Otolith-ocular Reflex Research Articles

Stereopsis Outweighs Gravity in the Control of the Eyes

The eyes are controlled by multiple brain circuits, some phylogenetically old and some new, whose aims may conflict. Old otolith reflexes counterroll the eyes when the head tilts relative to gravity. Newer vergence mechanisms coordinate the eyes to aid stereoptic vision. We show that counterroll hinders stereopsis, weakly when you look into the distance but strongly when you look near. The resolution of this conflict is that counterroll virtually vanishes when monkeys look close, i.e., stereopsis overrides gravity-driven reflexes but only on near gaze. This balance between gyroscopic and stereoptic mechanisms explains many other puzzling features of primate gaze control, such as the weakness of our otolith-ocular reflexes even during far viewing and the strange geometry of the primate counterpitch reflex, which rolls the eyes clockwise when monkeys look leftward while their heads are tipped nose up, but rolls them counterclockwise when the monkeys look rightward, and reverses this pattern when the head is tipped nose down.

Large Bielschowsky head-tilt phenomenon and inconspicuous vertical deviation in the diagnostic positions in congenital superior oblique palsy

PURPOSE: To report a case of congenital superior oblique palsy with an unusually large Bielschowsky head-tilt phenomenon (BHP) and disproportional inconspicuous vertical deviation. METHODS: Case report. RESULTS: An 18-year-old woman presented with slight compensatory head tilting and a Bielschowsky head-tilt phenomenon of 50 Δ on left tilting. Magnetic resonance imaging revealed atrophy of the left superior oblique muscle. A Hess screen test showed a slight underaction of the left superior oblique muscle, but neither an obvious overaction of the ipsilateral inferior oblique muscle nor inhibitory palsy of the contralateral superior rectus muscle was found. With a 3-mm recession of the ipsilateral superior rectus muscle, Bielschowsky head-tilt phenomenon decreased to 25 Δ. CONCLUSION: A large Bielschowsky head-tilt phenomenon was possibly caused by an increased gain of the otolith-ocular reflex affecting the vertical rectus muscle.

Otolith dysfunction in skew deviation after brain stem lesions

We investigated the horizontal and the vertical otolith-ocular reflex induced by off-vertical-axis rotation and subjective visual vertical in 14 patients with skew deviation due to brain stem lesion. Patients were divided into two groups: the group C ( N = 7) with caudal brain stem lesions and the group R ( N = 7) with rostral brain stem lesions as defined by the midpons level. The patient group was compared to a control group of 20 healthy subjects. The otolith-ocular reflex was evoked by constant velocity rotation in yaw plane around an axis tilted at 15 deg with respect to gravity. In group C, the horizontal off-vertical-axis nystagmus bias was negative i.e. anticompensatory to chair rotation, when directed toward the lesioned side. Furthermore, patients of group C were presenting with a significant tilt of subjective visual vertical. In group R, a vertical downward offset was induced predominantly in the hypotropic eye and in the direction of rotation away from the lesion. Finally, in patients of group R, horizontal and vertical modulation was increased for rotation away from the lesion. These results are discussed in terms of 1) asymmetrical horizontal and vertical dynamic otolith signals feeding the velocity storage network after brain stem lesion, 2) possible involvement of cerebellar function in OVAN modulation.

