The ability to decipher meaning from degraded sounds is critical for everyday hearing. A key strategy to extract signals buried in noise is to integrate stored acoustic representations with incoming sound streams. Such top-down/bottom-up interaction appears to be a fundamental feature in sensory systems. This seminar will describe our circuit-level analysis of a massive descending pathway from the auditory cortex to the inferior colliculus (IC) which is thought to be important for top-down modulation using the mouse as a model. We will focus on differences between layer 5 and layer 6-derived neurons from the auditory cortex and how they interface with the neurochemical heterogeneity that exists in the inferior colliculus.