The role of verbal cues in eliciting intrusive memories in a non-clinical population: a laboratory study

Distressing and intrusive reexperiencing of the trauma is a hallmark symptom of posttraumatic stress disorder (PTSD; American Psychiatric Association, 1994). However, unwanted memories of trauma are not a sign of pathology per se. In the initial weeks after a traumatic experience, intrusive memories are common. For most trauma survivors, intrusions become less frequent and distressing over time. A central question for understanding and treating patients with PTSD is therefore what maintains distressing intrusive reexperiencing in these people. Three factors appear to be important: (1) memory processes responsible for the easy triggering of intrusive memories, (2) the individuals’ interpretations of their trauma memories, and (3) their cognitive and behavioral responses to trauma memories.

The frequency and characteristics of involuntary autobiographical memories were compared in 25 stable dysphoric and 28 non-dysphoric participants, using a new laboratory-based task (Schlagman & Kvavilashvili, 2008). Participants detected infrequent target stimuli (vertical lines) in a simple vigilance task and recorded any involuntary autobiographical memories that came to mind, mostly in response to irrelevant words presented on the screen. Dysphoric participants reported involuntary memories as frequently and as quickly as non-dysphoric participants and their memories were not repetitive intrusive memories of negative or traumatic events. Additional content analysis showed that dysphoric participants did not recall more memories of objectively negative events (e.g., accidents, illnesses, deaths) than non-dysphoric participants. However, significant group differences emerged in terms of a mood congruency effect whereby dysphoric participants rated their memories as more negative than non-dysphoric participants. Moreover, the proportion of negatively rated involuntary memories was related to lower mood ratings at the end of the session in the dysphoric but not in the non-dysphoric group. Finally, groups did not differ on several memory characteristics such as vividness, specificity (high in both groups) and rates of rehearsal (low in both groups). Theoretical and practical implications of these findings for research on depression and autobiographical memory are discussed.

Involuntary autobiographical memories are memories of personal events that come to mind spontaneously-that is, with no conscious initiation of the retrieval process. Such spontaneously arising memories were long ignored in cognitive psychology, which generally has focused on controlled and strategic forms of remembering, studied in laboratory settings. Recent evidence shows that involuntary memories of past events are highly frequent in daily life, and that they represent a context-sensitive, and associative way of recollecting past events that involves little executive control. They operate by constraints that favour recent events and events with a distinct feature overlap to the current situation, which optimizes the probability of functional relevance to the ongoing situation. In addition to adults, they are documented in young children and great apes and may be an ontogenetic and evolutionary forerunner of strategic retrieval of past events. Findings suggest that intrusive involuntary memories observed clinically after traumatic events should be viewed as a dysfunctional subclass of otherwise functional involuntary autobiographical memories. Because of their highly constrained, situation-dependent and automatic nature, involuntary autobiographical memories form a distinct category of spontaneous thought that cannot be equated with mind wandering. This article is part of the theme issue 'Offline perception: voluntary and spontaneous perceptual experiences without matching external stimulation'.

Schizotypal personality and vulnerability to involuntary autobiographical memories

Intrusive memories are prominent features of post-traumatic stress disorder, but the mechanisms supporting their development, and their relationship to deliberate memories, are subject to competing theories. Are they strengthened examples of a unitary memory system, or fragmented representations lacking aspects of healthy memories? Given the importance of post-encoding processing in memory consolidation, we investigated the effects of a brief wakeful rest compared to a vigilance task immediately after the encoding of traumatic material on subsequent intrusive and deliberate memory. Across two experiments, participants watched emotionally negative film clips immediately followed by a brief wakeful rest or a simple vigilance (0-back) task. Brief wakeful rest had distinct effects on memory compared to the 0-back task, reducing intrusive memory frequency but not changing deliberate memory performance. These differential effects suggest that intrusive memory and deliberate memory reflect dissociable systems, arguing against unitary accounts. Our findings highlight the importance of post-encoding processing in the consolidation of traumatic material and the development of intrusive memories and provide a new perspective for interpreting mechanisms of therapeutic intervention.

After psychological trauma, recurrent intrusive visual memories may be distressing and disruptive. Preventive interventions post trauma are lacking. Here we test a behavioural intervention after real-life trauma derived from cognitive neuroscience. We hypothesized that intrusive memories would be significantly reduced in number by an intervention involving a computer game with high visuospatial demands (Tetris), via disrupting consolidation of sensory elements of trauma memory. The Tetris-based intervention (trauma memory reminder cue plus c. 20 min game play) vs attention-placebo control (written activity log for same duration) were both delivered in an emergency department within 6 h of a motor vehicle accident. The randomized controlled trial compared the impact on the number of intrusive trauma memories in the subsequent week (primary outcome). Results vindicated the efficacy of the Tetris-based intervention compared with the control condition: there were fewer intrusive memories overall, and time-series analyses showed that intrusion incidence declined more quickly. There were convergent findings on a measure of clinical post-trauma intrusion symptoms at 1 week, but not on other symptom clusters or at 1 month. Results of this proof-of-concept study suggest that a larger trial, powered to detect differences at 1 month, is warranted. Participants found the intervention easy, helpful and minimally distressing. By translating emerging neuroscientific insights and experimental research into the real world, we offer a promising new low-intensity psychiatric intervention that could prevent debilitating intrusive memories following trauma.

