Proprioceptive facilitation of voluntary motion in man.
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Humans↗
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Results for “REFLEX, PROPRIOCEPTIVE”
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Mode of action of dantrolene sodium in spasticity.
The mode of action of dantrolene sodium was studied in 11 multiple sclerosis patients with spastic paresis of the legs by measurements of changes in electromyographic and mechanomyographic proprioceptive reflex responses and in voluntary power. Dantrolene sodium 0.5 mg per kg body weight given intravenously clearly reduced monosynaptic reflex twitch tension, but voluntary power only moderately so. The electromyographic reflex responses were unchanged or slightly increased. The mode of action of the drug on spindle function is discussed on the basis of the present findings and the literature. It is concluded that dantrolene sodium does not reduce spindle stretch sensitivity, but probably reduces activity in group II and tonic 1a afferent fibers.
Dantrolene↗
Blockade of intrafusal neuromuscular junctions of cat muscle spindles with gallamine.
This is a report on the resistance to block of the motor terminals on intrafusal fibres of cat soleus muscle spindles using the drug gallamine triethiodide (Flaxedil). To minimize diffusion barriers and to permit accurate measurements of time courses, rather slow rates of gallamine infusion were used (0.15 mg min-1). The main finding made was that after gallamine infusion, when extrafusal tension had dropped to half, all dynamic fusimotor effects and eight of twenty static effects had fallen to 40% or less of their control value. The remaining static effects persisted at 60-80% of their control value. Where fusimotor fibres were stimulated together with one or two skeletomotor fibres, the influence of the skeletomotor axons was significant only after spindle biasing had fallen to low levels. When gallamine infusion was stopped extrafusal tension returned to control levels within 20-75 min, depending on the length of the block, while fusimotor responses did not fully recover within the recording period of up to 150 min. The combination for some fusimotor responses of an early fall and a late recovery when compared with extrafusal tension, suggested a greater sensitivity of these endings to the drug. A comparison of spindle responses to the drug succinyl choline (SCh) and to fusimotor stimulation in the presence of gallamine showed that SCh responses were rapidly reduced by gallamine and had a long recovery time course, as were some fusimotor responses. From this it is argued that fusimotor effects with a high sensitivity to gallamine blockade were associated with nuclear bag fibre contractions and the more resistant effects with nuclear chain fibre contraction. It is generally believed that intrafusal neuromuscular junctions are more resistant to neuromuscular blockers than extrafusal junctions. The present experiments provide evidence to the contrary for some intrafusal junctions. Since muscle relaxants are often used in general anaesthesia it is interesting to speculate about the recovery of function of proprioceptive reflexes and of kinaesthesia during the immediate post-anaesthetic period, in view of the large difference in recovery time for transmission at intrafusal and extrafusal junctions.
Animals↗
Rib motion modulates inspiratory intercostal activity in dogs.
1. A test was performed of the hypothesis that the motion of the ribs during inspiration modulates, via changes in spindle afferent activity, the activation of the inspiratory intercostal muscles. The electrical activity of the parasternal intercostal, external intercostal, and levator costae muscles in anaesthetized spontaneously breathing dogs was thus recorded during manipulation of the inspiratory displacement of the ribs over a wide range of rib motion. 2. In agreement with the hypothesis, the external intercostal and levator costae muscles lengthened and showed increased inspiratory activities when the normal inspiratory cranial motion of the lower rib was reduced or reversed into an inspiratory caudal motion. Conversely, the inspiratory activities decreased when the inspiratory cranial motion of the rib and the inspiratory shortening of the muscles was augmented. The inspiratory activity of the parasternal intercostal remained unchanged throughout. 3. However, when the two ribs making up the interspace were linked together so that the external intercostal muscle was constant in length, the relationship of muscle activity to rib motion was maintained. 4. In addition, when the upper rather than the lower rib of the interspace was manipulated, the relationship between the change in muscle length and inspiratory activity was reversed, so that activity decreased when the muscle was lengthened and increased when the muscle was shortened. The relationship of muscle activity to lower rib motion, however, was still maintained. 5. These observations thus indicate that rib motion triggers proprioceptive reflexes which, regardless of the changes in length of the individual muscles, make the external intercostal inspiratory activity exquisitely sensitive to the direction of rib displacement.
