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Wu Y, Temple BA, Sevilla N, Zhang J, Zhu H, Zolotavin P, Jin Y, Duarte D, Sanders E, Azim E, Nimmerjahn A, Pfaff SL, Luan L, Xie C. Ultraflexible electrodes for recording neural activity in the mouse spinal cord during motor behavior. Cell Rep 2024; 43:114199. [PMID: 38728138 PMCID: PMC11233142 DOI: 10.1016/j.celrep.2024.114199] [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: 11/10/2023] [Revised: 03/10/2024] [Accepted: 04/22/2024] [Indexed: 05/12/2024] Open
Abstract
Implantable electrode arrays are powerful tools for directly interrogating neural circuitry in the brain, but implementing this technology in the spinal cord in behaving animals has been challenging due to the spinal cord's significant motion with respect to the vertebral column during behavior. Consequently, the individual and ensemble activity of spinal neurons processing motor commands remains poorly understood. Here, we demonstrate that custom ultraflexible 1-μm-thick polyimide nanoelectronic threads can conduct laminar recordings of many neuronal units within the lumbar spinal cord of unrestrained, freely moving mice. The extracellular action potentials have high signal-to-noise ratio, exhibit well-isolated feature clusters, and reveal diverse patterns of activity during locomotion. Furthermore, chronic recordings demonstrate the stable tracking of single units and their functional tuning over multiple days. This technology provides a path for elucidating how spinal circuits compute motor actions.
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Affiliation(s)
- Yu Wu
- Department of Electrical and Computer Engineering, Rice University, Houston, TX 77005, USA; Rice Neuroengineering Initiative, Rice University, Houston, TX 77030, USA
| | - Benjamin A Temple
- Gene Expression Laboratory, Salk Institute for Biological Studies, La Jolla, CA 92037, USA; Neurosciences Graduate Program, University of California, San Diego, La Jolla, CA 92037, USA
| | - Nicole Sevilla
- Rice Neuroengineering Initiative, Rice University, Houston, TX 77030, USA; Department of Bioengineering, Rice University, Houston, TX 77030, USA
| | - Jiaao Zhang
- Department of Electrical and Computer Engineering, Rice University, Houston, TX 77005, USA; Rice Neuroengineering Initiative, Rice University, Houston, TX 77030, USA
| | - Hanlin Zhu
- Department of Electrical and Computer Engineering, Rice University, Houston, TX 77005, USA; Rice Neuroengineering Initiative, Rice University, Houston, TX 77030, USA
| | - Pavlo Zolotavin
- Department of Electrical and Computer Engineering, Rice University, Houston, TX 77005, USA; Rice Neuroengineering Initiative, Rice University, Houston, TX 77030, USA
| | - Yifu Jin
- Department of Electrical and Computer Engineering, Rice University, Houston, TX 77005, USA; Rice Neuroengineering Initiative, Rice University, Houston, TX 77030, USA
| | - Daniela Duarte
- Waitt Advanced Biophotonics Center, Salk Institute for Biological Studies, La Jolla, CA 92037, USA
| | - Elischa Sanders
- Molecular Neurobiology Laboratory, Salk Institute for Biological Studies, La Jolla, CA 92037, USA
| | - Eiman Azim
- Molecular Neurobiology Laboratory, Salk Institute for Biological Studies, La Jolla, CA 92037, USA
| | - Axel Nimmerjahn
- Waitt Advanced Biophotonics Center, Salk Institute for Biological Studies, La Jolla, CA 92037, USA
| | - Samuel L Pfaff
- Gene Expression Laboratory, Salk Institute for Biological Studies, La Jolla, CA 92037, USA.
| | - Lan Luan
- Department of Electrical and Computer Engineering, Rice University, Houston, TX 77005, USA; Rice Neuroengineering Initiative, Rice University, Houston, TX 77030, USA; Department of Bioengineering, Rice University, Houston, TX 77030, USA.
| | - Chong Xie
- Department of Electrical and Computer Engineering, Rice University, Houston, TX 77005, USA; Rice Neuroengineering Initiative, Rice University, Houston, TX 77030, USA; Department of Bioengineering, Rice University, Houston, TX 77030, USA.
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2
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Laflamme OD, Markin SN, Deska-Gauthier D, Banks R, Zhang Y, Danner SM, Akay T. Distinct roles of spinal commissural interneurons in transmission of contralateral sensory information. Curr Biol 2023; 33:3452-3464.e4. [PMID: 37531957 PMCID: PMC10528931 DOI: 10.1016/j.cub.2023.07.014] [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: 03/29/2023] [Revised: 05/29/2023] [Accepted: 07/10/2023] [Indexed: 08/04/2023]
Abstract
Crossed reflexes are mediated by commissural pathways transmitting sensory information to the contralateral side of the body, but the underlying network is not fully understood. Commissural pathways coordinating the activities of spinal locomotor circuits during locomotion have been characterized in mice, but their relationship to crossed reflexes is unknown. We show the involvement of two genetically distinct groups of commissural interneurons (CINs) described in mice, V0 and V3 CINs, in the crossed reflex pathways. Our data suggest that the exclusively excitatory V3 CINs are directly involved in the excitatory crossed reflexes and show that they are essential for the inhibitory crossed reflexes. In contrast, the V0 CINs, a population that includes excitatory and inhibitory CINs, are not directly involved in excitatory or inhibitory crossed reflexes but downregulate the inhibitory crossed reflexes. Our data provide insights into the spinal circuitry underlying crossed reflexes in mice, describing the roles of V0 and V3 CINs in crossed reflexes.
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Affiliation(s)
- Olivier D Laflamme
- Atlantic Mobility Action Project, Brain Repair Centre, Department of Medical Neuroscience, Dalhousie University, Halifax, NS B3T 0A6, Canada
| | - Sergey N Markin
- Department of Neurobiology and Anatomy, College of Medicine, Drexel University, Philadelphia, PA 19129, USA
| | - Dylan Deska-Gauthier
- Atlantic Mobility Action Project, Brain Repair Centre, Department of Medical Neuroscience, Dalhousie University, Halifax, NS B3T 0A6, Canada
| | - Rachel Banks
- Atlantic Mobility Action Project, Brain Repair Centre, Department of Medical Neuroscience, Dalhousie University, Halifax, NS B3T 0A6, Canada
| | - Ying Zhang
- Atlantic Mobility Action Project, Brain Repair Centre, Department of Medical Neuroscience, Dalhousie University, Halifax, NS B3T 0A6, Canada
| | - Simon M Danner
- Department of Neurobiology and Anatomy, College of Medicine, Drexel University, Philadelphia, PA 19129, USA
| | - Turgay Akay
- Atlantic Mobility Action Project, Brain Repair Centre, Department of Medical Neuroscience, Dalhousie University, Halifax, NS B3T 0A6, Canada.
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3
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Greaney MR, Wreden CC, Heckscher ES. Distinctive features of the central synaptic organization of Drosophila larval proprioceptors. Front Neural Circuits 2023; 17:1223334. [PMID: 37564629 PMCID: PMC10410283 DOI: 10.3389/fncir.2023.1223334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Accepted: 07/07/2023] [Indexed: 08/12/2023] Open
Abstract
Proprioceptive feedback is critically needed for locomotor control, but how this information is incorporated into central proprioceptive processing circuits remains poorly understood. Circuit organization emerges from the spatial distribution of synaptic connections between neurons. This distribution is difficult to discern in model systems where only a few cells can be probed simultaneously. Therefore, we turned to a relatively simple and accessible nervous system to ask: how are proprioceptors' input and output synapses organized in space, and what principles underlie this organization? Using the Drosophila larval connectome, we generated a map of the input and output synapses of 34 proprioceptors in several adjacent body segments (5-6 left-right pairs per segment). We characterized the spatial organization of these synapses, and compared this organization to that of other somatosensory neurons' synapses. We found three distinguishing features of larval proprioceptor synapses: (1) Generally, individual proprioceptor types display segmental somatotopy. (2) Proprioceptor output synapses both converge and diverge in space; they are organized into six spatial domains, each containing a unique set of one or more proprioceptors. Proprioceptors form output synapses along the proximal axonal entry pathway into the neuropil. (3) Proprioceptors receive few inhibitory input synapses. Further, we find that these three features do not apply to other larval somatosensory neurons. Thus, we have generated the most comprehensive map to date of how proprioceptor synapses are centrally organized. This map documents previously undescribed features of proprioceptors, raises questions about underlying developmental mechanisms, and has implications for downstream proprioceptive processing circuits.
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Affiliation(s)
- Marie R. Greaney
- Committee on Neurobiology, The University of Chicago, Chicago, IL, United States
| | - Chris C. Wreden
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL, United States
| | - Ellie S. Heckscher
- Committee on Neurobiology, The University of Chicago, Chicago, IL, United States
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL, United States
- Institute for Neuroscience, The University of Chicago, Chicago, IL, United States
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4
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Giorgi A, Cer AT, Mohan S, Perreault MC. Excitatory and Inhibitory Descending Commissural Interneurons Differentially Integrate Supraspinal and Segmental Sensory Signals. J Neurosci 2023; 43:5014-5029. [PMID: 37286348 PMCID: PMC10324999 DOI: 10.1523/jneurosci.2015-22.2023] [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: 10/27/2022] [Revised: 05/26/2023] [Accepted: 06/02/2023] [Indexed: 06/09/2023] Open
Abstract
The limited information about how descending inputs from the brain and sensory inputs from the periphery use spinal cord interneurons (INs) is a major barrier to understanding how these inputs may contribute to motor functions under normal and pathologic conditions. Commissural interneurons (CINs) are a heterogeneous population of spinal INs that has been implicated in crossed motor responses and bilateral motor coordination (ability to use the right and left side of the body in a coordinated manner) and, therefore, are likely involved in many types of movement (e.g., dynamic posture stabilization, jumping, kicking, walking). In this study, we incorporate mouse genetics, anatomy, electrophysiology, and single-cell calcium imaging to investigate how a subset of CINs, those with descending axons called dCINs, are recruited by descending reticulospinal and segmental sensory signals independently and in combination. We focus on two groups of dCINs set apart by their principal neurotransmitter (glutamate and GABA) and identified as VGluT2+ dCINs and GAD2+ dCINs. We show that VGluT2+ and GAD2+ dCINs are both extensively recruited by reticulospinal and sensory input alone but that VGluT2+ and GAD2+ dCINs integrate these inputs differently. Critically, we find that when recruitment depends on the combined action of reticulospinal and sensory inputs (subthreshold inputs), VGluT2+ dCINs, but not GAD2+ dCINs, are recruited. This difference in the integrative capacity of VGluT2+ and GAD2+ dCINs represents a circuit mechanism that the reticulospinal and segmental sensory systems may avail themselves of to regulate motor behaviors both normally and after injury.SIGNIFICANCE STATEMENT The way supraspinal and peripheral sensory inputs use spinal cord interneurons is fundamental to defining how motor functions are supported both in health and disease. This study, which focuses on dCINs, a heterogeneous population of spinal interneurons critical for crossed motor responses and bilateral motor coordination, shows that both glutamatergic (excitatory) and GABAergic (inhibitory) dCINs can be recruited by supraspinal (reticulospinal) or peripheral sensory inputs. Additionally, the study demonstrates that in conditions where the recruitment of dCINs depends on the combined action of reticulospinal and sensory inputs, only excitatory dCINs are recruited. The study uncovers a circuit mechanism that the reticulospinal and segmental sensory systems may avail themselves of to regulate motor behaviors both normally and after injury.
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Affiliation(s)
- Andrea Giorgi
- Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Abishag Tluang Cer
- Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Shruthi Mohan
- Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322
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5
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Cheng J, Guan NN. A fresh look at propriospinal interneurons plasticity and intraspinal circuits remodeling after spinal cord injury. IBRO Neurosci Rep 2023. [DOI: 10.1016/j.ibneur.2023.04.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2023] Open
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6
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Laflamme OD, Markin SN, Banks R, Zhang Y, Danner SM, Akay T. Distinct roles of spinal commissural interneurons in transmission of contralateral sensory information. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.16.528842. [PMID: 36824871 PMCID: PMC9949098 DOI: 10.1101/2023.02.16.528842] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
Abstract
Crossed reflexes (CR) are mediated by commissural pathways transmitting sensory information to the contralateral side of the body, but the underlying network is not fully understood. Commissural pathways coordinating the activities of spinal locomotor circuits during locomotion have been characterized in mice, but their relationship to CR is unknown. We show the involvement of two genetically distinct groups of commissural interneurons (CINs) described in mice, V0 and V3 CINs, in the CR pathways. Our data suggest that the exclusively excitatory V3 CINs are directly involved in the excitatory CR, and show that they are essential for the inhibitory CR. In contrast, the V0 CINs, a population that includes excitatory and inhibitory CINs, are not directly involved in excitatory or inhibitory CRs but down-regulate the inhibitory CR. Our data provide insights into the spinal circuitry underlying CR in mice, describing the roles of V0 and V3 CINs in CR.
