Gamma-band auditory steady-state response after frontal tDCS: A double-blind, randomized, crossover study

Yoshiaki Miyagishi; Takashi Ikeda; Tetsuya Takahashi; Kiwamu Kudo; Hirofumi Morise; Yoshio Minabe; Mitsuru Kikuchi

doi:10.1371/journal.pone.0193422

Gamma-band auditory steady-state response after frontal tDCS: A double-blind, randomized, crossover study

PLoS One. 2018 Feb 28;13(2):e0193422. doi: 10.1371/journal.pone.0193422. eCollection 2018.

Authors

Yoshiaki Miyagishi¹, Takashi Ikeda², Tetsuya Takahashi³, Kiwamu Kudo⁴, Hirofumi Morise⁴, Yoshio Minabe^{1

2}, Mitsuru Kikuchi²

Affiliations

¹ Department of Psychiatry and Neurobiology, Graduate School of Medical Science, Kanazawa University, Kanazawa, Japan.
² Research Center for Child Mental Development, Kanazawa University, Kanazawa, Japan.
³ Health Administration Center, University of Fukui, Fukui, Japan.
⁴ Ricoh Institute of Future Technology, Research and Development Division, Ricoh Company, Ltd., Kanazawa, Japan.

Abstract

The effects of transcranial direct current stimulation (tDCS) likely depend on cortical N-methyl-D-aspartic acid (NMDA) neurotransmission; however, no previous studies have reported tDCS-mediated modulation of cortical NMDA neurotransmission in humans. The gamma-band auditory steady-state response (ASSR) to a 40 Hz stimulation likely reflects the integrity of cortical NMDA neurotransmission. The present study tested whether the effect of tDCS is reflected in gamma-band ASSRs during a 40 Hz stimulation. Using a double-blind, randomized, crossover study, we performed magnetoencephalography (MEG) and measured the ASSR in 24 healthy participants during 40 Hz of auditory stimulation after prefrontal tDCS (2 mA) or sham (i.e., placebo) treatment. Our results failed to reveal significant differences in any brain between the two conditions after the application of a frequency of approximately 40 Hz. Based on these results, the ASSR is an insufficient method to detect the effect of tDCS on cortical NMDA neurotransmission. Unexpectedly, the results revealed an enhanced beta-band event-related spectral perturbation (ERSP) in the left motor cortex after tDCS compared with that observed after the sham stimuli. Given that beta-band oscillations reflect many functions in motor cortices, the tDCS for the frontal areas had some effect on the left motor cortex while the participants were focusing on not pressing the button with their right index finger. An additional study with an adequate psychological task is necessary to draw a conclusion regarding this unexpected result.

Publication types

Randomized Controlled Trial
Research Support, Non-U.S. Gov't

MeSH terms

Acoustic Stimulation*
Cross-Over Studies
Double-Blind Method
Evoked Potentials
Female
Frontal Lobe*
Healthy Volunteers
Humans
Male
Motor Cortex / physiology
N-Methylaspartate / metabolism
Transcranial Direct Current Stimulation*
Young Adult

Substances

N-Methylaspartate

Grants and funding

This work was supported by the Centre of Innovation Program from the Japan Science and Technology Agency (https://www.coistream.osaka-u.ac.jp/en) to Y.Minabe. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Ricoh Company, Ltd. provided support in the form of salaries for authors, KK and HM, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript, and only provided financial support in the form of some of the authors' salaries and a research material (a program for MEG data analysis).