Rewriting the valuation and salience of alcohol-related stimuli via memory reconsolidation

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

BACKGROUND

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

RESULTS

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

CONCLUSIONS

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

Requisite role of dorsal raphé in contextual cocaine-memory reconsolidation

Memory reconsolidation is a process by which labile drug memories are restabilized in long-term memory stores, permitting their enduring control over drug-seeking behaviors. In the present study, we investigated the involvement of the dorsal raphé nuclei (DRN) in cocaine-memory reconsolidation. Sprague-Dawley rats (male, female) were trained to self-administer cocaine in a distinct environmental context to establish contextual drug memories. They then received extinction training in a different context. Next, the rats were re-exposed to the cocaine-predictive context for 15 min to reactivate their cocaine memories or remained in their home cages (no-reactivation control). Memory reactivation was sufficient to increase c-Fos expression, an index of neuronal activation, in the DRN, but not in the median raphé nuclei, during reconsolidation, compared to no reactivation. To determine whether DRN neuronal activity was necessary for cocaine-memory reconsolidation, rats received intra-DRN baclofen plus muscimol (BM; GABAB/A agonists) or vehicle microinfusions immediately after or 6 h after a memory reactivation session conducted with or without lever access. The effects of DRN functional inactivation on long-term memory strength, as indicated by the magnitude of context-induced cocaine seeking, were assessed 72 h later. Intra-DRN BM treatment immediately after memory reactivation with or without lever access attenuated subsequent context-induced cocaine-seeking behavior, independent of sex. Conversely, BM treatment in the adjacent periaqueductal gray (PAG) immediately after memory reactivation, or BM treatment in the DRN 6 h after memory reactivation, did not alter responding. Together, these findings indicate that the DRN plays a requisite role in maintaining cocaine-memory strength during reconsolidation.

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.

The challenge of memory destabilisation: From prediction error to prior expectations and biomarkers

The re-ignition of memory reconsolidation research sparked by Karim Nader in the early 2000s led to great excitement that 'reconsolidation-based' interventions might be developed for mental health disorders such as post-traumatic stress disorder and substance use disorder. Two decades on, it is clear that reconsolidation-based interventions have been more challenging to translate to the clinic than initially thought. We argue that this challenge could be addressed with a better understanding of how prior expectations interact with information presented in a putative memory reactivation / cue reminder session, and through the identification of non-invasive biomarkers for memory destabilisation that would allow reminder sessions to be 'tuned' to enhance memory lability in an ad hoc manner.

New Approaches for Alcohol Use Disorder Treatment via Memory Retrieval and Reconsolidation Manipulations

Relapse to alcohol seeking and drinking is a major clinical challenge in alcohol use disorder and is frequently brought about by cue-induced craving, caused by exposure to cues that evoke alcohol-related memories. It has been postulated that memories become labile for manipulation shortly after their retrieval and then restabilize in a "memory reconsolidation" process. Disruption or 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 review literature demonstrating the capacity of behavioral or pharmacological manipulations to reduce relapse in animal models and humans when applied after a short retrieval of memories associated with alcohol, suggestively disrupting the reconsolidation of such memories. We suggest that while there is a clear potential of using post-retrieval manipulations to target specific relapse-evoking memories, future research should be more systematic, standardized, and translational. Specifically, we discuss several critical limitations and boundary conditions, which should be addressed to improve consistency and replicability in the field and lead to the development of an efficient reconsolidation-based relapse prevention therapy.

A critical perspective on updating drug memories through the integration of memory editing and brain stimulation

Addiction is a persistent, recurring condition characterized by repeated relapses despite the desire to control drug use or maintain sobriety. The attainment of abstinence is hindered by persistent maladaptive drug-associated memories, which drive drug-seeking and use behavior. This article examines the preliminary evidence supporting the combination of non-invasive brain stimulation (NIBS) techniques and memory editing (or reconsolidation) interventions as add-on forms of treatment for individuals with substance-related disorders (SUD). Studies have shown that NIBS can modestly reduce drug use and craving through improved cognitive control or other undetermined reasons. Memory reconsolidation, a process by which a previously consolidated memory trace can be made labile again, can potentially erase or significantly weaken SUD memories underpinning craving and the propensity for relapse. This approach conveys enthusiasm while also emphasizing the importance of managing boundary conditions and null results for interventions found on fear memory reconsolidation. Recent studies, which align with the state-dependency and activity-selectivity hypotheses, have shown that the combination of NIBS and behavioral interventions holds promise for treating SUD by reducing self-reported and physiological aspects of craving. Effective long-term outcomes for this procedure require better identification of critical memories, a deeper understanding of the brain mechanisms underlying SUD and memory reconsolidation and overcoming any boundary conditions of destabilized memories. This will enable the procedure to be personalized to the unique needs of individual patients.

The Treatment of Substance Use Disorders: Recent Developments and New Perspectives

Substance-related disorders are complex psychiatric disorders that are characterized by continued consumption in spite of harmful consequences. Addiction affects various brain networks critically involved in learning, reward, and motivation, as well as inhibitory control. Currently applied therapeutic approaches aim at modification of behavior that ultimately leads to decrease of consumption or abstinence in individuals with substance use disorders. However, traditional treatment methods might benefit from recent neurobiological and cognitive neuroscientific research findings. Novel cognitive-behavioral approaches in the treatment of addictive behavior aim at enhancement of strategies to cope with stressful conditions as well as craving-inducing cues and target erroneous learning mechanisms, including cognitive bias modification, reconsolidation-based interventions, mindfulness-based interventions, virtual-reality-based cue exposure therapy as well as pharmacological augmentation strategies. This review discusses therapeutic strategies that target dysregulated neurocognitive processes associated with the development and maintenance of disordered substance use and may hold promise as effective treatments for substance-related disorders.

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.

