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Results for “interlimb coordination”

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PubMed1985

Mathematical models of central pattern generators in locomotion: III. Interlimb model for the cat.

Possible neural connective patterns and functions with respect to interlimb coordination are studied theoretically with a mathematical model of the central pattern generating system for cat locomotion. Activities in populations of neurons controlling limb joint flexors and extensors in all four limbs are represented by a system of nonlinear differential equations. Solutions of the system for various parameter values simulate various gaits of the cat. The model is shown to be capable of generating all gaits of the cat and accounting for corresponding phase changes in interlimb coordination. The model also exhibits smooth changes of gait, and smooth initiation and termination of stepping. Further, within each limb, muscle sequencing, step cycle phases, and flexor-extensor interactions can be studied. The model suggests that one of the simplest mechanisms for a central command system to change the gait is via inhibition of specific interlimb propriospinal pathways. In a final section, properties of both proposed single limb and interlimb models are reviewed with specific reference to planning future experimental and theoretical studies.

Journal Article↗

PubMed2002

The rat lumbosacral spinal cord adapts to robotic loading applied during stance.

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.

Adaptation, Physiological↗

PubMed1986

Simultaneous control of two rhythmical behaviors. I. Locomotion with paw-shake response in normal cat.

We investigated the ability of normal cats, trained to maintain a constant position while walking on a treadmill, to combine the paw-shake response with quadrupedal locomotion. Hindlimb paw-shake responses were elicited during walking after the right hindpaw was wrapped with tape. To assess intralimb and interlimb coordination of the combined behaviors, electromyographic (EMG) recordings from forelimb extensor muscles and from selected flexor and extensor muscles at the three major hindlimb joints were correlated with joint motion by using high-speed, cinefilm analysis. When paw shaking was combined with walking, the response occurred during the swing phase of the taped hindlimb. To accommodate the paw-shake response, swing duration of the shaking hindlimb and of the homolateral forelimb increased and was followed by a brief recovery step. Concurrently, to compensate for the response, stance durations of the contralateral forelimb and hindlimb increased. The magnitude of these adjustments in interlimb coordination was influenced by the number of paw-shake cycles, which ranged from one to four oscillations. Transitions between the muscle synergies for the paw-shake response and swing were smooth in the shaking limb. Early in the swing phase, when the flexor muscles were still active (F phase), the paw shake was initiated by an early onset of knee extensor activity, which preceded extensor activity at the hip and ankle. This action provided a transition from the general reciprocal synergy between flexor and extensor muscles of locomotion to the mixed synergy that is typical of the paw shake (30). Following the last paw-shake cycle, an extensor synergy initiated the E-1 phase of swing, and the resultant joint motion was in-phase extension of the hip, knee, and ankle to lower the paw for stance. Average cycle period and burst duration for muscles participating in the paw-shake response were similar to those reported for normal cats assuming a standing posture (28, 30). The average number of paw-shake cycles, however, decreased from eight to three when the response occurred during walking, suggesting that the response was truncated to provide for continued locomotion. Further, hip motion was variable when the paw shake was combined with swing, and sometimes the hip failed to oscillate and its trajectory was similar to that of an unperturbed swing phase. When hip joint oscillations occurred during the paw-shake response, they were in-phase with ankle motions.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed2006

Inter-enlargement pathways in the ventrolateral funiculus of the adult rat spinal cord.

The ventrolateral funiculus (VLF) in the spinal cord contains important ascending and descending pathways related to locomotion and interlimb coordination. The primary purpose of this descriptive study was to investigate the distribution of inter-enlargement pathways in the adult rat spinal cord with an emphasis on the VLF. We made discrete unilateral injections of Fluoro-Gold (FG) into the right VLF at thoracic segment (T) 9, and either unilateral or bilateral injections of Fluoro-Ruby (FR) into the intermediate gray matter at the cervical (C) 5-6, C7-8, or lumbar (L) 2 segmental levels. Inter-enlargement neurons with ascending axons in the right VLF were found bilaterally in laminae VII and VIII throughout the rostral lumbar spinal cord (L1-L3) and predominantly contralaterally in the caudal lumbosacral (L4-S1) spinal cord. Following left unilateral FR injections at C5-6 or C7-8 and right unilateral VLF injections of FG at T9, very few double-labeled neurons could be found anywhere in the lumbar spinal cord. Similar injections of FR at L2 revealed an almost symmetrical bilateral distribution of double-labeled neurons throughout the cervical spinal cord (C1-8). These results describe ascending and descending pathways within the spinal cord that interconnect the two enlargements and involve both commissural and ipsilateral interneurons. The majority of inter-enlargement neurons had axons within the VLF at T9. These observations support the hypothesis that the VLF contains long ascending and descending axons with propriospinal inter-enlargement, commissural and ipsilateral connections that are anatomically well-suited to mediate interlimb coordination.

