COURSE OF PAVLOVIAN EXCITATION AND INHIBITION OF FEAR IN RATS

Gave 30 naive male Long-Evans rats, trained to turn a wheel to avoid unsignaled shocks, Pavlovian conditioning sessions wherein 1 stimulus (CS+) signaled shock, and another stimulus (CS-) signaled nonoccurrence of shock under 1 of 4 paradigms. Acquisition of discriminative functions by CS+ and CS- was monitored during interspersed avoidance sessions: CS+ increased responding uniformly across training, while depressed responding elicited by CS- developed gradually with training. In Exp. II with 32 Ss testing began after Pavlovian conditioning was discontinued. Increased responding elicited by CS+ extinguished rapidly with continued testing, while depressed responding elicited by CS- was considerably more durable. Results suggested possible relationships between Pavlovian inhibition and excitation, and illuminated the role of CS- in the reinforcement of avoidance behavior. (PsycINFO Database Record (c) 2006 APA, all rights reserved). © 1969 American Psychological Association.