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Peña E, Pelot NA, Grill WM. Computational models of compound nerve action potentials: Efficient filter-based methods to quantify effects of tissue conductivities, conduction distance, and nerve fiber parameters. PLoS Comput Biol 2024; 20:e1011833. [PMID: 38427699 PMCID: PMC10936855 DOI: 10.1371/journal.pcbi.1011833] [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: 10/19/2023] [Revised: 03/13/2024] [Accepted: 01/16/2024] [Indexed: 03/03/2024] Open
Abstract
BACKGROUND Peripheral nerve recordings can enhance the efficacy of neurostimulation therapies by providing a feedback signal to adjust stimulation settings for greater efficacy or reduced side effects. Computational models can accelerate the development of interfaces with high signal-to-noise ratio and selective recording. However, validation and tuning of model outputs against in vivo recordings remains computationally prohibitive due to the large number of fibers in a nerve. METHODS We designed and implemented highly efficient modeling methods for simulating electrically evoked compound nerve action potential (CNAP) signals. The method simulated a subset of fiber diameters present in the nerve using NEURON, interpolated action potential templates across fiber diameters, and filtered the templates with a weighting function derived from fiber-specific conduction velocity and electromagnetic reciprocity outputs of a volume conductor model. We applied the methods to simulate CNAPs from rat cervical vagus nerve. RESULTS Brute force simulation of a rat vagal CNAP with all 1,759 myelinated and 13,283 unmyelinated fibers in NEURON required 286 and 15,860 CPU hours, respectively, while filtering interpolated templates required 30 and 38 seconds on a desktop computer while maintaining accuracy. Modeled CNAP amplitude could vary by over two orders of magnitude depending on tissue conductivities and cuff opening within experimentally relevant ranges. Conduction distance and fiber diameter distribution also strongly influenced the modeled CNAP amplitude, shape, and latency. Modeled and in vivo signals had comparable shape, amplitude, and latency for myelinated fibers but not for unmyelinated fibers. CONCLUSIONS Highly efficient methods of modeling neural recordings quantified the large impact that tissue properties, conduction distance, and nerve fiber parameters have on CNAPs. These methods expand the computational accessibility of neural recording models, enable efficient model tuning for validation, and facilitate the design of novel recording interfaces for neurostimulation feedback and understanding physiological systems.
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Affiliation(s)
- Edgar Peña
- Department of Biomedical Engineering, Duke University, Durham, North Carolina, United States of America
| | - Nicole A. Pelot
- Department of Biomedical Engineering, Duke University, Durham, North Carolina, United States of America
| | - Warren M. Grill
- Department of Biomedical Engineering, Duke University, Durham, North Carolina, United States of America
- Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina, United States of America
- Department of Neurobiology, Duke University School of Medicine, Durham, North Carolina, United States of America
- Department of Neurosurgery, Duke University School of Medicine, Durham, North Carolina, United States of America
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Sharmin S, Karal MAS, Mahbub ZB, Rabbani KSE. Increase in conduction velocity in myelinated nerves due to stretch - An experimental verification. Front Neurosci 2023; 17:1084004. [PMID: 37139532 PMCID: PMC10149795 DOI: 10.3389/fnins.2023.1084004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2022] [Accepted: 03/28/2023] [Indexed: 05/05/2023] Open
Abstract
Background Based on published experimental evidence, a recent publication revealed an anomalous phenomenon in nerve conduction: for myelinated nerves the nerve conduction velocity (NCV) increases with stretch, which should have been the opposite according to existing concepts and theories since the diameter decreases on stretching. To resolve the anomaly, a new conduction mechanism for myelinated nerves was proposed based on physiological changes in the nodal region, introducing a new electrical resistance at the node. The earlier experimental measurements of NCV were performed on the ulnar nerve at different angles of flexion, focusing at the elbow region, but left some uncertainty for not reporting the lengths of nerve segments involved so that the magnitudes of stretch could not be estimated. Aims The aim of the present study was to relate NCV of myelinated nerves with different magnitudes of stretch through careful measurements. Method Essentially, we duplicated the earlier published NCV measurements on ulnar nerves at different angles of flexion but recording appropriate distances between nerve stimulation points on the skin carefully and assuming that the lengths of the underlying nerve segment undergoes the same percentages of changes as that on the skin outside. Results We found that the percentage of nerve stretch across the elbow is directly proportional to the angle of flexion and that the percentage increase in NCV is directly proportional to the percentage increase in nerve stretch. Page's L Trend test also supported the above trends of changes through obtained p values. Discussion Our experimental findings on myelinated nerves agree with those of some recent publications which measured changes in CV of single fibres, both myelinated and unmyelinated, on stretch. Analyzing all the observed results, we may infer that the new conduction mechanism based on the nodal resistance and proposed by the recent publication mentioned above is the most plausible one to explain the increase in CV with nerve stretch. Furthermore, interpreting the experimental results in the light of the new mechanism, we may suggest that the ulnar nerve at the forearm is always under a mild stretch, with slightly increased NCV of the myelinated nerves.
