Optogenetic Cochlear Implants Aim to Improve Quality of Sound

At the University of Göttingen in Germany researchers have managed to use light to stimulate the auditory nerves of gerbils, in the process allowing the deaf animals to hear sounds. The technology is being developed to improve the audio quality of cochlear implants, devices that can bring hearing to people with several types of hearing loss. Though cochlear implants are getting better and better, and their popularity has surged, they suffer from poor frequency resolution. This results in garbled sound when listening to speech surrounded by noise, such as inside of loud restaurants.

Using light may solve this problem because it may be possible to more selectively stimulate auditory cells with light rather than electric current. To make auditory cells listen to light, the researchers relied on genetic engineering to convert some of the target cells into ones that are sensitive to light, a technique known as optogenetics.

In part, the researchers tested their approach on gerbils that could hear, but that were also genetically modified and had a light source implanted. These animals were trained to respond to certain sounds by jumping to a different place in their cage. When these sounds were not actually produced, but rather stimulated inside their heads using light, they responded just the same as if the real sounds were produced. Similar experiments were tried on deaf gerbils, and they also seemed to be able to hear post implantation.

The next steps will reportedly involve trying this approach in larger animals with the hope of one day doing the same with humans. But, because there’s the genetic engineering step that is required, this future may be not as near as it may seem.

Here’s a cute demonstration of what an optical auditory stimulator looks like:

Side image: Reconstruction of the cochlea of a rat based on x-ray phase contrast tomoraphy. An about 300 µm wide encapsulated micro-LED implant (blue) has been inserted into the scala tympani (tympanic duct) of the cochlea (grey) of a rat. (insertion depth ca. 0.75 turns). The green structure indicates the basilar membrane with the sensory organ of Corti, which could not be reconstructed over its entire length.

Study in Science Translational Medicine: Optogenetic stimulation of cochlear neurons activates the auditory pathway and restores auditory-driven behavior in deaf adult gerbils…

More from the Institute for Auditory Neuroscience at University of Göttingen…