Dissociating response systems: Erasing fear from memory

Effects of cannabidiol on fear conditioning in anxiety disorders: decreased threat expectation during retention, but no enhanced fear re-extinction

RATIONALE

Preclinical research suggests that pharmacologically elevating cannabinoid levels may attenuate fear memory expression and enhance fear extinction.

OBJECTIVES

We studied the effects of cannabidiol (CBD) on fear memory expression and fear re-extinction in 69 patients with panic disorder with agoraphobia or with social anxiety disorder. Moderation by sex, diagnosis, and serotonergic antidepressant (AD) use was explored.

METHODS

A cued fear conditioning paradigm was applied before the first treatment session with 300 mg CBD/placebo augmented exposure therapy. Study medication was administered orally preceding 8 weekly sessions. Fear acquisition and suboptimal extinction took place prior to the first medication ingestion (T0). After the first medication ingestion (T1), we investigated effects on fear memory expression at retention and fear re-extinction. Subjective fear, shock expectancy, skin conductance, and startle responses to conditioned (CS+) and safety stimulus (CS-) were measured.

RESULTS

Across the sample, CBD reduced shock expectancy at retention under low and ambiguous threat of shock, but fear re-extinction at T1 was unaffected by CBD. However, in AD users, re-extinction of subjective fear was impaired in the CBD condition compared to placebo. In female AD users, CBD interfered with safety learning measured with fear-potentiated startle.

CONCLUSIONS

The current findings provide no evidence for enhanced fear re-extinction by CBD. However, CBD acutely decreased threat expectation at retention, without affecting other indices of fear. More studies are needed to elucidate possible interactions with AD use and sex, as well as potential effects of CBD on threat expectancies.

When does imagery rescripting become a double-edged sword? - Investigating the risk of memory distortion through imagery rescripting in an online Trauma film study

Imagery Rescripting (ImRs) has proven effective in reducing involuntary emotional memories. However, it is unclear whether and when it may lead to reduced accuracy of voluntary memory. Although previous analogue studies suggest that ImRs does not pose a general risk regarding memory distortion, it can not be ruled out that ImRs could cause memory impairment under certain risk conditions. In our three-day online trauma film study we investigated in a healthy sample (N = 267) whether specific instructions during ImRs as typically provided in clinical practice (i.e., detailed imagery with a sensory focus) increase the risk of memory distortions. Additionally, we examined whether the completeness of the original memory moderates these instruction effects. Contrary to our expectations, a sensory focus during ImRs was associated with higher memory accuracy in a recognition task, independently of the quality of the original memory. These results extend previous findings by suggesting that ImRs does not even impair memory performance when the quality of the original memory is poor and when the production of sensory-rich images is specifically encouraged. Our results question current practices employed to assess witness statement credibility, which are partly based on concerns that trauma-focused interventions like ImRs undermine memory accuracy.

Effects of imagery rescripting and imaginal exposure on voluntary memory

Trauma-focused imagery-based interventions, such as Imagery Rescripting (ImRs) and Imaginal Exposure (ImE), are effective in reducing involuntary re-experiencing in PTSD. However, it has been suggested that they may impair voluntary memory. This study investigates whether ImRs and ImE distort voluntary memory of an analogue trauma. We presented a trauma film to N = 120 healthy participants (Session 1) and randomly allocated them to one of two intervention conditions (receiving one session of ImRs or ImE) or to a no-intervention control condition (NIC) afterwards (Session 2). Voluntary memory was assessed using a free recall (Sessions 2 and 3), and a cued recall as well as a recognition task (both Sessions 3 and 4). The ImRs and ImE groups did not differ from NIC in the cued recall task and the recognition task. However, ImE (compared to ImRs and NIC) led to an increase in correct reported details in the free recall. In sum, the current findings do not suggest that ImRs or ImE impair voluntary memory.

Working hard to avoid: Fixed-ratio response effort and maladaptive avoidance in humans

Maladaptive avoidance of safe stimuli is a defining feature of anxiety and related disorders. Avoidance may involve physical effort or the completion of a fixed series of responses to prevent occurrence of, or cues associated with, the aversive event. Understanding the role of response effort in the acquisition and extinction of avoidance may facilitate the development of new clinical treatments for maladaptive avoidance. Despite this, little is known about the impact of response effort on extinction-resistant avoidance in humans. Here, we describe findings from two laboratory-based treatment studies designed to investigate the impact of high and low response effort on the extinction (Experiment 1) and return (Experiment 2) of avoidance. Response effort was operationalised as completion of fixed-ratio (FR) reinforcement schedules for both danger and safety cues in a multi-cue avoidance paradigm with behavioural, self-report, and physiology measures. Completion of the FR response requirements cancelled upcoming shock presentations following danger cues and had no impact on the consequences that followed safety cues. Both experiments found persistence of high response-effort avoidance across danger and safety cues and sustained (Experiment 1) and reinstated (Experiment 2) levels of fear and threat expectancy. Skin conductance responses evoked by all cues were similar across experiments. The present findings and paradigm have implications for translational research on maladaptive anxious coping and treatment development.

Effects of the retrieval-extinction paradigm with abstract reminders on fear memory extinction

Reactivated fear memories may enter an unstable state that could be interrupted by behavioral interventions such as the retrieval-extinction procedure. Studies of pharmacological interventions have shown that retrieval cues are not necessarily an exact reduplication of initial conditioned stimuli (CSs); they can instead be abstract word cues. However, the effectiveness of using abstract reminder cues in behavioral intervention procedures remains unknown, as do the conditions under which they are effective. The typicality of CS and the abstraction level of reminders are also likely to be important in the paradigm but have not been investigated to date. Here, in three experiments (n = 107), we manipulate the fear conditioning process, including single CS-unconditioned stimulus (US) and multiple CS-US connections, as well as the CS typicality and abstraction level of reminder cues, to explore the conditions for adopting retrieval-extinction with abstract reminders. The results of Experiments 1 and 2 show that the abstract cue is ineffective for use as a reminder in the procedure; this is the case for single exemplar category learning and perceptual discriminative learning, independent of the typicality of CS+ or the abstraction level of reminder cues. Only the outcome of Experiment 3, which contains multiple CS-US connections, shows no indication of fear return. The limitations of the study and possible interpretations of the results are discussed.

Fear memory in humans is consolidated over time independently of sleep

Fear memories can be altered after acquisition by processes, such as fear memory consolidation or fear extinction, even without further exposure to the fear-eliciting stimuli, but factors contributing to these processes are not well understood. Sleep is known to consolidate, strengthen, and change newly acquired declarative and procedural memories. However, evidence on the role of time and sleep in the consolidation of fear memories is inconclusive. We used highly sensitive electrophysiological measures to examine the development of fear-conditioned responses over time and sleep in humans. We assessed event-related brain potentials (ERP) in 18 healthy, young individuals during fear conditioning before and after a 2-hour afternoon nap or a corresponding wake interval in a counterbalanced within-subject design. The procedure involved pairing a neutral tone (CS+) with a highly unpleasant sound. As a control, another neutral tone (CS-) was paired with a neutral sound. Fear responses were examined before the interval during a habituation phase and an acquisition phase as well as after the interval during an extinction phase and a reacquisition phase. Differential fear conditioning during acquisition was evidenced by a more negative slow ERP component (stimulus-preceding negativity) developing before the unconditioned stimulus (loud noise). This differential fear response was even stronger after the interval during reacquisition compared with initial acquisition, but this effect was similarly pronounced after sleep and wakefulness. These findings suggest that fear memories are consolidated over time, with this effect being independent of intervening sleep.

