共查询到20条相似文献,搜索用时 15 毫秒
1.
T. Lempert C. Gianna G. Brookes A. Bronstein M. Gresty 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1998,118(4):533-540
We studied horizontal eye movements evoked by lateral whole body translation in nine patients who underwent vestibular nerve
section. Preoperatively, all had preserved caloric function on both sides. Testing was performed before, 1 week and 6–10 weeks
after surgery. Patients were seated upright in an electrically powered car running on a linear track. The car executed acceleration
steps of 0.24 g, randomly to the left and right in the dark. The normal response consisted of a bidirectionally symmetrical
nystagmus with compensatory slow phases. Response asymmetry of the slow-phase velocity of the desaccaded and averaged eye
position signal was less than 13% in normals (n = 21). Before surgery, patients’ responses were mostly symmetrical. Postoperatively, responses were diminished or absent
with head acceleration towards the operated ear in all patients, causing a marked asymmetry which averaged 56% after correction
for spontaneous nystagmus. On follow-up, responses regained symmetry. Thus, early after vestibular nerve section, a single
utricle produces a normal LVOR only with ipsilateral head translation. Therefore, afferents for the LVOR seem to originate
from the mid-lateral area of the macula, where hair cells are stimulated in their on-direction during ipsilateral head translation.
Compensation may depend on recovery of the off-directional responses from lateral hair cells of the remaining utricle.
Received: 9 December 1996 / Accepted: 15 July 1997 相似文献
2.
B. J. M. Hess D. E. Angelaki 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1993,95(1):77-83
Sinusoidal oscillation of rhesus monkeys about a head-fixed, earth-horizontal axis while rotating at constant velocity about an earth-vertical axis generates a characteristic ocular nystagmus where the three-dimensional slow phase eye velocity is compensatory to the spatially and temporally changing head angular velocity vector. This includes the generation of a unidirectional nystagmus characterised by a bias slow phase velocity component, albeit of small gain (0.2–0.7), that persists for the duration of the combined two-axes stimulation and is compensatory to the constant velocity earth-vertical axis rotation. Specifically, there is a torsional bias velocity in supine position, a vertical bias velocity in ear down position and a horizontal bias velocity in upright position. Since the semicircular canals can not sense prolonged constant velocity rotation, the ocular bias velocity must be centrally constructed from canal afferent signals using head position information. Thus, optimal performance of the vestibular system as a three-dimensional rate sensor relies on afferent information from both the semicircular canals and the otolith organs. 相似文献
3.
B. J. Yates M. Aoki P. Burchill A. M. Bronstein M. A. Gresty 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1999,125(4):476-484
Although activation of otolith receptors is known to elicit cardiovascular responses in animals, it is unclear whether vestibular
stimulation can evoke changes in blood pressure and heart rate (which are independent of motion sickness) in humans. In the
present study, ten normal subjects and three patients with profound bilateral reduction in vestibular function, who were seated
upright with the torso aligned with the gravitation vector, were subjected to fore, aft, or lateral linear acceleration (≈0.2
g, attaining ≈2 m/s in 900 ms, and decelerating for 3 s at 0.07 g). The head was fixed in the upright position, pitched maximally
downward (chin on chest) or maximally backward (≈40–50°) during the accelerations. In normal subjects, all directions of linear
acceleration produced an average increase in systolic blood pressure of approximately 7–9 mmHg and a rapid decrease in the
interval between R-waves of the electrocardiogram of 14–27 ms; these responses persisted for only a few seconds. In contrast,
the cardiovascular responses in patients with vestibular dysfunction were much smaller (e.g., the maximal pressor response
to forward linear acceleration was <4 mmHg). Head position during accelerations had little effect on the cardiovascular responses
that were elicited in the population of normal subjects. However, although the population response was similar across directions
of acceleration and head positions, many individuals exhibited larger cardiovascular changes during some stimulus conditions
than during others. These data suggest that vestibular stimulation during linear accelerations can produce cardiovascular
responses in humans and support the hypothesis that the vestibular system contributes to maintaining stable blood pressure
during movement and changes in posture.
Received: 22 September 1998 / Accepted: 5 January 1999 相似文献
4.
