A multiple electrode cochlear implant

Abstract

The receiving and stimulating component of a multiple-electrode cochlear implant hearing prosthesis [for man] which produces constant current stimulation was described. It had a stimulating pulse shape that minimized the production of toxic substances and loss of metal from the electrodes, and this was achieved with a biphasic rectangular waveform where the 1st phase was negative with respect to ground. The duration of each stimulus phase was 180 ms, which was long enough to allow low levels of current stimulation, and short enough to permit rates of 1000 pulses/s to be achieved. To be consistent with the present understanding of the perception of pitch, the device permitted the independent stimulation of a number of electrodes. To elastically isolate the stimulus to small areas, there was the capacity to vary the current and set the threshold independently at individual electrodes. The phase and amplitude of the pulses to neighboring electrodes was also be varied to assist in localizing the current flow. The pattern of stimulation to individual or groups of electrodes could be altered to enable studies to be carried out to determine ways of conveying frequency and intensity in formation over a more normal dynamic range.