The primate amygdala in social perception – insights from electrophysiological recordings and stimulation

•Individual neurons in the human and non-human amygdala are highly sensitive to faces.•Subpopulations of neurons respond to specific features such as eyes.•Stimulation of the amygdala is being explored as a possible treatment for post-traumatic stress disorder and autism.•Comparisons with responses in temporal cortex and across species are important future directions.

The role of the amygdala in emotion and social perception has been intensively investigated primarily through studies using functional magnetic resonance imaging (fMRI). Recently, this topic has been examined using single-unit recordings in both humans and monkeys, with a focus on face processing. The findings provide novel insights, including several surprises: amygdala neurons have very long response latencies, show highly nonlinear responses to whole faces, and can be exquisitely selective for very specific parts of faces such as the eyes. In humans, the responses of amygdala neurons correlate with internal states evoked by faces, rather than with their objective features. Current and future studies extend the investigations to psychiatric illnesses such as autism, in which atypical face processing is a hallmark of social dysfunction.