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Neuronal Polarity: Establishment and Maintenance

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889455171 Year: Pages: 172 DOI: 10.3389/978-2-88945-517-1 Language: English
Publisher: Frontiers Media SA
Subject: Science (General) --- Neurology
Added to DOAB on : 2019-01-23 14:53:42
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The term polarity in a biological context is used to describe an asymmetry in morphology and distribution of molecules. In neurons, their complex shape with typically one axon and several dendrites reflects this asymmetry. Although neurons assume many different shapes and sizes they always maintain these two domains, which are essential for neuronal function. In the most simple view, neurons use their axon to transmit signals over long distances due to its capacity to extend to enormous lengths. Dendrites, on the other hand, are shorter and receive and integrate signals from different locations. The selection of the site where the axon and dendrites initially emerge during embryonic development is a tightly regulated event, eventually important for the correct formation of neuronal circuits, and disturbances of these processes can have pathological consequences due to circuit malformation. An important question is which mechanisms neurons utilize to specify the sites where axonal and dendrite outgrowth occurs and how their identities are maintained during and after development. The formation of these functionally diverse domains is the result of polarized differences of membrane and protein delivery, mitochondria transport, actin dynamics and microtubule stability. However how and in which temporal order all those events which coordinate the selection and maintenance of axons and dendrites is still under investigation. This selection of articles shall highlight new findings, which help to unravel all molecular and cellular events important for neuronal polarity establishment and maintenance.

Mechanisms of Neural Circuit Formation

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889194032 Year: Pages: 179 DOI: 10.3389/978-2-88919-403-2 Language: English
Publisher: Frontiers Media SA
Subject: Neurology --- Science (General)
Added to DOAB on : 2015-12-10 11:59:06
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The formation of the proper pattern of neuronal circuits during development is critical for the normal function of the vertebrate brain and for the survival of the organism. Circuit tracing studies spanning the past 100 years have revealed the beauty and exquisite intricacy of this pattern, which represents the most complex biological system known. In humans, aberrant circuit formation is a likely underlying cause of a wide variety of birth defects and neurological disorders, including autism, intellectual disability, and schizophrenia. Furthermore, future therapeutic approaches to restoring the function of damaged neural circuits will require a better understanding of the developmental constraints under which those circuits were originally assembled. For these reasons, elucidating the molecular mechanisms of neural circuit formation is a major goal of neurobiology today.

Wiring Principles of Cerebral Cortex

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889196920 Year: Pages: 171 DOI: 10.3389/978-2-88919-692-0 Language: English
Publisher: Frontiers Media SA
Subject: Science (General) --- Neurology
Added to DOAB on : 2016-08-16 10:34:25
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Cerebral cortex is probably the most complex biological network. Here many millions of individual neurons, the functional units of cortex, are interconnected through a massive yet highly organized pattern of axonal and dendritic wiring. This wiring enables both near and distant cells to coordinate their responses and generate a rich variety of cognitions and behaviours. When the wiring is damaged through disease or trauma it may reorganize but this may lead to characteristic pathological behaviours. While there have been significant advances in mapping cortical connectivity, the organizing principles and function of this connectivity are not well understood. On the one hand, there appears to be general design constraints governing cortical wiring, as first recognised by Rámon y Cajal's in his laws of conduction, material, and volume conservation. Yet on the other hand, particular patterns of cortical wiring exist to serve specific functions. There is a wide gap in understanding how the response and connectivity properties of a single neuron contribute to emergent network functions such as in detecting perceptually relevant features. Unravelling this intimate causal relationship represents one of the major challenges in neuroscience. This Research Topic will examine progress in understanding cortical wiring principles. This Research Topic aims to draw together recent advances in methods and understanding as well as recent challenges to existing ideas about how cerebral cortex is wired. This is particularly timely because new automated techniques may soon yield huge datasets in need of explanation. Recent studies have, for instance, empirically evaluated Rámon y Cajal's conservation laws for cerebral cortex, while others have shown some unexpected connectivity features that may refine the traditional view of how corticocortical connections are organised with regard to functional representations of auditory, somatosensory and visual cortices. Understanding these data will help improve the fidelity of neural models of cerebral cortical function and take into account the diversity of connections at both micro- and mesoscopic scales not seen at such a depth before.

