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Jennifer K.E. Steeves, G. Keith Humphrey, Jody C. Culham, Ravi S. Menon, Melvyn A. Goodale; Scene classification and parahippocampal place area activation in an individual with visual form agnosia. Journal of Vision 2002;2(7):495. doi: 10.1167/2.7.495.
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Purpose: Color information is more important for quickly and accurately classifying natural scenes when color is predictive of scene category (color-diagnostic) than for classifying man-made scenes (color-nondiagnostic). Color-diagnostic (CD) scenes are classified faster when presented in the appropriate color than when colors are inverted (hues inverted 180° in color space), while classification of color-nondiagnostic (CND) scenes is unaffected by color inversion (Oliva & Schyns, 2000). We asked whether an individual with visual form agnosia, who has a profound deficit in object recognition but spared color perception, could classify scenes and, if so, whether appropriately colored CD scenes would be classified faster and more accurately than color-inverted scenes. We also used fMRI (4 Tesla) to determine whether viewing different scene colorations produced differential levels of activation in the parahippocampal place area (PPA). Methods: Subjects included DF, a 45 yr old woman with profound visual form agnosia, and normal control subjects. fMRI data were collected using a block design including faces and different scene colorations. Results: DF was able to classify scenes accurately but with high error rates for black & white scenes. Controls showed slowed classification for color-inverted scenes only when the scenes were CD. However, DF showed slower classification for color inversion for both CD and CND scenes. In all observers, viewing scenes produced greater activation in the PPA than did viewing faces, regardless of scene color content. Conclusions: The results demonstrate that an individual with visual form agnosia can readily classify scenes and this ability is reflected in activation within the PPA. For DF, color information is important for fast and accurate scene classification whether or not color is predictive of scene category. Furthermore, in both controls and visual form agnosia, PPA activation appears to be unaffected by scene color content.
Sponsored by the CIHR Group on Action and Perception grant to GKH, RSM and MAG.
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