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PubMed1997

Phasic activity in the human erector spinae during repetitive hand movements.

1. Phasic activity in the human back muscle erector spinae (ES) was studied during repetitive hand movements. The hand movements were elicited voluntarily by the subject or induced passively by the experimenter through a servomotor or through cyclical electrical stimulation of muscles acting about the wrist. The aim of the study was to determine whether the rhythmical activation of ES was of supraspinal, intersegmental or segmental origin. 2. When voluntary rhythmical hand movements were performed as fast as possible, cyclical ES EMG bursts occurred at the same frequency. This frequency was significantly higher than that reached when the task was to contract the back muscles as rapidly as possible. This suggests that the ES activity during the fast hand movements was not generated by direct commands descending to the ES muscles from the motor area of the cerebral cortex responsible for voluntary back muscle activation. 3. During imposed rhythmical hand movements, ES EMG bursts remained entrained to the hand movements, even when movement frequencies far exceeded those attainable voluntarily either for the hand or the back. This showed that ES EMG responses could be evoked by the hand movements even when these were not generated by descending neural commands. Two alternative mechanisms of ES activation were considered: (a) propriospinal transmission of afferent input entering the spinal cord from the upper extremity; (b) afferent input from ES and other trunk muscles, responding to local oscillations transmitted mechanically from the hand to the lower back. 4. Activation of ES via proprioceptive signals from the forearm was unlikely since (a) simultaneous electrical stimulation of wrist extensor and wrist flexor muscles did not result in repetitive ES EMG bursting; (b) cyclical vibration of the wrist extensors did not evoke ES EMG bursting; (c) when the forearm was constrained and the hand was moved passively, the lower trunk accelerations and cyclical ES EMG both occurred at a harmonic of the hand movement frequency. 5. We conclude that the repetitive ES EMG bursting during hand movements was probably due to a local segmental reflex rather than to descending commands. Remote mechanical oscillations of the trunk caused by hand movements evidently elicited proprioceptive reflexes in ES that presumably contributed to trunk stabilization.

Adult↗
PubMed1989

The role of stretch and vestibulo-spinal reflexes in the generation of human equilibrating reactions.

Equilibrating reactions in standing humans were examined for evidence that either vestibulo-spinal or proprioceptive long loop stretch reflexes from ankle muscles, or both, are responsible for the control and organization of rapid postural responses. Specifically, the hypothesis was tested that the same postural response could be evoked by rotation of the support surface that mimics the ankle rotation occurring during support surface translations. Rotation perturbations evoked postural responses in leg and trunk muscles that were different in strategy, synergy and coactivation from translation responses, even though the short-latency response in the stretched triceps surae muscles was equal in latency and size. Movement patterns consisted of a stiffening strategy and hardly any compensating ankle rotation for rotation stimuli, and a multi-link strategy with motion focused about the neck, hip and ankle joints for translation stimuli. Dorsiflexion rotations caused earlier and stronger responses in tibialis anterior and quadriceps muscles just post to the onset of paraspinal muscles, whereas rearward translation activated soleus and abdominals strongest, both just prior to hamstring muscles. Correlated activation strengths of agonist and antagonist activity was a common feature for both types of perturbation, albeit, only in the ankle muscles for rotations and only in the trunk muscles for translations. These data suggest that sensory inputs, other than those generated in the lower leg predominate, in the triggering and modulation of equilibrating reactions. Possible candidates are those of the vestibular system or proprioceptive inputs from the trunk.

Humans↗
PubMed1999

[The role of cervical proprioceptive afferentation in the mechanisms of vestibular dysfunction compensation. 2. The passive vestibulo-ocular reflex in bilateral labyrinth lesion].

The study was made of passive cervicoocular reflex in patients with bilateral labyrinthine involvement. Passive cervicoocular reflex was assessed by three parameters: direction of the nystagmus, reactivity rate and phasic shift. It is proved that patients with bilateral labyrinthine lesions desplay intensive cervicoocular reflex serving the basic mechanism of vestibular dysfunction compensation in these patients.

Adult↗
PubMed1995

Proprioceptive regulation of locomotion.

