10 20 system

Electroencephalography (EEG) data were recorded from a 63-electrodes scalp cap using the 10–20 system (Brain Products, Munich, Germany). The channel TP10 was used as the reference during recording. Two electrodes located above and below the left eye were used to measure the electrooculogram (EOG). EEG and EOG activities were amplified at 0.01–100 Hz band-passes and sampled at 500 Hz. All electrode impedances were maintained below 5 kΩ.
Electroencephalography (EEG) data were preprocessed and analyzed using MATLAB R2011b (MathWorks) and EEGLAB toolbox (Delorme and Makeig, 2004 (link)). EEG data at each electrode were re-referenced to the average of the left and right mastoids before further analysis. Then the signal passed with 0.01–30 Hz band-pass filter. Time windows of 200 ms before and 1000 ms after the onset of picture stimuli were segmented from EEG and the whole epoch was baseline-corrected by the 200 ms prior to the onset of the picture. EOG artifacts were corrected using an independent component analysis (ICA) (Jung et al., 2001 (link)). Epochs with amplitude values exceeding ± 50 μV at any electrode were excluded from the average, and all trials with incorrect responses were excluded from further analysis [Rejected epochs: 16.75 ± 6.04 (HCs); 18.25 ± 2.35 (IADs)].

The EEG was recorded from a 32-channel scalp standard cap using the 10/20 system (Brain Products, Munich, Germany). We monitored the vertical electrooculogram (VEOG) by placing electrodes 1 cm from the outer canthi of the right eye and the horizontal electrooculogram (HEOG) by placing electrodes above and below the left eye. All electrode recordings were referenced online to FCz, and inter-electrode impedances were maintained below 5kΩ. The EEG and EOG signals were amplified using a 0.01–100 Hz band-pass filter and continuously sampled at 500 Hz/channel for offline analysis.
After data acquisition, EEG data were imported into the open-source MATLAB toolboxes EEGLAB and Letswave for neurophysiological data analysis. The EEG recordings were re-referenced to the average of the two mastoids and band-pass filtered between 0.1 and 30 Hz. Independent component analysis (ICA) was used to isolate ocular (blink and saccade) and other remaining artifacts. Epochs were extracted from 200 ms prior to the stimulus onset to 1000 ms post-stimulus interval, and baseline correction was performed using the mean voltage in the 200 ms interval preceding stimulus onset. ERPs were computed offline by averaging according to the experimental design. The data analyses were conducted using MATLAB R2013b (MathWorks, Natick, USA) and SPSS Statistics 20.0 (IBM, Somers, USA).

The EEG was recorded from 32 channels using the standard 10–20 system (Brain Products, Gilching, Germany) with a bandpass from 0.01 to 100 Hz and a 500 Hz sampling rate. All channels were online referenced to FCz during recording. Recording impedance for all electrodes was held beneath 10 kΩ.

Electroencephalographic data were recorded from a 64-electrode scalp cap using the 10–20 system (Brain Products, Munich, Germany) with the reference on the left and right mastoids. A vertical electrooculogram (EOG) was recorded with electrodes placed above and below the left eye. EEG and EOG data were amplified, band-pass filtered (0.01–100 Hz), and sampled at 500 Hz. All electrode impedances were maintained below 5 kΩ.
EEG data were pre-processed and analyzed using MATLAB R2011b (Math Works, US) and EEGLAB toolbox (Delorme and Makeig, 2004 (link)). EEG data at each electrode were down-sampled to 250 Hz, re-referenced to the grand average, and band-pass filtered (0.01–30 Hz). EEG data from 200 ms before until 800 ms after the onset of the facial stimuli were extracted. In order to discard data that was contaminated by EOG artifacts, the data were decomposed by extended infomax ICA using binica, as implemented in EEGLAB (Jung et al., 2001 (link)). Epochs with amplitude values exceeding ± 50 μV at any electrode were excluded from the average.

The electroencephalogram (EEG) was recorded from 64 channels using the standard 10–20 system (Brain Products, Gilching, Germany) with an online reference to the left mastoid and an offline re-reference to the average of the left and right mastoids. The ocular artifacts of EEG data were removed by an off-line method proposed by Gratton et al. (1983) (link). The horizontal electrooculograms (EOGs) were recorded via two electrodes positioned at the outer canthi of both eyes. Vertical EOGs were recoded via two electrodes placed above and below the right eye. Recording impedance for all electrodes was held beneath 5 kΩ. Recording bandwidth was 0.01–100 Hz, at a sampling rate of 500 Hz. Signals were re-referenced offline to obtain a global average. The EEG and EOG were amplified and followed off-line. Eye movement artifacts and trials with EOG artifacts (defined as a mean EOG voltage exceeding ± 80 μV) were automatically removed. EEG data were accepted for analysis only for trials where the response for T1 and T2 was correct. The averages were then digitally filtered (0.01–30 Hz, 24 dB/octave).