and interest in this area. Although elderly people are at high risk for diseases that impair cognitive functioning (such as AD), cognitive impairment is potentially reversible in 5% to 20% of dementia cases (for example, in nutritional deficiencies). An understanding of precise neuropsy- chological deficits can improve the medical management even of patients with irreversible dementia. Neu- ropsychologists play an important role in comprehensive medical, functional, psychosocial, and neuropsy- chological assessment. Assessment of mental status and cognitive abilities yields valuable information about prognosis, and it is important in monitoring a patient’s health or illness and helping the patient make further life plans (Zillmer & Passuth, 1989; Zillmer, Fowler, Gutnick, & Becker, 1990).

C r i t i c a l T h i n k i n g Q u e s t i o n s

Will exercising one’s mind help ward off dementia? Must one “use it or lose it”? How is Alzheimer’s disease best identified in life? How can a neuropsychological profile aid dementia sufferers and their families? How does the concept of self of the patient with Alzheimer’s disease change with the progression of the disease?

Dementia Crystallized intelligence Fluid intelligence Neurofibrillary tangles Senile plaques

Atrophy Mild cognitive impairment

(MCI) Cortical dementia Subcortical dementia

Multiple infarcts (multi-infarct dementia)

Delirium Alzheimer’s disease (AD) Beta-amyloid ( -amyloid)

Acetylcholine (ACh) Bradyphrenia Metacognitive

awareness Neurotrophins

K e y Te r m s

422 PART THREE | Disorders of the Brain

We b C o n n e c t i o n s

http://www.mc.uky.edu/nunnet Official site of the “Nun Study,” a longitudinal study of aging and AD funded by the National Institute on Aging.

http://www.agelessdesign.com Ageless Design: Smarter, Safer Living for Seniors—Site of the first organization to dedicate its resources, imagination, and heart to creating smarter, safer living for seniors. By recommending logical, cost-effective home modifications, unique ideas, and products, homes can accommodate those dealing with age-related conditions and embrace the special needs of people as they age.

http://www.un.org/esa/socdev/ageing The United Nations Program on aging around the world.

http://www.alzforum.org Alzheimer’s Forum—a nonprofit foundation that has established this site to serve the scientific and clinical research community.

http://www.informatik.fh-luebeck.de/icd/icdchVF-D-Index.html ICD-10 Codes for Dementing Disorders—provides a classification system (the ICD-10) of mental and physical disorders used by the World Health Organization. This site includes a brief description and diagnostic crite- ria for most major brain diseases.

http://pni.med.jhu.edu Johns Hopkins University Division of Psychiatric Neuro-Imaging—these pages describe quantitative brain analyses of neuropsychiatric disorders such as AD, using MRI, functional MRI, and SPECT imaging.

http://dementia.ion.ucl.ac.uk Dementia Web—site is based at the National Hospital for Neurology and is supported by The Institute of Neurology and the Division Imperial College School of Medicine. This site provides updates on dementia research, a virtual chat room, a dementia support group, and other links.

http://www.neurologychannel.com/dementia Neurology Channel—has information about dementia and other neurologic disorders.

http://www.mentalhealth.com/dis/p20-or05.html Internet Mental Health: Dementia—provides diagnosis, treatment, and research reports for caregivers and specialists.

http://tv.cbc.ca/national/pgminfo/memory/index.html The National Online: In Search of Memory—provides information on three forms of memory: semantic, procedural, and episodic memory. It relates these memory forms to different dementia disorders.

http://www.mc.uky.edu

http://www.agelessdesign.com

http://www.un.org

http://www.alzforum.org

http://www.informatik.fh-luebeck.de

http://pni.med.jhu.edu

http://dementia.ion.ucl.ac.uk

http://www.neurologychannel.com

http://www.mentalhealth.com

http://tv.cbc.ca

Chapter 15

S U B C O RT I C A L D E M E N T I A S

Age is not determined by years, but by trouble and infirmities of mind and body.

—Mark Twain

Parkinson’s Disease Huntington’s Disease Creutzfeldt–Jakob Disease

Neuropsychology in Action

15.1 Understanding Subcortical Dementia 15.2 Pallidotomy Surgery: A Case Report 15.3 Testing Fate: Would You Want to Know If You

Were Going to Get Huntington’s Disease? 15.4 Creutzfeldt–Jakob Disease and Mad Cow

Disease: What’s the Connection? 15.5 The Neurologic Examination for Dementia

Checkoway & Nelson, 1999). PD rarely occurs before age 40, and the public case of actor Michael J. Fox, who developed PD at age 29, is highly unusual. PD appears more common in men than women, although no differ- ences in risk factors have been identified. Dementia in PD, however, does appear to be age related. Between 24% and 31% of those with PD meet the criteria for dementia (for review, see Aarsland, Zaccai, & Brayne, 2005). How- ever, only about 12% of patients with PD who are in their 50s have dementia, compared with about 70% of those older than 80 (Mayeux et al., 1992). Younger patients with PD are likely to function well, but dementia is more likely with increased age and disease severity. People most likely to have dementia appear to be those who have ei- ther had the disease for a longer period or are older at the time of diagnosis (Kay, 1995).

N E U R O P A T H O L O G Y O F P A R K I N S O N ’ S D I S E A S E

PD is marked by a degeneration of dopaminergic cells and pigmentation in the substantia nigra (black substance) (Figure 15.2). It is also characterized by Lewy bodies, which are small, tightly packed granular structures with

424 PART THREE | Disorders of the Brain

K e e p i n M i n d

How do the cortical and subcortical dementias differ from each other?

How do behavioral motor presentations differ among subcortical disorders?

What are the symptoms and progression of Huntington’s and Parkinson’s diseases?

How is Creutzfeldt–Jakob disease acquired?

Overview Subcortical dementias are so named because, although these conditions often affect cortical areas and functioning, the structures that are prominently damaged are subcortical. Parkinson’s disease (PD) and Huntington’s disease (HD) attack the basal ganglia; PD targets the substantia nigra, and HD targets the caudate nucleus. Creutzfeldt–Jakob disease (CJD) affects yet another noncortical structure, the cerebellum. The common behavioral feature characterizing these and most subcortical dementias is slowed cognitive and motor dysfunction (Neuropsychology in Action 15.1: Understanding Subcortical Dementia). What is interesting is the manner in which each disease affects the motor system in a different way. You can truly appreciate the complexities of the motor system by examining these diseases. Motor problems present great physical limitations and hardship. These dementias, however, do not represent only motor system dysfunction. The dementias we present in this chapter are progressive and involve multiple functional sys- tems. We present PD in greater detail than the other disorders because it is more common, and these patients are more likely to be seen by clinical neuropsychologists.

Parkinson’s Disease

Parkinson’s disease (PD) is a slowly progressive disease of the dopaminergic system that, like Alzheimer’s disease (AD), largely affects older adults. Later stages of the disease are associated with dementia. PD, or idio- pathic parkinsonism as it is also known, is the most com- mon manifestation of parkinsonism. Parkinsonism, like dementia, does not refer to a particular disease, but rather to a behavioral syndrome marked by the motor symptoms of tremor, rigidity, and slowness of movement. This clus- ter of motor symptoms may be caused by PD but also by drugs, encephalitis, toxins such as carbon monoxide and manganese, and injury. Mohammed Ali, the famous boxer, experienced parkinsonian symptoms (called dementia pugilistica) after repeated blows to the head (Figure 15.1). Parkinsonism occurring in the absence of PD can be a sta- tic condition. Although the cause of PD is unknown, and the disease is therefore called idiopathic, it is known to se- lectively affect the substantia nigra and the dopaminergic systems of the brain.

PD affects an estimated 1% of the population of the United States that is older than 50 years, with the incidence of new cases increasing with age (Bennett et al., 1999;

CHAPTER 15 | Subcortical Dementias 425

ringlike filaments found within dying cells. Although neurodegeneration and Lewy bodies are pathognomonic markers in cells of the substantia nigra, patients with PD may also have concentrations of them in other pigmented subcortical areas such as the locus ceruleus or unpigmented areas such as the nucleus basalis of Meynert, hypothalamus, cerebral cortex, cranial nerve motor nuclei, and compo- nents of the autonomic nervous system (for review, see Olanow & Tatton, 1999). Although the pattern of con- centration of Lewy bodies in the substantia nigra indi- cates PD, the presence of Lewy bodies in the brain is not specific to PD. They may also appear in normally aging people, individuals with AD, and those with other pro- gressive neurodegenerative conditions. This leads to spec- ulation that Lewy bodies are either (1) indicators of a gen- eral disease process or (2) markers of cell death.

The darkly pigmented, or melanized, substantia nigra is a midbrain structure that is part of a group of subcor- tical structures that collectively make up the basal gan- glia. The basal ganglia, which reciprocally connect to the premotor cortex and the supplementary motor areas via the thalamus, largely function to control the fluidity of over- learned and “semiautomatic” motor programs (Bradshaw & Mattingly, 1995). The loss of dopamine from the sub- stantia nigra is directly related to the problems of move-

ment initiation and motor rigidity in PD (Bradshaw & Mattingly, 1995). Aging itself takes a toll on the dopamine system, and some cell loss is expected. But the dopaminergic degeneration in PD is several times that of normal aging. Perhaps the reason that noticeable parkinsonian symptoms do not appear in older adults is because there is a “dopamine threshold,” estimated to be breached at between 50% and 80% cell loss (Bradshaw & Mattingly, 1995), before symptoms appear.

C L I N I C A L P R E S E N T A T I O N A N D N E U R O P S Y C H O L O G I C A L P R O F I L E O F P A R K I N S O N ’ S D I S E A S E

When a physician refers patients with PD to a consult- ing neuropsychologist, the diagnosis has usually been well established from the characteristic resting tremor and allied motor symptoms. In this case, the referral is usually to help determine the presence or extent of cog- nitive decline. However, physicians may refer patients to either a psychotherapist or a neuropsychologist to aid in diagnosis before the “classic” symptoms appear. Unlike stroke, which presents with sudden motor weakness, PD is insidious, slowly sneaking up on its victim. The pa- tient may first sense vague aches and pains and wonder whether arthritis is developing. A general feeling of tired- ness or malaise may come first, which could easily be at- tributed to overwork or “burnout.” Other patients with PD may first report feeling irritable or depressed. These symptoms may be met with assurances, a suggestion to undertake medical tests, or a referral to a psychologist to investigate possible psychosomatic problems or depres- sion. As the disease continues to progress, subtle motor

Figure 15.1 Mohammed Ali, who experienced development of Parkinsonian symptoms from injuries that occurred during his boxing career, lit the flame in the 1996 Summer Olympics. (© AP/Wide World Photos.)

Image not available due to copyright restrictions

symptoms begin to appear. Perhaps the person notices weakness in an arm or leg, including problems in writ- ing, holding a pen, or typing. Voice quality becomes

softer and more monotone, and facial expression appears flat to others. If the symptoms are limited to one side of the body, it may appear that the person has suffered a

426 PART THREE | Disorders of the Brain

Subcortical dementia is a clinical syndrome characterized by slowness of cognitive pro- cessing, executive dysfunction, difficulty retrieving learned information, and abnormali- ties of mood and motivation. The syndrome is produced by disorders affecting frontal- subcortical circuits, including lesions of the striatum, globus pallidus, and thalamus.

Kinnier Wilson (1912), in his original description of Wilson’s disease, recognized the clinical features of subcortical dementia, which von Stockert (1932) described again in the context of discussing postencephalitic Parkinson’s disease (PD). Martin Albert and colleagues (Albert, Feldman, & Willis, 1974) reintroduced the syndrome into clinical neurology in descriptions of the subcortical dementia of progressive supranuclear palsy at Boston University in 1975. Substantial controversy centered on this syndrome when researchers first introduced it. Critics of the concept suggested that most dementia syndromes include both cortical and subcor- tical abnormalities, and that the clinical phenomenology was not distinctive enough to guide differential diagnosis. Subsequent experiences have helped to remold the concept and to account for these criticisms. For example, the subcortical changes in AD in the nucleus basalis of Meynert lead to a cholinergic deficiency that manifests at the cortical level. Thus, although the pathology is subcortical in location, the dysfunction primarily affects the cerebral cortex. Likewise, although there are cortical changes in Hunt- ington’s disease, they are minor compared with the marked subcortical abnormalities, and the mental status changes correlate with the subcortical rather than the cortical abnormalities. Thus, even within these mixed syndromes, it is possible to identify cortical and subcortical patterns of dysfunction.

Researchers have increasingly docu- mented the clinical features of subcor tical dementia (Cummings, 1986). Slowing of cognition stems from the increased central processing time imposed by subcor tical disorders. Patients have prolonged re- sponse latencies and slowed complex reaction times. They show executive dys- function, including difficulty with set shift- ing, as measured by tests such as the Wisconsin Card Sor ting Test or Trails B of the Trail Making Test; reduced verbal flu- ency on tests of word list generation, such as the number of animals that can be named in 1 minute; impoverished motor programming, as measured by tests such as execution of serial hand sequences; and poor abstracting abilities when asked to interpret proverbs or to distinguish among similar concepts. Memory abnormalities are primarily of a retrieval deficit type. Patients store information at nearly normal rates but have difficulty retrieving the information in a timely way. Thus, on tests of recall they perform poorly, but on tests of recognition memory they may perform in the normal range. This recall deficit in- cludes both recent and remote information. Patients with subcor tical dementia show neuropsychiatric and neuropsychological abnormalities. Apathy and depression are par ticularly prominent. Less common are irritability, disinhibition, mania, and psy- chosis. Motor abnormalities also accom- pany most subcor tical dementias when the disease involves striatal structures, the substantia nigra, or globus pallidus. Parkin- sonism and chorea are the predominant motor manifestations in patients with subcor tical dementia.

Recent advances in neuroanatomy con- tribute to neuropsychological understanding

of subcortical dementia syndromes. Five frontal subcortical circuits link regions of the premotor cortex to areas of the striatum, globus pallidus, and thalamus. The dorsolat- eral prefrontal subcortical circuit mediates executive function and projects from dorsolat- eral prefrontal regions to the head of the caudate nucleus, globus pallidus, dorsome- dial thalamus, and back to the prefrontal cortex. The anterior cingulate region in the medial prefrontal region mediates motivated behavior via a frontal subcortical circuit including the nucleus accumbens, globus pallidus, dorsomedial thalamus, and anterior cingulate. An orbitofrontal subcortical circuit mediates the social governance of behavior and includes orbitofrontal cortex, inferior caudate nucleus, globus pallidus, and dorsomedial thalamus. Dysfunction in the lateral prefrontal-subcortical circuit produces executive dysfunction; abnormalities of the anterior cingulate-subcortical circuit result in apathy; and abnormalities of the orbitofrontal-subcortical circuit produce disinhibited, tactless behavior (Cummings, 1993).

Treatment of patients with subcor tical dementia depends on the specific cause of their syndrome. Parkinsonian disorders and PD are treated with levodopa and other dopaminergic agents. The depression syndrome in many patients with subcor tical dementia typically responds to antidepres- sant agents such as selective serotonin reuptake inhibitors. The apathetic syn- drome may respond to dopaminergic agonists or psychostimulants such as methylphenidate. Cognitive dysfunction in patients who have a cholinergic distur- bance, such as those with PD, may respond to cholinergic therapies such as cholinesterase inhibitors.

N e u r o p s y c h o l o g y i n A c t i o n 1 5 . 1

U n d e r s t a n d i n g S u b c o r t i c a l D e m e n t i a

by Jeffrey L. Cummings M.D., Professor of Neurology and Psychiatry, UCLA School of Medicine, Los Angeles, CA

tude. Semiautomatic movements such as walking, arm swinging, blinking, swallowing, and facial expressiveness may appear almost frozen, as if the person is robot-like and must consciously think to move. The description of a patient with PD as having “masked facies”—denoting a masklike face—captures the essence of an emotionless face. The person’s demeanor may seem depressed; a va- cant stare may be produced by the combination of re- duced facial emotion, slow speech, and decreased eye blinking. In addition to slowness, many movements de- cline in magnitude. Patients with PD do not take long steps and swing their arms high in the air, but rather ex- hibit a rapid, small, shuffling, festinating gait. Hand- writing also gets slower and smaller (micrographia), and the voice becomes softer as the ability to project the sound of one’s voice becomes increasingly difficult. Patients with PD also describe difficulty in initiating movement, or hy- pokinesia, and may have to consciously think to begin walking, to turn around, or to lift a fork. During the movement, the person may also freeze and may need to

mild stroke. It is nearly impossible to diagnose PD at this stage because the classic motor symptoms have not yet emerged. It would also be rare to even suspect PD, be- cause these initial symptoms could herald a multitude of different problems.

The cognitive profile of those diagnosed with PD is somewhat heterogeneous depending on the presence of dementia and the stage of the disease. Raskin and col- leagues (Raskin, Borod, & Tweedy, 1990) suggest two possibilities for the occurrence of dementia in patients with PD. First, demented PD patients may represent a qualitatively different subgroup, experiencing a later onset of symptoms and showing more subcortical and frontal atrophy. The second explanation is that this group may differ only in degree, with a more pronounced progres- sion of cognitive decline. Dementia in patients with PD has been contrasted and compared with both AD and Lewy body dementia (LBD). In LBD, Lewy bodies are prominent throughout the cortex and present a pattern similar to that seen in AD. A magnetic resonance imaging (MRI) study comparing patients with PD with and with- out dementia with patients with LBD showed that pa- tients with PD with dementia and patients with LBD had widespread cortical atrophy, but patients with PD with- out frank dementia had atrophy primarily in the frontal lobes (Burton et al., 2004).

This section examines the cognitive profile of non- demented patients with PD. Some authors suggest that the cognitive profile is heterogeneous; that is, there may be several subgroups of PD, possibly pointing to sub- groups of neuropathology (Dubois, Boller, Pillon, & Agid, 1991). Others have also raised questions about lateralization of cognitive deficits. Do cognitive deficits in any way parallel the type and degree of motor symp- tomatology?

Just as memory dysfunction is the hallmark of AD, motor dysfunction is characteristic of PD. Our review of functional systems begins with the clinical presenta- tion and neuropsychological dysfunction of the motor system.

M o t o r S y m p t o m s

The motor symptoms of PD generally fall into groups of positive and negative symptoms (Table 15.1). Positive symptoms indicate an excess of motor behavior, or abnor- mal motor reactivity, whereas negative symptoms indicate a diminution or loss of motor functioning. Some experts believe that negative symptoms may manifest before the positive symptoms, although they may be frequently missed. You can think of bradykinesia as a poverty of movement that is not only slowed but reduced in magni-

CHAPTER 15 | Subcortical Dementias 427

Positive Symptoms

Resting tremor

Rigidity (cogwheel)

Stooped posture

Impaired righting reflex/poor balance

Negative Symptoms

Bradykinesia: slowness of movement

Hypokinesia: reduced motor initiation

Gait disturbance

Slow

Festinating (rapid small steps)

Freezing

Masked facies: reduced facial expression

Slowed speech

Decreased voice amplitude

Ocular disturbances

Decreased blink rate

Decreased light accommodation

Slowed saccades

Table 15.1 Motor Symptoms of Parkinson’s Disease

“will” the action to continue. Ironically, it may also be difficult to stop an action such as walking or writing, which has led to the suggestion that PD results in a fun- damental deficit in initiating and terminating semiauto- matic motor programs (for example, see Bradshaw & Mattingly, 1995).

Despite the debilitating effect of the negative symp- toms of PD, the positive symptoms of PD are perhaps more noticeable, and most people recognize them as the hallmarks of the disease. Chief among these are a resting tremor and rigidity. Resting tremor, as opposed to a cere- bellar intention tremor, is often characterized as “pill rolling.” This rhythmic shaking, often first occurring in one hand or the other, looks as if the person might be rub- bing or rolling a coin or pill between thumb and forefinger. The tremor stops or lessens with voluntary movements such as reaching, swinging the arm, grasping, or manipu- lating objects. When the person is sleeping, the tremor usually disappears.

However, with heightened states of alertness, concen- tration, or nervousness, the tremor is likely to increase. The degree of tremor at any one time is partly due to the voluntary–involuntary nature of the movement, the level of alertness, and the level of stress. It is not always pre- dictable, coming in bursts, but it does increase in speed and may become more violent as the disease progresses. In the early stages of PD, it is not uncommon for the tremor to influence only one side of the body, affecting the hand and foot first and maybe one side of the face. Eventually, it moves to the contralateral side and affects all extremities.

Rigidity, the other major positive symptom, occurs as a tightening of muscles and joints. When a neurologist tries to move the person’s wrist, elbow, or knee, there is persistent resistance to this passive movement. Sometimes this resistance appears as a ratcheting movement, as if the person’s joint were a cogwheel (cogwheel rigidity). Mus- cles may appear tense and feel contracted to touch, even when the person is relaxing. This increasing rigidity may result in the characteristic stooped or hunched posture of PD. In addition to a more rigid posture, poor balance and the inability to adjust posture may be evident. The inabil- ity to catch oneself quickly, or impaired righting reflex, may appear if the person is pushed or missteps.

On neuropsychological testing of the motor system, patients with PD are extremely slow, with poor reaction times. This is certainly evident on basic tasks that may re- quire simple speeded movement, such as finger tapping. Poor motor performance is also evident on many other tasks that have a speeded motor component such as copy- ing geometric designs with blocks within a specified time

limit (such as WAIS-R, Wechsler Adult Intelligence Scale, Revised [WAIS-R] Block Design).

Because PD usually begins as a lateralized motor dis- order, some investigators have speculated that the cogni- tive profile may also show lateralized impairment. Indeed, this may be the case. People with hemiparkinsonism often do show a neuropsychological profile consistent with what would be expected from lateralized cortical damage (Raskin et al., 1990). Exclusively left-sided motor symp- toms link to more right hemisphere deficits. Raskin also suggests that this profile may reflect unilateral damage to basal-cortical pathways, resulting in disconnection, rather than unilateral lesions of the basal ganglia.

Motor symptoms may result in lateralized neuropsycho- logical profiles—but is there a relation between the degree of motor impairment and the severity of cognitive dysfunc- tion? Patients with PD followed for up to 10 years did not show evidence of such correspondence (Portin & Rinne, 1986). Although drugs that targeted the motor symptoms, such as levodopa (L-dopa), had great impact on motor per- formance, they had little effect on cognitive performance.

V i s u o s p a t i a l D e f i c i t s

Of nonmotor, higher cognitive functions, visuospatial deficits in nondemented PD are among the most com- monly reported in the literature and among the most con- troversial. Many studies have found that patients with PD perform poorly on spatial tasks that have a motor compo- nent. This is not surprising because evidence exists for im- pairment on visuospatial tasks regardless of whether there is a motor component (for review, see Raskin et al., 1990). However, enough studies show mixed results, or no im- pairment on visuospatial tasks, to throw the issue of spa- tial impairment into doubt (for review, see Dubois et al., 1991). To what can we attribute this discrepancy? It may be caused, in part, by the heterogeneity of presentation in patients with PD. Different patients may have somewhat different pathology, and thus different clinical presenta- tions. As discussed earlier, those with more left-sided motor impairment may show more right hemisphere damage (visuospatial deficits). Some studies include pa- tients in more advanced stages of the disease. Some pa- tients with PD may have a comorbid dementia. In any case, factors having to do with possible subgroups of pa- tients with PD continue to cloud the picture of visuospa- tial functioning.

In nondemented PD sufferers who have visuospatial dysfunction, does such dysfunction point to parietal im- pairment or some other mechanism? First, patients with PD may report having difficulty orienting themselves in space. For example, when having to walk around the

428 PART THREE | Disorders of the Brain

house in the dark without the aid of visible landmarks or outside in a fog, one person relates, “I used to walk alone in the wood, fog or no fog, but when the symptoms of PD appeared, I noticed that I could not orient myself any more, and in case of fog, I got lost” (Dubois et al., 1991, p. 203). Spatial abilities require the person to visualize the relative position of objects in three-dimensional space, and to make a motor response to orient himself or herself or other objects in that space. Therefore, the visual-spatial- motor aspects link in an overall spatial framework. Disease could theoretically disrupt this network in the parietal lobes or anywhere along the visuomotor system. Some investigators have suggested that the basal ganglia play a role in the visuomotor aspects of visuospatial prob- lems in patients with PD (Danta & Hilton, 1975; Dubois et al., 1991). But what about patients who have visual- perceptive difficulty, but no visuomotor problems? For example, a popular test used by neuropsychologists, Ben- ton’s Judgment of Line Orientation Test (Benton et al., 1983), requires matching drawings of lines in various ori- entations to a template (Figure 15.3). It does not require drawing or movement of the body. Yet, many nondemented PD patients have difficulty with this task (Goldenberg, Wimmer, Auff, & Schnaberth, 1986). One explanation is that any disruption in the visual-spatial-motor circuit may impair performance. Another suggestion is that even in tasks in which a person does not use a motor response, he

or she still has an internal representation of a perceptual- motor response (Villardita, Smirni, LaPira, Zappala, & Nicoletti, 1982).

In summary, although it is not clear whether all pa- tients with PD experience visuospatial dysfunction, a siz- able proportion does. Certain subgroups of patients, or those in more advanced stages of the disease, for example, may show the most difficulty. The parietal lobes per se do not appear chiefly responsible for the problem. Rather, the basal ganglia are implicated in a larger visuospatial network.

E x e c u t i v e F u n c t i o n i n g

Many patients with PD have executive functioning diffi- culties. Difficulties with specific executive functions can be evident, although most do not have difficulty with abstract thinking (Raskin et al., 1990). These deficits show up early in the disease process, and thus appear to result directly from the disease (for review, see Dubois et al., 1991).

Among executive dysfunctions reported in the litera- ture are difficulties with changing mental sets, maintain- ing mental sets, and temporal structuring. The inability to switch mental set in response to environmental de- mands, or perseveration, shows most clearly on neuropsy- chological testing through measures that require strategy shifts to solve problems (such as the Wisconsin Card Sort- ing Test) or an alternating response between two different types of stimuli (such as the Trail Making Test B or the Stroop Test). Someone who has set-shifting problems re- peatedly tries to use the same strategy, even if it is not working. Investigators have found that patients with PD do not make more total errors on these types of tasks, but the errors they do make are perseverative (Raskin et al., 1990; Dubois et al., 1991). The perseverative problem in maintaining set occurs after the patient tries a new or dif- ferent strategy. It is a tendency to revert back to a previ- ous strategy after switching “mental set.” Some authors have also explained the verbal fluency difficulties of this group as a problem of set maintenance (Dubois et al., 1991). Verbal fluency tasks typically require the person to list as many words as possible that begin with a specified letter or belong to a specified category. The problem ap- pears most evident when the person uses several different letters. First, the task is to name as many words, within a 1-minute time period, that start with the letter F, then to name all the possibilities that begin with A, then with S. In such tasks, during the middle of the S sequence, pa- tients with PD may revert to words that begin with F or A (Lees & Smith, 1983).

A difficulty in “time tagging” events is a problem in tem- poral structuring. Researchers have reported patients with

CHAPTER 15 | Subcortical Dementias 429

Text not available due to copyright restrictions

PD may have memory for news events without associated memory for the event order (Sagar, Sullivan, Gabrieli, Corkin, & Growdon, 1988). In daily life this can trans- late into problems remembering “when” medications have been taken or learning the sequence of new tasks. Tempo- ral ordering is an executive problem that interacts with memory.

Not all of the frontal lobe is involved in the dysexecu- tive problems of PD; rather, the premotor area and the basal ganglia with its associated projections to the frontal lobes are implicated.

L a n g u a g e / S p e e c h

PD typically does not produce classical aphasia. Also, few, if any, linguistic impairments appear involving grammar and sentence structure (Dubois et al., 1991). Thus, gen- eral language processing and comprehension are intact. Some researchers indicate that more subtle problems in understanding grammatic complexity may be evident on more sophisticated neuropsychological tests (Levin, Tomer, & Rey, 1992). However, close to 70% of patients with PD have difficulties with articulation and the neuro- mechanical aspects of speech production (Levin et al., 1992). We have mentioned that patients with PD lose voice amplitude and vocal emotional expression (dyspho- nia), which results in monotonous voice. Other speech irregularities may include segmented accelerated bursts of speech (tachyphemia) and compulsive word or phrase repetition (palilalia).

Tests that measure aspects of expressive or receptive aphasia show little impairment in patients with PD. How- ever, patients may perform poorly on semantic fluency and word-finding tasks (such as the Boston Naming Test). However, as discussed earlier, these tasks are better con- ceptualized as belonging in another domain (executive functioning). Behavioral assessment of speech is the method that will demonstrate the characteristic disarticu- lation problems.

M e m o r y

Compared with AD, memory functioning is relatively spared in PD, even in patients with PD with dementia (Sagar et al., 1988). Digit repetition and block-tapping repetition are usually preserved (for review, see Dubois et al., 1991). On tests involving episodic memory, paired associate learning, auditory verbal learning, and visual re- production of geometric designs, patients with PD do show a recall deficit but demonstrate encoding and regis- tration of declarative material through recognition tasks (for reviews, see Dubois et al., 1991; Levin et al., 1992). The implication of this pattern is that strategic memory

processes for organization and retrieval of declarative in- formation are defective.

Nondeclarative learning presents a mixed bag in PD. Verbal priming and perceptual-motor adaptation are largely unimpaired in patients with PD without dementia (Crosson, 1992; Heindel, Salmon, Shults, Wallcke, & Butters, 1989). However, nondeclarative learning, which relies on intact motor or executive functioning, is often deficient. The ability to learn new motor skills declines as the disease progresses (Crosson, 1992). This is not sur- prising, considering the general dysregulation of the motor system. Procedural learning, measured by rule- learning tasks, such as the Tower of London, may be defi- cient, but results are mixed. At times, patients with PD perform poorly because of a problem in maintaining men- tal set for the rule, again pointing more to a problem in executive functioning than to a memory registration problem.

Most of the apparent memory difficulties experi- enced by patients with PD stem from interactions among the executive, the memory registration, and the motor systems. Patients with PD may show difficulty in motor skill acquisition. Patients with PD without de- mentia can passively register declarative information in short- and long-term memory. However, many have trouble using this information effectively. This includes effectively organizing information to be recalled, main- taining a consistent mental set when trying to learn or retrieve information, and time tagging or knowing not only that something has occurred but “knowing when” it happened.

M o o d , E m o t i o n , P e r s o n a l i t y , a n d I n s i g h t

A large proportion of patients with PD suffer from de- pression. Debate continues whether the mood disorder is a primary dysfunction of the disease or a secondary result of the medications used to treat the disease. To those suf- fering from depression, the debate may seem academic. Some researchers also suggest that depression may be a natural reaction to realizing that the patient has PD. Al- though this probably occurs to some degree, it does not seem to adequately explain the occurrence of depression. Patients with PD appear to be more depressed than pa- tients with many other chronic diseases (Raskin et al., 1990).

Although few standardized neuropsychological tests measure expression of emotion, researchers have studied this in patients with PD. The findings are somewhat equivocal, but some suggest that patients with PD have a dysfunction in emotional expression associated with a

430 PART THREE | Disorders of the Brain

right-frontal focus (for example, see Ross, 1985). These patients may have difficulty in showing an angry face or a surprised face but may be able to recognize emotional expression. Does this finding suggest a cortical deficit in emotional expression? Or rather, a problem in the more mechanical aspects of emotional expression? Because of the “masked facies,” it is difficult to determine whether emotional expression is lost or just diminished in fre- quency and intensity. Future research may help answer this question.

T R E A T M E N T S F O R P A R K I N S O N ’ S D I S E A S E

Without treatment, patients with PD are souls trapped in the cages of their bodies, unable to command or coax their mutinous muscles into action. Out of the tragedy of this disease, however, has emerged a palette of treatments that are worth examining, not only for addressing PD but be- cause they represent creative and forward-thinking ap- proaches to the treatment of aging-related brain disorders in general. Interestingly, the treatment for PD appears to be traveling full circle from surgery to drugs to surgery. In addition, gene therapies, tissue implants, and various ap- proaches to prevention are on the horizon.

The first surgical approaches to PD in the late 1950s were based on the idea of alleviating symptoms by inter- fering with what was thought to be “malfunctioning cir- cuitry” in the basal ganglia through heat-induced surgical lesioning of the global pallidus. By 1960, a group of Swedish researchers could demonstrate motor improve- ment in a significant number of their patients. However, this treatment preceded the advent of computed transax- ial tomography (CT) scans, MRIs, and the precision stereotaxic and electrode recording tools needed to locate specific neurons. The imprecision of this surgery made negative side effects likely.

The discovery of L-dopa as a possible treatment for PD in 1961 (Birkmayer & Hornykiewicz, 1961) was revolu- tionary and heralded a new approach to the treatment of neurodegenerative diseases. With the advent of a seeming miracle drug, surgical approaches fell by the wayside by the late 1960s. Today, there exists a menu of drugs that act not only on the dopaminergic system but also on re- lated neurotransmitter systems.

In Paris in the 1860s, anticholinergics extracted from plant sources (such as scopolamine from jimsonweed, black henbane, or deadly nightshade) were the first treat- ments used for PD. Although the mechanism of action was not known initially, these solanaceous alkaloids acted by blocking the action of acetylcholine, offering some symptomatic control of motor systems for tremor and

rigidity. However, the side effects of “anticholinergic in- toxication” limit their usefulness. Possible systemic effects, including dry mouth, blurred vision, constipation, weak bladder, and cognitive effects such as memory problems, confusion, slurred speech, and visual hallucinations, can create more than a small nuisance for patients. Physicians now prescribe synthetic anticholinergics of different types, if at all, during the early stages of the disease, and usually in combination with levodopa.

L-Dopa is the left (levo) form of the dopa molecule, a simple amino acid. Prepared as a drug, it is called lev- odopa. Plants and animals manufacture it, and it appears naturally in fava beans and other legumes. Levodopa, being a dopamine precursor, directly metabolizes into dopamine. Cousins of levodopa include dopamine ago- nists and analogs that mimic the action of dopamine by stimulating its release, whereas reuptake blockers work by preventing reuptake at the synapse to retard metabolic re- moval. Drugs acting on the dopaminergic neurotransmit- ter system are still the best family of drugs found to alle- viate tremor, bradykinesia, and rigidity. The difficulty with these orally ingested drugs, however, is that they con- vert to dopamine in the body and do not easily penetrate the blood–brain barrier. Probably less than 1% actually crosses over to be useful to the striatum, causing systemic buildup of dopamine in organs such as the liver and kid- neys. Therefore, medications usually combine L-dopa with a decarboxylase inhibitor (such as carbidopa) to pre- vent the conversion to dopamine until it crosses the blood–brain barrier. Because carbidopa cannot cross the blood–brain barrier, it acts as a protector against conver- sion in the body until it releases the levodopa into the brain. This arrangement delivers about five times the dopamine to the targeted area, greatly enhancing the ef- fectiveness of the drug.

Physicians may also use other drugs to treat PD, either as adjuncts or to counteract side effects of long-term dopaminergic drug usage. Doctors may add monoamine oxidase B (MAO-B) inhibitors, antidepressants, and agents to counteract the effect of dyskinesia to the com- plex menu, which must be taken at intervals as frequently as every 4 hours. These drugs are extending the survival of patients with PD, but not without a price. The side ef- fects of dopaminergic drugs, including vivid nightmares, disturbed sleep, perceptual illusions, and hypomania can be very disturbing. Also, after a long course of treatment, usually 10 years or so, the drugs lose effectiveness, dopaminergic neurons become hypersensitive, and the therapeutic window becomes shorter in duration, result- ing in a severe on/off syndrome. During the “on” phase, the drug exerts its action but may overshoot, resulting in

CHAPTER 15 | Subcortical Dementias 431

432 PART THREE | Disorders of the Brain

The following case report profiles one “typi- cal” patient who underwent right pallidotomy in an attempt to alleviate some of his ad- verse motor fluctuations. M.J. is a 56-year- old, right-handed man with a 16-year history of Parkinson’s disease (PD). His symptoms first began on the left side of his body with abnormal spontaneous movements of his foot, including a rhythmic tapping and an involuntary curling up of his toes. After about 10 years, his motor deficits worsened and he suffered from significant bilateral symptoms including bradykinesia, rigidity, and motor fluctuations. He had dyskinesias when his medication was “on” and freezing when “off.” Other than PD, M.J. had no other major medical or psychiatric problems. He was forced to go on medical disability 3 years ago. He has few hobbies, spending his days maintaining the house, walking the dog, doing yard work, and some cooking. M.J. acknowledges a feeling of depression, which increases when he does not feel well.

When he arrived for his presurgical neuropsychological assessment, M.J. pre- sented as an alert, oriented, pleasant, and cooperative man with a stiff, slow gait. Dystonic posturing of his head and upper torso was evident when sitting. Although his facial expression was fixed, he displayed a range of affect. A moderate tremor, which was greater on the left, was also evident. His spontaneous speech was soft in volume, with a choppy cadence, but his language was intact.

No disturbance in thinking was noted during the interview. Results of neuropsycho- logical testing indicated a few areas of mild impairment that were consistent with PD. These included problems with speed of mental processing, working memory for both auditory-verbal and visuospatial information, visual scanning, graphomotor control, and retrieval of verbal and visuospatial material. Recognition memory was intact. Consistent with his self-reported history, M.J. was depressed, socially isolated, and withdrawn.

N e u r o p s y c h o l o g y i n A c t i o n 1 5 . 2

P a l l i d o t o m y S u r g e r y : A C a s e R e p o r t

by Barbara L. Malamut Ph.D.

Figure 15.4 In the pallidotomy surgery for Parkinson’s disease, the surgeon is using the triangulation of three coordinates of the frame to pinpoint the patient’s globus pallidus. (Reproduced from Ueckert, S. [1996, January 22]. In R. SoRelle, “New procedure slows effects of Parkinsons: Surgery can restore balance to system.” Houston Chronicle, 4a, by permission.)

(continued)

an effect akin to an overdose. In this phase, severe dyski- nesia resembling choreic movements and dystonia involv- ing muscular posturing may result. This may cycle quickly to “off ” symptoms, which include the disease symptoms, particularly freezing, severe tremor, and panic.

L-Dopa could not live up to the hopes that pharmaco- logic substitution of missing dopamine would be sufficient treatment. The debilitating “on/off ” drug phenomena led to the return of surgical techniques. These operations cur- rently are intended for those for whom the drug treatments are no longer effective. Now, however, high-tech precision imaging of the brain results in a greater chance of locating the offending neurons. Currently, two types of operations are being conducted. The first operations focus on surgical lesioning of offending neurons. The second wave of surg- eries, deep brain stimulation operations, involves nonde- structive electrical interference.

Pallidotomy, the PD surgery of the late 1950s, was re- vived in the early 1990s. Surgeons use it in an attempt to alleviate the abnormal uncontrolled movement of dyski- nesia and the frequent on/off symptoms. In pallidotomy, surgeons lesion the ventral (that is, the internal portion) of the globus pallidus by heat-coagulating the neurons.

Studies have shown that the decreased dopamine in the basal ganglia causes the motor portions of the pallidum to become overactive. This hyperfiring, in turn, inhibits the thalamus and portions of the brainstem (which causes bradykinesia and dyskinesia). Lesioning the posteroven- tral portion of the pallidum arrests this excessive output to the thalamus and brainstem (Neuropsychology in Ac- tion 15.2). Surgeons use a second lesioning procedure on a portion of the thalamus, thalotomy, to attack tremor. Interestingly, they also use this procedure for patients with tremor caused by multiple sclerosis, essential tremor of old age, cerebellar tremor, and poststroke tremor. These two operations are typically unilateral and not done in combination. In fact, the lesion sites for the two opera- tions are only millimeters apart. Bilateral lesions done at the same time appear to greatly increase the risk for cog- nitive deficits. In pallidotomy, the risk may be greatest for memory difficulty and confusion. For thalotomy, speech dysfunction appears to be the greatest risk.

Deep brain stimulation procedures represent the newest variation of these surgeries. The target site is the same as in thalotomy, except that instead of a destructive lesion, sur- geons transmit electrical interference to the neurons via a

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M.J. was a good candidate for pallido- tomy because he was generally in good physical and mental health, his neuropsy- chological profile did not indicate cognitive decline or dementia, and his medications had lost much of their effectiveness. The day of M.J.’s surgery, he was injected with a local anesthetic and fitted with a stereotactic frame necessary to locate the area to be lesioned (Figure 15.4). With the frame in place, a computed transaxial tomography scan was done and compared with his previ- ous magnetic resonance image, to identify the precise placement of critical brain struc- tures. After drilling a tiny hole through M.J.’s skull, the surgeon inserted a small canula, or tube, through the dura mater and snaked a microelectric probe through his brain toward his right pallidum. As the probe approached the area of neuronal hyperactivity, sound bursts became more frequent. The surgeon first stimulated the area to observe motor response. (M.J. was conscious so his re- sponses to stimulation could be tested and any adverse affects on vision or speech could be noted before actual lesions were made.) Being careful not to affect the nearby optic

tract, the surgeon then made a small heat- induced lesion to permanently destroy the overactive neurons of the pallidum. After this surgery, M.J. needed a few stitches and was released within 24 hours. M.J. experienced no surgical complications.

Six months later, M.J. returned for a neuropsychological re-evaluation to monitor his cognitive status. He reported that since surgery, his left-sided rigidity had disap- peared and he no longer had pain or involun- tary movements when walking. On observa- tion, he no longer had dystonic posturing but did continue to walk with a slow, shuffling gait. In addition, his speech was now normal in volume, but he had developed a mild stammer. Overall, M.J. was pleased with the results of his surgery, although he realized this was not a cure. Improvement relative to his preoperative neuropsychological evalua- tion was noted in speed of mental process- ing, working memory for both auditory-verbal and visuospatial information, and grapho- motor control. M.J.’s problems with depres- sion remained, and he began taking antide- pressant medication and agreed to begin psychotherapy.

This case raises several critical and common issues regarding pallidotomy surgery. Although pallidotomy effectively alleviates many motor symptoms and pain associated with later stages of PD, it does not cure the disease or return the patient to preinjury functioning. The long-term benefits and risks of pallidotomy are unknown. Studies currently under way are examining the cognitive sequelae of the pallidotomy procedure in comparison with the natural progression of the disease. The newest procedure, approved by the U.S. Food and Drug Administration in July 1997, is deep thalamic stimulation, which works as a type of electronic pacemaker interfering with the ventral intermediate thalamic nucleus. The surgery, performed like pallidotomy, primarily reduces tremor but may have little effect on the other PD symptoms. This surgery, unlike pallidotomy, does not result in permanent lesions. Other treatment modalities currently being explored, such as gene therapy and fetal implant surgery, may be promising avenues for the future. These procedures may actually arrest or reverse PD, rather than just ameliorate some of its motor symptoms.

permanently implanted lead. An implanted adjustable neurostimulator operates somewhat like a pacemaker and can be turned on and off by the patient.

Although these surgeries represent new hope for pa- tients for whom drugs are no longer effective, they are pal- liative, not curative. Patients experience relief of symp- toms, and about 80% may improve, but they must still take medication. The progression of the disease continues.

Huntington’s Disease

Huntington’s disease (HD), although rare, has been well studied in the last quarter of the 20th century. Why the resurgent interest in a disease that physicians de- scribed more than a century ago and then seemingly left to languish until the 1960s? From 1872, when George Huntington described this “hereditary chorea,” until the 1960s, researchers paid little attention to this neurologic disease, which causes adults in the prime of their lives to seemingly “go insane,” develop a tendency toward suicide, and suffer devastating motor impairment in the form of chorea. Families of HD sufferers have spearheaded the search for the gene that controls the disease. For neu- ropsychology, the specificity of this disease offers a win- dow to learn about the widespread behavioral effects of caudate nucleus deterioration.

George Huntington was not the first to describe the twisting, writhing, grimacing choreic movements, which are reminiscent of a puppet at the hands of a sinister mas- ter. In the 16th century, “peculiar” families were de- scribed, but the hereditary nature of the disease did not appear to come into the medical consciousness until evo- lutionary theory emerged in the mid-1800s (Wexler, 1995). Other physicians before Huntington hypothesized about the hereditary nature of the disease, but it was young George Huntington, just 22 years old, who in his 1872 article described the disorder most clearly and most completely. He emphasized the emotional and psycholog- ical aspects of the disease, describing “the tendency to in- sanity, and sometimes that form of insanity that leads to suicide.” This became the classic account of the disorder, forever after associated with the name Huntington.

The story of the search for the “Huntington’s gene” begins in the late 1960s. After years of relatively little sci- entific interest in this apparently incurable disorder, two families picked up the torch. Marjorie Guthrie, ex-wife of the singer Woody Guthrie, who had HD, founded an or- ganization of HD families to raise money for research. The Wexlers, whose story is told in the book Mapping

Fate (Neuropsychology in Action 15.3) were instrumental in pushing basic scientific research toward the search for the gene. Nancy Wexler, at risk for HD herself, was active in the study of colonies of HD families in Venezuela. Largely through the energy generated by these and other at-risk families, researchers pinpointed the offending gene in 1993. This discovery does not translate into an imme- diate cure or treatment. However, it does provide the first hopeful step in that direction.

HD is a progressive subcortical dementia. This rare disease, which affects about 5 to 10 in 100,000 people, is linked to the gene ITI5 on chromosome 4 and is passed on by one parent in an autosomal dominant inheritance pattern. As far as genes go, ITI5 is a big one, with more than 300,000 base pairs, and it is evident in all tissues of the body. People with normal versions of the gene have between 11 and 34 repeats of the trinucleotide CAG (cy- tosine, adenine, guanine), which codes the gene. How- ever, those with the HD-positive gene have 37 to as many as 100 or more repeats. More repeats entail earlier onset and greater severity of symptoms. Some overlap exists be- tween normal and abnormal functioning, making 35 to 40 a borderline range. When operating normally, ITI5 produces the amino acid glutamine. It is not clear how the body uses glutamine, or the exact function of ITI5, but researchers do know that expanded gene sequence re- peats on other genes characterize inherited diseases such as myotonic dystrophy and spinobulbar muscular dystro- phy, which affected President Kennedy.

Autosomal dominance translates into a 50% chance of acquiring the disease. Because this disorder runs in fami- lies, HD is not suspect unless there is a family history. In those with a family history, a simple genetic test can de- termine the presence of the disease, but much to the sur- prise of many scientists, most people at risk have chosen not to be tested (see Neuropsychology in Action 15.3).

N E U R O P A T H O L O G Y O F H U N T I N G T O N ’ S D I S E A S E

Deterioration of the caudate nucleus bilaterally plays a primary role in the neuropathology of HD, although ul- timately, HD affects multiple brain systems. The cau- date nucleus is one of the structures that comprise the striatum, together with the globus pallidus and puta- men. The striatum is part of the basal ganglia, which is responsible for modulating motor activity. However, the role of the striatum is somewhat different from that of the substantia nigra, which is primarily affected in PD. Although the substantia nigra is responsible for the proper initiation and termination of movements, the

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striatum controls the proper timing, ordering, and se- quencing of movement patterns (Bradshaw & Mattingly, 1995). The caudate nucleus has reciprocal projections (afferent and efferent neurons) to a number of limbic and prefrontal areas. Although HD primarily affects the caudate, it may also affect the putamen, other areas of the striatum, and possibly other limbic system structures such as the hippocampus. By the end stages of the dis- ease, the frontal lobes may also shrink by 20% to 30% (Vonsattel, 1992).

In patients with HD who are showing the symptoms of the disease, structural neuroimaging techniques such as CT or MRI clearly reveal the loss of cell mass in the cau- date and a widening of the ventricles. On MRI, the vol- ume of the caudate and other basal ganglia structures is clearly reduced. The apparent structural deterioration of the caudate corresponds to a downward progression of behavioral functioning. Functional neuroimaging via positron emission tomography scan is more sensitive to early changes and can show hypometabolism in the frontal and striatal regions before deterioration is evident

structurally (Hasselbalch et al., 1992) and before a clini- cal diagnosis (Penny & Young, 1993).

C L I N I C A L P R E S E N T A T I O N A N D N E U R O P S Y C H O L O G I C A L P R O F I L E O F H U N T I N G T O N ’ S D I S E A S E

How do the symptomatology and neuropsychological functioning of the HD sufferers differ from profiles of AD or PD? HD results in a unique pattern of impairment in which difficulties associated with frontal lobe function- ing and motor functioning are prominent. Although PD also results in frontal executive system and motor impair- ment, the presentation differs in some ways. The caudate nucleus, rather than the substantia nigra, is the main cul- prit in HD.

Many of the cognitive difficulties of patients with HD likely stem from a breakdown in premotor frontal lobe functioning and the connectivity of the caudate-frontal system. Early in the disease process, patients with HD show characteristic frontal signs of rigidity, perseveration,

CHAPTER 15 | Subcortical Dementias 435

Would you take a test to determine whether you would develop an inherited brain dis- ease in the future? This is the question facing family members of people with Huntington’s disease (HD), a subcortical dementia with devastating motor and cognitive consequences. Fortunately, the disease is rare, but if it runs in your family, you have a 50% chance of acquiring this autosomal dominant genetic disease. There is no cure and there is no treatment, and if you do have it, you may pass it on to your children. You are also likely to die while in your 50s. Would knowing this help you to plan? Plan not to have children, perhaps plan not to even marry, or perhaps try to pack a lot of living into a short time? Would knowing lessen your worry? Or would know- ing be a traumatic experience? Would you consider suicide? Would you always be on guard watching and waiting for the first symptoms to appear?

These questions face the 125,000 people at risk for the disease in the United States. In 1983, researchers discovered a genetic marker that paved the way for the first testing for HD. Then 10 years later, in 1993, researchers located the gene ITI5 (named “Interesting Transcript”) on the short arm of chromosome 4, and the test became much more accurate. Only a simple blood test is required. Scientists predicted a flood at testing centers, but there has been only a trickle of people, about 6% of those at risk. Why is this? The answers come from those at risk. Alice Wexler, author of the book Map- ping Fate, describes the story of her own family, and of her mother, who died of HD. After her mother’s diagnosis in 1968, the Wexler family, led by her father and sister, spearheaded one of the most innovative approaches to scientific investigation, bringing scientists and families together in collaborative efforts to search for the HD

gene. The book chronicles the scientific and personal odyssey of the discovery of the gene. Alice Wexler describes her own am- bivalence and the feelings of others who have struggled with the idea of getting tested. Some have taken the test, mention- ing control and relief from uncertainty as major reasons. Others are concerned about confidentiality of their medical records and possible denial of insurance coverage. For those who have tested positive, the experi- ence is often traumatic and, surprisingly, may not alleviate the anxiety because there is no certainty as to when the symptoms may develop. Even for those who test negative, the result may come as a shock as they realize they have built their lives around the possibility that they might acquire a fatal disease. Alice Wexler, like so many others, has decided against being tested. If you were at risk, you could test your fate. But would you want to?

N e u r o p s y c h o l o g y i n A c t i o n 1 5 . 3

T e s t i n g F a t e : W o u l d Y o u W a n t t o K n o w I f Y o u W e r e G o i n g t o G e t H u n t i n g t o n ’ s D i s e a s e ?

by Mary V. Spiers

and difficulty switching mental set in daily life, as well as on neuropsychological testing. Some dysfunctions stem from the impacts that poor executive organizational abili- ties and attention/concentration problems have on cogni- tive functioning. For example, the memory difficulties of patients with HD appear largely attributable to poor execu- tive functioning. Capacity for learning new information de- clines in HD, but the picture differs from the AD profile. Patients with HD demonstrate low levels of free recall but improve greatly if given a recognition test. Why? Apparently they encode new information, or multiple-choice recogni- tion tests would not aid performance. Patients with HD ap- pear to suffer primarily from a retrieval problem caused by ineffective memory search operations. They may have a poor ability to differentiate what they know from what they do not know (for review, see Brandt & Bylsma, 1993). This problem in strategic memory processing and metamemory (knowledge of one’s own memory) appears attributable largely to frontal lobe and executive functioning difficulties rather than to hippocampal involvement, although both may interact to some degree. Executive difficulties probably also interact with other cognitive processes such as verbal and spatial conceptualization and processing.

The final manner by which the striatofrontal lobe complex may exert its effects on cognitive functioning is through multiple connections to other areas of the brain. Patients with HD appear to have difficulty orienting themselves in space, which may be a parietal dysfunction. For example, the old-time child’s game of blind man’s bluff, in which one child is spun around blindfolded and then required to tag others by sound alone as they call out, would be difficult for patients with HD. Potegal (1971) has explained this egocentric spatial disorder as a problem in readjusting, or the ineffectiveness of the cau- date in modulating changes in spatial position. Although research has not yet confirmed this interpretation, it ap- pears reasonable, given the role of the striatum in modu- lating other motor activity.

The emotional difficulties experienced by many pa- tients with HD likely result from prefrontal and limbic system interactions. Patients with HD exhibit a dispro- portionately high degree of affective disturbance, in the form of depression and manic depression. The suicide rate of 6% (Farrer, 1986) in HD is greater than in other de- generative disorders. Are these emotional disturbances a response to a desperate situation, or perhaps a symptom of frontal-subcortical impairment? Suicide may be an un- derstandable response, given the severe cognitive devasta- tion that people in the early stages of the disease can an- ticipate. HD sufferers are no strangers to what will befall them. They have seen a parent, a grandparent, aunts, and

uncles succumb to the same horrible disease. However, the rate of emotional disturbance in HD is greater than expected. Depression is the most common affective dis- turbance (Brandt & Bylsma, 1993), but the literature re- ports a wide range of affective and psychiatric distur- bances in patients with HD. These include anxiety, apathy, irritability, impulsivity, aggression, sexual distur- bance, schizophreniform thought disorder, and psychosis involving hallucinations and delusions (for reviews, see Brandt & Bylsma, 1993; Bradshaw & Mattingly, 1995). Interestingly, the emotional disturbances often precede motor symptoms. At this point, the affected individual may not even be aware of his or her diagnosis. These emo- tional symptoms can be best conceptualized as a symp- tom of the disease, or a predisposition toward symptoms such as depression. However, this is not to say that reac- tions to the illness do not contribute to the picture of emotional disturbance. A reaction to the severity of the disease can compound a predisposition to depression.

The motor difficulties of HD are characterized by chorea: twisting, writhing, undulating, grimacing move- ments of the face and body. Interestingly, overmedicated PD patients also show choreic movements. This has led to the hypothesis that the dopamine system lies at the root of both these problems. Obviously, this gross-motor dys- function seriously hinders everyday activity. Like patients with PD, patients with HD are slow motorically (bradyki- nesia). Also, as in PD, the chorea tends to disappear with sleep and increase with stress. Unlike PD, patients with HD walk with a wide-based gait. Their speech is dysarthric, becoming increasingly erratic in its rate of pro- duction and staccato with intermittent pauses. They be- come clumsy and uncoordinated, unable to do fine- grained work. In testing patients with HD, these severe motor difficulties disrupt performance on other tests that have a motor component, even if the test is designed to measure other functions such as visual problem solving. In assessing the cognitive performance of patients with HD, motor-free tests provide the clearest picture. Cur- rently, no cure exists for HD, and the treatments that exist focus primarily on the relief of emotional symptoms such as depression and hallucinations.

Creutzfeldt–Jakob Disease

Creutzfeldt–Jakob Disease (CJD), a dementia long hidden in obscurity because of its rarity (one that most neuropsychologists have never seen personally in one of their patients), has suddenly leaped into the lime- light because of its connection to “mad cow disease” and

436 PART THREE | Disorders of the Brain

because of the fear that its incidence is increasing. CJD is a compelling disease, unlike the other dementias we have considered, because of both its speed of progression and mode of transmission. With a malignantly cascading de- cline over 3 to 4 months, it is the most quickly progress- ing dementia. Scientists have long known that humans can transmit this disease via transplants of affected neural tissue, cornea transplants, or contamination via medical procedures, but it is now also becoming clear that CJD and its variants can cross species through the consump- tion of tainted meat containing neural tissue. Extensive spongelike holes appear in the brains of its victims, giving it the fitting name “spongiform encephalopathy” (SE). The mechanism by which the brain becomes infected has eluded scientists for decades because CJD does not mani- fest the symptoms of typical acute infections. Virologists, biologists, and chemists are joining clinicians to unravel the mysteries of this disease.

In the early 1900s, Bertha, a 23-year-old German woman, was a patient of Hans Gerhard Creutzfeldt. Creutzfeldt, an assistant of Alois Alzheimer at the Munich Psychiatric Clinic, was, like Alzheimer, trying to clarify the differences and similarities between behaviors under- stood as “psychiatric” and “neurologic.” Creutzfeldt no- ticed that Bertha showed many behaviors typical of other mental illnesses, such as believing she was possessed by the devil, neglecting her hygiene, and posturing strangely. However, other symptoms suggested frank brain impair- ment. Bertha also had an unsteady gait, twitchy eyes, a voluntary tremor, and a tendency to giggle inappropri- ately. These latter symptoms, which we now recognize as indicating subcortical motor and emotional dysfunction, were Creutzfeldt’s clues. After Bertha died, Creutzfeldt examined her brain tissue under the microscope. What he saw were the little “stars” of astrogliosis (Figure 15.5) dotting her brain. In 1920, he published his article that describes Bertha. With the synchronicity that often oc- curs in science, Dr. Jakob reported a similar case in 1921. Creutzfeldt and Jakob thus share the distinction of discovery.

CJD is a quickly progressive subcortical dementia esti- mated to affect only 1 person in 1 million people per year. This is extremely rare even in comparison with HD, which affects 5 to 10 per 100,000 people. CJD appears around the world with the same prevalence and does not appear to vary across groups or cultures. Although Creutzfeldt’s patient was young, most cases have been in their 50s or 60s. For the most part, researchers have hy- pothesized that CJD spontaneously arises as a random mutation. As long as it is not passed on to others, the dis- ease dies out with its victim. Some variants of CJD may

manifest themselves differently in the behavior of those it afflicts. For example, the extremely rare familial CJD vari- ant termed Gerstmann-Straussler-Scheinker syndrome (GSS), reported in only a handful of families, results in a “fatal insomnia.” This is the only reported incidence of transmission other than through external infection. Re- searchers believe that in older people CJD incubates for years before manifesting.

One of the most alarming aspects of this disease, and the reason it has been catapulted out of obscurity, is its relation to other SEs. Variations of SE, as mentioned ear- lier, are aptly named: Portions of the brain actually resem- ble a sponge, because of the microscopic pattern of holes. Researchers have identified SEs in species from minks to sheep (scrapie) to cows (bovine spongiform encephalopa- thy [BSE] or “mad cow disease”) to humans (CJD and kuru). In his book Deadly Feasts, Richard Rhodes chroni- cles the history of the SEs. He describes the history and current status of research into CJD and kuru. Kuru is a SE that the Fore people of Papua New Guinea contract, which presented itself when they began ritually cannibal- izing their dead at the beginning of the 1900s. Rhodes (1997) also describes the history of the research, which suggests that SEs can easily leap across species, and that they are probably variations of the same disease process.

CHAPTER 15 | Subcortical Dementias 437

Figure 15.5 The dark stars of astrogliosis. (Courtesy D. Carlton Gajdusek.)

In his book he predicts an alarming increase in the inci- dence of CJD (Neuropsychology in Action 15.4).

N E U R O P A T H O L O G Y O F C R E U T Z F E L D T – J A K O B D I S E A S E

The cause of CJD has eluded scientists until recently be- cause it is a transmissible or infectious agent with none of the usual symptoms of acute infection. In fact, scientists first thought that kuru could be genetic, because it oc- curred primarily among the women and children of the Fore people. However, only the women and children were eating the dead in a mortuary love feast. Men believed contact with women weakened them, and they did not partake in the ritual. Acute infections are easily identified by noticing the body’s defensive immune system response. Inflammation, increased numbers of lymph cells in cere- brospinal fluid, and fever are typical, yet none of these symptoms occurs in CJD or any of the SEs.

No one knows from where this infectious agent origi- nally arose. Perhaps it originated from a randomly occur-

ring mutation. This might account for the rarity in the population at large and that CJD occurs with equal fre- quency throughout the world. However, in the last cen- tury, SE has also been transmitted by eating infected neural tissue. This has happened both within species such as cows (BSE or mad cow disease) and across species. SE has de- veloped in mice, hamsters, and even primates injected with kuru. CJD has developed in humans who have eaten in- fected meat (see Neuropsychology in Action 15.4). Many scientists now believe CJD to be a slow virus that incu- bates over years, perhaps in the spleen, and is camouflaged in cells so as not to be recognized as an invader. Some have also hypothesized that slow viruses are responsible for AD, PD, and amyotrophic lateral sclerosis (ALS).

What exactly do SEs, specifically CJD, do to the brain? Certain areas of the brain look spongy, taking on a charac- teristic spongiform pattern. CJD, like kuru, attacks the cere- bellum, but it also damages the cerebrum. Microscopically, the “stars” of astrogliosis that Creutzfeldt found were the re- sult of the glial cells, or the “cleanup machines” of the brain, filling in after neuronal tissue had died. Astrogliosis is the

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In his book Deadly Feasts (1997), Richard Rhodes traces the history of spongiform encephalopathies (SEs) in humans and other species. He reflects scientists’ views that these diseases are variations of the same infectious process, and that the ingestion or injection of diseased neural tissue can spread many SEs within or across species. He also forecasts an alarming increase in human encephalopathies over the next few years if people do not contain and eliminate the disease in the animal food supply.

