The effects of retrieval - extinction training on the restoration of Pavlovian conditioned fear

Abstract

Fear to a Pavlovian conditioned stimulus (CS) can be extinguished via repeated presentations of the CS alone. This extinction imposes a mask on conditioned responding so that fear is reduced in the time and place of extinction training but can be restored under a number of circumstances. This thesis investigated the effects on extinction of a novel procedure, retrieval – extinction training, reported to yield reductions in fear responding immune to restoration. The first series of experiments used auditory fear conditioning to study the effects of retrieval – extinction on renewal and reinstatement preparations. A single retrieval trial prior to extinction training augmented renewal and reinstatement. Augmentation of renewal was absent if retrieval and extinction training occurred in different contexts. The second series of experiments used auditory and contextual fear conditioning, while varying unconditioned stimulus intensity during training and retraining, to study the effects of retrieval – extinction on reacquisition of conditioned fear. A single retrieval trial prior to extinction training augmented reacquisition of conditioned responding, especially when initial contextual fear learning was strong. These results show that retrieval – extinction training does not reduce restoration of conditioned fear after extinction and show that under some conditions such restoration can be augmented. These results are interpreted with reference to: 1) the influences of occasion setting contextual associations versus direct context – CS associations formed as a consequence of the retrieval trial; 2) discrimination between acquisition, extinction, and test phases of the experiment; 3) the beneficial effects of prior fear memory retrieval on later fear memory retrieval.