*3.1. Dataset*

The dataset was provided by Intelligent Data Analysis Group is the IVa from the BCI competition III was used in current study. This consists of five healthy subjects sat in a comfortable chair with arms resting. The subjects are labeled as *aa*, *al*, *av*, *aw*, and *ay* [42]. Visual cues indicated for 3.5 s which of the following two MI the subject should perform: right hand (class1) and foot (class2) MI. The presentation of target cues were intermitted by periods of random length, 1.75 to 2.25 s, in which the subject could relax [43]. In Figure 1 is shown a diagram where it is illustrated the extraction of MI segments inside a trial, where the interest segment of MI occurs in time interval between 4.5 and 8 s. The recording was made using BrainAmp amplifiers and a 128 channel Ag/AgCl electrode cap from ECI. 118 EEG channels were measured at positions of the extended international 10–20-system. Signals were digitized at 1000 Hz with 16 bit (0.1 μV) accuracy.

**Figure 1.** Extraction of MI for each trial.

As mentioned above, *μ* rhythms are generated in the motor cortex [5], therefore, the selected electrodes for this region are *C*<sup>3</sup> for the left hemisphere and *C*<sup>4</sup> for the right hemisphere. In this work, 18 channels were located in both hemispheres around the sensorimotor cortex were selected. *FC*5, *FC*3, *FC*1, *C*5, *C*3, *C*1, *CP*5, *CP*3, *CP*<sup>1</sup> in left side, and *FC*2, *FC*4, *FC*6, *C*2, *C*4, *C*6, *CP*2, *CP*4,*CP*<sup>6</sup> in right side. The selected electrodes coincide with the regions reported in [21]. The two clusters left and right are filtered using a second-order IIR Butterworth, set as band-pass filter. To preserve the relevant information for MI, the selected cut-off frequencies were adjusted between 0.5 and 90 Hz.
