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Ch. 2 Cognitive Neuroscience

  • Brraains……

Why do we care about Cognitive Neuroscience?

Because cognition is interconnected with behavior & physiology

Cognitive Neuroscience is the physiological basis for cognition

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You are at a restaurant romantic dinner after a long week. It would be perfect except for the family with the wild kids at the table next to you. You try to ignore the noise and commotion when you look over the shoulder of your dinning companion and see one of the rugrats hurling a sippy cup right at your head….. What do you do?

Duck or block or just take it in the face, the kid can’t throw that hard, did you have time to contemplate and form a plan of response? No. you had a quick reaction… how does this information get communicated from your brain to your body?

Before any behavior, a neural impulse

must activate some part of the brain,

which signals a muscle

Before hitting snooze…

sound waves transduced into

electrical signals….auditory

area (hear alarm). Signal

many B areas …motor area.

….hand/arm

It all happens pretty fast!

How does it work?...

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You are at a restaurant romantic dinner after a long week. It would be perfect except for the family with the wild kids at the table next to you. You try to ignore the noise and commotion when you look over the shoulder of your dinning companion and see one of the rugrats hurling a sippy cup right at your head….. What do you do?

Duck or block or just take it in the face, the kid can’t throw that hard, did you have time to contemplate and form a plan of response? No. you had a quick reaction… how does this information get communicated from your brain to your body?

Levels of Analyses

  • Relationship between mind & brain
  • Study in different ways, at different levels
  • Behavior
  • Whole brain
  • Brain structures
  • Chemicals that create

electrical signals w/in

these structures

Central Nervous System (CNS)

the brain and spinal cord

Peripheral Nervous System (PNS)

the sensory and motor neurons that connect the central nervous system (CNS) to the rest of the body

Should be review from introductory psych.…

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Nervous System

the body’s speedy, electrochemical communication system

consists of all the nerve cells of the peripheral and central nervous systems

The Nervous System

Motor neurons

interneuron

Central

(brain and

spinal cord)

Nervous

system

Autonomic (controls

self-regulated action of

internal organs and glands)

Skeletal (controls

voluntary movements of

skeletal muscles)

Sympathetic

(arousing)

Parasympathetic

(calming)

Peripheral

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Fight or flight!!!

information is transmitted via neurons-

Interneurons

CNS neurons that internally communicate and intervene between the sensory inputs and motor outputs

Motor Neurons

carry outgoing information from the CNS to muscles and glands

Somatic Nervous System

the division of the peripheral nervous system that controls the body’s skeletal muscles

Nervous system: 3 main functions

Sensing specific information about external and internal conditions

Integrating information

Issuing commands for a response from the body’s muscles or glands

N.S. is the foundation for the ability to perceive, understand, and react to the environment.

What moves communication throughout the body?

Discovery!

  • 19th century anatomists stained brain

cells & viewed under microscope

  • Nerve net theory – continuous,

in all directions

  • Ramon y Cajal debunked this theory
  • Neuron doctrine – neurons are NOT continuous with other cells
  • Neurons are building blocks of the brain
  • Individual neurons transmit signals

Cell body - cell’s life support center

Dendrites - receive messages from other cells

Axon - sends messages away from the cell body to other neurons

Axonal Conduction

Electrical message is sent via:

Action Potential

Stimulation of the cell raising energy beyond a threshold leading to a reversal in electrical charge across the cell

Threshold > the level of stimulation required to trigger a neural impulse

Signal is sent (all-or-none)

Refractory period > recovery period where cell is less sensitive to stimulation

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Action potential - stimulation of the cell raising energy beyond a threshold leading to a reversal in electrical charge across the cell. ( like a big roller coaster)

Signal is sent

Refractory period - recovery period where cell is less sensitive to stimulation

Myelin sheath- fatty substance around axons of some cells, speeds up conduction (multiple sclerosis - destroys myelin leaving neurons unable to conduct action potentials)


Neural communication

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explain that: when a neuron is stimulated the nerve impulses travel down the axon into the terminals that causes release of neurotransmitters

Dendrite

the bushy, branching extensions of a neuron that receive messages and conduct impulses toward the cell body

Axon

the extension of a neuron, ending in branching terminal fibers, through which messages are sent to other neurons or to muscles or glands

Myelin [MY-uh-lin] Sheath

a layer of fatty cells segmentally encasing the fibers of many neurons

enables vastly greater transmission speed of neutral impulses

  • Neurotransmitters-

chemicals with various functions that work like a lock and key

** only certain NTs will work with certain receptors.**

Works in 2 ways:

reduce the likelihood of an AP

Increase the likelihood of an AP

Neural Communication

In this course our concern is with

neural communication in the brain

Much of what we know about the brain results from

abnormalities….

