Neural substrates of facial recognition.

Seventeen healthy normal volunteers performed three facial recognition tasks while their cerebral blood flow was measured with PET: categorizing faces according to gender, recognizing new faces, and recognizing familiar faces. These tasks activated three different pathways: respectively, the left inferior temporal lobe and left frontal cortex; a predominantly right frontal-right parietal-left cerebellar network; and left lingual and left and right fusiform gyri. These results suggest that humans use different brain regions in performing these three routine daily activities. The results are consistent with previous observations concerning organization of extrastriate visual cortex in human and nonhuman primate lesion studies, including studies of the unusual syndrome of prosopagnosia (loss of the ability to recognize familiar faces with intact ability to recognize a face as a face).