Implant Users Research Articles

The Role of Stimulus Type and Social Signal for Voice Perception in Cochlear Implant Users: Response to the Letter by Meister et al.

Purpose In their letter, Meister et al. (2020) appropriately point to a potential influence of stimulus type, arguing cochlear implant (CI) users may have the ability to use timbre cues only for complex stimuli such as sentences but not for brief stimuli such as vowel-consonant-vowel or single words. While we cannot exclude this possibility on the basis of Skuk et al. (2020) alone, we hold that there is a strong need to consider type of social signal (e.g., gender, age, emotion, speaker identity) to assess the profile of preserved and impaired aspects of voice processing in CI users. We discuss directions for further research to systematically consider interactive effects of stimulus type and social signal. In our view, this is crucial to understand and enhance nonverbal vocal perception skills that are relevant to successful communication with a CI.

Letter to the Editor Concerning Skuk et al., "Parameter-Specific Morphing Reveals Contributions of Timbre and Fundamental Frequency Cues to the Perception of Voice Gender and Age in Cochlear Implant Users".

Purpose The purpose of this letter is to compare results by Skuk et al. (2020) with Meister et al. (2016) and to point to a potential general influence of stimulus type. Conclusion Our conclusion is that presenting sentences may give cochlear implant recipients the opportunity to use timbre cues for voice perception. This might not be the case when presenting brief and sparse stimuli such as consonant-vowel-consonant or single words, which were applied in the majority of studies.

The evaluation of the efficacy of phonemic rehabilitations in Cochlear Implant users; a single subject study

Background and Aim: In many cochlear implant users, even after some time following cochlear implantation and adequate central auditory stimulation, certain hearing processing capabilities remain unresolved. These difficulties for cochlear implant (CI) users have a very similar manifestation to the decoding sub-category of the buffalo model of auditory processing which has a direct role in accurate phoneme processing. The present study was designed to investigate phoneme processing abilities in cochlear implant users and to evaluate the efficacy of phonemic rehabilitations in this population. Methods: Six prelingually deaf children aged between 8 and 11 years were referred to Ahvaz Cochlear implant center in 2019. A single-subject study design was used to examine the performance of the CI users during three phases of baseline, intervention and follow-up. Phonemic Training and Phonemic Synthesis programs were administered and the outcomes were compared based on performance of the children in Persian Phoneme Recognition Test (P-PRT), Persian Phonemic Synthesis Test (P-PST) and Phoneme Error Analysis (PEA). The children had four weeks follow up. Two methods were used to analyze the collected data including the C-Statistic and the percentage of all non-overlapping data (PAND) through SPSP version 19.p Results: The mean age was 9.16±1.16 years. There were two males and four females. The findings provide strong evidence demonstrating that Persian CI users are suffering from phoneme processing difficulties. All findings demonstrated that P-PRT, P-PST and PEA scores improved in all six cases. Conclusions: This study suggests that phoneme-based rehabilitation strategies improve the performance of deaf children with CIs and should be used in postoperative therapy batteries.

Evaluating and Comparing Behavioural and Electrophysiological Estimates of Neural Health in Cochlear Implant Users

Variations in neural health along the cochlea can degrade the spectral and temporal representation of sounds conveyed by cochlear implants (CIs). We evaluated and compared one electrophysiological measure and two behavioural measures that have been proposed as estimates of neural health patterns, in order to explore the extent to which the different measures provide converging and consistent neural health estimates. All measures were obtained from the same 11 users of the Cochlear Corporation CI. The two behavioural measures were multipulse integration (MPI) and the polarity effect (PE), both measured on each of seven electrodes per subject. MPI was measured as the difference between thresholds at 80 pps and 1000 pps, and PE as the difference in thresholds between cathodic- and anodic-centred quadraphasic (QP) 80-pps pulse trains. It has been proposed that good neural health corresponds to a large MPI and to a large negative PE (lower thresholds for cathodic than anodic pulses). The electrophysiological measure was the effect of interphase gap (IPG) on the offset of the ECAP amplitude growth function (AGF), which has been correlated with spiral ganglion neuron density in guinea pigs. This ‘IPG offset’ was obtained on the same subset of electrodes used for the behavioural measures. Despite high test–retest reliability, there were no significant correlations between the neural health estimates for either within-subject comparisons across the electrode array, or between-subject comparisons of the means. A phenomenological model of a population of spiral ganglion neurons was then used to investigate physiological mechanisms that might underlie the different neural health estimates. The combined experimental and modelling results provide evidence that PE, MPI and IPG offset may reflect different characteristics of the electrode-neural interface.

