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Magnetic Resonance Imaging of Healthy and Diseased Brain Networks

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889194353 Year: Pages: 365 DOI: 10.3389/978-2-88919-435-3 Language: English
Publisher: Frontiers Media SA
Subject: Neurology --- Science (General)
Added to DOAB on : 2016-01-19 14:05:46
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An important aspect of neuroscience is to characterize the underlying connectivity patterns of the human brain (i.e., human connectomics). Over the past few years, researchers have demonstrated that by combining a variety of different neuroimaging technologies (e.g., structural MRI, diffusion MRI and functional MRI) with sophisticated analytic strategies such as graph theory, it is possible to noninvasively map the patterns of structural and functional connectivity of human whole-brain networks. With these novel approaches, many studies have shown that human brain networks have nonrandom properties such as modularity, small-worldness and highly connected hubs. Importantly, these quantifiable network properties change with age, learning and disease. Moreover, there is growing evidence for behavioral and genetic correlates. Network analysis of neuroimaging data is opening up a new avenue of research into the understanding of the organizational principles of the brain that will be of interest for all basic scientists and clinical researchers. Such approaches are powerful but there are a number of challenging issues when extracting reliable brain networks from various imaging modalities and analyzing the topological properties, e.g., definitions of network nodes and edges and reproducibility of network analysis. We assembled contributions related to the state-of-the-art methodologies of brain connectivity and the applications involving development, aging and neuropsychiatric disorders such as Alzheimer’s disease, schizophrenia, attention deficit hyperactivity disorder and mood and anxiety disorders. It is anticipated that the articles in this Research Topic will provide a greater range and depth of provision for the field of imaging connectomics.

General Anesthesia: From Theory to Experiments

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889197491 Year: Pages: 138 DOI: 10.3389/978-2-88919-749-1 Language: English
Publisher: Frontiers Media SA
Subject: Neurology --- Science (General)
Added to DOAB on : 2016-04-07 11:22:02
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General anesthesia is a standard medical procedure in today's hospital practice. Although in most cases the administration of anesthetics does not affect severely the patients health, side effects of anesthesia are well-known, such as nausea or cognitive impairment. Moreover 1-2 out of 1000 patients under surgery report a partial wake up from anesthesia during the operation. The reason for such a partial lack of control of depth of anesthesia is that medical procedures are highly optimized based on experience but the neural dynamics during general anesthesia is far from being understood. One reason for this lack of understanding is both the complex neural interactions of neurons on different spatial and temporal scales and the poorly understood action of anesthetics on neural populations. For instance, anesthetic agents act on synaptic receptors on a microscopic scale essentially evoking a macroscopic change of population activity, such as Local Field Potentials, EEG/MEG or resulting change of cerebral blood flow. This population effect then triggers the loss of consciousness in patients. This Research Topic aims to address recent theoretical and experimental advances in the field. The theoretical and experimental studies represent a good overview over the current state of research in the field and provides a deeper insight into the underlying neural mechanisms. Each article in the issue focusses on a specific current research topic in general anesthesia research and several articles introduce to the topic in a pedagogical way. The issue covers various types of anaesthesia and the most important topics in the field, such as (but not limited to) recent advances in theoretical models and states of consciousness reflected in experimental data, the connectivity changes observed during anesthesia or effects of specific drugs on brain activity. The introduction style of the papers facilitates the reader to understand the background of the research aspect and even allows readers not familiar with general anesthesia research to enter the research domain. Hence the Research Topic aims to provide on one hand an overview of the current state of the art and on the other hand a good starting point for new researchers in the field.

