Effects of transcranial static magnetic stimulation over the primary motor cortex on local and network spontaneous electroencephalogram oscillations

Sumiya Shibata,Tatsuya Mima,Ryota Shimomura,Hikari Kirimoto,Yoshihiro Yukawa,Tatsunori Watanabe,Sachimori Ichimura,Masatoshi Minakuchi

doi:10.1038/s41598-021-87746-2

Sumiya Shibata, Tatsuya Mima + Show 6 more

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https://doi.org/10.1038/s41598-021-87746-2

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Abstract

Transcranial static magnetic stimulation (tSMS) is a novel non-invasive brain stimulation technique that reduces cortical excitability at the stimulation site. We investigated the effects of tSMS over the left primary motor cortex (M1) for 20 min on the local electroencephalogram (EEG) power spectrum and interregional EEG coupling. Twelve right-handed healthy subjects participated in this crossover, double-blind, sham-controlled study. Resting-state EEG data were recorded for 3 min before the intervention and 17 min after the beginning of the intervention. The power spectrum at the left central electrode (C3) and the weighted phase lag index (wPLI) between C3 and the other electrodes was calculated for theta (4–8 Hz), alpha (8–12 Hz), and beta (12–30 Hz) frequencies. The tSMS significantly increased theta power at C3 and the functional coupling in the theta band between C3 and the parietal midline electrodes. The tSMS over the left M1 for 20 min exhibited modulatory effects on local cortical activity and interregional functional coupling in the theta band. The neural oscillations in the theta band may have an important role in the neurophysiological effects induced by tSMS over the frontal cortex.

Highlights

Transcranial static magnetic stimulation is a novel non-invasive brain stimulation technique that reduces cortical excitability at the stimulation site
Through the static magnetic fields (SMFs) produced by a strong, compact neodymium magnet placed on the scalp, Transcranial static magnetic stimulation (tSMS) can suppress cortical excitability just below the m agnet[1,2,3,4]
The change was significant only in the theta band (p = 0.040) (Fig. 3). This demonstrates that tSMS could increase the EEG power in the theta band at the stimulation site

Summary

Introduction

Transcranial static magnetic stimulation (tSMS) is a novel non-invasive brain stimulation technique that reduces cortical excitability at the stimulation site. We investigated the effects of tSMS over the left primary motor cortex (M1) for 20 min on the local electroencephalogram (EEG) power spectrum and interregional EEG coupling. EEG is an electrophysiological technique that noninvasively records the oscillatory characteristics of neuronal activities It provides a direct index of neuronal functions with high temporal resolution unlike magnetic resonance imaging (MRI), functional MRI, positron emission tomography, and single-photon emission computed tomography. To evaluate the modulation of local cortical activity, the changes in the resting EEG power spectrum at the left central electrode (C3) was compared between the real and sham tSMS. To investigate the modulation of interregional functional coupling, the changes in the weighted phase lag index (wPLI)[15] between C3 and the other electrodes, was compared between the real and sham tSMS. Higher wPLI value indicates higher synchronization of the two signals, and vice versa

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