Our laboratory investigates molecular pathways that sculpt the connectivity of circuits, alter their performance, and shape behavior. In particular, we seek to identify regulatory mechanisms that control synaptic activity and to understand their contribution to nervous system development, as well as neural circuit output and behavior. To address these questions, we have developed tools for manipulating the activity of specific synapses in a genetically tractable model system, the nematode Caenorhabditis elegans. In addition to an abundance of available genetic tools, C. elegans offers a number of features that make it ideally suited for our work. The pattern of neural connectivity has been established by electron microscopy, allowing for detailed knowledge of synaptic partners in a circuit. The organism is optically transparent, enabling (1) easy imaging of the cellular and subcellular distribution of fluorescent reporters, (2) Ca2+ imaging studies, and (3) optogenetic approaches for cell-specific optical stimulation or inhibition of neurons, all in the intact animal. Finally, we have extensive expertise in patch clamp electrophysiology in order to measure synaptic currents from defined neurons or muscles in vivo.