1
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Azizi S, Moradi Birgani P, Ashtiyani M, Irani A, Shahrokhi A, Meydanloo K, Mirbagheri MM. The Relationship between Structure of the Corticoreticular Tract and Walking Capacity in Children with Cerebral Palsy. J Biomed Phys Eng 2024; 14:79-88. [PMID: 38357607 PMCID: PMC10862120 DOI: 10.31661/jbpe.v0i0.2104-1302] [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: 04/09/2021] [Accepted: 05/26/2021] [Indexed: 02/16/2024]
Abstract
Background Disruption in the descending pathways may lead to gait impairments in Cerebral Palsy (CP) children. Though, the mechanisms behind walking problems have not been completely understood. Objective We aimed to define the relationship between the structure of the corticoreticular tract (CRT) and walking capacity in children with CP. Material and Methods This is a retrospective, observational, and cross-sectional study. Twenty-six children with CP between 4 to 15 years old participated. Also, we used existed data of healthy children aged 4 to 15 years old. CRT structure was characterized using diffusion tensor imaging (DTI). The DTI parameters extracted to quantify CRT structure included: fractional anisotropy (FA), mean (MD), axial (AD), and radial (RD) diffusivity. Balance and walking capacity was evaluated using popular clinical measures, including the Berg balance scale (BBS), Timed-Up-and-Go (TUG; balance and mobility), six-minute walk test (6 MWT; gait endurance), and 10-meter walk Test (10 MWT; gait speed). Results There are significant differences between MD, AD, and RD in CP and healthy groups. Brain injury leads to various patterns of the CRT structure in children with CP. In the CP group with abnormal CRT patterns, DTI parameters of the more affected CRT are significantly correlated with walking balance, speed, and endurance measures. Conclusion Considering the high inter-subject variability, the variability of CRT patterns is vital for determining the nature of changes in CRT structure, their relationship with gait impairment, and understanding the underlying mechanisms of movement disorders. This information is also important for the development or prescription of an effective rehabilitation target for individualizing treatment.
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Affiliation(s)
- Shahla Azizi
- Department of Medical Physics and Biomedical Engineering, Faculty of Medicine, Tehran University of Medical, Tehran, Iran
- Department of Electrical and Electronic Engineering, Eastern Mediterranean University, Famagusta, Northern Cyprus, Mersin 10, Turkey
| | - Parmida Moradi Birgani
- Department of Medical Physics and Biomedical Engineering, Faculty of Medicine, Tehran University of Medical, Tehran, Iran
| | - Meghdad Ashtiyani
- Department of Biomedical Engineering and Medical Physics, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Ashkan Irani
- Department of Occupational Therapy, Faculty of Rehabilitation, Shahid Beheshti University of Medical Sciences Health Services, Tehran, Iran
| | - Amin Shahrokhi
- Faculty of Medicine, Tehran University of Medical, Tehran, Iran
| | - Khadijeh Meydanloo
- School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | - Mohammad Mehdi Mirbagheri
- Department of Medical Physics and Biomedical Engineering, Faculty of Medicine, Tehran University of Medical, Tehran, Iran
- Department of Physical Medicine and Rehabilitation, Northwestern University, Evanston, United States
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2
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Yang HH, Brezovec LE, Capdevila LS, Vanderbeck QX, Adachi A, Mann RS, Wilson RI. Fine-grained descending control of steering in walking Drosophila. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.15.562426. [PMID: 37904997 PMCID: PMC10614758 DOI: 10.1101/2023.10.15.562426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2023]
Abstract
Locomotion involves rhythmic limb movement patterns that originate in circuits outside the brain. Purposeful locomotion requires descending commands from the brain, but we do not understand how these commands are structured. Here we investigate this issue, focusing on the control of steering in walking Drosophila. First, we describe different limb "gestures" associated with different steering maneuvers. Next, we identify a set of descending neurons whose activity predicts steering. Focusing on two descending cell types downstream from distinct brain networks, we show that they evoke specific limb gestures: one lengthens strides on the outside of a turn, while the other attenuates strides on the inside of a turn. Notably, a single descending neuron can have opposite effects during different locomotor rhythm phases, and we identify networks positioned to implement this phase-specific gating. Together, our results show how purposeful locomotion emerges from brain cells that drive specific, coordinated modulations of low-level patterns.
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Affiliation(s)
- Helen H. Yang
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115 USA
| | - Luke E. Brezovec
- Department of Neurobiology, Stanford University, Stanford, CA 94305 USA
| | | | | | - Atsuko Adachi
- Department of Biochemistry and Molecular Biophysics, Department of Neuroscience, Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027 USA
| | - Richard S. Mann
- Department of Biochemistry and Molecular Biophysics, Department of Neuroscience, Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027 USA
| | - Rachel I. Wilson
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115 USA
- Lead contact
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3
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Hall KJ, Van Ooteghem K, McIlroy WE. Emotional state as a modulator of autonomic and somatic nervous system activity in postural control: a review. Front Neurol 2023; 14:1188799. [PMID: 37719760 PMCID: PMC10500443 DOI: 10.3389/fneur.2023.1188799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Accepted: 08/07/2023] [Indexed: 09/19/2023] Open
Abstract
Advances in our understanding of postural control have highlighted the need to examine the influence of higher brain centers in the modulation of this complex function. There is strong evidence of a link between emotional state, autonomic nervous system (ANS) activity and somatic nervous system (somatic NS) activity in postural control. For example, relationships have been demonstrated between postural threat, anxiety, fear of falling, balance confidence, and physiological arousal. Behaviorally, increased arousal has been associated with changes in velocity and amplitude of postural sway during quiet standing. The potential links between ANS and somatic NS, observed in control of posture, are associated with shared neuroanatomical connections within the central nervous system (CNS). The influence of emotional state on postural control likely reflects the important influence the limbic system has on these ANS/somatic NS control networks. This narrative review will highlight several examples of behaviors which routinely require coordination between the ANS and somatic NS, highlighting the importance of the neurofunctional link between these systems. Furthermore, we will extend beyond the more historical focus on threat models and examine how disordered/altered emotional state and ANS processing may influence postural control and assessment. Finally, this paper will discuss studies that have been important in uncovering the modulatory effect of emotional state on postural control including links that may inform our understanding of disordered control, such as that observed in individuals living with Parkinson's disease and discuss methodological tools that have the potential to advance understanding of this complex relationship.
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Affiliation(s)
- Karlee J. Hall
- Department of Kinesiology and Health Sciences, University of Waterloo, Waterloo, ON, Canada
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4
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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] [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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5
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Lacroix-Ouellette P, Dubuc R. Brainstem neural mechanisms controlling locomotion with special reference to basal vertebrates. Front Neural Circuits 2023; 17:910207. [PMID: 37063386 PMCID: PMC10098025 DOI: 10.3389/fncir.2023.910207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Accepted: 03/13/2023] [Indexed: 04/03/2023] Open
Abstract
Over the last 60 years, the basic neural circuitry responsible for the supraspinal control of locomotion has progressively been uncovered. Initially, significant progress was made in identifying the different supraspinal structures controlling locomotion in mammals as well as some of the underlying mechanisms. It became clear, however, that the complexity of the mammalian central nervous system (CNS) prevented researchers from characterizing the detailed cellular mechanisms involved and that animal models with a simpler nervous system were needed. Basal vertebrate species such as lampreys, xenopus embryos, and zebrafish became models of choice. More recently, optogenetic approaches have considerably revived interest in mammalian models. The mesencephalic locomotor region (MLR) is an important brainstem region known to control locomotion in all vertebrate species examined to date. It controls locomotion through intermediary cells in the hindbrain, the reticulospinal neurons (RSNs). The MLR comprises populations of cholinergic and glutamatergic neurons and their specific contribution to the control of locomotion is not fully resolved yet. Moreover, the downward projections from the MLR to RSNs is still not fully understood. Reporting on discoveries made in different animal models, this review article focuses on the MLR, its projections to RSNs, and the contribution of these neural elements to the control of locomotion. Excellent and detailed reviews on the brainstem control of locomotion have been recently published with emphasis on mammalian species. The present review article focuses on findings made in basal vertebrates such as the lamprey, to help direct new research in mammals, including humans.
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Affiliation(s)
| | - Réjean Dubuc
- Department of Neurosciences, Université de Montréal, Montréal, QC, Canada
- Department of Physical Activity Sciences, Université du Québec à Montréal, Montréal, QC, Canada
- Research Group for Adapted Physical Activity, Université du Québec à Montréal, Montréal, QC, Canada
- *Correspondence: Réjean Dubuc,
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6
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Howland DR, Trimble SA, Fox EJ, Tester NJ, Spiess MR, Senesac CR, Kleim JA, Spierre LZ, Rose DK, Johns JS, Ugiliweneza B, Reier PJ, Behrman AL. Recovery of walking in nonambulatory children with chronic spinal cord injuries: Case series. J Neurosci Res 2023; 101:826-842. [PMID: 36690607 DOI: 10.1002/jnr.25162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Revised: 11/12/2022] [Accepted: 12/15/2022] [Indexed: 01/25/2023]
Abstract
The immature central nervous system is recognized as having substantial neuroplastic capacity. In this study, we explored the hypothesis that rehabilitation can exploit that potential and elicit reciprocal walking in nonambulatory children with chronic, severe (i.e., lower extremity motor score < 10/50) spinal cord injuries (SCIs). Seven male subjects (3-12 years of age) who were at least 1-year post-SCI and incapable of discrete leg movements believed to be required for walking, enrolled in activity-based locomotor training (ABLT; clinicaltrials.gov NCT00488280). Six children completed the study. Following a minimum of 49 sessions of ABLT, three of the six children achieved walking with reverse rolling walkers. Stepping development, however, was not accompanied by improvement in discrete leg movements as underscored by the persistence of synergistic movements and little change in lower extremity motor scores. Interestingly, acoustic startle responses exhibited by the three responding children suggested preserved reticulospinal inputs to circuitry below the level of injury capable of mediating leg movements. On the other hand, no indication of corticospinal integrity was obtained with transcranial magnetic stimulation evoked responses in the same individuals. These findings suggest some children who are not predicted to improve motor and locomotor function may have a reserve of adaptive plasticity that can emerge in response to rehabilitative strategies such as ABLT. Further studies are warranted to determine whether a critical need exists to re-examine rehabilitation approaches for pediatric SCI with poor prognosis for any ambulatory recovery.
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Affiliation(s)
- Dena R Howland
- Department of Neurological Surgery, Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, Kentucky, USA.,Research Service, Robley Rex VA Medical Center, Louisville, Kentucky, USA
| | - Shelley A Trimble
- Spinal Cord Injury Outpatient Program, Pediatric NeuroRecovery, Frazier Rehab Institute, Louisville, Kentucky, USA
| | - Emily J Fox
- Department of Physical Therapy, University of Florida, Gainesville, Florida, USA.,Brooks Rehabilitation, Jacksonville, Florida, USA
| | - Nicole J Tester
- Movement Disorders & Neurorestoration Program, Norman Fixel Institute for Neurological Sciences, University of Florida Health, Gainesville, Florida, USA
| | - Martina R Spiess
- ZHAW Zurich University of Applied Sciences, School of Health Sciences, Institute of Occupational Therapy, Winterthur, Switzerland
| | - Claudia R Senesac
- Department of Physical Therapy, University of Florida, Gainesville, Florida, USA
| | - Jeffrey A Kleim
- School of Biological and Health Systems Engineering & Ira A. Fulton Schools of Engineering, Arizona State University, Tempe, Arizona, USA
| | - Louise Z Spierre
- University of Florida College of Medicine-Jacksonville, Department of Pediatrics, University of Florida Health Division of Community and Societal Pediatrics, Jacksonville, Florida, USA
| | - Dorian K Rose
- Department of Physical Therapy, University of Florida, Gainesville, Florida, USA.,Brooks Rehabilitation, Jacksonville, Florida, USA
| | - Jeffery S Johns
- Department of Physical Medicine and Rehabilitation, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Beatrice Ugiliweneza
- Department of Neurological Surgery, Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, Kentucky, USA
| | - Paul J Reier
- Department of Neuroscience, University of Florida, Gainesville, Florida, USA
| | - Andrea L Behrman
- Department of Neurological Surgery, Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, Kentucky, USA
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7
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Nakajima T, Fortier-Lebel N, Drew T. A secondary motor area contributing to interlimb coordination during visually guided locomotion in the cat. Cereb Cortex 2022; 33:290-315. [PMID: 35259760 PMCID: PMC9837607 DOI: 10.1093/cercor/bhac068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Revised: 02/01/2022] [Accepted: 02/01/2022] [Indexed: 01/19/2023] Open
Abstract
We investigated the contribution of cytoarchitectonic cortical area 4δc, in the caudal bank of the cruciate sulcus of the cat, to the control of visually guided locomotion. To do so, we recorded the activity of 114 neurons in 4δc while cats walked on a treadmill and stepped over an obstacle that advanced toward them. A total of 84/114 (74%) cells were task-related and 68/84 (81%) of these cells showed significant modulation of their discharge frequency when the contralateral limbs were the first to step over the obstacle. These latter cells included a substantial proportion (27/68 40%) that discharged between the passage of the contralateral forelimb and the contralateral hindlimb over the obstacle, suggesting a contribution of this area to interlimb coordination. We further compared the discharge in area 4δc with the activity patterns of cells in the rostral division of the same cytoarchitectonic area (4δr), which has been suggested to be a separate functional region. Despite some differences in the patterns of activity in the 2 subdivisions, we suggest that activity in each is compatible with a contribution to interlimb coordination and that they should be considered as a single functional area that contributes to both forelimb-forelimb and forelimb-hindlimb coordination.
