Multichannel Cochlear Implants Research Articles

Locus coeruleus activity improves cochlear implant performance.

Cochlear implants (CIs) are neuroprosthetic devices that can provide hearing to deaf people1. Despite the benefits offered by CIs, the time taken for hearing to be restored and perceptual accuracy after long-term CI use remain highly variable2,3. CI use is believed to require neuroplasticity in the central auditory system, and differential engagement of neuroplastic mechanisms might contribute to the variability in outcomes4-7. Despite extensive studies on how CIs activate the auditory system4,8-12, the understanding of CI-related neuroplasticity remains limited. One potent factor enabling plasticity is the neuromodulator noradrenaline from the brainstem locus coeruleus(LC). Here we examine behavioural responses and neural activity in LC and auditory cortex of deafened rats fitted with multi-channel CIs. The rats were trained on a reward-based auditory task, and showed considerable individual differences of learning rates and maximum performance. LC photometry predicted when CI subjects began responding to sounds and longer-term perceptual accuracy. Optogenetic LC stimulation produced faster learning and higher long-term accuracy. Auditory cortical responses to CI stimulation reflected behavioural performance, with enhanced responses to rewarded stimuli and decreased distinction between unrewarded stimuli. Adequate engagement of central neuromodulatory systems is thus a potential clinically relevant target for optimizing neuroprosthetic device use.

Consonant Repertoire of a Prelinguistically Deaf Child with Late-Mapping Cochlear Implants

Objective: The present case study aims to report on the consonant repertoire during the pre-linguistic and first linguistic stage of a Greek-Cypriot speaking child bilaterally implanted with multichannel Cochlear Implants (CIs). Background: Children with Hearing Loss (HL) produce canonical babble later, and consonantal inventories of HL children are smaller. However, the consonant repertoire of CI Greek-speaking children has not been examined thus far and research on types of consonantal errors during phonological acquisition is scant. Clinical Case: A pre-linguistically deaf child (CY, 7;0 years old) received the first CI at 7 months of age, but the external part of the device was fitted at 2;7 years. An investigation of the child’s speech at 7;0 years was conducted through auditory analysis. The child’s canonical utterances were transcribed in IPA and his consonants were classified into subcategories, depending on articulation place, articulation manner and resonance. Regarding place, alveolar consonants were the main category produced. As regards manner, closed consonants was the first category to appear, while in terms of voicing, voiceless consonants were recorded more often than voiced ones. The analysis also showed that consonants /t/, /s/ and /p/ were dominant in the child’s speech and revealed several phonological processes. Conclusion: The present case holds special interest as the child’s phonological system is still between the pre-linguistic/first linguistic stages due to the delayed CI mapping. The results agree in part with several studies in the literature, while specific phonological error patterns observed, remain to be verified in other CI Greek-speaking children.

Risk Factors for Facial Nerve and Other Nonauditory Side Effects Following Cochlear Implantation.

The purpose of this study was to characterize a cohort of patients with nonauditory side-effects (NASx) following cochlear implant (CI) surgery. Retrospective case review. Tertiary referral center. One hundred twenty three multichannel CI recipients with intraoperative facial nerve stimulation (FNS). Intraoperative electrical auditory brainstem responses (eABR) during CI surgery. Nonauditory side effects post-CI activation. Intraoperative FNS was identified in 2.26% of patients (123/5441), of whom, 34% (42/123) experienced VII stimulation on CI activation. Pain was experienced by 22% (27/123) and vestibular dysfunction was experienced by 4% (5/123) of cases. All case who experienced pain and/or vestibular NASx also experienced VII stimulation. The majority of cases were managed by CI remapping or observation and habituation.Significant relationships were found between etiology of hearing loss and presence of FNS upon initial activation (p < 0.05). No significance was found between FNS intraoperatively and at initial activation for all assumed mechanisms of hearing loss (p > 0.05) with the exceptions of acquired hearing loss of undetermined etiology and toxic etiology group (p < 0.05).There was no significant impact of implant array design (p > 0.05). This study has characterized patients with NASx in a large cohort of CI patients. One third of cases identified with FNS intraoperatively, developed NASx post-CI activation. Risk factors for NASx postactivation include high-risk etiologies and intraoperative objective measures (i.e., eABR). This may assist surgeons and audiologists to identify at-risk patients who may need modifications in CI program planning.

