“Vagal” refers to the many branches of the vagus nerve – the old pneumogastric nerve as it was called – which connects all the major organs including the brain, heart, lungs, stomach and intestines, all of which the vagus nerve interfaces with in sympathetic and parasympathetic control. Although it is usually referred to in the singular it is a paired nerve. It is the longest nerve in the autonomic nervous system in the human body and extends from the medulla oblongata through the face and thorax to the abdomen, reaching all the way to the colon. Besides having some role in output to various organs, some 80-90 per cent are afferent nerves whose role is to convey to the central nervous system the state of the body’s organs – or more psychologically “How am I, how am I doing?”. It does this through its axons which converge onto, or emerge from, four nuclei of the medulla oblongata. Parasympathetic output is sent to the viscera, especially the intestines, via the dorsal nucleus of the vagus nerve. From the nucleus ambiguous it gives rise to the preganglionic parasympathetic neurons that innervate the heart. The solitary nucleusreceives afferent taste information and other afferents from visceral organs (except the adrenals). The spinal trigeminal nucleus receives information about touch and pain, the temperature of the outer ear, the dura of the posterior cranial fossa and the mucosa of the larynx. As well as supplying parasympathetic motor fibres to all organs between the neck and the transverse colon, it also controls some muscles, chiefly those of the larynx and some others in this area associated with swallowing, the palatopharyngeus muscle for example.
Porges encourages the vagus to be thought of imaginally as, not a nerve, but as a cable that connects brain and body – a portal from the periphery telling the brain how the body is. So, when you feel good the vagus is conveying this to the brain, and when you feel bad this is also the vagus communicating to the brain.
The meaning of Porges’ term “polyvagal’ – poly meaning many – refers not to the meandering of the nerve fibres of the vagus nerve itself but to the phylogenetic history of our human nervous system; we have a heritage of neural circuits that have changed as they have evolved. There are two main principles of polyvagal theory. The first is that there is a uniquely mammalian pathway that is the newest neural feedback system and this one functionally takes precedence. This is the part of the vagal system that is super-diaphragmatic – above the diaphragm. It is a uniquely mammalian pathway that is myelinated and serves the heart and the bronchi and also to the muscles of the face and head. Since the facial muscles are wired into the vagus, then facial expressions can become a window to how the vagus is influencing the heart and bronchi. For example, if a person is stressed the muscle tone in the face if often flat, especially to the orbicularis oculiaround the eyes.
The other principle of polyvagal theory is that we functionally have 3 autonomic nervous systems, and these neural circuits provide a response hierarchy. When we are challenged we use the newest circuits, but if these turn out not to be fit for the task, then we regress and use older circuits from our phylogenetic history. From the bottom up the oldest vagal circuit would be the one we share reptiles and this circuit is geared to shut-down and immobilisation. Immobilisation is a common feature of trauma – for example during a mugging the autonomic nervous system might turn this response on. Immobilisation and shutdown would be a result of the old unmyelinated vagal system mobilising, and would be characterised by reduced blood flow, especially to the brain. Allied to this are a whole host of possible neurophysiological digestive problems, such as IBS – hence the prevalence of vagotmies in the 1950’s. Also immobilisation in a psychological sense of not being able to mobilise the creative aspects of one’s personality which is an almost ubiquitous feature of clients coming for psychotherapy. The protective features of immobilisation counteract what David Boadella has characterised as an “ability to surrender oneself wholly to an experience.” Also, immobilisation is related to “disappearance”, to dissociation – as though dissociation is our modern attempt to “play dead”, or go into hiding in the presence of a predator.
The next functional nervous system would be that of our flight/flight system. To fight the mugger off and run after him would be an example of this, associated with increased heart rate and prioritising the blood to the skeletal muscles and away from non-vital functions. This system is synonymous with the heart and bronchi branches of the vagus nerve. If successful, fight/flight is normally an excellent system for dealing with threat. But it does not always work, is not always mobilised – and this is the whole story underlying trauma– that this system fails to come online and the input is given over to the older functional system to process. The newest circuit – what Porges calls the face-heart connection or social support system – keeps us safe by keeping us in connection to others. When people convey to us that they feel safe then we feel comfortable and vice-versa and this is embedded in the newer vagal system, which includes the face as well as the heart/bronchi pathway.
This newer system is capable of regulating the other defensive physiological systems – if only it were given a chance. i.e. in deprived social circumstances this is seldom possible. The physiological features of the social engagement system have at least three components all geared towards regulation and the parasympathetics of calming down, of downregulating sympathetic activity. The muscles of the face associated with ingestion, the upper part of the face especially around the orbicularis oculiwhich is an important site for social engagement cues. Lastly the muscles of the middle ear where we can detect prosodic features in the voices of others and trigger the neural regulation of the middle ear muscles, which results in tuning out priorities for detecting lower frequency sounds phylogenetically associated with predators. According to Porges, this is the reason that people suffering from trauma cannot tolerate noisy places, because such places are filled with low frequency sounds – and because for functional reasons the neural regulation of the striated muscles of the face and head are turned off due to the mobilisation of the earlier vagal systems – and turning the top system off results in hypervigilance for a predator. All three systems, or certainly the oldest two, are not subject to voluntary control, for reasons discussed below.
