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1
Gerasimenko, Yury, Chet Preston, Hui Zhong, Roland R. Roy, V. Reggie Edgerton y Prithvi K. Shah. "Rostral lumbar segments are the key controllers of hindlimb locomotor rhythmicity in the adult spinal rat". Journal of Neurophysiology 122, n.º 2 (1 de agosto de 2019): 585–600. http://dx.doi.org/10.1152/jn.00810.2018.
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The precise location and functional organization of the spinal neuronal locomotor-related networks in adult mammals remain unclear. Our recent neurophysiological findings provided empirical evidence that the rostral lumbar spinal cord segments play a critical role in the initiation and generation of the rhythmic activation patterns necessary for hindlimb locomotion in adult spinal rats. Since added epidural stimulation at the S1 segments significantly enhanced the motor output generated by L2 stimulation, these data also suggested that the sacral spinal cord provides a strong facilitory influence in rhythm initiation and generation. However, whether L2 will initiate hindlimb locomotion in the absence of S1 segments, and whether S1 segments can facilitate locomotion in the absence of L2 segments remain unknown. Herein, adult rats received complete spinal cord transections at T8 and then at either L2 or S1. Rats with spinal cord transections at T8 and S1 remained capable of generating coordinated hindlimb locomotion when receiving epidural stimulation at L2 and when ensembles of locomotor related loadbearing input were present. In contrast, minimal locomotion was observed when S1 stimulation was delivered after spinal cord transections at T8 and L2. Results were similar when the nonspecific serotonergic agonists were administered. These results demonstrate in adult rats that rostral lumbar segments are essential for the regulation of hindlimb locomotor rhythmicity. In addition, the more caudal spinal networks alone cannot control locomotion in the absence of the rostral segments around L2 even when loadbearing rhythmic proprioceptive afferent input is imposed. NEW & NOTEWORTHY The exact location of the spinal neuronal locomotor-related networks in adult mammals remains unknown. The present data demonstrate that when the rostral lumbar spinal segments (~L2) are completely eliminated in thoracic spinal adult rats, hindlimb stepping is not possible with neurochemical modulation of the lumbosacral cord. In contrast, eliminating the sacral cord retains stepping ability. These observations highlight the importance of rostral lumbar segments in generating effective mammalian locomotion.
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Rossignol, S., G. Barrière, O. Alluin y A. Frigon. "Re-expression of Locomotor Function After Partial Spinal Cord Injury". Physiology 24, n.º 2 (abril de 2009): 127–39. http://dx.doi.org/10.1152/physiol.00042.2008.
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After a complete spinal section, quadruped mammals (cats, rats, and mice) can generally regain hindlimb locomotion on a treadmill because the spinal cord below the lesion can express locomotion through a neural circuitry termed the central pattern generator (CPG). In this review, we propose that the spinal CPG also plays a crucial role in the locomotor recovery after incomplete spinal cord injury.
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Rossignol, S., E. Brustein, L. Bouyer, D. Barthélemy, C. Langlet y H. Leblond. "Adaptive changes of locomotion after central and peripheral lesions". Canadian Journal of Physiology and Pharmacology 82, n.º 8-9 (1 de julio de 2004): 617–27. http://dx.doi.org/10.1139/y04-068.
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This paper reviews findings on the adaptive changes of locomotion in cats after spinal cord or peripheral nerve lesions. From the results obtained after lesions of the ventral/ventrolateral pathways or the dorsal/dorsolateral pathways, we conclude that with extensive but partial spinal lesions, cats can regain voluntary quadrupedal locomotion on a treadmill. Although tract-specific deficits remain after such lesions, intact descending tracts can compensate for the lesioned tracts and access the spinal network to generate voluntary locomotion. Such neuroplasticity of locomotor control mechanisms is also demonstrated after peripheral nerve lesions in cats with intact or lesioned spinal cords. Some models have shown that recovery from such peripheral nerve lesions probably involves changes at the supra spinal and spinal levels. In the case of somesthesic denervation of the hindpaws, we demonstrated that cats with a complete spinal section need some cutaneous inputs to walk with a plantigrade locomotion, and that even in this spinal state, cats can adapt their locomotion to partial cutaneous denervation. Altogether, these results suggest that there is significant plasticity in spinal and supraspinal locomotor controls to justify the beneficial effects of early proactive and sustained locomotor training after central (Rossignol and Barbeau 1995; Barbeau et al. 1998) or peripheral lesions.Key words: spinal lesions, nerve lesions, locomotion, neuroplisticity, locomotor training.
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Huang, A., B. R. Noga, P. A. Carr, B. Fedirchuk y L. M. Jordan. "Spinal Cholinergic Neurons Activated During Locomotion: Localization and Electrophysiological Characterization". Journal of Neurophysiology 83, n.º 6 (1 de junio de 2000): 3537–47. http://dx.doi.org/10.1152/jn.2000.83.6.3537.
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The objective of the present study was to determine the location of the cholinergic neurons activated in the spinal cord of decerebrate cats during fictive locomotion. Locomotion was induced by stimulation of the mesencephalic locomotor region (MLR). After bouts of locomotion during a 7–9 h period, the animals were perfused and the L3–S1 spinal cord segments removed. Cats in the control group were subjected to the same surgical procedures but no locomotor task. The tissues were sectioned and then stained by immunohistochemical methods for detection of the c-fos protein and choline acetyltransferase (ChAT) enzyme. The resultant c-fos labeling in the lumbar spinal cord was similar to that induced by fictive locomotion in the cat. ChAT-positive cells also clearly exhibited fictive locomotion induced c-fos labeling. Double labeling with c-fos and ChAT was observed in cells within ventral lamina VII, VIII, and possibly IX. Most of them were concentrated in the medial portion of lamina VII close to lamina X, similar in location to the partition and central canal cells found by Barber and collaborators. The number of ChAT and c-fos–labeled neurons was increased following fictive locomotion and was greatest in the intermediate gray, compared with dorsal and ventral regions. The results are consistent with the suggestion that cholinergic interneurons in the lumbar spinal cord are involved in the production of fictive locomotion. Cells in the regions positive for double-labeled cells were targeted for electrophysiological study during locomotion, intracellular filling, and subsequent processing for ChAT immunohistochemistry. Three cells identified in this way were vigorously active during locomotion in phase with ipsilateral extension, and they projected to the contralateral side of the spinal cord. Thus a new population of spinal cord cells can be defined: cholinergic partition cells with commissural projections that are active during the extension phase of locomotion.
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Liu, Jun, Turgay Akay, Peter B. Hedlund, Keir G. Pearson y Larry M. Jordan. "Spinal 5-HT7 Receptors Are Critical for Alternating Activity During Locomotion: In Vitro Neonatal and In Vivo Adult Studies Using 5-HT7 Receptor Knockout Mice". Journal of Neurophysiology 102, n.º 1 (julio de 2009): 337–48. http://dx.doi.org/10.1152/jn.91239.2008.
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5-HT7 receptors have been implicated in the control of locomotion. Here we use 5-HT7 receptor knockout mice to rigorously test whether 5-HT acts at the 5-HT7 receptor to control locomotor-like activity in the neonatal mouse spinal cord in vitro and voluntary locomotion in adult mice. We found that 5-HT applied onto in vitro spinal cords of 5-HT7+/+ mice produced locomotor-like activity that was disrupted and subsequently blocked by the 5-HT7 receptor antagonist SB-269970. In spinal cords isolated from 5-HT7−/− mice, 5-HT produced either uncoordinated rhythmic activity or resulted in synchronous discharges of the ventral roots. SB-269970 had no effect on 5-HT-induced rhythmic activity in the 5-HT7−/− mice. In adult in vivo experiments, SB-269970 applied directly to the spinal cord consistently disrupted locomotion and produced prolonged-extension of the hindlimbs in 5-HT7+/+ but not 5-HT7−/− mice. Disrupted EMG activity produced by SB-269970 in vivo was similar to the uncoordinated rhythmic activity produced by the drug in vitro. Moreover, 5-HT7−/− mice displayed greater maximal extension at the hip and ankle joints than 5-HT7+/+ animals during voluntary locomotion. These results suggest that spinal 5-HT7 receptors are required for the production and coordination of 5-HT-induced locomotor-like activity in the neonatal mouse and are important for the coordination of voluntary locomotion in adult mice. We conclude that spinal 5-HT7 receptors are critical for alternating activity during locomotion.
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Tresch, Matthew C. y Ole Kiehn. "Population Reconstruction of the Locomotor Cycle From Interneuron Activity in the Mammalian Spinal Cord". Journal of Neurophysiology 83, n.º 4 (1 de abril de 2000): 1972–78. http://dx.doi.org/10.1152/jn.2000.83.4.1972.