Erik S. Viirre Joseph L. Demer 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1996,112(2):313-324
The purpose of this study was to examine the effect of fixation target distance on the human vestibuloocular reflex (VOR) during eccentric rotation in pitch. Such rotation induces both angular and linear acceleration. Eight normal subjects viewed earth-fixed targets that were either remote or near to the eyes during wholebody rotation about an earth-horizontal axis that was either oculocentric or 15 cm posterior (eccentric) to the eyes. Eye and head movements were recorded using magnetic search coils. Using a servomotor-driven chair, passive whole-body rotations were delivered as trains of single-frequency sinusoids at frequencies from 0.8 to 2.0 Hz and as pseudorandom impulses of acceleration. In the light, the visually enhanced VOR (VVOR) was recorded while subjects were asked to fixate targets at one of several distances. In darkness, subjects were asked to remember targets that had been viewed immediately prior to the rotation. In order to eliminate slip of the retinal image of a near target when the axis of rotation of the head is posterior to the eyes, the ideal gain (compensatory eye velocity divided by head velocity) of the VVOR and VOR must exceed 1.0. Both the VOR and VVOR were found to have significantly enhanced gains during sinusoidal and pseudorandom impulses of rotation (P<0.05). Enhancement of VVOR gain was greatest at low frequencies of head rotation and decreased with increasing frequency. However, enhanced VOR gain only slightly exceeded 1.0, and VVOR gain enhancement was significantly lower than the expected ideal values for the stimulus conditions employed (P<0.05). During oculocentric rotations with near targets, both the VOR and VVOR tended to exhibit small phase leads that increased with rotational frequency. In contrast, during eccentric rotations with near targets, there were small phase lags that increased with frequency. Visual tracking contributes during ocular compensatory responses to sustained head rotation, although the latency of visual tracking reflexes exceeds 100 ms. In order to study initial vestibular responses prior to modification by visual tracking, we presented impulses of head acceleration in pseudorandom sequence of initial positions and directions, and evaluated the ocular response in the epoch from 25 to 80 ms after movement onset. As with sinusoidal rotations, pseudorandom eccentric head rotation in the presence of a near, earth-fixed target was associated with enhancement of VVOR and VOR gains in the interval from 25 to 80 ms from movement onset. Despite the inability of visual tracking to contribute to these responses, VVOR gain significantly exceeded VOR gain for pseudorandom accelerations. This gain enhancement indicates that target distance and linear motion of the head are considered by the human ocular motor system in adjustment of performance of the early VOR, prior to a contribution by visual following reflexes. Vergence was appropriate to target distance during all VVOR rotations, but varied during VOR rotations with remembered targets. For the 3-m target distance, vergence during the VOR was stable over each entire trial but slightly exceeded the ideal value. For the 0.1-m near target, instantaneous vergence during the VOR typically declined gradually in a manner not corresponding to the time course of instantaneous VOR gain change; mean vergence over entire trials ranged from 60 to 90% of ideal, corresponding to target distances for which ideal gain would be much higher than actually observed. These findings suggest a dissociation between vergence and VOR gain during eccentric rotation with near targets in the frequency range from 0.8 to 2.0 Hz. 相似文献
5.
C. Darlot P. Denise J. Droulez B. Cohen A. Berthoz 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1988,73(1):91-105
Summary Off-vertical rotation (OVAR) in darkness induced continuous horizontal nystagmus in humans at small tilts of the rotation axis (5 to 30 degrees). The horizontal slow eye velocity had two components: a mean velocity in the direction opposite to head rotation and a sinusoidal modulation around the mean. Mean velocity generally did not exceed 10 deg/s, and was less than or equal to the maximum velocity of optokinetic after-nystagmus (OKAN). Both the mean and modulation components of horizontal nystagmus increased with tilt angle and rotational velocity. Vertical slow eye velocity was also modulated sinusoidally, generally around zero. The amplitude of the vertical modulation increased with tilt angle, but not with rotational velocity. In addition to modulations in eye velocity, there were also modulations in horizontal and vertical eye positions. These would partially compensate for head position changes in the yaw and pitch planes during each cycle of OVAR. Modulations in vertical eye position were regular, increased with increases in tilt angle and were separated from eye velocity by 90 deg. These results are compatible with the interpretation that, during OVAR, mean slow velocity of horizontal nystagmus is produced by the velocity storage mechanism in the vestibular system. In addition, they indicate that the otolith organs induce compensatory eye position changes with regard to gravity for tilts in the pitch, yaw and probably also the roll planes. Such compensatory changes could be utilized to study the function of the otolith organs. A functional interpretation of these results is that nystagmus attempts to stabilize the image on the retina of one point of the surrounding world. Mean horizontal velocity would then be opposite to the estimate of head rotational velocity provided by the output of the velocity storage mechanism, as charged by an otolithic input during OVAR. In spite of the lack of actual translation, an estimate of head translational velocity could, in this condition, be constructed from the otolithic signal. The modulation in horizontal eye position would then be compensatory for the perceived head translation. Modulation of vertical eye velocity would compensate for actual changes in head orientation with respect to gravity. 相似文献
6.
