Decrease of motor cortex excitability following exposure to a 20 Hz magnetic field as generated by a rotating permanent magnet

Publication date: July 2018
Source:Clinical Neurophysiology, Volume 129, Issue 7
Author(s): Eugen Gallasch, Dietmar Rafolt, Magdalena Postruznik, Shane Fresnoza, Monica Christova
ObjectivesRotation of a static magnet over the motor cortex (MC) generates a transcranial alternating magnetic field (tAMF), and a linked alternating electrical field. The aim of this transcranial magnetic stimulation (TMS) study is to investigate whether such fields are able to influence MC excitability, and whether there are parallels to tACS induced effects.MethodsFourteen healthy volunteers received 20 Hz tAMF stimulation over the MC, over the vertex, and 20 Hz tACS over the MC, each with a duration of 15 min. TMS assessments were performed before and after the interventions. Changes in motor evoked potentials (MEP), short interval intra-cortical inhibition (SICI) and intra-cortical facilitation (ICF) were evaluated.ResultsThe tACS and the tAMF stimulation over the MC affected cortical excitability in a different way. After tAMF stimulation MEP amplitudes and ICF decreased and the effect of SICI increased. After tACS MEP amplitudes increased and there were no effects on SICI and ICF.ConclusionsThe recorded single and paired pulse MEPs indicate a general decrease of MC excitability following 15 min of tAMF stimulation.SignificanceThe effects demonstrate that devices based on rotating magnets are potentially suited to become a novel brain stimulation tool in clinical neurophysiology.



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