The relation between memory of the traumatic event and PTSD: evidence from studies of traumatic brain injury.

OBJECTIVE: This paper focuses on the relation between memory and posttraumatic stress disorder (PTSD). More specifically, it addresses the debate regarding the role of memory of the traumatic event in the development of PTSD. Traumatic brain injury (TBI) is used as a naturally occurring model for traumatic exposure that is often associated with memory impairment. METHOD: We present a critical review of the literature on studies assessing the relation between TBI and PTSD, with a focus on memory of the traumatic event as a critical factor. We also discuss results from recent studies conducted by our group. RESULTS: The literature review offers an inconclusive picture wherein a significant proportion of the studies indicate that PTSD and TBI are mutually exclusive, especially in individuals who exhibit lack of memory for the traumatic event. This finding supports the possibility that lack of memory may protect against the development of PTSD. However, some studies show that PTSD does occur in patients with head injury, suggesting that PTSD may develop in TBI survivors--even in those who cannot remember the traumatic event. Generally speaking, though, the overall balance of the findings (including our own findings) seems to support the possibility that, in subjects with TBI, impaired memory of the traumatic event is associated with reduced prevalence of PTSD. CONCLUSIONS: The suggestion that amnesia regarding the traumatic event may protect against the development of PTSD has both theoretical and practical importance. This review focused on the case of traumatic brain injury as a model for impaired memory for the traumatic event. However, it still remains to be proven that the conclusions based on these findings are generalizable beyond the case of TBI. While some patients with posttraumatic amnesia do develop PTSD despite lack of memory for the traumatic event, the majority of those who lack memory for the event seem to be protected from developing the disorder. Nevertheless, based on this assumption, we suggest that pharmacologic disruption of newly acquired--or even old--traumatic memories, which has been shown to be possible in animals, might therapeutically benefit trauma survivors.     

Traumatic Amnesia, Repression, and Hippocampus Injury Due to Emotional Stress, Corticosteroids and Enkephalins

The role of stress, arousal, emotional trauma, and corticosteroid and enkephalin secretion on memory and the hippocampus, and the development of traumatic amnesia and repressed memory syndrome are detailed. Animal and human studies are reviewed. Trauma-induced memory deficits appear to be secondary to abnormal neocortical and hippocampal arousal, and corticosteroid and enkephalin secretion which can induce atrophy or seizures within the hippocampus, suppress hippocampal theta activity and long term potentiation, as well as injure hippocampal pyramidal cells. Predisposing factors include individual, age, and sex differences in arousal, and previous emotional trauma or temporal lobe or hippocampal injury. However, as the amygdala processes and stores emotional experiences in memory, patients may also demonstrate trauma related symptoms, including flashbacks as well as shrinking retrograde amnesia.     

Post-traumatic retrograde amnesia

A case of post traumatic retrograde amnesia is described. The patient presented after an initial coma a global amnesia, but the fixation deficit rapidly disappeared, and a severe retrograde amnesia dating back to childhood experience and learning remained the main symptom. Amnesia for remote events was associated with didactic memory deficit and, at a lesser degree, with a verbal memory deficit. Recovery of fixation allowed a progressive relearning. This pattern of impairment was recently related to mesencephalic lesions, but we think that the role of temporal lobe involvement cannot be neglected.     

Intrusive images and "hotspots" of trauma memories in Posttraumatic Stress Disorder: an exploratory investigation of emotions and cognitive themes

This study aimed to investigate the emotions and cognitions contained in "hotspots" of memory for trauma, as well as their associated images. Thirty-two participants at a specialist outpatient trauma clinic had experienced a range of traumatic events and met diagnostic criteria for Posttraumatic Stress Disorder (PTSD). Data were collected within an agreed protocol, involving reliving therapy. Patients described the different intrusive images of the trauma that they were re-experiencing. Their reports of cognitions and emotions during "hotspots" in their memory of the traumatic experience were recorded as part of reliving therapy. Hotspots refer to moments of peak emotional distress during the event. There was a high degree of match reported between intrusive images and hotspots. The cognitive and emotional contents of hotspots were qualitatively analysed into themes. The relative of frequency of these peritraumatic themes is presented. The exploratory findings are discussed with respect to our understanding and treatment of intrusive imagery in PTSD.     

