Crossed effects of muscle vibration on motor-evoked potentials.
OBJECTIVE
Muscle vibration (MV) to a forearm muscle augments motor-evoked potentials (MEPs) following transcranial magnetic stimulation (TMS) and the underlying mechanism involves cortical structures. Although MV-induced cortical activation is bilateral, the effects of MV on MEPs in contralateral muscles have not been investigated.


METHODS
Low-amplitude MV (80 Hz, amplitude 0.5 mm, duration 4 s), subthreshold for the tonic vibration reflex, was applied to the right extensor carpi radialis muscle (ECR). MEPs were elicited (0.5, 3 and 5 s after MV onset) in the left and right ECR and flexor carpi radialis muscle (FCR) by TMS (120% of threshold at rest) to the left and right hemisphere, respectively.


RESULTS
During MV of right ECR the left ECR revealed a slight non-significant augmentation of MEPs. In contrast, the left FCR showed a gradual depression of MEPs with ongoing MV and at 3 s the reduction of MEPs was significant. The time course of MEP changes in left FCR correlated with the facilitation of the vibrated right ECR. Post-vibration MEPs at 1 s after the offset of MV were still significantly decreased.


CONCLUSIONS
The study demonstrates crossed effects of MV on motor cortex excitability, suggesting transcallosal MEP modulation.
Institute of Biophysics, Bulgarian Academy of Sciences, 1113, Sofia, Bulgaria.
A
A
Kossev
S
S
Siggelkow
H
H
Kapels
R
R
Dengler
J D
JD
Rollnik
D000328:Adult; D004558:Electric Stimulation; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D005542:Forearm; D006801:Humans; D008280:Magnetics; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D014732:Vibration