Memory control ability modulates intrusive memories after analogue trauma

Neural basis underlying the association between thought control ability and happiness: The moderating role of the amygdala

Thought control ability (TCA) plays an important role in individuals' health and happiness. Previous studies demonstrated that TCA was closely conceptually associated with happiness. However, empirical research supporting this relationship was limited. In addition, the neural basis underlying TCA and how this neural basis influences the relationship between TCA and happiness remain unexplored. In the present study, the voxel-based morphometry (VBM) method was adopted to investigate the neuroanatomical basis of TCA in 314 healthy subjects. The behavioral results revealed a significant positive association between TCA and happiness. On the neural level, there was a significant negative correlation between TCA and the gray matter density (GMD) of the bilateral amygdala. Split-half validation analysis revealed similar results, further confirming the stability of the VBM analysis findings. Furthermore, gray matter covariance network and graph theoretical analyses showed positive association between TCA and both the node degree and node strength of the amygdala. Moderation analysis revealed that the GMD of the amygdala moderated the relationship between TCA and happiness. Specifically, the positive association between TCA and self-perceived happiness was stronger in subjects with a lower GMD of the amygdala. The present study indicated the neural basis underlying the association between TCA and happiness and offered a method of improving individual well-being.

Everything you ever wanted to know about the Think/No-Think task, but forgot to ask

The Think/No-Think (TNT) task has just celebrated 20 years since its inception, and its use has been growing as a tool to investigate the mechanisms underlying memory control and its neural underpinnings. Here, we present a theoretical and practical guide for designing, implementing, and running TNT studies. For this purpose, we provide a step-by-step description of the structure of the TNT task, methodological choices that can be made, parameters that can be chosen, instruments available, aspects to be aware of, systematic information about how to run a study and analyze the data. Importantly, we provide a TNT training package (as Supplementary Material), that is, a series of multimedia materials (e.g., tutorial videos, informative HTML pages, MATLAB code to run experiments, questionnaires, scoring sheets, etc.) to complement this method paper and facilitate a deeper understanding of the TNT task, its rationale, and how to set it up in practice. Given the recent discussion about the replication crisis in the behavioral sciences, we hope that this contribution will increase standardization, reliability, and replicability across laboratories.

The Index of Intrusion Control (IIC): Capturing individual variability in intentional intrusion control in the laboratory

Intrusive memories can be downregulated using intentional memory control, as measured via the Think/No-Think paradigm. In this task, participants retrieve or suppress memories in response to an associated reminder cue. After each suppression trial, participants rate whether the association intruded into awareness. Previous research has found that repeatedly exerting intentional control over memory intrusions reduces their frequency. This decrease is often summarised with a linear index, which may miss more complex patterns characterising the temporal dynamics of intrusion control. The goal of this paper is to propose a novel metric of intrusion control that captures those dynamic changes over time as a single index. Results from a mega-analysis of published datasets revealed that the change in intrusion frequencies across time is not purely linear, but also includes non-linear dynamics that seem best captured by a log function of the number of suppression attempts. To capture those linear and non-linear dynamics, we propose the Index of Intrusion Control (IIC), which relies on the integral of intrusion changes across suppression attempts. Simulations revealed that the IIC best captured the linear and non-linear dynamics of intrusion suppression when compared with other linear or non-linear indexes of control, such as the regression slope or Spearman correlation, respectively. Our findings demonstrate how the IIC may therefore act as a more reliable metric to capture individual differences in intrusion control, and examine the role of non-linear dynamics characterizing the conscious access to unwanted memories.

Higher visceral adipose tissue is associated with decreased memory suppression ability on food-related thoughts: A 1-year prospective ERP study

Memory about food and eating is crucial in regulating appetite and eating behaviors. Successfully stopping vivid imagination of delicious food could help reduce food craving and thus reduce the possibility of further intake. Memory inhibition is a cognitive process that involves intentional suppression of certain memories coming to consciousness. Successful memory suppression derives from inhibitory control. Although considerable work has consistently observed the impairment in motor or response inhibitory control among individuals with obesity, there has been a lack of investigation into the influence of bodyweight status on memory inhibitory control. To fill this gap, current study investigated behavioral and neurophysiological correlates of memory suppression in young women. Using Think/No-Think task and event-related potentials among 47 females, we found that participants with higher visceral adipose tissue (VAT) showed a tendency towards decreased suppression ability for memories related to food but not memories related to nonfood items. In depth analysis showed that decrease in the differences in P2 amplitudes between suppression vs. retrieval of food-related memories mediated the impairment of suppression ability by high VAT. We then tested whether individual differences in memory suppression ability as well as ERP correlates predicted future BMI or VAT change over 1-year follow-up. Results showed that P2 amplitudes when retrieving food-related memory could predict VAT change at 1-year follow-up among participants with healthy BMI. These observations suggest a hypersensitivity inference hypothesis underlying memory control impairments. To be specific, deficits in memory suppression may be in part resulted from elevated sensitivity to the cues coupling with food-related memory. It extends previous studies of memory suppression with food rewards and provides the first evidence to help understand the relationship between inhibitory control on food-related memory and obesity.

Controlling intrusive thoughts of future fears under stress

Negative outlooks of our future may foster unwanted and intrusive thoughts. To some extent, individuals have control over their ability to suppress intrusions and downregulate their frequency. Acute stress impairs intentional suppression, leading to an increased frequency of intrusions. The aim of this study was to gain insight into the mechanism underlying stress-induced impairments in intentional suppression of intrusions by investigating the combined and independent roles of the two major stress hormones, noradrenaline and cortisol. Healthy participants (N = 181) were administered propranolol (to block the noradrenergic response), metyrapone (to block the cortisol response), or a placebo before being exposed to the Maastricht Acute Stress Test. Intrusive thoughts of autobiographical future fears were then measured via the Imagine/No-Imagine task. Results demonstrated that the stress response was successfully altered because of the drug and stress manipulations. In all groups, repeated suppression of future fears reduced intrusions. Across the sample, an enhanced decrease over time was associated with greater attenuation of anxiety towards the related fears. The groups did not differ in the total frequency of intrusions. Though, trait anxiety increased the total number of intrusions. Our findings show that stress hormones did not influence the ability to suppress intrusions. However, our results do add support to previous research linking anxiety to memory control deficits. When using autobiographical content, future research should focus on the quality and characteristics of the individual memories to explain more of the variation observed in intentional memory control.

