The data comes from BCI Competition IV (2008), datasets 2B . The dataset contains the brain activities of 9 different subjects. As the dataset description shown, “Three bipolar recordings (C3, Cz, and C4) were recorded with a sampling frequency of 250Hz. The recordings had a dynamic range of ±100µV for the screening and ±50µV for the feedback sessions. They were bandpassﬁltered between 0.5Hz and 100Hz, and a notch ﬁlter at 50Hz was enabled. The placement of the three bipolar recordings (large or small distances, more anterior or posterior) were slightly diﬀerent for each subject. The electrode position Fz served as EEG ground”. The recorded brain signals are then stored in the General Data Format. The GDF files can be loaded to Matlab using the BioSig toolbox.