The subjects were comfortably seated in front of a computer monitor screen placed one meter away in a dimly lit sound-attenuated RF-shielded room (IAC, Industrial Acoustics, The Bronx, NY). The EEG was recorded on a Neuroscan System (Versions 4.1, 4.2, and 4.3; (Neurosoft, Inc., El Paso, TX)) using a 61 channel electrode cap (Electro-cap International, Inc., Eaton, OH) that had electrode placements based on the 10-10 International System (Electrode Position Nomenclature, (Society, 1991); Fig. 2) with the notch filter off. The electrodes were referenced to the tip of the nose and subjects were grounded using an electrode placed on the forehead (frontal midline, 2 cm above nasion). Eye movements were recorded using a supraorbital vertical lead and a horizontal lead on the external canthus of the left eye. Electrode impedance was maintained below 5 kΩ throughout the recording. The continuous EEG signals were recorded marked with all stimulus, response, and feedback event codes at the sampling rates of 512 (16 bit A/D), and 500 Hz (32 bit A/D) depending on the amplifier version, with a band pass filter set at 0.02–100 Hz and were amplified 10,000 times using a set of amplifiers (SynAmps2, Neuroscan, TX).
