top of page
Valentina Carlile Osteopata
  • Instagram
  • Facebook
  • Writer's pictureValentina Carlile DO

Osteopathy and Voice - Impact of the auditory system on phonation


Osteopathy and Voice - Impact of the auditory system on phonation

The auditory system is believed to be a critical component in the development and maintenance of excellent and precise vocal quality. Subjects with profound hearing impairment or total deafness may have compromised voice quality, as well as other more frequent resonance and speech anomalies.

The production of speech begins in the brain with a premotor process that involves the integration of various types of information: auditory somatosensory and motor.

This information is located in the temporal, parietal, and frontal lobes, including areas of the brain specialized for speech, such as Broca and Wernicke, and other areas.

The premotor process consists of three general phases:

  • the production of an idea

  • the transformation into words

  • the syllabification or production of the sounds necessary to make each of the words sound.

After this process, the joint is created through three paths:

  • the key cerebellar motor neural pathway

  • pyramidal

  • descending traits.

These extrapyramidal tracts organize synapses in the medulla, where they control muscles involved in speech such as those of the tongue, lips, and larynx. Complex activities involving the larynx and vocal tract that result in phonation are known.

The auditory feedback system is thought to have three roles that serve to provide feedback on environmental conditions that may influence the quality of speech production and that contribute to the generation of internal models for the production of speech motor plans:

  1. The first role of feedback is important for corrections in pitch, volume, and other attributes that can affect speech understanding.

  2. The second role, important for example in noisy situations, so that the speaking subject can enunciate his speech more clearly, is to increase the amplitude and reduce the speed of speech to increase intelligibility.

  3. The third role is essential for maintaining a rapid reading speed through the development of internal models allowing the vocal tract and its related structures to be prepared before vocalizing and for continued speech without constant auditory feedback.

The precommand phase uses internal models to control speech rate and voice without dependence on real-time auditory feedback. Given the rapid speed of normal speech, it would be impossible for feedback to work and correct by implementing each strategy before each new segment of speech if the same speed must also be maintained.

The pre-control solves this problem by also allowing people to speak fluently and to perform comfortable speech production even if deafened or in loud noise. This system is used by singers who, when performing with orchestras or choirs, mask auditory feedback, for example.

DEAF PEOPLE

Hearing loss provides a clear, albeit extreme, example of the importance of hearing in phonation and speech. The voice changes in those who have severely damaged hearing are great, with alterations in breathing, phonation, and articulation.

BREATHING - The lungs provide the airflow that allows the vocal cords to oscillate. The chest contributes to the production of this airflow. The respiratory system also plays a control role through modulation of expiratory pressures which can increase or decrease the note.

Some scholars have demonstrated that, despite the presence of normal and healthy lung function, children with profound bilateral sensorineural deafness (SNHL) have a significantly lower vital capacity and greater sustained phonation compared to normal hearing children. The reduction in vital capacity leads these children with smaller lung volumes to use compensations for vocal production.

Smaller lung volumes force people to take more pauses during speech: as a result they are unable to produce the normal amount of syllables per breath or sustain a song string for as long as they normally would.

Maximum sustainable phonation reduction is a measure of the individual's ability to effectively manage air supply during speech production. These breathing problems combined lead to changes in pausing patterns during speech with the overall effect of a decrease in speech intelligibility.

PHONATION - Much of the literature on deaf people and voice production focuses on phonation.

Some scholars have found that in these subjects there is an uncoordinated contraction-relaxation phase of the intrinsic and extrinsic laryngeal muscles. They found a significant reduction in adduction velocity in children with profound bilateral SNHL compared to normal hearing children. From these findings, the authors concluded that people with SNHL have difficulties controlling subglottic pressure and vocal fold tension, and these difficulties affect phonation.