Alexander A. Tarnutzer Christopher J. Bockisch Dominik Straumann 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2009,195(4):621-626
We compared the variability of the subjective visual vertical (SVV) and static ocular counterroll (OCR), and hypothesized
a correlation between the measurements because of their shared macular input. SVV and OCR were measured simultaneously in
various whole-body roll positions [upright, 45° right-ear down (RED), and 75° RED] in six subjects. Gains of OCR were −0.18
(45° RED) and −0.12 (75° RED), whereas gains of compensation for body roll in the SVV task were −1.11 (45° RED) and −0.96
(75° RED). Normalized SVV and OCR variabilities were not significantly different (P > 0.05), i.e., both increased with increasing roll. Moreover, a significant correlation (R
2 = 0.80, slope = 0.29) between SVV and OCR variabilities was found. Whereas the gain of OCR is different from the gain of
SVV, trial-to-trial variability of OCR follows the same roll-dependent modulation observed in SVV variability. We propose
that the similarities in variability reflect a common otolith input, which, however, is subject to distinct central processing
for determining the gain of SVV and OCR. 相似文献
7.
C. A. Foster J. L. Demer M. J. Morrow R. W. Baloh 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1997,116(3):501-509
Abnormalities in the vestibulo-ocular reflex (VOR) after unilateral vestibular injury may cause symptomatic gaze instability.
We compared five subjects who had unilateral vestibular lesions with normal control subjects. Gaze stability and VOR gain
were measured in three axes using scleral magnetic search coils, in light and darkness, testing different planes of rotation
(yaw and pitch), types of stimulus (sinusoids from 0.8 to 2.4 Hz, and transient accelerations) and methods of rotation (active
and passive). Eye velocity during horizontal tests reached saturation during high-velocity/acceleration ipsilesional rotation.
Rapid vertical head movements triggered anomalous torsional rotation of the eyes. Gaze instability was present even during
active rotation in the light, resulting in oscillopsia. These abnormal VOR responses are a consequence of saturating nonlinearities,
which limit the usefulness of frequency-domain analysis of rotational test data in describing these lesions.
Received: 22 April 1996 / Accepted: 18 February 1997 相似文献
8.
Dickman JD Angelaki DE 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1999,129(3):391-400
During linear accelerations, compensatory reflexes should continually occur in order to maintain objects of visual interest
as stable images on the retina. In the present study, the three-dimensional organization of the vestibulo-ocular reflex in
pigeons was quantitatively examined during linear accelerations produced by constant velocity off-vertical axis yaw rotations
and translational motion in darkness. With off-vertical axis rotations, sinusoidally modulated eye-position and velocity responses
were observed in all three components, with the vertical and torsional eye movements predominating the response. Peak torsional
and vertical eye positions occurred when the head was oriented with the lateral visual axis of the right eye directed orthogonal
to or aligned with the gravity vector, respectively. No steady-state horizontal nystagmus was obtained with any of the rotational
velocities (8–58°/s) tested. During translational motion, delivered along or perpendicular to the lateral visual axis, vertical
and torsional eye movements were elicited. No significant horizontal eye movements were observed during lateral translation
at frequencies up to 3 Hz. These responses suggest that, in pigeons, all linear accelerations generate eye movements that
are compensatory to the direction of actual or perceived tilt of the head relative to gravity. In contrast, no translational
horizontal eye movements, which are known to be compensatory to lateral translational motion in primates, were observed under
the present experimental conditions.
