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PubMed1995

Discharge characteristics of vestibular and saccade neurons in the rostral midbrain of alert cats.

1. The interstitial nucleus of Cajal (INC) is involved in generation of vertical eye movements. To further explore the neural substrates of INC involvement in eye movements, we examined the discharge characteristics of neurons in the rostral midbrain that discharge for vestibular stimulation and saccades in alert cats. We analyzed 75 vestibular and saccade neurons (VSNs) that showed characteristic discharge during pitch rotation. Of these, 50 exhibited gradually increasing activity during upward slow phases and burst of action potentials during downward fast phases induced by downward pitch. The remaining 25 cells showed the opposite response pattern: gradually increasing activity during downward slow phases and a burst during upward fast phases induced by upward pitch. We classified these cells as downward VSNs and upward VSNs, respectively. The effects of electrical stimulation of the contralateral vestibular nerve were tested for 13 downward VSNs and 2 upward VSNs; all of them were activated at short latencies. 2. All vertical VSNs also showed burst activity associated with spontaneous saccades. The preferred direction for the burst was always the same for saccades and vestibular fast phases. The onset of burst activity preceded the onset of fast eye movement by an average of 35 +/- 14 ms (mean +/- SD). During fast eye movement in other directions, many of these cells also showed an inconsistent burst and the burst often began after the onset of saccades. Half of the upward VSNs examined showed a pause in activity during downward fast eye movement. 3. Burst parameters in the preferred directions were correlated with saccade parameters in half of the vertical VSNs examined, although the correlation coefficients were typically 0.5-0.6. 4. All vertical VSNs had irregular resting activity. Half of the downward VSNs examined showed eye-position sensitivity toward the direction opposite to the preferred direction for the burst activity but only if the period of analysis was restricted to discharge shortly before and after saccades. 5. All downward VSNs examined during sinusoidal rotation in several vertical planes received strong excitatory input from the contralateral anterior canal. Three of four upward VSNs examined received contralateral posterior canal excitation; the exception received ipsilateral posterior canal excitation.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1993

Latent herpes simplex virus type 1 in human vestibular ganglia.

Viral infection has been considered to be a possible pathogenesis of vestibular neuronitis, and reactivation of the herpes simplex virus (HSV) is one of the most likely causes. However, it remains unknown whether the human vestibular ganglia contain latent HSV. We examined 26 vestibular ganglia from autopsied adults in search of HSV type 1 (HSV-1). To detect HSV-1, we used polymerase chain reaction (PCR), in situ hybridization and immunohistochemical staining. HSV DNA was detected in 6 of 10 vestibular ganglia using the PCR method. However, the latency-associated transcript (LAT) of HSV-1 was negative in all of the 16 vestibular ganglia examined. No HSV antigen was detected in any of the ganglia. These results indicate that HSV-1 is latently infected in the human vestibular ganglia, and that LAT is transcribed weakly or not at all.

Adult↗
PubMedDate not supplied

[Equilibrium disorders in childhood].

Dizziness and imbalance are uncommon in children, but often alarming for their families. A detailed interview and otoneurological examination are important for reaching a specific diagnosis and treatment. The purpose of our study was to obtain our own etiological, clinical and diagnostic statistics, and to review the major related pathologies. We report a series of 76 children with imbalance or dizziness as the presenting symptom. Paroxysmal benign vertigo of childhood was the most common pathology in our study, followed by vestibular neuronitis. Our findings were compared to those of other authors. Early diagnosis is emphasized as the most important factor for achieving an effective vestibular rehabilitation in children.

Adolescent↗
PubMed1973

The neural signal of angular head position in primary afferent vestibular nerve axons.

1. The relation between discharge frequency and angular head position was determined for a population of regularly discharging single first-order vestibular neurones in the eighth nerve of the barbiturate anaesthetized cat.2. Each axon had a characteristic head position which was maximally excitatory to it, and a diametrically opposed head position which was minimally excitatory.3. After correction for phase shifts introduced by the orientation of preferred excitability, discharge rate in statoreceptor afferents varied as a power function of the sine of angular head position with exponents ranging from 0.9 to 1.6.4. Experimentally determined discharge rates were compared with the predictions of a computer simulation model incorporating the idea that shearing force acting on morphologically polarized receptors is the adequate stimulus for macular receptor cells.5. This approach permitted the identification of a population of first-order vestibular afferents whose discharge frequency varied with head position as did the magnitude of shear force computed for individual receptors, each most excited in a particular head position.6. The majority of the spatial orientations of maximal sensitivity defined a surface which is tilted by approximately 30 degrees with reference to the Horsley-Clarke horizontal plane, implying that most statoreceptor afferents are maximally sensitive to position changes when the cat's head is at or near its normal position.