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Affiliation(s)
- Olivier D. Laflamme
- Atlantic Mobility Action Project, Brain Repair Centre, Department of Medical Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Sergey N. Markin
- Department of Neurobiology and Anatomy, College of Medicine, Drexel University, Philadelphia, Pennsylvania, United States of America
| | - Rachel Banks
- Atlantic Mobility Action Project, Brain Repair Centre, Department of Medical Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Ying Zhang
- Atlantic Mobility Action Project, Brain Repair Centre, Department of Medical Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Simon M. Danner
- Department of Neurobiology and Anatomy, College of Medicine, Drexel University, Philadelphia, Pennsylvania, United States of America
| | - Turgay Akay
- Atlantic Mobility Action Project, Brain Repair Centre, Department of Medical Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada
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7
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Hsu LJ, Bertho M, Kiehn O. Deconstructing the modular organization and real-time dynamics of mammalian spinal locomotor networks. Nat Commun 2023; 14:873. [PMID: 36797254 PMCID: PMC9935527 DOI: 10.1038/s41467-023-36587-w] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Accepted: 02/07/2023] [Indexed: 02/18/2023] Open
Abstract
Locomotion empowers animals to move. Locomotor-initiating signals from the brain are funneled through descending neurons in the brainstem that act directly on spinal locomotor circuits. Little is known in mammals about which spinal circuits are targeted by the command and how this command is transformed into rhythmicity in the cord. Here we address these questions leveraging a mouse brainstem-spinal cord preparation from either sex that allows locating the locomotor command neurons with simultaneous Ca2+ imaging of spinal neurons. We show that a restricted brainstem area - encompassing the lateral paragigantocellular nucleus (LPGi) and caudal ventrolateral reticular nucleus (CVL) - contains glutamatergic neurons which directly initiate locomotion. Ca2+ imaging captures the direct LPGi/CVL locomotor initiating command in the spinal cord and visualizes spinal glutamatergic modules that execute the descending command and its transformation into rhythmic locomotor activity. Inhibitory spinal networks are recruited in a distinctly different pattern. Our study uncovers the principal logic of how spinal circuits implement the locomotor command using a distinct modular organization.
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Affiliation(s)
- Li-Ju Hsu
- Department of Neuroscience, University of Copenhagen, 2200, Copenhagen, Denmark.,Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden
| | - Maëlle Bertho
- Department of Neuroscience, University of Copenhagen, 2200, Copenhagen, Denmark.,Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden
| | - Ole Kiehn
- Department of Neuroscience, University of Copenhagen, 2200, Copenhagen, Denmark. .,Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden.
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8
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Spinal Cord Circuits: Models and Reality. NEUROPHYSIOLOGY+ 2022. [DOI: 10.1007/s11062-022-09927-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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9
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Garcia-Ramirez DL, Singh S, McGrath JR, Ha NT, Dougherty KJ. Identification of adult spinal Shox2 neuronal subpopulations based on unbiased computational clustering of electrophysiological properties. Front Neural Circuits 2022; 16:957084. [PMID: 35991345 PMCID: PMC9385948 DOI: 10.3389/fncir.2022.957084] [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: 05/30/2022] [Accepted: 07/08/2022] [Indexed: 11/13/2022] Open
Abstract
Spinal cord neurons integrate sensory and descending information to produce motor output. The expression of transcription factors has been used to dissect out the neuronal components of circuits underlying behaviors. However, most of the canonical populations of interneurons are heterogeneous and require additional criteria to determine functional subpopulations. Neurons expressing the transcription factor Shox2 can be subclassified based on the co-expression of the transcription factor Chx10 and each subpopulation is proposed to have a distinct connectivity and different role in locomotion. Adult Shox2 neurons have recently been shown to be diverse based on their firing properties. Here, in order to subclassify adult mouse Shox2 neurons, we performed multiple analyses of data collected from whole-cell patch clamp recordings of visually-identified Shox2 neurons from lumbar spinal slices. A smaller set of Chx10 neurons was included in the analyses for validation. We performed k-means and hierarchical unbiased clustering approaches, considering electrophysiological variables. Unlike the categorizations by firing type, the clusters displayed electrophysiological properties that could differentiate between clusters of Shox2 neurons. The presence of clusters consisting exclusively of Shox2 neurons in both clustering techniques suggests that it is possible to distinguish Shox2+Chx10- neurons from Shox2+Chx10+ neurons by electrophysiological properties alone. Computational clusters were further validated by immunohistochemistry with accuracy in a small subset of neurons. Thus, unbiased cluster analysis using electrophysiological properties is a tool that can enhance current interneuronal subclassifications and can complement groupings based on transcription factor and molecular expression.
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Affiliation(s)
| | | | | | | | - Kimberly J. Dougherty
- Department of Neurobiology and Anatomy, Marion Murray Spinal Cord Research Center, Drexel University College of Medicine, Philadelphia, PA, United States
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10
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Goetz SM, Howell B, Wang B, Li Z, Sommer MA, Peterchev AV, Grill WM. Isolating two sources of variability of subcortical stimulation to quantify fluctuations of corticospinal tract excitability. Clin Neurophysiol 2022; 138:134-142. [PMID: 35397278 PMCID: PMC9271909 DOI: 10.1016/j.clinph.2022.02.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Revised: 01/17/2022] [Accepted: 02/01/2022] [Indexed: 11/25/2022]
Abstract
OBJECTIVE Investigate the variability previously found with cortical stimulation and handheld transcranial magnetic stimulation (TMS) coils, criticized for its high potential of coil position fluctuations, bypassing the cortex using deep brain electrical stimulation (DBS) of the corticospinal tract with fixed electrodes where both latent variations of the coil position of TMS are eliminated and cortical excitation fluctuations should be absent. METHODS Ten input-output curves were recorded from five anesthetized cats with implanted DBS electrodes targeting the corticospinal tract. Goodness of fit of regressions with a conventional single variability source as well as a dual variability source model was quantified using a Schwarz Bayesian Information approach to avoid overfitting. RESULTS Motor evoked potentials (MEPs) through DBS of the corticospinal tract revealed short-term fluctuations in excitability of the targeted neuron pathway reflecting endogenous input-side variability at similar magnitude as TMS despite bypassing cortical networks. CONCLUSION Input-side variability, i.e., variability resulting in changing MEP amplitudes as if the stimulation strength was modulated, also emerges in electrical stimulation at a similar degree and is not primarily a result of varying stimulation, such as minor coil movements in TMS. More importantly, this variability component is present, although the cortex is bypassed. Thus, it may be of spinal origin, which can include cortical input from spinal projections. Further, the nonlinearity of the compound variability entails complex heteroscedastic non-Gaussian distributions and typically does not allow simple linear averages in statistical analysis of MEPs. As the average is dominated by outliers, it risks bias. With appropriate regression, the net effects of excitatory and inhibitory inputs to the targeted neuron pathways become noninvasively observable and quantifiable. SIGNIFICANCE The neural responses evoked by artificial stimulation in the cerebral cortex are variable. For example, MEPs in response to repeated presentations of the same stimulus can vary from no response to saturation across trials. Several sources of such variability have been suggested, and most of them may be technical in nature, but localization is missing.
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Affiliation(s)
- Stefan M Goetz
- Department of Engineering, University of Cambridge, Cambridge, CB2 1PZ, UK; Department of Psychiatry & Behavioral Sciences, Duke University, Durham, NC 27710, USA; Department of Neurosurgery, Duke University, Durham, NC 27710, USA; Department of Electrical & Computer Engineering, Duke University, Durham, NC 27708, USA; Duke Institute of Brain Sciences, Duke University, Durham, NC 27710, USA.
| | - Bryan Howell
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Boshuo Wang
- Department of Psychiatry & Behavioral Sciences, Duke University, Durham, NC 27710, USA
| | - Zhongxi Li
- Department of Electrical & Computer Engineering, Duke University, Durham, NC 27708, USA
| | - Marc A Sommer
- Duke Institute of Brain Sciences, Duke University, Durham, NC 27710, USA; Department of Biomedical Engineering, Duke University, Durham, NC 27708, USA; Department of Neurobiology, Duke University, Durham, NC 27710, USA
| | - Angel V Peterchev
- Department of Psychiatry & Behavioral Sciences, Duke University, Durham, NC 27710, USA; Department of Neurosurgery, Duke University, Durham, NC 27710, USA; Department of Electrical & Computer Engineering, Duke University, Durham, NC 27708, USA; Duke Institute of Brain Sciences, Duke University, Durham, NC 27710, USA; Department of Biomedical Engineering, Duke University, Durham, NC 27708, USA
| | - Warren M Grill
- Department of Neurosurgery, Duke University, Durham, NC 27710, USA; Department of Electrical & Computer Engineering, Duke University, Durham, NC 27708, USA; Duke Institute of Brain Sciences, Duke University, Durham, NC 27710, USA; Department of Biomedical Engineering, Duke University, Durham, NC 27708, USA; Department of Neurobiology, Duke University, Durham, NC 27710, USA
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11
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Merkulyeva N, Lyakhovetskii V, Gorskii O, Musienko P. Differences in backward and forward treadmill locomotion in decerebrated cats. J Exp Biol 2022; 225:jeb244210. [PMID: 35438747 PMCID: PMC9163443 DOI: 10.1242/jeb.244210] [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: 02/28/2022] [Accepted: 04/12/2022] [Indexed: 11/20/2022]
Abstract
Locomotion in different directions is vital for animal life and requires fine-adjusted neural activity of spinal networks. To compare the levels of recruitability of the locomotor circuitry responsible for forward and backward stepping, several electromyographic and kinematic characteristics of the two locomotor modes were analysed in decerebrated cats. Electrical epidural spinal cord stimulation was used to evoke forward and backward locomotion on a treadmill belt. The functional state of the bilateral spinal networks was tuned by symmetrical and asymmetrical epidural stimulation. A significant deficit in the backward but not forward stepping was observed when laterally shifted epidural stimulation was used but was not observed with central stimulation: only half of the cats were able to perform bilateral stepping, but all the cats performed forward stepping. This difference was in accordance with the features of stepping during central epidural stimulation. Both the recruitability and stability of the EMG signals as well as inter-limb coordination during backward stepping were significantly decreased compared with those during forward stepping. The possible underlying neural mechanisms of the obtained functional differences of backward and forward locomotion (spinal network organisation, commissural communication and supraspinal influence) are discussed.
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Affiliation(s)
| | | | - Oleg Gorskii
- Pavlov Institute of Physiology, 199034 St Petersburg, Russia
- Institute of Translational Biomedicine, St Petersburg State University, 199034 St Petersburg, Russia
| | - Pavel Musienko
- Pavlov Institute of Physiology, 199034 St Petersburg, Russia
- Institute of Translational Biomedicine, St Petersburg State University, 199034 St Petersburg, Russia
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12
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Zhang H, Shevtsova NA, Deska-Gauthier D, Mackay C, Dougherty KJ, Danner SM, Zhang Y, Rybak IA. The role of V3 neurons in speed-dependent interlimb coordination during locomotion in mice. eLife 2022; 11:e73424. [PMID: 35476640 PMCID: PMC9045817 DOI: 10.7554/elife.73424] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Accepted: 04/14/2022] [Indexed: 11/17/2022] Open
Abstract
Speed-dependent interlimb coordination allows animals to maintain stable locomotion under different circumstances. The V3 neurons are known to be involved in interlimb coordination. We previously modeled the locomotor spinal circuitry controlling interlimb coordination (Danner et al., 2017). This model included the local V3 neurons that mediate mutual excitation between left and right rhythm generators (RGs). Here, our focus was on V3 neurons involved in ascending long propriospinal interactions (aLPNs). Using retrograde tracing, we revealed a subpopulation of lumbar V3 aLPNs with contralateral cervical projections. V3OFF mice, in which all V3 neurons were silenced, had a significantly reduced maximal locomotor speed, were unable to move using stable trot, gallop, or bound, and predominantly used a lateral-sequence walk. To reproduce this data and understand the functional roles of V3 aLPNs, we extended our previous model by incorporating diagonal V3 aLPNs mediating inputs from each lumbar RG to the contralateral cervical RG. The extended model reproduces our experimental results and suggests that locally projecting V3 neurons, mediating left-right interactions within lumbar and cervical cords, promote left-right synchronization necessary for gallop and bound, whereas the V3 aLPNs promote synchronization between diagonal fore and hind RGs necessary for trot. The model proposes the organization of spinal circuits available for future experimental testing.
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Affiliation(s)
- Han Zhang
- Department of Medical Neuroscience, Brain Repair Centre, Faculty of Medicine, Dalhousie UniversityHalifaxCanada
| | - Natalia A Shevtsova
- Department of Neurobiology and Anatomy, College of Medicine, Drexel UniversityPhiladelphiaUnited States
| | - Dylan Deska-Gauthier
- Department of Medical Neuroscience, Brain Repair Centre, Faculty of Medicine, Dalhousie UniversityHalifaxCanada
| | - Colin Mackay
- Department of Medical Neuroscience, Brain Repair Centre, Faculty of Medicine, Dalhousie UniversityHalifaxCanada
| | - Kimberly J Dougherty
- Department of Neurobiology and Anatomy, College of Medicine, Drexel UniversityPhiladelphiaUnited States
| | - Simon M Danner
- Department of Neurobiology and Anatomy, College of Medicine, Drexel UniversityPhiladelphiaUnited States
| | - Ying Zhang
- Department of Medical Neuroscience, Brain Repair Centre, Faculty of Medicine, Dalhousie UniversityHalifaxCanada
| | - Ilya A Rybak
- Department of Neurobiology and Anatomy, College of Medicine, Drexel UniversityPhiladelphiaUnited States
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13
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Hop Mice Display Synchronous Hindlimb Locomotion and a Ventrally Fused Lumbar Spinal Cord Caused by a Point Mutation in Ttc26. eNeuro 2022; 9:ENEURO.0518-21.2022. [PMID: 35210288 PMCID: PMC8925726 DOI: 10.1523/eneuro.0518-21.2022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 02/01/2022] [Accepted: 02/05/2022] [Indexed: 11/28/2022] Open
Abstract
Identifying the spinal circuits controlling locomotion is critical for unravelling the mechanisms controlling the production of gaits. Development of the circuits governing left-right coordination relies on axon guidance molecules such as ephrins and netrins. To date, no other class of proteins have been shown to play a role during this process. Here, we have analyzed hop mice, which walk with a characteristic hopping gait using their hindlimbs in synchrony. Fictive locomotion experiments suggest that a local defect in the ventral spinal cord contributes to the aberrant locomotor phenotype. Hop mutant spinal cords had severe morphologic defects, including the absence of the ventral midline and a poorly defined border between white and gray matter. The hop mice represent the first model where, exclusively found in the lumbar domain, the left and right components of the central pattern generators (CPGs) are fused with a synchronous hindlimb gait as a functional consequence. These defects were associated with abnormal developmental processes, including a misplaced notochord and reduced induction of ventral progenitor domains. Whereas the underlying mutation in hop mice has been suggested to lie within the Ttc26 gene, other genes in close vicinity have been associated with gait defects. Mouse embryos carrying a CRISPR replicated point mutation within Ttc26 displayed an identical morphologic phenotype. Thus, our data suggest that the assembly of the lumbar CPG network is dependent on fully functional TTC26 protein.
