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Neuroscience is a scientific discipline that studies the structure, function, development, genetics, biochemistry, physiology, pharmacology, and pathology of the nervous system. Traditionally it is seen as a branch of biological sciences. However, recently there has been of convergence of interest from many allied disciplines, including psychology, computer science, statistics, physics, and medicine. The scope of neuroscience has now broadened to include any systematic scientific experimental and theoretical investigation of the central and peripheral nervous system of biological organisms. The methodologies employed by neuroscientists have been enormously expanded, from biochemical and genetic analysis of dynamics of individual nerve cells and their molecular constituents to imaging representations of perceptual and motor tasks in the brain. Neuroscience is at the frontier of investigation of the brain and mind. The study of the brain is becoming the cornerstone in understanding how we perceive and interact with the external world and, in particular, how human experience and human biology influence each other. Overview The scientific study of the nervous systems has exploded in the second half of the twentieth century, principally due to revolutions in molecular biology, neural networks and computational neuroscience. It has become possible to understand, in exquisite detail, the complex processes occuring inside a single neuron and in a network that eventually produces the intellectual behavior, cognition and physiological responses. The nervous system is composed of a network of neurons and other supportive cells (such as glial cells), each with a complete copy of the organism's genome. Neurons form functional circuits, each responsible for specific tasks to the behaviors at the organism level. Thus, neuroscience can be studied at many different levels, ranging from molecular level to cellular level to systems level to cognitive level. At the molecular level, the basic questions addressed in molecular neuroscience include the mechanisms by which neurons express and respond to molecular signals and how axons form complex connectivity patterns. At this level, tools from molecular biology and genetics are used to understand how neurons are born and die, and how genetic changes affect biological functions. The morphology, molecular identity and physiological characteristics of neurons and how they relate to different types of behavior are also of considerable interest. (The ways in which neurons and their connections are modified by experience are addressed at the physiological and cognitive levels.) At the cellular level, the fundamental questions addressed in cellular neuroscience are the mechanisms of how neurons process signals physiologically and electrochemically. They address how signals are processed by the dendrites, somas and axons, and how neurotransmitters and electrical signals are used to process signals in a neuron. At the systems level, the questions addressed in systems neuroscience include how the circuits are formed and used anatomically and physiologically to produce the physiological functions, such as reflexes, sensory integration, motor coordination, emotional responses, learning and memory, etc. In other words, they address how these neural circuits function and the mechanisms through which behaviors are generated. For example, systems level analysis addresses questions concerning specific sensory and motor modalities: how does vision work? How do songbirds learn new songs and bats localize with ultrasound? The related field of neuroethology, in particular, addresses the complex question of how neural substrates underlies specific animal behavior. At the cognitive level, cognitive neuroscience addresses the questions of how pyschological/cognitive functions are produced by the neural circuitry. The emergence of powerful experimental techniques such as fMRI, electrophysiology and human genetic analysis allows neuroscientists to address abstract questions such as how human cognition and emotion are mapped to specific neural circuitries. Many mental processes previously thought to be beyond scientific understanding have been shown to have robust neural correlates. Neuroscience is also beginning to become allied with social sciences, and burgeoning interdiciplinary fields of neuroeconomics, decision theory, social neuroscience are starting to address some of the most complex questions involving interactions of brain with environment. Neuroscience generally includes all scientific studies involving the nervous system. Psychology, as the scientific study of mental processes, may be considered a sub-field of neuroscience, although some mind/body theorists argue that the definition goes the other way — that psychology is a study of mental processeses that can be modeled by many other abstract principles and theories that are independent of the underlying neural circuitries. The term neurobiology is sometimes used interchangeably with neuroscience, though the former refers to the biology of nervous system, whereas the latter refers to science of mental functions that are built upon by the constituent neural circuitries. Neurology and Psychiatry are medical specialties and are generally considered, in academic research, subfields of neuroscience that specifically address the diseases of the nervous system. These terms also refer to clinical diciplines involving diagnosis and treatment of theses diseases. Neurology deals with diseases of the central and peripheral nervous systems such as ALS and stroke, while psychiatry focuses on mental illnesses. The boundaries between the two have been blurring recently and physicians who specialize in either generally receive training in both. Both neurology and psychiatry are heavily involved in and influenced by basic research in neuroscience. History of Neuroscience Even though it is believed that ancient hominods performed trepanation with the aim to cure, perhaps headaches or mental disorders, manuscripts dating 5000 years indicated that egyptians had some knowledge about symptoms of brain damage. Early views on the function of the brain, regarded it to be a form of “cranial stuffing” of sorts. In Egypt, from the late Middle Kingdom onwards, in preparation for mummification, the brain was regularly removed, for it was the heart that was assumed to be the seat of intelligence. According to Herodotus, during the first step of mummification: ‘The most perfect practice is to extract as much of the brain as possible with an iron hook, and what the hook cannot reach is mixed with drugs.’ The view that the heart was the source of conciousness was not challenged until the time of Hippocrates. He believed that the brain, not only was involved with sensation since most specialized organs (eyes, ears and tongue) are located in the head, but also was the seat of intelligence. However, Aristotle strung to the believe that the heart was the center of intelligence and thus, this the brain was a "cooling device". This view was accepted until the Roman Galen embraced Hippocrates belief. Galen was a physician of gladiators and had the opportunity to observe the consecuences of brain and spinal injury. He also performed numerous animal dissections and he described the cerebrum, cerebellum and ventricles. When he observed the fluid inside the ventricles his observations agreed with the general idea that the body functioned according to the balance of the four vital fluids or humors. Sophisticated studies of the brain were not possible until after the invention of the microscope and the development of a staining procedure by Camillo Golgi during the late 1890s that uses a silver chromate salt to reveal the intricate structures of single neurons. His technique was used by Santiago Ramón y Cajal and led to the formation of the "neuron doctrine," the hypothesis that the functional unit of the brain is the neuron. Golgi and Ramón y Cajal shared the Nobel Prize in Physiology or Medicine in 1906 for their extensive observations, descriptions and categorizations of neurons throughout the brain. The hypotheses of the neuron doctrine were supported by experiments following Galvani's pioneering work in the electrical excitability of muscles and neurons. In the late 19th cnetury, DuBois-Reymond, Müller, and von Helmholtz showed neurons were electrically excitable, and their activity predictably affected the electrical state of adjacent neurons. Further work with brain-damaged patients by Broca suggested that certain regions of the brain were responsible for certain functions. This hypothesis was supported by observations of epileptic patients conducted by John Hughlings Jackson, who correctly deduced the organization of motor cortex by watching the progression of seizures through the body. Wernicke developed the theory of the specialization of specific brain structures in language comprehension and production. ref: Principles of Neural Science, 4th ed. Eric R. Kandel, James H. Schwartz, Thomas M. Jessel, eds. McGraw-Hill:New York, NY. 2000. Andrea Vesalius (1514-1564) Rene Descartes (1596-1650) Major Branches of Neuroscience Current neuroscience research activities can be very roughly categorized into the following major branches, based on the subject and scale of the system in examination as well as distinct experimental approaches. Individual neuroscientists, however, often work on questions that span several distinct subfields. Major Themes of Research Neuroscience research from different areas can also be seen as focusing on a set of specific themes and questions. (Some of these are taken from http://www.northwestern.edu/nuin/fac/index.htm) Allied and Overlapping Fields Neuroscience, by its very interdiciplinary nature, overlaps with and emcompasses many different subjects. Bellow is a list of related subjects and fields. Future directions See also Textbooks Online textbooks Popular works Notes From Online Courses | |||||||
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