A 'Benefit' of Brain Damage

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A veteran hunkers beneath a table in his rural home, convinced he's under machine gun fire. A mother spends hours wandering her apartment, checking and rechecking the locks on the doors. A friend jumps inexplicably when a car backfires.

These stories epitomize post-traumatic stress disorder, or PTSD. Despite the sterile term, it refers to very real carnage inside a person's mind. And it's not an uncommon affliction: It's estimated that 7 percent of Americans have had PTSD at some point in their lives. And with the U.S. involved in two wars abroad, that number may rise: A study published earlier this year found that 1 in 7 of soldiers returning from Iraq and Afghanistan suffers from PTSD.

The horror of a life-threatening experience—perhaps encountered in war, or from natural disasters or accidents—hounds some people in the form of PTSD long after they're out of harm's way. Their minds replay the traumatic experiences over and over again, leaving them anxious, suspicious and emotionally numb.

These symptoms not only trap a person with fear, but they can lead to lost jobs, divorce, even homelessness.

It's as though the intensity of the traumatic event has seared itself into the brain. Indeed, scientists think that traumatic events can leave "invisible wounds" in the brain, disrupting how it normally works.

A study published earlier this year attempted to find exactly where PTSD takes hold inside the head, and identified two culprits that might eventually be targets for treatment.

Double trouble

Researchers at the National Institute for Neurological Disorders and Stroke studied 193 veterans who had both experienced combat and suffered brain damage during the Vietnam War. Though these vets had been twice unlucky, they offered a unique opportunity for science to analyze what parts of the brain were needed to develop PTSD.

These soldiers are remarkable in that they had survived their brain injuries, which were usually from shrapnel that had penetrated the brain. Participating in the research is serious work for the veterans, says Jordan Grafman, the neuroscientist who led the study. "It's very intense and there's no promise of direct benefit to them," he says. "But they're doing it because they believe they'll help guys in the future."

A step into the future here means working backwards. Like detectives retracing the steps of a suspect, the researchers evaluated each veteran for PTSD, then sorted through their wartime brain injuries to see if there was a link between getting the disorder and the precise location of brain damage. Surprisingly, they found a benefit to brain damage found in two specific areas.

Damage to two regions of the brain—the amygdala and the ventromedial prefrontal cortex (vmPFC)—was prevalent in the veterans who did not go on to develop PTSD ever in their lifetime. It seems the brain damage somehow protected them.

The results are striking: Not one veteran with amygdala damage developed PTSD, and only 18 percent of veterans with vmPFC damage developed it. Compare that to the 40 percent of veterans with damage elsewhere in the brain and 48 percent of veterans without brain damage who developed PTSD.

This indicates that a person needs an intact and working amygdala or vmPFC to turn harrowing experiences into PTSD.

A way to 'quiet down' PTSD?

It makes sense that these regions are important to PTSD, because they are known for emotionally charged memories. The amygdala creates memories of fearful events, and lends "emotional gas" to a memory, says Grafman, whereas the vmPFC stores personal details surrounding a memory.

Any time a specific brain region is fingered in a disorder, it becomes a potential target for treatment. But how could scientists accomplish this, short of having volunteers sign up for some prophylactic brain damage before combat operations?

Grafman suggests something less drastic: drugs or brain stimulation that can zero in on the amygdala or vmPFC and dampen their electrical activity. Though not yet available, Grafman says that targeting a region like the vmPFC might quiet it down enough so as to reduce the intensity of disruptive memories, without erasing them.

In fact, our memories are stored in a vast neural bureaucracy that safeguards them from easy erasure. The different elements of a memory, like where you were on September 11, who was with you, and how you felt, reside in different parts of the brain. It's a complex web that allows us to remember.

PTSD sufferers don't need to forget, but they do need to learn how to handle their disturbing memories differently. That's why talk therapy can be helpful, says Grafman. "[They] learn to reconstruct the memory in a different way so that [they] have better control over it and a better context for it."

Quieting down the vmPFC region combined with talk therapy could help the ever-increasing number of PTSD sufferers get a better handle on their memories—and their mental health.

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After spending 15 years in the lab doing her own neuroscience research, Michele Solis is now putting her Ph.D. to work as a science writer. Her work covers a variety of topics including autism, linguistics, and animal communication. She contributes regularly to the Autism Speaks, Simons Foundation, and Crosscut Web sites.