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At least 235 records · Page 13Linked to original sources
PubMed1990

Motor reflex responses elicited by cutaneous stimulation in the regenerating nerve of man: axon reflex or ephaptic response?

In 57 of 60 nerves (29 median and 31 ulnar) sutured at the wrist, forearm and arm, we recorded motor responses in thenar or hypothenar muscles by electrical stimulation of the corresponding fingers. Recordings were made at different times during the process of regeneration, ranging from 3 months up to 11 years. The responses showed a constant shape and latency to every stimulation (simple or repetitive). The latency was shorter the more distal the level of injury and the greater the elapsed time from the reinnervation. The point of "reflexion" of the responses is at or very near the line of nerve suture. The electrophysiological behavior of the responses fits well with either the criterion of axon reflex or ephaptic response. We discuss both possibilities and conclude that it is not possible, with the electrophysiological technique that we used, to distinguish between an axon reflex and an ephaptic response.

Adolescent↗
PubMed1992

Effect of knee joint laxity on long-loop postural reflexes: evidence for a human capsular-hamstring reflex.

The onset latency and discharge amplitude of preprogrammed postural responses were evaluated in order to determine if the structure of synergistic activation could be altered by ligamentous laxity at the knee joint. Twelve subjects with unilateral and one subject with bilateral anterior cruciate ligament (ACL) insufficiency were tested while standing on a moveable platform. External balance perturbations (6 cm anterior or posterior horizontal displacements of the platform) were presented at velocities ranging from 15 to 35 cm/s. Perturbations were presented under the following experimental conditions: unilateral and bilateral stance, knees fully straight or flexed, and with ankle motion restricted or free. These stance, knee position, and ankle motion conditions were introduced to alter the stress transmitted to the knee joint during movement of the support surface. The automatic postural response was recorded from the tibialis anterior (T), quadriceps (Q), and medial hamstrings muscles (H) bilaterally. The normal response to an externally induced backward sway involved the automatic activation of T and Q at latencies of 80 ms and 90 ms respectively. Activation of the hamstrings in the non-injured extremity was not coupled with the postural response. Hamstrings are not typically involved in the correction posterior sway because H activation would tend to pull the center of mass further backwards. However, when the response in the ACL-deficient extremity was compared to the non-injured limb: (1) the automatic postural response in the ACL-deficient extremity was restructured to include hamstrings activation (100 ms latency), (2) H activation time was faster and less variable in the ACL-deficient limb, and (3) the ratio of H/Q discharge amplitude integrated over 100 ms and 200 ms from the onset of EMG activation showed a dominance of hamstring activity during unilateral stance on the lax limb. In addition, H/Q ratios integrated over 200 ms showed dominant hamstring activity in the ACL-deficient limb during bilateral stance. (4) Cross-limb comparisons showed greater normalized IEMG amplitudes for T, H, and Q during unilateral stance on the lax limb. These results suggest that a capsular-hamstring reflex is integrated into the existing structure of a preprogrammed postural synergy in order to compensate for ligamentous laxity. Furthermore, the generalized increase of response gain observed during perturbations of unilateral stance on the lax limb indicates that joint afference can modulate central programming to control localized joint hypermobility. A concept of postural control is discussed with respect to the capsular reflex, joint loading and displacement of the center of gravity.

Adolescent↗
PubMed1976

Modulation of the functional stretch reflex by the segmental reflex pathway.

Electromyographic (EMG) reflex responses were examined in the biceps muscle of awake Cebus monkeys trained to resist perturbations of a handle with their forearm. In particular responses at latencies of 15-20 msec (M1) and 40-55 msec (M2), thought to correspond to segmental and suprasegmental reflex pathways respectively, were studied. The experiments demonstrated that the magnitude of the M1 response was large, as compared to M2, only when the muscle was tonically active and small perturbations were applied. For larger perturbations the magnitude of M1 saturated and the M2 response became functionally significant, its magnitude being directly related to the magnitude of the perturbation. By means of delayed reductions in torque, the magnitude of this M2 response was also shown to be very sensitive to changes in facilitatory drive provided by segmental pathways.

Afferent Pathways↗
PubMed1987

Reflex pathways from group II muscle afferents. 1. Distribution and linkage of reflex actions to alpha-motoneurones.

