Online

Broomer, Matthew Cyril

Psychology

2023

Ph. D.

Learning to stop responding is a fundamental process in instrumental learning. An animal might learn to stop responding under a variety of conditions including extinction--in which a response is no longer reinforced--and punishment--in which a response remains reinforced, but also earns an aversive stimulus. Evidence suggests that extinction and punishment are behaviorally similar; both are context- and response-specific forms of inhibitory learning. In each case, this inhibitory learning is thought to control behavior by retroactively interfering with the original instrumental learning. The infralimbic cortex (IL) is critically involved in the consolidation and retrieval of extinction learning. Despite the behavioral parallels between extinction and punishment, a corresponding role for IL in punishment has not been identified. Thus, the present experiments had three goals: 1) to perform an in-depth behavioral analysis of punishment and extinction within single experiments; 2) to examine the role of IL in extinction, punishment, and omission (i.e., "negative punishment"); and 3) to test a domain-general role for IL in retroactive interference in instrumental learning. Experiment 1 examined three basic recovery effects--renewal, spontaneous recovery, and reacquisition--following either punishment or extinction of an instrumental response. The results collectively indicated that punishment and extinction are similarly sensitive to the contexts in which they are learned/tested. This was a novel comparison of punishment and extinction within a single experiment. Experiment 2 examined the effect of IL inactivation on renewal following either punishment or extinction. IL is known to impair retrieval of context-dependent extinction learning; this result was replicated alongside a similar result following punishment, suggesting an overlapping role for IL in both punishment and extinction. Experiment 3 tested the role of IL in renewal following an omission contingency, where reinforcement was delivered contingent on not responding. In contrast with extinction and punishment, IL inactivation had no effect on context-dependent retrieval of omission learning, suggesting that omission may involve the formation of distinct associative structures. Experiment 4 examined IL involvement in response-specific inhibition in punishment and extinction. Two responses (R1 and R2) were trained in separate contexts (A and B), and then either punished or extinguished in the opposite context. When the responses were then tested in their original contexts, IL inactivation unexpectedly left response-specific suppression intact. This result further suggests the presence of associative structures capable of suppressing responding independent of IL activity.