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PubMed1991

Molecular biology of the vestibular system.

Molecular biology of the vestibular system has been limited by a number of technical difficulties including fixation, decalcification of the temporal bone and the small size of specific structures relative to their surroundings. In situ hybridization histochemistry and immunoelectron microscopy allow the subcellular study of gene expression and gene products, respectively. We developed the methodologies necessary to apply these techniques to the central and peripheral vestibular systems. The central and temporal bone distributions of the neuropeptide calcitonin gene-related peptide (CGRP) mRNA and two genes coding for gap junction proteins, connexin C32 and C43 mRNA, were studied. The cellular distributions of these mRNAs are presented. In addition, examples of pre-embedding and postembedding immunoelectron microscopy are presented demonstrating the usefulness of these techniques in studying the subcellular localization of specific antigens. The ultrastructural innervation of the vestibular periphery by the efferent neuropeptide CGRP and ultrastructural evidence of glycoprotein secretion by the human endolymphatic sac is presented.

Animals↗
PubMed1988

Panic disorder and the vestibular system.

This article reviews the interrelationship between panic disorder and vestibular function. There is a possibility of both somatopsychic and psychosomatic interactions between panic and the vestibular system. Another possibility is that vestibular dysfunction could be associated with certain mental disorders, including panic disorder, as a nonspecific marker. Somatopsychic interactions are suggested by findings of high prevalence of vestibular dysfunction in selected patients with panic disorder, by the occurrence of "space and motion phobia" in patients with panic disorder, and by the report of anxiety and pseudoagoraphobia in some patients with a primary complaint of vertigo. Psychosomatic influences include symptoms of dizziness and increased sensitivity of the vestibular system due to anxiety or hyperventilation. Vestibular dysfunction as a nonspecific marker is discussed in the context of a review of studies of the vestibular system in schizophrenia. Before more definite conclusions can be drawn whether panic disorder is related to vestibular dysfunction in some cases, further research is needed to establish the specificity of vestibular dysfunction for panic disorder.

Agoraphobia↗
PubMed1997

Sound-evoked activity in primary afferent neurons of a mammalian vestibular system.

HYPOTHESIS: Some primary vestibular afferents in the cat respond to sound at moderately intense sound levels. BACKGROUND: In fish and amphibians, parts of the vestibular apparatus are involved in audition. The possibility was explored that the vestibular system in mammals is also acoustically responsive. METHODS: Microelectrodes were used to record from single afferent fibers in the inferior vestibular nerve of the cat; some acoustically responsive fibers were labeled intracellularly with biocytin. RESULTS: Vestibular afferents with regular spontaneous activity were unresponsive to sound, whereas a sizable fraction of vestibular afferents with irregular activity were acoustically responsive. Labeling experiments demonstrated that acoustically responsive afferents innervate the saccule, have cell bodies in Scarpa's ganglion, and project to central regions both inside and outside the traditional boundaries of the vestibular nuclei. Acoustically responsive vestibular afferents responded to sound with shorter latencies than cochlear afferents but had higher thresholds (> 90 dB sound pressure level) and responded only in the range 0.1-3.0 kHz. In contrast to cochlear afferents, efferent stimulation excited background activity and proportionately increased sound-evoked responses in these vestibular afferents, that is, there was centrally mediated enhancement of gain (gain = spike-rate/motion). CONCLUSIONS: The evolutionary conservation of a saccular auditory pathway in mammals suggests that it confers survival advantages. Recent evidence suggests that acoustically responsive saccular afferents trigger acoustic reflexes of the sternocleidomastoid muscle, and hence measurement of such reflexes may provide a relatively simple test for saccular dysfunction.

Acoustic Stimulation↗
PubMed1988

Disorders of the vestibular system.

