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PubMed2005

Spatial properties of central vestibular neurons.

We studied the spatial characteristics of 45 vestibular-only (VO) and 12 vestibular-plus-saccade (VPS) neurons in two cynomolgus monkeys using angular rotation and static tilt. The purpose was to determine the contribution of canal and otolith-related inputs to central vestibular neurons whose activity is associated with the central velocity storage integrator. Lateral canal-related neurons responded maximally during vertical axis rotation when the head was tilted 25 +/- 6 and 22 +/- 3 degrees forward relative to the axis of rotation in the two animals, and vertical canal-related neurons responded maximally with the head tilted back 63+/- 5 and 57 +/- 7 degrees . The origin of the vertical canal-related input was verified by rotation about a spatial horizontal axis. Thirty-one percent of cells received input in a single canal plane. Sixty-seven percent of canal-related cells received otolith input, 31% of vertical canal neurons had lateral canal input, and 43% of lateral canal neurons had vertical canal input. Twenty percent of neurons had convergent input from the lateral canals, the vertical canals, and the otolith organs. Some VO and VPS cells had spatial-temporal convergent (STC) properties; more of these cells had STC properties at lower frequencies of rotation. Thus VO and VPS neurons associated with velocity storage receive a broad range of convergent inputs from each portion of the vestibular labyrinth. This convergence could provide the basis for gravity-dependent eye velocity orientation induced through velocity storage.

Acceleration↗
PubMed1980

Response of central vestibular neurons to utricular stimulations in cats.

In decerebrated, spinal transected cats with neck and forelimbs immobilized by plaster cats, the visual and proprioceptive cues were minimized when the animal was tilted. The contralateral labyrinth was acutely destroyed. The ipsilateral semicircular canals were plugged and the ipsilateral saccule extirpated leaving the ipsilateral utricle intact. Neurons in the vestibular nuclear complex driven by electrical stimulation of the utricle were shown to be highly sensitive to static pitch. Results suggest that the observed response to static pitch was due exclusively to input from the utricle.

Animals↗
PubMed2003

Receptors of glutamate and neurotrophin in vestibular neuronal functions.

The last decade has witnessed advances in understanding the roles of receptors of neurotrophin and glutamate in the vestibular system. In the first section of this review, the biological actions of neurotrophins and their receptors in the peripheral and central vestibular systems are summarized. Emphasis will be placed on the roles of neurotrophins in developmental plasticity and in the maintenance of vestibular function in the adult animal. This is reviewed in relation to the developmental expression pattern of neurotrophins and their receptors within the vestibular nuclei. The second part is focused on the functional role of different glutamate receptors on central vestibular neurons. The developmental expression pattern of glutamate receptor subunits within the vestibular nuclei is reviewed in relation to the potential role of glutamate receptors in regulating the development of vestibular function.

Animals↗
PubMed1982

Relationship of cat vestibular neurons to otolith-spinal reflexes.

The dynamics of neurons in the vestibular nuclei of canal-plugged, decerebrate cats were studied in response to lateral (roll) tilt. Forelimb and neck extensor reflexes recorded simultaneously develop a progressive phase lag above 0.1 Hz. Neurons which exhibited a muscle-like phase lag were excited during low frequency stimuli by ipsilateral side-up tilt (beta response). Neurons with alpha responses, excited during side-down tilt, exhibited a constant phase, without a high frequency lag. Vestibulospinal neurons were present in both of these response groups, as were units driven at monosynaptic latencies by electrical stimulation of the ipsilateral labyrinth. The phase-lagging beta responses are appropriate for contributing to the reflexes observed in the ipsilateral neck and contralateral forelimb.

Animals↗
PubMed1988

Axonal trajectories of posterior canal-activated secondary vestibular neurons and their coactivation of extraocular and neck flexor motoneurons in the cat.

