Effects of experimentally induced dissociation on attention and memory

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Abstract

Dissociation is an important aspect of responses to traumatic events. According to a number of influential theories, it negatively impacts cognitive performance including encoding of the trauma memories, leading to an increased risk of later conditions such as posttraumatic stress disorder (PTSD). We tested this hypothesis experimentally in two studies by inducing dissociation in the laboratory and investigating the effects on several aspects of cognition, including time estimation, digit and spatial span, and story recall. Dissociation was related to decrements in time estimation, digit span, and story retention, but did not affect perceptual attention, spatial span, or immediate story recall. The results are discussed in the context of theoretical models of PTSD and their implications for official questioning of traumatized individuals such as sexual assault survivors.

Highlights

► Gazing at one’s own face in the mirror reliably induces a dissociative reaction. ► Dissociation adversely affects several aspects of attention and memory. ► The effects of dissociation are greater on digit span than on spatial span. ► The results are highly relevant to the interviewing of traumatized individuals.

Introduction

Dissociation is a common response to a wide variety of highly stressful and traumatic events (Cardena and Spiegel, 1993, Classen et al., 1993, Morgan et al., 2001). Although it has long been thought to assist coping by temporarily reducing negative emotional states and physiological arousal (Dorahy & van der Hart, 2007), and to be related to the freezing response observed in animals (Nijenhuis, Spinhoven, Vanderlinden, van Dyck, & van der Hart, 1998), it also demonstrates a robust association with adverse longer-term outcomes such as posttraumatic stress disorder (PTSD) (Brewin and Patel, 2010, Lensvelt-Mulders et al., 2008). It has frequently been suggested that dissociative states affect the encoding of these events into memory, making them more likely to subsequently intrude into consciousness (Bremner and Brett, 1997, van der Kolk et al., 1996). Despite the theoretical and practical importance attributable to dissociation, there have been few experimental studies of how it affects cognitive processes. We report two studies in which dissociative states were induced in the laboratory using a recently developed technique and their cognitive effects on attention, memory, and time estimation measured.

Dissociation is defined as “a disruption in the usually integrated functions of consciousness, memory, identity, or perception of the environment” in the DSM-IV-TR (American Psychiatric Association, 2000). It takes many different forms, including depersonalization (alterations in the sense of self such as out-of-body experiences), derealization (alterations in the perception of the world such as people appearing unreal or as actors in a play), and changes in time estimation (a speeding up or slowing down of subjective time) (Ursano, Fullerton, & Benedek, 2007). Peri-traumatic dissociation is the term given to these reactions when they occur during and immediately after a traumatic event. There have been numerous retrospective studies demonstrating an association between reports of such reactions and subsequent PTSD (Lensvelt-Mulders et al., 2008). Two of the most characteristic symptoms of PTSD are the involuntary intrusion of detailed images of the traumatic scene and the prolongation of strong emotional reactions to trauma reminders. Reports of peri-traumatic dissociation in PTSD patients are consistently associated with independent ratings of fragmentation in narrative accounts of the traumatic event (Brewin, 2007). Moreover, in PTSD patients state dissociation contributed to the strength of perceptual priming for trauma-related stimuli (Lyttle, Dorahy, Hanna, & Huntjens, 2010).

Establishing a causal role for dissociation after actual traumatic events is problematic because of the retrospective measurement of these reactions. Nevertheless there is evidence that healthy individuals who report more dissociative states while watching a traumatic film in the laboratory subsequently experience more intrusive images of the film over the next week (Holmes, Brewin, & Hennessy, 2004). This combination of clinical and non-clinical research has supported earlier proposals that dissociative states may in some way impede the encoding of such events into memory, resulting in them being more likely to be subsequently retrieved involuntarily. More recently, the dual representation theory of PTSD proposed that the disorder arises because perception-near, viewpoint-dependent representations supporting action on the environment are encoded relatively strongly at the same time that contextualized, viewpoint-independent representations supporting language and higher cognitive functions are encoded relatively weakly (Brewin, Gregory, Lipton, & Burgess, 2010). Dissociative states may be important influences on these encoding processes.

The preponderance of research to date has investigated cognitive processing in individuals with high trait dissociation or with clinical disorders accompanied by high levels of dissociation. For example, although not consistent, findings have not generally supported the idea that high trait dissociators have working memory deficits (De Ruiter et al., 2004, Giesbrecht et al., 2007). In contrast, there is evidence that under divided-attention demands, high dissociators have impaired memory for words associated with trauma (e.g., incest) but not for neutral words, as compared with low dissociators (DePrince and Freyd, 2001, DePrince and Freyd, 2004). Similarly, studies of working memory capacity have failed to find consistent deficits in dissociative disorder patients compared with controls (Elzinga et al., 2007, Guralnik et al., 2000, Rossini et al., 1996). In contrast, a sample of people with depersonalization disorder showed compromised visual and verbal short-term memories, especially under information overload conditions, and had difficulty with early stimulus encoding tasks under conditions of heightened distraction (Guralnik et al., 2000).

