Selection and generation of limb movements by a combination of multifunctional and specialized spinal interneurons

University Of Oklahoma Norman Campus, Norman OK

Investigators

Abstract

This project will address how nervous systems are organized to produce the right movement at the right time. It will focus on networks of nerve cells in the spinal cord since understanding these components is a prerequisite to understanding complex movements in animals and helping patients with spinal cord injuries. It will also train a broad range of undergraduates and graduate students to perform experiments. Finally, the award will also support hands-on activities for schoolchildren to spark their interest in science. Recent studies suggest that the spinal cord uses a combination of behaviorally specialized and multifunctional nerve cells (interneurons) to generate movements, but how it does so for limb movements is unknown. This project will study how specialized and multifunctional spinal interneurons contribute to producing two kinds of leg movements, swimming and scratching. The turtle is the only animal for which this is now feasible and is ideal for such studies because turtles, being diving animals, have evolved unusual resistance to low-oxygen conditions such as occur during many physiological experiments. The project will investigate the roles of one previously identified class of behaviorally specialized interneurons, scratch-specialized neurons, and one previously identified class of multifunctional interneurons, transverse interneurons. The project will determine whether each of these two classes of interneurons is excitatory or inhibitory, based on the neurotransmitter it uses, and whether it makes synaptic connections directly with motor neurons, using a combination of intracellular electrophysiology in vivo, dye injection, and immunocytochemistry. The results of this study will reveal aspects of the organization of the spinal cord networks of neurons that generate different kinds of limb movements. The conclusions are likely to be broadly applicable to vertebrates, including humans, because the spinal cord is an evolutionarily conserved structure.