Context and ambiguity in the extinction of emotional learning: implications for exposure therapy

Resurgence of behavior during extinction depends on previous rate of response

In two experiments, food-deprived rat subjects leverpressed for food in three successive training phases. In the first phase of both experiments, rats were exposed to a multiple schedule, one component of which produced a high rate of response, and the other of which produced a lower rate of response (multiple random ratio [RR], random interval [RI] in Experiment 1, and multiple differential reinforcement of high rate, differential reinforcement of low rate in Experiment 2). Rats were then transferred to a multiple fixed interval (FI; 60-sec, 60-sec) schedule, until the effects of the first phase on response rate were no longer apparent and their response rates did not differ from those of rats responding on a multiple FI 60-sec, FI 60-sec schedule without previously experiencing a multiple RR, RI schedule. During the third stage oftraining, all rats were placed into extinction. During extinction, rates of responding were higher in the component previously associated with the high rate of responding in Phase 1, and they were lower in the component previously associated with low rates of responding in Phase 1. These results suggest that resurgence effects, like other history effects, are controlled by previous rates of responding.

Fear conditioning in posttraumatic stress disorder: Evidence for delayed extinction of autonomic, experiential, and behavioural responses

Aversive conditioning has been proposed as an important factor involved in the etiology of posttraumatic stress disorder (PTSD). However, it is not yet fully understood exactly which learning mechanisms are characteristic for PTSD. PTSD patients (n=36), and healthy individuals with and without trauma exposure (TE group, n=21; nTE group, n=34), underwent a differential fear conditioning experiment consisting of habituation, acquisition, and extinction phases. An electrical stimulus served as the unconditioned stimulus (US), and two neutral pictures as conditioned stimuli (CS+, paired; CS-, unpaired). Conditioned responses were quantified by skin conductance responses (SCRs), subjective ratings of CS valence and US-expectancy, and a behavioural test. In contrast to the nTE group, PTSD patients showed delayed extinction of SCRs to the CS+. Online ratings of valence and US-expectancy as well as the behavioural test confirmed this pattern. These findings point to a deficit in extinction learning and highlight the role of affective valence appraisals and cognitive biases in PTSD. In addition, there was some evidence that a subgroup of PTSD patients had difficulties in learning the CS-US contingency, thereby providing preliminary evidence of reduced discrimination learning.

Reinstatement of conditioned fear and the hippocampus: an attentional-associative model

An existing attentional-associative model of classical conditioning [Schmajuk N, Lam Y, Gray JA. Latent inhibition: a neural network approach. J Exp Psychol: Anim Behav Process 1996;22:321-49] is applied to the description of reinstatement in animals and humans. According to the model, inhibitory associations between the context (CX) and unconditioned stimulus (US) are formed during extinction, which help preserve the association between the conditioned stimulus (CS) and the US. However, summation and retardation tests fail to reveal these associations because (a) the CX is not attended or (b) a CX-CS configural stimulus formed during extinction is both poorly attended and weakly active during testing. When US presentations and testing occur in the same context, reinstatement is the consequence of a decreased CX inhibition and the increased attention to the CS, which activates the remaining CS-US association. When US presentations occur in the context of extinction but the CS is tested in a different context, reinstatement results from an increased attention to the CS and the combination of CS-CX and CX-US excitatory associations. The assumption that associations between CSs are impaired following neurotoxic hippocampal lesions or in amnesia, is sufficient to describe absence of reinstatement in those cases. However, additional assumptions might be needed to describe the effect of hippocampal lesions on other postextinction manipulations.

Recent fear is resistant to extinction

In some individuals, fearful experiences (e.g., combat) yield persistent and debilitating psychological disturbances, including posttraumatic stress disorder (PTSD). Early intervention (e.g., debriefing) after psychological trauma is widely practiced and argued to be an effective strategy for limiting subsequent psychopathology, although there has been considerable debate on this point. Here we show in an animal model of traumatic fear that early intervention shortly after an aversive experience yields poor long-term fear reduction. Extinction trials administered minutes after aversive fear conditioning in rats suppressed fear acutely, but fear suppression was not maintained the next day. In contrast, delivering extinction trials 1 day after fear conditioning produced an enduring suppression of fear memory. We further show that the recent experience of an aversive event, not the timing of the extinction intervention per se, inhibits the development of long-term fear extinction. These results reveal that the level of fear present at the time of intervention is a critical factor in the efficacy of extinction. Importantly, our work suggests that early intervention may not yield optimal outcomes in reducing posttraumatic stress, particularly after severe trauma.

