Voice Parameters in Children With Cochlear Implants: A Systematic Review and Meta-Analysis

Since the early 1990s, it has been possible to measure electrically evoked compound action potentials (ECAPs) from Nucleus cochlear implant users. Recording the ECAP does not require active participation by the subject, and the recordings are not adversely affected by attention or sleep, making this response an ideal tool for monitoring long-term changes. Previous research from our laboratory (Hughes et al, 2001) has shown that ECAP thresholds and slope of the ECAP growth functions are relatively stable over time. However, this conclusion was based on results obtained from a fairly limited number of study participants, each of whom used the Nucleus CI24M cochlear implant and were followed for less than two years. To evaluate the effect of long-term use of a cochlear implant on ECAP thresholds and slope of the ECAP input/output function for both pediatric and adult cochlear implant recipients. A longitudinal study that describes how ECAP thresholds and growth functions change over a period of 96 mo following initial activation. Changes over time in ECAP threshold and slope of the ECAP growth function were analyzed, and effects of the subject's age, type of CI (cochlear implant), and stimulating electrode are included in the analysis. 134 Nucleus CI users participated in this study. All were profoundly deaf. This subject pool included 84 individuals (40 adults and 44 children) who used the Nucleus CI24M cochlear implant and 50 individuals (21 adults and 29 children) who used the Nucleus CI24R cochlear implant. Electrodes 5, 10, 15, and 20 were stimulated, and ECAP growth functions were measured for each subject at regular intervals following the initial activation of the device. Small increases in mean ECAP thresholds were observed for both pediatric and adult CI users between an "early" visit that occurred within 3-6 mo following hookup and a "late" visit that occurred 4.8-6 yr later. For adults, the average increase in ECAP threshold was 3.94 CL (clinical programming units for Nucleus CIs). For children, the average increase was 4.16 CL. These differences, while small, were statistically significant. Slope of the ECAP growth functions measured over the same time interval did not change significantly. On average, pediatric CI users had ECAP thresholds that were 4-5 CL units higher than the adult CI recipients. The most striking outcome from this study, however, was the finding that when compared with postlingually deafened adults, pediatric CI users had ECAP growth functions that were substantially steeper. The differences between the results obtained from children and those obtained from adults were statistically significant and largely independent of device type or stimulating electrode. Results from this study show ECAP thresholds and growth functions to change very little over a 5-6 yr observation interval suggesting that long-term use of a CI is not likely to have a significant negative impact on the response of the peripheral auditory system. Pediatric CI users were shown to have, on average, higher ECAP thresholds and steeper ECAP growth functions than postlingually deafened adult CI users. This finding suggests potential differences between the two patient populations either in terms of the current fields within the cochlea or the effective distance between the stimulating electrode and the stimulable neural tissue.

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Aging may limit speech understanding outcomes in cochlear-implant (CI) users.Here, we examined age-related declines in auditory temporal processing as apotential mechanism that underlies speech understanding deficits associated withaging in CI users. Auditory temporal processing was assessed with acategorization task for the words dish and ditch (i.e., identify each token asthe word dish or ditch) on a continuum ofspeech tokens with varying silence duration (0 to 60 ms) prior to the finalfricative. In Experiments 1 and 2, younger CI (YCI), middle-aged CI (MCI), andolder CI (OCI) users participated in the categorization task across a range ofpresentation levels (25 to 85 dB). Relative to YCI, OCI required longer silencedurations to identify ditch and exhibited reduced ability to distinguish thewords dish and ditch (shallower slopes in the categorization function).Critically, we observed age-related performance differences only at higherpresentation levels. This contrasted with findings from normal-hearing listenersin Experiment 3 that demonstrated age-related performance differencesindependent of presentation level. In summary, aging in CI users appears todegrade the ability to utilize brief temporal cues in word identification,particularly at high levels. Age-specific CI programming may potentially improveclinical outcomes for speech understanding performance by older CIlisteners.

