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Dewolf AH, Ivanenko YP, Zelik KE, Lacquaniti F, Willems PA. Differential activation of lumbar and sacral motor pools during walking at different speeds and slopes. J Neurophysiol 2019; 122:872-887. [PMID: 31291150 DOI: 10.1152/jn.00167.2019] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Organization of spinal motor output has become of interest for investigating differential activation of lumbar and sacral motor pools during locomotor tasks. Motor pools are associated with functional grouping of motoneurons of the lower limb muscles. Here we examined how the spatiotemporal organization of lumbar and sacral motor pool activity during walking is orchestrated with slope of terrain and speed of progression. Ten subjects walked on an instrumented treadmill at different slopes and imposed speeds. Kinetics, kinematics, and electromyography of 16 lower limb muscles were recorded. The spinal locomotor output was assessed by decomposing the coordinated muscle activation profiles into a small set of common factors and by mapping them onto the rostrocaudal location of the motoneuron pools. Our results show that lumbar and sacral motor pool activity depend on slope and speed. Compared with level walking, sacral motor pools decrease their activity at negative slopes and increase at positive slopes, whereas lumbar motor pools increase their engagement when both positive and negative slope increase. These findings are consistent with a differential involvement of the lumbar and the sacral motor pools in relation to changes in positive and negative center of body mass mechanical power production due to slope and speed.NEW & NOTEWORTHY In this study, the spatiotemporal maps of motoneuron activity in the spinal cord were assessed during walking at different slopes and speeds. We found differential involvement of lumbar and sacral motor pools in relation to changes in positive and negative center of body mass power production due to slope and speed. The results are consistent with recent findings about the specialization of neuronal networks located at different segments of the spinal cord for performing specific locomotor tasks.
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Affiliation(s)
- A H Dewolf
- Laboratory of Biomechanics and Physiology of Locomotion, Institute of NeuroScience, Université catholique de Louvain, Louvain-la-Neuve, Belgium
| | - Y P Ivanenko
- Laboratory of Neuromotor Physiology, IRCCS Santa Lucia Foundation, Rome, Italy
| | - K E Zelik
- Laboratory of Neuromotor Physiology, IRCCS Santa Lucia Foundation, Rome, Italy.,Department of Mechanical Engineering, Vanderbilt University, Nashville, Tennessee.,Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee.,Department of Physical Medicine and Rehabilitation, Vanderbilt University, Nashville, Tennessee
| | - F Lacquaniti
- Laboratory of Neuromotor Physiology, IRCCS Santa Lucia Foundation, Rome, Italy.,Department of Systems Medicine and Center of Space Biomedicine, University of Rome Tor Vergata, Rome, Italy
| | - P A Willems
- Laboratory of Biomechanics and Physiology of Locomotion, Institute of NeuroScience, Université catholique de Louvain, Louvain-la-Neuve, Belgium
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102
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Welc SS, Flores I, Wehling-Henricks M, Ramos J, Wang Y, Bertoni C, Tidball JG. Targeting a therapeutic LIF transgene to muscle via the immune system ameliorates muscular dystrophy. Nat Commun 2019; 10:2788. [PMID: 31243277 PMCID: PMC6594976 DOI: 10.1038/s41467-019-10614-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Accepted: 05/22/2019] [Indexed: 12/18/2022] Open
Abstract
Many potentially therapeutic molecules have been identified for treating Duchenne muscular dystrophy. However, targeting those molecules only to sites of active pathology is an obstacle to their clinical use. Because dystrophic muscles become extensively inflamed, we tested whether expressing a therapeutic transgene in leukocyte progenitors that invade muscle would provide selective, timely delivery to diseased muscle. We designed a transgene in which leukemia inhibitory factor (LIF) is under control of a leukocyte-specific promoter and transplanted transgenic cells into dystrophic mice. Transplantation diminishes pathology, reduces Th2 cytokines in muscle and biases macrophages away from a CD163+/CD206+ phenotype that promotes fibrosis. Transgenic cells also abrogate TGFβ signaling, reduce fibro/adipogenic progenitor cells and reduce fibrogenesis of muscle cells. These findings indicate that leukocytes expressing a LIF transgene reduce fibrosis by suppressing type 2 immunity and highlight a novel application by which immune cells can be genetically modified as potential therapeutics to treat muscle disease.
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Affiliation(s)
- Steven S Welc
- Department of Integrative Biology and Physiology, University of California, Los Angeles, CA, 90095-1606, USA
| | - Ivan Flores
- Molecular, Cellular & Integrative Physiology Program, University of California, Los Angeles, CA, 90095-1606, USA
| | - Michelle Wehling-Henricks
- Department of Integrative Biology and Physiology, University of California, Los Angeles, CA, 90095-1606, USA
| | - Julian Ramos
- Department of Integrative Biology and Physiology, University of California, Los Angeles, CA, 90095-1606, USA
| | - Ying Wang
- Molecular, Cellular & Integrative Physiology Program, University of California, Los Angeles, CA, 90095-1606, USA
| | - Carmen Bertoni
- Department of Neurology, David Geffen School of Medicine at UCLA, University of California, Los Angeles, CA, 90095, USA
| | - James G Tidball
- Department of Integrative Biology and Physiology, University of California, Los Angeles, CA, 90095-1606, USA.
- Molecular, Cellular & Integrative Physiology Program, University of California, Los Angeles, CA, 90095-1606, USA.
- Department of Pathology and Laboratory Medicine, David Geffen School of Medicine at UCLA, University of California, Los Angeles, CA, 90095, USA.
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103
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Katoh H, Yokota K, Fehlings MG. Regeneration of Spinal Cord Connectivity Through Stem Cell Transplantation and Biomaterial Scaffolds. Front Cell Neurosci 2019; 13:248. [PMID: 31244609 PMCID: PMC6563678 DOI: 10.3389/fncel.2019.00248] [Citation(s) in RCA: 104] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Accepted: 05/17/2019] [Indexed: 12/20/2022] Open
Abstract
Significant progress has been made in the treatment of spinal cord injury (SCI). Advances in post-trauma management and intensive rehabilitation have significantly improved the prognosis of SCI and converted what was once an “ailment not to be treated” into a survivable injury, but the cold hard fact is that we still do not have a validated method to improve the paralysis of SCI. The irreversible functional impairment of the injured spinal cord is caused by the disruption of neuronal transduction across the injury lesion, which is brought about by demyelination, axonal degeneration, and loss of synapses. Furthermore, refractory substrates generated in the injured spinal cord inhibit spontaneous recovery. The discovery of the regenerative capability of central nervous system neurons in the proper environment and the verification of neural stem cells in the spinal cord once incited hope that a cure for SCI was on the horizon. That hope was gradually replaced with mounting frustration when neuroprotective drugs, cell transplantation, and strategies to enhance remyelination, axonal regeneration, and neuronal plasticity demonstrated significant improvement in animal models of SCI but did not translate into a cure in human patients. However, recent advances in SCI research have greatly increased our understanding of the fundamental processes underlying SCI and fostered increasing optimism that these multiple treatment strategies are finally coming together to bring about a new era in which we will be able to propose encouraging therapies that will lead to appreciable improvements in SCI patients. In this review, we outline the pathophysiology of SCI that makes the spinal cord refractory to regeneration and discuss the research that has been done with cell replacement and biomaterial implantation strategies, both by itself and as a combined treatment. We will focus on the capacity of these strategies to facilitate the regeneration of neural connectivity necessary to achieve meaningful functional recovery after SCI.
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Affiliation(s)
- Hiroyuki Katoh
- Division of Genetics and Development, Krembil Research Institute, Toronto, ON, Canada.,Department of Orthopaedic Surgery - Surgical Sciences, School of Medicine, Tokai University, Tokyo, Japan
| | - Kazuya Yokota
- Division of Genetics and Development, Krembil Research Institute, Toronto, ON, Canada.,Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Michael G Fehlings
- Division of Genetics and Development, Krembil Research Institute, Toronto, ON, Canada.,Institute of Medical Science, University of Toronto, Toronto, ON, Canada.,Division of Neurosurgery, University of Toronto, Toronto, ON, Canada.,Spine Program, Toronto Western Hospital, University Health Network, Toronto, ON, Canada
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104
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Dougherty KJ, Ha NT. The rhythm section: An update on spinal interneurons setting the beat for mammalian locomotion. CURRENT OPINION IN PHYSIOLOGY 2019; 8:84-93. [PMID: 31179403 PMCID: PMC6550992 DOI: 10.1016/j.cophys.2019.01.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
To initiate and support locomotion, rhythm generating neurons in the spinal central pattern generator convert descending input into a rhythmic signal which is conveyed to downstream neurons, leading to the recruitment of motor neurons and activation of muscles. Although two genetically-defined neuronal populations have been linked to rhythm generation, a single all-inclusive rhythm generating population has yet to be identified. Here, we consolidate recent work aimed at identifying rhythm generating neurons, summarize the evidence for the involvement of two neuronal populations in rhythm generation, describe the challenges in identifying a marker for rhythm generating neurons, and discuss potential directions to take in integrating spinal rhythm generating neurons into recently identified speed-dependent locomotor circuits.
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Affiliation(s)
- Kimberly J. Dougherty
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129, USA
| | - Ngoc T. Ha
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129, USA
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105
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Diversity of neurons and circuits controlling the speed and coordination of locomotion. CURRENT OPINION IN PHYSIOLOGY 2019. [DOI: 10.1016/j.cophys.2019.02.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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106
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Deska-Gauthier D, Zhang Y. The functional diversity of spinal interneurons and locomotor control. CURRENT OPINION IN PHYSIOLOGY 2019. [DOI: 10.1016/j.cophys.2019.01.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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107
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108
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Jay M, McLean DL. Reconciling the functions of even-skipped interneurons during crawling, swimming, and walking. CURRENT OPINION IN PHYSIOLOGY 2019; 8:188-192. [PMID: 31667448 DOI: 10.1016/j.cophys.2019.02.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In all bilaterally symmetric animals, movements across the body are coordinated by interneurons that traverse the midline. Recent work is beginning to tease apart the functional complexity of interneurons labeled by the homeodomain transcription factor even-skipped, which provide a phylogenetically-conserved source of commissural excitation during locomotion in both vertebrates and invertebrates. Here we review recent studies of the roles of even-skipped neurons during locomotion in flies (EL neurons), fishes, frogs, and mice (V0v neurons). Comparisons across species reveal commonalities, which include the functional organization of even-skipped circuits based on birth order, the link between increased muscular complexity and even-skipped neuron diversity, and the hierarchical organization of even-skipped circuits based on their control of escape versus exploratory movements. We discuss how stronger links between different species enable testable predictions to further the discovery of principles of locomotor network organization.
