The Influence of Transcranial Alternating Current Stimulation on the Excitability of the Unstimulated Contralateral Primary Motor Cortex
Objectives: 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 be...
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2025-05-01
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| author | Erik W. Wilkins Richard J. Young Ryder Davidson Reese Krider George Alhwayek Jonathan A. Park Armaan C. Parikh Zachary A. Riley Brach Poston |
| author_facet | Erik W. Wilkins Richard J. Young Ryder Davidson Reese Krider George Alhwayek Jonathan A. Park Armaan C. Parikh Zachary A. Riley Brach Poston |
| author_sort | Erik W. Wilkins |
| collection | DOAJ |
| description | Objectives: 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. Methods: 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 <i>condition</i> (tACS, SHAM) × 5 <i>test</i> (Pre, D5, D10, D15, Post) within-subjects ANOVA. Results: The main effect for <i>condition</i> (<i>p</i> = 0.704) and <i>condition</i> × <i>test</i> interaction (<i>p</i> = 0.349) were both non-statistically significant. There was a significant main effect for <i>test</i> (<i>p</i> = 0.003); however, post hoc analysis indicated that none of the pairwise comparisons were statistically significant. Conclusions: 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. |
| format | Article |
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| institution | OA Journals |
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| publishDate | 2025-05-01 |
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| spelling | doaj-art-7c55244f8dcb4f2b90bb1f0fb6ab104f2025-08-20T02:33:38ZengMDPI AGBrain Sciences2076-34252025-05-0115551210.3390/brainsci15050512The Influence of Transcranial Alternating Current Stimulation on the Excitability of the Unstimulated Contralateral Primary Motor CortexErik W. Wilkins0Richard J. Young1Ryder Davidson2Reese Krider3George Alhwayek4Jonathan A. Park5Armaan C. Parikh6Zachary A. Riley7Brach Poston8Department of Kinesiology and Nutrition Sciences, University of Nevada-Las Vegas, Las Vegas, NV 89154, USAInterdisciplinary Ph.D. Program in Neuroscience, University of Nevada-Las Vegas, Las Vegas, NV 89154, USASchool of Medicine, University of Nevada-Las Vegas, Las Vegas, NV 89154, USASchool of Medicine, University of Nevada-Las Vegas, Las Vegas, NV 89154, USASchool of Medicine, University of Nevada-Las Vegas, Las Vegas, NV 89154, USADepartment of Kinesiology and Nutrition Sciences, University of Nevada-Las Vegas, Las Vegas, NV 89154, USADepartment of Special Education, Vanderbilt University, Nashville, TN 37212, USADepartment of Kinesiology, Indiana University Purdue, Indianapolis, IN 46202, USADepartment of Kinesiology and Nutrition Sciences, University of Nevada-Las Vegas, Las Vegas, NV 89154, USAObjectives: 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. Methods: 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 <i>condition</i> (tACS, SHAM) × 5 <i>test</i> (Pre, D5, D10, D15, Post) within-subjects ANOVA. Results: The main effect for <i>condition</i> (<i>p</i> = 0.704) and <i>condition</i> × <i>test</i> interaction (<i>p</i> = 0.349) were both non-statistically significant. There was a significant main effect for <i>test</i> (<i>p</i> = 0.003); however, post hoc analysis indicated that none of the pairwise comparisons were statistically significant. Conclusions: 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.https://www.mdpi.com/2076-3425/15/5/512transcranial alternating current stimulationtranscranial direct current stimulationtranscranial magnetic stimulationcortical excitabilitymotor evoked potentialmotor skill |
| spellingShingle | Erik W. Wilkins Richard J. Young Ryder Davidson Reese Krider George Alhwayek Jonathan A. Park Armaan C. Parikh Zachary A. Riley Brach Poston The Influence of Transcranial Alternating Current Stimulation on the Excitability of the Unstimulated Contralateral Primary Motor Cortex Brain Sciences transcranial alternating current stimulation transcranial direct current stimulation transcranial magnetic stimulation cortical excitability motor evoked potential motor skill |
| title | The Influence of Transcranial Alternating Current Stimulation on the Excitability of the Unstimulated Contralateral Primary Motor Cortex |
| title_full | The Influence of Transcranial Alternating Current Stimulation on the Excitability of the Unstimulated Contralateral Primary Motor Cortex |
| title_fullStr | The Influence of Transcranial Alternating Current Stimulation on the Excitability of the Unstimulated Contralateral Primary Motor Cortex |
| title_full_unstemmed | The Influence of Transcranial Alternating Current Stimulation on the Excitability of the Unstimulated Contralateral Primary Motor Cortex |
| title_short | The Influence of Transcranial Alternating Current Stimulation on the Excitability of the Unstimulated Contralateral Primary Motor Cortex |
| title_sort | influence of transcranial alternating current stimulation on the excitability of the unstimulated contralateral primary motor cortex |
| topic | transcranial alternating current stimulation transcranial direct current stimulation transcranial magnetic stimulation cortical excitability motor evoked potential motor skill |
| url | https://www.mdpi.com/2076-3425/15/5/512 |
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