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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
    2014
    Co-Authors: Susan L. Wearne, Theodore Raphan, Bernard Cohen
    Abstract:

    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

  • Spatial Orientation of optokinetic nystagmus and ocular pursuit during orbital space flight.
    Experimental Brain Research, 2005
    Co-Authors: Steven T Moore, Bernard Cohen, Theodore Raphan, Alain Berthoz, Gilles Clément
    Abstract:

    On Earth, eye velocity of horizontal optokinetic nystagmus (OKN) orients to gravito-inertial acceleration (GIA), the sum of linear accelerations acting on the head and body. We determined whether adaptation to micro-gravity altered this Orientation and whether ocular pursuit exhibited similar properties. Eye movements of four astronauts were recorded with three-dimensional video-oculography. Optokinetic stimuli were stripes moving horizontally, vertically, and obliquely at 30 degrees/s. Ocular pursuit was produced by a spot moving horizontally or vertically at 20 degrees/s. Subjects were either stationary or were centrifuged during OKN with 1 or 0.5 g of interaural or dorsoventral centripetal linear acceleration. Average eye position during OKN (the beating field) moved into the quick-phase direction by 10 degrees during lateral and upward field movement in all conditions. The beating field did not shift up during downward OKN on Earth, but there was a strong upward movement of the beating field (9 degrees) during downward OKN in the absence of gravity; this likely represents an adaptation to the lack of a vertical 1-g bias in-flight. The horizontal OKN velocity axis tilted 9 degrees in the roll plane toward the GIA during interaural centrifugation, both on Earth and in space. During oblique OKN, the velocity vector tilted towards the GIA in the roll plane when there was a disparity between the direction of stripe motion and the GIA, but not when the two were aligned. In contrast, dorsoventral acceleration tilted the horizontal OKN velocity vector 6 degrees in pitch away from the GIA. Roll tilts of the horizontal OKN velocity vector toward the GIA during interaural centrifugation are consistent with the Orientation properties of velocity storage, but pitch tilts away from the GIA when centrifuged while supine are not. We speculate that visual suppression during OKN may have caused the velocity vector to tilt away from the GIA during dorsoventral centrifugation. Vertical OKN and ocular pursuit did not exhibit Orientation toward the GIA in any condition. Static full-body roll tilts and centrifugation generating an equivalent interaural acceleration produced the same tilts in the horizontal OKN velocity before and after flight. Thus, the magnitude of tilt in OKN velocity was dependent on the magnitude of interaural linear acceleration, rather than the tilt of the GIA with regard to the head. These results favor a 'filter' model of Spatial Orientation in which orienting eye movements are proportional to the magnitude of low frequency interaural linear acceleration, rather than models that postulate an internal representation of gravity as the basis for Spatial Orientation.

  • the nodulus and uvula source of cerebellar control of Spatial Orientation of the angular vestibulo ocular reflex
    Annals of the New York Academy of Sciences, 2002
    Co-Authors: Bernard Cohen, Padmore John, Sergei B Yakushin, Jean Buettnerennever, Theodore Raphan
    Abstract:

    : The nodulus and rostral-ventral uvula of the vestibulo-cerebellum play a critical role in orienting eye velocity of the slow component of the angular vestibulo-ocular reflex (aVOR) to gravito-inertial acceleration (GIA). This is done by altering the time constants of "velocity storage" in the vestibular system and by generating "cross-coupled" eye velocities that shift the eye velocity vector from along the body yaw axis to the yaw axis in a Spatial frame. In this report, we show that eye velocity generated through the aVOR by constant velocity centrifugation in the monkey orients to the GIA in space, regardless of the position of the head with respect to the axis of rotation. We also show that, after removal of the nodulus and rostral-ventral uvula, the Spatial Orientation of eye velocity to the GIA is lost and that eye velocity is then purely driven by the semicircular canals in a body frame of reference. These findings are further confirmation that these regions of the vestibulo-cerebellum control Spatial Orientation of the aVOR.

