Understanding the Brain

Neuroscience

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Neuroscience is the scientific study of the nervous system.[1] Traditionally, neuroscience has been seen as a branch of biology. However, it is currently an interdisciplinary science that collaborates with other fields such as chemistry, computer science, engineering, linguistics, mathematics, medicine and allied disciplines, philosophy, physics, and psychology. The term neurobiology is usually used interchangeably with the term neuroscience, although the former refers specifically to the biology of the nervous system, whereas the latter refers to the entire science of the nervous system.

Drawing by Santiago Ramón y Cajal (1899) of neurons in the pigeon cerebellum


The scope of neuroscience has broadened to include different approaches used to study the molecular, cellular, developmental, structural, functional, evolutionary, computational, and medical aspects of the nervous system. The techniques used by neuroscientists have also expanded enormously, from molecular and cellular studies of individual nerve cells to imaging of sensory and motor tasks in the brain. Recent theoretical advances in neuroscience have also been aided by the study of neural networks.

Given the increasing number of scientists who study the nervous system, several prominent neuroscience organizations have been formed to provide a forum to all neuroscientists and educators. For example, the International Brain Research Organization was founded in 1960,[2] the International Society for Neurochemistry in 1963,[3] the European Brain and Behaviour Society in 1968,[4] and the Society for Neuroscience in 1969.[5]

History

Illustration from Gray's Anatomy (1918) of a lateral view of the human brain, featuring the hippocampus among other neuroanatomical features

The study of the nervous system dates back to ancient Egypt. Evidence of trepanation, the surgical practice of either drilling or scraping a hole into the skull with the purpose 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 1700 BC indicated that the Egyptians had some knowledge about symptoms of brain damage.[6]

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, the first step of mummification is to "take a crooked piece of iron, and with it draw out the brain through the nostrils, thus getting rid of a portion, while the skull is cleared of the rest by rinsing with drugs."[7]

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. Plato also speculated that the brain was the seat of the rational part of the soul.[8] Aristotle, however, believed 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.

Abulcasis, Averroes, Avenzoar, and Maimonides, active in the Medieval Muslim world, described a number of medical problems related to the brain. In Renaissance Europe, Vesalius (1514–1564) and René Descartes (1596–1650) also made several contributions to neuroscience.

The Golgi stain first allowed for the visualization of individual neurons.

Studies of the brain became more sophisticated after the invention of the microscope and the development of a staining procedure by Camillo Golgi during the late 1890s. The procedure used a silver chromate salt to reveal the intricate structures of individual 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 neuron doctrine was supported by experiments following Luigi Galvani's pioneering work in the electrical excitability of muscles and neurons. In the late 19th century, Emil du Bois-Reymond, Johannes Peter Müller, and Hermann von Helmholtz demonstrated that neurons were electrically excitable and that their activity predictably affected the electrical state of adjacent neurons.

In parallel with this research, work with brain-damaged patients by Paul Broca suggested that certain regions of the brain were responsible for certain functions. At the time, Broca's findings were seen as a confirmation of Franz Joseph Gall's theory that language was localized and that certain psychological functions were localized in specific areas of the cerebral cortex.[9][10] The localization of function hypothesis was supported by observations of epileptic patients conducted by John Hughlings Jackson, who correctly inferred the organization of the motor cortex by watching the progression of seizures through the body. Carl Wernicke further developed the theory of the specialization of specific brain structures in language comprehension and production. Modern research still uses the Brodmann cerebral cytoarchitectonic map (referring to study of cell structure) anatomical definitions from this era in continuing to show that distinct areas of the cortex are activated in the execution of specific tasks.[11]

In 1952, Alan Lloyd Hodgkin and Andrew Huxley presented a mathematical model for transmission of electrical signals in neurons of the giant axon of a squid, action potentials, and how they are initiated and propagated, known as the Hodgkin-Huxley model. In 1961-2, Richard FitzHugh and J. Nagumo simplified Hodgkin-Huxley, in what is called the FitzHugh–Nagumo model. In 1962, Bernard Katz modeled neurotransmission across the space between neurons known as synapses. In 1981 Catherine Morris and Harold Lecar combined these models in the Morris-Lecar model. In 1984, J. L. Hindmarsh and R.M. Rose further modeled neurotransmission.

