151
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Gerasimenko Y, Roy RR, Edgerton VR. Epidural stimulation: comparison of the spinal circuits that generate and control locomotion in rats, cats and humans. Exp Neurol 2008; 209:417-25. [PMID: 17850791 PMCID: PMC2288525 DOI: 10.1016/j.expneurol.2007.07.015] [Citation(s) in RCA: 132] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2007] [Accepted: 07/20/2007] [Indexed: 11/24/2022]
Abstract
Although epidural stimulation is a technique that has been used for a number of years to treat individuals with a spinal cord injury, the intended outcome has been to suppress plasticity and pain. Over the last decade considerable progress has been made in realizing the potential of epidural stimulation to facilitate posture and locomotion in subjects with severe spinal cord injury who lack the ability to stand or to step. This progress has resulted primarily from experiments with mice, rats and cats having a complete spinal cord transection at a mid-thoracic level and in humans with a complete spinal cord injury. This review describes some of these experiments performed after the complete elimination of supraspinal input that demonstrates that the circuitry necessary to control remarkably normal locomotion appears to reside within the lumbosacral region of the spinal cord. These experiments, however, also demonstrate the essential role of processing proprioceptive information associated with weight-bearing stepping or standing by the spinal circuitry. For example, relatively simple tonic signals provided to the dorsum of the spinal cord epidurally can result in complex and highly adaptive locomotor patterns. Experiments emphasizing a significant complementary effect of epidural stimulation when combined with pharmacological facilitation, e.g., serotonergic agonists, and/or chronic step training also are described. Finally, a major point emphasized in this review is the striking similarity of the lumbosacral circuitry controlling locomotion in the rat and in the human.
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Affiliation(s)
- Yury Gerasimenko
- Department of Physiological Science, University of California, Los Angeles, Los Angeles, CA 90095
- Pavlov Institute of Physiology, St. Petersburg, 199034, Russia
| | - Roland R. Roy
- Brain Research Institute, University of California, Los Angeles, Los Angeles, CA 90095
| | - V. Reggie Edgerton
- Department of Physiological Science, University of California, Los Angeles, Los Angeles, CA 90095
- Department of Neurobiology, University of California, Los Angeles, Los Angeles, CA 90095
- Brain Research Institute, University of California, Los Angeles, Los Angeles, CA 90095
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152
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Lynskey JV, Belanger A, Jung R. Activity-dependent plasticity in spinal cord injury. JOURNAL OF REHABILITATION RESEARCH AND DEVELOPMENT 2008; 45:229-40. [PMID: 18566941 PMCID: PMC2562625 DOI: 10.1682/jrrd.2007.03.0047] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The adult mammalian central nervous system (CNS) is capable of considerable plasticity, both in health and disease. After spinal neurotrauma, the degrees and extent of neuroplasticity and recovery depend on multiple factors, including the level and extent of injury, postinjury medical and surgical care, and rehabilitative interventions. Rehabilitation strategies focus less on repairing lost connections and more on influencing CNS plasticity for regaining function. Current evidence indicates that strategies for rehabilitation, including passive exercise, active exercise with some voluntary control, and use of neuroprostheses, can enhance sensorimotor recovery after spinal cord injury (SCI) by promoting adaptive structural and functional plasticity while mitigating maladaptive changes at multiple levels of the neuraxis. In this review, we will discuss CNS plasticity that occurs both spontaneously after SCI and in response to rehabilitative therapies.
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Affiliation(s)
- James V. Lynskey
- Center for Adaptive Neural Systems, Ira A. Fulton School of Engineering, Arizona State University, Tempe, AZ
- Department of Physical Therapy, Arizona School of Health Sciences, A.T. Still University, Mesa, AZ
| | - Adam Belanger
- Center for Adaptive Neural Systems, Ira A. Fulton School of Engineering, Arizona State University, Tempe, AZ
- Harrington Department of Bioengineering, Ira A. Fulton School of Engineering, Arizona State University, Tempe, AZ
| | - Ranu Jung
- Center for Adaptive Neural Systems, Ira A. Fulton School of Engineering, Arizona State University, Tempe, AZ
- Harrington Department of Bioengineering, Ira A. Fulton School of Engineering, Arizona State University, Tempe, AZ
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153
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Abstract
A range of passive and active devices are under development or are already in clinical use to partially restore function after spinal cord injury (SCI). Prosthetic devices to promote host tissue regeneration and plasticity and reconnection are under development, comprising bioengineered bridging materials free of cells. Alternatively, artificial electrical stimulation and robotic bridges may be used, which is our focus here. A range of neuroprostheses interfacing either with CNS or peripheral nervous system both above and below the lesion are under investigation and are at different stages of development or translation to the clinic. In addition, there are orthotic and robotic devices which are being developed and tested in the laboratory and clinic that can provide mechanical assistance, training or substitution after SCI. The range of different approaches used draw on many different aspects of our current but limited understanding of neural regeneration and plasticity, and spinal cord function and interactions with the cortex. The best therapeutic practice will ultimately likely depend on combinations of these approaches and technologies and on balancing the combined effects of these on the biological mechanisms and their interactions after injury. An increased understanding of plasticity of brain and spinal cord, and of the behavior of innate modular mechanisms in intact and injured systems, will likely assist in future developments. We review the range of device designs under development and in use, the basic understanding of spinal cord organization and plasticity, the problems and design issues in device interactions with the nervous system, and the possible benefits of active motor devices.
