Role of context similarity in ABA, ABC, and AAB renewal paradigms: Implications for theories of renewal and for treating human phobias

Synthesized alternative reinforcement and resurgence

In treatments based on differential reinforcement of alternative behavior, applied researchers and clinicians often provide multiple, qualitatively different reinforcers (i.e., synthesized reinforcement) rather than a single reinforcer (i.e., isolated reinforcement) contingent on alternative behavior. Some research shows that providing synthesized reinforcement for alternative responses within such treatments produces more rapid and complete suppression of target behavior; however, there is limited research evaluating the durability of these effects during treatment disruptions. Conceptual explanations of resurgence (e.g., resurgence as choice, context theory) suggest that treatments that include synthesized alternative reinforcement may lead to more resurgence of target behavior when alternative reinforcement is disrupted relative to treatments using isolated reinforcement. We evaluated this hypothesis within a three-phase resurgence evaluation. We exposed rats to isolated or synthesized reinforcement for alternative responding in the second phase, and we exposed rats to extinction in the third phase. Synthesized alternative reinforcement produced more rapid and complete suppression of target behavior than did isolated reinforcement in the second phase; however, exposure to extinction following synthesized reinforcement produced more resurgence. We discuss these results in terms of their implications for applied research and their support for current conceptual explanations for resurgence.

Context-induced renewal of passive but not active coping behaviours in the shock-probe defensive burying task

Renewal is the return of extinguished responding after removal from the extinction context. Renewal has been extensively studied using classical aversive conditioning procedures that measure a passive freezing response to an aversive conditioned stimulus. However, coping responses to aversive stimuli are complex and can be reflected in passive and active behaviours. Using the shock-probe defensive burying task, we investigated whether different coping responses are susceptible to renewal. During conditioning, male, Long-Evans rats were placed into a specific context (Context A) where an electrified shock-probe delivered a 3 mA shock upon contact. During extinction, the shock-probe was unarmed in either the same (Context A) or a different context (Context B). Renewal of conditioned responses was assessed in the conditioning context (ABA) or in a novel context (ABC or AAB). Renewal of passive coping responses, indicated by an increased latency and a decreased duration of shock-probe contacts, was observed in all groups. However, renewal of passive coping, measured by increased time spent on the side of the chamber opposite the shock-probe, was only found in the ABA group. Renewal of active coping responses linked to defensive burying was not observed in any group. The present findings highlight the presence of multiple psychological processes underlying even basic forms of aversive conditioning and demonstrate the importance of assessing a broader set of behaviours to tease apart these different underlying mechanisms. The current findings suggest that passive coping responses may be more reliable indicators for assessing renewal than active coping behaviours associated with defensive burying.

A model for recovery-from-extinction effects in Pavlovian conditioning and exposure therapy

Exposure therapy is an effective intervention for anxiety-related problems. The mechanism of this intervention has been the extinction procedure in Pavlovian conditioning, and this application has provided many successful instances for the prevention of relapse. However, traditional associative theories cannot comprehensively explain many findings. In particular, it is difficult to explain the recovery-from-extinction effects, which is the reappearance of the conditioned response following extinction. In this paper, we propose an associative model that is a mathematical extension of Bouton's (1993, Psychological Bulletin, 114, 80-99) model for the extinction procedure. The core of our model is that the asymptotic strength of the inhibitory association depends on the degree of excitatory association retrieved in a context in which a conditioned stimulus (CS) is presented and that the retrieval is determined by the similarity between contexts during both reinforcement and non-reinforcement and the retrieval context. Our model provides an explanation of the recovery-from-extinction effects, and implications for exposure therapy.

ABA, AAB and ABC renewal with Pavlovian Conditioning of Tentacle Lowering procedure in the snail Cornu aspersum

This study assesses the recovery of the conditioned response (CR) due to a contextual change (renewal effect) in the Cornu aspersum, using the appetitive Pavlovian Conditioning of Tentacle Lowering procedure. Snails experienced an odorous conditioned stimulus (CS) paired with food (conditioning), followed by the exposition to the CS without any consequence (extinction). Then, they were exposed to the CS in a different context from the extinction one (renewal test). The contexts were three types of illumination. In Experiment 1a, the conditioning was performed in context A, the extinction was conducted in context B and the renewal test was performed in context A. For Experiment 1b, the conditioning and extinction were conducted in context A and renewal was performed in context B. In Experiment 1c, three dissimilar contexts were used for each experimental phase: context A for the conditioning, context B for the extinction and context C for the renewal. In Experiment 2, the renewal magnitude was compared among the three paradigms (ABA, AAB and ABC). Experiments 1a, 1b and 1c showed a recovery of the CR when subjects experienced a contextual change and Experiment 2 showed equivalent levels of renewal in the three paradigms. Learning processes and theories involved are discussed.

