Descriptive Psychopathology: The Signs and Symptoms of ...

73 Chapter 3: The brain and psychopathologyThe amygdala also provides emotional coloring to memory by evaluating andmodulating environmental cues based on their perceived salience. Amygdalectomizedlaboratory animals lose affectionate behavior, aggressiveness and sensitivityto social signals (analogous to emotional blunting). They respond to repeatedstimuli as if they were novel. They do not become sensitized or habituated tostimuli (as seen in untreated patients with phobias). 93Bilateral amygdala ablation has the most profound effect. In monkeys, it isassociated with placidity to the point of torpor, increased stereotypic masturbatorybehavior and repeatedly putting objects in the mouth. This Klüver–Bucy syndromeis also seen in persons with severe bilateral temporal lobe disease (e.g. traumaticbrain injury or degenerative disease). It is also reported as an aspect of temporallobe partial complex seizures, and in such patients the syndrome is transitory. 94Expression and modulation of emotion involves prefrontal cortical planning. 95Interactive with the hippocampus, the medial–dorsal prefrontal cortex inhibitsthe stress response cascade before it is fully released by subcortical structures (e.g.“it’s a bush not a mugger”). 96 Recurrent prolonged stress, however, is associatedwith hippocampal neuronal damage, 97 and inappropriate release of the stressresponse cascade driven by amygdala–hypothalamic hyperactivity. The failure ofhippocampal feedback to inhibit the cascade over-rides cortical modulation,and is part of the pathophysiologic chain underlying melancholia. 98 Dysfunctionin the related septal–hippocampal system that affects its capacity to inhibit therelease of the fear response is proposed as a mechanism for anxiety disorders. 99The dorsal anterior cingulate is involved in discriminative attention. Dysfunctionhere is associated with attentional deficits and other cognitive difficulties. 100Dorsomedial and dorsal anterolateral prefrontal cortical areas are involved incardiovascular responses to fear-inducing stimuli. Dorsolateral prefrontal cortexareas are involved in executive function and the generation of ideas. Lesionshere are associated with apathy, the loss of experiencing pleasure (anhedonia),and the loss of executive functions. 101Primary and secondary emotionsPrimary emotions are experienced by all social mammals (e.g. humans, monkeys,wolves, dogs, and dolphins) and are seen in all human societies, appearing withinthe first year of life. In most species their expression is not lateralized to onehemisphere. In humans there may be some lateralization of function with moreinvolvement of right hemisphere processes. Fear and anger are primary emotions.Happiness and sadness are common to primates, but whether other socialmammals experience these emotions is unclear. 102Primary emotions provide a selective advantage in the evolution of the species.Fear alerts the individual for fight or flight. Anger is required for combat. Both