Antennal lobe

The antennal lobe is the primary (first order) olfactory brain area in insects. The antennal lobe is a sphere-shaped deutocerebral neuropil in the brain that receives input from the olfactory sensory neurons in the antennae and mouthparts. Functionally, it shares some similarities with the olfactory bulb in vertebrates.[1]

Structure

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.[2] The antennal lobe is composed of densely packed neuropils, termed glomeruli, where the sensory neurons synapse with the two other kinds of neurons, the postsynaptic principle neurons (termed projection neurons) and local interneurons.[2] Each olfactory sensory neuron expresses a single odorant receptor type and targets the same glomeruli as other olfactory sensory neurons expressing that receptor type, such that each glomeruli houses all or the majority of sensory neurons of a given receptor type.[1][3][4] The number and identities of glomeruli are species specific; most species contain 40 to 160 individually identifiable glomeruli within the antennal lobe.[2] For instance, there are 32 glomeruli in mosquito,[2] 43 glomeruli in the fruit fly antennal lobe, and 203 glomeruli in cockroach.[5] The local neurons, which are primarily inhibitory, have their neurites restricted to the antennal lobe. Projection neurons, which generally receive information from a single glomerulus, project to higher brain centers such as the mushroom body and the lateral horn.[6] [7][8] 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.[9][10]

References
  1. Scott, Kristin; Brady, Roscoe; Cravchik, Anibal; Morozov, Pavel; Rzhetsky, Andrey; Zuker, Charles; Axel, Richard (March 2001). "A Chemosensory Gene Family Encoding Candidate Gustatory and Olfactory Receptors in Drosophila". Cell. 104 (5): 661–673. doi:10.1016/S0092-8674(01)00263-X. PMID 11257221.
  2. B. S. Hansson & S. Anton (2000). "Function and morphology of the antennal lobe: new developments". Annual Review of Entomology. 45: 203–231. doi:10.1146/annurev.ento.45.1.203. PMID 10761576.
  3. Leslie B. Vosshall, Allan M. Wong & Richard Axel (2000). "An olfactory sensory map in the fly brain". Cell. 102 (2): 147–159. doi:10.1016/S0092-8674(00)00021-0. PMID 10943836.
  4. Gregory S. X. E. Jefferis, Elizabeth C. Marin, Reinhard F. Stocker & Liqun Luo (2001). "Target neuron prespecification in the olfactory map of Drosophila" (PDF). Nature. 414 (6860): 204–208. Bibcode:2001Natur.414..204J. doi:10.1038/35102574. PMID 11719930.CS1 maint: multiple names: authors list (link)
  5. Watanabe, Hidehiro; Nishino, Hiroshi; Mizunami, Makoto; Yokohari, Fumio (5 May 2017). "Two Parallel Olfactory Pathways for Processing General Odors in a Cockroach". Frontiers in Neural Circuits. 11: 32. doi:10.3389/fncir.2017.00032. PMC 5418552. PMID 28529476.
  6. Mark Stopfer, Vivek Jayaraman & Gilles Laurent (2003). "Intensity versus identity coding in an olfactory system". Neuron. 39 (6): 991–1004. doi:10.1016/j.neuron.2003.08.011. PMID 12971898.
  7. Gronenberg, W.; López-Riquelme, G.O. (February 2014). "Multisensory convergence in the mushroom bodies of ants and bees". Acta Biologica Hungarica. 55 (1–4): 31–37. doi:10.1556/ABiol.55.2004.1-4.5. PMID 15270216.
  8. López-Riquelme, G.O. (June 2014). "Odotopic afferent representation of the glomerular antennal lobe organization in the mushroom bodies of ants (Hymenoptera: Formicidae): Comparisons between two species". TIP Revista Especializada en Ciencias Químico-Biológicas. 17 (1): 15–31. doi:10.1016/S1405-888X(14)70317-1.
  9. Gilles Laurent (2002). "Olfactory network dynamics and the coding of multidimensional signals". Nature Reviews Neuroscience. 3 (11): 884–895. doi:10.1038/nrn964. PMID 12415296.
  10. Mark Stopfer & Gilles Laurent (1999). "Short-term memory in olfactory network dynamics". Nature. 402 (6762): 664–668. Bibcode:1999Natur.402..664S. doi:10.1038/45244. PMID 10604472.

Further reading

Reviews of antennal lobe anatomy
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