Example: The story of Charles Whitman

A normal guy (literally an altar

boy & an eagle scout as a kid).

He grew up, went to U. of Texas,

and everything went to hell...

He assaulted his wife & got in several fights...

He started having violent

fantasies, so he went to a

psychiatrist....

Dr. did not help...

Chuck went home, KILLED his wife and then

killed his mom!

THEN he went up a bell tower with a

high-powered rifle to thin out the herd...

Eventually, he killed another 14 people and

wounded > 20 more.

The police killed him.

Autopsy revealed a walnut-sized

brain tumor on his amygdala...

There are many other

behavior disorders &( normal behaviors)

with organic causes...

Behavior is the result of

brain activity

Figure 2.4
Cross-section of the human brain, showing a number of the subcortical structures that are important for cognition.

Sensory hub=

Receives info

from all senses

except smell;

Routes to higher

brain function (hierarchical

processing)

Yikes!

Areas of Cerebral Cortex

Different lesions

Result in different

deficits

6th sense?

Proprioception -sense of relative position of body parts & movement

  • Receptors in skeletal muscles, tendons, & joints
  • Signals sent to brain in addition to vestibular info

  • Parietal lobe is involved in the integration of signals from different parts of the body
  • Involved in phantom limb syndrome….more on that next time!

Localization of function???

  • Phrenology
  • Franz Joseph Gall
  • Hey day in America 1830s, 40s

Principles of Phrenology

  • Brain is organ of the mind
  • Mind composed of multiple distinct innate faculties
  • So, each faculty must be a separate structure in the brain
  • SIZE of each structure is a measure of its “POWER”
  • Shape of brain is determined by the development of various structures
  • Skull takes its shape from the brain, so skull surface can be read as an index of psychological aptitudes/tendencies…
  • e.g., intelligence, personality, curiosity…

Applying phrenology

  • 1830s NY - readings
  • Character reference for jobs
  • Education
  • Criminal reform
  • Career advisement
  • Match-making (!)
  • Disbanded in 1967….yes, you

read that right…1967.

Localization of function

  • Support comes from brain damage pts
  • Damage to language areas = Lang deficits
  • Damage to occipital lobe causes blindness
  • Damage to frontal lobe causes problems with decision making, thinking, planning, risk
  • https://www.youtube.com/watch?v=MvpIRN9D4D4

Figure 2.18
Location of Broca’s and Wernicke’s areas, which are both involved in the processing of speech and language.

Inability to process/

comprehend

language

Inability to form words

Problems in these areas

result in speech disorders

Example of Wernicke’s aphasia

…Asked to describe a picture showing two boys stealing cookies behind a woman’s back, one patient responded: “Mother is away her working her work to get her better, but when she’s looking the two boys looking the other part…

Words are formed fine, just meaningless

Damage to L temporal gyrus (22)

https://www.youtube.com/watch?v=3oef68YabD0

Example of Broca’s aphasia

Stuttering?

  • Regions involved:
  • Temporal lobe for auditory processing
  • Motor strip for speech planning & execution
  • Those that stutter may have:
  • Developmental differences in these structures
  • Faulty connections b/w them
  • Results in a dis-fluency of speech

Figure 2.17
Side view of a monkey brain showing the locations of the inferotemporal (IT) and the medial temporal (MT) areas.

Damage results in

prosopagnosia

can’t recognize

familiar faces

Damage results

in motion agnosia-

can’t perceive movement…

pouring coffee

seems frozen

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Mt- motion

IT- form

There is also evidence for localization

of function through new technologies….

normal

schizophrenia

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MRI-strong magnetic field which disrupts the alignment of atoms in the brain cells, when they come back to their normal resting place, they send off detectable signal which are converted to computer generated images.

