Participants in the study undergo MRI brain scans to analyze the structures of the brain, as well as the fiber tracts that connect those structures. In addition, each group participates in functional MRI scans, which measure brain activity while subjects are engaged in a specific task.

“There’s a series of networks in the brain that are active, and there’s a natural rhythm to the network in our brains,” said Katz. “Various structures have more blood flow going to them at different times, and the brain oscillates in these different networks. The networks of people with psychological problems don’t oscillate the same way. Nobody really knows what that means at this point — it is a hot topic of research.”

Participants in the PCS or PCS healthy group are scanned while being presented with a series of military related pictures projected on a screen mounted inside the scanner. Some pictures are of disturbing events, animals and people, while some are ordinary, everyday objects. After the participant is presented with an image, he is asked to do one of three things: enhance, suppress or maintain his emotional response to the images. Katz said initial analyses are showing differences in brain activity during emotional regulation that may be related to the disease.

Participants in the PTSD or PTSD healthy group perform what is called a fear-conditioning task. During the scan, the participant is presented with a tone that is then followed by a burst of aversive white noise or a tone that is not followed by the noise. Using a track ball, participants continually report their expectancy of the noise’s occurrence on a scale of 0-100. During the scan, skin conductance response – a method of measuring the electrical conductance of the skin, which is related to emotional response – is collected to assess learning.

“Our initial analyses are showing differences in brain activity in PTSD patients during threat-related responses and learning-related differences in the predictability of the threat,” Katz said.