These inconsistent findings may reflect problems with the retrospective assessment of dissociation, or with the fact that the relation between dissociative tendencies and the presence of dissociative states at the particular point in time when cognitive processes are measured is weak. Individuals with dissociative disorders may have found ways of compensating for cognitive deficits that make these hard to detect. For these reasons the experimental manipulation of dissociation offers the opportunity to test clinical theories more rigorously. Mirror-gazing for approximately 10 min under dim illumination has been found to cause participants to perceive their reflected face in the mirror as distorted or as belonging to someone else (Caputo, 2010a, Caputo, 2010b). These reactions, including alterations in perceived identity, are similar to the depersonalization described in PTSD, although Caputo did not support these observations with standardized measures of dissociation. His technique nevertheless promises the opportunity to test theories about the causal role of dissociation in altering cognitive processing.

Section snippets

General discussion

Our data provide the first experimental evidence that dissociative states affect learning and memory, as hypothesized by clinical theories of PTSD (Bremner and Brett, 1997, van der Kolk et al., 1996). Previous investigations have induced dissociation prior to watching a traumatic film using either a dot-staring procedure or hypnotic induction, and then assessed recognition or recall of the film’s contents one week later. Despite successfully producing a dissociative response, neither of these

References (44)

  • M.B. De Ruiter et al.

    Dissociative style and individual differences in verbal working memory span

    Consciousness and Cognition

    (2004)
  • T. Giesbrecht et al.

    Dissociation, memory commission errors, and heightened autonomic reactivity

    Psychiatry Research

    (2007)
  • E.A. Holmes et al.

    Are there two qualitatively distinct forms of dissociation? A review and some clinical implications

    Clinical Psychology Review

    (2005)
  • American Psychiatric Association (2000). Diagnostic and statistical manual of mental disorders (4th ed., Text...
  • E.M. Bernstein et al.

    Development, reliability, and validity of a dissociation scale

    Journal of Nervous and Mental Disease

    (1986)
  • D. Bögner et al.

    Impact of sexual violence on disclosure during Home Office interviews

    British Journal of Psychiatry

    (2007)
  • J.D. Bremner et al.

    Trauma-related dissociative states and long-term psychopathology in posttraumatic stress disorder

    Journal of Traumatic Stress

    (1997)
  • J.D. Bremner et al.

    Measurement of dissociative states with the Clinician-Administered Dissociative States Scale (CADSS)

    Journal of Traumatic Stress

    (1998)
  • C.R. Brewin

    Autobiographical memory for trauma: Update on four controversies

    Memory

    (2007)
  • C.R. Brewin

    The nature and significance of memory disturbance in posttraumatic stress disorder

    Annual Review of Clinical Psychology

    (2011)
  • C.R. Brewin et al.

    Intrusive images in psychological disorders: Characteristics, neural mechanisms, and treatment implications

    Psychological Review

    (2010)
  • C.R. Brewin et al.

    Memory for emotionally neutral information in posttraumatic stress disorder: A meta-analytic investigation

    Journal of Abnormal Psychology

    (2007)
  • C.R. Brewin et al.

    Auditory pseudohallucinations in United Kingdom war veterans and civilians with posttraumatic stress disorder

    Journal of Clinical Psychiatry

    (2010)
  • G.B. Caputo

    Apparitional experiences of new faces and dissociation of self-identity during mirror gazing

    Perceptual and Motor Skills

    (2010)
  • G.B. Caputo

    Strange-face-in-the-mirror illusion

    Perception

    (2010)
  • E. Cardena et al.

    Dissociative reactions to the San Francisco Bay Area earthquake of 1989

    American Journal of Psychiatry

    (1993)
  • E.B. Carlson et al.

    An update on the dissociative experiences scale

    Dissociation

    (1993)
  • C. Classen et al.

    Trauma and dissociation

    Bulletin of the Menninger Clinic

    (1993)
  • P.M. Corsi

    Human memory and the medial temporal region of the brain

    Dissertation Abstracts International

    (1972)
  • J.R. Crawford et al.

    The positive and negative affect schedule (PANAS): Construct validity, measurement properties and normative data in a large non-clinical sample

    British Journal of Clinical Psychology

    (2004)
  • A.P. DePrince et al.

    Memory and dissociative tendencies: The roles of attentional context and word meaning

    Journal of Trauma and Dissociation

    (2001)
  • A.P. DePrince et al.

    Forgetting trauma stimuli

    Psychological Science

    (2004)
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