Coding of odor valence and intensity in the Drosophila olfactory circuit

Abstract

To internally reflect the sensory environment, animals create neural maps encoding the raw information of the external stimulus space. From that primary neural code relevant information has to be extracted for accurate navigation. We have characterized an olfactory-processing pathway comprised of inhibitory projection neurons (iPNs) at morphological, functional and behavioral levels. Our results show that iPNs shape innate odor-guided behavior in crucial ways. We demonstrate that the iPN population is split into two subgroups coding positive hedonic valence or intensity information and conveying these features into separate domains in the lateral horn (LH) via feed-forward inhibition. Silencing iPNs severely diminished flies’ attraction behavior and odor intensity discrimination. Moreover functional imaging disclosed an independent LH region tuned to repulsive odors comprised exclusively of ventrolateral protocerebral neurons. Our data demonstrate a feature-based spatial and functional arrangement of the LH, and elucidate its role as the center for integrating behaviorally relevant olfactory information.