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Affiliation(s)
- Michael Jay
- Department of Neurobiology Northwestern University EVANSTON, IL USA
| | - David L McLean
- Department of Neurobiology Northwestern University EVANSTON, IL USA
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109
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Ausborn J, Shevtsova NA, Caggiano V, Danner SM, Rybak IA. Computational modeling of brainstem circuits controlling locomotor frequency and gait. eLife 2019; 8:43587. [PMID: 30663578 PMCID: PMC6355193 DOI: 10.7554/elife.43587] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Accepted: 01/19/2019] [Indexed: 01/05/2023] Open
Abstract
A series of recent studies identified key structures in the mesencephalic locomotor region and the caudal brainstem of mice involved in the initiation and control of slow (exploratory) and fast (escape-type) locomotion and gait. However, the interactions of these brainstem centers with each other and with the spinal locomotor circuits are poorly understood. Previously we suggested that commissural and long propriospinal interneurons are the main targets for brainstem inputs adjusting gait (Danner et al., 2017). Here, by extending our previous model, we propose a connectome of the brainstem-spinal circuitry and suggest a mechanistic explanation of the operation of brainstem structures and their roles in controlling speed and gait. We suggest that brainstem control of locomotion is mediated by two pathways, one controlling locomotor speed via connections to rhythm generating circuits in the spinal cord and the other providing gait control by targeting commissural and long propriospinal interneurons.
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Affiliation(s)
- Jessica Ausborn
- Department of Neurobiology and Anatomy, College of Medicine, Drexel University, Philadelphia, United States
| | - Natalia A Shevtsova
- Department of Neurobiology and Anatomy, College of Medicine, Drexel University, Philadelphia, United States
| | | | - Simon M Danner
- Department of Neurobiology and Anatomy, College of Medicine, Drexel University, Philadelphia, United States
| | - Ilya A Rybak
- Department of Neurobiology and Anatomy, College of Medicine, Drexel University, Philadelphia, United States
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110
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Behavioral Role of the Reciprocal Inhibition between a Pair of Mauthner Cells during Fast Escapes in Zebrafish. J Neurosci 2018; 39:1182-1194. [PMID: 30578342 DOI: 10.1523/jneurosci.1964-18.2018] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 12/13/2018] [Accepted: 12/16/2018] [Indexed: 11/21/2022] Open
Abstract
During many behaviors in vertebrates, the CNS generates asymmetric activities between the left and right sides to produce asymmetric body movements. For asymmetrical activations of the CNS, reciprocal inhibition between the left and right sides is believed to play a key role. However, the complexity of the CNS makes it difficult to identify the reciprocal inhibition circuits at the level of individual cells and the contribution of each neuron to the asymmetric activity. Using larval zebrafish, we examined this issue by investigating reciprocal inhibition circuits between a pair of Mauthner (M) cells, giant reticulospinal neurons that trigger fast escapes. Previous studies have shown that a class of excitatory neurons, called cranial relay neurons, is involved in the reciprocal inhibition pathway between the M cells. Using transgenic fish, in which two of the cranial relay neurons (Ta1 and Ta2) expressed GFP, we showed that Ta1 and Ta2 constitute major parts of the pathway. In larvae in which Ta1/Ta2 were laser-ablated, the amplitude of the reciprocal IPSPs dropped to less than one-third. Calcium imaging and electrophysiological recording showed that the occurrence probability of bilateral M-cell activation upon sound/vibration stimuli was greatly increased in the Ta1/Ta2-ablated larvae. Behavioral experiments revealed that the Ta1/Ta2 ablation resulted in shallower body bends during sound/vibration-evoked escapes, which is consistent with the observation that increased occurrence of bilateral M-cell activation impaired escape performance. Our study revealed major components of the reciprocal inhibition circuits in the M cell system and the behavioral importance of the circuits.SIGNIFICANCE STATEMENT Reciprocal inhibition between the left and right side of the CNS is considered imperative for producing asymmetric movements in animals. It has been difficult, however, to identify the circuits at the individual cell level and their role in behavior. Here, we address this problem by examining the reciprocal inhibition circuits of the hindbrain Mauthner (M) cell system in larval zebrafish. We determined that two paired interneurons play a critical role in the reciprocal inhibition between the paired M cells and that the reciprocal inhibition prevents bilateral firing of the M cells and is thus necessary for the full body bend during M cell-initiated escape. Further, we discussed the cooperation of multiple reciprocal inhibitions working in the hindbrain and spinal cord to ensure high-performance escapes.
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111
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Lavorato M, Loro E, Debattisti V, Khurana TS, Franzini-Armstrong C. Elongated mitochondrial constrictions and fission in muscle fatigue. J Cell Sci 2018; 131:jcs221028. [PMID: 30404834 PMCID: PMC6288074 DOI: 10.1242/jcs.221028] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Accepted: 10/30/2018] [Indexed: 12/24/2022] Open
Abstract
Mitochondria respond to stress and undergo fusion and fission at variable rates, depending on cell status. To understand mitochondrial behavior during muscle fatigue, we investigated mitochondrial ultrastructure and expression levels of a fission- and stress-related protein in fast-twitch muscle fibers of mice subjected to fatigue testing. Mice were subjected to running at increasing speed until exhaustion at 45 min-1 h. In further experiments, high-intensity muscle stimulation through the sciatic nerve simulated the forced treadmill exercise. We detected a rare phenotype characterized by elongated mitochondrial constrictions (EMCs) connecting two separate segments of the original organelles. EMCs are rare in resting muscles and their frequency increases, albeit still at low levels, in stimulated muscles. The constrictions are accompanied by elevated phosphorylation of Drp1 (Dnm1l) at Ser 616, indicating an increased translocation of Drp1 to the mitochondrial membrane. This is indicative of a mitochondrial stress response, perhaps leading to or facilitating a long-lasting fission event. A close apposition of sarcoplasmic reticulum (SR) to the constricted areas, detected using both transmission and scanning electron microscopy, is highly suggestive of SR involvement in inducing mitochondrial constrictions.
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Affiliation(s)
- Manuela Lavorato
- Department of Cell and Developmental Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Genetics, Children's Hospital of Philadelphia, PA 19104, USA
| | - Emanuele Loro
- Department of Physiology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Valentina Debattisti
- MitoCare Center, Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Tejvir S Khurana
- Department of Physiology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Clara Franzini-Armstrong
- Department of Cell and Developmental Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
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112
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Deliagina TG, Musienko PE, Zelenin PV. Nervous mechanisms of locomotion in different directions. CURRENT OPINION IN PHYSIOLOGY 2018; 8:7-13. [PMID: 31468024 DOI: 10.1016/j.cophys.2018.11.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Locomotion, that is active propulsive movement of the body in space, is a vital motor function. Intensive studies of the main, for the majority of living beings, form of locomotion, forward locomotion, have revealed essential features of the organization and operation of underlying neural mechanisms. However, animals and humans are capable to locomote not only forward but also in other directions in relation to the body axis, e.g. backward, sideways, etc. Single steps in different directions are also used for postural corrections during locomotion and during standing. Recent studies of mechanisms underlying control of locomotion in different directions have greatly expanded our knowledge about locomotor system and can contribute to improvement of rehabilitation strategies aimed at restoration of locomotion and balance control in patients. This review outlines recent advances in the studies of locomotion in different directions in lower and higher vertebrates, with special attention given to the neuronal locomotor mechanisms.
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Affiliation(s)
- Tatiana G Deliagina
- Department of Neuroscience, Karolinska Institute, SE-17177, Stockholm, Sweden
| | - Pavel E Musienko
- Institute of Translational Biomedicine, St. Petersburg State University, 199034 St. Petersburg, Russia
- Pavlov Institute of Physiology, 199034 St. Petersburg, Russia
- Russian Research Center of Radiology and Surgical Technologies, Ministry of Healthcare of the RF, 197758 St. Petersburg, Russia
| | - Pavel V Zelenin
- Department of Neuroscience, Karolinska Institute, SE-17177, Stockholm, Sweden
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113
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Desrochers E, Harnie J, Doelman A, Hurteau MF, Frigon A. Spinal control of muscle synergies for adult mammalian locomotion. J Physiol 2018; 597:333-350. [PMID: 30334575 DOI: 10.1113/jp277018] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2018] [Accepted: 10/09/2018] [Indexed: 01/08/2023] Open
Abstract
KEY POINTS The control of locomotion is thought to be generated by activating groups of muscles that perform similar actions, which are termed muscle synergies. Here, we investigated if muscle synergies are controlled at the level of the spinal cord. We did this by comparing muscle activity in the legs of cats during stepping on a treadmill before and after a complete spinal transection that abolishes commands from the brain. We show that muscle synergies were maintained following spinal transection, validating the concept that muscle synergies for locomotion are primarily controlled by circuits of neurons within the spinal cord. ABSTRACT Locomotion is thought to involve the sequential activation of functional modules or muscle synergies. Here, we tested the hypothesis that muscle synergies for locomotion are organized within the spinal cord. We recorded bursts of muscle activity in the same cats (n = 7) before and after spinal transection during tied-belt locomotion at three speeds and split-belt locomotion at three left-right speed differences. We identified seven muscles synergies before (intact state) and after (spinal state) spinal transection. The muscles comprising the different synergies were the same in the intact and spinal states as well as at different speeds or left-right speed differences. However, there were some significant shifts in the onsets and offsets of certain synergies as a function of state, speed and left-right speed differences. The most notable difference between the intact and spinal states was a change in the timing between the knee flexor and hip flexor muscle synergies. In the intact state, the knee flexor synergy preceded the hip flexor synergy, whereas in the spinal state both synergies occurred concurrently. Afferent inputs also appear important for the expression of some muscle synergies, specifically those involving biphasic patterns of muscle activity. We propose that muscle synergies for locomotion are primarily organized within the spinal cord, although their full expression and proper timing requires inputs from supraspinal structures and/or limb afferents.
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Affiliation(s)
- Etienne Desrochers
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec, J1H 5N4, Canada
| | - Jonathan Harnie
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec, J1H 5N4, Canada
| | - Adam Doelman
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec, J1H 5N4, Canada
| | - Marie-France Hurteau
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec, J1H 5N4, Canada
| | - Alain Frigon
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec, J1H 5N4, Canada
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114
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Ferreira-Pinto MJ, Ruder L, Capelli P, Arber S. Connecting Circuits for Supraspinal Control of Locomotion. Neuron 2018; 100:361-374. [DOI: 10.1016/j.neuron.2018.09.015] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 08/27/2018] [Accepted: 09/07/2018] [Indexed: 12/21/2022]
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115
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Muzzu T, Mitolo S, Gava GP, Schultz SR. Encoding of locomotion kinematics in the mouse cerebellum. PLoS One 2018; 13:e0203900. [PMID: 30212563 PMCID: PMC6136788 DOI: 10.1371/journal.pone.0203900] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2018] [Accepted: 08/29/2018] [Indexed: 01/23/2023] Open
Abstract
The cerebellum is involved in coordinating motor behaviour, but how the cerebellar network regulates locomotion is still not well understood. We characterised the activity of putative cerebellar Purkinje cells, Golgi cells and mossy fibres in awake mice engaged in an active locomotion task, using high-density silicon electrode arrays. Analysis of the activity of over 300 neurons in response to locomotion revealed that the majority of cells (53%) were significantly modulated by phase of the stepping cycle. However, in contrast to studies involving passive locomotion on a treadmill, we found that a high proportion of cells (45%) were tuned to the speed of locomotion, and 19% were tuned to yaw movements. The activity of neurons in the cerebellar vermis provided more information about future speed of locomotion than about past or present speed, suggesting a motor, rather than purely sensory, role. We were able to accurately decode the speed of locomotion with a simple linear algorithm, with only a relatively small number of well-chosen cells needed, irrespective of cell class. Our observations suggest that behavioural state modulates cerebellar sensorimotor integration, and advocate a role for the cerebellar vermis in control of high-level locomotor kinematic parameters such as speed and yaw.
