Relationship between auditory function of nonimplanted ears and bimodal benefit

Effects of Interaural Latency and Frequency Mismatch on Speech Recognition for Bimodal Cochlear Implant Users

OBJECTIVES

Bimodal cochlear implant (CI) users vary in speech recognition outcomes. This variability may be influenced partly by the CI and contralateral hearing aid (HA) programming procedures, which can result in mismatches in latency and frequency. We assessed the performance of bimodal listeners when latency mismatches were corrected and analyzed how frequency mismatches influenced outcomes.

METHODS

Twelve adults with at least 1 year of bimodal use were evaluated in latency mismatched versus matched conditions. Masked sentence recognition was assessed in a 10-talker masker for three spatial configurations: target from the front and the masker either co-located, 90° toward the CI-ear, or 90° toward the HA-ear. Frequency mismatch for the most apical electrode (E1) was determined from postoperative imaging and the filter frequency assignment of their familiar CI map.

RESULTS

Participants had significantly better performance when latency mismatches were small or matched between the devices, with an approximately 10% improvement in the configuration with the masker toward the HA-ear. Significantly, poorer performance was observed with larger magnitudes of frequency mismatch, with a 2% drop in performance for every one semitone deviation increase in mismatch. The interaction between latency and frequency mismatch was nonsignificant, suggesting that the benefit of latency matching was approximately additive across the range of frequency mismatches.

CONCLUSIONS

Detrimental effects of interaural mismatches in latency and frequency were observed, even after long-term device use. These preliminary results suggest that bimodal CI users might benefit from individualized fitting procedures that match latency across devices and minimize frequency mismatch for the CI.

LEVEL OF EVIDENCE

3 Laryngoscope, 135:2139-2145, 2025.

Bilateral Cochlear Implants and Bimodal Hearing: A Comparison of Quality of Life

BACKGROUND

 Despite significant advances in the field of cochlear implants (CIs), there is no widely accepted criterion for when to counsel on bilateral CIs in adults. This is partly due to conflicting findings on the advantages of bilateral CIs versus bimodal hearing (i.e., CI with a contralateral hearing aid). Because of this, clinicians rely on a poorly defined combination of clinical measures and patient discussion to evaluate a patient's listening needs and preferences. Patients' needs and preferences are often used to guide recommendations on whether bilateral CIs or bimodal hearing is best for that individual, suggesting that an in-depth comparison of each group's self-reported outcomes is warranted.

PURPOSE

 Given the limited number of studies directly comparing quality of life (QoL) in bimodal and bilateral patients, the current study conducted a preliminary comparison of self-reported outcomes to better understand patient-reported benefits of each listening configuration.

RESEARCH DESIGN

 This was a between-subjects comparison.

STUDY SAMPLE

 Fifteen bimodal and nine bilateral adult CI users made the study sample.

DATA COLLECTION AND ANALYSIS

 Participants completed the Cochlear Implant Quality of Life (CIQOL) Profile 35. For group comparison purposes, monosyllabic word recognition and nonverbal intelligence were measured. Independent samples t-tests with Holm-Bonferroni corrections were used to compare bimodal and bilateral patients across domains of the CIQOL.

RESULTS

 Bilateral CI users self-reported better environmental, emotional, social, and global QoL when compared to bimodal users. The groups did not differ on age, nonverbal intelligence, speech recognition abilities, and duration of hearing loss; however, bimodal users had less experience listening with their CI than the bilateral CI users.

CONCLUSION

 Bilateral CI users showed widespread advantages in QoL when compared to bimodal users. Bilateral CI users self-reported significantly better environmental QoL which conflicts with previous in-lab and self-report results suggesting a bimodal advantage. Additionally, due to a lack of current literature, it is unclear why a bilateral advantage is observed for emotional and social QoL. Results of the current study not only provide additional support on the benefits of bilateral implantation but also stress the need to further explore the self-reported benefits of each listening configuration.

Interactions Between Slopes of Residual Hearing and Frequency Maps in Simulated Bimodal and Electric-Acoustic Stimulation Hearing

PURPOSE

The aim of this study was to determine the effects of residual hearing slopes and cochlear implant frequency map settings on bimodal and electric-acoustic stimulation (EAS) benefits in speech perception.

METHOD

Adults with normal hearing were recruited for simulated bimodal and EAS hearing. Sentence perception was measured unilaterally and bilaterally. For the acoustic stimulation, three slopes of high-frequency hearing loss were created using low-pass filters with a cutoff frequency of 500 Hz: steep (96 dB/octave), medium (48 dB/octave), and shallow (24 dB/octave). For the electric stimulation, an eight-channel sinewave vocoder was used with an output frequency range (1000-7938 Hz) with three input frequency ranges to create frequency maps, overlap (188-7938 Hz), meet (500-7938 Hz), and gap (750-7938 Hz), relative to the cutoff frequency in the acoustic stimulation.

RESULTS

The largest bimodal/EAS benefit occurred with the shallow slope, and the smallest occurred with the steep slope. The effects of the slopes on bimodal/EAS benefit were greatest with the meet or gap map and the least with the overlap map. EAS benefit was greater than bimodal benefit at higher signal-to-noise ratios regardless of frequency map.

CONCLUSIONS

The results indicate that correlation between bimodal/EAS benefit and residual hearing could potentially improve if slopes were considered. The optimal frequency map differed with different slopes, suggesting that the slopes of residual hearing should be carefully considered in fitting bimodal and EAS hearing. EAS hearing provided greater benefit over bimodal hearing, suggesting that spectrotemporal integration was better within one ear (i.e., EAS) than across ears (i.e., bimodal).

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.

Objective discrimination of bimodal speech using frequency following responses

Bimodal hearing, in which a contralateral hearing aid is combined with a cochlear implant (CI), provides greater speech recognition benefits than using a CI alone. Factors predicting individual bimodal patient success are not fully understood. Previous studies have shown that bimodal benefits may be driven by a patient's ability to extract fundamental frequency (f0) and/or temporal fine structure cues (e.g., F1). Both of these features may be represented in frequency following responses (FFR) to bimodal speech. Thus, the goals of this study were to: 1) parametrically examine neural encoding of f0 and F1 in simulated bimodal speech conditions; 2) examine objective discrimination of FFRs to bimodal speech conditions using machine learning; 3) explore whether FFRs are predictive of perceptual bimodal benefit. Three vowels (/ε/, /i/, and /ʊ/) with identical f0 were manipulated by a vocoder (right ear) and low-pass filters (left ear) to create five bimodal simulations for evoking FFRs: Vocoder-only, Vocoder +125 Hz, Vocoder +250 Hz, Vocoder +500 Hz, and Vocoder +750 Hz. Perceptual performance on the BKB-SIN test was also measured using the same five configurations. Results suggested that neural representation of f0 and F1 FFR components were enhanced with increasing acoustic bandwidth in the simulated "non-implanted" ear. As spectral differences between vowels emerged in the FFRs with increased acoustic bandwidth, FFRs were more accurately classified and discriminated using a machine learning algorithm. Enhancement of f0 and F1 neural encoding with increasing bandwidth were collectively predictive of perceptual bimodal benefit on a speech-in-noise task. Given these results, FFR may be a useful tool to objectively assess individual variability in bimodal hearing.

Frequency detection, frequency discrimination, and spectro-temporal pattern perception in older and younger typically hearing adults

Elderly adults often experience difficulties in speech understanding, possibly due to age-related deficits in frequency perception. It is unclear whether age-related deficits in frequency perception differ between the apical or basal regions of the cochlea. It is also unclear how aging might differently affect frequency discrimination or detection of a change in frequency within a stimulus. In the present study, pure-tone frequency thresholds were measured in 19 older (61-74 years) and 20 younger (22-28 years) typically hearing adults. Participants were asked to discriminate between reference and probe frequencies or to detect changes in frequency within a probe stimulus. Broadband spectro-temporal pattern perception was also measured using the spectro-temporal modulated ripple test (SMRT). Frequency thresholds were significantly poorer in the basal than in the apical region of the cochlea; the deficit in the basal region was 2 times larger for the older than for the younger group. Frequency thresholds were significantly poorer in the older group, especially in the basal region where frequency detection thresholds were 3.9 times poorer for the older than for the younger group. SMRT thresholds were 1.5 times better for the younger than for the older group. Significant age effects were observed for SMRT thresholds and for frequency thresholds only in the basal region. SMRT thresholds were significantly correlated with frequency thresholds only in the older group. The poorer frequency and spectro-temporal pattern perception may contribute to age-related deficits in speech perception, even when audiometric thresholds are nearly normal.

