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At least 127 records · Page 7Linked to original sources
PubMed1986

Adapting human postural reflexes following localized cerebrovascular lesion: analysis of bilateral long latency responses.

The symmetry and adaptability of long latency stretch responses was studied in a group of 4 adult hemiplegics and 5 normals of similar age. Subjects stood on a moveable platform which directly rotated the ankles unexpectedly during a series of horizontal anterioposterior (AP) translations. When the platform was rotated toes-up, long latency discharge of gastrocnemius and hamstring muscles enhanced loss of balance by pulling the body backwards. Toes-down platform rotation elicited a reflex response from tibialis anterior and quadriceps which inappropriately pulled the body forward. Attenuation of these long latency responses was necessary to minimize functional destabilization. Normal and stroke subjects demonstrated appropriate suppression of long latency responses, but the magnitude of attenuation was not uniform in hemiplegics. Adaptation was decreased in the proximal synergists compared to normal. Latency of muscle activation in the paretic limb was prolonged, and a preference for initial non-paretic limb activation was evident. Both lower extremities in hemiplegics showed a disruption of timing between distal and proximal synergists. These results suggest that stroke victims retain or recover the ability to modulate stretch reflex activity for balance. Temporal and spatial response asymmetries surface as critical factors underlying disequilibrium associated with localized cerebrovascular lesion.

Adaptation, Physiological↗
PubMed1988

Effects of benidipine hydrochloride on atrioventricular conduction time and postural reflex in gallamine-immobilized cats.

Using gallamine-immobilized cats, the effect of (+/-)-(R*)-2,6-dimethyl-4-(m-nitrophenyl)-1,4-dihydropyridine-3,5-dic arb oxylic acid (R*)-1-benzyl-3-piperidinyl ester, methyl ester hydrochloride (benidipine hydrochloride, KW-3049) was compared with those of other drugs in terms of the propensity for atrioventricular conduction disturbances and orthostatic hypotension. The administration of KW-3049 at doses of 1 to 300 micrograms/kg i.v. dose-dependently lowered the blood pressure and also reduced the heart rate. In terms of the maximum blood pressure lowering activity, KW-3049 was similar in degree to nifedipine and approximately 30 times as potent as diltiazem, verapamil and phenoxybenzamine. KW-3049 as well as nifedipine, at doses with which the mean blood pressure can be reduced by 50 mmHg, hardly affected the PR-interval of ECG, whereas diltiazem and verapamil at their hypotensive doses markedly prolonged the PR interval. These four calcium antagonists at their high doses elicited 2nd or 3rd degree atrioventricular blocks in some cases. On the other hand, phenoxybenzamine did not affect the atrioventricular conduction at its hypotensive doses. Inhibitory action on the pressor responses to head-up tilting in cats was observed neither in KW-3049, nifedipine, verapamil nor diltiazem. On the contrary, phenoxybenzamine strongly inhibited the orthostatic pressor reflexes. From these results, it was suggested that in terms of the prolongation action of atrioventricular conduction KW-3049 is less potent than diltiazem and verapamil but similar in degree to nifedipine, and that KW-3049 is not likely to cause orthostatic hypotension.

Animals↗
PubMedDate not supplied

[State of labyrinth tonic posture reflexes during administration to rabbits of microelements (copper, manganese and cobalt)].

The influence of varying doses of copper, manganese and cobalt chlorides on the labyrinthine tonic reflexes of rabbits was studied electromyographically. The presence and intensity of the reflexes were measured with respect to changes in the electric activity of muscles-extensors of forelimbs and occiput during the rotation of an animal along the bitemporal axis. Under the influence of cobalt (0.01 and 0.001 mg/kg), copper (0.1 mg/kg) and manganese (0.01 mg/kg) the threshold of adequate stimulation of the labyrinthine apparatus decreased and the time of the reflex response increased. This can be related to increased excitability of stem centers that are responsible for the realization of these reflexes. Larger doses of copper (1.0 mg/kg) and manganese (0.1 mg/kg) resulted in a significant and prolonged inhibition of tonic reflexes from the labyrinth to the limbs of rabbits. These data suggest an important role played by trace elements in the regulation and adjustment of the vestibular system.

Animals↗
PubMed1984

[Activity of motor cortex neurons in the cat during a conditioned postural change reflex].

Spike activity of unitary motor cortex (area 4) neurons was recorded during performance of conditioned reflex postural adjustment in cats. Changes in activity of most neurons (increase of discharge frequency) correlated with conditioned-reflex supporting movement of the forelimb. These neuronal reactions had specific polycomponent patterns and preceded the conditional movements by 50-600 ms. Neuronal reactions connected with erroneous positive movement responses to differential stimuli and spontaneous "interstimular" movements had the same direction but were less intensive and occurred in most cases synchronously with these movements. Neuronal reactions and postural adjustments simultaneously disappeared during reflex extinction. The proposed method of elaboration of conditioned reflex of postural adjustments permits obtaining standard natural coordinated forelimb movements which form the necessary initial component of more complex behavioral reactions.

Animals↗
PubMed1998

Fetal spinal cord transplants support the development of target reaching and coordinated postural adjustments after neonatal cervical spinal cord injury.

Neonatal midthoracic spinal cord injury disrupts the development of postural reflexes and hindlimb locomotion. The recovery of rhythmical alternating movements, such as locomotion, is enhanced in injured animals receiving fetal spinal cord transplants. Neonatal cervical spinal cord injury disrupts not only locomotion but also skilled forelimb movement. The aims of this study were to determine the consequences of cervical spinal cord injury on forelimb motor function and to determine whether transplants of fetal spinal cord support normal development of skilled forelimb use after this injury. Three-day-old rats received a cervical spinal cord lesion at C3, with or without a transplant of fetal cervical spinal cord (embryonic day 14); unoperated pups served as controls. Animals were examined daily during the first month of life using a behavioral protocol that assessed reflexes, postural reactions, and forelimb motor skills. They also were trained and tested as adults to assess performance in goal-directed reaching tasks. The onset of postural reflexes was delayed in the lesion-only group, and goal-directed reaching and associated postural adjustments failed to develop. The transplant group developed reflex responses and skilled forelimb activity that resembled normal movement patterns. Transplant animals developed both target reaching and accompanying postural adjustments. Target reaching requires integration of segmental, intersegmental, and supraspinal input to propriospinal and motor neurons over many spinal cord levels. Transplants may support the reestablishment of input onto these neurons, permitting the development of skilled forelimb activity after neonatal cervical spinal cord injury. The neuroanatomical reorganization of descending and propriospinal input was examined in the companion paper (Diener and Bregman, 1998).

Animals↗
PubMed1980

Spasticity: medical and surgical treatment.

Electromyographic (EMG) recordings from multiple muscle groups with surface electrodes during systematic evaluation of phasic and tonic stretch reflexes, cutaneomuscular reflexes, long loop reflexes, postural reflexes, and volitional activation have been used to provide a neurophysiologic basis for selection of the appropriate treatment for spasticity, and to gain further insights into the general mechanisms of spasticity. Pharmacologic methods are useful as a temporary measure. Hypertonia of a single muscle can be effectively treated with 40% alcohol injections to the motor points and hypertonia of a muscle group with partial denervation through 6% phenol in water injected into the nerve trunk. Hypertonia of several muscle groups can be treated by chemical or surgical rhizotomy or myelotomy. Generalized hypertonia involving limb and trunk muscles can be modified through chronic epidural stimulation of the spinal cord. Modification of reciprocal antagonistic muscle activity may be achieved through electrical stimulation of the involved nerve trunks.

Ambulatory Care↗