In normal subjects repetitive transcranial magnetic stimulation (rTMS) produces modifications of the size of motor evoked potentials (MEP). These changes might be due to a reduction of inhibitory intracortical connections or to an increase of excitatory pathways. To verify the importance of the first mechanism, we studied the behaviour of the cortical silent period (SP) during rTMS (20 stimuli at 5 Hz). A group of normal subjects partecipated to the experiments while they were exerting a voluntary contraction of the target muscle. Cortical motor areas were stimulated with a figure of eigh coil at an intensity of 120 % of motor threshold (calculated at rest). Repetitive stimulation at 5 Hz did not produce changes in the size of the MEPs whereas it decreased the duration of the SPs (the mean duration of the SP after the first magnetic stimulus. was 99±19.6 ms while the mean duration of the SP after the last stimulus of the train was 64±14.6 ms). These results support the possibility that rTMS at 5 Hz produces a reduction of the inhibitory cortical phenomena. It is possible that frequency other than 5 Hz of stimulation produces different modulation of the cortical silent period.
|Number of pages||1|
|Journal||Italian Journal of Neurological Sciences|
|Publication status||Published - 1997|
ASJC Scopus subject areas
- Clinical Neurology