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Blouin, J., J. L. Vercher, G. M. Gauthier, J. Paillard, C. Bard et Y. Lamarre. « Perception of passive whole-body rotations in the absence of neck and body proprioception ». Journal of Neurophysiology 74, no 5 (1 novembre 1995) : 2216–19. http://dx.doi.org/10.1152/jn.1995.74.5.2216.
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1. This study investigated whether accurate perception of body rotation after passive horizontal whole-body rotations in the dark requires the integration of both vestibular and neck-body proprioceptive signals. 2. In the first experiment, the gain of the vestibuloocular reflex (VOR) of normal subjects ("controls") and of a patient without proprioception of the neck and body muscles was assessed by the use of pulse and sinusoidal stimulation. In the second experiment, the subjects reported verbally the magnitude of the body rotations. Finally, in the third experiment, they shifted gaze to the position fixated before the rotation ("vestibular memory-contingent saccades" paradigm). 3. The VOR gain of the patient was similar to that of controls, although the body rotations of the patient were largely overestimated, regardless of whether the patient reported the perceived magnitude verbally or through a gaze shift toward the position gazed at before the rotation. 4. These results suggest that neck muscle proprioception contributes to the vestibular signal calibration at the perceptual level necessary for determining body orientation accurately after rotations in the dark.
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Lopez, Christophe, Dominique Vibert et Fred W. Mast. « Can imagined whole-body rotations improve vestibular compensation ? » Medical Hypotheses 76, no 6 (juin 2011) : 816–19. http://dx.doi.org/10.1016/j.mehy.2011.02.026.
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Bockisch, Christopher J., Dominik Straumann et Thomas Haslwanter. « Eye Movements During Multi-Axis Whole-Body Rotations ». Journal of Neurophysiology 89, no 1 (1 janvier 2003) : 355–66. http://dx.doi.org/10.1152/jn.00058.2002.
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The semi-circular canals and the otolith organs both contribute to gaze stabilization during head movement. We investigated how these sensory signals interact when they provide conflicting information about head orientation in space. Human subjects were reoriented 90° in pitch or roll during long-duration, constant-velocity rotation about the earth-vertical axis while we measured three-dimensional eye movements. After the reorientation, the otoliths correctly indicated the static orientation of the subject with respect to gravity, while the semicircular canals provided a strong signal of rotation. This rotation signal from the canals could only be consistent with a static orientation with respect to gravity if the rotation-axis indicated by the canals was exactly parallel to gravity. This was not true, so a cue-conflict existed. These conflicting stimuli elicited motion sickness and a complex tumbling sensation. Strong horizontal, vertical, and/or torsional eye movements were also induced, allowing us to study the influence of the conflict between the otoliths and the canals on all three eye-movement components. We found a shortening of the horizontal and vertical time constants of the decay of nystagmus and a trend for an increase in peak velocity following reorientation. The dumping of the velocity storage occurred regardless of whether eye velocity along that axis was compensatory to the head rotation or not. We found a trend for the axis of eye velocity to reorient to make the head-velocity signal from the canals consistent with the head-orientation signal from the otoliths, but this reorientation was small and only observed when subjects were tilted to upright. Previous models of canal-otolith interaction could not fully account for our data, particularly the decreased time constant of the decay of nystagmus. We present a model with a mechanism that reduces the velocity-storage component in the presence of a strong cue-conflict. Our study, supported by other experiments, also indicates that static otolith signals exhibit considerably smaller effects on eye movements in humans than in monkeys.
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Klier, Eliana M., Dora E. Angelaki et Bernhard J. M. Hess. « Human Visuospatial Updating After Noncommutative Rotations ». Journal of Neurophysiology 98, no 1 (juillet 2007) : 537–41. http://dx.doi.org/10.1152/jn.01229.2006.
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As we move our bodies in space, we often undergo head and body rotations about different axes—yaw, pitch, and roll. The order in which we rotate about these axes is an important factor in determining the final position of our bodies in space because rotations, unlike translations, do not commute. Does our brain keep track of the noncommutativity of rotations when computing changes in head and body orientation and then use this information when planning subsequent motor commands? We used a visuospatial updating task to investigate whether saccades to remembered visual targets are accurate after intervening, whole-body rotational sequences. The sequences were reversed, either yaw then roll or roll then yaw, such that the final required eye movements to reach the same space-fixed target were different in each case. While each subject performed consistently irrespective of target location and rotational combination, we found great intersubject variability in their capacity to update. The distance between the noncommutative endpoints was, on average, half of that predicted by perfect noncommutativity. Nevertheless, most subjects did make eye movements to distinct final endpoint locations and not to one unique location in space as predicted by a commutative model. In addition, their noncommutative performance significantly improved when their less than ideal updating performance was taken into account. Thus the brain can produce movements that are consistent with the processing of noncommutative rotations, although it is often poor in using internal estimates of rotation for updating.
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Van Pelt, S., J. A. M. Van Gisbergen et W. P. Medendorp. « Visuospatial Memory Computations During Whole-Body Rotations in Roll ». Journal of Neurophysiology 94, no 2 (août 2005) : 1432–42. http://dx.doi.org/10.1152/jn.00018.2005.
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We used a memory-saccade task to test whether the location of a target, briefly presented before a whole-body rotation in roll, is stored in egocentric or in allocentric coordinates. To make this distinction, we exploited the fact that subjects, when tilted sideways in darkness, make systematic errors when indicating the direction of gravity (an allocentric task) even though they have a veridical percept of their self-orientation in space. We hypothesized that if spatial memory is coded allocentrically, these distortions affect the coding of remembered targets and their readout after a body rotation. Alternatively, if coding is egocentric, updating for body rotation becomes essential and errors in performance should be related to the amount of intervening rotation. Subjects ( n = 6) were tested making saccades to remembered world-fixed targets after passive body tilts. Initial and final tilt angle ranged between −120° CCW and 120° CW. The results showed that subjects made large systematic directional errors in their saccades (up to 90°). These errors did not occur in the absence of intervening body rotation, ruling out a memory degradation effect. Regression analysis showed that the errors were closely related to the amount of subjective allocentric distortion at both the initial and final tilt angle, rather than to the amount of intervening rotation. We conclude that the brain uses an allocentric reference frame, possibly gravity-based, to code visuospatial memories during whole-body tilts. This supports the notion that the brain can define information in multiple frames of reference, depending on sensory inputs and task demands.
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Dumontheil, Iroise, Panagiota Panagiotaki et Alain Berthoz. « Dual adaptation to sensory conflicts during whole-body rotations ». Brain Research 1072, no 1 (février 2006) : 119–32. http://dx.doi.org/10.1016/j.brainres.2005.11.091.
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Falconer, Caroline J., et Fred W. Mast. « Balancing the Mind ». Experimental Psychology 59, no 6 (1 janvier 2012) : 332–39. http://dx.doi.org/10.1027/1618-3169/a000161.