Posttraumatic stress disorder in patients with neurogenic amnesia for the traumatic event

The development of symptoms of posttraumatic stress disorder (PTSD) in patients with neurogenic amnesia for the traumatic event is recorded in 2 own patients and in 19 cases from the clinical literature. With a single exception, all patients were accident victims with closed head injuries. Only about three quarters of the patients completely fulfilled DSM-III-R criteria of PTSD. Nineteen patients displayed involuntary conscious memories of aspects of the traumatic event (presenting as recurrent intrusive thoughts, images or dreams) co-existent with a complete or partial lack of voluntary conscious memories of the trauma, suggesting that different memory systems and distinct brain mechanisms subserve these phenomena. The said clinical observations are discussed against the background of current neuropsychological models of multiple memory systems. The recorded cases demonstrate that declarative episodic memory is not necessary for symptoms of PTSD to emerge, whereas preserved functions of non-declarative memory systems represent a sufficient condition for the development of PTSD symptoms.     

Individual predictors of traumatic reactions in firefighters

Increasingly, theorists and researchers in the area of trauma are pointing to the importance of individual differences in resilience and vulnerability as key determinants of the intensity and duration of trauma-related symptoms. Determining the relative influence of individual predictors is important for the further development of theoretical models for understanding trauma responses and for the subsequent development of intervention strategies that are sensitive to individual differences. This study explores the influence of individual factors and social support on traumatic reactions in firefighters exposed to tragic events in the line of duty. A total of 164 Australian firefighters completed questionnaires targeting locus of control, self-efficacy, patterns of interpersonal relating, social support and level of emotional distress. Results indicate that individuals with feelings of insecurity, lack of personal control, and alienation from others were more likely to experience higher levels of depression and posttraumatic stress symptoms subsequent to exposure to traumatic events on the job.     

Memories of childhood abuse: dissociation, amnesia, and corroboration.

OBJECTIVE: This study investigated the relationship between self-reported childhood abuse and dissociative symptoms and amnesia. The presence or absence of corroboration of recovered memories of childhood abuse was also studied. METHOD: Participants were 90 female patients admitted to a unit specializing in the treatment of trauma-related disorders. Participants completed instruments that measured dissociative symptoms and elicited details concerning childhood physical abuse, sexual abuse, and witnessing abuse. Participants also underwent a structured interview that asked about amnesia for traumatic experiences, the circumstances of recovered memory, the role of suggestion in recovered memories, and independent corroboration of the memories. RESULTS: Participants reporting any type of childhood abuse demonstrated elevated levels of dissociative symptoms that were significantly higher than those in subjects not reporting abuse. Higher dissociative symptoms were correlated with early age at onset of physical and sexual abuse and more frequent sexual abuse. A substantial proportion of participants with all types of abuse reported partial or complete amnesia for abuse memories. For physical and sexual abuse, early age at onset was correlated with greater levels of amnesia. Participants who reported recovering memories of abuse generally recalled these experiences while at home, alone, or with family or friends. Although some participants were in treatment at the time, very few were in therapy sessions during their first memory recovery. Suggestion was generally denied as a factor in memory recovery. A majority of participants were able to find strong corroboration of their recovered memories. CONCLUSIONS: Childhood abuse, particularly chronic abuse beginning at early ages, is related to the development of high levels of dissociative symptoms including amnesia for abuse memories. This study strongly suggests that psychotherapy usually is not associated with memory recovery and that independent corroboration of recovered memories of abuse is often present.     