The Major Discoveries of Cajal and His Disciples: Consolidated Milestones for the Neuroscience of the XXIst Century

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889450664 Year: Pages: 161 DOI: 10.3389/978-2-88945-066-4 Language: English
Publisher: Frontiers Media SA
Subject: Neurology --- Science (General)
Added to DOAB on : 2017-07-06 13:27:36
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When Santiago Ramón y Cajal started to unravel the fine structure of the nervous system in the last decades of the XIXth century maybe only his unbeatable soul of brave Spaniard imagined that most of the descriptions were scientific truths that lasted to date. Simple histological stainings, curiosity to ameliorate these, monocular microscopes, patience for drawing his observations and a rich imaginative open mind: this is the recipy for Cajal success. His descriptions of connectivity in the nervous system, compiled in Cajal's opus magna published in 1904 ("Textura del sistema nervioso del hombre y los vertebrados") and 1911 ("Histologie du systeme nerveux"), have been corroborated by modern techniques decade after decade. Even more, the main hypothesis that Cajal raised are universally recognised as biological laws, today: the neuron theory, the law on the dynamic polarization of the neuron and the chemotropic hypothesis. That is: the nervous system is not a sincitial network but is formed by individual cells; the transmission of the nerve impulses follow a main direction within a given neuron; the axons are guided by chemical substances in a chemotropic way, till form synapses with their targets. Attracted by Cajal's strong personality and scientific success, a number of medical students and doctors join him in the crusade to explore the nervous system. And the seed planted by the universal savant was really successful: Francisco Tello described interesting aspects of the regeneration of peripheral nerves which are very useful for neuroscientist currently working in this topic; Nicolás Achúcarro significantly contributed to study neuroglia and future microglia; Pío del Río-Hortega identified two out of the four main nervous cell types, the oligodendrocytes and microglia, and proposed an almost still valid classification for the CNS tumours; Fernando de Castro made was the first description of arterial chemoreceptors in the carotid body; Rafael Lorente de Nó was a dominant figure of Neuroscience for decades after the IInd World War, first describing the columnar organization of the cerebral cortex well before Mountcastle, Hubbel and Wiesel. Even less recognised co-workers and disciples of Cajal (his brother Pedro Ramón y Cajal, Domingo Sánchez, the neurologist Rodríguez-Lafora... protagonised discoveries that are consolidated scientific truths today). Altogether, it is difficult (if not impossible) to find a school in biology contributing in such a fundamental and variated way to the common acervo like the collectively known as Cajal School or Spanish Neurological School. Although the particular way to work of the Maestro, selecting a pleiade of brilliant collaborators with whom accomplish such a titanic feat, giving them freedom for their studies, has been recognised and confronted to antagonic systems followed by other relevant scientists and scientific schools, the general recognition of such a significant major milestones for Neuroscience and their vigency in the well-marched XXIst century is not: this is the purpose of this Ebook, to remind all these examples of how successful can be the scientific work when it is minutious, constant and performed by brilliant, imaginative and skilled scientists with a minimal conditions supporting their efforts.When Santiago Ramón y Cajal started to unravel the fine structure of the nervous system in the last decades of the XIXth century maybe only his unbeatable soul of brave Spaniard imagined that most of the descriptions were scientific truths that lasted to date. Simple histological stainings, curiosity to ameliorate these, monocular microscopes, patience for drawing his observations and a rich imaginative open mind: this is the recipy for Cajal success. His descriptions of connectivity in the nervous system, compiled in Cajal's opus magna published in 1904 ("Textura del sistema nervioso del hombre y los vertebrados") and 1911 ("Histologie du systeme nerveux"), have been corroborated by modern techniques decade after decade. Even more, the main hypothesis that Cajal raised are universally recognised as biological laws, today: the neuron theory, the law on the dynamic polarization of the neuron and the chemotropic hypothesis. That is: the nervous system is not a sincitial network but is formed by individual cells; the transmission of the nerve impulses follow a main direction within a given neuron; the axons are guided by chemical substances in a chemotropic way, till form synapses with their targets. Attracted by Cajal's strong personality and scientific success, a number of medical students and doctors join him in the crusade to explore the nervous system. And the seed planted by the universal savant was really successful: Francisco Tello described interesting aspects of the regeneration of peripheral nerves which are very useful for neuroscientist currently working in this topic; Nicolás Achúcarro significantly contributed to study neuroglia and future microglia; Pío del Río-Hortega identified two out of the four main nervous cell types, the oligodendrocytes and microglia, and proposed an almost still valid classification for the CNS tumours; Fernando de Castro made was the first description of arterial chemoreceptors in the carotid body; Rafael Lorente de Nó was a dominant figure of Neuroscience for decades after the IInd World War, first describing the columnar organization of the cerebral cortex well before Mountcastle, Hubbel and Wiesel. Even less recognised co-workers and disciples of Cajal (his brother Pedro Ramón y Cajal, Domingo Sánchez, the neurologist Rodríguez-Lafora... protagonised discoveries that are consolidated scientific truths today). Altogether, it is difficult (if not impossible) to find a school in biology contributing in such a fundamental and variated way to the common acervo like the collectively known as Cajal School or Spanish Neurological School. Although the particular way to work of the Maestro, selecting a pleiade of brilliant collaborators with whom accomplish such a titanic feat, giving them freedom for their studies, has been recognised and confronted to antagonic systems followed by other relevant scientists and scientific schools, the general recognition of such a significant major milestones for Neuroscience and their vigency in the well-marched XXIst century is not: this is the purpose of this Ebook, to remind all these examples of how successful can be the scientific work when it is minutious, constant and performed by brilliant, imaginative and skilled scientists with a minimal conditions supporting their efforts.

