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At least 1,135 records · Page 63Linked to original sources
PubMed1993

Dynamic properties of feed back control of human posture in subjects with vestibular neuritis.

Postural control was studied in 22 subjects with vestibular neruitis within 14 days after the onset of symptoms. Dynamic feed back control of posture were evaluated by analyzing the postural responses to vibration toward calf muscles applied according to a PRBS schedule. Properties of the dynamic control was normalized as swiftness, stiffness and damping of the responses. There was no prominent group differences between the 22 subjects with vestibular neuritis and 17 normal subjects. However, when studying the change in parameters evoked by presence or absence of visual information it was found that the abundant changes of control parameters, especially in stiffness, met in normal subjects had declined in subjects with vestibular neuritis. The present finding suggests that although subjects after an acute vestibular lesion may achieve a sufficient postural control by utilizing information from other somatosensory receptors, this is concomitant with changes of the feed back control.

Adult↗
PubMed1993

Contribution of the vestibular primary neuron and the sensory cell to posture recovery.

The right vestibular nerve of the frog was cut peripherally to the vestibular ganglion. The frog sustained a tilting posture toward the right side. This tilting disappeared and the frog returned to normal posture. Based on this finding, the following experiments were done: In experiment I, the right vestibular nerve was again cut after posture recovery. The tilting angle was smaller and the recovery period shorter than after the 1st neurectomy. In experiment II, the left nerve was cut after posture recovery. The tilting angle toward the left was greater than that of the 1st neurectomy. In experiment III, the frog underwent bilateral neurectomy. A piece of the bone was inserted into the cut ends of the right nerve to inhibit nerve regeneration. The frog slowly developed tilting toward the right side. The above results indicate that both reactivation of the endorgan and the central compensatory mechanism play essential roles, for postural recovery after vestibular neurectomy.

Animals↗
PubMed1993

Importance of cervical muscles in galvanic body sway test.

Retro-auricular galvanic stimulation in Romberg's posture elicits body sway which consists of an initial response (IR) and a deviation response (DR). Generally, anodal stimulation of the right side elicits IR to the left and DR to the right. We measured the deviation response (VDR) in various conditions in normal subjects. There was no significant difference between mean VDR in the standing posture weighted on the left foot (0.49 +/- 0.17 cm) and on the right foot (0.39 +/- 0.20 cm). Stimulation in the squatting posture also elicited IR to the left and DR to the right. Stimulation of the right side produced DR backward and to the right in the condition of the head facing to the right, and forward and to the right in the condition of the head facing to the left. The same body sway response as the after galvanic stimulation was also induced by non-galvanic maneuvers like inclining the head or moving the finger. Anodal stimulation in the sitting posture elicited slight but apparent head inclination to the stimulated side. These results suggest that cervical muscles play an important role in the galvanic body sway test (GBST), viz. IR and DR seemed to be secondarily produced by changes in the muscular tension of the neck.

Adult↗
PubMed1993

Vestibular neuronitis evaluated by the combined galvanic test.

Forty-two patients with unilateral vestibular neuronitis were examined by the combined galvanic test (CGT), consisting of the galvanic eye movement test (GEMT) and the galvanic body sway test (GBST). Results of the CGT were evaluated with respect to the time period from the onset of vestibular neuronitis. A favorable recovery was observed earlier with the GBST than the GEMT. We believe that this discrepancy may be due to the difference in compensation between the vestibulo-ocular reflex and the vestibulo-spinal reflex.

Adult↗
PubMed1993

Body sway response to experimental unbalance in normal subjects and patients with unilateral vestibular disorders.

The function of maintaining posture during temporary unbalance caused by experimental vestibular asymmetry was studied. Galvanic stimulation to the vestibular nerve causing body deviation to the stimulated ear was given to 31 normal subjects and 16 patients with peripheral vestibular disorders. The velocity of spontaneous body sway and that during body deviation caused by the galvanic stimulation were compared. The spontaneous body sway velocity was significantly higher than that of normal subjects. In normal subjects, the body sway velocity during body deviation remarkably increased, while that in patients did not. It is considered that large body sway in patients might conceal the fine compensatory body sway during the body deviation and that patients with unilateral vestibular dysfunction who have large body sway are always in a dysfunction state similar to that which normal subjects experience during body deviation caused by galvanic stimulation.

