The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Stephen G Lisberger - One of the best experts on this subject based on the ideXlab platform.
-
Neural substrate of modified and unmodified pathways for learning in monkey Vestibuloocular Reflex.
Journal of neurophysiology, 2008Co-Authors: Ramnarayan Ramachandran, Stephen G LisbergerAbstract:To understand how the brain learns, we need to identify the full neural circuit for a behavior; characterize how neural responses in the circuit change during behavioral learning; and understand the nature, location, and control of the cellular changes that are responsible for learning. This goal seems attainable for the Vestibuloocular Reflex (VOR), where the neural circuit basis for learning is already partially understood. The current hypothesis for VOR learning postulates cellular changes in the cerebellar cortex and the vestibular nucleus. It suggests that the brain stem contains two parallel pathways that have been modeled on the basis of extensive biological data as unmodified and modified VOR pathways with frequency-dependent internal gains and different time delays. We now show a correspondence between the responses of different groups of neurons in the vestibular nucleus and the signals emanating from the two pathways in the model. Floccular target neurons (FTNs) and position-vestibular-pause neurons (PVPs) were identified by their discharge during eye movements and by the presence or absence of inhibition by floccular stimulation. FTNs had response gains and phases that coincided with predictions for pathways that are modified in association with learning, whereas PVPs had responses in agreement with predictions for the unmodified pathways. The quantitative agreement of prior model predictions and new data supports the identity of FTNs and PVPs as brain stem interneurons in the modified and unmodified VOR pathways. Other aspects of the data make predictions about how vestibular inputs are transformed as they pass through the two pathways.
-
Transformation of vestibular signals into motor commands in the Vestibuloocular Reflex pathways of monkeys.
Journal of neurophysiology, 2006Co-Authors: Ramnarayan Ramachandran, Stephen G LisbergerAbstract:Parallel pathways mediate the rotatory Vestibuloocular Reflex (VOR). If the VOR undergoes adaptive modification with spectacles that change the magnification of the visual scene, signals in one neu...
-
neural basis for motor learning in the Vestibuloocular Reflex of primates iii computational and behavioral analysis of the sites of learning
Journal of Neurophysiology, 1994Co-Authors: Stephen G LisbergerAbstract:1. We have used a combination of eye movement recordings and computer modeling to study long-term adaptive modification (motor learning) in the Vestibuloocular Reflex (VOR). The eye movement record...
-
Neural basis for motor learning in the Vestibuloocular Reflex of primates. II. Changes in the responses of horizontal gaze velocity Purkinje cells in the cerebellar flocculus and ventral paraflocculus
Journal of neurophysiology, 1994Co-Authors: Stephen G Lisberger, T. A. Pavelko, Helen Bronte-stewart, L. S. StoneAbstract:1. We made extracellular recordings from Purkinje cells in the flocculus and ventral paraflocculus of awake monkeys before and after motor learning in the Vestibuloocular Reflex (VOR). Three sample...
-
Vestibular inputs to brain stem neurons that participate in motor learning in the primate Vestibuloocular Reflex.
Journal of neurophysiology, 1992Co-Authors: D. M. Broussard, Stephen G LisbergerAbstract:1. Previous studies have described a subpopulation of interneurons in the Vestibuloocular Reflex (VOR) pathways that express large changes in their responses to head turns in conjunction with motor learning in the VOR. These neurons are called flocculus target neurons (FTNs) because they are inhibited at monosynaptic latencies by stimulation of the flocculus and ventral paraflocculus. 2. Electrical stimulation of the vestibular labyrinth revealed that FTNs receive excitatory monosynaptic inputs from the ipsilateral vestibular labyrinth and longer-latency, excitatory inputs from the contralateral labyrinth. 3. Our data show that commissural inhibition, which has been thought to be an important feature of vestibular processing, does not provide the dominant inputs from the contralateral labyrinth to FTNs. Instead, the inputs from both labyrinths are excitatory and may be functionally antagonistic. Changes in the balance of excitatory inputs from the two horizontal canals to FTNs could contribute to motor learning in the VOR.