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Affiliation(s)
- Toshi Nakajima
- Department of Integrative Neuroscience, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan
| | - Nicolas Fortier-Lebel
- Département de Neurosciences, Centre Interdisciplinaire de Recherche sur le Cerveau et l'Apprentissage (CIRCA) Groupe de recherche sur la signalisation neurale et la circuiterie (SNC), Université de Montréal, Pavillon Paul-G. Desmarais, C.P. 6128, Succursale Centre-ville, Montréal, QC H3C 3J7, Canada
| | - Trevor Drew
- Département de Neurosciences, Centre Interdisciplinaire de Recherche sur le Cerveau et l'Apprentissage (CIRCA) Groupe de recherche sur la signalisation neurale et la circuiterie (SNC), Université de Montréal, Pavillon Paul-G. Desmarais, C.P. 6128, Succursale Centre-ville, Montréal, QC H3C 3J7, Canada
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8
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Le Ray D, Bertrand SS, Dubuc R. Cholinergic Modulation of Locomotor Circuits in Vertebrates. Int J Mol Sci 2022; 23:ijms231810738. [PMID: 36142651 PMCID: PMC9501616 DOI: 10.3390/ijms231810738] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Revised: 09/08/2022] [Accepted: 09/09/2022] [Indexed: 11/24/2022] Open
Abstract
Locomotion is a basic motor act essential for survival. Amongst other things, it allows animals to move in their environment to seek food, escape predators, or seek mates for reproduction. The neural mechanisms involved in the control of locomotion have been examined in many vertebrate species and a clearer picture is progressively emerging. The basic muscle synergies responsible for propulsion are generated by neural networks located in the spinal cord. In turn, descending supraspinal inputs are responsible for starting, maintaining, and stopping locomotion as well as for steering and controlling speed. Several neurotransmitter systems play a crucial role in modulating the neural activity during locomotion. For instance, cholinergic inputs act both at the spinal and supraspinal levels and the underlying mechanisms are the focus of the present review. Much information gained on supraspinal cholinergic modulation of locomotion was obtained from the lamprey model. Nicotinic cholinergic inputs increase the level of excitation of brainstem descending command neurons, the reticulospinal neurons (RSNs), whereas muscarinic inputs activate a select group of hindbrain neurons that project to the RSNs to boost their level of excitation. Muscarinic inputs also reduce the transmission of sensory inputs in the brainstem, a phenomenon that could help in sustaining goal directed locomotion. In the spinal cord, intrinsic cholinergic inputs strongly modulate the activity of interneurons and motoneurons to control the locomotor output. Altogether, the present review underlines the importance of the cholinergic inputs in the modulation of locomotor activity in vertebrates.
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Affiliation(s)
- Didier Le Ray
- Institut des Neurosciences Cognitives et Intégratives d’Aquitaine (INCIA), UMR 5287, Université de Bordeaux-CNRS, F-33076 Bordeaux, France
- Correspondence: (D.L.R.); (R.D.)
| | - Sandrine S. Bertrand
- Institut des Neurosciences Cognitives et Intégratives d’Aquitaine (INCIA), UMR 5287, Université de Bordeaux-CNRS, F-33076 Bordeaux, France
| | - Réjean Dubuc
- Department of Neurosciences, Université de Montréal, Montréal, QC H3C 3J7, Canada
- Department of Physical Activity Sciences and Research Group in Adapted Physical Activity, Université du Québec à Montréal, Montréal, QC H3C 3P8, Canada
- Correspondence: (D.L.R.); (R.D.)
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9
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Networking brainstem and basal ganglia circuits for movement. Nat Rev Neurosci 2022; 23:342-360. [DOI: 10.1038/s41583-022-00581-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/10/2022] [Indexed: 12/14/2022]
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10
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Abstract
When animals walk overground, mechanical stimuli activate various receptors located in muscles, joints, and skin. Afferents from these mechanoreceptors project to neuronal networks controlling locomotion in the spinal cord and brain. The dynamic interactions between the control systems at different levels of the neuraxis ensure that locomotion adjusts to its environment and meets task demands. In this article, we describe and discuss the essential contribution of somatosensory feedback to locomotion. We start with a discussion of how biomechanical properties of the body affect somatosensory feedback. We follow with the different types of mechanoreceptors and somatosensory afferents and their activity during locomotion. We then describe central projections to locomotor networks and the modulation of somatosensory feedback during locomotion and its mechanisms. We then discuss experimental approaches and animal models used to investigate the control of locomotion by somatosensory feedback before providing an overview of the different functional roles of somatosensory feedback for locomotion. Lastly, we briefly describe the role of somatosensory feedback in the recovery of locomotion after neurological injury. We highlight the fact that somatosensory feedback is an essential component of a highly integrated system for locomotor control. © 2021 American Physiological Society. Compr Physiol 11:1-71, 2021.
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Affiliation(s)
- Alain Frigon
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Quebec, Canada
| | - Turgay Akay
- Department of Medical Neuroscience, Atlantic Mobility Action Project, Brain Repair Center, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Boris I Prilutsky
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
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11
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Elias GJB, Loh A, Gwun D, Pancholi A, Boutet A, Neudorfer C, Germann J, Namasivayam A, Gramer R, Paff M, Lozano AM. Deep brain stimulation of the brainstem. Brain 2021; 144:712-723. [PMID: 33313788 DOI: 10.1093/brain/awaa374] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 07/31/2020] [Accepted: 08/17/2020] [Indexed: 01/02/2023] Open
Abstract
Deep brain stimulation (DBS) of the subthalamic nucleus, pallidum, and thalamus is an established therapy for various movement disorders. Limbic targets have also been increasingly explored for their application to neuropsychiatric and cognitive disorders. The brainstem constitutes another DBS substrate, although the existing literature on the indications for and the effects of brainstem stimulation remains comparatively sparse. The objective of this review was to provide a comprehensive overview of the pertinent anatomy, indications, and reported stimulation-induced acute and long-term effects of existing white and grey matter brainstem DBS targets. We systematically searched the published literature, reviewing clinical trial articles pertaining to DBS brainstem targets. Overall, 164 studies describing brainstem DBS were identified. These studies encompassed 10 discrete structures: periaqueductal/periventricular grey (n = 63), pedunculopontine nucleus (n = 48), ventral tegmental area (n = 22), substantia nigra (n = 9), mesencephalic reticular formation (n = 7), medial forebrain bundle (n = 8), superior cerebellar peduncles (n = 3), red nucleus (n = 3), parabrachial complex (n = 2), and locus coeruleus (n = 1). Indications for brainstem DBS varied widely and included central neuropathic pain, axial symptoms of movement disorders, headache, depression, and vegetative state. The most promising results for brainstem DBS have come from targeting the pedunculopontine nucleus for relief of axial motor deficits, periaqueductal/periventricular grey for the management of central neuropathic pain, and ventral tegmental area for treatment of cluster headaches. Brainstem DBS has also acutely elicited numerous motor, limbic, and autonomic effects. Further work involving larger, controlled trials is necessary to better establish the therapeutic potential of DBS in this complex area.
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Affiliation(s)
- Gavin J B Elias
- Division of Neurosurgery, Department of Surgery, University Health Network and University of Toronto, Toronto, Canada
| | - Aaron Loh
- Division of Neurosurgery, Department of Surgery, University Health Network and University of Toronto, Toronto, Canada
| | - Dave Gwun
- Division of Neurosurgery, Department of Surgery, University Health Network and University of Toronto, Toronto, Canada
| | - Aditya Pancholi
- Division of Neurosurgery, Department of Surgery, University Health Network and University of Toronto, Toronto, Canada
| | - Alexandre Boutet
- Division of Neurosurgery, Department of Surgery, University Health Network and University of Toronto, Toronto, Canada.,Joint Department of Medical Imaging, University of Toronto, Toronto, Canada
| | - Clemens Neudorfer
- Division of Neurosurgery, Department of Surgery, University Health Network and University of Toronto, Toronto, Canada
| | - Jürgen Germann
- Division of Neurosurgery, Department of Surgery, University Health Network and University of Toronto, Toronto, Canada
| | - Andrew Namasivayam
- Division of Neurosurgery, Department of Surgery, University Health Network and University of Toronto, Toronto, Canada
| | - Robert Gramer
- Division of Neurosurgery, Department of Surgery, University Health Network and University of Toronto, Toronto, Canada
| | - Michelle Paff
- Division of Neurosurgery, Department of Surgery, University Health Network and University of Toronto, Toronto, Canada
| | - Andres M Lozano
- Division of Neurosurgery, Department of Surgery, University Health Network and University of Toronto, Toronto, Canada
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12
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Fortier-Lebel N, Nakajima T, Yahiaoui N, Drew T. Microstimulation of the Premotor Cortex of the Cat Produces Phase-Dependent Changes in Locomotor Activity. Cereb Cortex 2021; 31:5411-5434. [PMID: 34289039 DOI: 10.1093/cercor/bhab167] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Revised: 05/20/2021] [Accepted: 05/20/2021] [Indexed: 11/14/2022] Open
Abstract
To determine the functional organization of premotor areas in the cat pericruciate cortex we applied intracortical microstimulation (ICMS) within multiple cytoarchitectonically identified subregions of areas 4 and 6 in the awake cat, both at rest and during treadmill walking. ICMS in most premotor areas evoked clear twitch responses in the limbs and/or head at rest. During locomotion, these same areas produced phase-dependent modifications of muscle activity. ICMS in the primary motor cortex (area 4γ) produced large phase-dependent responses, mostly restricted to the contralateral forelimb or hindlimb. Stimulation in premotor areas also produced phase-dependent responses that, in some cases, were as large as those evoked from area 4γ. However, responses from premotor areas had more widespread effects on multiple limbs, including the ipsilateral limbs, than did stimulation in 4γ. During locomotion, responses in both forelimb and hindlimb muscles were evoked from cytoarchitectonic areas 4γ, 4δ, 6aα, and 6aγ. However, the prevalence of effects in a given limb varied from one area to another. The results suggest that premotor areas may contribute to the production, modification, and coordination of activity in the limbs during locomotion and may be particularly pertinent during modifications of gait.
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Affiliation(s)
- Nicolas Fortier-Lebel
- Département de Neurosciences, Centre Interdisciplinaire de Recherche sur le Cerveau et l'Apprentissage (CIRCA) Groupe de recherche sur le système nerveux central (GRSNC), Université de Montréal, Québec H3C 3J7, Canada
| | - Toshi Nakajima
- Department of Integrative Neuroscience, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama 930-0194, Japan
| | - Nabiha Yahiaoui
- Département de Neurosciences, Centre Interdisciplinaire de Recherche sur le Cerveau et l'Apprentissage (CIRCA) Groupe de recherche sur le système nerveux central (GRSNC), Université de Montréal, Québec H3C 3J7, Canada
| | - Trevor Drew
- Département de Neurosciences, Centre Interdisciplinaire de Recherche sur le Cerveau et l'Apprentissage (CIRCA) Groupe de recherche sur le système nerveux central (GRSNC), Université de Montréal, Québec H3C 3J7, Canada
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13
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Klishko AN, Akyildiz A, Mehta-Desai R, Prilutsky BI. Common and distinct muscle synergies during level and slope locomotion in the cat. J Neurophysiol 2021; 126:493-515. [PMID: 34191619 DOI: 10.1152/jn.00310.2020] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Although it is well established that the motor control system is modular, the organization of muscle synergies during locomotion and their change with ground slope are not completely understood. For example, typical reciprocal flexor-extensor muscle synergies of level walking in cats break down in downslope: one-joint hip extensors are silent throughout the stride cycle, whereas hindlimb flexors demonstrate an additional stance phase-related electromyogram (EMG) burst (Smith JL, Carlson-Kuhta P, Trank TV. J Neurophysiol 79: 1702-1716, 1998). Here, we investigated muscle synergies during level, upslope (27°), and downslope (-27°) walking in adult cats to examine common and distinct features of modular organization of locomotor EMG activity. Cluster analysis of EMG burst onset-offset times of 12 hindlimb muscles revealed five flexor and extensor burst groups that were generally shared across slopes. Stance-related bursts of flexor muscles in downslope were placed in a burst group from level and upslope walking formed by the rectus femoris. Walking upslope changed swing/stance phase durations of level walking but not the cycle duration. Five muscle synergies computed using non-negative matrix factorization accounted for at least 95% of variance in EMG patterns in each slope. Five synergies were shared between level and upslope walking, whereas only three of those were shared with downslope synergies; these synergies were active during the swing phase and phase transitions. Two stance-related synergies of downslope walking were distinct; they comprised a mixture of flexors and extensors. We suggest that the modular organization of muscle activity during level and slope walking results from interactions between motion-related sensory feedback, CPG, and supraspinal inputs.NEW & NOTEWORTHY We demonstrated that the atypical EMG activities during cat downslope walking, silent one-joint hip extensors and stance-related EMG bursts in flexors, have many features shared with activities of level and upslope walking. Majority of EMG burst groups and muscle synergies were shared among these slopes, and upslope modulated the swing/stance phase duration but not cycle duration. Thus, synergistic EMG activities in all slopes might result from a shared CPG receiving somatosensory and supraspinal inputs.