Unit activities of 148 secondary vestibular neurons related to the posterior semicircular canal were recorded extracellularly in anesthetized cats. Axonal projections of these neurons were examined by their antidromic responses to stimulation of the excitatory target motoneurons of the contralateral (c-) inferior rectus muscle (IR) and bilateral (bi-) motoneuron pools of longus capitis muscles, neck flexors, in the C1 segment (C1LC). The neurons were classified into 4 groups according to their axonal projections. The first group of neurons, termed vestibulo-oculo-collic (VOC) neurons, sent axon collaterals both to the c-IR motoneuron pool and to the c-C1LC motoneuron pool. The majority of them (72%) were located in the descending nucleus. The second group of neurons were termed vestibuloocular (VO) neurons and sent their axons to the c-IR motoneuron pool but not to the cervical cord. Most of them (86%) were located in the medial nucleus. The third group of neurons, termed vestibulo-collic (contralateral) (VCc) neurons, sent axons to the c-C1LC motoneuron pool via the contralateral ventral funiculus but not to the oculomotor nuclei. They were mostly (75%) found in the descending nucleus. The last group of neurons were vestibulo-collic (ipsilateral) (VCi) neurons, which gave off axons to the ipsilateral (i-) C1LC motoneuron pool via the ipsilateral ventral funiculus but not to the oculomotor nuclei. One of them also sent an axon collateral to the c-C1LC motoneuron pool. The majority of them (74%) were located in the ventral part of the lateral nucleus. It was also observed in some of the VOC and VCi neurons that they produced unitary EPSPs in the c-C1LC and i-C1LC motoneurons, respectively. Their synaptic sites were estimated to be on the cell somata and/or proximal dendrites of the motoneurons.

Animals↗
PubMed1988

Response of vestibular neurons to head rotations in vertical planes. II. Response to neck stimulation and vestibular-neck interaction.

1. We have studied the responses of neurons in the lateral and descending vestibular nuclei of decerebrate cats to stimulation of neck receptors, produced by rotating the body in vertical planes with the head stationary. The responses to such neck stimulation were compared with the responses to vestibular stimulation produced by whole-body tilt, described in the preceding paper. 2. After determining the optimal vertical plane of neck rotation (response vector orientation), the dynamics of the neck response were studied over a frequency range of 0.02-1 Hz. The majority of the neurons were excited by neck rotations that brought the chin toward the ipsilateral side; most neurons responded better to roll than to pitch rotations. The typical neck response showed a low-frequency phase lead of 30 degrees, increasing to 60 degrees at higher frequencies, and a gain that increased about threefold per decade. 3. Neck input was found in about one-half of the vestibular-responsive neurons tested with vertical rotations. The presence of a neck response was correlated with the predominant vestibular input to these neurons; neck input was most prevalent on neurons with vestibular vector orientations near roll and receiving convergent vestibular input, either input from both ipsilateral vertical semicircular canals, or from canals plus the otolith organs. 4. Neurons with both vestibular and neck responses tend to have the respective orientation vectors pointing in opposite directions, i.e., a head tilt that produces an excitatory vestibular response would produce an inhibitory neck response. In addition, the gain components of these responses were similar. These results suggest that during head movements on a stationary body, these opposing neck and vestibular inputs will cancel each other. 5. Cancellation was observed in 12 out of 27 neurons tested with head rotation in the mid-frequency range. For most of the remaining neurons, the response to such a combined stimulus was greatly attenuated: the vestibular and neck interaction was largely antagonistic. 6. Neck response dynamics were similar to those of the vestibular input in many neurons, permitting cancellation to take place over a wide range of stimulus frequencies. Another pattern of interaction, observed in some neurons with canal input, produced responses to head rotation that had a relatively constant gain and remained in phase with position over the entire frequency range; such neurons possibly code head position in space.

Animals↗
PubMed1990

Vestibular neurones in the parieto-insular cortex of monkeys (Macaca fascicularis): visual and neck receptor responses.