The neurology of memory: quantitative assessment of retrograde amnesia in two groups of amnesic patients

The phenomenon of retrograde amnesia has important implications for understanding normal memory as well as its neural organization. Using 6 tests of remote memory, we evaluated the extent and severity of retrograde amnesia in 2 groups of amnesic patients--7 patients with alcoholic Korsakoff's syndrome and 5 other patients with amnesia (anoxia or ischemia, N = 3; thalamic infarction, N = 1; unknown etiology, N = 1). Although there were individual differences, Experiment 1 showed that the severity and extent of retrograde amnesia was similar for the 2 groups. Retrograde amnesia was temporally graded across a period of about 15 years and was not detectable in more remote time periods. In Experiment 2, repeated testing during a 3 year period showed that amnesic patients and control subjects were similarly consistent in their responses. Amnesic patients did not catch up to control subjects by eventually accumulating as many correct answers as the control subjects. In Experiment 3, amnesic patients performed normally on a test of very difficult general information questions, which were based on material likely to have been learned long ago. In all 3 experiments, the 2 groups of amnesic patients performed similarly. The results support the following conclusions: (1) Extensive, temporally graded retrograde amnesia, which has been observed frequently in patients with Korsakoff's syndrome, occurs readily in other amnesic patients as well, even when their memory impairment appears well circumscribed; (2) patients with presumed damage to either the medial temporal or the diencephalic brain structures linked to memory functions can produce a similar kind of retrograde amnesia; (3) the impairment reflects a loss of usable knowledge, not simply difficulty accessing an intact memory store that can then be overcome given sufficient retrieval opportunities; (4) very remote memory, at least for factual information, can be intact in amnesia; (5) the structures damaged in amnesia support memory storage, retrieval, or both during a lengthy period of reorganization, after which representations in memory can become independent of these structures.     

Widespread cognitive impairment in psychogenic anterograde amnesia

A 34-year-old man without a past history of any psychiatric or neurological disorder developed severe anterograde amnesia following a psychological trauma. Initial assessment of neuropsychological functions 3 months after the psychological trauma indicated severe memory deficits for acquiring new information in both verbal and visual modalities with widespread cognitive deficits in attention, executive functions, and intellectual ability. Importantly, working and remote memory were intact. The case illustrates that psychogenic anterograde amnesia might be associated with a wider range of cognitive deficits. Possible neurobiological explanations are discussed to explain large cognitive impairments associated with anterograde psychogenic amnesia.     

E. Weiss et G. Perec, ou la nécessité psychique de l’écriture autofictionnelle

This article is a comparative analysis of two autofictions: The Trial by Fire (Die Feuerprobe) by Ernst Weiss and W by Georges Perec. Both writers, who are well-versed in psychoanalysis, decide to search for their unconscious by writing autofiction. To Weiss and Perec, only this process will allow them to access the memory that has stored traumatic events occulted by childhood amnesia. The writers share a phantasmic — yet, anonymous — agreement with their attentive reader. In both texts, the analyst reader observes the figure of an inner witness who writes in order to capture a child lost in the writer's unconcious. This infantile part is psychotic, as it is caused by an early-childhood trauma, possibly the father's death, and it focuses on primary narcissism. It also involves an anal bunker that is supposed to serve as a protective barrier against any traumatic memory surge. The mental state of the child threatens the psychogenic integrity of the two writers. A clinical reading of the two works unveils the secret of autofictional writing: the inner witness, identified with Freud, becomes the mother/father analyst for the lost child. Thus, under the protective fantasy of self-procreating, a psychical rapport with the child has been recreated. As the inner witness brings back the father's law into the rules of language, the primitive scene is extirpated from amnesia and opens up to desire, even if only during the writing process. Thus, autofictional writing saves a precarious and borderline psychical equilibrium.     

Metacognition,memory disorganization and rumination in posttraumatic stress symptoms

The present study aimed to assess the relative contribution of memory disorganization and beliefs about trauma memory in the prediction of posttraumatic stress symptoms. A sample of 95 student nurses and midwives narrated their memory of the most distressing placement related event they had experienced. Several questionnaires were administered, including the Beliefs about Memory Questionnaire (BAMQ), which was devised for the study. Pearson's correlations, hierarchical analyses and mediation analyses were performed on the data. The reliability and validity of the BAMQ gained preliminary support. Beliefs about the trauma memory, but not memory disorganization within the trauma narrative, predicted a significant proportion of the variance in posttraumatic stress symptoms after control variables were accounted for. Consistent with the metacognitive model of PTSD, the use of rumination mediated the relationship between beliefs about the trauma memory and PTSD symptoms. The findings provide preliminary support for the role of meta-memory in the maintenance of PTSD symptoms and question the importance of memory disorganization.     

