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  • Study: Virtual Reality Systems Could Enhance Intermanual Transfer

    It's well-known that physical training in 1 hand can result in performance gains in the opposite, untrained hand—a phenomenon known as intermanual transfer—and that using a mirror to make it look as if the untrained hand is moving can speed up the process. But now researchers claim that allowing a subject to "see" the untrained hand move by way of virtual reality (VR) can further enhance the gains, and light up the neural networks that make it possible.

    In a series of experiments conducted on a total of 53 participants, researchers hooked up subjects to a VR system that used a headset and a pair of gloves that tracked finger movements and translated them into a visual representation of the participant's hands. Researchers could then make it seem as if, when the subject moved fingers on his or her right hand, the left hand was moving. Results were published in Cell Reports.

    The experiments themselves involved participants learning and then performing a set of rapid finger movement sequences in their right hands. During the learning stage, the visual images of their moving fingers were manipulated in 3 ways: as movement of the right-hand fingers (what authors call "congruent feedback"), as movement of the left-hand fingers even though the right-hand fingers were moving ("incongruent feedback"), and no feedback. Finally, participants were shown images of the left hand performing the movements while both hands remained immobile.

    Researchers found that while left-hand performance improved in all 3 scenarios that involved actual movement of the subject's right-hand fingers (not true of simply watching the movements while immobile), the most significant gains in left-hand performance were achieved when subjects received incongruent feedback—that is, when it looked like a participant's left-hand fingers were moving as they moved the fingers on the right.

    In the second experiment, researchers coupled the VR system with a device that passively moved the left-hand fingers in conjunction with images sent to the headset. Again, they applied the 3 basic visual elements—congruent, incongruent, and no image—employing the passive movement device along the way. Their findings: when participants weren't supplied with the visual representation of left-finger movements, the passive movement system didn't improve performance over what was observed the first experiment. However, when researchers coupled the visual element with the passive movements, participants experience the highest performance gains of all, "significantly higher than all other training types." Authors assert that the "gains across training conditions cannot be explained by differences in the number of self-paced movements or subliminal movement of the untrained hand."

    Finally, researchers used whole-brain functional magnetic resonance imaging (fMRI) to get a better idea of just how functional connectivity worked in the training scenarios from the first experiment (without the passive movement system). Focusing on the left and right superior parietal lobules (L-SPL and R-SPL, respectively), and the bilateral occipito-temporal visual regions (R-Visual and L-Visual), they found that only activity in the left and right SPL was correlated with performance gains, and that, somehow, the "incongruent" visual training created stronger activity in the SPLs. "This suggests an SPL-based mechanism that plays a significant role in the integration of input received from both the visual and motor cortex during training with incongruent visual feedback," authors write.

    Researchers believe that "exploiting the current novel approach has the potential for enhancing motor acquisition in clinical patients who exhibit mild to moderate upper extremity hemiparesis," asserting that, while direct training of the affected hand has "well-established" effects, it can be a very challenging approach, "especially in cases where…basic movement capability…is limited." Authors believe that the VR approach is a way to "bypass this challenge by combining the VR setup…with physical training of the nonaffected hand."

    "Our results suggest that, at least when motor skills are concerned, contrary to the popular idiom, my left hand actually does know what my right hand is doing, and this knowledge is likely medicated through information conveyed by the SPL," authors write.

    Research-related stories featured in PT in Motion News are intended to highlight a topic of interest only and do not constitute an endorsement by APTA. For synthesized research and evidence-based practice information, visit the association's PTNow website.

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