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
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
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
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