  • control of Spatial Orientation of the angular vestibulo ocular reflex by the nodulus and uvula of the vestibulocerebellum
    Annals of the New York Academy of Sciences, 1999
    Co-Authors: Boris M Sheliga, Sergei B Yakushin, Theodore Raphan, Adam Silvers, Bernard Cohen
    Abstract:

    : Eye velocity produced by the angular vestibulo-ocular reflex (aVOR) tends to align with the summed vector of gravity and other linear accelerations [gravito-inertial acceleration (GIA)]. Defined as "Spatial Orientation of the aVOR," we propose that it is controlled by the nodulus and uvula of the vestibulocerebellum. Here, electrical stimulation, injections of the GABAA agonist, muscimol, and single-cell recordings were utilized to investigate this Spatial Orientation. Stimulation, injection, and recording sites in the nodulus were determined in vivo by MRI and verified in histological sections. MRI proved to be a sensitive, reliable way to localize electrode placements. Electrical stimulation at sites in the nodulus and sublobule d of the uvula produced nystagmus whose slow-phase eye-velocity vectors were either head centric or Spatially invariant. When head centric, the eye velocity vector remained within +/- 45 degrees of the vector obtained with the animal upright, regardless of head position with respect to gravity. When Spatially oriented, the vector remained relatively constant in space in one on-side position, with respect to the vector determined with the animal upright. A majority of induced movements from the nodulus were Spatially oriented. Spatially oriented movements were generally followed by after-nystagmus, which had the characteristics of optokinetic after-nystagmus (OKAN), including Orientation to the GIA. After muscimol injections, horizontal-to-vertical cross-coupling was lost or reduced during OKAN in tilted positions. This supports the hypothesis that the nodulus mediates yaw-to-vertical or roll cross-coupling. The injections also shortened the yaw-axis time constant and produced contralateral horizontal spontaneous nystagmus, whose velocity varied as a function of head position with regard to gravity. Nodulus units were tested with static head tilt, sinusoidal oscillation around a Spatial horizontal axis with the head in different Orientations relative to the pitching plane, and off-vertical axis rotation (OVAR). The direction of the response vectors of the otolith-recipient units in the nodulus, determined from static and/or dynamic head tilts, were confirmed by OVAR. These vector directions lay close to the planes of the vertical canals in 7/10 units; many units also had convergent input from the vertical canals. It is postulated that the Orientation properties of the aVOR result from a transfer of otolith input regarding head tilt along canal planes to canal-related zones of the nodulus. In turn, Purkinje cells in these zones project to vestibular nuclei neurons to control eye velocity around axes normal to these same canal planes.

  • Control of Spatial Orientation of the Angular Vestibuloocular Reflex by the Nodulus and Uvula
    Journal of neurophysiology, 1998
    Co-Authors: Susan L. Wearne, Theodore Raphan, Bernard L. Cohen
    Abstract:

    Wearne, Susan, Theodore Raphan, and Bernard Cohen. Control of Spatial Orientation of the angular vestibuloocular reflex by the nodulus and uvula. J. Neurophysiol. 79: 2690–2715, 1998. Spatial orien...

Bernard Cohen - 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
    2014
    Co-Authors: Susan L. Wearne, Theodore Raphan, Bernard Cohen
    Abstract:

    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

  • Spatial Orientation of optokinetic nystagmus and ocular pursuit during orbital space flight.
    Experimental Brain Research, 2005
    Co-Authors: Steven T Moore, Bernard Cohen, Theodore Raphan, Alain Berthoz, Gilles Clément
    Abstract:

    On Earth, eye velocity of horizontal optokinetic nystagmus (OKN) orients to gravito-inertial acceleration (GIA), the sum of linear accelerations acting on the head and body. We determined whether adaptation to micro-gravity altered this Orientation and whether ocular pursuit exhibited similar properties. Eye movements of four astronauts were recorded with three-dimensional video-oculography. Optokinetic stimuli were stripes moving horizontally, vertically, and obliquely at 30 degrees/s. Ocular pursuit was produced by a spot moving horizontally or vertically at 20 degrees/s. Subjects were either stationary or were centrifuged during OKN with 1 or 0.5 g of interaural or dorsoventral centripetal linear acceleration. Average eye position during OKN (the beating field) moved into the quick-phase direction by 10 degrees during lateral and upward field movement in all conditions. The beating field did not shift up during downward OKN on Earth, but there was a strong upward movement of the beating field (9 degrees) during downward OKN in the absence of gravity; this likely represents an adaptation to the lack of a vertical 1-g bias in-flight. The horizontal OKN velocity axis tilted 9 degrees in the roll plane toward the GIA during interaural centrifugation, both on Earth and in space. During oblique OKN, the velocity vector tilted towards the GIA in the roll plane when there was a disparity between the direction of stripe motion and the GIA, but not when the two were aligned. In contrast, dorsoventral acceleration tilted the horizontal OKN velocity vector 6 degrees in pitch away from the GIA. Roll tilts of the horizontal OKN velocity vector toward the GIA during interaural centrifugation are consistent with the Orientation properties of velocity storage, but pitch tilts away from the GIA when centrifuged while supine are not. We speculate that visual suppression during OKN may have caused the velocity vector to tilt away from the GIA during dorsoventral centrifugation. Vertical OKN and ocular pursuit did not exhibit Orientation toward the GIA in any condition. Static full-body roll tilts and centrifugation generating an equivalent interaural acceleration produced the same tilts in the horizontal OKN velocity before and after flight. Thus, the magnitude of tilt in OKN velocity was dependent on the magnitude of interaural linear acceleration, rather than the tilt of the GIA with regard to the head. These results favor a 'filter' model of Spatial Orientation in which orienting eye movements are proportional to the magnitude of low frequency interaural linear acceleration, rather than models that postulate an internal representation of gravity as the basis for Spatial Orientation.

