Experience of trauma
Trauma leads to a variety of alterations in the human body impacting not only on our physical health also our emotions, our relationships and how we interact with the environment around us.
In the event of a traumatic experience the activation of the autonomic nervous system (increased heart rate, blood pressure, respiration, etc) in response to danger is a normal, adaptive, and protective biological function (fight or flight response), however, PTSD may occur when there is a continued engagement once the threat is no longer present, leaving the body in an active state of arousal.
This may occur if trauma is ongoing, as in repetitive abuse throughout childhood, or when a person is somehow unable to return to a sense of calm after exposure to trauma. The way our brain reacts to a traumatic event is shown in the individual memory when one element is triggered the traumatic experience and other elements are likely to follow.
Ordinary memory is a social human function, but traumatic memory is a reenactment of unchanged and frozen in time lonely, often humiliating and alienating experiences. The consequence of trauma elicit a survival response, it provides psychological distance by shutting down those memories, it becomes a survival coping mechanism. The therapist can help with the goal of treatment by association; by integrating the cut-off elements of the trauma into a narrative of life it empowers the brain to recognize the "there and then" to the "here and now".