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 Using 'Pacemakers' in spinal cord injuries
12.02.2016 | Charité – Universitätsmedizin Berlin

nachricht Fraunhofer ITEM takes over and continues development of inhalation technology assets from Takeda
10.02.2016 | Fraunhofer Institute for Toxicology and Experimental Medicine

All articles from Medical Engineering >>>

The most recent press releases about innovation >>>

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

Im Focus: Production of an AIDS vaccine in algae

Today, plants and microorganisms are heavily used for the production of medicinal products. The production of biopharmaceuticals in plants, also referred to as “Molecular Pharming”, represents a continuously growing field of plant biotechnology. Preferred host organisms include yeast and crop plants, such as maize and potato – plants with high demands. With the help of a special algal strain, the research team of Prof. Ralph Bock at the Max Planck Institute of Molecular Plant Physiology in Potsdam strives to develop a more efficient and resource-saving system for the production of medicines and vaccines. They tested its practicality by synthesizing a component of a potential AIDS vaccine.

The use of plants and microorganisms to produce pharmaceuticals is nothing new. In 1982, bacteria were genetically modified to produce human insulin, a drug...

Im Focus: The most accurate optical single-ion clock worldwide

Atomic clock experts from the Physikalisch-Technische Bundesanstalt (PTB) are the first research group in the world to have built an optical single-ion clock which attains an accuracy which had only been predicted theoretically so far. Their optical ytterbium clock achieved a relative systematic measurement uncertainty of 3 E-18. The results have been published in the current issue of the scientific journal "Physical Review Letters".

Atomic clock experts from the Physikalisch-Technische Bundesanstalt (PTB) are the first research group in the world to have built an optical single-ion clock...

Im Focus: Goodbye ground control: autonomous nanosatellites

The University of Würzburg has two new space projects in the pipeline which are concerned with the observation of planets and autonomous fault correction aboard satellites. The German Federal Ministry of Economic Affairs and Energy funds the projects with around 1.6 million euros.

Detecting tornadoes that sweep across Mars. Discovering meteors that fall to Earth. Investigating strange lightning that flashes from Earth's atmosphere into...

Im Focus: Flow phenomena on solid surfaces: Physicists highlight key role played by boundary layer velocity

Physicists from Saarland University and the ESPCI in Paris have shown how liquids on solid surfaces can be made to slide over the surface a bit like a bobsleigh on ice. The key is to apply a coating at the boundary between the liquid and the surface that induces the liquid to slip. This results in an increase in the average flow velocity of the liquid and its throughput. This was demonstrated by studying the behaviour of droplets on surfaces with different coatings as they evolved into the equilibrium state. The results could prove useful in optimizing industrial processes, such as the extrusion of plastics.

The study has been published in the respected academic journal PNAS (Proceedings of the National Academy of Sciences of the United States of America).

Im Focus: New study: How stable is the West Antarctic Ice Sheet?

Exceeding critical temperature limits in the Southern Ocean may cause the collapse of ice sheets and a sharp rise in sea levels

A future warming of the Southern Ocean caused by rising greenhouse gas concentrations in the atmosphere may severely disrupt the stability of the West...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Symposium on Climate Change Adaptation in Africa 2016

12.02.2016 | Event News

Travel grants available: Meet the world’s most proficient mathematicians and computer scientists

09.02.2016 | Event News

AKL’16: Experience Laser Technology Live in Europe´s Largest Laser Application Center!

02.02.2016 | Event News

 
Latest News

LIGO confirms RIT's breakthrough prediction of gravitational waves

12.02.2016 | Physics and Astronomy

Gene switch may repair DNA and prevent cancer

12.02.2016 | Life Sciences

Using 'Pacemakers' in spinal cord injuries

12.02.2016 | Medical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>