Pharmacological investigation of sharing vs. specialization of spinal cord central pattern generators for leg movements

This project will investigate how the central nervous system of vertebrates produces the right movement at the right time. More specifically, it will help reveal how the spinal cord is organized to appropriately control leg movements. The project will use turtles, which have technical advantages such as producing outputs for swimming, three forms of scratching, and leg withdrawal, even without input from the brain and movement-related input from the legs. Insights from this work will be important both for understanding how vertebrate behaviors are normally controlled and what may go wrong in the central nervous system in disorders that affect movement. In addition to these research goals, the project will support the training of students, including underrepresented minorities, outreach to local children using hands-on activities related to nervous system function, and the writing of science articles for a general audience. The spinal control of limb movements in an adult vertebrate will be addressed in turtle spinal cord in vivo, using pharmacological perturbations to investigate the sharing of circuitry. Pharmacology will be used to block the two major types of ionotropic inhibitory neurotransmitter receptors, glycine and GABAA as well as antagonize the primarily inhibitory and primarily excitatory serotonin receptors, 5-HT1 and 5-HT2. For each perturbation, effects on rhythm rates, numbers of cycles, and nerve burst phase relationships will be quantified for swimming and the three forms of scratching; nerve burst amplitudes and durations will be quantified for all of these motor patterns plus flexion reflex. The project findings should help clarify in general how vertebrate central nervous systems use a combination of multifunctional and specialized circuitry to select and generate the intended motor output at the right time. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.