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Shinichi Koyama, Akira Midorikawa, Atsunobu Suzuki, Haruo Hibino, Mitsuru Kawamura; A new type of prosopagnosia? A brain-damaged patient who can recognize faces but cannot discriminate races. Journal of Vision 2006;6(6):681. doi: 10.1167/6.6.681.
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[Case report] We report a case of a 61 year-old woman with brain damage in the left fusiform and parahippocampal gyri, as well as in the right fusiform gyrus. The patient claimed that she could not perceive “looks” of faces, although she could easily recognize pictures of famous people. She could also discriminate sex and facial expressions in the pictures normally. However, she frequently failed to discriminate races and occasionally failed to see the hollow-face illusion (Gregory 1970), although she could see shading-defined convexity and concavity (Ramachandran 1888). [Method] The patient and 3 normal controls judged if a person pictured was Asian or Middle-Eastern to examine whether perception of faces defined by edge, surface, or edge-surface integration was impaired. Using morphing, we mixed an Asian face and a Middle-Eastern face in 7 different proportions (20% Asian plus 80% Middle eastern => 80% Asian plus 20% Middle-Eastern). After morphing, 3 sets of pictures were made: (1) original pictures, (2) inverted pictures, and (3) edge-defined pictures. Each picture was presented 5 times. [Results] The classification of the inverted and edge-defined pictures by the patient was very similar to that of normal controls whereas the classification of the original pictures by the patient was significantly impaired. [Conclusion] We concluded that the integration of edge and surface was selectively impaired in this patient. These results suggest that integration of the edge and surface plays an important role in the perception of faces, especially in the discrimination of races.
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