The effects of dual-tasks on intrusive memories following analogue trauma

The effectiveness of two novel approaches to prevent intrusions: A pilot study comparing Tetris_dualtask and imagery rescripting to control

BACKGROUND AND OBJECTIVES

Post-traumatic stress disorder (PTSD) is a global health problem. Although effective treatments for it exist, early interventions that prevent PTSD from developing are lacking. The aim of this pilot analogue trauma study was to compare the effects of two potential early intervention strategies, namely Tetris_dualtask and imagery rescripting (IR) to a no-intervention control group on intrusion frequency and the vividness and emotionality of aversive film memory.

METHODS

Sixty healthy students were subjected to the trauma film paradigm and randomly allocated to either: Tetris_dualtask, IR or no-intervention. Main outcomes were the number of film-related intrusions at one week and vividness and emotionality ratings of the most aversive film memory. Secondary outcomes were PTSD-like symptoms, intrusion intensity, and explicit film memory.

RESULTS

The Tetris_dualtask group reported significant fewer intrusions compared to the no-intervention group; whereas the IR group did not. No effect was found on vividness and emotionality ratings, PTSD-like symptoms, intrusion intensity, and explicit memory.

LIMITATIONS

The sample size was small, and analogue trauma in healthy individuals was examined, thus generalizability may be limited. Also, to increase comparability between interventions, the duration of Tetris_dualtask and IR was standardized. As a result, the IR intervention was shorter compared to other studies, which might have decreased its efficacy.

CONCLUSIONS

The results of this pilot study suggest that playing Tetris during retrieval of traumatic images, might hold potential as an early intervention strategy to reduce intrusions in the early aftermath of trauma and adversity. However, future large-scale replication research is needed.

Bilateral eye movements disrupt the involuntary perceptual representation of trauma-related memories

Bilateral eye movement (EM) is a critical component in eye movement desensitization and reprocessing (EMDR), an effective treatment for post-traumatic stress disorder. However, the role of bilateral EM in alleviating trauma-related symptoms is unclear. Here we hypothesize that bilateral EM selectively disrupts the perceptual representation of traumatic memories. We used the trauma film paradigm as an analog for trauma experience. Nonclinical participants viewed trauma films followed by a bilateral EM intervention or a static Fixation period as a control. Perceptual and semantic memories for the film were assessed with different measures. Results showed a significant decrease in perceptual memory recognition shortly after the EM intervention and subsequently in the frequency and vividness of film-related memory intrusions across one week, relative to the Fixation condition. The EM intervention did not affect the explicit recognition of semantic memories, suggesting a dissociation between perceptual and semantic memory disruption. Furthermore, the EM intervention effectively reduced psychophysiological affective responses, including the skin conductance response and pupil size, to film scenes and subjective affective ratings of film-related intrusions. Together, bilateral EMs effectively reduce the perceptual representation and affective response of trauma-related memories. Further theoretical developments are needed to elucidate the mechanism of bilateral EMs in trauma treatment.

Can working memory account for EMDR efficacy in PTSD?

BACKGROUND

Although eye movement desensitization and reprocessing (EMDR) has been shown to be effective in the treatment of PTSD for years, it remains controversial due to the lack of understanding of its mechanisms of action. We examined whether the working memory (WM) hypothesis -the competition for limited WM resources induced by the dual task attenuates the vividness and emotionality of the traumatic memory - would provide an explanation for the beneficial effect induced by bilateral stimulation.

METHODS

We followed the Prisma guidelines and identified 11 articles categorized in two types of designs: studies involving participants with current PTSD symptoms and participants without PTSD diagnosis.

RESULTS

Regardless of the types of studies, the results showed a reduction of vividness and emotionality in the recall of traumatic stimuli under a dual-task condition compared to a control condition, such as recall alone. However, two studies used a follow-up test to show that this effect does not seem to last long.

CONCLUSION

Our results provide evidence for the WM hypothesis and suggest that recalling a traumatic memory while performing a secondary task would shift the individual's attention away from the retrieval process and result in a reduction in vividness and emotionality, also associated with the reduction of symptoms.

