Superior oblique muscle proprioception and the trochlear nerve.
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Animals↗
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Results for “REFLEX, PROPRIOCEPTIVE”
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Proprioceptive control of posture in the crayfish abdomen.
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Abdomen↗
Proprioceptive influence on supraspinal descending inhibitory mechanisms.
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Animals↗
[Epileptic seizures triggered by proprioceptive stimuli].
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Adolescent↗
[The differentiation between the reflex cervical nystagmus and the vascular cervical nystagmus (author's transl)].
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Diagnosis, Differential↗
Electromyographic activity in the cross-reinnervated soleus muscle of unrestrained cats.
Electromyographic (e.m.g.) activity was recorded from cross- and self-reinnervated soleus and extensor digitorum longus (e.d.l.) muscles of the cat during normal activity, including standing, walking and jumping. Activity patterns of normal soleus, e.d.l., and lateral gastrocnemius (l.g.) were essentially similar to those shown by other investigators. The self-reinnervated soleus fired phasically and synchronously with l.g. during walking but the activity was not trimmed to the extent that is seen in normal soleus. This is attributed to the relatively limited amount of proprioceptive information arising from such muscles. The activity pattern of the cross-reinnervated soleus muscles was variable. During walking, the phase of activity was sometimes coincident with that of a normal e.d.l., at other times (even in the same animal) it would be approximately coincident with l.g. The phase of activity usually consisted of an initial burst which was not sustained. Reflex activity elicited from the cross-reinnervated soleus was very similar to that of normal e.d.l., indicating the rigidity of connexions for reflex responses. reinnervated e.d.l. muscles; the activity attributable to the cross-reinnervated portion was similar to that seen in a self-reinnervated soleus. The activity pattern of soleus, reinnervated by the nerve to e.d.l. (an effective antagonist) is unlike that of either a normal soleus or e.d.l. muscle. This is attributed to a combination of lack of proprioceptive information and/or some degree of central remodelling.
Action Potentials↗
A cervical propriospinal system in man.
Peripheral stimuli facilitate, at a pre-motoneuronal level, the responses elicited in human upper limb motoneurons (MNs) by transcranial magnetic stimulation over the motor cortex (TMS). Several features indicate that the relevant premotoneurones are distinct from segmental interneurones and located rostral to MNs. Thus, corticospinal volleys would have an indirect (propriospinal) pathway to upper limb MNs, in addition to the direct cortico-motoneuronal pathway. Slightly increasing the corticospinal input causes the facilitation to be reversed to inhibition. This is consistent with a well-developed system of inhibitory intemeurones activated by corticospinal and afferent inputs inhibiting propriospinal neurones (PNs). Corticospinal activation of these inhibitory interneurones would explain why propriospinally-mediated corticospinal EPSPs are weak in primate MNs after artificial (electrical or magnetic) activation of the corticospinal system by itself. However, indirect evidence for descending facilitation of PNs can be provided during normal voluntary contractions, while using the modulation of the ongoing EMG or of the H reflex.
Cervical Vertebrae↗
[The role of the rapid neurogenic component and its constituents in the organization of working hyperpnea].
Rapid neurogenic components and their parts play a major role in the organisation of hyperpnoea in sports activity: the importance of conditioned reflex part in the ventilatory response is enhanced together with an increase in the load. Random loads give nearly the same values. As the metabolic value of the work rises, the importance of rapid neurogenic component in the overall value of hyperpnoea in work progressively decreases. The tendency towards a rapid of neurogenic component significance in sportsmen is a result of an adaptive change of the conditioned reflex part.
Adaptation, Physiological↗
Normal gait is differentially influenced by the otoliths.
Postural control depends on the integration of vestibular, somatosensory and visual orientation signals. The otolith contribution to postural control is achieved by the integration of otolith inputs and peripheral afferent inputs involved in crossed reflex pathways. This study shows that a functional linkage between otolith signals and activity in lower limb muscles is detectable in normal human gait. The otolith input appears to dominate particularly the neck proprioceptive and gaze motor influences during normal gait. This is demonstrated by an increase of tibialis anterior muscle activity during retroflexion of the head/neck, leading to an increased stability and counteracting possible perturbations. It is also shown by decrease of coordination during the movement caused by larger displacement of the centre of gravity demonstrated in vector diagrams.
Biomechanical Phenomena↗
Denny-Brown's views on the pathophysiology of dystonia.
