2019 Conference on Implantable Auditory Prostheses

14-19 July 2019

Granlibakken, Lake Tahoe

Page 40

P13: TOWARDS THE OPTICAL COCHLEAR IMPLANT:

OPTOGENETIC STIMULATION OF THE AUDITORY PATHWAY

Daniel Keppeler, Alexander Dieter, Eric Klein, Michael Schwaerzle,

Patrick Ruther, Tobias Moser

Institute for Auditory Neuroscience and InnerEarLab, Goettingen, DEU

University of Freiburg, Department of Microsystems Engineering (IMTEK), Freiburg, DEU

When hearing fails, cochlear implants (CIs) provide open speech perception to most of the

currently half a million CI users. CIs bypass the defective sensory organ and stimulate the

auditory nerve electrically. The major bottleneck of current CIs is the poor coding of spectral

information, which results from wide current spread from each electrode contact. As light can be

more conveniently confined, optical stimulation of the auditory nerve presents a promising

perspective for a fundamental advance of CIs. In this study we established reliable expression

of the ultra-fast channelrhodopsin Chronos in spiral ganglion neurons (SGNs) and demonstrated

its support of high temporal fidelity in the auditory nerve. Further, we developed multichannel

optical CIs based on microfabricated light-emitting diode (LED) arrays. We characterized them

for optical stimulation of channelrhodopsin-2 (ChR2)-expressing SGNs in transgenic rats or

gerbils using optical auditory brainstem responses (oABR) stimulated by individual or multiple

LEDs. Positioning of the probes and atraumatic implantation was validated with micro-CT

imaging. Multielectrode array recordings along the tonotopic axis of the inferior colliculus (IC)

indicate spectral selectivity of optical stimulation closer to acoustic than electrical stimulation.

This contribution will summarize the current state of optogenetic stimulation of the auditory

pathway and report on recent breakthroughs on achieving high temporal fidelity, frequency

resolution and establishing multichannel optical CIs.

The research leading to these results has received funding from the German Research

Foundation (DFG) through the Cluster of Excellence BrainLinks-BrainTools (EXC 1086), the

Collaborative Research Center 889, Cluster of Excellence Multiscale Bioimaging and the Leibniz

program, from the Federal Ministry of Education and Research (BMBF) via the project Optical

Cochlear Implant (No. 13N13728) as well from the European Research Council (ERC Advanced

Grant OptoHear).