The Polyvagal Theory and why should we care?

I came across the polyvagal theory during my Kinesiology studies. It has completely changed my perspective on what I thought I knew about our nervous system (acquired through my Pharmaceutical studies). It is a breakthrough work offering different understanding of human behaviours and trauma and I thought it was really worth a blog.

The polyvagal theory from Dr. Stephen W Porges revisits the anatomy and physiology of one the most important actor of the mind-body connection: the vagus nerve.

It presents new ways of approaching mental health, such as anxiety, depression, recovery from early trauma which can commonly keep individuals living in perpetual fight-or-flight state or in freeze state (emotionally shutdown or disconnected). It has also further application when dealing with children’s social engagement or behavioural issues. To me, it does reinforce again the importance of a mind-body approach in promoting health and wellbeing focusing on the importance of neuro-regulation.


Vagus is latin for “wandering” which is a perfect name considering that it is the longest of the 12 cranial nerves and that it has the widest distribution in the body.

It originates in the brainstem (at the back of the head) and regulate many organs: oesophagus, heart, lung, gut.

  • 80% of its fibers are sensory. This means they collect information from our internal organs and send the information to the brain stem and to higher structure.

  • 20% of its fibers are motor and regulated by the brain cause our heart to go faster or slower.

In its tonic state, the vagal nerve has an inhibitory function, that works like a brake on the heart’s pacemaker and allows us to calm down (commonly called the vagal brake).

It is said that 80% of the parasympathetic nervous system (PNS) neurology is carried through the vagus nerve. The PNS has a calming effect promoting health, growth and repair.


The autonomic nervous system (ANS) is the part of the nervous system that acts largely unconsciously, without you having to command it and regulates bodily functions such as the heart rate, digestion, respiratory rate, pupillary response, urination, and sexual arousal.

In many textbooks (including the way it was initially taught to me) the ANS is described in 2 parts: sympathetic nervous system (SNS), which is often considered the "fight or flight" system, while the parasympathetic nervous system (PNS) is often considered the "rest and digest" or "feed and breed" system. These 2 systems are seen having "opposite" actions where one system activates a physiological response and the other inhibits it.

Dr. Stephen Porges theory revolutionizes this idea showing that the Autonomic Nervous System (ANS) is not solely a paired antagonistic system (like PNS and SNS) but a hierarchical system in which newly evolved circuits inhibits older circuits.

Through studying the neuroanatomy of the vagus nerve, he shows that even though there is only 1 vagus nerve, mammals have in fact 2 vagal circuits:

  • an unmyelinated* shared with reptiles and retained through evolution.

  • a uniquely mammalian circuit that is myelinated.

*Myelinated means it is surrounded by a layer of fat.

The myelinated portion only represents 3%. These 2 vagal circuits originate in different areas of the brainstem.

“We have 2 circuits for defense, the popular fight-flight and a more ancient, reptilian one that causes “shut down”, “immobilisation”, “freeze”, “death feigning” and this one manifests in people who are restrained and have no options to get out (like for example in situations of abuse or trauma).

Reptilian style response, playing dead, stop breathing was adaptively useful for them (made it more difficult to be detected by predators) and they could do it for a very long time they don’t need much oxygen. But that response, which has been retained through evolution is not very adequate for mammals who required lots of oxygen. Freeze and shutting down respiration and heart rate can quickly lead to death”.

Interestingly Dr. Porges shows that this newest myelinated circuit appearing in mammalians is responsible for controlling facial & laryngeal muscles. Hence, controls vocalisations, facial expressivity, and the muscles in the middle ear that controls listening.

For example, studies show if myelinisation is not working people can get auditory hypersensitive and difficulties to understand human voice in background noise.

He called this circuit the Social Nervous System (SocNS), to acknowledge its importance for social interaction. Through evolution, mammals chose to live in groups, needed to communicate and bond in order to survive.


According to Dr. Porges the hierarchy to the basic survival responses is as below :

  • Absence of danger, safety cues: we can engage in social behaviour, bond (Social Nervous System)

  • Our nervous system detects danger (note that most of the danger cues are detected first unconsciously): we mobilise to fight or flee (SNS is engaged)

  • Severe life threating situation (e.g oxygen deprivation) where mobilising is not possible: immobilise, play dead, faint. PNS is overactive.

Perception of safety is necessary for social engagement behaviours to occur. When the social engagement is working and down regulating defenses, we feel calm, smile, we hug people, we make eye contact and we feel good.

Babies are great examples of fully functional SocNS, their emotions can be easily read on the face and in their eyes.

This state of the vagal nerve supports health, growth and restoration.

However the 2 defense mechanisms take priority when risk increases. In response to danger our Sympathetic Nervous System (SNS) takes control and supports metabolic motor activity for fight/flight. Then if that doesn’t help us become safe, we recruit the ancient reptilian unmyelinated vagal circuit and shut down.


There are specifics cues that our nervous system detects that shifts us into different states. Since the neural evaluation these cues does not require conscious awareness and may involve subcortical limbic structures, the term

neuroception” was introduced by Dr. Porges to emphasize a neural process, distinct from perception, that is capable of distinguishing environmental (and visceral) features that are safe, dangerous, or life-threatening.

