PROJECT SUMMARY The sense of olfaction allows animals to gather critical information about resources, dangers, and potential social interactions. A primary goal of olfactory neuroscience is to understand how neural circuit operations in the main olfactory system parse chemical signals in the environment and contribute to adaptive behavior. Neural circuits in piriform cortex (PCx), the primary olfactory cortex, are thought to transform elemental odor information received from the olfactory bulb into more holistic ‘odor object’ representations that signal the presence of unique odor sources in the environment. The olfactory system developed this ability over the course of evolution in contexts where information about the presence and identity of other animals, especially conspecifics, was critically important. Substantial progress has been made in understanding representations of neutral monomolecular odorants in PCx. By contrast, nothing is known about olfactory cortical processing of social scents. In support of a specialized role in social odor processing, PCx densely expresses receptors for the neuropeptide oxytocin (OT) involved in a wide range of social behaviors. However, the potential for OT modulation also suggests that PCx circuits may operate differently in social and nonsocial contexts. The objective of this proposal is to understand how cortical odor processing contributes to social behavior. The central hypothesis is that OT modulates PCx circuit dynamics in social contexts to allow distinct conspecific identity coding and support social recognition. The approach is to use calcium imaging and multi-electrode recordings to observe PCx population responses during social odor processing and to use targeted perturbations of PCx function to test its role in social behavior. The rationale is that observing and perturbing the system as it performs its natural role in an adaptive behavior provides the most accurate picture of PCx’s capabilities and contribution to fitness. The following aims address these goals: Aim 1: Determine how social recognition information is encoded in piriform cortex. We will image large populations of PCx neurons in freely interacting animals and compare dynamics and coding properties during social or nonsocial stimulus investigation to test our hypothesis that distinct circuit dynamics in social contexts enable reliable discrimination of individual social identity. Aim 2: Determine how oxytocin modulates social odor processing in piriform cortex. We will first measure dynamics of OT neuron activity during social interactions using fiber photometry, and then match these dynamics with optogenetic stimulation of OT neurons while recording PCx population responses to controlled presentation of social odors. Aim 3: Determine the role of piriform cortex in individualized social behavior. PCx function will be perturbed by chemogenetic inactivation or by deletion of OT receptors to test whether cortical processing and modu...