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Cecilia B Moens - One of the best experts on this subject based on the ideXlab platform.
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retinoic acid organizes the zebrafish vagus motor Topographic Map via spatiotemporal coordination of hgf met signaling
Developmental Cell, 2020Co-Authors: Adam J Isabella, Gabrielle R Barsh, Jason A Stonick, Cecilia B Moens, Julien DubrulleAbstract:Summary Information flow through neural circuits often requires their organization into Topographic Maps in which the positions of cell bodies and synaptic targets correspond. To understand how Topographic Map development is controlled, we examine the mechanism underlying targeting of vagus motor axons to the pharyngeal arches in zebrafish. We reveal that retinoic acid organizes topography by specifying anterior-posterior identity in vagus motor neurons. We then show that chemoattractant signaling between Hgf and Met is required for vagus innervation of the pharyngeal arches. Finally, we find that retinoic acid controls the spatiotemporal dynamics of Hgf/Met signaling to coordinate axon targeting with the developmental progression of the pharyngeal arches and show that experimentally altering the timing of Hgf/Met signaling is sufficient to redirect axon targeting and disrupt the Topographic Map. These findings establish a mechanism of Topographic Map development in which the regulation of chemoattractant signaling in space and time guides axon targeting.
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retinoic acid organizes the vagus motor Topographic Map via spatiotemporal regulation of hgf met signaling
bioRxiv, 2019Co-Authors: Adam J Isabella, Gabrielle R Barsh, Jason A Stonick, Cecilia B MoensAbstract:SUMMARY The Topographic Map, in which the positions of neuron cell bodies correspond with the positions of their synaptic targets, is a major organizational motif in the nervous system. To understand how Topographic axon targeting is controlled during development, we examine the mechanism underlying Topographic innervation of the pharyngeal arches by the vagus motor nerve in zebrafish. We reveal that Retinoic Acid organizes the Topographic Map by specifying anterior-posterior identity in post-mitotic vagus motor neurons. We then show that chemoattractant signaling between hepatocyte growth factor (Hgf) and the Met receptor is required for pharyngeal arch innervation by the vagus motor nerve. Finally, we find that Retinoic Acid controls the spatiotemporal dynamics of Hgf/Met signaling to coordinate axon targeting with the developmental progression of the pharyngeal arches and show that experimentally altering the timing of Hgf/Met signaling is sufficient to redirect axon targeting and disrupt the Topographic Map. These findings establish a new mechanism of Topographic Map development in which regulation of chemoattractant signaling in both space and time guides axon targeting.
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vagus motor neuron Topographic Map determined by parallel mechanisms of hox5 expression and time of axon initiation
Current Biology, 2017Co-Authors: Adam J Isabella, Gabrielle R Barsh, Cecilia B MoensAbstract:Summary Many networks throughout the nervous system are organized into Topographic Maps, where the positions of neuron cell bodies in the projecting field correspond with the positions of their axons in the target field. Previous studies of Topographic Map development show evidence for spatial patterning mechanisms, in which molecular determinants expressed across the projecting and target fields are matched directly in a point-to-point Mapping process. Here, we describe a novel temporal mechanism of Topographic Map formation that depends on spatially regulated differences in the timing of axon outgrowth and functions in parallel with spatial point-to-point Mapping mechanisms. We focus on the vagus motor neurons, which are Topographically arranged in both mammals and fish. We show that cell position along the anterior-posterior axis of hindbrain rhombomere 8 determines expression of hox5 genes, which are expressed in posterior, but not anterior, vagus motor neurons. Using live imaging and transplantation in zebrafish embryos, we additionally reveal that axon initiation is delayed in posterior vagus motor neurons independent of neuron birth time. We show that hox5 expression directs Topographic Mapping without affecting time of axon outgrowth and that time of axon outgrowth directs Topographic Mapping without affecting hox5 expression. The vagus motor neuron Topographic Map is therefore determined by two mechanisms that act in parallel: a hox5 -dependent spatial mechanism akin to classic mechanisms of Topographic Map formation and a novel axon outgrowth-dependent temporal mechanism in which time of axon formation is spatially regulated to direct axon targeting.