We review Denny-Brown's hypotheses on the mechanisms underlying motor behavior and his views on how dysfunction in these mechanisms can result in dystonia. His formulations were based upon clinical observations of patients with diseases of the central nervous system and on monkeys with surgically-induced lesions of structures affected by diseases in his patients. Denny-Brown viewed dystonia as resulting from an imbalance of reflex responses to natural stimulation, both tonically and phasically. The evidence for this view came from demonstration of alterations of dystonic postures by natural vestibular, cutaneous, proprioceptive and visual stimuli. His formulations remain highly useful to clinicians faced with a bewildering variety of postural and movement disorders.
Dystonia↗
Warming-up and stretching for improved physical performance and prevention of sports-related injuries.
Competitive and recreational athletes typically perform warm-up and stretching activities to prepare for more strenuous exercise. These preliminary activities are used to enhance physical performance and to prevent sports-related injuries. Warm-up techniques are primarily used to increase body temperature and are classified in 3 major categories: (a) passive warm-up - increases temperature by some external means; (b) general warm-up - increases temperature by nonspecific body movements; and (c) specific warm-up - increases temperature using similar body parts that will be used in the subsequent, more strenuous activity. The best of these appears to be specific warm-up because this method provides a rehearsal of the activity or event. The intensity and duration of warm-up must be individualised according to the athlete's physical capabilities and in consideration of environmental factors which may alter the temperature response. The majority of the benefits of warm-up are related to temperature-dependent physiological processes. An elevation in body temperature produces an increase in the dissociation of oxygen from haemoglobin and myoglobin, a lowering of the activation energy rates of metabolic chemical reactions, an increase in muscle blood flow, a reduction in muscle viscosity, an increase in the sensitivity of nerve receptors, and an increase in the speed of nervous impulses. Warm-up also appears to reduce the incidence and likelihood of sports-related musculoskeletal injuries. Improving flexibility through stretching is another important preparatory activity that has been advocated to improve physical performance. Maintaining good flexibility also aids in the prevention of injuries to the musculoskeletal system. Flexibility is defined as the range of motion possible around a specific joint or a series of articulations and is usually classified as either static or dynamic. Static flexibility refers to the degree to which a joint can be passively moved to the end-points in the range of motion. Dynamic flexibility refers to the degree which a joint can be moved as a result of a muscle contraction and may therefore not be a good indicator of stiffness or looseness of a joint. There are 3 basic categories of stretching techniques: (a) ballistic--which makes use of repetitive bouncing movements; (b) static--which stretches the muscle to the point of slight muscle discomfort and is held for an extended period; and (c) proprioceptive neuromuscular facilitation - which uses alternating contractions and stretching of the muscles. Each of these stretching methods is based on the neurophysiological phenomenon involving the stretch reflex.(ABSTRACT TRUNCATED AT 400 WORDS)
Athletic Injuries↗
Modulation of the soleus H reflex with different velocities of passive movement of the arm.
Modulation of the gain of the soleus H reflex pathway produced by passive movement of the elbow joint was investigated and compared to that produced by passively maintained displacement of the elbow joint position. Little modulation of the gain of the soleus H reflex pathway was observed during passive displacement of the elbow joint position. In contrast, passive movement of the elbow joint facilitated the gain of the soleus H reflex amplitude and the degree of modulation was large as the velocity increased. The degree of the facilitatory effect upon passive movement of the upper extremity ipsilateral to the leg under test was larger than that obtained upon passive movement of the upper extremity contralateral to the leg under test. The modulation may be caused by discharge at the primary endings of the spindles in the upper extremity which is likely to excite propriospinal interneurons connecting to motor neurons of the lower extremity.
Adult↗
Interest of peripheral anesthetic blocks as a diagnosis and prognosis tool in patients with spastic equinus foot: a clinical and electrophysiological study of the effects of block of nerve branches to the triceps surae muscle.