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Affiliation(s)
- Tomaso Muzzu
- Centre for Neurotechnology and Department of Bioengineering, Imperial College London, London, United Kingdom
| | - Susanna Mitolo
- Centre for Neurotechnology and Department of Bioengineering, Imperial College London, London, United Kingdom
| | - Giuseppe P. Gava
- Centre for Neurotechnology and Department of Bioengineering, Imperial College London, London, United Kingdom
| | - Simon R. Schultz
- Centre for Neurotechnology and Department of Bioengineering, Imperial College London, London, United Kingdom
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116
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Duysens J, Forner-Cordero A. Walking with perturbations: a guide for biped humans and robots. BIOINSPIRATION & BIOMIMETICS 2018; 13:061001. [PMID: 30109860 DOI: 10.1088/1748-3190/aada54] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
This paper provides an update on the neural control of bipedal walking in relation to bioinspired models and robots. It is argued that most current models or robots are based on the construct of a symmetrical central pattern generator (CPG). However, new evidence suggests that CPG functioning is basically asymmetrical with its flexor half linked more tightly to the rhythm generator. The stability of bipedal gait, which is an important problem for robots and biological systems, is also addressed. While it is not possible to determine how biological biped systems guarantee stability, robot solutions can be useful to propose new hypotheses for biology. In the second part of this review, the focus is on gait perturbations, which is an important topic in robotics in view of the frequent falls of robots when faced with perturbations. From the human physiology it is known that the initial reaction often consists of a brief interruption followed by an adequate response. For instance, the successful recovery from a trip is achieved using some basic reactions (termed elevating and lowering strategies), that depend on the phase of the step cycle of the trip occurrence. Reactions to stepping unexpectedly in a hole depend on comparing expected and real feedback. Implementation of these ideas in models and robotics starts to emerge, with the most advanced robots being able to learn how to fall safely and how to deal with complicated disturbances such as provided by walking on a split-belt.
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Affiliation(s)
- Jacques Duysens
- Biomechatronics Lab., Mechatronics Department, Escola Politécnica da Universidade de São Paulo, Av. Prof. Mello Moraes, 2231, Cidade Universitária 05508-030, São Paulo-SP, Brasil. Department of Kinesiology, FaBeR, Katholieke Universiteit Leuven, Leuven, Belgium
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117
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Schnerwitzki D, Perry S, Ivanova A, Caixeta FV, Cramer P, Günther S, Weber K, Tafreshiha A, Becker L, Vargas Panesso IL, Klopstock T, Hrabe de Angelis M, Schmidt M, Kullander K, Englert C. Neuron-specific inactivation of Wt1 alters locomotion in mice and changes interneuron composition in the spinal cord. Life Sci Alliance 2018; 1:e201800106. [PMID: 30456369 PMCID: PMC6238623 DOI: 10.26508/lsa.201800106] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 08/09/2018] [Accepted: 08/10/2018] [Indexed: 12/31/2022] Open
Abstract
Locomotion is coordinated by neuronal circuits of the spinal cord. Recently, dI6 neurons were shown to participate in the control of locomotion. A subpopulation of dI6 neurons expresses the Wilms tumor suppressor gene Wt1. However, the function of Wt1 in these cells is not understood. Here, we aimed to identify behavioral changes and cellular alterations in the spinal cord associated with Wt1 deletion. Locomotion analyses of mice with neuron-specific Wt1 deletion revealed a slower walk with a decreased stride frequency and an increased stride length. These mice showed changes in their fore-/hindlimb coordination, which were accompanied by a loss of contralateral projections in the spinal cord. Neonates with Wt1 deletion displayed an increase in uncoordinated hindlimb movements and their motor neuron output was arrhythmic with a decreased frequency. The population size of dI6, V0, and V2a neurons in the developing spinal cord of conditional Wt1 mutants was significantly altered. These results show that the development of particular dI6 neurons depends on Wt1 expression and that loss of Wt1 is associated with alterations in locomotion.
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Affiliation(s)
- Danny Schnerwitzki
- Molecular Genetics Lab, Leibniz Institute on Aging—Fritz Lipmann Institute, Jena, Germany
| | - Sharn Perry
- Department of Neuroscience, Uppsala University, Uppsala, Sweden
| | - Anna Ivanova
- Molecular Genetics Lab, Leibniz Institute on Aging—Fritz Lipmann Institute, Jena, Germany
| | - Fabio V Caixeta
- Department of Neuroscience, Uppsala University, Uppsala, Sweden
| | - Paul Cramer
- Molecular Genetics Lab, Leibniz Institute on Aging—Fritz Lipmann Institute, Jena, Germany
| | - Sven Günther
- Molecular Genetics Lab, Leibniz Institute on Aging—Fritz Lipmann Institute, Jena, Germany
| | - Kathrin Weber
- Molecular Genetics Lab, Leibniz Institute on Aging—Fritz Lipmann Institute, Jena, Germany
| | | | - Lore Becker
- German Mouse Clinic, Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
| | - Ingrid L Vargas Panesso
- German Mouse Clinic, Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
- Department of Neurology, Friedrich-Baur-Institut, Ludwig Maximilian University Munich, Munich, Germany
| | - Thomas Klopstock
- Department of Neurology, Friedrich-Baur-Institut, Ludwig Maximilian University Munich, Munich, Germany
- German Center for Neurodegenerative Diseases, Munich, Germany
- Munich Cluster for Systems Neurology, Adolf-Butenandt-Institut, Ludwig Maximilian University Munich, Munich, Germany
- German Center for Vertigo and Balance Disorders, University Hospital Munich, Campus Grosshadern, Munich, Germany
| | - Martin Hrabe de Angelis
- German Mouse Clinic, Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
- Chair of Experimental Genetics, School of Life Science Weihenstephan, Technical University of Munich, Freising, Germany
- German Center for Diabetes Research, Neuherberg, Germany
| | - Manuela Schmidt
- Institute of Systematic Zoology and Evolutionary Biology with Phyletic Museum, Friedrich Schiller University Jena, Jena, Germany
| | - Klas Kullander
- Department of Neuroscience, Uppsala University, Uppsala, Sweden
| | - Christoph Englert
- Molecular Genetics Lab, Leibniz Institute on Aging—Fritz Lipmann Institute, Jena, Germany
- Institute of Biochemistry and Biophysics, Friedrich-Schiller-University Jena, Jena, Germany
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118
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Brainstem Steering of Locomotor Activity in the Newborn Rat. J Neurosci 2018; 38:7725-7740. [PMID: 30037828 DOI: 10.1523/jneurosci.1074-18.2018] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 07/17/2018] [Accepted: 07/18/2018] [Indexed: 11/21/2022] Open
Abstract
Control of locomotion relies on motor loops conveying modulatory signals between brainstem and spinal motor circuits. We investigated the steering control of the brainstem reticular formation over the spinal locomotor networks using isolated brainstem-spinal cord preparations of male and female neonatal rats. First, we performed patch-clamp recordings of identified reticulospinal cells during episodes of fictive locomotion. This revealed that a spinal ascending phasic modulation of reticulospinal cell activity is already present at birth. Half of the cells exhibited tonic firing during locomotion, while the other half emitted phasic discharges of action potentials phase locked to ongoing activity. We next showed that mimicking the phasic activity of reticulospinal neurons by applying patterned electrical stimulation bilaterally at the ventral caudal medulla level triggered fictive locomotion efficiently. Moreover, the brainstem stimuli-induced locomotor rhythm was entrained in a one-to-one coupling over a range of cycle periods (2-6 s). Additionally, we induced turning like motor outputs by either increasing or decreasing the relative duration of the stimulation trains on one side of the brainstem compared to the other. The ability of the patterned descending command to control the locomotor output depended on the functional integrity of ventral reticulospinal pathways and the involvement of local spinal central pattern generator circuitry. Altogether, this study provides a mechanism by which brainstem reticulospinal neurons relay steering and speed commands to the spinal locomotor networks.SIGNIFICANCE STATEMENT Locomotor function allows the survival of most animal species while sustaining the expression of fundamental behaviors. Locomotor activities adapt from moment to moment to behavioral and environmental changes. We show that the brainstem can control the spinal locomotor network outputs through phasic descending commands that alternate bilaterally. Manipulating the periodicity and/or the relative durations of the left and right descending commands at the brainstem level is efficient to set the locomotor speed and sustain directional changes.
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119
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Vahedipour A, Haji Maghsoudi O, Wilshin S, Shamble P, Robertson B, Spence A. Uncovering the structure of the mouse gait controller: Mice respond to substrate perturbations with adaptations in gait on a continuum between trot and bound. J Biomech 2018; 78:77-86. [PMID: 30078638 DOI: 10.1016/j.jbiomech.2018.07.020] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 07/04/2018] [Accepted: 07/09/2018] [Indexed: 11/29/2022]
Abstract
Animals, including humans, have been shown to maintain a gait during locomotion that minimizes the risk of injury and energetic cost. Despite the importance of understanding the mechanisms of gait regulation, ethical and experimental challenges have prevented full exploration of these. Here we present data on the gait response of mice to rapid, precisely timed, spatially confined mechanical perturbations. Our data elucidate that after the mechanical perturbation, the mouse gait response is anisotropic, preferring deviations away from the trot towards bounding, over those towards other gaits, such as walk or pace. We quantified this shift by projecting the observed gait onto the line between trot and bound, in the space of quadrupedal gaits. We call this projection λ. For λ=0, the gait is the ideal trot; for λ=±π, it is the ideal bound. We found that the substrate perturbation caused a significant shift in λ towards bound during the stride in which the perturbation occurred and the following stride (linear mixed effects model: Δλ=0.26±0.07 and Δλ=0.21±0.07, respectively; random effect for animal, p < 0.05 for both strides, n = 8 mice). We hypothesize that this is because the bounding gait is better suited to rapid acceleration or deceleration, and an exploratory analysis of jerk showed that it was significantly correlated with λ (p < 0.05). Understanding how gait is controlled under perturbations can aid in diagnosing gait pathologies and in the design of more agile robots.