直線加速度の空間識，眼反射に及ぼす影響

Linear acceleration (CF) caused by centrifugal force results in ocular deviation and change in spatial orientation. Thirteen healthy human subjects and one labyrinthine defective (LD) subject were exposed to CF to examine the change in spatial orientation and eye position. CF was applied by rotating the subject at a 90 cm off-center position (eccentric rotation). Constant angular velocities of 80, 100, 120 and 140 deg/sec depicted CF of 0.18 to 0.55 G. CF was introduced in two chair positions as it affects along the inter-aural (X) or naso-occipital (Y) axes. Subjects were asked to adjust an LED bar to a perpendicular position while the chair was rotated in the darked room. Judgement for visual vertical was very accurate when the chair was stationary (with deviation of the bar within 1.1 degrees). Under CF along the X-axis, judgement for subjective perpendicular changed (i.e., toward the center of rotation). Amplitude of the tilting angle significantly increased as a function of CF (ANOVA, p<0.05). However, no significant change in bar deviation was found in one LD subject during the rotation. Also, CF along the Yaxis did not cause any significant deviation of the bar in healthy volunteers. Eye movement during eccentric rotation was analyzed by using an infrared video camera and computer analyzing system. Torsional eye deviations with amplitudes of 0.1 to 1.5 degrees were detected under CF along the X-axis. Under CF along the Y-axis, upward eye deviations with amplitudes of 1.6 to 3.2 degrees were detected. As the amplitude of eye deviation was very small in both conditions, it is assumed that the gain of otolithocular reflex had only a small gain. The linear acceleration acting upon the head had a larger influence upon spatial orientation than upon the oculomotor system.

Vestibulo-oculomotor research and measurement technology for the space station era

Recent improvements in measurement techniques and mathematical representations for eye, head and body movement have enhanced our appreciation of the complexity of spatial orientation and locomotion in three-dimensional space. The shortcomings of present measurement techniques, and their solution with emerging technologies are described. The prolonged microgravity conditions on the space station provide a unique opportunity to investigate these three-dimensional aspects of the vestibular and oculomotor systems, and in particular, the role of the otolith afferences. While the canal–ocular responses and their central pathways are reasonably well understood, the community has only recently become aware of the variety of functions fulfilled by otolith-mediated information, i.e., translational otolith–ocular reflex, inertial processing, gravitational reference, vergence control. Recent results, largely from experiments performed on the Mir Station, where the emphasis was on the otolith contribution to the vestibulo-ocular response mechanisms, are reviewed.

Smooth pursuit eye movements and otolith-ocular responses are differently impaired in cerebellar ataxia.

Horizontal and vertical smooth pursuit was compared with otolith-ocular responses in 11 patients with cerebellar ataxia and 21 normal subjects using three-dimensional magnetic search coil eye movement recordings. Otolith-ocular responses were investigated during off-vertical axis rotation. This stimulus induces nystagmus consisting of the exponentially decaying canalicular response, and an eye-velocity modulation and offset which arise from the excitation of the otoliths by the gravity vector, which lasts as long as the rotation continues. Otolith-ocular reflexes are intimately interrelated with visual tracking when real targets are viewed during linear motion. The responses of both the translational vestibulo-ocular reflex and the pursuit system have been shown to be linearly dependent on the inverse of the viewing distance, so that a common central pathway for the two systems has been suggested, probably travelling through the cerebellum. Thus, the aim of the study was to evaluate to what extent these reflexes are disturbed in cerebellar disease. The results confirm the earlier notion that in normal subjects pursuit performance is better for horizontal than for vertical tracking, and that it is better for upward than for downward tracking. This pattern is also found in patients. In addition, smooth pursuit performance is clearly degraded in patients, but the modulation of eye-velocity during off-vertical axis rotation is enhanced. Since the amount of this enhancement does not correlate with the amount of pursuit impairment, degradation of smooth pursuit and pathological enhancement of otolith-ocular responses seem to be independent effects of cerebellar degeneration. Thus, the increase in the otolith-ocular response in patients cannot be attributed to adaptational mechanisms trying to overcome the smooth pursuit deficiency; it is more likely to represent pathological disinhibition of otolith derived responses. The absence of compensatory eye-velocity offset during off-vertical axis rotation may reflect the fact that in patients the otolith signals are not utilized in computations thought to be important for spatial orientation mechanisms arising from the interaction of vestibular, visual and somatosensory signals.

Three-dimensional organization of otolith-ocular reflexes in rhesus monkeys. III. Responses To translation.