Animals↗

PubMed2002

Mutability of bifunctional thigh muscle activity in pedaling due to contralateral leg force generation.

Locomotion requires uninterrupted transitions between limb extension and flexion. The role of contralateral sensorimotor signals in executing smooth transitions is little understood even though their participation is crucial to bipedal walking. However, elucidating neural interlimb coordinating mechanisms in human walking is difficult because changes to contralateral sensorimotor activity also affect the ipsilateral mechanics. Pedaling, conversely, is ideal for studying bilateral coordination because ipsilateral mechanics can be independently controlled. In pedaling, the anterior and posterior bifunctional thigh muscles develop needed anterior and posterior crank forces, respectively, to dominate the flexion-to-extension and extension-to-flexion transitions. We hypothesized that contralateral sensorimotor activity substantially contributes to the appropriate activation of these bifunctional muscles during the limb transitions. Bilateral pedal forces and surface electromyograms (EMGs) from four thigh muscles were collected from 15 subjects who pedaled with their right leg against a right-crank servomotor, which emulated the mechanical load experienced in conventional two-legged coupled-crank pedaling. In one pedaling session, the contralateral (left) leg pseudo-pedaled (i.e., EMG activity and pedal forces were pedaling-like, but pedal force was not allowed to affect crank rotation). In other sessions, the mechanically decoupled contralateral leg was first relaxed and then produced rhythmic isometric force trajectories during either leg flexion or one of the two limb transitions of the pedaling leg. With contralateral force production in the extension-to-flexion transition (predominantly by the hamstrings), rectus femoris activity and work output increased in the pedaling leg during its flexion-to-extension transition, which occurs simultaneously with contralateral extension-to-flexion in conventional pedaling. Similarly, with contralateral force production in the other transition (i.e., flexion-to-extension; predominantly by rectus femoris), hamstrings activity and work output increased in the pedaling leg during its extension-to-flexion transition. Therefore rhythmic isometric force generation in the contralateral leg supported the ongoing bifunctional muscle activity and resulting work output in the pedaling leg. The results suggest that neural interlimb coordinating mechanisms fine-tune bifunctional muscle activity in rhythmic lower-limb tasks to ensure limb flexion/extension transitions are executed successfully.

Adult↗

PubMed1995

The detuning factor in the dynamics of interlimb rhythmic coordination.

Dynamical models of two coupled biological oscillators interpret the detuning term as an arithmetic difference between the uncoupled frequencies, delta omega = (omega 1-omega 2). This delta omega interpretation of detuning was addressed in four experiments in which human subjects oscillated pendulums in their right and left hands in 1:1 frequency locking in antiphase (Experiments 1-3) or inphase (Experiment 4). Differences between the uncoupled frequencies were manipulated through differences in the equivalent simple pendulum lengths, and the effects of this manipulation on the detuning of relative phase from pi or O and the standard deviation of relative phase SD phi were measured. In Experiment 1, the same values of omega i were satisfied by several different physical configurations. The experiment confirmed that the detuning term is related strictly to the uncoupled frequencies rather than to other physical characteristics of the oscillators. Experiments 2, 3 and 4 showed, however, that the particular dependency of fixed point drift and SD phi on delta omega depends on the particulars of omega 1 and omega 2. With variations in delta omega brought about by different omega 1 and omega 2 that always formed a constant ratio, fixed point drift related inversely to delta omega, and SD phi varied with delta omega in ways that depended on the magnitude of the constant ratio. These outcomes do not conform to expectations from models of coordination dynamics that interpret detuning as (omega 1-omega 2).

Adult↗

PubMed2003

Directional interference during bimanual coordination: is interlimb coupling mediated by afferent or efferent processes.

The role of afferent information in bimanual directional interference was studied by means of a modulation of the response-produced information in one of both limbs. In Experiment 1, visual information was either present, withdrawn, or shown with a directional transformation on a LCD screen. In Experiment 2, the technique of muscle tendon vibration was used to bias the kinesthetic afferent information associated with movement. The findings revealed strong evidence for directional interference between both limbs. Nevertheless, no evidence could be advanced that the observed interference from the right onto the left limb movement was modulated by manipulation of the afferent sources of information. It is concluded that directional interference primarily emerges at the efferent level of movement planning and organization.