Learning processes in relapse to alcohol use: lessons from animal models

RATIONALE

Alcohol use is reliably preceded by discrete and contextual stimuli which, through diverse learning processes, acquire the capacity to promote alcohol use and relapse to alcohol use.

OBJECTIVE

We review contemporary extinction, renewal, reinstatement, occasion setting, and sex differences research within a conditioning framework of relapse to alcohol use to inform the development of behavioural and pharmacological therapies.

KEY FINDINGS

Diverse learning processes and corresponding neurobiological substrates contribute to relapse to alcohol use. Results from animal models indicate that cortical, thalamic, accumbal, hypothalamic, mesolimbic, glutamatergic, opioidergic, and dopaminergic circuitries contribute to alcohol relapse through separable learning processes. Behavioural therapies could be improved by increasing the endurance and generalizability of extinction learning and should incorporate whether discrete cues and contexts influence behaviour through direct excitatory conditioning or occasion setting mechanisms. The types of learning processes that most effectively influence responding for alcohol differ in female and male rats.

CONCLUSION

Sophisticated conditioning experiments suggest that diverse learning processes are mediated by distinct neural circuits and contribute to relapse to alcohol use. These experiments also suggest that gender-specific behavioural and pharmacological interventions are a way towards efficacious therapies to prevent relapse to alcohol use.

Motivational state-dependent renewal and reinstatement of operant responding under food and water deprivation states

Most studies of operant relapse phenomena have studied the role of exteroceptive discriminative features of context in the recovery of behavior after extinction. Interoceptive stimuli (i.e., stimuli arising from the bodies of organisms) may also serve as a part of learning contexts and contribute to relapse. Recent studies have demonstrated that events that function as motivating operations (MOs) may contribute to relapse both by a) eliciting interoceptive conditions that serve as a discriminative context for relapse (i.e., discriminative function) and b) altering the amount of operant responding in the presence of discriminative stimuli associated with reinforcers (i.e., motivational function). The current study examined interactions between these functions of food and water deprivation MOs in the relapse of operant behavior. During acquisition of an operant response, one group of mice was food-deprived and another was water-deprived. The groups then received extinction sessions under the opposite condition. Renewal and reinstatement tests were conducted under both conditions, and more renewal and reinstatement were observed in the motivational states in which acquisition occurred for each. These results are discussed in the context of state-dependent learning.

Explaining the Return of Fear with Revised Rescorla-Wagner Models

Exposure therapy - exposure to a feared stimulus without harmful consequences - can reduce fear responses in many mental disorders. However, such relief is often partial and temporary: fear can return after the therapy has ended. Conditioning research has identified three mechanisms for the return of fear, viz. change in physical context (renewal), the passage of time (spontaneous recovery), and an encounter with the fear-producing unconditioned stimulus (reinstatement). To understand why fear returns and thereby develop more effective therapies, we develop mathematical learning models based on that of Rescorla and Wagner. According to this model, context cues present during extinction become conditioned inhibitors (i.e. safety signals) which prevent total erasure of the threat association. Adding various mechanisms to the model allows it to explain different facets of the return of fear. Among these mechanisms is decay of inhibitory associations, which provides a novel explanation for spontaneous recovery. To make the benefits of exposure robust and permanent, one must minimize the degree to which the extinction context becomes inhibitory in order to maximize unlearning. We simulate several experimental paradigms that reduce the return of fear and explain them according to this principle.

Translating Quantitative Theories of Behavior into Improved Clinical Treatments for Problem Behavior

The most important advancement in the treatment of destructive behavior has been the development of the functional analysis, which is used to prescribe effective treatments like functional communication training. Although this approach can be highly effective, extinction bursts and forms of treatment relapse commonly occur when function-based treatments are implemented by caregivers in natural community settings. In recent years, researchers have increasingly applied quantitative theories of behavior like behavioral momentum theory (BMT) and the temporally weighted matching law (TWML) to understand, prevent, or mitigate extinction bursts and treatment relapse. In this paper, we describe BMT and TWML and selectively review the basic, translational, and applied research supporting and opposing each theory. Then, we describe how function-based treatments may be refined based on these theories to improve the effectiveness, generality, and durability of function-based treatments for individuals with autism spectrum and related disorders who display problem behavior.