Hippocampus and retrograde amnesia in the rat model: A modest proposal for the situation of systems consolidation

The properties of retrograde amnesia after damage to the hippocampus have been explicated with some success using a rat model of human medial temporal lobe amnesia. We review the results of this experimental work with rats focusing on several areas of consensus in this growing literature. We evaluate the theoretically significant hypothesis that hippocampal retrograde amnesia normally exhibits a temporal gradient, affecting recent, but sparing remote memories. Surprisingly, the evidence does not provide much support for the idea that there is a lengthy process of systems consolidation following a learning episode. Instead, recent and remote memories tend to be equally affected. The extent of damage to the hippocampus is a significant factor in this work since it is likely that spared hippocampal tissue can support at least partial memory retrieval. With extensive hippocampal damage gradients are flat or, in the case of memory tasks with flavour/odour retrieval cues, the retrograde amnesia covers a period of about 1-3 days. There is consistent evidence that at the time of learning the hippocampus interferes with or overshadows memory acquisition by other systems. This contributes to the breadth and severity of retrograde amnesia relative to anterograde amnesia in the rat. The fact that multiple, distributed learning episodes can overcome this overshadowing is consistent with a parallel dual-store theory or a Distributed Reinstatement Theory in which each learning episode triggers a short period of memory replay that provides a brief hippocampal-dependent systems consolidation.     

The effect of moderate to severe traumatic brain injury (TBI) on different aspects of memory: a selective review

Deficient learning and memory are frequently reported as a consequence of traumatic brain injury (TBI). Because of the diffuse nature of the injury, patients with TBI are not the ideal group for studying brain-behavior relations. Nevertheless, characterization of the memory breakdown following TBI could contribute to the assessment and rehabilitation of this patient population. It is well documented that memory is not a unitary system. Accordingly, in this article I review studies that have investigated the long-term effect of moderate to severe TBI on different memory aspects, including explicit and implicit tests of memory. This review demonstrates that TBI affects a large range of memory aspects. One of the conclusions is that the memory impairment observed in TBI patients could be viewed, at least to some degree, as a consequence of a more general cognitive deficit. Thus, unlike patients suffering from global amnesia, memory in patients with TBI is not selectively impaired. Nevertheless, it is possible to detect a subgroup of patients that do meet the criteria of amnesia. However, the most common vulnerable memory processes following TBI very much resemble the memory deficits reported in patients following frontal lobe damage, e.g., difficulties in applying active or effortful strategy in the learning or retrieval process. The suggested similarity between patients with TBI and those suffering from frontal lobe injury should be viewed cautiously; considering the nature of TBI, patients suffering from such injuries are not a homogeneous group. In view of this limitation, the future challenge in this field will be to identify subgroups of patients, either a priori according to a range of factors such as severity of injury, or a posteriori based on their specific memory deficit characteristics. Such a research approach has the potential of explaining much of the variability in findings reported in the literature on the effect of TBI on memory.     

Trauma and memory

The study of traumatic memories challenges several basic notions about the nature of memory: (i) that memory always is a constructive process; (ii) that memory is primarily declarative (i.e. that people can articulate what they know in words and symbol) (iii) that memory is present in consciousness in a continuous and uninterrupted fashion; and (iv) that memory always disintegrates in accuracy over time. A century of study of traumatic memories shows that (i) semantic representations may coexist with sensory imprints; (ii) unlike trauma narratives, these sensory experiences often remain stable over time, unaltered by other life experiences; (iii) they may return, triggered by reminders, with a vividness as if the experience were happening all over again; and (iv) these flashbacks may occur in a mental state in which victims are unable to precisely articulate what they are feeling and thinking. The present paper reviews the literature on traumatic memories and discusses the recent neuroimaging studies which seem to clarify the neurobiological underpinnings of the differences between ordinary and traumatic memories.     

