Harnessing reconsolidation to weaken fear and appetitive memories: A meta-analysis of post-retrieval extinction effects

Memory Reconsolidation Updating in Substance Addiction: Applications, Mechanisms, and Future Prospects for Clinical Therapeutics

Persistent and maladaptive drug-related memories represent a key component in drug addiction. Converging evidence from both preclinical and clinical studies has demonstrated the potential efficacy of the memory reconsolidation updating procedure (MRUP), a non-pharmacological strategy intertwining two distinct memory processes: reconsolidation and extinction-alternatively termed "the memory retrieval-extinction procedure". This procedure presents a promising approach to attenuate, if not erase, entrenched drug memories and prevent relapse. The present review delineates the applications, molecular underpinnings, and operational boundaries of MRUP in the context of various forms of substance dependence. Furthermore, we critically examine the methodological limitations of MRUP, postulating potential refinement to optimize its therapeutic efficacy. In addition, we also look at the potential integration of MRUP and neurostimulation treatments in the domain of substance addiction. Overall, existing studies underscore the significant potential of MRUP, suggesting that interventions predicated on it could herald a promising avenue to enhance clinical outcomes in substance addiction therapy.

Conflict Dynamics of Post-Retrieval Extinction: A Comparative Analysis of Unconditional and Conditional Reminders Using Skin Conductance Responses and EEG

The post-retrieval extinction paradigm, rooted in reconsolidation theory, holds promise for enhancing extinction learning and addressing anxiety and trauma-related disorders. This study investigates the impact of two reminder types, mild US-reminder (US-R) and CS-reminder (CS-R), along with a no-reminder extinction, on fear recovery prevention in a categorical fear conditioning paradigm. Scalp EEG recordings during reminder and extinction processes were conducted in a three-day design. Results show that the US-R group exhibits a distinctive extinction learning pattern, characterized by a slowed-down yet successful process and pronounced theta-alpha desynchronization (source-located in the prefrontal cortex) during CS processing, followed by enhanced synchronization (source-located in the anterior cingulate) after shock cancellation in extinction trials. These neural dynamics correlate with the subtle advantage of US-R in the Day 3 recovery test, presenting faster spontaneous recovery fading and generally lower fear reinstatement responses. Conversely, the CS reminder elicits CS-specific effects in later episodic tests. The unique neural features of the US-R group suggest a larger prediction error and subsequent effortful conflict learning processes, warranting further exploration.

Peripheral Vision in Patients Following Intraocular Lens Implantation: A Systematic Review and Meta-Analysis

PURPOSE

To update the literature on peripheral optics and vision following intraocular lens (IOLs) implantation.

METHODS

We investigated how current IOLs influence peripheral visual function, peripheral optical quality, and visual perception and performance, in patients following cataract surgery. Peripheral vision is described as vision outside the central foveal region of the eye (beyond 4-5° of eccentricity). We systematically searched PubMed, Cochrane Central Register of Controlled Trials, Embase, and gray literature for relevant references. Randomized controlled trials and observational studies were eligible for inclusion. Finally, 47 studies with a total of 5963 participants were eligible for this review, of which 15 were included in the meta-analysis.

RESULTS

Regarding visual fields, the meta-analysis showed that the pooled estimate of mean deviation (MD) measured with perimetry tests (standard automated perimetry [SAP], short-wavelength automated perimetry [SWAP], and frequency doubling technology [FDT]) appears to be lower than the mean of healthy age-matched controls, regardless of IOL design. Results for pooled estimate show that localized defects (pattern standard deviation [PSD]) were higher than those in the healthy age-matched controls for FDT. We also collected evidence demonstrating that pseudophakia increases peripheral astigmatism and a myopic shift from 20° onward, leading to decreased peripheral image quality compared with that in phakic eyes. Patient-reported outcomes on peripheral vision showed a pooled score estimate of 95.19, indicating high satisfaction, and for the Steps & Stairs questions, a pooled score estimate at 0.23, indicating no to little difficulty seeing steps and stairs.

CONCLUSIONS

Peripheral image quality is degraded in eyes after cataract surgery. Nevertheless, whether this degradation leads to impaired visual function in the periphery requires further investigation.

Aversive memories can be weakened during human sleep via the reactivation of positive interfering memories

Recollecting painful or traumatic experiences can be deeply troubling. Sleep may offer an opportunity to reduce such suffering. We developed a procedure to weaken older aversive memories by reactivating newer positive memories during sleep. Participants viewed 48 nonsense words each paired with a unique aversive image, followed by an overnight sleep. In the next evening, participants learned associations between half of the words and additional positive images, creating interference. During the following non-rapid-eye-movement sleep, auditory memory cues were unobtrusively delivered. Upon waking, presenting cues associated with both aversive and positive images during sleep, as opposed to not presenting cues, weakened aversive memory recall while increasing positive memory intrusions. Substantiating these memory benefits, computational modeling revealed that cueing facilitated evidence accumulation toward positive affect judgments. Moreover, cue-elicited theta brain rhythms during sleep predominantly predicted the recall of positive memories. A noninvasive sleep intervention can thus modify aversive recollection and affective responses.

Carbon Dioxide Reactivity Differentially Predicts Fear Expression After Extinction and Retrieval-Extinction in Rats

Background

Cues present during a traumatic event may result in persistent fear responses. These responses can be attenuated through extinction learning, a core component of exposure therapy. Exposure/extinction is effective for some people, but not all. We recently demonstrated that carbon dioxide (CO2) reactivity predicts fear extinction memory and orexin activation and that orexin activation predicts fear extinction memory, which suggests that a CO2 challenge may enable identification of whether an individual is a good candidate for an extinction-based approach. Another method to attenuate conditioned responses, retrieval-extinction, renders the original associative memory labile via distinct neural mechanisms. The purpose of the current study was to examine whether we could replicate previous findings that retrieval-extinction is more effective than extinction at preventing the return of fear and that CO2 reactivity predicts fear memory after extinction. We also examined whether CO2 reactivity predicts fear memory after retrieval-extinction.

Methods

Male rats first underwent a CO2 challenge and fear conditioning and were assigned to receive either standard extinction (n = 28) or retrieval-extinction (n = 28). Then, they underwent a long-term memory (LTM) test and a reinstatement test.