Trajectories of fear learning in healthy participants are able to distinguish groups that differ in individual characteristics, chronicity of fear and intrusions

BACKGROUND AND OBJECTIVES

Studies on the development and treatment of anxiety disorders mostly focus on the comparison of predefined groups. An alternative approach is to use data-driven latent class growth analyses (LCGA) to determine differentiation between groups based on particular mechanistic factors. This study validated the use of LCGA on responses in a compact fear conditioning task and whether specific characteristics are associated with maladaptive fear learning trajectories.

METHODS

Healthy subjects (N = 300) completed a fear conditioning task that included uninstructed and instructed acquisition and extinction phases. Subjective fearfulness and US expectancy were used as outcome measures. Latent classes in the responses to the CS+ (coupled with a scream) and the CS- (control stimulus) were determined based on trajectories across the experimental phases. State and trait anxiety were measured during testing, and return of fear and intrusions were measured one and six weeks later.

RESULTS

Fear learning trajectories of poor extinction in responding to the CS+ and generalization of fear to the CS- were associated with higher state and trait anxiety. Individuals belonging to these trajectories reported more intrusions, fear and had higher US expectancy ratings after 1 week.

LIMITATIONS

Only 56% of participants completed the six weeks follow-up measures.

CONCLUSION

Fear learning trajectories are associated with individual characteristics, return of fear and intrusions. Next, this task will be implemented in clinical practice to assess its predictive power for the extent to which patients benefit from exposure treatments.

Comparing ABA, AAB, and ABC Renewal of Appetitive Pavlovian Conditioned Responding in Alcohol- and Sucrose-Trained Male Rats

Conditioned responding can be renewed by re-exposure to the conditioning context following extinction in a different context (ABA renewal) or by removal from the extinction context (AAB or ABC renewal). ABA renewal is robust in Pavlovian and operant conditioning paradigms. However, fewer studies have investigated AAB and ABC renewal of appetitive conditioning, and those that did predominantly used operant conditioning tasks. Renewal has theoretical relevance for extinction and for exposure-based treatments for substance use disorders that aim to extinguish reactivity to drug-predictive cues. We therefore investigated ABA, AAB, and ABC renewal of Pavlovian conditioned responding to cues that predicted either alcohol or sucrose. Male, Long-Evans rats (Charles River) were exposed to either 15% ethanol (Study 1: “alcohol”) or 10% sucrose (Study 2: “sucrose”) in their home cages. Next, they were trained to discriminate between two auditory stimuli (white noise and clicker; 10 s) in conditioning chambers equipped with distinct olfactory, visual, and tactile contextual stimuli (context A). One conditioned stimulus (CS+) was paired with fluid delivery (0.2 ml/CS+; 3.2 ml/session; alcohol or sucrose in separate experiments), and the second CS (CS−) was not. In all sessions (conditioning, extinction, and test), each CS was presented 16 times/session on a variable-time 67-s schedule, and entries into the fluid port were recorded. CS+ port entries were then extinguished by withholding fluid delivery either in context A or in a second, different context (context B). Next, we assessed ABA, AAB, and ABC renewal in the absence of fluid delivery. During extinction, CS+ port entries were initially elevated in context A relative to context B. ABA renewal of CS+ port entries occurred in both alcohol- and sucrose-trained rats. ABC renewal approached statistical significance when data from both experiments were combined. No AAB renewal was observed, and, in fact, alcohol-trained rats showed AAB suppression. These results corroborate the reliability of ABA renewal and suggest that ABC renewal is a modest effect that may require greater statistical power to detect. From a treatment perspective, the lack of AAB renewal suggests that exposure-based treatments for substance use disorders might benefit from implementation in real-world, drug-use contexts.