How exactly did mad cow disease (bovine spongiform encephalopathy [BSE]) arise and become a threat to humans? Farmers routinely give cattle protein supple- ments: dairy cows all through their life, and beef cattle for end-stage fattening. As long as farmers fed cattle largely vegetable protein (such as soy) or fish protein together with their diet of grass or hay, and no trans- mission from randomly affected cattle

occurred, BSE did not arise. However, during the 1980s, a series of events in Great Britain triggered a BSE epidemic. One factor was that, because the pound was devalued, the price of soy and fish meal increased, so the agricultural industry began to rely more heavily on animal sources of protein. Animal protein typically comes from the by-products of slaughterhouses—bones and offal (guts, heads, tails, and blood) are processed into bonemeal pellets or powder and fed to other cattle. As long as the rendering process killed any disease, bonemeal was a good source of protein. During the 1980s in Britain, changes in the rendering process decreased the bonemeal processing temper- ature and abandoned fat removal, no longer destroying BSE in tissue. By the late 1980s, BSE had spread throughout Great Britain and had infected more than 2000 cattle. Farmers noticed that their cattle were “be- coming aggressive, rather nervous, knocking

other cows. . . . and becoming dangerous to handle. . . . If you shooed her, she would stumble, particularly on the back legs, and go down, and then scrabble along” (p. 172). In 1988, the British government ordered milk from affected cows destroyed. However, not until an outbreak in humans occurred in 1996 were massive amounts of beef cattle destroyed. The base rate for CJD is 1 in 1 million people older than 50. CJD cases developing under that age are extremely rare. In the world, there had been only 10 known adolescent cases. Only with kuru- associated cannibalism did researchers notice that young people acquired spongi- form encephalopathy with a shortened incubation period. Between 1991 and 1996, 10 cases of a CJD variant of people younger than 40 emerged in Great Britain. According to statistical probability, this is an epidemic. Only time will tell whether awareness has stopped the spread of this disease.

N e u r o p s y c h o l o g y i n A c t i o n 1 5 . 4

C r e u t z f e l d t – J a k o b D i s e a s e a n d M a d C o w D i s e a s e : W h a t ’ s t h e C o n n e c t i o n ?

by Mary V. Spiers

aftereffect, not the cause of the disease. Amyloid plaques are also numerous, but as discussed earlier, these are not specific to CJD but are also found in other diseases such as AD.

Patricia Merz, with the aid of her electron microscope, first found small, twisted, sticklike fibers in the cells of tissue samples of sheep with the sheep version of SE, called “scrapie” (Merz, Somerville, Wisneiwski, & Iqbal, 1981). Interestingly, she could then correctly distinguish between healthy control subjects and affected victims with CJD from these scrapie-associated fibrils (SAFs) in spleen and neural tissue samples. Merz hypothesizes that SAFs may be the disease agent, which incubates in the spleen over years before affecting the brain. SAFs have been found in kuru and CJD brains, but not in AD, PD, or ALS brains. This was the first indication of a disease agent specific to SEs such as CJD.

The name that has become popular in referring to SAFs is prions (Pruisiner, 1982). Currently, several differ- ent variations or strains have been identified. Prion pro- teins (PrPs), the protein components of prions, which are present in both normal and afflicted individuals, have been the target of research interest in CJD. However, in- fected PrP resists normal protein digestion via enzymes. Interestingly, both diseased and normal PrP have the same DNA specifications. This helps explain the riddle of why the body’s immune system does not attack the infected protein. It does not recognize the protein as foreign! How- ever, one of the unsolved mysteries of this disease is to un- derstand how a normal protein changes to an abnormal protein with the same structural DNA. Several hypothe- ses exist to explain the mechanism of action. One is that there may be a small virus, termed a virion, that has not yet been identified. Proteins are not known to mutate on their own, but perhaps small bits of “naked” nucleic acid infected with the virion, divorced from their cells, attach themselves to proteins and force the mutation. Another explanation involves an interesting nonbiological form of replication. Carleton Gajdusek (1988), who won the Nobel Prize in Medicine, has postulated that something else must be transporting the infectious agent, because even when the nucleic acid is destroyed by radiation, the “infection” persists. He explains this as a crystal nucleation process. Similar to how crystals such as diamonds form in nature, the infection provides the pattern that is the nucleus, or catalyst, for the reaction. Successive proteins then mutate by patterning themselves after the original. If this sounds like science fiction, scientists have already dubbed this the “Ice-9” metaphor after a Kurt Vonnegut novel in which all the water on earth turns to ice, in a crystallization process.

Whether a yet undiscovered virion, nuclear crystalliza- tion, or some other process is causing CJD, scientists are

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pursuing this disease with renewed vigor because of its unfortunate recent resurgence. We now turn to the clini- cal aspects of CJD.

C L I N I C A L P R E S E N T A T I O N A N D N E U R O P S Y C H O L O G I C A L P R O F I L E O F C R E U T Z F E L D T – J A K O B D I S E A S E

Even though emotional symptoms may be first evident, the hallmark of CJD, as well as other SEs such as kuru, is motor symptomatology. The motor symptoms are those expected of cerebellar and subcortical dysfunction. Move- ments become uncoordinated, walking resembles a drunken stagger, and speech is slurred and inarticulate. Involuntary tremors and choreiform grimaces emerge, and finally victims cannot swallow and thus may die of starvation. Visual function alters, eventually leading to blindness in some people. These cerebellar and subcorti- cal motor problems may follow initial, emotionally re- lated complaints of mood disorders such as anxiety, de- pression or hypomania, fatigue, difficulty sleeping, and attention/concentration problems. As with the confusion over Creutzfeldt’s patient Bertha, these symptoms may lead one to first believe that a pure mood disorder is pres- ent, or in Bertha’s case, which was more advanced, a delu- sional or psychotic disorder. However, the classic motor symptoms quickly reveal themselves.

The dementia of CJD and its variants has a rapid pro- gression, typically less than a year and usually within 3 to 4 months. Kuru has a similar progression. The Fore peo- ple of Papua New Guinea categorized the disease (using pidgin) in five stages: (1) kuru laik i-kamap now (“kuru like he come up now”), the first stage before motor symp- toms are present; (2) wokabout yet (“walk-about yet”), motor and gait problems apparent; (3) sindaun pinis (“sit down finish”), inability to walk; (4) slip pinis (“sleep fin- ish”), stuporous state; and (5) klostu dai nau (“close to die now”), final stage during which swallowing is lost (Rhodes, 1997). Some have likened the progression to classical advanced parkinsonism, but it certainly has fea- tures of HD as well.

Neuropsychological testing of patients with CJD is rarely done, not only because of the rarity of the disease, but also because of its circumstances. By the time the dis- order is identified, patients are untestable. Unfortunately, at this time, there are no treatments and no cure. Perhaps the only fortunate aspect is that the disease dies out if it is not passed along. The level of kuru in the Fore people has decreased dramatically since they have stopped eating in- fected tissue.

440 PART THREE | Disorders of the Brain

Watching a neurologist at bedside can be perplexing. A process of inference is at work that is not apparent to the onlooker. It begins with history taking, which incorporates as data every symptom the patient describes and the form and pattern of the descriptive process. The physical aspects of examination are selective in some respects and elabo- rated in others, to serve an incipient process of hypothesis testing at work during the examination. An active set of principles working inwardly guides the conduct of the neurologist. I undertake here to make those inferential processes and those principles explicit, in a general form.

The neurologist examines the central nervous system (CNS) with an attitude that differs from the common attitude toward the body and its symptoms. The neurologist applies an invisible reference “map” derived from neuroanatomy and neurophysiology, and from encounters with past patients and syndromes. She or he seeks to define and localize a symptom as an epiphenomenon of unwitnessed internal mechanisms, respecting the rules of nervous tissue function rather than the culturally validated rules of somatic experience. In the examina- tion of aging and dementia, the neurologist is, in addition, sensitized to a number of pivotal issues in history taking, and pivotal physical signs that narrow the selection of possible causes. A set of diagnostic hy- potheses, ranked by priority, is the goal of the examination, then (most often) to be explored by laboratory and neuroimaging investigations, before the neurologist rec- ommends treatments.

The neurologist’s attitude is “phenome- nologic” in the sense that he or she must “bracket” or hold uninterpreted the symptom the patient presents until a precise neuro- logic meaning can be attributed to the symptom (we will call these “symptom hypotheses”). Therefore, most of the exami- nation effort focuses on the adept taking of a history, often from observers and family, as well as the patient. The neurologist applies

the tools of physical examination to clarify symptoms, achieve more precise localiza- tion, and select a favored hypothesis.

The model yielding symptom hypotheses always includes attention to the following seven issues:

1. Clinical Course Sudden onset (suggesting vascular or phar- macologic causes) Insidious progression (suggesting metabolic, neoplastic, inflammatory, infectious, or degenerative causes) Episodic or paroxysmal occurrence (suggest- ing epileptic or vascular causes) Exacerbating–remitting course (suggesting inflammatory or demyelinating causes, or disorders deriving from variable systemic illness, or related to neuromuscular junction fatigue)

2. Hierarchical Level of Advancement Within the nervous system as a whole, symptoms localize to a “level of organiza- tion”: muscle, neuromuscular junction, peripheral nerve, spinal root, spinal cord, brainstem, or brain. Within the brain “level,” symptoms will vary from simple (for example, segmental loss of light perception) to com- plex (smelling colors, misattributing meaning to objects), from unimodal (for example, primary motor outputs or primary sensory inputs) to heteromodal (for example, con- verging complex functions, personality, or the flexibility, anticipation, and organizing executive functions of the frontal lobe). The “level” and “complexity” of the symptom lead the inferential process selectively to parts of the nervous system in which these qualities must necessarily be generated.

Within the CNS, where neuropsychologi- cal dysfunction will arise, elicited history amplifies these issues:

3. “Central Quality” of Symptoms The presentation of a system may direct the inferential process away from the peripheral

nerves to the CNS, the spinal cord and brain. A patient may describe a limb as disobedient or clumsy, rather than weak or limp, and may describe a limb sensory deficit as a regional perversion of normal sensation, rather than numbness. In the visual system, lateralized inattention or distortions (for example, metamorphosis, color alteration, movement or space misperception, or appari- tions) are central in origin. Paroxysmal intru- sive experiences, seizures, unrealistic experi- ences, failure of reality testing, or any symptom reporting the disruption of the individual’s normal connection to the social or sensory environment raises the specter of brain disease.

4. Lateralization Co-occurrence of dysfunction in the same- side arm and face may place a suspect lesion contralaterally above the pons, and dysfunction in the same-side leg and arm may place a suspect lesion above the level of synapse within the cervical spinal cord. The presence of “crossed symptoms” (such as right face with left arm) invites exploration of localization within regions of anatomic crossing of specific projections, such as the crossing of paths in the brainstem. Coinci- dence of multiple lesions may imitate, in some cases, a single lesion in a complex region. Therefore, neuropsychologists must rewrite the logic of inference to entertain all possibilities. Neuroimaging and electro- physiologic tests can corroborate the infer- ence of a focal lateralized hemispheric syndrome, and lateralized neuropsychologi- cal findings can substantiate and clarify the diagnosis.

5. Heritable and Risk Factors Past nervous system insults (such as trauma), vascular disease outside the nervous system (such as coronary disease and cardiac arrhythmia), systemic illnesses (such as immune system compromise, hyperlipidemia, diabetes mellitus, and autoimmune diseases) all narrow the

N e u r o p s y c h o l o g y i n A c t i o n 1 5 . 5

T h e N e u r o l o g i c E x a m i n a t i o n f o r D e m e n t i a

by Allen J. Rubin M.D.

CHAPTER 15 | Subcortical Dementias 441

Summary Subcortical dementias primarily target subcortical structures in the brain. The hallmark of these dementias is motor system disorder, but the behavioral impairment also targets many higher cognitive functions. Patients with PD are more likely to experience development of dementia as they age, although dementia is not inevitable. This chapter has examined the neuropsychological profile of patients with PD without dementia. In addition to the characteristic motor symptoms, patients with PD often show lateralized motor

guesswork in selecting a specific pathologic process in brain. Occurrence of CNS diseases in preceding generations (such as dementias, Huntington’s disease) renders certain diagnoses more likely.

6. Confluence, Association, Dissociation, Disconnection Confluence of symptoms (such as ipsilat- eral motor and sensory findings), associa- tion (such as right-sided weakness with aphasia, chronic ver tigo with loss of facial sensation, right–lef t confusion with agraphia), or dissociation (such as preser- vation of pain sensation only on the right and preser vation of vibratory sensation only on the lef t; loss of voluntary facial movement but preser vation of automatic emotional facial mimicry) all point to a CNS localization. Last, history or examina- tion can identify disconnection of cerebral processes, which may be identified by history or examination (for example, alexia without agraphia, conduction aphasia with isolated loss of language repetition) and can place lesions in the interconnecting brain white matter connections.

7. Syndrome Recognition, Including Neurobehavioral Profiles A neuropsychologist may advance a “diag- nostic hypothesis” of a distinct disease syndrome, subject to confirmation with selected laboratory tests (genetic DNA studies, metabolic-hematologic studies, computed transaxial tomography or mag- netic resonance neuroimaging, Doppler or contrast angiography, electroencephalogra- phy, sensory-evoked responses, cerebral fluid examination, quantitative visual perimetry, and brain biopsy) and neuropsy- chological consultation.

The following three cases of progressive diseases among the elderly illustrate how

the symptoms and findings converge to allow diagnostic hypotheses.

Case 1 At 62, a female patient retired from her work as an effective office manager; at that time she was involved in dancing and was a competitive bridge player as recreation. At 75, she presented with an insidious course of handwriting shrinkage, tremor at rest, stooping, and shuffling in gait. At 79, she had the onset of tiredness and discourage- ment with lack of motivation and failure of initiative, dysphoric mood, and agoraphobia.

Pertinent examination: Her mental state was normal, with the exception of verbal memory, which benefited by cuing. Orthosta- tic hypotension was present. She exhibited masked facies and bradykinesia. A resting tremor was observed. Rigidity was present in passive movements. She required the aid of her arms to rise from a chair and walked with diminished arm swing and shortened steps. Coordinated movements were slow but accurate. Reflexes were normal.

Summary: An insidious CNS disorder with predominantly motor impairment respecting a specific degenerative pattern. A disorder of memory retrieval may be emerging.

Principal diagnostic hypothesis: Parkin- son’s disease with secondary depression and anxiety disorder. Possibly has an early subcortical dementia.

Case 2 At 58, a financial planner found himself taking additional time to perform routine tasks, and found that he could not manage phone transactions. His personality became irritable and obsessive, with reduced frustra- tion tolerance and temperamental flares over trivial matters. He found he could not plan or organize as before, and he had several “near misses” in driving over a short period.

His examination showed slowed velocity of ocular refixation movements (saccades),

motor impersistence of tongue protrusion, and poorly sustained grip. His speech was grammatic and expressive, but dysrhythmic. With mental effort, he showed choreic movement in the face and all extremities. His gait was slightly widened in base. His muscle stretch reflexes were hyperactive.

Summary: An insidious progressive brain disorder with frontal executive functional impairment and evolving irritable personal- ity, accompanied by an adult-onset choreic movement disorder. Frontal-subcortical localization is suspected.

Principal diagnostic hypothesis: Hunting- ton’s disease. If the family history is negative for this genetic disorder, confirmation of the diagnosis can be sought through DNA testing.

Case 3 A 65-year-old retired judge experiences slowly progressive impairment. He has difficulty in word finding and adopts a “circumlocutory” speech. He misplaces objects and cannot retain the content of his reading. He loses direction when he walks in unfamiliar places, and he finds that he cannot continue his hobby of constructing models. After several years, he loses insight that he is impaired, and accuses his wife of being a malevolent impostor. His memory impairment is not helped by cues or reminders.

The neurologic examination, other than the mental status, is entirely normal, although he has difficulty cooperating with the examiner.

Summary: A progressive disorder mani- festing anomic aphasia, visuospatial impair- ment, and apraxia, all cortical dysfunctions. Memory encoding is impaired and not benefited by recognition. The absence of any motor impairment is striking.

Principal diagnostic hypothesis: A cortical degenerative dementia such as Alzheimer’s disease is likely. The medical team will under- take a search for treatable and reversible conditions that imitate this pattern.

Subcortical dementia Parkinson’s disease (PD) Parkinsonism Rigidity Lewy bodies Resting tremor

Bradykinesia Masked facies Festinating gait Micrographia Hypokinesia Dysphonia

Tachyphemia Palilalia Anticholinergics Dyskinesia Pallidotomy Thalotomy

Huntington’s disease (HD) Chorea Creutzfeldt–Jakob disease (CJD) Gerstmann-Straussler-Scheinker

syndrome (GSS) Kuru

dysfunction. Visuospatial and executive dysfunction often are evident. Language difficulties are typically minor, and memory difficulties, in comparison with AD, primarily involve executive aspects of memory. Pa- tients with PD also frequently suffer from a concomitant mood disorder. The pharmacologic and surgical treatments for PD are among the most promising treatments for any of the dementias.

HD is a good example of a contrasting subcortical dementia with motor difficulties different from those of PD. It is also a good example of a progressive hereditary disease. The neuropsychological profile of HD illustrates the executive functioning problems caused by compromise of the striatofrontal lobe complex. Interestingly, patients with HD also show a significant affective disturbance. Finally, CJD, although quite rare, is a good example of a fast-acting dementia that is transmissible via infected neural tissue.

Differential diagnosis among dementia subtypes can be quite complex. This chapter, as well as Chapter 14, discusses only some of the major exemplars of dementia. Practicing neuropsychologists must come to recognize and differentiate many more subtypes. The study and recognition of dementias requires much experience with a number of dementia subtypes, and careful assessment and observation of behav- ioral differences. In this endeavor, neuropsychologists work in close conjunction with neurologists who specialize in geriatrics. We end this chapter with a look at how neurologists approach evaluation and diag- nosis in differentiating dementia subtypes (Neuropsychology in Action 15.5).

C r i t i c a l T h i n k i n g Q u e s t i o n s

It may soon be possible to test for many neurologic diseases. Would you want to be tested for the possibility of future dementia? How is the behavioral quality of subcortical motor disorders presented in this chapter similar or different from the cortical motor disorders such as apraxia presented in Chapter 7? How do the subcortical and cortical motor systems work together? What are the ethical and scientific issues in the treatment of dementias?

K e y Te r m s

442 PART THREE | Disorders of the Brain

We b C o n n e c t i o n s

http://www.parkinson.org/site/pp.asp?c=9dJFJLPwB&b=71117 National Parkinson’s Foundation—PD information and research.

http://www.ninds.nih.gov/disorders/huntington/huntington.htm National Institute of Neurological Disorders and Stroke (NINDS) Huntington’s Disease Information Page.

http://www.ninds.nih.gov/disorders/cjd/cjd.htm NINDS Creutzfeldt–Jakob Disease Information Page.

http://www.parkinson.org

http://www.ninds.nih.gov

Chapter 16

A LT E R AT I O N S O F C O N S C I O U S N E S S

Each mind fabricates itself. We sense its limits, for we have made them. —Rainer Maria Rilke

If we cannot understand such global and major changes in the state of the brain-mind as occur in sleep, what chance will we have with the far more subtle changes in consciousness that trouble our patients?

—Attributed to Edward Evarts, by J. Alan Hobson (1995)

Understanding Consciousness Rhythms of Consciousness The Brain and Mind in Sleep Runaway Brain: Seizure Disorders

Neuropsychology in Action

16.1 Self in the Mirror 16.2 The Case of the Last Coronation 16.3 Lucid Dreaming: A Paradox of Consciousness 16.4 Déjà Vu and Epilepsy 16.5 Epilepsy and the Case of the Sweeping Lady

experience? Is self-awareness a mind process, as William James thought, or a mind state? These questions have tan- talized philosophers, theologians, and scientists through- out time. Brain science has taken up the challenge of de- ciphering consciousness. This was once the domain of

444 PART THREE | Disorders of the Brain

K e e p i n M i n d

Can “brain” states differ from “mind” states?

How can awareness and consciousness be defined?

What brain mechanisms are responsible for the “paradox” of rapid eye movement sleep?

What alterations of consciousness are represented by different seizure types?

Do alterations in conscious alertness result from similar biological mechanisms?

Overview Consciousness can be conceptualized in a number of ways. Awareness, level of mental alertness, and level of attention are common representations. Consciousness can also imply the mind’s subjective experience of brain states and processes that are available to perception. These various definitions point to a number of different functional anatomic areas depending on the aspect of consciousness under consideration. Disor- ders of these disparate functional systems also result in a variety of disorders of consciousness. For exam- ple, we have discussed alterations in conscious “knowing,” or agnosias of the visual system. The total un- awareness of one side of the body, or neglect, is a dramatic dysfunction of normal conscious awareness. These disorders of lowered, distorted, or piecemeal awareness can occur in any sensory modality. Synesthesia, or the abnormal melding of sensory-perceptual experiences, represents yet another alteration of consciousness covered in this book.

This chapter revisits questions of brain and mind by considering conceptualizations of consciousness particularly for awareness and alertness. We discuss both normal and disordered aspects of consciousness through a discussion of normal sleep, sleep disorders, and seizure disorders. Throughout the day and night, alertness fluctuates according to preset circadian (derived from Latin, meaning “about a day”) rhythms. The study of these daily rhythms, as people move from waking to sleeping and dreaming, offers lessons in the limits of normal brain alterations of consciousness. Disrupted flow of these brain rhythms can result in a variety of sleep disorders. Some, such as the rare circadian rhythm disorder (see Neuropsychology in Action 16.2) can threaten life itself. Others, such as narcolepsy, show major disruptions of the REM (rapid eye movement sleep) cycle and result in sleep intrusions into wakefulness. Most sleep disorders disrupt cognition in some way. In sleep apnea, for example, memory and concentration difficulties are prevalent.

Seizures represent another set of disorders of consciousness. Seizure events of various types repre- sent alterations of daytime alertness and awareness. These internally generated brainstorms of activity manifest differently, largely according to the location of the seizure focus in the brain. Typically, neurologists categorize them as either generalized or partial seizures, depending on the extent of brain involvement during the seizure episode. We present these in the context of a general seizure classification scheme. Seizures can occur as a result of a variety of causes. Neurologists consider most people with repeat seizures to have an epileptic syndrome. This, of course, is potentially more threatening to brain function than is an isolated seizure event. We discuss the neuroanatomy and neurophysiology of epilepsy, as well as the neuropsychological consequences and types of treatments available.

Understanding Consciousness

What is consciousness? What makes human con- sciousness different from that of other animals? What sorts of brains or brain activity are necessary for conscious

psychology, spearheaded by Wilhelm Wundt and the early structuralists at the turn of the century; the strong behav- ioral movement in U.S. psychology later cast aside the study of consciousness as too subjective for serious study. Observable behavior was now paramount, and the brain was merely a “black box.” Psychologists now know that consciousness is fundamentally important to understand- ing the human condition. Conscious experience, how- ever, is difficult to measure and observe because of its highly private nature. Nobel prize laureate Francis Crick (Crick and James Watson discovered the structure of DNA) admonishes scientists not to worry too much over aspects of the problem that they cannot solve scientifically or, more precisely, cannot solve solely by using existing sci- entific ideas. Perhaps the only sensible approach is to press the experimental attack until scientists confront dilemmas that call for new ways of thinking (Crick & Koch, 1990).

Here we are concerned with defining the concept of consciousness, the mind–brain relation, and current the- ories related to how the brain represents consciousness. After considering the “how” of consciousness, we turn to theorist David Chalmer’s question related to the “why” of consciousness. Even if we can explain how the brain rep- resents conscious experience, we need to know why this is important to human functioning. Why are we not un- thinking and unfeeling automatons?

To begin, most people agree that consciousness implies awareness. This is the primary dictionary definition. The term consciousness also refers to a certain level of mental alertness and attention. It also connotes what one’s inner self knows or feels. Consciousness is above all a subjective and highly personal reckoning of external and internal events. Measuring it has also relied largely on the person’s ability to manifest internal experiences through verbal ex- pression. The issue of awareness raises interesting ques- tions for neuropsychology. If the mind is the subjective experience of brain states and processes, then the mind reflects awareness of brain and body functioning. Because of either external or internal stimulation, sometimes the mind may be able to show more awareness, whereas at other times it seems totally oblivious to the workings of the physical brain and body. One of the main questions that brain science must answer (to put it in what is now the common vernacular) is, What distinguishes the con- scious mind from the subconscious or unconscious mind?

M I N D A N D B R A I N

Popular culture often represents the brain in mechanistic terms, like a type of giant computer, reminiscent of New- tonian physics. However, machines can self-regulate behav- ior but do not have self-awareness or a subjective experience

of consciousness. Another interesting question is to what extent do animals show self-awareness (Neuropsychology in Action 16.1). An interesting theoretical question re- lates to whether computers will someday imitate the human brain, and presumably become conscious. Will artificial intelligence (AI) mimic human consciousness, as in the imagined character HAL, the supercomputer in the science fiction movie 2001: A Space Odyssey? During a space shuttle to Mars, HAL starts to display “his” own awareness and decision-making capability, finally killing off the shuttle crew.

Conceptualizing the brain as a computer has only lim- ited usefulness. After all, brains have built computers, not the other way around. It appears more useful to concep- tualize the brain as attached to the person, as a biological entity. The level of consciousness of biological entities partly responds to biological and cosmic rhythms, as evi- denced in the sleep/wake cycle and the rhythm of the sun. Consciousness also changes in response to internal physi- ology and chemistry, with inputs from food and drugs. The term mind is used to reflect subjective experience, and therefore consciousness, of the emanations of the brain and the body together. Can we assume that every state of mind links to a brain state, and that every state of brain reflects a mind state, be it conscious or unconscious?

Scientists have often wondered whether split-brain pa- tients, who have had the two hemispheres of their brain surgically disconnected, are “of two minds.” In an older method of treating seizures, surgeons cut the half-billion axons that allow interhemispheric cross-talk in many pa- tients with intractable seizures. Are these two hemispheres still conscious of each other? Do split-brain patients re- tain one consciousness, or do two separate realities or even two separate personalities exist? Immediately after surgery, some split-brain patients report having two competing hemispheres. When getting dressed, the right hand may reach for a blue shirt whereas the left hand is grabbing a red shirt. These apparently competing programs, how- ever, usually resolve within a matter of weeks. After that, split-brain patients typically report a unified conscious experience. In daily life their actions are not recognizably different from their presurgery state. Only specialized test- ing that presents information to only one hemisphere at a time continues to show differences. In effect, this testing appears to reveal more differences between right and left hemisphere processing than it shows a fundamental divi- sion of consciousness in those who have had a split-brain operation.

The stumbling block is that we usually document awareness via our ability to verbalize, a province largely of the left hemisphere. In individuals with an intact cor- pus callosum, the right hemisphere—and therefore the

CHAPTER 16 | Alterations of Consciousness 445

consciousness of the right hemisphere—is accessible to left hemisphere verbalizations. Split-brain patients must reformulate a sense of completeness by making their ex- periences accessible to both halves of their brains through external cross talk. They can largely do this by moving their eyes to capture both visual fields and verbalizing out loud so that each hemisphere hears what is available to the other hemisphere. Within us, many brain and body processes are either automatic or unavailable, and thus

typically remain unconscious to the mind. For split-brain patients, the hemispheres are physically unavailable to each other. The brain is not communicating internally, but the subjective experience is of one mind. The chal- lenge for the split-brain patient is to consciously integrate each half of the cerebral hemispheres that have been made surgically unconscious of each other.

Most people with intact brains agree that large areas of potential experience remain below the level of conscious

446 PART THREE | Disorders of the Brain

Have you ever caught your cat (or dog) shav- ing? Have you ever wondered why your (male) pet might not shave? Well outside of the fact that it is likely difficult to shave with no opposable thumb and challenging to balance yourself on two limbs when you are used to moving about on four, there is another, neurocognitive reason why your pets do not shave. They cannot recognize themselves in the mirror! That’s right, your pet (that is unless you own a pet chimpanzee) does not have the cognitive capacity to recognize itself in the mirror; in fact, your pet likely sees its mirror reflection as another member of the same species and reacts as such (for exam- ple, hisses, piloerection for cats).

In 1970, a comparative psychologist named Gordon Gallup (Gallup, Nash, Potter, & Donegan, 1970) was investigating the behavior of animals in front of mirrors as a way to measure social behavior systemati- cally when he stumbled on the fact that most organisms react to their mirror reflection as if it were a member of the same species; that is, they responded to their mirror reflection with species-specific social behaviors (threats, attempts to mate, spitting, barking, feces throwing, among other reactions). To scientifically test this notion, Gallup devel- oped the “mark test,” which entails marking areas of an animal’s body that cannot be seen without the mirror. Animals that can recognize themselves in mirrors ought to use the mirror to examine their newly marked anatomy. It turns out that only our closest

living relatives—the great apes (chimpanzees, orangutans, and gorillas)— posses the ability to use their mirror reflec- tion like humans do (Gallup, 1982).

What is the importance of mirror self- recognition for neuropsychology, and who cares whether chimps can do it? It turns out that the ability to recognize yourself in a mirror is strongly related to your sense of self, or self-awareness, which allows you to engage in a number of adaptive social behaviors, for example, empathy, sympathy, deception, and so on (Gallup, 1982). In addition, great apes’ frontal lobes are the most encephalized, second only to humans. Meaning relative to other parts of their brain and their body, great ape frontal lobes are larger than would be expected by chance. Therefore, the investigation of self-recognition in nonhuman primates provides us with insights into the neuropsychological and possible clinical underpinnings of self and consciousness in humans.

If I were to ask you: “Does everyone recognize themselves in a mirror?” You’d likely answer, “Of course!” Not true. In fact, there are several neuropsychological condi- tions that are marked by deficits in self- processing. The most notable is a condition known as “mirror sign,” or mirror self- misidentification syndrome (Breen, Caine, & Coltheart, 2001). Patients with mirror sign are able to use mirrors to recognize objects, and even other people, but when asked about their own reflection, they often

respond as if their mirror reflection was a stranger who was following him or her around. Usually untroubled by their disorder, family members report that patients act “funny” or “strange” at home, often surpris- ing themselves as they walk past mirrors. Some patients do complain that their new counterpart does not talk to them, which does create some frustration. Neuropsycho- logically, these patients are marked primarily by right hemisphere dysfunction, which suggests that the capability to process information about the self may be localized to regions of the right frontal lobe. This notion has recently been confirmed by several functional magnetic resonance imaging investigations of self-face recogni- tion (Platek, Keenan, Gallup, & Mohamed, 2004; Platek et al., 2005).

Several other neuropsychological condi- tions are marked by subtler deficits in self- processing. For example, patients with schizophrenia make many errors when asked to distinguish their own face from family members’ faces and are more likely than control subjects to classify unknown faces as being their own face.

Collectively. these data—from compara- tive, nonhuman studies to neuropsychiatric patient findings—suggest that the frontal lobes, and perhaps specifically the right frontal lobe, are involved in self-processing and when damaged or compromised might result in impairments in self-awareness and corresponding social intelligence.

N e u r o p s y c h o l o g y i n A c t i o n 1 6 . 1

S e l f i n t h e M i r r o r

by Steven M. Platek

experience. The common saying “we only use 10% of our brain” might be better thought of as “our conscious mind may be aware of only a percentage of what our brains do and are capable of.” Our brains control and monitor the entire nervous system of our bodies and respond to physi- ological mechanisms in the body, such as those of the en- docrine system, to maintain a state of brain–body home- ostasis. Many of these processes are automatic and reflexive. They are unconscious. But they can be brought into awareness via techniques such as biofeedback, and can then be modified by the conscious mind. Many have wondered what might be possible if aspects of the uncon- scious mind became conscious. What hidden potential could people then develop, such as becoming conscious during the “unconscious” state of sleep or developing senses and perception beyond what is now commonly thought possible? This may sound like the stuff of science fiction, but researchers have documented lucid dreaming (see later). It is also reasonable to assume that scientists will find ways to study the limits of sensory-perceptual experiences. Boundaries between the concepts of the con- scious mind and the unconscious mind are blurring. The challenge now before brain science is to understand the workings of these aspects of mind and to relate them to brain states and processes.

A N A T O M I C C O R R E L A T E S O F C O N S C I O U S N E S S

How are states of consciousness represented in brain anatomy and physiology? René Descartes thought the pineal gland was the center of conscious experience, but researchers have found no single location for conscious- ness. After several hundred more years, this question may still be somewhat premature, because brain science has not yet clearly defined the operations and boundaries of consciousness. Different areas of the brain may play roles in specific aspects of conscious perception and alertness. Brain science is also now providing interesting clues to how the brain “binds” disparate fragments of information from different cortical and subcortical regions into a sub- jective sense of coherent unity.

The candidates for brain regions or functional areas that have a role in conscious behavior have, depending on the behavior in question, included numerous areas of the brain, both cortical and subcortical. The various defini- tions of consciousness suggests that different brain corre- lates are implicated depending on whether the focus is on notions of awareness or perception, notions of alertness or attention, or notions of what is felt or known by one’s

inner self. Perceptual awareness, “knowing,” and therefore, perceptual consciousness, build up through modality- specific sensory systems of vision, audition, proprioception, olfaction, and taste. The brain correlates of sensory- perceptual consciousness depend on the integrity of each of these systems. Therefore, it is possible for one sensory modality to block access to “knowing,” whereas still show- ing awareness through other sensory modalities. Such is the case with the agnosias, as we have discussed in Chapters 7 and 8, which can occur after damage to any of the sensory systems. When speaking of level of consciousness, or alert- ness, researchers often identify the reticular activating system (RAS) in the midbrain as responsible for arousal, which we discuss in regard to sleep. Finally, if the self- referential, self-evaluative, and metacognitive aspects of con- sciousness are the focus, then researchers can consider aspects of executive system and frontal lobe functioning.

Brain researchers and theorists have been most in- trigued by how the brain creates a unitary experience of consciousness at one particular moment in time. This can be referred to as the binding problem. What is the mecha- nism that binds disparate neural elements together? A unitary experience of consciousness is an operation of the highest order and, therefore, requires a cortex. Thus, the more sophisticated the cortex, theoretically, the greater the ability for subjective experience and self-awareness.

Let us examine the role of the cortex in consciousness more closely. Neuroscientists commonly describe experi- ences represented in the cortex as stable spatial patterns. For example, vision is a complex constructional process resulting in object recognition by building and binding elements related to color, form, movement, and spatial position. This binding may occur as a simple structural pattern. Experience in seeing your grandmother increas- ingly hardwires the synaptic conjunctions between the neurons from various cortical areas forming the pattern that defines “grandmother.” This way of thinking is an advance over conceptualizations that first postulated the existence of single “grandmother” cells in which the recognition of grandmother, although the culmination of many processes, was ultimately embodied in one neuron or neuron group. Brain scientists soon realized that the model of single cumulative grandmother cells was grossly inefficient, because separate cells would have to be avail- able for every possible combination and permutation of people and objects. Even though the brain consists of billions of neurons, it would soon run out of neurons for every possible permutation of a memory. Having grand- mother represented in a large cortical neuronal assembly is a more efficient conceptualization in terms of processing. Individual neurons can participate in different assemblies,

CHAPTER 16 | Alterations of Consciousness 447

one representing grandmother, another father, another a teacher, and so on. The firing pattern within the web of neurons takes precedence over any individual neuron. If the pattern is disrupted at crucial points, the brain loses recognition of the person.

The neocortex unquestionably plays a major role in evaluating external and internal experiences, but subcorti- cal structures, and particularly the thalamus, may play a crucial role in orchestrating the higher cortical symphony. Francis Crick and Christof Koch (1990), in their study of visual consciousness, have postulated that the upper lay- ers of the cortex are largely unconscious, whereas the pyra- midal neurons in layer 5 may be “conscious.” Their rea- soning is that this is the only layer that “projects right out of the cortical system.” Layer 5 also shows an unusual propensity to fire in bursts. Others have also noted this important observation that groups of neurons fire to- gether in bursts, which appears to be an important clue to the binding problem. Researchers know that many cell assemblies throughout the brain fire in synchronous oscil- lations. For example, in the motor system, the inferior olive of the brainstem sends information in packets of bursts at an oscillation of 10 cycles/sec to the cerebellum. Much as with frames of a movie, the movement only ap- pears fluid because we cannot discriminate the fine breaks in continuity.

The thalamus, the sensory relay station of the brain, may also play a crucial role in synchronizing cortical processes. In an alert state, an electroencephalograph (EEG) records in the gamma frequency range (35–80 cycles/sec), averaging 40 cycles/sec from the cortex. This normal frequency decreases with relaxed wakefulness to 8 to 10 cycles/sec and with deep sleep and coma to 0.5 to 4 cycles/sec. Faster frequencies are asynchronous, whereas slower frequencies become increasingly synchronized and rhythmic. Rodolfo Llinas of New York University (cited in Becker & Seldon, 1985) postulates that the EEG fre- quency represents a binding wave that continuously sweeps the cortex like a huge radar arm. As the wave scans the brain, the brain synchronizes and interprets all infor- mation in that sweep as a unified experience. This action, then, could bind packets of information from widely dis- tributed and noncontiguous regions of the cortex by syn- chronizing them in time. The implication is that more hardwired spatial patterns of neurons do not act as the prime binding mechanism. Researchers have postulated this theory as a general explanation for how consciousness operates, as well as a specific explanation for how aspects of visual consciousness such as visual object recognition work (Bressler, Coppola, & Nakamura, 1993; Crick & Koch, 1990).

If there is a “binding wave,” from where does this fre- quency emanate? It appears as if the intralaminar nucleus of the thalamus generates a cortical binding signal every 12.5 thousandths of a second (that is, every 0.0125 sec- ond) (Llinas cited in Becker & Seldon, 1985). As men- tioned earlier, nearly all sensory and motor systems route through the thalamus. The thalamus is in constant two- way communication with the cortex through a feedback system of millions of thalamocortical loops. A number of investigators believe this system, which reaches through- out the cortex, is intimately involved with conscious ex- perience. Because nearly all information channels through the thalamus, it can act as the integrator, selecting, pack- aging, and tagging information that occur together in time from all areas of the brain, and sending it back for the cortex to record as an object or an event. The thala- mus and the thalamocortical projection system play an important role in arousal, sleep, and seizure disorders. It may also play a role in remapping phantom sensations. A temporal binding system, whether through the thalamus or other structures, would be highly efficient, because it could register any number of novel neural code combina- tions together and be experienced instantly without rely- ing on the hardware of contiguous, linear cortical con- nections. These findings suggest that, indeed, there is no single organ of consciousness; instead, the frequencies of temporal binding may coordinate experience. This would indicate that the whole brain can contribute to awareness depending on which systems activate at any one time to signal the effect of an experience. This view implies a dy- namic quality to the brain and conscious experience that is infinitely more flexible than former conceptualizations.

According to theorist David Chalmers (1996), the “how” question of consciousness is not the difficult ques- tion. The difficult question is not how conscious processes bind together, but how a subjective experience of mind arises from the functioning brain and its synchronized and bundled oscillations. By looking deeper into people’s direct subjective experiences, some of which are explicit and some of which are implicit, researchers will learn more about the relation of brain to mind.

People customarily link consciousness of external events with the tangible. Even our vocabulary reflects this: “I know something to be true because I saw it with my own eyes, I can feel it, I can sense it.” Most of what peo- ple experience they know by way of senses of smell, taste, sight, sound, and touch—the springtime smells of lilacs and freshly mown grass, the sight of children running across the yard, the sound of laughter, and the squeeze of a hand. But external realities exist that most of us cannot perceive directly through our senses. At the turn of the

448 PART THREE | Disorders of the Brain

20th century, people were just becoming aware that sound could travel through long distances, even through bodies, yet people cannot perceive such sound directly without a little box called a radio. In the animal world, whales, dogs, and bats communicate within their own species on differ- ent frequencies than humans can “consciously” perceive. We now know that low- and high-frequency sound exists, because we have instruments that can measure and trans- mit these “unconscious” ranges of sound. In the same vein, people know that electrical fields and microwave en- ergy exist. In 1933, Enrico Fermi, a physicist, predicted the presence of neutrinos, or energy particles, which per- meate the universe and freely flow through bodies with- out leaving a trace. In 1956, physicists definitively identi- fied neutrinos. What else might exist that people cannot consciously perceive? Modern science may be just begin- ning to unravel the mysteries that lie beyond limited human sensory abilities.

The Western empirical, materialistic tradition of sci- ence takes the stance that if something cannot be observed and measured it does not exist. To study the full range of consciousness, this archaic and human-centered view must give way to the possibility that the range of reality extends beyond ordinary human sensory-perceptual expe- rience. Brain dysfunction can truncate, extend, or other- wise bend sensory-perceptual experience. Many cases we present in this book certainly stretch the bounds of ordi- nary conscious experience. Supersensory abilities may also be possible. Some Chinese health practitioners diagnose and heal by working with only the energy fields of the body. Fortunately, new technologies may bring into awareness many aspects of sensory experience that are out of range to the “naked senses.” Scientists may now experi- mentally verify awareness of both pathologically altered and exceptional sensory perception, although few studies have considered these issues.

Previously, the limited means of measuring subjective experience have hampered scientists in studying con- sciousness. Primarily, they have had to rely on direct ex- perience of the senses and on language to reveal con- sciousness. In other words, people could demonstrate awareness if they could hear, see, taste, smell, or touch something and be able to describe it. Because the left hemisphere is more specialized for spoken words, some have characterized it as the seat of consciousness. But that simplistic notion equates awareness with an ability to de- scribe the phenomenon. Many people can probably recall experiences in which they had a sense of knowing with- out the ability to verbalize or touch what they felt.

Also, some processes that are now implicit may be made explicit. People can demonstrate implicit knowl-

edge through their actions based on that knowledge. Sci- entists also know that subliminal sound and scent, under the level of detectable awareness, can affect brains in a predictable manner. Similarly, scientists will also be able to determine whether some individuals can detect electri- cal energy fields of which most are not conscious. On the internal side of the coin, many of what are considered au- tomatic processes, such as breathing and heart rate, churn along without conscious awareness or control. But the means already exist to bring many of these processes into conscious awareness through various biofeedback tech- nologies such as heart-rate monitoring, galvanic skin re- sponse measurement, and EEG. Although these technolo- gies present a recent tool for more conscious body and mind control, masters of meditation have long exerted amazing control over many brain and body states. Given the increased ability to gain a window into automatic and subconscious processes through vivid functional brain imaging techniques, whole new areas of research are open- ing up that may now allow neuropsychologists to learn not only about the workings of the brain but also how to consciously control various brain states. The possibilities available for extending the range of normal conscious ex- perience represent an exciting frontier in brain science.

This chapter visits daily aspects of consciousness, as well as disorders of consciousness. What happens when the fundamental experiences of consciousness run amok because of brain dysfunction? The daily rhythms of alert- ness and arousal people all move through from waking to sleeping and dreaming provide directions for studying the limits of normal brain alterations of consciousness. Dis- rupted flow of these brain rhythms can cause a variety of sleep disorders, of which one of the more interesting is narcolepsy. Finally, seizures represent an alteration of con- sciousness that also affects level of alertness—an inter- nally generated brainstorm of synchronized activity.

Rhythms of Consciousness

Cyclic changes are inherent in the passing of sea- sons, in weather patterns, in tidal ebbs and flows, and in the rising and setting of the sun. In humans, mood and energy levels respond to seasonal shifts, menstruation cy- cles follow monthly rhythms, and sleep and wakefulness cycles oscillate daily in a circadian rhythm. Humans also respond to shorter ultradian 90-minute cycles of height- ened and lowered brain arousal. The autonomic system of the brain controls the rhythms of heart rate and respira- tion. The brain itself is a web of neuronal circuitry with a frequency measured in cycles per second on an EEG (see

CHAPTER 16 | Alterations of Consciousness 449

Chapter 2 for a detailed discussion of EEG). It alternates between periods of brain asynchronicity, usually indica- tive of an alert brain state, and periods of “altered con- sciousness” synchronicity, in which groups of neurons os- cillate rhythmically. Some of these synchronous oscillations, such as those occurring during sleep, represent normal variations. Others, which occur during seizures and coma, may suggest pathology. Many of the normal internal rhythms of the body and brain, such as sleep, are cali- brated in response to external environmental changes such as the light/dark cycle. Scientists do not yet understand a great deal about the complex interplay between the many human rhythms and external environmental rhythms that affect human functioning.

In addition to these questions, neuropsychology is in- terested in how brain states, measurable via dynamic imaging means such as EEG and positron emission to- mography, correspond to mind states in both ordinary and pathological functioning. In absence seizures, slow- wave synchronous activity abruptly interrupts the nor- mally asynchronous waking state. It would appear, then, that slow synchronous brain activity heralds pathology. But absence seizures in children, which are marked by brief lapses in consciousness, show the same 3 cycles/sec

synchronous brain waves characteristic of normal delta- stage sleep. The EEGs of people in coma also show this slow synchronous wave. Masters of meditation, however, can produce delta waves and remain seemingly “conscious.” Although the EEG can record similar brain states in two different people, mind states and awareness can range con- siderably. Therefore, similar brain-wave frequencies can imply pathologic “unconscious” mind states, normal sleep- ing mind states, or fully conscious mind states. Although the EEG provides clues as to whether one is thinking, it does not capture the subjective experience of the mind.

Many interesting questions of consciousness revolve around alertness and level of arousal. We examine sleep in some depth in this chapter because of its rhythmic brain activity and the paradoxical and fascinating nature of the dreaming REM (rapid eye movement) stage. Deep within the hypothalamus, a biological clock—in conjunction with the visual system—calibrates the sleep/wake cycle. A case example illustrates how chaotic sleep and health can become without this clock (Neuropsychology in Action 16.2). Sleep disorders such as narcolepsy also illustrate the manner in which sleep/wake rhythms may become confused, resulting in daytime sleep intrusions and frag- mented nighttime sleep.

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He was Italian, 53 years old, and an indus- trial manager whose health had been fine except for some problems with high blood pressure. Much to his misfortune, he was destined to show researchers how dire things can get when the body’s internal clock runs amok.

In 1985, the man experienced develop- ment of insomnia. His sleep fell to only 2 or 3 hours a night, he became impotent, and he began to have difficulties with his digestion and developed a high temperature. Within 2 months, he could sleep for only 1 hour a night and was often observed rising from his bed, standing, and giving a military salute. He told his family that he was dreaming of a coronation. By the time the man was admit- ted to the hospital in Bologna, he had

ceased to sleep normally at all. He was alert when spoken to, but when left alone would drift into a stupor in which he would gesture as if communicating in a dream. His doctors tried to treat him with a variety of strong drugs, none of which had a lasting effect. In the eighth month of his illness, the man’s stupor was relieved only by episodes in which he screamed and thrashed about. In the ninth month, he died.

Examining his otherwise normal brain, doctors found that certain regions of the thalamus had degenerated. The man’s rare disease supported suspicions that sleep, at least nondreaming NREM (non–rapid eye movement sleep) sleep, is affected by chemical processes in the thalamus. Just below that structure, near the base of the

brain, is a bean-sized region known as the hypothalamus. The hypothalamus sends out signals that regulate basic processes such as hunger and sex and affect emotions such as anger. It is also a central control for the biological clock that controls sleep; when the hypothalami of mice are damaged, the mice lose any semblance of orderly or regular sleep.

This man’s misfortune also displayed the genetic nature of this sleep disorder. The doctors learned from one of the man’s relatives, also a doctor, that in the last 6 generations of the man’s family at least 14 relatives, including his sisters, had died of the same bizarre condition. Source: Adapted from The Case of the Last Coronation. (1988, March–April). Hippocrates.

N e u r o p s y c h o l o g y i n A c t i o n 1 6 . 2

T h e C a s e o f t h e L a s t C o r o n a t i o n

Scientists are just beginning to understand the brain mechanisms underlying neuronal rhythm in sleep and in seizures. At a neuronal level, neurons and neuronal sys- tems maintain a fine balance between excitatory and in- hibitory balance. An individual neuron may receive both excitatory and inhibitory messages from the neurons that synapse on it. Whether the neuron fires depends on how these messages add up. Excitatory and inhibitory neurons may also synapse with each other in a loop and oscillate in their intercommunication. The thalamus, a powerful pacemaker, has afferent and efferent neural connections reaching throughout the cortex. At a cell assembly level, the same sort of oscillation, the thalamocortical loop, oper- ates between the thalamus and the cortex. Interestingly, the thalamus appears able to initiate thalamocortical syn- chronous oscillations without external input. Although researchers know that peculiarities in the ion channels of thalamic cell membranes allow these cells to generate and sustain a rhythm, it is unclear what triggers this behavior. In general, scientists can describe how certain local groups of cells begin to oscillate, and how certain widespread cor- tical brain-controlling mechanisms, such as the thalamus, generate rhythm, but why this occurs is a matter of spec- ulation. Studying rhythmic brain activity in behaviors such as sleep and seizures may help to elucidate these mechanisms.

The Brain and Mind in Sleep

Is sleep unconscious? As a laptop computer goes “to sleep,” it shuts down—it is unresponsive, and the hard disk spins down until it is “awakened” again with a touch. But the machine analogy of a steady state does not do jus- tice to the complex ebbs and flows of the sleeping human brain. Sleep is a drifting down into deeper levels of un- awareness of the world, which then lighten and deepen in a rhythmic pattern during the night. Seemingly unrespon- sive to the majority of external sensory stimuli, intense emotions and hallucinations arise created by the sponta- neous firings of the brain itself. How conscious are we or can we be during sleep? Delta waves at a frequency of 0.5 to 4 cycles/sec represent the deepest stage of sleep. Yet what of expert mediators who can produce delta waves and remain conscious? They describe their change in awareness of themselves as progressing from the experi- ence of “self ” to a “point of still awareness” (Kenyon, 1994). During REM sleep, dreams occur, but people are usually quite oblivious to that they are in a dream state and usually forget the dream. Some people, however, are “lucid” dreamers, knowing they are dreaming during their

dream, and able to influence theme and outcome, thoughts, and emotions (Neuropsychology in Action 16.3). There is much to learn in the emerging area of brain function during sleep. This section explores how consciousness, awareness, and arousal operate through the window of sleep and dreaming. We discuss the known brain mechanisms that govern levels of arousal through the neurology and physiology of normal sleep, and finally, sleep disorders of particular interest to neuropsychology.

S L E E P A R C H I T E C T U R E

The cycle of brain activity during sleep is embedded within the larger circadian rhythm of wakefulness and sleep. The sleep rhythm is a 90-minute cycle of descend- ing and ascending states of cortical arousal. It is punctu- ated at the end of each cycle by periods of such intense brain activity that the sleeping brain appears active, al- most in a waking state. This general pattern is highly sta- ble across people, although much variability exists in the amount of time spent in each phase, depending on such factors as age, physical condition, and other individual variables.

The two general stages of sleep are known as REM and NREM (non–rapid eye movement sleep). Both have char- acteristic EEG patterns and physiological correlates (Table 16.1). As discussed in Chapter 2, scientists describe EEG waves by their amplitude, which is a measure of micro- voltage, and their frequency or speed, measured as the cy- cles per second of a complete wave. Scientists may also describe the overall characterization, or pattern of waves, as synchronous or asynchronous (arrhythmic), according

CHAPTER 16 | Alterations of Consciousness 451

Stage Frequency Amplitude Time (cycles/sec) (microvolts) Waveform %

NREM (non– rapid eye movement)

1 4–8 50–100 Alpha, theta 5

2 8–15 50–150 Theta, sleep 45 K spindle complex

3 2–4 100–150 20–50% delta 12

4 0.5–2 100–200 >50% delta 13

REM (rapid Mixed 50–100 “Sawtooth” 25 eye movement)

Table 16.1 Electroencephalographic Sleep Stage Characteristics in Adults

to the degree or tendency of neural circuits to fire together in rhythm. The EEG provides a dynamic view of activity in the sleeping brain. Figure 16.1 portrays the characteris- tic EEG waves and patterns of each stage of sleep. Notice that as EEG slows, wave amplitude correspondingly in- creases. For each stage of sleep, there are characteristic wave- forms, such as alpha, theta, and delta, and for REM, a form that looks like a sawtooth. In addition, certain forms may be superimposed, such as sleep spindles and K complexes in stage 2 sleep. During the waking state, the neural cir- cuits fire in a characteristic 40-cycle/sec, low-voltage, de- synchronized pattern. Merely closing the eyes starts a shift toward coordinated rhythmic neural circuit oscillation. Synchronized bursts of alpha waves (8–12 cycles/sec)

appear superimposed on the background of the faster brain rhythm. The person literally descends into sleep as the EEG waves become slower, higher, and more rhythmic with each stage. Finally, in the deepest (stage 4) sleep, EEGs show 50% or more delta waves. This high-amplitude (100–200 mi- crovolts), slow-wave (0.5–2 cycles/sec) rhythm indicates that the cortical circuits are oscillating at the slowest peri- odicity. It is not surprising that if one is awakened from stage 4 sleep, which is likely to occur about 60 minutes after sleep onset, one takes several minutes to recover from deep-sleep grogginess.

NREM and REM sleep represent different states of consciousness. Progressing through the stages of NREM sleep, the person becomes increasingly difficult to arouse.

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Figure 16.1 Electroencephalographic (EEG) patterns representative of stages of sleep. As a person moves into deeper stages of sleep, the characteristic EEG pattern moves from low-amplitude fast waves to high-amplitude slow waves. REM (rapid eye movement) sleep more closely resembles waking. (Reproduced from Nairne, J. S. [1997]. The adaptive mind [p. 216, Figure 6.5]. Pacific Grove, CA: Brooks/Cole, adapted from Hauri, P. [1982]. Current concepts: The sleep disorders. Peapack, NJ: Pharmacia & Upjohn.)

Drowsy, relaxed Alpha waves

Awake Fast, random, low voltage

50 µv 1 sec.

Stage 1 sleep Theta waves

Theta waves

Stage 3/Stage 4 sleep Slow-wave sleep

Delta activity

Stage 2 sleep Sleep spindles, K complexes

Sleep spindle K complex

REM sleep Fast, random

Sawtooth waves

CHAPTER 16 | Alterations of Consciousness 453

Often when one is asleep, there is something in consciousness which declares that what then presents itself is but a dream.

—Aristotle

Can one be simultaneously conscious and dreaming? Although an ancient phenome- non, documented in stories throughout history, lucid dreaming has only recently caught the attention of scientists who are exploring the frontiers of human conscious- ness. Throughout history, most of the major religions have used lucid dreaming as a spiritual practice. Examples within Christian- ity, Islam, Hinduism, and Tibetan Buddhism show how to use lucid dreaming as a path to enlightenment. The assertions are that the meditative masters can maintain conscious awareness throughout sleep. This ability may emanate from incredible mental control in waking life and from long years of practice in the meditative arts. However, many ordinary people also report lucid dreams. Children have lucid dreams more naturally, without special training, but prevalence declines with age. Among 10-year-olds, 63% in one study reported lucid dreaming on a monthly basis, 58% of 11-year-olds, and 36% of 12-year- olds (Armstrong-Hickey, 1991).

Most dreams occur in a state of unaware- ness of their illusory nature. In fact, sleep itself is generally characterized as unconscious. Lucid dreaming is the ability, while dreaming, to become conscious of the fact that one is in a dream state. The following is a description of the first lucid dream of one man:

I was standing in a field in an open area when my wife pointed in the direction of the sunset. I looked at it and thought, “How odd; I’ve never seen colors like that before.” Then it dawned on me: “I must be dreaming!” Never had I experienced such clarity and perception— the colors were so beautiful and the sense of freedom so exhilarating that I started racing through this beautiful golden wheat field waving my hands in the air and yelling at the top of my voice, “I’m dreaming! I’m dreaming!” Suddenly, I started to lose the dream; it must

have been the excitement. I instantly woke up. As it dawned on me what had just happened, I woke my wife and said, “I did it, I did it!” I was conscious within the dream state and I’ll never be the same. Funny isn’t it? How a taste of it can affect one like that. It’s the freedom, I guess; we see that we truly are in control of our own universe. (LaBerge, 1990, pp. 1–2)

At once it is evident that lucid dreams differ from ordinary dreams. Lucid dreamers typically report vivid sensation and height- ened imagery and clarity, not only visual sensation, but auditory and kinesthetic as well. Hearing music, seeing bright light, and flying are common. Joy and exhilaration often distinguish these dreams. What often triggers lucidity is awareness of inconsistency or oddity. The dreamer abruptly shifts into con- scious awareness, sometimes accompanied by a feeling of mind expansion and greater self-knowledge. What is interesting in com- parison with ordinary dreams is that lucid dreams are not disjointed, lacking in judg- ment, or irrational. The dreamer has control and free will in the sense of deciding where to go and what to do, but cannot totally control the plot or outcome. For example, the dreamer may decide to travel to a certain place or meet various people, but may be surprised by what occurs. The person may also decide to use the dream to face prob- lems of living, which has ramifications for the study of lucid dreams in a healing or thera- peutic manner. A person with a fear of water reported the following dream:

In reality I have a great fear of water, and swimming was one of the possible choices for me to try in a lucid dream. In the dream I’m in my backyard and am immediately aware that I’m dreaming. I decide that it would be great fun to swim. Instantly there is water all around me. I swim several hundred feet and make many adjustments to my swimming form.

I start to stand up in what is chest deep water and start to feel fearful. I remind myself that in a dream there is no reason to fear. I immediately feel comfortable and start to

walk back around the house, when I observe that the water has disappeared. (LaBerge, 1990, p. 260)

The study of lucid dreams has revealed that dreams occur in real time, not in an instant or a blink of the eye. As dreamers, people may take shortcuts and transport themselves from place to place, but the story line of dream action occurs at ordinary speed. This is known because sleep re- searchers, such as the group at Stanford Sleep Research Center, have been able to correlate eye movement during lucid dreams with dream reports. First, a prearranged signal is set—for example, a light embedded in eye shades worn by the sleeper will flash three times when EEG recordings detect REM sleep. If the dreamer detects the light and becomes aware that this is the signal, he or she returns a signal by moving the eyes in a pattern that was practiced before sleep onset. This methodology is quite ingenious, because during the benign paralysis of REM sleep, the only way for the dreamer to signal to the external world is through the eyes. One lucid dreamer re- ported that in his dream he was walking along a beach when suddenly he saw the sun rise and set, rise and set, rise and set. He kept walking, and then suddenly thought how odd that was. In an “aha” experience, he recognized that this was the prearranged signal and was able to signal back to the researchers with his eyes. His report of the dream and the time period between the signal and the dreamer’s response corre- sponded to the eye movement tracings.

Are lucid dreams a melding of the conscious and unconscious mind states? During lucid dreams, the dreamer has knowledge of normally available waking thoughts and memories, as well as an awareness of the dream illusion. What is normally unconscious has become con- scious. Lucid dreams have been described, and they may reasonably be thought of as

(continued)

N e u r o p s y c h o l o g y i n A c t i o n 1 6 . 3

L u c i d D r e a m i n g : A P a r a d o x o f C o n s c i o u s n e s s

by Mary V. Spiers

It takes a bit of commotion to wake someone from stage 4 NREM sleep. The brain is less active and becomes less capable of organized activity. Some individuals may vo- calize, but this speech usually does not seem logical. Some motor behavior may occur as well, and sleepwalking sometimes accompanies NREM sleep. Although NREM sleep is associated with a sleeping brain, curiously the body is “awake,” twitching and turning. Sometimes the twitching is so strong that the person may kick. This is called nocturnal myoclonus (restless leg syndrome) and can be so strong that it may wake up the person.

After the first descent into deep sleep, there is a pro- gressive lightening that culminates at 90 minutes after sleep onset in the first REM period (named for the promi- nence of rapid eye movements). REM sleep shows many contrasts with NREM sleep (Table 16.2). The most strik- ing feature is the relatively high level of alertness during REM sleep, much like stage 1 sleep. In fact, the first time sleep researchers measured REM sleep via EEG they thought the subject had awakened.

The characteristic REM EEG pattern of low-voltage, random, fast “sawtooth” waves is a dynamic representa- tion of the sleeper’s internally generated heightened cor- tical arousal and is associated with intensive processing of the internal mind state of dreaming. The first REM period may be quite short, lasting less than 5 minutes. Thus, in REM sleep, the brain is active and seemingly awake. A person awakened during REM sleep often re- ports dreams. However, the body is immobile during REM sleep. In fact, all voluntary muscles are temporarily “paralyzed” from the neck down. Both female and male individuals show sexual response (lubrication or erec- tion). As the night progresses, Figure 16.2 illustrates how REM periods lengthen at the end of each 90-minute cycle. Correspondingly, sleep stages 3 and 4 taper off in the early morning hours. In general, normal sleepers spend 75% in NREM and 25% in REM sleep over a night’s sleep.

What we have just described is normal adult sleep. Variability in this cycle depends on age and several other factors (Figure 16.3). Infants, in contrast, spend 50% of their sleep time in REM sleep, and a large proportion of their NREM sleep in stage 4 sleep. By late middle age, most people have lost all of this physiologically restorative

stage 4 sleep and retain only a small proportion of REM sleep. Why this tremendous variation in the developmen- tal qualities of sleep? The answer may lie in the functions various types of sleep serve in growth and development.

Among other phasic events, the pituitary gland, under control of the hypothalamus, releases somatotrophin (growth hormone) during stage 4 sleep, and the immune system is particularly active. During rapid growth and development, stage 4 sleep may be more necessary. Stage 4 sleep is often termed restorative sleep because it also

454 PART THREE | Disorders of the Brain

Event NREM REM

Occurrence Greater in first Greater in second half of night half of night

Eye movement Slow, rolling Rapid, conjugate

Mentation Short, ordinary Dreams

Fragmented Vivid, emotional

Sensory processing Lowered Inhibited

Motor response Relaxed Atonic

Benign paralysis

Autonomic nervous Low High system variability

GSR variability High Low

CNS temperature Decreases Increases

Sexual response Low High

Neurotransmitter activity

Aminergic High Low

Cholinergic acetylcholine Low High

Hormonal secretion rate

Growth hormone High Low

Parathyroid hormone High Low

Luteinizing hormone Low High

NREM = non–rapid eye movement; REM = rapid eye movement; GSR = galvanic skin response; CNS = central nervous system.

Table 16.2 Comparison of NREM and REM Sleep Events

(continued) a cocreation between the two mind states,

sometimes marked by intense pleasure, but with a different twist from the Freudian

idea of a naughty “id” in that the dreamer often experiences these as mind-expanding growth opportunities filled with personal insight and a sense of personal accomplish-

ment. The scientific study of lucid dreaming may well represent the next wave of research in understanding the brain processes related to levels of consciousness.