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Lesion studies have shown that neuronal networks in the ventromedial regions of the neonatal rat spinal cord are critical for the production of locomotion. We examined whether the locomotor cycle could be accurately predicted based on the activity recorded in a population of spinal interneurons located in these regions during pharmacologically induced locomotion. We used a Bayesian probabilistic reconstruction procedure to predict the most likely phase of locomotion given the observed activity in the neuronal population. The population reconstruction was able to predict the correct locomotor phase with high accuracy using a relatively small number of neurons. This result demonstrates that although the spike activity of individual spinal interneurons in the ventromedial region is weak and varies from cycle to cycle, the locomotor phase can be accurately predicted when information from the population is combined. This result is consistent with the proposed involvement of interneurons within these regions of the spinal cord in the production of locomotion.
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Chen, Yi, Lu Chen, Rongliang Liu, Yu Wang, Xiang Yang Chen y Jonathan R. Wolpaw. "Locomotor impact of beneficial or nonbeneficial H-reflex conditioning after spinal cord injury". Journal of Neurophysiology 111, n.º 6 (15 de marzo de 2014): 1249–58. http://dx.doi.org/10.1152/jn.00756.2013.
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When new motor learning changes neurons and synapses in the spinal cord, it may affect previously learned behaviors that depend on the same spinal neurons and synapses. To explore these effects, we used operant conditioning to strengthen or weaken the right soleus H-reflex pathway in rats in which a right spinal cord contusion had impaired locomotion. When up-conditioning increased the H-reflex, locomotion improved. Steps became longer, and step-cycle asymmetry (i.e., limping) disappeared. In contrast, when down-conditioning decreased the H-reflex, locomotion did not worsen. Steps did not become shorter, and asymmetry did not increase. Electromyographic and kinematic analyses explained how H-reflex increase improved locomotion and why H-reflex decrease did not further impair it. Although the impact of up-conditioning or down-conditioning on the H-reflex pathway was still present during locomotion, only up-conditioning affected the soleus locomotor burst. Additionally, compensatory plasticity apparently prevented the weaker H-reflex pathway caused by down-conditioning from weakening the locomotor burst and further impairing locomotion. The results support the hypothesis that the state of the spinal cord is a “negotiated equilibrium” that serves all the behaviors that depend on it. When new learning changes the spinal cord, old behaviors undergo concurrent relearning that preserves or improves their key features. Thus, if an old behavior has been impaired by trauma or disease, spinal reflex conditioning, by changing a specific pathway and triggering a new negotiation, may enable recovery beyond that achieved simply by practicing the old behavior. Spinal reflex conditioning protocols might complement other neurorehabilitation methods and enhance recovery.
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Chen, Yi, Lu Chen, Yu Wang, Jonathan R. Wolpaw y Xiang Yang Chen. "Persistent beneficial impact of H-reflex conditioning in spinal cord-injured rats". Journal of Neurophysiology 112, n.º 10 (15 de noviembre de 2014): 2374–81. http://dx.doi.org/10.1152/jn.00422.2014.
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Operant conditioning of a spinal cord reflex can improve locomotion in rats and humans with incomplete spinal cord injury. This study examined the persistence of its beneficial effects. In rats in which a right lateral column contusion injury had produced asymmetric locomotion, up-conditioning of the right soleus H-reflex eliminated the asymmetry while down-conditioning had no effect. After the 50-day conditioning period ended, the H-reflex was monitored for 100 [±9 (SD)] (range 79–108) more days and locomotion was then reevaluated. After conditioning ended in up-conditioned rats, the H-reflex continued to increase, and locomotion continued to improve. In down-conditioned rats, the H-reflex decrease gradually disappeared after conditioning ended, and locomotion at the end of data collection remained as impaired as it had been before and immediately after down-conditioning. The persistence (and further progression) of H-reflex increase but not H-reflex decrease in these spinal cord-injured rats is consistent with the fact that up-conditioning improved their locomotion while down-conditioning did not. That is, even after up-conditioning ended, the up-conditioned H-reflex pathway remained adaptive because it improved locomotion. The persistence and further enhancement of the locomotor improvement indicates that spinal reflex conditioning protocols might supplement current therapies and enhance neurorehabilitation. They may be especially useful when significant spinal cord regeneration becomes possible and precise methods for retraining the regenerated spinal cord are needed.
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Minassian, Karen, Ursula S. Hofstoetter, Florin Dzeladini, Pierre A. Guertin y Auke Ijspeert. "The Human Central Pattern Generator for Locomotion: Does It Exist and Contribute to Walking?" Neuroscientist 23, n.º 6 (28 de marzo de 2017): 649–63. http://dx.doi.org/10.1177/1073858417699790.
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The ability of dedicated spinal circuits, referred to as central pattern generators (CPGs), to produce the basic rhythm and neural activation patterns underlying locomotion can be demonstrated under specific experimental conditions in reduced animal preparations. The existence of CPGs in humans is a matter of debate. Equally elusive is the contribution of CPGs to normal bipedal locomotion. To address these points, we focus on human studies that utilized spinal cord stimulation or pharmacological neuromodulation to generate rhythmic activity in individuals with spinal cord injury, and on neuromechanical modeling of human locomotion. In the absence of volitional motor control and step-specific sensory feedback, the human lumbar spinal cord can produce rhythmic muscle activation patterns that closely resemble CPG-induced neural activity of the isolated animal spinal cord. In this sense, CPGs in humans can be defined by the activity they produce. During normal locomotion, CPGs could contribute to the activation patterns during specific phases of the step cycle and simplify supraspinal control of step cycle frequency as a feedforward component to achieve a targeted speed. Determining how the human CPGs operate will be essential to advance the theory of neural control of locomotion and develop new locomotor neurorehabilitation paradigms.
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Frigon, Alain y Serge Rossignol. "Locomotor and Reflex Adaptation After Partial Denervation of Ankle Extensors in Chronic Spinal Cats". Journal of Neurophysiology 100, n.º 3 (septiembre de 2008): 1513–22. http://dx.doi.org/10.1152/jn.90321.2008.
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This work investigates the capacity of the spinal cord to generate locomotion after a complete spinal section and its ability to adapt its locomotor pattern after a peripheral nerve lesion. To study this intrinsic adaptive capacity, the left lateral gastrocnemius-soleus (LGS) nerve was sectioned in three cats that expressed a stable locomotion following a complete spinal transection. The electromyograph (EMG) of multiple hindlimb muscles and reflexes, evoked by stimulating the left tibial (Tib) nerve at the ankle, were recorded before and after denervation during treadmill locomotion. Following denervation, the mean amplitude of EMG bursts of multiple hindlimb muscles increased during locomotion, similar to what is found after an identical denervation in otherwise intact cats. Reflex changes were noted in ipsilateral flexors, such as semitendinosus and tibialis anterior, but not in the ipsilateral knee extensor vastus lateralis following denervation. The present results demonstrate that the spinal cord possesses the circuitry necessary to mediate increased EMG activity in multiple hindlimb muscles and also to produce changes in reflex pathways after a muscle denervation. The similarity of changes following LGS denervation in cats with an intact and transected spinal cord suggests that spinal mechanisms play a major role in the locomotor adaptation.
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Behrman, Andrea L. y Susan J. Harkema. "Locomotor Training After Human Spinal Cord Injury: A Series of Case Studies". Physical Therapy 80, n.º 7 (1 de julio de 2000): 688–700. http://dx.doi.org/10.1093/ptj/80.7.688.
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AbstractMany individuals with spinal cord injury (SCI) do not regain their ability to walk, even though it is a primary goal of rehabilitation. Mammals with thoracic spinal cord transection can relearn to step with their hind limbs on a treadmill when trained with sensory input associated with stepping. If humans have similar neural mechanisms for locomotion, then providing comparable training may promote locomotor recovery after SCI. We used locomotor training designed to provide sensory information associated with locomotion to improve stepping and walking in adults after SCI. Four adults with SCIs, with a mean postinjury time of 6 months, received locomotor training. Based on the American Spinal Injury Association (ASIA) Impairment Scale and neurological classification standards, subject 1 had a T5 injury classified as ASIA A, subject 2 had a T5 injury classified as ASIA C, subject 3 had a C6 injury classified as ASIA D, and subject 4 had a T9 injury classified as ASIA D. All subjects improved their stepping on a treadmill. One subject achieved overground walking, and 2 subjects improved their overground walking. Locomotor training using the response of the human spinal cord to sensory information related to locomotion may improve the potential recovery of walking after SCI.
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Dai, X., B. R. Noga, J. R. Douglas y L. M. Jordan. "Localization of Spinal Neurons Activated During Locomotion Using the c-fos Immunohistochemical Method". Journal of Neurophysiology 93, n.º 6 (junio de 2005): 3442–52. http://dx.doi.org/10.1152/jn.00578.2004.