Re-exposure to reinforcement in context a during treatment in context b reduces ABC renewal

Previous work from our laboratory showed that intermittently re-exposing rats to reinforcement for lever pressing in a training (A) context, while eliminating lever pressing in a second (B) context, increased ABA renewal of lever pressing relative to rats that experienced only Context B during response elimination. In the current study, we replicated these procedures while assessing renewal in the presence of a novel context (i.e., ABC renewal). Unlike the findings described above, renewal was reduced in the group that experienced re-exposure to Context A during lever-press elimination relative to rats that experienced only Context B. These findings suggest that alternating between contexts associated with reinforcement and extinction during treatment reduces the probability that organisms will respond in novel contexts. These outcomes may be the result of discrimination and/or generalization processes. Moreover, this training procedure may offer a potential mitigation strategy for ABC renewal.

Prior extinction increases acquisition context specificity in human predictive learning

One experiment evaluated the effect of extinction on the context dependence of non-extinguished information in a situation in which physical (images), rather than predominantly verbal, contexts were used in human predictive learning. Participants received training in which different foods (Cues) were associated with the presence or the absence of gastric illness (outcome) in customers of different restaurants (contexts). One cue was associated with the gastric illness while a different cue was either extinguished or not between groups. A change in the context at test led to a general decrease in both predictive judgments and the speed of responding to the non-extinguished cue. However, these decreases were greater when training was conducted during extinction of the different cue demonstrating the extinction makes acquisition context-specific (EMACS) effect. Results are contrasted with failures to find the effect in other reports and discussed in terms of extinction leading to an allocation of attentional resources to the context, facilitating the context dependence of information.

Context dependency as a Function of Prediction Error-Based Attention

Context dependence of information has been shown to be based, at least in part, on the attention contexts received at the time of training. Recent research suggests that attention to irrelevant contexts may be a byproduct of the activation of a general exploratory attentional mechanism prompted by high prediction errors associated with situations of uncertainty. Alternatively, low prediction errors may engage an attentional mechanism of exploitation in situations in which contexts play a relevant role. A selective review discusses the potential of this approach to explain context switch effects from an attentional perspective.

Removing but not adding elements of a context affects generalization of instrumental responses

Three experiments with rats investigated whether adding or removing elements of a context affects generalization of instrumental behavior. Each of the experiments used a free operant procedure. In Experiments 1 and 2, rats were trained to press a lever for food in a distinctive context. Then, transfer of lever pressing was tested in a context created either by adding an element to the context of initial acquisition or by removing one of the acquisition context's elements. In Experiment 3, a similar generalization test was conducted after rats received acquisition and extinction within the same context. For Experiments 1 and 2, we observed that removing elements from the acquisition context disrupted acquisition performance, whereas the addition of elements to the context did not. Experiment 3 revealed that removing elements from but not adding elements to the original context improved extinction performance. Our results are consistent with an elemental view of context representation.

A review of boundary conditions and variables involved in the prevention of return of fear after post-retrieval extinction

Experimental evidence suggests that the return of fear may be prevented by post-retrieval extinction (PRE), a procedure consisting of extinction training after the presentation of a retrieval cue. However, attempts to replicate these findings have yielded mixed results, with some studies showing diminished fear responses after PRE, whereas others show no effect on the return of fear following this procedure. The discrepancies across studies have been interpreted as evidence that there might be conditions under which PRE is not effective (boundary conditions), but these variables have yet to be fully described. We aimed to provide an overview of PRE in humans. We briefly present the theory and research that originated post-retrieval procedures with a focus on the experimental setup used in human studies. We continue with a compilation of possible experimental boundary conditions along with some questions for future research.

Renewed behavior produced by context change and its implications for treatment maintenance: A review

Behavioral treatment gains established in one setting do not always maintain in other settings. The present review examines the relevance of basic and translational research to understanding failures to maintain treatment gains across settings. Specifically, studies of the renewal effect examine how transitioning away from a treatment setting could evoke a return of undesirable behavior, rather than newly trained appropriate behavior. Studies of renewal typically arrange three phases, with a response trained and reinforced under a particular set of contextual stimuli in the first phase. Next, that response is extinguished, often under a different set of contextual stimuli. Finally, that response returns despite extinction remaining in effect upon returning to the original training context or transitioning to a novel context. Thus, removing the extinction context is sufficient to produce a recurrence of the response. The findings suggest treatment effects can become specific to the context in which the treatment was delivered. This literature offers promising methods for systematically assessing the factors contributing to treatment maintenance and improving generalization of treatment gains across contexts. Therefore, the present review suggests basic and translational research on renewal provides an empirical literature to bring greater conceptual systematization to understanding generalization and maintenance of behavioral treatment.