Received: 29 January 1999 / Accepted: 14 June 1999 相似文献
9.
G. Schweigart T. Mergner G. Barnes 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1999,127(1):54-66
During natural behaviour in a visual environment, smooth pursuit eye movements (SP) usually override the vestibular-ocular
reflex (VOR) and the optokinetic reflex (OKR), which stem from head-in-space and scene-relative-to-eye motion, respectively.
We investigated the interaction of SP, VOR, and OKR, which is not fully understood to date. Eye movements were recorded in
two macaque monkeys while applying various combinations of smooth eye pursuit, vestibular and optokinetic stimuli (sinusoidal
horizontal rotations of visual target, chair and optokinetic pattern, respectively, at 0.025, 0.05, 0.1, 0.2, 0.4, and 0.8
Hz, corresponding to peak stimulus velocities of 1.25–40°/s for a standard stimulus of ±8°). Slow eye responses were analysed
in terms of gain and phase. During SP at mid-frequencies, the eyes were almost perfectly on target (gain 0.98 at 0.1 Hz),
independently of a concurrent vestibular or optokinetic stimulus. Pursuit gain at lower frequencies, although being almost
ideal (0.98 at 0.025 Hz with pursuit-only stimulation), became modified by the optokinetic input (gain increase above unity
when optokinetic stimulus had the same direction as target, decrease with opposite direction). At higher stimulus frequencies,
pursuit gain decreased (down to 0.69 at 0.8 Hz), and the pursuit response became modified by vestibular input (gain increase
during functionally synergistic combinations, decrease in antagonistic combinations).Thus, the pursuit system in monkey dominates
during SP-OKR-VOR interaction, but it does so effectively only in the mid-frequency range. The results can be described in
the form of a simple dynamic model in which it is assumed that the three systems interact by linear summation. In the model
SP and OKR dominate VOR in the low- to mid-frequency/velocity range, because they represent closed loop systems with high
internal gain values (>>1) at these frequencies/velocities, whereas the VOR represents an open loop system with about unity-gain
(up to very high frequencies). SP dominance over OKR is obtained by allowing an ’attentional/volitional’ mechanism to boost
SP gain and a predictive mechanism to improve its dynamics.
Received: 27 November 1998 / Accepted: 8 March 1999 相似文献
10.
T. Mergner G. Schweigart F. Botti A. Lehmann 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1998,120(4):450-460
Proprioceptive input arising from torsional body movements elicits small reflexive eye movements. The functional relevance
of these eye movements is still unknown so far. We evaluated their slow components as a function of stimulus frequency and
velocity. The horizontal eye movements of seven adult subjects were recorded using an infrared device, while horizontal rotations
were applied at three segmental levels of the body [i.e., between head and shoulders (neck stimulus), shoulders and pelvis
(trunk stimulus), and pelvis and feet (leg stimulus)]. The following results were obtained: (1) Sinusoidal leg stimulation
evoked an eye response with the slow component in the direction of the movement of the feet, while the response to trunk and
neck stimulation was oriented in the opposite direction (i.e., in that of the head). (2) In contrast, the gain behavior of
all three responses was similar, with very low gain at mid- to high frequencies (tested up to 0.4 Hz) but increasing gain
at low frequencies (down to 0.0125 Hz). We show that this gain behavior is mainly due to a gain nonlinearity for low angular
velocities. (3) The responses were compatible with linear summation when an interaction series was tested in which the leg
stimulus was combined with a vestibular stimulus. (4) There was good correspondence of the median gain curves when eye responses
were compared with psychophysical responses (perceived body rotation in space; additionally recorded in the interaction series).
However, correlation of gain values on a single-trial basis was poor. (5) During transient neck stimulation (smoothed position
ramp), the neck response noticeably consisted of two components – an initial head-directed eye shift (phasic component) followed
by a shift in the opposite direction (compensatory tonic component). Both leg and neck responses can be described by one simple,
dynamic model. In the model the proprioceptive input is fed into the gaze network via two pathways which differ in their dynamics and directional sign. The model simulates either leg or neck responses by selecting
an appropriate weight for the gain of one of the pathways (phasic component). The interaction results can also be simulated
when a vestibular path is added. This model has similarities to one we recently proposed for human self-motion perception
and postural control. A major difference, though, is that the proprioceptive input to the gaze-stabilizing network is weak
(restricted to low velocities), unlike that used for perception and postural control. We hold that the former undergoes involution
during ontogenesis, as subjects depend on the functionally more appropriate vestibulo-ocular reflex. Yet, the weak proprioceptive
eye responses that remain may have some functional relevance. Their tonic component tends to stabilize the eyes by slowly
shifting them toward the primary head position relative to the body support. This applies solely to the earth-horizontal plane
in which the vestibular signal has no static sensitivity.
