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Guérit F, Middlebrooks JC, Gransier R, Richardson ML, Wouters J, Carlyon RP. Exploring the Use of Interleaved Stimuli to Measure Cochlear-Implant Excitation Patterns. J Assoc Res Otolaryngol 2024; 25:201-213. [PMID: 38459245 PMCID: PMC11018570 DOI: 10.1007/s10162-024-00937-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Accepted: 02/15/2024] [Indexed: 03/10/2024] Open
Abstract
PURPOSE Attempts to use current-focussing strategies with cochlear implants (CI) to reduce neural spread-of-excitation have met with only mixed success in human studies, in contrast to promising results in animal studies. Although this discrepancy could stem from between-species anatomical and aetiological differences, the masking experiments used in human studies may be insufficiently sensitive to differences in excitation-pattern width. METHODS We used an interleaved-masking method to measure psychophysical excitation patterns in seven participants with four masker stimulation configurations: monopolar (MP), partial tripolar (pTP), a wider partial tripolar (pTP + 2), and, importantly, a condition (RP + 2) designed to produce a broader excitation pattern than MP. The probe was always in partial-tripolar configuration. RESULTS We found a significant effect of stimulation configuration on both the amount of on-site masking (mask and probe on same electrode; an indirect indicator of sharpness) and the difference between off-site and on-site masking. Differences were driven solely by RP + 2 producing a broader excitation pattern than the other configurations, whereas monopolar and the two current-focussing configurations did not statistically differ from each other. CONCLUSION A method that is sensitive enough to reveal a modest broadening in RP + 2 showed no evidence for sharpening with focussed stimulation. We also showed that although voltage recordings from the implant accurately predicted a broadening of the psychophysical excitation patterns with RP + 2, they wrongly predicted a strong sharpening with pTP + 2. We additionally argue, based on our recent research, that the interleaved-masking method can usefully be applied to non-human species and objective measures of CI excitation patterns.
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Affiliation(s)
- François Guérit
- Cambridge Hearing Group, MRC Cognition & Brain Sciences Unit, University of Cambridge, Cambridge, England.
| | - John C Middlebrooks
- Department of Otolaryngology, University of California at Irvine, Irvine, CA, USA
- Department of Neurobiology and Behavior, University of California at Irvine, Irvine, CA, USA
- Department of Biomedical Engineering, University of California at Irvine, Irvine, CA, USA
| | - Robin Gransier
- Department of Neurosciences, ExpORL KU Leuven, Leuven, Belgium
- Leuven Brain Institute KU Leuven, Leuven, Belgium
| | - Matthew L Richardson
- Department of Otolaryngology, University of California at Irvine, Irvine, CA, USA
| | - Jan Wouters
- Department of Neurosciences, ExpORL KU Leuven, Leuven, Belgium
- Leuven Brain Institute KU Leuven, Leuven, Belgium
| | - Robert P Carlyon
- Cambridge Hearing Group, MRC Cognition & Brain Sciences Unit, University of Cambridge, Cambridge, England
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2
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Classification of electrically-evoked potentials in the parkinsonian subthalamic nucleus region. Sci Rep 2023; 13:2685. [PMID: 36792646 PMCID: PMC9932154 DOI: 10.1038/s41598-023-29439-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Accepted: 02/06/2023] [Indexed: 02/17/2023] Open
Abstract
Electrically evoked compound action potentials (ECAPs) generated in the subthalamic nucleus (STN) contain features that may be useful for titrating deep brain stimulation (DBS) therapy for Parkinson's disease. Delivering a strong therapeutic effect with DBS therapies, however, relies on selectively targeting neural pathways to avoid inducing side effects. In this study, we investigated the spatiotemporal features of ECAPs in and around the STN across parameter sweeps of stimulation current amplitude, pulse width, and electrode configuration, and used a linear classifier of ECAP responses to predict electrode location. Four non-human primates were implanted unilaterally with either a directional (n = 3) or non-directional (n = 1) DBS lead targeting the sensorimotor STN. ECAP responses were characterized by primary features (within 1.6 ms after a stimulus pulse) and secondary features (between 1.6 and 7.4 ms after a stimulus pulse). Using these features, a linear classifier was able to accurately differentiate electrodes within the STN versus dorsal to the STN in all four subjects. ECAP responses varied systematically with recording and stimulating electrode locations, which provides a subject-specific neuroanatomical basis for selecting electrode configurations in the treatment of Parkinson's disease with DBS therapy.
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Guevara N, Truy E, Hoen M, Hermann R, Vandersteen C, Gallego S. Electrical Field Interactions during Adjacent Electrode Stimulations: eABR Evaluation in Cochlear Implant Users. J Clin Med 2023; 12:jcm12020605. [PMID: 36675534 PMCID: PMC9865217 DOI: 10.3390/jcm12020605] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 01/06/2023] [Accepted: 01/10/2023] [Indexed: 01/15/2023] Open
Abstract
The present study investigates how electrically evoked Auditory Brainstem Responses (eABRs) can be used to measure local channel interactions along cochlear implant (CI) electrode arrays. eABRs were recorded from 16 experienced CI patients in response to electrical pulse trains delivered using three stimulation configurations: (1) single electrode stimulations (E11 or E13); (2) simultaneous stimulation from two electrodes separated by one (En and En+2, E11 and E13); and (3) stimulations from three consecutive electrodes (E11, E12, and E13). Stimulation level was kept constant at 70% electrical dynamic range (EDR) on the two flanking electrodes (E11 and E13) and was varied from 0 to 100% EDR on the middle electrode (E12). We hypothesized that increasing the middle electrode stimulation level would cause increasing local electrical interactions, reflected in characteristics of the evoked compound eABR. Results show that group averaged eABR wave III and V latency and amplitude were reduced when stimulation level at the middle electrode was increased, in particular when stimulation level on E12 reached 40, 70, and 100% EDR. Compound eABRs can provide a detailed individual quantification of electrical interactions occurring at specific electrodes along the CI electrode array. This approach allows a fine determination of interactions at the single electrode level potentially informing audiological decisions regarding mapping of CI systems.
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Affiliation(s)
- Nicolas Guevara
- Institut Universitaire de la Face et du Cou, Centre Hospitalier Universitaire de Nice, Université Côte d’Azur, 06100 Nice, France
| | - Eric Truy
- Department of Audiology and Otorhinolaryngology, Edouard Herriot Hospital, Lyon 1 University, 69437 Lyon, France
| | - Michel Hoen
- Clinical Evidence Department, Oticon Medical, 06220 Vallauris, France
- Correspondence:
| | - Ruben Hermann
- Department of Audiology and Otorhinolaryngology, Edouard Herriot Hospital, Lyon 1 University, 69437 Lyon, France
| | - Clair Vandersteen
- Institut Universitaire de la Face et du Cou, Centre Hospitalier Universitaire de Nice, Université Côte d’Azur, 06100 Nice, France
| | - Stéphane Gallego
- Institute for Readaptation Sciences and Techniques, Lyon 1 University, 69373 Lyon, France
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Sharma S, H.M. Mens L, F.M. Snik A, van Opstal AJ, van Wanrooij MM. Hearing Asymmetry Biases Spatial Hearing in Bimodal Cochlear-Implant Users Despite Bilateral Low-Frequency Hearing Preservation. Trends Hear 2023; 27:23312165221143907. [PMID: 36605011 PMCID: PMC9829999 DOI: 10.1177/23312165221143907] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Many cochlear implant users with binaural residual (acoustic) hearing benefit from combining electric and acoustic stimulation (EAS) in the implanted ear with acoustic amplification in the other. These bimodal EAS listeners can potentially use low-frequency binaural cues to localize sounds. However, their hearing is generally asymmetric for mid- and high-frequency sounds, perturbing or even abolishing binaural cues. Here, we investigated the effect of a frequency-dependent binaural asymmetry in hearing thresholds on sound localization by seven bimodal EAS listeners. Frequency dependence was probed by presenting sounds with power in low-, mid-, high-, or mid-to-high-frequency bands. Frequency-dependent hearing asymmetry was present in the bimodal EAS listening condition (when using both devices) but was also induced by independently switching devices on or off. Using both devices, hearing was near symmetric for low frequencies, asymmetric for mid frequencies with better hearing thresholds in the implanted ear, and monaural for high frequencies with no hearing in the non-implanted ear. Results show that sound-localization performance was poor in general. Typically, localization was strongly biased toward the better hearing ear. We observed that hearing asymmetry was a good predictor for these biases. Notably, even when hearing was symmetric a preferential bias toward the ear using the hearing aid was revealed. We discuss how frequency dependence of any hearing asymmetry may lead to binaural cues that are spatially inconsistent as the spectrum of a sound changes. We speculate that this inconsistency may prevent accurate sound-localization even after long-term exposure to the hearing asymmetry.
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Affiliation(s)
- Snandan Sharma
- Department of Biophysics, Radboud
University, Donders Institute for
Brain, Cognition and Behavior, Nijmegen, The
Netherlands
| | - Lucas H.M. Mens
- Department of Otorhinolaryngology, Radboud University Medical
Centre, Donders Institute for
Brain, Cognition and Behavior, Nijmegen, The
Netherlands
| | - Ad F.M. Snik
- Department of Biophysics, Radboud
University, Donders Institute for
Brain, Cognition and Behavior, Nijmegen, The
Netherlands
| | - A. John van Opstal
- Department of Biophysics, Radboud
University, Donders Institute for
Brain, Cognition and Behavior, Nijmegen, The
Netherlands
| | - Marc M. van Wanrooij
- Department of Biophysics, Radboud
University, Donders Institute for
Brain, Cognition and Behavior, Nijmegen, The
Netherlands
- Marc van Wanrooij, Department of
Biophysics, Radboud University, Donders Institute for Brain, Cognition and
Behavior, The Netherlands.
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5
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Söderqvist S, Sinkkonen ST, Sivonen V. The intraoperative relationship between intracochlear electrical field and excitability of the auditory nerve. Heliyon 2022; 8:e11970. [DOI: 10.1016/j.heliyon.2022.e11970] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 10/10/2022] [Accepted: 11/22/2022] [Indexed: 12/03/2022] Open
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Leterme G, Guigou C, Guenser G, Bigand E, Bozorg Grayeli A. Effect of Sound Coding Strategies on Music Perception with a Cochlear Implant. J Clin Med 2022; 11:jcm11154425. [PMID: 35956042 PMCID: PMC9369156 DOI: 10.3390/jcm11154425] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Revised: 07/15/2022] [Accepted: 07/26/2022] [Indexed: 11/21/2022] Open
Abstract
The goal of this study was to evaluate the music perception of cochlear implantees with two different sound processing strategies. Methods: Twenty-one patients with unilateral or bilateral cochlear implants (Oticon Medical®) were included. A music trial evaluated emotions (sad versus happy based on tempo and/or minor versus major modes) with three tests of increasing difficulty. This was followed by a test evaluating the perception of musical dissonances (marked out of 10). A novel sound processing strategy reducing spectral distortions (CrystalisXDP, Oticon Medical) was compared to the standard strategy (main peak interleaved sampling). Each strategy was used one week before the music trial. Results: Total music score was higher with CrystalisXDP than with the standard strategy. Nine patients (21%) categorized music above the random level (>5) on test 3 only based on mode with either of the strategies. In this group, CrystalisXDP improved the performances. For dissonance detection, 17 patients (40%) scored above random level with either of the strategies. In this group, CrystalisXDP did not improve the performances. Conclusions: CrystalisXDP, which enhances spectral cues, seemed to improve the categorization of happy versus sad music. Spectral cues could participate in musical emotions in cochlear implantees and improve the quality of musical perception.
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Affiliation(s)
- Gaëlle Leterme
- Otolaryngology, Head and Neck Surgery Department, Dijon University Hospital, 21000 Dijon, France; (G.L.); (G.G.); (A.B.G.)
- ImVia Research Laboratory, Bourgogne-Franche-Comté University, 21000 Dijon, France
| | - Caroline Guigou
- Otolaryngology, Head and Neck Surgery Department, Dijon University Hospital, 21000 Dijon, France; (G.L.); (G.G.); (A.B.G.)
- ImVia Research Laboratory, Bourgogne-Franche-Comté University, 21000 Dijon, France
- Correspondence: ; Tel.: +33-615718531
| | - Geoffrey Guenser
- Otolaryngology, Head and Neck Surgery Department, Dijon University Hospital, 21000 Dijon, France; (G.L.); (G.G.); (A.B.G.)
| | - Emmanuel Bigand
- LEAD Research Laboratory, CNRS UMR 5022, Bourgogne-Franche-Comté University, 21000 Dijon, France;
| | - Alexis Bozorg Grayeli
- Otolaryngology, Head and Neck Surgery Department, Dijon University Hospital, 21000 Dijon, France; (G.L.); (G.G.); (A.B.G.)
