How Trauma Affects the Nervous System

Trauma is a complex phenomenon. It’s a challenge to understand and a challenge to diagnose. Trauma is not just the effects of going to war or being abused as a child. Trauma can happen to anyone. Trauma is not necessarily about any specific event. Because what is traumatic can be different for everyone, it is best understood through the effects of the brain and nervous system.

Trauma is a person’s experience of an event in which their ability to integrate their emotional experience is overwhelmed. Trauma may be present if: the person can’t stay present during the event, understand what is happening, integrate their emotions or feelings, or make meaning of the experience. All four of the above are important because they are functions of a healthy brain and nervous system processing what had just happened in a coherent and integrated way.

Trauma can also happen if the situation is perceived as threatening one’s safety and survival, which will stimulate lower brain defensive responses. The threat doesn’t necessary have to be real, as long as we perceive our safety is at risk our brain and body react the same. In the body, the physical processes happen before cognition (thinking) and emotional perception, such as the body wanting to run, heart racing, or wanting to shrink back from the threat. These physical processes can be triggered in a nanosecond while the thinking and emotional processes could take much longer or not happen at all. The trauma activating processes in the body can often get “stuck” and all of the arousal hormones will continue to release into the system long after the threat is over, often years longer. This over-production of stress hormones can lead to many issues, disorders, and diseases.

Fight or flight is a very good way to stay safe. It is an automatic system in us that we don’t have to think to activate. But what happens when fight or flight doesn’t work? When a person can’t fight or escape from a threatening event, the human system of self-defense becomes disorganized. These failed attempts of action will tend to persist and come out even in times of non-danger. Because the fight or flight system is now disorganized, it can get confused about what is actually danger and what isn’t. An exaggerated flight response may be seen in people in ways such as wanting to run from stress, get a divorce, or move cities. An exaggerated fight defense may look like chronic fighting with their husband, anger at a cashier, or road rage.


Trauma survivors have symptoms instead of memories.


The person often “remembers” the incident not necessary in their memory but through reliving the trauma through their sensory-motor system (dis-regulated arousal, emotions, defensive responses, and hyper-vigilance). This may lead to mysterious physical symptoms that can’t be explained by doctors. Ogden (2006) says, if we don’t have verbal memory of the event, the event will typically remain un-integrated by the brain and nervous system and lead to a variety of disruptive symptoms.

Pat of this issue stems from the fact that we have new additions to our brain sitting atop the older parts of our brain. Our primitive and lowest brain center is in the brainstem. The Reptilian Brain responds to autonomic arousal and instinctive responses. This is the part responsible for pulling your hand back from a hot burner. We don’t think about it, it just happens automatically. This part of the brain is feels sensations and impulse. The second part of the brain is the Limbic System brain. It is in charge of emotions, somatic movements, and our attachment patterns for relationship. That is why our attachment relationships are more emotional than logical. The Limbic System is about emotion and attachment. The third and newest part of our brain is the Frontal Cortex. It is our thinking brain. It also has executive functioning and regulatory abilities. This part of the brain is responsible for verbal language and analytic reasoning.

In a life-threatening situation, if we had to think, we would probably die. To ensure survival, the brain has ways to circumvent needing to think. When a threat appears, the amygdala, in the Reptilian brain, rings the fire alarm that activates the sympathetic nervous system to response. The thalamus in the Limbic System is a gateway for sensory information to come in that helps us respond to the threat. The Frontal lobes or “thinking brain” shuts down or decreases activity to ensure we don’t think too much, therefore, we survive.

The amygdala, our fire alarm, can often become over sensitive to triggers. The amygdala is like an old camera. It takes a picture of the event that is really blurry. Then any part of that picture could send off triggers to the sympathetic nervous system. For example, if a perpetrator wore a yellow sweater, the color yellow could now be a trigger because the amygdala has that in it’s “picture” cue of threat. Triggers are anything that has a similarity to the event and therefore sets off the nervous system to think that event is happening again, therefore stimulating the same nervous system response. None of this goes through the thinking brain.

In the Limbic system, the post trauma fear network can still be active for years after the event. In the brain, the non-verbal memories such as body sensation and emotions are separated from the narrative of the event. These fear networks can be active in the limbic system with out the frontal cortex knowing. More or less, the brain is separating the mental part of the memory from the feeling part of the memory from the action part of the memory. Now we have 3 different memories but all separated. This helps to make the event less intense and helps the brain not get overwhelmed by fear, but causes complications in processing the memory in a healthy way.

