Spinal Cord Maps of Spatiotemporal Alpha-Motoneuron Activation in Humans Walking at Different Speeds

2006 ◽  
Vol 95 (2) ◽  
pp. 602-618 ◽  
Author(s):  
Y. P. Ivanenko ◽  
R. E. Poppele ◽  
F. Lacquaniti
Keyword(s):  
Spinal Cord ◽  
Center Of Mass ◽  
Trunk Muscles ◽  
Emg Activity ◽  
Step Cycle ◽  
Human Spinal Cord ◽  
Spinal Segments ◽  
Motoneuron Activity ◽  
Pattern Generators ◽  
Walking Speeds

Functional MRI (fMRI) imaging of motoneuron activity in the human spinal cord is still in its infancy, and it will remain difficult to apply to walking. Here we present a viable alternative for documenting the spatiotemporal maps of α-motorneuron (MN) activity in the human spinal cord during walking, similar to the method recently reported for the cat. We recorded EMG activity from 16 to 32 ipsilateral limb and trunk muscles in 13 healthy subjects walking on a treadmill at different speeds (1–7 km/h) and mapped the recorded patterns onto the spinal cord in approximate rostrocaudal locations of the motoneuron pools. This approach can provide information about pattern generator output during locomotion in terms of segmental control rather than in terms of individual muscle control. A striking feature we found is that nearly every spinal segment undergoes at least two cycles of activation in the step cycle, thus supporting the idea of half-center oscillators controlling MN activation at any segmental level. The resulting spatiotemporal map patterns seem highly stereotyped over the range of walking speeds studied, although there were also some systematic redistributions of MN activity with speed. Bursts of MN activity were either temporally aligned across several spinal segments or switched between different segments. For example, the center of mass of MN activity in the lumbosacral levels generally shifted from rostral to caudal positions in two cycles for each step, revealing four major activation foci: two in the upper lumbar segments and two in the sacral segments. The results are consistent with the presence of at least two and possibly more pattern generators controlling the activation of lumbosacral MNs.

scholarly journals Migration of Motor Pool Activity in the Spinal Cord Reflects Body Mechanics in Human Locomotion

2010 ◽  
Vol 104 (6) ◽  
pp. 3064-3073 ◽  
Author(s):  
Germana Cappellini ◽  
Yuri P. Ivanenko ◽  
Nadia Dominici ◽  
Richard E. Poppele ◽  
Francesco Lacquaniti
Keyword(s):  
Spinal Cord ◽  
Center Of Mass ◽  
Human Locomotion ◽  
The Body ◽  
Trunk Muscles ◽  
Mass Motion ◽  
Electromyographic Activity ◽  
Leg Muscles ◽  
Motoneuron Activity ◽  
Body Center

During the evolution of bipedal modes of locomotion, a sequential rostrocaudal activation of trunk muscles due to the undulatory body movements was replaced by more complex and discrete bursts of activity. Nevertheless, the capacity for segmental rhythmogenesis and the rostrocaudal propagation of spinal cord activity has been conserved. In humans, motoneurons of different muscles are arranged in columns, with a specific grouping of muscles at any given segmental level. The muscle patterns of locomotor activity and the biomechanics of the body center of mass have been studied extensively, but their interrelationship remains poorly understood. Here we mapped the electromyographic activity recorded from 30 bilateral leg muscles onto the spinal cord in approximate rostrocaudal locations of the motoneuron pools during walking and running in humans. We found that the rostrocaudal displacements of the center of bilateral motoneuron activity mirrored the changes in the energy due to the center-of-body mass motion. The results suggest that biomechanical mechanisms of locomotion, such as the inverted pendulum in walking and the pogo-stick bouncing in running, may be tightly correlated with specific modes of progression of motor pool activity rostrocaudally in the spinal cord.

scholarly journals Phase-Dependent Modulation of Percutaneously Elicited Multisegmental Muscle Responses After Spinal Cord Injury