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The c-fos immunohistochemical method of activity-dependent labeling was used to localize locomotor-activated neurons in the adult cat spinal cord. In decerebrate cats, treadmill locomotion was evoked by electrical stimulation of the mesencephalic locomotor region (MLR). Spontaneous or MLR-evoked fictive locomotion was produced in decerebrate animals paralyzed with a neuromuscular blocking agent. After bouts of locomotion during a 7- to 9-h time period, the animals were perfused and the L3–S1 spinal cord segments removed for immunohistochemistry. Control animals were subjected to the same surgical procedures but no locomotor task. Labeled cells were concentrated in Rexed's laminae III and IV of the dorsal horn and laminae VII, VIII, and X of the intermediate zone/ventral horn after treadmill locomotion. Cells in laminae VII, VIII, and X were labeled after fictive locomotion, but labeling in the dorsal horn was much reduced. In control animals, c- fos labeling was a small fraction of that observed in the locomotor animals. The results suggest that labeled cells in laminae VII, VIII, and X are premotor interneurons involved in the production of locomotion, whereas the laminae III and IV cells are those activated during locomotion due to afferent feedback from the moving limb. c-fos-labeled cells were most numerous in the L5–L7 segments, consistent with the distribution of locomotor activated neurons detected through the use of MLR-evoked field potentials.
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Hayes, Heather Brant, Young-Hui Chang y Shawn Hochman. "An In Vitro Spinal Cord–Hindlimb Preparation for Studying Behaviorally Relevant Rat Locomotor Function". Journal of Neurophysiology 101, n.º 2 (febrero de 2009): 1114–22. http://dx.doi.org/10.1152/jn.90523.2008.
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Although the spinal cord contains the pattern-generating circuitry for producing locomotion, sensory feedback reinforces and refines the spatiotemporal features of motor output to match environmental demands. In vitro preparations, such as the isolated rodent spinal cord, offer many advantages for investigating locomotor circuitry, but they lack the natural afferent feedback provided by ongoing locomotor movements. We developed a novel preparation consisting of an isolated in vitro neonatal rat spinal cord oriented dorsal-up with intact hindlimbs free to step on a custom-built treadmill. This preparation combines the neural accessibility of in vitro preparations with the modulatory influence of sensory feedback from physiological hindlimb movement. Locomotion induced by N-methyl d-aspartate and serotonin showed kinematics similar to that of normal adult rat locomotion. Changing orientation and ground interaction (dorsal-up locomotion vs ventral-up air-stepping) resulted in significant kinematic and electromyographic changes that were comparable to those reported under similar mechanical conditions in vivo. We then used two mechanosensory perturbations to demonstrate the influence of sensory feedback on in vitro motor output patterns. First, swing assistive forces induced more regular, robust muscle activation patterns. Second, altering treadmill speed induced corresponding changes in stride frequency, confirming that changes in sensory feedback can alter stride timing in vitro. In summary, intact hindlimbs in vitro can generate behaviorally appropriate locomotor kinematics and responses to sensory perturbations. Future studies combining the neural and chemical accessibility of the in vitro spinal cord with the influence of behaviorally appropriate hindlimb movements will provide further insight into the operation of spinal motor pattern-generating circuits.
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Yokoyama, Hikaru, Tetsuya Ogawa, Masahiro Shinya, Noritaka Kawashima y Kimitaka Nakazawa. "Speed dependency in α-motoneuron activity and locomotor modules in human locomotion: indirect evidence for phylogenetically conserved spinal circuits". Proceedings of the Royal Society B: Biological Sciences 284, n.º 1851 (29 de marzo de 2017): 20170290. http://dx.doi.org/10.1098/rspb.2017.0290.
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Coordinated locomotor muscle activity is generated by the spinal central pattern generators (CPGs). Vertebrate studies have demonstrated the following two characteristics of the speed control mechanisms of the spinal CPGs: (i) rostral segment activation is indispensable for achieving high-speed locomotion; and (ii) specific combinations between spinal interneuronal modules and motoneuron (MN) pools are sequentially activated with increasing speed. Here, to investigate whether similar control mechanisms exist in humans, we examined spinal neural activity during varied-speed locomotion by mapping the distribution of MN activity in the spinal cord and extracting locomotor modules, which generate basic MN activation patterns. The MN activation patterns and the locomotor modules were analysed from multi-muscle electromyographic recordings. The reconstructed MN activity patterns were divided into the following three patterns depending on the speed of locomotion: slow walking, fast walking and running. During these three activation patterns, the proportion of the activity in rostral segments to that in caudal segments increased as locomotion speed increased. Additionally, the different MN activation patterns were generated by distinct combinations of locomotor modules. These results are consistent with the speed control mechanisms observed in vertebrates, suggesting phylogenetically conserved spinal mechanisms of neural control of locomotion.
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Martinez, Marina, Hugo Delivet-Mongrain y Serge Rossignol. "Treadmill training promotes spinal changes leading to locomotor recovery after partial spinal cord injury in cats". Journal of Neurophysiology 109, n.º 12 (15 de junio de 2013): 2909–22. http://dx.doi.org/10.1152/jn.01044.2012.
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After a spinal hemisection at thoracic level in cats, the paretic hindlimb progressively recovers locomotion without treadmill training but asymmetries between hindlimbs persist for several weeks and can be seen even after a further complete spinal transection at T13. To promote optimal locomotor recovery after hemisection, such asymmetrical changes need to be corrected. In the present study we determined if the locomotor deficits induced by a spinal hemisection can be corrected by locomotor training and, if so, whether the spinal stepping after the complete spinal cord transection is also more symmetrical. This would indicate that locomotor training in the hemisected period induces efficient changes in the spinal cord itself. Sixteen adult cats were first submitted to a spinal hemisection at T10. One group received 3 wk of treadmill training, whereas the second group did not. Detailed kinematic and electromyographic analyses showed that a 3-wk period of locomotor training was sufficient to improve the quality and symmetry of walking of the hindlimbs. Moreover, after the complete spinal lesion was performed, all the trained cats reexpressed bilateral and symmetrical hindlimb locomotion within 24 h. By contrast, the locomotor pattern of the untrained cats remained asymmetrical, and the hindlimb on the side of the hemisection was still deficient. This study highlights the beneficial role of locomotor training in facilitating bilateral and symmetrical functional plastic changes within the spinal circuitry and in promoting locomotor recovery after an incomplete spinal cord injury.
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Fouad, K., M. M. Rank, R. Vavrek, K. C. Murray, L. Sanelli y D. J. Bennett. "Locomotion After Spinal Cord Injury Depends on Constitutive Activity in Serotonin Receptors". Journal of Neurophysiology 104, n.º 6 (diciembre de 2010): 2975–84. http://dx.doi.org/10.1152/jn.00499.2010.
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Following spinal cord injury (SCI) neurons caudal to the injury are capable of rhythmic locomotor-related activity that can form the basis for substantial functional recovery of stepping despite the loss of crucial brain stem-derived neuromodulators like serotonin (5-HT). Here we investigated the contribution of constitutive 5-HT2 receptor activity (activity in the absence of 5-HT) to locomotion after SCI. We used a staggered hemisection injury model in rats to study this because these rats showed a robust recovery of locomotor function and yet a loss of most descending axons. Immunolabeling for 5-HT showed little remaining 5-HT below the injury, and locomotor ability was not correlated with the amount of residual 5-HT. Furthermore, blocking 5-HT2 receptors with an intrathecal (IT) application of the neutral antagonist SB242084 did not affect locomotion (locomotor score and kinematics were unaffected), further indicating that residual 5-HT below the injury did not contribute to generation of locomotion. As a positive control, we found that the same application of SB242084 completely antagonized the muscle activity induced by exogenous application of the 5-HT2 receptor agonists alpha-methyl-5-HT (IT). In contrast, blocking constitutive 5-HT2 receptor activity with the potent inverse agonist SB206553 (IT) severely impaired stepping as assessed with kinematic recordings, eliminating most hindlimb weight support and overall reducing the locomotor score in both hind legs. However, even in the most severely impaired animals, rhythmic sweeping movements of the hindlimb feet were still visible during forelimb locomotion, suggesting that SB206553 did not completely eliminate locomotor drive to the motoneurons or motoneuron excitability. The same application of SB206553 had no affect on stepping in normal rats. Thus while normal rats can compensate for loss of 5-HT2 receptor activity, after severe spinal cord injury rats require constitutive activity in these 5-HT2 receptors to produce locomotion.
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Barrière, Grégory, Alain Frigon, Hugues Leblond, Janyne Provencher y Serge Rossignol. "Dual Spinal Lesion Paradigm in the Cat: Evolution of the Kinematic Locomotor Pattern". Journal of Neurophysiology 104, n.º 2 (agosto de 2010): 1119–33. http://dx.doi.org/10.1152/jn.00255.2010.