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14
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Abstract
Locomotion is a universal motor behavior that is expressed as the output of many integrated brain functions. Locomotion is organized at several levels of the nervous system, with brainstem circuits acting as the gate between brain areas regulating innate, emotional, or motivational locomotion and executive spinal circuits. Here we review recent advances on brainstem circuits involved in controlling locomotion. We describe how delineated command circuits govern the start, speed, stop, and steering of locomotion. We also discuss how these pathways interface between executive circuits in the spinal cord and diverse brain areas important for context-specific selection of locomotion. A recurrent theme is the need to establish a functional connectome to and from brainstem command circuits. Finally, we point to unresolved issues concerning the integrated function of locomotor control. Expected final online publication date for the Annual Review of Neuroscience, Volume 45 is July 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Roberto Leiras
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jared M. Cregg
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Ole Kiehn
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
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15
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Abstract
When animals walk overground, mechanical stimuli activate various receptors located in muscles, joints, and skin. Afferents from these mechanoreceptors project to neuronal networks controlling locomotion in the spinal cord and brain. The dynamic interactions between the control systems at different levels of the neuraxis ensure that locomotion adjusts to its environment and meets task demands. In this article, we describe and discuss the essential contribution of somatosensory feedback to locomotion. We start with a discussion of how biomechanical properties of the body affect somatosensory feedback. We follow with the different types of mechanoreceptors and somatosensory afferents and their activity during locomotion. We then describe central projections to locomotor networks and the modulation of somatosensory feedback during locomotion and its mechanisms. We then discuss experimental approaches and animal models used to investigate the control of locomotion by somatosensory feedback before providing an overview of the different functional roles of somatosensory feedback for locomotion. Lastly, we briefly describe the role of somatosensory feedback in the recovery of locomotion after neurological injury. We highlight the fact that somatosensory feedback is an essential component of a highly integrated system for locomotor control. © 2021 American Physiological Society. Compr Physiol 11:1-71, 2021.
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Affiliation(s)
- Alain Frigon
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Quebec, Canada
| | - Turgay Akay
- Department of Medical Neuroscience, Atlantic Mobility Action Project, Brain Repair Center, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Boris I Prilutsky
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
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16
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Hongo Y, Matsui T, Nakata T, Furukawa H, Ono T, Kaida K, Suzuki K, Miyahira Y, Kobayashi Y. Morphological characterization of cholinergic partition cells: A transmitter-specific tracing study by Cre/lox-dependent viral gene expression. Ann Anat 2021; 240:151857. [PMID: 34785323 DOI: 10.1016/j.aanat.2021.151857] [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: 05/24/2021] [Revised: 11/04/2021] [Accepted: 11/05/2021] [Indexed: 10/19/2022]
Abstract
BACKGROUND Partition cells are cholinergic interneurons located in lamina VII of the spinal cord. Some partition cells are the source of the cholinergic boutons, known as C-terminals or C-boutons, that modulate the activity of spinal motor neurons. Therefore, partition cells might play an important role in motor control. Previous studies categorized partition cells into three groups (medial, intermediate, and lateral partition cells) according to their distance from the central canal. However, the morphological characteristics of the three groups remain obscure. METHODS To analyze the morphology of partition cells, we developed an efficient technique for visualization of specific neurons at single-cell level in particular positions using adenovirus vectors and Cre/lox mediated recombination. Cre/lox conditional vectors were injected into the spinal cord of choline acetyltransferase-Cre transgenic mice, and partition cells labeled by green fluorescent protein were reconstructed from histological serial sections at the single-cell level. RESULTS This technique allowed for the visualization of partition cells at high resolution and revealed that partition cells had various patterns of dendrite orientations and fields. Most of the visualized partition cells had more than 60% of their dendrites located in lamina VII of the spinal cord. Partition cells had dendrites extending into various Rexed's laminae (V, VI, VII, VIII, IX, and X), but none of the cells had dendrites extending dorsal to lamina IV. The dendrites of partition cells terminated both ipsilaterally and bilaterally. We also found that C-terminals on motor neurons may be derived from the middle/outer group of partition cells. CONCLUSIONS Our results indicated that partition cells have various morphological features of the dendritic pattern and may receive differential inputs. Our results suggested that C-terminals originate not only from medial but also from intermediate/lateral cholinergic partition cells. The present study suggests that intermediate/lateral partition cells modulate activities of motor neurons through C-terminal synapses.
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Affiliation(s)
- Yu Hongo
- Department of Anatomy and Neurobiology, National Defense Medical College, Tokorozawa, Saitama, Japan; Department of Neurology, National Defense Medical College, Tokorozawa, Saitama, Japan
| | - Toshiyasu Matsui
- Department of Anatomy and Neurobiology, National Defense Medical College, Tokorozawa, Saitama, Japan; Laboratory of Veterinary Anatomy, Faculty of Veterinary Medicine, Okayama University of Science, Imabari, Ehime, Japan
| | - Takahiro Nakata
- Department of Molecular and Cellular Anatomy, Faculty of Health Promotional Sciences, Tokoha University, Shizuoka, Japan; Department of Health Science, Ishikawa Prefectural Nursing University, Ishikawa, Japan.
| | - Hiroyo Furukawa
- Department of Health Science, Ishikawa Prefectural Nursing University, Ishikawa, Japan; Department of Clinical Nutrition, Ageo Central General Hospital, Saitama, Japan
| | - Takeshi Ono
- Department of Global Infectious Diseases and Tropical Medicine, National Defense Medical College, Tokorozawa, Saitama, Japan
| | - Kenichi Kaida
- Department of Neurology, National Defense Medical College, Tokorozawa, Saitama, Japan; Department of Neurology, Saitama Medical Center, Saitama Medical University, Kawagoe, Saitama, Japan
| | - Kazushi Suzuki
- Department of Neurology, National Defense Medical College, Tokorozawa, Saitama, Japan
| | - Yasushi Miyahira
- Department of Global Infectious Diseases and Tropical Medicine, National Defense Medical College, Tokorozawa, Saitama, Japan
| | - Yasushi Kobayashi
- Department of Anatomy and Neurobiology, National Defense Medical College, Tokorozawa, Saitama, Japan.
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17
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Akay T, Murray AJ. Relative Contribution of Proprioceptive and Vestibular Sensory Systems to Locomotion: Opportunities for Discovery in the Age of Molecular Science. Int J Mol Sci 2021; 22:1467. [PMID: 33540567 PMCID: PMC7867206 DOI: 10.3390/ijms22031467] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Revised: 01/20/2021] [Accepted: 01/26/2021] [Indexed: 12/29/2022] Open
Abstract
Locomotion is a fundamental animal behavior required for survival and has been the subject of neuroscience research for centuries. In terrestrial mammals, the rhythmic and coordinated leg movements during locomotion are controlled by a combination of interconnected neurons in the spinal cord, referred as to the central pattern generator, and sensory feedback from the segmental somatosensory system and supraspinal centers such as the vestibular system. How segmental somatosensory and the vestibular systems work in parallel to enable terrestrial mammals to locomote in a natural environment is still relatively obscure. In this review, we first briefly describe what is known about how the two sensory systems control locomotion and use this information to formulate a hypothesis that the weight of the role of segmental feedback is less important at slower speeds but increases at higher speeds, whereas the weight of the role of vestibular system has the opposite relation. The new avenues presented by the latest developments in molecular sciences using the mouse as the model system allow the direct testing of the hypothesis.
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Affiliation(s)
- Turgay Akay
- Atlantic Mobility Action Project, Brain Repair Centre, Department of Medical Neuroscience, Life Science Research Institute, Dalhousie University, Halifax, NS B3H 4R2, Canada
| | - Andrew J. Murray
- Sainsbury Wellcome Centre for Neural Circuits and Behaviour, University College London, London W1T 4JG, UK
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18
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Merlet AN, Harnie J, Macovei M, Doelman A, Gaudreault N, Frigon A. Cutaneous inputs from perineal region facilitate spinal locomotor activity and modulate cutaneous reflexes from the foot in spinal cats. J Neurosci Res 2021; 99:1448-1473. [PMID: 33527519 DOI: 10.1002/jnr.24791] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 11/25/2020] [Accepted: 12/23/2020] [Indexed: 12/27/2022]
Abstract
It is well known that mechanically stimulating the perineal region potently facilitates hindlimb locomotion and weight support in mammals with a spinal transection (spinal mammals). However, how perineal stimulation mediates this excitatory effect is poorly understood. We evaluated the effect of mechanically stimulating (vibration or pinch) the perineal region on ipsilateral (9-14 ms onset) and contralateral (14-18 ms onset) short-latency cutaneous reflex responses evoked by electrically stimulating the superficial peroneal or distal tibial nerve in seven adult spinal cats where hindlimb movement was restrained. Cutaneous reflexes were evoked before, during, and after mechanical stimulation of the perineal region. We found that vibration or pinch of the perineal region effectively triggered rhythmic activity, ipsilateral and contralateral to nerve stimulation. When electrically stimulating nerves, adding perineal stimulation modulated rhythmic activity by decreasing cycle and burst durations and by increasing the amplitude of flexors and extensors. Perineal stimulation also disrupted the timing of the ipsilateral rhythm, which had been entrained by nerve stimulation. Mechanically stimulating the perineal region decreased ipsilateral and contralateral short-latency reflex responses evoked by cutaneous inputs, a phenomenon we observed in muscles crossing different joints and located in different limbs. The results suggest that the excitatory effect of perineal stimulation on locomotion and weight support is mediated by increasing the excitability of central pattern-generating circuitry and not by increasing excitatory inputs from cutaneous afferents of the foot. Our results are consistent with a state-dependent modulation of reflexes by spinal interneuronal circuits.
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Affiliation(s)
- Angèle N Merlet
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Jonathan Harnie
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Madalina Macovei
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Adam Doelman
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Nathaly Gaudreault
- School of Rehabilitation, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada.,Centre de Recherche du CHUS, Sherbrooke, QC, Canada
| | - Alain Frigon
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada.,Centre de Recherche du CHUS, Sherbrooke, QC, Canada
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19
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Hofstoetter US, Danner SM, Freundl B, Binder H, Lackner P, Minassian K. Ipsi- and Contralateral Oligo- and Polysynaptic Reflexes in Humans Revealed by Low-Frequency Epidural Electrical Stimulation of the Lumbar Spinal Cord. Brain Sci 2021; 11:brainsci11010112. [PMID: 33467053 PMCID: PMC7830402 DOI: 10.3390/brainsci11010112] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 01/11/2021] [Accepted: 01/12/2021] [Indexed: 01/16/2023] Open
Abstract
Epidural electrical stimulation (EES) applied over the human lumbosacral spinal cord provides access to afferent fibers from virtually all lower-extremity nerves. These afferents connect to spinal networks that play a pivotal role in the control of locomotion. Studying EES-evoked responses mediated through these networks can identify some of their functional components. We here analyzed electromyographic (EMG) responses evoked by low-frequency (2–6 Hz) EES derived from eight individuals with chronic, motor complete spinal cord injury. We identified and separately analyzed three previously undescribed response types: first, crossed reflexes with onset latencies of ~55 ms evoked in the hamstrings; second, oligosynaptic reflexes within 50 ms post-stimulus superimposed on the monosynaptic posterior root-muscle reflexes in the flexor muscle tibialis anterior, but with higher thresholds and no rate-sensitive depression; third, polysynaptic responses with variable EMG shapes within 50–450 ms post-stimulus evoked in the tibialis anterior and triceps surae, some of which demonstrated consistent changes in latencies with graded EES. Our observations suggest the activation of commissural neurons, lumbar propriospinal interneurons, and components of the late flexion reflex circuits through group I and II proprioceptive afferent inputs. These potential neural underpinnings have all been related to spinal locomotion in experimental studies.