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Affiliation(s)
- Sabrina Sharmin
- Department of Physics, Bangladesh University of Engineering and Technology, Dhaka, Bangladesh
- Department of Arts and Sciences, Ahsanullah University of Science and Technology, Dhaka, Bangladesh
- *Correspondence: Sabrina Sharmin,
| | - Mohammad Abu Sayem Karal
- Department of Physics, Bangladesh University of Engineering and Technology, Dhaka, Bangladesh
- Mohammad Abu Sayem Karal,
| | - Zaid Bin Mahbub
- Department of Mathematics and Physics, North South University, Dhaka, Bangladesh
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Lim T, Kim M, Akbarian A, Kim J, Tresco PA, Zhang H. Conductive Polymer Enabled Biostable Liquid Metal Electrodes for Bioelectronic Applications. Adv Healthc Mater 2022; 11:e2102382. [PMID: 35112800 DOI: 10.1002/adhm.202102382] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Revised: 01/14/2022] [Indexed: 12/11/2022]
Abstract
Gallium (Ga)-based liquid metal materials have emerged as a promising material platform for soft bioelectronics. Unfortunately, Ga has limited biostability and electrochemical performance under physiological conditions, which can hinder the implementation of its use in bioelectronic devices. Here, an effective conductive polymer deposition strategy on the liquid metal surface to improve the biostability and electrochemical performance of Ga-based liquid metals for use under physiological conditions is demonstrated. The conductive polymer [poly(3,4-ethylene dioxythiophene):tetrafluoroborate]-modified liquid metal surface significantly outperforms the liquid metal.based electrode in mechanical, biological, and electrochemical studies. In vivo action potential recordings in behaving nonhuman primate and invertebrate models demonstrate the feasibility of using liquid metal electrodes for high-performance neural recording applications. This is the first demonstration of single-unit neural recording using Ga-based liquid metal bioelectronic devices to date. The results determine that the electrochemical deposition of conductive polymer over liquid metal can improve the material properties of liquid metal electrodes for use under physiological conditions and open numerous design opportunities for next-generation liquid metal-based bioelectronics.
