Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Hearing with light: Optogenetics for Auditory Research and Prosthetics

04.03.2014

An international research team led by scientists of the University Medical Center Göttingen develops the optical stimulation of the inner ear. Publication in "Journal of Clinical Investigation"

Hearing impairment is the most common human sensory deficit and has major socioeconomic impact. Hearing can be partially restored to the deaf by cochlear implant (CI), which bypass the cochlear dysfunction via direct electric stimulation of spiral ganglion neurons (SGNs).


Electrical versus optical stimulation of the cochlea:

Top: in electrical CIs usually 12-24 electrodes are used to stimulate SGNs. Current spread leads to activation of a large population of neurons along the tonotopic axis, thereby limiting the frequency resolution and dynamic range of electrical coding.

Bottom: optical stimulation promises spatially confined activation of SGNs allowing for a higher number of independent stimulation channels and, thereby, improving frequency and intensity resolution. Graph: umg

CIs enable open speech comprehension in most users, but the quality of hearing is low. This results from low frequency and intensity resolution of coding due to the wide spread of electrical current from each electrode contact. CI users have problems to understand speech in background noise and typically do not appreciate music. An international research team led by scientists of the University Medical Center Göttingen proposes to overcome this fundamental problem of CI by establishing many independent coding channels via spatially confined optical stimulation of channelrhodopsin (ChR)-expressing SGNs by tens of microscale light emitters along the tonotopic axis of the cochlea (cochlear optogenetics).

They obtained proof of principle in rodents where they activated the auditory pathway with blue light stimulation of ChR-expressing SGNs and this way could restore auditory activity in deaf mice. 

Original publication (advanced online, in the press):

Victor H Hernandez, Anna Gehrt*, Kirsten Reuter*, Zhizi Jing*, Marcus Jeschke, Alejandro Mendoza Schulz, Gerhard Hoch, Matthias Bartels, Gerhard Vogt, Carolyn W Garnham, Hiromu Yawo, Yugo Fukazawa, George J Augustine, Ernst Bamberg, Sebastian Kügler, Tim Salditt, Livia de Hoz, Nicola Strenzke, Tobias Moser (2014) Optogenetic stimulation of the auditory pathway. Journal of Clinical Investigation.

The WHO estimated that in 2005 there were 278 million people in the world with disabling hearing impairment (HI). So far, a causal treatment is not available for its most common form: sensorineural HI. Therefore, hearing aids and auditory prostheses represent the only means to restore auditory function in most hearing impaired subjects. Cochlear implants (CIs) bypass the dysfunctional sensory organ of Corti in the cochlea via direct electric stimulation of spiral ganglion neurons (SGNs). CIs enable open speech comprehension in the majority of deaf or profoundly hearing impaired users. However, users of current CIs suffer from poor comprehension of speech in noisy environments and typically do not appreciate music.

This is largely attributed to the wide-spread current around an electrode contact which leads to channel-crosstalk and limits the number of useful frequency channels to less than ten. Information coding by CIs is also limited with respect to sound intensity: the dynamic range of their output is typically below 10 dB. Increasing the frequency and intensity resolution of auditory coding with CIs is a crucial objective for improving speech comprehension. Optical stimulation is expected to dramatically increase the frequency resolution of CIs, because light enables spatially confined stimulation of SGNs, and therefore promises to overcome the limitations of current CIs (Fig. 1). In addition, activation of smaller populations of neurons can also enhance the dynamic range of coding e.g. by varying recruitment of neighboring channels.

"Because light can be conveniently focused, optical stimulation promises the use of tens to hundreds of independent stimulation channels. This innovation has the potential to fundamentally improve the discrimination of sound frequency and intensity by CI users. However, before translation into the clinic can be achieved, cochlear optogenetics will already be of enormous use in auditory research.", says Dr. Tobias Moser of the Department of Otolaryngology at the University Medical Center Göttingen, the corresponding author and team leader. The research of the team is part of the BMBF-funded Göttingen Focus for Neurotechnology as well as of the DFG-funded Göttingen Center for Nanoscale Imaging and Molecular Physiology of the Brain (CNMPB).

HOW TO MAKE COCHLEAR NEURONS SENSITIVE TO LIGHT?

In order to render the neurons light sensitive the scientist used the novel optogenetic approach of expressing the light-gated microbial ion channel channelrhodopsin. To do so the team also used harmless viral vectors similar to those presently used in clinical trials on gene-therapy of blindness. They then implanted micro-light emitting diodes (µLED) and laser-coupled micro-fibers for optical stimulation.

RESULTS

"Optogenetic activation of the auditory pathway works in rodents! We could detect light-evoked nerve impulse of individual SGNs and summed activity of pathway" says Anna Gehrt, author of the study and clinician-scientist at the Department of Otolaryngology: "Using optogenetically-evoked potentials we could demonstrate an activation of the auditory pathway in mouse models of human deafness ". Finally, the team achieved a first assessment of the frequency selectivity of optogenetic stimulation in comparison to electrical stimulation. The results agree with the predictions of a mathematical model: optical stimulation achieved better frequency selectivity than amenable to electrical stimulation.

"Much remains to be done to translate cochlear optogenetics into clinical rehabilitation of hearing impairment.” says Dr. Moser. To further develop the approach the Göttingen team also collaborates with scientists of the Freiburg Fraunhofer Institute for Applied Physics and the University of Freiburg, who develop multichannel opttical cochlear implants with more than 100 µLEDs within the BMBF funded project "Light-Hearing". Dr. Moser identifies further hurdles to take: cochlear optogenetics requires fast channelrhodopsins that can drive spiking of SGN up to a few hundreds per second. With the introduction of Chronos, a rapidly gating and light sensitive channelrhodopsin characterized by the Boyden lab at MIT, Cambridge, MA this now seems within reach. Moreover, biosafety of gene transfer and optical stimulation need to be demonstrated. 

FURTHER INFORMATION
Websites of the laboratories of Dr. T. Moser und Dr. N. Strenzke at University Medical Center Göttingen: http://www.innerearlab.uni-goettingen.de

FURTHER INFORMATION
University Medical Center Göttingen
Prof. Dr. Tobias Moser
InnerEarLab, Dept. of Otolaryngology, Head and Neck Surgery
Fon: +49-551-39-8968, tmoser@gwdg.de
www.universitaetsmedizin-goettingen.de

Stefan Weller | Universitätsmedizin Göttingen

More articles from Medical Engineering:

nachricht A first look at interstitial fluid flow in the brain
05.07.2018 | American Institute of Physics

nachricht A sentinel to watch over ocular pressure
04.07.2018 | Fraunhofer Institute for Microelectronic Circuits and Systems

All articles from Medical Engineering >>>

The most recent press releases about innovation >>>

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

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Global study of world's beaches shows threat to protected areas

19.07.2018 | Earth Sciences

New creepy, crawly search and rescue robot developed at Ben-Gurion U

19.07.2018 | Power and Electrical Engineering

Metal too 'gummy' to cut? Draw on it with a Sharpie or glue stick, science says

19.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>