Disorders of the vestibular system are common in veterinary practice and result in a clinical syndrome characterized by head tilt, asymmetric ataxia, and nystagmus. These signs may occur with lesions involving the peripheral or central vestibular structures. Careful neurologic evaluation of the animal and knowledge of surrounding neuroanatomic structures and their functions enable the clinician to differentiate between peripheral and central disorders. Conditions resulting in peripheral vestibular symptoms include idiopathic syndromes, otitis interna, trauma, neoplasia, drug-induced ototoxicity, and congenital disorders. Radiographs of the petrous temporal bone and tympanic bulla and examination of the tympanic membrane are useful in determining the specific etiology. Central vestibular dysfunction may result from inflammatory CNS diseases, neoplasia, trauma, thiamine deficiency, and storage diseases. Cerebrospinal fluid analysis, skull radiographs, and computed tomography are diagnostic tests useful in animals with central vestibular symptoms. Once the etiology is identified, specific therapy may be provided and a more accurate prognosis can be determined.

Animals↗
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↗
PubMed2005

Roles of the vestibular system in controlling arterial pressure in conscious rats during a short period of microgravity.

In order to evaluate the roles of the vestibular system in controlling arterial pressure (AP) during exposure to a short period of microgravity (microG), the AP was measured in conscious free-moving rats having intact vestibular systems and those having vestibular lesions (FM-Intact and FM-VL groups, respectively). During free drop-induced microG, the AP increased in the FM-Intact group; it was 38+/-4 mmHg more than the AP observed during 1G. However, the increase in AP was significantly lower in the FM-VL group (20+/-2 mmHg). Further, to examine the sudden effect of a body floating in the midair in response to the AP during exposure to muG a body stabilizer was placed on the back of rats having intact vestibular systems and those having vestibular lesions (STAB-Intact and STAB-VL groups, respectively). The increase in the AP was significantly depressed in the STAB-Intact group; when compared with that in the FM-Intact group, but the increase was still significant (27+/-2 mmHg). On the other hand, the increase in the AP was completely eliminated in the STAB-VL group (7+/-5 mmHg). These results indicate that the AP increases during exposure to muG in conscious rats, and the vestibular system and body stability are significantly involved in this response.

Animals↗
PubMed2004

Signal processing in the vestibular system during active versus passive head movements.

In everyday life, vestibular receptors are activated by both self-generated and externally applied head movements. Traditionally, it has been assumed that the vestibular system reliably encodes head-in-space motion throughout our daily activities and that subsequent processing by upstream cerebellar and cortical pathways is required to transform this information into the reference frames required for voluntary behaviors. However, recent studies have radically changed the way we view the vestibular system. In particular, the results of recent single-unit studies in head-unrestrained monkeys have shown that the vestibular system provides the CNS with more than an estimate of head motion. This review first considers how head-in-space velocity is processed at the level of the vestibular afferents and vestibular nuclei during active versus passive head movements. While vestibular information appears to be similarly processed by vestibular afferents during passive and active motion, it is differentially processed at the level of the vestibular nuclei. For example, one class of neurons in vestibular nuclei, which receives direct inputs from semicircular canal afferents, is substantially less responsive to active head movements than to passively applied head rotations. The projection patterns of these neurons strongly suggest that they are involved in generating head-stabilization responses as well as shaping vestibular information for the computation of spatial orientation. In contrast, a second class of neurons in the vestibular nuclei that mediate the vestibuloocular reflex process vestibular information in a manner that depends principally on the subject's current gaze strategy rather than whether the head movement was self-generated or externally applied. The implications of these results are then discussed in relation to the status of vestibular reflexes (i.e., the vestibuloocular, vestibulocollic, and cervicoocular reflexes) and implications for higher-level processing of vestibular information during active head movements.

Afferent Pathways↗
PubMedDate not supplied

Physiological evidence that the vestibular system participates in autonomic and respiratory control.

