Enhanced Pitch Discrimination for Cochlear Implant Users with a New Haptic Neuroprosthetic

The cochlear implant (CI) is the most widely used neuroprosthesis, recovering hearing for more than half a million severely-to-profoundly hearing-impaired people. However, CIs still have significant limitations, with users having severely impaired pitch perception. Pitch is critical to speech understanding (particularly in noise), to separating different sounds in complex acoustic environments, and to music enjoyment. In recent decades, researchers have attempted to overcome shortcomings in CIs by improving implant technology and surgical techniques, but with limited success. In the current study, we take a new approach of providing missing pitch information through haptic stimulation on the forearm, using our new mosaicOne_B device. The mosaicOne_B extracts pitch information in real-time and presents it via 12 motors that are arranged in ascending pitch along the forearm, with each motor representing a different pitch. In normal-hearing subjects listening to CI simulated audio, we showed that participants were able to discriminate pitch differences at a similar performance level to that achieved by normal-hearing listeners. Furthermore, the device was shown to be highly robust to background noise. This enhanced pitch discrimination has the potential to significantly improve music perception, speech recognition, and speech prosody perception in CI users.

The effect of a coding strategy that removes temporally masked pulses on speech perception by cochlear implant users

Speech recognition in noisy environments remains a challenge for cochlear implant (CI) recipients. Unwanted charge interactions between current pulses, both within and between electrode channels, are likely to impair performance. Here we investigate the effect of reducing the number of current pulses on speech perception. This was achieved by implementing a psychoacoustic temporal-masking model where current pulses in each channel were passed through a temporal integrator to identify and remove pulses that were less likely to be perceived by the recipient. The decision criterion of the temporal integrator was varied to control the percentage of pulses removed in each condition. In experiment 1, speech in quiet was processed with a standard Continuous Interleaved Sampling (CIS) strategy and with 25, 50 and 75% of pulses removed. In experiment 2, performance was measured for speech in noise with the CIS reference and with 50 and 75% of pulses removed. Speech intelligibility in quiet revealed no significant difference between reference and test conditions. For speech in noise, results showed a significant improvement of 2.4 dB when removing 50% of pulses and performance was not significantly different between the reference and when 75% of pulses were removed. Further, by reducing the overall amount of current pulses by 25, 50, and 75% but accounting for the increase in charge necessary to compensate for the decrease in loudness, estimated average power savings of 21.15, 40.95, and 63.45%, respectively, could be possible for this set of listeners. In conclusion, removing temporally masked pulses may improve speech perception in noise and result in substantial power savings.

Automated remote intraoperative cochlear implant device testing (CR220). Is it clinically efficient?

OBJECTIVES

To compare the clinical efficiency of the CR220 intraoperative remote assistant device used by the surgical team with that of the custom sound (CS) system used by an audiologist.

METHODS

This was a prospective clinical study in a quaternary care center (King Abdullah Ear Specialist Centre) in Riyadh, Saudi Arabia, between October 2018 and March 2019. We included adult and pediatric patients who underwent cochlear implant (CI) surgeries. For every participant, the intraoperative CI testing was performed via both the aforementioned methods. The time taken to complete the measurements with both approaches, including the time required by the audiologist to reach the operating room (OR) and to complete the test, was recorded.

RESULTS

There were no significant differences in the number of responding electrodes between the 2 approaches. For the 25 participants, the time taken for the measurements was 566 minutes with the CS and 173 with the CR220 systems. This significant difference indicates that considerable time can be saved.

CONCLUSION

The CR220 enables intraoperative CI electrode tests and auto-NRT measurements. Its ergonomics and ease-of-use help the surgical team conduct the tests without an audiologist in the OR, resulting in the efficient use of clinical resources. Further, the results generated were consistent with those of the CS system.

Exploring the recruitment, ethical considerations, conduct and information dissemination of an audiology trial: a pretrial qualitative study (q-COACH)

INTRODUCTION

Randomised controlled trials (RCTs), while still considered the gold standard approach in medical research, can encounter impediments to their successful conduct and the dissemination of results. Pretrial qualitative research can usefully address some of these impediments, including recruitment and retention, ethical conduct, and preferred methods of dissemination. However, pretrial qualitative work is rarely undertaken in audiology. The Comparison of outcomes with hearing aids and cochlear implants in adults with moderately severe-to-profound bilateral sensorineural hearing loss (COACH) is a proposed RCT aiming to clarify when hearing aids (HAs) or cochlear implants (CIs) are the most suitable for different degrees of hearing loss and for which kinds of patients. q-COACH is a pretrial, qualitative study examining stakeholders' experiences of HAs and CIs, current clinical practices and stakeholders' perspectives of the design, conduct and dissemination plans for the proposed COACH study.

