Changes of inhibitory interneurons during transcallosal stimulations

The present study was performed in order to determine the influence of ipsilateral transcranial magnetic stimulations (TMS) on the silent period evoked by contralateral cortical stimulations. Ipsilateral TMS preceded the contralateral magnetic or electrical cortex stimulation by 0–50ms. In all subjects, the duration of the silent period was decreased in interstimulus intervals of 20–30ms when using magnetic ipsi- and contralateral stimuli. No change in the silent period was seen with ipsilateral magnetic and contralateral electrical stimulations. Decreases of motor evoked potential amplitudes were an inconsistant phenomenon.