Lloyd B. Minor - One of the best experts on this subject based on the ideXlab platform.
-
effects of canal plugging on the Vestibuloocular Reflex and vestibular nerve discharge during passive and active head rotations
Journal of Neurophysiology, 2009Co-Authors: Soroush G Sadeghi, Lloyd B. Minor, Jay M Goldberg, Kathleen E CullenAbstract:Mechanical occlusion (plugging) of the slender ducts of semicircular canals has been used in the clinic as well as in basic vestibular research. Here, we investigated the effect of canal plugging in two macaque monkeys on the horizontal Vestibuloocular Reflex (VOR) and the responses of vestibular-nerve afferents during passive head rotations. Afferent responses to active head movements were also studied. The horizontal VOR gain decreased after plugging to <0.1 for frequencies <2 Hz but rose to about 0.6 as frequency was increased to 15 Hz. Afferents innervating plugged horizontal canals had response sensitivities that increased with the frequency of passive rotations from <0.01 (spikes/s)/(°/s) at 0.5 Hz to values of about 0.2 and 0.5 (spikes/s)/(°/s) at 8 Hz for regular and irregular afferents, respectively (<50% of responses in controls). An increase in phase lead was also noted following plugging in afferent discharge, but not in the VOR. Because the phase discrepancy between the VOR and afferent discharge is much larger than that seen in control animals, this suggests that central adaptation shapes VOR dynamics following plugging. The effect of canal plugging on afferent responses can be modeled as an increase in stiffness and a reduction in the dominant time constant and gain in the transfer function describing canal dynamics. Responses were also evident during active head rotations, consistent with the frequency content of these movements. We conclude that canal plugging in macaques is effective only at frequencies <2 Hz. At higher frequencies, afferents show significant responses, with a nearly 90° phase lead, such that they encode near-rotational acceleration. Our results demonstrate that afferents innervating plugged canals respond robustly during voluntary movements, a finding that has implications for understanding the effects of canal plugging in clinical practice.
-
Effects of Canal Plugging on the Vestibuloocular Reflex and Vestibular Nerve Discharge During Passive and Active Head Rotations
Journal of neurophysiology, 2009Co-Authors: Soroush G Sadeghi, Lloyd B. Minor, Jay M Goldberg, Kathleen E CullenAbstract:Mechanical occlusion (plugging) of the slender ducts of semicircular canals has been used in the clinic as well as in basic vestibular research. Here, we investigated the effect of canal plugging in two macaque monkeys on the horizontal Vestibuloocular Reflex (VOR) and the responses of vestibular-nerve afferents during passive head rotations. Afferent responses to active head movements were also studied. The horizontal VOR gain decreased after plugging to
-
dynamics of the horizontal Vestibuloocular Reflex after unilateral labyrinthectomy response to high frequency high acceleration and high velocity rotations
Experimental Brain Research, 2006Co-Authors: Soroush G Sadeghi, Lloyd B. Minor, Kathleen E CullenAbstract:Loss of vestibular information from one labyrinth results in a marked asymmetry in the horizontal Vestibuloocular Reflex (VOR). The results of prior studies suggest that long-term deficits in VOR are more severe in response to rapid impulses than to sinusoidal head movements. The goal of the present study was to investigate the VOR following unilateral labyrinthectomy in response to different stimuli covering the full range of physiologically relevant head movements in macaque monkeys. The VOR was studied 1–39 days post-lesion using transient head perturbations (up to 12,000°/s2), rapid rotations (up to 500°/s), and sinusoidal rotations (up to 15 Hz). In response to rotations with high acceleration or velocity, both contra- and ipsilesional gains remained subnormal. VOR gains decreased as a function of increasing stimulus acceleration or velocity, reaching minimal values of 0.7–0.8 and 0.3–0.4 for contra and ipsilesional rotations, respectively. For sinusoidal rotations with low frequencies and velocities, responses to contralesional stimulation recovered within ∼ 4 days. With increasing velocities and frequencies of rotation, however, the gains of contra- and ipsilesional responses remained subnormal. For each of the most challenging stimuli tested (i.e., 12,000°/s2 transient head perturbations, 500°/s fast whole-body rotations and 15 Hz stimulation) no significant compensation was observed in contra- or ipsilesional responses over time. Moreover, we found that gain of the cervico-ocular Reflex (COR) remained negligible following unilateral loss indicating that neck Reflexes did not contribute to the observed compensation. VOR responses elicited by both sinusoidal and transient rotations following unilateral labyrinthectomy could be described by the same mathematical model. We conclude that the compensated VOR has comparable response dynamics for impulses and sinusoidal head movements.