Gabrielle R Barsh - One of the best experts on this subject based on the ideXlab platform.
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retinoic acid organizes the zebrafish vagus motor Topographic Map via spatiotemporal coordination of hgf met signaling
Developmental Cell, 2020Co-Authors: Adam J Isabella, Gabrielle R Barsh, Jason A Stonick, Cecilia B Moens, Julien DubrulleAbstract:Summary Information flow through neural circuits often requires their organization into Topographic Maps in which the positions of cell bodies and synaptic targets correspond. To understand how Topographic Map development is controlled, we examine the mechanism underlying targeting of vagus motor axons to the pharyngeal arches in zebrafish. We reveal that retinoic acid organizes topography by specifying anterior-posterior identity in vagus motor neurons. We then show that chemoattractant signaling between Hgf and Met is required for vagus innervation of the pharyngeal arches. Finally, we find that retinoic acid controls the spatiotemporal dynamics of Hgf/Met signaling to coordinate axon targeting with the developmental progression of the pharyngeal arches and show that experimentally altering the timing of Hgf/Met signaling is sufficient to redirect axon targeting and disrupt the Topographic Map. These findings establish a mechanism of Topographic Map development in which the regulation of chemoattractant signaling in space and time guides axon targeting.
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retinoic acid organizes the vagus motor Topographic Map via spatiotemporal regulation of hgf met signaling
bioRxiv, 2019Co-Authors: Adam J Isabella, Gabrielle R Barsh, Jason A Stonick, Cecilia B MoensAbstract:SUMMARY The Topographic Map, in which the positions of neuron cell bodies correspond with the positions of their synaptic targets, is a major organizational motif in the nervous system. To understand how Topographic axon targeting is controlled during development, we examine the mechanism underlying Topographic innervation of the pharyngeal arches by the vagus motor nerve in zebrafish. We reveal that Retinoic Acid organizes the Topographic Map by specifying anterior-posterior identity in post-mitotic vagus motor neurons. We then show that chemoattractant signaling between hepatocyte growth factor (Hgf) and the Met receptor is required for pharyngeal arch innervation by the vagus motor nerve. Finally, we find that Retinoic Acid controls the spatiotemporal dynamics of Hgf/Met signaling to coordinate axon targeting with the developmental progression of the pharyngeal arches and show that experimentally altering the timing of Hgf/Met signaling is sufficient to redirect axon targeting and disrupt the Topographic Map. These findings establish a new mechanism of Topographic Map development in which regulation of chemoattractant signaling in both space and time guides axon targeting.
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vagus motor neuron Topographic Map determined by parallel mechanisms of hox5 expression and time of axon initiation
Current Biology, 2017Co-Authors: Adam J Isabella, Gabrielle R Barsh, Cecilia B MoensAbstract:Summary Many networks throughout the nervous system are organized into Topographic Maps, where the positions of neuron cell bodies in the projecting field correspond with the positions of their axons in the target field. Previous studies of Topographic Map development show evidence for spatial patterning mechanisms, in which molecular determinants expressed across the projecting and target fields are matched directly in a point-to-point Mapping process. Here, we describe a novel temporal mechanism of Topographic Map formation that depends on spatially regulated differences in the timing of axon outgrowth and functions in parallel with spatial point-to-point Mapping mechanisms. We focus on the vagus motor neurons, which are Topographically arranged in both mammals and fish. We show that cell position along the anterior-posterior axis of hindbrain rhombomere 8 determines expression of hox5 genes, which are expressed in posterior, but not anterior, vagus motor neurons. Using live imaging and transplantation in zebrafish embryos, we additionally reveal that axon initiation is delayed in posterior vagus motor neurons independent of neuron birth time. We show that hox5 expression directs Topographic Mapping without affecting time of axon outgrowth and that time of axon outgrowth directs Topographic Mapping without affecting hox5 expression. The vagus motor neuron Topographic Map is therefore determined by two mechanisms that act in parallel: a hox5 -dependent spatial mechanism akin to classic mechanisms of Topographic Map formation and a novel axon outgrowth-dependent temporal mechanism in which time of axon formation is spatially regulated to direct axon targeting.
