Combined in vivo and in vitro studies of the turtle cerebellum, red nucleus and brain stem are proposed. The goal of these studies is to understand the mechanisms that may underlie the generation of motor programs. Previous work on the cerebellorubrospinal (CRS) system in mammals has led to the hypothesis that the intermediate cerebellum, via the red nucleus, functions as an array of adjustable motor pattern generators the outputs of which serve as motor programs that contribute to the control of limb movements. Here we propose to develop an in vitro turtle hindbrain preparation that preserves the connections between cerebellum, red nucleus and brainstem, and to use this preparation to study the membrane, synaptic and circuit properties that contribute to motor pattern generation. We further propose to study the fiber pathways, topography of interconnections, fine structure, chemical neuroanatomy, and patterns of metabolic activity of the Chelonian CRS pathway using contemporary neuroanatomic methods. These neuroanatomical studies represent a collaborative effort. Finally, we propose to study the sensory and motor signals transmitted through the CRS pathway in the turtle, using single unit recordings from the cerebellum and red nucleus and simultaneous electromyographic recordings from limb muscles. This in vivo neurophysiology component of our project will begin with anesthetized animals and will proceed to recordings from multiple single units in awake, relatively unrestrained turtles. These data will help us to understand how sensory information is used to control motor output, and this information should be valuable in the understanding and treatment of stroke, Parkinsons's disease and an other disorders of the motor system.
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