Piriform cortex multiplexes odor and spatial cues as odor-place associations are learned

Olfactory processing is shaped by experience, context, and internal state. To understand how learning reshapes responses within olfactory circuits, we trained mice on an associative task in a virtual-reality environment, where animals discriminated among four odor-context combinations for reward. We previously found that after training, odor-responsive neurons in piriform cortex (PCx) acquire mixed selectivity, jointly encoding contextual and associative information, but the process underlying this transition remained unknown. To address this, we recorded PCx activity across learning and applied behavioral and encoding/decoding models to track how representations evolve. Mice acquired the task sequentially: they first learned to discriminate odors (intermediate session) and only later learned to discriminate contexts (expert session). PCx activity followed the same trajectory: intermediate animals encoded mostly olfactory information, whereas expert animals encoded both odor and context, a result confirmed by population decoding. Expert neurons also showed greater multiplexing than those from earlier stages. We also showed that contextual enhancement of odor discrimination depends on an associative learning process, suggesting that the acquired PCx encoding arises specifically from linking odor cues to spatial information during correct task performance. We are now investigating the neural mechanisms underlying this association within PCx.