The primary goal of this research is to understand the operation of the spinal networks responsible for generating locomotor activity in the mouse. In the past year, we have been developing mice that express light-activated channels that can hyperpolarize and depolarize neurons. We hope to use these mice to test the role of specific spinal neuron types in the genesis of locomotor activity. We are also continuing our imaging studies and have published work in the spinal cord of the chick embryo showing that motoneurons, the output elements of the spinal cord, seem to be critical in activating the spinal network during each cycle of spontaneous rhythmic activity. [unreadable] In a collaborative project with Dr. Aharon Lev-Tov (Hebrew University, Israel) we have been investigating how locomotor activity in the lumbar cord can be triggered by stimulating sensory nerves that innervate the tail. We have identified a class of interneurons whose axons travel in the ventral part of the spinal cord that appear to mediate this effect. We are currently establishing if these neurons, or a subset of them, project to the cerebellum. We have also been developing a preparation of the spinal cord that will allow studies of locomotor activity in the adult spinal cord. Currently our work is restricted to the neonate because its isolated spinal cord can be maintained alive in vitro whereas the adult cord cannot. [unreadable] Finally, we have begun a new project working with the very simple organism - C.Elegans - to use optical methods to analyze its locomotor circuitry. This model system should allow us to rapidly evaluate the utility of specific calcium and voltage sensitive proteins as reporters of neural activity and generate hypotheses about the operation of motor circuits that can be tested in the more complex nervous system of the mouse.