Memory and Forgetting

Essential New Complexity-Based Themes for Patient-Centered Diagnosis and Treatment of Dementia and Predementia in Older People: Multimorbidity and Multilevel Phenomenology

Dementia is a highly prevalent condition with devastating clinical and socioeconomic sequela. It is expected to triple in prevalence by 2050. No treatment is currently known to be effective. Symptomatic late-onset dementia and predementia (SLODP) affects 95% of patients with the syndrome. In contrast to trials of pharmacological prevention, no treatment is suggested to remediate or cure these symptomatic patients. SLODP but not young onset dementia is intensely associated with multimorbidity (MUM), including brain-perturbating conditions (BPCs). Recent studies showed that MUM/BPCs have a major role in the pathogenesis of SLODP. Fortunately, most MUM/BPCs are medically treatable, and thus, their treatment may modify and improve SLODP, relieving suffering and reducing its clinical and socioeconomic threats. Regrettably, the complex system features of SLODP impede the diagnosis and treatment of the potentially remediable conditions (PRCs) associated with them, mainly due to failure of pattern recognition and a flawed diagnostic workup. We suggest incorporating two SLODP-specific conceptual themes into the diagnostic workup: MUM/BPC and multilevel phenomenological themes. By doing so, we were able to improve the diagnostic accuracy of SLODP components and optimize detecting and favorably treating PRCs. These revolutionary concepts and their implications for remediability and other parameters are discussed in the paper.

Apples and oranges: PTSD patients and healthy individuals are not comparable in their subjective and physiological responding to emotion induction and bilateral stimulation

Objectives

Bilateral stimulation is a core element of Eye Movement Desensitization and Reprocessing Therapy, a psychotherapeutic intervention for the treatment of Posttraumatic Stress Disorder (PTSD). Promising previous findings showed measurable physiological effects of bilateral stimulation in healthy individuals, but studies that replicated these findings in PTSD patients are sparse.

Methods

23 patients with PTSD and 30 healthy controls were confronted with affective standard scripts (pleasant, neutral, unpleasant) while bilateral tactile stimulation was applied. Monolateral and no stimulation served as control conditions. Noise-induced startle reflex response (valence measure) and galvanic skin response (arousal measure) were used for physiological responses and the valence and arousal scale of the Self-Assessment-Manikin for subjective responses.

Results

Both groups showed a subjective distress reduction for unpleasant scripts and a subjective attention increase for positive scripts under bilateral stimulation. In healthy individuals, this was also for physiological measures, and a general startle-reducing effect of bilateral stimulation in the absence of affective stimuli was found. In PTSD patients, however, the effects were restricted on the subjective level, and no concomitant physiological effects were observed.

Conclusions and significance

The findings indicate, that generalizing the effects of BLS in healthy individuals to PTSD patients may be problematic. The herein-reported group differences can be explained by PTSD-specific peculiarities in emotion processing and cognitive processing style.

Application of Ketamine in Pain Management and the Underlying Mechanism

Since ketamine was approved by the FDA as an intravenous anesthetic, it has been in clinical use for more than 50 years. Apart from its anesthetic effects, ketamine is one of the few intravenous anesthetics with potent analgesic properties. As part of the effort to develop pain management, renewed interest has focused on the use of ketamine for the treatment of acute and chronic pain. Ketamine is commonly used to treat various kinds of chronic pain syndromes and is also applied to control perioperative pain and reduce the consumption of postoperative analgesics. However, its precise mechanisms of action remain mysterious for a large part. Despite extensive research in the field, the mechanism of ketamine is still unclear. Its analgesic effect appears to be largely mediated by blockade of NMDARs, but opioid, GABA, and monoaminergic system seem to partly participate in the pain transmission procedure. Its metabolites also have an analgesic effect, which may prolong pain relief. More recently, the antidepressant effect of ketamine has been considered to reduce pain-related aversion to relieve chronic pain. Overall, the analgesic mechanism of ketamine seems to be a complex combination of multiple factors. Due to its potent analgesic properties, ketamine is an analgesic with great clinical application prospects. Exploring the precise mechanism of action of ketamine will help guide clinical medication and confirm indications for ketamine analgesia. This review aims to list the application of ketamine in pain management and discuss its analgesic mechanism.