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The body schema is a key component in accomplishing egocentric mental transformations, which rely on bodily reference frames. These reference frames are based on a plurality of different cognitive and sensory cues among which the vestibular system plays a prominent role. We investigated whether a bottom-up influence of vestibular stimulation modulates the ability to perform egocentric mental transformations. Participants were significantly faster to make correct spatial judgments during vestibular stimulation as compared to sham stimulation. Interestingly, no such effects were found for mental transformation of hand stimuli or during mental transformations of letters, thus showing a selective influence of vestibular stimulation on the rotation of whole-body reference frames. Furthermore, we found an interaction with the angle of rotation and vestibular stimulation demonstrating an increase in facilitation during mental body rotations in a direction congruent with rightward vestibular afferents. We propose that facilitation reflects a convergence in shared brain areas that process bottom-up vestibular signals and top-down imagined whole-body rotations, including the precuneus and tempero-parietal junction. Ultimately, our results show that vestibular information can influence higher-order cognitive processes, such as the body schema and mental imagery.
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Glasauer, Stefan, et Thomas Brandt. « Noncommutative Updating of Perceived Self-Orientation in Three Dimensions ». Journal of Neurophysiology 97, no 4 (avril 2007) : 2958–64. http://dx.doi.org/10.1152/jn.00655.2006.
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After whole body rotations around an earth-vertical axis in darkness, subjects can indicate their orientation in space with respect to their initial orientation reasonably well. This is possible because the brain is able to mathematically integrate self-velocity information provided by the vestibular system to obtain self-orientation, a process called path integration. For rotations around multiple axes, however, computations are more demanding to accurately update self-orientation with respect to space. In such a case, simple integration is no longer sufficient because of the noncommutativity of rotations. We investigated whether such updating is possible after three-dimensional whole body rotations and whether the noncommutativity of three-dimensional rotations is taken into account. The ability of ten subjects to indicate their spatial orientation in the earth-horizontal plane was tested after different rotational paths from upright to supine positions. Initial and final orientations of the subjects were the same in all cases, but the paths taken were different, and so were the angular velocities sensed by the vestibular system. The results show that seven of the ten subjects could consistently indicate their final orientation within the earth-horizontal plane. Thus perceived final orientation was independent of the path taken, i.e., the noncommutativity of rotations was taken into account.
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Reynolds, J. S., et G. T. Gdowski. « Head Movements Produced During Whole Body Rotations and Their Sensitivity to Changes in Head Inertia in Squirrel Monkeys ». Journal of Neurophysiology 99, no 5 (mai 2008) : 2369–82. http://dx.doi.org/10.1152/jn.00320.2007.
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The head's inertia produces forces on the neck when the body moves. One collective function of the vestibulocollic and cervicocollic reflexes (VCR and CCR) is thought to be to stabilize the head with respect to the trunk during whole body movements. Little is known as to whether their head-movement kinematics produced by squirrel monkeys during whole body rotations are similar to those of cats and humans. Prior experiments with cats and human subjects have shown that yaw head-movement kinematics are unaffected by changes in the head's inertia when the whole body is rotated. These observations have led to the hypothesis that the combined actions of the VCR and CCR accommodate for changes in the head's inertia. To test this hypothesis in squirrel monkeys, it was imperative to first characterize the behavior of head movements produced during whole body rotation and then investigate their sensitivity to changes in the head's inertia. Our behavioral studies show that squirrel monkeys produce only small head movements with respect to the trunk during whole body rotations over a wide range of stimulus frequencies and velocities (0.5–4.0 Hz; 0–100°/s). Similar head movements were produced when only small additional changes in the head's inertia occurred. Electromyographic recordings from the splenius muscle revealed that an active process was utilized such that increases in muscle activation occurred when the inertia of the head was increased. These results are consistent with prior cat and human studies, suggesting that squirrel monkeys have a similar horizontal VCR and CCR.
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Huterer, Marko, et Kathleen E. Cullen. « Vestibuloocular Reflex Dynamics During High-Frequency and High-Acceleration Rotations of the Head on Body in Rhesus Monkey ». Journal of Neurophysiology 88, no 1 (1 juillet 2002) : 13–28. http://dx.doi.org/10.1152/jn.2002.88.1.13.
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For frequencies >10 Hz, the vestibuloocular reflex (VOR) has been primarily investigated during passive rotations of the head on the body in humans. These prior studies suggest that eye movements lag head movements, as predicted by a 7-ms delay in the VOR reflex pathways. However, Minor and colleagues recently applied whole-body rotations of frequencies ≤15 Hz in monkeys and found that eye movements were nearly in phase with head motion across all frequencies. The goal of the present study was to determine whether VOR response dynamics actually differ significantly for whole-body versus head-on-body rotations. To address this question, we evaluated the gain and phase of the VOR induced by high-frequency oscillations of the head on the body in monkeys by directly measuring both head and eye movements using the magnetic search coil technique. A torque motor was used to rotate the heads of three Rhesus monkeys over the frequency range 5–25 Hz. Peak head velocity was held constant, first at ±50°/s and then ±100°/s. The VOR was found to be essentially compensatory across all frequencies; gains were near unity (1.1 at 5 Hz vs. 1.2 at 25 Hz), and phase lag increased only slightly with frequency (from 2° at 5 Hz to 11° at 25 Hz, a marked contrast to the 63° lag at 25 Hz predicted by a 7-ms VOR latency). Furthermore, VOR response dynamics were comparable in darkness and when viewing a target and did not vary with peak velocity. Although monkeys offered less resistance to the initial cycles of applied head motion, the gain and phase of the VOR did not vary for early versus late cycles, suggesting that an efference copy of the motor command to the neck musculature did not alter VOR response dynamics. In addition, VOR dynamics were also probed by applying transient head perturbations with much greater accelerations (peak acceleration >15,000°/s2) than have been previously employed. The VOR latency was between 5 and 6 ms, and mean gain was close to unity for two of the three animals tested. A simple linear model well described the VOR responses elicited by sinusoidal and transient head on body rotations. We conclude that the VOR is compensatory over a wide frequency range in monkeys and has similar response dynamics during passive rotation of the head on body as during passive rotation of the whole body in space.
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Navarro Morales, Deborah Cecilia, Alexis Laplanche, Olga Kuldavletova, Bithja Cantave, Adéla Kola, Thomas Fréret, Gaëlle Quarck, Gilles Clément et Pierre Denise. « Vestibular stimulation and space-time interaction affect the perception of time during whole-body rotations ». PLOS ONE 20, no 1 (15 janvier 2025) : e0313219. https://doi.org/10.1371/journal.pone.0313219.
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Among the factors, such as emotions, that distort time perception, vestibular stimulation causes a contraction in subjective time. Unlike emotions, the intensity of vestibular stimulation can be easily and precisely modified, making it possible to study the quantitative relationship between stimulation and its effect on time perception. We hypothesized that the contraction of subjective time would increase with the vestibular stimulation magnitude. In the first experiment, participants sat on a rotatory chair and reproduced time intervals between the start and the end of whole-body passive rotations (40° or 80°; dynamic condition) or between two consecutive low-amplitude shakes (static condition). We also assessed reaction time under the same conditions to evaluate the attentional effect of the stimuli. As expected, duration reproduction in the 40° rotation was shorter than that observed in the static condition, but this effect was partly reversed for 80° rotations. In other words, vestibular stimulation shortens the perceived time interval, but this effect weakens with stronger stimulation. Attentional changes do not explain this unexpected result, as reaction time did not change between conditions. We hypothesized that the space-time interaction (i.e., spatially larger stimuli are perceived as lasting longer) could explain these findings. To assess this, in a second experiment participants were subjected to the same protocol but with three rotation amplitudes (30°, 60°, and 120°). The duration reproductions were systematically shorter for the lower amplitudes than for the higher amplitudes; so much so that for the highest amplitude (120°), the duration reproduction increased so that it did not differ from the static condition. Overall, the experiments show that whole-body rotation can contract subjective time, probably at the rather low level of the interval timing network, or dilate it, probably at a higher level via the space-time interaction.