Received: 10 October 1997 / Accepted: 22 January 1998 相似文献
11.
T. Haslwanter L. B. Minor 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1999,124(1):25-32
We recorded three-dimensional eye and head movements during circular, horizontal, vertical, and torsional head shaking in
six human subjects with normal vestibular function. With circular head shaking, the stimulation of the canals by the termination
of the head movement is similar to that following a step in velocity about the naso-occipital axis. A large torsional nystagmus
with slow phase eye velocity of about 20°/s was observed upon cessation of circular head shaking. The three-dimensional eye
movements expected from stimulation of the semicircular canals by the head-shaking maneuvers were calculated. The predicted
activation of the canals was determined by projecting the head velocity (in head coordinates) into the canal planes and then
processing the signal with the transfer function of the canals. The torsional eye velocity components predicted by the stimulation
of the canals matched the recorded ones. We observed small horizontal eye velocities that could not be predicted by the stimulation
of the canals alone. No eye movements were observed after the end of head shaking about a fixed horizontal or vertical axis.
The eye velocities following the termination of head oscillations in the roll plane were small. The analysis methods developed
for this study may be useful in the investigation of eye movements elicited by other types of three-dimensional head movements.
Received: 24 April 1997 / Accepted: 8 July 1998 相似文献
12.
J. Blouin Loris Labrousse Martin Simoneau Jean-Louis Vercher Gabriel M. Gauthier 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1998,122(1):93-100
The accuracy of our spatially oriented behaviors largely depends on the precision of monitoring the change in body position
with respect to space during self-motion. We investigated observers’ capacity to determine, before and after head rotations
about the yaw axis, the position of a memorized earth-fixed visual target positioned 21° laterally. The subjects (n=6) showed small errors (mean=–0.6°) and little variability (mean=0.9°) in determining the position of an extinguished visual-target
position when the head (and gaze) remained in a straight-ahead position. This accuracy was preserved when subjects voluntary
rotated the head by various magnitudes in the direction of the memorized visual target (head rotations ranged between 5° and
60°). However, when the chair on which the subjects were seated was unexpectedly rotated about the yaw axis in the direction
of the target (chair rotations ranged between 6° and 36°) during the head-on-trunk rotations, the performance was markedly
decreased, both in terms of spatial precision (mean error=5.6°) and variability (mean=5.7°). A control experiment showed that
the prior knowledge of chair rotation occurrence had no effect on the perceived target position after head-trunk movements.
Updating an earth-fixed target position during head-on-trunk rotations could be achieved through both cervical and vestibular
signals processing, but, in the present experiment, the vestibular output was the only signal that had the potentiality to
contribute to accurate coding of the target position after simultaneous head and trunk movements. Our results therefore suggest
that the vestibular output is a noisy signal for the central nervous signal to update the visual space during head-in-space
motion.
Received: 2 June 1997 / Accepted: 16 March 1998 相似文献
13.
Benjamin T. Crane Erik S. Viirre J. L. Demer 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1997,114(2):304-320
We employed binocular magnetic search coils to study the vestibulo-ocular reflex (VOR) and visually enhanced vestibulo-ocular
reflex (VVOR) of 15 human subjects undergoing passive, whole-body rotations about a vertical (yaw) axis delivered as a series
of pseudorandom transients and sinusoidal oscillations at frequencies from 0.8 to 2.0 Hz. Rotations were about a series of
five axes ranging from 20 cm posterior to the eyes to 10 cm anterior to the eyes. Subjects were asked to regard visible or
remembered targets 10 cm, 25 cm, and 600 cm distant from the right eye. During sinusoidal rotations, the gain and phase of
the VOR and VVOR were found to be highly dependent on target distance and eccentricity of the rotational axis. For axes midway
between or anterior to the eyes, sinusoidal gain decreased progressively with increasing target proximity, while, for axes
posterior to the otolith organs, gain increased progressively with target proximity. These effects were large and highly significant.