Improving mental health by training the suppression of unwanted thoughts

Anxiety, posttraumatic stress, and depression markedly increased worldwide during the COVID-19 pandemic. People with these conditions experience distressing intrusive thoughts, yet conventional therapies often urge them to avoid suppressing their thoughts because intrusions might rebound in intensity and frequency, worsening the disorders. In contrast, we hypothesized that training thought suppression would improve mental health. One hundred and twenty adults from 16 countries underwent 3 days of online training to suppress either fearful or neutral thoughts. No paradoxical increases in fears occurred. Instead, suppression reduced memory for suppressed fears and rendered them less vivid and anxiety provoking. After training, participants reported less anxiety, negative affect, and depression with the latter benefit persisting at 3 months. Participants high in trait anxiety and pandemic-related posttraumatic stress gained the largest and most durable mental health benefits. These findings challenge century-old wisdom that suppressing thoughts is maladaptive, offering an accessible approach to improving mental health.

Inhibitory control as possible risk and/or resilience factor for the development of trauma related symptoms-a study of the Utøya terror attack survivors

PTSD symptomatology is known to be associated with executive dysfunction. Inhibitory control is a core component of executive functioning, and inhibitory skills are essential both for adequate functioning in everyday life and important in situations following trauma. The aim of the present study was to examine the relationship between trauma exposure, inhibitory control and PTSD symptomatology in adolescent survivors of the terror attack at Utøya, Norway on the 22nd of July, 2011. In this cross-sectional case-control study, 20 trauma exposed adolescents and 20 healthy controls matched in age and gender were compared on a neuropsychological test of cognitive inhibition (Color-Word Interference Test) and a self-report measure of inhibition ability (BRIEF-A). Our analyses revealed that the trauma exposed group differed significantly on the self-reported measure of inhibitory control compared to the control group, but there were no differences between groups on the objective measures of cognitive inhibition. Follow-up analyses with subgroups in the trauma exposed group based on PTSD symptomatology (PTSD + and PTSD-) and the control group revealed that the PTSD- group showed significantly better results than both the PTSD + and the control group on the measures of inhibitory control. Moreover, the follow-up analyses showed that the PTSD + group showed significantly poorer results from the other two groups on the measures of inhibitory control and self-reported inhibition. We conclude that impaired inhibitory control, measured both objectively and by self-reported questionnaire, is related to PTSD symptomatology. Findings suggest that inhibitory dysfunctions may be a vulnerability factor for the development of PTSD symptomatology in trauma exposed adolescents, and thus it seems that the ability to exhibit inhibitory control could be a possible resilience factor to prevent the development of PTSD symptoms.

On the role of inhibition in suppression-induced forgetting

Suppressing retrieval of unwanted memories can cause forgetting, an outcome often attributed to the recruitment of inhibitory control. This suppression-induced forgetting (SIF) generalizes to different cues used to test the suppressed content (cue-independence), a property taken as consistent with inhibition. But does cue-independent forgetting necessarily imply that a memory has been inhibited? Tomlinson et al. (Proc Natl Acad Sci 106:15588-15593, 2009) reported a surprising finding that pressing a button also led to cue-independent forgetting, which was taken as support for an alternative interference account. Here we investigated the role of inhibition in forgetting due to retrieval suppression and pressing buttons. We modified Tomlinson et al.'s procedure to examine an unusual feature they introduced that may have caused memory inhibition effects in their experiment: the omission of explicit task-cues. When tasks were uncued, we replicated the button-press forgetting effect; but when cued, pressing buttons caused no forgetting. Moreover, button-press forgetting partially reflects output-interference effects at test and not a lasting effect of interference. In contrast, SIF occurred regardless of these procedural changes. Collectively, these findings indicate that simply pressing a button does not induce forgetting, on its own, without confounding factors that introduce inhibition into the task and that inhibition likely underlies SIF.

The Active Inference Model of Coherence Therapy

Coherence Therapy is an empirically derived experiential psychotherapy based on Psychological Constructivism. Symptoms are viewed as necessary output from an implicit model of the world. The therapist curates experiences and directs attention toward discovering the model. Rendered explicit, the model is juxtaposed with contradictory knowledge driving memory re-consolidation with resolution of the symptom. The Bayesian Brain views perception and action as inferential processes. Prior beliefs are combined in a generative model to explain the hidden causes of sensations through a process of Active Inference. Prior beliefs that are poor fits to the real world are suboptimal. Suboptimal priors with optimal inference produce Bayes Optimal Pathology with behavioral symptoms. The Active Inference Model of Coherence Therapy posits that Coherence Therapy is a dyadic act of therapist guided Active Inference that renders the (probable) hidden causes of a client's behavior conscious. The therapist's sustained attention on the goal of inference helps to overcome memory control bias against retrieval of the affectively charged suboptimal prior. Serial experiences cue memory retrieval and re-instantiation of the physiological/affective state that necessitates production of the symptom in a particular context. As this process continues there is a break in modularity with assimilation into broader networks of experience. Typically, the symptom produced by optimal inference with the suboptimal prior is experienced as unnecessary/inappropriate when taken out of the particular context. The implicit construct has been re-represented and rendered consciously accessible, by a more complex but more accurate model in which the symptom is necessary in some contexts but not others. There is an experience of agency and control in symptom creation, accompanied by the spontaneous production of context appropriate behavior. The capacity for inference has been restored. The Active Inference Model of Coherence Therapy provides a framework for Coherence Therapy as a computational process which can serve as the basis for new therapeutic interventions and experimental designs integrating biological, cognitive, behavioral, and environmental factors.

