Estimation of optimal location of EEG reference electrode for motor imagery based BCI using fMRI

Brain computer interface (BCI) is based on brain activity from voluntary will, and controls a computer system through only the imagination or other mental activity. In order to improve the performance of the BCI system based on the scalp EEG, it is important to determine suitable locations for the EEG electrodes according to brain activity as well as the location of reference electrode of the EEG, while most of conventional studies do not much consider about the location of the reference electrode. In this paper, we estimate the proper reference electrode location of the BCI system whose mental tasks are left and right finger movement imagination. The suggested location of the reference electrode is obtained by analyzing the fMRI imaging results. Further online EEG experiment confirmed that choosing supplementary motor area (SMA) as the reference is effective in enhancing the performance of the BCI system.