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At least 19 recordsLinked to original sources
PubMed1975

[Lesions of the vertical and horizontal systems in the optokinetic vestibular system].

Symptoms of vestibulo-ocular disturbances may be classified into two major groups; i.e., vertical plane and horizontal plane disturbances. Vertical plane symptoms arise from midline lesions of the cerebellum or the brainstem and also from diffuse or symmetrical lesions to either. Vertical plane symptoms also arise from lesions which simultaneously effect both peripheral vestibular systems. Horizontal plane symptoms originate from a unilateral disturbance in the vestibular system. Thus, vertical plane symptoms indicate bilateral disturbances and the symptoms appear symmetrically in the eyes, trunk or extremities. Vertical plane symptoms appear in the sagittal plane, or the plane of the vertical semicircular canals. On the other hand, horizontal plane symptoms appear in the horizontal plane, or the plane of the horizontal semicircular canals.

Cerebellar Ataxia↗
PubMedDate not supplied

[Model of the effect of the vestibular system on blood pressure during sleep].

A structural model of the effect of vestibular system on blood pressure during sleep is proposed. This model reflects joint action of the otolyth system and semicircular canal system, vestibular nuclei, vasomotor centre, vagus nuclei and of the central control mechanism of the state awakeness -- sleep. Anatomic and physiological prerequisites involved in the model are expressed by chains with transmission functions, signal generators, summators etc.

Blood Pressure↗
PubMed1979

Effects of the vestibular system on human development, part 2: Effects of vestibular stimulation on mentally retarded, emotionally disturbed, and learning-disabled individuals.

In Part 1 of this two-part series, studies concerned with the effects of vestibular stimulation on human development and function were reviewed and some implications for therapy were suggested. In Part 2, three categories of dysfunction with possible links to the vestibular system are discussed. Studies in the category of mental retardation evaluate motor development and sensory preference. Possible vestibular associations with emotional disturbance are examined by review of studies concerned with etiology, motor activity, speech, and clinical observations. A brief review of studies concerned with early identification and speech and language factors of learning-disabled children constitutes the third category. Interpretations are drawn and some implications for therapy are made.

Affective Symptoms↗
PubMed1976

[Tonic conjugated action of receptor-receptor fibers and of the efferent vestibular system on the spontaneous afferene activity of a semicircular canal in the frog].

In the frog, the joint action of non-afferent vestibular systems [i.e. the efferent vestibular system and the receptor-receptor fibre system] on the afferent vestibular activity is null or very small. The receptor-receptor fibre system being inhibitory, it seems that the efferent vestibular system as a whole is facilitatory, which agrees with previous results.

Animals↗
PubMed1976

Tonic influence of the efferent vestibular system on the spontaneous afferent activity from semicircular canals in the frog (Rana esculenta L.).

In the frog we have recorded the spontaneous activity of single afferent fibres of the ampullary nerves of the left horizontal semicircular canal (HC) and vertical anterior canal (VAC) in isolated head preparations. The recordings have been made in 4 experimental situations: intact preparations; preparations whose brain was destroyed; preparations whose contralateral vestibular nerve had been cut between Scarpa's ganglion and the brain; preparations where either an ampullary nerve (that of the HC or of the VAC) or the utricular nerve had been cut contralaterally. From our results, it appears that the efferent vestibular system has a tonic influence on the afferent activity from HC and VAC; the influence of the part of the efferent vestibular system (EVS) activity depending on contralateral vestibular inputs is inhibitory, while the influence of the part of the EVS activity depending on ipsilateral vestibular inputs might be facilitatory.

Animals↗
PubMed1979

The influence of trichloroethylene and related drugs on the vestibular system.

A previously described experimental model for studying the effect of industrial solvents on the vestibular system of rabbits has been applied to trichloroethylene. Estimation of trichloroethylene and its metabolites in blood and cerebrospinal fluid was performed by gas chromatography. Vestibular function was studied by recording nystagmus, induced by positional changes or accelerated rotation. At blood levels of trichloroethylene above 30 p.p.m. "positional nystagmus" develops. Two metabolites of trichloroethylene, chloral hydrate and trichloroethanol, which are known as central nervous system (CNS) depressants, did not induce this abnormal nystagmus. However, alpha-chloralose, a derivative of chloral hydrate, induced positional nystagmus and also a markedly exaggerated nystagmus developed during rotatory acceleration. It is suggested that solvents like trichloroethylene elicit vestibular disturbances by stimulation of central subcortical vestibulo-oculomotor connections. The stimulation may be caused by a blockage of inhibitory systems.