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Affiliation(s)
- Simon F Giszter
- Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania 19129, USA.
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154
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Edgerton VR, Courtine G, Gerasimenko YP, Lavrov I, Ichiyama RM, Fong AJ, Cai LL, Otoshi CK, Tillakaratne NJK, Burdick JW, Roy RR. Training locomotor networks. BRAIN RESEARCH REVIEWS 2008; 57:241-54. [PMID: 18022244 PMCID: PMC2288528 DOI: 10.1016/j.brainresrev.2007.09.002] [Citation(s) in RCA: 219] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 09/10/2007] [Accepted: 09/11/2007] [Indexed: 12/16/2022]
Abstract
For a complete adult spinal rat to regain some weight-bearing stepping capability, it appears that a sequence of specific proprioceptive inputs that are similar, but not identical, from step to step must be generated over repetitive step cycles. Furthermore, these cycles must include the activation of specific neural circuits that are intrinsic to the lumbosacral spinal cord segments. For these sensorimotor pathways to be effective in generating stepping, the spinal circuitry must be modulated to an appropriate excitability level. This level of modulation is sustained from supraspinal input in intact, but not spinal, rats. In a series of experiments with complete spinal rats, we have shown that an appropriate level of excitability of the spinal circuitry can be achieved using widely different means. For example, this modulation level can be acquired pharmacologically, via epidural electrical stimulation over specific lumbosacral spinal cord segments, and/or by use-dependent mechanisms such as step or stand training. Evidence as to how each of these treatments can "tune" the spinal circuitry to a "physiological state" that enables it to respond appropriately to proprioceptive input will be presented. We have found that each of these interventions can enable the proprioceptive input to actually control extensive details that define the dynamics of stepping over a range of speeds, loads, and directions. A series of experiments will be described that illustrate sensory control of stepping and standing after a spinal cord injury and the necessity for the "physiological state" of the spinal circuitry to be modulated within a critical window of excitability for this control to be manifested. The present findings have important consequences not only for our understanding of how the motor pattern for stepping is formed, but also for the design of rehabilitation intervention to restore lumbosacral circuit function in humans following a spinal cord injury.
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Affiliation(s)
- V Reggie Edgerton
- Department of Physiological Science, University of California, Los Angeles, Los Angeles, CA 90095, USA.
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155
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Kubasak MD, Jindrich DL, Zhong H, Takeoka A, McFarland KC, Muñoz-Quiles C, Roy RR, Edgerton VR, Ramón-Cueto A, Phelps PE. OEG implantation and step training enhance hindlimb-stepping ability in adult spinal transected rats. Brain 2008; 131:264-76. [PMID: 18056162 PMCID: PMC2916741 DOI: 10.1093/brain/awm267] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Numerous treatment strategies for spinal cord injury seek to maximize recovery of function and two strategies that show substantial promise are olfactory bulb-derived olfactory ensheathing glia (OEG) transplantation and treadmill step training. In this study we re-examined the issue of the effectiveness of OEG implantation but used objective, quantitative measures of motor performance to test if there is a complementary effect of long-term step training and olfactory bulb-derived OEG implantation. We studied complete mid-thoracic spinal cord transected adult female rats and compared four experimental groups: media-untrained, media-trained, OEG-untrained and OEG-trained. To assess the extent of hindlimb locomotor recovery at 4 and 7 months post-transection we used three quantitative measures of stepping ability: plantar stepping performance until failure, joint movement shape and movement frequency compared to sham controls. OEG transplantation alone significantly increased the number of plantar steps performed at 7 months post-transection, while training alone had no effect at either time point. Only OEG-injected rats plantar placed their hindpaws for more than two steps by the 7-month endpoint of the study. OEG transplantation combined with training resulted in the highest percentage of spinal rats per group that plantar stepped, and was the only group to significantly improve its stepping abilities between the 4- and 7-month evaluations. Additionally, OEG transplantation promoted tissue sparing at the transection site, regeneration of noradrenergic axons and serotonergic axons spanning the injury site. Interestingly, the caudal stump of media- and OEG-injected rats contained a similar density of serotonergic axons and occasional serotonin-labelled interneurons. These data demonstrate that olfactory bulb-derived OEG transplantation improves hindlimb stepping in paraplegic rats and further suggest that task-specific training may enhance this OEG effect.
