Durable effect of very low-frequency repetitive transcranial magnetic stimulation for modulating cortico-spinal neuron excitability

Abstract Objective We studied the durable effects of 0.2 Hz-rTMS on the cortico-spinal neuron excitabilities by recording the motor-evoked potentials (MEPs) or Hoffman-reflex (H-reflex) before and after rTMS. Methods We employed a figure-of-eight coil for stimulating the primary motor (M1) or premotor cortex (PMC) or a round coil held over the vertex with subthreshold stimulus intensity (90% resting motor threshold). rTMS consisted of six blocks of 30 pulses (total 180 pulses). Changes in the MEP or H-reflex amplitudes in the forearm muscles following rTMS were expressed as the test/control ( t / c ) ratio. Results In comparison to sham stimulation, rTMS to PMC induced a significant reduction of t / c ratios of MEP amplitudes ( P t / c ratios of MEP amplitudes ( P Conclusions We therefore conclude that 0.2 Hz-rTMS appears to have inhibitory effects on the cortico-spinal neurons for an extended period, and the inhibitory action of rTMS on MEP sizes is attributable to a cortical mechanism.