Development of a chronically-implanted mouse model for studies of cochlear health and implant function

Mice with chronic cochlear implants can significantly contribute to our understanding of the relationship between cochlear health and implant function because of the availability of molecular tools for controlling conditions in the cochlea and transgenic lines modeling human disease. To date, research in implanted mice has mainly consisted of short-term studies, but since there are large changes in implant function following implant insertion trauma, and subsequent recovery in many cases, longer-term studies are needed to evaluate function and perception under stable conditions. Because frequent anesthetic administration can be especially problematic in mice, a chronic model that can be tested in the awake condition is desirable. Electrically-evoked compound action potentials (ECAPs) recorded with multichannel cochlear implants are useful functional measures because they can be obtained daily without anesthesia. In this study, we assessed changes and stability of ECAPs, electrically-evoked auditory brainstem responses (EABRs), ensemble spontaneous activity (ESA), and impedance data over time after implanting mice with multichannel implants. We then compared these data to histological findings in these implanted cochleae, and compared results from this chronic mouse model to data previously obtained in a well-established chronically-implanted guinea pig model. We determined that mice can be chronically implanted with cochlear implants, and ECAP recordings can be obtained frequently in an awake state for up to at least 42 days after implantation. These recordings can effectively monitor changes or stability in cochlear function over time. ECAP and EABR amplitude-growth functions (AGFs), AGF slopes, ESA levels and impedances in mice with multichannel implants appear similar to those found in guinea pigs with long-term multichannel implants. Animals with better survival of spiral ganglion neurons (SGNs) and inner hair cells (IHCs) have steeper AGF slopes, and larger ESA responses. The time course of post-surgical ear recovery may be quicker in mice and can show different patterns of recovery which seem to be dependent on the degree of insertion trauma and subsequent histological conditions. Histology showed varying degrees of cochlear damage with fibrosis present in all implanted mouse ears and small amounts of new bone in a few ears. Impedance changes over time varied within and across animals and may represent changes over time in multiple variables in the cochlear environment post-implantation. Due to the small size of the mouse, susceptibility to stress, and the higher potential for implant failure, chronic implantation in mice can be challenging, but overall is feasible and useful for cochlear implant research.

Assessment of Cochlear Implants for Adult Medicare Beneficiaries Aged 65 Years or Older Who Meet Expanded Indications of Open-Set Sentence Recognition