Recent investigations of proprioreceptors in the walking systems of cats, insects and crustaceans have identified reflex pathways that regulate the timing of the transition from stance to swing, and control the magnitude of ongoing motoneuronal activity. An important finding in the cat is that during locomotor activity, the influence of feedback from the Golgi tendon organs in extensor muscles onto extensor motoneurons is reversed from inhibition to excitation. The excitatory action of tendon organs during stance ensures that stance is maintained while extensor muscles are loaded, and may regulate the magnitude of extensor activity according to the load carried by the leg. Afferents from primary and secondary spindles in extensor and flexor muscles have also been found to influence the timing of the locomotor rhythm in a functionally relevant manner. Recent studies indicate that reflex reversals and the regulation of timing by multiple proprioceptive systems are also features of walking systems in arthropods.

Animals↗
PubMed2001

Proprioceptive influence on the optokinetic nystagmus.

The influence of neck and leg proprioceptive inputs on optokinetic-induced quick phases was studied in humans. Ten subjects received unidirectional horizontal optokinetic stimulation (10-20%/s) during sinusoidal neck, leg and combined neck + leg proprioceptive stimulation. The optokinetic reflex was measured by electro-oculography. Neck stimulation induced a shift in the nystagmus beating field in the opposite direction to body movement (gain 0.3 0.4, phase 140-180 degrees). The beating field shift resulted totally from the amplitude and frequency modulation of optokinetic quick phases, as slow phases were not affected. Leg proprioceptive stimulation induced a similar effect, but the phase of the response lagged by approximately 90 degrees compared with that of neck response. With combined neck + leg stimulation, the amplitude of the effect was a sum of the separate effects, but the phase coincided with that of the leg response. This suggests that neck and leg proprioceptive signals do not add linearly and that the leg signal determines the time of the response.

Adult↗
PubMed1985

Canadian medical experiments on Shuttle flight 41-G.

During the 41-G mission, two payload specialist astronauts took part in six Canadian medical experiments designed to measure how the human nervous system adapts to weightlessness, and how this might contribute to space motion sickness. Similar tests conducted pre-flight provided base-line data, and post-flight experiments examined re-adaptation to the ground. No changes were detected in the vestibulo-ocular reflex during this 8-day mission. Pronounced proprioceptive illusions were experienced, especially immediately post-flight. Tactile acuity was normal in the fingers and toes, but the ability to judge limb position was degraded. Estimates of the locations of familiar targets were grossly distorted in the absence of vision. There were no differences in taste thresholds or olfaction. Despite pre-flight tests showing unusual susceptibility to motion sickness, the Canadian payload specialist turned out to be less susceptible than normal on-orbit. Re-adaptation to the normal gravity environment occurred within the first day after landing.

Adaptation, Physiological↗
PubMed1995

Perception of passive whole-body rotations in the absence of neck and body proprioception.

1. This study investigated whether accurate perception of body rotation after passive horizontal whole-body rotations in the dark requires the integration of both vestibular and neck-body proprioceptive signals. 2. In the first experiment, the gain of the vestibuloocular reflex (VOR) of normal subjects ("controls") and of a patient without proprioception of the neck and body muscles was assessed by the use of pulse and sinusoidal stimulation. In the second experiment, the subjects reported verbally the magnitude of the body rotations. Finally, in the third experiment, they shifted gaze to the position fixated before the rotation ("vestibular memory-contingent saccades" paradigm). 3. The VOR gain of the patient was similar to that of controls, although the body rotations of the patient were largely overestimated, regardless of whether the patient reported the perceived magnitude verbally or through a gaze shift toward the position gazed at before the rotation. 4. These results suggest that neck muscle proprioception contributes to the vestibular signal calibration at the perceptual level necessary for determining body orientation accurately after rotations in the dark.

Afferent Pathways↗
PubMed2006

Lumbar spine reposition sense: the effect of a 'slouched' posture.