The three-dimensional (3-D) properties of the translational vestibulo-ocular reflexes (translational VORs) during lateral and fore-aft oscillations in complete darkness were studied in rhesus monkeys at frequencies between 0.16 and 25 Hz. In addition, constant velocity off-vertical axis rotations extended the frequency range to 0.02 Hz. During lateral motion, horizontal responses were in phase with linear velocity in the frequency range of 2-10 Hz. At both lower and higher frequencies, phase lags were introduced. Torsional response phase changed more than 180 degrees in the tested frequency range such that torsional eye movements, which could be regarded as compensatory to "an apparent roll tilt" at the lowest frequencies, became anticompensatory at all frequencies above approximately 1 Hz. These results suggest two functionally different frequency bandwidths for the translational VORs. In the low-frequency spectrum (<<0.5 Hz), horizontal responses compensatory to translation are small and high-pass-filtered whereas torsional response sensitivity is relatively frequency independent. At higher frequencies however, both horizontal and torsional response sensitivity and phase exhibit a similar frequency dependence, suggesting a common role during head translation. During up-down motion, vertical responses were in phase with translational velocity at 3-5 Hz but phase leads progressively increased for lower frequencies (>90 degrees at frequencies <0.2 Hz). No consistent dependence on static head orientation was observed for the vertical response components during up-down motion and the horizontal and torsional response components during lateral translation. The frequency response characteristics of the translational VORs were fitted by "periphery/brain stem" functions that related the linear acceleration input, transduced by primary otolith afferents, to the velocity signals providing the input to the velocity-to-position neural integrator and the oculomotor plant. The lowest-order, best-fit periphery/brain stem model that approximated the frequency dependence of the data consisted of a second order transfer function with two alternating poles (at 0.4 and 7.2 Hz) and zeros (at 0.035 and 3.4 Hz). In addition to clearly differentiator dynamics at low frequencies (less than approximately 0.5 Hz), there was no frequency bandwidth where the periphery/brain stem function could be approximated by an integrator, as previously suggested. In this scheme, the oculomotor plant dynamics are assumed to perform the necessary high-frequency integration as required by the reflex. The detailed frequency dependence of the data could only be precisely described by higher order functions with nonminimum phase characteristics that preclude simple filtering of afferent inputs and might be suggestive of distributed spatiotemporal processing of otolith signals in the translational VORs.

The Effect of Space Missions on Gravity-Responsive Torsional Eye Movements

Three astronauts underwent preflight, inflight, and postflight testing of spontaneous ocular torsion and of ocular counterrolling (OCR), reflexes governed by the gravity-responsive otolith organs in the inner ear. One astronaut, A, had a 30-day space mission on Euromir '94 and was examined monocularly with SensoMotoric Instruments video-oculography (VOG). The other two astronauts, B and C, were studied with a binocular VOG and flew an 180-day mission on Euromir '95. In space, spontaneous eye torsion in the upright position was found to be substantially offset from baseline Earth-based recordings in all three subjects for the duration of the flights. In addition, the binocular studies showed a marked torsional disconjugacy. On return to Earth, offset and torsional disconjugacy persisted for many days. OCR in response to 30 degrees right and left tilt was examined preflight and postflight. Compared to preflight, Astronaut A showed reduced OCR immediately postflight, which increased over the next few days. Both Astronauts B and C had increased OCR postflight, which gradually approached but did not achieve the preflight values over 13 days postflight. The adaptation of ocular torsion in space in one astronaut and not in the other two, and slow adaptation postflight, may reflect the lack of visual feed-back and the open loop nature of the otolith-ocular torsion reflex.

Long-term deficits in otolith, canal and optokinetic ocular reflexes of pigmented rats after unilateral vestibular nerve section

