FACE RECOGNITION AND POSTERO-INFERIOR HEMISPHERIC LESIONS

Two patients with severe and lasting prosopagnosia were studied for vi suo-cognitive functions and anatomo-clinical correlations. Both patien ts were deficient in recognizing familiar faces and items of previousl y well known categories (plants and fish for patient 1, mountains for patient 2). Patient 2, but not patient 1, was also deficient for match ing of unknown faces. Patient 1, but not patient 2, was achromatopsic. Both patients had bilateral symmetrical lesions. Patient 1 had a lesi on of the inferior occipito-temporal cortex, including inferior parts of early stage visual areas. Patient 2 had a lesion of the inferior te mporal and fusiform gyri anterior to the early stage visual areas. Whe n compared in Talairach space, th-lesions of both patients had minimal overlap. Thus, severe and lasting prosopagnosia was associated with t wo almost exclusive lesion sites in the postero-inferior part of the h emispheres. Comparison between activation studies of face processing ( by others) and our lesion study uncovered several paradoxes. Lesions o f regions involved in a given task in normal subjects do not produce a deficit in this task, as shown here for gender discrimination and par tially for face matching. Conversely, lesions of a region not specific ally involved in a given task in normal subjects can produce a deficit in the task, as shown here for face identification. (C) 1997 Elsevier Science Ltd. All rights reserved.