Continuous pressure monitoring in experimental obstructive hydrocephalus. II. The origin of undulating ventricular waves and periodic respirations.
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Animals↗
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Results for “REFLEX, PROPRIOCEPTIVE”
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Acrylamide neurotoxicity in the mouse: a behavioral, electrophysiological and morphological study.
The development of acrylamide induced neurotoxicity was followed for 3 weeks in the mouse by behavioral testing, determination of conduction velocities and electron microscopic examination of peripheral nerves. Neurotoxic signs began to appear during the second week of treatment. A condition of severe intoxication developed within 21 days. Behavioral assessment for neurological deficits proved to be more sensitive than sensory or motor conduction velocity determinations either in isolated preparations or in situ. In general, such electrophysiological determinations did not result in reproducible, statistically significant, differences from control animals until the third week of acrylamide administration. However, there was a suggestion that temperature reduction may provide a provocative change to increase the sensitivity of such electrophysiological measurements. Electron microscopic examination of the nerves of severely poisoned animals revealed myelin corrugation and delamination to be the most consistent damage. Acrylamide appeared to produce a nonselective attack since degenerating fibers were found intermingled with almost normal fibers of approximately the same diameter. In general, the production of neurotoxicity in the mouse closely resembled that seen in the rat but some differences were noted.
Acrylamides↗
Neural mechanisms underlying behavior in the locust Schistocerca gregaria. II. Integrative activity in metathoracic neurons.
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Action Potentials↗
A model of pattern generation of cockroach walking reconsidered.
Cockroaches that have been decapitated or that have cut thoracic connectives can show rhythmic bursting in motoneurons to intrinsic leg muscles. These preparations have been studied as models for walking and to evaluate the functions of leg proprioceptors. The present study demonstrates that headless cockroaches walk extremely poorly and slowly with considerable discoordination of motoneuronal activity, these preparations show rhythmic motoneuron bursting that is similar to righting responses (attempts to turn upright) of intact animals when placed on their backs, and bursting is inhibited when a headless animal is turned or turns itself upright. Thus, rhythmic motoneuron activity of these preparations is most probably attempted righting rather than walking. It is concluded that the headless cockroach is useful for understanding the motor mechanisms underlying righting and walking but is not of value in assessing the functions of proprioceptive feedback.
Animals↗
Failure to update the egocentric representation of the visual space through labyrinthine signal.
The present study evaluated the capacity to compare retinal and vestibular signals in a heterosensorial matching task. In the first experiment, subjects evaluated the magnitude of passive whole-body rotations in relation to the eccentricity of a visual target briefly presented before rotation. Such a task elicits multimodal sensory stimulations experienced by a subject during normal goal-oriented head movements, i.e., retinal and vestibular stimulations. A good capacity to evaluate vestibular signals in relation with retinal inputs might suggest that the labyrinthine output is part of a cognitive feedback-loop controlling active head movements oriented toward a visual target and/or that the labyrinthine signal might make a major contribution to judging the position of the target in space after goal-directed head movements. Results showed that body rotation magnitudes had to exceed the amplitude of the visual target by about 120 and 89% to be perceived as having a similar magnitude to a 10 degree and an 18 degree visual target, respectively. A second experiment was designed to test whether this major discrepancy originated either from (a) an overestimation of the peripheral visual target locations, (b) an underestimation of the labyrinthine signal, (c) a deficiency in matching sensory signals from different modalities, or (d) any combination of (a), (b), and (c). In the second experiment, the actual perception of retinal and labyrinthine signals, as indicated by verbal responses, was quantified. Results from this experiment showed that most of the large underestimation of the vestibular stimulation found in Experiment I ought to emerge from a poor capacity to integrate heterogeneous sensory signals by the perceptual system rather than from pure misperception of the retinal and/or labyrinthine signals. Overall, results from Experiments I and II argue for a deficiency of the CNS to integrate labyrinthine signals for updating the egocentric representation of the peripheral visual target during passive body (head) rotations.
Adult↗
Dizziness and vertigo in the posttraumatic syndrome. A physiological background.
Some important physiologic mechanisms involved in equilibrium control are briefly reviewed and a new method to study clinically the integration of vestibular and proprioceptive functions is presented.
Craniocerebral Trauma↗
Oculovestibular interactions under microgravity.
On a space mission in March 1992 a set of experiments were performed aimed at clarifying the interaction between visual, proprioceptive and vestibular inputs to the equilibrium system. Using the VESTA goggle facility from the European Space Agency we investigated the effect of pure neck receptor stimulation on eye position as measured by the flash afterimage method and on perception of a head-fixed luminous line in space. Space vestibular adaptation processes were measured by rotating pattern perception during prescribed head movements. It was found that static ocular counterrotation does not occur under microgravity conditions. This result suggests that the neck receptors apparently do not contribute to a measurable extent. The subjective orientation of a vertical line was perceived correctly inflight. Obviously neck receptors on the perception level can fully substitute for the ineffective equilibrium organs of the inner ear within less than 4 days. The rotating pattern perception during different head motion patterns is not influenced by the absence of a gravity reference.
