Out-of-focus: Fuzzy cochlear implant stimulation and how to avoid it

Cochlear Implants restore hearing in severe-to-profound hearing-impaired individuals. An array of electrodes placed in the inner ear serves as the interface to elicit sound perception via electrically presented pulses. Cochlear implant performance is reduced by channel interaction, which degrades the signal accuracy at the electrode-neuron interface. We developed and optimized a focused cochlear implant stimulation strategy that counteracts the fuzzy electric representation by reducing channel interaction thereby getting the signal back into focus. The proposed strategy combines two approaches to minimize channel interaction, dynamic focusing, and electrode deactivation, which have individually proven beneficial for speech performance. Dynamic focusing concentrates the electric fields of electrodes located far from the modiolus by applying stimulation currents on triplets of simultaneously activated electrodes, with one center electrode and two flanking returns. Deactivated electrodes reduce the negative influence of high currents when stimulating possible neural dead regions along the cochlea. Speech perception outcomes in background noise showed, that the overall performance increases when high-threshold electrodes are dynamically focused and deactivated. The suggested strategy, therefore, might be a promising approach to improve the signal accuracy in cochlear implant stimulation.