From covert to overt recognition of faces in a prosopagnosic patient.

Prosopagnosia is an inability to recognize known persons as a result of a failure to access relevant memories through the inspection of their faces. The nature of this disturbance, and the fate of memories related to faces, were investigated in a long-standing prosopagnosic woman (P.V.). An examination of P.V.'s perceptual capacities indicated no major impairment at matching faces, including different views of the same faces, and multidimensional scaling analysis showed that she could achieve configurational representations of faces as do normal subjects. In spite of her inability to evoke memories of known persons from their faces, P.V. displayed clear evidence that she could use pertinent memories related to these faces in tasks that did not explicitly call for their evocation. This covert recognition of faces was observed in perceptual learning and cued-recognized faces, attempts were made at surmounting the blocked activation of pertinent memories. Some of these attempts were successful in inducing P.V. into experiencing a sense of familiarity with the faces and identifying them, and this was the first occurrence of overt face recognition by P.V. since the onset of her illness. These findings provide clarification of the nature of the prosopagnosic disturbance and new information about the processes by which faces are recognized. They suggest that (1) prosopagnosia may result from a breakdown at different levels of face-recognition processes, (2) prosopagnosia may occur in spite of normal configurational encoding of facial representations, (3) covert recognition of overtly unrecognized faces requires the integrity of perceptual processes, and (4) failure of overt face recognition reflects a disturbance in the normal interactions between pertinent memories and facial representations which thus remain meaningless.