Functional Topography of Connections Linking Mirror-Symmetric Maps in the Mouse Olfactory Bulb

Lodovichi, Claudia; Belluscio, Leonardo; Katz, Lawrence C

doi:10.1016/s0896-6273(03)00194-6

Cited by 110 publications

(99 citation statements)

References 55 publications

(7 reference statements)

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“…The isofunctional (lateral and medial) glomeruli located within each OB are reciprocally connected by interneurons that may contribute to the refinement of odorant information in the OB (Lodovichi et al, 2003). Our preliminary data regarding rheological simulation indicates that temporal and spatial distribution patterns of an odorant in the nasal cavity are quite different depending on the breathing conditions (Y.…”

Section: Discussionmentioning

confidence: 86%

Nasal Airflow Rate Affects the Sensitivity and Pattern of Glomerular Odorant Responses in the Mouse Olfactory Bulb

Oka¹,

Tokura²,

Touhara³

2009

J. Neurosci.

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Sniffing is a characteristic odor sampling behavior in various mammalian species, which is associated with an increase in both nasal airflow rate and breathing frequency. Although the importance of sniffing in olfaction is well recognized, it has been challenging to separate the effect of airflow rate and sniffing frequency in vivo. In this study, we examined the individual effects of airflow rate and frequency on odorant responses of glomeruli in the mouse olfactory bulb (OB) using calcium imaging techniques and an artificial sniffing system. We found that nasal airflow rate, but not sniffing frequency, affected the apparent glomerular responses. When measured using OB imaging, apparent sensitivity for some of the odorants was significantly greater at the high nasal flow rates, while other odorants exhibited the opposite effect. In a single defined glomerulus, the sensitivity shift caused by changes in flow rate varied between odorants, suggesting that the flow rate effect is dependent on the chemical properties of an odorant rather than on the specific characteristics of the expressed olfactory receptor. Using natural flavors containing a variety of odorants, different glomerular activation patterns were observed between breathing and sniffing condition, likely due to odorant-dependent flow rate effects. Our results provide important information on in vivo odorant recognition and suggest that odor representation in the OB is not fixed but rather varies significantly depending on the respiratory state.

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Section: Discussionmentioning

confidence: 86%

Nasal Airflow Rate Affects the Sensitivity and Pattern of Glomerular Odorant Responses in the Mouse Olfactory Bulb

Oka¹,

Tokura²,

Touhara³

2009

J. Neurosci.

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“…Neural tracer injections were performed as described previously (Lodovichi et al, 2003). Briefly, for in vivo injections, mice were anesthetized with an intraperitoneal injection of 100 mg/kg ketamine hydrochloride and 10 mg/kg xylazine hydrochloride and maintained with 100% oxygen supplemented with a 1.0 -3.0% isofluorane gas inhalant.…”

Section: Methodsmentioning

confidence: 99%

“…This organization is less clear in the olfactory system in which olfactory sensory neurons (OSNs) that express a common odorant receptor are broadly scattered throughout the nasal turbinates but coalesce to form glomerular maps as their axons reach the bulb (Ressler et al, 1994;Vassar et al, 1994). Recent studies have shown that a second-order map also exists that precisely links the glomerular maps within each bulb through a reciprocal projection mediated by external tufted cells (ETCs) (Schoenfeld et al, 1985;Belluscio et al, 2002;Lodovichi et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

