Wilkins Erik W, Young Richard J, Davidson Ryder, Krider Reese, Alhwayek George, Park Jonathan A, Parikh Armaan C, Riley Zachary A, Poston Brach
Department of Kinesiology and Nutrition Sciences, University of Nevada-Las Vegas, Las Vegas, NV 89154, USA.
Interdisciplinary Ph.D. Program in Neuroscience, University of Nevada-Las Vegas, Las Vegas, NV 89154, USA.
Brain Sci. 2025 May 17;15(5):512. doi: 10.3390/brainsci15050512.
Transcranial alternating current stimulation (tACS) can enhance primary motor cortex (M1) excitability and improve motor skill when delivered unilaterally to the dominant hemisphere. However, the impact of tACS on contralateral M1 excitability both during and after application has not been studied. The purpose of this study was to examine the effects of tACS delivered to the dominant left M1 on the excitability of the unstimulated contralateral non-dominant right M1.
This study implemented a double-blind, randomized, SHAM-controlled, within-subjects, crossover experimental design. Eighteen young adults completed a tACS condition and a SHAM condition on two different days in counterbalanced order with a week washout period between days. Transcranial magnetic stimulation (TMS) was utilized to assess excitability of the contralateral right M1 while tACS was delivered to the left M1. TMS was administered in five test blocks (termed Pre, D5, D10, D15, and Post) relative to a 20 min application of tACS (70 Hz, 1 mA current strength). The Pre and Post TMS test blocks were conducted before and immediately after tACS was applied to the left M1, whereas the TMS test blocks performed during tACS were completed at time points starting at the 5, 10, and 15 min marks of the 20 min stimulation period. The primary dependent variable was the 1 mV motor evoked potential (MEP) amplitude. MEP data were analyzed with a 2 (tACS, SHAM) × 5 (Pre, D5, D10, D15, Post) within-subjects ANOVA.
The main effect for ( = 0.704) and × interaction ( = 0.349) were both non-statistically significant. There was a significant main effect for ( = 0.003); however, post hoc analysis indicated that none of the pairwise comparisons were statistically significant.
Overall, the findings indicate that tACS applied to the left M1 does not significantly modulate contralateral right M1 excitability during or immediately after stimulation, at least when utilizing the present tACS parameters.
经颅交流电刺激（tACS）单侧作用于优势半球时，可增强初级运动皮层（M1）兴奋性并改善运动技能。然而，tACS在施加期间及之后对侧M1兴奋性的影响尚未得到研究。本研究的目的是检验施加于优势侧左M1的tACS对未受刺激的对侧非优势侧右M1兴奋性的影响。
本研究采用双盲、随机、假刺激对照、受试者内交叉实验设计。18名年轻成年人在两个不同日期以平衡顺序完成tACS条件和假刺激条件，两次实验之间有一周的洗脱期。在向左M1施加tACS时，利用经颅磁刺激（TMS）评估对侧右M1的兴奋性。相对于20分钟的tACS施加（70赫兹，1毫安电流强度），在五个测试时段（称为预刺激、刺激后5分钟、刺激后10分钟、刺激后15分钟和刺激后）进行TMS。预刺激和刺激后TMS测试时段分别在向左M1施加tACS之前和之后立即进行，而在tACS施加期间进行的TMS测试时段在20分钟刺激期的第5、10和15分钟时间点完成。主要因变量是1毫伏运动诱发电位（MEP）幅度。MEP数据采用受试者内2（tACS，假刺激）×5（预刺激、刺激后5分钟、刺激后10分钟、刺激后15分钟、刺激后）方差分析进行分析。
时间因素（P = 0.704）和时间×条件交互作用（P = 0.349）均无统计学意义。条件因素有显著的主效应（P = 0.003）；然而，事后分析表明，两两比较均无统计学意义。
总体而言，研究结果表明，至少在使用当前tACS参数时，施加于左M1的tACS在刺激期间或刺激后立即不会显著调节对侧右M1的兴奋性。