Research in adults suggests that intrusive memories and intrusive thoughts (often referred to as intrusive cognitions) are common in members of the general population and are often seen in clinical disorders. However, little is known about the experience of intrusive cognitions in adolescents, particularly in adolescents with major depressive disorder (MDD) and post-traumatic stress disorder (PTSD). The present study sought to gather fundamental data on these phenomena (i.e., frequency, characteristics and appraisals of intrusive cognitions) in adolescents with MDD and PTSD. Adolescents aged 11-18 with MDD (n = 11), PTSD (n = 13) and a non-clinical control group (n = 25) completed structured interviews concerning their intrusive memories and thoughts. Intrusive thoughts were common in all three groups but were particularly frequently experienced in the MDD group. Intrusive memories were expectedly very common in the PTSD group but also experienced by over half of the adolescents with MDD. Both clinical groups reported more negative emotions in response to their intrusive thoughts or memories and appraised these cognitions more negatively than the non-clinical group. Intrusive memories and thoughts are common experiences in adolescents with MDD and PTSD. Emotions and appraisals relating to these cognitions may be targets for psychological intervention in this age group. However, small sample sizes limit the conclusions that can be drawn. Replication is needed with larger numbers of clinical participants.

Experiencing trauma leads to intrusive memories (IMs), a hallmark symptom of post-traumatic stress disorder (PTSD), which also occurs transdiagnostically. Understanding why IMs increase or decrease is pivotal in developing interventions to support mental health. In this preregistered meta-analysis (PROSPERO: CRD42021224835), we included 134 articles (131 techniques, 606 effect sizes and 12,074 non-clinical participants) to investigate how experimental techniques alter IM frequency, intrusion-related distress and symptoms arising from lab-analogue trauma exposure. Eligible articles were identified by searching eight databases until 12 December 2023. To test potential publication biases, we employed methods including Egger’s test and three-parameter selection models. We employed three-level multilevel modelling and meta-regressions to examine whether and how experimental techniques would modulate IM frequency and associated outcomes. Results showed that techniques (behavioural, pharmacological, neuromodulation) significantly reduced intrusion frequency (g = 0.16, 95% confidence interval [0.09, 0.23]). Notably, techniques aimed to reduce IMs also ameliorated intrusion-related distress and symptoms, while techniques that increased IMs exacerbated these related outcomes, thus highlighting IM’s centrality in PTSD-like symptoms. Techniques tapping into mental imagery processing (for example, trauma reminder followed by playing Tetris) reduced intrusions when administered immediately after, or at a delayed time after trauma. Although our meta-analysis is limited to symptoms induced by lab-analogue trauma exposure, some lab-based results have now generalized to real-world trauma and IMs, highlighting the promising utility of lab-analogue trauma paradigms for intervention development.

Involuntary autobiographical memories as a transdiagnostic factor in mental disorders.

There are also compelling reasons to conclude that the mechanisms underlying standard measures of recall and recognition are distinct from the mechanisms underlying involuntary memories. (Brewin, 2005, pp. 145–6) “Special, but not so special” is the ironic title of an article on flashbulb memories (Christianson, 1989). The same phrase expresses a relevant characteristic of involuntary autobiographical memories. They are special in some regards, as I will show in Chapter 6. However, they are not so special that they should be explained in terms of their own memory system or in terms of memory mechanisms that pertain only to them. Not all theorists share this view. On the contrary, some researchers argue that involuntary autobiographical memories are governed by processes that are fundamentally different from processes normally characterizing memory, as illustrated by the quotation from Brewin (2005) at the beginning of the chapter. Some researchers with a psychodynamic outlook on involuntary autobiographical memories have pursued the view that involuntary memories are primarily a medium for traumatic or stressful material (e.g., Brewin, 2005; Ehlers et al ., 2004; Horowitz, 1986; van der Kolk and Fisler, 1995; see also Chapter 2). Although these researchers have presented different theories, as we shall see in Chapter 7, a common assumption is that involuntary memories reflect the operations of a special memory system, such as “an active memory storage” dedicated to the processing of unresolved stressful events (Horowitz, 1986), or a memory system for emotional material that can be accessed only through situational cues (Brewin et al ., 1996b; Brewin and Holmes, 2003).

