October 3, 2012
Researchers Look To Understand How The Inner Ear Works
Michael Harper for redOrbit.com — Your Universe Online
The workings of the inner ear have been long thought to be well documented and understood. Previous research has found that tiny hairs, known as stereocilia, are attached to sensory cells in the inner ear and move side to side with the reverberations of sound, transferring this sound into the ear, where it is then picked up and translated by the brain.
In an effort to better understand these movements and how they are interpreted by the brain, a research team at the Karolinska Institutet in Sweden used a tiny, specially designed microscope to observe this behavior. Now, these researchers are saying these hairs not only wave from side to side, they can also change in length in cases of impaired hearing. One common cause of this inner-ear hair growth? Old age.
Working in collaboration with scientists from the Baylor College of Medicine in Texas, these researchers discovered new revelations about the way the ear can hear sound. Their research is now presented in the online scientific journal Nature Communications.
In order to “hear” these sounds, the reverberations and waves must first be converted in electronic impulses in the auditory nerve. This process is helped along by the sensory cells in the inner ear. According to prior research, this back and forth movement of the stereocilia open and close these sensitive ion channels in the ear, translating these waves into sound.
These sensory cells in humans are buried deep in thick bones, making the observation of this behavior a difficult chore. In Guinea pigs and gerbils, however, these cells are locked away in a thin layer of bone, giving these researchers an easier way with which to study the phenomenon. Using a specially developed microscope, the researchers studied the stereocilia cells on these animals instead, with some surprising results.
“This revealed something surprising“¦that the hairs not only bend sideways but also change in length,” said Dr. Anders Fridberger, a physician at the Centre for hearing and Communication Research at Karolinska Institutet´s Department of Clinical Science.
“These longitudinal changes have an important effect on the process of converting sound waves into electrical signals, which is necessary for hearing.”
According to their observations, these stereocilia hairs grew longer when the electronic potential of these sensory cells was low. These cells can lose electronic potential in cases of old age or other forms of hearing loss. As these hairs become softer, the ability with which their able to pick up on electronic singles decreases.
“Our findings might possibly help us understand why the ear doesn´t work as well in such cases,” said Dr. Fridberger, according to a press release.
“And maybe one day they can be put to use in the development of a new treatment for impaired hearing. If we can use a drug to restore the cilia´s normal stiffness we could make the ear work better, but this is something for the distant future, if it is even possible. What we must do now is to discover the exact mechanism that controls ciliary stiffness.”