Sound and the Vagus Nerve
The Vagus nerve is the longest nerve in the body.
It originates in the brain and travels all the way down to the lower internal organs. It is a fundamental regulator of the parasympathetic nervous system, which controls all the involuntary processes such as digestion, heartbeat, respiration, etc. and is responsible for restoring relaxation after a response to stress or danger (the sympathetic nervous system’s activation).
The strength of the vagus response is called “vagal tone” and it is determined by the variations in the heart-rate that can be measured between inhalation and exhalation. During the inhalation, the heart speeds up and during the exhalation, it slows down. The bigger the difference between these two phases, the higher the vagal tone. A high vagal tone is what we need in order to maintain a state of good health.
The ear and hearing have a substantial effect on the rest of the body because of their proximity to the vagus nerve.
The vagus nerve, or tenth cranial nerve does not play an active part in the process of hearing, therefore it is not normally taken into big consideration in things that relate to music, hearing and the like outside of the medical field. However, this incredibly important nerve is connected with the posterior wall of the external auditory canal, the lower part of the eardrum’s membrane and in the middle ear: the stapedius (stirrup) muscle. From these parts of the ear, it makes it's way all the way down to the lower internal organs and is responsible for a high number of regulatory functions in pharynx, larynx, thorax, and abdomen.
Basically, stimulating the ear means stimulating all the vital vegetative internal organs. This makes the ear a parasympathetic regulatory organ that uses innervation of the vagus nerve to affect the whole body. The vibrations of sound tend to have a very significant impact on all the areas of the body reached by this important nerve by resonating very close to it in the eardrums. In addition to that, the majority of cranial nerves are either directly or indirectly connected with the ear.
This is one of the reasons why the use of sound therapy instruments such as Himalayan singing bowls and gongs can be so instantly calming and relaxing, helping the body to come back to the nourishing state that is the opposite of the “fight or flight” mode triggered by stress. In fact, long and sustained sounds tend to be soothing and relaxing (parasympathetic response) whereas sharp and abrupt sounds tend to trigger alertness and alarm (sympathetic response).
Another interesting factor is that auditory stimulation of the vagus nerve can lead to reduced activity of the limbic system. The limbic system, located on both sides of the thalamus, includes the hypothalamus, the hippocampus, the amygdala, and a number of other nearby areas. It is considered to be primarily responsible for our emotional life and has a lot to do with the formation of memories.