Your brain handles a perceived threat differently depending on how close it is to you;
“Clinically, people who develop PTSD are more likely to have experienced threats that invaded their personal space, assaults or rapes or witnessing a crime at a close distance. They’re the people that tend to develop this long-lasting threat memory,” said Kevin LaBar, a professor of psychology and neuroscience at Duke University who is the senior author on a paper appearing this week in the Proceedings of the National Academy of Sciences.
“We’ve never been able to study that in the lab because you have a fixed distance to the computer screen,” LaBar said.
But Duke graduate student Leonard Faul and postdoc Daniel Stjepanovic figured out a way to do it, using a 3D television, a mirror and some MRI-safe 3D glasses.
“It’s like an IMAX experience,” LaBar said. “The threatening characters popped out of the screen and would either invade your personal space as you’re navigating this virtual world, or they were farther away.”
The VR simulation put 49 study subjects into a first-person view that had them moving down either a dark alley or a brighter, tree-lined street as they lay in the MRI tube having their brains scanned. Ambient sound and visual backgrounds were altered to provide some context for the threat versus safe memories.
On the first day of testing, subjects received a mild shock when the “threat avatar” appeared, either two feet away or 10 feet away, but not when they saw the safe avatar at the same distances.
The data from the first day showed that near threats were more frightening and they engaged limbic and mid-brain “survival circuitry,” in a way that the farther threats did not.
The following day, subjects encountered the same scenarios again but only a few shocks were given initially to remind them of the threatening context. Once again, the subjects showed a greater behavioral response to near threats than to distant threats.
“On the second day, we got fear reinstatement, both near and far threats, but it was stronger for the near threat,” LaBar said.
Tellingly, the nearby threats that engaged the survival circuits also proved harder to extinguish after they no longer produced shocks. The farther threats that engaged more higher-order thinking in the cortex were easier to extinguish. The near threats engaged the cerebellum, and the persistence of this signal predicted how much fear was reinstated the next day, LaBar said. “It’s the evolutionarily older cortex.”
The more distant threats showed greater connectivity between the amygdala, hippocampus and ventral medial prefrontal cortex and the areas of the cortex related to complex planning and visual processing, areas the researchers said are more related to thinking one’s way out of a situation and coping.
(Hat tip to Greg Ellifritz.)
I remain ever skeptical of these lab-experiment psychological studies. No matter how well-constructed, the fact is that the experimenters are still “in the loop”, and imposing their notions on things. Meanwhile, out in the real world, people are exposed to things that don’t include third parties either making it all worse, or all better.
There may be something to this idea of proximity; the idea rings true, but as I said… It’s all artificial, staged, and entirely constructed along the lines of the experimenter’s own ideas. Of course they’re going to get results that they’re expecting–What else could happen?
When you include humans as your experimental subjects, I think that what needs to happen is that you use pure observation of real-world events, and then try to form your ideas based off of observations, rather than construct artificial proxies. There are way too many variables with it all–I know guys who went for multiple tours in Iraq and Afghanistan, shrugging off crap that broke other men with utter aplomb. Then, when things changed in their lives, something relatively minor broke them, too.
Way too many variables in the human mind, I’m afraid. I’m a life-long observer of it, and even after fifty-plus years of doing it, I’m still surprised by how other people respond or don’t respond to things.
As well, there are different forms of PTSD–Some I think are due to empathy with victims, others to personal trauma. I watched one of our medics go through things, and I found it very interesting that he was sufficiently self-centered that even having to pull still-living crispy critters out of one of a vehicle that had burned after an IED strike, he was completely (seemingly, at least–Who the hell knows what really goes on in someone else’s mind?) unaffected. Yet, when he himself got wounded in a relatively minor fashion, he went full-bore shaking and losing his shit because he couldn’t handle things. I’d still like to know what was really going on with him–We all had several theories about it, one being that he didn’t internalize the risks he was taking until he got hurt himself, and the other was that he was a bit of a sociopath and the people he was working on didn’t register as “real”. Either way, it was not something that a lab experiment would have likely turned up…
Amazing. Psychologists have discovered that people have personal space, and that threats close enough to touch you are more dangerous (and thus frightening) than potential threats far enough away to run from.
Amazing what money gets spent on.
Oh, and PTSD is when the reaction to the threat doesn’t go away after a year.