-
Differential adaptation of the linear and nonlinear components of the horizontal Vestibuloocular Reflex in squirrel monkeys.
Journal of neurophysiology, 2002Co-Authors: Richard A. Clendaniel, David M Lasker, Lloyd B. MinorAbstract:Previous work in squirrel monkeys has demonstrated the presence of linear and nonlinear components to the horizontal Vestibuloocular Reflex (VOR) evoked by high-acceleration rotations. The nonlinear component is seen as a rise in gain with increasing velocity of rotation at frequencies more than 2 Hz (a velocity-dependent gain enhancement). We have shown that there are greater changes in the nonlinear than linear component of the response after spectacle-induced adaptation. The present study was conducted to determine if the two components of the response share a common adaptive process. The gain of the VOR, in the dark, to sinusoidal stimuli at 4 Hz (peak velocities: 20-150 degrees /s) and 10 Hz (peak velocities: 20 and 100 degrees /s) was measured pre- and postadaptation. Adaptation was induced over 4 h with x0.45 minimizing spectacles. Sum-of-sines stimuli were used to induce adaptation, and the parameters of the stimuli were adjusted to invoke only the linear or both linear and nonlinear components of the response. Preadaptation, there was a velocity-dependent gain enhancement at 4 and 10 Hz. In postadaptation with the paradigms that only recruited the linear component, there was a decrease in gain and a persistent velocity-dependent gain enhancement (indicating adaptation of only the linear component). After adaptation with the paradigm designed to recruit both the linear and nonlinear components, there was a decrease in gain and no velocity-dependent gain enhancement (indicating adaptation of both components). There were comparable changes in the response to steps of acceleration. We interpret these results to indicate that separate processes drive the adaptation of the linear and nonlinear components of the response.
-
Horizontal Vestibuloocular Reflex Evoked by High-Acceleration Rotations in the Squirrel Monkey. IV. Responses After Spectacle-Induced Adaptation
Journal of neurophysiology, 2001Co-Authors: Richard A. Clendaniel, David M Lasker, Lloyd B. MinorAbstract:The horizontal angular Vestibuloocular Reflex (VOR) evoked by sinusoidal rotations from 0.5 to 15 Hz and acceleration steps up to 3,000°/s2 to 150°/s was studied in six squirrel monkeys following a...
Kathleen E Cullen - One of the best experts on this subject based on the ideXlab platform.