The effects of response inhibition training following binge memory retrieval in young adults binge eaters: a randomised-controlled experimental study

Binge eating is increasingly prevalent among adolescents and young adults and can have a lasting harmful impact on mental and physical health. Mechanistic insights suggest that aberrant reward-learning and biased cognitive processing may be involved in the aetiology of binge eating. We therefore investigated whether recently developed approaches to catalyse brief interventions by putatively updating maladaptive memory could also boost the effects of cognitive bias modification training on binge eating behaviour. A non-treatment-seeking sample of 90 binge eating young adults were evenly randomised to undergo either selective food response inhibition training, or sham training following binge memory reactivation. A third group received training without binge memory reactivation. Laboratory measures of reactivity and biased responses to food cues were assessed pre-post intervention and bingeing behaviour and disordered eating assessed up to 9 months post-intervention. The protocol was pre-registered at https://osf.io/82c4r/ . We found limited evidence of premorbid biased processing in lab-assessed measures of cognitive biases to self-selected images of typical binge foods. Accordingly, there was little evidence of CBM reducing these biases and this was not boosted by prior 'reactivation' of binge food reward memories. No group differences were observed on long-term bingeing behaviour, caloric consumption or disordered eating symptomatology. These findings align with recent studies showing limited impact of selective inhibition training on binge eating and do not permit conclusions regarding the utility of retrieval-dependent memory 'update' mechanisms as a treatment catalyst for response inhibition training.

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.

Exposure to Olfactory Alcohol Cues During Non-rapid Eye Movement Sleep Did Not Decrease Craving in Patients With Alcohol Dependence

BACKGROUND AND OBJECTIVES

Cue exposure therapy (CET) has been used to reduce alcohol use, but the effect of CET during sleep on alcohol dependence (AD) is unclear. The present study examined the effect of repeated exposure to an olfactory stimulus during non-rapid eye movement (NREM) sleep on cue reactivity and craving in patients with AD.

METHODS

Thirty-five patients with AD were enrolled according to the Diagnostic and Statistical Manual of Mental Disorders-IV (DSM-IV). All the subjects were randomly assigned to the experimental or control group. The experimental group was exposed to alcohol odor for 10 min during NREM sleep. The other group (controls) was exposed to water [control stimulus (CtrS)] for 10 min during NREM sleep. Demographic, alcohol-related, and clinical characteristics were collected at baseline. A cue-reactivity test was conducted before and after exposure to evaluate the effect of memory manipulation on acute response to an alcohol stimulus.

RESULTS

There were no significant time × group interactions according to the visual analog scale (VAS) score of craving intensity, skin conductance response (SCR), systolic blood pressure (SBP), and diastolic blood pressure (DBP; all p > 0.05). Two-way ANOVA showed significant main effects of time on SCR [F _(1,33) = 4.453, p = 0.043], SBP [F _(1,33) = 14.532, p = 0.001], DBP [F _(1,33) = 8.327, p = 0.007], Craving-VAS [F _(1,33) = 1.997, p = 0.167] in two groups.

CONCLUSION

Exposure to olfactory alcohol cues during NREM sleep had no significant effect on alcohol craving in subjects with AD during hospitalization.

Long-term behavioural rewriting of maladaptive drinking memories via reconsolidation-update mechanisms

BACKGROUND

Alcohol use disorders can be conceptualised as a learned pattern of maladaptive alcohol-consumption behaviours. The memories encoding these behaviours centrally contribute to long-term excessive alcohol consumption and are therefore an important therapeutic target. The transient period of memory instability sparked during memory reconsolidation offers a therapeutic window to directly rewrite these memories using targeted behavioural interventions. However, clinically-relevant demonstrations of the efficacy of this approach are few. We examined key retrieval parameters for destabilising naturalistic drinking memories and the ability of subsequent counterconditioning to effect long-term reductions in drinking.

METHODS

Hazardous/harmful beer-drinking volunteers (N = 120) were factorially randomised to retrieve (RET) or not retrieve (No RET) alcohol reward memories with (PE) or without (No PE) alcohol reward prediction error. All participants subsequently underwent disgust-based counterconditioning of drinking cues. Acute responses to alcohol were assessed pre- and post-manipulation and drinking levels were assessed up to 9 months.

RESULTS

Greater long-term reductions in drinking were found when counterconditioning was conducted following retrieval (with and without PE), despite a lack of short-term group differences in motivational responding to acute alcohol. Large variability in acute levels of learning during counterconditioning was noted. 'Responsiveness' to counterconditioning predicted subsequent responses to acute alcohol in RET + PE only, consistent with reconsolidation-update mechanisms.

CONCLUSIONS

The longevity of behavioural interventions designed to reduce problematic drinking levels may be enhanced by leveraging reconsolidation-update mechanisms to rewrite maladaptive memory. However, inter-individual variability in levels of corrective learning is likely to determine the efficacy of reconsolidation-updating interventions and should be considered when designing and assessing interventions.

Memory destabilization during reconsolidation: a consequence of homeostatic plasticity?

Remembering is not a static process: When retrieved, a memory can be destabilized and become prone to modifications. This phenomenon has been demonstrated in a number of brain regions, but the neuronal mechanisms that rule memory destabilization and its boundary conditions remain elusive. Using two distinct computational models that combine Hebbian plasticity and synaptic downscaling, we show that homeostatic plasticity can function as a destabilization mechanism, accounting for behavioral results of protein synthesis inhibition upon reactivation with different re-exposure times. Furthermore, by performing systematic reviews, we identify a series of overlapping molecular mechanisms between memory destabilization and synaptic downscaling, although direct experimental links between both phenomena remain scarce. In light of these results, we propose a theoretical framework where memory destabilization can emerge as an epiphenomenon of homeostatic adaptations prompted by memory retrieval.

