2.4.1. EEG Preprocessing
Power line interference at 50 Hz and its harmonics were removed from the data with a band-stop ([49.5, 50.5] Hz) Butterworth filter. Additionally, a band-pass ([1, 70] Hz) Butterworth filter was applied to reduce the influence of various noise components and physiological artifacts. In the present EEG dataset, low-frequency interference consisted of stray effects and breathing artifacts, while high-frequency interference was associated with muscle artifacts. Since some artifacts, like eye movement and cardiac activity, interfere with the effective frequency range of EEG (1–30 Hz), we used the standard procedure based on an independent component analysis (ICA) to remove these artifacts [