Animals↗
PubMed1977

Psychophysical determination of the phase characteristic of the vestibular system of man for sinusoidal oscillation in yaw.

UNLABELLED: The phase characteristic of the vestibular system of man was determined for sinusoidal oscillation in yaw in the frequency range from 0.0025 to 0.4 Hz. Three different sets of experimental conditions were used: (1) a dark room with a fixation light; stimulus: sinusoidal rotation; (2) a dark room without a fixation light; stimulus: sinusoidal rotation + noise, and (3) a dark room without a fixation light; stimulus; sinusoidal rotation. RESULTS: the sensation leads the velocity by about 90 degrees at 0.005 Hz. The phase lead decreased for higher frequencies becoming nearly zero at 0.05 Hz and remaining constant in the frequency range 0.05 to 0.4 Hz. A phase lag was not found. At very low frequencies (less than 0.005 Hz), the phase lead was more than 90 degrees. The results can be described in terms of a second-order model with time constants Tau1 = 20 sec and Tau2 = 0.013 sec and an adaptation term with a time constant of Taau = 0.40 sec.

Humans↗
PubMed1978

Muscle responses and monosynaptic reflexes in falling monkey. Role of the vestibular system.

The free fall has been used in our laboratory as a way to test vestibular function in baboons in order to quantify vestibular compensation in the hemilabyrinthectomized animal. This study presents only those results that concern the contribution of the vestibular system to muscle responses due to sudden fall. EMG activity was recorded from the fully conscious animal using chronic electrodes implanted in various muscles. Spinal monosynaptic reflexes (Hoffmann's and tendon reflexes) were studied in the soleus muscle. Baboons were seated in a special chair suspended from an electromagnet and unexpectedly dropped 90 cm. Experiments were performed in normal, unilateral and bilateral vestibular neurectomized baboons. 1. In normal baboons, results showed a first short-latency response in all tested muscles, followed by a second peak of EMG activity in these muscles. Comparison with data from bilateral vestibular neurectomized baboons demonstrates that normal vestibular function is essential for the appearance of the first peak; the second peak rapidly disappears in our experimental situation where the animal's fall is mechanically braked and interrupted, so the animal does not have to make the postural adjustments necessary for landing, It is suggested that the first peak is concerned with the automatic and reflex control of landing, the second with the voluntary breaking of landing. 2. The modulation of monosynaptic spinal reflexes is closely related to the EMG response in soleus muscle. Facilitation of the H-reflex begins just prior to the onset of the EMG activity and continues as long as the baboon is falling. The T-reflex modulation presents a similar time course except in its early phase where it is depressed. Decrease in T and increase in H-reflexes suggest that the EMG response is most likely due to direct activation of alpha-motoneurons and not by means of the gamma-loop. 3. In unilateral vestibular neurectomized baboons, EMG and reflexological data show the classical asymmetry characterized by a strong decrease of the responses on the side of the lesion, and by a pronounced increase on the contralateral side. It is concluded that this represents the imbalance between the resting discharge of the vestibular neurons, and discloses the influence of labyrinthine afferences at the spinal level. We suggest consequently the use of EMG responses and modulation of spinal reflexes to fall in order to quantify vestibular compensation.

Animals↗
PubMed1979

Synaptic structures in the type II hair cell in the vestibular system of the guinea pig. A freeze-fracture and TEM study.

The synaptic contacts of the type II hair cell in the vestibular system of the guinea pig was described in thin-sectioned and freeze-fractured specimens. Synaptic bodies were present at the apposition with both large and small afferent terminals. About 20% of the synaptic bodies observed consisted of complexes of two or more adjacent synaptic discs. In freeze-fracture replicas, the cytoplasmic leaflet of the hair cell plamalemma beneath the synaptic body had a bar-shaped aggregate of large particles. The size and shape of the particle aggregate was the same as that of the synaptic body. Small plasmalemmal deformations, interpreted as sites of synaptic vesicle exocytosis, were found immediately adjacent to the particle aggregate. On the postsynaptic membrane, an aggregate of intramembrane particles was present at the synaptic junction. The type II hair cell had no gap junctions or close membrane appositions between it an the apposed afferent fiber. Efferent boutons ending on the type II hair cell had no intramembrane particle specialization on the postsynaptic membrane; however those efferent boutons ending on large and small afferent fibers had an aggregate of medium-sized particles on the external leaflet of the postsynaptic bouton beneath the presynaptic active zone.

