Light based cochlear implant restores hearing in gerbils

July 12, 2018 by Bob Yirka, Medical Xpress report
Deaf adult gerbils can hear again with optogenetic hearing restoration. Upon ototoxic treatment adult gerbils turned deaf due to loss of hair cells. With optogenetic stimulation they could hear again and perform a behavioural task. To this end a small optical fiber was implanted and stimulated parts of the snail shaped cochlea. The location of the auditory neurons in the cochlea is shown in orange while the stimulated area is shaded in blue. Credit: University Medical Center Göttingen, Germany

A team of researchers with members from a variety of institutions across Germany has developed a new type of cochlear implant—one based on light. In their paper published in the journal Science Translational Medicine, the group describes their new implant and how well it worked in test gerbils.

Over a half-century ago, scientists came up with a way to partially restore hearing in people with cochlear damage—a cochlear . The same basic technology is still in use today—such devices work by converting sounds to electrical signals, which are transmitted to neurons that carry the signal to the brain. And while the implants have helped many people to hear, they still suffer from one major problem. Too many simultaneous sounds, such as speech in a crowded room, become muffled. This is because the electrical signals run into one another, causing degradation of the messages carried to the brain. In this new effort, the researchers have converted sound to instead of electricity, because light can be directed more precisely.

The new implant fires light directly at cochlear neurons. But for that to have an effect, the researchers had to get the neurons in test gerbils to respond to it. To make that happen, they injected a virus carrying gene encoding for light sensitivity directly into the cochlea. To test their device, they trained some gerbils to jump from one part of their cage to another when they heard a certain sound before the device was implanted. Afterward, light from the implant was activated and that caused the gerbils to jump as they had before, showing their brains were receiving the same signals. Next, the team caused cochlear-based hearing loss in the test gerbils and once again fired up the new implant. They report that the gerbils jumped just as they had in response to the prior sound, proving their hearing had been restored.

The video illustrates the concept of new optogenetic cochlear implants: sound from the piano is picked up by a microphone and transmitted to a processor which translates the sound into optical stimulation patterns via LEDs placed within the cochlea. Credit: University Medical Center Göttingen, Germany

The researchers suggest their device is a proof of concept for a way to improve implants. The next logical step would be to add electronics to the to convert sound signals to light, which would then stimulate neurons in the ear in the same way have done in the past.

(A) electrical cochlear implants contain 12-24 electrodes which typically provide less than 10 independent frequency channels for users. This is due to the fact that current spread (light blue shade) leads to activation of a large population of neurons along the frequency axis of the cochlea and thereby limits the frequency resolution and dynamic range of electrical coding. (B) optical stimulation promises spatially confined activation of neurons in the auditory nerve allowing for a higher number of independent stimulation channels and, thereby, improving frequency and intensity resolution using future oCIs. (C) this preclinical animal study used single channel optical stimulation by inserting an optical fiber into the cochlea. Credit: University Medical Center Göttingen, Germany

Schematic illustration of the newly proposed optical cochlear implants. A strip of LEDs is inserted into the snail shaped cochlea. Optical cochlear implants promise spatially confined activation (blue shade indicates light from activitated LEDS) of neurons in the auditory nerve allowing for a higher number of independent stimulation channels and, thereby, improving frequency and intensity resolution. Credit: University Medical Center Göttingen, Germany

Explore further: Cochlear implants for advanced hearing loss

More information: C. Wrobel el al., "Optogenetic stimulation of cochlear neurons activates the auditory pathway and restores auditory-driven behavior in deaf adult gerbils," Science Translational Medicine (2018). stm.sciencemag.org/lookup/doi/ … scitranslmed.aao0540

Related Stories

Cochlear implants for advanced hearing loss

November 11, 2016
Dear Mayo Clinic: I'm 72 and have worn hearing aids for about a decade. Over the past several years, my hearing seems to be getting worse. Although I've tried several different kinds of hearing aids, I can't hear well with ...

Research finds brain responses to lip-reading can benefit cochlear implant users

August 15, 2017
A world-first study has found that lip-reading may have a beneficial effect on the brain and on a person's ability to hear with a cochlear implant, contrary to what was previously believed.

Engineering music to sound better with cochlear implants

February 26, 2016
When hearing loss becomes so severe that hearing aids no longer help, a cochlear implant not only amplifies sounds but also lets people hear speech clearly.

Getting devices to talk so patients can listen

January 29, 2016
While cochlear implants have opened up new worlds for deaf individuals, one Western researcher is looking to bring a balance to adult patients they have not previously experienced.

Infants benefit from implants with more frequency sounds

May 19, 2014
(Medical Xpress)—A new study from a UT Dallas researcher demonstrates the importance of considering developmental differences when creating programs for cochlear implants in infants.

Recommended for you

A Trojan Horse delivery for treating a rare, potentially deadly, blood-clotting disorder

September 21, 2018
In proof-of-concept experiments, University of Alabama at Birmingham researchers have highlighted a potential therapy for a rare but potentially deadly blood-clotting disorder, TTP. The researchers deliver this therapeutic ...

Researchers explore how changes in diet alter microbiome in artificial intestine

September 21, 2018
Using an artificial intestine they created, researchers have shown that the microbiome can quickly adapt from the bacterial equivalent of a typical western diet to one composed exclusively of dietary fats. That adaptation ...

Japanese team creates human oogonia using human stem cells in artificial mouse ovaries

September 21, 2018
A team of researchers with members from several institutions in Japan has successfully generated human oogonia inside of artificial mouse ovaries using human stem cells. In their paper published in the journal Science, the ...

A new approach to developing a vaccine against vivax malaria

September 21, 2018
A novel study reports an innovative approach for developing a vaccine against Plasmodium vivax, the most prevalent human malaria parasite outside sub-Saharan Africa. The study led by Hernando A. del Portillo and Carmen Fernandez-Becerra, ...

Study identifies stem cell that gives rise to new bone and cartilage in humans

September 20, 2018
A decade-long effort led by Stanford University School of Medicine scientists has been rewarded with the identification of the human skeletal stem cell.

Scientists grow human esophagus in lab

September 20, 2018
Scientists working to bioengineer the entire human gastrointestinal system in a laboratory now report using pluripotent stem cells to grow human esophageal organoids.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.