Electrically evoked auditory cortical responses elicited from individually fitted stimulation parameters in cochlear implant users

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An intact auditory system is essential for the development and maintenance of voice quality and speech prosody. On the contrary hearing loss affects the adjustments and appropriate use of organs involved in speech and voice production. Spectro-acoustic voice parameters have been evaluated in Cochlear Implant (CI) users, and the authors of previous systematic reviews on the topic concluded that fundamental frequency (F0) seemed preliminarily the most reliable parameter to evaluate voice alterations in adult CI users. The main aim of this systematic review and meta-analysis was to clarify the vocal parameters and prosodic alterations of speech in pediatric CI users. The protocol of the systematic review was registered on the PROSPERO database, International prospective register of systematic reviews. We conducted a search of the English literature published in the period between January 1, 2005 and April 1, 2022 on the Pubmed and Scopus databases. A meta-analysis was conducted to compare the values of voice acoustic parameters in CI users and non-hearing-impaired controls. The analysis was conducted using the standardized mean difference as the outcome measure. A random-effects model was fitted to the data. A total of 1334 articles were initially evaluated using title and abstract screening. After applying inclusion/exclusion criteria, 20 articles were considered suitable for this review. The age of the cases ranged between 25 and 132 months at examination. The most studied parameters were F0, Jitter, Shimmer and Harmonics-to-Noise Ratio (HNR); other parameters were seldom reported. A total of 11 studies were included in the meta-analysis of F0, with the majority of estimates being positive (75%); the estimated average standardized mean difference based on the random-effects model was 0.3033 (95% CI: 0.0605 to 0.5462; P = 0.0144). For Jitter (0.2229; 95% CI: -0.1862 to 0.7986; P = 0.2229) and shimmer (0.2540; 95% CI: -0.1404 to 0.6485; P = 0.2068) there was a trend toward positive values without reaching statistical significance. This meta-analysis confirmed that higher F0 values have been observed in the pediatric population of CI users compared to age-matched normal hearing volunteers, whereas the parameters of voice noise were not significantly different between cases and controls. Prosodic aspects of language need further investigations. In longitudinal contexts, prolonged auditory experience with CI has brought voice parameters closer to the norm. Following the available evidence, we stress the utility of inclusion of vocal acoustic analysis in the clinical evaluation and follow-up of CI patients to optimize the rehabilitation process of pediatric patients with hearing loss.

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.

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

A cochlear implant (CI) is a hearing device introduced in the 1980s for profoundly deaf subjects who gained little or no benefit from powerful hearing aids. This device comprises an electrode array inserted in the cochlea, connected to an internal receiver, and an externally worn speech processor. The CI transforms acoustic signals into electrical currents which directly stimulate the auditory nerve. Since the early 1990s, cochlear implantation in children has been developing rapidly. Although it is still difficult to predict how a child will perform with a cochlear implant, the success of cochlear implantation can no longer be denied. In this paper, some recent papers and reports, and the results of the various Nijmegen cochlear implant studies, are reviewed. Issues about selection, examinations, surgery and the outcome are discussed. Overall, our results were comparable with those of other authors. It can be concluded that cochlear implantation is an effective treatment for postlingually deaf as well as prelingually (congenital or acquired) deaf children with profound bilateral sensorineural deafness.

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.