Anterior Cingulate Cortex Signals the Need to Control Intrusive Thoughts during Motivated Forgetting

How do people limit awareness of unwanted memories? When such memories intrude, a control process engages the right DLPFC (rDLPFC) to inhibit hippocampal activity and stop retrieval. It remains unknown how the need for control is detected, and whether control operates proactively to prevent unwelcome memories from being retrieved, or responds reactively, to counteract intrusions. We hypothesized that dorsal ACC (dACC) detects the emergence of an unwanted trace in awareness and transmits the need for inhibitory control to rDLPFC. During a memory suppression task, we measured in humans (both sexes) trial-by-trial variations in the theta power and N2 amplitude of dACC, two EEG markers that are thought to reflect the need for control. With simultaneous EEG-fMRI recordings, we tracked interactions among dACC, rDLPFC, and hippocampus during suppression. We found a clear role of dACC in detecting the need for memory control and upregulating prefrontal inhibition. Importantly, we identified distinct early (300-450 ms) and late (500-700 ms) dACC contributions, suggesting both proactive control before recollection and reactive control in response to intrusions. Stronger early activity was associated with reduced hippocampal activity and diminished BOLD signal in dACC and rDLPFC, suggesting that preempting retrieval reduced overall control demands. In the later window, dACC activity was larger, and effective connectivity analyses revealed robust communication from dACC to rDLPFC and from rDLPFC to hippocampus, which are tied to successful forgetting. Together, our findings support a model in which dACC detects the emergence of unwanted content, triggering top-down inhibitory control, and in which rDLPFC countermands intruding thoughts that penetrate awareness.SIGNIFICANCE STATEMENT Preventing unwanted memories from coming to mind is an adaptive ability of humans. This ability relies on inhibitory control processes in the prefrontal cortex to modulate hippocampal retrieval processes. How and when reminders to unwelcome memories come to trigger prefrontal control mechanisms remains unknown. Here we acquired neuroimaging data with both high spatial and temporal resolution as participants suppressed specific memories. We found that the anterior cingulate cortex detects the need for memory control, responding both proactively to early warning signals about unwelcome content and reactively to intrusive thoughts themselves. When unwanted traces emerge in awareness, anterior cingulate communicates with prefrontal cortex and triggers top-down inhibitory control over the hippocampus through specific neural oscillatory networks.

Can't stop thinking: The role of cognitive control in suppression-induced forgetting

The ability to control unwanted memories is essential for emotional regulation and maintaining mental health. Previous evidence indicates that suppressing retrieval, which recruits executive control mechanisms to prevent unwanted memories entering consciousness, can cause forgetting, termed suppression-induced forgetting (SIF). Because these executive mechanisms involve multiple mental operations, their effects may be limited by individuals' capacity limitation of cognitive control. Here, we tested the hypothesis that cognitive control capacity (CCC, estimated by the backward masking majority function task) is an important factor that predicts SIF. Participants were assigned to two groups based on the median CCC and performed the think/no-think task with electrophysiological signals recorded. The results showed that the SIF effect was observed only in the high CCC group but not in the low CCC group. In accordance, repeated suppression attempts also resulted in a steeper reduction in intrusive thoughts in the high CCC group. Furthermore, ERP analysis revealed a decrease in recollection-related late parietal positivity (LPP) under the no-think condition in the high CCC group, indicating successful avoidance of recall. A mediation analysis revealed that the reduced intrusive memories mediated the effect of CCC on SIF. These findings suggest that suppressing retrieval could reduce traces of the unwanted memories, making them less intrusive and harder to recall. More importantly, successful SIF is constrained by the capacity of cognitive control which may be used to ensure the coordination of multiple cognitive processes during suppression.

Retrieval suppression induced forgetting on 1-week-old consolidated episodic memories

Retrieval suppression has been established to cause forgetting on a wide range of memory types, but mostly in newly formed memories. Over time, the consolidation process stabilizes memory and changes the memory locus in the brain, which may affect the effectiveness of retrieval suppression. In two experiments, we examined whether retrieval suppression can induce forgetting on consolidated episodic memories and explored its potential reliance on explicit memory reactivation or spontaneous memory intrusions to destabilize the consolidated memory. We found that, compared with associative interference, another well-established forgetting approach, retrieval suppression consistently induced forgetting on 1-week-old memories. This suppression-induced forgetting was uncovered stably via an independent retrieval cue, suggesting its effect being on the target memory itself. However, we did not find evidence of modulation on the suppression-induced forgetting by either explicit reactivation or spontaneous intrusions. Together, our results extend the suppression-induced forgetting to episodic memories that have been consolidated for 1 week and suggest that retrieval suppression could destabilize consolidated memories.

Effects of psychosocial stress on prosociality: the moderating role of current life stress and thought control

To date, only a few studies have examined whether and when stressed individuals are still prosocially motivated and willing to help others, which is in contrast to the relevance and importance that helping others has for our society. The present study investigates the impact of affective and biopsychological acute stress responses on prosociality (prosocial motivation, helping behavior) under controlled laboratory conditions. In addition, it was examined whether this relationship is affected by individuals' current life stress and the cognitive ability to keep stress-related thoughts at bay. To induce acute stress responses (heart rate, negative affect, salivary alpha-amylase, cortisol), 55 individuals (28 women, M = 24 years old, SD = 4.53) were exposed to the Trier Social Stress Test (TSST). Current life stress (cortisol) was assessed over two days of participants' everyday lives. Thought control ability was assessed with the think/no-think paradigm and was additionally manipulated after the acute stress intervention (TSST) via instructions. The results showed that acute stress was positively associated with prosociality. Specifically, negative affect was positively related to prosocial motivation and salivary alpha-amylase was positively associated with helping behavior. Current life stress moderated the relationship between salivary cortisol and helping behavior: the association was positive at low levels of current life stress. The instruction to control one's thoughts but not participants' general ability to do so reduced stress responses (negative affect). In sum, the findings suggest that prosociality increases following acute stress and that this effect depends on the level of current life stress. Additionally, adopting the strategy of controlling stress-related thoughts was found to be promising for attenuating individuals' stress responses.

Circadian influence on intrusive re-experiencing in trauma survivors' daily lives

BACKGROUND

The core clinical feature of posttraumatic stress disorder (PTSD) is recurrent re-experiencing in form of intrusive memories. While a great number of biological processes are regulated by sleep and internal biological clocks, the effect of 24-hour biological cycles, named circadian rhythm, has not been investigated in the context of intrusive memories.

OBJECTIVE

Here we examined effects of time of day on frequency and characteristics of intrusive re-experiencing.

METHODS

Fifty trauma survivors reported intrusive memories for 7 consecutive days using ecological momentary assessment in their daily life. We investigated (i) time-of-day dependent effects on frequency and distribution of intrusive re-experiencing in the overall sample as well as in PTSD versus non-PTSD and (ii) time-of-day dependent effects on the memory characteristics intrusiveness, vividness, nowness and fear.

