Scientists have developed a new type of cochlear implant that allows deaf gerbils to hear light. The breakthrough technique aims to activate key neurons that have been manipulated to respond to light. In the experiments, researchers showed the implanted gerbils were successfully stimulated by a blue light, which prompted them to jump over an obstacle like they had when previously trained to do so in response to an alarm. In the new study, the team equipped adult gerbils with a light-sensitive protein by injecting a virus known to carry the gene into their cochlea. According to the team from University Medical Center Gottingen, Germany, this could eventually pave the way for light-based implants in humans, too.
Cochlear implants that restore hearing could be improved by genetically modifying the nerve cells in people's ears so that they respond to light instead of electricity, a study in rats has shown. "This is so much better than what we currently have with electrical implants," says Tobias Moser at the University Medical Center Göttingen in Germany. Our hearing relies on hair cells inside the cochlea of our ears detecting sounds of different frequencies and then stimulating the right auditory nerve cells. Damage to these hair cells is a common cause of deafness. Cochlear implants can partly restore hearing by electrically stimulating nerve cells, bypassing the hair cells.
A cochlear implant is a device used to provide the sensation of sound to those who are profoundly deaf by means of electrical stimulation of residual auditory neurons. It generally consists of a directional microphone, a wearable speech processor, a headset transmitter and an implanted receiver-stimulator module with an electrode A Novel Channel Selection System in Cochlear Implants 911 array which all together provide an electrical representation of the speech signal to the residual nerve fibres of the peripheral auditory system (Clark et ai, 1990).
Can light restore hearing in deaf people? Researchers hope that through optogenetics, they can use micro-LED lights to make better cochlear implants than those used by deaf people today. Standard cochlear implants function by stimulating nerves using an electrode placed inside the cochlea, a tiny spiral cavity inside the ear. These work, but sounds are distorted and muffled. That's because people who aren't deaf can normally discriminate between about 2000 different sound frequencies, whereas cochlear implants allow only about a dozen to be distinguished.