A mirror mechanism for smiling in the anterior cingulate cortex.

It was recently proposed that the neural substrate mediating smile production might play a key role also in the recognition of others' smile. This hypothesis, however, has been challenged by difficulties in eliciting ecological smiling in standard laboratory settings. Here we report of a case where these difficulties were overcome by combining electrical stimulation and intracranial electroencephalogram recording in a patient with drug-resistant focal epilepsy. The stimulation of the pregenual anterior cingulate cortex (pACC) elicited a smiling facial expression. The same leads exploring pACC showed an increase of gamma band activity (50-100 Hz) during the observation of video-clips depicting actors laughing, relative to video-clips depicting actors crying or producing a neutral expression. These findings indicate that both smile production and recognition are encoded in pACC and further support the role of this region in social cognition. (PsycINFO Database Record