RESULTS

Intrusive memories showed a curvilinear pattern that peaked at 2pm. Intrusive memories in the PTSD group showed a constant level of intrusive re-experiencing in the afternoon and evening, whereas a descending slope was present in the non-PTSD group. In PTSD, intrusive memories might thus be experienced in a more time-scattered fashion throughout the day, indicating chronodisruption. Intrusion characteristics did not follow this pattern.

CONCLUSION

Although preliminary and based on a small sample size, these findings contribute to a better understanding of the everyday occurrence and characteristics of intrusive memories, and point to the added value of examining time-dependent effects, which can directly inform prevention and intervention science.

EEG evidence that morally relevant autobiographical memories can be suppressed

Remembering unpleasant events can trigger negative feelings. Fortunately, research indicates that unwanted retrieval can be suppressed to prevent memories from intruding into awareness, improving our mental state. The current scientific understanding of retrieval suppression, however, is based mostly on simpler memories, such as associations between words or pictures, which may not reflect how people control unpleasant memory intrusions in everyday life. Here, we investigated the neural and behavioural dynamics of suppressing personal and emotional autobiographical memories using a modified version of the Think/No-Think task. We asked participants to suppress memories of their own past immoral actions, which were hypothesised to be both highly intrusive and motivating to suppress. We report novel evidence from behavioural, ERP, and EEG oscillation measures that autobiographical memory retrieval can be suppressed and suggest that autobiographical suppression recruits similar neurocognitive mechanisms as suppression of simple laboratory associations. Suppression did fail sometimes, and EEG oscillations indicated that such memory intrusions occurred from lapses in sustained control. Importantly, however, participants improved at limiting intrusions with repeated practice. Furthermore, both behavioural and EEG evidence indicated that intentional suppression may be more difficult for memories of our morally wrong actions than memories of our morally right actions. The findings elucidate the neurocognitive correlates of autobiographical retrieval suppression and have implications for theories of morally motivated memory control.

Threat memory devaluation by a dual-task intervention: Testing return of fear and intrusive memory over 48 hours

BACKGROUND AND OBJECTIVES

In dual-tasking, individuals recall a threat-related memory while performing a demanding dual-task. This is a fruitful approach to reduce the unpleasantness and vividness of aversive memories and to reduce conditioned fear responses. Crucially, it remains unclear whether dual-tasking can also reduce conditioned fear responses and intrusive memories over time. In this pre-registered two-day fear conditioning paradigm, we examined whether a dual-task intervention reduces return of fear and the frequency of intrusive memories of an aversive film over time.

METHODS

On Day 1, 76 healthy participants underwent fear acquisition with aversive film clips. They were then randomly allocated to one of three conditions: dual-tasking, memory recall without a dual-task ('recall only'), or no task. Afterwards, they underwent an extinction phase and were asked to record intrusive film memories over 48 h. On Day 3, return of fear was assessed.

RESULTS

On Day 1, fear acquisition and extinction were successful. On Day 3, spontaneous recovery and renewal were evident, but, overall, participants reported few intrusions. The dual-task and recall only groups reported reduced unpleasantness of threat memory compared to the no task group, but they did not show reduced (return of) fear responses or fewer intrusions.

LIMITATIONS

Intrusion frequency was low in all three groups, which limits the detection of intervention effects.

CONCLUSIONS

Even though dual-tasking and recall only devalued threat memory temporarily compared to no task, these interventions did not reduce (return of) fear responses and intrusions. Future studies could focus on improving the potency of imagery-based interventions.

Are Individuals Always Aware of Their Trauma-Related Intrusive Thoughts? A Study of Meta-Awareness

Individuals are not always aware of their mental content. We tested whether lack of awareness occurs in those who have experienced trauma, with and without posttraumatic stress disorder (PTSD). We also examined the role of proposed cognitive mechanisms (working memory and inhibition) in explaining unnoticed intrusions. Individuals with PTSD (n = 44), and varying levels of symptoms (high posttraumatic stress [PTS]: n = 24; low PTS: n = 37) reported on intrusive thoughts throughout a reading task. Intermittently, participants responded to probes about whether their thoughts were trauma related. Participants were "caught" engaging in unreported trauma-related thoughts (unnoticed intrusions) for between 24 and 27% of the probes in the PTSD and high PTS groups, compared with 15% of occasions in the low PTS group. For trauma-related intrusions only, participants lacked meta-awareness for almost 40% of probes in the PTSD group, which was significantly less than that observed in the other groups (∼60%). Contrary to predictions, working memory and response inhibition did not predict unnoticed intrusions. The results suggest that individuals who have experienced significant trauma can lack awareness about the frequency of their trauma-related thoughts. Further research is warranted to identify the mechanisms underpinning the occurrence of unnoticed intrusions.

Influence of negative mood on restrained eaters' memory suppression of food cues: An event-related potentials study

Negative mood has been found to be a critical trigger for overeating in restrained eaters. The ability to suppress thinking of palatable food cues is crucial to control hedonic eating; nevertheless, little research has been conducted to explore inhibitory control in cognitive processes among restrained eaters. To address this gap, this study primed restrained eaters with negative (n = 23) or neutral emotions (n = 24) and applied a Think/No-think paradigm to explore their retrieval facilitation/suppression ability for food cues, while recording Electroencephalogram (EEG) data. Results indicated that the recall rate of the No-think condition (retrieval suppressing task) was higher than the Think condition (retrieval task). Negative affect did not influence the recall rate, but it did evoke smaller N2 amplitudes, larger P2 and P3 amplitudes, as well as late positive component (LPC) amplitudes. Among these components, P2 evoked by the No-think and Think conditions was larger than the perceptual control condition. Our findings suggested that in negative moods, restrained eaters need to allocate more attentional resources to suppress food cues. The findings further demonstrated that the influence of negative moods appeared at an early stage of cognitive processing and caused a resource depletion in memory suppression. This research provides a neurophysiological basis for understanding emotional influences on the process of restrained eaters' inhibition control for external food cues.

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.

