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Cindy M. Bukach, Daniel N. Bub, Isabel Gauthier, Michael Tarr; Spatially restricted perceptual expertise for faces in a case of prosopagnosia. Journal of Vision 2005;5(8):533. doi: 10.1167/5.8.533.
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© ARVO (1962-2015); The Authors (2016-present)
Impairments of face recognition have been associated with the failure of one or more of the following processes: fine-level discrimination, holistic processing (failure to selectively attend to a single part), and configural processing (use of the spatial relations between parts). We systematically investigated each of these factors in LR, who has severe prosopagnosia following damage to his anterior and inferior right temporal lobe. Surprisingly, LR showed preservation of all 3 processes: LR was able to detect subtle changes between faces (Exp 1), failed to ignore the irrelevant half of a face when judging whether the tops or bottoms of two faces matched (Exp 2), and also showed a disproportionate effect of inversion for detecting spatial versus feature changes (Exp 3). However, unlike his performance in Exp 1 and 2, LR seemed to process only the lower half of the face in Exp 3. Exp 3 differed from Exp 1 in that it involved a local unpredictable change, whereas the change in Exp 1 affected the entire face (thus attention to any one part of the face would be sufficient to detect a change in Exp 1, but not in Exp 3). Although the change in Exp 2 was also unpredictable, the nature of the change was subtler in Exp 3 than Exp 2 (isolated feature vs. half face). Our interpretation is that LR can encode coarse-level information from the entire face, but is able to extract precise internal details from only a small portion of a face at a time. Exp 4 confirmed that when attention to multiple face features was required, LR could determine the identity of only a single feature. This impairment was evident for nonface objects as well (Exp 5). We conclude that expert face mechanisms are not “all-or-none”, but rather can be impaired incrementally, such that they may remain functional over a restricted spatial area. This conclusion is consistent with previous research suggesting that perceptual expertise is acquired in a spatially incremental manner (Gauthier & Tarr, 2002).
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