Recovery from PTSD comes with key changes in the brain’s memory system, a new study finds. These differences were found in the brains of 19 people who developed post-traumatic stress disorder after the 2015 terrorist attacks in Paris — and then recovered over the following years.
The results, published January 8 in Science Advances, point to the complexity of PTSD, but also to ways that brains can reshape themselves as they recover.
With memory tasks and brain scans, the study provides a cohesive look at the recovering brain, says cognitive neuroscientist Vishnu Murty of the University of Oregon in Eugene. “It’s pulled together a lot of pieces that were floating around in the field.”
On the night of November 13, 2015, terrorists attacked a crowded stadium, a theater and restaurants in Paris. In the years after, PTSD researchers were able to study some of the people who endured that trauma. Just over half the 100 people who volunteered for the study had PTSD initially. Of those, 34 still had the disorder two to three years later; 19 had recovered by two to three years.
People who developed PTSD showed differences in how their brains handled intrusive memories, laboratory-based tests of memory revealed. Participants learned pairs of random words and pictures — a box of tissues with the word “work,” for example. PTSD involves pairs of associated stimuli too, though in much more complicated ways. A certain smell or sound, for instance, can be linked with the memory of trauma.
In the lab tests, the people were sometimes asked to conjure up the picture of tissues in their mind when they saw “work.” Other times, they were asked to look at the word while keeping their minds blank, suppressing the picture of tissues. All the while, their brain activity was being measured by a functional MRI scan.
In tests done eight to 18 months after the attacks, all the people with PTSD showed differences in how their brains suppressed memories compared with people who did not have PTSD. But over time, this brain activity changed for some: In tests two to three years after the attack, people who had recovered from PTSD showed brain activity during this memory suppression task that was more like that of people who never had PTSD.
PTSD is sometimes described as trouble with learning; people can’t update their memories to interpret a formerly “dangerous” context as safe. But the new results suggest that suppressing a memory, a sort of forgetting, is important, too, says coauthor Pierre Gagnepain, a cognitive neuroscientist at Inserm and Centre Cyceron in Caen, France. “Instead of viewing PTSD as a learning disorder, it could be viewed as a forgetting disorder,” he says. That doesn’t mean people who recover forget what happened, he adds. “They can explain to you everything that happened to them during the trauma, but it means that you … can put the memory in a state of silence,” he says.
Further brain scans showed that this recovery of memory control was linked with the volume of the hippocampus, a key memory center in the brain. People with chronic PTSD lost volume in certain parts of their hippocampi in the years after 2015. But as people recovered, their hippocampus stopped atrophying, the results suggest.
The new results don’t explain the full complexity of PTSD — “it’s like, everything, everywhere, all at once,” Murty says. “We call it PTSD and it’s probably a hundred disorders underneath one label.”
Gagnepain and his colleagues hope to understand more about the brain circuits that may be creating this ability to recover. He finds it a hopeful direction. “Your brain is still able to overcome [trauma] by developing these resilience mechanisms,” he says. “It’s not written in stone.”
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