“…EEG data were pre-processed in EEGLAB ( http://www.sccn.ucsd.edu/eeglab ). In order to remove noise including the direct current shifts and the power-line noise in time-series EEG and observe the ERD/ERS condition, that is the mu frequency power (8–13 Hz) and beta frequency power (13–30 Hz) in the central areas of the brain [ 6 , 7 ], a band-pass finite impulse response (FIR) filter between 8 and 30 Hz was applied. Subsequently, data were down-sampled to 250 Hz.…”