trauma occurs as a result of the initiation of an instinctual cycle that is not allowed to finish. When the neo-cortex overrides the instinctual responses that would initiate the completion of this cycle, we will be traumatized.
Levine argues that trauma is fundamentally a disruption of instinctual completion, caused by cortical override of the reptilian brain’s self-regulatory responses.
, Waking the Tiger: Healing Trauma - The Innate Capacity to Transform Overwhelming Experiences, 1997thesis