But first, coffee: The roles of arousal and inhibition in the resistance of compulsive cleansing in individuals with high contamination fears

Inhibition plays a crucial role in reducing intrusive thoughts and compulsive behaviors, such as handwashing, in response to the feeling of disgust. The current study examines whether manipulating arousal can facilitate inhibition and the resistance of compulsive cleansing. Forty-seven participants with high contamination fears were recruited for this study. Participants were divided into a caffeine group or a no-caffeine group. Participants touched a potentially contaminated and disgusting stimulus ("dirty" diapers) and were asked to wait as long as they could before washing their hands. Only the caffeine group exhibited greater pre-post stop-signal reaction time improvement in the stop-signal task, indicating improved inhibition. Participants in the caffeine group exhibited significantly lower subjective distress and urges-to-wash their hands both after touching the stimulus and while waiting to engage in the cleansing behavior. Similarly, the caffeine group resisted the urge to compulsively cleanse for about twice as long as those in the no-caffeine group. Time spent washing, subjective distress levels, and urge-to-wash levels after participants washed their hands were similar between groups. The current findings support the notion that increased arousal improves inhibition, which may play a role in improving our ability to resist intrusive disgust and compulsive cleansing behaviors.

Dysfunctional coupling of the parahippocampal cortex and inferior frontal gyrus during memory suppression in posttraumatic stress disorder

The current study aimed to identify alterations in brain activation and connectivity related to memory suppression in posttraumatic stress disorder (PTSD) using the Think/No-Think paradigm during functional magnetic resonance imaging (fMRI). Reduced activation in the parahippocampal cortex during No-Think vs. Baseline trials was found in participants with PTSD compared to controls with no history of trauma (pFWE<0.05). Trauma-related intrusive memories (r = 0.562, p = 0.046) and avoidance behaviors (r = 0.636, p = 0.020) were positively correlated with parahippocampal cortex activation during memory suppression in the PTSD group. Psychophysiological interactions (PPI) analysis identified increased functional connectivity between the inferior frontal gyrus and the parahippocampus during memory suppression in the PTSD group compared to trauma-free controls (pFWE<0.05). Our findings support a network-based phenotype for altered memory suppression in individuals with PTSD rooted in dysfunctional parahippocampal-prefrontal coupling. These data validate neural models of PTSD and offer a novel neural circuit for brain-based interventions targeting trauma-related memory.

Losing Control: Sleep Deprivation Impairs the Suppression of Unwanted Thoughts

Unwanted memories often enter conscious awareness when individuals confront reminders. People vary widely in their talents at suppressing such memory intrusions; however, the factors that govern suppression ability are poorly understood. We tested the hypothesis that successful memory control requires sleep. Following overnight sleep or total sleep deprivation, participants attempted to suppress intrusions of emotionally negative and neutral scenes when confronted with reminders. The sleep-deprived group experienced significantly more intrusions (unsuccessful suppressions) than the sleep group. Deficient control over intrusive thoughts had consequences: Whereas in rested participants suppression reduced behavioral and psychophysiological indices of negative affect for aversive memories, it had no such salutary effect for sleep-deprived participants. Our findings raise the possibility that sleep deprivation disrupts prefrontal control over medial temporal lobe structures that support memory and emotion. These data point to an important role of sleep disturbance in maintaining and exacerbating psychiatric conditions characterized by persistent, unwanted thoughts.

Active Forgetting: Adaptation of Memory by Prefrontal Control

Over the past century, psychologists have discussed whether forgetting might arise from active mechanisms that promote memory loss to achieve various functions, such as minimizing errors, facilitating learning, or regulating one's emotional state. The past decade has witnessed a great expansion in knowledge about the brain mechanisms underlying active forgetting in its varying forms. A core discovery concerns the role of the prefrontal cortex in exerting top-down control over mnemonic activity in the hippocampus and other brain structures, often via inhibitory control. New findings reveal that such processes not only induce forgetting of specific memories but also can suppress the operation of mnemonic processes more broadly, triggering windows of anterograde and retrograde amnesia in healthy people. Recent work extends active forgetting to nonhuman animals, presaging the development of a multilevel mechanistic account that spans the cognitive, systems, network, and even cellular levels. This work reveals how organisms adapt their memories to their cognitive and emotional goals and has implications for understanding vulnerability to psychiatric disorders.

Varieties of graded forgetting

Forgetting is typically viewed as counterproductive in everyday life. However, it may mainly be harmful when it is complete, that is, all-encompassing and permanent, and not when it is graded, that is, partial and fluctuating. I propose that forgetting is in fact mostly graded, and that this is an essential reason that it is often helpful. I delineate three ways in which forgetting may be graded. First, it may occur with respect to one, but not another, part of a memory. Second, it may occur in one context, but not in another. Third, forgetting may be present at one point in time, but not at another. Also, I propose that different levels of forgetting are possible, based on whether an engram or a context is unavailable, silent, restricted, latent, or potent. Overall, I hypothesize that forgetting is often helpful because it can be flexible and tailored to the circumstances.

Stop Thinking: An Experience Sampling Study on Suppressing Distractive Thoughts at Work

In modern work environments, it can be difficult for workers to avoid becoming distracted from their current task. This study investigates person-situation interactions to predict thought control activities (kind of self-control), which aim to stop distracting thoughts that enter the mind. Specifically, it was examined (1) how challenging work demands (time pressure, task complexity) activate workers' thought control to stop distractive thoughts (n level 2 = 143) and relate to the effort to do so (n level 2 = 91) in daily working life and (2) how these relationships differ according workers' general cognitive ability to suppress unwanted thoughts. To understand these person-situation interactions, an experience sampling study was combined with a laboratory task assessing the ability to suppress unwanted thoughts (think/no-think task). Multilevel modeling revealed that workers' engage more often and more intensively in thought control activities at a moderate level of time pressure but only when they had a higher general ability to suppress unwanted thoughts. For workers with a lower ability to suppress unwanted thoughts, increasing time pressure was negatively related to thought control activities, even at very low levels of time pressure. Thus, whether time pressure activates or hinders thought control depends on individuals' ability to suppress distractive thoughts.