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Affiliation(s)
- A Vahedipour
- Department of Bioengineering, Temple University, Philadelphia, PA 19122, USA.
| | - O Haji Maghsoudi
- Department of Bioengineering, Temple University, Philadelphia, PA 19122, USA
| | - S Wilshin
- Structure and Motion Laboratory, Royal Veterinary College, University of London, London, United Kingdom
| | - P Shamble
- Department of Bioengineering, Temple University, Philadelphia, PA 19122, USA
| | - B Robertson
- Department of Bioengineering, Temple University, Philadelphia, PA 19122, USA
| | - A Spence
- Department of Bioengineering, Temple University, Philadelphia, PA 19122, USA
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120
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Cellular Effects of Repetition Priming in the Aplysia Feeding Network Are Suppressed during a Task-Switch But Persist and Facilitate a Return to the Primed State. J Neurosci 2018; 38:6475-6490. [PMID: 29934354 DOI: 10.1523/jneurosci.0547-18.2018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Revised: 06/01/2018] [Accepted: 06/11/2018] [Indexed: 12/14/2022] Open
Abstract
Many neural networks are multitasking and receive modulatory input, which configures activity. As a result, these networks can enter a relatively persistent state in which they are biased to generate one type of output as opposed to another. A question we address is as follows: what happens to this type of state when the network is forced to task-switch? We address this question in the feeding system of the mollusc Aplysia This network generates ingestive and egestive motor programs. We focus on an identified neuron that is selectively active when programs are ingestive. Previous work has established that the increase in firing frequency observed during ingestive programs is at least partially mediated by an excitability increase. Here we identify the underlying cellular mechanism as the induction of a cAMP-dependent inward current. We ask how this current is impacted by the subsequent induction of egestive activity. Interestingly, we demonstrate that this task-switch does not eliminate the inward current but instead activates an outward current. The induction of the outward current obviously reduces the net inward current in the cell. This produces the decrease in excitability and firing frequency required for the task-switch. Importantly, however, the persistence of the inward current is not impacted. It remains present and coexists with the outward current. Consequently, when effects of egestive priming and the outward current dissipate, firing frequency and excitability remain above baseline levels. This presumably has important functional implications in that it will facilitate a return to ingestive activity.SIGNIFICANCE STATEMENT Under physiological conditions, an animal generating a particular type of motor activity can be forced to at least briefly task-switch. In some circumstances, this involves the temporary induction of an "antagonistic" or incompatible motor program. For example, ingestion can be interrupted by a brief period of egestive activity. In this type of situation, it is often desirable for behavioral switching to occur rapidly and efficiently. In this report, we focus on a particular aspect of this type of task-switch. We determine how the priming that occurs when a multitasking network repeatedly generates one type of motor activity can be retained during the execution of an incompatible motor program.
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121
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WT1-Expressing Interneurons Regulate Left-Right Alternation during Mammalian Locomotor Activity. J Neurosci 2018; 38:5666-5676. [PMID: 29789381 DOI: 10.1523/jneurosci.0328-18.2018] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2018] [Revised: 04/12/2018] [Accepted: 05/12/2018] [Indexed: 12/31/2022] Open
Abstract
The basic pattern of activity underlying stepping in mammals is generated by a neural network located in the caudal spinal cord. Within this network, the specific circuitry coordinating left-right alternation has been shown to involve several groups of molecularly defined interneurons. Here we characterize a population of spinal neurons that express the Wilms' tumor 1 (WT1) gene and investigate their role during locomotor activity in mice of both sexes. We demonstrate that WT1-expressing cells are located in the ventromedial region of the spinal cord of mice and are also present in the human spinal cord. In the mouse, these cells are inhibitory, project axons to the contralateral spinal cord, terminate in close proximity to other commissural interneuron subtypes, and are essential for appropriate left-right alternation during locomotion. In addition to identifying WT1-expressing interneurons as a key component of the locomotor circuitry, this study provides insight into the manner in which several populations of molecularly defined interneurons are interconnected to generate coordinated motor activity on either side of the body during stepping.SIGNIFICANCE STATEMENT In this study, we characterize WT1-expressing spinal interneurons in mice and demonstrate that they are commissurally projecting and inhibitory. Silencing of this neuronal population during a locomotor task results in a complete breakdown of left-right alternation, whereas flexor-extensor alternation was not significantly affected. Axons of WT1 neurons are shown to terminate nearby commissural interneurons, which coordinate motoneuron activity during locomotion, and presumably regulate their activity. Finally, the WT1 gene is shown to be present in the spinal cord of humans, raising the possibility of functional homology between these species. This study not only identifies a key component of the locomotor circuitry but also begins to unravel the connectivity among the growing number of molecularly defined interneurons that comprise this neural network.
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122
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Boije H, Kullander K. Origin and circuitry of spinal locomotor interneurons generating different speeds. Curr Opin Neurobiol 2018; 53:16-21. [PMID: 29733915 DOI: 10.1016/j.conb.2018.04.024] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Revised: 04/23/2018] [Accepted: 04/24/2018] [Indexed: 10/17/2022]
Abstract
The spinal circuitry governing the undulatory movements of swimming vertebrates consist of excitatory and commissural inhibitory interneurons and motor neurons. This locomotor network generates the rhythmic output, coordinate left/right alternation, and permit communication across segments. Through evolution, more complex movement patterns have emerged, made possible by sub-specialization of neural populations within the spinal cord. Walking tetrapods use a similar basic circuitry, but have added layers of complexity for the coordination of intralimbic flexor and extensor muscles as well as interlimbic coordination between the body halves and fore/hindlimbs. Although the basics of these circuits are known there is a gap in our knowledge regarding how different speeds and gaits are coordinated. Analysing subpopulations among described neuronal populations may bring insight into how changes in locomotor output are orchestrated by a hard-wired network.
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Affiliation(s)
- Henrik Boije
- Department of Neuroscience, Uppsala University, Box 593, 751 24 Uppsala, Sweden.
| | - Klas Kullander
- Department of Neuroscience, Uppsala University, Box 593, 751 24 Uppsala, Sweden.
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123
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Raffalt PC, Nielsen LR, Madsen S, Højberg LM, Pingel J, Nielsen JB, Alkjær T, Wienecke J. Assessment of intersegmental coordination of rats during walking at different speeds – Application of continuous relative phase. J Biomech 2018; 73:168-176. [DOI: 10.1016/j.jbiomech.2018.03.045] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Revised: 02/01/2018] [Accepted: 03/25/2018] [Indexed: 11/16/2022]
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124
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Sarnaik R, Raman IM. Control of voluntary and optogenetically perturbed locomotion by spike rate and timing of neurons of the mouse cerebellar nuclei. eLife 2018; 7:29546. [PMID: 29659351 PMCID: PMC5902160 DOI: 10.7554/elife.29546] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Accepted: 03/30/2018] [Indexed: 11/13/2022] Open
Abstract
Neurons of the cerebellar nuclei (CbN), which generate cerebellar output, are inhibited by Purkinje cells. With extracellular recordings during voluntary locomotion in head-fixed mice, we tested how the rate and coherence of inhibition influence CbN cell firing and well-practiced movements. Firing rates of Purkinje and CbN cells were modulated systematically through the stride cycle (~200–300 ms). Optogenetically stimulating ChR2-expressing Purkinje cells with light steps or trains evoked either asynchronous or synchronous inhibition of CbN cells. Steps slowed CbN firing. Trains suppressed CbN cell firing less effectively, but consistently altered millisecond-scale spike timing. Steps or trains that perturbed stride-related modulation of CbN cell firing rates correlated well with irregularities of movement, suggesting that ongoing locomotion is sensitive to alterations in modulated CbN cell firing. Unperturbed locomotion continued more often during trains than steps, however, suggesting that stride-related modulation of CbN spiking is less readily disrupted by synchronous than asynchronous inhibition.
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Affiliation(s)
- Rashmi Sarnaik
- Department of Neurobiology, Northwestern University, Evanston, United States
| | - Indira M Raman
- Department of Neurobiology, Northwestern University, Evanston, United States
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125
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Peng J, Ferent J, Li Q, Liu M, Da Silva RV, Zeilhofer HU, Kania A, Zhang Y, Charron F. Loss of Dcc in the spinal cord is sufficient to cause a deficit in lateralized motor control and the switch to a hopping gait. Dev Dyn 2018; 247:620-629. [DOI: 10.1002/dvdy.24549] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2017] [Revised: 06/22/2017] [Accepted: 06/23/2017] [Indexed: 11/10/2022] Open
Affiliation(s)
- Jimmy Peng
- Montréal Clinical Research Institute (IRCM); Montréal Quebec Canada
- Department of Biology; McGill University; Montréal Quebec Canada
| | - Julien Ferent
- Montréal Clinical Research Institute (IRCM); Montréal Quebec Canada
| | - Qingyu Li
- Department of Medical Neuroscience; Dalhousie University; Halifax Nova Scotia Canada
| | - Mingwei Liu
- Department of Medical Neuroscience; Dalhousie University; Halifax Nova Scotia Canada
| | - Ronan Vinicius Da Silva
- Montréal Clinical Research Institute (IRCM); Montréal Quebec Canada
- Integrated Program in Neuroscience; McGill University; Montréal Quebec Canada
| | | | - Artur Kania
- Montréal Clinical Research Institute (IRCM); Montréal Quebec Canada
- Integrated Program in Neuroscience; McGill University; Montréal Quebec Canada
- Department of Medicine; University of Montréal; Montréal Quebec Canada
| | - Ying Zhang
- Department of Medical Neuroscience; Dalhousie University; Halifax Nova Scotia Canada
| | - Frédéric Charron
- Montréal Clinical Research Institute (IRCM); Montréal Quebec Canada
- Department of Biology; McGill University; Montréal Quebec Canada
- Integrated Program in Neuroscience; McGill University; Montréal Quebec Canada
- Department of Medicine; University of Montréal; Montréal Quebec Canada
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126
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Wenning A, Norris BJ, Günay C, Kueh D, Calabrese RL. Output variability across animals and levels in a motor system. eLife 2018; 7:31123. [PMID: 29345614 PMCID: PMC5773184 DOI: 10.7554/elife.31123] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 11/22/2017] [Indexed: 01/10/2023] Open
Abstract
Rhythmic behaviors vary across individuals. We investigated the sources of this output variability across a motor system, from the central pattern generator (CPG) to the motor plant. In the bilaterally symmetric leech heartbeat system, the CPG orchestrates two coordinations in the bilateral hearts with different intersegmental phase relations (Δϕ) and periodic side-to-side switches. Population variability is large. We show that the system is precise within a coordination, that differences in repetitions of a coordination contribute little to population output variability, but that differences between bilaterally homologous cells may contribute to some of this variability. Nevertheless, much output variability is likely associated with genetic and life history differences among individuals. Variability of Δϕ were coordination-specific: similar at all levels in one, but significantly lower for the motor pattern than the CPG pattern in the other. Mechanisms that transform CPG output to motor neurons may limit output variability in the motor pattern.
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Affiliation(s)
- Angela Wenning
- Biology Department, Emory University, Atlanta, United States
| | - Brian J Norris
- Biology Department, Emory University, Atlanta, United States.,Biological Sciences, California State University, San Marcos, United States
| | - Cengiz Günay
- Biology Department, Emory University, Atlanta, United States.,School of Science and Technology, Georgia Gwinnett College, Lawrenceville, United States
| | - Daniel Kueh
- Biology Department, Emory University, Atlanta, United States
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127
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Kick DR, Schulz DJ. Variability in neural networks. eLife 2018; 7:34153. [PMID: 29345615 PMCID: PMC5773176 DOI: 10.7554/elife.34153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Accepted: 01/12/2018] [Indexed: 11/20/2022] Open
Abstract
Experiments on neurons in the heart system of the leech reveal why rhythmic behaviors differ between individuals.