2010 ◽  
Vol 103 (5) ◽  
pp. 2808-2820 ◽  
Author(s):  
Christine J. Dy ◽  
Yury P. Gerasimenko ◽  
V. Reggie Edgerton ◽  
Poul Dyhre-Poulsen ◽  
Grégoire Courtine ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Vastus Lateralis ◽  
Medial Gastrocnemius ◽  
Emg Activity ◽  
Step Cycle ◽  
Human Spinal Cord ◽  
Lumbosacral Spinal Cord ◽  
Weight Support ◽  
Cord Injury

Phase-dependent modulation of monosynaptic reflexes has been reported for several muscles of the lower limb of uninjured rats and humans. To assess whether this step-phase-dependent modulation can be mediated at the level of the human spinal cord, we compared the modulation of responses evoked simultaneously in multiple motor pools in clinically complete spinal cord injury (SCI) compared with noninjured (NI) individuals. We induced multisegmental responses of the soleus, medial gastrocnemius, tibialis anterior, medial hamstring, and vastus lateralis muscles in response to percutaneous spinal cord stimulation over the Th11–Th12 vertebrae during standing and stepping on a treadmill. Individuals with SCI stepped on a treadmill with partial body-weight support and manual assistance of leg movements. The NI group demonstrated phase-dependent modulation of evoked potentials in all recorded muscles with the modulation of the response amplitude corresponding with changes in EMG amplitude in the same muscle. The SCI group demonstrated more variation in the pattern of modulation across the step cycle and same individuals in the SCI group could display responses with a magnitude as great as that of modulation observed in the NI group. The relationship between modulation and EMG activity during the step cycle varied from noncorrelated to highly correlated patterns. These findings demonstrate that the human lumbosacral spinal cord can phase-dependently modulate motor neuron excitability in the absence of functional supraspinal influence, although with much less consistency than that in NI individuals.

scholarly journals Improved Intralimb Coordination in People With Incomplete Spinal Cord Injury Following Training With Body Weight Support and Electrical Stimulation

2002 ◽  
Vol 82 (7) ◽  
pp. 707-715 ◽  
Author(s):  
Edelle Carmen Field-Fote ◽  
Dejan Tepavac
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Body Weight ◽  
Electrical Stimulation ◽  
Body Weight Support ◽  
Step Cycle ◽  
Weight Support ◽  
Cord Injury ◽  
Intralimb Coordination ◽  
Walking Speeds

Abstract Background and Purpose. Limb coordination is an element of motor control that is frequently disrupted following spinal cord injury (SCI). The authors assessed intralimb coordination in subjects with SCI following a 12-week program combining body weight support, electrical stimulation, and treadmill training. Subjects. Fourteen subjects with long-standing (mean time post-SCI=70 months, range=12–171 months), incomplete SCI participated. Three subjects without SCI provided data for comparison. Methods. A vector-based technique was used to assign values to the frame-by-frame changes in hip/knee angle, and vector analysis techniques were used to assess how closely the hip/knee angles of each step cycle resembled those of every other step cycle. Overground and treadmill walking speeds also were measured. Results. Following training, 9 of the 14 subjects with SCI demonstrated greater intercycle agreement. Mean overground and treadmill walking speeds improved (84% and 158%, respectively). Discussion and Conclusion. The intervention used in this study is based on our current understanding of the role of afferent input in the production of walking. Although the study sample was small and there was no control group, results suggest that training may improve intralimb coordination in people with SCI.

Cat hindlimb motoneurons during locomotion. II. Normal activity patterns

1987 ◽  
Vol 57 (2) ◽  
pp. 530-553 ◽  
Author(s):  
J. A. Hoffer ◽  
N. Sugano ◽  
G. E. Loeb ◽  
W. B. Marks ◽  
M. J. O'Donovan ◽  
...  
Keyword(s):  
Firing Rate ◽  
Vastus Lateralis ◽  
Activity Patterns ◽  
Rectus Femoris ◽  
Emg Activity ◽  
Step Cycle ◽  
Firing Rates ◽  
Anterior Thigh ◽  
Thigh Muscles ◽  
Walking Speeds

