Long-Term Effects of Acute Stress on the Prefrontal-Limbic System in the Healthy Adult

Most
people are exposed to at least one traumatic event during the course of their lives, but large numbers of people do not develop
posttraumatic stress disorders. Although previous studies have shown that
repeated and chronic stress change the brain’s structure and function, few
studies have focused on the long-term
effects of acute
stressful exposure in a nonclinical sample,
especially the morphology and functional connectivity changes in brain regions
implicated in emotional reactivity and emotion regulation. Forty-one months
after the 5/12 Wenchuan earthquake, we investigated the effects of trauma exposure
on the structure and functional connectivity of the brains of trauma-exposed
healthy individuals compared with healthy controls matched for age, sex, and
education. We then used machine-learning algorithms with the brain structural
features to distinguish between the two groups at an individual level. In the trauma-exposed
healthy individuals, our results showed greater gray matter density in
prefrontal-limbic brain systems, including the dorsal anterior cingulate
cortex, medial prefrontal cortex, amygdala
and hippocampus, than in the controls. Further analysis showed stronger
amygdala-hippocampus functional connectivity in the trauma-exposed healthy
compared to the controls. Our findings revealed that survival of traumatic experiences, without developing
PTSD, was associated with greater gray matter density in the prefrontal-limbic
systems related to emotional regulation.