Our primary research goal is to understand the circuit mechanisms underlying how our brain synthesizes auditory information to extract complex sound features, such as our language. Towards this goal, we focus on mouse auditory cortex as the model system, and use multiple cutting-edge techniques in behaving animals to dissect the circuits that connect sound inputs to behavioral outputs. Specifically, we use in vivo whole-cell recordings to study synaptic events in single neurons, two-photon calcium imaging to study neuronal population dynamics in a bigger network, and combine these approaches with neuronal manipulation and behaviors. Through these experiments, we aim to bridge the gap between our knowledge at synaptic level and systems level, and elucidate the neuronal underpinnings of sound processing. Findings in the simple mouse auditory cortex should provide a first step towards the ultimate understanding of the complex human brain circuits that enable verbal communication, and how they fail in psychiatric disorders.