Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Vestibular Neuronitis”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 631 records · Page 35Linked to original sources
PubMed1997

Efferent neurons and vestibular cross talk in the frog.

A galvanic stimulus (30- to 120-s, 0.3-mA constant current pulse) was used to depolarize the spike-generating region of horizontal and anterior canal afferent neurons. The galvanically induced spike activity from these neurons served as a driving input to the efferent vestibular system in the bullfrog. Efferent-mediated effects were assessed by intracellular recordings of posterior canal afferent spike activity, either ipsilateral or contralateral to the driving stimulus. Ipsilateral to the driving stimulus, efferent-mediated spike rate changes occurred in 62 (39%) of 158 posterior canal afferent neurons. Ipsilateral efferent-mediated effects were overwhelmingly excitatory (92%). Of responding units, 3% were inhibited during stimulus application and 5% showed mixed responses involving 3-20 s of inhibition followed by facilitation. Contralateral to the driving stimulus, efferent-mediated spike rate changes occurred in 18 (23%) of 77 posterior canal afferent neurons. Contralateral efferent-mediated effects were overwhelmingly inhibitory (95%). Only one unit was facilitated during stimulation and no mixed responses to contralateral stimulation were observed. Analysis of the coefficient of variation in interspike intervals (CV) before and during stimulation showed no significant efferent-mediated effects on spike train noise. Comparisons of resting spike rates between units showing efferent-mediated effects and those that did not were in general agreement with previous studies. Responding units had a lower mean spike rate (6.8 +/- 0.70 spikes/s, mean +/- SE) than did nonresponding units (10.7 +/- 0.42 spikes/s, mean +/- SE; P < 0.001; 2-tailed t-test of log-normalized data). Comparison between groups in the regularity of their resting spike rates, as quantified by CV, showed considerable overlap. When responding and nonresponding units with similar resting spike rates were compared, responding units had more irregular resting spike rates than did nonresponding units (P < 0.004; 2-tailed, paired t-test). In most cases (77%) the temporal pattern and general shapes of efferent-mediated responses mirrored the driving input of the galvanically activated afferent neurons. The other 23% of efferent-mediated responses exhibited a marked adaptation of the response. Adapting and nonadapting units were not significantly different in their mean resting spike rates or in the regularity of their resting spike rates.

Animals↗
PubMed2001

The neurophysiological substrate for the cervico-ocular reflex in the squirrel monkey.

Passive rotation of the trunk with respect to the head evoked cervico-ocular reflex (COR) eye movements in squirrel monkeys. The amplitude of the reflex varied both within and between animals, but the eye movements were always in the same direction as trunk rotation. In the dark, the COR typically had a gain of 0.3-0.4. When animals fixated earth-stationary targets during low-frequency passive neck rotation or actively tracked moving visual targets with head movements, the COR was suppressed. The COR and vestibulo-ocular reflex (VOR) summed during passive head-on-trunk rotation producing compensatory eye movements whose gain was greater than 1.0. The firing behavior of VOR-related vestibular neurons and cerebellar flocculus Purkinje cells was studied during the COR. Passive neck rotation produced changes in firing rate related to neck position and/or neck velocity in both position-vestibular-pause neurons and eye-head-vestibular neurons, although the latter neurons were much more sensitive to the COR than the former. The neck rotation signals were reduced or reversed in direction when the COR was suppressed. Flocculus Purkinje cells were relatively insensitive to COR eye movements. However, when the COR was suppressed, their firing rate was modulated by neck rotation. These neck rotation signals summed with ocular pursuit signals when the head was used to pursue targets. We suggest that the neural substrate that produces the COR includes central VOR pathways, and that the flocculus plays an important role in suppressing the reflex when it would cause relative movement of a visual target on the retina.

Action Potentials↗
PubMed1981

[The vestibular nuclei as the integration center of central and peripheral afferent projections].

Responses of individual vestibular units were recorded in cat following electrical stimulation of the cerebral cortex and peripheral nerves. Convergence of central and peripheral inputs were recorded from 28 out of 75 cells (37%), localized in the lateral vestibular nucleus. The most important inputs to vestibular neurons come from the areas of sensorimotor cortex and peripheral nerves concerned with the same limb. However, crossed effects were observed in a limited number of vestibular neurons.