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The recovery of voluntary quadrupedal locomotion after an incomplete spinal cord injury can involve different levels of the CNS, including the spinal locomotor circuitry. The latter conclusion was reached using a dual spinal lesion paradigm in which a low thoracic partial spinal lesion is followed, several weeks later, by a complete spinal transection (i.e., spinalization). In this dual spinal lesion paradigm, cats can express hindlimb walking 1 day after spinalization, a process that normally takes several weeks, suggesting that the locomotor circuitry within the lumbosacral spinal cord had been modified after the partial lesion. Here we detail the evolution of the kinematic locomotor pattern throughout the dual spinal lesion paradigm in five cats to gain further insight into putative neurophysiological mechanisms involved in locomotor recovery after a partial spinal lesion. All cats recovered voluntary quadrupedal locomotion with treadmill training (3–5 days/wk) over several weeks. After the partial lesion, the locomotor pattern was characterized by several left/right asymmetries in various kinematic parameters, such as homolateral and homologous interlimb coupling, cycle duration, and swing/stance durations. When no further locomotor improvement was observed, cats were spinalized. After spinalization, the hindlimb locomotor pattern rapidly reappeared, but left/right asymmetries in swing/stance durations observed after the partial lesion could disappear or reverse. It is concluded that, after a partial spinal lesion, the hindlimb locomotor pattern was actively maintained by new dynamic interactions between spinal and supraspinal levels but also by intrinsic changes within the spinal cord.
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Martins, Ângela, Cátia Marina Silva, Débora Gouveia, Ana Cardoso, Tiago Coelho, Óscar Gamboa, Eduardo Marcelino y António Ferreira. "Spinal Locomotion in Cats Following Spinal Cord Injury: A Prospective Study". Animals 11, n.º 7 (3 de julio de 2021): 1994. http://dx.doi.org/10.3390/ani11071994.
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This article aimed to evaluate the safety and efficacy of intensive neurorehabilitation in paraplegic cats, with no deep pain perception (grade 0 on the modified Frankel scale), with more than three months of injury. Nine cats, admitted to the Arrábida Veterinary Hospital/Arrábida Animal Rehabilitation Center (CRAA), were subjected to a 12-week intensive functional neurorehabilitation protocol, based on ground and underwater treadmill locomotor training, electrostimulation, and kinesiotherapy exercises, aiming to obtain a faster recovery to ambulation and a modulated locomotor pattern of flexion/extension. Of the nine cats that were admitted in this study, 56% (n = 5) recovered from ambulation, 44% of which (4/9) did so through functional spinal locomotion by reflexes, while one achieved this through the recovery of deep pain perception. These results suggest that intensive neurorehabilitation can play an important role in ambulation recovery, allowing for a better quality of life and well-being, which may lead to a reduction in the number of euthanasia procedures performed on paraplegic animals.
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Grillner, Sten y Abdeljabbar El Manira. "Current Principles of Motor Control, with Special Reference to Vertebrate Locomotion". Physiological Reviews 100, n.º 1 (1 de enero de 2020): 271–320. http://dx.doi.org/10.1152/physrev.00015.2019.
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The vertebrate control of locomotion involves all levels of the nervous system from cortex to the spinal cord. Here, we aim to cover all main aspects of this complex behavior, from the operation of the microcircuits in the spinal cord to the systems and behavioral levels and extend from mammalian locomotion to the basic undulatory movements of lamprey and fish. The cellular basis of propulsion represents the core of the control system, and it involves the spinal central pattern generator networks (CPGs) controlling the timing of different muscles, the sensory compensation for perturbations, and the brain stem command systems controlling the level of activity of the CPGs and the speed of locomotion. The forebrain and in particular the basal ganglia are involved in determining which motor programs should be recruited at a given point of time and can both initiate and stop locomotor activity. The propulsive control system needs to be integrated with the postural control system to maintain body orientation. Moreover, the locomotor movements need to be steered so that the subject approaches the goal of the locomotor episode, or avoids colliding with elements in the environment or simply escapes at high speed. These different aspects will all be covered in the review.
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Ryczko, D., J. Knüsel, A. Crespi, S. Lamarque, A. Mathou, A. J. Ijspeert y J. M. Cabelguen. "Flexibility of the axial central pattern generator network for locomotion in the salamander". Journal of Neurophysiology 113, n.º 6 (15 de marzo de 2015): 1921–40. http://dx.doi.org/10.1152/jn.00894.2014.
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In tetrapods, limb and axial movements are coordinated during locomotion. It is well established that inter- and intralimb coordination show considerable variations during ongoing locomotion. Much less is known about the flexibility of the axial musculoskeletal system during locomotion and the neural mechanisms involved. Here we examined this issue in the salamander Pleurodeles waltlii, which is capable of locomotion in both aquatic and terrestrial environments. Kinematics of the trunk and electromyograms from the mid-trunk epaxial myotomes were recorded during four locomotor behaviors in freely moving animals. A similar approach was used during rhythmic struggling movements since this would give some insight into the flexibility of the axial motor system. Our results show that each of the forms of locomotion and the struggling behavior is characterized by a distinct combination of mid-trunk motor patterns and cycle durations. Using in vitro electrophysiological recordings in isolated spinal cords, we observed that the spinal networks activated with bath-applied N-methyl-d-aspartate could generate these axial motor patterns. In these isolated spinal cord preparations, the limb motor nerve activities were coordinated with each mid-trunk motor pattern. Furthermore, isolated mid-trunk spinal cords and hemicords could generate the mid-trunk motor patterns. This indicates that each side of the cord comprises a network able to generate coordinated axial motor activity. The roles of descending and sensory inputs in the behavior-related changes in axial motor coordination are discussed.
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Dietz, V. "Spinal cord pattern generators for locomotion". Clinical Neurophysiology 114, n.º 8 (agosto de 2003): 1379–89. http://dx.doi.org/10.1016/s1388-2457(03)00120-2.
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Shaw, Gina. "Restoring Locomotion After Spinal Cord Injury". Neurology Today 12, n.º 14 (julio de 2012): 10–11. http://dx.doi.org/10.1097/01.nt.0000417966.47278.74.
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Dietz, V. "Human locomotion following spinal-cord lesion". Gait & Posture 3, n.º 4 (diciembre de 1995): 266–67. http://dx.doi.org/10.1016/0966-6362(96)82859-1.
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Stewart, J. E., H. Barbeau y S. Gauthier. "Modulation of Locomotor Patterns and Spasticity with Clonidine in Spinal Cord Injured Patients". Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques 18, n.º 3 (agosto de 1991): 321–32. http://dx.doi.org/10.1017/s0317167100031887.
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ABSTRACT:This double blind cross-over study, involving 9 chronic spinal cord injured (SCI) patients (6 paraplegic and 3 paretic), was a first attempt to investigate the effects of the noradrenergic agonist, clonidine, on the modulation of the locomotor pattern and spasticity in patients with spinal cord lesions. Electromyographic (EMG), footswitch and video recordings were made as the patients walked on a treadmill with the support of an overhead harness if needed. Overground locomotion was also assessed in the paretic patients. All 3 spastic paretic patients had kinematic deviations and abnormal EMG recruitment profiles during the premedication or placebo sessions. With clonidine therapy one patient demonstrated a marked improvement in locomotor function. This patient progressed from non-ambulation to limited independent ambulation as the extent of coactivation in antogonist muscles decreased. The other 2 paretics who presented limited spasticity showed minimal changes while on clonidine. In the paraplegic patients, clonidine did not elicit locomotor activity, although there were marked reductions in stretch reactions and clonus during assisted locomotion. They remained incapable of locomotion, either during the control period or during the clonidine therapy. These results indicate that clonidine may be a potentially useful medication for both locomotion and certain manifestations of spasticity in SCI patients but further investigation is warranted.
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Kawashima, Noritaka, Daichi Nozaki, Masaki O. Abe y Kimitaka Nakazawa. "Shaping Appropriate Locomotive Motor Output Through Interlimb Neural Pathway Within Spinal Cord in Humans". Journal of Neurophysiology 99, n.º 6 (junio de 2008): 2946–55. http://dx.doi.org/10.1152/jn.00020.2008.
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Direct evidence supporting the contribution of upper limb motion on the generation of locomotive motor output in humans is still limited. Here, we aimed to examine the effect of upper limb motion on locomotor-like muscle activities in the lower limb in persons with spinal cord injury (SCI). By imposing passive locomotion-like leg movements, all cervical incomplete ( n = 7) and thoracic complete SCI subjects ( n = 5) exhibited locomotor-like muscle activity in their paralyzed soleus muscles. Upper limb movements in thoracic complete SCI subjects did not affect the electromyographic (EMG) pattern of the muscle activities. This is quite natural since neural connections in the spinal cord between regions controlling upper and lower limbs were completely lost in these subjects. On the other hand, in cervical incomplete SCI subjects, in whom such neural connections were at least partially preserved, the locomotor-like muscle activity was significantly affected by passively imposed upper limb movements. Specifically, the upper limb movements generally increased the soleus EMG activity during the backward swing phase, which corresponds to the stance phase in normal gait. Although some subjects showed a reduction of the EMG magnitude when arm motion was imposed, this was still consistent with locomotor-like motor output because the reduction of the EMG occurred during the forward swing phase corresponding to the swing phase. The present results indicate that the neural signal induced by the upper limb movements contributes not merely to enhance but also to shape the lower limb locomotive motor output, possibly through interlimb neural pathways. Such neural interaction between upper and lower limb motions could be an underlying neural mechanism of human bipedal locomotion.