CHAPTER 16 | Alterations of Consciousness 455

Figure 16.2 Polysomnograph of a typical night of adult sleep. At the beginning of the night, rapid eye movement (REM) periods (in black) are short and delta sleep (stages 3 and 4) is longer. As the night pro- gresses, delta periods become shorter and REM periods become longer. (Reproduced from Hauri, P. [1977]. Current concepts: The sleep disorders [p. 8, Figure 2]. Peapack, NJ: Pharmacia & Upjohn.)

Figure 16.3 Average changes in sleep stage percentages over the life span. Average daily sleep stage percentages are greatest in infancy, decline during childhood, and then are fairly stable throughout middle adulthood. (Reproduced from Weiten, W. [1998]. Psychology: Themes and variations [4th ed., Figure 5.8, p. 187]. Pacific Grove, CA: Brooks/Cole, originally adapted from Roffwarg, H. P., Muzio, J. N., & Dement, W. C. [1966]. Ontogenetic development of human sleep–dream cycle. Science, 152, 604–619, by permission.)

Percent of total sleep spent in REM

Non-REM sleep

Childhood AdolescenceInfancy

1–15 days

Adulthood Old age

3–5 mos

6–23 mos

2–3 yrs

3–5 yrs

10–13 yrs

14–18 yrs

19–30 yrs

33–45 yrs

50 yrs

90 yrs

5–9 yrs

50% 40% 25–30% 25% 20%

19%

20%

22%

19% 20–23%

Total daily sleep

Waking

REM sleep

T o

ta l

d ai

ly s

le ep

( h

o u

rs )

19%

increases in adults in response to intense physical exer- tion. At older ages, this growth-and-tissue-repair function of growth hormone becomes less available.

S L E E P A N A T O M Y A N D P H Y S I O L O G Y

Circadian clocks (derived from Latin, meaning “about a day,” as noted earlier), which set the daily pattern of sleep and wakefulness, are intrinsic to most living organisms. This clock might have been patterned in ancient times and embedded in DNA as all life on earth learned to re- spond to the rhythms of the cycles of days, months, seasons, and years. Even plants have a rudimentary circa- dian triggering mechanism. The heliotrope folds its leaves at night and opens them in the morning, but it is not di- rectly guided by the light of the sun. Even in a dark room it continues opening and closing, according to daily cy- cles and according to some internal timing mechanism.

In humans, and all mammals, a more specialized circa- dian clock nestles in the suprachiasmic nucleus (SCN) of the hypothalamus. If the SCN is removed from the brain, the neurons continue to fire according to the pro- grammed daily rhythms. However, if the SCN were to- tally dependent on genetic programming, what would happen when traveling to the other side of the world? The daily internal clock must have a way to resynchro- nize according to the light/dark cycle. That, indeed, is the case. In fact, if left without any natural light cues, humans will revert to about 25-hour/day cycles of waking and sleeping. Natural light, or in some cases an alarm clock, apparently resynchronizes the human circadian clock each day for functioning in accord with a 24-hour day. The halves of the SCN lie just above the optic chiasm and receive light via neural input from the two visual fields as they cross hemispheres to the opposite sides of the brain (Figure 16.4). When this internal clock runs amok, sleep patterns can be greatly, even fatally, disrupted (see Neuropsychology in Action 16.1).

Scientists do not yet know how the human circadian clocks signal sleep onset each night and awakening each morning—perhaps through qualitatively different signals, or via a gradual change in the release of neurotransmitter molecules. Clifford Saper, of Harvard University, and his colleagues (Saper, Chou, & Scammell, 2001) have sug- gested that the ventrolateral preoptic area of the hypo- thalamus may be the “master switch” to arousal (see Figure 16.3). Researchers have observed this somnolence region to be the only brain center that is more active dur- ing sleep than wakefulness. Other researchers have identi- fied a peptide molecule named “factor S” and claim it may

be one of the neurotransmitters most directly responsible for setting off the downward drift into sleepiness. Injected into the hypothalamus, factor S induces sleep and in- creases body temperature. It also appears to trigger the re- lease of interleukin-1, which raises many interesting ques- tions about the immunoprotective function of sleep. This collective evidence points to a strong role for the hypo- thalamus as the “biological sandman.”

When activated, the hypothalamus sends its molecular message to the thalamus and the RAS of the lower brain- stem. Gradually, the brain moves from a state of processing external sensory information to a closing off of inputs from vision, hearing, and touch. During alertness, the thalamus relays inputs from most sensory systems, except for smell. The thalamus constantly communicates with the cortex through a feedback system of millions of thala- mocortical loops. With high alertness, neuronal firing is frequent and finely tuned. Any external sensory “noise” against this background is easily picked up because the brain discriminates it from the high-frequency back- ground rhythm by its irregularity or novelty. As alertness drops, at a certain point the thalamocortical loops start oscillating to their own rhythm, in a sort of internal dance between the thalamus and the cortex.

On an EEG, this is also when the sleep spindles (12–14 cycles/sec) emerge, typical of stage 2 sleep. With the slowed frequency of thalamocortical firing, orientation to and processing of external stimuli is less likely. The brain turns inward, attention drifts, and the sleeper becomes oblivious to his or her surroundings. Currently, the thala- mocortical loop stands as the primary mechanism in sleep onset and in maintenance of reduced attention to exter- nal stimuli. As sleep continues to deepen, responsiveness to the outward environment lessens even further. Yet many parents of newborns apparently maintain vigilance to their baby’s stirrings while sleeping. Perhaps future re- search will reveal whether another mechanism monitors the environment during sleep, or whether sleep remains lighter for those who must remain alert. Animals in the wild, which must retain more alertness to danger, show lighter and more fragmented sleep than zoo and domestic animals. Perhaps this is also the case with humans.

R E T I C U L A R A C T I V A T I N G S Y S T E M A N D R A P I D E Y E M O V E M E N T S L E E P

Approximately every 90 minutes, and lengthening throughout the night, a sleeper enters REM stage sleep. The cortical activity of high-frequency sawtooth EEG

456 PART THREE | Disorders of the Brain

waves in the theta range nearly resembles a waking brain state, yet the sleeper is turned inward. The view is an inter- nal movie as scenes and images flash by and fall away. Will- ful movement is impossible, because the motoneurons have temporarily lost communication with the spinal cord. Sen- sation from the outside world is turned down to its lowest point. For all practical purposes, more than any other stage of sleep, the sleeper is in a cocoon, insulated from the out-

CHAPTER 16 | Alterations of Consciousness 457

Figure 16.4 The suprachiasmic nucleus (SCN) of the hypothalamus. A (a) sagittal and (b) horizontal section of the human brain showing the SCN in relation to the optic chiasm; (c) exploded view of the hypothalamus showing the SCN in relation to other nuclei. (a: Adapted from Kalat, J. W. [1998]. Biological psychology [6th ed., Figure 9.6c]. Pacific Grove, CA: Brooks/Cole, by permission; b, c: modified from Pinel, P. J., & Edwards, M. [1998]. A colorful introduction to the anatomy of the human brain [p. 195, Figure 11.6]. Boston: Allyn & Bacon, by permission.)

Optic chiasm

Retinohypothalamic tract

Optic chiasm

Pituitary

Hypothalamus Suprachaismic nucleus

Anterior commisure Ventrolateral preoptic area

Preoptic area

Ventromedial nucleus (thalamus)

Mammillary body

side world and unable to act on it, yet with a very active mind. What brain mechanisms are responsible for this paradox? Although science does not yet understand the complete workings of REM sleep, it is evident that the RAS is the primary mechanism for turning REM sleep on and off. This section discusses both the mechanical aspects and the chemical transmitters that play a role in REM sleep.

The RAS maintains cortical arousal. It arises from deep within the brainstem (Figure 16.5). During wakefulness, the high activity in the ascending RAS stimulates the brain via projections into many different neurologic systems in the cortex. The nuclei of the gigantocellular tegmental field (GTF) located in the higher pons appear to generate these brain waves. Left unchecked, they fire sponta- neously, producing a high level of activity. During stages 1 and 2, the nucleus ceruleus (NC) becomes active and acts as an inhibitory control on the GTF, dampening the firing. Cortical activation continues to slow through stages 3 and 4. Then, during REM sleep, the NC releases its inhibition of the GTF, leaving it free to activate again, sending spikes through the cortex and activating the cor- tex into a higher level of arousal. One particular set of dis- charges is termed PGO spikes because they travel from the pons (P) to the lateral geniculate nucleus (LGN) of the thalamus to the occipital cortex (OC). The lateral geniculate nucleus is part of the visual pathway from the retina to the occipital cortex. The internally generated PGO spikes intercept this pathway midway. Interestingly, the PGO spikes fire in pulsating bursts. This is an addi- tional indication that the thalamus may be synchronizing brain rhythms. Although it also happens during waking hours, PGO bursts are more active in REM sleep. The stimulation that finally reaches the occipital cortex creates dream images and the corresponding rapid REM charac-

teristic of this stage. The occipital lobes are therefore ex- cited without external visual input. Given this scenario, it is curious that eyes move. But they appear somehow cali- brated to move in conjunction with scene changes of dreams. Researchers think that bursts from the pons also stimulate nearby oculomotor neurons, resulting in corre- sponding eye movements (Hobson, 1995).

Areas other than the occipital lobes also activate dur- ing REM sleep. In rats, rabbits, and cats, single-neuron recording has demonstrated that the theta rhythm em- anates from the hippocampus, specifically in the dentate gyrus and the entorhinal cortex (Winson, 1972). How- ever, the signal to activate the theta rhythm has its trigger in the brainstem within the RAS. This hippocampal acti- vation during REM sleep has ramifications for proposing a role for memory within REM sleep. We discuss this issue further in considering the functions of REM sleep.

Many of the REM sleep occurrences listed in Table 16.2 have brainstem mechanisms. “Sleep paralysis” oc- curs because it is simply too dangerous to act out dreams. Although we may see or sense movement in dreams, through active central motoneuronal activity, the mo- toneurons responsible for actually carrying out the action are “turned off ” at the level of the spinal cord. The active reticular firing in the medulla during REM sleep inhibits the spinal motor pathways. This greatly reduces muscle tone (atonia), and for all practical purposes paralyzes the sleeper. When researchers surgically turned off cats’ medullar inhibitory mechanism, the cats actually became physically active during REM. They stalked, attacked, hissed, and otherwise acted out the drama of their dreams.

REM sleep dampens external sensory stimulation. The pontine excitement also inhibits peripheral nerve pathways where they synapse with the spinal cord. During all stages of sleep, after an initial increase in the first 2 hours, respira- tion rate and body temperature gradually diminish. Body movement and systolic blood pressure also increase during the night. These changes continue during REM but tend to fluctuate more than during NREM sleep. As the night progresses and REM periods lengthen, fluctuations become more variable from REM period to REM period.

As with all behavior, REM sleep combines structural and functional processes. The neurophysiological processes provide the fuel for the mechanical processes we have just discussed. Many brain neurotransmitters decline only slightly during REM sleep. The question is, Do certain neurotransmitters operate differently during REM sleep? This is apparently true. Researchers have observed within the locus ceruleus a cluster of neurons, which they labeled “REM off ” cells, that completely stop firing during REM sleep (Hobson, 1995). Because these cells otherwise release

458 PART THREE | Disorders of the Brain

Figure 16.5 Schematic diagram of the rapid eye movement (REM) system. OMN = oculomotor nuclei; MRF = midbrain reticular formation. (From Hauri, P. [1977]. Current concepts: The sleep disorders [p. 15, Figure 5]. Peapack, NJ: Pharmacia & Upjohn.)

Cortex

LGN

OMN

GTF NC

Brainstem (pulled out from under cortex)

Eye MRF

norepinephrine and serotonin, the consequence is a rela- tive unavailability of these substances to the brain during REM. J. Alan Hobson (1995) hypothesizes that the lower- ing of these aminergic transmitters plays a role in the “lack of self-reflective awareness, disorientation, and logical fal- lacy” in verbal reports of dreaming during REM sleep. Hobson also postulates that serotonin and norepinephrine act as long-term neuromodulators on the brain. As NREM sleep commences, “REM off ” cells begin to slow their fir- ing rate, with the functional result of slowly releasing their hold on the “rational” cortex. The mind becomes more disinhibited during sleep but is especially free to wander during REM because of a now complete lack of aminergic transmission. At the end of the REM cycle, the cells “turn on,” activating at a higher level of serotonin and norepi- nephrine. This level then tapers off, leading to the next REM period. From this information, it is possible to spec- ulate that lengthening REM periods during the night may result from progressively lower levels of aminergic neuro- transmitter release during the night.

Another neurotransmitter of interest in REM sleep is acetylcholine (ACh). Interestingly, ACh increases during REM sleep in animals and can trigger “spectacularly long and intense” REM periods when administered in high doses. As discussed in Chapters 4 and 9, ACh is impor- tant in facilitating memory processing. The next section explores the role of REM in memory consolidation.

F U N C T I O N S O F R A P I D E Y E M O V E M E N T S L E E P

Scientists know that slow-wave delta sleep is physically restorative, but the debate over the purpose of REM sleep has ranged from postulations that it serves as a type of men- tal “garbage dump” to Freud’s assertion that dreams are the “royal road to the unconscious.” Science is now aware of at least two behavioral functions that REM sleep may serve. The first is memory consolidation. The second function is the intrapsychic function of dreaming. With a nod to Freud, neuropsychologists now conceptualize the psycho- logical function of dreaming somewhat differently from Freud. Because scientists have again blessed the study of personal internal conscious processes, the study of dream function is once more opening up. Next, we introduce an area of study that is likely to provide many insights into the functioning of the conscious and subconscious minds.

M e m o r y C o n s o l i d a t i o n a n d R a p i d E y e M o v e m e n t S l e e p

The physiological means by which long-term memory stor- age occurs is most likely through long-term potentiation

(LTP) of special glutamate neurotransmitter receptors (N-methyl-D-aspartate [NMDA] receptors) in the hip- pocampus. Memory consolidation may also be inhibited by gamma-aminobutyric acid (GABA). The hippocampus actively produces theta waves during REM sleep, as well as during stage 1 and 2 sleep. The important link between sleep and memory is that LTP in the hippocampus occurs during the production of theta rhythms (Larson & Lynch, 1986). Researchers have long thought that memory con- solidates during sleep, because people can remember more after sleep. Sleeping pills may interfere with this process. However, it has been difficult to know whether sleep or REM itself accounts for the memory boost, or whether people just remember better when other information does not interfere. Now animal and human experiments have provided more evidence that memory is processed during sleep. Using rats, a team of researchers have recorded from individual neurons of the hippocampus (Pavlides & Win- son, 1989). While the rats were awake, and moving about learning their position, only specific spatial coding neu- rons fired. Later during sleep, and particularly during pro- duction of the theta rhythm, these same neurons, and only these same neurons, fired at an even higher rate than during waking learning. This finding suggests that rats were reprocessing and strengthening the information dur- ing sleep.

In another experiment, a group of Israeli researchers studied memory consolidation and sleep under three dif- ferent conditions. The task involved having to identify perceptual targets embedded in a visually noisy back- ground. With learning and practice, people can usually improve their speed in picking out targets. In the first condition, researchers let people sleep normally after their initial practice session. In the second condition, research- ers awakened people each time they entered REM sleep, effectively depriving them of REM sleep. In the same manner, in the third condition, researchers deprived peo- ple of delta sleep within stages 3 and 4. The two groups that were allowed REM sleep showed enhanced task learning on awakening. All those who underwent REM sleep deprivation, in contrast, showed either less im- provement or an actual decrement in performance (Karni, Tanne, Rubenstein, Askenasy, & Sagi, 1994). To- gether, the findings from both animal and human re- search suggest that stage REM sleep plays a role in mem- ory consolidation. However, whether REM plays a unique role in memory consolidation is still a matter of debate. This is a promising area of research for neuropsy- chologists and neuroscientists interested in the relations among REM, ACh, and hippocampal consolidation through LTP.

CHAPTER 16 | Alterations of Consciousness 459

T h e D r e a m i n g M i n d The aspects of consciousness discussed thus far involve the mind looking out. Dreams reflect the mind looking in. There is almost no physical input or output. Brains and minds are temporarily suspended from bodies. This is an amazing state, seemingly disjointed and illogical. Except for those who are “lucid” dreamers, dreaming minds wander from scene to scene with no conscious guidance. Dreamers are detached from their own self-consciousness and more critical selves. Dreams may be intensely emotional to strangely devoid of emotion. After a history of much debate on the function that dreams may serve, scientists are return- ing to the premise that dreams have a psychological core.

Aspects of the mind state of dreams may correlate with the physical aspects of a brain temporarily divorced from a body. Noted sleep researcher J. Alan Hobson (1995) has suggested that dreamers may feel they move effortlessly during dream states because they are being moved or guided by internally generated states and active central mo- toneurons. Perhaps in some measure, dream experiences of floating or flying also result from the brain being allowed to “float free” from the body, or perhaps in combination with, as Hobson suggests, spontaneous stimulation of ori- entation and position control centers in the brain. Hobson notices that when dreamers try to “will” dream movement while trying to escape from a pursuer, their feet and bodies may become leaden because of the conflicting motor mes- sages of “voluntarily commanded movement (saying go) and the involuntarily clamped muscles (saying stop).” He further suggests that this standoff may suddenly break off the dream, thrusting the person into wakefulness and vivid dream recall. Awakening from a particular terrifying dream is called a “sleep anxiety attack.” In fact, a large percentage of reported dreams are “hostile,” and the most frequent themes are those of being chased and falling.

Many other correspondences probably exist between brain–body states and mind states in dreaming. This is an interesting area of study in its own right, and work in it will help to explain “how” people dream. Another ques- tion fundamental to understanding consciousness is “why” people dream. The brain activity occurring during REM sleep, such as memory consolidation, does not re- quire conscious awareness. Biological functions of the brain could all occur without being brought to waking at- tention. Many dreams are not recalled. But why do some dreams bubble to the surface? This has been a matter of theoretical interest since Freud’s revolutionary The Inter- pretation of Dreams, written in 1899. Since Freud’s time, the history of dream theory has gone through a cycle from Freud’s ideas that dreams represented unconscious sexual and aggressive urges, to the behaviorist movement totally

turning away from the study of subjective states. Francis Crick’s utilitarian housekeeping notion that dreams may just be the images that float by as the brain rids itself of the day’s mental garbage suggests that dreaming is noth- ing more than a random firing of neurons. But many dream researchers have come back to a version of psycho- logical interpretations.

Freud laid some of the basic groundwork in thinking about the psychological function of dreams from which other theories could spring. Today, most dream theorists do not attribute the same negative sexual and aggressive moti- vations to dream images that Freud did, but some of his methods and ideas may still be useful in uncovering the psy- chological meaning of dreams for the dreamer. With expan- sion from recent conceptualizations, researchers may be closer to a neuropsychological understanding of dreaming. Freud divided mental processing into conscious and uncon- scious processes. He saw unconscious processes as primitive, ancient, and disguised. Dreams, he felt, arose from these “unconscious” areas of the brain. This conceptualization is not unlike recent ideas of explicit versus implicit informa- tion processing. That which is explicit is available to verbal conscious awareness. However, as in memory processing and in some disorders such as neglect, a level of processing and recognition may exist outside conscious awareness. Is this not unlike the unconscious or the subconscious? Freud did not have the ability to look deep into the brain, but his ideas that unconscious thoughts emerge from more primitive areas of the brain are not inconsistent with theories of im- plicit processing taking place in the more primitive subcor- tical and limbic centers of the brain.

Perhaps where modern dream interpretive approaches have advanced most is in moving away from Freud’s idea that even remembered dream content is unavailable psy- chologically to the dreamer unless interpreted by some- one, such as an analyst, who can slice through the mani- fest content, defense mechanisms, and symbols, to uncover the latent meaning. This is not to say that the perspectives of others regarding the meaning of one’s dreams are use- less. In fact, such perspectives may be quite revealing and helpful. However, some of the greatest understanding available of the meaning in a dream involves self-interpre- tation in light of personal current life circumstances. After all, the dream was generated by the person dreaming it. Self-interpretation may involve not only the content, but the associated emotion that the dream invokes.

Troubling life circumstances provide the fodder for sleep researcher Rosalind Cartwright (Cartwright, Lloyd, Knight, & Trenholme, 1984; Cartwright, Kavits, Eastman, & Wood, 1991). Her volunteers, all going through separation or divorce, agreed to go through psychological testing that

460 PART THREE | Disorders of the Brain

examined coping styles, and they consented to be awakened during REM sleep to report their dreams. Cartwright found that dream content and topics differed among subjects, but the themes were congruent with the waking response to the problem. Indeed, the content and themes of dreams may be useful in helping to solve many personal problems. But sometimes dreams accompany remarkable changes in wak- ing life. We once treated depression in a patient who was also a smoker trying to kick the habit. During one therapy session he reported a dramatic dream he had had. In his dream, his whole body was turned grotesquely inside out, showing his lung, which was full of tumors and pus, to the outside world. After this dream the patient quit smoking.

An interesting exercise in exploring your own “dream consciousness” is to keep a dream journal for collecting and analyzing the content and themes of your dreams. What sensory processes are operating? Do you see, hear, feel, taste, or smell things in your dreams? As we men- tioned earlier, sleep researcher J. Alan Hobson reminds us that the absurdity of dreams and the temporary “impair- ment” of judgment and cognition that occur during dreaming are common phenomena. Temporary disinhibi- tion of the cortex may very well represent a physiological disconnection of aspects of the frontal lobes from other cortical and limbic centers. This may help to explain our often bizarre logic and lack of self-reflection during dreams. But what of those brain-impaired individuals who have structural damage resulting in waking disinhi- bition? Will we find that their dreams are even more dis- inhibited? This is a question for future research.

S L E E P D I S O R D E R S

For most people, sleep is a pleasurable event. For some people, however, sleeping can become a medical emer- gency, as during sleep apnea, or intrude into wakefulness, as in narcolepsy.

S l e e p A p n e a

Sleep apnea has become the most common disorder the sleep literature describes and the most common presenting problem that sleep disorder centers evaluate (Guilleminault, 1982). Sleep apnea syndrome (SAS) is a serious disorder resulting from frequent episodes of apnea (cessation of airflow) during sleep. Apnea literally means “lack of breath.” It is normal for muscles to relax during REM sleep. In some people, however, excessive muscle relax- ation may disrupt breathing. The sleep apnea patient may actually stop breathing while asleep. This, of course, pre- sents an immediate crisis for the body, because of the dan- ger of hypoxia and of increased rapid heart rate and blood pressure. The apnea finally stops when, in an effort to breathe, the patient arouses, gasping for air. Each gasp for air is associated with a mini-awakening, as recorded on the EEG. If repeated apnea and awakening occur more than five times an hour, the patient is diagnosed with sleep apnea (Figure 16.6).

Patients with SAS may actually experience hundreds of apnea episodes per night, lasting up to a minute or longer. Serious cases may show more than 500 apneas per night, each one lasting more than 10 to 120 seconds and terminating with at least partial arousal. In addition to markedly disrupted sleep characterized by a significant absence of the normal progression of sleep stages, danger- ously low levels of oxygen to the brain may result. Apnea periods usually produce declines in sleep-related blood oxyhemoglobin saturation and increases in carbon dioxide. This condition, known as hypoxia, is associated with below-average levels of oxygenated blood, often below 60% (normal is 95%). These changes have a profound impact on numerous body systems. It is impossible to hold one’s breath indefinitely, even when a person is sleeping. Essen- tially, a reflex controls breathing. But in young children, this reflex has not yet developed, and cessation of breathing

CHAPTER 16 | Alterations of Consciousness 461

Figure 16.6 An electroencephalogram (EEG)-recorded episode of sleep apnea. The patient is fully awake at point 1 (EEG alpha waves). At point 2, he is starting to fall asleep (EEG theta waves). At point 3, the patient is fully asleep (notice the relaxation of the chin electromyogram and absence of breathing). At point 4, the patient awakens and breathing resumes. The cycle then repeats. (Reproduced from Hauri, P. [1977]. Current concepts: The sleep disor- ders. Peapack, NJ: Pharmacia & Upjohn.)

K-ComplexK-Complex

Theta Waves

Alpha Waves

Theta Waves

321431

2Left eye Right eye Chin EMG EEG (C /ear)

Respiration

during sleep may result in death. This is one of the possible causes of sudden infant death syndrome (SIDS); SIDS most often occurs between the ages of 2 and 4 months.

Two primary mechanisms are involved in sleep apnea. The first one is the more common obstructive sleep apnea. Apneas occur most often during REM sleep when either the upper airway collapses, not allowing air to pass, or the body weight of the patient on the chest compro- mises respiratory effort. In each case, the consequence is disordered breathing. In the second mechanism of sleep apnea, central sleep apnea, disordered breathing is re- lated to the brain failing to send the necessary signals to breathe. This may reflect brainstem abnormalities that manifest only during sleep. In either case, the disorder is serious and often associated with severe O2 desaturation. The terms central and obstructive do not represent a strict dichotomy, because obstructive sleep apnea may impair CNS control of muscles, and episodes of obstructive sleep apnea often precede central apnea. Such episodes are called mixed apnea. Complications of apnea result in poor physical health and associated neuropsychological deficits of poor concentration and memory (Barth, Findley, Zillmer, Gideon, & Surrat, 1993).

The cause of sleep apnea is not well understood, al- though age, obesity, and being male are all risks. Generally, researchers consider sleep apnea episodes to be caused by a complex interaction of physiologic and anatomic factors. Clinical features that are characteristic of the syndrome in- clude excessive daytime sleepiness, heart failure, hyperten- sion, headaches, disturbing snoring, irritability, sleep dis- ruption, and personality changes. The hypoxia of sleep apnea markedly affects central neurotransmitter function and cellular metabolism, disrupting the biochemical and hemodynamic (pertaining to blood circulation) state of the CNS. Hypoxia may also lead to disturbed fluid and elec- trolyte distribution within the sodium-potassium pump, and it alters brain adenosine levels in animals. In addition, in patients with sleep apnea, cerebral blood flow studies demonstrate abnormally decreased blood flow, which may further compromise neuropsychological functioning be- cause of decreased neuronal activity (Guilleminault & Dement, 1978). Sleep apnea can have serious psychosocial effects as well, including significant changes in adaptive functioning (Zillmer, Ware, Rose, & Bond, 1989).

Most treatment efforts focus on relief of apneas through surgical and mechanical means. The most effective treat- ment is continuous positive airway pressure (CPAP), which is a mask that “forces” air through the nose or mouth while sleeping. CPAP is not considered a “cure,” but it abolishes sleep apnea by maintaining upper airway flow during sleep. One of the most successful and least in- vasive treatments for SAS, CPAP acts as a pneumatic splint

to prevent upper airway collapse during the night. CPAP must be used every night by the patient but has few side effects as long as one can actually sleep (one patient de- scribed CPAP as analogous to holding your head out of the car window while driving at 50 miles/hour). Losing weight can also help, because obesity is a major risk factor in sleep apnea. More controversial treatments include surgery to increase the dimensions of the pharynx via uvu- lopalatopharyngoplasty (UPPP) and tracheotomy, to completely bypass the upper airway obstruction during sleep (Williams & Karacan, 1978). UPPP involves remov- ing the uvula, the small, fleshy tissue hanging from the center of the soft palate, which may relax and sag, ob- structing the upper airway. However, this treatment is not as successful as CPAP and may also alter the subject’s voice. Patients who have undergone treatment for SAS often re- port an improvement in their cognitive functioning.

N a r c o l e p s y

The most notable disorder resulting from impaired CNS control of the sleep/wake cycle is narcolepsy (derived from Greek meaning “a taking hold of numbness”). Narcoleptics are afflicted with irresistible daytime “sleep attacks.” They can fall asleep while at work, while driving a car, or dur- ing a conversation. Such sleep attacks can last from a few seconds to more than 30 minutes. Excessive daytime sleepiness is the primary symptom of narcolepsy, al- though patients are also subject to narcoleptic sleep at- tacks, cataplexy, sleep paralysis, and hypnagogic hallu- cinations. Narcolepsy is a central nervous system disorder of the region in the brainstem that controls and regulates sleep and wakefulness. Once the disorder is established, it typically persists for one’s entire life. Narcolepsy occurs in 1 of 1000 people. Symptoms typically begin to appear be- tween the onset of puberty and age 25.

Excessive Daytime Sleepiness—Pathologic daytime sleepiness is often the first sign to emerge in narcolepsy, typically as- sociated with normal amounts of sleep at night. Many narcoleptics are asleep or sleepy during much of the day. They often report poor concentration and memory. Espe- cially during the afternoon, after a meal, or when watch- ing TV, narcoleptics are at risk for falling asleep. It is as if no amount of sleep could satisfy the patient’s frequent and irresistible need for sleep. Excessive daytime sleepiness is the most prominent and troublesome component of nar- colepsy. The patient is typically miserable and fatigued, often demonstrating inappropriate sleep.

Cataplexy—Cataplexy is the most debilitating of the nar- coleptic symptoms. Cataplexy is a brief (seconds to

462 PART THREE | Disorders of the Brain

minutes) episode of muscle weakness, actual paralysis, or both. In a benign form of cataplexy, only the face and the head may droop. In a severe attack, all the muscles may become limp, resulting in the victim falling to the floor. After the attack, the patient quickly regains alertness and muscle tone. Cataplectic attacks occur during periods of sudden excitement and emotional change, including laughter, anger, and athletic activity. The sleep paralysis of cataplexy is always associated with pathologic REM sleep. If a cataplectic attack lasts long enough, it often becomes full-blown REM sleep. Thus, you can think of cataplexy as an inappropriate attack of REM sleep. The pathologic intrusion of REM sleep and associated motor inhibition relates to a variety of nervous system dysfunctions, includ- ing massive nonreciprocal excitation of spinal inhibitory interneurons and active inhibition of motoneurons.

Hypnagogic Hallucinations—Hypnagogic hallucinations are also a symptom of narcolepsy and occur in the transition between wakefulness and sleep onset. Most people do not experience imagery during the transition from waking to sleep, because they are moving into NREM sleep, a period of little imagery. Narcoleptics, in contrast, can experience hypnagogic hallucinations during their shorter transition from waking to REM sleep. Thus, narcoleptics may expe- rience vivid, dreamlike intrusions into wakefulness. The hallucinations can be mundane or nightmarish, and they can cause great anxiety.

Sleep Paralysis—Sleep paralysis is the momentary paralysis on awakening or at sleep onset. Although the person may be able to see what is happening in the room, the body is totally unable to move for seconds to minutes. People without narcolepsy have also described this sleep paralysis on awakening from a REM period in the early morning hours. To “break out” of this paralysis, they may start by moving their eyes, then willfully moving a finger. As soon

as the voluntary muscles engage, the person breaks out of the REM-controlled sleep paralysis.

Narcolepsy can be best conceptualized as an imbalance among the wake, REM, and NREM systems. In such pa- tients, wakefulness is weak, and REM sleep, or parts thereof, can intrude into it. This imbalance among the three stages can range from mild to severe. Narcolepsy is not a psychological disorder, although the socioeconomic and psychological toll on the patients can be great. The ca- sual observer often thinks narcoleptic attacks are related to epilepsy, but they are not. The cause is generally unknown, although a minority of patients manifests parts of the syn- drome after encephalitis, severe head injury, or brain tumor. Clinicians often make the differential diagnosis in a sleep disorder center using a procedure known as the multiple sleep latency test (MSLT). Interestingly, narcolep- tics are asked to arrive at the sleep disorder center, not in the evening, but during the morning. Around 10 A.M. they are put to “rest.” The reason for this is that the early morning would be the least likely time for most well-rested people to fall asleep and proceed into REM sleep. The sub- ject must fall asleep in less than 5 minutes (normal sleep latency is 15 minutes at nighttime) and must show at least two sleep-onset REM periods to diagnose narcolepsy (Fig- ure 16.7). Treatment of narcolepsy includes counseling for patient and family, developing good sleep habits including frequent naps, and the administration of medication, typi- cally stimulants (such as amphetamines) for sleepiness and tricyclics (such as imipramine) for cataplexy. Although narcolepsy cannot be cured, its symptoms can be con- trolled with proper behavioral and medical therapy.

Runaway Brain: Seizure Disorders

Seizures, like sleep, are reversible alterations of con- sciousness. But seizures occur suddenly during periods of expected wakefulness and are abnormal. For reasons not

CHAPTER 16 | Alterations of Consciousness 463

Figure 16.7 The narcoleptic goes quickly into rapid eye movement sleep. (Reproduced from Hauri, P. [1977]. Current concepts: The sleep disorders. Peapack, NJ: Pharmacia & Upjohn.)

Sawtooth Waves

EEG (C /ear)4

Chin EMG

Left eye

Right eye

Fully Awake

Narcoleptic Subject

REM Sleep

Rapid Eye

Movements

EMG Inhibition

fully explainable, groups of neurons fire excessively in syn- chronous oscillation, as opposed to their normal pattern of relatively independent electrical activity. During a seizure, the firing rate of neurons may be as high as 500 times a second, which is more than 6 times faster than the normal rate of 80 firings per second (National Institute of Neuro- logical Disorders and Stroke [NINDS], 2004). Seizures are transient alterations in consciousness and can be provoked by external stimuli such as pulsing lights or sounds, or inter- nal triggers such as psychological and physical stress, sleep deprivation, high fever, and hormonal changes. Although there are many types of seizures that can be categorized by focus, behavior, and the extent of abnormal brain ac- tivity, there are two main categories of seizures. If the ab- normal firing is confined to a particular brain area, the result will be a partial or focal seizure. If the abnormal discharge involves both hemispheres, the event is termed a generalized seizure. Episodes can also begin as a par- tial seizure and secondarily generalize to involve the whole brain.

The causes of seizures are varied. Seizures that first ap- pear in infants and young children may manifest due to genetic and developmental abnormalities of the brain, in- fections, fever, or other disorders in metabolism. In peo- ple of all ages, seizures may also be caused by traumatic brain injury, brain infections, tumors, vascular abnormal- ities, alcohol and drug use or withdrawal, or environmen- tal toxins. In about half of the seizures reported, however, there is no clearly identifiable cause.

Epilepsy is not a disease itself, but a syndrome in which brain seizure activity is a primary and chronic symptom. Older diagnostic schemes stated epilepsy could be diagnosed only if the seizures were recurrent (at least two separate seizures) and unpredictable. Newer consensus definitions state that people can be diagnosed with epilepsy after suffer- ing only one seizure if they also have an “enduring” alter- ation of the brain that makes it highly likely they will suffer future seizures (Fisher et al., 2005). Many people who have had a seizure, in fact, do not show the full epileptic syn- drome (Hauser, 1992). Adults may suffer “nonepileptic episodes” from such events as hyperventilation breath hold- ing, migraines, ischemic attacks, drug toxicity, narcolepsy, and extreme emotion such as anger. In summary, a person must have at least two seizures, or the high potential for more than one seizure, that cannot be attributed to another med- ical condition to be diagnosed with epilepsy.

Epilepsy affects approximately 1% of the U.S. popula- tion (NINDS, 2004) with an age-related increase in inci- dence to 3% by age 75. Many more people or approxi- mately 10% of the population may suffer a seizure during their life (Epilepsy Foundation, n.d.).

C L A S S I F I C A T I O N O F S E I Z U R E T Y P E S

Previously, classification of seizures was based on the origi- nal French classification scheme and was categorized ac- cording to behavioral observations of what happened dur- ing a seizure. For example, grand mal or “big bad” seizures were named for the most violent motoric abnormalities of stiffening (tonic) and jerking (clonic) episodes and the accompanying loss of consciousness. The petit mal or “little bad” seizures, in contrast, were considered seizures that do not result in violent physical loss of control but do cause an altered state of consciousness. Current seizure classifications depend on what is known of the origin or focus of the seizure within the brain. The current tax- onomies are divided into two primary classifications: gen- eralized and partial seizures. Generalized seizures involve both cortical hemispheres at the onset, whereas partial seizures are confined to a specific area. Partial seizures may be further divided into two types: simple partial and com- plex partial. In simple partial seizures, consciousness is pre- served, whereas in complex partial seizures, consciousness is impaired. In addition, a partial seizure can spread out, resulting in a secondary generalized seizure, which is a seizure that started being partial—limited to a specific brain area—and later generalized to both hemispheres. As you may imagine, besides the consciousness factor that divides partial seizures into simple or complex, there are many dif- ferent variations of partial seizures, depending on the site of origin. Generalized seizures can also be classified into different types. The epilepsy classification scheme presented in Table 16.3 shows the seizure types of both groups.

Regardless of the primary seizure type, up to 70% of people report having an aura before a seizure. This hap- pens in prodromal phase, or precursory phase, of the episode, in which one may experience odd transient symptoms such as nausea, dizziness, or numbness. Sensory

464 PART THREE | Disorders of the Brain

Generalized Seizures Partial or Focal Seizures

1. Absence 1. Simple: focal motor, somatosensory or special-sensory, psychic, and autonomic

2. Myoclonic 2. Complex partial: psychomotor, temporal lobe

3. Clonic 3. Secondarily generalized

4. Tonic

5. Tonic-clonic

6. Atonic

Table 16.3 Seizure Classification

alterations or hallucinations in any sensory domain may appear. For example, chemical sense disruptions may manifest as unpleasant metallic tastes or foul odors. Some people recognize their aura as an emotional change such as fear or anxiety. Others experience a temporary aphasia or a sense of forced thinking. Yet others describe auras as an otherworldly or surreal dream state, or a sense of déjà vu (Neuropsychology in Action 16.4). These symptoms are highly idiosyncratic but are likely to be consistent within

a person. Most seizure sufferers become adept at recog- nizing their own auras; however, some auras occur with- out awareness, although they may be recognized by oth- ers. Auras may point to the genesis, or the epileptogenic focus, of the seizure within the brain (Cascino, 1992). Interestingly, some people are also able to arrest the pro- gression of a seizure during this prodromal phase by learn- ing to counteract the sensation with its opposite. For ex- ample, if a foul smell is part of an aura, a strong pleasant

CHAPTER 16 | Alterations of Consciousness 465

We have all some experience of a feeling, that comes over us occasionally, of what we are saying and doing having been said and done before, in a remote time—of our having been surrounded, dim ages ago, by the same faces, objects, and circumstances—of our knowing perfectly what will be said next, as if we suddenly remember it!

—Charles Dickens, David Copperfield

Have you ever been in a situation where suddenly everything seems familiar, the place, the objects, the layout of the setting . . . even the movements taking place. . . and then, when you are still perplexed by such a bizarre feeling, it goes away? Then you probably are like the two thirds of the popu- lation who has experienced at least one déjà vu experience in their lifetime.

The phenomenon of déjà vu caught the attention of philosophers and writers for ages, and more recently has become the subject of scientific study. The most common definition for déjà vu (“already seen” in French) was proposed by V. M. Neppe (1983): “Any subjectively inappropriate impression of familiarity of a present experi- ence with an undefined past.” This definition implies that there is a certain insight into the nature of the impossibility of the situation.

Interestingly, a considerable number of patients with temporal lobe epilepsy report déjà vu auras. In the late 1800s, Hughlings Jackson first observed that seizures that arose in the medial temporal lobe could result in a “dreamy state” described as vivid

memory-like hallucinations and/or the sense of having previously lived through the exact same situation. Later, other researchers have tried to evoke that “dreamy state” by electri- cally stimulating different regions of the temporal lobe such as the lateral temporal neocortex, the hippocampal formation, and the amygdala (Mullan & Penfield, 1959; Halgren, Walter, Cherlow, & Crandall, 1978). Gloor (1990) proposes that this dreamy state could be evoked by lateral temporal lobe stimulation, but only if the brain activity spread medially toward the limbic system, thus emphasizing the importance of limbic rather than temporal neocortical structures. After much debate, in 1994, Bancaud and his colleagues studied 16 patients with temporal lobe epilepsy with presurgically implanted electrodes; measured the electri- cal activity of the temporal lobe, the amyg- dala, and the hippocampus; and at the same time, attempted to stimulate those areas of the brain. They found that déjà vu could be experimentally evoked by stimulation of any of those three sites, and that there was no one single place that was solely responsible for the experience in every epilepsy patient. However, they did find that the stimulation of the deeper structures (amygdala and hip- pocampus) was 10 times more likely to evoke those states, concluding that the temporal neocortex probably plays a secondary but still important role in the déjà vu experience.

Another area of interest in the field of déjà vu and epilepsy is that of lateralization,

because the presentation of a déjà vu could eventually help neurologists diagnose the site of seizure onset for those who present this type of aura. Mullan and Penfield (1959) suggest that déjà vu occurs in the nondomi- nant temporal lobe—usually, but not always, the right temporal lobe for right handed people. In accordance with this idea, Gloor (1990) asserts that having an aura of déjà vu would be sufficient to localize the focus of the seizure to the right temporal lobe. However, Weinand and colleagues (1994) later found that right-handed seizure patients with preictal déjà vu all had seizures arising in their left hemispheres. They concluded that handedness rather than language domi- nance appears to be a more consistent predictor of ictal déjà vu lateralization.

Many people have experienced at least one déjà vu experience, and this does not imply that they have epilepsy. However, a connection to the temporal lobe and limbic structures may exist, as well as a brief abnor- mal firing, which gives a false sense of familiarity. Researchers have suggested a positive correlation of déjà vu with higher socioeconomic level, more education, more travel, and better dream recall (Brown, 2003). The range of possible explanations for this fascinating phenomenon is extensive but not yet fully understood. Perhaps by better understanding déjà vu we will be able to discover more about the oddities of the brain and how our memories and experi- ences are processed and retrieved.

N e u r o p s y c h o l o g y i n A c t i o n 1 6 . 4

D é j à V u a n d E p i l e p s y

by Karen B. Friedman

smell may halt the seizure (Efron, 1957). We explore this aspect of seizure control further in our discussion of epilepsy treatment.

After a seizure episode is a postictal phase in which the person gradually emerges into full consciousness. Often symptoms of confusion, disorientation, depression, headache, or fatigue follow. Less common, the person may bite his or her tongue or lose bladder control. This phase may be momentary or may last for hours, some- what depending on seizure type.

The following sections discuss seizure types according to the epilepsy classification scheme of Table 16.3. Clini- cal descriptions correlate with what is known of their neu- rologic counterparts. A more generalized discussion of the brain mechanisms responsible for seizure activity follows.

G e n e r a l i z e d S e i z u r e s

Generalized seizures, formally known as grand mal seizures, are bilaterally symmetric episodes characterized by a tem- porary lack of awareness. The brain origin of these seizures has traditionally been considered unknown or generalized. Behaviorally, they typically have a motor component that onlookers consider frightening. The motor discharge is likely to consist of any combination of a tonic or clonic form. Some seizures have only the tonic component, others only the clonic component, and a number of seizures involve both aspects. In these tonic-clonic seizures, the behavior that alerts others to a seizure onset is the tonic stage. Patients de- scribe passing out, and onlookers are likely to witness a stiff- ening of the person’s whole body, jaw clenching, and a blue appearance to the face. The blueness may look like a respi- ratory arrest, but during a seizure this actually occurs be- cause peripheral blood vessel constriction allows more blood to flow to the brain. In any case, breathing stops only temporarily. After seconds to minutes, the second clonic stage appears. The body begins a rhythmic jerking of limbs and may involve the whole torso. This is followed by abrupt limpness (or atonia) and a gradual regaining of conscious awareness. Generalized seizures may take several forms, but usually include components of irregular motor discharge in the form of tonic and/or clonic movement.

Other types of generalized seizures resulting in abnor- mal muscular symptoms are myoclonic and atonic seizures. Myoclonic seizures manifest in arrhythmic bursts of jerky motor movements that usually do not last more than a second and tend to occur in clusters over a short period. People who experience them sometimes de- scribe them as “jumps.” Atonic seizures, in contrast, are characterized by a sudden loss of muscle tone and may re- sult in a fall. They last no longer than 15 seconds while the person remains conscious.

Absence seizures appear in some classification schemes as a partial seizure and in others as a generalized seizure. This may represent differences related to the brain areas responsible and the extent of cortical involvement. As seen in the following case example described by a neu- rologist, the typical gross-motor involvement of general- ized absence seizures is not present and is replaced by ictal automatisms.

[A] mother brought her delightful red-headed eight-year-old daughter to see me. Because the girl seemed so attentive, intelli- gent, and well-behaved, it was hard for me to believe that she was having a difficult time at school. Her teacher reported that she made frequent mistakes on the blackboard and was often unable to answer simple questions. In my office, I asked her to take some rapid shallow breaths. After thirty seconds, she stared vacantly into space with her eyelids fluttering. Ten seconds later, she was back to her usual self. I had witnessed a classic absence seizure. Her EEG showed a pattern of 3 cycles/sec spike and dome activity during overbreathing, typical of absence epilepsy. (Richard & Reiter, 1990, p. 30)

In the above case, the doctor precipitated a seizure by having the girl hyperventilate. This girl’s fluttering eyelids are an important behavioral clue to seizure activity. Addi- tional automatisms may include stereotyped hand move- ments or facial tics. Less typical for this type of seizure is a sudden myoclonic jerk or atonic loss of muscle tone. At the approach of an attack, some individuals may just stop talking midstream, stare blankly into space for the dura- tion of the attack, and then resume without noticing any lapse in consciousness. Absence attacks characteristically affect children from age 4 to 14. Interestingly, many chil- dren with absence attacks “outgrow” them, suggesting that a delay or anomaly in brain development plays an impor- tant role in their occurrence. It is rare for adults with no seizure or trauma history to develop absence attacks.

P a r t i a l S e i z u r e s

Partial or focal seizures may take several forms, but they always begin as a local neuronal discharge that may gen- eralize across the corpus callosum, eventually involving the entire brain in a secondarily generalized seizure. This seizure category represents the most common type, affect- ing about 800,000 people in the United States (Cascino, 1992). These seizures can be more frequently localized than generalized seizures, but still only a third of those af- flicted have identifiable causes. Head trauma, stroke, and viral brain diseases such as meningitis and encephalitis are a few of the conditions that may lead to partial seizures.

Partial seizures consist of three main types. First, sim- ple seizures are focal events that may involve sensorimo- tor expression or psychic expression (mood, emotion, or

466 PART THREE | Disorders of the Brain

altered consciousness). The behavior experienced reflects the area from which the seizure emanates. For example, discharges from the motor strip can cause sudden or stereotypic movement, such as jerking or twitching. Peo- ple have reported that their eyes may move to a certain position or that they turn their heads involuntarily. Occipi- tal lobe foci can result in seeing vivid images or flashing lights. Memory and personality alterations can be a result of temporal lobe foci, and intensive mood experiences can occur with limbic system foci. The behavioral results vary widely from person to person but are closely tied to the site of seizure focus. Because there is no further involvement, the person can also experience these events as an aura.

The second type of partial seizure is complex partial seizures, the most common forms being psychomotor or temporal lobe epilepsy. These are more “complex” than simple partial seizures in that they have an element of al- tered psyche or awareness in addition to sensory or motor components. About half of those with complex partial seizures experience an aura (Cascino, 1992). Complex partial seizures typically emanate from the temporal lobes but can also occur as the result of a frontal lesion. The al- teration of consciousness can take several forms. It may include a sense of déjà vu (“already seen”) in new environ- ments or jamais vu (“never seen”) in a familiar place. The person may experience a sense of forced thinking, illusions, panic, terror, or even ecstasy. The motor changes during the ictal phase often take the form of odd, catatonic-like posturing and automatisms such as lip smacking or undo- ing buttons. The shift into the ictal phase is abrupt, usu- ally commencing with a motionless stare. The postictal pe- riod of confusion and drowsiness can be quite long with complex partial seizures. The case of the “sweeping lady” is a good example of what may happen with complex partial seizures (Neuropsychology in Action 16.5).

The third type of partial seizure, a secondarily general- ized seizure, is actually a variation of the first type. If a sim- ple seizure spreads, this spreading can generalize throughout the whole brain as in the case of Jacksonian seizures. Jack- sonian seizures involve motor areas and have been called “marching seizures,” because they begin with jerking or tin- gling of a single body area and spread to other areas. The symptoms reflect their corresponding brain regions; thus, diagnosticians consult maps of the motor homunculus.

N E U R O A N A T O M Y A N D N E U R O P H Y S I O L O G Y O F S E I Z U R E S

Partial and secondarily generalized seizures are the most likely to be localized because both the aura and the behav- ior during a seizure can point to a seizure’s epileptogenic

focus (the anatomic site of onset). Generalized seizures are difficult to localize, because they quickly disrupt the entire range of behavior involving all cortical neurons and may arise from a central mechanism capable of having a global effect on the brain. If there is an identifiable seizure focus, EEG recording is useful in locating it if a seizure occurs sponta- neously or can be induced during EEG monitoring.

Seizures are a symptom, similar to the concept of fever, that something is going on in the brain. A seizure may be localized to a particular anatomic area of the brain, and technicians may be able to image a corresponding struc- tural pathology such as a lesion, a tumor, a vascular disease, or other anomaly. For example, the cause of some child- hood seizures may be malformed brain tissue (Figure 16.8).

Because seizures also arise from metabolic disturbances and infections that affect the delicate physiological balance of the brain, neurologists cannot always find a structural location of injury or neuronal destruction in the brain. Al- though many normal people may experience a seizure, the occurrence may indicate significant brain pathology and medical consultation should always be sought.

Normally, the brain maintains a balance of neuronal firing between excitatory discharges and inhibitory con- trol of excessive firing. Single neurons and neuronal cir- cuits fire according to their own direction and processing in what appear to be random patterns. Because so many different patterns are occurring simultaneously, and be- cause the EEG represents a summation of neuronal fir- ing, the resultant EEG tracing is fast and asynchronous. Seizures occur due to excessive excitatory synchronous neuronal firing. If you have ever been caught up in a “wave” in a packed football stadium, the analogy to the brain is similar. All the people represent individual neu- rons and are initially involved in their own behaviors. At first, although small groups of people may be involved in a rhythmic “give and take,” the summation of “stadium behavior” appears random, with occasional synchronous bursts of cheering from one side or the other. But if a small group of people successfully initiate a wave, before long the entire stadium of 50,000 people synchronizes in a rhythm that sweeps through the crowd.

Absence seizures provide a good example of a general- ized seizure that arises from a central mechanism. EEGs of classical absence seizures show characteristic synchro- nous bilateral spike-and-wave discharge with a 3 cycles/sec frequency. This EEG frequency is within the same range as delta waves, characteristic of deep sleep. A reasonable description of absence seizures is that they force a temporary disconnection within the arousal sys- tem of the RAS, thus pushing the whole cortex into a temporary sleeplike state.

CHAPTER 16 | Alterations of Consciousness 467

Both animal and human studies point to the thalamo- cortical circuitry as the source for the primary aberrant mechanism involved in absence attacks. As we have dis- cussed, during an alert state, neurons in the thalamocorti- cal loop are involved in continuous tonic firing. This al- lows signals from the external environment to pass through the thalamus to the cortex. External transmission to the cortex dampens when neurons begin firing according to an internally generated oscillating rhythm. Neurologists think that a group of neurons within the thalamus, the nucleus reticularis thalami (NRT), regulates oscillatory behavior of the thalamocortical loop. Direct recordings indicate that this is the source of rhythmic burst firing when the EEG becomes synchronized and also is a source of asyn- chronous firing during wakefulness. The NRT also proj- ect to the contralateral dorsal thalamus, and thus have the ability to influence both hemispheres. The NRT mainly consist of GABAergic neurons that project to each other within the NRT and other areas of the thalamus.

One of their main functions is in controlling cerebral ex- citability. Researchers report that during early development, one form of GABA receptors—the GABA-b type—increases and later is pruned to adult levels. Researchers also know that GABA agonist drugs make absence seizures worse. Some investigators believe that absence seizures in children may result from an error in development, resulting in a temporary overabundance of GABA receptors and, therefore, a temporary imbalance in the excitatory/inhibitory forces of the brain (Snead, 1995). They think what happens within this system of neurons that affects a shift between asynchronous and synchronous rhythms is a change in the calcium potential of the cellular membrane. This may explain why some antiepileptic drugs such as ethosuximide and trimethadione, which act on the calcium current of the membrane, are effective.

In addition to the GABAergic neurons within the thala- mus, numerous neurotransmitter systems may be involved in generalized absence seizures, because the ascending

468 PART THREE | Disorders of the Brain

Epilepsy is a common neurologic disorder, currently affecting more than 2 million people in the United States (for a detailed discussion of epilepsy, see Bennett, 1992). Diagnosis of epilepsy depends on clinical interview and EEG assessment showing abnormality in the interictal (between seizures) scalp electrode EEG tracings. The interictal spike is a marker for this disorder (McIntosh, 1992).

When psychic alterations occur, the seizures are called complex partial seizures. For neuropsychologists, these are the most interesting epileptic disorders (Bennett, 1987). They may be associated with motor automatisms consisting of stereotyped, repetitive movements such as chewing, blinking, lip smacking, pointing, or picking at one’s clothes. Complex partial seizures, because of their frequent temporal lobe and limbic system focus, may have an emotional

component to the psychic alterations. The most common emotion is fear, but the person may also report pleasure, sadness, or vague familiarity. Individuals with complex partial seizures also commonly report sen- sory hallucinations or misperceptions. These sensations may range throughout the spec- trum of visual, gustatory, olfactory, auditory, or somatic perceptions. Olfactory sensations are the most common type of sensory aura reported. These are typically quite displeas- ing (such as the smell of burning or rotting flesh), but may on occasion be pleasant (such as the smell of roses).

In the course of a complex partial seizure, the person may utter meaningless speech, laugh, or cry. Complex motor responses may also occur, including compulsive, purpose- less writing and even running. During a complex partial seizure, a person may be unaware of or unresponsive to her or his

environment, failing to respond to questions by others. The person may be vaguely aware of what is going on but unable to control it. While in a state of altered consciousness during a seizure, he or she may go into an- other room, wander through a public place, or leave a store and wander down the street. Imagine how upset you would be to find yourself in a different place from where you “just” were and to have lost several minutes or even hours of time, not knowing what you did during the interim. This is illustrated by the case of the sweeping lady.

This individual—let us call her Alice—has been a client of mine for almost 15 years. We meet on occasion as she continues to deal with the impact of her epilepsy on her life. Alice’s epilepsy has never been com- pletely controlled by antiepileptic drugs, a far too common experience for those with com- plex partial seizures. She has had to alter her

N e u r o p s y c h o l o g y i n A c t i o n 1 6 . 5

E p i l e p s y a n d t h e C a s e o f t h e S w e e p i n g L a d y

by Thomas L. Bennett Ph.D., Professor of Psychology, Colorado State University, Clinical Director, Brain Injury Recovery Program, Fort Collins, CO

neuronal pathways to the cortex involve cholinergic, no- radrenergic, dopaminergic, and serotonergic neurons. ACh and cholinergic projections emanating from the nu- cleus basalis to the cortex have an effect on arousal apart from the thalamocortical loop. Thus, the regulation and control of arousal, and therefore seizures, represent a complex interaction of anatomic and physiologic systems.

N E U R O P S Y C H O L O G I C A L P R E S E N T A T I O N

Although neurologists may diagnose many seizures via EEG and other imaging measures, this is not always pos- sible because seizures do not occur “at will.” The interic- tal intervals can range from minutes to months to years. Neuropsychological evaluation can help determine the probability, by level and extent, that functional deficits are caused by seizure activity, and can therefore aid in di- agnosis. A neuropsychological assessment can help iden- tify areas of the brain that may not be working properly and, therefore, provide an estimate of a possible area of

seizure onset. For example, if a person shows impaired memory for a list of words, this may indicate an abnor- mality in the left temporal region. Testing can also help determine the extent to which emotional components and stress may stem from seizures and help discriminate be- tween neurologically based epilepsy and pseudoseizures arising from a somatoform disorder. As with any other neurologic disorder, neuropsychological testing can demonstrate a pattern of individual cognitive strengths and weaknesses to make appropriate recommendations for better adjustment to daily life.

One of the most frequent uses of a neuropsychological evaluation in epilepsy is in the context of a presurgical evaluation. When medication or other treatment has proved ineffective to reduce or eliminate the seizures, then the resection of the possible epileptogenic focus is consid- ered. To perform a surgery of this type, the neurosurgeon needs to perform a series of tests to determine with preci- sion the site of the focus and to assess whether the person would not suffer undue loss of function from removal of

CHAPTER 16 | Alterations of Consciousness 469

lifestyle and goals in life significantly; but overall, she has adapted well to her disability. Before the onset of her seizure disorder in her early 20s, she was active in sports and the community, and she planned to return to college to complete a bachelor’s degree. Alice has two daughters. She has worked in a couple of settings, but overstimulation and fatigue can increase seizure frequency, and she currently is not working. Diagnostic electroencephalograms (EEGs) have pro- duced some normal and some abnormal results. (Normal EEGs are also observed in others with complex partial seizures, showing that a normal EEG does not rule out epilepsy.) Her seizure pattern is interesting, because it typically contains many of the phenomena I have discussed.

Early in the development of her epilepsy, and when the seizures were less frequent with a fairly long interictal interval, Alice typically experienced epigastric sensations (“butter- flies in the stomach”) and nausea during the day before her seizures. This phenomenon, which was a seizure event, actually led her to seek evaluation from a gastrointestinal specialist before complex partial seizures were diagnosed. During this interval, her time perception was distorted so that everything seemed to slow down around her. She felt detached from her surroundings.

As the abnormal electrical activity spread and overt signs of the seizure pattern began to develop, Alice experienced olfactory/ gustatory sensations, including detecting the odor of putrid, burning flesh, olfactory sensations, and the taste of soap. A blank stare preceded her motor automatisms, and she lost clear awareness of her surroundings at this point. She then began purposeless pacing and hand rubbing for 2 to 3 minutes. She repor ted that she was vaguely aware of these things happening, but she could not control them. She would typically emit a series of grunting and gasping sounds, which sounded to others as if she were having trouble getting enough air. Grimac- ing contor ted her face. She laughed uncon- trollably for several minutes, and then cried and rocked back and for th for several minutes more. The sequence ended when the spread of epileptic activity caused a generalized tonic contraction and she lost consciousness. This case illustrates the wealth of events that can occur during a complex par tial seizure episode.

Several times Alice lost all awareness of what she had done for several hours. This happened when she went into a grocery store or large department store during the day when things were busy, noisy, and visually overstimulating. She later discovered

that she must have just aimlessly wandered through the store, perhaps repeatedly examining objects, because she had lost up to 2 to 3 hours of time for which she had no recollection. One of the most unusual experi- ences she had during a complex partial seizure occurred several years ago. I have thought of this as the “great fugue,” or the “case of the sweeping lady.”

It was the middle of the day in late spring or early summer, and Alice was home alone. She remembers that she was in her kitchen and had decided to sweep the floor. She vaguely remembers starting to sweep the floor, but nothing of the next 45 to 60 min- utes. Apparently, she swept across the kitchen, down the hall, through the entryway, and out the front door! Her next memory was that she was lying on a stranger’s porch. At first, she did not know who she was or where she was. Over the next few minutes, she became reoriented and realized she was on someone’s porch. She stood up, walked down the sidewalk into the street, and recognized a friend’s house several houses away. That enabled her to reorient to where she was. It turned out that she had walked several blocks from her home, crossing several intersections, without awareness, while in an extended complex partial seizure fugue!

the affected brain area. A neuropsychological evaluation is in order; first, because it provides a baseline of the person’s level of performance, and second, because as mentioned earlier, it can help by providing clues as to where the focus of the seizures might be through analysis of the patterns of

dysfunction. To determine and localize brain impairment, the neuropsychologist will analyze the facts obtained by such an evaluation in conjunction with other sources of information such as clinical observation and structural and functional brain imaging. A procedure that is usually per- formed in a presurgical evaluation is inpatient video EEG monitoring (Figure 16.9). EEG monitoring is either done through noninvasive scalp electrodes (such as those used for sleep EEGs) or through depth electrodes that are surgically implanted. EEG and behavior (via video recording) are then continuously recorded together 24 hours a day. The purpose is to localize the seizure onset and learn as much as possible about the individual behavioral seizure charac- teristics. Even though the ultimate goal is to eliminate the seizures, this is a point in the treatment course where all involved want a seizure to happen! If a seizure does not occur spontaneously (as we mentioned earlier, interictal periods can take months, even years), actions can be taken within this controlled environment to provoke a seizure, such as reduce the antiepileptic medication or induce sleep deprivation or hyperventilation.

The presurgical neuropsychological evaluator is also looking for any fluctuations in consciousness or behavior that may herald a seizure. If seizures occur during testing, and if the patient is conscious and not in danger of in- jury, an assessment of consciousness and memory can be made. For example, after the seizure is over, the person can be asked to recall what happened or to remember what was said or shown to them during the episode. Sometimes an evaluation can be continued after a seizure if the person recovers quickly and does not expe- rience many postictal symptoms; but on some occasions, the person may show signs of confusion, and therefore the evaluation needs to be continued at another time.

Neuropsychologists are also typically involved in the administration of a specialized presurgery evaluation com- monly called the Wada test (it is also referred to as the in- tracarotid amobarbital procedure [IAP]). This is particu- larly useful before surgeries for partial complex seizures involving the temporal lobe (temporal lobe epilepsy/partial complex seizures), to determine the likely effect of remov- ing brain tissue on the functions of language and mem- ory. Named after its developer, Juhn Wada (Wada & Rasmussen, 1960), this procedure involves the injection by a radiologist of a barbiturate, sodium amytal, through the patient’s carotid artery to anesthetize one hemisphere at a time. Even though the two hemispheres are connected and irrigated by arteries, the sodium amytal reaches only one side because of equal pressure on both sides of the brain. The blood pressure on one side makes the barbitu- rate stay on the other side. The aim is to test the function

470 PART THREE | Disorders of the Brain

Figure 16.8 Malformed tissue, present and growing from birth, was the cause of seizures. After removal this person has been seizure free and able to attend college. (Courtesy H. McNiece.)

of each hemisphere individually for its relative dominance for language and its ability to support memory function- ing before temporal lobectomy. During the 6 to 8 minutes while one hemisphere remains “paralyzed,” the neuropsy- chologist tests the functioning of the “awake” hemisphere to model functioning without the other hemisphere. This is a gross measure of loss of function, typically focusing on speech and memory. If, for example, the Wada test shows that speech is atypically represented in the right hemi- sphere, then right temporal lobectomy is contraindicated.

