The Experts below are selected from a list of 1527 Experts worldwide ranked by ideXlab platform
John Simmers - One of the best experts on this subject based on the ideXlab platform.
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adaptive plasticity of spino extraocular motor coupling during locomotion in metamorphosing xenopus laevis
The Journal of Experimental Biology, 2016Co-Authors: Géraldine Von Uckermann, Francois M Lambert, Hans Straka, Denis Combes, John SimmersAbstract:ABSTRACT During swimming in the amphibian Xenopus laevis , Efference copies of rhythmic locomotor commands produced by the spinal central pattern generator (CPG) can drive extraocular motor output appropriate for producing image-stabilizing eye movements to offset the disruptive effects of self-motion. During metamorphosis, X. laevis remodels its locomotor strategy from larval tail-based undulatory movements to bilaterally synchronous hindlimb kicking in the adult. This change in propulsive mode results in head/body motion with entirely different dynamics, necessitating a concomitant switch in compensatory ocular movements from conjugate left–right rotations to non-conjugate convergence during the linear forward acceleration produced during each kick cycle. Here, using semi-intact or isolated brainstem/spinal cord preparations at intermediate metamorphic stages, we monitored bilateral eye motion along with extraocular, spinal axial and limb motor nerve activity during episodes of spontaneous fictive swimming. Our results show a progressive transition in spinal Efference Copy control of extraocular motor output that remains adapted to offsetting visual disturbances during the combinatorial expression of bimodal propulsion when functional larval and adult locomotor systems co-exist within the same animal. In stages at metamorphic climax, spino-extraocular motor coupling, which previously derived from axial locomotor circuitry alone, can originate from both axial and de novo hindlimb CPGs, although the latter9s influence becomes progressively more dominant and eventually exclusive as metamorphosis terminates with tail resorption. Thus, adaptive interactions between locomotor and extraocular motor circuitry allows CPG-driven Efference Copy signaling to continuously match the changing spatio-temporal requirements for visual image stabilization throughout the transitional period when one propulsive mechanism emerges and replaces another.
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spinal corollary discharge modulates motion sensing during vertebrate locomotion
Nature Communications, 2015Co-Authors: Boris P Chagnaud, John Simmers, Roberto Banchi, Hans StrakaAbstract:During active movements, neural replicas of the underlying motor commands may assist in adapting motion-detecting sensory systems to an animal's own behaviour. The transmission of such motor Efference copies to the mechanosensory periphery offers a potential predictive substrate for diminishing sensory responsiveness to self-motion during vertebrate locomotion. Here, using semi-isolated in vitro preparations of larval Xenopus, we demonstrate that shared efferent neural pathways to hair cells of vestibular endorgans and lateral line neuromasts express cyclic impulse bursts during swimming that are directly driven by spinal locomotor circuitry. Despite common efferent innervation and discharge patterns, afferent signal encoding at the two mechanosensory peripheries is influenced differentially by Efference Copy signals, reflecting the different organization of body/water motion-detecting processes in the vestibular and lateral line systems. The resultant overall gain reduction in sensory signal encoding in both cases, which likely prevents overstimulation, constitutes an adjustment to increased stimulus magnitudes during locomotion.
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Spinal Efference Copy Signaling and Gaze Stabilization during Locomotion in Juvenile Xenopus Frogs
Journal of Neuroscience, 2013Co-Authors: Géraldine Von Uckermann, Denis Combes, Hans Straka, Didier Le Ray, John SimmersAbstract:In swimming Xenopus laevis tadpoles, gaze stabilization is achieved by Efference copies of spinal locomotory CPG output that produce rhythmic extraocular motor activity appropriate for minimizing motion-derived visual disturbances. During metamorphosis, Xenopus switches its locomotory mechanism from larval tail-based undulatory movements to bilaterally synchronous hindlimb kick propulsion in the adult. The change in locomotory mode leads to body motion dynamics that no longer require conjugate left-right eye rotations for effective retinal image stabilization. Using in vivo kinematic analyses, in vitro electrophysiological recordings and specific CNS lesions, we have investigated spino-extraocular motor coupling in the juvenile frog and the underlying neural pathways to understand how gaze control processes are altered in accordance with the animal's change in body plan and locomotor strategy. Recordings of extraocular and limb motor nerves during spontaneous "fictive" swimming in isolated CNS preparations revealed that there is indeed a corresponding change in spinal Efference Copy control of extraocular motor output. In contrast to fictive larval swimming where alternating bursts occur in bilateral antagonistic horizontal extraocular nerves, during adult fictive limb-kicking, these motor nerves are synchronously active in accordance with the production of convergent eye movements during the linear head accelerations resulting from forward propulsion. Correspondingly, the neural pathways mediating spino-extraocular coupling have switched from contralateral to strictly ipsilateral ascending influences that ensure a coactivation of bilateral extraocular motoneurons with synchronous left-right limb extensions. Thus, adaptive developmental plasticity during metamorphosis enables spinal CPG-driven extraocular motor activity to match the changing requirements for eye movement control during self-motion.
