Listening Matters (by Kim Barthel)
Listening is much more than just processing sound and making sense of language! Sound waves energize many aspects of the whole brain. Approximately 60% of the brain’s arousal and alertness arises from the processing of sound. Why are movement and sound perceived by the same structure (the vestibulocochlear apparatus)? It is because movement and sound are connected. Some sounds are felt by the body as vibration and prompt us to move. When we move while we perceive sound, sounds become spatially mapped in relation to our bodies.
Curiously, the eardrum is innervated by four different cranial nerves, some of which at first glance seem to have nothing to do with listening. The glossopharyngeal nerve, the trigeminal nerve, the facial nerve, and the vagus nerve communicate with the eardrum, impacting the reception of sound and then collaborate in the creation of functional outcomes of the reception of sounds. One tiny muscle is connected to a bone that prepares the eardrum to receive sound, allowing the ear to fine-tune its listening process to human voice. The stapedius muscle (the smallest muscle in the human body) attaches to the stapes bone that looks like a stirrup from a saddle. The muscle is activated when there is a loud sound in the environment, and it is a muscle that is permanently online; even when you are sleeping this muscle is monitoring the environment for danger. The job of the stapedius muscle is to help to dampen the volume and intensity of loudness so the eardrum can filter out irrelevant or background noises and get ready to listen to what is most important: the voices of others.
How does listening with our eardrum impact the muscles of our face? Through the connection with the trigeminal nerve, listening becomes connected to speaking. When we listen, we move our articulatory muscles needed for talking at the same time. In a sense our tongue moves to listen. While listening we simultaneously speak in silence (inside our mind) and small imperceptible contractions of our talking muscles are activated while listening. The connection between listening and communication is closely integrated even at the level of the eardrum. In fact, the stapedius muscle moves in advance of when we vocalize speech so that we are not overwhelmed by the sound of our own voice. Our brain needs to dampen the intensity of our own vocal sounds in relation to the sounds around us. Chewing is also a way of activating the trigeminal nerve, which is also responsible for moving the eardrum. Kids who have trouble chewing will often be challenged with listening as well. Sometimes the stapedius muscle struggles to work, and the entire function of listening is altered. Sensitivity to sound or irritability in relationship to sounds may be an outcome when this aspect of our system is out of balance.
The facial nerve innervates all the muscles of the face responsible for the expression of emotions for social connection (except for the muscles that raise the eyelids). Our emotions cause the facial nerve to change the tension of the muscles giving the face expressions of anger, joy or surprise. When this happens, the facial nerve simultaneously influences the action of the stapedius muscle, allowing the eardrums to convey emotions from the face to the voice.
The vagus nerve (the parasympathetic rest and restore nerve) is a key to understanding the impact of listening on the autonomic nervous system. The vagus nerve extends over large areas of the ear including the eardrum. Throughout the vagal connection to the ear, there are vast intersections and intermingling of data from the vagus nerve with the trigeminal and glossopharyngeal nerves. In fact, when speaking or singing we literally “touch” this triad through with an outcome that sends stimulation extending throughout the body. The vagus nerve acts on both hearing and phonation simultaneously. Two of the vagal branches are responsible for activating the vocal cords, specifically related to the function of prosody which projects our mood state or state of health onto our voice. Other vagal fibers innervate the stapedius muscle directly helping to regulate the intracochlear pressure allowing us to listen actively and selectively. These two functions of the vagus nerve are intertwined and impact the outcome of each other.
Given the close relationship between the ear and the parasympathetic system, it is possible that the auditory system also may influence the gut where 90% of our serotonin and 50% of our dopamine are located.
Think of the implications of this physiology on function! Therapists can and do use therapeutic tools such as Therapeutic Listening, Integrated Listening Systems, and the Safe and Sound Protocol with clear intention to impact a clients’ entire functioning through sound. Listening matters not only for communication, but for social connection, well-being and our entire physiological balance.
