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. 2019 Mar;145(3):1556.
doi: 10.1121/1.5092350.

Speech recognition as a function of the number of channels in perimodiolar electrode recipients

Katelyn A Berg  1 , Jack H Noble  2 , Benoit M Dawant  2 , Robert T Dwyer  1 , Robert F Labadie  3 , René H Gifford  1
Affiliations

Speech recognition as a function of the number of channels in perimodiolar electrode recipients

Katelyn A Berg et al. J Acoust Soc Am. 2019 Mar.

Abstract

This study investigated the number of channels needed for maximum speech understanding and sound quality in 30 adult cochlear implant (CI) recipients with perimodiolar electrode arrays verified via imaging to be completely within scala tympani (ST). Performance was assessed using a continuous interleaved sampling (CIS) strategy with 4, 8, 10, and 16 channels and n-of-m with 16 maxima. Listeners were administered auditory tasks of speech understanding [monosyllables, sentences (quiet and +5 dB signal-to-noise ratio, SNR), vowels, consonants], spectral modulation detection, as well as subjective estimates of sound quality. Results were as follows: (1) significant performance gains were observed for speech in quiet (monosyllables and sentences) with 16- as compared to 8-channel CIS, (2) 16 channels in a 16-of-m strategy yielded significantly higher outcomes than 16-channel CIS for sentences in noise (percent correct and subjective sound quality) and spectral modulation detection, (3) 16 channels in a 16-of-m strategy yielded significantly higher outcomes as compared to 8- and 10-channel CIS for monosyllables, sentences (quiet and noise), consonants, spectral modulation detection, and subjective sound quality, (4) 16 versus 8 maxima yielded significantly higher speech recognition for monosyllables and sentences in noise using an n-of-m strategy, and (5) the degree of benefit afforded by 16 versus 8 maxima was inversely correlated with mean electrode-to-modiolus distance. These data demonstrate greater channel independence with perimodiolar electrode arrays as compared to previous studies with straight electrodes and warrant further investigation of the minimum number of maxima and number of channels needed for maximum auditory outcomes.

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Figures

FIG. 1.
FIG. 1.
Mean outcomes for 11 listeners with ST perimodiolar electrode arrays across all tested channel conditions for scores for CNC words, AzBio sentences in quiet, AzBio sentences at +5 dB SNR (Panel A), sound quality ratings for CNC words and AzBio sentences in quiet and noise (Panel B), and vowels, consonants, consonant features, and QSMD (Panel C). Error bars are +1 standard error measurement.
FIG. 2.
FIG. 2.
Individual speech recognition for CNC monosyllabic words in quiet and AzBio sentences at +5 dB with 16 maxima as a function of 8 maxima. The dashed lines represent the 95% confidence interval for each of the measures. Circles represent participants with confirmed ST electrode location, circles with cross represent participants with transcalar displacement (ST-SV), and diamonds represent participants with unknown scalar location.
FIG. 3.
FIG. 3.
Individual gain for AzBio sentence recognition at +5 dB SNR, in percentage points, with 16 versus 8 maxima is plotted as a function of mean electrode-to-modiolus distance, in mm.
See this image and copyright information in PMC

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