HALE, M. E.: The neural basis of aquatic locomotion: Examining neuron activity and behavior with functional imaging.

A major question in motor control research is: How do neural circuits in the spinal cord generate movements? Recently developed optical imaging techniques provide powerful ways to examine the neural basis of behavior in vertebrates. These methods are well suited for studies of locomotion in larval fishes because of the small size and transparency of fish during early life history. During an experiment, a confocal microscope is used to image calcium fluxes in neurons while video records regional body movements. Confocal and video images are synchronized to determine the relationship between neuron activity and behavior. Morphology of spinal interneurons of zebrafish and their locomotor functions are examined as a model system for spinal neural circuit design and function. Because the zebrafish has been developed as a genetic model, many complementary approaches are available including the use of mutant lines and transgenic lines expressing fluorescent proteins in neurons. New spinal interneuron cell types are identified including several classes of ascending and descending commissural interneurons. The activity of these cell types has been examined during swimming and escape behaviors. Comparisons are made to similar cells and systems in phylogenetically diverse taxa including lamprey and frog tadpoles in order to examine current models of central pattern generation in axial locomotion. In addition, imaging techniques are used to develop the neural circuit of the pectoral fin as a new model system for studying the neural basis of limb locomotion. Results of such neural imaging studies add to our understanding of the functional morphology of swimming and provide key insights into basic principles of neural circuit design and function. Supported by NIH NRSA Fellowship MH11861.