Antennal lobe

Axons of antennal ORCs project through the antennal nerve to enter the brain at the level of the ipsilateral antennal lobe (AL) of the deutocerebrum (52). ORC axons project from the flagellum to targets in the AL, but axons from antennal mechanosensory neurons bypass the AL and project instead to an "antennal mechanosensory and motor center" in the deutocerebrum posteroventral (with respect to the body axis of the animal) to the AL (52, 58, 64). In moths and certain other insect groups, sex-pheromonal information is processed in a prominent male-specific neuropil structure in each AL called the macroglomerular complex (MGC) (16, 52, 64, 65). 

Fig-1 Schematic view of the overall olfactory processing in insects. Pheromones and other semiochemicals are detected by specialized sensilla on the antennae, where the chemical signal is transduced into nervous activity. The olfactory receptor neurons in the semiochemi-cal-detecting sensilla are connected directly to the antennal lobe. Here the semiochemical-derived electrical signals are processed and sent out (through projection neurons) to the protocerebrum. Olfactory information is then integrated with other stimulus modalities, a decision is made, and the motor system is told what to do... 

The distal part of these receptor cells, the dendrites (0.1-0.5 pm in diameter), extend into the hair lumen (Fig. 3), whereas their axons are connected directly to the antennal lobes in the brain where they make the first synaptic contacts. In the giant silkmoth, Antheraeapolyphemus,for example, each male... 

Galizia, C. G., Sachse, S. and Mustaparta, H. (2000). Calcium responses to pheromones and plant odours in the antennal lobe of the male and female moth Heliothis virescens. Journal of Comparative Physiology A 186 1049-1063. 

Hansson, B. S. and Anton, S. (2000). Function and morphology of the antennal lobe new developments. Annual Review of Entomology 45 203-231. 

Sachse, S., Rappert, A. and Galizia, C. G. (1999). The spatial representation of chemical structures in the antennal lobe of honeybees steps towards the olfactory code. European Journal of Neuroscience 11 3970-3982. 

Axons originating in sensilla that are responsive to food odorants and those that originate in sex pheromone-responsive neurons terminate in different glomeruli, the first synaptic relay station within the antennal lobe (Boeckh and Ernst,... 

Ignell, R., Anton. S. and Hansson, B. S. (2001). The antennal lobe of orthoptera anatomy and evolution. Brain Behavior and Evolution 57 1-17. 

Prillinger, F. (1981). Postembryonic development of the antennal lobes in Periplaneta americana F. Cell and Tissue Research 215 563-575. 

Salecker, I. and Boeckh, J. (1995). Embryonic development of the antennal lobes of a hemimetabolous insect, the cockroach Periplaneta americana light and electron microscopic observations. Journal of Comparative Neurology 352 33-54. 

Carlsson, M. A., Galizia, C. G. and Hansson, B. S. (2002). Spatial representation of odours in the antennal lobe of the moth Spodoptera littoralis (Lepidoptera Noctuidae). Chemical Senses 27 231-244. 

Hansson, B. S. and Christensen, T. A. (1999). Functional characteristics of the antennal lobe. In Insect Olfaction, ed. B. S. Hansson, pp. 125-161. Berlin Springer-Verlag. 

Anton S. and Hansson B.S. (1995) Sex pheromone and plant-associated odour processing in antennal lobe intemeurons of male Spodoptera littoralis (Lepidoptera Noctuidae). J. Comp. Physiol. A. 176, 773-789. 

Hansson B. S., Christensen T. A. and Hildebrand J. G. (1991). Functionally distinct subdivisions of the macroglomerular complex in the antennal lobe of the male sphinx moth Manduca sexta. J. Comp. Neurol. 312, 264—278. 

Bausenwein B. and Nick P. (1998) Three dimensional reconstruction of the antennal lobe in the mosquito, Aedes aegypti. In New Neuroethology on the Move, eds R. Wehner and N. Eisner, p. 386. Thieme Stuttgart. 

Boeckh J., Distler P., Ernst K., Hosl M. and Malun D. (1990) Olfactory bulb and antennal lobe. In Chemosensory Information Processing, ed. D. Schild, pp. 201-228. Springer Heidelberg, Germany. 

Distler P. G. and Boeckh J. (1997b) Synaptic connections between identified neuron types in the antennal lobe glomeruli of the cockroach, Periplaneta americana II. Local multiglomerular interneurons. J. Comp. Neurol. 383, 529-540. 

Matsumoto S. and Hildebrand J. (1981) Olfactory mechanisms in the moth Manduca sexta response characteristics and morphology of central neurons in the antennal lobes. Proc. R. Soc. London Ser. B 213, 249-277. 

Rodrigues, V. (1988). Spatial coding of olfactory information in the antennal lobe of Drosophila melanogaster. Brain. Res. 453, 299-307. 

Sun X. J., Tolbert L. P. and Hildebrand J. G. (1997) Synaptic organization of the uniglomerular projection neurons of the antennal lobe of the moth Manduca sexta a laser scanning confocal and electron microscopic study. J. Comp. Neurol. 379, 2-20. Takken W., van Loon J. J. A. and Adam W. (2001) Inhibition of host-seeking response and olfactory responsiveness in Anopheles gambiae following blood feeding. J. Insect. Physiol. 47, 303-310. 

Stocker, 1994). While mammals possess millions of OSNs that relay information to thousands of olfactory bulb glomeruli, adult Drosophila have a mere 1300 OSNs connected to 43 antennal lobe glomeruli. This vastly simplified olfactory system, that nevertheless retains many of the anatomical features found in the mammalian olfactory system, make the fly an excellent model system in which to study the sense of smell. 

The fly antennal lobe contains at least 43 glomeruli which are likely to be the functional homologs of glomeruli in the vertebrate olfactory bulb (Laissue et al.,... 

Gao Q., Yuan B. and Chess A. (2000) Convergent projections of Drosophila olfactory neurons to specific glomeruli in the antennal lobe. Nat. Neurosci. 3, 780-785. 

Laissue R P., Reiter C., Hiesinger P. R., Halter S., Fischbach K. F. and Stocker R. F. (1999) Three-dimensional reconstruction of the antennal lobe in Drosophila melanogaster. J. Comp. Neurol. 405, 543-552. 

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