Animals↗
Clonus: beats provoked by the application of a rhythmic force.
(1) Clonus has been elicited by using a printed motor in nine patients with sustained ankle clonus. (2) When a dorsiflexing biasing force was applied to the foot the amplitude, but not the frequency, of the clonus varied according to the strength of the force. (3) When the biasing force was withdrawn there could be, for some seconds, continuing EMG evidence of a rhythmic discharge. (4) The clonus did not synchronise with an externally applied rhythmic force. In all relevant observations beats were set up between the clonus and the applied force. (5) When clonus was started by the abrupt application of bias the waveform in successive trials was fairly closely repeatable. (6) Beats were also established in two cases of wrist clonus. (7) It is concluded that clonus is not due to the self re-excitation of proprioceptive reflexes but is dependent on a spinal generator, the rate of beating of which is normally independent of peripheral circumstances, although it may be switched on and its activity maintained by appropriate events.
Adolescent↗
Central resetting of neuromuscular steady states may underlie rhythmical arm movements.
Changing the steady-state configuration of the body or its segments may be an important function of central pattern generators for locomotion and other rhythmical movements. Thereby, muscle activation, forces, and movement may emerge following a natural tendency of the neuromuscular system to achieve the current steady-state configuration. To verify that transitions between different steady states occur during rhythmical movements, we asked standing subjects to swing one or both arms synchronously or reciprocally at approximately 0.8 Hz from the shoulder joints. In randomly selected cycles, one arm was transiently arrested by an electromagnetic device. Swinging resumed after some delay and phase resetting. During bilateral swinging, the nonperturbed arm often stopped before resuming swinging at a position that was close to either the extreme forward or the extreme backward arm position observed before the perturbation. Oscillations usually resumed when both arms arrived at similar extreme positions when a synchronous bilateral pattern was initially produced or at the opposite positions if the initial pattern was reciprocal. Results suggest that a central generator controls both arms as a coherent unit by producing transitions between its steady state (equilibrium) positions. By controlling these positions, the system may define the spatial boundaries of movement. At these positions, the system may halt the oscillations, resume them at a new phase (as observed in the present study), or initiate a new motor action. Our findings are relevant to locomotion and suggest that walking may also be generated by transitions between several equilibrium configurations of the body, possibly accomplished by modulation and gating of proprioceptive reflexes.
Acoustic Stimulation↗
Mechanics of stretch in activated crustacean slow muscle. II. Dynamic changes in force in response to stretch.
1. The mechanical dynamics of the ventral superficial muscles (VSM) of the abdomen of the hermit crab, Pagurus pollicarus, have been analyzed to develop a quantitative model of gradedly excitable arthropod muscle. Such a model is important for understanding the role of proprioceptive reflexes in posture and movement. 2. The decay in force produced after ramp stretch of both passive and active muscle was approximated by the use of regression equations involving a direct term and one to three exponential terms. A second-order equation produced an acceptable description of this decay over short (0.5 s) sampling durations. 3. The rate constants of the regression equation did not vary with stretch length, velocity, or activation level of the muscle. For the two-exponential-term model, the rate constants were approximately 90 and 9 s-1 for a sample duration of 0.3 s. An additional rate constant of approximately 1 s-1 was needed to adapt the model to longer sample times. 4. The direct term and the middle-order (9 s-1) residual were both functions of stretch length and activation level. The high-order (90 s-1) residual was primarily a function of stretch length and velocity. Transfer functions omitting the velocity dependence adequately described the mechanical dynamics of the muscle for physiological ranges of stretch velocity. 5. White-noise length perturbations were used to calculate spectral density functions of muscle force and length. These measurements confirmed the principal observations of the ramp stretch analysis: the frequency response of the muscle was independent of the level of activation; the magnitude of the stiffness increased over the stretch frequency range of 4-40 Hz and was then almost constant; and the phase response of the muscle became slightly positive over the same range of stretch frequency. 6. The speed of activation of the muscle to different stimulus frequencies was estimated by fitting a single exponential equation to the rise in isometric tension at the onset of stimulation of the motor nerve. The rate constant increased with stimulus frequency, but its maximum value was only 1.8 s-1, about one-fourth of the middle mechanical rate constant. 7. Because muscle activation is slower than the mechanical dynamics, it is unlikely that the nervous system can regulate muscle dynamics. However, it is possible that mechanical impedance could be regulated to maintain a desired time-averaged value.