Boosting long-term effects of degraded memories via acute stress

Combining recall of an emotional memory with simultaneous horizontal eye movements (i.e., Recall + EM) reduces memory aversiveness. However, the long-term persistence of this effect is inconsistent across studies. Given that stress may aid in the consolidation of memories, we examined whether acute stress can boost the long-term effects of degraded memories. To test this, participants recalled two negative memories, which were assigned to a Recall + EM or Recall Only condition. Before and after each intervention they rated memory aversiveness (i.e., immediate effects) followed by a stress-induction or control procedure. After a 24h-period, participants rated each memory again (i.e., long-term effects). We found that Recall + EM produces immediate effects but that these effects dissolve over time. Moreover, acute stress did not boost potential long-term effects of Recall + EM. Degraded memories were not retained better by applying stress. We discuss these results and how long-term effectiveness may still be achieved.

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We examined whether stress boosts the long-term effects of degraded memories.

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Dual-task interventions robustly produce immediate memory degrading effects.

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Immediate memory degrading effects dissolve over time (24h later).

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The stress manipulation increased cardiovascular/neuroendocrine stress responses.

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Acute stress did not boost potential long-term effects of dual-task interventions.

No evidence for disruption of reconsolidation of conditioned threat memories with a cognitively demanding intervention

Simultaneous execution of memory retrieval and cognitively demanding interventions alter the subjective experience of aversive memories. This principle can be used in treatment to target traumatic memories. An often-used interpretation is that cognitive demand interferes with memory reconsolidation. Laboratory models applying this technique often do not meet some important procedural steps thought necessary to trigger reconsolidation. It remains therefore unclear whether cognitively demanding interventions can alter the reconsolidation process of aversive memories. Here, 78 (41 included) healthy participants completed an established 3-day threat conditioning paradigm. Two conditioned stimuli were paired with a shock (CS+ s) and one was not (CS-). The next day, one CS+ (CS+ R), but not the other (CS+), was presented as a reminder. After 10 min, participants performed a 2-back working memory task. On day three, we assessed retention. We found successful acquisition of conditioned threat and retention (CS+ s > CS-). However, SCRs to the CS+ R and the CS+ during retention did not significantly differ. Although threat conditioning was successful, the well-established cognitively demanding intervention did not alter the reconsolidation process of conditioned threat memories. These findings challenge current views on how cognitively demand may enhance psychotherapy-outcome.

A Case for Translation From the Clinic to the Laboratory

Laboratory procedures have been used for decades as analogues for clinical processes with the goal of improving our understanding of psychological treatments for emotional disorders and identifying strategies to make treatments more effective. This research has often focused on translation from the laboratory to the clinic. Although this approach has notable successes, it has not been seamless. There are many examples of strategies that work in the laboratory that fail to lead to improved outcomes when applied clinically. One possible reason for this gap between experimental and clinical research is a failure to focus on translation from the clinic to the laboratory. Here, we discuss potential benefits of translation from the clinic to the laboratory and provide examples of how this might be implemented. We first consider two well-established laboratory analogues (extinction and cognitive reappraisal), identify critical aspects of the related clinical procedures (exposure and cognitive restructuring) that are missing from these analogues, and propose variations to better capture the clinical process. Second, we discuss two clinical procedures that have more recently been brought into the laboratory (eye-movement desensitization and reprocessing and imagery rescripting). We conclude by highlighting potential implications of this proposed shift in focus for translational research.

Prosocial behaviour reduces unwanted intrusions of experimental traumatic memories

Following trauma exposure, people often experience involuntary intrusions of traumatic memories, i.e., flashbacks. How to reduce such unwanted intrusions attracts attention from basic and translational memory research, with a goal to safeguard mental well-being and promote resilience. Here, based on prosocial behaviour's well-documented psychological benefits, we hypothesized that post-trauma prosocial behaviour would causally reduce trauma-related symptoms, including involuntary intrusions. To test this novel hypothesis, we conducted two pre-registered lab studies (N = 180) using trauma films to induce lab-analogue trauma exposure. Following trauma exposure, participants were randomly assigned to prosocial or non-prosocial conditions. Specifically, in the prosocial condition, participants donated money to their preferred charities. In the non-prosocial conditions, participants completed either a neutral, number judgement task (Experiment 1) or a proself task (Experiment 2). Participants completed a 1-week intrusion diary and Impact of Event Scale-Revised (IES-R), to assess frequencies of traumatic intrusions and post-trauma stress disorder symptoms, respectively. Results showed that compared to non-prosocial behaviour, prosocial engagement (i.e. performing charitable donations) reduced involuntary traumatic intrusions in both lab settings and in their daily life as evidenced by 1-week intrusion diaries. While exploratory mediation analyses suggested that intrusion reduction was partly driven by enhanced positive affect afforded by prosocial behaviour, future studies are required to illuminate the underlying mechanisms. To the extent that post-trauma prosociality alleviated trauma-related symptoms, future research is warranted to investigate how various forms of prosocial behaviour in naturalistic setting could promote resilience following trauma exposure.