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Affiliation(s)
- Alexander N Klishko
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia
| | - Adil Akyildiz
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia
| | - Ricky Mehta-Desai
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia
| | - Boris I Prilutsky
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia
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Wu MY, Carbo-Tano M, Mirat O, Lejeune FX, Roussel J, Quan FB, Fidelin K, Wyart C. Spinal sensory neurons project onto the hindbrain to stabilize posture and enhance locomotor speed. Curr Biol 2021; 31:3315-3329.e5. [PMID: 34146485 DOI: 10.1016/j.cub.2021.05.042] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 03/12/2021] [Accepted: 05/19/2021] [Indexed: 12/11/2022]
Abstract
In the spinal cord, cerebrospinal fluid-contacting neurons (CSF-cNs) are GABAergic interoceptive sensory neurons that detect spinal curvature via a functional coupling with the Reissner fiber. This mechanosensory system has recently been found to be involved in spine morphogenesis and postural control but the underlying mechanisms are not fully understood. In zebrafish, CSF-cNs project an ascending and ipsilateral axon reaching two to six segments away. Rostralmost CSF-cNs send their axons ipsilaterally into the hindbrain, a brain region containing motor nuclei and reticulospinal neurons (RSNs), which send descending motor commands to spinal circuits. Until now, the synaptic connectivity of CSF-cNs has only been investigated in the spinal cord, where they synapse onto motor neurons and premotor excitatory interneurons. The identity of CSF-cN targets in the hindbrain and the behavioral relevance of these sensory projections from the spinal cord to the hindbrain are unknown. Here, we provide anatomical and molecular evidence that rostralmost CSF-cNs synapse onto the axons of large RSNs including Mauthner cells and V2a neurons. Functional anatomy and optogenetically assisted mapping reveal that rostral CSF-cNs also synapse onto the soma and dendrites of cranial motor neurons innervating hypobranchial muscles. During acousto-vestibular evoked escape responses, ablation of rostralmost CSF-cNs results in a weaker escape response with a decreased C-bend amplitude, lower speed, and deficient postural control. Our study demonstrates that spinal sensory feedback enhances speed and stabilizes posture, and reveals a novel spinal gating mechanism acting on the output of descending commands sent from the hindbrain to the spinal cord.
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Affiliation(s)
- Ming-Yue Wu
- Sorbonne Université, Institut du Cerveau (ICM), Inserm U 1127, CNRS UMR 7225, 75013 Paris, France
| | - Martin Carbo-Tano
- Sorbonne Université, Institut du Cerveau (ICM), Inserm U 1127, CNRS UMR 7225, 75013 Paris, France.
| | - Olivier Mirat
- Sorbonne Université, Institut du Cerveau (ICM), Inserm U 1127, CNRS UMR 7225, 75013 Paris, France
| | - Francois-Xavier Lejeune
- Sorbonne Université, Institut du Cerveau (ICM), Inserm U 1127, CNRS UMR 7225, 75013 Paris, France
| | - Julian Roussel
- Sorbonne Université, Institut du Cerveau (ICM), Inserm U 1127, CNRS UMR 7225, 75013 Paris, France
| | - Feng B Quan
- Sorbonne Université, Institut du Cerveau (ICM), Inserm U 1127, CNRS UMR 7225, 75013 Paris, France
| | - Kevin Fidelin
- Sorbonne Université, Institut du Cerveau (ICM), Inserm U 1127, CNRS UMR 7225, 75013 Paris, France
| | - Claire Wyart
- Sorbonne Université, Institut du Cerveau (ICM), Inserm U 1127, CNRS UMR 7225, 75013 Paris, France.
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Nakajima T, Fortier-Lebel N, Drew T. Premotor Cortex Provides a Substrate for the Temporal Transformation of Information During the Planning of Gait Modifications. Cereb Cortex 2020; 29:4982-5008. [PMID: 30877802 DOI: 10.1093/cercor/bhz039] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 01/18/2019] [Accepted: 02/12/2019] [Indexed: 12/21/2022] Open
Abstract
We tested the hypothesis that the premotor cortex (PMC) in the cat contributes to the planning and execution of visually guided gait modifications. We analyzed single unit activity from 136 cells localized within layer V of cytoarchitectonic areas 6iffu and that part of 4δ within the ventral bank of the cruciate sulcus while cats walked on a treadmill and stepped over an obstacle that advanced toward them. We found a rich variety of discharge patterns, ranging from limb-independent cells that discharged several steps in front of the obstacle to step-related cells that discharged either during steps over the obstacle or in the steps leading up to that step. We propose that this population of task-related cells within this region of the PMC contributes to the temporal evolution of a planning process that transforms global information of the presence of an obstacle into the precise spatio-temporal limb adjustment required to negotiate that obstacle.
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Affiliation(s)
- Toshi Nakajima
- The Research Center for Brain Function and Medical Engineering, Asahikawa Medical University 2-1, 1-1, Midorigaoka-Higashi, Asahikawa, Japan
| | - Nicolas Fortier-Lebel
- Département de Neurosciences, Université de Montréal, Montréal, Québec, Canada.,Groupe de recherche sur le système nerveux central (GRSNC), Université de Montréal, Pavillon Paul-G. Desmarais, C.P. 6128, Succursale Centre-ville, Montréal, Québec, Canada
| | - Trevor Drew
- Département de Neurosciences, Université de Montréal, Montréal, Québec, Canada.,Groupe de recherche sur le système nerveux central (GRSNC), Université de Montréal, Pavillon Paul-G. Desmarais, C.P. 6128, Succursale Centre-ville, Montréal, Québec, Canada
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Abstract
Neuronal circuits that regulate movement are distributed throughout the nervous system. The brainstem is an important interface between upper motor centers involved in action planning and circuits in the spinal cord ultimately leading to execution of body movements. Here we focus on recent work using genetic and viral entry points to reveal the identity of functionally dedicated and frequently spatially intermingled brainstem populations essential for action diversification, a general principle conserved throughout evolution. Brainstem circuits with distinct organization and function control skilled forelimb behavior, orofacial movements, and locomotion. They convey regulatory parameters to motor output structures and collaborate in the construction of complex natural motor behaviors. Functionally tuned brainstem neurons for different actions serve as important integrators of synaptic inputs from upstream centers, including the basal ganglia and cortex, to regulate and modulate behavioral function in different contexts.
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Affiliation(s)
- Ludwig Ruder
- Biozentrum, Department of Cell Biology, University of Basel, 4056 Basel, Switzerland; .,Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland
| | - Silvia Arber
- Biozentrum, Department of Cell Biology, University of Basel, 4056 Basel, Switzerland; .,Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland
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Soulard J, Huber C, Baillieul S, Thuriot A, Renard F, Aubert Broche B, Krainik A, Vuillerme N, Jaillard A. Motor tract integrity predicts walking recovery: A diffusion MRI study in subacute stroke. Neurology 2020; 94:e583-e593. [PMID: 31896618 DOI: 10.1212/wnl.0000000000008755] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Accepted: 08/12/2019] [Indexed: 12/18/2022] Open
Abstract
OBJECTIVE To identify candidate biomarkers of walking recovery with motor tract integrity measurements using fractional anisotropy (FA) from the corticospinal tract (CST) and alternative motor pathways in patients with moderate to severe subacute stroke. METHODS Walking recovery was first assessed with generalized linear mixed model (GLMM) with repeated measures of walking scores (WS) over 2 years of follow-up in a longitudinal study of 29 patients with subacute ischemic stroke. Baseline FA measures from the ipsilesional and contralesional CST (i-CST and c-CST), cortico-reticulospinal pathway (i-CRP and c-CRP), and cerebellar peduncles were derived from a 60-direction diffusion MRI sequence on a 3T scanner. We performed correlation tests between WS and FA measures. Third, we investigated using GLMM whether motor tract integrity contributes to predict walking recovery. RESULTS We observed significant improvements of WS over time with a plateau reached at ≈6 months after stroke. WS significantly correlated with FA measures from i-CST, c-CST, i-CRP, and bilateral cerebellar peduncles. Walking recovery was predicted by FA measures from 3 tracts: i-CST, i-CRP, and contralesional superior cerebellar peduncle (c-SCP). Diffusion tensor imaging (DTI) predictors captured 80.5% of the unexplained variance of the model without DTI. CONCLUSIONS We identified i-CST and alternative motor-related tracts (namely i-CRP and c-SCP) as candidate biomarkers of walking recovery. The role of the SCP in walk recovery may rely on cerebellar nuclei projections to the thalamus, red nucleus, and reticular formation. Our findings suggest that a set of white matter tracts, part of subcortical motor networks, contribute to walking recovery in patients with moderate to severe stroke.
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Affiliation(s)
- Julie Soulard
- From the Université Grenoble Alpes (J.S., A.T., F.R., A.B.B., N.V., A.J.), AGEIS, Faculté de Médecine; Stroke Unit (J.S., A.T.), Neurologie, Centre Hospitalier Universitaire Grenoble Alpes (CHUGA); Unité IRM 3T-Recherche-UMS IRMaGe-CHUGA (C.H., A.K., A.J.); IRMaGe-Inserm US-017 (C.H., A.K.), CNRS UMS-3552, UGA, Grenoble; Neuroradiologie-IRM-Pôle Imagerie-CHUGA (A.K.); Centre Hospitalier Métropole Savoie (C.H.), Chambéry; Laboratoire HP2 (S.B.), UGA; Pôle thorax et vaisseaux, CHUGA; Pôle Recherche (A.J.), CHUGA, Grenoble; and Institut Universitaire de France (N.V.), Paris, France
| | - Coline Huber
- From the Université Grenoble Alpes (J.S., A.T., F.R., A.B.B., N.V., A.J.), AGEIS, Faculté de Médecine; Stroke Unit (J.S., A.T.), Neurologie, Centre Hospitalier Universitaire Grenoble Alpes (CHUGA); Unité IRM 3T-Recherche-UMS IRMaGe-CHUGA (C.H., A.K., A.J.); IRMaGe-Inserm US-017 (C.H., A.K.), CNRS UMS-3552, UGA, Grenoble; Neuroradiologie-IRM-Pôle Imagerie-CHUGA (A.K.); Centre Hospitalier Métropole Savoie (C.H.), Chambéry; Laboratoire HP2 (S.B.), UGA; Pôle thorax et vaisseaux, CHUGA; Pôle Recherche (A.J.), CHUGA, Grenoble; and Institut Universitaire de France (N.V.), Paris, France
| | - Sebastien Baillieul
- From the Université Grenoble Alpes (J.S., A.T., F.R., A.B.B., N.V., A.J.), AGEIS, Faculté de Médecine; Stroke Unit (J.S., A.T.), Neurologie, Centre Hospitalier Universitaire Grenoble Alpes (CHUGA); Unité IRM 3T-Recherche-UMS IRMaGe-CHUGA (C.H., A.K., A.J.); IRMaGe-Inserm US-017 (C.H., A.K.), CNRS UMS-3552, UGA, Grenoble; Neuroradiologie-IRM-Pôle Imagerie-CHUGA (A.K.); Centre Hospitalier Métropole Savoie (C.H.), Chambéry; Laboratoire HP2 (S.B.), UGA; Pôle thorax et vaisseaux, CHUGA; Pôle Recherche (A.J.), CHUGA, Grenoble; and Institut Universitaire de France (N.V.), Paris, France
| | - Antoine Thuriot
- From the Université Grenoble Alpes (J.S., A.T., F.R., A.B.B., N.V., A.J.), AGEIS, Faculté de Médecine; Stroke Unit (J.S., A.T.), Neurologie, Centre Hospitalier Universitaire Grenoble Alpes (CHUGA); Unité IRM 3T-Recherche-UMS IRMaGe-CHUGA (C.H., A.K., A.J.); IRMaGe-Inserm US-017 (C.H., A.K.), CNRS UMS-3552, UGA, Grenoble; Neuroradiologie-IRM-Pôle Imagerie-CHUGA (A.K.); Centre Hospitalier Métropole Savoie (C.H.), Chambéry; Laboratoire HP2 (S.B.), UGA; Pôle thorax et vaisseaux, CHUGA; Pôle Recherche (A.J.), CHUGA, Grenoble; and Institut Universitaire de France (N.V.), Paris, France
| | - Felix Renard
- From the Université Grenoble Alpes (J.S., A.T., F.R., A.B.B., N.V., A.J.), AGEIS, Faculté de Médecine; Stroke Unit (J.S., A.T.), Neurologie, Centre Hospitalier Universitaire Grenoble Alpes (CHUGA); Unité IRM 3T-Recherche-UMS IRMaGe-CHUGA (C.H., A.K., A.J.); IRMaGe-Inserm US-017 (C.H., A.K.), CNRS UMS-3552, UGA, Grenoble; Neuroradiologie-IRM-Pôle Imagerie-CHUGA (A.K.); Centre Hospitalier Métropole Savoie (C.H.), Chambéry; Laboratoire HP2 (S.B.), UGA; Pôle thorax et vaisseaux, CHUGA; Pôle Recherche (A.J.), CHUGA, Grenoble; and Institut Universitaire de France (N.V.), Paris, France
| | - Bérengère Aubert Broche
- From the Université Grenoble Alpes (J.S., A.T., F.R., A.B.B., N.V., A.J.), AGEIS, Faculté de Médecine; Stroke Unit (J.S., A.T.), Neurologie, Centre Hospitalier Universitaire Grenoble Alpes (CHUGA); Unité IRM 3T-Recherche-UMS IRMaGe-CHUGA (C.H., A.K., A.J.); IRMaGe-Inserm US-017 (C.H., A.K.), CNRS UMS-3552, UGA, Grenoble; Neuroradiologie-IRM-Pôle Imagerie-CHUGA (A.K.); Centre Hospitalier Métropole Savoie (C.H.), Chambéry; Laboratoire HP2 (S.B.), UGA; Pôle thorax et vaisseaux, CHUGA; Pôle Recherche (A.J.), CHUGA, Grenoble; and Institut Universitaire de France (N.V.), Paris, France
| | - Alexandre Krainik
- From the Université Grenoble Alpes (J.S., A.T., F.R., A.B.B., N.V., A.J.), AGEIS, Faculté de Médecine; Stroke Unit (J.S., A.T.), Neurologie, Centre Hospitalier Universitaire Grenoble Alpes (CHUGA); Unité IRM 3T-Recherche-UMS IRMaGe-CHUGA (C.H., A.K., A.J.); IRMaGe-Inserm US-017 (C.H., A.K.), CNRS UMS-3552, UGA, Grenoble; Neuroradiologie-IRM-Pôle Imagerie-CHUGA (A.K.); Centre Hospitalier Métropole Savoie (C.H.), Chambéry; Laboratoire HP2 (S.B.), UGA; Pôle thorax et vaisseaux, CHUGA; Pôle Recherche (A.J.), CHUGA, Grenoble; and Institut Universitaire de France (N.V.), Paris, France
| | - Nicolas Vuillerme
- From the Université Grenoble Alpes (J.S., A.T., F.R., A.B.B., N.V., A.J.), AGEIS, Faculté de Médecine; Stroke Unit (J.S., A.T.), Neurologie, Centre Hospitalier Universitaire Grenoble Alpes (CHUGA); Unité IRM 3T-Recherche-UMS IRMaGe-CHUGA (C.H., A.K., A.J.); IRMaGe-Inserm US-017 (C.H., A.K.), CNRS UMS-3552, UGA, Grenoble; Neuroradiologie-IRM-Pôle Imagerie-CHUGA (A.K.); Centre Hospitalier Métropole Savoie (C.H.), Chambéry; Laboratoire HP2 (S.B.), UGA; Pôle thorax et vaisseaux, CHUGA; Pôle Recherche (A.J.), CHUGA, Grenoble; and Institut Universitaire de France (N.V.), Paris, France
| | - Assia Jaillard
- From the Université Grenoble Alpes (J.S., A.T., F.R., A.B.B., N.V., A.J.), AGEIS, Faculté de Médecine; Stroke Unit (J.S., A.T.), Neurologie, Centre Hospitalier Universitaire Grenoble Alpes (CHUGA); Unité IRM 3T-Recherche-UMS IRMaGe-CHUGA (C.H., A.K., A.J.); IRMaGe-Inserm US-017 (C.H., A.K.), CNRS UMS-3552, UGA, Grenoble; Neuroradiologie-IRM-Pôle Imagerie-CHUGA (A.K.); Centre Hospitalier Métropole Savoie (C.H.), Chambéry; Laboratoire HP2 (S.B.), UGA; Pôle thorax et vaisseaux, CHUGA; Pôle Recherche (A.J.), CHUGA, Grenoble; and Institut Universitaire de France (N.V.), Paris, France.
