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Xiaokun Xu, Irving Biederman; Face Detection Deficits in Acquired Prosopagnosia. Journal of Vision 2012;12(9):488. doi: 10.1167/12.9.488.
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Unlike their pronounced deficit in face individuation, prosopagnosics have been reported to not suffer a deficit in their detection of faces (de Gelder & Rouw, 2000; Rossion et al., 2003). MJH, a prosopagnosic with bilateral lesions to (what would be) FFA and OFA suffered from a fall 40 years ago but with an intact STS, expresses no subjective difficulty in face detection, suggesting that these posterior face areas do not mediate face detection. We have examined whether more rigorous testing would, however, reveal face detection deficits.
When a car and a face are flashed simultaneously either left/right or above/below fixation, when instructed to look at the car, controls often cannot resist a first saccade to the face (Crouzet et al., 2010) thus incurring costs in both RTs and accuracy. These costs were not apparent with MJH who, like controls, was equally fast to faces and cars when the stimuli were shown singly, suggesting a deficit in either face detectability of their automatic engagement of attention.
In a threshold experiment, we reduced the detectability of images (faces, inverted faces, or cars) by introducing phase noise (Dakin et al., 2002, Sadr & Sinha., 2004), while replacing the image′s original power-spectrum with the grand mean power-spectrum of all stimuli, including faces and cars. In a two-alternative choice, two images, one a target embedded in a variable level of noise staircased to achieve 75% accuracy, and the other composed of 100% noise, were flashed simultaneously with backward masking in each trial. Compared with controls, MJH showed lower tolerance to noise, reflected in his higher detection threshold for all target categories. Nevertheless, his deficits in detecting faces (upright or inverted) were greater than with cars.
MJH′s lesions in bilateral occipito-temporal cortices appear to have produced a deficit not only in face identification, but also in face detection.
Meeting abstract presented at VSS 2012
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