Effect of Different Pulse Numbers of Transcranial Magnetic Stimulation on Motor Cortex Excitability: Single-Blind, Randomized Cross-Over Design
CNS Neuroscience & Therapeutics. 25(11):1277-1281, 2019 11.
Tang ZM; Xuan CY; Li X; Dou ZL; Lan YJ; Wen HM.
We aimed to investigate the effect of different pulse numbers of high-frequency repetitive transcranial magnetic stimulation (rTMS) over the motor cortex on cortical excitability in healthy participants.
Fifteen healthy participants received 600 and 1200 pulses of 5-Hz rTMS on separate days in a random order. Stimulation (duration, 2 seconds and interval, 1 seconds) was delivered over the left primary motor cortex for the hand, at 90% of resting motor threshold (rMT). The rMT and motor evoked potential (MEP) were measured before stimulation, and at 0 and 30 minutes after rTMS.
No significant differences were observed between the two conditions for MEP (P = .919) or rMT (P = .266). Compared with baseline, MEP was increased significantly at 0 (P < .001) and 30 minutes (P < .001) after stimulation. After stimulation, rMT was decreased at 0 minute for the 600 and 1200 pulse conditions (P < .001), but had recovered by 30 minutes (P = .073).
Subthreshold 5-Hz rTMS increased motor cortex excitability in healthy humans. However, the number of pulses may exhibit a ceiling effect in that beyond a certain point, that is, increasing the number of pulses may exhibit no further increase in cortical excitability.