Now, isn’t all this just a fancy neuroanatomical way of saying that when your environment is safe and secure, and you know you are loved and respected because of the tones of voice and the expressions on the peoples face in your social world are all benign so you feel good? On one level it is, on another level it isn’t, chiefly because there is another complex of consciousness operant within the nervous system, working independently, which Porges calls neuroception. Largely out of cognitive awareness this neuroceptive system is constructing an interpretation of everything that is happening, evaluating risk and in doing so tries to trigger a neural component that fits the environmental context. The response is primarily a physiological response which is evaluated by the nervous system and out of this a personal narrative is created to account for the context that our neuroception has created. And sometimes this personal narrative, constructed chiefly from interpretations of sensation made by an atavistic neuroceptive system, may be totally irrational, may bear very little relationship to a current situation but only to neuroceptive templates, which presumably are instinctual. So, in shutting down or mobilising for fight or flight a narrative is needed for a person to make sense of the information being presented in their body, what their body is doing. The strength of polyvagal theory lies in the possibility of the other two systems being redeemed by the social engagement system, and by the educational possibilities of describing and enabling this in people suffering from trauma. For example, telling a client who has issues with relationships and trust that they should simply learn to trust people – the feel the fear and do it anyway school – does no good at all and is ineffective because the person has their own personal security guard (their neuroception) that is always on the look-out for danger.
I can illustrate some of the workings of the vagal system with a personal story, an event that occurred when I was 10 years old. It was not a life-threatening event, but a shocking one nevertheless, and occurred in the presence of many other people who were mainly in flight or flight mode. There was lots of noise, and a confusing array of visual stimuli for a young child. I arrived to this scene totally unprepared, like you would when you turn the corner of a street and find something shocking happening in front of your eyes. As I put my mind back into my 10 year old body I can feel my body become stiff like a board. My mouth opens slightly as if to speak but I can’t say anything, do not even know if anything can be said and I feel a constriction in my throat – the freeze response is kicking-in. However, although I am confused, at another level I am acutely aware of what is going on, and I scan the room noting and interpreting how everyone is. This is neuroception, but at that time I am not aware that I am aware and it is only looking back that I can detect it. I try to get eye contact with the person responsible for my care, i.e. I am looking to be regulated via the social engagement system. However, the care-giver is shut down and offers no response. Now there is no regulation from the top down available – and it is interesting to note that although my initial response is to immobilise I am still looking to be regulated via social engagement, this system is still available and wants to kick-in, Porges’ heirachy theory. This all happened within the space of, at most, 2 seconds and is instinctual and not volitional, i.e. it is orchestrated by the ANS. In the coming days I make a connection unconsciously to an event the day before; I had inexplicably been overtaken by a feeling that something was wrong, but I did not know what. This now becomes part of the narrative that accounts for what my body is telling me via feedback from the vagus – and so the intuitive event of the day before is now interpreted as a cause. The whole thing was my fault, I am responsible and this inevitably leads to feelings of low self-worth. Then two days later I am in hospital with suspected appendicitis due to severe abdominal pain, a product of the old unmyelinated vagus “surging”.
It is quite common to experience clients who have varying degrees of shut-down facilitated by the older unmyelated vagal system, which results in the social engagement system being shut off, often accompanied by low self-worth and feelings of shame. I am reminded of a male client in his late twenties who came to see me and had therapy with me for three years. He was quite possibly one of the most talented and engaging people I have ever had the pleasure to sit opposite to. I remember on our first session after he was telling me his story and near the end of the session I fed back to him how much I had been enjoying him, and communicated to him my embodied sense of it. He looked at me in astonishment and told me in an incredulous voice that he had not been expecting that. Towards the ending period that we had agreed some 6 months prior during our therapy, he came to this realisation himself; that he had never been enjoyed as a child, as a product of being engaged with by his caregivers, and that what had happened during our time together, despite all our clever interpretations, was that he had simply become acclimatised, and allowed himself to be enjoyed, and had discovered play, which had previously been a foreign concept to him. In Porges’ view play and seeking novelty is an essential part of nervous system regulation, recruiting aspects of defensive systems with social engagement. In play, aspects of the two older systems are played out while at the same time maintaining the social vagal system and safety. It is a unique feature seen in many species of mammals which enables them to excercise and hone all three systems. In trauma victims those who do not seek ‘novelty’ do not do so because they do not have a path back to safety, to being regulated from the top system down. In the case of the above client, when I first initiated play (rather cack-handedly as I remember) it led to a freeze response in the client. However I was able to attune myself to him and initiate play at a lower level with gradual increasing incrementations which were eventually initiated by him, and thinking back now I can see that in our engagements what was happening was that he was becoming au faitat moving between all three vagal systems and not just being stuck in the lowest one – so he could tolerate freezing, but was able to mobilise away from it using social engagement cues, and similarly was able to be aggressive and evasive while still being socially engaged.
Using Porges’ wiring analogy we could think of the “three nervous systems” as a house that is wired to receive power through its systems of wires within walls, and switches to turn lights on and off. A good functioning social engagement system would enable us to move from room to room seamlessly – be able to see where we are going because we know all the switches work. When the wiring does not work we are unable to see where we are going and where we are, and so we must stumble around and knock into things in the dark. We inherit the houses we live in, the wiring is provided by our good or bad care givers, but however badly we have been wired, there is always the possibility of a re-wire via social engagement in a safe environment in the present time, and thus we can undo the perpetual cycle that John Bowlby characterised as “we do as we have been done by”. Lastly, we might see people as poorly regulated rather than mentally ill, “…to recognise in the mental illness merely an exceptional reaction to emotional problems which are not strange to us”. (Jung) Such an exceptional reaction, in the polyvagal view, is caused by the mobilisation of older strata of the ANS that we share with reptiles in response to the lack of availability of the newer system of social engagement.