  • the nodulus and uvula source of cerebellar control of Spatial Orientation of the angular vestibulo ocular reflex
    Annals of the New York Academy of Sciences, 2002
    Co-Authors: Bernard Cohen, Padmore John, Sergei B Yakushin, Jean Buettnerennever, Theodore Raphan
    Abstract:

    : The nodulus and rostral-ventral uvula of the vestibulo-cerebellum play a critical role in orienting eye velocity of the slow component of the angular vestibulo-ocular reflex (aVOR) to gravito-inertial acceleration (GIA). This is done by altering the time constants of "velocity storage" in the vestibular system and by generating "cross-coupled" eye velocities that shift the eye velocity vector from along the body yaw axis to the yaw axis in a Spatial frame. In this report, we show that eye velocity generated through the aVOR by constant velocity centrifugation in the monkey orients to the GIA in space, regardless of the position of the head with respect to the axis of rotation. We also show that, after removal of the nodulus and rostral-ventral uvula, the Spatial Orientation of eye velocity to the GIA is lost and that eye velocity is then purely driven by the semicircular canals in a body frame of reference. These findings are further confirmation that these regions of the vestibulo-cerebellum control Spatial Orientation of the aVOR.

  • control of Spatial Orientation of the angular vestibulo ocular reflex by the nodulus and uvula of the vestibulocerebellum
    Annals of the New York Academy of Sciences, 1999
    Co-Authors: Boris M Sheliga, Sergei B Yakushin, Theodore Raphan, Adam Silvers, Bernard Cohen
    Abstract:

    : Eye velocity produced by the angular vestibulo-ocular reflex (aVOR) tends to align with the summed vector of gravity and other linear accelerations [gravito-inertial acceleration (GIA)]. Defined as "Spatial Orientation of the aVOR," we propose that it is controlled by the nodulus and uvula of the vestibulocerebellum. Here, electrical stimulation, injections of the GABAA agonist, muscimol, and single-cell recordings were utilized to investigate this Spatial Orientation. Stimulation, injection, and recording sites in the nodulus were determined in vivo by MRI and verified in histological sections. MRI proved to be a sensitive, reliable way to localize electrode placements. Electrical stimulation at sites in the nodulus and sublobule d of the uvula produced nystagmus whose slow-phase eye-velocity vectors were either head centric or Spatially invariant. When head centric, the eye velocity vector remained within +/- 45 degrees of the vector obtained with the animal upright, regardless of head position with respect to gravity. When Spatially oriented, the vector remained relatively constant in space in one on-side position, with respect to the vector determined with the animal upright. A majority of induced movements from the nodulus were Spatially oriented. Spatially oriented movements were generally followed by after-nystagmus, which had the characteristics of optokinetic after-nystagmus (OKAN), including Orientation to the GIA. After muscimol injections, horizontal-to-vertical cross-coupling was lost or reduced during OKAN in tilted positions. This supports the hypothesis that the nodulus mediates yaw-to-vertical or roll cross-coupling. The injections also shortened the yaw-axis time constant and produced contralateral horizontal spontaneous nystagmus, whose velocity varied as a function of head position with regard to gravity. Nodulus units were tested with static head tilt, sinusoidal oscillation around a Spatial horizontal axis with the head in different Orientations relative to the pitching plane, and off-vertical axis rotation (OVAR). The direction of the response vectors of the otolith-recipient units in the nodulus, determined from static and/or dynamic head tilts, were confirmed by OVAR. These vector directions lay close to the planes of the vertical canals in 7/10 units; many units also had convergent input from the vertical canals. It is postulated that the Orientation properties of the aVOR result from a transfer of otolith input regarding head tilt along canal planes to canal-related zones of the nodulus. In turn, Purkinje cells in these zones project to vestibular nuclei neurons to control eye velocity around axes normal to these same canal planes.