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Affiliation(s)
| | - Devin L. Jindrich
- Department of Physiological Science, UCLA, Los Angeles, CA
- Brain Research Institute, UCLA, Los Angeles, CA, USA
| | - Hui Zhong
- Brain Research Institute, UCLA, Los Angeles, CA, USA
| | - Aya Takeoka
- Department of Physiological Science, UCLA, Los Angeles, CA
| | | | | | - Roland R. Roy
- Brain Research Institute, UCLA, Los Angeles, CA, USA
| | - V. Reggie Edgerton
- Department of Physiological Science, UCLA, Los Angeles, CA
- Brain Research Institute, UCLA, Los Angeles, CA, USA
| | | | - Patricia E. Phelps
- Department of Physiological Science, UCLA, Los Angeles, CA
- Brain Research Institute, UCLA, Los Angeles, CA, USA
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156
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Gerasimenko YP, Ichiyama RM, Lavrov IA, Courtine G, Cai L, Zhong H, Roy RR, Edgerton VR. Epidural spinal cord stimulation plus quipazine administration enable stepping in complete spinal adult rats. J Neurophysiol 2007; 98:2525-36. [PMID: 17855582 DOI: 10.1152/jn.00836.2007] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We hypothesized that epidural spinal cord stimulation (ES) and quipazine (a serotonergic agonist) modulates the excitability of flexor and extensor related intraspinal neural networks in qualitatively unique, but complementary, ways to facilitate locomotion in spinal cord-injured rats. To test this hypothesis, we stimulated (40 Hz) the S(1) spinal segment before and after quipazine administration (0.3 mg/kg, ip) in bipedally step-trained and nontrained, adult, complete spinal (mid-thoracic) rats. The stepping pattern of these rats was compared with control rats. At the stimulation levels used, stepping was elicited only when the hindlimbs were placed on a moving treadmill. In nontrained rats, the stepping induced by ES and quipazine administration was non-weight bearing, and the cycle period was shorter than in controls. In contrast, the stepping induced by ES and quipazine in step-trained rats was highly coordinated with clear plantar foot placement and partial weight bearing. The effect of ES and quipazine on EMG burst amplitude and duration was greater in flexor than extensor motor pools. Using fast Fourier transformation analysis of EMG bursts during ES, we observed one dominant peak at 40 Hz in the medial gastrocnemius (ankle extensor), whereas there was less of dominant spectral peak in the tibialis anterior (ankle flexor). We suggest that these frequency distributions reflect amplitude modulation of predominantly monosynaptic potentials in the extensor and predominantly polysynaptic pathways in the flexor muscle. Quipazine potentiated the amplitude of these responses. The data suggest that there are fundamental differences in the circuitry that generates flexion and extension during locomotion.
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Affiliation(s)
- Yury P Gerasimenko
- Department of Physiological Science, University of California, Los Angeles, CA 90095, USA
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157
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Petruska JC, Ichiyama RM, Jindrich DL, Crown ED, Tansey KE, Roy RR, Edgerton VR, Mendell LM. Changes in motoneuron properties and synaptic inputs related to step training after spinal cord transection in rats. J Neurosci 2007; 27:4460-71. [PMID: 17442831 PMCID: PMC6672318 DOI: 10.1523/jneurosci.2302-06.2007] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Although recovery from spinal cord injury is generally meager, evidence suggests that step training can improve stepping performance, particularly after neonatal spinal injury. The location and nature of the changes in neural substrates underlying the behavioral improvements are not well understood. We examined the kinematics of stepping performance and cellular and synaptic electrophysiological parameters in ankle extensor motoneurons in nontrained and treadmill-trained rats, all receiving a complete spinal transection as neonates. For comparison, electrophysiological experiments included animals injured as young adults, which are far less responsive to training. Recovery of treadmill stepping was associated with significant changes in the cellular properties of motoneurons and their synaptic input from spinal white matter [ipsilateral ventrolateral funiculus (VLF)] and muscle spindle afferents. A strong correlation was found between the effectiveness of step training and the amplitude of both the action potential afterhyperpolarization and synaptic inputs to motoneurons (from peripheral nerve and VLF). These changes were absent if step training was unsuccessful, but other spinal projections, apparently inhibitory to step training, became evident. Greater plasticity of axonal projections after neonatal than after adult injury was suggested by anatomical demonstration of denser VLF projections to hindlimb motoneurons after neonatal injury. This finding confirmed electrophysiological measurements and provides a possible mechanism underlying the greater training susceptibility of animals injured as neonates. Thus, we have demonstrated an "age-at-injury"-related difference that may influence training effectiveness, that successful treadmill step training can alter electrophysiological parameters in the transected spinal cord, and that activation of different pathways may prevent functional improvement.