Mechanisms underlying firing in healthy and sick human motoneurons

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889195923 Year: Pages: 134 DOI: 10.3389/978-2-88919-592-3 Language: English
Publisher: Frontiers Media SA
Subject: Neurology --- Science (General)
Added to DOAB on : 2016-03-10 08:14:32
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Since the latter half of the twentieth century an enormous amount of knowledge about mammalian motoneuron pools has been collected. This progress was enabled mostly by the development of the precise techniques of intracellular recordings in acute animal experiments, many of which were conducted under deep anaesthesia. Recently obtained evidence indicates that anaesthetics used at that times changed certain properties of the cell membrane, which might affect firing of the neuron. Experiments on normal humans gets around this problem, which lets one compare MN firing characteristics in humans and reduced preparations. Firing pattern of human motoneurons is obtained indirectly by recording from a few muscle fibres of a motor unit. Since there is one-to-one relationship between motor unit and motoneuron firing, the statistical analysis of motor unit firing is equivalent to the analysis of motoneuron firing. This analysis, based on the essential knowledge about motoneuron physiology, gained from the direct measurements in animal experiments and verified by computer simulations, allows one to draw conclusions about the physiological properties of human motoneurons. For obvious reasons, the deductions made on properties of human motoneuron from these analyses should be accepted with caution. On the other hand, human experiments provide the unique opportunity to study intact motoneurons during normal physiological behavior. Thus, combining information obtained from animal and human experiments, and computer simulations, gives insight into underexplored problems of motor control. This E-book contains a collection of articles with range of exciting findings on the physiology and pathology of human motoneurons. The collection covers such important issues concerning firing of healthy motoneurons as recruitment and rate coding as well as motoneuron excitability, discusses intrinsic motoneuron properties disclosed by studying double discharges, and provides information on broad spectrum of motoneuron pathology. It is our hope that this collection promotes further expansion of knowledge on human motoneurons.

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