Adaptation, Physiological↗
Mechanisms underlying recovery of eye-head coordination following bilateral labyrinthectomy in monkeys.
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Adaptation, Ocular↗
Adjustment of saccade characteristics during head movements.
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Animals↗
Excitation of units in the lateral geniculate and contiguous nuclei of the cat by stretch of extrinsic ocular muscles.
In cats, anaesthetized with chloralose and paralysed, the responses of units in the right lateral thalamus were recorded while the extrinsic ocular muscles (EOM) of the right eye were stretched in the dark. Phasic responses were found in all layers of the dorsal lateral geniculate nucleus (LGNd) and in the perigeniculate nucleus (PGN). A given unit usually responded to stretch of more than one EOM and thus to more than one direction of rotation of the eye in the orbit. LGNd. Of a sample of 76 units in LGNd, 55 (72%) gave visula but no muscle responses and 21 (28%) responded to EOM stretch. In all, 40 units with EOM responses were examined and 25 of the 27 tested (93%) also had visual responses. Of the 40 units, 32 could be allocated to layers, thus; layer A, 8 (25%); layer A1, 20 (63%); layer B, 3 (9%); central interlaminar nucleus, 1 (3%). It is interesting that most of the EOM responses were found in layer A1 which recieves the excitatory visual input from the eye whose EOM were stretched. Muscle responsive units occurred with ON- and OFF-centre visual responses of sustained and transient types. PGN. In PGN, 21 units gave EOM responses and most of them were also excited by visual input. The conclusion is that the LGNd and PGN receive an extraretinal proprioceptive signal which should be present during at least large saccadic eye movements. The anatomical pathways which may be involved and the significance of the signal are discussed briefly.
Animals↗
Multichannel transmission of proprioceptive input to motoneurons.
A model has been developed to simulate the parallel channels of muscle spindles and their monosynaptic connections to a homonymous motoneuron in the turtle. Input to the model is muscle length and beta stimulation, output is motoneuronal membrane potential. Quality of transmission is greatly dependent upon dispersive properties of the system. The contributions of different dispersive features are compared and also cumulative effects are considered. Reference is made to conditions which are found in actual movements.
Action Potentials↗
Simulation of human arm movements controlled by peripheral feedback.
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Arm↗
A theory on the control of arbitrary movements.
A theory dealing with the control of human, arbitrary movements is proposed. A schema is set up to suggest how the relevant information flows and what kind of operations affect it. A number of successive steps are distinguished in the production of a movement. It is assumed that the intended movement is carried out in the imagination, and that this imaginary movement is composed of a spatial trajectory and an intensity course, which are considered to be independent features of the intended movement. The spatial trajectory will be encoded in a special coding, which is related to the lengths of the muscles that effect the movement. From this special coding of the intended movement static and dynamic control signals can be derived. Because afferent and efferent signals are encoded in the same way in this schema, the evaluation and correction of the performed movement is quite simple. The higher levels in the control schema may function in an abstract way, i.e. the signals at these levels are barely concerned with details of the peripheral motor system. This abstract functioning of the higher levels is based on the numerous feedback mechanisms involved at all levels of control and in the peripheral motor system. Nevertheless, it is possible to incorporate specific peripheral properties in the generation of the control signals. The assumptions in this theory will be discussed and aspects of the proposed control schema will be compared with general control principles.
Brain↗
The role of the labyrinth, proprioception and plantar mechanosensors in the maintenance of an upright posture.
The maintenance of an upright posture in man requires information from vision, the labyrinth, proprioception and plantar mechanosensors. In order to evaluate the role of the labyrinth, proprioception and plantar mechanosensors, stabilometry was performed in subjects with closed eyes. Ten patients with bilateral severe or complete labyrinthine paresis were studied, as well as 9 patients with severe proprioceptive disorders and 10 normal healthy persons whose plantar mechanosensors were anesthetized by hypothermia. Both the area of sway and the total locus length (accumulated shift distance length) were evaluated. On closing eyes, in patients with labyrinthine disorders demonstrated that the area of sway increased more than length. On the other hand, in patients with proprioceptive disorders, length increased more than the area. In plantar anesthetized subjects, similar to the labyrinthine disorder cases, the area of sway increased more than length. These findings suggest that the labyrinth is a main monitor of the area of body sway, while proprioception is a principle monitor of the velocity of body movement of sway (or locus length). The plantar mechanosensor monitors the area of body sway similar to the labyrinth, but works less than the labyrinth. The locus length is the distance per minute and reflects the velocity of body sway. Thus, the length per area is a parameter for the velocity of body sway per area. Since proprioceptive disorders increase both the locus length and the length per area, present findings suggest that if proprioception is damaged, the body begins to move faster. Compensated labyrinthine disorders have a tendency to increase the length per area, indicating that if a labyrinthine disorder is compensated, the body adapts and moves faster to maintain an upright posture.
Achilles Tendon↗
Effects of tendon vibration on the spatiotemporal characteristics of human locomotion.
