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Kerri Smith Halfway through a satellite meeting at the Federation of European Neurosciences conference in Amsterdam in July, researcher Ken McCarthy takes the stage to give his presentation. He sports a black shirt and jeans, and his strong cheekbones, shock of white hair and tanned skin give him the look of a film star. But he doesn't have the confidence to match. I find this a little bit daunting, he says, as he organizes his slides. McCarthy, a geneticist at the University of North Carolina School of Medicine in Chapel Hill, is about to fan the flames of a debate about whether glia, the largest contingent of non-neuronal cells in the brain, are important in transmitting electrical messages. For many years, neurons were thought to be alone in executing this task, and glia were consigned to a supporting role regulating a neuron's environment, helping it to grow, and even providing physical scaffolding (glia is Greek for 'glue'). In the past couple of decades, however, this picture has been changing. Some glia, known as astrocytes, have thousands of bushy tendrils that nestle close to the active junctions between neurons the synapses (see 'Neural threesome'). Here they seem to listen in on neuronal activity and, in turn, to influence it. Studies show that chemical transmitters released by neurons cause an increase in the levels of calcium inside astrocytes, spurring them to release transmitters of their own. These can enhance or mute the signalling between neurons, or influence the strength of their connections over time. Moreover, astrocytes activated at one synapse might communicate with other synapses and astrocytes with which they make contact. © 2010 Nature Publishing Group,

Related chapters from BN: Chapter 2: Functional Neuroanatomy: The Cells and Structure of the Nervous System; Chapter 3: Neurophysiology: The Generation, Transmission, and Integration of Neural Signals
Related chapters from MM:Chapter 1: Cells and Structures: The Anatomy of the Nervous System; Chapter 2: Neurophysiology: The Generation, Transmission, and Integration of Neural Signals
Link ID: 14649 - Posted: 11.11.2010

Miriam Frankel A type of brain cell thought to be responsible for supporting other cells may have a previously unsuspected role in controlling breathing. Star-shaped cells called astrocytes, found in the brain and spinal cord, can 'sense' changes in the concentration of carbon dioxide in the blood and stimulate neurons to regulate respiration, according to a study published online in Science today1. The research may shed some light on the role of astrocytes in certain respiratory illnesses, such as cot death, which are not well understood. Astrocytes are a type of glial cell — the most common type of brain cell, and far more abundant than neurons. "Historically, glial cells were only thought to 'glue' the brain together, providing neuronal structure and nutritional support but not more," explains physiologist Alexander Gourine of University College London, one of the authors of the study. "This old dogma is now changing dramatically; a few recent studies have shown that astrocytes can actually help neurons to process information." "The most important aspect of this study is that it will significantly change ideas about how breathing is controlled," says David Attwell, a neuroscientist at University College London, who was not involved in the study. During exercise, the amount of CO2 in the blood increases, making the blood more acidic. Until now, it was thought that this pH change was 'sensed' by specialized neurons that signal to the lungs to expel more CO2. But the study found that astrocytes can sense such a decrease in pH too — a change that causes an increase in the concentration of calcium ions (Ca2+) in the cells and the release of the chemical messenger adenosine-5'-triphosphate (ATP). © 2010 Nature Publishing Group,

Related chapters from BN: Chapter 2: Functional Neuroanatomy: The Cells and Structure of the Nervous System; Chapter 3: Neurophysiology: The Generation, Transmission, and Integration of Neural Signals
Related chapters from MM:Chapter 1: Cells and Structures: The Anatomy of the Nervous System; Chapter 2: Neurophysiology: The Generation, Transmission, and Integration of Neural Signals
Link ID: 14264 - Posted: 07.17.2010

by Roberta Friedman Research presented here is beginning to reveal the molecular signals that guide the assembly of the brain, and that perhaps can be tapped into for making repairs. The glial cells that most neuroscientists have regarded as merely support cells in fact take an active role in building a brain. A primitive type of glial cell serves as the stem cells that actually generate the brain's neurons. Even in adults, these glial cells can form new neurons, scientists are finding. Evidence presented in a symposium supports the idea that the radial glial cells are actually the stem cells that give rise to neurons, and are not just directing their migration passively. Magdalena Götz and colleagues at the Max-Plank Institute of Neurobiology find that a transcription factor, Pax6, is used in the radial glial cells that are forming neurons. © Elsevier Science Limited 2000

Related chapters from BN: Chapter 2: Functional Neuroanatomy: The Cells and Structure of the Nervous System
Related chapters from MM:Chapter 1: Cells and Structures: The Anatomy of the Nervous System
Link ID: 1050 - Posted: 06.24.2010