Auditory evoked response to an oddball paradigm in children wearing cochlear implants

OBJECTIVE

Although children with cochlear implants (CI) achieve remarkable success with their device, considerable variability remains in individual outcomes. Here, we explored whether auditory evoked potentials recorded during an oddball paradigm could provide useful markers of auditory processing in this pediatric population.

METHODS

High-density electroencephalography (EEG) was recorded in 75 children listening to standard and odd noise stimuli: 25 had normal hearing (NH) and 50 wore a CI, divided between high language (HL) and low language (LL) abilities. Three metrics were extracted: the first negative and second positive components of the standard waveform (N1-P2 complex) close to the vertex, the mismatch negativity (MMN) around Fz and the late positive component (P3) around Pz of the difference waveform.

RESULTS

While children with CIs generally exhibited a well-formed N1-P2 complex, those with language delays typically lacked reliable MMN and P3 components. But many children with CIs with age-appropriate skills showed MMN and P3 responses similar to those of NH children. Moreover, larger and earlier P3 (but not MMN) was linked to better literacy skills.

CONCLUSIONS

Auditory evoked responses differentiated children with CIs based on their good or poor skills with language and literacy.

SIGNIFICANCE

This short paradigm could eventually serve as a clinical tool for tracking the developmental outcomes of implanted children.

An overview of factors affecting bimodal and electric-acoustic stimulation (EAS) speech understanding outcomes

Improvements in device technology, surgical technique, and patient outcomes have resulted in a broadening of cochlear implantation criteria to consider those with increasing levels of useful low-to-mid frequency residual acoustic hearing. Residual acoustic hearing allows for the addition of a hearing aid (HA) to complement the cochlear implant (CI) and has demonstrated enhanced listening outcomes. However, wide inter-subject outcome variability exists and thus identification of contributing factors would be of clinical interest and may aid with pre-operative patient counselling. The optimal fitting procedure and frequency assignments for the two hearing devices used in combination to enhance listening outcomes also remains unclear. The understanding of how acoustic and electric speech information is fundamentally combined and utilised by the listener may allow for the optimisation of device fittings and frequency allocations to provide best bimodal and electric-acoustic stimulation (EAS) patient outcomes. This article will provide an overview of contributing factors to bimodal and EAS listening outcomes, explore areas of contention, and discuss common study limitations.

Integration of fundamental frequency and voice-onset-time to voicing categorization: Listeners with normal hearing and bimodal hearing configurations

This study investigates the integration of word-initial fundamental frequency (F0) and voice-onset-time (VOT) in stop voicing categorization for adult listeners with normal hearing (NH) and unilateral cochlear implant (CI) recipients utilizing a bimodal hearing configuration [CI + contralateral hearing aid (HA)]. Categorization was assessed for ten adults with NH and ten adult bimodal listeners, using synthesized consonant stimuli interpolating between /ba/ and /pa/ exemplars with five-step VOT and F0 conditions. All participants demonstrated the expected categorization pattern by reporting /ba/ for shorter VOTs and /pa/ for longer VOTs, with NH listeners showing more use of VOT as a voicing cue than CI listeners in general. When VOT becomes ambiguous between voiced and voiceless stops, NH users make more use of F0 as a cue to voicing than CI listeners, and CI listeners showed greater utilization of initial F0 during voicing identification in their bimodal (CI + HA) condition than in the CI-alone condition. The results demonstrate the adjunctive benefit of acoustic hearing from the non-implanted ear for listening conditions involving spectrotemporally complex stimuli. This finding may lead to the development of a clinically feasible perceptual weighting task that could inform clinicians about bimodal efficacy and the risk-benefit profile associated with bilateral CI recommendation.

Cochlear Implant Facilitates the Use of Talker Sex and Spatial Cues to Segregate Competing Speech in Unilaterally Deaf Listeners

OBJECTIVES

Talker sex and spatial cues can facilitate segregation of competing speech. However, the spectrotemporal degradation associated with cochlear implants (CIs) can limit the benefit of talker sex and spatial cues. Acoustic hearing in the nonimplanted ear can improve access to talker sex cues in CI users. However, it's unclear whether the CI can improve segregation of competing speech when maskers are symmetrically placed around the target (i.e., when spatial cues are available), compared with acoustic hearing alone. The aim of this study was to investigate whether a CI can improve segregation of competing speech by individuals with unilateral hearing loss.

DESIGN

Speech recognition thresholds (SRTs) for competing speech were measured in 16 normal-hearing (NH) adults and 16 unilaterally deaf CI users. All participants were native speakers of Mandarin Chinese. CI users were divided into two groups according to thresholds in the nonimplanted ear: (1) single-sided deaf (SSD); pure-tone thresholds <25 dB HL at all audiometric frequencies, and (2) Asymmetric hearing loss (AHL; one or more thresholds > 25 dB HL). SRTs were measured for target sentences produced by a male talker in the presence of two masker talkers (different male or female talkers). The target sentence was always presented via loudspeaker directly in front of the listener (0°), and the maskers were either colocated with the target (0°) or spatially separated from the target at ±90°. Three segregation cue conditions were tested to measure masking release (MR) relative to the baseline condition: (1) Talker sex, (2) Spatial, and (3) Talker sex + Spatial. For CI users, SRTs were measured with the CI on or off.

RESULTS

Binaural MR was significantly better for the NH group than for the AHL or SSD groups ( P < 0.001 in all cases). For the NH group, mean MR was largest with the Talker sex + spatial cues (18.8 dB) and smallest for the Talker sex cues (10.7 dB). In contrast, mean MR for the SSD group was largest with the Talker sex + spatial cues (14.7 dB), and smallest with the Spatial cues (4.8 dB). For the AHL group, mean MR was largest with the Talker sex + spatial cues (7.8 dB) and smallest with the Talker sex (4.8 dB) and the Spatial cues (4.8 dB). MR was significantly better with the CI on than off for both the AHL ( P = 0.014) and SSD groups ( P < 0.001). Across all unilaterally deaf CI users, monaural (acoustic ear alone) and binaural MR were significantly correlated with unaided pure-tone average thresholds in the nonimplanted ear for the Talker sex and Talker sex + spatial conditions ( P < 0.001 in both cases) but not for the Spatial condition.

CONCLUSION

Although the CI benefitted unilaterally deaf listeners' segregation of competing speech, MR was much poorer than that observed in NH listeners. Different from previous findings with steady noise maskers, the CI benefit for segregation of competing speech from a different talker sex was greater in the SSD group than in the AHL group.

Perception of speaker sincerity in complex social interactions by cochlear implant users

Understanding insincere language (sarcasm and teasing) is a fundamental part of communication and crucial for maintaining social relationships. This can be a challenging task for cochlear implant (CIs) users who receive degraded suprasegmental information important for perceiving a speaker's attitude. We measured the perception of speaker sincerity (literal positive, literal negative, sarcasm, and teasing) in 16 adults with CIs using an established video inventory. Participants were presented with audio-only and audio-visual social interactions between two people with and without supporting verbal context. They were instructed to describe the content of the conversation and answer whether the speakers meant what they said. Results showed that subjects could not always identify speaker sincerity, even when the content of the conversation was perfectly understood. This deficit was greater for perceiving insincere relative to sincere utterances. Performance improved when additional visual cues or verbal context cues were provided. Subjects who were better at perceiving the content of the interactions in the audio-only condition benefited more from having additional visual cues for judging the speaker's sincerity, suggesting that the two modalities compete for cognitive recourses. Perception of content also did not correlate with perception of speaker sincerity, suggesting that what was said vs. how it was said were perceived using unrelated segmental versus suprasegmental cues. Our results further showed that subjects who had access to lower-order resolved harmonic information provided by hearing aids in the contralateral ear identified speaker sincerity better than those who used implants alone. These results suggest that measuring speech recognition alone in CI users does not fully describe the outcome. Our findings stress the importance of measuring social communication functions in people with CIs.

