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Dubuc R, Cabelguen JM, Ryczko D. Locomotor pattern generation and descending control: a historical perspective. J Neurophysiol 2023; 130:401-416. [PMID: 37465884 DOI: 10.1152/jn.00204.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Revised: 07/11/2023] [Accepted: 07/12/2023] [Indexed: 07/20/2023] Open
Abstract
The ability to generate and control locomotor movements depends on complex interactions between many areas of the nervous system, the musculoskeletal system, and the environment. How the nervous system manages to accomplish this task has been the subject of investigation for more than a century. In vertebrates, locomotion is generated by neural networks located in the spinal cord referred to as central pattern generators. Descending inputs from the brain stem initiate, maintain, and stop locomotion as well as control speed and direction. Sensory inputs adapt locomotor programs to the environmental conditions. This review presents a comparative and historical overview of some of the neural mechanisms underlying the control of locomotion in vertebrates. We have put an emphasis on spinal mechanisms and descending control.
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Affiliation(s)
- Réjean Dubuc
- Groupe de Recherche en Activité Physique Adaptée, Département des Sciences de l'Activité Physique, Université du Québec à Montréal, Montreal, Quebec, Canada
- Groupe de Recherche sur le Système Nerveux Central, Département de Neurosciences, Université de Montréal, Montreal, Quebec, Canada
| | - Jean-Marie Cabelguen
- Institut National de la Santé et de la Recherche Médicale (INSERM) U 1215-Neurocentre Magendie, Université de Bordeaux, Bordeaux Cedex, France
| | - Dimitri Ryczko
- Département de Pharmacologie-Physiologie, Université de Sherbrooke, Sherbrooke, Quebec, Canada
- Centre de recherche du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, Quebec, Canada
- Neurosciences Sherbrooke, Sherbrooke, Quebec, Canada
- Institut de Pharmacologie de Sherbrooke, Sherbrooke, Quebec, Canada
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Ren J, Gosgnach S. Localization of Rhythm Generating Components of the Mammalian Locomotor Central Pattern Generator. Neuroscience 2023; 513:28-37. [PMID: 36702374 DOI: 10.1016/j.neuroscience.2023.01.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Revised: 01/11/2023] [Accepted: 01/16/2023] [Indexed: 01/24/2023]
Abstract
Locomotor movements in mammals are generated by neural networks, situated in the spinal cord, known as central pattern generators (CPGs). Recently, significant strides have been made in the genetic identification of interneuronal components of the locomotor CPG and their specific function. Despite this progress, a population of interneurons that is required for locomotor rhythmogenesis has yet to be identified, and it has been suggested that subsets of interneurons belonging to several genetically-defined populations may be involved. In this study, rather than hunt for rhythmogenic neurons, we take a different approach and attempt to identify the specific region of the spinal cord in which they are located. Focal application of 5-hydroxytryptamine creatine sulfate complex (5-HT) and N-methyl-D-aspartate (NMDA) to the central canal of the rostral lumbar segments of newborn male and female mouse spinal cords quickly generates a robust pattern of fictive locomotion, while inhibition or ablation of neurons in this region disrupts the locomotor rhythm in both rostral and caudal lumbar segments. When applied to the central canal at caudal lumbar levels a higher volume of 5-HT and NMDA are required to elicit fictive locomotion, while inhibition of neurons surrounding the central canal at caudal levels again interrupts rhythmic activity at local segmental levels with minimal effects rostrally. The results of this study indicate that interneurons in the most medial laminae of the neonatal mouse spinal cord are both necessary and sufficient for the generation of locomotor activity, and suggests that this is the region where the rhythm generating core of the locomotor CPG resides.
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Affiliation(s)
- Jun Ren
- University of Alberta, Dept. of Physiology, 3-020M Katz Building, Edmonton, AL T6G 2E1, Canada
| | - Simon Gosgnach
- University of Alberta, Dept. of Physiology, 3-020M Katz Building, Edmonton, AL T6G 2E1, Canada.