Results

We found that retrieval-extinction resulted in lower freezing during extinction, LTM, and reinstatement than standard extinction. Using the best subset approach to linear regression, we found that CO2 reactivity predicted LTM after extinction and also predicted LTM after retrieval-extinction, although to a lesser degree.

Conclusions

CO2 reactivity could be used as a screening tool to determine whether an individual may be a good candidate for an extinction-based therapeutic approach.

Memory persistence: from fundamental mechanisms to translational opportunities

Memory persistence is a double edge sword. Persistence of adaptive memories is essential for survival and even determines who we are. Neurodegenerative conditions with significant memory loss such as Alzheimer's disease, testify how defects of memory persistence have severe and irreversible effects on personality, among other symptoms. Yet, maintenance of overly strong maladaptive memories underlies highly debilitating psychiatric conditions including post-traumatic stress disorder, specific phobia, substance dependence and binge eating disorder. Here we review the neurobiological mechanisms supporting memory formation, persistence, inhibition and forgetting. We then shift the focus to how such mechanisms have been exploited to alter the persistence of laboratory-generated memories in human healthy volunteers as a proof of concept. Finally, we review the effect of behavioural and pharmacological interventions in anxiety and addiction disorder patients, highlighting key findings, gaps, and future directions for basic and translational research.

Drug memory reconsolidation: from molecular mechanisms to the clinical context

Since its rediscovery at the beginning of the 21st Century, memory reconsolidation has been proposed to be a therapeutic target for reducing the impact of emotional memories that can go awry in mental health disorders such as drug addiction (substance use disorder, SUD). Addiction can be conceptualised as a disorder of learning and memory, in which both pavlovian and instrumental learning systems become hijacked into supporting drug-seeking and drug-taking behaviours. The past two decades of research have characterised the details of the molecular pathways supporting the reconsolidation of pavlovian cue-drug memories, with more recent work indicating that the reconsolidation of instrumental drug-seeking memories also relies upon similar mechanisms. This narrative review considers what is known about the mechanisms underlying the reconsolidation of pavlovian and instrumental memories associated with drug use, how these approaches have translated to experimental medicine studies, and the challenges and opportunities for the clinical use of reconsolidation-based therapies.

Consensus design of a calibration experiment for human fear conditioning

Fear conditioning is a widely used laboratory model to investigate learning, memory, and psychopathology across species. The quantification of learning in this paradigm is heterogeneous in humans and psychometric properties of different quantification methods can be difficult to establish. To overcome this obstacle, calibration is a standard metrological procedure in which well-defined values of a latent variable are generated in an established experimental paradigm. These intended values then serve as validity criterion to rank methods. Here, we develop a calibration protocol for human fear conditioning. Based on a literature review, series of workshops, and survey of N = 96 experts, we propose a calibration experiment and settings for 25 design variables to calibrate the measurement of fear conditioning. Design variables were chosen to be as theory-free as possible and allow wide applicability in different experimental contexts. Besides establishing a specific calibration procedure, the general calibration process we outline may serve as a blueprint for calibration efforts in other subfields of behavioral neuroscience that need measurement refinement.

The relationship between sleep quality, snoring symptoms, night shift and risk of stroke in Chinese over 40 years old

Objectives

To analyze the relationship between sleep quality, snoring symptoms, night shift and risk of stroke in Chinese population over 40 years old.

Methods

Based on the national screening and intervention program for high-risk population of stroke in 2016, 15,016 people completed the study of “the association between sleep and stroke,” 58,696 people completed the snoring questionnaire, and 58,637 people completed the night shift questionnaire.

Results

The proportion of coronary heart disease, hypertension, hyperlipidemia, diabetes, snoring, atrial fibrillation, stroke and high-risk group of stroke risk rating were higher in the group with poor sleep quality (p < 0.05). The proportion of high blood pressure, hyperlipidemia, diabetes, atrial fibrillation, transient ischemic attack (TIA), or high-risk group of stroke risk rating was higher in snoring group (p < 0.05). The body mass index (BMI), waist circumference, neck circumference, fasting blood glucose, triglyceride (TG), total cholesterol (TC), low density lipoprotein (LDL) and homocysteine (Hcy) levels in snoring group were higher than the non-snoring group, and high density lipoprotein (HDL) levels were lower (p < 0.05). People with TIA, high risk for stroke, and high blood pressure were higher in night shift workers than non-night shift workers (p < 0.05). The levels of BMI, fasting blood glucose, 2 h postprandial blood glucose, glycated hemoglobin, TG, TC, LDL, HDL and Hcy in night shift group were lower than the non-night shift group (p < 0.05).

Conclusion

Sleep quality, snoring and night shift might be related to the risk factors of stroke.

Making Leaps and Hitting Boundaries in Reconsolidation: Overcoming Boundary Conditions to Increase Clinical Translatability of Reconsolidation-based Therapies

Reconsolidation results in the restabilisation, and thus persistence, of a memory made labile by retrieval, and interfering with this process is thought to enable modification or weakening of the original trace. As such, reconsolidation-blockade has been a focus of research aiming to target the maladaptive memories underlying mental health disorders, including post-traumatic stress disorder and drug addiction. Current first-line therapies are not effective for all patients, and a substantial proportion of those for whom therapies are effective later relapse. A reconsolidation-based intervention would be invaluable as an alternative treatment for these conditions. However, the translation of reconsolidation-based therapies to the clinic presents a number of challenges, with arguably the greatest being the overcoming of the boundary conditions governing the opening of the reconsolidation window. These include factors such as the age and strength of memory, and can broadly be divided into two categories: intrinsic features of the targeted memory itself, and parameters of the reactivation procedure used. With maladaptive memory characteristics inevitably varying amongst individuals, manipulation of the other limitations imposed by procedural variables have been explored to circumvent the boundary conditions on reconsolidation. Although several apparently discrepant results remain to be reconciled and these limitations yet to be truly defined, many studies have produced successful results which encouragingly demonstrate that boundary conditions may be overcome using various proposed strategies to enable translation of a reconsolidation-based intervention to clinical use.