Binaural Pitch Fusion: Binaural Pitch Averaging in Cochlear Implant Users With Broad Binaural Fusion.

Individuals who use hearing aids (HAs) or cochlear implants (CIs) can experience broad binaural pitch fusion, such that sounds differing in pitch by as much as 3 to 4 octaves are perceptually integrated across ears. Previously, it was shown in HA users that the fused pitch is a weighted average of the two monaural pitches, ranging from equal weighting to dominance by the lower pitch. The goal of this study was to systematically measure the fused pitches in adult CI users, and determine whether CI users experience similar pitch averaging effects as observed in HA users. Twelve adult CI users (Cochlear Ltd, Sydney, Australia) participated in this study: six bimodal CI users, who wear a CI with a contralateral HA, and six bilateral CI users. Stimuli to HA ears were acoustic pure tones, and stimuli to CI ears were biphasic pulse trains delivered to individual electrodes. Fusion ranges, the ranges of frequencies/electrodes in the comparison ear that were fused with a single electrode (electrode 22, 18, 12, or 6) in the reference ear, were measured using simultaneous, dichotic presentation of reference and comparison stimuli in opposite ears, and varying the comparison stimulus. Once the fusion ranges were measured, the fused binaural pitch of a reference-pair stimulus combination was measured by finding a pitch match to monaural comparison stimuli presented to the paired stimulus ear. Fusion pitch weighting in CI users varied depending on the pitch difference of the reference-pair stimulus combination, with equal pitch averaging occurring for stimuli closer in pitch and lower pitch dominance occurring for stimuli farther apart in pitch. The averaging region was typically 0.5 to 2.3 octaves around the reference for bimodal CI users and 0.4 to 1.5 octaves for bilateral CI users. In some cases, a bias in the averaging region was observed toward the ear with greater stimulus variability. Fusion pitch weighting effects in CI users were similar to those observed previously in HA users. However, CI users showed greater inter-subject variability in both pitch averaging ranges and bias effects. These findings suggest that binaural pitch averaging could be a common underlying mechanism in hearing-impaired listeners.

Application of Wireless Contralateral Routing of Signal (CROS) Technology in Unilateral Cochlear Implant Users

IntrodutionSingle cochlear implantation usually provides substantial speech intelligibility benefits but bilaterally deaf, unilaterally implanted subjects will continue to experience limitations due to the head shadow effect, like single-sided deaf individuals. In the treatment of individuals with single-sided deafness one option is contralateral routing of signal (CROS) devices, which constitute a non-surgical intervention of the second ear in unilaterally implanted individuals. MethodTwelve experienced adult cochlear implant (CI) users with Naída Q70 processor and the CROS device used in combination participated in the study. For the study three conditions were provided: CI only, omnidirectional microphone mode (CROS deactivated); CI plus CROS activated, omnidirectional microphone mode and CI plus CROS activated, UltraZoom mode. Speech reception thresholds were determined in quiet and noise. Subjective feedback regarding the practical usability of the CROS device and the perceived benefit were collected. ResultsThere was a 27.6% improvement in speech understanding in quiet and 32.5% improvement in noise when CROS device was activated. Using advanced directional microphones, a statistically significant benefit of 35% was obtained. The responses to the questionnaires revealed that the subjects perceived benefit in their everyday lives when using the CROS device with their CI. ConclusionThe investigated CROS device used by unilateral CI recipients in cases where bilateral implantation is not an option provides both subjective and objective speech recognition benefit when the signal is directed to the CROS device. Unfavourable conditions where speech is presented from the CI side and noise from the CROS side or diffusely were not included in this evaluation since the CROS device adds additional noise and performance is expected to decrease as has previously been shown.

