Have you ever thought about auditory development and its ability to change within the brain before, during, and after birth?
Wow! Did you know that infants can hear in the womb? In 1994, researchers Peter G Hepper and B Sara Shahidullah published the study, Development of Fetal Hearing. At 19 weeks of gestational age, infants begin to move in response to low-frequency sounds at 500 Hertz. Later, responses were found at 27 weeks of gestational age to an even lower frequency of sounds at 250 Hertz. Then, development continued in mid-frequencies up to 3000 Hertz.
According to researcher Ruth Litovsky, in The Development of the Auditory System, the physical structures of the auditory system are in place at birth. However, auditory development is a life-long process dependent on the naturally occurring development of physical structures and “in response to stimulation.”
An Example of Auditory Change Within the Brain
Your attention, memory, and inherited innate cognitive abilities affect how you respond to sound. Additionally, Litovsky shares that neural plasticity enables the auditory system to adapt and change throughout one’s life experiences. For example, an infant may express delight in music. Exposure to music influences the development of the infant’s brain. When musicians practice a song, they develop muscle memory. The interactions within the sensory system are endless.
Neuroplasticity Within the Brain
Neuroplasticity is the brain’s ability to change itself. As the brain develops, it takes in what is seen, heard, smelled, tasted, and felt through chronic exposure to sensory input. Additionally, you are also affected by how your muscles and tendons interact with gravity, your proprioceptive system. Norman Doidge shared that even what you think affects your brain.
When illnesses like ear infections occur, sounds still enter your hearing system. However, the ear infection weakens the intensity of sounds traveling through your hearing system, along your auditory neural pathways to the brain. Since ear infections rarely occur in both ears, sounds fail to synch up on their way up to the brain’s processing system. According to Norman Doidge, when sound travels along auditory neural pathways out-of-synch, you have “a noisy, dysregulated nervous system.” Thus, you are at risk of developing sound sensitivities. Sound sensitivities can be the result of a noisy, dysregulated nervous system.
Norman Doidge shares fascinating insights about brain neuroplasticity in his books, The Brain’s Way of Healing, and The Brain that Changes Itself.
Intervention Regulates the Nervous System
In contrast, positive changes occur within the nervous system through therapeutic listening using iLs Auditory Integrated Listening or Berard-based Auditory Integration Training. Through the use of a comprehensive hearing evaluation, I strive to synch up sounds from both ears. Thus, sending strong sound energy stimulation along auditory neural pathways up to the brain. As auditory neural pathways strengthen, the brain changes its response to sounds. As long as there is ear health, the person experiences gradual improvements in sound tolerance.
Importance of Auditory Behavioral Characteristics
In 2011, the most important lesson I learned as I began work as an auditory integration trainer resulted in help for numerous clients. A friend and mentor, Mrs. Kathy Jones emphasized that a client’s auditory behavioral characteristics are as important as their hearing test results. Even when the exact cause of hearing loss is unknown, clients with hearing loss behavioral characteristics may benefit from hearing aids.
To help you understand, I would like to share a memory Mrs. Kathy Jones shared with me:
One day, a man who struggled to listen and learn for thirty-three years came to her practice. He shared that all his past hearing test results were normal. Nevertheless, his behavioral characteristics indicated hearing loss concerns. Thus, Kathy completed additional hearing tests. His Uncomfortable Loudness Test results and Speech in Noise test results indicated hearing loss concerns. The gentleman agreed to try hearing aids. Almost immediately after putting on hearing aids for the first time, he heard the difference. In amazement, he shared that Kathy’s speech was easier to understand. He described her speech as crisp and clear. Later, he shared numerous improvements at work, at home, and while socializing.
Kathy Harvey Jones
After hearing Kathy’s story, I began to recheck the accuracy of client’s Uncomfortable Loudness test. Using headphones and therapeutic music, I asked clients to slowly turn up the volume until music sounded too loud. Surprisingly, clients who failed to respond during the Uncomfortable Loudness Test consistently choose unsafe listening levels. What I learned prompted me to observe auditory behaviors, ask new questions, and read more research publications.
References
- Hepper, Peter G., Shahidullah, Sara B.(Sept. 1994). Development of fetal hearing. US National
Library of Medicine National Institutes of Health. Arch Dis Child Fetal Neonatal Ed.
71(2): F81-F87. Doi: 10.1136/fn.71.2.f 81. - Litovsky, Ruth (2015). Development of the auditory system. US National Library of Medicine
National Institutes of Health. Handbook Clinical Neurology. 129 (55-72).
Doi: 10.1016/B978-0-444-62630-1.00003-2.
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