Abstract
BackgroundRobotic neurorehabilitation aims at promoting the recovery of lost function after neurological injury by leveraging strategies of motor learning. One important aspect of the rehabilitation process is the improvement of muscle coordination patterns, which can be drastically altered after stroke. However, it is not fully understood if and how robotic therapy can address these deficits. The aim of our study was to find how muscle coordination, analyzed from the perspective of motor modules, could change during motor adaptation to a dynamic environment generated by a haptic interface.MethodsIn our experiment we employed the traditional paradigm of exposure to a viscous force field to subjects that grasped the handle of an actuated joystick during a reaching movement (participants moved directly forward and back by 30 cm). EMG signals of ten muscles of the tested arm were recorded. We extracted motor modules from the pooled EMG data of all subjects and analyzed the muscle coordination patterns.ResultsWe found that the participants reacted by using a coordination strategy that could be explained by a change in the activation of motor modules used during free motion and by two complementary modules. These complementary modules aggregated changes in muscle coordination, and evolved throughout the experiment eventually maintaining a comparable structure until the late phase of re-adaptation.ConclusionsThis result suggests that motor adaptation induced by the interaction with a robotic device can lead to changes in the muscle coordination patterns of the subject.
Highlights
Robotic neurorehabilitation aims at promoting the recovery of lost function after neurological injury by leveraging strategies of motor learning
Pairwise post-hoc analyses indicated the presence of significant direct effects when the force field was first applied with a simultaneous change of the motion profile and an increase of the travel time
The performance at follow-up was the same as the baseline. These results demonstrate the ability of healthy subjects to learn a viscous force field, as already known in literature [1], and suggest that all changes in muscular activity observed in this study can be associated with motor adaptation
Summary
Robotic neurorehabilitation aims at promoting the recovery of lost function after neurological injury by leveraging strategies of motor learning. One important aspect of the rehabilitation process is the improvement of muscle coordination patterns, which can be drastically altered after stroke. It is not fully understood if and how robotic therapy can address these deficits. The aim of our study was to find how muscle coordination, analyzed from the perspective of motor modules, could change during motor adaptation to a dynamic environment generated by a haptic interface. Human subjects can adapt to a novel dynamic environment during reaching movements [1]. When subjects are abruptly exposed to the novel environment (dynamic perturbation), large trajectory errors (direct effect) are shown, compared with unperturbed movements (baseline). The same goal could be obtained by conserving most of the muscle coordination used during unperturbed motion
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