Efficiency of visual feedback integration differs between dominant and non-dominant arms during a reaching task.

Recent studies have shown that patterns of endpoint variability following double-step reach sequences reflect the influence of both planning and execution-related processes, but are strongly dominated by noise associated with the online updating of movement plans based on visual feedback. However, it is currently unclear whether these results reflect the dominant arm/hemisphere's postulated specialization for visual feedback processing, or whether these effects reflect a more general "arm/hemisphere independent" preference for visual feedback in the control of reaching. To explore this, twelve subjects performed double-step reach sequences with their dominant and non-dominant arms to targets in 3D space with and without visual feedback of the arm. Variability was quantified using the volumes, aspect ratios, and orientations of 95% confidence ellipsoids fit to the distributions of reach endpoints. In consonance with previous findings, the availability of visual feedback resulted in ellipsoids that were significantly smaller, had greater aspect ratios, and were more aligned with the depth axis than those performed without visual feedback. Moreover, the effects of vision on aspect ratio and orientation were similar in magnitude for the dominant and non-dominant arms, suggesting that noise associated with planning and execution-related processes is managed in a similar way by the sensorimotor systems of each arm. However, the degree to which vision decreased ellipsoid volume was found to be significantly greater for the dominant arm. This suggests that the feedback control system of the dominant arm uses visual information more efficiently to control reaches to visual targets.