Georg Kerkhoff - One of the best experts on this subject based on the ideXlab platform.

  • multimodal Spatial Orientation deficits in left sided visual neglect
    Neuropsychologia, 1999
    Co-Authors: Georg Kerkhoff
    Abstract:

    Patients with right-sided temporo-parietal lesions often show contralesional neglect. However, neglect patients may also show Spatial-perceptual deficits beyond the bisection and space exploration deficits frequently assessed in the horizontal plane, that is, deficits in the judgment of the subjective visual vertical or horizontal. In a recent study (Kerkhoff, G. & Zoelch, C.. Disorders of visuo-Spatial Orientation in the frontal plane in patients with visual neglect following right or left parietal lesions. Exp. Brain Res., 1998;122:108-120) we found significant perturbations in the perception of these three visual Spatial axes in patients with contralesional neglect from right or left parietal lesions. To examine if this finding extends also to another modality we investigated how neglect patients perform tasks of visual- and tactile-Spatial judgments of axis-Orientation in the frontal plane. Visual-Spatial and tactile-Spatial judgments of the subjective vertical, horizontal and a right oblique Orientation were obtained from patients with and without neglect as well as from normal subjects. Patients with left neglect showed a significant, contraversive tilt of all three visual-Spatial axes (+5.6 degrees to +9.5 degrees, counterclockwise), and of the three tactile-Spatial axes as well (+5.2 degrees to +10.5 degrees, counterclockwise). In contrast, right and left hemisphere lesioned control patients without neglect and normal control subjects showed unimpaired visual and tactile-Spatial judgments (constant errors: < 1.0 degree). Difference thresholds in the visual-Spatial tasks and unsigned errors in the tactile-Spatial tasks were selectively elevated in the neglect group in contrast to all other subject groups. Spatial Orientation deficits were significantly associated with the severity of clinical neglect (r = 0.55-0.88), and with the patients' ambulation performance (r = 0.45-0.70). Furthermore, crossmodal axis Orientation tests in two neglect patients showed a similar counterclockwise tilt of +5 degrees to +15 degrees, suggesting a similar Spatial deficit in both modalities. Orientation judgments were significantly aggravated by a 25 degree-tilt of the head to the left, as tested in one neglect patient, while a comparable rightward head-tilt improved Spatial judgments in both modalities. This suggests that Spatial Orientation judgments are significantly modulated by gravitational input in neglect patients. Together these results are interpreted as evidence for multisensory Spatial Orientation deficits in neglect patients which are modulated by head-position and are related to their accompanying postural impairment.

  • multimodal Spatial Orientation deficits in left sided visual neglect
    Neuropsychologia, 1999
    Co-Authors: Georg Kerkhoff
    Abstract:

    Abstract Patients with right-sided temporo-parietal lesions often show contralesional neglect. However, neglect patients may also show Spatial–perceptual deficits beyond the bisection and space exploration deficits frequently assessed in the horizontal plane, that is, deficits in the judgment of the subjective visual vertical or horizontal. In a recent study (Kerkhoff, G. & Zoelch, C., Disorders of visuo–Spatial Orientation in the frontal plane in patients with visual neglect following right or left parietal lesions. Exp. Brain Res. , 1998;122:108–120) we found significant perturbations in the perception of these three visual–Spatial axes in patients with contralesional neglect from right or left parietal lesions. To examine if this finding extends also to another modality we investigated how neglect patients perform tasks of visual– and tactile–Spatial judgments of axis-Orientation in the frontal plane. Visual–Spatial and tactile–Spatial judgments of the subjective vertical, horizontal and a right oblique Orientation were obtained from patients with and without neglect as well as from normal subjects. Patients with left neglect showed a significant, contraversive tilt of all three visual–Spatial axes (+5.6° to +9.5°, counterclockwise), and of the three tactile–Spatial axes as well (+5.2° to +10.5°, counterclockwise). In contrast, right and left hemisphere lesioned control patients without neglect and normal control subjects showed unimpaired visual and tactile–Spatial judgments (constant errors: r =0.55–0.88), and with the patients’ ambulation performance ( r =0.45–0.70). Furthermore, crossmodal axis Orientation tests in two neglect patients showed a similar counterclockwise tilt of +5° to +15°, suggesting a similar Spatial deficit in both modalities. Orientation judgments were significantly aggravated by a 25°-tilt of the head to the left, as tested in one neglect patient, while a comparable rightward head-tilt improved Spatial judgments in both modalities. This suggests that Spatial Orientation judgments are significantly modulated by gravitational input in neglect patients. Together these results are interpreted as evidence for multisensory Spatial Orientation deficits in neglect patients which are modulated by head-position and are related to their accompanying postural impairment.