Adult↗

PubMed2006

Interlimb postural coordination in the standing cat.

The dorsal-side-up body posture in standing quadrupeds is maintained by coordinated activity of four limbs. We studied this coordination in the cat standing on the platform periodically tilted in the frontal plane. By suspending different body parts, we unloaded one, two, or three limbs. The activity of selected extensor muscles and the contact forces under the limbs were recorded. With all four limbs on the platform, extensors of the fore- and hindlimbs increased their activity in parallel during ipsilateral downward tilt. With two forelimbs on the platform, this muscular pattern persisted in the forelimbs and in the suspended hindlimbs. With two hindlimbs on the platform, the muscular pattern persisted only in the hindlimbs, but not in the suspended forelimbs. These results suggest that coordination between the two girdles is based primarily on the influences of the forelimbs upon the hindlimbs. However, these influences do not necessarily determine the responses to tilt in the hindlimbs. This was demonstrated by antiphase tilting of the fore- and hindquarters. Under these conditions, the extensors of the fore- and hindlimbs appeared uncoupled and modulated in antiphase, suggesting an independent control of posture in the fore- and hindquarters. With only one limb supporting the shoulder or hip girdle, a muscular pattern with normal phasing was observed in both limbs of that girdle. This finding suggests that reflex mechanisms of an individual limb generate only a part of postural corrections; another part is produced on the basis of crossed influences.

Animals↗

PubMed2005

Interactions between interlimb and intralimb coordination during the performance of bimanual multijoint movements.

The simultaneous performance of movements involving different effectors gives rise to neural and biomechanical interactions between and within limbs. The present study addressed the role of interlimb and intralimb constraints during the control of bimanual multijoint movements. Thirteen participants performed eight tasks involving the bilateral elbows and wrists under different coordination conditions. With respect to interlimb coordination, coordination patterns referred to the in-phase and anti-phase coordination modes, involving the simultaneous timing of homologous versus non-homologous muscles, respectively. With respect to inter-segmental (intralimb) coordination, the isodirectional mode referred to simultaneous flexions and extensions in the ipsilateral wrist and elbow joints, whereas the non-isodirectional mode involved simultaneous flexion in one joint together with extension in the other joint, or vice versa. The analysis of the data focused upon measures of relative phasing between proximal and distal joints within a limb as well as between the homologous joints of both limbs. With respect to interlimb coordination, findings revealed that adoption of the in-phase mode resulted in a higher quality of interlimb coordination than the anti-phase mode. However, the mode adopted in the distal joints had a larger impact on the quality of interlimb coordination than the mode adopted in the proximal joints. More specifically, in-phase coordination of the distal joints had a positive, and anti-phase coordination a negative, influence on the global coordinative behavior of the system. Minor effects of intralimb coordination modes on interlimb coordination were observed. With respect to intralimb coordination between the ipsilateral elbow and wrist, the isodirectional mode was performed with higher stability than the non-isodirectional mode. The mode of interlimb coordination also affected the quality of intralimb coordination, such that generating anti-phase coordination patterns in the distal joints had a negative influence on the accuracy and stability of intralimb coordination. Taken together, the present findings suggest a hierarchical structure whereby interlimb coordination constraints have a stronger impact on the global coordinative behavior of the system than intralimb coordination constraints. Moreover, the global coordinative state of the system is more affected by the coordination between the distal than between the proximal joints. Overall, the findings suggest that the mirror-image symmetry constraint has a powerful influence on bimanual multijoint coordination.

Arm↗

PubMed1999

Kinematic and qualitative analysis of lower-extremity movements in preterm infants with brain lesions.

BACKGROUND AND PURPOSE: The purposes of this study were to evaluate the effects of preterm birth, severe brain lesions, and postterm age on kicking movements of young infants and to compare the prognostic value of kinematic analysis of kicking with a qualitative assessment of infants' spontaneous movements. SUBJECTS: The subjects were 12 full-term infants without brain injury, 12 low-risk preterm infants without brain injury, and 11 preterm infants with severe brain lesions (periventricular leukomalacia). METHODS: Videotape recordings of each infant's motor behavior in a supine position were made at 1 and 3 months postterm age. Kicking frequency, temporal organization of the kick cycle, coordination among different joints, and interlimb coordination were measured. A qualitative assessment for lower-extremity movements and a Gestalt judgment of general movement quality according to Prechtl's method were made from the same videotape recordings. RESULTS: Kinematic analysis showed only mild differences among the 3 groups of infants. Qualitative assessment of the lower-extremity movements, however, showed that preterm infants with brain lesions, and particularly those who later were found to have cerebral palsy, consistently had fewer segmental movements of the foot and abnormal general movements at both ages. CONCLUSION AND DISCUSSION: The data suggest that the mechanisms responsible for kicking movements in newborns and young infants do not appear to be influenced by the extrauterine environment or by brain lesions, at least at the ages studied. Qualitative assessment of lower-extremity and general movements seems to be more appropriate for clinical purposes.