Current indications for Medicare beneficiaries to receive a cochlear implant are outdated. Multichannel cochlear implant systems may be effective when provided to Medicare beneficiaries using expanded indications. To examine the effectiveness of cochlear implants, as measured by improvement on the AzBio Sentence Test, for newly implanted Medicare beneficiaries who meet the expanded indications of an AzBio Sentence Test score of 41% to 60% in their best-aided condition. A multicenter nonrandomized trial examined preoperative and postoperative speech recognition, telephone communication, hearing device benefit, health utility, and quality of life for 34 participants enrolled at 8 different centers who received a cochlear implant between September 17, 2014, and July 10, 2018. All participants were 65 years or older, had bilateral moderate to profound hearing loss, and had a best-aided preoperative AzBio Sentence Test score in quiet of 41% to 60%. Analysis was performed on an intention-to-treat basis. Statistical analysis of final results took place from July 29 to October 1, 2019. Multichannel cochlear implants. The study examined the a priori hypothesis that the cochlear implant would improve the AzBio Sentence Test score in the best-aided condition by 25% or more and in the implanted ear-alone condition by 30% or more. The study additionally examined word and telephone recognition and examined device benefit, health utility, and quality of life. A total of 34 participants received a cochlear implant; 31 (23 men [74%]; median age, 73.6 years [range, 65.7-85.1 years]) completed testing through the 6-month evaluation, and 29 completed testing through the 12-month evaluation. Median preoperative AzBio Sentence Test scores were 53% (range, 26%-60%) for the best-aided condition and 24% (range, 0%-53%) for the cochlear implant-alone condition; median scores 12 months after implantation improved to 89% (range, 36%-100%) for the best-aided condition and 77% (range, 13%-100%) for the cochlear implant-alone condition. This outcome represents a median change of 36% (range, -22% to 75%) for the best-aided condition (lower bound of 1-sided 95% CI, 31%) and a median change of 53% (range, -15% to 93%) for the cochlear implant-alone condition (lower bound of 1-sided 95% CI, 45%). Intervention with a cochlear implant was associated with improved sentence, word, and telephone recognition in adult Medicare beneficiaries whose preoperative AzBio Sentence Test scores were between 41% and 60%. These findings support expansion of the Center for Medicare & Medicaid current indications for cochlear implants. ClinicalTrials.gov Identifier: NCT02075229.

Device profile of the MED-EL cochlear implant system for hearing loss: overview of its safety and efficacy

ABSTRACT Introduction Patients suffering from severe to profound hearing loss or even deafness can achieve a hearing improvement with a cochlear implant (CI) treatment that is significantly higher than the results achieved with conventional hearing aids. The CI system consists of an implantable stimulator, which is inserted retro-auricularly into the mastoid, and an externally worn processor unit, which provides the pickup of sound and processing of acoustic information as well as the power supply for the stimulator and internal current sources. The stimulator has an electrode array that is inserted into the cochlea. Areas covered This is a descriptive overview of MED-EL’s multichannel CI system (MED-EL, Innsbruck, Austria), which was introduced to the European market in 1994. The continuing development of the implant as well as the external components is outlined and various other aspects (stimulation strategy, adaptation, results, reliability) are discussed. Expert commentary The strength of the company is the continuous pursuit of innovative ideas. This is evidenced by numerous innovations. The reliability of the implants has been continuously improved. The current SYNCHRONY models of the manufacturer show no indication of technically caused failures over an observation period of 5 years.

Discourse Prosody in Children's Rhyme Speech Produced by Prelingually Deaf Mandarin-Speaking Children With Cochlear Implants

Purpose This study aimed to obtain a comprehensive understanding about how Mandarin-speaking children with cochlear implants (CIs) performed speech prosody in a connected discourse and to what extent their prosodic scenario differed from those normal-hearing (NH) peers. Method Fifteen prelingually deaf Mandarin-speaking children with unilateral multichannel CIs were chosen and 15 age-matched NH controls were recruited. Speech samples were spontaneously elicited by children's rhyme speech genre and subject to phonetic annotation. Acoustic analysis was conducted on all speech samples, mainly focusing on the measurements of duration and fundamental frequency (F0). Tempo measures included temporal fluency, syllable-lengthening, and rhythm metrics, whereas melodic measures included both local and global F0 variations under different prosodic domains. Results The CI children generally achieved compatible temporal performance with the NH children in spontaneous discourse, except that they were somewhat arbitrary when operationalizing lengthening strategy and pausing strategy at different prosodic boundaries. With regard to melodic performance, CI children may not sufficiently modulate local phonetic nuances of F0 variation, and meanwhile, they performed atypically in the global F0 declination pattern and overall F0 resetting pattern, failing to signal the specific structure of children's rhyme discourse. Early age at implantation and longer CI experience did not play a significant role in the temporal performance of the CI children but did facilitate their articulation of dynamic pitch variation in the spontaneous discourse to some extent. Conclusion CI children did exhibit atypical prosodic patterns in discourse context, especially the overall mapping between the prosodic manifestation and the discourse structure.