Animals↗
PubMedDate not supplied

Vestibular system abnormalities in otosclerotic subjects.

A technique to quantify the tandem Romberg test (posturography) was used to study ten patients with otosclerosis before (series 1), 48 hours after (series 2), and between two to four months after (series 3) a stapedectomy. The results were analyzed by power spectrum analysis and then compared to findings from electronystagmographic testing performed with series 1 and 3. There was no significant change in the electronystagmography (ENG) test findings between series 1 and 3. Posturography, however, demonstrated an uncompensated vestibular pattern in the immediate postoperative period which, after two months, converted to a compensated vestibular pattern. Posturography serves as a useful quantitative test for the study of patients with balance disorders because the procedure supplements rather than complements the ENG. In addition, posturography detects vestibular reflex abnormalities in stapedectomized patients two months afterwards. Other testing modalities have not consistently demonstrated this postoperative vestibular system instability.

Adult↗
PubMed1979

Freeze-fracture studies on the synapse between the type I hair cell and the calyceal terminal in the guinea-pig vestibular system.

The apposition between type I hair cells and the calyceal terminals of vestibular ganglion cell peripheral processes was studied in the vestibular epithelium of the guinea-pig, using thin-sectioned and freeze-fractured specimens. Chemical synaptic junctions were exceedingly rare in thin-sectioned specimens, and were not seen in freeze-fracture replicas. Furthermore, no gap junctions were present between the hair cell and the calyx. There were, however, regions along the apposition where the membranes were closely apposed. At these regions, the hair cell was invaginated by cytoplasmic protrusions of the calyx and the plasmalemmata of the two cells were separated by only 6-7 nm. The number and conformation of the close appositions varied between different cells. In freeze-fracture replicas, the closely-apposed plasmalemmata of the hair cell and the calyx had no special distribution of intramembrane particles on either membrane leaflet. However, on the external membrane leaflet of the hair cell, a large patch of widely-spaced, large particles surrounded the regions of close apposition. The corresponding region of the plasmalemma of the calyx had no special distribution of particles on either membrane leaflet. The scarcity of chemical synaptic junctions, the absence of gap junctions between the cells and the unique arrangement of particles in the hair cell plasmalemma surrounding regions of close membrane apposition may indicate an unusual mode of synaptic transmission between the type I hair cell and the calyx.

Animals↗
PubMed1979

Effects of the vestibular system on human development, Part I. Overview of functions and effects of stimulation.

Studies concerned with the effects of vestibular stimulation on human development and function are reviewed and some implications for therapy are suggested in this paper. Studies are included that relate to changes in the vestibulo-ocular reflex with age, effects of vestibular stimulation on smiling, crying, general activity, and visual attentiveness of infants; and studies that show that typical sequelae to vestibular stimulation are reduced following long-term stimulation. The importance of reviews of the literature and transference of research results to therapeutic use are stressed, with the implication that vestibular-based therapy will improve as occupational therapists become more aware of related research.

Adolescent↗
PubMed1992

Immunocytochemical evidence for an afferent GABAergic neurotransmission in the guinea pig vestibular system.

To implicate gamma-aminobutyric acid (GABA) as an afferent neurotransmitter (AN), the localization of GABA synthesizing and degradation enzymes; L-glutamate decarboxylase (GAD) and GABA transaminase (GABA-T) was investigated by light and electron microscopy immunocytochemistry in guinea pig vestibular cristae and ganglion cells (GC). GAD-like immunoreactivity was exclusively confined to the sensory hair cell (HC) cytoplasm, suggesting that GAD synthesizes GABA in the HC. GABA-T like immunoreactivity was found within HC, nerve calyces, nerve fibers, and GC, suggesting its participation in terminating transmitter action. These results demonstrate the existence of a GABAergic system in the guinea pig vestibule and strongly support GABA as a vestibular AN.

Animals↗
PubMedDate not supplied

Permanent effects of low frequency vibration on the vestibular system.

Among 49 male workers, mean age 30 years, who had been working in conditions of extreme noise and vibration for between 6 months and 10 years vestibular disturbances could be shown (in the form of spontaneous nystagmus, lowered caloric excitability, or pathology in rotatory tests) in as high as 44.9%. The lesions were believed to have arisen in the peripheral vestibular organ as a consequence of the low frequency vibration.

Adult↗