PROJECT SUMMARY A central goal of neuroscience is to understand animal behavior in the context of the information processing properties of neuron ensembles. Neurons are circuit nodes in the brain information processing network, but they are also cells that express hundreds of genes that may make important contributions to determining their activity patterns. The relationship between gene expression, neuron projections, neuron activity, and behavior have been, individually, major avenues for investigation in both molecular and systems neuroscience. Integrating these levels of investigation would greatly advance understanding the influence of molecular properties on neuron information processing characteristics in healthy brains and disease states. In this project, which we refer to as CaRMA 2.0, we propose to develop and democratize methodologies to integrate measurements of transcriptomics, projectomics, calcium dynamics, and behavior in deep-brain structures. This proposal builds on our past success to develop and implement Calcium and RNA Multiplexed Activity (CaRMA) imaging, which combines these levels of investigation into a single large-scale experiment. This is achieved by deep-brain two-photon calcium imaging in a behaving mouse, followed by removing and sectioning the brain, aligning the ex vivo image volume with the in vivo-imaged neurons, and then performing multiple rounds of RNA-fluorescence in situ hybridization (FISH) on the same tissue. To reliably produce these high dimensional, multi-modal datasets requires significant advancements for “Optimization of Transformative Technologies for Large Scale Recording and Modulation in the Nervous System” as indicated in this RFA-NS-18-019 program announcement. We will develop improved technologies for deep-brain calcium imaging as well as highly multiplexed gene expression analysis on the same cells and apply this pipeline to investigate the mPFC, hindbrain, and the role of the lateral hypothalamus in hunger, thirst, and fear.