Last week, I talked about symptoms of post-traumatic stress occur when a person cannot release his or her sympathetic response (fight-or-flight response) at the material time of the event. In this case, the person cannot disable the alarm system of the brain and keeps responding as if there is a threat. What are the possible causes for the brain to have an oversensitive alarm system that keeps signaling false alarm?
To explain this, let me introduce three specific brain areas: the amygdala, the hippocampus, and the prefrontal cortex. The amygdala is located in the limbic area of the emotional brain. It interprets sensory information and responds quickly if there is a threat or danger to elicit fight-or-flight response. The hippocampus is the memory center. It registers the time sequence of an event and informs the rational brain. The prefrontal cortex is the rational brain. It helps us to understand the event and make the decision about the best actions.
The person, who develops post-traumatic stress symptoms, has a disintegration of these three brain areas. As mentioned in my last blog, a person will re-experience the trauma with continuous release of stress hormones, even though he or she knows there is no danger in the present moment, if the sympathetic response cannot be released. This is because the amygdala keeps signaling false alarm.
If at this point, the hippocampus kicks in and informs the prefrontal cortex that the traumatic event has actually ended, the rational brain can inhibit the response of the amygdala and restore the body to equilibrium. What causes the failure of the hippocampus? It is when the stress level at the material time of the trauma is very high, the stress hormones will disable the hippocampus. As a result, the time sequence of the event is not recorded accurately, so the rational brain never received the information that the trauma had ended. The amygdala is then not being inhibited by the prefrontal cortex. This results in a continuous release of stress hormones for fight-or-flight response.
With this understanding, we can be more empathetic to those who suffer from PTSD. It is not because of their personal weaknesses that contribute to their post-traumatic symptoms. It is actually a disintegration of brain mechanism.
