Restoration of frequency-dependent depression of the H-reflex by passive exercise in spinal rats

Reese, N.B.; Skinner, R.D.; Mitchell, Douglas; Yates, Charlotte; Barnes, Cynthia Carter; Kiser, Thomas S.; García‐Rill, Edgar

doi:10.1038/sj.sc.3101810

Cited by 83 publications

(78 citation statements)

References 41 publications

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“…There being different mechanisms underlying the middle and late responses is consistent with the complete inhibition of the late response at 3 Hz stimulation but only partial inhibition of the middle response even at 5-10 Hz (Skinner et al, 1996;Reese et al, 2006;Lavrov et al, 2006). The frequency-dependent depression of the middle response is similar to that observed for the H-reflex when tested acutely with sciatic nerve stimulation, suggesting a similar monosynaptic origin for both responses (Wolpaw and Chen, 2001;Lavrov et al, 2006).…”

Section: What Are the Middle And Late Responses Evoked By Epidural Stsupporting

confidence: 63%

“…The different time course for the restoration of the middle and late responses after transection also suggests a different origin for these two responses. The middle response and H-reflex are restored early (Thompson et al, 1993;Valero-Cabre et al, 2004) and show facilitation within 1-2 weeks after transection (Skinner et al, 1996;Valero-Cabre et al, 2004;Reese et al, 2006;Lavrov et al, 2006). In contrast, the late response shows a gradual recovery beginning 2-3 weeks after transection with a time course similar to the recovery of the polysynaptic components of flexor-extensor reflexes tested acutely after transection (Valero-Cabre et al, 2004).…”

Section: What Are the Middle And Late Responses Evoked By Epidural Stmentioning

confidence: 91%

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Epidural Stimulation Induced Modulation of Spinal Locomotor Networks in Adult Spinal Rats

Lavrov

Fong

et al. 2008

Journal of Neuroscience

142

122

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The importance of the in vivo dynamic nature of the circuitries within the spinal cord that generate locomotion is becoming increasingly evident. We examined the characteristics of hindlimb EMG activity evoked in response to epidural stimulation at the S1 spinal cord segment in complete midthoracic spinal cord-transected rats at different stages of postlesion recovery. A progressive and phasedependent modulation of monosynaptic (middle) and long-latency (late) stimulation-evoked EMG responses was observed throughout the step cycle. During the first 3 weeks after injury, the amplitude of the middle response was potentiated during the EMG bursts, whereas after 4 weeks, both the middle and late responses were phase-dependently modulated. The middle-and late-response magnitudes were closely linked to the amplitude and duration of the EMG bursts during locomotion facilitated by epidural stimulation. The optimum stimulation frequency that maintained consistent activity of the long-latency responses ranged from 40 to 60 Hz, whereas the shortlatency responses were consistent from 5 to 130 Hz. These data demonstrate that both middle and late evoked potentials within a motor pool are strictly gated during in vivo bipedal stepping as a function of the general excitability of the motor pool and, thus, as a function of the phase of the step cycle. These data demonstrate that spinal cord epidural stimulation can facilitate locomotion in a time-dependent manner after lesion. The long-latency responses to epidural stimulation are correlated with the recovery of weight-bearing bipedal locomotion and may reflect activation of interneuronal central pattern-generating circuits.

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Section: What Are the Middle And Late Responses Evoked By Epidural Stsupporting

confidence: 63%

Section: What Are the Middle And Late Responses Evoked By Epidural Stmentioning

confidence: 91%

Epidural Stimulation Induced Modulation of Spinal Locomotor Networks in Adult Spinal Rats

Lavrov

Fong

et al. 2008

Journal of Neuroscience

142

122

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“…The progressive nature of the training effect was evident. For example, after 15 or 30 days of training the H-reflex inhibition was only partially restored, whereas at 90 days the H-reflex frequency-dependent depression had normalized (Reese et al, 2006). A similar effect has been described in humans where motorized bicycle training provided recovery of H-reflex frequency-dependent depression within 10 weeks.…”

Section: Neurophysiological Plasticity In Response To Trainingsupporting

confidence: 59%

“…For example, stimulation of the ventrolateral funiculus (central-EPSP, cEPSP) induced higher amplitude polysynaptic cEPSPs recorded from motoneurons in trained than non-trained or poorly stepping spinal rats. Passive exercise (motorized bicycle training) in spinally transected rats also restored the frequency-dependent depression of the H-reflex to the level of intact animals (Reese et al, 2006). One of proposed mechanisms of training is a restoration of presynaptic inhibition.…”

Section: Neurophysiological Plasticity In Response To Trainingmentioning

confidence: 94%

Training locomotor networks

Edgerton

Courtine

Gerasimenko

et al. 2008

Brain Research Reviews

277

205

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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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“…Houle et al 18 found that cycle locomotor-trained animals showed an increase in hindlimb muscle size following SCI. Additionally, cycling training has been found to normalize hyperreflexia in spinal rats 28 as well as in humans with SCI. 15 In the present study, we performed a direct comparison between bicycle and treadmill locomotor training and showed that both training interventions effectively halt the atrophic process and accelerate the rate of muscle recovery.…”

Section: Discussionmentioning

confidence: 99%

A longitudinal study of skeletal muscle following spinal cord injury and locomotor training

et al. 2008

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Study design: Experimental rat model of spinal cord contusion injury (contusion SCI).Objective: The objectives of this study were (1) to characterize the longitudinal changes in rat lower hindlimb muscle morphology following contusion SCI by using magnetic resonance imaging and (2) to determine the therapeutic potential of two types of locomotor training, treadmill and cycling. Setting: University research setting. Methods: After moderate midthoracic contusion SCI, Sprague-Dawley rats were assigned to either treadmill training, cycle training or an untrained group. Lower hindlimb muscle size was examined prior to SCI and at 1-, 2-, 4-, 8-, and 12-week post injury. Results: Following contusion SCI, we observed significant atrophy in all rat hindlimb muscles with the posterior muscles (triceps surae and flexor digitorum) showing greater atrophy than the anterior muscles (tibialis anterior and extensor digitorum). The greatest amount of atrophy was measured at 2-week post injury (range from 11 to 26%), and spontaneous recovery in muscle size was observed by 4 weeks post-SCI. Both cycling and treadmill training halted the atrophic process and accelerated the rate of recovery. The therapeutic influence of both training interventions was observed within 1 week of training and no significant difference was noted between the two interventions, except in the tibialis anterior muscle. Finally, a positive correlation was found between locomotor functional scores and hindlimb muscle size following SCI. Conclusions: Both treadmill and cycle training diminish the extent of atrophy and facilitate muscle plasticity after contusion SCI.

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Restoration of frequency-dependent depression of the H-reflex by passive exercise in spinal rats

Cited by 83 publications

References 41 publications

Epidural Stimulation Induced Modulation of Spinal Locomotor Networks in Adult Spinal Rats

Epidural Stimulation Induced Modulation of Spinal Locomotor Networks in Adult Spinal Rats

Training locomotor networks

A longitudinal study of skeletal muscle following spinal cord injury and locomotor training

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