Beginning in 1966, Eric Kandel and James Schwartz examined the biochemical analysis of changes in neurons associated with learning and memory storage.

Foundations of modern neuroscience

File:Neuron colored.jpg
Photograph of a stained neuron in a chicken embryo

The scientific study of the nervous system increased significantly during the second half of the twentieth century, principally due to revolutions in molecular biology, electrophysiology, and computational neuroscience. It has become possible to understand, in much detail, the complex processes occurring within a single neuron. However, how networks of neurons produce complex cognitions and behaviors is still poorly understood.

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, 4th ed.

The nervous system is composed of a network of neurons along with other, supportive, cells (e.g., glial cells). Neurons form functional circuits, each responsible for specific functions of behavior at the organismal level. Thus, neuroscience can be studied at many different levels, ranging from the molecular and cellular levels to the systems and cognitive levels.

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 develop 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.

At the cellular level, the fundamental questions addressed in cellular neuroscience include the mechanisms of how neurons process signals physiologically and electrochemically. They address how signals are processed by dendrites, somas and axons, and how neurotransmitters and electrical signals are used to process signals in a neuron. Another major area of neuroscience is directed at investigations of the development of the nervous system. These questions include the patterning and regionalization of the nervous system, neural stem cells, differentiation of neurons and glia, neuronal migration, axonal and dendritic development, trophic interactions, and synapse formation.

At the systems level, the questions addressed in systems neuroscience include how neural circuits are formed and used anatomically and physiologically to produce functions such as reflexes, sensory integration, motor coordination, circadian rhythms, emotional responses, learning, and memory. 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? How does the somatosensory system process tactile information? The related fields of neuroethology and neuropsychology address the question of how neural substrates underlie specific animal and human behaviors. Neuroendocrinology and psychoneuroimmunology examine interactions between the nervous system and the endocrine and immune systems, respectively.

At the cognitive level, cognitive neuroscience addresses the questions of how psychological functions are produced by neural circuitry. The emergence of powerful new measurement techniques such as neuroimaging (e.g., fMRI, PET, SPECT), electrophysiology, and human genetic analysis combined with sophisticated experimental techniques from cognitive psychology allows neuroscientists and psychologists to address abstract questions such as how human cognition and emotion are mapped to specific neural substrates.

Neuroscience is also allied with the social and behavioral sciences as well as nascent interdisciplinary fields such as neuroeconomics, decision theory, and social neuroscience to address complex questions about interactions of the brain with its environment.

Neuroscience and medicine

Parasagittal MRI of the head of a patient with benign familial macrocephaly

Neurology, psychiatry, neurosurgery, psychosurgery, neuropathology, neuroradiology, clinical neurophysiology and addiction medicine are medical specialties that specifically address the diseases of the nervous system. These terms also refer to clinical disciplines involving diagnosis and treatment of these diseases. Neurology works with diseases of the central and peripheral nervous systems, such as amyotrophic lateral sclerosis (ALS) and stroke, and their medical treatment while psychiatry focuses on affective, behavioral, cognitive, and perceptual disorders. Neuropathology focuses upon the classification and underlying pathogenic mechanisms of central and peripheral nervous system and muscle diseases, with an emphasis on morphologic, microscopic, and chemically observable alterations. Neurosurgery and psychosurgery work primarily with surgical treatment of diseases of the central and peripheral nervous systems. The boundaries between these specialties have been blurring recently as they are all influenced by basic research in neuroscience. Brain imaging also enables objective, biological insights into mental illness, which can lead to faster diagnosis, more accurate prognosis, and help assess patient progress over time.[12]

Integrative neuroscience makes connections across these specialized areas of focus.

Major branches

Modern neuroscience education and 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 or curricular approaches. Individual neuroscientists, however, often work on questions that span several distinct subfields.

