Pointing and grasping in unilateral visual neglect: effect of on-line visual feedback in grasping

Three experiments are reported examining judgements of the centre of a stick in a patient with unilateral neglect after right hemisphere damage. Replicating previous data [35, 37], judgements showed more evidence of neglect when pointing rather than when a grasp response was used (Experiment 1), particularly when pointing preceded grasp (Experiment 2). Neglect also increased for longer sticks and when sticks fell in the patient's left hemispace; the effects of stick length and hemispace were additive with those of response (point vs grasp). Experiment 3 showed that the advantage for grasp over pointing responses occurred only when performance was guided by on-line visual feedback, and it emerged only during the end part of the reach trajectory. The results are discussed in relation to the role of visual feedback in movement control. (C) 1999 Elsevier Science Ltd. All rights reserved.