Hearing the light.
Researchers at the Institute for Bioengineering of Catalonia (IBEC) and the University Medical Center Göttingen have achieved, for the first time, in vivo light-activated auditory stimulation without the need for genetic manipulation. This new light-controlled drug, capable of triggering the neural pathways involved in hearing, can contribute to improving the spectral resolution of cochlear implants used by people with profound hearing loss or deafness.
One million people around the world use cochlear implants (CIs), surgically implanted devices which restore sound perception in case of deafness. Microphones convert sound into electric signals that then directly stimulate the auditory nerve in the cochlea, the structure in the inner ear involved in hearing.
Although CIs can recover understanding of speech in the quiet, users have difficulty following conversations in background noise and limited music appreciation due to their limited spectral resolution. This is caused by the spread of electrical stimulation in the liquid-filled cochlea. Stimulation with light has been proposed as an alternative, for example with optogenetics and light-emitting CIs pioneered by the University Medical Center Göttingen (UMCG).
In collaboration with the Institute for Bioengineering of Catalonia (IBEC), an alternative route to optogenetics has been developed to couple light and electrical activity in the neurons without using genetic manipulation. The researchers have developed a photopharmacological agent that chemically attaches to a neuroreceptor protein like a ‘molecular prosthesis’ and readily activates the neurons when illuminated. It was used to activate auditory neurons with light at kilohertz frequencies in adult gerbils and could ultimately contribute to improving the spectral resolution of cochlear implants.