Reconsolidation and Fear Extinction: An Update

Fear memories can be updated behaviorally by delivering extinction trials during the reconsolidation window, which results in a persistent attenuation of fear memories (Monfils et al., Science 324:951-955, 2009). This safe and non-invasive paradigm, termed retrieval-extinction (or post-retrieval extinction), has also been found to be successful at preventing the return of fear in healthy fear conditioned humans (Schiller et al., Nature 463:49-53, 2010), and in the time since its discovery, there has been an explosion of research on the use of retrieval-extinction in fear memories in humans and other animals, some of which have found a long-term reduction in conditioned responding, and some who have not. These discrepant findings have raised concerns as to whether retrieval-extinction really results in updating of the original fear memory, or if it simply enhances extinction. We will first review the progress made on elucidating the cellular mechanisms underlying the fear attenuating effects of retrieval-extinction and how they differ from traditional extinction. Special attention will be paid to the molecular events necessary for retrieval-extinction to successfully occur and how these reconsolidated memories are represented in the brain. Next, we will examine the parameters that determine whether or not a memory will be updated via extinction during the reconsolidation window (also known as boundary conditions). These boundary conditions will also be discussed as possible explanations for discrepant findings of the retrieval-extinction effect. Then we will examine the factors that can determine whether an individual's fears will successfully be attenuated by retrieval-extinction. These individual differences include genetics, age, and psychopathology. Finally, we will discuss recent attempts to bring the retrieval-extinction paradigm from the bench to the bedside for the behavioral treatment of anxiety and trauma disorders.

Causally mapping human threat extinction relevant circuits with depolarizing brain stimulation methods

Laboratory threat extinction paradigms and exposure-based therapy both involve repeated, safe confrontation with stimuli previously experienced as threatening. This fundamental procedural overlap supports laboratory threat extinction as a compelling analogue of exposure-based therapy. Threat extinction impairments have been detected in clinical anxiety and may contribute to exposure-based therapy non-response and relapse. However, efforts to improve exposure outcomes using techniques that boost extinction - primarily rodent extinction - have largely failed to date, potentially due to fundamental differences between rodent and human neurobiology. In this review, we articulate a comprehensive pre-clinical human research agenda designed to overcome these failures. We describe how connectivity guided depolarizing brain stimulation methods (i.e., TMS and DBS) can be applied concurrently with threat extinction and dual threat reconsolidation-extinction paradigms to causally map human extinction relevant circuits and inform the optimal integration of these methods with exposure-based therapy. We highlight candidate targets including the amygdala, hippocampus, ventromedial prefrontal cortex, dorsal anterior cingulate cortex, and mesolimbic structures, and propose hypotheses about how stimulation delivered at specific learning phases could strengthen threat extinction.

Locus coeruleus input-modulated reactivation of dentate gyrus opioid-withdrawal engrams promotes extinction

Extinction training during the reconsolidation window following memory recall is an effective behavioral pattern for promoting the extinction of pathological memory. However, promoted extinction by recall-extinction procedure has not been universally replicated in different studies. One potential reason for this may relate to whether initially acquired memory is successfully activated. Thus, the methods for inducing the memory into an active or plastic condition may contribute to promoting its extinction. The aim of this study is to find and demonstrate a manipulatable neural circuit that engages in the memory recall process and where its activation improves the extinction process through recall-extinction procedure. Here, naloxone-precipitated conditioned place aversion (CPA) in morphine-dependent mice was mainly used as a pathological memory model. We found that the locus coeruleus (LC)-dentate gyrus (DG) circuit was necessary for CPA memory recall and that artificial activation of LC inputs to the DG just prior to initiating a recall-extinction procedure significantly promoted extinction learning. We also found that activating this circuit caused an increase in the ensemble size of DG engram cells activated during the extinction, which was confirmed by a cFos targeted strategy to label cells combined with immunohistochemical and in vivo calcium imaging techniques. Collectively, our data uncover that the recall experience is important for updating the memory during the reconsolidation window; they also suggest a promising neural circuit or target based on the recall-extinction procedure for weakening pathological aversion memory, such as opioid withdrawal memory and fear memory.

Guided reactivation of personal phobic memories prior to exposure exercises prevents the renewal of fear responses in subjects with claustrophobic fears

BACKGROUND AND OBJECTIVES

Basic research suggest behavioral strategies for interferencing the reconsolidation of fear memories to be a promising approach in reducing clinical fears. However, first clinical studies revealed mixed results highlighting the need to identify boundary conditions. We experimentally tested the specific hypothesis that post-retrieval threat exposure prevents context renewal usually observed in protocols without fear memory reactivation.

METHODS

In a preliminary investigation forty-three individuals with claustrophobic fears reactivated the individual phobic memory or not during a guided emotional imagery task and then performed standardized threat exposure to provide new information for updating the original memory. During retests seven and 28 days later, the context was different from that during treatment in half of the subjects.

RESULTS

In those who were guided, the fear memory was successfully reactivated as indexed by increased skin conductance level (SCL) during the imagery of personal scenes relative to neutral scenes. During retests the subjects of the memory non-activation group showed a return of reported fear after context change that, however, was not observed after post-retrieval exposure. In line, autonomic arousal (SCL) decreased over time in the memory reactivation group only if the context changed during retest.

LIMITATIONS

Limited sample size and the inclusion of an analog sample reduce the generalizability of the results.

CONCLUSIONS

The reactivation of fear memory prior to treatment through guided imagery of past personal phobic situations prevented contextual renewal of phobic fears which was observed in those subjects without reactivation of memory.

Effects of Cannabis on PTSD Recovery: Review of the Literature and Clinical Insights

Purpose of Review

Individuals with posttraumatic stress disorder (PTSD) may use cannabis to reduce symptoms yet are also at risk for developing problematic use. This review outlines theories, summarizes recent empirical studies, and discusses clinical implications of cannabis use and PTSD recovery.

Recent Findings

Although naturalistic studies and open trials find a relationship between cannabinoids and PTSD symptom reduction, methodological limitations preclude definitive conclusions. The only randomized controlled trial to date found cannabis had no greater effect on PTSD symptoms than placebo.

Summary

Rigorous studies of the long-term impact of cannabis use on PTSD recovery are needed. Clinicians and researchers must weigh the potential therapeutic effect against the costs and risks associated with long-term cannabis use. Clinicians should consider all available PTSD treatment options, along with client level factors such as the function of cannabis use, motivation to change use, and the potential impact of cannabis on treatment engagement when making clinical recommendations.

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.

