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PTSD: 3 No, it’s not all in your head: the Vagus Nerve

Originally posted October 24, 2020.

In PTSD: 1 No, it’s not all in your head, we talked about the causes and the symptoms of PTSD.

In PTSD: 2 No, it’s not all in your head: The Neuroplatform of Emotion, we talked about the underlying neurobiological emotional platform, that forms the unconscious basis for our emotional responses in everyday life.

In this article, we’ll talk about the cranial nerves, and, more specifically, the vagus nerve and polyvagal theory.

Nerves need time to heal, just like any other physical part of us.

A little background about the brain, nervous system, trauma and traumatic memories … (stuff that you probably already know but maybe forgot…)

Nerves are actually physical entities that can suffer damage

  • Remember that the nervous system is actually a physical entity. We can’t see it, so we forget this. Different types of neurons, such as sensory and motor neurons, innervate the muscles and organs of the body. The neurons in your body communicate with, and are intricately entwined with, the brain. Since the nerves are actually physical they can suffer actual damage from physical and emotional trauma.

  • The nerves need time to heal, like any other physical part of us.

  • So, the nerves are the communication system connecting the brain and body. This communication system is a two way, back and forth, signaling system, with the brain and body receiving and sending messages to and from each other. When a person has PTSD, the communication signals between brain and body are changed.

The cranial nerves: 12 nerves that emerge directly from the brain and connect brain and body

Now let’s take a look at the cranial nerves which run from the brain throughout the body and serve our everyday functioning. There are 12 cranial nerves, and are identified by Roman Numerals. As you can see in the following illustration, they are intimately connected to our different body parts.

Cranial nerves illustration. Labeled diagram with brain sections and its functions with senses. Regions with olfactory, optic, abducent, facial and vagus parts.

The Vagus Nerve – the tenth cranial nerve

Current trauma work theories focus on the Vagus Nerve, or the X (10th) Cranial Nerve, as it is a link between the brain (memory, emotion) and all organs (think rapid heartbeat, gurgly stomach). It’s the longest nerve in the human body and is called the Wanderer, as it wanders throughout the body, innervating all of the human organs. All animals have this large, primitive nerve, including fish.

Vagus nerve illustration. Labeled anatomical structure scheme and location diagram of human body longest nerve.

The Vagus Nerve is the main nerve that interfaces with the parasympathetic (rest and digest) branch of the autonomic nervous system. There is also an interconnection with the Hypothalamic–Pituitary–Adrenal (HPA) axis. The HPA axis is a dynamic system that is intertwined with the nervous system and the endocrine system, and is responsible for release of hormones.

The Vagus Nerve is involved in mood, stress levels, pain levels, inflammatory responses, breathing, vocalization, and organ responses such as heart rate, gastric juice production, digestion, breathing rate, etc (Clancy, Deuchars, and Deuchars, 2013).

Because it connects to the brain and all of our organs and to the autonomic nervous system, the Vagus Nerve is of particular interest when working to heal trauma. (Think how fear, memories, rapid breathing, queasy stomach, fluttering heart are all connected.)

Vagus Nerve and the Polyvagal Theory

Stephen Porges’ Polyvagal Theory builds on the research of the past century about the Autonomic Nervous System (ANS). The ANS was traditionally believed to be composed of two branches: Fight/ Flight (sympathetic) and Rest/ Relaxation (parasympathetic). However, Dr. Porges has expanded on this and theorizes that there are other pathways besides the fight/ flight or rest/ relaxation path: the vagus nerve path.

Dr. Porges looked at how the vagus nerve pathways function. He looked at the functions of the two vagus nerve pathways: the dorsal and the ventral pathways. The dorsal pathway is an ancient pathway and is associated with survival through withdrawal and shutdown (think reptile just sitting there). The ventral pathway evolved later as mammals evolved and is associated with survival through social interaction (think groups of mammals banding together to tend and befriend).

Dr. Porges posits that there are three autonomic system pathways: Social Engagement (ventral vagal), Sympathetic (fight or flight) and Freeze (dorsal vagal).

What does all this have to do with PTSD? Alot!

In polyvagal theory, when we are frightened or threatened, our first survival route is to engage (using the ventral vagus nerve pathway) the aggressor. Wait. Talk to him. Negotiate.

If that doesn’t work, fight or flight responses (sympathetic nervous system) take over.

And if there is no way to fight to overcome or a path to flee the aggressor, the biological process of freeze, or tonic immobility, is the last resort. In the polyvagal world, freeze is dorsal vagal shutdown. In dorsal vagal shutdown, we are numb and dissociated. We protect ourselves from the horror of attack, or the possibility of death. Tonic immobility is a biological, automatic response; it is not a choice. The body is flooded with hormones that produce this altered state which, in the moment: protects against emotional and physical pain, interferes with rational thought, causes deep muscle paralysis and interferes with the efficient encoding of memory. It is estimated that at least 50% of sexual assault victims experience tonic immobility.

The body (the nervous system) of the trauma survivor holds these body based memories, or symptoms, associated with dorsal vagal shut down.

When talking about and recalling the trauma incident, the body (the nervous system) will re-experience the dissociation, the numbing, the lack of emotion, blankness, lack of coherent speech, the sweating, the entire freeze response. These biological, body based symptoms cannot be talked away. Somatic therapy targets the non-verbal responses. At the same time, the person develops a meaningful narrative about the his or her responses and about the incident.

The next blog discussion will be about another biological phenomena associated with PTSD: how the cascade of of hormones released during a an event highly charged with emotion (fear, anger, horror) interferes with the process of normally encoding memories.

PTSD: 2 No, it’s not all in your head: The Neuroplatform of Emotion


Clancy, Deuchars, & Deuchars, 2013. The wonders of the wanderer. Experimental Physiology, Jan, 98(1) p. 38-45.

Dana, D. (2018). The polyvagal theory in therapy. New York: W.W. Norton & Conpany.

Kain, K. and Terrell (2018). Nurturing resilience. Berkeley, California: North Atlantic Books

Hannaford, C. (1995), Smart Moves: Why learning is not all in your head. Salt Lake City, Utah: Great River Books

Rosenberg, S. (2017). Accessing the healing power of the vagus nerve. Berkeley, California: North Atlantic Books

Van Der Kolk, B. (2014). The body keeps the score. Penguin Books: New York.


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