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Hussain MA, Grill WM, Pelot NA. Highly efficient modeling and optimization of neural fiber responses to electrical stimulation. Nat Commun 2024; 15:7597. [PMID: 39217179 PMCID: PMC11365978 DOI: 10.1038/s41467-024-51709-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2024] [Accepted: 08/13/2024] [Indexed: 09/04/2024] Open
Abstract
Peripheral neuromodulation has emerged as a powerful modality for controlling physiological functions and treating a variety of medical conditions including chronic pain and organ dysfunction. The underlying complexity of the nonlinear responses to electrical stimulation make it challenging to design precise and effective neuromodulation protocols. Computational models have thus become indispensable in advancing our understanding and control of neural responses to electrical stimulation. However, existing approaches suffer from computational bottlenecks, rendering them unsuitable for real-time applications, large-scale parameter sweeps, or sophisticated optimization. In this work, we introduce an approach for massively parallel estimation and optimization of neural fiber responses to electrical stimulation using machine learning techniques. By leveraging advances in high-performance computing and parallel programming, we present a surrogate fiber model that generates spatiotemporal responses to a wide variety of cuff-based electrical peripheral nerve stimulation protocols. We used our surrogate fiber model to design stimulation parameters for selective stimulation of pig and human vagus nerves. Our approach yields a several-orders-of-magnitude improvement in computational efficiency while retaining generality and high predictive accuracy, demonstrating its robustness and potential to enhance the design and optimization of peripheral neuromodulation therapies.
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Affiliation(s)
- Minhaj A Hussain
- Department of Biomedical Engineering, Duke University, Durham, NC, 27708, USA
| | - Warren M Grill
- Department of Biomedical Engineering, Duke University, Durham, NC, 27708, USA
- Department of Electrical and Computer Engineering, Duke University, Durham, NC, 27708, USA
- Department of Neurobiology, Duke University, Durham, NC, 27708, USA
- Department of Neurosurgery, Duke University, Durham, NC, 27708, USA
| | - Nicole A Pelot
- Department of Biomedical Engineering, Duke University, Durham, NC, 27708, USA.
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2
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Ciotti F, John R, Katic Secerovic N, Gozzi N, Cimolato A, Jayaprakash N, Song W, Toth V, Zanos T, Zanos S, Raspopovic S. Towards enhanced functionality of vagus neuroprostheses through in silico optimized stimulation. Nat Commun 2024; 15:6119. [PMID: 39033186 PMCID: PMC11271449 DOI: 10.1038/s41467-024-50523-6] [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: 02/23/2024] [Accepted: 07/10/2024] [Indexed: 07/23/2024] Open
Abstract
Bioelectronic therapies modulating the vagus nerve are promising for cardiovascular, inflammatory, and mental disorders. Clinical applications are however limited by side-effects such as breathing obstruction and headache caused by non-specific stimulation. To design selective and functional stimulation, we engineered VaStim, a realistic and efficient in-silico model. We developed a protocol to personalize VaStim in-vivo using simple muscle responses, successfully reproducing experimental observations, by combining models with trials conducted on five pigs. Through optimized algorithms, VaStim simulated the complete fiber population in minutes, including often omitted unmyelinated fibers which constitute 80% of the nerve. The model suggested that all Aα-fibers across the nerve affect laryngeal muscle, while heart rate changes were caused by B-efferents in specific fascicles. It predicted that tripolar paradigms could reduce laryngeal activity by 70% compared to typically used protocols. VaStim may serve as a model for developing neuromodulation therapies by maximizing efficacy and specificity, reducing animal experimentation.
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Affiliation(s)
- Federico Ciotti
- Laboratory for Neuroengineering, Department of Health Sciences and Technology, Institute for Robotics and Intelligent Systems, ETH Zürich, Zürich, Switzerland
| | - Robert John
- Laboratory for Neuroengineering, Department of Health Sciences and Technology, Institute for Robotics and Intelligent Systems, ETH Zürich, Zürich, Switzerland
| | - Natalija Katic Secerovic
- Laboratory for Neuroengineering, Department of Health Sciences and Technology, Institute for Robotics and Intelligent Systems, ETH Zürich, Zürich, Switzerland
- The Mihajlo Pupin Institute, University of Belgrade, Belgrade, Serbia
| | - Noemi Gozzi
- Laboratory for Neuroengineering, Department of Health Sciences and Technology, Institute for Robotics and Intelligent Systems, ETH Zürich, Zürich, Switzerland
| | - Andrea Cimolato
- Laboratory for Neuroengineering, Department of Health Sciences and Technology, Institute for Robotics and Intelligent Systems, ETH Zürich, Zürich, Switzerland
| | - Naveen Jayaprakash
- Northwell Health, New Hyde Park, NY, USA
- Feinstein Institutes for Medical Research, Manhasset, NY, USA
| | - Weiguo Song
- Northwell Health, New Hyde Park, NY, USA
- Feinstein Institutes for Medical Research, Manhasset, NY, USA
| | - Viktor Toth
- Northwell Health, New Hyde Park, NY, USA
- Feinstein Institutes for Medical Research, Manhasset, NY, USA
| | - Theodoros Zanos
- Northwell Health, New Hyde Park, NY, USA
- Feinstein Institutes for Medical Research, Manhasset, NY, USA
- Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Hempstead, NY, USA
- Elmezzi Graduate School of Molecular Medicine, Manhasset, NY, USA
| | - Stavros Zanos
- Northwell Health, New Hyde Park, NY, USA
- Feinstein Institutes for Medical Research, Manhasset, NY, USA
- Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Hempstead, NY, USA
- Elmezzi Graduate School of Molecular Medicine, Manhasset, NY, USA
| | - Stanisa Raspopovic
- Laboratory for Neuroengineering, Department of Health Sciences and Technology, Institute for Robotics and Intelligent Systems, ETH Zürich, Zürich, Switzerland.
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.
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3
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Couppey T, Regnacq L, Giraud R, Romain O, Bornat Y, Kolbl F. NRV: An open framework for in silico evaluation of peripheral nerve electrical stimulation strategies. PLoS Comput Biol 2024; 20:e1011826. [PMID: 38995970 PMCID: PMC11268605 DOI: 10.1371/journal.pcbi.1011826] [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: 01/17/2024] [Revised: 07/24/2024] [Accepted: 06/20/2024] [Indexed: 07/14/2024] Open
Abstract
Electrical stimulation of peripheral nerves has been used in various pathological contexts for rehabilitation purposes or to alleviate the symptoms of neuropathologies, thus improving the overall quality of life of patients. However, the development of novel therapeutic strategies is still a challenging issue requiring extensive in vivo experimental campaigns and technical development. To facilitate the design of new stimulation strategies, we provide a fully open source and self-contained software framework for the in silico evaluation of peripheral nerve electrical stimulation. Our modeling approach, developed in the popular and well-established Python language, uses an object-oriented paradigm to map the physiological and electrical context. The framework is designed to facilitate multi-scale analysis, from single fiber stimulation to whole multifascicular nerves. It also allows the simulation of complex strategies such as multiple electrode combinations and waveforms ranging from conventional biphasic pulses to more complex modulated kHz stimuli. In addition, we provide automated support for stimulation strategy optimization and handle the computational backend transparently to the user. Our framework has been extensively tested and validated with several existing results in the literature.
