In world-first studies, Australian researchers have found a novel way that could improve the quality of hearing for people with cochlear implants.

Our researchers have established that by adding light via optogenetics to the existing electrical stimulation provided by a cochlear implant, the accuracy of nerve activation is improved, thus potentially improving hearing outcomes for recipients of cochlear implants.



For a person with normal hearing, sound waves travel in the fluid-filled cochlea of the inner ear, causing sensory hair cells to react and send signals to the brain via the auditory neurons. For those with hearing loss, these hair cells have died. To counter this, a cochlear implant can be inserted which uses electrical stimulation to mimic the function of a normal hearing response. Although cochlear implants have been a wonderful breakthrough, the quality of sound has room for improvement; the way that the electrodes activate the neurons is not very accurate. This leads to poor speech understanding when there is background noise, and poor perception of complex sounds such as music.

A/Prof Rachael Richardson leads a team at the Bionics Institute researching ways to improve the quality of hearing for people with cochlear implants. The team have used Optogenetics, which involves a simple genetic alteration of auditory nerves with a light sensitive molecule, enabling them to be activated via focused light beams. The results have proven that through the use of optogenetics the precision of bionic devices can be improved.

There is so much scope to improve the quality of information transfer from bionic devices to the brain. The ability to precisely control nerve activity will be a game changer for the treatment of many health conditions” explains A/Prof Richardson.

The findings have been published today in the Journal of Neural Engineering

Higher fidelity cochlear implants will be transformative for people with hearing impairment by improving both the quality and realism of hearing. This will reduce the disability experienced by people with hearing loss in everyday life.

Sam McLarty, a cochlear implant recipient is extremely appreciative of advancements in technology and the continuous research undertaken by the Bionics Institute to improve cochlear implant devices.” I look forward to being able to go out to a restaurant with my family and friends and not find the background noise a challenge.”

The study was supported by The Garnett Passe and Rodney Williams Memorial Foundation and Action on Hearing Loss.

Background Information

Cochlear implants

Cochlear implants electrically stimulate nerves in the cochlea enabling people with a profound hearing loss to communicate.

While cochlear implants offer up to 22 individual electrodes, the effective number of information channels is markedly lower.

A fundamental limitation of cochlear implants is the spread of electrical current through the fluid-filled inner ear. The amount of sound information delivered to the brain is reduced as current spread causes the information to become overlapped or 'blurred'. This leads to poor speech understanding when there is background noise, and poor perception of complex sounds such as music. An innovative change to the way we interface with neural tissue is required to improve sound perception.

Optogenetics

Optogenetics refers to the use of genetic engineering or gene therapy to introduce light sensitive molecules (opsins) into nerves to make them responsive to low-power light. Light can provide highly focussed stimuli and is not limited by conductive spread in the same way as electrical current. Our research is exploring the potential of optical stimulation to advance precision in neural stimulation and expand the range of health conditions that can be treated via bionic devices.

To read more on our Optogenetics research click here.