Multipolar current focusing increases spectral resolution in cochlear implants.

Cochlear implants are highly successful neural prostheses that restore hearing in the deaf, often resulting in high levels of speech understanding in quiet listening conditions. In more challenging conditions, however, cochlear implant subjects often score much lower than their normal-hearing peers, possibly reflecting limits of the electrode-neural interface. In this study, we compare monopolar stimulation versus focused stimulation, using multipolar channels, to test if current focusing can increase spectral resolution. Psychophysical results show that current focusing significantly improves subjects' ability to discriminate spectral features and detect dynamic modulations in sound stimuli. These results suggest that focused stimulation can successfully increase the number of effective channels with a cochlear implant and may lead to improved hearing in noisy conditions.