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PubMedDate not supplied

The effect of preceding tilt on the perceived vertical. Hysteresis in perception of the vertical.

The subjective vertical (SV) was measured at various positions of roll-tilt (R). Positions R90-right, R 45-right, R0, R45-left, R90-left were reached either in clockwise sequence (i.e. starting with R 90-left) or in counterclockwise sequence (starting with R90-right); position R135-right was attained from R 110-right or R 160-right. The SV was affected by the preceding tilt (hysteresis). Clockwise position sequence produced, for example, a counterclockwise SV deviation (from the medium value at the obtained position) as though indicating a more advanced tilt position (Fig. 5). It is concluded that the aftereffects and hysteresis differences in perception of position and of SV depend on adaptational processes in the somatoreception system which interacts with the labyrinth posture-receptors.

Adult↗
PubMedDate not supplied

Computer calculation of movement of body's center of gravity.

The movement of the body's center of gravity was calculated in normal subjects and in vertiginous patients by using a strain gauge platform system and a ditigal computer. The total length of the loci traced by the center of gravity in 40 normal subjects during normal standing for 1 minute was 52.0 +/- 18.5 cm with eyes open, and 81.5 +/- 52.3 cm with eyes closed. The ratio of the total length with the eyes closed compared with that with the eyes open during normal standing for 1 minute was 1.56 +/- 0.56. The time course of the length of the locus was calculated every 10 seconds, and characteric curves were obtained. The dependability of this test appeared to be fairly accurate and the usefulness of this technique for the diagnosis of vertiginous or ataxic diseases is recommended.

Adolescent↗
PubMed1980

Relationship between the head's and the body's center of gravity during normal standing.

An apparatus for the recording of head movements has been developed and a basic study was performed to determine the normal values of head movement and to estimate the significance of the head movement as a righting reflex. The locus traced by the head closely resembled that of the center of gravity, though shorter in overall length. The head also moves more slowly than the center of gravity. The phase delay of its movement was observed during standing with eyes closed. These results suggest that the head's movement is controlled by the body's center of gravity and that the latter moves in order to keep the head steady, maintaining the eyes in normal position.

Adolescent↗
PubMed1984

Postural and oculomotor signs in labyrinthine-defective subjects.

Bilabyrinthless subjects, i.e. subjects clinically devoid of labyrinthine responses, show a greater than normal decrease in postural stability following eye closure. Because changes in head position, which affect posture in healthy subjects, do not do so in bilabyrinthless patients, static afferent information from healthy neck receptors does not contribute to postural stabilization. Somatosensory nystagmus and dynamic cervico-ocular responses are equally greater in bilabyrinthless than normal subjects, which indicates that both categories of eye movements are mediated by the same mechanism. Optokinetic nystagmus is slightly diminished in bilabyrinthless patients and optokinetic after-nystagmus was mostly absent. In terms of the Raphan-Cohen model our findings confirm that destruction of the labyrinthine function abolishes the vestibulo-ocular integrator function.

Ear, Inner↗
PubMed1984

Vestibular compensation and nystagmus.

In healthy young subjects barbiturate induced vestibular nystagmus was sequentially studied with repeated electronystagmographic recordings. The analysed data together with our earlier studies indicated that, except for vertical nystagmus, spontaneous and different types of positional nystagmus by themselves are not diagnostic of site of lesion. The transition from spontaneous to positional to paroxysmal nystagmus observed in follow up studies of several of these cases indicates that these various types of vestibular nystagmus are likely a measure and reflection of different degrees of vestibular decompensation.

Adult↗
PubMedDate not supplied

Postural responses evoked by sinusoidal galvanic stimulation of the labyrinth. Influence of head position.

In 15 healthy subjects we studied body sway reactions to sinusoidal 0.3 Hz binaural bipolar galvanic current up to 2 mA under three conditions. With the head forward and eyes closed, there is only a periodic lateral displacement of the centre of gravity, following the stimulation with a phase lag. In two other conditions, the head turned to the left or to the right without trunk torsion, the direction of sway was modified in such a way that there were mainly anteroposterior movements. It is thought that this experiment shows the modulatory influence of neck afferents on the direction of vestibulospinal motor effects in man.

Adult↗
PubMedDate not supplied

Frequency analysis of body sway in the upright posture. Statistical study in cases of peripheral vestibular disease.

The frequency component of shift in the centre of gravity while standing upright was investigated in 14 normal subjects and 30 patients with peripheral vestibular disease. Relative changes in the square root value of the power in each small frequency band of 0.1 and 0.2 Hz in frequencies of less than 2 Hz were evaluated statistically for four groups, viz. a group of normal subjects, and patients with Ménière's disease, benign paroxysmal positional vertigo, and vestibular neuritis. The influence of visual control in each group and the difference between each pathological group and the normal subjects were examined statistically. The combination of a minor change in each small frequency band is considered to be utilizable to establish a differential diagnosis for the three groups of peripheral vestibular disease and versus the normal group.

Adult↗
PubMed1988

Computerized posturography, a development of the measuring system.

A computerized posturography system is composed of a custom made strain gauge force platform and it utilizes commercially available amplifiers. The body sway response signals are digitized for the calculation of the following parameters by a computer: average velocity of body sway, mean value for fore-aft and lateral body sway, and maximal amplitude of body sway. Calf muscles were exposed to vibration to disturb the postural control. The program contains appropriate filters to remove transient and quantification noise.

Humans↗
PubMedDate not supplied

Evidence for a vestibular input contributing to dynamic head stabilization in man.

