Re-examining the relationship between number of cochlear implant channels and maximal speech intelligibility

This study reconsiders the number of effective channels in contemporary cochlear implants. Subjects listened to matrix sentences with a competing talker using their clinical map (up to 22 electrodes) and reduced-channel maps using 12, 8, and 4 electrodes. Spectro-temporal modulation thresholds and reading span were measured to explore intersubject variability. Results show that speech understanding significantly improved with increasing active electrodes up to 22, particularly for subjects with better spectro-temporal resolution. These findings suggest some listeners may be able to utilize the full electrode array and may not be limited to eight channels of information as indicated in previous studies.