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.

Acoustic analysis of tone production in Mandarin-speaking bimodal cochlear implant users

The benefit of using a hearing aid with a cochlear implant (bimodal hearing) has been demonstrated for tone perception under certain conditions. The present study evaluated bimodal effects for tone production by comparing performance between a bimodal and a unimodal implant group. Results showed that acoustic differentiation of tones produced by the bimodal group was better than the unimodal implant group, and performance was dependent on the subject's acoustic thresholds but not related to implant experience or age at implantation. The findings support the use of amplified acoustic hearing in conjunction with the implant for better development of pitch production.

Distortion of Spectral Ripples Through Cochlear Implants Has Major Implications for Interpreting Performance Scores

The spectral ripple discrimination task is a psychophysical measure that has been found to correlate with speech recognition in listeners with cochlear implants (CIs). However, at ripple densities above a critical value (around 2 RPO, but device-specific), the sparse spectral sampling of CI processors results in stimulus distortions resulting in aliasing and unintended changes in modulation depth. As a result, spectral ripple thresholds above a certain number are not ordered monotonically along the RPO dimension and thus cannot be considered better or worse spectral resolution than each other, thus undermining correlation measurements. These stimulus distortions are not remediated by changing stimulus phase, indicating these issues cannot be solved by spectrotemporally modulated stimuli. Speech generally has very low-density spectral modulations, leading to questions about the mechanism of correlation between high ripple thresholds and speech recognition. Existing data showing correlations between ripple discrimination and speech recognition include many observations above the aliasing limit. These scores should be treated with caution, and experimenters could benefit by prospectively considering the limitations of the spectral ripple test.

Bimodal Hearing with Pediatric Cochlear Implant Recipients: Effect of Acoustic Bandwidth

OBJECTIVE

The primary purpose of this study was to examine the effect of acoustic bandwidth on bimodal benefit for speech understanding in pediatric cochlear implant (CI) recipients.

STUDY DESIGN

Ten children (6-13 years) with CIs utilizing a bimodal hearing configuration participated in this study. Speech understanding was assessed via recorded Pediatric AzBio sentences presented in a 10-talker babble. The CI stimulus was always unprocessed and the low-pass filtered acoustic stimuli were delivered to the non-CI ear with the following cutoff frequencies: 250, 500, 750, 1000, and 1500 Hz.

SETTING

Tertiary referral center.

MAIN OUTCOME MEASURES

Sentence recognition in noise for the acoustic-alone, CI-alone, and bimodal listening conditions.

RESULTS

The primary findings were: (1) children gained significant bimodal benefit with 250 Hz, and (2) children demonstrated no statistically significant additional bimodal benefit with increasing acoustic bandwidth.

CONCLUSIONS

Acoustic bandwidth effects for pediatric CI recipients were significantly different than those documented in the literature for adult CI recipients. Specifically, this group of pediatric CI recipients demonstrated no increases in bimodal benefit with increases in acoustic bandwidth, primarily consistent with a segregation theory of bimodal integration.

Systematic review of cochlear implantation in adults with asymmetrical hearing loss

BACKGROUND

Rapid advances in cochlear implantation has witnessed an expanding spectrum for candidacy worldwide. This includes a subgroup of adults with asymmetrical hearing loss who have a wide range in their hearing capacity between the two ears. As per guidelines they are not included in mainstream candidacy for CI across the world. Evidence is now emerging to support the benefits of CI in AHL.

METHODS

This review analyzed literature regarding the outcomes of CI in AHL. Primary outcome measure was to assess audiological benefits and secondary outcome measure was to assess hearing related quality of life. 15 relevant articles, published worldwide between 2009 and 2019 were chosen. CASP checklist for systematic reviews was used to ascertain the quality of literature. The strength of recommendations from each study was analyzed and classified as strong, moderate, weak or none based on GRADE guidelines.

RESULTS

Heterogeneity in samples was obvious and samples varied largely between the studies. The levels of evidence ranged from systematic review to expert opinion, but overall they reflected positively on both audiological and QOL benefits.

CONCLUSION

CI provides important auditory and QOL benefits in AHL, but there is no high level evidence as yet to strongly support CI for AHL. A long term multi-centric study is necessary to influence a change in practice for a growing population of AHL.Trial registration: ClinicalTrials.gov identifier: NCT03052920.

Bimodal Stimulation in Children With Bilateral Profound Sensorineural Hearing Loss: A Suitable Intervention Model for Children at the Early Developmental Stage

OBJECTIVE

To evaluate the auditory and speech benefit of bimodal stimulation for prelingual deafened cochlear implantation recipients.

STUDY DESIGN

Retrospective and comparative study.

SETTING

Tertiary referral center.

PATIENTS

Fifty-six children with bilateral prelingual profound sensorineural hearing loss were enrolled, including 28 consecutive children with unilateral cochlear implantation (CI group), and 28 consecutive children with bimodal stimulation (BI group) who used an additional hearing aid (HA) in the contralateral ear.

MAIN OUTCOME MEASURES

Hearing assessments included the Infant-Toddler Meaningful Auditory Integration Scale (IT-MAIS) and Categories of Auditory Performance (CAP). Speech evaluations included the Meaningful Use of Speech Scale (MUSS), and Speech Intelligibility Rating (SIR). These measurements were evaluated at the first mapping of cochlear implants and 0.5, 1, 3, 6, 12, 18, 24 months after. Data were analyzed by repeated measures analysis.

RESULTS

The mean ages of BI and CI groups were similar (17.6 ± 6.87 vs 19.0 ± 8.10 months, p = 0.497). The initial scores for hearing and speech assessments showed no differences between the two groups, apart from IT-MAIS (2.46 ± 0.631 in BI group vs 0.50 ± 0.279 in CI group, p = 0.004). The auditory and speech development over time were different in the two groups as seen in IT-MAIS (p < 0.001), CAP (p = 0.029), MUSS (p < 0.001), and SIR (p < 0.001). A continuing but stable difference was observed in CAP, MUSS, and SIR at 3, 18, and 12 months after the first mapping, respectively. In addition, the BI group had better IT-MAIS scores at 3 and 6 months compared with the CI group; however, the difference was not significant after 12 months.

CONCLUSION

Bimodal stimulation is beneficial for prelingually deafened CI recipients who have minimal contralateral residual hearing when bilateral CIs are not available. Hearing aid use in the contralateral ear might be recommended for children after unilateral cochlear implantation to facilitate the development of auditory and speech skills.

Spatial Release From Masking in Bimodal and Bilateral Pediatric Cochlear Implant Recipients

Purpose Traditional clinical measures of cochlear implant (CI) recipient performance may not fully evaluate the benefit of bimodal listening (hearing aid contralateral to a CI). The clinical assessment of spatial release from masking (SRM) may be a sensitive measure of the benefit of listening with bimodal stimulation. This study compared the SRM of pediatric bimodal and bilateral CI listeners using a clinically feasible method, and investigated variables that may contribute to speech recognition performance with spatially separated maskers. Method Forty pediatric bimodal (N = 20) and bilateral CI (N = 20) participants were assessed in their best aided listening condition on sentence recognition in a four-talker masker. Testing was completed with target and masker colocated at 0° azimuth, and with the masker directed at 90° to either ear. SRM was calculated as the difference in performance between the colocated and each 90° condition. A two-way mixed-methods analysis of variance was used to compare performance between groups in the three masker conditions. Multiple regression analyses were conducted to investigate potential predictors for SRM asymmetry including hearing history, unaided thresholds, word recognition, duration of device use, and acoustic bandwidth. Results Both groups demonstrated SRM, with significantly better recognition in each 90° condition as compared to the colocated condition. The groups did not differ significantly in SRM. The multiple regression analyses did not reveal any significant predictors of SRM asymmetry. Conclusions Bimodal and bilateral CI listeners demonstrated similar amounts of SRM. While no specific variables predicted SRM asymmetry in bimodal listeners, pediatric bimodal and bilateral CI recipients should expect similar amounts of SRM regardless of the side of the masker. SRM asymmetry in pediatric bimodal listeners may signal a need for consideration of a second CI.

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.

Self-assessment of unilateral and bimodal cochlear implant experiences in daily life

Objective

The subjective experiences were assessed of cochlear implant (CI) users either wearing or not wearing a hearing aid (HA) at the contralateral ear.

