After obtaining institutional review board (IRB)–approved parental permission and child assent, each child was seated 24 inches in front of a 19-inch computer LCD monitor. Each child’s head circumference was measured to determine the appropriate net size and to mark Cz as the juncture of the halfway point between nasion to inion and left and right preauricular notches. Next, a Hydrocel high-density array of 128 Ag/AgCl electrodes arranged into a net (Geodesic Sensor Net, EGI Inc.) was placed on the child’s head using standard procedures. Before this, the net was soaked in warm potassium chloride solution (KCl) that served as the electrolyte (concentration: 1.5 tsp. per liter of water). The KCl solution enabled EEG collection even through hair and without the need for abrading the participant’s scalp.
