LAUSR

Objective Continuous tetha burst stimulation (cTBS) protocol mainly consists of 3 stimulus bursts repeating every 200 ms at 50 Hz and It has been interpreted that cTBS had inhibitory effects on human motor cortex. On the other hand, there are some reports that 50 Hz cTBS had variability within and between subjects on cortical excitability. In addition, little was known about the effect of different cTBS modalities. The objective of this study is to investigate the effects of 50 Hz, 30 Hz and 100 Hz cTBS on motor cortical excitability healthy subjects. Method Resting motor treshold (rMT), short interval intracortical inhibition (SICI), intracortical facilitation (ICF) and motor evoked potential (MEP) amplitude were studied in 30 healthy subjects. Conditioning stimuli was 80% of rMT and test stimuli was 120% of rMT during SICI and ICF studies. rMT, MEP, SICI and ICF tests were repeated at just after and 30 min later than first 30, 50 and 100 Hz cTBS studies. Results In consistent with the current literature 50 Hz cTBS has inhibitory effects on MEP responses. 30 Hz cTBS has more greater inhibition than 50 Hz cTBS. On the other hand 100 Hz cTBS has facilitatory effects on cortical excitability. Discussion The effects of cTBS on motor cortical excitability depend on the studied paradigm. These results should be considered for selection of the research protocols or therapeutic application of cTBS.