Mapping Psychopathology with fMRI and Effective Connectivity Analysis

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889452071 Year: Pages: 140 DOI: 10.3389/978-2-88945-207-1 Language: English
Publisher: Frontiers Media SA
Subject: Neurology --- Science (General)
Added to DOAB on : 2017-10-13 14:57:01
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There is a growing appreciation that many psychiatric (and neurological) conditions can be understood as functional disconnection syndromes – as reflected in aberrant functional integration and synaptic connectivity. This Research Topic considers recent advances in understanding psychopathology in terms of aberrant effective connectivity – as measured noninvasively using functional magnetic resonance imaging (fMRI).Recently, there has been increasing interest in inferring directed connectivity (effective connectivity) from fMRI data. Effective connectivity refers to the influence that one neural system exerts over another and quantifies the directed coupling among brain regions – and how they change with pathophysiology. Compared to functional connectivity, effective connectivity allows one to understand how brain regions interact with each other in terms of context sensitive changes and directed coupling – and therefore may provide mechanistic insights into the neural basis of psychopathology.Established models of effective connectivity include psychophysiological interaction (PPI), structural equation modeling (SEM) and dynamic causal modelling (DCM). DCM is unique because it explicitly models the interaction among brain regions in terms of latent neuronal activity. Moreover, recent advances in DCM such as stochastic and spectral DCM, make it possible to characterize the interaction between different brain regions both at rest and during a cognitive task.

Motor Cortex Microcircuits (Frontiers in Brain Microcircuits Series)

Authors: --- --- ---
Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889193899 Year: Pages: 133 DOI: 10.3389/978-2-88919-389-9 Language: English
Publisher: Frontiers Media SA
Subject: Science (General) --- Neurology
Added to DOAB on : 2015-12-03 13:02:24
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How does the motor cortex enable mammals to generate accurate, complex, and purposeful movements? A cubic millimeter of motor cortex contains roughly ~10^5 cells, an amazing ~4 Km of axons and ~0.4 Km of dendrites, somehow wired together with ~10^9 synapses. Corticospinal neurons (a.k.a. Betz cells, upper motor neurons) are a key cell type, monosynaptically conveying the output of the cortical circuit to the spinal cord circuits and lower motor neurons. But corticospinal neurons are greatly outnumbered by all the other kinds of neurons in motor cortex, which presumably also contribute crucially to the computational operations carried out for planning, executing, and guiding actions. Determining the wiring patterns, the dynamics of signaling, and how these relate to movement at the level of specific excitatory and inhibitory cell types is critically important for a mechanistic understanding of the input-output organization of motor cortex. While there is a predictive microcircuit hypothesis that relates motor learning to the operation of the cerebellar cortex, we lack such a microcircuit understanding in motor cortex and we consider microcircuits as a central research topic in the field. This Research Topic covers any issues relating to the microcircuit-level analysis of motor cortex. Contributions are welcomed from neuroscientists at all levels of investigation, from in vivo physiology and imaging in humans and monkeys, to rodent models, in vitro anatomy, electrophysiology, electroanatomy, cellular imaging, molecular biology, disease models, computational modeling, and more.

Recent Advances and Challenges on Big Data Analysis in Neuroimaging

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889451289 Year: Pages: 195 DOI: 10.3389/978-2-88945-128-9 Language: English
Publisher: Frontiers Media SA
Subject: Science (General) --- Neurology
Added to DOAB on : 2017-07-06 13:27:36
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Big data is revolutionizing our ability to measure and study the human brain. New technology increases the resolution of images that are being study as well as enables researchers to study the brain as it functions. These technological advances are combined with efforts to collect neuroimaging data on large numbers of subjects, in some cases longitudinally. This combination of advances in measurement and scope of studies requires novel development in the statistical analysis. Fast, scalable, robust and accurate models and approaches need to be developed to make headway on these problems. This volume represents a unique collection of researchers providing deep insights on the statistical analysis of big neuroimaging data.