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Affiliation(s)
- Daniel R Kick
- Division of Biological Sciences, University of Missouri-Columbia, Columbia, United States
| | - David J Schulz
- Division of Biological Sciences, University of Missouri-Columbia, Columbia, United States
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128
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Midbrain circuits that set locomotor speed and gait selection. Nature 2018; 553:455-460. [PMID: 29342142 PMCID: PMC5937258 DOI: 10.1038/nature25448] [Citation(s) in RCA: 251] [Impact Index Per Article: 41.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 12/08/2017] [Indexed: 12/18/2022]
Abstract
Locomotion is a fundamental motor function common to the animal kingdom. It is executed episodically and adapted to behavioural needs including exploration, requiring slow locomotion, and escaping behaviour, necessitating faster speeds. The control of these functions originates in brainstem structures although the neuronal substrate(s) supporting them are debated. Here, we show in mice that speed/gait selection are controlled by glutamatergic excitatory neurons (GlutNs) segregated in two distinct midbrain nuclei: the Cuneiform Nucleus (CnF) and the Pedunculopontine Nucleus (PPN). GlutNs in each of those two regions are sufficient for controlling slower alternating locomotor behavior but only GlutNs in the CnF are necessary for high-speed synchronous locomotion. Additionally, PPN- and CnF-GlutNs activation dynamics and their input and output connectivity matrices support explorative and escape locomotion, respectively. Our results identify dual regions in the midbrain that act in common to select context dependent locomotor behaviours.
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129
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Structure of the Zebrafish Locomotor Repertoire Revealed with Unsupervised Behavioral Clustering. Curr Biol 2018; 28:181-195.e5. [DOI: 10.1016/j.cub.2017.12.002] [Citation(s) in RCA: 138] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Revised: 10/29/2017] [Accepted: 12/01/2017] [Indexed: 12/13/2022]
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130
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Reversible silencing of lumbar spinal interneurons unmasks a task-specific network for securing hindlimb alternation. Nat Commun 2017; 8:1963. [PMID: 29213073 PMCID: PMC5719045 DOI: 10.1038/s41467-017-02033-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Accepted: 11/02/2017] [Indexed: 12/05/2022] Open
Abstract
Neural circuitry in the lumbar spinal cord governs two principal features of locomotion, rhythm and pattern, which reflect intra- and interlimb movement. These features are functionally organized into a hierarchy that precisely controls stepping in a stereotypic, speed-dependent fashion. Here, we show that a specific component of the locomotor pattern can be independently manipulated. Silencing spinal L2 interneurons that project to L5 selectively disrupts hindlimb alternation allowing a continuum of walking to hopping to emerge from the otherwise intact network. This perturbation, which is independent of speed and occurs spontaneously with each step, does not disrupt multi-joint movements or forelimb alternation, nor does it translate to a non-weight-bearing locomotor activity. Both the underlying rhythm and the usual relationship between speed and spatiotemporal characteristics of stepping persist. These data illustrate that hindlimb alternation can be manipulated independently from other core features of stepping, revealing a striking freedom in an otherwise precisely controlled system. Intra- and interlimb coordination during locomotion is governed by hierarchically organized lumbar spinal networks. Here, the authors show that reversible silencing of spinal L2–L5 interneurons specifically disrupts hindlimb alternation leading to a continuum of walking to hopping.
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131
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Züchner M, Kondratskaya E, Sylte CB, Glover JC, Boulland JL. Rapid recovery and altered neurochemical dependence of locomotor central pattern generation following lumbar neonatal spinal cord injury. J Physiol 2017; 596:281-303. [PMID: 29086918 DOI: 10.1113/jp274484] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Accepted: 10/25/2017] [Indexed: 01/30/2023] Open
Abstract
KEY POINTS Spinal compression injury targeted to the neonatal upper lumbar spinal cord, the region of highest hindlimb locomotor rhythmogenicity, leads to an initial paralysis of the hindlimbs. Behavioural recovery is evident within a few days and approaches normal function within about 3 weeks. Fictive locomotion in the isolated injured spinal cord cannot be elicited by a neurochemical cocktail containing NMDA, dopamine and serotonin 1 day post-injury, but can 3 days post-injury as readily as in the uninjured spinal cord. Low frequency coordinated rhythmic activity can be elicited in the isolated uninjured spinal cord by NMDA + dopamine (without serotonin), but not in the isolated injured spinal cord. In both the injured and uninjured spinal cord, eliciting bona fide fictive locomotion requires the additional presence of serotonin. ABSTRACT Following incomplete compression injury in the thoracic spinal cord of neonatal mice 1 day after birth (P1), we previously reported that virtually normal hindlimb locomotor function is recovered within about 3 weeks despite substantial permanent thoracic tissue loss. Here, we asked whether similar recovery occurs following lumbar injury that impacts more directly on the locomotor central pattern generator (CPG). As in thoracic injuries, lumbar injuries caused about 90% neuronal loss at the injury site and increased serotonergic innervation below the injury. Motor recovery was slower after lumbar than thoracic injury, but virtually normal function was attained by P25 in both cases. Locomotor CPG status was tested by eliciting fictive locomotion in isolated spinal cords using a widely used neurochemical cocktail (NMDA, dopamine, serotonin). No fictive locomotion could be elicited 1 day post-injury, but could within 3 days post-injury as readily as in age-matched uninjured control spinal cords. Burst patterning and coordination were largely similar in injured and control spinal cords but there were differences. Notably, in both groups there were two main locomotor frequencies, but injured spinal cords exhibited a shift towards the higher frequency. Injury also altered the neurochemical dependence of locomotor CPG output, such that injured spinal cords, unlike control spinal cords, were incapable of generating low frequency rhythmic coordinated activity in the presence of NMDA and dopamine alone. Thus, the neonatal spinal cord also exhibits remarkable functional recovery after lumbar injuries, but the neurochemical sensitivity of locomotor circuitry is modified in the process.
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Affiliation(s)
- Mark Züchner
- Laboratory of Neural Development and Optical Recording (NDEVOR), Division of Physiology, Department of Molecular Medicine, University of Oslo, Oslo, Norway.,Norwegian Centre for Stem Cell Research, Oslo University Hospital, Oslo, Norway.,Department of Neurosurgery, Oslo University Hospital, Oslo, Norway
| | - Elena Kondratskaya
- Laboratory of Neural Development and Optical Recording (NDEVOR), Division of Physiology, Department of Molecular Medicine, University of Oslo, Oslo, Norway.,Norwegian Centre for Stem Cell Research, Oslo University Hospital, Oslo, Norway
| | - Camilla B Sylte
- Laboratory of Neural Development and Optical Recording (NDEVOR), Division of Physiology, Department of Molecular Medicine, University of Oslo, Oslo, Norway
| | - Joel C Glover
- Laboratory of Neural Development and Optical Recording (NDEVOR), Division of Physiology, Department of Molecular Medicine, University of Oslo, Oslo, Norway.,Norwegian Centre for Stem Cell Research, Oslo University Hospital, Oslo, Norway
| | - Jean-Luc Boulland
- Laboratory of Neural Development and Optical Recording (NDEVOR), Division of Physiology, Department of Molecular Medicine, University of Oslo, Oslo, Norway.,Norwegian Centre for Stem Cell Research, Oslo University Hospital, Oslo, Norway
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132
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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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133
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Delineating the Diversity of Spinal Interneurons in Locomotor Circuits. J Neurosci 2017; 37:10835-10841. [PMID: 29118212 DOI: 10.1523/jneurosci.1829-17.2017] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Revised: 09/27/2017] [Accepted: 10/11/2017] [Indexed: 11/21/2022] Open
Abstract
Locomotion is common to all animals and is essential for survival. Neural circuits located in the spinal cord have been shown to be necessary and sufficient for the generation and control of the basic locomotor rhythm by activating muscles on either side of the body in a specific sequence. Activity in these neural circuits determines the speed, gait pattern, and direction of movement, so the specific locomotor pattern generated relies on the diversity of the neurons within spinal locomotor circuits. Here, we review findings demonstrating that developmental genetics can be used to identify populations of neurons that comprise these circuits and focus on recent work indicating that many of these populations can be further subdivided into distinct subtypes, with each likely to play complementary functions during locomotion. Finally, we discuss data describing the manner in which these populations interact with each other to produce efficient, task-dependent locomotion.
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134
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Thiry L, Lemieux M, Bretzner F. Age- and speed-dependent modulation of gaits in DSCAM 2J mutant mice. J Neurophysiol 2017; 119:723-737. [PMID: 29093169 DOI: 10.1152/jn.00471.2017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Gaits depend on the interplay between distributed spinal neural networks, termed central pattern generators, generating rhythmic and coordinated movements, primary afferents, and descending supraspinal inputs. Recent studies demonstrated that the mouse displays a rich repertoire of gaits. Changes in gaits occur in mutant mice lacking particular neurons or molecular signaling pathways implicated in the normal establishment of these neural networks. Given the role of the Down syndrome cell adherence molecule (DSCAM) to the formation and maintenance of spinal interneuronal circuits and sensorimotor integration, we have investigated its functional contribution to gaits over a wide range of locomotor speeds using freely walking mice. We show in this study that the DSCAM2J mutation, while not precluding any gait, impairs the age- and speed-dependent modulation of gaits. It impairs the ability of mice to maintain their locomotion at high treadmill speeds. DSCAM2J mutation induces the dominance of lateral walk over trot and the emergence of aberrant gaits for mice, such as pace and diagonal walk. Gaits were also more labile in DSCAM2J mutant mice, i.e., less stable, less attractive, and less predictable than in their wild-type littermates. Our results suggest that the DSCAM mutation affects the behavioral repertoire of gaits in an age- and speed-dependent manner. NEW & NOTEWORTHY Gaits evolve throughout development, up to adulthood, and according to the genetic background. Using mutant mice lacking DSCAM (a cell adherence molecule associated with Down syndrome), we show that the DSCAM2J mutation alters the repertoire of gaits according to the mouse's age and speed, and prevents fast gaits. Such an incapacity suggests a reorganization of spinal, propriospinal, and supraspinal neuronal circuits underlying locomotor control in DSCAM2J mutant mice.
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Affiliation(s)
- Louise Thiry
- Centre de Recherche du Centre Hospitalier Universitaire de Québec, CHUL-Neurosciences, Quebec City, Quebec , Canada
| | - Maxime Lemieux
- Centre de Recherche du Centre Hospitalier Universitaire de Québec, CHUL-Neurosciences, Quebec City, Quebec , Canada
| | - Frédéric Bretzner
- Centre de Recherche du Centre Hospitalier Universitaire de Québec, CHUL-Neurosciences, Quebec City, Quebec , Canada.,Faculty of Medicine, Department of Psychiatry and Neurosciences, Université Laval , Quebec City, Quebec , Canada
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135
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Acton D, Miles GB. Gliotransmission and adenosinergic modulation: insights from mammalian spinal motor networks. J Neurophysiol 2017; 118:3311-3327. [PMID: 28954893 DOI: 10.1152/jn.00230.2017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Astrocytes are proposed to converse with neurons at tripartite synapses, detecting neurotransmitter release and responding with release of gliotransmitters, which in turn modulate synaptic strength and neuronal excitability. However, a paucity of evidence from behavioral studies calls into question the importance of gliotransmission for the operation of the nervous system in healthy animals. Central pattern generator (CPG) networks in the spinal cord and brain stem coordinate the activation of muscles during stereotyped activities such as locomotion, inspiration, and mastication and may therefore provide tractable models in which to assess the contribution of gliotransmission to behaviorally relevant neural activity. We review evidence for gliotransmission within spinal locomotor networks, including studies indicating that adenosine derived from astrocytes regulates the speed of locomotor activity via metamodulation of dopamine signaling.