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Knikou, Maria. "Plasticity of Corticospinal Neural Control after Locomotor Training in Human Spinal Cord Injury". Neural Plasticity 2012 (2012): 1–13. http://dx.doi.org/10.1155/2012/254948.
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Spinal lesions substantially impair ambulation, occur generally in young and otherwise healthy individuals, and result in devastating effects on quality of life. Restoration of locomotion after damage to the spinal cord is challenging because axons of the damaged neurons do not regenerate spontaneously. Body-weight-supported treadmill training (BWSTT) is a therapeutic approach in which a person with a spinal cord injury (SCI) steps on a motorized treadmill while some body weight is removed through an upper body harness. BWSTT improves temporal gait parameters, muscle activation patterns, and clinical outcome measures in persons with SCI. These changes are likely the result of reorganization that occurs simultaneously in supraspinal and spinal cord neural circuits. This paper will focus on the cortical control of human locomotion and motor output, spinal reflex circuits, and spinal interneuronal circuits and how corticospinal control is reorganized after locomotor training in people with SCI. Based on neurophysiological studies, it is apparent that corticospinal plasticity is involved in restoration of locomotion after training. However, the neural mechanisms underlying restoration of lost voluntary motor function are not well understood and translational neuroscience research is needed so patient-orientated rehabilitation protocols to be developed.
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Hurteau, Marie-France, Yann Thibaudier, Charline Dambreville, Corinne Desaulniers y Alain Frigon. "Effect of stimulating the lumbar skin caudal to a complete spinal cord injury on hindlimb locomotion". Journal of Neurophysiology 113, n.º 2 (15 de enero de 2015): 669–76. http://dx.doi.org/10.1152/jn.00739.2014.
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Sensory feedback is a potent modulator of the locomotor pattern generated by spinal networks. The purpose of this study was to assess the effect of cutaneous inputs from the back on the spinal-generated locomotor pattern. The spinal cord of six adult cats was transected at low thoracic levels. Cats were then trained to recover hindlimb locomotion. During experiments, the skin overlying lumbar vertebrae L2 to L7 was mechanically stimulated by a small calibrated clip or by manual pinching. Trials without and with cutaneous stimulation were performed at a treadmill speed of 0.4 m/s. Although manually pinching the skin completely stopped hindlimb locomotion and abolished weight support, cutaneous stimulation with the calibrated clip produced smaller effects. Specifically, more focalized cutaneous stimulation with the clip reduced flexor and extensor muscle activity and led to a more caudal positioning of the paw at contact and liftoff. Moreover, cutaneous stimulation with the clip led to a greater number of steps with improper nonplantigrade paw placements at contact and paw drag at the stance-to-swing transition. The most consistent effects on the hindlimb locomotor pattern were observed with cutaneous stimulation at midlumbar levels, from L3 to L5. The results indicate that cutaneous stimulation of the skin modulates the excitability of spinal circuits involved in generating locomotion and weight support, particularly at spinal segments thought to be critical for rhythm generation.
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Martinez, Marina, Hugo Delivet-Mongrain, Hugues Leblond y Serge Rossignol. "Recovery of hindlimb locomotion after incomplete spinal cord injury in the cat involves spontaneous compensatory changes within the spinal locomotor circuitry". Journal of Neurophysiology 106, n.º 4 (octubre de 2011): 1969–84. http://dx.doi.org/10.1152/jn.00368.2011.
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After incomplete spinal cord injury (SCI), compensatory changes occur throughout the whole neuraxis, including the spinal cord below the lesion, as suggested by previous experiments using a dual SCI paradigm. Indeed, cats submitted to a lateral spinal hemisection at T10-T11 and trained on a treadmill for 3–14 wk re-expressed bilateral hindlimb locomotion as soon as 24 h after spinalization, a process that normally takes 2–3 wk when a complete spinalization is performed without a prior hemisection. In this study, we wanted to ascertain whether similar effects could occur spontaneously without training between the two SCIs and within a short period of 3 wk in 11 cats. One day after the complete spinalization, 9 of the 11 cats were able to re-express hindlimb locomotion either bilaterally ( n = 6) or unilaterally on the side of the previous hemisection ( n = 3). In these 9 cats, the hindlimb on the side of the previous hemisection (left hindlimb) performed better than the right side in contrast to that observed during the hemispinal period itself. Cats re-expressing the best bilateral hindlimb locomotion after spinalization had the largest initial hemilesion and the most prominent locomotor deficits after this first SCI. These results provide evidence that 1) marked reorganization of the spinal locomotor circuitry can occur without specific locomotor training and within a short period of 3 wk; 2) the spinal cord can reorganize in a more or less symmetrical way; and 3) the ability to walk after spinalization depends on the degree of deficits and adaptation observed in the hemispinal period.
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Alluin, Olivier, Hugo Delivet-Mongrain y Serge Rossignol. "Inducing hindlimb locomotor recovery in adult rat after complete thoracic spinal cord section using repeated treadmill training with perineal stimulation only". Journal of Neurophysiology 114, n.º 3 (septiembre de 2015): 1931–46. http://dx.doi.org/10.1152/jn.00416.2015.
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Although a complete thoracic spinal cord section in various mammals induces paralysis of voluntary movements, the spinal lumbosacral circuitry below the lesion retains its ability to generate hindlimb locomotion. This important capacity may contribute to the overall locomotor recovery after partial spinal cord injury (SCI). In rats, it is usually triggered by pharmacological and/or electrical stimulation of the cord while a robot sustains the animals in an upright posture. In the present study we daily trained a group of adult spinal (T7) rats to walk with the hindlimbs for 10 wk (10 min/day for 5 days/wk), using only perineal stimulation. Kinematic analysis and terminal electromyographic recordings revealed a strong effect of training on the reexpression of hindlimb locomotion. Indeed, trained animals gradually improved their locomotion while untrained animals worsened throughout the post-SCI period. Kinematic parameters such as averaged and instant swing phase velocity, step cycle variability, foot drag duration, off period duration, and relationship between the swing features returned to normal values only in trained animals. The present results clearly demonstrate that treadmill training alone, in a normal horizontal posture, elicited by noninvasive perineal stimulation is sufficient to induce a persistent hindlimb locomotor recovery without the need for more complex strategies. This provides a baseline level that should be clearly surpassed if additional locomotor-enabling procedures are added. Moreover, it has a clinical value since intrinsic spinal reorganization induced by training should contribute to improve locomotor recovery together with afferent feedback and supraspinal modifications in patients with incomplete SCI.
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Dyck, Jason, Guillermo M. Lanuza y Simon Gosgnach. "Functional characterization of dI6 interneurons in the neonatal mouse spinal cord". Journal of Neurophysiology 107, n.º 12 (15 de junio de 2012): 3256–66. http://dx.doi.org/10.1152/jn.01132.2011.
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Our understanding of the neural control of locomotion has been greatly enhanced by the ability to identify and manipulate genetically defined populations of interneurons that comprise the locomotor central pattern generator (CPG). To date, the dI6 interneurons are one of the few populations that settle in the ventral region of the postnatal spinal cord that have not been investigated. In the present study, we utilized a novel transgenic mouse line to electrophysiologically characterize dI6 interneurons located close to the central canal and study their function during fictive locomotion. The majority of dI6 cells investigated were found to be rhythmically active during fictive locomotion and could be divided into two electrophysiologically distinct populations of interneurons. The first population fired rhythmic trains of action potentials that were loosely coupled to ventral root output and contained several intrinsic membrane properties of rhythm-generating neurons, raising the possibility that these cells may be involved in the generation of rhythmic activity in the locomotor CPG. The second population fired rhythmic trains of action potentials that were tightly coupled to ventral root output and lacked intrinsic oscillatory mechanisms, indicating that these neurons may be driven by a rhythm-generating network. Together these results indicate that dI6 neurons comprise an important component of the locomotor CPG that participate in multiple facets of motor behavior.
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Viana Di Prisco, Gonzalo y Simon Alford. "Quantitative Investigation of Calcium Signals for Locomotor Pattern Generation in the Lamprey Spinal Cord". Journal of Neurophysiology 92, n.º 3 (septiembre de 2004): 1796–806. http://dx.doi.org/10.1152/jn.00138.2004.