-
effects of canal plugging on the Vestibuloocular Reflex and vestibular nerve discharge during passive and active head rotations
Journal of Neurophysiology, 2009Co-Authors: Soroush G Sadeghi, Lloyd B. Minor, Jay M Goldberg, Kathleen E CullenAbstract:Mechanical occlusion (plugging) of the slender ducts of semicircular canals has been used in the clinic as well as in basic vestibular research. Here, we investigated the effect of canal plugging in two macaque monkeys on the horizontal Vestibuloocular Reflex (VOR) and the responses of vestibular-nerve afferents during passive head rotations. Afferent responses to active head movements were also studied. The horizontal VOR gain decreased after plugging to <0.1 for frequencies <2 Hz but rose to about 0.6 as frequency was increased to 15 Hz. Afferents innervating plugged horizontal canals had response sensitivities that increased with the frequency of passive rotations from <0.01 (spikes/s)/(°/s) at 0.5 Hz to values of about 0.2 and 0.5 (spikes/s)/(°/s) at 8 Hz for regular and irregular afferents, respectively (<50% of responses in controls). An increase in phase lead was also noted following plugging in afferent discharge, but not in the VOR. Because the phase discrepancy between the VOR and afferent discharge is much larger than that seen in control animals, this suggests that central adaptation shapes VOR dynamics following plugging. The effect of canal plugging on afferent responses can be modeled as an increase in stiffness and a reduction in the dominant time constant and gain in the transfer function describing canal dynamics. Responses were also evident during active head rotations, consistent with the frequency content of these movements. We conclude that canal plugging in macaques is effective only at frequencies <2 Hz. At higher frequencies, afferents show significant responses, with a nearly 90° phase lead, such that they encode near-rotational acceleration. Our results demonstrate that afferents innervating plugged canals respond robustly during voluntary movements, a finding that has implications for understanding the effects of canal plugging in clinical practice.
-
Effects of Canal Plugging on the Vestibuloocular Reflex and Vestibular Nerve Discharge During Passive and Active Head Rotations
Journal of neurophysiology, 2009Co-Authors: Soroush G Sadeghi, Lloyd B. Minor, Jay M Goldberg, Kathleen E CullenAbstract:Mechanical occlusion (plugging) of the slender ducts of semicircular canals has been used in the clinic as well as in basic vestibular research. Here, we investigated the effect of canal plugging in two macaque monkeys on the horizontal Vestibuloocular Reflex (VOR) and the responses of vestibular-nerve afferents during passive head rotations. Afferent responses to active head movements were also studied. The horizontal VOR gain decreased after plugging to
-
dynamics of the horizontal Vestibuloocular Reflex after unilateral labyrinthectomy response to high frequency high acceleration and high velocity rotations
Experimental Brain Research, 2006Co-Authors: Soroush G Sadeghi, Lloyd B. Minor, Kathleen E CullenAbstract:Loss of vestibular information from one labyrinth results in a marked asymmetry in the horizontal Vestibuloocular Reflex (VOR). The results of prior studies suggest that long-term deficits in VOR are more severe in response to rapid impulses than to sinusoidal head movements. The goal of the present study was to investigate the VOR following unilateral labyrinthectomy in response to different stimuli covering the full range of physiologically relevant head movements in macaque monkeys. The VOR was studied 1–39 days post-lesion using transient head perturbations (up to 12,000°/s2), rapid rotations (up to 500°/s), and sinusoidal rotations (up to 15 Hz). In response to rotations with high acceleration or velocity, both contra- and ipsilesional gains remained subnormal. VOR gains decreased as a function of increasing stimulus acceleration or velocity, reaching minimal values of 0.7–0.8 and 0.3–0.4 for contra and ipsilesional rotations, respectively. For sinusoidal rotations with low frequencies and velocities, responses to contralesional stimulation recovered within ∼ 4 days. With increasing velocities and frequencies of rotation, however, the gains of contra- and ipsilesional responses remained subnormal. For each of the most challenging stimuli tested (i.e., 12,000°/s2 transient head perturbations, 500°/s fast whole-body rotations and 15 Hz stimulation) no significant compensation was observed in contra- or ipsilesional responses over time. Moreover, we found that gain of the cervico-ocular Reflex (COR) remained negligible following unilateral loss indicating that neck Reflexes did not contribute to the observed compensation. VOR responses elicited by both sinusoidal and transient rotations following unilateral labyrinthectomy could be described by the same mathematical model. We conclude that the compensated VOR has comparable response dynamics for impulses and sinusoidal head movements.
-
Vestibuloocular Reflex Dynamics During High-Frequency and High-Acceleration Rotations of the Head on Body in Rhesus Monkey
Journal of neurophysiology, 2002Co-Authors: Marko Huterer, Kathleen E CullenAbstract: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 l...