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Affiliation(s)
- Ursula S. Hofstoetter
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, 1090 Vienna, Austria;
| | - Simon M. Danner
- Department of Neurobiology and Anatomy, College of Medicine, Drexel University, Philadelphia, PA 19129, USA;
| | - Brigitta Freundl
- Neurological Center, Klinik Penzing—Wiener Gesundheitsverbund, 1140 Vienna, Austria; (B.F.); (H.B.); (P.L.)
| | - Heinrich Binder
- Neurological Center, Klinik Penzing—Wiener Gesundheitsverbund, 1140 Vienna, Austria; (B.F.); (H.B.); (P.L.)
| | - Peter Lackner
- Neurological Center, Klinik Penzing—Wiener Gesundheitsverbund, 1140 Vienna, Austria; (B.F.); (H.B.); (P.L.)
| | - Karen Minassian
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, 1090 Vienna, Austria;
- Correspondence:
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20
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Kinany N, Pirondini E, Micera S, Van De Ville D. Dynamic Functional Connectivity of Resting-State Spinal Cord fMRI Reveals Fine-Grained Intrinsic Architecture. Neuron 2020; 108:424-435.e4. [PMID: 32910894 DOI: 10.1016/j.neuron.2020.07.024] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 06/23/2020] [Accepted: 07/18/2020] [Indexed: 12/24/2022]
Abstract
The neuroimaging community has shown tremendous interest in exploring the brain's spontaneous activity using functional magnetic resonance imaging (fMRI). On the contrary, the spinal cord has been largely overlooked despite its pivotal role in processing sensorimotor signals. Only a handful of studies have probed the organization of spinal resting-state fluctuations, always using static measures of connectivity. Many innovative approaches have emerged for analyzing dynamics of brain fMRI, but they have not yet been applied to the spinal cord, although they could help disentangle its functional architecture. Here, we leverage a dynamic connectivity method based on the clustering of hemodynamic-informed transients to unravel the rich dynamic organization of spinal resting-state signals. We test this approach in 19 healthy subjects, uncovering fine-grained spinal components and highlighting their neuroanatomical and physiological nature. We provide a versatile tool, the spinal innovation-driven co-activation patterns (SpiCiCAP) framework, to characterize spinal circuits during rest and task, as well as their disruption in neurological disorders.
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Affiliation(s)
- Nawal Kinany
- Medical Image Processing Laboratory, Center for Neuroprosthetics, Institute of Bioengineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1202 Geneva, Switzerland; Bertarelli Foundation Chair in Translational Neuroengineering, Center for Neuroprosthetics, Institute of Bioengineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1202 Geneva, Switzerland
| | - Elvira Pirondini
- Department of Radiology and Medical Informatics, University of Geneva, 1211 Geneva, Switzerland
| | - Silvestro Micera
- Bertarelli Foundation Chair in Translational Neuroengineering, Center for Neuroprosthetics, Institute of Bioengineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1202 Geneva, Switzerland; The BioRobotics Institute and Department of Excellence in Robotics and AI, Scuola Superiore Sant'Anna, 56025 Pontedera, Italy.
| | - Dimitri Van De Ville
- Medical Image Processing Laboratory, Center for Neuroprosthetics, Institute of Bioengineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1202 Geneva, Switzerland; Department of Radiology and Medical Informatics, University of Geneva, 1211 Geneva, Switzerland.
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21
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Nepveu JF, Mikhail Y, Pion CH, Gossard JP, Barthélemy D. Assessment of vestibulocortical interactions during standing in healthy subjects. PLoS One 2020; 15:e0233843. [PMID: 32497147 PMCID: PMC7272097 DOI: 10.1371/journal.pone.0233843] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Accepted: 05/13/2020] [Indexed: 01/03/2023] Open
Abstract
The vestibular system is essential to produce adequate postural responses enabling voluntary movement. However, how the vestibular system influences corticospinal output during postural tasks is still unknown. Here, we examined the modulation exerted by the vestibular system on corticospinal output during standing. Healthy subjects (n = 25) maintained quiet standing, head facing forward with eyes closed. Galvanic vestibular stimulation (GVS) was applied bipolarly and binaurally at different delays prior to transcranial magnetic stimulation (TMS) which triggered motor evoked potentials (MEPs). With the cathode right/anode left configuration, MEPs in right Soleus (SOL) muscle were significantly suppressed when GVS was applied at ISI = 40 and 130ms before TMS. With the anode right/cathode left configuration, no significant changes were observed. Changes in the MEP amplitude were then compared to changes in the ongoing EMG when GVS was applied alone. Only the decrease in MEP amplitude at ISI = 40ms occurred without change in the ongoing EMG, suggesting that modulation occurred at a premotoneuronal level. We further investigated whether vestibular modulation could occur at the motor cortex level by assessing changes in the direct corticospinal pathways using the short-latency facilitation of the SOL Hoffmann reflex (H-reflex) by TMS. None of the observed modulation occurred at the level of motor cortex. Finally, using the long-latency facilitation of the SOL H-reflex, we were able to confirm that the suppression of MEP at ISI = 40ms occurred at a premotoneuronal level. The data indicate that vestibular signals modulate corticospinal output to SOL at both premotoneuronal and motoneuronal levels during standing.
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Affiliation(s)
- Jean-François Nepveu
- Centre for Interdisciplinary Research in Rehabilitation of Greater Montreal, CRIR, Montreal, Canada
- Department of Neuroscience, Université de Montréal, Montreal, Canada
| | - Youstina Mikhail
- Centre for Interdisciplinary Research in Rehabilitation of Greater Montreal, CRIR, Montreal, Canada
- School of Rehabilitation, Université de Montréal, Montreal, Canada
| | - Charlotte H. Pion
- Centre for Interdisciplinary Research in Rehabilitation of Greater Montreal, CRIR, Montreal, Canada
- School of Rehabilitation, Université de Montréal, Montreal, Canada
| | | | - Dorothy Barthélemy
- Centre for Interdisciplinary Research in Rehabilitation of Greater Montreal, CRIR, Montreal, Canada
- School of Rehabilitation, Université de Montréal, Montreal, Canada
- * E-mail:
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22
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Muraoka T, Kurtzer I. Spinal Circuits Mediate a Stretch Reflex Between the Upper Limbs in Humans. Neuroscience 2020; 431:115-127. [PMID: 32062020 DOI: 10.1016/j.neuroscience.2020.02.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 01/29/2020] [Accepted: 02/05/2020] [Indexed: 11/15/2022]
Abstract
Inter-limb reflexes play an important role in coordinating behaviors involving different limbs. Previous studies have demonstrated that human elbow muscles express an inter-limb stretch reflex at long-latency (50-100 ms), a timing consistent with a trans-cortical linkage. Here we probe for inter-limb stretch reflexes in the shoulder muscles of human participants. Unexpected torque pulses displaced one or both shoulders while participants adopted a steady posture against background torques. The results demonstrated inter-limb stretch reflexes occurring at short-latency for both shoulder extensors and flexors; the rapid timing (36-50 ms) must involve a spinal linkage for the two arms. Inter-limb stretch reflexes were also observed at long-latency yet they were opposite to the preceding short-latency; when the short-latency stretch reflex was excitatory then the long-latency stretch reflex was inhibitory and vice versa. Comparing the responses to contralateral arm displacement to those during simultaneous displacement of both arms revealed that inhibitory inter-limb stretch reflexes are independent of within-limb stretch reflexes, but that excitatory inter-limb stretch reflexes are suppressed by within-limb stretch reflexes. Our results provide the first demonstration of short-latency inter-limb stretch reflexes in the upper limb of humans and reveal interacting spinal circuits for within-limb and inter-limb stretch reflexes.
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Affiliation(s)
- Tetsuro Muraoka
- College of Economics, Nihon University, Tokyo, Japan; Department of Biomedical Sciences, New York Institute of Technology - College of Osteopathic Medicine, Old Westbury, New York, USA.
| | - Isaac Kurtzer
- Department of Biomedical Sciences, New York Institute of Technology - College of Osteopathic Medicine, Old Westbury, New York, USA
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23
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Khong KYW, Galán F, Soteropoulos DS. Rapid crossed responses in an intrinsic hand muscle during perturbed bimanual movements. J Neurophysiol 2019; 123:630-644. [PMID: 31851557 PMCID: PMC7052646 DOI: 10.1152/jn.00282.2019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Mechanical perturbations in one upper limb often elicit corrective responses in both the perturbed as well as its contralateral and unperturbed counterpart. These crossed corrective responses have been shown to be sensitive to the bimanual requirements of the perturbation, but crossed responses (CRs) in hand muscles are far less well studied. Here, we investigate corrective CRs in an intrinsic hand muscle, the first dorsal interosseous (1DI), to clockwise and anticlockwise mechanical perturbations to the contralateral index finger while participants performed a bimanual finger abduction task. We found that the CRs in the unperturbed 1DI were sensitive to the direction of the perturbation of the contralateral index finger. However, the size of the CRs was not sensitive to the amplitude of the contralateral perturbation nor its context within the bimanual task. The onset latency of the CRs was too fast to be purely transcortical (<70 ms) in 12/12 participants. This confirms that during isolated bimanual finger movements, sensory feedback from one hand can influence the other, but the pathways mediating the earliest components of this interaction are likely to involve subcortical systems such as the brainstem or spinal cord, which may afford less flexibility to the task demands.NEW & NOTEWORTHY An intrinsic hand muscle shows a crossed response to a perturbation of the contralateral index finger. The crossed response is dependent on the direction of the contralateral perturbation but not on the amplitude or the bimanual requirements of the movement, suggesting a far less flexible control policy than those governing crossed responses in more proximal muscles. The crossed response is too fast to be purely mediated by transcortical pathways, suggesting subcortical contributions.
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Affiliation(s)
- Katie Y W Khong
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom.,Queen's University Belfast, Belfast, Northern Ireland
| | - Ferran Galán
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom.,Department of Basic Neurosciences, Faculty of Medicine, University of Geneva, Geneva, Switzerland
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24
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Danner SM, Zhang H, Shevtsova NA, Borowska-Fielding J, Deska-Gauthier D, Rybak IA, Zhang Y. Spinal V3 Interneurons and Left-Right Coordination in Mammalian Locomotion. Front Cell Neurosci 2019; 13:516. [PMID: 31824266 PMCID: PMC6879559 DOI: 10.3389/fncel.2019.00516] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2019] [Accepted: 11/04/2019] [Indexed: 01/05/2023] Open
Abstract
Commissural interneurons (CINs) mediate interactions between rhythm-generating locomotor circuits located on each side of the spinal cord and are necessary for left-right limb coordination during locomotion. While glutamatergic V3 CINs have been implicated in left-right coordination, their functional connectivity remains elusive. Here, we addressed this issue by combining experimental and modeling approaches. We employed Sim1Cre/+; Ai32 mice, in which light-activated Channelrhodopsin-2 was selectively expressed in V3 interneurons. Fictive locomotor activity was evoked by NMDA and 5-HT in the isolated neonatal lumbar spinal cord. Flexor and extensor activities were recorded from left and right L2 and L5 ventral roots, respectively. Bilateral photoactivation of V3 interneurons increased the duration of extensor bursts resulting in a slowed down on-going rhythm. At high light intensities, extensor activity could become sustained. When light stimulation was shifted toward one side of the cord, the duration of extensor bursts still increased on both sides, but these changes were more pronounced on the contralateral side than on the ipsilateral side. Additional bursts appeared on the ipsilateral side not seen on the contralateral side. Further increase of the stimulation could suppress the contralateral oscillations by switching to a sustained extensor activity, while the ipsilateral rhythmic activity remained. To delineate the function of V3 interneurons and their connectivity, we developed a computational model of the spinal circuits consisting of two (left and right) rhythm generators (RGs) interacting via V0V, V0D, and V3 CINs. Both types of V0 CINs provided mutual inhibition between the left and right flexor RG centers and promoted left-right alternation. V3 CINs mediated mutual excitation between the left and right extensor RG centers. These interactions allowed the model to reproduce our current experimental data, while being consistent with previous data concerning the role of V0V and V0D CINs in securing left–right alternation and the changes in left–right coordination following their selective removal. We suggest that V3 CINs provide mutual excitation between the spinal neurons involved in the control of left and right extensor activity, which may promote left-right synchronization during locomotion.
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Affiliation(s)
- Simon M Danner
- Department of Neurobiology and Anatomy, College of Medicine, Drexel University, Philadelphia, PA, United States
| | - Han Zhang
- Department of Medical Neuroscience, Brain Repair Centre, Faculty of Medicine, Dalhousie University, Halifax, NS, Canada
| | - Natalia A Shevtsova
- Department of Neurobiology and Anatomy, College of Medicine, Drexel University, Philadelphia, PA, United States
| | - Joanna Borowska-Fielding
- Department of Medical Neuroscience, Brain Repair Centre, Faculty of Medicine, Dalhousie University, Halifax, NS, Canada
| | - Dylan Deska-Gauthier
- Department of Medical Neuroscience, Brain Repair Centre, Faculty of Medicine, Dalhousie University, Halifax, NS, Canada
| | - Ilya A Rybak
- Department of Neurobiology and Anatomy, College of Medicine, Drexel University, Philadelphia, PA, United States
| | - Ying Zhang
- Department of Medical Neuroscience, Brain Repair Centre, Faculty of Medicine, Dalhousie University, Halifax, NS, Canada
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25
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Maxwell DJ, Soteropoulos DS. The mammalian spinal commissural system: properties and functions. J Neurophysiol 2019; 123:4-21. [PMID: 31693445 DOI: 10.1152/jn.00347.2019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Commissural systems are essential components of motor circuits that coordinate left-right activity of the skeletomuscular system. Commissural systems are found at many levels of the neuraxis including the cortex, brainstem, and spinal cord. In this review we will discuss aspects of the mammalian spinal commissural system. We will focus on commissural interneurons, which project from one side of the cord to the other and form axonal terminations that are confined to the cord itself. Commissural interneurons form heterogeneous populations and influence a variety of spinal circuits. They can be defined according to a variety of criteria including, location in the spinal gray matter, axonal projections and targets, neurotransmitter phenotype, activation properties, and embryological origin. At present, we do not have a comprehensive classification of these cells, but it is clear that cells located within different areas of the gray matter have characteristic properties and make particular contributions to motor circuits. The contribution of commissural interneurons to locomotor function and posture is well established and briefly discussed. However, their role in other goal-orientated behaviors such as grasping, reaching, and bimanual tasks is less clear. This is partly because we only have limited information about the organization and functional properties of commissural interneurons in the cervical spinal cord of primates, including humans. In this review we shall discuss these various issues. First, we will consider the properties of commissural interneurons and subsequently examine what is known about their functions. We then discuss how they may contribute to restoration of function following spinal injury and stroke.
