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At least 343 records · Page 19Linked to original sources
PubMed1992

Steady-state fluctuations of human walking.

In steady-state walking, fluctuations in space-time behavior are observed for normal adult subjects. In the present study, the intrinsic fluctuations of gait have been analyzed when walking on a subject-driven treadmill (with adjustable inertial forces). Furthermore, these intrinsic fluctuations have been compared with those observed in natural overground locomotion which involves a real subject's displacement and thus an optical flow. Four adult subjects participated in both experimental sessions. It was found that the frequency and amplitude of the instantaneous fluctuations of leg movement were weak and of equal magnitude with or without optical flow. This was also the case for instantaneous fluctuations in displacement speed. Secondly, a low-frequency fluctuation in walking speed was observed when no optical flow information was available to the subject. This fluctuation results from the addition of a series of leg-movement fluctuations, whose values are all either positive or negative. As the optical flow provides information about the displacement speed, it allows the subject to avoid such addition, and thus plays a role in maintaining steady leg movement. Theoretical models linking space-time behavior of rhythmic movement with stiffness strongly suggest that the observed low-frequency fluctuations in speed result from fluctuations in stiffness.

Adult↗
PubMed2001

Phasic modulation of corticomotor excitability during passive movement of the upper limb: effects of movement frequency and muscle specificity.

Modulations in the excitability of spinal reflex pathways during passive rhythmic movements of the lower limb have been demonstrated by a number of previous studies [4]. Less emphasis has been placed on the role of supraspinal pathways during passive movement, and on tasks involving the upper limb. In the present study, transcranial magnetic stimulation (TMS) was delivered to subjects while undergoing passive flexion-extension movements of the contralateral wrist. Motor evoked potentials (MEPs) of flexor carpi radialis (FCR) and abductor pollicus brevis (APB) muscles were recorded. Stimuli were delivered in eight phases of the movement cycle during three different frequencies of movement. Evidence of marked modulations in pathway excitability was found in the MEP amplitudes of the FCR muscle, with responses inhibited and facilitated from static values in the extension and flexion phases, respectively. The results indicated that at higher frequencies of movement there was greater modulation in pathway excitability. Paired-pulse TMS (sub-threshold conditioning) at short interstimulus intervals revealed modulations in the extent of inhibition in MEP amplitude at high movement frequencies. In the APB muscle, there was some evidence of phasic modulations of response amplitude, although the effects were less marked than those observed in FCR. It is speculated that these modulatory effects are mediated via Ia afferent pathways and arise as a consequence of the induced forearm muscle shortening and lengthening. Although the level at which this input influences the corticomotoneuronal pathway is difficult to discern, a contribution from cortical regions is suggested.

Adult↗
PubMed1990

The ventilatory movements of the avian pelvis and tail: function of the muscles of the tail region of the pigeon (Columba livia).

We have observed that birds of several different taxa move their tails in conjunction with sound production. These observations suggested to use that tail movements might also be associated with ventilation. Since we hypothesized that rhythmic movements of the tail and pelvis will ventilate the lungs, the activities of tail, epaxial and cloacal muscles of the pigeon were examined. Electromyograms (EMGs) were recorded from these muscles while ventilation was monitored. A muscle was considered to have ventilatory activity when the EMG activity had an obvious correlation to either inspiration or expiration. To obtain further information about the correlation between muscular activity and ventilation, we induced hyperpnea by administering 5% CO2. We report that the tail muscles that function as expiratory muscles are the M. caudofemoralis, the M. pubocaudalis internus and the M. pubocaudalis externus. We refer to these as the suprapubic abdominal muscles to distinguish them from the infrapubic (ventral) abdominal muscles. These muscles depress the pelvis and the uropygium and compress the thoracoabdominal cavity. M. transversus cloacae functions as an expiratory muscle by protracting the cloaca or by reducing its compliance. Of the suprapubic muscles we studied, the only inspiratory muscle is the axial muscle, M. longissimus dorsi. M. longissimus dorsi acts at the notarial-synsacral junction to elevate the pelvis. The rocking movements of the notarial-synsacral joint appear to be important for ventilation during conditions in which the sternum is 'fixed', such as when the bird is resting on its breast. We suggest that a division of labor may exist between the infra- and suprapubic abdominal muscles during ventilation such as panting or vocalization.

Abdominal Muscles↗
PubMed1991

Occlusal force pattern during rhythmic human tapping movement.

