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Tomatis, Autism and Sensory Integration

.middle ear high frequency audio vocal control right Ear in Audio-Vocal Control Right Ear - Lead Ear

M iddle ear is an air filled chamber that is comprised of three linked ossicles, (the malleus, the incus, and the stapes), the smallest bones in the body. They are attached by two striated muscles, the smallest muscles in the body to the tympanic membrane by the tensor tympani and to the oval window by the stapedius muscle.

The tensor tympani is connected to the neck of the malleus and is anchored in the wall of the Eustachian tube. The stapedius originates on the wall of the middle-ear cavity and inserts at the neck of the stapes, near its articulation point with the incus.

They contract reflexively about a tenth of a second after one or both ears are exposed to a loud external sound. The characteristics of this acoustic reflex are so well known that deviations from the normal response serve as a basis for diagnosing various hearing disorders and neurological conditions. Acoustic Stapedius Reflex (ASR). The reflex reduces sound transmission to the inner ear by 20 decibels or more.

They also contract immediately before a person vocalizes. This pre-vocalization reflex operates even when one speaks, sings or cries as softly as possible. Designed to protect the inner ear from the fatigue and interference caused by one's own voice.

F unctions of the Middle Ear Muscles: The muscles muffle primarily a loud sound's lower frequencies, which tend to overpower its higher frequencies. This improves hearing high-frequency sounds such as human speech. The stapedius muscle has a capacity for quick responses and is capable of contracting at rates in excess of a 100 times a second. It is also very fatigue resistant and its fibers have an abundant supply of mitochondria (energy).

The stapedius muscle has an even more important role in human communication in that the AS reflex maintains the ear's sensitivity to the frequencies encompassed by most speech sounds in spite of loud competing (low frequency) sounds. The ASR can improve the threshold for the detection of high-frequency sound in noise by as much as 50 decibels. The stapedius also enhances one's ability to hear while speaking. The pre-vocalization contraction of the middle ear muscles prevents one's own speech from masking ambient high-frequency sounds. The muscles are what make it possible to hear soft sounds while we speak. (We need to listen to the high frequency sounds of our own voice) The neural circuits that control the ASR and the pre-vocalization reflex are only now beginning to be understood. The ASR relies on a complex pathway through several brain-stem nuclei as well as the auditory and facial nerve neurons.

The primary neuronal pathway the controls the ASR in the ear being stimulated originates at the cochlear receptors, extends along the auditory nerve to the brainstem, where it includes parts of the ventral cochlear nucleus and the superior olive, and follows the facial nerve to its stapedial branch. There is evidence that he ASR is activated in the opposite ear by neurons from the ventral cochlear nucleus that communicate with the superior olive on the other side of the brain. There is a close relationship between the auditory neuronal pathway (processes signals from the receptor cells in the cochlear) and the motor neurons controlling the stapedius.

The role of the Middle Ear in Audio-Vocal Control Continued

In order to sing well there needed to exist a harmonious play in the tension of the two muscles of the middle ear. It can happen that one of the two muscles can take the upper hand or dominate. If for example the stapedius (extensor) dominates the regulation the internal cochlea-vestibular chamber will not take place because there will be too much muffling of the outward movement on the incus (anvil) and malleus (hammer), which will diminish the perception of high frequency sounds while augmenting the entry of lower frequency ones.

This often occurs with a general pattern of hyperextension in the body and a poor balance between the flexors and extensors. The opposite case of too much tension on the tensor tympani (flexion) there is a cut off of lower sounds, which Tomatis feels create difficulty in body image. In the singers case the person loses a sense of his corporal instrument. The needs to be a dialogue between these two muscles and in ideal conditions they act in a synergistic role.

The role of high frequency listening in Audio-Vocal Control

Tomatis experimented with his singers by imposing the singing curve of a greater singer would he be able to improve their singing.

In studying recordings of the greatest singer of all time, Enrico Caruso's Tomatis could actually hear a click as Caruso shifted into this mode of "high frequency" listening. Tomatis learned that this was a technique used by singers trained in the "Italian" methods. He also found that there was a real change in the quality of Caruso's voice later in his career after he had an operation to the right side of his face that damaged his eustachian tube, and prevented him from hearing the lower frequencies. Tomatis found that the ear needed to be able to tune into the high frequencies and simultaneously inhibit the lower frequencies in order to have the best audio-vocal control of the entire range. This ability involved the ability of the muscles of the middle ear to shift from a passive to an active state.

Tomatis incorporated this concept of the interchange between the two muscles of the middle ear into his first Electronic Ear and it is one of the fundamental features in the technique of re-educating the ear of his singers. 1954 Tomatis developed the gate for the electronic ear and christened it such. The gate is an electronic switch that makes it possible to switch from passive listening favorable to low frequencies to active listening, which is more favorable to high frequencies. The concept of the Gate is essential to all the listening programs I mentioned.

R ight Ear in Audio-Vocal Control Right Ear - Lead Ear Up to this point most of Tomatis' research on Audio-Vocal Control had focused on changes in the voice that occurred when you changed the auditory perception. At the same time it was observed that the responses were not identical between the two ears.

Tomatis' research led him to understand that when he altered the control mechanism of the leading ear he disturbed the spoken voice. He postulated that a directing ear played a role in Audio-Vocal Control. To look at this further he set the singers up at a microphone that would feed the singers voice back to them via two headphones, one the left ear and one to the right ear. The attenuator allowed the subjects to hear themselves either through the right ear, the left ear or both ears by changing the balance level.

For this experiment they took well known singers, known for their voice, and known for the familiarity with the piece, and known for their endurance. One of the singers they used had just finished 400 performances of the same work and every night he had done one or two encores of the same aria he was to sing during the experiment. During the experiment all the attempts were recorded. The following findings were observed:

Listening with the ear's balanced (equal for both ears) the voice was the same as when the singer was singing without any apparatus. Neither the singer nor others noted any change Suppressing the left ear, and leaving the right alone as in the controlling position, there was only slight modification. To the very trained ear, the sounds seemed lighter, more ethereal, more modulated, more precise, more distinct and the singer felt greater fluency but not necessarily observable to the general public. When this was reversed and the control and placed the left ear and eliminated in the right, the fluency vanished and all the professional qualities acquired by the singer broke down. The voice became heavy, coarse, less colorful and off pitch. Worst of all, the rhythm slowed down considerably.

The destruction of the rhythm is beyond the reach of the singer's will. In some instances it would take the person double the time normally to perform the musical phrase. He could become aware of it, if someone beats time for him, but he is incapable of following the tempo. The blockage is not limited to singing. During the experiment, the subject movements became slower, more robotic like and a diminished capacity for voluntary control. The same results were obtained when the ears were saturated with sound vs. blocking the sound as can be done with masking on an audiometer. So it wasn't lack of sound it was the cutting of control of the ear. Tomatis found the same phenomenon with the spoken voice. This time he did the same experiments with actors.