Musical and vocal emotion perception for cochlear implants users

Auditory brainstem implants (ABI) use the same processing strategy as was developed for cochlear implants (CI). However, the cochlear nucleus (CN), the stimulation site of ABIs, is anatomically and physiologically more complex than the auditory nerve and consists of neurons with differing roles in auditory processing. The aim of this study was to evaluate the hypotheses that ABI users are less able than CI users to access speech spectro-temporal information delivered by the existing strategies and that the sites stimulated by different locations of CI and ABI electrode arrays differ in encoding of temporal patterns in the stimulation. Six CI users and four ABI users of Nucleus implants with ACE processing strategy participated in this study. Closed-set perception of aCa syllables (16 consonants) and bVd words (11 vowels) was evaluated via experimental processing strategies that activated one, two, or four of the electrodes of the array in a CIS manner as well as subjects' clinical strategies. Three single-channel strategies presented the overall temporal envelope variations of the signal on a single-implant electrode located at the high-, medium-, and low-frequency regions of the array. Implantees' ability to discriminate within electrode temporal patterns of stimulation for phoneme perception and their ability to make use of spectral information presented by increased number of active electrodes were assessed in the single- and multiple-channel strategies, respectively. Overall percentages and information transmission of phonetic features were obtained for each experimental program. Phoneme perception performance of three ABI users was within the range of CI users in most of the experimental strategies and improved as the number of active electrodes increased. One ABI user performed close to chance with all the single and multiple electrode strategies. There was no significant difference between apical, basal, and middle CI electrodes in transmitting speech temporal information, except a trend that the voicing feature was the least transmitted by the basal electrode. A similar electrode-location pattern could be observed in most ABI subjects. Although the number of tested ABI subjects was small, their wide range of phoneme perception performance was consistent with previous reports of overall speech perception in ABI patients. The better-performing ABI user participants had access to speech temporal and spectral information that was comparable to that of average CI user. The poor-performing ABI user did not have access to within-channel speech temporal information and did not benefit from an increased number of spectral channels. The within-subject variability between different ABI electrodes was less than the variability across users in transmission of speech temporal information. The difference in the performance of ABI users could be related to the location of their electrode array on the CN, anatomy, and physiology of their CN or the damage to their auditory brainstem due to tumor or surgery.

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.

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.

Event Abstract Back to Event Altered hemispheric asymmetries of auditory evoked potentials after cochlear implantation Pascale Sandmann1*, T. Eichele2, S. Debener3, 4, M. Buechler5, L. Jancke1, N. Dillier5, Kenneth Hugdahl2, 6 and M. Meyer1 1 University of Zurich, Switzerland 2 University of Bergen, Norway 3 MRC Institute of Hearing Research of Southampton, United Kingdom 4 University of Southampton, United Kingdom 5 University Hospital Zurich, Switzerland 6 Haukeland University Hospital, Norway Hearing can be restored in individuals suffering from severe and profound hearing loss using a cochlear implant (CI). A CI bypasses the outer and middle ear and directly stimulates the (residual) fibres of the auditory nerve. To assess auditory cortex functions, late auditory evoked potentials (AEPs) are widely used in clinical context. However, in CI users electrophysiological measures are of limited utility due to the generation of electrical artefacts in the electroencephalogram (EEG). In order to evaluate the functional outcome after cochlear implantation, the present study examined hemispheric asymmetries of AEPs to complex sound processing in CI users. Two dyadic tonal intervals were presented in an active oddball design as well as in a passive listening condition. Using independent component analysis (ICA), CI-related artefacts could be successfully reduced in EEGs of CI users (n=12). BESA dipole source analysis of recovered AEPs allowed for the evaluation of hemispheric differences in the primary auditory cortex. The results are remarkable for two reasons. First, they indicate altered hemispheric asymmetries for complex sound processing in CI users compared to normal-hearing listeners. Second, the results demonstrate that ICA can solve the problem of CI-related artefacts, thereby enabling a detailed investigation of auditory cortex activity in CI users. This is of utmost clinical relevance to make AEP applicable in investigating auditory cortical reorganization after cochlear implantation. Conference: 10th International Conference on Cognitive Neuroscience, Bodrum, Turkey, 1 Sep - 5 Sep, 2008. Presentation Type: Poster Presentation Topic: Cerebral Asymmetry Citation: Sandmann P, Eichele T, Debener S, Buechler M, Jancke L, Dillier N, Hugdahl K and Meyer M (2008). Altered hemispheric asymmetries of auditory evoked potentials after cochlear implantation. Conference Abstract: 10th International Conference on Cognitive Neuroscience. doi: 10.3389/conf.neuro.09.2009.01.149 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 05 Dec 2008; Published Online: 05 Dec 2008. * Correspondence: Pascale Sandmann, University of Zurich, Zurich, Switzerland, p.sandmann@psychologie.uzh.ch Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Pascale Sandmann T. Eichele S. Debener M. Buechler L. Jancke N. Dillier Kenneth Hugdahl M. Meyer Google Pascale Sandmann T. Eichele S. Debener M. Buechler L. Jancke N. Dillier Kenneth Hugdahl M. Meyer Google Scholar Pascale Sandmann T. Eichele S. Debener M. Buechler L. Jancke N. Dillier Kenneth Hugdahl M. Meyer PubMed Pascale Sandmann T. Eichele S. Debener M. Buechler L. Jancke N. Dillier Kenneth Hugdahl M. Meyer Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