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Affiliation(s)
- Jeffrey C. Petruska
- Department of Neurobiology and Behavior, State University of New York at Stony Brook, Stony Brook, New York 11794-5230, and
| | - Ronaldo M. Ichiyama
- Department of Physiological Sciences, University of California, Los Angeles, Los Angeles, California 90095-1527
| | - Devin L. Jindrich
- Department of Physiological Sciences, University of California, Los Angeles, Los Angeles, California 90095-1527
| | - Eric D. Crown
- Department of Physiological Sciences, University of California, Los Angeles, Los Angeles, California 90095-1527
| | - Keith E. Tansey
- Department of Physiological Sciences, University of California, Los Angeles, Los Angeles, California 90095-1527
| | - Roland R. Roy
- Department of Physiological Sciences, University of California, Los Angeles, Los Angeles, California 90095-1527
| | - V. Reggie Edgerton
- Department of Physiological Sciences, University of California, Los Angeles, Los Angeles, California 90095-1527
| | - Lorne M. Mendell
- Department of Neurobiology and Behavior, State University of New York at Stony Brook, Stony Brook, New York 11794-5230, and
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158
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Cai L, Courtine G, Fong A, Burdick J, Roy R, Edgerton V. Plasticity of functional connectivity in the adult spinal cord. Philos Trans R Soc Lond B Biol Sci 2007; 361:1635-46. [PMID: 16939979 PMCID: PMC1664672 DOI: 10.1098/rstb.2006.1884] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
This paper emphasizes several characteristics of the neural control of locomotion that provide opportunities for developing strategies to maximize the recovery of postural and locomotor functions after a spinal cord injury (SCI). The major points of this paper are: (i) the circuitry that controls standing and stepping is extremely malleable and reflects a continuously varying combination of neurons that are activated when executing stereotypical movements; (ii) the connectivity between neurons is more accurately perceived as a functional rather than as an anatomical phenomenon; (iii) the functional connectivity that controls standing and stepping reflects the physiological state of a given assembly of synapses, where the probability of these synaptic events is not deterministic; (iv) rather, this probability can be modulated by other factors such as pharmacological agents, epidural stimulation and/or motor training; (v) the variability observed in the kinematics of consecutive steps reflects a fundamental feature of the neural control system and (vi) machine-learning theories elucidate the need to accommodate variability in developing strategies designed to enhance motor performance by motor training using robotic devices after an SCI.
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Affiliation(s)
- L.L Cai
- Bioengineering Option, California Institute of TechnologyPasadena, CA 91125-4100, USA
| | - G Courtine
- Department of Physiological Science, University of California1804 Life Sciences, 621 Charles E. Young Drive South, Los Angeles, CA 90095-1527, USA
| | - A.J Fong
- Bioengineering Option, California Institute of TechnologyPasadena, CA 91125-4100, USA
| | - J.W Burdick
- Bioengineering Option, California Institute of TechnologyPasadena, CA 91125-4100, USA
- Mechanical Engineering Option, California Institute of TechnologyPasadena, CA 91125-4100, USA
| | - R.R Roy
- Brain Research Institute, University of CaliforniaLos Angeles, CA 90095, USA
| | - V.R Edgerton
- Brain Research Institute, University of CaliforniaLos Angeles, CA 90095, USA
- Department of Physiological Science, University of California1804 Life Sciences, 621 Charles E. Young Drive South, Los Angeles, CA 90095-1527, USA
- Department of Neurobiology, University of CaliforniaLos Angeles, CA 90095-1763, USA
- Author for correspondence ()
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159
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Minassian K, Persy I, Rattay F, Pinter MM, Kern H, Dimitrijevic MR. Human lumbar cord circuitries can be activated by extrinsic tonic input to generate locomotor-like activity. Hum Mov Sci 2007; 26:275-95. [PMID: 17343947 DOI: 10.1016/j.humov.2007.01.005] [Citation(s) in RCA: 145] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We have demonstrated that non-patterned electrical stimulation of the lumbar cord can induce stepping-like activity in the lower limbs of complete spinal cord injured individuals. This result suggested the existence of a human lumbar locomotor pattern generator, which can convert a tonic input to a rhythmic motor output. We have studied the human lumbar cord in isolation from supraspinal input but under extrinsic tonic input delivered by spinal cord stimulation. Large-diameter afferents within the posterior roots are directly depolarized by the electrical stimulation. These afferents project to motoneurons as well as to lumbar interneurons involved in the motor control of lower limbs. Stimulation at 25-50 Hz can elicit rhythmic alternating flexion/extension movements of the lower limbs in supine individuals. Reducing the tonic input frequency to 5-15 Hz initiates lower limb extension. Epidural stimulation applied during manually assisted treadmill stepping in complete spinal cord injured persons immediately increases the central state of excitability of lumbar cord networks and enhances stepping-like functional motor outputs. Sustained, non-patterned tonic input via the posterior roots can activate human lumbar cord networks. Pattern generating configurations of these multifunctional circuitries can be set-up depending on the stimulation parameters and particularly on the input frequency.