Marc M Van Hulle - One of the best experts on this subject based on the ideXlab platform.
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self organizing Maps
Handbook of Natural Computing, 2012Co-Authors: Marc M Van HulleAbstract:A Topographic Map is a two-dimensional, nonlinear approximation of a potentially high-dimensional data manifold, which makes it an appealing instrument for visualizing and exploring high-dimensional data. The Self-Organizing Map (SOM) is the most widely used algorithm, and it has led to thousands of applications in very diverse areas. In this chapter, we will introduce the SOM algorithm, discuss its properties and applications, and also discuss some of its extensions and new types of Topographic Map formation, such as the ones that can be used for processing categorical data, time series and tree structured data.
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maximum likelihood Topographic Map formation
Neural Computation, 2005Co-Authors: Marc M Van HulleAbstract:We introduce a new unsupervised learning algorithm for kernel-based Topographic Map formation of heteroscedastic gaussian mixtures that allows for a unified account of distortion error (vector quantization), log-likelihood, and Kullback-Leibler divergence.
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kernel based Topographic Map formation achieved with an information theoretic approach
Neural Networks, 2002Co-Authors: Marc M Van HulleAbstract:A new information-theoretic learning algorithm is introduced for kernel-based Topographic Map formation. The kernels are allowed to overlap and move freely in the input space, and to have differing kernel ranges. We start with Linsker's infomax principle and observe that it cannot be readily extended to our case, exactly due to the presence of kernels. We then consider Bell and Sejnowski's generalization of Linsker's infomax principle, which suggests differential entropy maximization, and add a second component to be optimized, namely, mutual information minimization between the kernel outputs, in order to take into account the kernel overlap, and thus the Topographic Map's output redundancy. The result is joint entropy maximization of the kernel outputs, which we adopt as our learning criterion. We derive a learning algorithm and verify its performance both for a synthetic example, for which the optimal result can be derived analytically, and for a classic real-world example.
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kernel based Topographic Map formation by local density modeling
Neural Computation, 2002Co-Authors: Marc M Van HulleAbstract:We introduce a new learning algorithm for kernel-based Topographic Map formation. The algorithm generates a gaussian mixture density model by individually adapting the gaussian kernels' centers and radii to the assumed gaussian local input densities.
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kernel based equiprobabilistic Topographic Map formation
Neural Computation, 1998Co-Authors: Marc M Van HulleAbstract:We introduce a new unsupervised competitive learning rule, the kernel-based maximum entropy learning rule (kMER), which performs equiprobabilistic Topographic Map formation in regular, fixed-topology lattices, for use with nonparametric density estimation as well as nonparametric regression analysis. The receptive fields of the formal neurons are overlapping radially symmetric kernels, compatible with radial basis functions (RBFs); but unlike other learning schemes, the radii of these kernels do not have to be chosen in an ad hoc manner: the radii are adapted to the local input density, together with the weight vectors that define the kernel centers, so as to produce Maps of which the neurons have an equal probability to be active (equiprobabilistic Maps). Both an “online” and a “batch” version of the learning rule are introduced, which are applied to nonparametric density estimation and regression, respectively. The application envisaged is blind source separation (BSS) from nonlinear, noisy mixtures.
Tanzila Saba - One of the best experts on this subject based on the ideXlab platform.
