Bimodal benefits in Mandarin-speaking cochlear implant users with contralateral residual acoustic hearing

Lexical tone recognition in multi-talker babbles and steady-state noise by Mandarin-speaking children with unilateral cochlear implants or bimodal hearing

BACKGROUND AND OBJECTIVES

Lexical tone presents challenges to cochlear implant (CI) users especially in noise conditions. Bimodal hearing utilizes residual acoustic hearing in the contralateral side and may offer benefits for tone recognition in noise. The purpose of the present study was to evaluate tone recognition in both steady-state noise and multi-talker babbles by the prelingually-deafened, Mandarin-speaking children with unilateral CIs or bimodal hearing.

METHODS

Fifty-three prelingually-deafened, Mandarin-speaking children who received CIs participated in this study. Twenty-two of them were unilateral CI users and 31 wore a hearing aid (HA) in the contralateral ear (i.e., bimodal hearing). All subjects were tested for Mandarin tone recognition in quiet and in two types of maskers: speech-spectrum-shaped noise (SSN) and two-talker babbles (TTB) at four signal-to-noise ratios (-6, 0, +6, and +12 dB).

RESULTS

While no differences existed in tone recognition in quiet between the two groups, the Bimodal group outperformed the Unilateral CI group under noise conditions. The differences between the two groups were significant at SNRs of 0, +6, and +12 dB in the SSN conditions (all p < 0.05), and at SNRs of +6 and +12 dB of TTB conditions (both p < 0.01), but not significant at other conditions (p > 0.05). The TTB exerted a greater masking effect than the SSN for tone recognition in the Unilateral CI group as well as in the Bimodal group at all SNRs tested (all p < 0.05). Among demographic or audiometric variables, only age at implantation showed a weak but significant correlation with the mean tone recognition performance under the SSN conditions (r = -0.276, p = 0.045). However, when Bonferroni correction was applied to the correlation analysis results, the weak correlation became not significant.

CONCLUSION

Prelingually-deafened children with CIs face challenges in tone perception in noisy environments, especially when the noise is fluctuating in amplitude such as the multi-talker babbles. Wearing a HA on the contralateral side when residual hearing permits is beneficial for tone recognition in noise.

Benefits of Bimodal Stimulation to Speech Perception in Noise and Silence

Introduction  Understanding all the benefits of bimodality with self-assessment questionnaires on the effect of hearing on quality of life is still necessary. Objective  To present whether bimodality still offers hearing benefits to the population who uses acoustic stimulation associated with electrical stimulation. Methods  The present study included 13 participants aged between 16 and 80 years old who were users of cochlear implants from Cochlear Corporation and hearing aids. All patients underwent the Hearing in Noise Test, and their visual analog scale score was obtained. Four-tone means were collected, and the participants answered the Speech, Spatial and Hearing Qualities questionnaire. Results  Bimodal users had an average sentence recognition rate of 76.0% in silence and 67.6% in fixed noise, and the signal-to-noise ratio in adaptive noise was +2.89dB. In addition, a lower level of difficulty was observed in the test using the visual analog scale. The domain with the highest average was auditory qualities (6.50), followed by spatial hearing (6.26) and hearing for speech (5.81). Individuals with an average between 50 and 70 dB of hearing level showed better sentence recognition in silence and noise. Conclusion  Bimodal stimulation showed benefits for users with different degrees of hearing loss; however, individuals who presented greater hearing residue had better performance in speech recognition with noise and in silence in addition to a good perception of hearing quality.

Guidelines for Best Practice in the Audiological Management of Adults Using Bimodal Hearing Configurations

Clinics are treating a growing number of patients with greater amounts of residual hearing. These patients often benefit from a bimodal hearing configuration in which acoustic input from a hearing aid on 1 ear is combined with electrical stimulation from a cochlear implant on the other ear. The current guidelines aim to review the literature and provide best practice recommendations for the evaluation and treatment of individuals with bilateral sensorineural hearing loss who may benefit from bimodal hearing configurations. Specifically, the guidelines review: benefits of bimodal listening, preoperative and postoperative cochlear implant evaluation and programming, bimodal hearing aid fitting, contralateral routing of signal considerations, bimodal treatment for tinnitus, and aural rehabilitation recommendations.

Pitch Accuracy of Vocal Singing in Deaf Children With Bimodal Hearing and Bilateral Cochlear Implants

OBJECTIVES

The purpose of the present study was to investigate the pitch accuracy of vocal singing in children with severe to profound hearing loss who use bilateral cochlear implants (CIs) or bimodal devices [CI at one ear and hearing aid (HA) at the other] in comparison to similarly-aged children with normal-hearing (NH).

