National Research University, Higher School of Economics, 101000, Moscow, Russia.
Centre for Cognition and Decision making, Institute for Cognitive Neuroscience, National Research University, Higher School of Economics, 101000, Moscow, Russia.
Sci Rep. 2019 Sep 6;9(1):12858. doi: 10.1038/s41598-019-49166-1.
We applied transcranial alternating current stimulation (tACS) to the primary motor cortex (M1) at different frequencies during an index-thumb pinch-grip observation task. To estimate changes in the corticospinal output, we used the size of motor evoked potentials (MEPs) obtained by transcranial magnetic stimulation (TMS) of M1 using an online MRI-guided simultaneous TMS-tACS approach. The results of the beta-tACS confirm a non-selective increase in corticospinal excitability in subjects at rest; an increase was observed for both of the tested hand muscles, the first dorsal interosseous (FDI) and the abductor digiti minimi (ADM). However, during action observation of the pinch-grip movement, the increase of corticospinal excitability was only observed for the prime mover FDI muscle and took place during alpha-tACS, while gamma-tACS affected both the FDI and control muscle (ADM) responses. These phenomena likely reflect the hypothesis that the mu and gamma rhythms specifically index the downstream modulation of primary sensorimotor areas by engaging mirror neuron activity. The current neuromodulation approach confirms that tACS can be used to induce neurophysiologically detectable state-dependent enhancement effects, even in complex motor-cognitive tasks.
我们在进行示指-拇指捏夹观察任务时，应用经颅交流电刺激（tACS）于初级运动皮层（M1）的不同频率。为了评估皮质脊髓输出的变化，我们使用经颅磁刺激（TMS）于 M1 获得的运动诱发电位（MEPs）的大小，采用在线 MRI 引导的同时 TMS-tACS 方法。β-tACS 的结果证实，在休息状态下，皮质脊髓兴奋性呈非选择性增加；两种测试手部肌肉，即第一背间骨间肌（FDI）和小指展肌（ADM）均有增加。然而，在捏夹运动的动作观察期间，仅在 FDI 主运动肌观察到皮质脊髓兴奋性的增加，且发生在 α-tACS 期间，而 γ-tACS 影响 FDI 和对照肌肉（ADM）的反应。这些现象可能反映了这样一种假设，即 mu 和 gamma 节律专门索引通过参与镜像神经元活动对初级感觉运动区域的下游调制。当前的神经调节方法证实，tACS 可用于诱导神经生理学上可检测的状态依赖性增强效应，即使在复杂的运动认知任务中也是如此。
