The vagus nerve runs from our brain to our gut and along the way it connects with our heart. We used to think of it as a one-way signaling, but 80% of the activity in the vagus nerve travels the other way – from our gut to our brain.
As many times before, I read an article in The New York Times that made me dig deeper into a medical subject, this time the vagus nerve, and the term “Polyvagal Theory” got me going.
We now understand that there are three levels of activity in this system, and that each one of them can influence our bodily functions, our emotions and even our perception of reality.
This deeper understanding of the vagus nerve has been named the Polyvagal Theory.
The three functions of the vagus nerve represent three different stages in evolution and the newest one, involving our conscious mind, can’t necessarily override the older two.
The oldest part of the system regulates our intestinal functions and has the ability to decrease our heart rate to the point of unconsciousness and our brain function to the point of shutdown or, in psychological terms, dissociation – playing dead, if you will.
The middle aged system can raise pulse and blood pressure and is the carrier of our famous flight or fight responses.
The newest vagus function is involved with social connections and whatever conscious regulation of the influences of the other two systems we are capable of.
Dr. Stephen Porges explains this in his books, articles and videos:
The fight or flight response is well studied and well accepted and I think most of us understand fairly well how it works. What I find the most fascinating aspects of the vagal system are the other two.
The shutdown ability of the oldest part of the system appears to explain a lot of the late effects of trauma, including dissociation and some cases of irritable bowel syndrome, for example. These conditions are associated with heart rate variability differences resulting from altered vagus nerve signaling by this system.
The younger system of social regulation was one I hadn’t really heard of and it suddenly made me understand therapeutic relationships not only in a social context like mother and child, friends or loved ones but also clinical ones, in a way that I had only intuited up until this point. This part of the vagal system is involved with control of our facial expressions, intonation of voice, gestures and all kinds of emotions involved in human contact.
Our ability to interpret things like facial expressions and intonation is dependent on whether we feel threatened in any way, and the polyvagal theory includes something called neuroception. Dr. Porges writes:
“Neuroception is proposed as a ‘reflexive’ mechanism capable of instantaneously shifting physiological state. Neuroception is a plausible mechanism mediating both the expression and the disruption of positive social behavior, emotion regulation, and visceral homeostasis.”
Neuroception can make us misread facial expressions and impair our ability for social engagement, both aspects of the newer vagal system. It can trigger panic attacks with heart palpitations and impulses to flee when the middle aged system is activated. It can also make us faint or mess our pants if we are paralyzed with fear due to activation of the oldest vagal pathways.
Our social regulation happens on many levels, and has its foundation in mother-child bonding. The so-called social neuropeptides, oxytocin and vasopressin are present in the same anatomical areas that are involved in vagal stimulation. The vagus nerve also regulates cytokine activity, involved in immune reactions.
Dr. Porges points out that humans have an inherent but limited ability for self regulation of emotions and their bodily correlates, although we can learn more of that even as adults through yoga or meditation and by exposing ourselves to soothing music for example. The foundation of human emotional regulation however is interpersonal relationships.
He writes:
“In order to co-regulate with another person, we need certain social engagement behaviors to feel safe with that person. Engagement turns off defenses. There are 3 behaviors: Facial expressions, gestures and prosodic vocalizations (intonation of voice the higher more soothing the voice the more safer perceived). Eye gaze can be seen as a threat at times for some trauma clients but prosody of voice is more of a stronger behavior for eliciting safety. Therapists can be mindful of all three behaviors in their therapy sessions with clients. Humans need others because regulators of physiology are embedded in relationships.”
This brings me back to what I wrote earlier this month in a post titled “Ten Building Blocks of Therapeutic Relationships”:
“It is well known by now that a physician’s demeanor influences the clinical response patients have to any prescribed treatment. We also know that even when nothing is prescribed, a physician’s careful listening, examination and reassurance about the normalcy of common symptoms and experiences can decrease patients’ suffering in the broadest sense of the word.”
Sounds positively vagal, now that I know a little more…
A Country Doctor Writes: 
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