Positive and Neutral Updating Reconsolidate Aversive Episodic Memories via Different Routes

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

Disruption of relapse to alcohol seeking by aversive counterconditioning following memory retrieval

Relapse to alcohol abuse is often caused by exposure to potent alcohol-associated cues. Therefore, disruption of the cue-alcohol memory can prevent relapse. It is believed that memories destabilize and become prone for updating upon their reactivation through retrieval and then restabilize within 6 h during a "reconsolidation" process. We recently showed that relapse to cocaine seeking in a place-conditioning paradigm could be prevented by counterconditioning the cocaine cues with aversive outcomes following cocaine-memory retrieval. However, to better model addiction-related behaviors, self-administration models are necessary. Here, we demonstrate that relapse to alcohol seeking can be prevented by aversive counterconditioning conducted during alcohol-memory reconsolidation, in the place conditioning and operant self-administration paradigms, in mice and rats, respectively. We found that the reinstatement of alcohol-conditioned place preference was abolished only when aversive counterconditioning with water flooding was given shortly after alcohol-memory retrieval. Furthermore, rats trained to lever press for alcohol showed decreased context-induced renewal of alcohol-seeking responding when the lever pressing was punished with foot-shocks, shortly, but not 6 h, after memory retrieval. These results suggest that aversive counterconditioning can prevent relapse to alcohol seeking only when performed during alcohol-memory reconsolidation, presumably by updating, or replacing, the alcohol memory with aversive information. Finally, we found that aversive counterconditioning preceded by alcohol-memory retrieval was characterized by the upregulation of brain-derived neurotrophic factor (Bdnf) mRNA expression in the medial prefrontal cortex, suggesting that BDNF may play a role in the memory updating process.

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.

Instrumental and Pavlovian Mechanisms in Alcohol Use Disorder

Purpose of Review

Current theories of alcohol use disorders (AUD) highlight the importance of Pavlovian and instrumental learning processes mainly based on preclinical animal studies. Here, we summarize available evidence for alterations of those processes in human participants with AUD with a focus on habitual versus goal-directed instrumental learning, Pavlovian conditioning, and Pavlovian-to-instrumental transfer (PIT) paradigms.

Recent Findings

The balance between habitual and goal-directed control in AUD participants has been studied using outcome devaluation or sequential decision-making procedures, which have found some evidence of reduced goal-directed/model-based control, but little evidence for stronger habitual responding. The employed Pavlovian learning and PIT paradigms have shown considerable differences regarding experimental procedures, e.g., alcohol-related or conventional reinforcers or stimuli.

Summary

While studies of basic learning processes in human participants with AUD support a role of Pavlovian and instrumental learning mechanisms in the development and maintenance of drug addiction, current studies are characterized by large variability regarding methodology, sample characteristics, and results, and translation from animal paradigms to human research remains challenging. Longitudinal approaches with reliable and ecologically valid paradigms of Pavlovian and instrumental processes, including alcohol-related cues and outcomes, are warranted and should be combined with state-of-the-art imaging techniques, computational approaches, and ecological momentary assessment methods.

Profiles of patients with cocaine and alcohol use disorder based on cognitive domains and their relationship with relapse

BACKGROUND

Relapse in drug use constitutes a research topic on addiction that is relevant for understanding both the addictive process and its clinical implications. The objective of this study was to explore if it is possible to identify patient profiles according to their performance on cognitive tasks whilst examining the relationship between such profiles and relapse.

METHODS

The sample consisted of 222 patients with dependence on cocaine and / or alcohol, of which 86 % were men. Cognitive domains related to salience, decision- making, and emotional processing were measured.

RESULTS

Latent class analysis revealed three patient profiles that differ in terms of performance on cognitive tasks. Two of these profiles are clearly differentiated in terms of their execution of the impulsive decision-making task. The third patient profile, unlike the latter two, is composed of patients with severe alterations in the three domains evaluated. Analysis revealed that patients in Profile 3 are those with the highest rates of relapse in cocaine (Profile 1 = 40.3 %; Profile 2 = 35.6 %; Profile 3 = 69.2 %; Chi2 = 9.169; p < .05) and cocaine and alcohol use (Profile 1 = 55.1 %; Profile 2 = 54.1 %; Profile 3 = 80 %; Chi2 = 6.698; p < .05).

CONCLUSIONS

The results support the postulates of the I-RISA model. From a clinical perspective, these findings highlight the need for a comprehensive evaluation of the cognitive domains involved in addiction.

An assessment of rapamycin for weakening binge-eating memories via reconsolidation: a pre-registered, double-blind randomised placebo-controlled experimental study

BACKGROUND

Maladaptive learning linking environmental food cues to high-palatability food reward plays a central role in overconsumption in obesity and binge eating disorders. The process of memory reconsolidation offers a mechanism to weaken such learning, potentially ameliorating over-eating behaviour. Here we investigated whether putatively interfering with synaptic plasticity using the mammalian target of rapamycin (mTOR) inhibitor, rapamycin, could weaken retrieved chocolate reward memories through blockade of reconsolidation.

METHODS

Seventy five healthy volunteers with a tendency to binge eat chocolate were randomised to retrieve chocolate reward memory under 10 mg rapamycin (RET + RAP, active condition), or placebo (RET + PBO), or they received 10 mg rapamycin without subsequent retrieval (NO RET + RAP). Indices of chocolate reward memory strength were assessed one week pre and post manipulation and at one month follow-up.

RESULTS

Contrary to hypotheses, the RET + RAP group did not show any greater reduction than control groups on indices of motivational salience of chocolate cues, motivation to consume chocolate or liking of chocolate. Mild evidence of improvement in the RET + RAP group was found, but this was limited to reduced chocolate binge episodes and improved healthy food choices.

CONCLUSIONS

We did not find convincing evidence of comprehensive naturalistic chocolate reward memory reconsolidation blockade by rapamycin. The effects on chocolate bingeing and food choices may warrant further investigation. These limited positive findings may be attributable to insufficient interference with mTOR signalling with 10 mg rapamycin, or failure to destabilise chocolate memories during retrieval.

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.

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.

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.

Behavioral tagging underlies memory reconsolidation

Memory reconsolidation occurs when a retrieving event destabilizes transiently a consolidated memory, triggering thereby a new process of restabilization that ensures memory persistence. Although this phenomenon has received wide attention, the effect of new information cooccurring with the reconsolidation process has been less explored. Here we demonstrate that a memory-retrieving event sets a neural tag, which enables the reconsolidation of memory after binding proteins provided by the original or a different contiguous experience. We characterized the specific temporal window during which this association is effective and identified the protein kinase A (PKA) and the extracellular signal-regulated kinase 1 and 2 (ERK 1/2) pathways as the mechanisms related to the setting of the reconsolidation tag and the synthesis of proteins. Our results show, therefore, that memory reconsolidation is mediated by a "behavioral tagging" process, which is common to different memory forms. They represent a significant advance in understanding the fate of memories reconsolidated while being adjacent to other events, and provide a tool for designing noninvasive strategies to attenuate (pathological/traumatic) or improve (education-related) memories.