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Dunbar, Donald C. « The influence of segmental movements and design on whole-body rotations during the airborne phase of primate leaps ». Zeitschrift für Morphologie und Anthropologie 80, no 1 (29 novembre 1994) : 109–24. http://dx.doi.org/10.1127/zma/80/1994/109.
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Lott, Melanie B., et Gan Xu. « Joint Angle Coordination Strategies During Whole Body Rotations on a Single Lower-Limb Support : An Investigation Through Ballet Pirouettes ». Journal of Applied Biomechanics 36, no 2 (1 avril 2020) : 103–12. http://dx.doi.org/10.1123/jab.2019-0209.
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Despite the prevalence of turning maneuvers in everyday life, relatively little research has been conducted on joint angle kinematic coordination during whole-body rotations around a vertical axis. Ballet pirouettes provide an opportunity to study dynamically balanced, whole-body rotations on a single support and the potential to scale results to smaller angular displacements executed by general populations. The purpose of this study was to determine the supporting limb’s ankle, knee, hip, and pelvis-trunk joint angle excursions and kinematic coordination strategies utilized during the pirouette’s turn phase. Advanced dancers (n = 6) performed pirouettes while whole-body 3-dimensional kinematics were recorded. Group mean ankle ab/adduction excursion was significantly greater than all other excursions (P < .05). Principal components analysis was applied to joint angle time-series data (4 joints × 3 degrees of freedom = 12 variables). The first 4 principal components explained 92% (2%) of variance, confirming redundancy in joint angle data. Evolution of the data along the first principal component in successful pirouettes oscillated at the pirouette’s rotational frequency. Principal component eigenvector coefficients provided evidence of ankle–hip coordination, although specific coordination patterns varied between individuals and across trials. These results indicate that successful pirouettes are executed with continuous, oscillatory joint angle coordination patterns.
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Furman, Joseph M., Ian Shirey, Jillyn Roxberg et Alexander Kiderman. « The vertical computerized rotational head impulse test ». Journal of Vestibular Research 34, no 1 (22 février 2024) : 29–38. http://dx.doi.org/10.3233/ves-230121.
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The computerized rotational head impulse test (crHIT) uses a computer-controlled rotational chair to deliver whole-body rotational impulses to assess the semicircular canals. The crHIT has only been described for horizontal head plane rotations. The purpose of this study was to describe the crHIT for vertical head plane rotations. In this preliminary study, we assessed four patients with surgically confirmed unilateral peripheral vestibular abnormalities and two control subjects. Results indicated that the crHIT was well-tolerated for both horizontal head plane and vertical head plane stimuli. The crHIT successfully assessed each of the six semicircular canals. This study suggests that the crHIT has the potential to become a new laboratory-based vestibular test for both the horizontal and vertical semicircular canals.
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Pettorossi, Vito Enrico, Chiara Occhigrossi, Roberto Panichi, Fabio Massimo Botti, Aldo Ferraresi, Giampietro Ricci et Mario Faralli. « Induction and Cancellation of Self-Motion Misperception by Asymmetric Rotation in the Light ». Audiology Research 13, no 2 (2 mars 2023) : 196–206. http://dx.doi.org/10.3390/audiolres13020019.
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Asymmetrical sinusoidal whole-body rotation sequences with half-cycles at different velocities induce self-motion misperception. This is due to an adaptive process of the vestibular system that progressively reduces the perception of slow motion and increases that of fast motion. It was found that perceptual responses were conditioned by four previous cycles of asymmetric rotation in the dark, as the perception of self-motion during slow and fast rotations remained altered for several minutes. Surprisingly, this conditioned misperception remained even when asymmetric stimulation was performed in the light, a state in which vision completely cancels out the perceptual error. This suggests that vision is unable to cancel the misadaptation in the vestibular system but corrects it downstream in the central perceptual processing. Interestingly, the internal vestibular perceptual misperception can be cancelled by a sequence of asymmetric rotations with fast/slow half-cycles in a direction opposite to that of the conditioning asymmetric rotations.
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Shanidze, N., K. Lim, J. Dye et W. M. King. « Galvanic stimulation of the vestibular periphery in guinea pigs during passive whole body rotation and self-generated head movement ». Journal of Neurophysiology 107, no 8 (15 avril 2012) : 2260–70. http://dx.doi.org/10.1152/jn.00314.2011.
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Irregular vestibular afferents exhibit significant phase leads with respect to angular velocity of the head in space. This characteristic and their connectivity with vestibulospinal neurons suggest a functionally important role for these afferents in producing the vestibulo-collic reflex (VCR). A goal of these experiments was to test this hypothesis with the use of weak galvanic stimulation of the vestibular periphery (GVS) to selectively activate or suppress irregular afferents during passive whole body rotation of guinea pigs that could freely move their heads. Both inhibitory and excitatory GVS had significant effects on compensatory head movements during sinusoidal and transient whole body rotations. Unexpectedly, GVS also strongly affected the vestibulo-ocular reflex (VOR) during passive whole body rotation. The effect of GVS on the VOR was comparable in light and darkness and whether the head was restrained or unrestrained. Significantly, there was no effect of GVS on compensatory eye and head movements during volitional head motion, a confirmation of our previous study that demonstrated the extravestibular nature of anticipatory eye movements that compensate for voluntary head movements.
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Schubert, Michael C., et Americo A. Migliaccio. « New advances regarding adaptation of the vestibulo-ocular reflex ». Journal of Neurophysiology 122, no 2 (1 août 2019) : 644–58. http://dx.doi.org/10.1152/jn.00729.2018.
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This is a review summarizing the development of vestibulo-ocular reflex (VOR) adaptation behavior with relevance to rehabilitation over the last 10 years and examines VOR adaptation using head-on-body rotations, specifically the influence of training target contrast, position and velocity error signal, active vs. passive head rotations, and sinusoidal vs. head impulse rotations. This review discusses optimization of the single VOR adaptation training session, consolidation between repeated training sessions, and dynamic incremental VOR adaptation. Also considered are the effects of aging and the roles of the efferent vestibular system, cerebellum, and otoliths on angular VOR adaptation. Finally, this review examines VOR adaptation findings in studies using whole body rotations.
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PHILBECK, J. W., M. BEHRMANN et J. M. LOOMIS. « Updating of locations during whole-body rotations in patients with hemispatial neglect ». Cognitive, Affective, & ; Behavioral Neuroscience 1, no 4 (1 décembre 2001) : 330–43. http://dx.doi.org/10.3758/cabn.1.4.330.
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Siegler, Isabelle. « Idiosyncratic orientation strategies influence self-controlled whole-body rotations in the dark ». Cognitive Brain Research 9, no 2 (mars 2000) : 205–7. http://dx.doi.org/10.1016/s0926-6410(00)00007-0.
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Anastasopoulos, Dimitri, Nausica Ziavra, Mark Hollands et Adolfo Bronstein. « Gaze displacement and inter-segmental coordination during large whole body voluntary rotations ». Experimental Brain Research 193, no 3 (12 novembre 2008) : 323–36. http://dx.doi.org/10.1007/s00221-008-1627-y.
