Neuroscience

Drawing of the cells in the chicken cerebellum by S. Ramón y Cajal, about 1905

Neuroscience is a field devoted to the scientific study of the nervous system. The Society for Neuroscience was founded in 1969,^[1] but study of the brain started a long time ago. Such studies span the structure, function, evolutionary history, development, genetics, biochemistry, physiology, pharmacology, informatics, computational neuroscience and pathology of the nervous system. Traditionally it is seen as a branch of biological sciences. However, recently there has been a surge in the convergence of interest from many allied disciplines, including cognitive and neuro-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 empirical 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. Many recent theoretical advances in neuroscience have been aided by the use of computational modeling.

Overview

The scientific study of the nervous systems underwent a significant increase in 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 intellectual behavior, cognition, emotion and physiological responses is still poorly understood.

stained neuron

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 develop 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, circadian rhythms, emotional responses, learning and memory, et cetera. 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.

Para-sagittal MRI of the head in a patient with benign familial macrocephaly.

At the cognitive level, cognitive neuroscience addresses the questions of how psychological/cognitive functions are produced by the 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 circuitries.

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, such as behaviorism and traditional cognitive psychology, that are independent of the underlying neural processes. 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 form the foundation of the constituent neural circuitries. In Principles of Neural Science, nobel laureate Eric Kandel contends that cognitive psychology is one of the pillar disciplines for understanding the brain in neuroscience.

Neurology and Psychiatry 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 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 influenced by basic research in neuroscience.

History

See also: 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.'

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.

In al-Andalus, Abulcasis, the father of modern surgery, developed material and technical designs which are still used in neurosurgery. Averroes suggested the existence of Parkinson's disease and attributed photoreceptor properties to the retina. Avenzoar described meningitis, intracranial thrombophlebitis, mediastinal tumours and made contributions to modern neuropharmacology. Maimonides wrote about neuropsychiatric disorders and described rabies and belladonna intoxication.^[2] Elsewhere in medieval 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 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.

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 finding were seen as a confirmation of Franz Joseph Gall's theory that language was localized and certain psychological functions were localized in the cerebral cortex.^[3][4] The localization of function 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 further developed the theory of the specialization of specific brain structures in language comprehension and production. Modern research still uses the Brodmann cytoarchitectonic (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.^[5]

Major branches

Current 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.

Note: In 1990s, neuroscientist Jaak Panksepp coined the term "affective neuroscience"^[6] to emphasize that emotion research should be a branch of neurosciences, distinguishable from the nearby fields like cognitive neuroscience or behavioral neuroscience. More recently, the social aspect of the emotional brain has been integrated in what is called "social-affective neuroscience" or simply social neuroscience.

There has also been some research published arguing that some of fair play and the Golden Rule may be stated and rooted in terms of neuroscientific and neuroethical principles.^[7]

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 encompasses many different subjects. Below is a list of related subjects and fields.

Future directions

Main article: Unsolved problems in neuroscience

See also

• Brain types
• List of neuroscience topics
• List of neuroscientists
• Important publications in neuroscience
• Neuroscience journals
• Neuroscience research institutes, such as Monell Chemical Senses Center

References

Citations

Textbooks

Online textbooks

Popular works

Notes From Online Courses

• Intro to Neuroscience – Smith College Spring 2005

External links

• High-Resolution Cytoarchitectural Primate Brain Atlases
• Society for Neuroscience
• Neural Plasticity-Open Access Journal (Hindawi Publishing)
• Neuroscience. 2nd ed. by Purves et al (online textbook)
• Neuroscience News, Books, Links, Forum and Gifts
• Neuroscience for Kids
• Brain Research and Information Network B.R.A.I.N.
• Neuroscience Forum
• UAB Neuroscience
• UCL Neuroscience
• British Neuroscience Association
• Springer Protocols in neuroscience