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3
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Windhorst U. Spinal Cord Circuits: Models and Reality. NEUROPHYSIOLOGY+ 2022. [DOI: 10.1007/s11062-022-09927-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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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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Saltiel P, d’Avella A, Tresch MC, Wyler K, Bizzi E. Critical Points and Traveling Wave in Locomotion: Experimental Evidence and Some Theoretical Considerations. Front Neural Circuits 2017; 11:98. [PMID: 29276476 PMCID: PMC5727018 DOI: 10.3389/fncir.2017.00098] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Accepted: 11/20/2017] [Indexed: 11/13/2022] Open
Abstract
The central pattern generator (CPG) architecture for rhythm generation remains partly elusive. We compare cat and frog locomotion results, where the component unrelated to pattern formation appears as a temporal grid, and traveling wave respectively. Frog spinal cord microstimulation with N-methyl-D-Aspartate (NMDA), a CPG activator, produced a limited set of force directions, sometimes tonic, but more often alternating between directions similar to the tonic forces. The tonic forces were topographically organized, and sites evoking rhythms with different force subsets were located close to the constituent tonic force regions. Thus CPGs consist of topographically organized modules. Modularity was also identified as a limited set of muscle synergies whose combinations reconstructed the EMGs. The cat CPG was investigated using proprioceptive inputs during fictive locomotion. Critical points identified both as abrupt transitions in the effect of phasic perturbations, and burst shape transitions, had biomechanical correlates in intact locomotion. During tonic proprioceptive perturbations, discrete shifts between these critical points explained the burst durations changes, and amplitude changes occurred at one of these points. Besides confirming CPG modularity, these results suggest a fixed temporal grid of anchoring points, to shift modules onsets and offsets. Frog locomotion, reconstructed with the NMDA synergies, showed a partially overlapping synergy activation sequence. Using the early synergy output evoked by NMDA at different spinal sites, revealed a rostrocaudal topographic organization, where each synergy is preferentially evoked from a few, albeit overlapping, cord regions. Comparing the locomotor synergy sequence with this topography suggests that a rostrocaudal traveling wave would activate the synergies in the proper sequence for locomotion. This output was reproduced in a two-layer model using this topography and a traveling wave. Together our results suggest two CPG components: modules, i.e., synergies; and temporal patterning, seen as a temporal grid in the cat, and a traveling wave in the frog. Animal and limb navigation have similarities. Research relating grid cells to the theta rhythm and on segmentation during navigation may relate to our temporal grid and traveling wave results. Winfree's mathematical work, combining critical phases and a traveling wave, also appears important. We conclude suggesting tracing, and imaging experiments to investigate our CPG model.
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Affiliation(s)
- Philippe Saltiel
- Department of Brain and Cognitive Sciences and McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, MA, United States
- Département de Neurosciences, Faculté de Médecine, Université de Montréal, Montréal, QC, Canada
| | - Andrea d’Avella
- Department of Biomedical and Dental Sciences and Morphofunctional Imaging, University of Messina, Messina, Italy
- Laboratory of Neuromotor Physiology, Santa Lucia Foundation, Rome, Italy
| | - Matthew C. Tresch
- Departments of Biomedical Engineering, Physical Medicine and Rehabilitation, and Physiology, Northwestern University, Chicago, IL, United States
| | - Kuno Wyler
- Department of Brain and Cognitive Sciences and McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - Emilio Bizzi
- Department of Brain and Cognitive Sciences and McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, MA, United States
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Griener A, Zhang W, Kao H, Haque F, Gosgnach S. Anatomical and electrophysiological characterization of a population of dI6 interneurons in the neonatal mouse spinal cord. Neuroscience 2017; 362:47-59. [PMID: 28844009 DOI: 10.1016/j.neuroscience.2017.08.031] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Revised: 08/14/2017] [Accepted: 08/15/2017] [Indexed: 12/13/2022]
Abstract
The locomotor central pattern generator is a neural network located in the ventral aspect of the caudal spinal cord that underlies stepping in mammals. While many genetically defined interneurons that are thought to comprise this neural network have been identified and characterized, the dI6 cells- which express the transcription factors WT1 and/or DMRT3- are one population that settle in this region, are active during locomotion, whose function is poorly understood. These cells were originally hypothesized to be commissural premotor interneurons, however evidence in support of this is sparse. Here we characterize this population of cells using the TgDbx1Cre;R26EFP;Dbx1LacZ transgenic mouse line, which has been shown to be an effective marker of dI6 interneurons. We show dI6 cells to be abundant in laminae VII and VIII along the entire spinal cord and provide evidence that subtypes outside the WT1/DMRT3 expressing dI6 cells may exist. Retrograde tracing experiments indicate that the majority of dI6 cells project descending axons, and some make monosynaptic or disynaptic contacts onto motoneurons on either side of the spinal cord. Analysis of their activity during non-resetting deletions, which occur during bouts of fictive locomotion, suggests that these cells are involved in both locomotor rhythm generation and pattern formation. This study provides a thorough characterization of the dI6 cells labeled in the TgDbx1Cre;R26EFP;Dbx1LacZ transgenic mouse, and supports previous work suggesting that these cells play multiple roles during locomotor activity.
