Static magnetic field can transiently alter the human intracortical inhibitory system

OBJECTIVE: Although recent studies have shown the suppressive effects of static magnetic fields (SMFs) on the human primary motor cortex (M1) possibly due to the deformed neural membrane channels, the effect of the clinical MRI scanner bore has not been studied in the same way. METHODS: We tested whether the MRI scanner itself and compact magnet can alter the M1 function using single- and paired-pulse transcranial magnetic stimulation (TMS). RESULTS: We found the transient suppression of the corticospinal pathway in both interventions. In addition, the transient enhancement of the short-latency intracortical inhibition (SICI) was observed immediately after compact magnet stimulation. CONCLUSIONS: The present results suggest that not only the inhomogeneous SMFs induced by a compact magnet but also the homogeneous SMF produced by the MRI scanner bore itself can produce the transient cortical functional change. SIGNIFICANCE: Static magnetic stimulation can modulate the intracortical inhibitory circuit of M1, which might be useful for clinical purposes.