Modulation of excitability of human motor cortex (M1) by 1 Hz transcranial magnetic stimulation of the contralateral M1.
OBJECTIVE
Previous studies demonstrated that single-pulse transcranial magnetic stimulation (TMS) of one motor cortex (M1) exerts a brief inhibitory effect on the contralateral M1. The purpose of this study was to test the hypothesis that 30min of 1Hz TMS of M1 will result in a lasting increase in excitability in the contralateral M1.


METHODS
Healthy volunteers were tested on 2 separate days, before (baseline) and after one of two interventions: (a) stimulation of M1 with 1Hz TMS for 30min at 115% of resting motor threshold, and (b) sham stimulation. Recruitment curves to TMS, pinch force, and simple reaction time were assessed in the hand contralateral to the unstimulated motor cortex.


RESULTS
The main finding of this study was that 30min of 1Hz significantly increased recruitment curves in the contralateral motor cortex in the real stimulation condition relative to sham (P<0.005, factorial analysis of variance (ANOVA)). This change outlasted the stimulation period for at least 15min and occurred in the absence of changes in pinch force or reaction time.


CONCLUSIONS
These results raise the potential for inducing lasting modulation of excitability in M1 by 1Hz TMS of the other M1, a phenomenon possibly reflecting modulation of interhemispheric interactions.


CONCLUSIONS
It is conceivable that 1Hz TMS applied to M1 may be used to modulate excitability in the opposite motor cortex for therapeutic purposes.
Schambra
H M
HM
Human Cortical Physiology Section, Medical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bldg. 10, Rm 5N226, 10 Center Drive, MSC1428, Bethesda, MD 20892, USA.
Sawaki
L
L
Cohen
L G
LG
D000368:Aged; D000369:Aged, 80 and over; D004558:Electric Stimulation; D055590:Electromagnetic Phenomena; D019054:Evoked Potentials, Motor; D005260:Female; D006801:Humans; D007858:Learning; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology*; D011930:Reaction Time; D012016:Reference Values