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 implant (CI) electrode arrays typically do not reach the most apical regions of the cochlea that intrinsically encode low frequencies. This may contribute to diminished implant-mediated musical sound quality perception. The objective of this study was to assess the effect of varying degrees of apical cochlear stimulation (measured by angular insertion depth) on musical sound quality discrimination. Increased apical cochlear stimulation will improve low-frequency perception and musical sound quality discrimination. Standard (31.5 mm, n = 17) and medium (24 mm, n = 8) array Med-EL CI users, and normal hearing (NH) listeners (n = 16) participated. Imaging confirmed angular insertion depth. Participants completed a musical discrimination task in which they listened to a real-world musical stimulus (labeled reference) and provided sound quality ratings to versions of the reference, which included a hidden reference and test stimuli with increasing amounts of low-frequency removal. Scores for each CI users were calculated on the basis of how much their ratings differed from NH listeners for each stimulus version. Medium array and standard users had significantly different insertion depths (389.4 ± 64.5 and 583.9 ± 78.5 degrees, respectively; p < .001). A significant Pearson's correlation was observed between angular insertion depth and the hidden reference scores (p < 0.05). CI users with greater apical stimulation made sound quality discriminations that more closely resembled those of NH controls for stimuli that contained low frequencies (< 200 Hz of information). These findings suggest that increased apical cochlear stimulation improves musical low-frequency perception, which may provide a more satisfactory music listening experience for CI users.