Extinción y renovación de la memoria espacial en humanos

Participantes humanos fueron entrenados en un laberinto virtual de agua para localizar en dos fases sucesivas una plataforma cuya ubicación fue específica a la fase vigente. Posteriormente realizaron una prueba sin plataforma. El Grupo ABA realizó la primera fase y la prueba en un contexto A, y la segunda fase en un contexto B. El Grupo ABB realizó la primera fase en el contexto A, y la segunda fase y la prueba en el contexto B. Ambos grupos localizaron la plataforma en cada fase. Durante la prueba, la última ubicación de la plataforma fue preferida por el Grupo ABB, mientras que la primera ubicación fue preferida por el Grupo ABA. Estos resultados indican renovación de la memoria espacial en humanos.

Stepping back from 'persistence and relapse' to see the forest: Associative interference

Historically, there has been considerable interest in a large variety of forms of associative interference. However, various factors including interest in clinical application and perhaps recent funding priorities have resulted in a narrowed focus on one particular instance of interference, extinction, with relative neglect of other types of interference. We have been using the existing literature and conducting new experiments to determine whether there is a consistent set of rules governing the occurrence and persistence of two-phase associative interference across (a) proactive and retroactive interference, (b) cue and outcome interference, (c) the type of training in phase 1 (excitatory, inhibitory, or simple nonreinforcement), and (d) the type of training in phase 2 (excitatory, inhibitory, or simple nonreinforcement). Our hope is that a return to more general questions concerning associative interference might reveal broad truths concerning the nature of forgetting. Identifying global principles of associative interference may also help us better appreciate the nature of extinction, including how it can be enhanced and made more enduring, as well as how it can be minimized and made more fleeting.

Changes in Cue Configuration Reduce the Impact of Interfering Information in a Predictive Learning Task

Decades of research in extinction and interference show that contexts can play a critical role at disambiguating the meaning of cues that have been paired with different outcomes at different times. For instance, if a cue x is followed by outcome 1 in the first phase of an experiment and by outcome 2 in a second phase, responses to cue x tend to be consistent with outcome 2 when tested in a context similar to that of the second phase of the experiment. However, if participants are taken back to the original context of the first phase (i.e., ABA renewal) or to a completely new context (i.e., ABC or AAB renewal), their responses to x tend to be more consistent with outcome 1. Although the role of physical and temporal contexts has been well studied, other factors that can also modulate the selective retrieval of information after interference have received less attention. The present series of experiments shows how changes in cue configuration can modulate responding in a similar manner. Across five experiments using a human predictive learning task, we found that adding, removing or replacing elements from a compound cue that had undergone an interference treatment gave rise to a recovery of responding akin to that observed after context changes in AAB renewal. These results are consistent with those of previous studies exploring the effect of changes of cue configuration on interference. Taken together, these studies suggest that a change in cue configuration can have the functional properties of a context change, a finding with important implications for formal models of configural learning and for classical accounts of interference and information retrieval.

Intact renewal after extinction of conditioned suppression with lesions of either the retrosplenial cortex or dorsal hippocampus

Extinction of fear to a Pavlovian conditioned stimulus (CS) is known to be context-specific. When the CS is tested outside the context of extinction, fear returns, or renews. Several studies have demonstrated that renewal depends upon the hippocampus, although there are also studies where renewal was not impacted by hippocampal damage, suggesting that under some conditions context encoding and/or retrieval of extinction depends upon other regions. One candidate region is the retrosplenial cortex (RSC), which is known to contribute to contextual and spatial learning and memory. Using a conditioned-suppression paradigm, Experiment 1 tested the impact of pre-training RSC lesions on renewal of extinguished fear. Consistent with previous studies, lesions of the RSC did not impact acquisition or extinction of conditioned fear to the CS. Further, there was no evidence that RSC lesions impaired renewal, indicating that contextual encoding and/or retrieval of extinction does not depend upon the RSC. In Experiment 2, post-extinction lesions of either the RSC or dorsal hippocampus (DH) also had no impact on renewal. However, in Experiment 3, both RSC and DH lesions did impair performance in an object-in-place procedure, an index of place memory. RSC and DH contributions to extinction and renewal are discussed.