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Affiliation(s)
- Anna Griener
- Neuroscience and Mental Health Institute, University of Alberta, 3-020D Katz Building, Edmonton, Alberta T6G 2E1, Canada
| | - Wei Zhang
- Department of Physiology, University of Alberta, 3-020D Katz Building, Edmonton, Alberta T6G 2E1, Canada
| | - Henry Kao
- Department of Engineering Physics, University of British Columbia, Hennings Building, Room 333A, 6224 Agricultural Road, Vancouver, BC V6T 1Z1 Canada
| | - Farhia Haque
- Neuroscience and Mental Health Institute, University of Alberta, 3-020D Katz Building, Edmonton, Alberta T6G 2E1, Canada
| | - Simon Gosgnach
- Neuroscience and Mental Health Institute, University of Alberta, 3-020D Katz Building, Edmonton, Alberta T6G 2E1, Canada; Department of Physiology, University of Alberta, 3-020D Katz Building, Edmonton, Alberta T6G 2E1, Canada.
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9
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Stein PSG, Daniels-McQueen S, Lai J, Liu Z, Corman TS. Modular organization of the multipartite central pattern generator for turtle rostral scratch: knee-related interneurons during deletions. J Neurophysiol 2016; 115:3130-9. [PMID: 27030737 DOI: 10.1152/jn.00871.2015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Accepted: 03/27/2016] [Indexed: 11/22/2022] Open
Abstract
Central pattern generators (CPGs) are neuronal networks in the spinal cord that generate rhythmic patterns of motor activity in the absence of movement-related sensory feedback. For many vertebrate rhythmic behaviors, CPGs generate normal patterns of motor neuron activities as well as variations of the normal patterns, termed deletions, in which bursts in one or more motor nerves are absent from one or more cycles of the rhythm. Prior work with hip-extensor deletions during turtle rostral scratch supports hypotheses of hip-extensor interneurons in a hip-extensor module and of hip-flexor interneurons in a hip-flexor module. We present here single-unit interneuronal recording data that support hypotheses of knee-extensor interneurons in a knee-extensor module and of knee-flexor interneurons in a knee-flexor module. Members of knee-related modules are not members of hip-related modules and vice versa. These results in turtle provide experimental support at the single-unit interneuronal level for the organizational concept that the rostral-scratch CPG for the turtle hindlimb is multipartite, that is, composed of more than two modules. This work, when combined with experimental and computational work in other vertebrates, does not support the classical view that the vertebrate limb CPG is bipartite with only two modules, one controlling all the flexors of the limb and the other controlling all the extensors of the limb. Instead, these results support the general principle that spinal CPGs are multipartite.
