Separation of multiple motor memories through implicit and explicit processes

Abstract

Acquisition of multiple motor skills without interference is a remarkable ability in daily life. During adaptation to opposing perturbations, a common paradigm to study this ability, each perturbation can be successfully learned when a contextual follow-through movement is associated with the direction of the perturbation. It is still unclear, however, to what extent this learning engages the cognitive explicit process and the implicit process. Here, we untangled the individual contributions of the explicit and implicit components while participants learned opposing visuomotor perturbations, with a second unperturbed follow-through movement. In Exp. 1 we replicated previous adaptation results and showed that follow-through movements also allow learning for opposing visuomotor rotations. For one group of participants in Exp. 2 we isolated strategic explicit learning, while for another group we isolated the implicit component. Our data showed that opposing perturbations could be fully learned by explicit strategies; but when strategy was restricted, distinct implicit processes contributed to learning. In Exp.3, we examined whether learning is influenced by the disparity between the follow-through contexts. We found that the location of follow-through targets had little effect on total learning, yet it led to more instances in which participants failed to learn the task. In Exp. 4, we explored the generalization capability to untrained targets. Participants showed near-flat generalization of the implicit and explicit processes. Overall, our results indicate that follow-through contextual cues might activate, in part, top-down cognitive factors that influence not only the dynamics of the explicit learning, but also the implicit process.

Cerebellar degeneration impairs strategy discovery but not strategy recall

“…These individual differences may, in part, be driven by a generic cognitive deficit in a subset of the participants (i.e., inattention to the feedback, failure to understand the task). Indeed, there were some individuals whose late adaptation mean hand angles were close to baseline in both blocks; see (43,46)). These "non-learners" would also have non-sensical recall ratios since there was no learning to recall.…”

“…Critically, when visual feedback was provided (congruent or rotated), we imposed an 800 ms delay between the time at which the amplitude of the movement reached the target distance and onset of the visual feedback. By delaying the visual feedback, we sought to eliminate the contribution of implicit processes that occur during motor adaptation, and as such, isolate the contribution of strategic re-aiming (43)(44)(45)(46). The feedback cursor remained visible for 500 ms.…”

Contextual effects in sensorimotor adaptation adhere to associative learning rules

“…For instance, distinct motor memories should be retrieved when a skilled tennis player prepares to hit a service return on a clay court versus a grass court. A topic of considerable discussion in the adaptation literature centers on the constraints underlying effective contextual cues (Addou et al, 2011(Addou et al, , 2011Heald et al, 2021;Dawidowicz et al, 2021;Heald et al, 2018;Howard et al, 2012Howard et al, , 2013Howard et al, , 2015Karniel and Mussa-Ivaldi, 2002;Osu et al, 2004;Schween et al, 2019;Sheahan et al, 2016Sheahan et al, , 2018Forano and Franklin, 2020;Forano et al, 2021). Contextual cues are highly effective when the cue is directly relevant to properties of the movement.…”

Implicit sensorimotor adaptation is preserved in Parkinson’s Disease

“…A related phenomenon involves tasks in which the participant must successively learn multiple visuomotor mappings (e.g., 45° clockwise rotation block followed by 45° counterclockwise rotation block). Performance on these tasks is facilitated by the successful utilization of multiple aiming strategies (76). Here, too, an impairment has been observed in PD (77).…”