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predictability of visual perturbation during locomotion implications for corrective Efference Copy signaling
Biological Cybernetics, 2012Co-Authors: Boris P Chagnaud, John Simmers, Hans StrakaAbstract:In guiding adaptive behavior, Efference Copy signals or corollary discharge are traditionally considered to serve as predictors of self-generated sensory inputs and by interfering with their central processing are able to counter unwanted consequences of an animal's own actions. Here, in a speculative reflection on this issue, we consider a different functional role for such intrinsic predictive signaling, namely in stabilizing gaze during locomotion where resultant changes in head orientation in space require online compensatory eye movements in order to prevent retinal image slip. The direct activation of extraocular motoneurons by locomotor-related Efference copies offers a prospective substrate for assisting self-motion derived sensory feedback, rather than being subtracted from the sensory signal to eliminate unwanted reafferent information. However, implementing such a feed-forward mechanism would be critically dependent on an appropriate phase coupling between rhythmic propulsive movement and resultant head/visual image displacement. We used video analyzes of actual locomotor behavior and basic theoretical modeling to evaluate head motion during stable locomotion in animals as diverse as Xenopus laevis tadpoles, teleost fish and horses in order to assess the potential suitability of spinal Efference copies to the stabilization of gaze during locomotion. In all three species, and therefore regardless of aquatic or terrestrial environment, the head displacements that accompanied locomotor action displayed a strong correlative spatio-temporal relationship in correspondence with a potential predictive value for compensatory eye adjustments. Although spinal central pattern generator-derived Efference copies offer appropriately timed commands for extraocular motor control during self-generated motion, it is likely that precise image stabilization requires the additional contributions of sensory feedback signals. Nonetheless, the predictability of the visual consequences of stereotyped locomotion renders intrinsic Efference Copy signaling an appealing mechanism for offsetting these disturbances, thus questioning the exclusive role traditionally ascribed to sensory-motor transformations in stabilizing gaze during vertebrate locomotion.
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gaze stabilization by Efference Copy signaling without sensory feedback during vertebrate locomotion
Current Biology, 2012Co-Authors: Francois M Lambert, John Simmers, Denis Combes, Hans StrakaAbstract:Summary Background Self-generated body movements require compensatory eye and head adjustments in order to avoid perturbation of visual information processing. Retinal image stabilization is traditionally ascribed to the transformation of visuovestibular signals into appropriate extraocular motor commands for compensatory ocular movements. During locomotion, however, intrinsic "Efference copies" of the motor commands deriving from spinal central pattern generator (CPG) activity potentially offer a reliable and rapid mechanism for image stabilization, in addition to the slower contribution of movement-encoding sensory inputs. Results Using a variety of in vitro and in vivo preparations of Xenopus tadpoles, we demonstrate that spinal locomotor CPG-derived Efference copies do indeed produce effective conjugate eye movements that counteract oppositely directed horizontal head displacements during undulatory tail-based locomotion. The Efference Copy transmission, by which the extraocular motor system becomes functionally appropriated to the spinal cord, is mediated by direct ascending pathways. Although the impact of the CPG feedforward commands matches the spatiotemporal specificity of classical vestibulo-ocular responses, the two fundamentally different signals do not contribute collectively to image stabilization during swimming. Instead, when the CPG is active, horizontal vestibulo-ocular reflexes resulting from head movements are selectively suppressed. Conclusions These results therefore challenge our traditional understanding of how animals offset the disruptive effects of propulsive body movements on visual processing. Specifically, our finding that predictive Efference copies of intrinsic, rhythmic neural signals produced by the locomotory CPG supersede, rather than supplement, reactive vestibulo-ocular reflexes in order to drive image-stabilizing eye adjustments during larval frog swimming, represents a hitherto unreported mechanism for vertebrate ocular motor control.