1. One hundred and fifty-two vestibularly activated neurones were recorded in the parieto-insular vestibular cortex (PIVC) of four awake Java monkeys (Macaca fascicularis): sixty-two were tested systematically with visual stimulation and seventy-nine were tested with various somatosensory stimuli. With very few exceptions all vestibular neurones tested responded to visual and somatosensory stimulation, therefore being classified as polymodal vestibular units. 2. A most effective stimulus for all fifty-eight visually activated PIVC units was movement of a large structured visual pattern in an optimal direction. From forty-four units responsive to a horizontally moving optokinetic striped drum, twenty-nine were activated with optokinetic movement in the opposite direction to the activating vestibular stimulus ('synergistic' response), thirteen were activated optokinetically and vestibularly in the same direction ('antagonistic' responses) and two were biphasic. The gain of the optokinetic response to sinusoidal stimulation (average 0.28 (impulses s-1) (deg s-1)-1 at 0.2 Hz, 56 deg amplitude) was in a range similar to that of the vestibular gain at low frequencies. At 1 Hz some units only showed weak optokinetic responses or none at all, but the vestibular response was still strong. 3. With different 'conflicting' or 'enhancing' combinations of optokinetic and vestibular stimulation no generalized type of interaction was observed, but the responses varied from nearly 'algebraic' summation to no discernible changes in the vestibular responses by additional optokinetic stimuli. With all visual-vestibular stimulus combinations the responses to the vestibular stimulus remained dominant. 4. The optokinetic preferred direction was not related to gravitational coordinates since the optokinetic responses were related to the head co-ordinates and remained constant with respect to the head co-ordinates at different angles of steady tilt. 5. Almost all PIVC units were activated by somatosensory stimulation, whereby mainly pressure and/or movement of neck and shoulders (bilateral) and movement of the arm joints elicited vigorous responses. Fewer neurones were activated by lightly touching shoulders/arms or neck, by vibration and/or pressure to the vertebrae, pelvis and legs. 6. A most effective somatosensory stimulus was sinewave rotation of the body with head stationary. The gain of this directionally selective neck receptor response was in the range of vestibular stimulation. Interaction of vestibular and neck receptor stimulation was either of a cancellation or facilitation type.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMedDate not supplied

Responses of squirrel monkey vestibular neurons to audio-frequency sound and head vibration.

A study was made of the response of peripheral vestibular neurons in the squirrel monkey to head vibration and air-borne sound in the frequency range from 50-4 00 Hz. Responses were measured in terms of the phase locking of discharge and changes in firing rate. The lowest phase-locking thresholds for vibration were -70 to -80 dB re 1 g, and median values in the most sensitive frequency range (200-400 Hz) were -20 to -40 dB re 1 g; the minimum and median thresholds for sound were 76 and 120-130 dB SPL, respectively. Rate-change thresholds were 10-30 dB above phase-locking thresholds. The squirrel monkey sacculus has no special sensitivity to vibration in comparison with the other vestibular end-organs; the median phase-locking threshold to sound of saccular neurons exceeded 100 dB SPL. Irregularly discharging neurons are more sensitive than regularly discharging units. Evidence is presented that the response to intense sound involves a hair-cell mechanism.

Acoustic Stimulation↗
PubMed2005

Herpes encephalitis preceded by ipsilateral vestibular neuronitis.

A 74-year-old woman developed vertigo and jerk nystagmus to the left with normal cerebral imaging. Three days later she developed fever, altered mental state and left medial temporal lobe hypodensity, confirmed on lumbar puncture to be due to herpes simplex type 1 encephalitis. We propose that the patient had vestibular neuronitis caused by HSV-1 that progressed to ipsilateral temporal lobe encephalitis.

Aged↗
PubMedDate not supplied

Efferent vestibular neurons. Electrophysiological evidence for axon collateralization to cristae ampullares in the pigeon (Columba livia).

Extracellular spikes were recorded under general anaesthesia from the cell bodies of efferent vestibular neurons located in the caudal pontine reticular nucleus of the pigeon. Discrete electrical stimuli, applied directly to the three ampullary nerve branches in one labyrinth and to the anterior ramus of the vestibular nerve trunk in the other labyrinth, evoked antidromic spikes which served to identify efferent neurons. Most cells could be antidromically driven only by stimuli to the vestibular nerve trunk (anterior ramus). The majority of cells exhibiting direct axonal connections to one individual semicircular canal crista ampullaris showed axon collateralization to one or two other cristae as well. Sixty percent of the efferent neurons responded with antidromic spikes to ipsilateral labyrinthine stimuli, 34% to contralateral stimuli, and 6% to both. Synaptic activation was observed in a few efferent and adjacent unidentified neurons. It is concluded that efferent neurons often send collaterals to various cristae in one labyrinth, and less frequently, to both labyrinths. Such projections are incompatible with the assumption that vestibular efferents provide a simple control mechanism which is related to the direction of head movement.

Animals↗
PubMed1991

Distribution of the vestibular neurons projecting to the oculomotor and trochlear nuclei in rabbits.

