These signals were recorded from 16 electrodes(Fp1, Fp2, F7, F3, F4, F8,T3, C3, C4, T4, T5, P3, P4, T6, O1 and O2 ) 
at a rate of 256 Hz with reference to Cz.
The measurement protocol is as follows:

The user was asked to perform succesive subtractions (-3) from a given 3-digits number during five seconds. This mental
activity was called MA3.
Then he was asked to perform any mental activity (including artifacts)but substraction for 5 seconds. This mental activity
was called MA0.
The entire measurement session lasted for 15 minutes.

The data file is of .mat  type and it contains five matrices:

ARTIFACTS that contains one-second eeg segments (arranged on the form of a 3D matrix) that were automatically rejected 
during the recording process.

MA0: one-second eeg segments (5 seconds correspond to a trial) recorded during the performance of MA0.
MA1: empty matrix (normally corresponding to MA1: imagined left index finger movement)
MA2: empty matrix (normally corresponding to MA2: imagined right index finger movement)
MA3: five-second eeg segments recorded during the performance of MA3.
