scholarly journals Spatiotemporal Activation of Lumbosacral Motoneurons in the Locomotor Step Cycle

2002 ◽  
Vol 87 (3) ◽  
pp. 1542-1553 ◽  
Author(s):  
Sergiy Yakovenko ◽  
Vivian Mushahwar ◽  
Veronique VanderHorst ◽  
Gert Holstege ◽  
Arthur Prochazka
Keyword(s):  
Spinal Cord ◽  
Stance Phase ◽  
Three Dimensional ◽  
Swing Phase ◽  
Caudal Part ◽  
Step Cycle ◽  
Lumbosacral Spinal Cord ◽  
Sensory Inputs ◽  
Hindlimb Muscles ◽  
Rostral Part

The aim of this study was to produce a dynamic model of the spatiotemporal activation of ensembles of alpha motoneurons (MNs) in the cat lumbosacral spinal cord during the locomotor step cycle. The coordinates of MNs of 27 hindlimb muscles of the cat were digitized from transverse sections of spinal cord spanning the entire lumbosacral enlargement from the caudal part of L4 to the rostral part of S1 segments. Outlines of the spinal cord gray matter were also digitized. Models of the spinal cord were generated from these digitized data and displayed on a computer screen as three-dimensional (3-D) images. We compiled a chart of electromyographic (EMG) profiles of the same 27 muscles during the cat step cycle from previous studies and used these to modulate the number of active MNs in the 3-D images. The step cycle was divided into 100 equal intervals corresponding to about 7 ms each for gait of moderate speed. For each of these 100 intervals, the level of EMG of each muscle was used to scale the number of dots displayed randomly within the volume of the corresponding MN pool in the digital model. One hundred images of the spinal cord were thereby generated, and these could be played in sequence as a continuous-loop movie representing rhythmical stepping. A rostrocaudal oscillation of activity in hindlimb MN pools emerged. This was confirmed by computing the locus of the center of activation of the MNs in the 100 consecutive frames of the movie. The caudal third of the lumbosacral enlargement showed intense MN activity during the stance phase of locomotion. During the swing phase, the focus of activation shifted abruptly to the rostral part of the enlargement. At the stance-swing transition, a transient focus of activity formed in the most caudal part of the lumbosacral enlargement. This was associated with activation of gracilis, posterior biceps, posterior semimembranosus, and semitendinosus muscles. These muscles move the foot back and up to clear the ground during locomotion, a role that could be described as retraction. The spatiotemporal distribution of neuronal activity in the spinal cord during normal locomotion with descending control and sensory inputs intact has not been visualized before. The model can be used in the future to characterize spatiotemporal activity of spinal MNs in the absence of descending and sensory inputs and to compare these to spatiotemporal patterns in spinal MNs in normal locomotion.

scholarly journals H-Reflex Modulation During Walking in Spastic Paretic Subjects

1991 ◽  
Vol 18 (4) ◽  
pp. 443-452 ◽  
Author(s):  
J.F. Yang ◽  
J. Fung ◽  
M. Edamura ◽  
R. Blunt ◽  
R.B. Stein ◽  
...  
Keyword(s):  
Tibialis Anterior ◽  
Stance Phase ◽  
Normal Subjects ◽  
Swing Phase ◽  
H Reflex ◽  
Reflex Modulation ◽  
Healthy Individuals ◽  
Step Cycle ◽  
Common Pattern ◽  
Slight Depression

ABSTRACT:Hoffmann (H) reflexes were elicited from the soleus muscle during treadmill walking in 21 spastic paretic patients. The soleus and tibialis anterior muscles were reciprocally activated during walking in most patients, much like that observed in healthy individuals. The pattern of H-reflex modulation varied considerably between patients, from being relatively normal in some patients to a complete absence of modulation in others. The most common pattern observed was a lack of H-reflex modulation through the stance phase and slight depression of the reflex in the swing phase, considerably less modulation than that of normal subjects under comparable walking conditions. The high reflex amplitudes during periods of the step cycle such as early stance seems to be related to the stretch-induced large electromyogram bursts in the soleus in some subjects. The abnormally active reflexes appear to contribute to the clonus encountered during walking in these patients. In three patients who were able to walk for extended periods, the effect of stimulus intensity was examined. Two of these patients showed a greater degree of reflex modulation at lower stimulus intensities, suggesting that the lack of modulation observed at higher stimulus intensities is a result of saturation of the reflex loop. In six other patients, however, no reflex modulation could be demonstrated even at very low stimulus intensities.

