Counterconditioned fear responses exhibit greater renewal than extinguished fear responses

Out with the bad, in with the good: A review on augmented extinction learning in humans

Several leading therapies for anxiety-related disorders rely on the principles of extinction learning. However, despite decades of development and research, many of these treatments remain only moderately effective. Developing techniques to improve extinction learning is an important step towards developing improved and mechanistically-informed exposure-based therapies. In this review, we highlight human research on strategies that might augment extinction learning through reward neurocircuitry and dopaminergic pathways, with an emphasis on counterconditioning and other behaviorally-augmented forms of extinction learning (e.g., novelty-facilitated extinction, positive affect training). We also highlight emerging pharmacological and non-pharmacological methods of augmenting extinction, including L-DOPA and aerobic exercise. Finally, we discuss future directions for augmented extinction learning and memory research, including the need for more work examining the influence of individual differences and psychopathology.

Reward processes in extinction learning and applications to exposure therapy

Anxiety disorders are common and highly distressing mental health conditions. Exposure therapy is a gold-standard treatment for anxiety disorders. Mechanisms of Pavlovian fear learning, and particularly fear extinction, are central to exposure therapy. A growing body of evidence suggests an important role of reward processes during Pavlovian fear extinction. Nonetheless, predominant models of exposure therapy do not currently incorporate reward processes. Herein, we present a theoretical model of reward processes in relation to Pavlovian mechanisms of exposure therapy, including a focus on dopaminergic prediction error signaling, coinciding positive emotional experiences (i.e., relief), and unexpected positive outcomes. We then highlight avenues for further research and discuss potential strategies to leverage reward processes to maximize exposure therapy response, such as pre-exposure interventions to increase reward sensitivity or post-exposure rehearsal (e.g., savoring, imaginal recounting strategies) to enhance retrieval and retention of learned associations.

Memory Trace for Fear Extinction: Fragile yet Reinforceable

Fear extinction is a biological process in which learned fear behavior diminishes without anticipated reinforcement, allowing the organism to re-adapt to ever-changing situations. Based on the behavioral hypothesis that extinction is new learning and forms an extinction memory, this new memory is more readily forgettable than the original fear memory. The brain's cellular and synaptic traces underpinning this inherently fragile yet reinforceable extinction memory remain unclear. Intriguing questions are about the whereabouts of the engram neurons that emerged during extinction learning and how they constitute a dynamically evolving functional construct that works in concert to store and express the extinction memory. In this review, we discuss recent advances in the engram circuits and their neural connectivity plasticity for fear extinction, aiming to establish a conceptual framework for understanding the dynamic competition between fear and extinction memories in adaptive control of conditioned fear responses.

Perceived stress and renewal: The effects of long-term stress on the renewal effect

Two online experiments evaluated the relationship between long-term stress, as measured with the Perceived Stress Scale-10, and the Renewal Effect. In the first experiment renewal was assessed with a behavioral suppression task in a science-fiction based video game. Participants learned to suppress mouse clicking during a signal for an upcoming attack to avoid losing points. The signal was first paired with an attack in Context A and extinguished in Context B and tested back in Context A. The contexts were different space galaxies where the gameplay took place. Experiment 2 used a food/illness predictive-learning paradigm. Two food items were paired with stomachache in one restaurant (A) and extinguished in Context B prior to testing in both contexts without feedback. Positive correlations were obtained between renewal and stress in each experiment. Unlike acute stress (Drexler et al., 2017), long term stress was associated with greater renewal. The effects of stress, both chronic and punctual, on renewal are discussed.

Renewal in human fear conditioning: A systematic review and meta-analysis

Renewal is a 'return of fear' manipulation in human fear conditioning to investigate learning processes underlying anxiety and trauma. Even though renewal paradigms are widely used, no study has compared the strength of different renewal paradigms. We conduct a systematic review (N = 80) and meta-analysis (N = 23) of human fear conditioning studies assessing renewal. Our analysis shows that the classic ABA design is the most effective paradigm, compared to ABC and ABBA designs. We present evidence that conducting extinction in multiple contexts and increasing the similarity between acquisition and extinction contexts reduce renewal. Furthermore, we show that additional cues can be used as safety and 'protection from extinction' cues. The review shows that alcohol weakens the extinction process and that older adults appear less sensitive to context changes and thus show less renewal. The large variability in approaches to study renewal in humans suggests that standardisation of fear conditioning procedures across laboratories would be of great benefit to the field.

