Reaching Within a Dynamic Virtual Environment

Planning and execution of reaching movements requires a series of computational processes that involves the localization of both the target and initial arm position, and the translation of this spatial information into appropriate motor commands that will bring the hand to the target. Voluntary and/or involuntary changes in the spatial relationship between our hand and the space in which we plan to reach may occur at any time. In the current study we investigated the effects of shifting both the central and peripheral visual field on visuomotor control using a virtual visual environment. In two separate experiments, six seated healthy subjects were exposed to either stationary or roll motion of a 3D virtual scene while reaching for a visual target that remained stationary in space or unexpectedly shifted to a second position with different inter-stimulus intervals. Our initial results suggest that both temporal and spatial aspects of the reaching movement were affected by roll of the visual field. Whereas the results indicate that subjects were able to amend their ongoing motion to match the target position with both scene conditions, the presence of peripheral visual field motion produced significantly longer pauses during the reach movement when the target shifted in space. We conclude from this that motion in the peripheral field of view interfered with the ability to simultaneously process two consecutive stimuli. The terminal arm posture also exhibited a drift in the direction opposite to the roll motion suggesting that subjects were compensating for a perceived change in their visual reference frame