Organization: Brain Imaging

  • Magnetic Resonance Imaging (MRI)
  • Functional Magnetic Resonance Imaging (fMRI)

Figure 2.20
When a blue ball rolls by, a number of different cortical areas are activated.

fMRI shows what part of the brain is activated when we are processing different information

PET

  • Positron Emission Tomography uses trace amounts of short-lived radioactive material to map functional processes in the brain
  • When the material undergoes radioactive decay a positron is emitted, which can be picked up be the detector
  • Areas of high radioactivity are associated with brain activity

EEG

  • Electroencephalography is the measurement of the electrical activity of the brain by recording from electrodes placed on the scalp
  • non-invasive
  • Can detect changes in electrical activity on a millisecond-level
  • It is one of the few techniques available that has such high temporal resolution

MEG

  • Magnetoencephalography is used to measure the magnetic fields produced by electrical activity in the brain via extremely sensitive devices known as SQUIDs
  • Used to:
  • assisting researchers in determining the function of various parts of the brain
  • assisting surgeons in localizing a

pathology

  • neurofeedback

NIRS

  • Near infrared spectroscopy

measures blood oxygenation in the brain

  • By shining light in the near infrared part of the spectrum (700-900nm) through the skull & detecting how much the remerging light is attenuated
  • How much the light is attenuated depends on blood oxygenation
  • provides an indirect measure of brain activity

DTI

  • Tracks the diffusion of water molecules in living tissue
  • Reveals microscopic details about tissue, either normal or diseased
  • Reveals neural pathways/circuits
  • in vivo and non-invasive

Now we have some brain basics…

  • Lets look at how we put all this stuff to use

Neural Representation

  • Principle of neural representation
  • Object perception is NOT based on direct contact w the object, but on the way its represented by APs in the Brain

To understand cognition, must understand how our experiences are represented in our mind (behaviorally) AND in the brain (physiologically)

Neural specialization…….

Classic data from Hubel & Weisel (1957)

Feature detectors in cats...

Electrodes used to record

from individual neurons...

More in perception chapter

Table 2.1
Properties of Neurons in the Visual Cortex
Neurons in visual system fire BEST to specific types of stimuli

Figure 2.14
How a neuron in the cat’s optic nerve responds as the size of a spot of light increases. Notice that the best response occurs to the medium-sized spot of light in (b), but decreases when the spot is made larger, as in (c) and (d).

Figure 2.16
Neurons have been found in the cortex that respond to (a) complex geometrical figures; (b) common objects in the environment; and (c) faces. Also for spatial layouts & body parts!

For example…

How can we tell friend from foe or
my house from your house?

  • Different patterns of firing are associated with different people and different brain activity

Neural circuit is a group of interconnected

neurons that respond best to a specific stimuli – circuits include

synapses that are excitatory &/or inhibitory

A- light from a short bar activates neuron 3 which activates the main neuron

B- light from a medium bar excites neurons 2,3,4, so main neuron

responds very rapidly

C- light from a large bar excites neurons 2,3,4 but 1 & 5 are inhibitory, reducing overall response of the main neuron

**** this neuron responds best to medium length lines****

Ex. Neuron A

Y synapse- excite

T synapse- inhibit

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How a neural circuit works. “Y” synapses are excitatory and “T” synapses are inhibitory. (a) When receptor 3 is stimulated by light, excitatory neurotransmitter is released onto neuron A, and action potentials are recorded from A’s axon.
(b) When receptors 2, 3, and 4 are stimulated neuron A receives more excitatory neurotransmitter and firing increases. (c) When all five neurons are stimulated, excitatory transmitter is released from 2, 3, and 4, but the release of inhibitory neurotransmitter from neurons 1 and 5 causes a decrease in firing. This circuit therefore causes neuron A to fire best to a bar of light of medium length.

Figure 2.19
How five different neurons respond to three different faces. Notice that the pattern of firing across the five neurons is different for each face.

Neuronal coding

  • Population coding – representation of a particular object by the pattern of firing of a LARGE number of neurons

  • Sparse coding – particular object is represented by a pattern of finding on only a SMALL group of neurons

Distributed Representation Across the Brain

  • Distributed representation – cognitive functions activate MANY B areas
  • E.g., ffa most strongly activates for faces, is weaker but still activates for other stimuli
  • E.g., Several areas activate for face perception according to:
  • Your reaction to the face
  • Attraction
  • Expression
  • Emotions

Distributed Representation

  • Same is true for other processes such as memory
  • Take home: cog processes are created by many specialized B areas – all working together – to create a distributed pattern of activity