By Victoria Stern The deadliest and most common type of brain cancer has a strange bedfellow: cytomegalovirus, a kind of herpes present in about 80 percent of the U.S. population. Now scientists are exploiting this coincidence to treat the cancer with a vaccine that targets the virus and slows tumor regrowth. In 2002 scientists showed that cytomegalovirus, or CMV, was active in the brain tumors but not the surrounding healthy tissue of all 27 patients they tested who had glioblastoma multiforme. CMV is dormant and undetectable in most people. Neuroscientist Duane Mitchell of Duke University Medical Center and his colleagues confirmed in 2007 that CMV is active in at least 90 percent of glioblastoma tumors. Now Mitchell’s team has developed an experimental vaccine that triggers the immune system to attack CMV, thereby attacking its tumor tissue home. As reported at the American Society of Clinical Oncology meeting in June, the vaccine, together with radiation and chemotherapy, prevented the brain tumor from reemerging after surgery for 12 months as compared with the typical six to seven months with no vaccine. Patients’ average life span increased from 14 months to more than 20. So does this herpes virus cause cancer? The answer is unclear: tumor cells may simply be a fertile ground for growing the virus, as cells such as these often lack the normal immune functions that suppress CMV reproduction. But University of Wisconsin–Madison researchers reported in May that the virus has the ability to take over a cell’s braking mechanism and cause uncontrolled reproduction. Even so, the numbers do not seem to add up: four of five Americans has CMV, but only about one in 30,000 ends up with glioblastoma. And a small number of glioblastoma patients do not have CMV in their tumors. © 1996-2008 Scientific American Inc.

Related chapters from BN: Chapter 2: Functional Neuroanatomy: The Cells and Structure of the Nervous System; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 1: Cells and Structures: The Anatomy of the Nervous System; Chapter 11: Emotions, Aggression, and Stress
Link ID: 11777 - Posted: 06.24.2010

Roxanne Khamsi The brains and spinal cords of male mice contain more of the protective, fatty substance called myelin, which insulates nerve cells, than their female counterparts, new research reveals. The finding could help to explain why some neurological diseases, including multiple sclerosis, strike one sex more than another. Robert Skoff of the Wayne State University School of Medicine in Detroit, US, and colleagues found an unexpected difference when they compared the composition of white matter in the brains of male and female mice. White matter consists of nerve cells coated with insulating myelin, which helps the cells to relay signals efficiently. Skoff’s team determined the density of oligodendrocytes – cells which produce myelin – in the male and female mouse central nervous system by testing for their molecular signature. They found that these specialised cells are roughly one-third more dense within the brains and spinal cords of male rodents. They add that the differences are present in young and old mice, and independent of strain and species. © Copyright Reed Business Information Ltd.

Related chapters from BN: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 2: Functional Neuroanatomy: The Cells and Structure of the Nervous System
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 1: Cells and Structures: The Anatomy of the Nervous System
Link ID: 8471 - Posted: 06.24.2010

WEST LAFAYETTE, Ind. – Purdue University researchers have shown that extremely thin carbon fibers called "nanotubes" might be used to create brain probes and implants to study and treat neurological damage and disorders. Probes made of silicon currently are used to study brain function and disease but may one day be used to apply electrical signals that restore damaged areas of the brain. A major drawback to these probes, however, is that they cause the body to produce scar tissue that eventually accumulates and prevents the devices from making good electrical contact with brain cells called neurons, said Thomas Webster, an assistant professor of biomedical engineering. New findings showed that the nanotubes not only caused less scar tissue but also stimulated neurons to grow 60 percent more fingerlike extensions, called neurites, which are needed to regenerate brain activity in damaged regions, Webster said.

Related chapters from BN: Chapter 2: Functional Neuroanatomy: The Cells and Structure of the Nervous System
Related chapters from MM:Chapter 1: Cells and Structures: The Anatomy of the Nervous System
Link ID: 4771 - Posted: 06.24.2010