Behavioral and pharmacological interventions for the prevention and treatment of psychiatric disorders with children exposed to maltreatment

There is a well-established relation between exposure to child maltreatment and the onset and course of multiple, comorbid psychiatric disorders. Given the heterogeneous clinical presentations at the time services are initiated, interventions for children exposed to maltreatment need to be highly effective to curtail the lifelong burden and public health costs attributable to psychiatric disorders. The current review describes the most effective, well-researched, and widely-used behavioral and pharmacological interventions for preventing and treating a range of psychiatric disorders common in children exposed to maltreatment. Detailed descriptions of each intervention, including their target population, indicated age range, hypothesized mechanisms of action, and effectiveness demonstrated through randomized controlled trials research, are presented. Current limitations of these interventions are noted to guide specific directions for future research aiming to optimize both treatment effectiveness and efficiency with children and families exposed to maltreatment. Strategic and programmatic future research can continue the substantial progress that has been made in the prevention and treatment of psychiatric disorders for children exposed to maltreatment.

The effectiveness of dual-task interventions for modulating emotional memories in the laboratory: A meta-analysis

Dual-tasks (e.g., making horizontal eye-movements) while recollecting a memory are often used both in the lab and the clinic (such as in EMDR therapy) to attenuate emotional memories and intrusive mental images. According to working memory theory, dual-task interventions are effective because they limit cognitive resources available for the processing of emotional memories. However, there is still ongoing debate about the extent to which and under what conditions dual-task interventions are effective to interfere with emotional memories. In this meta-analysis, we assessed k = 53 laboratory studies investigating the effects of dual-task interventions on negative and positive memories. The effects were measured with the raw mean reduction in vividness and emotionality self-report ratings of emotional memories before compared to after the intervention on 100-point rating scales. Results showed that the dual-task interventions made both negative and positive memories less vivid (mean reduction negative images = 9.18, 95% CI [7.06, 11.29]; mean reduction positive images = 11.73, 95% CI [8.59, 14.86]) and less emotional (mean reduction negative images = 6.22, 95% CI [4.50, 7.94]; mean reduction positive images = 6.71, 95% CI [2.21, 11.20]). Several moderators were tested and are discussed in the light of working memory theory.

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.

Does valence contribute to the effects of dual tasking in aversive autobiographical memory? Some unexpected findings

BACKGROUND AND OBJECTIVES

Lab experiments show that engaging in a working memory task while recalling an aversive memory reduces emotionality and vividness of memories. Studies targeting lab induced negative memory with valenced secondary tasks show promise, but work is needed on autobiographical memories to make it more in line with the original dual tasking research and PTSD treatment in clinical populations. In this study, we address this gap by evaluating differential effectiveness of valenced dual tasks on emotionality and vividness of aversive autobiographical memories.

METHODS

University students (N = 178) recalled an aversive autobiographical memory while rating either positive pictures, negative pictures, or while looking at a cross in the exposure only condition. Participants were randomized to one of three aforementioned conditions and rated their memories before and after each intervention on emotionality and vividness.

RESULTS

Against expectations, memories became more emotional and vivid regardless of condition. With regard to vividness, this effect was characterized by an interaction effect: memories became more vivid in the exposure only condition than in the combined dual tasking conditions. All effect sizes were small.

LIMITATIONS

Working memory load in the dual tasking conditions might have been insufficient.

CONCLUSIONS

The current study did not extend findings with regard to (valenced) dual tasking and revealed a possible sensitization effect of script driven autobiographical memory induction. Our study highlights the importance of aspects such as the total amount of exposure and characteristics of memory induction, specifically the addition of a script driven approach to the usual self-initiated memory activation in dual tasking research.

Taxing working memory to modulate mental imagery of the 9/11 terrorist attacks following media exposure during childhood: a pilot study in young adult UK residents

BACKGROUND AND OBJECTIVES

Media trauma in civilians is linked to intrusive imagery-based memory symptoms. We investigated whether mental imagery of the 9/11 terrorist attacks following media exposure is dampened by taxing working memory (WM).

METHODS

Forty-five young adult UK residents, who were exposed to the 9/11 terrorist attacks as children via the media, identified a personally-relevant mental image of the attacks. They were then randomly allocated to: (1) recall + Tetris, (2) recall + eye movements (EMs), or (3) recall-only. Ratings on imagery vividness and emotionality were provided at three time points: pre-, post-manipulations, and at 24-hr follow-up.

