nerves of the face

«The theory has two important parts. The first is the link between the
nerves of the face and the nerves that regulate the heart and the
lungs. The second is the phylogenetic hierarchy that describes the
evolutionary sequence from a primitive, unmyelinated vagus related to
conservation of metabolic resources, to a sympathetic-adrenal system
involved in mobilization strategies, to a myelinated vagus related to
modulating calm bodily states and social engagement behaviors. The
hierarchy emphasizes that the newer "circuits" inhibit the older ones.
We use the newest circuit to promote calm states, to self-soothe and
to engage. When this doesn't work, we use the sympathetic-adrenal
system to mobilize for fight and flight behaviors. And when that
doesn't work, we use a very old vagal system, the freeze or shutdown
system. So the theory states that our physiological responses are
hierarchically organized in the way we react to challenge, and the
hierarchy of reactions follows the sequence in which the systems
evolved. Additionally, the linkage between the nerves that regulate
the face and the nerves that regulate the heart and lungs implies that
we can use the facial muscles to calm us down. Think about it: when
we're stressed or anxious, we use our facial muscles, which include
the ears. We eat or drink, we listen to music, and we talk to people
to calm down.»

«So we could use dramatic facial expressions to calm down?»

«Absolutely. Think about how pranayama (a yogic breathing technique)
works. When you do these breathing exercises, you're actually
"exercising" both the sensory and motor nerves regulating the facial
muscles; you are controlling breath and maneuvering the oral motor
cavity. It's a very efficient way of working on the system. A lot of
people don't like to teach pranayama because they think it's too
powerful. Polyvagal theory explains how pranayama might work and how
other methods of stimulating the same system, including social
interactions, can result in similar benefits to our health and mental
state. The social engagement system includes the nerves regulating the
face and the myelinated vagus regulating the heart and bronchi. The
power of the social engagement system is amazing both in terms of its
effects on behavior and mental state, but also in terms of the speed
with which it works.»

-- Stephen Porges interviewed by Ravi Dykema,
http://www.nexuspub.com/articles_2006/interview_porges_06_ma.php