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Synaptic Plasticity in Neuromorphic Systems

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889198771 Year: Pages: 176 DOI: 10.3389/978-2-88919-877-1 Language: English
Publisher: Frontiers Media SA
Subject: Neurology --- Science (General)
Added to DOAB on : 2016-01-19 14:05:46
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Emergent neural computation from the interaction of different forms of plasticity

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889197880 Year: Pages: 193 DOI: 10.3389/978-2-88919-788-0 Language: English
Publisher: Frontiers Media SA
Subject: Neurology --- Science (General)
Added to DOAB on : 2016-04-07 11:22:02
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From the propagation of neural activity through synapses, to the integration of signals in the dendritic arbor, and the processes determining action potential generation, virtually all aspects of neural processing are plastic. This plasticity underlies the remarkable versatility and robustness of cortical circuits: it enables the brain to learn regularities in its sensory inputs, to remember the past, and to recover function after injury. While much of the research into learning and memory has focused on forms of Hebbian plasticity at excitatory synapses (LTD/LTP, STDP), several other plasticity mechanisms have been characterized experimentally, including the plasticity of inhibitory circuits (Kullmann, 2012), synaptic scaling (Turrigiano, 2011) and intrinsic plasticity (Zhang and Linden, 2003). However, our current understanding of the computational roles of these plasticity mechanisms remains rudimentary at best. While traditionally they are assumed to serve a homeostatic purpose, counterbalancing the destabilizing effects of Hebbian learning, recent work suggests that they can have a profound impact on circuit function (Savin 2010, Vogels 2011, Keck 2012). Hence, theoretical investigation into the functional implications of these mechanisms may shed new light on the computational principles at work in neural circuits. This Research Topic of Frontiers in Computational Neuroscience aims to bring together recent advances in theoretical modeling of different plasticity mechanisms and of their contributions to circuit function. Topics of interest include the computational roles of plasticity of inhibitory circuitry, metaplasticity, synaptic scaling, intrinsic plasticity, plasticity within the dendritic arbor and in particular studies on the interplay between homeostatic and Hebbian plasticity, and their joint contribution to network function.

(Pushing) the Limits of Neuroplasticity Induced by Adult Language Acquisition

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889456406 Year: Pages: 157 DOI: 10.3389/978-2-88945-640-6 Language: English
Publisher: Frontiers Media SA
Subject: Science (General) --- Psychology --- Media and communication
Added to DOAB on : 2019-01-23 14:53:43
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Most adults attempt to learn a second or even third language at some point in their life. Since language exposure is one of the most intense cognitive training regimes one can encounter, it is not surprising that previous research has shown that multilingualism can induce profound change in the brain or ‘neuroplasticity’.What remains unclear is the scope of such adult language learning induced neuroplasticity. In other words, much is yet to be investigated about the factors that limit or promote adult language learning induced neuroplasticity.On the one hand, the present research topic discusses research that sheds light on neural mechanisms that limit adult language learning induced neuroplasticity such as: neural mechanisms of first language interference in the acquisition of a second language and reduced opportunity for language induced neuroplasticity due to aging. On the other hand, the Research Topic discusses factors that could enhance non-native language learning (and underlying neuroplastic mechanisms), such as the duration of the training regime, language aptitude, and meta-linguistic awareness.Therefore, the goal of the present Research Topic is to examine both the limits of neuroplasticity in adult language learning and the ways to push beyond those limits. Understanding of such limits and frontiers to push beyond the limits is not only theoretically fundamental but could also have practical implications for enhancing language training programmes.