Dynamic Force Properties of Soleus, And Sensorimotor Interactions of Soleus, Medial Gastrocnemius, and Tibialis Anterior in the Freely Moving Cat

1997 ◽  
Vol 01 (02) ◽  
pp. 95-109 ◽  
Author(s):  
W. Herzog ◽  
T. R. Leonard
Keyword(s):  
Nerve Stimulation ◽  
Tibialis Anterior ◽  
Stance Phase ◽  
Tibialis Anterior Muscle ◽  
Force Production ◽  
Swing Phase ◽  
Medial Gastrocnemius ◽  
Active Force ◽  
Step Cycle ◽  
Sensorimotor Interactions

The dynamic properties of the cat soleus muscle were studied in freely walking animal preparations. The force and EMG responses of the soleus following supramaximal, ins tants of the step cycle. The sensorimotor interactions of soleus with the medial head of the gastrocnemius (a functional agonist of the soleus at the ankle) and the tibialis anterior (a functional antagonist of soleus at the ankle) were studied by measuring their force and EMG responses following the artifical stimulation of the soleus nerve. Supramaximal nerve stimulation showed distinct increases in the soleus forces during the entire swing phase and the second part (after peak forces had been reached) of the stance phase. Soleus forces could only be increased slightly in the first part of stance (from paw contact to peak force). These results suggest that force production of the soleus is virtually maximal during the early phases of stance but is submaximal for the remainder of the step cycle. Forces and EMGs of the medial gastrocnemius muscle were affected by the soleus nerve stimulation only in the latter part of the swing phase. In these cases, the force and EMG of the medial gastrocnemius were reduced significantly for the step cycle following the perturbation. The active force production of soleus during late swing causes an inhibition of medial gastrocnemius activity and force. Forces and EMGs of the tibialis anterior muscle were always affected by the soleus nerve stimulation during the swing phase of the step cycle. In these case, the force EMG of the medial gastrocnemius were reduced significantly for the step cycle following the perturbation. The active force production of soleus during late swing causes an inhibition of medial gastrocnemius activity and force. Forces and EMGs of the tibialis anterior muscle were always affected by the soleus nerve stimulation during the swing phase of the step cycle. In these instances, forces and EMGs of the tibialis anterior were significantly increased compared to step cycles preceding or following the perturbation. Part of the force enhancement is caused by the stretch of the activated tibialis anterior by the soleus, and part of the enhancement is caused by reflex activation. No effects on forces or EMGs of the tibialis anterior were observed when the soleus nerve stimulation showed its effects during the stance phase of the step cycle. The results of theis study suggest that the magnitude and the quality of ensorimotor interactions of soleus with medial gastrocnemius and tibialis anterior depend on the phase of the step cycle. The strongest interactions appear to exist during the swing phase; no observable interactions were found during stance.

scholarly journals A genetically defined asymmetry underlies the inhibitory control of flexor–extensor locomotor movements

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Olivier Britz ◽  
Jingming Zhang ◽  
Katja S Grossmann ◽  
Jason Dyck ◽  
Jun C Kim ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Inhibitory Control ◽  
Motor Neurons ◽  
Stance Phase ◽  
Genetic System ◽  
Swing Phase ◽  
Timely Initiation ◽  
Flexion Extension ◽  
Limb Flexion ◽  
Caudal Spinal Cord

V1 and V2b interneurons (INs) are essential for the production of an alternating flexor–extensor motor output. Using a tripartite genetic system to selectively ablate either V1 or V2b INs in the caudal spinal cord and assess their specific functions in awake behaving animals, we find that V1 and V2b INs function in an opposing manner to control flexor–extensor-driven movements. Ablation of V1 INs results in limb hyperflexion, suggesting that V1 IN-derived inhibition is needed for proper extension movements of the limb. The loss of V2b INs results in hindlimb hyperextension and a delay in the transition from stance phase to swing phase, demonstrating V2b INs are required for the timely initiation and execution of limb flexion movements. Our findings also reveal a bias in the innervation of flexor- and extensor-related motor neurons by V1 and V2b INs that likely contributes to their differential actions on flexion–extension movements.

scholarly journals Integrating multiple sensory systems to modulate neural networks controlling posture

