Transient hemispheric lateralization is associated with intensity-dependent aftereffects of low-frequency rTMS

Low-frequency repetitive transcranial magnetic stimulation (rTMS) can alter brain activity during and after stimulation, but the relationship between these immediate responses and subsequent effects remains unclear. In a randomized, single-blind crossover design, twenty healthy adults receive 1 Hz rTMS over the left motor cortex at sham, 80%, 100%, and 120% of resting motor threshold (RMT). electroencephalography (EEG) is recorded before, during, and after rTMS. Stimulation at and above threshold elicits robust transient responses, characterized by enhanced TMS-evoked potentials, increased beta-band power, increased beta-band lateralization and recruited bilateral cortical activities. Also, they induce significant aftereffect with a decrease in hemispheric lateralization after rTMS. Mediation analyses links stimulation intensity to this subsequent rebalancing through transient beta-band lateralization. In an exploratory stroke cohort, lower beta-band lateralization is associated with better motor function. These findings suggest that low-frequency rTMS induces intensity-dependent transient responses and aftereffects. Transient beta-band lateralization is associated with subsequent interhemispheric rebalancing and may serve as a marker for optimizing personalized neurorehabilitation.