In the first set of periadolescent participants (n=19) [49] seven channels of ERP data (FZ, CZ, PZ, F3, F4, F7, F8 and referenced to linked ear lobes with a forehead ground, international 10-20 system) were obtained by using gold-plated electrodes with impedance held below 5k ohms. An electrode placed left lateral infraorbitally and referenced to the left earlobe was used to monitor both horizontal and vertical eye movement. ERP recording signals were amplified (time constant 0.1 s, 35 Hz low-pass filter) using a Nihon Kohden EEG machine and transferred to a computer for digitization. Auditory stimuli and ERPs were elicited using an oddball plus “noise” paradigm identical to that used in the adults and described previously [49]. In the second set of periadolescent participants (n=12), recordings were obtained using an electrode cap. Unipolar recordings from FZ, CZ, and PZ were referenced to linked earlobes. The auditory stimuli and ERPs were elicited using a “passive” oddball plus “noise” paradigm identical to the one used for the first set of periadolescent participants however, the noise tone was 20 dB louder and the participants were not asked to respond to any of the stimuli.