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Affiliation(s)
- Thomas Couppey
- Laboratoire ETIS, Cergy Paris Université, ENSEA, CNRS UMR 8051, Cergy, France
| | - Louis Regnacq
- Laboratoire ETIS, Cergy Paris Université, ENSEA, CNRS UMR 8051, Cergy, France
- Univ. Bordeaux, CNRS, Bordeaux INP, IMS, UMR 5218, Talence, France
| | - Roland Giraud
- Laboratoire ETIS, Cergy Paris Université, ENSEA, CNRS UMR 8051, Cergy, France
- Univ. Bordeaux, CNRS, Bordeaux INP, IMS, UMR 5218, Talence, France
| | - Olivier Romain
- Laboratoire ETIS, Cergy Paris Université, ENSEA, CNRS UMR 8051, Cergy, France
| | - Yannick Bornat
- Univ. Bordeaux, CNRS, Bordeaux INP, IMS, UMR 5218, Talence, France
| | - Florian Kolbl
- Laboratoire ETIS, Cergy Paris Université, ENSEA, CNRS UMR 8051, Cergy, France
- Univ. Bordeaux, CNRS, Bordeaux INP, IMS, UMR 5218, Talence, France
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Couppey T, Regnacq L, Giraud R, Romain O, Bornat Y, Kölbl F. NRV: An open framework for in silico evaluation of peripheral nerve electrical stimulation strategies. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.15.575628. [PMID: 38293181 PMCID: PMC10827078 DOI: 10.1101/2024.01.15.575628] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2024]
Abstract
Electrical stimulation of peripheral nerves has been used in various pathological contexts for rehabilitation purposes or to alleviate the symptoms of neuropathologies, thus improving the overall quality of life of patients. However, the development of novel therapeutic strategies is still a challenging issue requiring extensive in vivo experimental campaigns and technical development. To facilitate the design of new stimulation strategies, we provide a fully open source and self-contained software framework for the in silico evaluation of peripheral nerve electrical stimulation. Our modeling approach, developed in the popular and well-established Python language, uses an object-oriented paradigm to map the physiological and electrical context. The framework is designed to facilitate multi-scale analysis, from single fiber stimulation to whole multifascicular nerves. It also allows the simulation of complex strategies such as multiple electrode combinations and waveforms ranging from conventional biphasic pulses to more complex modulated kHz stimuli. In addition, we provide automated support for stimulation strategy optimization and handle the computational backend transparently to the user. Our framework has been extensively tested and validated with several existing results in the literature.
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Affiliation(s)
| | - Louis Regnacq
- ETIS CNRS UMR 8051, CY Cergy Paris University, ENSEA
- Univ. Bordeaux, Bordeaux INP, IMS CNRS UMR 5218, Aquitaine, Talence, France
| | - Roland Giraud
- ETIS CNRS UMR 8051, CY Cergy Paris University, ENSEA
- Univ. Bordeaux, Bordeaux INP, IMS CNRS UMR 5218, Aquitaine, Talence, France
| | | | - Yannick Bornat
- Univ. Bordeaux, Bordeaux INP, IMS CNRS UMR 5218, Aquitaine, Talence, France
| | - Florian Kölbl
- ETIS CNRS UMR 8051, CY Cergy Paris University, ENSEA
- Univ. Bordeaux, Bordeaux INP, IMS CNRS UMR 5218, Aquitaine, Talence, France
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Xie Y, Qin P, Guo T, Al Abed A, Lovell NH, Tsai D. Modulating individual axons and axonal populations in the peripheral nerve using transverse intrafascicular multichannel electrodes. J Neural Eng 2023; 20:046032. [PMID: 37536318 DOI: 10.1088/1741-2552/aced20] [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: 02/13/2023] [Accepted: 08/03/2023] [Indexed: 08/05/2023]
Abstract
Objective.A transverse intrafascicular multichannel electrode (TIME) may offer advantages over more conventional cuff electrodes including higher spatial selectivity and reduced stimulation charge requirements. However, the performance of TIME, especially in the context of non-conventional stimulation waveforms, remains relatively unexplored. As part of our overarching goal of investigating stimulation efficacy of TIME, we developed a computational toolkit that automates the creation and usage ofin siliconerve models with TIME setup, which solves nerve responses using cable equations and computes extracellular potentials using finite element method.Approach.We began by implementing a flexible and scalable Python/MATLAB-based toolkit for automatically creating models of nerve stimulation in the hybrid NEURON/COMSOL ecosystems. We then developed a sciatic nerve model containing 14 fascicles with 1,170 myelinated (A-type, 30%) and unmyelinated (C-type, 70%) fibers to study fiber responses over a variety of TIME arrangements (monopolar and hexapolar) and stimulation waveforms (kilohertz stimulation and cathodic ramp modulation).Main results.Our toolkit obviates the conventional need to re-create the same nerve in two disparate modeling environments and automates bi-directional transfer of results. Our population-based simulations suggested that kilohertz stimuli provide selective activation of targeted C fibers near the stimulating electrodes but also tended to activate non-targeted A fibers further away. However, C fiber selectivity can be enhanced by hexapolar TIME arrangements that confined the spatial extent of electrical stimuli. Improved upon prior findings, we devised a high-frequency waveform that incorporates cathodic DC ramp to completely remove undesirable onset responses.Conclusion.Our toolkit allows agile, iterative design cycles involving the nerve and TIME, while minimizing the potential operator errors during complex simulation. The nerve model created by our toolkit allowed us to study and optimize the design of next-generation intrafascicular implants for improved spatial and fiber-type selectivity.
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Affiliation(s)
- Yuyang Xie
- Graduate School of Biomedical Engineering, UNSW Sydney, NSW 2052, Australia
| | - Peijun Qin
- Graduate School of Biomedical Engineering, UNSW Sydney, NSW 2052, Australia
| | - Tianruo Guo
- Graduate School of Biomedical Engineering, UNSW Sydney, NSW 2052, Australia
| | - Amr Al Abed
- Graduate School of Biomedical Engineering, UNSW Sydney, NSW 2052, Australia
| | - Nigel H Lovell
- Graduate School of Biomedical Engineering, UNSW Sydney, NSW 2052, Australia
- Tyree Institute of Health Engineering (IHealthE), UNSW Sydney, NSW 2052, Australia
| | - David Tsai
- Graduate School of Biomedical Engineering, UNSW Sydney, NSW 2052, Australia
- School of Electrical Engineering & Telecommunications, UNSW Sydney, NSW 2052, Australia
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Johnson MD, Dweiri YM, Cornelius J, Strohl KP, Steffen A, Suurna M, Soose RJ, Coleman M, Rondoni J, Durand DM, Ni Q. Model-based analysis of implanted hypoglossal nerve stimulation for the treatment of obstructive sleep apnea. Sleep 2021; 44:S11-S19. [PMID: 33647987 DOI: 10.1093/sleep/zsaa269] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 11/12/2020] [Indexed: 11/15/2022] Open
Abstract
STUDY OBJECTIVES Individuals with obstructive sleep apnea (OSA), characterized by frequent sleep disruptions from tongue muscle relaxation and airway blockage, are known to benefit from on-demand electrical stimulation of the hypoglossal nerve. Hypoglossal nerve stimulation (HNS) therapy, which activates the protrusor muscles of the tongue during inspiration, has been established in multiple clinical studies as safe and effective, but the mechanistic understanding for why some stimulation parameters work better than others has not been thoroughly investigated. METHODS In this study, we developed a detailed biophysical model that can predict the spatial recruitment of hypoglossal nerve fascicles and axons within these fascicles during stimulation through nerve cuff electrodes. Using this model, three HNS programming scenarios were investigated including grouped cathode (---), single cathode (o-o), and guarded cathode bipolar (+-+) electrode configurations. RESULTS Regardless of electrode configuration, nearly all hypoglossal nerve axons circumscribed by the nerve cuff were recruited for stimulation amplitudes <3 V. Within this range, monopolar configurations required lower stimulation amplitudes than the guarded bipolar configuration to elicit action potentials within hypoglossal nerve axons. Further, the spatial distribution of the activated axons was more uniform for monopolar versus guarded bipolar configurations. CONCLUSIONS The computational models predicted that monopolar HNS provided the lowest threshold and the least sensitivity to rotational angle of the nerve cuff around the hypoglossal nerve; however, this setting also increased the likelihood for current leakage outside the nerve cuff, which could potentially activate axons in unintended branches of the hypoglossal nerve. CLINICAL TRIAL REGISTRATION NCT01161420.
