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1. Perception of two-dimensional (2-D) whole-body passive motion in the horizontal plane was studied in twelve blindfolded healthy volunteers: pure rotation in place (180 deg), linear motion (4.5 m) and a semicircular trajectory (radius, 1.5 m; angular acceleration, 0.2 rad s-2) were applied in random sequence by means of a remote-controlled robot equipped with a racing-car seat. The seat orientation in the horizontal plane was controlled by the experimenter, independent of the robot trajectory. Thus different degrees of otolith-canal interaction were obtained. The maximal linear acceleration during the semicircular trajectory was 0.1 g; however, the linear acceleration vector was complex as it rotated relative to the subject's head. 2. In the first of two sessions, subjects were instructed to maintain an angular pointer oriented towards a remote (15 m) previously seen target during the passive movements. In the second session they had to make a drawing of the path of the perceived trajectory, after the movement was finished. 3. The results showed that, on average, the movement of the pointer matched the dynamics of the rotatory component of the 2-D motion well. This suggests that, in the range of linear accelerations used in this study, no appreciable influence of otolith input on canal-mediated perception of angular motion occurred. 4. The curvature of the drawn paths was mostly explained by the input to the semicircular canals. Subjects' reconstruction of motion did not account for the directional dynamics of the input to the otoliths occurring during passive motion. 5. This finding proves that reconstructing trajectory in space does not imply a mathematically perfect transformation of the linear and angular motion-related inputs into a Cartesian or polar 2-D representation. Physiological constraints on the interaction between motion direction and change of heading play an important role in motion perception.
Perception of tilt (somatogravic illusion) in response to sustained linear acceleration is generally attributed to the otolithic system which reflects either a translation of the head or a reorientation of the head with respect to gravity (tilt/translation ambiguity). The main aim of this study was to compare the tilt perception during prolonged static tilt and translation between 8 and 20 degrees of tilt relative to the gravitoinertial forces (i.e., G and GIF, respectively) when the semicircular cues were no more available. An indirect measure of tilt perception was estimated by means of a visual and kinesthetic judgment of the gravitational horizon. The main results contrast with the interpretation regarding the tilt/translation ambiguity as the same orientation relative to the shear forces G for the true tilt or GIF in the centrifuge did not induce the same horizon perception. Visual adjustment and arm pointing in the centrifuge were always above the ones observed in a G environment. Part of the lowering of the judgment in the centrifuge may be related to the mechanical effect of GIF on the effectors as shown by the shift of the egocentric coordinates in the direction of GIF. The role of the extravestibular graviceptors in the judgment of the degree of tilt of one's own body relative to G or GIF was discussed.
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OBJECTIVE: We aimed to develop a clinical test of 3D canal dysfunction by perceptual matching of motion stimuli as an alternative to vestibular ocular reflex assessment. STUDY DESIGN: The study was a comparison with age-matched controls. SETTING: The study was performed in a clinical neurophysiology laboratory. PATIENTS: Ten patients with acute unilateral vestibular nerve section and 9 patients in the chronic stage of recovery, 2 acute-stage and 2 chronic-stage patients with posterior canal plugging, and 35 healthy individuals were studied. INTERVENTIONS: Seated on a motorized rotating chair in darkness, subjects were exposed to discrete, raised cosine velocity (60 degrees/s peak) rotations, for random displacements < or = 180 degrees rightward and leftward. They responded by rotating themselves back to the starting position with a joystick control. Horizontal canals were tested with head upright, ipsilateral versus contralateral vertical canal pairs were tested with the head down, face horizontal and co-planar anterior-posterior canal pairs were tested with the head down and turned approximately 45 degrees to the left or right. MAIN OUTCOME MEASURES: These were accuracy and symmetry of responses. RESULTS: Normal responses were approximately accurate returns to start. Nine patients with acute nerve section were hypometric (undershooting start) when displaced toward the lesion but normometric to the intact side. Eight chronic-stage nerve section patients with chronic dysfunction were hypometric to the lesion for vertical canal stimuli, but one third showed normal responses for horizontal canal testing. Patients with posterior canal plugging were hypometric specifically toward the plugged canal. CONCLUSIONS: The method reliably identifies acute and chronic dysfunction of vertical canals and acute dysfunction of horizontal canals. Dysfunction of a single canal can be specified.