-
Vestibuloocular Reflex signal modulation during voluntary and passive head movements.
Journal of neurophysiology, 2002Co-Authors: Jefferson E. Roy, Kathleen E CullenAbstract:The Vestibuloocular Reflex (VOR) effectively stabilizes the visual world on the retina over the wide range of head movements generated during daily activities by producing an eye movement of equal ...
Stephen M. Highstein - One of the best experts on this subject based on the ideXlab platform.
-
computer simulation of Vestibuloocular Reflex motor learning using a realistic cerebellar cortical neuronal network model
International Conference on Neural Information Processing, 2007Co-Authors: Kayichiro Inagaki, Yutaka Hirata, Pablo M. Blazquez, Stephen M. HighsteinAbstract:The Vestibuloocular Reflex (VOR) is under adaptive control to stabilize our vision during head movements. It has been suggested that the acute VOR motor learning requires long-term depression (LTD) and potentiation (LTP) at the parallel fiber --- Purkinje cell synapses in the cerebellar flocculus. We simulated the VOR motor learning basing upon the LTD and LTP using a realistic cerebellar cortical neuronal network model. In this model, LTD and LTP were induced at the parallel fiber --- Purkinje cell synapses by the spike timing dependent plasticity rule, which considers the timing of the spike occurrence in the climbing fiber and the parallel fibers innervating the same Purkinje cell. The model was successful to reproduce the changes in eye movement and Purkinje cell simple spike firing modulation during VOR in the dark after low and high gain VOR motor learning.
-
Memory retention of Vestibuloocular Reflex motor learning in squirrel monkeys.
Neuroreport, 2004Co-Authors: Y. Kuki, Yutaka Hirata, Pablo M. Blazquez, Shane A. Heiney, Stephen M. HighsteinAbstract:The Vestibuloocular Reflex (VOR) motor learning can be induced chronically by wearing lenses for several weeks to months, or acutely by visual-vestibular mismatch for several hours. Cerebellar long term depression (LTD) has been proposed as a causal mechanism for acute learning. We demonstrate differences in retention of acutely and chronically acquired VOR gains in squirrel monkeys and discuss neuronal correlates and possible roles of cerebellar LTD. Our data is compatible with the idea that cerebellar LTD might be a mechanism responsible for acute VOR adaptation.
-
A dynamical model for the vertical Vestibuloocular Reflex and optokinetic response in primate.
Neurocomputing, 2003Co-Authors: Yutaka Hirata, Ichiro Takeuchi, Stephen M. HighsteinAbstract:The Vestibuloocular Reflex (VOR) in concert with the optokinetic response (OKR) stabilizes vision during head motion. The VOR system characteristics are both compensatory and adaptively self-calibrated. A model was constructed to aid in the understanding of the roles of the cerebellum and other neuronal sites in the performance and adaptation of the vertical VOR. The model structure was based upon the known neuroanatomy, and model parameters were estimated using experimental data. The model can reproduce and predict eye movements and cerebellar Purkinje cell firing patterns during VOR, OKR, and various visual-vestibular mismatch paradigms.
-
Acute Adaptation of the Vestibuloocular Reflex: Signal Processing by Floccular and Ventral Parafloccular Purkinje Cells
Journal of neurophysiology, 2001Co-Authors: Yutaka Hirata, Stephen M. HighsteinAbstract:The gain of the vertical Vestibuloocular Reflex (VVOR), defined as eye velocity/head velocity was adapted in squirrel monkeys by employing visual-vestibular mismatch stimuli. VVOR gain, measured in...