Many variations of the procedures are used during the Wada test, but the core involves brief testing of both ex- pressive and receptive language and short- and long-term memory in both the verbal and visuospatial domains. The premise behind this assessment procedure is that the neu- ropsychological testing shows the distribution of brain function and can help predict the sparing of memory and language functioning after temporal lobe resection. This aspect is usually quite helpful; however, some controversy exists over whether sodium amytal injections indeed anes- thetize memory functions. For one reason, the injection into the anterior carotid artery only perfuses into the ante- rior portion of the hippocampus, leaving posterior aspects free to function. To handle this problem, some medical

centers also selectively inject the middle or posterior cere- bral artery, although this is more risky. The change in a pa- tient undergoing a Wada procedure is usually quite dra- matic, in that the brain anesthetizes quickly and speech abruptly halts if the dampened hemisphere is dominant for speech. Because many patients being considered for epilepsy surgery have a long-standing history of epilepsy, often dating back to early developmental years, cerebral representation of speech can show a variety of patterns, presumably because the brain, responding to seizures, may have developed atypically. For example, there could be re- versed dominance for speech with both expressive and receptive aspects controlled by the right hemisphere, equal disruption in each hemisphere, or a dissociation of expres- sive speech in one hemisphere and receptive speech in the other (for review, see Jones-Gotman, 1996).

Neuropsychological presentation of seizures is highly individualistic, depending on seizure locus, type of seizure, and chronicity of disorder. No typical pattern of cognitive dysfunction is associated with epilepsy, and some patients may show few to no discernible problems. However, many seizure sufferers exhibit attention and memory problems. This is particularly evident in tests that require sustained or divided attention. In general, cognitive functioning

CHAPTER 16 | Alterations of Consciousness 471

Figure 16.9 Inpatient electroencephalographic and video monitoring of a patient during a seizure. (Courtesy Astro-Med, Inc.)

tends to be more impaired with longer duration (younger age of onset) and increased frequency of seizures (Haynes & Bennett, 1990). Lowered cognitive functioning is also linked with greater EEG abnormality. In general, the type of seizure activity parallels the functional deficits expected. For example, generalized tonic-clonic seizures are more likely to result in widespread functional impairment of both hemispheres. Partial seizures (which have not gener- alized) are most likely to be associated with lateralized im- pairment related to the side of abnormal discharge. As mentioned earlier, behavior during auras and the type of motor or sensory behavior evident during a seizure can also provide clues to seizure locus and are likely to corre- spond to neuropsychological assessment.

People with complex partial seizures that involve the temporal lobe show the most consistent neuropsychological and behavioral pattern. This group most commonly re- ports problems with learning, memory, and language and is less affected by attentional difficulties. Verbal fluency and verbal retrieval deficits are common manifestations of the interaction between memory and language. However, all aspects of memory encoding, organization, and re- trieval may be affected. Emotional and behavioral distur- bances, although prevalent among seizure sufferers in gen- eral, are most common with those who have complex partial seizures that involve the temporal lobe.

T R E A T M E N T O F E P I L E P S Y

The treatment of epilepsy is a collaborative effort between the patient and various health care professionals. As in many chronic diseases, patients are often the best experts on the symptoms of their conditions and the situations most likely to provoke a seizure. The various treatments available for epilepsy range from behavioral management, to nutritional therapy, to pharmacologic treatments, to neurosurgery; however, medication remains the most widely used form of treatment, and for most patients, seizures can be controlled with medication.

The decision to take regular medication for seizures re- quires a neurologist’s full evaluation as to its necessity, as well as a commitment from the patient. As we have dis- cussed, seizures may occur in isolation, but epilepsy de- notes a pattern of seizure activity. If a neurologist can es- tablish a diagnosis of epilepsy, then a physician often prescribes specific drugs according to seizure type. For ex- ample, generalized tonic-clonic seizures often respond to anticonvulsants that prolong the inhibitory action of GABA in the brain. These drugs include phenytoin (Dilantin), carbamazepine (Tegretol), or sodium valproate (Depakote) barbiturates and benzodiazepines. As de-

scribed earlier, absence seizures appear to involve a mecha- nism that is pharmacologically different from GABA. Ab- sence seizures are worsened by GABAergic drugs such as Dilantin, Tegretol, or barbiturates (Snead, 1995) and are treated by GABA-b antagonists ethosuximide (Zarontin), but may also be treated with Depakote. Physicians may treat partial seizures with the preceding drugs or, for seizures involving motor disturbances, often use clon- azepam (Klonopin) or acetazolamide (Diamox). In in- stances when drugs have not effectively controlled seizures, surgery as a treatment method has also been used. The pathologic brain area, if it can be localized, is simply cut out. This is where the neuropsychological evaluation, and specifically the Wada test, can be particularly useful in ad- vising the surgeon as to areas of function, such as speech and memory, that might be affected by the procedure.

In recent years, a dietary treatment called the “keto- genic diet” has been gaining popularity. It was first devel- oped in the 1920s based on anecdotal reports about the effectiveness of strict dietary regimens that date back even to Biblical times. It was not until the early 1990s when in- terest in this diet was renewed after a 2-year-old boy with intractable seizures was treated successfully at the John Hopkins Hospital. This diet mimics the effects of biochem- ical changes that occur during fasting (acidosis, dehydra- tion, and ketosis). It is mainly a very “low-carb” diet, based on an intake of proteins, fat, and little carbohydrates. Its mechanism of action is not fully understood yet, but scien- tists consider that calorie restriction, acidosis, ketosis, or dehydration may be possible mediators of its effect on seizure control. This treatment is generally used when seizures are difficult to control; when the patient responds poorly to medication; or when there is adequate control, but the drug’s side effects are not well tolerated. A recent study has shown that 37% of patients have a 90% reduc- tion in seizures and an additional 30% experience a 50% to 90% reduction (Thiele, 2003). It has also been suggested that even though this treatment works for adults, it appears to be more effective in children (Vining, 1999).

Some people with seizures have also learned to con- trol their attacks by noticing their auras and arresting the seizure before the ictal episode fully materializes. One pi- oneer in seizure research, Wilder Penfield, made the fol- lowing observation: “When an attack is just beginning, strong stimulation of the part threatened may avert the further development of a seizure” (Penfield, 1975, p. 39). Sensory auras including smell, touch, and taste appear par- ticularly amenable to natural arrest. For example, if the aura involves the sensation of a putrid smell, countering this with a pleasant smell may interrupt the progression of a seizure. In an early case study, Robert Efron (1957) reports

472 PART THREE | Disorders of the Brain

that one of his patients, a concert singer, had seizures pre- ceded by the aura of a bad smell. He gave her a vial of es- sential oil of jasmine to sniff at the onset of her aura. The jasmine served as a natural counteractant to the halluci- nated bad smell and apparently stopped the seizure. Through behavioral conditioning, Efron also taught the patient to arrest her seizures by imagining the odor of jas- mine. In a similar vein, some patients find that they can halt gustatory auras such as metallic tastes by eating some- thing pleasant tasting. Tactile auras have been stopped by such methods as tickling and squeezing. It is reasonable to assume that because the type of aura experienced by any one person is highly individual, patients would need to experiment to find what works for them. Efron’s patient was able to control her seizures well enough that her med- ications could be reduced. In another interesting example (Pritchard, Holmstrom, & Giacinto, 1985), a patient with complex partial seizures developed his own technique of blinking or shutting his eyes and visualized himself fishing. What was most striking was that EEG monitoring corrobo- rated that he could arrest his seizure through this specific vi- sualization, but not through other mental tasks suggested to him such as mental arithmetic or reading.

In addition to these self-control methods, other behav- ioral techniques have been explored to control seizures. These involve stress reduction measures, as well as biofeedback. Because seizures have often been associated with increased levels of stress, progressive relaxation tech- niques have offered some effectiveness (Rousseau, Hermann, & Whitman, 1985). This technique involves tightening and relaxing isolated muscle groups and also learning how to apply this procedure when facing situa- tions and feelings that are associated with a high risk for seizure activity (Dahl, Melin, & Lund, 1987). Besides the notion that stress can, on some occasions, precipitate seizures, it has also been suggested that sudden changes in arousal may be associated with seizure upsurge. There- fore, a technique called “countermeasures” has been ap- plied to fight the onset of seizures. With this technique, the goal is to change the arousal level when early signs of a seizure appear. For example, if a person experiences drowsiness at the time of the seizure onset, the objective of the countermeasure technique would be to teach the person to heighten the arousal level at this point to pre- vent the progression of the seizure (Dahl, Brorson, & Melin, 1992). Biofeedback based on galvanic skin re- sponse has also been used to reduce seizure frequency. This practice is based on the notion that an increase in sympathetic arousal (galvanic skin response) is associated with reduced abnormal cortical activity present in epilepsy (Nagai, Goldstein, Fenwick, & Trimble, 2004).

EEG biofeedback is another method that has been used to attempt seizure reduction, particularly for those who do not respond to conventional drug treatments. The idea of neurofeedback is for the person to learn to iden- tify the EEG patterns that may lead to seizures. The EEG signals occurring in real time are “fed back” to the person in a form that is easily understood. While being monitored, a person could, for example, receive feedback via a tone that would sound lower on the musical scale if the direc- tion of the neuronal pattern was to de-emphasize seizure activity and sound higher if seizure activity was more likely. By training people to recognize their brain and mind states, the idea is that they can also learn to control them. The purpose of this technique is to apply “operant conditioning” principles to brain activity. In addition to tones, this is often done by presenting to the patient his or her own brain activity in a creative way and providing rewards whenever the brain signals move in the desired direction. For example, some protocols of neurofeedback for children use spaceship races in which each spaceship represents a type of brain wave captured by the EEG and the goal is to make the desired spaceship “win the race,” which, in fact, means that the targeted brain activity mea- sured by the EEG is moving in the desired direction. Overall, EEG biofeedback or “neurofeedback” for the treatment of epilepsy has shown positive results along the years; however, no consensus has been reached as to which particular protocol works the best, because few studies are available, and the ones that exist are quite variable in sub- ject selection and also lack rigorously controlled designs. Nevertheless, recent improvements in quantitative EEG (qEEG) may facilitate this endeavor. qEEG uses digital technology to capture brain-wave activity, which is recorded and converted into a color map of brain func- tions. The advantages of qEEG as compared with a regu- lar EEG are that data can be more easily interpreted and a patient’s performance can be compared statistically with its own or with that of a large population database. With this technology a new window of opportunity is opened for the development of neurofeedback, because it be- comes easier to target and quantify particular sites of ab- normal brain activity for each individual and also detect incoherences in neuronal firing between different brain locations that may contribute to seizure activity. A pre- liminary study by Walker and Kozlowski (2005) has re- ported several cases for whom qEEG biofeedback was ap- plied where seizures decreased considerably and many of the subjects even become medication free. Controlling seizures by learning how to recognize and manipulate brain activation is an exciting field that deserves further exploration.

CHAPTER 16 | Alterations of Consciousness 473

Consciousness Circadian rhythm Narcolepsy Seizures Partial seizures Epileptic syndrome Epilepsy Lucid dreaming Reticular activating system

(RAS)

Ultradian Absence seizures REM (rapid eye movement)

sleep NREM (non–rapid eye

movement) sleep Nocturnal myoclonus Suprachiasmic nucleus (SCN) Sleep paralysis Atonia

Sleep apnea syndrome (SAS)

Apnea Hypoxia Sudden infant death syndrome

(SIDS) Obstructive sleep apnea Central sleep apnea Uvulopalatopharyngoplasty

(UPPP)

Excessive daytime sleepiness

Cataplexy Hypnagogic hallucinations Generalized seizure Grand mal seizure Tonic Clonic Petit mal seizure Complex partial seizure

Summary Consciousness is a frontier of brain science that presents some of the most intriguing puzzles of the human mind. Although issues of changing alertness, such as sleep and sleep disorders, may be easier to map out and understand within the workings of the brain, issues of awareness, particularly understanding of the brain mechanisms of self-awareness and unity of experience, still present many mysteries. Throughout this book, we have considered many brain disorders that result in altered states of awareness. In this chapter, we went further into defining normal consciousness and considered two types of disorders of conscious- ness: sleep disorders and seizure disorders.

With normal alertness, circadian peaks and valleys occur on about a 24-hour cycle in accordance with the sleep/wake cycle. In general, EEG indicates level of alertness, as seen in normal sleep and wakefulness patterns. However, EEG, which is the outward measure of brain rhythm, is not necessarily an accurate indicator of mind state. Two people may show similar EEG patterns but have very different levels of conscious alertness. For example, although sleep is often called “unconscious,” some people show “lucidity” during REM sleep. Slow delta waves accompany deep sleep and coma, but accomplished meditators can also produce this “deep” brain state whereas maintaining a more alert “mind” state. The mind state of dreaming during the brain state of REM has fascinated philosophers and scientists alike as they endeavor to understand potential connections to problem solving, memory, and psychological adjustment.

The hypothalamus, the thalamus, and the RAS are particularly important in the sleep/wake cycle. When this clocklike rhythm is disrupted, sleep disorders such as life-threatening insomnia or narcolepsy can occur. Excessive daytime sleepiness occurs with most sleep disorders, often associated with patient reports of poor memory and concentration.

Seizures suddenly alter consciousness during wakefulness and often result in abnormal movement and mentation. Seizures are the outward behavioral manifestation of excessive excitatory synchronous neuronal firing. The behavioral symptoms of seizures relate to the scope and the location of the brain focus, and the classifications of generalized and partial seizures are well documented. Neuropsychologists assess seizure patients for treatment planning and surgical evaluations. Although treatment of seizures primarily relies on medications, behavioral interventions may also be possible in the future as scientists and individu- als learn more about controlling aspects of their own consciousness.

C r i t i c a l T h i n k i n g Q u e s t i o n s

What is the biological or psychological function of “rhythms” of consciousness? How fluid are the boundaries between conscious and subconscious awareness? How do REM sleep and dreaming change in people who have various neurologic disorders? In what ways might neuropsychology be able to contribute to treatments for people with sleep disorders or epilepsy?

K e y Te r m s

474 PART THREE | Disorders of the Brain

We b C o n n e c t i o n s

http://www.stanford.edu/~dement/sleepinfo.html Stanford University Sleep Center—a complete guide to various sleep disorders including all the disorders discussed in the text. In addition, discussions of the relation of sleep disorders to specific psychiatric and medical diagnosis may provide an interesting link between previously discussed disorders and sleep disturbances.

http://www.sleepnet.com/disorder.htm SleepNet—provides an overview of sleep, including sleep disorders, research, sleep labs, and more.

http://www.efa.org Epilepsy Foundation—presents research as well as advocacy information.

http://neuro.med.cornell.edu/NYH-CMC/ne-general.html Cornell University Epilepsy Center—this overview of epilepsy covers the basics, such as the definition of a seizure, to more advanced discussions of treatment options and surgical procedures available for patients with epilepsy.

http://neurosurgery.mgh.harvard.edu/epilepsy.htm Harvard Epilepsy Site—not only is this site an excellent source for discussions of surgical options in epilepsy, it also provides general resources and other links on this topic, as well as the more general topic of epilepsy as a whole.

CHAPTER 16 | Alterations of Consciousness 475

Aura Prodromal phase Epileptogenic focus Postictal phase

Myoclonic seizures Atonic seizures Automatisms Simple seizure

Psychomotor or temporal lobe epilepsy

Secondarily generalized seizure

Jacksonian seizure Nucleus reticularis thalami

(NRT) Benzodiazepines

http://www.stanford.edu

http://www.sleepnet.com

http://www.efa.org

http://neuro.med.cornell.edu

http://neurosurgery.mgh.harvard.edu

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Ablation experiment Developed by Pierre Flourens, and involved removing parts of the brain of pigeons and hens. Flourens reported that excising any part of the brain in birds led to generalized, not local- ized, disorders of behavior.

Absence seizures Occur when the normally asyn- chronous waking state is abruptly interrupted by low-wave synchronous activity; characterized by synchronous bilateral spike-and-wave discharge.

Abulia A syndrome similar to that of akinetic mutism, but of lesser severity. The syndrome is characterized by significant reduction in drive, interest, and spontaneous behavior. The syndrome is associated with medial damage to the frontal lobes.

Acceleration The brain experiencing a significant physical force that propels it quickly, from station- ary to moving.

Acetylcholine (ACh) Also called choline; the first neu- rotransmitter to be identified; plays a prominent role in the peripheral nervous system, influencing motor control, and in autonomic nervous system functioning.

Achievement tests Most influenced by past education- al attainment; measures how well a subject has profited by learning and experience compared with others.

Achromatopsia The complete loss of ability to detect color.

Acidophilic adenoma A functioning type of pituitary tumor that usually appears in the anterior lobe of the pituitary gland. The acidophilic adenoma cre- ates excessive secretion of growth hormones often resulting in giantism (excessive growth of hands and feet).

Acoustic neuroma Progressively enlarging, benign tumor within the auditory canal arising from Schwann cells of the VIIIth cranial nerve.

Acquired sociopathy See Pseudopsychopathy. Action potential An electrical potential across the

neuron membrane. The action potential spreads down the axon as the voltage-controlled sodium

channels open up sequentially, like falling dominoes.

Adrenocorticotropic hormone (ACTH) A hormone secreted by the anterior pituitary gland that mediates the release of hormones from the adrenal cortex. Increased and decreased secretions of ACTH have been associated with a various disorders and disease states.

Affective significance of stimuli The binding or attachment of emotion to novel and social stimuli.

Afferent nerves (sensory nerves) Convey incoming messages from the sensory receptors to the central nervous system.

Agenesis Complete or partial failure of an organ to develop.

Ageusia Inability to recognize tastes. Agnosia An absence of knowing. The distinction

between the ability to recognize an object and the inability to name it. Term first coined by Sigmund Freud.

Agyria, or lissencephaly A congenital disorder in which the normal gyri and sulci of the brain fail to develop. Believed to occur between the third and fourth month of gestation.

Air encephalogram or pneumoencephalography The radiographic visualization of the fluid-containing structures of the brain, the ventricles, and spinal column. It is similar to the X-ray, but it involves the withdrawal of cerebrospinal fluid by lumbar punc- ture, which is then replaced with a gas including air, oxygen, or helium.

Akinesia A difficulty in initiating and maintaining behavior. Patients with akinesia may be extremely slow to start or perform a movement, may become rapidly fatigued when performing repetitive move- ments, or may have problems in performing simul- taneous or sequential movements.

Akinetic mutism A syndrome associated with medial frontal damage involving a loss of initiative, apathy, reduced verbal and motor behaviors, and profound indifference.

Akinetopsia The specific inability to identify objects in motion.

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511

Alcohol-related neurodevelopmental disabilities (ARND) See Fetal alcohol effect.

Alternating attention The ability to switch back and forth between tasks.

Alzheimer’s disease (AD) An irreversible cortical dementia, not due to an identifiable cause, that is characterized by neuropathologic markers including neurofibrillary tangles and senile plaques.

Amino acids A group of neurotransmitters that plays a major role in the more basic type of neuronal trans- mission that depends on rapid communication among neurons.

Amygdala Literally “almond,” because of its shape; has a specific role in fear conditioning and impacts the strength of stored memory.

Amyotrophic lateral sclerosis (ALS) Disease of the motor system in which people experience a gradual to total loss of muscle control and muscle function.

Anastomosis Communication between blood vessels by collateral channels. See Collateral blood vessel.

Androgen hormone Any steroid hormone, primarily produced by the testes, that has a “masculinizing” effect on development. Effects include the masculin- ization of the fetus, production of sperm, and devel- opment of secondary sexual characteristics.

Androgen insensitivity Refers to a set of genetic dis- orders resulting from mutation of the gene encoding for the androgen receptor. Affected males demon- strate varying degrees of under-development of male-sex physical characteristics.

Anencephaly A congenital condition characterized by a failure in development of the two hemispheres, mesencephalon, and diencephalon of the brain. The brain is represented by a vascular mass. The condi- tion produces severe neurologic deficits and is incompatible with life.

Aneurysms Weak areas in the walls of an artery that cause the vessel to balloon.

Angiography X-raying blood vessels in the brain after introducing contrast material into the arterial or venous bloodstream. Angiography is the most useful technique for examining the blood supply to and from the brain.

Anomia Problems in word finding. Only a word or two, here and there, is lost, and the communication can proceed pretty much as normal. In more severe cases, most or all words can be lost.

Anopias Term for visual difficulties. Anosmia Total loss of smell. Anosognosia A term first coined by Babinski to indi-

cate the inability or refusal to recognize that one has a particular disease or disorder.

Anoxia The complete cessation of oxygen supply to the brain. Anoxia often occurs with stroke or other severe traumas of the brain, such as are often seen in gunshot wounds to the head.

Anterior Toward the front or front end. Anterior attention system (executive attention system)

An attentional system of the brain mediating the voluntary control of attention that is supported by the frontal and medial cortices of the brain.

Anterior cerebral artery Resulting from half of the division of an internal carotid artery, it supplies the anterior medial portion of its corresponding cerebral hemisphere.

Anterior commissure Minor intercerebral fibers. Anterior communicating artery Connects the left and

right anterior cerebral arteries. Anterograde amnesia The loss of memory for events

after trauma or disease onset. Anterograde degeneration The degeneration of the

axon after the cell body has been damaged. Anticholinergics Treatment for Parkinson’s disease; act

by blocking the action of acetylcholine. Anton’s syndrome Actual denial of cerebral blindness;

a behavioral mirror of apperceptive agnosia. Aortic arch Arises from the left ventricle of the heart. Aphasia A disturbance of language usage or compre-

hension. It may involve the impairment of the power to speak, write, read, gesture, or comprehend spoken, written, or gestured language.

Apnea The cessation of airflow; literally means “a lack of breath.”

Apperceptive visual agnosia A visual problem with object perception as the primary difficulty.

Apraxia An absence of action, but the term is most often used to describe a variety of missing or inap- propriate actions that cannot be clearly attributed to primary motor deficits or the lack of comprehension or motivation. Thus, apraxia refers to an inability to perform voluntary actions despite an adequate amount of motor strength and control.

Arachnoid granulations Small “pockets” of cauliflower- like veins within the subarachnoid space, which serve as pathways for the subarachnoid cere- brospinal fluid to be absorbed and re-enter the venous circulation.

Arachnoid membrane A “spiderlike” avascular mem- brane of the meninges.

Arborization The sprouting and branching of den- drites during brain development.

Aristotle (Greek, 384–322 B.C.) a disciple of Plato; erroneously believed that the heart is the source of

512 Glossary

all mental processes. Aristotle argued that because the brain is bloodless, it fills the function of a “radi- ator,” cooling hot blood ascending from the heart.

Arteriovenous malformations (AVM) Abnormal, often redundant vessels that result in abnormal blood flow. Because AVMs have inherently weak vessel walls, they may lead to slow bleeding or inad- equate distribution of blood in the regions sur- rounding the vessels.

Articulation The ability to form phonetic sounds of vowels and consonants, which then are placed in different combinations to form words and sen- tences.

Articulatory phonologic loop A working memory “slave system” that stores speech-based information and is important in the acquisition of vocabulary.

Ascending spinal-thalamic tract Carries sensory information related to pain and temperature and runs in parallel to the spinal cord. It synapses over a wide region of the thalamus, primarily on the intralaminar and ventral posterior nuclei of the thal- amus, and then to the somatosensory cortex.

Asociality Denotes a lack of social interest and related- ness. This anomaly is hypothesized to be one of the mechanisms responsible for autistic behaviors.

Asperger’s syndrome A pervasive developmental disor- der characterized by symptoms of autism, including impairments in social relatedness and atypical pat- terns of behavior, interest, or activity. However, in contrast with autism, impairment in language, adaptive skills (with the exception of social skills), and curiosity about the environment are not pro- nounced. The disorder tends to have a later age of onset than autism.

Association or polymodal areas Brain regions involved in the integration of sensory information from different sensory cortices and linking the sen- sory cortices to the motor cortices. These associative cortices support complex mental and behavioral functions.

Associative visual agnosia A visual problem having to do with difficulty in assigning meaning to an object.

Astereognosia Inability to recognize an object by touch.

Astereognosis See Tactile agnosia. Astrocytes Non-neural, star-shaped glia cells that are

highly branched and occupy much space between neurons in the gray matter. Their multiple functions include supporting neurons by interweaving among nerve fibers, contributing to the metabolism of synaptic transmitters, and regulating the balance of

ions. Astrocytes join together to provide a barrier between parts of the central nervous system (CNS) and non-CNS tissue.

Astrocytomas A form of malignant tumors primarily composed of astrocytes, a type of glia cell.

Atharva-Veda 700 B.C. Indian text that proposed that the soul was nonmaterial and never died.

Atherosclerosis A neuropathologic process character- ized by irregularly distributed yellow fatty plaques in large and medium-sized arteries.

Atonia Lack or reduction of muscle tone. Atonic seizures Are characterized by a sudden loss of

muscle tone and may result in a fall. They last no longer than 15 seconds while the person remains conscious.

Atrial fibrillation A disorder that upsets the heart’s rhythm, which may cause it to not pump enough blood to meet the body’s needs. A normal heart contracts and relaxes to a regular beat. In atrial fib- rillation the heart contracts at a very irregular and sometimes very rapid rate, which results in an irreg- ular heart rhythm.

Atrophy Brain shrinkage. Attention-deficit/hyperactivity disorder (ADHD) A

neuropsychological developmental disorder charac- terized by age-inappropriate inattention, impulsivi- ty, and overactivity.

Aura A neurologic event that occurs before the onset of a migraine or a seizure. The aura presents usually as a visual symptom including flashing lights, zigzag lines, or blurred or partial loss of vision.

Autism Previously referred to as infantile autism or Kanner’s autism. A pervasive developmental disorder, evident before age 3, involving impaired communi- cation, socialization, and behavioral adaptation. Atypical behaviors, preoccupations, or interests are frequently evident. The cause of the disorder is unknown, and the prognosis is poor.

Autistic aloneness A term proposed by Leo Kanner in his description of autistic children, referring to one of the central symptoms of the disorder, namely, the profound separation and disconnection of autistic individuals from other people.

Automatisms Stereotyped hand movements or facial tics often seen during an absence seizure.

Autonomic nervous system (ANS) Provides the “automatic” neural control of internal organs (such as heart, intestines). Most autonomic organs receive both sympathetic and parasympathetic input.

Autosomes A non-sex chromosome. Humans generally have 22 pairs of autosomes in each cell of the body.

Glossary 513

These chromosomes are involved in transmitting all genetic traits and conditions other than those that are sex-linked.

Axon Extends from cell body. Its main function is to transmit information in the form of an action potential.

Babinski, Joseph (1857–1932) Founder of British neurology.

Balint’s syndrome Related to damage of the parieto- occipital area of both hemispheres; includes visual agnosia together with other visuospatial difficulties such as misreaching and left-sided neglect.

Basal forebrain Structure of the telencephalon, sur- rounding the inferior tip of the frontal horn; strongly interconnects with limbic structures; includes various structures such as the amygdala and the septum.

Basal ganglia Also called the basal nuclei; deep nuclei of the telencephalon. Structures include the caudate nucleus, putamen, globus pallidus, substantia nigra, and subthalamic nuclei. Important relay stations in motor behavior (for example, the striato-pallido- thalamic loop). Coordinate stereotyped postural and reflexive motor activity.

Basal nuclei See Basal ganglia. Base rate The frequency with which a pathologic con-

dition is diagnosed in the population. Basilar artery Formed from a joining of the two verte-

bral arteries at the level of the brainstem. Basolateral circuit Anatomic circuit centered around

the amygdala; its most likely role is in emotional processing.

Basophilic adenomas A functioning type of tumor of the pituitary gland in the anterior lobe of the pitu- itary gland, which causes excessive secretion of adrenocorticotropic hormone, which can cause Cushing’s syndrome.

Behavioral-adaptive scales Tests that examine what an individual usually and habitually does, not what he or she can do. Such scales are most frequently used in evaluating the daily self-care skills of people who are quite impaired.

Benign Describes cell growth that is usually surrounded by a fibrous capsule, is typically noninfiltrative (that is, noninvasive), and will not spread to other parts of the body.

Benton, Arthur American neuropsychologist who pio- neered the role of the right cerebral hemisphere in behavior.

Benzodiazepines A family of sedating drugs used to treat anxiety and sleep disorders.

Beta-amyloid Amino acid peptide protein core found in the center of senile plaques. Also written as �-amyloid.

Bipolar neurons Neurons with two axons. Blindsight The ability in those with cortical blindness

to indicate that a stimulus is present, that it has moved, or that it is in a certain location, even though they have no conscious ability to “see” in the conventional sense.

Blood–brain barrier Affords protection from potentially harmful substances circulating in the body through the bloodstream. It bars certain drugs totally from the brain, and other substances require an active transport system across the blood–brain barrier.

Bradykinesia A poverty of movement that is not only slowed but reduced in magnitude; negative motor symptom of Parkinson’s disease.

Bradyphrenia Extremely slow information processing speed characteristic of patients with subcortical dementias.

Brain The anterior portion of the central nervous sys- tem located within the skull. It is continuous with the spinal cord and comprised of white/gray matter.

Brain abscesses A “walled-off,” localized pocket of pus within the brain often related to an infection.

Brain herniation A pathologic process associated with increasing intracranial pressure that occurs in the cranium, which may result in a displacement and deformation of the brain.

Brain hypothesis Suggests that the brain is the source of all behavior.

Brainstem Evolutionary old brain structure involved in regulating brain activation. It emerges from the uppermost portion of the spinal cord and includes all the subdivisions below the telencephalon (that is, the diencephalon, the mesencephalon, the meten- cephalon, and the myelencephalon), except for the cerebellum.

Broca, Paul (1824–1880) French anthropologist and scientist who advanced surgery, neuroanatomy, neu- rophysiology, and neuropathology.

Brodmann’s areas Cytoarchitectural scheme dividing the cortex into 52 sections.

Canalesthesia The fragmentation of the processing of incoming information from the sensory modalities. The anomaly is believed to be one of the causative factors of autistic behaviors.

Cannon–Bard theory Opposite of James–Lange theory. Walter Cannon, and later Philip Bard, argued the

514 Glossary

conscious emotional experience can be divorced from bodily sensation or expression. Although today most scientists agree that there is a correspondence between cognitive experience of emotion and sensory experience, types of emotion, emotional intensity, and individual variation appear to vary considerably.

Cardiac hypothesis Proposed that the heart was the seat of such emotions as love and anger.

Cataplexy The most debilitating of the narcolepsy symptoms; a brief episode of muscle weakness, actual paralysis, or both.

Catecholamines A class of neurotransmitters that includes dopamine and norepinephrine.

Caudal Toward the rear, away from the head. Caudate nucleus Structure of the basal ganglia. Cell doctrine A hypothesis that assumed the ventricles

were the location of the mind. Today, the cell doc- trine is known to be entirely inaccurate.

Central executive Concept from the theory of work- ing memory in which the central executive is an attention-controlling system; supervises and coordi- nates slave systems and is the proposed deficit in Alzheimer’s disease.

Central nervous system (CNS) The CNS includes the brain and the spinal cord. It is located within and protected by the bony cavities of the skull and the spine.

Central sleep apnea Apnea that occurs most often during rapid eye movement sleep in which disor- dered breathing is related to the brain failing to send the necessary signals to breathe. This may reflect brainstem abnormalities that manifest only during sleep.

Central sulcus Separates the frontal and parietal lobes. Cerebellar peduncles Large neural tracts connecting

the cerebellum to the midbrain. Cerebellum Means “little brain”; sits posterior to the

brainstem and inferior to the telencephalon, and functions in coordinating motor and sensory infor- mation.

Cerebral (or Sylvian) aqueduct A narrow channel passing through the midbrain connecting the third to the fourth ventricle.

Cerebral achromatopsia Total color blindness. Cerebral hemispheres (cerebrum) Includes structures

of the frontal, parietal, occipital, and temporal lobes; plays a role in higher cognitive functioning.

Cerebrospinal fluid (CSF) A protective fluid that sur- rounds and supports the brain and spinal cord.

Cerebrovascular accident (CVA) A technical term for stroke; describes a heterogeneous groups of vascular

disorders associated with damage to the brain’s blood vessels and decreased blood flow within and to the brain.

Cerebrum The largest part of the brain, consisting of the left and right hemisphere, and the corpus callo- sum. The cerebrum does not include the medulla, pons, and cerebellum.

Chemoreceptors Structures that respond to various chemicals on the surface of the skin and mucous membranes. They range from detecting levels of stomach acidity to skin irritations. Smell and taste are special examples of chemoreception and are discussed separately. Thermoreceptors detect heat and cold.

Chorea Twisting, writhing, undulating, grimacing movements of the face and body. Commonly associ- ated with Huntington’s disease.

Choroid plexus A highly vascularized network of small blood vessels that protrudes into the ventricles from the pia mater and secretes cerebrospinal fluid.

Chromophobic adenoma A functioning type of tumor of the pituitary gland localized in the ante- rior aspects of the pituitary gland that is often associated with hyperpituitarism or hypopitu- itarism.

Chromosomal disorders A disorder that is the conse- quence of either an abnormal number of chromo- somes or some defect in the structure of the chro- mosome.

Cingulate gyrus A structure of the limbic system, the medial cortex surrounding the corpus callosum.

Cingulate motor area (CMA) or cingulate motor cortex Structures of the secondary motor cortex involved in higher order voluntary movement.

Cingulum A major intracerebral fiber. Circadian rhythm Daily biorhythm oscillation of

heightened and lowered brain arousal observed throughout the wake/sleep cycle.

Circle of Willis A spiderlike arterial structure formed by the anterior cerebral branches of the internal carotid artery and its connections, the anterior com- municating artery, the posterior communicating artery, and the posterior cerebral branches of the basilar artery. It allows for a certain degree of redun- dancy among blood vessels and blood supply to the various areas of the brain.

Cisterns Cavities that are expansions of the subarach- noid space in the central nervous system.

Clonic Motoric jerking. Closed head injuries A type of head injury that is

associated with a blow to the head, but that does not penetrate the skull.

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Cocktail party syndrome Hyperverbal; a form of speech featuring excessive verbiage that is lacking in clarity, organization, depth, and relevance.

Collateral blood vessel Allows redundant blood sup- ply to take more than one route to a given region. The term collateral describes redundant blood flow present in the vascular network after occlusion of an artery. If one vessel is blocked, a given region might be spared an infarct because the blood has an alter- native route.

Coma Loss of consciousness. Communicating hydrocephalus A form of hydro-

cephalus that includes the presence of blood or blood products that are mixed with cerebrospinal fluid. This is most often caused by a hemorrhage or infection. Also see Nonobstructive hydrocephalus.

Complex partial seizure A type of seizure that has an element of altered psyche or awareness in addition to sensory or motor components.

Computed transaxial tomography (CT scan) An imaging process that renders an anatomic image of brain density based on multiple radiographic images of the brain. CT, which is readily available and can be used with almost anyone, provides a three- dimensional perspective of the brain with acceptable differentiation of brain structures.

Conceptual apraxia A subtype of apraxia in which the knowledge of the action has been lost.

Congenital adrenal hyperplasia An inherited endocrine disorder characterized by over-production of the androgen hormone and insufficient produc- tion of the cortisol and aldosterone hormones. It affects both males and females and results is an early or inappropriate appearance of male characteristics.

Consciousness Awareness, level of mental alertness, and level of attention; the mind’s subjective experi- ence of brain states and processes that are available to perception.

Construct validity Focuses primarily on a test score as a measure of the psychological construct of interest. If a neuropsychological test measures a specific con- struct (memory, attention, for example), then it has construct validity.

Content validity Pertains to the degree to which a sample of items or tasks make conceptual sense or represent some defined psychological domain.

Contralateral On the opposite side. Coronal plane A plane ( y-axis) that shows the brain as

seen from the front (frontal section). Typically, this plane is viewed from behind to provide consistency for right and left directions of the brain and the picture.

Corpus callosum A large set of myelinated axons con- necting the right and left cerebral hemispheres, functions in information exchange between the two hemispheres.

Cortical dementias Dementias affecting the cerebral cortex.

Corticogenesis The development of the cortex of the brain.

Countercoup injury A type of closed head injury sus- tained at the pole opposite from where the primary injury occurs because the brain “tears” away from the skull.

Cranial nerves Carry specific sensory and motor infor- mation directly to the brain, bypassing the spinal cord. These nerves are also very old from an evolu- tionary point of view.

Creutzfeldt–Jakob disease (CJD) A subcortical dementia characterized by a quick progression; con- nected to “mad cow disease”; transmitted between humans via transplants of affected neural tissue, through cornea transplants, or contamination via medical procedures, and its variants can cross species through consumption of tainted meat con- taining neural tissue.

Criterion validity Demonstrates that scores are related systematically to one or more outcome criteria, either now (concurrent validity) or in the future (predictive validity).

Crystallized functions Thought to be most depen- dent on cultural factors and learning. Spelling and factual knowledge are examples of crystallized functions.

Crystallized intelligence An accumulation of acquired skills and general information, most related to for- mal education or diverse social experiences.

Cubitus valgus A deformity of the arm in which the forearm deviates laterally, resulting in an increased carrying angle at the elbow.

Cushing’s syndrome Named after Boston surgeon Harvey Cushing (1869–1939); a severe systemic ill- ness most often seen in female individuals, which includes neurologic symptoms and changes in bone structure, hypertension, and diabetes. The adreno- corticotropic hormone–secreting tumor is the most serious condition encountered by any of the pitu- itary tumors and can result in a necessary complete removal of the tumor, including the pituitary gland.

Cutoff score Often used in neuropsychology to deter- mine a range of impaired functioning. A patient scoring worse than the cutoff score is labeled as

516 Glossary

impaired; a patient scoring better is labeled as with- in normal limits (WNL).

Cytoarchitectonic dysplasia A focal pathologic change of the cellular organization of brain cells.

da Vinci, Leonardo (1452–1519) Italian painter, sculptor, architect, and scientist.

Deceleration Describes an event in which the brain is in motion traveling at a certain speed and then stops abruptly.

Declarative memory A form of memory that is explicit, verbalizable, and accessible to conscious awareness.

Decussating Switching the transmission of informa- tion from one side of the body to the contralateral side of the brain.

Deep dyslexia A reading disorder characterized by an impaired ability to sound out words, while whole- word skills are unimpaired.

Defective response inhibition The act of inappropri- ately, displaying a motor response when it is unwanted.

Deficit measurement An approach to neuropsycho- logical assessment for understanding general condi- tions and disease states about a patient by examin- ing scores that are impaired and comparing them with other factors known about the patient.

Delirium A transient cognitive problem associated with a confused state caused by specific organic problems.

Dementia A pattern of impairment with varying causes characterized by a deteriorating progression in mem- ory, as well as other areas of cognitive functioning.

Dendrites Feathery extensions that branch from the neuron into the immediate neighborhood of the cell body.

Dendritic spines Short outgrowths on the dendrites that contain synapses for gathering information to be sent to the neurons.

Descartes, René (French, 1596–1650); proposed a strict split or schism between mental processes and physical abilities. He hypothesized that the mind and body are separate, but interact with each other.

Diaschisis A passive process of uncovering working neural systems after temporary neuronal disruption in areas far removed from the lesion site.

Diencephalon Composed primarily of the thalamus and hypothalamus and a structure of the brainstem, also known as the interbrain or “between brain.”

Differentiation process A phase of prenatal central nervous system development that commences when

migrating neural cells reach their predetermined des- tinations within the brain. As the neural cells reach their destination, they develop the unique character- istics of the cells specific to that brain region.

Digital subtraction angiography A procedure in which the x-ray image of the brain is stored and subtracted after the images of the contrast material have been acquired. The process is particularly effec- tive in enhancing the visualization of blood vessels, including the morphologic and physiologic states of the arterial, capillary, and venous phases of the cere- bral circulation.

Disengage attention The withdrawal or decoupling of attentional focus from a stimulus.

Disinhibition Impulsivity and inappropriate behavior; may result from losing inhibitory neurons to trauma or disease.

Dissimulation A form of malingering in which the patient is consciously denying that there is anything wrong with him or her, to achieve some secondary gain (for example, to avoid hospitalization, to gain employment).

Dissociation A separation between functional contri- butions of two different brain areas.

Distal Away from the center, toward the periphery, away from the origin of attachment.

Divided attention Partialing out one’s attentional resources at the same time rather than switching back and forth, however quickly.

Dominance Hand (and to a lesser extent, eye and foot) preferences and proficiencies in performing tasks or to the cerebral organization of the brain.

Dopamine A neurotransmitter that plays an important role in the organization of motor behavior.

Doppler-ultrasonography (fTCD) A noninvasive diagnostic procedure that uses an ultrasound scan- ner to convert sound waves into images of blood flow within body tissue and organs. It is used to assess the direction, velocity, and turbulence of blood flow.

Dorsal Toward the back. The top of the brain is dorsal in humans.

Dorsal column medial lemniscal pathway Carries information pertaining to touch and vibration. It is so named because it is routed up the dorsal aspects of the spinal cord to a white matter tract termed the medial lemniscus that courses through the contralat- eral side of the brainstem through the medulla, pons, and midbrain to be routed up through the thalamus (ventral posterior nucleus) and on to the primary somatosensory cortex.

Glossary 517

Dorsal simultagnosia A visual disorder related to damage of the parieto-occipital area of both hemi- spheres. Even though parts of a picture may be rec- ognized, the whole is not perceived.

Dorsolateral prefrontal cortex This area is located, functionally, in the prefrontal cortex, which is responsible for orchestrating and organizing many functions of the brain. The dorsolateral prefrontal cortex is not a “movement center” in and of itself but is instrumental in deploying movement. Sensory information from the integrative association area of the parietal lobes is relayed to this motor planning area.

Double-deficit hypothesis Poses that reading disor- ders can be traced to deficits in phonological pro- cessing and/or naming speed. The presence of both a deficit in phonological processing and slow nam- ing speed is predictive of the most severe reading problem.

Double dissociation A logical progression of scientific assumptions in localizing functional areas in the brain. For example, if symptom A appears with lesions in brain structure X, but not with those in Y, and symptom B appears with lesions of Y, but not of X, then those specific areas of the brain each have a specific function.

Down’s syndrome Also referred to as trisomy 21. A genetic disorder due to an extra chromosome on the 21st pair. The disorder is characterized by recogniz- able facial features, short stature, and mild to severe cognitive deficits.

Dura mater “Tough mother”; a dense, inelastic, double- layered, vascularized membrane of the meninges that adheres to the inner surface of the skull.

Dysarthria A specific motor apraxia involving the vocal musculature. People with dysarthria differ from pure aphasiacs, although the two conditions may occur together in that such patients know what they want to say but are unable to formulate words because of a problem with motor control.

Dyscalculia A disorder of mathematics involving impaired ability to comprehend number concepts, spatially orient numbers, reason mathematically, or perform mathematical operations.

Dysgenesis Abnormal or defective development of an organ.

Dysgraphia An impairment of the ability to write or express oneself in writing. Deficits are evident in one or more of the following areas: (1) letter forma- tion, speed of writing, and spatial organization of writing; (2) written expression; (3) mechanical

knowledge of spelling, grammar, punctuation, and capitalization; and (4) organization and thematic construction of written expression.

Dysgeusia Distorted taste sensation. Dyskinesia Uncontrolled involuntary movement. Dyslexia A developmental or acquired disorder of

reading involving the disruption of one or more of the component skills of reading. Central reading skills include letter identification, phonologic aware- ness and processing, and decoding of the written word.

Dysosmia Distorted smell sensation. Dysphonia Loss of vocal emotional expression result-

ing in a monotonous voice tone.

Echolalia An atypical communication behavior char- acterized by the repetition or “echoing” of the words or phrases just spoken by another person. Often dis- played by children with pervasive developmental disorders.

Ectopias Also referred to as “brain warts.” Small areas of abnormally placed brain neurons.

Edema The swelling of the brain Efferent nerves Motor nerves carry outgoing signals

for action from the central nervous system to the muscles.

Elastin A protein within elastic fibers of connective tissue accounting for the elasticity of structures such as the skin, blood vessels, heart, lungs and tendons.

Electroconvulsive therapy (ECT) Shock therapy; administering a large amount of electricity to the skull causing the collective firing of neurons: an induced seizure. ECT sometimes improves severe forms of depression within a few days. Although the mechanism is not clearly understood, therapists use ECT when it is important to intervene quickly to prevent the patient from acting on suicidal thoughts.

Electrocorticogram (ECoG) A form of EEG in which electrodes are placed directly on the exposed cortex during surgery to isolate a precise location of brain pathology.

Electroencephalography (EEG) One of the most widely used techniques in neurology. In EEG, the electrical activity of nerve cells of the brain are recorded through electrodes attached to various locations on the scalp.

Epileptogenic focus The anatomic site of onset. Embolism Derived from Greek embolos, meaning

“plug” or “wedge”; a type of occlusion of an artery in which the clot forms in one area of the body

518 Glossary

and travels through the arterial system to another area, in this case, the brain, where it becomes lodged and obstructs cranial blood flow. Approximately 14% of all CVAs are caused by an embolism.

Emotional perception The ability to identify and comprehend the emotions of others from both ver- bal and nonverbal behavioral cues.

Encode attention An element of attention that is involved in short-term or working memory.

Endorphins The most prominent neuropeptide with opioid properties. Endorphins have received much scientific attention for their analgesic effects and their possible role in a pain-inhibiting neuronal system.

Endothelium The layer of epithelial cells that line the blood vessels. When the endothelium is breached, the blood-clotting properties of the platelets are activated. They change shape and adhere to the vessel wall, each other, and red blood cells. If this occurs pathologically (that is, in a normal vessel), it leads to a thrombosis, ultimately occluding the vessel.

Engaging attention The attentional operation of focusing, or centering of attention on a stimulus.

Enhanced computed transaxial tomography (CT) A CT scan that involves the injection of a contrast agent to provide better visualization of brain struc- tures, particularly bleeds.

Enuresis The continuation of frequent bed-wetting beyond the age of 5 that is not a consequence of a physiological dysfunction.

Environmental dependency syndrome (stimulus- bound) Neuropsychological syndrome character- ized by an over-responsiveness to environmental stimuli due to a loss of inhibitory control, often as a consequence of bilateral frontal damage.

Ependymal glioma A bulky, solid, firm vascular tumor of the fourth ventricle.

Epidural hematoma Represents a bleed between the meninges and the skull and occurs in 1% to 3% of major closed head injuries. The cause of an epidural is most often related to the rupture of an artery.

Epidural space The space between the two dural lay- ers of the meninges.

Epilepsy “Falling sickness”; a syndrome in which brain seizure activity is a primary symptom.

Epileptic syndrome Most people with repeat seizures are considered to have an epileptic syndrome, which is more serious than a single seizure.

Episodic buffer A component of Baddeley’s working memory model that is hypothesized to temporarily maintain and integrate the information of different sensory inputs (visual and auditory) through its rela- tionship with long-term memory.

Episodic memory Individual episodes, usually autobi- ographical, that have specific spatial and temporal tags in memory.

Equipotentiality Term first coined by Flourens to describe the notion that mental abilities depend on the brain functioning as a whole. Thus, the effects of brain injury are determined by the size of the injury rather than its location.

Evoked potential (EP) Also called event-related potentials (ERPs); an electrophysiologic diagnostic test that involves the stimulation of specific sensory fibers, which, in turn, generate electrical activity along the central and peripheral pathways, as well as the specific primary receptive areas in the brain.

Excessive daytime sleepiness Pathologic daytime sleepiness; the most frequent first sign in narcolepsy.

Excitatory postsynaptic potential (EPSP) Depolarization that increases the probability of the postsynaptic cell to reach its threshold and fire.

Executive attention system See Anterior attention system.

Executive functions Higher order regulatory and supervisory functions that researchers believe are subserved, in part, by the frontal lobes. Cognitive operations such as planning, mental flexibility, atten- tional allocation, working memory, and inhibitory control are considered executive functions.

Executive planning Higher order problem solving necessary for the generation and organization of behavior to achieve a goal. Executive planning requires the ability to anticipate change, respond objectively, generate and select alternatives, and sus- tain attention.

Explicit memory Information that can be consciously recalled and verbalized.

Expressive aphasia A disorder of speech output. Extended paraphasia See Word salad. Extended selective attention Overly extended atten-

tional focus and an inappropriate delay in shifting attention. The anomaly is considered one of the causative factors in the symptoms of autism.

Extradural hematoma Less frequent than the subdural hematoma, a bleed that occurs between the skull and the dura. Extradural hematomas are most likely caused by a tearing of the large middle meningeal arteries.

Glossary 519

Extrapyramidal motor system Responsible for stereo- typed postural and reflexive motor activity. The sys- tem also acts to keep individual muscles ready to respond.

False positive Also known as a Type I error or false alarm. Refers to a case in which a neuropsychologi- cal test erroneously indicates the presence of a pathologic condition.

Familial sinistrality The degree of left-handedness within the nuclear and extended family.

Femorocerebral angiography Angiography that intro- duces a catheter into the arterial system via the femoral artery.

Festinating gait The rapid, shuffling gait characteristic of Parkinson’s disease.

Fetal alcohol effect (FAE) A developmental disorder that involves the cognitive and behavioral deficits associated with FAS, but without the physical stig- mata of FAS. Also see Fetal alcohol syndrome.

Fetal alcohol syndrome (FAS) A developmental disor- der caused by the pregnant mother ingesting alco- hol. The disorder is characterized by recognizable physical stigmata, neurologic abnormalities, and cognitive and behavioral impairments. Unlike many of the congenital disorders, FAS is preventable.

Fibers See Tracts. Finger agnosia Inability to recognize or orient to one’s

own fingers. Fissure A very deep sulcus in the cortex. Flicker fusion rate Denotes the speed at which two

separate visual images appear to fuse visually into a single image.

Flourens, Pierre (French, 1794–1867) The foremost early advocate of an alternative to localization theories.

Fluent aphasia A disorder of speech in which the patient remains able to talk, but his or her speech makes no sense, often sounding like some unknown foreign language.

Fluid functions Believed to be culture-free and inde- pendent of learning. Problem solving and abstract reasoning are considered fluid functions.

Fluid intelligence Novel reasoning and the efficiency of solving new problems or responding to abstract ideas.

Fluorescent in situ hybridization (FISH) A labora- tory technique in which a DNA probe is labelled with a fluorescent dye to detect chromosomal abnormalities.

Focus-execute attention The ability to respond and pick out the important elements or “figure” of

attention from the “ground” or background of external and internal stimulation. Also implies a measure of concentration or effortful processing.

Focused attention A form of selective attention involving the restriction of attention to a specific feature, or set of features, to the exclusion of other features.

Fontanelles Literally “small springs or fountains”; membranous gaps between the bony skull plates that are evident in newborns.

Foramen of Magendie The middle opening, of three, of the membranous roof of the fourth ventricle, allowing the cerebrospinal fluid to flow outside the brain and recirculate.

Foramen magnum The largest of the foramina; pro- vides a large median opening in the occipital bone for the spinal cord to pass through to the brain- stem.

Foramen of Monro See Interventricular foramen. Foramina More-or-less symmetric orifices in the base

of the skull that provide passage for nerves and blood vessels.

Foramina of Luschka The two lateral openings, of three, of the membranous roof of the fourth ventri- cle, allowing the cerebrospinal fluid to flow outside the brain and recirculate.

Forebrain, or prosencephalon The topmost division of the developing brain.

Fornix A structure of the limbic system that contains nearly 1 million fibers; it rises out of the hippocam- pal complex and arches anteriorly under the corpus callosum. The fornix relays information to the mammillary bodies.

Fossae Conspicuous ridges in the base of the skull that hold the brain in place.

Fragile X A genetic disorder frequently associated with mental retardation and other cognitive deficits and distinctive physical features. The disor- der is related to a compression or break of the X chromosome.

Freud, Sigmund (Austrian, 1856–1939) Best known as the founder of psychoanalysis and the father of clinical psychology. Freud’s initial love was neurology and investigating the secrets of the central nervous system.

Frontal lobe One of the four cortical lobes; contains the primary motor cortex and the prefrontal lobe. Its functions are motor processing and executive, including planning, inhibition, and formulation of behavior.

Frontal operculum Broca’s area.

520 Glossary

Functional systems A concept first formulated by Luria in which behavior results from interaction among many areas of the brain.

Functioning adenomas Pituitary tumors that play an “uninvited” role in the operation of the pituitary gland, often affecting the release of the gland’s hor- mones.

Galen (A.D. 129–201) Roman anatomist and physi- cian who identified many of the major brain struc- tures and described behavioral changes as a function of brain trauma.

Gall, Franz (1758–1828) Austrian anatomist who pos- tulated that mental faculties were innate and related to the topical structures of the brain.

Gamma-aminobutyric acid (GABA) One of more than 20 amino acids, GABA is a neurotransmitter known to have strong inhibitory properties.

Ganglia (singular, ganglion) A strategic collection of nerve cells in the peripheral nervous system.

Generalized seizure A seizure caused by an abnormal rhythm of the entire brain; formally known as “grand mal”; bilaterally symmetric episodes characterized by a temporary lack of awareness, or what appears on observation to be a complete loss of consciousness.

Gerstmann-Straussler-Scheinker syndrome (GSS) An extremely rare familial Creutzfeldt–Jakob disease variant that results in a “fatal insomnia.”

Geschwind, Norman (1926–1984) American neurolo- gist who proposed that behavioral disturbances were based on the destruction of specific brain pathways that he called disconnections.

Gigantocellular tegmental field (GTF) Located in the higher pons; appears to generate brain waves. Left unchecked, the neurons fire spontaneously, produc- ing a high level of activity. One particular set of dis- charges is termed PGO spikes because they travel from the pons (P) to the lateral geniculate (G) nucleus of the thalamus and to the occipital (O) cortex.

Gilles de la Tourette syndrome See Tourette’s syn- drome.

Glasgow Coma Scale (GCS) A three-item scale often used in the medical setting to assess the severity of coma. The GCS ranges from 3 to 15 points, with lower scores indicating severe coma and higher scores suggesting a confusional state.

Glia Greek meaning “glue”; glia cells outnumber neu- rons and provide supportive structure and metabolic function to the neuron.

Glioblastoma multiforme (GBM) A particularly destructive and fatal glioma.

Gliomas A type of brain tumor, gliomas are a rela- tively fast growing brain tumor that arises from supporting glia cells. Gliomas are the most com- mon infiltrative brain tumor, which make up approximately 40% to 50% of all brain tumors. The term glioma is often used to describe all pri- mary, intrinsic neoplasms of the brain and the spinal cord.

Globus pallidus A structure of the basal ganglia. Glutamate One of more than 20 amino acids, gluta-

mate is the major excitatory neurotransmitter of the brain.

Golgi, Camillo (1843–1926) Italian physician who made the discovery in the early 1870s that silver chromate stained dead neurons black. This allowed people to visualize individual neurons for the first time.

Gonadotropins Hormonal substances that stimulate the functions of the testes and ovaries.

Grading of tumors A method of evaluating the malignant features of brain tumors. Grading is from 1 to 4, with a grade 1 tumor representing a slow-growing tumor accompanied by few neu- ropsychological deficits. Grades 2 and 3 represent intermediate rates of growth and neuropsycholog- ical dysfunction. Grade 4 tumors are fast grow- ing and typically have a poor prognosis for recovery.

Grand mal seizure Literally “big bad” seizure; consist of violent motoric abnormalities of stiffening and jerking episodes and the accompanying loss of con- sciousness.

Gray matter Areas of the brain that are dense in cell bodies such as the cortex and that appear gray.

Gyri (singular, gyrus) Ridges of the cortex between sulci.

Halstead–Reitan Neuropsychological Battery (HRNB) The first neuropsychology laboratory in the United States was founded in 1935 by Ward Halstead at the University of Chicago. Halstead worked closely with neurosurgery patients and developed assessment devices that differentiated between patients with and without brain damage. Halstead later developed, with Ralph Reitan, the HRNB, which represented an empirical approach to the assessment of brain damage.

Hebb, Donald Publisher of the classic The Organization of Behavior: A Neuropsychological Theory. This book brought much growth to the field of neuropsychology.

Glossary 521

Hécaen, Henry French neuropsychologist (born 1912) who made important contributions to brain–behavior relations in health and disease, especially the role of the right hemisphere.

Hematoma The massive accumulation of blood within the cranium.

Hemianopia Also called homonymous hemianopia; half-blindness. Partial blindness on the same side, or visual field, of each eye. The partial blindness is not related to a malfunction of the eye, but to the brain connection to the occipital lobes. This problem is also attributed to unilateral damage to the right or left occipital lobes.

Hemiplegia The loss of voluntary movement to one side of the body, often as a result of stroke.

Hemispatial neglect A failure to attend to either the right or left visual field. Often associated with right, posterior brain damage.

Hemispheric asymmetry The differentiation in mor- phology and physiology of the brain between the right and left hemispheres.

Hemorrhage Type of stroke related to a significant bleed in the brain. Hemorrhages are the most severe form of stroke and often result in permanent brain damage or death.

Heraclitus Sixth century B.C. Greek philosopher who referred to the mind as an enormous space whose boundaries could never be reached.

Herpes encephalitis An infection that aggressively attacks the medial temporal and orbital frontal areas, resulting in the destruction of much of the limbic system, especially the hippocampus.

Heschl’s gyrus A gyrus of the superior temporal lobes known as the primary auditory cortex; often larger in area in the right hemisphere because two gyri are often present. Plays a role in nonspeech and musical processing.

Hindbrain Also called rhombencephalon; the lower division of the developing brain.

Hippocampal commissure Minor intercerebral fibers. Hippocampal formation A set of structures of the

limbic system centered around the hippocampus; includes the hippocampus, dentate gyrus, and subiculum.

Hippocampus Anatomic brain structure of the limbic system thought to be involved in consolidating memory.

Hippocrates (460–377 B.C.) Greek physician who has been honored as the father of medicine, also shared the belief that the brain controlled all senses and movements. He was the first to recognize that paral-

ysis occurred on the side of the body opposite the side of a head injury.

Homonymous Same-sided. Homonymous hemianopia Same-sided half-blindness.

Partial blindness on the same side, or visual field, of each eye. The partial blindness is not related to a malfunction of the eye, but to the brain connection to the occipital lobes. This problem is also attrib- uted to unilateral damage to the right or left occipi- tal lobes.

Horizontal plane A plane (x-axis) that shows the brain as seen from above or parallel to the ground.

Horseradish peroxidase (HRP) An enzyme, found in the roots of horseradish, that allows mapping of neu- ronal pathways using an axonal transport mechanism.

Human immunodeficiency virus (HIV) The HIV/ AIDS virus has a wide effect on the brain as it pro- gressively destroys the immune system. The virus itself may have direct consequences for the brain. It also opens the brain to opportunistic infections and other diseases that can attack the brain.

Humors Medieval physicians believed that humors, body liquids, were influential in health and disease.

Huntington’s disease (HD) Also called Huntington’s chorea. A genetic, autosomal dominant progressive subcortical dementia that inflicts devastating motor impairment in the form of chorea, as well as cogni- tive decline on adults in the prime of their lives.

Hydrocephalus (HC) A condition in which the ven- tricles become abnormally enlarged, most often related to a problem with cerebrospinal fluid flow, production, or absorption.

Hyperacusis Abnormally high sound acuity that is often accompanied by low tolerance for loud sounds.

Hypercalcemia Elevated concentrations of calcium in the blood stream.

Hyperdensity Increased density of brain tissue that typically signals an abnormal density such as seen in tumor or bleeding.

Hyperlexia Early reading acquisition (decoding) with- out adequate comprehension. An anomaly exhibited by some children with developmental disorders, such as autism.

Hyperserotonemia Elevated or excessive levels of sero- tonin in the body.

Hypertonia Abnormally high muscle tone or strength. Hypnagogic hallucinations Vivid, dreamlike intru-

sions into wakefulness; occur in the transition between wakefulness and sleep onset.

Hypodensity Low density of brain mass. Hypogeusia Diminished taste sensitivity.

522 Glossary

Hypokinesia Reduced motor initiation; negative motor symptom of Parkinson’s disease.

Hyposmia Diminished smell sensation. Hypothalamus A structure of the diencephalon, part of

the limbic system; considered instrumental in con- trolling the autonomic system. Activates, controls, and integrates the peripheral autonomic mecha- nisms, endocrine activity, and somatic functions, including body temperature, food intake, and devel- opment of secondary sexual characteristics.

Hypotonia Abnormally low muscle tone or strength. Hypoxia The reduced oxygenation of brain. Hypoxia

is typically not associated with cell death, but some possible interference in the functioning of the neu- ron. Hypoxia is usually related to inadequate breathing, such as experienced during sleep apnea, can occur at high altitude, or is related to carbon monoxide poisoning.

Ideomotor apraxia See Motor apraxia. Impact injury A type of closed head injury in which

the physical forces act on the brain tissue at the point of impact.

Impaired affective assignment A failure to link the appropriate emotional meaning to both internal and external stimuli. Considered a key deficit of autism.

Implicit memory Demonstrated by means whereby conscious awareness is not always necessary, such as implicit priming, skill learning, and conditioning.

Implicit priming The phenomenon in which, if “primed” with three-letter word stems, people are more likely to complete the stem with a word they have already seen.

Infarction A severe loss of blood caused by a blockage of an artery, often resulting in more lasting neu- ropsychological deficits.

