By Bower, Bruce
Science News , Vol. 173, No. 1
Brain damage suffered while fighting in a war can undermine core aspects of a soldier's personality and behavior. In two particular neural regions, however, such wounds actually protect combat veterans against developing the severe stress reaction known as post-traumatic stress disorder (PTSD), a new study finds.
These brain structures play crucial roles in causing PTSD after exposure to traumatic experiences, concludes a team led by neuroseientist Michael Koenigs of the National Institute of Neurological Disorders and Stroke (NINDS) in Bethesda, Md.
Psychiatrists classify PTSD as an anxiety disorder characterized by frequent re-experiencing of a traumatic event, emotional numbing, avoidance of reminders of the upsetting event, and excessive vigilance. Previous brain-imaging studies had suggested that PTSD involves overactivation of the amygdala, a structure that mediates fear responses, as a result of reduced activity in the ventromedial prefrontal cortex, an area that tamps down emotional reactions. The same studies also implicated deficient activity in the hippocampus, a memory-related structure, in PTSD. Still, it wasn't clear whether these brain alterations caused PTSD or resulted from it.
The new study, slated to appear in the February Nature Neuroscience, looked for neural causes of the stress disorder by probing PTSD development in interviews with 193 Vietnam combat veterans who had experienced various types of brain damage as well as traumatic war events. Another 52 combat vets in the study had no brain injuries.
Magnetic resonance imaging produced detailed images of participants' brain structure. …