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Affiliation(s)
- David Acton
- School of Psychology and Neuroscience, University of St Andrews, St Andrews, Fife , United Kingdom
| | - Gareth B Miles
- School of Psychology and Neuroscience, University of St Andrews, St Andrews, Fife , United Kingdom
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136
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Knafo S, Fidelin K, Prendergast A, Tseng PEB, Parrin A, Dickey C, Böhm UL, Figueiredo SN, Thouvenin O, Pascal-Moussellard H, Wyart C. Mechanosensory neurons control the timing of spinal microcircuit selection during locomotion. eLife 2017; 6:e25260. [PMID: 28623664 PMCID: PMC5499942 DOI: 10.7554/elife.25260] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Accepted: 06/17/2017] [Indexed: 12/22/2022] Open
Abstract
Despite numerous physiological studies about reflexes in the spinal cord, the contribution of mechanosensory feedback to active locomotion and the nature of underlying spinal circuits remains elusive. Here we investigate how mechanosensory feedback shapes active locomotion in a genetic model organism exhibiting simple locomotion-the zebrafish larva. We show that mechanosensory feedback enhances the recruitment of motor pools during active locomotion. Furthermore, we demonstrate that inputs from mechanosensory neurons increase locomotor speed by prolonging fast swimming at the expense of slow swimming during stereotyped acoustic escape responses. This effect could be mediated by distinct mechanosensory neurons. In the spinal cord, we show that connections compatible with monosynaptic inputs from mechanosensory Rohon-Beard neurons onto ipsilateral V2a interneurons selectively recruited at high speed can contribute to the observed enhancement of speed. Altogether, our study reveals the basic principles and a circuit diagram enabling speed modulation by mechanosensory feedback in the vertebrate spinal cord.
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Affiliation(s)
- Steven Knafo
- Institut du Cerveau et de la Moelle épinière (I.C.M.), Sorbonne Universités, UPMC Univ Paris 06, Inserm, CNRS, Institut du Cerveau et la Moelle épinière, Hôpital Pitié-Salpêtrière, Paris, France
- AP-HP, Hôpital Pitié-Salpêtrière, Paris, France
| | - Kevin Fidelin
- Institut du Cerveau et de la Moelle épinière (I.C.M.), Sorbonne Universités, UPMC Univ Paris 06, Inserm, CNRS, Institut du Cerveau et la Moelle épinière, Hôpital Pitié-Salpêtrière, Paris, France
| | - Andrew Prendergast
- Institut du Cerveau et de la Moelle épinière (I.C.M.), Sorbonne Universités, UPMC Univ Paris 06, Inserm, CNRS, Institut du Cerveau et la Moelle épinière, Hôpital Pitié-Salpêtrière, Paris, France
| | - Po-En Brian Tseng
- Institut du Cerveau et de la Moelle épinière (I.C.M.), Sorbonne Universités, UPMC Univ Paris 06, Inserm, CNRS, Institut du Cerveau et la Moelle épinière, Hôpital Pitié-Salpêtrière, Paris, France
| | - Alexandre Parrin
- Institut du Cerveau et de la Moelle épinière (I.C.M.), Sorbonne Universités, UPMC Univ Paris 06, Inserm, CNRS, Institut du Cerveau et la Moelle épinière, Hôpital Pitié-Salpêtrière, Paris, France
| | - Charles Dickey
- Institut du Cerveau et de la Moelle épinière (I.C.M.), Sorbonne Universités, UPMC Univ Paris 06, Inserm, CNRS, Institut du Cerveau et la Moelle épinière, Hôpital Pitié-Salpêtrière, Paris, France
| | - Urs Lucas Böhm
- Institut du Cerveau et de la Moelle épinière (I.C.M.), Sorbonne Universités, UPMC Univ Paris 06, Inserm, CNRS, Institut du Cerveau et la Moelle épinière, Hôpital Pitié-Salpêtrière, Paris, France
| | - Sophie Nunes Figueiredo
- Institut du Cerveau et de la Moelle épinière (I.C.M.), Sorbonne Universités, UPMC Univ Paris 06, Inserm, CNRS, Institut du Cerveau et la Moelle épinière, Hôpital Pitié-Salpêtrière, Paris, France
| | - Olivier Thouvenin
- Institut du Cerveau et de la Moelle épinière (I.C.M.), Sorbonne Universités, UPMC Univ Paris 06, Inserm, CNRS, Institut du Cerveau et la Moelle épinière, Hôpital Pitié-Salpêtrière, Paris, France
| | - Hugues Pascal-Moussellard
- Institut du Cerveau et de la Moelle épinière (I.C.M.), Sorbonne Universités, UPMC Univ Paris 06, Inserm, CNRS, Institut du Cerveau et la Moelle épinière, Hôpital Pitié-Salpêtrière, Paris, France
- AP-HP, Hôpital Pitié-Salpêtrière, Paris, France
| | - Claire Wyart
- Institut du Cerveau et de la Moelle épinière (I.C.M.), Sorbonne Universités, UPMC Univ Paris 06, Inserm, CNRS, Institut du Cerveau et la Moelle épinière, Hôpital Pitié-Salpêtrière, Paris, France
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137
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Broom L, Ellison BA, Worley A, Wagenaar L, Sörberg E, Ashton C, Bennett DA, Buchman AS, Saper CB, Shih LC, Hausdorff JM, VanderHorst VG. A translational approach to capture gait signatures of neurological disorders in mice and humans. Sci Rep 2017; 7:3225. [PMID: 28607434 PMCID: PMC5468293 DOI: 10.1038/s41598-017-03336-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Accepted: 04/26/2017] [Indexed: 01/08/2023] Open
Abstract
A method for capturing gait signatures in neurological conditions that allows comparison of human gait with animal models would be of great value in translational research. However, the velocity dependence of gait parameters and differences between quadruped and biped gait have made this comparison challenging. Here we present an approach that accounts for changes in velocity during walking and allows for translation across species. In mice, we represented spatial and temporal gait parameters as a function of velocity and established regression models that reproducibly capture the signatures of these relationships during walking. In experimental parkinsonism models, regression curves representing these relationships shifted from baseline, implicating changes in gait signatures, but with marked differences between models. Gait parameters in healthy human subjects followed similar strict velocity dependent relationships which were altered in Parkinson’s patients in ways that resemble some but not all mouse models. This novel approach is suitable to quantify qualitative walking abnormalities related to CNS circuit dysfunction across species, identify appropriate animal models, and it provides important translational opportunities.
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Affiliation(s)
- Lauren Broom
- Department of Neurology, Division of Movement Disorders, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, 02215, USA
| | - Brian A Ellison
- Department of Neurology, Division of Movement Disorders, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, 02215, USA
| | - Audrey Worley
- Department of Neurology, Division of Movement Disorders, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, 02215, USA
| | - Lara Wagenaar
- Department of Neurology, Division of Movement Disorders, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, 02215, USA
| | - Elina Sörberg
- Department of Neurology, Division of Movement Disorders, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, 02215, USA
| | - Christine Ashton
- Department of Neurology, Division of Movement Disorders, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, 02215, USA
| | - David A Bennett
- Rush Alzheimer's Disease Center, Rush University Medical Center, Chicago, Il 60612, USA
| | - Aron S Buchman
- Rush Alzheimer's Disease Center, Rush University Medical Center, Chicago, Il 60612, USA
| | - Clifford B Saper
- Department of Neurology, Division of Movement Disorders, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, 02215, USA
| | - Ludy C Shih
- Department of Neurology, Division of Movement Disorders, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, 02215, USA
| | - Jeffrey M Hausdorff
- Center for the Study of Movement Cognition and Mobility, Tel-Aviv Sourasky Medical Center, Tel Aviv, 64239, Israel.,Sagol School of Neuroscience and Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Veronique G VanderHorst
- Department of Neurology, Division of Movement Disorders, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, 02215, USA.
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138
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Vidal PM, Karadimas SK, Ulndreaj A, Laliberte AM, Tetreault L, Forner S, Wang J, Foltz WD, Fehlings MG. Delayed decompression exacerbates ischemia-reperfusion injury in cervical compressive myelopathy. JCI Insight 2017; 2:92512. [PMID: 28570271 DOI: 10.1172/jci.insight.92512] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Accepted: 04/27/2017] [Indexed: 01/21/2023] Open
Abstract
Degenerative cervical myelopathy (DCM) is the most common progressive nontraumatic spinal cord injury. The most common recommended treatment is surgical decompression, although the optimal timing of intervention is an area of ongoing debate. The primary objective of this study was to assess whether a delay in decompression could influence the extent of ischemia-reperfusion injury and alter the trajectory of outcome in DCM. Using a DCM mouse model, we show that decompression acutely led to a 1.5- to 2-fold increase in levels of inflammatory cytokines within the spinal cord. Delayed decompression was associated with exacerbated reperfusion injury, astrogliosis, and poorer neurological recovery. Additionally, delayed decompression was associated with prolonged elevation of inflammatory cytokines and an exacerbated peripheral monocytic inflammatory response (P < 0.01 and 0.001). In contrast, early decompression led to resolution of reperfusion-mediated inflammation, neurological improvement, and reduced hyperalgesia. Similar findings were observed in subjects from the CSM AOSpine North America and International studies, where delayed decompressive surgery resulted in poorer neurological improvement compared with patients with an earlier intervention. Our data demonstrate that delayed surgical decompression for DCM exacerbates reperfusion injury and is associated with ongoing enhanced levels of cytokine expression, microglia activation, and astrogliosis, and paralleled with poorer neurological recovery.
