Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

MIT finds new hearing mechanism

11.10.2007
Discovery could lead to improved hearing aids

MIT researchers have discovered a hearing mechanism that fundamentally changes the current understanding of inner ear function. This new mechanism could help explain the ear's remarkable ability to sense and discriminate sounds. Its discovery could eventually lead to improved systems for restoring hearing.

The research is described in the advance online issue of the Proceedings of the National Academy of Sciences the week of October 8.

MIT Professor Dennis M. Freeman, working with graduate student Roozbeh Ghaffari and research scientist Alexander J. Aranyosi, found that the tectorial membrane, a gelatinous structure inside the cochlea of the ear, is much more important to hearing than previously thought. It can selectively pick up and transmit energy to different parts of the cochlea via a kind of wave that is different from that commonly associated with hearing.

Ghaffari, the lead author of the paper, is in the Harvard-MIT Division of Health Sciences and Technology, as is Freeman. All three researchers are in MIT's Research Laboratory of Electronics. Freeman is also in MIT's Department of Electrical Engineering and Computer Science and the Massachusetts Eye and Ear Infirmary.

It has been known for over half a century that inside the cochlea sound waves are translated into up-and-down waves that travel along a structure called the basilar membrane. But the team has now found that a different kind of wave, a traveling wave that moves from side to side, can also carry sound energy. This wave moves along the tectorial membrane, which is situated directly above the sensory hair cells that transmit sounds to the brain. This second wave mechanism is poised to play a crucial role in delivering sound signals to these hair cells.

In short, the ear can mechanically translate sounds into two different kinds of wave motion at once. These waves can interact to excite the hair cells and enhance their sensitivity, "which may help explain how we hear sounds as quiet as whispers," says Aranyosi. The interactions between these two wave mechanisms may be a key part of how we are able to hear with such fidelity - for example, knowing when a single instrument in an orchestra is out of tune.

"We know the ear is enormously sensitive" in its ability to discriminate between different kinds of sound, Freeman says. "We don't know the mechanism that lets it do that." The new work has revealed "a whole new mechanism that nobody had thought of. It's really a very different way of looking at things."

The tectorial membrane is difficult to study because it is small (the entire length could fit inside a one-inch piece of human hair), fragile (it is 97 percent water, with a consistency similar to that of a jellyfish), and nearly transparent. In addition, sound vibrations cause nanometer-scale displacements of cochlear structures at audio frequencies. "We had to develop an entirely new class of measurement tools for the nano-scale regime," Ghaffari says.

The team learned about the new wave mechanism by suspending an isolated piece of tectorial membrane between two supports, one fixed and one moveable. They launched waves at audio frequencies along the membrane and watched how it responded by using a stroboscopic imaging system developed in Freeman's lab. That system can measure nanometer-scale displacements at frequencies up to a million cycles per second.

The team's discovery has implications for how we model cochlear mechanisms. "In the long run, this could affect the design of hearing aids and cochlear implants," says Ghaffari. The research also has implications for inherited forms of hearing loss that affect the tectorial membrane. Previous measurements of cochlear function in mouse models of these diseases "are consistent with disruptions of this second wave," Aranyosi adds.

Because the tectorial membrane is so tiny and so fragile, people "tend to think of it as something that's wimpy and not important," Freeman says. "Well, it's not wimpy at all." The new discovery "that it can transport energy throughout the cochlea is very significant, and it's not something that's intuitive."

This research was funded by the National Institutes of Health.

Written by David Chandler, MIT News Office

Elizabeth A. Thomson | MIT News Office
Further information:
http://web.mit.edu/newsoffice/www

More articles from Health and Medicine:

nachricht Millions through license revenues
27.04.2017 | Rheinische Friedrich-Wilhelms-Universität Bonn

nachricht New High-Performance Center Translational Medical Engineering
26.04.2017 | Fraunhofer ITEM

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Fighting drug resistant tuberculosis – InfectoGnostics meets MYCO-NET² partners in Peru

28.04.2017 | Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

 
Latest News

Wireless power can drive tiny electronic devices in the GI tract

28.04.2017 | Medical Engineering

Ice cave in Transylvania yields window into region's past

28.04.2017 | Earth Sciences

Nose2Brain – Better Therapy for Multiple Sclerosis

28.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>