Musical experience prior to traumatic exposure as a resilience factor: a conceptual analysis

Resilience mechanisms can be dynamically triggered throughout the lifecourse by resilience factors in order to prevent individuals from developing stress-related pathologies such as posttraumatic stress disorder (PTSD). Some interventional studies have suggested that listening to music and musical practice after experiencing a traumatic event decrease the intensity of PTSD, but surprisingly, no study to our knowledge has explored musical experience as a potential resilience factor before the potential occurrence of a traumatic event. In the present conceptual analysis, we sought to summarize what is known about the concept of resilience and how musical experience could trigger two key mechanisms altered in PTSD: emotion regulation and cognitive control. Our hypothesis is that the stimulation of these two mechanisms by musical experience during the pre-traumatic period could help protect against the symptoms of emotional dysregulation and intrusions present in PTSD. We then developed a new framework to guide future research aimed at isolating and investigating the protective role of musical experience regarding the development of PTSD in response to trauma. The clinical application of this type of research could be to develop pre-trauma training that promotes emotional regulation and cognitive control, aimed at populations at risk of developing PTSD such as healthcare workers, police officers, and military staffs.

Narrative Review of the Complex Interaction between Pain and Trauma in Children: A Focus on Biological Memory, Preclinical Data, and Epigenetic Processes

The incidence and collective impact of early adverse experiences, trauma, and pain continue to increase. This underscores the urgent need for translational efforts between clinical and preclinical research to better understand the underlying mechanisms and develop effective therapeutic approaches. As our understanding of these issues improves from studies in children and adolescents, we can create more precise preclinical models and ultimately translate our findings back to clinical practice. A multidisciplinary approach is essential for addressing the complex and wide-ranging effects of these experiences on individuals and society. This narrative review aims to (1) define pain and trauma experiences in childhood and adolescents, (2) discuss the relationship between pain and trauma, (3) consider the role of biological memory, (4) decipher the relationship between pain and trauma using preclinical data, and (5) examine the role of the environment by introducing the importance of epigenetic processes. The ultimate scope is to better understand the wide-ranging effects of trauma, abuse, and chronic pain on children and adolescents, how they occur, and how to prevent or mitigate their effects and develop effective treatment strategies that address both the underlying causes and the associated physiological and psychological effects.

Male Victims of Sexual Abuse: Impact and Resilience Processes, a Qualitative Study

The increasing prevalence of sexual abuse calls for exceptional awareness of its multidimensional impact on the mental, sexual, and social wellbeing of male adults. This study aims to deepen the overall understanding of sexual abuse consequences; to highlight some common resilience factors; and to strengthen therapeutic and social support. In this qualitative research, we conducted seven semi-structured interviews with male victims of sexual violence. The data were analysed with the interpretative phenomenological analysis. They shed light on the great suffering linked to sexual violence, and on seven themes which are seemingly pillars of resilience: bond to others, bond to the body, making sense of things, expression, rediscovering oneself, institutions, and finally, learning and commitment. The exploration of these themes reveals several avenues for adjusting care, most of which imply the importance of raising awareness so that spaces receiving the victims' word can emerge.

Cueing natural event boundaries improves memory in people with post-traumatic stress disorder

People with post-traumatic stress disorder (PTSD) often report difficulty remembering information in their everyday lives. Recent findings suggest that such difficulties may be due to PTSD-related deficits in parsing ongoing activity into discrete events, a process called event segmentation. Here, we investigated the causal relationship between event segmentation and memory by cueing event boundaries and evaluating its effect on subsequent memory in people with PTSD. People with PTSD (n = 38) and trauma-matched controls (n = 36) watched and remembered videos of everyday activities that were either unedited, contained visual and auditory cues at event boundaries, or contained visual and auditory cues at event middles. PTSD symptom severity varied substantial within both the group with a PTSD diagnosis and the control group. Memory performance did not differ significantly between groups, but people with high symptoms of PTSD remembered fewer details from the videos than those with lower symptoms of PTSD. Both those with PTSD and controls remembered more information from the videos in the event boundary cue condition than the middle cue or unedited conditions. This finding has important implications for translational work focusing on addressing everyday memory complaints in people with PTSD.

Identifying women with postdelivery posttraumatic stress disorder using natural language processing of personal childbirth narratives

BACKGROUND

Maternal mental disorders are considered a leading complication of childbirth and a common contributor to maternal death. In addition to undermining maternal welfare, untreated postpartum psychopathology can result in child emotional and physical neglect and associated significant pediatric health costs. Some women may experience traumatic childbirth and develop posttraumatic stress disorder symptoms after delivery (childbirth-related posttraumatic stress disorder). Although women are routinely screened for postpartum depression in the United States, there is no recommended protocol to inform the identification of women who are likely to experience childbirth-related posttraumatic stress disorder. Advancements in computational methods of free text have shown promise in informing the diagnosis of psychiatric conditions. Although the language in narratives of stressful events has been associated with posttrauma outcomes, whether the narratives of childbirth processed via machine learning can be useful for childbirth-related posttraumatic stress disorder screening is unknown.