Hans Straka - One of the best experts on this subject based on the ideXlab platform.
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adaptive plasticity of spino extraocular motor coupling during locomotion in metamorphosing xenopus laevis
The Journal of Experimental Biology, 2016Co-Authors: Géraldine Von Uckermann, Francois M Lambert, Hans Straka, Denis Combes, John SimmersAbstract:ABSTRACT During swimming in the amphibian Xenopus laevis , Efference copies of rhythmic locomotor commands produced by the spinal central pattern generator (CPG) can drive extraocular motor output appropriate for producing image-stabilizing eye movements to offset the disruptive effects of self-motion. During metamorphosis, X. laevis remodels its locomotor strategy from larval tail-based undulatory movements to bilaterally synchronous hindlimb kicking in the adult. This change in propulsive mode results in head/body motion with entirely different dynamics, necessitating a concomitant switch in compensatory ocular movements from conjugate left–right rotations to non-conjugate convergence during the linear forward acceleration produced during each kick cycle. Here, using semi-intact or isolated brainstem/spinal cord preparations at intermediate metamorphic stages, we monitored bilateral eye motion along with extraocular, spinal axial and limb motor nerve activity during episodes of spontaneous fictive swimming. Our results show a progressive transition in spinal Efference Copy control of extraocular motor output that remains adapted to offsetting visual disturbances during the combinatorial expression of bimodal propulsion when functional larval and adult locomotor systems co-exist within the same animal. In stages at metamorphic climax, spino-extraocular motor coupling, which previously derived from axial locomotor circuitry alone, can originate from both axial and de novo hindlimb CPGs, although the latter9s influence becomes progressively more dominant and eventually exclusive as metamorphosis terminates with tail resorption. Thus, adaptive interactions between locomotor and extraocular motor circuitry allows CPG-driven Efference Copy signaling to continuously match the changing spatio-temporal requirements for visual image stabilization throughout the transitional period when one propulsive mechanism emerges and replaces another.
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spinal corollary discharge modulates motion sensing during vertebrate locomotion
Nature Communications, 2015Co-Authors: Boris P Chagnaud, John Simmers, Roberto Banchi, Hans StrakaAbstract:During active movements, neural replicas of the underlying motor commands may assist in adapting motion-detecting sensory systems to an animal's own behaviour. The transmission of such motor Efference copies to the mechanosensory periphery offers a potential predictive substrate for diminishing sensory responsiveness to self-motion during vertebrate locomotion. Here, using semi-isolated in vitro preparations of larval Xenopus, we demonstrate that shared efferent neural pathways to hair cells of vestibular endorgans and lateral line neuromasts express cyclic impulse bursts during swimming that are directly driven by spinal locomotor circuitry. Despite common efferent innervation and discharge patterns, afferent signal encoding at the two mechanosensory peripheries is influenced differentially by Efference Copy signals, reflecting the different organization of body/water motion-detecting processes in the vestibular and lateral line systems. The resultant overall gain reduction in sensory signal encoding in both cases, which likely prevents overstimulation, constitutes an adjustment to increased stimulus magnitudes during locomotion.
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Spinal Efference Copy Signaling and Gaze Stabilization during Locomotion in Juvenile Xenopus Frogs
Journal of Neuroscience, 2013Co-Authors: Géraldine Von Uckermann, Denis Combes, Hans Straka, Didier Le Ray, John SimmersAbstract:In swimming Xenopus laevis tadpoles, gaze stabilization is achieved by Efference copies of spinal locomotory CPG output that produce rhythmic extraocular motor activity appropriate for minimizing motion-derived visual disturbances. During metamorphosis, Xenopus switches its locomotory mechanism from larval tail-based undulatory movements to bilaterally synchronous hindlimb kick propulsion in the adult. The change in locomotory mode leads to body motion dynamics that no longer require conjugate left-right eye rotations for effective retinal image stabilization. Using in vivo kinematic analyses, in vitro electrophysiological recordings and specific CNS lesions, we have investigated spino-extraocular motor coupling in the juvenile frog and the underlying neural pathways to understand how gaze control processes are altered in accordance with the animal's change in body plan and locomotor strategy. Recordings of extraocular and limb motor nerves during spontaneous "fictive" swimming in isolated CNS preparations revealed that there is indeed a corresponding change in spinal Efference Copy control of extraocular motor output. In contrast to fictive larval swimming where alternating bursts occur in bilateral antagonistic horizontal extraocular nerves, during adult fictive limb-kicking, these motor nerves are synchronously active in accordance with the production of convergent eye movements during the linear head accelerations resulting from forward propulsion. Correspondingly, the neural pathways mediating spino-extraocular coupling have switched from contralateral to strictly ipsilateral ascending influences that ensure a coactivation of bilateral extraocular motoneurons with synchronous left-right limb extensions. Thus, adaptive developmental plasticity during metamorphosis enables spinal CPG-driven extraocular motor activity to match the changing requirements for eye movement control during self-motion.