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Siegler, I., I. Viaud-Delmon, I. Israël et A. Berthoz. « Self-motion perception during a sequence of whole-body rotations in darkness ». Experimental Brain Research 134, no 1 (23 août 2000) : 66–73. http://dx.doi.org/10.1007/s002210000415.
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Bourdin, C., V. Nougier, L. Bringoux, G. M. Gauthier, P. A. Barraud et C. Raphel. « Accuracy level of pointing movements performed during slow passive whole-body rotations ». Experimental Brain Research 138, no 1 (17 avril 2001) : 62–70. http://dx.doi.org/10.1007/s002210000674.
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Gavrilov, Vladimir V., Sidney I. Wiener et Alain Berthoz. « Enhanced hippocampal theta EEG during whole body rotations in awake restrained rats ». Neuroscience Letters 197, no 3 (septembre 1995) : 239–41. http://dx.doi.org/10.1016/0304-3940(95)11918-m.
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Féry, Yves-André, Richard Magnac et Isabelle Israël. « Commanding the direction of passive whole-body rotations facilitates egocentric spatial updating ». Cognition 91, no 2 (mars 2004) : B1—B10. http://dx.doi.org/10.1016/j.cognition.2003.05.001.
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Reynolds, J. S., D. Blum et G. T. Gdowski. « Reweighting Sensory Signals to Maintain Head Stability : Adaptive Properties of the Cervicocollic Reflex ». Journal of Neurophysiology 99, no 6 (juin 2008) : 3123–35. http://dx.doi.org/10.1152/jn.00793.2007.
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A major goal of this study was to characterize the cervicocollic reflexes (CCRs) in awake squirrel monkeys and compare it to observations in cat. This was carried out by stabilizing the head in space while rotating the lower body. The magnitude and phase of the torque produced between the head and the restraint system was used as an indicator of the CCR. Many properties of the squirrel monkey's CCR were found to be similar to those of the cat. The torque decreased as a function of frequency and amplitude. In addition, the static level of torque increased with head eccentricity. One difference was that the torque was 90× smaller in squirrel monkeys. Biomechanical differences, such as differences in head inertia, could account for these differences. The second goal was to determine if the CCR was sensitive to increases in the head's inertia. To test this, we increased the head's inertia by a factor of 36 and allowed the reflexes to adapt by rotating the whole body while the head was free to move. The CCR was rapidly assessed by periodically stabilizing the head in space during whole-body rotations. The magnitude of the torque increased by nearly 60%, suggesting that the CCR may adapt when changes in the head's inertia are imposed. Changes in the torque were also consistent with changes in head-movement kinematics during whole-body rotation. This suggests that the collic reflexes may dynamically adapt to maintain the performance and kinematics of reflexive head movement.
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Zanelli, Giulia, Maurizio Petrarca, Paolo Cappa, Enrico Castelli et Alain Berthoz. « Reorientation ability of adults and healthy children submitted to whole body horizontal rotations ». Cognitive Processing 10, S2 (20 août 2009) : 346–50. http://dx.doi.org/10.1007/s10339-009-0301-z.
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Dunbar, Donald C. « Aerial maneuvers of leaping lemurs : The physics of whole-body rotations while airborne ». American Journal of Primatology 16, no 4 (1988) : 291–303. http://dx.doi.org/10.1002/ajp.1350160402.
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Gruzdev, V. « Mechanics of torsion of the pedicle of ovarian tumors ». Kazan medical journal 20, no 4 (11 août 2021) : 433. http://dx.doi.org/10.17816/kazmj76546.
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DeStefino, V. J., D. A. Reighard, Y. Sugiyama, T. Suzuki, L. A. Cotter, M. G. Larson, N. J. Gandhi, S. M. Barman et B. J. Yates. « Responses of neurons in the rostral ventrolateral medulla to whole body rotations : comparisons in decerebrate and conscious cats ». Journal of Applied Physiology 110, no 6 (juin 2011) : 1699–707. http://dx.doi.org/10.1152/japplphysiol.00180.2011.
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The responses to vestibular stimulation of brain stem neurons that regulate sympathetic outflow and blood flow have been studied extensively in decerebrate preparations, but not in conscious animals. In the present study, we compared the responses of neurons in the rostral ventrolateral medulla (RVLM), a principal region of the brain stem involved in the regulation of blood pressure, to whole body rotations of conscious and decerebrate cats. In both preparations, RVLM neurons exhibited similar levels of spontaneous activity (median of ∼17 spikes/s). The firing of about half of the RVLM neurons recorded in decerebrate cats was modulated by rotations; these cells were activated by vertical tilts in a variety of directions, with response characteristics suggesting that their labyrinthine inputs originated in otolith organs. The activity of over one-third of RVLM neurons in decerebrate animals was altered by stimulation of baroreceptors; RVLM units with and without baroreceptor signals had similar responses to rotations. In contrast, only 6% of RVLM neurons studied in conscious cats exhibited cardiac-related activity, and the firing of just 1% of the cells was modulated by rotations. These data suggest that the brain stem circuitry mediating vestibulosympathetic reflexes is highly sensitive to changes in body position in space but that the responses to vestibular stimuli of neurons in the pathway are suppressed by higher brain centers in conscious animals. The findings also raise the possibility that autonomic responses to a variety of inputs, including those from the inner ear, could be gated according to behavioral context and attenuated when they are not necessary.
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Golomer, Eveline M. E., Robynne M. Gravenhorst et Yann Toussaint. « Influence of vision and motor imagery styles on equilibrium control during whole-body rotations ». Somatosensory & ; Motor Research 26, no 4 (janvier 2009) : 105–10. http://dx.doi.org/10.3109/08990220903384968.
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Shanidze, N., A. H. Kim, Y. Raphael et W. M. King. « Eye–head coordination in the guinea pig I. Responses to passive whole-body rotations ». Experimental Brain Research 205, no 3 (5 août 2010) : 395–404. http://dx.doi.org/10.1007/s00221-010-2374-4.
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Kasper, J., R. H. Schor et V. J. Wilson. « Response of vestibular neurons to head rotations in vertical planes. II. Response to neck stimulation and vestibular-neck interaction ». Journal of Neurophysiology 60, no 5 (1 novembre 1988) : 1765–78. http://dx.doi.org/10.1152/jn.1988.60.5.1765.
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1. We have studied the responses of neurons in the lateral and descending vestibular nuclei of decerebrate cats to stimulation of neck receptors, produced by rotating the body in vertical planes with the head stationary. The responses to such neck stimulation were compared with the responses to vestibular stimulation produced by whole-body tilt, described in the preceding paper. 2. After determining the optimal vertical plane of neck rotation (response vector orientation), the dynamics of the neck response were studied over a frequency range of 0.02-1 Hz. The majority of the neurons were excited by neck rotations that brought the chin toward the ipsilateral side; most neurons responded better to roll than to pitch rotations. The typical neck response showed a low-frequency phase lead of 30 degrees, increasing to 60 degrees at higher frequencies, and a gain that increased about threefold per decade. 3. Neck input was found in about one-half of the vestibular-responsive neurons tested with vertical rotations. The presence of a neck response was correlated with the predominant vestibular input to these neurons; neck input was most prevalent on neurons with vestibular vector orientations near roll and receiving convergent vestibular input, either input from both ipsilateral vertical semicircular canals, or from canals plus the otolith organs. 4. Neurons with both vestibular and neck responses tend to have the respective orientation vectors pointing in opposite directions, i.e., a head tilt that produces an excitatory vestibular response would produce an inhibitory neck response. In addition, the gain components of these responses were similar. These results suggest that during head movements on a stationary body, these opposing neck and vestibular inputs will cancel each other. 5. Cancellation was observed in 12 out of 27 neurons tested with head rotation in the mid-frequency range. For most of the remaining neurons, the response to such a combined stimulus was greatly attenuated: the vestibular and neck interaction was largely antagonistic. 6. Neck response dynamics were similar to those of the vestibular input in many neurons, permitting cancellation to take place over a wide range of stimulus frequencies. Another pattern of interaction, observed in some neurons with canal input, produced responses to head rotation that had a relatively constant gain and remained in phase with position over the entire frequency range; such neurons possibly code head position in space.