Memory biases in alcohol use disorder: enhanced memory for contexts associated with alcohol prospectively predicts alcohol use outcomes

Memory for prior drinking experiences may powerfully drive later alcohol use in familiar drinking contexts, yet we know little about what patients with alcohol use disorder (AUD) remember of alcohol-related episodes. Although animal and theoretical models of addiction emphasize the importance of different memory systems for understanding maladaptive use, clinical research parsing what AUD patients remember from alcohol-related episodes is lacking. The current study applied a novel memory task in which moderate drinkers (N = 30) and treatment-seeking individuals with alcohol use disorder (AUD: N = 29) encoded associations between photographs of objects (alcoholic beverages and neutral items) and photographs of neutral scenes. At least 24 h later, two types of memory were assessed: item memory (object recognition) and associative memory (cued recognition of scenes associated with objects). To assess which memories predicted drinking, real-world behavior was assessed in patients with AUD at baseline and for 4 weeks following memory tests. Despite demographic differences, the results showed broadly impaired item memory in AUD compared with moderate drinkers (p < 0.001), but enhanced associative memory for scenes paired with alcohol (p = 0.015). These associative memory biases were especially pronounced for stimuli rated as more affectively salient. Furthermore, stronger but less detailed memory for alcohol-related associations (i.e., choosing the correct scene but the incorrect photograph) significantly predicted heavier baseline (p = 0.002) and higher subsequent (p = 0.01) drinking in patients with AUD. These findings reveal a novel alcohol-related memory bias in AUD, and uncover the importance of associative memory for understanding real-world heavy alcohol use.

Glutamatergic basolateral amygdala to anterior insular cortex circuitry maintains rewarding contextual memory

Findings have shown that anterior insular cortex (aIC) lesions disrupt the maintenance of drug addiction, while imaging studies suggest that connections between amygdala and aIC participate in drug-seeking. However, the role of the BLA → aIC pathway in rewarding contextual memory has not been assessed. Using a cre-recombinase under the tyrosine hydroxylase (TH+) promoter mouse model to induce a real-time conditioned place preference (rtCPP), we show that photoactivation of TH+ neurons induced electrophysiological responses in VTA neurons, dopamine release and neuronal modulation in the aIC. Conversely, memory retrieval induced a strong release of glutamate, dopamine, and norepinephrine in the aIC. Only intra-aIC blockade of the glutamatergic N-methyl-D-aspartate receptor accelerated rtCPP extinction. Finally, photoinhibition of glutamatergic BLA → aIC pathway produced disinhibition of local circuits in the aIC, accelerating rtCPP extinction and impairing reinstatement. Thus, activity of the glutamatergic projection from the BLA to the aIC is critical for maintenance of rewarding contextual memory.

Memory Retrieval-Extinction Combined With Virtual Reality Reducing Drug Craving for Methamphetamine: Study Protocol for a Randomized Controlled Trial

BACKGROUND

Relapse, often precipitated by drug-associated cues that evoke craving, is a key problem in the treatment of methamphetamine use disorder (MUD). Drug-associated memories play a major role in the maintenance of relapse. Extinction training is a common method for decreasing drug craving by suppressing drug-associated memories. However, the effects are often not permanent, which is evident in form of spontaneous recovery or renewal of cue-elicited responses. Based on memory reconsolidation theory, the retrieval-extinction (R-E) paradigm may be more effective in decreasing spontaneous recovery or renewal responses than extinction. After the original memory reactivated to a labile state, extinction will be introduced within the reconsolidation window, thereby updating drug-associated memories. However, there are still some controversial results, which suggest that the reactivation of drug-associated memories and the 10 min-6 h of limited time window are two main elements in the R-E protocol. Virtual reality (VR) is supposed to promote memory reactivation by providing vivid drug-related stimuli when compared with movies.

OBJECTIVE

The aim of this study is to examine the effectiveness of R-E training combined with VR on reducing spontaneous recovery or renewal of cue-elicited responses, in comparison to extinction, R-E training provided outside the time window of 6 h and R-E training retrieved using videos, in methamphetamine abusers.

METHODS

The study is a parallel matched controlled study including 95 participants with MUD. Participants will be randomly assigned to either a R-10 min-E group (methamphetamine-related cues retrieval in VR followed by extinction after 10 min) or a NR-10 min-E group (neutral cues retrieval in VR followed by extinction after 10 min) or a R-6 h-E group (methamphetamine-related cues retrieval in VR followed by extinction after 6 h) or a RV-10 min-E group (methamphetamine-related cues retrieval in videos followed by extinction after 10 min). Cue-evoked craving and reactivity will be assessed at pre-test and at 1 day, 1 week, 1 month, and 6-month post-tests.

DISCUSSION

To our knowledge, this study will probably be the first study to examine the efficacy of R-E training combined with VR to reduce cue-evoked responses in people with MUD. This innovative non-pharmacological intervention targeting drug-associated memories may provide significant clinical implications for reducing relapse, providing the study confirms its efficacy.

CLINICAL TRIAL REGISTRATION

The trial is registered with Chinese Clinical Trial Registry at 17 October 2018, number: ChiCTR1800018899, URL: http://www.chictr.org.cn/showproj.aspx?proj=30854.

Evidence for incentive salience sensitization as a pathway to alcohol use disorder

The incentive salience sensitization (ISS) theory of addiction holds that addictive behavior stems from the ability of drugs to progressively sensitize the brain circuitry that mediates attribution of incentive salience (IS) to reward-predictive cues and its behavioral manifestations. In this article, we establish the plausibility of ISS as an etiological pathway to alcohol use disorder (AUD). We provide a comprehensive and critical review of evidence for: (1) the ability of alcohol to sensitize the brain circuitry of IS attribution and expression; and (2) attribution of IS to alcohol-predictive cues and its sensitization in humans and non-human animals. We point out gaps in the literature and how these might be addressed. We also highlight how individuals with different alcohol subjective response phenotypes may differ in susceptibility to ISS as a pathway to AUD. Finally, we discuss important implications of this neuropsychological mechanism in AUD for psychological and pharmacological interventions attempting to attenuate alcohol craving and cue reactivity.