Recurrent involuntary autobiographical memories: characteristics and links to mental health status

Memories of events from one's personal past that come to mind unintentionally and effortlessly are termed involuntary autobiographical memories (IAMs). Recurrent IAMs are known as relevant to many disorders within clinical literature. However, less is known about their links with mental health status in the general population. In the current study, 2184 undergraduate students completed surveys assessing occurrence of any recurrent IAMs. Participants also wrote a description of their most frequently recurring IAM and rated it on phenomenological characteristics, such as frequency, valence, vividness, and centrality. Results showed that the majority of our sample experienced recurrent IAMs, replicating previous findings, but most of these memories were emotionally negative, unlike past work. Importantly, negative recurrent IAMs were associated with significantly more mental health concerns, including symptoms of depression, anxiety, and posttraumatic stress. We also found that frequency of IAM recurrence was predicted by the memory's age, level of completeness/detail, emotional intensity, and centrality to one's life story. Further, descriptions of positive recurrent IAMs contained significantly more episodic detail compared to negative or neutral ones, suggesting that emotional regulation may play a role in how recurrent IAMs are recounted. Recurrent IAMs, and their characteristics, serve as a window into mental health status.

Rescripting experimental trauma: Effects of imagery and writing as a way to reduce the development of intrusive memories

BACKGROUND AND OBJECTIVES

Imagery rescripting is an effective treatment strategy for trauma related disorders, but its underlying mechanisms are still largely unknown. The aim of the present study was to test whether a) imagery (versus writing) is essential in the process of rescripting, and b) rescripting affects emotional memories on an implicit level.

METHODS

Healthy participants were subjected to an experimental trauma ('trauma film'), and randomly allocated to four conditions: recall of film + Imagery Rescripting (ImRs), recall of film + Writing Rescripting (WRs), recall only (ImRE), or no recall + no manipulation (NM). Next, participants recorded intrusion frequency and distress during one week, after which they executed a visual interference task (VIT) including neutral and trauma film stills, to access implicit emotional memory.

RESULTS

Main findings were that ImRs and WRs resulted in fewer intrusions than NM, with no differences between both rescripting conditions. We did not find an effect on intrusion distress and the VIT.

LIMITATIONS

Stills in the VIT were distracted from all four film scenes, whereas rescripting was done on one scene only, possibly obscuring the effect. Also, an analogue sample was used, which may limit generalizability to clinical samples.

CONCLUSIONS

We replicated previous effects of ImRs on intrusion development. Furthermore, no superior effect of imagery as key modality for rescripting was found; writing seems a viable alternative. Measures for implicit emotional memory such as the VIT may have to be applied relatively soon after the experimental session (e.g., same day as the experimental session).

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.

Emotional conflict adaptation predicts intrusive memories

Why do some individuals experience intrusive emotional memories following stressful or traumatic events whereas others do not? Attentional control may contribute to the development of such memories by shielding attention to ongoing tasks from affective reactions to task-irrelevant emotional stimuli. The present study investigated whether individual differences in theability to exert cognitive control are associated with experiencing intrusive emotional memories after laboratory trauma. Sixty-one healthy women provided self-reported and experimentally derived measures of attentional control. They then viewed a trauma film in the laboratory and recorded intrusive memories for one week using a diary. Gaze avoidance during trauma film exposure was associated with more intrusive memories. Greater attentional control over emotion prior to film viewing, as assessed with the experimental task, predicted fewer intrusive memories while self-reported attentional control was unrelated to intrusive memories. Preexisting capacity to shield information processing from distraction may protect individuals from developing intrusive emotional memories following exposure to stress or trauma. These findings provide important clues for prevention and intervention science.

Time to Forget

Abstract. Emerging technologies at work encourage the collection and storage of large amounts of data. However, these vast quantities of data are likely to impair efficient work decisions by employees over time, with negative consequences for the organization. As human attention increasingly represents the scarce resource at work, the present paper focuses on a mechanism of attentional control at work – namely, intentionally forgetting unwanted and outdated internal (e. g., knowledge) and external (e. g., digital objects) information. The purpose of this paper is threefold. Based on a short review of the research on intentional forgetting, a prototypical conceptualization of an interactive assistive system (Dare2Del, cognitive companion) is provided, which should support employees in temporally ignoring or permanently deleting outdated information. Then, we completed a critical incident study to examine why and when employees might want to forget information at work, and to identify in which working situations an assistive system should be particularly helpful.

Reconsidering unconscious persistence: Suppressing unwanted memories reduces their indirect expression in later thoughts

When we seek to forget unwelcome memories, does the suppressed content still exert an unconscious influence on our thoughts? Although intentionally stopping retrieval of a memory reduces later episodic retention for the suppressed trace, it remains unclear the extent to which suppressed content persists in indirectly influencing mental processes. Here we tested whether inhibitory control processes underlying retrieval suppression alter the influence of a memory's underlying semantic content on later thought. To achieve this, across two experiments, we tested whether suppressing episodic retrieval of to-be-excluded memories reduced the indirect expression of the unwanted content on an apparently unrelated test of problem solving: the remote associates test (RAT). Experiment 1 found that suppressed content was less likely than unsuppressed content to emerge as solutions to RAT problems. Indeed, suppression abolished evidence of conceptual priming, even when participants reported no awareness of the relationship between the memory and the problem solving tasks. Experiment 2 replicated this effect and also found that directing participants to use explicit memory to solve RAT problems eliminated suppression effects. Experiment 2 thus rules out the possibility that suppression effects reflect contamination by covert explicit retrieval strategies. Together, our results indicate that inhibitory control processes underlying retrieval suppression not only disrupt episodic retention, but also reduce the indirect influence of suppressed semantic content during unrelated thought processes. Considered with other recent demonstrations of implicit suppression effects, these findings indicate that historical assumptions about the persisting influence of suppressed thoughts on mental health require closer empirical scrutiny and need to be reconsidered.

The impact of retrieval suppression on conceptual implicit memory

When people suppress retrieval of episodic memories, it can induce forgetting on later direct tests of memory for those events. Recent reports indicate that suppressing retrieval affects less conscious, unintentional retrieval of unwanted memories as well, at least on perceptually-oriented indirect tests. In the current study we examined how suppressing retrieval affects conceptual implicit memory for the suppressed content, using a category verification task. Participants studied cue-target words pairs in which the targets were exemplars of 22 semantic categories, such as vegetables or occupations. They then repeatedly retrieved or suppressed the targets in response to the cues for some of those pairs. Afterwards, they were exposed to the targets intermixed with novel items, one at a time, and asked to verify the membership of each of the words in a semantic category, as quickly as possible. Judgment response times to studied words were faster than to unstudied exemplars, reflecting repetition priming, as has been previously observed. Strikingly, the beneficial effects of prior exposure on response time were eliminated for targets that had been suppressed. Follow-up explicit memory tests also demonstrated that retrieval suppression continued to disrupt episodic recall for the items that had been just been re-exposed on the category verification test. These findings support the contention that the effects of retrieval suppression are not limited to episodic memory, but also affect indirect expressions of those memories on conceptually oriented tests, raising the possibility that underlying semantic representations of suppressed content are affected.

