Amygdala processing of social cues from faces: an intracrebral EEG study.

The amygdala is a key structure for monitoring the relevance of environmental stimuli. Yet, little is known about the dynamics of its response to primary social cues such as gaze and emotion. Here, we examined evoked amygdala responses to gaze and facial emotion changes in five epileptic patients with intracerebral electrodes. Patients first viewed a neutral face that would then convey social cues: it turned either happy or fearful with or without gaze aversion. This social cue was followed by a laterally presented target, the detection of which was faster if it appeared in a location congruent with the averted gaze direction. First, we observed pronounced evoked amygdala potentials to the initial neutral face. Second, analysis of the evoked responses to the cue showed an early effect of gaze starting at 123 ms in the right amygdala. Differential effects of fearful vs happy valence were individually present but more variable in time and therefore not observed at group-level. Our study is the first to demonstrate such an early effect of gaze in the amygdala, in line with its particular behavioral relevance in the spatial attention task.