Activity patterns were recorded from 51 motoneurons in the fifth lumbar ventral root of cats walking on a motorized treadmill at a range of speeds between 0.1 and 1.3 m/s. The muscle of destination of recorded motoneurons was identified by spike-triggered averaging of EMG recordings from each of the anterior thigh muscles. Forty-three motoneurons projected to one of the quadriceps (vastus medialis, vastus lateralis, vastus intermedius, or rectus femoris) or sartorius (anterior or medial) muscles of the anterior thigh. Anterior thigh motoneurons always discharged a single burst of action potentials per step cycle, even in multifunctional muscles (e.g., sartorius anterior) that exhibited more than one burst of EMG activity per step cycle. The instantaneous firing rates of most motoneurons were lowest upon recruitment and increased progressively during a burst, as long as the EMG was still increasing. Firing rates peaked midway through each burst and tended to decline toward the end of the burst. The initial, mean, and peak firing rates of single motoneurons typically increased for faster walking speeds. At any given walking speed, early recruited motoneurons typically reached higher firing rates than late recruited motoneurons. In contrast to decerebrated cats, initial doublets at the beginning of bursts were seen only rarely. In the 4/51 motoneurons that showed initial doublets, both the instantaneous frequency of the doublet and the probability of starting a burst with a doublet decreased for faster walking speeds. The modulations in firing rate of every motoneuron were found to be closely correlated to the smoothed electromyogram of its target muscle. For 32 identified motoneurons, the unit's instantaneous frequencygram was scaled linearly by computer to the rectified smoothed EMG recorded from each of the anterior thigh muscles. The covariance between unitary frequencygram and muscle EMG was computed for each muscle. Typically, the EMG profile of the target muscle accounted for 0.88-0.96 of the variance in unitary firing rate. The EMG profiles of the other anterior thigh muscles, when tested in the same way, usually accounted only for a significantly smaller fraction of the variance. Brief amplitude fluctuations observed in the EMG envelopes were usually also reflected in the individual motoneuron frequencygrams. To further demonstrate the relationship between unitary frequencygrams and EMG, EMG envelopes recorded during walking were used as templates to generate depolarizing currents that were applied intracellularly to lumbar motoneurons in an acute spinal preparation.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Neurophysiological Changes After Paired Brain and Spinal Cord Stimulation Coupled With Locomotor Training in Human Spinal Cord Injury

2021 ◽  
Vol 12 ◽  
Author(s):  
Timothy S. Pulverenti ◽  
Morad Zaaya ◽  
Monika Grabowski ◽  
Ewelina Grabowski ◽  
Md. Anamul Islam ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Motor Cortex ◽  
Stance Phase ◽  
Training Session ◽  
H Reflex ◽  
Locomotor Training ◽  
Step Cycle ◽  
Human Spinal Cord ◽  
Cord Injury

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.

scholarly journals Locomotor training improves reciprocal and nonreciprocal inhibitory control of soleus motoneurons in human spinal cord injury

2015 ◽  
Vol 113 (7) ◽  
pp. 2447-2460 ◽  
Author(s):  
Maria Knikou ◽  
Andrew C. Smith ◽  
Chaithanya K. Mummidisetty
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Spinal Injury ◽  
Reciprocal Inhibition ◽  
H Reflex ◽  
Medial Gastrocnemius ◽  
Locomotor Training ◽  
Step Cycle ◽  
Human Spinal Cord ◽  
Cord Injury

Pathologic reorganization of spinal networks and activity-dependent plasticity are common neuronal adaptations after spinal cord injury (SCI) in humans. In this work, we examined changes of reciprocal Ia and nonreciprocal Ib inhibition after locomotor training in 16 people with chronic SCI. The soleus H-reflex depression following common peroneal nerve (CPN) and medial gastrocnemius (MG) nerve stimulation at short conditioning-test (C-T) intervals was assessed before and after training in the seated position and during stepping. The conditioned H reflexes were normalized to the unconditioned H reflex recorded during seated. During stepping, both H reflexes were normalized to the maximal M wave evoked at each bin of the step cycle. In the seated position, locomotor training replaced reciprocal facilitation with reciprocal inhibition in all subjects, and Ib facilitation was replaced by Ib inhibition in 13 out of 14 subjects. During stepping, reciprocal inhibition was decreased at early stance and increased at midswing in American Spinal Injury Association Impairment Scale C (AIS C) and was decreased at midstance and midswing phases in AIS D after training. Ib inhibition was decreased at early swing and increased at late swing in AIS C and was decreased at early stance phase in AIS D after training. The results of this study support that locomotor training alters postsynaptic actions of Ia and Ib inhibitory interneurons on soleus motoneurons at rest and during stepping and that such changes occur in cases with limited or absent supraspinal inputs.