OBJECTIVE

This study aimed to examine the use of written narrative accounts of personal childbirth experiences for the identification of women with childbirth-related posttraumatic stress disorder. To this end, we developed a model based on natural language processing and machine learning algorithms to identify childbirth-related posttraumatic stress disorder via the classification of birth narratives.

STUDY DESIGN

Overall, 1127 eligible postpartum women who enrolled in a study survey during the COVID-19 pandemic provided short written childbirth narrative accounts in which they were instructed to focus on the most distressing aspects of their childbirth experience. They also completed a posttraumatic stress disorder symptom screen to determine childbirth-related posttraumatic stress disorder. After the exclusion criteria were applied, data from 995 participants were analyzed. A machine learning-based Sentence-Transformers natural language processing model was used to represent narratives as vectors that served as inputs for a neural network machine learning model developed in this study to identify participants with childbirth-related posttraumatic stress disorder.

RESULTS

The machine learning model derived from natural language processing of childbirth narratives achieved good performance (area under the curve, 0.75; F1 score, 0.76; sensitivity, 0.8; specificity, 0.70). Moreover, women with childbirth-related posttraumatic stress disorder generated longer narratives (t test results: t=2.30; p=.02) and used more negative emotional expressions (Wilcoxon test: sadness: p=8.90e-04; W=31,017; anger: p=1.32e-02; W=35,005.50) and death-related words (Wilcoxon test: p=3.48e-05; W=34,538) in describing their childbirth experience than those with no childbirth-related posttraumatic stress disorder.

CONCLUSION

This study provided proof of concept that personal childbirth narrative accounts generated in the early postpartum period and analyzed via advanced computational methods can detect with relatively high accuracy women who are likely to endorse childbirth-related posttraumatic stress disorder and those at low risk. This suggests that birth narratives could be promising for informing low-cost, noninvasive tools for maternal mental health screening, and more research that used machine learning to predict early signs of maternal psychiatric morbidity is warranted.

Oxytocin vs. placebo effects on intrusive memory consolidation using a trauma film paradigm: a randomized, controlled experimental study in healthy women

Oxytocin administration during a trauma analogue has been shown to increase intrusive memories, which are a core symptom of post-traumatic stress disorder (PTSD). However, it is unknown whether oxytocin influences the acquisition or the consolidation of the trauma. The current study investigates the effect of the activation of the oxytocin system during the consolidation of an analogue trauma on the formation of intrusive memories over four consecutive days and whether this effect is influenced by individual neurobiological, genetic, or psychological factors. We conducted a randomized double-blind placebo-controlled study in 217 healthy women. They received either a single dose of intranasal oxytocin (24 IU) or placebo after exposure to a trauma film paradigm, which reliably induces intrusive memories. We used a general random forest to examine a potential heterogeneous treatment effect of oxytocin on the consolidation of intrusive memories. Furthermore, we used a poisson regression to examine whether salivary alpha amylase activity (sAA) as a marker of noradrenergic activity and cortisol response to the film, polygenic risk score (PRS) for psychiatric disorders, and psychological factors influence the number of intrusive memories. We found no significant effect of oxytocin on the formation of intrusive memories (F(2, 543.16) = 0.75, p = 0.51, ηp2 = 0.00) and identified no heterogeneous treatment effect. We replicated previous associations of the PRS for PTSD, sAA and the cortisol response on intrusive memories. We further found a positive association between high trait anxiety and intrusive memories, and a negative association between the emotion regulation strategy reappraisal and intrusive memories. Data of the present study suggest that the consolidation of intrusive memories in women is modulated by genetic, neurobiological and psychological factors, but is not influenced by oxytocin. Trial registration: NCT03875391.

Pathophysiological aspects of complex PTSD - a neurobiological account in comparison to classic posttraumatic stress disorder and borderline personality disorder

Despite a great diagnostic overlap, complex posttraumatic stress disorder (CPTSD) has been recognised by the ICD-11 as a new, discrete entity and recent empirical evidence points towards a distinction from simple posttraumatic stress disorder (PTSD) and borderline personality disorder (BPD). The development and maintenance of these disorders is sustained by neurobiological alterations and studies using functional magnetic resonance imaging (fMRI) may further contribute to a clear differentiation of CPTSD, PTSD and BPD. However, there are no existing fMRI studies directly comparing CPTSD, PTSD and BPD. In addition to a summarization of diagnostic differences and similarities, the current review aims to provide a qualitative comparison of neuroimaging findings on affective, attentional and memory processing in CPTSD, PTSD and BPD. Our narrative review alludes to an imbalance in limbic-frontal brain networks, which may be partially trans-diagnostically linked to the degree of trauma symptoms and their expression. Thus, CPTSD, PTSD and BPD may underlie a continuum where similar brain regions are involved but the direction of activation may constitute its distinct symptom expression. The neuronal alterations across these disorders may conceivably be better understood along a symptom-based continuum underlying CPTSD, PTSD and BPD. Further research is needed to amend for the heterogeneity in experimental paradigms and sample criteria.