Static and dynamic otolith, horizontal vestibular and optokinetic ocular reflexes were investigated in pigmented rats 1-6 and more months after unilateral vestibular nerve (UVN) section. Evoked responses were compared with published data from control rats studied under identical conditions. Static lateral tilt of UVN rats in the light evoked a vertical deviation in static eye position that was as large as in controls. In darkness, the evoked responses in UVN rats 6 months after the lesion were consistently smaller than in controls. Linear horizontal acceleration in darkness evoked vertical and torsional response components in UVN rats that were parallel-shifted towards lower gains and larger phase lags. Off-vertical axis rotation on a platform provoked responses that differed markedly from those recorded in intact rats with respect to the bias velocity component. These results suggest a permanent deficiency in the static and dynamic otolith-ocular reflex performance of UVN rats. Ocular responses to horizontal table velocity steps in darkness exhibited a direction-specific asymmetry in UVN rats. Step responses evoked by acceleration towards the intact side were larger in gain and longer in duration than responses evoked by acceleration towards the operated side. When compared with control data, responses to either side were reduced in UVN rats and the velocity store mechanism was barely activated by velocity steps towards the operated side. Responses evoked by horizontal optokinetic stimulation with constant pattern velocities were below control values in either direction. Slow-phase eye velocity saturated at much lower values than in intact rats, particularly during pattern motion towards the intact side. The duration of the optokinetic afternystagmus was asymmetrically reduced with respect to control data. Practically identical reductions in duration were found for vestibulo-ocular responses in the opposite directions. Behaving animals exhibited no obvious impairment in their spontaneous locomotory or exploratory activities. However, each UVN rat was impaired, even 2 years after the lesion, in its postural reaction to being lifted by the tail in the air. This observation suggests the presence of a permanent deficit in static and dynamic otolith-spinal reflexes that may be substituted on the ground by proprioceptive inputs.

Maculo-ocular reflex and visual perception during vertical acceleration

We investigated the effect of vertical acceleration upon the otolithic-ocular reflex of 22 healthy people. The study was performed to obtain standard values for subsequent investigations at patients. People sitting on a chair were accelerated in the vertical axis with an amplitude of 4 cm and the frequencies of 0.5 Hz, 1 Hz, 1.5 Hz, 2 Hz, 2.5 Hz and 2.7 Hz. The movements of the ocular globe were initially recorded during vertical acceleration with the eyes closed. Then visual acuity was tested during linear acceleration with the eyes open. As parameters of evaluation we used coherence and alteration of the visual acuity. When the frequency was increased while the eyes were closed, coherence increased and the number of people with vertical eye movements increased. Amplitude was observed to increase and a phase shift occurred. A significant value of coherence (> 0.8) was observed at a frequency above 2.5 Hz. During the test of visual acuity, coherence also increased but did not reach quantity we observed initially. A significant loss of visual acuity occurred at a frequency above 2.5 Hz. A phase shift was also observed. The reason for the loss of visual acuity was the increment of amplitude and the phase shift, which had a negative influence on fixation. In summary, reactions with closed eyes are best tested at frequencies of 2.5 and 2.7 Hz. We recommended frequencies of 1.5 and 2 Hz for testing visual acuity.

Effect of otolith dysfunction. Impairment of visual acuity during linear head motion in labyrinthine defective subjects.

Visual symptoms emerging after the loss of vestibular function are usually attributed to the dysfunction of semicircular canal vestibulo-ocular reflexes, as they have been shown to stabilize vision during angular head movements. However, natural head displacements involve both angular and linear motion, and therefore visual instability may occur because of defective otolith-ocular reflexes (OORs) which are the eye movements evoked by linear head acceleration. In this paper, the relationship between OORs and visual acuity during linear head motion was studied in normal subjects and 14 patients with bilateral loss of caloric responses. OORs were elicited in darkness by step acceleration (0.24 g) of the whole body along the interaural axis. Latency, slow phase velocity and asymmetry of the OOR were measured from the desaccaded and averaged electrooculographic trace. Visual acuity was assessed during sinusoidal lateral oscillation of the subject viewing an earth-fixed target, and vice versa with the subject stationary and the target moving at 0.5, 1.0 and 1.5 Hz. The task was to recognize numbers flashing up on a three digit light-emitting diode visual display. Normal subjects had symmetrical OORs with short latencies (< 130 ms). In patients, OORs were either absent (n = 2) or abnormal with asymmetries (n = 8), diminished velocities (n = 4) or prolonged latencies (n = 6). At high frequency oscillation (1.5 Hz), normal subjects invariably recognized more numbers during self-motion compared with target motion, whereas most patients did not. In patients, abnormal dynamic visual acuity was correlated with absent or delayed OOR responses. This is the first demonstration of a functional role of the OORs in that they contribute to visual stabilization during high frequency linear head motion. Bilateral vestibular failure commonly affects the OORs and thereby compromises dynamic visual acuity.