The influence of dispositional cognitive reappraisal and expressive suppression on post-retrieval and standard extinction

Individual differences in the ability to habitually regulate emotion may impact the efficacy of fear memory extinction. The aim of this study was to assess the relationship between dispositional cognitive reappraisal and expressive suppression with post-retrieval and standard extinction. Fear memory and extinction were measured with the recovery of skin conductance responses. We also examined the relationship between a temporal feature of electrodermal responding (half-recovery time) and each of the emotion regulation strategies. University students (N = 80) underwent a three-day fear conditioning procedure using a within-subject design consisting of acquisition on day one, post-retrieval extinction and standard extinction on day two, and recovery test on day three. Individual difference data on self-reported levels of cognitive reappraisal, expressive suppression, trait anxiety, and depression were collected. We did not detect a relationship between the two emotion regulation strategies measured in this study and acquisition or extinction. We found, however, that increased dispositional use of cognitive reappraisal was associated with lower spontaneous recovery to both the post-retrieval extinction and standard extinction stimulus after controlling for age, trait anxiety, and depression. There were no associations between expressive suppression and conditioned responses. We also observed patterns of faster dissipation of arousal for reappraisal and slower for suppression to the conditioned stimulus during extinction training, which may represent the unique influence of each emotion strategy on the regulation of fear. We conclude greater daily use of cognitive reappraisal, but not expressive suppression, associates with extinction retention after receiving both standard and post-retrieval extinction.

Using Extinction-Renewal to Circumvent the Memory Strength Boundary Condition in Fear Memory Reconsolidation

Reconsolidation is a process by which memories are destabilized, updated, and then restabilized. Strong memories are resistant to undergoing reconsolidation. Here, we addressed whether an overtrained fear memory could be made susceptible to reconsolidation by first extinguishing, and then renewing, the memory. Rats were trained with ten tone-footshock pairings, followed by eight days of tone extinction in the training context. The next day, rats were placed into a second context and memory for the tone was renewed/reactivated with a single tone presentation. Immediately following reactivation, rats received an injection of midazolam or vehicle. Rats were then tested for freezing to the tone in a third context. Midazolam had no effect in rats that did not undergo tone extinction, but significantly attenuated freezing to the tone in extinguished rats. Thus, rats that received tone extinction underwent tone memory reconsolidation following its renewal. In a second experiment, we administered the reactivation session and midazolam injections prior to extinction. Midazolam had no effect and rats extinguished at a rate similar to controls. These data suggest that strong emotional memories are capable of updating following weakening of memory expression through extinction.

A virtual reality study on postretrieval extinction of smoking memory reconsolidation in smokers

Exposure to smoking-related stimuli may induce the reconsolidation of smoking-related memories in smokers. Research has proposed that extinction applied after the retrieval of a smoking memory may inhibit reconsolidation and prevent craving. The aim of this study was to test the effect of postretrieval extinction (PRE) on the reconsolidation of smoking memory by using a virtual reality (VR) simulation in smokers. On the day 1 session, the study exposed 46 smokers to a neutral and then to a smoking VR scenario under a fixed-block protocol. On day 2, the study randomized participants into three groups (G) and exposed them to a 15-s VR immersion in smoking (G1, G3) or neutral (G2) scenario for memory retrieval. After 15 min, the study exposed G1 and G2 to a VR PRE during the temporal window of memory vulnerability, whereas the study exposed G3 to extinction immediately after retrieval. On day 3, the study exposed all groups to neutral and smoking scenarios similar to day 1. All groups significantly increased craving for cigarettes after exposure to the smoking scenario on day 1 (p < 0.01). On day 3, VR PRE after a 15-second VR smoking memory retrieval was able to inhibit reconsolidation in G1, but not in G3 exposed to PRE before the window of vulnerability, or in G2 not exposed to the smoking memory retrieval. These findings show the superiority of VR PRE after smoking memory retrieval compared to a standard extinction procedure.

Destabilizing Different Strengths of Fear Memories Requires Different Degrees of Prediction Error During Retrieval

Reactivation of consolidated memories can induce a labile period, in which these reactivated memories might be susceptible to change and need reconsolidation. Prediction error (PE) has been recognized as a necessary boundary condition for memory destabilization. Moreover, memory strength is also widely accepted as an essential boundary condition to destabilize fear memory. This study investigated whether different strengths of conditioned fear memories require different degrees of PE during memory reactivation in order for the memories to become destabilized. Here, we assessed the fear-potentiated startle and skin conductance response, using the post-retrieval extinction procedure. A violation of expectancy (PE) was induced during retrieval to reactivate enhanced (unpredictable-shock) or ordinary (predictable-shock) fear memories that were established the day before. Results showed that a PE retrieval before extinction can prevent the return of predictable-shock fear memory but cannot prevent the return of unpredictable-shock fear memory, indicating that a single PE is insufficient to destabilize enhanced fear memory. Therefore, we further investigated whether increasing the degree of PE could destabilize enhanced fear memory using different retrieval strategies (multiple PE retrieval and unreinforced CS retrieval). We found that spontaneous recovery of enhanced fear memory was prevented in both retrieval strategies, but reinstatement was only prevented in the multiple PE retrieval group, suggesting that a larger amount of PE is needed to destabilize enhanced fear memory. The findings suggest that behavioral updating during destabilization requires PE, and the degree of PE needed to induce memory destabilization during memory retrieval depends on the strength of fear memory. The study indicates that memory reconsolidation inference can be used to destabilize stronger memories, and the findings shed lights on the treatment of posttraumatic stress disorders and anxiety disorders.

Generalization and recovery of post-retrieval amnesia

Selective amnesia for previously established memories can be induced by administering drugs that impair protein synthesis shortly after memory reactivation. Competing theoretical accounts attribute this selective post-retrieval amnesia to drug-induced engram degradation (reconsolidation blockade) or to incorporation of sensory features of the reactivation experience into the memory representation, hampering later retrieval in a drug-free state (memory integration). Here we present evidence that critically challenges both accounts. In contextual fear conditioning in rats, we find that amnesia induced by administration of midazolam (MDZ) after reexposure to the training context A generalizes readily to a similar context B. Amnesia is also observed when animals are exposed to the similar context B prior to MDZ administration and later tested for fear to context B but recovers when instead testing for fear to the original training context A or an equally similar but novel context C. Next to their theoretical implications for the nature of forgetting, our findings raise important questions about the viability of reconsolidation-based interventions for the treatment of emotional disorders. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Targeting the reconsolidation of traumatic memories with a brief 2-session imaginal exposure intervention in post-traumatic stress disorder

BACKGROUND

Evidence suggests that extinction during memory reconsolidation diminishes the return of defensive responses. In order to translate these effects to the clinical setting, we tested whether retrieving a traumatic memory and delivering a brief two-sessions imaginal exposure intervention during its reconsolidation would produce stronger decreases in reactivity to these memories than standard imaginal exposure method.