Action Potentials↗
PubMed1994

Surgery for non-Menière's vertigo.

Neurootologists are fortunate in having a considerable number of surgical options available to them for the treatment of patients with disabling vertigo. Most surgery for vertigo is performed on patients suffering from the ravages of Meniere's disease. In addition, other forms of disabling peripheral vertigo may also be surgically managed. Over a 3 year period, the author performed surgery on 14 patients suffering from disabling non-Meniere's vertigo. During the same period, 60 patients with Meniere's disease underwent surgical treatment. There were three non-Meniere's conditions for which surgery was performed: chronic vestibular neuronitis, delayed onset vertigo (after sensorineural hearing loss), and labyrinthine injury following temporal bone fracture. Two surgical operations were utilized: transmastoid labyrinthectomy and selective vestibular neurectomy. At 1 year follow-up all of the patients involved in this study enjoyed either total relief of symptoms or marked improvement, demonstrating that satisfactory surgical results can be obtained for non-Meniere's vertigo. However, surgeons must exercise extreme caution in selecting non-Meniere's patients for surgery. Moreover, proper patient selection, accurate diagnosis and the exclusion of central disease are crucial in obtaining good surgical results.

Ear, Inner↗
PubMed1990

Expression of neurofilament proteins in the vestibular ganglion cells of the rat.

Vestibular neurons from adult rats were studied by immunofluorescence microscopy using ten polyclonal and monoclonal antibodies reacting with different subunits of neurofilament (NF) polypeptides. Most antibodies strongly immunolabeled axons and dendrites. With the majority of antibodies the vestibular ganglion cells showed two distinct subpopulations: those with intense immunoreactivity and those without it. The intensely immunoreactive somata, staining with anti-70 kDa and anti-200 kDa NF antibodies but not with anti-150 kDa NF antibodies, comprised 32% of the ganglion cells (range: 27-40%). These cells were larger than the weakly immunoreactive majority of cells. Comparisons of adjacent sections revealed that at least a part of the distinctly immunostained cells were the same regardless of the antibody used. Thus, about one-third of the vestibular ganglion cells seem to form a subpopulation containing 200 kDa and 70 kDa subunits of NF polypeptides. Similar compositions of NF subunits have been demonstrated in such cells as the large dorsal root ganglion cells. The high percentage of neuronal somata with phosphorylated subunits of NF polypeptides demonstrated in this study is exceptional in other normal neurons and has been demonstrated only in experimental models and disease states.

Animals↗
PubMed2000

Co-localization of NMDA receptors and AMPA receptors in neurons of the vestibular nuclei of rats.

We are interested in studying the co-localization of NMDA glutamate receptor subunits (NR1, NR2A/B) and AMPA glutamate receptor subunits (GluR1, GluR2, GluR2/3 and GluR4) in individual neurons of the rat vestibular nuclei. Immunoreactivity for NR1, NR2A/B, GluR1, GluR2, GluR2/3 and GluR4 was found in the somata and dendrites of neurons in the four major subdivisions (superior, medial, lateral, and spinal vestibular nuclei) and in two minor groups (groups x and y) of the vestibular nuclei. Double immunofluorescence showed that all the NR1-containing neurons exhibited NR2A/B immunoreactivity, indicating that native NMDA receptors are composed of NR1 and NR2A/B in a hetero-oligomeric configuration. Co-expression of NMDA receptor subunits and AMPA receptor subunits was demonstrated by double labeling of NR1/GluR1, NR1/GluR2/3, NR1/GluR4 and NR2A/B/GluR2 in individual vestibular nuclear neurons. All NR1-containing neurons expressed GluR2/3 immunoreactivity, and all NR2A/B-containing neurons expressed GluR2 immunoreactivity. However, only about 52% of NR1-immunoreactive neurons exhibited GluR1 immunoreactivity and 46% of NR1-containing neurons showed GluR4 immunoreactivity. The present data reveal that NMDA receptors are co-localized with variants of AMPA receptors in a large proportion of vestibular nuclear neurons. These results suggest that cross-modulation between NMDA receptors and AMPA receptors may occur in individual neurons of the vestibular nuclei during glutamate-mediated excitatory neurotransmission and may in turn contribute to synaptic plasticity within the vestibular nuclei.

