PROJECT SUMMARY Sensory processing is a way to understand the nervous system in action. Behavioral context strongly affects sensory processing. For example, a brief visual stimulus is easier to detect if it appears in a predictable spatial location. This attention to visual space strongly enhances neural and behavioral responses to stimuli in those locations, but the detailed neural mechanisms spanning multiple brain areas remain unknown. This is largely because we lack the ability to measure specific neurons and circuits across multiple brain areas in real-time during behavior that elicits visual spatial attention. We are uniquely positioned to bridge this critical knowledge gap by leveraging tools for functionally targeted, multi-area recordings from genetically defined neuron subtypes to establish the timing and organization of attentional signal flow throughout the visual system during behavior. This innovative combination of techniques will enable us to 1) Establish neural timing of spatial attention across visual cortical areas 2) Establish organization of visual spatial attention networks 3) Establish laminar and cellular substrates for multi-area visual spatial attention networks SIGNIFICANCE. This project will meet a significant need to understand how an internal cognitive state—attention—modulates the intensity of external sensory events. Establishing a detailed blueprint for neural substrates of attention and sensory processing will provide greater understanding of cognitive flexibility, and provide insight for conditions characterized by deficits of attention and sensory perception. INNOVATION. This work provides technical innovation by pairing a visual attention task with optically targeted, multi-area Neuropixels population recordings from genetically resolved neuron subtypes and functionally resolved input, feedforward, and feedback pathways. We provide conceptual innovation by defining how an internal cognitive factor like attention coordinates and enhances information processing across multiple stages of a major sensory pathway.