Cortisol administration after extinction in a fear-conditioning paradigm with traumatic film clips prevents return of fear

Cortisol is a stress hormone and potent modulator of learning and memory processes. If administered after learning, cortisol can enhance memory consolidation. Yet it is unknown whether cortisol administration after fear extinction learning strengthens extinction memory. Extinction is a crucial mechanism underlying psychotherapy of posttraumatic stress disorder (PTSD). The present study examined whether extinction can be enhanced by administering cortisol after extinction training. In a registered, randomized, double-blind and placebo controlled trial, 50 healthy participants were exposed to a differential fear-conditioning paradigm with neutral faces as conditioned stimuli (CS) and traumatic film clips as unconditioned stimuli (US). They received either cortisol (n = 25) or placebo (n = 25) immediately after extinction. The cortisol group showed less fear during a return of fear manipulation (reinstatement) evidenced by attenuated fear potentiated startle responses and US-expectancy ratings than the placebo group. Results indicate that cortisol administration after fear extinction strengthens extinction memory and suggest that it might be advantageous to administer cortisol subsequent to successful exposure treatment sessions.

Intrusive memories of trauma: A target for research bridging cognitive science and its clinical application

Intrusive memories of a traumatic event can be distressing and disruptive, and comprise a core clinical feature of post-traumatic stress disorder (PTSD). Intrusive memories involve mental imagery-based impressions that intrude into mind involuntarily, and are emotional. Here we consider how recent advances in cognitive science have fueled our understanding of the development and possible treatment of intrusive memories of trauma. We conducted a systematic literature search in PubMed, selecting articles published from 2008 to 2018 that used the terms "trauma" AND ("intrusive memories" OR "involuntary memories") in their abstract or title. First, we discuss studies that investigated internal (neural, hormonal, psychophysiological, and cognitive) processes that contribute to intrusive memory development. Second, we discuss studies that targeted these processes using behavioural/pharmacological interventions to reduce intrusive memories. Third, we consider possible clinical implications of this work and highlight some emerging research avenues for treatment and prevention, supplemented by new data to examine some unanswered questions. In conclusion, we raise the possibility that intrusive memories comprise an alternative, possibly more focused, target in translational research endeavours, rather than only targeting overall symptoms of disorders such as PTSD. If so, relatively simple approaches could help to address the need for easy-to-deliver, widely-scalable trauma interventions.

The Prospective Influence of Trait Alexithymia on Intrusive Memories: What Is the Role of Emotional Recognition Memory?

Posttraumatic stress disorder (PTSD) is often considered to be a disorder of memory as patients suffer from fragmented uncontrollable memories (intrusions) whilst experiencing difficulties in intentionally retrieving details of the traumatic event. Recent research suggests that trait-related deficits in the identification of emotional states (alexithymia) may impact emotional memory processes in a way that promotes intrusion formation in PTSD. Therefore, we investigated the influence of alexithymia on intrusive re-experiencing and emotional recognition memory in a prospective analog study. Twenty-six healthy participants took part in a laboratory experiment, which combined two independent paradigms. Participants were exposed to a traumatic film (first session) and completed an episodic memory task comprising neutral and emotional stimuli (second session). In between sessions, participants recorded intrusive memories of the film. Individuals with higher trait alexithymia (HTA) reported an increased number of intrusions on the day of film presentation. Moreover, analyses of memory performance revealed a negative correlation between alexithymia and emotional recognition memory. Further analyses suggest that reduced emotional recognition memory, as evident in individuals with HTA, may, in turn, be associated with enhanced intrusive re-experiencing. As such, the current findings provide first indications regarding the role of alexithymia in emotional learning and PTSD. Future studies should further investigate these associations as well as potential implications for the treatment of PTSD.

What doesn't kill you makes you stronger: Psychological trauma and its relationship to enhanced memory control

Control processes engaged in halting the automatic retrieval of unwanted memories have been shown to reduce the later recallability of the targets of suppression. Like other cognitive skills that benefit from practice, we hypothesized that memory control is similarly experience dependent, such that individuals with greater real-life experience at stopping retrieval would exhibit better inhibitory control over unwanted memories. Across two experiments, we found that college students reporting a greater history of trauma exhibited more suppression-induced forgetting of both negative and neutral memories than did those in a matched group who had reported experiencing little to no trauma. The association was especially evident on a test of suppression-induced forgetting involving independent retrieval cues that are designed to better isolate the effects of inhibitory control on memory. Participants reporting more trauma demonstrated greater generalized forgetting of suppressed material. These findings raise the possibility that, given proper training, individuals can learn to better manage intrusive experiences, and are broadly consistent with the view that moderate adversity can foster resilience later in life. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Memory Control: A Fundamental Mechanism of Emotion Regulation

Memories play a ubiquitous role in our emotional lives, both causing vivid emotional experiences in their own right and imbuing perception of the external world with emotional significance. Controlling the emotional impact of memories therefore poses a major emotion-regulation challenge, suggesting that there might be a hitherto unexplored link between the neurocognitive mechanisms underlying memory control (MC) and emotion regulation. We present here a theoretical account of how the mechanisms of MC constitute core component processes of cognitive emotion regulation (CER), and how this observation may help to understand its basic mechanisms and their disruption in psychiatric disorders.

Mnemonic emotion regulation: a three-process model

Emotion regulation comprises attempts to influence when and how emotions are experienced and expressed. It has mostly been conceived of as proactive (e.g. situation selection) or reactive (e.g. attentional distraction), but it may also be retroactive and involve memory. I term such past-oriented activity mnemonic emotion regulation and propose that it involves increasing or decreasing access to or altering the characteristics of a memory. People may increase access to a memory and make it more likely that it will be retrieved in the future, for example by rehearsing a pleasant memory. They may decrease access to a memory and make it less likely that intrusions will be experienced in the future, for example by repeatedly trying to stop an unpleasant memory from being retrieved. Finally, people may alter the characteristics of a memory and change its content or context, for example by replacing a negative impression with a productive interpretation. I discuss how mnemonic emotion regulation may be instigated (e.g. via elaborate rehearsal) as well as the different motives (e.g. hedonic motives) people may have for engaging in regulation. Also, I discuss possible benefits of, variations in, and improvements of mnemonic emotion regulation.

