Visual depth processing in Williams–Beuren syndrome
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Patients with Williams–Beuren Syndrome (WBS, also known as Williams Syndrome) show many problems in motor activities requiring visuo-motor integration, such as walking stairs. We tested to what extent these problems might be related to a deficit in the perception of visual depth or to problems in using this information in guiding movements. Monocular and binocular visual depth perception was tested in 33 patients with WBS. Furthermore, hand movements to a target were recorded in conditions with and without visual feedback of the position of the hand. The WBS group was compared to a group of control subjects. The WBS patients were able to perceive monocular depth cues that require global processing, but about 49% failed to show stereopsis. On average, patients with WBS moved their hand too far when no visual feedback on hand position was given. This was not so when they could see their hand. Patients with WBS are able to derive depth from complex spatial relationships between objects. However, they seem to be impaired in using depth information for guiding their movements when deprived of visual feedback. We conclude that the problems that WBS patients have with tasks such as descending stairs are not due to an inability to judge distance.
KeywordsWilliams–Beuren syndrome Visual depth Perception Motor coordination Sensorimotor integration
The authors are grateful to the patients with Williams–Beuren Syndrome and their families for participating in this study. JN van der Geest was supported by grants from the NWO (903-68-394) and the Revolving Fund of the Erasmus MC. MA Frens was supported by a VIDI grant from the NWO.
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