Horseradish peroxidase and Fast Blue were injected into the oculomotor and trochlear nuclei of rabbits so as to study the distribution of vestibular neurons that project to these nuclei. After the oculomotor nucleus was injected, labelled neurons were found in the superior, medial, and descending vestibular nuclei as well as in cell group Y. In the superior nucleus, most of the neurons (510 +/- 46) were ipsilateral to the injection, although contralaterally labelled neurons were also observed (104 +/- 19) more peripherally. In cell group Y, 186 +/- 24 contralaterally labelled neurons were observed, whereas hardly any (8 +/- 3) were found on the ipsilateral side. The largest group of labelled neurons (811 +/- 65) constituted a neuronal band located contralaterally in the medial nucleus and rostral part of the descending nucleus. This band rostromedially continued with the caudal part of the group of internuclear neurons of the abducens nucleus. Only 190 +/- 31 neurons were labelled in the medial and descending nucleus ipsilateral to the injected oculomotor nucleus. After injection of the trochlear nucleus, labelled neurons were found in the ipsilateral superior nucleus and contralateral medial and descending nuclei: a few labelled cells were also observed in the ipsilateral medial and descending nuclei as well as in the contralateral cell group Y.

Abducens Nerve↗
PubMed1995

Comparative study on gait abnormality in patients with vestibular neuronitis and patients with large acoustic neuroma.

A comparative study on gait analysis comprising 11 patients with vestibular neuronitis and 10 patients with large acoustic neuroma was undertaken by the use of foot switches and electromyography. Central disorders in the neuroma group were evidenced by neurotological examinations. Fourteen healthy adults served as controls. Variables employed for the analysis were time from heel strike to forefoot strike (HA-I), time from heel off to forefoot off (HA-II) as well as duration of stance, swing and double supports (DS), location of maximum contraction of the gastrocnemius during stance, and location of the first and second peak of muscle contraction of the tibialis anterior from early swing phase (TA-off) to early stance phase (TA-on). The occurrence rate of abnormality of HA-I was the highest in both groups and most of the variables showed a higher rate in the large acoustic neuroma cases. In addition, a significantly higher CV value was obtained in HA-II of the lesion side's foot in the AN group. These changes could reflect the pathophysiological difference in the gait control systems between the two groups.

Adolescent↗
PubMed1996

An in vitro investigation of the effects of the ACTH/MSH(4-9) analogue, Org 2766, on guinea pig medial vestibular nucleus neurons.

Vestibular compensation is a process of CNS plasticity that is correlated to a return of resting activity in medial vestibular nucleus (MVN) neurons ipsilateral to a peripheral vestibular deafferentation. Systemic administration of melanocortin peptides accelerates the compensation process; the ACTH/MSH(4-9) analogue, Org 2766, accelerates this process at smaller doses than ACTH/MSH(4-10). The present study investigated the effect of Org 2766 on MVN neurons in vitro using extracellular single-cell recording. Org 2766 was less potent at the neuronal level than ACTH/MSH(4-10). When Org 2766 and ACTH/MSH (4-10) were tested consecutively on the same neuron, the response was often different. Org 2766 and ACTH/MSH (4-10) may have a different mode and/or site of action.

Adrenocorticotropic Hormone↗
PubMed1996

Basic fibroblast growth factor (FGF-2) affects development of acoustico-vestibular neurons in the chick embryo brain in vitro.

The effects of basic fibroblast growth factor (FGF-2) on presumptive auditory and vestibular neurons from the medulla were studied in primary cell cultures. The part of the rhombic lip that forms nucleus magnocellularis (homologue of the mammalian anteroventral cochlear nucleus) was explanted from white leghorn chicken embryos at Hamburger-Hamilton stage 28 (E5.5), the time when precursors of the magnocellularis bushy cells migrate and begin to differentiate in situ. In vitro the neuroblasts migrated onto 2-D substrates of purified collagen, differentiated, and expressed neuronal markers. One-half of the cultures were supplemented with human recombinant FGF-2 (10 ng/ml daily) for 5-7 days; the others, with fetal bovine serum. FGF-2 more than doubled the length of neurite outgrowth during the first 3 day treatment compared to serum, but the number of migrating neuroblasts was unaffected. Although neurites attained greater lengths in FGF-2, they usually degenerated after 4-5 days; in serum their growth continued for several weeks. Differentiation of neuronal structure, including axons and dendrites, began within 1-2 days in bFGF but required at least 5-7 days in serum. Histochemical observations in vitro and in situ with antibodies to FGF receptor demonstrated immunopositive patches on acoustico-vestibular neuroblasts at stage 28, when they are migrating and first forming their axons. The findings suggest that FGF-2 stimulates neurite outgrowth in the cochlear and vestibular nuclei. FGF-2 may accelerate cell death by overstimulating neuroblasts, but other factors are needed to sustain their further development.