Animals↗
PubMed2001

Dynamic locomotor function in normals and patients with vertigo.

Gait analysis was performed in patients with various vestibular systems using a tactile sensor. There were 4 patients with vestibular neuronitis, 6 patients with large acoustic neuroma and 6 patients with spino-cerebellar degeneration (SCD). Gait phase related parameters such as stance, swing and double support were studied to assess gait stability. Also the area ratio of trajectories of center of force during stance and progression of foot pressure were checked. The calculated value of each variable became high in pathological cases compared with normal controls, and the highest value was obtained in the SCD group. As regards the effect of visual deprivation on stability of gait, the most striking change was found in the large acoustic neuroma group. In a case with a unilateral lesion such as vestibular neuronitis and large acoustic neuroma, foot pressure was greater on the lesion side, especially during gait with eyes closed. As for the foot pressure progression curve, the SCD group showed the most irregular pattern in general, although there were some individual variations. Those results could reflect a functional disorder of the gait control system caused by each disease. Significance of gait analysis is also discussed.

Adult↗
PubMed1997

Effects of newly developed excitatory amino acid antagonists on vestibular type I neurons in the cat.

A newly synthesized compound NC-1200 (oxazolidinone) has been shown to have a powerful inhibitory action on the glutamate response at the neuromuscular junction in crayfish where glutamate is thought to be an excitatory neurotransmitter. However, the pharmacological function of NC-1200 in the CNS of mammals remains unknown. We examined the glutamate blocking action of NC-1200 on various glutamate receptors of cat's vestibular neurons. The effects of NC-1200 on secondary vestibular neurons were studied by intra-venous (3-5 mg/kg) and iontophoretic application using multi-barreled electrodes filled with NMDA, kainic acid and NC-1200 in decerebrated cats. After identification of type 1 neurons, the chemicals were applied to examine their effects on neuronal activity. The results were as follows; i) Systemic application of NC-1200 suppressed type 1 responses to yaw rotation; ii) both NMDA-mediated and kainate-mediated excitations on the vestibular neurons were abolished by application of NC-1200; iii) the suppression of various glutamic receptors was dose-dependent; and iv) the kainate receptor was more strongly suppressed than the NMDA receptor by NC-1200.

Animals↗
PubMed1990

Secondary vestibulocerebellar projections to the flocculus and uvulo-nodular lobule of the rabbit: a study using HRP and double fluorescent tracer techniques.

The distribution of vestibular neurons projecting to the flocculus and the nodulus and uvula of the caudal vermis (Larsell's lobules X and IX) was investigated with retrograde axonal transport of horseradish peroxidase and the fluorescent tracers Fast Blue, Nuclear Yellow and Diamindino Yellow. The presence of collateral axons innervating the flocculus on one hand and the nodulus and uvula on the other was studied with simultaneous injection of the different fluorescent racers. The distribution of vestibular neurons projecting to either flocculus or caudal vermis is rather similar and has a bilateral symmetry. The projection from the magnocellular medial vestibular nucleus is very sparse, while that from the lateral vestibular nucleus is absent. The majority of labeled neurons was found in the medial, superior, and descending vestibular nuclei, in that order. Double labeled neurons were distributed in a similar way as the single labeled ones. Labeled neurons project to the nodulus and uvula, the flocculus, and to both parts of the cerebellum simultaneously in a ratio of 12:4:1. Five different populations of vestibulocerebellar neurons can be distinguished on the basis of their projection to the: (1) ipsilateral flocculus, (2) contralateral flocculus, (3) ipsilateral flocculus and nodulus/uvula, (4) contralateral flocculus and nodulus/uvula, and (5) nodulus/uvula.

Animals↗
PubMed1989

[MR imaging of the inner ear; findings of Ménière's syndrome].

