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A hydraulically driven, digitally servo-controlled multi-axes rotary chair is described. This device generates motion profiles with the subjects head in the center of rotation mainly in order to adequately stimulate the semicircular canals which are sensitive sensors for angular accelerations. This newly developed apparatus allows for motion stimuli which are below the vestibular threshold up to accelerations of 12 rad/s2 (688 degrees/s2) and is thus suitable for a variety of experiments in the field of vestibular, oculomotor, and intersensory research in 3-dimensional space.
Otocysts explanted from 12th-gestation-day mice and maintained in organ culture under went a series of developmental changes which paralleled those that occurred in vivo and which resulted in the formation of a sensory epithelium of the vestibular type. At the time of explantation presumptive vestibular sensory epithelium consisted of cells that were undifferentiated, pseudostratified and rapidly proliferating. The only microtubules present were those of the mitotic apparatus. After 4 days of in vitro development cells comprising the presumptive vestibular sensory epithelium were less pseudostratified and more elongate; their nuclei had assumed a basal orientation and there was a clear maginal velum. Longitudinally oriented cytoplasmic microtubules were present at the apices of some cells; they were often grouped around a centriole which may have served as a nucleation centre for their assembly. After 7 days of in vitro development mitosis had ceased and supporting cells had innervated hair cells were present: both types of cells were always longer than they were broad and were often highly asymmetrical. Hair cells were flask- or columnar-shaped, with a nucleus situated in the basal third of the cell. Most mitochondria in hair cells were located in the apical third of the cell. The same distribution of mitochondria and nuclei was evident in supporting cells. Microtubules occurred throughout the length of the supporting cell and were always parallel to its longitudinal axis. In hair cells microtubules were more frequent than in supporting cells: the majority were parallel to the longitudinal axis of the cell but there were two exceptions. First, at the apex of hair cells some microtubules were oriented transversely and diagnonally: these were probably involved in the development and maintenance of the constricted apex of these cells. Secondly, microtubules appeared to be randomly arranged in the narrow region of the cytoplasm between the ventral surface of the nucleus and the base of the hair cells. Microfilaments were confined to the basal third of hair cells where their orientation paralleled that of microtubules. The possible functions of microtubules and microfilaments in the development of hair cells and supporting cells of the mouse vestibular epithelium are discussed.
An original analysis by computer has been imagined. Etiological diagnosis in recurrence's cases is based on asymmetry. Different levels were investigated: dental arch, ridge, basal bone and mandibular position. Dental shift, deformed bone, eccentric mandibular and occlusal distortion were found. Each molar is independently moving. Mandibular basal bone is stabilized in the transverse dimension. Mandibular deviation induces compression or stretching in temporo-mandibular articulation. Occlusal interferences involve distortion of cuspal plans. To reach stable objectives, molars require symmetrical position below one millimeter discrepancy, molar locking is to be had for the disto-vestibular cusp and ovoid arch. A special anchor apparatus allows to correct every wrong position of each individual molar, in each three-directional space. Mini-positioner or mini-splint perfect anterior misalignment. Sometimes, thermical memory archs are required. Ten fundamental rules that regulate occlusal and mandibular stability have been checked after treatment.
This laboratory has shown that age-related vestibular ganglion cell loss does not occur in the Wistar rat as it does in humans. However, in that study, intracellular changes were evident. The purpose of the present study was to quantitate some of these changes. The volume densities of mitochondria, rough endoplasmic reticulum (RER), Golgi apparatus, and aging pigment, as well as the diameter of the vestibular ganglion cells, of young (3 to 5 months) and old (24 to 31 months) female Wistar rats were determined by electron microscopy and stereological techniques. The data show a significant decrease in the volume densities of mitochondria (11.4%), Golgi apparatus (8.1%), and RER (8.9%), a significant increase in aging pigment (327%), and no change in mean profile diameter. These results suggest a decreased capacity for oxidative metabolism and protein synthesis that may reflect a decrease in the number of hair cells innervated by each ganglion cell and/or in the number of central connections. In either case, these findings suggest impaired metabolic and functional capabilities.
