Prosopagnosia associated with a left occipitotemporal lesion

Abstract

Acquired prosopagnosia is usually associated with bilateral or right-sided lesions of the occipital or temporal lobes. In rare cases of prosopagnosia after left-sided lesions in left-handed subjects, it is attributed to a reversed hemispheric specialization for face processing. This study examines the face-processing functions of a left-handed prosopagnosic patient with a left-sided lesion affecting the region of the occipital face area and possibly the fusiform face area, to contrast his deficits with those of prosopagnosic patients with right-hemispheric lesions. Similar to those patients, he has a moderately severe reduction in familiarity judgments, is impaired in processing face configuration, and shares with some of those patients a greater failure to process eye than mouth information, indicating an altered pattern of facial saliency. He has a mild reduction in the identification of exemplars of non-face objects. Unlike those patients, he has better residual familiarity on a two-alternative forced-choice task and can processing facial configuration if given more time, indicating a reduction in efficiency rather than a severe limitation. He has more difficulty accessing semantic-biographic information from names. He has trouble with facial feature imagery but not imagery for global face shape. Thus this subject's deficits represent a combination of impaired familiarity and configuration processing (normally right-sided functions in right-handed subjects), and impaired feature processing and access to semantic-biographic information (normally left-sided functions). His prosopagnosia likely reflects partially anomalous rather than reversed lateralization of hemispheric perceptual functions.