GRAVITATIONAL INPUTS MODULATE VISUOSPATIAL NEGLECT

Right brain-damaged patients with left visuospatial neglect were requi red to bisect a line placed in front of them in two different body pos itions (upright and supine) and two different light conditions (light and dark). The neglect patients, unlike right brain-damaged patients w ithout neglect, strongly reduced their rightward directional error in the supine compared with the upright position. No systematic changes w ere produced by the light-dark manipulation. The present result cannot be ex plained with an attentional interpretation of hemispatial negle ct. We suggest that the present data provide futher evidence that hemi neglect is the consequence of a mis-match between different afferent i nformation integrated into an egocentric space representation. Accordi ng to this model, the presence of a lateralized brain lesion produces asymmetries in some intermediate spatial representations (eye-head, he ad-trunk, body-environment) but not in the retinotopic one. Any experi mental manipulation that reduces the asymmetry of the intermediate rep resentation such as the reduction of gravitational inputs may improve the dynamic integration of the egocentric coordinates.