Widespread cognitive impairment in psychogenic anterograde amnesia

Believing in dissociative amnesia relates to claiming it: a survey of people's experiences and beliefs about dissociative amnesia

Dissociative amnesia is one of the most controversial categories in the field of psychiatry and clinical psychology. Self-reports of dissociative amnesia in the general population, and beliefs about this topic, have so far not been subjected to empirical scrutiny. Here, we surveyed a sample from the general population (N = 1017), revealing that about a tenth (n = 102) claimed to have experienced dissociative amnesia. Some claims pertained to amnesia for traumatic autobiographical experiences (e.g., sexual assault), while other claims reflected memory loss for experiences that can be regarded as non-traumatic or non-stressful (e.g., dissociative amnesia for an anniversary). Importantly, many participants believed in the existence of dissociative amnesia, and those who claimed dissociative amnesia indicated even more belief in this phenomenon than the rest of the sample. Finally, many participants indicated to have at least once claimed to have feigned memory loss in their life, and that they experienced some form of forgetting when trying to retrieve events for which they lied upon. Overall, our findings suggest that claiming dissociative amnesia goes hand in hand with believing in dissociative amnesia.

Dissociative amnesia

Dissociative amnesia is one of the most enigmatic and controversial psychiatric disorders. In the past two decades, interest in the understanding of its pathophysiology has surged. In this report, we review new data about the epidemiology, neurobiology, and neuroimaging of dissociative amnesia and show how advances in memory research and neurobiology of dissociation inform proposed pathogenetic models of the disorder. Dissociative amnesia is characterised by functional impairment. Additionally, preliminary data suggest that affected people have an increased and possibly underestimated suicide risk. The prevalence of dissociative amnesia differs substantially across countries and populations. Symptoms and disease course also vary, indicating a possibly heterogeneous disorder. The accompanying clinical features differ across cultural groups. Most dissociative amnesias are retrograde, with memory impairments mainly involving the episodic-autobiographical memory domain. Anterograde dissociative amnesia occurring without significant retrograde memory impairments is rare. Functional neuroimaging studies of dissociative amnesia with prevailing retrograde memory impairments show changes in the network that subserves autobiographical memory. At present, no evidence-based treatments are available for dissociative amnesia and no broad framework exists for its rehabilitation. Further research is needed into its neurobiology, course, treatment options, and strategies to improve differential diagnoses.

Towards solving the riddle of forgetting in functional amnesia: recent advances and current opinions

Remembering the past is a core feature of human beings, enabling them to maintain a sense of wholeness and identity and preparing them for the demands of the future. Forgetting operates in a dynamic neural connection with remembering, allowing the elimination of unnecessary or irrelevant information overload and decreasing interference. Stress and traumatic experiences could affect this connection, resulting in memory disturbances, such as functional amnesia. An overview of clinical, epidemiological, neuropsychological, and neurobiological aspects of functional amnesia is presented, by preponderantly resorting to own data from patients with functional amnesia. Patients were investigated medically, neuropsychologically, and neuroradiologically. A detailed report of a new case is included to illustrate the challenges posed by making an accurate differential diagnosis of functional amnesia, a condition that may encroach on the boundaries between psychiatry and neurology. Several mechanisms may play a role in "forgetting" in functional amnesia, such as retrieval impairments, consolidating defects, motivated forgetting, deficits in binding and reassembling details of the past, deficits in establishing a first person autonoetic connection with personal events, and loss of information. In a substantial number of patients, we observed a synchronization abnormality between a frontal lobe system, important for autonoetic consciousness, and a temporo-amygdalar system, important for evaluation and emotions, which provides empirical support for an underlying mechanism of dissociation (a failure of integration between cognition and emotion). This observation suggests a mnestic blockade in functional amnesia that is triggered by psychological or environmental stress and is underpinned by a stress hormone mediated synchronization abnormality during retrieval between processing of affect-laden events and fact-processing.

The remains of the day in dissociative amnesia

Memory is not a unity, but is divided along a content axis and a time axis, respectively. Along the content dimension, five long-term memory systems are described, according to their hierarchical ontogenetic and phylogenetic organization. These memory systems are assumed to be accompanied by different levels of consciousness. While encoding is based on a hierarchical arrangement of memory systems from procedural to episodic-autobiographical memory, retrieval allows independence in the sense that no matter how information is encoded, it can be retrieved in any memory system. Thus, we illustrate the relations between various long-term memory systems by reviewing the spectrum of abnormalities in mnemonic processing that may arise in the dissociative amnesia—a condition that is usually characterized by a retrieval blockade of episodic-autobiographical memories and occurs in the context of psychological trauma, without evidence of brain damage on conventional structural imaging. Furthermore, we comment on the functions of implicit memories in guiding and even adaptively molding the behavior of patients with dissociative amnesia and preserving, in the absence of autonoetic consciousness, the so-called “internal coherence of life”.