Paraventricular thalamus to nucleus accumbens circuit activation decreases long-term relapse of alcohol-seeking behaviour in male mice

BACKGROUND

Some studies have highlighted the crucial role of aversion in addiction treatment. The pathway from the anterior paraventricular thalamus (PVT) to the shell of the nucleus accumbens (NAc) has been reported as an essential regulatory pathway for processing aversion and is also closely associated with substance addiction. However, its impact on alcohol addiction has been relatively underexplored. Therefore, this study focused on the role of the PVT-NAc pathway in the formation and relapse of alcohol addiction-like behaviour, offering a new perspective on the mechanisms of alcohol addiction.

RESULTS

The chemogenetic inhibition of the PVT-NAc pathway in male mice resulted in a notable decrease in the establishment of ethanol-induced conditioned place aversion (CPA), and NAc-projecting PVT neurons were recruited due to aversive effects. Conversely, activation of the PVT-NAc pathway considerably impeded the formation of ethanol-induced conditioned place preference (CPP). Furthermore, during the memory reconsolidation phase, activation of this pathway effectively disrupted the animals' preference for alcohol-associated contexts. Whether it was administered urgently 24 h later or after a long-term withdrawal of 10 days, a low dose of alcohol could still not induce the reinstatement of ethanol-induced CPP.

CONCLUSIONS

Our results demonstrated PVT-NAc circuit processing aversion, which may be one of the neurobiological mechanisms underlying aversive counterconditioning, and highlighted potential targets for inhibiting the development of alcohol addiction-like behaviour and relapse after long-term withdrawal.

Intermixed safety cues facilitate extinction retention in adult and adolescent mice

Extinction learning is tremendously adaptive as it allows an animal to adjust their behavior in a changing environment. Yet, extinction is not without limitations and fear often reemerges over time (i.e. spontaneous recovery). Relative to adults, adolescent rodents and humans are particularly prone to spontaneous recovery following extinction. In this study, we aimed to address whether combining methods of fear regulation (extinction and conditioned inhibition) can facilitate extinction retention. Early adolescent (29 days old, n = 81) and adult (70 days old, n = 80) mice underwent extinction with or without a safety cue present. Safety cue presentations were systematically varied to overlap with or alternate with fear cue presentations. We found that initial safety learning was faster in adolescent mice. In addition, intermixing safety cues into extinction reduced spontaneous recovery during a test two weeks later. The decrease in spontaneous recovery relative to a standard extinction protocol was greater in adolescents than adults. Together, our findings provide initial evidence that safety learning may be inherently stronger during adolescence. These results inform the parameters by which conditioned safety and extinction learning may be merged to augment the inhibition of fear. While methods to enhance fear regulation are valuable for any age, the potential to do so during adolescence is particularly striking.

Counterconditioning reduces contextual renewal in a novel context but not in the acquisition context

As extinction is a context-dependent form of learning, conditioned responses tend to return when the conditioned stimulus (CS) is encountered outside the extinction context, known as contextual renewal. Counterconditioning is a technique that may lead to a more persistent reduction of the conditioned response. However, the effects of aversive-to-appetitive counterconditioning on contextual renewal in rodent studies are mixed. Further, research in humans is sparse, particularly direct statistical comparisons between counterconditioning and standard extinction techniques within the same study. Using a causal associative learning framework (the allergist task) implemented online, we compared the effectiveness of counterconditioning to standard extinction in preventing the renewal of judgements on the allergic properties of different food items (CSs). In a between-subjects design, 328 participants first learned that particular food items (CSs) lead to an allergic reaction in a specific restaurant (context A). Next, one CS was extinguished (no allergic reaction) while another CS was counterconditioned (positive outcome) in restaurant B. Causal judgements of the allergic properties of food items occurred in either the response acquisition context (ABA group, N = 112), the response reduction context where extinction and counterconditioning had occurred (ABB group, N = 107), or a novel context (ABC group, N = 109). Results showed that counterconditioning, compared to extinction, diminished the renewal of causal judgements to the CS in a novel context (ABC group). Still, casual judgements returned for both counter-conditioned and extinguished CSs in the response acquisition context (ABA group). Counterconditioning and extinction were similarly effective at preventing recovery of causal judgements in the response reduction context (ABB group); however, only in context B did participants choose the counter-conditioned CS as less likely to cause an allergic reaction in comparison to the extinguished CS. These findings indicate scenarios in which counterconditioning is more effective than standard extinction at diminishing the return of threat associations, with implications for improving the generalization of safety learning.