OBJECTIVE: To evaluate clinically and electrophysiologically the effects of selective anesthetic blocks of motor nerve branches to the triceps surae muscle on lower limb stretch reflex in patients with spastic equinus foot. METHODS: Eleven patients were assessed before and after selective anesthetic block of the superior soleus nerve or the gastrocnemius nerves, performed by lidocaine injection. The stretch reflex (SR) of the ankle with the knee flexed or extended and the Achilles tendon reflex (TR) were scored clinically. Additionally, the direct M response and the H reflex to tibial nerve stimulation were recorded on the three heads of the triceps surae muscle. The ratio of H reflex to M response of maximal amplitudes (H(max)/M(max)) was calculated. RESULTS: The SR and TR mean scores were significantly reduced after soleus nerve block but not after gastrocnemius nerve block. Electrophysiologically, H(max) and H(max)/M(max) ratios were significantly reduced for the soleus muscle after soleus nerve block and for the lateral (but not medial) gastrocnemius muscle after gastrocnemius nerve block. CONCLUSIONS: Soleus nerve block appeared more appropriate than gastrocnemius nerve block to relieve spasticity clinically. In addition, the decrease in H(max)/M(max) ratio suggested that lidocaine preferentially blocked proprioceptive Ia fibers rather than A-alpha motor fibers. SIGNIFICANCE: Selective anesthetic blocks of nerve branches to the triceps surae muscle are useful in the assessment of lower limb spasticity and can benefit from H reflex investigation. H reflex recordings showed a preferential susceptibility of muscle spindle afferents to local anesthetics and supported the hypothesis of a prominent role of the soleus muscle in spastic ankle. The clinical and electrophysiological effects induced by anesthetic blocks may help to guide therapeutic interventions, such as neurotomy, neurolysis or botulinum toxin injection.
Adolescent↗
Motor function in a patient with bilateral lesions of the globus pallidus.
This study describes the long-term deficits of a patient who, after a toxic encephalopathy, sustained extensive bilateral damage to both segments of the globus pallidus (GP) and the right substantia nigra (SN). There were no signs of lesions of the pyramidal tracts or of other motor structures. The most obvious deficits were an abnormal gait with an exaggerated knee extension and a tendency to fall slowly, especially when pushed backward. In contrast, Romberg's test on an unstable platform was normal, as were long-latency leg reflexes induced by perturbations. Inadequate anticipatory and compensatory postural responses, in particular across the hip and knee joints, and slow movements seemed responsible for the falls. Muscle tone was normal but reflex studies showed signs of abnormal facilitation and inhibition at various levels of the neuraxis. We conclude that the GP and SN lesions caused defective input to premotor cortical and brain stem target zones. Dysfunctioning of these zones leads to improper control of the descending ventromedial motor system responsible for locomotion, postural control, and reflex status. The deficits in upper extremity motor performance included delayed and slow movements, inaccurate amplitudes of ballistic responses, a lack of predictive control, and deficits in bimanual coordination. Sensory feedback, proprioceptive more than visual, played a powerful compensating role in rapid aiming movements. Regional blood flow (studied using 15(O)2) was reduced in multiple frontal cortical regions, among which are the hand areas of the supplementary and premotor cortex. We hypothesize that this reflected impaired functioning of these areas, caused by defective bilateral output from GP and SN, and resulting in the motor deficits of the arm and hand.
Adult↗
Pretrigeminal preparation.
The pretrigeminal preparation (pretrigeminal animal) is obtained by transection the pons in front of roots of the trigeminal nerves. The rostral part of the preparation (isolated cerebrum) has olfactory, visual and humoral inputs and controls vertical position of eye and their pupillary diameter and accommodation. The pretrigeminal preparation was described in the cat and rat. During the acute stage the isolated cerebrum is continuously awake, alternatively alert and drowsy. In the chronic stage a sleep-waking cycle recovers, but paradoxical sleep remains absent and synchronized sleep is reduced. Thus the cerebrum can largely compensate for the withdrawal of influences from the deactivating structures of the lower brain stem. Olfactory and visual stimuli produce a virtually normal arousal response. Its major components are: dilatation of pupils, desynchronization of cortical EEG activity, appearance of theta activity in the hippocampal EEG, and an increase of the cerebral blood flow. If the stimulus is repeated, the arousal response habituates with a normal rate. In the pretrigeminal cat there are two ocular targeting reflexes: vertical fixation and accommodation. The fixation reflex has a normal general course and shows normal habituation, but it is less precise than in the intact cat. The accommodation reflex is normal. Classical and instrumental ocular conditioned reflexes can be elaborated in the pretrigeminal cat. The conditioned pupillary dilatation appears at a normal rate. On the other hand, the elaboration of the conditioned vertical eye movement is slower than in the intact cat, possibly as a result of the lack of the proprioceptive feedback from the extraocular muscles. In conclusion, excitability, integrity and plasticity of the isolated cerebrum of the pretrigeminal preparation seem to be virtually normal. In contrast to the pretrigeminal preparation, the "cerveau isolé" is comatose during the acute stage. In the chronic stage, however, the sleep-waking cycle recovers and with time it becomes similar to that in the pretrigeminal preparation. However, the vertical fixation reflex remains impaired in the low "cerveau isolé" and is obviously absent in the high "cerveau isolé". The caudal part of the preparation has a normal contact with the outside world, but it cannot largely make use of it. However, it satisfactorily controls the circulation and respiration. Rats are superior than cats: pretrigeminal cat cannot turn over from one side to the other and is fed by stomach tube, whereas pretrigeminal rat can crawl and eat food introduced into the mouth.(ABSTRACT TRUNCATED AT 400 WORDS)
Animals↗
Neural and mechanical responses of the triceps surae muscle group after 1 h of repeated fast passive stretches.
