Neuroscience

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

Neuroscience is the scientific study of the nervous system. Traditionally, neuroscience has been seen as a branch of biology. Nevertheless, it is currently an interdisciplinary science that involves other disciplines such as psychology, computer science, mathematics, physics, philosophy, and medicine. 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, developmental, structural, functional, evolutionary, computational, and medical aspects of the nervous system. The techniques used by neuroscientists have also expanded enormously, from biophysical and molecular studies of individual nerve cells to imaging of perceptual and motor tasks in the brain. Recent theoretical advances in neuroscience have also been aided by the study of neural networks.

Given the ever-increasing number of neuroscientists that 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,^[1] the European Brain and Behaviour Society in 1968,^[2] and the Society for Neuroscience in 1969.^[3]

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 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 1700BC^[4] 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.^[5] 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 findings 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.^[6][7] The localization of function hypothesis was supported by observations of epileptic patients conducted by John Hughlings Jackson, who correctly inferred 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 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.^[8]

Foundations of modern neuroscience

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. Another major area of neuroscience is directed at investigations of the development of the nervous system. These questions of neural development 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 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. 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 field of neuroethology addresses the complex question of how neural substrates underlie specific animal behaviors, and neuropsychology does likewise with psychology. Neuroendocrinology and psychoneuroimmunology examine interactions between the nervous system and the endocrine and immune systems, respectively.

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 allied with the social and behavioral sciences, and burgeoning interdisciplinary fields such as neuroeconomics, decision theory, social neuroscience are addressing complex questions on the interactions of the brain with its environment.

Neuroscience and medicine

Neurology, psychiatry, and neuropathology 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 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. The boundaries between these specialties have been blurring recently, and they are all influenced by basic research in neuroscience.

Integrative neuroscience makes connections across these specialized areas of focus.

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"^[9] 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 aspects of fair play and the Golden Rule may be stated and rooted in terms of neuroscientific and neuroethical principles.^[10]

Future directions

Despite several advances that have been made 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, sleep, perception, learning and memory, neuroplasticity, and decision making. Moreover several questions on development and evolution of the brain remained unsolved. Finally, researchers have yet to fully delineate the neural bases of mental diseases like psychotic disorders (e.g. mania, schizophrenia), Parkinson's disease, Alzheimer's disease or addiction. Thus, neuroscientists are continuously working and collaborating with other scientists and researchers to address many of these unresolved problems.^[11]

Public education and outreach

In addition to conducting traditional research in laboratory settings, neuroscientists have also been involved in the promotion of knowledge and awareness about the nervous system among the general public and government officials. Such promotions have been done by individual neuroscientists to 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.^[12] Large organizations such as the Society for Neuroscience in the United States have promoted neuroscience education by developing a primer called Brain Facts,^[13] collaborating with members of public education to develop Neuroscience Core Concepts for K-12 teachers and students,^[14] and cosponsoring a campaign called Brain Awareness Week with the Dana Foundation to increase public awareness about the progress and benefits of brain research.^[15]

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.^[16] 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

• List of neuroscience topics
• List of neuroscientists
• Important publications in neuroscience
• List of neuroscience databases
• Neuroscience journals

References

Further reading

External links

• Neuroscience Information Framework (NIF)
• Neurobiology at the Open Directory Project
• IBRO (International Brain Research Organization)
• Society for Neuroscience (SFN)
• American Society for Neurochemistry
• Neuroscience Online (electronic neuroscience textbook)
• Faculty for Undergraduate Neuroscience (FUN)
• Neuroscience for Kids
• Neuroscience Discussion Group in ResearchGate
• Neuroscience Discussion Forum
• HHMI Neuroscience lecture series - Making Your Mind: Molecules, Motion, and Memory