Consonant and Vowel Identification in Cochlear Implant Users Measured by Nonsense Words: A Systematic Review and Meta-Analysis.

The purpose of this systematic review and meta-analysis was to establish a baseline of the vowel and consonant identification scores in prelingually and postlingually deaf users of multichannel cochlear implants (CIs) tested with consonant-vowel-consonant and vowel-consonant-vowel nonsense syllables. Six electronic databases were searched for peer-reviewed articles reporting consonant and vowel identification scores in CI users measured by nonsense words. Relevant studies were independently assessed and screened by 2 reviewers. Consonant and vowel identification scores were presented in forest plots and compared between studies in a meta-analysis. Forty-seven articles with 50 studies, including 647 participants, thereof 581 postlingually deaf and 66 prelingually deaf, met the inclusion criteria of this study. The mean performance on vowel identification tasks for the postlingually deaf CI users was 76.8% (N = 5), which was higher than the mean performance for the prelingually deaf CI users (67.7%; N = 1). The mean performance on consonant identification tasks for the postlingually deaf CI users was higher (58.4%; N = 44) than for the prelingually deaf CI users (46.7%; N = 6). The most common consonant confusions were found between those with same manner of articulation (/k/ as /t/, /m/ as /n/, and /p/ as /t/). The mean performance on consonant identification tasks for the prelingually and postlingually deaf CI users was found. There were no statistically significant differences between the scores for prelingually and postlingually deaf CI users. The consonants that were incorrectly identified were typically confused with other consonants with the same acoustic properties, namely, voicing, duration, nasality, and silent gaps. A univariate metaregression model, although not statistically significant, indicated that duration of implant use in postlingually deaf adults predict a substantial portion of their consonant identification ability. As there is no ceiling effect, a nonsense syllable identification test may be a useful addition to the standard test battery in audiology clinics when assessing the speech perception of CI users.

Postoperative objective detecting techniques for cochlear implant children with inner ear malformation

ObjectivesThis study aims to investigate the changing characteristics and rules of electrically-evoked auditory brainstem response (EABR), electrically-evoked stapedius reflex threshold (ESRT) and neural response telemetry (NRT) after cochlear implant in children with inner ear malformation, and guide postoperative equipment debug. MethodsA total of 88 children with either normal cochlea (control group) or inner ear malformation (test group) received Australian 24 multi-channel cochlear implants. The EABR, ESRT and NRT thresholds at different time points within one year postoperatively and behavioral responses (T-level and C-level) after one year were detected. Furthermore, the changing characteristics and rules of these thresholds were analyzed. ResultsThe EABR, ESRT and NRT thresholds were all significantly higher at all time points in the test group than in the control group, but the general changing trends were similar. Particularly, these thresholds worsened at low frequencies and improved at high frequencies. Furthermore, EABR, ESRT and NRT thresholds gradually increased during the one year postoperative period. In addition, an extremely significant correlation was found between EABR and T-level and between ESRT and C-level, but a less significant correlation was found between NRT threshold and T-level in both groups. ConclusionsThe postoperative changes in characteristics and rules of EABR, ESRT and NRT thresholds among cochlear implant children with inner ear malformation were all the same as those with normal cochlea. Thus, these thresholds can be used to guide the postoperative equipment debug for cochlear implants into patients with inner ear malformation.

