Intensity-dependent effects of 1 Hz rTMS on human corticospinal excitability

Objectives: This study explored whether the effects of repetitive transcranial magnetic stimulation (rTMS) on corticospinal excitability are dependent on the stimulation intensity and examined the effect of rTMS on inhibitory function. Methods: Nine normal volunteers received 15 min of 1 Hz rTMS at 85 and 115% of the resting motor threshold (RMT). Cortical excitability was measured before and after rTMS. Results: rTMS at both intensities produced an increase in the RMT but only 115% stimulation reduced the size of motor evoked potentials (MEPs). rTMS had no effects on the cortical silent period or cortical inhibition measured with paired pulse TMS. Conclusions: The effects of 1 Hz rTMS on motor cortex excitability are partially dependent on stimulus intensity and the effects of rTMS on motor thresholds and MEP size may differ.