Hippocampal place cells show location-specific firing as animals locomote in an environment. A possible explanation for these place fields is that each cell is simply driven by environmental sensory inputs available in its field. This cannot provide the full explanation, however, since cells can maintain stable place fields even in the absence of reliable environmental orienting cues. This suggests the cells are also influenced by movement-related information, since this is the only available, ongoing indicator of current location when external orienting cues are not present. Two candidates for the movement-related information are vestibular activation, and visual motion. To test for these influences, place cells were recorded as animals locomoted in a cylindrical apparatus that was made so that its wall (painted with vertical black and white stripes) and floor could be independently rotated, to provide visual motion and vestibular inputs, respectively. The results showed that both these inputs could influence place fields. Sometimes they caused a predictable locational shift, so that the field rotated its location on the apparatus floor in a way that was compatible with the movement indicated by the vestibular and/or visual motion input. This updating was most reliably obtained when the two inputs were presented in combination. In other cases, the apparatus rotations caused unpredictable changes in firing characteristics, so that cells either stopped firing, or developed place fields that were altered in overall size, shape, and eccentricity. Interestingly, the probability of these changes increased with experience with the rotational manipulations, suggesting a learned component.
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Visual-vestibular interactions were assessed for eleven human subjects during earth-horizontal axis rotation. The apparatus consisted of a rotating chair and an independently controlled rotating optokinetic surround. Subjects underwent ten different test runs where vestibular and optokinetic stimuli were given independently and in combination. The resultant nystagmus slow component velocity was analyzed. When vestibular stimuli were given, the typical slow component velocity response consisted of an exponential decay to a non-zero baseline value (bias component). Superimposed on this was a cyclic modulation of the slow component velocity whose period was equal to the time required for one complete revolution. Our data indicate that the addition of visual input to otolith input does not affect the slow component velocity modulation component during earth horizontal axis rotation. The average bias component during otolith stimulation alone was much lower than the stimulus velocity. The bias component during optokinetic stimulation produce velocity dependent saturation. Thus, neither input alone was adequate to produce a bias component that matched the higher stimulus velocities. In contrast, the average bias component during otolith-visual interaction runs produced responses that were nearly equal to the relative target velocity. This occurred despite large individual variability of the otolith alone and optokinetic response alone. Thus, the brain compensates to match the target velocity when otolith and visual stimuli are presented together.
The cumulogram of slow nystagmus phases has proved as a useful method for the analysis of vestibular nystagmus. However, its computation depends on the availability of special apparatuses. Therefore, the relations are studied between the cumulogram of slow phases and the cumulogram of fast phases that can be determined more easily. The analysis of 57 pendular tests shows the close correlation (r = 0,98) of the respective values for vestibular gain. Considering the statistical connection the comparison of these two methods and their results, resp., is well practicable.
The paper discusses the results of the author's own studies concerning the recording of electrical responses evoked from a remote field in the vestibular part of the eighth nerve. The studies are of experimental nature and they were carried out repetitively in guinea pigs. Particular attention is paid to an apparatus specially designed and constructed, permitting to obtain stimulation of adequate quality of vestibular organs, and to receive and average short (up to 10 ms) evoked vestibular potentials. Different variants of elimination of bioelectrical muscular disturbances and of the auditory pathway are proposed.
Morphologic changes in ipsilateral superior vestibulo-ocular neurons (SVON) and the vestibular nerve were measured in 4 cats 8 weeks after labyrinthectomy and 4 cats 1 year after labyrinthectomy. There is a 20% decrease in SVON size and 30% decrease in rough endoplasmic reticulum and ribosomes with no change in the volume fractions of Golgi apparatus or mitochondria. In the central nervous system degeneration of the vestibular nerve terminals ipsilateral to the labyrinthectomy was represented by a 25% loss of synaptic profiles (SP) on SVON at 8 weeks and 57% loss of SP at 1 year after labyrinthectomy. There was no significant loss of fiber number in the vestibular nerve at 8 weeks post lesion but a 35% loss of fibers primarily of the large size at 1 year post lesion.
Rats were trained in an eight-arm radial maze to explore the apparatus in search of a food reward. After completion of the training phase, some animals were submitted to a hemicerebellectomy (HCbed group), while others were used as a control group. To study the effects of vestibular stimulation on the recall of ongoing working memory information, both groups were exposed to radial maze sessions: in the first session (no-rotation), animals were confined for 30 s to the fourth arm visited without being further manipulated; in the second session (rotation), the animals were again confined for 30 s to the fourth arm visited, while the apparatus was rotated five times around its vertical axis. The effects of these manipulations on successive visits to complete the task were assessed, as well as the solving time and kinds of errors made. Errors were significantly more frequent in the control animals during the rotation session; HCbed animals were unaffected by confinement alone or by vestibular stimulation, but showed a decreased search speed. It was concluded that vestibular input is required for an adequate functioning of the working memory system devoted to the formation and consolidation of spatial mnesic traces and that the amnesic effect due to vestibular stimulation is both anterograde and retrograde in nature.
