title: Spinal efference copy signaling and gaze stabilization during locomotion in juvenile Xenopus frogs.
abstract: 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.
authors: Université Bordeaux, Institut de Neurosciences Cognitives et Intégratives d'Aquitaine, Centre National de la Recherche Scientifique Unité Mixte de Recherche 5287, 33076 Bordeaux, France.
authors: Géraldine
authors: G
authors: von Uckermann
authors: Didier
authors: D
authors: Le Ray
authors: Denis
authors: D
authors: Combes
authors: Hans
authors: H
authors: Straka
authors: John
authors: J
authors: Simmers
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001001:Anura; D001696:Biomechanical Phenomena; D001933:Brain Stem / Q000293:injuries / Q000502:physiology; D005121:Extremities / Q000294:innervation; D005260:Female; D005403:Fixation, Ocular / Q000502:physiology*; D007839:Functional Laterality; D066298:In Vitro Techniques; D008297:Male; D008675:Metamorphosis, Biological / Q000502:physiology; D009415:Nerve Net / Q000502:physiology; D009434:Neural Pathways / Q000502:physiology; D020221:Optic Nerve Injuries / Q000503:physiopathology; D013116:Spinal Cord / Q000502:physiology*; D013119:Spinal Cord Injuries / Q000503:physiopathology; D018709:Statistics, Nonparametric; D013550:Swimming / Q000502:physiology*; D014741:Video Recording; D014982:Xenopus laevis / Q000502:physiology*