Learned Odor Discrimination in Drosophila without Combinatorial Odor Maps in the Antennal Lobe

• DOI: 10.1016/j.cub.2008.08.071
• Publication Date: 2008-10-24T11:32:49Z
• Authors: Shamik DasGupta; Scott Waddell
• Keywords: 0301 basic medicine; 570; 0303 health sciences; Drosophila Proteins/metabolism; Olfactory Perception/physiology; Agricultural and Biological Sciences(all); Biochemistry, Genetics and Molecular Biology(all); Odorant/metabolism; Drosophila/physiology; Brain; Brain/physiology; Olfactory Perception; Receptors, Odorant; Olfactory Receptor Neurons; Discrimination Learning; 03 medical and health sciences; Discrimination Learning/physiology; Olfactory Receptor Neurons/physiology; Receptors; Animals; Drosophila Proteins; Drosophila; SYSNEURO

A unifying feature of mammalian and insect olfactory systems is that olfactory sensory neurons (OSNs) expressing the same unique odorant-receptor gene converge onto the same glomeruli in the brain [1-7]. Most odorants activate a combination of receptors and thus distinct patterns of glomeruli, forming a proposed combinatorial spatial code that could support discrimination between a large number of odorants [8-11]. OSNs also exhibit odor-evoked responses with complex temporal dynamics [11], but the contribution of this activity to behavioral odor discrimination has received little attention [12]. Here, we investigated the importance of spatial encoding in the relatively simple Drosophila antennal lobe. We show that Drosophila can learn to discriminate between two odorants with one functional class of Or83b-expressing OSNs. Furthermore, these flies encode one odorant from a mixture and cross-adapt to odorants that activate the relevant OSN class, demonstrating that they discriminate odorants by using the same OSNs. Lastly, flies with a single class of Or83b-expressing OSNs recognize a specific odorant across a range of concentration, indicating that they encode odorant identity. Therefore, flies can distinguish odorants without discrete spatial codes in the antennal lobe, implying an important role for odorant-evoked temporal dynamics in behavioral odorant discrimination.