A paradigm shift in the treatment of emotional memory disorders: Lessons from basic science

Experiments demonstrating post-reactivation amnesia for learned fear in animals have generated a novel and influential hypothesis on the plasticity of memory, usually referred to as memory reconsolidation. The clinical potential of pharmacologically disrupting the process of memory reconsolidation has sparked a wave of interest into whether this phenomenon can also be demonstrated in humans, and ultimately harnessed for therapeutic purposes. In this essay we outline how the work of Karim Nader and colleagues has moved the field forward from a focus on extinction learning to the prospect of disrupting memory reconsolidation. We then review some promising findings on the necessary conditions, as well as potential boundary conditions, of pharmacologically disrupting the process of memory reconsolidation obtained in our laboratory. Even though laboratory experiments in animals and humans suggest that we may be at the brink of a breakthrough in fundamentally changing emotional memories, the necessary and sufficient conditions for targeting and disrupting memory reconsolidation in clinical practice are largely unknown. There is likely no universally effective reactivation procedure for triggering the reconsolidation of clinically significant emotional memories, and the impact of subtle boundary conditions observed in basic experiments compounds this issue. Notwithstanding these challenges, the discovery of changing emotional memory through disrupting the process of memory reconsolidation has unquestionably invigorated the field.

Understanding Human Fear Extinction: Insights from Psychophysiology

The study of fear extinction has been driven largely by Pavlovian fear conditioning methods across the translational spectrum. The primary methods used to study these processes in humans have been recordings of skin conductance (historically termed galvanic skin response) and fear-potentiation of the acoustic startle reflex. As outlined in the following chapter, the combined corpus of this work has demonstrated the value of psychophysiology in better understanding the underlying neurobiology of extinction learning in healthy humans as well as those with psychopathologies. In addition, psychophysiological approaches, which allow for the preservation of methods between species, have shown their applicability to the assessment of wide-ranging treatment effects. The chapter concludes with potential trajectories for future study in this area.

Sometimes I feel the fear of uncertainty: How intolerance of uncertainty and trait anxiety impact fear acquisition, extinction and the return of fear

It is hypothesized that the ability to discriminate between threat and safety is impaired in individuals with high dispositional negativity, resulting in maladaptive behavior. A large body of research investigated differential learning during fear conditioning and extinction protocols depending on individual differences in intolerance of uncertainty (IU) and trait anxiety (TA), two closely-related dimensions of dispositional negativity, with heterogenous results. These might be due to varying degrees of induced threat/safety uncertainty. Here, we compared two groups with high vs. low IU/TA during periods of low (instructed fear acquisition) and high levels of uncertainty (delayed non-instructed extinction training and reinstatement). Dependent variables comprised subjective (US expectancy, valence, arousal), psychophysiological (skin conductance response, SCR, and startle blink), and neural (fMRI BOLD) measures of threat responding. During fear acquisition, we found strong threat/safety discrimination for both groups. During early extinction (high uncertainty), the low IU/TA group showed an increased physiological response to the safety signal, resulting in a lack of CS discrimination. In contrast, the high IU/TA group showed strong initial threat/safety discrimination in physiology, lacking discriminative learning on startle, and reduced neural activation in regions linked to threat/safety processing throughout extinction training indicating sustained but non-adaptive and rigid responding. Similar neural patterns were found after the reinstatement test. Taken together, we provide evidence that high dispositional negativity, as indicated here by IU and TA, is associated with greater responding to threat cues during the beginning of delayed extinction, and, thus, demonstrates altered learning patterns under changing environments.

Propranolol versus Other Selected Drugs in the Treatment of Various Types of Anxiety or Stress, with Particular Reference to Stage Fright and Post-Traumatic Stress Disorder

Propranolol, a non-cardioselective β_1,2 blocker, is most commonly recognised for its application in the therapy of various cardiovascular conditions, such as hypertension, coronary artery disease, and tachyarrhythmias. However, due to its ability to cross the blood–brain barrier and affinity towards multiple macromolecules, not only adrenoreceptors, it has also found application in other fields. For example, it is one of the very few medications successfully applied in the treatment of stage fright. This review focuses on the application of propranolol in the treatment of various types of anxiety and stress, with particular reference to stage fright and post-traumatic stress disorder (PTSD). Both mechanisms of action as well as comparison with other therapies are presented. As those indications for propranolol are, in most countries, considered off-label, this review aims to gather information that can be useful while making a decision about the choice of propranolol as a drug in the treatment of those mental conditions.

Verbal manipulations of learning expectancy do not enhance reconsolidation

Objectives

Pharmacological studies using propranolol suggest that if reactivation signals that new information will be learned (i.e., there is an expectation for learning) reconsolidation can be enhanced. We examined if the verbal instructions to expect new learning will enhance reconsolidation of fear memories using the post-retrieval extinction paradigm.

Methods

On day one, participants (n = 48) underwent differential fear conditioning to two images (CS+ and CS-). On day two, participants were randomly assigned to one of three groups; groups one and two had their memory for the CS+ reactivated (i.e., a single presentation of the CS+) 10 minutes prior to extinction, whereas group three did not have their memory reactivated but went right to extinction (no reactivation group). One reactivation group was told that they would learn something new about the images (expectation for learning group), and the other group was told that they would not learn anything new (no expectation for learning group). On day three, return of fear was measured following reinstatement (i.e., four shocks). Fear potentiated startle (FPS) and skin conductance response (SCR) were measured throughout.

Results

There was evidence of fear acquisition for participants for SCR but not FPS. With regards to reconsolidation, SCR increased for the CS+ and CS-in all groups from the end of extinction to the beginning of re-extinction (i.e., return of fear). For FPS, post-hoc tests conducted on the sub-group of participants showing fear learning showed that FPS remained stable in the two reactivation groups, but increased to the CS+, but not the CS- in the no reactivation group.

Implications

These findings suggest that a verbal manipulation of the expectation for learning may not be salient enough to enhance reconsolidation. Results are discussed in relation to theories on differences in between SCR, as a measure of cognitive awareness, and FPS, as a measure of fear.

Highly Demand Working Memory Intervention Weakens a Reactivated Threat Memory and the Associated Cognitive Biases

Anxiety disorders are the most frequent type of mental disorder. Threat-conditioning memory plays a central role in anxiety disorders, impacting complex cognitive systems by modifying behavioral responses to fearful stimuli and inducing an overestimation of potential threats. Here, we analyzed the reminder-dependent amnesia on physiological responses, unconditioned stimulus (US) expectancy ratings, and measures of cognitive bias towards the threat of a threat-conditioning memory. Subjects received differential threat-conditioning. Twenty-four hours later, after reactivation of the memory of threat-conditioning, one group performed a high demand working memory task (HWM) and a second group a low demand working memory task (LWM). A third group only performed the HWM task. Retention of conditioned threat memory was tested on Day 3 in an extinction session followed by a reinstatement test. Tasks targeting stimulus representation, valuation, and attentional bias towards threat were performed. We show that the reminder-dependent intervention with an HWM weakened memory retention as expressed in skin conductance response (SCR) and faded the representation and valuation towards the threat, but it did not affect US expectancy or attentional bias. Our findings provide evidence for the experimental psychopathology approach opening the possibility to weaken both Threat conditioning memory and the systems associated with the maintenance of anxiety features.

