Polyvagal theory for Dummies

Polyvagal Theory it has been formulated by Stephen Porges in 1994 and is a cornerstone for anyone that works with traumas, stress experiences and post-traumatic stress disorder (PTSD)

By Davide Casiraghi
Oct 13, 2019 |
7 min read


Vagus nerveWhen I started working in the field of bodywork I heard speaking about Polyvagal theory and its importance from many sources. So I tried reading the Stephen Porges book but  I found it very academic and complicated.

So in the article below, I try to summarize and simplify what I’ve got through reading many articles and resources on this topic.

This theory helps to understand how the nervous system limits our behavior concerning how safe or in danger we feel.

Before going deep in the Polyvagal theory we need to get some brief view on the fight-or-flight response of our nervous system.

The Fight-or-flight response

fight or flightOur ancestors during the Stone Age, when they were threatened by a dinosaur and their level of stress increased due to this they had two options: fight or flight.

Nowadays since the causes of stress and the responses are much different and less physical than that time, like being late for work, a divorce or a car accident, when the level of stress rises the same physiological reflexes kick in and many times we can’t release it physically.

The Autonomic Nervous System

The autonomic nervous system (ANS), also known as vegetative or visceral nervous system, is that set of cells and fibers that innervate the internal organs and glands, controlling the so-called vegetative functions, ie those functions that are generally outside the voluntary control, for this reason, it is also called "Involuntary Nervous System".

It has the function of regulating the homeostasis of the organism and is a neuromotor system not influenced by the will that operates with precisely autonomous mechanisms, related to peripheral reflexes subjected to central control.

Subdivisions of the ANS

The two divisions of the autonomic nervous system are the sympathetic system associated with the fight-or-flight response, and the parasympathetic system is referred to as rest and digest.

Homeostasis is the balance between the two systems.
It's the ability to live organisms to maintain an internal balance and preserve their characteristics while varying external conditions through self-regulation mechanisms.

Each organ receives connections from both the sympathetic and parasympathetic divisions, for instance, the heart, one causes the heart rate to increase, whereas the other causes heart rate to decrease.

 Sympathetic system (SNS) Parasympathetic system (PSNS) 
Left hemisphere Right hemisphere
Sees everything fragmented He sees the whole, creates connections.
Reactivity: fight / flight. (survival) Rest and digest
Rational Creative
Number skills, Math / scientific skills, Written language, Spoken language, Objectivity, Analytical, Logic, Reasoning Work with art and music, creativity, don't think in a Cartesian way, in an intuitive mode
  Vagus nerve is part of this system

The vagus nerve

Vagus nerveThe vagus nerve is a part of the parasympathetic system, dubbed the rest-and-digest system. Although there are numerous other nerves in this system, this one reaches the majority of the body’s organs. It is the longest cranial nerve.

The vagus nerve has two branches:

Dorsal branch Ventral branch 
Regulates organs below the diaphragm. Affects body functioning above the diaphragm. Controls the muscles of the face, heart, and lungs - parts of the body used to interact with others.
From an evolutionary standpoint, this is a much older part of the nervous system.
The roots of the dorsal vagal pathway lie with our reptilian ancestors.
From an evolutionary standpoint, it’s the most recent addition and is unique to mammals.
It is instrumental in activating the “shutdown” of the body seen in cases of overwhelming trauma. This distinctively mammalian system thus fosters what Porges calls “social engagement”.
According to Dr. Porges, social engagement, in turn, tends to “down-regulate” (calm) the sympathetic nervous system, and the fight response.
When we experience our environment as threatening, we operate from a fight-or-flight response mode. When we experience our environment as safe, we operate from our social engagement system.

The Polyvagal theory

Dr. Stephen Porges has expanded our view of the ANS explaining the role of the vagus nerve, through its branches, in regulating the heart, face, abdominal viscera, and breath.

The Polyvagal Theory provides us and understanding of three neural circuits that support different types of behavior:

  • social engagement behaviors in safe environments
  • fight or flight immobilization behavior
  • shutting down (second level of defense)

Unresolved trauma will create this high-tone dorsal, or sympathetic, or blend of both.