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Affiliation(s)
- K Minassian
- Ludwig Boltzmann Institute for Electrical Stimulation and Physical Rehabilitation, Vienna, Austria
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160
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Yakovenko S, Kowalczewski J, Prochazka A. Intraspinal Stimulation Caudal to Spinal Cord Transections in Rats. Testing the Propriospinal Hypothesis. J Neurophysiol 2007; 97:2570-4. [PMID: 17215510 DOI: 10.1152/jn.00814.2006] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Many laboratories have reported the successful regeneration of neurons across damaged portions of the spinal cord. Associated improvements in hindlimb locomotor movements have been attributed to the formation of functional neuronal connections with the locomotor central pattern generator (CPG). However, regenerating axons generally extend no more than 10 mm caudal to the lesion sites, terminating about 20 mm short of the lumbar segments thought to contain the CPG. It has therefore tacitly been assumed that the locomotor improvements arose from activation of propriospinal neurons relaying excitation to the CPG. Here we report a test of this assumption, which we call the propriospinal hypothesis. Intraspinal microstimulation (ISMS) was used to activate the putative propriospinal relay neurons. Approximately 2–3 wk after complete spinal cord transection at T8–T9 in rats, an array of six Pt–Ir microwires was chronically implanted in the intermediate and ventral gray matter of T10–T12 segments. ISMS pulse trains with amplitudes of 0.8–0.9 times threshold for activating axial muscles were delivered during open-field locomotor tests (BBB). ISMS significantly increased BBB scores over control tests, but did not produce limb coordination and weight bearing sufficient for locomotion. These results support the main assumption of the propriospinal hypothesis: that neuronal activity elicited in thoracic spinal segments caudal to a complete spinal cord transection may propagate caudally and activate the locomotor CPG.
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Affiliation(s)
- Sergiy Yakovenko
- Département de Physiologie, Université de Montréal, Pavillon Paul-G. Desmarais, C.P. 6128, Succursale Centre-ville, Montreal, Quebec, H3C 3J7, Canada.
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161
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Rattay F, Resatz S. Dipole distance for minimum threshold current to stimulate unmyelinated axons with microelectrodes. IEEE Trans Biomed Eng 2007; 54:158-62. [PMID: 17260868 DOI: 10.1109/tbme.2006.883730] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Excitation thresholds for long nerve or muscle fibers with two point sources parallel to the fiber axis depend on the dipole length. The aim of this study was to find the optimal interelectrode distance for the minimum stimulation current. For a specific electrode-fiber distance (z_el) dipole length is constrained by the energy efficacy of the electrodes requiring small interelectrode distances, and by rather low stimulation currents requiring large dipole distances. Far-field values for optimal dipole distance (approximately 1.4 *z_el) can be explained by the superposition of the positive parts of the activating functions for the monopolar elements of the dipole. A current redistribution effect in a target fiber close to the electrodes shifts the dipole length for threshold stimulation from the theoretical optimal activating function approach value towards greater dipole distances. Spike initiations in straight fibers and retinal ganglion cell axons are investigated.
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Affiliation(s)
- Frank Rattay
- Institute for Analysis and Scientific Computing at the Vienna University of Technology, Wiedner Hauptstr. 8-10/101, A-1040 Vienna, Austria.
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162
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Barthélemy D, Leblond H, Rossignol S. Characteristics and mechanisms of locomotion induced by intraspinal microstimulation and dorsal root stimulation in spinal cats. J Neurophysiol 2007; 97:1986-2000. [PMID: 17215509 DOI: 10.1152/jn.00818.2006] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Intraspinal microstimulation (ISMS) through a single microelectrode can induce locomotion in cats spinalized at T(13) 1 wk before (untrained) or after 3-5 wk of treadmill training. Here we study the optimal parameters of ISMS and the characteristics of locomotion evoked. ISMS was applied in the dorsal region of segments L(3)-S(1) at different lateralities (midline to 2.5 mm) and after an intravenous injection of clonidine (noradrenergic agonist). Kinematics and electromyographic recordings were used to characterize locomotion. ISMS could induce a bilateral locomotor pattern similar to that obtained with perineal stimulation, and the characteristics of locomotion varied according to the spinal segment stimulated. Mechanisms by which ISMS could evoke locomotion were then investigated by stimulating, inactivating, or lesioning different spinal structures. Dorsal root stimulation (DRS), just like ISMS, could evoke a variety of ipsi- and bilateral nonlocomotor movements as well as locomotor responses. This suggests that sensory afferent pathways are involved in the production of locomotion by ISMS. Microinjections of yohimbine (noradrenergic antagonist) in L(3) and L(4) segments or a complete second spinal lesion at L(3)-L(4) abolished all locomotor activity evoked by ISMS applied at more caudal segments. Progressive dorsoventral spinal lesions at L(3) or L(4) and restricted ventral lesions at L(4) further suggest that the integrity of the ventral or ventrolateral funiculi as well as the L(3)-L(4) segments are critical for the induction of locomotion by ISMS at L(5) to S(1) or by DRS at these caudal segments.
