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Results for “REFLEX, PROPRIOCEPTIVE”

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PubMed1993

[Primary suture of the anterior cruciate ligament. A critical analysis].

Recently some authors have claimed that primary repair of an acute tear in the anterior cruciate ligament will fail in the long run. A review of the literature reveals that this opinion is mainly based on an American study in 1976. However, the poor results presented in this study were never reproduced. The study is critically analyzed, and 14 more papers presenting successful primary reconstructions of the anterior cruciate ligament are discussed. Preserving proprioceptive structures may be an important advantage of this technique, as it is hypothesized that the anterior cruciate ligament functions as a significant sensory organ, not only providing proprioceptive information, but also initiating protective and stabilizing muscular reflexes. In conclusion, it is recommended that primary suture be used combined with intra-articular semitendinosus tendon augmentation for rapid rehabilitation in cases of acute tears in the anterior cruciate ligament.

Anterior Cruciate Ligament↗

PubMed1991

Short- and long-term effects of transection of the ophthalmic nerve on optokinetic nystagmus in the rabbit.

The role of extraocular proprioception in optokinetic nystagmus (OKN) was examined, using adult pigmented rabbits following transection of the ophthalmic branch of the trigeminal nerve. OKN was induced by rotation of a drum at an angular velocity of 0.85 and 3.7 degrees/s. The eye on the operated side showed a delay in the transition from the OKN-induced quick phase to the slow phase regardless of closure of the eye on either the operated or unoperated side. In addition, the eye on the operated side showed an anticompensatory response in the vestibulo-ocular reflex (VOR) with an unstable drift in the dark. The above abnormalities in OKN and VOR following rhizotomy disappeared after 1-1.5 months. These results suggest that proprioception in the extraocular muscle plays an important role in the fine regulations of eye position for gaze accuracy. The recovery demonstrated appears to be due to a compensatory mechanism in the central nervous system.

Animals↗

PubMedDate not supplied

Electrophysiology of the palmomental reflex in normal and parkinsonian subjects.

The palmomental reflex (PMR), obtained by mechanical stimulation of the skin of the thenar and hypothenar eminences of the hand and recording the surface EMG response from the chin muscles homolateral and contralateral to the side of stimulation, was studied in normal subjects and in a group of akinetic parkinsonians, both de novo and treated. PMR was present in most subjects of both groups. No differences regarding the incidence of the PMR homolateral to stimulation of the thenar eminence was found between controls and patients, and it was non-habituating in both groups. When the hypothenar eminence was stimulated, the PMR was present in about half of the subjects of both groups. PMR was present contralaterally in both normal and patients, whereas bilateral PMR prevailed in parkinsonians. Latency and duration of the reflex were significantly shorter in parkinsonians than in controls. The data are discussed in the light of the pathophysiology of the PMR putative pathways in normal subjects and in Parkinson's disease.

Afferent Pathways↗

PubMed1996

Simulated micro-gravity and cortical inhibition: a study of the hemodynamic-brain interaction.

The present study was carried out to determine the inhibitory cortical processes induced by changes in hemodynamics. Previous experiments in humans conducted in our laboratory have shown that there is a close relationship between posture and delta and theta EEG activity. The most pronounced effects were obtained during the 6 degrees head-down tilt (HDT) position. In space medicine the HDT procedure is very frequently employed to simulate micro-gravity and to determine the neurohormonal counter-regulations evoked by the expansion of central volume. Twenty male subjects spent 23 h in bed in 6 degrees HDT and 23 h in 6 degrees HUT (head-up tilt) positions during which EEG (frontal, central, parietal, occipital), startle responses, and reaction-times were measured every 2 h (from 10:00 h till 20:00 h). The effects of cardiovascular deconditioning (CD) regularly occurring after HDT were assessed by examining orthostatic tolerance and the physical work capacity (bicycle ergometry). As expected, 23 h HDT led to more pronounced CD than HUT. Spectral power analyses of EEG revealed increases in delta and theta frequency hands similar to those found during HDT in previous EEG studies. In addition, subjects responded more slowly (S1-S2 reaction-time task) during HDT as compared with HUT bedrest. The influence of HDT on startle response, however, was not in keeping with the initial hypothesis (i.e. dampening of reflex activity). The EEG data and the sensorimotor performance indicated that the body fluid shift towards the thoracic cavity induced by HDT resulted in signs of cortical inhibition. In addition to neural mechanisms, other processes must be postulated which are closely related to the counter-regulation evoked by the varying body positions.

