Abstract
The purpose of this study was to examine the effect of motor training on motor imagery (MI), by comparing motor performance and motor cortex excitability changes with and without intermanual transfer of motor learning. Intermanual transfer was investigated in terms of excitability changes in the motor cortex and motor performance from right hand training to left hand performance. Participants were assigned to a transfer training group and a control group. We recorded motor evoked potentials (MEPs) induced by transcranial magnetic stimulation (TMS), applied to the left extensor carpi radialis (ECR) both with and without intermanual transfer. The results showed that after learning by the right hand, MEPs decreased during left hand MI. MEPs during MI were significantly decreased by unilateral training in the transfer training group. Since intermanual transfer plays an important role in stabilizing performance by the contralateral side, this result suggests that unilateral training decreases MEPs during MI on the contralateral side. In the control group, without right hand training, MEPs significantly increased after left hand training during MI. In the trained side, we found increased excitability in the agonist muscle area of the primary motor cortex. However, in the untrained side, excitability decreased in the homonymous muscle area of the primary motor cortex. This constitutes an increase in inhibitory effects and suggests that excitability changes in the respective neural circuit contribute to skilled performance by the ipsilateral and contralateral sides in the same motor task.
Highlights
Intermanual transfer is the phenomenon in which unilateral training induces improvements in contralateral motor performance (Ruddy and Carson, 2013)
Written informed consent was obtained from all participants, and the study was approved by the Ethical Committee of the Kanagawa University of Human Services
The results of this study revealed that motor learning of the trained limb changes the motor performance and effects of motor imagery (MI) on the untrained side
Summary
Intermanual transfer is the phenomenon in which unilateral training induces improvements in contralateral motor performance (Ruddy and Carson, 2013). Exercise using the non-paralytic limb is sometimes applied in stroke patients and patients with motor disorders to improve contralateral performance. Magnus et al (2010) conducted a study by applying cross-training for 4 weeks, after unilateral limb immobilization, using a shoulder sling and swathe, to investigate the effects on muscle. Ausenda and Carnovali (2011) examined the ability of intermanual transfer in facilitating the motor skills of a paretic hand in stroke patients. The results suggested that this regime improved the ability of the affected hand Taken together, these investigations suggest that intermanual transfer could be a useful approach for rehabilitation of patients with motor disorders
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