Keywords

bilingualism --- plasticity --- Language --- Brain

Plasticity in the sensory systems of invertebrates

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889192816 Year: Pages: 78 DOI: 10.3389/978-2-88919-281-6 Language: English
Publisher: Frontiers Media SA
Subject: Science (General) --- Physiology
Added to DOAB on : 2015-12-10 11:59:06
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The visual, olfactory, auditory and gustatory systems of invertebrates are often used as models to study the transduction, transmission and processing of information in nervous systems, and in recent years have also provided powerful models of neural plasticity. This Research Topic presents current views on plasticity and its mechanisms in invertebrate sensory systems at the cellular, molecular and network levels, approached from both physiological and morphological perspectives. Plasticity in sensory systems can be activity- dependent, or occur in response to changes in the environment, or to endogenous stimuli. Plastic changes have been reported in receptor neurons, but are also known in other cell types, including glial cells and sensory interneurons. Also reported are dynamic changes among neuronal circuits involved in transmitting sensory stimuli and in reorganizing of synaptic contacts within a particular sensory system. Plastic changes within sensory systems in invertebrates can also be reported during development, after injury and after short or long- term stimulation. All these changes occur against an historical backdrop which viewed invertebrate nervous systems as largely hard-wired, and lacking in susceptibility especially to activity-dependent changes. This Research Topic examines how far we have moved from this simple view of simple brains, to the realization that invertebrate sensory systems exhibit all the diversity of plastic changes seen in vertebrate brains, but among neurons in which such changes can be evaluated at single-cell level.

The Transcriptional Regulation of Memory

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889198658 Year: Pages: 116 DOI: 10.3389/978-2-88919-865-8 Language: English
Publisher: Frontiers Media SA
Subject: Neurology --- Science (General)
Added to DOAB on : 2016-01-19 14:05:46
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The formation of various forms of memory involves a series of distinct cellular and molecular mechanisms, many of which are not fully understood. There are highly conserved pathways that are involved in learning, memory, and synaptic plasticity, which is the primary substrate for memory storage. The formation of short-term (across minutes) memory is mediated by local changes in synapses, while long-term (across hours to days) memory storage is associated with activation of transcription and synthesis of proteins that modify synaptic function. Transcription factors, which can either repress or activate transcription, play a vital role in driving protein synthesis underlying synaptic plasticity and memory, whereby protein synthesis provides the necessary building blocks to accommodate structural changes at the synapse that foster memory formation. Recent data implicate several families of transcription factors that appear critically important in the regulation of memory.In this Topic we will focus on the families of transcription factors thus far found to be critically involved in synaptic plasticity and memory formation. These include cAMP response element binding protein (CREB), Rel/nuclear factor B (Rel/NFB), CCAAT enhancer binding protein (C/EBP), and early growth response factor (Egr). In recent years, numerous studies have implicated epigenetic mechanisms, changes in gene activity and expression that occur without alteration in gene sequence, in the memory consolidation process. DNA methylation and chromatin remodeling are critically involved in learning and memory, supporting a role of epigenetic mechanisms. Here we provide more evidence of the importance of DNA methylation, histone posttranslational modifications and the role of histone acetylation and HDAC inhibitors in above mentioned processes.

Sleep and Chronobiology in Plasticity and Memory

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889197460 Year: Pages: 120 DOI: 10.3389/978-2-88919-746-0 Language: English
Publisher: Frontiers Media SA
Subject: Neurology --- Science (General)
Added to DOAB on : 2016-04-07 11:22:02
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Chronobiological mechanisms regulating time-of-day mediated behaviors, such as sleep and circadian rhythms, are thought to interact with and/or share cellular and molecular signaling cascades that shape synaptic plasticity and neural excitability. These same factors are also known to underlie events that govern higher-order cognitive processing, including learning and memory formation, and often through phylogenetically conserved pathways. This suggests that factors which contribute to adaptive responses to changing environmental stimuli are likely derived from basic evolutionarily ancient processes, and underscores the importance of using both invertebrate and vertebrate models to study the interaction of chronobiology and cognitive processing. This issue highlights current views along with original research on sleep and circadian features of plasticity and memory in multiple species, models, and systems.

