Improvement of cochlea with light waves is expected to benefit from hearing loss.

At present, about 500 thousand hearing impaired people around the world use electronic equipment to restore some hearing. Cochlear implant is one of them. Under the guidance of Tobias Moser, a professor of hearing neuroscience at the University of Canton, Germany, researchers will improve with light, hoping to break through the limitations of the existing cochlear implant.

The cochlea is the spiral structure of the inner ear, which can analyze the frequency of sound. The different frequencies presented in the speech will cause the membrane to vibrate in the cochlea. Vibration will activate cells like hair, stimulate hearing neurons, and transmit relevant information of the sound through the auditory nerve to the brain.

People with sensorineural hearing loss stimulate neurons in the cochlea by using electrodes (electrode) because they lose hair like cells. However, because the current generated by the electrodes is not straight to the hearing neurons, it will disperse through the process, so if the electrodes are too close, they will cause crosstalk. Therefore, the current cochlear implant restricts the number of electrodes to avoid interference with each other, but it also limits the user's hearing performance.

The Moser team used optical genetics technology (Optogenetics) to replace electrodes with light. Photogenetics is usually used in animal research. It stimulates genes to produce photosensitive proteins into neurons and stimulates neurons through light.

The research team took gerbils as an experimental object, transformed the adult mice into genes, shortened the time needed for the recovery of retinal proteins between the two activation times, then injected the bacteria into the cochlea of the gerbils, took the retina protein gene to the hearing neurons, and then used optical fibers to pass the light through the round window in the ear to the cochlea. Results in the gerbils, the auditory part of the brainstem was similar to that of the stimulus.

At present, the research team uses only one light wave, and the next step will be to develop a device that can produce multiple light waves. The device may be designed to use Micro LED array or waveguide technology to guide the light generated by optical fibers. Because optical fiber consumes a lot of electricity, it is expected that the device will be very cumbersome. Daniel Lee, an ear surgeon at Harvard Medical School, points out that LED is a better choice, but the light is relatively vague, so there is a need for breakthroughs in technology.

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