NEURAL ACTIVATION DURING COVERT PROCESSING OF POSITIVE EMOTIONAL FACIAL EXPRESSIONS

Lesion studies indicate distinct neural systems for recognition of fac ial identity and emotion. Split-brain experiments also suggest that em otional evaluation of a stimulus can occur without conscious identific ation, The present study tested a hypothesis of a differential neural response, independent of explicit conscious mediation, to emotional co mpared to nonemotional faces, The experimental paradigm involved holdi ng in mind an image of a face across a 45-s delay while regional cereb ral blood flow was measured using positron emission tomography, Prior to the delay, a single face was presented with an explicit instruction to match it to one of two faces, photographed at different angles fro m the target face, presented at the end of the delay, Repeated blood f low measures were obtained while subjects held happy or neutral faces in mind or during a neutral control fixation condition without initial face presentation, The representation of emotional faces over a delay period, compared to either the nonemotional or the fixation condition , was associated with significant activation in the left ventral prefr ontal cortex, the left anterior cingulate cortex, and the right fusifo rm gyrus, The findings support our hypothesis of a differential neural response to facial emotion, independent of conscious mediation, in re gions implicated in the processing of faces and of emotions. (C) 1996 Academic Press, Inc.