BACKGROUND: Horizontal canal benign paroxysmal positional vertigo is characterized by horizontal direction-changing nystagmus induced by lateral head turning in supine position. According to Ewald's second law, the direction of head turning that creates a stronger response represents the affected side in geotropic nystagmus and the healthy side in apogeotropic nystagmus. However, it may not always be possible to lateralize the involved ear only by comparing the intensity of the nystagmus. We studied the values of nystagmus induced by position change from sitting to supine in the lateralization of horizontal canal benign paroxysmal positional vertigo. METHODS: A retrospective study of 54 patients who had been diagnosed as having horizontal canal benign paroxysmal positional vertigo at the Dizziness Clinic of Seoul National University Bundang Hospital from May 2003 to February 2004 was performed. The directions of the nystagmus induced by lying down were compared with those determined by Ewald's second law. RESULTS: Of the 54 patients, 32 (20 apogeotropic and 12 geotropic) showed horizontal nystagmus induced by lying down. The nystagmus tended to be ipsilesional in apogeotropic patients (80%) and contralesional in their geotropic counterparts (75%). CONCLUSION: In horizontal canal benign paroxysmal positional vertigo, lying-down nystagmus mostly beats toward the involved ear in the apogeotropic type and directs to the healthy ear in the geotropic type. The direction of lying-down nystagmus may help lateralizing the involved ear in horizontal canal benign paroxysmal positional vertigo.
The review briefly describes the structure and function of complex carbohydrates of glycoproteins and proteoglycans both in general and with particular respect to the potential roles sugar chains may play in the cupula, i.e. the molecular organization of these constituents, their biophysical properties, and their biological functions.
Dynamic changes of deficits in canal and otolith vestibulo-ocular reflexes (VORs) to high acceleration, eccentric yaw rotations were investigated in five subjects aged 25-65 years before and at frequent intervals 3-451 days following unilateral vestibular deafferentation (UVD) due to labyrinthectomy or vestibular neurectomy. Eye and head movements were recorded using magnetic search coils during transients of directionally random, whole-body rotation in darkness at peak acceleration 2,800 degrees/s2. Canal VORs were characterized during rotation about a mid-otolith axis, viewing a target 500 cm distant until rotation onset in darkness. Otolith VOR responses were characterized by the increase in VOR gain during identical rotation about an axis 13 cm posterior to the otoliths, initially viewing a target 15 cm distant. Pre-UVD canal gain was directionally symmetrical, averaging 0.87 +/- 0.02 (+/-SEM). Contralesional canal gain declined from pre-UVD by an average of 22% in the first 3-5 days post-UVD, before recovering to an asymptote of close 90% of pre-UVD level at 1-3 months. This recovery corresponded to resolution of spontaneous nystagmus. Ipsilesional gain declined to 59%, and showed no consistent recovery afterwards. Pre-UVD otolith gain was directionally symmetrical, averaging 0.56 +/- 0.02. Immediately after UVD, the contralesional otolith gain declined to 0.30 +/- 0.02, and did not recover. Ipsilesional otolith gain declined profoundly to 0.08 +/- 0.03 (P < 0.01), and never recovered. In contrast to the modest and directionally symmetrical effect of UVD on the human otolith VOR during pure translational acceleration, otolith gain during eccentric yaw rotation exhibited a profound and lasting deficit that might be diagnostically useful in lateralizing otolith pathology. Most recovery of the human canal gain to high acceleration transients following UVD is for contralesional head rotation, occurring within 3 months as spontaneous nystagmus resolves.
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.
The response properties of cat horizontal canal afferents (N = 81) were characterized by three parameters: their long time constants (tau), low frequency gain constants (G1), and middle frequency gain constants (Gm). An average value of each of these parameters was calculated for each of eight animals and comparisons were made across animals. There were significant differences between individual animals in their average values of tau and Gm. There was also a significant negative correlation between tau's and Gm's. An animal with a larger average tau tended to have a smaller average Gm. We also used anatomic data on membranous canal duct diameter from the literature to independently estimate the potential effect of interanimal anatomic variability on the predicted range of tau and Gm values in a population. We then compared the data from our 81 afferents with the predictions from the anatomic data.
Meningiomas rarely arise from or remain limited to the temporal bone. When the diagnosis of temporal bone meningioma is made, it is mandatory to investigate the possibility of an intracranial component. Computerized axial tomography with contrast enhancement is of limited value in detecting small tumors adjacent to the temporal bone or within the internal auditory canal. If the computerized tomogram is normal, a positive contrast posterior fossa myelogram is indicated. The pitfall of depending solely upon computerized tomography to detect intracranial extension became clear in the evaluation of a patient found to have an unusual trilobed meningioma.
This study assessed the eye movement responses to active head rotation in six subjects with complete unilateral vestibular loss (UVL), five subjects with posterior canal plugging (PCP) and age- and sex-matched normal subjects. Subjects performed head rotations in the pitch and yaw planes at frequencies ranging from 2 to 6 Hz, while looking at an earth-fixed target. Vertical eye movement gains obtained in UVL, PCP and normal subjects were not significantly different. Vertical phases decreased with increasing head movement frequencies in both UVL and PCP subjects. Although this decrease produced significantly different vertical phases between UVL and normal subjects for head movements above 3.9 Hz, vertical phases in some normal subjects were similar to those obtained in UVL subjects. We conclude that active head oscillations in the pitch plane are not clinically useful for the detection of vertical canal impairment limited to one ear. As expected, UVL subjects showed reduced horizontal gains, and eye velocity asymmetries during active head rotation in the yaw plane. Results in some PCP subjects suggested possible minor impairments of horizontal vestibulo-ocular reflexes.