Figure: © iStock/chaossCochlear implants (CIs) have allowed users to understand speech and interact with the auditory world. However, CI recipients still have difficulty perceiving nonspeech sounds, especially music. Music appreciation is important to evaluate in CI users because of its association with quality of life, personal expression, and social connectedness.Figure: Alice HeCochlear implant recipients have difficulty recognizing musical melodies, identifying instrument sounds, and differentiating pitch. However, perceptual accuracy is not the only important aspect in music listening. The way music sounds as a whole through the cochlear implant has clinical relevance, as it relates to the user's ability to appreciate and enjoy music in everyday life.Figure: Charles J. Limb, MDWhile one might anticipate a direct link between cochlear implant recipients’ ability to perceive music accurately and their degree of music appreciation, the early literature has not supported this idea. In fact, some studies suggest exactly the opposite—that there is little to no relationship between music perception and appraisal in CI users ( J Am Acad Audiol 2012;23[5]:350-365http://aaa.publisher.ingentaconnect.com/content/aaa/jaaa/2012/00000023/00000005/art00006). However, these previous results were obtained from small cohorts of cochlear implant recipients in controlled laboratory settings, with tests that require significant time to administer, limiting their applicability in clinical settings. In a new study, Ward R. Drennan, PhD, and colleagues evaluated the correlation between music perception and appraisal among a large cohort of CI users in clinical settings. The authors used shorter music tests to determine if these assessments could be administered in the clinic and whether findings would be consistent with previous results from smaller sample sizes. Clinical Evaluation of Music Perception, Appraisal, and Experience in Cochlear Implant Users Drennan WR, Oleson JJ, Gfeller K, et al Int J Audiol Sept. 1, 2014; e-pub ahead of printhttp://informahealthcare.com/doi/abs/10.3109/14992027.2014.948219 The Clinical Assessment of Music Perception (CAMP) test is commonly used in some laboratories to study CI users’ music perception ( Otol Neurotol 2008;29[2]:149-155http://journals.lww.com/otology-neurotology/Abstract/2008/02000/Clinical_Assessment_of_Music_Perception_in.10.aspx; Ear Hear 2009;30[4]:411-418http://journals.lww.com/ear-hearing/Abstract/2009/08000/Development_and_Validation_of_the_University_of.4.aspx). The CAMP includes three separate perception tests, each designed to evaluate a different element of music perception ability: pitch direction discrimination, familiar melody recognition, and timbre recognition. Since these three elements are relevant to music listening and enjoyment, Dr. Drennan et al used the CAMP test to study music perception. To assess music appraisal, the researchers used the Iowa Musical Background Questionnaire (IMBQ). In the IMBQ, CI recipients described the quality of music heard through their cochlear implant by rating six bipolar adjectives on a scale of zero to 10: clear versus fuzzy, easy to follow versus difficult to follow, like versus dislike, sounds unlike music versus sounds like music, unnatural versus natural, and unpleasant versus pleasant. Prior research identified these comparisons as relevant to music listening. The CAMP test and IMBQ were administered to 145 CI listeners across 14 clinical sites in the United States and Canada. It took 30 minutes to 35 minutes to administer the CAMP test, and another 15 minutes to 25 minutes to complete the IMBQ. These time frames are reasonable for administration in the clinic—a major advantage in terms of practical feasibility, the authors noted. WEAK RELATIONSHIP REPORTED In their group of cochlear implant users from several clinical settings, Dr. Drennan and colleagues found weak relationships between CAMP results and IMBQ musical sound quality scores. There was a statistically significant but slight correlation between the CAMP's timbre test component and music appraisal, suggesting a relatively weak association between the two. All other relationships were deemed insignificant. This lack of a strong association, which is consistent with the findings of previous studies ( J Am Acad Audiol 2012;23[5]:350-365http://aaa.publisher.ingentaconnect.com/content/aaa/jaaa/2012/00000023/00000005/art00006; J Am Acad Audiol 2008;19[2]:120-134http://aaa.publisher.ingentaconnect.com/content/aaa/jaaa/2008/00000019/00000002/art00003) means that in order to fully evaluate CI music functionality, it is not sufficient to test either music perception or music appraisal alone. Both measures need to be evaluated, as sufficiency or deficiency in one aspect does not correlate with the same result in the other aspect. These results also highlight the limitations of subjective musical sound quality assessment and the possible benefits of objective approaches ( Otol Neurotol 2012;33[3]:319-327http://journals.lww.com/otology-neurotology/Abstract/2012/04000/Assessment_of_Sound_Quality_Perception_in_Cochlear.7.aspx). In an objective approach, the goal is not to evaluate how pleasant or unpleasant music may sound, or whether the CI user enjoys it. Rather, the goal is to measure the capacity of a cochlear implant user to detect a deterioration of sound quality in response to experimental manipulation of any given sound parameter. MANY FACTORS AFFECT ENJOYMENT Dr. Drennan and colleagues noted limitations of their study design. For example, the CAMP was conducted without hearing aids, even if listeners used hearing aids regularly. While the IMBQ questionnaire asked about music appraisal based on real-world musical listening experiences, the CAMP used simple, controlled sound stimuli to assess basic music perception abilities instead of using real-world stimuli. To some extent, these study design decisions might have affected CI users’ music test scores. Despite these potential limitations, the authors make a compelling argument that perceptual acuity is not closely related to music appraisal ratings. In other words, cochlear implant users can have poor perceptual abilities and still feel that music sounds good or is highly enjoyable. Conversely, CI users can perceive various aspects of music well while feeling that music sounds poor or not enjoying what they are able to hear. The study by Dr. Drennan and colleagues underscores the notion that the musical experience is linked to many factors. Furthermore, these findings suggest that studying individual elements of music in isolation may not accurately reflect the perceptual salience of music when it's presented in its natural form—a composite of a wide range of components. In this study, the authors demonstrated that there is little to no relationship between music acuity and music appraisal. Both aspects are important clinical outcomes, as one addresses patient functionality and ability (acuity), while the other addresses patient feeling and overall satisfaction with music quality (appraisal). These findings strongly suggest the need for further research to overcome limitations in cochlear implant users’ ability to perceive music, and to understand the factors that limit enjoyment or satisfaction in music listening.

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.