Static magnetic field can transiently alter the human intracortical inhibitory system

• Homogeneous and inhomogeneous static magnetic fields suppress the human motor cortex.
• Short-latency intracortical inhibition was increased after magnetic exposure.
• The enhancement of the GABAergic system can be used for clinical purposes.

ObjectiveAlthough 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.MethodsWe tested whether the MRI scanner itself and compact magnet can alter the M1 function using single- and paired-pulse transcranial magnetic stimulation (TMS).ResultsWe 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.ConclusionsThe 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.SignificanceStatic magnetic stimulation can modulate the intracortical inhibitory circuit of M1, which might be useful for clinical purposes.