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Affiliation(s)
- Matthew D Johnson
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN
| | - Yazan M Dweiri
- Department of Biomedical Engineering, Jordan University of Science and Technology, Irbid, Jordan
| | - Jason Cornelius
- Minneapolis Clinic of Neurology and North Memorial Help Sleep Medicine, Maple Grove, MN
| | - Kingman P Strohl
- Division of Pulmonary, Critical Care, and Sleep Medicine, Louis Stokes Veterans Affairs Medical Center and Case Medical Center, Case Western Reserve University, Cleveland, OH
| | - Armin Steffen
- Department of Otorhinolaryngology, University of Lübeck, Lübeck, Germany
| | - Maria Suurna
- Department of Otolaryngology-Head and Neck Surgery, Weill Cornell Medicine, New York, NY
| | - Ryan J Soose
- Department of Otolaryngology, University of Pittsburgh, Pittsburgh, PA
| | | | | | - Dominique M Durand
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH
| | - Quan Ni
- Inspire Medical Systems, Inc., Minneapolis, MN
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Cracchiolo M, Ottaviani MM, Panarese A, Strauss I, Vallone F, Mazzoni A, Micera S. Bioelectronic medicine for the autonomic nervous system: clinical applications and perspectives. J Neural Eng 2021; 18. [PMID: 33592597 DOI: 10.1088/1741-2552/abe6b9] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 02/16/2021] [Indexed: 12/11/2022]
Abstract
Bioelectronic medicine (BM) is an emerging new approach for developing novel neuromodulation therapies for pathologies that have been previously treated with pharmacological approaches. In this review, we will focus on the neuromodulation of autonomic nervous system (ANS) activity with implantable devices, a field of BM that has already demonstrated the ability to treat a variety of conditions, from inflammation to metabolic and cognitive disorders. Recent discoveries about immune responses to ANS stimulation are the laying foundation for a new field holding great potential for medical advancement and therapies and involving an increasing number of research groups around the world, with funding from international public agencies and private investors. Here, we summarize the current achievements and future perspectives for clinical applications of neural decoding and stimulation of the ANS. First, we present the main clinical results achieved so far by different BM approaches and discuss the challenges encountered in fully exploiting the potential of neuromodulatory strategies. Then, we present current preclinical studies aimed at overcoming the present limitations by looking for optimal anatomical targets, developing novel neural interface technology, and conceiving more efficient signal processing strategies. Finally, we explore the prospects for translating these advancements into clinical practice.
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Affiliation(s)
- Marina Cracchiolo
- The BioRobotics Institute and Department of Excellence in Robotics & AI, The BioRobotics Institute, Scuola Superiore Sant'Anna, Pisa, Italy
| | - Matteo Maria Ottaviani
- The BioRobotics Institute and Department of Excellence in Robotics & AI, The BioRobotics Institute, Scuola Superiore Sant'Anna, Pisa, Italy
| | - Alessandro Panarese
- The BioRobotics Institute and Department of Excellence in Robotics & AI, The BioRobotics Institute, Scuola Superiore Sant'Anna, Pisa, Italy
| | - Ivo Strauss
- The BioRobotics Institute and Department of Excellence in Robotics & AI, The BioRobotics Institute, Scuola Superiore Sant'Anna, Pisa, Italy
| | - Fabio Vallone
- The BioRobotics Institute and Department of Excellence in Robotics & AI, The BioRobotics Institute, Scuola Superiore Sant'Anna, Pisa, Italy
| | - Alberto Mazzoni
- The BioRobotics Institute and Department of Excellence in Robotics & AI, The BioRobotics Institute, Scuola Superiore Sant'Anna, Pisa, Italy
| | - Silvestro Micera
- The BioRobotics Institute and Department of Excellence in Robotics & AI, The BioRobotics Institute, Scuola Superiore Sant'Anna, Pisa, Italy.,Bertarelli Foundation Chair in Translational NeuroEngineering, Centre for Neuroprosthetics and Institute of Bioengineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
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State-dependent bioelectronic interface to control bladder function. Sci Rep 2021; 11:314. [PMID: 33431964 PMCID: PMC7801663 DOI: 10.1038/s41598-020-79493-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Accepted: 12/09/2020] [Indexed: 11/23/2022] Open
Abstract
Electrical stimulation therapies to promote bladder filling and prevent incontinence deliver continuous inhibitory stimulation, even during bladder emptying. However, continuous inhibitory stimulation that increases bladder capacity (BC) can reduce the efficiency of subsequent voiding (VE). Here we demonstrate that state-dependent stimulation, with different electrical stimulation parameters delivered during filling and emptying can increase both BC and VE relative to continuous stimulation in rats and cats of both sexes. We show that continuous 10 Hz pudendal nerve stimulation increased BC (120–180% of control) but decreased VE (12–71%, relative to control). In addition to increasing BC, state-dependent stimulation in both rats and cats increased VE (280–759% relative to continuous stimulation); motor bursting in cats increased VE beyond the control (no stimulation) condition (males: 323%; females: 161%). These results suggest that a bioelectronic bladder pacemaker can treat complex voiding disorders, including both incontinence and retention, which paradoxically are often present in the same individual.
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Pelot NA, Goldhagen GB, Cariello JE, Musselman ED, Clissold KA, Ezzell JA, Grill WM. Quantified Morphology of the Cervical and Subdiaphragmatic Vagus Nerves of Human, Pig, and Rat. Front Neurosci 2020; 14:601479. [PMID: 33250710 PMCID: PMC7672126 DOI: 10.3389/fnins.2020.601479] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 10/13/2020] [Indexed: 12/27/2022] Open
Abstract
It is necessary to understand the morphology of the vagus nerve (VN) to design and deliver effective and selective vagus nerve stimulation (VNS) because nerve morphology influences fiber responses to electrical stimulation. Specifically, nerve diameter (and thus, electrode-fiber distance), fascicle diameter, fascicular organization, and perineurium thickness all significantly affect the responses of nerve fibers to electrical signals delivered through a cuff electrode. We quantified the morphology of cervical and subdiaphragmatic VNs in humans, pigs, and rats: effective nerve diameter, number of fascicles, effective fascicle diameters, proportions of endoneurial, perineurial, and epineurial tissues, and perineurium thickness. The human and pig VNs were comparable sizes (∼2 mm cervically; ∼1.6 mm subdiaphragmatically), while the rat nerves were ten times smaller. The pig nerves had ten times more fascicles-and the fascicles were smaller-than in human nerves (47 vs. 7 fascicles cervically; 38 vs. 5 fascicles subdiaphragmatically). Comparing the cervical to the subdiaphragmatic VNs, the nerves and fascicles were larger at the cervical level for all species and there were more fascicles for pigs. Human morphology generally exhibited greater variability across samples than pigs and rats. A prior study of human somatic nerves indicated that the ratio of perineurium thickness to fascicle diameter was approximately constant across fascicle diameters. However, our data found thicker human and pig VN perineurium than those prior data: the VNs had thicker perineurium for larger fascicles and thicker perineurium normalized by fascicle diameter for smaller fascicles. Understanding these differences in VN morphology between preclinical models and the clinical target, as well as the variability across individuals of a species, is essential for designing suitable cuff electrodes and stimulation parameters and for informing translation of preclinical results to clinical application to advance the therapeutic efficacy of VNS.
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Affiliation(s)
- Nicole A. Pelot
- Department of Biomedical Engineering, Duke University, Durham, NC, United States
| | - Gabriel B. Goldhagen
- Department of Biomedical Engineering, Duke University, Durham, NC, United States
| | - Jake E. Cariello
- Department of Biomedical Engineering, Duke University, Durham, NC, United States
| | - Eric D. Musselman
- Department of Biomedical Engineering, Duke University, Durham, NC, United States
| | - Kara A. Clissold
- Histology Research Core, The University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - J. Ashley Ezzell
- Histology Research Core, The University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Warren M. Grill
- Department of Biomedical Engineering, Duke University, Durham, NC, United States
- Department of Electrical and Computer Engineering, Duke University, Durham, NC, United States
- Department of Neurobiology, Duke University, Durham, NC, United States
- Department of Neurosurgery, School of Medicine, Duke University, Durham, NC, United States
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10
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Tovbis D, Agur A, Mogk JPM, Zariffa J. Automatic three-dimensional reconstruction of fascicles in peripheral nerves from histological images. PLoS One 2020; 15:e0233028. [PMID: 32407341 PMCID: PMC7224505 DOI: 10.1371/journal.pone.0233028] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Accepted: 04/27/2020] [Indexed: 11/24/2022] Open
Abstract
Computational studies can be used to support the development of peripheral nerve interfaces, but currently use simplified models of nerve anatomy, which may impact the applicability of simulation results. To better quantify and model neural anatomy across the population, we have developed an algorithm to automatically reconstruct accurate peripheral nerve models from histological cross-sections. We acquired serial median nerve cross-sections from human cadaveric samples, staining one set with hematoxylin and eosin (H&E) and the other using immunohistochemistry (IHC) with anti-neurofilament antibody. We developed a four-step processing pipeline involving registration, fascicle detection, segmentation, and reconstruction. We compared the output of each step to manual ground truths, and additionally compared the final models to commonly used extrusions, via intersection-over-union (IOU). Fascicle detection and segmentation required the use of a neural network and active contours in H&E-stained images, but only simple image processing methods for IHC-stained images. Reconstruction achieved an IOU of 0.42±0.07 for H&E and 0.37±0.16 for IHC images, with errors partially attributable to global misalignment at the registration step, rather than poor reconstruction. This work provides a quantitative baseline for fully automatic construction of peripheral nerve models. Our models provided fascicular shape and branching information that would be lost via extrusion.