-
predictability of visual perturbation during locomotion implications for corrective Efference Copy signaling
Biological Cybernetics, 2012Co-Authors: Boris P Chagnaud, John Simmers, Hans StrakaAbstract:In guiding adaptive behavior, Efference Copy signals or corollary discharge are traditionally considered to serve as predictors of self-generated sensory inputs and by interfering with their central processing are able to counter unwanted consequences of an animal's own actions. Here, in a speculative reflection on this issue, we consider a different functional role for such intrinsic predictive signaling, namely in stabilizing gaze during locomotion where resultant changes in head orientation in space require online compensatory eye movements in order to prevent retinal image slip. The direct activation of extraocular motoneurons by locomotor-related Efference copies offers a prospective substrate for assisting self-motion derived sensory feedback, rather than being subtracted from the sensory signal to eliminate unwanted reafferent information. However, implementing such a feed-forward mechanism would be critically dependent on an appropriate phase coupling between rhythmic propulsive movement and resultant head/visual image displacement. We used video analyzes of actual locomotor behavior and basic theoretical modeling to evaluate head motion during stable locomotion in animals as diverse as Xenopus laevis tadpoles, teleost fish and horses in order to assess the potential suitability of spinal Efference copies to the stabilization of gaze during locomotion. In all three species, and therefore regardless of aquatic or terrestrial environment, the head displacements that accompanied locomotor action displayed a strong correlative spatio-temporal relationship in correspondence with a potential predictive value for compensatory eye adjustments. Although spinal central pattern generator-derived Efference copies offer appropriately timed commands for extraocular motor control during self-generated motion, it is likely that precise image stabilization requires the additional contributions of sensory feedback signals. Nonetheless, the predictability of the visual consequences of stereotyped locomotion renders intrinsic Efference Copy signaling an appealing mechanism for offsetting these disturbances, thus questioning the exclusive role traditionally ascribed to sensory-motor transformations in stabilizing gaze during vertebrate locomotion.
-
gaze stabilization by Efference Copy signaling without sensory feedback during vertebrate locomotion
Current Biology, 2012Co-Authors: Francois M Lambert, John Simmers, Denis Combes, Hans StrakaAbstract:Summary Background Self-generated body movements require compensatory eye and head adjustments in order to avoid perturbation of visual information processing. Retinal image stabilization is traditionally ascribed to the transformation of visuovestibular signals into appropriate extraocular motor commands for compensatory ocular movements. During locomotion, however, intrinsic "Efference copies" of the motor commands deriving from spinal central pattern generator (CPG) activity potentially offer a reliable and rapid mechanism for image stabilization, in addition to the slower contribution of movement-encoding sensory inputs. Results Using a variety of in vitro and in vivo preparations of Xenopus tadpoles, we demonstrate that spinal locomotor CPG-derived Efference copies do indeed produce effective conjugate eye movements that counteract oppositely directed horizontal head displacements during undulatory tail-based locomotion. The Efference Copy transmission, by which the extraocular motor system becomes functionally appropriated to the spinal cord, is mediated by direct ascending pathways. Although the impact of the CPG feedforward commands matches the spatiotemporal specificity of classical vestibulo-ocular responses, the two fundamentally different signals do not contribute collectively to image stabilization during swimming. Instead, when the CPG is active, horizontal vestibulo-ocular reflexes resulting from head movements are selectively suppressed. Conclusions These results therefore challenge our traditional understanding of how animals offset the disruptive effects of propulsive body movements on visual processing. Specifically, our finding that predictive Efference copies of intrinsic, rhythmic neural signals produced by the locomotory CPG supersede, rather than supplement, reactive vestibulo-ocular reflexes in order to drive image-stabilizing eye adjustments during larval frog swimming, represents a hitherto unreported mechanism for vertebrate ocular motor control.
Denis Combes - One of the best experts on this subject based on the ideXlab platform.
