Neurons And Interneuronal Connections Of The Central Visual System

This century has witnessed the creation of new sciences extending the frontiers of knowledge to an unprecedented degree. We have seen the birth of cybernetics and bionics, bringing together such apparently distantly related branches of science as neurohistology and automation, synaptology and electronics. The electron microscope has resolved tissues almost down to the molecular level, and histochemistry has led to the fine analysis of brain structure. However, before these and other new sciences can develop properly and scientifically, a precise knowledge of the structure of the material with which they are concerned is absolutely essential. That is why the need exists at the present time for a detailed study of the larger units, i. e. , the neurons, their interrelationships and the pathways by which excitation is conducted. Biologists, neurologists, physicists, and specialists in other technical disci plines will find this study highly useful. During recent years many advances have been made in knowledge of the central visual system and its pathways. Above all, it has been found that the visual system is very extensive. The optic tract is connected, not only with the lateral geniculate body, but with the superior colliculus and the pulvinar. Besides the discovery of these principal pathways, connections have also been studied with the hypothalamus, the pretectal region, the medial geniculate body, subthalamus, and other parts of the brain stem. The visual system is thus connected with the reflex apparatus, the autonomic nervous system, and the auditory and reticular systems.

This century has witnessed the creation of new sciences extending the frontiers of knowledge to an unprecedented degree. We have seen the birth of cybernetics and bionics, bringing together such apparently distantly related branches of science as neurohistology and automation, synaptology and electronics. The electron microscope has resolved tissues almost down to the molecular level, and histochemistry has led to the fine analysis of brain structure. However, before these and other new sciences can develop properly and scientifically, a precise knowledge of the structure of the material with which they are concerned is absolutely essential. That is why the need exists at the present time for a detailed study of the larger units, i. e. , the neurons, their interrelationships and the pathways by which excitation is conducted. Biologists, neurologists, physicists, and specialists in other technical disci plines will find this study highly useful. During recent years many advances have been made in knowledge of the central visual system and its pathways. Above all, it has been found that the visual system is very extensive. The optic tract is connected, not only with the lateral geniculate body, but with the superior colliculus and the pulvinar. Besides the discovery of these principal pathways, connections have also been studied with the hypothalamus, the pretectal region, the medial geniculate body, subthalamus, and other parts of the brain stem. The visual system is thus connected with the reflex apparatus, the autonomic nervous system, and the auditory and reticular systems.

This century has witnessed the creation of new sciences extending the frontiers of knowledge to an unprecedented degree. We have seen the birth of cybernetics and bionics, bringing together such apparently distantly related branches of science as neurohistology and automation, synaptology and electronics. The electron microscope has resolved tissues almost down to the molecular level, and histochemistry has led to the fine analysis of brain structure. However, before these and other new sciences can develop properly and scientifically, a precise knowledge of the structure of the material with which they are concerned is absolutely essential. That is why the need exists at the present time for a detailed study of the larger units, i. e. , the neurons, their interrelationships and the pathways by which excitation is conducted. Biologists, neurologists, physicists, and specialists in other technical disci plines will find this study highly useful. During recent years many advances have been made in knowledge of the central visual system and its pathways. Above all, it has been found that the visual system is very extensive. The optic tract is connected, not only with the lateral geniculate body, but with the superior colliculus and the pulvinar. Besides the discovery of these principal pathways, connections have also been studied with the hypothalamus, the pretectal region, the medial geniculate body, subthalamus, and other parts of the brain stem. The visual system is thus connected with the reflex apparatus, the autonomic nervous system, and the auditory and reticular systems.

The brain ... There is no other part of the human anatomy that is so intriguing. How does it develop and function and why does it sometimes, tragically, degenerate? The answers are complex. In Discovering the Brain, science writer Sandra Ackerman cuts through the complexity to bring this vital topic to the public. The 1990s were declared the "Decade of the Brain" by former President Bush, and the neuroscience community responded with a host of new investigations and conferences. Discovering the Brain is based on the Institute of Medicine conference, Decade of the Brain: Frontiers in Neuroscience and Brain Research. Discovering the Brain is a "field guide" to the brainâ€"an easy-to-read discussion of the brain's physical structure and where functions such as language and music appreciation lie. Ackerman examines: How electrical and chemical signals are conveyed in the brain. The mechanisms by which we see, hear, think, and pay attentionâ€"and how a "gut feeling" actually originates in the brain. Learning and memory retention, including parallels to computer memory and what they might tell us about our own mental capacity. Development of the brain throughout the life span, with a look at the aging brain. Ackerman provides an enlightening chapter on the connection between the brain's physical condition and various mental disorders and notes what progress can realistically be made toward the prevention and treatment of stroke and other ailments. Finally, she explores the potential for major advances during the "Decade of the Brain," with a look at medical imaging techniquesâ€"what various technologies can and cannot tell usâ€"and how the public and private sectors can contribute to continued advances in neuroscience. This highly readable volume will provide the public and policymakersâ€"and many scientists as wellâ€"with a helpful guide to understanding the many discoveries that are sure to be announced throughout the "Decade of the Brain."

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.

The invitation by the editors of the series "studies of brain function" to contribute a monograph on the visual cortex gives me the opportunity to present in a concentrated manner much of the work I have done on the visual cortical areas of cat and monkey. However, the field of visual cortical physi ology is so active and so diverse that the presentation of only my own work would have given a very incomplete view of visual cortical functioning. Therefore this monograph also reviews most of the studies carried out on the subject in the last two decades. Where possible I have tried not only to describe the cortical machinery but also its possible functional purpose regarding vision. In doing this I have expressed my personal views rather than just reviewing the experimental facts. Much of the work presented in this monograph has been supported by the National Research Council of Belgium and the Research Council of the Catholic University of Leuven. I express my gratitude to them. I have en joyed collaborating in these studies with P. O. Bishop, H. Kato, H. Kennedy, K. P. Hoffmann, H. Maes, J. Duysens, E. Vandenbussche, and H. van der Glas. I am much indebted to all those who have commented on earlier versions of this monograph: J. Allman, H. Barlow, J. BuBier, M. Callens, J. Duysens, O. J. Griisser, P. Heggelund, H. Kennedy, L. C. Orban and L. Palmer.