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Affiliation(s)
- Paul S G Stein
- Department of Biology, Washington University, St. Louis, Missouri
| | | | - Jessica Lai
- Department of Biology, Washington University, St. Louis, Missouri
| | - Z Liu
- Department of Biology, Washington University, St. Louis, Missouri
| | - Tanya S Corman
- Department of Biology, Washington University, St. Louis, Missouri
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Acevedo J, Santana-Almansa A, Matos-Vergara N, Marrero-Cordero LR, Cabezas-Bou E, Díaz-Ríos M. Caffeine stimulates locomotor activity in the mammalian spinal cord via adenosine A1 receptor-dopamine D1 receptor interaction and PKA-dependent mechanisms. Neuropharmacology 2015; 101:490-505. [PMID: 26493631 DOI: 10.1016/j.neuropharm.2015.10.020] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Revised: 09/16/2015] [Accepted: 10/15/2015] [Indexed: 01/31/2023]
Abstract
Caffeine is a potent psychostimulant that can have significant and widely variable effects on the activity of multiple neuronal pathways. The most pronounced caffeine-induced behavioral effect seen in rodents is to increase locomotor activity which has been linked to a dose-dependent inhibition of A1 and A(2A) receptors. The effects of caffeine at the level of the lumbar spinal central pattern generator (CPG) network for hindlimb locomotion are lacking. We assessed the effects of caffeine to the locomotor function of the spinal CPG network via extracellular ventral root recordings using the isolated neonatal mouse spinal cord preparation. Addition of caffeine and of an A1 receptor antagonist significantly decreased the cycle period accelerating the ongoing locomotor rhythm, while decreasing burst duration reversibly in most preparations suggesting the role of A1 receptors as the primary target of caffeine. Caffeine and an A1 receptor antagonist failed to stimulate ongoing locomotor activity in the absence of dopamine or in the presence of a D1 receptor antagonist supporting A1/D1 receptor-dependent mechanism of action. The use of caffeine or an A1 receptor blocker failed to stimulate an ongoing locomotor rhythm in the presence of a blocker of the cAMP-dependent protein kinase (PKA) supporting the need of this intracellular pathway for the modulatory effects of caffeine to occur. These results support a stimulant effect of caffeine on the lumbar spinal network controlling hindlimb locomotion through the inhibition of A1 receptors and subsequent activation of D1 receptors via a PKA-dependent intracellular mechanism.
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Affiliation(s)
- JeanMarie Acevedo
- Department of Anatomy and Neurobiology and Institute of Neurobiology, University of Puerto Rico, Medical Sciences Campus, San Juan, PR 00936, USA
| | - Alexandra Santana-Almansa
- Department of Anatomy and Neurobiology and Institute of Neurobiology, University of Puerto Rico, Medical Sciences Campus, San Juan, PR 00936, USA
| | - Nikol Matos-Vergara
- Department of Anatomy and Neurobiology and Institute of Neurobiology, University of Puerto Rico, Medical Sciences Campus, San Juan, PR 00936, USA
| | - Luis René Marrero-Cordero
- Department of Anatomy and Neurobiology and Institute of Neurobiology, University of Puerto Rico, Medical Sciences Campus, San Juan, PR 00936, USA
| | - Ernesto Cabezas-Bou
- Department of Anatomy and Neurobiology and Institute of Neurobiology, University of Puerto Rico, Medical Sciences Campus, San Juan, PR 00936, USA
| | - Manuel Díaz-Ríos
- Department of Anatomy and Neurobiology and Institute of Neurobiology, University of Puerto Rico, Medical Sciences Campus, San Juan, PR 00936, USA.
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McLean DL, Dougherty KJ. Peeling back the layers of locomotor control in the spinal cord. Curr Opin Neurobiol 2015; 33:63-70. [PMID: 25820136 DOI: 10.1016/j.conb.2015.03.001] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Revised: 03/03/2015] [Accepted: 03/04/2015] [Indexed: 11/18/2022]
Abstract
Vertebrate locomotion is executed by networks of neurons within the spinal cord. Here, we describe recent advances in our understanding of spinal locomotor control provided by work using optical and genetic approaches in mice and zebrafish. In particular, we highlight common observations that demonstrate simplification of limb and axial motor pool coordination by spinal network modularity, differences in the deployment of spinal modules at increasing speeds of locomotion, and functional hierarchies in the regulation of locomotor rhythm and pattern. We also discuss the promise of intersectional genetic strategies for better resolution of network components and connectivity, which should help us continue to close the gap between theory and function.
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Affiliation(s)
- David L McLean
- Department of Neurobiology, Northwestern University, Evanston, IL, USA.
| | - Kimberly J Dougherty
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA, USA.
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