The relative strengths of vertical canal and otolithic factors influencing downbeat nystagmus (DBN) were investigated in a patient whose nystagmus was of maximum intensity with the head in the upright position and abolished with the head in the supine position. The vestibuloocular reflex (VOR) was assessed by oscillating the patient about both the supine and upright positions. During oscillation about the supine position both the upward and downward VORs had equal gains in the dark (0.6) and unity gain in the light. In contrast, during oscillation about the upright, the upward VOR became hyperactive with a gain of 1.8 in the dark and 1.2 in the light, whereas the downward VOR became hypoactive with a maximum gain of 0.86 in the light. This degree of asymmetry of the VOR is greater than would be expected from a summation of spontaneous nystagmus with normal canal reflexes. We concluded that the DBN arose from an asymmetry of vertical canal function, which became manifest when the otoliths were tilted with respect to gravity. Contrasting findings are presented in a patient whose DBN was insensitive to tilt. It would seem that other cases of DBN lie on a continuum between these extreme examples.
The cranio-mandibular syndrome (CMS) is often secondary to an cranio-facial asymmetry (CFA); it associate a painful masticatory dysfunction syndrome with functional and aching clinical signs in relation with a functional torticollis required for oculo-labyrinthal equilibration maintenance. Our anatomical and functional MRI protocol uses tridimensional study of semi-circular canals (SCC) up relation to the medial cerebral axis (MCA), and permit to measure precisely these CFA and propose, with a multispecialist approach, an adapted treatment of the SCM. Application of MRI to SCC asymmetry looks to its future use for spatial intracranial referencial of cerebral structures.
The ampullae of horizontal, anterior and posterior canals of the alert pigeon were stimulated with short electrical pulses. The double pulses evoke synchronized biphasic short-latency disynaptic responses in neck muscles, their amplitudes depending on interpulse delay. Facilitation occurred between 80-100 mcsec and 3-4 msec. The amplitudes of contralateral responses were higher. The short-latency responses are under control of the otolithic input. The angular acceleration or short pulse trains evoke eye movements in the plane of the stimulated canal, as well as their neck correlates the polysynaptic responses that form the nystagmic rhythm. Changing of the stimuli parameters induce di- and polysynaptic neck responses as different components of the reaction. The eye nystagmus evoked with electrical stimulation of ampullae in the wide frequency band of stimulation, depended on stimuli parameters. The data obtained are discussed using concept of central vestibulo-oculomotor integrator.
The vestibulo-ocular reflex (VOR) of 162 normal subjects was evaluated using two rotational testing procedures. Data from 79 subjects were collected using a set of five single-frequency stimuli (0.01 to 0.16 Hz) and 83 subjects were tested using multifrequency stimuli (0.01 to 0.27 Hz). The use of multifrequency stimuli in place of single frequencies reduced testing time from 75 min to 20 min per subject. The diagnostically useful phase response of the VOR, as estimated by the two tests, were not statistically different. Equivalent phase measures may be obtained within a shorter testing period using the multifrequency procedure.
Inflight and post-landing "immunity" to the "coriolis sickness susceptibility test", observed during the Skylab M131 experiment, suggests that the otolith organs play a major role in space motion sickness (SMS). This view is supported by the report that ocular counter-torsion asymmetries correlate with SMS incidence and severity. Further data indicate that sensory-motor adaptation to microgravity includes a process whereby central interpretation of otolith signals is biased from "tilt" toward translation. However, unexpected responses to linear acceleration suggest the importance of graviceptors distributed throughout the body in addition to the vestibular otolith organs. Research is needed to assess distributed graviceptor effects.
The effect of Gentamicin (GM) on the vestibular organ was studied using bullfrogs. The ototoxicity was compared among 3 different ways of administration, i.e., intraperitoneal (IP), intramuscular (IM) and intralabyrinthine (IL) injections. Morphological change of the posterior canal crista was observed by SEM. The posterior canal ampullary nerve action potentials (AP) were recorded, and were compared with SEM findings of the sensory epithelia. Morphological and physiological changes were severe in the order of IL greater than IM greater than IP. Morphological and physiological changes developed as the postinjection time elapsed. Morphological damage started at the narrow portion of the crista and developed towards the center and finally towards the periphery. Physiological change was already observed before the morphological damage. Physiological change tended to correlate with the morphological damage.