-
ICONIP (1) - Computer Simulation of Vestibuloocular Reflex Motor Learning Using a Realistic Cerebellar Cortical Neuronal Network Model
Neural Information Processing, 1Co-Authors: Kayichiro Inagaki, Yutaka Hirata, Pablo M. Blazquez, Stephen M. HighsteinAbstract:The Vestibuloocular Reflex (VOR) is under adaptive control to stabilize our vision during head movements. It has been suggested that the acute VOR motor learning requires long-term depression (LTD) and potentiation (LTP) at the parallel fiber --- Purkinje cell synapses in the cerebellar flocculus. We simulated the VOR motor learning basing upon the LTD and LTP using a realistic cerebellar cortical neuronal network model. In this model, LTD and LTP were induced at the parallel fiber --- Purkinje cell synapses by the spike timing dependent plasticity rule, which considers the timing of the spike occurrence in the climbing fiber and the parallel fibers innervating the same Purkinje cell. The model was successful to reproduce the changes in eye movement and Purkinje cell simple spike firing modulation during VOR in the dark after low and high gain VOR motor learning.
Theodore Raphan - One of the best experts on this subject based on the ideXlab platform.
-
RAPID COMMUNICATION Contribution of Vestibular Commissural Pathways to Spatial Orientation of the Angular Vestibuloocular Reflex
2014Co-Authors: Susan L. Wearne, Theodore Raphan, Bernard CohenAbstract:bution of vestibular commissural pathways to spatial orientation and horizontal components of eye movements were re-of the angular Vestibuloocular Reflex. J. Neurophysiol. 78: 1193 – corded. Here we analyze three-dimensional eye movements 1197, 1997. During nystagmus induced by the angular vestibulooc- to determine whether GIA tilts with regard to the head in ular Reflex (aVOR), the axis of eye velocity tends to align with any direction would affect the trajectories of eye velocitythe direction of gravitoinertial acceleration (GIA), a process we after velocity storage is abolished leaving only the directterm ‘‘spatial orientation of the aVOR.’ ’ We studied spatial orienta-pathways intact.tion of the aVOR in rhesus and cynomolgus monkeys before and after midline section of the rostral medulla abolished all oculomotor functions related to velocity storage, leaving the direct optokinetic M E T H O D Sand vestibular pathways intact. Optokinetic afternystagmus and the bias component of off-vertical-axis rotation were lost, and the Juvenile rhesus monkeys (M502 and M613) were prepared with aVOR time constant was reduced to a value commensurate with eye coils to record eye position in three dimensions, and the midlinethe time constants of primary semicircular canal afferents. Spatial was surgically sectioned in the rostral medulla. The experiments orientation of the aVOR, induced either during optokinetic or ves
-
Dependence of the Roll Angular Vestibuloocular Reflex (aVOR) on Gravity
Journal of neurophysiology, 2009Co-Authors: Sergei B. Yakushin, Bernard Cohen, Yongqing Xiang, Theodore RaphanAbstract:Little is known about the dependence of the roll angular Vestibuloocular Reflex (aVOR) on gravity or its gravity-dependent adaptive properties. To study gravity-dependent characteristics of the roll aVOR, monkeys were oscillated about a naso-occipital axis in darkness while upright or tilted. Roll aVOR gains were largest in the upright position and decreased by 7–15% as animals were tilted from the upright. Thus the unadapted roll aVOR gain has substantial gravitational dependence. Roll gains were also decreased or increased by 0.25 Hz, in- or out-of-phase rotation of the head and the visual surround while animals were prone, supine, upright, or in side-down positions. Gain changes, determined as a function of head tilt, were fit with a sinusoid; the amplitudes represented the amount of the gravity-dependent gain change, and the bias, the gravity-independent gain change. Gravity-dependent gain changes were absent or substantially smaller in roll (≈5%) than in yaw (25%) or pitch (17%), whereas gravity-independent gain changes were similar for roll, pitch, and yaw (≈20%). Thus the high-frequency roll aVOR gain has an inherent dependence on head orientation re gravity in the unadapted state, which is different from the yaw/pitch aVORs. This inherent gravitational dependence may explain why the adaptive circuits are not active when the head is tilted re gravity during roll aVOR adaptation. These behavioral differences support the idea that there is a fundamental difference in the central organization of canal-otolith convergence of the roll and yaw/pitch aVORs.
