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PubMed1981

Function of sensory input in insect motor systems.

The organization and function of sensory input has been examined in three insect motor systems: locust jumping, cockroach walking, and locust flight. In these three systems sensory input is primarily involved in the production of the normal patterns of motor activity rather than in the compensation for sudden changes in the external environment. At least two general functions for sensory input in the normal patterning of motor activity can be identified: (1) compensation for changes in the peripheral elements of the motor system which occur as a result of use and maturation and (2) regulation of switching from one phase of a movement to another following the attainment of a specific state by peripheral structures. Reflex pathways may exist for compensating for sudden environmental disturbances but these have not yet been clearly demonstrated.

Animals↗

PubMed1993

Vestibular evaluation--electronystagmography, rotational testing, and posturography.

This report describes a battery of tests that is utilized by several clinical laboratories to investigate vestibular and balance function. The electronystagmogram evaluates eye movements, inner ear function, brainstem function and cerebellar function. Sinusoidal vertical axis rotation is a sensitive measure of horizontal semicircular canal function that is often complimentary to the caloric stimulation portion of the electronystagmogram. Visual-vestibular interaction rotation testing is designed to evaluate brainstem, cerebellar and oculomotor function. Dynamic posturography facilitates measurement of standing balance and permits a quantification of the role of proprioception, vision and the vestibular system in the maintenance of standing balance.

Adrenocorticotropic Hormone↗

PubMed1990

[Neurogenic bladder in patients with cervical cord compression disorders].

Bladder and urethral functions were evaluated urodynamically in 62 patients with cervical cord compression disorder caused by either ossification of the posterior longitudinal ligament of the cervical spine (32 patients), cervical spondylosis (14 patients), prolapsed cervical intervertebral disc (14 patients) or cervical spinal canal stenosis (2 patients). The patients included 46 males and 16 females with average age of 57 years (range 39 to 73 years). Symptomatic organic infravesical obstruction was excluded by physical and radiographic examination. Cystometry revealed preoperative neurogenic bladder in 22 patients (35%) including overactive detrusor in 10 patients (45%) and underactive in 6 (27%). Twenty-one of them underwent electromyographic examination of external sphincter and 14 (67%) had overactive sphincter. Bladder and urethral functions appeared to be impaired in association with myelopathy of the pyramidal and spinothalamic tract of the cervical cord, because of high incidence of neurogenic bladder associated with positive Babinski's reflex and sensory disturbance at the perineal and lower extremity area. Furthermore, since many patients with deep sensory disturbance in the lower extremities had underactive detrusor, it appears likely that underactive detrusor was accompanied with myelopathy in the posterior funiculus of the cervical cord which mediates bladder proprioceptive sensation. Of twenty-two neurogenic bladder patients, seventeen underwent a cervical bone operation and eleven received postoperative urodynamic evaluation. The average interval from the operation to urodynamic evaluation was 1.6 months (range 1.1 to 2.3 months). Over half of the patients were found to be improved urodynamically as well as neurologically.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMedDate not supplied

[Cervicogenic proprioceptive vertigo: etiopathogenesis, clinical manifestations, diagnosis and therapy with special emphasis on manual therapy].

Cervical proprioceptive system (CPS) consisting of mechanoreceptors of cervical intervertebral joints, mechanoreceptors of neck muscles and ligament's insertions, muscle spindles located in deep short muscles of cervical spine and sensitive fibers connecting neck's proprioceptors with neurons of cornu posteriori of spinal cord, plays an essential part in maintaining bodily balance. CPS, via tractus spinovestibularis, is connected to vestibular nuclei. Clinical and neurophysiological studies have shown that functional disorders and/or organic lesions of CPS cause identical symptoms as vestibular diseases: vertigo, nystagmus and balance disorders. Dysfunction (functional blockade) of craniocervical joints is the most frequent cause of cervicogenic proprioceptive vertigo (CPV). The constant tension of the capsule of a blocked joint irritates mechanoreceptors protecting the joint's capsules. The increased activity of mechanoreceptors results in confusion of vestibular system. That is, the impulses from the blocked craniocervical joints do not correspond to the impulses from the vestibular organ and other sensory systems that take part in maintaining bodily balance. The disharmony of impulses results in an inadequate vestibulo-spinal and vestibulo-ocular reaction manifesting as vertigo and nystagmus. Hyperactivity of craniocervical mechanoreceptors also causes disturbances in reflex regulation of postural muscle tonus manifesting as "general instability". Knowledge of CPV as a separate clinical entity is important from diagnostical and therapeutical aspect. As it concerns a peripheral vestibular disorder still unknown to a wider circle of physicians, the article describes etiopathogenesis, clinical manifestations, diagnosis and therapy of CPV with special emphasis on manual therapy.

