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

Objective: 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. Methods: 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. Results: 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. Conclusions: 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. Significance: 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.