Criteria of professional rehabilitation potential, rehabilitation forecasting of disabled persons were developed based on clinical data and results of the commission of experts. 412 patients with vestibular dysfunction as a result of previous cranio-cerebral trauma, chronic suppurative medium otitis, compromised neurosensory apparatus of an internal ear have been observed. Optimized variants of social-labour rehabilitation of persons with compromised vestibular analyzer were proposed.
Previous authors have postulated that a dense band of keratinized, attached gingiva prevents the spread of inflammation from the gingival margin to the subjacent attachment apparatus. Chronically inflamed mucogingival defects were created over the vestibular surface of 12 central incisors in miniature swine. The untreated contralateral incisors were identified as paired controls. Placement of horizontal reference notches on the tooth surfaces was followed by measurement of Probing Depth (PD) and Probing Attachment Level (PAL) on the vestibular aspect of each experimental and control tooth. No plaque removal was accomplished at any time during the study. One year following the attainment of baseline data, all measurements were repeated. Results show an increase in PD and a loss of PAL in both experimental and control regions. No difference in increase of PD or loss of PAL between the groups could be discerned.
Two important questions concerning the organs of equilibrium are posed by orbital and space flights. The first is whether exposure to weightlessness may evoke symptoms of vestibular origin, and the second is how to prevent symptoms of vestibular origin should it be decided to abolish weightlessness by causing the spacecraft to spin. It is important to determine whether vestibular symptoms are to be ascribed to the otolith apparatus or to the semicircular canals, or to both. During exposure to weightlessness the usual gravitational stimulus to the otolith apparatus is lost, and this reduction in afferent input might be expected to disturb the integrative patterns in the central nervous system. All such disturbances are special instances of a common cause for the appearance of functional syndromes such as seasickness. If orbiting vehicles are caused to rotate in order to abolish weightlessness, the angular velocity will be determined by the effective radius of rotation and the rate of spin, i.e., how nearly it is desired to simulate 1 g. At very short radii the complicating effects of exposure of the body to variations in centripetal force must be considered. With longer radii the principal stress will arise as a result of constant rotation, which, in combination with head movements, generates Coriolis forces. These forces cause bizarre patterns of stimulation of the semicircular canals which in turn may result in illusions and "canal sickness". This type of motion sickness has its origin in the semicircular canals and deserves the term "canal sickness". The angular velocities which represent a negligible stress or a tolerable stress are defined. A brief description is given of illusory phenomena and other manifestations together with the time-course of the adaptive process.
The author examined 55 patients with disorders of circulation in the vertebrobasillar basin where the most prevalent clinical signs were expressed in a cochleo-vestibular syndrome due to a lesion of the receptor apparatus of the inner ear. It was marked that in the clinical respect this syndrome was very similar to genuine Meniere's disease. The differential diagnosis of this disease is frequently very complicated. A detailed neurological and otoneurological examination demonstrated a combined lesion in the form of a simultaneous involvement into the process, of the inner ear, the brain stem and cerebellar hemisphere (in different varieties). Inasmuch as the blood supply is provided by the different branches of the anterior inferior cerebellar artery in a vascular brain disorder the clinical signs may be qualified as a variant of the syndrome of the anterior inferior cerebellar artery.
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A study was designed to establish baseline normative responses to the MIT/Canadian Spacelab vestibular test battery. Three tests used a linear acceleration sled to measure otolith function: 1) perception of linear motion (threshold determination); 2) compensatory eye movements (linear VOR); 3) closed-loop nulling, in which the blindfolded subject nulls his velocity with a joystick under the influences of a pseudorandom sled disturbance. Rotational VOR was measured at 0.3 and 0.8 Hz in the dark and the light. Static visual-vestibular interaction was tested with a standard rod and frame apparatus, while dynamic interaction was assessed by susceptibility to roll vection induced by a rotating peripheral visual field. Two examples are presented of how results from this study can aid in the interpretation of data from preflight/postflight testing of Space Shuttle/Spacelab crews on these same experiments.