Effects of electrode deactivation on speech recognition in multichannel cochlear implant recipients

Objectives: The objective of the current study is to evaluate how speech recognition performance is affected by the number of active electrodes that are turned off in multichannel cochlear implants. Several recent studies have demonstrated positive effects of deactivating stimulation sites based on an objective measure in cochlear implant processing strategies. Previous studies using an analysis of variance have shown that, on average, cochlear implant listeners’ performance does not improve beyond eight active electrodes. We hypothesized that using a generalized linear mixed model would allow for better examination of this question.Methods: Seven peri- and post-lingual adult cochlear implant users (eight ears) were tested on speech recognition tasks using experimental MAPs which contained either 8, 12, 16 or 20 active electrodes. Speech recognition tests included CUNY sentences in speech-shaped noise, TIMIT sentences in quiet as well as vowel (CVC) and consonant (CV) stimuli presented in quiet and in signal-to-noise ratios of 0 and +10 dB.Results: The speech recognition threshold in noise (dB SNR) significantly worsened by approximately 2 dB on average as the number of active electrodes was decreased from 20 to 8. Likewise, sentence recognition scores in quiet significantly decreased by an average of approximately 12%.Discussion/conclusion: Cochlear implant recipients can utilize and benefit from using more than eight spectral channels when listening to complex sentences or sentences in background noise. The results of the current study suggest a conservative approach for turning off stimulation sites is best when using site-selection procedures.

Comparison of Single-Channel and Multi-Channel Cochlear Implants in Terms of Encoding Strategy and Speech Understanding: A Systematic Review

Introduction: The term channel in cochlear implant systems refers to the number of stimulation sites within the inner ear or cochlea that determines the range of frequencies or pitches. Unlike single-channel cochlear implant, a multi-channel cochlear implant system divides the incoming signal into various frequency bands, and then, transmits it to various stimulation areas within the inner ear. Having more stimulation sites entails two main goals: 1- As the auditory nerve fibers in the cochlea are tonotopically organized, higher number of electrodes leads to better frequency separation; 2- The areas in the cochlea with inappropriate or no response to electrical stimulation will be avoided in the programming of the device, and the components of the processed input frequency will accompany the stimulation. The goal of the present study was to compare the frequency encoding strategy and its effect on speech understanding of the recipients of single-channel and multi-channel cochlear implant systems. Materials and Methods: Published researches were identified by reviewing scientific databases (PubMed, Science Direct, and Google Scholar) from 1965 to 2016 using relevant keywords. The researches were selected based on the inclusion and exclusion criteria. Results: Single-channel cochlear implants encode the frequency based on the rate of firing of electrical impulses. Multi-channel cochlear implants ‎use the spatial strategy theory for frequency encoding, wherein the different frequencies of the auditory signal are separated and presented in a tonotopic manner along the length of the cochlea via the electrode array. The spatial and temporal encoding of the sound frequencies can be partly replicated by multi-channel stimulation of the auditory nerve. Encoding strategy in multi-channel cochlear implant consists of feature extraction and wave form. The resulting speech understanding of the single-channel and multi-channel systems was also assessed. Conclusion: Based on the findings, it can be concluded that single-channel cochlear implant systems with temporal encoding of frequency do not adequately convey speech information, whereas multi-channel cochlear implants ‎have more similarities to the tonotopic map of the cochlea and provide a better speech understanding in comparison to single channel devices.

Multichannel cochlear implant for selective neuronal activation and chronic use in the free-moving Mongolian gerbil

BackgroundAnimal models for chronic multichannel cochlear implant stimulation and selective neuronal activation contribute to a better understanding of auditory signal processing and central neural plasticity. New methodThis paper describes the design and surgical implantation of a multichannel cochlear implant (CI) system for chronic use in the free-moving gerbil. For chronic stimulation, adult-deafened gerbils were connected to a multichannel commutator that allowed low resistance cable rotation and stable electric connectivity to the current source. ResultsDespite the small scale of the gerbil cochlea and auditory brain regions, final electrophysiological mapping experiments revealed selective and tonotopically organized neuronal activation in the auditory cortex. Contact impedances and electrically evoked auditory brainstem responses were stable over several weeks demonstrating the long-term integrity of the implant and the efficacy of the stimulation. Comparison with existing methodsMost animal models on multichannel signal processing and stimulation-induced plasticity are limited to larger animals such as ferrets, cats and primates. Multichannel CI stimulation in the free-moving rodent and evidence for selective neuronal activation in gerbil auditory cortex have not been previously reported. ConclusionsOverall, our results show that the gerbil is a robust rodent model for selective and tonotopically organized multichannel CI stimulation. We anticipate that this model provides a useful tool to develop and test both passive stimulation and behavioral training strategies for plastic reorganization and restoration of degraded unilateral and bilateral central auditory signal processing in the hearing impaired and deaf central auditory system.

