Researchers at Duke University Medical Center have found a pre-existing electrical pattern in the brains of mice that may help identify a predisposition for developing a stress-related mental illness, such as post-traumatic stress disorder (PTSD) and depression. The new findings, published July 29th in Nature Communications, may also support the development of new treatments.
“In soldiers, we have this dramatic, major stress exposure, and in some individuals it’s leading to major issues, such as problems sleeping or being around other people,” said senior author Kafui Dzirasa, M.D., Ph.D., recipient of the Brain & Behavior Research Foundation 2013 Sidney R. Baer, Jr. Prize for Innovative and Promising Schizophrenia Research. “If we can find that common trigger or common pathway and tune it, we may be able to prevent the emergence of a range of mental illnesses down the line.”
The research team at Duke analyzed the interaction between two interconnected brain areas—the prefrontal cortex and the amygdala—in genetically identical mice. The prefrontal cortex is involved in planning and other higher-level executive functions and the amygdala plays a role in the ‘fight-or-flight’ response. When smoothly functioning, the prefrontal cortex helps suppress the amygdala’s reactivity to danger, enabling continued functioning in stressful situations.
By implanting electrodes into the brains of the mice, the research team was able to listen to the speed at which the two sections of the brain fired and analyze how they were linked. They found that the mice’s response to a chronically stressful situation depended on the degree to which the prefrontal cortex was linked to—and able to control the activity of—the amygdala.
The researchers wanted to understand if these differences in linkage and firing were present prior to exposure to the chronic stress and they found that the mice with more severe reactions to chronic stress showed an exaggerated response in the prefrontal cortex-amygdala circuit, compared with resilient mice, even before they were exposed to the chronically stressful situation.
“We were really both surprised and excited to find that this signature was present in the animals before they were chronically stressed,” said Dr. Dzirasa, Assistant Professor of Psychiatry and Behavioral Sciences at Duke University Medical Center and a member of the Duke Institute for Brain Sciences.
The group hopes to delve further into the brain to see whether these circuit electrical patterns play a role in psychiatric disorders such as schizophrenia. These new findings will enable researchers to identify stress-susceptible and resilient animals before they are exposed to stress and analyze their biological differences, potentially paving the way for preventative interventions and new treatments for stress-related mental illness.
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