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Perlmutter, S. I., Y. Iwamoto, J. F. Baker et B. W. Peterson. « Spatial Alignment of Rotational and Static Tilt Responses of Vestibulospinal Neurons in the Cat ». Journal of Neurophysiology 82, no 2 (1 août 1999) : 855–62. http://dx.doi.org/10.1152/jn.1999.82.2.855.
Texte intégralRésumé :
The responses of vestibulospinal neurons to 0.5-Hz, whole-body rotations in three-dimensional space and static tilts of whole-body position were studied in decerebrate and alert cats. The neurons’ spatial properties for earth-vertical rotations were characterized by maximum and minimum sensitivity vectors ( R max and R min) in the cat’s horizontal plane. The orientation of a neuron’s R max was not consistently related to the orientation of its maximum sensitivity vector for static tilts ( T max). The angular difference between R max and T max was widely distributed between 0° and 150°, and R max and T max were aligned (i.e., within 45° of each other) for only 44% (14/32) of the neurons. The alignment of R max and T max was not correlated with the neuron’s sensitivity to earth-horizontal rotations, or to the orientation of R max in the horizontal plane. In addition, the extent to which a neuron exhibited spatiotemporal convergent (STC) behavior in response to vertical rotations was independent of the angular difference between R max and T max. This suggests that the high incidence of STC responses in our sample (56%) reflects not only canal-otolith convergence, but also the presence of static and dynamic otolith inputs with misaligned directionality. The responses of vestibulospinal neurons reflect a complex combination of static and dynamic vestibular inputs that may be required by postural reflexes that vary depending on head, trunk, and limb orientation, or on the frequency of stimulation.
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Peterson, B. W., J. Goldberg, G. Bilotto et J. H. Fuller. « Cervicocollic reflex : its dynamic properties and interaction with vestibular reflexes ». Journal of Neurophysiology 54, no 1 (1 juillet 1985) : 90–109. http://dx.doi.org/10.1152/jn.1985.54.1.90.
Texte intégralRésumé :
Electromyographic activity of dorsal neck muscles elicited by sinusoidal rotations of the body and head was studied in decerebrate cats over a wide range of rotational frequencies and amplitudes. Rotation of the body with the head held fixed in space elicited a cervicocollic reflex (CCR) in the biventer cervicis, complexus, obliquus capitis inferior, rectus capitis major, and splenius muscles. As stimulus amplitude increased, CCR amplitude increased first rapidly and then more slowly, displaying two linear incremental sensitivity ranges. In contrast, the vestibulocollic reflex (VCR) elicited by whole body rotation had a minimum stimulus threshold below which no response was observed, whereas the vestibuloocular reflex (VOR) saturated at intermediate stimulus intensities. When stimulus frequency was varied, the CCR exhibited second-order dynamic behavior. At frequencies below 0.5 Hz, muscle EMG activation was in phase with peak platform angular deviation in the direction that stretched the muscle, and the gain measured as the percent modulation of EMG activity per degree of rotation remained constant. As frequency increased to 3-4 Hz, response phase advanced by 120 deg or more and gain increased with a slope approaching 40 dB/decade. The data were well-fitted by second-order transfer functions containing two zeros. Both the dynamic behavior of the CCR and its high sensitivity to small stimuli resemble the properties of muscle spindle primary afferents, suggesting that the latter may provide the major input responsible for the CCR. Dynamic properties and gains of the CCR and VCR were quite similar at frequencies between 0.2 and 3-4 Hz. Transfer functions of both reflexes contained two zeros whose time constants were correlated in a population of 11 cats, suggesting that reflex dynamics may be matched to the mechanical properties of each animal's head-neck system. Interaction of the CCR and VCR was studied under two conditions. When the head was driven by a servomotor while the body remained stationary, EMG activation by the two reflexes added linearly to produce a large response. When the body was rotated with the head allowed to counterrotate about the C1-C2 joint, the two reflexes combined linearly in an antagonistic fashion: the CCR acted to oppose head rotations produced by the VCR, thus preventing the ratio of head counterrotation to body rotation from exceeding 0.5. The data indicate that the CCR and VCR behave approximately linearly, both individually and in combination. Acting together, the two reflexes assist each other in preventing oscillation of the head on a stationary body.(ABSTRACT TRUNCATED AT 400 WORDS)
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Bresciani, Jean-Pierre, Gabriel M. Gauthier, Jean-Louis Vercher et Jean Blouin. « On the nature of the vestibular control of arm-reaching movements during whole-body rotations ». Experimental Brain Research 164, no 4 (14 mai 2005) : 431–41. http://dx.doi.org/10.1007/s00221-005-2263-4.
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Chang, Nai-Yuan Nicholas, Alex K. Malone et Timothy E. Hullar. « Changes in temporal binding related to decreased vestibular input ». Seeing and Perceiving 25 (2012) : 107. http://dx.doi.org/10.1163/187847612x647397.
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Imbalance among patients with vestibular hypofunction has been related to inadequate compensatory eye movements in response to head movements. However, symptoms of imbalance might also occur due a temporal mismatch between vestibular and other balance-related sensory cues. This temporal mismatch could be reflected in a widened temporal binding window (TBW), or the length of time over which simultaneous sensory stimuli may be offset and still perceived as simultaneous. We hypothesized that decreased vestibular input would lead to a widening of the temporal binding window. We performed whole-body rotations about the earth-vertical axis following a sinusoidal trajectory at 0.5 Hz with a peak velocity of 60°/s in four normal subjects. Dichotic auditory clicks were presented through headphones at various phases relative to the rotations. Subjects were asked to indicate whether the cues were synchronous or asynchronous and the TBW was calculated. We then simulated decreased vestibular input by rotating at diminished peak velocities of 48, 24 and 12°/s in four normal subjects. TBW was calculated between ±1 SD away from the mean on the psychometric curve. We found that the TBW increases as amplitude of rotation decreases. Average TBW of 251 ms at 60°/s increased to 309 ms at 12°/s. This result leads to the novel conclusion that changes in temporal processing may be a mechanism for imbalance in patients with vestibular hypofunction.
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Sadeghi, Soroush G., Lloyd B. Minor et Kathleen E. Cullen. « Response of Vestibular-Nerve Afferents to Active and Passive Rotations Under Normal Conditions and After Unilateral Labyrinthectomy ». Journal of Neurophysiology 97, no 2 (février 2007) : 1503–14. http://dx.doi.org/10.1152/jn.00829.2006.