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Lemieux M, Bretzner F. Glutamatergic neurons of the gigantocellular reticular nucleus shape locomotor pattern and rhythm in the freely behaving mouse. PLoS Biol 2019; 17:e2003880. [PMID: 31017885 PMCID: PMC6502437 DOI: 10.1371/journal.pbio.2003880] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Revised: 05/06/2019] [Accepted: 04/10/2019] [Indexed: 12/02/2022] Open
Abstract
Because of their intermediate position between supraspinal locomotor centers and spinal circuits, gigantocellular reticular nucleus (GRN) neurons play a key role in motor command. However, the functional contribution of glutamatergic GRN neurons in initiating, maintaining, and stopping locomotion is still unclear. Combining electromyographic recordings with optogenetic manipulations in freely behaving mice, we investigate the functional contribution of glutamatergic brainstem neurons of the GRN to motor and locomotor activity. Short-pulse photostimulation of one side of the glutamatergic GRN did not elicit locomotion but evoked distinct motor responses in flexor and extensor muscles at rest and during locomotion. Glutamatergic GRN outputs to the spinal cord appear to be gated according to the spinal locomotor network state. Increasing the duration of photostimulation increased motor and postural tone at rest and reset locomotor rhythm during ongoing locomotion. In contrast, photoinhibition impaired locomotor pattern and rhythm. We conclude that unilateral activation of glutamatergic GRN neurons triggered motor activity and modified ongoing locomotor pattern and rhythm.
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Affiliation(s)
- Maxime Lemieux
- Centre de Recherche du CHU de Québec, CHUL-Neurosciences, Québec (QC), Canada
| | - Frederic Bretzner
- Centre de Recherche du CHU de Québec, CHUL-Neurosciences, Québec (QC), Canada
- Faculty of Medicine, Department of Psychiatry and Neurosciences, Université Laval, Québec (QC), Canada
- * E-mail:
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Abstract
Reticulospinal (RS) neurons provide the spinal cord with the executive signals for a large repertoire of motor and autonomic functions, ensuring at the same time that these functions are adapted to the different behavioral contexts. This requires the coordinated action of many RS neurons. In this mini-review, we examine how the RS neurons that carry out specific functions distribute across the three parts of the brain stem. Extensive overlap between populations suggests a need to explore multi-functionality at the single cell-level. We next contrast functional diversity and homogeneity in transmitter phenotype. Then, we examine the molecular genetic mechanisms that specify brain stem development and likely contribute to RS neurons identities. We advocate that a better knowledge of the developmental lineage of the RS neurons and a better knowledge of RS neuron activity across multiple behaviors will help uncover the fundamental principles behind the diversity of RS systems in mammals.
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Affiliation(s)
| | - Andrea Giorgi
- Department of Physiology, Emory University School of Medicine, Atlanta, Georgia, USA
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A Brainstem Neural Substrate for Stopping Locomotion. J Neurosci 2018; 39:1044-1057. [PMID: 30541913 DOI: 10.1523/jneurosci.1992-18.2018] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Revised: 11/20/2018] [Accepted: 12/03/2018] [Indexed: 01/04/2023] Open
Abstract
Locomotion occurs sporadically and needs to be started, maintained, and stopped. The neural substrate underlying the activation of locomotion is partly known, but little is known about mechanisms involved in termination of locomotion. Recently, reticulospinal neurons (stop cells) were found to play a crucial role in stopping locomotion in the lamprey: their activation halts ongoing locomotion and their inactivation slows down the termination process. Intracellular recordings of these cells revealed a distinct activity pattern, with a burst of action potentials at the beginning of a locomotor bout and one at the end (termination burst). The termination burst was shown to be time linked to the end of locomotion, but the mechanisms by which it is triggered have remained unknown. We studied this in larval sea lampreys (Petromyzon marinus; the sex of the animals was not taken into account). We found that the mesencephalic locomotor region (MLR), which is known to initiate and control locomotion, stops ongoing locomotion by providing synaptic inputs that trigger the termination burst in stop cells. When locomotion is elicited by MLR stimulation, a second MLR stimulation stops the locomotor bout if it is of lower intensity than the initial stimulation. This occurs for MLR-induced, sensory-evoked, and spontaneous locomotion. Furthermore, we show that glutamatergic and, most likely, monosynaptic projections from the MLR activate stop cells during locomotion. Therefore, activation of the MLR not only initiates locomotion, but can also control the end of a locomotor bout. These results provide new insights onto the neural mechanisms responsible for stopping locomotion.SIGNIFICANCE STATEMENT The mesencephalic locomotor region (MLR) is a brainstem region well known to initiate and control locomotion. Since its discovery in cats in the 1960s, the MLR has been identified in all vertebrate species tested from lampreys to humans. We now demonstrate that stimulation of the MLR not only activates locomotion, but can also stop it. This is achieved through a descending glutamatergic signal, most likely monosynaptic, from the MLR to the reticular formation that activates reticulospinal stop cells. Together, our findings have uncovered a neural mechanism for stopping locomotion and bring new insights into the function of the MLR.
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Baude M, Nielsen JB, Gracies JM. The neurophysiology of deforming spastic paresis: A revised taxonomy. Ann Phys Rehabil Med 2018; 62:426-430. [PMID: 30500361 DOI: 10.1016/j.rehab.2018.10.004] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Revised: 10/22/2018] [Accepted: 10/22/2018] [Indexed: 11/30/2022]
Abstract
This paper revisits the taxonomy of the neurophysiological consequences of a persistent impairment of motor command execution in the classic environment of sensorimotor restriction and muscle hypo-mobilization in short position. Around each joint, the syndrome involves 2 disorders, muscular and neurologic. The muscular disorder is promoted by muscle hypo-mobilization in short position in the context of paresis, in the hours and days after paresis onset: this genetically mediated, evolving myopathy, is called spastic myopathy. The clinician may suspect it by feeling extensibility loss in a resting muscle, although long after the actual onset of the disease. The neurologic disorder, promoted by sensorimotor restriction in the context of paresis and by the muscle disorder itself, comprises 4 main components, mostly affecting antagonists to desired movements: the first is spastic dystonia, an unwanted, involuntary muscle activation at rest, in the absence of stretch or voluntary effort; spastic dystonia superimposes on spastic myopathy to cause visible, gradually increasing body deformities; the second is spastic cocontraction, an unwanted, involuntary antagonist muscle activation during voluntary effort directed to the agonist, aggravated by antagonist stretch; it is primarily due to misdirection of the supraspinal descending drive and contributes to reducing movement amplitude; and the third is spasticity, one form of hyperreflexia, defined by an enhancement of the velocity-dependent responses to phasic stretch, detected and measured at rest (another form of hyperreflexia is "nociceptive spasms", following flexor reflex afferent stimulation, particularly after spinal cord lesions). The 3 main forms of overactivity, spastic dystonia, spastic cocontraction and spasticity, share the same motor neuron hyperexcitability as a contributing factor, all being predominant in the muscles that are more affected by spastic myopathy. The fourth component of the neurologic disorder affects the agonist: it is stretch-sensitive paresis, which is a decreased access of the central command to the agonist, aggravated by antagonist stretch. Improved understanding of the pathophysiology of deforming spastic paresis should help clinicians select meaningful assessments and refined treatments, including the utmost need to preserve muscle tissue integrity as soon as paresis sets in.
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Affiliation(s)
- Marjolaine Baude
- Service de rééducation neurolocomotrice, EA 7377 BIOTN, laboratoire analyse et restauration du mouvement, université Paris-Est Créteil, hôpitaux universitaires Henri-Mondor, Assistance publique-Hôpitaux de Paris, 51, avenue du Maréchal-de-Lattre-de-Tassigny, 94010 Créteil, France.
| | - Jens Bo Nielsen
- Department of Neuroscience, University of Copenhagen, Blegdamsvej 3, 2200 Copenhagen N, Denmark
| | - Jean-Michel Gracies
- Service de rééducation neurolocomotrice, EA 7377 BIOTN, laboratoire analyse et restauration du mouvement, université Paris-Est Créteil, hôpitaux universitaires Henri-Mondor, Assistance publique-Hôpitaux de Paris, 51, avenue du Maréchal-de-Lattre-de-Tassigny, 94010 Créteil, France
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Abstract
STUDY DESIGN Case-control. OBJECTIVE The aim of this study was to understand the role of high-resolution magnetic resonance (MR) in identifying regional cord volume loss in cervical spondylotic myelopathy (CSM). SUMMARY OF BACKGROUND DATA Preliminary studies suggest that compression of the ventral region of the cord may contribute disproportionately to CSM symptomology; however, tract-specific data are lacking in the CSM population. The current study is the first to use 3T MR imaging (MRI) images of CSM patients to determine specific volume loss at the level of detail of individual descending white matter tracts. METHODS Twelve patients with CSM and 14 age-matched were enrolled prospectively and underwent 3-Tesla MRI of the cervical spine. Using the high-resolution images of the spinal cord, straightening and alignment with a template was performed and specific spinal cord tract volumes were measured using Spinal Cord Tool-box version 3.0.7. Modified Japanese orthopedic association (mJOA) and Nurick disability scores were collected in a prospective manner and were analyzed in relation to descending spinal tract volumes. RESULTS Having CSM was predicted by anterior/posterior diameter, eccentricity of the cord [odds ratio (OR) 0.000000621, P = 0.004], ventral reticulospinal tract volume (OR 1.167, P = 0.063), lateral corticospinal tract volume (OR 1.034, P = 0.046), rubrospinal tract volume (OR 1.072, P = 0.011), and ventrolateral reticulospinal tract volume (OR 1.474, P = 0.005) on single variable logistic regression. Single variable linear regression showed decreases in anterior/posterior spinal cord diameter (P = 0.022), ventral reticulospinal tract volumes (P = 0.007), and ventrolateral reticulospinal tract volumes (P = 0.017) to significantly predict worsening mJOA scores. Similarly, decreases in ventral reticulospinal tract volumes significantly predicted increasing Nurick scores (P = 0.039). CONCLUSION High-resolution 3T MRI can detect tract-specific volume loss in descending spinal cord tracts in CSM patients. Anterior/posterior spinal cord diameter, ventral reticulospinal tract, ventrolateral reticulospinal tract, lateral corticospinal tract, and rubrospinal tract volume loss are associated with CSM symptoms. LEVEL OF EVIDENCE 2.
