Selection and Generation of Rhythmic Motor Patterns by the Spinal Cord

University Of Oklahoma Norman Campus, Norman OK

Investigators

Abstract

How does the central nervous system "choose" an appropriate movement? In principle, it may either activate a separate set of specialized neurons for each behavior or may differentially activate a common pool of multipurpose neurons. The turtle spinal cord is an excellent vertebrate model system to investigate this issue. It can generate multiple types of hindlimb scratching and swimming, even without input from the brain. Many spinal cord neurons are activated during all three types of scratching as well as swimming, suggesting that multipurpose neuronal circuitry is important. Some neurons ("scratch-specialized neurons"), however, are activated during scratching but suppressed during swimming, suggesting that specialized circuitry is also important. This project will use electrophysiological, neuroanatomical, and pharmacological methods to address roles and mechanisms of multipurpose and specialized circuitry, including: 1) What is the regional distribution of spinal cord neurons involved in swimming vs. scratching? Dyes that selectively stain strongly activated neurons will be applied to the spinal cord, while either scratching or swimming is induced, to compare the sets of spinal neurons activated during each of these behaviors. 2) What are the morphologies of each type of spinal neuron activated during scratching and/or swimming? The electrical activity of individual spinal neurons will be monitored during scratching and swimming and then each neuron will be injected with a dye, to reveal, for example, if specialized and multipurpose spinal neurons have distinct morphologies. 3) How are scratch-specialized neurons suppressed during swimming? The electrical activity of individual spinal neurons will be monitored while drugs that block neuronal inhibition are applied, to reveal pharmacological mechanisms through which scratch-specialized neurons are inhibited during swimming. This project will clarify how specialized and multipurpose neuronal networks for behavioral choice are combined in a vertebrate model system. The project will provide training to undergraduates and a post-doctoral fell. This experience will be especially valuable to Oklahoma students, who have fewer research opportunities than many east and west coast schools.