Inferior Toward the bottom, or below. Inferior colliculi Two elevations within the roof of the

tectum, which serve as an important relay center for the auditory pathway.

Infiltrative tumors Tumors that take over or infiltrate neighboring areas of the brain and destroy its tissue.

Inhibitory control Inhibition of behavior through involuntary and voluntary neuropsychological processes. At a voluntary level, this capacity is consid- ered an executive function and connotes the volitional capacity to withhold behavior, particularly when invoking environmental contingencies are evident.

Inhibitory postsynaptic potential (IPSP) The pres- ence of an ionic current flow that hyperpolarizes the postsynaptic neuron. As a result, a greater depolar-

ization than normal is required for excitation and there is only a small probability that there will be an action potential.

Intelligence The aggregate or global capacity involving an individual’s ability to act purposefully, to think rationally, and to deal effectively with the environment.

Intelligence tests Complex composite measures of ver- bal and performance abilities that are related partly to achievement (for example, factual knowledge) and partly to aptitude (for example, problem solv- ing). Although there are well over 100 different tests of intelligence, the scales that David Wechsler devel- oped have become widely used throughout the world and typically include a variety of scales mea- suring verbal-comprehension skills and tests tapping perceptual-organization abilities.

Intercerebral fibers Connect structures between two hemispheres.

Interference control The ability to screen or block out internal or external distractions that could intrude into and disrupt attentional focus.

Interictal Between seizures. Internal carotid arteries Two of the four major arter-

ies to the brain, supplying the anterior portions of the brain.

Interneurons Neurons with short axons or no axons. Interpretive hypotheses Inferences about the patient’s

cognitive status that the neuropsychologist makes in the process of interpreting neuropsychological assessment data.

Interventricular foramen (foramen of Monro) A small opening connecting the lateral ventricles.

Intracerebral “Within the cerebrum” or brain. Intracerebral fibers Fibers that connect regions within

one hemisphere. Intracranial pressure (ICP) Related to the presence

of a bleed (or hemorrhage) within the cranium (skull) usually associated with the development of a space-occupying mass or pocket of blood, which may press on nearby brain structures, affecting their integrity.

Intraventricular hemorrhage (IVH) Bleeding within the ventricles of the brain. A common cause of hydrocephalus in premature infants. Vessels in the area surrounding the ventricles rupture, and the blood and cellular debris obstruct the structures that allow for the reabsorption of the cerebrospinal fluid into the bloodstream.

Ions Atoms or molecules that have acquired an electri- cal charge by gaining or losing one or more elec- trons. Four ions that are important in neuronal

Glossary 523

communication are sodium (NA+), potassium (K+), calcium (Ca++), and chloride (Cl–).

Ipsilateral On the same side. Ischemia A restriction or insufficiency of blood supply

to an area of the brain, with possible damage or dysfunction depending on the duration of the ischemia. These events can also be short-lasting, with transient deficits.

Isochromosome An abnormal karyotype characterized by identical arms on the X (female) chromosome. The chromosomal anomaly is associated with Turner’s syndrome.

Jackson, Hughlings British neurologist (1835–1911) who wrote on the integration of the localization and equipotentiality models of brain function. He sug- gested that behavior resulted from interactions among all areas of the brain, but that each area in the nervous system had a specific function that con- tributed to the overall system.

Jacksonian seizure Involves motor areas; such events have been called marching seizures because they begin with jerking or tingling of a single body area and spread to other areas.

James–Lange theory of emotion Promoted by American psychologist William James and Danish psychologist Carl Lange, postulating that emotion is consciously experienced as a reaction to physical sensory experience. In other words, we feel fear because our hearts are racing; we are sad because we are crying. Although critics saw this as an overstate- ment, the James–Lange theory did correctly insist that sensory and cognitive experiences were inti- mately entwined and could not be separated from each other.

Joint attention The reciprocal attention evident in the interaction of individuals. Disruption of this inter- actional capacity of mother and child has been asso- ciated with autism.

Joint contractures An abnormal shortening of the elastic tissue of a joint resulting in distortion or deformity.

Karyotype A visual representation of an individual’s chromosomes that displays the structural compo- nents and integrity of the chromosomes.

Kennard principle A principle of neural recovery that bears the name of its originator, Margaret Kennard. The principle holds that earlier brain injury is associated with less impairment and bet- ter recovery of functions than injury occurring

later in development. Subsequent clinical and experimental studies have not fully supported this principle.

Kinesthetic sense A sense of one’s physical body is supplied by a combination of vision, the vestibular organs, and the proprioceptive sense.

Kuru A spongiform encephalopathy suffered by the Fore people of Papua New Guinea.

Lancisi, Giovanni (1654–1720) Italian clinician who contributed greatly to the knowledge of aneurysm: abnormal blood-filled ballooning of an artery in the brain.

Lashley, Karl (1890–1958) American neuropsycholo- gist who was one of the first to combine behavioral sophistication in experiments with neurologic sophistication, thereby creating the field of experi- mental neuropsychology.

Lateral Toward the side, away from the midline. Lateral fissure Separates the frontal and parietal lobes. Lateralization With dominance, refers to the differ-

ences in functional specialization between the two brain hemispheres.

Lesions Derived from Latin laesio, meaning “to hurt”; any pathologic or traumatic discontinuity of brain tissue. Depending on their size and location, lesions result in minor or major behavioral effects.

Lewy bodies Small, tightly packed granular structures with ringlike filaments, found within dying cells.

Lexicon store A “storehouse” of words that an individ- ual knows or understands.

Lezak, Muriel American neuropsychologist who pio- neered the assessment approach in clinical neu- ropsychology.

Limb-kinetic apraxia A subtype of apraxia involving problems in executing precise, independent, or coordinated finger movements.

Limbic system Includes the fornix; some brainstem areas, particularly the mammillary bodies of the hypothalamus; and specific basal forebrain struc- tures, including the amygdala (“almond” because of its shape) and the septum.

Lissencephaly See Agyria. Localization theory Assigns specific functions to par-

ticular places in the cerebral cortex. Locus ceruleus Located below the wall of the fourth

ventricle, it has been implicated as an important norepinephrine pathway.

Longitudinal fissure The space between the two hemispheres.

Long-term memory (LTM) Theoretically of unlimited capacity and relatively permanent except for models

524 Glossary

suggesting that loss of information through forget- ting is possible.

Lucid dreaming The ability while dreaming to become conscious of that one is in a dream state.

Lumbar puncture Also known as a spinal tap; a med- ical technique for collecting a specimen of cere- brospinal fluid surrounding the spinal cord for diag- nostic study.

Luria, Alexander (1902–1977) Russian neuropsychol- ogist who was responsible for the most profound changes in the scientific understanding of the brain and mind.

Magnetic resonance imaging (MRI) A visualization procedure that provides the most detailed images of brain structures. The advantage of functional MRI over other functional procedures, such as positron emission tomography, is that it provides good spa- tial resolution and images in short time periods, or “real time.”

Magnetoencephalogram (MEG) The magnetic equivalent of the electroencephalogram in which a three-dimensional magnetic field of the brain can then be calculated. Superconducting quantum interference device (SQUID) detects the small magnetic fields in the brain that are a marker of neural activity. A disadvantage of MEG is related to that it is expensive and not readily available for clinical applications.

Magnocellular visual system One of the two visual systems that extends from the eyes to the visual cor- tex. It consists of large cells that are inferiorly located in the lateral geniculate bodies that are highly sensi- tive to movement, low contrast, and spatial location.

Magnus, Albertus (German, ca. 1200–1280) De- emphasized the role of the ventricles in brain func- tioning.

Malignant tumors Tumors whose cells invade other tissues and are likely to regrow or spread.

Malingering The intentional exaggeration or presenta- tion of neuropsychological symptoms.

Mammillary bodies Two small nuclei on the floor of the posterior hypothalamus.

Masked facies Used to describe the masklike expres- sion of patients with Parkinson’s disease.

Mass action The extent to which behavioral impair- ments are directly proportional to the mass of the removed brain tissue.

Materialism A theory that brain–behavior functions are produced by matter in motion, favoring a mech- anistic view of the brain as a machine.

Mechanical receptors Structures that transduce energy from touch, vibration, and the stretching and bend- ing of skin, muscle, internal organs, and blood vessels.

Medial Toward the middle/midline, away from the side.

Medial lemniscus A white matter tract that courses through the contralateral side of the brainstem through the medulla, pons, and midbrain to be routed up through the thalamus (ventral posterior nucleus, VP) and on to the primary somatosensory cortex.

Medulla oblongata Myelencephalon; a structure of the brainstem.

Medulloblastoma A brain tumor seen most frequently in children; rapidly growing and very malignant; located in the inferior vermis close to the exit of cerebrospinal fluid from the fourth ventricle. This type of tumor accounts for about two thirds of all tumors in children and produces increased intracra- nial pressure caused by obstructive hydrocephalus.

Membrane potential See Resting potential. Meninges Protective covering of the brain and spinal

cord consisting of the pia mater, the arachnoid membrane, and the dura mater.

Meningiomas Highly encapsulated, benign tumors that arise from the arachnoid layer of the meninges. Meningiomas represent approximately 15% of all brain tumors.

Meningitis Inflammation of the meninges caused by bacterial infection or viral infection. It can progress quickly, within 24 hours, from a respira- tory illness, with fever, headache, and a stiff neck, to changes in consciousness including stupor, coma, and death.

Mental rotation Refers to the ability to mentally visu- alize and rotate forms, objects, or scenes in two- or three-dimensional space.

Mesencephalon One of the five principal divisions of the brain, part of the brainstem.

Meta-analysis A statistical technique designed to ana- lyze the results from a number of different and inde- pendent studies. The technique allows for the identi- fication of significant relationships and outcomes.

Metacognition A higher order cognitive ability that enables an individual to examine and analyze the manner in which he or she thinks, solves problems, encodes and retrieves information, and performs cognitive operations.

Metacognitive awareness An ability to monitor one’s own behavior and performance.

Glossary 525

Metastasis A form of tumor spreading in which tissue from a malignant tumor “travels” to other organs in the body through the bloodstream. The capacity for metastasis is a characteristic of all malignant tumors. Metastatic brain tumors typically originate from sites other than the brain, most frequently the lung or the breast.

Metastatic tumors Growths that arise secondarily to cancerous tumors that have their primary site in other parts of the body, such as the lungs, breasts, or the lymphatic system. The secondary growths arise because cancer cells from the primary neoplasm detach and travel to other sites through the blood system.

Metencephalon One of the five principal divisions of the brain, part of the brainstem.

Microcephaly A congenital disorder characterized by an abnormally small head in relation to the rest of the body. The head is more than two standard devi- ations below the average circumference for a child of a similar age and sex. The size of the brain is also subnormal, and the condition is associated with mental retardation.

Microglia Small cells within the CNS that undergo rapid proliferation in response to tissue destruction, migrat- ing toward the site of injured or dead cells, where they act as scavengers and metabolize tissue debris.

Micrographia Small handwriting; a common motor symptom of Parkinson’s disease.

Midbrain (mesencephalon) The middle division of the developing brain.

Middle cerebral artery Resulting from half of the division of an internal carotid artery, it supplies the lateral hemisphere and most of the basal ganglia of its corresponding cerebral hemisphere.

Migraine stroke A rare type of stroke in which a transient ischemic attack, typically associated with classic migraine, is severe enough to cause a stroke.

Migratory process A phase of prenatal central nervous system development characterized by the movement of neural cells along the wall of the neural tube to genetically predetermined locations.

Mild cognitive impairment (MCI) Implies an inter- mediary, and perhaps transitional, stage between normal aging and dementia.

Mind-blindness A neuropsychological deficit in which an animal’s behavior suggests that it can “see” objects—that is, the test subjects do not bump into the object—but fail to recognize its significance (for example, as an object of fear).

Molecular cytogenic disorders Disorders or diseases related to chromosome abnormalities (extra, miss- ing, or rearranged).

Monopolar neurons Unipolar neurons; neurons with a single axon.

Mosaic karyotypes The presence of both structurally normal and abnormal female chromosomes that produces one form of Turner’s syndrome.

Motor apraxia Ideomotor apraxia; an inability to access a stored motor sequence or an inability to relay that information to the motor association areas. An example is the inability to show me how you would make a telephone call from beginning to end.

Motor neurons Neurons responsible for contracting muscles or changing the activity of a gland.

Motor perseveration The act of continuing in the same motor behavior, or constantly selecting it in the presence of other choices.

Move attention A cognitive-attentional operation involving the shifting or movement of attentional focus from one stimuli to the next.

Multi-infarct dementia A dementia caused by multi- ple small strokes or ischemic attacks.

Multipolar neurons Neurons with more than two axons.

Munk, Hermann (German, 1839–1912) Found that experimental lesions in the visual association cortex produced temporary mind-blindness in dogs.

Muscarinic choline One of two main subtypes of acetylcholine, a neurotransmitter known to stimu- late receptors.

Myelencephalon One of the five principal divisions of the brain; part of the brainstem.

Myelin A lipid sheath that surrounds and insulates the axons of the central and peripheral nervous systems. It serves to increase the speed of nerve conduction.

Myelin sheath Fatty-type covering of axons that increases the speed of axonal transmission.

Myelin staining Selectively dyes the sheaths of myeli- nated axons. As a result, white matter, which con- sists of myelinated axons, stains black, unlike other areas of the brain that consist mostly of cell bodies and nuclei.

Myoclonic seizures Manifest in arrhythmic bursts of jerky motor movements that usually do not last more than a second and tend to occur in clusters over a short period.

Narcolepsy A disorder that consists of irresistible day- time “sleep attacks”; a central nervous system disor-

526 Glossary

der of the region of the brainstem that controls and regulates sleep and wakefulness. The primary symp- tom of this disorder is excessive daytime sleepiness.

Necrosis (or neuronal cell death) A direct result of a critical interference with the cellular metabolism of the neuron. In general, a period of 4 to 6 minutes of anoxia may cause necrosis.

Neologism Atypical language characterized by the gen- eration or production of words that are meaningless.

Neoplasm Literally “new tissue.” The neurologic term for tumor.

Neostriatum This structure, also known as the striatal complex, includes the caudate and putamen and receives projected information from cortical sensory areas. From the neostriatum, information is then funneled through the globus pallidus, then on to the thalamus, where it projects to the premotor and prefrontal areas.

Nerves A large collection of axons located in the peripheral nervous system, primarily composed of white matter.

Neural tube The embryonic tube that develops into the central nervous system, specifically the brain and spinal cord. The neural tube develops during the third week of gestation. Abnormalities in neural tube development can lead to congenital develop- mental disorders.

Neurofibrillary tangles Excessive collections of tau proteins resembling entwined and twisted pairs of rope within the cytoplasm of swollen cell bodies in the brain. These are pathologic markers of Alzheimer’s disease.

Neurogenesis The congenital process by which the neurons of the brain develop.

Neurologic examination A routine introductory evalu- ation performed by a neurologist—a physician who has specialized in evaluating and treating neurologic disorders. Although there are many variations, in principle, the neurologic examination involves a detailed history of the patient’s medical history and a careful assessment of the patient’s reflexes, cranial nerve functioning, gross movements, muscle tone, and ability to perceive sensory stimuli.

Neuromas Tumors or new growths that are largely made up of nerve cells and nerve fibers.

Neuronal ectopias Also known as “brain warts.” An abnormal placement and development of neural cells often associated with a disruption of the migra- tory phase of brain development.

Neurons Specialized nerve cells that allow complex information exchange.

Neuropsychological evaluation Involves a detailed examination, often using standardized tests, to describe an individual’s cognitive strengths and weaknesses. Often used in conjunction with other pertinent information, for diagnosis, patient man- agement, intervention, rehabilitation, and discharge planning.

Neuropsychological tests Traditionally defined as those measures that are sensitive indicators of brain functioning.

Neuropsychology The study of the relations between brain functions and behavior; specifically, changes in thoughts and behaviors that relate to the structural or cognitive integrity of the brain.

Neurotransmitters Chemicals that influence neuronal behavior.

Neurotrophins Neuron-feeding nutrients. Neurulation The congenital process involving the

formation and closure of the neural tube that sub- sequently develops into the brain and spinal cord.

Nicotinic choline One of two main subtypes of acetylcholine, a neurotransmitter named after nico- tine (from tobacco, Nicotiana tabacum), a bitter- tasting alkaloid that stimulates receptors.

Nissl, Franz (1860–1919) German histologist who discovered in the 1880s that a simple dye can stain the cell bodies in neurons. The Nissl method is par- ticularly useful for detecting the distribution of cell bodies in specific regions of the brain.

Nocioceptors Derived from Latin nocere, meaning “to hurt.” Receptors that serve as monitors to alert the brain to damage or threat of damage. They can be mechanical or chemical but are specifically acti- vated by potentially damaging stimulation such as heat or cold, painful pressure or pricking, or chem- ical damage such as exposure to noxious chemicals.

Nocturnal myoclonus Restless leg syndrome; twitch- ing of muscles that occurs during non–rapid eye movement sleep. In severe cases, this will wake up the subject.

Nodes of Ranvier Regular gaps along the axon where the myelin is interrupted.

Noncommunicating hydrocephalus See Obstructive hydrocephalus.

Nondeclarative memory Knowledge that is implicit and inaccessible to conscious recall or verbalization. This form of memory is demonstrated through per- formance (e.g., riding a bicycle).

Nonfluent aphasia A difficulty in the flow of articula- tion, so that speech becomes broken or halting.

Glossary 527

Nonfunctioning adenomas Benign neoplasms of the pituitary gland.

Noninfiltrative tumors Invasive tumors; encapsulated and differentiated (easily distinguished from brain tissue); cause dysfunction by compressing surround- ing brain tissue.

Nonobstructive hydrocephalus Also referred to as communicating hydrocephalus. A form of hydro- cephalus produced by blockage that disrupts reab- sorption of cerebrospinal fluid into the blood- stream.

Norepinephrine (NE) A neurotransmitter that is important to the regulation of mood, memory, hor- mones (via the hypothalamus), cerebral blood flow, and motor behavior.

Normal distribution A frequency distribution in which the values or scores group around a mean. In neuropsychological testing, many test scores display such distributions.

Normal-pressure hydrocephalus (NPH) A neuro- logic condition involving ventricular enlargement in the absence of elevated intracranial pressure. Most frequently evident in older adults and char- acterized by a triad of progressive neurologic signs (postural imbalance, dementia, and urinary incon- tinence).

Normative data These data compare the patient’s score on a test to an expected score, or norm. The expected test score is determined from the perfor- mance of a normative sample of patients and con- trol subjects.

NREM sleep (non–rapid eye movement sleep) Includes sleep stages 1 through 4.

Nuclei (singular, nucleus) A strategic collection of nerve cells in the central nervous system.

Nuclei of the raphe A collection of neurons located throughout the midline of the brainstem; implicated in serotonin pathways.

Nucleus basalis of Meynert Named after its discoverer; a collection of neurons implicated in Alzheimer’s disease.

Nucleus reticularis thalami (NRT) A group of neu- rons within the thalamus that regulates oscillatory behavior of the thalamocortical loop.

Object permanence A cognitive capacity described by the developmental psychologist Jean Piaget, which is initially absent in the infant, but subsequently devel- ops. The infant is unable to store in memory a repre- sentation of an object that is removed from view. In essence, what is out of sight is “out of mind.”

Objective personality tests Typically use the question- naire technique of measurement (for example, true/false or multiple-choice questions).

Obsessive-compulsive disorder A psychiatric disorder characterized by recurrent thoughts or images (obsessions) that are intrusive and anxiety producing which prompt or compel overt or mental behaviors (compulsions) to reduce this anxiety. Although obsessive-compulsive behaviors are viewed by the patient as irrational and excessive, this awareness does not alter the symptoms.

Obstructive hydrocephalus Also referred to as noncom- municating hydrocephalus. A form of hydrocephalus produced by obstruction within the ventricular system of the brain. The obstruction can be a consequence of congenital malformation, tumors, or scarring.

Obstructive sleep apnea Apnea that occurs most often during rapid eye movement sleep when either the upper airway collapses, not allowing air to pass, or the body weight of the patient on the chest com- promises respiratory effort.

Occipital lobe One of the four cortical lobes, primari- ly dedicated to visual processing.

Occipital notch Sulci within the medial occipital lobe. Occupational therapy Rehabilitation specialty that

focuses on improving self-care activities such as grooming, bathing, dressing, and feeding, as well as activities concerned with a person’s occupation and avocation.

Oligodendrocytes A type of non-neural cell; the projections of the surface membrane of each such cell fan out and coil around the axon of neurons in the central nervous system to form the myelin sheath.

Oligodendroglioma A rare, slowly growing tumor that mostly affects young adults and is derived from and composed of oligodendrogliocytes.

Optic gliomas A slowly growing glioma of the optic nerve or optic chiasm; associated with visual loss and loss of ocular movement.

Orientation A patient’s basic awareness of himself or herself in relation to the world around.

Orthotic Customizable cognitive adjunct, such as a computer, used in rehabilitating people with brain injury.

Overcorrection An aversive behavior modification technique that involves having a child practice a positive response that is incompatible with an inap- propriate behavior. Overcorrection is particularly effective in reducing self-stimulating and other inap- propriate behaviors.

528 Glossary

Palilalia Compulsive word or phrase repetition. Pallidotomy A surgical treatment for Parkinson’s dis-

ease; in this technique, the ventral, or internal por- tion, of the globus pallidus is lesioned via heat coag- ulation of the neurons.

Papez circuit Anatomic circuit centered around the hippocampus; plays a role in declarative memory processing.

Papillae Bumps on which lie from one to several hun- dred taste buds consisting of between 50 to 150 taste receptor cells.

Paragrammatism See Word salad. Parahippocampal gyrus Structure of the limbic system. Parasympathetic nervous system Division of the auto-

nomic nervous system; functions to store energy by facilitating functions such as digestion through gastric and intestinal motility.

Parental imprinting disorders Also known as genomic imprinting. A child receives two sets of chromosomes, one set from the mother, and the other from the father. The expression of the genes in each set is in accordance with the parent of origin. If the child receives both sets of chromosomes from the same par- ent, there will be a loss of expression of the genes of the other parent. This abnormal imprinting has been associated with several neurodevelopmental disorders.

Paresthesia Spontaneous crawling, burning, or “pins and needles sensation.”

Parietal lobe One of the four cortical lobes, concerned with the integration of information from sensory areas.

Parkinson’s disease (PD) A progressive disease process characterized by a dopamine deficiency of the sub- stantia nigra; results in resting tremors and allied motor symptoms; may cause a subcortical dementia.

Parkinsonism A behavioral syndrome marked by motor symptoms including tremor, rigidity, and slowness of movement.

Partial seizure A seizure caused by an abnormal rhythm confined to a particular brain area; also known as focal seizures; always begins as a local neuronal discharge; the most common type of seizure.

Parvocellular visual system One of the two visual sys- tems extending from the eyes to the visual cortex. It consists of small cells dorsally located in the lateral geniculate bodies that are sensitive to viewing sta- tionary objects, high contrasts, and fine spatial details.

Pathognomonic signs Neurologic symptoms from which a specific diagnosis can be made.

Pathways See Tracts. Pattern analysis Examines the relations among the

scores in a test battery. Penetrating head injury A type of head injury associ-

ated with a penetrating mechanism such as a bullet from a gun, a knife, or scissors.

Penfield, Wilder Famous neurosurgeon who made advancements in the understanding of the relation between brain anatomy and behavior.

Peptides A group of neurotransmitters, peptides are short chains of amino acid. More than 60 neuroac- tive peptides have been identified.

Perception The process of “knowing”; depends on intact sensation.

Peripheral nervous system (PNS) The PNS includes all the portions of the nervous system outside the central nervous system. The PNS consists of the somatic and the autonomic nervous systems.

Peripheral neuropathy Peripheral nervous system dys- function causing sensory loss (as in diabetes).

Personality tests Measures of such characteristics as emotional states, interpersonal relations, and moti- vation.

Petit mal seizure Literally “little bad” seizure; causes an altered state of consciousness but lacks the vio- lent physical loss of control seen during the grand mal seizure.

Phantogeusia Experience of a phantom or hallucina- tory taste.

Phantom limb pain A feeling of pain in a nonexistent limb.

Phantosmia Experience of a phantom or hallucinatory smell.

Phenylketonuria (PKU) A genetic disorder affecting the metabolism of phenylalanine. If untreated, mental retardation and other cognitive deficits can result. Dietary control, particularly if started early, can reduce or eliminate the negative effects of the disorder.

Phonemic paraphasias Errors of word usage of similar- sounding words (for example, using the word bark for tarp).

Phonologic awareness The awareness of and ability to differentiate between individual phonemes or speech sounds.

Phonologic processing The application of codes for translating letters and letter sequences into the appropriate speech–sound equivalents. Deficits in this processing have been linked to dyslexia.

Phrenology An obsolete theory proposing that if a given brain area was larger in an individual, then the corresponding skull at that point should be

Glossary 529

enlarged, indicating a well-developed area of the brain. Conversely, a depression signaled an underde- veloped area of the cortex. Phrenology involved, in its most popular form, the reading of cranial bumps to ascertain which of the cerebral areas were largest.

Physiatry The medical specialty of combining physical medicine and rehabilitation.

Physical therapy A rehabilitation specialty that focuses on improving motor control and physical functioning.

Pia mater Literally “pious mother”; a vascularized part of the meninges that directly adheres to the surface of the central nervous system.

Pinealoma A type of tumor of the pineal body. Pituitary adenoma Tumors of the pituitary gland that

are often classified into functioning (changing the secretion of the pituitary gland) and nonfunctioning (benign).

Pituitary stalk Also known as the infundibular stalk. It is the axon bundle extending from the hypothala- mus to the posterior region of the pituitary. This connection mediates the release of oxytocin and antidiuretic hormone directly into the bloodstream.

Pituitary tumors Tumors that arise from the pituitary gland. It is traditional to divide pituitary tumors into functioning and nonfunctioning adenomas.

Planum temporale Region of the posterior surface of the temporal lobes between the Heschl’s gyrus and the Sylvian fissure. The planum temporale of the left hemisphere is involved in mediating phonologic processing and language comprehension.

Plasticity Behavioral or neural ability to reorganize after brain injury.

Platelets Disk-shaped cells found in the blood of all mammals. They are important for their role in blood coagulation and are produced in large num- bers in the bone marrow. From there they are released into the bloodstream, where they circulate for approximately 10 days.

Plato (Greek, 420–347 B.C.) Suggested that the soul can be divided into three parts: appetite, reason, and temper. Plato also discussed the concept of health as being related to the harmony between the body and the mind. Thus, he has been credited as being the first to propose the concept of mental health.

Pluripotentiality The multiple, functional role of the brain. That is, any given area of the brain can be involved in relatively few or relatively many behaviors.

Polymicrogyria A congenital disorder that can be traced to a disruption of the structure of the developing

brain during the fifth to sixth month of gestation. As a consequence of this disruption, the gyri fail to develop appropriately. On inspection, the gyri are found to be small and crowded together. Learning disorders, mental retardation, epilepsy, and other neuropsychological anomalies are linked to the disorder.

Pons Metencephalon; a “bridge” resembling two bulbs, a structure of the brainstem.

Porencephaly A congenital disorder of brain forma- tion in which cystic lesions are on the surface of the brain.

Positron emission tomography (PET) A visualiza- tion technique that tracks blood flow, which is associated with brain activity. It is mostly used to assess brain physiology, including glucose and oxy- gen metabolism, and the presence of specific neuro- transmitters.

Posterior Toward the back or tail. Posterior attention system One of the attentional sys-

tems of the brain that mediates visuospatial orient- ing and is supported by the parietal, midbrain, and thalamic regions.

Posterior cerebral arteries Formed by a division of the basilar artery.

Posterior communicating arteries Arise from the internal carotid arteries and connect the middle and posterior cerebral arteries.

Postictal phase Phase in which the person gradually emerges into full consciousness; follows the seizure episode.

Post-traumatic amnesia (PTA) A patient’s memory of events surrounding an accident.

Pragmatics of language Aspects of language that extend beyond the literal.

Precursor or progenitor cells Early cells lining the neural tube that proliferate to create the neurons and glia cells of the brain.

Prefrontal motor cortex Section of the frontal lobe. This area is considered to be the “conductor” or “executor” of the brain. Also called prefrontal cortex.

Premorbid functioning The cognitive and neuropsy- chological status occurring before the development of disease or trauma.

Premotor area (PMA) See Premotor cortex. Premotor cortex Also known as premotor area. Located

in Brodmann’s area 6 of the frontal lobes; receives neuronal input from posterior parietal areas, sec- ondary somatosensory areas, and cerebellum; plays a role in motor planning and sequencing, and may aid in the procedural aspects of carrying out motor plans.

530 Glossary

Prepotent response A response that has been “primed” to occur through reinforcement, repeated use, habit, or reflex.

Prestriate cortex See Secondary association. Primary motor cortex Part of the frontal lobe, con-

cerned with the initiation, activation, and perfor- mance of motor activity.

Procedural memory Memory that is usually implicit and is demonstrated via performance. Procedural memory’s domain is that of rules and procedures rather than information that can be verbalized, although procedural memory has not been clearly operationally defined and includes a hodgepodge of tasks such as motor skill learning, mirror reading, and verbal priming.

Process approach Also known as the “hypothesis approach”; based on the idea that each examination should be adapted to the individual patient. Rather than using a standard battery of tests, the neuropsy- chologist selects the tests and procedures for each examination, based on hypotheses made from impressions of the patient and from information available about the patient. As a result, each exami- nation may vary considerably from patient to patient for length and test selection.

Prodromal phase A phase before the seizure, in which an aura occurs; odd, transient symptoms such as nausea, dizziness, or numbness may occur, as well as sensory alterations or hallucinations in any sensory domain.

Progenitor cells See Precursor cells. Projection fibers Neurons that connect sets of brain

structures to each other (e.g. subcortical structures to the cortex and vice versa).

Projective personality test Tests that rely on relatively ambiguous, vague, and unstructured stimuli, such as inkblots.

Proprioception The position of the body in extraper- sonal space. Sensory dysfunctions that result in pro- prioceptive disorders include altered sense of bodily sensation and bodily position.

Proprioceptive disorder Loss of body position sense. Proprioceptors Derived from Latin proprius, meaning

“one’s own”; structures on skeletal muscles that detect movement via degree of stretch, angle, and relative position of limbs. Proprioceptors on the hands help identify the shapes of objects via touch.

Prosencephalon See Forebrain. Prosody An aspect of speech that conveys meaning

through intonation, tempo, pitch, word stress, flu- ency, and rhythm. It augments the meaning of spo-

ken language and is important in communicating the emotional content of language.

Prosopagnosia The special case of inability to recog- nize people by their faces.

Prospective memory The intention to remember to perform an action in the future.

Prosthetic Cognitive replacement, such as a computer, used in the rehabilitation of people with brain injury.

Proximal Near the trunk or center, close to the origin of attachment.

Pruning The process of eliminating excessive neurons and synapses in the developing brain. The elimina- tion appears to reflect a purposeful “sculpting” of the brain to promote neural efficiency.

Pseudopsycopathy Also known as “acquired sociopa- thy.” The emergence of uninhibited and poorly modulated behavior, poor judgment and violation of social norms following orbitofrontal damage. Unlike the true psychopath or sociopath, the patient with orbitofrontal damage experiences remorse for inappropriate actions and does not demonstrate the intentional viciousness or planning with regard to committing antisocial acts.

Psychology The study of describing, explaining, pre- dicting, and modifying behavior.

Psychometrics The science of measuring human traits or abilities. Concerned with the standardization of psychological and neuropsychological tests.

Psychomotor epilepsy See Temporal lobe epilepsy. Purkinje cells A specific type of neuron that is found

in the cerebellum. The dendrites characteristically spread out in one plane.

Putamen Structure of the basal ganglia. Pyramidal cells A specific type of neuron that is

found in all areas of the cerebral cortex. These cells have bodies that are pyramidal or conical in shape.

Pyramidal motor system This system originates in the cerebral cortex and controls voluntary move- ment.

Pythagoras (ca. 580–500 B.C.) Greek scholar who suggested that the brain is at the center of human reasoning and plays a central role in the “soul’s life.”

Receptive aphasia A difficulty in auditory comprehen- sion. Also see Wernicke’s aphasia.

Receptor cells Receptor cells detect numerous stimuli, including sight, sound, pressure, pain, chemical irri- tation, smell, and taste. Not technically neurons, although they create energy that is transduced into

Glossary 531

an electrical stimulus that is carried to neurons and then processed in the brain.

Receptor sites Sites on the postsynaptic neuron to which neurotransmitters are delivered.

Reductionism Investigating complex phenomena by dividing them into more easily understood compo- nents. Related to brain research, reductionists argue that behavior is no more than the results of chemi- cal and structural relation among neurons.

Refractory period A recovery period after a neuron has fired. During this period, which lasts one or more milliseconds, the neuron resists re-excitation and is incapable of firing.

Reliability The stability or dependability of a test score as reflected in its consistency on repeated mea- surement of the same individual. A reliable test should produce similar findings on each administra- tion.

REM sleep Rapid eye movement sleep; state of sleep where dreams occur.

Remote memory Memory for long-past events. Response cost A behavioral modification technique

that involves removing or taking away an already present positive reinforcer contingent on the display of a specific undesirable behavior. The technique is used to inhibit or suppress a specific behavior.

Response inhibition Three interrelated control processes: (1) stopping an ongoing response, (2) blocking or screening out distractions, and (3) restraining a response primed for release.

Resting potential Membrane potential; a slight electri- cal imbalance between the inner and outer surfaces of the membrane caused by the separation of electri- cally charged ions.

Resting tremor Rhythmic shaking that often occurs in one hand first; positive motor symptom of Parkinson’s disease; characterized as “pill rolling.”

Restitution One of two primary approaches to brain injury rehabilitation; stresses the retraining of an impaired skill in the hope that the brain can rebuild axonal connections through retraining.

Reticular activating system (RAS) Also called reticu- lar formation; a neural network located within the lower brainstem transversing between the medulla and the midbrain. Functions in nonspecific arousal and activation, sleep and wakefulness.

Retrograde amnesia In this disorder, the patient has no recollection of the interval preceding the injury; the loss of old memories before an event or illness.

Retrograde degeneration The degeneration of the axon back to the cell body, once the axon has been damaged. This process may lead to cell death.

Rhinencephalon Evolutionarily old “smell brain.” Rhombencephalon See Hindbrain. Rigidity Tightening of muscles and joints; positive

motor symptom of Parkinson’s disease. Ring X karyotypes A relatively rare karyotype that is

associated with one variant of Turner’s syndrome. Mental retardation frequently occurs in this form of Turner’s syndrome.

Röntgen, Wilhelm Conrad (1845–1923) Physicist who made a remarkable discovery that an invisible ray that, unlike heat or light waves, could pass through wood, metal, and other materials. This ray, also called X-ray, gave rise to radiology.

Rostral Toward the head.

Saccadic eye movements Quick eye movements made when the eye moves from one point of fixation to the next.

Sagittal plane Derived from Latin sagitta, meaning “arrow.” A plane (z-axis) that shows the brain as seen from the side or perpendicular to the ground, bisecting the brain into right and left halves.

Savant skills Extraordinary skills possessed by an indi- vidual who otherwise displays limited capacity. For example, the ability of a retarded child to mentally calculate complex square roots is a savant skill.

Schwann cells Type of non-neural cells. The projec- tions of the surface membrane of each of those cells fan out and coil around the axons of neurons in the peripheral nervous system to form myelin sheaths.

Secondarily generalized seizure A simple seizure that crosses the corpus callosum and eventually involves the entire brain.

Secondary association Prestriate cortex; processes pri- mary features of visual information such as light wavelength, line orientation, and features of shape.

Secondary motor cortex Functions in strategic plan- ning of the specific aspects of movement. The inten- tion to move is also a function of this area.

Seizures Massive waves of synchronized nerve cell acti- vation that can involve the entire brain. Seizures may have dramatic behavioral manifestations, including uncontrolled muscles contractions, changes in per- ception, and alterations in mood and consciousness.

Semantic memory Memory for information and facts that have no specific time-tag reference.

Senile plaques Also called neuritic plaques. Round aggregates of beta-amyloid that on disintegration

532 Glossary

leave holes and misshapen neurons where there once were active connections.

Sensation The elementary process when a stimulus has excited a receptor and results in a detectable experi- ence in any sensory modality.

Sensitivity How sensitive a test is in measuring a par- ticular neuropsychological construct.

Sensory association area An area of the cortex that functions to integrate information from different sensory areas.

Sensory neurons Neurons that respond directly to changes in light, touch, temperature, or odor.

Septum In general, refers to a thin plate of brain tis- sue separating two cavities or tissue areas. The sep- tal area stretches between the fornix and the cor- pus callosum, forming one of the walls of the frontal horn of the lateral ventricle. The septal area interconnects with the hippocampus and the hypo- thalamus.

Serotonin A neurotransmitter that is involved in sleep, depression, memory, and other neurologic processes.

Sex chromosomes A chromosome that determines the sex of a person. Humans have two sex chromo- somes, X and Y, with the former determining female sexual characteristics, and the latter, male sexual characteristics. A male is defined by the pair- ing of XY chromosomes, and a female, by the pair- ing of XX chromosomes.

Shifting attention An element of attention involving the movement of attentional focus from one stimuli or task to another.

Short-term memory (STM) Memory of limited capacity (7 ± 2 bits of information); degrades quickly over a matter of seconds if information is not held via a means such as rehearsal or transfer to long- term memory.

Shunt A medical procedure to drain excessive cere- brospinal fluid from the ventricular system to the stomach. The procedure is used with people who have acquired hydrocephalus.

Simple seizures Focal events that may involve sensori- motor expression or psychic expression (mood, emotion, altered consciousness).

Simulation A form of malingering in which the patient is faking or exaggerating an illness or the severity of the symptoms, usually to gain some sec- ondary gain (such as attention, hospitalization, or a financial settlement).

Single-gene disorders A disease or disorder that is due to a mutation of a single gene. An example of a single gene disorder is Tay-Sachs disease.

Single-photon emission computed tomography (SPECT) A visualization technique that measures blood flow, a correlate of brain activity. Because it takes the radioactive tracer almost 2 days to be elimi- nated from the body, SPECT cannot be used to mon- itor the brain’s mental activity “moment to moment.”

Sleep apnea Derived from Greek a pnoia, meaning “negative breathing”; refers to breathing that is dis- turbed while sleeping and often completely stops for periods as long as a minute.

Sleep apnea syndrome A serious sleeping disorder resulting from frequent episodes of apnea.

Sleep paralysis Momentary paralysis on awakening or at sleep onset; the body is totally unable to move for seconds to minutes.

Social emotional learning disability Disturbed socio- emotional behavior that is directly related to neu- ropsychological processing deficits and does not reflect a secondary reaction to a learning disability such as dyslexia.

Sodium–potassium pump An active transport system across the membrane of the axon that exchanges three sodium ions for every two potassium ions.

Somatic nervous system (SNS) That part of the peripheral nervous system that provides “voluntary” neural control with the external environment. Communicates with the central nervous system through spinal and cranial nerves.

Somatopic organization Organization that follows the distorted figure of the sensory homunculus mapped onto the primary somatosensory cortex, which represents the relative importance and distri- bution of touch in various areas of the body rather than the actual size of the body part.

Somatosensory cortex Structure found in the anterior portion of the parietal lobe, concerned with primary tactile sensory processing.

Somatosensory system Body system that involves two types of sensory stimulation, external and internal. The somatosensory system can monitor sensations such as cold and heat, whether the sensation comes from the handling of an ice cube or from a fever. So the system processes external stimulation of touch (pressure, shape, texture, heat) in recognizing objects by feel and is also concerned with the position of the body in extrapersonal space (proprioception).

Spatial perception Refers to the ability to mentally visualize forms, objects or scenes in two- or three- dimensional space.

Glossary 533

Specificity A factor in setting a cutoff score on a test. Neuropsychological tests with high specificity exam- ine specific aspects of neuropsychological functions; that is, they are not correlated with other tests or factors.

Speech apraxia See Dysarthria. Speech therapy A rehabilitation specialty that focuses

on communication difficulties such as deficits in speech production, understanding speech, reading, and writing.

Spina bifida A congenital developmental disorder char- acterized by an opening in the spinal cord, commonly found in the lower region of the cord. The disorder is a consequence of a failure of the posterior end of the neural tube to close during gestation.

Spinal cord Part of the central nervous system that acts as the conduit for the majority of sensory and motor information to and from the body.

Spurzheim, Johann (1776–1832) Austrian student of Gall; lectured extensively on phrenology in the United States.

Stable attention An element of attention referring to the consistency of attentional performance over time.

Standard battery approach In this approach, the same tests are given to all patients, regardless of the clini- cian’s impression of the patient or the referral question. Typically, a technician gives the tests and administers them according to standardized rules of procedures.

Standardized test A task or set of tasks administered under standard conditions. Designed to assess some aspect of a person’s knowledge or skill. Standardized psychological tests typically yield one or more objec- tively obtained quantitative scores, which permit systematic comparisons to be made among different groups of individuals regarding some psychological or cognitive concept.

Stem cells Undifferentiated cells; they do not yet have either an identified or specialized function. They eventually differentiate into the building blocks of tissues and organs.

Stenosis Narrowing of an artery. Striatal complex This group of structures includes the

caudate and putamen and receives projected infor- mation from cortical sensory areas. From the stria- tum, information then funnels through the globus pallidus, then on to the thalamus, where it projects to the premotor and prefrontal areas. Also see Neostriatum.

Striate cortex A collection of brain structures involved in the motor system named after their striped or stri- ated appearance. It is located in the most posterior

aspect of the occipital lobes, but a major portion of it extends onto the medial portion of each hemi- sphere. Also see Striatal complex.

Striatum A collection of brain structures (including the caudate nucleus and the putamen) involved in the motor system; named after their striped or stri- ated appearance. It is located in the most posterior aspect of the occipital lobes, but a major portion of it extends onto the medial portion of each hemi- sphere.

Stroke A neurologic event, also known as cerebrovascu- lar accident (CVA), that always occurs in the brain and is the most common type of cerebrovascular disease.

Stuck-in-set perseveration Maintenance of a problem- solving approach when changing demands signal the need for an altered or modified approach or response.

Subarachnoid hemorrhage Occurs when a blood vessel on the surface of the brain bursts and blood flows into the small cavity that surrounds the brain, the subarachnoid space.

Subarachnoid space Space containing cerebrospinal fluid; below the arachnoid membrane.

Subcallosal anterior cingulate The subcallosal gyrus covers the inferior aspects of the rostrum of the cor- pus callosum. It continues posteriorly as the cingu- late and parahippocampal gyrus. It is considered part of the limbic system of the brain.

Subcortical Below the cortex. Subcortical dementia Dementia that primarily affects

subcortical areas of the brain; characterized by slow- ness of cognitive processing, executive dysfunction, difficulty retrieving learned information, and abnor- malities of mood and motivation; examples include Parkinson’s, Huntington’s, and Creutzfeldt–Jakob diseases.

Subdural hematoma Bleeding into the subdural space; often encountered after a head injury.

Subdural space The space between the dura and the arachnoid parts of the meninges.

Sublenticular nuclei Nuclei of the extended amyg- dala, a forebrain continuum, that projects into the centromedial amygdala.

Substantia nigra Structure of the basal ganglia. A col- lection of neurons and nuclei known to be impor- tant dopamine pathways.

Substitution One of two primary approaches to brain injury; focuses on searching for adaptations to the person’s environment in the context in which they will be used.

534 Glossary

Subthalamic nucleus Structure of the basal ganglia. Sudden infant death syndrome (SIDS) Death caused

by the cessation of breathing during sleep. Sulci (singular, sulcus) Valleys formed by infolding of

the cortex. Superior Toward the top or above. Superior colliculi Two elevations within the roof of

the tectum functioning as important reflex centers for visual information.

Superior sagittal sinus Large sinus of the brain. Supplementary motor area Located on the dorsal

and medial portion of each frontal lobe; functions as a motor sequencer and planner. It receives input from the somatosensory strip and the basal ganglia.

Suprachiasmic nucleus (SCN) A nucleus of the hypo- thalamus, hypothesized to be a biological clock that calibrates the sleep/wake cycle.

Supravalvar aortic stenosis (SVAS) An acquired or congenital condition in which there is a narrowing of the aortic value impeding the flow of blood from the left ventricle to the arteries. The resulting car- diac problem can be life threatening.

Surface dyslexia A developmental or acquired reading disorder characterized by impaired whole-word reading, but preserved phonological skills.

Sustained attention The ability to maintain an effort- ful response over time. A form of attention involv- ing the maintenance of attentional focus over time. Sometimes referred to as “time-on-task perfor- mance,” or “behavioral persistence.”

Sydenham’s chorea (SC) A neurologic movement dis- order characterized by chorea of the face, neck, trunk, and limbs; diminished muscle tone and strength; and psychological disturbances, especially obsessive-compulsive behaviors. The disorder fre- quently affects children and adolescents after a streptococcal infection (a beta-hemolytic). It has been proposed that the disorder is caused by an abnormal autoimmune response to the streptococcal bacteria that reacts against the basal ganglia. The disorder often resolves spontaneously, and treatment is generally reserved for severe or chronic cases.

Sylvian aqueduct See Cerebral aqueduct. Sylvian fissure The large fissure separating the frontal

from the temporal and parietal lobes. Sympathetic nervous system Division of the auto-

nomic nervous system that mobilizes the energy necessary for psychological arousal in response to, or anticipation of, a stressful event based on the “fight- or-flight” response. Sympathetic activation includes

an increase in blood flow, blood pressure, heart rate, and sweating, and a decrease in digestion and sexual arousal.

Synapse The tiny gap between the terminal button and the receptors of the two neurons. Neurons communicate through synapses. The anatomic location of this communication is known as the synapse.

Synaptic knobs Ends of neurons that have characteris- tic swelling to increase the area of contact with the postsynaptic neuron.

Synaptic vesicles Oval structures within the termi- nal that typically cluster close to the presynaptic membrane and where neurotransmitters are synthesized.

Synaptogenesis The developmental process by which the synapses and dendrites of the brain form.

Tachyphemia Segmented accelerated bursts of speech. Tactile agnosia Also called astereognosis; a disorder in

which there is an inability to recognize objects by touch.

Tactile extinction/suppression/inattention Suppression of touch sensation on one side of body.

Tardive dyskinesia A disorder with Parkinson-like symptoms, including writhing movements of the mouth, face, and tongue, often develops in schizo- phrenics after long-term medication use.

Tectum “Roof ”; structure of the midbrain. Tegmentum “Covering”; a structure of the midbrain

that surrounds the cerebral aqueduct. Telencephalon Also called the endbrain; one of the

five principal divisions of the brain; consists of the two cerebral hemispheres, which are connected by a massive bundle of fibers, the corpus callosum.

Temporal lobe One of the four cortical lobes, con- cerned with the reception and interpretation of auditory information; also plays a role in memory.

Temporal lobe (psychomotor) epilepsy A form of seizure originating from the temporal lobe; emotional symptoms often present (such as changes in mood).

Tensile strength The amount of physical, longitudinal stress that an axon can withstand before it ruptures.

Teratogen Any agent that disrupts the normal devel- opment of the embryo and fetus.

Terminal buttons Also called axon terminals. The site of interneuronal contact, where neurochemical infor- mation is transmitted from one neuron to another.

Teuber, Hans-Lukas (American, 1916–1977) Credited for first using the term neuropsychology in a national

Glossary 535

forum during a presentation to the American Psychological Association in 1948.

Thalamus A structure of the diencephalon, an impor- tant sensory relay station.

Thalotomy A surgical treatment for Parkinson’s disease and other disorders causing tremor; used to attack tremor by lesioning the thalamus.

Theory of mind The cognitive capacity to under- stand, attribute, and predict the mental state of oth- ers, and the relation of these mental states to behav- ior. Deficits in this capacity have been observed in autistic children and other developmental disorders.

Therapeutic recreation An approach to treatment that emphasizes the importance of recreational and leisure time activities in brain injury rehabilitation, to help in the “transfer” of learning. Therapeutic recreation also allows patients to begin socializing with each other in a structured, but less formal, atmosphere than that afforded in other therapy settings.

Thermoreceptors Receptors that serve as monitors to detect heat and cold throughout the body.

Thrombosis A type of occlusion in which a clot or thrombus (Greek meaning “clot”) forms in an artery and obstructs blood flow at the site of its formation. This is the most common form of stroke and accounts for approximately 65% of all cerebrovascular accidents.

Tonic Motorically stiffened. Tonotopic map Projected onto the auditory cortex in

a manner similar to the retinopic mapping of the visual system. Because the cortical bands can respond to multiple frequencies, there is no strict one-to-one correspondence, but bands are more attuned to certain frequencies than others.

Tourette’s syndrome A tic disorder defined by multi- ple involuntary motor and vocal tics. The disorder appears familial in origin. The cause is unclear, but dysfunction of the basal ganglia has been implicated. Also called Gilles de la Tourette syndrome.

Tracts Also known as pathways or fibers. Large collec- tion of axons located in the central nervous system. Primarily composed of white matter.

Transduction Derived from Latin transducere, mean- ing “to lead across.” An environmental stimulus activates a specific receptor cell, and this energy is transduced into an electrical stimulus, which is then carried to neurons to be processed by the brain.

Transient ischemic attack (TIA) A temporary (tran- sient) lack of oxygen (ischemia) to the brain, which may cause a time-limited set of neuropsychological

deficits. TIAs are technically not considered a stroke, because neuronal death typically does not occur.

Transtentorial herniation Associated with high intracranial pressure and generalized swelling of the brain. As a result, the brain is displaced downward.

Tremor Involuntary shaking, usually of a limb, tremors may be resting or occur with intentional movement.

Trephination An ancient procedure in which small holes were scraped or cut into the skull deliberately for either surgical or mystical reasons.

Tumor The morbid enlargement or new growth of tis- sue in which the multiplication of cells is uncon- trolled and progressive. The tumor growth is often arranged in nonorganized ways, does not serve any functional purpose, and often grows at the expense of surrounding intact tissue.

Turner’s syndrome (TS) A syndrome characterized by a failure to develop secondary sexual characteristics, short stature, webbed neck, and cubitus valgus. It is caused by an anomaly in the X chromosome (female).

Ultradian rhythm Ninety-minute cycles of heightened and lowered brain arousal observed throughout the wake/sleep cycle.

Ultrasonography A procedure for imaging the internal structures of the body by introducing and recording the reflection of high-frequency sound waves.

Utilization behavior A characteristic behavior of envi- ronmental dependency syndrome that involves the ten- dency to grasp and use objects that are within reach. The use of the object is in accordance with its func- tion, but inappropriate for the situation. It is often associated with bilateral frontal damage.

Uvulopalatopharyngoplasty (UPPP) The removal of the uvula, the small, fleshy tissue hanging from the center of the soft palate, which may relax and sag, obstructing the upper airway. A surgical approach to the treatment of sleep apnea.

Validity The validity of a test is the meaningfulness of the test scores. Validity gauges whether a specific test really measures what it was intended to mea- sure. There are different types of validity: construct, content, and criterion validity.

Vascular system The blood supply system of arteries and veins.

Ventral Toward the belly. The bottom of the brain is ventral in humans.

Ventricles Four interconnected, fluid-filled cavities in the brain.

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Ventricular localization hypothesis Theory that postulated that mental and spiritual processes were located in the ventricular chambers of the brain.

Ventricular system Four interconnected, fluid-filled cavities in the brain.

Vermis A structure of the cerebellum; two large, oval hemispheres connected by a single median portion.

Vertebral arteries Two of the four major arteries to the brain, supplying the posterior portions of the brain.

Vertebral column The bony structure that extends from the cranium to the coccyx and encloses the spinal cord.

Vesalius, Andreas (1514–1564) Belgian-born anato- mist who advanced neuroanatomy through continual dissections and careful scientific observations.

Vestigial ovarian streaks A failure of gonadal develop- ment characteristic of Turner’s syndrome. Reproductive cells are evident in the gonads of Turner’s syndrome embryos but begin to deteriorate late in fetal development. By early childhood, the gonads consist only of fibrous streaks.

Vigilance attention system One of the attentional sys- tems of the brain that mediates sustained attention.

Visual agnosia Inability to recognize a person or object by sight.

Visual cortex The cerebral cortex of the occipital lobe of the brain that is responsible for vision.

Visual object agnosia Failing to recognize objects at all, or in milder cases, confusing objects if they are observed from different angles or in different light- ing conditions.

Visuospatial sketch pad A working memory “slave system” that manipulates visual and spatial images.

Vitalism A theory that suggests that behavior is only partly controlled by mechanical or logical forces.

Vocational inventories Tests that measure opinions and attitudes indicating an individual’s interest in different fields of work or occupational settings.

Wada technique Also known as the Wada test, after its developer. Similar to the angiogram in that it places a catheter, typically in the left or right internal carotid artery. Then sodium amytal, a barbiturate, is injected, which temporarily anesthetizes one hemi- sphere. In this way, neuropsychologists can study the precise functions of one hemisphere whereas the other one “sleeps.” Also called the intracarotid sodium amytal procedure (IAP).

Wada test A technique for determining language later- alization and memory functions that involves anes- thetizing one cerebral hemisphere, and then present-

ing cognitive tasks to the patient. The process is then repeated with the other hemisphere. Impaired performance of the cognitive tasks specific to the anesthetized hemisphere suggests the lateralization or presentation of language/memory functions in that hemisphere.

Wernicke, Carl (German, 1848–1904) Announced that the understanding of speech was located in the superior, posterior aspects of the temporal lobe. Wernicke noted that a loss of speech comprehension due to damage in this area was not accompanied by any motor deficit; only the ability to understand speech was disrupted.

Wernicke’s aphasia Damage to the left hemisphere auditory processing areas results in the partial or total inability to decipher spoken words. This con- dition is also known as receptive aphasia.

Wernicke’s area A structure that includes the sec- ondary auditory cortex and is located on the poste- rior aspect of the superior temporal gyrus. It is responsible for auditory processing of speech.

Wernicke–Korsakoff ’s syndrome A disorder associated with memory function of the limbic system, typically observed in severe alcoholics who show multiple nutritional deficiencies. Such patients may develop a confusional state over time, as well as severe new- learning and motor difficulties.

White matter Myelinated axons. Areas of the brain that are mostly made up of myelinated axons, such as neuronal tracts and pathways, which are charac- teristically white in appearance.

Williams syndrome (WS) A neurodevelopmental dis- order characterized by a recognizable pattern of dys- morphic facial features, cardiovascular and physical abnormalities, mental retardation, a specific cogni- tive profile, and a distinct personality.

Willis, Thomas (1621–1675) English anatomist best known for his work on the blood circulation of the brain.

Word salad Unconnected words and word sounds. This feature of Wernicke’s aphasia is a deficit in plac- ing words together in proper grammatical and syn- tactical form. This condition is more formally known as paragrammatism or extended paraphasia, and it is characterized by running speech that is logi- cally incoherent, often sounding like an exotic for- eign language.

Working memory A concept introduced by Alan Baddeley, also referred to as short-term memory, or “working on memory.” Working memory directs the temporary storage of information being processed in

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any range of tasks from reading to math to problem solving. It includes the concepts of the central execu- tive, the articulatory phonologic loop, and the visu- ospatial sketch pad.

X-rays A type of light ray that is useful for clinical work of various parts of the body, because they show the presence and position of bones, fractures, and foreign bodies. A clinical disadvantage of X-rays, and specifi-

cally X-ray films of the brain, is that there is little dif- ferentiation between the brain structures and the cerebrospinal fluid, making the clinical use of this procedure ineffective.

Zangwill, Oliver (1913–1987) British neuropsycholo- gist who contributed significantly to an understand- ing of the nature of neuropsychological deficits asso- ciated with unilateral brain disease or injury.

C H A P T E R 1

How does localization brain theory differ from equipoten- tiality brain theory? What are the lasting contributions of each theory? Localization brain theory assumes that detailed brain processes in specific anatomic locations cause specific mental processes. Phrenology is a good example of localization theory. Equipoten- tiality brain theory assumes that the brain functions more or less as a unit. One proponent of equipotentiality brain theory is Flourens, who suggested that the entire brain is greater than the sum of its parts. The lasting contribution of localization theory is that, indeed, some brain functions appear to be localized to a specific brain region. For example, Broca’s area specifically con- trols verbal motor output. However, many functions, such as thinking and problem solving, do not appear to have a strict or precise anatomic representation in the brain. The lasting contri- bution of equipotentiality theory is the idea that redundancy may be built into the brain and that if one area of the brain is dam- aged, another area may be able to compensate for the function.

Has the quest for the search of the organ of the soul been completed? Yes and no. Yes, the search for the organ has been completed. There is no question that the healthy brain gives rise to the mind and the soul. The question that is not yet answered is, How ex- actly does the brain accomplish this? Much has been learned from recent research involving neuropsychology and modern imaging technology, but the precise mechanism—that is, how the soul arises from brain matter—has remained elusive.

Why is Luria’s functional model of the brain such an impor- tant step in understanding brain functions? Luria combined both the localization and equipotentiality ap- proaches to neuropsychology into one model. As with equipo- tential theory, Luria regards behavior as the result of an interac- tion of many different areas of the brain. As with localization theory, Luria also assigns a specific role to each area of the brain. In Luria’s functional model, each function depends on the inter- action of specific brain systems. Luria suggests that behavior is the result of the brain operating as a whole. At the same time, each area within the brain has a specific role in the formation of behavior. The importance of any one area depends on the be- havior to be performed. This model has been useful in rehabili- tating patients with neuropsychological disorders, such as stroke and brain trauma, where one function may be damaged, but an- other function may compensate for the loss.

C H A P T E R 2

What are the differences among electrical, magnetic, and metabolic technologies in imaging? Electrical measures record the electrical activity of nerve cells of the brain through electrodes attached to various locations on the scalp. This procedure, known as electroencephalography (EEG), is most sensitive to the actual firing rate of large collec- tions of neurons. Magnetic imaging measures the concentra- tion of the hydrogen nucleus, which is present in high concen- tration in biologic systems and generates a small magnetic field. This procedure is known as magnetic resonance imaging (MRI). With MRI researchers can accurately calculate brain tissue densities and can generate a computer-constructed anatomic representation. The imaging of brain metabolism provides a completely different approach to the examination of the brain. For example, measuring glucose metabolism is a direct correlate of neuronal activity and can lead to a clearer understanding of the functioning brain. Medical technologies that use this approach are single-photon emission computed tomography (SPECT) and positron emission tomography (PET).

Why is co-registration, that is, the use of multiple assess- ments using different technologies, an important advance- ment in neuropsychology? A major advancement in imaging technology has been to merge different assessment technologies, such as the anatomic detail of MRI with the ability of PET to localize function using the imag- ing of brain metabolism. Such co-registration of different ap- proaches has resulted in multimodal approaches to neuroimag- ing, often providing new insights, as well as corroborating established findings.

Which medical technology to examine your brain would you volunteer for? Why? We personally do not mind having our brains imaged using dif- ferent technologies. A risk is always associated with this, how- ever, namely, that some previously unknown pathology may be detected, but those chances are relatively small. The only other risk, then, is the inconvenience of an invasive procedure. On a continuum from least to most invasive, those procedures are (in our opinion): radiography, EEG, EP, MRI, MEG, SPECT, PET, EMG, lumbar puncture, and angiography. Because MRI is relatively noninvasive but allows for precise anatomic pic- tures of the brain, it would be the procedure we would volun- teer for first.

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Will neuropsychology be outdated by the increased use of sophisticated brain imaging technology? Why or why not? No. Modern imaging technologies and the study of neuropsy- chology are compatible. Certainly, the advances in modern imaging technology have been spectacular in showing the anatomy of the brain. Furthermore, the domains previously held by neurologists and that by neuropsychologists are getting much closer, and both disciplines have much to learn from each other. But neuropsychologists are bringing special knowledge to the area of brain research and are participating in the research using this technology because of their expertise in the functional as- pects of neuroanatomic structures, their knowledge of neuropsy- chological tests, and their background in scientific methodology and design. Thus, neuropsychologists play an important role in providing functional assessments of patients with brain injuries. Neuropsychologists also diagnose conditions (such as concus- sions) that are not easily detected using modern imaging tech- nologies, and they evaluate a patient’s potential for adapting to a specific neurologic disorder, their capacity to work, and their quality of life.

C H A P T E R 3

Why are the concepts of reliability and validity so important in psychological and neuropsychological assessment? If a test is not repeatable, it is not reliable and thus can pro- vide no consistent score on a specific dimension. Think of weighing yourself on a scale that gives you a different weight every time you step on it. Such a scale could not be trusted, could it? Validity is important because it relates to the mean- ingfulness of a psychological test score. What if a psychologi- cal measure of depression does not really measure depression, but something else, such as stress? Such a scale would not be an appropriate measure of depression. Let us go back to the example of the scale. This time it is reliable. (Remember, if a test is not reliable, it cannot be valid.) A scale would not be a valid measure for anything other than estimating weight. For example, you would not use the scale to determine the room temperature. This is the assumption of validity, that is, whether a psychological or neuropsychological test measures what it is intended to measure.

What kinds of questions and tests do neuropsychologists use in a neuropsychological evaluation? Neuropsychologists use primarily standardized tests and ques- tions in a neuropsychological examination. That is, they may use specific tests and scales that have questions that every sub- ject receives more or less in the same way. As a result, the neu- ropsychologist knows what it means if a person does not know the answer to a particular set of questions. Neuropsychologists use many different tests, tasks, puzzles, and questions to get an overview of an individual’s cognitive strength and weaknesses. Thus, it is not uncommon to have a battery of tests that include measures of memory, attention, intelligence, personality func- tioning, and so on. The neuropsychologist uses a specific set of

procedures to answer the referral question. For example, he or she may treat a referral question about diagnosis differently from a referral question about employment capacity, in terms of se- lecting neuropsychological tests.