- ImVia Research Laboratory, Bourgogne-Franche-Comté University, 21000 Dijon, France
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7
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Leblans M, Sismono F, Vanpoucke F, van Dinther J, Lerut B, Kuhweide R, Offeciers E, Zarowski A. Novel Impedance Measures as Biomarker for Intracochlear Fibrosis. Hear Res 2022; 426:108563. [DOI: 10.1016/j.heares.2022.108563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Revised: 04/05/2022] [Accepted: 06/15/2022] [Indexed: 11/04/2022]
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Biesheuvel JD, Briaire JJ, Kalkman RK, Frijns JH. The effect of stimulus level on excitation patterns of individual electrode contacts in cochlear implants. Hear Res 2022; 420:108490. [DOI: 10.1016/j.heares.2022.108490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 03/18/2022] [Accepted: 03/23/2022] [Indexed: 11/26/2022]
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Joly CA, Reynard P, Hermann R, Seldran F, Gallego S, Idriss S, Thai-Van H. Intra-Cochlear Current Spread Correlates with Speech Perception in Experienced Adult Cochlear Implant Users. J Clin Med 2021; 10:jcm10245819. [PMID: 34945115 PMCID: PMC8709369 DOI: 10.3390/jcm10245819] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 12/03/2021] [Accepted: 12/08/2021] [Indexed: 11/16/2022] Open
Abstract
Broader intra-cochlear current spread (ICCS) implies higher cochlear implant (CI) channel interactions. This study aimed to investigate the relationship between ICCS and speech intelligibility in experienced CI users. Using voltage matrices collected for impedance measurements, an individual exponential spread coefficient (ESC) was computed. Speech audiometry was performed to determine the intelligibility at 40 dB Sound Pressure Level (SPL) and the 50% speech reception threshold: I40 and SRT50 respectively. Correlations between ESC and either I40 or SRT50 were assessed. A total of 36 adults (mean age: 50 years) with more than 11 months (mean: 34 months) of CI experience were included. In the 21 subjects for whom all electrodes were active, ESC was moderately correlated with both I40 (r = −0.557, p = 0.009) and SRT50 (r = 0.569, p = 0.007). The results indicate that speech perception performance is negatively affected by the ICCS. Estimates of current spread at the closest vicinity of CI electrodes and prior to any activation of auditory neurons are indispensable to better characterize the relationship between CI stimulation and auditory perception in cochlear implantees.
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Affiliation(s)
- Charles-Alexandre Joly
- Institut de l’Audition, Institut Pasteur, Université de Paris, INSERM, 75012 Paris, France; (C.-A.J.); (P.R.)
- Université Claude Bernard Lyon 1, 69100 Villeurbanne, France; (R.H.); (S.G.)
- Service d’Audiologie et d’Explorations Otoneurologiques, Hôpital Edouard Herriot, Hospices Civils de Lyon, 69003 Lyon, France;
| | - Pierre Reynard
- Institut de l’Audition, Institut Pasteur, Université de Paris, INSERM, 75012 Paris, France; (C.-A.J.); (P.R.)
- Université Claude Bernard Lyon 1, 69100 Villeurbanne, France; (R.H.); (S.G.)
- Service d’Audiologie et d’Explorations Otoneurologiques, Hôpital Edouard Herriot, Hospices Civils de Lyon, 69003 Lyon, France;
| | - Ruben Hermann
- Université Claude Bernard Lyon 1, 69100 Villeurbanne, France; (R.H.); (S.G.)
- Integrative, Multisensory, Perception, Action and Cognition Team (IMPACT), Inserm U1028, CNRS UMR5292, Lyon Neuroscience Research Center, 69675 Bron, France
- Service d’ORL, Chirurgie Cervico-Faciale et d’Audiophonologie, Hospices Civils de Lyon, Hôpital Edouard Herriot, 69003 Lyon, France
| | | | - Stéphane Gallego
- Université Claude Bernard Lyon 1, 69100 Villeurbanne, France; (R.H.); (S.G.)
- Neuronal Dynamics and Audition Team (DNA), Laboratory of Cognitive Neuroscience, CNRS UMR7291, Aix-Marseille University, CEDEX 3, 13331 Marseille, France
| | - Samar Idriss
- Service d’Audiologie et d’Explorations Otoneurologiques, Hôpital Edouard Herriot, Hospices Civils de Lyon, 69003 Lyon, France;
| | - Hung Thai-Van
- Institut de l’Audition, Institut Pasteur, Université de Paris, INSERM, 75012 Paris, France; (C.-A.J.); (P.R.)
- Université Claude Bernard Lyon 1, 69100 Villeurbanne, France; (R.H.); (S.G.)
- Service d’Audiologie et d’Explorations Otoneurologiques, Hôpital Edouard Herriot, Hospices Civils de Lyon, 69003 Lyon, France;
- Correspondence:
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Electro-Tactile Stimulation Enhances Cochlear-Implant Melody Recognition: Effects of Rhythm and Musical Training. Ear Hear 2021; 41:106-113. [PMID: 31884501 DOI: 10.1097/aud.0000000000000749] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES Electro-acoustic stimulation (EAS) enhances speech and music perception in cochlear-implant (CI) users who have residual low-frequency acoustic hearing. For CI users who do not have low-frequency acoustic hearing, tactile stimulation may be used in a similar fashion as residual low-frequency acoustic hearing to enhance CI performance. Previous studies showed that electro-tactile stimulation (ETS) enhanced speech recognition in noise and tonal language perception for CI listeners. Here, we examined the effect of ETS on melody recognition in both musician and nonmusician CI users. DESIGN Nine musician and eight nonmusician CI users were tested in a melody recognition task with or without rhythmic cues in three testing conditions: CI only (E), tactile only (T), and combined CI and tactile stimulation (ETS). RESULTS Overall, the combined electrical and tactile stimulation enhanced the melody recognition performance in CI users by 9% points. Two additional findings were observed. First, musician CI users outperformed nonmusicians CI users in melody recognition, but the size of the enhancement effect was similar between the two groups. Second, the ETS enhancement was significantly higher with nonrhythmic melodies than rhythmic melodies in both groups. CONCLUSIONS These findings suggest that, independent of musical experience, the size of the ETS enhancement depends on integration efficiency between tactile and auditory stimulation, and that the mechanism of the ETS enhancement is improved electric pitch perception. The present study supports the hypothesis that tactile stimulation can be used to improve pitch perception in CI users.
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11
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Jiang C, Singhal S, Landry T, Roberts I, de Rijk S, Brochier T, Goehring T, Tam Y, Carlyon R, Malliaras G, Bance M. An Instrumented Cochlea Model for the Evaluation of Cochlear Implant Electrical Stimulus Spread. IEEE Trans Biomed Eng 2021; 68:2281-2288. [PMID: 33587694 PMCID: PMC8215857 DOI: 10.1109/tbme.2021.3059302] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Cochlear implants use electrical stimulation of the auditory nerve to restore the sensation of hearing to deaf people. Unfortunately, the stimulation current spreads extensively within the cochlea, resulting in “blurring” of the signal, and hearing that is far from normal. Current spread can be indirectly measured using the implant electrodes for both stimulating and sensing, but this provides incomplete information near the stimulating electrode due to electrode-electrolyte interface effects. Here, we present a 3D-printed “unwrapped” physical cochlea model with integrated sensing wires. We integrate resistors into the walls of the model to simulate current spread through the cochlear bony wall, and “tune” these resistances by calibration with an in-vivo electrical measurement from a cochlear implant patient. We then use this model to compare electrical current spread under different stimulation modes including monopolar, bipolar and tripolar configurations. Importantly, a trade-off is observed between stimulation amplitude and current focusing among different stimulation modes. By combining different stimulation modes and changing intracochlear current sinking configurations in the model, we explore this trade-off between stimulation amplitude and focusing further. These results will inform clinical strategies for use in delivering speech signals to cochlear implant patients.
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Söderqvist S, Lamminmäki S, Aarnisalo A, Hirvonen T, Sinkkonen ST, Sivonen V. Intraoperative transimpedance and spread of excitation profile correlations with a lateral-wall cochlear implant electrode array. Hear Res 2021; 405:108235. [PMID: 33901994 DOI: 10.1016/j.heares.2021.108235] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 03/21/2021] [Accepted: 03/25/2021] [Indexed: 01/18/2023]
Abstract
A limiting factor of cochlear implant technology is the spread of electrode-generated intracochlear electrical field (EF) leading to spread of neural excitation (SOE). In this study, we investigated the relation of the spread of the intracochlear EF, assessed via transimpedance matrix (TIM), and SOE. A total of 43 consecutive patients (ages 0.7-82 years; 31.0 ± 25.7 years, mean ± SD) implanted with a Cochlear Nucleus CI522 or CI622 cochlear implant with Slim Straight electrode array (altogether 51 ears) were included in the study. Cochlear nerve was visualized for all patients in preoperative imaging and there were no cochlear anomalies in the study sample. The stimulated electrodes were in the basal, middle, and apical parts of the electrode array (electrode numbers 6, 11, and 19, respectively). The stimulation level was 210 CL on average for the TIM measurement and always 230 CL for the SOE measurement. Approximately 90% of the individual TIM and SOE profiles correlated with each other (p < .05; r = 0.61-0.99). Also, the widths of the TIM and SOE peaks, computed at 50% of the maximum height, exhibited a weak correlation (r = 0.39, p = .007). The 50% widths of TIM and SOE were the same only in the apical part of the electrode array; in the basal part SOE was wider than TIM, and in the middle part TIM was wider than SOE (p < .01 and p = .048, respectively). Within each measurement, TIM 50% widths were different between all three parts of the electrode array, while for SOE, only the basal electrode differed from the middle electrode. Finally, the size of the cochlea and the 50% widths of TIM and SOE had the strongest correlation in the middle part of the electrode array (r = -0.63, and -0.37, respectively). Our results suggest that there is a correlation between the spread of intracochlear EF and neural SOE at least in the apical part of the electrode array used in this study, and that larger cochleae are associated with more focused TIM and SOE.
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Affiliation(s)
- Samuel Söderqvist
- Department of Otorhinolaryngology - Head and Neck Surgery, Head and Neck Center, Helsinki University Hospital and University of Helsinki, Kasarmikatu 11-13, 00130 Helsinki, Finland.
| | - Satu Lamminmäki
- Department of Otorhinolaryngology - Head and Neck Surgery, Head and Neck Center, Helsinki University Hospital and University of Helsinki, Kasarmikatu 11-13, 00130 Helsinki, Finland
| | - Antti Aarnisalo
- Department of Otorhinolaryngology - Head and Neck Surgery, Head and Neck Center, Helsinki University Hospital and University of Helsinki, Kasarmikatu 11-13, 00130 Helsinki, Finland
| | - Timo Hirvonen
- Department of Otorhinolaryngology - Head and Neck Surgery, Head and Neck Center, Helsinki University Hospital and University of Helsinki, Kasarmikatu 11-13, 00130 Helsinki, Finland
| | - Saku T Sinkkonen
- Department of Otorhinolaryngology - Head and Neck Surgery, Head and Neck Center, Helsinki University Hospital and University of Helsinki, Kasarmikatu 11-13, 00130 Helsinki, Finland
| | - Ville Sivonen
- Department of Otorhinolaryngology - Head and Neck Surgery, Head and Neck Center, Helsinki University Hospital and University of Helsinki, Kasarmikatu 11-13, 00130 Helsinki, Finland
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13
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Agarwal A, Tan X, Xu Y, Richter CP. Channel Interaction During Infrared Light Stimulation in the Cochlea. Lasers Surg Med 2021; 53:986-997. [PMID: 33476051 DOI: 10.1002/lsm.23360] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 10/21/2020] [Accepted: 11/07/2020] [Indexed: 12/22/2022]
Abstract
BACKGROUND AND OBJECTIVES The number of perceptually independent channels to encode acoustic information is limited in contemporary cochlear implants (CIs) because of the current spread in the tissue. It has been suggested that neighboring electrodes have to be separated in humans by a distance of more than 2 mm to eliminate significant overlap of the electric current fields and subsequent interaction between the channels. It has also been argued that an increase in the number of independent channels could improve CI user performance in challenging listening environments, such as speech in noise, tonal languages, or music perception. Optical stimulation has been suggested as an alternative modality for neural stimulation because it is spatially selective. This study reports the results of experiments designed to quantify the interaction between neighboring optical sources in the cochlea during stimulation with infrared radiation. STUDY DESIGN/MATERIALS AND METHODS In seven adult albino guinea pigs, a forward masking method was used to quantify the interaction between two neighboring optical sources during stimulation. Two optical fibers were placed through cochleostomies into the scala tympani of the basal cochlear turn. The radiation beams were directed towards different neuron populations along the spiral ganglion. Optically evoked compound action potentials were recorded for different radiant energies and distances between the optical fibers. The outcome measure was the radiant energy of a masker pulse delivered 3 milliseconds before a probe pulse to reduce the response evoked by the probe pulse by 3 dB. Results were compared for different distances between the fibers placed along the cochlea. RESULTS The energy required to reduce the probe's response by 3 dB increased by 20.4 dB/mm and by 26.0 dB/octave. The inhibition was symmetrical for the masker placed basal to the probe (base-to-apex) and the masker placed apical to the probe (apex-to-base). CONCLUSION The interaction between neighboring optical sources during infrared laser stimulation is less than the interaction between neighboring electrical contacts during electrical stimulation. Previously published data for electrical stimulation reported an average current spread in human and cat cochleae of 2.8 dB/mm. With the increased number of independent channels for optical stimulation, it is anticipated that speech and music performance will improve. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.
