Learned odor discrimination in Drosophila without combinatorial odor maps in the antennal lobe
Department of Neurobiology
Medical Subject Headings
Animals; Brain; Discrimination Learning; Drosophila; Drosophila Proteins; Olfactory Perception; Olfactory Receptor Neurons; Receptors, Odorant
Life Sciences | Medicine and Health Sciences | Neuroscience and Neurobiology
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 , but the contribution of this activity to behavioral odor discrimination has received little attention . 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.
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Citation: Curr Biol. 2008 Nov 11;18(21):1668-74. Epub 2008 Oct 23. Link to article on publisher's site