Effect of different pulse numbers of transcranial magnetic stimulation on motor cortex excitability: Single‐blind, randomized cross‐over design

Abstract

Aims 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. Methods 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. Results 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). Conclusion 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.

Low-intensity transcranial ultrasound stimulation facilitates hand motor function and cortical excitability: A crossover, randomized, double blind study

“…The coil was then moved until the best location to record the MEP was found (“hotspot”), the intensity was reduced, and the handle was positioned at a 45° angle to the middle line of the body. The resting motor threshold (rMT) was set at an intensity capable of inducing MEPs higher than 50 μV in at least five out of ten trials ( 19 ). The latency and amplitude of the hand MEPs before and after stimulation were recorded using a 120% rMT intensity.…”

“…In this study, we used the tapping action and motor evoked potentials (MEPs) ( 19 ) to investigate the effect of low-intensity TUS on hand motor function and cortical excitability in healthy adults.…”

Evidence of Neuroplastic Changes after Transcranial Magnetic, Electric, and Deep Brain Stimulation

“…The duration of after-effects is thought to be dependent on the number of pulses given in a protocol, i.e., a higher number of pulses tends to produce greater and longer-lasting effects [ 42 , 45 ]. Nevertheless, it should be mentioned that succeeding studies did not consistently support these results [ 46 ] and the direction of effects can even be reversed with varying pulse numbers [ 47 , 48 , 49 ]. Stimulation intensity is often set as a certain percentage of an individual’s motor threshold (MT), which is defined as the minimum stimulus strength that produces a small MEP (usually 50–100 μV) in the target muscle, in about 50% of 10–20 consecutive trials [ 50 ].…”

Clinical and functional connectivity outcomes of 5-Hz repeated transcranial magnetic stimulation as an add-on treatment in cocaine use disorder: a double-blind randomized controlled trial

“…week during the acute phase to 10,000 pulses per week in the maintenance phase. However, the number of pulses may not be related to clinical outcome, at least in depression (54) as there may be a ceiling effect for cortical excitability (55) . Another factor may be our use of 5-Hz rTMS, which is in the low-end of excitatory frequencies, instead of 10-20 Hz, at the higher-end.…”