Electrical or natural stimulation of the vestibular system results in changes in blood pressure and respiratory motor output. An increase in excitatory drive on the sympathetic nervous system occurs during nose-up vestibular stimulation in cats; this response is appropriate to offset orthostatic hypotension that could result from nose-up body rotations during movements such as vertical climbing. In addition, transection of the vestibular nerves in anesthetized or awake cats compromises the ability to correct decreases in blood pressure that result from nose-up body tilt. The vestibular system also has influences on respiratory muscles; these effects are appropriate to participate in making adjustments in the activity of respiratory muscles that are necessary to offset mechanical constraints on these muscles that occur during changes in body position. These data thus suggest that the influences of the vestibular system on the autonomic and respiratory systems serve to maintain homeostasis during movement.

Animals↗
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↗
PubMed2003

Agreement between functional and electrophysiologic measures in patients with unilateral peripheral vestibular system impairment.

This investigation was conducted to determine whether there was congruence between "physiology-based" definitions of compensated and uncompensated unilateral peripheral vestibular system impairment and "functional" measures of self-perceived dizziness disability/handicap. A retrospective analysis was performed on data obtained from 122 patients evaluated in the Balance Function Laboratory at Henry Ford Hospital over a 4-year period. Both electronystagmography and rotational test data were tabulated. Additionally, results of a self-report measure of dizziness disability/handicap were tabulated. Patients were placed into four groups, with one group representing normal vestibulometric test results, one group representing compensated unilateral peripheral vestibular system impairment, and two groups representing increasing magnitudes of uncompensated unilateral peripheral vestibular system impairment. The total and subscale scores on the self-report measure served as the dependent variable. Results showed a lack of congruence between the physiologic and functional measures. We interpret these findings as evidence that factors other than semiobjective evidence of vestibular system compensation probably impact functional recovery following unilateral peripheral vestibular system impairment.

Adult↗
PubMed2002

A general framework for neurobiological modeling: an application to the vestibular system.

The otolith organs in the vestibular system are excellent detectors of linear accelerations. However, any measurement of linear acceleration is ambiguous between a tilt in a gravitational field and an inertial acceleration. Angelaki et al. have put forward a general hypothesis about how inertial accelerations can be computed based on vestibular signals (J. Neurosci. 19 (1999) 316). We have constructed a realistic, detailed model of the relevant systems to test this hypothesis. The model produces useful predictions about what kinds of neurons should be found in the vestibular nucleus if such a computation is actually performed in the vestibular system. The model is constructed using general principles of neurobiological simulation (J. Neurophys. 84 (2000) 2113).

Acceleration↗
PubMed1989

[Study of dynamic counterrolling of the eye--quantitative analysis of effects by visual and vestibular systems].

Dynamic counterrolling of the eye is induced when the head is tilted to one side: it includes cyclorotatory nystagmus, which is affected by visual and vestibular systems. Both of these two ocular movements were measured quantitatively through a video recording system, and the role of visual and vestibular systems in visual stabilization was analyzed. The relationship between the optokinetic and vestibulo-ocular systems was variable in relation to the velocity of head tilting. The optokinetic system contributed more in slow head tilting. As the velocity of head tilting increased, the suppression by the optokinetic system was decreased and eventually the vestibulo-ocular system became more dominant. This suggests that the role of visual and vestibular systems in head tilting is similar to that in head rotation. Visual and vestibular systems seem to work together mutually with some individual variation in stabilizing vision with sensory control in the higher level of the visual cortex.

Adult↗
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↗
PubMed1999

Effects of otitis media with effusion on the vestibular system in children.

Middle ear effusion has been considered the most common cause of vestibular disturbance in children. However, there have been only a few studies on vestibular disturbance in children with otitis media with effusion. We studied the vestibular systems of 30 children with otitis media with effusion aged 8 to 13 years and compared the results with 15 age- and sex-matched controls. A questionnaire relating to vestibular disturbance was given to patients and their parents. Spontaneous nystagmus and positional nystagmus were recorded by electronystagmography as diagnostic tests of the vestibular system. Romberg's and past-pointing tests were performed on children with otitis media with effusion and controls. After vestibular tests were completed, myringotomy was performed, and a ventilation tube was inserted. The questionnaire and the vestibular tests were repeated after the operation and during the first month after surgery. Our study showed that there was a history of vestibular disturbance in 33% of children with otitis media with effusion. Electronystagmography and Romberg's test findings demonstrated that 33% of the children had vestibular dysfunction (p < 0.05). After myringotomy with ventilation tube insertion, vestibular test results returned to normal, and symptoms related to vestibular disturbance improved. These findings confirm the assumption that middle ear effusion may affect the vestibular system, which can be resolved after myringotomy with ventilation tube insertion.

