https://orcid.org/0000-0001-7516-5473
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ABSTRACT
Background: Based on our Phantom study on transcranial direct current stimulation (tDCS), we hypothesized that EEG band power and field confinement would be greater following left dorsolateral prefrontal cortex (DLPFC – F3) tDCS using circular vs. rectangular electrodes.
Methods: Double-blind-randomized trial comparing tDCS with anode over left DLPFC (groups: rectangular electrodes, circular electrodes, sham) and 2 active subgroup references (right shoulder vs. right DLPFC).
Results: Twenty-four randomized participants were assessed. We indeed found higher average EEG power spectral density (PSD) across bands for circular vs. rectangular electrodes, largely confined to F3 and there was a significant increase at AF3 for low alpha (p = 0.037). Significant differences included: increased PSD in low beta (p = 0.024) and theta bands (p = 0.021) at F3, and in theta (p = 0.036) at FC5 for the right DLPFC vs. shoulder with no coherence changes. We found PSD differences between active vs. sham tDCS at Fz for alpha (p = 0.043), delta (p = 0.036), high delta (p = 0.030); and at FC1 for alpha (p = 0.031), with coherence differences for F3-Fz in beta (p = 0.044), theta (p = 0.044), delta (p = 0.037) and high delta (p = 0.009).
Conclusion: This pilot study despite low statistical power given its small sample size shows that active left DLPFC tDCS modulates EEG frontocentrally and suggests that electrode shapes/reference locations affect its neurophysiological effects, such as increased low alpha power at AF3 using circular vs. rectangular electrodes. Further research with more participants is warranted.
Acknowledgments
We acknowledge the fellows at the Spaulding Neuromodulation Center for their work, and we acknowledge the participants who volunteered for this trial.
Author contributions
L Morales-Quezada, MM El-Hagrassy, P Lv, F Fregni were involved in the design of the study. MM El-Hagrassy, D Duarte, M Munger and E Uygur-Kucukseymen were involved in data acquisition. J Lu and P Lv wrote the Python program and developed the GUI app for EEG data processing in discussion with MM El-Hagrassy and L Morales-Quezada. MM El-Hagrassy, D Duarte, E Uygur-Kucukseymen were involved in data analysis. MM El-Hagrassy, L Morales-Quezada, D Duarte, E Uygur-Kucukseymen were involved in data interpretation. MM El-Hagrassy drafted the paper, and MM El-Hagrassy, L Morales-Quezada, D Duarte, E Uygur-Kucukseymen, A Thibaut, M Munger, P Lv, J Lu and F Fregni revised it for important intellectual content. J Lu provided the contour map. All authors approved the final version and agree to be accountable for all aspects of the work.
Clinical trials registry
This pilot exploratory study was not registered.
Data availability statement
Data used in this publication can be requested from the corresponding authors.
Reviewer disclosures
Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.
Declaration of interest
The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.
Geolocation information
All the procedures of this study were performed at the Spaulding Neuromodulation Center, Boston, Massachusetts. EEG data processing was performed at Wilmington, DE, USA.
Supplementary material
Supplemental data for this article can be accessed here.