Brain regions associated with the expression and contextual regulation of anxiety in primates

Background: A key to successful adaptation is the ability to regulate emotional responses in relation to changing environmental demands or contexts. Methods: High-resoltuion PET(18)fluoro-deoxyglucose (FDG) scanning in rhesus monkeys was performed during two contexts (alone, and human with no eye contact) during which the duration of anxiety related freezing behavior was assessed. Correlations between individual differences in freezing duration and brain activity were performed for each of the two conditions, as well as for the contextual regulation between the two conditions. Results: In both conditions, activity in the basal forebrain, including the bed nucleus of teh stria terminalis and the nucleus accumbens were correlated with individual differences in freezing duration. In contract, individual differences in the ability to regulate freezing behavior between contexts were correlated with activity in the dorsal anterior cingulate cortex, the thalamus and the dorsal raphe nucleus. Conclusions: These findings demonstrate differences in the neural circuitry mediating the expression compared to the contextual regulation of freezing behavior. These findings are relevant since altered regulatory since altered regulatory processes may underlie anxiety disorders.