Adult↗

PubMed1984

[Functional differentiation of afferents of the superior laryngeal nerve in the cat].

Excitability of the electrically stimulated superior laryngeal nerve afferents and reflex discharges in the respiratory motor nerves were studied on cats under light nembutal anesthesia. Three types of group A afferent fibres were differentiated according to their functional role in reflex response initiation. Low-threshold afferent fibres (A beta) are concerned with proprioceptive activation of laryngeal muscles, the group of A gamma afferents participates in regulation of the respiratory phase-switching mechanisms and high-threshold afferent fibres (A delta) support protective respiratory reflexes.

Animals↗

PubMedDate not supplied

Neuromuscular properties and functional aspects of taped ankles.

We used electromyographic and goniometric methods to test 40 subjects to describe the neuromuscular and biomechanical adaptation of the ankle with respect to application of two different adhesive tapes and to exercises. The neuromuscular responses to inversion injury simulation, together with the mechanical displacements of the joint complex, were analyzed before and after controlled athletic exercises. The proprioceptive amplification ratio was calculated on the basis of the integrated reflex electromyographic results and on the maximum inversion amplitude. Relevant stability gains were achieved immediately after applying tape. There was reduced tape stability after athletic exercise for one of the two tape materials tested. No further loosening was detected, even after prolonged wearing of tape (24 hours). Compared with the unprotected ankle, the taped ankle had a significant increase in the proprioceptive amplification ratio. Both fatigue and mechanical loosening may be responsible for the significant reduction in this ratio immediately after exercise. After the 24-hour interval, the ratio was increased, which could be explained by physiologic neuromuscular regeneration and mechanical restabilization of the tape itself. The sensitivity of the proprioceptive amplification ratio, both to external stabilization and to internal fatigue, supports its potential value to quantify functional joint stability.

Adolescent↗

PubMed1998

Enhancement and resetting of locomotor activity by muscle afferents.

The generation of the normal motor pattern for walking in mammals requires feedback from muscle proprioceptors. Two characteristics of the motor pattern particularly dependent on proprioceptive signals are (1) the magnitude of activity in knee and ankle extensor muscles and (2) the duration of extensor bursts during stance. Sensory regulation of these characteristics ensures that the level of activity in extensor muscles during stance is appropriate for the load carried by the leg and that the swing phase is not initiated when a leg is loaded. Many different groups of afferents from flexor and extensor muscles can influence the locomotor pattern. Most attention has focused on the action of group I afferents from ankle extensors. Electrical stimulation of these afferents during extension increases the duration and the magnitude of extensor activity. The prolongation of extensor activity depends in part on excitation of the extensor half-center by group Ib afferents from Golgi tendon organs. The enhancement of the magnitude of extensor bursts is produced primarily via disynaptic and polysynaptic pathways opened only during locomotion. The involvement of the proprioceptive signals in the generation of locomotor activity means that the gains in reflex pathways must be constantly calibrated according to the biomechanical properties of the locomotor system. Alteration of these properties by weakening ankle extensor muscles has recently been found to produce compensatory changes in proprioceptive influences on the locomotor pattern.

Animals↗

PubMed1992

Recovery of function after spinal cord hemisection in newborn and adult rats: differential effects on reflex and locomotor function.

