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Novel and direct access to the human locomotor spinal circuitry.

ABSTRACT: The degree of automaticity of locomotion in primates compared with other mammals remains unclear. Here, we examine the possibility for activation of the spinal locomotor circuitry in noninjured humans by spinal electromagnetic stimulation (SEMS). SEMS (3 Hz and 1.3-1.82 tesla) at the T11-T12 vertebrae induced involuntary bilateral locomotor-like movements in the legs of individuals placed in a gravity-neutral position. The formation of locomotor-like activity during SEMS started with a latency of 0.68 +/- 0.1 s after delivering the first stimulus, unlike continuous vibration of muscles, which requires several seconds. The first EMG burst in response to SEMS was observed most often in a proximal flexor muscle. We speculate that SEMS directly activates the circuitry intrinsic to the spinal cord, as suggested by the immediate response and the electrophysiological observations demonstrating an absence of strictly time-linked responses within the EMG burst associated with individual stimuli during SEMS. SEMS in the presence of vibration of the leg muscles was more effective in facilitating locomotor-like activity than SEMS alone. The present results suggest that SEMS could be an effective noninvasive clinical tool to determine the potential of an individual to recover locomotion after a spinal cord injury, as well as being an effective rehabilitation tool itself.

SUBMITTER: Gerasimenko Y

PROVIDER: S-EPMC2847395 | biostudies-literature | 2010 Mar

REPOSITORIES: biostudies-literature

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Novel and direct access to the human locomotor spinal circuitry.

Gerasimenko Yury Y Gorodnichev Ruslan R Machueva Ekaterina E Pivovarova Elena E Semyenov Denis D Savochin Alexandr A Roy Roland R RR Edgerton V Reggie VR

The Journal of neuroscience : the official journal of the Society for Neuroscience 20100301 10

The degree of automaticity of locomotion in primates compared with other mammals remains unclear. Here, we examine the possibility for activation of the spinal locomotor circuitry in noninjured humans by spinal electromagnetic stimulation (SEMS). SEMS (3 Hz and 1.3-1.82 tesla) at the T11-T12 vertebrae induced involuntary bilateral locomotor-like movements in the legs of individuals placed in a gravity-neutral position. The formation of locomotor-like activity during SEMS started with a latency o ...[more]

PMID: 20220003

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Project description:BackgroundAmbulation is an essential aspect of daily living and is often impaired after brain and spinal cord injuries. Despite the implementation of standard neurorehabilitative care, locomotor recovery is often incomplete.ObjectiveIn this randomized, sham-controlled, double-blind, parallel design study, we aimed to determine if anodal transcutaneous spinal direct current stimulation (anodal tsDCS) could improve training effects on locomotion compared to sham (sham tsDCS) in healthy subjects.Methods43 participants underwent a single backwards locomotion training (BLT) session on a reverse treadmill with concurrent anodal (n = 22) or sham (n = 21) tsDCS. The primary outcome measure was speed gain measured 24 h post-training. We hypothesized that anodal tsDCS + BLT would improve training effects on backward locomotor speed compared to sham tsDCS + BLT. A subset of participants (n = 31) returned for two additional training days of either anodal (n = 16) or sham (n = 15) tsDCS and underwent (n = 29) H-reflex testing immediately before, immediately after, and 30 min post-training over three consecutive days.ResultsA single session of anodal tsDCS + BLT elicited greater speed gain at 24 h relative to sham tsDCS + BLT (p = 0.008, two-sample t-test, adjusted for one interim analysis after the initial 12 subjects). Anodal tsDCS + BLT resulted in higher retention of the acquired skill at day 30 relative to sham tsDCS + BLT (p = 0.002) in the absence of significant group differences in online or offline learning over the three training days (p = 0.467 and p = 0.131). BLT resulted in transient down-regulation of H-reflex amplitude (Hmax/Mmax) in both test groups (p < 0.0001). However, the concurrent application of anodal-tsDCS with BLT elicited a longer lasting effect than sham-tsDCS + BLT (p = 0.050).ConclusiontsDCS improved locomotor skill acquisition and retention in healthy subjects and prolonged the physiological exercise-mediated downregulation of excitability of the alpha motoneuron pool. These results suggest that this strategy is worth exploring in neurorehabilitation of locomotor function.

Project description:Neurophysiological changes that involve activity-dependent neuroplasticity mechanisms via repeated stimulation and locomotor training are not commonly employed in research even though combination of interventions is a common clinical practice. In this randomized clinical trial, we established neurophysiological changes when transcranial magnetic stimulation (TMS) of the motor cortex was paired with transcutaneous thoracolumbar spinal (transspinal) stimulation in human spinal cord injury (SCI) delivered during locomotor training. We hypothesized that TMS delivered before transspinal (TMS-transspinal) stimulation promotes functional reorganization of spinal networks during stepping. In this protocol, TMS-induced corticospinal volleys arrive at the spinal cord at a sufficient time to interact with transspinal stimulation induced depolarization of alpha motoneurons over multiple spinal segments. We further hypothesized that TMS delivered after transspinal (transspinal-TMS) stimulation induces less pronounced effects. In this protocol, transspinal stimulation is delivered at time that allows transspinal stimulation induced action potentials to arrive at the motor cortex and affect descending motor volleys at the site of their origin. Fourteen individuals with motor incomplete and complete SCI participated in at least 25 sessions. Both stimulation protocols were delivered during the stance phase of the less impaired leg. Each training session consisted of 240 paired stimuli delivered over 10-min blocks. In transspinal-TMS, the left soleus H-reflex increased during the stance-phase and the right soleus H-reflex decreased at mid-swing. In TMS-transspinal no significant changes were found. When soleus H-reflexes were grouped based on the TMS-targeted limb, transspinal-TMS and locomotor training promoted H-reflex depression at swing phase, while TMS-transspinal and locomotor training resulted in facilitation of the soleus H-reflex at stance phase of the step cycle. Furthermore, both transspinal-TMS and TMS-transspinal paired-associative stimulation (PAS) and locomotor training promoted a more physiological modulation of motor activity and thus depolarization of motoneurons during assisted stepping. Our findings support that targeted non-invasive stimulation of corticospinal and spinal neuronal pathways coupled with locomotor training produce neurophysiological changes beneficial to stepping in humans with varying deficits of sensorimotor function after SCI.

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Novel and direct access to the human locomotor spinal circuitry.

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Novel and direct access to the human locomotor spinal circuitry.

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