Brainamp dc amplifier system

EEG waves were recorded from 62 Ag/AgCl electrodes in an elastic cap (Easycap, Brain Products GmbH), which correspond to the following sites of the international 10–20 system: Fp1, Fpz, Fp2, AF7, AF3, AFz, AF4, AF8, F7, F5, F3, F1, Fz, F2, F4, F6, F8, FT7, FC5, FC3, FC1, FC2, FC4, FC8, FT8, T7, C5, C3, C1, Cz, C2, C4, C6, T8, TP9, TP7, CP5, CP3, CP1, CPz, CP2, CP4, CP6, TP8, TP10, P7, P5, P3, P1, Pz, P2, P4, P6, P8, PO7, PO3, POz, PO4, PO8, O1, Oz, and O2. The vertical electrooculogram (VEOG) was recorded from electrodes below the left eye, and the horizontal electrooculogram (HEOG) from electrodes at the outer canthus of the right eye. Electrode impedances were maintained below 5 kΩ. The EEG signal was amplified by the BrainAmp DC amplifier system (Brain Products GmbH) with a bandpass from 0.01 to 100 Hz and was continuously sampled at 500 Hz.

Six minutes of eyes-closed resting-state EEG were obtained using 64 active channel actiCap electrode caps coupled to a BrainAmp DC amplifier system (Brain Products Gmbh, Gilching, Germany) at a sampling rate of 1000 Hz. The Ag/AgCl electrodes were places according to the 10/5 position system⁷² , using the frontal electrode FCz as online reference and AFz as ground electrode. All impedances were kept below 15 kΩ. For all pre-processing steps, we used the FieldTrip toolbox in MATLAB^{73 (link)}. Data were filtered off-line with a low-pass filter of 80 Hz, a high-pass filter of 0.5 Hz and a band stop filter between 49.5 and 50.5 Hz. Noisy channels were removed following visual screening. For the ICA, data were re-referenced to the average reference and high-pass filtered at 1 Hz. Artefactual components (blinks, saccades, EKG artefacts) were removed after visual inspection. Finally, noisy channels were interpolated using spline interpolation, and the continuous EEG was then segmented into trials of 3 s, removing trials containing gross artefacts manually.

Eight minutes of resting-state EEG was obtained in a soundproof and electrically shielded room using 64 active channel actiCap electrode caps coupled to a BrainAmp DC amplifier system (Brain Products GmbH, Gilching, Germany). Following the established 10/5 position system (Oostenveld & Praamstra 2001 (link)), the Ag/AgCl electrodes were set in the corresponding array. The central frontal electrode FCz was used as online reference and AFz as ground electrode. All impedances were kept below 10 kΩ. The resting-state EEG data was acquired with a sampling rate of 1000 Hz and a direct current (DC) mode with a high-cutoff filter of 1000 Hz with a slope of 12 dB/octave. Electrolyte gel was used to attain conductivity between the skin and the electrodes.