”The Polyvagal Theory” is a medical text written by by Steven Porges. Mr. Porges has been studying infancy trauma since 1970 and has developed a theory around the evolution of our vagus nerve (early brain) and mental health implications of early development.
There are 12 cranial nerves that are for sensory (in), motor control (out) or both and the vagus is both (directions) and is the longest running from the brainstem to the colon area
The sensory functions of the vagus nerve are divided into two components:
Somatic components. These are sensations felt on the skin or in the muscles.
Visceral components. These are sensations felt in the organs of the body.
Sensory functions of the vagus nerve include:
providing somatic sensation information for the skin behind the ear, the external part of the ear canal, and certain parts of the throat
supplying visceral sensation information for the larynx, esophagus, lungs, trachea, heart, and most of the digestive tract
playing a small role in the sensation of taste near the root of the tongue
Motor functions of the vagus nerve include:
stimulating muscles in the pharynx, larynx, and the soft palate, which is the fleshy area near the back of the roof of the mouth
stimulating muscles in the heart, where it helps to lower resting heart rate
stimulating involuntary contractions in the digestive tract, including the esophagus, stomach, and most of the intestines, which allow food to move through the tract
The Porges Polyvagal Theory describes how when we were reptiles our vagus nerve gave us the ability to communicate with gill flapping and mouth contorting but our trauma response was limited to freeze/shit because we had no respiratory system to excite at that time. Porges goes on the describe how our vagus nerve nuclei (control center) evolved when we were reptiles to have a more sophisticated trauma response of fight/flight. The important point here is that while fight/flight was the evolved capability our system still has the fallback response of freeze/shit when fight/flight fails......our trauma response
When describing human development issues within the human vagus nerve context, Porges goes into detail about the development of the two nuclei of the vagus nerve, the lower (everything below diaphragm) Dorsal and the upper (everything above diaphragm) Ambiguus nuclei. I want to report about the development and role of the nucleus Ambiguus because of its effects on mental health. The nucleus Ambiguus does not fully form in humans until a period between the last trimester in the womb and the first year out of the womb. The emotional control role of the nucleus Ambiguus is significant as it has THE (autonomic nervous system) pacemaker control line to the sinoatrial node of the heart. According to Porges the nucleus Ambiguus in that development period sets the default pre-cortextual mammillian/reptilian response mode to everything we encounter that is then passed up to the cortextual level to handle if our fight/flight or freeze/shit trauma response is not enabled. …..think about the neural network rhythm issues that could arise from poor nucleus ambiguus development.