The dynamic occlusal force patterns associated with the performance of rhythmic tapping movement were analysed in normal subjects, who were instructed to make tapping movements at four frequencies, 2, 2.5, 3.3 and 5 Hz, with as constant a magnitude of force as possible. The occlusal force recorded by an intra-oral customized device showed a triphasic pattern which could be divided into two components, and this pattern was more clearly defined during slower tapping movements. Of the two components, the first was relatively stable, regardless of changes in tapping frequency, while the second was highly dependent on the tapping cycle duration, and its duration was shortened with increases in tapping frequency. Furthermore, there was a significant correlation between the changes in the occlusal power phase and those in the burst duration of the masseter EMG simultaneously recorded by a pair of surface electrodes. On the basis of these findings, it is suggested that the tapping rhythm is modulated by the duration of the occlusal power phase and the associated jaw elevator muscle activity.

Adult↗
PubMed1997

The influence of peripheral load on resetting voluntary movement by cortical stimulation: importance of the induced twitch.

We studied the effects of changes in loading torque on the effectiveness of magnetic cortical stimulation in evoking phase resetting of voluntary wrist movement. Nine normal subjects were studied (five on two occasions), while making rhythmical movements of the right wrist, at their preferred rate, against extension torque loads of 0.35 Nm, 0.26 Nm and 0.18 Nm, flexion torque loads of 0.09 Nm and 0.18 Nm and without external load. The position records of individual trials were used to measure the effectiveness of resetting (resetting index: the slope of the phase-response curve) and the "null phase", the phase to which the trials were being reset. The loading torque had a strong influence upon both the resetting index and the null phase, generated by a constant intensity of cortical stimulation such that the largest resetting indices were obtained for movements made against the largest extension torque load (mean resetting index 0.72). The degree of resetting and null phase were related to the mean amplitude and direction of the first poststimulus position peak, which in turn was largely determined by the twitch induced by the cortical shock. The timings of the averaged poststimulus position peaks following the first were simple multiples of the prestimulus movement period. Our results indicate that loading conditions profoundly influence the effectiveness of magnetic cortical stimulation in resetting a voluntary movement and that these effects appear to be largely explicable by the changes in the muscle twitch evoked by the stimulus with the different loads. We suggest that the magnetic shock is therefore unlikely to reset voluntary movement by an action directly upon the motor programme. We propose that the main method by which magnetic cortical stimulation resets repetitive wrist movement is indirect: normal generation of repetitive wrist flexion and extension is disrupted by the cortical shock, following which afferent information related to the twitch induced is able to reset the movement.

Adult↗
PubMed2007

Does horseback riding therapy or therapist-directed hippotherapy rehabilitate children with cerebral palsy?

Quantitative (not qualitative) studies were sought investigating whether horseback riding used as therapy improves gross motor function in children with cerebral palsy (CP). Eleven published studies on instructor-directed, recreational horseback riding therapy (HBRT) and licensed-therapist-directed hippotherapy were identified, reviewed, and summarized for research design, methodological quality, therapy regimen, internal/external validity, results, and authors'conclusions. Methodological quality was moderate to good for all studies; some studies were limited by small sample size or lack of non-riding controls. HBRT improved gross motor function in five of six studies (one study was inconclusive); hippotherapy improved gross motor function in all five studies. The studies found that during HBRT and hippotherapy: (1) the three-dimensional, reciprocal movement of the walking horse produced normalized pelvic movement in the rider, closely resembling pelvic movement during ambulation in individuals without disability; (2) the sensation of smooth, rhythmical movements made by the horse improved co-contraction, joint stability, and weight shift, as well as postural and equilibrium responses; and (3) that HBRT and hippotherapy improved dynamic postural stabilization, recovery from perturbations, and anticipatory and feedback postural control. The evidence suggests that HBRT and hippotherapy are individually efficacious, and are both medically indicated as therapy for gross motor rehabilitation in children with CP. Recommendations for future research are discussed.

Animals↗
PubMed1994

Ergonomic analyses of downhill skiing.

