All six collaborating sites used identical experimental procedures and EEG acquisition hardware and software programs. Subjects were seated comfortably 1 m from a monitor in a dimly lit sound-attenuated RF-shielded booth (Industrial Acoustics Company, Bronx, NY, USA), and wore a 19-channel electrode cap (Electro-Cap International, Inc., Eaton, OH, USA) as specified by the International 10-20 System for Electrode Placement (Figure S2). The nose served as reference and the forehead served as ground. Electrode impedances were maintained below 5 kΩ. Electrical activity was amplified 10,000 times using Sensorium EPA-2 Electrophysiology amplifiers (Charlotte, VT, USA) was recorded continuously over a bandwidth of 0.02 - 100.0 Hz on a Neuroscan system (Version 4.1 to 4.5; Neurosoft, Inc., El Paso, TX, USA) at sampling rates of 256 Hz, 500 Hz and 512 Hz, and stored for further analysis. During analysis all signals were re-sampled to 256 Hz and bandpass filtered between 0.05 and 55.0 Hz. Artifact rejection threshold was set at 100 μV. A minimum of 20 epochs of 100 milliseconds pre-stimulus to 750 milliseconds post-stimulus artifact free trials for each stimulus was required for analysis.