Visual and Auditory Verbal Memory in Older Adults: Comparing Postlingually Deaf Cochlear Implant Users to Normal-Hearing Controls

Purpose The aim of this study was to test whether a group of older postlingually deafened cochlear implant users (OCIs) use similar verbal memory strategies to those used by older normal-hearing adults (ONHs). Verbal memory functioning was assessed in the visual and auditory modalities separately, enabling us to eliminate possible modality-based biases. Method Participants performed two separate visual and auditory verbal memory tasks. In each task, the visually or aurally presented study words were learned by vocal production (saying aloud) or by no production (reading silently or listening), followed by a free recall test. Twenty-seven older adults (> 60 years) participated (OCI = 13, ONH = 14), all of whom demonstrated intact cognitive abilities. All OCIs showed good open-set speech perception results in quiet. Results Both ONHs and OCIs showed production benefits (higher recall rates for vocalized than nonvocalized words) in the visual and auditory tasks. The ONHs showed similar production benefits in the visual and auditory tasks. The OCIs demonstrated a smaller production effect in the auditory task. Conclusions These results may indicate that different modality-specific memory strategies were used by the ONHs and the OCIs. The group differences in memory performance suggest that, even when deafness occurs after the completion of language acquisition, the reduced and distorted external auditory stimulation leads to a deterioration in the phonological representation of sounds. Possibly, this deterioration leads to a less efficient auditory long-term verbal memory.

Spatial Release From Informational and Energetic Masking in Bimodal and Bilateral Cochlear Implant Users.

Purpose Spatially separating speech and background noise improves speech understanding in normal-hearing listeners, an effect referred to as spatial release from masking (SRM). In cochlear implant (CI) users, SRM has often been demonstrated using asymmetric noise configurations, which maximize benefit from head shadow and the potential availability of binaural cues. In contrast, SRM in symmetrical configurations has been minimal to absent in CI users. We examined the interaction between two types of maskers (informational and energetic) and SRM in bimodal and bilateral CI users. We hypothesized that SRM would be absent or "negative" using symmetrically separated noise maskers. Second, we hypothesized that bimodal listeners would exhibit greater release from informational masking due to access to acoustic information in the non-CI ear. Method Participants included 10 bimodal and 10 bilateral CI users. Speech understanding in noise was tested in 24 conditions: 3 spatial configurations (S0N0, S0N45&315, S0N90&270) × 2 masker types (speech, signal-correlated noise) × 2 listening configurations (best-aided, CI-alone) × 2 talker gender conditions (different-gender, same-gender). Results In support of our first hypothesis, both groups exhibited negative SRM with increasing spatial separation. In opposition to our second hypothesis, both groups exhibited similar magnitudes of release from informational masking. The magnitude of release was greater for bimodal listeners, though this difference failed to reach statistical significance. Conclusions Both bimodal and bilateral CI recipients exhibited negative SRM. This finding is consistent with CI signal processing limitations, the audiologic factors associated with SRM, and known effects of behind-the-ear microphone technology. Though release from informational masking was not significantly different across groups, the magnitude of release was greater for bimodal listeners. This suggests that bimodal listeners may be at least marginally more susceptible to informational masking than bilateral CI users, though further research is warranted.

Perception and prediction of loudness in sound coding strategies using simultaneous electric stimulation

Cochlear Implant (CI) sound coding strategies based on simultaneous stimulation lead to an increased loudness percept when compared to sequential stimulation using the same current levels. This is due to loudness summation as a result of channel interactions. Studying the loudness perception evoked by dual-channels compared to single-channels can be useful to optimize sound coding strategies that use simultaneous current pulses. Fourteen users of HiRes90k implants and one user of a CII implant loudness balanced single-channel to dual-channel stimuli with varying distance between simultaneous channels. In this study each component of a dual channel was a virtual channel, which shared current across two adjacent electrodes. Balancing was performed at threshold and comfortable level, for two spatial references (apical and basal) and for dual-channels with different relative current ratios. Increasing distance between dual-channels decreased the amount of current compensation in the dual-channel required to reach equal loudness to a single channel component by an average of 0.24 dB / mm without a significant difference between threshold and most comfortable level. If the components of the dual-channels were not at equal loudness, the loudness summation was reduced with respect to the equal loudness case. The results were incorporated into an existing loudness model by McKay et al. (2003). The predictions from the adapted model were evaluated by comparing the loudness evoked by simultaneous and sequential sound coding strategies. The application of the adapted model resulted in a deviation between predicted and actual behavioral loudness balancing adjustments in electrical level between simultaneous and sequential processing strategies of 0.24 dB on average.