The purpose of this study was to provide electromyographic feedback for (1) pedagogical advice in motor learning, (2) the ergonomics of materials choice and (3) competition. For these purposes: (1) EMG data were collected for the Stem Christie, the Stem Turn and the Parallel Christie (three basic ski initiation drills) and verified for the complexity of patterns; (2) integrated EMG (iEMG) and linear envelopes (LEs) were analysed from standardized positions, motions and slopes using compact, soft and competition skis; (3) in a simulated 'parallel special slalom', the muscular activity pattern and intensity of excavated and flat snow conditions were compared. The EMG data from the three studies were collected on location in the French Alps (Tignes). The analog raw EMG was recorded on the slopes with a portable seven-channel FM recorder (TEAC MR30) and with pre-amplified bipolar surface electrodes supplied with a precision instrumentation amplifier (AD 524, Analog Devices, Norwood, USA). The raw signal was full-wave rectified and enveloped using a moving average principle. This linear envelope was normalized according to the highest peak amplitude procedure per subject and was integrated in order to obtain a reference of muscular intensity. In the three studies and for all subjects (elite skiers: n = 25 in studies 1 and 2, n = 6 in study 3), we found a high level of co-contractions in the lower limb extensors and flexors, especially during the extension phase of the ski movement. The Stem Christie and the Parallel Christie showed higher levels of rhythmic movement (92 and 84%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Electromyography↗
PubMed2003

Disrupted timing of discontinuous but not continuous movements by cerebellar lesions.

Patients with cerebellar damage are known to exhibit deficits in the temporal control of movements. We report that these deficits are restricted to discontinuous movements. Cerebellar patients exhibited no deficit in temporal variability when producing continuous, rhythmic movements. We hypothesize that the temporal properties of continuous movements are emergent and reflect the operation of other control parameters not associated with the cerebellum. In contrast, discontinuous movements require an explicit representation of the temporal goal, a function of the cerebellum. The requirement for explicit temporal representation provides a parsimonious account of cerebellar involvement in a range of tasks.

Adult↗
PubMed1996

Jaw movement dysfunction related to Parkinson's disease and partially modified by levodopa.

OBJECTIVES: To test the hypotheses that Parkinson's disease can differentially produce deficits in voluntary and rhythmic jaw movements, which involve different neuronal circuits, and that levodopa treatment improves specific components of the motor deficit. METHODS: Patients with idiopathic Parkinson's disease and control subjects were tested on a series of jaw motor tasks that included simple voluntary movement, isometric clenching, and natural and paced rhythmic movements. Jaw movements were measured by changes in electromagnetic fields and EMG activity. Patients with Parkinson's disease with fluctuations in motor responses to levodopa were tested while off and on. RESULTS: During the off state, patients with Parkinson's disease were significantly worse than the control subjects on most tasks. The deficits included a decrease in amplitude and velocity during jaw opening and closing, aberrant patterns and low amplitude of EMG activity during clenching, and low vertical amplitude and prolonged durations of occlusion during rhythmic movements. No decrements were found in the amplitude of voluntary lateral jaw movements or the frequency of rhythmic movements. During the on state, improvements occurred in the patterns and level of EMG activity during clenching and in the vertical amplitude and duration of occlusion during rhythmic movements, although a significant decrement occurred in the lateral excursion of the jaw. CONCLUSIONS: Parkinson's disease affects the central programming of functionally related muscles involved in voluntary and rhythmic jaw movements and levodopa replacement influences only certain aspects of jaw movement, most likely those requiring sensory feedback.

Antiparkinson Agents↗
PubMed1992

Role of proprioceptors in neural control.

The conventional notion that peripheral muscle-related signals provide the basis for resistance to external perturbations is no longer sufficient. Proprioceptive information seems to be required for spatial steering of multi-joint movements, and also for temporal coordination among the joints in certain tasks. In rhythmic movements, peripheral and centrally generated signals appear to interact in a complementary manner. The complex effects of proprioceptive afferents on motor output continue to be delineated vigorously. Global effects of local perturbation in multi-joint contexts are emerging as being particularly significant.

Animals↗
PubMedDate not supplied

Functional multimodality of axonal tree in invertebrate neurons.

This review, based on invertebrate neuron examples, aims at highlighting the functional consequences of axonal tree organization. The axonal organization of invertebrate neurons is very complex both morphologically and physiologically. The first part shows how the transfer of information along sensory axons is modified by presynaptic inhibition mechanisms. In primary afferents, presynaptic inhibition is involved in: 1) increasing the dynamic range of the sensory response; 2) processing the sensory information such as increasing spatial and/or temporal selectivity; 3) discriminating environmental information from sensory activities generated by the animal's own movement; and 4) modulating the gain of negative feedback (resistance reflex) during active rhythmic movements such as locomotion. In a second part, the whole organization of other types of neurons is considered, and evidence is given that a neuron may not work as a unit, but rather as a mosaic of disconnected 'integrate-and-fire' units. Examples of invertebrate neurons are presented in which several spike initiating zones exist, such as in some stomatogastric neurons. The separation of a neuron into two functionally distinct entities may be almost total with distinct arborizations existing in different ganglia. However, this functional separation is not definitive and depends on the state of the neuron. In conclusion, the classical integrate-and-fire representation of the neuron, with its dendritic arborization, its spike initiating zone, its axon and axonal tree seems to be no more applicable to invertebrate neurons. A better knowledge of the function of vertebrate neurons would probably demonstrate that it is the case for a large number of them, as suggested by the complex architecture of some reticular interneurons in vertebrates.