By Carolyn Y. Johnson They have long been dismissed as the brain’s Bubble Wrap, packing material to protect precious cells that do the real work of the mind. But glial cells — the name literally means “glue’’ — are now being radically recast as neuroscientists explore the role they play in disease and challenge longstanding notions about how the brain works. More than a century ago, scientists proposed the “neuron doctrine,’’ a theory that individual brain cells called neurons are the main players in the nervous system. It became an underpinning of modern neuroscience and led to major advances in understanding the brain, but it has become increasingly apparent that the other 85 percent of brain cells, glia, do more than just housekeeping. “In a play in a theater, it’s not just the actors on the stage, but the whole ensemble that is critical for that production to be perfect,’’ said Philip Haydon, chairman of the neuroscience department at Tufts University School of Medicine. “The players on the stage are neurons, but if you don’t have every person backstage, you don’t have a production, and what we’re now realizing is this whole support cast [of glia] is essential for normal brain function.’’ Haydon became curious about glia nearly two decades ago as an unintentional consequence of an experiment. He killed neurons in a dish of brain cells and left the glia, expecting to see the chemical signals that neurons use to communicate with one another disappear. To his surprise, the signals did not stop — suggesting the glia were not passive. © 2010 NY Times Co

Related chapters from BN: Chapter 2: Functional Neuroanatomy: The Cells and Structure of the Nervous System; Chapter 17: Learning and Memory
Related chapters from MM:Chapter 1: Cells and Structures: The Anatomy of the Nervous System; Chapter 13: Memory and Learning
Link ID: 14124 - Posted: 06.24.2010

by Carl Zimmer Some of the common words we use are frozen mistakes. The term influenza comes from the Italian word meaning “influence”—an allusion to the influence the stars were once believed to have on our health. European explorers searching for an alternate route to India ended up in the New World and uncomprehendingly dubbed its inhabitants indios, or Indians. Neuroscientists have a frozen mistake of their own, and it is a spectacular blunder. In the mid-1800s researchers discovered cells in the brain that are not like neurons (the presumed active players of the brain) and called them glia, the Greek word for “glue.” Even though the brain contains about a trillion glia—10 times as many as there are neurons—the assumption was that those cells were nothing more than a passive support system. Today we know the name could not be more wrong. Glia, in fact, are busy multitaskers, guiding the brain’s development and sustaining it throughout our lives. Glia also listen carefully to their neighbors, and they speak in a chemical language of their own. Scientists do not yet understand that language, but experiments suggest that it is part of the neurological conversation that takes place as we learn and form new memories. If you had to blame one thing for the mistaken impression about glia, it would have to be electricity. The 18th-century physiologist Luigi Galvani discovered that if he touched a piece of electrified metal to an exposed nerve in a frog’s leg, the leg twitched. He and others went on to show that a slight pulse of electricity moving through the metal to the nerve was responsible. For two millennia physicians and philosophers had tried to find the “animal spirits” that moved the body, and Galvani discovered that impetus: It was the stuff of lightning.

Related chapters from BN: Chapter 2: Functional Neuroanatomy: The Cells and Structure of the Nervous System
Related chapters from MM:Chapter 1: Cells and Structures: The Anatomy of the Nervous System
Link ID: 13188 - Posted: 06.24.2010

By Nathan Seppa Mutations in two genes, IDH1 and IDH2, might provide markers that enable doctors to discern malignant from benign brain tumors and catch some cancers early, scientists report in the Feb. 19 New England Journal of Medicine. The study adds to a growing list of molecular clues that doctors may ultimately use to diagnosis and treat cancers, says study coauthor D. Williams Parsons, a pediatric oncologist and Howard Hughes Medical Institute investigator at Johns Hopkins University in Baltimore. Doctors diagnose nearly 200,000 brain cancers each year in the United States. Most get their start elsewhere in the body and spread to the brain. But in about 22,000 of these patients, the cancer originates in the brain or central nervous system. These primary brain tumors are most often gliomas — clusters of tumor cells that derive from the brain’s glial cells. Gliomas vary in virulence from benign (grade 1) to fast-growing and rapidly lethal (grade 4). The IDH genes are so-named because they encode an enzyme called isocitrate dehydrogenase. While the role of the enzyme is poorly understood, the mutations in IDH genes attracted interest after turning up last year in brain tumors but not in other cancer tissues. In the new study, the researchers tested samples of benign and cancerous primary brain tumors removed from 445 people and from tumors obtained from 494 others who had cancers of the colon, prostate, pancreas, breast, stomach, ovary or blood (leukemia). © Society for Science & the Public 2000 - 2009

Related chapters from BN: Chapter 2: Functional Neuroanatomy: The Cells and Structure of the Nervous System
Related chapters from MM:Chapter 1: Cells and Structures: The Anatomy of the Nervous System
Link ID: 12574 - Posted: 06.24.2010