How are neuropsychology assessment procedures the same? How are they different? All neuropsychological assessment procedures are similar in that the same rules of reliability and validity apply. Also, almost all neuropsychological tests are given in a standardized format and environment, and are administered to the patient individually. They are different in that they measure different aspects of be- havior. Tests can measure memory, problem solving, and atten- tion, to name just a few aspects. Some tests measure personality functioning, adaptive skills, intelligence, vocational skills, and educational attainment. These types of tests are strictly not neu- ropsychological tests, even though they depend on brain func- tioning, because they are not sensitive indicators of cortical dys- function. A test is considered to be a neuropsychological test if a change in brain function systematically relates to a change in test behavior.

What sort of recommendations and treatments can neu- ropsychologists give to brain-impaired people that will be useful in their daily lives? How to make recommendations to individuals about their every- day lives has become an important issue in neuropsychological assessment. This is important because many neuropsychological tests appear to be somewhat abstract on the surface. For exam- ple, a test of driving capacity has not been developed yet, so neu- ropsychologists rely on traditional measures of attention, mem- ory, and eye-hand coordination to make inferences about whether a person with brain injury should be allowed to drive. In addition to driving, there are many instances in which neu- ropsychologists can help their patients regarding activities that have a cognitive component, but are performed almost every day. Those activities can range from balancing a checkbook, going shopping, and finding one’s way around, to more basic activities such as getting dressed, taking a bath, or brushing one’s teeth. Neuropsychologists can determine which everyday tasks patients with brain injuries may have problems performing. Neuropsy- chologists then recommend what task may be strengthened through rehabilitation or through compensation of other intact skills. For example, if a right hemisphere patient has trouble find- ing his or her way around a hospital and often gets lost, the pa- tient may learn specific right/left directions and also compensate by learning to ask bystanders for directions. The patient may also rely on a notepad that always reminds him or her what the desti- nation is. Thus, neuropsychologists play an important role in treating and rehabilitating patients with brain injuries.

How do the two major approaches (process and battery) to interpreting neuropsychological data differ? The two approaches are different in a variety of ways (see Table 3.4); therefore, it is almost a philosophical difference in terms of neuropsychological assessment. The principal difference is that the battery approach is a standardized approach to assessment,

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whereas the process approach is a clinical analysis of a patient. The former is akin to having a patient undergo a series of tests and standardized questions to understand his or her abilities and deficits. The latter is based on the idea that each patient’s pre- sentation is so unique that it is of most importance to under- stand the unique problems for which the patient is seeking treat- ment, and thus to tailor the examination to the individual. The standard battery approach has evolved through empirical analy- sis and the extensive testing history of psychological testing. The process approach has evolved in the clinical setting. Although proponents of the process approach would disagree with this conclusion, research supporting the process approach is not as robust as the empirical foundation of the standard battery ap- proach. As with many issues that are so polarized, most neu- ropsychologists borrow certain aspects from each approach in their own approach to neuropsychological assessment.

C H A P T E R 4

Will it be possible one day to “map” the circuits of the human brain? Various “mapping systems” of the brain are discussed in the chapters that deal with brain anatomy. Mapping systems gener- ally have focused on major structures of the brain as they per- tain to function, or to various “architectural” layers of the brain and cortex. From these the correspondence of various structures with their functions has been demonstrated. However, here we are asking about mapping brain circuits that revolve around neu- ronal pathways and interconnections. As discussed in this chap- ter, there are billions of neurons and glial cells with multiple connections. It has been estimated that the human brain per- forms more than 1 quadrillion operations per second, which is more than a thousand times faster than the current supercom- puters. The shear size and power of the human brain still makes it the most complex structure in the known universe. Attempts at mapping circuitry of simple organisms, such as the honeybee, have been accomplished. So is this just a matter of scale that computing power will one day be able to conquer? The answer to this question also lies in considering that there are vast indi- vidual differences in the way each person’s brain is “wired,” and that brain communication networks can modify themselves and change with experience, development, and learning. Mapping the circuitry of the human brain is not only extremely complex, it is a moving target.

Actor Christopher Reeve suffered a severe spinal cord injury and died without fulfilling his pledge to walk again. What is the outlook for other people with paralysis caused by spinal cord injury? Not long ago, the traditional wisdom on neuronal damage to the spinal cord presumed that little healing occurs once a neuron in the brain or the spinal cord has been damaged. At best, the process called collateral sprouting, which occurs in nearby intact neurons, might facilitate a functional reorganization. The com- plexities involved in the regrowth of neurons and their millions

of projections to other neurons are daunting. All these connec- tions can be lost within a split second due to brain trauma. The likelihood that these connections regrow spontaneously was thought to be quite small. Although Christopher Reeve never walked again, through intensive rehabilitation aimed at keeping his muscles toned and moving his limbs as he normally would in walking or cycling, he did recover some sensation even after 5 years. Was this actual neuronal repair, regrowth, or functional reorganization? The answer is unknown. However, it is now known that some function can return long after what was previ- ously believed. In addition, current research in neuronal repair, either through stem cell research or in coaxing CNS neurons to act like PNS neurons, is promising. The current outlook is much more promising for people with paralysis caused by spinal cord injury.

Is it possible for a drug to be effective if it does not activate a naturally occurring brain chemical receptor? The human brain is affected not only by internally produced chemical messengers, but also by externally originating chemi- cals that find their way to the synapse. The discovery that the brain has receptors for endogenous opiates, such as endorphins, which produce similar behavioral responses as external opiates, provides the fodder for this question. Why do substances such as caffeine, cocaine, nicotine, and alcohol affect the brain? The nervous system has specific receptor sites that bind drugs such as nicotine and opiate compounds. Others may work because they are a close enough mimic, or act as a blocking agent. Certain drugs, however, are totally barred from the brain, and other sub- stances require an active transport system to cross the blood– brain barrier. In general, drugs at the synapse either increase or decrease the likelihood of neuronal transmission. Therefore, drugs can exert their actions in various ways, but it appears that brain receptors must react to them even if they are not perfect mimics.

What scientific and ethical questions will need to be resolved for research into neuronal repair and neurogenesis to be suc- cessful? Scientifically, the primary question pertaining to neuronal repair is, “What is different about the growth and repair mechanisms be- tween a CNS and a PNS neuron?” Current research suggests that some characteristics of myelin may be part of the issue, and much attention has focused on this. Interestingly, because myelin is an issue, research in multiple sclerosis and spinal cord injury may help to inform each other. One of the main questions pertaining to neu- rogenesis is, “What causes neurons to grow and die?” Both of these issues raise many other questions such as, “At what developmental stage do neurons decide to quit replicating?” and “What are the adaptative and maladaptive implications of naturally occurring and induced neurogenesis?” Ethically, for treatment of injury and disease, the questions revolve around a debate between the extent that science could be helpful in intervening to find cures for dis- eases and disorders against the issues of using embryonic stem cells to advance the research. Unfortunately, the debate is often framed as an “either/or” question. Scientists and the public will benefit

Answers to Critical Thinking Questions 541

from creative ways to solve this problem if informed solutions and ethical decision making is encouraged.

C H A P T E R 5

Why is an understanding of the stages and processes of brain development important to the neuropsychologist? The stages and processes of brain development are important to the neuropsychologist for a number of reasons. First, knowledge of the stages and timing of brain maturation allows for the iden- tification of emerging cognitive-behavioral functions. Second, a recognized association exists between specific disorders and dis- ruption/retardation at specific stages of brain development. For example, lissencephaly (absence of cortical sulci and gyri) is caused by disruption of neural cell migration during the 11th to 13th week of brain development. This knowledge can increase our understanding of the etiologies of the disorders and poten- tially shape preventive interventions. Third, knowledge of the relation between brain maturation and behavior provides a yard- stick for determining whether the child’s observed behaviors are consistent with healthy brain development. Fourth, studies of the interplay between environmental influences and brain de- velopment allow for a determination of conditions that support, enhance, or retard cognitive-behavioral development. Finally, knowledge of the stages and processes of brain maturation can prompt the development of restorative and rehabilitative inter- ventions for treating those who have suffered early brain injury.

If a child was born without the telencephalon region of the brain, would the child be able to orient to visual and audi- tory stimuli, perform reflexive movements, and sit up? Ex- plain why or why not. Removal of the telencephalon would result in the loss of the fol- lowing brain structures: cerebral cortex, basal ganglia, limbic system, and olfactory bulbs. Despite this loss, the child would be able to orient to visual and auditory stimuli, demonstrate re- flexive movements, and sit up because of the preservation of sub- cortical and spinal structures and systems. For example, auto- matic orientation to visual and auditory stimuli is supported by the superior and inferior colliculi, respectively, of the midbrain. In addition, the child would be able to perform most elemen- tary functions such as ambulation, eating, drinking, and sleep- ing. However, the ability to link automatic movements to vol- untary movements and to respond flexibly and adaptively to environmental demands would be compromised. Furthermore, the ability to provide meaning, value, emotion, and voluntary intent to behavior would be lost.

To what extent can behavioral functions be localized to spe- cific brain structures? The structures presented in this chapter represent important topographic features on which the various processing systems of the brain depend. Aspects of behavior can be attributed directly to many of these structures. In general, the structures described in depth here, such as the brainstem structures, are responsible for rudimentary aspects of behavior. Many of the structures are necessary for sustaining life, for controlling wakefulness and

sleep, and for controlling other drive states. As a general rule, more basic and fundamental aspects of behavior are more easily traced to specific structures. In the following chapters it will be- come evident that as behavior becomes more complex, there is a move from specific structure-function correspondence to an em- phasis on larger functional systems that subserve the complexi- ties of human behavior.

What level of brain mapping is most useful to the neuropsy- chologist? When it comes to understanding the relationship of the human brain to behavior, mapping at the level of the cell or the neuron is usually considered too minuscule to provide an accurate pic- ture of the complexity of human behavior. Also, some functions are basic and automatic, and of less interest related to their psy- chological functions, such as the role of CSF as a waste product remover. Finally, understanding the complex organization of the brain, as a whole, would not provide useful information for neu- ropsychologists, who are often asked to respond to questions such as, “What effect does an injury to the basal ganglia have on behavior?” or “If a person has poor motor coordination, which areas of the brain are most likely to be affected?” In general, re- searchers tend to think of behavior related to its function, so it is most useful to consider the brain structures and systems that relate to that function. In this chapter, basic structures were pre- sented with ties to function. However, in the following chap- ters, more complex functions such as visual perception or mem- ory, as well as more complex and interconnected systems within the brain, emerge as the most useful level in describing most human behaviors.

C H A P T E R 6

How would you explain the functional differences between the right and left hemispheres? Several points should be made when describing the functional differences of the two brain hemispheres. First, although gener- alizations can be drawn, it is important to remember that there are notable exceptions. For example, although speech is gener- ally considered to be lateralized to the left hemisphere, some in- dividuals possess bilateral or right-lateralized speech. Second, hemispheric functional differences relate to the interaction of a number of variables to include the nature of the stimulus (e.g., visual vs auditory), mental computations required (e.g., detail vs global processing), routine or novel nature of processing de- mands, and manner of task presentation. Third, hemispheric function is rarely “either/or”; that is, both hemispheres function in a complementary manner to support a given function. For example, the left hemisphere is typically involved in the verbal aspects of speech, while the right hemisphere provides the affec- tive or prosodic aspects to speech. Fourth, there are indications that the left hemisphere is more proficient in linear, sequential, and rule-bound processing, whereas the right hemisphere shows greater proficiency in holistic, simultaneous, and integrative per- formance. However, other conceptualizations provide equally

542 Answers to Critical Thinking Questions

meaningful descriptions of the functional differences of the hemispheres. Finally, we await further research to clarify the functioning of the brain as a whole, as well as the individual contributions of the respective hemispheres.

Are there adaptive reasons why the cerebral hemispheres would gravitate toward either a bilateral or asymmetric or- ganization? Explain. Although science does not provide a definitive answer to this issue, to approach this question it is important to think about what factors lead to differences in hemispheric organization. One of these factors is handedness. About 90% of the popu- lation is right-handed, with a tendency toward left hemisphere dominance for speech. Another factor is sex. Sex hormones affect brain organization starting during fetal development. Women tend to be more bilaterally organized than men. Con- sidering these two factors, it is interesting to speculate whether, for example, men needed to have more lateralized brains for stereotypically “male” activities such as visuospatial abilities, and women needed to have more bilaterally orga- nized brains for stereotypically “female” activities such as su- perior language function. And what advantages might right- handers have, if any?

What ecologic or evolutionary factors could account for the advantage of males in visuospatial abilities? From an evolutionary perspective, a number of hypotheses have been posed to account for the advantage of male relative to female individuals in visuospatial abilities. Each of these hy- potheses has met with criticism and countering interpreta- tions. The hunter role of early man has been posed as a reason for the advanced visuospatial performance of the male sex. Specifically, the use of weapons (such as throwing a spear to kill game) is hypothesized to account for the visuospatial pro- ficiency of the male sex. Another hypothesis that relates to the hunter role of early man proposes that the distances that hunters would have to travel in the pursuit of game would fa- cilitate the development of visuospatial abilities. Similarly, wars throughout the ages (early clans through modern wars) have generally been fought by men, experiences that may have served to reinforce the development of spatial abilities. From an early age, male and female individuals encounter different socialization experiences regarding their roles as male or fe- male. Male individuals are more likely to involve themselves in play involving active and spatially related activities. Whether this preference is solely a function of socialization continues to be an area of debate. However, it is clear, from a historical per- spective, that the male sex has been expected to show more in- terest and involvement in play and work activities (e.g., sports, construction) that emphasize visuospatial abilities. Thus, male individuals have been provided greater exposure, experience, and training in visuospatial activities. As the distinction be- tween male and female roles with regard to academic, voca- tional, athletic, and other life pursuits become less distinct (and limiting), it would be expected, from a socialization per- spective, that the difference between male and female visu- ospatial abilities would be reduced or eliminated.

C H A P T E R 7

In what ways do the study of sensory-perceptual and motor disorders inform us about intact brain functioning? In what instances might the study of damaged brains lead us astray? The study of patients with damaged brains has provided impor- tant clues to the workings of brain systems. For example, by ex- amining patients with lesions in Broca’s or Wernicke’s areas, or damage to area V4 (occipital cortex), functions of language and vision, respectively, have been mapped. However, this strategy can lead to erroneous information in that a lesioned area does not always “contain” the function, but it may, instead, act as a “cable” in the network that serves to join two or more functions.

Do conditions such as phantoms, neglect, and synesthesia represent altered states of consciousness? Explain. Phantoms, such as phantom limbs, appear as sensory-perceptual “hallucinations.” A neglect patient can show a total unawareness of the left side of the body and even deny the ownership of a limb. A synesthete can feel jaggedness when eating chocolate. These examples appear to be distortions from the “norm” of conscious awareness. Yet, these deviations of “reality testing” are not labeled as psychotic processes. Why not? Perhaps the most interesting fact here is the variations one can experience in con- scious awareness. And for some, such as synesthetes, the meld- ing of sensory perceptions may have constituted a “nornal” real- ity since birth.

Does intact motor processing require intact sensory- perceptual processing? Explain. Consider the example of speech presented in this chapter. To what extent does speaking require the ability to understand speech? This chapter discusses the extent to which expressive speech is damaged in those with Wernicke’s aphasia. Would this be more or less of a problem in a child who is born with a diffi- culty in understanding speech? Do you think this is the case in all sensory modalities? Can you think of any exceptions?

C H A P T E R 8

What does the neuropsychology of sensory-perceptual pro- cessing have to contribute to the idea that there is an objec- tive reality related to object perception? This question is the fodder for philosophical debate. However, from a neuropsychological point of view, consider that the chap- ter began by saying, “The range of what humans can detect is unique to our species.” The sensory detectors of other species may result in detection of different stimuli or experiences in a wider or narrower range than for humans. For example, many animals do not detect color, but can detect faint smells or have visual acuity that is far superior to humans. Whose actuality is real? Even if this question is limited to human experiences, con- sider that being “objective” implies being unbiased by personal experience. Sensory information comes in fragments; for exam- ple, an object’s name, the intensity of pain, or the pleasantness of a smell must be attached at secondary and higher processing cen- ters. At each level of processing, more aspects of interpretation

Answers to Critical Thinking Questions 543

are required. So, are there aspects of sensory perception where general agreement can constitute objective reality? Where would you draw a line between the seeming “realness” of sensation and the “personal experience” of perception?

How might it be possible to imagine or conjure up images in all sensory domains despite a lack of sensory input? Although the mechanisms are not fully understood, it is known that one can have a sensory illusion or hallucination in any sen- sory domain. This most commonly occurs with psychiatric ill- nesses such as schizophrenia. In schizophrenia, the most com- mon type of hallucination is auditory. This question also foreshadows a future discussion of consciousness to be presented in Chapter 16, which discusses seizures and epilepsy. Abnormal brain firing in regions concerned with sensory functioning often produces a sensory aura before a seizure. This may be an odd taste or smell, a tingling feeling in a part of the body, or unusual visual or auditory sensations. Thus, the brain can produce sen- sory “feeling” without external input. In the case of normal brain functioning, does this also happen? Take dreaming, for example. When you sleep, you conjure up visual images with your eyes closed. How does this happen? (Look ahead to Chapter 16.)

Can one be “conscious” in one sensory domain but not in another? Yes. This chapter explores the example of neglect. Unilateral neglect is a condition in which the impaired individual loses “conscious awareness of an aspect of spatial or personal space despite adequately functioning sensory and motor systems.” Also, in any type of agnosia, by definition, there is a “not know- ing.” Chapter 7 introduces this term and states that agnosia can occur in any sensory domain. Thus, for example, astereognosis is an inability to recognize or “know” objects by touch. Chap- ter 7 also discusses smell and taste agnosias. This chapter dis- cusses language and vision. Although when discussing language we do not refer to a hearing agnosia but rather aphasia, the idea is the same. If damage occurs to a specific area, it is possible to lose conscious awareness in just one sensory domain while re- taining a sense of meaning or awareness in the other sensory modalities.

C H A P T E R 9

Do the higher cognitive functions discussed in this chapter represent more intelligent thought processes than those functions discussed in previous chapters? Explain. The implication is that “higher” cognitive processes indicate the pinnacle of intellectual functioning, given that we often equate abstract and complex thought with the highest levels of human achievement. This may well be the case from the human point of view. Can you think of examples to dispute this statement from what you have read in previous chapters?

The memory, attention, and executive function systems interact. How would you explain this interaction? Memory, attention, and executive function represent relatively distinct processes, although in some cases, disagreement exists whether a particular attentional or memory process is better

classified as an executive function (e.g., working memory). Clearly, these processes are interrelated, but specifying the exact nature of this interrelation remains to be defined and specified. Nonetheless, some agreement exists that executive functions rep- resent overarching controlling, organizing, integration, and su- pervisory computations. Attention and memory processes are subject to varying degrees of executive orchestration depending on the nature and type of attention and memory processes in- volved. From a neuroanatomic perspective, memory, attention, and executive functions are served by relatively distinct yet in- terconnected and overlapping neural systems. Furthermore, the interrelation of these functions is evident when one realizes that executive functions would be of little value if memory and at- tentional systems were not present. Jointly, attention, memory, and executive functions play a central role in thinking, reason- ing, language, visuoconstruction skills, and sensorimotor and perceptual motor skills. Finally, attentional systems are neces- sary for the processing of relevant ongoing and novel events, memory systems for the symbolic maintenance of these experi- ences over time, and executive functions for the generation, guidance, and evaluation of behavior necessary to attain future goals (Eslinger, 1996).

Do disorders of executive functioning represent a greater dis- ability for humans than sensory-perceptual and motor dis- orders? Why or why not? Although some may answer unequivocally yes, it can also be ar- gued that with sensory-perceptual and motor disorders, the building blocks of functioning may be so compromised that in- tact higher functions may not be able to be expressed adequately. What arguments can you make for each case?

Do emotions represent a higher cognitive function or a lower basic function? Explain. In many ways, emotions represent the most basic of functions evolutionarily. Fear, anger, and other primary emotions are shared with the most primitive of creatures. We included emo- tions in the chapter on higher cognitive functioning because in humans, the interpretation and higher perception of emotions, particularly social emotions, by the cortex requires a high degree of cortical processing.

Are there advantages to multiple brain memory systems as contrasted to a single memory system? Since it is highly unlikely that a single brain memory system could accommodate all the different types and processes of memory that have been identified, there are clear advantages to multiple brain memory systems. That is, differential memory systems allow for the support of a wide range of memory forms and computations. Furthermore, multiple memory systems are potentially an asset if an individual suffers injury to a neural net- work that supports a relatively specific memory system. Al- though this would result in the disruption of certain memory functions, other forms of memory supported by the uninjured memory systems would be preserved. Also, the knowledge of which memory systems are compromised and which are unim- paired provides the neuropsychologist with a framework for de- veloping individualistic rehabilitation interventions.

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In light of the devastating effects of many of the genetic and chromosomal disorders, do you think that potential parents should seek genetic counseling before having children? Explain. Genetic and chromosomal disorders can have devastating effects on the developing brain and other body systems of the child. Many of these disorders are not currently detectable before the child’s conception, so genetic counseling would not necessarily prevent their occurrence. Fortunately, only a small percentage of children are afflicted. However, it is advisable that individuals with family histories of genetic/chromosomal disorders or of ethnic or regional origins often associated with specific disorders such as Tay-Sachs disease, seek genetic counseling.

In recent years, an increasing number of teratogens have been identified in the environment. Are our children at greater risk for brain anomalies than children of earlier gen- erations? Why or why not? An increasing number of teratogens have been identified, sug- gesting, at first glance, greater risk to our children. Although many of these teratogens have been present for years, the injuri- ous effects to the unborn child have only recently been recog- nized. The identification of previously existing and new agents helps reduce birth defects by prompting appropriate control, avoidance, or elimination of these agents. Ideally, greater atten- tion should be given to identifying and regulating potential ter- atogens before they are released into the environment. Unfortu- nately, identifying and regulating teratogens does not necessarily prevent their impact on our children. For example, the in- trauterine teratogenic effects of alcohol have been documented for years; yet, children affected with FAS/FAE continue to be born.

What steps can be taken to prevent FAS? The use of alcohol is an established fact in our society, and moderate use does not necessarily lead to deleterious effects. Unfortunately, some women fail to make the necessary modi- fications in drinking patterns when pregnant because they lack awareness or understanding of the potential effects of al- cohol consumption on the developing child. In other cases, women continue drinking because alcohol consumption is a lifestyle preference or because they are struggling with alco- holism. Improving prevention would involve increasing pub- lic awareness of FAS, starting with early and appropriate edu- cation provided by medical agencies, schools, social agencies, and public health alerts. Women with chronic drinking prob- lems require special attention because of difficulty in altering established drinking patterns. These individuals should be ad- vised to forestall pregnancy until they can abstain from alco- hol, and treatment options should be provided. If pregnancy has occurred, the risks of continued drinking to the fetus should be explained and treatment options quickly identified and provided.

What do the neuropsychological profiles associated with TS and WS tell us about the organization of the brain?

The studies of TS and WS have expanded our understanding of the organization of the brain. The relatively unique neurocogni- tive profiles of these two disorders suggest the following: (1) a number of cognitive functions are relatively independent of gen- eral cognitive ability, whereas others are strongly related to over- all ability; (2) similar behaviors can be supported by different anatomic regions/circuitry; (3) the development of comparable skills and abilities by individuals with TS or WS are achieved by different processes; (4) there is significant intraindividual vari- ability in the neurocognitive performance of individuals with TS and WS, indicating that factors other than genetic/chromo- somal abnormalities affect performance outcomes; and (5) the neurocognitive profiles do not support a “modular” organiza- tion of the brain. For the latter, a modular view of brain organi- zation proposes the presence of inborn, behaviorally designated, and independently functioning brain units. Injury to a given module results in the disruption of neurocognitive functions supported by that unit, while functions specific to other mod- ules remain unaffected. In essence, the modular view of an in- jured brain is that of a normal brain with some “components” impaired and others preserved (Karmiloff-Smith, Brown, Grice, & Paterson, 2003). Several findings argue against the neurocog- nitive profiles of TS and WS as validating evidence for a modu- lar conceptualization of brain functioning. First, the neurocog- nitive dissociations of TS and WS are “relative” and not “absolute.” That is, preserved functions are “relative” rather than “absolute” strengths. For example, the language skills of a child with WS or TS may be more advanced than their visuoconstruc- tive skills; however, both sets of skills are generally lower than those of typically developing children. A cognitive dissociation consistent with a modular conceptualization would predict that the aforementioned language skills would be unimpaired. Sec- ond, as noted earlier, similar neurocognitive behavior can be supported by different brain circuitry/regions and develop in different ways. Thus, neurocognitive behaviors are not localized to specific brain units or follow invariant steps or processes dur- ing their development.

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Why are the symptoms of NVLD and ADHD so often dis- played by children exhibiting a wide range of developmental disorders? As we have discussed, Rourke and associates hypothesize that white matter tissue damage causes NVLD. Insofar as white mat- ter damage is evident across a number of developmental disor- ders, NVLD symptoms would be expected to occur, varying in number and intensity, depending on the extent and location of the impairment. Likewise, the functional neural systems that support attention and behavioral regulation are distributed throughout the brain, and accordingly, the injurious effects to different regions or circuits of the brain could result in behav- iors of inattention, impulsivity, and overactivity. Thus, the symptoms of ADHD could potentially be evident across a vari- ety of developmental disorders.

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Can a child with autism or Asperger’s syndrome develop nor- mal social awareness and attachment? If so, how would this be accomplished? A primary impairment of both autism and Asperger’s syndrome is a significant deficit in social awareness and attachment. Un- fortunately, these social deficits are rarely, if ever, fully resolved. Although therapists have used social skills training and other in- terventions, they have met little success. The amelioration of so- cial impairments of autism and Asperger’s syndrome is ham- pered by lack of understanding of the neuropsychological basis and determinants of social functioning. Specifically, neuropsy- chologists need to identify the developing relations of neural systems to special classes of social behavior (such as attachment), the effects of environmental influences on neural-social devel- opment, the causative factors specific to different types and forms of social impairments, and the malleability of and means of modifying neural-social behaviors necessary for altering social deficits. Once they gain this knowledge, people should be able to develop interventions necessary for the development of nor- mal social relatedness and interaction.

How would you respond to the comment, “ADHD does not exist, it is merely a diagnosis to excuse lazy and undisci- plined children?” Some challenge the very existence of ADHD as an excuse for lazy and undisciplined children. To counter this challenge, cite the voluminous research that supports the existence of the disorder, the converging clinical and empirical studies that delineate the key symptoms and potential etiologies of the disorder, and the outcome studies that show significant improvement in regula- tory control for children with ADHD who receive appropriate medical and psychological treatment. Finally, present specific be- cause differences between the child who is exhibiting ADHD and one who is showing lazy and undisciplined behaviors.

As our understanding of the neural correlates of learning and neuropsychiatric disorders expands, what impact will this have on traditional psychological and educational treatment? As researchers increasingly identify neural correlates of learning and neuropsychiatric disorders, significant changes will become evident in psychological and educational interventions. Al- though the potential changes are both numerous and unknown, several have been predicted. First, the discovery of genetic and chromosomal links to specific developmental disorders and ac- companying neurogenetic interventions will enable children to be born relatively free of neuropsychological deficits. The need for traditional medical and psychological services specific to these disorders will be rendered virtually obsolete. Second, neu- rogenetic, molecular, and chemical advances will guide the de- velopment of medical interventions to repair and regenerate damaged brain tissue. In such cases, neuropsychological treat- ment will primarily focus on developing plans and interven- tions to enable parents and other caretakers to provide the experiences necessary to stimulate development and recovery of functions. Third, advances in the understanding of brain– behavior relations will encourage the development of increas- ingly complex neuropsychological models to predict appropriate

treatment options for specific brain disorders as affected by socioenvironmental factors, age, sex, health status, cognitive abilities, and other variables. Fourth, as understanding of brain– cognitive functioning expands, people will be able to develop specific educational strategies and interventions that will ex- pand and maximize the learning of children, both disabled and nondisabled.

Does the finding that the symptoms of GTS often attenuate or resolve in later adolescence or early adulthood support a conceptualization of the disorder as a developmental lag? How do you account for individuals who do not show such improvement and struggle with GTS as a lifelong disorder? The concept of developmental lag indicates a delay in the onset or rate of development of motor, communication, socialization, or other expected behaviors. The concept further assumes that a mature level of functioning ultimately will be achieved, and thus does not denote a disability. Clearly, the attenuation or resolu- tion of GTS during late adolescence or early adulthood does not meet the standard of a slowly emerging or developing set of ex- pected behaviors. Yet, inhibitory (motor) control is a develop- mental phenomenon that begins in infancy and continues to maturity in adolescence/adulthood. If research determines that tic behaviors are a function of a lag in the maturation of motor control, greater support will be provided for conceptualizing GTS as a developmental delay. However, the finding that a num- ber of individuals with GTS do not show improvement with age, the complexity of behaviors that can constitute a “tic,” the involuntary-voluntary quality of some tics, and the “waxing and waning” nature of tic behaviors argues against a simple causative explanation for GTS, such as developmental delay. The factors that determine whether an individual will or will not recover from GTS remain unclear. It is possible that there are yet to be identified subtypes of GTS that differ with regard to the pro- gression and resolution of tic behaviors. Other factors that may affect the chronicity of GTS are tic severity, age at onset, pres- ence of other comorbid conditions, and types and duration of treatment.

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What are the neurologic, behavioral, and emotional symp- toms of a stroke? The initial neurologic symptoms of stroke include a sudden headache, nausea, and loss of behavioral function, which may be relatively specific in nature. Because a stroke can affect many different areas of the brain, the neurologic symptoms may vary, but there can be an associated loss of consciousness. Behavioral symptoms relate to the precise area of the brain that has been af- fected. For those affected with left-hemisphere stroke, a com- mon behavioral symptom is difficulty in understanding and ex- pressing speech. Visual symptoms indicate posterior or basilar involvement, but a precise understanding of the behavioral symptoms is often not possible until a comprehensive neuropsy- chological evaluation is completed. Emotional symptoms can include depression for left-hemisphere stroke or irritability for

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right-hemisphere stroke. Again, a comprehensive neuropsycho- logical evaluation may include a measure of emotional and per- sonality functioning.

What are the major forms of treatment for stroke? The acute treatment of the stroke patient involves medical sta- bilization and control of bleeding, through medication or surgery. Common medications include anticoagulants to dis- solve blood clots or prevent clotting, vasodilators to dilate or ex- pand the vessels, and blood pressure medication and steroids to control cerebral edema. Surgery can include clipping a bleeding aneurysm or evacuating blood to control the intracranial pres- sure often associated with a hemorrhage. Treatment for TIA symptoms is more difficult because of the ambiguous nature of the symptoms and is often restricted to pharmacologic interven- tion with anticoagulants. Long-term treatment of stroke patients may include intensive rehabilitation, including speech therapy, occupational training, and vocational training. Often, basic ac- tivities of daily living must be “relearned.” Periodic re-evalua- tion by a neuropsychologist may determine treatment and reha- bilitation progress and outcome.

Why do some stroke victims downplay their illness, whereas others go into a deep depression? The symptoms of a right-hemisphere stroke are quite different from those of a left-hemisphere CVA because of the lateraliza- tion of many functions in the brain. A right-hemisphere stroke may result in a “lack of awareness” associated with poor insight and disinhibition. Patients with right brain damage tend to be unaware of their dysfunction associated with the consequences of the stroke. In fact, such patients often deny that there is any- thing wrong with them. Many patients with right brain damage display a range of emotions from indifference to euphoria. This contrasts with the depression that patients with left brain dam- age often show. Therefore, it is easy to assume that deficits from right brain damage are not as serious as those from left brain damage. As a result, right-hemisphere stroke patients may be blamed for being “rude,” “disruptive,” or “inappropriate” when they are actually exhibiting symptoms of right brain injury, in- cluding impulsivity, verbosity, inattention, and poor judgment. Obviously, these problems can be highly disruptive to the pa- tient and family alike, often even exceeding the problems associ- ated with left-hemisphere CVAs. Because right-hemisphere stroke patients and their families underestimate the severity of the condition, those patients are not diagnosed as rapidly as are left-hemisphere stroke patients.

Describe the most common neuropsychological deficits associated with stroke. Almost always, neuropsychological disruption appears in stroke survivors; thus, neuropsychologists often evaluate stroke pa- tients. Both the right and left hemispheres are associated with changes in motor and sensory functioning after a stroke. Those changes can be as benign as mild motor slowing to effects as de- bilitating as complete paralysis, particularly if there are lesions in the thalamic area or the motor and premotor area of the frontal lobes. Right-hemisphere stroke motor deficiencies, how- ever, are generally less severe, because the nondominant left

hand is not as important for skilled tasks. Deficits that affect the right cerebral artery involve areas responsible for spatial, rhyth- mic, and nonverbal processing. Right-hemisphere symptoms, although serious in the patient’s overall functioning, can be less striking in the acute phase, particularly if they do not involve motor dysfunction. Research has shown consistently that pa- tients with right-hemisphere stroke are hospitalized longer in re- habilitation facilities than are patients with left-hemisphere strokes. This fact is related to the pervasive deficits that right- hemisphere patients present with in the area of visuospatial abil- ities and the extended rehabilitation process that is required in rehabilitating these patients in areas of dressing, ambulating, and other self-care behaviors. The capacity to drive after a stroke continues to be one of the most sensitive issues facing health care workers, as well as the stroke patients and their families.

Would you want to know what type of cell a tumor arises from if one of your family members had brain cancer? Why? Should physicians routinely inform their patients of such medical details? Yes, I (E.A.Z.) would like to know. The reason for knowing is that the more information the patient and family has, the easier it is to make personal decisions, such as estate management, is- sues of quality of life, and life expectancy. The specific type of brain tumor, and the type of cell it has arisen from, often signals a clear course of the disease. For example, the glioblastoma mul- tiforme (GBM) is a particularly destructive and fatal glioma. Conversely, the presence of a meningioma often has little conse- quence to one’s long-term well-being. Many physicians share detailed medical information with their patients and treat them as educated consumers. But many do not. My Aunt Edna died of a brain tumor, but the doctors never told her or her family what kind of tumor she had, even though clearly (to me) it was a GBM. As a result, the family had great hopes for her recovery, which unfortunately was not realistic; she passed away within 8 months. Would you like to know?

What is the neuropsychologist’s role in diagnosing and treat- ing patients with brain tumors? What is his or her role with the patient’s family? Since the advent of modern imaging technologies, neuropsy- chologists play only a minor role in the diagnosis of brain tu- mors. CT and MRI technology can often pinpoint the precise location and size of a brain tumor. If the tumor is thought to be fatal, neuropsychologists often provide counseling and educa- tion to patients with brain tumor and their families. If the brain tumor is operable and recovery is likely, neuropsychologists can provide a baseline assessment to which future evaluations (after surgery) can be compared. Treatment choices are complex and should have input from a team of oncologic professionals in- cluding neurosurgeon, oncologist-hematologist, radiation thera- pist, neuroradiologist, neurologist, and neuropsychologist. In general, neuropsychologists can play an important role in as- sessing brain tumor survivors and in providing rehabilitation care and intervention. As with other neurologic disorders, neu- ropsychologists can play an important role in helping people to understand the cognitive changes associated with brain tumor

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diagnosis and treatment, and assist families in coping with this medical illness.

How do children who have brain tumors react differently to their disease from the way adults do? How do their families react? In general, children are quite resistant to the psychological con- sequences of life-threatening diseases. When they are adoles- cents, the burden on them physically and psychologically may manifest itself by experiencing depressed mood and irritability. But young children seem to cope surprisingly well when con- fronted with cancer. The parents of those children seem to ab- sorb much of the psychological distress, however, often feeling guilty and being overprotective. Families often view the cancer and its consequences as severe and insurmountable. As a result, when a child is diagnosed with a brain tumor, it has become es- sential to work with the entire family to understand the subjec- tive appraisals or perspectives of the child and the family and to provide a realistic but optimistic framework. This crisis is not only the child’s but also the entire family’s. Thus, diagnosis and treatment of cancer in children affects family functioning in sub- tle ways, and family functioning affects cancer and its treatment in children. Psychologists play an important role in managing the emotional consequences of the families and children with brain tumor.

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Can a head injury change a person’s life? Yes, often dramatically. The consequences of moderate and se- vere traumatic head injury can be profound, with obvious emo- tional and cognitive changes in the patients who survive head injuries. It is not unusual in such cases that a spouse reports that a head injury victim is not the person that he or she married. The patient’s quality of life, marital status, and employment sta- tus often change significantly. The consequences of mild head injury (MHI) and concussions are more subtle, even to the pa- tients themselves. Nevertheless, they can change a person’s life, because the mild cognitive deficits that are often associated with MHI affect the person’s quality of life. Often, depression and somatic complaints appear in MHI patients, as do cognitive deficits in memory and attention. However, many individuals who have sustained an MHI completely recover. Often, neu- ropsychologists can determine the level of recovery by making a neuropsychological assessment.

What is the potential for the human brain to adapt and re- cover after brain injury? In this chapter, as well as in previous chapters, we have presented cases in which patients had to adapt to the devastating effects of brain injury. Some patients have adapted well even in the face of little to no recovery. Other patients, particularly younger chil- dren, have made dramatic recoveries of function. The practicing neuropsychologist must weigh multiple factors, including injury severity, age, previous level of functioning, available resources, as well as the patient’s psychological state and level of motivation in predicting potential for recovery. This remains an inexact science,

but neuropsychologists are often surprised by the ability of peo- ple to adapt to their injuries.

What are the challenges for rehabilitation in the twenty-first century? After reading this chapter, where do you think neuropsychologi- cal rehabilitation should head in this century? Should it be in the area of technology? Inpatient treatment? Community rein- tegration and job skills? Family and patient counseling related to adapting to the injury or illness? The practicing neuropsy- chologist must weigh multiple factors, including injury severity, age, previous level of functioning, available resources as well as the person’s psychological state and level of motivation in pre- dicting potential for recovery. The biggest potential for rehabili- tation may, however, be in the area of research and development. Right now scientists can program the nervous system of only the simplest invertebrates. However, changes in technology are occurring at lightning speed. For example, will those paralyzed from the neck down walk again through the aid of technology?

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Will exercising one’s mind help ward off dementia? Must one “use it or lose it”? Debate continues among researchers that maintaining flexibility of thought and keeping mentally active contributes to one’s cog- nitive reserve. However, even researchers who have not found confirming results are still hopeful that an active, healthy lifestyle, both mentally and physically, may help ward off some disorders of aging.

How is Alzheimer’s disease best identified in life? Because Alzheimer’s disease (AD) is a diagnosis of exclusion, only confirmed later by biopsy at autopsy, behavioral and cogni- tive profiles are crucial to the differential diagnosis of AD and of various dementia subtypes. In addition to differentiating be- tween AD and normal aging, Chapter 14 makes clear that dif- ferent dementia subtypes show distinct neuropsychological pro- files. Knowing the behavioral and cognitive profile is one of the best means of differentiating between some types of cortical (AD) and vascular dementias and normal aging. This is because once all other medical causes have been ruled out, imaging and physiologic testing often cannot detect minute vascular changes or patterns of brain necrosis. This is also because, as we have said, degree of cortical shrinkage is not reliably associated with declines in cognitive functioning. Changes in behavioral func- tioning, however, are the hallmark of dementia and they must be documented carefully.

How can a neuropsychological profile aid dementia sufferers and their families? As is evident from the previous question, in addition to aiding in diagnosis, one of the best things a cognitive profile can pro- vide is a picture of the person’s pattern of strengths and weak- nesses, and an estimation of degree of decline from former abili- ties. This picture is a “snapshot in time,” but it serves to educate patients and caretakers about the degree to which the person is

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currently able to manage independently and in what areas he or she is likely to need assistance. The neuropsychological profile can also serve as a planning aid for future caretaking and treat- ment needs. Although there is no “cure” for AD, ameliorative treatments can help the AD patient. Knowing, for example, that an AD patient has preserved nondeclarative motor skill learning means that the patient may be taught relaxation techniques that require progressive muscle relaxation, even though they retain no declarative knowledge of learning. Such behavioral treat- ments used by psychologists show promise in calming restless- ness and agitation that can occur in later stages of the disease. In sum, the neuropsychological profile helps show the problematic brain functioning, educate regarding strengths and weaknesses, plan for individualized caretaking needs, and suggest possible behavioral treatments.

How does the concept of self of the patient with Alzheimer’s disease change with the progression of the disease? This question allows speculation, given what has been presented of the neuropsychological profile of the patients with Alzheimer’s disease (AD). If you look at each area where decline is evident, how do you think this would affect a person’s self- concept? New learning deficits and declarative memory loss are hallmarks of the disease. Considering the possibility that aspects of our selves are built on memories of our own experiences, do you think a person’s self-concept would change as he or she lost aspects of his or her memory, as the person has increasing trou- ble learning, or as the person is having trouble doing certain things he or she once did well? Are there certain people whose sense of self may be more affected by AD than others would?

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It may soon be possible to test for many neurologic diseases. Would you want to be tested for the possibility of future de- mentia? A positive genetic test for Huntington’s disease (HD) indicates almost certain manifestation of the disease. But what about other neurologic diseases, where a positive test could indicate much lower odds of disease certainty? There are cases of AD pa- tients with normal identical twins. Factors other than inheri- tance play into whether dementia develops in a person. Would you want to know about your tendency toward a certain dis- ease? Would you want others to know? Why do you think most people at risk for HD have declined to be tested?

How is the behavioral quality of subcortical motor disorders presented in this chapter similar or different from the corti- cal motor disorders such as apraxia presented in Chapter 7? Is the behavioral quality of the motor dysfunction of Parkin- son’s, Huntington’s, or Creutzfeldt–Jakob disease different from that of, say, apraxia (see Chapter 7)? Most clinicians would say yes. With subcortical motor problems, the movement is usually not orchestrated or regulated well, but apraxia is a problem of not “knowing.” For example, if asked to pantomime “pouring and serving tea,” an apraxic patient may have no idea of how to demonstrate this or may mime an incorrect action. In contrast,

a patient with Parkinson’s disease is more likely to demonstrate the correct movement, but may have trouble initiating the movement or show slowness in performing the movement (tremor may be evident in later stages of the disease during in- tentional movements). In what other ways might the behavioral quality of subcortical motor disorders differ from that of corti- cal motor disorders?

How do the subcortical and cortical motor systems work together? Chapter 7 describes two theories of how the motor system may work. First, the hierarchy theory states that the primary motor cortex sits at the top and is the funnel for all bodily informa- tion. A competing theory suggests that the motor system works in a parallel processing mode with several motor processing circuits working in coordination with the primary motor cor- tex. Although these theories remain debatable, we also know that much of the initiation for motor behavior and executive programming for movement originates in the higher associa- tion area of the prefrontal cortex, which is responsible for or- chestrating and organizing motor behavior. The dorsolateral prefrontal cortex (contained within) is not a “movement cen- ter” in and of itself, but it is instrumental in deploying move- ment. Much of the input to this area comes from the subcorti- cal motor centers. Therefore, the subcortical and cortical motor functions must coordinate and may do so through the dorsolateral prefrontal cortex. Although there appears to be some hierarchy of functioning, it may also be that parallel cir- cuits relate to different aspects of motor behavior within this hierarchy.

What are the ethical and scientific issues in the treatment of dementias? This chapter and Chapter 14 discuss a number of different treat- ments for dementias. These treatments include drug, behavioral, and even surgical interventions. The most ethically controversial treatments include genetic treatments and surgical interventions with “fetal” brain tissue. Also, to what extent should society seek to develop drugs to ameliorate symptoms of dementia? What are the costs versus the benefits?

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What is the biological or psychological function of “rhythms” of consciousness? This chapter discusses the idea that there are preset circadian rhythms of human consciousness. It also discusses how these operate in normal waking, sleeping, and dreaming. It is also ap- parent that narcolepsy disrupts the flow of this rhythm so that sleep attacks may occur during wakefulness. Also, the rare circa- dian rhythm disorder can be life threatening (see “The Case of the Last Coronation,” Neuropsychology in Action 16.2). Given what you know of this, can you speculate on the biological rea- sons for daily and 90-minute periods of relatively more active to more quiet brain activity? Does this somehow “tone” the brain, as some suggest? Psychologically, is it adaptive for humans to al- ternate between periods of activity and quiet?

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How fluid are the boundaries between conscious and sub- conscious awareness? This question concerns not only this chapter, but also ideas of conscious awareness, which have been presented throughout the book, as well as general ideas of consciousness debated in psy- chology. To approach this issue, first one must conceptualize and operationalize a definition of “conscious awareness” with particular attention to how conscious awareness is demon- strated. Must this always be in a verbal manner? Can one demonstrate awareness just through performance of an action? When one is in a state of consciousness, which is other than being “fully awake,” what sense of awareness can there be? How does your knowledge of the functional and dysfunctional brain help to inform your ideas of consciousness?

How do REM sleep and dreaming change in people who have various neurologic disorders? This issue presents an exciting and relatively underexplored area in neuropsychology. A number of case reports of people with abnormalities in dreaming from global cessation of dreaming, to decreased or odd qualities of dreaming, to problems in remem-

bering dreams are in the literature. How do you think dreams of people with frontal lesions differ from those of people with pari- etal lesions? Do you think that people with motor problems will also have motor problems in their dreams?

In what ways might neuropsychology be able to contribute to treatments for people with sleep disorders or epilepsy? If you consider the range of behavioral treatments of clinical psychology and the neuropsychological problems represented by the disorders presented in this chapter, you can see that a num- ber of treatment strategies are possible. For example, memory and concentration problems are common in sleep apnea and, to a certain extent, in narcolepsy. Do you think strategies that aid memory will be useful for sleep apnea patients? Narcolepsy pa- tients may have sleep attacks in response to emotional stimuli. Might relaxation techniques help them? With seizure patients, if auras are related to the foci of the seizure, might visualization techniques help to ward off visual auras, and therefore the seizure? What else can you think of? These areas are ripe for future investigation.

550 Answers to Critical Thinking Questions

Aarsland, D., 424 Abikoff, H., 322, 323 Abramowitz, A., 324 Abrigo, E., 205 Achten, E., 169, 170 Adams, R. D., 98 Adler, N. E., 405 Adolphs, R., 262, 264 Ager, J. W., 292 Aggarwal, N. T., 405 Agid, Y., 427, 429, 430 Agnew, J., 168 Ahmad, S. A., 307, 308 Akshoomoff, N., 316 Alarcón, M., 302 Albert, M., 406 Albert, M. L., 26, 408, 426 Alcazar, B., 342 Aleman, A., 167 Alexander, M. P., 251, 320 Allan, J. D., 174 Allen, G., 283 Allen, S. J., 413 Alsobrook, J. P., 334 Altmann, D., 174 Alvarez-Buylla, A., 110 Alves, W. M., 383 Alvord, E. C., 116 Alzheimer, A., 410, 418, 437 Aman, M. G., 322 Amedi, A., 205 Amin, Z., 169 Aminoff, M. J., 277 Amirikian, B., 169, 170 Andersen, A. R., 435 Anderson, A. W., 317, 318 Anderson, C. M., 325 Anderson, G. M., 251, 316, 333 Anderson, P., 117, 281 Anderson, R. A., 214 Anderson, S. L., 325 Anderson, S. W., 253, 257 Anderson, V. A., 117, 166, 167,

247, 270, 273, 280, 281 Andrew, R., 289 Andrews, C., 263 Andy, O. J., 146 Angold, A., 333 Anker, S., 289 Annett, M., 173 Appelbaum, L. G., 288, 290 Archer, R. P., 15 Archibald, S. J., 250, 256, 293 Aristotle, 7 Armony, J. L., 260, 261 Armstrong, C. L., 364–365 Armstrong, Lance, 360

Armstrong, R. J., 111 Armstrong-Hickey, D., 453 Arndt, S., 321 Arnold, L. E., 322, 323 Arsten, A. F., 333, 334 Artru, A. A., 317 Asbell, S. O., 364 Asberg, M., 108 Asbjornsen, A., 304 Asgharian, M., 409 Ashburner, J., 167 Ashford, J. W., 420 Ashwin, C., 319 Askenasy, J. J. M., 459 Asperger, H., 311 Assheuer, J., 157 Aston-Jones, G., 241 Athawes, R., 402 Atkinson, J., 289 Au, R., 409 Auff, E., 429 Augustine, G. J., 128, 146 Autti-Rämö, I., 292, 294 Awh, E., 240 Aylward, E. H., 317, 325

Babcock, R. L., 403 Babinski, J., 20 Bachen, N. I., 385 Bachevalier, J., 196, 234, 237 Bäckman, L., 168, 402, 403 Baddeley, A. D., 237, 238, 239,

302 Bailey, A. D., 311, 312, 313, 316 Bailey, J. N., 323 Bailey, P., 135 Baird, A. D., 174, 345, 351 Bakker, D. J., 308 Balasubramanian, V., 150–151 Balej, J., 195 Ball, G. F., 109 Banerjee, S., 333 Banich, M. T., 136 Bannister, R., 343, 347 Barakat, L. P., 310, 366–367 Barbieri, S., 212 Barch, D. M., 257 Bard, P., 259 Barkley, R. A., 323, 326, 329, 331 Barnes, M. A., 277, 279 Barnett, H. J., 346 Baron, I. S., 277, 279–280 Baron-Cohen, S., 317, 319 Barr, H. M., 292, 293, 294, 324 Barrash, J., 257 Barratt-Boyes, B. G., 285 Barres, B. A., 101

Barrett, J. H., 323 Barth, J. T., 23, 41, 73, 192, 196,

365, 367, 371, 379, 381, 383, 462

Basso, A., 237 Bates, E., 273 Battersby, W. S., 20 Beadle-Lindsay, M., 87, 146 Bear, M. F., 180, 194, 261 Beatty, J., 96, 105 Bechara, A., 255, 256, 257, 258 Beck, L. H., 246 Becker, J. T., 406 Becker, R. O., 448 Beckett, L. A., 405, 424 Beeman, J. J., 167 Beh-Yishay, Y., 397 Beiser, A., 409 Bell, M. A., 168, 169, 170, 252 Bellgowan, P. S. F., 162, 167, 169 Bellugi, U., 287, 290 Bender, B. G., 283, 285 Bender, M. B., 20 Bennett, D. A., 405, 424 Bennett, M. V. L., 100 Bennett, T. L., 468–469, 472 Benson, D. F., 208, 256, 324,

416, 417 Benton, A. L., 25, 26, 74, 252,

288, 375, 376, 379, 380, 385, 429

Benton, J. S., 413 Berch, D. B., 283 Berg, E. A., 246 Berg, S., 77, 403 Berger, H., 40 Berger, O. G., 272 Berlin, L., 330 Berman, K., 49 Bernstein, J. H., 273 Berquin, P. C., 325 Berthier, M. L., 314 Bertilsson, L., 108 Berttrand, J., 287, 288, 290 Best, M., 301 Biddle, K. R., 247, 273, 274 Biederman, J., 324, 325 Bigler, E. D., 58, 59, 95, 302,

315, 343, 372, 384, 405, 411, 413

Bilker, W., 167 Binder, J. R., 162, 167, 169 Birch, S., 299 Birkmayer, W., 431 Bishop, D., 287 Bisiach, E., 212 Bjoerklund, A., 108

Black, K., 304 Black, S. E., 226 Blackburn, E. H., 405 Blaine, H., 325 Blake, C., 323 Blakemore, C., 20 Blasey, C., 317 Blatter, D. D., 58 Bleeker, M. L., 168 Bloch, F., 51 Blume, W., 464 Blumenthal, J., 325 Blumer, D., 256 Bobe, L., 162, 167, 169 Bocian, K. M., 301 Boeve, B. F., 406 Bohan, T. P., 277 Bohlin, G., 330 Boles, D. B., 167 Boll, T. J., 371, 383 Bolla-Wilson, K., 168 Boller, F., 74, 427, 429, 430 Bollich, A. M., 167 Bolton, P., 313 Bond, T., 462 Bonfort, S., 328 Bookheimer, S. Y., 317 Bookstein, F. L., 292, 293, 294 Bornschein, R. L., 272 Bornstein, R. A., 196 Borod, J. C., 262, 263, 427, 428 Borteryu, J. P., 291 Bouma, A., 167 Bourne, G. H., 404 Bowen, D. M., 413 Bowirrat, A., 409 Boynton, G. M., 301 Braddick, O., 289 Bradshaw, J. L., 161, 189, 191,

196, 209, 211, 212, 213, 214, 218, 220, 323, 332, 334, 412, 425, 428, 435, 436

Brady, James, 373 Braithwaite, V. A., 173 Brandt, J. A., 436 Bransome, F. D., 246 Braun, A. R., 335 Braver, T. S., 257 Brayne, C., 424 Brazier, M. A. B., 40 Bressler, S. L., 448 Brewer, B. W., 42 Brewer, V. R., 328 Brickenkamp, R., 72 Briggs, J. H., 282 Broca, P., 16, 149, 162 Brodal, A., 35

N A M E I N D E X

Note: Names of patients are listed under Patient.

