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|Title:||SIMILAR ADAPTATION TO VISUAL AND FORCE PERTURBATIONS FOR VARIOUS AND REPETITIVE REACH PRACTICE.|
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|Authors/Affiliations:||1 Jason L Neva*; 1 Denise Y.P. Henriques; |
1 York University, Toronto, ON, Canada
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|Content:||Objective: Forming an internal model for adapted reaching movements to visual and force perturbations requires a certain amount of practice. Numerous studies have shown the brain can quickly adapt to these perturbations while performing reaching movements to targets. It has also been found that the brain can generalize this adaptation to novel target locations. But many of these studies have participants reach to only a small number of target locations repeatedly. Is learning comparable in the case where target locations are constantly different and participants only have a chance to reach once to each of them? |
Materials & Methods: We addressed this question by having subjects adapt their reaches to altered visual feedback of the hand either when repeatedly reaching to four targets (Repeated practice) or reaching only once to numerous target directions (Single practice). This altered visual feedback was produced by having the cursor rotated 30° relative to hand motion. We also examined the extent to which this adaptation could transfer to untrained target locations. In a second study using the same paradigm, we investigated adaptation to force perturbations. The perturbation was produced by the InMotion2 robot manipulandum that was programmed to exert a velocity-dependent force.
Results: We found there is very little difference in learning rate between the two practice conditions. That is, participants were just as fast at learning a new visual or force perturbation when reaching once to each new target as they were when reaching over and over to the same targets. Likewise, we found that participants generalized to untrained target locations similarly across exposure conditions.
Conclusion: This suggests that the brain is as capable of deducing the required visuomotor and force adjustments following variable practice with unique targets as it is with repeated practice to the same targets. We are now investigating this same paradigm for learning and generalization over a greater workspace.
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