Dominance, Cerebral↗
PubMed1993

The contribution of proprioception to posture control in normal subjects.

In order to investigate the contribution of proprioceptive input to maintaining an upright position, stabilometry via 100-Hz vibratory stimulation applied to the Achilles tendon was studied and analyzed with respect to area, length and power spectra according to the method of fast Fourier transform (FFT). Twenty-one young medical students were analyzed in this study. When vibration was applied, the body sway was significantly greater than that of control in area and length with both eyes open and closed. There was a significant increase of total power in both the lateral (X) and antero-posterior (Y) directions with the eyes closed. With the eyes open, an increase was found only in the antero-posterior direction. The frequency band indicating the maximum spectrum did not shift. Significant increases in power spectra were found in the frequency range of more than 2 Hz in both two directions with the eyes closed. It was concluded that a vibration given to the Achilles tendon provoked a pronounced high frequency body sway especially in the antero-posterior direction when visual information was nullified, and that proprioceptive information may have a minor role compared with visual information.

Achilles Tendon↗
PubMed1993

Contribution of vision to the stabilization of body sway in patients with spinocerebellar degeneration.

Body sway was recorded with closed eyes, open eyes and visual feedback for 30 s each. Thirteen patients with spinocerebellar degeneration and 17 age-matched normal controls underwent the examination. Four parameters (area, length, sums of frequency spectrum in the anterior-posterior and lateral directions) were computed. Furthermore, Romberg ratios between closed and open eye conditions [Romberg c/o] and Romberg ratios between closed eyes and visual feedback conditions [Romberg c/f] were computed. Four parameters were significantly greater in the patients with spinocerebellar degeneration than in the normal controls. However, three of eight Romberg ratios were significantly greater in the patients with spinocerebellar degeneration than in the normal controls. The results implied that the proprioceptive-posture loop was mainly disordered while the visuo-postural loop was intact in patients with spinocerebellar degeneration.

Cerebellum↗
PubMed1993

Evaluation of vestibular function by dynamic posturography and other equilibrium examinations.

We evaluated the significance of dynamic posturography (EquiTest) in vestibular function assessment by comparing it with our routine equilibrium examinations comprised of nystagmographic data and other postural tests. Fifty-two patients with unilateral peripheral vestibular disorders were examined. Differences in test results between pendular rotation test and dynamic posturography were found in 23 out of 52 (44%) patients with unilateral peripheral vestibular disorders. In 5 patients, no abnormality of vestibular function could be detected by means of a three-test battery (spontaneous and positional nystagmus and pendular rotation test) used for evaluating vestibular compensation. In spite of these results, the patients complained of vertigo of dizziness and showed abnormal results in dynamic posturography. Dynamic posturography was superior to other postural tests in the detection of pathology corresponding with the patients' complaints. From these results, dynamic posturography (EquiTest) appeared to provide new information about such conditions of vestibular patients which other equilibrium examinations have not heretofore been able to detect.

Adult↗
PubMed1993

Randomized perturbed posturography: methodology and effects of midazolam sedation.

To study quiescent stance without applying external disturbances is not a theoretically appealing way to unveil the dynamic properties of human equilibrium. Methods to disturb equilibrium range from standing on foam surface, attaching vibrators to the calves to interfere with somatosensation, and exposure to body-position tracking environments, as in dynamic posturography (EquiTest). The EquiTest apparatus was modified by a menu-driven software to allow arbitrary movements of the support surface and visual surround, and force data were recorded for subsequent analysis. The support surface was randomly moved in the antero-posterior direction. First equilibrium was studied on the stable support surface, then low (RMS 1.3 cm) and high (RMS 2.6 cm) amplitude movements were used. Vision was either present or absent at all test amplitudes. Equilibrium was evaluated by the confidence (61%) ellipse sway area and average sway velocity during 45 s. Eleven healthy subjects aged 23-36 years (mean 29) were sedated with a short acting sedative, midazolam 0.1 mg/kg. Randomized perturbed posturography was conducted at baseline, and at about 60, 120 and 180 min after injection. Psychomotor tests were conducted at baseline, and at 30, 90, 150 and 210 min. Large interindividual variations were found. One subject could not be tested at all at 60 min due to sleepiness, whereas some subjects felt nearly full awake at 30 min. Sway areas were larger at 60 min, but not subsequently. At 60 min, sway velocities with open eyes were higher, just as when vision was absent and low amplitude movements were used. Later no effects could be shown.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Effects of increased inertial load in dynamic and randomized perturbed posturography.