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removal of pectoral muscle based on Topographic Map and shape shifting silhouette
BMC Cancer, 2018Co-Authors: Bushra Mughal, Nazeer Muhammad, Amjad Rehman, M Sharif, Tanzila SabaAbstract:Background In digital mammography, finding accurate breast profile segmentation of women’s mammogram is considered a challenging task. The existence of the pectoral muscle may mislead the diagnosis of cancer due to its high-level similarity to breast body. In addition, some other challenges due to manifestation of the breast body pectoral muscle in the mammogram data include inaccurate estimation of the density level and assessment of the cancer cell. The discrete differentiation operator has been proven to eliminate the pectoral muscle before the analysis processing.
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removal of pectoral muscle based on Topographic Map and shape shifting silhouette
BMC Cancer, 2018Co-Authors: Bushra Mughal, Nazeer Muhammad, Amjad Rehman, M Sharif, Tanzila SabaAbstract:In digital mammography, finding accurate breast profile segmentation of women’s mammogram is considered a challenging task. The existence of the pectoral muscle may mislead the diagnosis of cancer due to its high-level similarity to breast body. In addition, some other challenges due to manifestation of the breast body pectoral muscle in the mammogram data include inaccurate estimation of the density level and assessment of the cancer cell. The discrete differentiation operator has been proven to eliminate the pectoral muscle before the analysis processing. We propose a novel approach to remove the pectoral muscle in terms of the mediolateral-oblique observation of a mammogram using a discrete differentiation operator. This is used to detect the edges boundaries and to approximate the gradient value of the intensity function. Further refinement is achieved using a convex hull technique. This method is implemented on dataset provided by MIAS and 20 contrast enhanced digital mammographic images. To assess the performance of the proposed method, visual inspections by radiologist as well as calculation based on well-known metrics are observed. For calculation of performance metrics, the given pixels in pectoral muscle region of the input scans are calculated as ground truth. Our approach tolerates an extensive variety of the pectoral muscle geometries with minimum risk of bias in breast profile than existing techniques.
David A Feldheim - One of the best experts on this subject based on the ideXlab platform.
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high frequency hearing is required for generating a Topographic Map of auditory space in the mouse superior colliculus
bioRxiv, 2021Co-Authors: Shinya Ito, A M Litke, David A FeldheimAbstract:A Topographic Map of auditory space is a feature found in the superior colliculus (SC) of many species, including CBA/CaJ mice. In this genetic background, high-frequency monaural spectral cues and interaural level differences are used to generate spatial receptive fields (RFs) that form a Topographic Map along the azimuth. Unfortunately, C57BL/6 mice, a strain widely used for transgenic manipulation, display age-related hearing loss (AHL) due to an inbred mutation in the Cadherin 23 gene (Cdh23) that affects hair cell mechanotransduction. To overcome this problem, researchers have used young C57BL/6 mice in their studies, as they have been shown to have normal hearing thresholds. However, important details of the auditory response characteristics of the SC such as spectral responses and spatial localization, have not been characterized in young C57BL/6 mice. Here we show that 2-4-month C57BL/6 mice lack neurons with frontal auditory RFs and therefore lack a Topographic representation of auditory space in the SC. Analysis of the spectrotemporal receptive fields (STRFs) of the SC auditory neurons shows that C57BL/6 mouse SC neurons lack the ability to detect the high-frequency(>40kHz) spectral cues that are needed to compute frontal RFs. We also show that crossing C57BL/6 mice with CBA/CaJ mice or introducing one copy of the wild-type Cdh23 to C57BL/6 mice rescues the high-frequency hearing deficit and improves the Topographic Map of auditory space. Taken together, these results demonstrate the importance of high-frequency hearing in computing a Topographic Map of auditory space.
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spectral cues are necessary to encode azimuthal auditory space in the mouse superior colliculus
Nature Communications, 2020Co-Authors: Shinya Ito, David A Feldheim, A M LitkeAbstract:Sound localization plays a critical role in animal survival. Three cues can be used to compute sound direction: interaural timing differences (ITDs), interaural level differences (ILDs) and the direction-dependent spectral filtering by the head and pinnae (spectral cues). Little is known about how spectral cues contribute to the neural encoding of auditory space. Here we report on auditory space encoding in the mouse superior colliculus (SC). We show that the mouse SC contains neurons with spatially-restricted receptive fields (RFs) that form an azimuthal Topographic Map. We found that frontal RFs require spectral cues and lateral RFs require ILDs. The neurons with frontal RFs have frequency tunings that match the spectral structure of the specific head and pinna filter for sound coming from the front. These results demonstrate that patterned spectral cues in combination with ILDs give rise to the Topographic Map of azimuthal auditory space.
