Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Hearing the light: how artificial hearing could become more natural


Researchers at the University Medical Center Göttingen (UMG) and the German Primate Center – Leibniz Institute for Primate Research (DPZ) are demonstrating improved frequency resolution of artificial hearing using optical stimulation of the inner ear. Publication in Nature Communications.

In a recently published study, scientists led by Prof. Tobias Moser, Director of the Institute for Auditory Neuroscience at the University Medical Center Göttingen (UMG) and Head of the Auditory Neuroscience and Optogenetics research group at the German Primate Center – Leibniz Institute for Primate Research (DPZ), have characterized the spectral resolution of natural and artificial hearing.

Reconstruction of the inner ear of a Mongolian gerbil with cochlea and vestibular apparatus.

FIGURE: Carlos Duque-Afonso, Institute for Auditory Neuroscience

In Mongolian gerbils, they compared optogenetic excitation of the auditory nerve – a technique which was recently developed in Göttingen – with acoustic hearing and with clinically used electrical stimulation of the auditory nerve.

To stimulate the auditory nerve optically, light-sensitive ion channels were introduced into the nerve cells of the inner ear using viral gene transfer. By studying neuronal activity in the midbrain, the spectral resolution of acoustic, optical and electrical hearing was compared.

The results demonstrate that the artificial excitation of the auditory pathway by light allows a much higher spectral resolution than the excitation by electric current. At low levels of activity in the midbrain, the spectral resolution was even as good as that of acoustic hearing.

These results spur hope that future optical cochlear implants will improve the ability of hearing impaired to hear more naturally, improve speech understanding in noise and music perception.

Original publication:
Dieter A, Duque-Afonso CJ, Rankovic V, Jeschke M, Moser T (2019): Near physiological spectral selectivity of cochlear optogenetics. Nature Communications (doi: 10.1038/s41467-019-09980-7).


Hearing is more than just the perception of acoustic signals from our surroundings which facilitate our daily navigation in everyday life: it forms the basis for communication and thus enables us to exchange information with our fellow human beings and actively participate in social life. For many of the approximately 460 million people affected worldwide, a hearing impairment or even deafness means not only the inability to perceive acoustic signals, but also social isolation and the resulting impairment of quality of life. Hearing impairment is often caused by the loss of hair cells in the cochlea of the inner ear, which in normal hearing people convert the sound waves of acoustic signals into electrical signals that are then sent to the brain via the auditory nerve.

Up to today, hearing prostheses, so-called cochlear implants (CI), are used to restore hearing in people with severe hearing loss or deafness. These CIs are inserted into the cochlea and stimulate the auditory nerve using electrical current. Cochlear implants provide more than 500,000 patients worldwide with an artificial sense of hearing, which in the majority of cases enables open speech understanding. However, electrical CIs are limited in the precise transmission of fine gradations of pitch (frequency). For CI users, this means e.g. difficulties in speech perception in environments with background noise and in recognizing melodies. The limited spectral resolution of today's cochlear implants is caused by the relatively wide spread of electrical current in the cochlea. This activates large sections of the auditory nerve at the same time, hampering the representation of different pitches by artificial hearing. The problem can nicely be illustrated by a piano: "While natural hearing can follow pressing individual keys, the sound perception by means of a cochlear implant is more comparable to simultaneously pressing many piano keys. In order to restore more natural hearing, it has to be possible to distinguish between individual pitches," explains Tobias Moser. This could be achieved by stimulating the auditory nerve with light: "Since light can be focused better than electric current, it allows more precise stimulation of the auditory nerve.” Together with his Göttingen team and cooperation partners, Moser is pursuing the development of optical cochlear implants. Since the auditory nerve is not light-sensitive, genetically encoded light sensors have to be inserted into the neurons of the auditory nerve. This approach, known as optogenetics, was developed recently in deafened rodents whose auditory pathway was subsequently stimulated by light to restore hearing. However, the question of spectral resolution remained largely unaddressed.

In their latest study, the researchers around Professor Moser have now characterized the spectral resolution of the optogenetic excitation of the auditory nerve and compared it to the frequency resolution of electrical and acoustic stimulation. While the inner ear of the Mongolian gerbils was stimulated optically, electrically, or acoustically, the researchers recorded neuronal activity in the auditory midbrain. The spectral resolution of the different excitation modes was determined by an activity-based analysis of the excitation width. The results show that the frequency resolution of artificial hearing can be significantly improved by optical compared to electrical stimulation. At low and moderate levels of activity, the frequency resolution of optogenetic excitation was indistinguishable from the resolution of acoustic stimulation. "Our results demonstrate for the first time that the spectral resolution of optogenetic stimulation of the auditory nerve is higher than the electrical stimulation used clinically," says Alexander Dieter, PhD student at the Institute of Auditory Neuroscience and first author of the study: "This lets us hope that the restoration of hearing with a future optical cochlear implant will enable patients to hear more naturally.”