The interneuronally mediated reflex actions evoked by electrical stimulation of group II muscle afferents in low spinal cats have been reinvestigated with intracellular recording with motoneurones to knee flexors and ankle extensors. The results of Eccles and Lundberg (1959) have been confirmed and extended. There was wide convergence from flexors and extensors of group II excitation to flexor and group II inhibition to extensor motoneurones. Some quantitative differences in the effect from the different nerves are described. Latency measurements suggest that the minimal linkage is disynaptic in the excitatory interneuronal pathways and trisynaptic in the inhibitory pathways. Disynaptic group II EPSPs were found in 14% of the ankle extensor motoneurones but were much more common in unanaesthetized high spinal cats (Wilson and Kato 1965). From these results and corresponding ones on flexors (Holmqvist and Lundberg 1961) it is postulated that secondary afferents in addition to the weak monosynaptic connexions (Kirkwood and Sears 1975) have disynaptic excitatory pathways and trisynaptic inhibitory pathways to both flexor and extensor motoneurones. It is proposed that the group II actions of the flexor reflex pattern characterizing the anaesthetized low spinal cat are due to suppression of the inhibitory pathway to flexor motoneurones and the excitatory pathway to extensor motoneurones. In some ankle extensor motoneurones the disynaptic group II EPSPs occurred in combination with IPSPs from the FRA (including group II and III muscle afferents). The possibility is considered that these group II EPSPs are mediated by an interneuronal group II pathway with little or no input from group III muscle afferents but probably from extramuscular receptors. In other ankle extensor motoneurones group II EPSPs were combined with EPSPs from group III muscle afferents, cutaneous afferents and joint afferents. It is postulated that these group II EPSPs are mediated by an interneuronal pathway from the FRA which also supply interneuronal pathways giving inhibition to extensor or/and flexor motoneurones and excitation to flexors as postulated by Eccles and Lundberg (1959) and Holmqvist and Lundberg (1961).

Animals↗
PubMed1976

[Orbicularis oculi reflex after facial paralysis: decreased amplitude of reflex response and spreading to all hemifacial muscles after reinnervation (author's transl)].

After the acute stage of peripheral facial paralysis with nerve degeneration we find some signs of paresis after reinnervation due to insufficient motor recovery and associated movements due to faulty reinnervation. Electromyographical investigation of the orbicularis oculi reflex can be used for the objective evaluation of these two phenomena. This shows the following typical signs: 1. The amplitudes of the early and late reflex response are decreased on the affected side proportionate to the degree of paresis. 2. The response occurs in all reinnervated hemifacial muscles as a result of misdirection of fibres which originally innervated the orbicularis oculi muscle.

Eyelids↗
PubMed1981

Vestibulo-ocular reflex (VOR), cervico-ocular reflex (COR) and its interaction in active head movements.

In normal adults the vestibulo-ocular reflex (VOR) and the cervico-ocular reflex (COR) were investigated during passive and active head or body movements, respectively. Sinusoidal rotations around the vertical axis of the body at frequencies of 0.05, 0.1, and 0.2s-1 and total amplitudes of 20 degrees, 40 degrees, 60 degrees, or 80 degrees were employed. The average eye deviations (Schlagfeld) during VOR were directed opposite to the direction of the head turning. During COR, however, slow eye deviations of higher amplitude were anticompensatory relative to the fixed head. During active head turnings the average eye deviations showed the same anticompensatory direction as in COR, but were still larger. The increased with stimulus amplitudes up to 60 degrees. At least a weak cervical nystagmus was elicited in all subjects, with its fast phases beating in the direction of the relative head movement. Its gain reached marked values up to 0.5, but only for peak stimulus velocities below 25%. The nystagmus gain during active head turnings was only slightly higher than during VOR. With higher stimulus velocities, large anticompensatory saccades appeared just before the change of stimulus direction; these are typical for active head movements, but were also found during COR.

Adult↗
PubMed1983

Capsaicin-induced reflex fall in rat blood pressure is mediated by afferent substance P-containing neurones via a reflex centre in the brain stem.

