June 20, 2021

Light signals against deafness, an unexpected and promising use of optogenetics

Treat blindness with optogenetics, yes. But deafness? This is a more unexpected application of this avant-garde technique. Because as much as it seems logical to use photosensitive proteins to improve vision, this approach seems less intuitive to restore hearing. How, indeed, to convert sounds into light, then into nerve signals?

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This challenge was taken up by a German ENT surgeon, Professor Tobias Moser of the Max Planck Institute, who in 2015 founded an Institute for Hearing Neuroscience in Göttingen, Germany. For nearly thirty years, this doctor-researcher has been exploring the way in which sound is encoded in the brain. By what processes (cellular and molecular) are the sound vibrations picked up by the ear transformed into electrical impulses, then transmitted to the brain by the auditory nerve? This conversion takes place in a small organ in the inner ear, the cochlea. It involves close interactions between the sensory cells which receive sound vibrations (hair cells) and the neurons of the auditory nerve.

“This breakthrough innovation suggests a considerable qualitative leap in the restitution of audible sounds, in particular music”, estimates the Foundation for hearing

On the strength of this knowledge, Tobias Moser’s team has been developing, since 2007, a new generation of cochlear implants. It must be said that conventional, electronic hearing implants have technical limits. In these devices, “Electrical stimulation of the auditory nerve by electrodes implanted in the cochlea is imprecise”, indicates the Foundation for hearing in Paris. “It does not make it possible to restore the range of frequencies normally perceived by the ear. Thus, following a conversation in a noisy atmosphere or listening to music is still impossible. “

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To improve the performance of these medical devices, Tobias Moser therefore relies on optogenetics. “The idea is to replace electrical stimulation of the auditory nerve with light stimulation focused on a smaller group of neurons,” he explains. In this way, we hope to provide deaf people with much better frequency resolution. “ Concretely, this would result in the ability to perceive speech in a noisy environment or to follow a melody, for example. “This breakthrough innovation suggests a considerable qualitative leap in the restitution of audible sounds, in particular music”, estimates the Foundation for hearing, which in 2020 presented its scientific prize to Tobias Moser.

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