For understanding normal and pathological circuit function, capitalizing on the full potential of recent advances in fast optical neural circuit control will depend crucially on fast, intact-circuit readout technology. First, millisecond-scale optical control will be best leveraged with simultaneous millisecond-scale optical imaging. Second, both fast circuit control and imaging should be adaptable to intact-circuit preparations from normal and diseased subjects. Here we illustrate integration of fast optical circuit control and fast circuit imaging, review recent work demonstrating utility of applying fast imaging to quantifying activity flow in disease models, and discuss integration of diverse optogenetic and chemical genetic tools that have been developed to precisely control the activity of genetically specified neural populations. Together these neuroengineering advances raise the exciting prospect of determining the role-specific cell types play in modulating neural activity flow in neuropsychiatric disease.