A topographical organization in the primary olfactory cortex.

A key principle of most sensory cortices is their topographic organization, in which neurons in proximity exhibit similar tuning properties, typically varying along a specific stimulus feature. However, such an organization has not yet been identified in the olfactory system. Here, we developed a method that reveals the set of glomerular inputs to multiple Piriform Cortex neurons. We found that, on average, each Piriform neuron receives input from ~60 glomeruli. Putative interneurons tend to receive input from more glomeruli. Most neurons were activated when multiple distinct subsets of 2-4 glomeruli were active. Notably, the input glomeruli of nearby Piriform neurons were positioned close to each other, sharing a few glomeruli. The similarity of glomerular input maps decreased with increased distance between Piriform neurons. Furthermore, this similarity principle aligned with an increase in odor-tuning similarity of nearby neurons in both awake and anesthetized mice. These results indicate that the primary olfactory cortex adheres to an organizational principle based on how it processes glomerular inputs.