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Results for “interlimb coordination”

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PubMed1975

Neuronal activity in the lateral vestibular nucleus of the cat. V. Topographical distribution of inhibitory effects mediated by the spino-olivocerebellar pathway.

The spatial distribution of inhibitory effects mediated by spinoolivocerebellar pathways and evoked by stimulation of the FRA was studied in Deiters' nucleus by intracellular recordings and extracellular measurements of positive field potentials. At a geven recording site individual nerves greatly varied in their effectiveness: Q and Saph, Tib and FDL were usually the most effective, while GS had very little effect. When comparing several recording sites, various patterns of dominating and nondominating nerves were found, resulting in a somewhat patchy distribution of responses. The results were supported by intracellular recordings, which showed that CF-mediated IPSPs can be evoked from a limited number of nerves only. The findings show that a discriminative pattern exists in the FRA-evoked spino-olivocerebellar-mediated inhibition. In addition, Deiters neurones were found in which the inhibition was evoked from a large number of fore- and hindlimb nerves. Such a generalized inhibitory pattern may be involved in interlimb coordination during locomotion.

Afferent Pathways↗

PubMedDate not supplied

Facilitation of transmission via inhibitory pathway 1a to spinal extensor motoneurons in response to stimulation of the forelimb nerves in cats.

Activation of forelimb flexor reflex afferent in cats anesthetized with a mixture of Chloralose and Nembutal evoked temporospatial facilitation in the reciprocal inhibitory pathways to spinal extensor motoneurons. The amplitude of disynaptic reciprocal 1a inhibitory postsynaptic potentials (IPSP) evoked in the extensor motoneurons by activation of the most excitable fibers of the nerve supplying the antagonist muscle increased several-fold using conditioning stimulation of the forelimb nerve. Facilitation of 1a IPSP occurred on a background of IPSP evoked by descending inter-limb discharges. Facilitation of 1a IPSP had a latent period of 18-20 msec and could last to 60 msec. The possible role of inhibitory 1a interneurons in interlimb coordination is discussed.

Animals↗

PubMed1998

Time course of changes in EMG activity of fast muscles after partial denervation.

After partial denervation, the remaining motor units (MUs) of adult fast extensor digitorum longus muscle (EDL) expand their peripheral field. The time course of this event was studied using tension measurement and recordings of electromyographic (EMG) activity. The results show that after section of the L4 spinal nerve, when only 5.3 +/- 0.63 of the 40 MUs normally supplying EDL muscle remain, the force of individual motor units starts to increase between the 1st and 2nd week after the operation and continues to do so for a further week. The drastic reduction of the number of motoneurones supplying the fast EDL leads to an increase in activity of the remaining MUs. In the 1st week after partial denervation, there was a sharp increase in the EMG activity of remaining motor units. During the next 12 days, this increase became less marked, but EMG activity remained nevertheless significantly higher than that of the unoperated EDL muscle. Many MUs became tonically active during posture. The EMG activity pattern during locomotion was also altered, so that the burst duration was positively correlated with the step cycle duration. Moreover, shortly after partial denervation, the interlimb coordination was disturbed but returned to its original symmetrical use 1-2 weeks later.

Animals↗

PubMed2000

Recovery of hindlimb motor functions after spinal cord transection is enhanced by grafts of the embryonic raphe nuclei.

In this study, a piece of embryonic tissue from the raphe nucleus was transplanted into the spinal cord below the lesion 1 month after transection. Two months later the recovery of hindlimb motor function in rats which had received a transplant of neural tissue (ST rats) was much better than in spinal control animals without the graft (SC rats). Analysis of the electromyographic (EMG) activity showed that the timing of muscle activity during locomotor-like movement of hindlimbs in ST rats was more regular than in SC rats. In SC rats the relationships between EMG burst duration (soleus, tibialis anterior) and step cycle duration were significantly altered. The restoration of hindlimb motor function of ST rats was also reflected in the better interlimb coordination during locomotor-like hindlimb movements. The results of several behavioural tests demonstrated that the responses to stimulation of various receptors, such as tactile or proprioceptive, in ST rats were more complex than in SC rats. Additionally, unlike in SC animals, in ST rats long-lasting spontaneous episodes of air stepping movement of hindlimbs accompanied by a relatively high amplitude of EMG activity were obtained. These results confirm that grafted embryonic raphe nuclei which contain serotoninergic cells are likely to increase the excitability of neuronal circuitry in the injured spinal cord. Moreover, transplantation of embryonic raphe nuclei encourages the recovery of hindlimb motor function in adult rats even when the grafting is carried out several weeks after spinal cord injury.