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Affiliation(s)
- Aditi Agarwal
- Department of Otolaryngology, Feinberg School of Medicine, Northwestern University, 320 E. Superior Street, Searle 12-561, Chicago, Illinois, 60611
| | - Xiaodong Tan
- Department of Otolaryngology, Feinberg School of Medicine, Northwestern University, 320 E. Superior Street, Searle 12-561, Chicago, Illinois, 60611
| | - Yingyue Xu
- Department of Otolaryngology, Feinberg School of Medicine, Northwestern University, 320 E. Superior Street, Searle 12-561, Chicago, Illinois, 60611
| | - Claus-Peter Richter
- Department of Otolaryngology, Feinberg School of Medicine, Northwestern University, 320 E. Superior Street, Searle 12-561, Chicago, Illinois, 60611.,Department of Biomedical Engineering, Northwestern University, 2145 Sheridan Road, Tech E310, Evanston, Illinois, 60208.,Department of Communication Sciences and Disorders, Northwestern University, Evanston, Illinois, 60208.,Department of Communication Sciences and Disorders, The Hugh Knowles Center, Northwestern University, Evanston, Illinois, 60208
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McKay CM. Applications of Phenomenological Loudness Models to Cochlear Implants. Front Psychol 2021; 11:611517. [PMID: 33519626 PMCID: PMC7838155 DOI: 10.3389/fpsyg.2020.611517] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 12/11/2020] [Indexed: 11/13/2022] Open
Abstract
Cochlear implants electrically stimulate surviving auditory neurons in the cochlea to provide severely or profoundly deaf people with access to hearing. Signal processing strategies derive frequency-specific information from the acoustic signal and code amplitude changes in frequency bands onto amplitude changes of current pulses emitted by the tonotopically arranged intracochlear electrodes. This article first describes how parameters of the electrical stimulation influence the loudness evoked and then summarizes two different phenomenological models developed by McKay and colleagues that have been used to explain psychophysical effects of stimulus parameters on loudness, detection, and modulation detection. The Temporal Model is applied to single-electrode stimuli and integrates cochlear neural excitation using a central temporal integration window analogous to that used in models of normal hearing. Perceptual decisions are made using decision criteria applied to the output of the integrator. By fitting the model parameters to a variety of psychophysical data, inferences can be made about how electrical stimulus parameters influence neural excitation in the cochlea. The Detailed Model is applied to multi-electrode stimuli, and includes effects of electrode interaction at a cochlear level and a transform between integrated excitation and specific loudness. The Practical Method of loudness estimation is a simplification of the Detailed Model and can be used to estimate the relative loudness of any multi-electrode pulsatile stimuli without the need to model excitation at the cochlear level. Clinical applications of these models to novel sound processing strategies are described.
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Affiliation(s)
- Colette M. McKay
- Bionics Institute, Melbourne, VIC, Australia
- Department of Medical Bionics, University of Melbourne, Melbourne, VIC, Australia
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15
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Heshmat A, Sajedi S, Johnson Chacko L, Fischer N, Schrott-Fischer A, Rattay F. Dendritic Degeneration of Human Auditory Nerve Fibers and Its Impact on the Spiking Pattern Under Regular Conditions and During Cochlear Implant Stimulation. Front Neurosci 2020; 14:599868. [PMID: 33328872 PMCID: PMC7710996 DOI: 10.3389/fnins.2020.599868] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Accepted: 10/22/2020] [Indexed: 12/04/2022] Open
Abstract
Due to limitations of human in vivo studies, detailed computational models enable understanding the neural signaling in the degenerated auditory system and cochlear implants (CIs). Four human cochleae were used to quantify hearing levels depending on dendritic changes in diameter and myelination thickness from type I of the auditory nerve fibers (ANFs). Type I neurons transmit the auditory information as spiking pattern from the inner hair cells (IHCs) to the cochlear nucleus. The impact of dendrite diameter and degree of myelination on neural signal transmission was simulated for (1) synaptic excitation via IHCs and (2) stimulation from CI electrodes. An accurate three-dimensional human cochlear geometry, along with 30 auditory pathways, mimicked the CI environment. The excitation properties of electrical potential distribution induced by two CI were analyzed. Main findings: (1) The unimodal distribution of control dendrite diameters becomes multimodal for hearing loss cases; a group of thin dendrites with diameters between 0.3 and 1 μm with a peak at 0.5 μm appeared. (2) Postsynaptic currents from IHCs excite such thin dendrites easier and earlier than under control conditions. However, this advantage is lost as their conduction velocity decreases proportionally with the diameter and causes increased spike latency and jitter in soma and axon. Firing probability reduces through the soma passage due to the low intracellular current flow in thin dendrites during spiking. (3) Compared with dendrite diameter, variations in myelin thickness have a small impact on spiking performance. (4) Contrary to synaptic excitation, CIs cause several spike initiation sites in dendrite, soma region, and axon; moreover, fiber excitability reduces with fiber diameter. In a few cases, where weak stimuli elicit spikes of a target neuron (TN) in the axon, dendrite diameter reduction has no effect. However, in many cases, a spike in a TN is first initiated in the dendrite, and consequently, dendrite degeneration demands an increase in threshold currents. (5) Threshold currents of a TN and co-stimulation of degenerated ANFs in other frequency regions depend on the electrode position, including its distance to the outer wall, the cochlear turn, and the three-dimensional pathway of the TN.
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Affiliation(s)
- Amirreza Heshmat
- Faculty of Mathematics and Geoinformation, Institute for Analysis and Scientific Computing, Vienna University of Technology, Vienna, Austria.,Laboratory for Inner Ear Biology, Department of Otorhinolaryngology, Medical University of Innsbruck, Innsbruck, Austria
| | - Sogand Sajedi
- Faculty of Mathematics and Geoinformation, Institute for Analysis and Scientific Computing, Vienna University of Technology, Vienna, Austria
| | - Lejo Johnson Chacko
- Laboratory for Inner Ear Biology, Department of Otorhinolaryngology, Medical University of Innsbruck, Innsbruck, Austria
| | - Natalie Fischer
- Laboratory for Inner Ear Biology, Department of Otorhinolaryngology, Medical University of Innsbruck, Innsbruck, Austria
| | - Anneliese Schrott-Fischer
- Laboratory for Inner Ear Biology, Department of Otorhinolaryngology, Medical University of Innsbruck, Innsbruck, Austria
| | - Frank Rattay
- Faculty of Mathematics and Geoinformation, Institute for Analysis and Scientific Computing, Vienna University of Technology, Vienna, Austria
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Abstract
INTRODUCTION Cochlear implants (CIs) are biomedical devices that restore sound perception for people with severe-to-profound sensorineural hearing loss. Most postlingually deafened CI users are able to achieve excellent speech recognition in quiet environments. However, current CI sound processors remain limited in their ability to deliver fine spectrotemporal information, making it difficult for CI users to perceive complex sounds. Limited access to complex acoustic cues such as music, environmental sounds, lexical tones, and voice emotion may have significant ramifications on quality of life, social development, and community interactions. AREAS COVERED The purpose of this review article is to summarize the literature on CIs and music perception, with an emphasis on music training in pediatric CI recipients. The findings have implications on our understanding of noninvasive, accessible methods for improving auditory processing and may help advance our ability to improve sound quality and performance for implantees. EXPERT OPINION Music training, particularly in the pediatric population, may be able to continue to enhance auditory processing even after performance plateaus. The effects of these training programs appear generalizable to non-trained musical tasks, speech prosody and, emotion perception. Future studies should employ rigorous control groups involving a non-musical acoustic intervention, standardized auditory stimuli, and the provision of feedback.
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Affiliation(s)
- Nicole T Jiam
- Department of Otolaryngology-Head and Neck Surgery, University of California San Francisco School of Medicine , San Francisco, CA, USA
| | - Charles Limb
- Department of Otolaryngology-Head and Neck Surgery, University of California San Francisco School of Medicine , San Francisco, CA, USA
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Langner F, McKay CM, Büchner A, Nogueira W. Perception and prediction of loudness in sound coding strategies using simultaneous electric stimulation. Hear Res 2020; 398:108091. [PMID: 33059310 DOI: 10.1016/j.heares.2020.108091] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 09/03/2020] [Accepted: 09/22/2020] [Indexed: 10/23/2022]
Abstract
Cochlear Implant (CI) sound coding strategies based on simultaneous stimulation lead to an increased loudness percept when compared to sequential stimulation using the same current levels. This is due to loudness summation as a result of channel interactions. Studying the loudness perception evoked by dual-channels compared to single-channels can be useful to optimize sound coding strategies that use simultaneous current pulses. Fourteen users of HiRes90k implants and one user of a CII implant loudness balanced single-channel to dual-channel stimuli with varying distance between simultaneous channels. In this study each component of a dual channel was a virtual channel, which shared current across two adjacent electrodes. Balancing was performed at threshold and comfortable level, for two spatial references (apical and basal) and for dual-channels with different relative current ratios. Increasing distance between dual-channels decreased the amount of current compensation in the dual-channel required to reach equal loudness to a single channel component by an average of 0.24 dB / mm without a significant difference between threshold and most comfortable level. If the components of the dual-channels were not at equal loudness, the loudness summation was reduced with respect to the equal loudness case. The results were incorporated into an existing loudness model by McKay et al. (2003). The predictions from the adapted model were evaluated by comparing the loudness evoked by simultaneous and sequential sound coding strategies. The application of the adapted model resulted in a deviation between predicted and actual behavioral loudness balancing adjustments in electrical level between simultaneous and sequential processing strategies of 0.24 dB on average.
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Affiliation(s)
- Florian Langner
- Department of Otolaryngology, Medical University Hannover and Cluster of Excellence Hearing4all, Karl-Wiechert-Allee 3, Hannover 30625, Germany.
| | - Colette M McKay
- Bionics Institute, East Melbourne, Australia; University of Melbourne, Medical Bionics Department, Australia
| | - Andreas Büchner
- Department of Otolaryngology, Medical University Hannover and Cluster of Excellence Hearing4all, Karl-Wiechert-Allee 3, Hannover 30625, Germany
| | - Waldo Nogueira
- Department of Otolaryngology, Medical University Hannover and Cluster of Excellence Hearing4all, Karl-Wiechert-Allee 3, Hannover 30625, Germany
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Precompensating for spread of excitation in a cochlear implant coding strategy. Hear Res 2020; 395:107977. [PMID: 32653106 DOI: 10.1016/j.heares.2020.107977] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Revised: 03/11/2020] [Accepted: 04/15/2020] [Indexed: 11/22/2022]
Abstract
Cochlear implant users' limited ability to understand speech in noisy environments has been linked to the poor spatial resolution and the high degree of spectral smearing associated with the spread of neural excitation. A sound coding algorithm that aims to improve the spectro-temporal representation of the sound signal at the implanted ear by precompensating the electrical stimulation for the spread of excitation is presented in this study. The spread precompensation algorithm was integrated into the standard clinical advanced combination encoder (ACE) strategy and the resulting strategy was called SPACE. SPACE was evaluated acutely with a group of six implant users and was compared to their daily used ACE strategy in terms of preference rating and speech recognition in four-talker babble and stationary speech-shaped noise. While no significant differences in preference rating were observed, speech recognition in four-talker babble was improved by SPACE processing. Analysis of the group results revealed a significant improvement in mean speech reception threshold (SRT) over the ACE strategy of 1.4 dB in four-talker babble, whereas the difference of 0.9 dB in stationary noise did not reach statistical significance. Assessment of individual differences showed that four out of six listeners obtained significant SRT improvements with SPACE and that no subject scored significantly worse compared to ACE. The results suggest that the proposed sound coding strategy has the potential to improve speech perception for cochlear implant users in challenging listening situations.