Biomechanical Phenomena↗

PubMed1985

Development and characteristics of airstepping in chronic spinal cats.

Airstepping, walking-like movements of the hindlimbs, is a commonly observed behavior in chronic spinal animals when they are held vertically. The purpose of this study was to: describe the development of airstepping after spinalization and compare it to the onset of segmental reflexes, characterize the EMG pattern of muscle activity during spontaneous airstepping, and examine the effects of sensory perturbation on the characteristic pattern. Airstepping was analyzed during three conditions of tonic sensory perturbation which included: tail pinching, tape applied to one hindpaw, and immobilization of the ankle and knee in a plaster cast. Seven adult cats were spinalized at T-12, and bipolar electrode wires were surgically implanted in selected hindlimb muscles at the hip, knee, and ankle. Testing began within 48 hr of transection. Segmental reflexes and paw-shake responses were present in the first week; however, the earliest observed airstepping occurred during tail pinching at 2 weeks after surgery, and the average onset of spontaneous airstepping (without exteroceptive stimuli) was at 33 days. The average cycle period of spontaneous airstepping (691 msec) was comparable to the shortest periods reported for fictive rhythms and to treadmill walking between 1 and 2 m/sec. Intralimb coordination was characterized by flexor and extensor synergies typical of locomotion, while interlimb coordination was characterized by alternating cycles similar to that reported for treadmill walking and fictive locomotion. Neither intralimb nor interlimb patterns of coordination were altered by conditions of sensory perturbation, although cycle period and EMG recruitment level were variable. Many characteristics of airstepping are similar to those of treadmill and fictive locomotion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2003

Effect of rhythmic arm movement on reflexes in the legs: modulation of soleus H-reflexes and somatosensory conditioning.

During locomotor tasks such as walking, running, and swimming, the arms move rhythmically with the legs. It has been suggested that connections between the cervical and lumbosacral spinal cord may mediate some of this interlimb coordination. However, it is unclear how these interlimb pathways modulate reflex excitability during movement. We hypothesized that rhythmic arm movement would alter the gain of reflex pathways in the stationary leg. Soleus H-reflexes recorded during arm cycling were compared with those recorded at similar positions with the arms stationary. Nerve stimulation was delivered with the right arm at approximately 70 degrees shoulder flexion or 10 degrees shoulder extension. H-reflexes were evoked alone (unconditioned) or with sural or common peroneal nerve (CP) conditioning to decrease or increase soleus IA presynaptic inhibition, respectively. Both conditioning stimuli were also delivered with no H-reflex stimulation. H-reflex amplitudes were compared at similar M-wave amplitudes and activation levels of the soleus. Arm cycling significantly reduced (P < 0.05) unconditioned soleus H-reflexes at shoulder flexion by 21.7% and at shoulder extension by 8.8% compared with static controls. The results demonstrate a task-dependent modulation of soleus H-reflexes between arm cycling and stationary trials. Sural nerve stimulation facilitated H-reflexes at shoulder extension but not at shoulder flexion during static and cycling trials. CP nerve stimulation significantly reduced H-reflex amplitude in all conditions. Reflexes in soleus when sural and CP nerve stimulation were delivered alone, were not different between cycling and static trials; thus the task-dependent change in H reflex amplitude was not due to changes in motoneuron excitability. Therefore modulation occurred at a pre-motoneuronal level, probably by presynaptic inhibition of the IA afferent volley. Results indicate that neural networks coupling the cervical and lumbosacral spinal cord in humans are activated during rhythmic arm movement. It is proposed that activation of these networks may assist in reflex linkages between the arms and legs during locomotor tasks.

Adult↗

PubMed1997

The dynamics of bimanual circle drawing.

