Dr Rachael Richardson’s research is exploring the use of light to improve the perception of sounds conveyed by cochlear implants. Cochlear implants have restored hearing to hundreds of thousands of people world-wide. They work very well in quiet conditions, but in noisy environments speech perception can become quite difficult. Cochlear implants also do not convey the rich complexity of music and tonal languages effectively.
Rachael said, “Imagine listening to a piano concerto where one note of the piano is activating your high and low-pitch nerves at the same time – the perception of the note would be blurred. Add more notes and you can imagine that the experience of this complex sound would rapidly deteriorate. This is because electrical current spreads through the fluid-filled inner ear. It means that the nerves stimulated in one part of the inner ear – for example, high-pitch – can be activated by more than one electrode in the cochlear implant”.
Dr Richardson and colleagues are examining the use of light to activate the hearing nerve since light can be focussed more precisely than electrical stimulation. For light-based stimulation to work, nerves must first be made responsive to light by the addition of a gene by gene therapy. This field of science is called ‘optogenetics’.
Optogenetics has been used successfully to activate nerves in the brain, heart and other organs with high precision. Bionics Institute research has demonstrated the feasibility of the technique in the inner ear, and opens up the exciting possibility of improving the precision of auditory nerve stimulation and therefore the quality and complexity of sounds perceived by cochlear implant recipients.
There are several key research questions that need to be answered before optogenetics can be used clinically. We need to know whether light-based stimulation results in a meaningful difference to the way sounds are perceived, and that it is safe.
We gratefully acknowledge a recent grant from Action on Hearing Loss, a UK philanthropic organisation. This funding will help Rachael and her colleagues explore the possibility of a light-based cochlear implant over the next three years.