Animals↗
PubMed1994

Monosynaptic and disynaptic connections in the utriculo-ocular reflex arc of the cat.

1. Connections from the utricular (UT) nerve to motoneurons and interneurons in the ipsilateral abducens (AB) nucleus were studied in anesthetized and decerebrated cats. Bipolar electrodes were fixed on the left UT nerve under visual observation. The other branches of the vestibular nerve and the facial nerve were transected in the left inner ear. 2. Stimulation of the UT nerve evoked a small positive-negative (P/N) deflection and a negative (N1) potential in the vestibular nuclei, with mean latencies of 0.56 and 0.84 ms, respectively. In the AB nucleus a small P/N deflection with a mean latency of 0.72 ms was recorded, which was considered as a incoming volley of the UT nerve. 3. Excitatory postsynaptic potentials (EPSPs) were recorded from AB motoneurons with short latencies after UT nerve stimulation. They were classified into two types, M and D. M-type EPSPs, which followed repetitive high-frequency stimuli and were recorded from the majority of AB motoneurons, had latencies ranging from 0.9 to 1.2 ms. Double shocks to the UT nerve evoked EPSPs that had the same latency. It was suggested that the AB motoneurons had monosynaptic connections with the UT nerve. D-type EPSPs, which were recorded from most of the AB motoneurons, had slightly longer latencies ranging from 1.2 to 1.8 ms. They showed temporal facilitation when double shocks were provided to the UT nerve. They did not follow repetitive high-frequency stimuli (< or = 2.5-ms interval). It was suggested that D-type EPSPs were di-synaptically evoked via secondary vestibular neurons. Interneurons in the AB nucleus had the same characteristics as AB motoneurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Abducens Nerve↗
PubMed2001

A systematic review of vertigo in primary care.

The symptom of vertigo is usually managed in primary care without further referral. This review examines the evidence on which general practitioners can base clinical diagnosis and management of this relatively common complaint. Research in this area has in the main been from secondary and tertiary centres and has been of variable quality. Indications are that the conditions that present in general practice are most likely to be benign positional vertigo, acute vestibular neuronitis, and Ménière's disease; however, vascular incidents and neurological causes, such as multiple sclerosis, must be kept in mind. An important practice point is that vestibular sedatives are not recommended on a prolonged basis for any type of vertigo. There is a need for basic epidemiological and clinical management research of vertigo in general practice.

Dizziness↗
PubMed1996

Localization of somatostatin-like immunoreactive neurons in the vestibular ganglion of the rabbit.

The presence of somatostatin-like immunoreactive neurons was examined in the rabbit vestibular ganglion by using immunohistochemical techniques. About 22% (n = 153) of the total ganglion cells (n = 699) examined were somatostatin-immunoreactive and they were diffusely present throughout the ganglion. Majority of the somatostatin-immunoreactive cells were large (long diameter, 23-31 microns, 74%; short diameter, 20-25 microns, 76%) and they had oval or spherical cell bodies with well developed Nissl's body. However, about 78% (n = 546) of the total ganglion cells examined were not immunoreactive to the somatostatin. The presence of the somatostatin-immunoreactive neurons in the vestibular ganglion suggests a possibility that somatostatin may be involved in the modulation of afferent sensory transmission from the vestibular organ of the rabbit.

Animals↗
PubMed1999

Evidence for a microglial reaction within the vestibular and cochlear nuclei following inner ear lesion in the rat.

