Excitability Change in the Ipsilateral Primary Motor Cortex during a Unilateral Rhythmic Contraction of Finger Muscles : a Neurophysiological Study Using Transcranial Magnetic Stimulation

Recent transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI) studies in human demonstrated that while performing a unilateral movement, activity of primary motor cortex (M1) ipsilateral to the movement side contributes to motor performance. been well known that the modulations of ipsilateral M1 (ipsi-M1) excitability are dependent on type of motor task and difference in muscle force output level. Although the modulations of ipsi-M1 excitability depend on these task properties, little is known about the effect of rhythmic movement on modulations of ipsi-M1 excitability. In the recent stroke rehabilitation, it has been also reported that rhythmic movement training with affected limb in response to auditory cues is able to induce improvement of motor function and to produce reorganization in damaged hemisphere (Stinear et al., 2004; Waller et al., 2008). Hence, revealing effects of a unilateral rhythmic movement with auditory cues on modulations of ipsi-M1 excitability is important to enhance an understanding of human motor control. The main goal of the present study is to reveal effects of unilateral rhythmic contractions with isochronal auditory cues at three different frequencies on changes in ipsi-M1 excitability in healthy subjects by measuring motor evoked potential (MEP) induced in response to TMS. In general introduction, author explained background of the present study and relationships