Fig.2 Schematic diagram of the standing - sitting experiment
EEGs was recoded with a 32-electrode cap arranged with the international 10-20 system using the SAGA 32+ device (TMSi, Netherlands), with an averaged reference during data recording. Four electrodes were placed laterally to right and left eyes to record the horizontal and vertical electrooculograms (EOG). The impedance of the electrode was set below 10KΩ and EEGs was recorded at the laptop with 1024Hz sampling rate and the online sampling frequency band is 0-200Hz.
Besides the 32 channel EEG signal, 4 extra channel which record the IMU data were fixed on the left upper leg and four pressure sensors (FSR sensors) were fixed under the left foot to record the foot pressure synchronously, which is shown in Fig.3. The preprocessing of all subjects was completed one by one in EEGLAB. Firstly, all sessions’ data of each subject were merged together, then the data were down sampled to 250Hz and the band-pass filtering from 0.1Hz to 48Hz was completed. Cleanline tool was used to do the linear filtering to the signals and the electrode positioning of all the channels was completed according to the electrode position of SAGA system, and finally all the bad electrodes and irrelevant channels were removed.