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Locomotor pattern generation requires the network coordination of spinal ventral horn neurons acting in concert with the oscillatory properties of individual neurons. In the spinal cord, N-methyl-d-aspartate (NMDA) activates neuronal oscillators that are believed to rely on Ca2+ entry to the cytosol through voltage-operated Ca2+ channels and synaptically activated NMDA receptors. Ca2+ signaling in lamprey ventral horn neurons thus plays a determinant role in the regulation of the intrinsic membrane properties and network synaptic interaction generating spinal locomotor neural pattern activity. We have characterized aspects of this signaling quantitatively for the first time. Resting Ca2+ concentrations were between 87 and 120 nM. Ca2+ concentration measured during fictive locomotion increased from soma to distal dendrites [from 208 ± 27 (SE) nM in the soma to 335 ± 41 nM in the proximal dendrites to 457 ± 68 nM in the distal dendrites]. We sought to determine the temporal and spatial properties of Ca2+ oscillations, imaged with Ca2+-sensitive dyes and correlated with fluctuations in membrane potential, during lamprey fictive locomotion. The Ca2+ signals recorded in the dendrites showed a great deal of spatial heterogeneity. Rapid changes in Ca2+-induced fluorescence coincided with action potentials, which initiated significant Ca2+ transients distributed throughout the neurons. Ca2+ entry to the cytosol coincided with the depolarizing phase of the locomotor rhythm. During fictive locomotion, larger Ca2+ oscillations were recorded in dendrites compared with somata in motoneurons and premotor interneurons. Ca2+ fluctuations were barely detected with dyes of lower affinity providing alternative empirical evidence that Ca2+ responses are limited to hundreds of nanomolars during fictive locomotion.
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Martinez, Marina, Hugo Delivet-Mongrain, Hugues Leblond y Serge Rossignol. "Incomplete spinal cord injury promotes durable functional changes within the spinal locomotor circuitry". Journal of Neurophysiology 108, n.º 1 (1 de julio de 2012): 124–34. http://dx.doi.org/10.1152/jn.00073.2012.
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While walking in a straight path, changes in speed result mainly from adjustments in the duration of the stance phase while the swing phase remains relatively invariant, a basic feature of the spinal central pattern generator (CPG). To produce a broad range of locomotor behaviors, the CPG has to integrate modulatory inputs from the brain and the periphery and alter these swing/stance characteristics. In the present work we raise the issue as to whether the CPG can adapt or reorganize in response to a chronic change of supraspinal inputs, as is the case after spinal cord injury (SCI). Kinematic data obtained from six adult cats walking at different treadmill speeds were collected to calculate the cycle and subphase duration at different stages after a first spinal hemisection at T10 and after a subsequent complete SCI at T13 respectively aimed at disconnecting unilaterally and then totally the spinal cord from its supraspinal inputs. The results show, first, that the neural control of locomotion is flexible and responsive to a partial or total loss of supraspinal inputs. Second, we demonstrate that a hemisection induces durable plastic changes within the spinal locomotor circuitry below the lesion. In addition, this study gives new insights into the organization of the spinal CPG for locomotion such that phases of the step cycle (swing, stance) can be independently regulated for adapting to speed and also that the CPGs controlling the left and right hindlimbs can, up to a point, be regulated independently.
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Manuel, Marin, Yaqing Li, Sherif M. ElBasiouny, Katie Murray, Anna Griener, C. J. Heckman y David J. Bennett. "NMDA induces persistent inward and outward currents that cause rhythmic bursting in adult rodent motoneurons". Journal of Neurophysiology 108, n.º 11 (1 de diciembre de 2012): 2991–98. http://dx.doi.org/10.1152/jn.00518.2012.
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N-methyl-d-aspartate (NMDA) receptors are of critical importance for locomotion in the developing neonatal spinal cord in rats and mice. However, due to profound changes in the expression of NMDA receptors in development between the neonatal stages and adulthood, it is unclear whether NMDA receptors are still an important component of locomotion in the adult rodent spinal cord. To shed light on this issue, we have taken advantage of recently developed preparations allowing the intracellular recording of adult motoneurons that control the tail in the sacrocaudal spinal cord of adult mice and rats. We show that in the adult sacrocaudal spinal cord, NMDA induces rhythmic activity recorded on the ventral roots, often coordinated from left to right, as in swimming motions with the tail (fictive locomotion). The adult motoneurons themselves are intrinsically sensitive to NMDA application. That is, when motoneurons are synaptically isolated with TTX, NMDA still causes spontaneous bursts of rhythmic activity, depending on the membrane potential. We show that these bursts in motoneurons depend on an NMDA-mediated persistent inward current and are terminated by the progressive activation of a persistent outward current. These results indicate that motoneurons, along with the central pattern generator, can actively participate in the production of swimminglike locomotor activity in adult rodents.
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Sławińska, Urszula, Henryk Majczyński, Anna Kwaśniewska, Krzysztof Miazga, Anna M. Cabaj, Marek Bekisz, Larry M. Jordan y Małgorzata Zawadzka. "Unusual Quadrupedal Locomotion in Rat during Recovery from Lumbar Spinal Blockade of 5-HT7 Receptors". International Journal of Molecular Sciences 22, n.º 11 (2 de junio de 2021): 6007. http://dx.doi.org/10.3390/ijms22116007.
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Coordination of four-limb movements during quadrupedal locomotion is controlled by supraspinal monoaminergic descending pathways, among which serotoninergic ones play a crucial role. Here we investigated the locomotor pattern during recovery from blockade of 5-HT7 or 5-HT2A receptors after intrathecal application of SB269970 or cyproheptadine in adult rats with chronic intrathecal cannula implanted in the lumbar spinal cord. The interlimb coordination was investigated based on electromyographic activity recorded from selected fore- and hindlimb muscles during rat locomotion on a treadmill. In the time of recovery after hindlimb transient paralysis, we noticed a presence of an unusual pattern of quadrupedal locomotion characterized by a doubling of forelimb stepping in relation to unaffected hindlimb stepping (2FL-1HL) after blockade of 5-HT7 receptors but not after blockade of 5-HT2A receptors. The 2FL-1HL pattern, although transient, was observed as a stable form of fore-hindlimb coupling during quadrupedal locomotion. We suggest that modulation of the 5-HT7 receptors on interneurons located in lamina VII with ascending projections to the forelimb spinal network can be responsible for the 2FL-1HL locomotor pattern. In support, our immunohistochemical analysis of the lumbar spinal cord demonstrated the presence of the 5-HT7 immunoreactive cells in the lamina VII, which were rarely 5-HT2A immunoreactive.
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van Hedel, Hubertus J. A. y Volker Dietz. "Rehabilitation of locomotion after spinal cord injury". Restorative Neurology and Neuroscience 28, n.º 1 (2010): 123–34. http://dx.doi.org/10.3233/rnn-2010-0508.
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Dietz, V. "Locomotion in Patients with Spinal Cord Injury". Critical Reviews in Physical and Rehabilitation Medicine 12, n.º 2 (2000): 163–90. http://dx.doi.org/10.1615/critrevphysrehabilmed.v12.i2.60.
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Dietz, Volker, Markus Wirz y Lars Jensen. "Locomotion in Patients With Spinal Cord Injuries". Physical Therapy 77, n.º 5 (1 de mayo de 1997): 508–16. http://dx.doi.org/10.1093/ptj/77.5.508.
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de Leon, Ray D., Roland R. Roy y V. Reggie Edgerton. "Is the Recovery of Stepping Following Spinal Cord Injury Mediated by Modifying Existing Neural Pathways or by Generating New Pathways? A Perspective". Physical Therapy 81, n.º 12 (1 de diciembre de 2001): 1904–11. http://dx.doi.org/10.1093/ptj/81.12.1904.
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Abstract The recovery of stepping ability following a spinal cord injury may be achieved by restoring anatomical connectivity within the spinal cord. However, studies of locomotor recovery in animals with complete spinal cord transection suggest that the adult mammalian spinal cord can acquire the ability to generate stepping after all descending input is eliminated and in the absence of neuronal regeneration. Moreover, rehabilitative gait training has been shown to play a crucial role in teaching existing spinal pathways to generate locomotion and appropriately respond to sensory feedback. This brief review presents evidence that neural networks in the mammalian spinal cord can be modulated pharmacologically and/or with task-specific behavioral training to generate weight-bearing stepping after a spinal injury. Further, the role that spinal learning can play in the management of humans with spinal cord injury is discussed in relation to interventions that are designed primarily to enhance neuronal regeneration.
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Giroux, Nathalie, Connie Chau, Hugues Barbeau, Tomás A. Reader y Serge Rossignol. "Effects of Intrathecal Glutamatergic Drugs on Locomotion. II. NMDA and AP-5 in Intact and Late Spinal Cats". Journal of Neurophysiology 90, n.º 2 (agosto de 2003): 1027–45. http://dx.doi.org/10.1152/jn.00758.2002.
