Origin of facilitation in repetitive, 1.5ms interval, paired pulse transcranial magnetic stimulation (rPPS) of the human motor cortex.
OBJECTIVE
Repetitive paired-pulse TMS (rPPS) given at an interstimulus interval (ISI) of 1.5 ms has been reported to induce a lasting motor evoked potential (MEP) facilitation. This after-effect was considered to be a cortical event because F-waves were not affected by the same rPPS. To confirm its cortical facilitation, we compared the after-effects of rPPS on MEPs to single pulse TMS over the motor cortex (motor cortical MEPs) with those to brainstem stimulation (brainstem MEPs).


METHODS
Subjects were 10 healthy volunteers. Suprathreshold paired-pulse TMS at an ISI of 1.5 ms was applied to the motor cortex for 30 min at a rate of 0.2 Hz. After intervention, we measured motor cortical MEPs for 30 min. We also studied brainstem MEPs in five subjects.


RESULTS
Motor cortical MEPs were facilitated to about 190% of baseline (p<0.001) for 10 min post rPPS intervention and returned to the baseline at 10-15 min post intervention. Brainstem MEPs were not affected by the intervention.


CONCLUSIONS
The facilitation of MEPs after rPPS at an interval of 1.5 ms occurs at the motor cortex.


CONCLUSIONS
rPPS at an interval of 1.5 ms is an effective method for increasing motor cortical excitability.
Hamada
Masashi
M
Department of Neurology, Division of Neuroscience, Graduate School of Medicine, The University of Tokyo, 7-3-1, Hongo, Tokyo, Japan. mhamada-tky@umin.ac.jp
Hanajima
Ritsuko
R
Terao
Yasuo
Y
Arai
Noritoshi
N
Furubayashi
Toshiaki
T
Inomata-Terada
Satomi
S
Yugeta
Akihiro
A
Matsumoto
Hideyuki
H
Shirota
Yuichiro
Y
Ugawa
Yoshikazu
Y
D000328:Adult; D001933:Brain Stem / Q000502:physiology; D004558:Electric Stimulation; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology; D013116:Spinal Cord / Q000502:physiology; D050781:Transcranial Magnetic Stimulation