It is often assumed that the response of the immature nervous system to injury is more robust and exhibits greater anatomical reorganization and greater recovery of function than in the adult. In the present experiments the extent of recovery of function after spinal cord injury at birth or at maturity was assessed. We used a series of quantitative tests of motor behavior to measure reflex responses and triggered movements and to examine different components of locomotion. Rats received a midthoracic "over-hemisection" at birth or as adults. The neonatal operates were allowed to mature and the adult operates were allowed to recover. The animals were trained to walk on a treadmill and to cross runways of varying difficulty. The animals were tested for reflex responses and triggered movements, videotaped while crossing the runways, and footprinted while walking on the treadmill. The adult operates had greater deficits in the reflex responses than the neonatal operates. The adult operates lost the contact placing response and had a decreased hopping response in the ipsilateral limb, while these responses were not impaired in the neonatal operates. Although the contact placing response in the neonatal operates was spared, a greater stimulus was necessary to induce the response than in control animals. In contrast, the neonatal operates had greater deficits in locomotion. Footprint analysis revealed that the animals' base of support was significantly greater after the neonatal injury than after the adult injury, and deficits in limb rotation were larger in the neonatal operates than in the adult operates. Both groups crossed the grid with a similar number of steps but the adult operates made significantly more errors with the hindlimb ipsilateral to the lesion than the contralateral one, while the neonatal operates made an equivalent number of errors with both limbs. The neonatal operates took longer to execute the climb test and used a different movement pattern than the adult operates. The neonatal operates had a different locomotor pattern than the adult operates. Despite greater recovery of reflex responses after spinal cord injury at birth, the pattern of locomotion exhibits greater deficits when compared with the same lesion in the adult. Just as the anatomical consequences of injury to the developing nervous system are not uniform, similarly, the behavioral consequences are also not uniform. Spinal cord injury before the mature pattern of locomotion has developed results in a different motor strategy than after injury in the adult.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗

PubMed2004

Short-term adaptation of the cervico-ocular reflex.

The cervico-ocular reflex (COR) works in conjunction with the vestibulo-ocular reflex (VOR) and the optokinetic reflex (OKR) in order to prevent visual slip over the retina during head movement. The COR induces eye movements in response to proprioceptive signals from the neck. We investigated whether the COR gain can be adapted by inducing a mismatch between vision and neck proprioception, in analogy to VOR adaptation. Thirteen healthy subjects were rotated in the dark in a trunk-to-head manner (the head fixed in space while the body passively rotated sinusoidally with a peak velocity of 1.25 degrees /s). Eye movements were recorded with infrared video-oculography under various adaptive conditions. Analysis showed a small but significant reduction in COR gain in the suppression conditions. This means that the cervico-ocular reflex can be modified after only 10 min of concurrent visual and cervical stimulation.

Adaptation, Physiological↗

PubMed1998

Proprioceptive information processing in weightlessness.

The "illusions" experiment carried out on five astronauts during the last two French-Russian flights (Antarès in 1992 and Altaïr in 1993) and in the Russian Post-Antarès mission (1993) was designed to investigate the adaptive changes in human proprioceptive functions occurring in weightlessness at both the sensorimotor and cognitive levels, focusing on two kinds of responses: (1) whole-body postural reflexes, and (2) whole-body movement perception. These kinesthetic and motor responses were induced using the tendon-vibration method, which is known to selectively activate the proprioceptive muscular sensory channel and to elicit either motor reactions or illusory movement sensations. Vibration (70 Hz) was therefore applied to ankle (soleus or tibialis) and neck (splenii) muscles. The subject's whole-body motor responses were analyzed from EMG and goniometric recordings. The perceived vibration-induced kinesthetic sensations were mimicked by the subjects with a joystick. The main results show that a parallel in-flight attenuation of the vibration-induced postural responses and kinesthetic illusions occurred, which seems to indicate that the proprioceptive system adapts to the microgravity context, where standing posture and conscious coding of anteroposterior body movements are no longer relevant. The same sensory messages are used at the same time in different sensory motor loops and in the coding of newly developed behavioral movements under microgravity. These results suggest that the human proprioceptive system has a high degree of adaptive functional plasticity, at least as far as the perceptual and motor aspects are concerned.

Adaptation, Physiological↗

PubMed2006

4-chloro-3-hydroxyanthranilate reduces local quinolinic acid synthesis, improves functional recovery, and preserves white matter after spinal cord injury.

Inflammatory processes within the central nervous system (CNS) contribute significantly to the pathogenesis of a broad range of neurologic diseases, including spinal cord injury (SCI). One mechanism by which immune activation causes neurologic symptoms and tissue injury is via the production of neurotoxins by activated macrophages and microglia. In the present study, the role of the endogenous tryptophan metabolite and neurotoxin quinolinic acid (QUIN) in secondary pathology following traumatic SCI was investigated. Adult Hartley guinea pigs were injured by lateral compression of the spinal cord at the 12th thoracic segment (T12). QUIN had accumulated at the site of injury on day 12 post-injury in proportion to the severity of functional neurologic deficits (as assessed by the cutaneus trunci muscle reflex and motor function score at 5 h post-injury). Systemic administration of the 3-hydroxyanthranilate-3,4-dioxygenase (3-HAD) inhibitor, 4-chloro-3-hydroxyanthranilate (4Cl-3HAA; approximately 100 mg/kg every 12 h, beginning 5 h after injury) attenuated local QUIN production and reduced QUIN accumulation at the site of injury by approximately 50% at day 12, without enhanced accumulations of the neuroprotective metabolite kynurenic acid (KYNA). The severity of secondary functional deficits was also reduced by 4Cl-3HAA. In toluidine blue-stained spinal cord sections, the area of surviving intact white matter at the injury site was increased by approximately 100% in the 4Cl-3HAA-treated group. Sparing of both axons and myelin contributed to this increase. These results support the conclusion that QUIN accumulations at the site of injury contribute to secondary functional deficits and tissue damage following SCI.