On the relationship between auditory cognition and speech intelligibility in cochlear implant users: An ERP study

Adult cochlear implant (CI) recipients obtain varying levels of speech perception from their device. Adult CI users adapt quickly to their CI if they have no peripheral "bottom-up" or neurocognitive "top-down" limiting factors. Our objective here was to understand the influence of limiting factors on the progression of sentence understanding in quiet and in noise, initially and over time. We hypothesized that the presence of limiting factors, detected using a short test battery, would predictably influence sentence recognition with practical consequences. We aimed to validate the test battery by comparing the presence of limiting factors and the success criteria of >90% sentence understanding in quiet 1 month after activation. The study was a single-clinic, cross-sectional, retrospective design incorporating 32 adult unilateral Nucleus CI users aged 27 to 90 years (mean = 70, SD = 13.5). Postoperative outcome was assessed through sentence recognition scores in quiet and in varying signal to noise ratios at 1 day, 1 to 2 months, and up to 2 years. Our clinic's standard test battery comprises physiological and neurocognitive measures. Physiological measures included electrically evoked compound action potentials for recovery function, spread of excitation, and polarity effect. To evaluate general cognitive function, inhibition, and phonological awareness, the Montreal Cognitive Assessment screening test, the Stroop Color-Word Test, and tests 3 and 4 of the French Assessment of Reading Skills in Adults over 16 years of age, respectively were performed. Physiological scores were considered abnormal, and therefore limiting, when total neural recovery periods and polarity effects, for both apical and basal electrode positions, were >1.65 SDs from the population mean. A spread of excitation of >6 electrode units was also considered limiting. For the neurocognitive tests, scores poorer than 1.65 SDs from published normal population means were considered limiting. At 1 month, 13 out of 32 CI users scored ≥90% sentence recognition in quiet with no significant dependence on age. Subjects with no limiting peripheral or neurocognitive factors were 8.5 times more likely to achieve ≥90% score in quiet at 1 month after CI switch-on ( p = 0.010). In our sample, we detected 4 out of 32 cases with peripheral limiting factors that related to neural health or poor electrode-neural interface at both apical and basal positions. In contrast, neurocognitive limiting factors were identified in 14 out of 32 subjects. Early sentence recognition scores were predictive of long-term sentence recognition thresholds in noise such that limiting factors appeared to be of continuous influence. Both peripheral and neurocognitive processing factors affect early sentence recognition after CI activation. Peripheral limiting factors may have been detected less often than neurocognitive limiting factors because they were defined using sample-based criteria versus normal population-based criteria. Early performance was generally predictive of long-term performance. Understanding the measurable covariables that limit CI performance may inform follow-up and improve counseling. A score of ≥90% for sentence recognition in quiet at 1 month may be used to define successful progress; whereas, lower scores indicate the need for diagnostic testing and ongoing rehabilitation. Our findings suggest that sentence test scores as early as 1 day after activation can provide vital information for the new CI user and indicate the need for rehabilitation follow-up.

Cochlear implants (CIs), which are designed to support spoken communication of persons with severe to profound hearing loss, can provide improved hearing capability through passive exposure. However, auditory training may optimize perception of spectrally complex sounds such as music or speech. Reviews of music-based training for pediatric CI users have reported modest though variable benefits, as well as problems with attrition. It is presumed that more substantial changes may result from longer, more intensive training; however, the development of protocols sufficiently motivating for sustained intensity is challenging. This article examined the experiences of star pediatric CI users, whose years of music training have yielded exceptional auditory benefits. Greater understanding of their experiences and attitudes may suggest best practices for music-based training. Research aims included: (a) characterizing the musical behaviors and perceptual learning processes of music-centric (Music-centric, for purposes of this paper, refers to CI users who engage in sustained and successful music making such as music lessons and ensembles and focused music listening over a period of years, and who derive deep satisfaction from those experiences.) pediatric CI users, and (b) identifying psychosocial and auditory factors that motivated persistence in auditory training. We used qualitative and patient-engaged research methodologies, gathering data through questionnaires with open-ended questions. The participants, six music-centric CI users and five parents, described their experiences and attitudes regarding music training, and factors that supported or undermined those experiences. Data were analyzed using reflexive thematic analysis. The codes were consolidated into five themes and organized into a Model of Music-Based Learning for Pediatric Cochlear Implant Recipients. Sustained participation in music training was perceived as a dynamic process including varied musical stimuli, and moderated by intrinsic (attitude, perceived behavioral control) and extrinsic (parents, teachers, peers) influences, hearing status, sound access and background factors. These themes highlighted motivational factors that pediatric CI users and parents considered important to sustained, intensive and successful music learning throughout childhood and adolescence. These factors should be considered in the development of music-based training for pediatric CI recipients.