METHODS

Twenty-four participants including general practitioners, audiologists, adult HA users, and adult support networks undertook either semi-structured individual or paired interviews and completed demographic questionnaires. Data were analysed thematically.

RESULTS

Four key themes arose from this study: 1) rethinking sampling and recruitment strategies, 2) ethical considerations, 3) refining trial conduct, and 4) interconnected, appropriate and accessible methods of results dissemination.

CONCLUSIONS

This qualitative investigation identified key considerations for the proposed RCT design, conduct and dissemination to help with successful implementation of COACH, and to indicate a plan of action at all RCT stages that would be acceptable to potential participants. By drawing on the perspectives of multiple key stakeholders and including a more general discussion of their experience and opinions of hearing loss, hearing device use and service availability, the study revealed experiential and ethical paradigms in which stakeholders operate. In so doing, q-COACH has exposed the benefits of preliminary qualitative investigations that enable detailed and rich understandings of the phenomenon at stake, forestalling problems and improving the quality of trial design, conduct and dissemination, while informing future RCT development discussions.

Vestibular Implantation and the Feasibility of Fluoroscopy-Guided Electrode Insertion

Recent research has shown promising results for the development of a clinically feasible vestibular implant in the near future. However, correct electrode placement remains a challenge. It was shown that fluoroscopy was able to visualize the semicircular canal ampullae and electrodes, and guide electrode insertion in real time. Ninety-four percent of the 18 electrodes were implanted correctly (<1.5 mm distance to target). The median distances were 0.60 mm, 0.85 mm, and 0.65 mm for the superior, lateral, and posterior semicircular canal, respectively. These findings suggest that fluoroscopy can significantly improve electrode placement during vestibular implantation.

Sequential stream segregation with bilateral cochlear implants

Sequential stream segregation on the basis of binaural 'ear-of-entry', modulation rate and electrode place-of-stimulation cues was investigated in bilateral cochlear implant (CI) listeners using a rhythm anisochrony detection task. Sequences of alternating 'A' and 'B' bursts were presented via direct electrical stimulation and comprised either an isochronous timing structure or an anisochronous structure that was generated by delaying just the 'B' bursts. 'B' delay thresholds that enabled rhythm anisochrony detection were determined. Higher thresholds were assumed to indicate a greater likelihood of stream segregation, resulting specifically from stream integration breakdown. Results averaged across subjects showed that thresholds were significantly higher when monaural 'A' and 'B' bursts were presented contralaterally rather than ipsilaterally, and that diotic presentation of 'A', with a monaural 'B', yielded intermediate thresholds. When presented monaurally and ipsilaterally, higher thresholds were also found when successive bursts had mismatched rather than matched modulation rates. In agreement with previous studies, average delay thresholds also increased as electrode separation between bursts increased when presented ipsilaterally. No interactions were found between ear-of-entry, modulation rate and place-of-stimulation. However, combining moderate electrode difference cues with either diotic-'A' ear-of-entry cues or modulation-rate mismatch cues did yield greater threshold increases than observed with any of those cues alone. The results from the present study indicate that sequential stream segregation can be elicited in bilateral CI users by differences in the signal across ears (binaural cues), in modulation rate (monaural cues) and in place-of-stimulation (monaural cues), and that those differences can be combined to further increase segregation.

Age-sensitive associations of segmental and suprasegmental perception with sentence-level language skills in Mandarin-speaking children with cochlear implants

BACKGROUND AND AIM

It remains unclear how recognition of segmental and suprasegmental phonemes contributes to sentence-level language processing skills in Mandarin-speaking children with cochlear implants (CIs). Our study examined the influence of implantation age on the recognition of consonants, lexical tones and sentences respectively, and more importantly, the contribution of phonological skills to sentence repetition accuracy in Mandarin-speaking children with CIs.

METHODS

The participants were three groups of prelingually deaf children who received cochlear implants at various ages and their age-matched controls with normal hearing. Three tasks were administered to assess their consonant perception, lexical tone recognition and language skills in open-set sentence repetition.