Cervical Vertebrae↗

PubMed1981

Effect of transrespiratory pressure on PETCO2-PaCO2 and ventilatory reflexes in humans.

Inspiratory muscle activity increases when lung volume is increased by continuous positive-pressure breathing in conscious human subjects (Green et al., Respir. Physiol. 35: 283-300, 1978). Because end-tidal CO2 pressure (PETCO2) does not change, these increases have not been attributed to chemoreflexes. However, continuous positive-pressure breathing at 20 cmH2O influences the end-tidal to arterial CO2 pressure differences (Folkow and Pappenheimer, J. Appl. Physiol. 8: 102-110, 1955). We have compared PETCO2 with arterial CO2 pressure (PaCO2). We have compared PETCO2 with arterial CO2 pressure (PaCO2) in healthy human subjects exposed to continuous positive airway pressure (10 cmH2O) or continuous negative pressure around the torso (-15 cmH2O) sufficient to increase mean lung volume by about 650 ml. The difference between PETCO2 and PaCO2 was not decreased, and we conclude that PETCO2 is a valid measure of chemical drive to ventilation in such circumstances. We observed substantial increases in respiratory muscle electromyograms during pressure breathing as seen previously and conclude this response must originate by proprioception. On average, the compensation of tidal volume thus afforded was complete, but the wide variability of individual responses suggests that there was a large cerebral cortical component in the responses seen here.

Arteries↗

PubMed1978

Vestibulogenic imbalance.

Vestibular lesions may cause imbalance that long outlasts vertigo. Photographic analysis in five cases showed defects not only of the tilting reactions, which are of labyrinthine origin, but also of certain other postural reactions, notably the counterpoising and protective stepping reactions. All of these reflexes are unconscious and consequently such patients are rendered unstable in several ways simultaneously and may have difficulty describing their symptoms.

Adult↗

PubMed1995

Postural adjustments associated with different unloadings of the forearm: effects of proprioceptive and cutaneous afferent deprivation.

Postural adjustments to imposed (passive) and voluntary (active) unloading conditions of the forearm were studied in normal subjects and a deafferented patient. The latency of the postural behaviour (deactivation of the biceps supporting the weight) was linearly related to the displacement amplitude of the unloaded forearm, independent of the unloading conditions. The postural behaviour consisted of an anticipatory postural adjustment (APA) occurring prior to active unloading (in both normals and the patient) and conversely in an unloading reflex response following passive unloading (only in the normals). In both the deafferented and the normal subjects, the amplitudes of the displacement during active unloadings were much smaller (3x) than in the passive conditions and an APA was present in both the deafferented and the normal subjects. The APA could not be triggered by some types of active movement and was absent when the movement was not directly producing the unloading. The EMG latencies of the APA and of the contralateral muscles used to unload were tightly coupled. However, the latency would sometimes be decoupled, particularly when a temporal delay was introduced between the active movement and the unloading in normal subjects. In contrast to the normal subjects, who were able to adapt quickly to an unusual unloading condition (produced by voluntary knee flexion), the deafferented patient did not show an APA in this task. It was concluded that, although the APA is of central origin, it cannot be generated only on the basis of internal timing cues and must rely on afferent information for its generation during unfamiliar unloading conditions.

Adult↗

PubMed1989

Current concepts of the vestibular system reviewed: 1. The role of the vestibulospinal system in postural control.

This paper reviews the research findings that support the presence of vestibulospinal reflexes in corrections for head and body instability. Studies of the importance of labyrinthine inputs to the central nervous system organization of eye, head, and body movements demonstrate that the vestibular nuclei are more than a simple relay station for labyrinthine activity. At all levels of the vestibular system beyond the primary vestibular afferents, parallel processing of labyrinthine signals occurs with input from other sensory systems. Thus, output of the vestibular nuclear complex (VNC) is not equivalent to the labyrinthine input. It is the VNC output that influences motor behavior. Various sensory inputs are available to the nervous system to detect and correct postural instability. Most notably, vestibular, visual, and proprioceptive signals contribute significantly to the stabilizing responses in humans. The intent of this paper is to review experimental results rather than to discuss treatment interventions. Wherever possible, conclusions are drawn as to the clinical implications of current research findings.

Ear, Inner↗

PubMed1992

[The role of skin reception in controlling movements].