Animals↗
PubMed1990

[Fetal respiratory movements and their regulation].

In 1972, fetal breathing movements were clinically rediscovered. Details of their episodic occurrence, frequency, inspired volume, pleural pressure, and the nearly absolute independence of fetal blood gases were investigated in animal experiments. In the human being, there is also an association between fetal breathing and sleep state: fetal breathing movements were confined almost exclusively to periods of REM sleep. The pattern of respiratory frequency changes as gestation progresses; the rates decrease as term approaches. Hardly any breathing movement can be detected during labor. The fetal respiratory centre is capable of rhythmic movements, but there is a lack of response to basic chemical stimuli from the periphery of the body. The association between fetal breathing and REM sleep implies that the connection between breathing and behaviour is already established before birth; but in the fetus, the link between breathing and metabolism is not yet forged. Throughout postnatal life this linkage predominantly regulates breathing. The difference between fetus and newborn in the reaction to chemical stimuli implies a change at birth related to the glomera cells of the carotid bodies. Under the influence of the marked increase in the sympathetic tone there is a major increase in the sensitivity of the receptor cells to oxygen deficiency immediately after birth.

Asphyxia Neonatorum↗
PubMed1995

Oculofacial-skeletal myorhythmia in central nervous system Whipple's disease: additional case and review of the literature.

A case of oculofacial-skeletal myorhythmia associated with cerebral Whipple's disease is presented. This peculiar abnormal movement disorder consists of a convergent-divergent pendular nystagmus associated with a synchronous, rhythmic movement of the mouth, jaw, and extremities. The movements in previous cases have responded inconsistently to a variety of broad-spectrum antibiotic drugs, and antiepileptic, muscle relaxant, antispastic, and psychotropic drugs. The current patient's mental status improved after starting intravenous ceftriaxone but improvement of the abnormal movements occurred only after the addition of oral valproate. Current treatment consists of intravenous trimethoprim-sulfamethoxazole for 2 weeks followed by oral trimethoprim-sulfamethoxazole twice daily for 1 year. Presented here is an alternative treatment of intravenous ceftriazone followed by oral trimethoprim-sulfamethoxazole in combination with valproate for abnormal movements not responsive to antibiotic drugs alone.

Adult↗
PubMed2004

Lateralized regular spatial patterns in oscillating drawing arm movements of right-handed young women.

There is a lacuna in literature with reference to the spatial lateral difference in fast rhythmical movements produced by the whole dominant and nondominant whole arm, where spinal regulation has a significant role. Based on a fast oscillating zigzag drawing task, this study focused on (a) creation of a specific model of the task based on the intermittencies of coupled vectors of the fast motion, (b) identification of the spatial patterns that triggered these vectors, and (c) identification of quantified lateral differences between the spatial rhythmical patterns. 12 strongly right-handed young women performed 9 to 11 trials drawing zigzag lines. Each participant was required to extend her arm and perform this task using the left and right arm selectively on a frontally positioned graphic design system. The spatial patterns produced on each trial were identified in terms of five constant combinations of horizontal (X) and vertical (Y) projections of each line on the zigzag drawings. The dominant arm differed from the nondominant arm in preferred patterns. Because the duration of each line in the zigzag was highly restricted in time, the appearance of the patterns with different block schemes of movement could be explained as being associated with lower levels of the central nervous system. Initiation of fast movement of the total upper arm is probably associated with selection of the block scheme of motor control appropriate to each arm. Each block scheme is grounded on the coupled vectors of motion organised with particular muscle groups. Some block schemes seemed linked specifically to the dominant arm.

Adult↗
PubMed1993

Stability and movement of a one-link neuromusculoskeletal sagittal arm.