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23
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Fregosi M, Contestabile A, Badoud S, Borgognon S, Cottet J, Brunet JF, Bloch J, Schwab ME, Rouiller EM. Changes of motor corticobulbar projections following different lesion types affecting the central nervous system in adult macaque monkeys. Eur J Neurosci 2018; 48:2050-2070. [PMID: 30019432 PMCID: PMC6175012 DOI: 10.1111/ejn.14074] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 06/28/2018] [Accepted: 07/07/2018] [Indexed: 01/03/2023]
Abstract
Functional recovery from central nervous system injury is likely to be partly due to a rearrangement of neural circuits. In this context, the corticobulbar (corticoreticular) motor projections onto different nuclei of the ponto-medullary reticular formation (PMRF) were investigated in 13 adult macaque monkeys after either, primary motor cortex injury (MCI) in the hand area, or spinal cord injury (SCI) or Parkinson's disease-like lesions of the nigro-striatal dopaminergic system (PD). A subgroup of animals in both MCI and SCI groups was treated with neurite growth promoting anti-Nogo-A antibodies, whereas all PD animals were treated with autologous neural cell ecosystems (ANCE). The anterograde tracer BDA was injected either in the premotor cortex (PM) or in the primary motor cortex (M1) to label and quantify corticobulbar axonal boutons terminaux and en passant in PMRF. As compared to intact animals, after MCI the density of corticobulbar projections from PM was strongly reduced but maintained their laterality dominance (ipsilateral), both in the presence or absence of anti-Nogo-A antibody treatment. In contrast, the density of corticobulbar projections from M1 was increased following opposite hemi-section of the cervical cord (at C7 level) and anti-Nogo-A antibody treatment, with maintenance of contralateral laterality bias. In PD monkeys, the density of corticobulbar projections from PM was strongly reduced, as well as that from M1, but to a lesser extent. In conclusion, the densities of corticobulbar projections from PM or M1 were affected in a variable manner, depending on the type of lesion/pathology and the treatment aimed to enhance functional recovery.
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Affiliation(s)
- Michela Fregosi
- Faculty of Science and Medicine, Section of Medicine, Department of Neurosciences and Movement Sciences, University of Fribourg, Fribourg, Switzerland.,Fribourg Cognition Center, Fribourg, Switzerland.,Platform of Translational Neurosciences, Fribourg, Switzerland.,Swiss Primate Competence Center for Research (SPCCR), Fribourg, Switzerland
| | - Alessandro Contestabile
- Faculty of Science and Medicine, Section of Medicine, Department of Neurosciences and Movement Sciences, University of Fribourg, Fribourg, Switzerland.,Fribourg Cognition Center, Fribourg, Switzerland.,Platform of Translational Neurosciences, Fribourg, Switzerland.,Swiss Primate Competence Center for Research (SPCCR), Fribourg, Switzerland
| | - Simon Badoud
- Faculty of Science and Medicine, Section of Medicine, Department of Neurosciences and Movement Sciences, University of Fribourg, Fribourg, Switzerland.,Fribourg Cognition Center, Fribourg, Switzerland.,Platform of Translational Neurosciences, Fribourg, Switzerland.,Swiss Primate Competence Center for Research (SPCCR), Fribourg, Switzerland
| | - Simon Borgognon
- Faculty of Science and Medicine, Section of Medicine, Department of Neurosciences and Movement Sciences, University of Fribourg, Fribourg, Switzerland.,Fribourg Cognition Center, Fribourg, Switzerland.,Platform of Translational Neurosciences, Fribourg, Switzerland.,Swiss Primate Competence Center for Research (SPCCR), Fribourg, Switzerland
| | - Jérôme Cottet
- Faculty of Science and Medicine, Section of Medicine, Department of Neurosciences and Movement Sciences, University of Fribourg, Fribourg, Switzerland.,Fribourg Cognition Center, Fribourg, Switzerland.,Platform of Translational Neurosciences, Fribourg, Switzerland.,Swiss Primate Competence Center for Research (SPCCR), Fribourg, Switzerland
| | - Jean-François Brunet
- Cell production center (CPC), Lausanne University Hospital (CHUV), Lausanne, Switzerland
| | - Jocelyne Bloch
- Department of Neurosurgery, Lausanne University Hospital (CHUV), Lausanne, Switzerland
| | - Martin E Schwab
- Brain Research Institute, University of Zürich, Zürich, Switzerland
| | - Eric M Rouiller
- Faculty of Science and Medicine, Section of Medicine, Department of Neurosciences and Movement Sciences, University of Fribourg, Fribourg, Switzerland.,Fribourg Cognition Center, Fribourg, Switzerland.,Platform of Translational Neurosciences, Fribourg, Switzerland.,Swiss Primate Competence Center for Research (SPCCR), Fribourg, Switzerland
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24
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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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25
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Brownstone RM, Chopek JW. Reticulospinal Systems for Tuning Motor Commands. Front Neural Circuits 2018; 12:30. [PMID: 29720934 PMCID: PMC5915564 DOI: 10.3389/fncir.2018.00030] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2017] [Accepted: 03/29/2018] [Indexed: 11/26/2022] Open
Abstract
The pontomedullary reticular formation (RF) is a key site responsible for integrating descending instructions to execute particular movements. The indiscrete nature of this region has led not only to some inconsistencies in nomenclature, but also to difficulties in understanding its role in the control of movement. In this review article, we first discuss nomenclature of the RF, and then examine the reticulospinal motor command system through evolution. These command neurons have direct monosynaptic connections with spinal interneurons and motoneurons. We next review their roles in postural adjustments, walking and sleep atonia, discussing their roles in movement activation or inhibition. We propose that knowledge of the internal organization of the RF is necessary to understand how the nervous system tunes motor commands, and that this knowledge will underlie strategies for motor functional recovery following neurological injuries or diseases.
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Affiliation(s)
- Robert M. Brownstone
- Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College LondonLondon, United Kingdom
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26
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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: 248] [Impact Index Per Article: 41.3] [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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27
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Abstract
The review demonstrates that control of posture and locomotion is provided by systems across the caudal-to-rostral extent of the neuraxis. A common feature of the neuroanatomic organization of the postural and locomotor control systems is the presence of key nodes for convergent input of multisensory feedback in conjunction with efferent copies of the motor command. These nodes include the vestibular and reticular nuclei and interneurons in the intermediate zone of the spinal cord (Rexed's laminae VI-VIII). This organization provides both spatial and temporal coordination of the various goals of the system and ensures that the large repertoire of voluntary movements is appropriately coupled to either anticipatory or reactive postural adjustments that ensure stability and provide the framework to support the intended action. Redundancies in the system allow adaptation and compensation when sensory modalities are impaired. These alterations in behavior are learned through reward- and error-based learning processes implemented through basal ganglia and cerebellar pathways respectively. However, neurodegenerative processes or lesions of these systems can greatly compromise the capacity to sufficiently adapt and sometimes leads to maladaptive changes that impair movement control. When these impairments occur, the risk of falls can be significantly increased and interventions are required to reduce morbidity.
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Affiliation(s)
- Colum D MacKinnon
- Department of Neurology and Institute for Translational Neuroscience, University of Minnesota, Minneapolis, MN, United States.
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28
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Lorentzen J, Pradines M, Gracies JM, Bo Nielsen J. On Denny-Brown's 'spastic dystonia' - What is it and what causes it? Clin Neurophysiol 2017; 129:89-94. [PMID: 29161622 DOI: 10.1016/j.clinph.2017.10.023] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Revised: 09/29/2017] [Accepted: 10/02/2017] [Indexed: 01/04/2023]
Abstract
In this review, we will work around two simple definitions of two different entities, which most often co-exist in patients with lesions to central motor pathways: Spasticity is "Enhanced excitability of velocity-dependent responses to phasic stretch at rest", which will not be the subject of this review, while Spastic dystonia is tonic, chronic, involuntary muscle contraction in the absence of any stretch or any voluntary command (Gracies, 2005). Spastic dystonia is a much less well understood entity that will be the subject this review. Denny-Brown (1966) observed involuntary sustained muscle activity in monkeys with lesions restricted to the motor cortices . He further observed that such involuntary muscle activity persisted following abolition of sensory input to the spinal cord and concluded that a central mechanism rather than exaggerated stretch reflex activity had to be involved. He coined the term spastic dystonia to describe this involuntary tonic activity in the context of otherwise exaggerated stretch reflexes. Sustained involuntary muscle activity in the absence of any stretch or any voluntary command contributes to burdensome and disabling body deformities in patients with spastic paresis. Yet, little has been done since Denny-Brown's studies to determine the pathophysiology of this non- stretch or effort related sustained involuntary muscle activity following motor lesions and there is a clear need for research studies in order to improve current therapy. The purpose of the present review is to discuss some of the possible mechanisms that may be involved in the hope that this may guide future research. We discuss the existence of persistent inward currents in spinal motoneurones and present the evidence that the channels involved may be upregulated following central motor lesions. We also discuss a possible contribution from alterations in synaptic inputs from surviving or abnormally branched sensory and descending fibres leading to over-activity and lack of motor coordination. We finally discuss evidence of alterations in motor cortical representational maps and basal ganglia lesions.
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Affiliation(s)
- Jakob Lorentzen
- Section for Integrative Neuroscience, Center for Neuroscience, University of Copenhagen, Denmark; Elsass Institute, Holmegårdsvej 28, 2920 Charlottenlund, Denmark.
| | - Maud Pradines
- EA 7377 BIOTN, Université Paris-Est, Hospital Albert Chenevier-Henri Mondor, Service de Rééducation Neurolocomotrice, APHP, Créteil, France
| | - Jean-Michel Gracies
- EA 7377 BIOTN, Université Paris-Est, Hospital Albert Chenevier-Henri Mondor, Service de Rééducation Neurolocomotrice, APHP, Créteil, France
| | - Jens Bo Nielsen
- Section for Integrative Neuroscience, Center for Neuroscience, University of Copenhagen, Denmark; Elsass Institute, Holmegårdsvej 28, 2920 Charlottenlund, Denmark
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29
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Kim LH, Sharma S, Sharples SA, Mayr KA, Kwok CHT, Whelan PJ. Integration of Descending Command Systems for the Generation of Context-Specific Locomotor Behaviors. Front Neurosci 2017; 11:581. [PMID: 29093660 PMCID: PMC5651258 DOI: 10.3389/fnins.2017.00581] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Accepted: 10/04/2017] [Indexed: 11/23/2022] Open
Abstract
Over the past decade there has been a renaissance in our understanding of spinal cord circuits; new technologies are beginning to provide key insights into descending circuits which project onto spinal cord central pattern generators. By integrating work from both the locomotor and animal behavioral fields, we can now examine context-specific control of locomotion, with an emphasis on descending modulation arising from various regions of the brainstem. Here we examine approach and avoidance behaviors and the circuits that lead to the production and arrest of locomotion.
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Affiliation(s)
- Linda H Kim
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada.,Department of Neuroscience, University of Calgary, Calgary, AB, Canada
| | - Sandeep Sharma
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada.,Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, AB, Canada
| | - Simon A Sharples
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada.,Department of Neuroscience, University of Calgary, Calgary, AB, Canada
| | - Kyle A Mayr
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada.,Department of Neuroscience, University of Calgary, Calgary, AB, Canada
| | - Charlie H T Kwok
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada.,Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, AB, Canada
| | - Patrick J Whelan
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada.,Department of Neuroscience, University of Calgary, Calgary, AB, Canada.,Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, AB, Canada
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30
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On the Role of the Pedunculopontine Nucleus and Mesencephalic Reticular Formation in Locomotion in Nonhuman Primates. J Neurosci 2017; 36:4917-29. [PMID: 27147647 DOI: 10.1523/jneurosci.2514-15.2016] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Accepted: 02/22/2016] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED The mesencephalic reticular formation (MRF) is formed by the pedunculopontine and cuneiform nuclei, two neuronal structures thought to be key elements in the supraspinal control of locomotion, muscle tone, waking, and REM sleep. The role of MRF has also been advocated in modulation of state of arousal leading to transition from wakefulness to sleep and it is further considered to be a main player in the pathophysiology of gait disorders seen in Parkinson's disease. However, the existence of a mesencephalic locomotor region and of an arousal center has not yet been demonstrated in primates. Here, we provide the first extensive electrophysiological mapping of the MRF using extracellular recordings at rest and during locomotion in a nonhuman primate (NHP) (Macaca fascicularis) model of bipedal locomotion. We found different neuronal populations that discharged according to a phasic or a tonic mode in response to locomotion, supporting the existence of a locomotor neuronal circuit within these MRF in behaving primates. Altogether, these data constitute the first electrophysiological characterization of a locomotor neuronal system present within the MRF in behaving NHPs under normal conditions, in accordance with several studies done in different experimental animal models. SIGNIFICANCE STATEMENT We provide the first extensive electrophysiological mapping of the two major components of the mesencephalic reticular formation (MRF), namely the pedunculopontine and cuneiform nuclei. We exploited a nonhuman primate (NHP) model of bipedal locomotion with extracellular recordings in behaving NHPs at rest and during locomotion. Different MRF neuronal groups were found to respond to locomotion, with phasic or tonic patterns of response. These data constitute the first electrophysiological evidences of a locomotor neuronal system within the MRF in behaving NHPs.