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adaptive plasticity of spino extraocular motor coupling during locomotion in metamorphosing xenopus laevis
The Journal of Experimental Biology, 2016Co-Authors: Géraldine Von Uckermann, Francois M Lambert, Hans Straka, Denis Combes, John SimmersAbstract:ABSTRACT During swimming in the amphibian Xenopus laevis , Efference copies of rhythmic locomotor commands produced by the spinal central pattern generator (CPG) can drive extraocular motor output appropriate for producing image-stabilizing eye movements to offset the disruptive effects of self-motion. During metamorphosis, X. laevis remodels its locomotor strategy from larval tail-based undulatory movements to bilaterally synchronous hindlimb kicking in the adult. This change in propulsive mode results in head/body motion with entirely different dynamics, necessitating a concomitant switch in compensatory ocular movements from conjugate left–right rotations to non-conjugate convergence during the linear forward acceleration produced during each kick cycle. Here, using semi-intact or isolated brainstem/spinal cord preparations at intermediate metamorphic stages, we monitored bilateral eye motion along with extraocular, spinal axial and limb motor nerve activity during episodes of spontaneous fictive swimming. Our results show a progressive transition in spinal Efference Copy control of extraocular motor output that remains adapted to offsetting visual disturbances during the combinatorial expression of bimodal propulsion when functional larval and adult locomotor systems co-exist within the same animal. In stages at metamorphic climax, spino-extraocular motor coupling, which previously derived from axial locomotor circuitry alone, can originate from both axial and de novo hindlimb CPGs, although the latter9s influence becomes progressively more dominant and eventually exclusive as metamorphosis terminates with tail resorption. Thus, adaptive interactions between locomotor and extraocular motor circuitry allows CPG-driven Efference Copy signaling to continuously match the changing spatio-temporal requirements for visual image stabilization throughout the transitional period when one propulsive mechanism emerges and replaces another.
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Spinal Efference Copy Signaling and Gaze Stabilization during Locomotion in Juvenile Xenopus Frogs
Journal of Neuroscience, 2013Co-Authors: Géraldine Von Uckermann, Denis Combes, Hans Straka, Didier Le Ray, John SimmersAbstract:In swimming Xenopus laevis tadpoles, gaze stabilization is achieved by Efference copies of spinal locomotory CPG output that produce rhythmic extraocular motor activity appropriate for minimizing motion-derived visual disturbances. During metamorphosis, Xenopus switches its locomotory mechanism from larval tail-based undulatory movements to bilaterally synchronous hindlimb kick propulsion in the adult. The change in locomotory mode leads to body motion dynamics that no longer require conjugate left-right eye rotations for effective retinal image stabilization. Using in vivo kinematic analyses, in vitro electrophysiological recordings and specific CNS lesions, we have investigated spino-extraocular motor coupling in the juvenile frog and the underlying neural pathways to understand how gaze control processes are altered in accordance with the animal's change in body plan and locomotor strategy. Recordings of extraocular and limb motor nerves during spontaneous "fictive" swimming in isolated CNS preparations revealed that there is indeed a corresponding change in spinal Efference Copy control of extraocular motor output. In contrast to fictive larval swimming where alternating bursts occur in bilateral antagonistic horizontal extraocular nerves, during adult fictive limb-kicking, these motor nerves are synchronously active in accordance with the production of convergent eye movements during the linear head accelerations resulting from forward propulsion. Correspondingly, the neural pathways mediating spino-extraocular coupling have switched from contralateral to strictly ipsilateral ascending influences that ensure a coactivation of bilateral extraocular motoneurons with synchronous left-right limb extensions. Thus, adaptive developmental plasticity during metamorphosis enables spinal CPG-driven extraocular motor activity to match the changing requirements for eye movement control during self-motion.