2015 ◽  
Vol 114 (6) ◽  
pp. 3306-3314 ◽  
Author(s):  
I. Lavrov ◽  
Y. Gerasimenko ◽  
J. Burdick ◽  
H. Zhong ◽  
R. R. Roy ◽  
...  
Keyword(s):  
Neural Networks ◽  
Spinal Cord ◽  
Weight Bearing ◽  
Cumulative Effect ◽  
Epidural Stimulation ◽  
Lumbosacral Spinal Cord ◽  
Hindlimb Muscles ◽  
Neuronal Mechanisms ◽  
Cord Injury ◽  
Complete Spinal Cord Injury

In this study we investigated the ability of sensory input to produce tonic responses in hindlimb muscles to facilitate standing in adult spinal rats and tested two hypotheses: 1) whether the spinal neural networks below a complete spinal cord transection can produce tonic reactions by activating different sensory inputs and 2) whether facilitation of tonic and rhythmic responses via activation of afferents and with spinal cord stimulation could engage similar neuronal mechanisms. We used a dynamically controlled platform to generate vibration during weight bearing, epidural stimulation (at spinal cord level S1), and/or tail pinching to determine the postural control responses that can be generated by the lumbosacral spinal cord. We observed that a combination of platform displacement, epidural stimulation, and tail pinching produces a cumulative effect that progressively enhances tonic responses in the hindlimbs. Tonic responses produced by epidural stimulation alone during standing were represented mainly by monosynaptic responses, whereas the combination of epidural stimulation and tail pinching during standing or epidural stimulation during stepping on a treadmill facilitated bilaterally both monosynaptic and polysynaptic responses. The results demonstrate that tonic muscle activity after complete spinal cord injury can be facilitated by activation of specific combinations of afferent inputs associated with load-bearing proprioception and cutaneous input in the presence of epidural stimulation and indicate that whether activation of tonic or rhythmic responses is generated depends on the specific combinations of sources and types of afferents activated in the hindlimb muscles.

scholarly journals The Biomechanical Effect of the Sensomotor Insole on a Pediatric Intoeing Gait

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
Akiyoshi Mabuchi ◽  
Hiroshi Kitoh ◽  
Masato Inoue ◽  
Mitsuhiko Hayashi ◽  
Naoki Ishiguro ◽  
...  
Keyword(s):  
Gait Analysis ◽  
Internal Rotation ◽  
Stance Phase ◽  
Three Dimensional ◽  
Step Length ◽  
Femoral Anteversion ◽  
Swing Phase ◽  
Gait Patterns ◽  
Abnormal Gait ◽  
Biomechanical Effect

Background. The sensomotor insole (SMI) has clinically been shown to be successful in treating an intoeing gait. We investigated the biomechanical effect of SMI on a pediatric intoeing gait by using three-dimensional gait analysis. Methods. Six patients with congenital clubfeet and four patients with idiopathic intoeing gait were included. There were five boys and five girls with the average age at testing of 5.6 years. The torsional profile of the lower limb was assessed clinically. Three-dimensional gait analysis was performed in the same shoes with and without SMI. Results. All clubfeet patients exhibited metatarsal adductus, while excessive femoral anteversion and/or internal tibial torsion was found in patients with idiopathic intoeing gait. SMI showed significant decreased internal rotation of the proximal femur in terminal swing phase and loading response phase. The internal rotation of the tibia was significantly smaller in mid stance phase and terminal stance phase by SMI. In addition, SMI significantly increased the walking speed and the step length. Conclusions. SMI improved abnormal gait patterns of pediatric intoeing gait by decreasing femoral internal rotation through the end of the swing phase and the beginning of the stance phase and by decreasing tibial internal rotation during the stance phase.

Forms of forward quadrupedal locomotion. I. A comparison of posture, hindlimb kinematics, and motor patterns for normal and crouched walking

1996 ◽  
Vol 76 (4) ◽  
pp. 2316-2326 ◽  
Author(s):  
T. V. Trank ◽  
C. Chen ◽  
J. L. Smith
Keyword(s):  
Activity Patterns ◽  
Swing Phase ◽  
Average Height ◽  
Normal Walking ◽  
Step Cycle ◽  
Hindlimb Muscles ◽  
Ankle Joints ◽  
Hindlimb Kinematics ◽  
Treadmill Belt ◽  
Mtp Joints