Stress effects on memory retrieval of aversive and appetitive instrumental counterconditioning in men

Extinction training creates a second inhibitory memory trace and effectively reduces conditioned responding. However, acute stress inhibits the retrieval of this extinction memory trace. It is not known whether this also applies to other forms of associative learning such as instrumental counterconditioning, where previously learned associations are reversed and paired with the opposite valence. Therefore, the current preregistered study investigates whether stress decreases the retrieval of instrumental counterconditioning memories with aversive and appetitive consequences. Fifty-two healthy men were randomly assigned to either a stress or control group and took part in a two-day instrumental learning paradigm. During a first phase, participants learned that pressing specific buttons in response to the presentation of four neutral stimuli either leads to gaining or losing money. During a second phase, two stimuli reversed their contingencies (counterconditioning). One day later, participants were exposed to acute stress or a control condition prior to the same task, which no longer included feedback about gains or losses. Stressed participants showed more approach behavior towards appetitive and less avoidance behavior towards aversive stimuli as compared to non-stressed participants. Our findings indicate that stress effects on memory retrieval differ depending on the associative learning approach in men. These differences might be related to stress effects on decision making and different motivational systems involved.

Rewarded Extinction Increases Amygdalar Connectivity and Stabilizes Long-Term Memory Traces in the vmPFC

Neurobiological evidence in rodents indicates that threat extinction incorporates reward neurocircuitry. Consequently, incorporating reward associations with an extinction memory may be an effective strategy to persistently attenuate threat responses. Moreover, while there is considerable research on the short-term effects of extinction strategies in humans, the long-term effects of extinction are rarely considered. In a within-subjects fMRI study with both female and male participants, we compared counterconditioning (CC; a form of rewarded-extinction) to standard extinction at recent (24 h) and remote (approximately one month) retrieval tests. Relative to standard extinction, rewarded extinction diminished 24-h relapse of arousal and threat expectancy, and reduced activity in brain regions associated with the appraisal and expression of threat (e.g., thalamus, insula, periaqueductal gray). The retrieval of reward-associated extinction memory was accompanied by functional connectivity between the amygdala and the ventral striatum, whereas the retrieval of standard-extinction memories was associated with connectivity between the amygdala and ventromedial prefrontal cortex (vmPFC). One month later, the retrieval of both standard-extinction and rewarded-extinction was associated with amygdala-vmPFC connectivity. However, only rewarded extinction created a stable memory trace in the vmPFC, identified through overlapping multivariate patterns of fMRI activity from extinction to 24-h and one-month retrieval. These findings provide new evidence that reward may generate a more stable and enduring memory trace of attenuated threat in humans.SIGNIFICANCE STATEMENT Prevalent treatments for pathologic fear and anxiety are based on the principles of Pavlovian extinction. Unfortunately, extinction forms weak memories that only temporarily inhibit the retrieval of threat associations. Thus, to increase the translational relevance of extinction research, it is critical to investigate whether extinction can be augmented to form a more enduring memory, especially after long intervals. Here, we used a multiday fMRI paradigm in humans to compare the short-term and long-term neurobehavioral effects of aversive-to-appetitive counterconditioning (CC), a form of augmented extinction. Our results provide novel evidence that including an appetitive stimulus during extinction can reduce short-term threat relapse and stabilize the memory trace of extinction in the ventromedial prefrontal cortex (vmPFC), for at least one month after learning.

