Featured Research

from universities, journals, and other organizations

Novel laser technique reveals how the inner ear amplifies sound

Date:
December 11, 2012
Source:
American Hearing Research Foundation
Summary:
Researchers have described how the ear amplifies incoming sound using an innovative laser technique.

It has long been known that the inner ear actively amplifies sounds it receives, and that this amplification can be attributed to forces generated by outer hair cells in the cochlea. How the ear actually accomplishes this, however, has remained somewhat of a mystery. Now, Jonathan A. N. Fisher, PhD, and colleagues at The Rockefeller University, in New York, describe how the cochlea actively self-amplifies sound it receives to help increase the range of sounds that can be heard.

The results of their research were published in the Dec. 6, 2012 issue of Neuron. The cover shows the study animal the researchers used to investigate amplification in the inner ear- the chinchilla. This animal is often used for hearing-related research because of the similarity it has with humans in terms of hearing and the structure of its inner ear.

Dr. Fisher received a grant for this research from the American Hearing Research Foundation in 2011.

Fisher and colleagues used a new optical technique that inactivates prestin, a motor protein involved in the movement of the outer hair cells. The outer hair cells are part of the hair cell bundles (which also include the inner hair cells)- the true sensory cells of the inner ear. The main body of the hair cells sits in the basilar membrane- the tissue that lines the interior of the bony cochlea. The "hair" part of these cells, called the stereocilia, sticks up into the fluid-filled space of the cochlea, where they are pushed by the fluid as sound waves travel through it.

The sound waves traveling down the cochlea produce actual waves that can be observed along the basilar membrane as visualized in the animation below (from the Howard Hughes Medical Institute). The cochlea picks up different sound frequencies along its length, with higher frequency sounds picked up at center of the "snail" and the lower frequency sounds being picked up at the part of the cochlea closest to the eardrum.

The outer hair cells have been known to provide amplification of sound waves picked up by the inner hair cells by actively changing their shape to increase the amplitudes of the sound waves. These outer hair cells can do this because the membrane protein can contract and cause the stereocillia to be deflected by the overlying tectorial membrane.

Fisher and colleagues developed a light-sensitive drug that when illuminated by an ultraviolet laser can inactivate prestin in select locations within the cochlea. Using this novel technique, the researchers were able to affect prestin at very specific locations along the basilar membrane.

The researchers found that by inactivating prestin at very specific locations, the sound-evoked waves that carry mechanical signals to sensory hair cells were re-shaped and of smaller amplitude- indicating that without prestin, amplification is dampened compared to what the researchers saw when prestin was allowed to function normally. Their findings reveal how prestin's molecular forces pump energy into the waves within the cochlea, and how this energy is pushed forward as the wave travels. The research also demonstrates the importance of prestin in locally amplifying these sound evoked traveling waves.


Story Source:

The above story is based on materials provided by American Hearing Research Foundation. Note: Materials may be edited for content and length.


Journal Reference:

  1. JonathanA.N. Fisher, Fumiaki Nin, Tobias Reichenbach, RevathyC. Uthaiah, A.J. Hudspeth. The Spatial Pattern of Cochlear Amplification. Neuron, 2012; 76 (5): 989 DOI: 10.1016/j.neuron.2012.09.031

Cite This Page:

American Hearing Research Foundation. "Novel laser technique reveals how the inner ear amplifies sound." ScienceDaily. ScienceDaily, 11 December 2012. <www.sciencedaily.com/releases/2012/12/121211130214.htm>.
American Hearing Research Foundation. (2012, December 11). Novel laser technique reveals how the inner ear amplifies sound. ScienceDaily. Retrieved April 17, 2014 from www.sciencedaily.com/releases/2012/12/121211130214.htm
American Hearing Research Foundation. "Novel laser technique reveals how the inner ear amplifies sound." ScienceDaily. www.sciencedaily.com/releases/2012/12/121211130214.htm (accessed April 17, 2014).

Share This



More Health & Medicine News

Thursday, April 17, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Could Even Casual Marijuana Use Alter Your Brain?

Could Even Casual Marijuana Use Alter Your Brain?

Newsy (Apr. 16, 2014) A new study conducted by researchers at Northwestern and Harvard suggests even casual marijuana use can alter your brain. Video provided by Newsy
Powered by NewsLook.com
Thousands Of Vials Of SARS Virus Go Missing

Thousands Of Vials Of SARS Virus Go Missing

Newsy (Apr. 16, 2014) A research institute in Paris somehow misplaced more than 2,000 vials of the deadly SARS virus. Video provided by Newsy
Powered by NewsLook.com
Formerly Conjoined Twins Released From Dallas Hospital

Formerly Conjoined Twins Released From Dallas Hospital

Newsy (Apr. 16, 2014) Conjoined twins Emmett and Owen Ezell were separated by doctors in August. Now, nearly nine months later, they're being released from the hospital. Video provided by Newsy
Powered by NewsLook.com
Ebola Outbreak Now Linked To 121 Deaths

Ebola Outbreak Now Linked To 121 Deaths

Newsy (Apr. 15, 2014) The ebola virus outbreak in West Africa is now linked to 121 deaths. Health officials fear the virus will continue to spread in urban areas. Video provided by Newsy
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