The Polyvagal Theory

In recent years, neuroanatomical discoveries have given us a basis for understanding how this work of the PNE creates dynamic, global, long-lasting, life-changing, seemingly miraculous healing, resulting in less reactive responses and a greater sense of loving contentment, regardless of the circumstances of life. The saga begins with memory and patterns of trauma that become submerged in the ancient aspect of the brain called the limbic system. 

The limbic system is the feeling, instinctual, reactive brain, which lies between the thinking neo-cortex and the hypothalamic endocrine and neurologic outflow via the septal nuclei.  The limbic system is involved in memory storage, emotions, attention, and focus, all which are vital for survival reflexes. 

When threat occurs, metabolic activity decreases. There is often a “freeze response,” as in death feigning and shutdown behaviors, which engages the unmyelinated, visceral, vagal response system via the dorsal root motor neuron in the medulla. This is the first and most ancient response of the autonomic nervous system (ANS) to threat.

The second evolutionary adaption to a threat is the well-known fight-or-flight mechanism. This response is derived from a predominate sympathetic outflow via the adrenal glands, which release epinephrine into the blood. Since epinephrine cannot cross the blood-brain barrier, it stimulates the ascending vagal norepinephrine-based fibers and via the nucleus of the solitary tract in the medulla, it activates the amygdala and the hippocampus.

The third evolution of the autonomic nervous system’s response, in this case to perceived safety, is called the communication-mamamallian myelinated vagal pathway or the smart vagus-ventral vagus system. Alternatively, it is also called the social engagement system by Stephen Porges.

Porges states that this system was developed in mammals to optimize oxygen resources. This myelinated vagal system, which processes through the nucleus ambiguous in the medulla, can inhibit the two previous systems. It regulates the cardiac output and aligns cranial nerve function to create social facial expressions and vocalizations to ward off threat. The increase in cardiac output and bronchi relaxation promotes increased oxygen, with a concomitant calming effect. The increase of the influence of the nucleus ambiguous effect allows for higher cognitive process to calm the stress response and establish effective communications with people via facial expression, voice inflections, listening and eye contact.  The further calm turns off the stress via the myelinated vagus and decreases the HPA axis activation (fight or flight). This system is modulated through the neurotransmittors of oxytocin and vasopressin and allows for adaptive behavior, courting, sexual arousal, and establishing enduring social bonds.  For us mammals, if this system does not work, then we revert to the use of the two earlier evolutionary brain reactions to stress.

In a PNE session, we may re-experience somaticized traumas that have previously been imprinted through the earlier evolutionary adaptations of the unmyelinated vagal response systems, only now we have the opportunity to bring to bear the higher cognitive processes available in the social engagement system that predominates in safety. In this way, we can re-establish healthy choices, where we were previously unconscious, triggered and reactive.

For example, a somaticized freeze response that keeps the body in a state or relative paralysis can be released even many years after the experience. Peter Levine notes that unlike many of us, animals in the wild routinely shake off the terror of a threat or attack, an immediate, healthy response that makes them virtually immune to the symptomology of somaticized trauma. He describes the need for this release to regain health in his book Waking the Tiger. 

When unwinding this form of unresolved trauma response from the nervous system, the person will begin to shake from deep within. Sometimes the shaking is global and sometimes it is a local area such as a finger or arm. A gratifying sense of release and freedom is attained, and primitive, limiting beliefs that were taken on at the time of the event are reevaluated from a new perspective within a perception of current safety.