Rats were required to learn a discrimination daily for food reward; on alternate days, the right or the left of 2 visually-distinct levers was rewarded. After learning scores had stabilized, brain stimulation in the form of ½ sec. trains every 3 sec. were introduced on some days. Stimulation of negatively-reinforcing points or of primary sensory areas produced no consistent change in learning scores. Stimulation of positively-reinforcing areas produced impairment in learning scores, presumably due to partial reinforcement of the wrong response. From Psyc Abstracts 36:02:2DE20O. (PsycINFO Database Record (c) 2006 APA, all rights reserved)