An ongoing study of Vietnam veterans with head injuries has yielded an important clue about abnormal brain activity in post-traumatic stress disorder (PTSD), which causes intrusive memories, flashbacks, and hair-trigger anxiety in some 15 million sufferers worldwide, according to the World Health Organization.
Imaging studies have shown abnormal activity in several brain areas involved in memory and emotion, such as the amygdala and hippocampus, but whether these findings show causes or effects of PTSD has been unclear.
Beginning in the mid-1980s, Jordan Grafman and colleagues at the National Institute for Neurological Disorders and Stroke used computer-assisted tomography to study the specific patterns of rain injury in a group of these veterans. (Magnetic imaging studies were not an option because many patients still had shrapnel fragments in their brains.) Study participants returned periodically for a research evaluation.
In a study reported in the February Nature Neuroscience, the researchers compared patterns of brain damage with the psychiatric profiles of veterans who did and did not go on to develop PTSD. Damage to two brain areas, the amygdala and the ventromedial prefrontal cortex, reduced the disorder’s occurrence—suggesting that these structures, when intact, contribute to the development of PTSD.
The amygdala is a nexus of strong emotions, especially fear. The ventromedial prefrontal cortex is thought to be involved in reactivating past emotions and “placing a sense of self within this context,” Grafman says. “It makes perfect sense that these areas play a role in PTSD.” Because the disorder is notoriously treatment-resistant, a better understanding of the parts of the brain involved could lead to better therapies targeted to these areas, such as transcranial magnetic stimulation and deep brain stimulation, Grafman notes.