Alzheimer's disease (AD) is characterized by severe memory alterations, affecting especially memories of personal past events. Until now, autobiographical memory impairments have been characterized using formal memory assessments, requiring patients to strategically and deliberately recall past events. However, contrary to this highly cognitively demanding mode of memory recall, autobiographical memories frequently come to mind unexpectedly based on automatic associative processes. The involuntary recall of personal memories is effortless and possibly represents a preserved way for AD patients to remember past events. This study aimed to investigate involuntary autobiographical memory in AD patients and compare the characteristics of these memories with those of healthy controls. Involuntary autobiographical memory was measured in 24 AD patients and 24 matched control participants using self-report measures. Participants were asked to report the frequency with which involuntary autobiographical memories were experienced in their daily life and to describe and self-assess one example of an involuntary memory. We showed that AD patients and control participants did not differ in terms of the frequency or subjective characteristics of their involuntary autobiographical memories in daily life, except for feelings of intrusiveness. Compared to control participants, AD patients reported their involuntary autobiographical memories as being more intrusive. In addition, more negative and vague involuntary autobiographical memories were associated with greater depressive symptoms. These findings open up a new avenue for research to better understand the extent to which involuntary autobiographical memory might be preserved in AD patients and why these memories may in turn become intrusive to patients.

Individuals with psychotic-like experiences exhibit enhanced involuntary autobiographical memories

Recent research has shown that the activation of semantic memories leads to the activation of autobiographical memories. Known as semantic-to-autobiographical memory priming, this form of priming has been demonstrated to prime involuntary and voluntary autobiographical memories with a wide variety of different primes (i.e., various verbal and non-verbal stimuli). However, only verbal cues have been used in the memory measures, leaving open the question of how non-verbal cues might function. Our goal in the current study was to show that non-verbal cues are also involved in semantic-to-autobiographical memory priming. Participants were primed with words, and then they were treated to an involuntary autobiographical memory task (the vigilance task) where they received either word cues or pictorial cues. The results showed that both the word cues and the pictorial cues had captured primed involuntary memories on the vigilance task relative to controls. The results support the idea that semantic-to-autobiographical memory primes occur with both verbal and non-verbal cues, potentially indicating substantial cue diversity. The results also further support the idea that semantic-to-autobiographical memory priming may play an important role in the production of involuntary autobiographical memories in everyday life.

Involuntary autobiographical memories are mental representations of personally experienced past events that come to mind spontaneously, with no preceding attempt to recall them. They have been showed to be more frequent and more emotional in the psychosis continuum. Although schizophrenia is strongly associated with thought disorders, including cognitive intrusions of thought, images, semantic knowledge, research on patients' involuntary autobiographical memories is limited. We undertook two studies to compare involuntary and voluntary remembering in schizophrenia and the conditions in which involuntary memories occurs in those patients, both in daily life (n = 40), using a diary method, and in an experimental context (n = 50). Overall, results showed that the conditions of elicitation of involuntary memories differ in patients, as patients were more sensitive to memory triggers, especially internal triggers, in comparison to controls. Relatedly, patients' involuntary memories—mostly related to mundane events with low emotional load—were experienced more frequently. Although patients' involuntary and voluntary memories were less clear, more poorly contextualized and associated with a lower belief in occurrence than those of controls, patients considered them as more central to the self, in comparison to controls. The results are discussed in relation to patients' self-reflective impairments.

Indeed, I believe that if more psychologists were themselves willing to undergo the tests they devise or the experimental procedures to which they subject others, we would find a marked upsurge in the significance and vitality of research. (Singer 1966, p. 15) Why have cognitive psychologists been reluctant to study involuntary autobiographical memories, while voluntary autobiographical memory has been studied at length? Probably some of the answer has to do with the challenge of developing a useful method. In this regard, it is useful to remember George Miller's (1962) hesitation: “Consider the difficulties that would face any scientist who wanted to study such mental phenomena. His first difficulty would be that he has no way to capture the things he wishes to study. He can only sit and wait, hoping for the improbable” (p. 180; see also Chapter 1). Obviously, I am much more optimistic than Miller. Nonetheless, I do not think that his skepticism was completely unwarranted. Although useful methods have been developed, methodology is still a problem that involuntary memory researchers have to consider very seriously. In this chapter, I will discuss various empirical approaches to involuntary autobiographical memories, including sampling, survey, diary, and laboratory methods. The diary method has been the most frequently used approach for studying everyday involuntary memories. Later in this chapter, I will therefore describe my first diary study on involuntary autobiographical memories, which had only me as a participant.