Is There Any Correlation between Spread of Excitation Width and the Refractory Properties of the Auditory Nerve in Cochlear Implant Users?

Background: The spread of excitation (SOE) and auditory nerve recovery function (REC) are objective measures recorded by neural response telemetry and may interfere in cochlear implant (CI) stimulation. Objective: To analyze and correlate SOE with the refractory periods in subjects with pre- and postlingual deafness implanted with different electrode arrays. Methods: This was a retrospective study of 323 ears separated by perimodiolar or straight arrays and by pre- or postlingually deaf recipients. Measures were collected intraoperatively on electrode 11. The SOE width was measured in millimeters at the 0.75 point of the curve, and the relative (tau) and absolute (t0) refractory periods were measured in microseconds. Results: There was a statistical correlation between the SOE and the t0 in the patients with postlingual deafness implanted with the perimodiolar array. The SOE width was statistically different between the straight and perimodiolar arrays and between the pre- and postlingual groups in the perimodiolar array. Tau was statistically different between the pre- and postlingual groups with the straight array and the t0, between the pre- and postlingual groups with the perimodiolar array. Neural response threshold and amplitude of the neural response were not statistically different among groups. Conclusion: There was a correlation between SOE width and t0 only in patients with acquired deafness. The findings suggest that different factors influence SOE and REC, considering SOE is different according to the electrode array and REC being different according the onset of deafness.

Spatial Hearing by Bilateral Cochlear Implant Users With Temporal Fine-Structure Processing.

Several studies have demonstrated the advantages of the bilateral vs. unilateral cochlear implantation in listeners with bilateral severe to profound hearing loss. However, it remains unclear to what extent bilaterally implanted listeners have access to binaural cues, e.g., accurate processing of interaural timing differences (ITDs) for low-frequency sounds (<1.5 kHz) and interaural level differences (ILDs) for high frequencies (>3 kHz). We tested 25 adult listeners, bilaterally implanted with MED-EL cochlear implant (CI) devices, with and without fine-structure (FS) temporal processing as encoding strategy in the low-frequency channels. In order to assess whether the ability to process binaural cues was affected by fine-structure processing, we performed psychophysical ILD and ITD sensitivity measurements and free-field sound localization experiments. We compared the results of the bilaterally implanted listeners with different numbers of FS channels. All CI listeners demonstrated good sensitivity to ILDs, but relatively poor to ITD cues. Although there was a large variability in performance, some bilateral CI users showed remarkably good localization skills. The FS coding strategy for bilateral CI hearing did not improve fine-structure ITD processing for spatial hearing on a group level. However, some CI listeners were able to exploit weakly informative temporal cues to improve their low-frequency spatial perception.

Electrocochleography in Cochlear Implant Users with Residual Acoustic Hearing: A Systematic Review.

(1) Objectives: This study reviews the use of electrocochleography (ECoG) as a tool for assessing the response of the peripheral auditory system and monitoring hearing preservation in the growing population of cochlear implant (CI) users with preserved hearing in the implanted ear. (2) Methods: A search was conducted in PubMed and CINAHL databases up to August 2020 to locate articles related to the ECoG measured during or after the cochlear implant (CI) surgery for monitoring purposes. Non-English articles, animal studies, literature reviews and editorials, case reports, and conference papers were excluded. The quality of studies was evaluated using the National Institute of Health (NIH) “Study Quality Assessment Tool for Case Series Studies”. (3) Results: A total 30 articles were included for the systematic review. A total of 21 articles were intraoperative ECoG studies, while seven articles were postoperative studies. Two studies were conducted ECoG both during and after the surgery. Intraoperative ECoG studies focused on monitoring changes in ECoG response amplitudes during and/or after electrode insertion and predicting the scalar location of the electrode array. Postoperative ECoG studies focused on using the ECoG measurements to estimate behavioral audiometric thresholds and monitor pathophysiological changes related to delayed onset hearing loss postimplant. (4) Conclusions: ECoG is feasible to provide real-time feedback intraoperatively and has a potential clinical value to monitor the status of hearing preservation postoperatively in this CI population with residual acoustic hearing.