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We investigated the possible contribution of signals carried by vestibular-nerve afferents to long-term processes of vestibular compensation after unilateral labyrinthectomy. Semicircular canal afferents were recorded from the contralesional nerve in three macaque monkeys before [horizontal (HC) = 67, anterior (AC) = 66, posterior (PC) = 50] and 1–12 mo after (HC = 192, AC = 86, PC = 57) lesion. Vestibular responses were evaluated using passive sinusoidal rotations with frequencies of 0.5–15 Hz (20–80°/s) and fast whole-body rotations reaching velocities of 500°/s. Sensitivities to nonvestibular inputs were tested by: 1) comparing responses during active and passive head movements, 2) rotating the body with the head held stationary to activate neck proprioceptors, and 3) encouraging head-restrained animals to attempt to make head movements that resulted in the production of neck torques of ≤2 Nm. Mean resting discharge rate before and after the lesion did not differ for the regular, D (dimorphic)-irregular, or C (calyx)-irregular afferents. In response to passive rotations, afferents showed no change in sensitivity and phase, inhibitory cutoff, and excitatory saturation after unilateral labyrinthectomy. Moreover, head sensitivities were similar during voluntary and passive head rotations and responses were not altered by neck proprioceptive or efference copy signals before or after the lesion. The only significant change was an increase in the proportion of C-irregular units postlesion, accompanied by a decrease in the proportion of regular afferents. Taken together, our findings show that changes in response properties of the vestibular afferent population are not likely to play a major role in the long-term changes associated with compensation after unilateral labyrinthectomy.
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Crane, Benjamin T., et Joseph L. Demer. « Effect of Adaptation to Telescopic Spectacles on the Initial Human Horizontal Vestibuloocular Reflex ». Journal of Neurophysiology 83, no 1 (1 janvier 2000) : 38–49. http://dx.doi.org/10.1152/jn.2000.83.1.38.
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Gain of the vestibuloocular reflex (VOR) not only varies with target distance and rotational axis, but can be chronically modified in response to prolonged wearing of head-mounted magnifiers. This study examined the effect of adaptation to telescopic spectacles on the variation of the VOR with changes in target distance and yaw rotational axis for head velocity transients having peak accelerations of 2,800 and 1,000°/s2. Eye and head movements were recorded with search coils in 10 subjects who underwent whole body rotations around vertical axes that were 10 cm anterior to the eyes, centered between the eyes, between the otoliths, or 20 cm posterior to the eyes. Immediately before each rotation, subjects viewed a target 15 or 500 cm distant. Lighting was extinguished immediately before and was restored after completion of each rotation. After initial rotations, subjects wore 1.9× magnification binocular telescopic spectacles during their daily activities for at least 6 h. Test spectacles were removed and measurement rotations were repeated. Of the eight subjects tolerant of adaptation to the telescopes, six demonstrated VOR gain enhancement after adaptation, while gain in two subjects was not increased. For all subjects, the earliest VOR began 7–10 ms after onset of head rotation regardless of axis eccentricity or target distance. Regardless of adaptation, VOR gain for the proximate target exceeded that for the distant target beginning at 20 ms after onset of head rotation. Adaptation increased VOR gain as measured 90–100 ms after head rotation onset by an average of 0.12 ± 0.02 (SE) for the higher head acceleration and 0.19 ± 0.02 for the lower head acceleration. After adaptation, four subjects exhibited significant increases in the canal VOR gain only, whereas two subjects exhibited significant increases in both angular and linear VOR gains. The latencies of linear and early angular target distance effects on VOR gain were unaffected by adaptation. The earliest significant change in angular VOR gain in response to adaptation occurred 50 and 68 ms after onset of the 2,800 and 1,000°/s2 peak head accelerations, respectively. The latency of the adaptive increase in linear VOR gain was ∼50 ms for the peak head acceleration of 2,800°/s2, and 100 ms for the peak head acceleration of 1,000°/s2. Thus VOR gain changes and latency were consistent with modification in the angular VOR in most subjects, and additionally in the linear VOR in a minority of subjects.
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Demer, Joseph L., et Benjamin T. Crane. « Vision and vestibular adaptation ». Otolaryngology–Head and Neck Surgery 119, no 1 (juillet 1998) : 78–88. http://dx.doi.org/10.1016/s0194-5998(98)70176-7.
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This article summarizes six recent degree-of-freedom studies of visual-vestibular interaction during natural activities and relates the findings to canalotolith interactions evaluated during eccentric axis rotations. Magnetic search coils were used to measure angular eye and head movements of young and elderly subjects. A flux gate magnetometer was used to measure three-dimensional head translation. Three activities were studied: standing quietly, walking in place, and running in place. Each activity was evaluated with three viewing conditions: a visible target viewed normally, a remembered target in darkness, and a visible target viewed with x2 binocular telescopic spectacles. Canal-otolith interaction was assessed with passive, whole-body, transient, and steady-state rotations in pitch and yaw at multiple frequencies about axes that were either oculocentric or eccentric to the eyes. For each rotational axis, subjects regarded visible and remembered targets located at various distances. Horizontal and vertical angular vestibulo-ocular reflexes were demonstrable in all subjects during standing, walking, and running. When only angular gains were considered, gains in both darkness and during normal vision were less than 1.0 and were generally lower in elderly than in young subjects. Magnified vision with x2 telescopic spectacles produced only small gain increases as compared with normal vision. During walking and running all subjects exhibited significant mediolateral and dorsoventral head translations that were antiphase locked to yaw and pitch head movements, respectively. These head translations and rotations have mutually compensating effects on gaze in a target plane for typical viewing distances and allow angular vestibulo-ocular reflex gains of less than 1.0 to be optimal for gaze stabilization during natural activities. During passive, whole-body eccentric pitch and yaw head rotations, vestibulo-ocular reflex gain was modulated as appropriate to stabilize gaze on targets at the distances used. This modulation was evident within the first 80 msec of onset of head movement, too early to be caused by immediate visual tracking. Modeling suggests a linear interaction between canal signals and otolith signals scaled by the inverse of target distance. Vestibulo-ocular reflex performance appears to be adapted to stabilize gaze during translational and rotational perturbations that occur during natural activities, as is appropriate for relevant target distances. Although immediate visual tracking contributes little to gaze stabilization during natural activities, visual requirements determine the performance of vestibulo-ocular reflexes arising from both canals and otoliths. (Otolaryngol Head Neck Surg 1998;119:78-88.)
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Baker, J., J. Goldberg et B. Peterson. « Spatial and temporal response properties of the vestibulocollic reflex in decerebrate cats ». Journal of Neurophysiology 54, no 3 (1 septembre 1985) : 735–56. http://dx.doi.org/10.1152/jn.1985.54.3.735.