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Potrusil T, Heshmat A, Sajedi S, Wenger C, Johnson Chacko L, Glueckert R, Schrott-Fischer A, Rattay F. Finite element analysis and three-dimensional reconstruction of tonotopically aligned human auditory fiber pathways: A computational environment for modeling electrical stimulation by a cochlear implant based on micro-CT. Hear Res 2020; 393:108001. [PMID: 32535276 DOI: 10.1016/j.heares.2020.108001] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Revised: 05/14/2020] [Accepted: 05/23/2020] [Indexed: 01/01/2023]
Abstract
The application of cochlear implants can be studied with computational models. The electrical potential distribution induced by an implanted device is evaluated with a volume conductor model, which is used as input for neuron models to simulate the reaction of cochlear neurons to micro-stimulation. In order to reliably predict the complex excitation profiles it is vital to consider an accurate representation of the human cochlea geometry including detailed three-dimensional pathways of auditory neurons reaching from the organ of Corti through the cochlea-volume. In this study, high-resolution micro-CT imaging (Δx = Δy = Δz = 3 μm) was used to reconstruct the pathways of 30 tonotopically organized nerve fiber bundles, distributed over eight octaves (11500-40 Hz). Results of the computational framework predict: (i) the peripheral process is most sensitive to cathodic stimulation (CAT), (ii) in many cases CAT elicits spikes in the peripheral terminal at threshold but with larger stimuli there is a second spike initiation site within the peripheral process, (iii) anodic stimuli (ANO) can excite the central process even at threshold, (iv) the recruitment of fibers by electrodes located in the narrowing middle- and apical turn is complex and impedes focal excitation of low frequency fibers, (v) degenerated cells which lost the peripheral process are more sensitive to CAT when their somata are totally covered with 2 membranes of a glial cell but they become ANO sensitive when the myelin covering is reduced.
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Affiliation(s)
- Thomas Potrusil
- Innsbruck Medical University, Department of Otorhinolaryngology, Laboratory for Inner Ear Biology, Anichstrasse 35, A-6020, Innsbruck, Austria
| | - Amirreza Heshmat
- Innsbruck Medical University, Department of Otorhinolaryngology, Laboratory for Inner Ear Biology, Anichstrasse 35, A-6020, Innsbruck, Austria; TU Wien, Institute for Analysis and Scientific Computing, Wiedner Hauptstraße 8-10, A- 1040, Vienna, Austria
| | - Sogand Sajedi
- TU Wien, Institute for Analysis and Scientific Computing, Wiedner Hauptstraße 8-10, A- 1040, Vienna, Austria
| | - Cornelia Wenger
- TU Wien, Institute for Analysis and Scientific Computing, Wiedner Hauptstraße 8-10, A- 1040, Vienna, Austria
| | - Lejo Johnson Chacko
- Innsbruck Medical University, Department of Otorhinolaryngology, Laboratory for Inner Ear Biology, Anichstrasse 35, A-6020, Innsbruck, Austria
| | - Rudolf Glueckert
- Innsbruck Medical University, Department of Otorhinolaryngology, Laboratory for Inner Ear Biology, Anichstrasse 35, A-6020, Innsbruck, Austria
| | - Anneliese Schrott-Fischer
- Innsbruck Medical University, Department of Otorhinolaryngology, Laboratory for Inner Ear Biology, Anichstrasse 35, A-6020, Innsbruck, Austria.
| | - Frank Rattay
- TU Wien, Institute for Analysis and Scientific Computing, Wiedner Hauptstraße 8-10, A- 1040, Vienna, Austria
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Neurophysiological Differences in Emotional Processing by Cochlear Implant Users, Extending Beyond the Realm of Speech. Ear Hear 2020; 40:1197-1209. [PMID: 30762600 DOI: 10.1097/aud.0000000000000701] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
OBJECTIVE Cochlear implants (CIs) restore a sense of hearing in deaf individuals. However, they do not transmit the acoustic signal with sufficient fidelity, leading to difficulties in recognizing emotions in voice and in music. The study aimed to explore the neurophysiological bases of these limitations. DESIGN Twenty-two adults (18 to 70 years old) with CIs and 22 age-matched controls with normal hearing participated. Event-related potentials (ERPs) were recorded in response to emotional bursts (happy, sad, or neutral) produced in each modality (voice or music) that were for the most part correctly identified behaviorally. RESULTS Compared to controls, the N1 and P2 components were attenuated and prolonged in CI users. To a smaller degree, N1 and P2 were also attenuated and prolonged in music compared to voice, in both populations. The N1-P2 complex was emotion-dependent (e.g., reduced and prolonged response to sadness), but this was also true in both populations. In contrast, the later portion of the response, between 600 and 850 ms, differentiated happy and sad from neutral stimuli in normal hearing but not in CI listeners. CONCLUSIONS The early portion of the ERP waveform reflected primarily the general reduction in sensory encoding by CI users (largely due to CI processing itself), whereas altered emotional processing (by CI users) could be found in the later portion of the ERP and extended beyond the realm of speech.
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Abstract
OBJECTIVE The purpose of this study was to assess the long-term changes in music perception among cochlear implant (CI) patients using the Korean version of the Clinical Assessment of Music Perception test and questionnaires for music listening. METHODS Twenty-seven CI patients participated in this study. Their music perception ability was evaluated using the Korean version of the Clinical Assessment of Music Perception test, which consisted of pitch discrimination, melody, and timbre identification. The test was conducted at least twice after CI. A questionnaire was also used to quantify listening habits (LH) and level of musical experience (LE). RESULTS The participants were divided into two groups according to the average of each test result from the first test. In the pitch discrimination test, the just-noticeable-difference limen values increased as the base frequency increased, and significant differences were observed between the results of 262 and 391 Hz (p = 0.006). In the good performance group, pitch discrimination in the second test did not significantly differ from the first test, but the pitch discrimination score significantly improved in the poor performance group. Similarly, timbre test results were significantly improved in the poor performance group. Neither group exhibited changes in the second test for melody identification. The scores for LH and LE significantly decreased postoperatively and did not recover during the follow-up period. CONCLUSIONS Pitch discrimination and timbre identification improved in CI listeners who exhibited poor musical performance shortly after surgery. However, melody identification did not improve over time. LH and LE scores decreased after CI surgery without time-dependent improvement.
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Tran P, Richardson ML, Zeng FG. Input-Output Functions in Human Heads Obtained With Cochlear Implant and Transcranial Electric Stimulation. Neuromodulation 2019; 24:1402-1411. [PMID: 31710408 DOI: 10.1111/ner.13065] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 09/18/2019] [Accepted: 09/23/2019] [Indexed: 11/27/2022]
Abstract
OBJECTIVES Electric stimulation is used to treat a number of neurologic disorders such as epilepsy and depression. However, delivering the required current to far-field neural targets is often ineffective because of current spread through low-impedance pathways. Here, the specific aims are to develop an empirical measure for current passing through the human head and to optimize stimulation strategies for targeting deeper structures, including the auditory nerve, by utilizing the cochlear implant (CI). MATERIALS AND METHODS Outward input/output (I/O) functions were obtained by CI stimulation and recording scalp potentials in five CI subjects. Conversely, inward I/O functions were obtained by noninvasive transcranial electric stimulation (tES) and recording intracochlear potentials using the onboard recording capability of the CI. RESULTS I/O measures indicate substantial current spread, with a maximum of 2.2% gain recorded at the inner ear target during tES (mastoid-to-mastoid electrode configuration). Similarly, CI stimulation produced a maximum of 1.1% gain at the scalp electrode nearest the CI return electrode. Gain varied with electrode montage according to a point source model that accounted for distances between the stimulating and recording electrodes. Within the same electrode montages, current gain patterns varied across subjects suggesting the importance of tissue properties, geometry, and electrode positioning. CONCLUSION These results provide a novel objective measure of electric stimulation in the human head, which can help to optimize stimulation parameters that improve neural excitation of deep structures by reducing the influence of current spread.
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Affiliation(s)
- Phillip Tran
- Center for Hearing Research, University of California, Irvine, CA, USA
| | | | - Fan-Gang Zeng
- Center for Hearing Research, University of California, Irvine, CA, USA
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Zeng FG, Tran P, Richardson M, Sun S, Xu Y. Human Sensation of Transcranial Electric Stimulation. Sci Rep 2019; 9:15247. [PMID: 31649289 PMCID: PMC6813324 DOI: 10.1038/s41598-019-51792-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Accepted: 10/08/2019] [Indexed: 01/22/2023] Open
Abstract
Noninvasive transcranial electric stimulation is increasingly being used as an advantageous therapy alternative that may activate deep tissues while avoiding drug side-effects. However, not only is there limited evidence for activation of deep tissues by transcranial electric stimulation, its evoked human sensation is understudied and often dismissed as a placebo or secondary effect. By systematically characterizing the human sensation evoked by transcranial alternating-current stimulation, we observed not only stimulus frequency and electrode position dependencies specific for auditory and visual sensation but also a broader presence of somatic sensation ranging from touch and vibration to pain and pressure. We found generally monotonic input-output functions at suprathreshold levels, and often multiple types of sensation occurring simultaneously in response to the same electric stimulation. We further used a recording circuit embedded in a cochlear implant to directly and objectively measure the amount of transcranial electric stimulation reaching the auditory nerve, a deep intercranial target located in the densest bone of the skull. We found an optimal configuration using an ear canal electrode and low-frequency (<300 Hz) sinusoids that delivered maximally ~1% of the transcranial current to the auditory nerve, which was sufficient to produce sound sensation even in deafened ears. Our results suggest that frequency resonance due to neuronal intrinsic electric properties need to be explored for targeted deep brain stimulation and novel brain-computer interfaces.
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Affiliation(s)
- Fan-Gang Zeng
- Center for Hearing Research, Departments of Anatomy and Neurobiology, Biomedical Engineering, Cognitive Sciences, Otolaryngology - Head and Neck Surgery, University of California Irvine, Irvine, California, 92697, USA.
| | - Phillip Tran
- Center for Hearing Research, Departments of Anatomy and Neurobiology, Biomedical Engineering, Cognitive Sciences, Otolaryngology - Head and Neck Surgery, University of California Irvine, Irvine, California, 92697, USA
| | - Matthew Richardson
- Center for Hearing Research, Departments of Anatomy and Neurobiology, Biomedical Engineering, Cognitive Sciences, Otolaryngology - Head and Neck Surgery, University of California Irvine, Irvine, California, 92697, USA
| | - Shuping Sun
- Center for Hearing Research, Departments of Anatomy and Neurobiology, Biomedical Engineering, Cognitive Sciences, Otolaryngology - Head and Neck Surgery, University of California Irvine, Irvine, California, 92697, USA
- Department of Otolaryngology - Head and Neck Surgery, The First Affiliated Hospital, Zhengzhou University, Henan, 450052, China
| | - Yuchen Xu
- Center for Hearing Research, Departments of Anatomy and Neurobiology, Biomedical Engineering, Cognitive Sciences, Otolaryngology - Head and Neck Surgery, University of California Irvine, Irvine, California, 92697, USA
- Department of Precision Instrument, Tsinghua University, Beijing, 100084, China
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24
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Zhou N. Longitudinal effect of deactivating stimulation sites based on low-rate thresholds on speech recognition in cochlear implant users. Int J Audiol 2019; 58:587-597. [PMID: 31012771 DOI: 10.1080/14992027.2019.1601779] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Objective: The objective of the current study was to examine the longitudinal effect of deactivating stimulation sites estimated to produce broad neural excitation on speech recognition. Design: Spatial patterns of neural excitation were estimated based on a previously established psychophysical measure, that is, detection threshold for low-rate pulse trains. Stimulation sites with relatively poor thresholds were deactivated in an experimental map. The acute effect was evaluated, in quiet and in noise, immediately after the experimental map was created (baseline), after the subjects practiced with the experimental map for two months (treatment), and after the subjects' daily map was switched back again to the clinical map for another two months (withdrawal). Study sample: Eight Cochlear Nucleus device users participated in the study. Results: For both listening in noise and in quiet, the greatest effect of deactivation was observed after the subjects were given time to adapt to the new frequency allocations. The effect was comparable for listening in fluctuating and steady-state noises. All subjects benefited from deactivation for listening in noise, but subjects with greater variability in thresholds were more likely to benefit from deactivation for listening in quiet. Conclusion: The benefit of electrode deactivation for speech recognition can increase with practice.
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Affiliation(s)
- Ning Zhou
- a Department of Communication Sciences and Disorders , East Carolina University , Greenville , NC , USA
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25
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Grimm R, Pettinato M, Gillis S, Daelemans W. Simulating speech processing with cochlear implants: How does channel interaction affect learning in neural networks? PLoS One 2019; 14:e0212134. [PMID: 30811448 PMCID: PMC6392264 DOI: 10.1371/journal.pone.0212134] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Accepted: 01/28/2019] [Indexed: 11/18/2022] Open
Abstract
We introduce a novel machine learning approach for investigating speech processing with cochlear implants (CIs)—prostheses used to replace a damaged inner ear. Concretely, we use a simple perceptron and a deep convolutional network to classify speech spectrograms that are modified to approximate CI-delivered speech. Implant-delivered signals suffer from reduced spectral resolution, chiefly due to a small number of frequency channels and a phenomenon called channel interaction. The latter involves the spread of information from neighboring channels to similar populations of neurons and can be modeled by linearly combining adjacent channels. We find that early during training, this input modification degrades performance if the networks are first pre-trained on high-resolution speech—with a larger number of channels, and without added channel interaction. This suggests that the spectral degradation caused by channel interaction alters the signal to conflict with perceptual expectations acquired from high-resolution speech. We thus predict that a reduction of channel interaction will accelerate learning in CI users who are implanted after having adapted to high-resolution speech during normal hearing. (The code for replicating our experiments is available online: https://github.com/clips/SimulatingCochlearImplants).
