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 Home > By Career > Medicine, Health Care > Neurosciences
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Neuroscience is the scientific study of the nervous system. 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.
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.
History
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.
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."
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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 regulated the amount
of heat from the heart.[9] 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.
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.[10][11] 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.
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 collaborators examined biochemical changes in
neurons associated with learning and memory storage.
Modern Neuroscience
The scientific study of the nervous system has increased significantly during the
second half of the twentieth century, principally due to advances in molecular biology,
electrophysiology, and computational neuroscience. This has allowed neuroscientists
to study the nervous system in all its aspects: how it is structured, how it works,
how it develops, how it malfunctions, and how it can be changed. For example, it
has become possible to understand, in much detail, the complex processes occurring
within a single neuron. Neurons are cells specialized for communication. They are
able to contact with neurons and other cell types through specialized junctions
called synapses, at which electrical or electrochemical signals can be transmitted
from one cell to another. Many neurons extrude long thin filaments of protoplasm
called axons, which may extend to distant parts of the body and are capable of rapidly
carrying electrical signals, influencing the activity of other neurons, muscles,
or glands at their termination points. A nervous system emerges from the assemblage
of neurons that are connected to each other.
In vertebrates, the nervous system can be split into two parts, the central nervous
system (brain and spinal cord), and the peripheral nervous system. In many species
— including all vertebrates — the nervous system is the most complex organ system
in the body, with most of the complexity residing in the brain. The human brain
alone contains around a hundred billion neurons and a hundred trillion synapses;
it consists of thousands of distinguishable substructures, connected to each other
in synaptic networks whose intricacies have only begun to be unraveled. The majority
of genes belonging to the human genome are expressed specifically in the brain.
Thus the challenge of making sense of all this complexity is formidable.
Molecular and cellular neuroscience
The study of the nervous system can be done at multiple 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.[clarification needed]
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.
Neural circuits and systems
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. Despite many advancements,
the way networks of neurons produce complex cognitions and behaviors is still poorly
understood.
Cognitive and behavioral neuroscience
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.
Ultimately neuroscientists would like to understand every aspect of the nervous
system, including how it works, how it develops, how it malfunctions, and how it
can be altered or repaired. The specific topics that form the main foci of research
change over time, driven by an ever-expanding base of knowledge and the availability
of increasingly sophisticated technical methods. Over the long term, improvements
in technology have been the primary drivers of progress. Developments in electron
microscopy, computers, electronics, functional brain imaging, and most recently
genetics and genomics, have all been major drivers of progress.
Translational research and medicine
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. 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.
Integrative neuroscience makes connections across these specialized areas of focus.
Neuroscience organizations
The largest professional neuroscience organization is the Society for Neuroscience
(SFN), which is based in the United States but includes many members from other
countries. Since its founding in 1969 the SFN has grown steadily: as of 2010 it
recorded 40,290 members from 83 different countries.[16] Annual meetings, held each
year in a different American city, draw attendance from researchers, postdoctoral
fellows, graduate students, and undergraduates, as well as educational institutions,
funding agencies, publishers, and hundreds of businesses that supply products used
in research.
Other major organizations devoted to neuroscience include the International Brain
Research Organization (IBRO), which holds its annual meetings in a country from
a different part of the world each year, and the Federation of European Neuroscience
Societies (FENS), which holds annual meetings in European cities. FENS comprises
a set of 32 national-level organizations, including the British Neuroscience Association,
the German Neurowissenschaftliche Gesellschaft, and the French Societé des Neurosciences.
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. In the United States, large organizations
such as the Society for Neuroscience have promoted neuroscience education by developing
a primer called Brain Facts,[18] collaborating with public school teachers to develop
Neuroscience Core Concepts for K-12 teachers and students,[19] and cosponsoring
a campaign with the Dana Foundation called Brain Awareness Week to increase public
awareness about the progress and benefits of brain research.
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.[21] Federal agencies in the United
States, such as the National Institute of Health (NIH)[22] and National Science
Foundation (NSF),[23] have also funded research that pertains to best practices
in teaching and learning of neuroscience concepts.
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