Vestibular contribution to the orientration of cervico-ocular reflex in rabbit (original) (raw)
Related papers
The effect of gravity on the horizontal and vertical vestibulo-ocular reflex in the rat
Experimental Brain Research, 2000
Horizontal and vertical eye movements were recorded in alert pigmented rats using chronically implanted scleral search coils or temporary glue-on coils to test the dependence of the vestibulo-ocular reflex (VOR) upon rotation axis and body orientation. The contributions of semicircular-canal versus otolith-organ signals to the VOR were investigated by providing canal-only (vertical axis) and canal plus otolith (horizontal axis) stimulation conditions. Rotations that stimulated canals only (upright yaw and nose-up roll) produced an accurate VOR during middle-and high-frequency rotations (0.2-2 Hz). However, at frequencies below 0.2 Hz, the canal-only rotations elicited a phase-advanced VOR. The addition of a changing gravity stimulus, and thus dynamic otolith stimulation, to the canal signal (nose-up yaw, on-side yaw, and upright roll) produced a VOR response with accurate phase down to the lowest frequency tested (0.02 Hz). In order to further test the dependence of the VOR on gravitational signals, we tested vertical VOR with the head in an inverted posture (inverted roll). The VOR in this condition was advanced in phase across all frequencies tested. At low frequencies, the VOR during inverted roll was anticompensatory, characterized by slow-phase eye movement in the same direction as head movement. The substantial differences between canalonly VOR and canal plus otolith VOR suggest an important role of otolith organs in rat VOR. Anticompensatory VOR during inverted roll suggests that part of the otolith contribution arises from static tilt signals that are inverted when the head is inverted.
Experimental Brain Research, 1993
The guinea-pig is an attractive model for investigating gaze stabilization because it is suitable for in vitro and in vivo studies. However, few data are available on its oculomotor performance. We therefore investigated spontaneous eye movements, horizontal vestibulo-ocular (HVOR) and vestibulo-collic reflexes (HVCR) in the alert head-fixed guinea-pig using the magnetic search coil method. First the characteristics of the spontaneous saccades in the light were analysed. They occurred with a mean frequency of 4.6/rain and with a mean amplitude and duration of 7.41 _ 3.57 deg and 30.9 +_ 9.5 ms, respectively (n = 340). Saccadic duration and velocity were linearly related to the amplitude of the eye movement. The HVOR was studied in response to sinusoidal rotations (0.01 Hz to 2 Hz, peak head velocity of 40 deg/s) in the dark. Vestibular responses were linear at 0.5 and 0.05 Hz for peak head velocities between 40 and 80 deg/s. As in other species, the gain increased and the phase lead decreased with increasing frequencies. The number of fast phases per second increased with peak head velocity and with increasing frequencies from 0.01 to 0.5 Hz, with a plateau between 0.2 and 0.5 Hz. The HVOR time constant, when measured in response to velocity steps, was 7.0 _+ 1.5 s and the latency of the vestibular responses averaged 21 _+ 4 ms. Finally, the HVCR was assessed in unrestrained guinea-pigs subjected to horizontal sinusoidal rotation in the frequency range of 0.05-2 Hz. Exploratory behaviour was prevalent and there were few head stabilization episodes. However, when it occurred, the HVCR gain and phase were relatively flat over a frequency range from 0.1 to 2 Hz, reaching values close to 0.9 and 12 deg, respectively. In summary, the saccadic eye movements, the HVOR and the HVCR in the guinea-pig appear to be sufficiently similar to those of other vertebrates, including humans, to allow this species to be used as a model for studies of new pharmacological agents for vestibular disorders and post-lesional plasticity.
