Evolutionary Neurophysiology Holds the Key to Healing Trauma

As humans, we share with other mammals a biological response to life threats and dangers that if not completed and discharged naturally can lead to trauma. Our “primitive” brain holds the key to understanding—and effectively treating—a host of chronic syndromes, including PTSD. In an Unspoken Voice: How the Body Releases Trauma and Restores Goodness, Dr.Peter A Levine’s most recent work, he explores at length this remarkable interconnection between animal behavior and trauma in humans. This interconnection is neither far-fetched nor scientifically flawed. In fact, years of research as well as extensive clinical observation have confirmed the interconnection. There is much documentation to support Dr. Levine’s sensation-based approach to healing trauma, including Dr. Stephen Porges’ groundbreaking Poly-Vagal Theory.

Safety: A Biological Response

The basic human desire to be “safe” is an ancient, primitive response hardwired in our bodies. The Poly-Vagal Theory substantiates this by providing an explanation of how the vagal pathways (the vagus being the 10th cranial nerve) regulate heart rate in response to novelty and to a variety of stressors.

As mammalian nervous systems evolved, two vagal systems developed. The older branch is a phylogenetic amphibian/reptilian relic that originates in the dorsal motor nucleus (DMX); the other branch is an evolutionary modification that is unique to mammals. It originates in the nucleus ambiguous (NA).

These two vagal pathways are neuroanatomically distinct and employ very different adaptive strategies. The oldest system “handles” primary survival strategies and defensive behaviors. The NA branch, only found in mammals, actually moderates the fight/flight response because its focus became primarily social engagement, communication and behavior.

Very simply stated, mammalian response strategies to threat are activated in our newer neural structures (the NA branch) first, but revert to the older structures (the DMX branch) when initial response strategies fail, for whatever reason. Those “older” structures are the ones that prompt us to fight, flee or freeze. You could say that our “reptilian brain” takes over when we’re threatened and feel trapped.

Although coming from a different discipline and a clinical approach, Dr. Levine’s research and observations on trauma evidenced the same outcomes and drew a corresponding conclusion: it’s our evolutionary heritage—our basic human biology—that responds to threats and danger, and which can ultimately lead to trauma.  

When we experience a threat—be it an act of violence or a car crash—and all strategies of “escape” appear exhausted, a sense of helplessness sets in and we revert or “fall back” on our oldest neural structures. Evolutionarily speaking, “immobilization” in the face of a life threat is the oldest strategy. As Dr. Porges explained it, when people are scared to death, they are not “hyper-mobilized” so much as they are “immobilized.”   

Indeed, tonic immobility is commonly observed in wild animals. In humans, our protective reflexes also shut down completely. We may not be “feigning death” per se, but we cannot connect and, unfortunately, we cannot move forward either.

Trauma is Physiological

Let’s take a step back and recap what ethology (the study of animals in the wild) has taught us. In order to remain healthy following a threat, all mammals must discharge the energy they mobilize for survival. This discharge completes the activated responses to threat and allows the body to return to normal functioning. However, when an individual cannot discharge or “complete” the response to a threat, trauma sets in.

Trauma originates when we are stuck in a permanent state of arousal, on “high alert” in other words. Moreover, ethology points to the “thwarting” of escape as the root cause of distress-anxiety. Anxiety occurs when our flight from danger is somehow thwarted or aborted; when we don’t get to complete our response to it. The result is we no longer feel “safe.”

When mammals carry out orienting and defensive behaviors smoothly and effectively, anxiety is not generated. But, without active, available defensive responses, we are unable to deal effectively with danger and so we become anxious. Because the normal orientation and defensive escape resources have failed to resolve the situation, we “realize” life hangs in the balance. The body then responds with frenzied flight, freezing on the spot, or collapse.

In the wild, tonic immobility, or freezing, is a potent adaptive strategy for animals where active escape is prevented because it can “buy time” for an animal to escape. In humans, this can become the crippling, fixating experience of traumatic and panic anxiety.

Immobilization, Not Dissociation

“Dissociation” is of course the term that most readily comes to mind when working with trauma sufferers. However, as Dr. Porges has lamented, “Immobilization with fear is a missing concept in psychology and psychiatry and medicine.” Dr. Levine concurs. Immobilization is the keyword to understanding trauma, not dissociation, and if we ever hope to effectively and successfully heal trauma, we must acknowledge this fundamental, scientifically demonstrated reality—trauma is physiological, not psychological.

We humans perceive threat through our primitive brain structures. Healing trauma therefore can only be achieved through therapies that put us back in touch with our bodies and those biological responses to threat triggered deep within the DMX.

Polyvagal theory, evolution, science and mind-body practice are all thoroughly discussed in  Dr. Levine’s book, In an Unspoken Voice: How the Body Releases Trauma and Restores Goodness. Professionals and practitioners will find this book to be an accessible, articulate guide to both understanding and treating trauma. 

To reference the complete document PolyVagal Theory and Trauma for the Author’s reference and text.

In an Unspoken Voice: How the Body Releases Trauma and Restores Goodness 
Peter A. Levine, PhD
North Atlantic Books, 2010

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