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Affiliation(s)
- Taehwan Lim
- Department of Chemical Engineering University of Utah Salt Lake City Utah 84112 USA
| | - Minju Kim
- Department of Mechanical Engineering University of Utah Salt Lake City Utah 84112 USA
| | - Amir Akbarian
- Department of Ophthalmology and Visual Science University of Utah Salt Lake City Utah 84112 USA
| | - Jungkyu Kim
- Department of Mechanical Engineering University of Utah Salt Lake City Utah 84112 USA
| | - Patrick A. Tresco
- Department of Biomedical Engineering University of Utah Salt Lake City Utah 84112 USA
| | - Huanan Zhang
- Department of Chemical Engineering University of Utah Salt Lake City Utah 84112 USA
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Raabe W, Walk D. Median amplitude and frequency analysis of sensory nerve responses to intraepidermal stimulation. J Neurosci Methods 2022; 365:109377. [PMID: 34634281 DOI: 10.1016/j.jneumeth.2021.109377] [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: 07/03/2021] [Revised: 09/30/2021] [Accepted: 10/01/2021] [Indexed: 11/16/2022]
Abstract
BACKGROUND In clinical practice, small myelinated sensory fibers conveying pain and other sensations, Aδ-fibers, cannot be examined with available nerve conduction study techniques. NEW METHOD Equipment available in clinical neurophysiology laboratories is used to record from human sensory nerves multiple averaged responses to non-painful stimulation of intraepidermal nerves. Ten averaged responses are analyzed in all possible pair combinations with an algorithm applied to a 0.45 ms period of amplitude and frequency (power spectrum). The median of the algorithms is compared to control data to identify potentials generated as response to intraepidermal stimulation. RESULTS Median analysis of the algorithm applied to amplitude and frequency of multiple record pairs identifies potentials with conduction velocities of Aδ-fibers. The analysis of frequency (power spectrum) adds data to the analysis of amplitude. Median analysis of multiple record pairs yields more data than analysis of one pair of alternate averages with the same algorithms. COMPARISON WITH EXISTING METHOD(S) At present, analysis of one pair of alternate average records with an algorithm is the only method to identify Aδ-fiber generated potentials. Median analysis of the same algorithm applied to the amplitude of multiple record pairs increases the number of Aδ-fiber generated potentials identified. Neither median analysis of amplitude nor frequency of multiple records pairs has ever been used for conduction studies of nerve fibers, including Aδ-fibers. CONCLUSIONS Stimulation, recording and data analysis methods used in this study can be applied in the clinical EMG laboratory to identify the conduction velocities of Aδ-fibers in human sensory nerves.
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Affiliation(s)
- W Raabe
- Department of Neurology, University of Minnesota, Minneapolis, MN, USA.
| | - D Walk
- Department of Neurology, University of Minnesota, Minneapolis, MN, USA
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Eiber CD, Keast JR, Osborne PB. Simulating bidirectional peripheral neural interfaces in EIDORS. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2020; 2020:2934-2937. [PMID: 33018621 DOI: 10.1109/embc44109.2020.9175921] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Bioelectronic neural interfaces that deliver adaptive therapeutic stimulation in an intelligent manner must be able to sense and stimulate activity within the same nerve. Existing minimally-invasive peripheral neural interfaces can provide a read-out of the aggregate level of activity via electrical recordings of nerve activity, but these recordings are limited in terms of their specificity. Computational simulations can provide fine-grained insight into the contributions of different neural populations to the extracellular recording, but integration of the signals from individual nerve fibers requires knowledge of spread of current in the complex (heterogenous, anisotropic) extracellular space. We have developed a model which uses the open-source EIDORS package for extracellular stimulation and recording in the pelvic nerve. The pelvic nerve is the primary source of autonomic innervation to the pelvic organs, and a prime target for electrical stimulation to treat a variety of voiding disorders. We simulated recordings of spontaneous and electrically-evoked activity using biophysical models for myelinated and unmyelinated axons. As expected, stimulus thresholds depended strongly on both fibre type and electrode-fibre distance. In conclusion, EIDORS can be used to accurately simulate extracellular recording in complex, heterogenous neural geometries.
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Guo T, Chen L, Tran K, Ghelich P, Guo YS, Nolta N, Emadi S, Han M, Feng B. Extracellular single-unit recordings from peripheral nerve axons in vitro by a novel multichannel microelectrode array. SENSORS AND ACTUATORS. B, CHEMICAL 2020; 315:128111. [PMID: 32494111 PMCID: PMC7269151 DOI: 10.1016/j.snb.2020.128111] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The peripheral nervous system (PNS) is an attractive target for modulation of afferent input (e.g., nociceptive input signaling tissue damage) to the central nervous system. To advance mechanistic understanding of PNS neural encoding and modulation requires single-unit recordings from individual peripheral neurons or axons. This is challenged by multiple connective tissue layers surrounding peripheral nerve fibers that prevent electrical recordings by existing electrodes or electrode arrays. In this study, we developed a novel microelectrode array (MEA) via silicon-based microfabrication that consists of 5 parallel hydrophilic gold electrodes surrounded by silanized hydrophobic surfaces. This novel hydrophilic/hydrophobic surface pattern guides the peripheral nerve filaments to self-align towards the hydrophilic electrodes, which dramatically reduces the technical challenges in conducting single-unit recordings. We validated our MEA by recording simultaneous single-unit action potentials from individual axons in mouse sciatic nerves, including both myelinated A-fibers and unmyelinated C-fibers. We confirmed that our recordings were single units from individual axons by increasing nerve trunk electrical stimulus intensity, which did not alter the spike shape or amplitude. By reducing the technical challenges, our novel MEA will likely allow peripheral single-unit recordings to be adopted by a larger research community and thus expedite our mechanistic understanding of peripheral neural encoding and modulation.
