The effects of awareness of the perturbation during motor adaptation on hand localization

ABSTRACTExplicit awareness of a task is often evoked during rehabilitation and sports training with the intention of accelerating learning and improving performance. However, the effects of awareness of perturbations on the resulting sensory and motor changes produced during motor learning are not well understood. Here, we use explicit instructions as well as large rotation sizes to generate awareness of the perturbation during a visuomotor rotation task and test the resulting changes in both perceived and predicted sensory consequences as well as implicit motor changes.We split participants into 4 groups which differ in both magnitude of the rotation (either 30° or 60°) during adaptation, and whether they receive a strategy to counter the rotation or not prior to adaptation. Performance benefits of explicit instruction are largest during early adaptation but continued to lead to improved performance through 90 trials of training. We show that with either instruction, or with large perturbations, participants become aware of countering the rotation. However, we find a base amount of implicit learning, with equal magnitudes, across all groups, even when asked to exclude any strategies while reaching with no visual feedback of the hand.Participants also estimate the location of the unseen hand when it is moved by the robot (passive localization) and when they generate their own movement (active localization) following adaptation. These learning-induced shifts in estimates of hand position reflect both proprioceptive recalibration and updates in the predicted consequences of movements. We find that these estimates of felt hand position, which reflect updates in both proprioception and efference based estimates of hand position, shift significantly for all groups and were not modulated by either instruction or perturbation size.Our results indicate that not all processes of motor learning benefit from an explicit awareness of the task. Particularly, proprioceptive recalibration and the updating of predicted sensory consequences are largely implicit processes.

Spatial numerical estimation within proprioceptive recalibration

Research has emphasized that the body's position in space and patterns of visual searching for stimuli are crucial variables to explain the ability to estimate distances numerically. In this paper, we tested the hypothesis that proprioception recalibration interferes in the ability to numerically estimate fixed peri-personal space. The Rubber Hand Illusion (RHI) experimental paradigm was applied as a tool to temporally manipulate the sense of proprioception in participant’s right hand. Seventeen college students were asked to estimate fixed horizontal spatial cues before and after two conditions of tactile stimulation within RHI (synchronous versus asynchronous stroking). Results evidenced that proprioceptive recalibration of the hand were temporally altered by both stroking patterns. However, the effects of numerically estimate fixed horizontal cues towards the body midline were only consistently observed in the synchronous stroking condition. Those findings suggest that numerical estimates of peri-personal fixed cues are strongly associated with proprioceptive recalibration, corroborating the literature on multisensory integration of perception.