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31
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Owen M, Ingo C, Dewald JPA. Upper Extremity Motor Impairments and Microstructural Changes in Bulbospinal Pathways in Chronic Hemiparetic Stroke. Front Neurol 2017; 8:257. [PMID: 28659855 PMCID: PMC5468392 DOI: 10.3389/fneur.2017.00257] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2017] [Accepted: 05/22/2017] [Indexed: 12/20/2022] Open
Abstract
Following hemiparetic stroke, precise, individuated control of single joints is often replaced by highly stereotyped patterns of multi-joint movement, or abnormal limb synergies, which can negatively impact functional use of the paretic arm. One hypothesis for the expression of these synergies is an increased dependence on bulbospinal pathways such as the rubrospinal (RubST) tract and especially the reticulospinal (RetST) tracts, which co-activate multiple muscles of the shoulder, elbow, wrist, and fingers. Despite indirect evidence supporting this hypothesis in humans poststroke, it still remains unclear whether it is correct. Therefore, we used high-resolution diffusion tensor imaging (DTI) to quantify white matter microstructure in relation to severity of arm synergy and hand-related motor impairments. DTI was performed on 19 moderately to severely impaired chronic stroke individuals and 15 healthy, age-matched controls. In stroke individuals, compared to controls, there was significantly decreased fractional anisotropy (FA) and significantly increased axial and radial diffusivity in bilateral corona radiata and body of the corpus callosum. Furthermore, poststroke, the contralesional (CL) RetST FA correlated significantly with both upper extremity (UE) synergy severity (r = -0.606, p = 0.003) and hand impairment (r = -0.609, p = 0.003). FA in the ipsilesional RubST significantly correlated with hand impairment severity (r = -0.590, p = 0.004). For the first time, we separately evaluate RetST and RubST microstructure in chronic stroke individuals with UE motor impairment. We demonstrate that individuals with the greatest UE synergy severity and hand impairments poststroke have the highest FA in the CL RetST a pattern consistent with increased myelination and suggestive of neuroplastic reorganization. Since the RetST pathway microstructure, in particular, is sensitive to abnormal joint coupling and hand-related motor impairment in chronic stroke, it could help test the effects of specific, and novel, anti-synergy neurorehabilitation interventions for recovery from hemiparesis.
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Affiliation(s)
- Meriel Owen
- Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States.,Interdepartmental Neuroscience Program, Northwestern University, Chicago, IL, United States
| | - Carson Ingo
- Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States
| | - Julius P A Dewald
- Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States.,Interdepartmental Neuroscience Program, Northwestern University, Chicago, IL, United States.,Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, IL, United States
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32
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Lan Y, Yao J, Dewald JP. The Impact of Shoulder Abduction Loading on Volitional Hand Opening and Grasping in Chronic Hemiparetic Stroke. Neurorehabil Neural Repair 2017; 31:521-529. [PMID: 28506146 PMCID: PMC5505320 DOI: 10.1177/1545968317697033] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Up to 60% of individuals with moderate to severe chronic hemiparetic stroke experience excessive involuntary wrist/finger flexion that constrains functional hand movements including hand opening. It's not known how stroke-induced brain injury impacts volitional hand opening and grasping forces as a result of the expression of abnormal coupling between shoulder abduction and wrist/finger flexion or the flexion synergy. OBJECTIVE The goal of this study is to understand how shoulder abduction loading affects volitional hand opening and grasping forces in individuals with moderate to severe chronic hemiparetic stroke. METHODS Thirty-six individuals (stroke, 26; control, 10) were recruited for this study. Each participant was instructed to perform maximal hand opening and grasping forces while the arm was either fully supported or lifted with a weight equal to 25% or 50% of the participant's maximal shoulder abduction torque. Hand pentagon area, defined as the area formed by the tips of thumb and fingers, was calculated during hand opening. Forces were recorded during grasping. RESULTS In individuals with moderate stroke, increasing shoulder abduction loading reduced the ability to maximally open the hand. In individuals with severe stroke, who were not able to open the hand, grasping forces were generated and increased with shoulder abduction loading. Stroke individuals also showed a reduced ability to control volitional grasping forces due to the enhanced expression of flexion synergy. CONCLUSIONS Shoulder abduction loading reduced the ability to volitionally open the hand and control grasping forces after stroke. Neural mechanisms and clinical implications of these findings are discussed.
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Affiliation(s)
- Yiyun Lan
- Interdepartmental Neuroscience Program, Northwestern University, Chicago, IL, 60611
- Department of Physical Therapy and Human Movement Sciences, Northwestern University, Chicago, IL, 60611
| | - Jun Yao
- Interdepartmental Neuroscience Program, Northwestern University, Chicago, IL, 60611
- Department of Physical Therapy and Human Movement Sciences, Northwestern University, Chicago, IL, 60611
| | - Julius P.A. Dewald
- Interdepartmental Neuroscience Program, Northwestern University, Chicago, IL, 60611
- Department of Physical Therapy and Human Movement Sciences, Northwestern University, Chicago, IL, 60611
- Department of Biomedical Engineering, Northwestern University, Chicago, IL, 60611
- Department of Physical Medicine and Rehabilitation, Northwestern University, Chicago, IL, 60611
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33
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Fregosi M, Contestabile A, Hamadjida A, Rouiller EM. Corticobulbar projections from distinct motor cortical areas to the reticular formation in macaque monkeys. Eur J Neurosci 2017; 45:1379-1395. [PMID: 28394483 DOI: 10.1111/ejn.13576] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 03/31/2017] [Accepted: 04/03/2017] [Indexed: 12/31/2022]
Abstract
Corticospinal and corticobulbar descending pathways act in parallel with brainstem systems, such as the reticulospinal tract, to ensure the control of voluntary movements via direct or indirect influences onto spinal motoneurons. The aim of this study was to investigate the corticobulbar projections from distinct motor cortical areas onto different nuclei of the reticular formation. Seven adult macaque monkeys were analysed for the location of corticobulbar axonal boutons, and one monkey for reticulospinal neurons' location. The anterograde tracer BDA was injected in the premotor cortex (PM), in the primary motor cortex (M1) or in the supplementary motor area (SMA), in 3, 3 and 1 monkeys respectively. BDA anterograde labelling of corticobulbar axons were analysed on brainstem histological sections and overlapped with adjacent Nissl-stained sections for cytoarchitecture. One adult monkey was analysed for retrograde CB tracer injected in C5-C8 hemispinal cord to visualise reticulospinal neurons. The corticobulbar axons formed bilateral terminal fields with boutons terminaux and en passant, which were quantified in various nuclei belonging to the Ponto-Medullary Reticular Formation (PMRF). The corticobulbar projections from both PM and SMA tended to end mainly ipsilaterally in PMRF, but contralaterally when originating from M1. Furthermore, the corticobulbar projection was less dense when originating from M1 than from non-primary motor areas (PM, SMA). The main nuclei of bouton terminals corresponded to the regions where reticulospinal neurons were located with CB retrograde tracing. In conclusion, the corticobulbar projection differs according to the motor cortical area of origin in density and laterality.
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Affiliation(s)
- Michela Fregosi
- Department of Medecine, University of Fribourg, Chemin du Musée 5, 1700, Fribourg, Switzerland
| | - Alessandro Contestabile
- Department of Medecine, University of Fribourg, Chemin du Musée 5, 1700, Fribourg, Switzerland
| | - Adjia Hamadjida
- Department of Medecine, University of Fribourg, Chemin du Musée 5, 1700, Fribourg, Switzerland
| | - Eric M Rouiller
- Department of Medecine, University of Fribourg, Chemin du Musée 5, 1700, Fribourg, Switzerland
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Neurons in the pontomedullary reticular formation receive converging inputs from the hindlimb and labyrinth. Exp Brain Res 2017; 235:1195-1207. [PMID: 28188328 DOI: 10.1007/s00221-017-4875-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Accepted: 01/04/2017] [Indexed: 12/14/2022]
Abstract
The integration of inputs from vestibular and proprioceptive sensors within the central nervous system is critical to postural regulation. We recently demonstrated in both decerebrate and conscious cats that labyrinthine and hindlimb inputs converge onto vestibular nucleus neurons. The pontomedullary reticular formation (pmRF) also plays a key role in postural control, and additionally participates in regulating locomotion. Thus, we hypothesized that like vestibular nucleus neurons, pmRF neurons integrate inputs from the limb and labyrinth. To test this hypothesis, we recorded the responses of pmRF neurons to passive ramp-and-hold movements of the hindlimb and to whole-body tilts, in both decerebrate and conscious felines. We found that pmRF neuronal activity was modulated by hindlimb movement in the rostral-caudal plane. Most neurons in both decerebrate (83% of units) and conscious (61% of units) animals encoded both flexion and extension movements of the hindlimb. In addition, hindlimb somatosensory inputs converged with vestibular inputs onto pmRF neurons in both preparations. Pontomedullary reticular formation neurons receiving convergent vestibular and limb inputs likely participate in balance control by governing reticulospinal outflow.
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35
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Field-Fote EC, Yang JF, Basso DM, Gorassini MA. Supraspinal Control Predicts Locomotor Function and Forecasts Responsiveness to Training after Spinal Cord Injury. J Neurotrauma 2016; 34:1813-1825. [PMID: 27673569 DOI: 10.1089/neu.2016.4565] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Restoration of walking ability is an area of great interest in the rehabilitation of persons with spinal cord injury. Because many cortical, subcortical, and spinal neural centers contribute to locomotor function, it is important that intervention strategies be designed to target neural elements at all levels of the neuraxis that are important for walking ability. While to date most strategies have focused on activation of spinal circuits, more recent studies are investigating the value of engaging supraspinal circuits. Despite the apparent potential of pharmacological, biological, and genetic approaches, as yet none has proved more effective than physical therapeutic rehabilitation strategies. By making optimal use of the potential of the nervous system to respond to training, strategies can be developed that meet the unique needs of each person. To complement the development of optimal training interventions, it is valuable to have the ability to predict future walking function based on early clinical presentation, and to forecast responsiveness to training. A number of clinical prediction rules and association models based on common clinical measures have been developed with the intent, respectively, to predict future walking function based on early clinical presentation, and to delineate characteristics associated with responsiveness to training. Further, a number of variables that are correlated with walking function have been identified. Not surprisingly, most of these prediction rules, association models, and correlated variables incorporate measures of volitional lower extremity strength, illustrating the important influence of supraspinal centers in the production of walking behavior in humans.
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Affiliation(s)
- Edelle C Field-Fote
- 1 Shepherd Center, Crawford Research Institute and Division of Physical Therapy, Emory University , Atlanta, Georgia
| | - Jaynie F Yang
- 2 Department of Physical Therapy, Faculty of Rehabilitation Medicine and Neuroscience and Mental Health Institute, Faculty of Medicine & Dentistry, University of Alberta , Edmonton, Alberta, Canada
| | - D Michele Basso
- 3 School of Health and Rehabilitation Sciences, The Ohio State University , Columbus, Ohio
| | - Monica A Gorassini
- 4 Department of Biomedical Engineering, Neuroscience and Mental Health Institute, Faculty of Medicine and Dentistry, University of Alberta , Edmonton, Alberta, Canada
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Takakusaki K, Takahashi M, Obara K, Chiba R. Neural substrates involved in the control of posture. Adv Robot 2016. [DOI: 10.1080/01691864.2016.1252690] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Kaoru Takakusaki
- The Research Center for Brain Function and Medical Engineering, Asahikawa Medical University, Asahikawa, Japan
| | - Mirai Takahashi
- The Research Center for Brain Function and Medical Engineering, Asahikawa Medical University, Asahikawa, Japan
| | - Kazuhiro Obara
- The Research Center for Brain Function and Medical Engineering, Asahikawa Medical University, Asahikawa, Japan
| | - Ryosuke Chiba
- The Research Center for Brain Function and Medical Engineering, Asahikawa Medical University, Asahikawa, Japan
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Thibaudier Y, Hurteau MF, Dambreville C, Chraibi A, Goetz L, Frigon A. Interlimb Coordination during Tied-Belt and Transverse Split-Belt Locomotion before and after an Incomplete Spinal Cord Injury. J Neurotrauma 2016; 34:1751-1765. [PMID: 27219842 DOI: 10.1089/neu.2016.4421] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Coordination between the arms/forelimbs and legs/hindlimbs is often impaired in humans and quadrupedal mammals after incomplete spinal cord injury. In quadrupeds, the forelimbs often take more steps than the hindlimbs, producing a two-to-one forelimb-hindlimb (2-1 FL-HL) coordination. In locomotor performance scales, this is generally considered a loss of FL-HL coordination. Here, FL-HL coordination was quantified before and 8 weeks after a lateral spinal hemisection at the sixth thoracic segment in six adult cats. Cats were tested during tied-belt locomotion (equal front and rear speeds) and transverse split-belt locomotion with the forelimbs or hindlimbs stepping faster. The results show that consistent phasing between forelimb and hindlimb movements was maintained after hemisection, even with the appearance of 2-1 FL-HL coordination, indicating that new stable forms of coordination emerge. Moreover, transverse split-belt locomotion potently modulated interlimb coordination and was capable of restoring a one-to-one FL-HL coordination with a faster treadmill speed for the hindlimbs. In conclusion, the results suggest that neural communication persists after an incomplete spinal cord injury, despite an unequal number of steps between the forelimbs and hindlimbs, and that interlimb coordination can be modulated by having the forelimbs or hindlimbs move at a faster frequency. We propose that locomotor recovery scales incorporate more sensitive methods to quantify FL-HL coordination, to better reflect residual functional capacity and possible cervicolumbar neural communication. Lastly, devising training protocols that make use of the bidirectional influences of the cervical and lumbar locomotor pattern generators could strengthen interlimb coordination and promote locomotor recovery.