Muscular weakness is present in many diseases. The present study attempted to model a relative weakness of postural control muscles by loading the subjects with extra weight, and the effects on EquiTest dynamic posturography and randomized perturbed posturography were assessed. Ten healthy subjects aged 15-39 years (mean 26 years) were used. Their weights ranged 53-82 kg. Equilibrium was measured with and without an extra 20% of body weight attached to the upper part of the trunk by means of pieces of lead metal placed in a specially sewn shirt. Dynamic posturography (EquiTest) comprises a sensory organization test in which the support surface and visual surround are either stable or referenced to the patient's sway, his or her eyes open or closed. In a movement coordination part the platform makes active movements. Antero-posterior sway on a stable support surface with absent or distorted visual cues was marred, and the correction pattern was altered on a movable support surface when the vision was absent. Furthermore, the EquiTest apparatus was driven by special software to produce randomized antero-posterior movements during 45 s. In addition to stable conditions, small and large amplitude perturbations were used. The subject's ability to remain in equilibrium was estimated by the sway velocity and a confidence ellipse sway area during 45 s. During weightbearing, sway areas were larger on the stable support surface both with and without vision. Postural sway velocity was lower when vision was absent both using small and large amplitudes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Stepping analysis in patients with spinocerebellar degeneration and Parkinson's disease.

POLGON (Polarized light goniometer) was used to evaluate ataxia during stepping movements in patients with spinocerebellar degeneration (SCD) and Parkinson's disease. The measurements included mean angular change of shoulders (M.A.C.S.) and its coefficient of variation (C.V.). In patients with SCD, the values of M.A.C.S. were significantly larger at 1.0 step/s than those at other stepping rhythms. This results suggests that the stepping rhythm of 1.0 step/s is useful for the detection of cerebellar ataxia. The values of C.V. correlated with the degree of advancement of SCD. In patients with Parkinson's disease, the values of M.A.C.S. tended to decrease because of the restricted elevation of the knee, while those of C.V. were increased. The results showed that the stepping test using the POLGON was useful for estimation of the characteristic disequilibrium of SCD and Parkinson's disease.

Adult↗
PubMed1994

Comparison of body sway analysis techniques. Assessment with subjects standing on a stable surface.

Different analysis methods for the objective measurements of body sway were examined to establish the most sensitive method for identifying changes in stability. Changes between stability with eyes open and eyes closed were used to assess the techniques. Body sway was measured in a group of normal subjects standing on a stable surface using "sway magnetometry," which measures hip movement in the sagittal and coronal planes by magnetic field detectors worn at the waist. The following analysis methods were studied; path length, mean distance from the centre, the area enclosed by the path of movement, and the areas of a convex hull, an ellipse and a circle enclosing the sampled points. The results showed that the path length technique had the smallest inter-subject variability, both with eyes open and eyes closed, and was the only technique whose mean Romberg Coefficient (Eyes Open/Eyes Closed) was more than two standard derivations from 1.0 (0.74 +/- 0.11, mean +/- S.D.), indicating that this technique showed greatest sensitivity for detecting changes in body sway.

Adult↗
PubMed1995

Subjective vertical and vestibular lesion.

