HORIZONTAL VISUAL-MOTION MODULATES FOCAL ATTENTION IN LEFT UNILATERALSPATIAL NEGLECT

Patients with unilateral spatial neglect are impaired in directing foc al attention toward the contralesional side of space. Provision of sta tic spatial cues on the neglected side has previously been shown to he lp overcome this deficit. Common movement of visual stimuli may also g uide the allocation of spatial attention, although examined in patient s with unilateral spatial neglect. Eleven patients with right hemisphe re damage and clinical evidence of left: unilateral spatial neglect, a nd 11 matched, healthy controls were tested on a task of horizontal li ne bisection. Lines were presented on a computer display, with a neutr al, static, or slowly drifting, random dot background. Under condition s of motion, background stimuli drifted either leftward or rightward, across the full width of the display, at speeds that did not elicit op tokinetic nystagmus or perceptual aftereffects. Controls were accurate in all conditions, and showed minimal effects of background condition s. By contrast, patients with left unilateral spatial neglect were sen sitive to leftward background motion, showing a significant leftward s hift in bisection error, relative to neutral, static, and rightward mo ving backgrounds. There was no significant effect of rightward motion in comparison with the neutral and static conditions. The extent to wh ich patients were susceptible to the effects of background motion was not related to severity of unilateral spatial neglect, as measured by clinical tests. The benefits of leftward motion may reflect activity o f preserved motion processing mechanisms, which provide input to an ot herwise dysfunctional attentional network. The use of visual motion to assist in contralesionally guiding focal attention may be useful in t he rehabilitation of unilateral spatial neglect.