When targets were remote, rotational axis eccentricity nevertheless had a small but significant effect on sinusoidal gain.
For sinusoidal rotational axes midway between or anterior to the eyes, a phase lead was present that increased with rotational
frequency, while for axes posterior to the otolith organs phase lag increased with rotational frequency. Transient trials
were analyzed during the first 25 ms and from 25 to 80 ms after the onset of the head rotation. During the initial 25 ms of
transient head rotations, VOR and VVOR gains were not significantly influenced by rotational eccentricity or target distance.
Later in the transient responses, 25–80 ms from movement onset, both target distance and eccentricity significantly influenced
gain in a manner similar to the behavior during sinusoidal rotation. Vergence angle generally remained near the theoretically
ideal value during illuminated test conditions (VVOR), while in darkness vergence often varied modestly from the ideal value.
Regression analysis of instantaneous VOR gain as a function of vergence demonstrated only a weak correlation, indicating that
instantaneous gain is not likely to be directly dependent on vergence. A model was proposed in which linear acceleration as
sensed by the otoliths is scaled by target distance and summed with angular acceleration as sensed by the semicircular canals
to control eye movements. The model was fit to the sinusoidal VOR data collected in darkness and was found to describe the
major trends observed in the data. The results of the model suggest that a linear interaction exists between the canal and
otolithic inputs to the VOR.
Received: 1 April 1996 / Accepted: 15 October 1996 相似文献
14.
C. J. S. Collins M. Jahanshahi G. R. Barnes 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1998,120(3):325-334
We assessed the suitability of using the Wing and Kristofferson model for timing repetitive motor responses to analyse timing
variability during repetitive saccadic eye movements. The model decomposes total timing variability (TV) into a central timing
component (CV) and a peripheral motor delay component (MV). Eight normal subjects made voluntary horizontal saccades, in darkness,
in synchrony with a regular auditory metronome. After 20 saccades had been produced, the metronome was switched off and subjects
continued responding at the same frequency until 31 further saccades had been made. Inter-saccade intervals (ISIs) from the
unpaced phase were used to calculate TV, CV and MV. Three different target intervals, paced by auditory cues, were used –
496 ms, 752 ms and 1000 ms. In the paced phase, subjects’ ISIs closely matched the auditory cue intervals. In the unpaced
phase, subjects were clearly able to respond at three different frequencies. As predicted by the Wing and Kristofferson model,
the durations of successive ISIs tended to be negatively correlated. As expected, TV and CV increased with increasing ISI.
Contrary to the expectation of the model that MV would remain constant, we found that it increased with increasing interval.
Our results do not conclusively demonstrate the validity of applying the Wing and Kristofferson model to the analysis of timing
variability during repetitive saccadic eye movements. However, comparison with previous studies shows that, at least in normal
subjects, it is equally valid to apply the model to the analysis of repetitive saccadic eye movements as it is to apply it
to the analysis of data from other effectors.
Received: 5 December 1996 / Accepted: 3 November 1997 相似文献
15.
A. Buizza A. Léger J. Droulez Dr. A. Berthoz R. Schmid 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1980,39(2):165-176
Summary Several studies in the past have demonstrated the existence of an Otolith-Ocular Reflex (OOR) in man, although much less sensitive than canal ocular reflex. The present paper 1 confirms these previous results. Nystagmic eye movements (L-nystagmus) appear in the seated subject during horizontal acceleration along the interaural axis in the dark for an acceleration level (1 m/s2) about ten times the perception threshold with a sensitivity of about 0.035 rad/m.When sinusoidal linear acceleration is combined with optokinetic stimulation, the recorded nystagmus slow phase velocity exhibits strong periodic modulation related to subject motion. This marked effect of linear acceleration on the optokinetic nystagmus (OKN) appears at a level (0.1 m/s2) close to the acceleration perception threshold and has a 4-fold higher sensitivity than L-nystagmus. Modulation of OKN can reach a peak-to-peak amplitude as great as 20 °/s; for a given optokinetic field size it increases with the velocity of the optokinetic stimulus, i.e. with the slow phase eye velocity. In parallel with changes in OKN slow phase velocity, linear acceleration induces a motion related decrease in the perceived velocity of the visual scene and modifications in selfmotion perception.The results are interpreted in terms of a mathematical model of visual-vestibular interaction. They show that sensory interaction processes can magnify the contribution given to the control of eye movements by the otolithic system and provide a way of exploring its function at low levels of acceleration.The present work has been presented at III European Neurosciences Meeting, Rome, September 1979 相似文献
16.
