rTMS combined with motor training changed the inter-hemispheric lateralization

Repetitive transcranial magnetic stimulation combined with motor training (rTMS-MT) can be an effective method for enhancing motor function. However, the effects of rTMS-MT on inter-hemispheric lateralization remain unclear. Nineteen healthy volunteers were recruited. The volunteers were randomized to receive 2 weeks of rTMS-MT or MT to improve the motor function of the nondominant hand. Hand dexterity was tested by the Nine-Hole Peg Test. Resting motor threshold (RMT), motor evoked potentials (MEP) and electroencephalography (EEG) in the resting state with eyes closed were recorded, to calculate inter-hemispheric lateralization before and after rTMS-MT or MT. rTMS-MT and MT improved the dexterity and MEP amplitude of the nondominant hand. Furthermore, there were significant changes in the lateralization of not only power spectral density, but also information transmission efficiency between regions following rTMS-MT, especially between the central cortices of both hemispheres. However, although the lateralization change of the power spectral density between the central cortices was observed following MT, there was no such change for information transmission efficiency between any cortices. These results suggested that rTMS-MT could modulate inter-hemispheric lateralization. Changes in inter-hemispheric lateralization might be an important neural mechanism by which rTMS-MT improves motor function. These results could be helpful for understanding the brain mechanism of rTMS-MT.