4.1.13 What later discoveries have added to this knowledge?

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Some later discoveries that have added knowledge are the neurophysiological model of tinnitus and the science of brain plasticity.

The science of brain plasticity over the last twenty years has proven that new brain pathways are created as a result of stimulation.

Therefore, we now know that listening to Sound Therapy physically builds and enhances our neural network.

Sound impacts not just our hearing but our entire nervous system, via the cranial nerves. (Weeks, 1989) In fact ten out of our twelve cranial nerves are linked in some way to the ear.

The auditory (8th cranial nerve) controls balance and hearing. A branch of this nerve arborises around (surrounds) the 3rd or oculomotor nerve. This means that the four cranial nerves concerned with vision are to some extent controlled by the auditory nerve.

The trigeminal (5th cranial nerve) is the major nerve of the head, face and jaw. This nerve controls the tension on the ear drum via the tensor tympani muscle. It therefore plays a significant role in the voluntary act of listening.

The facial (7th cranial nerve) controls facial expression and also the door to the inner ear chamber via the stapedius muscle. Thus it influences balance as well as the inner receptivity to sound.

The glossopharyngeal (9th cranial nerve) links hearing and speech. It contacts several parts of the ear concerned with pressure and links them to the tongue and throat.

The vagus (10th cranial nerve) accounts for the powerful relationship between hearing and emotion. After sending a twig across the ear drum the vagus wanders through the larynx, chest, heart, stomach and intestine, enabling our hearing to have an effect on all these organs.

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The spinal accessory (11th cranial nerve), affecting posture in the neck and shoulders is also linked to the ear via its connection with the vagus.

Thus we see that the ear is not just a minor part of the nervous system, but is intricately and centrally linked with nearly all of our sensory processing mechanisms, placing it in a primary position as coordinator of our interface with the world.

The Twelve Cranial Nerves — Table

No.	Name	Contact with ear	Primary function/ organs of contact	Branches
1	Olfactory		Olfactory bulb – smell
2	Optic	Interacts with 8th	Eyeball – sight	3rd
3	Occulomotor	Under control of 8^th	Link between hearing and sight Movement of the eye
4	Trochlear	Under control of 8^th	Turns eye up and down	3^rd – lateral sinus upper jaw
5	Trigeminal	Ear Drum Outer ear canal Tensor tympani	Link between face, jaw and middle ear The great sensory nerve of the head and face Motor nerve muscles of mastication	Upper eyelid, facial nerve, forehead, nose, iris, cornea, teeth, lower eyelid, upper lip and lower lip, mucous membrane of mouth, palate, gums, uvula, tonsils, Eustachian tube, muscles of mastication, tempero-mandibular joint, tongue
6	Abducent	Under control of 8^th	Eye movement	Optic, oculomotor
7	Facial	Stapedius Meatus Chorda tympani Malleus Tympanum	Link between face and inner ear Facial expression Taste – back of tongue Upper part of neck muscles behind ear on back of pinna	3^rd, 10^th, 9^th, 5^th Shares filaments with auditory nerve in meatus
8	Auditory	Inner ear	Hearing and balance	Oculomotor Vestibular – arborises around the nuclei of the oculomotor nerve Medulla Cochlear-facial nerve in meatus
9	Glossopharyngeal	Oval window Round window Tympanum Eustachian tube	Link between hearing and speech Pharynx/throat Tonsils Tongue – taste Spinal accessory	Vagus
10	Vagus/ Pneumogastric	Tympanum Posterior auricular nerve Meatus, pinna	Link between hearing and emotion Neck thorax/chest, abdomen	Motor sensory – voice, respiration Motor – heart, stomach glossopharyngeal, facial, spinal accessory
11	Spinal Accessory	Interacts with vagus	Link between hearing and posture Spinal, neck and trapezius	Vagus – pharynx, larynx 2^nd, 3^rd, 4^th cervical nerve
12	Hypoglossal		Motor nerve of tongue Vagus	1^st and 2^nd cervical nerves, lingual

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