Effect of current focusing on the sensitivity of inferior colliculus neurons to amplitude-modulated stimulation.

In multichannel cochlear implants (CIs), current is delivered to specific electrodes along the cochlea in the form of amplitude-modulated pulse trains, to convey temporal and spectral cues. Our previous studies have shown that focused multipolar (FMP) and tripolar (TP) stimulation produce more restricted neural activation and reduced channel interactions in the inferior colliculus (IC) compared with traditional monopolar (MP) stimulation, suggesting that focusing of stimulation could produce better transmission of spectral information. The present study explored the capability of IC neurons to detect modulated CI stimulation with FMP and TP stimulation compared with MP stimulation. The study examined multiunit responses of IC neurons in acutely deafened guinea pigs by systematically varying the stimulation configuration, modulation depth, and stimulation level. Stimuli were sinusoidal amplitude-modulated pulse trains (carrier rate of 120 pulses/s). Modulation sensitivity was quantified by measuring modulation detection thresholds (MDTs), defined as the lowest modulation depth required to differentiate the response of a modulated stimulus from an unmodulated one. Whereas MP stimulation showed significantly lower MDTs than FMP and TP stimulation (P values <0.05) at stimulation ≤2 dB above threshold, all stimulation configurations were found to have similar modulation sensitivities at 4 dB above threshold. There was no difference found in modulation sensitivity between FMP and TP stimulation. The present study demonstrates that current focusing techniques such as FMP and TP can adequately convey amplitude modulation and are comparable to MP stimulation, especially at higher stimulation levels, although there may be some trade-off between spectral and temporal fidelity with current focusing stimulation.

Impact of cochlear implantation on quality of life and mental comorbidity in patients aged 80 years.

The objective of this study was to evaluate the outcome of cochlear implantation in elderly patients (80 or older) with progressive bilateral deafening. The measured outcomes included the quality of life, speech understanding, tinnitus distress, stress level, anxiety, and depressiveness. Prospective cohort study. Seventeen 80+ years (mean 82.9 ± 2.7 years) patients with progressive, postlingual, bilateral deafness were unilaterally implanted with multichannel cochlear implants. Data about their health-related quality of life (Nijmegen Cochlear Implantation Questionnaire) and their comorbidities were collected using specific validated questionnaires (tinnitus questionnaire, General Anxiety Disorder-7, Depression Scale, Perceived Stress Questionnaire). The speech understanding was assessed with the Freiburg Monosyllabic Test, whereas the subjective hearing was evaluated with the Oldenburg Inventory. After the surgery, not only the subjective hearing but also health-related quality of life, speech understanding, and tinnitus distress of the implanted patients improved significantly. The perceived stress, general anxiety, and depressiveness were low or normal prior and after surgery. This study demonstrates a significant improvement in the quality of life and speech understanding in a group of elderly patients who underwent cochlear implantation. An additional positive indicator of a promising hearing rehabilitation was a significant improvement of the tinnitus distress. Perceived stress level, general anxiety, and the depressiveness of implanted patients were low and remained unaffected. 4. Laryngoscope, 126:2811-2816, 2016.