Injection of 0.03 micrograms capsaicin into one femoral artery elicited a fall in blood pressure in the rat. This effect was completely and reversibly abolished following intrathecal injection of 1 nmol of the specific substance P antagonist, [D-Pro2,D-Trp7,9] substance P. The capsaicin-evoked depressor reflex is therefore exclusively mediated by substance P-containing primary afferent fibres. Using spinal rats or decerebration experiments, the centre of the capsaicin-evoked reflex fall in blood pressure could be localized in the brain stem.

Animals↗
PubMed1975

Amygdala and masseteric reflex. I. Facilitation, inhibition and diphasic modifications of the reflex, induced by localized amygdaloid stimulation.

The changes in amplitude of the monosynaptic masseteric reflex (MR), induced by stimulation of the amygdaloid area for the defence reaction (N. basalis, pars magnocellularis) and in other subdivisions of the amygdaloid complex, were studied in cats with spinal section maintained under Flaxedil. Simultaneously, the the effects of stimulation on the tonic activity of the masseteric nerve were observed. A maintained facilitation of the MR was elicited by stimulation of the lateral nucleus, the parvocellular portion of the basal nucleus and the cortical nucleus, while the reflex was inhibited during stimulation of the medial-most portion of the posterior amygdala. Diphasic changes of the MR amplitude (initial facilitation followed by delayed inhibition) were regularly observed when stimulating the magnocellular portion of the basal nucleus. These diphasic changes were closely correlated with the previously described diphasic resporatory and cardiac responses elicited from the same are (Bonvallet and Gary Bobo 1972). The initial facilitation probably corresponds to the "alerting" stage of the defence reaction and the delayed inhibition, associated with cortical, respiratory and cardiac activation, to the "defensive" stage of the reaction. Stimulation of the same area also provokes tonic or rhythmical discharges of the masseteric motoneurons which frequently occur during the delayed inhibition of the MR. The main efferent pathway mediating these motor effects is probably the ansa lenticularis.

Amygdala↗
PubMed1982

The abdominal cutaneous reflex circuit in the rat: a spinobulbo-spinal reflex in phenobarbital-anesthetized animals.

A description is given of an abdominal reflex (ACR) in the rat evoked by cutaneous stimulation. Latency of the ACR in response to stimulation of the contralateral hindlimb was 28.5 +/- 3.2 msec. Data from the analysis of discharges in dorsal and ventral roots and from bulbar reticular neurons triggered by ACR stimuli reveal that a spino-bulbo-spinal loop seems to be implicated. This is also supported by the chronic effects of pontile and spinal transections. ACR-concomitant discharges were also recorded in other axial (digastric m. and internal intercostal m.) and proximal limb muscles. The possible spino-bulbo-spinal mechanism of this cutaneous reflex is discussed.

Abdominal Muscles↗
PubMed1983

Classical conditioning of the flexion reflex in spinal cat: features of the reflex circuitry.

Classically conditioned facilitation of the flexor withdrawal reflex of spinal cat occurs in knee and ankle flexor muscles but not in a flexor muscle of the toes. Furthermore, the spinal circuitry activated by a component of the conditioned stimulus (A alpha cutaneous fibers) is not by itself involved in the reflex conditioning. The results suggest that increases in both cutaneous afferent output and motoneuron excitability may be eliminated as mechanisms contributing to conditioning and point to certain interneuronal pools as the locus of learning in this preparation.

Animals↗
PubMed1995

Combined action of optokinetic reflex (OKR) and vestibulo-ocular reflex (VOR) in macaque monkey during transient stimulation.

Interaction of vestibulo-ocular reflex (VOR) and optokinetic reflex (OKR) was studied in macaque monkeys by recording horizontal eye movements during transient rotations of their heads and/or an optokinetic pattern in space. At low peak velocities of the stimuli (1.25 degrees/s, 10.0 degrees/s) the eyes were rather well stabilized on the optokinetic pattern, independently of whether the head, the pattern, or both were rotated. At higher velocities (40.0 degrees/s), the OKR gain was attenuated and, when combining vestibular and optokinetic stimuli, the eyes became increasingly stabilized in space. The data could be simulated by a computer model previously designed to describe VOR-OKR interaction during sinusoidal rotations. In this model eye stabilization primarily relies on the OKR, while the role of the VOR is to compensate for the limited bandwidth of the OKR.

Animals↗
PubMed1996

Multiple reflex sympathetic dystrophy. Which patients are at risk for developing a recurrence of reflex sympathetic dystrophy in the same or another limb.