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Affiliation(s)
- David J Maxwell
- Spinal Cord Group, Institute of Neuroscience and Psychology, College of Medicine, Veterinary Medicine and Life Sciences, University of Glasgow, Glasgow, United Kingdom
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Iyengar RS, Pithapuram MV, Singh AK, Raghavan M. Curated Model Development Using NEUROiD: A Web-Based NEUROmotor Integration and Design Platform. Front Neuroinform 2019; 13:56. [PMID: 31440153 PMCID: PMC6693358 DOI: 10.3389/fninf.2019.00056] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Accepted: 07/11/2019] [Indexed: 11/24/2022] Open
Abstract
Decades of research on neuromotor circuits and systems has provided valuable information on neuronal control of movement. Computational models of several elements of the neuromotor system have been developed at various scales, from sub-cellular to system. While several small models abound, their structured integration is the key to building larger and more biologically realistic models which can predict the behavior of the system in different scenarios. This effort calls for integration of elements across neuroscience and musculoskeletal biomechanics. There is also a need for development of methods and tools for structured integration that yield larger in silico models demonstrating a set of desired system responses. We take a small step in this direction with the NEUROmotor integration and Design (NEUROiD) platform. NEUROiD helps integrate results from motor systems anatomy, physiology, and biomechanics into an integrated neuromotor system model. Simulation and visualization of the model across multiple scales is supported. Standard electrophysiological operations such as slicing, current injection, recording of membrane potential, and local field potential are part of NEUROiD. The platform allows traceability of model parameters to primary literature. We illustrate the power and utility of NEUROiD by building a simple ankle model and its controlling neural circuitry by curating a set of published components. NEUROiD allows researchers to utilize remote high-performance computers for simulation, while controlling the model using a web browser.
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Affiliation(s)
- Raghu Sesha Iyengar
- Spine Labs, Department of Biomedical Engineering, Indian Institute of Technology, Hyderabad, India
| | - Madhav Vinodh Pithapuram
- Spine Labs, Department of Biomedical Engineering, Indian Institute of Technology, Hyderabad, India
| | - Avinash Kumar Singh
- Spine Labs, Department of Biomedical Engineering, Indian Institute of Technology, Hyderabad, India
| | - Mohan Raghavan
- Spine Labs, Department of Biomedical Engineering, Indian Institute of Technology, Hyderabad, India
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Zelenin PV, Lyalka VF, Orlovsky GN, Deliagina TG. Changes in Activity of Spinal Postural Networks at Different Time Points After Spinalization. Front Cell Neurosci 2019; 13:387. [PMID: 31496938 PMCID: PMC6712497 DOI: 10.3389/fncel.2019.00387] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Accepted: 08/06/2019] [Indexed: 11/25/2022] Open
Abstract
Postural limb reflexes (PLRs) are an essential component of postural corrections. Spinalization leads to disappearance of postural functions (including PLRs). After spinalization, spastic, incorrectly phased motor responses to postural perturbations containing oscillatory EMG bursting gradually develop, suggesting plastic changes in the spinal postural networks. Here, to reveal these plastic changes, rabbits at 3, 7, and 30 days after spinalization at T12 were decerebrated, and responses of spinal interneurons from L5 along with hindlimb muscles EMG responses to postural sensory stimuli, causing PLRs in subjects with intact spinal cord (control), were characterized. Like in control and after acute spinalization, at each of three studied time points after spinalization, neurons responding to postural sensory stimuli were found. Proportion of such neurons during 1st month after spinalization did not reach the control level, and was similar to that observed after acute spinalization. In contrast, their activity (which was significantly decreased after acute spinalization) reached the control value at 3 days after spinalization and remained close to this level during the following month. However, the processing of postural sensory signals, which was severely distorted after acute spinalization, did not recover by 30 days after injury. In addition, we found a significant enhancement of the oscillatory activity in a proportion of the examined neurons, which could contribute to generation of oscillatory EMG bursting. Motor responses to postural stimuli (which were almost absent after acute spinalization) re-appeared at 3 days after spinalization, although they were very weak, irregular, and a half of them was incorrectly phased in relation to postural stimuli. Proportion of correct and incorrect motor responses remained almost the same during the following month, but their amplitude gradually increased. Thus, spinalization triggers two processes of plastic changes in the spinal postural networks: rapid (taking days) restoration of normal activity level in spinal interneurons, and slow (taking months) recovery of motoneuronal excitability. Most likely, recovery of interneuronal activity underlies re-appearance of motor responses to postural stimuli. However, absence of recovery of normal processing of postural sensory signals and enhancement of oscillatory activity of neurons result in abnormal PLRs and loss of postural functions.
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Qi W, Nakajima T, Sakamoto M, Kato K, Kawakami Y, Kanosue K. Walking and finger tapping can be done with independent rhythms. Sci Rep 2019; 9:7620. [PMID: 31110194 PMCID: PMC6527701 DOI: 10.1038/s41598-019-43824-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Accepted: 05/02/2019] [Indexed: 11/16/2022] Open
Abstract
Rhythmic movements occur in many aspects of daily life. Examples include clapping the hands and walking. The production of two independent rhythms with multiple limbs is considered to be extremely difficult. In the present study we evaluated whether two different, independent rhythms that involved finger tapping and walking could be produced. In Experiment I, twenty subjects that had no experience of musical instrument training performed rhythmic finger tapping with the right index finger and one of four different lower limb movements; (1) self-paced walking, (2) given-paced walking, (3) alternative bilateral heel tapping from a sitting position, and (4) unilateral heel tapping with the leg ipsilateral to the tapping finger from a sitting position. The target intervals of finger tapping and heel strikes for walking step/heel tapping were set at 375 ms and 600 ms, respectively. The even distribution of relative phases between instantaneous finger tapping and heel strike was taken as the criteria of independency for the two rhythms. In the self-paced walking and given-paced walking tasks, 16 out of 20 subjects successfully performed finger tapping and walking with independent rhythms without any special practice. On the other hand, in the bipedal heels striking and unipedal heel striking tasks 19 subjects failed to perform the two movements independently, falling into interrelated rhythms with the ratio mostly being 2:1. In Experiment II, a similar independency of finger tapping and walking at a given pace was observed for heel strike intervals of 400, 600, and 800 ms, as well as at the constant 375 ms for finger tapping. These results suggest that finger tapping and walking are controlled by separate neural control mechanisms, presumably with a supra-spinal locus for finger tapping, and a spinal location for walking.
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Affiliation(s)
- Weihuang Qi
- Graduate School of Sport Sciences, Waseda University, Saitama, Japan
| | - Tsuyoshi Nakajima
- Department of Integrative Physiology, Kyorin University School of Medicine, Tokyo, Japan
| | - Masanori Sakamoto
- Faculty of Education, Department of Physical Education, Kumamoto University, Kumamoto, Japan
| | - Kouki Kato
- Faculty of Sport Sciences, Waseda University, Saitama, Japan
| | - Yasuo Kawakami
- Faculty of Sport Sciences, Waseda University, Saitama, Japan
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Wu TL, Yang PF, Wang F, Shi Z, Mishra A, Wu R, Chen LM, Gore JC. Intrinsic functional architecture of the non-human primate spinal cord derived from fMRI and electrophysiology. Nat Commun 2019; 10:1416. [PMID: 30926817 PMCID: PMC6440970 DOI: 10.1038/s41467-019-09485-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2018] [Accepted: 03/05/2019] [Indexed: 02/07/2023] Open
Abstract
Resting-state functional MRI (rsfMRI) has recently revealed correlated signals in the spinal cord horns of monkeys and humans. However, the interpretation of these rsfMRI correlations as indicators of functional connectivity in the spinal cord remains unclear. Here, we recorded stimulus-evoked and spontaneous spiking activity and local field potentials (LFPs) from monkey spinal cord in order to validate fMRI measures. We found that both BOLD and electrophysiological signals elicited by tactile stimulation co-localized to the ipsilateral dorsal horn. Temporal profiles of stimulus-evoked BOLD signals covaried with LFP and multiunit spiking in a similar way to those observed in the brain. Functional connectivity of dorsal horns exhibited a U-shaped profile along the dorsal-intermediate-ventral axis. Overall, these results suggest that there is an intrinsic functional architecture within the gray matter of a single spinal segment, and that rsfMRI signals at high field directly reflect this underlying spontaneous neuronal activity.
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Affiliation(s)
- Tung-Lin Wu
- Vanderbilt University Institute of Imaging Science, Nashville, TN, 37232, USA.
- Biomedical Engineering, Vanderbilt University, Nashville, TN, 37232, USA.
| | - Pai-Feng Yang
- Vanderbilt University Institute of Imaging Science, Nashville, TN, 37232, USA
- Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - Feng Wang
- Vanderbilt University Institute of Imaging Science, Nashville, TN, 37232, USA
- Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - Zhaoyue Shi
- Vanderbilt University Institute of Imaging Science, Nashville, TN, 37232, USA
- Biomedical Engineering, Vanderbilt University, Nashville, TN, 37232, USA
| | - Arabinda Mishra
- Vanderbilt University Institute of Imaging Science, Nashville, TN, 37232, USA
- Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - Ruiqi Wu
- Vanderbilt University Institute of Imaging Science, Nashville, TN, 37232, USA
| | - Li Min Chen
- Vanderbilt University Institute of Imaging Science, Nashville, TN, 37232, USA
- Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
| | - John C Gore
- Vanderbilt University Institute of Imaging Science, Nashville, TN, 37232, USA
- Biomedical Engineering, Vanderbilt University, Nashville, TN, 37232, USA
- Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, 37232, USA
- Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, 37232, USA
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Laflamme OD, Akay T. Excitatory and inhibitory crossed reflex pathways in mice. J Neurophysiol 2018; 120:2897-2907. [PMID: 30303749 DOI: 10.1152/jn.00450.2018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Sensory information from one leg has been known to elicit reflex responses in the contralateral leg, known as "crossed reflexes," and these have been investigated extensively in cats and humans. Furthermore, experiments with mice have shown commissural pathways in detail by using in vitro and in vivo physiological approaches combined with genetics. However, the relationship between these commissural pathways discovered in mice and crossed reflex pathways described in cats and humans is not known. In this study, we analyzed the crossed reflex in mice by using in vivo electromyographic recording techniques combined with peripheral nerve stimulation protocols to provide a detailed description of the crossed reflex pathways. We show that excitatory crossed reflexes are mediated by both proprioceptive and cutaneous afferent activation. In addition, we provide evidence for a short-latency inhibitory crossed reflex pathway likely mediated by cutaneous feedback. Furthermore, the short-latency crossed inhibition is downregulated in the knee extensor muscle and the ankle flexor muscle during locomotion. In conclusion, this article provides an analysis of excitatory and inhibitory crossed reflex pathways during resting and locomoting mice in vivo. The data presented in this article pave the way for future research aimed at understanding crossed reflexes using genetics in mice. NEW & NOTEWORTHY We describe for the first time excitatory and inhibitory crossed reflex pathways in mouse spinal cord in vivo and show that the inhibitory pathways are modulated during walking. This is a first step toward an understanding of crossed reflexes and their function during walking using in vivo recording techniques combined with mouse genetics.
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Affiliation(s)
- Olivier D Laflamme
- Atlantic Mobility Action Project, Brain Repair Center, Department of Medical Neuroscience, Dalhousie University , Halifax, Nova Scotia , Canada
| | - Turgay Akay
- Atlantic Mobility Action Project, Brain Repair Center, Department of Medical Neuroscience, Dalhousie University , Halifax, Nova Scotia , Canada
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Fisher KM, Lilak A, Garner J, Darian-Smith C. Extensive somatosensory and motor corticospinal sprouting occurs following a central dorsal column lesion in monkeys. J Comp Neurol 2018; 526:2373-2387. [PMID: 30014461 DOI: 10.1002/cne.24491] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 06/08/2018] [Accepted: 06/11/2018] [Indexed: 01/16/2023]
Abstract
The corticospinal tract (CST) forms the major descending pathway mediating voluntary hand movements in primates, and originates from ∼nine cortical subdivisions in the macaque. While the terminals of spared motor CST axons are known to sprout locally within the cord in response to spinal injury, little is known about the response of the other CST subcomponents. We previously reported that following a cervical dorsal root lesion (DRL), the primary somatosensory (S1) CST terminal projection retracts to 60% of its original terminal domain, while the primary motor (M1) projection remains robust (Darian-Smith et al., J. Neurosci., 2013). In contrast, when a dorsal column lesion (DCL) is added to the DRL, the S1 CST, in addition to the M1 CST, extends its terminal projections bilaterally and caudally, well beyond normal range (Darian-Smith et al., J. Neurosci., 2014). Are these dramatic responses linked entirely to the inclusion of a CNS injury (i.e., DCL), or do the two components summate or interact? We addressed this directly, by comparing data from monkeys that received a unilateral DCL alone, with those that received either a DRL or a combined DRL/DCL. Approximately 4 months post-lesion, the S1 hand region was mapped electrophysiologically, and anterograde tracers were injected bilaterally into the region deprived of normal input, to assess spinal terminal labeling. Using multifactorial analyses, we show that following a DCL alone (i.e., cuneate fasciculus lesion), the S1 and M1 CSTs also sprout significantly and bilaterally beyond normal range, with a termination pattern suggesting some interaction between the peripheral and central lesions.
