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February 12, 2006

Ribbon Cochlear Implant Directly Stimulates Auditory Nerve

From: Stereophile Magazine, NY - Feb 12, 2006

By Wes Phillips

February 12, 2006 — A University of Michigan research team under Kensall D. Wise has developed a ribbon-like cochlear implant that substantially increases the amount of auditory stimuli over the current models. Approximately 100,000 patients have had cochlear implants to ameliorate profound deafness; however, Wise described these implants as limited in frequency sensitivity, as well as bulky and difficult for surgeons to insert.

Wise, who is J. Reid and Polly Anderson Professor of Manufacturing Technology, a professor of Electrical Engineering and Computer Science, and director for the Center for Wireless Integrated MicroSystems, an NSF Engineering Research Center, spearheaded the development of a thin-film electrode that can directly stimulate up to 128 sites within the spiral canal of the cochlea—significantly more than the 16 to 22 sites stimulated with current designs.

The design is currently being tested on guinea pigs and cats, Wise announced, with projected availability for human subjects within the next four to five years. The new implant is made with the same processes that produce integrated circuits, which means implants can be mass-produced in batches.

The current technology employs electrodes consisting of a bundle of wires that must be inserted into the cochlea, the spiral cavity of the inner ear, which contains the organ of Corti, where vibrations are converted into electrical nerve impulses. The size of the cochlea and the difficulties of deep insertion make it hard for contemporary devices to stimulate lower frequencies, because the wires must be inserted close to the apex of the spiral canal. If the wires collide with the wall of the cochlea, damage to the residual hearing might result.

Wise explains that the ribbon-film technology of the new implant allows the addition of new functions, such as location sensors that would allow microsurgeons to monitor the implant's progress as they insert it. "The idea is to be able to take the signals from the position sensors and use them to control actuators in an insertion tool, so that the electrode array can achieve deep insertion and navigate around any obstacles in its path."

Additionally, "More sites mean greater tonal range and better frequency perception, and the implant's flexibility will minimize damage to existing hearing."

Another positive aspect to the new implants is that they are compatible with the existing implants and current users can "upgrade" to the new models with minimally invasive procedures.

The announcement does not mention other additional functions that can be built in, but it is impossible not to speculate that they might include DSP or other capabilities that have been developed in other IC designs.

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