Branch Description
Behavioral neuroscience Behavioral neuroscience (also known as biological psychology, biopsychology, or psychobiology) is the application of the principles of biology (viz., neurobiology) to the study of genetic, physiological, and developmental mechanisms of behavior in humans and non-human animals.
Cellular neuroscience Cellular neuroscience is the study of neurons at a cellular level including morphology and physiological properties.
Clinical neuroscience This consists of medical specialties such as neurology and psychiatry, among others. Neurology is the medical specialty that works with disorders of the nervous system. Psychiatry is the medical specialty that works with the disorders of the mind—which include various affective, behavioral, cognitive, and perceptual disorders. (Also see note below.)
Cognitive neuroscience Cognitive neuroscience is the study of biological substrates underlying cognition with a specific focus on the neural substrates of mental processes.
Computational neuroscience Computational neuroscience is the study of brain function in terms of the information processing properties of the structures that make up the nervous system. Computational neuroscience can also refer to the use of computer simulations and theoretical models to study the function of the nervous system.
Cultural neuroscience Cultural neuroscience is the study of how cultural values, practices and beliefs shape and are shaped by the mind, brain and genes across multiple timescales.[13]
Developmental neuroscience Developmental neuroscience studies the processes that generate, shape, and reshape the nervous system and seeks to describe the cellular basis of neural development to address underlying mechanisms.
Molecular neuroscience Molecular neuroscience is a branch of neuroscience that examines the biology of the nervous system with molecular biology, molecular genetics, protein chemistry, and related methodologies.
Neuroengineering Neuroengineering is a discipline within biomedical engineering that uses engineering techniques to understand, repair, replace, or enhance neural systems.
Neuroimaging Neuroimaging includes the use of various techniques to either directly or indirectly image the structure and function of the brain.
Neuroinformatics Neuroinformatics is a discipline within bioinformatics that conducts the organization of neuroscience data and application of computational models and analytical tools.
Neurolinguistics Neurolinguistics is the study of the neural mechanisms in the human brain that control the comprehension, production, and acquisition of language.
Neurophysiology Neurophysiology is the study of the functioning of the nervous system, generally using physiological techniques that include measurement and stimulation with electrodes or optically with ion- or voltage-sensitive dyes or light-sensitive channels.
Social neuroscience Social neuroscience is an interdisciplinary field devoted to understanding how biological systems implement social processes and behavior, and to using biological concepts and methods to inform and refine theories of social processes and behavior.
Systems neuroscience Systems neuroscience is the study the function of neural circuits and systems.

In 1990s, neuroscientist Jaak Panksepp coined the term "affective neuroscience" to emphasize that research of emotion should be a branch of the neurosciences, distinguishable from the nearby fields of cognitive neuroscience or behavioral neuroscience.[14] More recently, the social aspect of the emotional brain has been integrated in what is called "social-affective neuroscience" or simply social neuroscience.

Future directions

At this time in neuroscience research, several major questions remained unsolved, especially in cognitive neuroscience. For example, neuroscientists have yet to fully explain the neural basis of consciousness, learning, memory, perception, sensation, and sleep. Several questions regarding the development and evolution of the brain remain unsolved. Researchers have also yet to fully delineate the neural bases of mental disorders such as addiction, Alzheimer's disease, Parkinson's disease, and psychotic disorders (e.g., schizophrenia). Neuroscientific research on free will is also in the early stages of understanding.[15] Thus, neuroscientists are continuously collaborating with other scientists and researchers to address many of these unresolved problems.[16] Finally, proponents of the science of morality, such as the neuroscientist and writer Sam Harris, maintain that neuroscience will play an important role in the search for optimal moral systems.[17]

Public education and outreach

In addition to conducting traditional research in laboratory settings, neuroscientists have also been involved in the promotion of awareness and knowledge about the nervous system among the general public and government officials. Such promotions have been done by both individual neuroscientists and large organizations. For example, individual neuroscientists have promoted neuroscience education among young students by organizing the International Brain Bee (IBB), which is an academic competition for high school or secondary school students worldwide.[18] In the United States, large organizations such as the Society for Neuroscience have promoted neuroscience education by developing a primer called Brain Facts,[19] collaborating with members of public education to develop Neuroscience Core Concepts for K-12 teachers and students,[20] and cosponsoring a campaign with the Dana Foundation called Brain Awareness Week to increase public awareness about the progress and benefits of brain research.[21]

Finally, neuroscientists have also collaborated with other education experts to study and refine educational techniques to optimize learning among students, an emerging field called educational neuroscience.[22] Federal Agencies in the United States, such as the National Institute of Health (NIH) and National Science Foundation (NSF), have also funded research that pertain to best practices in teaching and learning of neuroscience concepts.