Animals↗
[Magnetomyography with the SQUID].
The results of investigations of the neuromuscular system in man using a SQUID magnetometer with a second-order gradiometer detector are presented. After electrical stimulation of the tibial nerve in the hollow of the knee and the triggering of a monosynaptic proprioceptic reflex (Hoffmann-(H-)reflex), the biomagnetic field was recorded from the dorsal surface of the lower leg (soleus muscle of the m. triceps surae). The results obtained indicate that, over and beyond the data provided by electromyography, diagnostic information is provided on the state of the neuronal reflex pathways including muscle effector function. The biomagnetic field was evaluated in terms of latency, intensity, composition, characteristic behaviour and site of generation of the signal. In the geometry used, this noninvasive measuring technique can be employed for office observation of the spread of excitation through the muscle, as demonstrated by the response obtained following supramaximal stimulation of the supply nerve.
Electric Stimulation↗
An overview of the clinical use of dynamic posturography in the differential diagnosis of balance disorders.
Dynamic posturography comprises a series of balance control tests which help physicians overcome numerous diagnostic and treatment challenges arising when examining patients complaining of a debilitating balance disorder. These challenges include the specific differential diagnosis, documentation of symptoms and assessment of functional disability. It must be determined whether the cause of the disability is an organic sensory, deficit, a central nervous system (CNS) lesion or a non-organic (that is, possibly psychogenic or just overtly simulated) disorder. This review is targeted towards providing the reader (a) an overview of the effects sensorimotor deficits have on balance control, specifically vestibulospinal and proprioceptive reflex deficits; and, (b) how these effects may be assessed objectively in a clinical setting to differentiate between various organic and non-organic balance-disorders. The techniques used to study these effects are based on the analysis of both rapid balance-correcting and slow balance-stabilizing responses to fast and slow movements in the pitch plane of the support surface on which the test subject stands.
Diagnosis, Differential↗
[Effect of adrenalin stimulation of the diencephalon on spinal dominance in frogs].
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Animals↗
Third-degree lesions of the external compartment of the ankle: results of conservative treatment.
Ankle sprains are one of the most common lesions of the musculo-skeletal system. In some sports they are the most common reason that athletes seek medical care. For this reason many publications are dedicated to this subject, and specifically to the treatment of lesions of the external compartment, which account for about 85% of all ligamentous lesions of the ankle (O'Donoghue, 1958). The treatment of these lesions is very controversial. Some orthopedists propose early surgical treatment to restore normal healing with minimal functional lengthening. Others favor conservative treatment, while still others recommend functional treatment with the objective of accelerating the recovery of proprioceptive reflexes affected by the ligamentous lesion as well as stimulating healing by movement. The authors' diagnostic and therapeutic approach to lesions of the external compartment of the ankle is explained with special reference to lesions in athletes, who must be guaranteed perfect joint stability in order to tolerate the intense stress of sports activity without danger of relapse.
Adolescent↗
Inhibitory interactions between spiking and nonspiking local interneurons in the locust.
