One question the researchers want to explore through the lens of the [November 13, 2015] Paris attacks is why some people who experience trauma develop PTSD, while others do not.
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The researchers designed a behavioral experiment in which the volunteers memorized word-image pairs, to the point where, upon seeing one of the words on a screen, the participants would automatically think of the associated image. The researchers then had the participants lie down in an fMRI machine and try to avoid recalling some of the images they’d just been trained to think of: if a cue word appeared in red, they were to try to prevent the associated image from entering their awareness, or to push it out of their thoughts if it did so.
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The researchers found that participants differed in the amount of connectivity between certain brain regions—specifically, between inhibitory control regions of the prefrontal cortex and structures involved in memory such as the hippocampus. People with PTSD showed much weaker connections between these regions than did people without the disorder. “It seems that vulnerable individuals have a problem with control,” says [neuroscientist Karen] Ersche, who wrote a perspective article that accompanied the study but was not involved in the research. “What I really liked about this paper is it says it’s not the severity of the trauma that leads to PTSD; it’s the ability to control it. And that is key.”