Renewal of cue-elicited urge to smoke: Implications for cue exposure treatment

The effects of cue exposure therapy are limited, because renewal after extinction is an important source of relapse. In this study, 33 smokers were exposed to a cue predicting smoking availability and a cue predicting smoking unavailability in one context (acquisition context A). Following extinction in another context (extinction context B), a test for renewal took place in the original acquisition context A (i.e. ABA renewal). Urge to smoke was measured using a Visual Analogue Scale. Renewal of differential conditioned urge responding occurred when participants were tested in the acquisition context, while differential urge responding remained extinguished when tested in the extinction context. This experiment provides evidence that ABA renewal occurred in smokers. Clinical implications are discussed.

Extinction in human fear conditioning

Although most extinction research is conducted in animal laboratories, the study of extinction learning in human fear conditioning has gained increasing attention over the last decade. The most important findings from human fear extinction are reviewed in this article. Specifically, we review experimental investigations of the impact of conditioned inhibitors, conditioned exciters, context renewal, and reinstatement on fear extinction in human samples. We discuss data from laboratory studies of the extinction of aversively conditioned stimuli, as well as results from experimental clinical work with fearful or anxious individuals. We present directions for future research, in particular the need for further investigation of differences between animal and human conditioning outcomes, and research examining the role of both automatic and higher-order cognitive processes in human conditioning and extinction.

Priming and trial spacing in extinction: effects on extinction performance, spontaneous recovery, and reinstatement in appetitive conditioning

Previous research in this laboratory suggests that priming of the conditional stimulus (CS) in short-term memory may play a role in the trial-spacing effects in appetitive conditioning. For example, a non-reinforced presentation of a CS 60 s before a reinforced trial with the same CS produced slower acquisition than a CS presentation that occurred 240 s before the reinforced trial. The results were consistent with the self-generated priming mechanism proposed by Wagner (e.g., Wagner 1978, 1981). The present experiments extended the earlier work by examining the effects of trial spacing in extinction rather than acquisition. After conditioning with a mixture of intertrial intervals (ITIs), rats received extinction with ITIs of 60 or 240 s, longer or shorter values, or different ways of "chunking" extinction trials in time. Although trial spacing produced effects on extinction performance that were consistent with our previous research on acquisition, there were few long-term differences in spontaneous recovery or in reinstatement. Short ITIs in extinction appear to affect extinction performance more than they affect extinction learning. Mechanisms of trial spacing in conditioning and extinction are discussed.

Hypervigilance to Learned Pain Signals: A Componential Analysis

We report 2 experiments investigating hypervigilance to pain signals in healthy individuals. In order to allow a detailed analysis, we decomposed attention in 3 different processes: 1) initial shifting, 2) engagement, and 3) disengagement. We used a spatial cueing paradigm in which the location of targets is validly or invalidly predicted by spatial cues. In the first experiment, cues were differentially conditioned to create pain signals, allowing the investigation of engagement and disengagement of attention. Because this procedure does not allow an adequate isolation of the shift component, we introduced a new adaptation of the spatial cueing paradigm in the second experiment, in which targets instead of cues were differentially conditioned. We replicated previous findings, showing enhanced engagement to and retarded disengagement from pain signals compared to control signals. In addition, we demonstrated that participants were still hypervigilant to pain signals after extinction. We were not able to demonstrate speeded shifting to pain signals. Instead we found a generally faster detection of pain signals compared to control signals. We conclude that hypervilance to pain signals does not emerge as rapid initial shifting to the pain signal but rather as enhanced processing once it is detected. Theoretical and clinical implications of these findings are discussed.

PERSPECTIVE

We investigated the fundamental processes associated with hypervigilance to pain. Our findings suggest that treatment approaches using attention techniques should not focus on preventing patients to shift their attention to the pain but rather on diminishing the threat value and learning to disengage from their pain.

Mental reinstatement of context and return of fear in spider-fearful participants

Extant findings in the animal and human conditioning literature demonstrate that renewal, termed return of fear in studies with humans, occurs when reexposure to a previously feared phobic stimulus occurs in a context different than the one present during extinction. The present study investigated whether mental reinstatement of the treatment context at follow-up could attenuate context-based return of fear. Forty-eight spider-fearful individuals received exposure therapy in one of two contexts, and were followed-up 1 week later in the treatment or a new context. Half of the participants received instructions to mentally reinstate the treatment context before the follow-up test. Self-report data replicated previous research on contextually driven return of fear. Furthermore, participants who mentally reinstated the treatment context, before encountering the phobic stimulus in a new context at follow-up, had less return of fear than those who did not. Limitations of the current study, as well as implications for phobia treatment, are discussed.

