Hearing vs. the Brain and How We Process Sound

Sensory learning develops from birth in the form of taste, touch, sight, smell, and sound. Without one of these senses, the ability to combine and build upon these senses decreases. For example, as a child, when you smell freshly mowed grass you might be standing on the lawn. You’ll see the green of the grass, feel the wisps of it touching your hands or feet. You’ll hear the lawnmower or the wind in the trees.
If you are without one of these senses, such as hearing, the experience will be more difficult to fully embrace. You can see it, smell it, even touch it but if you’ve got mild to moderate hearing loss, you won’t hear the sounds around you that can add to the overall sensations you have from the experience.
As a child, the ability to process sounds in the brain develops over the course of childhood. Being exposed to different sounds builds a library of information within the brain that is associated with certain noises.
For children who are profoundly deaf, this auditory learning is restructured in a way that children utilize visual observations more fully. The ability to hear is based on a series of occurrences that the ears and brain respond to automatically and almost immediately.
When sound waves occur, they enter into the outer ear through the ear canal, a small, narrow channel that carries sound waves to the eardrum. Upon reaching the eardrum, the sound waves make the eardrum vibrate sending these vibrations to the three small bones of the middle ear; the malleus, the incus, and the stapes.
The cochlea, a snail shaped area within the inner ear is filled with fluid. The sound vibrations from the air mingle with this fluid and cause it to ripple along the basilar membrane. This membrane divides the cochlea into an upper and lower area and acts as the bottom or base for the main hearing structure to sit on.
The ripple this vibration causes moves a wave along the membrane. Sensory hairline cells called cilia sit upon the top of this basilar membrane and much like the ocean, flow along with the sound wave. When these hair cells move in an up and down motion, the stereocilia or microscopic hair rub and bend against any structures nearby.
This movement opens up the pore-type areas at the ends of the stereocilia and allows chemicals to enter the cells which creates an electrical signal. This electrical signal is then transmitted to the brain where we perceive it as a sound that we can recognize based on previous experience and respond to what we are hearing.
Sounds like the school bell ringing means it’s time for you to head to your next class of the day. A phone rings and you answer it. The dog barks and you react in various ways based on your experience and understanding of what it needs.
A study led by Dr. Lorna Halliday of the MRC Cognition and Brain Sciences Unit of the University of Cambridge, utilized the method of using an electroencephalogram (EEG) to gauge the brains responses to listening to certain sounds.
For children ages 8 to 12 years old with hearing loss, there was a similar brain response when compared with those with normal hearing. For children in the older group, ages 12-16, the responses were comparatively smaller in those with hearing loss than their hearing counterparts.
Of these two groups, the younger was retested after six years. The findings once again revealed that as children grew older, responses of the brain to sounds changed in those with hearing loss. This follow-up study revealed that there was no deterioration of the test subjects hearing loss over the timeframe involved from initial testing to follow-up.
“We know that children’s brains develop in response to exposure to sounds, so it should not be too surprising that even mild-to-moderate levels of hearing loss can lead to changes in the brain,” says Dr. Axelle Calcus, lead author of the paper, from PSL University, Paris. “However, this does suggest that we need to identify these problems at an earlier stage than is currently the case.”
“Current screening programs for newborn babies are good at picking up moderate-to-profound levels of hearing loss, but not at detecting mild hearing loss. This means that children with mild hearing impairment might not be detected until later in childhood, if at all,” says Dr. Lorna Halliday from the University of Cambridge.
“Children with hearing problems tend to do less well than their peers in terms of language development and academic performance. Detecting even mild degrees of hearing impairment earlier could lead to earlier intervention that would limit these brain changes and improve children’s chances of developing normal language.”
If you suspect that your child has a mild to moderate hearing loss, schedule an appointment with your hearing health professional today. The quicker a diagnosis is made, the quicker a treatment plan can be put into place. The longer you wait, the farther behind your child may fall in learning skills that will help them throughout life.

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