A multiple-electrode cochlear implant.

A multiple-electrode cochlear implant comprised of three intracochlear and four extracochlear electrodes is described. A percutaneous plug allowed for direct electrical measurements and presentation of stimuli to selected electrode combinations. Electrical impedance measurements revealed functions that decreased as frequency increase to about 20 kHz. Absolute impedance magnitude varied across electrodes. Equal loudness contours were similar in shape for all three cochlear electrodes, although dynamic range was significantly reduced for the most apical electrode. Periodicity and place pitch were demonstrated; effects were most salient for low frequency stimuli. A 3-channel sound processor was built and multiple-channel stimulation was compared to single-channel stimulation. Significant performance differences were not found between single-channel and multiple-channel systems for environmental or speech sounds. However, the patient subjectively reported superior quality with the multiple-channel system.