Interfering With Contextual Fear Memories by Post-reactivation Administration of Propranolol in Mice: A Series of Null Findings

Post-reactivation amnesia of contextual fear memories by blockade of noradrenergic signaling has been shown to have limited replicability in rodents. This is usually attributed to several boundary conditions that gate the destabilization of memory during its retrieval. How these boundary conditions can be overcome, and what neural mechanisms underlie post-reactivation changes in contextual fear memories remain largely unknown. Here, we report a series of experiments in a contextual fear-conditioning paradigm in mice, that were aimed at solving these issues. We first attempted to obtain a training paradigm that would consistently result in contextual fear memory that could be destabilized upon reactivation, enabling post-retrieval amnesia by the administration of propranolol. Unexpectedly, our attempts were unsuccessful to this end. Specifically, over a series of experiments in which we varied different parameters of the fear acquisition procedure, at best small and inconsistent effects were observed. Additionally, we found that propranolol did not alter retrieval-induced neural activity, as measured by the number of c-Fos⁺ cells in the hippocampal dentate gyrus. To determine whether propranolol was perhaps ineffective in interfering with reactivated contextual fear memories, we also included anisomycin (i.e., a potent and well-known amnesic drug) in several experiments, and measures of synaptic glutamate receptor subunit GluA2 (i.e., a marker of memory destabilization). No post-retrieval amnesia by anisomycin and no altered GluA2 expression by reactivation was observed, suggesting that the memories did not undergo destabilization. The null findings are surprising, given that the training paradigms we implemented were previously shown to result in memories that could be modified upon reactivation. Together, our observations illustrate the elusive nature of reactivation-dependent changes in non-human fear memory.

Effects of propranolol on the modification of trauma memory reconsolidation in PTSD patients: A systematic review and meta-analysis

Post-traumatic stress disorder (PTSD) develops after an exposure to a life-threatening event and is characterized by intrusive memories. According to memory reconsolidation theory retrieval of memory under certain conditions leads to its labilization and subsequent re-storage which could be disrupted by drugs. Propranolol has been the most commonly investigated drug for memory reconsolidation therapy in clinical trials. Intervention with propranolol have shown mixed results in PTSD patients with some studies showing improvement in symptoms while other failing to replicate these findings. We conducted a systematic review and meta-analysis to determine the efficacy of trauma memory disruption by propranolol on PTSD symptoms and physiological responses in PTSD patients. 3224 publications were assessed for eligibility. Seven studies on effects of propranolol on PTSD symptoms and 3 studies on effects of propranolol on physiological responses were incorporated in the meta-analyses. Overall, results indicate that propranolol did not show a beneficial effect on PTSD symptoms (standardized mean difference: 1.29; 95% CI = -2.16 - 0.17). Similarly, propranolol did not influence skin conductance (standardized mean difference: 0.77; 95% CI = -1.85 - 0.31) or EMG response (standardized mean difference: 0.16; 95% CI = -0.65 - 0.33). However, propranolol significantly reduced heart rate after trauma memory recall compared to placebo (standardized mean difference: 0.67; 95% CI = -1.27 to -0.07). This study finds a lack of evidence for the efficacy of propranolol on traumatic memory disruption, in PTSD patients, to recommend its routine clinical use. However, a high level of heterogeneity, variation in propranolol dosage and inadequate sample sizes mean that these findings require cautious interpretation.

The evidence for and against reactivation-induced memory updating in humans and nonhuman animals

Systematic investigation of reactivation-induced memory updating began in the 1960s, and a wave of research in this area followed the seminal articulation of "reconsolidation" theory in the early 2000s. Myriad studies indicate that memory reactivation can cause previously consolidated memories to become labile and sensitive to weakening, strengthening, or other forms of modification. However, from its nascent period to the present, the field has been beset by inconsistencies in researchers' abilities to replicate seemingly established effects. Here we review these many studies, synthesizing the human and nonhuman animal literature, and suggest that these failures-to-replicate reflect a highly complex and delicately balanced memory modification system, the substrates of which must be finely tuned to enable adaptive memory updating while limiting maladaptive, inaccurate modifications. A systematic approach to the entire body of evidence, integrating positive and null findings, will yield a comprehensive understanding of the complex and dynamic nature of long-term memory storage and the potential for harnessing modification processes to treat mental disorders driven by pervasive maladaptive memories.

Diverse therapeutic developments for post-traumatic stress disorder (PTSD) indicate common mechanisms of memory modulation

Post-traumatic stress disorder (PTSD), characterized by abnormally persistent and distressing memories, is a chronic debilitating condition in need of new treatment options. Current treatment guidelines recommend psychotherapy as first line management with only two drugs, sertraline and paroxetine, approved by U.S. Food and Drug Administration (FDA) for treatment of PTSD. These drugs have limited efficacy as they only reduce symptoms related to depression and anxiety without producing permanent remission. PTSD remains a significant public health problem with high morbidity and mortality requiring major advances in therapeutics. Early evidence has emerged for the beneficial effects of psychedelics particularly in combination with psychotherapy for management of PTSD, including psilocybin, MDMA, LSD, cannabinoids, ayahuasca and ketamine. MDMA and psilocybin reduce barrier to therapy by increasing trust between therapist and patient, thus allowing for modification of trauma related memories. Furthermore, research into the memory reconsolidation mechanisms has allowed for identification of various pharmacological targets to disrupt abnormally persistent memories. A number of pre-clinical and clinical studies have investigated novel and re-purposed pharmacological agents to disrupt fear memory in PTSD. Novel therapeutic approaches like neuropeptide Y, oxytocin, cannabinoids and neuroactive steroids have also shown potential for PTSD treatment. Here, we focus on the role of fear memory in the pathophysiology of PTSD and propose that many of these new therapeutic strategies produce benefits through the effect on fear memory. Evaluation of recent research findings suggests that while a number of drugs have shown promising results in preclinical studies and pilot clinical trials, the evidence from large scale clinical trials would be needed for these drugs to be incorporated in clinical practice.

Embodiment of an Emotional State Concurs with a Stress-Induced Reconsolidation Impairment Effect on an Auditory Verbal Word-List Memory

Stress alters memory. Understanding how and when acute stress improves or impairs memory is a challenge. Stressors can affect memory depending on a combination of factors. Typically, mild stressors and stress hormones might promote consolidation of memory processing and impair memory retrieval. However, studies have shown that during reconsolidation, stressors may either enhance or impair recalled memory. We propose that a function of reconsolidation is to induce changes in the behavioral expression of memory. Here, we adapted the Rey Auditory Verbal Learning Test (RAVLT) to evaluate the effect of cold pressor stress (CPS) during the reconsolidation of this declarative memory. A decay in memory performance attributable to forgetting was found at the time of memory reactivation 5 d after training (day 6). Contrary to our initial predictions, the administration of CPS after memory reactivation impaired long-term memory expression (day 7), an effect dependent on the presence of a mismatch during Reactivation Session. No differences in recognition tests were found. To assess putative sources of the negative memory modulation effects induced during reconsolidation, current emotional state was evaluated immediately after Testing Session (day 7). An increase in arousal was revealed only when CPS was administered concurrently with memory reactivation-labilization. The possibility of integration during reconsolidation of independent associations of these emotive components in the trace is a critical factor in modulating neutral memories during reconsolidation by stressors.

