Full-array channel discrimination in cochlear implants: validation and clinical application

Abstract

Objective: We sought to validate our proposed tool for estimating channel discrimination of cochlear implant (CI) users along the full electrode array and to assess associations between place-pitch discrimination and speech perception. Design: In two tests, participants identified one stimulus (probe) as the odd-one-out compared with two reference stimuli. Probe stimuli were evoked using dual electrode stimulation characterised by the current steering coefficient alpha. The first test measured psychometric functions (PFs) on pre-defined contacts, with just a noticeable difference (JND alpha) as the outcome variable. The second test estimated channel discrimination on the full electrode array, yielding a discrimination score of D alpha. We measured speech perception as free-field consonant-vowel-consonant phoneme recognition scores. Study sample: We included 25 adults with at least 6 months of CI experience. Results: JND alpha and D alpha scores measured on the same contact correlated significantly (r(s) = 0.64, p < 0.001). Mean JND alpha and speech perception scores showed significant relationships in quiet and in noise. Conclusions: D alpha correlated strongly with JND alpha scores obtained with the PFs. For poor performers, the full-array test may underestimate JND alpha. The full-array pitch discrimination test could be a helpful clinical tool, such as for fitting regions of lesser pitch discrimination ability.