Research: Artificial hearing without artificial power

October 25, 2011

Kyoto University press release:

Researchers find that a battery-free cochlear implant can generate auditory responses in deaf animals. Current cochlear implants partially restore hearing in people who have inner ear hair-cell damage with a series of electronic sensors, actuators, and a battery power source.

Senior Lecturer Takayuki Nakagawa at Graduate School of Medicine in Kyoto University and colleagues built a membrane implant using a material that generates electricity in response to bending, and inserted the device in the cochlea of deafened guinea pigs.

Sound transmitted through the guinea pigs’ ear canals generated vibrations in the membrane, which created electrical pulses that varied with the sound frequency. The membrane’s sound tuning aligned similarly with tuning in the inner ear’s basal membrane, the researchers report. In other tests, the researchers artificially stimulated the implants and recorded auditory brain stem activity in electrodes placed under the animals’ skin.

The researchers suggest that the device could be described as the “technological regeneration of [inner ear] hair cells,” but caution that the device’s electrical output must be increased to stimulate auditory primary neurons in the ear like current implants. Together, the results suggest that one day deaf patients may be able to use small prosthetics that mimic natural cochlear function, without the need for a battery. The results were published in PNAS.

Link to the journal paper:
Inaoka T, Shintaku H, Nakagawa T, Kawano S, Ogita H, Sakamoto T, Hamanishi S, Wada H, Ito J. Piezoelectric materials mimic the function of the cochlear sensory epithelium. PNAS 2011 ; published ahead of print October 24, 2011, doi:10.1073/pnas.1110036108

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