Sasaki Keisuke, Fujishige Yuki, Kikuchi Yutaka, Odagaki Masato
Department of Environment and Life Engineering, Graduate School of Maebashi Institute of Technology, Maebashi, Japan.
Department of Systems Life Engineering, Maebashi Institute of Technology, Maebashi, Japan.
JMIR Biomed Eng. 2021 Jun 7;6(2):e28902. doi: 10.2196/28902.
Transcranial magnetic stimulation (TMS), when applied over the primary motor cortex, elicits a motor-evoked potential (MEP) in electromyograms measured from peripheral muscles. MEP amplitude has often been observed to fluctuate trial to trial, even with a constant stimulus. Many factors cause MEP fluctuations in TMS. One of the primary factors is the weak stationarity and instability of cortical activity in the brain, from which we assumed MEP fluctuations originate. We hypothesized that MEP fluctuations are suppressed when TMS is delivered to the primary motor cortex at a time when several electroencephalogram (EEG) channels measured on the scalp are highly similar in the frequency domain.
We developed a TMS triggering system to suppress MEP fluctuations using EEG coherence analysis, which was performed to detect the EEG signal similarity between the 2 channels in the frequency domain.
Seven healthy adults participated in the experiment to confirm whether the TMS trigger system works adequately, and the mean amplitude and coefficient of the MEP variation were recorded and compared with the values obtained during the control task. We also determined the experimental time under each condition and verified whether it was within the predicted time.
The coefficient of variation of MEP amplitude decreased in 5 of the 7 participants, and significant differences (P=.02) were confirmed in 2 of the participants according to an F test. The coefficient of variation of the experimental time required for each stimulus after threshold modification was less than that without threshold modification, and a significant difference (P<.001) was confirmed by performing an F test.
We found that MEP could be suppressed using the system developed in this study and that the TMS trigger system could also stabilize the experimental time by changing the triggering threshold automatically.
经颅磁刺激（TMS）作用于初级运动皮层时，可在从外周肌肉测得的肌电图中诱发运动诱发电位（MEP）。即使刺激恒定，MEP波幅也常被观察到逐次波动。TMS中许多因素会导致MEP波动。主要因素之一是大脑皮层活动的弱平稳性和不稳定性，我们认为MEP波动源于此。我们假设当在头皮上测量的几个脑电图（EEG）通道在频域高度相似时，将TMS施加到初级运动皮层，MEP波动会受到抑制。
我们开发了一种TMS触发系统，利用EEG相干分析来抑制MEP波动，EEG相干分析用于检测频域中两个通道之间的EEG信号相似性。
7名健康成年人参与实验，以确认TMS触发系统是否能充分发挥作用，记录MEP变化的平均波幅和系数，并与对照任务期间获得的值进行比较。我们还确定了每种条件下的实验时间，并验证其是否在预测时间内。
7名参与者中有5人的MEP波幅变异系数降低，根据F检验，2名参与者确认有显著差异（P = 0.02）。阈值修改后每次刺激所需实验时间的变异系数小于未进行阈值修改时的变异系数，通过F检验确认有显著差异（P < 0.001）。
我们发现使用本研究开发的系统可以抑制MEP，并且TMS触发系统还可以通过自动改变触发阈值来稳定实验时间。
