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Structure, function, and plasticity of hippocampal dentate gyrus microcircuits

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889193875 Year: Pages: 133 DOI: 10.3389/978-2-88919-387-5 Language: English
Publisher: Frontiers Media SA
Subject: Neurology --- Science (General)
Added to DOAB on : 2015-12-03 13:02:24
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Abstract

The hippocampus mediates several higher brain functions, such as learning, memory, and spatial coding. The input region of the hippocampus, the dentate gyrus, plays a critical role in these processes. Several lines of evidence suggest that the dentate gyrus acts as a preprocessor of incoming information, preparing it for subsequent processing in CA3. For example, the dentate gyrus converts input from the entorhinal cortex, where cells have multiple spatial fields, into the spatially more specific place cell activity characteristic of the CA3 region. Furthermore, the dentate gyrus is involved in pattern separation, transforming relatively similar input patterns into substantially different output patterns. Finally, the dentate gyrus produces a very sparse coding scheme in which only a very small fraction of neurons are active at any one time. How are these unique functions implemented at the level of cells and synapses? Dentate gyrus granule cells receive excitatory neuron input from the entorhinal cortex and send excitatory output to the hippocampal CA3 region via the mossy fibers. Furthermore, several types of GABAergic interneurons are present in this region, providing inhibitory control over granule cell activity via feedback and feedforward inhibition. Additionally, hilar mossy cells mediate an excitatory loop, receiving powerful input from a small number of granule cells and providing highly distributed excitatory output to a large number of granule cells. Finally, the dentate gyrus is one of the few brain regions exhibiting adult neurogenesis. Thus, new neurons are generated and functionally integrated throughout life. How these specific cellular and synaptic properties contribute to higher brain functions remains unclear. One way to understand these properties of the dentate gyrus is to try to integrate experimental data into models, following the famous Hopfield quote: "Build it, and you understand it." However, when trying this, one faces two major challenges. First, hard quantitative data about cellular properties, structural connectivity, and functional properties of synapses are lacking. Second, the number of individual neurons and synapses to be represented in the model is huge. For example, the dentate gyrus contains ~1 million granule cells in rodents, and ~10 million in humans. Thus, full scale models will be complex and computationally demanding. In this Frontiers Research Topic, we collect important information about cells, synapses, and microcircuit elements of the dentate gyrus. We have put together a combination of original research articles, review articles, and a methods article. We hope that the collected information will be useful for both experimentalists and modelers. We also hope that the papers will be interesting beyond the small world of "dentology", i.e., for scientists working on other brain areas. Ideally, the dentate gyrus may serve as a blueprint, helping neuroscientists to define strategies to analyze network organization of other brain regions.

Cell and molecular signaling, and transport pathways involved in growth factor control of synaptic development and function

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889196432 Year: Pages: 112 DOI: 10.3389/978-2-88919-643-2 Language: English
Publisher: Frontiers Media SA
Subject: Neurology --- Science (General)
Added to DOAB on : 2016-08-16 10:34:25
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Brain derived neurotophic factor (BDNF) and its receptor tropomyosin receptor kinase B (TrkB) signaling has been extensively studied for its roles in the central nervous system (CNS) ranging from cell survival, axonal and dendritic growth and synapse formation. Intracellular signaling pathways triggered by BDNF activate gene transcription, translation, post-translational functions, trafficking of key synaptic proteins, and synaptic release mechanism. BDNF-TrkB signaling mediates long-lasting activity-modulated synaptic changes on excitatory and inhibitory neurons and plays significant roles in circuit development and modulation. Furthermore, this pathway is critical for learning, memory, sensory processing and other cognitive functions, and is implicated in neurological and psychiatric diseases. In addition to BDNF, more recent studies have identified new “growth” factors that play important roles in the development, maturation and maintenance and modulation of synaptic function. However, details of the cytoplamic signaling systems downstream of these synaptogenic factors are often less understood than conventional neurotophin signaling. This e-Book has collected original studies and review articles that present cellular and molecular mechanisms concerning activity-dependent synapse formation and their implications for behavior and brain disorders. It is our hope that readers will perceive this volume as a showcase for diversity and complexity of synaptogenic growth factors, and will stimulate further studies in this field.

In Search of In Vivo MSC

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889452354 Year: Pages: 102 DOI: 10.3389/978-2-88945-235-4 Language: English
Publisher: Frontiers Media SA
Subject: Science (General) --- Biology
Added to DOAB on : 2017-10-13 14:57:01
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