scholarly journals Neuronal Actions of Transspinal Stimulation on Locomotor Networks and Reflex Excitability During Walking in Humans With and Without Spinal Cord Injury

2021 ◽  
Vol 15 ◽  
Author(s):  
Md. Anamul Islam ◽  
Timothy S. Pulverenti ◽  
Maria Knikou
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Single Pulse ◽  
H Reflex ◽  
Spinal Reflex ◽  
Emg Activity ◽  
Step Cycle ◽  
Reflex Excitability ◽  
Cord Injury ◽  
Modulation Pattern

This study investigated the neuromodulatory effects of transspinal stimulation on soleus H-reflex excitability and electromyographic (EMG) activity during stepping in humans with and without spinal cord injury (SCI). Thirteen able-bodied adults and 5 individuals with SCI participated in the study. EMG activity from both legs was determined for steps without, during, and after a single-pulse or pulse train transspinal stimulation delivered during stepping randomly at different phases of the step cycle. The soleus H-reflex was recorded in both subject groups under control conditions and following single-pulse transspinal stimulation at an individualized exactly similar positive and negative conditioning-test interval. The EMG activity was decreased in both subject groups at the steps during transspinal stimulation, while intralimb and interlimb coordination were altered only in SCI subjects. At the steps immediately after transspinal stimulation, the physiological phase-dependent EMG modulation pattern remained unaffected in able-bodied subjects. The conditioned soleus H-reflex was depressed throughout the step cycle in both subject groups. Transspinal stimulation modulated depolarization of motoneurons over multiple segments, limb coordination, and soleus H-reflex excitability during assisted stepping. The soleus H-reflex depression may be the result of complex spinal inhibitory interneuronal circuits activated by transspinal stimulation and collision between orthodromic and antidromic volleys in the peripheral mixed nerve. The soleus H-reflex depression by transspinal stimulation suggests a potential application for normalization of spinal reflex excitability after SCI.

scholarly journals Features of hand-foot crawling behavior in human adults

2012 ◽  
Vol 107 (1) ◽  
pp. 114-125 ◽  
Author(s):  
M. J. MacLellan ◽  
Y. P. Ivanenko ◽  
G. Cappellini ◽  
F. Sylos Labini ◽  
F. Lacquaniti
Keyword(s):  
Spinal Cord ◽  
Neural Control ◽  
The Body ◽  
Bipedal Walking ◽  
Emg Activity ◽  
Gradual Transition ◽  
Spatiotemporal Pattern ◽  
Plantar Flexors ◽  
Pattern Generators ◽  
Hands And Feet

Interlimb coordination of crawling kinematics in humans shares features with other primates and nonprimate quadrupeds, and it has been suggested that this is due to a similar organization of the locomotor pattern generators (CPGs). To extend the previous findings and to further explore the neural control of bipedal vs. quadrupedal locomotion, we used a crawling paradigm in which healthy adults crawled on their hands and feet at different speeds and at different surface inclinations (13°, 27°, and 35°). Ground reaction forces, limb kinematics, and electromyographic (EMG) activity from 26 upper and lower limb muscles on the right side of the body were collected. The EMG activity was mapped onto the spinal cord in approximate rostrocaudal locations of the motoneuron pools to characterize the general features of cervical and lumbosacral spinal cord activation. The spatiotemporal pattern of spinal cord activity significantly differed between quadrupedal and bipedal gaits. In addition, participants exhibited a large range of kinematic coordination styles (diagonal vs. lateral patterns), which is in contrast to the stereotypical kinematics of upright bipedal walking, suggesting flexible coupling of cervical and lumbosacral pattern generators. Results showed strikingly dissimilar directional horizontal forces for the arms and legs, considerably retracted average leg orientation, and substantially smaller sacral vs. lumbar motoneuron activity compared with quadrupedal gait in animals. A gradual transition to a more vertical body orientation (increasing the inclination of the treadmill) led to the appearance of more prominent sacral activity (related to activation of ankle plantar flexors), typical of bipedal walking. The findings highlight the reorganization and adaptation of CPG networks involved in the control of quadrupedal human locomotion and a high specialization of the musculoskeletal apparatus to specific gaits.