Simultaneous intracellular recordings were made from pairs of spiking and nonspiking local interneurons in the metathoracic ganglion of the locust to search for interactions that might underlie tactile and proprioceptive reflexes of a leg. A spike in a spiking local interneuron is followed after a consistent latency (0.6 +/- 0.12 msec, mean +/- SD) by an IPSP in a particular nonspiking interneuron. The connection appears to be direct and chemically mediated. By contrast, manipulating the membrane potential of a nonspiking interneuron by injecting current through the recording electrode has no direct effect on a spiking local interneuron. The direct interactions between pairs of these local interneurons are thus one-way. If, however, the current injected into a nonspiking interneuron is sufficient to evoke a movement by exciting motor neurons, then the spiking interneuron can be excited or inhibited by the resulting reafference. The spiking local interneurons have excitatory regions in their receptive fields formed by arrays of exteroreceptors or by proprioceptors at specific joints. The inhibitory connections mean that the postsynaptic nonspiking interneurons have corresponding inhibitory regions to their receptive fields. Several spiking local interneurons with similar receptive fields may converge onto one nonspiking interneuron. Some nonspiking interneurons, however, have larger receptive fields than an individual spiking interneuron, again indicating convergence of inputs. The specificity of the inhibitory connections preserves the spatial representation of sensory information for use in particular reflexes. For example, touching hairs on the ventral femur evokes a reflex extension of the tibia. Spiking interneurons excited by these receptors inhibit a nonspiking interneuron that would cause the opposing and therefore unwanted flexion movement. Viewed in this behavioral context, the pattern of connections between the local interneurons forms the basis of the circuitry for the local reflex adjustments of posture and locomotion.
Action Potentials↗
Alfred Bielschowsky's 1940 legacy for neuro-ophthalmology.
OBJECTIVES: The author was stimulated to write this article by a 1996 visit to the University where Professor Alfred Bielschowsky was Chairman of Ophthalmology in the 1930s. Dr. Bielschowsky was one of the founders of neuro-ophthalmology. This review, with biographical notes, is presented in his honor. Dr. Bielschowsky and the author had similar disruptive experiences, of historic interest, during the Hitler regime in Nazi Germany. REVIEW: Professor Bielschowsky's legacy begins with his contributions to ocular physiology. For instance, his after-image test establishes the presence of retinal correspondence, important for stereoscopic vision. Alfred Bielschowsky taught how an ocular examination is critical for neuro-ophthalmologic diagnosis, localization, prognostication, and treatment. Much of our knowledge is linked with his name. Examples include "Bielschowsky's Phenomenon", explaining dissociated vertical movements, and "Bielschowsky's Doll's Head Phenomenon" (Doll's Eyes), describing proprioceptive reflexes important for localizing intracranial lesions. Dr. Bielschowsky emphasized many pitfalls in the differential diagnosis of oculomotor anomalies. For example, he cautioned against mistaking the compensatory head position in congenital fourth cranial nerve paresis for neck muscle disease. CONCLUSION: Dr. Bielschowsky's emphasis on the clinical examination remains critical despite today's advanced diagnostic equipment. His legacy is the application of physiology to patient care.
Germany↗
Haloperidol exaggerates proprioceptive-tactile support reflexes and diminishes vestibular dominance over them.
Rats made immobile and cataleptic by haloperidol, a dopamine receptor blocker, maintain their static stable equilibrium by employing a variety of allied postural support reflexes. Under some test conditions, competition between such reflexes occurs, and in haloperidol-treated rats, unlike undrugged controls, proprioceptive-tactile stimuli appear to be dominant over vestibular stimuli. We investigated this relationship in rats by testing their air-righting with and without simultaneous contact of the tail on a wooden platform. The rats were lightly held in a supine position by the shoulders and pelvis, with or without tail contact on a small wooden platform 47 cm above the ground. Undrugged rats showed the normal pattern of righting which involves axial rotation with cephalocaudal recruitment whether the tail is contacting the platform or not. Upon release, the haloperidol-treated rats (2.5 mg/kg) gripped the platform with their tail, which interfered with the air-righting reflex. This demonstrates that in haloperidol-treated rats, the dominance of tactile-proprioceptive postural support reflexes over those triggered vestibularly.