RESULTS

Children with CIs lagged behind NH peers in all the three tests, and performances on segmental, suprasegmental and sentence-level processing were differentially modulated by implantation age. Furthermore, performances on recognition of consonants and lexical tones were significant predictors of sentence repetition accuracy in the children with CIs.

CONCLUSION

Overall, segmental and suprasegmental perception as well as sentence-level processing is impaired in Mandarin-speaking children with CIs compared with age-matched children with NH. In children with CIs recognition of segmental and suprasegmental phonemes at the lower level predicts sentence repetition accuracy at the higher level. More importantly, implantation age plays an important role in the development of phonological skills and higher-order language skills, suggesting that age-appropriate aural rehabilitation and speech intervention programs need to be developed in order to better help CI users who receive CIs at different ages.

Surgical approach for complete cochlear coverage in EAS-patients after residual hearing loss

Introduction

In cases with residual-hearing (RH) loss after cochlear implantation, a safe method is needed to provide full spectral resolution and as much auditory information as possible without implant replacement. Aim of this study was to prove the feasibility of accessing a partially inserted cochlear-implant-electrode for complete insertion to its maximum length through the external ear canal using a transcanal approach.

Methods

Two CI electrodes were customized with 18 stimulating channels. The electrode design enables the use of 12 active channels available for electrical stimulation inside the cochlea both after partial and full insertion. 10 CI electrodes were implanted in 10 fresh human cadaveric temporal bones. After initial partial insertion by posterior tympanotomy, the electrode was inserted to its maximum length via a transcanal approach. Radiographs and CT scans were performed to confirm the electrode position. The electrodes were investigated via x-ray after removal.

Results

X-ray and CT-scans confirmed the electrode prototypes covering an angular insertion depth between 236° to 307° after initial insertion. Accessing the electrode in the middle ear space was feasible and insertion to its full length was successful. Post-insertion CT confirmed insertion of the 28mm and 31.5mm electrode arrays covering an angular insertion depth between 360° and 540° respectively. No tip foldovers were detected.

Conclusion

This study confirms the feasibility of extending the electrode insertion to its maximum insertion length using a transcanal approach in temporal bone specimens. This constitutes a second stage procedure on demand in EAS-surgery. This may be beneficial for EAS-patients providing electrical stimulation beyond the basal turn of the cochlea once the functional residual hearing is lost, without replacing the entire CI.

Differences in the impedance of cochlear implant devices within 24 hours of their implantation

Cochlear implantation is a surgical procedure, which is performed on severely hearing-impaired patients. Impedance field telemetry is commonly used to determine the integrity of the cochlear implant device during and after surgery. At the Department of Otolaryngology, Cheng Hsin General Hospital (Taipei, Taiwan), the cochlear implant devices are switched on within 24 hours of their implantation. In the present study, the impedance changes of Advanced Bionics^™ cochlear implant devices were compared with previous studies and other devices. The aim was to confirm previous hypotheses and to explore other potential associated factors that could influence impedance following cochlear implantation. The current study included 12 patients who underwent cochlear implantation at Cheng Hsin General Hospital with Advanced Bionics cochlear implant devices. The cochlear devices were all switched on within 24 hours of their implantation. The impedance was measured and compared across all contact channels of the electrode, both intra-operatively and post-operatively. The intra-operative impedance was compared with the switch-on impedance (within 24 hours of the cochlear implantation); the impedance was notably increased for all contact channels at switch-on. Of the 16 channels examined, 4 channels had a significant increase in impedance between the intra-operative measurement and the switch-on measurement. To the best of our knowledge, the impedance of a cochlear implant device can be affected by the diameter of the electrode, the position of the electrode arrays in the scala tympani, sheath formation and fibrosis surrounding the electrode after implantation and electrical stimulation during or after surgery. When the results of the current study were compared with previous studies, it was found that the impedance changes were opposite to that of Cochlear^™ implant devices. This may be explained by the position of the electrode arrays, sheath formation, the blow-out effect and differences in electrical stimulation.

Design and In Vivo Verification of a CMOS Bone-Guided Cochlear Implant Microsystem

OBJECTIVE

To develop and verify a CMOS bone-guided cochlear implant (BGCI) microsystem with electrodes placed on the bone surface of the cochlea and the outside of round window for treating high-frequency hearing loss.

