Vassar, R. et al. Topographic organization of sensory projections to the olfactory bulb. Cell 79, 981-992

Columbia University, New York, New York, United States
Cell (Impact Factor: 32.24). 01/1995; 79(6):981-91. DOI: 10.1016/0092-8674(94)90029-9
Source: PubMed


The detection of odorant receptor mRNAs within the axon terminals of sensory neurons has permitted us to ask whether neurons expressing a given receptor project their axons to common glomeruli within the olfactory bulb. In situ hybridization with five different receptor probes demonstrates that axons from neurons expressing a given receptor converge on one, or at most, a few glomeruli within the olfactory bulb. Moreover, the position of specific glomeruli is bilaterally symmetric and is constant in different individuals within a species. These data support a model in which exposure to a given odorant may result in the stimulation of a spatially restricted set of glomeruli, such that the individual odorants would be associated with specific topographic patterns of activity within the olfactory bulb.

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    • "While there has always been a great interest in developing instruments that mimic olfaction, so far, no apparatus having the same performance as biological olfaction exists. Understanding of the olfactory structure [2] [3] [4] [5] [6] [7] and coding mechanisms have stimulated new bioinspired computational solutions for signal processing. However, without realistic sensor data inputs such models can neither be benchmarked nor completely exploited. "
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    ABSTRACT: Biological olfactory systems show high sensitivity and exquisite discriminatory capacity to odorants. These characteristics are due to hierarchical signal processing of the large numbers of sensory inputs that occurs within the olfactory system. In testing realistic computational models of the olfactory system, large numbers of chemical sensor inputs are required. So far, sensory devices that may serve as model inputs to an artificial olfactory system do not exist. The development of a large scale array of chemical sensors able to mimic the olfactory receptor neurons is described, and these have been characterised in terms of their variability and degree of redundancy. Using this device it is possible to start testing computational hypotheses appropriate to biological chemosensory systems and adapt them to the artificial olfaction.
    Full-text · Article · Dec 2014 · Procedia Engineering
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    • "Each OSN expresses a single type of odorant receptor (OR), and within each bulb all OSNs expressing the same OR project to one of two glomeruli whose spatial positions are consistent from animal to animal, thus establishing a highly stereotyped glomerular map. Since all OSNs projecting to a single glomerulus express the same OR and respond to the same set of olfactory stimuli, the glomerular map is considered to represent olfactory space (Ressler et al., 1994; Vassar et al., 1994; Mombaerts, 2001). "
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    ABSTRACT: The olfactory system relies on precise circuitry connecting olfactory sensory neurons (OSNs) and appropriate relay and processing neurons of the olfactory bulb (OB). In mammals, the exact correspondence between specific olfactory receptor types and individual glomeruli enables a spatially precise map of glomerular activation that corresponds to distinct odors. However, the mechanisms that govern the establishment and maintenance of the glomerular circuitry are largely unknown. Here we show that high levels of Sonic Hedgehog (Shh) signaling at multiple sites enable refinement and maintenance of olfactory glomerular circuitry. Mice expressing a mutant version of Shh (Shh(Ala/Ala) ), with impaired binding to proteoglycan co-receptors, exhibit disproportionately small olfactory bulbs containing fewer glomeruli. Notably, in mutant animals the correspondence between individual glomeruli and specific olfactory receptors is lost, as olfactory sensory neurons expressing different olfactory receptors converge on the same glomeruli. These deficits arise at late stages in post-natal development and continue into adulthood, indicating impaired pruning of erroneous connections within the olfactory bulb. In addition, mature Shh(Ala/Ala) mice exhibit decreased proliferation in the subventricular zone (SVZ), with particular reduction in neurogenesis of calbindin-expressing periglomerular cells. Thus, Shh interactions with proteoglycan co-receptors function at multiple locations to regulate neurogenesis and precise olfactory connectivity, thereby promoting functional neuronal circuitry. © 2014 Wiley Periodicals, Inc. Develop Neurobiol, 2014.
    Full-text · Article · Dec 2014 · Developmental Neurobiology
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    • "Odorant receptors and other components of the signal transduction machinery that are present in cilia of sensory neurons are also present in axon terminals and participate in the establishment of the topographic organization of glomeruli (Ressler et al. 1994; Vassar et al. 1994; Imai et al. 2006; Maritan et al. 2009). Known mechanisms underlying glomerular convergence have been nicely reviewed elsewhere (Takeuchi and Sakano 2014) and involve differential expression of axon guidance molecules by sensory neurons in an odorant receptor-dependent fashion. "
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    ABSTRACT: Enormous advances have been made in the recent years in regard to the mechanisms and neural circuits by which odors are sensed and perceived. Part of this understanding has been gained from parallel studies in insects and rodents that show striking similarity in the mechanisms they use to sense, encode and perceive odors. In the present review we provide a short introduction to the functioning of olfactory systems from transduction of odorant stimuli into electrical signals in sensory neurons to the anatomical and functional organization of the networks involved in neural representation of odors in the central nervous system. We make emphasis on the functional and anatomical architecture of the first synaptic relay of the olfactory circuit, the olfactory bulb in vertebrates and the antennal lobe in insects. We discuss how the exquisite and conserved architecture of this structure is established and how different odors are encoded in mosaic activity patterns. Finally, we discuss the validity of methods used to compare activation patterns in relation to perceptual similarity.This article is protected by copyright. All rights reserved.
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