The present study addressed the involvement of proprioceptive input of the muscle spindles in the spatiotemporal control of human locomotion. Blindfolded subjects walked along a walkway while tendon vibration, a powerful stimulus of Ia afferents, was applied to various muscles of the lower limb. The effects of tendon vibration were measured on joint kinematics and on intralimb and interlimb coordination. Tendon vibration of the tibialis anterior during locomotion led to a decreased plantar flexion at toe-off, whereas vibration of the triceps surae led to a decreased dorsiflexion during swing. Vibration of the quadriceps femoris at the knee led to a decreased knee flexion during swing. These local effects of vibration can be explained in the light of a lengthening illusion of the vibrated muscle in that phase of the gait cycle where the muscle is lengthened. Tendon vibration did not affect the qualitative features of intralimb coordination. With respect to interlimb coordination, only vibration of the biceps femoris showed a significant increase in phase lead of the vibrated limb. The present results suggest the involvement of Ia afferent input in the online control of joint rotations. Additionally it is hypothesized that the proprioceptive input of biceps femoris might be involved in the control of coordination between the limbs, whereas the coordination between the segments of one limb appears to be unaffected by disturbance of muscle spindle input of one muscle.
Adult↗
Postural adjustments due to external perturbations during sitting in 1-month-old infants: evidence for the innate origin of direction specificity.
The aim of the study was to examine whether infants, at an age when they have no or little experience in sitting, can produce direction specific postural adjustments, i.e. synergies of muscle activity on the ventral side of the body during backward sway and on the dorsal side during forward sway. In addition, we addressed the question whether postural adjustments at this young age are restricted to single muscle responses or consist of a variable repertoire of muscle activation patterns including one during which all direction specific muscles participate ('complete' pattern). Postural adjustments due to external perturbations in a sitting position were studied in eight healthy infants aged 1 month. Multiple surface EMGs of neck, trunk and leg muscles and kinematics were recorded while the infants were exposed to horizontal forward (Fw) and backward (Bw) displacements of the surface of support. Direction specific postural adjustments, defined as adjustments during which agonist activation or antagonist inhibition preceded antagonist activation, were present in 85% of Bw and 72% of Fw translations. The direction specific adjustments showed a large variability with the repertoire of adjustments including the activation of one, two or all of the recorded direction specific muscles. The finding of direction specific adjustments at 1 month of age support the opinion that the basic level of organisation of postural adjustments has an innate origin. The finding of a variable repertoire of muscle response patterns, including the 'complete' pattern, refutes the idea that the development of postural adjustments results from gradual addition of appropriate muscles to the synergies.
Biomechanical Phenomena↗
Modulatory effect of repetitive peripheral magnetic stimulation on skeletal muscle tone in healthy subjects: stabilization of the elbow joint.
To investigate the role of repetitive peripheral magnetic stimulation (RPMS) on the postural component of motor performances, the long-lasting modulatory effect of RPMS on the stabilization of the elbow joint was examined in 13 healthy subjects. The resistance against very slow passive movements in the relaxed state was recorded simultaneously with the electromyogram (EMG) of the forearm extensor and flexor muscles. The experiments show that RPMS performed on the forearm flexor muscles increased the degree of stabilization of the elbow joint, whereas RPMS on the forearm extensor muscles caused a decrease in stabilization. This leads to the assumption that the postural component of motor tasks depends on the motor task itself: motor tasks like manipulation, pointing or grasping which are fine skilled movements require an increase in stabilization while goal-directed movements require a decrease in stabilization. Therefore RPMS is involved in sensorimotor integration and may modulate the motor program at the cortical level.
Adult↗
Idiopathic spasmodic torticollis is not associated with abnormal kinesthetic perception from neck proprioceptive and vestibular afferences.
Proceeding from recent evidence for a sensory involvement in the pathophysiology of idiopathic spasmodic torticollis (ST), we asked whether the abnormal head posture of these patients is associated with distortions of their internal spatial reference frames due to abnormal processing of neck proprioceptive and/or vestibular input. Twelve ST patients were instructed to estimate, by adjusting a light pointer in the dark, their head and trunk mid-sagittal directions (as representatives of ego-centric references) and to reproduce a remembered target location in space (space centric reference). They did so before and after horizontal head and trunk rotations, which evoked isolated or combined vestibular and/or neck stimulation. In ST patients, unlike in normal controls, pre-stimulus estimates of the head and trunk mid-sagittal directions (baselines) showed a pronounced across-subjects variability, with essentially normal mean values. Their post-stimulus estimates in all tasks, after correction for the individual baseline errors, were normal with respect to both amplitude and variability, independent of stimulus direction, modality and rotation dynamics. Our findings suggest that ST patients have a rather inaccurate knowledge of their head posture, but can effectively use neck proprioceptive input and vestibular cues when estimating head and trunk displacements in ego-centric and space centric spatial orientation tasks. We propose that an offset of a non-sensory set point signal in the neck proprioceptive loop for head-on-trunk control may be responsible for the pathological head deviation in ST.
Adult↗