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Affiliation(s)
- Tiantian Guo
- Department of Biomedical Engineering, University of Connecticut, CT 06269, USA
| | - Longtu Chen
- Department of Biomedical Engineering, University of Connecticut, CT 06269, USA
| | - Khanh Tran
- Department of Biomedical Engineering, University of Connecticut, CT 06269, USA
| | - Pejman Ghelich
- Department of Biomedical Engineering, University of Connecticut, CT 06269, USA
| | - Yi-Syuan Guo
- Department of Biomedical Engineering, University of Connecticut, CT 06269, USA
| | - Nicholas Nolta
- Department of Biomedical Engineering, University of Connecticut, CT 06269, USA
| | - Sharareh Emadi
- Department of Biomedical Engineering, University of Connecticut, CT 06269, USA
| | - Martin Han
- Department of Biomedical Engineering, University of Connecticut, CT 06269, USA
| | - Bin Feng
- Department of Biomedical Engineering, University of Connecticut, CT 06269, USA
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Chen L, Ilham SJ, Guo T, Emadi S, Feng B. In vitro multichannel single-unit recordings of action potentials from mouse sciatic nerve. Biomed Phys Eng Express 2017; 3:045020. [PMID: 29568573 PMCID: PMC5858727 DOI: 10.1088/2057-1976/aa7efa] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Electrode arrays interfacing with peripheral nerves are essential for neuromodulation devices targeting peripheral organs to relieve symptoms. To modulate (i.e., single-unit recording and stimulating) individual peripheral nerve axons remains a technical challenge. Here, we report an in vitro setup to allow simultaneous single-unit recordings from multiple mouse sciatic nerve axons. The sciatic nerve (~30 mm) was harvested and transferred to a tissue chamber, the ~5mm distal end pulled into an adjacent recording chamber filled with paraffin oil. A custom-built multi-wire electrode array was used to interface with split fine nerve filaments. Single-unit action potentials were evoked by electrical stimulation and recorded from 186 axons, of which 49.5% were classed A-type with conduction velocities (CV) greater than 1 m/s and 50.5% were C-type (CV < 1 m/s). The single-unit recordings had no apparent bias towards A- or C-type axons, were robust and repeatable for over 60 minutes, and thus an ideal opportunity to assess different neuromodulation strategies targeting peripheral nerves. For instance, ultrasonic modulation of action potential transmission was assessed using the setup, indicating increased nerve conduction velocity following ultrasound stimulus. This setup can also be used to objectively assess the design of next-generation electrode arrays interfacing with peripheral nerves.
