Different scalp topography of brain potentials related to expression and identity matching of faces.

Event-related potentials (ERPs) and behavioral data were recorded while subjects performed two tasks on the same set of faces (presented in pairs). One task was identity matching and the other expression matching. Two groups of subjects participated, one familiar and the other unfamiliar with the faces. Subjects were less accurate in matching expressions than identity. Familiarity facilitated identity but not expression matching. ERPs to mismatches in both tasks elicited a negativity around 400 ms, which was similar in latency and amplitude in the two tasks, but differed in scalp topography. Whereas the mismatch negativity had the same landscape over the left hemisphere for both tasks, the component related to expression had larger amplitudes over the right-temporal regions. Familiarity had no effect on these negativities, although it affected a late positivity (LP). These results support the idea of distinct neural systems subserving face processing, and agree with a role of the right hemisphere for the processing of emotional expressions.