Proprioceptive control is considered important for spinal stability and prevention of injury. However there is evidence that proprioceptive structures, that are reflexive and viscoelastic, are challenged by commonly adopted 'slouched' postures. The aim of this study was to investigate the effect of such postures on proprioceptive control. The reliability of a flexible electrogoniometer was established (ICC=0.89). Using a repeated measures design (n=32, 80% power detecting 0.5 degrees difference at 95% significance) subjects repositioned their lumbar spine immediately (3 s) and following 300 s in a 'slouched' posture, with a 15-min interval in between. Results showed a significantly reduced lumbar spine reposition sense following 300 s in a 'slouched' posture as compared with 3 s in a 'slouched' posture (P<0.001), mean difference 3.92 degrees (SD 4.35). Based on this sample, there was evidence that a 'slouched' posture, of 5 min duration, would increase reposition error by more than 2.35 degrees and less than 5.48 degrees (n=32, CI 95%). These findings support the practice of postural education to reduce potential to proprioceptive loss and injury. The electrogoniometer shows potential for use in clinical practice.

Adolescent↗
PubMed1987

Selective mechanical stimulation of an identified proprioceptor in freely moving locusts: role of resistance reflexes in active posture.

Direct mechanical stimulation of an identified proprioceptive sense organ, the femoral chordotonal organ of the locust hindleg, has been applied in freely moving animals to evaluate its function in maintenance of posture. A piezo-electric crystal mounted on the leg produced displacements of the main ligament of the organ mimicking 10-15 degree changes in joint angle. These stimuli produced consistent responses that (1) occurred as resistance reflexes to oppose the apparent joint movement and (2) demonstrated strong, tonic coupling of motoneuron activity to afferent input. These experiments have, therefore, directly demonstrated that the chordotonal organ functions in posture to aid in load compensation and to set the level of tonic motoneuron activity.

Animals↗
PubMed1997

Primary- and secondary-like jaw-muscle spindle afferents have characteristic topographic distributions.

Single jaw-muscle spindle afferent axons were characterized physiologically and intracellularly stained to determine whether particular physiological types of spindle afferent show distinctive morphologies. Microelectrodes filled with either horseradish peroxidase (HRP) or biotinamide (Neurobiotin) were advanced into the mesencephalic trigeminal nucleus (Vme) in anesthetized rats. Intracellular recordings then were characterized by their response: to palpation of the jaw muscles; when pressure was applied to the teeth and during passive ramp and hold and sinusoidal jaw movement. Seventy-one afferents were characterized physiologically and injected with HRP; an additional 61 afferents were typed and injected with biotinamide. The response of 43 stained neurons was recorded in the presence of suxamethonium. The major projection areas of these afferents were the: trigeminal motor nucleus (Vmo); region dorsal to Vmo; reticular formation, spinal trigeminal nucleus, superior cerebellar peduncle and Vme. One afferent type was modulated strongly during stretching of the jaw-elevator muscles. Based on their high sensitivity during stretching of the jaw muscles and/or their silencing during the release phase of muscle stretch, these afferents were classified as primary-like spindle afferents. These afferents projected most strongly to Vmo. A second type of afferent was modulated only modestly during stretching of the jaw-elevator muscles. These tonic afferents were classified as secondary-like spindle afferents because of their low dynamic sensitivity during ramp muscle stretch and their continued discharge during the release phase of muscle stretch. Secondary-like afferents projected most strongly to the region dorsal to Vmo. Boutons (n = 3,834) from 11 afferents were studied in detail. Secondary-like afferents had statistically larger boutons within Vmo. In both secondary- and primary-like spindle afferents, only a small number of boutons were associated closely with the somata and proximal dendrites of trigeminal motoneurons. In these cases, however, two to five boutons appeared to contact individual motoneurons, implying multiple monosynaptic inputs to a selective subset of jaw-elevator motoneurons. Some "giant" boutons were present dorsal to Vmo and in Vme. These results demonstrate that dynamically sensitive and nondynamically sensitive jaw-elevator muscle spindle afferents project preferentially to different regions. Primary-like spindle afferents are capable of providing feedback related to the dynamic phases of muscle stretch and project most heavily to Vmo. Secondary-like spindle afferents can transmit a feedback signal associated with muscle length and project most strongly to the supratrigeminal region. Both types of afferent have projections caudal to Vmo that may serve longer latency jaw-muscle stretch reflexes and/or the projection of proprioceptive information to the thalamus and cerebellum.