Ketamine can reduce harmful drinking by pharmacologically rewriting drinking memories

Maladaptive reward memories (MRMs) are involved in the development and maintenance of acquired overconsumption disorders, such as harmful alcohol and drug use. The process of memory reconsolidation - where stored memories become briefly labile upon retrieval - may offer a means to disrupt MRMs and prevent relapse. However, reliable means for pharmacologically weakening MRMs in humans remain elusive. Here we demonstrate that the N-methyl D-aspartate (NMDA) antagonist ketamine is able to disrupt MRMs in hazardous drinkers when administered immediately after their retrieval. MRM retrieval + ketamine (RET + KET) effectively reduced the reinforcing effects of alcohol and long-term drinking levels, compared to ketamine or retrieval alone. Blood concentrations of ketamine and its metabolites during the critical ‘reconsolidation window’ predicted beneficial changes only following MRM reactivation. Pharmacological reconsolidation interference may provide a means to rapidly rewrite maladaptive memory and should be further pursued in alcohol and drug use disorders.

Memories linking environmental cues to alcohol reward are involved in the development and maintenance of heavy drinking. Here, the authors show that a single dose of ketamine, given after retrieval of alcohol-reward memories, disrupts the reconsolidation of these memories and reduces drinking in humans.

Addiction-Focused Eye Movement Desensitization and Reprocessing Therapy as an Adjunct to Regular Outpatient Treatment for Alcohol Use Disorder: Results From a Randomized Clinical Trial

BACKGROUND

This study examined the feasibility, safety, and efficacy of addiction-focused eye movement desensitization and reprocessing (AF-EMDR) treatment, as an add-on intervention to treatment as usual (TAU).

METHODS

Adult outpatients with alcohol use disorder (AUD) (N = 109) who already received or had just started with TAU (Community Reinforcement Approach) were recruited at 6 outpatient addiction care facilities. They were randomly assigned to either TAU + 7 weekly 90-minute sessions of AF-EMDR (N = 55) or TAU-only (N = 54). Assessments were made at baseline, after AF-EMDR therapy (+ 8 weeks in the TAU-only group), and at 1- and 6-month follow-up. The primary outcomes were changes in drinking behavior as reported by the participant and biomarker indices.

RESULTS

Data were analyzed as intent-to-treat with linear mixed models. Additionally, sensitivity analyses were performed. No group or interaction effects were found for any of the outcome variables. Only limited change over time was seen with regard to indices of personal and societal recovery and in some secondary indices of clinical recovery (craving, desire thinking, and rumination). Reliable Change Index calculations showed that more TAU-only participants showed clinical improvement with regard to alcohol consumption while a somewhat higher proportion of participants in the TAU + AF-EMDR group experienced less craving. The acceptability, safety, and feasibility of the treatments received in both groups were comparable.

CONCLUSIONS

There was no add-on effect of AF-EMDR on TAU with regard to drinking behavior in outpatients with an AUD. Possible explanations are discussed. Future studies should first establish proof of principle regarding the potential of AF-EMDR therapy to disrupt operant learning and habits relevant in addiction.

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.

A virtual reality counterconditioning procedure to reduce methamphetamine cue-induced craving

The present work developed a virtual reality (VR) counterconditioning procedure (VRCP), and investigated its efficacy in treatment of cue-induced craving in individuals with methamphetamine (METH) dependence. In study 1, thirty-one patients diagnosed with METH dependence received VRCP, while twenty-nine METH-dependent patients in waiting-list group did not. In study 2, the VRCP was computerized as a VR treatment system. Six-hundred and twelve abstinent individuals with a history of METH dependence received the computerized VRCP, while two-hundred seventy-six abstinent individuals with a history of METH dependence in waiting-list group did not. Patients with METH dependence who received VRCP showed a significantly larger decrease on the score of METH-craving and METH-liking from baseline to follow-up assessments, compared to those who did not received VRCP. Participants received VRCP showed a significantly larger decrease in HRV indexes on time domain and non-linear domain from baseline to follow-up assessments during exposure to VR cues, compared to those in waiting-list group. These findings indicate that the counterconditioning procedure under VR environment may be a useful strategy in suppressing cue-induced reactivity for patients with METH dependence.

Resistance to fear memory destabilization triggers exaggerated emotional-like responses following memory reactivation

Fear memory reactivation does not always lead to memory destabilization-reconsolidation. For instance, fear memories formed following withdrawal from chronic ethanol consumption or a stressful event are less likely to become destabilized after reactivation, with the effect of recall of these memories on the affective state still requiring elucidation. Here, we investigated the negative emotional-like responses following fear memory reactivation in ethanol-withdrawn (ETOH) rats by focusing on the possible role played by destabilization. Our findings indicated that ETOH rats displayed an increased freezing in a novel context and an anxiogenic-like response in the elevated plus maze (EPM) following memory reactivation, whereas the behavior of CON animals was not affected. The destabilization blockade by pre-reactivation nimodipine (16 mg/kg, s.c) administration promoted in CON animals a similar behavior in the EPM and in a novel environment as that exhibited by ETOH rats after the reminder. Moreover, facilitating destabilization by pre-reactivation d-cycloserine (5 mg/kg, i.p) administration prevented the emotional-like disturbances observed in ETOH rats. Finally, using restraint stress, which is also an inductor of a fear memory resistant to destabilization, an increased fear response in an unconditioned environment and an anxiogenic-like state was also found after the presentation of the fear reminder in stressed rats. Our results suggest that, in the context of resistant fear memories, the occurrence of destabilization influences how animals respond to subsequent environmental challenges following reactivation.