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In a previous article, we have shown that, in cats, intrathecal injections of N-methyl-d-aspartate (NMDA) in the first few days after spinalization at T13 do not induce locomotion as in many other spinal preparations. This is in contrast to alpha-2 noradrenergic receptor stimulation, which can trigger locomotion at this early stage. However, it is known that spinal cats do recover spontaneous locomotion in the absence of descending noradrenergic pathways and that the spinal pattern generator must then depend on other neurotransmitters still present in the cord such as excitatory amino acids. In the present paper, therefore we look at the effects of intrathecal NMDA, a glutamatergic agonist, and 2-amino-5-phosphonovaleric acid (AP-5), an NMDA receptor blocker, in both intact and late spinal cats. Low doses of NMDA had no major effect on the locomotor pattern in both intact and late spinal cats. Larger doses of NMDA in the chronic spinal cat initially produced an increase in the general excitability followed by more regular locomotion. AP-5 in intact cats caused a decrease in the amplitude of the flexion reflex and induced a bilateral foot drag as well as some decrease in weight support but it did not prevent locomotion. However, in late spinal cats, the same dose of AP-5 blocked locomotion completely. These results indicate that NMDA receptors may be critical for the spontaneous expression of spinal locomotion. It is proposed that the basic locomotor rhythmicity in cats is NMDA-dependent and that normally this glutamatergic mechanism is modulated by other neurotransmitters, such as 5-HT and NA.
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Delivet-Mongrain, Hugo, Melvin Dea, Jean-Pierre Gossard y Serge Rossignol. "Recovery of locomotion in cats after severe contusion of the low thoracic spinal cord". Journal of Neurophysiology 123, n.º 4 (1 de abril de 2020): 1504–25. http://dx.doi.org/10.1152/jn.00498.2019.
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The recovery of quadrupedal treadmill locomotion after a large bilateral contusion at the low thoracic T10 spinal level and the ability to negotiate obstacles were studied for 5 wk in 16 cats. Ten cats were further completely spinalized at T13 and were found to walk with the hindlimbs within 24–72 h. We conclude that the extent of locomotor recovery after large spinal contusions hinges both on remnant supraspinal pathways and on a spinal pattern generator.
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Zhong, Guisheng, Manuel Díaz-Ríos y Ronald M. Harris-Warrick. "Serotonin Modulates the Properties of Ascending Commissural Interneurons in the Neonatal Mouse Spinal Cord". Journal of Neurophysiology 95, n.º 3 (marzo de 2006): 1545–55. http://dx.doi.org/10.1152/jn.01103.2005.
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The interneuron populations that constitute the central pattern generator (CPG) for locomotion in the mammalian spinal cord are not well understood. We studied the properties of a set of commissural interneurons whose axons cross and ascend in the contralateral cord (aCINs) in the neonatal mouse. During N-methyl-d-aspartate (NMDA) and 5-HT–induced fictive locomotion, a majority of lumbar (L2) aCINs examined were rhythmically active; most of them fired in phase with the ipsilateral motoneuron pool, but some fired in phase with contralateral motoneurons. 5-HT plays a critical role in enabling the locomotor CPG to function. We found that 5-HT increased the excitability of aCINs by depolarizing the membrane potential, reducing the postspike afterhyperpolarization amplitude, broadening the action potential, and decreasing the action potential threshold. Serotonin had no significant effect on the input resistance and sag amplitude of aCINs. These results support the hypothesis that aCINs play important roles in coordinating left–right movements during fictive locomotion and thus may be component neurons in the locomotor CPG in neonatal mice.
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Dambreville, Charline, Audrey Labarre, Yann Thibaudier, Marie-France Hurteau y Alain Frigon. "The spinal control of locomotion and step-to-step variability in left-right symmetry from slow to moderate speeds". Journal of Neurophysiology 114, n.º 2 (agosto de 2015): 1119–28. http://dx.doi.org/10.1152/jn.00419.2015.
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When speed changes during locomotion, both temporal and spatial parameters of the pattern must adjust. Moreover, at slow speeds the step-to-step pattern becomes increasingly variable. The objectives of the present study were to assess if the spinal locomotor network adjusts both temporal and spatial parameters from slow to moderate stepping speeds and to determine if it contributes to step-to-step variability in left-right symmetry observed at slow speeds. To determine the role of the spinal locomotor network, the spinal cord of 6 adult cats was transected (spinalized) at low thoracic levels and the cats were trained to recover hindlimb locomotion. Cats were implanted with electrodes to chronically record electromyography (EMG) in several hindlimb muscles. Experiments began once a stable hindlimb locomotor pattern emerged. During experiments, EMG and bilateral video recordings were made during treadmill locomotion from 0.1 to 0.4 m/s in 0.05 m/s increments. Cycle and stance durations significantly decreased with increasing speed, whereas swing duration remained unaffected. Extensor burst duration significantly decreased with increasing speed, whereas sartorius burst duration remained unchanged. Stride length, step length, and the relative distance of the paw at stance offset significantly increased with increasing speed, whereas the relative distance at stance onset and both the temporal and spatial phasing between hindlimbs were unaffected. Both temporal and spatial step-to-step left-right asymmetry decreased with increasing speed. Therefore, the spinal cord is capable of adjusting both temporal and spatial parameters during treadmill locomotion, and it is responsible, at least in part, for the step-to-step variability in left-right symmetry observed at slow speeds.
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Barthe, J. Y. y S. Grillner. "Neurotensin-induced modulation of spinal neurons and fictive locomotion in the lamprey". Journal of Neurophysiology 73, n.º 3 (1 de marzo de 1995): 1308–12. http://dx.doi.org/10.1152/jn.1995.73.3.1308.
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1. Neurotensin containing interneurons are present in the spinal cord of both mammalian and nonmammalian vertebrates, but as yet little is known about their functional role. In this study we examine the effect of neurotensin on spinal cells and on the central pattern generator for locomotion in the lamprey spinal cord. 2. Bath application of neurotensin (10(-8) to 10(-6) M) slowed down the fictive locomotor activity induced by the glutamate agonist N-methyl-D-aspartate in the isolated spinal cord. The duration of the bursts of activity in the ventral roots increased in proportion to the increase of the locomotor cycle duration. 3. Intracellular recordings from grey matter neurons and intraspinal stretch receptors neurons showed that neurotensin induced a depolarization [4.4 +/- 0.5 (SE) mV, n = 19]. This depolarization could still be obtained after a blockade of voltage-sensitive sodium channels with tetrodotoxin (1.5 +/- 0.5 mV; n = 6), and after removal of calcium (2.8 +/- 0.4 mV; n = 5). Moreover no consistent change occurred in the fast and slow phase of the afterhyperpolarization (AHP) both of which are carried by potassium currents.
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Schnerwitzki, Danny, Sharn Perry, Anna Ivanova, Fabio V. Caixeta, Paul Cramer, Sven Günther, Kathrin Weber et al. "Neuron-specific inactivation of Wt1 alters locomotion in mice and changes interneuron composition in the spinal cord". Life Science Alliance 1, n.º 4 (agosto de 2018): e201800106. http://dx.doi.org/10.26508/lsa.201800106.
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Locomotion is coordinated by neuronal circuits of the spinal cord. Recently, dI6 neurons were shown to participate in the control of locomotion. A subpopulation of dI6 neurons expresses the Wilms tumor suppressor gene Wt1. However, the function of Wt1 in these cells is not understood. Here, we aimed to identify behavioral changes and cellular alterations in the spinal cord associated with Wt1 deletion. Locomotion analyses of mice with neuron-specific Wt1 deletion revealed a slower walk with a decreased stride frequency and an increased stride length. These mice showed changes in their fore-/hindlimb coordination, which were accompanied by a loss of contralateral projections in the spinal cord. Neonates with Wt1 deletion displayed an increase in uncoordinated hindlimb movements and their motor neuron output was arrhythmic with a decreased frequency. The population size of dI6, V0, and V2a neurons in the developing spinal cord of conditional Wt1 mutants was significantly altered. These results show that the development of particular dI6 neurons depends on Wt1 expression and that loss of Wt1 is associated with alterations in locomotion.
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Rossignol, Serge. "Plasticity of connections underlying locomotor recovery after central and/or peripheral lesions in the adult mammals". Philosophical Transactions of the Royal Society B: Biological Sciences 361, n.º 1473 (4 de agosto de 2006): 1647–71. http://dx.doi.org/10.1098/rstb.2006.1889.
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This review discusses some aspects of plasticity of connections after spinal injury in adult animal models as a basis for functional recovery of locomotion. After reviewing some pitfalls that must be avoided when claiming functional recovery and the importance of a conceptual framework for the control of locomotion, locomotor recovery after spinal lesions, mainly in cats, is summarized. It is concluded that recovery is partly due to plastic changes within the existing spinal locomotor networks. Locomotor training appears to change the excitability of simple reflex pathways as well as more complex circuitry. The spinal cord possesses an intrinsic capacity to adapt to lesions of central tracts or peripheral nerves but, as a rule, adaptation to lesions entails changes at both spinal and supraspinal levels. A brief summary of the spinal capacity of the rat, mouse and human to express spinal locomotor patterns is given, indicating that the concepts derived mainly from work in the cat extend to other adult mammals. It is hoped that some of the issues presented will help to evaluate how plasticity of existing connections may combine with and potentiate treatments designed to promote regeneration to optimize remaining motor functions.