Better, worse, or different than expected: on the role of value and identity prediction errors in fear memory reactivation

Although reconsolidation-based interventions constitute a promising new avenue to treating fear and anxieties disorders, the success of the intervention is not guaranteed. The initiation of memory reconsolidation is dependent on whether a mismatch between the experienced and predicted outcome-a prediction error (PE)-occurs during fear memory reactivation. It remains, however, elusive whether any type of PE renders fear memories susceptible to reconsolidation disruption. Here, we investigated whether a value PE, elicited by an outcome that is better or worse than expected, is necessary to make fear memories susceptible to reconsolidation disruption or whether a model-based identity PE, i.e., a PE elicited by an outcome equally aversive but different than expected, would be sufficient. Blocking beta-adrenergic receptors with propranolol HCl after reactivation did, however, not reduce the expression of fear after either type of PE. Instead, we observed intact fear memory expression 24 h after reactivation in the value-, identity- and a no-PE control group. The present results do not corroborate our earlier findings of reconsolidation disruption and point towards challenges that the field is currently facing in observing evidence for memory reconsolidation at all. We provide potential explanations for the unexpected failure of replicating reconsolidation disruption and discuss future directions.

Parsing neural circuits of fear learning and extinction across basic and clinical neuroscience: Towards better translation

Over the past decades, studies of fear learning and extinction have advanced our understanding of the neurobiology of threat and safety learning. Animal studies can provide mechanistic/causal insights into human brain regions and their functional connectivity involved in fear learning and extinction. Findings in humans, conversely, may further enrich our understanding of neural circuits in animals by providing macroscopic insights at the level of brain-wide networks. Nevertheless, there is still much room for improvement in translation between basic and clinical research on fear learning and extinction. Through the lens of neural circuits, in this article, we aim to review the current knowledge of fear learning and extinction in both animals and humans, and to propose strategies to fill in the current knowledge gap for the purpose of enhancing clinical benefits.

Demarcating the boundary conditions of memory reconsolidation: An unsuccessful replication

Disrupting memory reconsolidation provides an opportunity to abruptly reduce the behavioural expression of fear memories with long-lasting effects. The success of a reconsolidation intervention is, however, not guaranteed as it strongly depends on the destabilization of the memory. Identifying the necessary conditions to trigger destabilization remains one of the critical challenges in the field. We aimed to replicate a study from our lab, showing that the occurrence of a prediction error (PE) during reactivation is necessary but not sufficient for destabilization. We tested the effectiveness of a reactivation procedure consisting of a single PE, compared to two control groups receiving no or multiple PEs. All participants received propranolol immediately after reactivation and were tested for fear retention 24 h later. In contrast to the original results, we found no evidence for a reconsolidation effect in the single PE group, but a straightforward interpretation of these results is complicated by the lack of differential fear retention in the control groups. Our results corroborate other failed reconsolidation studies and exemplify the complexity of experimentally investigating this process in humans. Thorough investigation of the interaction between learning and memory reactivation is essential to understand the inconsistencies in the literature and to improve reconsolidation interventions.

A role for deficits in GABAergic neurosteroids and their metabolites with NMDA receptor antagonist activity in the pathophysiology of posttraumatic stress disorder

Trauma-focused psychotherapies show general efficacy in post-traumatic stress disorder (PTSD), although outcomes vary substantially among individuals with PTSD and many patients do not achieve clinically meaningful symptom improvement. Several factors may contribute to poor treatment response, including genetic or environmental (e.g., stress) effects on neurobiological factors involved in learning and memory processes critical to PTSD recovery. In this review, we discuss the relationship between deficient GABAergic neurosteroid metabolites of progesterone, allopregnanolone (Allo) and pregnanolone (PA), and PTSD symptoms in men and women or PTSD-like behavioral abnormalities observed in male rodent models of PTSD. We also review the role and molecular underpinnings of learning and memory processes relevant to PTSD recovery, including extinction, extinction retention, reconsolidation of reactivated aversive memories and episodic non-aversive memory. We then discuss preclinical and clinical research that supports a role in these learning and memory processes for GABAergic neurosteroids and sulfated metabolites of Allo and PA that allosterically antagonize NMDA receptor function. Studies supporting the possible therapeutic impact of appropriately timed, acutely administered Allo or Allo analogs to facilitate extinction retention and/or block reconsolidation of aversive memories are also reviewed. Finally, we discuss important future directions for research in this area. Examining the varied and composite effects in PTSD of these metabolites of progesterone, as well as neuroactive derivatives of other parent steroids produced in the brain and the periphery, will likely enable a broadening of targets for treatment development. Defining contributions of these neuroactive steroids to common PTSD-comorbid psychiatric and medical conditions, as well as subpopulation-specific underlying dysfunctional physiological processes such as hypothalamic-pituitary-adrenal axis and immune system dysregulation, may also enable development of more effective multisystem precision medicines to prevent and treat the broader, polymorbid sequelae of extreme and chronic stress.

Using Translational Models of Fear Conditioning to Uncover Sex-Linked Factors Related to PTSD Risk

Post-traumatic stress disorder (PTSD) is a debilitating neuropsychiatric disorder that follows exposure to a traumatic event; however, not every person who experiences trauma will develop PTSD. Women are more likely to be diagnosed with PTSD than men even when controlling for type and amount of trauma exposure. Circulating levels of gonadal hormones such as estradiol, progesterone, and testosterone may contribute to differential risk for developing PTSD. In this review, we briefly consider the influence of gonadal hormones on fear conditioning processes including fear acquisition, fear inhibition, extinction learning, and extinction recall within translational neuroscience models. We discuss findings from human studies incorporating samples from both community and traumatized clinical populations to further understand how these hormones might interact with exposure to trauma. Additionally, we propose that special attention should be paid to the specific measure used to examine fear conditioning processes as there is evidence that common psychophysiological indices such as skin conductance response and fear-potentiated startle can reveal quite different results and thus necessitate nuanced interpretations. Continued research to understand the influence of gonadal hormones in fear learning and extinction processes will provide further insight into the increased risk women have of developing PTSD and provide new targets for the treatment and prevention of this disorder.

Perioperative Propranolol Against Dental Anxiety: A Randomized Controlled Trial

BACKGROUND

Promising results from a trauma reactivation study on post-traumatic stress disorder suggest that propranolol is capable of attenuating symptoms of traumatically induced mental disorders by blocking memory reconsolidation.

