# Re-evaluating transcranial static magnetic stimulation (tSMS): No inhibitory effects on motor cortex across hemispheres

## TL;DR

This study finds that transcranial static magnetic stimulation does not inhibit motor cortex activity in either hemisphere of the brain.

## Contribution

The study is the first to directly compare tSMS effects on both hemispheres using neuronavigation and robust protocols.

## Key findings

- tSMS did not alter motor-evoked potentials or intracortical inhibition/facilitation.
- Intracortical inhibition showed higher reliability than facilitation.
- Results suggest earlier tSMS findings may stem from methodological limitations.

## Abstract

•Transcranial static magnetic stimulation did not alter motor-evoked potentials.•tSMS did not affect short-interval intracortical inhibition or facilitation.•intracortical inhibition showed higher reliability than intracortical facilitation.

Transcranial static magnetic stimulation did not alter motor-evoked potentials.

tSMS did not affect short-interval intracortical inhibition or facilitation.

intracortical inhibition showed higher reliability than intracortical facilitation.

To investigate whether transcranial static magnetic stimulation (tSMS) exerts inhibitory effects on the human motor cortex and whether these effects differ between dominant and non-dominant hemispheres.

Participants underwent tSMS (20 min) and sham stimulation, targeting either the left (dominant, n = 19) or right (non-dominant, n = 19) motor cortex in a between-subject design. Corticospinal excitability was assessed with transcranial magnetic stimulation (TMS), using single-pulse motor evoked potentials (MEPs) and paired-pulse paradigms (short-interval intracortical inhibition SICI, intracortical facilitation ICF). Neuronavigation ensured stable hotspot localization.

No significant differences in MEP amplitudes were observed between tSMS and sham stimulation. Paired-pulse measures confirmed robust inhibition and facilitation, with higher reliability for SICI. However, neither SICI nor ICF showed modulation by tSMS.

tSMS modulated excitability in neither the dominant nor the non– dominant hemisphere. The results suggest that previously reported effects may reflect methodological limitations, particularly absence of neuronavigation or low trial numbers.

This study provides the first direct hemispheric comparison of tSMS using neuronavigation and robust stimulation protocols, questioning the robustness of earlier findings and highlighting methodological standards for future research.