Effect of sleep manipulations on intrusive memories after exposure to an experimental analogue trauma: A meta-analytic review

Sleep plays an important role in memory processing and is disrupted in individuals with post-traumatic stress disorder (PTSD). A growing body of research has experimentally investigated how sleep - or lack thereof - in the early aftermath of a traumatic experience contributes to intrusive memory formation. The aim of this meta-analytic review was to examine the effects of various experimental sleep manipulations (e.g., sleep deprivation, daytime naps) on intrusive memories following exposure to an experimentally induced analogue traumatic event. Eight eligible studies were systematically identified through PsycInfo and PubMed and provided sufficient data to contribute to a meta-analysis of the effects of sleep versus wakefulness on intrusive memory frequency. Sleep was found to reduce intrusive memory frequency when compared to wakefulness at a small but significant effect size (Hedge's g = 0.29). There was no evidence of publication bias and heterogeneity of effect sizes across studies was moderate. Results suggest that sleep plays a protective role in the aftermath of exposure to a traumatic event with implications for early post-trauma intervention efforts.

Peritraumatic unconditioned and conditioned responding explains sex differences in intrusions after analogue trauma

Higher prevalence of posttraumatic stress disorder (PTSD) in women than men may be explained by sex differences in fear learning processes. Initial evidence points to elevated unconditioned and conditioned fear responding as well as to elevated state anxiety in women as potential peritraumatic mechanisms. Using the "conditioned-intrusion-paradigm", which combines differential fear conditioning with the trauma-film paradigm, neutral sounds were presented as predictors of the occurrence (CS+) or non-occurrence (CS-) of highly aversive films. Intrusions were elicited by these sounds in the laboratory after conditioning and naturalistic intrusions were assessed in daily-life on subsequent days. Compared to men (n = 62), women (n = 60) reported more intrusions and associated distress following analogue trauma. Sex differences in intrusive symptoms were mediated by a) higher unconditioned trauma responding, b) slowed extinction of differential CS valence ratings, and c) elevated state anxiety increase across conditioning in women. Secondary analyses revealed that state anxiety was the strongest mediator, followed by slowed extinction learning. Mediation models were unrelated to sex differences in trait anxiety or depressive symptoms. Thus, associative (extinction learning) and non-associative (state anxiety, trauma responding) mechanisms contribute to sex differences in intrusive symptoms after analogue trauma and might add to the heightened vulnerability to PTSD in women.

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.

Contextual representations of negative images modulate intrusion frequency in an intrusion provocation paradigm

BACKGROUND AND OBJECTIVES

To understand how memories of negative events become highly accessible in the context of trauma, we tested the hypothesis that contextual information modulates how easily intrusions can be provoked by perceptual stimuli..

METHODS

Healthy participants viewed pictures depicting trauma scenes either with or without accompanying moderate (i.e. survival, recovery) or severe (i.e. fatality, permanent injury) outcome information. All participants viewed the same depictions of trauma scenes. Involuntary memories for the pictures were assessed using self-report diaries and an adapted version of the Impact of Event Scales (IES). A blurred picture perceptual priming paradigm was adapted to be used as an intrusion provocation task.

RESULTS

The severe outcome group experienced a significantly higher frequency of intrusions on the intrusion provocation task in comparison to both moderate outcome and control (no-context) conditions. The severe outcome condition did not increase intrusions on the self-report diaries or the adapted IES. There was no effect of condition on ratings for the emotionality, self-relevance, valence, or seriousness of the trauma scenes.

LIMITATIONS

The analogue method should not be generalized directly to incidences of real-life trauma. It was unclear why differences in intrusion frequency were found in the provocation task only. The relative amount of individual conceptual and data-driven processing adopted by the participants was not assessed.

CONCLUSIONS

Manipulating contextual information that determines the meaning of sensory-perceptual features for a trauma scene can modulate subsequent intrusion frequency in response to visually similar cues.

Encoding disorganized memories for an analogue trauma does not increase memory distortion or analogue symptoms of PTSD

BACKGROUND AND OBJECTIVES

Empirical studies with objective measures and control conditions have failed to demonstrate disorganization; yet people tend to self-report disorganization in their trauma narratives, which may have other effects. Thus, we investigated whether a disorganized trauma memory produces more analogue PTSD symptoms and memory distortion, compared to an organized memory.

METHODS

Participants watched a traumatic film with missing scenes. Some saw the scenes in their correct temporal sequence; others saw a random sequence; thus for some participants we implanted a disorganized memory. We also told some participants to focus on the meaning of the event (conceptual), some on the sensory details (data-driven), and some received no instruction (control). Participants recorded their intrusions for a week. Then, they reported analogue symptoms and we tested their memory for the film and their confidence in what they remembered.

RESULTS

Analogue symptoms and number of reported intrusions did not differ across conditions, nor did the degree of memory distortion or confidence in those memories. However, participants who self-reported feeling more memory disorganization reported more avoidance symptoms and more memory distortion.

LIMITATIONS

We did not measure memory for real trauma, nor did we assess for a history of PTSD. Our results may also be restricted to temporal disorganization.

CONCLUSIONS

Although objective assessments of disorganization do not appear important, people's feelings regarding the disorganization of their memories not only affect their assessment of the severity of their PTSD symptoms, but also the kinds of memory errors they make.

Intrusive images and voluntary memory for affective pictures: contextualization and dual-task interference

BACKGROUND AND OBJECTIVES

The present study addressed the role of context information and dual-task interference during the encoding of negative pictures on intrusion development and voluntary recall.

METHODS

Healthy participants were shown negative pictures with or without context information. Pictures were either viewed alone or concurrently with a visuospatial or verbal task. Participants reported their intrusive images of the pictures in a diary. At follow-up, perceptual and contextual memory was tested.

RESULTS

Participants in the context group reported more intrusive images and perceptual voluntary memory than participants in the no context group. No effects of the concurrent tasks were found on intrusive image frequency, but perceptual and contextual memory was affected according to the cognitive load of the task.

LIMITATIONS

The analogue method cannot be generalized to real-life trauma and the secondary tasks may differ in cognitive load.

CONCLUSIONS

The findings challenge a dual memory model of PTSD but support an account in which retrieval strategy, rather than encoding processes, accounts for the experience of involuntary versus voluntary recall.