Before optogenetic hearing restoration can be tested in clinical trials on patients, how-ever, many more studies need to be conducted. "A logical next step is to extend single-channel stimulation, as in the current study, to multi-channel stimulation using, for example, microLED arrays," says Marcus Jeschke, head of a junior research group at the DPZ and one of the senior authors of the study. "We hope to use these to investigate whether the activations of LEDs located close to each other can be discriminated and how and whether the activations of the individual LEDs interact," continues Jeschke. "If future experiments in marmoset monkeys confirm our results, and the biosafety of our technology can be demonstrated, we have great hope that optical cochlear implants will also work in humans.”

The scientists are still a long way from their goal of an improved cochlear implant for the hearing impaired, but the demonstration of improved frequency resolution in the rodent model is an important milestone on this path. Preclinical research was supported by the "OptoHear" project of the European Research Council.

FIGURE: Spread of neural activity in the auditory midbrain for acoustic (top), optical (mid) and electrical (bottom) stimulation of different strength. Activity (from low: blue to strong: yellow) upon different stimulation levels (horizontal axis) spreads little (area covered along the vertical axis) for acoustic and optical stimulation: high spectral resolution. In contrast, activity spreads massively for electrical stimulation: low spectral resolution. Figure by Alexander Dieter, Institute for Auditory Neuroscience/umg

University Medical Center Göttingen
Prof. Dr. Tobias Moser
Institute for Auditory Neuroscience and InnerEarLab
Telefon +49 (0)551 / 39-63070; Email:

Wissenschaftliche Ansprechpartner:

University Medical Center Göttingen
Prof. Dr. Tobias Moser
Institute for Auditory Neuroscience and InnerEarLab
Telefon +49 (0)551 / 39-63070; Email:


Dieter A, Duque-Afonso CJ, Rankovic V, Jeschke M, Moser T (2019): Near physiological spectral selectivity of cochlear optogenetics. Nature Communications (doi: 10.1038/s41467-019-09980-7).

Stefan Weller | idw - Informationsdienst Wissenschaft
Further information:

More articles from Life Sciences:

nachricht Super salty, subzero Arctic water provides peek at possible life on other planets
12.07.2019 | University of Washington

nachricht The nucleolus – a known organelle with new tasks
12.07.2019 | Max-Planck-Institut für Biochemie

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Artificial neural network resolves puzzles from condensed matter physics: Which is the perfect quantum theory?

For some phenomena in quantum many-body physics several competing theories exist. But which of them describes a quantum phenomenon best? A team of researchers from the Technical University of Munich (TUM) and Harvard University in the United States has now successfully deployed artificial neural networks for image analysis of quantum systems.

Is that a dog or a cat? Such a classification is a prime example of machine learning: artificial neural networks can be trained to analyze images by looking...

Im Focus: Extremely hard yet metallically conductive: Bayreuth researchers develop novel material with high-tech prospects

An international research group led by scientists from the University of Bayreuth has produced a previously unknown material: Rhenium nitride pernitride. Thanks to combining properties that were previously considered incompatible, it looks set to become highly attractive for technological applications. Indeed, it is a super-hard metallic conductor that can withstand extremely high pressures like a diamond. A process now developed in Bayreuth opens up the possibility of producing rhenium nitride pernitride and other technologically interesting materials in sufficiently large quantity for their properties characterisation. The new findings are presented in "Nature Communications".

The possibility of finding a compound that was metallically conductive, super-hard, and ultra-incompressible was long considered unlikely in science. It was...

Im Focus: Modelling leads to the optimum size for platinum fuel cell catalysts: Activity of fuel cell catalysts doubled

An interdisciplinary research team at the Technical University of Munich (TUM) has built platinum nanoparticles for catalysis in fuel cells: The new size-optimized catalysts are twice as good as the best process commercially available today.

Fuel cells may well replace batteries as the power source for electric cars. They consume hydrogen, a gas which could be produced for example using surplus...

Im Focus: The secret of mushroom colors

Mushrooms: Darker fruiting bodies in cold climates

The fly agaric with its red hat is perhaps the most evocative of the diverse and variously colored mushroom species. Hitherto, the purpose of these colors was...

Im Focus: First results of the new Alphatrap experiment

Physicists at the Max Planck Institute for Nuclear Physics in Heidelberg report the first result of the new Alphatrap experiment. They measured the bound-electron g-factor of highly charged (boron-like) argon ions with unprecedented precision of 9 digits. In comparison with a new highly accurate quantum electrodynamic calculation they found an excellent agreement on a level of 7 digits. This paves the way for sensitive tests of QED in strong fields like precision measurements of the fine structure constant α as well as the detection of possible signatures of new physics. [Physical Review Letters, 27 June 2019]

Quantum electrodynamics (QED) describes the interaction of charged particles with electromagnetic fields and is the most precisely tested physical theory. It...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

2nd International Conference on UV LED Technologies & Applications – ICULTA 2020 | Call for Abstracts

24.06.2019 | Event News

SEMANTiCS 2019 brings together industry leaders and data scientists in Karlsruhe

29.04.2019 | Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

Latest News

Hubble discovers mysterious black hole disc

12.07.2019 | Physics and Astronomy

Super salty, subzero Arctic water provides peek at possible life on other planets

12.07.2019 | Life Sciences

UC San Diego cancer scientists identify new drug target for multiple tumor types

12.07.2019 | Health and Medicine

Science & Research
Overview of more VideoLinks >>>