Representation of the Centre of a Perceptual Group in Neglect: A Case Study

Abstract

Abstract We attempted to study how patients with visual neglect represent the centre of a perceptual group determined by the Gestalt principles of proximity and/or similarity. Patient LJ, with lesions of the right frontal, temporal and parietal regions, was instructed to mark the centre of a horizontal array of triangles or arrows. In Experiment 1, we held the position of the array constant on the page but In some conditions plus signs were added to the right or left of the array. Adding plus signs to the right increased neglect in bisection, indicating effects due to shifting the centre of a group based on the proximity of elements. However, this effect of additional right-side Items could be overcome by moving the whole array into the patient's right hemifield. The data suggest that visual neglect can be affected by the position of a stimulus relative to a proximity-based group, but this effect can be overridden by the effect of stimulus position in body space. The results support the proposal that the effects of object-coding Interact with those due to the hemispace of presentation, to influence the magnitude of visual neglect.