METHODS

Participants with Post-Traumatic Stress Disorder (PTSD) had either their traumatic (n = 21) or a neutral (n = 21) memory retrieved 1 h before an imaginal exposure session for two consecutive days. One day before and one day after, participants were exposed to script-driven imagery of their traumatic event, during which skin conductance responses were measured and, immediately after, subjective responses were assessed by means of Visual Analogue Scales.

RESULTS

Traumatic retrieval improved the physiological, but not the subjective effects of imaginal exposure intervention on over-reactivity to traumatic memories.

CONCLUSIONS

Our results suggest that delivering extinction-based treatments over the reconsolidation of traumatic memories may enhance its effects. These results suggest that this is a promising path toward the development of new therapeutic techniques.

Augmenting exposure therapy with pre-extinction fear memory reactivation and deepened extinction: A randomized controlled trial

BACKGROUND

Pre-extinction fear memory reactivation (PE-FMR) and deepened extinction (DE) enhance long-term extinction of shock-conditioned fear, and may also enhance long-term extinction of naturally acquired fear. Preliminary data suggest that PE-FMR may additionally boost the speed of fear reduction during exposure therapy.

DESIGN

Randomized controlled trial, factorial design.

METHODS

Participants with elevated fears of either spiders or snakes were randomized to (1) exposure therapy alone (n = 41), (2) exposure therapy + PE-FMR (n = 42), (3) exposure therapy + DE (n = 41), or (4) exposure therapy + PE-FMR + DE (n = 42). Participants were assessed at baseline, post-treatment, and one-week follow-up on subjective and behavioral indices of phobia. Because treatment length was tailored to speed of fear reduction, survival analyses were used to examine the speed of fear reduction during treatment.

RESULTS

DE did not improve clinical outcomes at post-treatment or follow-up, whereas PE-FMR produced more rapid fear reduction and was able to achive equivalent outcomes even when the duration of exposure therapy (tailored to speed of fear reduction) was shortened by an average of 21%.

CONCLUSIONS

Data suggest that PE-FMR is a promising strategy for reducing the overall duration of exposure-based therapies.

CLINICAL TRIAL REGISTRATION

(clinicaltrials.gov)NCT02160470.

Investigating the efficacy of the reminder-extinction procedure to disrupt contextual threat memories in humans using immersive Virtual Reality

Upon reactivation, consolidated memories can enter a temporary labile state and require restabilisation, known as reconsolidation. Interventions during this reconsolidation period can disrupt the reactivated memory. However, it is unclear whether different kinds of memory that depend on distinct brain regions all undergo reconsolidation. Evidence for reconsolidation originates from studies assessing amygdala-dependent memories using cue-conditioning paradigms in rodents, which were subsequently replicated in humans. Whilst studies providing evidence for reconsolidation of hippocampus-dependent memories in rodents have predominantly used context conditioning paradigms, studies in humans have used completely different paradigms such as tests for wordlists or stories. Here our objective was to bridge this paradigm gap between rodent and human studies probing reconsolidation of hippocampus-dependent memories. We modified a recently developed immersive Virtual Reality paradigm to test in humans whether contextual threat-conditioned memories can be disrupted by a reminder-extinction procedure that putatively targets reconsolidation. In contrast to our hypothesis, we found comparable recovery of contextual conditioned threat responses, and comparable retention of subjective measures of threat memory, episodic memory and exploration behaviour between the reminder-extinction and standard extinction groups. Our result provide no evidence that a reminder before extinction can prevent the return of context conditioned threat memories in humans.

Behavioral, neurobiological, and neurochemical mechanisms of ethanol self-administration: A translational review

Alcohol use disorder has multiple characteristics including excessive ethanol consumption, impaired control over drinking behaviors, craving and withdrawal symptoms, compulsive seeking behaviors, and is considered a chronic condition. Relapse is common. Determining the neurobiological targets of ethanol and the adaptations induced by chronic ethanol exposure is critical to understanding the clinical manifestation of alcohol use disorders, the mechanisms underlying the various features of the disorder, and for informing medication development. In the present review, we discuss ethanol's interactions with a variety of neurotransmitter systems, summarizing findings from preclinical and translational studies to highlight recent progress in the field. We then describe animal models of ethanol self-administration, emphasizing the value, limitations, and validity of commonly used models. Lastly, we summarize the behavioral changes induced by chronic ethanol self-administration, with an emphasis on cue-elicited behavior, the role of ethanol-related memories, and the emergence of habitual ethanol seeking behavior.

Boundary conditions of post-retrieval extinction: A direct comparison of low and high partial reinforcement

Research has shown that a single presentation of the conditioned stimulus prior to extinction training can diminish conditioned responses. However, replication has proven difficult and appears to be limited by boundary conditions. Here we tested the boundary condition of memory strength by comparing the effect of reinforcement rate to assess its role in post-retrieval extinction. Eighty university students had undergone a three-day fear conditioning experiment in which two partial reinforcement schedules (40%, 80%) were applied. The findings indicated that both low and high partial reinforcement groups did not demonstrate recovery of conditioned responses after post-retrieval extinction. In contrast, both groups demonstrated significant recovery to standard extinction with significantly greater recovery in the 80% group relative to the 40% group. Additionally, we found that greater physiological arousal during memory retrieval significantly predicted recovery of fear at test phase. We conclude that when compared to a lower partial reinforcement schedule, a higher partial reinforcement resulted in the formation of a stronger memory as indicated by greater physiological arousal during memory reactivation and recovery of conditioned responses after standard extinction, but that it does not function as a boundary condition of post-retrieval extinction. These data are significant because it is the first study to investigate the effect of varying partial reinforcement schedules on fear recovery and add to the body of literature that continue to identify sources of failure in the application of post-retrieval extinction.