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Affiliation(s)
- Yann Thibaudier
- 1 Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Centre de Recherche du CHUS, Université de Sherbrooke , Sherbrooke, Quebec, Canada
| | - Marie-France Hurteau
- 1 Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Centre de Recherche du CHUS, Université de Sherbrooke , Sherbrooke, Quebec, Canada
| | - Charline Dambreville
- 1 Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Centre de Recherche du CHUS, Université de Sherbrooke , Sherbrooke, Quebec, Canada
| | - Anass Chraibi
- 1 Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Centre de Recherche du CHUS, Université de Sherbrooke , Sherbrooke, Quebec, Canada
| | - Laurent Goetz
- 2 Centre de Recherche de l'Institut Universitaire en Santé Mentale de Québec , Quebec, Canada
| | - Alain Frigon
- 1 Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Centre de Recherche du CHUS, Université de Sherbrooke , Sherbrooke, Quebec, Canada
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Bouvier J, Caggiano V, Leiras R, Caldeira V, Bellardita C, Balueva K, Fuchs A, Kiehn O. Descending Command Neurons in the Brainstem that Halt Locomotion. Cell 2015; 163:1191-1203. [PMID: 26590422 PMCID: PMC4899047 DOI: 10.1016/j.cell.2015.10.074] [Citation(s) in RCA: 154] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Revised: 09/21/2015] [Accepted: 10/28/2015] [Indexed: 01/21/2023]
Abstract
The episodic nature of locomotion is thought to be controlled by descending inputs from the brainstem. Most studies have largely attributed this control to initiating excitatory signals, but little is known about putative commands that may specifically determine locomotor offset. To link identifiable brainstem populations to a potential locomotor stop signal, we used developmental genetics and considered a discrete neuronal population in the reticular formation: the V2a neurons. We find that those neurons constitute a major excitatory pathway to locomotor areas of the ventral spinal cord. Selective activation of V2a neurons of the rostral medulla stops ongoing locomotor activity, owing to an inhibition of premotor locomotor networks in the spinal cord. Moreover, inactivation of such neurons decreases spontaneous stopping in vivo. Therefore, the V2a "stop neurons" represent a glutamatergic descending pathway that favors immobility and may thus help control the episodic nature of locomotion.
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Affiliation(s)
- Julien Bouvier
- Mammalian Locomotor Laboratory, Department of Neuroscience, Karolinska Institutet, 17177 Stockholm, Sweden; Paris-Saclay Institute of Neuroscience, UMR 9197 - CNRS and Université-Paris 11, 91190 Gif-sur-Yvette, France.
| | - Vittorio Caggiano
- Mammalian Locomotor Laboratory, Department of Neuroscience, Karolinska Institutet, 17177 Stockholm, Sweden
| | - Roberto Leiras
- Mammalian Locomotor Laboratory, Department of Neuroscience, Karolinska Institutet, 17177 Stockholm, Sweden
| | - Vanessa Caldeira
- Mammalian Locomotor Laboratory, Department of Neuroscience, Karolinska Institutet, 17177 Stockholm, Sweden
| | - Carmelo Bellardita
- Mammalian Locomotor Laboratory, Department of Neuroscience, Karolinska Institutet, 17177 Stockholm, Sweden
| | - Kira Balueva
- Institute of Physiology, Christian Albrechts University of Kiel, 24098 Kiel, Germany
| | - Andrea Fuchs
- Mammalian Locomotor Laboratory, Department of Neuroscience, Karolinska Institutet, 17177 Stockholm, Sweden
| | - Ole Kiehn
- Mammalian Locomotor Laboratory, Department of Neuroscience, Karolinska Institutet, 17177 Stockholm, Sweden.
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Leiras R, Martín-Cora F, Velo P, Liste T, Canedo A. Cat's medullary reticulospinal and subnucleus reticularis dorsalis noxious neurons form a coupled neural circuit through collaterals of descending axons. J Neurophysiol 2015; 115:324-44. [PMID: 26581870 DOI: 10.1152/jn.00603.2015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Accepted: 11/04/2015] [Indexed: 12/17/2022] Open
Abstract
Animals and human beings sense and react to real/potential dangerous stimuli. However, the supraspinal mechanisms relating noxious sensing and nocifensive behavior are mostly unknown. The collateralization and spatial organization of interrelated neurons are important determinants of coordinated network function. Here we electrophysiologically studied medial medullary reticulospinal neurons (mMRF-RSNs) antidromically identified from the cervical cord of anesthetized cats and found that 1) more than 40% (79/183) of the sampled mMRF-RSNs emitted bifurcating axons running within the dorsolateral (DLF) and ventromedial (VMF) ipsilateral fascicles; 2) more than 50% (78/151) of the tested mMRF-RSNs with axons running in the VMF collateralized to the subnucleus reticularis dorsalis (SRD) that also sent ipsilateral descending fibers bifurcating within the DLF and the VMF. This percentage of mMRF collateralization to the SRD increased to more than 81% (53/65) when considering the subpopulation of mMRF-RSNs responsive to noxiously heating the skin; 3) reciprocal monosynaptic excitatory relationships were electrophysiologically demonstrated between noxious sensitive mMRF-RSNs and SRD cells; and 4) injection of the anterograde tracer Phaseolus vulgaris leucoagglutinin evidenced mMRF to SRD and SRD to mMRF projections contacting the soma and proximal dendrites. The data demonstrated a SRD-mMRF network interconnected mainly through collaterals of descending axons running within the VMF, with the subset of noxious sensitive cells forming a reverberating circuit probably amplifying mutual outputs simultaneously regulating motor activity and spinal noxious afferent input. The results provide evidence that noxious stimulation positively engages a reticular SRD-mMRF-SRD network involved in pain-sensory-to-motor transformation and modulation.
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Affiliation(s)
- Roberto Leiras
- Department of Physiology, Faculty Medicine, University Santiago de Compostela, Santiago de Compostela, Spain
| | - Francisco Martín-Cora
- Department of Physiology, Faculty Medicine, University Santiago de Compostela, Santiago de Compostela, Spain
| | - Patricia Velo
- Department of Physiology, Faculty Medicine, University Santiago de Compostela, Santiago de Compostela, Spain
| | - Tania Liste
- Department of Physiology, Faculty Medicine, University Santiago de Compostela, Santiago de Compostela, Spain
| | - Antonio Canedo
- Department of Physiology, Faculty Medicine, University Santiago de Compostela, Santiago de Compostela, Spain
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Ryczko D, Auclair F, Cabelguen JM, Dubuc R. The mesencephalic locomotor region sends a bilateral glutamatergic drive to hindbrain reticulospinal neurons in a tetrapod. J Comp Neurol 2015; 524:1361-83. [PMID: 26470600 PMCID: PMC5019149 DOI: 10.1002/cne.23911] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Revised: 10/01/2015] [Accepted: 10/07/2015] [Indexed: 01/09/2023]
Abstract
In vertebrates, stimulation of the mesencephalic locomotor region (MLR) on one side evokes symmetrical locomotor movements on both sides. How this occurs was previously examined in detail in a swimmer using body undulations (lamprey), but in tetrapods the downstream projections from the MLR to brainstem neurons are not fully understood. Here we examined the brainstem circuits from the MLR to identified reticulospinal neurons in the salamander Notophthalmus viridescens. Using neural tracing, we show that the MLR sends bilateral projections to the middle reticular nucleus (mRN, rostral hindbrain) and the inferior reticular nucleus (iRN, caudal hindbrain). Ca2+ imaging coupled to electrophysiology in in vitro isolated brains revealed very similar responses in reticulospinal neurons on both sides to a unilateral MLR stimulation. As the strength of MLR stimulation was increased, the responses increased in size in reticulospinal neurons of the mRN and iRN, but the responses in the iRN were smaller. Bath‐application or local microinjections of glutamatergic antagonists markedly reduced reticulospinal neuron responses, indicating that the MLR sends glutamatergic inputs to reticulospinal neurons. In addition, reticulospinal cells responded to glutamate microinjections and the size of the responses paralleled the amount of glutamate microinjected. Immunofluorescence coupled with anatomical tracing confirmed the presence of glutamatergic projections from the MLR to reticulospinal neurons. Overall, we show that the brainstem circuits activated by the MLR in the salamander are organized similarly to those previously described in lampreys, indicating that the anatomo‐physiological features of the locomotor drive are well conserved in vertebrates. J. Comp. Neurol. 524:1361–1383, 2016. © 2015 The Authors The Journal of Comparative Neurology Published by Wiley Periodicals, Inc.
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Affiliation(s)
- Dimitri Ryczko
- Groupe de Recherche sur le Système Nerveux Central, Département de neurosciences, Université de Montréal, Montréal, Québec, Canada
| | - Francois Auclair
- Groupe de Recherche sur le Système Nerveux Central, Département de neurosciences, Université de Montréal, Montréal, Québec, Canada
| | - Jean-Marie Cabelguen
- INSERM U862 - Neurocentre Magendie, Motor System Diseases Team, Bordeaux Cedex, France
| | - Réjean Dubuc
- Groupe de Recherche sur le Système Nerveux Central, Département de neurosciences, Université de Montréal, Montréal, Québec, Canada.,Groupe de Recherche en Activité Physique Adaptée, Département des sciences de l'activité physique, Université du Québec à Montréal, Québec, Canada
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41
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Takakusaki K, Chiba R, Nozu T, Okumura T. Brainstem control of locomotion and muscle tone with special reference to the role of the mesopontine tegmentum and medullary reticulospinal systems. J Neural Transm (Vienna) 2015; 123:695-729. [PMID: 26497023 PMCID: PMC4919383 DOI: 10.1007/s00702-015-1475-4] [Citation(s) in RCA: 130] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Accepted: 10/13/2015] [Indexed: 01/12/2023]
Abstract
The lateral part of the mesopontine tegmentum contains functionally important structures involved in the control of posture and gait. Specifically, the mesencephalic locomotor region, which may consist of the cuneiform nucleus and pedunculopontine tegmental nucleus (PPN), occupies the interest with respect to the pathophysiology of posture-gait disorders. The purpose of this article is to review the mechanisms involved in the control of postural muscle tone and locomotion by the mesopontine tegmentum and the pontomedullary reticulospinal system. To make interpretation and discussion more robust, the above issue is considered largely based on our findings in the experiments using decerebrate cat preparations in addition to the results in animal experimentations and clinical investigations in other laboratories. Our investigations revealed the presence of functional topographical organizations with respect to the regulation of postural muscle tone and locomotion in both the mesopontine tegmentum and the pontomedullary reticulospinal system. These organizations were modified by neurotransmitter systems, particularly the cholinergic PPN projection to the pontine reticular formation. Because efferents from the forebrain structures as well as the cerebellum converge to the mesencephalic and pontomedullary reticular formation, changes in these organizations may be involved in the appropriate regulation of posture-gait synergy depending on the behavioral context. On the other hand, abnormal signals from the higher motor centers may produce dysfunction of the mesencephalic-reticulospinal system. Here we highlight the significance of elucidating the mechanisms of the mesencephalic-reticulospinal control of posture and locomotion so that thorough understanding of the pathophysiological mechanisms of posture-gait disorders can be made.
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Affiliation(s)
- Kaoru Takakusaki
- Research Center for Brain Function and Medical Engineering, Asahikawa Medical University, Midorigaoka-Higashi 2-1, 1-1, Asahikawa, 078-8511, Japan.
| | - Ryosuke Chiba
- Research Center for Brain Function and Medical Engineering, Asahikawa Medical University, Midorigaoka-Higashi 2-1, 1-1, Asahikawa, 078-8511, Japan
| | - Tsukasa Nozu
- Department of Regional Medicine and Education, Asahikawa Medical University, Asahikawa, Japan
| | - Toshikatsu Okumura
- Department of General Medicine, Asahikawa Medical University, Asahikawa, Japan
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42
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Coefficients of impairment in deforming spastic paresis. Ann Phys Rehabil Med 2015; 58:173-8. [DOI: 10.1016/j.rehab.2015.04.004] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2014] [Revised: 04/06/2015] [Accepted: 04/07/2015] [Indexed: 12/19/2022]
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Abstract
Following damage to the motor system (e.g., after stroke or spinal cord injury), recovery of upper limb function exploits the multiple pathways which allow motor commands to be sent to the spinal cord. Corticospinal fibers originate from premotor as well as primary motor cortex. While some corticospinal fibers make direct monosynaptic connections to motoneurons, there are also many connections to interneurons which allow control of motoneurons indirectly. Such interneurons may be placed within the cervical enlargement, or more rostrally (propriospinal interneurons). In addition, connections from cortex to the reticular formation in the brainstem allow motor commands to be sent over the reticulospinal tract to these spinal centers. In this review, we consider the relative roles of these different routes for the control of hand function, both in healthy primates and after recovery from lesion.
