Extinction Delay and Reinstated Fear Generalization

Abstract

Background: After classical conditioning and extinction of fear, presentation of an unconditioned stimulus can produce a re-emergence of the extinguished fear response, a reinstatement effect. Previous research has reported that reinstatement of fear of contextual cues after a post-extinction delay could generalize over time to similar contexts. Objective: Two experiments were designed to investigate reinstated fear to a discrete stimulus with either a post-reinstatement delay (Experiment 1) or a post-extinction delay (Experiment 2). Methods: In Experiment 1 rat subjects were randomly assigned to four groups which received fear conditioning and extinction with a 3000 Hz tone CS. Reinstatement conditioning was then conducted with either the same or different CS, and testing for reinstated fear with the original CS was conducted after either a short or long delay following reinstatement. In Experiment 2 all procedures were the same except the long or short delay employed was between extinction and reinstatement instead of after reinstatement. Results: Reinstated fear increased with time to the same CS, and an increase in generalization of reinstated fear over time was observed with a different reinstatement CS (Experiment 1). When the delay employed was between extinction and reinstatement no increase in fear generalization was observed (Experiment 2). Conclusion: The results indicated support for the notion that reinstated fear to a discrete stimulus may generalize over time, but that generalization only takes place when reinstatement is administered a short interval after extinction. The results have implications for clinical behavior therapy treatments of anxiety disorders.