Relapse after incentivized choice treatment in humans: A laboratory model for studying behavior change

Behavior change interventions that incentivize desired behavior are highly effective for improving personal health, but difficult to maintain long term. Relapse is common and examining the mechanisms that contribute to relapse in experimental settings can identify processes relevant to substance abuse treatment. We developed a laboratory task that parallels a recent operant model of relapse after incentivized choice reported in the rodent laboratory. In two experiments, undergraduate participants first learned to make an operant response (keyboard button; R1) to earn a reinforcer consisting of an image of a preferred snack food (O1). In a second phase (Phase 2), R1 was still reinforced, but a new response (R2) was introduced and reinforced with a different reinforcer (a coin; O2). In a test phase, contingent incentives for R2 were removed (extinction) and relapse of R1 was assessed. Experiment 1 found that the O2 contingency suppressed R1 during Phase 2, and R1 relapsed rapidly in the test. Neither effect was consistently related to O2 value. Experiment 2 examined whether noncontingent presentations of O1 or O2 during the test could weaken relapse. Here, we found that noncontingent reinforcers did little to reduce or slow the increase in R1 responding. The present experiments highlight a laboratory approach to studying variables that may influence relapse after incentivized treatment. We identify and discuss areas for development to address differences between the present results and prior observations from animal and clinical studies. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Comparing three extinction methods to reduce fear expression and generalization

Fear extinction is easy to achieve but difficult to maintain, as evidenced by the relapse of fear after extinction. Counterconditioning and novelty-facilitated extinction have been shown to interfere with fear expression without erasing it. Because of the similarity between the two extinction paradigms, we extended the standard extinction, which merely omitted the expected threat outcomes after exposure to original threat cues. The modified paradigm provided a stimulus (neutral picture or positive picture) to replace the omitted threat outcomes during extinction. Sixty-four healthy volunteers were randomized into three groups for a three-day procedure: fear acquisition (day 1), fear extinction (day 2), and fear recall and generalization test (day 3). Our results showed the modified extinction paradigm failed to prevent fear expression in spontaneous recovery and reinstatement tests. However, novelty-facilitated extinction showed powerful effects in preventing fear generalization. Besides, there was a negative correlation between spontaneous recovery index and emotion regulation scores. We speculated that emotion and prediction error may be important factors influencing fear extinction and affect fear recall and generalization. Overall, this study suggests that novelty-facilitated extinction had a superior effect in preventing fear generalization, providing new perspectives for enhancing the effect of exposure therapy.

Positive and Neutral Updating Reconsolidate Aversive Episodic Memories via Different Routes

Aversive memories are long-lasting and prone to burden our emotional wellbeing and mental health. Yet, how to remedy the maladaptive effects of aversive memories remains elusive. Using memory reactivation and emotional updating manipulations, we investigated how positive and neutral emotion may update aversive memories for reconsolidation in humans. We found that positive updating after reactivation was equivalent to neutral updating in impairing true memories of a previous aversive event after a 12-hour wakeful delay, but induced more false memory. Moreover, additional 12-hour delay with overnight sleep did not further enlarge true memory differences, but attenuated the effect of reactivation and updating on false memory. Interestingly, the neutral rather than the positive updating reduced the emotional arousal of the aversive memory 24 hours later. Our findings could serve as references for real-world therapeutic applications regarding how positive and neutral updating may reshape aversive memories, especially when taking wake- and sleep-filled reconsolidation into account.

BEHAVIORAL AND NEUROBIOLOGICAL MECHANISMS OF PAVLOVIAN AND INSTRUMENTAL EXTINCTION LEARNING

This article reviews the behavioral neuroscience of extinction, the phenomenon in which a behavior that has been acquired through Pavlovian or instrumental (operant) learning decreases in strength when the outcome that reinforced it is removed. Behavioral research indicates that neither Pavlovian nor operant extinction depends substantially on erasure of the original learning but instead depends on new inhibitory learning that is primarily expressed in the context in which it is learned, as exemplified by the renewal effect. Although the nature of the inhibition may differ in Pavlovian and operant extinction, in either case the decline in responding may depend on both generalization decrement and the correction of prediction error. At the neural level, Pavlovian extinction requires a tripartite neural circuit involving the amygdala, prefrontal cortex, and hippocampus. Synaptic plasticity in the amygdala is essential for extinction learning, and prefrontal cortical inhibition of amygdala neurons encoding fear memories is involved in extinction retrieval. Hippocampal-prefrontal circuits mediate fear relapse phenomena, including renewal. Instrumental extinction involves distinct ensembles in corticostriatal, striatopallidal, and striatohypothalamic circuits as well as their thalamic returns for inhibitory (extinction) and excitatory (renewal and other relapse phenomena) control over operant responding. The field has made significant progress in recent decades, although a fully integrated biobehavioral understanding still awaits.

