Visuospatial neglect: Veridical coding of size for grasping but not for perception

Abstract

Previous studies have shown that patients with symptoms of unilateral visuospatial neglect see objects as smaller than they really are when they view them within the left half of the spatial scene. This underestimation of size is manifest in the tendency of most neglect patients to mark the subjective midpoint of a horizontal line well to the right of centre. A patient is described here who suffers from neglect following a stroke affecting chiefly the occipito-temporal region of the right hemisphere. Like most other neglect patients, EC underscales the size of objects perceived in the left half of her extrapersonal space. Despite this misperception, however, EC is able to reach out and grasp objects in the affected part of space without any abnormality. This particular neglect patient shows distortions in her perceptual experience that do not extend to her brain's processing of visual information for the guidance of action. It is therefore argued that the critical brain systems that are damaged in neglect are largely independent of the occipito-parietal mechanisms underlying visuomotor control.