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Affiliation(s)
- Robert Grimm
- Computational Linguistics & Psycholinguistics Research Center, Department of Linguistics, University of Antwerp, Antwerp, Belgium
- * E-mail:
| | - Michèle Pettinato
- Computational Linguistics & Psycholinguistics Research Center, Department of Linguistics, University of Antwerp, Antwerp, Belgium
| | - Steven Gillis
- Computational Linguistics & Psycholinguistics Research Center, Department of Linguistics, University of Antwerp, Antwerp, Belgium
| | - Walter Daelemans
- Computational Linguistics & Psycholinguistics Research Center, Department of Linguistics, University of Antwerp, Antwerp, Belgium
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Xu Y, Luo C, Zeng FG, Middlebrooks JC, Lin HW, You Z. Design, Fabrication, and Evaluation of a Parylene Thin-Film Electrode Array for Cochlear Implants. IEEE Trans Biomed Eng 2019; 66:573-583. [PMID: 30004866 PMCID: PMC6328340 DOI: 10.1109/tbme.2018.2850753] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
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.
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Litovsky RY, Goupell MJ, Kan A, Landsberger DM. Use of Research Interfaces for Psychophysical Studies With Cochlear-Implant Users. Trends Hear 2019; 21:2331216517736464. [PMID: 29113579 PMCID: PMC5764139 DOI: 10.1177/2331216517736464] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
A growing number of laboratories are using research interfaces to conduct experiments with cochlear-implant (CI) users. Because these interfaces bypass a subject’s clinical sound processor, several concerns exist regarding safety and stimulation levels. Here we suggest best-practice approaches for how to safely and ethically perform this type of research and highlight areas of limited knowledge where further research is needed to help clarify safety limits. The article is designed to provide an introductory level of technical detail about the devices and the effects of electrical stimulation on perception and neurophysiology. From this, we summarize what should be the best practices in the field, based on the literature and our experience. Findings from the review of the literature suggest that there are three main safety concerns: (a) to prevent biological or neural damage, (b) to avoid presentation of uncomfortably loud sounds, and (c) to ensure that subjects have control over stimulus presentation. Researchers must pay close attention to the software–hardware interface to ensure that the three main safety concerns are closely monitored. An important area for future research will be the determination of the amount of biological damage that can occur from electrical stimulation from a CI placed in the cochlea, not in direct contact with neural tissue. As technology used in research with CIs evolve, some of these approaches may change. However, the three main safety principles outlined here are not anticipated to undergo change with technological advances.
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Affiliation(s)
| | - Matthew J Goupell
- 2 Department of Hearing and Speech Sciences, University of Maryland-College Park, MD, USA
| | - Alan Kan
- 1 University of Wisconsin-Madison, WI, USA
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Mangado N, Pons-Prats J, Coma M, Mistrík P, Piella G, Ceresa M, González Ballester MÁ. Computational Evaluation of Cochlear Implant Surgery Outcomes Accounting for Uncertainty and Parameter Variability. Front Physiol 2018; 9:498. [PMID: 29875673 PMCID: PMC5975103 DOI: 10.3389/fphys.2018.00498] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Accepted: 04/18/2018] [Indexed: 11/13/2022] Open
Abstract
Cochlear implantation (CI) is a complex surgical procedure that restores hearing in patients with severe deafness. The successful outcome of the implanted device relies on a group of factors, some of them unpredictable or difficult to control. Uncertainties on the electrode array position and the electrical properties of the bone make it difficult to accurately compute the current propagation delivered by the implant and the resulting neural activation. In this context, we use uncertainty quantification methods to explore how these uncertainties propagate through all the stages of CI computational simulations. To this end, we employ an automatic framework, encompassing from the finite element generation of CI models to the assessment of the neural response induced by the implant stimulation. To estimate the confidence intervals of the simulated neural response, we propose two approaches. First, we encode the variability of the cochlear morphology among the population through a statistical shape model. This allows us to generate a population of virtual patients using Monte Carlo sampling and to assign to each of them a set of parameter values according to a statistical distribution. The framework is implemented and parallelized in a High Throughput Computing environment that enables to maximize the available computing resources. Secondly, we perform a patient-specific study to evaluate the computed neural response to seek the optimal post-implantation stimulus levels. Considering a single cochlear morphology, the uncertainty in tissue electrical resistivity and surgical insertion parameters is propagated using the Probabilistic Collocation method, which reduces the number of samples to evaluate. Results show that bone resistivity has the highest influence on CI outcomes. In conjunction with the variability of the cochlear length, worst outcomes are obtained for small cochleae with high resistivity values. However, the effect of the surgical insertion length on the CI outcomes could not be clearly observed, since its impact may be concealed by the other considered parameters. Whereas the Monte Carlo approach implies a high computational cost, Probabilistic Collocation presents a suitable trade-off between precision and computational time. Results suggest that the proposed framework has a great potential to help in both surgical planning decisions and in the audiological setting process.
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Affiliation(s)
- Nerea Mangado
- BCNMedTech, Universitat Pompeu Fabra, Barcelona, Spain
| | - Jordi Pons-Prats
- International Center for Numerical Methods in Engineering, Barcelona, Spain
| | - Martí Coma
- International Center for Numerical Methods in Engineering, Barcelona, Spain
| | | | - Gemma Piella
- BCNMedTech, Universitat Pompeu Fabra, Barcelona, Spain
| | - Mario Ceresa
- BCNMedTech, Universitat Pompeu Fabra, Barcelona, Spain
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Lopez-Poveda EA, Eustaquio-Martín A. Objective speech transmission improvements with a binaural cochlear implant sound-coding strategy inspired by the contralateral medial olivocochlear reflex. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2018; 143:2217. [PMID: 29716283 DOI: 10.1121/1.5031028] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
It has been recently shown that cochlear implant users could enjoy better speech reception in noise and enhanced spatial unmasking with binaural audio processing inspired by the inhibitory effects of the contralateral medial olivocochlear (MOC) reflex on compression [Lopez-Poveda, Eustaquio-Martin, Stohl, Wolford, Schatzer, and Wilson (2016). Ear Hear. 37, e138-e148]. The perceptual evidence supporting those benefits, however, is limited to a few target-interferer spatial configurations and to a particular implementation of contralateral MOC inhibition. Here, the short-term objective intelligibility index is used to (1) objectively demonstrate potential benefits over many more spatial configurations, and (2) investigate if the predicted benefits may be enhanced by using more realistic MOC implementations. Results corroborate the advantages and drawbacks of MOC processing indicated by the previously published perceptual tests. The results also suggest that the benefits may be enhanced and the drawbacks overcome by using longer time constants for the activation and deactivation of inhibition and, to a lesser extent, by using a comparatively greater inhibition in the lower than in the higher frequency channels. Compared to using two functionally independent processors, the better MOC processor improved the signal-to-noise ratio in the two ears between 1 and 6 decibels by enhancing head-shadow effects, and was advantageous for all tested target-interferer spatial configurations.
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Affiliation(s)
- Enrique A Lopez-Poveda
- Instituto de Neurociencias de Castilla y León, Universidad de Salamanca, Calle Pintor Fernando Gallego 1, Salamanca 37007, Spain
| | - Almudena Eustaquio-Martín
- Instituto de Neurociencias de Castilla y León, Universidad de Salamanca, Calle Pintor Fernando Gallego 1, Salamanca 37007, Spain
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Xu Y, Luo C, You Z. Optimization of cochlear implant stimulation resolution using an intracochlear electric potential model. Comput Biol Med 2018; 94:99-105. [PMID: 29408002 DOI: 10.1016/j.compbiomed.2017.12.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Revised: 12/06/2017] [Accepted: 12/20/2017] [Indexed: 10/18/2022]
Abstract
Designing an electrode array with a high stimulation resolution (SR) is the main challenge in cochlear implant development. In this work, a thin-film electrode array (TFEA) and partial tripolar (pTP) mode were combined in the design stage to optimize the SR. A finite-element model of the intracochlear electric potential Ve incorporating a TFEA and pTP mode was built and validated using previous experimental measurements. Based on this model, the SR was analyzed by using a defined stimulation factor Vs, which takes both the amplitude and bandwidth of Ve into account. A co-simulation method integrating the model and genetic algorithm was employed to maximize Vs with an optimized parameter set including the electrode diameter d, electrode interval g, and compensation coefficient σ. The results indicated that a TFEA combined with pTP mode outperforms their individual utilization to improve the SR and that d has an independent negative correlation with the SR, but it is more effective and feasible to consider all three parameters in the design stage with the proposed model and co-simulation optimization method. In our design, the optimized parameters were d = 150 μm, g = 200.5 μm, and σ = 0.746.
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Affiliation(s)
- Yuchen Xu
- State Key Laboratory of Precision Measurement Technology and Instrument, Tsinghua University, Beijing 100083, China; Department of Precision Instrument, Tsinghua University, Beijing 100083, China; Beijing Laboratory for Biomedical Detection Technology and Instrument, Tsinghua University, Beijing 100083, China
| | - Chuan Luo
- State Key Laboratory of Precision Measurement Technology and Instrument, Tsinghua University, Beijing 100083, China; Department of Precision Instrument, Tsinghua University, Beijing 100083, China; Beijing Laboratory for Biomedical Detection Technology and Instrument, Tsinghua University, Beijing 100083, China.
| | - Zheng You
- State Key Laboratory of Precision Measurement Technology and Instrument, Tsinghua University, Beijing 100083, China; Department of Precision Instrument, Tsinghua University, Beijing 100083, China; Beijing Laboratory for Biomedical Detection Technology and Instrument, Tsinghua University, Beijing 100083, China.
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Völker J, Kohm F, Jürgens L, Scherzad A, Schendzielorz P, Schraven SP, Mlynski R, Radeloff A, Hagen R, Rak K. Patterned semiconductor structures modulate neuronal outgrowth: Implication for the development of a neurobionic interface. J Biomed Mater Res A 2017; 106:65-72. [PMID: 28884492 DOI: 10.1002/jbm.a.36203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Revised: 08/09/2017] [Accepted: 08/15/2017] [Indexed: 11/10/2022]
Abstract
Auditory implants stimulate the neurons by broad electrical fields, which leads to a low number of spectral channels. A reduction in the distance between the electrode and the neuronal structures might lead to better electrical transduction. The use of microstructured semiconductors offers a large number of contacts, which could attract neurons and stimulate them individually. To investigate the interaction between neurons and semiconductors, differentiated neuronal precursor cells were cultured on silicon wafers. Different structures were added on the wafers by electron beam lithography, and deep reactive ion etching in different depths (2 and 7 µm). Grooved surfaces guided the neurons and resulted in straight oriented axons, but neuronal outgrowth was impaired by the 7 µm grooves. Within the 7 µm structures, the neuronal cell body was totally encased and the nuclei were deformed from a round to an elliptical shape. On both square and cylindrical structures neuronal bridging could be detected in different forms, either between the tops of the structures or between the bottom and the top. Furthermore, neuronal bridges were established on the lateral part of the structures, and change in direction of neuronal growth was induced by the structure. Finally, it could be shown that neuronal growth cones were particularly attracted by the top of the cylinders, which might allow for the stimulation of neurons via this structure. In conclusion, study results indicate that structured semiconductors can modulate neuronal growth and its direction, offering a novel method for the development of new implants with improved neuronal stimulation. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 65-72, 2018.
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Affiliation(s)
- Johannes Völker
- Department of Oto-Rhino-Laryngology, Plastic, Aesthetic and Reconstructive Head and Neck Surgery and the Comprehensive Hearing Center, University of Wuerzburg, Würzburg, Germany
| | - Fabian Kohm
- Department of Oto-Rhino-Laryngology, Plastic, Aesthetic and Reconstructive Head and Neck Surgery and the Comprehensive Hearing Center, University of Wuerzburg, Würzburg, Germany
| | - Lukas Jürgens
- Department of Oto-Rhino-Laryngology, Plastic, Aesthetic and Reconstructive Head and Neck Surgery and the Comprehensive Hearing Center, University of Wuerzburg, Würzburg, Germany
| | - Agmal Scherzad
- Department of Oto-Rhino-Laryngology, Plastic, Aesthetic and Reconstructive Head and Neck Surgery and the Comprehensive Hearing Center, University of Wuerzburg, Würzburg, Germany
| | - Philipp Schendzielorz
- Department of Oto-Rhino-Laryngology, Plastic, Aesthetic and Reconstructive Head and Neck Surgery and the Comprehensive Hearing Center, University of Wuerzburg, Würzburg, Germany
| | - Sebastian P Schraven
- Department of Oto-Rhino-Laryngology, Plastic, Aesthetic and Reconstructive Head and Neck Surgery and the Comprehensive Hearing Center, University of Wuerzburg, Würzburg, Germany
| | - Robert Mlynski
- Department of Otorhinolaryngology, Head and Neck Surgery "Otto Koerner", Rostock University Medical Center, Rostock, Germany
| | - Andreas Radeloff
- Department of Oto-Rhino-Laryngology, Head and Neck Surgery, University of Oldenburg, Oldenburg, Germany
| | - Rudolf Hagen
- Department of Oto-Rhino-Laryngology, Plastic, Aesthetic and Reconstructive Head and Neck Surgery and the Comprehensive Hearing Center, University of Wuerzburg, Würzburg, Germany
| | - Kristen Rak
- Department of Oto-Rhino-Laryngology, Plastic, Aesthetic and Reconstructive Head and Neck Surgery and the Comprehensive Hearing Center, University of Wuerzburg, Würzburg, Germany
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van de Velde DJ, Schiller NO, van Heuven VJ, Levelt CC, van Ginkel J, Beers M, Briaire JJ, Frijns JHM. The perception of emotion and focus prosody with varying acoustic cues in cochlear implant simulations with varying filter slopes. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2017; 141:3349. [PMID: 28599540 PMCID: PMC5436976 DOI: 10.1121/1.4982198] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Revised: 03/15/2017] [Accepted: 04/11/2017] [Indexed: 06/07/2023]
Abstract
This study aimed to find the optimal filter slope for cochlear implant simulations (vocoding) by testing the effect of a wide range of slopes on the discrimination of emotional and linguistic (focus) prosody, with varying availability of F0 and duration cues. Forty normally hearing participants judged if (non-)vocoded sentences were pronounced with happy or sad emotion, or with adjectival or nominal focus. Sentences were recorded as natural stimuli and manipulated to contain only emotion- or focus-relevant segmental duration or F0 information or both, and then noise-vocoded with 5, 20, 80, 120, and 160 dB/octave filter slopes. Performance increased with steeper slopes, but only up to 120 dB/octave, with bigger effects for emotion than for focus perception. For emotion, results with both cues most closely resembled results with F0, while for focus results with both cues most closely resembled those with duration, showing emotion perception relies primarily on F0, and focus perception on duration. This suggests that filter slopes affect focus perception less than emotion perception because for emotion, F0 is both more informative and more affected. The performance increase until extreme filter slope values suggests that much performance improvement in prosody perception is still to be gained for CI users.
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Affiliation(s)
- Daan J van de Velde
- Leiden University Centre for Linguistics, Leiden University, Van Wijkplaats 3, 2311 BX, Leiden, the Netherlands
| | - Niels O Schiller
- Leiden University Centre for Linguistics, Leiden University, Van Wijkplaats 3, 2311 BX, Leiden, the Netherlands
| | - Vincent J van Heuven
- Department of Applied Linguistics, Pannon Egyetem, 10 Egyetem Utca, 8200 Veszprém, Hungary
| | - Claartje C Levelt
- Leiden University Centre for Linguistics, Leiden University, Van Wijkplaats 3, 2311 BX, Leiden, the Netherlands
| | - Joost van Ginkel
- Leiden University Centre for Child and Family Studies, Wassenaarseweg 52, 2333 AK, Leiden, the Netherlands
| | - Mieke Beers
- Leiden University Medical Center, Ears, Nose, and Throat Department, Postbus 9600, 2300 RC, Leiden, the Netherlands
| | - Jeroen J Briaire
- Leiden University Medical Center, Ears, Nose, and Throat Department, Postbus 9600, 2300 RC, Leiden, the Netherlands
| | - Johan H M Frijns
- Leiden University Medical Center, Ears, Nose, and Throat Department, Postbus 9600, 2300 RC, Leiden, the Netherlands
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Scheperle RA. Suprathreshold compound action potential amplitude as a measure of auditory function in cochlear implant users. J Otol 2017; 12:18-28. [PMID: 29937833 PMCID: PMC6011805 DOI: 10.1016/j.joto.2017.01.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Revised: 01/02/2017] [Accepted: 01/04/2017] [Indexed: 10/28/2022] Open
Abstract
Electrically evoked compound action potential (eCAP) amplitudes elicited at suprathreshold levels were assessed as a measure of the effectiveness of cochlear implant (CI) stimulation. Twenty-one individuals participated; one was excluded due to facial stimulation during eCAP testing. For each participant, eCAPs were elicited with stimulation from seven electrodes near the upper limit of the individual's electrical dynamic range. A reduced-channel CI program was created using those same seven electrodes, and participants performed a vowel discrimination task. Consistent with previous reports, eCAP amplitudes varied across tested electrodes; the profiles were unique to each individual. In 6 subjects (30%), eCAP amplitude variability was partially explained by the impedance of the recording electrode. The remaining amplitude variability within subjects, and the variability observed across subjects could not be explained by recording electrode impedance. This implies that other underlying factors, such as variations in neural status across the array, are responsible. Across-site mean eCAP amplitude was significantly correlated with vowel discrimination scores (r2 = 0.56). A single eCAP amplitude measured from the middle of the array was also significantly correlated with vowel discrimination, but the correlation was weaker (r2 = 0.37), though not statistically different from the across-site mean. Normalizing each eCAP amplitude by its associated recording electrode impedance did not improve the correlation with vowel discrimination (r2 = 0.52). Further work is needed to assess whether combining eCAP amplitude with other measures of the electrode-neural interface and/or with more central measures of auditory function provides a more complete picture of auditory function in CI recipients.
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Gao X, Grayden DB, McDonnell MD. Modeling Electrode Place Discrimination in Cochlear Implant Stimulation. IEEE Trans Biomed Eng 2016; 64:2219-2229. [PMID: 27925583 DOI: 10.1109/tbme.2016.2634461] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
OBJECTIVE By modeling the cochlear implant (CI) electrode-to-nerve interface and quantifying electrode discriminability in the model, we address the questions of how many individual channels can be distinguished by CI recipients and the extent to which performance might be improved by inserting electrodes deeper into the cochlea. METHOD We adapt an artificial neural network to model electrode discrimination as well as a commonly used psychophysical measure (four-interval forced-choice) in CI stimulation and predict how well the locations of the stimulating electrodes can be inferred from simulated auditory nerve spiking patterns. RESULTS We show that a longer electrode leads to better electrode place discrimination in our model. For a simulated four-interval forced-choice procedure, correct classification rates significantly reduce with decreasing distance between the test electrodes and the reference electrodes, and higher correct classification rates may be achieved by the basal electrodes than apical electrodes. CONCLUSION Our results suggest that enhanced electrode discriminability results from a longer CI electrode array, and the locations where the errors occur along the electrode array are not only affected by the distance between electrodes but also the twirling angle between electrodes. SIGNIFICANCE Our models and simulations provide theoretical insights into several important clinically relevant problems that will inform future designs of CI electrode arrays and stimulation strategies.
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van Eijl RHM, Buitenhuis PJ, Stegeman I, Klis SFL, Grolman W. Systematic review of compound action potentials as predictors for cochlear implant performance. Laryngoscope 2016; 127:476-487. [PMID: 27804133 DOI: 10.1002/lary.26154] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Revised: 05/07/2016] [Accepted: 05/31/2016] [Indexed: 11/10/2022]
Abstract
OBJECTIVES/HYPOTHESIS The variability in speech perception between cochlear implant users is thought to result from the degeneration of the auditory nerve. Degeneration of the auditory nerve, histologically assessed, correlates with electrophysiologically acquired measures, such as electrically evoked compound action potentials (eCAPs) in experimental animals. To predict degeneration of the auditory nerve in humans, where histology is impossible, this paper reviews the correlation between speech perception and eCAP recordings in cochlear implant patients. DATA SOURCES PubMed and Embase. REVIEW METHODS We performed a systematic search for articles containing the following major themes: cochlear implants, evoked potentials, and speech perception. Two investigators independently conducted title-abstract screening, full-text screening, and critical appraisal. Data were extracted from the remaining articles. RESULTS Twenty-five of 1,429 identified articles described a correlation between speech perception and eCAP attributes. Due to study heterogeneity, a meta-analysis was not feasible, and studies were descriptively analyzed. Several studies investigating presence of the eCAP, recovery time constant, slope of the amplitude growth function, and spatial selectivity showed significant correlations with speech perception. In contrast, neural adaptation, eCAP threshold, and change with varying interphase gap did not significantly correlate with speech perception in any of the identified studies. CONCLUSIONS Significant correlations between speech perception and parameters obtained through eCAP recordings have been documented in literature; however, reporting was ambiguous. There is insufficient evidence for eCAPs as a predictive factor for speech perception. More research is needed to further investigate this relation. Laryngoscope, 2016 127:476-487, 2017.
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Affiliation(s)
- Ruben H M van Eijl
- Department of Otorhinolaryngology and Head & Neck Surgery, University Medical Center Utrecht, Utrecht, the Netherlands.,Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Patrick J Buitenhuis
- Department of Otorhinolaryngology and Head & Neck Surgery, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Inge Stegeman
- Department of Otorhinolaryngology and Head & Neck Surgery, University Medical Center Utrecht, Utrecht, the Netherlands.,Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Sjaak F L Klis
- Department of Otorhinolaryngology and Head & Neck Surgery, University Medical Center Utrecht, Utrecht, the Netherlands.,Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Wilko Grolman
- Department of Otorhinolaryngology and Head & Neck Surgery, University Medical Center Utrecht, Utrecht, the Netherlands.,Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, the Netherlands
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Zhou N. Monopolar Detection Thresholds Predict Spatial Selectivity of Neural Excitation in Cochlear Implants: Implications for Speech Recognition. PLoS One 2016; 11:e0165476. [PMID: 27798658 PMCID: PMC5087957 DOI: 10.1371/journal.pone.0165476] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Accepted: 10/12/2016] [Indexed: 12/12/2022] Open
Abstract
The objectives of the study were to (1) investigate the potential of using monopolar psychophysical detection thresholds for estimating spatial selectivity of neural excitation with cochlear implants and to (2) examine the effect of site removal on speech recognition based on the threshold measure. Detection thresholds were measured in Cochlear Nucleus® device users using monopolar stimulation for pulse trains that were of (a) low rate and long duration, (b) high rate and short duration, and (c) high rate and long duration. Spatial selectivity of neural excitation was estimated by a forward-masking paradigm, where the probe threshold elevation in the presence of a forward masker was measured as a function of masker-probe separation. The strength of the correlation between the monopolar thresholds and the slopes of the masking patterns systematically reduced as neural response of the threshold stimulus involved interpulse interactions (refractoriness and sub-threshold adaptation), and spike-rate adaptation. Detection threshold for the low-rate stimulus most strongly correlated with the spread of forward masking patterns and the correlation reduced for long and high rate pulse trains. The low-rate thresholds were then measured for all electrodes across the array for each subject. Subsequently, speech recognition was tested with experimental maps that deactivated five stimulation sites with the highest thresholds and five randomly chosen ones. Performance with deactivating the high-threshold sites was better than performance with the subjects' clinical map used every day with all electrodes active, in both quiet and background noise. Performance with random deactivation was on average poorer than that with the clinical map but the difference was not significant. These results suggested that the monopolar low-rate thresholds are related to the spatial neural excitation patterns in cochlear implant users and can be used to select sites for more optimal speech recognition performance.
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Affiliation(s)
- Ning Zhou
- Department of Communication Sciences and Disorders, East Carolina University, Greenville, NC, United States of America
- * E-mail:
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Guevara N, Hoen M, Truy E, Gallego S. A Cochlear Implant Performance Prognostic Test Based on Electrical Field Interactions Evaluated by eABR (Electrical Auditory Brainstem Responses). PLoS One 2016; 11:e0155008. [PMID: 27149268 PMCID: PMC4858145 DOI: 10.1371/journal.pone.0155008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Accepted: 04/22/2016] [Indexed: 11/18/2022] Open
Abstract
Background Cochlear implants (CIs) are neural prostheses that have been used routinely in the clinic over the past 25 years. They allow children who were born profoundly deaf, as well as adults affected by hearing loss for whom conventional hearing aids are insufficient, to attain a functional level of hearing. The “modern” CI (i.e., a multi-electrode implant using sequential coding strategies) has yielded good speech comprehension outcomes (recognition level for monosyllabic words about 50% to 60%, and sentence comprehension close to 90%). These good average results however hide a very important interindividual variability as scores in a given patients’ population often vary from 5 to 95% in comparable testing conditions. Our aim was to develop a prognostic model for patients with unilateral CI. A novel method of objectively measuring electrical and neuronal interactions using electrical auditory brainstem responses (eABRs) is proposed. Methods and Findings The method consists of two measurements: 1) eABR measurements with stimulation by a single electrode at 70% of the dynamic range (four electrodes distributed within the cochlea were tested), followed by a summation of these four eABRs; 2) Measurement of a single eABR with stimulation from all four electrodes at 70% of the dynamic range. A comparison of the eABRs obtained by these two measurements, defined as the monaural interaction component (MIC), indicated electrical and neural interactions between the stimulation channels. Speech recognition performance without lip reading was measured for each patient using a logatome test (64 "vowel-consonant-vowel"; VCV; by forced choice of 1 out of 16). eABRs were measured in 16 CI patients (CIs with 20 electrodes, Digisonic SP; Oticon Medical ®, Vallauris, France). Significant correlations were found between speech recognition performance and the ratio of the amplitude of the V wave of the eABRs obtained with the two measurements (Pearson's linear regression model, parametric correlation: r2 = 0.26, p<0.05). Conclusions This prognostic model allowed a substantial amount of the interindividual variance in speech recognition scores to be explained. The present study used measurements of electrical and neuronal interactions by eABR to assess patients' bio-electric capacity to use multiple information channels supplied by the implant. This type of prognostic information may be valuable in several ways. On the patient level, it allows customizing of individual treatments. ClinicalTrials.gov Identifier: NCT01805167
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Affiliation(s)
- Nicolas Guevara
- University Head and Neck Institute, CHU de Nice, 31 Avenue de Valombrose, 06107 Nice cedex 2, France
| | - Michel Hoen
- Oticon Medical, Clinical and Scientific Research Department, 2720 chemin St Bernard, 06220 Vallauris, France
| | - Eric Truy
- Department of Audiology and Otorhinolaryngology, Edouard Herriot Hospital, 5 Place d'Arsonval, 69437 Lyon, France
| | - Stéphane Gallego
- Institute for Readaptation Sciences and Techniques, 8 Avenue Rockefeller, 69373 Lyon Cedex 08, France
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Wu CC, Luo X. Excitation Patterns of Standard and Steered Partial Tripolar Stimuli in Cochlear Implants. J Assoc Res Otolaryngol 2015; 17:145-58. [PMID: 26691160 DOI: 10.1007/s10162-015-0549-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2015] [Accepted: 11/25/2015] [Indexed: 11/25/2022] Open
Abstract
Current steering in partial tripolar (pTP) mode has been shown to improve pitch perception and spectral resolution with cochlear implants (CIs). In this mode, a fraction (σ) of the main electrode current is returned within the cochlea and steered between the basal and apical flanking electrodes (with a proportion of α and 1 - α, respectively). Pitch generally decreases when α increases from 0 to 1, although the salience of pitch change varies across CI users. This study aimed to identify the mechanism of pitch changes with pTP-mode current steering and the factors contributing to the intersubject variability in pitch-ranking sensitivity. The electrical fields were measured for steered pTP stimuli on the same main electrode with α = 0, 0.5, and 1 in five implanted ears using electrical field imaging (EFI). The related excitation patterns were also measured physiologically using evoked compound action potential (ECAP) and psychophysically using psychophysical forward masking (PFM). Consistent with the pitch-ranking results in this study, the EFI, ECAP, and PFM centroids shifted apically with increasing α. An apical shift was also observed for the PFM peak but not for the EFI or ECAP peak. The pattern width was similar with different α values within a given measure (e.g., EFI, ECAP, or PFM), but the ECAP patterns were broader than the EFI and PFM patterns, possibly because ECAP was measured with smaller σ values than EFI and PFM. The amount of pattern shift with α depended on σ (i.e., the total amount of current used for steering) but was not correlated with the pitch-ranking sensitivity across subjects. The results revealed that the pitch changes elicited by pTP-mode current steering were not only driven by the shifts of excitation centroid.
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Affiliation(s)
- Ching-Chih Wu
- Department of Speech, Language, and Hearing Sciences, Purdue University, 715 Clinic Drive, West Lafayette, IN, 47907, USA
- School of Electrical and Computer Engineering, Purdue University, 715 Clinic Drive, West Lafayette, IN, 47907, USA
| | - Xin Luo
- Department of Speech, Language, and Hearing Sciences, Purdue University, 715 Clinic Drive, West Lafayette, IN, 47907, USA.
- Department of Speech and Hearing Science, Arizona State University, Coor Hall, 975 S. Myrtle Av., P. O. Box 870102, Tempe, AZ, 85287, USA.
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Thin-film micro-electrode stimulation of the cochlea in rats exposed to aminoglycoside induced hearing loss. Hear Res 2015; 331:13-26. [PMID: 26471198 DOI: 10.1016/j.heares.2015.10.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Revised: 09/30/2015] [Accepted: 10/07/2015] [Indexed: 11/22/2022]
Abstract
The multi-channel cochlear implant (CI) provides sound and speech perception to thousands of individuals who would otherwise be deaf. Broad activation of auditory nerve fibres when using a CI results in poor frequency discrimination. The CI also provides users with poor amplitude perception due to elicitation of a narrow dynamic range. Provision of more discrete frequency perception and a greater control over amplitude may allow users to better distinguish speech in noise and to segregate sound sources. In this research, thin-film (TF) high density micro-electrode arrays and conventional platinum ring electrode arrays were used to stimulate the cochlea of rats administered sensorineural hearing loss (SNHL) via ototoxic insult, with neural responses taken at 434 multiunit clusters in the central nucleus of the inferior colliculus (CIC). Threshold, dynamic range and broadness of response were used to compare electrode arrays. A stronger current was required to elicit CIC threshold when using the TF array compared to the platinum ring electrode array. TF stimulation also elicited a narrower dynamic range than the PR counterpart. However, monopolar stimulation using the TF array produced more localised CIC responses than other stimulation strategies. These results suggest that individuals with SNHL could benefit from micro stimulation of the cochlea using a monopolar configuration which may provide discrete frequency perception when using TF electrode arrays.
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George SS, Shivdasani MN, Wise AK, Shepherd RK, Fallon JB. Electrophysiological channel interactions using focused multipolar stimulation for cochlear implants. J Neural Eng 2015; 12:066005. [DOI: 10.1088/1741-2560/12/6/066005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Malherbe T, Hanekom T, Hanekom J. The effect of the resistive properties of bone on neural excitation and electric fields in cochlear implant models. Hear Res 2015; 327:126-35. [DOI: 10.1016/j.heares.2015.06.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Revised: 05/18/2015] [Accepted: 06/02/2015] [Indexed: 11/16/2022]
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Scheperle RA, Abbas PJ. Relationships Among Peripheral and Central Electrophysiological Measures of Spatial and Spectral Selectivity and Speech Perception in Cochlear Implant Users. Ear Hear 2015; 36:441-53. [PMID: 25658746 PMCID: PMC4478147 DOI: 10.1097/aud.0000000000000144] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVES The ability to perceive speech is related to the listener's ability to differentiate among frequencies (i.e., spectral resolution). Cochlear implant (CI) users exhibit variable speech-perception and spectral-resolution abilities, which can be attributed in part to the extent of electrode interactions at the periphery (i.e., spatial selectivity). However, electrophysiological measures of peripheral spatial selectivity have not been found to correlate with speech perception. The purpose of this study was to evaluate auditory processing at the periphery and cortex using both simple and spectrally complex stimuli to better understand the stages of neural processing underlying speech perception. The hypotheses were that (1) by more completely characterizing peripheral excitation patterns than in previous studies, significant correlations with measures of spectral selectivity and speech perception would be observed, (2) adding information about processing at a level central to the auditory nerve would account for additional variability in speech perception, and (3) responses elicited with spectrally complex stimuli would be more strongly correlated with speech perception than responses elicited with spectrally simple stimuli. DESIGN Eleven adult CI users participated. Three experimental processor programs (MAPs) were created to vary the likelihood of electrode interactions within each participant. For each MAP, a subset of 7 of 22 intracochlear electrodes was activated: adjacent (MAP 1), every other (MAP 2), or every third (MAP 3). Peripheral spatial selectivity was assessed using the electrically evoked compound action potential (ECAP) to obtain channel-interaction functions for all activated electrodes (13 functions total). Central processing was assessed by eliciting the auditory change complex with both spatial (electrode pairs) and spectral (rippled noise) stimulus changes. Speech-perception measures included vowel discrimination and the Bamford-Kowal-Bench Speech-in-Noise test. Spatial and spectral selectivity and speech perception were expected to be poorest with MAP 1 (closest electrode spacing) and best with MAP 3 (widest electrode spacing). Relationships among the electrophysiological and speech-perception measures were evaluated using mixed-model and simple linear regression analyses. RESULTS All electrophysiological measures were significantly correlated with each other and with speech scores for the mixed-model analysis, which takes into account multiple measures per person (i.e., experimental MAPs). The ECAP measures were the best predictor. In the simple linear regression analysis on MAP 3 data, only the cortical measures were significantly correlated with speech scores; spectral auditory change complex amplitude was the strongest predictor. CONCLUSIONS The results suggest that both peripheral and central electrophysiological measures of spatial and spectral selectivity provide valuable information about speech perception. Clinically, it is often desirable to optimize performance for individual CI users. These results suggest that ECAP measures may be most useful for within-subject applications when multiple measures are performed to make decisions about processor options. They also suggest that if the goal is to compare performance across individuals based on a single measure, then processing central to the auditory nerve (specifically, cortical measures of discriminability) should be considered.
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Affiliation(s)
- Rachel A. Scheperle
- Department of Communication Sciences and Disorders, University of Iowa, Iowa
City, IA, USA
| | - Paul J. Abbas
- Department of Communication Sciences and Disorders, University of Iowa, Iowa
City, IA, USA
- Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, IA,
USA
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Abstract
OBJECTIVES The primary goal of this study was to describe relationships between peripheral and central electrophysiologic measures of auditory processing within individual cochlear implant (CI) users. The distinctiveness of neural excitation patterns resulting from the stimulation of different electrodes, referred to as 'spatial selectivity,' was evaluated. The hypothesis was that if central representations of spatial interactions differed across participants semi-independently of peripheral input, then the within-subject relationships between peripheral and central electrophysiologic measures of spatial selectivity would reflect those differences. Cross-subject differences attributable to processing central to the auditory nerve may help explain why peripheral electrophysiologic measures of spatial selectivity have not been found to correlate with speech perception. DESIGN Eleven adults participated in this and a companion study. All were peri- or post-lingually deafened with more than 1 year of CI experience. Peripheral spatial selectivity was evaluated at 13 cochlear locations using 13 electrodes as probes to elicit electrically evoked compound action potentials (ECAPs). Masker electrodes were varied across the array for each probe electrode to derive channel-interaction functions. The same 13 electrodes were used to evaluate spatial selectivity represented at a cortical level. Electrode pairs were stimulated sequentially to elicit the auditory change complex (ACC), an obligatory cortical potential suggestive of discrimination. For each participant, the relationship between ECAP channel-interaction functions (quantified as channel-separation indices) and ACC N1-P2 amplitudes was modeled using the saturating exponential function y = a * (1-e). Both a and b coefficients were varied using a least-squares approach to optimize the fits. RESULTS Electrophysiologic measures of spatial selectivity assessed at peripheral (ECAP) and central (ACC) levels varied across participants. The results indicate that differences in ACC amplitudes observed across participants for the same stimulus conditions were not solely the result of differences in peripheral excitation patterns. This finding supports the view that processing at multiple points along the auditory neural pathway from the periphery to the cortex may vary across individuals with different etiologies and auditory experiences. CONCLUSIONS The distinctiveness of neural excitation resulting from electrical stimulation varies across CI recipients, and this variability was observed in both peripheral and cortical electrophysiologic measures. The ACC amplitude differences observed across participants were partially independent from differences in peripheral neural spatial selectivity. These findings are clinically relevant because they imply that there may be limits (1) to the predictive ability of peripheral measures and (2) in the extent to which improving the selectivity of electrical stimulation via programming options (e.g., current focusing/steering) will result in more specific central neural excitation patterns or will improve speech perception.
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Affiliation(s)
- Rachel A. Scheperle
- Department of Communication Sciences and Disorders, University of Iowa, Iowa City, IA, USA
| | - Paul J. Abbas
- Department of Communication Sciences and Disorders, University of Iowa, Iowa City, IA, USA
- Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, IA, USA
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Abbas PJ, Brown CJ. Assessment of responses to cochlear implant stimulation at different levels of the auditory pathway. Hear Res 2014; 322:67-76. [PMID: 25445817 DOI: 10.1016/j.heares.2014.10.011] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Revised: 09/22/2014] [Accepted: 10/21/2014] [Indexed: 11/30/2022]
Abstract
This paper reviews characteristics of both the electrically evoked compound action potential (ECAP) and analogous measures of cortically evoked responses (CAEP) to electrical stimulation in cochlear implant users. Specific comparisons are made between the two levels of processing for measures of threshold, growth of responses with increasing stimulus level, changes in stimulation electrode and, finally, in temporal response properties. The results are interpreted in a context that ECAPs primarily reflect the characteristics of the electrode-neural interface for an individual ear. CAEPs clearly are dependent on those peripheral responses but also reflect differences in central processing among individual implant users. The potential applicability of combined measures in clinical situations is discussed. This article is part of a Special Issue entitled <Lasker Award>.
