Author Identifier
Dylan J. Edwards: https://orcid.org/0000-0001-7346-3100
Document Type
Journal Article
Publication Title
Imaging Neuroscience
Volume
3
Publisher
Massachusetts Institute of Technology
School
Exercise Medicine Research Institute / School of Medical and Health Sciences
Publication Unique Identifier
10.1162/imag_a_00431
Funders
National Institute of Neurological Disorders and Stroke (R01NS130484)
Abstract
Multiple studies have demonstrated that transcranial direct current stimulation (tDCS) of the primary motor cortex (M1) can influence corticospinal excitability and motor skill acquisition. However, the evidence for these effects is inconsistent, and a common neural substrate for these effects has not been directly demonstrated. To address this, we hypothesized that higher tDCS intensities would produce more robust effects, and uncover their relationship. In this preregistered study, 120 participants engaged in a motor skill learning task while receiving tDCS with posterior-to-anterior currents through M1. We employed a double-blind, between-subjects design, with groups of 4 mA, 6 mA, or sham stimulation, while ensuring balanced groups in terms of typing speed. Cortical excitability was assessed via motor-evoked potentials (MEPs) and TMS-evoked potentials (TEPs) before and after motor skill learning with concurrent tDCS. tDCS at these higher intensities was well tolerated, and motor learning correlated with pretraining typing speed. Planned analyses found no dose–response effect of tDCS on motor skill performance or MEP amplitude. This suggests that, under our experimental conditions, tDCS did not significantly modulate motor skill learning or corticospinal excitability. Furthermore, there was no correlation between motor performance and MEP, and thus no evidence for a common neural substrate. Exploratory analyses found an increase in MEP and TEP amplitudes following the sequence learning task. Motor skill gains positively correlated with TEP changes over the stimulated M1, which were more negative with increasing tDCS intensity. The effects of tDCS on motor skill learning and MEPs, if they exist, may require particular experimental conditions that have not been tested here. Preregistration: https://osf.io/jyuev (in-principle acceptance: 2024/06/05)
DOI
10.1162/imag_a_00431
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.
Comments
Hsu, G., Jafari, Z. H., Ahmed, A., Edwards, D. J., Cohen, L. G., & Parra, L. C. (2025). Dose–response of tDCS effects on motor learning and cortical excitability: A preregistered study. Imaging Neuroscience, 3. https://doi.org/10.1162/imag_a_00431