Following unilateral inner ear lesion, astrocytes undergo hypertrophy in the deafferented vestibular and cochlear nuclei as shown by an increase in the level of glial fibrillary acid. The present study extends our understanding of vestibular and cochlear system plasticity by examining microglial changes in these deafferented nuclei. The microglial reaction was studied 1, 2, 4, 8, 14, 21, 28 and 42 days following the lesion with a monoclonal OX-42 antibody and lectins (Griffonia simplicifolia, B4 isolectin) labelled with horseradish peroxidase or fluorescein. The deafferented nuclei were also examined for apoptotic cells by terminal transferase-mediated nick end labelling of nuclear DNA fragments. In control and sham-operated rats, the distribution of the resting microglial cells was uniform in both the vestibular and cochlear nuclei. In the deafferented vestibular complex, the microglial cells increased in number, became hypertrophied and were distributed in the medial, lateral, superior and inferior vestibular nuclei. Reactive microglial cells were also detected in the ipsilateral cochlear nuclei. Some of the immunostained cells were hypertrophic whereas others presented an ameboid morphology with few short and stout processes. The microglial reaction was confined to the antero- and posteroventral cochlear nuclei. Finally, reactive microglia was also observed in the prepositus hypoglossi ipsilateral to the lesion. The microglial reactions within the prepositus hypoglossi, the vestibular and the cochlear nuclei were detectable as early as one day after the lesion and persisted several weeks in both the vestibular and cochlear nuclei. Apoptotic cells were not detected in the vestibular nuclei at any stage following the lesion. In contrast, terminal deoxynucleotidyl transferase-mediated digoxygenin-11-dUTP nick end labelling-positive cells were first detected in the deafferented cochlear nuclei on the 3rd day following the lesion. They reached an apparent maximum by day 8 and then declined until day 24. Double labelling experiments demonstrate that these cochlear terminal deoxynucleotidyl transferase-mediated digoxygenin-11-dUTP nick end labelling-positive cells were also lectin-positive suggesting that reactive cochlear lectin-positive microglia cells were eliminated by a programmed cell death. Our results establish the two experimental models as reliable tools to understand the role of microglia in adult brain plasticity. The cochlear microglial reaction was probably induced by the degeneration of the acoustic nerve which follows the acoustic ganglion destruction. Interestingly, the same reasoning cannot apply to the vestibular microglial reaction following unilateral labyrinthectomy: the vestibular ganglion was spared and the primary vestibular neurons did not degenerate, at least during the first week following the lesion.

Animals↗
PubMed1991

Cell and molecular anatomy of nicotinic acetylcholine receptor subunits and calcitonin gene-related peptide in the rat vestibular system.

In this report we demonstrate the pattern of calcitonin gene-related peptide (CGRP) mRNA and immunoreactivity in the central and peripheral vestibular system of the rat, using a CGRP cRNA probe and a polyclonal CGRP antiserum. We present evidence that somata in all regions of efferent vestibular neurons contain CGRP based on the correspondence between in situ hybridization (mRNA) and immunohistochemistry (mRNA translation product). CGRP immunohistochemistry (CGRPi) and in situ hybridization confirm that CGRPi axons and terminals present in the vestibular neuroepithelium are efferent in origin. Immunoelectron microscopy revealed an extensive innervation of the afferent vestibular pathway by CGRPi terminals that was not limited to the primary afferent chalice, as previously reported by Tanaka et al. (Brain Res 1989;504:31-5). An efferent neuromodulatory role of CGRP can be inferred from the distribution of terminals found on the primary afferent fibers, and type I and type II hair cells. In addition, we present evidence that nicotinic acetylcholine receptor (nAChR) subunit mRNA is expressed by primary afferent cell bodies. On the basis of these data, a hypothetical molecular mechanism of vestibular efferent modulation of the primary afferent pathway is proposed.

Animals↗
PubMed1995

Spatial orientation in the lamprey. I. Control of pitch and roll

Two major tasks must be fulfilled during locomotion: propulsion and spatial orientation. In the lamprey, the propulsive force is generated by laterally directed body undulations propagated from the rostral to the caudal end of the body. The neuronal networks underlying this basic locomotor pattern have been described in considerable detail. The present study was undertaken to provide the necessary behavioural background for parallel studies of the vestibular neuronal networks responsible for spatial orientation during locomotion. The following results were obtained. 1. The lamprey actively stabilized its pitch angle during swimming and usually kept a linear trajectory in the sagittal plane, despite large changes in the speed of swimming. During repeated tests, a certain preferred pitch angle could be maintained over a period of several minutes, even if the initial starting angle of the animal was changed considerably. 2. Two different strategies were observed for active turning in the downward direction: a smooth turn accomplished by weak ventral flexion of the whole body, and a sharp turn accomplished by localized ventral flexion of a region of the body just posterior to the gills. 3. The lampreys were oriented with the dorsal side up while swimming at any pitch angle. The control systems for pitch and roll can thus operate independently. When swimming, lampreys kept the tail region flexed somewhat ventrally. This body configuration will cause lateral movements of the tail to generate a torque that rotates the body around its longitudinal axis. This mechanism is presumably used to correct deviations from the dorsal-side-up orientation. After amputation of the dorsal and tail fins, lampreys maintained a proper spatial orientation during swimming. 4. After a unilateral labyrinthectomy, swimming lampreys continuously rolled towards the lesioned side. Unilaterally labyrinthectomized animals displayed a tonic twisting of the body into a helical shape. This presumably represents an additional strategy for performing roll turns. Bilaterally labyrinthectomized animals never maintained a linear trajectory in any plane, but turned continuously in all directions.