RESULTS

Repeated measures ANOVAs revealed that recall + Tetris and recall + EMs (relative to recall-only) significantly reduced imagery vividness and emotionality from pre- to post-manipulations, but not to follow-up.

LIMITATIONS

A passive control group is needed to fully rule out the role of natural memory decay; the follow-up was exploratory and took place outside the laboratory with reduced experimental control.

CONCLUSIONS

Aversive memory imagery from media trauma in civilians can be dampened by taxing WM, at least temporarily, which could be therapeutically useful. The use of such cognitive techniques may also hold relevance for public health approaches to address the impact of collective trauma.

The messy landscape of eye movements and false memories

Eye-Movement Desensitisation and Reprocessing (EMDR) therapy is a common treatment for PTSD. However, skeptics like James Ost question the theoretical underpinnings, highlight inconsistency of empirical findings surrounding the efficacy of such therapy, and warn against unknown drawbacks. Little is known about the impact of the eye movements, a critical component in EMDR, on susceptibility to false memories, and the existing literature is contradictory. We review the literature and present new findings to help tell the story of the effects of eye movements on memory. Taken as a whole, this small body of work suggests that eye movements do not reliably affect susceptibility to misinformation, nor do they appear to enhance memory, but they do seem to increase spontaneous false memories.

Arresting visuospatial stimulation is insufficient to disrupt analogue traumatic intrusions

Intrusive memories are a core symptom of Post-Traumatic Stress Disorder (PTSD). A growing body of analogue studies using trauma films suggest that carrying out specific demanding tasks (e.g., playing the video game Tetris, pattern tapping) after the analogue trauma can reduce intrusive memories. To examine the mechanism behind this effect, we tested whether mere engagement with attention-grabbing and interesting visual stimuli disrupts intrusive memories, and whether this depends on working memory resources and/or the concurrent activation of trauma film memories. In a total sample of 234 healthy participants, we compared no-task control conditions to a perceptual rating task with visually arresting video clips (i.e., non-emotional, complex, moving displays), to a less arresting task with non-moving, blurred pictures (Study 1), and to more demanding imagery tasks with and without repetitive reminders of the trauma film (Study 2). Generally, we found moderate to strong evidence that none of the conditions lead to differences in intrusion frequency. Moreover, our data suggest that intrusive memories were neither related to individual differences in working memory capacity (i.e., operation span performance; Study 1), nor to the degree of engagement with a visuospatial task (i.e., one-week recognition performance; Study 2). Taken together, our findings suggest that the boundary conditions for successful interference with traumatic intrusions may be more complex and subtle than assumed. Future studies may want to test the role of prediction errors during (re-)consolidation, deliberate efforts to suppress thoughts, or the compatibility of the task demands with the individual's skills.

On EMDR: Measuring the working memory taxation of various types of eye (non-)movement conditions

BACKGROUND AND OBJECTIVE

A recent, large randomized controlled trial employing different forms of eye (non-)movements in eye movement desensitization and reprocessing (EMDR) showed that fixating the eyes either on a therapist's moving or non-moving hand led to equal reductions in symptoms of post-traumatic stress disorder (PTSD). However, numerous EMDR lab analogue studies found that eye movements produce larger memory effects than eyes stationary. These beneficial effects are typically explained by differences in working memory (WM) taxation. We tested the degree of WM taxation of several eye (non-)movement conditions used in the clinical trial.

METHODS

All participants (N = 40) performed: (1) eyes moving by following the experimenter's moving finger, (2) eyes fixed on the experimenter's stationary finger, (3) eyes closed, or (4) looking unfocused into the room. Simultaneously they performed a simple reaction time task. Reaction times are an objective index of the extent to which different dual attention tasks tax WM.

RESULTS

Eyes moving is more taxing than eyes fixed, while eyes fixed did not differ from eyes unfocused. All conditions were more taxing than eyes closed.

LIMITATIONS

We studied WM taxation in a laboratory setting; no clinical interventions were applied.

CONCLUSIONS

In line with previous lab studies, making eye movements was more taxing than eyes fixed. We discuss why this effect was not observed for reductions in PTSD symptoms in the clinical trial (e.g., differences in dependent variables, sample population, and intervention duration). For more comprehensive future insights, we recommend integration of mechanistically focused lab analogue studies and patient-oriented clinical studies.