Design

Unilateral CI-recipients were asked to fill out a set of daily-life questionnaires on bimodal HA use, hearing disability, hearing handicap and general quality of life.

Study sample

Twenty-six CI-recipients who regularly use a contralateral HA (bimodal group) and twenty-two CI-recipients who do not use a HA in the contralateral ear (unilateral group).

Results

Comparisons between both groups (bimodal versus unilateral) showed no difference in self-rated disability, hearing handicap or general quality of life. However within the group of bimodal listeners, participants did report a benefit of bimodal hearing ability in various daily life listening situations.

Conclusions

Bimodal benefit in daily life can consistently be experienced and reported within the group of bimodal users.

Frequency Following Response and Speech Recognition Benefit for Combining a Cochlear Implant and Contralateral Hearing Aid

Multiple studies have shown significant speech recognition benefit when acoustic hearing is combined with a cochlear implant (CI) for a bimodal hearing configuration. However, this benefit varies greatly between individuals. There are few clinical measures correlated with bimodal benefit and those correlations are driven by extreme values prohibiting data-driven, clinical counseling. This study evaluated the relationship between neural representation of fundamental frequency (F0) and temporal fine structure via the frequency following response (FFR) in the nonimplanted ear as well as spectral and temporal resolution of the nonimplanted ear and bimodal benefit for speech recognition in quiet and noise. Participants included 14 unilateral CI users who wore a hearing aid (HA) in the nonimplanted ear. Testing included speech recognition in quiet and in noise with the HA-alone, CI-alone, and in the bimodal condition (i.e., CI + HA), measures of spectral and temporal resolution in the nonimplanted ear, and FFR recording for a 170-ms/da/stimulus in the nonimplanted ear. Even after controlling for four-frequency pure-tone average, there was a significant correlation (r = .83) between FFR F0 amplitude in the nonimplanted ear and bimodal benefit. Other measures of auditory function of the nonimplanted ear were not significantly correlated with bimodal benefit. The FFR holds potential as an objective tool that may allow data-driven counseling regarding expected benefit from the nonimplanted ear. It is possible that this information may eventually be used for clinical decision-making, particularly in difficult-to-test populations such as young children, regarding effectiveness of bimodal hearing versus bilateral CI candidacy.

Are There Real-world Benefits to Bimodal Listening?

OBJECTIVE

To assess the benefits of bimodal listening (i.e., addition of contralateral hearing aid) for cochlear implant (CI) users on real-world tasks involving high-talker variability speech materials, environmental sounds, and self-reported quality of life (quality of hearing) in listeners' own best-aided conditions.

STUDY DESIGN

Cross-sectional study between groups.

SETTING

Outpatient hearing clinic.

PATIENTS

Fifty experienced adult CI users divided into groups based on normal daily listening conditions (i.e., best-aided conditions): unilateral CI (CI), unilateral CI with contralateral HA (bimodal listening; CIHA), or bilateral CI (CICI).

INTERVENTION

Task-specific measures of speech recognition with low (Harvard Standard Sentences) and high (Perceptually Robust English Sentence Test Open-set corpus) talker variability, environmental sound recognition (Familiar Environmental Sounds Test-Identification), and hearing-related quality of life (Nijmegen Cochlear Implant Questionnaire).

MAIN OUTCOME MEASURES

Test group differences among CI, CIHA, and CICI conditions.

RESULTS

No group effect was observed for speech recognition with low or high-talker variability, or hearing-related quality of life. Bimodal listeners demonstrated a benefit in environmental sound recognition compared with unilateral CI listeners, with a trend of greater benefit than the bilateral CI group. There was also a visual trend for benefit on high-talker variability speech recognition.

CONCLUSIONS

Findings provide evidence that bimodal listeners demonstrate stronger environmental sound recognition compared with unilateral CI listeners, and support the idea that there are additional advantages to bimodal listening after implantation other than speech recognition measures, which are at risk of being lost if considering bilateral implantation.

A Cross-Language Comparison of Sentence Recognition Using American English and Mandarin Chinese HINT and AzBio Sentences

OBJECTIVES

The aim of this study was to perform a cross-language comparison of two commonly used sentence-recognition materials (i.e., Hearing in Noise Test [HINT] and AzBio) in American English (AE) and Mandarin Chinese (MC).

DESIGNS

Sixty normal-hearing, native English-speaking and 60 normal-hearing, native Chinese-speaking young adults were recruited to participate in three experiments. In each experiment, the subjects were tested in their native language. In experiments I and II, noise and tone vocoders were used to process the HINT and AzBio sentences, respectively. The number of channels varied from 1 to 9, with an envelope cutoff frequency of 160 Hz. In experiment III, the AE AzBio and the MC HINT sentences were tested in speech-shaped noise at various signal to noise ratios (i.e., -20, -15, -10, -5, and 0 dB). The performance-intensity functions of sentence recognition using the two sets of sentence materials were compared.

RESULTS

Results of experiments I and II using vocoder processing indicated that the AE and MC versions of HINT and AzBio sentences differed in level of difficulty. The AE version yielded higher recognition performance than the MC version for both HINT and AzBio sentences. The type of vocoder processing (i.e., tone and noise vocoders) produced little differences in sentence-recognition performance in both languages. Incidentally, the AE AzBio sentences and the MC HINT sentences had similar recognition performance under vocoder processing. Such similarity was further confirmed under noise conditions in experiment III, where the performance-intensity functions of the two sets of sentences were closely matched.

CONCLUSIONS

The HINT and AzBio sentence materials developed in AE and MC differ in level of difficulty. The AE AzBio and the MC HINT sentence materials are similar in level of difficulty. In cross-language comparative research, the MC HINT and the AE AzBio sentences should be chosen for the respective language as the target sentence-recognition test materials.

Evaluation of a novel bimodal fitting formula in Advanced Bionics cochlear implant recipients

Purpose: The study's objectives were to (1) evaluate benefit from a novel bimodal fitting formula (Adaptive Phonak Digital Bimodal Fitting Formula [APDB]), and (2) compare outcomes with APDB and a traditional fitting formula (NAL-NL2). Methods: This prospective study evaluated outcomes in ten adults with unilateral Advanced Bionics (AB) cochlear implants (CI). Participants were tested bimodally with NAL-NL2 and APDB programed on Naída Link UP HAs. Measures of speech perception, sound quality, and preference were obtained with two bimodal configurations (CI + HANAL-NL2 and CI + HAAPDB). Participants used the CI + HAAPDB configuration for an acclimation period, after which measures were repeated. Results: Significant bimodal benefit was measured from both HA fitting formulae for speech perception in noise compared to the CI-only condition. Improved individual outcomes with the APDB were observed, but group differences were not statistically significant. Participants reported subjective benefit from APDB on blind comparisons of preference and sound quality. Conclusions: Significant benefit was found with both bimodal conditions compared to the CI-only condition; however, bimodal speech perception results were not significantly different. Users reported benefit from the APDB formula over NAL-NL2 formula. Due to individual improved speech perception and overall subjective preference for APDB, clinicians should consider APDB with AB CI recipients.

Evaluating hearing performance with cochlear implants within the same patient using daily randomization and imaging-based fitting - The ELEPHANT study

Background

Prospective research in the field of cochlear implants is hampered by methodological issues and small sample sizes. The ELEPHANT study presents an alternative clinical trial design with a daily randomized approach evaluating individualized tonotopical fitting of a cochlear implant (CI).

Methods

A single-blinded, daily-randomized clinical trial will be implemented to evaluate a new imaging-based CI mapping strategy. A minimum of 20 participants will be included from the start of the rehabilitation process with a 1-year follow-up period. Based on a post-operative cone beam CT scan (CBCT), mapping of electrical input will be aligned to natural place-pitch arrangement in the individual cochlea. The CI’s frequency allocation table will be adjusted to match the electrical stimulation of frequencies as closely as possible to corresponding acoustic locations in the cochlea. A randomization scheme will be implemented whereby the participant, blinded to the intervention allocation, crosses over between the experimental and standard fitting program on a daily basis, and thus effectively acts as his own control, followed by a period of free choice between both maps to incorporate patient preference. With this new approach the occurrence of a first-order carryover effect and a limited sample size is addressed.

