64-Channel High-Density EEG Recording

Neurophysiological data were recorded with an equidistant 64-channel Ag/AgCl EEG cap (Easycap GmbH, Hersching, Germany), including a fronto-polar ground electrode, a reference electrode positioned on the tip of the nose, and two electrooculogram (EOG) electrodes, one positioned below each eye. Impedances were kept below 20 kΩ using Abralyt HiCl gel (Easycap GmbH). We intentionally did not collect data from the five most occipital electrodes due to their large distance to the scalp as well as from 10 electrodes around the ears due to concurrent around-the-ear EEG recording with cEEGrids (Debener et al., 2015 (link)). Results obtained with cEEGrid will be presented elsewhere. EEG cap data were sampled at 500 Hz using a stationary BrainAmp amplifier (Brain Products GmbH, Gilching, Germany) with a recording band-pass filter from 0.0159 to 250 Hz. To reduce artifacts, participants were instructed to direct their gaze to a white fixation cross on a gray computer screen in front of them and to move as little as possible.