The auditory process of transmitting and interpreting sound is an intimate procedure that is seldom appreciated for how incredible it truly is. We all may somewhat comprehend the overall gist of how sound is transferred; sound waves vibrating through the air, reaching the outer ear, being channeled through various tubes and bones until it is transported to the brain, but even when you try to truly grasp the concept, the act of hearing still sounds unfathomable. What could be even more complex is how the brain is taught to learn, interpret and understand sounds, a subject that was recently explored in an extensive research study.

Scientists from the University of Pittsburgh School of Medicine analyzed the developmental process of how the brain actually learns how to hear. In an attempt to map neural connectivity between the inner workings of the ear and the brain, the researchers examined how precise rhythms of electrical impulses eventually are transmitted from thousands of tiny hair cells in the middle ear region, which in turn help coach the brain precisely “how” to hear.

To test their theory, the colleagues used laboratory mice, inspecting their brains and auditory pathways to see exactly how sound is able to trigger the nerve cells and generate an electrical impulse sent to the brain. Mice are actually born without the ability to hear, and their auditory development starts to begin around two weeks after birth. Before their brains can even process hearing, their ears are already producing rhythmic bursts of electrical activity, which in turn starts to stimulate the brain’s auditory processing centers. During this time, these rhythmic bursts produce a steady beat, which provides a consistent connection for the brain to organize its auditory cortex.

The researchers then tested what happens to the mice’s auditory development when that rhythmic beat is altered, discovering that the neural connectivity between the ear and brain gets off task, resulting in potential hearing loss disorders.

Dr. Karl Kandler, a professor at the University of Pittsburgh and senior investigator in the study, explained how important it is for the ears to maintain these patterned bursts that help shape the inner hair cells in the cochlea, assisting the brain in processing sound.

“In normal mice, the wiring diagram of the brain gets sharper and more efficient over time and they begin to hear,” Kandler said in a statement. “But this doesn’t happen when the inner ear beats in a different rhythm, which means the brain isn’t getting the instructions it needs to wire itself correctly. Our findings suggest that an abnormal rhythm of electrical impulses early in life may be an important contributing factor in the development of CAPD (Central Auditory-Processing Disorders).”

The potential to curve hearing loss
The implications of the team’s research could provide a clue into how hearing loss is developed at an early age for humans. There are currently an estimated 2 to 3 percent of children in the United States that are affected with CAPD, a auditory condition that can often result in the need for hearing aids. If further testing is able to uncover how to get these rhythmic bursts back on track once they have been altered offbeat, auditory development could be restored and severe hearing loss could potentially be avoided. The ability to restore consistency in the origins of auditory electric activity could also allow other learning disabilities to be prevented, such as speech impairment or dyslexia. Time will tell whether or not audiologists will possess these capabilities, but in the mean time, frequent hearing screenings are a primary source for detecting auditory damage at a young age.

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