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Affiliation(s)
- Daniel Tovbis
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada
- KITE, Toronto Rehab, University Health Network, Toronto, Ontario, Canada
| | - Anne Agur
- Division of Anatomy, Department of Surgery, University of Toronto, Toronto, Ontario, Canada
- Rehabilitation Sciences Institute, University of Toronto, Toronto, Ontario, Canada
| | - Jeremy P. M. Mogk
- Division of Anatomy, Department of Surgery, University of Toronto, Toronto, Ontario, Canada
| | - José Zariffa
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada
- KITE, Toronto Rehab, University Health Network, Toronto, Ontario, Canada
- Rehabilitation Sciences Institute, University of Toronto, Toronto, Ontario, Canada
- Edward S. Rogers Sr. Department of Electrical and Computer Engineering, University of Toronto, Toronto, Ontario, Canada
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11
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Bucksot JE, Wells AJ, Rahebi KC, Sivaji V, Romero-Ortega M, Kilgard MP, Rennaker RL, Hays SA. Flat electrode contacts for vagus nerve stimulation. PLoS One 2019; 14:e0215191. [PMID: 31738766 PMCID: PMC6862926 DOI: 10.1371/journal.pone.0215191] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Accepted: 10/30/2019] [Indexed: 02/01/2023] Open
Abstract
The majority of available systems for vagus nerve stimulation use helical stimulation electrodes, which cover the majority of the circumference of the nerve and produce largely uniform current density within the nerve. Flat stimulation electrodes that contact only one side of the nerve may provide advantages, including ease of fabrication. However, it is possible that the flat configuration will yield inefficient fiber recruitment due to a less uniform current distribution within the nerve. Here we tested the hypothesis that flat electrodes will require higher current amplitude to activate all large-diameter fibers throughout the whole cross-section of a nerve than circumferential designs. Computational modeling and in vivo experiments were performed to evaluate fiber recruitment in different nerves and different species using a variety of electrode designs. Initial results demonstrated similar fiber recruitment in the rat vagus and sciatic nerves with a standard circumferential cuff electrode and a cuff electrode modified to approximate a flat configuration. Follow up experiments comparing true flat electrodes to circumferential electrodes on the rabbit sciatic nerve confirmed that fiber recruitment was equivalent between the two designs. These findings demonstrate that flat electrodes represent a viable design for nerve stimulation that may provide advantages over the current circumferential designs for applications in which the goal is uniform activation of all fascicles within the nerve.
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Affiliation(s)
- Jesse E. Bucksot
- The University of Texas at Dallas, Erik Jonsson School of Engineering and
Computer Science, Richardson, Texas, United States of America
| | - Andrew J. Wells
- The University of Texas at Dallas, Erik Jonsson School of Engineering and
Computer Science, Richardson, Texas, United States of America
| | - Kimiya C. Rahebi
- Texas Biomedical Device Center, Richardson, Texas, United States of
America
| | - Vishnoukumaar Sivaji
- The University of Texas at Dallas, Erik Jonsson School of Engineering and
Computer Science, Richardson, Texas, United States of America
| | - Mario Romero-Ortega
- The University of Texas at Dallas, Erik Jonsson School of Engineering and
Computer Science, Richardson, Texas, United States of America
- Texas Biomedical Device Center, Richardson, Texas, United States of
America
| | - Michael P. Kilgard
- The University of Texas at Dallas, Erik Jonsson School of Engineering and
Computer Science, Richardson, Texas, United States of America
- Texas Biomedical Device Center, Richardson, Texas, United States of
America
- The University of Texas at Dallas, School of Behavioral Brain Sciences,
Richardson, Texas, United States of America
| | - Robert L. Rennaker
- The University of Texas at Dallas, Erik Jonsson School of Engineering and
Computer Science, Richardson, Texas, United States of America
- Texas Biomedical Device Center, Richardson, Texas, United States of
America
- The University of Texas at Dallas, School of Behavioral Brain Sciences,
Richardson, Texas, United States of America
| | - Seth A. Hays
- The University of Texas at Dallas, Erik Jonsson School of Engineering and
Computer Science, Richardson, Texas, United States of America
- Texas Biomedical Device Center, Richardson, Texas, United States of
America
- The University of Texas at Dallas, School of Behavioral Brain Sciences,
Richardson, Texas, United States of America
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12
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Spike-Conducting Integrate-and-Fire Model. eNeuro 2018; 5:eN-TNC-0112-18. [PMID: 30225348 PMCID: PMC6140110 DOI: 10.1523/eneuro.0112-18.2018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2018] [Revised: 08/13/2018] [Accepted: 08/14/2018] [Indexed: 11/29/2022] Open
Abstract
Modeling is a useful tool for investigating various biophysical characteristics of neurons. Recent simulation studies of propagating action potentials (spike conduction) along axons include the investigation of neuronal activity evoked by electrical stimulation from implantable prosthetic devices. In contrast to point-neuron simulations, where a large variety of models are readily available, Hodgkin–Huxley-type conductance-based models have been almost the only option for simulating axonal spike conduction, as simpler models cannot faithfully replicate the waveforms of propagating spikes. Since the amount of available physiological data, especially in humans, is usually limited, calibration, and justification of the large number of parameters of a complex model is generally difficult. In addition, not all simulation studies of axons require detailed descriptions of nonlinear ionic dynamics. In this study, we construct a simple model of spike generation and conduction based on the exponential integrate-and-fire model, which can simulate the rapid growth of the membrane potential at spike initiation. In terms of the number of parameters and equations, this model is much more compact than conventional models, but can still reliably simulate spike conduction along myelinated and unmyelinated axons that are stimulated intracellularly or extracellularly. Our simulations of auditory nerve fibers with this new model suggest that, because of the difference in intrinsic membrane properties, the axonal spike conduction of high-frequency nerve fibers is faster than that of low-frequency fibers. The simple model developed in this study can serve as a computationally efficient alternative to more complex models for future studies, including simulations of neuroprosthetic devices.
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Cassar IR, Titus ND, Grill WM. An improved genetic algorithm for designing optimal temporal patterns of neural stimulation. J Neural Eng 2018; 14:066013. [PMID: 28747582 DOI: 10.1088/1741-2552/aa8270] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
OBJECTIVE Electrical neuromodulation therapies typically apply constant frequency stimulation, but non-regular temporal patterns of stimulation may be more effective and more efficient. However, the design space for temporal patterns is exceedingly large, and model-based optimization is required for pattern design. We designed and implemented a modified genetic algorithm (GA) intended for design optimal temporal patterns of electrical neuromodulation. APPROACH We tested and modified standard GA methods for application to designing temporal patterns of neural stimulation. We evaluated each modification individually and all modifications collectively by comparing performance to the standard GA across three test functions and two biophysically-based models of neural stimulation. MAIN RESULTS The proposed modifications of the GA significantly improved performance across the test functions and performed best when all were used collectively. The standard GA found patterns that outperformed fixed-frequency, clinically-standard patterns in biophysically-based models of neural stimulation, but the modified GA, in many fewer iterations, consistently converged to higher-scoring, non-regular patterns of stimulation. SIGNIFICANCE The proposed improvements to standard GA methodology reduced the number of iterations required for convergence and identified superior solutions.