Different types of behavior​
Safe and social mode Mobilized - Fear or Flight mode Immobilized mode
Neural circuits that support this behavior
Parasympathetic dorsal vagal Sympathetic Parasympathetic ventral vagal
The ventral branch of the vagal nerve affects the body functioning above the diaphragm.   In addition to affecting the heart and lungs, the dorsal branch affects the body functioning below the diaphragm and is involved in digestive issues.
When we feel comfortable and connected our ventral vagal system is online and in charge We sense a threat and freeze to scan the surroundings for real danger. When we feel frozen, numb, or “not here” the dorsal vagal system has taken control.
We feel normal happiness, openness, peace, and curiosity about life.
Our body feels calm and grounded.

We feel anxious, afraid, or angry.

If positive emotions are present, they usually look forced.

Emotionally, it feels like dissociation, numbness, dizziness, hopelessness, shame, a sense of feeling trapped, out of the body, disconnected from the world. 

We may have difficulty getting words out or feel constriction around our throat

Face expression

Our face is expressive.
We emotionally relate to others.

We more easily understand and listen to others.

There may be flashes of facial expressions of fear and anger, with the background of more of a still face.
All our senses focus. 
The decreased facial expression, our eyes may look fixed and spaced out. 
Good level of oxytocin We release cortisol, epinephrine and norepinephrine to help us accomplish what we need to—get away, or fight our enemy. Serotonin, Dopamine, Endorphin
Heart rate
Heart rate is regulated, our
breath is full
In this state our heart rate speeds up, our breath is short and shallow Slower heart rate, Decreased blood pressure, Slower, deeper respiration
To summarize what happens inside us
What he wants to empathize with is that social interaction behavior is neural exercise using newer mammalian structures to inhibit very primitive defensive systems.

So if we feel that we are in a safe environment will use our face, the intonation of our voice and will negotiate a relationship or maintain safety by doing that.
This is what friends and lovers do, and teachers and therapists suppose to do.

When we are in an environment perceived as threatening we enter in a fear or flight mode. And in that state, we are gonna miss other people's cues.

So you are more likely neutral faces as being aggressive. You are more likely to see fearful faces as if they are angry. So you can found difficult relationships.

So you won't be able to use people to self-regulate

What if we can't go away from danger? What if we are trapped in a car or a bathroom and someone is now going to hurt us. So the third circuit is triggered, and it shuts us down.

It's important to understand this to deal with traumas. Because most of the other models previous of Polyvagal Theory speak just about the Fight or Flight system. 

To summarize

What the Polyvagal Theory wants to emphasize in summary is that when our autonomic nervous system is continually engaged in defensive activities, as can happen in traumatic situations or prolonged stress, these can become potentially harmful to our physical and mental health because it is chronically lacking the balance between the different branches of the autonomic nervous system.

When our sympathetic nervous system has kicked into overdrive, and we still can’t escape and feel impending death the dorsal vagal parasympathetic nervous system takes control. It causes freezing or shutdown, as a form of self-preservation.
When the dorsal vagal nerve shuts down the body, it can move us into immobility or dissociation. It takes us out of connection, out of awareness and into a protective state of collapse. When we feel frozen, numb, or “not here” the dorsal vagal system has taken control.


Kellie Hynds
Thank you so much for this! I am an LMFT and I have been interested in this theory but, like you said, the information is so academic and you're explanation is just what I needed.
There is an error under "neural circuits that support this behaviour", on the first line you have written dorsal vagal and ventral vagal in the opposite columns towhere they should be
Got a chuckle here. A purportedly science driven article on a major area of psychosocial thought talking about primitive humans "running from dinosaurs." I know you were trying to be cute there, but let's be real. Saber-Tooths, Dire Wolves, or Giant Bears, perhaps, but Not dinos. Best -
Thank you for this simple summary! I believe there is one little mistake at the top of the table - dorsal and ventral vegal are reversed ;)
Jan Lilghtfoot
Thank you!
Cecilia García Barrios
hola,, soy Cecilia García Barrios, soy médica en el área de la salud mental y me ha interesado mucho la teoría vagal para a yudar a reducir el estrés entre el presonal de salud. hace poco leí un artículo de Grossman desacreditando la teoría polivagal. Me podría porfavor explicar un poco en qué se basan y si los ejercicos que plantea PORGES y sus seguidores, en sus libros, también estaría desacreditados científicamente para la disminución del estrés? Graciasss
This sure is simplified! Thanks.
Thank you for sharing your clear explanation.
Alosia Carlson LCSW
This information is extremely helpful. It provides the foundational explanation of the functioning of the vagal nerve rather than just the clinical practicality.

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