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spectral cues are necessary for encoding the azimuthal Map of auditory space in the mouse superior colliculus
bioRxiv, 2019Co-Authors: Shinya Ito, David A Feldheim, A M LitkeAbstract:Sound localization plays a critical role in animal survival. Three cues can be used to compute sound direction: interaural timing differences (ITDs), interaural level differences (ILDs) and the direction-dependent spectral filtering by the head and pinnae (spectral cues). Little is known about how spectral cues contribute to the neural encoding of auditory space. Here we report on auditory space encoding in the mouse superior colliculus (SC). We show that the mouse SC contains neurons with spatially-restricted receptive fields (RFs) that form an azimuthal Topographic Map. We found that frontal RFs require spectral cues and lateral RFs require ILDs. The neurons with frontal RFs have frequency tunings that match the spectral structure of the specific head and pinna filter for sound coming from the front. These results demonstrate that patterned spectral cues in combination with ILDs give rise to the Topographic Map of azimuthal auditory space.
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developmental mechanisms of Topographic Map formation and alignment
Annual Review of Neuroscience, 2013Co-Authors: Jianhua Cang, David A FeldheimAbstract:Brain connections are organized into Topographic Maps that are precisely aligned both within and across modalities. This alignment facilitates coherent integration of different categories of sensory inputs and allows for proper sensorimotor transformations. Topographic Maps are established and aligned by multistep processes during development, including interactions of molecular guidance cues expressed in gradients; spontaneous activity-dependent axonal and dendritic remodeling; and sensory-evoked plasticity driven by experience. By focusing on the superior colliculus, a major site of Topographic Map alignment for different sensory modalities, this review summarizes current understanding of Topographic Map development in the mammalian visual system and highlights recent advances in Map alignment studies. A major goal looking forward is to reveal the molecular and synaptic mechanisms underlying Map alignment and to understand the physiological and behavioral consequences when these mechanisms are disrupted at various scales.
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competition is a driving force in Topographic Mapping
Proceedings of the National Academy of Sciences of the United States of America, 2011Co-Authors: Jason W Triplett, Cory Pfeiffenberger, Jena Yamada, Ben K Stafford, Neal T Sweeney, A M Litke, Alexander Sher, Alexei A Koulakov, David A FeldheimAbstract:Topographic Maps are the primary means of relaying spatial information in the brain. Understanding the mechanisms by which they form has been a goal of experimental and theoretical neuroscientists for decades. The projection of the retina to the superior colliculus (SC)/tectum has been an important model used to show that graded molecular cues and patterned retinal activity are required for Topographic Map formation. Additionally, interaxon competition has been suggested to play a role in Topographic Map formation; however, this view has been recently challenged. Here we present experimental and computational evidence demonstrating that interaxon competition for target space is necessary to establish topography. To test this hypothesis experimentally, we determined the nature of the retinocollicular projection in Math5 (Atoh7) mutant mice, which have severely reduced numbers of retinal ganglion cell inputs into the SC. We find that in these mice, retinal axons project to the anteromedialj portion of the SC where repulsion from ephrin-A ligands is minimized and where their attraction to the midline is maximized. This observation is consistent with the chemoaffinity model that relies on axon–axon competition as a Mapping mechanism. We conclude that chemical labels plus neural activity cannot alone specify the retinocollicular projection; instead axon–axon competition is necessary to create a Map. Finally, we present a mathematical model for Topographic Mapping that incorporates molecular labels, neural activity, and axon competition.