METHODS

The BGCI microsystem consists of an external unit and an implanted unit. The external system-on-chip is designed to process acoustic signals through an acquisition circuit and an acoustic DSP processor to generate stimulation patterns and commands that are transmitted to the implanted unit through a 13.56 MHz wireless power and bidirectional data telemetry. In the wireless power telemetry, a voltage doubler/tripler (2X/3X) active rectifier is used to enhance the power conversion efficiency and generate 2 and 3 V output voltages. In the wireless data telemetry, phase-locked loop based binary phase-shift keying and load-shift keying modulators/demodulators are adopted for the downlink and uplink data through high-Q coils, respectively. The implanted chip with four-channel high-voltage-tolerant stimulator generates biphasic stimulation currents up to 800 μA.

RESULTS

Electrical tests on the fabricated BGCI microsystem have been performed to verify the chip functions. The in vivo animal tests in guinea pigs have shown the evoked third wave of electrically evoked auditory brainstem response waveforms. It is verified that auditory nerves can be successfully stimulated and acoustic hearing can be partially preserved.

CONCLUSION AND SIGNIFICANCE

Different from traditional cochlear implants, the proposed BGCI microsystem is less invasive, preserves partially acoustic hearing, and provides an effective alternative for treating high-frequency hearing loss.

Design, Fabrication, and Evaluation of a Parylene Thin-Film Electrode Array for Cochlear Implants

OBJECTIVE

To improve the existing manually assembled cochlear implant electrode arrays, a thin-film electrode array (TFEA) was microfabricated having a maximum electrode density of 15 sites along an 8-mm length, with each site having a 75 μm × 1.8 μm (diameter × height) disk electrode.

METHODS

The microfabrication method adopted photoresist transferring, lift-off, two-step oxygen plasma etching, and fuming nitric acid release to reduce lift-off complexity, protect the metal layer, and increase the release efficiency.

RESULTS

Systematic in vitro characterization showed that the TFEA's bending stiffness was 6.40 × 10-10 N·m2 near the base and 1.26 × 10-10 N·m2 near the apex. The TFEA electrode produced an average impedance of 16 kΩ and a maximum current limit of 800 μA, measured with 1-kHz sinusoidal current using monopolar stimulation in saline. A TFEA prototype was implanted in a cat cochlea to obtain in vivo measurements of electrically evoked auditory brainstem and inferior colliculus responses to monopolar stimulation with 41-μs/phase biphasic pulses. Both physiological responses produced a threshold of ∼300 μA and a dynamic range of 5-8 dB above the threshold. Compared with existing arrays, the present TFEA had 104 times less bending stiffness, 97% less electrode area, and comparable physiological thresholds.

CONCLUSION

Using a simplified structure and stable fabrication method, the present TEFA produced physical and physiological performance comparable to existing commercial devices.

SIGNIFICANCE

The present TFEA represents a step closer toward an automated process replacing the labor-intensive and expensive manual assembly of the cochlear implant electrode arrays.

An improved method of obtaining electrocochleography recordings from Nucleus Hybrid cochlear implant users

Interest in electrocochleography (ECoG) has recently resurged as a potential tool to assess peripheral auditory function in cochlear implant (CI) users. ECoG recordings can be evoked using acoustic stimulation and recorded from an extra- or intra-cochlear electrode in CI users. Recordings reflect contributions from cochlear hair cells and the auditory nerve. We recently demonstrated the feasibility of using Custom Sound EP (clinically available software) to record ECoG responses in Nucleus Hybrid CI users with preserved acoustic hearing in the implanted ear (Abbas et al, 2017). While successful, the recording procedures were time intensive, limiting clinical applications. The current report describes how we improved data collection efficiency by writing custom software using Python programming language. The software interfaced with Nucleus Implant Communicator (NIC) routines to record responses from an intracochlear electrode. ECoG responses were recorded in eight CI users with preserved acoustic hearing using Custom Sound EP and the Python-based software. Responses were similar across both recording systems, but the recording time decreased significantly using the Python-based software. Seven additional CI users underwent repeated testing using the Python-based software and showed high test-retest reliability. The improved efficiency and high reliability increases the likelihood of translating intracochlear ECoG to clinical practice.

Phonological Development in a Bilingual Arabic-English-Speaking Child With Bilateral Cochlear Implants: A Longitudinal Case Study

PURPOSE

This longitudinal study examined the phonological development of a bilingual Arabic-English-speaking child with bilateral cochlear implants (CIs). The focus of the study was to observe the interaction between her two languages and to observe the effect of CIs on the acquisition of two speech sound systems.

