Featured Research

from universities, journals, and other organizations

New findings on the workings of the inner ear

Date:
October 2, 2012
Source:
Karolinska Institutet
Summary:
The sensory cells of the inner ear have tiny hairs called stereocilia that play a critical part in hearing. It has long been known that these stereocilia move sideways back and forth in a wave-like motion when stimulated by a sound wave. After having designed a microscope to observe these movements, a research team in Sweden has discovered that the hairs not only move sideways but also change in length.

Still image from a video showing the movements of a sensory cell of the inner ear. The sensory cell is oblong and the hairs are sticking out from the top of the cell. In reality the sensory cell moves about 200 times per second, but here the movements have been slowed down to make them visible to the human eye.
Credit: Nature Communications and Dr Anders Fridberger, Karolinska Institutet

The sensory cells of the inner ear have tiny hairs called stereocilia that play a critical part in hearing. It has long been known that these stereocilia move sideways back and forth in a wave-like motion when stimulated by a sound wave. After having designed a microscope to observe these movements, a research team at Karolinska Institutet in Sweden has discovered that the hairs not only move sideways but also change in length.

The discovery, which was made in collaboration with scientists at Baylor College of Medicine in Texas, USA provides new fundamental knowledge about the mechanisms of hearing. It is presented in the online scientific journal Nature Communications.

Before we can perceive speech, music and other sounds, the sound waves must be converted into electric impulses in the auditory nerve, a process mediated by the sensory cells of the inner ear. Previous studies revealed that sound causes a lateral movement of the tiny hairs that project from these cells that opens and closes mechanically sensitive ion channels to create the sensation of hearing.

It is impossible the study the movement of the human cilia because the sensory cells are deeply embedded in thick bone, but in guinea pigs and gerbils the inner ear is surrounded by thin bone. Using a special in-house designed microscope, the scientists have been able to observe the sound-induced ciliary motion.

"This revealed something surprising -- that the hairs not only bend sideways but also change in length," says Dr Anders Fridberger, docent and physician at the Centre for Hearing and Communication Research at Karolinska Institutet's Department of Clinical Science, Intervention and Technology. "These longitudinal changes have an important effect on the process of converting sound waves into electrical signals, which is necessary for hearing."

The scientists show that the stereocilia's ability to change length was greater when the electric potential around the sensory cells was low, which is known to happen in connection with noise damage and age-related hearing loss. The voltage drop causes the hairs to become overly soft, thus impairing ear function.

"Our findings might possibly help us understand why the ear doesn't work as well in such cases," says Dr Fridberger. "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."

The study was financed with grants from the Swedish Research Council, the Swedish Council for Working Life and social research, the Wallenberg Foundations, the Tysta Skolan (Silent School) Foundation, the Swedish Association of Hard of Hearing People and the National Institutes of Health in the USA.


Story Source:

The above story is based on materials provided by Karolinska Institutet. Note: Materials may be edited for content and length.


Journal Reference:

  1. Pierre Hakizimana, William E. Brownell, Stefan Jacob, Anders Fridberger. Sound-induced length changes in outer hair cell stereocilia. Nature Communications, 2012; 3: 1094 DOI: 10.1038/ncomms2100

Cite This Page:

Karolinska Institutet. "New findings on the workings of the inner ear." ScienceDaily. ScienceDaily, 2 October 2012. <www.sciencedaily.com/releases/2012/10/121002113414.htm>.
Karolinska Institutet. (2012, October 2). New findings on the workings of the inner ear. ScienceDaily. Retrieved July 30, 2014 from www.sciencedaily.com/releases/2012/10/121002113414.htm
Karolinska Institutet. "New findings on the workings of the inner ear." ScienceDaily. www.sciencedaily.com/releases/2012/10/121002113414.htm (accessed July 30, 2014).

Share This




More Health & Medicine News

Wednesday, July 30, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Health Insurers' Profits Slide

Health Insurers' Profits Slide

Reuters - Business Video Online (July 30, 2014) Obamacare-related costs were said to be behind the profit plunge at Wellpoint and Humana, but Wellpoint sees the new exchanges boosting its earnings for the full year. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com
Concern Grows Over Worsening Ebola Crisis

Concern Grows Over Worsening Ebola Crisis

AFP (July 30, 2014) Pan-African airline ASKY has suspended all flights to and from the capitals of Liberia and Sierra Leone amid the worsening Ebola health crisis, which has so far caused 672 deaths in Guinea, Liberia and Sierra Leone. Duration: 00:43 Video provided by AFP
Powered by NewsLook.com
At Least 20 Chikungunya Cases in New Jersey

At Least 20 Chikungunya Cases in New Jersey

AP (July 30, 2014) At least 20 New Jersey residents have tested positive for chikungunya, a mosquito-borne virus that has spread through the Caribbean. (July 30) Video provided by AP
Powered by NewsLook.com
Generics Eat Into Pfizer's Sales

Generics Eat Into Pfizer's Sales

Reuters - Business Video Online (July 29, 2014) Pfizer, the world's largest drug maker, cut full-year revenue forecasts because generics could cut into sales of its anti-arthritis drug, Celebrex. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

    Environment News

    Technology News



      Save/Print:
      Share:

      Free Subscriptions


      Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

      Get Social & Mobile


      Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

      Have Feedback?


      Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
      Mobile: iPhone Android Web
      Follow: Facebook Twitter Google+
      Subscribe: RSS Feeds Email Newsletters
      Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins