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Callejón-Leblic MA, Lazo-Maestre M, Fratter A, Ropero-Romero F, Sánchez-Gómez S, Reina-Tosina J. A full-head model to investigate intra and extracochlear electric fields in cochlear implant stimulation. Phys Med Biol 2024; 69:155010. [PMID: 38925131 DOI: 10.1088/1361-6560/ad5c38] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Accepted: 06/26/2024] [Indexed: 06/28/2024]
Abstract
Objective.Despite the widespread use and technical improvement of cochlear implant (CI) devices over past decades, further research into the bioelectric bases of CI stimulation is still needed. Various stimulation modes implemented by different CI manufacturers coexist, but their true clinical benefit remains unclear, probably due to the high inter-subject variability reported, which makes the prediction of CI outcomes and the optimal fitting of stimulation parameters challenging. A highly detailed full-head model that includes a cochlea and an electrode array is developed in this study to emulate intracochlear voltages and extracochlear current pathways through the head in CI stimulation.Approach.Simulations based on the finite element method were conducted under monopolar, bipolar, tripolar (TP), and partial TP modes, as well as for apical, medial, and basal electrodes. Variables simulated included: intracochlear voltages, electric field (EF) decay, electric potentials at the scalp and extracochlear currents through the head. To better understand CI side effects such as facial nerve stimulation, caused by spurious current leakage out from the cochlea, special emphasis is given to the analysis of the EF over the facial nerve.Main results.The model reasonably predicts EF magnitudes and trends previously reported in CI users. New relevant extracochlear current pathways through the head and brain tissues have been identified. Simulated results also show differences in the magnitude and distribution of the EF through different segments of the facial nerve upon different stimulation modes and electrodes, dependent on nerve and bone tissue conductivities.Significance.Full-head models prove useful tools to model intra and extracochlear EFs in CI stimulation. Our findings could prove useful in the design of future experimental studies to contrast FNS mechanisms upon stimulation of different electrodes and CI modes. The full-head model developed is freely available for the CI community for further research and use.
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Affiliation(s)
- M A Callejón-Leblic
- Otorhinolaryngology Department, Virgen Macarena University Hospital, Seville 41009, Spain
- Oticon Medical, 28108 Madrid, Spain
- Dept. Signal Theory and Communications, Biomedical Engineering Group, University of Seville, Seville 41092, Spain
| | - M Lazo-Maestre
- Otorhinolaryngology Department, Virgen Macarena University Hospital, Seville 41009, Spain
| | - A Fratter
- Oticon Medical, 06220 Vallauris, France
| | - F Ropero-Romero
- Otorhinolaryngology Department, Virgen Macarena University Hospital, Seville 41009, Spain
| | - S Sánchez-Gómez
- Otorhinolaryngology Department, Virgen Macarena University Hospital, Seville 41009, Spain
| | - J Reina-Tosina
- Dept. Signal Theory and Communications, Biomedical Engineering Group, University of Seville, Seville 41092, Spain
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2
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Steinhardt CR, Mitchell DE, Cullen KE, Fridman GY. Pulsatile electrical stimulation creates predictable, correctable disruptions in neural firing. Nat Commun 2024; 15:5861. [PMID: 38997274 PMCID: PMC11245474 DOI: 10.1038/s41467-024-49900-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Accepted: 06/21/2024] [Indexed: 07/14/2024] Open
Abstract
Electrical stimulation is a key tool in neuroscience, both in brain mapping studies and in many therapeutic applications such as cochlear, vestibular, and retinal neural implants. Due to safety considerations, stimulation is restricted to short biphasic pulses. Despite decades of research and development, neural implants lead to varying restoration of function in patients. In this study, we use computational modeling to provide an explanation for how pulsatile stimulation affects axonal channels and therefore leads to variability in restoration of neural responses. The phenomenological explanation is transformed into equations that predict induced firing rate as a function of pulse rate, pulse amplitude, and spontaneous firing rate. We show that these equations predict simulated responses to pulsatile stimulation with a variety of parameters as well as several features of experimentally recorded primate vestibular afferent responses to pulsatile stimulation. We then discuss the implications of these effects for improving clinical stimulation paradigms and electrical stimulation-based experiments.
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Affiliation(s)
- Cynthia R Steinhardt
- Department of Biomedical Engineering, Johns Hopkins School of Medicine, Baltimore, MD, USA.
- Center for Theoretical Neuroscience, Columbia University, New York, NY, USA.
| | - Diana E Mitchell
- Department of Biomedical Engineering, Johns Hopkins School of Medicine, Baltimore, MD, USA
- Department of Neurosciences, Faculty of Medicine, University of Montreal, Montreal, QC, Canada
| | - Kathleen E Cullen
- Department of Biomedical Engineering, Johns Hopkins School of Medicine, Baltimore, MD, USA
- Department of Otolaryngology, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Gene Y Fridman
- Department of Biomedical Engineering, Johns Hopkins School of Medicine, Baltimore, MD, USA
- Department of Otolaryngology, Johns Hopkins School of Medicine, Baltimore, MD, USA
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Sriperumbudur KK, Appali R, Gummer AW, van Rienen U. Understanding the impact of modiolus porosity on stimulation of spiral ganglion neurons by cochlear implants. Sci Rep 2024; 14:9593. [PMID: 38671022 PMCID: PMC11053021 DOI: 10.1038/s41598-024-59347-2] [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: 09/29/2023] [Accepted: 04/09/2024] [Indexed: 04/28/2024] Open
Abstract
Moderate-to-profound sensorineural hearing loss in humans is treatable by electrically stimulating the auditory nerve (AN) with a cochlear implant (CI). In the cochlea, the modiolus presents a porous bony interface between the CI electrode and the AN. New bone growth caused by the presence of the CI electrode or neural degeneration inflicted by ageing or otological diseases might change the effective porosity of the modiolus and, thereby, alter its electrical material properties. Using a volume conductor description of the cochlea, with the aid of a 'mapped conductivity' method and an ad-hoc 'regionally kinetic' equation system, we show that even a slight variation in modiolus porosity or pore distribution can disproportionately affect AN stimulation. Hence, because of porosity changes, an inconsistent CI performance might occur if neural degeneration or new bone growth progress after implantation. Appropriate electrical material properties in accordance with modiolar morphology and pathology should be considered in patient-specific studies. The present first-of-its-kind in-silico study advocates for contextual experimental studies to further explore the utility of modiolus porous morphology in optimising the CI outcome.
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Affiliation(s)
- Kiran K Sriperumbudur
- Institute of General Electrical Engineering, University of Rostock, Rostock, Germany.
- Research and Development, MED-EL Medical Electronics GmbH, Innsbruck, Austria.
| | - Revathi Appali
- Institute of General Electrical Engineering, University of Rostock, Rostock, Germany
- Ageing of Individuals and Society, Interdisciplinary Faculty, University of Rostock, Rostock, Germany
| | - Anthony W Gummer
- Department of Otolaryngology, University of Tübingen, Tübingen, Germany.
- Department of Otolaryngology, University of Melbourne, Melbourne, Australia.
| | - Ursula van Rienen
- Institute of General Electrical Engineering, University of Rostock, Rostock, Germany
- Ageing of Individuals and Society, Interdisciplinary Faculty, University of Rostock, Rostock, Germany
- Life, Light and Matter, Interdisciplinary Faculty, University of Rostock, Rostock, Germany
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4
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Hrncirik F, Roberts I, Sevgili I, Swords C, Bance M. Models of Cochlea Used in Cochlear Implant Research: A Review. Ann Biomed Eng 2023; 51:1390-1407. [PMID: 37087541 PMCID: PMC10264527 DOI: 10.1007/s10439-023-03192-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 03/20/2023] [Indexed: 04/24/2023]
Abstract
As the first clinically translated machine-neural interface, cochlear implants (CI) have demonstrated much success in providing hearing to those with severe to profound hearing loss. Despite their clinical effectiveness, key drawbacks such as hearing damage, partly from insertion forces that arise during implantation, and current spread, which limits focussing ability, prevent wider CI eligibility. In this review, we provide an overview of the anatomical and physical properties of the cochlea as a resource to aid the development of accurate models to improve future CI treatments. We highlight the advancements in the development of various physical, animal, tissue engineering, and computational models of the cochlea and the need for such models, challenges in their use, and a perspective on their future directions.
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Affiliation(s)
- Filip Hrncirik
- Cambridge Hearing Group, Cambridge, UK.
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, CB2 0QQ, UK.
| | - Iwan Roberts
- Cambridge Hearing Group, Cambridge, UK
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, CB2 0QQ, UK
| | - Ilkem Sevgili
- Cambridge Hearing Group, Cambridge, UK
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, CB2 0QQ, UK
| | - Chloe Swords
- Cambridge Hearing Group, Cambridge, UK
- Department of Physiology, Development and Neurosciences, University of Cambridge, Cambridge, CB2 3DY, UK
| | - Manohar Bance
- Cambridge Hearing Group, Cambridge, UK
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, CB2 0QQ, UK
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Herrmann DP, Kalkman RK, Frijns JHM, Bahmer A. Intra-cochlear differences in the spread of excitation between biphasic and triphasic pulse stimulation in cochlear implants: A modeling and experimental study. Hear Res 2023; 432:108752. [PMID: 37019060 DOI: 10.1016/j.heares.2023.108752] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2022] [Revised: 03/21/2023] [Accepted: 03/27/2023] [Indexed: 03/30/2023]
Abstract
Triphasic pulse stimulation can prevent unpleasant facial nerve stimulation in cochlear implant users. Using electromyographic measurements on facial nerve effector muscles, previous studies have shown that biphasic and triphasic pulse stimulations produce different input-output functions. However, little is known about the intracochlear effects of triphasic stimulation and how these may contribute to the amelioration of facial nerve stimulation. The present study used a computational model of implanted human cochleae to investigate the effect of pulse shape on the intracochlear spread of excitation. Biphasic and triphasic pulse stimulations were simulated from three different cochlear implant electrode contact positions. To validate the model results, experimental spread of excitation measurements were conducted with biphasic and triphasic pulse stimulation from three different electrode contact positions in 13 cochlear implant users. The model results depict differences between biphasic and triphasic pulse stimulations depending on the position of the stimulating electrode contact. While biphasic and triphasic pulse stimulations from a medial or basal electrode contact caused similar extents of neural excitation, differences between the pulse shapes were observed when the stimulating contact was located in the cochlear apex. In contrast, the experimental results showed no difference between the biphasic and triphasic initiated spread of excitation for any of the tested contact positions. The model was also used to study responses of neurons without peripheral processes to mimic the effect of neural degeneration. For all three contact positions, simulated degeneration shifted the neural responses towards the apex. Biphasic pulse stimulation showed a stronger response with neural degeneration compared to without degeneration, while triphasic pulse stimulation showed no difference. As previous measurements have demonstrated an ameliorative effect of triphasic pulse stimulation on facial nerve stimulation from medial electrode contact positions, the results imply that a complementary effect located at the facial nerve level must be responsible for reducing facial nerve stimulation.
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Affiliation(s)
- David P Herrmann
- Department of Otorhinolaryngology, Plastic, Aesthetic and Reconstructive Head and Neck Surgery and the Comprehensive Hearing Center, University Hospital Würzburg, Josef-Schneider-Str. 11, Würzburg 97080, Germany.
| | - Randy K Kalkman
- Department of Otorhinolaryngology and Head & Neck Surgery, Leiden University Medical Centre, PO Box 9600, RC Leiden 2300, the Netherlands
| | - Johan H M Frijns
- Department of Otorhinolaryngology and Head & Neck Surgery, Leiden University Medical Centre, PO Box 9600, RC Leiden 2300, the Netherlands; Leiden Institute for Brain and Cognition, PO Box 9600, RC Leiden 2300, the Netherlands
| | - Andreas Bahmer
- Department of Otorhinolaryngology, Plastic, Aesthetic and Reconstructive Head and Neck Surgery and the Comprehensive Hearing Center, University Hospital Würzburg, Josef-Schneider-Str. 11, Würzburg 97080, Germany
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6
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van Groesen NRA, Briaire JJ, de Jong MAM, Frijns JHM. Dynamic Current Focusing Compared to Monopolar Stimulation in a Take-Home Trial of Cochlear Implant Users. Ear Hear 2023; 44:306-317. [PMID: 36279119 DOI: 10.1097/aud.0000000000001282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
OBJECTIVES This study compared the performance of a dynamic partial tripolar cochlear implant speech encoding strategy termed dynamic current focusing (DCF) to monopolar stimulation (MP) using spectro-temporal, temporal, and speech-in-noise recognition testing. DESIGN DCF is a strategy that utilizes tripolar or high partial tripolar stimulation at threshold level and increases loudness by slowly widening current spread towards most comfortable level. Thirteen cochlear implant users were fitted with DCF and a non-steered MP matched on pulse rate, pulse width, and active electrodes. Nine participants completed the single-blinded within-subject crossover trial. Repeated testing consisted of four sessions. Strategies were allocated in a DCF-MP-DCF-MP or MP-DCF-MP-DCF design. Three-week adaptation periods ended with a test session in which speech-in-noise recognition (matrix speech-in-noise sentence test), spectro-temporal ripple tests (SMRT and STRIPES) and a temporal amplitude modulation detection test were conducted. All participants recorded their subjective experiences with both strategies using the Speech, Spatial and Qualities of Hearing Scale questionnaire. RESULTS Participants' SMRT thresholds improved 0.40 ripples per octave ( p = 0.02, Bonferroni-corrected: p = 0.1) with DCF over MP at 65 dB SPL. No significant differences between the strategies were found on speech-in-noise recognition at conversational (65 dB SPL) and soft (45 dB SPL) loudness levels, temporal testing, STRIPES, or the SMRT at 45 dB SPL. After Bonferroni correction, a learning effect remained on the matrix speech-in-noise sentence test at both loudness levels (65 dB SPL: p = 0.01; 45 dB SPL: p = 0.02). There was no difference in learning effects over time between DCF and MP. Similarly, no significant differences were found in subjective experience on the Speech, Spatial and Qualities of Hearing Scale questionnaire. DCF reduced average battery life by 48% (5.1 hours) ( p < 0.001) compared to MP. CONCLUSIONS DCF may improve spectral resolution over MP at comfortable loudness (65 dB SPL) in cochlear implant users. However, the evidence collected in this study was weak and the significant result disappeared after Bonferroni correction. Also, not all spectral tests revealed this improvement. As expected, battery life was reduced for DCF. Although the current study is limited by its small sample size, considering previous studies, DCF does not consistently improve speech recognition in noise over MP strategies.
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Affiliation(s)
| | - Jeroen Johannes Briaire
- Otorhinolaryngology and Head and Neck Surgery, Leiden University Medical Center, Leiden, the Netherlands
| | - Monique Anna Maria de Jong
- Otorhinolaryngology and Head and Neck Surgery, Leiden University Medical Center, Leiden, the Netherlands
| | - Johannes Hubertus Maria Frijns
- Otorhinolaryngology and Head and Neck Surgery, Leiden University Medical Center, Leiden, the Netherlands
- Leiden Institute for Brain and Cognition, Leiden, the Netherlands
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7
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Ren LJ, Yu Y, Zhang YH, Liu XD, Sun ZJ, Yao WJ, Zhang TY, Wang C, Li CL. Three-dimensional finite element analysis on cochlear implantation electrode insertion. Biomech Model Mechanobiol 2022; 22:467-478. [PMID: 36513945 DOI: 10.1007/s10237-022-01657-3] [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: 09/20/2022] [Accepted: 11/19/2022] [Indexed: 12/14/2022]
Abstract
Studying the insertion process of cochlear implant (CI) electrode array (EA) is important to ensure successful, sufficient, and safe implantation. A three-dimensional finite element (FE) model was developed to simulate the insertion process. The cochlear structures were reconstructed from an average statistical shape model (SSM) of human cochlea. The electrode is simplified as a long and tapered beam of homogeneous elastic materials, contacting and interacting with the stiff cochlear structures. A quasi-static insertion simulation was conducted, the insertion force and the contact pressure between the electrode and the cochlear wall, were calculated to evaluate the smoothness of insertion and the risk of potential cochlear trauma. Based on this model, different EA designs were analyzed, including the Young's modulus, the straight or bended shape, the normal or a more tapped section size. The influence of the insertion angle was also discussed. Our simulations indicate that reducing the EA Young's modulus, tapering and pre-bending are effective ways to ensure safe and successful EA implantation. This model is beneficial for optimizing EA designs and is potentially useful for designing patient-specific CI surgery.
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Affiliation(s)
- Liu-Jie Ren
- Department of Facial Plastic Reconstructive Surgery, ENT Institute, Eye and ENT Hospital, NHC Key Laboratory of Hearing Medicine (Fudan University), Shanghai, 200031, China
| | - Yi Yu
- School of Medical Instrumentation, Shanghai University of Medicine and Health Sciences, Shanghai, 201318, China
| | - Yu-Heng Zhang
- Shanghai Engineering Research Center of Cochlear Implants, Shanghai, 201318, China
| | - Xin-Dong Liu
- Shanghai Engineering Research Center of Cochlear Implants, Shanghai, 201318, China
| | - Zeng-Jun Sun
- Shanghai Engineering Research Center of Cochlear Implants, Shanghai, 201318, China
| | - Wen-Juan Yao
- School of Mechanics and Engineering Science, Shanghai Institute of Applied Mathematics and Mechanics, Shanghai University, Shanghai, 200444, China
| | - Tian-Yu Zhang
- Department of Facial Plastic Reconstructive Surgery, ENT Institute, Eye and ENT Hospital, NHC Key Laboratory of Hearing Medicine (Fudan University), Shanghai, 200031, China
| | - Cheng Wang
- Shanghai Engineering Research Center of Cochlear Implants, Shanghai, 201318, China.
| | - Chen-Long Li
- Department of Facial Plastic Reconstructive Surgery, ENT Institute, Eye and ENT Hospital, NHC Key Laboratory of Hearing Medicine (Fudan University), Shanghai, 200031, China.
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8
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Recent Advances in Cochlear Implant Electrode Array Design Parameters. MICROMACHINES 2022; 13:mi13071081. [PMID: 35888898 PMCID: PMC9323156 DOI: 10.3390/mi13071081] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Revised: 06/29/2022] [Accepted: 06/30/2022] [Indexed: 02/04/2023]
Abstract
Cochlear implants are neural implant devices that aim to restore hearing in patients with severe sensorineural hearing impairment. Here, the main goal is to successfully place the electrode array in the cochlea to stimulate the auditory nerves through bypassing damaged hair cells. Several electrode and electrode array parameters affect the success of this technique, but, undoubtedly, the most important one is related to electrodes, which are used for nerve stimulation. In this paper, we provide a comprehensive resource on the electrodes currently being used in cochlear implant devices. Electrode materials, shape, and the effect of spacing between electrodes on the stimulation, stiffness, and flexibility of electrode-carrying arrays are discussed. The use of sensors and the electrical, mechanical, and electrochemical properties of electrode arrays are examined. A large library of preferred electrodes is reviewed, and recent progress in electrode design parameters is analyzed. Finally, the limitations and challenges of the current technology are discussed along with a proposal of future directions in the field.
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9
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Abstract
OBJECTIVES Postimplantation facial nerve stimulation is a common side-effect of intracochlear electrical stimulation. Facial nerve stimulation occurs when electric current intended to stimulate the auditory nerve, spread beyond the cochlea to excite the nearby facial nerve, causing involuntarily facial muscle contractions. Facial nerve stimulation can often be resolved through adjustments in speech processor fitting but, in some instances, these measures exhibit limited benefit or may have a detrimental effect on speech perception. In this study, apical reference stimulation mode was investigated as a potential intervention to facial nerve stimulation. Apical reference stimulation is a bipolar stimulation strategy in which the most apical electrode is used as the reference electrode for stimulation on all the other intracochlear electrodes. DESIGN A person-specific model of the human cochlea, facial nerve and electrode array, coupled with a neural model, was used to predict excitation of auditory and facial nerve fibers. These predictions were used to evaluate the effectiveness in reducing facial nerve stimulation using apical reference stimulation. Predictions were confirmed in psychoacoustic tests by determining auditory comfort and threshold levels for the apical reference stimulation mode while capturing electromyography data in two participants. RESULTS Models predicted a favorable outcome for apical reference stimulation, as facial nerve fiber thresholds were higher and auditory thresholds were lower, in direct comparison to conventional monopolar stimulation. Psychophysical tests also illustrated decreased auditory thresholds and increased dynamic range during apical reference stimulation. Furthermore, apical reference stimulation resulted in lower electromyography energy levels, compared to conventional monopolar stimulation, which suggests a reduction in facial nerve stimulation. Subjective feedback corroborated that apical reference stimulation alleviated facial nerve stimulation. CONCLUSION Apical reference stimulation may be a viable strategy to alleviate facial nerve stimulation considering the improvements in dynamic range and auditory thresholds, complemented with a reduction in facial nerve stimulation symptoms.
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10
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Kalkman RK, Briaire JJ, Dekker DMT, Frijns JHM. The relation between polarity sensitivity and neural degeneration in a computational model of cochlear implant stimulation. Hear Res 2021; 415:108413. [PMID: 34952734 DOI: 10.1016/j.heares.2021.108413] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 11/19/2021] [Accepted: 12/06/2021] [Indexed: 12/22/2022]
Abstract
The main aim of this computational modelling study was to test the validity of the hypothesis that sensitivity to the polarity of cochlear implant stimulation can be interpreted as a measure of neural health. For this purpose, the effects of stimulus polarity on neural excitation patterns were investigated in a volume conduction model of the implanted human cochlea, which was coupled with a deterministic active nerve fibre model based on characteristics of human auditory neurons. The nerve fibres were modelled in three stages of neural degeneration: intact, with shortened peripheral terminal nodes and with complete loss of the peripheral processes. The model simulated neural responses to monophasic, biphasic, triphasic and pseudomonophasic pulses of both polarities. Polarity sensitivity was quantified as the so-called polarity effect (PE), which is defined as the dB difference between cathodic and anodic thresholds. Results showed that anodic pulses mostly excited the auditory neurons in their central axons, while cathodic stimuli generally excited neurons in their peripheral processes or near their cell bodies. As a consequence, cathodic thresholds were more affected by neural degeneration than anodic thresholds. Neural degeneration did not have a consistent effect on the modelled PE values, though there were notable effects of electrode contact insertion angle and distance from the modiolus. Furthermore, determining PE values using charge-balanced multiphasic pulses as approximations of monophasic stimuli produced different results than those obtained with true monophasic pulses, at a degree that depended on the specific pulse shape; in general, pulses with lower secondary phase amplitudes showed polarity sensitivities closer to those obtained with true monophasic pulses. The main conclusion of this study is that polarity sensitivity is not a reliable indicator of neural health; neural degeneration affects simulated polarity sensitivity, but its effect is not consistently related to the degree of degeneration. Polarity sensitivity is not simply a product of the state of the neurons, but also depends on spatial factors.
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Affiliation(s)
- Randy K Kalkman
- ENT-department, Leiden University Medical Centre, PO box 9600, 2300, RC, Leiden, the Netherlands
| | - Jeroen J Briaire
- ENT-department, Leiden University Medical Centre, PO box 9600, 2300, RC, Leiden, the Netherlands; Leiden Institute for Brain and Cognition, PO box 9600, 2300, RC, Leiden, the Netherlands
| | - David M T Dekker
- ENT-department, Leiden University Medical Centre, PO box 9600, 2300, RC, Leiden, the Netherlands
| | - Johan H M Frijns
- ENT-department, Leiden University Medical Centre, PO box 9600, 2300, RC, Leiden, the Netherlands; Leiden Institute for Brain and Cognition, PO box 9600, 2300, RC, Leiden, the Netherlands
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11
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Carlyon RP, Goehring T. Cochlear Implant Research and Development in the Twenty-first Century: A Critical Update. J Assoc Res Otolaryngol 2021; 22:481-508. [PMID: 34432222 PMCID: PMC8476711 DOI: 10.1007/s10162-021-00811-5] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Accepted: 08/02/2021] [Indexed: 12/22/2022] Open
Abstract
Cochlear implants (CIs) are the world's most successful sensory prosthesis and have been the subject of intense research and development in recent decades. We critically review the progress in CI research, and its success in improving patient outcomes, from the turn of the century to the present day. The review focuses on the processing, stimulation, and audiological methods that have been used to try to improve speech perception by human CI listeners, and on fundamental new insights in the response of the auditory system to electrical stimulation. The introduction of directional microphones and of new noise reduction and pre-processing algorithms has produced robust and sometimes substantial improvements. Novel speech-processing algorithms, the use of current-focusing methods, and individualised (patient-by-patient) deactivation of subsets of electrodes have produced more modest improvements. We argue that incremental advances have and will continue to be made, that collectively these may substantially improve patient outcomes, but that the modest size of each individual advance will require greater attention to experimental design and power. We also briefly discuss the potential and limitations of promising technologies that are currently being developed in animal models, and suggest strategies for researchers to collectively maximise the potential of CIs to improve hearing in a wide range of listening situations.
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Affiliation(s)
- Robert P Carlyon
- Cambridge Hearing Group, MRC Cognition & Brain Sciences Unit, University of Cambridge, Cambridge, CB2 7EF, UK.
| | - Tobias Goehring
- Cambridge Hearing Group, MRC Cognition & Brain Sciences Unit, University of Cambridge, Cambridge, CB2 7EF, UK
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12
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Recugnat M, Undurraga JA, McAlpine D. Spike-rate adaptation in a computational model of human-shaped spiral ganglion neurons. IEEE Trans Biomed Eng 2021; 69:602-612. [PMID: 34347592 DOI: 10.1109/tbme.2021.3102129] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
OBJECTIVES The purpose of this study is to develop a biophysical model of human spiral ganglion neurons (SGNs) that includes voltage-gated hyperpolarization-activated cation (HCN) channels and low-threshold potassium voltage-gated, delayed-rectifier low-threshold potassium (KLT) channels, providing for a more complete simulation of spike-rate adaptation, a feature of most spiking neurons in which spiking activity is reduced in response to sustained stimulation. METHODS Our model incorporates features of spike-rate adaptation reported from in vivo studies, whilst also displaying similar behaviour to existing models of human SGNs, including the dependence of electrically evoked thresholds on the polarity of electrical pulses. RESULTS Hypothesizing that the mode of stimulation intracellular or extracellular predicts features of spike-rate adaptation similar to in vivo studies, including the influence of stimulus intensity and pulse-rate, we find that the mode of stimulation alters features of spike-rate adaptation. In particular, the reduction in spiking over time with sustained input was generally greater for extracellular, compared to intracellular, stimulation, when simulating a multi-compartment SGN with human morphological features. In contrast, time-constants of spike-rate adaption reported for in vivo data did not fit our predicted responses, highlighting the need for a more complete physiological understanding of the factors contributing to spike-rate adaptation in electrically stimulated human SGNs. CONCLUSION Our model extends previous computational models of SGNs with human morphology with ionic channels accounting for features of spike-rate adaptation. SIGNIFICANCE The significance of this work resides in the ability to improve the modeling of cochlear implant (CI) stimulation and its effects on neural responses. This will help develop novel, and perhaps personalised, stimulation strategies to reduce variability in CI user outcomes.
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Beauchamp MS, Oswalt D, Sun P, Foster BL, Magnotti JF, Niketeghad S, Pouratian N, Bosking WH, Yoshor D. Dynamic Stimulation of Visual Cortex Produces Form Vision in Sighted and Blind Humans. Cell 2021; 181:774-783.e5. [PMID: 32413298 DOI: 10.1016/j.cell.2020.04.033] [Citation(s) in RCA: 103] [Impact Index Per Article: 34.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 09/27/2019] [Accepted: 04/17/2020] [Indexed: 11/28/2022]
Abstract
A visual cortical prosthesis (VCP) has long been proposed as a strategy for restoring useful vision to the blind, under the assumption that visual percepts of small spots of light produced with electrical stimulation of visual cortex (phosphenes) will combine into coherent percepts of visual forms, like pixels on a video screen. We tested an alternative strategy in which shapes were traced on the surface of visual cortex by stimulating electrodes in dynamic sequence. In both sighted and blind participants, dynamic stimulation enabled accurate recognition of letter shapes predicted by the brain's spatial map of the visual world. Forms were presented and recognized rapidly by blind participants, up to 86 forms per minute. These findings demonstrate that a brain prosthetic can produce coherent percepts of visual forms.
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Affiliation(s)
- Michael S Beauchamp
- Department of Neurosurgery, Baylor College of Medicine, Houston, TX 77030, USA
| | - Denise Oswalt
- Department of Neurosurgery, Baylor College of Medicine, Houston, TX 77030, USA
| | - Ping Sun
- Department of Neurosurgery, Baylor College of Medicine, Houston, TX 77030, USA
| | - Brett L Foster
- Department of Neurosurgery, Baylor College of Medicine, Houston, TX 77030, USA
| | - John F Magnotti
- Department of Neurosurgery, Baylor College of Medicine, Houston, TX 77030, USA
| | - Soroush Niketeghad
- Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Nader Pouratian
- Department of Neurosurgery, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - William H Bosking
- Department of Neurosurgery, Baylor College of Medicine, Houston, TX 77030, USA
| | - Daniel Yoshor
- Department of Neurosurgery, Baylor College of Medicine, Houston, TX 77030, USA.
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Neural Tissue Degeneration in Rosenthal's Canal and Its Impact on Electrical Stimulation of the Auditory Nerve by Cochlear Implants: An Image-Based Modeling Study. Int J Mol Sci 2020; 21:ijms21228511. [PMID: 33198187 PMCID: PMC7697226 DOI: 10.3390/ijms21228511] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 11/06/2020] [Accepted: 11/09/2020] [Indexed: 11/24/2022] Open
Abstract
Sensorineural deafness is caused by the loss of peripheral neural input to the auditory nerve, which may result from peripheral neural degeneration and/or a loss of inner hair cells. Provided spiral ganglion cells and their central processes are patent, cochlear implants can be used to electrically stimulate the auditory nerve to facilitate hearing in the deaf or severely hard-of-hearing. Neural degeneration is a crucial impediment to the functional success of a cochlear implant. The present, first-of-its-kind two-dimensional finite-element model investigates how the depletion of neural tissues might alter the electrically induced transmembrane potential of spiral ganglion neurons. The study suggests that even as little as 10% of neural tissue degeneration could lead to a disproportionate change in the stimulation profile of the auditory nerve. This result implies that apart from encapsulation layer formation around the cochlear implant electrode, tissue degeneration could also be an essential reason for the apparent inconsistencies in the functionality of cochlear implants.
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Badenhorst W, Hanekom T, Gross L, Hanekom JJ. Facial nerve stimulation in a post-meningitic cochlear implant user: using computational modelling as a tool to probe mechanisms and progression of complications on a case-by-case basis. Cochlear Implants Int 2020; 22:68-79. [PMID: 32993463 DOI: 10.1080/14670100.2020.1824431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Facial nerve stimulation (FNS) is a side-effect of cochlear implantation that can result in severe discomfort for the user and essentially limits the optimal use of the implant. Three-dimensional cochlear implant modelling research has led to the progression from generic models to user-specific models with one of the intentions to develop model-based diagnostic tools. The objective of this study is to investigate the mechanisms that underlie the manifestation of FNS in the post-meningitic cochleae of a specific CI user through computational modelling. Bilateral models were created using a method previously developed for the construction of a three-dimensional user-specific volume conduction model of the cochlea and was expanded to include the facial nerve geometry. Reduced temporal bone density based on bone densitometry, cochlear duct ossification and degenerate auditory neural fibres were incorporated into a comprehensive FNS model. Auditory and facial nerve thresholds were predicted with the models showing good correspondence to perceptual thresholds and the user's FNS experience. Ossified cochlear ducts appear to aggravate the increase in thresholds caused by the otic capsule's decreased resistivity. This translational case study demonstrates the application of computational modelling as a clinical instrument in the assessment and management of complications with cochlear implantation.
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Affiliation(s)
- Werner Badenhorst
- Bioengineering, Department of Electrical, Electronic and Computer Engineering, University of Pretoria, Pretoria, South Africa
| | - Tania Hanekom
- Bioengineering, Department of Electrical, Electronic and Computer Engineering, University of Pretoria, Pretoria, South Africa
| | - Liezl Gross
- Bioengineering, Department of Electrical, Electronic and Computer Engineering, University of Pretoria, Pretoria, South Africa
| | - Johan J Hanekom
- Bioengineering, Department of Electrical, Electronic and Computer Engineering, University of Pretoria, Pretoria, South Africa
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Strauss I, Valle G, Artoni F, D'Anna E, Granata G, Di Iorio R, Guiraud D, Stieglitz T, Rossini PM, Raspopovic S, Petrini FM, Micera S. Characterization of multi-channel intraneural stimulation in transradial amputees. Sci Rep 2019; 9:19258. [PMID: 31848384 PMCID: PMC6917705 DOI: 10.1038/s41598-019-55591-z] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Accepted: 11/20/2019] [Indexed: 11/29/2022] Open
Abstract
Although peripheral nerve stimulation using intraneural electrodes has been shown to be an effective and reliable solution to restore sensory feedback after hand loss, there have been no reports on the characterization of multi-channel stimulation. A deeper understanding of how the simultaneous stimulation of multiple electrode channels affects the evoked sensations should help in improving the definition of encoding strategies for bidirectional prostheses. We characterized the sensations evoked by simultaneous stimulation of median and ulnar nerves (multi-channel configuration) in four transradial amputees who had been implanted with four TIMEs (Transverse Intrafascicular Multichannel Electrodes). The results were compared with the characterization of single-channel stimulation. The sensations were characterized in terms of location, extent, type, and intensity. Combining two or more single-channel configurations caused a linear combination of the sensation locations and types perceived with such single-channel stimulations. Interestingly, this was also true when two active sites from the same nerve were stimulated. When stimulating in multi-channel configuration, the charge needed from each electrode channel to evoke a sensation was significantly lower than the one needed in single-channel configuration (sensory facilitation). This result was also supported by electroencephalography (EEG) recordings during nerve stimulation. Somatosensory potentials evoked by multi-channel stimulation confirmed that sensations in the amputated hand were perceived by the subjects and that a perceptual sensory facilitation occurred. Our results should help the future development of more efficient bidirectional prostheses by providing guidelines for the development of more complex stimulation approaches to effectively restore multiple sensations at the same time.
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Affiliation(s)
- I Strauss
- Center for Neuroscience, Neurotechnology, and Bioelectronic Medicine and The BioRobotics Institute, Scuola Superiore Sant'Anna, Pisa, Italy
- Bertarelli Foundation Chair in Translational Neuroengineering, Centre for Neuroprosthetics and Institute of Bioengineering, School of Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
- Department of Excellence in Robotics & AI, Scuola Superiore Sant'Anna, Pisa, Italy
| | - G Valle
- Center for Neuroscience, Neurotechnology, and Bioelectronic Medicine and The BioRobotics Institute, Scuola Superiore Sant'Anna, Pisa, Italy
- Bertarelli Foundation Chair in Translational Neuroengineering, Centre for Neuroprosthetics and Institute of Bioengineering, School of Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
- Department of Excellence in Robotics & AI, Scuola Superiore Sant'Anna, Pisa, Italy
| | - F Artoni
- Bertarelli Foundation Chair in Translational Neuroengineering, Centre for Neuroprosthetics and Institute of Bioengineering, School of Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - E D'Anna
- Bertarelli Foundation Chair in Translational Neuroengineering, Centre for Neuroprosthetics and Institute of Bioengineering, School of Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - G Granata
- Fondazione Policlinico Agostino Gemelli-IRCCS, Roma, Italy
| | - R Di Iorio
- Institute of Neurology, Catholic University of The Sacred Heart, Policlinic A. Gemelli Foundation, Roma, Italy
| | - D Guiraud
- University of Montpellier, INRIA, CAMIN team, 860 Rue St Priest, 34090, Montpellier, France
| | - T Stieglitz
- Laboratory for Biomedical Microtechnology, Department of Microsystems Engineering-IMTEK, Bernstein Center, BrainLinks-BrainTools Cluster of Excellence, University of Freiburg, Freiburg, D-79110, Germany
| | - P M Rossini
- Fondazione Policlinico Agostino Gemelli-IRCCS, Roma, Italy
- Institute of Neurology, Catholic University of The Sacred Heart, Policlinic A. Gemelli Foundation, Roma, Italy
| | - S Raspopovic
- Laboratory for Neuroengineering, Department of Health Sciences and Technology, Institute for Robotics and Intelligent Systems, ETH Zürich (ETH), Zürich, 8092, Switzerland
| | - F M Petrini
- Bertarelli Foundation Chair in Translational Neuroengineering, Centre for Neuroprosthetics and Institute of Bioengineering, School of Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
- Laboratory for Neuroengineering, Department of Health Sciences and Technology, Institute for Robotics and Intelligent Systems, ETH Zürich (ETH), Zürich, 8092, Switzerland.
| | - S Micera
- Center for Neuroscience, Neurotechnology, and Bioelectronic Medicine and The BioRobotics Institute, Scuola Superiore Sant'Anna, Pisa, Italy.
- Bertarelli Foundation Chair in Translational Neuroengineering, Centre for Neuroprosthetics and Institute of Bioengineering, School of Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
- Department of Excellence in Robotics & AI, Scuola Superiore Sant'Anna, Pisa, Italy.