Using collaboration networks to identify authorship dependence in meta-analysis results

Meta-analytic methods are powerful resources to summarize the existing evidence concerning a given research question and are widely used in many academic fields. Meta-analyzes can also be used to study sources of heterogeneity and bias among results, which should be considered to avoid inaccuracies. Many of these sources can be related to study authorship, as both methodological heterogeneity and researcher bias may lead to deviations in results between different research groups. In this work, we describe a method to objectively attribute study authorship within a given meta-analysis to different research groups by using graph cluster analysis of collaboration networks. We then provide empirical examples of how the research group of origin can impact effect size in distinct types of meta-analyzes, demonstrating how non-independence between within-group results can bias effect size estimates if uncorrected. Finally, we show that multilevel random-effects models using research group as a level of analysis can be a simple tool for correcting for authorship dependence in results.

Preventing the return of fear in humans using reconsolidation update mechanisms: A verification report of Schiller et al. (2010)

In a highly influential report, Schiller et al. (2010) demonstrated long-lasting fear reduction in humans when conducting extinction training shortly following fear memory reactivation. While trying to experimentally replicate the critical conditions of Schiller et al. (2010, Experiment 1), we discovered several irregularities in their paper. Criteria for participant exclusion and the number of excluded participants were misreported; qualitative experimenter decisions actually determined their participant inclusions. Moreover, their statistical analyses were internally inconsistent. After corresponding with the original authors, we received their original data files, allowing us to replicate the reported analyses to verify their results. Here, we report the results of seven separate sets of analyses, three replicating the analyses reported by Schiller et al. (2010) and four applying more principled approaches to participant exclusion, thus including different subsets of the total datasets available, to deduce the influence of specific exclusions and experimenter decisions on the results. For Experiment 1, we were mostly able to replicate the analyses contained in the original report when applying the same qualitative exclusions. However, we found that all of the differences in fear recovery between reactivation-extinction and regular extinction reported by Schiller et al. (2010) were dependent on the qualitative exclusions that they made. With any of the principled approaches to participant exclusion, the degree of fear recovery was highly similar between groups. For Experiment 2, a similar analysis was not possible due to a lack of available data for the excluded participants. Hence, we conducted a verification analysis on the original sample only, which failed to confirm the differences in fear recovery reported by Schiller et al. (2010). Together with the re-analyses, we report a number of additional issues with the way Schiller et al. (2010) processed, analyzed, and reported their data that indicate that their results are unreliable and flawed.

No persistent attenuation of fear memories in humans: A registered replication of the reactivation-extinction effect

It has been proposed that memory retrieval can destabilize consolidated memories, after which they need to be reconsolidated in order to be retained. The presentation of relevant information during memory reconsolidation could then result in the modification of a destabilized memory trace, by allowing the memory trace to be updated before being reconsolidated. In line with this idea, Schiller et al. (2010) have demonstrated that memory retrieval shortly before extinction training can prevent the later recovery of conditioned fear responding that is observed after regular extinction training. Those findings have been the subject of considerable controversy, due in part to theoretical reasons but also due to a number of failures to obtain similar results in conceptual replication attempts. Here, we report the results of a highly powered, direct, independent replication of the critical conditions of Schiller et al. (2010, Experiment 1). Due to misrepresentation of the exclusion criteria in the original Schiller et al. (2010) report, data collection was considerably delayed. When we eventually managed to attain our pre-registered sample size, we found that we could not observe any benefit of reactivation-extinction over regular extinction training in preventing recovery of conditioned fear. The results of the present study, along with the mixed findings in the literature and the misreporting in Schiller et al. (2010), give cause to question whether there is robust evidence that reactivation-extinction prevents the return of fear in humans.

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.

Promoting memory consolidation during sleep: A meta-analysis of targeted memory reactivation

Targeted memory reactivation (TMR) is a methodology employed to manipulate memory processing during sleep. TMR studies have great potential to advance understanding of sleep-based memory consolidation and corresponding neural mechanisms. Research making use of TMR has developed rapidly, with over 70 articles published in the last decade, yet no quantitative analysis exists to evaluate the overall effects. Here we present the first meta-analysis of sleep TMR, compiled from 91 experiments with 212 effect sizes (N = 2,004). Based on multilevel modeling, overall sleep TMR was highly effective (Hedges' g = 0.29, 95% CI [0.21, 0.38]), with a significant effect for two stages of non-rapid-eye-movement (NREM) sleep (Stage NREM 2: Hedges' g = 0.32, 95% CI [0.04, 0.60]; and slow-wave sleep: Hedges' g = 0.27, 95% CI [0.20, 0.35]). In contrast, TMR was not effective during REM sleep nor during wakefulness in the present analyses. Several analysis strategies were used to address the potential relevance of publication bias. Additional analyses showed that TMR improved memory across multiple domains, including declarative memory and skill acquisition. Given that TMR can reinforce many types of memory, it could be useful for various educational and clinical applications. Overall, the present meta-analysis provides substantial support for the notion that TMR can influence memory storage during NREM sleep, and that this method can be useful for understanding neurocognitive mechanisms of memory consolidation. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

Shifting from fear to safety through deconditioning-update

Aversive memories are at the heart of psychiatric disorders such as phobias and post-traumatic stress disorder (PTSD). Here, we present a new behavioral approach in rats that robustly attenuates aversive memories. This method consists of ‘deconditioning’ animals previously trained to associate a tone with a strong footshock by replacing it with a much weaker one during memory retrieval. Our results indicate that deconditioning-update is more effective than traditional extinction in reducing fear responses; moreover, such effects are long lasting and resistant to renewal and spontaneous recovery. Remarkably, this strategy overcame important boundary conditions for memory updating, such as remote or very strong traumatic memories. The same beneficial effect was found in other types of fear-related memories. Deconditioning was mediated by L-type voltage-gated calcium channels and is consistent with computational accounts of mismatch-induced memory updating. Our results suggest that shifting from fear to safety through deconditioning-update is a promising approach to attenuate traumatic memories.

