BCI Competition 2008 – Graz data set A
C. Brunner
1
, R. Leeb
1
, G. R. M¨uller-Putz
1
, A. Schl¨ogl
2
, and G.
Pfurtscheller
1
1
Institute for Knowledge Discovery, Graz University of Technology,
Austria
2
Institute for Human-Computer Interfaces, Graz University of
Technology, Austria
Experimental paradigm
This data set consists of EEG data from 9 subjects. The cue-based BCI
paradigm consisted of four different 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 different 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 influence. The recording was divided
into 3 blocks: (1) two minutes with eyes open (looking at a fixation cross
on the screen), (2) one minute with eyes closed, and (3) one minute with
eye movements. The timing scheme of one session is illustrated in Figure 1.
Note that due to technical problems the EOG block is shorter for subject
A04T and contains only the eye movement condition (see Table 1 for a list
of all subjects).
The subjects were sitting in a comfortable armchair in front of a com-
puter screen. At the beginning of a trial (t = 0 s), a fixation cross appeared
on the black screen. In addition, a short acoustic warning tone was pre-
sented. After two seconds (t = 2 s), a cue in the form of an arrow pointing
either to the left, right, down or up (corresponding to one of the four classes
Figure 1: Timing scheme of one session.
1
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