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I. Kovacs, A. Lukacs, A. Feher, M. Racsmany, C. Pleh; Contour integration deficit in Williams Syndrome children. Journal of Vision 2001;1(3):146. doi: 10.1167/1.3.146.
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Williams syndrome (WMS) is a developmental disorder where a relatively small genetic deletion seems to result in severely impaired visual abilities. Behavioral studies mostly involve neuropsychological tests of higher visual functions, and reveal, e.g., a dissociation between spatial cognition (impaired) and face processing (preserved). Gross anatomical studies reveal more pronounced cortical volumetric reductions in parietal as compared to temporal areas indicating a dorsal/ventral dichotomy behind the behavioral dissociation. However, the most severe volumetric changes are found in the occipital lobe (Reiss et al, 2000). Occipital involvement is indicated also by cytoarchitectonic measurements: while most cortical areas appear relatively normal, signs of abnormal neural connectivity have recently been discovered in area 17 (Galaburda & Bellugi, 2000). These anatomical findings seem to call for studies addressing early levels of visual processing in WMS. We studied early visual cortical processing in WMS by employing a contour integration task. The task involves the detection of a path of high contrast Gabor signals embedded in a random background of Gabor signals, and it is believed to be mediated by relatively low-level, long-range spatial interactions. Typically developing children show an extended developmental period in their ability to integrate orientation information across the visual field in this task (Kovacs et al, 1999). WMS subjects in our study lag behind typical age-norms, and never reach typical adult performance levels. This result supports the possibility of abnormal long-range spatial interactions and neural connectivity in WMS visual cortex. The correlation between anatomical and behavioral data in this case opens up a new dimension in the understanding of the neuroperceptual profile in WMS; and it predicts that WMS subjects will encounter difficulties in tasks involving long-range interactions, and contextual integration.
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