Producing and Analyzing Macro-Connectomes: Current State and Challenges

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889199815 Year: Pages: 139 DOI: 10.3389/978-2-88919-981-5 Language: English
Publisher: Frontiers Media SA
Subject: Science (General) --- Neurology
Added to DOAB on : 2016-01-19 14:05:46
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Construction of comprehensive and detailed brain regions neuroanatomical connections matrices (macro-connectomes) is necessary to understand how the nervous system is organized and to elucidate how its different parts interact. Macro-connectomes also are the structural foundation of any finer granularity approaches at the neuron classes and types (meso-connectomes) or individual neuron (micro-connectomes) levels. The advent of novel neuroanatomical methods, as well as combinations of classic techniques, form the basis of several large scale projects with the ultimate goal of producing publicly available connectomes at different levels. A parallel approach, that of systematic and comprehensive collation of connectivity data from the published literature and from publicly accessible neuroinformatics platforms, has produced macro-connectomes of different parts of the central nervous system (CNS) in several mammalian species. The emergence of these public platforms that allow for the manipulation of rich connectivity data sets and enable the construction of CNS macro-connectomes in different species may have significant and long lasting implications. Moreover, when these efforts are leveraged by novel statistical methods, they may influence our way of thinking about the brain. Hence, the present brain region-centric paradigm may be challenged by a network-centric one. Ultimately, these projects will provide the information and knowledge for understanding how different neuronal parts communicate and function, developing novel approaches to diseases and disorders, and facilitating translational efforts in neurosciences. With this Research Topic we bring together the current state of macro-connectome related projects including the large scale production of thousands of publicly available neuronatomical experiments, databases with tens of thousands of connectivity records collated from the published literature, and the newest methods for displaying and analyzing this information. This topic also includes a wide range of challenges and how they are addressed - from platforms designed to integrate connectivity data across different sources, species and CNS levels of organization, to languages specifically designed to use these data in models at different scales of resolution, to efforts of 3D reconstruction and data integration, and to approaches for extraction and representation of this knowledge. Finally, we address the present state of different efforts of meso-connectomes construction, and of computational modeling in the context of the

Brain Connectivity in Autism

Authors: --- --- --- --- et al.
Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889192823 Year: Pages: 264 DOI: 10.3389/978-2-88919-282-3 Language: English
Publisher: Frontiers Media SA
Subject: Science (General) --- Neurology
Added to DOAB on : 2015-12-10 11:59:06
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The brain's ability to process information crucially relies on connectivity. Understanding how the brain processes complex information and how such abilities are disrupted in individuals with neuropsychological disorders will require an improved understanding of brain connectivity. Autism is an intriguingly complex neurodevelopmental disorder with multidimensional symptoms and cognitive characteristics. A biological origin for autism spectrum disorders (ASD) had been proposed even in the earliest published accounts (Kanner, 1943; Asperger, 1944). Despite decades of research, a focal neurobiological marker for autism has been elusive. Nevertheless, disruptions in interregional and functional and anatomical connectivity have been a hallmark of neural functioning in ASD. Theoretical accounts of connectivity perceive ASD as a cognitive and neurobiological disorder associated with altered functioning of integrative circuitry. Neuroimaging studies have reported disruptions in functional connectivity (synchronization of activated brain areas) during cognitive tasks and during task-free resting states. While these insights are valuable, they do not address the time-lagged causality and directionality of such correlations. Despite the general promise of the connectivity account of ASD, inconsistencies and methodological differences among studies call for more thorough investigations. A comprehensive neurological account of ASD should incorporate functional, effective, and anatomical connectivity measures and test the diagnostic utility of such measures. In addition, questions pertaining to how cognitive and behavioral intervention can target connection abnormalities in ASD should be addressed. This research topic of the Frontiers in Human Neuroscience addresses “Brain Connectivity in Autism” primarily from cognitive neuroscience and neuroimaging perspectives.

Spiking Neural Network Connectivity and its Potential for Temporal Sensory Processing and Variable Binding