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Affiliation(s)
- Pia M Vidal
- Division of Genetics & Development, Toronto Western Research Institute and Spine Program, Krembil Neuroscience Center, University Health Network, Toronto, Ontario, Canada
| | - Spyridon K Karadimas
- Division of Genetics & Development, Toronto Western Research Institute and Spine Program, Krembil Neuroscience Center, University Health Network, Toronto, Ontario, Canada.,Institute of Medical Science
| | - Antigona Ulndreaj
- Division of Genetics & Development, Toronto Western Research Institute and Spine Program, Krembil Neuroscience Center, University Health Network, Toronto, Ontario, Canada.,Institute of Medical Science
| | - Alex M Laliberte
- Division of Genetics & Development, Toronto Western Research Institute and Spine Program, Krembil Neuroscience Center, University Health Network, Toronto, Ontario, Canada.,Institute of Medical Science
| | - Lindsay Tetreault
- Department of Surgery, Division of Neurosurgery and Spine Program, University of Toronto, Toronto, Ontario, Canada
| | - Stefania Forner
- Department of Pharmacology, Universidade Federal de Santa Catarina, Florianópolis, Brazil
| | - Jian Wang
- Division of Genetics & Development, Toronto Western Research Institute and Spine Program, Krembil Neuroscience Center, University Health Network, Toronto, Ontario, Canada
| | - Warren D Foltz
- Spatio-Temporal Targeting and Amplification of Radiation Responses (STTARR) Innovation Centre, Department of Radiation Oncology, University Health Network, Toronto, Ontario, Canada
| | - Michael G Fehlings
- Division of Genetics & Development, Toronto Western Research Institute and Spine Program, Krembil Neuroscience Center, University Health Network, Toronto, Ontario, Canada.,Department of Surgery, Division of Neurosurgery and Spine Program, University of Toronto, Toronto, Ontario, Canada
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139
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Investigation of the Intra- and Inter-Limb Muscle Coordination of Hands-and-Knees Crawling in Human Adults by Means of Muscle Synergy Analysis. ENTROPY 2017. [DOI: 10.3390/e19050229] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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140
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Frigon A. The neural control of interlimb coordination during mammalian locomotion. J Neurophysiol 2017; 117:2224-2241. [PMID: 28298308 DOI: 10.1152/jn.00978.2016] [Citation(s) in RCA: 101] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Revised: 03/02/2017] [Accepted: 03/15/2017] [Indexed: 01/06/2023] Open
Abstract
Neuronal networks within the spinal cord directly control rhythmic movements of the arms/forelimbs and legs/hindlimbs during locomotion in mammals. For an effective locomotion, these networks must be flexibly coordinated to allow for various gait patterns and independent use of the arms/forelimbs. This coordination can be accomplished by mechanisms intrinsic to the spinal cord, somatosensory feedback from the limbs, and various supraspinal pathways. Incomplete spinal cord injury disrupts some of the pathways and structures involved in interlimb coordination, often leading to a disruption in the coordination between the arms/forelimbs and legs/hindlimbs in animal models and in humans. However, experimental spinal lesions in animal models to uncover the mechanisms coordinating the limbs have limitations due to compensatory mechanisms and strategies, redundant systems of control, and plasticity within remaining circuits. The purpose of this review is to provide a general overview and critical discussion of experimental studies that have investigated the neural mechanisms involved in coordinating the arms/forelimbs and legs/hindlimbs during mammalian locomotion.
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Affiliation(s)
- Alain Frigon
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec, Canada
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141
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Nonlinear Modulation of Cutaneous Reflexes with Increasing Speed of Locomotion in Spinal Cats. J Neurosci 2017; 37:3896-3912. [PMID: 28292829 DOI: 10.1523/jneurosci.3042-16.2017] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Revised: 03/05/2017] [Accepted: 03/06/2017] [Indexed: 11/21/2022] Open
Abstract
Cutaneous reflexes are important for responding rapidly to perturbations, correcting limb trajectory, and strengthening support. During locomotion, they are modulated by phase to generate functionally appropriate responses. The goal of the present study was to determine whether cutaneous reflexes and their phase-dependent modulation are altered with increasing speed and if this is accomplished at the spinal level. Four adult cats that recovered stable hindlimb locomotion after spinal transection were implanted with electrodes to record hindlimb muscle activity chronically and to stimulate the superficial peroneal nerve electrically to evoke cutaneous reflexes. The speed-dependent modulation of cutaneous reflexes was assessed by evoking and characterizing ipsilateral and contralateral responses in semitendinosus, vastus lateralis, and lateral gastrocnemius muscles at four treadmill speeds: 0.2, 0.4, 0.6, and 0.8 m/s. The amplitudes of ipsilateral and contralateral responses were largest at intermediate speeds of 0.4 and 0.6 m/s, followed by the slowest and fastest speeds of 0.2 and 0.8 m/s, respectively. The phase-dependent modulation of reflexes was maintained across speeds, with ipsilateral and contralateral responses peaking during the stance-to-swing transition and swing phase of the ipsilateral limb or midstance of the contralateral limb. Reflex modulation across speeds also correlated with the spatial symmetry of the locomotor pattern, but not with temporal symmetry. That the cutaneous reflex amplitude in all muscles was similarly modulated with increasing speed independently of the background level of muscle activity is consistent with a generalized premotoneuronal spinal control mechanism that could help to stabilize the locomotor pattern when changing speed.SIGNIFICANCE STATEMENT When walking, receptors located in the skin respond to mechanical pressure and send signals to the CNS to correct the trajectory of the limb and to reinforce weight support. These signals produce different responses, or reflexes, if they occur when the foot is contacting the ground or in the air. This is known as phase-dependent modulation of reflexes. However, when walking at faster speeds, we do not know if and how these reflexes are changed. In the present study, we show that reflexes from the skin are modulated with speed and that this is controlled at the level of the spinal cord. This modulation could be important in preventing sensory signals from destabilizing the walking pattern.
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142
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Acton D, Miles GB. Differential regulation of NMDA receptors by d-serine and glycine in mammalian spinal locomotor networks. J Neurophysiol 2017; 117:1877-1893. [PMID: 28202572 PMCID: PMC5411468 DOI: 10.1152/jn.00810.2016] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Revised: 01/11/2017] [Accepted: 02/11/2017] [Indexed: 12/11/2022] Open
Abstract
We provide evidence that NMDARs within murine spinal locomotor networks determine the frequency and amplitude of ongoing locomotor-related activity in vitro and that NMDARs are regulated by d-serine and glycine in a synapse-specific and activity-dependent manner. In addition, glycine transporter-1 is shown to be an important regulator of NMDARs during locomotor-related activity. These results show how excitatory transmission can be tuned to diversify the output repertoire of spinal locomotor networks in mammals. Activation of N-methyl-d-aspartate receptors (NMDARs) requires the binding of a coagonist, either d-serine or glycine, in addition to glutamate. Changes in occupancy of the coagonist binding site are proposed to modulate neural networks including those controlling swimming in frog tadpoles. Here, we characterize regulation of the NMDAR coagonist binding site in mammalian spinal locomotor networks. Blockade of NMDARs by d(−)-2-amino-5-phosphonopentanoic acid (d-APV) or 5,7-dichlorokynurenic acid reduced the frequency and amplitude of pharmacologically induced locomotor-related activity recorded from the ventral roots of spinal-cord preparations from neonatal mice. Furthermore, d-APV abolished synchronous activity induced by blockade of inhibitory transmission. These results demonstrate an important role for NMDARs in murine locomotor networks. Bath-applied d-serine enhanced the frequency of locomotor-related but not disinhibited bursting, indicating that coagonist binding sites are saturated during the latter but not the former mode of activity. Depletion of endogenous d-serine by d-amino acid oxidase or the serine-racemase inhibitor erythro-β-hydroxy-l-aspartic acid (HOAsp) increased the frequency of locomotor-related activity, whereas application of l-serine to enhance endogenous d-serine synthesis reduced burst frequency, suggesting a requirement for d-serine at a subset of synapses onto inhibitory interneurons. Consistent with this, HOAsp was ineffective during disinhibited activity. Bath-applied glycine (1–100 µM) failed to alter locomotor-related activity, whereas ALX 5407, a selective inhibitor of glycine transporter-1 (GlyT1), enhanced burst frequency, supporting a role for GlyT1 in NMDAR regulation. Together these findings indicate activity-dependent and synapse-specific regulation of the coagonist binding site within spinal locomotor networks, illustrating the importance of NMDAR regulation in shaping motor output. NEW & NOTEWORTHY We provide evidence that NMDARs within murine spinal locomotor networks determine the frequency and amplitude of ongoing locomotor-related activity in vitro and that NMDARs are regulated by d-serine and glycine in a synapse-specific and activity-dependent manner. In addition, glycine transporter-1 is shown to be an important regulator of NMDARs during locomotor-related activity. These results show how excitatory transmission can be tuned to diversify the output repertoire of spinal locomotor networks in mammals.
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Affiliation(s)
- David Acton
- School of Psychology and Neuroscience, University of St Andrews, St Andrews, Fife, United Kingdom
| | - Gareth B Miles
- School of Psychology and Neuroscience, University of St Andrews, St Andrews, Fife, United Kingdom
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143
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Ruder L, Takeoka A, Arber S. Long-Distance Descending Spinal Neurons Ensure Quadrupedal Locomotor Stability. Neuron 2016; 92:1063-1078. [PMID: 27866798 DOI: 10.1016/j.neuron.2016.10.032] [Citation(s) in RCA: 80] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Revised: 10/07/2016] [Accepted: 10/13/2016] [Indexed: 12/18/2022]
Abstract
Locomotion is an essential animal behavior used for translocation. The spinal cord acts as key executing center, but how it coordinates many body parts located across distance remains poorly understood. Here we employed mouse genetic and viral approaches to reveal organizational principles of long-projecting spinal circuits and their role in quadrupedal locomotion. Using neurotransmitter identity, developmental origin, and projection patterns as criteria, we uncover that spinal segments controlling forelimbs and hindlimbs are bidirectionally connected by symmetrically organized direct synaptic pathways that encompass multiple genetically tractable neuronal subpopulations. We demonstrate that selective ablation of descending spinal neurons linking cervical to lumbar segments impairs coherent locomotion, by reducing postural stability and speed during exploratory locomotion, as well as perturbing interlimb coordination during reinforced high-speed stepping. Together, our results implicate a highly organized long-distance projection system of spinal origin in the control of postural body stabilization and reliability during quadrupedal locomotion.
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Affiliation(s)
- Ludwig Ruder
- Biozentrum, Department of Cell Biology, University of Basel, Klingelbergstrasse 70, 4056 Basel, Switzerland; Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland
| | - Aya Takeoka
- Biozentrum, Department of Cell Biology, University of Basel, Klingelbergstrasse 70, 4056 Basel, Switzerland; Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland
| | - Silvia Arber
- Biozentrum, Department of Cell Biology, University of Basel, Klingelbergstrasse 70, 4056 Basel, Switzerland; Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland.
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144
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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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Distinct sets of locomotor modules control the speed and modes of human locomotion. Sci Rep 2016; 6:36275. [PMID: 27805015 PMCID: PMC5090253 DOI: 10.1038/srep36275] [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: 04/13/2016] [Accepted: 09/29/2016] [Indexed: 12/25/2022] Open
Abstract
Although recent vertebrate studies have revealed that different spinal networks are recruited in locomotor mode- and speed-dependent manners, it is unknown whether humans share similar neural mechanisms. Here, we tested whether speed- and mode-dependence in the recruitment of human locomotor networks exists or not by statistically extracting locomotor networks. From electromyographic activity during walking and running over a wide speed range, locomotor modules generating basic patterns of muscle activities were extracted using non-negative matrix factorization. The results showed that the number of modules changed depending on the modes and speeds. Different combinations of modules were extracted during walking and running, and at different speeds even during the same locomotor mode. These results strongly suggest that, in humans, different spinal locomotor networks are recruited while walking and running, and even in the same locomotor mode different networks are probably recruited at different speeds.
