| Prosopagnosia is defined as the inability to recognize familiar faces, with relatively unimpaired recognition of other stimuli. In the present study, a single case diagnosed as prosopagnosic was studied, with two aims: to investigate general questions about face perception, and to address questions about the specific deficits underlying not only the syndrome of prosopagnosia, but all visual agnosias.; With respect to face recognition issues, the prosopagnosic subject exhibited more impaired performance on facial stimuli than on other stimuli, suggesting that faces were processed differently from other stimulus classes. However, it was not stimulus complexity or contrast level which distinguished the facial category. Furthermore, it was not difficulty in perceiving or recognizing the stimuli, as assessed by the performance of a matched group of normal subjects, that caused the prosopagnosic's differential impairment with faces.; As to the deficits underlying the agnosia in the present case, perceptual impairment could be demonstrated, but could not account entirely for the disability. There were some stimuli which could be perceived clearly enough to allow intact matching, but which could not be recognized. These recognition failures were not naming failures; in fact, the patient's verbal memory was shown to be quite good. Rather, they were failures to associate the visual stimulus with any associations or memories. The patient's pattern of deficits, therefore, was reminiscent of the classical description of agnosic functioning: The patient receives "a percept...stripped of its meaning."; Thus, the study of a single prosopagnosic subject was employed to investigate issues of face perception and to pinpoint behavioral deficits. Furthermore, additional directions for research involving prosopagnosia were indicated. First, much more extensive testing with non-facial stimuli would be informative in future case studies of prosopagnosia. In addition, an exact description of the deficits in each new case will require testing in all possible areas of deficit: perception, associations, visual memory, and naming. |
