Economic choice behavior is specifically disrupted in a variety of mental and neurological disorders including frontotemporal dementia, major depression and drug addiction. Thus to better understand the origins of these disorders and to pave the way for treatments it is critical to understand the neural underpinnings of this behavior. Evidence from neurophysiology in non-human primates, functional imaging in humans and lesions in multiple species establishes a link between economic choice and the orbitofrontal cortex (OFC). In particular, previous research in the PI’s lab examined the activity of single neurons in the OFC of monkeys choosing between different liquid rewards. This work identified three groups of cells encoding the identity and subjective values of offered and chosen goods. The variables encoded in OFC capture both the input and the output of the choice process, suggesting that the cell groups identified in this area constitute the building blocks of a circuit in which decisions are formed. A series of theoretical and experimental results support this hypothesis, but many aspects of this circuit are poorly understood. For example, we don’t know whether different cell groups identified in OFC correspond to different anatomical cell types, whether they populate different cortical layers, and how they are connected with each other and with other brain regions. To address these and related questions, we brought our investigation to a genetically tractable species – the mouse. In a first study, we developed a mouse model of economic choice behavior and we demonstrated that optogenetic inactivation of the lateral orbital area (LO) disrupts choices (Kuwabara et al, eLife, 2020). In preparation for this proposal, we developed a protocol for two-photon (2P) calcium (Ca2+) imaging of area LO in mice performing choices. We thus identified three groups of neurons analogous to those previously found in primates. The overarching goal of this proposal is to link the functional cell groups identified in LO to anatomically defined cell types. To do so, we will combine 2P Ca2+ imaging with genetic markers and viral tracing. In a series of experiments, we will assess (Aim 1) whether different cell groups defined in relation to behavior reside preferentially in different layers, (Aim 2) whether different cell groups are differentially connected with sensory and/or motor regions, and (Aim 3) the relation between functional cell groups and inhibitory interneurons. In addition, (Aim 4) we will use Granger causality analysis to assess the effective connectivity between different cell groups. This is a collaboration between Dr. Padoa-Schioppa (PI), an expert in economic decisions, and Dr. Holy (co-I), an expert in mouse olfaction and optical imaging. Our collaboration has been ongoing for several years and we already published a first report. The experiments proposed here will break new ground and extend previous work in a new and promising direction. If s...