Study yields potential biomarker for PTSD-resistant brains
The PTSD-resistant brain— Drs. Apostolos Georgopoulos and Lisa James and colleagues at the Minneapolis VA Medical Center used a MEG scanner, which captures neuron activity, to understand what makes "resilient" brains tick. (Photo by April Eilers)
Scientists at the Minneapolis VA Medical Center have identified patterns of brain activity that appear to be a marker of resilience to trauma. They say the findings, published online Feb. 20 in JAMA Psychiatry, help explain why some people who are exposed to trauma never develop posttraumatic stress disorder (PTSD).
Using a type of brain scan called magnetoencephalography, or MEG, the team compared the brains of nearly 200 Veterans. MEG detects magnetic fields that are produced above the head when groups of brain cells "talk" to each other.
The study volunteers had been exposed to potentially traumatic events to varying degrees—in combat or in other life situations—but only 86 of them had gone on to develop PTSD.
The MEG scans of PTSD-affected brains showed clusters of neurons that were locked into long-term interactions with other clusters.
"We believe these neuron networks were stuck in the trauma-encoding phase," says lead author Lisa James, PhD. "The trauma had a hold on them. They weren't available to encode new information."
She compares the phenomenon to a"phone network where every line is busy."
The non-PTSD volunteers showed no such patterns. Their neural networks were flexible, adaptable, available. They were free to link up with other neuron groups as needed to react to new incoming experiences. The scientists call this "decorrelation."
"This is a biomarker of resilience," notes James."The deficit that we see in PTSD is the absence of that ability to modulate."
Neuron groups in 'tight handshake'
Coauthor Brian Engdahl, PhD, uses another analogy, that of a handshake, to describe how healthy neural networks respond to traumas:"When a trauma comes in, everyone [populations of neurons within the brain] is shaking hands tightly. The neurons are very tied up with processing this experience. Over time, the handshake weakens. It gets less intense. The network eventually gets released and is free to respond to other events."
In normal brains, he explains, the traumatic memory eventually gets consolidated and deposited in other brain regions. The neuron groups that initially processed the trauma move on to new tasks. The memory remains housed in the brain, but it's not pathological. It doesn't impair function.
The brain area where the researchers saw the sharpest difference between the two groups of study volunteers was the right superior temporal gyrus. Part of this brain region helps with auditory processing, but the researchers say the area they were probing was the anterior part of the superior temporal gyrus, the role of which is not clearly known.
"It's no man's land," says senior author Apostolos Georgopoulos, MD, PhD, director of the Brain Sciences Center at the Minneapolis VA. He points out, though, that some studies have linked the region to the re-experiencing of past events, which clearly plays a role in PTSD.
"Our patients with PTSD tell us that the intrusive memories have a life of their own," says Georgopoulos. "They pop into their minds when they don't want them. And that's what we're seeing on the brain scans."
Scans reflect brain's resting state
The study volunteers completed the one-minute MEG tests while lying on their back in the scanner, staring at a spot about two feet away.
"The scans were done in a resting state," says Georgopoulos. "It's like a car that's idling. There were no challenges, no images to evoke the traumatic event. What we see is ongoing brain activity."
The new study complements research published by the group in 2010 in which it first described distinctive PTSD brain patterns, as detected by MEG.
"This new paper helps explain why we found what we found in those earlier studies," notes Georgopoulos."Based on this work, we hope to develop reliable biomarkers for PTSD and for emotional resilience."
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