Effects of dual-mode non-invasive brain stimulation on motor function

The purpose of this study was to investigate the effects of dual-mode non-invasive brain stimulation (NBS) on motor function and cortical excitability using both repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) over the bilateral primary motor cortices (M1s) of healthy individuals. Fifteen healthy right-handed volunteers (8 women; mean age 23.2 years) participated in this sham-controlled random-ordered crossover study. All of the participants received four randomly arranged dual-mode stimulations with a 24-h washout period: condition 1, preconditioning with cathodal tDCS over the left M1 followed by 10 Hz rTMS over the right M1; condition 2, preconditioning Lt. anodal tDCS followed by Rt. 10 Hz rTMS; condition 3, Lt. sham tDCS followed by Rt. 10 Hz rTMS; and condition 4, Lt. sham tDCS followed by Rt. sham rTMS. Corticomotor excitability and motor function were assessed in the left hand before and after stimulation. The motor evoked potential (MEP) amplitudes significantly increased after dual-mode stimulation in conditions 1 and 3, and significantly decreased in condition 2. The MEP latency became significantly shorter in condition 1. The motor function tests revealed a significant improvement in the Purdue pegboard test in condition 1, and in the box and block tests in conditions 1 and 3. The preconditioning tDCS over the contralateral M1 modulated the effects of subsequent rTMS on cortical excitability and motor function.