Effects of body to head rotation on the labyrinthine responses of rat vestibular neurons
Neuroscience, 2013
Vestibulospinal reflexes elicited by head displacement in space depend on the direction of body displacement, because the neuronal responses to labyrinthine stimulation are tuned by neck displacement: a directional tuning takes place in the medial cerebellum and in spinal motoneurons, while a gain and a basal activity tuning can be observed in the reticular formation, a target structure of the medial cerebellum. In the present study, we investigated whether also the response of vestibular nuclear neurons (another target of the medial cerebellum) to labyrinthine stimulation is tuned by neck displacement and which parameters of the response are modulated by it. In urethane-anaesthetized Wistar rats, single-unit activity was recorded from the vestibular nuclei at rest and during wobble of the whole animal at 0.156 Hz. This stimulus tilted the animal's head by a constant amplitude (5°), in a direction rotating at a constant velocity over the horizontal plane, either in clockwise or counter clockwise direction. The gain and the direction of neuronal responses to wobble were evaluated through Fourier analysis, in the control position (with coincident head and body axes) and following a body-to-head rotation of 5-30°over the horizontal plane, in both directions. Most of the vestibular neurons modified their response gain and/or their basal activity following body-to-head rotation, as it occurs in the reticular formation. Only few neurons modified their response direction, as occurs in the cerebellum and in spinal motoneurons. The different behaviour of cerebellar neurons and of their vestibular and reticular target cells, suggests that the role played by the cerebellum in the neck tuning of vestibulospinal reflexes has to be reconsidered. Ó
Vision Research, 2001
The 3D orientation and amplitude of the movement of each eye evoked by predictable, sinusoidal and non-predictable, sum-of-sines rotation about roll, yaw, pitch and intermediate axes were measured in seven subjects. The rotation axis of the eyes was not always perfectly aligned with the stimulus axis but showed systematic deviations that depended on the orientation of the rotation axis of the head. Misalignment of the oculomotor response with the stimulus axis is equivalent to adding an orthogonal, non-compensatory vector that potentially could introduce retinal slip, rather than compensate for it. The variations in orientation could not be readily explained as an artifact arising from the differential processing of the roll component. Instead, differences in the movements of the left and right eyes had trends appropriate for compensating for the geometrical demands of the translation of the eyes that must necessarily accompany natural head rotation.
Vestibular control of the head: possible functions of the vestibulocollic reflex
Experimental Brain Research, 2011
Here, we review the angular vestibulocollic reflex (VCR) focusing on its function during unexpected and voluntary head movements. Theoretically, the VCR could (1) stabilize the head in space during body movements and/or (2) dampen head oscillations that could occur as a result of the head's underdamped mechanics. The reflex appears unaffected when the simplest, trisynaptic VCR pathways are severed. The VCR's efficacy varies across species; in humans and monkeys, head stabilization is ineffective during low-frequency body movements in the yaw plan. While the appearance of head oscillations after the attenuation of semicircular canal function suggests a role in damping, this interpretation is complicated by defects in the vestibular input to other descending motor pathways such as gaze premotor circuits. Since the VCR should oppose head movements, it has been proposed that the reflex is suppressed during voluntary head motion. Consistent with this idea, vestibular-only (VO) neurons, which are possible vestibulocollic neurons, respond vigorously to passive, but not active, head rotations. Although VO neurons project to the spinal cord, their contribution to the VCR remains to be established. VCR cancelation during active head movements could be accomplished by an efference copy signal negating afferent activity related to active motion. Oscillations occurring during active motion could be eliminated by some combination of reflex actions and voluntary motor commands that take into account the head's biomechanics. A direct demonstration of the status of the VCR during active head movements is required to clarify the function of the reflex.
Vision Research, 2006
We examined how the gain of the torsional vestibulo-ocular reflex (VOR) (defined as the instantaneous eye velocity divided by inverted head velocity) in normal humans is affected by eye position, target distance, and the plane of head rotation. In six normal subjects we measured three-dimensional (3D) eye and head rotation axes using scleral search coils, and 6D head position using a magnetic angular and linear position measurement device, during low-amplitude ($20°), high-velocity ($200°/s), high-acceleration ($4000°/s 2 ) rapid head rotations or 'impulses.' Head impulses were imposed manually and delivered in five planes: yaw (horizontal canal plane), pitch, roll, left anterior-right posterior canal plane (LARP), and right anterior-left posterior canal plane (RALP). Subjects were instructed to fix on one of six targets at eye level. Targets were either straight-ahead, 20°left or 20°right from midline, at distance 15 or 124 cm from the subject. Two subjects also looked at more eccentric targets, 30°left or 30°right from midline. We found that the vertical and horizontal VOR gains increased with the proximity of the target to the subject. Previous studies suggest that the torsional VOR gain should decrease with target proximity. We found, however, that the torsional VOR gain did not change for all planes of head rotation and for both target distances. We also found a dynamic misalignment of the vertical positions of the eyes during the torsional VOR, which was greatest during near viewing with symmetric convergence. This dynamic vertical skew during the torsional VOR arises, in part, because when the eyes are converged, the optical axes are not parallel to the naso-occipital axes around which the eyes are rotating. In five of six subjects, the average skew ranged 0.9°-2.9°and was reduced to <0.4°by a 'torsional' quick-phase (around the naso-occipital axis) occurring <110 ms after the onset of the impulse. We propose that the torsional quick-phase mechanism during the torsional VOR could serve at least three functions: (1) resetting the retinal meridians closer to their usual orientation in the head, (2) correcting for the 'skew' deviation created by misalignment between the axes around which the eyes are rotating and the line of sight, and (3) taking the eyes back toward Listing's plane.
