The JE-212 amplifier (Nihon Kohdenn) was used to record common average ECoG potentials. A cup Ag/AgCl electroencephalogram electrode placed on the subject’s forehead was set as the ground. Signals were recorded at a sampling rate of 2000 Hz, bandpass filtered at 0.08 and 600 Hz and amplified ×195. We used a DC channel to synchronize ECoG potentials and the optoelectronic motion capture system. In the offline analysis, the ECoG potentials of each contact were re-referenced to its closest contact, resulting in seven bipolar cortical channels. We used a notch filter (Butterworth filter, bandwidth = 4 Hz, order = 3) to reject the ambient noise of 50 Hz and harmonics and the stimulation artefact of 60/130 Hz and harmonics. Signals were downsampled to 1000 Hz for further analysis. Out of the seven bipolar channels, the channel selected for analysis was constituted by the contact pair where at least one of the contacts was landed on M1. This could be the premotor-M1, the M1-M1 or the M1-S1 contact pairs, depending on which pair demonstrated the highest PAC during rest sitting.17 The coordinates
