Memory of Traumatic Stress

Extreme stress alters the coding of events in memory and may lead to disorders of the trauma spectrum, such as post-traumatic stress disorder (PTSD). In order to understand the physiological basis and the common thread underlying PTSD, the concept of memory as it is related to trauma must be understood. Autobiographic memory can be divided into cold memories, including knowledge about life-time periods and specific events and hot memories, comprising emotional and sensory memories. Cold memories (On September 18 at 20:30 I was still working in my office) are usually connected with hot sensory memories, (black-masked, dark night, shooting) as well as with cognitive (I can't do anything), emotional (fear, sadness) and physiological elements (heart racing, fast breathing, sweating). Through this string of hot memories a fear network is built. Physiological changes in the brain and body of the survivor of a life-threatening experience, such as a response of the stress-related messengers (e.g., of the HPA axis) or the functioning and even structure of the medial temporal lobe and connected limbic networks in the brain, have been shown to be affected by traumatic stressors and are linked to the organization of memory. When we drive the organism down the defense cascade, when flight is not possible, fight futile and only a startling freeze is left in our evolutionary repertoire, functioning of the structures in the medial temporal lobe that are the portal for autobiographic memory is altered such that hot and cold memories lose their interconnectivity. Our data from survivors of severe violence and torture demonstrate functional alteration of fronto-temporal regions. In over 100 victims of severe and repeated torture, we observed a 94% prevalence of PTSD. In these patients, generators of abnormal slow waves indicated dysfunctional networks in the frontal lobe. Abnormalities in left fronto-temporal regions were connected with dissociative states. In addition a hyper-responsive fear-network can be demonstrated by rapid visual presentation of emotional material. In torture victims but not in controls, rapid presentation of affective pictorial stimuli activates frontal cortex. We hypothesize that it is this disconnection between hot and cold memories, indicated by abnormal brain waves, that leaves those experiencing flashbacks entangled in fear and anxiety. The victim is unable to place the flashback in time and space because the hot memory is not connected to the autobiographical cold memory. If this connection can be restored, the horror of the memory might be alleviated.