From Forbes.com: Health: Brain
Region May Govern Resilience to Trauma
TUESDAY, July 12 (HealthDay News) -- It may not be
thick skin that protects you from emotional pain, but a thick brain.
Scientists have discovered that variations in the size of an area of the
brain called the ventromedial prefrontal cortex may explain why some people
recover from trauma better than others. Specifically, people with a thicker
ventromedial prefrontal cortex (vmPFC) exhibited better ability to inhibit
fear.
The research, which appears in this week's issue of the Proceedings of the
National Academy of Sciences, may be an important clue in the age-old
mystery of why some people react severely and continuously to emotional
trauma while others don't.
There may be numerous clinical implications to the research, the study
authors said.
"One would be the idea that perhaps people with a thinner cortex in
this area might be at greater vulnerability for developing anxiety
disorders, but that's still a speculation," said senior study author
Dr. Scott Rauch, director of the Psychiatric Neuroscience Research Division
at Massachusetts General Hospital, in Boston. "This could also be a
potential predictor of responses to [certain types of] behavior
therapy."
Some people associate certain cues with traumatic memories so that, when
they are exposed to the cue, the memory comes flooding back. In other words,
certain sounds or sights trigger a recall of the previous, traumatic
experience. The most obvious example of this is post traumatic stress
disorder (PTSD).
For most people, this sensitivity diminishes over time and the fearful
response goes away, something called "extinction memory." For
others, however, the fear persists.
Earlier animal and other studies had indicated that the vmPFC, on the lower
surface of the brain, might be involved in this process. To see if
individual differences in fear extinction correlated to vmPFC size, the
study authors recruited 14 healthy volunteers. On the first day, each person
was given photos to look at, and then an electric shock. Then they viewed
the photos without the shock.
The next day, the volunteers looked at the same photos while researchers
monitored changes in electrical activity in the skin -- an indication of
anxiety level. The participants then underwent brain scans with structural
magnetic resonance imaging.
Those who had smaller skin responses -- in other words, less anxiety -- also
had a thicker vmPFC, the researchers said. "This was the only region in
the brain that showed the significant relationship to extinction
memory," said study author Mohammed Milad, a research fellow in the
department of psychiatry at Massachusetts General Hospital.
Although the finding is an important one, many questions remain, said Paul
Sanberg, director of the University of South Florida Center for Aging and
Brain Repair, in Tampa.
For instance, do some people just have a thicker vmPFC and, therefore, a
better ability to recover from trauma, or is the ability to cope with stress
acquired? Some studies have shown the brains of people and animals tend to
get bigger in a mentally stimulating environment, Sanberg said. It's also
not clear what mechanisms are at work in that region of the brain, Sanberg
said. "Is it more neurons or more glial cells, is it connections, or is
it the neurochemistry?" he asked.
Rauch said, "The most obvious connection [of the research] would
probably be to PTSD, but we believe it certainly has implications for panic
disorder and potentially for other anxiety disorders such as phobias."
The research may have broader implications for treatment, he added.
"All of those anxiety disorders are responsive to extinction-based
behavior therapy," Rauch said.
Dr. Rodrigo Kuljis is a professor of neurology and psychiatry at the
University of Miami School of Medicine. He said the new research "is
interesting. It tends to support the feeling that certain aspects of memory
are mediated by certain parts of the brain. It could be used eventually as a
measure to determine if someone is more susceptible to certain conditions
and also to predict treatment."
The real question, Kuljis said, is whether the new findings can be
corroborated. "It's very sophisticated imaging but the bottom line is
you are measuring something [the vmPFC] that is around a centimeter thick at
best, probably thinner," he said. "The resolution of the
instrument is marginal, but it's the best we have. The margin of error is
enormous."