It is not the event itself that matters but how it is detected by our nervous system. This can be variable from an individual to another.

Danger “neuroception” particularly involves analysis of the body, facial movements, tone of voice. Use of acoustic features are most potent triggers of “neuroception”. For example, low frequency sounds are cues of danger (through evolution these sounds have been associated to predators). If you think about babies, mother’s lullabies, folk music or love songs they are using high frequencies which allows soothing.

In the same way, social engagement depends on how well we can regulate muscles of face and neck. This ability also helps us being able to distinguish human voice from background noise by attenuating low frequency sounds. One common symptom (and test) in kids with learning or behavioural difficulties, is that they can get easily distracted and cannot really distinguish human voices in loud noises.


To understand the clinical application, let's take a look first at the cost of staying in one of the defense state:

A constant state of fight-flight leads to a rise in heart rate and blood pressure, increase of serum blood sugar, impaired cortical brain function, increased sensitivity to low frequency sounds, increased sensitivity to movement, particularly in the periphery, increased sensitivity to touch.

Also bowel motility will be impaired, our gastric juice secretion decreases as well as our digestive enzyme production, there is also less tissue repair and regeneration.

If a person remains in SNS for long periods, this will put pressure on the heart, depleting the body of nutrients and impede digestion.

The toning down of the SocNS prompts eye lids to droop, voice to lose inflection, less positive facial expression, more difficulty distinguishing human voice, less sensitivity to other people social engagement. Intimacy is also compromised in this state.

Dr. Porges recognises these as being common symptoms in autism, trauma (PTSD), depression or schizophrenia.

From this theory, we understand emotional and bodily response as an evolutionary expression of how safe we are in the world and pick actions which can help us work in partnership with our autonomic nervous system.

Enhancing feeling of safety and vagal tone can be used for helping people stuck in “fight-flight” SNS state (in other words when working with stress) or when working with anxiety, panic disorders, trauma, child behavioural difficulties.

Encouraging people in freeze state to mobilise can activate the SNS which can then be a state that can be used as a way to re-engage in social interaction (to be done under the supervised care of a therapist).


  • Use sounds & music: Music engages Soc NS. Violins, flutes, clarinets, trumpets, oboes and French horns are in the human vocal range (Hz). Listening to baroque music or even classical music in general can really help relaxing.

  • Spend time in quiet spaces: Spend time in nature, far from city and road noises. Set up or choose homes, offices & schools far from road noise to remove low frequency sounds. (When in danger noises are prioritised according to intensity and the person’s awareness of lower frequency (predator frequencies) are enhanced)

  • Practice slow rhythmic breathing: Breathe in quickly and breathe out slowly – out breath engages vagal brake. Another example is alternate nostril breathing.

Get kids to play games such as blowing ping pong balls across the table with a straw or blowing bubbles.

  • Sing your favorite songs: Singing encourages the type of breathing described above and engages middle ear muscles.

  • Engage in social interactions (only if desired) or with a pet: Call or visit a trusted friend and share what’s going on.

  • Get a massage: Relax the muscles of your neck, head & massage your scalp. Touch is the first of the senses to develop in the human infant.

  • Coming or brushing hair: great for calming kids (the scalp is innervated by several nerves that also innervate the face, the eye, the ear).

  • Reach out for online text/chat or phone based crisis supports listed below to connect with another human who cares.

  • Journal, express thoughts and emotions

  • Consciously change your facial expression: SMILE more!

  • Be mindful of your posture: sitting up straight, shoulders back, head high, looking straight

  • Eat slowly and calmly in reasonable portions.

  • Consciously try to slow your heart rate: Imagine or visualise heart rate falling, relaxing

  • Use acupressure points that sedate and calm or diffuse stress in areas of the brain associated with danger perception

I use the principles above in my clinic and also work on addressing beliefs and behaviours to enhance safety.

For more information please feel free to book a 15 min complimentary session or contact me on

Just in case you want to access support right now (most of these services are operating 24h)

Domestic Violence Hotline: 1800RESPECT; 1800 737 732
Lifeline: 13 11 14
Kids Help Line: 1800 551 800
Mensline Australia: 1300 789 978

Or visit:

Bibliography & further reading:

  • The polyvagal Theory, Neurophysiological Fundations of emotions, attachment, communication, self-regulation, book by Stephen W. Porges.

  • Clinical Applications of the Polyvagal Theory, the emergence of polyvagal-informed therapies, book by Stephen W. Porges, Deb A. Dana.

  • Attachment and Bonding – A New Synthesis Paperback – 10 Jan 2006, by C Sue Carter (Author)

  • The polyvagal theory: New insights into adaptive reactions of the autonomic nervous system, STEPHEN W. PORGES, Cleve Clin J Med. 2009 Apr; 76 (Suppl 2): S86–S90.

  • Porges SW. Neuroception: a subconscious system for detecting threat and safety. Zero to Three: Bulletin of the National Center for Clinical Infant Programs. 2004;24(5):19–24.

  • The Polyvagal Theory for Treating Trauma, teleseminar session with Stephen W. Porges & Ruth Buczynski, The National Institute for Clinical Application of Behavioral Medicine

#kinesiology #polyvagaltheory #trauma #vagusnerve #safety #fightflight