Other researchers studied the fundamental frequency (F0) and its variability in 40 postlingually deaf adults, before and after cochlear implant (CI). Although these individuals have internal motor models based on their previous hearing experience, there was still a significant difference in phonation without feedback control of the auditory system. Specifically, there was a significant reduction in fundamental frequency (in males) and a significant reduction in frequency variation during sustained vocal production (in both sexes) after CI compared to their performance before CI. However, once these results were compared to the no-CI control group at both time periods, only the variability in males remained statistically significant. The reduction in variation with sustained speech production after CI demonstrated that, with auditory feedback, subjects can control their voices better and with less frequency variation.

Another group of scholars studied 21 children, 7 prelingually deaf children with cochlear implants and 14 children with normal hearing and their ability to sing appropriately. Each child sang a song, and the fundamental frequencies of each note were analyzed. Although there was no difference between the two groups in terms of rhythm, the children with CI performed significantly poorer in terms of timing accuracy.

Children with CI had a mean deviation of time intervals of 2.86 semitones compared to those with normal hearing and with significant deviation of only 1.51 semitones.

Despite this deficit in tone, scholars have given an opinion on the difficulty of singing in children with CI, also considering the obstacles caused by imperfect information about the tempo provided by the CI. Scholars have hypothesized that deficits in singing skills are the result of poor on-field discrimination skills in children with CI.

ARTICULATION - The unique shape of each individual's vocal tract creates vocal individuality and affects audibility. Changes to the voice can be made by changing the position of the tongue and soft palate and the shape of the pharynx. It is known that these adjustments are generally made based on auditory feedback.

Among the investigators, Das and his team found that children with profound bilateral SNHL have more nasal voices than those with normal hearing. Hypernasality is caused by incomplete closure of the velopharyngeal sphincter during speech production. The additional escape of air causes a more rapid reduction in the volume of air and this in turn leads to anomalous pauses during speech.

Studies carried out on men and women after cochlear implantation have, however, demonstrated a reduction in hypernasality. In these cases it was hypothesized that the cause of hypernasality was the result of poor velopharyngeal control and that this in turn depended on the lack of auditory feedback during speech production.

AUDITORY DISCRIMINATORY ABILITIES

Several studies have examined the topic of better hearing and better voice by examining auditory discrimination abilities and vocal accuracy. All subjects with superior hearing abilities were found to have more accurate speech production.

INTERNAL MODEL

The internal model is a neural pathway for motor patterns that underlies speech production and that allows the interface of the note output and the neural motor patterns that control the voice muscles creating the note.

The production of these internal models relies on auditory feedback. Control of the fundamental frequency depends on both the internal model and auditory feedback. A comparative study between a group of musician singers and a group of non-musicians showed that the non-musicians were less accurate than the musician singers but that both groups recruited used similar neural areas: bilateral auditory areas, primary motor and premotor areas , right insula area in the dorsal half, somatosensory areas, thalamus, and cerebellum. In the singing study when participants were asked to ignore auditory feedback, musician singers were more accurate than non-musicians. The latter had statistically greater neural activity in the supramarginal gyrus and in the mouth region of the primary motor cortex. In musician singers there was significantly greater neural activity in the bilateral auditory cortex and left putamen compared to non-musicians.

The involvement of the putamen in musical singers indicates that they are using a developed and ingrained vocal motor program to perform the activity of singing. The researchers explained this by the fact that it is the dorsal premotor cortex that acts as the basic interface of the two systems, but with the formation of the auditory cortex, putamen and anterior cingulate cortex these are recruited to monitor their auditory feedback more sensitively.

PROFESSIONAL SINGING

Professional singing is based on precision intonation and excellent control of the fundamental frequency (F0). During normal speech, note targets are relative to one's amplified voice, but in singing, targets are absolute notes with fundamental frequencies that should match almost exactly the musical notes being played. Auditory feedback becomes more critical and fundamental as the technical difficulty of the performance increases.

Vocal training has an effect on the neuromuscular control of the larynx, so that the note produced is accurate and consistent.

Training in instrumental music allows for an advanced auditory perception-laryngeal musculature relationship.

1 view0 comments

Recent Posts

See All

Comments


bottom of page