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44
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Volitional walking via upper limb muscle-controlled stimulation of the lumbar locomotor center in man. J Neurosci 2014; 34:11131-42. [PMID: 25122909 DOI: 10.1523/jneurosci.4674-13.2014] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Gait disturbance in individuals with spinal cord lesion is attributed to the interruption of descending pathways to the spinal locomotor center, whereas neural circuits below and above the lesion maintain their functional capability. An artificial neural connection (ANC), which bridges supraspinal centers and locomotor networks in the lumbar spinal cord beyond the lesion site, may restore the functional impairment. To achieve an ANC that sends descending voluntary commands to the lumbar locomotor center and bypasses the thoracic spinal cord, upper limb muscle activity was converted to magnetic stimuli delivered noninvasively over the lumbar vertebra. Healthy participants were able to initiate and terminate walking-like behavior and to control the step cycle through an ANC controlled by volitional upper limb muscle activity. The walking-like behavior stopped just after the ANC was disconnected from the participants even when the participant continued to swing arms. Furthermore, additional simultaneous peripheral electrical stimulation to the foot via the ANC enhanced this walking-like behavior. Kinematics of the induced behaviors were identical to those observed in voluntary walking. These results demonstrate that the ANC induces volitionally controlled, walking-like behavior of the legs. This paradigm may be able to compensate for the dysfunction of descending pathways by sending commands to the preserved locomotor center at the lumbar spinal cord and may enable individuals with paraplegia to regain volitionally controlled walking.
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45
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Spanne A, Geborek P, Bengtsson F, Jörntell H. Simulating spinal border cells and cerebellar granule cells under locomotion--a case study of spinocerebellar information processing. PLoS One 2014; 9:e107793. [PMID: 25226298 PMCID: PMC4166671 DOI: 10.1371/journal.pone.0107793] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Accepted: 08/23/2014] [Indexed: 11/18/2022] Open
Abstract
The spinocerebellar systems are essential for the brain in the performance of coordinated movements, but our knowledge about the spinocerebellar interactions is very limited. Recently, several crucial pieces of information have been acquired for the spinal border cell (SBC) component of the ventral spinocerebellar tract (VSCT), as well as the effects of SBC mossy fiber activation in granule cells of the cerebellar cortex. SBCs receive monosynaptic input from the reticulospinal tract (RST), which is an important driving system under locomotion, and disynaptic inhibition from Ib muscle afferents. The patterns of activity of RST neurons and Ib afferents under locomotion are known. The activity of VSCT neurons under fictive locomotion, i.e. without sensory feedback, is also known, but there is little information on how these neurons behave under actual locomotion and for cerebellar granule cells receiving SBC input this is completely unknown. But the available information makes it possible to simulate the interactions between the spinal and cerebellar neuronal circuitries with a relatively large set of biological constraints. Using a model of the various neuronal elements and the network they compose, we simulated the modulation of the SBCs and their target granule cells under locomotion and hence generated testable predictions of their general pattern of modulation under this condition. This particular system offers a unique opportunity to simulate these interactions with a limited number of assumptions, which helps making the model biologically plausible. Similar principles of information processing may be expected to apply to all spinocerebellar systems.
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Affiliation(s)
- Anton Spanne
- Neural Basis of Sensorimotor Control, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Pontus Geborek
- Neural Basis of Sensorimotor Control, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Fredrik Bengtsson
- Neural Basis of Sensorimotor Control, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Henrik Jörntell
- Neural Basis of Sensorimotor Control, Department of Experimental Medical Science, Lund University, Lund, Sweden
- * E-mail:
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Dyson KS, Miron JP, Drew T. Differential modulation of descending signals from the reticulospinal system during reaching and locomotion. J Neurophysiol 2014; 112:2505-28. [PMID: 25143539 DOI: 10.1152/jn.00188.2014] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We tested the hypothesis that the same spinal interneuronal pathways are activated by the reticulospinal system during locomotion and reaching. If such were the case, we expected that microstimulation within the pontomedullary reticular formation (PMRF) would evoke qualitatively similar responses in muscles active during both behaviors. To test this, we stimulated in 47 sites within the PMRF during both tasks. Stimulation during locomotion always produced a strongly phase-dependent, bilateral pattern of activity in which activity in muscles was generally facilitated or suppressed during one phase of activity (swing or stance) and was unaffected in the other. During reaching, stimulation generally activated the same muscles as during locomotion, although the modulation of the magnitude of the evoked responses was less limb dependent than during locomotion. An exception was found for some forelimb flexor muscles that were strongly facilitated by stimulation during the swing phase of locomotion but were not influenced by stimulation during the transport phase of the reach. We suggest that during locomotion the activity in interneuronal pathways mediating signals from the reticulospinal system is subject to strong modulation by the central pattern generator for locomotion. During reach, we suggest that, for most muscles, the same spinal interneuronal pathways are used to modify muscle activity but are not as strongly gated according to limb use as during locomotion. Finally, we propose that the command for movement during discrete voluntary movements suppresses the influence of the reticulospinal system on selected forelimb flexor muscles, possibly to enhance fractionated control of movement.
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Affiliation(s)
- Kenneth S Dyson
- Département de Neurosciences, Université de Montréal, Montreal, Quebec, Canada; and Groupe de recherche sur le système nerveux central (GRSNC), Université de Montréal, Montreal, Quebec, Canada
| | - Jean-Philippe Miron
- Département de Neurosciences, Université de Montréal, Montreal, Quebec, Canada; and
| | - Trevor Drew
- Département de Neurosciences, Université de Montréal, Montreal, Quebec, Canada; and Groupe de recherche sur le système nerveux central (GRSNC), Université de Montréal, Montreal, Quebec, Canada
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47
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Gating of steering signals through phasic modulation of reticulospinal neurons during locomotion. Proc Natl Acad Sci U S A 2014; 111:3591-6. [PMID: 24550483 DOI: 10.1073/pnas.1401459111] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The neural control of movements in vertebrates is based on a set of modules, like the central pattern generator networks (CPGs) in the spinal cord coordinating locomotion. Sensory feedback is not required for the CPGs to generate the appropriate motor pattern and neither a detailed control from higher brain centers. Reticulospinal neurons in the brainstem activate the locomotor network, and the same neurons also convey signals from higher brain regions, such as turning/steering commands from the optic tectum (superior colliculus). A tonic increase in the background excitatory drive of the reticulospinal neurons would be sufficient to produce coordinated locomotor activity. However, in both vertebrates and invertebrates, descending systems are in addition phasically modulated because of feedback from the ongoing CPG activity. We use the lamprey as a model for investigating the role of this phasic modulation of the reticulospinal activity, because the brainstem-spinal cord networks are known down to the cellular level in this phylogenetically oldest extant vertebrate. We describe how the phasic modulation of reticulospinal activity from the spinal CPG ensures reliable steering/turning commands without the need for a very precise timing of on- or offset, by using a biophysically detailed large-scale (19,600 model neurons and 646,800 synapses) computational model of the lamprey brainstem-spinal cord network. To verify that the simulated neural network can control body movements, including turning, the spinal activity is fed to a mechanical model of lamprey swimming. The simulations also predict that, in contrast to reticulospinal neurons, tectal steering/turning command neurons should have minimal frequency adaptive properties, which has been confirmed experimentally.
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48
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Beyeler A, Rao G, Ladepeche L, Jacques A, Simmers J, Le Ray D. Vestibular lesion-induced developmental plasticity in spinal locomotor networks during Xenopus laevis metamorphosis. PLoS One 2013; 8:e71013. [PMID: 23951071 PMCID: PMC3741378 DOI: 10.1371/journal.pone.0071013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Accepted: 06/25/2013] [Indexed: 01/08/2023] Open
Abstract
During frog metamorphosis, the vestibular sensory system remains unchanged, while spinal motor networks undergo a massive restructuring associated with the transition from the larval to adult biomechanical system. We investigated in Xenopus laevis the impact of a pre- (tadpole stage) or post-metamorphosis (juvenile stage) unilateral labyrinthectomy (UL) on young adult swimming performance and underlying spinal locomotor circuitry. The acute disruptive effects on locomotion were similar in both tadpoles and juvenile frogs. However, animals that had metamorphosed with a preceding UL expressed restored swimming behavior at the juvenile stage, whereas animals lesioned after metamorphosis never recovered. Whilst kinematic and electrophysiological analyses of the propulsive system showed no significant differences in either juvenile group, a 3D biomechanical simulation suggested that an asymmetry in the dynamic control of posture during swimming could account for the behavioral restoration observed in animals that had been labyrinthectomized before metamorphosis. This hypothesis was subsequently supported by in vivo electromyography during free swimming and in vitro recordings from isolated brainstem/spinal cord preparations. Specifically, animals lesioned prior to metamorphosis at the larval stage exhibited an asymmetrical propulsion/posture coupling as a post-metamorphic young adult. This developmental alteration was accompanied by an ipsilesional decrease in propriospinal coordination that is normally established in strict left-right symmetry during metamorphosis in order to synchronize dorsal trunk muscle contractions with bilateral hindlimb extensions in the swimming adult. Our data thus suggest that a disequilibrium in descending vestibulospinal information during Xenopus metamorphosis leads to an altered assembly of adult spinal locomotor circuitry. This in turn enables an adaptive compensation for the dynamic postural asymmetry induced by the vestibular imbalance and the restoration of functionally-effective behavior.
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Affiliation(s)
- Anna Beyeler
- Université de Bordeaux – CNRS UMR 5287 (INCIA), Bordeaux, France
| | - Guillaume Rao
- Aix-Marseille Université – CNRS UMR 7287 (ISM), Marseille, France
| | | | - André Jacques
- Aix-Marseille Université – CNRS UMR 7287 (ISM), Marseille, France
| | - John Simmers
- Université de Bordeaux – CNRS UMR 5287 (INCIA), Bordeaux, France
| | - Didier Le Ray
- Université de Bordeaux – CNRS UMR 5287 (INCIA), Bordeaux, France
- * E-mail:
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The representation of egocentric space in the posterior parietal cortex. Behav Brain Sci 2013; 15 Spec No 4:691-700. [PMID: 23842408 DOI: 10.1017/s0140525x00072605] [Citation(s) in RCA: 244] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The posterior parietal cortex (PPC) is the most likely site where egocentric spatial relationships are represented in the brain. PPC cells receive visual, auditory, somaesthetic, and vestibular sensory inputs; oculomotor, head, limb, and body motor signals; and strong motivational projections from the limbic system. Their discharge increases not only when an animal moves towards a sensory target, but also when it directs its attention to it. PPC lesions have the opposite effect: sensory inattention and neglect. The PPC does not seem to contain a "map" of the location of objects in space but a distributed neural network for transforming one set of sensory vectors into other sensory reference frames or into various motor coordinate systems. Which set of transformation rules is used probably depends on attention, which selectively enhances the synapses needed for making a particular sensory comparison or aiming a particular movement.
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Krouchev N, Drew T. Motor cortical regulation of sparse synergies provides a framework for the flexible control of precision walking. Front Comput Neurosci 2013; 7:83. [PMID: 23874287 PMCID: PMC3708143 DOI: 10.3389/fncom.2013.00083] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Accepted: 06/12/2013] [Indexed: 12/24/2022] Open
Abstract
We have previously described a modular organization of the locomotor step cycle in the cat in which a number of sparse synergies are activated sequentially during the swing phase of the step cycle (Krouchev et al., 2006). Here, we address how these synergies are modified during voluntary gait modifications. Data were analysed from 27 bursts of muscle activity (recorded from 18 muscles) recorded in the forelimb of the cat during locomotion. These were grouped into 10 clusters, or synergies, during unobstructed locomotion. Each synergy was comprised of only a small number of muscles bursts (sparse synergies), some of which included both proximal and distal muscles. Eight (8/10) of these synergies were active during the swing phase of locomotion. Synergies observed during the gait modifications were very similar to those observed during unobstructed locomotion. Constraining these synergies to be identical in both the lead (first forelimb to pass over the obstacle) and the trail (second limb) conditions allowed us to compare the changes in phase and magnitude of the synergies required to modify gait. In the lead condition, changes were observed particularly in those synergies responsible for transport of the limb and preparation for landing. During the trail condition, changes were particularly evident in those synergies responsible for lifting the limb from the ground at the onset of the swing phase. These changes in phase and magnitude were adapted to the size and shape of the obstacle over which the cat stepped. These results demonstrate that by modifying the phase and magnitude of a finite number of muscle synergies, each comprised of a small number of simultaneously active muscles, descending control signals could produce very specific modifications in limb trajectory during locomotion. We discuss the possibility that these changes in phase and magnitude could be produced by changes in the activity of neurones in the motor cortex.
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Affiliation(s)
- Nedialko Krouchev
- Groupe de Recherche sur le Système Nerveux Central, Département de Physiologie, Université de Montréal Montréal, QC, Canada
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