Section Brain Stimulation and Cognition, Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands.
Language and Computation in Neural Systems Group, Max Planck Institute for Psycholinguistics, Nijmegen, The Netherlands.
PLoS One. 2021 Sep 16;16(9):e0255815. doi: 10.1371/journal.pone.0255815. eCollection 2021.
The evaluation of transcranial magnetic stimulation (TMS)-induced motor evoked potentials (MEPs) promises valuable information about fundamental brain related mechanisms and may serve as a diagnostic tool for clinical monitoring of therapeutic progress or surgery procedures. However, reports about spontaneous fluctuations of MEP amplitudes causing high intra-individual variability have led to increased concerns about the reliability of this measure. One possible cause for high variability of MEPs could be neuronal oscillatory activity, which reflects fluctuations of membrane potentials that systematically increase and decrease the excitability of neuronal networks. Here, we investigate the dependence of MEP amplitude on oscillation power and phase by combining the application of single pulse TMS over the primary motor cortex with concurrent recordings of electromyography and electroencephalography. Our results show that MEP amplitude is correlated to alpha phase, alpha power as well as beta phase. These findings may help explain corticospinal excitability fluctuations by highlighting the modulatory effect of alpha and beta phase on MEPs. In the future, controlling for such a causal relationship may allow for the development of new protocols, improve this method as a (diagnostic) tool and increase the specificity and efficacy of general TMS applications.
经颅磁刺激（TMS）诱发运动诱发电位（MEPs）的评估有望提供有关基本大脑相关机制的有价值信息，并可作为临床监测治疗进展或手术过程的诊断工具。然而，关于导致个体内变异性高的 MEP 幅度自发波动的报告，导致人们对该测量方法的可靠性产生了更多的担忧。MEPs 高度变异性的一个可能原因可能是神经元振荡活动，它反映了膜电位的波动，这些波动系统地增加和减少神经网络的兴奋性。在这里，我们通过将单次脉冲 TMS 应用于初级运动皮层与肌电图和脑电图的同时记录相结合，研究了 MEP 幅度对振荡功率和相位的依赖性。我们的结果表明，MEP 幅度与 alpha 相位、alpha 功率以及 beta 相位相关。这些发现可能有助于通过强调 alpha 和 beta 相位对 MEP 的调制作用来解释皮质脊髓兴奋性波动。将来，控制这种因果关系可能允许开发新的协议，改善这种方法作为（诊断）工具，并提高一般 TMS 应用的特异性和效果。
