Planning and online control of goal directed movements when the eyes are 'relocated'

We investigated the effects of different viewpoints on remapping visuo-motor space, and whether remapping happens differently during the planning and the online control phase of goal-directed movements. Participants tapped targets on a monitor that was placed horizontally flat and flush with the table in front of them. They viewed the layout of the scene, including the monitor, and their hand, through video goggles attached to a camera. The camera could be moved along a semi-circle with the monitor as the circle's center. On each trial, the camera was randomly positioned at one of seven locations on the semi-circle (-90 to +90 degrees in 30 degrees steps), always at eye height. The time needed to tap the target was quickest when the camera was approximately facing the participant and progressively increased when the camera was located more to the sides (Experiment 1). There was no effect of camera location on performance when participants only saw the static layout of the scene and were not allowed to see the scene or their hand during the movement (Experiment 2). By comparison, the dependency of performance on camera location increased when participants did not have information about the layout of the scene at the start of the trial, and could only perform remapping when their hand was visible during the movement (Experiment 3). These results indicate that visuo-motor remapping happens differently during the planning phase when only static information about the layout is available, and during the control phase when dynamic information about the moving hand is also available.