Keywords

Sleep --- circadian rhythms --- Memory --- plasticity --- Learning --- synapse

Neuroplasticity and Extracellular Proteolysis

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889198511 Year: Pages: 151 DOI: 10.3389/978-2-88919-851-1 Language: English
Publisher: Frontiers Media SA
Subject: Neurology --- Science (General)
Added to DOAB on : 2016-01-19 14:05:46
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Neuroplasticity refers to the ability of the Central Nervous System (CNS) to alter its structure and function in response to a variety of physiological and pathological processes such as development, cognition, injury or neurological diseases. Since more than four decades, studies on synaptic plasticity in the context of memory and learning attracted a remarkable interest. Soon after first seminal works on synaptic plasticity were published, research in this field was extended by studies on non-synaptic as wells as structural plasticity towards a goal to understand cellular and molecular determinants of cognition. Over the past two decades, yet two additional crucial players in neuroplastic phenomena started to be intensely investigated – glial cells and the extracellular matrix (ECM). Growing awareness that glial cells, especially astrocytes, are important regulators of synaptic functions gave rise to a novel concept of a tri-partite synapse. Also, over the last two decades, a growing body of evidence has accumulated that the extracellular matrix (ECM) in the brain is strongly involved in regulation of neurons, in particular, in synaptic plasticity. Thus, a concept of tetra-partite synapse was put forward by some neuroscientists. The cross-talk between neuron-glia-ECM system involves enzymatic degradation of proteins or peptides and amino acids occurring in each of these brain constituents by means of a variety of proteases. Importantly, it has been realized that proteases such as serine proteases and matrix metalloproteinases, not only accompany “robust” phenomena such as cell division, or development or neurodegnerative conditions but may play a very subtle signaling functions, particularly important in memory acquisition. Indeed, the repertoire of substrates for these enzymes covers a wide variety of proteins known to play important role in the neuroplastic phenomena (e.g. BDNF, TNF-a, ephrin systems, various cell adhesion molecules, etc.). In result, the role of metalloproteinases and such serine proteases as tissue plasminogen activator (tPA), neuropsin or neurotrypsin in synaptic plasticity as well as in learning and memory has been particularly well demonstrated. It needs to be emphasized, however, that in spite of a remarkable progress in this field, several basic questions regarding molecular and cellular mechanisms remain unanswered. Potential involvement of so many important players (various proteases and their substrates in neurons, glia and in ECM) points to an enormous potential for plasticity phenomena but makes also studies into underlying mechanisms particularly difficult. In the proposed Research Topic we provide both review of the current state of the art and present some original reports on specific aspects of the role of proteolysis in neuroplasticity phenomena. The present ebook starts with extensive reviews describing involvement of proteolysis not only in synaptic plasticity but also in regulating endogenous excitability and structural changes at the network, cellular and subcellular levels. Cross-talk between neuroplasticity and proteolysis is also emphasized in the context of development and in relation to various pathologies. Whereas in the first part of the present ebook, the major focus is on metalloproteinases, the successive articles address the role of neuropsin and thrombin. The Research Topic is concluded with a series of articles describing the components of extracellular matrix and adhesion proteins and their elaboration by mechanisms dependent directly or indirectly on proteolysis. We do hope that the present ebook will further stimulate the interest in the fascinating investigations into neuroplasticity-proteolysis cross-talk.

What can neuroscience learn from contemplative practices?

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889199716 Year: Pages: 166 DOI: 10.3389/978-2-88919-971-6 Language: English
Publisher: Frontiers Media SA
Subject: Science (General) --- Psychology
Added to DOAB on : 2016-01-19 14:05:46
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A recent wave of brain research has advanced our understanding of the neural mechanisms of conscious states, contents and functions. A host of questions remain to be explored, as shown by lively debates between models of higher vs. lower-order aspects of consciousness, as well as global vs. local models. (Baars 2007; Block, 2009; Dennett and Cohen, 2011; Lau and Rosenthal, 2011). Over some twenty-five centuries the contemplative traditions have also developed explicit descriptions and taxonomies of the mind, to interpret experiences that are often reported in contemplative practices (Radhakrishnan & Moore, 1967; Rinbochay & Naper, 1981). These traditional descriptions sometimes converge on current scientific debates, such as the question of conceptual vs. non-conceptual consciousness; reflexivity or “self-knowing” associated with consciousness; the sense of self and consciousness; and aspects of consciousness that are said to continue during sleep. These real or claimed aspects of consciousness have not been fully integrated into scientific models so far. This Research Topic in Consciousness Research aims to provide a forum for theoretical proposals, new empirical findings, integrative literature reviews, and methodological improvements inspired by meditation-based models. We include a broad array of topics, including but not limited to: replicable findings from a variety of systematic mental practices; changes in brain functioning and organization that can be attributed to such practices; their effects on adaptation and neural plasticity; measurable effects on perception, cognition, affect and self-referential processes. We include contributions that address the question of causal attribution. Many published studies are correlational in nature, because of the inherent difficulty of conducting longitudinal experiments based on a major lifestyle decision, such as the decision to commit to a mental practice over a period of years. We also feature clinical and case studies, integrative syntheses and significant opinion articles.