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van Gendt MJ, Briaire JJ, Frijns JHM. Effect of neural adaptation and degeneration on pulse-train ECAPs: A model study. Hear Res 2019; 377:167-178. [PMID: 30947041 DOI: 10.1016/j.heares.2019.03.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Revised: 01/13/2019] [Accepted: 03/13/2019] [Indexed: 01/17/2023]
Abstract
Electrically evoked compound action potentials (eCAPs) are measurements of the auditory nerve's response to electrical stimulation. ECAP amplitudes during pulse trains can exhibit temporal alternations. The magnitude of this alternation tends to diminish over time during the stimulus. How this pattern relates to the temporal behavior of nerve fibers is not known. We hypothesized that the stochasticity, refractoriness, adaptation of the threshold and spike-times influence pulse-train eCAP responses. Thirty thousand auditory nerve fibers were modeled in a three-dimensional cochlear model incorporating pulse-shape effects, pulse-history effects, and stochasticity in the individual neural responses. ECAPs in response to pulse trains of different rates and amplitudes were modeled for fibers with different stochastic properties (by variation of the relative spread) and different temporal properties (by variation of the refractory periods, adaptation and latency). The model predicts alternation of peak amplitudes similar to available human data. In addition, the peak alternation was affected by changing the refractoriness, adaptation, and relative spread of auditory nerve fibers. As these parameters are related to factors such as the duration of deafness and neural survival, this study suggests that the eCAP pattern in response to pulse trains could be used to assess the underlying temporal and stochastic behavior of the auditory nerve. As these properties affect the nerve's response to pulse trains, they are of uttermost importance to sound perception with cochlear implants.
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Affiliation(s)
- M J van Gendt
- ENT-Department, Leiden University Medical Centre, PO Box 9600, 2300, RC Leiden, the Netherlands.
| | - J J Briaire
- ENT-Department, Leiden University Medical Centre, PO Box 9600, 2300, RC Leiden, the Netherlands
| | - J H M Frijns
- ENT-Department, Leiden University Medical Centre, PO Box 9600, 2300, RC Leiden, the Netherlands; Leiden Institute for Brain and Cognition, PO Box 9600, 2300, RC Leiden, the Netherlands
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18
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Schafer F, Enke J, Bohnke F, Hemmert W, Bai S. Influence of the Cochlear Implant Electrode Array Placement on the Current Spread in the Cochlea. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2018; 2018:6145-6148. [PMID: 30441737 DOI: 10.1109/embc.2018.8513666] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Three-dimensional (3D) computational models of the inner ear have been utilised to assist in investigating the factors that influence cochlear implant (CI) outcomes. A volume conductor cochlear model with an implanted electrode array was reconstructed from X-ray microtomography $(\mu$ CT) scans of a cadaveric human temporal bone. To mimic an in-vivo setting, the cochlea was embedded in a head model. The finite element (FE) method was used to analyse the electrical potential $\varphi$ in the cochlear nerve as a result of CI stimulation. In order to study the influence of electrode array placement on the current spread within the cochlea and the modiolus, computer simulations with six electrode array placements were conducted. $\varphi$ was evaluated at the tip of nerve fibres reconstructed within the cochlear nerve so as to predict the stimulation of a neuron population. It was found in most cases that a medial electrode array placement produced a narrower $\varphi$ peak at the fibre tip than a lateral one, although the differences were small.
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van den Boogert T, van Hoof M, Handschuh S, Glueckert R, Guinand N, Guyot JP, Kingma H, Perez-Fornos A, Seppen B, Johnson Chacko L, Schrott-Fischer A, van de Berg R. Optimization of 3D-Visualization of Micro-Anatomical Structures of the Human Inner Ear in Osmium Tetroxide Contrast Enhanced Micro-CT Scans. Front Neuroanat 2018; 12:41. [PMID: 29872380 PMCID: PMC5972190 DOI: 10.3389/fnana.2018.00041] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Accepted: 04/27/2018] [Indexed: 11/30/2022] Open
Abstract
Introduction: Knowledge of the neuro-anatomical architecture of the inner ear contributes to the improvement and development of cochlear and vestibular implants. The present knowledge is mainly based on two-dimensional images (histology) or derived models that simplify the complexity of this architecture. This study investigated the feasibility of visualizing relevant neuro-anatomical structures of the inner ear in a dynamic three-dimensional reproduction, using a combination of staining, micro-CT imaging and an image processing algorithm. Methods: Four fresh cadaveric temporal bones were postfixed with osmium tetroxide (OsO4) and decalcified with EDTA. Micro-CT was used for scanning at 10 μm (4 scans) and 5.5 μm (1 scan) voxel resolution. A new image processing algorithm was developed and the scans were visualized in open source software. Results: OsO4 enhanced the contrast in all scans and the visualization was substantially improved by the image processing algorithm. The three-dimensional renderings provided detailed visualization of the whole inner ear. Details were visible up to the size of individual neurons, nerve crossings and the specific neuro-anatomical structures such as the tunnel of Corti. Conclusion: The combination of OsO4, micro-CT and the proposed image processing algorithm provides an accurate and detailed visualization of the three-dimensional micro-anatomy of the human inner ear.