Animals↗

PubMed2006

The configuration and relaxation of motor task sets.

Often the performance of a task does not only require the processing of certain stimuli in certain ways, but also certain patterns of interlimb coordination. We studied shifts between different tasks involving different patterns of intermanual coupling by means of the timed-response procedure, which allows to trace state variables related to task sets. The tasks required the production of rapid bimanual reversal movements with symmetric or parallel directions. Symmetric movements are associated with symmetric coupling, as indicated by positive intermanual correlations between the directions of left-hand and right-hand movements, whereas parallel movements are associated with parallel coupling, as indicated by negative intermanual correlations. Task switches were associated with gradual changes of the intermanual correlations, which indicate the state of intermanual coupling as a major ingredient of a task set, in the course of action preparation. At short preparation intervals intermanual correlations were those appropriate for the preceding trial; with increasing preparation time they were replaced by those appropriate for the current trial, but the influence of the preceding trial did not disappear completely. In-between trials, intermanual coupling drifted toward a symmetric coupling, but not to uncoupled limbs. After a change of the task the specification of movement directions was slowed, but its initiation was not delayed. According to these results, task sets relax toward attractors which can be different from the absence of task sets. They are gradually configured during task preparation with a persistent influence of the preceding task, and the specification of response characteristics does not wait until the configuration of the new task set is completed.

Adult↗

PubMed1977

Phasic gain control of reflexes from the dorsum of the paw during spinal locomotion.

In chronic spinal cats walking with their hindlimbs on a treadmill belt, tactile stimuli were applied to the dorsum of the paw during various phases of the step cycle. A stimulation during the swing phase evoked a flexion response with a concomitant crossed extension, whereas in stance it induced an increased ipsilateral extension. EMG-recordings show short latency reflex responses in flexors and extensors, respectively. The responses are organized such that latencies of knee muscles are shorter than those of ankle and hip muscles. The movements induced by the stimulations appear to be very meaningful during normal conditions in compensating for any unpredicted obstacle disturbing the movement of the paw during locomotion. Responses during forward flexion and during the support phase are well adapted to the ongoing locomotor activity and do not influence the interlimb coordination whereas a stimulation when the foot approaches the ground after the end of flexion disturbs the regular alternating pattern. Different possible mechanisms underlying this phase-dependent reflex reversal are discussed.

Animals↗

PubMed1980

Responses of long descending propriospinal neurons to natural and electrical types of stimuli in cat.

Long descending propriospinal (LDP) neurons (antidromically identified) having cell bodies of origin in the cervical enlargement and projecting axons at least as far as the L2 segment were studied. Extracellular recording of responses to natural and electrical stimuli was done in high-spinal cats. (1) A receptive field for natural stimuli was found for 123 LDP neurons. An additional 108 LDP cells were not activated by the natural stimuli used, but some of these fired spike potentials in response to electrical stimulation of peripheral nerves of the forelimb. There was no distinction between neurons activated and those not activated by natural stimuli on the basis of location or conduction velocity. (2) The most effective natural stimuli were mechanical manipulation of the skin (both low and high threshold), movement of joints of the paw, and pressure to the deep tissues, especially to the extensor side of the arm. These modalities of stimuli were most often excitatory, but could be inhibitory as well. (3) On the basis of modality, 4 subgroups of LDP cells were identified: those which were responsive only to mechanical-cutaneous, joint-movement, or deep-pressure stimuli, and those which responded to several of these modalities of stimuli, the multimodal group. These subgroups could not be distinguished on the basis of conduction velocity. (4) The receptive fields varied in size from small (one digit) to large (all of a forelimb). For single LDP cells they included ones with single and/or multimodal input from one or both forelimbs and various combinations of excitation and/or inhibition. However, those in the dorsal horn had only ipsilateral receptive fields, mainly of the mechanical-cutaneous type. Cells with bilateral receptive fields were mainly located medially in the ventral gray in laminae VII and VIII. (5) A comparison of the location of the subtypes of LDP cells revealed that neurons activated by mechanical-cutaneous stimuli were in laminae I and IV-VIII; whereas deep-pressure and multimodal activated neurons were almost exclusively in laminae VII and VIII. (6) LDP cells receiving input from deep-pressure receptors of the paw probably relay position or weight-bearing information about the forelimbs to the lumbosacral spinal cord. This arrangement suggests that LDP neruons function in interlimb coordination and would be active during locomotion. They probably participate also in other reflexes elicited by cutaneous and deep stimuli.

