Higher Visual Gain Contributions to Bilateral Motor Synergies and Force Control Stabilization

Abstract Visual information is a critical component that influences bimanual force control stabilization. The purpose of this study was to determine the effects of altered visual gain levels on bimanual force control strategies between multiple trials and within a trial. Twelve healthy young participants performed bimanual submaximal force control tasks by executing index finger abduction isometric movements across four different visual gain conditions (i.e., 8, 80, 256, and 512 pixels/N). We followed the uncontrolled manifold (UCM) approach to determine synergistic coordination patterns between two hands across multiple trials (i.e., bilateral motor synergies). Within a trial, force accuracy and variability were calculated to quantify bimanual force control capabilities (i.e., task stabilization). Further, we examined correlations between changes in UCM variables and force control performance from the lowest to higher visual gain conditions, respectively. The findings revealed that the values of bilateral motor synergies at 80, 256, and 512 pixels/N were significantly higher than those at 8 pixels/N. Further, force error at 80, 256, and 512 pixels/N were significantly less than those at 8 pixels/N. In UCM terms, as visual gain increased from 8 pixels/N, less amount of bad variability across multiple trials was significantly related to a reduction of force error within a trial. These findings provide supporting evidence that higher values of visual gain contribute to improved bimanual coordination function across multiple trials as well as task stabilization within trials.