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Przysada, Grzegorz, Justyna Wyszyóska, Mariusz Drużbicki, Anna Pajda, Justyna Leszczak, Justyna Podgórska-Bednarz y Krzysztof Kołodziej. "Selected factors affecting the efficiency of wheelchair mobility in individuals with spinal cord injury". Advances in Rehabilitation 30, n.º 2 (1 de junio de 2016): 5–15. http://dx.doi.org/10.1515/rehab-2015-0039.
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Abstract Introduction: Locomotion efficiency levels in individuals with spinal cord injury deal cord injury depend upon the level of spinal cord injury. Rehabilitation of people with spinal cord injury aims to prepare them to function in society in the best possible manner. One of the significant tasks of rehabilitation is to develop the skill of moving in a wheelchair, which becomes the only means of locomotion for most people. The aim of the study was to assess the influence of selected factors such as age, sex, time from the occurrence of the injury, the level of spinal cord injury, participation in Active Rehabilitation camps and the level of physical activity on the efficiency of locomotion in a wheelchair in individuals with spinal cord injury. Material and methods: The study included 55 patients after a complete spinal cord injury (39 males and 16 females using manual wheelchairs), aged 19 to 59. The level of spinal cord injury was assessed on the basis of a subjective classification of ASIA. The efficiency of wheelchair mobility was evaluated using the wheelchair manoeuvring technique test by Tasiemski (evaluation of performance of 14 tasks taking into account architectural barriers). Results: The majority of respondents (n = 28) obtained medium level of the efficiency, 16 participants scored low, while 11 individuals scored high. The highest score which women obtained was the medium level. It was men only (n = 11) who scored high. There was no statistically significant correlation between the efficiency of wheel-chair mobility and the level of spinal cord injury. It was observed that younger individuals and those practising sport daily achieved the best test results. Conclusions: Participants’ age affected their locomotion efficiency in a wheelchair. Females demonstrated lower levels of efficiency wheelchair mobility than their male counterparts. Regular physical activity affected the participants’ efficiency of wheeled mobility significantly.
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Winchester, Patricia, Roderick McColl, Ross Querry, Nathan Foreman, James Mosby, Keith Tansey y Jon Williamson. "Changes in Supraspinal Activation Patterns following Robotic Locomotor Therapy in Motor-Incomplete Spinal Cord Injury". Neurorehabilitation and Neural Repair 19, n.º 4 (diciembre de 2005): 313–24. http://dx.doi.org/10.1177/1545968305281515.
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Objectives. Body weight-supported treadmill training (BWSTT) is a task-specific rehabilitation strategy that enhances functional locomotion in patients following spinal cord injury (SCI). Supraspinal centers may play an important role in the recovery of over-ground locomotor function in patients with motor-incomplete SCI. The purpose of this study was to evaluate the potential for supraspinal reorganization associated with 12 weeks of robotic BWSTT using functional magnetic resonance imaging (fMRI). Methods. Four men with motor-incomplete SCI participated in this study. Time since onset ranged from 14 weeks to 48 months post-SCI injury. All subjects were trained with BWSTT 3 times weekly for 12 weeks. This training was preceded and followed by fMRI study of supraspinal activity during a movement task. Testing of locomotor disability included the Walking Index for Spinal Cord Injury (WISCI II) and over-ground gait speed. Results. All subjects demonstrated some degree of change in the blood-oxygen-level-dependent (BOLD) signal following BWSTT. fMRI results demonstrated greater activation in sensorimotor cortical regions (S1, S2) and cerebellar regions following BWSTT. Conclusions. Intensive task-specific rehabilitative training, such as robotic BWSTT, can promote supraspinal plasticity in the motor centers known to be involved in locomotion. Furthermore, improvement in over-ground locomotion is accompanied by an increased activation of the cerebellum.
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Tresch, Matthew C. y Ole Kiehn. "Coding of Locomotor Phase in Populations of Neurons in Rostral and Caudal Segments of the Neonatal Rat Lumbar Spinal Cord". Journal of Neurophysiology 82, n.º 6 (1 de diciembre de 1999): 3563–74. http://dx.doi.org/10.1152/jn.1999.82.6.3563.
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Several experiments have demonstrated that rostral segments of the vertebrate lumbar spinal cord produce a rhythmic motor output more readily and of better quality than caudal segments. Here we examine how this rostrocaudal gradient of rhythmogenic capability is reflected in the spike activity of neurons in the rostral (L2) and caudal (L5) lumbar spinal cord of the neonatal rat. The spike activity of interneurons in the ventromedial cord, a region necessary for the production of locomotion, was recorded intracellularly with patch electrodes and extracellularly with tetrodes during pharmacologically induced locomotion. Both L2 and L5 neurons tended to be active in phase with their homologous ventral root. L5 neurons, however, had a wider distribution of their preferred phases of activity throughout the locomotor cycle than L2 neurons. The strength of modulation of the activity of individual L2 neurons was also larger than that of L5 neurons. These differences resulted in a stronger rhythmic signal from the L2 neuronal population than from the L5 population. These results demonstrate that the rhythmogenic capability of each spinal segment was reflected in the activity of interneurons located in the same segment. In addition to paralleling the rostrocaudal gradient of rhythmogenic capability, these results further suggest a colocalization of motoneurons and their associated interneurons involved in the production of locomotion.
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Gad, Parag, Igor Lavrov, Prithvi Shah, Hui Zhong, Roland R. Roy, V. Reggie Edgerton y Yury Gerasimenko. "Neuromodulation of motor-evoked potentials during stepping in spinal rats". Journal of Neurophysiology 110, n.º 6 (15 de septiembre de 2013): 1311–22. http://dx.doi.org/10.1152/jn.00169.2013.
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The rat spinal cord isolated from supraspinal control via a complete low- to midthoracic spinal cord transection produces locomotor-like patterns in the hindlimbs when facilitated pharmacologically and/or by epidural electrical stimulation. To evaluate the role of epidural electrical stimulation in enabling motor control (eEmc) for locomotion and posture, we recorded potentials evoked by epidural spinal cord stimulation in selected hindlimb muscles during stepping and standing in adult spinal rats. We hypothesized that the temporal details of the phase-dependent modulation of these evoked potentials in selected hindlimb muscles while performing a motor task in the unanesthetized state would be predictive of the potential of the spinal circuitries to generate stepping. To test this hypothesis, we characterized soleus and tibialis anterior (TA) muscle responses as middle response (MR; 4–6 ms) or late responses (LRs; >7 ms) during stepping with eEmc. We then compared these responses to the stepping parameters with and without a serotoninergic agonist (quipazine) or a glycinergic blocker (strychnine). Quipazine inhibited the MRs induced by eEmc during nonweight-bearing standing but facilitated locomotion and increased the amplitude and number of LRs induced by eEmc during stepping. Strychnine facilitated stepping and reorganized the LRs pattern in the soleus. The LRs in the TA remained relatively stable at varying loads and speeds during locomotion, whereas the LRs in the soleus were strongly modulated by both of these variables. These data suggest that LRs facilitated electrically and/or pharmacologically are not time-locked to the stimulation pulse but are highly correlated to the stepping patterns of spinal rats.
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de Leon, R. D., H. Tamaki, J. A. Hodgson, R. R. Roy y V. R. Edgerton. "Hindlimb Locomotor and Postural Training Modulates Glycinergic Inhibition in the Spinal Cord of the Adult Spinal Cat". Journal of Neurophysiology 82, n.º 1 (1 de julio de 1999): 359–69. http://dx.doi.org/10.1152/jn.1999.82.1.359.
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Adult spinal cats were trained initially to perform either bipedal hindlimb locomotion on a treadmill or full-weight-bearing hindlimb standing. After 12 wk of training, stepping ability was tested before and after the administration (intraperitoneal) of the glycinergic receptor antagonist, strychnine. Spinal cats that were trained to stand after spinalization had poor locomotor ability as reported previously, but strychnine administration induced full-weight-bearing stepping in their hindlimbs within 30–45 min. In the cats that were trained to step after spinalization, full-weight-bearing stepping occurred and was unaffected by strychnine. Each cat then was retrained to perform the other task for 12 wk and locomotor ability was retested. The spinal cats that were trained initially to stand recovered the ability to step after they received 12 wk of treadmill training and strychnine was no longer effective in facilitating their locomotion. Locomotor ability declined in the spinal cats that were retrained to stand and strychnine restored the ability to step to the levels that were acquired after the step-training period. Based on analyses of hindlimb muscle electromyographic activity patterns and kinematic characteristics, strychnine improved the consistency of the stepping and enhanced the execution of hindlimb flexion during full-weight-bearing step cycles in the spinal cats when they were trained to stand but not when they were trained to step. The present findings provide evidence that 1) the neural circuits that generate full-weight-bearing hindlimb stepping are present in the spinal cord of chronic spinal cats that can and cannot step; however, the ability of these circuits to interpret sensory input to drive stepping is mediated at least in part by glycinergic inhibition; and 2) these spinal circuits adapt to the specific motor task imposed, and that these adaptations may include modifications in the glycinergic pathways that provide inhibition.