Prosopagnosia: anatomic basis and behavioral mechanisms.

Critical analysis of postmortem and CT scan data indicates that prosopagnosia is associated with bilateral lesions of the central visual system. Those lesions are located in the mesial occipitotemporal region and are functionally symmetric. The prime factor in the appearance of prosopagnosia is the requirement to evoke the specific context of a given visual stimulus. The "ambiguity" of the stimulus (the frequency with which different members of a group are visually similar) is an adjuvant factor. But prosopagnosia is not specific to human faces. The phenomenon appears in relation to any visually "ambiguous" stimulus whose recognition depends on contextual memory evocation.