The Claustrum

The present day is witnessing an explosion of our understanding of how the brain works at all levels, in which complexity is piled on complexity, and mechanisms of astonishing elegance are being continually discovered. This process is most developed in the major areas of the brain, such as the cortex, thalamus, and striatum. The Claustrum instead focuses on a small, remote, and, until recently, relatively unknown area of the brain. In recent years, researchers have come to believe that the claustrum is concerned with consciousness, a bold hypothesis supported by the claustrum’s two-way connections with nearly every other region of the brain and its seeming involvement with multisensory integrations—the hallmark of consciousness. The claustrum, previously in a humble position at the back of the stage, might in fact be the conductor of the brain’s orchestra. The Claustrum brings together leading experts on the claustrum from the varied disciplines of neuroscience, providing a state-of-the-art presentation of what is currently known about the claustrum, promising lines of current research (including epigenetics), and projections of new lines of investigation on the horizon. Develops a unifying hypothesis about the claustrum’s role in consciousness, as well as the integration of sensory information and other higher brain functions. Discusses the involvement of the claustrum with autism, schizophrenia, epilepsy, Alzheimer’s disease, and Parkinson’s disease Coverage of all aspects of the claustrum, from its evolution and development to promising new lines of research, including epigenetics, provides a platform and point of reference for future investigative efforts

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.

Volume 5 of Cerebral Cortex completes the sequence of three volumes on the individual functional areas of the cerebral cortex by covering the somatosensory and motor areas. However, the chapters on these areas lead naturally to a series of others on patterns of connectivity in the cortex, intracortical and subcortical, so that the volume as a whole achieves a much broader viewpoint. The individual chapters on the sensory-motor areas reflect the considerable diversity of interest within the field, for each of the authors has given his or her chapter a different emphasis, reflecting in part topical interest and in part the body of data resulting from work in a particular species. In considering the functional organization of the somatosensory cortex, Robert Dykes and Andre Ruest have chosen to concentrate on the nature of the mapping process and its significance. Harold Burton, in his chapter on the somatosensory fields buried in the sylvian fissure, shows how critical is an understanding of this mapping process in the functional subdivision of the cortex. A frequently overlooked subdivision of the cortex, the vestibular region, is given the emphasis it deserves in a chapter by John Fredrickson and Allan Rubin. The further functional subdivisions that occur within the first somatosensory area are given an anatom ical basis in the review by Edward Jones of connectivity in the primate sensory motor cortex.

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 information provided by macro-connectomes.

The present edition of The Human Central Nervous System differs considerably from its predecessors. In previous editions, the text was essentially confined to a section dealing with the various functional systems of the brain. This section, which has been rewritten and updated, is now preceded by 15 newly written chapters, which introduce the pictorial material of the gross anatomy, the blood vessels and meninges and the microstructure of its various parts and deal with the development, topography and functional anatomy of the spinal cord, the brain stem and the cerebellum, the diencephalon and the telencephalon. Great pains have been taken to cover the most recent concepts and data. As suggested by the front cover, there is a focus on the evolutionary development of the human brain. Throughout the text numerous correlations with neuropathology and clinical n- rology have been made. After much thought, we decided to replace the full Latin terminology, cherished in all previous editions, with English and Anglicized Latin terms. It has been an emotional farewell from beautiful terms such as decussatio hipposideriformis W- nekinkii and pontes grisei caudatolenticulares. Not only the text, but also the p- torial material has been extended and brought into harmony with the present state of knowledge. More than 230 new illustrations have been added and many others have been revised. The number of macroscopical sections through the brain has been extended considerably. Together, these illustrations now comprise a complete and convenient atlas for interpreting neuroimaging studies.

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.

Details the development, structure, function and behavioural ecology of the monotremes.