Effect of adding a positive memories’ module in a trauma-focused cognitive-behavioural treatment for female survivors of intimate partner violence: trial protocol

Background

Trauma-focused cognitive-behavioural treatments have been proven to be effective for reducing symptoms in female survivors of intimate partner violence (IPV), although they still present some difficulties (e.g. significant drop-out rates, low adherence). Based on existing evidence about the difficulty of accessing memories of positive experiences among these women, we considered integrating positive memory evocation in trauma-focused treatments. The present study aims to test the effect of adding a positive memory module to trauma-focused CBT for female survivors of IPV.

Methods

The study is a single-blind, randomized controlled trial (RCT) comparing two trauma-focused CBT (with and without a positive memory module) for female survivors of IPV and a wait-list condition (superiority trial), including pretreatment and posttreatment measures, and follow-ups at 3, 6 and 12 months. Assessors of treatment outcome will be blinded to the trial arm. We aim to recruit 135 participants who will be randomized to one of the experimental conditions. The primary outcome is PTSD symptom severity. Secondary outcome measures include IPV, attitudes towards IPV, posttraumatic cognitions, centrality of trauma, self-concept, positive and negative affect, depression, anxiety, emotional dysregulation or health-related quality of life, as well as satisfaction with treatment. Moreover, adherence to and satisfaction with treatment will be considered.

Discussion

This study first analyses the effect of including positive memory evocation into a trauma-focused treatment for female survivors of IPV. This strategy aims to improve the effect of the treatments and enhance the healing of the trauma by developing a more integrated and emotionally modulated autobiographical narrative that contributes to the recovery and well-being of the victims.

Trial registration

ISRCTN73702156. Registered on 10 March 2022.

Sex hormones and cortisol during experimental trauma memory consolidation: Prospective association with intrusive memories

Background Trauma- and stress-related disorders, such as post-traumatic stress disorder (PTSD), are more common in females than in males. Sex hormones affect learning and emotional memory formation and may be associated with the development of PTSD. Most previous studies have indexed these hormones in isolation. Objectives: To investigate associations of sex hormones and cortisol during memory consolidation on the development of intrusive memories. Methods: We employed an experimental trauma film paradigm in 61 healthy women and indexed salivary testosterone, progesterone, estradiol, and cortisol on day one and day two post experimental trauma exposure and their effects on intrusion frequency, distress, and vividness. Intrusive trauma memories were indexed by means of a diary in which participants documented intrusion frequency, distress, and vividness. Results and conclusion: Participants reported an average of 5.3 intrusions over the course of seven days (SD = 4.6, range 0-26). Progesterone, and estradiol indexed on day one predicted intrusion frequency, with higher progesterone and lower estradiol predicting more intrusive memories (p-values AUC progesterone 0.01 and estradiol 0.02). There was no evidence for associations between hormone concentration indices on day two and intrusion outcomes. Further research on the roles of gonadal and adrenal hormones in trauma memory formation is needed to advance our efforts to understand their influence on PTSD development.

Adult hippocampal neurogenesis shapes adaptation and improves stress response: a mechanistic and integrative perspective

Adult hippocampal neurogenesis (AHN) represents a remarkable form of neuroplasticity that has increasingly been linked to the stress response in recent years. However, the hippocampus does not itself support the expression of the different dimensions of the stress response. Moreover, the main hippocampal functions are essentially preserved under AHN depletion and adult-born immature neurons (abGNs) have no extrahippocampal projections, which questions the mechanisms by which abGNs influence functions supported by brain areas far from the hippocampus. Within this framework, we propose that through its computational influences AHN is pivotal in shaping adaption to environmental demands, underlying its role in stress response. The hippocampus with its high input convergence and output divergence represents a computational hub, ideally positioned in the brain (1) to detect cues and contexts linked to past, current and predicted stressful experiences, and (2) to supervise the expression of the stress response at the cognitive, affective, behavioral, and physiological levels. AHN appears to bias hippocampal computations toward enhanced conjunctive encoding and pattern separation, promoting contextual discrimination and cognitive flexibility, reducing proactive interference and generalization of stressful experiences to safe contexts. These effects result in gating downstream brain areas with more accurate and contextualized information, enabling the different dimensions of the stress response to be more appropriately set with specific contexts. Here, we first provide an integrative perspective of the functional involvement of AHN in the hippocampus and a phenomenological overview of the stress response. We then examine the mechanistic underpinning of the role of AHN in the stress response and describe its potential implications in the different dimensions accompanying this response.