Eye movements induced by lateral acceleration steps. Effect of visual context and acceleration levels.

Eye movement responses were obtained from six normal subjects exposed to randomly ordered rightwards/leftwards linear acceleration steps of 0.05 g, 0.1 g or 0.24 g amplitude and 650 ms duration along the interaural axis. With the instruction to gaze passively into the darkness, compensatory nystagmus was evoked with slow-phase velocity sensitivity of 49 degrees s(-1) g(-1). When subjects viewed earth-fixed targets at 30 cm, 60 cm or 280 cm, eye movements at 130 ms from motion onset were proportional to acceleration and inversely proportional to target distance, before the onset of visually guided eye movements. Our results show that a modulation with viewing distances of the earliest human otolith-ocular reflexes occurs in the presence of pure linear acceleration. However, full compensation was not attained for the nearer targets and higher accelerations.

Modification of Vertical OKN and Vertical OKAN Asymmetry in Humans During Parabolic Flight

Characteristics of human vertical optokinetic nystagmus (OKN) and afternystagmus (OKAN) were examined by ISCAN imaging system on the ground and on board NASA's KC-135 aircraft in a parabolic flight study. The aircraft produced alternating periods of micro-(ca. 10(-2) G) and hyper-(ca. 1.8 G) gravitoinertial forces. Each phase lasted approximately 20 to 25 s. As compared to the baseline data on the ground, there was a significant increase of downward OKN/OKAN, whereas the upward OKN/OKAN did not change significantly in either micro- or hyper-G. As a consequence, the asymmetry of vertical OKN/OKAN, normally seen on the ground, was lost. It is postulated that the increase of downward OKN/OKAN in non-1-G conditions was governed by two different mechanisms. In micro-G, the normal inhibition effect in 1 G on the downward eye movement mediated by otolith organ activity to vertical velocity storage was removed. In hyper-G, downward OKN/OKAN was facilitated by augmented otolith-ocular reflex because of increased gravitoinertial force, so as to produce enhanced compensatory downward eye movement.

Yaw Sensory Rearrangement Alters Pitch Vestibulo-Ocular Reflex Responses

Ten male subjects underwent two types of adaptation paradigm designed either to enhance or to attenuate the gain of the canal-ocular reflex (COR), before undergoing otolith-ocular reflex (OOR) testing with constant velocity, earth horizontal axis and pitch rotation. The adaptation paradigm paired a 0.2 Hz sinusoidal rotation about an earth vertical axis with a 0.2 Hz optokinetic stimulus that was deliberately mismatched in peak velocity or phase and was designed to produce short-term changes in the COR. Preadaptation and postadaptation OOR tests occurred at a constant velocity of 60%sec in the dark and produced a modulation component of the slow phase velocity with a frequency of 0.16 Hz due to otolithic stimulation by the sinusoidally changing gravity vector. Of the seven subjects who showed enhancement of the COR gain, six also showed enhancement of the OOR modulation component. Of the seven subjects who showed attenuation of the COR gain, five also showed attenuation of the OOR modulation component. The probability that these two cross-axis adaptation effects would occur by chance is less than 0.02. This suggests that visual-vestibular conditioning of the yaw axis COR also induced changes in the pitch axis OOR. We thus postulate that the central nervous system pathways that process horizontal canal yaw stimuli have elements in common with those processing otolithic stimuli about the pitch axis.

Three-dimensional organization of otolith-ocular reflexes in rhesus monkeys. I. Linear acceleration responses during off-vertical axis rotation.