Many aspects of bilateral presentation or recurrence of reflex sympathetic dystrophy (RSD) are unknown. For this reason 1183 consecutive patients with RSD were analyzed. In 10 patients RSD started in symmetrical limbs. In 34 patients RSD recurred in the same limb after a period of no or few complaints and in 76 patients RSD recurred in one or more limbs other than the first limb. Compared to 1065 patients with RSD without these features, these patients were younger (P < 0.01) and RSD started more frequently with a cold skin temperature (P = 0.02). Patients did not differ in gender or primary localization of RSD. Involvement of a second limb concerned in 47% the symmetrical limb. Recurrences were in 53% of spontaneous origin and often characterized by few signs and symptoms. The incidence of a recurrence was 1.8% per patient per year. No measures are known to prevent recurrence. Reflex sympathetic dystrophy may recur in the same or in another limb, although only in a minority of patients. Recurrences occur especially in younger patients and in the symmetrical limb. Diagnosis of a recurrence is difficult, for often the recurrence is spontaneous and presents with few signs and symptoms.

Adolescent↗
PubMed1985

Somatosensory systems and the milk-ejection reflex in the rat. I. Lesions of the mesencephalic lateral tegmentum disrupt the reflex and damage mesencephalic somatosensory connections.

Bilateral electrolytic lesions and unilateral tracer injections were performed in lactating rats in order to study the participation of the mesencephalic lateral tegmentum in the milk-ejection reflex. The release of oxytocin was detected as a rise in intramammary pressure during each milk ejection. In animals with lesions, the lateral part of the deep grey layers of the superior colliculus, the intercollicular area and the rostromedial portion of the external nucleus of the inferior colliculus were destroyed. The mesencephalic lateral tegmentum of animals in which the milk-ejection reflex was blocked sustained a larger damage than in rats where the frequency of the milk-ejection response was only slowed down. Solutions of True Blue, horseradish peroxidase or horseradish peroxidase coupled to wheat germ agglutinin were injected in the mesencephalic lateral tegmentum of rats with and without lesions. Retrogradely labelled cells were found in several nuclei of the somatosensory pathways: the principal sensory and spinal parts of the trigeminal complex, the cuneate and gracile nuclei, the lateral cervical nucleus and the nucleus proprius of the spinal cord. Labelled cells were also found in the ventral nucleus of the lateral lemniscus, the ventral parabrachial nucleus, the gigantocellular reticular nucleus, the lateral nucleus of the substantia nigra, the prerubral nucleus of the thalamus, the hypothalamic ventromedial nucleus, the zona incerta and in the anterior and lateral hypothalamic areas. Labelled fibres and "terminal-like" labelling were found in the anterior pretectal area, in the thalamic parafascicular nucleus, in the posterior nucleus and the ventroposterior complex, in the zona incerta and in the fields of Forel, but none were observed in the supraoptic or paraventricular nuclei. Injections made in the area of the lateral cervical nucleus and in the cuneate and gracile nuclei labelled fibres and "terminal-like" fields in the external nucleus of the inferior colliculus, the intercollicular area, the deep grey layers of the superior colliculus and in the mesencephalic lateral tegmentum. After injections in the posterior nucleus and ventroposterior complex of the thalamus, retrogradely labelled cells were found in the lateral tegmentum, the intercollicular area and the external nucleus of the inferior colliculus. These results indicate that bilateral lesioning of the mesencephalic lateral tegmentum, which disrupts the milk-ejection response, could damage somatosensory projections originating from the dorsal horn of the spinal cord, the lateral cervical nucleus, the dorsal column nuclei and the sensory and spinal trigeminal nuclei.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1997

Gaze stabilization by optokinetic reflex (OKR) and vestibulo-ocular reflex (VOR) during active head rotation in man.

