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This study investigated the number of channels available to cochlear implant (CI) recipients for maximum speech understanding and sound quality for lateral wall electrode arrays-which result in large electrode-to-modiolus distances-featuring the greatest inter-electrode distances (2.1-2.4 mm), the longest active lengths (23.1-26.4 mm), and the fewest number of electrodes commercially available. Participants included ten post-lingually deafened adult CI recipients with MED-EL electrode arrays (FLEX28 and STANDARD) entirely within scala tympani. Electrode placement and scalar location were determined using computerized tomography. The number of channels was varied from 4 to 12 with equal spatial distribution across the array. A continuous interleaved sampling-based strategy was used. Speech recognition, sound quality ratings, and a closed-set vowel recognition task were measured acutely for each electrode condition. Participants did not demonstrate statistically significant differences beyond eight channels at the group level for almost all measures. However, several listeners showed considerable improvements from 8 to 12 channels for speech and sound quality measures. These results suggest that channel interaction caused by the greater electrode-to-modiolus distances of straight electrode arrays could be partially compensated for by a large inter-electrode distance or spacing.

This study investigated the effects of cochlear implant (CI) electrode array type and scalar location on the number of channels available to CI recipients for maximum speech understanding and sound quality. Eighteen post-lingually deafened adult CI recipients participated, including 11 recipients with straight electrode arrays entirely in scala tympani and 7 recipients with translocated precurved electrode arrays. Computerized tomography was used to determine electrode placement and scalar location. In each condition, the number of channels varied from 4 to 22 with equal spatial distribution across the array. Speech recognition (monosyllables, sentences in quiet and in noise), subjective speech sound quality, and closed-set auditory tasks (vowels, consonants, and spectral modulation detection) were measured acutely. Recipients with well-placed straight electrode arrays and translocated precurved electrode arrays performed similarly, demonstrating asymptotic speech recognition scores with 8–10 channels, consistent with the classic literature. This finding contrasts with recent work [Berg, Noble, Dawant, Dwyer, Labadie, and Gifford. (2019). J. Acoust. Soc. Am. 145, 1556–1564] that found precurved electrode arrays well-placed in scala tympani demonstrate continuous performance gains beyond 8–10 channels. Given these results, straight and translocated precurved electrode arrays are theorized to have less channel independence secondary to their placement farther away from neural targets.

This study investigated the number of channels required for asymptotic speech recognition for ten pediatric cochlear implant (CI) recipients with precurved electrode arrays. Programs with 4–22 active electrodes were used to assess word and sentence recognition in noise. Children demonstrated significant performance gains up to 12 electrodes for continuous interleaved sampling (CIS) and up to 22 channels with 16 maxima. These data are consistent with the latest adult CI studies demonstrating that modern CI recipients have access to more than 8 independent channels and that both adults and children exhibit performance gains up to 22 channels.

This study investigated the number of channels needed for maximum speech understanding and sound quality in 5 (anticipated n = 10) adult cochlear implant (CI) recipients with mid-scala electrode arrays completely within scala tympani (ST). CI programs with 4–16 active electrodes using a CIS-based strategy were created along with two n-of-m programs (8-of-16 and 12-of-16). Measures of speech understanding and sound quality were assessed. Our hypothesis was that individuals with precurved electrodes localized in ST would have greater channel independence than previous studies demonstrating gains in performance beyond 8 channels. Participants demonstrated performance gains up to 8–10 electrodes for speech recognition and sound quality ratings. Significantly poorer performance was observed using an n-of-m strategy as compared to CIS conditions with 8+ electrodes. These data are in contrast with recent studies for precurved arrays (e.g., Croghan et al., 2017; Berg et al., in review) reporting significant improvement up to 16 to 22 channels. However, the current results are consistent with previous literature (e.g., Fishman et al., 1997; Friesen et al., 2001; Shannon et al., 2011), demonstrating no more than 8–10 independent channels for CI recipients with straight arrays. Implications for device selection and the impact of electrode-to-modiolus distance will be discussed.