1. The dynamic properties of otolith-ocular reflexes elicited by sinusoidal linear acceleration along the three cardinal head axes were studied during off-vertical axis rotations in rhesus monkeys. As the head rotates in space at constant velocity about an off-vertical axis, otolith-ocular reflexes are elicited in response to the sinusoidally varying linear acceleration (gravity) components along the interaural, nasooccipital, or vertical head axis. Because the frequency of these sinusoidal stimuli is proportional to the velocity of rotation, rotation at low and moderately fast speeds allows the study of the mid-and low-frequency dynamics of these otolith-ocular reflexes. 2. Animals were rotated in complete darkness in the yaw, pitch, and roll planes at velocities ranging between 7.4 and 184 degrees/s. Accordingly, otolith-ocular reflexes (manifested as sinusoidal modulations in eye position and/or slow-phase eye velocity) were quantitatively studied for stimulus frequencies ranging between 0.02 and 0.51 Hz. During yaw and roll rotation, torsional, vertical, and horizontal slow-phase eye velocity was sinusoidally modulated as a function of head position. The amplitudes of these responses were symmetric for rotations in opposite directions. In contrast, mainly vertical slow-phase eye velocity was modulated during pitch rotation. This modulation was asymmetric for rotations in opposite direction. 3. Each of these response components in a given rotation plane could be associated with an otolith-ocular response vector whose sensitivity, temporal phase, and spatial orientation were estimated on the basis of the amplitude and phase of sinusoidal modulations during both directions of rotation. Based on this analysis, which was performed either for slow-phase eye velocity alone or for total eye excursion (including both slow and fast eye movements), two distinct response patterns were observed: 1) response vectors with pronounced dynamics and spatial/temporal properties that could be characterized as the low-frequency range of "translational" otolith-ocular reflexes; and 2) response vectors associated with an eye position modulation in phase with head position ("tilt" otolith-ocular reflexes). 4. The responses associated with two otolith-ocular vectors with pronounced dynamics consisted of horizontal eye movements evoked as a function of gravity along the interaural axis and vertical eye movements elicited as a function of gravity along the vertical head axis. Both responses were characterized by a slow-phase eye velocity sensitivity that increased three- to five-fold and large phase changes of approximately 100-180 degrees between 0.02 and 0.51 Hz. These dynamic properties could suggest nontraditional temporal processing in utriculoocular and sacculoocular pathways, possibly involving spatiotemporal otolith-ocular interactions. 5. The two otolith-ocular vectors associated with eye position responses in phase with head position (tilt otolith-ocular reflexes) consisted of torsional eye movements in response to gravity along the interaural axis, and vertical eye movements in response to gravity along the nasooccipital head axis. These otolith-ocular responses did not result from an otolithic effect on slow eye movements alone. Particularly at high frequencies (i.e., high speed rotations), saccades were responsible for most of the modulation of torsional and vertical eye position, which was relatively large (on average +/- 8-10 degrees/g) and remained independent of frequency. Such reflex dynamics can be simulated by a direct coupling of primary otolith afferent inputs to the oculomotor plant. (ABSTRACT TRUNCATED)

Three-dimensional organization of otolith-ocular reflexes in rhesus monkeys. II. Inertial detection of angular velocity.

