Researchers at the University Medical Center Göttingen (UMG) have demonstrated in an animal model that optical cochlear implants generate nerve signals that are more distinguishable than those produced by conventional electrical implants. Nerve signals transmit auditory information — such as pitch, and volume — to the brain, enabling a comprehensive hearing experience. In total, up to ten different light-emitting diodes (LEDs) were able to specifically trigger different nerve signals using very low levels of light energy. This underscores the potential of optical cochlear implants for improved hearing restoration. The results have been published in the journal “EMBO Molecular Medicine.”
Today’s cochlear implants use electrical impulses to stimulate the auditory nerve. This enables many people who are deaf or have severe hearing loss to understand speech. The electrical current spreads through the conductive fluids of the cochlea, activating larger population of the auditory nerve fibres to be simultaneously and causing nerve signals to overlap. This limits the spacial precision of the stimulation and makes it particularly difficult to understand speech in the presence of background noise. Modern cochlear implants have 12 to 24 “stimulation channels.” These channels can be used to electrically stimulate the auditory nerve, generating various nerve signals that are transmitted to the brain. In most cases, however, a maximum of ten channels can be distinguished. Results from previous research have shown that the auditory nerve can be activated more precisely with light than with electrical impulses. This promises nerve signals that are more distinguishable from one another and, as a result, improved hearing restoration.
A team led by Prof. Dr. Tobias Moser, director of the Institute for Auditory Neuroscience at the University Medical Center Göttingen (UMG), genetically engineered the auditory nerve of Mongolian gerbils to contain particularly light-sensitive ion channels that can be selectively turned on and off like a “molecular light switch.” Pioneers of this method of optogenetics were awarded the 2026 Nobel prize for Physiology or Medicine and its potential for clinical applications is currently being evaluated worldwide, including for hearing restoration as done here. Even low light energies were sufficient to stimulate the auditory nerve and thus trigger various nerve signals. These nerve signals are transmitted to the brain, where they are perceived as sounds, noises, or speech. The researchers were able to demonstrate that the nerve signals triggered by light could be distinguished from one another more clearly than with conventional stimulation using electrical impulses. “Our goal is to use optical cochlear implants to enable more distinguishable stimulation channels than conventional electrical implants,” says Prof. Moser. “This would allow acoustic information to be transmitted to the hearing aid in a more nuanced way. This could be of great benefit in restoring hearing for people who are deaf or have severe hearing loss, particularly in terms of speech comprehension in the presence of background noise.”
The findings have been published in the EMBO Molecular Medicine journal.
Original publication:
Albrecht N, Koert E, Vavakou A et al. Multichannel optical cochlear implants enable spectrally distinct auditory activity. EMBO Molecular Medicine (2026). DOI: https://doi.org/10.1038/s44321-026-00541-2
How the hearing system reacts to light
The team studied neural activity in a region of the midbrain in Mongolian gerbils that is important for auditory processing. The researchers aimed to determine how information about different frequencies and intensities can be transmitted using light. To this end, they compared the neural signals triggered by light with those elicited by sounds or electrical cochlear implants.
The study showed that optical stimulation using LEDs could elicit nerve signals that were roughly as strong as those triggered by electrical impulses or a sound with a sound pressure level of 51 decibels. “We were able to trigger distinct nerve signals with just a single LED,” says Niels Albrecht, M.D. candidate at the Institute for Auditory Neuroscience at UMG and the study’s first author. “What is particularly interesting, however, is that the nerve signals triggered by different LEDs could be distinguished from one another more easily than with electrical stimulation — even when the LEDs were spaced close together.”
Toward optical hearing restoration
The study represents another important step toward the development of optical cochlear implants. Since optogenetic hearing restoration requires gene therapy in addition to an implant, potential benefits and risks must be examined with particular care. The results from the animal model provide important insights in this regard and, at the same time, highlight the questions that need to be addressed in future studies. This includes, for example, determining whether stronger nerve signals can be achieved using more powerful light sources or even more light-sensitive ion channels. In addition, it is necessary to investigate how more complex auditory information — such as speech — can be transmitted through the stimulation of multiple optical channels.
Participating partners
In addition to UMG, researchers from the University of Göttingen, the German Primate Center — Leibniz Institute for Primate Research, the Max Planck Institute for Multidisciplinary Natural Sciences, and the University of Freiburg participated in the study. The work was supported, among others, by the Else Kröner Fresenius Center for Optogenetic Therapies (EKFZ-OT), the Göttingen Cluster of Excellence “Multiscale Bioimaging: From Molecular Machines to Networks of Excitable Cells” (MBExC), and the Collaborative Research Center 1690 „Disease mechanisms and functional restoration of sensory and motor systems“.
Contact person:
Prof. Dr. Tobias Moser, Institute for Auditory Neuroscience, tmoser[atgwdg.de
Press contact:
University Medical Center Göttingen, University of Göttingen
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Link to the UMG press release
Link to the EMBO Molecular Medicine article
