Spatio-motor cueing in unilateral left neglect: the role of hemispace, hand and motor activation.

Reported beneficial effects of left arm activation on neglect are experimentally examined. The present study of a subject with left visual neglect compared left hand finger movement with an instruction to visually anchor perception on the left arm during letter cancellation. Only the finger movements significantly reduced neglect. Another comparison was between "out of sight" finger movements of the left hand in left and right hemispace, respectively. Only left hemispace "blind" finger movements significantly reduced neglect compared to the standard condition. Thirdly, blind left finger movements in left hemispace were compared with passive visual cueing (reading a changing number) and again it was found that only the finger movements reduced neglect. Finally, right finger movements in left hemispace were compared with left finger movements in left hemispace: only the latter reduced neglect. The implications of these findings for theory and therapy of neglect are discussed.