Featured Research

from universities, journals, and other organizations

Pitch-detection secrets of the inner ear revealed by research

Date:
May 20, 2014
Source:
University of Virginia Health System
Summary:
The ability to discern pitch – to hear the difference between “cat,” “bat” and “hat,” for example – hinges on remarkable gradations in specialized cells within the inner ear. New research has explained, for the first time, what controls these cells’ development and patterning – findings crucial to efforts to reverse hearing loss caused by age, loud sounds or other factors.

Scanning electron micrograph of chick embryo inner ear hair cells. The surface of the hair cells (approximately 10 microns wide) are orange with blue “hair bundles” (stereo cilia). Hair cells are each surrounded by about 6 support cells, shown in green.
Credit: Image courtesy of University of Virginia Health System

The ability to discern pitch -- to hear the difference between "cat," "bat" and "hat," for example -- hinges on remarkable gradations in specialized cells within the inner ear. New research from the University of Virginia School of Medicine and the National Institute on Deafness and Communication Disorders has explained, for the first time, what controls these cells' development and patterning -- findings crucial to efforts to reverse hearing loss caused by age, loud sounds or other factors.

The researchers have been studying the development of these cells in chickens, which, like many creatures, have a remarkable capacity humans lack: the ability to regrow the sound-detecting cells after suffering hearing loss. Jeffrey T. Corwin, PhD, of UVA's Departments of Neuroscience and Cell Biology, noted that if both a human and a hen were to be exposed to a sound loud enough to destroy the ability to hear a certain pitch, the outcomes would be very different: "We would lose the ability to hear that sound for the rest of our lives. The bird also would lose the ability, but within 10 days, it would have its cells back -- they would hook back up to the nerves, and within a few weeks its hearing would be back and almost indistinguishable from before."

Understanding that process, then, may one day allow scientists to replicate it in humans. "Eventually therapies will come about from this regenerative approach, and these new discoveries will be a critical component," Corwin said.

Detecting Pitch

Pitch detection occurs within the cochlea, a small spiral structure within the inner ear. Inside the cochlea are specialized cells, known as hair cells, which are tuned to different sound pitches based, in part, on their locations along the cochlea's spiral and the number and the length of their stereocilia -- hair-like microscopic protrusions that give the cells their name. High-pitched sounds are detected by cells with shorter hair bundles, located closest to where sound enters the ear; lower-pitched sounds are detected by cells with taller hair bundles located further in, and that pattern progresses through the several thousand hair cells that are essential for hearing. "When you hear different sounds, not every single hair cell in the cochlea is responding, only the ones that are sensitive to the specific sound frequencies," explained Benjamin R. Thiede, lead author of a paper outlining the new discovery.

Until now, scientists have not understood what orchestrates the formation of this critical pattern of individually distinct hair cells. The researchers, however, have solved that mystery, demonstrating that two specific molecules, Bmp7 and retinoic acid, guide cells to acquire location-specific attributes. Bmp7 starts the initial patterning process, and retinoic acid regulates how the cells' hair bundles grow to different lengths.

Thiede found evidence that there are different levels of retinoic acid activity along the length of the cochlea, so he tried adding more retinoic acid in cells grown in a lab dish and found that they produced longer hair bundles. Then he used a drug to block retinoic acid's activity and found that resulted in shorter bundles.

Thiede noted that when chickens regenerate damaged hair cells, the new cells develop with just the right characteristics for cells in those particular locations along the cochlea. "So the question is, are developmental signals like Bmp7 and retinoic acid involved in reestablishing the pattern of hair cells and restoring hearing to the regenerating cochlea?" he asked. "If we look at the mammalian system, which can't regenerate, are these signals lost? … Does the mammal turn off these important signals once development is completed, so they're not reactivated for regeneration?"

That's a matter for further investigation, but it suggests a tantalizing path for developing new treatments.


Story Source:

The above story is based on materials provided by University of Virginia Health System. Note: Materials may be edited for content and length.


Journal References:

  1. Zoë F. Mann, Benjamin R. Thiede, Weise Chang, Jung-Bum Shin, Helen L. May-Simera, Michael Lovett, Jeffrey T. Corwin, Matthew W. Kelley. A gradient of Bmp7 specifies the tonotopic axis in the developing inner ear. Nature Communications, 2014; 5 DOI: 10.1038/ncomms4839
  2. Benjamin R. Thiede, Zoë F. Mann, Weise Chang, Yuan-Chieh Ku, Yena K. Son, Michael Lovett, Matthew W. Kelley, Jeffrey T. Corwin. Retinoic acid signalling regulates the development of tonotopically patterned hair cells in the chicken cochlea. Nature Communications, 2014; 5 DOI: 10.1038/ncomms4840

Cite This Page:

University of Virginia Health System. "Pitch-detection secrets of the inner ear revealed by research." ScienceDaily. ScienceDaily, 20 May 2014. <www.sciencedaily.com/releases/2014/05/140520115508.htm>.
University of Virginia Health System. (2014, May 20). Pitch-detection secrets of the inner ear revealed by research. ScienceDaily. Retrieved August 1, 2014 from www.sciencedaily.com/releases/2014/05/140520115508.htm
University of Virginia Health System. "Pitch-detection secrets of the inner ear revealed by research." ScienceDaily. www.sciencedaily.com/releases/2014/05/140520115508.htm (accessed August 1, 2014).

Share This




More Health & Medicine News

Friday, August 1, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

House Republicans Vote to Sue Obama Over Healthcare Law

House Republicans Vote to Sue Obama Over Healthcare Law

Reuters - US Online Video (July 31, 2014) — The Republican-led House of Representatives votes to sue President Obama, accusing him of overstepping his executive authority in making changes to the Affordable Care Act. Mana Rabiee reports. Video provided by Reuters
Powered by NewsLook.com
Despite Health Questions, E-Cigs Are Beneficial: Study

Despite Health Questions, E-Cigs Are Beneficial: Study

Newsy (July 31, 2014) — Citing 81 previous studies, new research out of London suggests the benefits of smoking e-cigarettes instead of regular ones outweighs the risks. Video provided by Newsy
Powered by NewsLook.com
Dangerous Bacteria Kills One in Florida

Dangerous Bacteria Kills One in Florida

AP (July 31, 2014) — Sarasota County, Florida health officials have issued a warning against eating raw oysters and exposing open wounds to coastal and inland waters after a dangerous bacteria killed one person and made another sick. (July 31) Video provided by AP
Powered by NewsLook.com
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

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