The experimental subjects were 15 male periadolescent (Post Natal Day (PD) 23) on arrival, weighing 58-79 grams) and 19 male adult (PD90 on arrival, weighing 351-387 grams) Wistar rats. At least 1 week prior to the electrophysiological recordings rats were surgically prepared with screw electrodes placed in the skull overlying the frontal (Adults: AP +1.5, ML ± 3.0; Periadolescents: AP +1.5, ML ± 2.0), parietal lobe (Adults: AP -4.5, ML ± 4.5; Periadolescents: AP -4.0, ML ± 3.5) and an electrode placed over the cerebellum was used as ground. Two electromyography (EMG) wire electrodes were also inserted into the rat's neck muscles on the right and left. The rats were anesthetized with isoflurane and atropine (0.03mL for periadolescents and 0.06mL for adults; subcutaneously) was co-administered to minimize respiratory suppression during the surgical procedures. EMG and EEG electrode connections were made to either an Amphenol 5-pin connector (adult rats) or were assembled into a custom 5-pin cap (for the periadolescent rats), and the assembly was anchored to the skull with dental acrylic and anchor screws. All the animals were pair-housed in
