EEG Recording and ICA-based Artifact Correction

During the experiment, the electroencephalogram (EEG) was recorded from 29 electrodes including all 19 standard locations of the 10–20 system [24 ] with Ag-AgCl electrodes mounted in an elastic cap (Electro Caps International, Eaton, OH) relative to two reference electrode placed on both ear lobes. Eye-movements were recorded with electrodes affixed at the right and left external canthi (horizontal electrooculogram (hEOG), bipolar recording) and at the left and right orbital ridges (vertical electrooculogram (vEOG), bipolar recording). Impedances of all electrodes were kept below 5 kΩ. Biosignals were amplified with a band-pass from 0.05 to 30 Hz with a digitization rate of 250 Hz using Neuroscan amplifiers and Acquire recording software (Neuroscan Inc., Sterling, VA).
Artifact correction and averaging. Prior to ERP data analysis, all trials containing eye-movement artifacts were corrected using ICA-based artifact correction implemented in EEGlab [25 (link), 26 (link)]. Stimulus-locked ERPs (time-locked to the onset of the flanker stimulus) were averaged for epochs of 1200 ms starting 200 ms prior to stimulus. A pre-stimulus period of 100 ms served as a baseline for ERP-computation. All ERP figures and all ERP statistics are slightly band-pass-filtered (0.1 to 30 Hz).