Plasticity of GABAergic synapses

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889197323 Year: Pages: 175 DOI: 10.3389/978-2-88919-732-3 Language: English
Publisher: Frontiers Media SA
Subject: Neurology --- Science (General)
Added to DOAB on : 2016-04-07 11:22:02
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Learning and memory are believed to depend on plastic changes of neuronal circuits due to activity-dependent potentiation or depression of specific synapses. During the last two decades, plasticity of brain circuits was hypothesized to mainly rely on the flexibility of glutamatergic excitatory synapses, whereas inhibitory synapses were assumed relatively invariant, to ensure stable and reliable control of the neuronal network. As a consequence, while considerable efforts were made to clarify the main mechanisms underlying plasticity at excitatory synapses, the study of the cellular/molecular mechanisms of inhibitory plasticity has received much less attention. Nevertheless, an increasing body of evidence has revealed that inhibitory synapses undergo several types of plasticity at both pre- and postsynaptic levels. Given the crucial role of inhibitory interneurons in shaping network activities, such as generation of oscillations, selection of cell assemblies and signal integration, modifications of the inhibitory synaptic strength represents an extraordinary source of versatility for the fine control of brain states. This versatility also results from the rich diversity of GABAergic neurons in several brain areas, the specific role played by each inhibitory neuron subtype within a given circuit, and the heterogeneity of the properties and modulation of GABAergic synapses formed by specific interneuron classes. The molecular mechanisms underlying the potentiation or depression of inhibitory synapses are now beginning to be unraveled. At the presynaptic level, retrograde synaptic signaling was demonstrated to modulate GABA release, whereas postsynaptic forms of plasticity involve changes in the number/gating properties of GABAA receptors and/or shifts of chloride gradients. In addition, recent research indicates that GABAergic tonic inhibition can also be plastic, adding a further level of complexity to the control of the excitatory/inhibitory balance in the brain. The present Topic will focus on plasticity of GABAergic synapses, with special emphasis on the molecular mechanisms of plasticity induction and/or expression.

Regulatory RNAs in the Nervous System

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889194834 Year: Pages: 344 DOI: 10.3389/978-2-88919-483-4 Language: English
Publisher: Frontiers Media SA
Subject: Science (General) --- Neurology
Added to DOAB on : 2015-11-16 15:44:59
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Until about a decade ago, the non-coding part of the genome was considered without function. RNA sequencing studies have shown, however, that a considerable part of the non-coding genome is transcribed and that these non-coding RNAs (nc-RNAs) can regulate gene expression. Almost on weekly basis, new findings reveal the regulatory role of nc-RNAs exert in many biological processes. Overall, these studies are making increasingly clear that, both in model organisms and in humans, complexity is not a function of the number of protein-coding genes, but results from the possibility of using combinations of genetic programs and controlling their spatial and temporal regulation during development, senescence and in disease by regulatory RNAs. This has generated a novel picture of gene regulatory networks where regulatory nc-RNAs represent novel layers of regulation. Particularly well-characterized is the role of microRNAs (miRNAs), small nc-RNAs, that bind to mRNAs and regulate gene expression after transcritpion. This message is particularly clear in the nervous system, where miRNAs have been involved in regulating cellular pathways controlling fundamental functions during development, synaptic plasticity and in neurodegenerative disease. It has also been shown that neuronal miRNAs are tightly regulated by electrical activity at the level of transcription, biogenesis, stability and specifically targeted to dendrites and synapsis. Deregulation of expression of miRNAs is proposed not only as potential disease biomarker, but it has been implicated directly in the pathogenesis of complex neurodegenerative disease. This so-called RNA revolution also lead to the exploitation of RNA interference and the development of related tools as potential treatment of a vast array of CNS disease that could benefit from regulation of disease-associated genes. In spite of these advancements, the relatively young age of this field together with the inherent high molecular complexity of RNA regulation of biological processes have somewhat hindered its communication to the whole of the neuroscience community. This Research Topic aims at improving this aspect by putting around the same virtual table scientists covering aspects ranging from basic molecular mechanisms of regulatory RNAs in the nervous system to the analysis of the role of specific regulatory RNAs in neurobiological processes of development, plasticity and aging. Furthermore, we will welcome papers analyzing the role of regulatory RNAs in disease models from neuromuscular to higher cognitive functions, and we will also encourage submission of more technically oriented papers dealing with new methodologies to study regulatory RNA biology and its translational potential.

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