Activity-Dependent Plasticity in the Olfactory Intrabulbar Map

Marks¹,

Cheng²,

Cummings³

et al. 2006

J. Neurosci.

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In mammals, each olfactory bulb contains two mirror-symmetric glomerular maps. Isofunctional glomeruli within each bulb are specifically linked through a set of reciprocal intrabulbar projections (IBPs) to form an intrabulbar map. We injected neural tracers into the glomerular layer on one side of the bulb and examined the resulting projection on the opposite side. In adult mice, the size of the projection tuft is directly proportional to the size of the injected region. Using this ratio as a measure of IBP maturity, we find an immature 5:1 projection to injection ratio at 1 week of age that gradually refines to a mature 1:1 by 7 weeks. Moreover, whereas the glomerular map is able to form despite the elimination of odorant-induced activity, the intrabulbar map shows clear activity dependence for its precise formation. Here we show through experiments with both naris-occluded and anosmic mice that odorant-induced activity is not required to establish IBPs but is crucial for projection refinement. In contrast, increased glomerular activation through exposure to distinct odorants during map development can accelerate the refinement of projections associated with the activated glomeruli. These findings illustrate a clear role for odorant-induced activity in shaping the internal circuitry of the bulb. Interestingly, activity deprivation can alter the organization of both the developing and the mature map to the same degree, demonstrating that intrabulbar map plasticity is maintained into adulthood with no discernible critical period.

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“…Each glomerulus is innervated by 20 -50 mitral/tufted cells, each of which innervates a single glomerulus with a single primary dendrite. Tufted cells project axon branches to the isotypic olfactory columns on the mirrorsymmetrical positions, forming intrabulbar connections (Lodovichi et al 2003). In addition to the excitatory neurons, there are several types of inhibitory interneurons, the periglomerular cells and granule cells (reviewed in Wilson and Mainen 2006).…”

Section: Olfactory Circuits In the Brain Axonal Convergence And The Tmentioning

confidence: 99%

Topographic Mapping--The Olfactory System

Imai¹,

Sakano²,

Vosshall³

2010

Cold Spring Harbor Perspectives in Biology

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Sensory systems must map accurate representations of the external world in the brain. Although the physical senses of touch and vision build topographic representations of the spatial coordinates of the body and the field of view, the chemical sense of olfaction maps discontinuous features of chemical space, comprising an extremely large number of possible odor stimuli. In both mammals and insects, olfactory circuits are wired according to the convergence of axons from sensory neurons expressing the same odorant receptor. Synapses are organized into distinctive spherical neuropils-the olfactory glomeruli-that connect sensory input with output neurons and local modulatory interneurons. Although there is a strong conservation of form in the olfactory maps of mammals and insects, they arise using divergent mechanisms. Olfactory glomeruli provide a unique solution to the problem of mapping discontinuous chemical space onto the brain.T he olfactory system detects airborne organic and inorganic chemicals that originate from plant and animal metabolites and environmental and industrial sources. Odors mediate both innate and learned behaviors such as attraction and aversion, governing decisions to eat, mate, attack or flee from aggressors and predators. A remarkable feature of the olfactory system is the extraordinary diversity of possible odor molecules that exist. Although accurate measurements can be made of the detection range of visual wavelengths or auditory frequencies in humans, there are no reliable estimates of the number of odorous molecules that exist on earth or those that can be detected by a given animal species (Gilbert 2008). Nevertheless, the number of possible odorants is thought to be high, in the range of many thousands. Beyond odor detection lies the problem of odor discrimination: how can chemicals with slightly different physical properties be discriminated and associated with distinct odor percepts?Experiments investigating the molecular logic of olfaction over the last 20 years have led to major insights into how animals solve the problem of detecting and discriminating a vast number of different odor stimuli (Axel 1995). Four organizational principles have emerged from this work. First, large numbers of distinct odorant receptor (OR) genes are dedicated

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Functional Topography of Connections Linking Mirror-Symmetric Maps in the Mouse Olfactory Bulb

Cited by 110 publications

References 55 publications

Nasal Airflow Rate Affects the Sensitivity and Pattern of Glomerular Odorant Responses in the Mouse Olfactory Bulb

Nasal Airflow Rate Affects the Sensitivity and Pattern of Glomerular Odorant Responses in the Mouse Olfactory Bulb

Activity-Dependent Plasticity in the Olfactory Intrabulbar Map

Topographic Mapping--The Olfactory System

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