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Affiliation(s)
- Paul J Abbas
- Department of Communication Sciences and Disorders, Department of Otolaryngology, Head and Neck Surgery, University of Iowa, Iowa City, I A, USA.
| | - Carolyn J Brown
- Department of Communication Sciences and Disorders, Department of Otolaryngology, Head and Neck Surgery, University of Iowa, Iowa City, I A, USA
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Won JH, Humphrey EL, Yeager KR, Martinez AA, Robinson CH, Mills KE, Johnstone PM, Moon IJ, Woo J. Relationship among the physiologic channel interactions, spectral-ripple discrimination, and vowel identification in cochlear implant users. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2014; 136:2714-25. [PMID: 25373971 DOI: 10.1121/1.4895702] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The hypothesis of this study was that broader patterns of physiological channel interactions in the local region of the cochlea are associated with poorer spectral resolution in the same region. Electrically evoked compound action potentials (ECAPs) were measured for three to six probe electrodes per subject to examine the channel interactions in different regions across the electrode array. To evaluate spectral resolution at a confined location within the cochlea, spectral-ripple discrimination (SRD) was measured using narrowband ripple stimuli with the bandwidth spanning five electrodes: Two electrodes apical and basal to the ECAP probe electrode. The relationship between the physiological channel interactions, spectral resolution in the local cochlear region, and vowel identification was evaluated. Results showed that (1) there was within- and across-subject variability in the widths of ECAP channel interaction functions and in narrowband SRD performance, (2) significant correlations were found between the widths of the ECAP functions and narrowband SRD thresholds, and between mean bandwidths of ECAP functions averaged across multiple probe electrodes and broadband SRD performance across subjects, and (3) the global spectral resolution reflecting the entire electrode array, not the local region, predicts vowel identification.
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Affiliation(s)
- Jong Ho Won
- University of Tennessee Health Science Center, Knoxville, Tennessee 37996
| | | | - Kelly R Yeager
- University of Tennessee Health Science Center, Knoxville, Tennessee 37996
| | - Alexis A Martinez
- University of Tennessee Health Science Center, Knoxville, Tennessee 37996
| | - Camryn H Robinson
- University of Tennessee Health Science Center, Knoxville, Tennessee 37996
| | - Kristen E Mills
- University of Tennessee Health Science Center, Knoxville, Tennessee 37996
| | - Patti M Johnstone
- University of Tennessee Health Science Center, Knoxville, Tennessee 37996
| | - Il Joon Moon
- Department of Otorhinolaryngology-Head and Neck Surgery, Samsung Medical Center, School of Medicine, Sungkyunkwan University, Seoul, 135-710, South Korea
| | - Jihwan Woo
- Department of Biomedical Engineering, University of Ulsan, Ulsan, 680-749, South Korea
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Zeng FG, Rebscher SJ, Fu QJ, Chen H, Sun X, Yin L, Ping L, Feng H, Yang S, Gong S, Yang B, Kang HY, Gao N, Chi F. Development and evaluation of the Nurotron 26-electrode cochlear implant system. Hear Res 2014; 322:188-99. [PMID: 25281795 DOI: 10.1016/j.heares.2014.09.013] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Revised: 08/18/2014] [Accepted: 09/03/2014] [Indexed: 11/29/2022]
Abstract
Although the cochlear implant has been widely acknowledged as the most successful neural prosthesis, only a fraction of hearing-impaired people who can potentially benefit from a cochlear implant have actually received one due to its limited awareness, accessibility, and affordability. To help overcome these limitations, a 26-electrode cochlear implant has been developed to receive China's Food and Drug Administration (CFDA) approval in 2011 and Conformité Européenne (CE) Marking in 2012. The present article describes design philosophy, system specification, and technical verification of the Nurotron device, which includes advanced digital signal processing and 4 current sources with multiple amplitude resolutions that not only are compatible with perceptual capability but also allow interleaved or simultaneous stimulation. The article also presents 3-year longitudinal evaluation data from 60 human subjects who have received the Nurotron device. The objective measures show that electrode impedance decreased within the first month of device use, but was stable until a slight increase at the end of two years. The subjective loudness measures show that electric stimulation threshold was stable while the maximal comfort level increased over the 3 years. Mandarin sentence recognition increased from the pre-surgical 0%-correct score to a plateau of about 80% correct with 6-month use of the device. Both indirect and direct comparisons indicate indistinguishable performance differences between the Nurotron system and other commercially available devices. The present 26-electrode cochlear implant has already helped to lower the price of cochlear implantation in China and will likely contribute to increased cochlear implant access and success in the rest of the world. This article is part of a Special Issue entitled <Lasker Award>.
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Affiliation(s)
- Fan-Gang Zeng
- Center for Hearing Research, University of California, Irvine, CA 92697, USA.
| | - Stephen J Rebscher
- Department of Otolaryngology - Head and Neck Surgery, University of California, San Francisco, CA 94143, USA
| | - Qian-Jie Fu
- Department of Otolaryngology - Head and Neck Surgery, University of California, Los Angeles, CA 90095, USA
| | - Hongbin Chen
- Nurotron Biotechnology Inc., Hangzhou, Zhejiang 310011, China
| | - Xiaoan Sun
- Nurotron Biotechnology Inc., Hangzhou, Zhejiang 310011, China
| | - Li Yin
- Nurotron Biotechnology Inc., Hangzhou, Zhejiang 310011, China
| | - Lichuan Ping
- Nurotron Biotechnology Inc., Hangzhou, Zhejiang 310011, China
| | - Haihong Feng
- Shanghai Acoustics Laboratory, Institute of Acoustics, Chinese Academy of Sciences, Shanghai 200032, China
| | - Shiming Yang
- Department of Otolaryngology - Head and Neck Surgery, Chinese PLA General Hospital, Beijing 100853, China
| | - Shusheng Gong
- Department of Otolaryngology - Head and Neck Surgery, Beijing Tongren Hospital of Capital Medical University, Beijing 100730, China
| | - Beibei Yang
- Department of Otolaryngology - Head and Neck Surgery, The Second Affiliated Hospital of Zhejiang University, Hangzhou 310000, China
| | - Hou-Yong Kang
- Department of Otolaryngology - Head and Neck Surgery, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, China
| | - Na Gao
- Department of Otolaryngology - Head and Neck Surgery, The Eye and ENT Hospital of Fudan University, Shanghai 200031, China
| | - Fanglu Chi
- Department of Otolaryngology - Head and Neck Surgery, The Eye and ENT Hospital of Fudan University, Shanghai 200031, China.
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Wu CC, Luo X. Electrode spanning with partial tripolar stimulation mode in cochlear implants. J Assoc Res Otolaryngol 2014; 15:1023-36. [PMID: 24865767 DOI: 10.1007/s10162-014-0464-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Accepted: 05/07/2014] [Indexed: 11/26/2022] Open
Abstract
The perceptual effects of electrode spanning (i.e., the use of nonadjacent return electrodes) in partial tripolar (pTP) mode were tested on a main electrode EL8 in five cochlear implant (CI) users. Current focusing was controlled by σ (the ratio of current returned within the cochlea), and current steering was controlled by α (the ratio of current returned to the basal electrode). Experiment 1 tested whether asymmetric spanning with α = 0.5 can create additional channels around standard pTP stimuli. It was found that in general, apical spanning (i.e., returning current to EL6 rather than EL7) elicited a pitch between those of standard pTP stimuli on main electrodes EL8 and EL9, while basal spanning (i.e., returning current to EL10 rather than EL9) elicited a pitch between those of standard pTP stimuli on main electrodes EL7 and EL8. The pitch increase caused by apical spanning was more salient than the pitch decrease caused by basal spanning. To replace the standard pTP channel on the main electrode EL8 when EL7 or EL9 is defective, experiment 2 tested asymmetrically spanned pTP stimuli with various α, and experiment 3 tested symmetrically spanned pTP stimuli with various σ. The results showed that pitch increased with decreasing α in asymmetric spanning, or with increasing σ in symmetric spanning. Apical spanning with α around 0.69 and basal spanning with α around 0.38 may both elicit a similar pitch as the standard pTP stimulus. With the same σ, the symmetrically spanned pTP stimulus was higher in pitch than the standard pTP stimulus. A smaller σ was thus required for symmetric spanning to match the pitch of the standard pTP stimulus. In summary, electrode spanning is an effective field-shaping technique that is useful for adding spectral channels and handling defective electrodes with CIs.
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Affiliation(s)
- Ching-Chih Wu
- School of Electrical and Computer Engineering, Purdue University, 500 Oval Drive, West Lafayette, IN, 47907, USA,
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Zeng FG, Tang Q, Lu T. Abnormal pitch perception produced by cochlear implant stimulation. PLoS One 2014; 9:e88662. [PMID: 24551131 PMCID: PMC3923805 DOI: 10.1371/journal.pone.0088662] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Accepted: 01/14/2014] [Indexed: 11/19/2022] Open
Abstract
Contemporary cochlear implants with multiple electrode stimulation can produce good speech perception but poor music perception. Hindered by the lack of a gold standard to quantify electric pitch, relatively little is known about the nature and extent of the electric pitch abnormalities and their impact on cochlear implant performance. Here we overcame this obstacle by comparing acoustic and electric pitch perception in 3 unilateral cochlear-implant subjects who had functionally usable acoustic hearing throughout the audiometric frequency range in the non-implant ear. First, to establish a baseline, we measured and found slightly impaired pure tone frequency discrimination and nearly perfect melody recognition in all 3 subjects' acoustic ear. Second, using pure tones in the acoustic ear to match electric pitch induced by an intra-cochlear electrode, we found that the frequency-electrode function was not only 1-2 octaves lower, but also 2 times more compressed in frequency range than the normal cochlear frequency-place function. Third, we derived frequency difference limens in electric pitch and found that the equivalent electric frequency discrimination was 24 times worse than normal-hearing controls. These 3 abnormalities are likely a result of a combination of broad electric field, distant intra-cochlear electrode placement, and non-uniform spiral ganglion cell distribution and survival, all of which are inherent to the electrode-nerve interface in contemporary cochlear implants. Previous studies emphasized on the "mean" shape of the frequency-electrode function, but the present study indicates that the large "variance" of this function, reflecting poor electric pitch discriminability, is the main factor limiting contemporary cochlear implant performance.
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Affiliation(s)
- Fan-Gang Zeng
- Center for Hearing Research, Departments of Anatomy and Neurobiology, Biomedical Engineering, Cognitive Sciences, and Otolaryngology – Head and Neck Surgery, University of California Irvine, Irvine, California, United States of America
- * E-mail:
| | - Qing Tang
- Center for Hearing Research, Departments of Anatomy and Neurobiology, Biomedical Engineering, Cognitive Sciences, and Otolaryngology – Head and Neck Surgery, University of California Irvine, Irvine, California, United States of America
| | - Thomas Lu
- Center for Hearing Research, Departments of Anatomy and Neurobiology, Biomedical Engineering, Cognitive Sciences, and Otolaryngology – Head and Neck Surgery, University of California Irvine, Irvine, California, United States of America
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Limb CJ, Roy AT. Technological, biological, and acoustical constraints to music perception in cochlear implant users. Hear Res 2014; 308:13-26. [DOI: 10.1016/j.heares.2013.04.009] [Citation(s) in RCA: 138] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/17/2013] [Revised: 04/04/2013] [Accepted: 04/22/2013] [Indexed: 11/30/2022]
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Lin P, Lu T, Zeng FG. Central masking with bilateral cochlear implants. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2013; 133:962-969. [PMID: 23363113 PMCID: PMC3574098 DOI: 10.1121/1.4773262] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Revised: 11/29/2012] [Accepted: 12/03/2012] [Indexed: 06/01/2023]
Abstract
Across bilateral cochlear implants, contralateral threshold shift has been investigated as a function of electrode difference between the masking and probe electrodes. For contralateral electric masking, maximum threshold elevations occurred when the position of the masker and probe electrode was approximately place-matched across ears. The amount of masking diminished with increasing masker-probe electrode separation. Place-dependent masking occurred in both sequentially implanted ears, and was not affected by the masker intensity or the time delay from the masker onset. When compared to previous contralateral masking results in normal hearing, the similarities between place-dependent central masking patterns suggest comparable mechanisms of overlapping excitation in the central auditory nervous system.
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Affiliation(s)
- Payton Lin
- Department of Biomedical Engineering, University of California, Irvine, California 92617, USA.
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