Copyright © 2006 by Allyn and Bacon

Chapter 17 Biopsychology of Emotion, Stress, and

HealthFear, the Dark Side of Emotion

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Copyright © 2006 by Allyn and Bacon

Phineas Gage

• Why would a tamping iron through the skull lead to dramatic changes in personality?

• Damage to the medial prefrontal lobes

Darwin’s Theory of the Evolution of Emotional Expression

• Expressions of emotion evolve from behaviors that indicate what an animal is likely to do next.

• If emotional signals are beneficial, they will evolve to more effectively communicate and may lose their original meaning.

Theories of Emotion

• James-Lange– Stimulus > autonomic/skeletal response > emotion– Autonomic/skeletal response necessary for emotion– I run therefore I am afraid

• Cannon-Bard– Stimulus > autonomic/skeletal response & emotion– Autonomic/skeletal response independent of emotion– Can be interpreted as Parallel emotion/response

• Both are wrong

Theories of Emotion

Bard – Sham Rage

• Decorticated cats exhibit extreme and unfocused aggressive responses

• Hypothalamus must be intact • Perhaps hypothalamus is needed for expression

of aggression and cortex serves to inhibit and direct responses

• Papez proposed emotional circuit – limbic system, that includes hypothalamus

Kluver-Bucy Syndrome

• Rare cerebral neurological disorder

• Major symptoms - urge to put objects into mouth, memory loss, extreme sexual behavior, placidity, visual distractibility.

• Bilateral temporal lobes.

Emotions and the Autonomic Nervous System (ANS)

• Which patterns of ANS activity are associated with specific emotions?

• There is NOT a separate ANS profile for each emotion.

Emotions and Facial Expression

• The meanings of facial expressions appear to be universal

• 6 primary emotions – all others are a mixture of these

• 6 primary emotions– Surprise– Anger– Disgust– Fear– Sadness– Happiness

Facial Expressions

• Facial Feedback Hypothesis – Smiling does make you happier – facial muscles may

feedback and influence emotional experience• Microexpressions – brief facial expressions that

reveal true feelings often break through false ones

• Different muscles involved in fake and real smiles

Fear, Defense, and Aggression

• Fear – emotional reaction to threat• Defensive behaviors – designed to protect

from threat or harm, motivated by fear• Aggressive behaviors – function to threaten

or harm

Aggression and Testosterone (T)

• Nonprimates – relationship between T and aggression is clear

• Human males – aggression does not increase at puberty, is not eliminated by castration, and not increased by T injection

• But – violent male criminals and aggressive male athletes have slightly elevated T levels

• Aggressive encounters may increase T, rather than vice versa

Stress and Health

• Stress – reaction to harm to threat

• Stressors – stimuli that cause stress

• Chronic psychological stress – most clearly linked to ill health

• In the short-term stress is adaptive, in the long-term it is maladaptive

Selye and the Stress Response

• Activation of the anterior-pituitary adrenal-cortex system

• Selye neglected the role of the sympathetic nervous system

• All common psychological stressors are associated with high levels of glucocorticoids, epinephrine, and norepinephrine

Effects of Stress

Stress and Immune Function

• If stress affects immune function, how might it do so?

• Why is stress initially adaptive and then, when chronic, harmful?

Meta-Analysis of Stress Studies

• Effects of stress on immune function depend on the kind of stress– Acute stressor improve immune function– Chronic stressor impair

• Many ways that stress could impact immune function

Stress and the Hippocampus

• Hippocampus has many glucocorticoid receptors• Following stress

– Dendrites of pyramidal cells are shorter and less branched– Adult neurogenesis of granule cells reduced

• Effects blocked with adrenalectomy, produced with corticosteroids

• Effects seen with only a few hours of stress

Stress and the Hippocampus

• Natural stressors produce more pathology than artificial ones

• Effects are severe enough to disrupt behaviors mediated by the hippocampus

• Effects of stress tend to be greater in males (estradiol protects – promotes neurogenesis and recovery)

Fear Conditioning

• Auditory fear conditioning blocked with medial geniculate nucleus (MGN) lesions – not affected by auditory cortex lesions

• Critical pathways: MGN to amygdala• Amygdala lesion blocks fear conditioning

Auditory Fear Conditioning

Brain Mechanisms of Human Emotion

• Neuropsychological studies of the brain damaged

• Functional imaging of the healthy

• Amygdala and prefrontal cortex clearly play a role

Emotion

• What unique challenges must be overcome in the study of emotion?

• Why is it important to develop an understanding of the brain mechanisms that underlie emotion?