DESIGN

The participants included four groups: (1) 26 children with NH, (2) 13 children with bimodal devices, (3) 31 children with bilateral CIs that were implanted sequentially, and (4) 10 children with bilateral CIs that were implanted simultaneously. All participants were aged between 7 and 11 years old. Each participant was recorded singing a self-chosen song that was familiar to him or her. The fundamental frequencies (F0) of individual sung notes were extracted and normalized to facilitate cross-subject comparisons. Pitch accuracy was quantified using four pitch-based metrics calculated with reference to the target music notes: mean note deviation, contour direction, mean interval deviation, and F0 variance ratio. A one-way ANOVA was used to compare listener-group difference on each pitch metric. A principal component analysis showed that the mean note deviation best accounted for pitch accuracy in vocal singing. A regression analysis examined potential predictors of CI children's singing proficiency using mean note deviation as the dependent variable and demographic and audiological factors as independent variables.

RESULTS

The results revealed significantly poorer performance on all four pitch-based metrics in the three groups of children with CIs in comparison to children with NH. No significant differences were found among the three CI groups. Among the children with CIs, variability in the vocal singing proficiency was large. Within the group of 13 bimodal users, the mean note deviation was significantly correlated with their unaided pure-tone average thresholds (r = 0.582, p = 0.037). The regression analysis for all children with CIs, however, revealed no significant demographic or audiological predictor for their vocal singing performance.

CONCLUSION

Vocal singing performance in children with bilateral CIs or bimodal devices is not significantly different from each other on a group level. Compared to children with NH, the pediatric bimodal and bilateral CI users, in general, demonstrated significant deficits in vocal singing ability. Demographic and audiological factors, known from previous studies to be associated with good speech and language development in prelingually-deafened children with CIs, were not associated with singing accuracy for these children.

Speech production in Mandarin-speaking children with cochlear implants: a systematic review

OBJECTIVE

This study aimed to systematically review and critically appraise the literature describing the phonetic characteristics and accuracy of the consonants, vowels and tones produced by Mandarin-speaking children with cochlear implants (CIs).

DESIGN

The protocol in this review was designed in conformity with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. EBSCOhost, PubMed, Scopus, PsycINFO, ProQuest Central databases were searched for relevant articles which met the inclusion criteria.

STUDY SAMPLE

A total of 18 journal papers were included in this review.

RESULTS

The results revealed that Mandarin-speaking children with CIs perform consistently more poorly in their production of consonants, in particular on fricatives, have a smaller and less well-defined vowel space, and exhibit greater difficulties in tone realisation, notably T2 and T3, when compared to their normal-hearing (NH) peers. The results from acoustic and accuracy analyses are negatively correlated with CI implantation age, but largely positively correlated with hearing age.

CONCLUSIONS

Findings of this review highlight the factors that influence consonant, vowel and tone production in Mandarin-speaking children with CIs, thereby providing critical information for clinicians and researchers working with this population.

Categorical perception of lexical tones based on acoustic-electric stimulation

The effect of low-frequency acoustic input on the categorical perception of lexical tones was investigated with simulated electric-acoustic hearing. A synthesized T1-T2 (flat-rising) tone continuum of Mandarin monosyllables /i/ was used, and they were manipulated as five conditions: unprocessed, low-frequency acoustic-only, electric-only, electric-acoustic stimulation, and bimodal stimulation. Results showed the performance under electric-only condition was the significantly lowest, and the difference of other pairwise comparisons between conditions was quite small. These findings suggest that the low-frequency acoustic input can shape the categorical perception, and the combinations of acoustic and electric hearing within or across ears have no significant effect.

Duration of deafness impacts auditory performance after cochlear implantation: A meta-analysis

OBJECTIVE

Hearing loss is a highly disabling condition. Cochlear implantation is an established remedy if conventional hearing aids have failed to alleviate the level of disability. Unfortunately, cochlear implant (CI) performance varies dramatically. This study aims to examine the effects of duration of deafness (DoD) prior to cochlear implantation and the postoperative duration of implant experience with resulting hearing performance in postlingually deaf patients.

METHODS

A systematic literature review and two meta-analyses were conducted using the search terms cochlear implant AND duration deafness. Included studies evaluate the correlation between the DoD and auditory performance after cochlear implantation using monosyllabic and sentence tests. Correlation coefficients were determined using Pearson's correlation and Spearman rho.

RESULTS

A total of 36 studies were identified and included data on cochlear implantations following postlingual deafness and postoperative speech testing of hearing outcomes for 1802 patients. The mean age ranged from 44 to 68 years with a DoD of 0.1 to 77 years. Cochlear implant use varied from 3 months to 14 years of age. Speech perception, which was assessed by sentence and monosyllabic word perception, was negatively correlated with DoD. Subgroup analyses revealed worse outcomes for longer DoD and shorter postoperative follow-up.