Effect of Spectral Contrast Enhancement on Speech-on-Speech Intelligibility and Voice Cue Sensitivity in Cochlear Implant Users.

Speech intelligibility in the presence of a competing talker (speech-on-speech; SoS) presents more difficulties for cochlear implant (CI) users compared with normal-hearing listeners. A recent study implied that these difficulties may be related to CI users' low sensitivity to two fundamental voice cues, namely, the fundamental frequency (F0) and the vocal tract length (VTL) of the speaker. Because of the limited spectral resolution in the implant, important spectral cues carrying F0 and VTL information are expected to be distorted. This study aims to address two questions: (1) whether spectral contrast enhancement (SCE), previously shown to enhance CI users' speech intelligibility in the presence of steady state background noise, could also improve CI users' SoS intelligibility, and (2) whether such improvements in SoS from SCE processing are due to enhancements in CI users' sensitivity to F0 and VTL differences between the competing talkers. The effect of SCE on SoS intelligibility and comprehension was measured in two separate tasks in a sample of 14 CI users with Cochlear devices. In the first task, the CI users were asked to repeat the sentence spoken by the target speaker in the presence of a single competing talker. The competing talker was the same target speaker whose F0 and VTL were parametrically manipulated to obtain the different experimental conditions. SoS intelligibility, in terms of the percentage of correctly repeated words from the target sentence, was assessed using the standard advanced combination encoder (ACE) strategy and SCE for each voice condition. In the second task, SoS comprehension accuracy and response times were measured using the same experimental setup as in the first task, but with a different corpus. In the final task, CI users' sensitivity to F0 and VTL differences were measured for the ACE and SCE strategies. The benefit in F0 and VTL discrimination from SCE processing was evaluated with respect to the improvement in SoS perception from SCE. While SCE demonstrated the potential of improving SoS intelligibility in CI users, this effect appeared to stem from SCE improving the overall signal to noise ratio in SoS rather than improving the sensitivity to the underlying F0 and VTL differences. A second key finding of this study was that, contrary to what has been observed in a previous study for childlike voice manipulations, F0 and VTL manipulations of a reference female speaker (target speaker) toward male-like voices provided a small but significant release from masking for the CI users tested. The present findings, together with those previously reported in the literature, indicate that SCE could serve as a possible background-noise-reduction strategy in commercial CI speech processors that could enhance speech intelligibility especially in the presence of background talkers that have longer VTLs compared with the target speaker.

Parameter-Specific Morphing Reveals Contributions of Timbre and Fundamental Frequency Cues to the Perception of Voice Gender and Age in Cochlear Implant Users.

Purpose Using naturalistic synthesized speech, we determined the relative importance of acoustic cues in voice gender and age perception in cochlear implant (CI) users. Method We investigated 28 CI users' abilities to utilize fundamental frequency (F0) and timbre in perceiving voice gender (Experiment 1) and vocal age (Experiment 2). Parameter-specific voice morphing was used to selectively control acoustic cues (F0; time; timbre, i.e., formant frequencies, spectral-level information, and aperiodicity, as defined in TANDEM-STRAIGHT) in voice stimuli. Individual differences in CI users' performance were quantified via deviations from the mean performance of 19 normal-hearing (NH) listeners. Results CI users' gender perception seemed exclusively based on F0, whereas NH listeners efficiently used timbre. For age perception, timbre was more informative than F0 for both groups, with minor contributions of temporal cues. While a few CI users performed comparable to NH listeners overall, others were at chance. Separate analyses confirmed that even high-performing CI users classified gender almost exclusively based on F0. While high performers could discriminate age in male and female voices, low performers were close to chance overall but used F0 as a misleading cue to age (classifying female voices as young and male voices as old). Satisfaction with CI generally correlated with performance in age perception. Conclusions We confirmed that CI users' gender classification is mainly based on F0. However, high performers could make reasonable usage of timbre cues in age perception. Overall, parameter-specific morphing can serve to objectively assess individual profiles of CI users' abilities to perceive nonverbal social-communicative vocal signals.

