The effects of rotation on spatial attention.

Unilateral spatial neglect can be reduced by cold water caloric stimulation of the contralesional ear. Three hypotheses may account for this response. Caloric stimulation may increase the arousal of the damaged hypoaroused hemisphere. Moving stimuli to ipsilesional space improves the performance of patients with neglect. Caloric stimulation may move viewer-centered spatial maps in an ipsilesional direction. Unilateral neglect may be related to a spatial attentional bias. Vestibular stimulation may temporarily influence this bias. To learn if vestibular stimulation may induce an attentional spatial bias, the authors studied eight normal subjects by having these subjects attempt to bisect lines before and during vestibular stimulation. If caloric stimulation alters neglect because it changes the attentional spatial bias, the authors should be able to induce neglect in normal subjects by pertubating the vestibular system. Vestibular stimulation was induced by spinning a chair and then abruptly stopping the spinning chair. The authors found that after normal subjects were rotated to the left, they misbisected lines to the left but did not misbisect lines after they were rotated to the right. Although these results support the postulate that vestibular stimulation can induce an attentional spatial bias, the authors' results also suggest that there are intrinsic attentional asymmetries.