Discussion

The experimental fitting strategy is thought to give rise to a steeper learning curve, result in better performance in challenging listening situations, improve sound quality, better complement residual acoustic hearing in the contralateral ear and be preferred by recipients of a CI. Concurrently, the suitability of the novel trial design will be considered in investigating these hypotheses.

Trial registration

ClinicalTrials.gov: NCT03892941. Registered 27 March 2019.

Clinical Application of Spectral Modulation Detection: Speech Recognition Benefit for Combining a Cochlear Implant and Contralateral Hearing Aid

Purpose The purpose of this study was to investigate the relationship between speech recognition benefit derived from the addition of a hearing aid (HA) to the nonimplanted ear (i.e., bimodal benefit) and spectral modulation detection (SMD) performance in the nonimplanted ear in a large clinical sample. An additional purpose was to investigate the influence of low-frequency pure-tone average (PTA) of the nonimplanted ear and age at implantation on the variance in bimodal benefit. Method Participants included 311 unilateral cochlear implant (CI) users who wore an HA in the nonimplanted ear. Participants completed speech recognition testing in quiet and in noise with the CI-alone and in the bimodal condition (i.e., CI and contralateral HA) and SMD in the nonimplanted ear. Results SMD performance in the nonimplanted ear was significantly correlated with bimodal benefit in quiet and in noise. However, this relationship was much weaker than previous reports with smaller samples. SMD, low-frequency PTA of the nonimplanted ear from 125 to 750 Hz, and age at implantation together accounted for, at most, 19.1% of the variance in bimodal benefit. Conclusions Taken together, SMD, low-frequency PTA, and age at implantation account for the greatest amount of variance in bimodal benefit than each variable alone. A large portion of variance (~80%) in bimodal benefit is not explained by these variables. Supplemental Material https://doi.org/10.23641/asha.12185493.

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.

Spatial Speech-in-Noise Performance in Bimodal and Single-Sided Deaf Cochlear Implant Users

This study compared spatial speech-in-noise performance in two cochlear implant (CI) patient groups: bimodal listeners, who use a hearing aid contralaterally to support their impaired acoustic hearing, and listeners with contralateral normal hearing, i.e., who were single-sided deaf before implantation. Using a laboratory setting that controls for head movements and that simulates spatial acoustic scenes, speech reception thresholds were measured for frontal speech-in-stationary noise from the front, the left, or the right side. Spatial release from masking (SRM) was then extracted from speech reception thresholds for monaural and binaural listening. SRM was found to be significantly lower in bimodal CI than in CI single-sided deaf listeners. Within each listener group, the SRM extracted from monaural listening did not differ from the SRM extracted from binaural listening. In contrast, a normal-hearing control group showed a significant improvement in SRM when using two ears in comparison to one. Neither CI group showed a binaural summation effect; that is, their performance was not improved by using two devices instead of the best monaural device in each spatial scenario. The results confirm a "listening with the better ear" strategy in the two CI patient groups, where patients benefited from using two ears/devices instead of one by selectively attending to the better one. Which one is the better ear, however, depends on the spatial scenario and on the individual configuration of hearing loss.

Bimodal Hearing or Bilateral Cochlear Implants? Ask the Patient

OBJECTIVE

The objectives of this study were to assess the effectiveness of various measures of speech understanding in distinguishing performance differences between adult bimodal and bilateral cochlear implant (CI) recipients and to provide a preliminary evidence-based tool guiding clinical decisions regarding bilateral CI candidacy.

DESIGN

This study used a multiple-baseline, cross-sectional design investigating speech recognition performance for 85 experienced adult CI recipients (49 bimodal, 36 bilateral). Speech recognition was assessed in a standard clinical test environment with a single loudspeaker using the minimum speech test battery for adult CI recipients as well as with an R-SPACE 8-loudspeaker, sound-simulation system. All participants were tested in three listening conditions for each measure including each ear alone as well as in the bilateral/bimodal condition. In addition, we asked each bimodal listener to provide a yes/no answer to the question, "Do you think you need a second CI?"

RESULTS

This study yielded three primary findings: (1) there were no significant differences between bimodal and bilateral CI performance or binaural summation on clinical measures of speech recognition, (2) an adaptive speech recognition task in the R-SPACE system revealed significant differences in performance and binaural summation between bimodal and bilateral CI users, with bilateral CI users achieving significantly better performance and greater summation, and (3) the patient's answer to the question, "Do you think you need a second CI?" held high sensitivity (100% hit rate) for identifying likely bilateral CI candidates and moderately high specificity (77% correct rejection rate) for correctly identifying listeners best suited with a bimodal hearing configuration.

CONCLUSIONS

Clinics cannot rely on current clinical measures of speech understanding, with a single loudspeaker, to determine bilateral CI candidacy for adult bimodal listeners nor to accurately document bilateral benefit relative to a previous bimodal hearing configuration. Speech recognition in a complex listening environment, such as R-SPACE, is a sensitive and appropriate measure for determining bilateral CI candidacy and also likely for documenting bilateral benefit relative to a previous bimodal configuration. In the absence of an available R-SPACE system, asking the patient whether or not s/he thinks s/he needs a second CI is a highly sensitive measure, which may prove clinically useful.

Bilateral Cochlear Implantation Versus Bimodal Hearing in Patients With Functional Residual Hearing: A Within-subjects Comparison of Audiologic Performance and Quality of Life

OBJECTIVE

Evaluate performance and quality of life changes after sequential bilateral cochlear implantation in patients with preoperative residual hearing functioning in a bimodal hearing configuration.

STUDY DESIGN

Retrospective analysis using within-subjects repeated measures design.

SETTING

Tertiary otologic center.

PATIENTS

Twenty-two adult patients with bilateral sensorineural hearing loss who used bimodal hearing before second cochlear implant (CI) meeting the following criteria: 1) preoperative residual hearing (≤80 dB HL at 250 Hz) in the ear to be implanted, 2) implantation with current CI technology (2013-2016), 3) consonant-nucleus-consonant (CNC) speech recognition testing in the bimodal condition preoperatively and bilateral CI condition postoperatively.

INTERVENTION

Cochlear implantation.

MAIN OUTCOME MEASURES

CNC and AzBio sentence scores in quiet and noise (+5 SNR). Subjective measures of communication difficulty and sound quality were also administered.

RESULTS

Twenty-two patients (mean 64 yr, 68% men) were included. At an average follow-up of 11.8 months, CNC scores in the bilateral CI condition (mean 63%, standard deviation [SD] = 22) were significantly better than preoperative bimodal scores with repeated measures analysis (mean 55%, SD = 22) (p = 0.03). AzBio scores in quiet were also higher with bilateral CI (mean 76%, SD = 24) compared with bimodal listening (mean 69%, SD = 29) (p = 0.0007). Global abbreviated profile of hearing aid benefit (APHAB) and overall speech, spatial, and qualities of hearing (SSQ) scores exhibited significant improvement following bilateral implantation (p = 0.006 for both analyses).

CONCLUSIONS

For patients using a bimodal hearing configuration with substantial residual hearing in the non-CI ear, bilateral cochlear implantation yields improved audiologic performance and better subjective quality of life, irrespective of the ability to preserve acoustic hearing during the second sided implantation.

Bimodal Cochlear Implant Listeners' Ability to Perceive Minimal Audible Angle Differences

BACKGROUND

Bilateral inputs should ideally improve sound localization and speech understanding in noise. However, for many bimodal listeners [i.e., individuals using a cochlear implant (CI) with a contralateral hearing aid (HA)], such bilateral benefits are at best, inconsistent. The degree to which clinically available HA and CI devices can function together to preserve interaural time and level differences (ITDs and ILDs, respectively) enough to support the localization of sound sources is a question with important ramifications for speech understanding in complex acoustic environments.

PURPOSE

To determine if bimodal listeners are sensitive to changes in spatial location in a minimum audible angle (MAA) task.

RESEARCH DESIGN

Repeated-measures design.

STUDY SAMPLE

Seven adult bimodal CI users (28-62 years). All listeners reported regular use of digital HA technology in the nonimplanted ear.

