How Trauma Sticks—The Mechanism of PTSD

An excerpt from my book Walking Your Blues Away: How to Heal the Mind and Create Emotional Well-Being

Walking Your Blues Away

Chapter 1

How Trauma Sticks—The Mechanism of PTSD

No experience is a cause of success or failure. We do not suffer from the shock of our experiences or so-called trauma—but we make out of them just what suits our purposes.
—Alfred Adler

One of the enduring mysteries in the field of psychology is why the same event produces such different memories and responses in different people. As the New York Times reported in a July 1, 2004 article by Anahad O’Connor, one out of every six soldiers coming home from the war in Iraq are showing signs of emotional difficulties, particularly post-traumatic stress disorder.

         Citing a report in the New England Journal of Medicine, the reporter noted, “The researchers surveyed more than 6,000 soldiers in the months before and after service in Iraq or Afghanistan. Almost 17 percent of those who fought in Iraq reported symptoms of major depression, severe anxiety or post-traumatic stress disorder, compared with about 11 percent of the troops who served in Afghanistan.”

         In World War II, post-war depression and anxiety was called “battle fatigue”; in World War I it was referred to as “shell shock.” The question isn’t so much why it happens—we know GIs in war do and see horrific things. The question that perplexes is why post-war anxiety and depression haunts some veterans and not others. Of course, some vets see harder combat than others. But even that doesn’t entirely account for the statistics. There are still huge variations among individual soldiers in how they respond to the same event.

The One-Day Scratch Pad

In order to understand why some people are still “shocked” months and even years after a traumatic event, it’s necessary to first understand how the brain and the mind process trauma.

The brain is a complex collection of deeply interconnected parts and processes; I will vastly oversimplify here for the purpose of description. There is a part of the limbic brain, or “visceral brain,” called the hippocampus that essentially functions as a one-day scratch pad for memory. Everything you experience throughout the day is stored as sense impressions in the hippocampus; in order for an impression to become a long-term memory it must pass through the hippocampus. Although the larger brain is able to discern time and therefore understand that one thing happened a week ago and another thing happened a month ago, the hippocampus only knows one time: today.

         During the night, as we sleep, the hippocampus dumps its information from the day into the rest of the brain for processing, sorting, storing, and disposing of irrelevant information; as the brain is processing the details of the day from the hippocampus, we experience a state that we call “dreaming.” Most sleep researchers are convinced that the time when we experience rapid eye movement (REM) sleep—when our eyes move back and forth rapidly underneath our eyelids—is when most of the traumas of our daily life are processed. The process of information management completed, when we wake up in the morning the hippocampus is once again empty and ready to record another day.

         The problem emerges when the hippocampus is carrying information that’s too much, or too “hot,” for the larger brain/mind to handle. When a sensory experience is too strong to be easily and unremarkably processed, then it presents in our dream world as a nightmare. If that still doesn’t “download” the information from the hippocampus, then the trauma either becomes buried in the subconscious (the process that Freud termed repression), or it gets thrown back to the conscious mind the next morning. It’s as if the brain says, “Whoa, that’s too much for me to process in one evening, so please just hang on to it for now.” When the person wakes up the next morning, the information is still there in the hippocampus, still “remembered” and known and felt as if it had happened that very day

         The conjecture that the hippocampus knows nothing at all about the past accounts for the unique feature of true post-traumatic stress disorder (PTSD): that the person feels, every day, as if the past event were happening today. The trauma is always front and center, new, fresh and raw. The consequences can be psychologically and emotionally disastrous. Every day is affected by a past event; the traumatic event never passes from “now” into “then,” and is never processed and filed away in a memory bank, where it no longer has the power to cause pain and problems on a daily basis. The impact of this on the mind and the emotions is staggering.

         Brain scans even demonstrate that before a PTSD event has been processed, the amygdala—a part of the brain responsible for strong/survival emotional states—and the hippocampus are not functioning normally. The brain scan makes it possible to, in a way, “see” the stuck memory. After processing the memory, these parts of the brain can return to normal functioning.

Access to Resource States

One of the key concepts of many schools of psychology is that human beings are most functional when every part of the mind has access to all other parts. In particular, this functionality is a matter of having full access to positive resources, such as memories of times when we were successful in our undertakings and the good feelings we associate with those accomplishments. Working from this level of functionality, then, when we take on a new task, for example, we first remember times in the past when we attempted something similar and accomplished our goals. This functionality can be accessed in all new endeavors, from embarking on a new love relationship to taking on a first public-speaking engagement.

         <T>Memories of past accomplishments and capabilities are stored in parts of the brain far from the amygdala and hippocampus. The amygdala and hippocampus, parts of our nervous system’s most primary and primitive structures, lie deep in the brain. (Humans share the amygdala and hippocampus structures with all mammals, unlike our frontal lobes, which we only share with the highest of the apes.) Thus, having a negative memory stuck deep in the hippocampus blocks the pain and fear associated with that memory from reaching and “associating with” positive memories and resource states, which are housed in more distant parts of the brain.

One of the most elegant and truly useful aspects of walking therapy (and other forms of bilateral intervention) is that, by their very process of side-to-side motion, they cause the right and left lobes of the brain to alternately take responsibility for processing information. When you look to your left, the right side of your brain is processing what it is you’re seeing; as your line of sight travels past your centerline and to your right, the information travels across the corpus callosum, the bundle of nerve fibers that connect the two hemispheres, and is handed off to the left side of the brain for processing.

         Normally the left and right sides of the brain have a certain amount of separation of function. For example, Broca’s region, in the left side of the brain, is responsible for speech, whereas we “listen” to sound and speech with the “silent” part of the brain, Wernicke’s region, in the right hemisphere.

         The hippocampus lies deep within the brain, closer to the ancient midbrain than most of the more evolutionarily recent “thinking-function” parts of the brain. These are closer to the surface and generally reside specifically on either the right or left side of the brain. This physical/anatomical detail has led researchers to guess that one very significant way in which bilateral therapies function is by keeping the hippocampus (and the amygdala) engaged through actively recalling the traumatizing memory, while simultaneously and alternately activating the left and right hemispheres of the brain. This process integrates the function of the hippocampus with the two hemispheres of the brain while also connecting the two hemispheres. Because the hippocampus is engaged, the processing that would normally happen during sleep happens instead while the person is wide awake, provoking an “emptying” of the hippocampus and the filing and storing of the information it had contained in an appropriate “this-is-the-past” part of the brain.

         When people who undergo bilateral therapy wake up the next day, they know that what had been bothering them is now in the past. (Often they will dream of the original event overnight). With the walking therapy that I have developed, in most cases this recognition that the experience is in the past happens during the walk itself. That is the key indicator that the session has been successful.