METHODS

A randomized, parallel, placebo-controlled, quadruple-blind trial was designed to determine the effectiveness of perioperative propranolol during exposure to dental extractions in reducing dental anxiety in patients with dental anxiety or dental phobia. Between November 2014 and December 2018, 52 patients with high levels of fear in anticipation of dental extractions who were referred to a department of oral and maxillofacial surgery for at least two tooth and/or molar removals with 1 month in between were included. On the first visit participants received either 120 mg of perioperative oral propranolol (n = 19) or placebo (n = 17), and a core fear memory was reactivated 1 h preoperatively. The primary outcome was change in severity of dental anxiety from baseline to 1-month follow-up, as indexed by the short version of the dental anxiety inventory (S-DAI). Secondary outcome measures were change in intra-operative state anxiety and specific phobia diagnoses.

RESULTS

Linear mixed model (LMM) yielded no statistically significant difference in change of dental trait anxiety from baseline to 1-month follow-up between propranolol and placebo groups (Cohen's d = 0.23). S-DAI scores decreased in both study arms from baseline to follow-up (propranolol arm: from 32.1 [SD = 7.3] to 29.1 [SD = 8.8]; placebo arm: from 31.6 [SD = 7.5] to 27.1 [SD = 6.5]). Also, administering propranolol was not associated with a significant difference in change of intra-operative state anxiety or phobia diagnoses between groups over time.

CONCLUSIONS

The results do not concur with earlier findings regarding post-traumatic stress disorder, and suggest that individuals with traumatically induced fears or phobias do not benefit from the application of perioperative propranolol.

Can contingency rehearsal during the interval between a retrieval cue and extinction training change the effects of post-retrieval extinction?

Return of fear may be prevented by post-retrieval extinction (PRE), a procedure consisting of presenting a stimulus that was present during conditioning (retrieval cue) prior to extinction training. However, recent evidence suggests that there might be circumstances under which PRE is not effective to prevent the return of fear (boundary conditions), but some of these conditions remain unknown. We explored if rehearsing the CS, US or CS-US contingency during the interval between the retrieval cue and extinction training might change the effects of PRE. One day after differential fear conditioning, healthy human participants (n = 83) underwent either standard extinction (control condition, n = 31) or two different PRE procedures, one in which participants rehearsed the CS-US contingency during the interval between the retrieval cue and extinction (rehearsal condition, n = 25), or another in which they underwent a verbal fluency task directing their attention away from the experimental contingencies during this interval (nonrehearsal condition, n = 27). Return of fear in a reinstatement test was observed in both control and rehearsal conditions, whereas in the nonrehearsal condition there was a generalized increase in response to the CS+ and CS-. Differential response in the rehearsal condition had values slightly smaller than the control group with no significant differences from both control and nonrehearsal conditions. These results suggest that the overt behavior of participants during the interval between a retrieval cue and extinction training might change the effects of PRE in healthy human participants, but further manipulations of these variables are needed to confirm these findings.

Indoor or outdoor? Generalization of costly pain-related avoidance behavior to conceptually related contexts

When pain persists beyond healing time and becomes a "false alarm" of bodily threat, protective strategies, such as avoidance, are no longer adaptive. More specifically, generalization of avoidance based on conceptual knowledge may contribute to chronic pain disability. Using an operant robotic-arm avoidance paradigm, healthy participants (N=50), could perform more effortful movements in the threat context (e.g. pictures of outdoor scenes) to avoid painful stimuli, whereas no pain occured in the safe context (e.g. pictures of indoor scenes). Next, we investigated avoidance generalization to conceptually related contexts (i.e. novel outdoor/indoor scenes). As expected, participants avoided more when presented with novel contexts conceptually related to the threat context than in novel exemplars of the safe context. Yet, exemplars belonging to one category (outdoor/indoor scenes) were not interchangeable; there was a generalization decrement. Posthoc analyses revealed that contingency-aware participants (n=27), but not non-aware participants (n=23), showed the avoidance generalization effect and also generalized their differential pain-expectancy and pain-related fear more to novel background scenes conceptually related to the original threat context. In contrast, the fear-potentiated startle response was not modulated by context.

Placebo and Non-specific Effects in Reconsolidation-Based Treatment for Arachnophobia

The idea that maladaptive memories may be rendered susceptible to interference after reactivation raises the possibility of reactivating and neutralizing clinically-relevant emotional memories. In this study, we sought to investigate the feasibility of such a "reconsolidation-based" intervention for arachnophobia, drawing upon previous research that successfully reduced fear of spiders in a subclinical sample. In Experiment 1, we piloted several reactivation procedures for conducting a reconsolidation-based treatment for arachnophobic individuals. All procedures involved some form of brief exposure to a fear-provoking spider, followed by the administration of 40 mg propranolol. In Experiment 2, we conducted a double-blind, placebo-controlled assessment of one procedure tested in Experiment 1. In Experiment 1, we found that most reactivation procedures produced drops in self-reported fear of spiders from pre- to post-treatment, including fear declines that were apparent up to 6- and even 14-months later. However, in Experiment 2, we found no evidence that the participants receiving propranolol were better off than those who received placebo. While our findings are limited by the small sample sizes used, they nevertheless show a different pattern of responses than was observed in a previous reconsolidation-based intervention for subclinical spider fearful participants. Alterations to the protocol made to accommodate the clinical participants may have led to greater opportunities for non-specific effects (e.g., exposure, placebo effects) to drive change in the participants. Our findings highlight both the challenges of translating reconsolidation-based procedures into clinical interventions, as well as the importance of controls for non-specific effects in reconsolidation-based research.

Paternal expressed emotion influences psychobiological indicators of threat and safety learning in daughters: A preliminary study

This preliminary study examined the association of children's anxiety, paternal expressed emotion (EE), and their interaction with psychophysiological indices of children's threat and safety learning. Participants included 24 father-daughter dyads. Daughters (ages 8-13 years, 100% Latina) self-reported their anxiety levels and completed a differential threat conditioning and extinction paradigm, during which psychophysiological responding was collected. Fathers completed a Five-Minute Speech Sample, from which paternal EE (i.e., criticism, emotional overinvolvement) was assessed. Anxiety-dependent associations emerged between paternal EE and individual differences in daughters' psychophysiological responding to safety signals during threat conditioning. Paternal EE was positively associated with psychophysiological responding to safety in daughters with high and mean, but not low, levels of anxiety. Although previous work suggests that chronic harsh maternal parenting is a potential risk factor for children's general threat and safety learning, these preliminary findings implicate milder forms of negative parenting behavior in fathers, particularly for highly anxious children.

Interfering with fear memories by eye movement desensitization and reprocessing

OBJECTIVE

Pharmacologic and behavioral interventions that block reconsolidation of reactivated fear memory have demonstrated only limited success in modifying stronger and long-standing fear memories. Given the efficacy of Eye Movement Desensitization and Reprocessing (EMDR) in treating PTSD, pursuit eye movements are a promising and novel intervention for studies of human memory reconsolidation. Here, we examined the efficacy of pursuit eye movements in interfering with reconsolidation of conditioned fear memories.

METHODS

We conducted a 3-day differential Pavlovian fear conditioning procedure in healthy adults, using videos of biologically prepared stimuli (tarantulas), partly reinforced with electrical shocks while recording skin conductance response (SCR) as a measure of autonomic conditioned responses. Fear conditioning was performed on Day 1. On Day 2, 38 participants were randomized into groups performing pursuit eye movements either immediately after fear memory reactivation, when the fear memory was stable, or 10 min later, when the fear memory was assumed to be more labile. On Day 3, fear memory strength was assessed by SCR to both reactivated and nonreactivated fear memories.