Patients with peripheral vestibular disorders may experience postural instability in the standing position, which means disorientation in their environment. The disturbed vestibular function in light reflects the postural instability in space. The present study investigates the relationship between the subjective vertical and the vestibular lesion. The subjects were patients with unilateral vestibular lesion, and the control subjects had no past history of vestibular lesion or any present vestibular lesion. A straight line consisting of 5 spotlights projected on a dome-shaped screen was concentrically moved like a stylus by pressing buttons. We measured the subjective vertical of the subjects using a 5-spotlight straight-line (spotlight-line) on a dome-shaped screen in front of which the subjects were placed. The result showed that the patients with unilateral peripheral disorder had a statistically significantly larger deviation to the impaired ear side, especially when the spotlight-line was moved from the impaired side, as compared with controls.

Adult↗
PubMed1995

Postural control in Menière's disease and acoustic neurinoma when studied on a linearly oscillating platform.

We investigated the effect of visual control on postural stability on a moving platform in 36 patients with Menière's disease (MD) in 25 patients with operated acoustic neurinoma (AN) and in 19 healthy controls. The force platform was placed on rails and oscillated linearly at frequencies from 0.2 to 5 Hz at a constant velocity of 30 mm/s. In all subjects, the support surface oscillation produced postural instability that differed significantly from the base line stability. The body sway velocity increased almost linearly with the increase of stimulation frequency. The MD patients swayed more than the AN patients at base line measurements in non-visual conditions but not during platform movement. In visual conditions the AN patients stabilized their posture significantly better than the MD patients, who showed deteriorating visual control of posture during platform movement. The controls differed from the patients in all test conditions except 5 Hz stimulation, which causes the body segment to fall into resonance. The Romberg quotients (RQ) in MD patients was significantly poorer during platform movement than in controls, except at 5 Hz stimulation. The AN patients had higher RQ values than controls, and mainly used vision to compensate their vestibular deficit. Thus, patients with MD fail to control their posture efficiently with vision during movement which may explain the visually induced dizziness in MD patients.

Adult↗
PubMed1995

Discrimination of patients with acoustic neuroma and peripheral vestibular lesions with human posture dynamics.

A group of normal subjects (n = 17) was compared with groups of patients with a diagnosis of vestibular neuritis (n = 18), and acoustic neuromas (n = 35). Fisher linear discriminant analysis was applied to distinguish clusters of parameters characteristic for each disease. Hence it was possible to distinguish the vestibular neuritis patients from the normal group with statistical significance (p < 0.01). Also the patients with an acoustic neuroma could be distinguished from the normal subjects with statistical significance (p < 0.05).

Diagnosis, Differential↗
PubMed1995

Role of the spinocerebellum in adaptive gain control of cat's vestibulospinal reflex.

In decerebrate cats, a 3-h period of sustained roll tilt of the head (at 0.15 Hz. +/- 10) leading to selective stimulation of labyrinth receptors, associated with a synchronous roll tilt of the body (at 0.15 Hz., +/- 12.5) leading to 2.5 degrees out-of-phase neck rotation produced an adaptive increase in gain of the vestibulospinal reflex (VSR) elicited by roll tilt of the animal at 0.15 Hz, +/- 10 degrees. This increase reached the maximum at the end of the third h of stimulation and persisted unmodified during the first h after stimulation. Microinjection into zone B of the cerebellar anterior vermis of the GABA-A agonist muscimol (0.25 microliter at 8 micrograms/microliters saline), producing only a slight or negligible depression of the VRS gain in non-adaptive conditions, prevented the occurrence of the adapted increase in gain of the VSR following a 3-h period of sustained head-body rotation. Moreover, intravermal injection of the GABA-A agonist muscimol or the GABA-B agonist baclofen (0.25 microliter at 8 or 2 micrograms/microliters saline, respectively) suppressed the already adapted VSR gain. It is postulated that the adaptive increase in gain of the VSR following a sustained neck-vestibular stimulation depends on plastic changes which affect the Purkinje cells of the cerebellar anterior vermis.

Animals↗
PubMed1995

Evidence of somatic graviception from new and classical investigations.

Recent psychophysical experiments have provided evidence of an influence of graviceptors in the human trunk on the perception of body posture that equals or even surpasses the contribution of the otoliths. A reinterpretation of classical results on mammals, notably of the Utrecht school, leads to the conclusion that somatic graviceptors also partake in controlling the posture of eyes, neck and limbs.

Animals↗