Differential contributions of implicit and explicit learning mechanisms to various contextual cues in dual adaptation

The ability to switch between different tasks accurately and efficiently is an invaluable feature to a flexible and adaptive human motor system. This can be examined in dual adaptation paradigms where the motor system is challenged to perform under randomly switching, opposing perturbations. Typically, dual adaptation doesn’t proceed unless each mapping is trained in association with a predictive cue. To investigate this, we first explored whether dual adaptation occurs under a variety of contextual cues including active follow-through movements, passive follow-through movements, active three-part lead-in movements, and static visual cues. In a final intervention, we provided our Instructed group with a compensatory strategy about the perturbations (30° CW/CCW rotations) and their relationships to each context (static visual cues). This allowed us to explore the extent by which dual learning is supported by both implicit and explicit mechanisms, regardless of whether or not they elicited dual adaptation across all the various cues. To this end, following perturbed training, participants from all experiments were asked to either use or ignore the strategy as they reached without visual feedback. This Process Dissociation Procedure teased apart the implicit and explicit contributions to dual adaptation. We found that active movement cues, but not passive ones, elicited dual adaptation. Expectedly, static visual cues didn’t elicit dual adaptation, but those in the Instruction group compensated by implementing aiming strategies. Critically, we found no implicit contributions in this Instruction group, but an effect of instruction, suggesting that explicit aiming strategies inhibit implicit mechanisms in dual adaptation. Thus, by implementing conscious strategies, dual adaptation can be easily facilitated even in cases where learning would not occur otherwise.