BRAIN IMAGINGERP abnormalities of illusory contour perception in Williams SyndromeGrice, Sarah J.1 2; Haan, Michelle de3; Halit, Hanife1; Johnson, Mark H.1 CA; Csibra, Gergely1; Grant, Julia2; Karmiloff-Smith, Annette2Author Information 1Centre for Brain and Cognitive Development, School of Psychology, Birkbeck College, University of London, Malet Street, London WC1E 7HX 2Neurocognitive Development Unit 3Developmental Cognitive Neuroscience Unit, Institute of Child Health, London, UK CACorresponding Author: Mark.Johnson@psych.bbk.ac.uk Received 23 June 2003; accepted 22 July 2003 NeuroReport: October 6th, 2003 - Volume 14 - Issue 14 - p 1773-1777 Buy Abstract Williams syndrome is a genetic disorder in which visuo-spatial performance is poor. Theorists have claimed that the deficit lies in high-level processing, leaving low-level visual processes intact. We investigated this claim by examining an aspect of low-level processing, perceptual completion, i.e. the ability of this clinical group to perceive illusory Kanizsa squares. We then used event-related potentials to examine neural correlates of perceptual completion. While participants were able to perceive illusory contours, the neural correlates of this apparently normal perception were different from controls. Such differences in low-level visual processes may significantly impact on the development of higher-level visual processes. We conclude that, contrary to earlier claims, there is atypical neural processing during low-level visual perception in Williams syndrome. © 2003 Lippincott Williams & Wilkins, Inc.