1. Posture, hindlimb kinematics, and activity patterns of selected hindlimb muscles were compared for normal and crouched treadmill walking (0.5-0.6 m/s) for eight cats. To elicit crouched walking in which the trunk and head were lowered, cats were encouraged to walk under a light-weight Plexiglas ceiling suspended 17-20 cm above the treadmill belt. Kinematic data were obtained from high-speed cine film, and electromyograms (EMGs)-synchronized with the kinematic records-were taken from 11 hindlimb muscles. 2. The postures for the two forms of walking were distinctly different. During crouched walking, each cat lowered its entire body keeping its trunk horizontal to the treadmill belt. Also the head was lowered, with the top of the head in line with the dorsal surface of the trunk. Hip height, used as a measure for hindlimb crouch, was reduced by 30%, from an average height of 23 cm to an average height of 16 cm above the belt during the entire step cycle. 3. Average cycle periods (766 +/- 30 ms, mean +/- SD) and percentage of time devoted to swing (30%) and stance (70%) were similar for normal and crouched walking. The profiles of the hindlimb kinematics were also similar for the hip, knee, ankle, and metatarsophalangeal (MTP) joints during the step cycle, but the timing of some of the motion reversal, as well as the ranges of motion during various phases, were different at some joints for the two forms of walking. 4. During the swing phase, the transition between the flexion and extension (F-E1 reversal) occurred later in the normalized swing phase at the hip, knee, and ankle joints, and the range of flexion was increased at each joint. With greater flexion at these joints, the anatomic axis of the hindlimb (measured from hip joint to toe) was decreased and the hind paw advanced in the narrow space between the abdomen and treadmill belt. At contact, the position of the paw was less anterior to the perpendicular reference line (hip joint marker to belt) and all joints were more flexed for crouched than normal walking. 5. Throughout the stance phase, the knee and ankle joints remained significantly more flexed by 41-45 deg during crouched than normal walking. Although the hip and MTP joints started in a more flexed position at paw contact, both joints extended more during stance for crouched than normal walking, and at the time of peak extension (just before paw lift-off), the degree of extension at the hip and MTP joints was similar for both forms of walking. 6. Muscle patterns for crouched and normal walking were similar with some exceptions. The burst durations for three primary flexor muscles, the semitendinosus (knee flexor), extensor digitorum longus (EDL, ankle flexor), and flexor digitorum longus (digit flexor) were longer for crouched than normal walking, and this was consistent with the increased range and duration of flexion during the swing phase of crouched walking. Also, two muscles that normally showed mainly swing-related activity during normal walking, the EDL and the extensor digitorum brevis, had distinct stance-related bursts that occurred after midstance during crouched walking. 7. Crouched walking requires a postural change that typically occurs when cats stalk prey and when cats walk up and down sleep slopes. Postural set during walking appears to be determined by brain stem and diencephalic centers, and the postural orientation of the cat may require adjustments in the motor program provided by spinal centers for the cat to walk. The role of posture and locomotion and the adjustments in hindlimb kinematics and EMG activity patterns have been studied for forward and backward walking in the cat and now for crouched walking on the treadmill. These data will assist us in understanding the role of posture, especially crouched posture, during other walking behaviors.

Differential Effects of the Reticulospinal System on Locomotion in Lamprey

1998 ◽  
Vol 80 (1) ◽  
pp. 103-112 ◽  
Author(s):  
T. Wannier ◽  
T. G. Deliagina ◽  
G. N. Orlovsky ◽  
S. Grillner
Keyword(s):  
Spinal Cord ◽  
Brain Stem ◽  
Reticular Formation ◽  
Reticular Nucleus ◽  
Caudal Part ◽  
Ventral Roots ◽  
Reticular Nuclei ◽  
The Brain ◽  
Rostral Part ◽  
Different Parts