Animals↗
Effects of vibration in inline skating on the Hoffmann reflex, force, and proprioception.
PURPOSE: The objective of this study was to examine the effects of vibrations induced by inline skating on the Hoffmann (H) reflex, maximal voluntary isometric (MVC) force, and ankle proprioception. METHODS: Accelerometers were used to measure the frequencies and amplitudes of the vibrations encountered at the skate and mid-tibia levels. The soleus H reflex was recorded before and after (for 30 min) inline skating for 30 min. Maximal plantarflexor contractions were performed against a strain gauge while EMG was recorded from the soleus and medial gastrocnemius muscles. An ankle position-matching test was carried out to measure proprioception at the ankle. A Modified Borg Scale was used to obtain the appreciation of leg numbness and fatigue during inline skating. RESULTS: The vibrations measured at the skate chassis level had a mean frequency of 141.8 +/- 25.2 Hz and an amplitude of </=5 g. These vibrations were transmitted to the lower limb as measured by a mean frequency of 34.4 +/- 27.7 Hz and an amplitude of </=2 g at the mid-tibia level. The results demonstrate a clear inhibition ( approximately 35%) of the H reflex after skating that persisted for >35 min after skating. A 10% drop in MVC plantarflexor force was observed after inline skating. There was no accompanying change in EMG signal parameters. The ankle proprioception of the subjects decreased after skating, resulting in reproduction errors twice as large as before skating. CONCLUSION: Vibrations encountered during inline skating resulted in modifications of neuromotor functions related to the muscle spindles' primary afferent. These changes may partially be explained by presynaptic inhibition; however, a more plausible mechanism may be a decrease in the Ia afferent transmission induced by the vibration.
Acceleration↗
Reflections on spinal reflexes.
Over the past four decades, the understanding of proprioceptive spinal reflexes has advanced far more rapidly than generally considered. This problem could be largely obviated in undergraduate and graduate training programs if the topic of reflexes was introduced subsequent to the concept and mechanisms of pattern generation within the central nervous system. The key advantage would then be that the neuroscience community as a whole would gain appreciation of the fact that proprioceptive reflexes are not hard-wired but rather are context- and phase-dependent, with the central nervous system selecting input-output pathways appropriate for the task at hand.
Animals↗
Effect of counterforce forearm bracing on wrist extensor muscles performance.
OBJECTIVES: We examined (1) the effect of a counterforce forearm brace on isokinetic strength, stretch reflex, passive stretching, and proprioception of the forearm muscles in healthy subjects and (2) the effect of different strap tensions of the brace on the above variables. DESIGN: The dominant hand of 15 healthy subjects were tested under four randomized conditions: (1) no brace, (2) brace with minimal tension, (3) brace with 2.5 kg force tension, and (4) brace with 5 kg force tension. The tests included isokinetic wrist extensors strength, passive stretching to the wrist extensors until onset of pain, joint proprioception, and reflex latency of forearm extensor muscles. A repeated measures multivariate analysis of variance test was used to analyze the data, and significant results were further analyzed with post hoc linear contrasts with alpha at 0.0083. RESULTS: There was no difference in isokinetic strength, proprioception, and stretch reflex latency among the four conditions. For passive stretching, there was a significant difference (P = 0.001) in that using a brace produced a higher pain threshold than without a brace. CONCLUSION: A forearm counterforce brace has no effect on strength, proprioception, and stretch reflex latency, but it increases the pain threshold.
Adult↗
Proprioceptive modification of reflex patterns.
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Humans↗