The relationship between the electrical stapedial muscle reflex threshold and electrical and behavioral measures in cochlear implant patients

Programming of multichannel cochlear implants (CIs) requires subjective responses to a series of sophisticated psychophysical percepts. It is often difficult for young prelinguistically deaf children to provide adequate responses for device fitting. This is especially true in setting levels of maximum comfortable loudness, whereby failure to indicate growth of loudness may result in elevation of stimulus levels to the threshold of pain. The acoustic or stapedial muscle reflex has been used previously to provide objective confirmation of acoustic stimulation, and there have been attempts to use the reflex in hearing-aid fitting. It has also been suggested that electrically elicited middle-ear muscle reflexes [electrically evoked stapedial reflex threshold (ESRT)] may have applicability in confirming and quantifying electrical stimulation through a CI. To assess the relationship between ESRT characteristics and levels of loudness perception with CIs, determine the reliability of the response, and investigate the potential use of ESRT in CI programming, 26 prelinguistically deafened CI users were evaluated. Reflexes have also been attempted on 312 electrodes, with responses present in 213 (68.3%). Comfort levels predicted by subjective judgments were highly correlated with the ESRT in individuals with CI. ESRT provides an objective, accurate, and rapid method of estimating maximum comfortable loudness levels, which may be useful in the initial programming of young implant recipients.

A comparison between neural response telemetry via cochleostomy or the round window approach in cochlear implantation

There are two techniques for cochlear implant (CI) electrode placement: cochleostomy and the round window (RW) approach.Objective: This study aims to compare neural response telemetry (NRT) results immediately after surgery to check for possible differences on auditory nerve stimulation between these two techniques.Materials and Methods: This is a prospective cross-sectional study. Twenty-three patients were enrolled. Six patients underwent surgery by cochleostomy and 17 had it through the RW approach.Results: Mean charge units (MCU) for high frequency sounds: patients submitted to the RW approach had a mean value of 190.4 (±29.2) while cochleostomy patients averaged 187.8 (±32.7); p = 0.71. MCU for mid frequency sounds: patients submitted to the RW approach had a mean value of 192.5 (±22) while cochleostomy patients averaged 178.5 (±18.5); p = 0.23. MCU for low frequency sounds: patients submitted to the RW approach had a mean value of 183.3 (±25) while cochleostomy patients averaged 163.8 (±19.3); p = 0.19.Conclusion: This study showed no differences in the action potential of the distal portion of the auditory nerve in patients with multichannel cochlear implants submitted to surgery by cochleostomy or through the RW approach, using the implant itself to generate stimuli and record responses. Both techniques equally stimulate the cochlear nerve. Therefore, the choice of approach can be made based on the surgeon's own preference and experience.

Electrophysiological channel interactions using focused multipolar stimulation for cochlear implants

Objective. Speech intelligibility with existing multichannel cochlear implants (CIs) is thought to be limited by poor spatial selectivity and interactions between CI channels caused by overlapping activation with monopolar (MP) stimulation. Our previous studies have shown that focused multipolar (FMP) and tripolar (TP) stimulation produce more restricted neural activation in the inferior colliculus (IC), compared to MP stimulation. Approach. This study explored interactions in the IC produced by simultaneous stimulation of two CI channels. We recorded multi-unit neural activity in the IC of anaesthetized cats with normal and severely degenerated spiral ganglion neuron populations in response to FMP, TP and MP stimulation from a 14 channel CI. Stimuli were applied to a ‘fixed’ CI channel, chosen toward the middle of the cochlear electrode array, and the effects of simultaneously stimulating a more apical ‘test’ CI channel were measured as a function of spatial separation between the two stimulation channels and stimulus level of the fixed channel. Channel interactions were quantified by changes in neural responses and IC threshold (i.e., threshold shift) elicited by simultaneous stimulation of two CI channels, compared to stimulation of the test channel alone. Main results. Channel interactions were significantly lower for FMP and TP than for MP stimulation (p < 0.001), whereas no significant difference was observed between FMP and TP stimulation. With MP stimulation, threshold shifts increased with decreased inter-electrode spacing and increased stimulus levels of the fixed channel. For FMP and TP stimulation, channel interactions were found to be similar for different inter-electrode spacing and stimulus levels of the fixed channel. Significance. The present study demonstrates how the degree of channel interactions in a CI can be controlled using stimulation configurations such as FMP and TP; such knowledge is essential in enhancing CI function in complex acoustic environments.

