It is a handicap that is often invisible and yet major for those who suffer from it. Highlighted in particular by the attacks of November 13, 2015, post-traumatic stress disorder (PTSD) affects direct or indirect witnesses of extraordinary events, assailed by flashbacks, intrusive images or distressing thoughts…
Between 5 and 12% of the population suffer from it, according to Inserm. In 20% of cases, these difficulties persist over time, becoming a chronic condition. How to explain it? Why do some people recover from it, when others, just as strong-willed and eager to get through it, are still struggling years later?
It is on this crucial question that neuroscientist Pierre Gagnepain and researchers from the neuropsychology and human memory imaging laboratory at Inserm, in Caen, have been working since 2016, as part of the 13-Novembre transdisciplinary program. Published on January 8 in the journal Science advance, their study called “Remember”, is based on the long-term monitoring of one hundred people exposed to the attacks of November 13, in Paris and Saint-Denis.
Plasticity of the brain and hippocampus
Among them, 34 suffered from chronic PTSD, 19 had recovered from it, 43 had not developed it. Seventy-two volunteers not directly exposed to these events were also recruited to serve as a “control group”. By subjecting participants to MRIs (magnetic resonance imaging) twice – first in 2016-2017 then in 2018-2019 – they hoped to understand the mechanisms at work in their brain and observe their evolution over time. .
These examinations allowed them to discover that in people who have recovered from PTSD, the memory control mechanisms – and therefore the ability to regulate intrusive thoughts or images – evolve over time. This is what we call brain plasticity, or its ability to modify its networks and, in the case of people freed from PTSD, to get back on the path to “normal” brain activity.
-A reality which materializes concretely, through the hippocampus, a central brain region in memory. “For a number of years now, we have known that in PTSD there is a structural modification of the hippocampusexplains Professor Francis Eustache, neuropsychologist and co-head of the November 13 research program. Thus, if we compare the brain of a person who does not have PTSD to that of a person who does, we see in the latter a reduction in the volume of the hippocampus. What the study shows is that in remitted people (recovered from PTSD), this alteration of the hippocampus ceases. Something gets fixed somehow. »
Therapeutic avenues
Clearly, the brain is capable of resilience. “The publication of this study at the very moment when we commemorate the attacks of January 2015 is a coincidence of timing, but it has the merit of carrying a positive message in these difficult times: no, memory is not fixed, it changes, and we see that certain people have the capacity to gradually regain control of their memories,” underlines Francis Eustache. This could also open up therapeutic avenues, “perhaps with techniques that would strengthen these memory control mechanisms when they are failing. »
The team’s work continues, and other publications are to come. “The composition of this cohort is very interesting from a scientific point of view because usually, studies focusing on PTSD include all kinds of traumatic situations. There, all the people experienced the same event,” specifies Francis Eustache, pointing out the character “a bit special about this study”. “We regularly check in with participants and they can call us. If one of them seems in distress, we will try to find a solution. We are certainly following a scientific approach, but there is obviously a human dimension. »