1. The dynamic contribution of otolith signals to three-dimensional angular vestibuloocular reflex (VOR) was studied during off-vertical axis rotations in rhesus monkeys. In an attempt to separate response components to head velocity from those to head position relative to gravity during low-frequency sinusoidal oscillations, large oscillation amplitudes were chosen such that peak-to-peak head displacements exceeded 360 degrees. Because the waveforms of head position and velocity differed in shape and frequency content, the particular head position and angular velocity sensitivity of otolith-ocular responses could be independently assessed. 2. During both constant velocity rotation and low-frequency sinusoidal oscillations, the otolith system generated two different types of oculomotor responses: 1) modulation of three-dimensional eye position and/or eye velocity as a function of head position relative to gravity, as presented in the preceding paper, and 2) slow-phase eye velocity as a function of head angular velocity. These two types of otolith-ocular responses have been analyzed separately. In this paper we focus on the angular velocity responses of the otolith system. 3. During constant velocity off-vertical axis rotations, a steady-state nystagmus was elicited that was maintained throughout rotation. During low-frequency sinusoidal off-vertical axis oscillations, dynamic otolith stimulation resulted primarily in a reduction of phase leads that characterize low-frequency VOR during earth-vertical axis rotations. Both of these effects are the result of an internally generated head angular velocity signal of otolithic origin that is coupled through a low-pass filter to the VOR. No change in either VOR gain or phase was observed at stimulus frequencies larger than 0.1 Hz. 4. The dynamic otolith contribution to low-frequency angular VOR exhibited three-dimensional response characteristics with some quantitative differences in the different response components. For horizontal VOR, the amplitude of the steady-state slow-phase velocity during constant velocity rotation and the reduction of phase leads during sinusoidal oscillation were relatively independent of tilt angle (for angles larger than approximately 10 degrees). For vertical and torsional VOR, the amplitude of steady-state slow-phase eye velocity during constant velocity rotation increased, and the phase leads during sinusoidal oscillation decreased with increasing tilt angle. The largest steady-state response amplitudes and smallest phase leads were observed during vertical/torsional VOR about an earth-horizontal axis. 5. The dynamic range of otolith-borne head angular velocity information in the VOR was limited to velocities up to approximately 110 degrees/s. Higher head velocities resulted in saturation and a decrease in the amplitude of the steady-state response components during constant velocity rotation and in increased phase leads during sinusoidal oscillations. 6. The response characteristics of otolith-borne angular VORs were also studied in animals after selective semicircular canal inactivation. Otolith angular VORs exhibited clear low-pass filtered properties with a corner frequency of approximately 0.05-0.1 Hz. Vectorial summation of canal VOR alone (elicited during earth-vertical axis rotations) and otolith VOR alone (elicited during off-vertical axis oscillations after semicircular canal inactivation) could not predict VOR gain and phase during off-vertical axis rotations in intact animals. This suggests a more complex interaction of semicircular canal and otolith signals. 7. The results of this study show that the primate low-frequency enhancement of VOR dynamics during off-vertical axis rotation is independent of a simultaneous activation of the vertical and torsional "tilt" otolith-ocular reflexes that have been characterized in the preceding paper. (ABSTRACT TRUNCATED)

A Model That Relates Canal-Ocular to Otolith-Ocular Responses

Rotation about the vertical stimulates primarily the horizontal semicircular canals and produces compensatory horizontal nystagmus whose slow component velocity response during constant velocity can be approximated as having a simple exponential decay time constant, Tvor. Constant velocity yaw rotation about a horizontal axis stimulates both the horizontal canals and the otolith organs, producing two additional nystagmus components thought to be of otolithic origin: a steady component called bias and a periodic component known as modulation. We tested a group of 7 human subjects using rotation about each of these axes. We found a strong, negative correlation (r = 0.956) between these individuals' dominant time constants, Tvor, and the magnitude of their modulation components. Canal and otolith signals originate from different parts of the same endorgan and travel separately to the vestibular nucleus. The reflexive eye movements in response to these inputs are thought to be the result of additional processing by the central vestibular and ocular motor systems. Thus, the source of these strongly correlated otolith-ocular and canal-ocular reflex components could logically be due to common factors affecting peripheral transduction or to a subsequent common central processing step. Using anatomical measurements of human vestibular end organs, biophysical endorgan models, and models of central vestibular processes, we examined the alternatives to determine which was the most likely. Correlations were not found between Tvor and the anatomical data or between the Tvor and the biophysical model elements. However, modifications of the velocity storage integrator of Raphan to incorporate either a highpass filter (HPF) or a lowpass filter input for otolith modulation signals allowed for the desired strong negative correlation between Tvor and modulation. We argue in favor of the HPF configuration because it better explains the tendency for the modulation component to increase in amplitude as the modulation frequency is increased. In the above mentioned representation of the central processing of vestibular afferent inputs, we conclude that the modulation component input to the vestibuloocular reflex is within the indirect pathway, but it is "down stream" from the velocity storage integrator.

