For decades, neuroscientists and physicians have tried to get to the bottom of the age-old mystery of post-traumatic stress disorder, to explain why only some people are vulnerable and why they experience so many symptoms and so much disability.
All experts in the field now agree that PTSD indeed has its roots in very real, physical processes within the brain – and not in some sort of psychological “weakness”. But no clear consensus has emerged about what exactly has gone “wrong” in the brain.
In a Perspective article published in Neuron, a pair of University of Michigan Medical School professors – who have studied PTSD from many angles for many years – put forth a theory of PTSD that draws from and integrates decades of prior research. They hope to stimulate interest in the theory and invite others in the field to test it.
The bottom line, they say, is that people with PTSD appear to suffer from disrupted context processing. That’s a core brain function that allows people and animals to recognize that a particular stimulus may require different responses depending on the context in which it is encountered. It’s what allows us to call upon the “right” emotional or physical response to the current encounter.
A simple example, they write, is recognizing that a mountain lion seen in the zoo does not require a fear or “flight” response, while the same lion unexpectedly encountered in the backyard probably does.
For someone with PTSD, a stimulus associated with the trauma they previously experienced – such as a loud noise or a particular smell – triggers a fear response even when the context is very safe. That’s why they react even if the noise came from the front door being slammed, or the smell comes from dinner being accidentally burned on the stove.
Context processing involves a brain region called the hippocampus, and its connections to two other regions called the prefrontal cortex and the amygdala. Research has shown that activity in these brain areas is disrupted in PTSD patients. The U-M team thinks their theory can unify wide-ranging evidence by showing how a disruption in this circuit can interfere with context processing and can explain most of the symptoms and much of the biology of PTSD.
Source & further reading:http://www.uofmhealth.org/news/archive/201610/what%E2%80%99s-really-going-ptsd-brains-u-m-experts-suggest-new
Paper:http://www.cell.com/neuron/abstract/S0896-6273(16)30640-7?_returnURL=http%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0896627316306407%3Fshowall%3Dtrue
Corina Marinescu
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