After obtaining IRB-approved parental permission and child assent, each child was seated 24 inches in front of a 19-inch computer LCD monitor. The E-prime v.2.0 (PST, Inc.) software package controlled the stimulus presentation. The task lasted approximately 10 minutes and each child's electroencephalogram (EEG) and behavior were continuously monitored across the session so that stimulus presentation occurred only when the child was sitting still and looking at the monitor. The location of coordinate Cz was marked as the juncture of the halfway point between nasion to inion and left and right preauricular notches. Recordings were done using a Hydrocel high-density electroencephalogram net of 128 Ag/AgCl electrodes (Geodesic Sensor Net, EGI Inc.). The filter was set at 100 Hz low pass. Brain wave data were recorded through the Netstation v.4.4 software package (EGI, Inc.) and EGI high impedance amplifiers, sampling at 250 Hz (EGI, Inc. Series 300 amplifier). All electrodes were referenced to Cz for recording and then re-referenced offline for data analysis. All impedances were assessed at or under 40 kohms before recording.