Avoidance behaviour generalizes to eye processing in posttraumatic stress disorder

BACKGROUND

Avoidance describes any action designed to prevent an uncomfortable situation or emotion from occurring. Although it is a common reaction to trauma, avoidance becomes problematic when it is the primary coping strategy, and plays a major role in the development and maintenance of posttraumatic stress disorder (PTSD). Avoidance in PTSD may generalize to non-harmful environmental cues that are perceived to be unsafe.

OBJECTIVE

We tested whether avoidance extends to social cues (i.e. emotional gazes) that are unrelated to trauma.

METHOD

A total of 159 participants (103 who had been exposed to the 2015 Paris terrorist attacks and 56 who had not) performed a gaze-cueing task featuring sad, happy and neutral faces. Attention to the eye area was recorded using an eyetracker. Of the exposed participants, 52 had been diagnosed with PTSD (PTSD+) and 51 had not developed PTSD (PTSD-). As a result of the preprocessing stages, 52 PTSD+ (29 women), 50 PTSD- (20 women) and 53 nonexposed (31 women) participants were included in the final analyses.

RESULTS

PTSD+ participants looked at sad eyes for significantly less time than PTSD- and nonexposed individuals. This effect was negatively correlated with the intensity of avoidance symptoms. No difference was found for neutral and happy faces.

CONCLUSIONS

These findings suggest that maladaptive avoidance in PTSD extends to social processing, in terms of eye contact and others' emotions that are unrelated to trauma. New therapeutic directions could include targeting sociocognitive deficits. Our findings open up new and indirect avenues for overcoming maladaptive avoidance behaviours by remediating eye processing.Trial registration: ClinicalTrials.gov identifier: NCT02810197.

HIGHLIGHTS

Avoidance is a key symptom of posttraumatic stress disorder (PTSD).Avoidance is often viewed as limited to reminders linked to the trauma.Results show that attention to the eyes of sad faces is also affected by PTSD. This effect is correlated with avoidance symptoms in PTSD.

Autobiographical recall of a stressful negative event in veterans with PTSD

Posttraumatic stress disorder (PTSD) is characterised by alterations in autobiographical memory for traumatic and non-traumatic events. Studies that focus on event construction - the ability to search for and identify a specific event - have documented overgeneral memory in PTSD. However, the quality of autobiographical memory also depends on the ability to elaborate on an event once constructed by providing additional details. In a prior study, individuals with PTSD generated as many episodic (event-specific) details as trauma-exposed controls when demands on event construction were minimized, albeit the PTSD group generated more non-episodic details. The current study sought to further characterize PTSD-related alterations in event elaboration by asking participants to describe a stressful negative event specified by the experimenter, thus minimizing event construction demands. Narratives were scored for episodic and non-episodic details and relations with measures of executive function and self-reported avoidance were examined. Compared to controls, the PTSD group generated narratives with equivalent episodic detail but greater non-episodic detail, including semantic information and repeated or extended events. Non-episodic detail generation was associated with greater avoidance but not executive functions. Elaborated non-trauma memories may be perceived as overgeneral in PTSD due to greater generation of non-episodic details, rather than diminished episodic detail.

Stress, memory, and implications for major depression

The stress response comprises a phylogenetically conserved set of cognitive, physiological, and behavioral responses that evolved as a survival strategy. In this context, the memory of stressful events would be adaptive as it could avoid re-exposure to an adverse event, otherwise the event would be facilitated in positively stressful or non-distressful conditions. However, the interaction between stress and memory comprises complex responses, some of them which are not yet completely understood, and which depend on several factors such as the memory system that is recruited, the nature and duration of the stressful event, as well as the timing in which this interaction takes place. In this narrative review, we briefly discuss the mechanisms of the stress response, the main memory systems, and its neural correlates. Then, we show how stress, through the action of its biochemical mediators, influences memory systems and mnemonic processes. Finally, we make use of major depressive disorder to explore the possible implications of non-adaptive interactions between stress and memory to psychiatric disorders, as well as possible roles for memory studies in the field of psychiatry.

