During development, motile dendritic filopodia expand and make contacts with growing axonal terminals. Thus, central synapse formation and stabilization occurs in a highly dynamic environment. The activity-dependent molecular mechanisms regulating local dendritic growth and synapse stabilization are incompletely understood, and technical limitations have restricted their examination in vivo. I propose to characterize functional connections between singly identified motoneurons and sensory cells in the Drosophila larval CNS using electrophysiological, anatomical and imaging methods. I will test the hypothesis that synapse formation and refinement in the CNS is regulated by second messenger signaling as observed in NMJ development. I will also test consequences of altered sensory-motor connectivity in the maturation of peristaltic/crawling behavior.