Nose-referenced EEG was recorded (low pass 100 Hz, sampling rate 500 Hz) using a 64-channel electrode cap (Virtanen et al., 1996) in an electrically shielded room. Stimulus-locked 900-millisecond EEG epochs (100-millisecond prestimulus baseline) were filtered off-line at 0.01 to 24 Hz, and averaged off-line separately for the standards, targets, and novel sounds. Horizontal and vertical eye movements were monitored with electro-oculogram (EOG) electrodes placed below and lateral to the left eye. Epochs containing deflections >150 μV at any of the EOG or EEG channels were rejected.
