The overarching goal of the proposed study is to identify the molecular and cellular mechanisms underlying response inhibition in Drosophila. The preliminary data point to dopamine as an important neuromodulator for response inhibition. The flies with enhanced dopamine signaling or with deficient dopamine transporter display abnormal response inhibition. By taking advantage of powerful genetic tools and resources available in Drosophila the proposed research aims to uncover additional molecules and signaling pathways that regulate response inhibition. This will provide a baseline to further delineate comprehensive neural, cellular and molecular mechanisms.