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. Author manuscript; available in PMC: 2013 Apr 1.
Published in final edited form as: Curr Opin Neurobiol. 2012 Jan 3;22(2):216–222. doi: 10.1016/j.conb.2011.12.010

Figure 1. Organization of the early olfactory system in Drosophila.

Figure 1

Each olfactory receptor neuron (ORN) typically expresses a single odorant receptor, and all the ORNs that express the same receptor project their axons to the same compartment (glomerulus) in the antennal lobe. There, ORNs make excitatory synapses onto second-order projection neurons (PNs). Each PN dendrite innervates a single glomerulus, and receives direct input from all the ORNs that target that glomerulus. Glomeruli are also interconnected by local neurons (LNs), most of which are GABAergic. The major target of GABAergic inhibition in each glomerulus is the ORN axon terminal.