Animals↗

PubMed1993

Hemicerebellectomy and motor behaviour in rats. III. Kinematics of recovered spontaneous locomotion after lesions at different developmental stages.

The locomotion of rats with a right hemicerebellectomy (HCb) performed in adulthood was compared by means of kinematic analysis with the locomotion of rats with a similar lesion performed on the first postnatal day. The age at which the animals received cerebellar lesion made a significant difference with respect to the locomotor strategies utilized in adulthood. During stance, neonatal operate rats showed a clear hyperextension of both hindlimbs but not of the forelimbs. Their locomotor posture was characterized by spinal flexion with the head held lower than normal. During swing, they showed a tendency towards 'high stepping'. Their steps were regular and symmetrical but hypometric. Adult lesioned animals displayed a marked extensor hypotonia, ipsilateral to the lesion during stance and a relevant hyperflexion affecting both sides, during swing. Alteration of the interlimb coordination and modified sequence of steps were also observed. Thus, a highly asymmetrical, impaired and unstable locomotion was displayed by this group of animals. The present findings demonstrate the importance of the age-at-lesion factor in determining the motor strategies in the recovery of locomotor function after HCb in the rat. This evidence is discussed in the light of the widespread anatomical remodelling already demonstrated following neonatal, but not adult, HCb in rats.

Aging↗

PubMed1985

Responses of cerebellar Purkinje cells to mechanical perturbations during locomotion of decerebrate cats.

During the locomotion of cats which had been decerebrated at the precollicular and premammillary level, mechanical perturbations (taps of 50-550 g wt.) were applied to the paw dorsum of the left forelimb. Purkinje cells were recorded from the vermis of the cerebellar anterior lobe, and those connected to Deiters' neurons controlling the right forelimb were identified by antidromic and orthodromic stimuli. Taps on the left forelimb induced in these Purkinje cells two types of responses; I-type is a depression of simple spike discharge, often preceded by a brief phase of facilitation, and E-type is entirely a facilitation of simple spike discharge. Complex spikes, representing activation through climbing fiber afferents, were frequently evoked by the taps in both I- and E-types. The I-type depression in Purkinje cells closely corresponds to the previously reported facilitation in Deiters' neurons and forelimb extensor muscles, suggesting that the interlimb coordination during cat's locomotion is effected by linked activity of vermal Purkinje cells and Deiters' neurons.

Animals↗

PubMed2004

Partial recovery after treatment of chronic paraplegia in rat.

While acute spinal cord injury has been the object of intensive research, chronic spinal cord injury has received less attention although most clinical cases of spinal cord injury become chronic. We attempted to surgically "repair" chronic and acute spinal cord injury in a complete transection rat model using a multiple peripheral nerve grafting protocol. The lesion extent was assessed by magnetic resonance imaging (MRI) before the repair procedure. Rats were treated immediately after injury or at 2, 4, or 8 months postinjury. Standard behavioral methods were used to evaluate functional recovery. Two novel tests, the Bipedal Test and the Head-scratch test, were also employed to evaluate hindpaw positioning, interlimb coordination, and stepping rhythmicity, and to indicate rostrocaudal pathway regeneration. MRI helped guide the treatment procedure that was applied to animals with chronic injury. Treated animals demonstrated significant motor recovery. Axonal regeneration resultant to treatment was demonstrated histologically. The results suggest that not only acute but also chronic total paraplegia can be reversed to a moderate degree in rats with regard to hindlimb motor function.

Acute Disease↗

PubMed2005

Mirrored EMG activity during unimanual rhythmic movements.

We studied instances of mirror movements--in the form of coherent EMG activity of the muscles in the arm not intended to move--during the performance of a unimanual rhythmic task in healthy adults. Epochs of involuntary muscle activity were detected and analyzed using time-resolved spectral methods. The observed frequency and phase locking between EMG patterns derived from homologous extensor muscles indicated the presence of neural cross-talk, which is relevant to the study of interlimb coordination.

Adolescent↗

PubMed2005

Neural plasticity and bilateral movements: A rehabilitation approach for chronic stroke.