551

Brodmann, K., 158 Brody, I. A., 18 Broman, S. H., 282 Bronen, R., 315, 316, 335 Bronstein, Y. L., 252 Brooks, W., 325 Brookshire, B. L., 277 Brorson, L. O., 473 Brown, A. S., 465 Brown, G. L., 108, 345, 351 Brown, J. E., 325 Brown, R. G., 416 Brown, R. T., 337 Brown, S., 325 Brown, T., 272 Brown, W. E., 283 Brown, W. S., 168, 173 Bruce, E., 25 Brunner, R., 174 Bruno, J. P., 241 Bryden, M. P., 167, 168, 169, 174 Buchanan, L., 283, 284 Buela-Casal, G., 342 Bullmore, E. T., 319 Bullock, P. R., 319 Bundick, W. T., 87, 146 Burlingame, G. M., 302 Burns, A., 413 Burns, B. J., 333 Burr, R. B., 58 Burt, A. M., 132, 134, 137 Burt. A. M., 230 Burton, L. A., 168 Busch, S., 446 Buskist, W., 203 Busse, O., 351 Butler, D. W., 319 Butryn, M. L., 110–111 Butters, N., 227, 237, 415, 416,

430 Bylsam, F. W., 173, 281, 436

Cabeza, R., 226, 229, 253, 258 Cahill, L., 169, 260 Cairns, P., 415 Cajal, R., 34 Calarco, K. E., 294 Calhoun, S. L., 313 Campbell, J. J., 258 Campbell, R. A., 324, 325 Canfield, R. L., 271, 272 Canli, T., 169 Cannon, W., 259 Cantu, R. C., 382, 384 Cantwell, D. P., 323, 328 Capirci, O., 287 Cardon, L. R., 300 Carey, M. E, 310, 366 Carey, S., 249 Carlson, C. D., 302 Carlson, N., 203 Carlson-Green, B., 366 Carmichael Olson, H., 292, 294 Carney, R. A., 283 Caron, M. G., 324 Carpenter, M. K., 111 Carper, R., 316 Carroll, A., 196

Carter, C. S., 257 Carter, L. P., 465 Cartwright, R. D., 460 Caruit, M., 310 Cascino, G. D., 465, 466, 467 Caselli, M. C., 287 Casey, B. J., 120, 325, 334, 335 Casey, R., 366 Casse-Perrot, C., 288 Casson, I. R., 383 Castellanos, F. X., 324, 325, 336 Catroppa, C., 117 Catt, K. E., 409 Catts, H. W., 302 Celnik, P., 205 Cenci, M. A., 108 Chalmer, D., 445 Chalmers, D., 448 Changeux, J. P., 156, 157 Channon, S., 335 Chapieski, L., 323, 334 Chapman, L. F., 21 Charcot, J-. M., 19 Charles, A. C., 100 Charman, T., 311 Chase, C., 299 Chase, T. N., 335 Chavaillon, J., 156, 157 Checkoway, H., 424 Chelder, M. J., 73, 74, 75, 77 Chelune, G. J., 77 Chen, J., 409 Chen, W. J., 293 Cherlow, D. G., 465 Cheung, A. M., 325 Chiarello, C., 167 Chiles, M., 287, 290 Chou, T. C., 456 Chow, T. W., 255 Christensen, A. L., 82 Chugani, D., 120 Chugani, H., 120, 283 Chui, H., 412 Churchland, P. S., 95 Chusid, J. G., 135, 145 Ciesielski, K. T., 319 Cirino, P., 323, 334 Civin, C. I., 111 Cohen, D. J., 315, 332, 333, 334,

335 Cohen, J. D., 55, 241, 257 Cohen, L. G., 205 Cohen, N. J., 227, 234 Cohen, R. A., 241, 242, 243, 244 Cohen, R. M., 324 Cohen-Kettenis, P. T., 173 Colcombe, S., 174, 405 Cole, K., 287, 290 Commenges, D., 409 Como, P. G., 335 Conners, C. K., 322, 323 Connor, P. D., 292, 293, 294 Connors, B. W., 180, 194, 261 Constable, R. T., 167, 169, 304 Convit, A., 405 Conway, J. A., 307, 318 Cook, E. H., Jr., 318 Copeland, M., 406

Coppola, R., 448 Corder, E. H., 412 Corey, D. M., 167 Corey-Bloom, J., 412 Corkin, S., 150, 235, 430 Cornoldi, C., 310 Corwell, B., 205 Corwin, J., 173, 281 Cory-Slechta, D. A., 271, 272 Costa, L., 305–306 Costello, E. J., 333 Cote, L. J., 412, 424 Cottington, E. M., 319 Coull, J. T., 243 Courchesne, E., 316 Covassin, T., 384 Cowan, W. C., 115 Cowan, W. M., 95 Cowart, B. J., 187 Cox, C., 272 Cox, R. W., 167, 169 Coyle, J. T., 413 Craik, F. I. M., 229 Crandall, P. H., 465 Craven-Thuss, B., 336 Crawford, J. R., 403 Crawfrod, T. O., 111 Crick, F., 445, 448, 460 Crinella, F., 328 Cron, B. W., 364 Crosson, B., 147, 218, 430 Culbertson, J. L., 292, 294, 298,

299 Culbertson, W. C., 77, 78,

250–251, 275–276, 327 Culhane, K. A., 247 Cullum, C. M., 45, 95, 343, 372 Cummings, J. L., 252, 255, 258,

325, 412, 416, 417, 419, 426 Curran, T., 235, 236 Curran, W., 289 Curtis, G., 77 Cytowic, R., 179 Cytrynbaum, C., 291

D’Andrea, E. A., 173 D’Esposito, M., 245 da Vinci, L., 7, 128, 130 Dabholkar, A. S., 117, 272 Dahl, J., 473 Dahlgren, S. O., 318 Daly, D. D., 146 Daly, E. M., 283, 404, 406 Daly, G., 324 Damasio, A. M., 255, 256 Damasio, A. R., 257, 258, 260,

262, 263, 411 Damasio, H., 169, 170, 255, 256,

264 Dambrosia, J., 205 Dann, M., 189 Danta, G., 429 Dapretto, M., 317 Dartigues, J. F., 409 Darwin, C., 16, 156 Davidson, K. C., 277, 328 Davidson, R. J., 252 Davies, P., 413

Davis, E. A., 243 Davis, M., 262 Davision, L. A., 246 Dawson, M. E., 242 de Almeida, J. C., 282 De Haan, E. H. F., 168 De Jong, J., 108 De La Granja, M., 283 de la Tourette, G., 332 de Lange, F. P., 169, 170 de Leon, M., 405 de Schonen, S., 288 Dean, R. S., 163 DeAngelis, L., 364 Deary, I. J., 402 Deaton, A. V., 397 DeCari, C., 283 DeFries, J. C., 300, 302 Deiber, M. P., 205 DeKosky, S. T., 406, 412 Del Bigio, M. R., 277 Del Dotto, J. E., 307, 309 Del’Homme, M. A., 323 Delattre, J. Y., 364 Delis, D. C., 291, 292, 293, 294 DeLuca, J. W., 306, 307 Demarest, R. J., 148 Demb, J. B., 301 Dement, W. C., 455, 462 Denaro, J., 412, 424 Denckla, M. B., 250, 325 Dennis, M., 277, 280, 281, 291 Deppe, M., 162, 167, 169 Derns, D., 110–111 Deruelle, C., 288 DeSantis, M., 194 Descartes, R., 4, 9–10, 447 DeTeresa, R., 411 Deutsch, G., 51, 151 Devinsky, O., 196, 257 Dhabhar, F. S., 405 Diamond, A., 147, 247–249 Dieber, M. P., 169 DiGirolamo, G. J., 241, 245 DiLavore, P. C., 318 Diller, L., 395 Dissanayake, C., 313, 318 Dodge, H. H., 406 Dolan, R. J., 262 Don, A., 291, 294 Donohue, B. C., 303 Dool, C. B., 307 Dostie, D., 166 Doty, R. L., 189 Douglas, R. J., 150 Dowd, M., 316 Downs, J. H., 165 Drachman, D. A., 413 Dräger, B., 162, 167, 169 Drake, E. B., 168, 173 Dubois, B., 427, 429, 430 Duffy, F. H., 44 Duffy, J. D., 258 Dulberg, C., 406 Dunne, C., 110, 331 Dunner, S. B., 420 Dunnett, S. B., 111 Dykens, E. M., 285

552 Name Index

Eals, M., 168 Eastman, C. I., 460 Ebbinghaus, H., 24 Ebers, G. C., 98 Echelard, D. A., 317 Echemendia, R. J., 384 Eckburg, P., 324, 325 Eden, G. F., 299 Edgell, D., 270, 272, 281, 298 Edmonds, J. E., 298, 299 Edwards, M., 230, 232–233, 457 Efron, R., 466, 472, 473 Efthimiou, J., 73, 74, 75 Ehlers, S., 318 Eichhorn, G. R., 169, 170 Einstein, G. O., 403 Eiraldi, R. B., 323 Eisenberg, H. M., 379 Eisenmajer, R., 312 El-Hai, J., 22 Elavsky, S., 174 Elger, C., 464 Elias, L. J., 167 Eliez, S., 283, 287 Eliopulos, D., 304, 324 Elliott, F. A., 108 Elliott, T. K., 283 Elsass, L., 396 Emerson, J., 328 Engel, J., 464 England, M. A., 99 Epel, E. S., 405 Erickson, K., 174, 277, 279–280 Erickson, K. I., 405 Erkanli, A., 333 Erlanger, D. M., 172, 174 Ernst, M., 324 Erwin, R., 327 Esiri, M., 404 Eslinger, P. J., 247, 252, 253, 258,

273, 274 Espeland, M. A., 174 Espir, M. L. E., 150 Espy, K. A., 250 Evankovitch, K., 247 Evans, A. C., 166 Evans, D. A., 405, 424 Ewing-Cobbs, L., 277, 279

Fallon, J., 169 Falz, L., 205 Fan, J., 244, 245, 325 Fantie, B. D., 116, 277, 279–280 Farah, M. J., 208 Faraone, S. V., 325 Farran, E. K., 288, 289 Farrer, L. A., 436 Feifel, D., 108 Fein, D., 312, 316, 320 Feirtag, M., 231 Feldman, R. G., 408, 426 Feldman, R. S., 107, 187 Fenwick, P. B., 473 Fermi, E., 449 Fernandez-Duque, D., 243, 244,

245, 326 Ferris, S. H., 406 Fields, R. D., 101

Filipek, P. A., 302, 303, 324, 328 Findley, L. J., 462 Fine, D., 277, 281, 282, 312 Fink, M., 278 Fiore, C., 328 Firth, C. D., 243 Fisher, N. J., 306, 307 Fisher, R. S., 464 Fisk, L. J., 308, 309 Fitzgerald, M., 324 Fitzpatrick, A., 406 Fitzpatrick, D., 128, 146 Fitzpatrick, H., 323 Flaherty-Craig, C. V., 252 Fletcher, J. M., 277, 279, 281,

302, 328 Fletcher-Janzen, E., 279 Flicker, C., 406 Flodman, P., 328 Flöel, A., 162, 169 Flourens, P., 18–20 Flowers, D. L., 302 Foley, B., 310, 366 Folstein, M. F., 407 Folstein, S. E., 314, 316 Fombonne, E., 312, 313 Foorman, B. R., 302 Ford, C. E., 282 Forrest, B.J., 310 Forstl, H., 413 Fossella, J., 334, 335 Foundas, A. L., 167 Fowler, P. C., 146, 343, 354 Fox, P. T., 165, 207, 252 Frackowizk, R. S. J., 167 Francis, D. J., 277, 302 Francis, J. P., 381 Frank, R., 255 Freedman, A. M., 12 Freeman, W., 22–24, 25 Freidman, S. D., 317 Freud, S., 4, 18–19, 460 Freund, L. S., 283 Friedland, R. P., 409 Friedman, H. R., 78 Friedman, K. B., 465 Frijda, N. H., 173 Friston, K. J., 167 Frith, U., 311 Frost, J. A., 162, 167, 169 Fuerst, D., 305, 306, 308 Fuerst, D. E., 308 Fulbright, R. K., 167, 169, 317,

318 Fulker, D. W., 300 Fullbright, R. K., 303, 304 Fuster, J. M., 254

Gabrieli, J. D. E., 235, 335, 430 Gaddes, W. H., 298 Gage, P., 110 Gage, R., 163 Gainetdinov, R. R., 324 Gajdusek, D. C., 437, 439 Galaburda, A. M., 255, 287, 301 Galen, 8 Gall, F., 13–14 Gallup, G. G., Jr., 320, 446

Galton, F., 237 Ganguli, M., 406 Garcia-Verdugo, J. M., 110 Gardner, H., 86, 208 Garrido, E., 342 Gaskell, P. C., 412 Gatenby, J. C., 262 Gauna, K., 166 Gauthier, I., 317, 318 Gautier, T., 174 Gazzaniga, M. S., 163, 165 Geiman, R., 249 Gendle, M. H., 271 Gennarelli, T. A., 383 Genton, P., 464 Georgopoulos, A. P., 169, 170 Georgopoulos, M. A., 169, 170 Gerbaldo, H., 410 Geschwind, M., 27 Geschwind, N., 18 Geva, A., 240 Giacinto, J., 473 Gibb, R., 272 Gideon, D. A., 462 Giedd, J. N., 118, 120, 324, 325 Gill, M., 324 Gillberg, C., 318 Gillin, J. C., 107 Gillispie, M., 302 Gilman, S., 280 Gilzenrat, M. S., 241 Giordani, B., 371 Giraud, A. I., 166 Gitelman, D. R., 242, 246 Givens, B., 241 Glanzman, M., 327 Glaser, G.H., 150 Glidden, R. A., 23 Glisky, M. L., 250 Glod, C. A., 325 Gloor, P., 465 Goetz, C. G., 335, 424 Gogtay, N., 118, 120 Goldberg, E., 305–306 Golden, C. J., 21, 103, 358 Goldenberg, G., 429 Goldman, S. A., 101, 109 Goldman-Rakic, P. S., 78,

239–240, 247, 250, 274, 316 Goldstein, E. B., 140, 144 Goldstein, L. H., 473 Goldstein, S., 286 Golgi, C., 34, 35 Gonzales, J. J., 304 Good, C. D., 167 Gooren, L. J., 173 Gooren, L. J. G., 173 Gordon, A., 64, 65, 84 Gore, J. C., 262 Gorny, G., 272 Gould, J., 312 Gould, S. J., 157 Grabowski, T. J., 169, 170, 255 Grady, C., 283 Grady, D., 174 Graf, P., 234 Grafman, J., 282 Gramling, L., 291, 292, 293

Grant, D. A., 246 Grattan, L. M., 247, 273, 274 Green, L. A., 312, 316, 320 Greenberg, D. A., 277 Greene, H., 28, 66, 78 Greenhill, L. L., 322, 323 Greenlaw, R., 283 Greenstein, D., 118 Greiner, L. H., 402 Grelotti, D. J., 286, 287, 317, 318 Griffith, E. M., 319 Grigorenko, E. L., 300, 302 Grill-Spector, K., 200 Grillon, C., 262 Groisser, D. B., 247, 250 Grön, G., 168, 169 Gronwall, D. M. A., 380 Grossman, R. G., 70, 375, 376,

380, 385 Growdon, J., 430 Gui, Q. P., 409 Gunter, J. L., 406 Gur, R. C., 48, 51, 167, 446 Gur, R. E., 48, 51 Gurland, B. J., 409 Guthrie, P. B., 100 Guy, S. C, 309 Gyato, K., 310, 366

Haberecht, M. F., 283 Haberl, R. L., 351 Haeger, K., 36, 48 Hafetz, J., 168 Hagerman, R. J., 286, 291 Haier, R. J., 169 Haines, D. E., 189, 191 Hainse, J. L., 316 Halgren, E., 465 Hall, J., 304 Hallervorden, J., 262 Hallett, M., 169, 205 Hallgren, B., 300 Halligan, P. W., 212 Halpern, D. F., 168 Halpern, J. M., 325 Halstead, W., 25, 80 Hamburger, S. D., 325 Hamilton, R., 205 Hammeke, T. A., 162, 167, 169 Hampson, E., 172, 174 Hamsher, K. D., 74, 288 Hamshet, K. D., 429 Hanin, I., 412 Hanson, J. W., 292 Hari, R., 56 Hariri, A. R., 317 Harlow, H. F., 21 Harlow, J. M., 255 Harnadek, M. C. S., 305, 307 Harper, J., 321 Harris, B., 146, 343, 354 Harris, J. C., 282, 293 Harris, J. G., 45 Harris, R. J., 319 Harrower, M., 15, 25 Harrowsseau, H., 291 Hart, B., 324 Hart, L. A., 300, 302

Name Index 553

Hartlage, L. C., 163 Hartmann, J., 247 Harvey, A. S., 167 Harvey, T., 15 Harward, H., 247 Hasselbalch, S. G., 435 Haug, H., 404 Hauri, P., 452, 455, 458, 461, 463 Hauser, P., 323 Hauser, W. A., 464 Hawi, Z., 324 Haxby, J. V., 283 Hayaski, K. M., 118 Haynes, S. D., 472 Haywood, C. S., 262, 263 Healy, S. D., 173 Heaton, R. K., 77 Hebb, D. O., 20, 21, 25 Heben, N., 82 Hécaen, H., 26 Hechtman, L. T., 330 Heeger, D. J., 301 Heilman, K. M., 167, 195, 210,

212 Heindel, W. C., 430 Heiss, G., 174 Helland, T., 304 Heller, K. W., 11, 18, 167 Helmer, C., 409 Hemenegildo, N., 412, 424 Henderson, C. R., 272 Henderson, V. W., 168, 173 Hendrix, S., 174 Hendy, J., 166, 270, 273, 280 Henkenius, A. L., 324 Henninger, D., 168 Henry, J. D., 403 Henson, R. N. A., 167 Hentschel, F., 413 Heraclitus, 6 Herman-Liu, A., 366 Hermann, B., 465, 473 Hern, K., 304 Herrup, K., 96 Herscovitch, P., 335 Hever, T., 323 Hewson, J., 110, 331 Hiemenz, J. R., 302, 303 Hill, D. E., 324, 325 Hill, M., 416 Hillary, F., 55, 378 Hilton, R., 429 Hinckley, John Jr., 373 Hippocrates, 6, 8 Hiroyuki, O., 264 Hirsch, H. V. B., 389 Hirsch, T. B., 165 Hiscock, M., 328 Hitch, G. J., 302 Hjlemquist, E., 318 Hobbins, J. C., 293 Hobson, J. A., 458, 459, 460, 461 Hodges, J. R., 416 Hoekstra, P. J., 335 Hoien, T., 304 Holiger, D. P., 287 Holmes, J., 323 Holmstrom, V. L., 473

Honda, H., 313 Hooper, H. E., 81 Hooper, S. R., 299, 304 Hopyan, T., 291 Hornak, J., 212, 263, 264 Hornsey, H., 333 Hornykiewicz, O., 431 Horoupian, D. S., 411 Horwitz, B., 303 Houle, S., 229 Howes, N. L., 302 Howieson, D. B., 27, 51, 65, 82,

140, 353, 396 Howlin, P. Hoyert, D. L., 409 Hughes, C., 319 Hughett, P., 167 Hulse, S. H., 109 Humphrey, L. L., 174 Hungerbuhler, J. P., 48 Hunter, D., 402 Huntington, G., 434 Hutt, M. L., 74 Huttenlocher, P. R., 117, 247, 272 Hyde, J. S., 167 Hynd, G. W., 117, 274, 277, 279,

281, 302, 303, 304, 324

Ibañez, V., 169, 205 Imperato-McGinley, J., 174 Ingham, J. C., 165 Ingham, R. J., 165 Iqbal, K., 439 Irani, D. N., 111 Ivers, C. E., 337 Ives, D., 87, 146 Ivnik, R. J., 405, 406 Izendoorn, R., 168

Jack, C. R., Jr., 406 Jackson, H., 20–21, 465 Jacobs, A. R., 172, 174 Jacobs, D., 415 Jacobs, R., 117, 167, 247, 281 Jacobson, J. L., 292 Jacobson, M., 389 Jacobson, S. W., 292 Jacoby, R., 413 Jagust, W. J., 406 Jahanshahi, M., 416 James, E. M., 299, 304 James, T. W., 168 James, W., 259, 444 Jane, J. A., 371, 383 Janols, L-O., 330 Jarrold, C., 288, 289, 319 Jasper, H. H., 44 Jeffires, K. J., 335 Jenkins, M. R., 292, 294 Jennett, B., 375, 376, 396 Jensen, J., 319, 335 Jensen, P. S., 322, 323 Jessell, T. M., 116, 118, 301 Jimenez, F., 319 Joanette, Y., 255 Johansson, B., 403, 404, 411 Johnson, D. A., 396 Johnson, S. C., 58

Johnsrude, I., 167 Joly, P., 409 Jones, A. W. R., 418 Jones, C. M., 173 Jones, E., 19 Jones, K. L., 291, 292, 293, 294 Jones, K. W., 282 Jones, R., 317, 319 Jones, Z., 287 Jones-Gotman, M., 471 Jonides, J., 240 Jons, P. H., 324 Jordon, H., 313 Joy, S., 312, 316, 320 Judd, T., 208 Junqué, C., 277, 278, 280 Jurko, M. F., 146 Jusko, T. A., 272

Kaemingk, K., 293 Kahn, R. S., 167 Kail, R. V., 302 Kalat, J. W., 34, 37, 49, 97, 100,

103, 105, 106, 111, 121, 137, 138–139, 142, 143, 148, 151, 182, 186, 188, 201, 216, 217, 234, 457

Kalen, P., 108 Kallenber, C. G. M., 335 Kaminaris, C., 28, 371, 385 Kanappenberger, J., 100 Kandel, E., 301 Kandel, E. R., 106 Kane, M. J., 335 Kanner, L., 311 Kansaku, K., 169 Kant, I., 4 Kaplan, E., 82 Kaplan, H. I., 12 Kapur, S., 229 Karacan, I., 462 Karmiloff-Smith, A., 285, 288 Karni, A., 459 Kater, S. B., 100 Katona, C., 409 Katz, L. C., 128, 146 Kaufer, D. I., 409 Kaufman, A. S., 272, 402 Kaufman, O., 264 Kaufmann, P. M., 250 Kaushall, P. I., 227 Kawas, C., 168 Kawasaki, H., 264 Kay, D. W. K., 409, 424 Kay, G. G., 77 Kaysen, D., 324, 325 Kazak, A. E., 366 Keane, M. M., 235 Kedersha, N., 100 Keenan, J. P., 446 Kemp, S., 294 Kemper, T. L., 404 Kemper,S. J., 402 Kennard, M., 272 Kennedy, C. H., 15, 29, 386–387 Kennedy, D., 324 Kennedy, Michael, 371 Keraclitus, 6

Kerns, K. A., 250, 256, 291, 293, 294

Kerr, D. A., 111 Kertesz, A., 389 Kesler, S. R., 283 Kettunen, S., 292, 294 Kety, S. S., 48 Khan, F., 146, 343, 354 Kibby, M. Y., 302 Kiehl, K. A., 165 Kietrich, K. N., 272 Kigar, D. L., 15 Killeffer, E. H., 409 Kilpatrick, L., 169 Kim, S. W., 255, 256 Kim, Y. H., 242, 246 Kimberling, W. J., 300 Kimura, D., 168 King, G., 196 Kinsbourne, M., 214 Kinsella, G., 396 Kippenhan, J. S., 289 Kirk, U., 294 Kitazawa, S., 169 Kitchen, G., 409 Klatt, E. C., 411, 412, 425 Klein, B. P., 288 Klein-Tasman, B. P., 288, 290 Kleinman, J., 317, 318 Kleist, K., 24 Klin, A., 312, 313, 315, 316, 317,

318 Klunk, W., 409 Knaus, T. A., 167 Knecht, S., 162, 167, 169 Knight, R. T., 238, 256 Knight, S., 460 Knopman, D. S., 406, 412 Knowlton, B. J., 231, 235, 236 Koch, C., 445, 448 Koeppe, R. A., 240 Koff, E., 262, 263 Kohn, P., 289 Kokmen, E., 405 Kolb, B., 116, 124, 158, 159, 160,

163, 168, 272, 273, 276, 315 Koller, K., 272 Kooperberg, C., 174 Kopp, U., 412 Korczyn, A. D., 409 Korf, J., 335 Korkman, M., 292, 294 Korol, D., 174 Kovach, C., 264 Kozel, S. T., 324 Kozinska, D., 44, 46, 54, 58, 359 Kozlowski, G. P., 473 Krakauer, J., 341 Kramer, A. F., 405 Krasuski, J. S., 404 Kravits, D. O., 460 Krawiecki, N., 366 Kraywinkel, K., 351 Krech, D., 18–19, 21 Kringelbach, M. L., 263 Kuller, L., 174 Kunin-Batson, A., 327 Kunkel, D., 97

554 Name Index

Kupfermann, I., 141 Kurth, T., 351 Kushner, H., 283, 284 Kuter, K. C., 174 Kutner, K. C., 172 Kwitny, S., 288, 290 Kwon, H., 317

LaBar, K. S., 242, 246 LaBerge, S., 453 Labiner, D., 465 Lai, Z., 287, 290 Laitinen, V., 146 LaMantia, A., 128 LaMantia, L. C., 146 Lambrecht, L., 318 Lanbphear, B. P., 272 Lancisi, G., 11 Landry, S. H., 277 Lane, D. S., 174 Lang, A. R., 294 Lange, C., 259 Langleben, D. D., 446 Lantigua, R., 409 LaPira, F., 429 Larsen, B., 191 Larsen, J. P., 304 Larson, J., 459 Larsson, M., 168, 402 LaRue, A., 413 Lashley, K., 20 Lassen, N. A., 191 Lawrence, C., 169 Laws, G., 287 Lawson, J. S., 302, 319 Le Courteur, A., 318 Leckman, J. F., 332, 333, 334,

335 Lecours, A. R., 255 LeDoux, J. E., 150, 259–260, 261 Lee, G., 195 Lee, H. C., 404 Lee, K. T., 294 Lee, P., 464 Leech, R. W., 116 Leekam, S., 312 Lees, A. J., 429 Legault, C., 174 Leiguarda, R. C., 195 Lemen, L. C., 167 Lemire, R. J., 116 Lemke, G., 101 Lemoine, P., 291 Leonard, L. B., 302 Letenneur, L., 409 Leventhal, B. L., 318 Levin, B. E., 430 Levin, H. S., 70, 247, 375, 379,

380, 385 Levine, B., 226 Levitin, D. J., 287, 290 Levitsky, W., 27 Levy, J., 51, 167 Levy, L., 272 Levy, R., 413 Lezak, M. D., 27, 51, 65, 82, 140,

353, 365, 396 Li, C. S., 214

Li, X. H., 409 Liberzon, I., 171 Libon, D., 417 Lichter, D. G., 258, 325 Liddle, P. F., 165 Liebenauer, M. A., 324 Lieberburg, I., 174 Lifton, R. J., 15 Lim, K. O., 118 Lima, 25 Limacher, M., 174 Lin, J., 405 Lincoln, A., 287, 290 Linden, M. G., 285 Linnoila, M. I., 108 Lippe, B., 283 Lisowski, F. P., 5 Litchter, D. G., 255 Little, S. S., 309 Litvan, I., 409 Livet, M. O., 288 Livingston, G., 409 Livingstone, M., 301 Lladó, J., 111 Llinas, R., 448 Lloyd, S., 460 Lockhart, P., 325 Loeser, J. D., 116 Lohmann, H., 162, 167, 169 Lois, C., 110 Lombroso, P. J., 117 Long, C. J., 302 Lopez, O. L., 406, 409 Lord, C., 318 Lord,C., 312, 313, 316 Loring, D. W., 27, 51, 65, 82,

140, 195, 353 Lorys, A. R., 304, 324 Lotspeich, L., 317 Loughead, J. W., 446 Loveland, K. A., 328 Lovell, M. R., 383 Lowe, J. B., 285 Lowry, L. D., 187 Lucci, K., 365 Lund, L., 473 Lupien, S. J., 405 Luria, A. R., 21–22, 24, 81, 82,

150, 179 Lusk, L., 118 Lynch, G., 459 Lyon, G. R., 303

M’Lan, C. E., 409 Macciocchi, S. N., 383 MacDonald, A. W., 257 Macintoch, K. E., 313, 318 Macko, K. A., 204 MacLean, P. D., 260 MacLeod, M., 403 Macmillan, M., 255 Madison, A., 45 Magnus, A., 8 Mai, J. K., 157 Maier, S., 293 Majovski, L. V., 120 Malach, R., 200, 205 Malamut, B., 196, 234, 237

Malamut, B. L., 432–433 Mallory, M., 405 Mancini, J., 288 Mandel, R. J., 108 Manela, M., 409 Manson, J. E., 174 Maquet, C. D., 243 Maragakks, N. J., 111 Marans, W. D., 315, 316 Marder, K., 412, 424 Marie, P., 20 Marino, B. S., 277, 281, 282 Marks, D. J., 325 Marks, W., 302 Marois R., 317, 318 Marriott, A. J., 283, 284 Marsden, C. D., 416 Marsh, W. L., 324, 325 Marshall, J. C., 212 Marshall, L. F., 380 Marshuetz, C., 240 Martier, S. S., 292 Martin, C., 165 Martin, D., 323 Martin, J. H., 116, 118, 120 Martinez, A. J., 412 Martinez, P., 323 Martini, D. R., 327 Masliah, E., 405 Mason, C., 301 Massman, P., 323, 334 Mataró, M., 277, 278, 280 Mateer, C. A., 256, 291, 293,

294 Mathalon, D. H., 118 Matochik, J. A., 323 Matsui, M., 167 Mattingly, J. B., 189, 191, 196,

209, 211, 212, 213, 214, 218, 220, 412, 425, 428, 435, 436

Mattson, A. J., 247 Mattson, M., 111 Mattson, S. N., 291, 292, 293,

294 Maurer, K., 410 Maximin, A., 342 Mayes, S. D., 313 Mayeux, R., 409, 412, 424 Mazziota, J. C., 50 Mazzocco, M. M. M., 283 McAuley, E., 174 McCandliss, B. D., 245 McCleary, C. A., 168, 173 McCormick, C. M., 173 McCormick, P. A., 170 McCracken, J. T., 322 McDaniel, M. A., 402 McDiarmid, M. D., 250 McDonough, L., 311 McDougle, C. J., 322 McDowell, S., 245 McGaugh, J. L., 260 McGough, J. J., 323 McIntosh, G. C., 468 McIntosh, J. P., 226 McKeever, W. F., 168, 170 McKinlay, B. D., 336 McLardy, T., 150

McLean, J. E., 402 McMenamin, D., 287 McMillian, J. A., 277, 281, 282 McNamara, J. O., 128, 146 McNulty, K., 409 McPherson, M. W., 20 McxCarthy, R. A., 235 Meador, K. J., 195 Meadows, A. T., 366 Meehl, P., 82, 83 Meeske, K., 366 Melin, L., 473 Mencel, W. E., 304 Menon, V., 283, 317 Mentis, M. J., 283, 404 Menuet, J. C., 291 Merabet, L. B., 205 Merello, M., 195 Mervis, C. B., 285–286, 287, 288,

289, 290 Merz, P. A., 439 Messa, C., 283 Mesulam, M. M., 214, 240, 242,

243, 246 Meyer, J. R., 242 Meyer, M. S., 300, 302 Meyer-Lindenberg, A., 289 Meyer. J. S., 107 Meyers, P. S., 167 Middleton, F. A., 252 Mikiewicz, O., 281 Milberg, W. P., 82 Miller, A., 405 Miller, C. A., 302 Milner, B., 150 Minderaa, R. B., 335 Mink, J., 301 Minoshima, S., 240 Minshew, N. J., 318 Mintun, M. A., 240 Minzer, K., 335 Mirsky, A. F., 242, 245, 246, 326,

327 Mishkin, M., 196, 204, 234, 236,

237 Mitchell, D. R. D., 403 Mixon, A. J., 323 Mobbs, D., 317 Modahl, C., 312, 320 Moffat, S. D., 172 Mohamed, F. B., 446 Mohn, K., 173 Mohr, J. H., 324 Mohr, J. P., 346 Mollowy, E., 325 Molloy, P., 366 Moniz, A. C. E., 25 Monk, C. S., 116, 117 Montenegro, L., 367 Monuteaux, M. C., 323 Moore, A. M., 107 Moore, K., 271 Moossy, J., 412 Morecraft, R. J., 254 Morgan, A. E., 117, 274, 277,

279, 281, 302 Morgan, S., 302 Morrell, M. J., 257

Name Index 555

Morris, C. A., 285–286, 288, 289, 290

Morris, J. D., 204 Morris, J. S., 262 Morris, R. D., 366 Morris, R. G., 319 Morrow, J. D., 405 Mortimer, J. A., 402 Moscovitch, M., 229, 238 Moser, R. S., 381 Mostofsky, S. H., 325 Mueller, F. O., 382 Mullan, S., 465 Mullarkey, S., 283 Muller, R., 120 Munk, H., 20 Munro Culum, C., 415 Murias, M., 328 Murphy, D. G., 283 Murray, A. M., 424 Murray, H. W., 110–111 Muzio, J. N., 455

Nagai, Y., 473 Nagamoto, H., 45 Nair, N. P., 405 Nakamura, R., 448 Nalcioglu, O., 328 Nanayakkara, N., 402 Naugle, R. I., 95, 343, 372 Nauta, W. J. H., 231 Naylor, C. E., 302 Nedergaard, M., 101 Nehme, E., 314 Nelson, C. A., 116, 117 Nelson, D. F., 364 Nelson, H. D., 174 Nelson, L. M., 424 Neppe, V. M., 465 Netter, F. H., 145 Newcorn, J. H., 325 Newman, A. C., 196 Newman, S. W., 280 Newton, A., 396 Nezu, C. M., 323 Nichols, M., 195 Nicoletti, F., 429 Nicolson, R., 336 Nigg, J. T., 271, 329 Nikelski, E. J., 166 Nissanov, J., 52 Nissl, F., 34–35 Noback, C. R., 148 Nobre, A. C., 242, 243, 246 Nockleby, D. M., 397 Nogues, M., 195 Noll, D. C., 257 Nordahl, T. E., 162 Northam, E., 117, 166, 270, 273,

281 Northrup, H., 277, 280 Norton, A. M., 328 Nottebohm, F., 109 Nouzeilles, M. I., 195 Novey, E. S., 304, 324 Nuechterlein, K. H., 242 Nuland, S. B., 343 Nurmi, E. L., 313, 316

Nyberg, L., 229, 253, 258, 330 Nyden, A., 318 Nygren, P., 174

O’Brien, P. C., 406 O’Connor, K. J., 262 O’Doherty, J., 263 O’Donnell, V. M., 70 O’Neal, J. H., 106 O’Riordan, M., 317, 319 Öberg, C., 168 Oberg, G., 435 Obrist, W. D., 48 Ockene, J. K., 174 Odegaard, H., 304 Ogden, J. A., 214 Öhman, A., 262 Ojemann, G. A., 46 Olanow, C. W., 425 Oldfield, R. C., 162 Olds, S. W., 115 Olsen, R. K., 289 Olson, L., 420 Ommaya, A. K., 383 Oommen, K. J., 465 Oosterlaan, J., 328 Osborn, L. M., 335 Osborne, L., 286, 287 Osler, W., 25 Ostbye, T., 409 Osterrieth, P. A., 75, 77 Ozonoff, S., 318, 319, 326, 335

Palmer, C. G., 323 Palmer, P., 321 Palmon, R., 403 Palov, I., 396 Palumbo, D. R., 335 Pantelis, C., 323, 334, 335 Panyavin, I. S., 446 Papalia, D. E., 115 Papez, J. W., 231 Paquette, A., 293 Paradiso, M. A., 180, 194, 261 Pargman, D., 384 Parke, L. A., 299 Parnell, S. E., 293 Parrish, T. B., 242, 246 Pascual-Leone, A., 205 Paterniti, M., 102 Paterson, A., 211 Patient Alice, 468–469 Patient Anna O., 47 Patient Auguste D., 410 Patient B. C., 327 Patient Bertha, 437 Patient David, 86–87 Patient Dr. P., 207 Patient Frank, 377 Patient George, 196 Patient H. M., 229, 234–235 Patient Jeanne, 63 Patient John, 386–387 Patient Jonathan, 206 Patient K. F., 237–238 Patient Leborgne, 17 Patient Lisa, 366–367 Patient M. J., 432–433

Patient Mr. S., 419 Patient Mr. T, 417 Patient Mrs. C., 414 Patient Mrs. R., 414 Patient N. A., 227, 231 Patient Phineas Gage, 255, 259 Patient S. B., 275–276 Patient T. J., 254 Patient Theresa, 386–387 Patient Tom Z., 313, 314–316 Patient U., 253–254 Patrick, R., 401 Pattie, A., 402 Patwardham, A., 283 Pauls, D. L., 333, 334 Pavlides, C., 459 Pavlovic, J., 283 Pavolic, J., 284 Paxinos, G., 157 Payton, A., 323 Peake, T., 365 Pearlson, G., 314 Pearson, D. A., 328 Peck, A., 411 Peele, T. L., 202 Pelletier, P. M., 307, 308 Pellman, E. J., 383 Penfield, W., 25, 44, 150, 183,

465, 472 Pennington, B. F., 247, 250, 251,

284, 299, 300, 301, 302, 305, 313, 319, 320, 321, 322, 326, 334, 336

Penny, J. B., 435 Perry, W., 78 Persaud, T., 271 Persutte, W. H., 293 Petersen, R. C., 405, 406 Petersen, S. E., 204, 207, 240 Peterson, A. C., 110, 331 Peterson, B. S., 324, 333, 334,

335 Petitto, L. A., 166 Petri, H. L., 236 Petrides, M., 240 Petropoulos, H., 324 Pfefferbaum, A., 118 Pfrieger, F. W., 101 Phan, K. L., 171 Phelps, E., 50 Phelps, E. A., 262 Phend, N., 446 Phillips, L., 403 Phillips, P.C., 310, 366 Phillips, S. M., 174 Phillips, W., 311 Piaget, J., 248 Pianka, P., 205 Pichardo, M., 174 Pietrini, P., 283 Piggot, J., 317 Pilgrim, D. M., 424 Pillon, B., 427, 429, 430 Pincus, J. H., 95, 150 Pinel, P. J., 190, 230, 232–233,

457 Piven, J., 314, 321 Plaisted, K., 317, 319

Platek, S. M., 446 Plato, 4, 6 Pliszka, S. R., 299, 324 Pober, B., 286, 287 Poca, M. A., 277, 278, 280 Polani, P. E., 282 Polcari, A., 325 Polkey, C. E., 319 Polster, M. R., 107 Pons, T., 185 Poppel, E., 389 Popplestone, J. A., 20 Portin, R., 428 Posner, J., 364 Posner, M. I., 240, 243, 244, 245,

326, 327, 328 Postma, A., 168 Potegal, M., 436 Pouk, J. A., 396 Powell, M. P., 284, 285 Power, T. J., 323 Powers, W. J., 344, 345 Pratt, P., 335 Presley, R., 304 Preston, J. D., 106 Pribram, K. H., 150 Price, C. J., 166 Prigatano, G. P., 396, 397 Primeua, M., 327 Prior, J., 313 Prior, M., 312 Pritchard, P. B., 473 Pruisiner, S. B., 439 Pugh, K. R., 167, 169, 303, 304 Purcell, E., 51 Purcell, R., 323, 334, 335 Purves, D., 128, 146 Purves, K. L., 329 Pythagoras, 6

Quenzer, L. F., 107

Radcliffe, J., 366 Raichle, M. E., 49, 207 Rakic, P., 117 Ranamurthi, B., 150–151 Ransom, B., 101 Rao, G. R., 412 Rao, M. S., 111, 167, 169 Rapp, S. R., 174 Raskin, S. A., 427, 428 Rasmussen, T., 40, 470 Rawles, J. M., 118 Raz, A., 245 Raz, N., 205, 404, 405 Read, S., 416, 417 Reader, M. J., 325 Reagan, Ronald, 373 Rebok, G. W., 407 Rees, J. R., 15 Reilly, J., 274 Reisberg, B., 406 Reiss, A. L., 283, 287, 325 Reitan, R. M., 25, 71, 80, 183,

246, 353 Reiter, J., 466 Relkin, N., 412 Renshaw, P., 324, 325

556 Name Index

Rey, G. J., 75, 173, 281, 430 Reynolds, B. A., 110, 331 Reynolds, C. R., 163, 252, 279,

286, 396–397, 402 Rhodes, R., 437 Richard, A., 466 Richardson, J. S., 418 Richter, K., 169, 170, 323 Richters, J. E., 322 Riepe, M. W., 168, 169 Riley, E. P., 291, 292, 293, 294 Rimel, R. W., 371, 383 Ring, H. A., 319 Ringelstein, E. B., 167 Rinne, U., 428 Ris, M. D., 272 Risi, S., 318 Risser, A. T., 270, 272, 281 Ritzler, B., 15 Rivero, A., 195 Rizzo, J. R., 205 Robbins, T. W., 254, 319 Robert, A. C., 254 Roberts, J. E., 168, 169, 170 Robertson, M. M., 333, 335 Robinson, A., 285 Robinson, B. F., 287 Robinson, B. W., 287 Robinson, D. L., 204 Rockwood, K., 409 Rodgers, M. A., 170 Roe, K., 274 Roeltgen, D. P., 283, 284 Roffwarg, H. P., 455 Rogers, S. J., 311, 319 Roland, P. E., 191 Rolls, E. T., 186, 256, 263, 264 Romans, S. M., 283, 284 Romanski, L. M., 316, 317 Romine, C. B., 252 Röntgen, W. C., 36 Ropper, A. H., 142 Rose, V., 342, 462 Rosen, A. D., 48 Rosenberg, H. M., 409 Rosenblum, J. A., 150 Ross, E., 431 Ross, J. L., 283, 284 Rosser, A. E., 111 Rosvold, H. E., 246 Rotman, M., 364 Rourke, B. P., 298, 305, 306, 307,

308, 309, 318 Rousseau, A., 473 Rovee-Collier, C., 236 Rovet, J. F., 174, 283, 284, 285 Rowe, A. D., 319 Rowe, D. C., 324 Rowland, L. P., 278 Roy, A., 108 Rubens, A. B., 208 Rubenstein, B. S., 459 Rubin, A. J., 440–441 Rubin, L., 278 Ruchinskas, R. A., 381 Ruff, R. M., 380–381 Rumsey, J. M., 299, 301, 303,

311

Ruparel, K., 446 Rusconi, M. L., 212 Russell, J., 319 Russell, W. R., 150 Rutherford, M. D., 311, 319 Rutledge, N., 315 Rutter, M., 313, 318 Rutter, W., 311 Ryan, T. V., 383

Sabb, F. W., 257 Sach, M. L., 384 Sache-Lee, C., 302 Sacks, O., 184, 206, 207, 259 Sadato, N., 169, 205 Sadock, B. J., 12 Sadovnick, A. D., 98 Sagar, H., 430 Sagi, D., 459 Sahuquillo, J., 277, 278, 280 Saint-Cyr, J. A., 252 Saitoh, O., 316 Sakamoto, M., 173 Salmon, D. P., 415, 416, 430 Salo, R., 162 Salthouse, T. A., 403 Sampson, P. D., 292, 293, 294 Samuel, W., 405 Sandberg, A. D., 318 Sanders, G., 173 Sandroni, P., 212 Santi, S., 405 Santoro, J. M., 396 Saper, C. B., 456 Sarason, I., 246 Sarter, M., 241 Saucier, D. M., 167 Saunders, A. M., 412 Sawaya, G., 174 Scahill, L., 322, 335 Scalf, P., 174 Schacter, D. L., 227, 234, 235,

236 Schatschneider, C., 302 Schatz, P., 381 Schechter, R., 411 Schiller, F., 17, 149 Schmahmann, J., 406 Schmechel, D. E., 412 Schmidt, J. F., 435 Schmitt, J. E., 287 Schnaberth, G., 429 Schneider, J. A., 28, 371, 385, 405 Schneider, W., 55 Schoenbach, C., 335 Schooler, C., 335 Schreibman, L., 311 Schubert, A. B., 325 Schuck, S., 328 Schulte, T., 284, 285 Schultz, K. P., 325 Schultz, R. T., 286, 287, 312, 313,

315, 316, 317, 318, 325, 333, 335

Schwartz, J. H., 106, 301 Scott, C. B., 364 Scoville, W. B., 150 Segal, M., 100

Seldon, G., 448 Selman, W. R., 131 Selz, M., 299, 304 Semendeferi, K., 254 Semrud-Clikeman, M., 304, 324 Seshadri, S., 409 Seurinck, R., 169, 170 Shallice, T., 237, 320 Shaman, P., 189 Shamblott, M. J., 111 Shannon, K. M., 424 Sharp, W., 325 Shatz, M. W., 345, 351 Shaw, D. W., 317 Shaywitz, B. A., 167, 169, 301,

303, 304 Shaywitz, S. E., 167, 169, 301,

303, 304 Shen, C., 406 Sheppard, D. M., 323, 334, 335 Sherman, G. F., 287 Sherman, S. L., 324 Sherwin, B. B., 174 Shimizu, Y., 313 Shiung, M. M., 406 Shults, C. W., 430 Shumaker, S. A., 174 Shuster, A., 300, 302 Siegel, L. S., 299 Siegel-Hinson, R. I., 168, 170 Sigman, M., 317, 321 Silverman, I., 168 Silverstein, S. M., 335 Simon, R. P., 277 Sinder, M., 226 Singer, H. S., 325, 335 Singh, J., 335 Sitaram, N., 107 Sjöstrand, L., 108 Skinholf, E., 191 Skinner, B. F., 396 Skottun, B. C., 299 Skovronek, E., 403 Skudlarski, P., 167, 169, 304 Slabbekoorn, D., 173 Small, B. J., 402 Small, G. W., 412 Smalley, S. L., 323 Smernoff, E., 45 Smirni, P., 429 Smith, A., 72 Smith, C. A., 168, 173 Smith, C. C., 413 Smith, D. W., 185, 291, 292 Smith, E. E., 240, 429 Smith, G. E., 405, 406 Smith, J., 336 Smith, S., 284 Smith, S. D., 300 Snead, O. C., 468, 472 Snowdon, D. A., 402 Snyder, A. Z., 207 Snyder, J. L., 384 Snyder, L. H., 214 Sokol, R. J., 292 Soliveri, P., 416 Somers, D. C., 205 Somerville, R. A., 439

Sommer, I. E. C., 167 Sommer, T., 245 Sorensen, S., 435 Sowell, E. R., 324 Sparks, E. R., 317 Sparrow, S., 315, 316 Speed, W. C., 300, 302 Spence, M. A., 328 Spencer, T. J., 322 Sperry, R. W., 151 Spiers, M. V., 21, 103, 109, 173,

179, 184–185, 211, 227, 358, 396, 410, 414, 435, 438, 453–454

Spillane, J. A., 413 Spinnler, H., 237 Spitzer, M., 168, 169 Spohr, H. L., 294 Spreen, O., 270, 272, 281, 288,

429 Springer, J. A., 162, 167, 169,

255 Springer, S. P., 51, 151 Spurgeon, A., 272 Spurzheim, J., 14 Spyker, D., 365, 367 Squire, L. R., 227, 231, 234, 235,

236, 237 Squrie, L. R., 415 Stahl, S. M., 108 Stahmer, L., 311 Stanczyk, F. Z., 168, 173 Stangl, D. K., 333 Starkstein, S. E., 314 Starr, J. M., 402 Stebbins, G. T., 335 Stein, B. M., 346 Stein, J. F., 299 Steingard, R., 324 Steinhausen, H. C., 294 Stelmack, R. M., 307 Stenger, V. A., 257 Stern, C., 294 Stern, Y., 409, 412, 424 Stevens, T., 409 Stevens-Graham, B., 101 Stewart, B., 383 Stiles, J., 273, 274 Stone, B. H., 299 Stone, V., 317, 319 Storili, O. V., 385 Stowe, R., 409 Strang, J. D., 308, 309 Strassburger, T. L., 404 Straus, E., 287 Streissguth, A. P., 291, 292, 293,

294 Stricanne, B., 214 Strick, P. L., 252 Strittmatter, W. J., 412 Stroop, J. R., 246 Stuber, M. L., 366 Stuss, D. T., 238, 251, 256, 320 Succop, P. A., 272 Sullivan, E. V., 118, 430 Sullivan, K., 287 Surrat, P. M., 462 Sutcliffe, J. S., 313, 316

Name Index 557

Svendsen, C. N., 111 Swanik, C. B., 384 Swanson, H. L., 301, 302, 328 Swanson, J., 328 Swanson, S. J., 162 Szczepaik, J., 404

Tadevosyan-Leyfer, O., 316 Tagaris, G. A., 169, 170 Tager-Flusberg, H., 287 Talaga, M. C., 106 Talley, J. L., 77 Tamm, L., 283 Tang, M. X., 325, 412, 424 Tangalos, E. G., 405 Tanguay, P. E., 311, 313, 316,

321, 323 Tanne, D., 459 Tannock, R., 329 Tarshish, C., 405 Tatton, W. G., 425 Taylor, S. F., 171 Teasdale, G., 375, 376, 396 Teicher, M. H., 325 Teillon, S. M., 173 Temple, C. M., 283, 284, 288 Terry, R. D., 407, 411, 413 Teuber, H. L., 18, 20, 25 Teutsch, S. M., 174 Thagard, P., 257 Thal, D., 274 Thal, L., 174 Thiede, K., 292 Thiele, E. A., 472 Thomas, K. M., 120 Thomas, P., 335 Thompsen, I. V., 396 Thompson, P. M., 324 Thompson, S. J., 311 Tierney, E., 322 Tinker, J., 28, 371, 385 Toga, A. W., 324 Tombaugh, T. N., 78 Tomczak, R., 168, 169 Tomer, R., 430 Tonucci, F., 287 Toole, J. F., 346 Toth, J. P., 226 Tottenham, M., 334, 335 Townsend, J. P., 316 Tran, T., 325 Tranel, D., 169, 170, 253, 255,

256, 257, 258, 262 Träskmann, L., 108 Trauner, D., 274 Trenholme, I., 460 Treves, T. A., 409 Trimble, M. R., 473 Troster, A. I., 415 Trumpter, A. L., 323 Tsatsanis, K. D., 316, 317 Tucher, A. M., 383 Tuciker, D., 328 Tucker, G. J., 95 Tulandi, T., 174 Tulving, E., 228, 229 Turetsky, B. I., 167 Turner, Tina, 401

Tweed, D. L., 333 Tweedy, J., 427, 428 Tysvaer, A. T., 385

Ueckert, S., 432 Ulleland, C. N., 291 Ullrich, O., 282 Ullsperger, M., 257 Ungerleider, L., 204

Vaituzis, A. C., 118 Vaituzis, C. V., 324, 325 Valenstein, E., 23, 210, 212 Vallar, G., 212, 237 van de Poll, N. E., 173 Van den Broeck, W., 299 Van der Gaag, C., 317, 318 van Emde Boas, W., 464 van Goozen, S. H., 173 Van Hoesen, G. W., 218, 254,

411 Van Raalte, J. L., 42 Vandenberghe, R., 243 Vanneste, J. A. L., 130, 131 Varney, N. R., 288, 429 Vaughn, M., 117, 274, 277, 279,

281 Venneri, A., 310 Verrees, M., 131 Vesalius, A., 8–9 Viano, D. C., 383 Vicarti, S., 287 Victor, M., 98, 142 Vienbergs, I., 405 Vigil, J., 324, 325 Vignolo, L. A., 74 Vilkki, J., 146 Villardita, C., 429 Vingerhoets, G., 169, 170 Vining, E. P., 472 Virchow. R., 344 Virues-Ortega, J., 342 Vitiello, B., 323 Voeller, K. K. S., 308 Vogt, B. A., 257 Vogt, M. B., 185 Volk, S., 410 Volkmar, F. R., 312, 313, 315,

316, 317, 318 Volterra, V., 287 von Cramon, D. Y., 257 von Monakow, C., 388 von Senden, M., 205 von Stockert, F. G., 426 Vonsattel, J. P., 435 von Steinbuchel, N., 389 Vouloumanos, A., 165 Voyer, D., 167, 168, 169, 170,

174 Voyer, S., 167, 168, 169 Vygotsky, L. S., 21

Waber, D. P., 273 Wada, J., 40, 470 Wade, D., 264 Waechtler, C., 146, 343, 354 Wagar, B. M., 257 Wager, T. D., 171, 257

Wagner, M., 351 Wahlin, A., 402 Wakely, J., 99 Waldemar, G., 435 Waldman, I. D., 324 Waldo, M., 45 Walker, J. F., 473 Walker, Z., 409 Wallace, R. B., 174 Wallcke, P. A., 430 Wallesch, C., 255 Walt, V., 172 Walter, J. M., 325 Walter, R. D., 465 Walton, J. N., 348 Wang, A. T., 317 Wang, L. N., 409 Wang, Q. S., 405 Wapner, W., 208 Ware, J. C., 342, 462 Waring, S. C., 405 Warosfsky, I. S., 283 Warrington, E. K., 235, 237 Warsofsky, I. S., 283 Wass, T. S., 293 Wassertheil-Smoller, S., 174 Waterhouse, L., 312, 316, 320 Watkins, J. M., 283 Watson, J., 20, 212, 445 Watson, T., 304 Wattam-Bell, J., 289 Watts, C., 111 Watts, J. W., 22, 25 Webb, A. G., 405 Webb, S. J., 116, 117 Webbe, F., 385 Wechler, D., 246 Weigand, S. D., 406 Weimar, C., 351 Weinand, M. F., 465 Weinberger, D., 49 Weiner, J., 335 Weiskrantz, L., 254 Weiss, G., 330 Weiss, M., 331 Weiss, S., 110 Weiten, W., 228, 455 Weksberg, R., 291 Welch, M. C., 247, 250 Welcome, S. E., 324 Wells, S., 14 Weng, X-C, 325 Werker, J. F., 165 Wernicke, C., 18, 25 West, J. R., 293 West, L. L., 335 Wexler, A., 434 Whalley, L. J., 402 Whang, K., 169, 170 Wheatley, M., 110, 331 Wheelwright, S., 319 Whishaw, I. Q., 168, 276, 315 White, B. J., 283 White, C. D., 283 White, N. S., 169 White, R., 409 Whitman, S., 473 Whyte, J., 245, 395

Wickramaserkera, I., 122 Wigal, S., 328 Wilder, D. E., 409 Wilens, T. E., 323 Wilkins, R. H., 18 Willerman, L., 315 William, S. D., 146 William, S. M., 128 Williams, J. C. P., 285 Williams, R. L., 462 Williams, R. W., 96 Williams, S. C., 319 Willis, A. L., 408, 426 Willis, K. E., 278, 279,

281 Willis, T., 11, 131 Willis, W. G., 277, 299 Willms, J., 294 Wilson, R. S., 335, 405 Wilson, S. A. K., 426 Wimmer, A., 429 Wing, L., 312 Winner, E., 287 Winocur, G., 238 Winson, J., 458, 459 Wiser, J., 367 Wishaw, I. Q., 124, 158, 159,

160, 163 Wisneiwski, H. M., 439 Witelson, S. F., 15 Witol, A., 385 Wohl, C., 110, 331 Wolf, P. A., 409 Wolff, H., 21 Wolfson, C., 409 Wolfson, D. B., 25, 71, 80, 183,

353, 409 Wood, E., 460 Wood, F. B., 299, 300, 302 Wood, M. H., 299 Wrennall, J., 166, 270, 273,

280 Wright, R., 19 Wrightson, P., 380 Wunderlich, A. P., 168, 169 Wundt, W., 445 Wyler, A. R., 465

Xu, Y., 406

Yaffe, K., 174 Yaffee, L. S., 328 Yamura, A., 169 Yan, M., 167 Yang, L., 325 Yao, R. A., 325 Yatsu, F. M., 346 Yeo, R. A., 324 Yeterian, E. H., 218 Young, A. B., 435 Young, I. M., 187 Youpa, D., 328 Yousem, D. M., 364 Yunkin, D., 48

Zaccai, J., 424 Zahory, E., 205 Zaichik, D., 406

558 Name Index

Zald, D.H., 255, 256 Zamerkin, A. J., 323 Zametkin, A. J., 324 Zang, Y-F., 325 Zangwill, O. L., 27, 211 Zanobio, M. F., 237 Zappala, G., 429 Zarit, S. H., 403

Zatorre, R. J., 166 Zec, R. F., 417, 420 Zeitlin, H., 333 Zeki, S., 204 Zelko, F., 327 Zeng, Y-W., 325 Zetin, M., 227 Zhang, H., 335

Zhou, J. N., 405 Zhu, M. W., 409 Zihl, J., 204 Zillmer, E. A., 15, 19, 21, 22, 23,

28, 29, 36, 37, 38, 42, 52, 53, 64, 65, 66, 72, 73, 74, 75, 77, 78, 84, 86–87, 98, 103–104, 122, 146, 156–157, 196,

250–251, 327, 341, 342, 343, 346, 348, 354–355, 358, 365, 367, 371, 373–374, 381, 384, 462

Zin, Z., 325 Zipursky, R. B., 118 Zola-Morgan, S., 231 Zubenko, G. S., 412

Name Index 559

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Ablation experiment, 19 Abscesses, 363 Absence seizures, 450, 467 Abulia, 258 Acceleration, 373 Accidents, 371 Acetylcholine (ACh), 106

Alzheimer’s disease impact on, 412–414 characterization of, 107 cognitive enhancement, 420 orientation systems and, 244 REM sleep and, 459

ACh. See Acetylcholine Achievement tests, 68 Achromatopsia, 204 Acidophilic adenomas, 361 Acoustic neuroma, 360 Acquired dyslexia, 299 Acquired sociopathy, 256 ACTH. See Adrenocorticotropic hormone Action potential, 97, 102–104 Activities of daily living (ADL), 392, 394–395 ADHD. See Attention-deficit/hyperactive

disorder ADL. See Activities of daily living Adolescence, 294 Adrenocorticotropic hormone (ACTH),

142, 142 Affective assignment, impaired, 320 Agenesis, 270 Ageusia, 187 Aging

Alzheimer’s disease versus, 414 brain changes associated with, 404–405 cognitive changes, 401–404 dementia and, 406–409 environmental factors, 404–405 genetic factors, 404–405 intelligence and, 401–403 MCI and, 405–406 normal, 400–405 Nun Study, 402 sleep pattern changes, 454

Agnosia, 18, 178 apperceptive visual, 207, 208, 209 associative visual, 207, 208, 210 tactile, 178 visual object, 207

Agyria, 117 Air encephalography, 36 Akinesia, 193 Akinetic mutism, 258 Akinetopsia, 204 Alcohol

anticoagulant properties, 377 consumption, 351

Alcohol-related neurodevelopmental disabilities (ARND), 292

Alexia. See Acquired dyslexia Alpha activity, 41 Alpha waves, 452 ALS. See Amyotrophic lateral sclerosis Alternating attention, 241 Alzheimer’s disease, 237, 409–421

ACh agonists and, 107 clinical presentation, 413–420, 415

attention, 418 consciousness, 418 executive functioning, 418 intellectual functioning, 417–418 language deficits, 416–417 memory, 413 motor functions, 418 personality changes, 418–419 semantic knowledge breakdown,

415–416 sensory functions, 418 speech deficits, 416–417 visuospatial functioning, 417

diagnostic problems, 409–410 discovery of, 410 environmental factors, 404–405 genetic factors, 404–405 histologic markers, 411–413 imaging, 78–79, 413 incidences, 409 MCI versus, 405–406 neuropathology of, 411 neurotransmitters and, 412–413 normal aging and, 414 treatment, 420–421

Alzheimer, Alois, 410, 437 Amino acid glutamate, 413 Amino acids, 108, 108–109 Amnesia

anterograde, 386–387 case study, 227 causes of, 226 declarative memory and, 231, 234–235 nondeclarative memory and, 235–236 retrograde, 386–387 types of, 226

Amygdala, 149 Alzheimer’s disease and, 411 autism and, 317, 318 connections, 150 emotions and, 260–262 epilepsy and, 465 fear conditioning, 261 smell processing and, 188–189

Amyloid plaques, 412 Amyotrophic lateral sclerosis (ALS), 111

Androgens, 171 Anencephaly, 117, 276 Angiography, 349, 362

application, 38–39 clinical use, 40 defined, 38 digital subtraction, 39 femorocerebral, 39 intravenous, 39 technique, 39

Angular gyrus, 217, 303 Anomia, 220 Anomic aphasia, 221 Anopias, 201 Anosmia, 189 Anosognosia, 20 Anoxia, 341–342 ANS. See Autonomic nervous system Anterior attention system, 245 Anterior cerebral arteries, 132 Anterior cingulate circuit, 257–258 Anterior commissure, 151 Anterograde amnesia, 226

Alzheimer’s patients with, 415 head injuries and, 386–387 long-term memory, 227

Anterograde degeneration, 372 Anticholinergic drugs, 431, 433 Antidiuretic hormones, 141 Apathy, CVA-induced, 356–357 Aphasia

characterization, 219 CVA-induced, 356 fluent aphasia, 18 Freud’s view of, 19 frontal operculum damage and, 162 in seizures, 465 origins of, 16 subtypes, 221 types, 219–221

Apnoia, 342 ApoE3, 412 ApoE4, 412 Apperceptive visual agnosia, 207,

208, 209 Apraxia

CVA-induced, 356 defined, 72 speech, 219 subtypes, 193, 195 types, 72–73

Arachnoid membrane, 126 Arachnoid villi, 129 Aristotle, 157 Armagan, Esref, 205 Armstrong, Lance, 360

S U B J E C T I N D E X

Note: Page numbers in boldface type indicate pages on which terms are defined or introduced.

