Measurement of spectral resolution and listening effort in people with cochlear implants

Abstract

Cochlear implants (CIs) provide notably poor spectral resolution, which poses significant challenges for speech understanding, and places greater demands on listening effort. We evaluated a CI stimulation strategy designed to improve spectral resolution by measuring its impact on listening effort (as quantified by pupil dilation, which is considered to be a reliable index of cognitive load). Specifically, we investigated dichotic interleaved processing channels (where odd channels are active in one ear, and even channels are active in the contralateral ear). We used a sentence listening and repetition task where listeners alternated between their everyday clinical CI configurations and the interleaved channel strategy, to test which offered better resolution and demanded less effort. Methods and analyses stemmed from previous experiments confirming that spectral resolution has a systematic impact on listening effort in individuals with normal hearing. Pupil dilation measures were generally consistent with speech perception (r2 = 0.48, p < 0.001), suggesting that spectral resolution plays an important role in listening effort for listeners with CIs. When using interleaved channels, both speech perception performance and pupillary responses were variable across individuals, underscoring the need for individualized measurement for CI listeners rather than group analysis, in the pursuit of better clinical fitting.