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Jung R, Abbas JJ, Kuntaegowdanahalli S, Thota AK. Bionic intrafascicular interfaces for recording and stimulating peripheral nerve fibers. ACTA ACUST UNITED AC 2017; 1:55-69. [PMID: 29480906 DOI: 10.2217/bem-2017-0009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Accepted: 11/13/2017] [Indexed: 12/16/2022]
Abstract
The network of peripheral nerves presents extraordinary potential for modulating and/or monitoring the functioning of internal organs or the brain. The degree to which these pathways can be used to influence or observe neural activity patterns will depend greatly on the quality and specificity of the bionic interface. The anatomical organization, which consists of multiple nerve fibers clustered into fascicles within a nerve bundle, presents opportunities and challenges that may necessitate insertion of electrodes into individual fascicles to achieve the specificity that may be required for many clinical applications. This manuscript reviews the current state-of-the-art in bionic intrafascicular interfaces, presents specific concerns for stimulation and recording, describes key implementation considerations and discusses challenges for future designs of bionic intrafascicular interfaces.
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Affiliation(s)
- Ranu Jung
- Department of Biomedical Engineering, Florida International University, EC2602, 10555 W Flagler Street, Miami, FL 33134, USA.,Department of Biomedical Engineering, Florida International University, EC2602, 10555 W Flagler Street, Miami, FL 33134, USA
| | - James J Abbas
- Center for Adaptive Neural Systems, School of Biological & Health Systems Engineering, PO Box 879709 Arizona State University, Tempe, AZ 85287-9709, USA.,Center for Adaptive Neural Systems, School of Biological & Health Systems Engineering, PO Box 879709 Arizona State University, Tempe, AZ 85287-9709, USA
| | - Sathyakumar Kuntaegowdanahalli
- Department of Biomedical Engineering, Florida International University, EC2602, 10555 W Flagler Street, Miami, FL 33134, USA.,Department of Biomedical Engineering, Florida International University, EC2602, 10555 W Flagler Street, Miami, FL 33134, USA
| | - Anil K Thota
- Department of Biomedical Engineering, Florida International University, EC2602, 10555 W Flagler Street, Miami, FL 33134, USA.,Department of Biomedical Engineering, Florida International University, EC2602, 10555 W Flagler Street, Miami, FL 33134, USA
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15
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Brill NA, Tyler DJ. Quantification of human upper extremity nerves and fascicular anatomy. Muscle Nerve 2017; 56:463-471. [PMID: 28006854 PMCID: PMC5712902 DOI: 10.1002/mus.25534] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Revised: 12/04/2016] [Accepted: 12/20/2016] [Indexed: 01/09/2023]
Abstract
INTRODUCTION In this study we provide detailed quantification of upper extremity nerve and fascicular anatomy. The purpose is to provide values and trends in neural features useful for clinical applications and neural interface device design. METHODS Nerve cross-sections were taken from 4 ulnar, 4 median, and 3 radial nerves from 5 arms of 3 human cadavers. Quantified nerve features included cross-sectional area, minor diameter, and major diameter. Fascicular features analyzed included count, perimeter, area, and position. RESULTS Mean fascicular diameters were 0.57 ± 0.39, 0.6 ± 0.3, 0.5 ± 0.26 mm in the upper arm and 0.38 ± 0.18, 0.47 ± 0.18, 0.4 ± 0.27 mm in the forearm of ulnar, median, and radial nerves, respectively. Mean fascicular diameters were inversely proportional to fascicle count. CONCLUSION Detailed quantitative anatomy of upper extremity nerves is a resource for design of neural electrodes, guidance in extraneural procedures, and improved neurosurgical planning. Muscle Nerve 56: 463-471, 2017.
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Affiliation(s)
- Natalie A Brill
- Department of Biomedical Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio, 44104, USA
| | - Dustin J Tyler
- Department of Biomedical Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio, 44104, USA
- Louis Stokes Cleveland VA Medical Center, Cleveland, Ohio, USA
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16
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Pelot NA, Behrend CE, Grill WM. Modeling the response of small myelinated axons in a compound nerve to kilohertz frequency signals. J Neural Eng 2017; 14:046022. [PMID: 28361793 PMCID: PMC5677574 DOI: 10.1088/1741-2552/aa6a5f] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
OBJECTIVE There is growing interest in electrical neuromodulation of peripheral nerves, particularly autonomic nerves, to treat various diseases. Electrical signals in the kilohertz frequency (KHF) range can produce different responses, including conduction block. For example, EnteroMedics' vBloc® therapy for obesity delivers 5 kHz stimulation to block the abdominal vagus nerves, but the mechanisms of action are unclear. APPROACH We developed a two-part computational model, coupling a 3D finite element model of a cuff electrode around the human abdominal vagus nerve with biophysically-realistic electrical circuit equivalent (cable) model axons (1, 2, and 5.7 µm in diameter). We developed an automated algorithm to classify conduction responses as subthreshold (transmission), KHF-evoked activity (excitation), or block. We quantified neural responses across kilohertz frequencies (5-20 kHz), amplitudes (1-8 mA), and electrode designs. MAIN RESULTS We found heterogeneous conduction responses across the modeled nerve trunk, both for a given parameter set and across parameter sets, although most suprathreshold responses were excitation, rather than block. The firing patterns were irregular near transmission and block boundaries, but otherwise regular, and mean firing rates varied with electrode-fibre distance. Further, we identified excitation responses at amplitudes above block threshold, termed 're-excitation', arising from action potentials initiated at virtual cathodes. Excitation and block thresholds decreased with smaller electrode-fibre distances, larger fibre diameters, and lower kilohertz frequencies. A point source model predicted a larger fraction of blocked fibres and greater change of threshold with distance as compared to the realistic cuff and nerve model. SIGNIFICANCE Our findings of widespread asynchronous KHF-evoked activity suggest that conduction block in the abdominal vagus nerves is unlikely with current clinical parameters. Our results indicate that compound neural or downstream muscle force recordings may be unreliable as quantitative measures of neural activity for in vivo studies or as biomarkers in closed-loop clinical devices.
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Affiliation(s)
- N A Pelot
- Department of Biomedical Engineering, Duke University, Room 1427, Fitzpatrick CIEMAS, 101 Science Drive, Campus Box 90281, Durham, NC 27708, United States of America
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Burns J, Mueller A, Chevallier J, Sriram TS, Lewis SJ, Chew D, Achyuta A, Fiering J. High density penetrating electrode arrays for autonomic nerves. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2017; 2016:2802-2805. [PMID: 28268900 DOI: 10.1109/embc.2016.7591312] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Electrode arrays for recording and stimulation in the central nervous system have enabled numerous advances in basic science and therapeutic strategies. In particular, micro-fabricated arrays with precision size and spacing offer the benefit of accessing single neurons and permit mapping of neuronal function. Similar advances are envisioned toward understanding the autonomic nervous system and developing therapies based on its modulation, but appropriate electrode arrays are lacking. Here, we present for the first time, a multi-channel electrode array suitable for penetration of peripheral nerves having diameters as small as 0.1mm, and demonstrate performance in vivo. These arrays have the potential to access multiple discrete nerve fibers in small nerves. We fabricated and characterized five-channel arrays and obtained preliminary recordings of activity when penetrating rat carotid sinus nerve. The electrodes were constructed using hybrid microfabrication processes. The individual electrode shafts are as small as 0.01mm in diameter and at its tip each has a defined site that is addressable via a standard electronic connector. In addition to acute in vivo results, we evaluate the device by electrochemical impedance spectroscopy. Having established the fabrication method, our next steps are to incorporate the arrays into an implantable configuration for chronic studies, and here we further describe concepts for such a device.
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Greenwald E, Maier C, Wang Q, Beaulieu R, Etienne-Cummings R, Cauwenberghs G, Thakor N. A CMOS Current Steering Neurostimulation Array With Integrated DAC Calibration and Charge Balancing. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2017; 11:324-335. [PMID: 28092575 PMCID: PMC5496821 DOI: 10.1109/tbcas.2016.2609854] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
An 8-channel current steerable, multi-phasic neural stimulator with on-chip current DAC calibration and residue nulling for precise charge balancing is presented. Each channel consists of two sub-binary radix DACs followed by wide-swing, high output impedance current buffers providing time-multiplexed source and sink outputs for anodic and cathodic stimulation. A single integrator is shared among channels and serves to calibrate DAC coefficients and to closely match the anodic and cathodic stimulation phases. Following calibration, the differential non-linearity is within ±0.3 LSB at 8-bit resolution, and the two stimulation phases are matched within 0.3%. Individual control in digital programming of stimulation coefficients across the array allows altering the spatial profile of current stimulation for selection of stimulation targets by current steering. Combined with the self-calibration and current matching functions, the current steering capabilities integrated on-chip support use in fully implanted neural interfaces with autonomous operation for and adaptive stimulation under variations in electrode and tissue conditions. As a proof-of-concept we applied current steering stimulation through a multi-channel cuff electrode on the sciatic nerve of a rat.