METHOD

This study followed a 3;6-year-old (2;5 hearing age) bilingual Arabic-English-speaking child with bilateral CIs to age 4;4 (3;2 hearing age). Single-word samples were collected bimonthly in both languages. Phon software (Rose et al., 2006) was used to transcribe and analyze speech samples. Measures derived included Percent Consonants Correct-Revised (Shriberg & Kwiatkowski, 1994), percent vowels correct, phonetic inventory complexity, and common phonological patterns for both English and Arabic.

RESULTS

Our findings supported previous research on phonological development exhibited by children with CIs, with the gradual suppression of typical and atypical error patterns and gradual increase in segmental accuracy with maturation. In addition, language interaction and separation between English and Arabic were found, supporting previous cross-linguistic work on bilingual phonological acquisition (e.g., Fabiano-Smith & Goldstein, 2010b).

CONCLUSION

Bilingual children with CIs have the capability to learn both of their languages and perform similarly to, and even surpass in accuracy, monolingual children with CIs; however, it is also possible to exhibit a slower rate of acquisition of segmental accuracy as compared to their typically developing, hearing peers. Clinical implications of bilingual early intervention are discussed.

Cochlear Implant Users' Vocal Control CorrelatesAcross Tasks

Cochlear implants (CIs) provide access to auditory information that can affect vocal control. For example, previous research shows that, when producing a sustained vowel, CI users will alter the pitch of their voice when the feedback of their own voice is perceived to shift. Although these results can be informative as to how perception and production are linked for CI users, the artificial nature of the task raises questions as to the applicability of the results to real-world vocal productions. To examine how vocal control, when producing sustained vowels, relates to vocal control for more ecologically valid tasks, 10 CI users' vocal control was measured across two tasks: (1) sustained vowel production, and (2) singing. The results found that vocal control, as measured by the variability of the participants' fundamental frequency, was significantly correlated when producing sustained vowels and when singing, although variability was significantly greater when singing. This suggests that, despite the artificial nature of sustained vowel production, vocal control on such tasks is related to vocal control for more ecologically valid tasks. However, the results also suggest that vocal control may be overestimated with sustained vowel production tasks.

Development and validation of a spectro-temporal processing test for cochlear-implant listeners

Psychophysical tests of spectro-temporal resolution may aid the evaluation of methods for improving hearing by cochlear implant (CI) listeners. Here the STRIPES (Spectro-Temporal Ripple for Investigating Processor EffectivenesS) test is described and validated. Like speech, the test requires both spectral and temporal processing to perform well. Listeners discriminate between complexes of sine sweeps which increase or decrease in frequency; difficulty is controlled by changing the stimulus spectro-temporal density. Care was taken to minimize extraneous cues, forcing listeners to perform the task only on the direction of the sweeps. Vocoder simulations with normal hearing listeners showed that the STRIPES test was sensitive to the number of channels and temporal information fidelity. An evaluation with CI listeners compared a standard processing strategy with one having very wide filters, thereby spectrally blurring the stimulus. Psychometric functions were monotonic for both strategies and five of six participants performed better with the standard strategy. An adaptive procedure revealed significant differences, all in favour of the standard strategy, at the individual listener level for six of eight CI listeners. Subsequent measures validated a faster version of the test, and showed that STRIPES could be performed by recently implanted listeners having no experience of psychophysical testing.

Postoperative Electrocochleography from Hybrid Cochlear Implant users: An Alternative Analysis Procedure

OBJECTIVE

Shorter electrode arrays and soft surgical techniques allow for preservation of acoustic hearing in many cochlear implant (CI) users. Recently, we developed a method of using the Neural Response Telemetry (NRT) system built in Custom Sound EP clinical software to record acoustically evoked electrocochleography (ECoG) responses from an intracochlear electrode in Nucleus Hybrid CI users (Abbas et al., 2017). We recorded responses dominated by the hair cells (cochlear microphonic, CM/DIF) and the auditory nerve (auditory nerve neurophonic, ANN/SUM). Unfortunately, the recording procedure was time consuming, limiting potential clinical applications. This report describes a modified method to record the ECoG response more efficiently. We refer to this modified technique as the "short window" method, while our previous technique (Abbas et al., 2017) is referred as the "long window" method. In this report, our goal was to 1) evaluate the feasibility of the short window method to record the CM/DIF and ANN/SUM responses, 2) characterize the reliability and sensitivity of the measures recorded using the short window method, and 3) evaluate the relationship between the CM/DIF and ANN/SUM measures recorded using the modified method and audiometric thresholds.