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Affiliation(s)
- D Barthélemy
- Centre de Recherche en Sciences Neurologiques, Pavillon Paul-G.-Desmarais, 2960 Chemin de la Tour, Université de Montréal, Montréal, Québec H3T 1J4, Canada
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163
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Guevremont L, Renzi CG, Norton JA, Kowalczewski J, Saigal R, Mushahwar VK. Locomotor-related networks in the lumbosacral enlargement of the adult spinal cat: activation through intraspinal microstimulation. IEEE Trans Neural Syst Rehabil Eng 2006; 14:266-72. [PMID: 17009485 DOI: 10.1109/tnsre.2006.881592] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
It is commonly accepted that locomotor-related neuronal circuitry resides in the lumbosacral spinal cord. Pharmacological agents, epidural electrical stimulation, and sensory stimulation can be used to activate these instrinsic networks in in vitro neonatal rat and in vivo cat preparations. In this study, we investigated the use of low-level tonic intraspinal microstimulation (ISMS) as a means of activating spinal locomotor networks in adult cats with complete spinal transections. Trains of low-amplitude electrical pulses were delivered to the spinal cord via groups of fine microwires implanted in the ventral horns of the lumbosacral enlargement. In contrast to published reports, tonic ISMS applied through microwires in the caudal regions of the lumbosacral enlargement (L7-S1) was more effective in eliciting alternating movements in the hindlimbs than stimulation in the rostral regions. Possible mechanisms of action of tonic ISMS include depolarization of locally oscillating networks in the lumbosacral cord, backfiring of primary afferents, or activation of propriospinal neurons.
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Affiliation(s)
- Lisa Guevremont
- Department of Biomedical Engineering, University of Alberta, Edmonton, AB T6G 2V2, Canada.
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164
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Rossignol S. Plasticity of connections underlying locomotor recovery after central and/or peripheral lesions in the adult mammals. Philos Trans R Soc Lond B Biol Sci 2006; 361:1647-71. [PMID: 16939980 PMCID: PMC1664667 DOI: 10.1098/rstb.2006.1889] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
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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Affiliation(s)
- Serge Rossignol
- Department of Physiology, Centre for Research in Neurological Sciences, Faculty of Medicine, Université de Montréal, PO Box 6128, Station Centre-Ville, Montréal, Québec, Canada H3C 3J7.
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165
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Abstract
Spinal cord injury (SCI) can lead to paraplegia or quadriplegia. Although there are no fully restorative treatments for SCI, various rehabilitative, cellular and molecular therapies have been tested in animal models. Many of these have reached, or are approaching, clinical trials. Here, we review these potential therapies, with an emphasis on the need for reproducible evidence of safety and efficacy. Individual therapies are unlikely to provide a panacea. Rather, we predict that combinations of strategies will lead to improvements in outcome after SCI. Basic scientific research should provide a rational basis for tailoring specific combinations of clinical therapies to different types of SCI.
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Affiliation(s)
- Sandrine Thuret
- Centre for the Cellular Basis of Behaviour, Institute of Psychiatry, King's College London, P.O. Box 39, 1-2 WW Ground, Denmark Hill, London SE5 8AF, UK
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166
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Vogelstein RJ, Etienne-Cummings R, Thakor NV, Cohen AH. Phase-Dependent Effects of Spinal Cord Stimulation on Locomotor Activity. IEEE Trans Neural Syst Rehabil Eng 2006; 14:257-65. [PMID: 17009484 DOI: 10.1109/tnsre.2006.881586] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
This paper examines how electrical stimulation of the spinal cord can modulate the output of the central pattern generator (CPG) for locomotion. Application of discrete current pulses to a single spinal segment was shown to affect multiple parameters of an ongoing locomotor pattern in an in vitro spinal cord. For any given stimulus, the effects on frequency, duration, and symmetry of locomotor output were strongly dependent on the phase at which stimulation was applied within the CPG cycle. Additionally, most stimuli had an immediate impact and evinced no effects on subsequent cycles. The most dramatic changes were seen when stimulation was applied during motor bursting: stimuli applied to the ipsilateral spinal hemicord increased the burst length, while stimuli applied to the contralateral spinal hemicord decreased the burst length. Smaller changes were observed when stimulating during delays between motor bursts. Thus, phasic stimulation was shown to influence the behavior of the CPG and spinal locomotion circuits on a cycle-by-cycle basis. This work represents the first step toward our ultimate goal of developing a neuroprosthetic device to restore locomotion after a severe spinal cord injury.
