In the blog of last week, I mentioned about people with Post-traumatic Stress Disorder (PTSD) frequently experience feared responses as if he or she is re-experiencing the trauma. What happens to their brain during and after the trauma?
Neuroscientist Stephen Porges described that there are three subsystems in the Autonomic Nervous System (ANS). When a person is having a relaxed walk in the street on a Sunday afternoon, the Ventral Vagal Complex (VVC) activated the social engagement system. This allows the person to chat humorously with his friends and all his present moment experiences are in sync.
However, when a car is approaching the sidewalk from the road, the person suddenly perceives danger that activates his Sympathetic Nervous System (SNS). Adrenaline and Cortisol are released for the activation of a fight or flight response. If the person is able to run away from the car to a safe place, he would be able to return to equilibrium after the danger passed. The stress-related hormones would be metabolised and his running will reduce his arousal.
What if he is knocked down? The person is forced to freeze as he cannot run away. This activated the most primitive subsystem, the Dorsal Vagal System (DVS). The person become immobile and endorphins is released to block the pain. As the person is immobile, he may not elicit the fight or flight response, he is trapped in a dysregulated state with the SNS being constantly activated after the trauma. He sweats more often, heart rates frequently increase, and mouth is constantly dry. His physiological urge to flee had not discharged.
Symptoms of post-traumatic stress occur when a person cannot release his or her sympathetic response. That is, the energy that helps us to fight or flee is being bottled up in our body. This is why a person with PTSD frequently re-experiences the trauma with constant release of stress hormones, even though he or she knows there is no danger in the present moment.
Why some people being knocked down by a car did not develop PTSD and some did? I will explain more in the next blog in the coming week. Stay tuned.
