Utilization of visual feedback of the hand according to target view availability in the online control of prehension movements.

The aim of this study was to investigate the role of online vision of a target object and the participant's moving hand in the early phase of reach-to-grasp movements. We designed an experiment that separately manipulated the visibility of a moving hand and the target object by using two liquid crystal shutter plates placed in the same horizontal plane (25 cm above the experimental table). When target view was available immediately after movement onset, the effect of hand view in the early phase of movement was very limited. The effect of hand view appeared when target view in the early phase of movement was not available. This was even the case for the condition where the temporal range of non-availability of target view after movement initiation was 150 ms. Therefore, online vision (of target and hand) for controlling grasping was utilized in a flexible fashion that depended on the visual environment.