RESULTS

Strong differential conditioning to the spider stimuli were observed during both fear acquisition and fear memory reactivation. Reactivated fear memory conditioned responses of participants performing pursuit eye movements after a 10-min delay were significantly smaller in the reinstatement phase (0.16 μS; 95% CI [0.02, 0.31]).

CONCLUSIONS

Pursuit eye movements were effective in reducing fear-conditioned SCR in reinstatement. This result supports the theoretical proposition that EMDR can interfere with reactivated fear memory reconsolidation.

Targeting the Reconsolidation of Licit Drug Memories to Prevent Relapse: Focus on Alcohol and Nicotine

Alcohol and nicotine are widely abused legal substances worldwide. Relapse to alcohol or tobacco seeking and consumption after abstinence is a major clinical challenge, and is often evoked by cue-induced craving. Therefore, disruption of the memory for the cue–drug association is expected to suppress relapse. Memories have been postulated to become labile shortly after their retrieval, during a “memory reconsolidation” process. Interference with the reconsolidation of drug-associated memories has been suggested as a possible strategy to reduce or even prevent cue-induced craving and relapse. Here, we surveyed the growing body of studies in animal models and in humans assessing the effectiveness of pharmacological or behavioral manipulations in reducing relapse by interfering with the reconsolidation of alcohol and nicotine/tobacco memories. Our review points to the potential of targeting the reconsolidation of these memories as a strategy to suppress relapse to alcohol drinking and tobacco smoking. However, we discuss several critical limitations and boundary conditions, which should be considered to improve the consistency and replicability in the field, and for development of an efficient reconsolidation-based relapse-prevention therapy.

Measuring fear: Association among different measures of fear learning

BACKGROUND AND OBJECTIVES

Fear conditioning paradigms use various measures to assess learned fear, including autonomic arousal responses like skin conductance, and self-reports of both associative (US-expectancies) and evaluative (affective ratings) learning. The present study uses a dimensional approach to examine associations among fear indices directly.

METHODS

Seventy-three participants completed a differential fear conditioning experiment, during which a neutral stimulus (CS+) was paired with an electric shock (US), while another stimulus (CS-) was never paired with the shock (partially instructed fear acquisition). Ten minutes later, both stimuli were presented without any shocks (fear extinction). Skin conductance responses and US-expectancy ratings were recorded during each phase, while self-reported negative affect was assessed for each CS at the end of extinction.

RESULTS

Results showed a positive association among US-expectancy ratings and skin conductance responses during acquisition and early extinction. US-expectancy ratings during overall extinction were positively associated with post-extinction negative affect.

LIMITATIONS

The lack of affective ratings post-acquisition may have obscured associations between associative and evaluative learning indices.

CONCLUSIONS

Results provide evidence for the expected correspondence among different indices of associative fear learning. Findings emphasize the need for incorporating both associative and evaluative learning measures in fear conditioning paradigms.

Impaired fear learning and extinction, but not generalization, in anxious and non-anxious depression

Fear conditioning and generalization are well-known mechanisms in the pathogenesis of anxiety disorders. Extinction of conditioned fear responses is crucial for the psychotherapeutic treatment of these diseases. Anxious depression as a subtype of major depression shares characteristics with anxiety disorders. We therefore aimed to compare fear learning mechanisms in patients with anxious versus non-anxious depression. Fear learning mechanisms in patients with major depression (n = 79; for subgroup analyses n = 41 patients with anxious depression and n = 38 patients with non-anxious depression) were compared to 48 healthy participants. We used a well-established differential fear conditioning paradigm investigating acquisition, generalization, and extinction. Ratings of valence, arousal and probability of expected threat were assessed as well as skin conductance response as an objective psychophysiological measure. Patients with major depression showed impaired acquisition of conditioned fear. In addition, depressed patients showed impaired extinction of conditioned fear responses after successful fear conditioning. Generalization was not affected. However, there was no difference between patients with anxious and non-anxious depression. Results differed between objective and subjective measures. Our findings show altered fear acquisition and extinction in major depression as compared to healthy controls, but they do not favor differential fear learning and extinction mechanisms in the pathogenesis of anxious versus non-anxious depression. The results of impaired extinction warrant future studies addressing extinction learning elements in the treatment of depression.

Is romantic partner betrayal a form of traumatic experience? A qualitative study

According to a growing body of research, betrayal by a romantic partner is increasingly considered as a form of interpersonal trauma. Between 30% and 60% of betrayed individuals experience symptoms of post-traumatic stress disorder (PTSD), depression and anxiety to clinically meaningful levels. From a clinical perspective, this constellation of symptoms can be conceptualized as a stressor-related adjustment disorder. Yet, no qualitative research has examined the association between romantic betrayal and traumatic stress from the perspective of betrayed individuals. Face-to-face semi-structured interviews were conducted with 13 participants who had completed a clinical trial for a new treatment for adjustment disorder stemming from betrayal. Data were analysed using thematic content analysis. Although betrayal was experienced as a shocking and destabilizing event, and participants used trauma or 'feeling traumatized' as a metaphor to describe their experience, few had constructed their reaction as traumatic stress. In fact, participants reported experiencing difficulties understanding the intensity of their experience. However, when exposed to external sources (e.g., books and interviews by psychologists and researchers) that used a trauma and PTSD framework to explain the effects of betrayal, participants reported feeling clarity, validation and relief. Findings are discussed in the light of theoretical and clinical implications.

Personality and Authenticity in Light of the Memory-Modifying Potential of Optogenetics

There has been a growing interest in research concerning memory modification technologies (MMTs) in recent years. Neuroscientists and psychologists are beginning to explore the prospect of controllable and intentional modification of human memory. One of the technologies with the greatest potential to this end is optogenetics-an invasive neuromodulation technique involving the use of light to control the activity of individual brain cells. It has recently shown the potential to modify specific long-term memories in animal models in ways not yet possible with other MMTs. As the therapeutic potential of optogenetics has already prompted approval of the first human trials, it is especially important and timely to consider the opportunities and dangers this technology may entail. In this article, we focus on possible consequences of optogenetics as an MMT by analyzing fundamental threats potentially associated with memory modifications: the potential disruption of personality and authenticity.

Retrieval-Dependent Mechanisms Affecting Emotional Memory Persistence: Reconsolidation, Extinction, and the Space in Between

Maladaptive emotional memories contribute to the persistence of many mental health disorders, and therefore the prospect of disrupting these memories to produce long-term reductions in relapse is of great clinical appeal. Reducing the impact of maladaptive emotional memories on behaviour could be achieved by two retrieval-dependent manipulations that engage separate mnemonic processes: "reconsolidation disruption" and "extinction enhancement." Extinction occurs during a prolonged re-exposure session in the absence of the expected emotional outcome and is widely accepted as reflecting the formation of a new, inhibitory memory that prevents behavioural expression of the original trace. Reconsolidation, by contrast, involves the destabilisation of the original memory, allowing for subsequent updating and restabilisation in specific brain regions, unless the re-stabilization process is prevented through specific pharmacological or behavioural interventions. Both destabilisation of the original memory and memory extinction require that re-exposure induces prediction error-a mismatch between what is expected and what actually occurs-but the parameters that allow reconsolidation and extinction to occur, and control the transition between them, have not been well-characterised. Here, we review what is known about the induction of memory destabilisation and extinction, and the transition period that separates these mnemonic processes, drawing on preclinical and clinical examples. A deeper understanding of the processes that determine the alternative routes to memory persistence or inhibition is critical for designing new and more reliable clinical treatments targeting maladaptive emotional memories.