Stroke interferes with voluntary control of motor actions. Although spontaneous recovery of function can occur, restoration of normal motor function in the hemiplegic upper limb is noted in fewer than 15% of individuals. However, there is increasing evidence to suggest that in addition to injury-related reorganization, motor cortex functions can be altered by individual motor experiences. Such neural plasticity has major implications for the type of rehabilitative training administered post-stroke. This review proposes that noteworthy upper extremity gains toward motor recovery evolve from activity-dependent intervention based on theoretical motor control constructs and interlimb coordination principles. Founded on behavioral and neurophysiological mechanisms, bilateral movement training/practice has shown great promise in expediting progress toward chronic stroke recovery in the upper extremity. Planning and executing bilateral movements post-stroke may facilitate cortical neural plasticity by three mechanisms: (a) motor cortex disinhibition that allows increased use of the spared pathways of the damaged hemisphere, (b) increased recruitment of the ipsilateral pathways from the contralesional or contralateral hemisphere to supplement the damaged crossed corticospinal pathways, and (c) upregulation of descending premotorneuron commands onto propriospinal neurons.

Chronic Disease↗

PubMed1997

Quantification of upper extremity function using kinematic analysis.

OBJECTIVE: To illustrate the applicability of motor control analytical techniques to the assessment of upper limb dysfunction in children with ataxia. DESIGN: Descriptive case series. SETTING: The study sample was selected from an outpatient pediatric rehabilitation clinic and testing was performed in a research laboratory. PARTICIPANTS: Four children with upper limb ataxia and seven healthy children were examined. All subjects were recruited on a volunteer basis. Criteria for inclusion (ataxic group) included: (1) age 6 to 15 yrs; (2) ambulatory with assistive devices. MAIN OUTCOME MEASURES: Quantitative measures of elbow kinematics (movement speed and duration) and spatio-temporal "portraits" of elbow movement during unilateral and bilateral forward reaching movements. RESULTS: Movements made by ataxic subjects were characterized by lower peak velocities, prolonged durations, and increased variability compared with normal subjects. In the one subject with unilateral ataxia, interlimb coordination was severely disrupted during the performance of coupled, bilateral arm movements. In addition to changes in specific kinematic values (eg, peak velocity), phase plane and angle-angle displacement curves revealed marked spatio-temporal variability throughout the movement, the magnitude of which was correlated with severity of ataxia. CONCLUSION: The application of the quantitative motor control methods described in this report can provide rehabilitation specialists with a simple yet sensitive means to evaluate treatment and progression of a wide variety of motor disorder conditions. These techniques are particularly well suited to pediatric populations as young as 6 years.

Adolescent↗

PubMed1993

Gating of reflexes in ankle muscles during human stance and gait.

Holding the body's centre of gravity steady represents the crucial variable for the stabilization of posture in upright stance in man. Results from two experimental approaches suggest that force-dependent receptors are required, in addition to the well-known systems involved in sway stabilization, for equilibrium control. One approach concerns bilateral leg muscle activation during stance. Unilateral or bilateral leg displacements were induced while subjects stood on a treadmill with split belts. A unilateral displacement induced a bilateral EMG response. During bilateral displacements the EMG activity was linearly summed or subtracted, depending on whether the legs were displaced in the same or opposite directions. Both legs acted in a cooperative manner: each limb affected the strength of muscle activation and the time-space behaviour of the other. This interlimb coordination is suggested to be mediated by spinal interneuronal circuits, which are themselves under supraspinal (e.g., cerebellar) control. The other approach concerns the modulation of postural reflexes under stimulated "microgravity" ir. water immersion. An approximately linear relationship was found between contact forces and impulse-directed EMG response amplitudes in the leg muscles. Out of water loading of the subjects resulted in no further increase of the response amplitude. It was concluded that the function of proprioceptive reflexes involved in the stabilization of posture depends on the presence of contact forces opposing gravity. Extensor load receptors are thought to signal changes of the projection of body's centre of mass with respect to the feet. The interaction of the afferent input from these receptors with the other systems involved in postural control is not yet fully understood.

Ankle↗

PubMed2000

Abnormalities in cerebellar Purkinje cells in the novel ataxic mutant mouse, pogo.

