Psychophysical metrics and speech recognition in cochlear implant users

Intersubject variability in perception is a prominent characteristic of people with cochlear implants. This study characterized intersubject differences using simple metrics based on psychophysical measures: maximum comfortable loudness levels (C levels) and dynamic ranges (DRs). In a group of 17 subjects, we assessed across-site variation (ASV) and across-site mean (ASM) values of C levels and DRs for bipolar (BP) and monopolar (MP) stimulation, and examined the relation of these metrics to speech recognition across subjects. Significant negative correlations with speech recognition were found for ASVs of C levels for BP stimulation; i.e., subjects with high ASVs of BP C levels had poor speech recognition. Positive correlations with speech recognition were found for ASMs of C levels and ASMs of DRs for both BP and MP stimulation; i.e., subjects with high mean C levels and large mean DRs had better speech recognition. Thus, these psychophysical metrics are effective for diagnosis of individual differences in performance of subjects with cochlear implants. Furthermore, they point to some potentially useful treatment procedures.