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Affiliation(s)
- Karen M Fisher
- Department of Comparative Medicine, Stanford University School of Medicine, Stanford, California
| | - Alayna Lilak
- Department of Comparative Medicine, Stanford University School of Medicine, Stanford, California
| | - Joseph Garner
- Department of Comparative Medicine, Stanford University School of Medicine, Stanford, California
| | - Corinna Darian-Smith
- Department of Comparative Medicine, Stanford University School of Medicine, Stanford, California
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V2a interneuron diversity tailors spinal circuit organization to control the vigor of locomotor movements. Nat Commun 2018; 9:3370. [PMID: 30135498 PMCID: PMC6105610 DOI: 10.1038/s41467-018-05827-9] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Accepted: 07/31/2018] [Indexed: 01/12/2023] Open
Abstract
Locomotion is a complex motor task generated by spinal circuits driving motoneurons in a precise sequence to control the timing and vigor of movements, but the underlying circuit logic remains to be understood. Here we reveal, in adult zebrafish, how the diversity and selective distribution of two V2a interneuron types within the locomotor network transform commands into an appropriate, task-dependent circuit organization. Bursting-type V2a interneurons with unidirectional axons predominantly target distal dendrites of slow motoneurons to provide potent, non-linear excitation involving NMDA-dependent potentiation. A second type, non-bursting V2a interneurons with bidirectional axons, predominantly target somata of fast motoneurons, providing weaker, non-potentiating excitation. Together, this ensures the rapid, first-order recruitment of the slow circuit, while reserving the fast circuit for highly salient stimuli involving synchronous inputs. Our results thus identify how interneuron diversity is captured and transformed into a parsimonious task-specific circuit design controlling the vigor of locomotion.
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Gervasio S, Finocchietti S, Stevenson AJT, Mrachacz-Kersting N. Delayed muscle onset soreness in the gastrocnemius muscle attenuates the spinal contribution to interlimb communication. Eur J Appl Physiol 2018; 118:2393-2402. [PMID: 30132112 DOI: 10.1007/s00421-018-3966-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Accepted: 08/08/2018] [Indexed: 11/30/2022]
Abstract
PURPOSE Delayed onset muscle soreness (DOMS) has been shown to induce changes in muscle activity during walking. The aim of this study was to elucidate whether DOMS also affects interlimb communication during walking by investigating its effect on short-latency crossed responses (SLCRs). METHODS SLCRs were elicited in two recording sessions by electrically stimulating the tibial nerve of the ipsilateral leg, and quantified in the contralateral gastrocnemius muscle. The second recording session occurred 24-36 h after the participants (n = 11) performed eccentric exercises with the ipsilateral calf. RESULTS DOMS caused a decreased magnitude of the spinally mediated component of the SLCR in the contralateral gastrocnemius medialis. CONCLUSIONS The results of the current study provide insight on the relationship between pain and motor control. Muscle pain affects the spinal pathway mediating interlimb communication, which might result in a reduced ability to maintain dynamical stability during walking.
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Affiliation(s)
- Sabata Gervasio
- Department of Health Science and Technology, Center for Sensory-Motor Interaction (SMI), Aalborg University, Fredrik Bajers Vej 7 D-3, 9220, Aalborg, Denmark.
| | - Sara Finocchietti
- U-VIP: Unit for Visually Impaired People, Center for Human Technologies, Italian Institute of Technology (IIT), Genova, Italy
| | - Andrew J T Stevenson
- Department of Health Science and Technology, Center for Sensory-Motor Interaction (SMI), Aalborg University, Fredrik Bajers Vej 7 D-3, 9220, Aalborg, Denmark
| | - Natalie Mrachacz-Kersting
- Department of Health Science and Technology, Center for Sensory-Motor Interaction (SMI), Aalborg University, Fredrik Bajers Vej 7 D-3, 9220, Aalborg, Denmark
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Mrachacz-Kersting N, Gervasio S, Marchand-Pauvert V. Evidence for a Supraspinal Contribution to the Human Crossed Reflex Response During Human Walking. Front Hum Neurosci 2018; 12:260. [PMID: 30008667 PMCID: PMC6034574 DOI: 10.3389/fnhum.2018.00260] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2018] [Accepted: 06/06/2018] [Indexed: 01/07/2023] Open
Abstract
In humans, an ipsilateral tibial nerve (iTN) stimulation elicits short-latency-crossed-responses (SLCR) comprised of two bursts in the contralateral gastrocnemius lateralis (cGL) muscle. The average onset latency has been reported to be 57-69 ms with a duration of 30.4 ± 6.6 ms. The aim of this study was to elucidate if a transcortical pathway contributes to the SLCR. In Experiment 1 (n = 9), single pulse supra-threshold transcranial magnetic stimulation (supraTMS) was applied alone or in combination with iTN stimulation (85% of the maximum M-wave) while participants walked on a treadmill (delay between the SLCR and the motor evoked potentials (MEP) varied between -30 and 200 ms). In Experiment 2 (n = 6), single pulse sub-threshold TMS (subTMS) was performed and the interstimulus interval (ISI) varied between 0-30 ms. In Experiment 3, somatosensory evoked potentials (SEPs) were recorded during the iTN stimulation to quantify the latency of the resulting afferent volley at the cortical level. SLCRs and MEPs in cGL occurred at 63 ± 6 ms and 29 ± 2 ms, respectively. The mean SEP latency was 30 ± 3 ms. Thus, a transcortical pathway could contribute no earlier than 62-69 ms (SEP+MEP+central-processing-delay) after iTN stimulation. Combined iTN stimulation and supraTMS resulted in a significant MEP extra-facilitation when supraTMS was timed so that the MEP would coincide with the late component of the SLCR, while subTMS significantly depressed this component. This is the first study that demonstrates the existence of a strong cortical control on spinal pathways mediating the SLCR. This likely serves to enhance flexibility, ensuring that the appropriate output is produced in accord with the functional demand.
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Affiliation(s)
| | - Sabata Gervasio
- Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
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Brownstone RM, Chopek JW. Reticulospinal Systems for Tuning Motor Commands. Front Neural Circuits 2018; 12:30. [PMID: 29720934 PMCID: PMC5915564 DOI: 10.3389/fncir.2018.00030] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2017] [Accepted: 03/29/2018] [Indexed: 11/26/2022] Open
Abstract
The pontomedullary reticular formation (RF) is a key site responsible for integrating descending instructions to execute particular movements. The indiscrete nature of this region has led not only to some inconsistencies in nomenclature, but also to difficulties in understanding its role in the control of movement. In this review article, we first discuss nomenclature of the RF, and then examine the reticulospinal motor command system through evolution. These command neurons have direct monosynaptic connections with spinal interneurons and motoneurons. We next review their roles in postural adjustments, walking and sleep atonia, discussing their roles in movement activation or inhibition. We propose that knowledge of the internal organization of the RF is necessary to understand how the nervous system tunes motor commands, and that this knowledge will underlie strategies for motor functional recovery following neurological injuries or diseases.
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Affiliation(s)
- Robert M. Brownstone
- Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College LondonLondon, United Kingdom
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Gregor RJ, Maas H, Bulgakova MA, Oliver A, English AW, Prilutsky BI. Time course of functional recovery during the first 3 mo after surgical transection and repair of nerves to the feline soleus and lateral gastrocnemius muscles. J Neurophysiol 2017; 119:1166-1185. [PMID: 29187556 DOI: 10.1152/jn.00661.2017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Locomotion outcomes after peripheral nerve injury and repair in cats have been described in the literature for the period immediately following the injury (muscle denervation period) and then again for an ensuing period of long-term recovery (at 3 mo and longer) resulting in muscle self-reinnervation. Little is known about the changes in muscle activity and walking mechanics during midrecovery, i.e., the early reinnervation period that takes place between 5 and 10 wk of recovery. Here, we investigated hindlimb mechanics and electromyogram (EMG) activity of ankle extensors in six cats during level and slope walking before and every 2 wk thereafter in a 14-wk period of recovery after the soleus (SO) and lateral gastrocnemius (LG) muscle nerves in one hindlimb were surgically transected and repaired. We found that the continued increase in SO and LG EMG magnitudes and corresponding changes in hindlimb mechanics coincided with the formation of neuromuscular synapses revealed in muscle biopsies. Throughout the recovery period, EMG magnitude of SO and LG during the stance phase and the duration of the stance-related activity were load dependent, similar to those in the intact synergistic medial gastrocnemius and plantaris. These results and the fact that EMG activity of ankle extensors and locomotor mechanics during level and upslope walking recovered 14 wk after nerve transection and repair suggest that loss of the stretch reflex in self-reinnervated muscles may be compensated by the recovered force-dependent feedback in self-reinnervated muscles, by increased central drive, and by increased gain in intermuscular motion-dependent pathways from intact ankle extensors. NEW & NOTEWORTHY This study provides new evidence that the timeline for functional recovery of gait after peripheral nerve injury and repair is consistent with the time required for neuromuscular junctions to form and muscles to reach preoperative tensions. Our findings suggest that a permanent loss of autogenic stretch reflex in self-reinnervated muscles may be compensated by recovered intermuscular force-dependent and oligosynaptic length-dependent feedback and central drive to regain adequate locomotor output capabilities during level and upslope walking.
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Affiliation(s)
- Robert J Gregor
- School of Biological Sciences, Georgia Institute of Technology , Atlanta, Georgia.,Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, California
| | - Huub Maas
- Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam , The Netherlands
| | | | - Alanna Oliver
- School of Biological Sciences, Georgia Institute of Technology , Atlanta, Georgia
| | - Arthur W English
- Department of Cell Biology, Emory University School of Medicine , Atlanta, Georgia
| | - Boris I Prilutsky
- School of Biological Sciences, Georgia Institute of Technology , Atlanta, Georgia
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Danner SM, Shevtsova NA, Frigon A, Rybak IA. Computational modeling of spinal circuits controlling limb coordination and gaits in quadrupeds. eLife 2017; 6:e31050. [PMID: 29165245 PMCID: PMC5726855 DOI: 10.7554/elife.31050] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2017] [Accepted: 11/21/2017] [Indexed: 01/27/2023] Open
Abstract
Interactions between cervical and lumbar spinal circuits are mediated by long propriospinal neurons (LPNs). Ablation of descending LPNs in mice disturbs left-right coordination at high speeds without affecting fore-hind alternation. We developed a computational model of spinal circuits consisting of four rhythm generators coupled by commissural interneurons (CINs), providing left-right interactions, and LPNs, mediating homolateral and diagonal interactions. The proposed CIN and diagonal LPN connections contribute to speed-dependent gait transition from walk, to trot, and then to gallop and bound; the homolateral LPN connections ensure fore-hind alternation in all gaits. The model reproduces speed-dependent gait expression in intact and genetically transformed mice and the disruption of hindlimb coordination following ablation of descending LPNs. Inputs to CINs and LPNs can affect interlimb coordination and change gait independent of speed. We suggest that these interneurons represent the main targets for supraspinal and sensory afferent signals adjusting gait.
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Affiliation(s)
- Simon M Danner
- Department of Neurobiology and AnatomyDrexel University College of MedicinePhiladelphiaUnited States
| | - Natalia A Shevtsova
- Department of Neurobiology and AnatomyDrexel University College of MedicinePhiladelphiaUnited States
| | - Alain Frigon
- Department of Pharmacology-PhysiologyUniversité de SherbrookeSherbrookeCanada
| | - Ilya A Rybak
- Department of Neurobiology and AnatomyDrexel University College of MedicinePhiladelphiaUnited States
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Li W, Szczecinski NS, Quinn RD. A neural network with central pattern generators entrained by sensory feedback controls walking of a bipedal model. BIOINSPIRATION & BIOMIMETICS 2017; 12:065002. [PMID: 28748830 DOI: 10.1088/1748-3190/aa8290] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
A neuromechanical simulation of a planar, bipedal walking robot has been developed. It is constructed as a simplified, planar musculoskeletal model of the biomechanics of the human lower body. The controller consists of a dynamic neural network with central pattern generators (CPGs) entrained by force and movement sensory feedback to generate appropriate muscle forces for walking. The CPG model is a two-level architecture, which consists of separate rhythm generator and pattern formation networks. The biped model walks stably in the sagittal plane without inertial sensors or a centralized posture controller or a 'baby walker' to help overcome gravity. Its gait is similar to humans' and it walks at speeds from 0.850 m s-1 up to 1.289 m s-1 with leg length of 0.84 m. The model walks over small unknown steps (6% of leg length) and up and down 5° slopes without any additional higher level control actions.
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Affiliation(s)
- Wei Li
- Case Western Reserve University, Cleveland, OH 44106, United States of America
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Duenas-Jimenez SH, Castillo Hernandez L, de la Torre Valdovinos B, Mendizabal Ruiz G, Duenas Jimenez JM, Ramirez Abundis V, Aguilar Garcia IG. Hind limb motoneurons activity during fictive locomotion or scratching induced by pinna stimulation, serotonin, or glutamic acid in brain cortex-ablated cats. Physiol Rep 2017; 5:5/18/e13458. [PMID: 28963128 PMCID: PMC5617936 DOI: 10.14814/phy2.13458] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Revised: 09/01/2017] [Accepted: 09/04/2017] [Indexed: 12/18/2022] Open
Abstract
In brain cortex‐ablated cats (BCAC), hind limb motoneurons activity patterns were studied during fictive locomotion (FL) or fictive scratching (FS) induced by pinna stimulation. In order to study motoneurons excitability: heteronymous monosynaptic reflex (HeMR), intracellular recording, and individual Ia afferent fiber antidromic activity (AA) were analyzed. The intraspinal cord microinjections of serotonin or glutamic acid effects were made to study their influence in FL or FS. During FS, HeMR amplitude in extensor and bifunctional motoneurons increased prior to or during the respective electroneurogram (ENG). In soleus (SOL) motoneurons were reduced during the scratch cycle (SC). AA in medial gastrocnemius (MG) Ia afferent individual fibers of L6‐L7 dorsal roots did not occur during FS. Flexor digitorum longus (FDL) and MG motoneurons fired with doublets during the FS bursting activity, motoneuron membrane potential from some posterior biceps (PB) motoneurons exhibits a depolarization in relation to the PB (ENG). It changed to a locomotor drive potential in relation to one of the double ENG, PB bursts. In FDL and semitendinosus (ST) motoneurons, the membrane potential was depolarized during FS, but it did not change during FL. Glutamic acid injected in the L3‐L4 spinal cord segment favored the transition from FS to FL. During FL, glutamic acid produces a duration increase of extensors ENGs. Serotonin increases the ENG amplitude in extensor motoneurons, as well as the duration of scratching episodes. It did not change the SC duration. Segregation and motoneurons excitability could be regulated by the rhythmic generator and the pattern generator of the central pattern generator.