Wannier, T., T. G. Deliagina, G. N. Orlovsky, and S. Grillner. Differential effects of the reticulospinal system on locomotion in lamprey. J. Neurophysiol. 80: 103–112, 1998. Specific effects of stimulating different parts of the reticulospinal (RS) system on the spinal locomotor pattern are described in lamprey. In the in vitro brain stem and spinal cord preparation, microstimulation in different areas of the reticular formation was performed by ejecting a small amount of d-glutamate from a micropipette. These areas were distributed over the four reticular nuclei of the brain stem: the mesencephalic reticular nucleus (MRN) and the anterior, middle and posterior rhombencephalic reticular nuclei (ARRN, MRRN, and PRRN, respectively). To prevent synaptic spread of excitation within the brain stem, the synaptic transmission was blocked by using a low Ca2+, high Mn2+ physiological saline in the brain stem pool. “Fictive” locomotion was evoked by applying N-methyl-d-aspartate (NMDA) to the spinal cord. Rhythmical discharges of motoneurons were recorded bilaterally in the midbody area, from the ventral roots that had been subdivided in dorsal and ventral branches, supplying the dorsal and ventral part of the myotome, respectively. Two major effects of brain stem stimulation were elicited: a change in the frequency of the locomotory rhythm and an induction of asymmetry (left/right, dorsal/ventral) in the segmental motor output. Approximately 50% of the stimulated sites evoked a change in locomotor frequency. In the PRRN almost all effective sites evoked an increase in frequency (10–50%). In the other nuclei, increase and decrease (10–30%) were observed equally frequently. Most of the stimulated sites (50–80%) in any reticular nucleus evoked asymmetry in the segmental motor output. Distortion of the segmental output symmetry was classified into eight categories by comparing the intensity of locomotor bursts in the dorsal and ventral branches of the two ventral roots, ipsilateral and contralateral to the stimulated side. These categories differed in the direction of the body flexion, which would be evoked during normal swimming: ipsilateral (I), contralateral (C), dorsal (D), ventral (V), ipsilateral and dorsal (ID), ipsilateral and ventral (IV), contralateral and dorsal (CD), and contralateral and ventral (CV). The different categories were not equally represented in each nucleus and across the nuclei. The most pronounced categories for each nucleus were as follow. In MRN: I (33%); ARRN: C (44%); MRRN: rostral part, I (36%) and caudal part, CV (42%); and PRRN: rostral part, I (40%) and caudal part, IV (35%). Other categories were also present but less common in each nucleus. To examine if the effects of brain stem stimulation were uniform along the spinal cord, recordings were performed from distal parts of the cord. Stimulation of a given point in the brain stem produced similar pattern of effects in 59% of cases and different patterns in 41% of cases. The main conclusion of the present study is that the proportion of RS neurons with different influences on the spinal locomotor network differs significantly among different parts of the reticular formation of the lamprey. The specificity of RS influences may represent a basis for modifications of the segmental locomotor output necessary for the control of equilibrium and steering during locomotion.

The Rat Lumbosacral Spinal Cord Adapts to Robotic Loading Applied During Stance

2002 ◽  
Vol 88 (6) ◽  
pp. 3108-3117 ◽  
Author(s):  
W. K. Timoszyk ◽  
R. D. de Leon ◽  
N. London ◽  
R. R. Roy ◽  
V. R. Edgerton ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Force Field ◽  
Muscle Activation ◽  
Interlimb Coordination ◽  
Medial Gastrocnemius ◽  
Step Cycle ◽  
Adult Rats ◽  
Robotic Arms ◽  
Lumbosacral Spinal Cord ◽  
Muscle Activation Patterns

Load-related afferent information modifies the magnitude and timing of hindlimb muscle activity during stepping in decerebrate animals and spinal cord–injured humans and animals, suggesting that the spinal cord mediates load-related locomotor responses. In this study, we found that stepping on a treadmill by adult rats that received complete, midthoracic spinal cord transections as neonates could be altered by loading the hindlimbs using a pair of small robotic arms. The robotic arms applied a downward force to the lower shanks of the hindlimbs during the stance phase and measured the position of the lower shank during stepping. No external force was applied during the swing phase of the step. When applied bilaterally, this stance force field perturbed the hindlimb trajectories so that the ankle position was shifted downward during stance. In response to this perturbation, both the stance and step cycle durations decreased. During swing, the hindlimb initially accelerated toward the normal, unperturbed swing trajectory and then tracked the normal trajectory. Bilateral loading increased the magnitude of the medial gastrocnemius electromyographic (EMG) burst during stance and increased the amplitude of the semitendinosus and rectus femoris EMG bursts. When the force field was applied unilaterally, stance duration decreased in the loaded hindlimb, while swing duration was decreased in the contralateral hindlimb, thereby preserving interlimb coordination. These results demonstrate the feasibility of using robotic devices to mechanically modulate afferent input to the injured spinal cord during weight-supported locomotion. In addition, these results indicate that the lumbosacral spinal cord responds to load-related input applied to the lower shank during stance by modifying step timing and muscle activation patterns, while preserving normal swing kinematics and interlimb coordination.

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