Vestibulo-ocular reflex (VOR)-optokinetic reflex (OKR) interaction was studied in normal human subjects during active sine-like head movements in the horizontal plane for a variety of vestibular-optokinetic stimulus combinations (frequency range, 0.05-1.6 Hz). At low to mid frequencies (< 0.2 Hz) the eyes tended to be stabilized on the optokinetic pattern, independently of whether the head, the pattern, or both were rotated. At higher frequencies, the OKR gain was attenuated and, in each of the differing stimulus combinations, the eyes became increasingly stabilized in space. Qualitatively similar results were obtained when, for the same visual-vestibular combinations, the head was passively rotated at 0.05 and 0.8 Hz. The data could be simulated by a model which assumes a linear interaction of vestibular and optokinetic signals. It considers the OKR with its negative feedback loop of primordial importance for image stabilization on the retina and the VOR only as a useful addition which compensates for the limited bandwidth of the OKR during high frequency/velocity head rotations in a stationary visual environment.

Adult↗
PubMed2003

Combined action of smooth pursuit eye movements, optokinetic reflex and vestibulo-ocular reflex in macaque monkey during transient stimulation.

The interaction of smooth pursuit eye movements, vestibulo-ocular reflex (VOR) and optokinetic reflex (OKR) is still not well understood. We therefore measured in macaque monkeys horizontal eye movements using transient horizontal rotations of a visual target, of monkeys' heads and/or of an optokinetic background pattern (ten combinations; smoothed position ramps of 16 degrees ). With intermediate peak velocity of target motion (v(max)=12.8 degrees /s), pursuit held the eyes rather well on target, almost independent of concurrent vestibular or optokinetic stimuli (pursuit gain, 0.73-0.91). With v(max)=1.6 degrees /s, in contrast, pursuit gain became strongly modified by the optokinetic stimulus. With v(max)=51.2 degrees /s, pursuit gain became modified by vestibular stimulation. Although not intuitive, the experimental data can be explained by linear interaction (summation) of the neural driving signals for pursuit, VOR and OKR, as ascertained by simulations of a dynamic model.

Animals↗
PubMed2003

Antro-pancreatic reflexes: long- and short-route reflexes in exocrine and endocrine pancreatic secretion in dogs.

Pancreatic exocrine secretion is known to be facilitated by gastric antral distension via long- and short-route reflexes. In this study, we studied the effects of gastric distension on intra-pancreatic nerve discharges and blood insulin level as well as pancreatic exocrine secretion. Mongrel dogs were anesthetized with ketamine and thiopental, and immediately decerebrated. This study consisted of two series of experiments. In the first series, efferent discharges in an intra-pancreatic nerve branch were recorded, and its responses to antral distension were analyzed. In the second series, effects of antral distension on pancreatic exocrine secretion and blood insulin level were observed before and after vagotomy in splanchnicectomized dogs. Efferent discharges in a pancreatic nerve branch were increased by antral distension. Neither vagotomy nor splanchnicectomy produced obvious changes in the neural response. In splanchnicectomized dogs, antral distension elevated blood insulin level and increased pancreatic exocrine secretion. After subsequent vagotomy, these effects were reduced, but the increases were still greater than 50%. These results indicate that the antro-pancreatic short-route reflex plays a significant role in exocrine secretion, and also suggest that insulin release is increased by antral distension independent of blood glucose level.

Action Potentials↗
PubMedDate not supplied

[Reflex studies of the patellar tendon reflex in patients with varus gonarthrosis].

We discuss the role of the neuromuscular system following biomechanical circumstances for the development of osteoarthritis of the knee joint. We examined in 58 patients suffering from osteoarthritis with varus deformity and 22 healthy people the latency and velocity of the patellar tendon reflex. We found with increasing age and by osteoarthritis of the knees shorter reflex latencies, that we see as disintegration of motor system.

Electromyography↗
PubMed1961

Activation of the feeding reflex in Hydra littoralis. I. Role played by reduced glutathione and quantitative assay of the feeding reflex.

A simple and accurate quantitative assay of the glutathione-activated feeding reflex in Hydra is described. The results show: (a) There are a limited number of receptor-effector systems, probably localized in the area immediately around the mouth and on the tentacles. (b) Concentrations of glutathione greater than 5 x 10(-6)M activate all these systems; 10(-5)M glutathione elicits a half-maximum response. (c) Glutathione must be constantly present at the receptor site in order for a response to occur. (d) The response stops in the presence of excess glutathione because of some change within the Hydra, and not as a result of any alteration to the glutathione. The present state of knowledge concerning the mechanism by which glutathione combines with and activates the glutathione receptor to elicit the feeding reflex is summarized.

Animals↗