Counterconditioning following memory retrieval diminishes the reinstatement of appetitive memories in humans

Appetitive memories play a crucial role in learning and behavior, but under certain circumstances, such memories become maladaptive and play a vital role in addiction and other psychopathologies. Recent scientific research has demonstrated that memories can be modified following their reactivation through memory retrieval in a process termed memory reconsolidation. Several nonpharmacological behavioral manipulations yielded mixed results in their capacity to alter maladaptive memories in humans. Here, we aimed to translate the promising findings observed in rodents to humans. We constructed a novel three-day procedure using aversive counterconditioning to alter appetitive memories after short memory retrieval. On the first day, we used appetitive conditioning to form appetitive memories. On the second day, we retrieved these appetitive memories in one group (Retrieval group) but not in a second group. Subsequently, all participants underwent counterconditioning. On the third day, we attempted to reinstate the appetitive memories from day one. We observed a significant reduction in the reinstatement of the original appetitive memory when counterconditioning was induced following memory retrieval. Here, we provide a novel human paradigm that models several memory processes and demonstrate memory attenuation when counterconditioned after its retrieval. This paradigm can be used to study complex appetitive memory dynamics, e.g., memory reconsolidation and its underlying brain mechanisms.

Differential effects of unipolar versus bipolar depression on episodic memory updating

Episodic memories, when reactivated, can be modified or updated by new learning. Since such dynamic memory processes remain largely unexplored in psychiatric disorders, we examined the impact of depression on episodic memory updating. Unipolar and bipolar depression patients, and age/education matched controls, first learned a set of objects (List-1). Two days later, participants in all three groups were either reminded of the first learning session or not followed by the learning of a new set of objects (List-2). Forty-eight hours later, List-1 recall was impaired in unipolar and bipolar patients compared to control participants. Further, as expected, control participants who received a reminder spontaneously recalled items from List-2 during recall of List-1, indicative of an updated List-1 memory. Such spontaneous intrusions were also seen in the unipolar and bipolar patients that received the reminder, suggesting that memory updating was unaffected in these two patient groups despite impaired recall of List 1. Unexpectedly, we observed a trend towards higher intrusions, albeit statistically insignificant, not only in the reminder but also in the no-reminder subgroups of bipolar patients. We probed this further in a second cohort by testing recall of List-2, which was also impaired in both depression groups. Again bipolar patients showed intrusions, but this time in the reverse order from List-1 into List-2, independent of a reminder. Taken together, despite impaired recall, updating of episodic memories was intact and unidirectional in unipolar depression. In contrast, indiscriminate updating, as evidenced by bidirectional interference between episodic memories, was seen in bipolar depression. These findings reveal a novel distinction between unipolar versus bipolar depression using a reactivation-dependent memory updating paradigm.

Relevance of ERK1/2 Post-retrieval Participation on Memory Processes: Insights in Their Particular Role on Reconsolidation and Persistence of Memories

Back in 1968, Misanin and his group posited that reactivation of consolidated memories could support changes in that trace, similar to what might happen during the consolidation process. Not until 2000, when Nader et al. (2000) studied the behavioral effect of a protein synthesis inhibitor on retrieved memories, could this previous statement be taken under consideration once again; suggesting that consolidated memories can become labile after reactivation. The process of strengthening after memory labilization was named memory reconsolidation. In recent years, many studies pointed towards a critical participation of the extracellular signal-regulated kinase (ERK)/mitogen activated protein kinases (MAPKs) pathway in different memory processes (e.g., consolidation, extinction, reconsolidation, among others). In this review article, we will focus on how this system might be modulating the processes triggered after retrieval of well-consolidated memories in mice.

Prospects for reconsolidation-focused treatments of substance use and anxiety-related disorders

Memories are often conceptualized as permanent entities; however, retrieval of memories via stimulus prompts can return them to an active state, which initiates a period of lability before the memories are reconsolidated into long-term storage. Importantly, during this period, memories can be disrupted/altered. A growing body of work has focused on translating animal and experimental science into reconsolidation-based interventions for clinical disorders maintained by maladaptive memories. Interventions targeting reward-based and fear-based memories undergirding substance use and anxiety-related disorders, respectively, have shown significant potential. There are several promising pharmacological agents and behavioral approaches that have been used to therapeutically target memory reconsolidation. Here, we discuss the current state of science with special emphasis on the clinical utility of these approaches.

Post Traumatic Stress Disorder and Substance Use Disorder as Two Pathologies Affecting Memory Reactivation: Implications for New Therapeutic Approaches

In the present review, we provide evidence indicating that although post traumatic stress disorder (PTSD) and substance use disorder (SUD) are two distinct pathologies with very different impacts on people affected by these chronic illnesses, they share numerous common characteristics, present high rates of co-morbidity, and may result from common physiological dysfunctions. We propose that these pathologies result from hyper reactivity to reminders, and thus should be considered as two disorders of memory, treated as such. We review the different possibilities to intervene on pathological memories such as extinction therapy and reconsolidation blockade. We also introduce new therapeutic avenues directly indicate by our recent proposal to replace the consolidation/reconsolidation hypothesis by the integration concept. State dependency and emotional remodeling are two innovative treatments that have already provided encouraging results. In summary, this review shows that the discovery of reactivation-dependent memory malleability has open new therapeutic avenues based on the reprocessing of pathological memories, which constitute promising approaches to treat PTSD and SUD.

Advances in behavioral animal models of alcohol use disorder

Alcohol use disorder (AUD) is a multifaceted neuropsychiatric disease that combines behavioral, psychosocial, and neurobiological aspects. Over the previous decade, animal models have advanced in modeling the major psychological constructs that characterize AUD. These advances pave the road for more sophisticated behavioral models that capture addiction-related aspects, such as alcohol craving, compulsive seeking and intake, dependence, and relapse. In this review, we survey the recent progress in behavioral animal modeling of five aspects of AUD: alcohol consumption, dependence, and seeking; compulsivity in alcohol intake despite adverse outcomes; vulnerability and resilience factors in alcohol addiction; relapse despite treatment; and relapse prevention by manipulating alcohol-associated memory reconsolidation. These advances represent a general attempt to grasp the complexity and multidimensional nature of AUD, and to focus on behavioral characteristics that better reflect and model this disorder.