DATA COLLECTION AND ANALYSIS

Seven bimodal listeners were asked to balance the loudness of prerecorded single syllable utterances. The loudness-balanced stimuli were then presented via direct audio inputs of the two devices with an ITD applied. The task of the listener was to determine the perceived difference in processing delay (the interdevice delay [IDD]) between the CI and HA devices. Finally, virtual free-field MAA performance was measured for different spatial locations both with and without inclusion of the IDD correction, which was added with the intent to perceptually synchronize the devices.

RESULTS

During the loudness-balancing task, all listeners required increased acoustic input to the HA relative to the CI most comfortable level to achieve equal interaural loudness. During the ITD task, three listeners could perceive changes in intracranial position by distinguishing sounds coming from the left or from the right hemifield; when the CI was delayed by 0.73, 0.67, or 1.7 msec, the signal lateralized from one side to the other. When MAA localization performance was assessed, only three of the seven listeners consistently achieved above-chance performance, even when an IDD correction was included. It is not clear whether the listeners who were able to consistently complete the MAA task did so via binaural comparison or by extracting monaural loudness cues. Four listeners could not perform the MAA task, even though they could have used a monaural loudness cue strategy.

CONCLUSIONS

These data suggest that sound localization is extremely difficult for most bimodal listeners. This difficulty does not seem to be caused by large loudness imbalances and IDDs. Sound localization is best when performed via a binaural comparison, where frequency-matched inputs convey ITD and ILD information. Although low-frequency acoustic amplification with a HA when combined with a CI may produce an overlapping region of frequency-matched inputs and thus provide an opportunity for binaural comparisons for some bimodal listeners, our study showed that this may not be beneficial or useful for spatial location discrimination tasks. The inability of our listeners to use monaural-level cues to perform the MAA task highlights the difficulty of using a HA and CI together to glean information on the direction of a sound source.

Intraoperative Electrically Evoked Compound Action Potential (ECAP) Measurements in Traditional and Hearing Preservation Cochlear Implantation

BACKGROUND

In current practice, the status of residual low-frequency acoustic hearing in hearing preservation cochlear implantation (CI) is unknown until activation two to three weeks postoperatively. The intraoperatively measured electrically evoked compound action potential (ECAP), a synchronous response from electrically stimulated auditory nerve fibers, is one of the first markers of auditory nerve function after cochlear implant surgery and such may provide information regarding the status of residual low-frequency acoustic hearing.

PURPOSE

This study aimed to evaluate the relationship between intraoperative ECAP at the time of CI and presence of preoperative and postoperative low-frequency acoustic hearing.

RESEARCH DESIGN

A retrospective case review.

STUDY SAMPLE

Two hundred seventeen adult ears receiving CI (42 Advanced Bionics, 82 Cochlear, and 93 MED-EL implants).

INTERVENTIONS

Intraoperative ECAP and CI.

DATA COLLECTION AND ANALYSIS

ECAP measurements were obtained intraoperatively, whereas residual hearing data were obtained from postoperative CI activation audiogram. A linear mixed model test revealed no interaction effects for the following variables: manufacturer, electrode location (basal, middle, and apical), preoperative low-frequency pure-tone average (LFPTA), and postoperative LFPTA. The postoperative residual low-frequency hearing status was defined as preservation of unaided air conduction thresholds ≤90 dB at 250 Hz. Electrode location and hearing preservation data were analyzed individually for both the ECAP threshold and ECAP maximum amplitude using multiple t-tests, without assuming a consistent standard deviation between the groups, and with alpha correction.

RESULTS

The maximum amplitude, in microvolts, was significantly higher throughout apical and middle regions of the cochlea in patients who had preserved low-frequency acoustic hearing as compared with those who did not have preserved hearing (p = 0.0001 and p = 0.0088, respectively). ECAP threshold, in microamperes, was significantly lower throughout the apical region of the cochlea in patients with preserved low-frequency acoustic hearing as compared with those without preserved hearing (p = 0.0099). Basal electrode maximum amplitudes and middle and basal electrode thresholds were not significantly correlated with postoperative low-frequency hearing.

CONCLUSIONS

Apical and middle electrode maximum amplitudes and apical electrode thresholds detected through intraoperative ECAP measurements are significantly correlated with preservation of low-frequency acoustic hearing. This association may represent a potential immediate feedback mechanism for postoperative outcomes that can be applied to all CIs.

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.

Current Profile of Adults Presenting for Preoperative Cochlear Implant Evaluation

Considerable advancements in cochlear implant technology (e.g., electric acoustic stimulation) and assessment materials have yielded expanded criteria. Despite this, it is unclear whether individuals with better audiometric thresholds and speech understanding are being referred for cochlear implant workup and pursuing cochlear implantation. The purpose of this study was to characterize the mean auditory and demographic profile of adults presenting for preoperative cochlear implant workup. Data were collected prospectively for all adult preoperative workups at Vanderbilt from 2013 to 2015. Subjects included 287 adults (253 postlingually deafened) with a mean age of 62.3 years. Each individual was assessed using the minimum speech test battery, spectral modulation detection, subjective questionnaires, and cognitive screening. Mean consonant-nucleus-consonant word scores, AzBio sentence scores, and pure-tone averages for postlingually deafened adults were 10%, 13%, and 89 dB HL, respectively, for the ear to be implanted. Seventy-three individuals (25.4%) met labeled indications for Hybrid-L and 207 individuals (72.1%) had aidable hearing in the better hearing ear to be used in a bimodal hearing configuration. These results suggest that mean speech understanding evaluated at cochlear implant workup remains very low despite recent advancements. Greater awareness and insurance accessibility may be needed to make cochlear implant technology available to those who qualify for electric acoustic stimulation devices as well as individuals meeting conventional cochlear implant criteria.

The Relationship Between Spectral Modulation Detection and Speech Recognition: Adult Versus Pediatric Cochlear Implant Recipients

Adult cochlear implant (CI) recipients demonstrate a reliable relationship between spectral modulation detection and speech understanding. Prior studies documenting this relationship have focused on postlingually deafened adult CI recipients—leaving an open question regarding the relationship between spectral resolution and speech understanding for adults and children with prelingual onset of deafness. Here, we report CI performance on the measures of speech recognition and spectral modulation detection for 578 CI recipients including 477 postlingual adults, 65 prelingual adults, and 36 prelingual pediatric CI users. The results demonstrated a significant correlation between spectral modulation detection and various measures of speech understanding for 542 adult CI recipients. For 36 pediatric CI recipients, however, there was no significant correlation between spectral modulation detection and speech understanding in quiet or in noise nor was spectral modulation detection significantly correlated with listener age or age at implantation. These findings suggest that pediatric CI recipients might not depend upon spectral resolution for speech understanding in the same manner as adult CI recipients. It is possible that pediatric CI users are making use of different cues, such as those contained within the temporal envelope, to achieve high levels of speech understanding. Further investigation is warranted to investigate the relationship between spectral and temporal resolution and speech recognition to describe the underlying mechanisms driving peripheral auditory processing in pediatric CI users.

The Benefits of Bimodal Aiding on Extended Dimensions of Speech Perception: Intelligibility, Listening Effort, and Sound Quality

The benefits of combining a cochlear implant (CI) and a hearing aid (HA) in opposite ears on speech perception were examined in 15 adult unilateral CI recipients who regularly use a contralateral HA. A within-subjects design was carried out to assess speech intelligibility testing, listening effort ratings, and a sound quality questionnaire for the conditions CI alone, CIHA together, and HA alone when applicable. The primary outcome of bimodal benefit, defined as the difference between CIHA and CI, was statistically significant for speech intelligibility in quiet as well as for intelligibility in noise across tested spatial conditions. A reduction in effort on top of intelligibility at the highest tested signal-to-noise ratio was found. Moreover, the bimodal listening situation was rated to sound more voluminous, less tinny, and less unpleasant than CI alone. Listening effort and sound quality emerged as feasible and relevant measures to demonstrate bimodal benefit across a clinically representative range of bimodal users. These extended dimensions of speech perception can shed more light on the array of benefits provided by complementing a CI with a contralateral HA.

Speech Recognition in Noise for Adults With Normal Hearing: Age-Normative Performance for AzBio, BKB-SIN, and QuickSIN

OBJECTIVE

Characterize performance for adults aged 20 to 79 years with normal hearing on tasks of AzBio, Bamford-Kowal-Bench speech-in-noise (BKB-SIN), quick speech-in-noise (QuickSIN), and acoustic Quick Spectral Modulation Detection (QSMD) in the sound field.