-
Modeling Gravity-Dependent Plasticity of the Angular Vestibuloocular Reflex With a Physiologically Based Neural Network
Journal of neurophysiology, 2006Co-Authors: Yongqing Xiang, Sergei B. Yakushin, Bernard L. Cohen, Theodore RaphanAbstract:dore Raphan. Modeling gravity-dependent plasticity of the angular Vestibuloocular Reflex with a physiologically based neural network. J Neurophysiol 96: 3349‐3361, 2006. First published September 13, 2006; doi:10.1152/jn.00430.2006. A neural network model was developed to explain the gravity-dependent properties of gain adaptation of the angular Vestibuloocular Reflex (aVOR). Gain changes are maximal at the head orientation where the gain is adapted and decrease as the head is tilted away from that position and can be described by the sum of gravity-independent and gravity-dependent components. The adaptation process was modeled by modifying the weights and bias values of a three-dimensional physiologically based neural network of canal‐otolith-convergent neurons that drive the aVOR. Model parameters were trained using experimental vertical aVOR gain values. The learning rule aimed to reduce the error between eye velocities obtained from experimental gain values and model output in the position of adaptation. Although the model was trained only at specific head positions, the model predicted the experimental data at all head positions in three dimensions. Altering the relative learning rates of the weights and bias improved the model-data fits. Model predictions in three dimensions compared favorably with those of a double-sinusoid function, which is a fit that minimized the mean square error at every head position and served as the standard by which we compared the model predictions. The model supports the hypothesis that gravity-dependent adaptation of the aVOR is realized in three dimensions by a direct otolith input to canal‐otolith neurons, whose canal sensitivities are adapted by the visual-vestibular mismatch. The adaptation is tuned by how the weights from otolith input to the canal‐otolith-convergent neurons are adapted for a given head orientation.
-
Spatial Distribution of Gravity-Dependent Gain Changes in the Vestibuloocular Reflex
Journal of neurophysiology, 2005Co-Authors: Sergei B. Yakushin, Theodore Raphan, Yongqing Xiang, Bernard L. CohenAbstract:This study determined whether dependence of angular Vestibuloocular Reflex (aVOR) gain adaptation on gravity is a fundamental property in three dimensions. Horizontal aVOR gains were adaptively increased or decreased in two cynomolgus monkeys in upright, side down, prone, and supine positions, and aVOR gains were tested in darkness by yaw rotation with the head in a wide variety of orientations. Horizontal aVOR gain changes peaked at the head position in which the adaptation took place and gradually decreased as the head moved away from this position in any direction. The gain changes were plotted as a function of head tilt and fit with a sinusoid plus a bias to obtain the gravity-dependent (amplitude) and gravity-independent (bias) components. Peak-to-peak gravity-dependent gain changes in planes containing the position of adaptation and the magnitude of the gravity-independent components were both ∼25%. We assumed that gain changes over three-dimensional space could be described by a sinusoid the amplitude of which also varied sinusoidally. Using gain changes obtained from the head position in which the gains were adapted, a three-dimensional surface was generated that was qualitatively similar to a surface obtained from the experimental data. This extends previous findings on vertical aVOR gain adaptation in one plane and introduces a conceptual framework for understanding plasticity in three dimensions: aVOR gain changes are composed of two components, one of which depends on head position relative to gravity. It is likely that this gravitational dependence optimizes the stability of retinal images during movement in three-dimensional space.
-
Context-Specific Adaptation of the Vertical Vestibuloocular Reflex With Regard to Gravity
Journal of neurophysiology, 2000Co-Authors: Sergei B. Yakushin, Theodore Raphan, Bernard CohenAbstract:We determined whether head position with regard to gravity is an important context for angular Vestibuloocular Reflex (aVOR) gain adaptation. Vertical aVOR gains were adapted with monkeys upright o...