Modulation of PARP-1 Activity in a Broad Time Window Attenuates Memorizing Fear

The amygdala plays a critical role in the acquisition and consolidation of fear-related memories. Recent studies have demonstrated that ADP-ribosylation of histones, accelerated by PARPs, affects the chromatin structure and the binding of chromatin remodeling complexes with transcription factors. Inhibition of PARP-1 activity during the labile phase of re-consolidation may erase memory. Accordingly, we investigated the possibility of interfering with fear conditioning by PARP-1 inhibition. Herein, we demonstrate that injection of PARP-1 inhibitors, specifically into the CeA or i.p., in different time windows post-retrieval, attenuates freezing behavior. Moreover, the association of memory with pharmacokinetic timing of PARP inhibitor arrival to the brain enabled/achieved attenuation of a specific cue-associated memory of fear but did not hinder other memories (even traumatic events) associated with other cues. Our results suggest using PARP-1 inhibitors as a new avenue for future treatment of PTSD by disrupting specific traumatic memories in a broad time window, even long after the traumatic event. The safety of using these PARP inhibitors, that is, not interfering with other natural memories, is an added value.

Variations in response to trauma and hippocampal subfield changes

Models of posttraumatic stress disorder (PTSD) suggest that the hippocampus is key to the persistence of traumatic memory. Yet very little is known about the precise changes that take place in this structure, nor their relation with PTSD symptoms. Previous studies have mostly used magnetic resonance imaging (MRI) at low resolutions, making it impossible to identify sensitive anatomical landmarks, or compared groups often unequally matched in terms of traumatic exposure. The present cross-sectional study included 92 individuals who had all been exposed to the terrorist attacks in Paris on November 13, 2015 (53 of whom subsequently developed PTSD) and 56 individuals who had not been exposed. Hippocampal subfield volumes were estimated using cross-validated automatic segmentation of high-resolution MRI images. Results revealed changes in CA1 and CA2-3/dentate gyrus (DG) volumes in individuals with PTSD, but not in resilient (i.e., exposed but without PTSD) individuals, after controlling for potential nuisance variables such as previous traumatic exposure and substance abuse. In line with current models of hippocampal subfield functions, CA1 changes were linked to the uncontrollable re-experiencing of intrusive memories, while CA2-3/DG changes, potentially exacerbated by comorbid depression, fostered the overgeneralization of fear linked to avoidance and hypervigilance behaviors. Additional analyses revealed that CA1 integrity was linked to optimum functioning of the memory control network in resilient individuals. These findings shed new light on potential pathophysiological mechanisms in the hippocampus subtending the development of PTSD and the failure to recover from trauma.

Forgetting Unwanted Memories: Active Forgetting and Implications for the Development of Psychological Disorders

Intrusive memories are a common feature of many psychopathologies, and suppression-induced forgetting of unwanted memories appears as a critical ability to preserve mental health. In recent years, biological and cognitive studies converged in revealing that forgetting is due to active processes. Recent neurobiological studies provide evidence on the active role of main neurotransmitter systems in forgetting, suggesting that the brain actively works to suppress retrieval of unwanted memories. On the cognitive side, there is evidence that voluntary and involuntary processes (here termed "intentional" and "incidental" forgetting, respectively) contribute to active forgetting. In intentional forgetting, an inhibitory control mechanism suppresses awareness of unwanted memories at encoding or retrieval. In incidental forgetting, retrieval practice of some memories involuntarily suppresses the retrieval of other related memories. In this review we describe recent findings on deficits in active forgetting observed in psychopathologies, like post-traumatic stress disorder, depression, schizophrenia, and obsessive-compulsive disorder. Moreover, we report studies in which the role of neurotransmitter systems, known to be involved in the pathogenesis of mental disorders, has been investigated in active forgetting paradigms. The possibility that biological and cognitive mechanisms of active forgetting could be considered as hallmarks of the early onset of psychopathologies is also discussed.

The relationship between early administration of morphine or nitrous oxide gas and PTSD symptom development

BACKGROUND

Posttraumatic Stress Disorder (PTSD) is a debilitating mental health disorder. Certain drugs, such as morphine and nitrous oxide gas (N₂O), are administered to individuals who just experienced a traumatic event (e.g., soldiers, injured civilians). It is therefore crucial to understand if they incidentally affect PTSD symptom development. Furthermore, such observations could pave the way for the development of pharmacological prevention strategies of PTSD.

METHODS

In this prospective population-based cohort study (n = 2,070), we examined the relationship between morphine or N₂O administration during childbirth, and subsequent childbirth-related PTSD symptoms at eight weeks postpartum. Pain during labour, prior PTSD symptoms, and birth medical severity were included as covariates in the analyses.

RESULTS

In women who developed PTSD symptoms, N₂O administration during childbirth predicted reduced PTSD symptom severity (p < .001, small to medium effect size). A similar tendency was observed for morphine, but was not significant (p < .065, null to small effect size). Both drugs predicted increased PTSD symptoms when combined with severe pain during labour.

LIMITATIONS

This study was observational, thus drug administration was not randomised. Additionally, PTSD symptoms were self-reported.

