What are the neural correlates of dissociative amnesia? A systematic review of the functional neuroimaging literature

International audienceAim Dissociative amnesia is an emblematic psychiatric condition in which patients experience massive memory loss ranging from focal to global amnesia. This condition remains poorly understood and this review aims to investigate the neuroanatomical feature of this disease. Methods We conducted a systematic review of the scientific literature available on PubMed, up to December 1, 2022, using a combination of keywords referring to dissociative amnesia. We included every scientific report involving patients undergoing a functional imaging procedure. Results Twenty-two studies met our inclusion criteria (gathering 49 patients). Only one was a controlled study with a large sample. The other 21 were case reports and case series. In resting state, neuroimaging studies mostly showed a hypo-activated right inferolateral prefrontal cortex, associated with limbic hypoactivity and lesser activation of the hippocampal and para-hippocampal structures. The patients also presented abnormal patterns of cerebral activation when performing memory tasks. When testing recognition of memories from the amnestic period, patients showed increased activation across temporal areas (hippocampal and para-hippocampal gyri) and the limbic network. When trying to recollect memories from an amnestic period compared to a non-amnestic period, patients failed to activate these structures efficiently. Most of these patterns tended to return to normal when symptoms resolved. Conclusion This review identified a paucity of controlled studies in the field of dissociative amnesia neuroimaging, which restricts the extrapolation of results. Patients with dissociative amnesia present a broad prefronto-temporo-limbic network dysfunction. Some of the brain areas implicated in this network might represent potential targets for innovative treatments

Efficacy of traumatic memory reactivation with or without propranolol in PTSD with high dissociative experiences

Background: Post-traumatic stress disorder (PTSD) with dissociative symptoms is now a full-fledged subtype of this disorder. The dissociative subtype is associated with a greater number of psychiatric comorbidities. To date, the impact of dissociation on the efficacy of PTSD treatment remains unclear. Objective: The aim of this study was to compare the efficacy of a traumatic memory reactivation procedure with the administration of propranolol or a placebo once a week for six consecutive weeks in reducing PTSD and MDE symptoms between PTSD subjects with or without high dissociative symptoms. Method: For that, we conducted a randomized clinical trial in 66 adults diagnosed with longstanding PTSD and measured the SCID PTSD module, the PTSD Checklist (PCL-S), Beck’s Depression Inventory-II (BDI-II), and the Dissociative Experiences Scale (DES). Results: Patients with and without high dissociative experience had significant improvement in their PCL-S scores over the 6 treatment sessions, and PCL-S scores continued to decline in all patients during the post-treatment period. However, there was no correlation between the presence/absence of high dissociative experiences and no specific effect of propranolol treatment. We found exactly the same results for MDE symptoms. Interestingly, patients with high dissociative experiences before treatment exhibited very significant improvement in their DES scores after the 6 treatment sessions, and patients maintained this improvement 3 months post-treatment. Conclusions: The traumatic memory reactivation procedure is an effective way to treat dissociative symptoms in patients with PTSD, and improvement of these dissociative symptoms was associated with a decrease in both PTSD and depression severity