SETTING

Cochlear implant (CI) program.

PATIENTS

Eighty-one adults with normal hearing and cognitive function were recruited evenly across four age groups (20-49, 50-59, 60-69, and 70-79 yr).

INTERVENTIONS

Subjects completed AzBio sentence recognition testing in quiet and in five signal-to-noise ratios (SNRs: +10, +5, 0, -5, -10 dB), as well as the BKB-SIN, QuickSIN, and QSMD tasks.

MAIN OUTCOME MEASURES

AzBio, BKB-SIN, QuickSIN, and acoustic QSMD scores were analyzed to characterize typical sound field performance in an older adult population with normal hearing.

RESULTS

AzBio sentence recognition performance approached ceiling for sentences presented at ≥ 0 dB SNR with mean scores ranging from 3.5% at -10 dB SNR to 99% at +10 dB SNR. Mean QuickSIN SNR-50 was -0.02. Mean BKB-SIN SNR-50 was -1.31 dB. Mean acoustic QSMD score was 88%. Performance for all measures decreased with age.

CONCLUSION

Adults with age-normative hearing achieve ceiling-level performance for AzBio sentence recognition at SNRs used for clinical cochlear implant and/or hearing aid testing. Thus, these tasks are not inherently contraindicated for older listeners. Older adults with normal hearing, however, demonstrated greater deficits for speech in noise compared to younger listeners-an effect most pronounced at negative SNRs. Lastly, BKB-SIN data obtained in the sound field replicated previous normative data for only the youngest age group, suggesting that new norms should be considered for older populations.

The effect of presentation level on spectrotemporal modulation detection

The understanding of speech in noise relies (at least partially) on spectrotemporal modulation sensitivity. This sensitivity can be measured by spectral ripple tests, which can be administered at different presentation levels. However, it is not known how presentation level affects spectrotemporal modulation thresholds. In this work, we present behavioral data for normal-hearing adults which show that at higher ripple densities (2 and 4 ripples/oct), increasing presentation level led to worse discrimination thresholds. Results of a computational model suggested that the higher thresholds could be explained by a worsening of the spectrotemporal representation in the auditory nerve due to broadening of cochlear filters and neural activity saturation. Our results demonstrate the importance of taking presentation level into account when administering spectrotemporal modulation detection tests.

Bimodal benefit for cochlear implant listeners with different grades of hearing loss in the opposite ear

OBJECTIVE

To determine speech perception in quiet and noise of adult cochlear implant listeners retaining a hearing aid contralaterally. Second, to investigate the influence of contralateral hearing thresholds and speech perception on bimodal hearing.

PATIENTS AND METHODS

Sentence recognition with hearing aid alone, cochlear implant alone and bimodally at 6 months after cochlear implantation were assessed in 148 postlingually deafened adults. Data were analyzed for bimodal summation using measures of speech perception in quiet and in noise.

RESULTS

Most of the subjects showed improved sentence recognition in quiet and in noise in the bimodal condition compared to the hearing aid-only or cochlear implant-only mode. The large variability of bimodal benefit in quiet can be partially explained by the degree of pure tone loss. Also, subjects with better hearing on the acoustic side experience significant benefit from the additional electrical input.

CONCLUSIONS

Bimodal summation shows different characteristics in quiet and noise. Bimodal benefit in quiet depends on hearing thresholds at higher frequencies as well as in the lower- and middle-frequency ranges. For the bimodal benefit in noise, no correlation with hearing threshold in any frequency range was found.

Segmental and Suprasegmental Perception in Children Using Hearing Aids

BACKGROUND

Suprasegmental perception (perception of stress, intonation, "how something is said" and "who says it") and segmental speech perception (perception of individual phonemes or perception of "what is said") are perceptual abilities that provide the foundation for the development of spoken language and effective communication. While there are numerous studies examining segmental perception in children with hearing aids (HAs), there are far fewer studies examining suprasegmental perception, especially for children with greater degrees of residual hearing. Examining the relation between acoustic hearing thresholds, and both segmental and suprasegmental perception for children with HAs, may ultimately enable better device recommendations (bilateral HAs, bimodal devices [one CI and one HA in opposite ears], bilateral CIs) for a particular degree of residual hearing. Examining both types of speech perception is important because segmental and suprasegmental cues are affected differentially by the type of hearing device(s) used (i.e., cochlear implant [CI] and/or HA). Additionally, suprathreshold measures, such as frequency resolution ability, may partially predict benefit from amplification and may assist audiologists in making hearing device recommendations.

PURPOSE

The purpose of this study is to explore the relationship between audibility (via hearing thresholds and speech intelligibility indices), and segmental and suprasegmental speech perception for children with HAs. A secondary goal is to explore the relationships among frequency resolution ability (via spectral modulation detection [SMD] measures), segmental and suprasegmental speech perception, and receptive language in these same children.

RESEARCH DESIGN

A prospective cross-sectional design.

STUDY SAMPLE

Twenty-three children, ages 4 yr 11 mo to 11 yr 11 mo, participated in the study. Participants were recruited from pediatric clinic populations, oral schools for the deaf, and mainstream schools.

DATA COLLECTION AND ANALYSIS

Audiological history and hearing device information were collected from participants and their families. Segmental and suprasegmental speech perception, SMD, and receptive vocabulary skills were assessed. Correlations were calculated to examine the significance (p < 0.05) of relations between audibility and outcome measures.

RESULTS

Measures of audibility and segmental speech perception are not significantly correlated, while low-frequency pure-tone average (unaided) is significantly correlated with suprasegmental speech perception. SMD is significantly correlated with all measures (measures of audibility, segmental and suprasegmental perception and vocabulary). Lastly, although age is not significantly correlated with measures of audibility, it is significantly correlated with all other outcome measures.

CONCLUSIONS

The absence of a significant correlation between audibility and segmental speech perception might be attributed to overall audibility being maximized through well-fit HAs. The significant correlation between low-frequency unaided audibility and suprasegmental measures is likely due to the strong, predominantly low-frequency nature of suprasegmental acoustic properties. Frequency resolution ability, via SMD performance, is significantly correlated with all outcomes and requires further investigation; its significant correlation with vocabulary suggests that linguistic ability may be partially related to frequency resolution ability. Last, all of the outcome measures are significantly correlated with age, suggestive of developmental effects.

Dietrich M, Dorman MF. Speech Understanding in Noise for Adults With Cochlear Implants: Effects of Hearing Configuration, Source Location Certainty, and Head Movement

Purpose

The primary purpose of this study was to assess speech understanding in quiet and in diffuse noise for adult cochlear implant (CI) recipients utilizing bimodal hearing or bilateral CIs. Our primary hypothesis was that bilateral CI recipients would demonstrate less effect of source azimuth in the bilateral CI condition due to symmetric interaural head shadow.

Method

Sentence recognition was assessed for adult bilateral (n = 25) CI users and bimodal listeners (n = 12) in three conditions: (1) source location certainty regarding fixed target azimuth, (2) source location uncertainty regarding roving target azimuth, and (3) Condition 2 repeated, allowing listeners to turn their heads, as needed.

Results

(a) Bilateral CI users exhibited relatively similar performance regardless of source azimuth in the bilateral CI condition; (b) bimodal listeners exhibited higher performance for speech directed to the better hearing ear even in the bimodal condition; (c) the unilateral, better ear condition yielded higher performance for speech presented to the better ear versus speech to the front or to the poorer ear; (d) source location certainty did not affect speech understanding performance; and (e) head turns did not improve performance. The results confirmed our hypothesis that bilateral CI users exhibited less effect of source azimuth than bimodal listeners. That is, they exhibited similar performance for speech recognition irrespective of source azimuth, whereas bimodal listeners exhibited significantly poorer performance with speech originating from the poorer hearing ear (typically the nonimplanted ear).

Conclusions

Bilateral CI users overcame ear and source location effects observed for the bimodal listeners. Bilateral CI users have access to head shadow on both sides, whereas bimodal listeners generally have interaural asymmetry in both speech understanding and audible bandwidth limiting the head shadow benefit obtained from the poorer ear (generally the nonimplanted ear). In summary, we found that, in conditions with source location uncertainty and increased ecological validity, bilateral CI performance was superior to bimodal listening.