Intensivierte Exposition zur Förderung des Inhibitionslernens bei Angststörungen

Zusammenfassung. Die Wirksamkeit von Expositionsverfahren bei Angststörungen ist hervorragend belegt. Dennoch profitieren viele Patient_innen nicht oder nicht ausreichend, was die Notwendigkeit zur Verbesserung der Verfahren deutlich macht. Vielversprechende Optimierungsstrategien lassen sich aus Modellen des Inhibitionslernens ableiten, andererseits aus der Beobachtung, dass die in expositionsbasierten klinischen Trials erreichten hohen Effektstärken in der Mehrzahl durch deutlich kürzere und intensivere Therapien verglichen mit der Routineversorgung erreicht werden. Der Forschungsverbund PROTECT-AD (Providing Tools for Effective Care and Treatment of Anxiety Disorders) untersucht in einer multizentrischen randomisierten Studie die Effekte einer intensivierten Expositionstherapie (Intensivierte psychotherapeutische Intervention, IPI) mit zeitlich ausgedehnter Selbstmanagementphase im Vergleich zu einem inhaltlich identischen, aber zeitlich gestreckten treatment as ususal (TAU) bei über 600 Patient_innen mit verschiedenen Angststörungen. Hier berichten wir, wie Intensivierung als Optimierungsstrategie therapeutisch umgesetzt werden kann. Unsere Erfahrungen zeigen, dass intensivierte Exposition von den Patient_innen sehr gut angenommen wird und eine Reihe praktischer und gesundheitsökonomischer Vorteile bieten kann.

Reactivation of the Unconditioned Stimulus Inhibits the Return of Fear Independent of Cortisol

Reconsolidation is the post-retrieval stabilization of memories, a time-limited process during which reactivated (i.e., retrieved) memories can be updated with new information, become stronger or weaker, depending on the specific treatment. We have previously shown that the stress hormone cortisol has an enhancing effect on the reconsolidation of fear memories in men. This effect was specific, i.e., limited to the conditioned stimulus (CS) that was reactivated, and did not generalize to other previously reinforced, but not reactivated CS. Based on these results, we suggested that cortisol plays a critical role in the continuous strengthening of reactivated emotional memories, contributing to their persistence and robustness. In the current study, we aimed to achieve a more generalized reconsolidation enhancement using an alternative reactivation method, i.e., by a low-intensity unconditioned stimulus (UCS) presentation instead of the more common unreinforced CS presentation. In previous studies, UCS reactivation was shown to lead to a more generalized reconsolidation effect. Therefore, we hypothesized that the combination of cortisol treatment and UCS reactivation would lead to an enhanced fear memory reconsolidation, which would generalize from previously reinforced CS to stimuli that resemble it. We tested 75 men in a 3-day fear conditioning paradigm: fear acquisition training on day 1; UCS reactivation/no reactivation and pharmacological treatment (20 mg hydrocortisone/placebo) on day 2; extinction training, reinstatement and test (of original and modified stimuli) on day 3. In contrast to our hypothesis, UCS reactivation prevented the return of fear [observed in skin conductance responses (SCR)] regardless of the pharmacological manipulation: while reinstatement to the original CS was found in the no-reactivation group, both reactivation groups (cortisol and placebo) showed no reinstatement. As the only methodological difference between our previous study and the current one was the reactivation method, we focus on UCS reactivation as the main explanation for these unexpected findings. We suggest that the robust prediction error generated by the UCS reactivation method (as opposed to CS reactivation), combined with the lower UCS intensity, has by itself weakened the emotional value of the UCS, thus preventing the return of fear to the CS that was associated with it. We call for future research to support these findings and to examine the potential of this reactivation method, or variations thereof, as a tool for therapeutic use.

Limited replicability of drug-induced amnesia after contextual fear memory retrieval in rats

With the ultimate goal of investigating boundary conditions for post-reactivation amnesia, we set out to replicate studies in which systemic, post-reactivation administration of midazolam, propranolol, or cycloheximide resulted in amnesia for contextual fear memories. Our experiments involved conceptual as well as exact replications of previously published studies. In most of our experiments, we adopted a procedure that conformed to the standard 3-day protocol typically used in the literature, with contextual fear conditioning on day 1, unreinforced re-exposure to the conditioning context followed by systemic injection of the amnestic drug on day 2, and a memory retention test on day 3. Given the plethora of successful studies with large effects sizes and the absence of any failed replications in the literature, we were surprised to find that we were generally unable to replicate those findings. Our results suggest that post-reactivation amnesia by systemic drug administration in rats is more difficult to obtain than what would be expected based on published empirical reports. At present, it remains unclear which conditions determine the success of this procedure.

Effect of d-cycloserine on fear extinction training in adults with social anxiety disorder

Preclinical and clinical data have shown that D-cycloserine (DCS), a partial agonist at the N-methyl-d-aspartate receptor complex, augments the retention of fear extinction in animals and the therapeutic learning from exposure therapy in humans. However, studies with non-clinical human samples in de novo fear conditioning paradigms have demonstrated minimal to no benefit of DCS. The aim of this study was to evaluate the effects of DCS on the retention of extinction learning following de novo fear conditioning in a clinical sample. Eighty-one patients with social anxiety disorder were recruited and underwent a previously validated de novo fear conditioning and extinction paradigm over the course of three days. Of those, only 43 (53%) provided analyzable data. During conditioning on Day 1, participants viewed images of differently colored lamps, two of which were followed by with electric shock (CS+) and a third which was not (CS-). On Day 2, participants were randomly assigned to receive either 50 mg DCS or placebo, administered in a double-blind manner 1 hour prior to extinction training with a single CS+ in a distinct context. Day 3 consisted of tests of extinction recall and renewal. The primary outcome was skin conductance response to conditioned stimuli, and shock expectancy ratings were examined as a secondary outcome. Results showed greater skin conductance and expectancy ratings in response to the CS+ compared to CS- at the end of conditioning. As expected, this difference was no longer present at the end of extinction training, but returned at early recall and renewal phases on Day 3, showing evidence of return of fear. In contrast to hypotheses, DCS had no moderating influence on skin conductance response or expectancy of shock during recall or renewal phases. We did not find evidence of an effect of DCS on the retention of extinction learning in humans in this fear conditioning and extinction paradigm.

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.

