BCI Competition 2008–Graz data set A

This data set consists of EEG data from 9 subjects. The cue-based BCI paradigm consisted of four di erent motor imagery tasks, namely the imag ination of movement of the left hand (class 1), right hand (class 2), both feet (class 3), and tongue (class 4). Two sessions on di erent days were recorded for each subject. Each session is comprised of 6 runs separated by short breaks. One run consists of 48 trials (12 for each of the four possible classes), yielding a total of 288 trials per session.At the beginning of each session, a recording of approximately 5 minutes was performed to estimate the EOG inuence. The recording was divided into 3 blocks: (1) two minutes with eyes open (looking at a xation cross on the screen), (2) one minute with eyes closed, and (3) one minute with eye movements. Note that due to technical problems the EOG block is shorter for subject A04T and contains only the eye movement condition.The subjects were sitting in a comfortable armchair in front of a com puter screen. At the beginning of a trial (t = 0s), a xation cross appeared on the black screen. In addition, a short acoustic warning tone was pre sented. After two seconds (t = 2s), a cue in the form of an arrow pointing either to the left, right, down or up (corresponding to one of the four classesleft hand, right hand, foot or tongue) appeared and stayed on the screen for 1.25s. This prompted the subjects to perform the desired motor imagery task. No feedback was provided. The subjects were ask to carry out the motor imagery task until the xation cross disappeared from the screen at t = 6s. A short break followed where the screen was black again.