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Affiliation(s)
- R Jacob Vogelstein
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21205, USA.
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167
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Barthélemy D, Leblond H, Provencher J, Rossignol S. Nonlocomotor and locomotor hindlimb responses evoked by electrical microstimulation of the lumbar cord in spinalized cats. J Neurophysiol 2006; 96:3273-92. [PMID: 16943319 DOI: 10.1152/jn.00203.2006] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
As a preliminary step to using intraspinal microstimulation (ISMS) for rehabilitation purposes, the distribution of various types of hindlimb responses evoked by ISMS in spinal cats (T(13)) is described. The responses to ISMS applied through a single electrode was assessed, before and after an intravenous injection of clonidine (noradrenergic agonist), using kinematics and electromyographic recordings in subacute (5-7 days, untrained) or chronic (3-5 wk trained on a treadmill) spinal cats. ISMS was applied in the dorsal, intermediate and ventral areas of segments L(3)-L(7), from midline to 3 mm laterally. Uni- and bilateral non-locomotor responses as well as rhythmical locomotor responses were evoked. In the subacute cats, ipsilateral flexion was elicited in the dorsal region of L(3)-L(7), whereas ipsilateral extension was evoked more ventrally and mainly in the caudal segments. Dorsal stimuli could induce ipsilateral flexion followed by ipsilateral extension. Sites inducing bilateral flexion and bilateral extension were similarly distributed to those evoking ipsilateral flexion and extension in the rostrocaudal axis but were evoked from more medial sites. Ipsilateral flexion with crossed extension was evoked from intermediate and ventral zones of all segments and lateralities. Unilateral ipsilateral locomotion was rarely observed. Contralateral locomotion was more frequent and mainly evoked medially, whereas bilateral locomotion was evoked exclusively from dorsal regions. With some exceptions, those distribution gradients were similar in the four conditions (subacute, chronic, pre- and postclonidine), but the proportion of each response could vary. The distribution of ISMS-evoked responses is discussed as a function of known localization of interneurons and motoneurons.
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Affiliation(s)
- Dorothy Barthélemy
- Centre de Recherche en Sciences Neurologiques, Pavillon Paul-G.-Desmarais, 2960 Chemin de la Tour, Université de Montréal, Montréal, Québec H3T 1J4 Canada
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168
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Lavrov I, Gerasimenko YP, Ichiyama RM, Courtine G, Zhong H, Roy RR, Edgerton VR. Plasticity of spinal cord reflexes after a complete transection in adult rats: relationship to stepping ability. J Neurophysiol 2006; 96:1699-710. [PMID: 16823028 DOI: 10.1152/jn.00325.2006] [Citation(s) in RCA: 146] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Changes in epidurally induced (S1) spinal cord reflexes were studied as a function of the level of restoration of stepping ability after spinal cord transection (ST). Three types of responses were observed. The early response (ER) had a latency of 2.5 to 3 ms and resulted from direct stimulation of motor fibers or motoneurons. The middle response (MR) had a latency of 5 to 7 ms and was monosynaptic. The late response (LR) had a latency of 9 to 11 ms and was polysynaptic. After a complete midthoracic ST, the LR was abolished, whereas the MR was facilitated and progressively increased. The LR reappeared about 3 wk after ST and increased during the following weeks. Restoration of stepping induced by epidural stimulation at 40 Hz coincided with changes in the LR. During the first 2 wk post-ST, rats were unable to step and electrophysiological assessment failed to show any LR. Three weeks post-ST, epidural stimulation resulted in a few steps and these coincided with reappearance of the LR. The ability of rats to step progressively improved from wk 3 to wk 6 post-ST. There was a continuously improved modulation of rhythmic EMG bursts that was correlated with restoration of the LR. These results suggest that restoration of polysynaptic spinal cord reflexes after complete ST coincides with restoration of stepping function when facilitated by epidural stimulation. Combined, these findings support the view that restoration of polysynaptic spinal cord reflexes induced epidurally may provide a measure of functional restoration of spinal cord locomotor networks after ST.
