Dr. Stephen Porges, a leading expert in developmental behavioural neuroscience has studied the connection between human behaviour and the vagus nerve. Polyvagal theory describes the autonomic nervous system as having three subdivisions. The oldest subdivision is the ‘dorsal vagus’, a part of the parasympathetic nervous system that enables us to shut down, or ‘freeze’ when a situation feels uncontrollable and we are overwhelmed. The second is our sympathetic nervous system, or ‘fight/flight’ system. And the most evolved is the parasympathetic social engagement system (ventral vagus). If the environment is safe, we use the ventral vagus and are able to express feelings, use facial expressions, modulate voice and filter human language from background noise. When we detect our environment is not safe, we fall into the ‘fight or flight’ mode. If that system fails too, we fall back into the ‘freezing’ mode, which is the most primitive mode where a person has less ability to relate to the world socially.
The polyvagal theory has great relevance in explaining complex developmental trauma and autism spectrum disorders.
Watch Dr. Stephen Porges talk about his Polyvagal Theory.