Acoustic Impedance Tests↗
PubMedDate not supplied

Click evoked neurogenic vestibular potentials (NVESTEPs): a method of assessing the function of the vestibular system.

OBJECTIVES: To obtain neurogenic vestibular evoked potentials (NVESTEPs) with surface scalp recording using high intensity auditory clicks. The same stimulus is used in myogenic vestibular evoked potentials which has been shown to evoke potentials in the vestibular division of the vestibulocochlear nerve. METHODS: A whole head recording with surface EEG electrodes was performed using high intensity clicks in one normal volunteer to determine the best recording position for vestibular evoked potentials. The results were compared to responses at moderate click intensities used for brainstem auditory evoked potentials (BAEPs). The difference in the location of the two responses on the scalp was assumed to be from the vestibular system. RESULTS: Responses specific to the high intensity clicks were best obtained in the parietal areas, with no reproducible responses obtained in the same area with moderate intensity clicks normally used in BAEPs. Recordings in neurologically normal volunteers showed a consistent response with a negative polarity at around 3 ms, which we therefore called N3. Two case studies are presented. The first case is a patient with unilateral sensorineural hearing loss with NVESTEPs present, suggesting that NVESTEPs is not a cochlear response. The second case is a patient with multiple sclerosis with demyelinating lesions in the pons and an unobtainable NVESTEP response. CONCLUSION: NVESTEPs is a possible new diagnostic technique that may be specific for the vestibular pathway. It has potential use in patients with symptoms of dizziness, subclinical symptoms in multiple sclerosis, and in disorders specific for the vestibular nerve.

Adolescent↗
PubMed2004

Functional and anatomic alterations in the gentamicin-damaged vestibular system in the guinea pig.

HYPOTHESIS: The purpose of this study was to investigate the expected functional and morphologic effect of gentamicin on the vestibular system simultaneously by measurement of vestibular evoked potentials and electron microscopic evaluation. BACKGROUND: Vestibular short-latency evoked potentials to linear acceleration have been shown to be a useful parameter of vestibular function. In gentamicin-treated animals, the morphologic damage has been well documented, although this has seldom been quantified. METHODS: Fifteen guinea pigs were divided into three equal groups. Two groups received different dosages of intramuscular gentamicin for 3 weeks; the third group was the control group. Vestibular short-latency evoked potentials to linear acceleration pulses were measured. After the last gentamicin dose, the utricles were prepared for scanning and transmission electron microscopy. On scanning electron microscopy photographs, the surface area damage ratio of the utricles, a simple method of quantifying gross morphologic damage, was calculated. RESULTS: The vestibular short-latency evoked potential of gentamicin-treated guinea pigs showed a slow-developing, damaging, dose-response effect on the function of the vestibular system (p = 0.01). Scanning electron microscopy and transmission electron microscopy showed severe morphologic damage in the sensory hair cells of the utricle. The surface area damage ratio showed a dose-response relationship (p = 0.01). CONCLUSION: Functional and anatomic alterations in the gentamicin-damaged vestibular system in the guinea pig are related.

Animals↗
PubMed1989

Current concepts of the vestibular system reviewed: 2. Visual/vestibular interaction and spatial orientation.

The vestibular system contributes to the generation of conjugate eye movements, spatial orientation, and postural control. The functional connections of the vestibular end-organs and of the descending vestibulospinal pathways and their importance to postural control were reviewed in the previous paper by Keshner and Cohen (pp. 320-330). This paper reviews the ascending vestibular pathways, the visual/vestibular interactions, and the role of the vestibular system in oculomotor control and spatial orientation.

Eye Movements↗