Abstract: Background: 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. However, it is not fully understood if and how robotic therapy can address these decits. The aim of our study was to nd how muscle coordination, analyzed from the perspective of motor modules, could change during motor adaptation to a dynamic environment generated by a haptic interface.
Methods: In 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 30cm). 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.
Results: We found that participants initially reacted to the perturbation by adapting the activation of motor modules used during free motion and by adopting two temporary complementary modules. Further adaptation to the force field led to the use of two dierent and enduring complementary motor modules, which evolved throughout the experiment maintaining a comparable structure until the late phase of re-adaptation.
Conclusions: This 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.