Prior imaging studies of people with PTSD have shown that these brain regions can over- or underreact in response to stressful tasks, such as recalling a traumatic event or reacting to a photo of a threatening face.
Researchers now believe chronic trauma can inflict lasting damage to brain regions associated with fear and anxiety.
In the new study, researchers at New York University School of Medicine explored for the first time what happens in the brains of combat veterans with PTSD in the absence of external triggers.
Investigators say the findings, published in Neuroscience Letters, show that the effects of trauma persist in certain brain regions even when combat veterans are not engaged in cognitive or emotional tasks, and face no immediate external threats.
Experts believe this knowledge is a critical step toward better diagnostics and treatments for PTSD as it shows which areas of the brain provoke traumatic symptoms.
PTSD can plague victims with disturbing memories, flashbacks, nightmares and emotional instability. Among the 1.7 million men and women who have served in the wars in Iraq and Afghanistan, an estimated 20 percent have PTSD. Research shows that suicide risk is higher in veterans with PTSD.
Tragically, more soldiers committed suicide in 2012 than the number of soldiers who were killed in combat in Afghanistan that year.
“It is critical to have an objective test to confirm PTSD diagnosis as self-reports can be unreliable,” said co-author Charles Marmar, M.D.
The study, led by Xiaodan Yan, a research fellow at NYU School of Medicine, examined “spontaneous” or “resting” brain activity in 104 veterans of combat from the Iraq and Afghanistan wars using functional MRI, which measures blood-oxygen levels in the brain.
The researchers found that spontaneous brain activity in the amygdala, a key structure in the brain’s “fear circuitry” that processes fearful and anxious emotions, was significantly higher in the 52 combat veterans with PTSD than in the 52 combat veterans without PTSD.
The PTSD group also showed elevated brain activity in the anterior insula, a brain region that regulates sensitivity to pain and negative emotions.
Moreover, the PTSD group had lower activity in the precuneus, a structure tucked between the brain’s two hemispheres that helps integrate information from the past and future, especially when the mind is wandering or disengaged from active thought.
Decreased activity in the precuneus correlates with more severe “re-experiencing” symptomsâ€”that is, when victims re-experience trauma over and over again through flashbacks, nightmares and frightening thoughts.