Skin receptors have been studied in the aspect of diverse phenomenology of their participation in organization of motor activity: from the protective flexor reflex to fine correcting effects from the skin which covers the muscle and the tendon. Analysis of the character of exteroceptive effects on reflector responses, cyclic motions and arbitrary activity has revealed a distinct determination of the effect, its dependence on localization and intensity of the exteroceptive stimulus, a moment of its application (state of motor centres) and so on. It is shown that the proprioceptive correction of the motion which underlies the ring control of the motion is inevitably added by exteroceptive effects incorporated into the same system due to their convergence to the same neuronal mechanisms. Basic moments of neuronal organization and basic mechanisms of sensory (exteroceptive) correction of motor activity are considered. Proceeding from the results of the author's investigations, the role of the premotor zone (the ventral horn, L6,7) interneurons which are not connected initially with afferents in the processes of sensomotor interaction in polysynaptic ways to the motoneuron is determined. It is supposed that these neurons integrate already selected information and form a discrete premise to output systems.

Afferent Pathways↗

PubMed1989

Significance of proprioceptive mechanisms in the regulation of stance.

Compensatory electromyographic (EMG) responses and several biomechanical parameters were studied following impulsive disturbance of the limbs during stance of human volunteers on a treadmill. Treadmill acceleration impulses were backwards or forwards directed, or their initial direction was reversed after 30 ms. Backwards directed impulses were followed by gastrocnemius, forwards directed ones by tibialis anterior EMG responses (latency 65 to 75 ms) whose durations depended on impulse duration. When the direction of the impulse was reversed, the respective antagonistic leg muscles were activated again with a delay of 68 to 75 ms after onset of stretch of these muscles. The behaviour of the EMG responses could best be correlated to the displacement at the ankle joint and may be described in terms of a stretch reflex response. The results indicate that these stretch reflex responses help control of the body's centre of gravity thereby preventing falling. Head movements induced by the impulses showed little correlation with the appearance of the EMG responses, suggesting that the vestibular system is unlikely to be directly involved in the generation of these responses. Vestibular signals may, however, significantly contribute to slow body sway stabilization.

Adult↗

PubMed1983

Effect of vision on development of multiply handicapped children.

The effect of vision on (abnormal) development was studied in a group of 81 visually and/or hearing impaired rubella children, 18 of whom had bi-lateral cataracts operated between 2-18 months, 3 children had uni-lateral cataract, and 60 children had clear media. In this group of children the effect of visual impairment on (abnormal) behaviour is enormous. Vision has in these children a greater impact on their development than hearing impairment or prenatal variables such as low birthweight. This justifies the conclusion of cataract surgery as early as possible. After surgery the environment should be manipulated in such a way, that it becomes visually attractive for the child. This might prevent strong light-gazing and/or exhibiting the phenomenon of HBE (Hand Before the Eyes). The desire for rocking and jumping should be seen in connection with stimulus deprivation, especially social ones. It is therefore recommended that these children should be offered ample experience and interaction with the environment, such as giving the child proprioceptive stimuli, rocking him in the crib or on the lap. The interest in the world outside his own body should be encouraged by manipulating the children's special interest (such as changing the objects for light gazing). The purpose for this kind of management is to develop orientation reflex, in other words to stimulate the child to give attention to the world around him and therefore learn from it. When this sort of early stimulation is provided the child's development may be not so retarded as without appropriate intervention.

Animals↗

PubMed1973

Effect of lateral cervical cord lesions on the respiratory rhythm of anaesthetized, decerebrate cats after vagotomy.

1. The lateral cervical cord of vagotomized, anaesthetized cats was superficially lesioned at the C3 or the C7 level before or after midcollicular decerebration.2. These cord lesions eliminated the inhibition of diaphragmatic discharge caused by chest compression. Previous work (Remmers, 1973) indicates that this change can be attributed to loss of reflex inhibition of inspiratory activity by intercostal afferents, probably as a result of interruption of tracts ascending in the lateral columns.3. Decerebrate cats with bilateral cervical cord lesions displayed abnormal respiratory patterns, ranging from apnoea to apneusis.4. The results are consistent with the hypothesis that the lateral columns carry proprioceptive feed-back from intercostal mechanoreceptors which promotes rhythmic breathing in the anaesthetized decerebrate cat.

Action Potentials↗

PubMed1981

Comparison of monosynaptic tendon reflexes during preparation for ballistic or ramp movement.