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gaze stabilization by Efference Copy signaling without sensory feedback during vertebrate locomotion
Current Biology, 2012Co-Authors: Francois M Lambert, John Simmers, Denis Combes, Hans StrakaAbstract:Summary Background Self-generated body movements require compensatory eye and head adjustments in order to avoid perturbation of visual information processing. Retinal image stabilization is traditionally ascribed to the transformation of visuovestibular signals into appropriate extraocular motor commands for compensatory ocular movements. During locomotion, however, intrinsic "Efference copies" of the motor commands deriving from spinal central pattern generator (CPG) activity potentially offer a reliable and rapid mechanism for image stabilization, in addition to the slower contribution of movement-encoding sensory inputs. Results Using a variety of in vitro and in vivo preparations of Xenopus tadpoles, we demonstrate that spinal locomotor CPG-derived Efference copies do indeed produce effective conjugate eye movements that counteract oppositely directed horizontal head displacements during undulatory tail-based locomotion. The Efference Copy transmission, by which the extraocular motor system becomes functionally appropriated to the spinal cord, is mediated by direct ascending pathways. Although the impact of the CPG feedforward commands matches the spatiotemporal specificity of classical vestibulo-ocular responses, the two fundamentally different signals do not contribute collectively to image stabilization during swimming. Instead, when the CPG is active, horizontal vestibulo-ocular reflexes resulting from head movements are selectively suppressed. Conclusions These results therefore challenge our traditional understanding of how animals offset the disruptive effects of propulsive body movements on visual processing. Specifically, our finding that predictive Efference copies of intrinsic, rhythmic neural signals produced by the locomotory CPG supersede, rather than supplement, reactive vestibulo-ocular reflexes in order to drive image-stabilizing eye adjustments during larval frog swimming, represents a hitherto unreported mechanism for vertebrate ocular motor control.
Géraldine Von Uckermann - One of the best experts on this subject based on the ideXlab platform.
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adaptive plasticity of spino extraocular motor coupling during locomotion in metamorphosing xenopus laevis
The Journal of Experimental Biology, 2016Co-Authors: Géraldine Von Uckermann, Francois M Lambert, Hans Straka, Denis Combes, John SimmersAbstract:ABSTRACT During swimming in the amphibian Xenopus laevis , Efference copies of rhythmic locomotor commands produced by the spinal central pattern generator (CPG) can drive extraocular motor output appropriate for producing image-stabilizing eye movements to offset the disruptive effects of self-motion. During metamorphosis, X. laevis remodels its locomotor strategy from larval tail-based undulatory movements to bilaterally synchronous hindlimb kicking in the adult. This change in propulsive mode results in head/body motion with entirely different dynamics, necessitating a concomitant switch in compensatory ocular movements from conjugate left–right rotations to non-conjugate convergence during the linear forward acceleration produced during each kick cycle. Here, using semi-intact or isolated brainstem/spinal cord preparations at intermediate metamorphic stages, we monitored bilateral eye motion along with extraocular, spinal axial and limb motor nerve activity during episodes of spontaneous fictive swimming. Our results show a progressive transition in spinal Efference Copy control of extraocular motor output that remains adapted to offsetting visual disturbances during the combinatorial expression of bimodal propulsion when functional larval and adult locomotor systems co-exist within the same animal. In stages at metamorphic climax, spino-extraocular motor coupling, which previously derived from axial locomotor circuitry alone, can originate from both axial and de novo hindlimb CPGs, although the latter9s influence becomes progressively more dominant and eventually exclusive as metamorphosis terminates with tail resorption. Thus, adaptive interactions between locomotor and extraocular motor circuitry allows CPG-driven Efference Copy signaling to continuously match the changing spatio-temporal requirements for visual image stabilization throughout the transitional period when one propulsive mechanism emerges and replaces another.
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Spinal Efference Copy Signaling and Gaze Stabilization during Locomotion in Juvenile Xenopus Frogs
Journal of Neuroscience, 2013Co-Authors: Géraldine Von Uckermann, Denis Combes, Hans Straka, Didier Le Ray, John SimmersAbstract:In swimming Xenopus laevis tadpoles, gaze stabilization is achieved by Efference copies of spinal locomotory CPG output that produce rhythmic extraocular motor activity appropriate for minimizing motion-derived visual disturbances. During metamorphosis, Xenopus switches its locomotory mechanism from larval tail-based undulatory movements to bilaterally synchronous hindlimb kick propulsion in the adult. The change in locomotory mode leads to body motion dynamics that no longer require conjugate left-right eye rotations for effective retinal image stabilization. Using in vivo kinematic analyses, in vitro electrophysiological recordings and specific CNS lesions, we have investigated spino-extraocular motor coupling in the juvenile frog and the underlying neural pathways to understand how gaze control processes are altered in accordance with the animal's change in body plan and locomotor strategy. Recordings of extraocular and limb motor nerves during spontaneous "fictive" swimming in isolated CNS preparations revealed that there is indeed a corresponding change in spinal Efference Copy control of extraocular motor output. In contrast to fictive larval swimming where alternating bursts occur in bilateral antagonistic horizontal extraocular nerves, during adult fictive limb-kicking, these motor nerves are synchronously active in accordance with the production of convergent eye movements during the linear head accelerations resulting from forward propulsion. Correspondingly, the neural pathways mediating spino-extraocular coupling have switched from contralateral to strictly ipsilateral ascending influences that ensure a coactivation of bilateral extraocular motoneurons with synchronous left-right limb extensions. Thus, adaptive developmental plasticity during metamorphosis enables spinal CPG-driven extraocular motor activity to match the changing requirements for eye movement control during self-motion.