Chiju Chen-Huang R. A. McCrea 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1998,119(1):116-130
The contribution of irregular vestibular afferents to viewing distance-related changes in the angular vestibulo-ocular reflex
(AVOR) and combined angular and linear VOR (CVOR) was studied in squirrel monkeys trained to fixate earth-stationary targets
that were near (10 cm) and distant (90–170 cm) from their eyes. Perilymphatic anodal galvanic currents were used to reversibly
silence irregular vestibular afferents for periods of 4–5 s during the AVOR and CVOR evoked by 0.5- to 4-Hz sinusoidal rotations
(6–20°/s peak velocity) or 250–400°/s2 acceleration steps. The direction and magnitude of linear translation were changed by positioning the monkeys at different
distances off the axis of turntable rotation. The effects of irregular afferent galvanic ablation (GA) on viewing distance-related
changes in the AVOR were studied in four animals. Viewing distance-related changes in the AVOR could not always be evoked
and were frequently small in amplitude. GA reduced viewing distance-related change in the AVOR by an average of 64% when it
was present. Thus vestibular irregular afferents appear to play an important and necessary role in viewing distance-related
changes in the AVOR – on those occasions when the changes occur. Viewing distance-related changes in the CVOR were large and
reliably evoked. GA had very little effect on the gain or phase of viewing distance-related changes in the CVOR, although
the viewing distance-related CVOR responses of individual central vestibular neurons were affected. We conclude that irregular
afferents probably contribute to central signal processing related to both the AVOR and the CVOR, but the signals carried
by these afferents are only essential for viewing distance-related changes in AVOR.
Received: 13 June 1997 / Accepted: 12 August 1997 相似文献
17.
Hidekazu Furuse Hatsue Waki Kenya Kaneko Satoshi Fujii Masami Miura Hiroshi Sasaki Ken-Ichi Ito H. Kato Susumu Ando 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1998,123(3):307-314
Effects of the mono- and tetra-sialogangliosides, GM1 and GQ1b, on long-term potentiation (LTP) were investigated in the
CA1 neurons of guinea-pig hippocampal slices. The magnitude of LTP induced by a strong tetanus (100 Hz, 100 pulses) was not
significantly affected by application of either ganglioside. In contrast, when LTP was induced by a weak tetanus (100 Hz,
4 pulses), a significantly greater LTP was induced in the presence of either ganglioside. Similarly, when slices were incubated
in low-Ca2+ (1.0–1.1 mM) medium for more than 2 h, the LTP was usually small or absent, but showed a significant increase in amplitude
of population spike (A-PS) when the slices were incubated with either GM1 or GQ1b (4–5 μg/ml). In addition, the application
of GQ1b (4 μg/ml) reversed the blocking effect of an NMDA-receptor antagonist, APP-5 (10 μM), on the induction of LTP and
resulted in forming LTP. Based on these findings, we conclude that GM1 and GQ1b exert positive modulatory effects on the induction
of LTP in hippocampal CA1 neurons and suggest that GM1 and GQ1b may participate in the induction of LTP as donors of Ca2+ ions.
Received: 21 April 1998 / Accepted: 5 May 1998 相似文献
18.
S. G. Wells Graham R. Barnes 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1998,120(1):129-133
Anticipatory smooth pursuit before the expected appearance of a moving target can reduce the initial retinal blur caused by
the 100-ms delay of visual feedback. Humans, though, can only voluntarily generate smooth velocities up to about 5°/s without
a moving target. However, previous experiments have shown that repetitive brief presentations of a moving target every few
seconds appear to charge an internal store, the contents of which can later be released to generate higher velocity anticipatory
movements. This store’s longevity was assessed here by repetitively presenting a moving target for 500 ms at different known
intervals up to 7.2 s. Target motion at 25°/s or 50°/s was tested, with presentations in alternate directions or the same
direction. Anticipatory velocity, measured 100 ms after target onset, decreased with increasing interval for all target motion
conditions. A decrease was still seen when accurate timing cues were given before each presentation, suggesting that the drive
for anticipatory pursuit is held in a short-term store lasting a few seconds which can enhance the low velocities produced
by volition alone. The results also demonstrate that high-velocity anticipatory pursuit helps to overcome the temporal delays
in the system and allows target velocity to be matched at an earlier time.