Losing memories overnight: a unique form of human amnesia

Since an automobile accident in 2005, patient FL has reported difficulty retaining information from one day to the next. During the course of any given day, she describes her memory as normal. However, memory for each day disappears during a night of sleep. She reports good memory for events that occurred before the accident. Although this pattern of memory impairment is, to our knowledge, unique to the medical literature, it was depicted in the fictional film "50 First Dates". On formal testing, FL performed moderately well when trying to remember material that she had learned during the same day, but she exhibited no memory at all for material that she knew had been presented on a previous day. For some tests, unbeknownst to FL, material learned on the previous day was intermixed with material learned on the same day as the test. On these occasions, FL's memory was good. Thus, she was able to remember events from earlier days when memory was tested covertly. FL performed differently in a number of ways from individuals who were instructed to consciously feign her pattern of memory impairment. It was also the impression of those who worked with FL that she believed she had the memory impairment that she described and that she was not intentionally feigning amnesia. On the basis of her neuropsychological findings, together with a normal neurological exam, normal MRI findings, and psychiatric evaluation, we suggest that FL exhibits a unique form of functional amnesia and that its characterization may have been influenced by knowledge of how amnesia was depicted in a popular film. She subsequently improved (and began retaining day-to-day memory) at Johns Hopkins University where she was in a supportive in-patient environment and was shown how to take control of her condition by interrupting her sleep at 4-h intervals.

A woman lost in the cemetery: A case of time-limited amnesia

A 43-year-old woman one day experienced a dissociative fugue which she could not recall. She was married, nulliparous, with no history of dissociative disorder or other psychiatric disorders. She had been sexually abused during late childhood-early adolescence. She was examined thoroughly from both psychiatric and medical standpoints to exclude organic causes for her condition. Magnetic Resonance Imaging showed only some non-specific abnormalities. On personality tests, a histrionic structure of personality emerged, with obsessive and narcissistic traits accompanied by rigidity and anxiety, dysphoria and high risk for depression; some impairment was found in executive function tests. Final diagnosis was one of dissociative fugue. In fact, organic traits were not sufficient to establish a diagnosis of Transient Global Amnesia.

Searching for the Anatomy of Dissociative Amnesia

Brain damage was traditionally seen as the product of a neurological disease or injury. Nevertheless, modern brain imaging techniques have provided increasing evidence for alterations in brain tissue and metabolism for a number of psychiatric disorders. Though for a while “dissociated” ( Spiegel, 2006 ) from the clinical and scientific arena, dissociative disorders have in the last several years received a renewed interest among several groups of researchers, who embarked on the work of disentangling their neural correlates. We review data from our own research as well as others, which point to distinct changes in brain regions underlying dissociative amnes(t)ic disorders. These changes may consist of overall reductions in brain metabolism or more selective alterations primarily in the right temporo-frontal cortices. Recent evidence with refined magnetic resonance imaging techniques furthermore reveals selective fiber degenerations in these regions. While these changes may persist and probably even intensify in some patients, they may be reversible in others – especially if treatment is carried out successfully within short time after onset. Implications of these findings for the pathogenetic conceptualization of dissociative amnes(t)ic disorders are outlined.

Functional brain imaging in 14 patients with dissociative amnesia reveals right inferolateral prefrontal hypometabolism

Dissociative amnesia is a condition usually characterized by severely impaired retrograde memory functioning in the absence of structural brain damage. Recent case studies nevertheless found functional brain changes in patients suffering from autobiographical-episodic memory loss in the cause of dissociative amnesia. Functional changes were demonstrated in both resting state and memory retrieval conditions. In addition, some but not all cases also showed other neuropsychological impairments beyond retrograde memory deficits. However, there is no group study available that examined potential functional brain abnormalities and accompanying neuropsychological deteriorations in larger samples of patients with dissociative retrograde amnesia. We report functional imaging and neuropsychological data acquired in 14 patients with dissociative amnesia following stressful or traumatic events. All patients suffered from autobiographical memory loss. In addition, approximately half of the patients had deficits in anterograde memory and executive functioning. Accompanying functional brain changes were measured by [18F]fluorodeoxyglucose positron emission tomography (FDG-PET). Regional glucose utilization of the patients was compared with that of 19 healthy subjects, matched for age and gender. We found significantly decreased glucose utilization in the right inferolateral prefrontal cortex in the patients. Hypometabolism in this brain region, known to be involved in retrieval of autobiographical memories and self-referential processing, may be a functional brain correlate of dissociative amnesia.