Francois M Lambert - One of the best experts on this subject based on the ideXlab platform.
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adaptive plasticity of spino extraocular motor coupling during locomotion in metamorphosing xenopus laevis
The Journal of Experimental Biology, 2016Co-Authors: Géraldine Von Uckermann, Francois M Lambert, Hans Straka, Denis Combes, John SimmersAbstract:ABSTRACT During swimming in the amphibian Xenopus laevis , Efference copies of rhythmic locomotor commands produced by the spinal central pattern generator (CPG) can drive extraocular motor output appropriate for producing image-stabilizing eye movements to offset the disruptive effects of self-motion. During metamorphosis, X. laevis remodels its locomotor strategy from larval tail-based undulatory movements to bilaterally synchronous hindlimb kicking in the adult. This change in propulsive mode results in head/body motion with entirely different dynamics, necessitating a concomitant switch in compensatory ocular movements from conjugate left–right rotations to non-conjugate convergence during the linear forward acceleration produced during each kick cycle. Here, using semi-intact or isolated brainstem/spinal cord preparations at intermediate metamorphic stages, we monitored bilateral eye motion along with extraocular, spinal axial and limb motor nerve activity during episodes of spontaneous fictive swimming. Our results show a progressive transition in spinal Efference Copy control of extraocular motor output that remains adapted to offsetting visual disturbances during the combinatorial expression of bimodal propulsion when functional larval and adult locomotor systems co-exist within the same animal. In stages at metamorphic climax, spino-extraocular motor coupling, which previously derived from axial locomotor circuitry alone, can originate from both axial and de novo hindlimb CPGs, although the latter9s influence becomes progressively more dominant and eventually exclusive as metamorphosis terminates with tail resorption. Thus, adaptive interactions between locomotor and extraocular motor circuitry allows CPG-driven Efference Copy signaling to continuously match the changing spatio-temporal requirements for visual image stabilization throughout the transitional period when one propulsive mechanism emerges and replaces another.
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gaze stabilization by Efference Copy signaling without sensory feedback during vertebrate locomotion
Current Biology, 2012Co-Authors: Francois M Lambert, John Simmers, Denis Combes, Hans StrakaAbstract:Summary Background Self-generated body movements require compensatory eye and head adjustments in order to avoid perturbation of visual information processing. Retinal image stabilization is traditionally ascribed to the transformation of visuovestibular signals into appropriate extraocular motor commands for compensatory ocular movements. During locomotion, however, intrinsic "Efference copies" of the motor commands deriving from spinal central pattern generator (CPG) activity potentially offer a reliable and rapid mechanism for image stabilization, in addition to the slower contribution of movement-encoding sensory inputs. Results Using a variety of in vitro and in vivo preparations of Xenopus tadpoles, we demonstrate that spinal locomotor CPG-derived Efference copies do indeed produce effective conjugate eye movements that counteract oppositely directed horizontal head displacements during undulatory tail-based locomotion. The Efference Copy transmission, by which the extraocular motor system becomes functionally appropriated to the spinal cord, is mediated by direct ascending pathways. Although the impact of the CPG feedforward commands matches the spatiotemporal specificity of classical vestibulo-ocular responses, the two fundamentally different signals do not contribute collectively to image stabilization during swimming. Instead, when the CPG is active, horizontal vestibulo-ocular reflexes resulting from head movements are selectively suppressed. Conclusions These results therefore challenge our traditional understanding of how animals offset the disruptive effects of propulsive body movements on visual processing. Specifically, our finding that predictive Efference copies of intrinsic, rhythmic neural signals produced by the locomotory CPG supersede, rather than supplement, reactive vestibulo-ocular reflexes in order to drive image-stabilizing eye adjustments during larval frog swimming, represents a hitherto unreported mechanism for vertebrate ocular motor control.