Mechanism which underlie preparation for movement were studied in man using the method of 'monosynaptic tendon reflexes' during the preparatory period (PP) preceding the execution of ramp or ballistic tracking movements. Reflex reactivity is more important during the whole of the PP to a ramp rather than a ballistic movement; the increasing facilitation preceding the execution signal is greater and occurs earlier for the ramp than for the ballistic movement. These results were observed for 'fast' or 'slow' subjects in a reaction time task, but were more marked for the latter. On the one hand, preparation for movement is represented at the spinal level by a competition between activating influences, which allows for the speeding up of peripheral execution of central control, and inhibitory influences brought into play both by the need to suppress the movement until the execution signal and by the isolation of motor structures from postural proprioceptive servo-mechanisms. On the other hand, this preparation can imply a control of the level of activity in proprioceptive fusorial afferent pathways which depends on whether the movement to be executed is open-loop (ballistic) or closed (ramp). Comparison between the results obtained from fast and slow subjects underlines the importance of an active inhibitory process in spinal structures which would accompany temporal adjustment.

Female↗

PubMed1998

Influence of body load on the gait pattern in Parkinson's disease.

The influence of body unloading (to 75, 50, and 25% body weight) on lower leg muscle activation during treadmill walking was investigated in patients with Parkinson's disease, age-matched and young healthy subjects. The aim of the study was to test the hypothesis that patients suffer from impaired extensor load receptor function. Although lower leg flexor muscle electromyographic (EMG) activity was relatively independent of body load, lower leg extensor EMG activity was markedly load sensitive. The EMG amplitude of the latter decreased with body unloading during stepping in all three groups of subjects. The load sensitivity progressively increased from patients to age-matched to young healthy subjects. In addition, the absolute level of leg extensor EMG amplitude during the stance phase of stepping became progressively larger from patients to age-matched subjects to young healthy subjects. It is suggested that decreased sensitivity of extensor load reflex mechanisms contributes to impaired gait in elderly subjects and is more pronounced in parkinsonian patients.

Aged↗

PubMedDate not supplied

Idiopathic scoliosis and the central nervous system: a motor control problem. The Harrington lecture, 1983. Scoliosis Research Society.

An etiologic concept linking an impaired axial motor control system to the structural deformity of idiopathic scoliosis (ISc) is proposed. Postural studies reveal that during quiet stance, adaptation is marked in conditions associated with visual control of sway, particularly of lateral sway; during imposed perturbations of the body, destabilized postural reactions are pronounced in tests requiring visual-vestibular coupling. Observations of visual and/or vestibular generated eye movements indicate ocular instability among a high proportion of the ISc. Previously, the authors argued that a direct relationship exists between visual and/or vestibular functioning and a disordered axial motor system. This was attributed to an aberrant brain stem mechanism. In this presentation, however, we propose that a higher level CNS disturbance may be responsible for reports of EEG abnormalities, visuo-spatial impairment, motor adaptation, and learning deficits. Among the wide range of visual-vestibular variables studied, those representing processing of vestibular signals within the CNS yield the highest degree of correlation with the magnitude of the curve. Moreover, differences in vestibular processing between two subsets of ISc, namely ISc with (70%) and without (30%) normal academic achievement are significant. Variables referable to both vestibular and visual processing correctly classify 87% of the ISc with normal academic achievement and 100% of the ISc with a history of academic problems. The association between learning deficits, altered processing of vestibular information, and ISc suggest a unique syndrome complex, and an important role of cortical structures in the etiology of this disorder. The presence of a visuo-spatial perceptual impairment may be the common feature of ISc. In an attempt to restore perceptual dysfunction (by rearrangement), the ISc adopts a new axial and vestibular motor control strategy based upon recalibration or reinterpretation of proprioceptive signals arising from the axial musculature.

Adaptation, Physiological↗

PubMed1981

Load compensating responses of human abdominal muscles.

