The cerebral cortex is a laminar neural structure which serves as a critical substrate for higher cognitive abilities in humans and other mammals. Here, I use single-neuron recordings to investigate primary auditory cortex, the first cortical area to process aural information, in the brains of awake mice. Neurons in primary auditory cortex are sensitive to sounds of certain frequencies and intensities. I explore the synaptic bases for those preferences and demonstrate that they can be modulated on a moment-by-moment basis by changes in brain state.