Changes in spinal motoneuron excitability during the improvement of fingertip dexterity by actual execution combined with motor imagery practice

Yuki Fukumoto; Marina Todo; Makoto Suzuki; Daisuke Kimura; Toshiaki Suzuki

doi:10.1016/j.heliyon.2024.e30016

Changes in spinal motoneuron excitability during the improvement of fingertip dexterity by actual execution combined with motor imagery practice

Heliyon. 2024 Apr 23;10(9):e30016. doi: 10.1016/j.heliyon.2024.e30016. eCollection 2024 May 15.

Authors

Yuki Fukumoto^{1

2}, Marina Todo^{1

2}, Makoto Suzuki³, Daisuke Kimura⁴, Toshiaki Suzuki^{1

2}

Affiliations

¹ Kansai University of Health Sciences, Faculty of Health Sciences, Department of Physical Therapy, 2-11-1 Wakaba Sennangun Kumatori, Osaka, 590-0482, Japan.
² Graduate School of Kansai University of Health Sciences, Graduate School of Health Sciences, 2-11-1 Wakaba Sennangun Kumatori, Osaka, 590-0482, Japan.
³ Bukkyo University, Faculty of Health Sciences, Department of Occupational Therapy, 7 Higashitochio-cho Nishinokyo Nakagyo-ku, Kyoto, 604-8418, Japan.
⁴ Nagoya Women's University, Faculty of Medical Science, Department of Occupational Therapy, 3-40 Shioji Mizuho Nagoya, Aichi, 467-8610, Japan.

Abstract

Since there is an upper limit to skill improvement through the repetition of actual execution, we examined whether motor imagery could be used in combination with actual execution to maximize motor skill improvement. Fingertip dexterity was evaluated in 25 healthy participants performing a force adjustment task using a pinch movement with the left thumb and index finger. In the intervention condition, six sets of repetitions of combined actual execution and motor imagery were performed, while in the control condition, the same flow was performed, but with motor imagery replaced by rest. Changes in the excitability of spinal motoneurons during motor imagery compared to rest were compared in terms of the F/M amplitude ratio. Motor skill changes were compared before and after repeated practice and between the conditions, respectively, using the absolute amount of adjustment error between the target pinch force value and the delivered pinch force value (absolute error) as an index. The results showed that the repetition of exercise practice and motor imagery decreased the absolute error, which was greater than that of exercise practice alone in terms of motor skill improvement. The F/M amplitude ratio for motor imagery compared to rest did not increase. This suggests that motor imagery is involved in the degree of the increase of spinal motoneuron excitability based on the real-time prediction of motor execution and that there may be no need for an increase in excitability during motor skill control.

Keywords: F-wave; F/M amplitude ratio; Force adjustment task; Motor learning; Motor skill; Repetition training.