Inverse Correlation Between Resting Motor Threshold and Corticomotor Excitability After Static Magnetic Stimulation of Human Motor Cortex

Safety Study of Transcranial Static Magnetic Field Stimulation (tSMS) of the Human Cortex

“…Reduced motor output after tSMS can be explained by reduced motor cortex excitability. These results have been recently replicated by a different group [3 ]. tSMS using small magnets may thus be a promising tool to modulate cerebral excitability in a non-invasive, painless and reversible way.…”

“…The rationale for using EEG recordings to assess NIBS safety is because of the increased risk of seizures with protocols that increase cortical excitability. tSMS was shown to reduce cortical excitability both in the sensorimotor cortex of humans [2,3,24], and in the visual cortex of cats and monkeys [23]. Decreased cortical excitability should reduce rather than increase the risk of seizures.…”

The Resting Motor Threshold – Restless or Resting? A Repeated Threshold Hunting Technique to Track Dynamic Changes in Resting Motor Threshold

“…These methods use a 50% probability criterion for evoking MEPs and enable a reliable RMT estimation with fewer pulses [13,14] hence allowing to track changes in RMT with a similar temporal resolution as MEP amplitude measures. Adaptive RMT measurements have been successfully applied to demonstrate changes in RMT following different NIBS interventions [15,16]. However, a systematic investigation of online state-dependent RMT fluctuations in a noninterventional context is still lacking [17].…”

Transcranial static magnetic field stimulation - new non-invasive brain stimulation tool

“…This result, alongside previous cellular and animal studies 10,12) , led to the inference that SMFs applied to the human cortex act primarily at the synapse and alter the membrane ion channels. However, it has also been postulated that tSMS reduces corticomotor excitability in association with modulation of the resting motor threshold, as with TMS 4) . Hence, tSMS may not only alter the function of membrane ion channels, but also reduce membrane excitability, suggesting a possible role for non-synaptic (intrinsic) plasticity mechanisms.…”

“…Since then, tSMS has received significant attention as a new NIBS technique alongside conventional methods, such as rTMS and tDCS. In recent tSMS over M1 studies, Silbert et al showed that tSMS could reduce M1 excitability correlating to modulation of resting motor threshold of TMS 4) , while Nojima et al demonstrated enhanced short latency intracortical inhibition (SICI) 5) . In addition, we have previously reported that SMFs over the sensorimotor cortex (C3 of the international 10-20 system of electrode placement) reduced the amplitudes of the N20 component of somatosensory evoked potentials (SEPs) 6) .…”