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Affiliation(s)
- Igor Lavrov
- Department of Physiological Science, University of California, Los Angeles, CA 90095-1527, USA
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169
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Gerasimenko YP, Lavrov IA, Courtine G, Ichiyama RM, Dy CJ, Zhong H, Roy RR, Edgerton VR. Spinal cord reflexes induced by epidural spinal cord stimulation in normal awake rats. J Neurosci Methods 2006; 157:253-63. [PMID: 16764937 DOI: 10.1016/j.jneumeth.2006.05.004] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2005] [Revised: 04/06/2006] [Accepted: 05/02/2006] [Indexed: 10/24/2022]
Abstract
Motor responses in hindlimb muscles to epidural spinal cord stimulation in normal awake rats during bipedal standing were studied. Stimulation at L2 or S1 induced simultaneous and bilateral responses in the vastus lateralis, semitendinosus, tibialis anterior, and medial gastrocnemius muscles. Stimulation at S1 evoked an early (ER), middle (MR) and late (LR) response: stimulation at L2 elicited only a MR and LR. Vibration and double epidural stimulation testing suggests that the ER is a direct motor response, whereas the MR and LR are mediated synaptically. MR has properties of a monosynaptic reflex, i.e., inhibited during vibration and depressed during the second pulse of a double stimulation. Some components of the LR seem to be mediated by afferents associated with the flexor reflex and probably involve group II afferents. During bipedal treadmill stepping, the MR was modulated in extensors, whereas the LR was modulated in flexors. These results show differential modulation of monosynaptic and polysynaptic reflexes in flexor and extensor motor pools during locomotion. Monosynaptic responses to stimulation at either L2 or S1 generally were amplified in extensors during the stance phase and in flexors during the swing phase of the step cycle. No correlation was found between the ER and the EMG background during stepping, whereas both the MR and LR were closely correlated with the changes in the EMG activity level of the corresponding muscle. These data demonstrate the feasibility of using epidural stimulation for examining monosynaptic and polysynaptic pathways to motor pools associated with multiple muscles during movement and over a prolonged period.
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Affiliation(s)
- Yury P Gerasimenko
- Department of Physiological Science, University of California, Los Angeles, CA 90095, USA
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170
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Filipe VM, Pereira JE, Costa LM, Maurício AC, Couto PA, Melo-Pinto P, Varejão ASP. Effect of skin movement on the analysis of hindlimb kinematics during treadmill locomotion in rats. J Neurosci Methods 2006; 153:55-61. [PMID: 16337686 DOI: 10.1016/j.jneumeth.2005.10.006] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2005] [Revised: 09/20/2005] [Accepted: 10/08/2005] [Indexed: 11/28/2022]
Abstract
In rat gait kinematics, the method most frequently used for measuring hindlimb movement involves placing markers on the skin surface overlying the joints being analyzed. Soft tissue movement around the knee joint has been considered the principle source of error when estimating hindlimb joint kinematics in rodents. However, the motion of knee marker was never quantified, nor the different variations in joint angle associated with this gait analysis system. The purpose of this study was two-fold. The first purpose was to expand upon the limited pool of information describing the effect of soft tissue movement over the knee upon the angular positions of the hip, knee and ankle of rats during treadmill locomotion. Secondly, it was a goal of this study to document the magnitude of the skin displacement when using markers that were attached superficially to the knee joint. This was examined by comparing the hindlimb kinematics in sagittal plane during treadmill locomotion determined from the marker attached to the knee and when the knee position was determined indirectly by computer analysis. Results showed that there is a considerable skin movement artefact which propagates to knee joint position and hindlimb kinematics estimates. It was concluded that these large errors can decrease data reliability in the research of rat gait analysis.
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Affiliation(s)
- Vitor M Filipe
- Department of Engineering, CETAV, University of Trás-os-Montes e Alto Douro, P.O. Box 1013, 5001-911 Vila Real, Portugal
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171
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Abstract
Locomotion results from intricate dynamic interactions between a central program and feedback mechanisms. The central program relies fundamentally on a genetically determined spinal circuitry (central pattern generator) capable of generating the basic locomotor pattern and on various descending pathways that can trigger, stop, and steer locomotion. The feedback originates from muscles and skin afferents as well as from special senses (vision, audition, vestibular) and dynamically adapts the locomotor pattern to the requirements of the environment. The dynamic interactions are ensured by modulating transmission in locomotor pathways in a state- and phase-dependent manner. For instance, proprioceptive inputs from extensors can, during stance, adjust the timing and amplitude of muscle activities of the limbs to the speed of locomotion but be silenced during the opposite phase of the cycle. Similarly, skin afferents participate predominantly in the correction of limb and foot placement during stance on uneven terrain, but skin stimuli can evoke different types of responses depending on when they occur within the step cycle. Similarly, stimulation of descending pathways may affect the locomotor pattern in only certain phases of the step cycle. Section ii reviews dynamic sensorimotor interactions mainly through spinal pathways. Section iii describes how similar sensory inputs from the spinal or supraspinal levels can modify locomotion through descending pathways. The sensorimotor interactions occur obviously at several levels of the nervous system. Section iv summarizes presynaptic, interneuronal, and motoneuronal mechanisms that are common at these various levels. Together these mechanisms contribute to the continuous dynamic adjustment of sensorimotor interactions, ensuring that the central program and feedback mechanisms are congruous during locomotion.
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Affiliation(s)
- Serge Rossignol
- Department of Physiology, Centre for Research in Neurological Sciences, Faculty of Medicine, Université de Montréal, PO Box 6128, Station Centre-Ville, Montreal, Quebec, Canada H3C 3J7.
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