The role of the intertrial interval in the loss of context conditioned fear responses.

Abstract

Eight experiments examined the role of the intertrial interval in the extinction of conditioned fear to a context. Rats were shocked in one context (A) but not in another (B) and freezing responses to Context A were extinguished. The interval between extinction trials was spent in the home cages. Experiments 1a and 1b showed that massed extinction trials produced better response loss but worse learning than spaced trials. Experiment 2 demonstrated that the interval between the final extinction trial and test mediated the level of responding on a test exposure. Experiments 3 and 4 showed that the duration of the extinction trial affected long term response loss, whereby long durations facilitate response loss compared to shorter durations. Subsequent experiments (Experiments 5 to 8) demonstrated that the first in the series of massed extinction trials reduced the associability of subsequent trials. Associability was restored by alternating extinction trials between Context A and Context B. The results are discussed in terms of the role accorded to self-generated priming in the models developed by A. R. Wagner (1978; 1981).