Interneurons in olfactory cortex, central importance for the function of cortical circuits, comprise a wide range of different cell types that may be involved in different microcircuits and computations. However, the fine architecture of synaptic microcircuits which support computational processing in cortex is still poorly understood. The aim of this project is to address connectivities and functions of inhibitory microcircuit in the olfactory system by combining viral tracing of synaptically connected microcircuits with neuronal activity measurements in the intact zebrafish brain. First, I will ask whether different types of interneurons define specific microcircuits by mono-synaptic virus tracer and electrophysiology. To explore the detailed and quantitative data on connectivity motifs in olfactory cortex, I will then visualize microcircuits from single starter interneurons using Gal4-UAS system and DNA transfer to single neuron. Using this visualized microcircuit from single starter cell, I will also ask the physiological characters of each microcircuit by measurement of odor responses by 2-photon imaging. Finally, I will provide direct insights into the computational functions of synaptic microcircuits using optogenetics to manipulate the connected presynaptic neurons. These experiments will uncover general design principles of inhibitory microcircuit that will help to understand relationship between circuit structure and their function.