Functional force stimulation alters motor neuron discharge patterns

Yaodan Xu; Zuyu Du; Anyi Cheng; Runwei Lin; Kaichen Wang; Yibin Jin; Chenyun Dai; Lin Xu

doi:10.3389/fnins.2023.1293017

Functional force stimulation alters motor neuron discharge patterns

Front Neurosci. 2023 Dec 5:17:1293017. doi: 10.3389/fnins.2023.1293017. eCollection 2023.

Authors

Yaodan Xu^#^{1

2

3}, Zuyu Du^#¹, Anyi Cheng^{1

2

3}, Runwei Lin¹, Kaichen Wang¹, Yibin Jin¹, Chenyun Dai⁴, Lin Xu^{1

5}

Affiliations

¹ School of Information Science and Technology, ShanghaiTech University, Shanghai, China.
² Shanghai Advanced Research Institute, Chinese Academy of Science, Shanghai, China.
³ University of Chinese Academy of Science, Beijing, China.
⁴ School of Information Science and Technology, Fudan University, Shanghai, China.
⁵ Shanghai Engineering Research Center of Energy Efficient and Custom AI IC, Shanghai, China.

^# Contributed equally.

Abstract

Introduction: Beneficial effects have been observed for mechanical vibration stimulation (MVS), which are mainly attributed to tonic vibration reflex (TVR). TVR is reported to elicit synchronized motor unit activation during locally applied vibration. Similar effects are also observed in a novel vibration system referred to as functional force stimulation (FFS). However, the manifestation of TVR in FFS is doubted due to the use of global electromyography (EMG) features in previous analysis. Our study aims to investigate the effects of FFS on motor unit discharge patterns of the human biceps brachii by analyzing the motor unit spike trains decoded from the high-density surface EMG.

Methods: Eighteen healthy subjects volunteered in FFS training with different amplitudes and frequencies. One hundred and twenty-eight channel surface EMG was recorded from the biceps brachii and then decoded after motion-artifact removal. The discharge timings were extracted and the coherence between different motor unit spike trains was calculated to quantify synchronized activation.

Results and discussion: Significant synchronization within the vibration cycle and/or its integer multiples is observed for all FFS trials, which increases with increased FFS amplitude. Our results reveal the basic physiological mechanism involved in FFS, providing a theoretical foundation for analyzing and introducing FFS into clinical rehabilitation programs.

Keywords: blind source separation; discharge timings; functional force stimulation; high-density surface electromyography; motor unit synchronization.

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This work was supported in part by the National Natural Science Foundation of China under Grant 62171284 and in part by a start-up funding from the ShanghaiTech University.