Antennal lobe

Antennal lobe is the deutocerebral neuropil of the insect which receives the input from the olfactory sensory neurons on the antenna. Functionally, it shares some similarities with the olfactory bulb in vertebrates.

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In insects, the olfactory pathway starts at the antennae (though in some insects like Drosophila there are olfactory sensory neurons in other parts of the body) from where the sensory neurons carry the information about the odorant molecules impinging on the antenna to the antennal lobe. The antennal lobe is composed of densely packed neuropils, termed glomeruli, where the sensory neurons synapse with the two other kinds of neurons, the projection neurons and the local neurons. There are 43 glomeruli in the Drosophila antennal lobe. The projection neurons project to higher brain centers such as the mushroom body and lateral horn of the protocerebrum. The local neurons, which are primarily inhibitory, have their neurites restricted to the antennal lobe. In Drosophila, each olfactory sensory neuron generally expresses a single olfactory receptor gene, and the neurons expressing a given gene all transmit information to one or two spatially invariant glomeruli in the antennal lobe. Moreover, each projection neuron generally receives information from a single glomerulus. The interaction between the olfactory receptor neurons, local neurons and projection neurons reformats the information input from the sensory neurons into a spatio temporal code before it is sent to higher brain centers.

The plasticity and coding properties of the projection neurons are currently under intensive investigation at several laboratories.

References

• Buck, Linda and Richard Axel. (1991). A Novel Multigene Family May Encode Odorant Receptors: A Molecular Basis for Odor Recognition. Cell 65:175-183.
• Keller, A and Vosshall, LB. (2004). A psychophysical test of the vibration theory of olfaction. Nature Neuroscience 7:337-338. See also the editorial on p. 315.
• Turin, Luca. (1996). A spectroscopic mechanism for primary olfactory reception. Chemical Senses, 21, 773-791.
• Turin, Luca. (2002). A method for the calculation of odor character from molecular structure. Journal of Theoretical Biology, 216, 367-385.
• Stopfer, Mark.; Jayaraman, Vivek.; Laurent, Gilles. (2003) Intensity versus Identity Coding in an Olfactory System, Neuron 39, 991-1004.
• Stopfer, Mark. and Laurent, Gilles. (1999). Short-term memory in olfactory network dynamics, Nature 402, 664-668.
• Chandler Burr. (2003). The Emperor of Scent : A Story of Perfume, Obsession, and the Last Mystery of the Senses. ISBN 0-375-50797-3
• Laurent, Gilles. Olfactory network dynamics and the coding of multidimensional signals Nature Reviews Neuroscience 3:884-895 (2002)
• Jefferis GS, Marin EC, Stocker RF, and Luo, L. (2001). Target neuron prespecification in the olfactory map of Drosophila. Nature 414(6860):204-8.
• Vosshall LB, Wong AM, Axel R. (2000). An olfactory sensory map in the fly brain. Cell 102(2):147-59.