Is family special to the brain? An event-related fMRI study of familiar, familial, and self-face recognition.

The face-processing network has evolved to respond differentially to different classes of faces depending on their relevance to the perceiver. For example, self-, familiar, and unknown faces are associated with activation in different neural substrates. Family should represent a special class of face stimuli that is of high relevance to individuals, because incorrect assignment of kinship can have dire consequences (e.g., incest, cuckoldry). Therefore evolution should have favored redundant mechanisms for detection of kin. We used fMRI to investigate the neural substrates associated with viewing faces of kin compared to other classes of faces (e.g., self-face, familiar face, and unknown face), and to examine the degree to which self-facial resemblance activated similar neural substrates. Contrasting kin faces with unknown faces activated substrates associated with self-face recognition, while comparing kin faces to friend faces activated posterior cingulate and cuneus. Similar posterior medial substrates were recruited when contrasting self-resembling faces with morphed faces of kin, suggesting these regions potentially represent computational processing about facial familiarity and identity. On the other hand, discrimination of self-resembling faces from familiar morphs activated anterior medial substrates (anterior cingulate cortex, ACC, medial prefrontal cortex, MPFC). These findings, and a region of interest (ROI) analysis, highlight the role of the extended face-processing network for discrimination of kin from familiar non-kin members of one's social group based on self-referent phenotypic cues.