At present, there are about 500,000 hearing-impaired people in the world who use electronic equipment to recover some hearing. The cochlear implant is one of them. Led by Tobias Moser, a hearing neuroscientist at the University of Göttingen in Germany, the researchers will improve with light and hope to break through the limitations of existing cochlear implants.
The cochlea is a helical structure of the inner ear that analyzes the frequency of sound. The different frequencies present in the speech will cause the membrane in the cochlea to vibrate. Vibration will activate cells like "hair", stimulate the hearing neurons, and transmit information about the sound to the brain through the auditory nerve.
People who feel neurotic deafness use neurons to stimulate neurons through the cochlear implant because they lose hair-like cells. However, because the current generated by the electrodes is not straight to the hearing neurons, but will be dispersed through the process, if the electrodes are placed too close, crosstalk will occur. Therefore, the current cochlear implant limits the number of electrodes to avoid mutual interference, but also limits the user's hearing performance.
The Moser team used Optogenetics to replace the electrodes with light. The optogenetic technique is commonly used in animal research to stimulate genes to produce light-sensitive proteins into neurons and to stimulate neurons through light.
The research team used gerbils as experimental subjects to genetically transform adult mice, shortening the recovery time required for retinal protein between activations, and then injecting bacteria into the gerbil cochlea to bring retinal protein genes to the hearing neurons for reuse. The optical fibers pass light through the round window in the ear into the cochlea. As a result, the part of the gerbil brain stem that is responsible for hearing is similar to the response when stimulated by sound.
At present, the research team only uses one light wave. The next step is to develop a device that can produce multiple light waves. The device design may use Micro LED array or waveguide technology to guide the light generated by the optical fiber. Since optical fibers consume a lot of power, it is expected that the device will be very bulky. Daniel Lee, an otologist at Harvard Medical School, pointed out that LED is a good choice, but the light is relatively vague, so there is still a need for breakthroughs in technology.
