Differences in the way people learn and unlearn fear could explain why some suffer from severe post-traumatic stress disorder after a traumatic event while others are fine, a Yale study says.
Researchers from Yale and the Icahn School of Medicine at Mount Sinai in New York studied combat veterans to find out why some developed severe symptoms of PTSD.
They found pronounced differences in associative learning rates — the ability to distinguish between harmful and safe stimuli — between those who later developed severe PTSD and those who did not.
Published Monday in the journal Nature Neuroscience, the findings provide new insight into the neurobiology of PTSD that could help refine future treatment, Yale researchers said.
“We are shedding new light on how people learn fear and unlearn it,” said Ilan Harpaz-Rotem, associate professor of psychiatry at Yale and an author of the study.
Researchers measured the brain activity of the veterans, who had experienced intense events during combat, through functional Magnetic Resonance Imaging (fMRI) after showing them pictures of two different faces.
The subjects were administered slight electric shocks after viewing one of the faces, but not the other. Later, the faces accompanying the shock were switched in an attempt to have the veterans “unlearn” their original fear conditioning, the study says.
Using computational modeling, the researchers found two areas of the brain — the amygdala and striatum — were less able to track changes in threat level in those with severe PTSD symptoms.
Subjects with severe symptoms tended to overreact to a mismatch between their expectations and what they actually experienced, the researchers said.
Daniela Schiller of the Ichan School of Medicine was also an author of the study. The research was funded primarily by the National Institute of Mental Health and the National Center for PTSD.
Contact Natalie Missakian at news@newhavenbiz.com