Combined Electric and Acoustic Stimulation With Hearing Preservation: Effect of Cochlear Implant Low-Frequency Cutoff on Speech Understanding and Perceived Listening Difficulty

OBJECTIVE

The primary objective of this study was to assess the effect of electric and acoustic overlap for speech understanding in typical listening conditions using semidiffuse noise.

DESIGN

This study used a within-subjects, repeated measures design including 11 experienced adult implant recipients (13 ears) with functional residual hearing in the implanted and nonimplanted ear. The aided acoustic bandwidth was fixed and the low-frequency cutoff for the cochlear implant (CI) was varied systematically. Assessments were completed in the R-SPACE sound-simulation system which includes a semidiffuse restaurant noise originating from eight loudspeakers placed circumferentially about the subject's head. AzBio sentences were presented at 67 dBA with signal to noise ratio varying between +10 and 0 dB determined individually to yield approximately 50 to 60% correct for the CI-alone condition with full CI bandwidth. Listening conditions for all subjects included CI alone, bimodal (CI + contralateral hearing aid), and bilateral-aided electric and acoustic stimulation (EAS; CI + bilateral hearing aid). Low-frequency cutoffs both below and above the original "clinical software recommendation" frequency were tested for all patients, in all conditions. Subjects estimated listening difficulty for all conditions using listener ratings based on a visual analog scale.

RESULTS

Three primary findings were that (1) there was statistically significant benefit of preserved acoustic hearing in the implanted ear for most overlap conditions, (2) the default clinical software recommendation rarely yielded the highest level of speech recognition (1 of 13 ears), and (3) greater EAS overlap than that provided by the clinical recommendation yielded significant improvements in speech understanding.

CONCLUSIONS

For standard-electrode CI recipients with preserved hearing, spectral overlap of acoustic and electric stimuli yielded significantly better speech understanding and less listening effort in a laboratory-based, restaurant-noise simulation. In conclusion, EAS patients may derive more benefit from greater acoustic and electric overlap than given in current software fitting recommendations, which are based solely on audiometric threshold. These data have larger scientific implications, as previous studies may not have assessed outcomes with optimized EAS parameters, thereby underestimating the benefit afforded by hearing preservation.

Top-Down Processes in Simulated Electric-Acoustic Hearing: The Effect of Linguistic Context on Bimodal Benefit for Temporally Interrupted Speech

OBJECTIVES

Previous studies have documented the benefits of bimodal hearing as compared with a cochlear implant alone, but most have focused on the importance of bottom-up, low-frequency cues. The purpose of the present study was to evaluate the role of top-down processing in bimodal hearing by measuring the effect of sentence context on bimodal benefit for temporally interrupted sentences. It was hypothesized that low-frequency acoustic cues would facilitate the use of contextual information in the interrupted sentences, resulting in greater bimodal benefit for the higher context (CUNY) sentences than for the lower context (IEEE) sentences.

DESIGN

Young normal-hearing listeners were tested in simulated bimodal listening conditions in which noise band vocoded sentences were presented to one ear with or without low-pass (LP) filtered speech or LP harmonic complexes (LPHCs) presented to the contralateral ear. Speech recognition scores were measured in three listening conditions: vocoder-alone, vocoder combined with LP speech, and vocoder combined with LPHCs. Temporally interrupted versions of the CUNY and IEEE sentences were used to assess listeners' ability to fill in missing segments of speech by using top-down linguistic processing. Sentences were square-wave gated at a rate of 5 Hz with a 50% duty cycle. Three vocoder channel conditions were tested for each type of sentence (8, 12, and 16 channels for CUNY; 12, 16, and 32 channels for IEEE) and bimodal benefit was compared for similar amounts of spectral degradation (matched-channel comparisons) and similar ranges of baseline performance. Two gain measures, percentage-point gain and normalized gain, were examined.

RESULTS

Significant effects of context on bimodal benefit were observed when LP speech was presented to the residual-hearing ear. For the matched-channel comparisons, CUNY sentences showed significantly higher normalized gains than IEEE sentences for both the 12-channel (20 points higher) and 16-channel (18 points higher) conditions. For the individual gain comparisons that used a similar range of baseline performance, CUNY sentences showed bimodal benefits that were significantly higher (7% points, or 15 points normalized gain) than those for IEEE sentences. The bimodal benefits observed here for temporally interrupted speech were considerably smaller than those observed in an earlier study that used continuous speech. Furthermore, unlike previous findings for continuous speech, no bimodal benefit was observed when LPHCs were presented to the LP ear.

CONCLUSIONS

Findings indicate that linguistic context has a significant influence on bimodal benefit for temporally interrupted speech and support the hypothesis that low-frequency acoustic information presented to the residual-hearing ear facilitates the use of top-down linguistic processing in bimodal hearing. However, bimodal benefit is reduced for temporally interrupted speech as compared with continuous speech, suggesting that listeners' ability to restore missing speech information depends not only on top-down linguistic knowledge but also on the quality of the bottom-up sensory input.

Relationship between spectrotemporal modulation detection and music perception in normal-hearing, hearing-impaired, and cochlear implant listeners

The objective of this study was to examine the relationship between spectrotemporal modulation (STM) sensitivity and the ability to perceive music. Ten normal-hearing (NH) listeners, ten hearing aid (HA) users with moderate hearing loss, and ten cochlear Implant (CI) users participated in this study. Three different types of psychoacoustic tests including spectral modulation detection (SMD), temporal modulation detection (TMD), and STM were administered. Performances on these psychoacoustic tests were compared to music perception abilities. In addition, psychoacoustic mechanisms involved in the improvement of music perception through HA were evaluated. Music perception abilities in unaided and aided conditions were measured for HA users. After that, HA benefit for music perception was correlated with aided psychoacoustic performance. STM detection study showed that a combination of spectral and temporal modulation cues were more strongly correlated with music perception abilities than spectral or temporal modulation cues measured separately. No correlation was found between music perception performance and SMD threshold or TMD threshold in each group. Also, HA benefits for melody and timbre identification were significantly correlated with a combination of spectral and temporal envelope cues though HA.

The Effects of Acoustic Bandwidth on Simulated Bimodal Benefit in Children and Adults with Normal Hearing

OBJECTIVES

The primary purpose of this study was to examine the effect of acoustic bandwidth on bimodal benefit for speech recognition in normal-hearing children with a cochlear implant (CI) simulation in one ear and low-pass filtered stimuli in the contralateral ear. The effect of acoustic bandwidth on bimodal benefit in children was compared with the pattern of adults with normal hearing. Our hypothesis was that children would require a wider acoustic bandwidth than adults to (1) derive bimodal benefit, and (2) obtain asymptotic bimodal benefit.

DESIGN

Nineteen children (6 to 12 years) and 10 adults with normal hearing participated in the study. Speech recognition was assessed via recorded sentences presented in a 20-talker babble. The AzBio female-talker sentences were used for the adults and the pediatric AzBio sentences (BabyBio) were used for the children. A CI simulation was presented to the right ear and low-pass filtered stimuli were presented to the left ear with the following cutoff frequencies: 250, 500, 750, 1000, and 1500 Hz.

RESULTS

The primary findings were (1) adults achieved higher performance than children when presented with only low-pass filtered acoustic stimuli, (2) adults and children performed similarly in all the simulated CI and bimodal conditions, (3) children gained significant bimodal benefit with the addition of low-pass filtered speech at 250 Hz, and (4) unlike previous studies completed with adult bimodal patients, adults and children with normal hearing gained additional significant bimodal benefit with cutoff frequencies up to 1500 Hz with most of the additional benefit gained with energy below 750 Hz.

CONCLUSIONS

Acoustic bandwidth effects on simulated bimodal benefit were similar in children and adults with normal hearing. Should the current results generalize to children with CIs, these results suggest pediatric CI recipients may derive significant benefit from minimal acoustic hearing (<250 Hz) in the nonimplanted ear and increasing benefit with broader bandwidth. Knowledge of the effect of acoustic bandwidth on bimodal benefit in children may help direct clinical decisions regarding a second CI, continued bimodal hearing, and even optimizing acoustic amplification for the nonimplanted ear.