Journal Article↗
PubMed1982

Location and vestibular responses of interstitial and midbrain reticular neurons that project to the vestibular nuclei in the cat.

Experiments were performed on cats anesthetized with alpha chloralose to locate neurons in and around the interstitial nucleus of Cajal (INC) that project to the vestibular nuclei, and to study labyrinthine inputs to these neurons. Neurons that project to the vestibular nuclei were identified by microstimulation confined to the vestibular nuclei on both sides. All neurons thus identified were activated antidromically from the ipsilateral (but not contralateral) vestibular nuclei. Vestibular projecting neurons were found in the INC and the reticular formation rostral, dorsal and caudal to the INC. About 23% of these neurons were vestibular branching spinal projecting neurons. The median conduction velocity of vestibular projecting neurons was estimated to be in the neighborhood of 12-16 m/s. Stimulation of the contralateral vestibular nerve evoked firing in 29% of neurons projecting to the vestibular nuclei, but not to the spinal cord. Interstitial neurons responded more frequently than reticular neurons (45% vs 11% chi 2 test, p less than 0.001). By stimulation of individual semicircular canal nerves, it was shown that vestibular projecting neurons receive excitation from the contralateral vertical canals, but do not receive substantial inputs from the horizontal canal. Stimulation of the ipsilateral vestibular nerve excited 10% of neurons; suppression of activity was observed for six cells and four of the six were excited by stimulation of the contralateral vestibular nerve. Stimulation of ipsilateral individual semicircular canal nerve did not excite any cells tested; the activity of a few cells was suppressed by stimulation of the vertical canal nerves. One neuron received excitation from the contralateral anterior canal and suppression from the ipsilateral posterior canal. Vestibular branching spinal projecting neurons rarely received labyrinthine inputs as already reported (Fukushima et al. 1980a). These results suggested that vestibular projecting neurons may be involved in vertical vestibular reflexes.U

Action Potentials↗
PubMed1987

Modification of vestibular-induced pause neuron firing during anesthesia and light sleep.

Anatomic and electrophysiologic evidence suggests there is a vestibular input to eye movement-related pause neurons in the midline of the pontine reticular formation of the cat. The present investigation sought to explore the functional significance of this vestibular drive by examining pause neuron response to horizontal rotational stimulation as cats were anesthetized with halothane or went into natural light sleep. Anesthesia unmasks the vestibular input to pause neurons in that during anesthesia, pause neurons continue to fire but their firing rate is modulated by vestibular stimulation. The particular response patterns of pause neurons to anesthesia are not uniform. We suggest that the results observed could be explained if pause neurons received input from both vestibular nuclei, either directly or possibly via the prepositus hypoglossi.

Abducens Nerve↗
PubMed1999

[Orientational evaluation of otolith function by eye counter-rolling in patients with various kinds of vertigo].

BACKGROUND: Measurement of ocular counterrolling (OCR) is well known as a simple method to evaluate the peripheral vestibular organ, especially the otolith organ. But it has rarely been used because of the difficulty in differentiating between pathologically reduced OCR and the wide physiological variation of this parameter. PATIENTS: In this study, the OCR of 55 patients with unclarified vertigo (n = 20), vestibular neuronitis (n = 15), Menière's disease (n = 10), and benign paroxysmal positional nystagmus (n = 10) were evaluated and compared to a control group (n = 30) with the intention of diagnosing peripheral vestibular dysfunction and establishing a differential diagnosis. The test sequence was carried out with Vesta goggles by Panares and included head tilts of 5 degrees, 15 degrees, and 30 degrees to the left and right. RESULTS: The results show a significantly reduced OCR in patients suffering from peripheral vestibular disorders when compared to the control group. CONCLUSION: There is no specific finding for a specific type of vestibular lesion, but otolith function is affected in several disorders as measured by ocular counterrolling.

Adult↗
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↗