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.
Kossev
A
A
Institute of Biophysics, Bulgarian Academy of Sciences, 1113, Sofia, Bulgaria.
Siggelkow
S
S
Kapels
H
H
Dengler
R
R
Rollnik
J D
JD
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