Biased connectivity shapes food odor categorization in the Drosophila mushroom body.

Animals rely on neural representations of sensory stimuli to rapidly recognize familiar environments and precisely identify salient cues. In the Drosophila mushroom body, odors are represented by the activity of Kenyon cells (KCs), whose random wiring with olfactory projection neurons (PNs) is generally thought to promote odor discrimination. Here, we investigated how deviations from this random wiring shape odor representations. By recording the responses of individual KC types to odors, we found that food-related odor representations formed by αβ and, in part, α'β' KCs were separated from representations of odors with other ethological relevance, supporting odor categorization. In contrast, representations formed by γ KCs did not differ across odor ethological groups. Computational simulations constrained by our functional data indicated that the biased PN input to αβ KCs largely accounts for these representations. Thus, individual KC types process information differently, supporting not only discrimination of odors but also their ethological categorization.