Activity in the amygdala and networks that process sensory stimuli increased.
The amygdala is a part of the brain that will dictate reactions to crisis before you can consciously process it. It's called "amygdala hijack" and is responsible for people doing things like leaping into a river to save a drowning child before they fully register the child consciously, so they find themselves in a river going "Why the hell am I here?" and then realize there's a child drowning in front of them.
This is potentially dangerous. Vietnam vets and others with PTSD sometimes strongly overreact to stimuli that aren't actually a signal of a problem. For example, waking a Vietnam vet can get you assaulted before they realize you aren't a danger to them, sort of like that scene where Wolverine skewers Rogue because she wakes him from a nightmare, though usually not that dramatic. (I have heard of people winding up in the ER though.)
