EEG was continuously recorded using a high-density array of 128 Ag/AgCl electrodes (Electrical Geodesics Inc., Tucker, 1993). Impedance was kept below 50 kΩ. The signal was amplified (×1000), filtered on line with a band-pass of 0.01–80 Hz, then digitized at a sampling rate of 1 kHz. The electro-oculogram (EOG) was recorded from bipolar electrode pairs located at the outer canthi and above and below the left and right eyes. Data were referenced to the vertex electrode, and were stored on the hard drive of a G4 Macintosh power PC.