Analysis of Variance↗
PubMed1985

Vestibular neuronitis: neurotological findings and progress.

Neurotological follow-up observations were conducted on 38 of 43 cases of vestibular neuronitis treated between 1972 and 1983. The average observation period was 1 year and 3 months (range from 1 month to 9 years and 4 months) and 17 cases were followed for more than 1 year. The tests used for evaluation in this series were the following: spontaneous nystagmus, head positional nystagmus, a caloric test and a computed galvanic body sway test (GBST) conducted by Yamaguchi University. Changes in subjective symptoms are also noted. The main subjective complaint was vertigo (whirling; 93%). The remaining subjects noticed a floating sensation and unsteadiness of gait. In 50% of the cases, vertigo subsided by the end of the 3-month period, but 6 subjects suffered from an intractable dizzy sensation for over 1 year. Even after 3 years, 3 of these 6 cases were bothered by dizzy sensations. Especially in the central lesion, these 3 subjects had no other causative disease. Spontaneous nystagmus, which was usually horizontal and direction fixed, remained in 50% of the cases after the 1-year period. All of the cases tested showed reduced caloric responses. 21 of the 38 cases showed no response in cold caloric stimulation (including ice water) at the initial test. 13 of the 21 cases were followed satisfactorily and examined twice or more by caloric testing. 5 of these 13 cases did not recover in the caloric test even after more than 1 year.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1980

Responses to step and repeated impulse accelerations in second order vestibular neurons of the cat.

The characteristics of response of 98 vestibular nuclei neurons were investigated in the barbiturate anesthetized cat. All type I and type II neurons (tonic and kinetic) responded to stimulation of the horizontal canals with step and impulse accelerations. Seventy-seven (79 per cent) neurons of all types demonstrated adaptation, while the remaining 21 (21 per cent) neurons showed either reverse adaptation or no adaptation. When the interval between impulses with impulse accelerations reached a critical minimum, the averaged response was remarkably like the response to step acceleration, including the rate of adaptation. A previously undescribed response decline to repetitive impulse acceleration was seen, which, while sharing some characteristics with habituation, appears to be more closely related to adaptation. Furthermore, the data suggest that adaptation seen at the vestibular nuclear level is more likely a central phenomenon rather than a peripheral one.

Acceleration↗
PubMed1987

Evidence for N-methyl-D-aspartic acid receptor-mediated modulation of the commissural input to central vestibular neurons of the frog.

We have investigated the role of N-methyl-D-aspartate (NMDA) receptors in the excitatory synaptic transmission to central vestibular neurons in the isolated superfused brainstem of the frog. In superfusate containing 1 mM Mg2+ field potentials in the vestibular nuclei evoked by electrical stimulation of either the ipsi- or the contralateral VIIIth nerve were not affected by bath-applied D-2-amino-5-phosphonovaleric acid (D-APV, 25-50 microM), a selective NMDA antagonist. In a low Mg2+ solution postsynaptic field potential components were larger than control but still unaffected by D-APV. Ipsi- and contralaterally evoked excitatory postsynaptic potentials (EPSPs) differed in their shape parameters as well as in their pharmacological sensitivity. Ipsilaterally evoked EPSPs were not affected by D-APV and has a rise time that was faster than that of contralaterally evoked EPSPs. The peak amplitude of hte latter was reduced by D-APV (25-50 microM) to about 65% of the control value in the presence of 1 mM Mg2+. During bath application of NMDA (100 microM) an increased input resistance and repetitive de- and hyperpolarizing membrane potential shifts were observed. Similar events were observed during a reduction of the Mg2+ concentration. Bath application of NMDA (0.1-1 microM) resulted in an enhanced size of the recorded EPSPs. Dendritic and somatic EPSPs were simulated on a computer with the assumption of a constant NMDA receptor activation and a pulse-like non-NMDA receptor activation. The results of these simulations are consistent with the hypothesis that the efficacy of non-NMDA-mediated vestibular commissural synaptic transmission is modulated through tonically activated NMDA receptors.

2-Amino-5-phosphonovalerate↗