MONDAY, Jan. 24 (HealthDay News) -- Continual exposure to stress prompts neural activity changes in those parts of the brain that control fear, vigilance and emotion, a new study suggests.

The finding stems from an analysis of brain scans taken among troops recently deployed to Afghanistan, and is reported in the Jan. 18 issue of the journal Molecular Psychiatry.

"For the first time we can now conclude that the effects on the brain really are due to experiences in combat," study first author Guido van Wingen, of the Donders Institute for Brain, Cognition and Behaviour at Radboud University Nijmegen in the Netherlands, said in a university news release.

Van Wingen along with colleagues at the Military Mental Health Research Centre and the Rudolf Magnus Institute of Neuroscience in Utrecht tracked 36 soldiers who were deployed to Afghanistan as part of the International Security Assistance Force (ISAF) mission between 2008 and 2010.

Before and after their mission, the soldiers underwent brain scans, which were compared with those taken among a group of soldiers who were not deployed and had instead remained in their barracks back in the Netherlands during the study period. Questionnaires regarding combat experience were also completed.

The research team found that although none of the deployed troops developed post-traumatic stress disorder, all of the soldiers in Afghanistan had experienced a ratcheting up of activity in the amygdala and insula regions of the brain, which are responsible for regulating fear and vigilance.

Such increased activity appeared to last for a minimum of two months post-deployment.

What's more, the investigators observed that neural activity in the region of the brain that is responsible for emotional regulation differed among the deployed soldiers. The kind of changes that took place depended on how the soldiers perceived the experiences to which they were exposed, the study authors noted. For example, the degree to which a soldier perceived a roadside bomb explosion to be a threat predicted the degree of activity change in their brain's emotional control center.

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