The current study examined the neural mechanisms underlying auditory outcomes in pediatric cochlear implant (CI) users using event-related potentials, focusing on the frontocentral Novelty P3 (indexing automatic attention) and the parietal Target P3 (reflecting controlled attention). By comparing CI children with normal-hearing peers, we aimed to elucidate how these attention mechanisms contribute to post-implantation auditory performance variability. Prelingually deaf children with early bilateral CIs (n = 25) and normal-hearing (NH) controls (n = 28), matched for gender and age (7–13 years), completed an oddball paradigm during ERP recording and performed speech-in-noise and memory tasks. CI users showed reduced Novelty P3 amplitudes compared to NH peers, suggesting impaired automatic attention mechanisms, while Target P3 amplitudes were comparable between groups, indicating preserved controlled attention. CI users demonstrated poorer performance on speech-in-noise recognition and forward digit span tasks. Larger Novelty P3 and Target P3 amplitudes both correlated positively with speech-in-noise performance across all participants. In contrast, in CI users specifically, Target P3 amplitudes showed positive associations with short-term memory performance. This study provides novel evidence that pediatric CI users exhibit reduced automatic attention shifting in response to acoustic changes while maintaining intact controlled attention processes that may serve as a compensatory mechanism. The neural markers’ associations with behavioral performance suggest potential intervention targets: rehabilitation efforts might focus on strengthening automatic attention shifting while leveraging preserved controlled attention pathways.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-24476-9.

Objective To investigate electrically evoked auditory cortical responses (eACR) elicited from the stimulation of intracochlear electrodes based on individually fitted stimulation parameters in cochlear implant (CI) users. Design An eACR setup based on individual fitting parameters is proposed. A 50-ms alternating biphasic pulse train was used to stimulate apical, medial, and basal electrodes and to evoke auditory cortical potentials (N1-P2 complex). Study sample The eACR setup proposed was validated with 14 adult CI users. Results Individual and grand-average eACR waveforms were obtained. The eACR amplitudes were lower in the basal than in the apical and medial regions. Earlier N1 latencies were found in CI users with lower maximum comfortable loudness levels and shorter phase duration in response to apical stimulation, while medial and basal stimulation resulted in earlier N1 latencies and larger N1-P2 amplitudes in users with longer CI experience. Conclusions eACR could be elicited by direct intracochlear stimulation using individual fitting parameters with a success rate of 71%. The highest cortical peak-to-peak amplitudes were obtained in response to apical stimulation. Unlike the P2, the N1 component appeared to be a consistent cortical potential to determine eACR and gain knowledge of the auditory processing beyond the cochlea in CI users. Highlights eACR can be elicited through direct stimulation of intracochlear electrodes. Stimulation of apical and medial regions yielded the highest N1-P2 amplitudes. CI users with lower maximum comfortable loudness levels had shorter N1 latencies during apical stimulation. The present dataset of mainly well-performing CI users suggests better cortical processing, that is, higher amplitudes and shorter latencies of N1. The N1 potential appears a more consistent and reliable potential than the P2 to determine eACR responses in CI users.