This paper's focus is the stability, point-to-point, and rhythmic movements of a one-link sagittal arm. The system is highly nonlinear in all its physical and physiological attributes. The major physiological characteristics of this system are simultaneous activation of a pair of nonlinear muscle-like actuators for control purposes, existence of nonlinear spindle-like sensors, and actions of gravity and loading. Transmission delays are included in the afferent and efferent neural paths to account for a more accurate representation of the reflex loops. An algorithm for computation of the actuator forces and the feedback signals in the system is provided. It automatically renders positive forces and positive neural signals. The positiveness of the forces represents the unidirectional character of muscular forces, i.e., natural muscles can only pull in the direction of shortening. The positiveness of the neural signals implies these signals can correspond to firing rates. The stability of the system is analyzed. The role of the nonlinearities in the dynamics, actuators, and feedback signals, and the delays in the feedback loops in destabilizing the system, and the consequently undesirable oscillations are studied by simulation. The system is designed to perform stable point-to-point movement. The effects of the presetting of the input signals, gain of the feedback loops, and the duration of delays in generating undesirable tremor-like oscillations at the end of the movement are studied and demonstrated by digital computer simulations.

Algorithms↗
PubMed2002

Rhythmic contractions in chick amnio-yolk sac and snake amnion during embryogenesis.

The rhythmic movements of fetal membranes in chick and reptile embryos were studied to explore the developmental role of the extra-embryonic motor activity. In the snakes Lamprophis fuliginosus and Elaphe radiata, rhythmic contractions of amnion inside the developing egg were recorded from the 11th incubation day until pre-hatching stages (ca. day 60-72). The duration of these contractions averaged 2.02+/-0.27 min. The frequency ranged from 2 to 6 per 10 min and averaged 4.61+/-0.57 per 10 min. A tendency of frequency to increase toward the end of embryogenesis was observed. Lowering the temperature from 28 to 20 degrees C significantly decreased the frequency of amnion contractions to 2.85+/-0.91 per 10 min. The isolated snake amnion retained its capacity for spontaneous contraction. Noradrenaline inhibited, acetylcholine stimulated and serotonin did not affect the rhythmic activity of the isolated snake amnion. Similar effects were found when these agents were applied into the snake amniotic cavity. In the chick, yolk sac rhythmic contractions were recorded from the fifth until the 12th incubation days. The duration of these contractions ranged from 15 to 60 s, their frequency averaged 11.8+/-3.18 per 10 min and depended on temperature. The low temperature threshold was approximately 30 degrees C. After surgical removal of the amnion and embryo, the yolk sac continued contracting inside the egg. The yolk sac rhythmic contractions likely participate in the space movement of the embryo inside the egg during embryogenesis.

Amnion↗
PubMed2004

Effect of stimulation of subthalamic nucleus on grooming movements and their rhythmicity in pups and mature rats.

The effect of rhythmic stimulation of subthalamic nucleus on grooming movements and their rhythmicity was studied on mature rats and on 13- and 14-day rat pups. Unilateral monopolar stimulation of subthalamic nucleus was performed on unrestrained animals via implanted electrodes. This stimulation activated virtually all grooming movements (scratching, hair-plucking, licking, and body-shaking); the effect was most pronounced in pups. Acceleration of the rhythm of grooming movements was observed only in rat pups for hair-plucking and scratching on the contralateral side relatively to the stimulated nucleus. In mature rats stimulation of the subthalamic nucleus prolonged grooming movements in most cases, but did not increase their number and rhythm.

Animals↗
PubMed2005

Chewing pattern in patients with Meige's syndrome.

Meige's syndrome presents with a combination of upper and lower facial motor dysfunction, including eye closing spasms and oromandibular dystonia. While the pathophysiology of eye closing spasms has been extensively studied using the blink reflex and other trigeminofacial reflexes, very few studies have been carried out with regard to the abnormal perioral movements. We hypothesized that action-related dystonic features could be revealed by the analysis of the semiautomatic rhythmic movements required for chewing and swallowing. A total of 7 patients with Meige's syndrome that complained of chewing problems and 7 age-matched healthy volunteers were studied. Subjects were instructed to munch and swallow a small muffin while surface electromyographic (EMG) activity of masseter (MAS) and orbicularis oris (OOr) of the dominant side was recorded. In healthy subjects, MAS and OOr showed a rhythmic alternating phasic EMG pattern during chewing, which changed to a tonic cocontraction of both muscles during swallowing. Mean duration of MAS and OOr EMG bursts was, respectively, 297 +/- 28 msec and 328 +/- 29 msec. Patients exhibited the following alterations: excess duration of muscle activity, frequent cocontraction, loss of rhythmicity during chewing, and abnormalities in the chewing to swallowing transition phase. These abnormalities, similar in type to those encountered in other forms of focal dystonia, may be the expression of an abnormal motor control of basal ganglia over mastication-related movement pattern generators of the brainstem.

Aged↗