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Affiliation(s)
- Thomas van den Boogert
- Division of Balance Disorders, Department of Otorhinolaryngology, Head, and Neck Surgery, Faculty of Health Medicine and Life Sciences, School for Mental Health and Neuroscience, Maastricht University Medical Centre, Maastricht, Netherlands
| | - Marc van Hoof
- Division of Balance Disorders, Department of Otorhinolaryngology, Head, and Neck Surgery, Faculty of Health Medicine and Life Sciences, School for Mental Health and Neuroscience, Maastricht University Medical Centre, Maastricht, Netherlands
| | - Stephan Handschuh
- VetCore Facility for Research, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Rudolf Glueckert
- Department of Otorhinolaryngology, Medical University Innsbruck, Innsbruck, Austria
| | - Nils Guinand
- Department of Clinical Neurosciences, Service of Otorhinolaryngology, Head, and Neck Surgery, Geneva University Hospitals, Geneva, Switzerland
| | - Jean-Philippe Guyot
- Department of Clinical Neurosciences, Service of Otorhinolaryngology, Head, and Neck Surgery, Geneva University Hospitals, Geneva, Switzerland
| | - Herman Kingma
- Division of Balance Disorders, Department of Otorhinolaryngology, Head, and Neck Surgery, Faculty of Health Medicine and Life Sciences, School for Mental Health and Neuroscience, Maastricht University Medical Centre, Maastricht, Netherlands
- Vestibular Laboratory, Faculty of Physics, Tomsk State National Research University, Tomsk, Russia
| | - Angelica Perez-Fornos
- Department of Clinical Neurosciences, Service of Otorhinolaryngology, Head, and Neck Surgery, Geneva University Hospitals, Geneva, Switzerland
| | - Bart Seppen
- Division of Balance Disorders, Department of Otorhinolaryngology, Head, and Neck Surgery, Faculty of Health Medicine and Life Sciences, School for Mental Health and Neuroscience, Maastricht University Medical Centre, Maastricht, Netherlands
| | - Lejo Johnson Chacko
- Department of Otorhinolaryngology, Medical University Innsbruck, Innsbruck, Austria
| | | | - Raymond van de Berg
- Division of Balance Disorders, Department of Otorhinolaryngology, Head, and Neck Surgery, Faculty of Health Medicine and Life Sciences, School for Mental Health and Neuroscience, Maastricht University Medical Centre, Maastricht, Netherlands
- Vestibular Laboratory, Faculty of Physics, Tomsk State National Research University, Tomsk, Russia
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Badenhorst W, Hanekom T, Hanekom JJ. Analysis of a purely conductance-based stochastic nerve fibre model as applied to compound models of populations of human auditory nerve fibres used in cochlear implant simulations. BIOLOGICAL CYBERNETICS 2017; 111:439-458. [PMID: 29063191 DOI: 10.1007/s00422-017-0736-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Accepted: 10/07/2017] [Indexed: 06/07/2023]
Abstract
The study presents the application of a purely conductance-based stochastic nerve fibre model to human auditory nerve fibres within finite element volume conduction models of a semi-generic head and user-specific cochleae. The stochastic, threshold and temporal characteristics of the human model are compared and successfully validated against physiological feline results with the application of a mono-polar, bi-phasic, cathodic first stimulus. Stochastic characteristics validated include: (i) the log(Relative Spread) versus log(fibre diameter) distribution for the discharge probability versus stimulus intensity plots and (ii) the required exponential membrane noise versus transmembrane voltage distribution. Intra-user, and to a lesser degree inter-user, comparisons are made with respect to threshold and dynamic range at short and long pulse widths for full versus degenerate single fibres as well as for populations of degenerate fibres of a single user having distributed and aligned somas with varying and equal diameters. Temporal characteristics validated through application of different stimulus pulse rates and different stimulus intensities include: (i) discharge rate, latency and latency standard deviation versus stimulus intensity, (ii) period histograms and (iii) interspike interval histograms. Although the stochastic population model does not reduce the modelled single deterministic fibre threshold, the simulated stochastic and temporal characteristics show that it could be used in future studies to model user-specific temporally encoded information, which influences the speech perception of CI users.
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Affiliation(s)
- Werner Badenhorst
- Department of Electrical, Electronic and Computer Engineering, University of Pretoria, Lynnwood Road, Pretoria, 0002, South Africa.
| | - Tania Hanekom
- Department of Electrical, Electronic and Computer Engineering, University of Pretoria, Lynnwood Road, Pretoria, 0002, South Africa
| | - Johan J Hanekom
- Department of Electrical, Electronic and Computer Engineering, University of Pretoria, Lynnwood Road, Pretoria, 0002, South Africa
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Nogueira W, Schurzig D, Büchner A, Penninger RT, Würfel W. Validation of a Cochlear Implant Patient-Specific Model of the Voltage Distribution in a Clinical Setting. Front Bioeng Biotechnol 2016; 4:84. [PMID: 27933290 PMCID: PMC5120131 DOI: 10.3389/fbioe.2016.00084] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Accepted: 10/14/2016] [Indexed: 11/13/2022] Open
Abstract
Cochlear Implants (CIs) are medical implantable devices that can restore the sense of hearing in people with profound hearing loss. Clinical trials assessing speech intelligibility in CI users have found large intersubject variability. One possibility to explain the variability is the individual differences in the interface created between electrodes of the CI and the auditory nerve. In order to understand the variability, models of the voltage distribution of the electrically stimulated cochlea may be useful. With this purpose in mind, we developed a parametric model that can be adapted to each CI user based on landmarks from individual cone beam computed tomography (CBCT) scans of the cochlea before and after implantation. The conductivity values of each cochlea compartment as well as the weighting factors of different grounding modes have also been parameterized. Simulations were performed modeling the cochlea and electrode positions of 12 CI users. Three models were compared with different levels of detail: a homogeneous model (HM), a non-patient-specific model (NPSM), and a patient-specific model (PSM). The model simulations were compared with voltage distribution measurements obtained from the backward telemetry of the 12 CI users. Results show that the PSM produces the lowest error when predicting individual voltage distributions. Given a patient-specific geometry and electrode positions, we show an example on how to optimize the parameters of the model and how to couple it to an auditory nerve model. The model here presented may help to understand speech performance variability and support the development of new sound coding strategies for CIs.
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Affiliation(s)
- Waldo Nogueira
- Department of Otolaryngology, Cluster of Excellence "Hearing4all", Medical University Hannover , Hannover , Germany
| | - Daniel Schurzig
- Department of Otolaryngology, Cluster of Excellence "Hearing4all", Medical University Hannover , Hannover , Germany
| | - Andreas Büchner
- Department of Otolaryngology, Cluster of Excellence "Hearing4all", Medical University Hannover , Hannover , Germany
| | - Richard T Penninger
- Department of Otolaryngology, Cluster of Excellence "Hearing4all", Medical University Hannover , Hannover , Germany
| | - Waldemar Würfel
- Department of Otolaryngology, Cluster of Excellence "Hearing4all", Medical University Hannover , Hannover , Germany
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Seeber BU, Bruce IC. The history and future of neural modeling for cochlear implants. NETWORK (BRISTOL, ENGLAND) 2016; 27:53-66. [PMID: 27726506 DOI: 10.1080/0954898x.2016.1223365] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
This special issue of Network: Computation in Neural Systems on the topic of "Computational models of the electrically stimulated auditory system" incorporates review articles spanning a wide range of approaches to modeling cochlear implant stimulation of the auditory system. The purpose of this overview paper is to provide a historical context for the different modeling endeavors and to point toward how computational modeling could play a key role in the understanding, evaluation, and improvement of cochlear implants in the future.
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Affiliation(s)
- Bernhard U Seeber
- a Audio Information Processing, Department of Electrical and Computer Engineering , Technical University of Munich , Munich , Germany
| | - Ian C Bruce
- b Department of Electrical and Computer Engineering , McMaster University , Hamilton , Ontario , Canada
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