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Vestibulocollic reflex responses of several neck muscles in decerebrate cats were studied during angular rotations of the whole body in a large number of vertical and horizontal rotation planes, at frequencies from 0.07 to 1.6 Hz. Vestibulocollic responses were compared to eye muscle and forelimb muscle vestibular responses. Electromyographic activity was recorded by fine wires inserted in biventer cervicis, complexus, longus capitis, obliquus capitis inferior, occipitoscapularis, rectus capitis major, splenius, lateral rectus, and triceps brachii. At frequencies of approximately 0.5 Hz and above, neck muscle electromyographic response gains were sinusoidal functions of stimulus orientation within a set of vertical or horizontal planes, and a muscle's response phase remained constant across rotation planes, or reversed by 180 degrees. Response patterns at high frequencies were consistent with vestibulocollic reflex activation by semicircular canals through brain circuitry that modifies canal dynamics. At frequencies of approximately 0.5 Hz and above, the stimulus orientation in which a given neck muscle's response was maximal remained nearly constant across frequencies. Thus, we used responses to rotations at high frequencies to calculate axes of maximal response of each muscle in three-dimensional space. Lateral rectus, obliquus, and to a lesser extent, splenius and longus capitus were activated predominantly by horizontal rotations. Biventer was activated predominantly by pitch, triceps predominantly by roll, and complexus, occipitoscapularis, and rectus major significantly excited by rotations in all three coordinate planes. In some cases, at frequencies less than 0.5 Hz, neck muscle response phase varied depending on the vertical plane in which the cat was rotated, and the optimal response plane was poorly defined and varied with frequency. These responses indicated that, at some frequencies, neck muscle activity can result from summation of inputs with differing spatial orientation and dynamics (spatial-temporal convergence). Differences between responses to vertical and horizontal rotations suggested that low-frequency spatial-temporal convergence behavior of the vestibulocollic reflex during vertical rotations was due to convergent semicircular canal and otolith receptor inputs.(ABSTRACT TRUNCATED AT 400 WORDS)
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Anderson, John H., et Stephen L. Liston. « Asymmetry of Vestibulo-Ocular Reflex in the Cat ». Otolaryngology–Head and Neck Surgery 93, no 5 (octobre 1985) : 597–600. http://dx.doi.org/10.1177/019459988509300505.
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Vertical eye movements were recorded in alert, restrained cats that were subjected to whole-body rotations which stimulated the vertical semicircular canals. The results showed a significant asymmetry between the upward and downward slow-phase eye movements, which suggests differences in the CNS processing of vertical canal inputs vis-à-vis the vestibulo-ocular reflex.
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Prsa, Mario, Steven Gale et Olaf Blanke. « Self-motion leads to mandatory cue fusion across sensory modalities ». Journal of Neurophysiology 108, no 8 (15 octobre 2012) : 2282–91. http://dx.doi.org/10.1152/jn.00439.2012.
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When perceiving properties of the world, we effortlessly combine multiple sensory cues into optimal estimates. Estimates derived from the individual cues are generally retained once the multisensory estimate is produced and discarded only if the cues stem from the same sensory modality (i.e., mandatory fusion). Does multisensory integration differ in that respect when the object of perception is one's own body, rather than an external variable? We quantified how humans combine visual and vestibular information for perceiving own-body rotations and specifically tested whether such idiothetic cues are subjected to mandatory fusion. Participants made extensive size comparisons between successive whole body rotations using only visual, only vestibular, and both senses together. Probabilistic descriptions of the subjects' perceptual estimates were compared with a Bayes-optimal integration model. Similarity between model predictions and experimental data echoed a statistically optimal mechanism of multisensory integration. Most importantly, size discrimination data for rotations composed of both stimuli was best accounted for by a model in which only the bimodal estimator is accessible for perceptual judgments as opposed to an independent or additive use of all three estimators (visual, vestibular, and bimodal). Indeed, subjects' thresholds for detecting two multisensory rotations as different from one another were, in pertinent cases, larger than those measured using either single-cue estimate alone. Rotations different in terms of the individual visual and vestibular inputs but quasi-identical in terms of the integrated bimodal estimate became perceptual metamers. This reveals an exceptional case of mandatory fusion of cues stemming from two different sensory modalities.
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Golomer, Eveline, Yann Toussaint, Arnaud Bouillette et Jean Keller. « Spontaneous whole body rotations and classical dance expertise : How shoulder–hip coordination influences supporting leg displacements ». Journal of Electromyography and Kinesiology 19, no 2 (avril 2009) : 314–21. http://dx.doi.org/10.1016/j.jelekin.2007.08.004.
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Allum, J. H. J., et T. Ledin. « Recovery of vestibulo-ocular reflex-function in subjects with an acute unilateral peripheral vestibular deficit ». Journal of Vestibular Research 9, no 2 (1 avril 1999) : 135–44. http://dx.doi.org/10.3233/ves-1999-9208.
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The centrally controlled compensation for a reduced horizontal vestibulo-ocular reflex (VOR) gain caused by a unilateral afferent deficit is usually studied following a selective surgical procedure which completely lesions the vestibular nerve or blocks the horizontal semicircular canal. The more common, unilateral, vestibular deficit encountered clinically, is a partial loss of peripheral vestibular function, following which peripheral recovery and/or central compensation may occur. We investigated changes of the VOR gain in response to a sudden, idiopathic, unilateral vestibular deficit in 64 subjects by examining the responses to low-frequency, whole-body, rotations about an earth vertical axis with different accelerations (5, 20 and 40 deg / sec 2 ) during in- and out-patient visits separated by 4 months in an attempt to identify changes brought about by peripheral recovery and by central compensation processes. Peripheral function was assumed to be measured by the response to caloric irrigation. It improved some 30% between the two visits. VOR responses for rotations towards the deficit side also improved between the two visits. Most improvement occurred for 20 deg / sec 2 accelerations. However, the correlation coefficient between rotation and caloric responses was always less than 0.6. Unlike caloric responses which improved over time, responses for rotations to the intact side did not change between the visits. For this reason, the majority of observed VOR rotation responses were nearly symmetrical at the time of the second visit, despite being below normal levels. These findings suggest that both peripheral recovery and central compensation processes help restore symmetrical VOR function for head rotations after a partial unilateral vestibular deficit. However the improvement of VOR response symmetry, particularly to slow ( < 40 deg / sec 2 ) accelerations, is largely independent of the recovery of peripheral sensitivity.
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Peters, Ryan M., Brandon G. Rasman, J. Timothy Inglis et Jean-Sébastien Blouin. « Gain and phase of perceived virtual rotation evoked by electrical vestibular stimuli ». Journal of Neurophysiology 114, no 1 (juillet 2015) : 264–73. http://dx.doi.org/10.1152/jn.00114.2015.
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Galvanic vestibular stimulation (GVS) evokes a perception of rotation; however, very few quantitative data exist on the matter. We performed psychophysical experiments on virtual rotations experienced when binaural bipolar electrical stimulation is applied over the mastoids. We also performed analogous real whole body yaw rotation experiments, allowing us to compare the frequency response of vestibular perception with (real) and without (virtual) natural mechanical stimulation of the semicircular canals. To estimate the gain of vestibular perception, we measured direction discrimination thresholds for virtual and real rotations. Real direction discrimination thresholds decreased at higher frequencies, confirming multiple previous studies. Conversely, virtual direction discrimination thresholds increased at higher frequencies, implying low-pass filtering of the virtual perception process occurring potentially anywhere between afferent transduction and cortical responses. To estimate the phase of vestibular perception, participants manually tracked their perceived position during sinusoidal virtual and real kinetic stimulation. For real rotations, perceived velocity was approximately in phase with actual velocity across all frequencies. Perceived virtual velocity was in phase with the GVS waveform at low frequencies (0.05 and 0.1 Hz). As frequency was increased to 1 Hz, the phase of perceived velocity advanced relative to the GVS waveform. Therefore, at low frequencies GVS is interpreted as an angular velocity signal and at higher frequencies GVS becomes interpreted increasingly as an angular position signal. These estimated gain and phase spectra for vestibular perception are a first step toward generating well-controlled virtual vestibular percepts, an endeavor that may reveal the usefulness of GVS in the areas of clinical assessment, neuroprosthetics, and virtual reality.