Meta-Analysis on the Identification of Linguistic and Emotional Prosody in Cochlear Implant Users and Vocoder Simulations.

This study quantitatively assesses how cochlear implants (CIs) and vocoder simulations of CIs influence the identification of linguistic and emotional prosody in nontonal languages. By means of meta-analysis, it was explored how accurately CI users and normal-hearing (NH) listeners of vocoder simulations (henceforth: simulation listeners) identify prosody compared with NH listeners of unprocessed speech (henceforth: NH listeners), whether this effect of electric hearing differs between CI users and simulation listeners, and whether the effect of electric hearing is influenced by the type of prosody that listeners identify or by the availability of specific cues in the speech signal. Records were found by searching the PubMed Central, Web of Science, Scopus, Science Direct, and PsycINFO databases (January 2018) using the search terms "cochlear implant prosody" and "vocoder prosody." Records (published in English) were included that reported results of experimental studies comparing CI users' and/or simulation listeners' identification of linguistic and/or emotional prosody in nontonal languages to that of NH listeners (all ages included). Studies that met the inclusion criteria were subjected to a multilevel random-effects meta-analysis. Sixty-four studies reported in 28 records were included in the meta-analysis. The analysis indicated that CI users and simulation listeners were less accurate in correctly identifying linguistic and emotional prosody compared with NH listeners, that the identification of emotional prosody was more strongly compromised by the electric hearing speech signal than linguistic prosody was, and that the low quality of transmission of fundamental frequency (f0) through the electric hearing speech signal was the main cause of compromised prosody identification in CI users and simulation listeners. Moreover, results indicated that the accuracy with which CI users and simulation listeners identified linguistic and emotional prosody was comparable, suggesting that vocoder simulations with carefully selected parameters can provide a good estimate of how prosody may be identified by CI users. The meta-analysis revealed a robust negative effect of electric hearing, where CIs and vocoder simulations had a similar negative influence on the identification of linguistic and emotional prosody, which seemed mainly due to inadequate transmission of f0 cues through the degraded electric hearing speech signal of CIs and vocoder simulations.

Effectiveness of Phantom Stimulation in Shifting the Pitch Percept in Cochlear Implant Users.

Phantom electrode stimulation was developed for cochlear implant (CI) systems to provide a lower pitch percept by stimulating more apical regions of the cochlea, without inserting the electrode array deeper into the cochlea. Phantom stimulation involves simultaneously stimulating a primary and a compensating electrode with opposite polarity, thereby shifting the electrical field toward the apex and eliciting a lower pitch percept. The current study compared the effect sizes (in shifts of place of excitation) of multiple phantom configurations by matching the perceived pitch with phantom stimulation to that perceived with monopolar stimulation. Additionally, the effects of electrode location, type of electrode array, and stimulus level on the perceived pitch were investigated. Fifteen adult advanced bionics CI users participated in this study, which included four experiments to eventually measure the shifts in place of excitation with five different phantom configurations. The proportions of current delivered to the compensating electrode, expressed as σ, were 0.5, 0.6, 0.7, and 0.8 for the symmetrical biphasic pulses (SBC0.5, SBC0.6, SBC0.7, and SBC0.8) and 0.75 for the pseudomonophasic pulse shape (PSA0.75). A pitch discrimination experiment was first completed to determine which basal and apical electrode contacts should be used for the subsequent experiments. An extensive loudness balancing experiment followed where both the threshold level (T-level) and most comfortable level (M-level) were determined to enable testing at multiple levels of the dynamic range. A pitch matching experiment was then performed to estimate the shift in place of excitation at the chosen electrode contacts. These rough shifts were then used in the subsequent experiment, where the shifts in place of excitation were determined more accurately. Reliable data were obtained from 20 electrode contacts. The average shifts were 0.39, 0.53, 0.64, 0.76, and 0.53 electrode contacts toward the apex for SBC0.5, SBC0.6, SBC0.7, SBC0.8, and PSA0.75, respectively. When only the best configurations per electrode contact were included, the average shift in place of excitation was 0.92 electrode contacts (range: 0.25 to 2.0). While PSA0.75 leads to equal results as the SBC configurations in the apex, it did not result in a significant shift at the base. The shift in place of excitation was significantly larger at the apex and with lateral wall electrode contacts. The stimulus level did not affect the shift. Phantom stimulation results in significant shifts in place of excitation, especially at the apical part of the electrode array. The phantom configuration that leads to the largest shift in place of excitation differs between subjects. Therefore, the settings of the phantom electrode should be individualized so that the phantom stimulation is optimized for each CI user. The real added value to the sound quality needs to be established in a take-home trial.