Do You Need To Talk About It? Prolonged Exposure for the Treatment of Chronic PTSD

Is addressing the traumatic memory a necessary component of the treatment of posttraumatic stress disorder (PTSD)? Perhaps not for everyone, but in the present paper, we suggest that prolonged exposure, a cognitive behavioral treatment that includes repeated recounting of the traumatic memory, is a viable and robust treatment option. Prolonged exposure (PE) is widely regarded as an efficacious treatment for chronic posttraumatic stress disorder (Foa, Keane, & Friedman, 2000). The present paper reviews the efficacy and effectiveness of PE for the treatment of chronic PTSD and for a broader range of trauma-related symptoms. We will also review issues surrounding the acceptability of PE to mental health providers and potential clients. We conclude with a discussion the need for dissemination, additional dismantling studies, and further cross-cultural research.

Reinstatement of conditioned fear in humans is context dependent and impaired in amnesia

A contextual reinstatement procedure was developed to assess the contributions of environmental cues and hippocampal function in the recovery of conditioned fear following extinction in humans. Experiment 1 showed context specificity in the recovery of extinguished skin conductance responses after presentations of an auditory unconditioned stimulus. Experiment 2 demonstrated that fear recovery did not generalize to an explicitly unpaired conditioned stimulus. Experiment 3 replicated the context dependency of fear recovery with a shock as an unconditioned stimulus. Two amnesic patients failed to recover fear responses following reinstatement in the same context, despite showing initial fear acquisition. These results extend the known functions of the human hippocampus and highlight the importance of environmental contexts in regulating the expression of latent fear associations.

Effects of multiple exposures to d-cycloserine on extinction of conditioned fear in rats

Previous research has shown that an acute, post-training injection of D-cycloserine (DCS) facilitates extinction of conditioned fear in rats; however, the effects of multiple exposures to DCS in this situation are not known. In Experiment 1, rats were conditioned (light-shock pairings) and 24 h later given six extinction (light-alone) trials followed by an injection of DCS (15 mg/kg) or saline. The next day, all rats were tested for light-elicited freezing. In Experiment 2, the effect of DCS on extinction was tested in the same manner, except that rats were pre-exposed to DCS (0, 1, or 5 injections) just prior to conditioning. In Experiment 3, rats received five pre-exposures of DCS but conditioning occurred either 2 or 28 days after the last pre-exposure. The results showed that DCS facilitated extinction of conditioned freezing to the light CS when no drug pre-exposure had occurred, but pre-exposure to DCS just prior to conditioning disrupted the facilitation of extinction effect. When 28 days were interposed between pre-exposure and conditioning, the facilitatory effects of DCS on extinction were restored. These findings suggest that DCS has significant clinical value but that behavioral desensitization may occur with multiple exposures; however, desensitization is not permanent and is reduced by the passage of time.

Reinstatement of fear responses in human aversive conditioning

The treatment of choice for a number of anxiety disorders is exposure therapy. However, successful reduction of fear through exposure is sometimes followed by a (partial) return of symptoms of fear (return of fear, ROF; Clin. Psychol. Rev. 9 (1989) 147). Several possible learning mechanisms have been suggested to explain ROF (e.g. mechanisms related to spontaneous recovery, renewal, reacquisition and reinstatement). The present study focuses on reinstatement, which refers to the observation that mere US-only presentations can 'reinstate' previously extinguished fear responses. Although animal research has repeatedly demonstrated this phenomenon, little is known about fear reinstatement in humans. The present study employed a differential aversive conditioning procedure: after acquisition and a subsequent extinction procedure, a series of four unpredicted US-only trials was scheduled in the reinstatement group. The control group did not receive additional US presentations. A significant reinstatement effect was observed for US-expectancy ratings and fear ratings in the reinstatement group, but not in the control group. No differences were observed in a reaction time measure of resource allocation to the conditioned stimuli. These findings constitute a first demonstration of reinstatement of conditioned fear responses in humans. Implications for exposure treatment and suggestions for future research are discussed.

