Comprehensive Maps of Drosophila Higher Olfactory Centers: Spatially Segregated Fruit and Pheromone Representation

TLDR

Drosophila olfactory information is conveyed by ~50 ORN classes that project to corresponding glomeruli, and uniglomerular projection neurons relay this input to the mushroom body and lateral horn. The authors aimed to generate high‑resolution, quantitative maps of the mushroom body and lateral horn for 35 projection‑neuron channels and several LH neuron groups. They accomplished this by combining single‑cell labeling with image registration to produce the maps. PN inputs to the mushroom body are stereotyped, PN partners of ORNs from distinct sensillar groups cluster in the lateral horn, fruit odors are mainly encoded in the posterior‑dorsal LH while pheromone‑responsive PNs project to the anterior‑ventral LH, and individual LH neuron dendrites overlap with specific PN axon subsets, indicating that the lateral horn is organized by the biological value of olfactory input.

Abstract

In Drosophila, approximately 50 classes of olfactory receptor neurons (ORNs) send axons to 50 corresponding glomeruli in the antennal lobe. Uniglomerular projection neurons (PNs) relay olfactory information to the mushroom body (MB) and lateral horn (LH). Here, we combine single-cell labeling and image registration to create high-resolution, quantitative maps of the MB and LH for 35 input PN channels and several groups of LH neurons. We find (1) PN inputs to the MB are stereotyped as previously shown for the LH; (2) PN partners of ORNs from different sensillar groups are clustered in the LH; (3) fruit odors are represented mostly in the posterior-dorsal LH, whereas candidate pheromone-responsive PNs project to the anterior-ventral LH; (4) dendrites of single LH neurons each overlap with specific subsets of PN axons. Our results suggest that the LH is organized according to biological values of olfactory input.