A fundamental feature of cortical circuits is a division of labor among cell types: glutamatergic excitatory neurons propagate neuronal activity, but it is GABAergic inhibitory interneurons that control the excitability of glutamatergic neurons. Thus, GABAergic interneurons are a primary determinant of the spatial and temporal flow of activity in the cortex. With the goal of understanding the complex computations performed by cortical circuits, we systematically disturb inhibitory neuron function and assess the consequence on circuit function. To accomplish this experimentally, we manipulate molecular signaling pathways within specific classes of GABAergic neurons and probe the impact of such manipulation on functional responses of both excitatory and inhibitory neurons in-vivo using 2-photon guided electrophysiological recording of identified neurons in anesthetized and awake mice.