Modulation of interhemispheric interactions across symmetric and asymmetric bimanual force regulations

Authors

  • Toshiki Tazoe,

    Corresponding author
    1. Division of Health and Sport Education, United Graduate School of Education, Tokyo Gakugei University, Chiba, Japan
    2. Department of Rehabilitation for Movement Functions, Research Institute, National Rehabilitation Center for Persons with Disabilities, Tokorozawa, Japan
    • Department of Health and Sport Sciences, Faculty of Education, Chiba University, Chiba, Japan
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  • Syusaku Sasada,

    1. Division of Health and Sport Education, United Graduate School of Education, Tokyo Gakugei University, Chiba, Japan
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  • Masanori Sakamoto,

    1. Division of Health and Sport Education, United Graduate School of Education, Tokyo Gakugei University, Chiba, Japan
    2. Department of Physical Education, Faculty of Education, Kumamoto University, Kumamoto, Japan
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  • Tomoyoshi Komiyama

    1. Department of Health and Sport Sciences, Faculty of Education, Chiba University, Chiba, Japan
    2. Division of Health and Sport Education, United Graduate School of Education, Tokyo Gakugei University, Chiba, Japan
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Correspondence: T. Tazoe, 3Department of Rehabilitation for Movement Functions, as above.

E-mail: tazoe-toshiki@rehab.go

Abstract

The corpus callosum is essential for neural communication between the left and right hemispheres. Although spatiotemporal coordination of bimanual movements is mediated by the activity of the transcallosal circuit, it remains to be addressed how transcallosal neural activity is involved in the dynamic control of bimanual force execution in human. To address this issue, we investigated transcallosal inhibition (TCI) elicited by single-pulse transcranial magnetic stimulation (TMS) in association with the coordination condition of bimanual force regulation. During a visually-guided bimanual force tracking task, both thumbs were abducted either in-phase (symmetric condition) or 180° out-of-phase (asymmetric condition). TMS was applied to the left primary motor cortex to elicit the disturbance of ipsilateral left force tracking due to TCI. The tracking accuracy was equivalent between the two conditions, but the synchrony of the left and right tracking trajectories was higher in the symmetric condition than in the asymmetric condition. The magnitude of force disturbance and TCI were larger during the symmetric condition than during the asymmetric condition. Right unimanual force tracking influenced neither the force disturbance nor TCI during tonic left thumb abduction. Additionally, these TMS-induced ipsilateral motor disturbances only appeared when the TMS intensity was strong enough to excite the transcallosal circuit, irrespective of whether the crossed corticospinal tract was activated. These findings support the hypotheses that interhemispheric interactions between the motor cortices play an important role in modulating bimanual force coordination tasks, and that TCI is finely tuned depending on the coordination condition of bimanual force regulation.

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