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Characterizing the reduction of stimulation artifact noise in a tripolar nerve cuff electrode by application of a conductive shield layer. Med Eng Phys 2017; 40:39-46. [DOI: 10.1016/j.medengphy.2016.11.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Revised: 11/14/2016] [Accepted: 11/27/2016] [Indexed: 11/24/2022]
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20
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Xiang Z, Sheshadri S, Lee S, Wang J, Xue N, Thakor NV, Yen S, Lee C. Mapping of Small Nerve Trunks and Branches Using Adaptive Flexible Electrodes. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2016; 3:1500386. [PMID: 27981020 PMCID: PMC5039981 DOI: 10.1002/advs.201500386] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Revised: 01/21/2016] [Indexed: 05/29/2023]
Abstract
Selective stimulation is delivered to the sciatic nerve using different paris of contacts on a split-ring electrode, while simulatneous recordings are acquired by the neural ribbon electrodes on three different branches. Two hook electrodes are also implanted in the muscle to monitor the activated muscle responses. It shows that the high precision implantation of electrodes, increases the efficacy and reduces the incidence of side effects.
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Affiliation(s)
- Zhuolin Xiang
- Department of Electrical and Computer EngineeringNational University of Singapore4 Engineering Drive 3Singapore117583Singapore
- Singapore Institute for Neurotechnology (SiNAPSE)National University of Singapore28 Medical Drive, #05‐CORSingapore117456Singapore
- Center for Intelligent Sensors and MEMSNational University of Singapore4 Engineering Drive 3Singapore117576Singapore
| | - Swathi Sheshadri
- Department of Electrical and Computer EngineeringNational University of Singapore4 Engineering Drive 3Singapore117583Singapore
- Singapore Institute for Neurotechnology (SiNAPSE)National University of Singapore28 Medical Drive, #05‐CORSingapore117456Singapore
| | - Sang‐Hoon Lee
- Department of Electrical and Computer EngineeringNational University of Singapore4 Engineering Drive 3Singapore117583Singapore
- Singapore Institute for Neurotechnology (SiNAPSE)National University of Singapore28 Medical Drive, #05‐CORSingapore117456Singapore
- Center for Intelligent Sensors and MEMSNational University of Singapore4 Engineering Drive 3Singapore117576Singapore
| | - Jiahui Wang
- Department of Electrical and Computer EngineeringNational University of Singapore4 Engineering Drive 3Singapore117583Singapore
- Singapore Institute for Neurotechnology (SiNAPSE)National University of Singapore28 Medical Drive, #05‐CORSingapore117456Singapore
- Center for Intelligent Sensors and MEMSNational University of Singapore4 Engineering Drive 3Singapore117576Singapore
| | - Ning Xue
- Institute of Microelectronics (IME)Agency for Science, Technology and Research (A*STAR)11 Science Park Road, Singapore Science Park IISingapore117685Singapore
| | - Nitish V. Thakor
- Department of Electrical and Computer EngineeringNational University of Singapore4 Engineering Drive 3Singapore117583Singapore
- Singapore Institute for Neurotechnology (SiNAPSE)National University of Singapore28 Medical Drive, #05‐CORSingapore117456Singapore
- Department of Biomedical EngineeringSchool of MedicineJohns Hopkins University BaltimoreMD21205USA
| | - Shih‐Cheng Yen
- Department of Electrical and Computer EngineeringNational University of Singapore4 Engineering Drive 3Singapore117583Singapore
- Singapore Institute for Neurotechnology (SiNAPSE)National University of Singapore28 Medical Drive, #05‐CORSingapore117456Singapore
| | - Chengkuo Lee
- Department of Electrical and Computer EngineeringNational University of Singapore4 Engineering Drive 3Singapore117583Singapore
- Singapore Institute for Neurotechnology (SiNAPSE)National University of Singapore28 Medical Drive, #05‐CORSingapore117456Singapore
- Center for Intelligent Sensors and MEMSNational University of Singapore4 Engineering Drive 3Singapore117576Singapore
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Implantable neurotechnologies: a review of micro- and nanoelectrodes for neural recording. Med Biol Eng Comput 2016; 54:23-44. [PMID: 26753777 DOI: 10.1007/s11517-015-1430-4] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 12/10/2015] [Indexed: 12/22/2022]
Abstract
Electrodes serve as the first critical interface to the biological organ system. In neuroprosthetic applications, for example, electrodes interface to the tissue for either signal recording or tissue stimulation. In this review, we consider electrodes for recording neural activity. Recording electrodes serve as wiretaps into the neural tissues, providing readouts of electrical activity. These signals give us valuable insights into the organization and functioning of the nervous system. The recording interfaces have also shown promise in aiding treatment of motor and sensory disabilities caused by neurological disorders. Recent advances in fabrication technology have generated wide interest in creating tiny, high-density electrode interfaces for neural tissues. An ideal electrode should be small enough and be able to achieve reliable and conformal integration with the structures of the nervous system. As a result, the existing electrode designs are being shrunk and packed to form small form factor interfaces to tissue. Here, an overview of the historic and state-of-the-art electrode technologies for recording neural activity is presented first with a focus on their development road map. The fact that the dimensions of recording electrode sites are being scaled down from micron to submicron scale to enable dense interfaces is appreciated. The current trends in recording electrode technologies are then reviewed. Current and future considerations in electrode design, including the use of inorganic nanostructures and biologically inspired or biocomapatible materials are discussed, along with an overview of the applications of flexible materials and transistor transduction schemes. Finally, we detail the major technical challenges facing chronic use of reliable recording electrode technology.
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Kent AR. Modeling the impact of spinal cord stimulation paddle lead position on impedance, stimulation threshold, and activation region. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2016; 2015:5801-4. [PMID: 26737610 DOI: 10.1109/embc.2015.7319710] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The effectiveness of spinal cord stimulation (SCS) for chronic pain treatment depends on selection of appropriate stimulation settings, which can be especially challenging following posture change or SCS lead migration. The objective of this work was to investigate the feasibility of using SCS lead impedance for determining the location of a SCS lead and for detecting lead migration, as well as the impact of axial movement and rotation of the St. Jude Medical PENTA™ paddle in the dorsal-ventral or medial-lateral directions on dorsal column (DC) stimulation thresholds and neural activation regions. We used a two-stage computational model, including a finite element method model of field potentials in the spinal cord during stimulation, coupled to a biophysical cable model of mammalian, myelinated nerve fibers to calculate tissue impedance and nerve fiber activation within the DC. We found that SCS lead impedance was highly sensitive to the distance between the lead and cerebrospinal fluid (CSF) layer. In addition, among all the lead positions studied, medial-lateral movement resulted in the most substantial changes to SC activation regions. These results suggest that impedance can be used for detecting paddle position and lead migration, and therefore for guiding SCS programming.
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Shiraz AN, Leaker B, Demosthenous A. Optimization of a wearable pudendal nerve stimulator using computational models. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2016; 2015:3395-8. [PMID: 26737021 DOI: 10.1109/embc.2015.7319121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
After spinal cord injury, lower urinary tract functions may be disrupted. Trans-rectal stimulation of the pudendal nerve may enable patients to regain these functions via minimally invasive means. Using a finite element model of a wearable trans-rectal stimulator in the pelvic region, and a computational model of mammalian nerve fiber, various electrode configurations and the corresponding required current levels were studied. A configuration requiring considerably lower current level than previously reported was identified. For this configuration, the strength-duration curve was simulated and the effect of different stimulus waveforms on the required current was studied. In addition, the study examined whether a multi-electrode device could selectively activate different terminal branches of the pudendal nerve.
