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Melanie Palomares, Abha Gupta, Barbara Landau, Howard Egeth; Visuospatial interpolation within illusory contours: Evidence from Williams Syndrome and normal children. Journal of Vision 2006;6(6):294. https://doi.org/10.1167/6.6.294.
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Visuospatial interpolation is the estimation of object position or contour shape computed from known “anchor” positions as in Vernier acuity tasks. Our study investigates how illusory contours affect explicit interpolation of multiple positions in normal children, normal adults and in individuals with Williams Syndrome (WS), a genetic disorder that results in severely impaired global visuospatial construction abilities with a relatively spared language abilities. The visuospatial cognitive profile of WS individuals reflects abnormalities in dorsal visual areas with relative sparing in ventral visual areas (Meyer-Lindenberg et al, 2004). Do illusory contours, which involve ventral visual areas (Ritzl et al, 2003), improve judgment of relative position in normal children and WS individuals?
We measured positional thresholds by asking participants to judge the position of a target relative to two flanking objects (target-flanker distances of 1.5–11.5 deg), which either formed an illusory rectangle or not. Our results suggest that integration of distal and proximal information is mediated by separate visual areas. For interpolating positions of distal elements, normal children and WS individuals have higher positional thresholds than normal adults, because they may have immature dorsal stream functions. Moreover, illusory contours, which are examples of implicit integration and recruit ventral visual areas, improve positional thresholds in all participant groups at large inter-element distances. For interpolating proximal elements, neither participant group nor the presence of illusory contours affected positional thresholds. Ventral visual areas might be involved in integration of proximal elements since they are likely to be grouped together as part of the same object.
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