7-1 neuropsych

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Emotion Processing in the Brain and the Stress Response

Emotion is a difficult construct to describe. It is difficult to describe in part because it is so difficult to measure. One description of emotion is a nonbehavioral reaction to an experience (Carlson, 2014). Many theories have been used to describe emotion. These theories include the following:

• The James-Lange theory: emotion follows internal physiological states
• The Cannon-Bard theory: physiological reactions and felt emotion occur simultaneously
• The Schachter-Singer theory: people’s cognitive interpretations result in felt emotions

The main brain system involved in emotion is the limbic system. The system is involved in many functions. The mnemonic HOME can help remember the four primary limbic functions: homeostasis, olfaction, memory, and emotion (Blumenfeld, 2010). The heart of the limbic system is the Papez circuit. It includes the amygdala, hippocampus, thalamus, mammillary bodies, and cingulate gyrus. The amygdala is an almond-shaped structure seated at the front of the hippocampus. It is particularly important when it comes to emotions. The amygdala gives emotional salience to stimuli and integrates input related to an emotional response, particularly with negative emotions such as fear and rage. For example, Klüver-Bucy syndrome results from bilateral ablation of the amygdala leading to loss of aggression and generalized docility, as well as hyperorality, hypersexuality, and visual agnosias (Jargin, 2020).

Another important part of the brain relevant to emotion is the frontal lobes. These are the final areas of the brain to fully develop. In addition to motor control (primary, supplementary, and premotor areas) and expressive speech (Broca’s area), Stuss (2011) summarized four main functions of the frontal lobes:

• Executive functions
• Energization
• Metacognition, and
• Behavioral and emotional regulation

Most relevant to emotion is the area of the prefrontal cortex known as the orbitofrontal or ventromedial prefrontal cortex (vmPFC). It is the area at the very front, the bottom part of the brain, above the eyes. It functions to self-regulate emotions. The late development of this brain area is, in part, the reason children and even adolescents cannot control their emotional responses very well. For example, Phineas Gage had a steel rod thrust through his orbitofrontal cortex in a work accident. As a result, Gage became disinhibited and showed anger outbursts following the accident. This famous case highlights the role of the brain in emotional regulation (de Freitas et al., 2022).

Highly relevant to a discussion on emotion is the stress response. Stress is related to the emotional responses of fear and anger. The hypothalamus-pituitary-adrenal axis (HPA axis) is the main circuit that regulates stress. The system relies on fast-acting chemicals like neurotransmitters such as norepinephrine. The system also relies on slow-acting chemicals like hormones, such as cortisol. The stress response encompasses the sympathetic nervous system. It responds quickly to an immediate threat. The system deregulates when the stressor is extreme or continuous. This deregulation can result in post-traumatic stress disorder (PTSD).

An example of the effects of an overactive stress system in children is complex trauma. Researchers have used the term complex or developmental trauma to describe children who are exposed to repetitive traumas at an early age and by a person who is familiar to them (such as with chronic physical or sexual abuse by a relative) (Briere & Scott, 2006). These children show very different symptoms from adults exposed to a single trauma, such as a car crash. In essence, while the brain is still developing and personality forming, chronic stress can result in long-term difficulties due to developmental changes in brain structure and functioning. An inability to self-regulate emotion due to a constant state of arousal is a hallmark of these trauma cases.

The amygdala integrates emotions and ties emotional salience to experience. The vmPFC regulates emotional response. The HPA axis and related structures drive the fight-flight-freeze response. Maladaptive behaviors are shown when any of these systems do not function properly. These include alterations of aggression, inability to regulate emotion, and, at the extreme, mental disorders such as PTSD.

References

Blumenfeld, H. (2010). Neuroanatomy through clinical cases (2nd ed.). Sinauer Associates.

Briere, J., & Scott, C. (2006). Principles of trauma therapy: A guide to symptoms, evaluation, and treatment. Sage Publications, Inc.

Carlson, N. R. (2014). Foundations of behavioral neuroscience (9th ed.). Boston, MA: Pearson Education, Inc.

de Freitas, P. H. M., Monteiro, R. C., Bertani, R., Perret, C. M., Rodrigues, P. C., Vicentini, J., de Morais, T. M. G., Rozental, S. F. A., Galvão, G. F., de Mattos, F., Vasconcelos, F. A., Dorio, I. S., Hayashi, C. Y., Dos Santos, J. R. L., Werneck, G. L., Tocquer, C. T. F., Capitão, C., da Cruz, L. C. H., Jr, Tulviste, J., … & Rozental, R. (2022). E. L., a modern-day Phineas Gage: Revisiting frontal lobe injury. Lancet Regional Health. Americas, 14, 100340. https://doi-org.ezproxy.snhu.edu/10.1016/j.lana.2022.100340.

Jargin, S. V. (2020). Klüver-Bucy syndrome after a head trauma in conditions of child abuse and neglect. Psychiatria Danubina, 32(3–4), 434–435.

Stuss, D. T. (2011). Functions of the frontal lobes: Relation to executive functions. Journal of the International Neuropsychological Society, 17(5), 759–765. https://doi-org.ezproxy.snhu.edu/10.1017/S1355617711000695.