Accuracy instructions differently modulate visual and nonvisual contributions to ongoing reaches.

The control of ongoing goal-directed reaches is influenced by both visual and nonvisual sensorimotor processes. Notably, intentions to produce accurate movements also influence reaching performance. However, it is not known whether these improvements associated with accuracy-based intentions can be attributed to changes in movement planning and/or online control. Notably, such improvements may come about via both visual and nonvisual online control processes. Using frequency domain analyses, the relative online contributions of visual and nonvisual subprocesses to reaching performance have been previously identified (e.g., de Grosbois & Tremblay. 2018a, 2018b). Thus, the current study tested whether the relative contributions of these online control subprocesses are influenced by instructions to be accurate. Reaching movements were completed in the presence of 3 experimental manipulations. First, vision during voluntary reaches was either provided or occluded. Second. high- and low-accuracy instruction sets were provided. And third, the predictability of visual information was manipulated through blocked and randomized feedback scheduling. The results indicated that the contribution of online visuomotor processes (i.e., visual subprocess) was increased by the availability of online vision and instructions to be accurate. In contrast, the nonvisual subprocess was promoted in the absence of online vision, but suppressed when a randomized feedback schedule was implemented with instructions to be accurate. Ultimately, instructions to be accurate increase the relative contribution of vision-based online sensorimotor processes and can decrease the contributions of nonvisual online sensorimotor processes.