Psychophysiological modelling and the measurement of fear conditioning

Quantification of fear conditioning is paramount to many clinical and translational studies on aversive learning. Various measures of fear conditioning co-exist, including different observables and different methods of pre-processing. Here, we first argue that low measurement error is a rational desideratum for any measurement technique. We then show that measurement error can be approximated in benchmark experiments by how closely intended fear memory relates to measured fear memory, a quantity that we term retrodictive validity. From this perspective, we discuss different approaches commonly used to quantify fear conditioning. One of these is psychophysiological modelling (PsPM). This builds on a measurement model that describes how a psychological variable, such as fear memory, influences a physiological measure. This model is statistically inverted to estimate the most likely value of the psychological variable, given the measured data. We review existing PsPMs for skin conductance, pupil size, heart period, respiration, and startle eye-blink. We illustrate the benefit of PsPMs in terms of retrodictive validity and translate this into sample size required to achieve a desired level of statistical power. This sample size can differ up to a factor of three between different observables, and between the best, and the current standard, data pre-processing methods.

Impact of a reminder/extinction procedure on threat-conditioned pupil size and skin conductance responses

A reminder can render consolidated memory labile and susceptible to amnesic agents during a reconsolidation window. For the case of threat memory (also termed fear memory), it has been suggested that extinction training during this reconsolidation window has the same disruptive impact. This procedure could provide a powerful therapeutic principle for treatment of unwanted aversive memories. However, human research yielded contradictory results. Notably, all published positive replications quantified threat memory by conditioned skin conductance responses (SCR). Yet, other studies measuring SCR and/or fear-potentiated startle failed to observe an effect of a reminder/extinction procedure on the return of fear. Here we sought to shed light on this discrepancy by using a different autonomic response, namely, conditioned pupil dilation, in addition to SCR, in a replication of the original human study. N = 71 humans underwent a 3-d threat conditioning, reminder/extinction, and reinstatement, procedure with 2 CS+, of which one was reminded. Participants successfully learned the threat association on day 1, extinguished conditioned responding on day 2, and showed reinstatement on day 3. However, there was no difference in conditioned responding between the reminded and the nonreminded CS, neither in pupil size nor SCR. Thus, we found no evidence that a reminder trial before extinction prevents the return of threat-conditioned responding.

Effects of intranasal insulin as an enhancer of fear extinction: a randomized, double-blind, placebo-controlled experimental study

Fear-extinction based psychotherapy (exposure) is the most effective method for treating anxiety disorders. Notwithstanding, since some patients show impairments in the unlearning of fear and insufficient fear remission, there is a growing interest in using cognitive enhancers as adjuvants to exposure. As insulin plays a critical role in stress processes and acts as a memory enhancer, this study aimed to assess the capacity of intranasal insulin to augment fear extinction. A double-blind, placebo-controlled differential fear-conditioning paradigm was conducted in 123 healthy participants (63 females). Pictures of faces with neutral expressions were used as conditioned stimuli and electric shocks as unconditioned stimuli. The paradigm consisted of four phases presented on three consecutive days: acquisition (day 1), extinction (day 2), reinstatement and re-extinction (day 3). A single intranasal dose of insulin (160 IU) or placebo was applied on day 2, 45 min before fear extinction. Skin conductance response (SCR), fear-potentiated startle (FPS) and expectancy ratings were assessed. During extinction, the insulin group (independent of sex) showed a significantly stronger decrease in differential FPS in comparison with the placebo group. Furthermore, a sex-specific effect was found for SCR, with women in the insulin group showing a greater decrease of differential SCR both at early extinction and at late re-extinction. Our results provide first evidence that intranasal insulin facilitates fear extinction processes and is therefore a promising adjuvant for extinction-based therapies in anxiety and related disorders. Sex-specific effects should be taken into consideration in future studies.

Exposure Therapy for Post-Traumatic Stress Disorder: Factors of Limited Success and Possible Alternative Treatment

Recent research indicates that there is mixed success in using exposure therapies on patients with post-traumatic stress disorder (PTSD). Our study argues that there are two major reasons for this: The first is that there are nonassociative aspects of PTSD, such as hyperactive amygdala activity, that cannot be attenuated using the exposure therapy; The second is that exposure therapy is conceptualized from the theoretical framework of Pavlovian fear extinction, which we know is heavily context dependent. Thus, reducing fear response in a therapist's office does not guarantee reduced response in other situations. This study also discusses work relating to the role of the hippocampus in context encoding, and how these findings can be beneficial for improving exposure therapies.

Enhanced noradrenergic activity by yohimbine and differential fear conditioning in patients with major depression with and without adverse childhood experiences

Major depressive disorder (MDD) has been associated with changes in the biological stress systems, including the locus coeruleus-noradrenergic system. Accumulated evidence suggests an upregulation of central alpha2-receptors, leading to decreased noradrenergic activity on a central level in MDD patients. Adverse childhood experiences (ACE) such as physical or sexual abuse might contribute to those changes. Furthermore, noradrenaline can affect cognitive processes, e.g. learning and memory. Cognitive dysfunctions constitute an important symptom of MDD. We aimed to investigate the relationship of alpha2-receptor dysregulation with learning processes in MDD by conducting a differential fear conditioning paradigm after double-blind administration of the alpha2-receptor antagonist yohimbine versus placebo. To investigate the role of ACE systematically, we included four groups of healthy participants and MDD patients with and without ACE (MDD-/ACE-: N = 44, MDD-/ACE+: N = 26, MDD+/ACE-: N = 24, MDD+/ACE+: N = 24; without antidepressant medication). We found increased noradrenergic activity after yohimbine administration across groups as measured by alpha-amylase and blood pressure. Overall, fear responses were higher after yohimbine as indicated by skin conductance responses and fear-potentiated startle responses. While we found no significant MDD effect, ACE had significant impact on the ability to discriminate between both conditioned stimuli (CS+ predicting an aversive stimulus, CS- predicting none), depending on drug condition. After yohimbine, CS discrimination decreased in individuals without ACE, but not in individuals with ACE. Differences in the response to yohimbine might be explained by aberrant alpha2-receptor regulation in individuals with ACE. Impaired discrimination of threat and safety signals might contribute to enhanced vulnerability following ACE.

Renewal of conditioned fear responses using a film clip as the aversive unconditioned stimulus

BACKGROUND AND OBJECTIVES

Pavlovian fear conditioning paradigms are valuable to investigate fear learning and the return of extinguished fear in the lab. However, their validity is limited, because the aversive stimuli (e.g., electric shocks) typically lack the modalities and complexity of real-world aversive experiences. To overcome this limitation, we examined fear acquisition, extinction and contextual renewal using an audiovisual unconditioned stimulus (US).

