Rafaele J. C. Huntjens

Interidentity amnesia for neutral, episodic information in dissociative identity disorder

Interidentity amnesia is considered a hallmark of dissociative identity disorder (DID) in clinical practice. In this study, objective methods of testing episodic memory transfer between identities were used. Tests of both recall (interference paradigm) and recognition were used. A sample of 31 DID patients was included. Additionally, 50 control subjects participated, half functioning as normal controls and the other half simulating interidentity amnesia. Twenty-one patients subjectively reported complete one-way amnesia for the learning episode. However, objectively, neither recall nor recognition scores of patients were different from those of normal controls. It is suggested that clinical models of amnesia in DID may be specified to exclude episodic memory impairments for emotionally neutral material.

Inter-identity amnesia in dissociative identity disorder: a simulated memory impairment?

BACKGROUND Although included in the current edition of the DSM, there does not seem to be consensus among mental health professionals regarding the diagnostic status and scientific validity of dissociative identity disorder (DID). This study was aimed at the detection of simulation of inter-identity amnesia in DID. METHOD A sample of 22 DID patients was included, together with a matched control sample of subjects instructed to simulate inter-identity amnesia, a guessor group that had no knowledge of the stimulus material and a normal control group. A multiple-choice recognition test was included. The rate of incorrect answers was determined. Moreover, the specific simulation strategy used was examined by providing subjects with a range of choices that varied in extent of disagreement with the correct answer and determining whether plausible or implausible answer alternatives were selected. RESULTS On the recognition test DID patients selected incorrect answers above chance like simulators. Patients thus seem to use their knowledge of the correct answer in determining their given answer. They were not characterized by a well-thought-out simulating behaviour style, as indicated by the differences in selection of specific answer alternatives found between patients and simulators. CONCLUSIONS DID patients were found not to be characterized by an actual memory retrieval inability, in contrast to their subjective reports. Instead, it is suggested that DID may more accurately be considered a disorder characterized by meta-memory problems, holding incorrect beliefs about their own memory functioning.

Autobiographical memory specificity and symptoms of complicated grief, depression, and posttraumatic stress disorder following loss

This study examined the specificity and content of autobiographical memories among bereaved individuals. Self-report measures of bereavement-related distress and a standard and trait version of the Autobiographical Memory Test (AMT) were administered to 109 bereaved people. We examined associations of memory specificity with (a) demographic and loss-related variables and with (b) symptom-levels of complicated grief (CG), depression, and posttraumatic stress disorder (PTSD), (c) associations of the content of memories (related vs. unrelated to the loss/lost person) with symptoms, and (d) the degree to which associations of symptom-levels with memory specificity and content differed between the standard and trait version of the AMT. Findings showed that (a) memory specificity varied as a function of age, education, and kinship; (b) reduced memory specificity was significantly associated with symptom-levels of CG, but not depression and PTSD; (c) symptom-levels of CG and PTSD were associated with a preferential retrieval of specific memories that were related to the loss/lost person on the standard AMT, whereas all three symptom-measures were associated with preferential retrieval of loss-related specific memories on the trait AMT; and (d) on the trait AMT, but not the standard AMT, symptom-measures remained significantly associated with a preferential retrieval of loss-related specific memories, when controlling for relevant background variables. Among other things, these results show that reduced memory specificity is associated with self-reported CG-severity but not depression and PTSD following loss. Moreover, the results are consistent with recent research findings showing that memories tied to the source of an individuals distress (e.g., loss) are immune to avoidant processes involved in the standard reduced specificity effect.

Intrusive images in grief: An exploratory study

The relevance of intrusive mental imagery to the understanding and treatment of psychological disorders is increasingly acknowledged. Little research has been done on intrusive imagery in grief. Using a sample of 131 mourners, recruited from professional and lay mental health care workers, the current study examined the frequency and correlates of four specific intrusive images: (a) positive intrusive memories of the lost person; (b) intrusive images of the death event; (c) re-enactment fantasies; and (d) negative images of the future. Findings revealed that these intrusions were common and that the occurrence of these intrusions hardly varied across subgroups of mourners. All four intrusions were correlated with the severity of complicated grief symptoms, and intrusions (b), (c) and (d) were also correlated with the severity of symptoms of depression and anxiety. Findings have potential theoretical and clinical implications and indicate that a more comprehensive study of intrusions among bereaved people is warranted.