Return of fear in a human differential conditioning paradigm caused by a stimulus change after extinction

In a human fear conditioning experiment, 32 participants were trained in a differential conditioning procedure with geometrical shapes as CS+ and CS- (four presentations each), and an electric shock as US. Measures of conditioned responding were skin conductance response (SCR) and retrospective US-expectancy ratings. For half of the participants (Generalization Group, GG), the subsequent extinction phase consisted of four nonreinforced presentations of generalization stimuli (GS+ and GS-). Participants from the Extinction control Group received an equal amount of nonreinforced presentations of the CSs. Finally, all participants were tested with the original CSs. The results from both measures clearly show an increase in the size of the discrimination upon the stimulus change after extinction in the GG. Because this pattern is not observed in the Extinction control Group, extinction performance appears to be somehow restricted to the perceptual characteristics of the extinction stimulus. Interestingly, the size of the conditioned SCR discrimination in the GG is not influenced by the stimulus change after acquisition. This observation points to a differential impact of stimulus change after acquisition vs. extinction treatment. The findings are discussed from the theoretical perspective of renewal and the clinical perspective of Return of Fear.

Context-dependency of cue-elicited urge to smoke

AIMS

Earlier studies have suggested that the cue-induced urge to smoke depends on the expectation of the availability of smoking. The present study investigated whether a 'room context' change could undo the learned discrimination between two stimuli, respectively, predicting smoking availability or smoking unavailability.

DESIGN

A 2 (smoking cue) x 2 (availability context cue) x 6 (trial) x 2 (room context change) within-subjects design was used. Participants were repeatedly presented with a context cue predicting smoking availability (blue serving tray) and a context cue predicting unavailability (yellow serving tray) in one room and tested for an effect of context change in a different room.

SETTING

Two distinct rooms located in different department buildings of Maastricht University.

PARTICIPANTS

Seventeen daily smokers who had smoked at least five cigarettes a day for at least 2 years.

MEASUREMENTS

Self-reported urge to smoke using a visual analogue scale (VAS).

FINDINGS AND CONCLUSIONS

Results replicated the finding that a context cue that predicted smoking elicited greater urges to smoke than a context cue that predicted no smoking, irrespective of the presence of smoking cues. In addition, this study showed that this differential effect on the urge to smoke was generalized to a context other than the context in which learning took place. These findings are discussed in relation to the significance of a context change regarding the predictive value of smoking availability.

Return of fear in a human differential conditioning paradigm caused by a return to the original acquistion context

In a differential human fear conditioning paradigm evidence for ABA-renewal was obtained manipulating the lighting in the experimental room. During acquisition in either a dark or illuminated room, one neutral slide was sometimes paired with a loud aversive noise whereas another slide was not. Subsequently, extinction took place in the opposite lighting context. When afterwards the participants were tested again in the original acquisition context, measurements revealed a recovery of the conditioned electrodermal response and an increase in the retrospective verbal US-expectancy ratings. No response recovery was obtained in an AAA-group that received acquisition, extinction and test trials in one and the same context. Several theoretical explanations for this type of return of fear as well as implications for clinical practice are discussed.

Recovery of the rabbit's conditioned nictitating membrane response without direct reinforcement after extinction

Three experiments demonstrated that, following the extinction of an established conditioned stimulus (CSA--e.g., tone), the pairing of a novel, cross-modal stimulus (CSB--e.g., light) with the unconditioned stimulus (US) results in strong recovery of responding to the extinguished CSA. Experiment 1 demonstrated that the recovery of responding to CSA is not the result of US reinstatement but is attributable to pairings of CSB with the US. Experiment 2 demonstrated that the recovery of responding is specific to CSA and is not the result of cross-modal generalization. Experiment 3 revealed that a large number of CSB-US pairings in Stage 1 significantly reduced the amount of recovery to CSA during subsequent CSB-US trials. Experiment 3 also provided unexpected evidence of cross-modal secondary extinction. The extinction and subsequent recovery of responding seen in the present experiments is discussed with respect to possible contributions from contextual associations, CS processing, US processing, conditioned response expression, and layered excitatory associations.

Emotional perseveration: an update on prefrontal-amygdala interactions in fear extinction

Fear extinction refers to the ability to adapt as situations change by learning to suppress a previously learned fear. This process involves a gradual reduction in the capacity of a fear-conditioned stimulus to elicit fear by presenting the conditioned stimulus repeatedly on its own. Fear extinction is context-dependent and is generally considered to involve the establishment of inhibitory control of the prefrontal cortex over amygdala-based fear processes. In this paper, we review research progress on the neural basis of fear extinction with a focus on the role of the amygdala and the prefrontal cortex. We evaluate two competing hypotheses for how the medial prefrontal cortex inhibits amygdala output. In addition, we present new findings showing that lesions of the basal amygdala do not affect fear extinction. Based on this result, we propose an updated model for integrating hippocampal-based contextual information with prefrontal-amygdala circuitry.