METHOD

Thirty-four postlingually deafened adult Hybrid CI users participated in this study. Acoustic tone bursts were presented at four frequencies (250, 500, 750, and 1000 Hz) at various stimulation levels via an insert earphone in both condensation and rarefaction polarities. Acoustically evoked ECoG responses were recorded from the most apical electrode in the intracochlear array. These two responses were subtracted to emphasize the CM/DIF responses and added to emphasize the ANN/SUM responses. Response thresholds were determined based on visual inspection of time waveforms, and trough-to-peak analysis technique was used to quantify response amplitudes. Within-subject comparison of responses measured using both short and long window methods were obtained from seven subjects. We also assessed the reliability and sensitivity of the short window method by comparing repeated measures from 19 subjects at different times. Correlations between CM/DIF and ANN/SUM measures using the short window recording method and audiometric thresholds were also assessed.

RESULTS

Regardless of the recording method, CM/DIF responses were larger than ANN/SUM responses. Responses obtained using the short window method were positively correlated to those obtained using the conventional long window method. Subjects who had stable acoustic hearing at two different time points had similar ECoG responses at those points, confirming high test-retest reliability of the short window method. Subjects who lost hearing between two different time points showed increases in ECoG thresholds, suggesting that physiologic ECoG responses are sensitive to audiometric changes. Correlations between CM/DIF and ANN/SUM thresholds and audiometric thresholds at all tested frequencies were significant.

CONCLUSION

This study compares two different recording methods. Intracochlear ECoG measures recorded using the short window technique were efficient, reliable, and repeatable. We were able to collect more frequency specific data with the short window method, and observed similar results between the long window and short window methods. Correlations between physiological thresholds and audiometric thresholds were similar to those reported previously using the long window method (Abbas et al., 2017). This is an important finding because it demonstrates that clinically-available software can be used to measure frequency-specific ECoG responses with enhanced efficiency, increasing the odds that this technique might move from the laboratory into clinical practice.

Proof of Concept for an Intracochlear Acoustic Receiver for Use in Acute Large Animal Experiments

(1) Background: The measurement of intracochlear sound pressure (ICSP) is relevant to obtain better understanding of the biomechanics of hearing. The goal of this work was a proof of concept of a partially implantable intracochlear acoustic receiver (ICAR) fulfilling all requirements for acute ICSP measurements in a large animal. The ICAR was designed not only to be used in chronic animal experiments but also as a microphone for totally implantable cochlear implants (TICI). (2) Methods: The ICAR concept was based on a commercial MEMS condenser microphone customized with a protective diaphragm that provided a seal and optimized geometry for accessing the cochlea. The ICAR was validated under laboratory conditions and using in-vivo experiments in sheep. (3) Results: For the first time acute ICSP measurements were successfully performed in a live specimen that is representative of the anatomy and physiology of the human. Data obtained are in agreement with published data from cadavers. The surgeons reported high levels of ease of use and satisfaction with the system design. (4) Conclusions: Our results confirm that the developed ICAR can be used to measure ICSP in acute experiments. The next generation of the ICAR will be used in chronic sheep experiments and in TICI.

Radiologic measurement of cochlea and hearing preservation rate using slim straight electrode (CI422) and round window approach

Hearing preservation surgery constitutes a considerable branch of cochlear implantation surgery and is being steadily developed and perfected. The aim of the study was to verify if insertion of a cochlear implant electrode according to individually calculated linear insertion depth improves hearing preservation. We evaluated the relations between the size of a cochlea, insertion depth angle, linear insertion depth and hearing preservation rate (HP) according to Hearing Preservation Classification in a retrospective case review of 54 patients implanted with a slim straight electrode Nucleus CI422 in 2008-2011. Group HP was 0.75 at activation, 0.67 at 12 months (for 53 patients) and 0.60 at 24 months. In 53 cases, the mean insertion depth angle was 375° (SD 17°); mean calculated cochlear duct length 35.87 mm (SD 1.95); mean calculated linear insertion depth 23.14 mm (SD 1.68). There was no significantly relevant relation between HP values and angular insertion depth or insertion depth. Preoperative measurements of cochlea and specific parameters such as linear insertion depth have no effect on hearing preservation. Poor hearing preservation in some deep insertion cases cannot be explained entirely by the electrode position.

