Offline, the EEG data were first processed through a 0.1 Hz first order high-pass filter and a 30 Hz low-pass filter. Continuous data were segmented into 2-second epochs containing a 1000ms pre-stimulus baseline and a 1000ms post-stimulus interval. Eye channels were inspected visually. Those likely reflecting a poor connection to the scalp, either flat (no discernable EEG signal) or reflecting white noise, were manually marked as contaminated and interpolated by surrounding channels. Automatic artifact rejection removed any segments containing extreme voltage fluctuations (threshold 200 μV) or muscle activity association with saccades and eye blinks (threshold 150 μV). Epochs with any eye blink or eye movement (threshold 150 μV) were rejected. Epochs with more than 10 bad channels (40% or more segments marked bad) were rejected as well. Then the remaining bad channels were replaced by surrounding channels. The single trial data were re-referenced from the vertex (Cz) to an average reference of all electrodes because the latter is thought to be a better representation of a true zero (Junghofer, Elbert, Tucker, & Braun, 1999). The data were baseline corrected to the 1000 ms pre-stimulus interval.