Inter-Identity Autobiographical Amnesia in Patients with Dissociative Identity Disorder

Background A major symptom of Dissociative Identity Disorder (DID; formerly Multiple Personality Disorder) is dissociative amnesia, the inability to recall important personal information. Only two case studies have directly addressed autobiographical memory in DID. Both provided evidence suggestive of dissociative amnesia. The aim of the current study was to objectively assess transfer of autobiographical information between identities in a larger sample of DID patients. Methods Using a concealed information task, we assessed recognition of autobiographical details in an amnesic identity. Eleven DID patients, 27 normal controls, and 23 controls simulating DID participated. Controls and simulators were matched to patients on age, education level, and type of autobiographical memory tested. Findings Although patients subjectively reported amnesia for the autobiographical details included in the task, the results indicated transfer of information between identities. Conclusion The results call for a revision of the DID definition. The amnesia criterion should be modified to emphasize its subjective nature.

The time course of spatial memory processing in the two hemispheres.

Previous studies have shown that memories for positions are often distorted in systematic ways, indicating the influence of categorical positions codes which can bias responses in object-relocation tasks towards stored spatial prototypes. In the present study, we examined the time course of these categorical influences. Subjects had to relocate the position of a tachistoscopically presented dot within a circle, which could appear in either the left visual field (i.e. initially to the right hemisphere) or the right visual field (i.e. initially to the left hemisphere). Three retention intervals between presentation and relocation were used: 500, 2000 and 5000 ms. Performance was most accurate with left visual field/right hemisphere presentation. Systematic distortions were found for angular errors (dot relocations regressed towards the 45 degrees with a quadrant) as well as for radial errors (dots were replaced in the direction of the circles circumference, and this more so when the dot was further away from the circumference). Importantly, these categorical biases became stronger with retention interval and initial left hemispheric processing. These results suggest that categorical spatial coding might be the default manner in which spatial information is remembered over time. Finally, the left hemisphere may play an important role for such a categorical spatial coding.

Perceptual and conceptual priming in patients with dissociative identity disorder.

The present study examined implicit memory transfer in patients with dissociative identity disorder (DID). To determine priming impairments in DID, we included both several perceptual priming tasks and a conceptual priming task using neutral material. We tested a large sample of DID patients (n=31), in addition to 25 controls and 25 DID simulators, comparable on sex, age, and education. Controls replicated conceptual priming results of Vriezen, Moscovitch, and Bellos (1995) by showing that conceptual priming seems to require the formation of domain-specific semantic representations, denoting either sensory or functional object attributes. We extended a study performed by Schacter, Cooper, and Delaney (1990) by demonstrating priming for impossible objects using the sensitive priming index of response times. The simulators in the study were not able to simulate interidentity amnesia on the implicit memory tasks employed. Partly in contrast to participants in previous studies, DID patients showed evidence of perceptual priming as well as conceptual priming comparable to that of controls. DID patients thus displayed normal implicit memory performance.

Procedural memory in dissociative identity disorder: when can inter-identity amnesia be truly established?

In a serial reaction time task, procedural memory was examined in Dissociative Identity Disorder (DID). Thirty-one DID patients were tested for inter-identity transfer of procedural learning and their memory performance was compared with 25 normal controls and 25 controls instructed to simulate DID. Results of patients seemed to indicate a pattern of inter-identity amnesia. Simulators, however, were able to mimic a pattern of inter-identity amnesia, rendering the results of patients impossible to interpret as either a pattern of amnesia or a pattern of simulation. It is argued that studies not including DID-simulators or simulation-free memory tasks, should not be taken as evidence for (or against) amnesia in DID.

Identity state-dependent attentional bias for facial threat in dissociative identity disorder

Biased attention for threatening stimuli has been associated with many forms of psychopathology. Attention to threatening faces presented below perceptual thresholds was assessed in patients diagnosed with dissociative identity disorder using a pictorial emotional Stroop task. Patients were tested in two different identity states, in one of which they claimed strong awareness of trauma. Attentional bias for social threat proved state-dependent in the patients and deviated from the patterns observed in controls.

Self-Reported Sleep Disturbances in Patients with Dissociative Identity Disorder and Post-Traumatic Stress Disorder and How They Relate to Cognitive Failures and Fantasy Proneness

Sleep disturbances, fantasy proneness, cognitive failures, and dissociative symptoms are related to each other. However, the co-occurrence of these phenomena has been primarily studied in non-clinical samples. We investigated the correlations between these phenomena in dissociative identity disorder (DID) patients, post-traumatic stress disorder (PTSD) patients, and healthy controls. Both patient groups reported more sleep problems and lower sleep quality and displayed higher levels of fantasy proneness and cognitive failures than controls. However, the two patient groups did not differ with regard to these variables. Moreover, a higher level of unusual sleep experiences tended to predict participants belonging to the DID group, while specifically a lower sleep quality and more cognitive failures tended to predict participants belonging to the PTSD group.