Local Cortical Circuits

Neurophysiologists are often accused by colleagues in the physical sci ences of designing experiments without any underlying hypothesis. This impression is attributable to the ease of getting lost in the ever-increasing sea of professional publications which do not state explicitly the ultimate goal of the research. On the other hand, many of the explicit models for brain function in the past were so far removed from experimental reality that they had very little impact on further research. It seems that one needs much intimate experience with the real nerv-. ous system before a reasonable model can be suggested. It would have been impossible for Copernicus to suggest his model of the solar system without the detailed observations and tabulations of star and planet motion accu mulated by the preceeding generations. This need for intimate experience with the nervous system before daring to put forward some hypothesis about its mechanism of action is especially apparent when theorizing about cerebral cortex function. There is widespread agreement that processing of information in the cor tex is associated with complex spatio-temporal patterns of activity. Yet the vast majority of experimental work is based on single neuron recordings or on recordings made with gross electrodes to which tens of thousands of neurons contribute in an unknown fashion. Although these experiments have taught us a great deal about the organization and function of the cor tex, they have not enabled us to examine the spatio-temporal organization of neuronal activity in any detail.

In order to focus on principles, each chapter in this work is brief, organized around 1-3 wiring diagrams of the key circuits, with several pages of text that distil the functional significance of each microcircuit

While the nature of local neuronal circuits has been addressed in previous reviews and articles scattered among a variety of publications, a precise definition has been difficult to formulate. This collection of articles, a special issue of the journal Cerebral Cortex, provides a multi-faceted survey of current concepts and issues in the field of local cortical circuits. It is an invaluable collection of the latest research in this vital, growing area.

This elegant book presents current evidence on the organization of the mammalian cerebral cortex. The focus on synapses and their function provides the basis for understanding how this critical part of the brain could work. Dr. White and his colleague Dr. Keller have collated an impressive mass of material. This makes the crucial information accessible and coherent. Dr. White pioneered an area of investigation that to most others, and occasionally to himself, seemed a bottomless pit of painstaking at tention to detail for the identification and enumeration of cortical syn apses. I do not recall that he or anyone else suspected, when he began to publish his now classic papers, that the work would be central to an accelerating convergence of information and ideas from neurobiology and computer science, especially artificial intelligence (AI) (Rumelhart and McClelland, 1986). The brain is the principal organ responsible for the adaptive capacities of animals. What has impressed students of biology, of medicine, and, to an extent, of philosophy is the correlation between the prominence of the cerebral cortex and the adaptive "complexity" of a particular spe cies. Most agree that the cortex is what sets Homo sapiens apart from other species quantitatively and qualitatively (Rakic, 1988). This is summarized in the first chapter.

In Fast Oscillations in Cortical Circuits, the authors use a combination of electrophysiological and computer modeling techniques to analyze how large networks of neurons can produce both epileptic seizures and functionally relevant synchronized oscillations.

This book offers a timely overview of theories and methods developed by an authoritative group of researchers to understand the link between criticality and brain functioning. Cortical information processing in particular and brain function in general rely heavily on the collective dynamics of neurons and networks distributed over many brain areas. A key concept for characterizing and understanding brain dynamics is the idea that networks operate near a critical state, which offers several potential benefits for computation and information processing. However, there is still a large gap between research on criticality and understanding brain function. For example, cortical networks are not homogeneous but highly structured, they are not in a state of spontaneous activation but strongly driven by changing external stimuli, and they process information with respect to behavioral goals. So far the questions relating to how critical dynamics may support computation in this complex setting, and whether they can outperform other information processing schemes remain open. Based on the workshop “Dynamical Network States, Criticality and Cortical Function", held in March 2017 at the Hanse Institute for Advanced Studies (HWK) in Delmenhorst, Germany, the book provides readers with extensive information on these topics, as well as tools and ideas to answer the above-mentioned questions. It is meant for physicists, computational and systems neuroscientists, and biologists.

This book has brought together leading investigators who work in the new arena of brain connectomics. This includes ‘macro-connectome’ efforts to comprehensively chart long-distance pathways and functional networks; ‘micro-connectome’ efforts to identify every neuron, axon, dendrite, synapse, and glial process within restricted brain regions; and ‘meso-connectome’ efforts to systematically map both local and long-distance connections using anatomical tracers. This book highlights cutting-edge methods that can accelerate progress in elucidating static ‘hard-wired’ circuits of the brain as well as dynamic interactions that are vital for brain function. The power of connectomic approaches in characterizing abnormal circuits in the many brain disorders that afflict humankind is considered. Experts in computational neuroscience and network theory provide perspectives needed for synthesizing across different scales in space and time. Altogether, this book provides an integrated view of the challenges and opportunities in deciphering brain circuits in health and disease.