Abstract
Visuomotor rotation tasks have proven to be a powerful tool to study adaptation of the motor system. While adaptation in such tasks is seemingly automatic and incremental, participants may gain knowledge of the perturbation and invoke a compensatory strategy. When provided with an explicit strategy to counteract a rotation, participants are initially very accurate, even without on-line feedback. Surprisingly, with further testing, the angle of their reaching movements drifts in the direction of the strategy, producing an increase in endpoint errors. This drift is attributed to the gradual adaptation of an internal model that operates independently from the strategy, even at the cost of task accuracy. Here we identify constraints that influence this process, allowing us to explore models of the interaction between strategic and implicit changes during visuomotor adaptation. When the adaptation phase was extended, participants eventually modified their strategy to offset the rise in endpoint errors. Moreover, when we removed visual markers that provided external landmarks to support a strategy, the degree of drift was sharply attenuated. These effects are accounted for by a setpoint state-space model in which a strategy is flexibly adjusted to offset performance errors arising from the implicit adaptation of an internal model. More generally, these results suggest that strategic processes may operate in many studies of visuomotor adaptation, with participants arriving at a synergy between a strategic plan and the effects of sensorimotor adaptation.
Highlights
When learning a new motor skill, verbal instruction often proves useful to hasten the learning process
We started with the standard state-space model (Eq 1 and 2), and incrementally modified it to accommodate the use of an explicit strategy
Modeling strategy use during visuomotor adaptation When informed of an appropriate strategy that will compensate for the rotation, participants immediately counteract the rotation and show on-target accuracy
Summary
When learning a new motor skill, verbal instruction often proves useful to hasten the learning process. A new driver is instructed on the sequence of steps required to change gears when using a standard transmission. As the skill becomes consolidated, the driver no longer requires explicit reference to these instructions. Operating a vehicle with a stiffer or looser clutch does not generally require further instruction, but rather entails a subtle recalibration, or adaptation of the previously learned skill. The use of an explicit strategy may even lead to degradation in the expert’s performance. Consideration of these contradictory issues brings into question the role of instructions or explicit strategies in sensorimotor learning
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