Contextual control of operant behavior: evidence for hierarchical associations in instrumental learning

Recent research has suggested that operant responses can be weakened when they are tested in new contexts. The present experiment was therefore designed to test whether animals can learn a context-(R-O) relation. Rats were given training sessions in context A, in which one response (R1; lever pressing or chain pulling) produced one outcome (O1) and another response (R2; chain pulling or lever pressing) produced another outcome (O2) on variable interval reinforcement schedules. These sessions were intermixed with training in context B, where R1 now produced O2 and R2 produced O1. Given the arrangement, it was possible for the animal to learn two distinct R-O associations in each specific context. To test for them, rats were then given aversion conditioning with O2 by pairing its presentation with lithium-chloride-induced illness. Following the aversion conditioning, the rats were given an extinction test with both R1 and R2 available in each context. During testing, rats showed a selective suppression in each context of the response that had been paired with the reinforcer subsequently associated with illness. Rats could not have performed this way without knowledge of the R-O associations in effect in each specific context, lending support to the hypothesis that rats learn context-(R-O) associations. However, despite a complete aversion to O2, responding was not completely suppressed, leaving the possibility open that rats form context-R associations in addition to context-(R-O) associations.

Occasion setting, inhibition, and the contextual control of extinction in Pavlovian and instrumental (operant) learning

An occasion setter is a stimulus that modulates the ability of another stimulus to control behavior. A rich history of experimental investigation has identified several important properties that define occasion setters and the conditions that give rise to occasion setting. In this paper, we first consider the basic hallmarks of occasion setting in Pavlovian conditioning. We then review research that has examined the mechanisms underlying the crucial role of context in Pavlovian and instrumental extinction. In Pavlovian extinction, evidence suggests that the extinction context can function as a negative occasion setter whose role is to disambiguate the current meaning of the conditioned stimulus; the conditioning context can also function as a positive occasion setter. In operant extinction, in contrast, the extinction context may directly inhibit the response, and the conditioning context can directly excite it. We outline and discuss the key results supporting these distinctions.

Renewal of extinguished instrumental responses: independence from Pavlovian processes and dependence on outcome value

The source of renewal of instrumental responding in rats was investigated. In Experiment 1, two responses (R1 and R2) were reinforced with one outcome (O1) in contexts A and B (i.e., R1→O1, R2→O1), and then R2 was extinguished in A and R1 was extinguished in B. At test, the rate of R1 was higher than that of R2 in context A, and the reverse was the case in context B: Renewed responding was independent of the Pavlovian context→O1 associations. In Experiment 2, all rats received R1→O1 and R2→O2 trials in A and then were placed in B, where they were sated on O2 and either did (Group Extinction) or did not (Group No Extinction) receive concurrent extinction of R1 and R2. At test, we found more responding in A than in B for Group Extinction, but not for Group No Extinction, and the renewed responding in A was as sensitive to the current value of the outcome as responding that had not been subject to extinction (i.e., the rate was higher for R1 than for R2). That is, the renewed responding was goal-directed. These results identify the removal of contextual inhibion of either the response or the response→outcome associaon as potenal bases for renewal, and the response→outcome associaon as the source of renewed responding.

Reinstatement of an extinguished fear conditioned response in infant rats

Although it is currently accepted that the extinction effect reflects new context-dependent learning, this is not so clear during infancy, because some studies did not find recovery of the extinguished conditioned response (CR) in rodents during this ontogenetic stage. However, recent studies have shown the return of an extinguished CR in infant rats. The present study analyzes the possibility of recovering an extinguished CR with a reinstatement procedure in a fear conditioning paradigm, on PD17 (Experiments 1-4) and on PD24 (Experiment 5), while exploring the role of the olfactory content of the context upon the reinstatement effect during the preweanling period. Preweanling rats expressed a previously extinguished CR after a single experience with an unsignaled US. Furthermore, this result was only found when subjects were trained and tested in contexts that included an explicit odor, but not in standard experimental cages. Finally, Experiment 5 demonstrated the reinstatement effect on PD24 in a standard context. These results support the notion that extinction during infancy has the same characteristics as those described for extinction that occurs in adulthood. Instead of postulating a different mechanism for extinction during infancy, we propose that it may be more accurate to view the problem in terms of the variables that may differentially modulate the extinction effect according to the stages of ontogeny.