A New Measure for Assessing the Intensity of Addiction Memory in Illicit Drug Users: The Addiction Memory Intensity Scale

Disrupting the process of memory reconsolidation could be a promising treatment for addiction. However, its application may be constrained by the intensity of addiction memory. This study aimed to develop and initially validate a new measure, the Addiction Memory Intensity Scale (AMIS), for assessing the intensity of addiction memory in illicit drug users. Two studies were conducted in China for item analysis (n = 345) and initial validation (n = 1550) of the AMIS. The nine-item AMIS was found to have two factors (labelled Visual Clarity and Other Sensory Intensity), which accounted for 64.11% of the total variance. The two-factor structure provided a reasonable fit for sample data and was invariant across groups of different genders and different primary drugs of use. Significant correlations were found between scores on the AMIS and the measures of craving. The AMIS and its factors showed good internal consistency (Cronbach's α: 0.72⁻0.89) and test-retest reliability (r: 0.72⁻0.80). These results suggest that the AMIS, which demonstrates an advantage as it is brief and easy to administer, is a reliable and valid tool for measuring the intensity of addiction memory in illicit drug users, and has the potential to be useful in future clinical research.

The top-down regulation from the prefrontal cortex to insula via hypnotic aversion suggestions reduces smoking craving

Hypnosis has been shown to have treatment effects on nicotine addiction. However, the neural basis of these effects is poorly understood. This preliminary study investigated the neural mechanisms of hypnosis-based treatment on cigarette smoking, specifically, whether the hypnosis involves a top-down or bottom-up mechanism. Two groups of 45 smokers underwent a smoking aversion suggestion and viewed smoking-related pictures and neutral pictures. One group underwent functional magnetic resonance imaging scanning twice (control and hypnotic states), whereas the other group underwent two electroencephalograph sessions. Our study found that self-reported smoking craving decreased in both groups following hypnosis. Smoking cue-elicited activations in the right dorsal lateral prefrontal cortex (rDLPFC) and left insula (lI) and the functional connectivity between the rDLPFC and lI were increased in the hypnotic state compared with the control state. The delta band source waveforms indicated the activation from 390 to 862 ms at the rDLPFC and from 490 to 900 ms at the lI was significantly different between the smoking and neutral conditions in the hypnotic state, suggesting the activation in the rDLPFC preceded that in the lI. These results suggest that the decreased smoking craving via hypnotic aversion suggestions may arise from the top-down regulation of the rDLPFC to the lI. Our findings provide novel neurobiological evidence for understanding the therapeutic effects of hypnosis on nicotine addiction, and the prefrontal-insula circuit may serve as an imaging biomarker to monitor the treatment efficacy noninvasively.

Memory integration: An alternative to the consolidation/reconsolidation hypothesis

The original concept of consolidation considers that memory requires time to be fixed. Since 2000, a comparable protein-dependent re-stabilization phase, called reconsolidation, has been assumed to take place after memory retrieval. This consolidation/reconsolidation hypothesis, has dominated the literature for more than 50 years, despite compelling evidence that is inconsistent with it. In this review, we present an historical overview and explain how, despite serious criticisms, this hypothesis has persisted for decades and become accepted as a dogma. Based on both older and more recent evidence, we next propose the concept of memory integration which involves the linkage or embedding of new material into an already existing representation. We believe integration provides a viable explanation for retrograde amnesia in place of the consolidation/reconsolidation hypothesis. Integration can further be the basis for several major cases of memory alteration such as time dependent memory enhancement, interference, counter-conditioning, updating and other instances of memory malleability. In a final section we consider the implications this new concept may have for memory processes and its translational applications.

Modulation of naturalistic maladaptive memories using behavioural and pharmacological reconsolidation-interfering strategies: a systematic review and meta-analysis of clinical and 'sub-clinical' studies

BACKGROUND

Consolidated memories can undergo enduring modification through retrieval-dependent treatments that modulate reconsolidation. This represents a potentially transformative strategy for weakening or overwriting the maladaptive memories that underlie substance use and anxiety/trauma-related disorders. However, modulation of naturalistic maladaptive memories may be limited by 'boundary conditions' imposed on the reconsolidation process by the nature of these memories.

METHODS

We conducted a systematic review and meta-analyses of behavioural and pharmacological studies examining retrieval-dependent modulation of reward- and threat-related memories in (sub) clinical substance use and anxiety/trauma, respectively.

RESULTS

Of 4938 publications assessed for eligibility, 8 studies of substance use and 10 of anxiety (phobia)- and trauma-related symptoms were included in the meta-analyses. Overall, the findings were in the predicted direction, with most studies favouring the 'retrieval + treatment' condition. However, the magnitude of effects was dependent upon the nature of treatment, with pharmacological interventions showing a medium-sized effect (g = 0.59, p = 0.03) and behavioural treatments, a relatively small effect (g = 0.32, p = 0.10) in studies of phobia/trauma. Among studies of substance use, post-retrieval behavioural interventions yielded a larger effect (g = 0.60, p < 0.001) relative to pharmacological treatments (g = - 0.03, p = 0.91), with treatment type being a statistically significant moderator (χ2(1) = 4.20, p = 0.04).

CONCLUSION

Modification of naturalistic maladaptive memories during reconsolidation appears to be a viable treatment strategy for substance use and phobias/trauma disorders. However, high levels of heterogeneity and methodological variation limit the strength of conclusions that can be drawn from the reviewed studies at this stage.

Positive emotional induction interferes with the reconsolidation of negative autobiographical memories, in women only

After reactivation, a previously consolidated memory can enter into a labile state followed by a re-stabilization process defined as reconsolidation. The aim of this study was to explore whether an existing negative autobiographical memory can be modified by using a non-invasive interference (audiovisual positive preparation) after reactivation and to determine if this effect could be dependent on the reconsolidation process. We found that the presentation of a positive inductor after a negative autobiographical memory reactivation may lead to a change in the emotional information of the original trace and that such effect can be mediated by the reconsolidation process. The modification of the memory has been shown in women only. These results suggest that a positive audiovisual induction may play a potential role in psychotherapeutic techniques for the modification of dysfunctional autobiographical memories.

