Amygdala

AbstractThe amygdala is a collection of anatomically and functionally distinct nuclei buried deep within the temporal lobes of the brain. It has long been appreciated that the amygdala has a critical role in emotion and emotional memory. For instance, work in the 1930s by Kluver and Bucy revealed striking changes in the emotional responses of monkeys after temporal lobe lesions that included the amygdala (Kluver & Bucy, 1937). These changes in emotion were later shown to be reproduced by amygdala damage alone and linked to deficits in assigning emotional significance to biologically relevant stimuli (Weiskrantz, 1956). Indeed, humans with amygdala damage show similar deficits in emotional processing. For example, patient S.M., who has a rare illness that caused selective and complete bilateral damage to her amygdala, is impaired in recognizing facial expressions of emotion, particularly fear. Furthermore, when presented with fear‐inducing stimuli, such as a movie clip, S.M. is unable to produce normal emotional responses, although she can explain that most people would feel afraid when watching these clips (Adolphs et al., 1999). Consistent with this, normal subjects who view facial expressions of fear exhibit increased regional cerebral blood flow in the amygdala.