Social and emotional attachment in the neural representation of faces.

To dissociate the role of visual familiarity from the role of social and emotional factors in recognizing familiar individuals, we measured neural activity using functional magnetic resonance imaging (fMRI) while subjects viewed (1) faces of personally familiar individuals (i.e. friends and family), (2) faces of famous individuals, and (3) faces of strangers. Personally familiar faces evoked a stronger response than did famous familiar faces and unfamiliar faces in areas that have been associated with 'theory of mind', and a weaker response in the amygdala. These response modulations may reflect the spontaneous activation of social knowledge about the personality and attitudes of close friends and relatives and the less guarded attitude one has around these people. These results suggest that familiarity causes changes in neural response that extend beyond a visual memory for a face.