METHOD

On day 1, 50 healthy participants completed an acquisition phase in a specific context (i.e., desk or bookcase, 'context A'). Pictures of colored lamps served as conditioned stimuli and an aversive film clip was used as US. On day 2, extinction took place in the same context ('context A') or in a different context ('context B'). Afterwards, renewal was tested in the acquisition context (AAA vs. ABA design).

RESULTS

As hypothesized, fear acquisition and extinction, as measured by US expectancy ratings, fear potentiated startle (FPS), and skin conductance responses (SCRs), were successful. Most importantly, conditioned responding was renewed on all measures in the ABA condition, but not in the AAA condition. Differential renewal (i.e., larger renewal for CS + than for CS-) was only observed for US expectancy ratings.

LIMITATIONS

The return of conditioned responses was non-differential for FPS and SCR.

CONCLUSIONS

The current set-up enables investigation of fear renewal using an audiovisual US. Future studies can utilize this paradigm to investigate interventions that aim to reduce fear renewal by modifying the US memory, such as Eye Movement Desensitization and Reprocessing and imagery rescripting.

Intrusive memories and voluntary memory of a trauma film: Differential effects of a cognitive interference task after encoding

Methods to reduce intrusive memories (e.g., of traumatic events) should ideally spare voluntary memory for the same event (e.g., to report on the event in court). Single-trace memory accounts assume that interfering with a trace should impact both its involuntary and voluntary expressions, whereas separate-trace accounts assume these two can dissociate, allowing for selective interference. This possibility was investigated in 3 experiments. Nonclinical participants viewed a trauma film followed by an interference task (Tetris game-play after reminder cues). Next, memory for the film was assessed with various measures. The interference task reduced the number of intrusive memories (diary-based, Experiments 1 and 2), but spared performance on well-matched measures of voluntary retrieval-free recall (Experiment 1) and recognition (Experiments 1 and 2)-challenging single-trace accounts. The interference task did not affect other measures of involuntary retrieval-perceptual priming (Experiment 1) or attentional bias (Experiment 2). However, the interference task did reduce the number of intrusive memories in a laboratory-based vigilance-intrusion task (Experiments 2 and 3), irrespective of concurrent working memory load during intrusion retrieval (Experiment 3). Collectively, results reveal a robust dissociation between intrusive and voluntary memories, having ruled out key methodological differences between how these two memory expressions are assessed, namely cue overlap (Experiment 1), attentional capture (Experiment 2), and retrieval load (Experiment 3). We argue that the inability of these retrieval factors to explain the selective interference is more compatible with separate-trace than single-trace accounts. Further theoretical developments are needed to account for this clinically important distinction between intrusive memories and their voluntary counterpart. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Cholinergic Modulation of Exposure Disrupts Hippocampal Processes and Augments Extinction: Proof-of-Concept Study With Social Anxiety Disorder

BACKGROUND

In rodents, context specificity of Pavlovian extinction is attenuated by manipulations that impair hippocampal function, including systemic administration of scopolamine, a muscarinic-cholinergic receptor antagonist. Context renewal translates into return of fear following exposure therapy to feared situations. We evaluated the effectiveness of scopolamine for attenuating context renewal of phobic fear in humans.

METHODS

A total of 60 participants (35 female, 22 male, 1 transgender, 2 undeclared) with social anxiety disorder and fear of public speaking were randomized to placebo, 0.5 mg scopolamine, or 0.6 mg scopolamine. They completed seven exposure sessions in an exposure context and subsequently tested in the exposure context (extinction retest) versus a different context (context renewal test), which were counterbalanced. Testing 1 month later occurred in the exposure context (long-term extinction retest). Fear measures included skin conductance and self-reported distress during speeches. Hippocampus-dependent cognitive tasks were completed as well.

RESULTS

Scopolamine augmented extinction across exposure sessions on skin conductance response and skin conductance level. Lower skin conductance response at context renewal in scopolamine groups relative to the placebo group was constrained to simple effects and complicated by unexpected outcomes within placebo and on self-reported fear. Scopolamine led to lower skin conductance response at long-term extinction retest. Scopolamine impaired performance on a cognitive task of hippocampal function.

CONCLUSIONS

Noninvasive and well-tolerated scopolamine impaired hippocampal processes and augmented extinction during exposure. Drug-free effects persisted 1 month later. Findings at context renewal were limited and suggestive only. Further investigation is warranted with varying scopolamine dosages.

Detrimental Effects of a Retrieval-Extinction Procedure on Nicotine Seeking, but Not Cocaine Seeking

Retrieval-extinction memory reactivation procedures have been used to prevent the return of learned fear and drug seeking in preclinical models. These procedures first reactivate the original memory with a brief cue exposure (i.e., retrieval) session, and then disrupt memory reconsolidation by conducting extinction training within the reconsolidation window. The original memory is thought to be updated with the new information conveyed by extinction learning, resulting in a persistent therapeutic effect beyond that observed with extinction training alone (i.e., no retrieval). Here, we attempted to replicate the therapeutic effects on cocaine seeking reported by Xue et al. (2012), and extend these findings to nicotine seeking. Rats self-administered either cocaine or nicotine with contingent cues for weeks, and were then divided into two groups. The retrieval group underwent a 10-min retrieval session wherein drug cues were available, but drug was not. Ten minutes later, they were allowed to continue cue extinction training for an additional 60 min. The no retrieval group underwent a contiguous 70-min cue extinction session. These procedures continued for weeks, followed by a test for spontaneous recovery of drug seeking. No group differences were observed on any measure of cocaine seeking, although both groups exhibited extinction and spontaneous recovery. By contrast, for nicotine seeking, the retrieval group exhibited resistance to extinction, an effect that persisted on the spontaneous recovery test. These findings underscore the importance of drug type in the outcome of retrieval-extinction procedures and moreover indicate that retrieval-extinction procedures can be detrimental to nicotine seeking.

Pharmacological interventions during the process of reconsolidation of aversive memories: A systematic review

Reconsolidation is the return of a memory to a transient state of lability, following memory consolidation, that can occur when memories are evoked. During the process of reconsolidation, memories may be modified by different means, including the administration of drugs, during a period called the "reconsolidation window”. This process has been widely studied in animals, but human studies are limited and include several methodological pitfalls. Our objective was to conducte a systematic review of the literature that utilizes pharmacological interventions during the process of reconsolidation of aversive memories in humans, with a critical analysis of the methodologies used. Searches were made in the electronic databases PubMed, Scopus, Web of Science and SciELO using the following search terms: (memory) AND (consolidation OR reconsolidation) AND (pharmacological manipulation OR pharmacological intervention). We found 294 references and ten (3.4%) were included in the review, based on preestablished eligibility criteria. All studies were randomized, double-blind clinical trials. The most commonly studied drug was propranolol. Two studies used a protocol involving autobiographical aversive memories, while in the remaining aversive memories were produced in the laboratory. The timing of pharmacological interventions is a controversial issue in the field, as drug activity must occur within the reconsolidation window. The small number of studies and some methodological difficulties of this type of research highlights the need for studies that individually evaluate some of the issues discussed, particularly the timing of pharmacological interventions and the duration of reconsolidation windows.