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Affiliation(s)
- L Chen
- Department of Biomedical Engineering, University of Connecticut, Storrs, CT 06269, USA
| | - S J Ilham
- Department of Biomedical Engineering, University of Connecticut, Storrs, CT 06269, USA
| | - T Guo
- Department of Biomedical Engineering, University of Connecticut, Storrs, CT 06269, USA
| | - S Emadi
- Department of Biomedical Engineering, University of Connecticut, Storrs, CT 06269, USA
| | - B Feng
- Department of Biomedical Engineering, University of Connecticut, Storrs, CT 06269, USA
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Rossel O, Soulier F, Bernard S, Guiraud D, Cathébras G. A phantom axon setup for validating models of action potential recordings. Med Biol Eng Comput 2016; 54:1257-67. [PMID: 27016364 DOI: 10.1007/s11517-016-1463-3] [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: 09/05/2014] [Accepted: 01/30/2016] [Indexed: 10/22/2022]
Abstract
Electrode designs and strategies for electroneurogram recordings are often tested first by computer simulations and then by animal models, but they are rarely implanted for long-term evaluation in humans. The models show that the amplitude of the potential at the surface of an axon is higher in front of the nodes of Ranvier than at the internodes; however, this has not been investigated through in vivo measurements. An original experimental method is presented to emulate a single fiber action potential in an infinite conductive volume, allowing the potential of an axon to be recorded at both the nodes of Ranvier and the internodes, for a wide range of electrode-to-fiber radial distances. The paper particularly investigates the differences in the action potential amplitude along the longitudinal axis of an axon. At a short radial distance, the action potential amplitude measured in front of a node of Ranvier is two times larger than in the middle of two nodes. Moreover, farther from the phantom axon, the measured action potential amplitude is almost constant along the longitudinal axis. The results of this new method confirm the computer simulations, with a correlation of 97.6 %.
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Affiliation(s)
| | - Fabien Soulier
- LIRMM (Laboratoire d'Informatique de Robotique et de Microélectronique de Montpellier), Université Montpellier, Montpellier, France
| | - Serge Bernard
- LIRMM (Laboratoire d'Informatique de Robotique et de Microélectronique de Montpellier), CNRS, Montpellier, France
| | | | - Guy Cathébras
- LIRMM (Laboratoire d'Informatique de Robotique et de Microélectronique de Montpellier), Université Montpellier, Montpellier, France
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Yoshida K, Stieglitz T, Qiao S. Bioelectric interfaces for the peripheral nervous system. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2015; 2014:5272-5. [PMID: 25571183 DOI: 10.1109/embc.2014.6944815] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The peripheral nervous system (PNS) is an attractive target for those developing neural interfaces as an access point to the information flow coursing within our bodies. A successful neural interface could not only offer the means to understand basic neurophysiological mechanisms, such as how the body accomplishes complex coordinated control of multi degree of freedom body segments, but also could serve as the means of delivering treatment or therapies to restore physiological functions lost due to injury or disease. Our work in the development of such a neural interface focuses upon multi-microelectrode devices that are placed within the body of the nerve fascicle; mulit-channel intra-fascicular devices called the thin-film Longitudinal Intra-Fascicular Electrode (tfLIFE) and the Transversely Implanted Multi-Electrode (TIME). These structures provide high resolution access to the PNS and have demonstrated promise in animal work as well as in preliminary sub-acute work in human volunteers. However, work remains to improve upon their longevity and biocompatibility before full translation to clinical work can occur.
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Qiao S, Stieglitz T, Yoshida K. Estimation of the Electrode-Fiber Bioelectrical Coupling From Extracellularly Recorded Single Fiber Action Potentials. IEEE Trans Neural Syst Rehabil Eng 2015; 24:951-960. [PMID: 26469339 DOI: 10.1109/tnsre.2015.2489924] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Selective peripheral neural interfaces are currently capable of detecting minute electrical signals from nearby nerve fibers as single fiber action potential (SFAP) waveforms. Each detected single unit has a distinct shape originating from the unique bioelectrical coupling that exists between the neuroprosthetic electrode, the nerve fiber and the extracellular milieu. The bioelectrical coupling manifests itself as a series of low-pass Bessel filters acting on the action currents along the nerve fiber. Here, we present a method to estimate the electrode-fiber bioelectrical coupling through a quantitative analysis of the spectral distribution of the single units extracellularly recorded with the thin-film longitudinal intrafascicular electrode (tfLIFE) in an in vivo mammalian peripheral nerve animal model. The bioelectrical coupling estimate is an estimate of the electrode sensitivity function traversed by the nerve fiber, suggesting that it is as a means to directly measure the spatial relationship between the nerve fiber and electrode. It not only reflects a shape change to the SFAP, but has implications for in situ nerve fiber location tracking, in situ diagnostics of nerves and neuroproshetic electrodes, and assessment of the biocompatibility of neural interfaces and the health of the reporting nerve fibers.
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