Project Summary: Behavior Core Long-term (days to months) and continuous (24 hours/day, 7 days/week) behavioral monitoring of mouse socio- spatial behavior is fundamental to this BRAIN Initiative proposal on “Oxytocin Modulation of Neural Circuit Function and Behavior”. Each Project requires behavioral assessment of mice in home cages or in larger more complex environments, often longitudinally and in conjunction with neural recordings, optogenetics, or other manipulations of cellular and network-level activity. A number of recent technical advances across levels now enable a deeper understanding of neuromodulation on flexible information processing and behavior in mice. Some of these innovations have been pioneered by our laboratories and the Projects/Cores of the Oxytocin U19 in the previous funding cycle. Specifically, it is now possible- if not routine- to apply advanced machine learning and computer vision methods for quantitative behavioral analysis of animal poses and trajectories from video data. This includes video tracking of multiple animals interacting, from different camera angles, across the light/dark cycle, and with simultaneous neural recordings. Over the last five years we have developed hardware, software, and other infrastructure to perform this continuous behavioral monitoring in our facility. Our successes have led to considerable investment in space and computer storage for this facility by NYU Langone. We now capitalize on the development of this facility and behavioral monitoring system to support the next-generation studies of multi-animal behavior and modulation of neural circuit function by the Oxytocin U19 teams. Aim 1 is to improve our capacity for behavioral home cage monitoring, both in terms of number of animals monitored per cage and the pipeline for data collection and analysis. Aim 2 is to develop more complex housing environments for studies of socio-spatial behavior and decision-making in mouse colonies of small to moderate sizes. Aim 3 is to provide a suite of additional social, spatial and other oxytocin-related testing available to Project teams and assisted by Behavior Core staff, including breeding and housing the set of transgenic mouse lines required for this U19 proposal.