CONCLUSION

DoD is one of the most important factors to predict speech perception after cochlear implantation in postlingually deaf patients. The meta-analyses revealed a negative correlation between length of auditory deprivation and postoperative sentence and monosyllabic speech perception. Longer DoD seems to lead to worse CI performance, whereas more experience with CI mitigates the effect.

Bimodal Benefits Revealed by Categorical Perception of Lexical Tones in Mandarin-Speaking Kindergarteners With a Cochlear Implant and a Contralateral Hearing Aid

Purpose Pitch reception poses challenges for individuals with cochlear implants (CIs), and adding a hearing aid (HA) in the nonimplanted ear is potentially beneficial. The current study used fine-scale synthetic speech stimuli to investigate the bimodal benefit for lexical tone categorization in Mandarin-speaking kindergarteners using a CI and an HA in opposite ears. Method The data were collected from 16 participants who were required to complete two classical tasks for speech categorical perception (CP) with CI + HA device condition and CI alone condition. Linear mixed-effects models were constructed to evaluate the identification and discrimination scores across different device conditions. Results The bimodal kindergarteners showed CP for the continuum varying from Mandarin Tone 1 and Tone 2. Moreover, the additional acoustic information from the contralateral HA contributes to improved lexical tone categorization, with a steeper slope, a higher discrimination score of between-category stimuli pair, and an improved peakedness score (i.e., an increased benefit magnitude for discriminations of between-category over within-category pairs) for the CI + HA condition than the CI alone condition. The bimodal kindergarteners with better residual hearing thresholds at 250 Hz level in the nonimplanted ear could perceive lexical tones more categorically. Conclusion The enhanced CP results with bimodal listening provide clear evidence for the clinical practice to fit a contralateral HA in the nonimplanted ear in kindergarteners with unilateral CIs with direct benefits from the low-frequency acoustic hearing.

Factors Affecting Bimodal Benefit in Pediatric Mandarin-Speaking Chinese Cochlear Implant Users

OBJECTIVES

While fundamental frequency (F0) cues are important to both lexical tone perception and multitalker segregation, F0 cues are poorly perceived by cochlear implant (CI) users. Adding low-frequency acoustic hearing via a hearing aid in the contralateral ear may improve CI users' F0 perception. For English-speaking CI users, contralateral acoustic hearing has been shown to improve perception of target speech in noise and in competing talkers. For tonal languages such as Mandarin Chinese, F0 information is lexically meaningful. Given competing F0 information from multiple talkers and lexical tones, contralateral acoustic hearing may be especially beneficial for Mandarin-speaking CI users' perception of competing speech.

DESIGN

Bimodal benefit (CI+hearing aid - CI-only) was evaluated in 11 pediatric Mandarin-speaking Chinese CI users. In experiment 1, speech recognition thresholds (SRTs) were adaptively measured using a modified coordinated response measure test; subjects were required to correctly identify 2 keywords from among 10 choices in each category. SRTs were measured with CI-only or bimodal listening in the presence of steady state noise (SSN) or competing speech with the same (M+M) or different voice gender (M+F). Unaided thresholds in the non-CI ear and demographic factors were compared with speech performance. In experiment 2, SRTs were adaptively measured in SSN for recognition of 5 keywords, a more difficult listening task than the 2-keyword recognition task in experiment 1.

RESULTS

In experiment 1, SRTs were significantly lower for SSN than for competing speech in both the CI-only and bimodal listening conditions. There was no significant difference between CI-only and bimodal listening for SSN and M+F (p > 0.05); SRTs were significantly lower for CI-only than for bimodal listening for M+M (p < 0.05), suggesting bimodal interference. Subjects were able to make use of voice gender differences for bimodal listening (p < 0.05) but not for CI-only listening (p > 0.05). Unaided thresholds in the non-CI ear were positively correlated with bimodal SRTs for M+M (p < 0.006) but not for SSN or M+F. No significant correlations were observed between any demographic variables and SRTs (p > 0.05 in all cases). In experiment 2, SRTs were significantly lower with two than with five keywords (p < 0.05). A significant bimodal benefit was observed only for the 5-keyword condition (p < 0.05).

CONCLUSIONS

With the CI alone, subjects experienced greater interference with competing speech than with SSN and were unable to use voice gender difference to segregate talkers. For the coordinated response measure task, subjects experienced no bimodal benefit and even bimodal interference when competing talkers were the same voice gender. A bimodal benefit in SSN was observed for the five-keyword condition but not for the two-keyword condition, suggesting that bimodal listening may be more beneficial as the difficulty of the listening task increased. The present data suggest that bimodal benefit may depend on the type of masker and/or the difficulty of the listening task.