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889192397 Year: Pages: 123 DOI: 10.3389/978-2-88919-239-7 Language: English
Publisher: Frontiers Media SA
Subject: Neurology --- Science (General)
Added to DOAB on : 2015-11-16 15:44:59
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The most biologically-inspired artificial neurons are those of the third generation, and are termed spiking neurons, as individual pulses or spikes are the means by which stimuli are communicated. In essence, a spike is a short-term change in electrical potential and is the basis of communication between biological neurons. Unlike previous generations of artificial neurons, spiking neurons operate in the temporal domain, and exploit time as a resource in their computation. In 1952, Alan Lloyd Hodgkin and Andrew Huxley produced the first model of a spiking neuron; their model describes the complex electro-chemical process that enables spikes to propagate through, and hence be communicated by, spiking neurons. Since this time, improvements in experimental procedures in neurobiology, particularly with in vivo experiments, have provided an increasingly more complex understanding of biological neurons. For example, it is now well understood that the propagation of spikes between neurons requires neurotransmitter, which is typically of limited supply. When the supply is exhausted neurons become unresponsive. The morphology of neurons, number of receptor sites, amongst many other factors, means that neurons consume the supply of neurotransmitter at different rates. This in turn produces variations over time in the responsiveness of neurons, yielding various computational capabilities. Such improvements in the understanding of the biological neuron have culminated in a wide range of different neuron models, ranging from the computationally efficient to the biologically realistic. These models enable the modelling of neural circuits found in the brain. In recent years, much of the focus in neuron modelling has moved to the study of the connectivity of spiking neural networks. Spiking neural networks provide a vehicle to understand from a computational perspective, aspects of the brain's neural circuitry. This understanding can then be used to tackle some of the historically intractable issues with artificial neurons, such as scalability and lack of variable binding. Current knowledge of feed-forward, lateral, and recurrent connectivity of spiking neurons, and the interplay between excitatory and inhibitory neurons is beginning to shed light on these issues, by improved understanding of the temporal processing capabilities and synchronous behaviour of biological neurons. This research topic aims to amalgamate current research aimed at tackling these phenomena.

Identifying the Epileptic Network

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889192960 Year: Pages: 126 DOI: 10.3389/978-2-88919-296-0 Language: English
Publisher: Frontiers Media SA
Subject: Neurology --- Medicine (General)
Added to DOAB on : 2015-12-10 11:59:07
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An important area of current research in epilepsy focuses on identifying the specific regions within the brain that are affected in individuals with recurring seizures. The epileptogenic process may result not only in pathology in focal cortical regions, but abnormalities in subcortical structures, such as thalamus and basal ganglia, and in intercortical and intracortical connecting white matter pathways. Novel methods of treating refractory epilepsy are urgently needed. The goal of identifying for each affected individual the specific brain regions that are involved offers the promise that novel methods of treatment will one day be developed that specifically target those abnormal regions. Researchers from disparate fields are required to develop and advance this area of research, and this current topic proposes to place a spotlight on the “state of the art” of methods to identify the abnormal networks. Recent work covering a wide variety of disciplines and technologies, including dense array electroencephalography (dEEG), novel methods of analyses of both the interictal dEEG and intracranial EEG (icEEG), magnetoencephalography (MEG), high-resolution magnetic resonance imaging (MRI), functional MRI (fMRI), simultaneous fMRI-EEG, fMRI connectivity measures, simultaneous dEEG-icEEG, and techniques to coregister patient-specific MRI (including white matter pathways) and dEEG, are all examples of areas of research that have contributed to a greater understanding of potential epileptogenic regions. We asked for individuals with expertise in an area of research that expands an understanding of identifying epileptic networks to contribute to this research topic.

The Claustrum: charting a way forward for the brain's most mysterious nucleus

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889195428 Year: Pages: 141 DOI: 10.3389/978-2-88919-542-8 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 claustrum is a long, band-like grey matter structure situated in the ventrolateral telencephalon of most, if not all, mammalian brains. Due to its shape and close proximity to white matter structures and insular cortex, the anatomy and behavioral relevance of the claustrum have proven difficult to study. As a result, disagreements in the literature exist over ontogeny, phylogeny, anatomical boundaries, and connectivity. Despite this, it is generally regarded that the claustrum contains excitatory projection neurons that reciprocally connect to most regions of the cerebral cortex, a feature that has fostered varying hypotheses as to its function. These hypotheses propose multisensory integration, coordination of cortical activity for the generation of conscious percepts, or saliency filtration. The articles of this e-book consider the historical and recent highlights in claustrum structure, hodology, and function and seek to provide a compelling way forward for this “hidden” nucleus.

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