Motor Patterns in Human Walking and Running

2006 ◽  
Vol 95 (6) ◽  
pp. 3426-3437 ◽  
Author(s):  
G. Cappellini ◽  
Y. P. Ivanenko ◽  
R. E. Poppele ◽  
F. Lacquaniti
Keyword(s):  
Muscle Activation ◽  
Human Locomotion ◽  
Trunk Muscles ◽  
Emg Activity ◽  
Step Cycle ◽  
Motor Patterns ◽  
Leg Muscles ◽  
Shoulder Muscles ◽  
The Difference ◽  
Muscle Activations

Despite distinct differences between walking and running, the two types of human locomotion are likely to be controlled by shared pattern-generating networks. However, the differences between their kinematics and kinetics imply that corresponding muscle activations may also be quite different. We examined the differences between walking and running by recording kinematics and electromyographic (EMG) activity in 32 ipsilateral limb and trunk muscles during human locomotion, and compared the effects of speed (3–12 km/h) and gait. We found that the timing of muscle activation was accounted for by five basic temporal activation components during running as we previously found for walking. Each component was loaded on similar sets of leg muscles in both gaits but generally on different sets of upper trunk and shoulder muscles. The major difference between walking and running was that one temporal component, occurring during stance, was shifted to an earlier phase in the step cycle during running. These muscle activation differences between gaits did not simply depend on locomotion speed as shown by recordings during each gait over the same range of speeds (5–9 km/h). The results are consistent with an organization of locomotion motor programs having two parts, one that organizes muscle activation during swing and another during stance and the transition to swing. The timing shift between walking and running reflects therefore the difference in the relative duration of the stance phase in the two gaits.

scholarly journals The role of the load-dependent sensory input in control of balance during gait

2021 ◽  
Author(s):  
Popov Alexander ◽  
Lyakhovetskii Vsevolod ◽  
Bazhenova Elena ◽  
Gorskii Oleg ◽  
Kalinina Daria ◽  
...  
Keyword(s):  
Locomotor Activity ◽  
Balance Control ◽  
Center Of Mass ◽  
Afferent Input ◽  
Hindlimb Unloading ◽  
Emg Activity ◽  
Control Mechanisms ◽  
Step Cycle ◽  
Hindlimb Muscle ◽  
Before And After

Locomotor activity requires fine balance control that strongly depends on the afferent input from the load receptors. Following hindlimb unloading (HU), the kinematic and EMG activity of the hindlimbs is known to change significantly. However, the effects of HU on the integrative control mechanisms of posture and locomotion are not clear. The goal of the present study was to evaluate the center of mass (CoM) dynamic stabilization and associated adaptive changes in the trunk and hindlimb muscle activity during locomotion after 7 days of HU. The EMG signals from the muscles of the low lumbar trunk (m. longissimus dorsi [VERT]) and the hind limb (m. tibialis anterior [TA], m. semitendinosus [ST], m. soleus [SOL]) were recorded together with the hindquarter kinematics during locomotion on a treadmill in 6 rats before and after HU. The CoM lateral shift in the step cycle significantly increased after HU and coincided with the enhanced activity of VERT. The mean EMG of the TA and the ST flexor activity increased significantly with reduction of their burst duration. These data demonstrate the disturbances of body balance after HU that can influence the basic parameters of locomotor activity. The load-dependent mechanisms resulted in compensatory adjustments of flexor activity toward a faster gait strategy, such as a trot or gallop, which presumably have supraspinal origin. The neuronal underpinnings of these integrative posture and locomotion mechanisms and their possible reorganization after HU are discussed.

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