Savings in sensorimotor adaptation without an explicit strategy

Abstract

The hallmark of long-term retention of sensorimotor adaptation is a faster relearning when similar perturbations are encountered again. However, what processes underlie this saving effect is in debate. Though motor adaptation is traditionally viewed as a type of procedural learning, its savings has been recently shown to be solely based on a quick recall of explicit adaptation strategy. Here, we showed that adaptation to a novel error-invariant perturbation without an explicit strategy could enable subsequent savings. We further showed that adaptation to gradual perturbations could enable savings, which was supported by enhanced implicit learning. Our study provides supporting evidence that long-term retention of motor adaptation is possible without forming or recalling a cognitive strategy, and the interplay between implicit and explicit learning critically depends on the specifics of learning protocol and available sensory feedback. NEW & NOTEWORTHY Savings in motor learning sometimes refers to faster learning when one encounters the same perturbation again. Previous studies assert that forming a cognitive strategy for countering perturbations is necessary for savings. We used novel experimental techniques to prevent the formation of a cognitive strategy during initial adaptation and found that savings still existed during relearning. Our findings suggest that savings in sensorimotor adaptation do not exclusively depend on forming and recalling an explicit strategy.

Re-exposure to a sensorimotor perturbation produces opposite effects on explicit and implicit learning processes

“…This attenuation of implicit learning, observed in both Experiments 1 and 2, was surprising given that past studies have presented evidence showing savings (Coltman et al, 2019; Yin and Wei, 2020). Despite several studies showing no savings (Haith et al, 2015; Leow et al, 2020; Morehead et al, 2015), we were unaware of any prior reports of attenuation in implicit adaptation.…”

“…Attenuation of implicit adaptation is also observed in studies that have required participants to explicitly report their aiming location, and thus allowed estimates to be made of implicit adaption by taking the difference between the actual hand angle and the reported aiming location (Taylor et al, 2014). In one study (Wilterson and Taylor, 2020; see also Yin and Wei, 2020), this aiming report task was repeated over multiple days with a 45° rotation. The estimate of implicit adaptation decreased over days (Fig.…”

“…Indeed, in many contexts, especially those involving small perturbations, most of the learning is implicit (Bond and Taylor, 2015; Kagerer et al, 1997; Morehead et al, 2015). Whether and how implicit adaptation contributes to savings remains unclear: While some studies have proposed that faster relearning is attributed to implicit processes (Coltman et al, 2019; Herzfeld et al, 2014; Yin and Wei, 2020), others reported no change in the rate of implicit adaptation upon relearning (Haith et al, 2015; Leow et al, 2020; Morehead et al, 2015). Importantly, it can be difficult to obtain a clean assessment of the time course of implicit adaptation across multiple experimental blocks given potential influences from explicit processes and the extended resilience of adaptation over time (Hadjiosif and Smith, 2013).…”

“…In studies of sensorimotor learning, a central component of savings is attributed to the explicit recall of the task structure and appropriate compensatory strategies. Whether implicit adaptation also contributes to savings remains subject to debate (Leow et al, 2020; Yin and Wei, 2020). We tackled this question by measuring, in parallel, explicit and implicit adaptive responses in a visuomotor rotation task, employing a protocol that typically elicits savings.…”

Individual differences in proprioception predict the extent of implicit sensorimotor adaptation

“…Having established that these dependent variables were reliable across days, we next asked whether differences in implicit adaptation could be accounted for by individual differences in proprioception. We opted to focus on aftereffects on day 1 data given the evidence that adaptation can change across sessions, either from interference (Avraham et al, 2020) or savings (Yin & Wei, 2020), with our own data showing the former pattern. For a more stable measure of proprioceptive shift and proprioceptive variability, we averaged the data from both days.…”