Morales Fajardo Kenya, Yan Xuanteng, Lungoci George, Casado Sánchez Monserrat, Mitsis Georgios D, Boudrias Marie-Hélène
School of Physical and Occupational Therapy, McGill University, Montréal, QC H3G 1Y5, Canada.
Center for Interdisciplinary Research in Rehabilitation of Greater Montreal (CRIR), Montréal, QC H3S 1M9, Canada.
Brain Sci. 2024 Dec 20;14(12):1284. doi: 10.3390/brainsci14121284.
In the last few years, transcranial alternating current stimulation (tACS) has attracted attention as a promising approach to interact with ongoing oscillatory cortical activity and, consequently, to enhance cognitive and motor processes. While tACS findings are limited by high variability in young adults' responses, its effects on brain oscillations in older adults remain largely unexplored. In fact, the modulatory effects of tACS on cortical oscillations in healthy aging participants have not yet been investigated extensively, particularly during movement. This study aimed to examine the after-effects of 20 Hz and 70 Hz High-Definition tACS on beta oscillations both during rest and movement. We recorded resting state EEG signals and during a handgrip task in 15 healthy older participants. We applied 10 min of 20 Hz HD-tACS, 70 Hz HD-tACS or Sham stimulation for 10 min. We extracted resting-state beta power and movement-related beta desynchronization (MRBD) values to compare between stimulation frequencies and across time. We found that 20 Hz HD-tACS induced a significant reduction in beta power for electrodes C3 and CP3, while 70 Hz did not have any significant effects. With regards to MRBD, 20 Hz HD-tACS led to more negative values, while 70 Hz HD-tACS resulted in more positive ones for electrodes C3 and FC3. These findings suggest that HD-tACS can modulate beta brain oscillations with frequency specificity. They also highlight the focal impact of HD-tACS, which elicits effects on the cortical region situated directly beneath the stimulation electrode.
在过去几年中，经颅交流电刺激（tACS）作为一种有望与正在进行的振荡性皮层活动相互作用从而增强认知和运动过程的方法，已引起关注。虽然tACS的研究结果受年轻成年人反应高度变异性的限制，但其对老年人脑振荡的影响在很大程度上仍未得到探索。事实上，tACS对健康老龄化参与者皮层振荡的调节作用尚未得到广泛研究，尤其是在运动过程中。本研究旨在检查20赫兹和70赫兹高清tACS在休息和运动期间对β振荡的后效应。我们记录了15名健康老年参与者的静息态脑电图信号以及在握力任务期间的信号。我们施加了10分钟的20赫兹高清tACS、70赫兹高清tACS或10分钟的假刺激。我们提取了静息态β功率和与运动相关的β去同步化（MRBD）值，以比较刺激频率之间以及不同时间的情况。我们发现，20赫兹高清tACS导致电极C3和CP3的β功率显著降低，而70赫兹则没有任何显著影响。关于MRBD，20赫兹高清tACS导致电极C3和FC3的值更负，而70赫兹高清tACS导致的值更正。这些发现表明，高清tACS可以以频率特异性调节脑β振荡。它们还突出了高清tACS的局部影响，即对直接位于刺激电极下方的皮层区域产生影响。