See also

References

  1. "Neuroscience". Merriam-Webster Medical Dictionary. http://www.merriam-webster.com/medlineplus/neuroscience. 
  2. "History of IBRO". International Brain Research Organization. 2010. http://www.ibro.info/Pub/Pub_Main_Display.asp?LC_Docs_ID=2343. 
  3. The Beginning, International Society for Neurochemistry
  4. "About EBBS". European Brain and Behaviour Society. 2009. http://www.ebbs-science.org/cms/general/about-ebbs.html. 
  5. "About SfN". Society for Neuroscience. http://www.sfn.org/index.aspx?pagename=about_sfn. 
  6. Mohamed W (2008). "The Edwin Smith Surgical Papyrus: Neuroscience in Ancient Egypt". IBRO History of Neuroscience. http://www.ibro.info/Pub/Pub_Main_Display.asp?LC_Docs_ID=3199. 
  7. Herodotus (440BCE). The Histories: Book II (Euterpe). http://classics.mit.edu/Herodotus/history.mb.txt. 
  8. Plato (360BCE). Timaeus. http://classics.mit.edu/Plato/timaeus.1b.txt. 
  9. Greenblatt SH (1995). "Phrenology in the science and culture of the 19th century". Neurosurg 37 (4): 790–805. PMID 8559310. http://journals.lww.com/neurosurgery/Abstract/1995/10000/Phrenology_in_the_Science_and_Culture_of_the_19th.25.aspx. 
  10. Bear MF, Connors BW, Paradiso MA (2001). Neuroscience: Exploring the Brain (4th ed.). Philedelphia, PA: Lippincott Williams & Wilkins. ISBN 0781739446. 
  11. Kandel ER, Schwartz JH, Jessel TM (2000). Principles of Neural Science (4th ed.). New York, NY: McGraw-Hill. ISBN 0838577016. 
  12. Lepage M (2010). "Research at the Brain Imaging Centre". Douglas Mental Health University Institute. http://www.douglas.qc.ca/page/imagerie-cerebrale?locale=en. 
  13. Chiao, J.Y. & Ambady, N. (2007). Cultural neuroscience: Parsing universality and diversity across levels of analysis. In Kitayama, S. and Cohen, D. (Eds.) Handbook of Cultural Psychology, Guilford Press, NY, pp. 237-254.
  14. Panksepp J (1990). "A role for "affective neuroscience" in understanding stress: the case of separation distress circuitry". In Puglisi-Allegra S, Oliverio A. Psychobiology of Stress. Dordrecht, Netherlands: Kluwer Academic. pp. 41–58. ISBN 0792306821. 
  15. Balaguer M (2009). Free Will as an Open Scientific Problem. Cambridge, MA: MIT Press. ISBN 9780262013543. 
  16. Hemmen JL, Sejnowski TJ (2006). 23 Problems in Systems Neuroscience. New York NY: Oxford University Press. ISBN 0195148223. http://papers.cnl.salk.edu/PDFs/23%20Problems%20in%20Systems%20Neuroscience%202005-2921.pdf. 
  17. Koizumi H (2007). The Concept of “Brain-Science and Ethics. Journal Seizon and Life Sciences. 
  18. "About the International Brain Bee". The International Brain Bee. http://www.internationalbrainbee.com/about_bee.html. 
  19. "Brain Facts: A Primer on the Brain and Nervous System". Society for Neuroscience. http://www.sfn.org/index.aspx?pagename=brainfacts. 
  20. "Neuroscience Core Concepts: The Essential Principles of Neuroscience". Society for Neuroscience. http://www.sfn.org/index.aspx?pagename=core_concepts. 
  21. "Brain Awareness Week Campaign". The Dana Foundation. http://www.dana.org/brainweek/. 
  22. Goswami U (2004). "Neuroscience, education and special education". Br J of Spec Educ 31 (4): 175–183. doi:10.1111/j.0952-3383.2004.00352.x. http://onlinelibrary.wiley.com/doi/10.1111/j.0952-3383.2004.00352.x/abstract. 

Further reading

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External links