Nitrous oxide may interfere with the reconsolidation of drinking memories in hazardous drinkers in a prediction-error-dependent manner

Weakening drinking-related reward memories by blocking their reconsolidation is a potential novel strategy for treating alcohol use disorders. However, few viable pharmacological options exist for reconsolidation interference in humans. We therefore examined whether the NMDA receptor antagonising gas, Nitrous Oxide (N₂O) could reduce drinking by preventing the post-retrieval restabilisation of alcohol memories in a group of hazardous drinkers. Critically, we focussed on whether prediction error (PE; a key determinant of reconsolidation) was experienced at retrieval. Sixty hazardous drinkers were randomised to one of three groups that retrieved alcohol memories either with negative PE (Retrieval + PE), no PE (Retrieval no PE) or non-alcohol memory retrieval with PE (No-retrieval +PE). All participants then inhaled 50% N₂O for 30 min. The primary outcome was change in beer consumption and alcohol cue-driven urge to drink from the week preceding manipulation (baseline) to the week following manipulation (test). The manipulation did not affect drinking following the intended retrieval+/- PE conditions However, a manipulation check, using a measure of subjective surprise, revealed that the group-level manipulation did not achieve the intended differences in PE at retrieval. Assessment of outcomes according to whether alcohol-relevant PE was actually experienced at retrieval, showed N₂O produced reductions in drinking in a retrieval and PE-dependent fashion. These preliminary findings highlight the importance of directly testing assumptions about memory reactivation procedures in reconsolidation research and suggest that N₂O should be further investigated as a potential reconsolidation-blocking agent.

Characterizing conditioned reactivity to sequential alcohol-predictive cues in well-trained rats

Implicit learning about antecedent stimuli and the unconditional stimulus (US) properties of alcohol may facilitate the progressive loss of control over drinking. To model this learning, Cofresí et al. (2017) developed a procedure in which a discrete, visual conditional stimulus (houselight illumination; CS) predicted the availability of a retractable sipper that rats could lick to receive unsweetened alcohol [Alcoholism: Clinical and Experimental Research, 41, 608-617]. Here we investigated the possibility that houselight illumination, sipper presentation, and oral alcohol receipt might each exert control over alcohol seeking and drinking. We also determined the relationship between ingested dose and blood alcohol concentration, in order to validate the idea that the US is a post-ingestive action of alcohol. Finally, we tested a major prediction from the conditioning account of problematic drinking [Tomie, A., & Sharma, N. (2013). Current Drug Abuse Reviews, 6, 201-219], which is that once learned, responses elicited by a CS will promote drinking. We found that despite having constrained opportunities to drink alcohol during the conditioning procedure, ingested doses produced discriminable blood concentrations that supported cue conditioning. Based on our analysis of the dynamics of cue reactivity in well-trained rats, we found that houselight illumination triggered conditioned approach, sipper presentation evoked licking behavior, and alcohol receipt promoted drinking. Reactivity to these cues, which varied in terms of their temporal proximity to the alcohol US, persisted despite progressive intoxication or satiety. Additionally, rats with the greatest conditioned reactivity to the most distal alcohol cue were also the fastest to initiate drinking and drank the most. Our findings indicate that the post-ingestive effects of alcohol may condition multiple cues simultaneously in adult rats, and these multiple cues help to trigger alcohol seeking and drinking. Moreover, identification and characterization of these cues should be helpful for designing interventions that attenuate the power of these cues over behavior.

A high working memory load prior to memory retrieval reduces craving in non-treatment seeking problem drinkers

BACKGROUND

Reconsolidation-based interventions have been suggested to be a promising treatment strategy for substance use disorders. In this study, we aimed to investigate the effectiveness of a working memory intervention to interfere with the reconsolidation of alcohol-related memories in a sample of non-treatment seeking heavy drinkers.

METHODS

Participants were randomized to one of the two conditions that underwent a 3-day intervention: in the experimental condition, a 30-min working memory training was performed immediately after a 15-min memory retrieval session (i.e., within the memory reconsolidation time-window), whereas in the control condition, the working memory training was performed prior to a memory retrieval session.

RESULTS

In contrast to our original hypothesis, a high working memory load after memory retrieval did not interfere with the reconsolidation of those memories while a high working memory load prior to memory retrieval (the original control condition) strongly reduced retrieval-induced craving and craving for alcohol at follow-up.

CONCLUSION

Whereas the neurocognitive mechanism behind this effect needs to be further investigated, the current findings suggest that, if replicated, working memory training prior to addiction-related memory retrieval has the potential to become an effective (adjunctive) intervention in the treatment of substance use disorders.

A Prediction Error-driven Retrieval Procedure for Destabilizing and Rewriting Maladaptive Reward Memories in Hazardous Drinkers

Maladaptive reward memories (MRMs) can become unstable following retrieval under certain conditions, allowing their modification by subsequent new learning. However, robust (well-rehearsed) and chronologically old MRMs, such as those underlying substance use disorders, do not destabilize easily when retrieved. A key determinate of memory destabilization during retrieval is prediction error (PE). We describe a retrieval procedure for alcohol MRMs in hazardous drinkers that specifically aims to maximize the generation of PE and therefore the likelihood of MRM destabilization. The procedure requires explicitly generating the expectancy of alcohol consumption and then violating this expectancy (withholding alcohol) following the presentation of a brief set of prototypical alcohol cue images (retrieval + PE). Control procedures involve presenting the same cue images, but allow alcohol to be consumed, generating minimal PE (retrieval-no PE) or generate PE without retrieval of alcohol MRMs, by presenting orange juice cues (no retrieval + PE). Subsequently, we describe a multisensory disgust-based counterconditioning procedure to probe MRM destabilization by re-writing alcohol cue-reward associations prior to reconsolidation. This procedure pairs alcohol cues with images invoking pathogen disgust and an extremely bitter-tasting solution (denatonium benzoate), generating gustatory disgust. Following retrieval + PE, but not no retrieval + PE or retrieval-no PE, counterconditioning produces evidence of MRM rewriting as indexed by lasting reductions in alcohol cue valuation, attentional capture, and alcohol craving.