Posted on Monday, June 18, 2012

Hearing Health News

Photo: Anna Lysakowski with Robstein Chidavaenzi

Researchers at the University of Illinois at Chicago College of Medicine have discovered the hair cells of the inner ear have a previously unknown "root" extension. This root may be responsible for allowing hair cells to communicate with the brain. The brain plays essential parts in hearing and regulating head position. This finding, reported online in advance of print in the Proceedings of the National Academy of Sciences could help advance hearing health and hearing loss treatments.

Photo: Anna Lysakowski with Robstein Chidavaenzi

Discovery of Hair-Cell Roots Suggests the Brain Modulates Sound Sensitivity

Inside the ear are delicate hair-like structures, called stereocilia. When you move your head, or when a sound vibration enters your ear, motion of fluid in the ear causes the tips of these hair to get displaced and stretched, opening up channels which can then relay information to the brain, says Anna Lysakowski, professor of anatomy and cell biology at the UIC College of Medicine and principal study investigator.

Lysakowski and her colleagues did research on a part of the hair-like structure called the striated organelle, which is believed to be responsible for its stability. Florin Vranceanu, a recent doctoral student in Lysakowski's lab, was able to use a high tech imagining microscope from the University of California in San Diego to construct a picture of unknown aspects of this hair cell.

"When I saw the pictures, I was amazed," said Lysakowski.

Hair Cell and RootsHair Cell and RootsTextbooks, she said, describe the roots one way, ending bluntly in the cuticle palate, but the new pictures showed that the roots continue through, make a sharp 110-degree angle, and extend all the way to where they connect with the striated organelle.

Researchers have known for some time that hearing and the brain work together. Prior research has shown that lack of stimulation from untreated hearing loss can negatively impact the brain and lead to increased risk of dementia and Alzheimer's. This new hearing health news, for Lysakowski, suggest a new way to envision how hair cells work with the brain. Just as the brain adjusts the sensitivity of retinal cells in the eye to light, it may also modulate the sensitivity of hair cells in the inner ear to sound and head position.

When the eye detects light, there is feedback from the brain to the eye. "If it's too bright the brain can say, okay, I'll detect less light -- or, it's not bright enough, let me detect more," Lysakowski said. This new finding suggest the brain works subtly to increase or diminish sound in a way similar to how it perceives light.

With the striated organelle connecting the rootlets to the cell membrane, it creates the possibility of feedback from the cell to the very detectors that detect motion. Feedback from the brain could alter the tension on the rootlets and thereby their sensitivity to stimuli. In other words, the ties between the brain and hearing might be even more intricate and involved than previously thought. Knowledge of this kind can help researchers as they develop new ways to treat hearing loss and understand the complex nature of hearing.

"This may revolutionize the way we think about the hair cells in the inner ear," Lysakowski said.

The study was supported by the grants from the National Institutes of Deafness and other Communication Disorders, the American Hearing Research Foundation, the National Center for Research Resources, and the 2008 Tallu Rosen Grant in Auditory Science from the National Organization for Hearing Research Foundation.

Thanks to Dr. Lysakowski for allowing us to reprint this exciting article. Hearing health news continues to advance knowledge and open up new treatments for hearing loss. Already studies are showing how essential hearing is to the proper function of the brain as people age. If you haven't treated your hearing loss yet and want to find out how the latest news on hearing health has advanced hearing loss technology, talk to your audiologist.

*Reprinted articles may have been edited for tone and content.

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