Improved electrode design for next generation cochlear implants

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Researchers have developed designs for higher-performance electrodes that could provide substantial improvements in sound perception for the next generation of cochlear implants.

The cochlear implant is a device that uses digital speech processing coupled with a surgically-implanted electrode to stimulate hearing nerves – allowing severely hearing-impaired adults and children to hear sound and understand speech.
University of Melbourne Research Fellow Dr Carrie Newbold has been working with the HEARing Cooperative Research Centre (HEARing CRC) and Cochlear Limited since 2001, exploring ways to improve the transmission of sound information through the electrode array that is surgically inserted into the cochlea – the organ that senses sound.

Dr Newbold said the manufacture of small devices is a challenge  “I have been observing how the cochlear implant’s electrodes interact with the tiny nerve cells of the cochlea that transmit the sense of sound, and how to improve the efficiency of the electrodes to enhance the quality of sound heard by implantees.”
“The current design of cochlear implant uses 22 individual electrodes, spaced along the electrode array to stimulate different nerve cell groups located along the cochlea.  Each of these electrodes is very small and connected to the implant by even thinner wires that are around a quarter the thickness of human hair.  Currently, the electrode arrays are almost completely made by hand which can limit how many can be made.”

The membranes and internal structures in the cochlea are extremely delicate and present an additional challenge. These new designs will impact on the array’s physical characteristics, ease of surgical insertion, and reliability. The aim is to insert a device without causing any damage to these delicate sensory and neural structures.”

The HEARing CRC’s research, conducted in collaboration with Cochlear, is investigating new less intrusive slim electrode designs, as well as the use of new biomaterials and manufacturing techniques to produce electrodes with higher capacity for information transmission.

New plastics (polymers) that conduct electricity have the potential to be useful in improving the transmission of sensation of hearing in the cochlea. These plastics are more efficient with electricity and are less brittle than current electrode materials.

Dr Newbold’s research and the arrival of suitable, non-metal electrode materials could mean the development of next generation cochlear implants is just around the corner. These new implants may improve performance to allow the wearer to communicate easily in noisy environments and to enjoy the pleasure of music.

HEARing CRC research is financially supported by the Cooperative Research Centres Program – a Commonwealth Government Initiative. (Greg Lawrence/HEARing Cooperative Research Centre)