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Neuroscience

Revision as of 11:24, 21 June 2007 by Robin Patterson (Message Wall | contribs) (Neuroscience Wikia)
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CajalCerebellum

Drawing of the cells in the chicken cerebellum by S. Ramón y Cajal

Neuroscience is a field that is devoted to the scientific study of the nervous system. Such studies may include 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 occurring inside a single neuron and in a network that eventually produces the intellectual behavior, cognition and physiological responses.

Neuron colored

A stained neuron.

“ The task of neural science is to explain behavior in terms of the activities of the brain. How does the brain marshal its millions of individual nerve cells to produce behavior, and how are these cells influenced by the environment...? The last frontier of the biological sciences--their ultimate challenge--is to understand the biological basis of consciousness and the mental processes by which we perceive, act, learn, and remember. — Eric Kandel, Principles of Neural science, Fourth Edition ”

The nervous system is composed of a network of neurons and other supportive cells (such as glial cells). 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.

User-FastFission-brain

a movie of MRI sections through the Z-axis in a normal human adult

At the cognitive level, cognitive neuroscience addresses the questions of how psychological/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 interdisciplinary 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 processes 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 disciplines involving diagnosis and treatment of theses diseases. Neurology deals with diseases of the central and peripheral nervous systems such as amyotrophic lateral sclerosis (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

Main article: History of the brain

Evidence of trepanation, the surgical practice of either drilling or scraping a hole into the skull with the aim of curing headaches or mental disorders or relieving cranial pressure, being performed on patients dates back to Neolithic times and has been found in various cultures throughout the world. Manuscripts dating back to 5000BC indicated that the Egyptians had some knowledge about symptoms of brain damage.

Early views on the function of the brain regarded it to be a "cranial stuffing" of sorts. In Egypt, from the late Middle Kingdom onwards, the brain was regularly removed in preparation for mummification. It was believed at the time that the heart was 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.'[How to reference and link to summary or text]

The view that the heart was the source of consciousness was not challenged until the time of Hippocrates. He believed that the brain was not only involved with sensation, since most specialized organs (e.g., eyes, ears, tongue) are located in the head near the brain, but was also the seat of intelligence. Aristotle, however, believed that the heart was the center of intelligence and that the brain served to cool the blood. This view was generally accepted until the Roman physician Galen, a follower of Hippocrates and physician to Roman gladiators, observed that his patients lost their mental faculties when they had sustained damage to their brains.

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 1890's that used 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 century, DuBois-Reymond, Müller, and von Helmholtz showed neurons were electrically excitable and that 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.

Branch Major Topics and Concepts Experimental and Theoretical Methods
Molecular and Cellular Neuroscience behavioral genetics, neurocytology, glia, protein trafficking, ion channel, synapse, action potential, neurotransmitters, neuroimmunology PCR, immunohistochemistry, patch clamp, voltage clamp, molecular cloning, gene knockout, biochemical assays, linkage analysis, fluorescent in situ hybridization, Southern blots, DNA microarray, GFP, calcium imaging, two-photon microscopy
Systems Neuroscience primary visual cortex, perception, audition, sensory integration, population coding, pain, spontaneous and evoked activity, color vision, olfaction, taste, motor system, spinal cord, sleep, homeostasis, arousal, attention, play single unit recording, intrinsic signal imaging, microstimulation, voltage sensitive dyes, fMRI, patch clamp, genomics, training awake behaving animals, local field potential, ROC, cortical cooling, calcium imaging, two-photon microscopy
Developmental Neuroscience axon guidance, neural crest, growth factors, growth cone, neuromuscular junction, cell proliferation, neuronal differentiation, cell survival and apoptosis, synaptic formation, motor differentiation, injury and regeneration Xenopus oocyte, protein chemistry, genomics, Drosophila, Hox gene
Cognitive Neuroscience language, emotion, motor learning, sexual behavior, decision making, behavioral genetics, motivation, social neuroscience psychometrics, EEG, MEG, fMRI, PET, SPECT, single unit recording, human genetics
Computational and Theoretical Neuroscience cable theory, Hodgkin-Huxley model, neural networks, voltage-gated currents, Hebbian learning Markov chain Monte Carlo, simulated annealing, high performance computing, partial differential equations, self-organizing nets, pattern recognition
Neuroscience of Diseases and Aging dementia, peripheral neuropathy, spinal cord injury, autonomic nervous system, depression, anxiety, Parkinson's disease, addiction, memory loss clinical trials, neuropharmacology, deep brain stimulation, neurosurgery
Neural engineering Neuroprosthetic, brain-computer interface

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)

  • Neurobiology of the neuron
  • Sensation and perception
  • Sleep
  • Autonomic systems and homeostasis
  • Arousal, attention and emotion
  • Genetics of the nervous system
  • Injury of the nervous systems

Allied and Overlapping Fields

Neuroscience, by its very interdiciplinary nature, overlaps with and encompasses many different subjects. Bellow is a list of related subjects and fields.

Future directions

Main article: Unsolved problems in neuroscience

See also

References

Textbooks

  • Bear, M. F. et. al. Eds. (1995). Neuroscience: Exploring The Brain. Baltimore, Maryland, Williams and Wilkins. ISBN 0781739446
  • Kandel ER, Schwartz JH, Jessell TM. Principles of Neural Science, 4th ed. McGraw-Hill, New York (2000). ISBN 0838577016
  • Squire, L. et al. (2003). Fundamental Neuroscience, 2nd edition. Academic Press; ISBN 0126603030
  • Byrne and Roberts (2004). From Molecules to Networks. Academic Press; ISBN 0121486605
  • Sanes, Reh, Harris (2005). Development of the Nervous System, 2nd edition. Academic Press; ISBN 0126186219
  • Siegel et al. (2005). Basic Neurochemistry, 7th edition. Academic Press; ISBN 012088397X
  • Rieke, F. et. al. (1999). Spikes: Exploring the Neural Code. The MIT Press; Reprint edition ISBN 0262681080


Online textbooks

  • Neuroscience 2nd ed. Dale Purves, George J. Augustine, David Fitzpatrick, Lawrence C. Katz, Anthony-Samuel LaMantia, James O. McNamara, S. Mark Williams. Published by Sinauer Associates, Inc., 2001.
  • Basic Neurochemistry: Molecular, Cellular, and Medical Aspects 6th ed. by George J. Siegel, Bernard W. Agranoff, R. Wayne Albers, Stephen K. Fisher, Michael D. Uhler, editors. Published by Lippincott, Williams & Wilkins, 1999.

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