Roland Strauss - One of the best experts on this subject based on the ideXlab platform.

  • analysis of a Spatial Orientation memory in drosophila
    Nature, 2008
    Co-Authors: Kirsa Neuser, Tilman Triphan, Markus Mronz, Burkhard Poeck, Roland Strauss
    Abstract:

    Flexible goal-driven Orientation requires that the position of a target be stored, especially in case the target moves out of sight. The capability to retain, recall and integrate such positional information into guiding behaviour has been summarized under the term Spatial working memory. This kind of memory contains specific details of the presence that are not necessarily part of a long-term memory. Neurophysiological studies in primates indicate that sustained activity of neurons encodes the sensory information even though the object is no longer present. Furthermore they suggest that dopamine transmits the respective input to the prefrontal cortex, and simultaneous suppression by GABA Spatially restricts this neuronal activity. Here we show that Drosophila melanogaster possesses a similar Spatial memory during locomotion. Using a new detour setup, we show that flies can remember the position of an object for several seconds after it has been removed from their environment. In this setup, flies are temporarily lured away from the direction towards their hidden target, yet they are thereafter able to aim for their former target. Furthermore, we find that the GABAergic (stainable with antibodies against GABA) ring neurons of the ellipsoid body in the central brain are necessary and their plasticity is sufficient for a functional Spatial Orientation memory in flies. We also find that the protein kinase S6KII (ignorant) is required in a distinct subset of ring neurons to display this memory. Conditional expression of S6KII in these neurons only in adults can restore the loss of the Orientation memory of the ignorant mutant. The S6KII signalling pathway therefore seems to be acutely required in the ring neurons for Spatial Orientation memory in flies.

  • analysis of a Spatial Orientation memory in drosophila
    Nature, 2008
    Co-Authors: Kirsa Neuser, Tilman Triphan, Markus Mronz, Burkhard Poeck, Roland Strauss
    Abstract:

    Visual Orientation in a complex environment requires a memory for the positions of the various targets present in case they become temporarily out of sight. Vertebrates are equipped with this faculty, known as 'Spatial working memory', a form of working memory that lasts at least for several seconds. Using a virtual-reality arena to present visual targets to walking flies, Neuser et al. show that insects also possess this faculty. Drosophila fruit flies lured away from a trip towards a hidden target remember the position of an object for several seconds after its removal. The neurons involved in the process are GABAergic ring neurons. Visual Orientation in a complex environment requires a memory for targets' Spatial position, in case they become temporarily out of sight, a faculty known as 'Spatial working memory' in vertebrates. Use of a virtual-reality arena to present visual targets to walking fruit flies shows that insects share the faculty. Cell-specific gene rescue in learning mutants, ablation of brain areas and neuron-specific silencing experiments revealed that a distinct subset of neurons in the central brain is required for a Spatial working memory in flies. Flexible goal-driven Orientation requires that the position of a target be stored, especially in case the target moves out of sight. The capability to retain, recall and integrate such positional information into guiding behaviour has been summarized under the term Spatial working memory1. This kind of memory contains specific details of the presence that are not necessarily part of a long-term memory. Neurophysiological studies in primates2 indicate that sustained activity of neurons encodes the sensory information even though the object is no longer present. Furthermore they suggest that dopamine transmits the respective input to the prefrontal cortex, and simultaneous suppression by GABA Spatially restricts this neuronal activity3. Here we show that Drosophila melanogaster possesses a similar Spatial memory during locomotion. Using a new detour setup, we show that flies can remember the position of an object for several seconds after it has been removed from their environment. In this setup, flies are temporarily lured away from the direction towards their hidden target, yet they are thereafter able to aim for their former target. Furthermore, we find that the GABAergic (stainable with antibodies against GABA) ring neurons4 of the ellipsoid body in the central brain are necessary and their plasticity is sufficient for a functional Spatial Orientation memory in flies. We also find that the protein kinase S6KII (ignorant)5 is required in a distinct subset of ring neurons to display this memory. Conditional expression of S6KII in these neurons only in adults can restore the loss of the Orientation memory of the ignorant mutant. The S6KII signalling pathway therefore seems to be acutely required in the ring neurons for Spatial Orientation memory in flies.

Bernard L. Cohen - One of the best experts on this subject based on the ideXlab platform.