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146
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Trendelenburg-Like Gait, Instability and Altered Step Patterns in a Mouse Model for Limb Girdle Muscular Dystrophy 2i. PLoS One 2016; 11:e0161984. [PMID: 27627455 PMCID: PMC5023177 DOI: 10.1371/journal.pone.0161984] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Accepted: 08/13/2016] [Indexed: 11/29/2022] Open
Abstract
Limb-girdle muscular dystrophy type 2i (LGMD2i) affects thousands of lives with shortened life expectancy mainly due to cardiac and respiratory problems and difficulty with ambulation significantly compromising quality of life. Limited studies have noted impaired gait in patients and animal models of different muscular dystrophies, but not in animal models of LGMD2i. Our goal, therefore, was to quantify gait metrics in the fukutin-related protein P448L mutant (P448L) mouse, a recently developed model for LGMD2i. The Noldus CatWalk XT motion capture system was used to identify multiple gait impairments. An average galloping body speed of 35 cm/s for both P448L and C57BL/6 wild-type mice was maintained to ensure differences in gait were due only to strain physiology. Compared to wild-type mice, P448L mice reach maximum contact 10% faster and have 40% more paw surface area during stance. Additionally, force intensity at the time of maximum paw contact is roughly 2-fold higher in P448L mice. Paw swing time is reduced in P448L mice without changes in stride length as a faster swing speed compensates. Gait instability in P448L mice is indicated by 50% higher instances of 3 and 4 paw stance support and conversely, 2-fold fewer instances of single paw stance support and no instance of zero paw support. This leads to lower variation of normal step patterns used and a higher use of uncommon step patterns. Similar anomalies have also been noted in muscular dystrophy patients due to weakness in the hip abductor muscles, producing a Trendelenburg gait characterized by “waddling” and more pronounced shifts to the stance leg. Thus, gait of P448L mice replicates anomalies commonly seen in LGMD2i patients, which is not only potentially valuable for assessing drug efficacy in restoring movement biomechanics, but also for better understanding them.
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147
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High-speed video gait analysis reveals early and characteristic locomotor phenotypes in mouse models of neurodegenerative movement disorders. Behav Brain Res 2016; 311:340-353. [DOI: 10.1016/j.bbr.2016.04.044] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Revised: 04/25/2016] [Accepted: 04/26/2016] [Indexed: 12/20/2022]
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148
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Björnfors ER, El Manira A. Functional diversity of excitatory commissural interneurons in adult zebrafish. eLife 2016; 5. [PMID: 27559611 PMCID: PMC5039025 DOI: 10.7554/elife.18579] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Accepted: 08/24/2016] [Indexed: 01/18/2023] Open
Abstract
Flexibility in the bilateral coordination of muscle contraction underpins variable locomotor movements or gaits. While the locomotor rhythm is generated by ipsilateral excitatory interneurons, less is known about the commissural excitatory interneurons. Here we examined how the activity of the V0v interneurons – an important commissural neuronal class – varies with the locomotor speed in adult zebrafish. Although V0v interneurons are molecularly homogenous, their activity pattern during locomotion is not uniform. They consist of two distinct types dependent on whether they display rhythmicity or not during locomotion. The rhythmic V0v interneurons were further subdivided into three sub-classes engaged sequentially, first at slow then intermediate and finally fast locomotor speeds. Their order of recruitment is defined by scaling their synaptic current with their input resistance. Thus we uncover, in an adult vertebrate, a novel organizational principle for a key class of commissural interneurons and their recruitment pattern as a function of locomotor speed. DOI:http://dx.doi.org/10.7554/eLife.18579.001 During movements such as swimming and walking, the left and right sides of the body are kept coordinated by specific neurons in the spinal cord. Some of these neurons – called V0 neurons – can either excite or inhibit neurons on the opposite side of the spinal cord. In mice, the inhibitory V0 neurons are responsible for left-right coordination when the mice are moving slowly, while the excitatory neurons operate when the animals are moving more quickly. However, in zebrafish larvae a group of excitatory V0 neurons are only active when the larvae are swimming slowly. Björnfors and El Manira investigated whether excitatory V0 neurons in adult zebrafish behave like those in the larvae, or whether they act more like those in mice. The experiments show that the excitatory V0 neurons in adult zebrafish can be separated into three groups that are activated either at slow, intermediate or fast speeds of movement. The activation of the excitatory V0 neurons depends on the properties of the neurons themselves in combination with signals they receive from other neurons in the spinal cord. Although the excitatory V0 neurons could be active across all speeds, Björnfors and El Manira found that more neurons were active at faster speeds. This suggests that, in the adult zebrafish, there are both similarities and differences in how the V0 neurons are organised compared to larval zebrafish and mice. The next step following on from this work would be to find out the specific roles of excitatory and inhibitory V0 neurons during movement. DOI:http://dx.doi.org/10.7554/eLife.18579.002
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149
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Cabaj AM, Majczyński H, Couto E, Gardiner PF, Stecina K, Sławińska U, Jordan LM. Serotonin controls initiation of locomotion and afferent modulation of coordination via 5-HT 7 receptors in adult rats. J Physiol 2016; 595:301-320. [PMID: 27393215 DOI: 10.1113/jp272271] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Accepted: 06/30/2016] [Indexed: 12/16/2022] Open
Abstract
KEY POINTS Experiments on neonatal rodent spinal cord showed that serotonin (5-HT), acting via 5-HT7 receptors, is required for initiation of locomotion and for controlling the action of interneurons responsible for inter- and intralimb coordination, but the importance of the 5-HT system in adult locomotion is not clear. Blockade of spinal 5-HT7 receptors interfered with voluntary locomotion in adult rats and fictive locomotion in paralysed decerebrate rats with no afferent feedback, consistent with a requirement for activation of descending 5-HT neurons for production of locomotion. The direct control of coordinating interneurons by 5-HT7 receptors observed in neonatal animals was not found during fictive locomotion, revealing a developmental shift from direct control of locomotor interneurons in neonates to control of afferent input from the moving limb in adults. An understanding of the afferents controlled by 5-HT during locomotion is required for optimal use of rehabilitation therapies involving the use of serotonergic drugs. ABSTRACT Serotonergic pathways to the spinal cord are implicated in the control of locomotion based on studies using serotonin type 7 (5-HT7 ) receptor agonists and antagonists and 5-HT7 receptor knockout mice. Blockade of these receptors is thought to interfere with the activity of coordinating interneurons, a conclusion derived primarily from in vitro studies on isolated spinal cord of neonatal rats and mice. Developmental changes in the effects of serotonin (5-HT) on spinal neurons have recently been described, and there is increasing data on control of sensory input by 5-HT7 receptors on dorsal root ganglion cells and/or dorsal horn neurons, leading us to determine the effects of 5-HT7 receptor blockade on voluntary overground locomotion and on locomotion without afferent input from the moving limb (fictive locomotion) in adult animals. Intrathecal injections of the selective 5-HT7 antagonist SB269970 in adult intact rats suppressed locomotion by partial paralysis of hindlimbs. This occurred without a direct effect on motoneurons as revealed by an investigation of reflex activity. The antagonist disrupted intra- and interlimb coordination during locomotion in all intact animals but not during fictive locomotion induced by stimulation of the mesencephalic locomotor region (MLR). MLR-evoked fictive locomotion was transiently blocked, then the amplitude and frequency of rhythmic activity were reduced by SB269970, consistent with the notion that the MLR activates 5-HT neurons, leading to excitation of central pattern generator neurons with 5-HT7 receptors. Effects on coordination in adults required the presence of afferent input, suggesting a switch to 5-HT7 receptor-mediated control of sensory pathways during development.
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Affiliation(s)
- Anna M Cabaj
- Department of Neurophysiology, Nencki Institute of Experimental Biology PAS, 02-093, Warsaw, Poland.,Department of Nerve-Muscle Engineering, Institute of Biocybernetics and Biomedical Engineering PAS, 02-109, Warsaw, Poland
| | - Henryk Majczyński
- Department of Neurophysiology, Nencki Institute of Experimental Biology PAS, 02-093, Warsaw, Poland
| | - Erika Couto
- Department of Physiology & Pathophysiology, Spinal Cord Research Centre, University of Manitoba, Winnipeg, MB, R3E 0J9, Canada
| | - Phillip F Gardiner
- Department of Physiology & Pathophysiology, Spinal Cord Research Centre, University of Manitoba, Winnipeg, MB, R3E 0J9, Canada
| | - Katinka Stecina
- Department of Physiology & Pathophysiology, Spinal Cord Research Centre, University of Manitoba, Winnipeg, MB, R3E 0J9, Canada
| | - Urszula Sławińska
- Department of Neurophysiology, Nencki Institute of Experimental Biology PAS, 02-093, Warsaw, Poland
| | - Larry M Jordan
- Department of Physiology & Pathophysiology, Spinal Cord Research Centre, University of Manitoba, Winnipeg, MB, R3E 0J9, Canada
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150
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Shevtsova NA, Rybak IA. Organization of flexor-extensor interactions in the mammalian spinal cord: insights from computational modelling. J Physiol 2016; 594:6117-6131. [PMID: 27292055 DOI: 10.1113/jp272437] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Accepted: 06/07/2016] [Indexed: 12/28/2022] Open
Abstract
KEY POINTS Alternation of flexor and extensor activity in the mammalian spinal cord is mediated by two classes of genetically identified inhibitory interneurons, V1 and V2b. The V1 interneurons are essential for high-speed locomotor activity. They secure flexor-extensor alternations in the intact cord but lose this function after hemisection, suggesting that they are activated by inputs from the contralateral side of the cord. The V2b interneurons are involved in flexor-extensor alternations in both intact cord and hemicords. We used a computational model of the spinal network, simulating the left and right rhythm-generating circuits interacting via several commissural pathways, and extended this model by incorporating V1 and V2b neuron populations involved in flexor-extensor interactions on each cord side. The model reproduces multiple experimental data on selective silencing and activation of V1 and/or V2b neurons and proposes the organization of their connectivity providing flexor-extensor alternation in the spinal cord. ABSTRACT Alternating flexor and extensor activity represents the fundamental property underlying many motor behaviours including locomotion. During locomotion this alternation appears to arise in rhythm-generating circuits and transpires at all levels of the spinal cord including motoneurons. Recent studies in vitro and in vivo have shown that flexor-extensor alternation during locomotion involves two classes of genetically identified, inhibitory interneurons: V1 and V2b. Particularly, in the isolated mouse spinal cord, abrogation of neurotransmission derived by both V1 and V2b interneurons resulted in flexor-extensor synchronization, whereas selective inactivation of only one of these neuron types did not abolish flexor-extensor alternation. After hemisection, inactivation of only V2b interneurons led to the flexor-extensor synchronization, while inactivation of V1 interneurons did not affect flexor-extensor alternation. Moreover, optogenetic activation of V2b interneurons suppressed extensor-related activity, while similar activation of V1 interneurons suppressed both flexor and extensor oscillations. Here, we address these issues using the previously published computational model of spinal circuitry simulating bilateral interactions between left and right rhythm-generating circuits. In the present study, we incorporate V1 and V2b neuron populations on both sides of the cord to make them critically involved in flexor-extensor interactions. The model reproduces multiple experimental data on the effects of hemisection and selective silencing or activation of V1 and V2b neurons and suggests connectivity profiles of these neurons and their specific roles in left-right (V1) and flexor-extensor (both V2b and V1) interactions in the spinal cord that can be tested experimentally.
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Affiliation(s)
- 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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