GRAVITY AND HEMINEGLECT

SPATIAL cognition requires the integration of visual inputs with propr ioceptive and vestibular information about the position of the eye, th e head and the body. All these sources are used by the brain to produc e multiple higher-order (e.g. egocentric) representations of space, su bserving accurate spatial behaviour. Such spatial representations are disrupted by unilateral cerebral damage producing neglect in the contr alateral side of space. In eight brain-damaged patients with left unil ateral neglect the manipulation of gravitational-otolithic information , obtained by placing patients in a supine position, produced a signif icant reduction of the rightward directional error in the line bisecti on task in all cases. This finding suggests that, in patients with neg lect, gravitational information is processed in a non-symmetrical fash ion, with a rightward bias towards the side of the lesion. This is the first study showing that manipulation of gravitational input affects neuropsychological disorders of visuo-spatial processing.