The interaction of the human linear otolith-ocular and angular horizontal vestibulo-ocular reflexes in darkness.

Annals of the New York Academy of SciencesVolume 781, Issue 1 p. 580-582 The Interaction of the Human Linear Otolith-Ocular and Angular Horizontal Vestibulo-Ocular Reflexes in Darkness D. ANASTASOPOULOS, D. ANASTASOPOULOS MRC Human Movement and Balance Unit Institute of Neurology, National Hospital Queen Square London WC1N 3BG, EnglandSearch for more papers by this authorC. GIANNA, C. GIANNA MRC Human Movement and Balance Unit Institute of Neurology, National Hospital Queen Square London WC1N 3BG, EnglandSearch for more papers by this authorA. M. BRONSTEIN, A. M. BRONSTEIN MRC Human Movement and Balance Unit Institute of Neurology, National Hospital Queen Square London WC1N 3BG, EnglandSearch for more papers by this authorM. A. GRESTY, M. A. GRESTY MRC Human Movement and Balance Unit Institute of Neurology, National Hospital Queen Square London WC1N 3BG, EnglandSearch for more papers by this author D. ANASTASOPOULOS, D. ANASTASOPOULOS MRC Human Movement and Balance Unit Institute of Neurology, National Hospital Queen Square London WC1N 3BG, EnglandSearch for more papers by this authorC. GIANNA, C. GIANNA MRC Human Movement and Balance Unit Institute of Neurology, National Hospital Queen Square London WC1N 3BG, EnglandSearch for more papers by this authorA. M. BRONSTEIN, A. M. BRONSTEIN MRC Human Movement and Balance Unit Institute of Neurology, National Hospital Queen Square London WC1N 3BG, EnglandSearch for more papers by this authorM. A. GRESTY, M. A. GRESTY MRC Human Movement and Balance Unit Institute of Neurology, National Hospital Queen Square London WC1N 3BG, EnglandSearch for more papers by this author First published: June 1996 https://doi.org/10.1111/j.1749-6632.1996.tb15729.xCitations: 3AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume781, Issue1New Directions in Vestibular ResearchJune 1996Pages 580-582 RelatedInformation

Visual otolith-ocular reflex in normal subjects: A preliminary report

The influence of the otolith-ocular reflex (OOR) induced by the linear (along Y-axis) acceleration was evaluated 12 healthy subjects. The elicited maximum eye velocity (MV) was comparatively analyzed under three stimulus conditions; (1) ) sinusoidal linear acceleration with eyes covered, (2) sinusoidal optokinetic stimulus and (3) sinusoidal linear acceleration with eyes open (visual-vestibular interaction). By the linear acceleration level of 78 cm 2, i.e. 0.08 G, the MV of the optokinetic response (OKR) showed no change in spite of the existence of the OOR.

半規管‐眼反射における適応現象が耳石‐眼反射に及ぼす影響

It has been demonstrated that chronic exposure to certain visual environments, for example those generated by magnifying lenses and reversing prisms, alter the gain and phase of the vestibulo-ocular reflex (VOR) in the dark in numerous species. Most experiments concerning such modification of the VOR have used semicircular canal stimulation. So far, there has been no investigation of the effect of adaptive plasticity of the semicircular canal-ocular reflex (SCOR) to an off-vertical axis rotation (OVAR), a dynamic otolith stimulation. The purposes of this study are to study physiologic alteration of the VOR using otolithic stimulation and to determine whether the bias and modulation component during OVAR change following adaptation of the SCOR. In this study, using OVAR, we tested the hypothesis that the otolith-ocular reflex (OOR) is altered by changes in the SCOR. Our study showed no convincing evidence for a transfer of SCOR adaptation to OOR using OVAR. There are two possibilities that could explain why we are unable to obtain this evidence, either there is no transfer to OOR, or there is an undiscovered technical problem. Future studies of transfer of adaptation will decrease OVAR exposure and assess OOR variability.