Motivational competition and the paraventricular thalamus

Although significant progress has been made in understanding the behavioral and brain mechanisms for motivational systems, much less is known about competition between motivational states or motivational conflict (e.g., approach - avoidance conflict). Despite being produced under diverse conditions, behavior during motivational competition has two signatures: bistability and metastability. These signatures reveal the operation of positive feedback mechanisms in behavioral selection. Different neuronal architectures can instantiate this selection to achieve bistability and metastability in behavior, but each relies on circuit-level inhibition to achieve rapid and stable selection between competing tendencies. Paraventricular thalamus (PVT) is identified as critical to this circuit level inhibition, resolving motivational competition via its extensive projections to local inhibitory networks in the ventral striatum and extended amygdala, enabling adaptive responding under motivational conflict.

Behavioral and neural processes in counterconditioning: Past and future directions

Counterconditioning refers both to the technique and putative process by which behavior is modified through a new association with a stimulus of an opposite valence. Similar to extinction, counterconditioning is considered a form of inhibition that interferes with the expression of the originally learned response without erasing it. But whereas interest in extinction continues to rise, counterconditioning has received far less attention. Here, we provide an in-depth review of counterconditioning research and detail whether counterconditioning is any more effective than extinction at preventing relapse of the originally learned behavior. We consider the clinical implications of counterconditioning, describe recent neurobiological and neuroimaging research in this area, and consider future avenues in need of further investigation.

The effects of aversive-to-appetitive counterconditioning on implicit and explicit fear memory

Counterconditioning (CC) is a form of retroactive interference that inhibits expression of learned behavior. But similar to extinction, CC can be a fairly weak and impermanent form of interference, and the original behavior is prone to relapse. Research on CC is limited, especially in humans, but prior studies suggest it is more effective than extinction at modifying some behaviors (e.g., preference or valence ratings) than others (e.g., physiological arousal). Here, we used a within-subjects design to compare the effects of aversive-to-appetitive CC versus standard extinction on two separate tests of long-term memory in human adults: implicit physiological arousal and explicit episodic memory. Participants underwent Pavlovian fear conditioning to two semantic categories (animals, tools) paired with an electric shock. Conditioned stimuli (i.e., category exemplars) from one category were then extinguished, while stimuli from the other category were paired with a positive outcome. Participants returned 24-h later for a test of skin conductance responses (SCR) to the conditioned exemplars, as well as a surprise recognition memory test for stimuli encoded the previous day. Results showed reduced SCRs at a test for unique stimuli from a category that had undergone CC, relative to stimuli from a category that had undergone standard extinction. Additionally, participants selectively remembered more stimuli encoded during CC than extinction. These results provide new evidence that aversive-to-appetitive CC, as compared to extinction, strengthens memory for items directly associated with a positive outcome, which may provide stronger retrieval competition against a fear memory at test to help diminish fear relapse.

Reducing negative stimulus valence does not attenuate the return of fear: Two counterconditioning experiments

Exposure-based treatment for anxiety disorders is effective for many patients, but relapse is not uncommon. One predictor of the return of fear is the negative valence of fear-relevant stimuli. The aim of the current experiments was to examine whether counterconditioning with positive film clips reduces this negative stimulus valence as well as the return of fear, compared to standard extinction training and to an extinction training with non-contingent exposure to the positive film clips. Participants were 87 students in Experiment 1 (three-day paradigm), and 90 students in Experiment 2 (one-day paradigm). They first underwent a differential acquisition phase, in which one of three pictures was paired with an electric shock. They were then randomly allocated to one of the three intervention groups. Afterwards, they underwent a test phase in which pictures were presented without shock (to measure spontaneous recovery of fear), which was followed by unsignaled shocks to induce reinstatement of extinguished fear. Outcome variables were self-reported stimulus valence, shock expectancy, skin conductance, and fear-potentiated startle. In both experiments, counterconditioning decreased negative stimulus valence, relative to the other interventions, but it did not reduce spontaneous fear recovery or fear reinstatement. Overall, our findings do not support the notion that counterconditioning reduces return of fear.

