Effect of Channel Interaction on Vocal Cue Perception in Cochlear Implant Users

Abstract

Speech intelligibility in multitalker settings is challenging for most cochlear implant (CI) users. One possibility for this limitation is the suboptimal representation of vocal cues in implant processing, such as the fundamental frequency (F0), and the vocal tract length (VTL). Previous studies suggested that while F0 perception depends on spectrotemporal cues, VTL perception relies largely on spectral cues. To investigate how spectral smearing in CIs affects vocal cue perception in speech-on-speech (SoS) settings, adjacent electrodes were simultaneously stimulated using current steering in 12 Advanced Bionics users to simulate channel interaction. In current steering, two adjacent electrodes are simultaneously stimulated forming a channel of parallel stimulation. Three such stimulation patterns were used: Sequential (one current steering channel), Paired (two channels), and Triplet stimulation (three channels). F0 and VTL just-noticeable differences (JNDs; Task 1), in addition to SoS intelligibility (Task 2) and comprehension (Task 3), were measured for each stimulation strategy. In Tasks 2 and 3, four maskers were used: the same female talker, a male voice obtained by manipulating both F0 and VTL (F0+VTL) of the original female speaker, a voice where only F0 was manipulated, and a voice where only VTL was manipulated. JNDs were measured relative to the original voice for the F0, VTL, and F0+VTL manipulations. When spectral smearing was increased from Sequential to Triplet, a significant deterioration in performance was observed for Tasks 1 and 2, with no differences between Sequential and Paired stimulation. Data from Task 3 were inconclusive. These results imply that CI users may tolerate certain amounts of channel interaction without significant reduction in performance on tasks relying on voice perception. This points to possibilities for using parallel stimulation in CIs for reducing power consumption.

Prelingually Deaf Children With Cochlear Implants Show Better Perception of Voice Cues and Speech in Competing Speech Than Postlingually Deaf Adults With Cochlear Implants

“…The results from this study show significant differences between the voice-perception abilities of prelingually deaf CI children and postlingually deaf CI adults (Fuller et al 2014;Gaudrain & Başkent, 2018;El Boghdady et al 2019Nogueira et al 2021). Based on the high VTL JNDs of CI adults (Gaudrain & Başkent, 2018), the explanation that VTL cues are not transmitted via the CI signal seemed more plausible at the time than the alternative that the distorted VTL cues prevented their utilization (Fuller et al 2014).…”

“…Hence, this study investigated prelingually deaf CI children’s ability to perceive voice cues and benefit from voice differences for perceiving speech in competing speech. We also examined how their abilities compare to those of NH children and postlingually deaf CI adults who were tested in previous studies using similar experiments ( Fuller et al 2014 ; Gaudrain & Başkent 2018 ; El Boghdady et al 2019 , 2021 ; Nogueira et al 2021 ). Finally, we examined the relationship between three voice-perception abilities involving different cognitive processes, ranging from voice discrimination to voice categorization and the perception of speech in competing speech.…”

“…In this study, we aimed to investigate the perception and use of F0 and VTL in CI children, taking into account developmental effects using data from NH children and adults from previous studies ( Nagels et al 2020a , 2021a ) and data collected from postlingually deaf CI adults from previous studies using similar experiments ( Fuller et al 2014 ; Gaudrain & Başkent, 2018 ; El Boghdady et al 2019 , 2021 ; Nogueira et al 2021 ). In three experiments, we examined CI children’s voice cue discrimination (experiment 1), voice gender categorization (experiment 2), and perception of speech in competing speech and benefit from target-masker F0 and VTL differences (experiment 3), using the same experimental tasks from previous studies in the same project on the perception of indexical cues in kids and adults ( Nagels et al 2020a , 2020b , 2021a ).…”

Investigating the effect of blurring and focusing current in cochlear implant users with the Panoramic ECAP method

“…However, there may also be physiological or device-related reasons for a location-specific effect of blurring along the cochlea. The evidence to date does suggest that a wider current profile or more channel interaction is achieved when stimulating with multiple electrodes at once than when stimulating in MP mode with a single electrode or in sequential mode (Nogueira, et al, 2021). However, there is variation between CI users as to how many electrodes are needed to be simultaneously stimulated in order to degrade spectral resolution and/or speech perception.…”

A computational model to simulate spectral modulation and speech perception experiments of cochlear implant users

“…Simultaneous stimulation allows to increase the pulse duration and consequently decrease the maximum current needed (Langner et al, 2017 ). The drawback is that simultaneous stimulation produces electric interaction that causes spectral smearing across channels, which also causes temporal smearing since temporal modulations may be reduced (Nogueira et al, 2021 ). The balance between power savings and CI users' performance was investigated by Langner et al ( 2017 ) using three variations of the F120.…”