Context and behavioral processes in extinction

This article provides a selective review and integration of the behavioral literature on Pavlovian extinction. The first part reviews evidence that extinction does not destroy the original learning, but instead generates new learning that is especially context-dependent. The second part examines insights provided by research on several related behavioral phenomena (the interference paradigms, conditioned inhibition, and inhibition despite reinforcement). The final part examines four potential causes of extinction: the discrimination of a new reinforcement rate, generalization decrement, response inhibition, and violation of a reinforcer expectation. The data are consistent with behavioral models that emphasize the role of generalization decrement and expectation violation, but would be more so if those models were expanded to better accommodate the finding that extinction involves a context-modulated form of inhibitory learning.

New vistas on amygdala networks in conditioned fear

It is currently believed that the acquisition of classically conditioned fear involves potentiation of conditioned thalamic inputs in the lateral amygdala (LA). In turn, LA cells would excite more neurons in the central nucleus (CE) that, via their projections to the brain stem and hypothalamus, evoke fear responses. However, LA neurons do not directly contact brain stem-projecting CE neurons. This is problematic because CE projections to the periaqueductal gray and pontine reticular formation are believed to generate conditioned freezing and fear-potentiated startle, respectively. Moreover, like LA, CE may receive direct thalamic inputs communicating information about the conditioned and unconditioned stimuli. Finally, recent evidence suggests that the CE itself may be a critical site of plasticity. This review attempts to reconcile the current model with these observations. We suggest that potentiated LA outputs disinhibit CE projection neurons via GABAergic intercalated neurons, thereby permitting associative plasticity in CE. Thus plasticity in both LA and CE would be necessary for acquisition of conditioned fear. This revised model also accounts for inhibition of conditioned fear after extinction.

Cognitive approaches to posttraumatic stress disorder: the evolution of multirepresentational theorizing

The evolution of multirepresentational cognitive theorizing in psychopathology is illustrated by detailed discussion and analysis of a number of prototypical models of posttraumatic stress disorder (PTSD). Network and schema theories, which focus on a single, explicit aspect/format of mental representation, are compared with theories that focus on 2 or more explicit representational elements. The author argues that the latter theories provide a more complete account of PTSD data, though are not without their problems. Specifically, it is proposed that at least 3 separate representational elements-associative networks, verbal/propositional representations, and schemas-are required to generate a comprehensive cognitive theory of PTSD. The argument that the development of multirepresentational cognitive theory in PTSD is a paradigm case for the development of similar theories in other forms of psychopathology is elaborated, and a brief agenda is proposed promoting 2 levels of theorizing-deep, formal theory alongside more localized, applied theory.

Genetically-based behavioral traits influence the effects of Shuttle Box avoidance overtraining and extinction upon intertrial responding: a study with the Roman rat strains

In the present study, we evaluated the effects of extended exposure procedures to contextual fear cues as a way of reducing intertrial responses (ITRs), a characteristic stereotyped behavior displayed in 2-way Shuttle Box avoidance overtraining. We used rat strains psychogenetically selected for efficient (Roman high-avoidance; RHA) versus poor 2-way Shuttle Box performance (Roman low-avoidance; RLA), the former being fearless/impulsive relative to the latter. Additionally, Sprague-Dawley (SD) rats were compared with RHAs to have a measure of the ITRs exhibited by another, non-selected group of animals. The main findings were that after extended exposure RHAs diminished their ITRs without affecting avoidance performance, although they emitted a pattern of ITRs somewhat excessive as compared with SDs. We concluded that three factors could influence the expression of ITRs in RHA rats: (1) the repetitive and stereotyped responding induced by 2-way Shuttle Box overtraining; (2) contextual fear conditioning; and (3) a genetic background associated with high impulsiveness.

Increasing the efficacy of cue exposure treatment in preventing relapse of addictive behavior

Theoretically, cue exposure treatment should be able to prevent relapse by extinguishing conditioned drug responding (e.g. cue-elicited craving). According to contemporary learning theory, though, extinction does not eliminate conditioned responding. Analogous cue exposure with response prevention (CERP) as a treatment of addictive behavior might not eliminate the learned relation between drug-related cues and drug use. This does not necessarily mean that cue exposure cannot successfully prevent relapse. Various suggestions for increasing the efficacy of cue exposure treatment are being discussed from a contemporary learning theory perspective. It is suggested that cue exposure treatment incorporating retrieval cues can be a beneficial treatment in preventing relapse of addictive behavior.