CONCLUSIONS

Peritraumatic N₂O administration may reduce subsequent PTSD symptom severity and thus be a potential avenue for PTSD secondary prevention. This might also be the case for morphine. However, the role of severe peritraumatic pain in context of drug administration deserves further investigation.

The reconstructive nature of involuntary autobiographical memories

Influential clinical theories propose that parts of traumatic or stressful events are stored in an unprocessed, purely perceptual form, which is inaccessible for voluntary retrieval but may spontaneously return to consciousness involuntarily in response to matching cues. This leads to perceptually vivid, and largely veridical involuntary memories of the traumatic scene, remembered with the original emotions and from the same vantage point as during the event. Several lines of evidence contradict this position. First, involuntary memories are not more veridical than memories retrieved deliberately. Second, involuntary memories for trauma-related events are not more frequently remembered with the original first-person perspective, and individuals with PTSD do not report more first-person involuntary memories than individuals without PTSD. Third, involuntary memories of stressful moments that are subjectively experienced as repetitive do not come to mind in a fixed and unchangeable form. Fourth, involuntary memories do not have privileged access to the most emotional moments (so-called hotspots) of a stressful event and the content and choice of hotspots change over time. Fourth, although involuntary memories are associated with enhanced emotional impact, this does not imply reactivation of the original emotion. We conclude that involuntary memories, although effortless, are products of (re)constructive processes.

Feelings, Thoughts, and Behaviors During Disaster

Thoughts, feelings, and behaviors during traumatic events, that is, peritraumatic reactions, are key to post-trauma psychopathology development. Qualitative research is required to investigate whether existing quantitative methods capture the range and complexity of peritraumatic reactions as described by survivors. Semi-structured interviews were conducted with 104 earthquake survivors. Participants reported experiencing various peritraumatic reactions (M = 21, range = 6-43). The survivors' accounts confirmed presence and overall phenomenological characteristics of commonly studied peritraumatic reactions such as dissociation, distress, mental defeat, and immobility. In addition, novel and understudied reactions were identified: cognitive overload, hyperfocus, and emotion regulation, as well as positive affect. Finally, a number of cross-cutting phenomena were identified such as the social nature of many reactions and survivors evaluating their reactions as difficult to put into words. These findings have implications for the conceptualization of peritraumatic reactions, for trauma-focused psychotherapeutic interventions, and for the wellbeing of disaster survivors.

Effects of ∆9-tetrahydrocannabinol on aversive memories and anxiety: a review from human studies

BACKGROUND

Posttraumatic stress disorder (PTSD) may stem from the formation of aberrant and enduring aversive memories. Some PTSD patients have recreationally used Cannabis, probably aiming at relieving their symptomatology. However, it is still largely unknown whether and how Cannabis or its psychotomimetic compound Δ⁹-tetrahydrocannabinol (THC) attenuates the aversive/traumatic memory outcomes. Here, we seek to review and discuss the effects of THC on aversive memory extinction and anxiety in healthy humans and PTSD patients.

METHODS

Medline, PubMed, Cochrane Library, and Central Register for Controlled Trials databases were searched to identify peer-reviewed published studies and randomized controlled trials in humans published in English between 1974 and July 2020, including those using only THC and THC combined with cannabidiol (CBD). The effect size of the experimental intervention under investigation was calculated.

RESULTS

At low doses, THC can enhance the extinction rate and reduce anxiety responses. Both effects involve the activation of cannabinoid type-1 receptors in discrete components of the corticolimbic circuitry, which could couterbalance the low "endocannabinoid tonus" reported in PTSD patients. The advantage of associating CBD with THC to attenuate anxiety while minimizing the potential psychotic or anxiogenic effect produced by high doses of THC has been reported. The effects of THC either alone or combined with CBD on aversive memory reconsolidation, however, are still unknown.

CONCLUSIONS

Current evidence from healthy humans and PTSD patients supports the THC value to suppress anxiety and aversive memory expression without producing significant adverse effects if used in low doses or when associated with CBD. Future studies are guaranteed to address open questions related to their dose ratios, administration routes, pharmacokinetic interactions, sex-dependent differences, and prolonged efficacy.

Resilience after trauma: The role of memory suppression

In the aftermath of trauma, little is known about why the unwanted and unbidden recollection of traumatic memories persists in some individuals but not others. We implemented neutral and inoffensive intrusive memories in the laboratory in a group of 102 individuals exposed to the 2015 Paris terrorist attacks and 73 nonexposed individuals, who were not in Paris during the attacks. While reexperiencing these intrusive memories, nonexposed individuals and exposed individuals without posttraumatic stress disorder (PTSD) could adaptively suppress memory activity, but exposed individuals with PTSD could not. These findings suggest that the capacity to suppress memory is central to positive posttraumatic adaptation. A generalized disruption of the memory control system could explain the maladaptive and unsuccessful suppression attempts often seen in PTSD, and this disruption should be targeted by specific treatments.