Symptoms in Ménière's disease are explained by hydrops of endolymphatic system with recurrent ruptures of the membranous labyrinth. The primary cause of the increased endolymphatic volume appears to be an imbalance between secretion and resorption of endolymph which may be due to an obstruction of the endolymphatic duct and sac, located in the vestibular aqueduct. Non-visualization or narrowing of the vestibular aqueduct of the paper have been demonstrated by conventional tomography and high resolution computed tomography (HR-CT). But the endolymphatic duct and sac can not be obtained by HR-CT and conventional tomography. Whereas, on MRI, these are identified. By MRI, we prospectively tried to demonstrate morphological alterations in 10 patients with Ménière's disease and in 4 patients with vestibular neuronitis. These were compared with a group of 20 normal men. Visualization of the endolymphatic duct and sac (vestibular aqueduct) on MRI was assessed. There was a distinctly decreased visualization of the vestibular aqueduct in the Ménière group and vestibular neuronitis group. We were able to confirm a statistically proven usefulness of the MRI technique in identifying an anatomical abnormality which is directly in correlation with the side of the lesion in cases of unilateral Ménière's disease.

Adult↗
PubMed2001

Otolith-activated vestibulothalamic neurons in cats.

The components of the vestibular ascending pathway that transmit otolith information to the thalamus were studied electrophysiologically in anesthetized cats. Thalamic-projecting vestibular neurons (confirmed antidromically) were recorded extracellularly in the various vestibular nuclei. Otolith inputs to these neurons were examined with selective stimulation of the utricular (UT) or the saccular (SAC) nerves. Vestibular nerve branches other than the tested nerve were transected. Of 40 UT-activated vestibulothalamic neurons, 40% (16/40) were activated by UT nerve stimulation with latencies ranging between 0.9-1.4 ms, suggesting they were second-order neurons from the UT nerve. UT-activated vestibulothalamic neurons were recorded in the medial vestibular nucleus (MVN; 24/40), the lateral vestibular nucleus (LVN; 9/40), the descending vestibular nucleus (DVN; 6/40), and the superior vestibular nucleus (SVN; 1/40). Most of the neurons (38/40) were antidromically activated by focal stimulation of the ventral part of the ipsilateral thalamus. Antidromic stimulation of the pontine area revealed that trajectories of the ascending axons (14 of 38 neurons) to the ipsilateral thalamus passed through the pontine reticular formation, ventral to the ascending tract of Deiters (ATD) and the medial longitudinal fasciculus (MLF). Only three SAC-activated vestibulothalamic neurons were encountered in the LVN. All these neurons were second-order neurons from the SAC nerve and were antidromically activated by stimulation of the contralateral thalamus, in marked contrast to the UT-activated vestibulothalamic neurons. Only three UT-activated and two SAC-activated neurons sent descending collaterals to the spinal cord.

Action Potentials↗
PubMedDate not supplied

The origin of efferent vestibular fibres in the guinea pig. A horseradish peroxidase study.

The origin of efferent vestibular neurons was determined in the guinea pig by means of retrograde axonal transport of horseradish peroxidase. After injection of a horseradish peroxidase solution into the ampulla of the horizontal and anterior semicircular canal, efferent vestibular neurons labelled by the granular reaction product were found in the medulla oblongata bilaterally at two locations. The first is lateral to the genu of the facial nerve. It has a bilateral and symmetric origin. The second is the nucleus reticularis pontis caudalis. Here there were more labelled neurons contralateral to the injection site.

Animals↗
PubMed1990

Cervical afferent pathway to inferior oblique motoneuron in the cat.

The neuronal pathway implicated in the vertical cervico-ocular reflex (COR) was investigated electrophysiologically in chloralose anesthetized cats. The effect of bilateral C2 dorsal root afferent stimulation on inferior oblique motoneurons (IO-MN) was investigated by intracellular recording. Control disynaptic excitatory postsynaptic potentials elicited in IO-MNs following stimulation of the contralateral anterior semicircular canal nerve (ACN) were invariably facilitated by conditioning stimulation to both ipsilateral and contralateral C2 dorsal roots (DR) in all motoneurons tested. This result indicates that inputs from the C2 DR of both sides and the contralateral ACN converge onto secondary vestibular neurons ('common interneurons') which project directly to the IO-MN. Common interneurons mediating vestibular and cervical excitation to the IO-MNs were studied in the vestibular nuclei on the side opposite to the motoneurons by extracellular recording. Nineteen vestibular neurons were identified as common interneurons; they were distributed in the caudal half of the lateral nucleus and the rostral half of the descending nucleus. The present experiment provides electrophysiological evidence of the projection of upper cervical afferents to the ipsilateral vestibular nuclei. The difference in neuronal organization between the horizontal and vertical COR is also briefly discussed.

Action Potentials↗