Results with a cochlear implant channel-picking strategy based on “Selected Groups”

A novel channel-picking strategy for cochlear implants (CIs) which considers the spatial distribution and the spectral relevance of the channels selected for stimulation is described. In the proposed strategy, the available channels are subdivided into groups, designated as “Selected Groups” (SG), and within each group, a specified number of active channels with the largest amplitudes are selected for stimulation. The hypothesis is that most of the spectral information that can be perceived by CI listeners is conveyed by taking the highest filter band outputs within a stimulation area represented by a group of neighboring channels. Two experiments were conducted in subjects with MED-EL implant systems, measuring recognition of sentences in speech-shaped noise. In experiment 1, the SG group size was varied from two to four while selecting one active channel per group and keeping the pulse phase durations constant. Results showed no significant difference in sentence recognition between continuous interleaved sampling and SG configurations up to a group size of three. In experiment 2, phase durations were doubled, using groups of two channels with one active channel each. This resulted in a reduction of pulse amplitudes by about 40%. Intelligibility of sentences in noise was unaffected, making a substantial reduction of implant supply voltages feasible. In all experiments, the stimulation frame rate was kept constant in order to avoid rate-change effects.