Authors
Albrecht N, Koert E, Vavakou A, Roos L, Jablonski L, Marcoleta JP, Cardona Audi J, Alfken J, Klein E, Ruther P, Mager T, Kusch K, Moser T
Journal
EMBO Molecular Medicine
Citation
EMBO Mol Med. 2026 Oct 22
Abstract
When hearing fails, cochlear implants (CIs) restore auditory perception. Yet, coding of spectral information remains a bottleneck because each electrode broadly activates the auditory nerve. As light can be more conveniently confined in space, optical (o)CIs present an alternative. Here, we combined expression of the potent channelrhodopsin ChReef in spiral ganglion neurons (SGNs) with oCIs comprising 5-10 green LEDs in gerbils. This combination enabled systematic comparison of encoding intensity and spectral information by individual oCI channels to acoustic and electrical stimulation within a translationally feasible energy range. Recordings from the inferior colliculus (ICC) showed that ChReef aligned SGN light sensitivity with LED radiant fluxes: ICC activity had thresholds <200 nJ and reached a maximum equivalent to that achieved with 51 dB SPL pure tones. Multichannel oCIs enabled tonotopically ordered, spectrally distinct stimulation more closely resembled acoustic than did electrical stimulation. Some LEDs elicited multiple spectral peaks at higher intensities. Linear discriminant analysis of ICC activity indicated improved channel discriminability for optical over In summary, µJ-oCI-stimulation achieves resolution state-of-the-art