Perception of Child-Directed Versus Adult-Directed Emotional Speech in Pediatric Cochlear Implant Users.

Cochlear implants (CIs) are remarkable in allowing individuals with severe to profound hearing loss to perceive speech. Despite these gains in speech understanding, however, CI users often struggle to perceive elements such as vocal emotion and prosody, as CIs are unable to transmit the spectro-temporal detail needed to decode affective cues. This issue becomes particularly important for children with CIs, but little is known about their emotional development. In a previous study, pediatric CI users showed deficits in voice emotion recognition with child-directed stimuli featuring exaggerated prosody. However, the large intersubject variability and differential developmental trajectory known in this population incited us to question the extent to which exaggerated prosody would facilitate performance in this task. Thus, the authors revisited the question with both adult-directed and child-directed stimuli. Vocal emotion recognition was measured using both child-directed (CDS) and adult-directed (ADS) speech conditions. Pediatric CI users, aged 7-19 years old, with no cognitive or visual impairments and who communicated through oral communication with English as the primary language participated in the experiment (n = 27). Stimuli comprised 12 sentences selected from the HINT database. The sentences were spoken by male and female talkers in a CDS or ADS manner, in each of the five target emotions (happy, sad, neutral, scared, and angry). The chosen sentences were semantically emotion-neutral. Percent correct emotion recognition scores were analyzed for each participant in each condition (CDS vs. ADS). Children also completed cognitive tests of nonverbal IQ and receptive vocabulary, while parents completed questionnaires of CI and hearing history. It was predicted that the reduced prosodic variations found in the ADS condition would result in lower vocal emotion recognition scores compared with the CDS condition. Moreover, it was hypothesized that cognitive factors, perceptual sensitivity to complex pitch changes, and elements of each child's hearing history may serve as predictors of performance on vocal emotion recognition. Consistent with our hypothesis, pediatric CI users scored higher on CDS compared with ADS speech stimuli, suggesting that speaking with an exaggerated prosody-akin to "motherese"-may be a viable way to convey emotional content. Significant talker effects were also observed in that higher scores were found for the female talker for both conditions. Multiple regression analysis showed that nonverbal IQ was a significant predictor of CDS emotion recognition scores while Years using CI was a significant predictor of ADS scores. Confusion matrix analyses revealed a dependence of results on specific emotions; for the CDS condition's female talker, participants had high sensitivity (d' scores) to happy and low sensitivity to the neutral sentences while for the ADS condition, low sensitivity was found for the scared sentences. In general, participants had higher vocal emotion recognition to the CDS condition which also had more variability in pitch and intensity and thus more exaggerated prosody, in comparison to the ADS condition. Results suggest that pediatric CI users struggle with vocal emotion perception in general, particularly to adult-directed speech. The authors believe these results have broad implications for understanding how CI users perceive emotions both from an auditory communication standpoint and a socio-developmental perspective.

Effect of the Relative Timing between Same-Polarity Pulses on Thresholds and Loudness in Cochlear Implant Users

The effect of the relative timing between pairs of same-polarity monophasic pulses has been studied extensively in single-neuron animal studies and has revealed fundamental properties of the neurons. For human cochlear implant listeners, the requirement to use charge-balanced stimulation and the typical use of symmetric, biphasic pulses limits such measures, because currents of opposite polarities interact at the level of the neural membrane. Here, we propose a paradigm to study same-polarity summation of currents while keeping the stimulation charge-balanced within a short time window. We used pairs of mirrored pseudo-monophasic pulses (a long-low phase followed by a short-high phase for the first pulse and a short-high phase followed by a long-low phase for the second pulse). We assumed that most of the excitation would stem from the two adjacent short-high phases, which had the same polarity. The inter-pulse interval between the short-high phases was varied from 0 to 345 μs. The inter-pulse interval had a significant effect on the perceived loudness, and this effect was consistent with both passive (membrane-related) and active (ion-channel-related) neuronal mechanisms contributing to facilitation. Furthermore, the effect of interval interacted with the polarity of the pulse pairs. At threshold, there was an effect of polarity, but, surprisingly, no effect of interval nor an interaction between the two factors. We discuss possible peripheral origins of these results.

