Effects of repetitive transcranial magnetic stimulation on masseter motor-neuron pool excitability.
OBJECTIVE
Repetitive transcranial magnetic stimulation (rTMS) has been widely used to modulate the excitability of the cortical control of limbs muscles, but rarely in the cortical control of human masseter muscles. This study aims to investigate the effects of rTMS on masseter motor-neuron pool excitability in humans.


METHODS
A total of 20 healthy participants were selected and received a total of three rTMS sessions involving stimulation of the right masseter-motor complex: one session of 10-Hz rTMS, one session of 1-Hz rTMS and one session of sham rTMS at an intensity of 80% of the active motor threshold (AMT). The masseter AMT, motor-evoked potentials (MEPs), cortical-silent period (CSP), and short-interval intracortical inhibition (SICI) were measured before and after each rTMS session.


RESULTS
The masseter SICI was significantly decreased following 10-Hz rTMS, with no significant changes in AMT, MEPs or CSP. No significant differences in masseter AMT, MEPs, CSP or SICI were observed in either the 1-Hz, or sham rTMS groups.


CONCLUSIONS
The present findings demonstrate that high-frequency rTMS increases masseter motor-neuron pool excitability.
Department of Stomatology, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou 325000, PR China.
Huang
H
Huang
Laboratory of Oral Biomedical Science and Translational Medicine, School of Stomatology, Tongji University, Middle Yanchang Road 399, Shanghai 200072, PR China. Electronic address: weicai_liu@tongji.edu.cn.
Wei Cai
WC
Liu
Laboratory of Oral Biomedical Science and Translational Medicine, School of Stomatology, Tongji University, Middle Yanchang Road 399, Shanghai 200072, PR China.
Yu Han
YH
Song
D000328:Adult; D004307:Dose-Response Relationship, Radiation; D004576:Electromyography / Q000379:methods; D019054:Evoked Potentials, Motor / Q000502:physiology / Q000528:radiation effects*; D005260:Female; D006801:Humans; D008297:Male; D008406:Masseter Muscle / Q000294:innervation; D009044:Motor Cortex / Q000502:physiology / Q000528:radiation effects*; D009046:Motor Neurons / Q000502:physiology / Q000528:radiation effects*; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology; D009433:Neural Inhibition / Q000502:physiology / Q000528:radiation effects; D050781:Transcranial Magnetic Stimulation / Q000379:methods*
Cortical-silent period; Intracortical inhibition; Masseter; Motor-evoked potential; Repetitive transcranial magnetic stimulation