Evaluation of Outcome Variability Associated With Lateral Wall, Mid-scalar, and Perimodiolar Electrode Arrays When Controlling for Preoperative Patient Characteristics

OBJECTIVE

Determine the impact of electrode array selection on audiometric performance when controlling for baseline patient characteristics.

STUDY DESIGN

Retrospective evaluation of a prospective cochlear implant (CI) database (January 1, 2012-May 31, 2017).

SETTING

Tertiary Care University Hospital.

PATIENTS

Three hundred twenty-eight adult CI recipients.

INTERVENTIONS/MAIN OUTCOMES MEASURED

Hearing outcomes were measured through unaided/aided pure tone thresholds and speech recognition testing before and after cochlear implantation. All reported postoperative results were performed at least 6 months after CI activation. All device manufacturers were represented.

RESULTS

Of the 328 patients, 234 received lateral wall (LW) arrays, 46 received perimodiolar (PM) arrays, and 48 received mid-scalar (MS) arrays. Patients receiving PM arrays had significantly poorer preoperative earphone and aided PTAs and SRTs, and aided Consonant-Nucleus-Consonant(CNC) word and AzBio +10 SNR scores compared with patients receiving LW arrays (all p ≤ 0.04), and poorer PTAs and AzBio +10 SNR scores compared with MS recipients (all p ≤ 0.02). No preoperative audiological variables were found to significantly differ between MS and LW patients. After controlling for preoperative residual hearing and speech recognition ability in a hierarchical multiple regression analysis, no statistically significant difference in audiological outcomes was detected (CNC words, AzBio quiet, or AzBio +10 SNR) among the three electrode array types (all p > 0.05).

CONCLUSION

While previous studies have demonstrated superior postoperative speech recognition scores in LW electrode array recipients, these differences lose significance when controlling for baseline hearing and speech recognition ability. These data demonstrate the proclivity for implanting individuals with greater residual hearing with LW electrodes and its impact on postoperative results.

Electric and acoustic harmonic integration predicts speech-in-noise performance in hybrid cochlear implant users

BACKGROUND

Pitch perception of complex tones relies on place or temporal fine structure-based mechanisms from resolved harmonics and the temporal envelope of unresolved harmonics. Combining this information is essential for speech-in-noise performance, as it allows segregation of a target speaker from background noise. In hybrid cochlear implant (H-CI) users, low frequency acoustic hearing should provide pitch from resolved harmonics while high frequency electric hearing should provide temporal envelope pitch from unresolved harmonics. How the acoustic and electric auditory inputs interact for H-CI users is largely unknown. Harmonicity and inharmonicity are emergent features of sound in which overtones are concordant or discordant with the fundamental frequency. We hypothesized that some H-CI users would be able to integrate acoustic and electric information for complex tone pitch perception, and that this ability would be correlated with speech-in-noise performance. In this study, we used perception of inharmonicity to demonstrate this integration.

METHODS

Fifteen H-CI users with only acoustic hearing below 500 Hz, only electric hearing above 2 kHz, and more than 6 months CI experience, along with eighteen normal hearing (NH) controls, were presented with harmonic and inharmonic sounds. The stimulus was created with a low frequency component, corresponding with the H-CI user's acoustic hearing (fundamental frequency between 125 and 174 Hz), and a high frequency component, corresponding with electric hearing. Subjects were asked to identify the more inharmonic sound, which requires the perceptual integration of the low and high components. Speech-in-noise performance was tested in both groups using the California Consonant Test (CCT), and perception of Consonant-Nucleus-Consonant (CNC) words in quiet and AzBio sentences in noise were tested for the H-CI users.

RESULTS

Eight of the H-CI subjects (53%), and all of the NH subjects, scored significantly above chance level for at least one subset of the inharmonicity detection task. Inharmonicity detection ability, but not age or pure tone average, predicted speech scores in a linear model. These results were significantly correlated with speech scores in both quiet and noise for H-CI users, but not with speech in noise performance for NH listeners. Musical experience predicted inharmonicity detection ability, but did not predict speech performance.

CONCLUSIONS

We demonstrate integration of acoustic and electric information in H-CI users for complex pitch sensation. The correlation with speech scores in H-CI users might be associated with the ability to segregate a target speaker from background noise using the speaker's fundamental frequency.