561

ARND. See Alcohol-related neurodevelopmental disabilities

Arousal. See Orientation Arteries, cerebral, 131–133 Arteriovenous malformations (AVMs), 347 Articulation, 220 Articulatory difficulties. See Dysarthrias Articulatory phonologic loop, 238, 302 Artificial grammar, 236 Ascending spinal-thalamic tract, 181 Asociality, 320 Asperger’s syndrome, 311

autism versus, 313 case study, 314–316 characterization, 312 cognitive profiles, 318 neuroimaging testing, 314–315 research on, 312–313

Association areas, 160 Associative visual agnosia, 207, 208, 210 Astereognosis. See Tactile agnosia Astrocytes, 99, 100–102 Astrocytomas, 359 Astrogliosis, 438–439 Asymmetry, 161–163 Ataxia, 351 Atherosclerosis, 345 Atomoxetine (Strattera), 331, 336 Atonia, 458 Attention, 240–246

Alzheimer’s patients, 418 assessing, 71–72 cerebral cortex, 241–242 characterization of, 241–242 CVAs effect on, 352–353 disorders, 242 executive function and, 258–259 extended selective, 320 memory and, 258–259 models of

Mesulam’s, 242–243 Mirsky’s elements, 245–246 Posner’s, 243–245

neuropsychology of, 240 subcortical structures influencing, 240–241

Attention-deficit/hyperactive disorder (ADHD)

assessment, 326 autism and, 319 case study, 327 characterization, 322 clinical presentation, 322 comorbid conditions, 323 demographics, 322–323 developmental course, 330–331 executive planning and, 250–251 FAS and, 294–295 genetic influences, 323–324 neural substrates, 324–325 neuropsychological modes

Barkley’s, 328–330 Mirsky’s, 326–327 Posner’s, 327–328

pathogenesis, 323–325 treatment, 331, 336 TS and, 283

Auditory pathways, 45 Auditory processing. See also Language; Speech

Alzheimer’s patients, 415 damage to, 217–218 higher, 215–219 mechanical receptors, 215 pathways, 216 primary, 215

Auras, 348, 464–465 epileptogenic focus, 465 sensory, 472 tactile, 473

Autism assessment, 318–320 brain size and, 316 characterization, 311 clinical presentation, 311 cognitive profiles, 318 comorbid conditions, 311–312 comprehensive neurofunctional model,

320–321 demographics, 311–312 developmental course, 321 high-functioning, 312–313 musicality and, 290 pathogenesis, 313–318 social cognition, 319–320 treatment, 321–322

Autistic aloneness, 311 Automatic processes, 449 Autonomic nervous system (ANS),

121, 122 Autosomes, 282 AVMs. See Arteriovenous malformations Awareness, phonologic, 301, 302 Axonal sprouting, 372 Axons, 95, 96–98

development, 117 firing, 95 function of, 96 regrowth, 389 speed transmission, 97 terminal buttons, 98

BAER. See Brainstem auditory-evoked response

Balint’s syndrome, 208 Basal forebrain, 107

anatomy, 233 characterization, 134 declarative memory and, 231

Basal forebrain cholinergic complex (BFCC), 413

Basal ganglia ADHD and, 325 anatomic features, 147 characterization, 147 function, 148–149 GTS and, 334–335 hyperfiring, 433 implicit memory and, 237 Parkinson’s and, 425 structure, 147–148

Basal nuclei. See Basal ganglia Base rates, 68 Basilar arteries, 131 Basolateral circuit, 149 Basophilic adenomas, 361 BEAM. See Brain electrical activity mapping Behavior

Alzheimer’s patients, 421 anterior cirgulate circuit role, 257–258 as tumor symptom, 361 autism and, 311 compulsive, 334 CVA-induced changes, 356–357 disruptive (See Disruptive behavioral

disorders) impulsive displays, 357 utilization, 256

Behavioral examinations, 56–57 Behavioral therapies, 396–397 Behavioral-adaptive scales, 68 Bell-shaped curve. See Normal probability

distribution Bender Gestalt test, 74–75 Benign tumors, 358 Benton Visual Retention Test (BVRT), 26 Benzodiazepines, 472 Beta activity, 41 Beta-amyloid, 412 BFCC. See Basal forebrain cholinergic complex Binding problem, 447 Biofeedback, 449, 473 Bipolar neurons, 98 Bleeding, intracranial, 378 Blindness

case study, 205 hemianopia, 203 homonymous, 203

Blindsight, 204 Blood clots. See Thrombosis Blood oxygen level dependent MRI, 54 Blood vessels, 349–350 Blood-brain barrier

ACh crossing of, 107 astrocytes’ role, 100 chemotherapy complications, 362 impairment of, 344

BOLD. See Blood oxygen level dependent MRI Bovine spongiform encephalopathy (BSE),

437–438 Brady, James, 373 Bradykinesia, 427 Bradyphrenia, 418 Brain. See also specific regions

ACh role, 107 adult’s, 273–274 amino acids’ role in, 108–109 anatomic divisions of, 136 anomalies, dyslexia and, 302–304 arteries to, 131–133 autonomic system, 449–450 axon development, 117 basic anatomy of, 11 cell bodies, 95 child’s, 273–274 CNS anatomic relationship, 122–123 computer conceptualization, 445 consciousness and, 444–447 convolutional development, 118–119 death, 104 dendrite development, 117 development

anatomic, 116–121 anatomic abnormalities, 274–281 chromosomal disorders, 281–291 functional, 116–121

562 Subject Index

genetic disorders, 281–291 injurious effects on, 271–273 lead exposure and, 271–272 lobular, 118–119 plasticity, 270–273 postnatal, 120 regional, 118 ventricular, 119–120 vulnerability, 270–273

divisions of, 133–134 evolution of, 156–157 hemispheres (See Cerebral hemispheres) herniation, 376–377 injury (See Traumatic brain injury) lobes of, 9 metabolism imaging (See Imaging

techniques) myelination, 117–118 Nazi’s views of, 15 neuron formation, 109 nuclei in, 99 peptide role in, 109 planes of, 123 plasticity of, 205, 272–273, 389 protection of

meninges, 125–127 skull, 125 vascular system, 131–133 venous system, 133 ventricular system, 127–131

pruning, 118 size, 156–157, 316 stem cells in, 110 structure, gender differences, 168–169 synaptogenesis, 117 total volume, 120 trephination, 5–6, 13 tumors (See Tumors) vascular system, 125 ventricular system, 125

Brain damage pathologic process, 340–341

anoxia, 341–342 hydrocephalus, 342 lesions, 340–341

Brain disorders abscesses, 363 developmental

acquired disorders, 291–295 case study, 275–276 chromosomal disorders, 281–291 FAS, 291–295 genetic disorders, 281–291 hydrocephalus, 276–281 NVLD-associated, 307 TS, 282–285 WS, 285–291

disruptive behavioral, 322–332 infections, 363–364 neglect and, 208, 210–211 neurotoxin-associated, 365 pervasive developmental, 310–322 tic, 332–337

Brain electrical activity mapping (BEAM), 44 Brain function

anatomic discoveries, 8 cell doctrine, 7–8 early hypotheses, 5–13

functional model, 21, 24 Greek hypotheses, 6–7 integrated theories, 20–24 localization theory, 13–20 non-Western attitudes, 12–13 nonscientific theories, 4

Brain hypothesis, 6 Brain injuries. See also Head injuries

brain reorganization following, 389 complications, 376–379

edema, 376 hemorrhages, 377–378 herniation, 376–377 intracranial bleeding, 378 post-traumatic epilepsy, 379 skull fractures, 378–379

forensics and, 28 impact of, 274

Brain warts. See Neuronal ectopias Brain waves, 41–42 Brainstem, 134, 134–147

ACh in, 107 characterization, 134 lower

cranial nerves in, 138 function, 138 reticular formation, 139–141 structure, 137–138

REM sleep and, 458 strokes in, 350 upper

evolution, 141 hypothalamus, 141–146 thalamus in, 143–146

Brainstem auditory-evoked response (BAER), 44–46

Broadmann’s areas 1, 182 17, 203 18, 203 19, 203 2, 182 3, 182 5, 182 7, 182

Broca’s aphasia, 220 Broca’s area

discovery of, 16–18 dyslexia and, 304 hemispheric differences, 163 lesions in, 18 major cortical language area and, 217

Brodmann’s area, 159, 160 Brodmann’s areas, 158 BSE. See Bovine spongiform encephalopathy BVRT. See Benton Visual Retention Test

CAH. See Congenital adrenal hyperplasia Canalesthesia, 320 Cannon-Bard theory, 259 Carbidopa, 431 Cardiac hypothesis, 7 Cartographers, 58 Cataplexy, 462, 463 Catechol-O-methyltransferase (COMPT), 324 Catecholamines, 106, 413 Category test, 196 Caudate nucleus, 147, 434–435

CBF. See Cerebral blood flow CD. See Conduct disorder Cell bodies, 95, 99 Cell doctrine, 7, 8 Cells, 94

nerve (See Neurons) receptor, 177, 184

Cellular migration, 116–117 Central executive, 238 Central nervous system (CNS), 94. See also

Spinal cord ACh function in, 107 as dementia reference map, 440 brain anatomic relationship, 122–123 cellular migration, 116–117 collateral sprouting, 111–112 components of, 122–124 microglia in, 100 neurogenesis, 116–117 planes of, 123 PNS communication, 121 protection of, 122, 124 stem cells in, 110–111

Central sleep apnea, 462 Central sulcus, 158 Cerebellar peduncles, 137 Cerebellum

ADHD and, 325 anatomic features, 146 autism and, 316–317 characterization, 134 CJD and, 438 function, 147 motor processing by, 195 structure, 146–147

Cerebral aqueduct, 128 Cerebral blood flow (CBF), 47 Cerebral cortex

Alzheimer’s disease and, 411–412 attention and, 241–242 blood supply to, 135 consciousness and, 447 primary auditory, 215 primary emotions and, 260–262 smell processing and, 188–189

Cerebral hemispheres anatomic differences, 163–167 anatomic features, 155 asymmetry, 161–163 behavioral differences, 166–167 child’s, 273 consciousness and, 445–446, 449 CVA-induced deficits, 353–356 differences in, discovery, 16 dominance, 161–163 dyslexia and, 303 function, 159–161 functional differences, 163–167 gender differences

empirical studies, 167–171 examples, 167 sex hormone’s role, 171–175

gray matter composition, 163–164 higher order processing, 166 language processing and, 218 lateralization, 88, 161–163, 165 major divisions, 158 neuropsychological differences, 166–167

Subject Index 563

Cerebral hemispheres (continued) NVLD and, 306–307 secondary emotions and, 262–264 specialization, 167–175 structure, 155–159 white matter composition, 163–164

Cerebrospinal fluid (CSF), 36 Alzheimer’s patients, 412 function of, 119–120 hydrocephalus and, 276, 342 sample collection, 56 severed neurons and, 341 in ventricular system, 128–130

Cerebrovascular accidents (CVAs), 131 anterior, 356 attention deficits, 352–353 behavioral changes following, 356–357 characterization, 343 clinical presentation, 344 diagnosing, 343, 347–349 disconnection syndrome, 352 disinhibition, 352 emotional changes following, 356–357 ethnically-based risks, 351 heredity, 351 left-hemisphere, case study, 354–355 lifestyle indices, 351 location, 350 migraines and, 348 neuropsychological deficits, 351–357 posterior, 356 premorbid factors, 350 prevention, 350–351 recovery, 349 rehabilitation, 390 risks factors, 351–352 treatment, 350

Cerebrovascular disorders diagnosing, 347–349 onset age, 343 overview, 342–343 stroke (See Cerebrovascular accidents) types of, 344–347

Cerebrum, 134 Chemical senses

evolution of, 184 smell, 187–189 taste, 184–187

Chemical transmission, 104–105 Chemoreceptors, 180 Chemotherapy, 362, 364 CHIs. See Closed head injuries Children

absence seizures in, 450 behavioral therapy for, 396–397 brain tumors, 361 brain tumors, case study, 366–367 chemotherapy’s effects, 364 with FAS, 291–295 with Turner’s syndrome, 283–285 with WS, 286–291

Chlordane, 365, 367 Chlorinated hydrocarbons, 365, 367 Cholesterol, 351 Choline, 107 Chorea, 436 Choroid plexus, 128 Chromophobic adenomas, 361

Chromosomal disorders, 281, 283 Chromosomal parental imprinting, 281 Cigarette smoking, 351 Cingulate gyrus, 149 Cingulate motor area (CMA), 190, 191 Cingulum, 151 Circadian rhythms, 444

light and, 456 patterning of, 456 sleep onset, 456 specialization, 456

Circle of Willis, 131, 132, 134 Circuit of Papez, 231, 234, 260 Cisterns, 129 CJD. See Creutzfeldt-Jakob disease Clomipramine (Anafranil), 336 Clonidine (Catapres), 336 Closed head injuries (CHIs)

causes, 373, 375 forces and, 375 sports related, 28 types of, 373

CMA. See Cingulate motor area CNS. See Central nervous system Cocktail party syndrome (CPS), 280 Cognition

aging effects on, 401–404 Alzheimer’s patients, 421 control, 335 CVA-induced deficits, 353–356 EEG abnormality and, 472 enhancement, 420–421 HD patients, 435–436 menopause and, 174–175 mental exercises effects, 403 post-THI changes, 386 retraining, 395 subcortical dementia and, 426

Collateral blood vessels, 349 Collateral sprouting, 111 Colorblindness, 206 Comas, 375, 450 Complex partial seizures, 464, 468–469 Complex tics, 332–333 Comprehensive neurofunctional model,

320–321 COMPT. See Catechol-O-methyltransferase Compulsive behaviors, 334 Computed transaxial tomography (CT)

behavior-based assessments, 78–79 cerebrovascular disorder detection by, 349 defined, 36 development of, 33 enhanced, 38 history of, 36–37 neuropsychological evaluation, 57 scan interpretation, 38 TBI assessment by, 331 technique, 37–38 tumors diagnosis by, 361–362

Computer model of mind, 445 Concentration, 71–72 Conceptual apraxia, 195 Concussions. See Closed head injuries (CHIs) Conduct disorder (CD), 323 Conduction aphasia, 221 Confrontation naming tests, 416 Congenital adrenal hyperplasia (CAH), 174

Consciousness, 444 Alzheimer’s patients, 418 anatomic correlates, 447–449 rhythms of, 449–451 self, 446 understanding, 444–449

Construct validity, 67 Content validity, 67 Contiguous object task, 248 Continuous positive airway pressure (CPAP),

462 Controlled Oral Word Association (COWA), 74 Coprolalia, 333 Copropraxia, 333 Corpus callosum, 151

ADHD and, 324 anatomic features, 151 dyslexia and, 304 function, 151–152 structure, 151

Cortical dementia, 408, 411 Cortical localization

critics of, 18–20 Equipotential versus, 20 era of, 16–18

Cortical visual processing, 203 Corticogenesis, 117 Corticotrophin, 413 Countercoup injury, 375 Covert orientation, 244 COWA. See Controlled Oral Word Association CPAP. See Continuous positive airway pressure CPS. See Cocktail party syndrome Cranial nerves

characterization, 121 function, 139 location, 138

Cresyl violet, 34 Creutzfeldt, Hans Gerhard, 437 Creutzfeldt-Jakob disease (CJD)

characterization, 436–437 clinical presentation, 439 neuropathology, 438–439 neuropsychological profile, 439

Criterion validity, 67 Cronbach’s alpha, 67 Crystallized functions, 69 Crystallized intelligence

Alzheimer’s patients, 418 characterization, 401 sexuality and, 387

CSF. See Cerebrospinal fluid CT. See Computed transaxial tomography Cubitus valgus, 282 Cushing’s syndrome, 361 Cutoff score, 84 CVAs. See Cerebrovascular accidents CYLN2. See Cytoplasmic linker 2 Cytoplasmic linker 2 (CYLN2), 286

D4 receptor gene, 323 DA. See Dopamine Data interpretation, 79–89

deficit measurement, 86–88 pathognomonic signs, 88–89 process approach, 81–84 standard battery approach, 80–81 statistical approaches, 85

564 Subject Index

Deadly Feasts (Rhodes), 437, 438 Death

accident-associated, 371 brain, 104 gunshot-induced, 373 neuronal firing and, 104

Deceleration, 373 Declarative memory, 227

brain structures, 229, 231 consolidation, 229, 231 encoding, 229 function of, 229 retrieval, 229

Decussate, 137, 201 Deep brain stimulation, 433–434 Deep dyslexia, 299 Defective response inhibition, 193 Deficit measurement, 86–88 Delayed response task, 248–249 Delta activity, 41 Delta waves, 452 Dementia, 406–409. See also Alzheimer’s disease

advancement, hierarchical level, 440 case studies, 441 clinical course, 440 diagnostic criteria, 407 drug-related, 409 heritable factors, 440–441 idea density studies, 402 lateralization, 440 neurologic examination, 440–441 Parkinsonism and, 424 respite care, 421 risk factors, 440–441 subcortical, 237 subtypes, 408–409 symptoms, 440–441 syndrome, 406, 441

Dendrites, 95 development, 117 function, 95–96 Purkinje cells, 96

Depolarization, 102–103 Depression

Alzheimer’s patients, 419–420 CVA-induced, 356 dorsolateral circuit and, 253–254

Detour reaching task, 249 Developmental dyslexia, 299 Diabetes, 351 Diaschisis, 388–389 Diencephalon, 118

anatomy, 232 declarative memory and, 231 evolution of, 141 hypothalamus in, 141–142 thalamus in, 143–146

Differential score approach, 87–88 Differential-preservation hypothesis, 403 Differentiation, 116 Digital subtraction angiography, 39 Directional impairment, 207 Disconnection syndrome, 352 Disengage, move, and engage, 328 Disinhibition, 103 Disruptive behavioral disorders, 322–332. See

also Attention-deficit/hyperactive disorder

Dissociation, 191, 195 Disturbances of motility, 311 Divided attention, 241 Dominance, 161–163 Dopamine (DA), 108

pathways, 108 receptor genes, 324, 334 thresholds, 425 transporter gene (DAT1), 324

Doppler-ultrasonography (fTDC), 163 Dorsal column medial lemniscal pathway, 181 Dorsal processing systems

coordination of, 204 disorders of, 204, 207–208 dyslexia and, 304 WS effects on, 289

Dorsolateral circuit, 253–254 Dorsolateral prefrontal cortex, 192 Double dissociation, 18 Down’s syndrome, 287, 290 Dreaming

conscious, 453 lucid, 447, 453–454 REM sleep and, 451, 460–461 theories of, 460

Drugs and medication anticholinergic, 409, 431, 433 antiepileptic, 468, 472 antipsychotic, 149 cholinergic, 420 neuronal firing and, 104 opiate receptors, 109–110 psychoactive, 104 psychostimulant, 331–332, 336 stroke treatment, 350

Dysarthrias, 219, 393 Dysgenesis, 270 Dysgeusia, 187 Dyskinesia, 431 Dyslexia, 299–304

autism and, 318 brain regions associated with, 302–304 genetics and, 300, 302 neuropathogenesis, 302–304 phonologic model of, 301–302 prevalence, 299 twin studies, 302 types of, 299 visual processing model, 299–301

Dysosmia, 189

Echolalia, 311 ECoG. See Electrocorticography Ectopias, neuronal, 303 Edema, 376 Edinburgh Inventory, 162 EEG. See Electroencephalography Ego, 19 Einstein, Albert, 157 Elastin (ELN) gene, 286 Electrical stimulation, 45–46 Electroconvulsive therapy, 104 Electrocorticography (ECoG), 43 Electrodermal nonresponders, 242 Electroencephalography (EEG), 40–44

biofeedback, 473 brain wave activity, 41–42 clinical use, 43

consciousness and, 448 development of, 33 emotional expression and, 252 neuropsychology and, 43–44 SAS, 461 seizures and, 42–43, 470 technique, 41 while sleeping, 451–452, 454

Electromyography (EMG), 47 Electrophysiologic procedures, 40–47

EEG, 40–44 electrical stimulation, 45–46 EMG, 47 evoked potential, 44–45

Embolisms, 346, 350 EMG. See Electromyography Emotions, 259–264

Alzheimer’s patients, 418–420 brain organization and, 260–264 CVA-induced changes, 356–357 dorsolateral circuit and, 253–254 frontal lobe maturation and, 252 frontal lobe mediation, 253–258 gender differences, 171 HD patients, 436 impulsive displays, 357 in NVLD children, 308 memory and, 260 orbitofrontal circuit and, 254–257 Parkinson’s patients, 430–431 phantoms of, 184–185 primary, 260–262 secondary, 262–264 theories of, 259–260 WS and, 290

Encode attention, 246 Endorphins, 109 Endothelium, 345 Enhanced CT, 38 Enuresis, 294 Environmental dependency syndrome, 256 Epidural space, 126 Epilepsy, 444

case study, 468–469 characterization, 464 déjà vu, 465 EEG and, 43 post-traumatic, 379 postictal phase, 466 seizures

anatomy, 467–469 clinical presentation, 469–472 complex partial, 464 generalized, 466 grand mal, 464 neurophysiology, 467–469 partial, 466–467 petit mal, 464 simple, 466–467

treatment, 472–473 Epileptic syndrome, 444 Epileptogenic focus, 465 Episodic buffer, 238 Episodic memory, 228 EPSP. See Excitatory postsynaptic potential Equipotentiality, 19, 20 ERP. See Evoked potential Euphoria, CVA-induced, 357

Subject Index 565

Evoked potential BAER, 44–46 SER, 45 technique, 44 VER, 45

Evolution brain size, 156–157 chemical senses, 184 diencephalon, 141 medulla oblongata, 137 midbrain, 137 upper brainstem, 141

Excessive daytime sleepiness, 462 Excitatory postsynaptic potential (EPSP), 106 Executive attention system, 245 Executive functioning, 246–258

ADHD children and, 250–251, 326 Alzheimer’s patients, 418 anterior cingulate circuit, 257–258 attention and, 258–259 autism and, 318–319 case study, 255 development, 247, 250–252 dyslexia and, 302, 304 frontal lobe mediation

anterior cingulate circuit, 257–258 dorsolateral circuit, 253–254 orbitofrontal circuit, 254–257

HC effects on, 281 memory and, 258–259 Parkinson’s patients, 429–431 subcortical dementia and, 426 tasks, 248–249

Executive planning, 319 Explicit memory, 227–228 Expressive aphasia, 219 Extended paraphasia. See Paragrammatism Extended selective attention, 320 Extradural hematomas, 377 Extrapyramidal motor system, 148, 148

Facial expressions autism and, 317 secondary emotions and, 263 WS and, 288

Faculty psychology, 13–20 FAE. See Fetal alcohol effects False positives, 67–68 Familial sinistrality, 173 Family therapy, 355–367 FAS. See Fetal alcohol syndrome Fear conditioning, 261 Feelings. See Emotions Femorocerebral angiography, 39 Festinating gait, 427 Fetal alcohol effects (FAE), 292

assessment, 293–294 development course, 294 treatment, 294–295

Fetal alcohol syndrome (FAS), 291 assessment, 293–294 clinical features, 291–292 comorbid conditions, 293 development course, 294 incidence, 292 neuropathogenesis, 292–293 treatment, 294–295

FFA. See Fusiform face area Fibers, 99 Fibrin, 351 FISH. See Fluorescent in situ hybridization Fissures, 156 5-HT. See Serotonin Flicker fusion rate, 299 Fluency tasks, 415–416 Fluent aphasia, 18, 219 Fluid functions, 69 Fluid intelligence, 402, 403–404 Fluorescent in situ hybridization (FISH), 286 Focus-execute attention, 246 Focused attention, 241 Fontanelles, 125 Football injuries, 382–383 Foramen of Magendie, 129 Foramen magnum, 125 Foramen of Monro, 127 Foramina, 125 Forebrain (prosencephalon), 118 Forensic neuropsychology, 28, 78 Fornix, 149, 231 Fossae, 125 Fragile X syndrome, 316 Frontal lobes, 158

ADHD and, 324–325 aging and, 404 anterior cingulate circuit, 257–258 autism and, 317 dyslexia and, 304 function, 160 functioning (See Executive functioning) injury to, 396 orbitofrontal circuit, 254–257 stroke-damage, 352

Frontal operculum, 162 fTCD. See Doppler-ultrasonography Functional MRI, 54, 55 Functional systems, 24 Functioning adenomas, 360 Fusiform face area, 317, 318

G-meters, 375 GABA. See Gamma-aminobutyric acid Galveston Orientation and Amnesia Test

(GOAT), 70 Gamma activity, 41 Gamma-aminobutyric acid (GABA), 43

memory consolidation and, 459 properties of, 109 seizures and, 468, 472

Ganglia, 99 GBM. See Glioblastoma multiforme GCS. See Glasgow Coma Scale Gender differences

Alzheimer’s disease rates, 409 autism, 312 emotions, 171 GTS, 333 hemispheric specialization

examples of, 167 sex hormone’s role, 171–175 studies of, 167–171

math skills, 172 meningioma incidences, 359 sexual hormones and, 171–175

spatial processing, 169–170 sports injury risks, 384 verbal ability, 174

General transcription factor 2-1 (GTF21), 286–287

Genetics ADHD, 323–324 autism and, 313, 314, 316 brain aging and, 404 HD and, 434 learning disabilities, 300, 302 WS and, 286–287

Gerstmann-Straussler-Scheinker syndrome (GSS), 437

Gigantocellular tegmental field (GTF), 458 Gilles de La Tourette syndrome. See Tourette

syndrome Glasgow Coma Scale (GCS), 375–376 Glial cells, 94

characterization, 99 myelin sheath formation and, 97 tumors (See Gliomas) types of, 99–100

Glioblastoma multiforme (GBM), 359 gender differences, 361 neuropsychological deficits, 363

Gliomas, 100, 359 Global aphasia, 221 Global processing, 289 Globus pallidus, 147 Glucose, 120 Glutamate, 109 GOAT. See Galveston Orientation and

Amnesia Test Golgi stain, 34 Gonadotropins, 284 Grade of tumor, 358 Grand mal seizure, 464 Grandmother cells, 447 Granulations. See Arachnoid villi Gray matter, 95

autism and, 316 cerebral hemispheres and, 164

Group therapy, 395 GSS. See Gerstmann-Straussler-Scheinker

syndrome GTF. See Gigantocellular tegmental field GTF21. See General transcription factor 2-1 GTS. See Tourette syndrome Guanfacine, 336 Guanfacine (Tenex), 336 Gunshot wounds, 373 Gyrification, 118, 119

Haldol (haloperidol), 149 Hallucinations, hypnagogic, 463 Haloperidol (Haldol), 334, 336 Halstead-Reitan Neuropsychological Battery, 77 Handedness, 162 HC. See Hydrocephalus HD. See Huntington’s disease Head injuries. See also Brain injuries

adaptation, 388–389 mild, 379–385

impact of, 380 postconcussional syndrome, 385 postconcussive syndromes, 381

566 Subject Index

research on, 379–380 sports-related, 381–382

traumatic (See Traumatic brain injury) Headaches. See Migraines Hematomas, 346, 377 Hemianopia blindness, 203 Hemiplegia, 386 Hemispheres. See Cerebral hemispheres Hemispheric-Encoding-Retrieval-Asymmetry

model (HERA), 229 Hemorrhage, 346, 350 Hemorrhages, 344, 377–378 Heparin, 350 HERA. See Hemispheric-Encoding-Retrieval-

Asymmetry model Herpes encephalitis, 363–364 Heschl’s gyrus, 163, 215, 217 Hidden object task, 248 High blood pressure. See Hypertension High vocal center (HVC), 109 Higher order processing, 166 Higher order systems, 225 Higher visual processing

case studies, 205–206 dorsal streams

coordination of, 204 disorders of, 204, 207–208, 210–215

identification, 204 ventral streams disorders, 204

Hinckley, John Jr., 373 Hindbrain (rhombencephalon), 118 Hippocampus

Alzheimer’s disease and, 412 commissure, 151 complex, 230 declarative memory and, 229 epilepsy and, 465 formation, 149 REM sleep and, 458 smell processing and, 188–189 strokes in, 350, 353

HIV/AIDS, 363–364, 408 Homonymous blindness, 203 Hooper Visual Organization Test, 81 Hormones. See Sexual hormones Horseradish peroxidase (HRP), 35 HRP. See Horseradish peroxidase Humors, 8 Huntington’s disease (HD), 109, 436

characterization, 434 clinical presentation, 435–436 development, 237 diagnostic imaging of, 435 heritability of, 435 impaired learning and, 235 neuropathology, 434–435 neuropsychological profile, 435–436

HVC. See High vocal center Hydrocephalus, 342 Hydrocephalus (HC), 130

assessment, 279–281 clinical presentation, 276 executive functions and, 281 impact of, 277–278 incidence, 276 memory deficits, 280 neuropathogenesis, 277

obstructive, 277 physiological dynamics, 277 treatment, 278, 281

Hyperacusis, 286 Hypercalcemia, 286 Hyperdensity, 38 Hyperserotonemia, 316 Hypertension

aneurysms and, 347 CVAs and, 351 TIAs and, 345

Hypertonia, 286 Hypnagogic hallucinations, 462, 463 Hypodensity, 38 Hypogeusia, 187 Hypokinesia, 427 Hypometabolism, 413 Hyposmia, 189 Hypothalamus

anatomic features, 141 function, 141–142 sleep onset and, 456 structure, 141

Hypothesis approach. See Process approach Hypoxia

causes, 341–342 SAS and, 461 sleep apnea, 461

Hypotonia, 286

Ice-9, 439 ICP. See Intracranial pressure Id, 19 Idea density, 402 Ideomotor apraxia, 72–73, 195 Imaging techniques

3-D, 57–58 advances in, 57–60 behavioral examinations and, 56–57 CBF, 47–48 diagnostic applications, 59–60 future directions, 58 MRI, 51–56 PET, 49–51 SPECT, 48–49

Impact injury, 375 Impaired affective assignment, 320 Implicit memory, 227–228, 235–236 Implicit priming, 235–236 Impulsiveness, 357 Infarctions, 345–346

aneurysms, 347 AVMs, 347 embolism, 346 hemorrhage, 346 intracerebral hemorrhage, 346 left middle cerebral artery, 355 subarachnoid hemorrhage, 347 thrombosis, 345–346

Infections, 363–364 Inferior colliculi, 138 Infiltrative tumors, 358 Inhibitory control, 329, 330 Inhibitory postsynaptic potential (IPSP), 106 Initiation, lack of, 357 Innerbrain. See Diencephalon Insecticides, 365

Insomnia, 450 Intelligence

aging and, 401–403 Alzheimer’s patients, 417–418 autism and, 312 tests, 68 verbal scales of, 401

Intercerebral fibers, 99 Interference control, 328, 330 Internal carotid arteries, 131 Interneurons, 98 Interpretation of Dreams, The (Freud),

460 Intracerebral fibers, 99 Intracerebral hemorrhage, 346 Intracranial bleeding, 378 Intracranial pressure (ICP), 344

head injury and, 376, 377 reducing, 385–386 tumor and, 361

Intracranial tumors characteristics, 358 infiltrating, 359 noninfiltrating

acoustic neuroma, 360 meningiomas, 359–360 metastatic, 360 pituitary, 360–361

Intravenous angiography, 39 Intraventricular hemorrhage (IVH), 277 Ions, 102 IPSP. See Inhibitory postsynaptic potential Irreversible dementia, 408–409 Ischemia, 344 Isochromosomes, 283 IT15 gene, 434 IVH. See Intraventricular hemorrhage

Jacksonian seizures, 467 Jamais vu, 467 James-Lang theory, 259 Joint attention, 311 Joint contractures, 286 Judgment

CVA-induced deficits, 353, 357 neuropsychological tests, 76–78

Judgment of Line Orientation Test, 429

K neurons. See Pacemaker cells Karyotype, 282 Kennard principle, 272 Kennedy, John F., 434 Ketogenic diet, 472 Kinesthetic sense, 183 Korsakoff ’s syndrome, 231, 237, 415 Kuru, 437, 438

Lacunar infarctions, 346 Language

brain systems and, 218 breakdown of, 219–221 fluency tasks, 415–416 function, in childhood, 273–274 learning, 216–217 neuropsychological tests, 73–74 Parkinson’s patients, 430 pragmatics of, 308

Subject Index 567

Language (continued) stroke damage to, 356 written, 356 WS effects on, 287–288

Lateral fissures, 158 Lateralization, 161–163, 165 Lead exposure, 271–272 Learning. See also Memory

aging effects on, 402 classic, 236 motor skills, 416 procedural, 234

Learning disabilities, 298–310 diseases associated with, 235, 436 genetics of, 300 incidents of, 298 nonverbal, 305–310 verbal (See Dyslexia)

Left brain strokes, 355–356 Lesions

brain, 340–341 thalamus, 146

LevoDopa, 431 Lewy bodies, 424–425 Lewy body dementia, 427 Lexicon stores, 304 Lifestyles, 351 LIM-Kinase (LIMK1), 286 LIMK1. See LIM-Kinase Limb-kinetic apraxia, 195 Limbic system

Alzheimer’s disease and, 411 anatomic features, 149 autism and, 317 characterization, 149 function, 149–151 smell processing and, 188–189 structure, 149

Lissencephaly. See Agyria Lobotomies, 22–24 Lobular development, 118–119 Localization theories, 13

cortical, 16–20 modern, 24–27 phrenology, 13–15

Locus ceruleus, 108 Long-term memory (LTM), 226

Alzheimer’s patients, 415 STM versus, 237–240 subtypes

declarative, 227–229, 231 episodic, 228 explicit, 227–228 implicit, 227–228 nondeclarative, 227, 231, 234–237 procedural, 227 semantic, 228

taxonomy, 228 Long-term potentiation (LTP), 459 Longitudinal fissure, 151 Lou Gehrig’s disease. See Amyotrophic lateral

sclerosis LTM. See Long-term memory LTP. See Long-term potentiation Lucid dreaming, 447, 453–454 Lumbar puncture, 56 Lyme disease, 86–87

MacCracken, Henry M., 383 Magnetic resonance imaging (MRI), 51–56

Alzheimer’s patients, 413 behavior-based assessments, 78–79 case study, 52 clinical use, 54–55 development of, 33, 51, 53 functional, 54, 55 HD patients, 435 MEG, 56 neuropsychological evaluation, 57 procedures, 56 TBI assessment by, 381 technique, 53 tumors diagnosis by, 361–362 VBR and, 58

Magnetoencephalography (MEG), 56 Magnocellular visual system, 299, 300 Magnocellular-deficit theory, 299 Malignant tumors, 358 Malingering, 78 Mammillary bodies, 149 Man Who Mistook His Wife for a Hat, The

(Sacks), 178, 207 MAO. See Monoamine oxidase MAO-B. See Monoamine oxidase B Masked facies, 427 Masking, 262 Materialism, 4 Math skills, 172 MCI. See Mild cognitive impairment (MCI) Measles-mumps-rubella immunization, 313 Mechanical receptors, 180, 215 Medial lemniscus, 182 Medial temporal lobe, 229, 231 Medication. See Drugs and medication Medulla oblongata, 134, 137 Medulloblastomas, 361 MEG. See Magnetoencephalography Membrane potential. See Resting potential Memory. See also Learning

Alzheimer’s patients, 413, 415 attention and, 258–259 characterization, 225–226 CVA-induced deficits, 353 disorders, 226 emotions and, 260 epilepsy and, 472 executive function and, 258–259 gender differences, 168 HC children, 280 long-term

Alzheimer’s patients, 415 components of, 227 conceptualization, 226 STM versus, 237–240 subtypes, 227–237

neuropsychological tests, 75–76 Parkinson’s patients, 430 prospective, 402–403 radiation-induced deficits, 364 REM sleep and, 459 scientific understanding of, 226 short-term

Alzheimer’s patients, 416 conceptualization, 226 LTM versus, 237–240

temporal order, 302 verbal, 76–77 visual, 77 working, 238

Meningiomas, 359–360 Meninges, 122

function, 126–127 structure, 125–126

Meningiomas, 125 Meningitis, 126

causes, 126–127 characterization, 363–364

Menopause, 174 Mental rotation, 169 Mentalism. See Theory of mind Metacognition, 307 Metastasis, 358 Metastatic tumors, 360, 363 Metencephalon, 118 Methylene blue, 34 Methylphenidate (Ritalin), 334 Microglia, 99, 100 Micrographia, 427 Midbrain (mesencephalon), 118, 137 Middle cerebral arteries, 132 Migraines, 348 Migratory process, 116 Mild cognitive impairment (MCI),

405–406 Mind-blindness, 20 Mind-brain relationship

dualism, founder of, 11 in sleep, 451–463

anatomy, 456 architecture, 451–456 dreams and, 460–461 physiology, 456 RAS and, 456–459

relationship, 445–447 Mirror self-misidentification syndrome,

446 MMR. See Measles-mumps-rubella

immunization Mohammed Ali, 424 Molecular cytogenic anomalies, 281 Monoamine oxidase (MAO), 324 Monoamine oxidase B (MAO-B), 431 Monopolar neurons, 98 Mood. See Emotions Mosaic karyotypes, 283 Motility, disturbances of, 311 Motor apraxia, 72 Motor learning tasks, 416 Motor neurons, 98 Motor perseveration, 193 Motor processing

Alzheimer’s patients, 418 cerebellum, 195 CJD patients, 439 CVA-induced deficits, 352–353, 355 HD patients, 436 sleep and, 454 subcortical, 195–197 TS-induced deficits, 284

Motor systems, 189–197 characterization, 189 cortical areas of, 189–192

568 Subject Index

disorders of, 193, 195 extrapyramidal, 148 functions, testing, 192–193 Parkinson’s and, 427–428

MRI. See Magnetic resonance imaging MS. See Multiple sclerosis Multiple infarcts dementia, 408 Multiple sclerosis (MS), 98 Multipolar neurons, 98 Muscarinic choline, 107 Musicality, 289–290 Mutism, 258 Myelencephalon, 118 Myelin sheath, 97 Myelin stain, 35 Myelination, 97, 117–118

Naming speed, 302 NAN. See National Academy of

Neuropsychology Narcolepsy, 444, 462–463 National Academy of Neuropsychology

(NAN), 30 NE. See Norepinephrine Neanderthals, 156–157 Necrosis, 341, 351–352 Neglect

case study, 211 clinical presentation, 212–213 neuropathology of, 211–212 theories of, 213–214

Neocortex, 448 Neologism, 311 Neoplasms. See Tumors Nerve growth factor (NGF), 420 Nerve tissues, 45–46 Nervous system. See also Central Nervous

System; Peripheral nervous system brain’s control of, 447 immature, 389 opiate receptor sites, 109 organization of, 121

Neural tube, 116, 117 Neuritic plaques, 411–412 Neurofibrillary tangles, 404 Neurohistology, 34–35 Neurologic examinations, 56–57 Neurologists, 27 Neuromas, 358 Neuronal cell death. See Necrosis Neuronal ectopias, 303 Neuronal firing, 104 Neurons, 4, 94–102

action potential, 102–104 axons, 96–98 cell body, 95 chlordane effects on, 367 classification, 98–99 communication among, 105–110 communication within, 102–104 conduction speed, 97–98 development, 116–117 features, 96 function, 95–99 grandmother, 447–448 in seizures, 464 neurotransmitters, 106–110

new, formation of, 109 organization of, 99 pruning of, 118 random patterns, 467 regeneration, 110–112 resting potential, 102 severed, 340–341 short-circuiting, case study, 98 spatial coding, 459 stroke-damage, 351–352 structure of, 95 supersensitivity, 389 synaptic transmission, 105–106 TBI-induced changes, 372 terminology, 98–99

Neuropsychiatrists, 27 Neuropsychological Assessment (Lezak), 27 Neuropsychological evaluations, 57

epilepsy, 469–472 orientation, 69–70 rational, 65–66 reasons for, 63–65 referrals for, 66 rehabilitation programs, 390 websites, 89–90

Neuropsychological tests, 67–79, 75–76

attention, 71–72 base rates, 68 concentration, 71–72 data interpretation, 79–84 defined, 68 false positives, 67–68 general considerations, 63–66 judgment, 76–78 language, 73–74 memory, 75–76 motor skills, 72–73 norms, use of, 84 perception, 70–71 problem solving, 76–78 psychometric issues, 66–68 reliability, 67 sensation, 70–71 sports injury related, 384 stroke damage assessment, 355 symptom validity, 78 types, 68–69 validity, 67 verbal function, 73 visuospatial organization, 74–75 websites, 90

Neuropsychologists, 27 Neuropsychology, 4

careers in, 27 EEG and, 43–44 emerging research in, 27–29 forensic, 28 major journals, 26 modern history of, 24–27 NAN’s home page, 30 PET and, 50–51 in rehabilitation, 391–392 sports and, 28 term origin, 25 terrorism and, 28–29 time line, 29

Neuroscientists, 27 Neurosurgeons, 27 Neurotoxins, 365, 367 Neurotransmitters, 95. See also specific

neurotransmitters active in REM sleep, 458 Alzheimer’s disease impact on, 412–413 classification of, 107–110 distribution of, 106 function of, 103–104 pathways, 107 seizures and, 468–469 structure, 106

NGF. See Nerve growth factor Nicotinic choline, 107 Nissl stains, 34–35 Nociceptors, 180 Nocturnal myoclonus, 454 Nodes of Ranvier, 97 Non-rapid eye movement (NREM) sleep,

42 characterization, 450 EEG during, 451–452, 454 state of consciousness during, 452, 454

Noncommunicating hydrocephalus. See Obstructive hydrocephalus

Nondeclarative memory, 227 amnesia and, 235–236 brain circuitry governing, 236–237 characterization, 231 implicit priming, 235–236 learning and, 234–235 Parkinson’s patients, 430

Nondeclarative tasks, 416 Nonfluent aphasia, 219 Nonfunctioning adenomas, 360 Noninfiltrative tumors, 358 Nonverbal learning disability syndrome

(NVLD), 304 assessment, 307–308 brain anomalies and, 306–307 clinical features, 306 clinical presentation, 305 comorbid conditions, 305 core features, 306 developmental course, 309 evolution, 309–310 neuropsychological model, 308–309 pathogenesis, 305–307 prevalence, 305 socioemotional characteristics, 308 treatment, 309

Norepinephrine (NE), 108 orientating systems, 245 REM sleep and, 459

Normal probability distribution, 85 Normal-pressure hydrocephalus (NPH),

130, 131 Novelty seeking, 323 NPH. See Normal-pressure hydrocephalus NREM. See Non-rapid eye movement NRT. See Nucleus reticularis thalami Nuclei, 99

basal, 147 hypothalamic, 141 thalamus, 144, 146

Nuclei of the raphe, 108

Subject Index 569

Nucleus ceruleus, 458 Nucleus reticularis thalami (NRT), 468 Nun Study, 402 NVLD. See Nonverbal learning disability

syndrome

Obesity, 351 Object permanence, 247 Observations, qualitative, 88–89 Obsessions, 334 Obsessive-compulsive disorder (OCD)

characterization, 334 effects of, 337 treatment for, 336

Obstructive hydrocephalus, 277 Obstructive sleep apnea, 462 Occipital lobes, 158

blindness and, 205, 389 function, 160 REM sleep and, 458 seizures and, 467 visual processing and, 203–204

Occipital notch, 158 Occlusion, 345 Occupational therapy, 392, 393 OCD. See Obsessive-compulsive disorder ODD. See Oppositional defiant disorder Olfactory information processing, 166 Olfactory system, 187–189 Oligodendrocytes, 97 Oligodendrogliomas, 359, 363 On Narcissism (Freud), 19 On the Origin of Species (Darwin), 16, 156 Opiate receptors, 109–110 Oppositional defiant disorder (ODD), 323,

326 Orbitofrontal circuit, 254–257 Organization of Behavior, The: A

Neuropsychology Theory (Hebb), 25 Organs, definitions of, 13 Orientation

GOAT, 70 spheres, 69–70 testing, 69

Overcorrection, 322 Oxygen uptake. See Necrosis Oxygen, positron-labeled, 51 Oxytocin, 141

Pacemaker cells, 42 Pallidotomy, 433–434 PANDAS, 334 Papez circuit, 149 Papillae, 184 Paragrammatism, 220 Parahippocampal gyrus, 149 Parasympathetic Nervous System (PNS),

121 Parietal lobes, 158 Parkinson’s disease (PD), 424–434

case study, 432–433 characterization, 424 clinical presentation, 425–431

executive functioning, 429–431 language, 430 memory, 430 motor system, 427–428 personality changes, 430–431

speech, 430 visuospatial deficits, 428–429

impaired learning and, 235 neuropathology, 424–425 symptoms, 424 treatments, 431–434

Paroxetine (Paxil), 336 Partial seizures, 444, 466–467 Parvocellular visual system, 299 Pathognomonic signs, 88–89 Pathways, 99

auditory, 45, 216 DA, 108 neurotransmitter, 107 somatosensory, 181–182 visual, 201

Patrick, Ruth, 401 Pattern analysis, 88 Pattern theory of taste, 185 PD. See Parkinson’s disease Penetrating head injuries, 373, 374 Peptides, 109, 110 Perception, 70–71 Performance, assessing level of, 84–86 Peripheral nervous system (PNS)

ACh function in, 107 ANS function in, 122 cellular migration, 116–117 CNS communication, 121 components of, 122 ganglia in, 99 neurogenesis and, 116–117 Schwann cells in, 97, 100 stem cells in, 110

Personality tests, 68 Pervasive developmental disorders, 310–322

autism clinical presentation, 311 comorbid conditions, 311–312 demographics, 311–312 developmental course, 321 neurofunctional model, 320–321 neuropsychological assessment, 318–320 pathogenesis, 313–318 treatment, 321–322 types, 312–313

distinguishing features, 310 etiology, 310

PET. See Positron emission tomography Petit mal seizure, 464 Phantogeusia, 187 Phantoms, 184–185 Phantosmia, 189 Phenylketonuria (PKU), 270 Phonemic paraphasias, 221 Phonologic awareness, 301, 302 Phonologic model of dyslexia, 301–302 Phrenology, 13–20 Physical therapy, 392, 393 Physostigmine (Synapton), 420 Pia mater, 126 Pinealomas, 361 Pittsburgh Sports Concussion Program, 383 Pituitary stalk, 141 Pituitary tumors, 360–361, 363 PKU. See Phenylketonuria Planum temporale, 163, 302 Plaques

amyloid, 412 neuritic, 411–412 sclerotic, 98

Plasticity, 272, 389 Platelets, 345 Pluripotentiality, 24 PMA. See Premotor area Pneumoencephalography. See Air

encephalography PNS. See Peripheral nervous system Polymicrogyria, 271 Polymodal areas. See Association areas Pons, 134, 137 Porencephaly, 271 Positron emission tomography (PET), 33

Alzheimer’s patients, 413 behavior-based assessments, 78–79 characterization, 49 neuropsychology and, 50–51 postnatal development studies, 120 subtraction procedures, 57 technique, 49–50 verbal encoding using, 48

Positron-labeled oxygen, 51 Post-traumatic amnesia (PTA), 387 Post-traumatic epilepsy, 379 Posterior attention system, 244 Posterior cerebral arteries, 131 Posterior communicating arteries, 132 Postictal phase, 466 Postnatal development, 120–121 Pragmatics of language, 308 Precursor cells, 116 Prefontal cortex, 117 Pregnancy, 292 Premotor area (PMA), 190, 191 Prepotent response, 328 Preserved-differentiation hypothesis, 403 Prestriate cortex. See Secondary association Primary auditory cortex. See Heschl’s gyrus Primary emotions, 260–262 Primary motor cortex, 160

anatomy of, 178 role of, 190 somatosensory cortex and, 190–191

Primary sensory cortex, 178 Primary visual processing, 201–204

characterization, 201 disorders of, 201–203 functional areas, 203–204 retinotopic map, 203–204

Priming tasks, 416 Prion proteins (PrPs), 439 Problem solving tests, 76–78 Procedural learning, 234 Procedural memory, 227 Process approach, 81–84 Progenitor cells, 116 Progressive dementia, 408 Projection fibers, 99 Proprioception, 178, 183 Proprioceptors, 181 Prosopagnosia, 207 Prospective memory, 402–403 PrPs. See Prion proteins Pruning, 95, 118 Pseudopsychopathic sociopathy. See Acquired

sociopathy

570 Subject Index

Psychoactive drugs, 104 Psychologist, 27 Psychology, 4 Psychometrics, 67 Psychomotor epilepsy, 467 Psychostimulant medication, 331–332 Psychosurgery, 25 Psychotherapy, 395–397 PTA. See Post-traumatic amnesia Purkinje cells, 96 Putamen, 147 Pyramidal system, 148

Quantification analysis, 57–58

RA. See Robust nucleus of the archistriatum Radiation damage, 364–365 Radio-frequency (RF) signal, 53 Radiologic procedures, 35–40

air encephalography, 36 angiography, 38–40 CT, 36–38 skull x-ray, 36 Wada technique, 40

Rapid eye movement (REM), 450 ACh role, 107 cataplexy and, 463 dreaming and, 451 EEG during, 451–452, 454 function of, 459–461 hypoxia and, 342 reticular activating system and, 456–459 state of consciousness during, 452, 454

RAS. See Reticular activating system Receptors

auditory, 215 cells, 177 mechanical, 180 sites, 105 on skin, 179–181

Recognition disorders, 207–208 processing systems, 204 tests, 209

Refractory period, 103 Regional CBF, 47–48 Rehabilitation, 389–397

admission to programs, 390–395 discharge planning, 393–394 everyday activities assessment, 394–395 goal evaluation, 393–394 outpatient treatment, 394 specialties

neuropsychology, 391–392 occupational therapy, 392 physical therapy, 392 speech therapy, 392–393 therapeutic recreation, 393

stroke, 352 team approach, 391 treatment methods, 395–397 treatment planning, 394

Reliability, 67 REM. See Rapid eye movement Republic, The (Plato), 6 Response cost, 322 Resting potential, 102 Resting tremor, 425

Restless leg syndrome. See Nocturnal myoclonus

Restorative sleep, 454, 456 Reticular activating system (RAS), 107

comas and, 375 cortical arousal, 458 function, 240–241 location, 137 REM sleep and, 456–459 stimulation, 140

Reticular formation anatomic feature, 139 function, 140–141 structure, 139–140

Retrograde amnesia, 226, 386–387 Retrograde degeneration, 372 Reversible dementia, 408–409 Rey-Osterrieth Complex Figure Test, 75 RF. See Radio frequency Rhinencephalon, 149 Right brain strokes, 353–355 Rigidity, 424 Risperidone (Risperdal), 336 Robust nucleus of the archistriatum (RA), 109 Roosevelt, Theodore, 382

Saccadic eye movement, 299 SAFs. See Scrapie-associated fibrils SAS. See Sleep apnea SCEA. See Sexual Consent and Education

Assessment Schizophrenia

attentional deficits in, 242 drug treatments, 149 lobotomy and, 23

Schwann cells, 97 acoustic neuroma-associated, 360 function of, 100

Sclerotic plaques, 98 SCN. See Suprachiasmic nucleus Scopolamine, 107 Scrapie-associated fibrils (SAFs), 439 SDAT. See Senile dementia of the

Alzheimer’s type SDMT. See Symbol Digit Modalities Test Secondarily generalized seizures, 467 Secondary association, 203 Secondary emotions, 262–264 Seizures, 444, 463–473

anatomy, 467–469 causes, 464, 467 characterization, 464 classification

complex partial, 464 generalized, 466 partial, 466–467 petit mal, 464 simple, 466–467

classifications, 464–467 clinical presentation, 469–472 EEG and, 42–43 neuronal firing and, 104 neurophysiology, 467–469 postictal phase, 466

Semantic knowledge breakdown, 415–416 Semantic memory, 228 Senile dementia of the Alzheimer’s type

(SDAT), 410–411, 413, 418

Senile plaques, 404 Sensation, 70–71, 177 Sensitivity, 84 Sensory association areas, 189 Sensory auras, 472 Sensory neurons, 99 Sensory system

Alzheimer’s patients, 418 chemical senses, 184–189 CVA-induced deficits, 352–353 somatosensory processing, 178–184

Septum, 149 SER. See Somatosensory-evoked response Serotonin (5-HT), 106

CVAs and, 348 distribution, 108 function, 316 GTS and, 334 REM sleep and, 459

Serotonin reuptake inhibitors (SSRIs), 336 Set-shifting problems, 429 7-repeat allele, 323–324 Sex chromosomes, 282 Sexual Consent and Education Assessment

(SCEA), 387 Sexual hormones

cerebral specialization and, 171–175 circulating levels, 173 effects of, 171 menopause and, 174

Sexuality, 386–387 Shifting attention, 246 Short-term memory (STM), 226

Alzheimer’s patients, 416 deficits, 237–238 LTM versus, 237–240 working memory and, 238–240

SIDS. See Sudden infant death syndrome Simple drawing tasks, 417 Simple seizures, 466–467 Simple tics, 332–333 Single-gene, 281 Single-photon emission computed

tomography (SPECT) Alzheimer’s patients, 413 development, 33 technique, 48–49

Skulls, 125 anatomy, 126, 127 fractures, 378–379 newborn, 125 x-ray, 36

Sleep anatomy, 456 architecture, 451–456 mechanisms, 450–451 normal, 454 NREM, 42

characterization, 450 EEG during, 451–452, 454 state of consciousness during, 452, 454

onset, 456 phasic events, 454, 456 physiology, 456 REM, 450

ACh role, 107 cataplexy and, 463 dreaming and, 451

Subject Index 571

Sleep (continued) EEG during, 451–452, 454 function of, 459–461 hypoxia and, 342 reticular activating system and,

456–459 state of consciousness during, 452, 454

rhythms, 451–452 stages of, 451–452

Sleep apnea (SAS), 342, 461–462 Sleep disorders

case study, 450 narcolepsy, 462–463 SAS, 461–462

Sleep paralysis, 458, 463 Sleepwalking, 454 SMA. See Supplementary motor area SMDT. See Symbol Digit Modalities Test Smell

characterization, 187 disorders of, 189 olfactory system, 187–189

Smell Identification Test (UPSIT), 189 SNS. See Somatic nervous system Sociability

autism and, 311 GTS, 337 in NVLD children, 308 WS and, 290

Social brain network theory, 317–318 Social cognition, 319–320 Sociopathy, 255–256 Sodium amytal injections, 40

hemisphere dominance evaluations, 161 speech, 470–471

Sodium-potassium pump, 102 Somatic markers, 256 Somatic nervous system (SNS), 121 Somatosensory cortex, 159, 190–191 Somatosensory system

dysfunctions of, 183–184 pathways, 181–182 primary cortex, 182–183 receptors, 179–181 types of sensory stimulation and, 178

Somatosensory-evoked response (SER), 45 Somatostatin, 413 Songbirds, 109 Soul

non-Western views, 12 parts, Plato’s views, 6 spiritual, 8

Space-occupying clots, 378 Spatial ability

Alzheimer-induced deficits, 413, 417, 428–429

CVA-induced deficits, 354–355 disorders, 208, 210–215 egocentric disorder, 436 gender differences, 169–170 processing system, 204, 207 TS-induced deficits, 284

Spatial coding neurons, 459 Spatial perception, 169 Specificity, test, 84 SPECT. See Single-photon emission computed

tomography

Speech apraxia, 219 brain systems and, 218 Broc’s area, 16–18 disorders, 219–221 locus of, 16 loss of, 21 Parkinson’s patients, 430 requirements, 215–216 stroke damage to, 355–356 Wernicke’s area, 18

Speech therapy conditions treated by, 393 goal, 393 specialties, 392

Spina bifida, 116, 277 Spinal cord

development, 119–120 function of, 123–124 protection of, 125–127 segmentation of, 120 structure of, 123

Spinal tap. See Lumbar puncture Split-brain patients, 445–446 Sports neuropsychology, 28 Sports-related concussions

CHI, 28 contemporary research, 384 history of, 382–383 mild THI, 381–382 prevention efforts, 383–385 Virginia football studies, 383

SQUID. See Superconductoring quantum interference device

SSRIs. See Serotonin reuptake inhibitors Stains

Golgi, 34 myelin, 35 Nissl, 34–35

Standard battery approach, 80–81 Standardized scores, 85 Static dementia, 408 Stelazine (trifluoperazine), 149 Stem cells, 110, 111 Stenosis, 349 STM. See Short-term memory Stress and aging studies, 405 Striatal complex, 196 Striate cortex, 203 Striatum, 107, 148 Strokes. See Cerebrovascular accidents Stroop test, 245 Stuck-in-set perseveration, 319 STX1A. See Syntaxin 1A Subarachnoid hemorrhage, 347 Subarachnoid space, 126 Subcallosal anterior cingulate, 171 Subconscious processes, 449 Subcortical dementias, 237

characterization of, 408 CJD as, 436–438 HD as, 434–436 PD as, 424–434 regions associated with, 411 understanding, 426

Subcortical motor processing, 195–197, 448 Subdural hematomas, 377

Subdural space, 126 Substantia nigra, 108

functions, 147–148 HD and, 434–435 Parkinson’s and, 425

Subthalamic nucleus, 147 Subtraction procedures, 57 Sudden infant death syndrome (SIDS), 462 Summer, Larry, 172 Superconductoring quantum interference

device (SQUID), 56 Superego, 19 Superior colliculi, 138 Supplementary motor area (SMA), 191 Suprachiasmic nucleus (SCN), 456, 457 Supravalvar aortic stenosis (SVAS), 286 Surface dyslexia, 299 Sustained attention, 241, 246 SVAS. See Supravalvar aortic stenosis Sydenham’s chorea, 335 Sylvian (lateral) fissure, 118 Sylvian aqueduct. See Cerebral aqueduct Sylvian fissures, 163 Symbol Digit Modalities Test (SMDT), 72 Symptom validity testing, 78 Synapses, 103

structure of, 105 transmissions, 105–106

Synaptic cleft, 105 Synaptic knobs, 105 Synaptic vesicles, 105 Synaptogenesis, 117 Synchronous brain activity. See Seizures Synesthesia, 179 Syntaxin 1A (STX1A), 286

Tactile agnosia, 178, 183 Tactile auras, 473 Tangles, 411–412 Tardive dyskinesia, 149 Taste

disorders of, 186–187 function of, 186 receptor cells, 184 theories of, 185

Tau proteins, 411, 412 TBI. See Traumatic brain injury Tectum, 138 Tegmentum, 138 Telencephalon, 118, 147–152

basal ganglia, 147–149 corpus callosum, 151–152 hemispheres, 147 limbic system, 149–151

Telomeres, 405 Temporal lobes, 158

autism and, 317 dyslexia and, 302 epilepsy and, 465, 467 function, 161 strokes in, 350

Temporal order memory, 302 Tensile strength, 372 Teratogens, 270 Terminal buttons, 95, 98 Terrorism, 28–29 Test battery, 69

572 Subject Index

Tests apperceptive agnosia, 209 attention, 245 confrontation naming, 416 executive functioning, 429 fluid intelligence, aging and, 402 line orientation, 417 motor system functions, 192–193 neuropsychological (See Neuropsychological

tests) psychometric, 419

Thalamocortical projection system, 448 Thalamus

anatomic features, 143 consciousness and, 448 declarative memory and, 231 function, 143–144 lesions, 146 nuclei, 144, 146 REM sleep and, 458 sleep and, 451 structure, 143 tumors of, 363

Thalotomy, 433 Theory of mind (TOM), 317

autism understanding and, 320 deficits, 319–320 higher levels of, 317

Thermoreceptors, 180 Theta activity, 41 Thorazine (chlorpromazine), 149 Three-dimensional images, 57–58 Thrill seeking, 323 Thrombosis, 345

common site for, 345–346 effects of, 346 head injury-associated, 377–379 neuropathologic process, 345

TIAs. See Transient ischemic attacks Tics. See also Tourette syndrome

classification, 332 development of, 332–333 severity mean, 333

Time tagging events, 429–430 TOH. See Tower of Hanoi TOLsupdx/sup. See Tower of London-Drexel

University TOM. See Theory of mind Tonotopic map, 215 Tourette syndrome (GTS)

assessment, 335–336 case study, 196 characterization, 332 clinical presentation, 332–333 comorbid conditions, 334 effects of, 337 pathogenesis, 334–335 prevalence, 333 treatment, 336–337

Tower of Hanoi, 326 Tower of London-Drexel University test

(TOLsupdx/sup) ADHD executive planning, 250–251 autism, 319 description, 77–78

Tracts, 99 Trail Making Test B, 77, 429

Transcortical motor aphasia, 221 Transcortical sensory aphasia, 221 Transduction, 177 Transient ischemic attacks (TIAs), 344–345, 350 Transsexuals, 173–174 Transtentorial herniation, 376 Traumatic brain injury (TBI), 370–376

amnesia following, 386–387 case study, 374 closed, 373, 375 consensual sex after, 386–387 epidemiology, 371 evaluations, 387–388 mechanism, 371–376 neuropsychological manifestations, 386–388 penetrating, 373 recovery, 388–389 rehabilitation, 388–397

admission to programs, 390–395 discharge planning, 393–394 everyday activities assessment, 394–395 goal evaluation, 393–394 outpatient treatment, 394 specialties, 391–393 team approach, 391 treatment methods, 395–397 treatment planning, 394

severity, assessing, 375–376 treatment, 385–388

Treatise on Man (Decartes), 11 Tremors, 195, 428 Trephination, 5, 13 TS. See Turner’s syndrome Tumors, 357–363, 358

brain, 125 chemotherapy, 362 diagnosis, 361–362 glial cell-induced, 100 intracranial

characteristics, 358 infiltrating, 359 noninfiltrating, 359–361

principle forms, 358 treatment, 362 treatment, case study, 364–365 types of, 361

Turner’s syndrome (TS) assessment, 284 chromosomal defect and, 283 clinical presentation, 282 comorbid conditions, 282, 283 developmental course, 284–285 incidences, 283 neuropathogenesis, 283–284 treatment, 285

Turner, Tina, 401

Ultradian, 449 Ultrasonography, 281 Umami, 185 Unconsciousness, 447 Understanding of Aphasia, An (Freud), 19 Unilateral neglect. See Neglect UPPP. See Uvulopalatopharyngoplasty UPSIT. See Smell Identification Test Utilization behavior, 256 Uvulopalatopharyngoplasty (UPPP), 462

Validity, 67 Vascular disorder. See Infarctions Vascular system, 125

arteries, 131 cerebral arteries, 132–133 circle of Willis, 131–132

VBR. See Ventricle-to-brain ratio Venous system, 133 Ventral processing systems

coordination of, 204 disorders of, 204 dyslexia and, 304 WS effects on, 289

Ventricle-to-brain ratio (VBR), 58 Ventricles, 127 Ventricular development, 119–120 Ventricular localization hypothesis, 7 Ventricular system, 125

CSF in, 128–130 function, 129–131 structure, 127–129

VER. See Visual-evoked response Verbal ability

fluency tasks, 429 function, 73 gender differences, 174

Vertebral arteries, 131 Vestigial ovarian streaks, 282 Vigilance attention system, 245 Virginia football studies, 383 Virion, 439 Visual agnosias, 207 Visual cortex, 118 Visual field defects, 202 Visual processing, 200–215

Alzheimer’s patients, 413, 417 characterization, 200–201 CJD patients, 439 cortical, 203 CVA-induced deficits, 354–355 disorders of, 201–202 dyslexia model, 299–301 higher

dorsal streams, 207, 208, 210–215 ventral streams, 207–208

in NVLD children, 310 Parkinson’s patients, 428–429 pathways, 201 pituitary tumors and, 360 primary, 201–204

Visual-evoked response, 45 Visuoconstructive skills, 288–289 Visuospatial deficits. See Spatial ability; Visual

processing Visuospatial organization, 74–75 Visuospatial sketch pad, 238 Vitalism, 4 Vocational inventories, 69

Wada technique. See Sodium amytal injections WAIS-R. See Wechsler Adult Intelligence

Scales WCST. See Wisconsin Card Sorting Test Wechsler Adult Intelligence Scales (WAIS-R),

402 Wechsler Memory Scale (WMS), 76 Wernicke’s aphasia, 220–221

Subject Index 573

Wernicke’s area, 18 Wernicke-Korsakoff ’s syndrome, 151 Wexler, Nancy, 434 What systems. See Ventral processing Where systems. See Dorsal processing White matter, 97

autism and, 316 cerebral hemispheres and, 164 destruction, NVLD and, 306

Williams syndrome (WS) anatomic brain anomalies in, 287 characterization, 285 clinical presentation, 285–286 comorbid conditions, 285 dorsal processing and, 289 emotionality and, 290

facial processing, 288 genetic defects and, 286–287 incidence, 285 intellectual performance and, 287–288 language abilities and, 287–288 musicality and, 289–290 neuropsychological profile, 287 sociability and, 290 treatment, 290–291 ventral processing and, 289 visuoconstructive skills, 288–289

Wilson’s disease, 426 Wisconsin Card Sorting Test (WCST), 77 WMS. See Wechsler Memory Scale Word decoding, 301 Word salad, 220

Working memory aging and, 403 as distinct system, 238 dyslexia and, 302

WS. See Williams syndrome

X-rays, 36 in CT technique, 37 tumors diagnosis by, 362

Xenon 133, 48

Yellow Emperor’s Classic of Internal Medicine, The, 13

Zentralorgan, 104

574 Subject Index

Front Cover
Title Page
Copyright
Contents
Preface
About the Authors
Acknowledgments
Part One: Introduction

Chapter 1 A History of Neuropsychology

Keep in Mind
Overview
The Brain in Antiquity: Early Hypotheses
Localization Theory
Localization versus Equipotentiality
Integrated Theories of Brain Function
Modern Neuropsychology
Emerging Research Areas in Neuropsychology
Summary
Critical Thinking Questions
Key Terms
Web Connections

Chapter 2 Methods of Investigating the Brain

Keep in Mind
Overview
Neurohistology Techniques
Radiologic Procedures
Electrophysiologic Procedures
Imaging of Brain Metabolism
Magnetic Imaging Procedures
Cerebrospinal Fluid Studies: Lumbar Puncture
Behavioral Examinations
New Advances in Imaging Techniques: Mapping the Brain
Summary
Critical Thinking Questions
Key Terms
Web Connections

Chapter 3 Neuropsychological Assessment and Diagnosis

Keep in Mind
Overview
General Considerations in Neuropsychological Testing
Psychometric Issues in Neuropsychological Assessment
Neuropsychological Tests
Interpreting Neuropsychological Assessment Data
Summary
Critical Thinking Questions
Key Terms
Web Connections

Part Two: The Functioning Brain

Chapter 4 Cells of Thought

Keep in Mind
Overview
Neurons and Glial Cells
Communication within a Neuron: The Neural Impulse
Communication among Neurons
Regeneration of Neurons
Summary
Critical Thinking Questions
Key Terms
Web Connections

Chapter 5 Functional Neuroanatomy

Keep in Mind
Overview
Anatomic and Functional Development of the Brain
Organization of the Nervous System
Peripheral Nervous System
Central Nervous System
Gross Anatomy: Protection and Sustenance of the Brain
Principal Divisions of the Brain
Brainstem and Cerebellum
Telencephalon
Summary
Critical Thinking Questions
Key Terms
Web Connections

Chapter 6 Cerebral Specialization

Keep in Mind
Overview
The Cerebral Hemispheres
Hemispheric Anatomic and Functional Differences
Sex Differences and Hemispheric Specialization
Summary
Critical Thinking Questions
Key Terms
Web Connections

Chapter 7 Somatosensory, Chemical, and Motor Systems

Keep in Mind
Overview
Somatosensory Processing
Chemical Senses
Motor Systems
Summary
Critical Thinking Questions
Key Terms
Web Connections

Chapter 8 Vision and Language

Keep in Mind
Overview
Visual Processing
Auditory and Language Processing
Summary
Critical Thinking Questions
Key Terms
Web Connections

Chapter 9 Memory, Attention, Emotion, and Executive Functioning

Keep in Mind
Overview
Memory Systems
Attention
Executive Functioning
Relation of Memory, Attention, and Executive Function
Neuropsychology of Emotional Processing
Summary
Critical Thinking Questions
Key Terms
Web Connections

Part Three: Disorders of the Brain

Chapter 10 Developmental Disorders of Childhood

Keep in Mind
Overview
Vulnerability and Plasticity of the Developing Brain
Child and Adult Brain: Structural and Functional Differences
Specific Developmental Disorders
Summary
Critical Thinking Questions
Key Terms
Web Connections

Chapter 11 Learning and Neuropsychiatric Disorders of Childhood

Keep in Mind
Overview
Learning Disabilities
Pervasive Developmental Disorders
Disruptive Behavioral Disorders
Tic Disorders
Summary
Critical Thinking Questions
Key Terms
Web Connections

Chapter 12 Cerebrovascular Disorders and Tumors

Keep in Mind
Overview
Pathologic Process of Brain Damage
Overview of Cerebrovascular Disorders
Types of Cerebrovascular Disorders
Diagnosing Cerebrovascular Disease
Treatment and Prognosis of Vascular Disorders
Neuropsychological Deficits Associated with Stroke
Tumors of the Brain
Types of Intracranial Tumors
Brain Tumors and Neuropsychology
Other Neurologic Disorders
Summary
Critical Thinking Questions
Key Terms
Web Connections

Chapter 13 Traumatic Head Injury and Rehabilitation

Keep in Mind
Overview
Traumatic Head Injury
Epidemiology of Traumatic Head Injury
Mechanism of Impact: Neuronal Shearing, Stretching, and Tearing
Complications of Moderate and Severe Brain Injury
Mild Head Injury: "Concussions"
Treatment of Head Injuries
Recovery, Rehabilitation, and Intervention of Traumatic Brain Injury
Adaptation and Recovery
Overview of the Rehabilitation Process
Treatment Methods for Neuropsychological Rehabilitation
Summary
Critical Thinking Questions
Key Terms
Web Connections

Chapter 14 Normal Aging and Dementia: Alzheimer's Disease

Keep in Mind
Overview
Normal Aging
Mild Cognitive Impairment
Defining Dementia
Alzheimer's Disease
Treatment
Summary
Critical Thinking Questions
Key Terms
Web Connections

Chapter 15 Subcortical Dementias

Keep in Mind
Overview
Parkinson's Disease
Huntington's Disease
Creutzfeldt–Jakob Disease
Summary
Critical Thinking Questions
Key Terms
Web Connections

Chapter 16 Alterations of Consciousness

Keep in Mind
Overview
Understanding Consciousness
Rhythms of Consciousness
The Brain and Mind in Sleep
Runaway Brain: Seizure Disorders
Summary
Critical Thinking Questions
Key Terms
Web Connections

References
Glossary
Answers to Critical Thinking Questions
Name Index
Subject Index