Effects of analysis window on 40-Hz auditory steady-state responses in cochlear implant users

First, to establish the feasibility of the observer-based psychophysical procedure (OPP) in measuring sound detection in infant and toddler cochlear implant (CI) recipients. Second, to measure the psychometric function for detection (PFD) from individual subjects. Third, to determine whether reaction time (RT) provides information about the auditory sensitivity of young CI users. Twelve CI recipients, 11 to 32 mo old, participated in our study. Initially, tones were presented in sound field, and children learned to respond when they heard tones but not at other times. Once an 80% correct criterion was met in sound field, a novel stimulation paradigm was used to present stimuli to a single electrode while the child listened to acoustic input on most other electrodes using their usual map. The PFD and RT were measured using this single-electrode stimulation paradigm. Eleven subjects met criterion, 6 within the minimum possible number of trials. For eight subjects, the asymptotic level of detecting single-electrode stimuli averaged 86% correct, similar to levels achieved by normal-hearing infants and toddlers detecting pure tones. The PFD slope of infant and toddler CI recipients was less than or equal to the slope for adult CI users reported in previous studies. RT decreased significantly with stimulus level in four children. These preliminary results suggest that psychophysical detection data can be obtained from infant and toddler CI recipients using OPP. The PFD of young CI users may be shallower than that of adult CI users. Relatively good asymptotic detection performance implies that young CI users are more attentive to sound than has been suggested in previous studies. RT tended to be a less reliable measure of detection, but methodological changes could improve its utility.

Some cochlear implant (CI) users report having difficulty accessing indexical information in the speech signal, presumably due to limitations in the transmission of fine spectrotemporal cues. The purpose of this review article was to systematically review and evaluate the existing research on talker processing in CI users. Specifically, we reviewed the performance of CI users in three types of talker- and voice-related tasks. We also examined the different factors (such as participant, hearing, and device characteristics) that might influence performance in these specific tasks. We completed a systematic search of the literature with select key words using citation aggregation software to search Google Scholar. We included primary reports that tested (a) talker discrimination, (b) voice perception, and (c) talker identification. Each report must have had at least one group of participants with CIs. Each included study was also evaluated for quality of evidence. The searches resulted in 1,561 references, which were first screened for inclusion and then evaluated in full. Forty-three studies examining talker discrimination, voice perception, and talker identification were included in the final review. Most studies were focused on postlingually deafened and implanted adult CI users, with fewer studies focused on prelingual implant users. In general, CI users performed above chance in these tasks. When there was a difference between groups, CI users performed less accurately than their normal-hearing (NH) peers. A subset of CI users reached the same level of performance as NH participants exposed to noise-vocoded stimuli. Some studies found that CI users and NH participants relied on different cues for talker perception. Within groups of CI users, there is moderate evidence for a bimodal benefit for talker processing, and there are mixed findings about the effects of hearing experience. The current review highlights the challenges faced by CI users in tracking and recognizing voices and how they adapt to it. Although large variability exists, there is evidence that CI users can process indexical information from speech, though with less accuracy than their NH peers. Recent work has described some of the factors that might ease the challenges of talker processing in CI users. We conclude by suggesting some future avenues of research to optimize real-world speech outcomes.

Cochlear implantation constitutes a successful therapy of inner ear deafness, with the majority of patients showing good outcomes. There is, however, still some unexplained variability in outcomes with a number of cochlear-implant (CI) users, showing major limitations in speech comprehension. The current study used a multimodal diagnostic approach combining single-photon emission computed tomography (SPECT) and electroencephalography (EEG) to examine the mechanisms underlying speech processing in postlingually deafened CI users (N = 21). In one session, the participants performed a speech discrimination task, during which a 96-channel EEG was recorded and the perfusions marker 99mTc-HMPAO was injected intravenously. The SPECT scan was acquired 1.5 h after injection to measure the cortical activity during the speech task. The second session included a SPECT scan after injection without stimulation at rest. Analysis of EEG and SPECT data showed N400 and P600 event-related potentials (ERPs) particularly evoked by semantic violations in the sentences, and enhanced perfusion in a temporo-frontal network during task compared to rest, involving the auditory cortex bilaterally and Broca’s area. Moreover, higher performance in testing for word recognition and verbal intelligence strongly correlated to the activation in this network during the speech task. However, comparing CI users with lower and higher speech intelligibility [median split with cutoff + 7.6 dB signal-to-noise ratio (SNR) in the Göttinger sentence test] revealed for CI users with higher performance additional activations of parietal and occipital regions and for those with lower performance stronger activation of superior frontal areas. Furthermore, SPECT activity was tightly coupled with EEG and cognitive abilities, as indicated by correlations between (1) cortical activation and the amplitudes in EEG, N400 (temporal and occipital areas)/P600 (parietal and occipital areas) and (2) between cortical activation in left-sided temporal and bilateral occipital/parietal areas and working memory capacity. These results suggest the recruitment of a temporo-frontal network in CI users during speech processing and a close connection between ERP effects and cortical activation in CI users. The observed differences in speech-evoked cortical activation patterns for CI users with higher and lower speech intelligibility suggest distinct processing strategies during speech rehabilitation with CI.

