Nexus, Colorado’s Holistic Health and Spirituality Journal.

This interview with Dr. Stephen Porges, whose career is based on understanding the evolution of the human nervous system, outlines some of the basics of polyvagal theory.

This theory is being tested in trauma recovery sessions. It’s exciting because it helps explain how and why people freeze or experience fight-flight reactions in response to trauma — and the route back to normal, healthy functioning, no matter how long ago the trauma occurred or how often it happened.

Polyvagal theory is increasingly becoming part of the training of bodyworkers, therapists, and educators. In a future post, I will describe how to tell which nervous system (freeze, fight or flight, or parasympathetic) is dominant at any given moment.

This theory is based on an in-depth understanding of the vagus nerve, also known as the 10th cranial nerve, which wanders (the Latin word vagus means wandering, like vagabond and vagrant) from the brain stem down through the body, affecting the face, heart, lungs, and gut.

The brain evolved hierarchically in vertebrates, and the neural circuits of the older nervous systems are still present, accessed hierarchically.

RD: So one thing happens then another thing happens then another thing?

SP: Right. This influences how we react to the world. The hierarchy is composed of three neural circuits. One circuit may override another. We usually react with our newest system, and if that doesn’t work, we try an older one, then the oldest. We start with our most modern systems, and work our way backward.

So polyvagal theory considers the evolution of the autonomic nervous system and its organization; but it also emphasizes that the vagal system is not a single unit, as we have long thought. There are actually two vagal systems, an old one and a new one. That’s where the name polyvagal comes from.

The final, or newest stage, which is unique to mammals, is characterized by a vagus having myelinated pathways. The vagus is the major nerve of the parasympathetic nervous system. There are two major branches. The most recent is myelinated and is linked to the cranial nerves that control facial expression and vocalization.

Here’s how it works in action:

SP: Let’s say you’re a therapist or a parent or a teacher, and one of your clients, students or children’s faces is flat, with no facial expression. The face has no muscle tone, the eyelids droop and gaze averts. It is highly likely that individual will also have auditory hypersensitivities and difficulty regulating his or her bodily state. These are common features of several psychiatric disorders, including anxiety disorders, borderline personality, bipolar, autism and hyperactivity. The neural system that regulates both bodily state and the muscles of the face goes off-line. Thus, people with these disorders often lack affect in their faces and are jittery, because their nervous system is not providing information to calm them down.

RD: How will polyvagal theory change treatment options for people with these disorders?

SP: Once we understand the mechanisms mediating the disorder, there will be ways to treat it. For example, you would no longer say “sit still” or punish a person because they can’t sit still. You would never say, “Why aren’t you smiling?” or “Try to listen better” or “Look in my eyes,” when these behaviors are absent. Often treatment programs attempt to teach clients to make eye contact. But teaching someone to make eye contact is often virtually impossible when the individual has a disorder, such as autism or bipolar disorder, because the neural system controlling spontaneous eye gaze is turned off. This newer, social engagement system can only be expressed when the nervous system detects the environment as safe.

There’s much more fascinating information you can read by clicking the link at the top of this post.