Project Summary The function of the nervous system is dependent on complex interactions between networks of neurons composed of multiple neuron types. Understanding how these networks function both in health and disease is dependent on understanding the precise connectivity between specific neuron types and their functional interactions in the intact brain. It is therefore apparent that, in order to have an adequate understanding of the nervous system, it is necessary to have detailed descriptions of neuronal connectivity with the same level of precision at which these systems operate and to selectively manipulate and measure the activity of specific cell types in the context of the normal functioning network. Such studies would be greatly facilitated by the ability to target gene expression to specific cell types in the context of AAV vectors. The aims of this proposal are designed to first test and overcome possible limitations in the use of AAV vectors targeting gene expression to SST- and PV-expressing inhibitory internueon in the visual cortex, and then to use these tools to selectively manipulate the activity and characterize the functions of these inhibitory subclasses. The establishment of the utility of these reagents will allow future studies testing the functional contributions of specific inhibitory neuron types to perception,cognition and behavior.