Bimodal Benefits for Lexical Tone Recognition: An Investigation on Mandarin-speaking Preschoolers with a Cochlear Implant and a Contralateral Hearing Aid

Pitch perception is known to be difficult for individuals with cochlear implant (CI), and adding a hearing aid (HA) in the non-implanted ear is potentially beneficial. The current study aimed to investigate the bimodal benefit for lexical tone recognition in Mandarin-speaking preschoolers using a CI and an HA in opposite ears. The child participants were required to complete tone identification in quiet and in noise with CI + HA in comparison with CI alone. While the bimodal listeners showed confusion between Tone 2 and Tone 3 in recognition, the additional acoustic information from the contralateral HA alleviated confusion between these two tones in quiet. Moreover, significant improvement was demonstrated in the CI + HA condition over the CI alone condition in noise. The bimodal benefit for individual subjects could be predicted by the low-frequency hearing threshold of the non-implanted ear and the duration of bimodal use. The findings support the clinical practice to fit a contralateral HA in the non-implanted ear for the potential benefit in Mandarin tone recognition in CI children. The limitations call for further studies on auditory plasticity on an individual basis to gain insights on the contributing factors to the bimodal benefit or its absence.

Bilaterally Combined Electric and Acoustic Hearing in Mandarin-Speaking Listeners: The Population With Poor Residual Hearing

The hearing loss criterion for cochlear implant candidacy in mainland China is extremely stringent (bilateral severe to profound hearing loss), resulting in few patients with substantial residual hearing in the nonimplanted ear. The main objective of the current study was to examine the benefit of bimodal hearing in typical Mandarin-speaking implant users who have poorer residual hearing in the nonimplanted ear relative to those used in the English-speaking studies. Seventeen Mandarin-speaking bimodal users with pure-tone averages of ∼80 dB HL participated in the study. Sentence recognition in quiet and in noise as well as tone and word recognition in quiet were measured in monaural and bilateral conditions. There was no significant bimodal effect for word and sentence recognition in quiet. Small bimodal effects were observed for sentence recognition in noise (6%) and tone recognition (4%). The magnitude of both effects was correlated with unaided thresholds at frequencies near voice fundamental frequencies (F0s). A weak correlation between the bimodal effect for word recognition and unaided thresholds at frequencies higher than F0s was identified. These results were consistent with previous findings that showed more robust bimodal benefits for speech recognition tasks that require higher spectral resolution than speech recognition in quiet. The significant but small F0-related bimodal benefit was also consistent with the limited acoustic hearing in the nonimplanted ear of the current subject sample, who are representative of the bimodal users in mainland China. These results advocate for a more relaxed implant candidacy criterion to be used in mainland China.

Effects of fundamental frequency contour on understanding Mandarin sentences in bimodal hearing simulations

Fundamental frequency (F0) contour carries important information for understanding a tonal language. The present work assessed the effects of F0 contour on understanding Mandarin sentences in bimodal hearing simulations, including three conditions of acoustic-only, electric-only, and combined stimulations. Test stimuli were synthesized Mandarin sentences, each word with a normal, flat, or randomly assigned lexical tone, and presented to normal-hearing Mandarin-speaking listeners to recognize. Experimental results showed that changing F0 contour significantly affected the perception of Mandarin sentences under all conditions of acoustic-only, electric-only, and combined stimulations. The combined-stimulation advantage was only observed for test stimuli with the normal F0 contour.

The Benefits of Residual Hair Cell Function for Speech and Music Perception in Pediatric Bimodal Cochlear Implant Listeners

Objective

The aim of this study was to investigate the benefits of residual hair cell function for speech and music perception in bimodal pediatric Mandarin-speaking cochlear implant (CI) listeners.

Design

Speech and music performance was measured in 35 Mandarin-speaking pediatric CI users for unilateral (CI-only) and bimodal listening. Mandarin speech perception was measured for vowels, consonants, lexical tones, and sentences in quiet. Music perception was measured for melodic contour identification (MCI).

Results

Combined electric and acoustic hearing significantly improved MCI and Mandarin tone recognition performance, relative to CI-only performance. For MCI, performance was significantly better with bimodal listening for all semitone spacing conditions (p < 0.05 in all cases). For tone recognition, bimodal performance was significantly better only for tone 2 (rising; p < 0.05). There were no significant differences between CI-only and CI + HA for vowel, consonant, or sentence recognition.

Conclusions

The results suggest that combined electric and acoustic hearing can significantly improve perception of music and Mandarin tones in pediatric Mandarin-speaking CI patients. Music and lexical tone perception depends strongly on pitch perception, and the contralateral acoustic hearing coming from residual hair cell function provided pitch cues that are generally not well preserved in electric hearing.