Mark E. Bouton

While the infralimbic cortex (IL) is recognized as critical for behavioral inhibition, the content of the inhibitory memories stored in this region remains elusive. To probe this content, we examined some of the conditions that allow retrieval and facilitation of an inhibitory memory stored in the IL using optogenetic stimulation in female and male rats. We found that IL stimulation did not facilitate an initial fear extinction session. However, prior experience with fear extinction enabled IL stimulation to facilitate subsequent fear extinction. Importantly, the facilitative effects of IL stimulation were not limited to fear extinction experience, as prior exposure to backward fear conditioning also enabled IL stimulation to enhance later fear extinction. The effects were stimulus-specific and did not depend on the motivational context present during the prior experience, as backward appetitive conditioning allowed IL stimulation to facilitate later fear extinction. Additional experiments ruled out stimulus familiarity as an explanation for the facilitative effects of IL stimulation and demonstrated that IL-mediated facilitations occur in procedures other than fear extinction. Together, these findings demonstrate that the IL stores inhibitory memories that are extremely flexible since they can be retrieved and used across many inhibitory procedures and distinct motivational contexts. These features establish the IL as a critical hub for the flexible application of inhibitory knowledge that allows adaptive responses in dynamic environments.

While the infralimbic cortex (IL) is recognized as critical for behavioral inhibition, the content of the inhibitory memories stored in this region remains elusive. To probe this content, we examined some of the conditions that allow retrieval and facilitation of an inhibitory memory stored in the IL using optogenetic stimulation in female and male rats. We found that IL stimulation did not facilitate an initial fear extinction session. However, prior experience with fear extinction enabled IL stimulation to facilitate subsequent fear extinction. Importantly, the facilitative effects of IL stimulation were not limited to fear extinction experience, as prior exposure to backward fear conditioning also enabled IL stimulation to enhance later fear extinction. The effects were stimulus-specific and did not depend on the motivational context present during the prior experience, as backward appetitive conditioning allowed IL stimulation to facilitate later fear extinction. Additional experiments ruled out stimulus familiarity as an explanation for the facilitative effects of IL stimulation and demonstrated that IL-mediated facilitations occur in procedures other than fear extinction. Together, these findings demonstrate that the IL stores inhibitory memories that are extremely flexible since they can be retrieved and used across many inhibitory procedures and distinct motivational contexts. These features establish the IL as a critical hub for the flexible application of inhibitory knowledge that allows adaptive responses in dynamic environments.

Previous research on Pavlovian conditioning has shown that the duration of the intertrial interval (ITI) can function like a contextual stimulus, modulating responding to an upcoming conditioned stimulus. Here, four operant learning experiments with rats investigated whether ITIs can similarly modulate operant responding occasioned by a discriminative stimulus (SD). In Experiment 1, responding for one group was reinforced during a 10-s SD when it was preceded by a 4-min ITI but not when it was preceded by a 1-min ITI (4+/1- discrimination). A second group had the opposite discrimination, 1+/4-. As seen with Pavlovian conditioning, rats could acquire discriminative control with the 4+/1- but not with the 1+/4- discrimination. Additional experiments investigated whether control by a temporal context in the 4+/1- discrimination transfers across physical contexts (i.e., the context provided by the operant chamber). In Experiment 2, rats learned the 4+/1- discrimination in one context (Context A), and the discrimination failed to transfer to a different context (Context B). In Experiment 3, the 4+/1- discrimination also failed to transfer to Context B when experience with reinforcers was equated across contexts. Experiment 4 found evidence of transfer, however, when rats had learned a second, nontemporal discrimination, in Context B. Overall, the findings suggest that ITI duration can acquire conditional control of discriminated operants in a manner similar to Pavlovian conditioned responses. The ITI arguably sets the occasion for a stimulus that itself sets the occasion for responding. Moreover, the control created by time can transfer across physical contexts under some conditions. (PsycInfo Database Record (c) 2025 APA, all rights reserved).

Taste aversion learning has sometimes been considered a specialized form of learning. In several other conditioning preparations, after a conditioned stimulus (CS) is conditioned and extinguished, reexposure to the unconditioned stimulus (US) by itself can reinstate the extinguished conditioned response. Reinstatement has been widely studied in fear and appetitive Pavlovian conditioning, as well as operant conditioning, but its status in taste aversion learning is more controversial. Six taste-aversion experiments with rats therefore sought to discover conditions that might encourage it there. The results often yielded little to no evidence of reinstatement, and we also found no evidence of concurrent recovery, a related phenomenon in which responding to a CS that has been conditioned and extinguished is restored if a second CS is separately conditioned. However, a key result was that reinstatement occurred when the conditioning procedure involved multiple closely spaced conditioning trials that could have allowed the animal to learn that a US presentation signaled or set the occasion for another trial with a US. Such a mechanism is precluded in many taste aversion experiments because they often use very few conditioning trials. Overall, the results suggest that taste aversion learning is experimentally unique, though not necessarily biologically or evolutionarily unique. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Voluntary behaviors (operants) can come in two varieties: Goal‐directed actions, which are emitted based on the remembered value of the reinforcer, and habits, which are evoked by antecedent cues and performed without the reinforcer's value in active memory. The two are perhaps most clearly distinguished with the reinforcer‐devaluation test: Goal‐directed actions are suppressed when the reinforcer is separately devalued and responding is tested in extinction, and habitual behaviors are not. But what is the function of habit learning? Habits are often thought to be strong and unusually persistent. The present selective review examines this idea by asking whether habits identified by the reinforcer‐devaluation test are more resistant to extinction, resistant to the effects of other contingency change, vulnerable to relapse, resistant to the weakening effects of context change, or permanently in place once they are learned. Surprisingly little evidence supports the idea that habits are permanent or more persistent. Habits are more context‐specific than goal‐directed actions are. Methods that make behavior persistent do not necessarily work by encouraging habit. The function of habit learning may not be to make a behavior strong or more persistent but to make it automatic and efficient in a particular context.