Topographic Mapping--The Olfactory System

Imai, Takeshi; Sakano, Hitoshi; Vosshall, Leslie B.

doi:10.1101/cshperspect.a001776

Cited by 85 publications

(80 citation statements)

References 136 publications

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“…Our study suggests that guidance cues with complementary expression patterns within and surrounding the CC play a significant role in establishing the D-V position of axons within the CC. This ordering is analogous to the axon order observed in the olfactory nerve, where the guidance cues within and surrounding the olfactory nerve are essential for maintaining the correct axon topography and for ordered axon projection to the olfactory bulb (17,29). The complementary expression pattern of guidance cues within the thalamocortical tracts and along their routes (12)(13)(14) before their arrival in the cortex also contributes to the correct axon organization within the thalamocortical tract and the orderly projection of thalamocortical axons to the cortex.…”

Section: M1mentioning

confidence: 94%

Axon position within the corpus callosum determines contralateral cortical projection

Zhou

Wen

She

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

116

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How developing axons in the corpus callosum (CC) achieve their homotopic projection to the contralateral cortex remains unclear. We found that axonal position within the CC plays a critical role in this projection. Labeling of nearby callosal axons in mice showed that callosal axons were segregated in an orderly fashion, with those from more medial cerebral cortex located more dorsally and subsequently projecting to more medial contralateral cortical regions. The normal axonal order within the CC was grossly disturbed when semaphorin3A/neuropilin-1 signaling was disrupted. However, the order in which axons were positioned within the CC still determined their contralateral projection, causing a severe disruption of the homotopic contralateral projection that persisted at postnatal day 30, when the normal developmental refinement of contralateral projections is completed in wild-type (WT) mice. Thus, the orderly positioning of axons within the CC is a primary determinant of how homotopic interhemispheric projections form in the contralateral cortex.axon development | axon fiber order | cortical axon guidance | cortical development T he largest commissural tract in the human brain is the corpus callosum (CC), with more than 200 million axons connecting the two cerebral hemispheres. Callosal axons originate primarily from neurons of layer II/III and layer V of the neocortex (1) and project homotopically to the contralateral cortex. For example, callosal axons of the primary motor cortex (M1) and primary somatosensory cortex (S1) project to topographically equivalent locations in the contralateral M1 and S1, respectively. This pattern of homotopic projection is essential for coordinated motor and somatosensory functions as well as for higher associative and cognitive processes (2-4). Abnormal CC development has been noted in psychiatric and developmental disorders (5, 6), and deviant asymmetry of cortical areas found in patients with developmental dyslexia also may be attributed to callosal abnormalities (7,8). However, the mechanism by which normal homotopic projection pattern is achieved during development remains largely unknown.The majority of axonal projections in the nervous system are organized topographically. To facilitate the formation of orderly projections over long distances, axons originating from adjacent areas may preserve their topographic order within the nerve tract along their entire path toward the target region (9, 10). This preservation of topographic order has been shown in the thalamocortical tract (11)(12)(13)(14) and in the optic and olfactory nerves (15-17). By performing a series of random microinjections of biotinylated dextran amine in the dorsal thalamus and reconstructing the labeled fibers, Powell et al. (14) showed that labeled axons within the thalamocortical tract preserve a topography similar to that in the ventral telencephalon before they reach the cortex. In the developing olfactory system, axons within the olfactory nerve from three different regions of the olfactory epitheli...

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Section: M1mentioning

confidence: 94%

Axon position within the corpus callosum determines contralateral cortical projection

Zhou

Wen

She

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

116

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“…Fig. 4; [22,41,42,52]). Thus it appears that the two-dimensional problem of target site determination is broken down into two one-dimensional problems, which appear to be solved by independent molecular mechanisms.…”

Section: Ontogenesis Of the Receptotopic Map In The Olfactory Bulbmentioning

confidence: 94%

The peripheral olfactory system of vertebrates: molecular, structural and functional basics of the sense of smell

Manzini

Korsching

2011

E-Neuroforum

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The sense of smell provides people and animals with an abundance of information about their environment, helping them to navigate, detect potential threats, control food intake, choose sexual partners and significantly influence intraspecies social behavior. The perception of odors begins with the binding of odor molecules to specialized olfactory receptor proteins, which nearly all belong to the superfamily of G protein-coupled receptors. Altogether, five different olfactory receptor gene families have been described to date, among them the largest gene family in the genome with over 1000 genes in rodents. The signal transduction cascade coupled to the receptors has already been well characterized for this family. Three different classes of receptor neurons-ciliated, microvillous and crypt receptor neurons-can be distinguished by their anatomical and molecular characteristics. Generally, an individual receptor neuron expresses only a single olfactory receptor gene, and olfactory receptor neurons that express the same receptor converge into a common target structure, a glomerulus, which generates a receptotopic map in the first olfactory brain region, the olfactory bulb. This review article provides a general overview of the peripheral detection of odorants on the one hand, while on the other it focuses on recent advances in the field, including new findings on the peripheral modulation of olfactory signals.

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“…This review describes our current understanding of OB circuit function and discusses the development of wiring specificity in the OB. Due to space limitation, this review will only focus on OB circuitry and does not mention mechanisms of olfactory map formation by OSNs, which has been discussed previously [4][5][6]. For introduction to olfactory cortical circuitry, please see the following recent excellent reviews [7,8].…”

Section: Introductionmentioning

confidence: 97%

Construction of functional neuronal circuitry in the olfactory bulb

Imai

2014

Seminars in Cell & Developmental Biology

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Recent studies using molecular genetics, electrophysiology, in vivo imaging, and behavioral analyses have elucidated detailed connectivity and function of the mammalian olfactory circuits. The olfactory bulb is the first relay station of olfactory perception in the brain, but it is more than a simple relay: olfactory information is dynamically tuned by local olfactory bulb circuits and converted to spatiotemporal neural code for higher-order information processing. Because the olfactory bulb processes ∼1000 discrete input channels from different odorant receptors, it serves as a good model to study neuronal wiring specificity, from both functional and developmental aspects. This review summarizes our current understanding of the olfactory bulb circuitry from functional standpoint and discusses important future studies with particular focus on its development and plasticity.

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Topographic Mapping--The Olfactory System

Cited by 85 publications

References 136 publications

Axon position within the corpus callosum determines contralateral cortical projection

Axon position within the corpus callosum determines contralateral cortical projection

The peripheral olfactory system of vertebrates: molecular, structural and functional basics of the sense of smell

Construction of functional neuronal circuitry in the olfactory bulb

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