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Kent AR, Min X, Rosenberg SP, Fayram TA. Computational modeling analysis of a spinal cord stimulation paddle lead reveals broad, gapless dermatomal coverage. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2015; 2014:6254-7. [PMID: 25571426 DOI: 10.1109/embc.2014.6945058] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Spinal cord stimulation (SCS) is an effective therapy for treating chronic pain. The St. Jude Medical PENTA(TM) paddle lead features a 4 × 5 contact array for achieving broad, selective coverage of dorsal column (DC) fibers. The objective of this work was to evaluate DC activation regions that correspond to dermatomal coverage with use of the PENTA lead in conjunction with a lateral sweep programming algorithm. We used a two-stage computational model, including a finite element method model of field potentials in the spinal cord during stimulation, coupled to a biophysical cable model of mammalian, myelinated nerve fibers to determine fiber activation within the DC. We found that across contact configurations used clinically in the sweep algorithm, the activation region shifted smoothly between left and right DC, and could achieve gapless medio-lateral coverage in dermatomal fiber tract zones. Increasing stimulation amplitude between the DC threshold and discomfort threshold led to a greater area of activation and number of dermatomal zones covered on the left and/or right DC, including L1-2 zones corresponding to dermatomes of the lower back. This work demonstrates that the flexibility in contact selection offered by the PENTA lead may enable patient-specific tailoring of SCS.
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Min X, Kent AR, Rosenberg SP, Fayram TA. Modeling dermatome selectivity of single-and multiple-current source spinal cord stimulation systems. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2015; 2014:6246-9. [PMID: 25571424 DOI: 10.1109/embc.2014.6945056] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
A recently published computational modeling study of spinal cord stimulation (SCS) predicted that a multiple current source (MCS) system could generate a greater number of central points of stimulation in the dorsal column (DC) than a single current source (1 CS) system. However, the clinical relevance of this finding has not been established. The objective of this work was to compare the dermatomal zone selectivity of MCS and 1 CS systems. A finite element method (FEM) model was built with a representation of the spinal cord anatomy and a 2 × 8 paddle electrode array. Using a contact configuration with two aligned tripoles, the FEM model was used to solve for DC field potentials across incremental changes in current between the two cathodes, modeling the MCS and 1 CS systems. The activation regions within the DC were determined by coupling the FEM output to a biophysical nerve fiber model, and coverage was mapped to dermatomal zones. Results showed marginal differences in activated dermatomal zones between 1 CS and MCS systems. This indicates that a MCS system may not provide incremental therapeutic benefit as suggested in prior analysis.
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Shiraz AN, Craggs M, Leaker B, Demosthenous A. Minimizing Stimulus Current in a Wearable Pudendal Nerve Stimulator Using Computational Models. IEEE Trans Neural Syst Rehabil Eng 2015; 24:506-15. [PMID: 26415182 DOI: 10.1109/tnsre.2015.2480755] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
After spinal cord injury, functions of the lower urinary tract may be disrupted. A wearable device with surface electrodes which can effectively control the bladder functions would be highly beneficial to the patients. A trans-rectal pudendal nerve stimulator may provide such a solution. However, the major limiting factor in such a stimulator is the high level of current it requires to recruit the nerve fibers. Also, the variability of the trajectory of the nerve in different individuals should be considered. Using computational models and an approximate trajectory of the nerve derived from an MRI study, it is demonstrated in this paper that it may be possible to considerably reduce the required current levels for trans-rectal stimulation of the pudendal nerve compared to the values previously reported in the literature. This was corroborated by considering an ensemble of possible and probable variations of the trajectory. The outcome of this study suggests that trans-rectal stimulation of the pudendal nerve is a plausible long term solution for treating lower urinary tract dysfunctions after spinal cord injury.
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Model-based analysis and design of waveforms for efficient neural stimulation. PROGRESS IN BRAIN RESEARCH 2015; 222:147-62. [PMID: 26541380 DOI: 10.1016/bs.pbr.2015.07.031] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The design space for electrical stimulation of the nervous system is extremely large, and because the response to stimulation is highly nonlinear, the selection of stimulation parameters to achieve a desired response is a challenging problem. Computational models of the response of neurons to extracellular stimulation allow analysis of the effects of stimulation parameters on neural excitation and provide an approach to select or design optimal parameters of stimulation. Here, I review the use of computational models to understand the effects of stimulation waveform on the energy efficiency of neural excitation and to design novel stimulation waveforms to increase the efficiency of neural stimulation.
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Taghipour-Farshi H, Frounchi J, Ahmadiasl N, Shahabi P, Salekzamani Y. Effect of contacts configuration and location on selective stimulation of cuff electrode. Biomed Mater Eng 2015; 25:237-48. [DOI: 10.3233/bme-151281] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
| | - Javad Frounchi
- Department of Electrical and Computer Engineering, Tabriz University, Tabriz, Iran
| | - Nasser Ahmadiasl
- Department of Neurosciences, School of Advanced Medical Sciences, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Parviz Shahabi
- Department of Neurosciences, School of Advanced Medical Sciences, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Yaghoub Salekzamani
- Physical Medicine and Rehabilitation Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
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Update in facial nerve paralysis: tissue engineering and new technologies. Curr Opin Otolaryngol Head Neck Surg 2015; 22:291-9. [PMID: 24979369 DOI: 10.1097/moo.0000000000000062] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
PURPOSE OF REVIEW To present the recent advances in the treatment of facial paralysis, emphasizing the emerging technologies. This review will summarize the current state of the art in the management of facial paralysis and discuss the advances in nerve regeneration, facial reanimation, and use of novel biomaterials. This review includes surgical innovations in reinnervation and reanimation as well as progress with bioelectrical interfaces. RECENT FINDINGS The last decade has witnessed major advances in the understanding of nerve injury and approaches for management. Key innovations include strategies to accelerate nerve regeneration, provide tissue-engineered constructs that may replace nonfunctional nerves, approaches to influence axonal guidance, limiting of donor-site morbidity, and optimization of functional outcomes. Approaches to muscle transfer continue to evolve, and new technologies allow for electrical nerve stimulation and use of artificial tissues. SUMMARY The fields of biomedical engineering and facial reanimation increasingly intersect, with innovative surgical approaches complementing a growing array of tissue engineering tools. The goal of treatment remains the predictable restoration of natural facial movement, with acceptable morbidity and long-term stability. Advances in bioelectrical interfaces and nanotechnology hold promise for widening the window for successful treatment intervention and for restoring both lost neural inputs and muscle function.
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McGee MJ, Amundsen CL, Grill WM. Electrical stimulation for the treatment of lower urinary tract dysfunction after spinal cord injury. J Spinal Cord Med 2015; 38:135-46. [PMID: 25582564 PMCID: PMC4397195 DOI: 10.1179/2045772314y.0000000299] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Electrical stimulation for bladder control is an alternative to traditional methods of treating neurogenic lower urinary tract dysfunction (NLUTD) resulting from spinal cord injury (SCI). In this review, we systematically discuss the neurophysiology of bladder dysfunction following SCI and the applications of electrical stimulation for bladder control following SCI, spanning from historic clinical approaches to recent pre-clinical studies that offer promising new strategies that may improve the feasibility and success of electrical stimulation therapy in patients with SCI. Electrical stimulation provides a unique opportunity to control bladder function by exploiting neural control mechanisms. Our understanding of the applications and limitations of electrical stimulation for bladder control has improved due to many pre-clinical studies performed in animals and translational clinical studies. Techniques that have emerged as possible opportunities to control bladder function include pudendal nerve stimulation and novel methods of stimulation, such as high frequency nerve block. Further development of novel applications of electrical stimulation will drive progress towards effective therapy for SCI. The optimal solution for restoration of bladder control may encompass a combination of efficient, targeted electrical stimulation, possibly at multiple locations, and pharmacological treatment to enhance symptom control.
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Affiliation(s)
- Meredith J. McGee
- Department of Biomedical Engineering, Duke University, Durham, NC, USA
| | | | - Warren M. Grill
- Correspondence to: Warren M. Grill, Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Box 90281, Durham, NC 27708-0281 USA.