Horizontal head movements in response to unpredictable horizontal oscillations of the trunk were studied in 6 patients lacking vestibular function and in 6 normal subjects. In order to obtain compensatory (i.e. stabilizing with respect to earth) head movements, all subjects were required to look at an earth-fixed target, using their eyes and head. The turning points (maxima and minima) were determined from head and trunk position records. It was found that normal subjects reversed the direction of head movements in advance of trunk movements (mean lead = 82 ms) whereas the patients reversed head direction after the trunk (mean lag = 169 ms). The coherence function between head and trunk movements, measured with a spectral analyser in an additional labyrinthineless patient, was considerably lower than in normal controls. It is concluded that patients lacking vestibular function have impaired stabilization of the head in space, which can be taken as indirect evidence of the existence of active dynamic vestibulo-collic reflex (VCR) mechanisms in normal man. The lead found in normal subjects, notwithstanding the unpredictability of the stimuli, may reflect the detection of early acceleration signals by the vestibular apparatus to organize compensatory head movements.

Adult↗
PubMed1988

Presentation of a posturographic test with loading of the proprioceptive system.

Postural control is maintained by sensory feedback from visual, vestibular and somatosensory receptors. Recently several methods for evaluating postural control have been devised, utilizing an imposed perturbation. Most of these methods use stimuli which simultaneously affect more than one of the sensory feedback loops. In the present paper a posturographic technique is presented with specific loading of the proprioceptive system, using a computer controlled vibratory stimulus and computerized analysis of the results.

Central Nervous System Diseases↗
PubMed1988

Differential diagnosis of vertigo--combined galvanic test and MRI.

Differential diagnosis of the disease entities of vertigo are important in clinical investigations. Many concepts and procedures have been proposed for available diagnostic tests. Recent basic and clinical studies proved the efficacy and reliability of galvanic tests, including galvanic nystagmus test (GNT) and galvanic body sway test (GBST), emphasizing that the effects of galvanization are: 1) on the action potential in vestibular nerve and 2) on the resting discharge of the vestibular nerve. These suggest further that galvanic nystagmus reaction (GNT) is mainly a manifested reaction of the semicircular canal system, while galvanic body sway such as spinal reflexes (includ. GBST) are mainly a reaction of the otolithic system. The purpose of this paper is to review briefly the previous results of GBST in our laboratory; and to introduce a newly devised combined galvanic test, simultaneous recording of both GBST and GNT; and also introduce magnetic resonance imaging (MRI) of the brain including the cerebrum, cerebellum with brainstem relating the central vestibular system, both of which help us to make a more defined diagnosis of the central origin vertigo. On CGT of a normal subject, galvanic eye movements are constantly induced showing the initial eye deviation and the following main deviation during galvanization, on both eyes, which are almost similar and occur synchronously. Galvanic body sway is also induced well with individual components, as described in the previous papers. CGT of the cases with vertigo revealed abnormal response patterns in each disease.

Aged↗
PubMedDate not supplied

The contribution of vestibulo-spinal mechanisms to the maintenance of human upright posture.

The maintenance of upright stance in humans requires the integrative evaluation of vestibular, visual, and proprioceptive information. Recent experiments prove the existence of fast vestibulo-spinal reactions in humans. Their physiological significance for the compensation of sudden external displacements of the body is minor. For low frequency stabilization of the body, however, vestibulo-spinal afferents as well as vision and proprioception are important. Unilateral loss of vestibular function initially causes a tendency to fall to the ipsilateral side as well as nystagmus and vertigo. After the first days of compensation, the remaining functional disturbance can only be detected by exposing the patient to conflicting sensory reafferents or by reducing proprioceptive and visual inputs simultaneously. The loss of vestibular function not only alters low frequency stabilization and to some extent also reflex-like fast motor patterns, but also interferes with the selection of preprogrammed motor synergies.

Afferent Pathways↗
PubMedDate not supplied

Posturography findings in workers exposed to industrial solvents.

Postural control was investigated by static posturography in 18 workers exposed to industrial solvents, 9 patients with psycho-organic syndrome due to industrial solvent exposure, and 52 controls. Both groups of exposed subjects showed larger sway areas with eyes open as well as closed, compared with the controls. No differences were found in the Romberg quotient (the relationship between sway areas with eyes closed/open). The correlation between static posturography and the otoneurological test battery was positive for the visual suppression test in the styrene group. In the industrial solvent group no significant correlations were found. The visual suppression test and some auditory tests were pathological in the exposed groups. The otoneurological test battery--especially the visual suppression test and static posturography--seems to contribute in the assessment of solvent related CNS lesions.

Adult↗
PubMed1989

Does impulse noise induce vestibular disturbances?

The effect of impulse noise on postural stability was evaluated in 54 subjects from the Finnish army, who were suffering from acute hearing loss caused by exposure to firearms noise. For referents we used 20 non-exposed army recruits and 39 civilian volunteers. The effects of vision, pressoreceptor function and proprioception were stepwise excluded or altered, leaving mainly the vestibular guidance of postural control intact. Since the postural perturbation was fairly smooth during these instances we assume that the condition evaluates mainly the function of the otolith organs in guiding stance. We found no difference in any of the test conditions used, between normal controls, army controls and impulse noise exposed subjects. Furthermore, there was no dose response with body sway and severity of hearing loss. The results indicate that impulse noise may not be the cause of significant functional changes in the vestibular system that can account for noise-induced postural instability.

Adult↗