Citation/Abstract

Lesion studies in primates have indicated that the amygdala plays a prominent role in socioemotional behavior. That is, monkeys with bilateral amygdalectomies show decreased social contact and social status as well as increased social fear. However, the lesion methodology itself introduces an array of problems that may affect the outcome of the study and thus the conclusions established from the data. Our studies use pharmacological manipulations through acute drug infusions into specific areas of the amygdala to further understand the role of specific amygdalar nuclei in socioemotional behavior. In Specific Aim 1, GABAA agonists and antagonists were infused into the basolateral division of the amygdala (BLA) to assess the role of BLA in social behavior of primates in a familiar dyad setting. BLA activation using the GABAA antagonist bicuculline methiodide leads to decreases in total social contact while increasing withdrawal during social interactions with familiar conspecifics. BLA inactivation using the GABAA agonist muscimol results in increased total social contact and solicitation of grooming during social interactions. Thus BLA seems to be important for inhibition of social behaviors during familiar dyadic social encounters. In Specific Aim 2, the same GABAA drugs were infused into the central nucleus of the primate amygdala (Ce) to investigate the role of Ce in social behavior of familiar dyads. Ce activation using the GABAA antagonist bicuculline methiodide leads to decreased frequency of approach. Ce inactivation using the GABAA agonist muscimol results in increased total social contact. Thus it appears that Ce is important for expression of social behaviors during familiar dyadic social interactions. Specific Aim 3 explores the GABAergic role in BLA on the registration and expression of changes in reward value. Our data indicate that BLA is necessary for registration but not the subsequent expression of the behavioral changes in reward value. Taken together, it is evident that regions of the amygdala play different roles in social behavior as well as changes in reward value.