Afferent Pathways↗
PubMed1990

Neurological examination in subjects over 65 years: an epidemiological survey.

The frequency of abnormal findings at neurological examination was analyzed in an unselected sample of elderly people aged 67-87 years. Absent deep tendon reflexes and impairment of proprioceptive sensation rarely occurred in the elderly. Limitation of upward gaze and convergence appear a common finding, especially in the very old. Overall, the presence of cortical disinhibition signs (primitive reflexes and paratonia) did not discriminate well between subjects without CNS disease and demented patients. Only the presence of a prominent and persistent response to the stimulus and the number of cortical disinhibition signs found in the same subject appear useful criteria to distinguish between normality and dementia.

Aged↗
PubMed2006

Interaction between ocular stabilization reflexes in patients with whiplash injury.

PURPOSE: In the past few decades, the automobile has become an increasingly more popular means of transport, which has led to an increasing number of rear-end collisions and consequently has resulted in more patients with whiplash-associated disorders (WADs). Recently, it was found that the gain of one of the ocular stabilization reflexes-the cervico-ocular reflex (COR)-is elevated in patients with whiplash injury. The COR responds to proprioceptive signals from the neck and acts in conjunction with the vestibulo-ocular reflex (VOR) and the optokinetic reflex (OKR) to preserve stable vision on the retina during head motion. Therefore, an investigation was conducted to determine whether the reported elevation of the COR in WADs is accompanied by changes in VOR or OKR. METHODS: Eye movements of 13 patients and 18 age-matched healthy controls were recorded with an infrared eye-tracking device. RESULTS: Analysis confirmed a significant increase in COR gain in whiplash patients. Meanwhile the VOR and OKR gains remained the same. No correlation was found between the gains of the reflexes in individual patients. This is in contrast to earlier observations in elderly subjects and subjects with labyrinthine defects, who showed increases in COR gain and decreases in VOR gain. CONCLUSIONS: Impaired neck motion, altered proprioception of the neck, or disorganization in the process of VOR plasticity could explain the lack of change in VOR gain.

Adult↗
PubMed1989

An artificial myotatic reflex: a potential avenue to fine motor control.

When a striated muscle becomes paralyzed, not only its motor function, but its sensory innervation may be impaired. Methods of rehabilitation have previously focused only on motor innervation, although striated muscles are submitted to self-regulation of length and tension. Indeed, reinnervated muscle may not contract appropriately unless sensory information is available, nor is it known whether sensory receptors are included in the reinnervation process. We hypothesized that the myotatic reflex (MR) would be absent in the event these sensory organs are not reinnervated, and that an artificial myotatic reflex (AMR) would be useful in reestablishing fine motor control. The strap muscles were exposed in six anesthetized rabbits. The MR was verified by stretching an intact sternohyoid muscle. Next, loss of the reflex was documented after the ipsilateral ansa hypoglossi was divided, and a crossover nerve-muscle pedicle (NMP) was brought in from the opposite sternothyroid. After 3 months, the MR was still absent; however, stretch of the contralateral sternohyoid produced a reflex response on the reinnervated side. A strain gauge sutured to the reinnervated muscle was linked to an electronic modulator so that stretch induced electric stimulation of the NMP and contraction (the AMR). We conclude that (1) proprioception is not reestablished in the reinnervated muscle; (2) by contrast, sensory information from the muscle of origin of the NMP is conveyed to the reinnervated side; and (3) the AMR offers promise toward more sophisticated control of paralyzed (i.e., facial, laryngeal) musculature.

Animals↗
PubMed1986

Effects of pressure stimulation of the body surface on placing reactions.

