Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich-Heine-University Duesseldorf, Germany ; Department of Neurology, Medical Faculty, Duesseldorf University Hospital Duesseldorf, Germany.
Front Hum Neurosci. 2013 Aug 29;7:511. doi: 10.3389/fnhum.2013.00511. eCollection 2013.
Synchronous oscillatory activity at alpha (8-12 Hz), beta (13-30 Hz), and gamma (30-90 Hz) frequencies is assumed to play a key role for motor control. Corticomuscular coherence (CMC) represents an established measure of the pyramidal system's integrity. Transcranial alternating current stimulation (tACS) offers the possibility to modulate ongoing oscillatory activity. Behaviorally, 20 Hz tACS in healthy subjects has been shown to result in movement slowing. However, the neurophysiological changes underlying these effects are not entirely understood yet. The present study aimed at ascertaining the effects of tACS at 10 and 20 Hz in healthy subjects on CMC and local power of the primary sensorimotor cortex. Neuromagnetic activity was recorded during isometric contraction before and at two time points (2-10 min and 30-38 min) after tACS of the left primary motor cortex (M1), using a 306 channel whole head magnetoencephalography (MEG) system. Additionally, electromyography (EMG) of the right extensor digitorum communis (EDC) muscle was measured. TACS was applied at 10 and 20 Hz, respectively, for 10 min at 1 mA. Sham stimulation served as control condition. The data suggest that 10 Hz tACS significantly reduced low gamma band CMC during isometric contraction. This implies that tACS does not necessarily cause effects at stimulation frequency. Rather, the findings suggest cross-frequency interplay between alpha and low gamma band activity modulating functional interaction between motor cortex and muscle.
同步振荡活动在 alpha（8-12 Hz）、beta（13-30 Hz）和 gamma（30-90 Hz）频率下被认为对运动控制起着关键作用。皮质肌电相干性（CMC）代表了锥体系统完整性的一种既定测量方法。经颅交流电刺激（tACS）提供了调制当前振荡活动的可能性。在健康受试者中，20 Hz 的 tACS 已被证明导致运动速度减慢。然而，这些影响的神经生理变化尚不完全清楚。本研究旨在确定健康受试者中左初级运动皮层（M1）的 10 和 20 Hz 的 tACS 对 CMC 和初级感觉运动皮层局部功率的影响。在 tACS 之前和之后（2-10 分钟和 30-38 分钟），使用 306 通道全头脑磁图（MEG）系统记录等长收缩期间的神经磁活动。此外，还测量了右侧伸肌 digitorum communis（EDC）肌肉的肌电图（EMG）。分别以 1 mA 的强度施加 10 和 20 Hz 的 tACS，持续 10 分钟。假刺激作为对照条件。数据表明，10 Hz 的 tACS 显著降低了等长收缩期间的低 gamma 波段 CMC。这意味着 tACS 不一定会在刺激频率下产生影响。相反，研究结果表明，alpha 和低 gamma 波段活动之间的交叉频率相互作用调节了运动皮层和肌肉之间的功能相互作用。
