Abstract
Visuomotor feedback gains vary in magnitude throughout a reach, commonly explained by optimal control. However, this pattern also matches the hand velocity profile, suggesting a simpler, perhaps hardwired, controller. Here we test between these alternatives, examining whether movement velocity regulates visuomotor gains. Feedback gain profiles were modulated across five conditions, with significant effects for altered hand, but not cursor, kinematics. Using optimal control we show that visuomotor feedback gains exhibit a consistent relation with time-to-target, rather than velocity, across a range of kinematics. Although our model suggests a time beyond which feedback gains should be down-regulated to minimise cost, our participants deliberately extend their movement durations for late perturbations, where feedback gains are reduced due to the lack of time for correction. Finally, we qualitatively replicate participant results within our model, but only when accounting for this extension of time-to-target, suggesting that expected time-to-target is critical in online feedback control.