1. We studied abdominal muscle responses to positive pressure loads applied suddenly to the external airway while subjects held a constant lung volume against steady pressure. The pre-loading holding pressure was 6 cm H(2)O, and the loading pressures were 6 or 12 cm H(2)O lasting for 2 sec.2. Surface electromyograms (e.m.g.) were recorded over the internal oblique, external oblique, and rectus abdominis muscles. The latency and pattern of the e.m.g. reactions were studied by measuring the raw record for each loading trial, and by averaging the rectified e.m.g. for many trials.3. No responses were obtained if subjects were instructed not to respond to the loads. When instructed and trained to maintain their pre-load position in spite of the load, a two-phase compensatory response was found. The initial response (phase I) was 100-300 msec in duration; it was followed by a continuous e.m.g. discharge (phase II) which continued to the offset of the pressure load. Subjects were also trained to make a single respiratory effort as quickly as possible after the load onset or after just an auditory stimulus. These were simple reaction time tasks of a traditional kind and the e.m.g. responses elicited were single, brief bursts.4. For all subjects and experimental conditions the e.m.g. response of the internal oblique occurred first, followed by the external oblique and then the rectus abdominis. For the ;maintain position' task, phase I latencies (internal oblique) averaged 66-90 msec for individual subjects, but for single trials with optimal conditions of practice and preparatory intervals these ranged from 42 to 110 msec with a third of the reactions occurring within 50-60 msec.5. The latencies for reaction time responses to loading were about 6 msec shorter than the phase I latencies. The latency distributions for the two types of responses were similar, and both were affected to the same degree by practice, and changing the length and variability of the preparatory interval. Because of these similarities we suggest that the phase I reaction was a learned response of a ;simple reaction time' type, and not comparable to late stretch reflexes such as the M2 of limb muscles.6. Arm muscle responses to respiratory pressure changes were measured in three subjects under identical conditions used to obtain load reaction times of abdominal muscles. These simple reaction times averaged 61-71 msec, and ranged from 42 to 97 msec. Therefore very short proprioceptive reaction times are not peculiar to the respiratory system, or to load perturbations of the responding muscle.7. Mechanical adjustments of airway pressure and lung volume in response to loading are first expressed at the mouth about 90 msec after abdominal muscle activity begins. In the ;maintain position' task, the accuracy with which pressure and volume adjustments were made during the last 1.5 sec of the loading period approximated that reported in the literature for trained singers holding a tone using constant expiratory pressure.

Abdominal Muscles↗

PubMed2002

Positive proprioceptive feedback elicited by isometric contractions of ankle flexors on pretibial motoneurons in cats.

Pretibial flexor motoneurons were recorded intracellularly in anesthetized cats during unfused isometric contractions of a subpopulation of motor units from either tibialis anterior (TA) or extensor digitorum longus (EDL) muscles. The contractions elicited excitatory postsynaptic potentials in 23 of 28 pretibial flexor motoneurons. No effect was observed in the remaining motoneurons. In control experiments, the effects of electrical stimulation of afferents within the TA nerve were investigated to help identify afferents responsible for the contraction-induced positive feedback. This feedback was ascribed to actions of Ia fibers because the pattern of the contraction-induced excitatory potentials was consistent with the known pattern of Ia discharge; in control experiments, electrical stimulation of group I fibers elicited only monosynaptic excitatory potentials; and the distribution of both the contraction-induced positive feedback among motor nuclei as well as the electrically evoked Ia excitatory monosynaptic potentials were restricted to homonymous and synergic motoneurons. Observation of the Ia contraction-induced positive feedback was facilitated by the absence of Ib autogenic inhibition. This contraction-induced Ia excitatory feedback in ankle flexors might either reinforce Ia-induced reflexes when these muscles are lengthened or help to lift the leg over an obstacle.

Anesthesia↗

PubMed1993

Corticofugal projections to the vestibular nuclei in squirrel monkeys: further evidence of multiple cortical vestibular fields.

Single- and multiple-unit recordings were made from nerve cells located in the different nuclei of the brainstem vestibular nuclear complex (VNC) of anaesthetized squirrel monkeys (Saimiri sciureus) by conventional stereotaxic techniques. After neurons responding to semicircular canal stimulation in a yaw, roll, or pitch direction or to otholith stimulation were identified, small amounts of retrograde tracer substances were deposited at the recording sites. Up to three different tracers were administered to different parts of the VNC in the same animal (Fast Blue, HRP-WGA, and Rhodamine-dextranes). After adequate survival times, the animals were sacrificed. Following histological processing, the cortical grey matter was screened systematically for cells labelled with the retrograde tracers (fluorescence microscopy or light microscopy for HRP processing). Labelled nerve cells which clearly project to the VNC directly were found predominantly in the cytoarchitectonic layer 5 of seven different cortical areas: 1) The parieto-insular vestibular cortex PIVC, which in squirrel monkeys consists mainly of the medial area Ri and parts of the anterior area Ig; 2) area 7ant, which presumably corresponds to the macaque area 2v; 3) area 3aV, a vestibular field of area 3a; 4) the temporal area T3 bordering on area Ri; 5) the premotor area 6a; and 6, 7) the areas 6c and 23c of the anterior cingulate cortex. The PIVC, area 7ant, and area 3aV form the "inner cortical vestibular circuit" (Guldin et al.: J. Comp. Neurol. 326:375-401, '92), while the other cortical areas mentioned also have direct projections to the structures of the inner cortical vestibular circuit. It is speculated that the direct projections of the cortical vestibular structures to the brainstem vestibular nuclei regulate the vestibulo-ocular, the vestibulo-spinal, and the optokinetic reflexes mediated through the VNC, thus preventing counteractions of these reflexes during voluntary, goal-directed head movements or locomotion.

Animals↗