Maintenance of intrusive memories in posttraumatic stress disorder: a cognitive approach

Intrusive recollections are very common immediately after traumatic events and are considered necessary aspects of emotional processing. However, if these intrusive recollections persist over a long time, they are linked to long-term psychiatric disorder, especially Posttraumatic Stress Disorder (PTSD). This paper discusses the need to investigate factors involved in the maintenance of intrusive traumatic recollections. It is suggested that the idiosyncratic meaning of the intrusive recollections predicts the distress caused by them, and the degree to which the individual engages in strategies to control the intrusions. These control strategies maintain the intrusive recollections by preventing a change in the meaning of the trauma and of the traumatic memories. It is further suggested that what is needed is a comprehensive assessment of the processes that prevent change in meaning, going beyond the assessment of avoidance. In particular, safety behaviours, dissociation and numbing, suppression of memories and thoughts about trauma, rumination, activation of other emotions such as anger and guilt and corresponding cognitions, and selective information processing (attentional and memory biases) may be involved in the maintenance of intrusive recollections. Preliminary data supporting these suggestions from studies of individuals involved in road traffic accidents and survivors of child sexual abuse are described.     

Post-traumatic stress disorder and head injury as a dual diagnosis: "islands" of memory as a mechanism.

This case study describes post-traumatic stress disorder (PTSD) and head injury after a road traffic accident involving a pedestrian. Previous studies have proposed two mechanisms by which this dual diagnosis may occur: (1) when post-traumatic amnesia and retrograde amnesia are small or non-existent and (2) when non-declarative memory systems for the traumatic event are in operation. This case study demonstrates a third mechanism--"islands" of memory within post-traumatic amnesia.     

Post-traumatic stress disorder and memory: prescient medicolegal testimony at the International War Crimes Tribunal?

The nature of remembrance of traumatic events has been particularly controversial during the past decade as vigorous new research has reshaped thinking about trauma and memory. Memory alterations in traumatized individuals have been investigated within both theoretical and biological frameworks. There are different types of memory, and empirical studies have associated post-traumatic stress disorder (PTSD) with a simultaneous weakening and a strengthening of memory. Memory deficiencies in PTSD have been found to be related to problems in new learning (explicit memory), but other specific deficiencies are unvalidated. Recently, accuracy of memory has received particular scrutiny because considerable importance is attached to victims' recollections. In 1998, at the International War Crimes Tribunal in The Hague, The Netherlands, a Bosnian-Croatian soldier was tried for aiding and abetting the rape of a Muslim woman. The defendant's lawyers suggested that the woman's memory was inaccurate, having been adversely affected by her traumatic experiences, and that the defendant whom she identified was not present during her interrogation and abuse. The prosecution disagreed and argued that memories of traumatic experiences in individuals with PTSD are characteristically hyperaccessible. Expert witnesses on both sides were brought in to provide medicolegal testimony about the scientific parameters of stress and its long-term effects on brain regions associated with memory. With the expert witness discussion as background, this article reviews the most recent research about the nature of memory in the aftermath of trauma and the politics of psychological trauma and the law.     

Anisomycin, a protein synthesis inhibitor, disrupts traumatic memory consolidation and attenuates posttraumatic stress response in rats.

BACKGROUND: Paradoxical changes in memory represent a troublesome characteristic of posttraumatic stress disorder (PTSD). Exceptionally vivid intrusive memories of some aspects of the trauma are mingled with patchy amnesia regarding other important aspects. Molecular studies of the memory process suggest that the conversion from labile short-term memory into long-term fixed traces involves protein synthesis. This study assessed the effects of administration of anisomycin, a protein synthesis inhibitor, after initial exposure, after exposure to a cue associated with triggering experience, and after reexposure to the triggering trauma in an animal model of PTSD. METHOD: Magnitude of changes in prevalence of anxiety-like behaviors on the elevated plus-maze and nonhabituated exaggerated startle reaction were compared in rats that were exposed to predator stress, with and without microinjection of anisomycin. RESULTS: Microinjection of anisomycin before and after stress exposure reduced anxiety-like and avoidant behavior, reduced the mean startle amplitude, and reversed the stress-induced habituation deficit 7 days later. The persistent anxiety-like behaviors that were seen after stress exposure do not appear to be sensitive to anisomycin after reexposure to a cue associated with the event or after reexposure to the index experience. CONCLUSIONS: Disruption of the process of traumatic memory consolidation may be useful for mitigating PTSD symptoms.