A wider range of sounds for the deaf

7 June 2007

A tiny electrode array placed directly in the auditory nerve could overcome the limitations of cochlear implants.

Scientists at the University of Michigan Kresge Hearing Research Institute have shown that it's possible to implant a tiny, ultra-thin electrode array in the auditory nerve of animals that can successfully transmit a wide range of sounds to the brain.

If the idea pans out in further animal and human studies, profoundly and severely deaf people would have another option that could allow them to hear low-pitched sounds common in speech, talk in a noisy room, identify high and low voices, and appreciate music — areas where cochlea implants, though a boon, have significant limitations.

"In nearly every measure, these work better than cochlear implants," says John C Middlebrooks, who led a study requested by the National Institutes of Health to re-evaluate the potential of auditory nerve implants.

The possible auditory nerve implants would be suitable for the same people who are candidates today for cochlear implants: the profoundly deaf, who can't hear at all, and the severely deaf, whose hearing ability is greatly reduced. Also, the animal studies suggest that implantation of the devices has little impact on normal hearing, offering the possibility of restoring sensitivity to high frequencies while preserving remaining low-frequency hearing.

Middlebrooks says it's possible that the low power requirements of the auditory nerve implants might lead to development of totally implantable devices. That would be an improvement over the external speech processor and battery pack cochlear implant users need to wear and often have to recharge daily.

"If our work continues to go very well, we might begin human trials in no less than five years" he says.

Source: University of Michigan press release
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