The effects of extinction and an explicitly unpaired treatment on the reinforcing properties of a Pavlovian conditioned stimulus

• Published in: Neurobiology of learning and memory 2024-01, Vol.207, p.107879, Article 107879
• Main Authors: Kennedy, Nicholas G.W., Holmes, Nathan M., Peng, Lily W.T., Frederick Westbrook, R.
• Format: Article
• Language: English
• Subjects: Animals; Conditioned reinforcement; Conditioning, Classical; Conditioning, Operant; Extinction; Extinction, Psychological; Fear conditioning; Pavlovian conditioning; Rat; Rats; Reinforcement, Psychology; Rescorla-Wagner
• ISSN: 1074-7427; 1095-9564; 1095-9564
• DOI: 10.1016/j.nlm.2023.107879

•Rats will press a lever to procure a CS that had been previously paired with food.•The number of CS-food pairings determines whether the reinforcing properties of the CS can be disrupted by extinction.•Where extinction fails to disrupt these properties, they can be disrupted by shifting rats from CS-food pairings to explicitly unpaired presentations of the CS and food.•This effect of the unpaired treatment (disruption) differs from its effect in studies of Pavlovian-to-instrumental transfer (no disruption), suggesting that it disrupts the reinforcing properties of the CS (assessed here) while sparing its other properties (assessed in PIT).•These findings are consistent with the Rescorla-Wagner (1972) model, according to which the unpaired treatment is more effective than extinction in reducing the strength of the CS-US association. This series of experiments examined the effects of extinction and an explicitly unpaired treatment on the ability of a conditioned stimulus (CS) to function as a reinforcer. Rats were trained to lever press for food, exposed to pairings of a noise CS and food, and, finally, tested for their willingness to lever press for the CS in the absence of the food. Experiment 1 provided a demonstration of conditioned reinforcement (using controls that were only exposed to unpaired presentations of the CS and food) and showed that it was equivalent after one or four sessions of CS-food pairings. Experiments 2 and 3 showed that, after one session of CS-food pairings, repeated presentations of the CS alone reduced its reinforcing properties; but after four sessions of CS-food pairings, repeated presentations of the CS alone had no effect on these properties. Experiment 4 showed that, after four sessions of CS-food pairings, explicitly unpaired presentations of the CS and food completely undermined conditioned reinforcement. Finally, Experiment 5 provided within-experiment evidence that, after four sessions of CS-food pairings, the reinforcing properties of the CS were disrupted by explicitly unpaired presentations of the CS and food but spared by repeated presentations of the CS alone. Together, these findings indicate that the effectiveness of extinction in undermining the reinforcing properties of a CS depends on its level of conditioning; and that, where extinction fails to disrupt these properties, they are successfully undermined by an explicitly unpaired treatment. They are discussed with respect to findings in the literature on Pavlo