A bimanual circle drawing task was employed to elucidate the dynamics of intralimb and interlimb coordination. Right-handed subjects were required to produce circles with both hands in either a symmetrical (mirror) mode (i.e. one hand moving clockwise, the other counter-clockwise) or in an asymmetrical mode (i.e. both hands moving clockwise or counter-clockwise). The frequency of movement was scaled by an auditory metronome from 1.50 Hz to 3.25 Hz in 8 (8-sec) steps. In the asymmetrical mode, distortions of the movement trajectories, transient departures from the target pattern of coordination, and phase wandering were evidence as movement frequency was increased. These features suggested loss of stability. Deviations from circular trajectories were most prominent for movements of the left hand. Transient departures from the required mode of coordination were also largely precipitated by the left hand. The results are discussed with reference to manual asymmetries and mechanisms of interlimb and intersegmental coordination.

Adult↗

PubMed1996

Between-limb asynchronies during bimanual coordination: effects of manual dominance and attentional cueing.

Whereas previous studies on interlimb coordination have mainly underscored the ubiquitous tendency to synchronize the motions of the limbs, the present experiment revealed a small, but distinct, interlimb asynchrony or phase offset, i.e. the dominant limb led the non-dominant limb during the production of bimanual circle drawing. This asynchrony was clearly evident in the majority of right-handers, but not in left-handers. Moreover, attentional cueing affected the size of the asynchrony. Instructions to visually monitor the dominant limb or non-dominant limb strengthened and weakened the phase offset, respectively. A multifactorial neural account is proposed to underly the temporal asynchrony.

Adult↗

PubMed1995

Frequency detuning of the phase entrainment dynamics of visually coupled rhythmic movements.

An order parameter equation for correlated limb movements was applied to rhythmic coordination between the limbs of two people. The interlimb coordination was established and maintained through vision. Manipulations of frequency competition, coupled frequency, and intended mode (in-phase or anti-phase) produced equilibria and fluctuations in relative phase predicted by the order parameter equation and confirmed originally in within-person coordination. It was concluded that there is an elementary coordination dynamics governing the rhythmic coordination between organisms as well as between components of a single organism.

Adult↗

PubMed1983

Shifting patterns of bilateral coordination and lateral dominance in the leg movements of young infants.

Patterns of interlimb coordination and lateral preference of spontaneous leg kicks were described for 8 normal human infants observed biweekly from 2 to 26 weeks of age. Newborn infants showed a high percentage of alternating movements, which were often supplanted by unilateral movements between 1 and 4 months. Simultaneous (in-phase) kicks matured later than alternating kicks. No consistent lateral preferences were detected. The developmental course was marked by variability and discontinuities within each infant. We propose that asynchronous and asymmetrical maturation of subcortical tracts and/or muscle strength could account for these behavioral shifts.

Arousal↗

PubMed1999

Dynamics of 1:2 Coordination: Sources of Symmetry Breaking.

Three asymmetries in the dynamics of 1:2 interlimb coordination were examined: the asymmetry in uncoupled frequencies, the asymmetry in coupled frequencies, and the left-right functional asymmetry of the body. In a bimanual 1:2 task, participants (N = 8) oscillated hand-held pendulums whose uncoupled frequencies were adjusted so that the first kind of asymmetry could be manipulated. For any given pendulum pair, the pendulum assuming the faster motion in the 1:2 coordination was oscillated in the right and the left hands. By assigning combinations of uncoupled eigenfrequencies and coupled task-specified frequencies across hands, the authors studied the interaction of all 3 asymmetries. The results confirm the appropriateness of generalized relative phase as a collective variable for 1:2 coordination. Additionally, they suggest that the generalized form of the detuning parameter represents the first asymmetry and that the coupling function expresses the second asymmetry. In 1:2 coordination, the body's functional asymmetry plays a limited role.

Journal Article↗

PubMed2004

Bimanual coordination and musical experience: the role of intrinsic dynamics and behavioral information.

Rhythmic interlimb coordination arises from the interaction of intrinsic dynamics and behavioral information, that is, intention, memory, or external information specifying the required coordination pattern. This study investigates the influence of the content of memorized behavioral information on coordination in musically experienced and inexperienced participants. These groups are hypothesized to have different intrinsic dynamics for this task. Stability was assessed in a switching task (variability and switching time). The in-phase, anti-phase, and 90 degrees -phase difference were specified in a neutral and an ecologically relevant manner. Musicians showed more stable coordination than nonmusicians did. No interaction effect was found with memorized behavioral information. Behavioral information showed an interaction effect with phase pattern on coordination variability, with the strongest effect for the 90 degrees -phase pattern. Switching time was affected largely in line with the findings for coordination variability. Participants showed an intraindividual preference for one type of gallop and one type of switch strategy, suggesting different hand roles for the two hands.

Adult↗