Changes in caffeine states enhance return of fear in spider phobia

Treatment of phobias is sometimes followed by a return of fear. Animal and human research has shown that changes in external and internal contexts between the time of treatment and follow-up tests often enhance return of fear. The present study examined whether shifts in caffeine (C) state would enhance return of fear. Participants who were highly afraid of spiders (n = 43) were treated in 1-session exposure-based therapy and tested for follow-up 1 week later. Participants were randomly assigned to 1 of 4 groups and received either placebo (P) or C at treatment and follow-up sessions: CC, PP, CP, and PC. Results demonstrated state-dependent learning. Participants experiencing incongruent drug states during treatment and follow-up (CP and PC) exhibited greater return of fear than those experiencing congruent drug states (CC and PP).

Savings in classical conditioning in the rabbit as a function of extended extinction

In the present experiments, savings phenomena following a limited amount of initial acquisition and extended extinction were examined. Experiments 1 and 2 compared rates of reacquisition following brief acquisition and various amounts of extinction in conditioning of the rabbit's nictitating membrane and heart rate response, respectively. Experiment 3 compared rates of acquisition to a novel stimulus (e.g., light) following brief acquisition and various amounts of extinction to another stimulus (e.g., tone). In addition, in Experiment 3 recovery of responding to the extinguished stimulus during acquisition to the novel, cross-modal stimulus was examined. Experiments 1, 2, and 3 demonstrated that with a limited number of acquisition trials (1) there was a graded reduction in the rate of reacquisition as a function of the number of extinction trials in both conditioning preparations, (2) there was a graded reduction in the rate of cross-modal acquisition as a function of the number of extinction trials, but (3), in Experiment 3, recovery of responding to the extinguished stimulus during cross-modal training of the novel stimulus appeared uniformly robust even in the face of extended extinction.

Context, ambiguity, and unlearning: sources of relapse after behavioral extinction

There is now ample evidence that extinction, the loss of learned performance that occurs when a Pavlovian signal or an instrumental action is repeatedly presented without its reinforcer, does not reflect a destruction of the original learning. This article summarizes the evidence and extends and updates earlier reviews. The main alternative to "unlearning" is the idea that extinction (as well as other retroactive interference processes, including counterconditioning) involves new learning that is stored along with the old. One consequence is that the Pavlovian signal or instrumental action has two available "meanings" and thus has the properties of an ambiguous word: its current meaning (and the resulting behavioral output) depends on what the current context retrieves. Contexts can be provided by a variety of background stimuli, including the physical environment, internal drug state, and time. The second thing learned (e.g., extinction, counterconditioning) seems especially dependent on the context for retrieval. A variety of evidence is consistent with this analysis, which highlights several important sources of relapse after extinction. The article concludes with several issues for future research, among them the question of how we can optimize extinction and other putative "unlearning" treatments so as to prevent the various forms of relapse discussed here.

Behavioral analysis of the saccharin deprivation effect in rats

The deprivation effect (DE)--an increase in the level of free-choice consumption of alcohol after a period of forced abstinence--may reflect relapselike drinking and be relevant for modeling alcohol abuse. However, the behavioral mechanisms of the DE are unclear. In these experiments, rats had unlimited free-choice access to water and saccharin-containing solutions and underwent repeated episodes of saccharin deprivation. It was found that DE magnitude correlates positively with the deprivation phase duration, expression of the DE is highly context dependent, and the DE can be prevented by extinguishing response to the saccharin-associated stimuli. Thus, DE procedures may be useful for studying the effects of continued exposure to stimuli associated with various primary reinforcers such as drugs of abuse.

The treatment of fear of movement/(re)injury in chronic low back pain: further evidence on the effectiveness of exposure in vivo

BACKGROUND AND OBJECTIVE

Several cognitive-behavioral factors contribute to the persistence of pain disability in patients with chronic back pain. Fear-avoidance beliefs and fear of movement/(re)injury in particular have been shown to be strong predictors of physical performance and pain disability. Patients reporting substantial pain-related fear might benefit from exposure in vivo to a set of individually tailored, fear-eliciting, and hierarchically ordered physical movements rather than more general graded activity.

