2.6.1. Electroencephalography (EEG) Signal Response
muscle movements, blinks
BRAIN
To record the EEG signals, a standard protocol was followed to place the electrodes on the scalp based on the international 10–20 placement system [The EEG, EOG, and sternocleidomastoid EMG signals were acquired and amplified at a sampling rate of 1000 Hz with the help of a brain vision recorder system (Brain Products GmbH, Germany). The contact impedance between all electrodes and the skin was kept under 20 kΩ. Electrode impedances were adjusted before raw data collection by filling the electrodes with electrolyte gel. Electrolyte gel was applied by syringe to create a stable electrical connection between each electrode and the scalp. The raw EEG data contains artifacts that have non-neural origins and are usually the result of eye movements, eye blinks, jaw movements, and muscle movements. The recorded EEG signals were initially inspected visually for these suspicious artifacts and then preprocessed using EEGLAB [The EEG data were processed using wavelet packet analysis and decomposed using a six-octave wavelet, with the dB4 mother wavelet being chosen as the most appropriate function [