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Morgan D. Barense, K.W. Joan Ngo, Mary A. Peterson; Figure-ground perception is impaired in medial temporal lobe amnesia. Journal of Vision 2010;10(7):749. doi: 10.1167/10.7.749.
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Amnesia resulting from medial temporal lobe lesions is traditionally considered to be a selective deficit in long-term declarative memory. In contrast to this view, recent studies suggest that high-level perceptual processing may also be compromised in the disorder (e.g., Lee et al., 2005; Barense et al., 2007). Here, we tested figure-ground segmentation in two densely amnesic patients with focal lesions to the medial temporal lobes resulting from herpes viral simplex encephalitis. For each display, two adjacent regions shared a contour and participants reported whether they perceived the left or the right region as the figure (e.g., Peterson et al., 2000). In experimental stimuli, the central contour portrayed a familiar object on one, high-denotative, side. In control stimuli, no known objects were portrayed on either side of the central contour, but one side was a part-scrambled version of one of the high-denotative regions. Relative to age and education matched controls, the patients failed to show effects of familiarity on figure assignment, with neither patient reporting seeing the figure on the high-denotative side of the edge any more often than on the matched scrambled side. The lack of a difference arose because the patients were highly likely to see both the part-scrambled and the high denotative regions as figure. Moreover, both patients identified less than half of the familiar objects they saw as figures. The pattern of performance suggests that the patients may have been responding on the basis of the familiarity of the individual features of the objects, rather than on the basis of the overall familiar configuration of the object as a whole. These results suggest that fast access to familiar configurations and conscious object recognition of portions of figures may be impaired in medial temporal lobe amnesia.
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