PATIENTS AND INTERVENTIONS

Six consecutive patients with chronic low back pain who reported substantial fear of movement/(re)injury were included in the study. After a no-treatment baseline measurement period, the patients were randomly assigned to one of two interventions. In the first intervention, patients received exposure in vivo first, followed by graded activity. In the second intervention, the sequence of treatment modules was reversed. Before each treatment module, treatment credibility was assessed. Daily measures of pain-related fear, pain catastrophizing, and pain intensity were completed using visual analog scales. In addition, standardized measures of pain disability, pain-related fear, and pain vigilance were taken before and after each treatment module and at the 1-year follow-up. To obtain more objective data on actual activity levels, an ambulatory activity monitor was carried by the patients during 1 week before and after each treatment module.

RESULTS

Time series analysis of the daily measures showed that improvements in pain-related fear and pain catastrophizing occurred only during the exposure in vivo and not during the graded activity, irrespective of the treatment order. Analysis of the pretreatment to post-treatment differences also revealed that decreases in pain-related fear also concurred with decreases in pain disability and pain vigilance and an increase in physical activity levels. All improvements remained at the 1-year follow-up.

Spontaneous recovery of tolerance to the analgesic effect of morphine

There is now substantial evidence that associative processes contribute to the development and expression of narcotic tolerance. Like other conditioned responses, the compensatory response (CR) thought to mediate tolerance can be extinguished by repeatedly presenting the conditioned stimulus (CS, drug-paired contextual cues) alone. In the present experiments, rats were used to determine if conditioned tolerance to the analgesic effect of morphine would spontaneously recover following a sufficient delay between the last extinction trial and reexposure to the CS. It was found that tolerance spontaneously recovered 72, but not 24 h following the last of nine extinction trials. As well as providing support for a Pavlovian model of narcotic tolerance, this finding has important clinical implications for cue-exposure drug and alcohol rehabilitation strategies.

The urge to smoke depends on the expectation of smoking

AIMS

An earlier study (Dols et al. 2000) suggested that cue-induced urge to smoke depends on the expectation of smoking. The present study tried to replicate the findings under stringently controlled conditions.

DESIGN

A 2 (context) x 2 (cues) x 6 (trial) within-subject design. Each smoker entered two different contexts; one context predicted the future occurrence of smoking (i.e. one puff of a cigarette) and one context predicted the non-occurrence of smoking. In each context smokers were exposed to smoking cues (i.e. cigarettes and lighter) or not.

SETTING

Laboratory at Maastricht University.

PARTICIPANTS

Thirty-two daily smokers, smoking at least five cigarettes a day for at least 2 years.

MEASUREMENTS

Participants reported their urge to smoke in each context in the presence and absence of smoking cues using a computerized visual analogue scale (VAS).

FINDINGS

The results revealed that the urge to smoke was higher in a context in which smoking was expected relative to a context in which it was not expected. As in the previous study the urge-inducing effect of smoking cues was larger in the smoking context than in the non-smoking context. Moreover, smoking cues did not have a significant effect in the non-smoking context.

CONCLUSIONS

It was shown that smoking cues elicit craving due mainly to a generated expectation of the occurrence of smoking and less due to salience or long history of associative learning. Theoretical and practical implications of the results are discussed.

Two-year follow-up after a randomised controlled trial of self- and clinician-accompanied exposure for phobia/panic disorders

BACKGROUND

Long-term follow-up has rarely been reported after self-exposure therapy for phobias.

AIMS

Completion of such a follow-up.

METHOD

Two-year follow-up was achieved in 68 (85%) of 80 patients with phobias who had completed a previous 14-week randomised controlled trial comparing therapist-accompanied self-exposure, self-exposure or self-relaxation. Measures were self-reported ratings of symptoms, satisfaction and use of other treatment.

RESULTS

Improvement at week 14 was maintained 2 years later. Clinician-accompanied exposure and self-exposure did not differ on any measure. Compliance with self-exposure homework during weeks 0-8 predicted more improvement 2 years later. Patients who failed to improve with relaxation by week 14 improved after subsequent crossover to exposure. A need for more treatment for their phobias was still felt by 33 patients (49%).

CONCLUSIONS

Patients with phobias maintained their improvement to 2-year follow-up after the end of self-exposure therapy.

