Abstract
Training to reach with rotated visual feedback results in adaptation of hand movements, which persist when the perturbation is removed (reach aftereffects). Training also leads to changes in felt hand position, which we refer to as proprioceptive recalibration. The rate at which motor and proprioceptive changes develop throughout training is unknown. Here, we aim to determine the timescale of these changes in order to gain insight into the processes that may be involved in motor learning. Following six rotated reach training trials (30° rotation), at three radially located targets, we measured reach aftereffects and perceived hand position (proprioceptive guided reaches). Participants trained with opposing rotations one week apart to determine if the original training led to any retention or interference. Results suggest that both motor and proprioceptive recalibration occurred in as few as six rotated-cursor training trials (7.57° & 3.88° respectively), with no retention or interference present one week after training. Despite the rapid speed of both motor and sensory changes, these shifts do not saturate to the same degree. Thus, different processes may drive these changes and they may not constitute a single implicit process.
Highlights
Healthy participants adapt their reaching behavior when movement dynamics or visual feedback are altered, such as in velocity dependent force-fields [1, 2] or in visuomotor adaptation paradigms [3, 4, 5, 6, 7]
In addition to reach aftereffects, our lab has repeatedly demonstrated that sensory changes accompany training with rotated visual feedback: the felt hand position shifts toward the visual feedback [8, 9, 10, 11]
It has remained unclear when and how quickly during training reach aftereffects and proprioceptive recalibration emerge. This kind of information would provide insight into the types of mechanisms and processes associated with visuomotor learning. We found that these changes emerged surprisingly quickly during training, with proprioceptive recalibration reaching a plateau and reach aftereffects increasing with further training
Summary
Healthy participants adapt their reaching behavior when movement dynamics or visual feedback are altered, such as in velocity dependent force-fields [1, 2] or in visuomotor adaptation paradigms [3, 4, 5, 6, 7]. These changes in motor behavior persist even after the perturbation is removed, called reach aftereffects. We will be able to establish how PLOS ONE | DOI:10.1371/journal.pone.0163695 October 12, 2016
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