Experiments were carried out to examine interaction between mechanical changes of the muscle-tendon unit and reduced reflex sensitivity after repeated and prolonged passive muscle stretching (RPS). There is some evidence that this interaction might be relevant also during active stretch-shortening cycle type of fatigue tasks. The results demonstrated a clear deterioration of voluntarily and electrically induced muscle contractions after RPS. Maximal voluntary contraction (MVC), average electromyographic activities of the gastrocnemius and soleus muscles, and maximal twitch contraction decreased on average by 13.8, 10.4, 7.6, and 16.8%, respectively. In addition, there was a 14% lengthening in the total duration of the twitch. MVCs measured at different ankle joint angles revealed a downward and rightward shift in the torque-fascicle length curve after RPS. Interestingly, there was a crossing in the torque-fascicle length curves while measured at different activation levels but at the same joint angle before and after RPS. Even though no changes were observed in the activation level during MVCs, all the reflex parameters showed a clear reduction after RPS. This study presents evidence that repeated and prolonged passive muscle stretching can lead to some modification of material behavior of the aponeurosis-tendon system, such as stress relaxation and/or plastic deformation. In addition, altered material properties seem to affect proprioceptive feedback and, therefore, the motor unit activation in proportion to the contractile failure.
Adult↗
Sensorimotor control of the spine.
The spinal viscoelastic structures including disk, capsule and ligaments were reviewed with special focus on their sensory motor functions. Afferent capable of monitoring proprioceptive and kinesthetic information are abundant in the disc, capsule and ligament. Electrical stimulation of the lumbar afferents in the discs, capsules and ligaments seem to elicit reflex contraction of the multifidus and also longissimus muscles. The muscular excitation is pronounced in the level of excitation and with weaker radiation 1 to 2 levels above and below. Similarly, mechanical stimulation of the spinal viscoelastic tissues excites the muscles with higher excitation intensity when more than one tissue (ligaments and discs for example) is stimulated. Overall, it seems that spinal structures are well suited to monitor sensory information as well as to control spinal muscles and probably also provide kinesthetic perception to the sensory cortex.
Afferent Pathways↗
Voluntary activation of human motor axons in the absence of muscle afferent feedback. The control of the deafferented hand.
The ability to activate human motoneurons supplying individual intrinsic muscles of the hand was examined during acute deafferentation of the muscles. Tungsten microelectrodes were inserted percutaneously into motor fascicles of the ulnar nerve of 5 subjects, which was then blocked distally with local anaesthetic. In 4 subjects unitary action potentials were recorded from 16 motor axons, which were identified with respect to their target muscles. In the complete absence of muscle afferent feedback, subjects could voluntarily recruit motoneurons, grade their discharge and sustain a constant level of activity. Significant facilitation of motor efforts was provided by cutaneous feedback from the digits via the median nerve. During attempted maximal voluntary efforts the mean discharge frequencies of single motor axons were significantly lower than those of normally-innervated motor units. This finding suggests that peripheral afferents have a net facilitatory influence on motoneurons. However, during prolonged (20-30 s) maximal voluntary efforts the deafferented motoneurons did not display the progressive decline in discharge frequency shown by normally-innervated motor units during contractile fatigue, a finding consistent with two possible explanations: disfacilitation or reflex inhibition of the motoneuron pool by peripheral afferents. The results also indicate that the otherwise intact nervous system can perform some simple motor tasks with no proprioceptive input other than knowledge of the motor commands. Other factors may contribute to the poor motor performance reported for patients with severe sensory deficits.
Adult↗