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Affiliation(s)
| | - Luis Castillo Hernandez
- Basic Center, Department of Physiology and Pharmacology, Universidad Autónoma de Aguascalientes, Aguascalientes, Mexico
| | | | - Gerardo Mendizabal Ruiz
- Department of Computational Sciences CUCEI, Universidad de Guadalajara, Guadalajara, Jalisco, Mexico
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Ziskind-Conhaim L, Hochman S. Diversity of molecularly defined spinal interneurons engaged in mammalian locomotor pattern generation. J Neurophysiol 2017; 118:2956-2974. [PMID: 28855288 DOI: 10.1152/jn.00322.2017] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Revised: 08/29/2017] [Accepted: 08/30/2017] [Indexed: 01/18/2023] Open
Abstract
Mapping the expression of transcription factors in the mouse spinal cord has identified ten progenitor domains, four of which are cardinal classes of molecularly defined, ventrally located interneurons that are integrated in the locomotor circuitry. This review focuses on the properties of these interneuronal populations and their contribution to hindlimb locomotor central pattern generation. Interneuronal populations are categorized based on their excitatory or inhibitory functions and their axonal projections as predictors of their role in locomotor rhythm generation and coordination. The synaptic connectivity and functions of these interneurons in the locomotor central pattern generators (CPGs) have been assessed by correlating their activity patterns with motor output responses to rhythmogenic neurochemicals and sensory and descending fibers stimulations as well as analyzing kinematic gait patterns in adult mice. The observed complex organization of interneurons in the locomotor CPG circuitry, some with seemingly similar physiological functions, reflects the intricate repertoire associated with mammalian motor control and is consistent with high transcriptional heterogeneity arising from cardinal interneuronal classes. This review discusses insights derived from recent studies to describe innovative approaches and limitations in experimental model systems and to identify missing links in current investigational enterprise.
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Affiliation(s)
- Lea Ziskind-Conhaim
- Department of Neuroscience, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin; and
| | - Shawn Hochman
- Department of Physiology, Emory University School of Medicine, Atlanta, Georgia
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Hunt A, Szczecinski N, Quinn R. Development and Training of a Neural Controller for Hind Leg Walking in a Dog Robot. Front Neurorobot 2017; 11:18. [PMID: 28420977 PMCID: PMC5378996 DOI: 10.3389/fnbot.2017.00018] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Accepted: 03/15/2017] [Indexed: 11/17/2022] Open
Abstract
Animals dynamically adapt to varying terrain and small perturbations with remarkable ease. These adaptations arise from complex interactions between the environment and biomechanical and neural components of the animal's body and nervous system. Research into mammalian locomotion has resulted in several neural and neuro-mechanical models, some of which have been tested in simulation, but few “synthetic nervous systems” have been implemented in physical hardware models of animal systems. One reason is that the implementation into a physical system is not straightforward. For example, it is difficult to make robotic actuators and sensors that model those in the animal. Therefore, even if the sensorimotor circuits were known in great detail, those parameters would not be applicable and new parameter values must be found for the network in the robotic model of the animal. This manuscript demonstrates an automatic method for setting parameter values in a synthetic nervous system composed of non-spiking leaky integrator neuron models. This method works by first using a model of the system to determine required motor neuron activations to produce stable walking. Parameters in the neural system are then tuned systematically such that it produces similar activations to the desired pattern determined using expected sensory feedback. We demonstrate that the developed method successfully produces adaptive locomotion in the rear legs of a dog-like robot actuated by artificial muscles. Furthermore, the results support the validity of current models of mammalian locomotion. This research will serve as a basis for testing more complex locomotion controllers and for testing specific sensory pathways and biomechanical designs. Additionally, the developed method can be used to automatically adapt the neural controller for different mechanical designs such that it could be used to control different robotic systems.
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Affiliation(s)
- Alexander Hunt
- Department of Mechanical and Materials Engineering, Portland State UniversityPortland, OR, USA
| | - Nicholas Szczecinski
- Department of Mechanical and Aerospace Engineering, Case Western Reserve UniversityCleveland, OH, USA
| | - Roger Quinn
- Department of Mechanical and Aerospace Engineering, Case Western Reserve UniversityCleveland, OH, USA
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Eippert F, Kong Y, Winkler AM, Andersson JL, Finsterbusch J, Büchel C, Brooks JCW, Tracey I. Investigating resting-state functional connectivity in the cervical spinal cord at 3T. Neuroimage 2016; 147:589-601. [PMID: 28027960 PMCID: PMC5315056 DOI: 10.1016/j.neuroimage.2016.12.072] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Revised: 12/20/2016] [Accepted: 12/23/2016] [Indexed: 12/12/2022] Open
Abstract
The study of spontaneous fluctuations in the blood-oxygen-level-dependent (BOLD) signal has recently been extended from the brain to the spinal cord. Two ultra-high field functional magnetic resonance imaging (fMRI) studies in humans have provided evidence for reproducible resting-state connectivity between the dorsal horns as well as between the ventral horns, and a study in non-human primates has shown that these resting-state signals are impacted by spinal cord injury. As these studies were carried out at ultra-high field strengths using region-of-interest (ROI) based analyses, we investigated whether such resting-state signals could also be observed at the clinically more prevalent field strength of 3 T. In a reanalysis of a sample of 20 healthy human participants who underwent a resting-state fMRI acquisition of the cervical spinal cord, we were able to observe significant dorsal horn connectivity as well as ventral horn connectivity, but no consistent effects for connectivity between dorsal and ventral horns, thus replicating the human 7 T results. These effects were not only observable when averaging along the acquired length of the spinal cord, but also when we examined each of the acquired spinal segments separately, which showed similar patterns of connectivity. Finally, we investigated the robustness of these resting-state signals against variations in the analysis pipeline by varying the type of ROI creation, temporal filtering, nuisance regression and connectivity metric. We observed that – apart from the effects of band-pass filtering – ventral horn connectivity showed excellent robustness, whereas dorsal horn connectivity showed moderate robustness. Together, our results provide evidence that spinal cord resting-state connectivity is a robust and spatially consistent phenomenon that could be a valuable tool for investigating the effects of pathology, disease progression, and treatment response in neurological conditions with a spinal component, such as spinal cord injury.
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Affiliation(s)
- Falk Eippert
- Oxford Centre for Functional Magnetic Resonance Imaging of the Brain, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK.
| | - Yazhuo Kong
- Oxford Centre for Functional Magnetic Resonance Imaging of the Brain, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK; Magnetic Resonance Imaging Research Centre, Institute of Psychology, Chinese Academy of Sciences, Beijing, China
| | - Anderson M Winkler
- Oxford Centre for Functional Magnetic Resonance Imaging of the Brain, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Jesper L Andersson
- Oxford Centre for Functional Magnetic Resonance Imaging of the Brain, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Jürgen Finsterbusch
- Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Christian Büchel
- Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | | | - Irene Tracey
- Oxford Centre for Functional Magnetic Resonance Imaging of the Brain, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
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Field-Fote EC, Yang JF, Basso DM, Gorassini MA. Supraspinal Control Predicts Locomotor Function and Forecasts Responsiveness to Training after Spinal Cord Injury. J Neurotrauma 2016; 34:1813-1825. [PMID: 27673569 DOI: 10.1089/neu.2016.4565] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Restoration of walking ability is an area of great interest in the rehabilitation of persons with spinal cord injury. Because many cortical, subcortical, and spinal neural centers contribute to locomotor function, it is important that intervention strategies be designed to target neural elements at all levels of the neuraxis that are important for walking ability. While to date most strategies have focused on activation of spinal circuits, more recent studies are investigating the value of engaging supraspinal circuits. Despite the apparent potential of pharmacological, biological, and genetic approaches, as yet none has proved more effective than physical therapeutic rehabilitation strategies. By making optimal use of the potential of the nervous system to respond to training, strategies can be developed that meet the unique needs of each person. To complement the development of optimal training interventions, it is valuable to have the ability to predict future walking function based on early clinical presentation, and to forecast responsiveness to training. A number of clinical prediction rules and association models based on common clinical measures have been developed with the intent, respectively, to predict future walking function based on early clinical presentation, and to delineate characteristics associated with responsiveness to training. Further, a number of variables that are correlated with walking function have been identified. Not surprisingly, most of these prediction rules, association models, and correlated variables incorporate measures of volitional lower extremity strength, illustrating the important influence of supraspinal centers in the production of walking behavior in humans.
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Affiliation(s)
- Edelle C Field-Fote
- 1 Shepherd Center, Crawford Research Institute and Division of Physical Therapy, Emory University , Atlanta, Georgia
| | - Jaynie F Yang
- 2 Department of Physical Therapy, Faculty of Rehabilitation Medicine and Neuroscience and Mental Health Institute, Faculty of Medicine & Dentistry, University of Alberta , Edmonton, Alberta, Canada
| | - D Michele Basso
- 3 School of Health and Rehabilitation Sciences, The Ohio State University , Columbus, Ohio
| | - Monica A Gorassini
- 4 Department of Biomedical Engineering, Neuroscience and Mental Health Institute, Faculty of Medicine and Dentistry, University of Alberta , Edmonton, Alberta, Canada
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Zelenin PV, Lyalka VF, Orlovsky GN, Deliagina TG. Effect of acute lateral hemisection of the spinal cord on spinal neurons of postural networks. Neuroscience 2016; 339:235-253. [PMID: 27702647 PMCID: PMC5118056 DOI: 10.1016/j.neuroscience.2016.09.043] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Revised: 08/10/2016] [Accepted: 09/25/2016] [Indexed: 01/24/2023]
Abstract
In quadrupeds, acute lateral hemisection of the spinal cord (LHS) severely impairs postural functions, which recover over time. Postural limb reflexes (PLRs) represent a substantial component of postural corrections in intact animals. The aim of the present study was to characterize the effects of acute LHS on two populations of spinal neurons (F and E) mediating PLRs. For this purpose, in decerebrate rabbits, responses of individual neurons from L5 to stimulation causing PLRs were recorded before and during reversible LHS (caused by temporal cold block of signal transmission in lateral spinal pathways at L1), as well as after acute surgical LHS at L1. Results obtained after Sur-LHS were compared to control data obtained in our previous study. We found that acute LHS caused disappearance of PLRs on the affected side. It also changed a proportion of different types of neurons on that side. A significant decrease and increase in the proportion of F- and non-modulated neurons, respectively, was found. LHS caused a significant decrease in most parameters of activity in F-neurons located in the ventral horn on the lesioned side and in E-neurons of the dorsal horn on both sides. These changes were caused by a significant decrease in the efficacy of posture-related sensory input from the ipsilateral limb to F-neurons, and from the contralateral limb to both F- and E-neurons. These distortions in operation of postural networks underlie the impairment of postural control after acute LHS, and represent a starting point for the subsequent recovery of postural functions.
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Affiliation(s)
- P V Zelenin
- Department of Neuroscience, Karolinska Institute, SE-17177 Stockholm, Sweden
| | - V F Lyalka
- Department of Neuroscience, Karolinska Institute, SE-17177 Stockholm, Sweden
| | - G N Orlovsky
- Department of Neuroscience, Karolinska Institute, SE-17177 Stockholm, Sweden
| | - T G Deliagina
- Department of Neuroscience, Karolinska Institute, SE-17177 Stockholm, Sweden.
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Danner SM, Wilshin SD, Shevtsova NA, Rybak IA. Central control of interlimb coordination and speed-dependent gait expression in quadrupeds. J Physiol 2016; 594:6947-6967. [PMID: 27633893 DOI: 10.1113/jp272787] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Accepted: 09/13/2016] [Indexed: 12/29/2022] Open
Abstract
KEY POINTS Quadrupeds express different gaits depending on speed of locomotion. Central pattern generators (one per limb) within the spinal cord generate locomotor oscillations and control limb movements. Neural interactions between these generators define interlimb coordination and gait. We present a computational model of spinal circuits representing four rhythm generators with left-right excitatory and inhibitory commissural and fore-hind inhibitory interactions within the cord. Increasing brainstem drive to all rhythm generators and excitatory commissural interneurons induces an increasing frequency of locomotor oscillations accompanied by speed-dependent gait changes from walk to trot and to gallop and bound. The model closely reproduces and suggests explanations for multiple experimental data, including speed-dependent gait transitions in intact mice and changes in gait expression in mutants lacking certain types of commissural interneurons. The model suggests the possible circuit organization in the spinal cord and proposes predictions that can be tested experimentally. ABSTRACT As speed of locomotion is increasing, most quadrupeds, including mice, demonstrate sequential gait transitions from walk to trot and to gallop and bound. The neural mechanisms underlying these transitions are poorly understood. We propose that the speed-dependent expression of different gaits results from speed-dependent changes in the interactions between spinal circuits controlling different limbs and interlimb coordination. As a result, the expression of each gait depends on (1) left-right interactions within the spinal cord mediated by different commissural interneurons (CINs), (2) fore-hind interactions on each side of the spinal cord and (3) brainstem drives to rhythm-generating circuits and CIN pathways. We developed a computational model of spinal circuits consisting of four rhythm generators (RGs) with bilateral left-right interactions mediated by V0 CINs (V0D and V0V sub-types) providing left-right alternation, and conditional V3 CINs promoting left-right synchronization. Fore and hind RGs mutually inhibited each other. We demonstrate that linearly increasing excitatory drives to the RGs and V3 CINs can produce a progressive increase in the locomotor speed accompanied by sequential changes of gaits from walk to trot and to gallop and bound. The model closely reproduces and suggests explanations for the speed-dependent gait expression observed in vivo in intact mice and in mutants lacking V0V or all V0 CINs. Specifically, trot is not expressed after removal of V0V CINs, and only bound is expressed after removal of all V0 CINs. The model provides important insights into the organization of spinal circuits and neural control of locomotion.
