The effects of theta burst transcranial magnetic stimulation over the human primary motor and sensory cortices on cortico-muscular coherence

Abstract

Recent studies proposed a new paradigm of repetitive transcranial magnetic stimulation (rTMS), "theta burst stimulation" (TBS); to primary motor cortex (M1) or sensory cortex (S1) can influence cortical excitability in humans. Particularly it has been shown that TBS can induce the long-lasting effects with the stimulation duration shorter than those of conventional rTMSs. However, in those studies, effects of TBS over M1 or S1 were assessed only by means of motor- and/or somatosensory-evoked-potentials. Here we asked how the coherence between electromyographic (EMG) and electroencephalographic (EEG) signals during isometric contraction of the first dorsal interosseous muscle is modified by TBS. The coherence magnitude localizing for the C3 scalp site, and at 13-30Hz band, significantly decreased 30-60 minutes after the TBS on M1, but not that on S1, and recovered to the original level in 90-120 minutes. These findings indicate that TBS over M1 can suppress the cortico-muscular synchronization. © 2008 Springer-Verlag Berlin Heidelberg.