Effect of frequency mismatch and band partitioning on vocal tract length perception in vocoder simulations of cochlear implant processing

The vocal tract length (VTL) of a speaker is an important voice cue that aids speech intelligibility in multi-talker situations. However, cochlear implant (CI) users demonstrate poor VTL sensitivity. This may be partially caused by the mismatch between frequencies received by the implant and those corresponding to places of stimulation along the cochlea. This mismatch can distort formant spacing, where VTL cues are encoded. In this study, the effects of frequency mismatch and band partitioning on VTL sensitivity were investigated in normal hearing listeners with vocoder simulations of CI processing. The hypotheses were that VTL sensitivity may be reduced by increased frequency mismatch and insufficient spectral resolution in how the frequency range is partitioned, specifically where formants lie. Moreover, optimal band partitioning might mitigate the detrimental effects of frequency mismatch on VTL sensitivity. Results showed that VTL sensitivity decreased with increased frequency mismatch and reduced spectral resolution near the low frequencies of the band partitioning map. Band partitioning was independent of mismatch, indicating that if a given partitioning is suboptimal, a better partitioning might improve VTL sensitivity despite the degree of mismatch. These findings suggest that customizing the frequency partitioning map may enhance VTL perception in individual CI users.

Effects of spectral resolution on spectral contrast effects in cochlear-implant users

The identity of a speech sound can be affected by the long-term spectrum of a preceding stimulus. Poor spectral resolution of cochlear implants (CIs) may affect such context effects. Here, spectral contrast effects on a phoneme category boundary were investigated in CI users and normal-hearing (NH) listeners. Surprisingly, larger contrast effects were observed in CI users than in NH listeners, even when spectral resolution in NH listeners was limited via vocoder processing. The results may reflect a different weighting of spectral cues by CI users, based on poorer spectral resolution, which in turn may enhance some spectral contrast effects.

When singing with cochlear implants, are two ears worse than one for perilingually/postlingually deaf individuals?

Many individuals with bilateral cochlear implants hear different pitches when listening with their left versus their right cochlear implant. This conflicting information could potentially increase the difficulty of singing with cochlear implants. To determine if bilateral cochlear implants are detrimental for singing abilities, ten perilingually/postlingually deaf bilateral adult cochlear implant users were asked to sing "Happy Birthday" when using their left, right, both, or neither cochlear implant. The results indicated that bilateral cochlear implant users have more difficulty singing the appropriate pitch contour when using both cochlear implants as opposed to the better ear alone.

The design and validation of a hybrid digital-signal-processing plug-in for traditional cochlear implant speech processors

BACKGROUND AND OBJECTIVE

Cochlear implants (CIs) are electronic devices restoring partial hearing to deaf individuals with profound hearing loss. In this paper, a new plug-in for traditional IIR filter-banks (FBs) is presented for cochlear implants based on wavelet neural networks (WNNs). Having provided such a plug-in for commercially available CIs, it is possible not only to use available hardware in the market but also to optimize their performance compared with the-state-of-the-art.

METHODS

An online database of Dutch diphone perception was used in our study. The weights of the WNNs were tuned using particle swarm optimization (PSO) on a training set (speech-shaped noise (SSN) of 2 dB SNR), while its performance was assessed on a test set in terms of objective and composite measures in the hold-out validation framework. The cost function was defined based on the combination of mean square error (MSE), short‑time objective intelligibility (STOI) criteria on the training set. Variety of performance indices were used including segmental signal- to -noise ratio (SNRseg), MSE, STOI, log-likelihood ratio (LLR), weighted spectral slope (WSS), and composite measures C_sig,C_bak and C_ovl. Meanwhile, the following CI speech processing techniques were used for comparison: traditional FBs, dual resonance nonlinear (DRNL) and simple dual path nonlinear (SPDN) models.

RESULTS

The average SNRseg, MSE, and LLR values for the WNN in the entire data set were 2.496 ± 2.794, 0.086 ± 0.025 and 2.323 ± 0.281, respectively. The proposed method significantly improved MSE, SNR, SNRseg, LLR, C_sig C_bak and C_ovl compared with the other three methods (repeated-measures analysis of variance (ANOVA); P < 0.05). The average running time of the proposed algorithm (written in Matlab R2013a) on the training and test sets for each consonant or vowel on an Intel dual-core 2.10 GHz CPU with 2GB of RAM was 9.91 ± 0.87 (s) and 0.19 ± 0.01 (s), respectively.

CONCLUSIONS

The proposed algorithm is accurate and precise and is thus a promising new plug-in for traditional CIs. Although the tuned algorithm is relatively fast, it is necessary to use efficient vectorized implementations for real-time CI speech signal processing.