Pharmacological manipulations of the extinction process of fear-induced ultrasonic vocalization in rats

The effects of pharmacological manipulation on the extinction process of fear-induced ultrasonic vocalizations (USVs), which are considered distress calls related to anxiety, were investigated. Male Wistar rats were conditioned to emit USVs by being given repeated electrical foot-shocks while in a chamber. After 10 sessions of conditioning, the animals started to emit USVs upon mere exposure to the shock chamber without being shocked. Using these animals, the extinction process of the USVs was examined. With repeated exposure to the chamber without shocks, the USVs first increased and then gradually decreased. i.e., the extinction burst was observed. Daily intraperitoneal injections of a benzodiazepine-GABA receptor agonist diazepam (DZP; 1.0 mg/kg) or a tricyclic antidepressant clomipramine (CLM; 20 mg/kg) inhibited this extinction burst. Moreover, CLM, but not DZP, shortened the period required for extinction as compared with the vehicle-treated animals. Following the extinction phase, the emission of USVs was enhanced by the cessation of both drug treatments. These results suggest that CLM would be useful for reducing anxiety-related behaviors in the extinction process, as long as withdrawal symptoms after long-term drug treatments are taken into consideration.

Cognitive biases in anxiety disorders and their effect on cognitive-behavioral treatment

Cognitive theorists hypothesize that cognitive biases are a major component in the development and maintenance of anxiety disorders. These include attentional biases toward threat-related information, distorted judgments of risk, and selective memory processing. The empirical evidence for these cognitive biases in anxiety disorder populations is reviewed. Potential deleterious effects of these biases on the process of cognitive-behavioral therapy are also discussed, as are possible ways of overriding those effects and maximizing treatment efficacy.

A modern learning theory perspective on the etiology of panic disorder

Several theories of the development of panic disorder (PD) with or without agoraphobia have emerged in the last 2 decades. Early theories that proposed a role for classical conditioning were criticized on several grounds. However, each criticism can be met and rejected when one considers current perspectives on conditioning and associative learning. The authors propose that PD develops because exposure to panic attacks causes the conditioning of anxiety (and sometimes panic) to exteroceptive and interoceptive cues. This process is reflected in a variety of cognitive and behavioral phenomena but fundamentally involves emotional learning that is best accounted for by conditioning principles. Anxiety, an anticipatory emotional state that functions to prepare the individual for the next panic, is different from panic, an emotional state designed to deal with a traumatic event that is already in progress. However, the presence of conditioned anxiety potentiates the next panic, which begins the individual's spiral into PD. Several biological and psychological factors create vulnerabilities by influencing the individual's susceptibility to conditioning. The relationship between the present view and other views, particularly those that emphasize the role of catastrophic misinterpretation of somatic sensations, is discussed.

Protection from extinction in human fear conditioning

Two experiments examined the ability of an added stimulus to interfere with extinction of a target excitatory fear stimulus (a predictor of shock) in human autonomic conditioning. Both experiments demonstrated disruption of extinction when the added stimulus was inhibitory (a predictor of no shock, or safety signal). Subjects showed a return of fear when the target stimulus was tested alone, on both self-reported shock expectancy and skin conductance measures. The second experiment also demonstrated disruption of extinction when the added stimulus was excitatory. This results suggests that protection from extinction may occur even when the added stimulus is not inhibitory. Additional factors that may contribute to protection from extinction include context-specificity, occasion-setting and external inhibition. The results highlight the role that concurrent stimuli play in extinction, and emphasise the need to keep concurrent stimuli as similar as possible to the desired transfer context in practical applications of extinction such as exposure therapy for anxiety.

Training history affects magnitude of spontaneous recovery from extinction of appetitive conditioned responding

Three experiments examined spontaneous recovery from extinction of appetitive conditioned responding (CR) as a function of training history. Rats first received reinforced and non-reinforced conditioning trials. Groups of rats were equated for total number of reinforced trials but differed in the number of non-reinforced trials, or in the order of reinforced and non-reinforced trials. CR was then extinguished in all groups. Subsequently, the extent of recovery of CR was assessed in a test session performed either 1 or 17 days after the last extinction session. After a 17-day delay, rats that had received all reinforced trials immediately prior to the first extinction session showed stronger recovery than did rats having received all reinforced trials at the beginning of training, or interspersed among non-reinforced trials. No significant spontaneous recovery was observed after a 1-day test delay. These results, which may be of clinical relevance with respect to relapse after therapy, are explained in terms of the training schedules generating differences in strength of inhibitory associations, and a relatively long, but not a short, test delay attenuating these associations.