Threat Memory Reminder Under Matrix Metalloproteinase 9 Inhibitor Doxycycline Globally Reduces Subsequent Memory Plasticity

Associative memory can be rendered malleable by a reminder. Blocking the ensuing reconsolidation process is suggested as a therapeutic target for unwanted aversive memories. Matrix metalloproteinase-9 (MMP-9) is required for structural synapse remodeling involved in memory consolidation. Inhibiting MMP-9 with doxycycline is suggested to attenuate human threat conditioning. Here, we investigated whether MMP-9 inhibition also interferes with threat memory reconsolidation. Male and female human participants (N = 78) learned the association between two visual conditioned stimuli (CS⁺) and a 50% chance of an unconditioned nociceptive stimulus (US), and between CS^- and the absence of US. On day 7, one CS⁺ was reminded without reinforcement 3.5 h after ingesting either 200 mg of doxycycline or placebo. On day 14, retention of CS memory was assessed under extinction by fear-potentiated startle. Contrary to our expectations, we observed a greater CS⁺/CS^- difference in participants who were reminded under doxycycline compared with placebo. Participants who were reminded under placebo showed extinction learning during the retention test, which was not observed in the doxycycline group. There was no difference between the reminded and the nonreminded CS⁺ in either group. In contrast, during relearning after the retention test, the CS⁺/CS^- difference was more pronounced in the placebo group than in the doxycycline group. To summarize, a single dose of doxycycline before threat memory reminder appeared to have no specific impact on reconsolidation, but to globally impair extinction learning, and threat relearning, beyond drug clearance.SIGNIFICANCE STATEMENT Matrix metalloproteinase-9 inhibition appears to attenuate memory consolidation. It could also be a target for blocking reconsolidation. Here, we test this hypothesis in human threat conditioning. We find that doxycycline has no specific impact on a reminded cue, but confers a global reduction in extinction learning and threat learning beyond the clearance of the drug. This may point toward a more long-lasting impact of doxycycline treatment on memory plasticity.

The role of prediction error and memory destabilization in extinction of cued-fear within the reconsolidation window

Extinction of a cued-fear memory within the reconsolidation window has been proposed to prevent fear reacquisition by reconsolidation interference. This 'retrieval-extinction' procedure has received interest for its therapeutic potential to reduce the impact of fear memories on behavior. To fully exploit its therapeutic potential, it is critical to understand the mechanisms that underlie the 'retrieval-extinction' effect. If the effect depends upon reconsolidation of the original memory, then it would be predicted that destabilization, induced by prediction error, would be critical for observing the effect. Here, the dependency of the retrieval-extinction effect on memory destabilization or prediction error was investigated in pavlovian cued-fear conditioned adult male rats. The requirement for memory destabilization, and thus reconsolidation, for the retrieval-extinction effect was subsequently investigated using region-specific pharmacological blockade of dopamine D1-receptors. Intra-basolateral amygdala antagonism of dopamine D1-receptors did not prevent the reacquisition of fear associated with the retrieval-extinction procedure. The requirement for prediction error was assessed by using a reinforced or non-reinforced memory retrieval trial before extinction, compared to a no-retrieval, extinction-only control. Both the reinforced (no prediction error) and non-reinforced retrieval sessions led to a decrease in fear reacquisition, suggesting that engagement of prediction error does not influence the occurrence of retrieval-extinction. Together, these data suggest that retrieval-extinction does not require memory destabilization, since behavioral or pharmacological interventions that prevent destabilization did not disrupt any capacity to attenuate fear.

From Extinction Learning to Anxiety Treatment: Mind the Gap

Laboratory models of extinction learning in animals and humans have the potential to illuminate methods for improving clinical treatment of fear-based clinical disorders. However, such translational research often neglects important differences between threat responses in animals and fear learning in humans, particularly as it relates to the treatment of clinical disorders. Specifically, the conscious experience of fear and anxiety, along with the capacity to deliberately engage top-down cognitive processes to modulate that experience, involves distinct brain circuitry and is measured and manipulated using different methods than typically used in laboratory research. This paper will identify how translational research that investigates methods of enhancing extinction learning can more effectively model such elements of human fear learning, and how doing so will enhance the relevance of this research to the treatment of fear-based psychological disorders.

Interfering with emotional processing resources upon associative threat memory reactivation does not affect memory retention

Ample evidence suggests that memories enter a labile state upon retrieval, requiring reconsolidation processes in order to be retained. During this period of instability, various interventions can be applied to modify problematic memories. A novel behavioral intervention was designed, aimed at disrupting amygdala-based cognitive processing following the retrieval of a conditioned threat memory, in order to prevent its reconsolidation. We fear-conditioned participants on day 1, and reactivated their memory on day 2. Following reactivation, the reactivation plus emotional working memory task (R + EWMT) group completed an EWMT, while the reactivation only (RO) group served as a no-task control. On day 3, all participants were tested for memory retention, followed by a test for sensitivity to reinstatement. We observed successful acquisition and reactivation in fear-potentiated startle responding, skin conductance responding and US expectancies in both groups. Differential fear responding was fully preserved in the R + EWMT group relative to the RO group at the beginning of retention testing, and both groups were comparably sensitive to reinstatement. Thus, we failed to obtain any evidence that the execution of an EWMT after threat memory reactivation impairs reconsolidation. Further research is indicated to clarify whether threat memory reconsolidation can be disrupted by taxing relevant WM resources.

Propofol-induced deep sedation reduces emotional episodic memory reconsolidation in humans

The adjustment of maladaptive thoughts and behaviors associated with emotional memories is central to treating psychiatric disorders. Recent research, predominantly with laboratory animals, indicates that memories can become temporarily sensitive to modification following reactivation, before undergoing reconsolidation. A method to selectively impair reconsolidation of specific emotional or traumatic memories in humans could translate to an effective treatment for conditions such as posttraumatic stress disorder. We tested whether deep sedation could impair emotional memory reconsolidation in 50 human participants. Administering the intravenous anesthetic propofol following memory reactivation disrupted memory for the reactivated, but not for a non-reactivated, slideshow story. Propofol impaired memory for the reactivated story after 24 hours, but not immediately after propofol recovery. Critically, memory impairment occurred selectively for the emotionally negative phase of the reactivated story. One dose of propofol following memory reactivation selectively impaired subsequent emotional episodic memory retrieval in a time-dependent manner, consistent with reconsolidation impairment.

Current practices in meta-regression in psychology, education, and medicine

Having surveyed the history and methods of meta-regression in a previous paper, in this paper, we review which and how meta-regression methods are applied in recent research syntheses. To do so, we reviewed studies published in 2016 across four leading research synthesis journals: Psychological Bulletin, the Journal of Applied Psychology, Review of Educational Research, and the Cochrane Library. We find that the best practices defined in the previous review are rarely carried out in practice. In light of the identified discrepancies, we consider how to move forward, first by identifying areas where further methods development is needed to address persistent problems in the field and second by discussing how to more effectively disseminate points of methodological consensus.