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Van Pelt, Stan, et W. Pieter Medendorp. « Gaze-Centered Updating of Remembered Visual Space During Active Whole-Body Translations ». Journal of Neurophysiology 97, no 2 (février 2007) : 1209–20. http://dx.doi.org/10.1152/jn.00882.2006.
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Various cortical and sub-cortical brain structures update the gaze-centered coordinates of remembered stimuli to maintain an accurate representation of visual space across eyes rotations and to produce suitable motor plans. A major challenge for the computations by these structures is updating across eye translations. When the eyes translate, objects in front of and behind the eyes’ fixation point shift in opposite directions on the retina due to motion parallax. It is not known if the brain uses gaze coordinates to compute parallax in the translational updating of remembered space or if it uses gaze-independent coordinates to maintain spatial constancy across translational motion. We tested this by having subjects view targets, flashed in darkness in front of or behind fixation, then translate their body sideways, and subsequently reach to the memorized target. Reach responses showed parallax-sensitive updating errors: errors increased with depth from fixation and reversed in lateral direction for targets presented at opposite depths from fixation. In a series of control experiments, we ruled out possible biasing factors such as the presence of a fixation light during the translation, the eyes accompanying the hand to the target, and the presence of visual feedback about hand position. Quantitative geometrical analysis confirmed that updating errors were better described by using gaze-centered than gaze-independent coordinates. We conclude that spatial updating for translational motion operates in gaze-centered coordinates. Neural network simulations are presented suggesting that the brain relies on ego-velocity signals and stereoscopic depth and direction information in spatial updating during self-motion.
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Buttner, U., A. F. Fuchs, G. Markert-Schwab et P. Buckmaster. « Fastigial nucleus activity in the alert monkey during slow eye and head movements ». Journal of Neurophysiology 65, no 6 (1 juin 1991) : 1360–71. http://dx.doi.org/10.1152/jn.1991.65.6.1360.
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1. Single units were recorded extracellularly from the fastigial nucleus of three macaque monkeys. Two untrained animals were subjected to whole-body yaw rotations in the light and dark and to full-field horizontal optokinetic stimuli provided by a drum with vertical stripes. The third also was subjected to sinusoidal yaw rotations but, in addition, was trained to follow a small spot, which moved in various ways relative to the animal, to reveal possible smooth pursuit and vestibular sensitivities. 2. On the basis of their responses to vestibular and optokinetic stimuli and their responses during smooth pursuit, fastigial neurons could be divided functionally into a rostral and a caudal group. 3. Most rostral neurons exhibited an increased firing for contralateral head rotations and ipsilateral optokinetic stimuli. A few had the opposite combination of directional preferences. The average firing rates increased monotonically both with contralateral head velocity and ipsilateral drum velocity and decreased monotonically for the oppositely directed movements. There was no change in firing rate for either spontaneous saccades or smooth pursuit of a small moving spot. 4. In contrast, neurons in the caudal fastigial nuclei not only have a robust vestibular sensitivity, but respond during smooth pursuit as well. Most discharge during contralateral head velocity and contralateral smooth pursuit so that they exhibit very little modulation during the vestibuloocular reflex (VOR) or when the rotating animal is fixating a target stationary in the world (SIW). The remaining neurons discharge during contralateral head rotations but ipsilateral eye rotations; these units exhibit their greatest modulation during the SIW condition. 5. Because they respond during quite different behavioral situations, it seems likely that rostral fastigial neurons are involved with descending control of the somatic musculature, whereas the caudal neurons are involved in oculomotor control. The sparse anatomic and lesion data that is available is consistent with this idea.
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McCall, Andrew A., Derek M. Miller et Carey D. Balaban. « Integration of vestibular and hindlimb inputs by vestibular nucleus neurons : multisensory influences on postural control ». Journal of Neurophysiology 125, no 4 (1 avril 2021) : 1095–110. http://dx.doi.org/10.1152/jn.00350.2019.
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Vestibular nucleus neurons receive convergent information from hindlimb somatosensory inputs and vestibular inputs. In this study, extracellular single-unit recordings of vestibular nucleus neurons during conditions of passively applied limb movement, passive whole body rotations, and combined stimulation were well fit by an additive model. The integration of hindlimb somatosensory inputs with vestibular inputs at the first stage of vestibular processing suggests that vestibular nucleus neurons account for limb position in determining vestibulospinal responses to postural perturbations.
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Shenoy, Krishna V., David C. Bradley et Richard A. Andersen. « Influence of Gaze Rotation on the Visual Response of Primate MSTd Neurons ». Journal of Neurophysiology 81, no 6 (1 juin 1999) : 2764–86. http://dx.doi.org/10.1152/jn.1999.81.6.2764.
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Influence of gaze rotation on the visual response of primate MSTd neurons. When we move forward, the visual image on our retina expands. Humans rely on the focus, or center, of this expansion to estimate their direction of heading and, as long as the eyes are still, the retinal focus corresponds to the heading. However, smooth rotation of the eyes adds nearly uniform visual motion to the expanding retinal image and causes a displacement of the retinal focus. In spite of this, humans accurately judge their heading during pursuit eye movements and during active, smooth head rotations even though the retinal focus no longer corresponds to the heading. Recent studies in macaque suggest that correction for pursuit may occur in the dorsal aspect of the medial superior temporal area (MSTd) because these neurons are tuned to the retinal position of the focus and they modify their tuning during pursuit to compensate partially for the focus shift. However, the question remains whether these neurons also shift focus tuning to compensate for smooth head rotations that commonly occur during gaze tracking. To investigate this question, we recorded from 80 MSTd neurons while monkeys tracked a visual target either by pursuing with their eyes or by vestibulo-ocular reflex cancellation (VORC; whole-body rotation with eyes fixed in head and head fixed on body). VORC is a passive, smooth head rotation condition that selectively activates the vestibular canals. We found that neurons shift their focus tuning in a similar way whether focus displacement is caused by pursuit or by VORC. Across the population, compensation averaged 88 and 77% during pursuit and VORC, respectively (tuning shift divided by the retinal focus to true heading difference). Moreover the degree of compensation during pursuit and VORC was correlated in individual cells ( P< 0.001). Finally neurons that did not compensate appreciably tended to be gain-modulated during pursuit and VORC and may constitute an intermediate stage in the compensation process. These results indicate that many MSTd cells compensate for general gaze rotation, whether produced by eye-in-head or head-in-world rotation, and further implicate MSTd as a critical stage in the computation of heading. Interestingly vestibular cues present during VORC allow many cells to compensate even though humans do not accurately judge their heading in this condition. This suggests that MSTd may use vestibular information to create a compensated heading representation within at least a subpopulation of cells, which is accessed perceptually only when additional cues related to active head rotations are also present.
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GAVRILOV, VLADIMIR V., SIDNEY I. WIENER et ALAIN BERTHOZ. « Whole-Body Rotations Enhance Hippocampal Theta Rhythmic Slow Activity in Awake Rats Passively Transported on a Mobile Robot ». Annals of the New York Academy of Sciences 781, no 1 Lipids and Sy (juin 1996) : 385–98. http://dx.doi.org/10.1111/j.1749-6632.1996.tb15714.x.
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