Static magnetic field stimulation over motor cortex modulates resting functional connectivity in humans

Abstract

Focal application of transcranial static magnetic field stimulation (tSMS) over the human motor cortex induces local changes in cortical excitability. Whether tSMS can also induce distant network effects, and how these local and distant effects may vary over time, is currently unknown. In this study, we applied 10 min tSMS over the left motor cortex of healthy subjects using a real/sham parallel design. To measure tSMS effects at the sensori-motor network level, we used resting-state fMRI. Real tSMS, but not sham, reduced functional connectivity within the stimulated sensori-motor network. This effect of tSMS showed time-dependency, returning to sham levels after the first 5 min of fMRI scanning. With 10 min real tSMS over the motor cortex we did not observe effects in other functional networks examined (default mode and visual system networks). In conclusion, 10 min of tSMS over a location within the sensori-motor network reduces functional connectivity within the same functional network.

Effects of transcranial static magnetic field stimulation over the left dorsolateral prefrontal cortex on random number generation

“…tSMS is based on the transcranial application of a static magnetic field (120-200 mT at 2-3 cm from the magnet surface) (Rivadulla et al, 2014) over the skull. Recently, a number of studies applying tSMS over different cortical areas (e.g., visual, motor, supplementary motor and somatosensory cortices) have demonstrated neurophysiological and/or behavioral effects in healthy subjects and patients (Arias et al, 2017;Carrasco-López et al, 2017;Dileone et al, 2018;Gonzalez-Rosa et al, 2015;Kirimoto et al, 2020Kirimoto et al, , 2018Kirimoto et al, , 2014Lacroix et al, 2019;Lozano-Soto et al, 2018;Nakagawa et al, 2019;Nakagawa and Nakazawa, 2018;Nojima et al, 2019Nojima et al, , 2016Oliviero et al, 2011;Sheffield et al, 2019;Shibata et al, 2021;Silbert et al, 2013;Soto-León et al, 2022). These studies support the main idea that tSMS has general inhibitory effects by a reduction in the neuronal excitability, and one of the proposed mechanisms for this to happen is a mechanical mechanism (Hernando et al, 2020).…”