3-Hydroxyanthranilic Acid↗

PubMed2000

Task dependence of Ia presynaptic inhibition in human wrist extensor muscles: a single motor unit study.

OBJECTIVE: Task-dependent changes in the Ia presynaptic inhibition generated by flexor group I afferents were investigated in 25 identified motor units (MUs) located in human extensor carpi radialis (ECR) muscles. METHODS: Seven subjects had to voluntarily contract their ECR muscles either alone during isometric wrist extension or concurrently with their wrist and finger flexor muscles while clenching their hand around a manipulandum. The MU reflex responses to the radial nerve stimulation (test stimulation) yielded narrow peaks in the post-stimulus time histograms (PSTH). The Ia presynaptic inhibition induced while stimulating the median nerve (conditioning stimulation) 20 and 40 ms before the radial nerve was assessed from the changes in the contents of the first 0.5 ms in the peaks. RESULTS: With both stimulation intervals, the Ia presynaptic inhibition, as assessed from the first 0.5 ms of the PSTH peaks, was consistently weaker during hand clenching. With both motor tasks, the Ia presynaptic inhibition was strongest at the 20 ms interval, in which it showed a downward gradient, working from slow to fast contracting MUs. With both intervals, the presynaptic inhibition was consistently weaker during hand clenching. The decrease in the Ia presynaptic inhibition observed at the 40 ms conditioning-test interval was less pronounced during wrist extension. CONCLUSION: It is suggested that the reason why Ia presynaptic inhibition was weaker during hand clenching may have been that this task involved numerous cutaneous inputs originating from the palm and finger tips. During gripping tasks, these cutaneous inputs may therefore contribute to adjusting the wrist stiffness by relieving the presynaptic inhibition.

Action Potentials↗

PubMed1975

Evidence for a monosynaptic mechanism in the tonic vibration reflex of the human masseter muscle.

Vibration of the masseter and temporalis muscles in normal human adult subjects elicits a tonic vibration reflex with unexpected features. The electromyographic response is not asynchronous as in the limb muscles, but involves well-defined spikes with a one-to-one temporal relation to the vibration cycles. The effect of various parameters such as muscle stretch, vibration frequency or amplitude, etc, has been investigated. The small latency fluctuation of the vibration-induced spikes is compatible with a monosynaptic reflex mechanism which is considered to be assisted by a polysynaptic facilitatory background of proprioceptive origin.

Adult↗

PubMed1999

Proprioceptive control of wrist extensor motor units in humans: dependence on handedness.

The effectiveness of the monosynaptic proprioceptive assistance to the wrist extensor motoneurone activity was investigated during voluntary contraction in relation to the subjects' handedness. The reflex responses of 411 single motor units to homonymous tendon taps were recorded in the wrist extensor carpi radialis muscles in both arms of five right-handed and five left-handed subjects. In the right-handed subjects, the motor unit reflex responses were clearly lateralized in favour of their right arm, whereas no side-related differences were observed in the left-handed subjects, whatever the motor units' mechanical properties and firing rates. When the muscle spindle sensitivity was by-passed by electrically stimulating the primary afferents in both arms of three right-handed and three left-handed subjects, no side-related differences were observed in the Hoffmann reflex (H-reflex) amplitude in either of the two lateralization groups. The effectiveness of the primary afferent synapses on to the motoneurones therefore does not seem to depend on the subject's handedness. Without excluding the possibility of structural changes being involved at the periphery, the comparisons carried out on the data obtained using electrical vs mechanical stimulation suggest that the asymmetrical effectiveness of the proprioceptive assistance observed in favour of the right arm in the right-handed subjects might result from either the gamma or beta drive being more efficient. This asymmetry might result from the preferential use of the right hand in skilled movements. In a predominantly right-handed world, however, left-handed people might tend to develop the ability to use their right arm almost as skillfully as their preferred left arm, which could explain the symmetrical effectiveness of the proprioceptive assistance observed here in the left-handers' wrist extensor muscles.

