Chapter 15: Emotions, Aggression & Stress

The text critically evaluates historical and contemporary theories of emotional processing, contrasting the Folk Psychology perspective with the James-Lange theory, which posits that physiological responses precede emotional experience, and the Cannon-Bard theory, which argues for simultaneous occurrence. Further complexity is added through Schachter's cognitive attribution model, demonstrating how environmental context is required to label nonspecific autonomic arousal. The evolutionary significance of emotions is examined through Darwin's observations on universal facial expressions and the concept of individual response stereotypy in development. The discussion on facial expression includes the neuroanatomy of superficial and deep facial muscles, cranial nerve innervation, and the facial feedback hypothesis. Significant attention is given to the neural circuitry of emotion, detailing the phenomenon of brain self-stimulation, decorticate rage, and the anatomical components of the Papez circuit and limbic system. The amygdala is identified as a critical structure for fear processing, illustrated by fear conditioning pathways—distinguishing between the direct low road and the cortical high road—and clinical case studies of amygdala damage such as Urbach-Wiethe disease. The chapter then transitions to the biology of violence, analyzing the correlation between androgens like testosterone and intermale aggression, the inhibitory role of serotonin, and the dysregulation observed in psychopathy. Finally, the physiological impact of stress is broken down via the General Adaptation Syndrome and the dual activation of the sympathetic nervous system and the HPA axis (hypothalamic-pituitary-adrenal), leading to the release of epinephrine, norepinephrine, and cortisol. The field of psychoneuroimmunology is introduced to explain the reciprocal interactions between the nervous, endocrine, and immune systems, highlighting how chronic stress and hostility suppress immune function, delay wound healing, and contribute to cardiovascular pathology through mechanisms like epigenetic regulation and cytokine modulation.