TUM – Technical University of Munich Menu
Prof. Werner Hemmert, director of the department for Bio-Inspired Information Processing at the TUM - Photo: Astrid Eckert/TUM
Prof. Werner Hemmert, director of the department for Bio-Inspired Information Processing at the TUM - Photo: Astrid Eckert/TUM
  • Research news

Computer models of neuronal sound processing in the brain lead to cochlear implant improvementsUnderstanding hearing

Children learning to speak depend on functional hearing. So-called cochlear implants allow people with severe hearing loss to hear again by stimulating the auditory nerve directly. Researchers at the Technische Universität München (TUM) are working to overcome current limits of the technology. They are investigating the implementation of signals in the auditory nerve and the subsequent neuronal processing in the brain. Using the computer models developed at the TUM manufacturers of cochlear implants improve their devices.

Intact hearing is a prerequisite for learning to speak. This is why children who are born deaf are fitted with so-called cochlear implants as early as possible. Cochlear implants consist of a speech processor and a transmitter coil worn behind the ear, together with the actual implant, an encapsulated microprocessor placed under the skin to directly stimulate the auditory nerve via an electrode with up to 22 contacts.

Adults who have lost their hearing can also benefit from cochlear implants. The devices have advanced to the most successful neuroprostheses. They allow patients to understand the spoken word quite well again. But the limits of the technology are reached when listening to music, for example, or when many people speak at once. Initial improvements are realized by using cochlear implants in both ears.

A further major development leap would ensue if spatial hearing could be restored. Since our ears are located a few centimeters apart, sound waves form a given source generally reach one ear before the other. The difference is only a few millionths of a second, but that is enough for the brain to localize the sound source. Modern microprocessors can react sufficiently fast, but a nerve impulse takes around one hundred times longer. To achieve a perfect interplay, new strategies need to be developed.

Modeling the auditory system

The perception of sound information begins in the inner ear. There, hair cells translate the mechanical vibrations into so-called action potentials, the language of nerve cells. Neural circuitry in the brain stem, mesencephalon and diencephalon transmits the signals to the auditory cortex, where around 100 million nerve cells are responsible for creating our perception of sound. Unfortunately, this “coding” is still poorly understood by science.

“Getting implants to operate more precisely will require strategies that are better geared to the information processing of the neuronal circuits in the brain. The prerequisite for this is a better understanding of the auditory system,” explains Professor Werner Hemmert, director of the Department for Bio-Inspired Information Processing, at the TUM Institute of Medical Engineering (IMETUM).

Based on physiological measurements of neurons, his working group successfully built a computer model of acoustic coding in the inner ear and the neuronal information processing by the brain stem. This model will allow the researchers to further develop coding strategies and test them in experiments on people with normal hearing, as well as people carrying implants.

The fast track to better hearing aids

For manufacturers of cochlear implants collaborating with the TUM researchers, these models are very beneficial evaluation tools. Preliminary testing at the computer translates into enormous time and cost savings. “Many ideas can now be tested significantly faster. Then only the most promising processes need to be evaluated in cumbersome patient trials,” says Werner Hemmert. The new models thus have the potential to significantly reduce development cycles. “In this way, patients will benefit from better devices sooner.”

Video on cochlea implant research of Prof. Hemmert's group (YouTube)

 

Publication:

The working group reports on its work in the newly published book, “The Technology of Binaural Listening,” which will be presented at the 166th conference of the Acoustical Society of America in San Francisco (2nd – 6th December 2013).

M. Nicoletti, C. Wirtz, W. Hemmert: Modeling Sound Localization with Cochlear Implants, The Technology of Binaural Listening, Springer-Verlag Berlin Heidelberg, 2013

Contact:

Prof. Dr.-Ing. Werner Hemmert
Technische Universität München
Institute for Medical Engineering (IMETUM)
Boltzmannstr. 11, 85748 Garching, Germany
Tel.: +49 89 289 10853E-MailInternet

Corporate Communications Center

Technical University of Munich Dr. Andreas Battenberg
battenberg(at)zv.tum.de

Article at tum.de

Prof. Dr. Werner Hemmert and Dr. Siwei Bai have developed a computer model which predicts the neuronal activation patterns that cochlea implants create in the auditory nerve.

Research towards improved cochlear implants

Cochlear implants restore hearing in deaf people to an amazingly high level. In order to optimize such implants, researchers at the Technical University of Munich (TUM) have developed a computer model which predicts the...

Eine Illustration von Tyrannosaurus Rex.

Hearing like a dinosaur

Alligators use neural maps to localize the source of a sound the same way birds do, as Dr. Lutz Kettler of the Technical University of Munich (TUM) and Prof. Catherine Carr of the University of Maryland have determined in a...

Ein luftgefüllter Kanal verbindet die Ohren der Eidechse im Inneren und ermöglicht ihr das Richtungshören – Bild: Frieder Mugele, Universität Twente

A tunnel through the head

Humans as well as most other land-living vertebrates use the time delay between the arrival of a sound wave at each ear to discern the direction of the source. In frogs, lizards and birds the distance between the ears is...

What happens in our brain when we unlock a door?

People who are unable to button up their jacket or who find it difficult to insert a key in lock suffer from a condition known as apraxia. This means that their motor skills have been impaired – as a result of a stroke, for...

An Fledermäusen der Art "Kleine Lanzennase" untersuchte das Team von Dr. Uwe Firzlaff die räumliche Orientierung.

Zooming in for a safe flight

Bats do not use sight to navigate when flying. Instead, they emit ultrasound pulses and measure the echoes reflected from their surroundings. They have an extremely flexible internal navigation system that enables them to...