Aligning Hearing Aid and Cochlear Implant Improves Hearing Outcome in Bimodal Cochlear Implant Users.

Patients with unilateral deafness and residual hearing on the contralateral ear can benefit from a cochlear implant (CI) on one side and a hearing aid (HA) on the other. However, hearing improvement among these patients is heterogenous. Interindividual differences in bimodal benefit may be caused by a mismatch of CI and HA. The aim of this study was to clinically apply a HA fitting strategy and to evaluate hearing outcome with and without a dedicated bimodal fitting formula. Prospective non-randomized study. Tertiary referral center. Twelve patients using a CI processor and a conventional HA were enrolled. Before and after the new HA had been adjusted to the patient and linked to the CI, pure-tone audiometry and localization tests were performed. Speech perception was determined in quiet and noise. Tests were repeated after 6 and 12 weeks. To evaluate the subjective listening comfort two questionnaires (Oldenburg Inventory and HISQUI19) were assessed. Therapeutic. Word recognition in quiet, sentence recognition in noise. Speech perception in noise improved significantly: directed suppression of noise helped to segregate the target speech signal from a mixture of sounds or competing speakers. Evaluation of the questionnaires revealed a positive subjective hearing experience compared with patients' initial settings of the devices. By linking CI and HA hearing and speech perception can be improved. However, good counselling at the outset is essential to obtain enhanced outcome.

SoftVoice Improves Speech Recognition and Reduces Listening Effort in Cochlear Implant Users.

The ability to perceive soft speech by cochlear implant (CI) users is restricted in part by the inherent system noise produced by the speech processor, and in particular by the microphone(s). The algorithm "SoftVoice" (SV) was developed by Advanced Bionics to enhance the perception of soft speech by reducing the system noise in speech processors. The aim of this study was to examine the effects of SV on speech recognition and listening effort. Seventeen adult Advanced Bionics CI recipients were recruited and tested in two sessions. The effect of SV on speech recognition was tested by determining the SRT in quiet using the Matrix test. Based on the individual subjects' SRTs, we investigated speech-recognition scores at fixed speech levels, namely SRT -5 dB, SRT +0 dB, SRT +5 dB, and SRT +10 dB, again in quiet and using the Matrix test. Listening effort was measured at each of these speech levels subjectively by using a rating scale, and objectively by determining pupil dilation with pupillometry. To verify whether SoftVoice had any negative effects on speech perception in noise, we determined the SRT in steady state, speech-weighted noise of 60 dBA. Our results revealed a significant improvement of 2.0 dB on the SRT in quiet with SoftVoice. The average SRT in quiet without SoftVoice was 38 dBA. SoftVoice did not affect the SRT in steady state, speech-weighted noise of 60 dB. At an average speech level of 33 dBA (SRT -5 dB) and 38 dBA (SRT +0 dB) in quiet, significant improvements of 17% and 9% on speech-recognition scores were found with SoftVoice, respectively. At higher speech levels, SoftVoice did not significantly affect speech recognition. Pupillometry did not show significant effects of SoftVoice at any speech level. However, subjective ratings of listening effort indicated a decrease of listening effort with SoftVoice at a speech level of 33 dBA. We conclude that SoftVoice substantially improves recognition of soft speech and lowers subjective listening effort at low speech levels in quiet. However, no significant effect of SoftVoice was found on pupil dilation. As SRTs in noise were not statistically significantly affected by SoftVoice, we conclude that SoftVoice can be used in noisy listening conditions with little negative impact on speech recognition, if any. The increased power demands of the algorithm are considered to be negligible. It is expected that SoftVoice will reduce power consumption at low ambient sound levels. These results support the use of SoftVoice as a standard feature of Advanced Bionics CI fittings for everyday use.