Received: 27 August 1997 / Accepted: 22 December 1997 相似文献
19.
J. Bloomberg G. Melvill Jones B. Segal 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1991,84(1):47-56
Summary Results from Bloomberg et al. (1991) led to the hypothesis that saccades which accompany the darktested vestibulo-ocular reflex (VOR) tend to move the eyes towards a vestibularly derived percept of an intended oculomotor goal: also that this is so even when that percept has been adaptively modified by suitably prolonged visual-vestibular conflict. The present experiments investigate these implications by comparing the combined VOR+saccade performance with a presumed motor readout of the normal and adaptively modified vestibular percept. The methods employed were similar to those of an earlier study Bloomberg et al. (1988) in which it was found that after cessation of a. brief passive whole body rotation in the dark, a previously seen earth-fixed target can be accurately located by saccadic eye movements based on a vestibular memory of the preceding head rotation; the so-called Vestibular Memory-Contingent Saccade (VMCS) paradigm. The result showed that the vestibular perceptual response, as measured after rotation by means of the VMCS paradigm was on average indistinguishable from the combined VOR + saccade response measured during rotation. Furthermore, this was so in both the normal and adapted states. We conclude that these findings substantiate the above hypothesis. The results incidentally reaffirm the adaptive modifiability of vestibular perception, emphasing the need for active maintenance of its proper calibration according to behavioural context. 相似文献
20.
Moore ST Hirasaki E Cohen B Raphan T 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1999,129(3):347-361
Vertical head and eye coordination was studied as a function of viewing distance during locomotion. Vertical head translation
and pitch movements were measured using a video motion analysis system (Optotrak 3020). Vertical eye movements were recorded
using a video-based pupil tracker (Iscan). Subjects (five) walked on a linear treadmill at a speed of 1.67 m/s (6 km/h) while
viewing a target screen placed at distances ranging from 0.25 to 2.0 m at 0.25-m intervals. The predominant frequency of vertical
head movement was 2 Hz. In accordance with previous studies, there was a small head pitch rotation, which was compensatory
for vertical head translation. The magnitude of the vertical head movements and the phase relationship between head translation
and pitch were little affected by viewing distance, and tended to orient the naso-occipital axis of the head at a point approximately
1 m in front of the subject (the head fixation distance or HFD). In contrast, eye velocity was significantly affected by viewing
distance. When viewing a far (2-m) target, vertical eye velocity was 180° out of phase with head pitch velocity, with a gain
of 0.8. This indicated that the angular vestibulo-ocular reflex (aVOR) was generating the eye movement response. The major
finding was that, at a close viewing distance (0.25 m), eye velocity was in phase with head pitch and compensatory for vertical
head translation, suggesting that activation of the linear vestibulo-ocular reflex (lVOR) was contributing to the eye movement
response. There was also a threefold increase in the magnitude of eye velocity when viewing near targets, which was consistent
with the goal of maintaining gaze on target. The required vertical lVOR sensitivity to cancel an unmodified aVOR response
and generate the observed eye velocity magnitude for near targets was almost 3 times that previously measured. Supplementary
experiments were performed utilizing body-fixed active head pitch rotations at 1 and 2 Hz while viewing a head-fixed target.
Results indicated that the interaction of smooth pursuit and the aVOR during visual suppression could modify both the gain
and phase characteristics of the aVOR at frequencies encountered during locomotion. When walking, targets located closer than
the HFD (1.0 m) would appear to move in the same direction as the head pitch, resulting in suppression of the aVOR. The results
of the head-fixed target experiment suggest that phase modification of the aVOR during visual suppression could play a role
in generating eye movements consistent with the goal of maintaining gaze on targets closer than the HFD, which would augment
the lVOR response.
Received: 23 November 1998 / Accepted: 17 May 1999 相似文献