Contrasting ABA, AAB and ABC Renewal in a Free Operant Procedure

One experiment used a free operant procedure with rats to compare ABA, AAB and ABC renewal by using a within-subject testing procedure. All rats were first trained to press a lever for food in context A. Lever pressing was then extinguished in either context A or context B. For rats in the groups ABA and ABC extinction took place in context B, while the rats in group AAB received extinction in the same context in which acquisition took place (context A). Finally, all rats were tested for renewal in two sessions. One extinction session was carried out in the same extinction context and another session in a different context. Rats in the group ABA were tested in context B and in context A; rats in the group AAB were tested in contexts A and B, whereas the group ABC was tested in contexts B and C. The results of the ANOVA showed context renewal since all groups had higher rates of responding when they were tested outside the extinction context, F(2, 21) = 15.32, p = .001, ηp2 = .59; however, AAB and ABC renewal was lesser than ABA renewal, F(1, 21) = 16.70, p = .0001, ηp2 = .61.

Context-dependent latent inhibition in preweanling rats

Preexposure to a conditioned stimulus (CS) usually weakens conditioning, an effect known as latent inhibition. Similar to other learning interference effects, latent inhibition has been characterized as context-dependent, which means that the magnitude of this effect can be attenuated by changing the context between the different phases of the procedure (e.g., preexposure and conditioning). Latent inhibition has been found with a variety of procedures in infant rats, but the few studies that examined the context-dependency of this phenomenon during this ontogenetic period found no context-change effect. The present study explored the context-dependency of latent inhibition during infancy using a conditioned taste aversion preparation and employing contexts enriched with distinctive odors to increase the possible efficacy of the context manipulation. Experiment 1 showed that three preexposures to the CS (saccharin) were sufficient to retard conditioning to the same CS, although this effect was also observed in a control group preexposed to an alternative taste stimulus (saline), in comparison with a non-preexposed control group. In Experiment 2a, the CS-preexposure effect was found to be specific to the preexposed CS when the number of preexposures was increased. This effect was revealed as context-dependent in Experiment 2b, since it was attenuated by changing the context between preexposure and conditioning. The present result is consistent with recent studies showing the context-dependency of extinction in preweanling rats, thus demonstrating these animals' capacity to learn about context early on in their development.

ABA renewal involves enhancements in both GluA2-lacking AMPA receptor activity and GluA1 phosphorylation in the lateral amygdala

Fear renewal, the context-specific relapse of fear following fear extinction, is a leading animal model of post-traumatic stress disorders (PTSD) and fear-related disorders. Although fear extinction can diminish fear responses, this effect is restricted to the context where the extinction is carried out, and the extinguished fear strongly relapses when assessed in the original acquisition context (ABA renewal) or in a context distinct from the conditioning and extinction contexts (ABC renewal). We have previously identified Ser831 phosphorylation of GluA1 subunit in the lateral amygdala (LA) as a key molecular mechanism for ABC renewal. However, molecular mechanisms underlying ABA renewal remain to be elucidated. Here, we found that both the excitatory synaptic efficacy and GluA2-lacking AMPAR activity at thalamic input synapses onto the LA (T-LA synapses) were enhanced upon ABA renewal. GluA2-lacking AMPAR activity was also increased during low-threshold potentiation, a potential cellular substrate of renewal, at T-LA synapses. The microinjection of 1-naphtylacetyl-spermine (NASPM), a selective blocker of GluA2-lacking AMPARs, into the LA attenuated ABA renewal, suggesting a critical role of GluA2-lacking AMPARs in ABA renewal. We also found that Ser831 phosphorylation of GluA1 in the LA was increased upon ABA renewal. We developed a short peptide mimicking the Ser831-containing C-tail region of GluA1, which can be phosphorylated upon renewal (GluA1S); thus, the phosphorylated GluA1S may compete with Ser831-phosphorylated GluA1. This GluA1S peptide blocked the low-threshold potentiation when dialyzed into a recorded neuron. The microinjection of a cell-permeable form of GluA1S peptide into the LA attenuated ABA renewal. In support of the GluA1S experiments, a GluA1D peptide (in which the serine at 831 is replaced with a phosphomimetic amino acid, aspartate) attenuated ABA renewal when microinjected into the LA. These findings suggest that enhancements in both the GluA2-lacking AMPAR activity and GluA1 phosphorylation at Ser831 are required for ABA renewal.