Predictors of language and auditory skills in Egyptian children with a cochlear implant

Abstract The aim of this study was to investigate the prognostic factors contributing toward the comprehension and production of Arabic language as well as auditory abilities after cochlear implantation of Egyptian children. A total of 150 children with severe to profound sensory neural congenital hearing loss were implanted with multichannel cochlear implants. Children had received their implants 3 months to 2 years before the onset of the study. They had received their implants between the age range of 3 and 6 years. Tests of receptive, expressive language, and sets of auditory abilities were administered. Characteristics of the child and the family (age before implant and duration of implant use, preimplant use of hearing aids and language therapy, parents’ involvement in therapy, mode of communication at home, type of the implant, and geographic distribution) were considered the predictors. Predictors of total language and auditory abilities were determined using statistical analysis by univariate and multivariate analyses. Some significant predictors of language and auditory skills in this study included duration of implant use, use of auditory mode of communication and parent interaction. There is a positive correlation between language age and both individual and total auditory abilities scores. Prognostic factors for language and auditory abilities are useful in a rehabilitation program after cochlear implantation.

A Comparison of Persian Vowel Production in Hearing-Impaired Children Using a Cochlear Implant and Normal-Hearing Children

Normal-hearing (NH) acuity and auditory feedback control are crucial for human voice production and articulation. The lack of auditory feedback in individuals with profound hearing impairment changes their vowel production. The purpose of this study was to compare Persian vowel production in deaf children with cochlear implants (CIs) and that in NH children. The participants were 20 children (12 girls and 8 boys) with age range of 5 years; 1month to 9years. All patients had congenital hearing loss and received a multichannel CI at an average age of 3years. They had at least 6months experience of their current device (CI). The control group consisted of 20 NH children (12 girls and 8boys) with age range of 5 to 9years old. The two groups were matched by age. Participants were native Persian speakers who were asked to produce the vowels /i/, /e/, /ӕ/, /u/, /o/, and /a/. The averages for first formant frequency (F1) and second formant frequency (F2) of six vowels were measured using Praat software (Version 5.1.44, Boersma & Weenink, 2012). The independent samples t test was conducted to assess the differences in F1 and F2 values and the area of the vowel space between the two groups. Mean values of F1 were increased in CI children; the mean values of F1 for vowel /i/ and /a/, F2 for vowel /a/ and /o/ were significantly different (P<0.05). The changes in F1 and F2 showed a centralized vowel space for CI children. F1 is increased in CI children, probably because CI children tend to overarticulate. We hypothesis this is due to a lack of auditory feedback; there is an attempt by hearing-impaired children to compensate via proprioceptive feedback during articulatory process.

Lessons learned from multichannel cochlear implants that are relevant to a visual prosthesis

The clinical success of the multichannel cochlear implant was built on the successful outcomes of the multidisciplinary research program led by Professor Graeme Clark at the University of Melbourne and many of the outcomes from these studies can also be applied to other sensory prostheses, including the visual prosthesis. A primary requirement of any neural prosthesis is that it is safe, and this presentation will include studies that define stimulus parameters that allow stable long term responses, with no evidence of metabolic overload or neural degeneration. Any device that is chronically implanted for the life of a patient must be reliable, with a low likelihood of need for replacement because of device failure or infection, and the presentation will include both the results from Clark's infection studies and long term cochlear implant reliability observations. The presentation will describe the design of an experimental retinal prosthesis that uses an electrode array that is based on an array that was used to stimulate the cochlear nucleus of profoundly deaf patients. It will include preliminary results for volunteer patients, and approaches that may improve these pilot study outcomes.