Neurocognitive and Information Processing Biases in Posttraumatic Stress Disorder

PURPOSE OF REVIEW

We review recent research addressing neurocognitive and information processing abnormalities in posttraumatic stress disorder (PTSD), including studies informing direction of causality. We additionally consider neurocognition in the context of co-morbid mild traumatic brain injury (TBI) and psychosocial treatments for PTSD.

RECENT FINDINGS

Learning, memory, attention, inhibitory functions, and information processing biases frequently accompany PTSD, reflecting potential bi-directional relationships with PTSD. Although mild TBI is associated with increased risk of PTSD development and maintenance, TBI does not typically contribute significantly to sustained neurocognitive deficits in individuals with PTSD. Whereas better learning and memory is associated with mildly enhanced response to psychosocial interventions, such interventions may also improve neurocognitive performance and can be effectively provided to patients with TBI history. PTSD is associated with cognitive abnormalities in processing both emotionally relevant and emotionally neutral information and, although mild, may underlie some PTSD symptom expression.

Therapy Dogs as a Crisis Intervention After Traumatic Events? - An Experimental Study

Animal-assisted therapy has been proposed as a treatment adjunct for traumatized patients. In animal-assisted crisis response, dogs are used directly after a traumatic event to reduce stress and anxiety. However, to date there are few controlled studies investigating the effects of therapy dogs on PTSD symptoms and to our knowledge there is no study investigating the effects of a therapy dog intervention directly after a traumatic event. In this study, 60 healthy female participants were randomly assigned to one of three groups: after exposure to a “traumatic” film clip (trauma-film paradigm), one group of participants interacted with a friendly dog for 15 min, another group of participants watched a film clip showing a person interacting with a friendly dog and the last group was instructed to relax. Participants who had interacted with the dog after the film reported lower anxiety levels, less negative affect, and more positive affect after the intervention as compared to the other two groups. However, the participants who interacted with the dog showed a smaller decrease in physiological arousal after the traumatic film clip compared to both other groups. There were no differences in intrusion symptoms between the three groups. Our results show that dogs are able to lessen subjectively experienced stress and anxiety after a “traumatic” stress situation.

The neural dynamics of deficient memory control in heavily traumatized refugees

Victims of war, torture and natural catastrophes are prone to develop posttraumatic stress disorder (PTSD). These individuals experience the recurrent, involuntary intrusion of traumatic memories. What neurocognitive mechanisms are driving this memory disorder? Here we show that PTSD symptoms in heavily traumatized refugees are related to deficits in the effective control of memory retrieval. In a think/no-think task, PTSD patients were unable to forget memories that they had previously tried to suppress when compared to control participants with the same trauma history but without PTSD. Deficits in voluntary forgetting were clinically relevant since they correlated with memory intrusions in everyday life. Magnetoencephalography (MEG) recorded during suppression attempts revealed that PTSD patients were unable to downregulate signatures of sensory long-term memory traces in the gamma frequency band (70-120 Hz). Thus, our data suggest that the inability to suppress unwanted memories through modulation of gamma activity is related to PTSD symptom severity.

Frequency of Intrusions and Appraisal of Related Distress After Analogue Trauma: A Comparative Ecological Momentary Assessment Methods Study

Intrusive thoughts, images, and their appraisal remain difficult to study despite their clinical relevance. Clinical studies typically used time-based (frequency and distress per observation period), while analogue studies mainly used event-based (report upon occurrence) assessment. A comparison of intrusion frequency, distress appraisal, compliance, and reactivity across different assessments is mostly lacking, particularly with regard to analogue research. Here, intrusions were induced via aversive films and assessed by a smart phone application for 4 days. Three sampling modes were compared by randomizing participants to one of three conditions: either one, or five time-based daily prompts, or event-based assessment. At the end of the study, all participants reported intrusions once again in a retrospective summary assessment. Results indicate that intrusions and their distress decayed over a few days. The three assessments did not differ in intrusion frequency, distress appraisal, compliance (generally high), reactivity (generally low), or retrospective summary assessment. Across groups, the more aversive and arousing participants rated the film clips and the more reactivity to the electronic-diary assessment they reported, the more intrusive memories they had; assessment modes did not differ on this. Thus, no general differences were found between electronic-diary assessment modes for analogue intrusions, giving researchers flexibility for tailoring ecological momentary assessment to specific study aims.

Conditioned responses to trauma reminders: How durable are they over time and does memory integration reduce them?

BACKGROUND AND OBJECTIVES

Stimuli associated with the trauma are important triggers for intrusive memories after a traumatic event. Clinical models assume that fear conditioning for neutral stimuli encountered during traumatic events is a potential cause of these intrusions, and that memory integration has the effect of reducing these associations, thereby also reducing intrusions. This study examines whether conditioned associations lead to intrusive trauma memories and how they are affected by memory integration.

METHODS

Forty-eight healthy participants watched a neutral and a "traumatic" film, both containing neutral sounds, and, on the following day, were randomly allocated to memory integration of either the "traumatic" film or the neutral film. Intrusive memories were monitored for one week. Participants repeatedly completed a memory triggering task, in order to assess how durable conditioned intrusive memories are over time.

RESULTS

Trauma-associated sounds elicited intrusive memories and anxiety when encountered directly after film presentation, as well as one and seven days later. Furthermore, enhanced conditionability predicted subsequent ambulatory trauma intrusions. No evidence was found for the assumption that memory integration of the "traumatic" film reduced conditioned reactions.

LIMITATIONS

The presented film is a relatively mild stressor as compared to a real-life trauma. Further studies are needed to explore the role of conditioned intrusions for real-life trauma.

CONCLUSIONS

This study provides evidence for the assumption that intrusive trauma memories can be explained by conditioned responses to neutral stimuli encountered during the trauma and that these effects are stable over time. Implications for PTSD and its treatment are discussed.