Visuomotor Learning Generalizes Around the Intended Movement

Abstract

Human motor learning is useful if it generalizes beyond the trained task. Here, we introduce a new idea about how human visuomotor learning generalizes. We show that learned reaching movements generalize around where a person intends to move (i.e., aiming direction) as opposed to where they actually move. We used a visual rotation paradigm that allowed us to disentangle whether generalization is centered on where people aim to move, where they actually move, or where visual feedback indicates they moved. Participants reached to a visual target with their arm occluded from view. The cursor feedback was rotated relative to the position of their unseen hand to induce learning. Participants verbally reported their aiming direction, reached, and then were shown the outcome. We periodically introduced single catch trials with no feedback to measure learning. Results showed that learning was maximal at the participants’ aiming location, and not at the actual hand position or where the cursor was displayed. This demonstrates that visuomotor learning generalizes around where we intend to move rather than where we actually move, and thus introduces a new role for cognitive processes beyond simply reducing movement error.

Structural Learning in a Visuomotor Adaptation Task Is Explicitly Accessible

“…However, this interpretation stands in contrast to a recent series of findings demonstrating that explicitly accessible re-aiming processes constitute the majority of learning (Heuer and Hegele, 2008; Hegele and Heuer, 2010; Taylor et al, 2014; Bond and Taylor, 2015; McDougle et al, 2015; Brudner et al, 2016; Day et al, 2016; Poh et al, 2016). We previously found that explicit re-aiming composed the flexible component of performance across a range of rotation magnitudes while implicit recalibration exhibited a stereotyped response (Bond and Taylor, 2015).…”

Motor Planning, Not Execution, Separates Motor Memories

“…First, by using a dynamic perturbation alone our study is the first to show that simply having different motor plans, without the confounding effect of dissociating the visual and physical location of the hand, allows opposing perturbations to be learned. Second, studies of visuomotor learning have not separated the concept of a plan from desired state (as noted in Day et al., 2016). Studies such as (Hirashima and Nozaki, 2012) show that subjects can map different desired states (i.e., left and right targets) to different force fields.…”

Taking Aim at the Cognitive Side of Learning in Sensorimotor Adaptation Tasks

“…1D, [35]). This non-monotonicity, together with evidence using various other methods, has made clear that strategy use and implicit recalibration constitute dissociable and relatively independent learning processes, with their dynamic integration resulting in the observed task performance [24,34–45]. …”

“…However, it doesn't address how or whether people develop and modify strategies in a more spontaneous manner; that is, when the experimenter does not intervene and provide explicit instructions. To address this issue, we developed a task that provides a trial-by-trial measure of the contributions of explicit aiming and implicit recalibration [24,37–39,45]. To assay strategic aiming, participants verbally report their aim direction prior to each reach, providing these reports both before the perturbation and over the course of learning (Figs.…”

“…Note that in most experimental contexts, and in the natural world, these two types of errors are confounded: We usually aim at the target of our movements, so the expected outcome is the same as the goal. However, experimental manipulations such as the instructed-strategy task [34] or aiming report task [24,37–39,45] decouple these error signals. Thus, in the strategy task, the drift phenomenon described above occurs because the recalibration system is presented with a large error signal — the difference between the aiming location and the rotated cursor, even when performance error is negligible (as in the first aiming trials).…”