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Affiliation(s)
- Simon M Danner
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA, USA
| | - Simon D Wilshin
- Structure and Motion Laboratory, The Royal Veterinary College, University of London, London, UK
| | - Natalia A Shevtsova
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA, USA
| | - Ilya A Rybak
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA, USA
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Cappellini G, Ivanenko YP, Martino G, MacLellan MJ, Sacco A, Morelli D, Lacquaniti F. Immature Spinal Locomotor Output in Children with Cerebral Palsy. Front Physiol 2016; 7:478. [PMID: 27826251 PMCID: PMC5078720 DOI: 10.3389/fphys.2016.00478] [Citation(s) in RCA: 85] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Accepted: 10/05/2016] [Indexed: 12/29/2022] Open
Abstract
Detailed descriptions of gait impairments have been reported in cerebral palsy (CP), but it is still unclear how maturation of the spinal motoneuron output is affected. Spatiotemporal alpha-motoneuron activation during walking can be assessed by mapping the electromyographic activity profiles from several, simultaneously recorded muscles onto the anatomical rostrocaudal location of the motoneuron pools in the spinal cord, and by means of factor analysis of the muscle activity profiles. Here, we analyzed gait kinematics and EMG activity of 11 pairs of bilateral muscles with lumbosacral innervation in 35 children with CP (19 diplegic, 16 hemiplegic, 2-12 years) and 33 typically developing (TD) children (1-12 years). TD children showed a progressive reduction of EMG burst durations and a gradual reorganization of the spatiotemporal motoneuron output with increasing age. By contrast, children with CP showed very limited age-related changes of EMG durations and motoneuron output, as well as of limb intersegmental coordination and foot trajectory control (on both sides for diplegic children and the affected side for hemiplegic children). Factorization of the EMG signals revealed a comparable structure of the motor output in children with CP and TD children, but significantly wider temporal activation patterns in children with CP, resembling the patterns of much younger TD infants. A similar picture emerged when considering the spatiotemporal maps of alpha-motoneuron activation. Overall, the results are consistent with the idea that early injuries to developing motor regions of the brain substantially affect the maturation of the spinal locomotor output and consequently the future locomotor behavior.
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Affiliation(s)
- Germana Cappellini
- Centre of Space Bio-medicine, University of Rome Tor Vergata Rome, Italy
| | - Yury P Ivanenko
- Laboratory of Neuromotor Physiology, Istituti di Ricovero e Cura a Carattere Scientifico (IRCCS) Santa Lucia Foundation Rome, Italy
| | - Giovanni Martino
- Centre of Space Bio-medicine, University of Rome Tor Vergata Rome, Italy
| | | | - Annalisa Sacco
- Department of Pediatric Neurorehabilitation, Istituti di Ricovero e Cura a Carattere Scientifico (IRCCS) Santa Lucia Foundation Rome, Italy
| | - Daniela Morelli
- Department of Pediatric Neurorehabilitation, Istituti di Ricovero e Cura a Carattere Scientifico (IRCCS) Santa Lucia Foundation Rome, Italy
| | - Francesco Lacquaniti
- Centre of Space Bio-medicine, University of Rome Tor VergataRome, Italy; Laboratory of Neuromotor Physiology, Istituti di Ricovero e Cura a Carattere Scientifico (IRCCS) Santa Lucia FoundationRome, Italy; Department of Systems Medicine, University of Rome Tor VergataRome, Italy
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Maguire CC, Sieben JM, de Bie RA. The influence of walking-aids on the plasticity of spinal interneuronal networks, central-pattern-generators and the recovery of gait post-stroke. A literature review and scholarly discussion. J Bodyw Mov Ther 2016; 21:422-434. [PMID: 28532887 DOI: 10.1016/j.jbmt.2016.09.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Revised: 09/10/2016] [Accepted: 09/20/2016] [Indexed: 12/27/2022]
Abstract
BACKGROUND Many aspects of post-stroke gait-rehabilitation are based on low-level evidence or expert opinion. Neuroscientific principles are often not considered when evaluating the impact of interventions. The use of walking-aids including canes and rollators, although widely used for long periods, has primarily been investigated to assess the immediate kinetic, kinematic or physiological effects. The long-term impact on neural structures und functions remains unclear. METHODS A literature review of the function of and factors affecting plasticity of spinal interneuronal-networks and central-pattern-generators (CPG) in healthy and post-stroke patients. The relevance of these mechanisms for gait recovery and the potential impact of walking-aids is discussed. RESULTS Afferent-input to spinal-networks influences motor-output and spinal and cortical plasticity. Disrupted input may adversely affect post-stroke plasticity and functional recovery. Joint and muscle unloading and decoupling from four-limb CPG control may be particularly relevant. CONCLUSIONS Canes and rollators disrupt afferent-input and may negatively affect the recovery of gait.
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Affiliation(s)
- Clare C Maguire
- Department of Physiotherapy, Bildungszentrum Gesundheit Basel-Stadt, 4142, Muenchenstein, Switzerland; CAPHRI School for Public Health and Primary Care, Maastricht University, 6200 MD, Maastricht, The Netherlands.
| | - Judith M Sieben
- CAPHRI School for Public Health and Primary Care, Maastricht University, 6200 MD, Maastricht, The Netherlands; Department of Anatomy and Embryology, Maastricht University, 6200 MD, Maastricht, The Netherlands
| | - Robert A de Bie
- CAPHRI School for Public Health and Primary Care, Maastricht University, 6200 MD, Maastricht, The Netherlands; Department of Epidemiology, Maastricht University, 6200 MD, Maastricht, The Netherlands
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Calderon DP, Kilinc M, Maritan A, Banavar JR, Pfaff D. Generalized CNS arousal: An elementary force within the vertebrate nervous system. Neurosci Biobehav Rev 2016; 68:167-176. [PMID: 27216213 PMCID: PMC5003634 DOI: 10.1016/j.neubiorev.2016.05.014] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Revised: 05/19/2016] [Accepted: 05/19/2016] [Indexed: 01/13/2023]
Abstract
Why do animals and humans do anything at all? Arousal is the most powerful and essential function of the brain, a continuous function that accounts for the ability of animals and humans to respond to stimuli in the environment by producing muscular responses. Following decades of psychological, neurophysiological and molecular investigations, generalized CNS arousal can now be analyzed using approaches usually applied to physical systems. The concept of "criticality" is a state that illustrates an advantage for arousal systems poised near a phase transition. This property provides speed and sensitivity and facilitates the transition of the system into different brain states, especially as the brain crosses a phase transition from less aroused to more aroused states. In summary, concepts derived from applied mathematics of physical systems will now find their application in this area of neuroscience, the neurobiology of CNS arousal.
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Affiliation(s)
- D P Calderon
- Laboratory for Neurobiology and Behavior, the Rockefeller University, New York, NY 10065, United States; Department of Anaesthesiology, Weill Cornell Medical College, New York, NY 10021, United States.
| | - M Kilinc
- Laboratory for Neurobiology and Behavior, the Rockefeller University, New York, NY 10065, United States
| | - A Maritan
- Department of Physics, University of Padova, Istituto Nazionale di Fisica Nucleare and Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia, 35131 Padova, Italy
| | - J R Banavar
- Department of Physics, University of Maryland, College Park, MD 20742, United States
| | - D Pfaff
- Laboratory for Neurobiology and Behavior, the Rockefeller University, New York, NY 10065, United States
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49
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Zelenin PV, Lyalka VF, Hsu LJ, Orlovsky GN, Deliagina TG. Effects of acute spinalization on neurons of postural networks. Sci Rep 2016; 6:27372. [PMID: 27302149 PMCID: PMC4908393 DOI: 10.1038/srep27372] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 05/18/2016] [Indexed: 11/15/2022] Open
Abstract
Postural limb reflexes (PLRs) represent a substantial component of postural corrections. Spinalization results in loss of postural functions, including disappearance of PLRs. The aim of the present study was to characterize the effects of acute spinalization on two populations of spinal neurons (F and E) mediating PLRs, which we characterized previously. For this purpose, in decerebrate rabbits spinalized at T12, responses of interneurons from L5 to stimulation causing PLRs before spinalization, were recorded. The results were compared to control data obtained in our previous study. We found that spinalization affected the distribution of F- and E-neurons across the spinal grey matter, caused a significant decrease in their activity, as well as disturbances in processing of posture-related sensory inputs. A two-fold decrease in the proportion of F-neurons in the intermediate grey matter was observed. Location of populations of F- and E-neurons exhibiting significant decrease in their activity was determined. A dramatic decrease of the efficacy of sensory input from the ipsilateral limb to F-neurons, and from the contralateral limb to E-neurons was found. These changes in operation of postural networks underlie the loss of postural control after spinalization, and represent a starting point for the development of spasticity.
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Affiliation(s)
- Pavel V. Zelenin
- Department of Neuroscience, Karolinska Institute, SE-17177, Stockholm, Sweden
| | - Vladimir F. Lyalka
- Department of Neuroscience, Karolinska Institute, SE-17177, Stockholm, Sweden
| | - Li-Ju Hsu
- Department of Neuroscience, Karolinska Institute, SE-17177, Stockholm, Sweden
| | - Grigori N. Orlovsky
- Department of Neuroscience, Karolinska Institute, SE-17177, Stockholm, Sweden
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50
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Stevenson AJT, Kamavuako EN, Geertsen SS, Farina D, Mrachacz-Kersting N. Short-latency crossed responses in the human biceps femoris muscle. J Physiol 2016; 593:3657-71. [PMID: 25970767 DOI: 10.1113/jp270422] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Accepted: 05/08/2015] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS The present study is the first to show short-latency crossed-spinal reflexes in the human upper leg muscles following mechanical rotations to the ipsilateral knee (iKnee) joint. The short-latency reflex in the contralateral biceps femoris (cBF) was inhibitory following iKnee extension perturbations, and facilitatory following iKnee flexion perturbations. The onset latency was 44 ms, indicating that purely spinal pathways mediate the cBF reflexes. The short-latency cBF inhibitory and facilitatory reflexes followed the automatic gain control principle, becoming larger as the level of background contraction in the cBF increased. The short-latency cBF reflexes were observed at the motor unit level using i.m. electromyography recordings, and the same population of cBF motor units that was inhibited following iKnee extensions was facilitated following iKnee flexions. Parallel interneuronal pathways from ipsilateral afferents to common motoneurons in the contralateral leg can therefore probably explain the perturbation direction-dependent reversal in the sign of the short-latency cBF reflex. ABSTRACT Interlimb reflexes contribute to the central neural co-ordination between different limbs in both humans and animals. Although commissural interneurons have only been directly identified in animals, spinally-mediated interlimb reflexes have been discovered in a number of human lower limb muscles, indicating their existence in humans. The present study aimed to investigate whether short-latency crossed-spinal reflexes are present in the contralateral biceps femoris (cBF) muscle following ipsilateral knee (iKnee) joint rotations during a sitting task, where participants maintained a slight pre-contraction in the cBF. Following iKnee extension joint rotations, an inhibitory reflex was observed in the surface electromyographic (EMG) activity of the cBF, whereas a facilitatory reflex was observed in the cBF following iKnee flexion joint rotations. The onset latency of both cBF reflexes was 44 ms, which is too fast for a transcortical pathway to contribute. The cBF inhibitory and facilitatory reflexes followed the automatic gain control principle, with the size of the response increasing as the level of background pre-contraction in the cBF muscle increased. In addition to the surface EMG, both short-latency inhibitory and facilitatory cBF reflexes were recorded directly at the motor unit level by i.m. EMG, and the same population of cBF motor units that were inhibited following iKnee extension joint rotations were facilitated following iKnee flexion joint rotations. Therefore, parallel interneuronal pathways (probably involving commissural interneurons) from ipsilateral afferents to common motoneurons in the contralateral leg can probably explain the perturbation direction-dependent reversal in the sign of the short-latency cBF reflex.
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Affiliation(s)
- Andrew J T Stevenson
- Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Aalborg University, Fredrik Bajers Vej 7 D-3, Aalborg, Denmark
| | - Ernest N Kamavuako
- Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Aalborg University, Fredrik Bajers Vej 7 D-3, Aalborg, Denmark
| | - Svend S Geertsen
- Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark.,Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Dario Farina
- Department of Neurorehabilitation Engineering, Bernstein Center for Computational Neuroscience, University Medical Center Göttingen, Georg-August University, Göttingen, Germany
| | - Natalie Mrachacz-Kersting
- Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Aalborg University, Fredrik Bajers Vej 7 D-3, Aalborg, Denmark
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