Assessing asylum seekers, refugees and undocumented migrants

Identifying the causes of psychiatric and physical symptoms in asylum seekers, refugees and other migrants and making definitive diagnoses can be challenging. Ethical and legal challenges in the UK include the likely deterrent effects of upfront charging for National Health Service (NHS) services. This paper focuses on the fictitious case of an asylum seeker presenting to a mental health service in England, highlighting some of the difficulties in assessing and treating this patient group and providing advice to clinicians on clinical and practical management. Current NHS entitlements for migrants are summarised and a list is presented in the online supplement of non-governmental organisations that can provide further support.

The neural correlates of trauma-related autobiographical memory in posttraumatic stress disorder: A meta-analysis

BACKGROUND

Autobiographical memory (AM) refers to memories of events that are personally relevant and are remembered from one's own past. The AM network is a distributed brain network comprised largely by prefrontal medial and posteromedial cortical brain regions, which together facilitate AM. Autobiographical memories with high arousal and negatively valenced emotional states are thought to be retrieved more readily and re-experienced more vividly. This is critical in the case of trauma-related AMs, which are related to altered phenomenological experiences as well as aberrations to the underlying neural systems in posttraumatic stress disorder (PTSD). Critically, these alterations to the AM network have not been explored recently and have never been analyzed with consideration to the different processes of AM, them being retrieval and re-experiencing.

METHODS

We conducted a series of effect-size signed differential mapping meta-analyses across twenty-eight studies investigating the neural correlates of trauma-related AMs in participants with PTSD as compared with controls. Studies included either trauma-related scripts or trauma-related materials (i.e., sounds, images, pictures) implemented to evoke the recollection of a trauma-related memory.

RESULTS

The meta-analyses revealed that control and PTSD participants displayed greater common brain activation of prefrontal medial and posteromedial cortices, respectively. Whereby the prefrontal medial cortices are suggested to facilitate retrieval monitoring, the posteromedial cortices are thought to enable the visual imagery processes of AM.

CONCLUSIONS

Taken together, reduced common activation of prefrontal cortices may be interpreted as a bias toward greater re-experiencing, where the more salient elements of the traumatic memory are relived as opposed to retrieved in a controlled manner in PTSD.

Basolateral Amygdala Connectivity With Subgenual Anterior Cingulate Cortex Represents Enhanced Fear-Related Memory Encoding in Anxious Humans

BACKGROUND

The amygdala can enhance emotional memory encoding as well as anxiogenesis via corticotropin-releasing factor neurons. However, the amygdala's explicit role in emotional encoding remains unclarified in humans. We examined how functional connectivity (FC) of amygdala subnuclei affects emotional encoding, considering its mechanism in which anxiety, attention, and cortisol conceivably participate.

METHODS

A total of 65 healthy humans underwent resting-state functional magnetic resonance imaging scans and saliva collection at 10 points in time over 2 days. FC analysis was performed for basolateral amygdala subnucleus (BLA) and centromedial amygdala subnucleus. We assessed attentional control via an emotional Stroop task and assessed emotional encoding via a facial identification task that examines how strongly a neutral face is memorized when accompanied by an emotional face (fearful, sad, or happy). FC and task performance were compared between high-anxious and non-high-anxious groups classified by anxious personality scores.

RESULTS

BLA connected with subgenual anterior cingulate cortex (sgACC) in proportion to the strength of fear-related encoding, whereas centromedial subnucleus connected with caudate nucleus for happy-related encoding. The high-anxious group showed more enhanced fear-related encoding but impaired happy-related encoding compared with the non-high-anxious group. BLA-sgACC FC was more intensified in the high-anxious group than in the non-high-anxious group; however, centromedial-caudate FC did not differ between them. Although emotional encoding was uncorrelated with either attentional control or cortisol, BLA-sgACC was positively correlated with cortisol increase after awakening.

CONCLUSIONS

The study revealed that neural interactions of BLA, specifically with sgACC, might play a critical role in fear-related memory encoding, depending on the individual's level of anxiety. These findings aid in understanding the complicated mechanisms of emotional memory in anxiety disorders.

PTSD in asylum-seekers: Manifestations and relevance to the asylum process

Post-Traumatic Stress Disorder (PTSD) is common among asylum-seekers and manifests with symptoms uniquely problematic to the United States asylum-seeking process. Chiefly, hyper-vigilance, avoidance behavior, dissociative amnesia and a tendency towards non-linear narratives hinder the articulation of an effective asylum claim. Moreover, the format and environmental circumstances of the asylum-seeking process further heighten these difficulties.