Social cognition related neural responses in the monkey amygdala

Abstract

The previous neuropsychological studies demonstrated that the human amygdala (AM) increased its response to emotional facial expressions and gaze direction toward to the subject, and suggested that the AM is essential in social cognition. In the present study, the monkey AM neuronal activity was recorded during performance of a delayed non-matching to sample task using human photos with various facial expressions and gaze direction. Some neurons were further tested with various human actions such as approaching toward the monkey. Autonomic activity (pupil radius) of the monkey, which reflected emotional expression, was simultaneously recorded. The results indicated that the AM neurons differentially responded to various emotional expressions and/or gaze directions. These facial expression-differential neurons were most sensitive to those of the familiar persons to the monkeys. These results suggest that social cognition might develop based on learning through social interaction, and the AM is involved in such learning. Activity of other AM neurons increased when the experimenter approached toward the monkey, or when the experimenter moved its arm or leg. Pupil radius also increased during this approaching. These results suggest that the AM is essential in primate social cognition as well as emotional expression. [J Physiol Sci. 2006;56 Suppl:S39]