Parallel Specification of Visuomotor Feedback Gains during Bimanual Reaching to Independent Goals

Abstract

During goal-directed reaching, rapid visuomotor feedback processes enable the human motor system to quickly correct for errors in the trajectory of the hand that arise from motor noise and, in some cases, external perturbations. To date, these visuomotor responses, the gain of which is sensitive to features of the task and environment, have primarily been examined in the context of unimanual reaching movements towards a single target. However, many natural tasks involve moving both hands together, often to separate targets, such that errors can occur in parallel and at different spatial locations. Here, we examined the resource capacity of automatic visuomotor corrective mechanisms by comparing feedback gains during bimanual reaches, towards two targets, to feedback gains during unimanual reaches towards single targets. To investigate the sensitivity of the feedback gains and their relation to visual-spatial processing, we manipulated the widths of the targets and participants’ gaze location. We found that the gain of corrective responses to cursor displacements, while strongly modulated by target width and gaze position, were only slightly reduced during bimanual control. Our results show that automatic visuomotor corrective mechanisms can efficiently operate in parallel across multiple spatial locations.

Significance Statement During goal-directed reaching, rapid visuomotor feedback processes enable the motor system to quickly correct for viewed errors in the trajectory of the hand. To date, these visuomotor responses have mostly been examined in the context of unimanual reaching movements to a single target. However, many natural tasks involve moving both hands at the same time such that errors can occur in parallel and at different locations. We examined the resource capacity of automatic visuomotor corrective mechanisms by comparing feedback gains during bimanual reaches, toward two separate targets, to feedback gains during unimanual reaches toward single targets. We show that automatic visuomotor corrective mechanisms can efficiently operate in parallel across multiple spatial locations, with little cost for bimanual control.