In this MEDICA-tradefair.com interview, Prof. Tobias Moser explains how the "OptoHear" project designs an optical cochlear implant that could overcome the limitations of today’s implants and reveals what lies ahead for the researchers.
Prof. Moser, you are developing an optical cochlear implant as part of the "OptoHear" project. Why is there a need for this type of implant?
Prof. Tobias Moser: Half a year to a year of auditory training helps cochlear implant wearers to recognize and understand speech in quiet environments without visual cues. This becomes more difficult if there is background noise or other ambient sounds.
People with normal hearing ability can resolve around 2000 different tone pitches. Today's cochlear implants only have 12 to 24 frequency channels, the stimulation current of which spreads extensively within the saline solution of the cochlea. This means, many nerve fibers are being stimulated at once versus individual fibers. Implant wearers thus can find it difficult to distinguish between pitches, which means they have a harder time understanding spoken language, and this often also affects their enjoyment of music.
How does an optical cochlear implant solve this problem?
Moser: Since light can be more easily focused and spatially confined, certain regions in the cochlea can be stimulated better with light versus electrical pulses. By nature, nerve cells are not light-sensitive, which means they need to be adapted via gene therapy. To do this, we use non-pathogenic viruses to introduce new genetic information into the cells. These form a channel in the cell membrane that opens when light hits. This excites the nerve fiber and sends an impulse to the brain.
Instead of electrical conductors, we would use waveguides - optical fibers - to guide light into the cochlea. Nerve fibers near the lower end of the cochlea resonate to higher frequency sound. Those near the upper end respond to lower frequencies. When a high tone is received, we would activate an optical fiber that only stimulates the nerve cells for the higher frequency sound.