Meaning making is an important function that happens in the brain that we are often unconscious to. Making meaning of the experience may be a rape victim thinking she’s at fault or someone getting teased at school and assuming that he is unworthy. We make meaning all the time, unconsciously, but sometimes the meaning we’ve made isn’t always true and can inhibit us from actually moving on and healing the experience, such as a child making sense of their parent’s divorce by thinking they are the reason behind the divorce and carrying guilt and shame about it into adulthood.

There are two main types of memory. Explicit memory is noticed as a narrative, cognitive, autobiographical, and declarative. We often remember what year our daughter was born and the series of events that happened at the hospital. You can tell the story in a coherent way. Implicit memory is much different. It is felt as emotional, somatic and sensory “memories”. They don’t feel as if you are recalling a memory. Dan Siegel says, “we act, feel, and imagine without realizing that there is an influence of past experience on our present reality” (1999). We don’t realize we are “remembering” a memory. For example, a client may think they have to be perfect, because making a mistake will mean criticism or abandonment. This may have been their experience as a child with a very strict parent. They may not realize the thought of needing to be perfect, the feelings of fear, or the sensations of tightness in their chest are connected to an implicit memory network.

Procedural learning is part of our implicit memory based on function, such as riding a bike, brushing our teeth, automatic behaviors and physical habits (slouching, shoulders slumped, chest puffed out), stimulus-response (hearing a phone ring or baby cry could set off an automatic response), and cognitive schemas (people can’t be trusted, my needs can’t be met). Most human behavior is driven by procedural memory. This is how we don’t have to relearn to dress ourselves or drive our car every day. It is a function that has helped our species survive.
The problem with procedural memory can happen if the survival strategies and triggers are now wired into this type of memory. Long after the trauma has ended, we often remain in a state of readiness to perform the fight or flight actions that were needed in the past.


Once our actions become part of procedural memory, they do not require conscious thought.


They are an automatic and non-conscious performance of actions that is efficient and automatic. For example, if your husband uses a certain tone of voice that unconsciously reminds you of your father, you may pull back without realizing it, or when I think of going to work, I may get a headache.

As a therapist, it is important that we work with this procedural memory, the sensorimotor response, and the cognitive schemas developed. We must get to the unconscious memories that are controlling the client’s life. Talk therapy or cognitive therapies often can’t get past the frontal cortex’s limited experience or lack of memory. The inability to activate the implicit memory network will inhibit the ability of the therapy to create change on a deeper level.

Allan Shore says that the “focus of treatment is not on re-constructing the trauma, but on the effects of the trauma on the right brain regulatory processes.” Bessel Van Der Kolk says we need to “work with the left brain and the body instead of the story.” The story is not the important part in therapy. We now know that to change trauma and attachment patterns we need to activate the right brain through the “experience” of the story, or how the memory is stored in the body as feelings, actions, images, and emotions. At the same time we activate the left brain through the talking about the experience.


We need to feel, notice and observe what happens in our body as we remember the event.


“Traumatized people are continuing the action, or rather the attempt of the action (from the lower brain center) which began in response to the original trauma, and they exhaust themselves in these everlasting commencements. “ (Janet Pierre). A recommencement is trying to complete the original action that tried to happen, such as crying out for help or running away. If the original action wasn’t possible at the time of trauma, we will always find ourselves stopped from resolution. For example, if the client wanted to yell “Stop!” and push the abuser away, but the best chance of survival was to keep quiet and not fight back, there will still be an impulse in the body to say stop and to push away. These actions got truncated because they were the automatic response to danger, but because they weren’t the best chance for survival, the body automatically stopped them. We need to help release these truncated responses to complete the action and to help the client free themselves of the recommencement.

Working in the present moment is the vehicle to reprocessing these truncated responses. Present moment experiencing is noticing the current response to a past memory. Pat Ogden says, “while telling the story provides crucial information about the clients past and current life experience, treatment must address the here-and-now experience of the traumatic past, rather than the “story” in order to challenge and transform the procedural learning. Thus the emotional reactions, thoughts, images, body sensations, and movements that emerge spontaneously in the therapy hour are the focal points of exploration and change.” For example you may say to the client, when you think of that moment, what do you notice in your body now? Or, when you think of your father, I notice your hands move up. The hand movement is an unconscious preparation for action from the lower brain center. There will most likely be an action, an emotion, a memory, and meaning making from that one little action that we would want to explore to find the implicit or procedural memory.

We need to understand how the body is making meaning of the story and organizing the experience. The “story” is not as important as how the system is organizing the experience and preparing for action. This preparing for action could stay stuck in the system for years and lead to failed relationships, depression and anxiety, illness, addiction, and the need for medications.


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