Combat veterans with certain types of brain damage are less likely to develop post-traumatic stress disorder (PTSD), reports a study in the February 2008 issue of Nature Neuroscience. This finding indicates that certain brain regions are important for the development of this disorder.
PTSD is an anxiety disorder characterized by recurrent distressing memories of traumatic events, such as combat, which can significantly impair day-to-day functioning. Previous functional imaging studies found that PTSD is associated with reduced activity in a part of the brain known as the ventromedial prefrontal cortex. PTSD is also associated with increased activity in another part of the brain, the amygdala, which is involved in processing fear. Thus, its excessive activity in PTSD is consistent with patients responding fearfully to normally harmless stimuli. However, functional imaging cannot prove that changes in activity in these regions actually cause PTSD, as both could be an effect of some other process.
Jordan Grafman and colleagues now take steps toward proving this causal link by studying a unique sample of Vietnam war veterans who had suffered brain injury, as well as a traumatic emotional event. They used structural magnetic resonance imaging to produce a detailed picture of the brains of this group, and then compared veterans with PTSD to those without the illness.
This comparison identifies differences in a bilateral frontal area (including the ventromedial prefrontal cortex) and an anterior area including the amygdala. Damage to either of these regions was associated with reduced occurrence of PTSD. These results confirm that the ventromedial prefrontal cortex and the amygdala are critically involved in the processes that lead to PTSD.
Jordan Grafman (National Institute of Neurological Disorders and Stroke, Bethesda, MD, USA)
Abstract available online.
(C) Nature Neuroscience press release.
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