Everyday communication requires not only the ability to recognize speech but also the ability to comprehend and remember what has been said. However, when the speech signal is degraded, as for cochlear implants (CIs), additional cognitive effort may be required. Other challenges, such as speaking rate alterations, may further strain the listener’s limited cognitive resources, with implications for comprehension and memory. The current study examined the effects of spectral degradation and speaking rate on comprehension and recognition memory in adult CI users and normal-hearing (NH) listeners under CI simulation. Participants completed a sentence verification task in which they classified sentences as true or false, and a sentence recognition memory task (SRMT) in which they classified sentences as new or old (from the SVT). Sentences were altered to have fast, average, and slow speaking rates. Results demonstrated that both CI and NH listeners achieved highly accurate sentence comprehension and recognition memory, emphasizing the robustness of speech processing to spectral degradation. However, slower speaking rates enhanced comprehension and memory, particularly for CI users. Faster speaking rates may exacerbate the cognitive demands imposed by spectral degradation, hindering speech communication. Comprehension and memory tasks may provide valuable insights into CI users’ real-world listening challenges.

ABSTRACTNormal auditory feedback contributes to moment-to-moment control of speech production. Effects of auditory feedback’s absence on hearing-impaired individuals are widely documented, but auditory perturbation has not been investigated. Our objective was to evaluate the effect of delayed auditory feedback (DAF) and frequency altered feedback (FAF) on speech production among prelingual cochlear implant (CI) users and normal hearing (NH) individuals, to evaluate CI users’ reliance on auditory feedback. Twenty young adults (10 CI, 10 NH), without developmental and cognitive impairments, participated in the study. Under variable auditory feedback conditions, speech production (spontaneous or reading aloud) was measured using speech rate, percentage of interruptions, fundamental frequency (F0), and relative intensity. Results showed that (1) both DAF and FAF caused slower speech rates and more interruptions while reading aloud, with DAF having larger effect; (2) altered feedback produced no differences between groups, except an increase in F0 for CI users during DAF; and (3) CI users’ ability to understand speech via phone and without lip-reading was positively correlated with performance under DAF. These findings suggest that auditory perturbation similarly affects speech production among prelingual CI users and NH individuals, indicating CI users depend on auditory feedback to the same degree as normal hearing individuals.

Objectives Cochlear implants (CI) have dramatically improved speech perception for patients with sensorineural hearing impairment. However, listening to music is a great challenge for them. This study examined the perception and appraisal of Iranian musical instruments comparing with similar Western instruments. Methods Eleven adult CI users and 25 normal hearing (NH) individuals participated in this study. Musical stimuli of three commonly heard instrument pairs were prepared. Participants were asked to identify the instruments and rate their appraisal on a ten-point Likert scale (0 = dislike very much, 10 = like very much). Results The instrument recognition rate was 40.6% among the CI users, and the mean appraisal score was 5.2 ± 2.7. NH listeners had none significant higher scores on both tasks with a recognition rate of 50.0% and the mean appraisal score of 6.9 ± 1.5. Iranian instruments were more recognized in both groups. Regarding their appraisal, the mean score for both types was almost equal in the NH group, while CI users more appraised Iranian instruments. Conclusion In addition to better recognition of Iranian instruments, they were particularly better appraised in the CI group. Iranian instruments provide suitable musical pieces for CI recipients that can be considered in rehabilitation programs.