From Spectral Resolution to Speech Perception: A Review of Findings in Postlingually Deafened Adult Cochlear Implant Listeners

Reduced spectral resolution ability limits speech recognition in cochlear implant (CI) listeners. While several studies have examined the association between spectral resolution and speech perception, uncertainties persist regarding the strength of this link and related methodological and clinical factors. This review synthesizes prior findings on this relationship in postlingually deafened adult CI listeners using psychophysical measures of spectral resolution, evaluated based on four criteria: (1) whether they consider the categorization nature of speech recognition task, (2) whether they account for modulation frequency within and across spectral channels while capturing essential spectral modulations in speech, (3) whether they assess spectral resolution globally or at a channel-specific level, and (4) their relative time efficiency for clinical application. Many studies report a significant association, with some measures--such as test of spectral ripple discrimination threshold and its modified versions--demonstrating superior predictive capacity, yet no single measure meets all criteria. Our review highlights the critical role of methodological factors and calls for more refined, effective, and channel-specific assessment techniques that better capture the link between spectral resolution and speech perception in CI listeners. These approaches may improve clinical CI programming by addressing poorly functioning electrodes and enhancing perceptual outcomes in postlingually deafened adult CI listeners.