The horizontal vestibulo-ocular reflex in the hemilabyrinthectomized guinea-pig
Experimental Brain Research, 1993
The horizontal vestibulo-ocular reflex (HVOR) in the alert guinea-pig elicited by sinusoidal rotations and by velocity steps was studied with scleral search coil measurement between 3 and 7 days (short term) and between 35 and 160 days (long term) after hemilabyrinthectomy. Animals of the short-term group were always tested after spontaneous nystagmus in darkness had disappeared. The HVOR gain in response to sinusoidal rotations (peak angular velocity: 40 deg/s) in the short-term group was bilaterally depressed compared to normal animals. The HVOR phase showed a shift towards larger phase leads over the whole frequency range tested (from 0.05 to 3 Hz). In addition, both the mean number of fast phases per half-cycle of sinusoidal rotation and the mean amplitude were reduced. HVOR responses to velocity steps at a constant acceleration of 300 deg/s 2 up to final velocity (0 to 100 deg/s) and of 1000 deg/s 2 up to final velocity (0 to 300 deg/s) were depressed bilaterally and asymmetrically such that the gain for rotation towards the intact side greatly exceeded that obtained for rotation towards the lesioned side. Finally, the latency of the vestibular responses was increased and the time constant reduced for both sides of rotation. The HVOR gain values for sinusoidal rotations in the long-term group were lower than normal but higher than in the short-term group: they were asymmetric as a result of a greater compensation for rotation towards the intact side. Neither the phase lead nor the HVOR latency and time constant recovered values close to normal. Finally, the mean number of fast phases per half-cycle remained depressed although the mean amplitude recovered. These results demonstrate that in the guinea-pig, the dynamic deficits show a certain degree of recovery after unilateral labyrinthectomy. However, compared to the compensation of the static deficits previously quantified, the rate of recovery is much lower. This suggests that different processes may be involved in the compensation of the static and dynamic deficits.
Experimental Brain Research, 2003
This study used visual-vestibular conflict to effect short-term torsional and horizontal adaptation of the vestibulo-ocular reflex (VOR). Seven normal subjects underwent sinusoidal whole-body rotation about the earth-vertical axis for 40 min (€37/s, 0.3 Hz) while viewing a stationary radial pattern fixed to the chair (0 viewing). During adaptation and testing in darkness, the head was pitched either up or down 35 to excite both the horizontal and torsional VOR. The eyes were kept close to zero orbital elevation. Eye movements were recorded with a dual search coil in a three-field magnetic system. VOR gain was determined by averaging peak eye velocity from ten cycles of chair oscillation in complete darkness. The gain of the angular horizontal VOR (response to rotation about the head rostral-caudal axis) was significantly reduced after training in both head orientations. Angular torsional VOR gain (head rotation about the naso-occipital axis) was reduced in both head orientations, but this reached statistical significance only in the head down position. These results suggest that torsional and horizontal VOR gain adaptation, even when elicited together, may be subject to different influences depending upon head orientation. Differences between head up and down could be due to the relatively greater contribution of the horizontal semicircular canals with nose-down pitch. Alternatively, different VOR-adaptation processes could depend on the usual association of the head down posture to near viewing, in which case the torsional VOR is relatively suppressed.
Journal of Neurophysiology, 2009
Yakushin, Sergei B., Theodore Raphan, Jun-Ichi Suzuki, Yaresults in three push-pull pairs, right and left lateral (RLLL), suko Arai, and Bernard Cohen. Dynamics and kinematics of the right anterior and left posterior (RALP), and left anterior angular vestibulo-ocular reflex in monkey: effects of canal plugand right posterior (LARP), that code all angular head ging. J. Neurophysiol. 80: 3077-3099, 1998. Horizontal and roll movements. The precise angles of the individual semicircucomponents of the angular vestibulo-ocular reflex (aVOR) were lar canals have been estimated in several studies, which elicited by sinusoidal rotation at frequencies from 0.2 Hz (60Њ/s) indicate that the canal planes form a nonorthogonal basis to 4.0 Hz (É6Њ/s) in cynomolgus monkeys. Animals had both for sensing head acceleration (Blanks et al. 1985; Curthoys lateral canals plugged (VC, vertical canals intact), both lateral et al . 1977; Dickman 1996; Reisine et al. 1985. The canals and one pair of the vertical canals plugged (RALP, right 0022-3077/98 $5.00