Alterations in Motor Cortical Excitability Induced by Peripheral Stimulation With Magnetic Stimulation

2018 ◽  
Vol 54 (11) ◽  
pp. 1-4 ◽  
Author(s):  
A. Sato ◽  
T. Torii ◽  
M. Iwahashi ◽  
K. Iramina
2007 ◽  
Vol 118 (1) ◽  
pp. 140-145 ◽  
Author(s):  
Eman M. Khedr ◽  
John C. Rothwell ◽  
Mohamed A. Ahmed ◽  
Ola A. Shawky ◽  
Mona Farouk

2006 ◽  
Vol 101 (2) ◽  
pp. 500-505 ◽  
Author(s):  
Gabrielle Todd ◽  
Stanley C. Flavel ◽  
Michael C. Ridding

Repetitive transcranial magnetic stimulation of the motor cortex (rTMS) can be used to modify motor cortical excitability in human subjects. At stimulus intensities near to or above resting motor threshold, low-frequency rTMS (∼1 Hz) decreases motor cortical excitability, whereas high-frequency rTMS (5–20 Hz) can increase excitability. We investigated the effect of 10 min of intermittent rTMS on motor cortical excitability in normal subjects at two frequencies (2 or 6 Hz). Three low intensities of stimulation (70, 80, and 90% of active motor threshold) and sham stimulation were used. The number of stimuli were matched between conditions. Motor cortical excitability was investigated by measurement of the motor-evoked potential (MEP) evoked by single magnetic stimuli in the relaxed first dorsal interosseus muscle. The intensity of the single stimuli was set to evoke baseline MEPs of ∼1 mV in amplitude. Both 2- and 6-Hz stimulation, at 80% of active motor threshold, reduced the magnitude of MEPs for ∼30 min ( P < 0.05). MEPs returned to baseline values after a weak voluntary contraction. Stimulation at 70 and 90% of active motor threshold and sham stimulation did not induce a significant group effect on MEP magnitude. However, the intersubject response to rTMS at 90% of active motor threshold was highly variable, with some subjects showing significant MEP facilitation and others inhibition. These results suggest that, at low stimulus intensities, the intensity of stimulation may be as important as frequency in determining the effect of rTMS on motor cortical excitability.


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