Reinstatement and a resurgence-like effect in an odor-signaled multiple schedule in rats

This study examined determinants of relapse in rats within a multiple schedule signaled by three odor stimuli (S1, S2, S3). In both experiments, reinforcement was programmed for all components in Phase A, extinction in S1 was programmed in Phase B, extinction in both S1 and S2 in Phase C, and extinction in all components in Phase D. In Experiment 1, an increase of S1 responding was observed in Phase C when extinction was introduced in S2. This resurgence-like effect was not observed in Phase D when extinction was present in all three components. Experiment 2 tested whether the mitigation of relapse observed in Phase D was due to the absence of reinforcement in any component, but the results were equivocal. In Phase E, noncontingent food was delivered in the intercomponent interval or at the termination of S1. Reinstatement was generally highest in S3, which was associated with the greatest overall reinforcement amount and recency. When total reinforcement amount was equated across S1 and S2, more reinstatement was observed in the more recently reinforced component. Results demonstrate the utility of using a multiple schedule with odors to examine relapse in rats.