The neural substrate of emotion encompasses a large brain circuit in which the amygdala plays a key role. The long-term goal of the proposed research is to determine how specific functions attributed to the amygdala are carried out at the neural level. One of the functions of the amygdala is to select from the environment stimuli with inherent emotional value and respond to them adequately, e.g., withdraw or fight when threatened. This process might rely on innately programmed and relatively inflexible pathways to ensure enduring and reliable reactions in response to objects and events of survival value. In parallel, the amygdala is required to update the reinforcing value of many stimuli that gain or lose emotional significance through learning and experience. Both functions are used for social behavior. The intricacy of primate societies requires that humans and monkeys respond reliably to facial expressions and other signals with emotional significance but also to adjust responses to social context or to the history of interactions between individuals. The neural basis of these complex and diverse functions are largely unknown. The central hypothesis of this proposal is that the lateral, basal, and central amygdaloid nuclei carry out a sequence of dissociable but complementary functions. The objective of the proposed studies is to identify in the amygdala the neural signature of stimulus differentiation, evaluation, and the initiation of emotional responses. This will be achieved by relating autonomic, behavioral, and neural ensemble responses to manipulations of the reinforcing value of face and non-face stimuli. This approach will determine (1) whether negative or positive stimuli are processed preferentially or differentially in the amygdala, (2) whether facial expressions that carry inherent positive or negative valence engage the same neuronal processes as neutral objects paired with reward or punishment, (3) whether neural activity in the amygdale predicts the autonomic and somatic expressions of emotion. These studies will determine the neural mechanism by which the amygdala evaluates stimuli of significance and relays the results of this process to a complex brain circuits that control emotional and social behavior. Understanding the neural processes carried out at each level of this circuit holds promise for more effective interventions in emotional disorders.