Associative Accounts of Recovery-from-Extinction Effects

Recovery-from-extinction effects (e.g., spontaneous recovery, renewal, reinstatement, and facilitated reacquisition) have become the focus of much research in recent years. However, despite a great deal of empirical data, there are few theoretical explanations for these effects. This paucity poses a severe limitation on our understanding of these behavioral effects, impedes advances in uncovering neural mechanisms of response recovery, and reduces our potential to prevent relapse after exposure therapy. Towards correcting this oversight, this review takes prominent models of associative learning that have been used in the past and continue to be used today to explain Pavlovian conditioning and extinction, and assesses how each model can be applied to account for recovery-from-extinction effects. The models include the Rescorla-Wagner (1972) model, Mackintosh's (1975) attentional model, Pearce and Hall's (1980) attentional model, Wagner's (1981) SOP model, Pearce's (1987) configural model, McLaren and Mackintosh's (2002) elemental model, and Stout and Miller's (2007) SOCR (comparator hypothesis) model. Each model is assessed for how well it explains or does not explain the various recovery-from-extinction phenomena. We offer some suggestions for how the models might be modified to account for these effects in those instances in which they initially fail.

A fundamental role for context in instrumental learning and extinction

The purpose of this article is to review recent research that has investigated the effects of context change on instrumental (operant) learning. The first part of the article discusses instrumental extinction, in which the strength of a reinforced instrumental behavior declines when reinforcers are withdrawn. The results suggest that extinction of either simple or discriminated operant behavior is relatively specific to the context in which it is learned: As in prior studies of Pavlovian extinction, ABA, ABC, and AAB renewal effects can all be observed. Further analysis supports the idea that the organism learns to refrain from making a specific response in a specific context, or in more formal terms, an inhibitory context-response association. The second part of the article then discusses research suggesting that the context also controls instrumental behavior before it is extinguished. Several experiments demonstrate that a context switch after either simple or discriminated operant training causes a decrement in the strength of the response. Over a range of conditions, the animal appears to learn a direct association between the context and the response. Under some conditions, it can also learn a hierarchical representation of context and the response-reinforcer relation. Extinction is still more context-specific than conditioning, as indicated by ABC and AAB renewal. Overall, the results establish that the context can play a significant role in both the acquisition and extinction of operant behavior.

On the differences in degree of renewal produced by the different renewal designs

This paper addresses sources contributing to the differences in the degree of recovery from extinction observed with different renewal paradigms. In two lick suppression experiments with rats, we assessed the role of the associative status of the acquisition context in both the weakness of AAC renewal and the sometimes observed weaker renewal resulting from an ABC design relative to an ABA design. In Experiment 1, we observed that AAC renewal relative to an AAA control group was small unless Context A had undergone associative deflation (i.e., extinction of Context A). Deflation of Context A not only decreased behavioral control by the CS in the AAA condition, but increased it in the AAC condition, thereby implicating a comparator process in addition to associative summation between the CS and test context. In Experiment 2, an excitatory acquisition context was found to enhance the difference between ABC and ABA renewal. Associative deflation of the acquisition context decreased ABA renewal more than ABC renewal. Thus, the associative value of the acquisition context (A) was more positively related to the level of renewal when the target CS (X) was tested in this context than when it was tested in a neutral but equally familiar context (C), consistent with the frequently observed greater renewal in an ABA condition than an ABC condition arising from associative summation of the CS and test context. These findings demonstrate that the excitatory status of the acquisition context influences the observed degree of renewal.

Special issue on computational models of classical conditioning guest editors' introduction

In the present special issue, the performance of current computational models of classical conditioning was evaluated under three requirements: (1) Models were to be tested against a list of previously agreed-upon phenomena; (2) the parameters were fixed across simulations; and (3) the simulations used to test the models had to be made available. These requirements resulted in three major products: (a) a list of fundamental classical-conditioning results for which there is a consensus about their reliability; (b) the necessary information to evaluate each of the models on the basis of its ordinal successes in accounting for the experimental data; and (c) a repository of computational models ready to generate simulations. We believe that the contents of this issue represent the 2012 state of the art in computational modeling of classical conditioning and provide a way to find promising avenues for future model development.