The effects of pressure stimulation of the body surface on placing reactions were investigated in intact unanesthetized cats. A slight contact applied to the dorsum of the fore- and hindpaws produced the typical placing reactions in these preparations. These reflexes, however, became more prominent if, in addition to the exteroceptive input, a proprioceptive input was elicited after plantar flexion of the paws. Slight pressure applied to the upper part of the body greatly depressed not only tactile placing reactions, but also to a lesser extent proprioceptive placing reactions. Moreover, these reflexes were less prominent and more sluggish and fatiguable than in the normal cats. The depression of the placing reactions elicited by the cutaneous input during pressure applied to the body surface mainly affected the forelimbs. However, as soon as the pressure stimulation was removed, the placing reactions reappeared or became as prominent as usual. We postulate that the exteroceptive input resulting from body pressure decreased the placing reactions by exciting the Purkinje cells of the intermediate cortex of the cerebellum, which are in turn inhibitory on the interpositus nucleus, thus reducing the neuronal discharge of the interpositorubrospinal pathway acting on flexor motoneurons.

Animals↗
PubMedDate not supplied

Reflex muscle contraction in anterior shoulder instability.

Reduced proprioception may contribute to recurrent anterior shoulder instability. Twelve patients with unilateral shoulder instability were investigated for evidence of deficient proprioception with an activated pneumatic cylinder and surface electromyography electrodes; the contralateral normal shoulder was used as a control. The latency between onset of movement and the detection of muscle contraction was used as an index of proprioception. No significant difference in muscle contraction latency was detected between the stable and unstable shoulders, suggesting that there was no significant defect in muscular reflex activity. This study does not support the use proprioception-enhancing physiotherapy in the treatment of posttraumatic anterior shoulder instability.

Adult↗
PubMed1976

Identity of sensory and motor systems that are critical to the immobility reflex ("animal hypnosis").

This review presents an analysis of the sensory and motor mechanisms as they are now understood that cause the immobility reflex (IR). Of the sensory systems that conceivably could trigger and sustain the IR, as commonly induced experimentally by inversion and manual restraint, evidence has been presented to eliminate some senses (vestibular, vision, sound, many visceral sensations, olfaction, taste, temperature), while incriminating tactile and proprioceptive influences. Of the motor systems which could cause the profound immobility during IR, neurosurgical and electrophysiological evidence identifies the locus of the inhibitory neurons in the brain stem and/or spinal cord. The evidence reviewed leads to a unified working hypothesis of IR mechanisms. IR is considered to be caused by a group of neurons in the brain stem which inhibit spinal motoneurons, either directly or indirectly, when those inhibitory neurons are activated by a specific pattern of tactile and proprioceptive input. Modulation of the IR control system appears to come from the limbic system, which under fear-producing conditions, potentiates the IR in part by release of epinephrine. Inhibition of the IR control system appears to come from the neocortex, as well as the brain stem reticulum, when it is activated by nonspecific, arousing somaesthetic sensations that produce generalized activation of the neocortex and skeletal muscle.

Animals↗
PubMed1997

Proprioceptors and fast antennal reflexes in the ant Odontomachus (Formicidae, Ponerinae).

In ants, antennal movements support the stimulus perception of olfactory and mechanosensory sensilla, most of which are located on the distal part of the antenna. In addition, sensory hair plates, campaniform sensilla, and Janet's organ provide the ant with proprioceptive information about the position, velocity, and acceleration of their antennae. We describe the morphology of these proprioceptors and their afferent neurons with special reference to the trap-jaw ant genus Odontomachus. All these sensory neurons terminate in the dorsal lobe, the part of the brain that also contains antennal motor neurons and that controls antennal movements. Neurons originating from campaniform sensilla and Janet's organ send additional collaterals into the subesophageal ganglion. Particularly fast antennal movements occur during protective withdrawal of the antenna. Under natural conditions, antennal retraction in Odontomachus always precedes the rapid mandible strike. We have found no indication of monosynaptic coupling between the antennal proprioceptive afferents and the trigger motor neurons that release the mandible strike. Instead, complex neuronal interactions in the involved neuromeres are more likely to control the timing of the two reflexes. The normal behavioral sequence of antennal retraction can be reversed by artificially releasing the mandible strike earlier than normal. The significance of fast antennal reflexes and of proprioceptive control is discussed.

Aggression↗