The role of right side objects in left side neglect: a dissociation between perceptual and directional motor neglect.

Based on a test introduced by Tegnér and Levander, Brain 114, 1943-1951, 1991, right brain-damaged patients were assigned to a group with unilateral perceptual neglect and a group with directional motor neglect. Brain scans showed that all directional motor neglect patients had frontal lesions, whereas in perceptual neglect patients the frontal lobes were always spared. All patients were asked to execute two tasks, which were also administered to a control group. One task consisted in pointing to tokens symmetrically distributed on a display. The other task consisted in picking up the same tokens. The tasks were first executed with the aid of vision and then in a blindfolded condition. In the case of patients with perceptual neglect, performance on the left side was better in the pick-up task than in the pointing task and improved in the blindfolded condition. Neither patients with directional motor neglect nor control patients showed these effects. The results were explained in terms of the hyperattentional hypothesis of perceptual neglect, according to which, in this form of neglect, attention is captured by the objects that lie on the right side of space.