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University of Tokyo scientists have found a link between posttraumatic stress disorder among survivors of the 1995 Tokyo subway sarin attack and the size of the area of the brain that regulates emotion, the National Academy of Sciences said Tuesday.

A recently developed technique to scan the whole brain allowed a team led by Hidenori Yamasue to find that brain area involved in modulating emotional responses — the anterior cingulate cortex — was smaller in sarin victims suffering PTSD than sarin attack survivors without the condition, the U.S. academy said on its Web site.

Previous studies linked PTSD to structural abnormalities in the brain, especially in the hippocampus, an area associated with long-term memory, but yielded inconsistent results, it said, adding that few areas other than the hippocampus have been thoroughly investigated.

Yamasue and professor Nobumasa Kato, both of the university’s graduate school of medicine, and their colleagues used a technique known as voxel-based morphometry and found that the left anterior cingulate cortex was “significantly smaller” in PTSD sufferers.

The researchers also found that the severity of PTSD symptoms was directly linked to the extent of the reduction in size. No other significant differences were found between the two groups.

Whether PTSD causes the size reduction or vice versa has yet to be determined, but the researchers have contributed to the pathology of PTSD by suggesting that abnormalities in the anterior cingulate cortex may interfere with emotional regulation, according to the academy.

The March 20, 1995, subway sarin gas attack by Aum Shinrikyo members left 12 people dead and more than 5,000 injured.