“Why do some people who have experienced trauma suffer from post-traumatic stress disorder (PTSD), while others never develop the disorder? What is it about the brain that explains why some people recover from PTSD and others have it chronically? » These are the questions that the team of Pierre Gagnepain, Inserm researcher (neuropsychology and imaging of human memory laboratory)*, is trying to answer, through the Remember study that he is leading. New results published in Science Advancesthis January 8 highlight the plasticity of brain mechanisms in the face of trauma and show how they transform over time, leading to a reduction in post-traumatic stress symptoms.
Supported by Inserm, Remember was launched in the months following the attacks of November 13, 2015, in Paris and Saint-Denis, as part of the transdisciplinary 13-November** program. The study compares the results of brain imaging conducted in 120 participants exposed to the attacks and 80 non-exposed who have been followed since 2015. The objective: to observe the effects of a traumatic event on the structures and functioning of the brain, identify neurobiological markers of post-traumatic stress and resilience, and ultimately, lead to new therapeutic avenues, complementary to those already existing (cognitive-behavioral therapies, EMDR, etc.).
Normalization of memory control mechanisms in resilient people
In their previous work published in 2020 in Sciencethe researchers highlighted a dysfunction of the brain networks controlling memory in people suffering from PTSD: these mechanisms fail to inhibit the activity of the hippocampus, which opens the way to the intrusion of visual memories , olfactory and sensory, associated with the trauma experienced. Conversely, the functioning of these mechanisms is largely preserved in individuals without PTSD, who manage to effectively combat intrusive memories.
In this new work, Pierre Gagnepain’s team wanted to know if these mechanisms could be modulated over time, until the disorder was eventually cured.
A total of 100 people exposed to the November 13 terrorist attacks were included: among them, 34 suffered from chronic PTSD, while 19 had recovered from an initial disorder. The control group includes 72 participants not exposed to the attacks. All participated twice in brain imaging studies (in 2016-2017 then in 2018-2019) in order to study the structural and functional changes of their brain over time. They also answered a questionnaire about their possible PTSD symptoms in 2020-2021.
Researchers observe that, in people who have recovered from PTSD, the memory control mechanisms are reshaped over time and eventually become normalized, to resemble those of the control group. Concretely, this is reflected in brain imaging by a more effective action of the prefrontal regions to inhibit hippocampal activity and prevent access to intrusive memories. In participants who suffer from chronic PTSD, these phenomena are still impaired. Nevertheless, the appearance of a beginning of plasticity of the memory control mechanisms, observed during the second stage of imaging in some of them, predicts a future reduction of the intrusive symptoms reported in the third part of the study. study, in the questionnaire.
« Our study shows that nothing is set in stone. Human resilience to trauma is characterized by the plasticity of memory control circuits, particularly those that regulate hippocampal activity. It also highlights that impaired control mechanisms are much more likely the cause than the consequence of PTSD. », Underlines Giovanni Leone, first author of the study, in a press release.
-Resilience “is not innate, even if there are factors that favor it. It can be developed and acquired,” summarizes Pierre Gagnepain to AFP. “Initially we had people who were not resilient and who somehow became resilient through the mobilization of these control mechanisms.”
From a clinical point of view, “ we could imagine new therapies to stimulate memory control mechanisms and encourage plasticity. The advantage of this approach would be to act on the brain networks without acting on the emotional system and without making the patient relive traumatic emotions. further specifies Pierre Gagnepain.
The team is continuing work on the subject: the next step will consist of studying the role of a particular brain receptor (called “Gaba alpha 5”), mainly located within the hippocampus, and which could be involved in the forgetting and silencing memories.
* Unit 1077 Neuropsychology and imaging of human memory (Inserm/University of Caen Normandy/École Pratique des Hautes Études/CHU Caen/GIP Cyceron)
** co-directed by the neuropsychologist Francis Eustache, director of the Inserm Neuropsychology and Imaging of Human Memory laboratory, and the historian Denis Peschanski, research director at the CNRS, the program studies the construction and evolution of memory, individual and collective , of these traumatic events.
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