Complementarity between the feedforward and feedback mechanisms is necessary for anticipatory activity in hand tracking

Anticipatory activity arising from characteristic predictive mechanisms is observed in human and animal sensory-motor control systems. The quantitative features of anticipatory activity have been reported in terms of the amount of hand precedence from the target with various conditions in tasks that involve tracking and synchronizing a visual and auditory target. However, the mechanism of anticipatory activity has not been investigated in detail. In the present study, numerical simulations were performed with a hand-tracking model that exhibited anticipatory activity with a focus on the relationship between feedforward and feedback control elements. Rhythmic components and an on-off mechanism were introduced to the feedforward control element and the feedback control element, respectively, depending on whether or not the visual target was displayed. Anticipatory activity of hand-motion was observed when feedback control was activated with weaker operation of feedforward control. In addition, hand motion was delayed when feedback control was activated with stronger operation of feedforward control. This suggests that in sensory-motor control systems, feedforward and feedback control work complementarity rather than simultaneously.