The pogo mouse is a novel neurological mutant, which was discovered, in an inbred strain (KJR/MsKist) derived from a Korean wild mouse. The pathological manifestations include difficulty in maintaining normal posture, failures of interlimb coordination and the inability to walk straight. The ataxia is first apparent from about 2 weeks of age and progresses throughout life. The mutation is inherited as an autosomal recessive trait. In this report, we describe abnormalities in the pogo/pogo cerebellum. Nissl staining shows that the pogo/pogo cerebellum is normal in size and lobulation. Similarly, immunocytochemical staining for a granule cell marker, 10B5, shows no differences in the thickness of the granular layer between pogo/pogo homozygote and pogo/+ heterozygote littermate controls. By using anti-parvalbumin immunocytochemistry, the cells of molecular layer of the pogo/pogo cerebellum also appeared similar in distribution as compared to normal wild type mouse. In anti-neurofilament immunocytochemistry, the basket cells axons of the pogo/pogo cerebellum appeared normal. Purkinje cell abnormalities were identified by using anti-calbindin D immunocytochemistry. In 120-day-old pogo/pogo mutant mice there was a loss of Purkinje cells throughout the cerebellar vermis. Furthermore, the somata and dendrites were extensively vacuolated in the pogo/pogo Purkinje cells and the primary dendrites were frequently swollen. Focal axonal swellings were commonly observed in the Purkinje cell axons of pogo/pogo mutant mice as they traversed the granular layer. These data suggest that the progressive ataxia seen in pogo mice may be due to a failure of normal Purkinje cell activity.

Animals↗

PubMed2000

Visual perception of mean relative phase and phase variability.

Perception of relative phase and phase variability may play a fundamental role in interlimb coordination. This study was designed to investigate the perception of relative phase and of phase variability and the stability of perception in each case. Observers judged the relative phasing of two circles rhythmically moving on a computer display. The circles moved from side to side, simulating movement in the frontoparallel plane, or increased and decreased in size, simulating movement in depth. Under each viewing condition, participants observed the same displays but were to judge either mean relative phase or phase variability. Phase variability interfered with the mean-relative-phase judgments, in particular when the mean relative phase was 0 degrees. Judgments of phase variability varied as a function of mean relative phase. Furthermore, the stability of the judgments followed an asymmetric inverted U-shaped relation with mean relative phase, as predicted by the Haken-Kelso-Bunz model.

Adolescent↗

PubMed2001

Sinusoidal visuomotor tracking: intermittent servo-control or coupled oscillations?

In visuomotor tasks that involve accuracy demands, small directional changes in the trajectories have been taken as evidence of feedback-based error corrections. In the present study variability, or intermittency, in visuomanual tracking of sinusoidal targets was investigated. Two lines of analyses were pursued: First, the hypothesis that humans fundamentally act as intermittent servo-controllers was re-examined, probing the question of whether discontinuities in the movement trajectory directly imply intermittent control. Second, an alternative hypothesis was evaluated: that rhythmic tracking movements are generated by entrainment between the oscillations of the target and the actor, such that intermittency expresses the degree of stability. In 2 experiments, participants (N = 6 in each experiment) swung 1 of 2 different hand-held pendulums, tracking a rhythmic target that oscillated at different frequencies with a constant amplitude. In 1 line of analyses, the authors tested the intermittency hypothesis by using the typical kinematic error measures and spectral analysis. In a 2nd line, they examined relative phase and its variability, following analyses of rhythmic interlimb coordination. The results showed that visually guided corrective processes play a role, especially for slow movements. Intermittency, assessed as frequency and power components of the movement trajectory, was found to change as a function of both target frequency and the manipulandum's inertia. Support for entrainment was found in conditions in which task frequency was identical to or higher than the effector's eigenfrequency. The results suggest that it is the symmetry between task and effector that determines which behavioral regime is dominant.

Adult↗

PubMed2002

Infants return to two-handed reaching when they are learning to walk.

The authors examined whether infants of about 1 year return to 2-handed reaching when they begin to walk independently. Infants (N = 9) were followed longitudinally before, during, and after their transition to upright locomotion. Every week, the infants' reaching responses and patterns of interlimb coordination were screened in 3 tasks involving different adaptive reaching responses. Before the onset of upright locomotion, the infants responded to each task adaptively. Following walking onset, they increased their rate of 2-handed responses in all tasks. The 2-handed responses declined when the infants gained better balance control. The results suggest that infants' return to 2-handed reaching is experience dependent. Those findings are discussed in terms of the integration of new developing motor skills into existing cognitive and motor repertoires.

Child Development↗