Prediction and control of operant behavior: What you see is not all there is

Prediction and control of operant behavior are major goals of behavior analysis. We suggest that achieving these goals can benefit from doing more than identifying the three-term contingency between the behavior, its setting stimulus, and its consequences. Basic research now underscores the idea that prediction and control require consideration of the behavior's history. As one example, if an operant is a goal-directed action, it is controlled by the current value of the reinforcer, as illustrated by the so-called reinforcer devaluation effect. In contrast, if the behavior is a habit, it occurs automatically, without regard to the reinforcer's value, as illustrated by its insensitivity to the reinforcer devaluation effect. History variables that distinguish actions and habits include the extent of their prior practice and their schedule of reinforcement. Other operants can appear to have very low or zero strength. However, if the behavior has reached that level through extinction or punishment, it may precipitously increase in strength by changing the context, allowing time to pass, presenting the reinforcer contingently or noncontingently, or extinguishing an alternative behavior. Behaviors that are not suppressed by extinction or punishment are not affected the same way. When predicting the strength of an operant behavior, what you see is not all there is. The behavior's history counts.

Common neurocircuitry mediating drug and fear relapse in preclinical models

BACKGROUND

Comorbidity of anxiety disorders, stressor- and trauma-related disorders, and substance use disorders is extremely common. Moreover, therapies that reduce pathological fear and anxiety on the one hand, and drug-seeking on the other, often prove short-lived and are susceptible to relapse. Considerable advances have been made in the study of the neurobiology of both aversive and appetitive extinction, and this work reveals shared neural circuits that contribute to both the suppression and relapse of conditioned responses associated with trauma or drug use.

OBJECTIVES

The goal of this review is to identify common neural circuits and mechanisms underlying relapse across domains of addiction biology and aversive learning in preclinical animal models. We focus primarily on neural circuits engaged during the expression of relapse.

KEY FINDINGS

After extinction, brain circuits involving the medial prefrontal cortex and hippocampus come to regulate the expression of conditioned responses by the amygdala, bed nucleus of the stria terminalis, and nucleus accumbens. During relapse, hippocampal projections to the prefrontal cortex inhibit the retrieval of extinction memories resulting in a loss of inhibitory control over fear- and drug-associated conditional responding.

CONCLUSIONS

The overlapping brain systems for both fear and drug memories may explain the co-occurrence of fear and drug-seeking behaviors.

A dopaminergic switch for fear to safety transitions

Overcoming aversive emotional memories requires neural systems that detect when fear responses are no longer appropriate so that they can be extinguished. The midbrain ventral tegmental area (VTA) dopamine system has been implicated in reward and more broadly in signaling when a better-than-expected outcome has occurred. This suggests that it may be important in guiding fear to safety transitions. We report that when an expected aversive outcome does not occur, activity in midbrain dopamine neurons is necessary to extinguish behavioral fear responses and engage molecular signaling events in extinction learning circuits. Furthermore, a specific dopamine projection to the nucleus accumbens medial shell is partially responsible for this effect. In contrast, a separate dopamine projection to the medial prefrontal cortex opposes extinction learning. This demonstrates a novel function for the canonical VTA-dopamine reward system and reveals opposing behavioral roles for different dopamine neuron projections in fear extinction learning.

Fear memories are overcome only when it is ascertained that fearful responses are not appropriate. Here the authors demonstrate that activity in dopamine neurons is necessary to extinguish fear responses and two distinct dopamine neuron projections exert opposing effects on extinction learning.

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.

Preventing relapse after incentivized choice treatment: A laboratory model

Two experiments with rats examined relapse of an operant behavior that occurred after the behavior was suppressed by reinforcing (incentivizing) an alternative behavior. In the first phase, a target response (R1) was reinforced. In a treatment phase, R1 was still reinforced, but a new response (R2) was introduced and associated with a larger reinforcer. As in human contingency management treatments, incentivizing R2 this way was effective at suppressing R1. However, when R2's reinforcement was discontinued, there was a robust and immediate relapse to R1. Experiment 1 found that the strength of R1 during relapse testing was not different from that seen in a no treatment control. Experiment 2 found that relapse could nevertheless be reduced by presenting reinforcers not contingent on responding during the test. Either the reinforcer for R1 or the reinforcer for R2 (which were qualitatively different types of food pellets) were effective. The experiments introduce a laboratory method for studying relapse and how to prevent it after contingency management treatments, and suggest at least one treatment that discourages relapse. The incentivized choice paradigm differs from other models of relapse of operant behavior (e.g., resurgence, renewal, reinstatement) in that it does not focus on the return of behaviors that are inhibited by extinction.

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.