Action Potentials↗

PubMed1999

Special sensory ataxia in Miller Fisher syndrome detected by postural body sway analysis.

To investigate whether ataxia in Miller Fisher syndrome (MFS) is caused by loss of proprioception or cerebellar dysfunction, we studied the power spectrum peak of the body sway frequency in 10 MFS patients, and compared the results with those of patients with cerebellar or sensory ataxia. The cerebellar patients had a peak at 2.4 Hz, whereas sensory ataxia patients had a 1-Hz peak. Nine of the MFS patients had a distinct 1-Hz peak. Clinical sensory loss or abnormal sensory nerve potentials were present in only 3 patients, whereas soleus H-reflexes were absent in all the MFS patients. MFS patients have dysfunction of the proprioceptive afferent system, and the special sensory ataxia may be caused by the selective involvement of muscle spindle afferents.

Adult↗

PubMed1994

Severe pan-sensory neuropathy in leprosy.

The sensory loss which occurs in leprosy is essentially cutaneous, resulting from centripetally ascending infection, the host cellular response and fibrosis, from dermal to certain mixed nerves. The hallmark is pain/temperature and touch/pressure loss. Muscle denervation is a byproduct of mixed nerve involvement. Leprous sensory and motor neuropathy presents a stereotyped picture, with preservation of position sense, noninvolvement of the large girdle muscles, and retained deep tendon reflexes. We report clinical and investigative details of 7 patients (3 males, 4 females) with mild-to-moderate polyneuritic leprosy who manifested severe proprioceptive loss in the upper per limbs; the lower limbs were similarly affected in 4 of them. Tendon reflexes were absent in the ataxic limbs. No other cause was found for the ataxia. Electrophysiological studies confirmed damage to large cutaneous and muscle afferents, and a normal EMG pattern in hip and shoulder muscles. Of great interest was the histology of a lumbar sensory ganglion biopsied in a severely disabled patient. There was extensive neuron loss and degeneration and reactive proliferation of capsular cells ("nodules of Nageotte"), an inflammatory focus of lymphocytes, and no bacilli. This suggests to us that the proprioceptive loss in these patients could well be the result of an unusual "leprous ganglionitis." Further clarification of the mechanism of ganglion degeneration and the frequency of inflammation could come from immunohistology of tissues from African green monkeys with experimental polyneuritic leprosy.

Adult↗

PubMed1986

Extraocular proprioceptive signals affect ocular motor activity neither directly nor parametrically in the presence of optokinetic or vestibular stimulation in the frog.

Direct and parametric effects of stretch receptors in the extraocular muscles on abducens nerve activity were investigated in the unanesthetized immobilized frog. Horizontal passive rotations of one eye in the physiological range (+/- 5 degrees) did not elicit responses in the activity of abducens nerve on either side; however, larger rotations or pull of one eye evoked long latency direction-unspecific responses simultaneously in both nerves. When the animal was stimulated vestibulary in the horizontal plane with sinusoidal or constant acceleration, abducens activity was not altered in correlation to passive eye movements in the physiological range. Similarly, the activity of either nerve evoked by simultaneous or preceding optokinetic stimulation of one eye with constant pattern velocity was not modified by passive rotation of the contralateral eye.

Abducens Nerve↗

PubMed2001

[Peroneal reaction time: study of a normal sample].

Chronic functional instability is a residual problem after acute ankle sprain. Reasons may be weak ligaments and/or a deficit in the proprioceptive system. Studies have shown that peroneal reaction time (PRT) can be used to quantify proprioceptive performance. To test the influence of anthropometric data on PRT, an experimental study with 120 healthy volunteers was performed. Surface electrodes recorded the activity of the peroneal muscles after a sudden inversion on a tilting platform. It was found that PRT is not influenced by extrinsic or anthropometric data. Furthermore, the results prove a significant slackening in PRT with increasing age. Therefore, the patient's age must to be considered in judging the PRT.

Adolescent↗