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Wark HAC, Black SR, Mathews KS, Cartwright PC, Gustafson KJ, Normann RA. Restoration from acute urinary dysfunction using Utah electrode arrays implanted into the feline pudendal nerve. Neuromodulation 2014; 18:317-23. [PMID: 25430001 DOI: 10.1111/ner.12259] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Accepted: 09/22/2014] [Indexed: 11/27/2022]
Abstract
OBJECTIVES To investigate intrafascicular pudendal nerve stimulation in felines as a means to restore urinary function in acute models of urinary incontinence, overactive bladder, and underactive bladder. MATERIALS AND METHODS Felines were anesthetized, and high-electrode-count (48 electrodes; 25 electrodes/mm(2) ) electrode arrays were implanted intrafascicularly into the pudendal nerve trunk. Electrodes were mapped for their ability to selectively or nonselectively excite the external anal sphincter, external urethral sphincter, and the detrusor bladder muscle. Statistical analysis was carried out to quantify reflexive voiding efficiencies, mean impedances of the microelectrodes used in this study, and to determine what differences, if any, in bladder contraction amplitudes were evoked by different electrode configurations. RESULTS Multielectrode arrays implanted into the pudendal nerve trunk were able to selectively and nonselectively excite genitourinary muscles. After inducing urinary incontinence with bilateral pudendal nerve transections (proximal to the implants), electrical stimulation delivered through certain microelectrodes was able to significantly reduce leaking (p = 0.008). Electrical stimulation delivered through detrusor selective electrodes was able to inhibit reflexive bladder contractions and excite bladder contractions, depending on the stimulation frequency. Specific electrode configurations were able to drive significantly (p < 0.001) larger bladder contractions than other electrode configurations, depending on the preparation. Successful reflexively or electrically driven bladder contractions were achieved in 46% and 38% of the preparations, respectively, an observation that has not been noted in previously published feline pudendal stimulation studies. CONCLUSIONS Multielectrode arrays implanted intrafascicularly into the pudendal nerve trunk may provide a promising new clinical neuromodulation therapy for the restoration of urinary function.
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Affiliation(s)
| | - Shana R Black
- Department of Bioengineering, University of Utah, Salt Lake City, UT, USA
| | | | - Patrick C Cartwright
- Department of Urology and Urological Surgery, University of Utah, Salt Lake City, UT, USA
| | - Kenneth J Gustafson
- Department of Bioengineering, Case Western Reserve University, Cleveland, OH, USA
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Grahn PJ, Mallory GW, Berry BM, Hachmann JT, Lobel DA, Lujan JL. Restoration of motor function following spinal cord injury via optimal control of intraspinal microstimulation: toward a next generation closed-loop neural prosthesis. Front Neurosci 2014; 8:296. [PMID: 25278830 PMCID: PMC4166363 DOI: 10.3389/fnins.2014.00296] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2014] [Accepted: 08/31/2014] [Indexed: 11/13/2022] Open
Abstract
Movement is planned and coordinated by the brain and carried out by contracting muscles acting on specific joints. Motor commands initiated in the brain travel through descending pathways in the spinal cord to effector motor neurons before reaching target muscles. Damage to these pathways by spinal cord injury (SCI) can result in paralysis below the injury level. However, the planning and coordination centers of the brain, as well as peripheral nerves and the muscles that they act upon, remain functional. Neuroprosthetic devices can restore motor function following SCI by direct electrical stimulation of the neuromuscular system. Unfortunately, conventional neuroprosthetic techniques are limited by a myriad of factors that include, but are not limited to, a lack of characterization of non-linear input/output system dynamics, mechanical coupling, limited number of degrees of freedom, high power consumption, large device size, and rapid onset of muscle fatigue. Wireless multi-channel closed-loop neuroprostheses that integrate command signals from the brain with sensor-based feedback from the environment and the system's state offer the possibility of increasing device performance, ultimately improving quality of life for people with SCI. In this manuscript, we review neuroprosthetic technology for improving functional restoration following SCI and describe brain-machine interfaces suitable for control of neuroprosthetic systems with multiple degrees of freedom. Additionally, we discuss novel stimulation paradigms that can improve synergy with higher planning centers and improve fatigue-resistant activation of paralyzed muscles. In the near future, integration of these technologies will provide SCI survivors with versatile closed-loop neuroprosthetic systems for restoring function to paralyzed muscles.
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Affiliation(s)
- Peter J. Grahn
- Mayo Clinic College of Medicine, Mayo ClinicRochester, MN, USA
| | | | | | - Jan T. Hachmann
- Department of Neurologic Surgery, Mayo ClinicRochester, MN, USA
| | | | - J. Luis Lujan
- Department of Neurologic Surgery, Mayo ClinicRochester, MN, USA
- Department of Physiology and Biomedical Engineering, Mayo ClinicRochester, MN, USA
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Bruns TM, Weber DJ, Gaunt RA. Microstimulation of afferents in the sacral dorsal root ganglia can evoke reflex bladder activity. Neurourol Urodyn 2014; 34:65-71. [PMID: 24464833 DOI: 10.1002/nau.22514] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Accepted: 09/19/2013] [Indexed: 11/07/2022]
Abstract
AIMS Pudendal afferent fibers can be excited using electrical stimulation to evoke reflex bladder activity. While this approach shows promise for restoring bladder function, stimulation of desired pathways, and integration of afferent signals for sensory feedback remains challenging. At sacral dorsal root ganglia (DRG), the convergence of pelvic and pudendal afferent fibers provides a unique location for access to lower urinary tract neurons. Our goal in this study was to demonstrate the potential of microstimulation in sacral DRG for evoking reflex bladder responses. METHODS Penetrating microelectrode arrays were inserted in the left S1 and S2 DRG of six anesthetized adult male cats. While the bladder volume was held at a level below the leak volume, single and multiple channel stimulation was performed using various stimulation patterns. RESULTS Reflex bladder excitation was observed in five cats, for stimulation in either S1 or S2 DRG at 1 Hz and 30-33 Hz with a pulse amplitude of 10-50 µA. Bladder relaxation was observed during a few trials. Adjacent electrodes frequently elicited very different responses. CONCLUSIONS These results demonstrate the potential of low-current microstimulation to recruit reflexive bladder responses. An approach such as this could be integrated with DRG recordings of bladder afferents to provide a closed-loop bladder neuroprosthesis.
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Affiliation(s)
- Tim M Bruns
- Department of Physical Medicine and Rehabilitation, University of Pittsburgh, Pittsburgh, Pennysylvania
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McGee MJ, Grill WM. Selective co-stimulation of pudendal afferents enhances bladder activation and improves voiding efficiency. Neurourol Urodyn 2013; 33:1272-8. [PMID: 23934615 DOI: 10.1002/nau.22474] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Accepted: 07/08/2013] [Indexed: 11/07/2022]
Abstract
AIMS Clinical application of pudendal nerve (PN) afferent stimulation to restore bladder emptying in persons with neurological disorders requires increased stimulation-evoked voiding efficiencies (VEs). We tested the hypothesis that selective co-stimulation of multiple PN branches, either bilateral dorsal nerve of the penis (DNP) stimulation or selective stimulation of both the cranial sensory nerve (CSN) and DNP, will evoke larger reflex bladder contractions and result in higher VEs than stimulation of any single afferent pathway alone. METHODS We measured the strength of bladder contractions, threshold volumes, and VEs produced by unilateral and bilateral stimulation of the DNP as well as singular and selective unilateral co-stimulation of the DNP and CSN in cats anesthetized with α-chloralose. RESULTS Co-stimulation of afferent pathways generated significantly larger isovolumetric bladder contractions and evoked contractions at lower threshold volumes than individual stimulation. Co-stimulation of pudendal afferents also suppressed dyssynergic activity in the external anal sphincter produced by low frequency individual stimulation. VE was significantly improved with co-stimulation (172 ± 6% of distention evoked volumes) over individual stimulation (141 ± 6%). CONCLUSIONS Both types of co-stimulation evoked larger bladder contractions and increased VE over individual branch PN afferent stimulation and distention-evoked voiding. The decreased threshold volumes required for reflex bladder activation and increased VEs with co-stimulation support the use of stimulation of multiple individual stimulation-evoked reflexes to improve voiding efficiency.
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Affiliation(s)
- Meredith J McGee
- Department of Biomedical Engineering, Duke University, Durham, North Carolina
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