Molecular and functional heterogeneity of hypothalamic preoptic neurons

The preoptic area of the hypothalamus (POA) has been long known for its involvement in brain functions that are critical for the survival of the individual and the species. The POA regulates essentially all homeostatic functions: sleep, temperature, stress responses, fluid and nutrient balance. Additionally, it plays a prominent role in reproduction and in social behaviors including sexual behavior, parenting, affiliative behaviors, and aggression. These functions are fundamental for the fitness of animal species, are heavily controlled by the POA and are regulated in a sex-specific and hormone-dependent manner. In the past decade, the use of modern genetic approaches, biosensors, and circuit mapping, has identified subpopulations of neurons in the POA based on molecular profile and connectivity. Uncovering the functional roles of these diverse neuronal populations is key to elucidating how the POA controls key homeostatic functions and social behaviors. Here, we review new and past studies to offer an updated description of POA neuronal sub-divisions and their functional relevance. By synthesizing this knowledge, we discuss how the circuit anatomy and molecular heterogeneity of the POA inform its function, particularly how these features shape this region as an integrator of sensory cues and internal state, and as a key filter for behavioral selection.