By Tina Hesman Saey Two groups of researchers — one at MIT, the other at Harvard — have shown that astrocytes get the blood pumping to parts of the brain that are thinking hard. These cells may use blood flow and other tricks to rev up communication between neurons or slow it down, and may even play a role in storing information. The findings indicate that astrocytes are not just supporting actors for neurons; they deserve recognition as true costars. “Astrocytes are typically forgotten,” says Venkatesh Murthy, leader of the Harvard group, but they “are right in the thick of things.” Neurons have typically gotten the most attention from researchers because they are the brain cells that do all the thinking. But neurons cohabit the brain with a class of cells called glia, which means “glue” in Greek. Glia outnumber neurons in the human brain by a factor of 10 to one, and astrocytes are the most abundant type of glial cell. The view of astrocytes has changed slowly over the past decade. Astrocytes were once thought to do little more than hold the brain together and they were largely ignored. In recent years, though, scientists have learned that the star-shaped cells have a hand in guiding connections between neurons and controlling levels of chemical messengers in the brain. But those activities were viewed mainly as supporting roles. Now their central function in controlling blood flow indicates that astrocytes deserve higher billing. Without astrocytes, in fact, one of the most powerful tools of neuroscience — functional MRI — would not be possible. © Society for Science & the Public 2000 - 2008

Related chapters from BN: Chapter 2: Functional Neuroanatomy: The Cells and Structure of the Nervous System
Related chapters from MM:Chapter 1: Cells and Structures: The Anatomy of the Nervous System
Link ID: 11810 - Posted: 06.24.2010

By Nikhil Swaminathan Nearly a century after the discovery of strange star-shaped cells in the brain, scientists say they have finally begun to unravel their function. Researchers from the Massachusetts Institute of Technology report in Science that it appears astrocytes—named for their stellar form—provide nerve cells (neurons) with the energy they need to function and communicate with one another, by signaling blood to deliver the cell fuels glucose and oxygen to them. When astrocytes were first discovered, it was believed that they were bit players in the brain. But the new research indicates they may actually be major operators that, when out of whack, may help trigger mental disorders such as autism and schizophrenia. Study coauthor Mriganka Sur, a neuroscientist and head of MIT's Department of Brain and Cognitive Science, says his team saw astrocytes in action while examining brain activity in ferrets. Using technology called two-photon microscopy, Sur and his colleagues observed that astrocytes in the visual cortex (part of the brain responsible for vision) activated and blood flow increased to nerve cells just seconds after the neurons had fired or sent out signals. © 1996-2008 Scientific American Inc.

Related chapters from BN: Chapter 2: Functional Neuroanatomy: The Cells and Structure of the Nervous System
Related chapters from MM:Chapter 1: Cells and Structures: The Anatomy of the Nervous System
Link ID: 11733 - Posted: 06.24.2010

ST. PAUL, Minn. - On the slaughterhouse floor at Quality Pork Processors Inc. is an area known as the "head table," but not because it is the place of honor. It is where workers cut up pigs' heads and then shoot compressed air into the skulls until the brains come spilling out. But now the grisly practice has come under suspicion from U.S. health authorities. Over eight months from last December through July, 11 workers at the Austin, Minn., plant — all of them employed at the head table — developed numbness, tingling or other neurological symptoms, and some scientists suspect inhaled airborne brain matter may have somehow triggered the illnesses. The use of compressed air to remove pig brains was suspended at Quality Pork earlier this week while authorities try to get to the bottom of the mystery. "I'm still in shock, I guess," said 37-year-old Susan Kruse, who worked at the plant for 15 years until she got too weak to do her job last February. "But it was very surprising to hear that there was that many other people that have gotten this." Five of the workers — including Kruse, who has been told she may never work again — have been diagnosed with chronic inflammatory demyelinating polyneuropathy, or CIDP, a rare immune disorder that attacks the nerves and produces tingling, numbness and weakness in the arms and legs, sometimes causing lasting damage. © 2007 The Associated Press.

Related chapters from BN: Chapter 3: Neurophysiology: The Generation, Transmission, and Integration of Neural Signals; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 2: Neurophysiology: The Generation, Transmission, and Integration of Neural Signals; Chapter 11: Emotions, Aggression, and Stress
Link ID: 11062 - Posted: 06.24.2010

Declan Butler Two children with a common neurodegenerative disease are seeing early signs of success from a pioneering gene-therapy treatment, researchers report this week. The results raise hopes for a treatment for adrenoleukodystrophy (ALD), and, the researchers add, mark the first successful use of an attenuated HIV virus to carry a therapeutic gene into a patient’s cells. HIV is a promising vector for transferring corrective genes into a host — it can penetrate directly into cell nuclei, making it a theoretically efficient way to introduce new genetic material. But until now it hadn’t been proven in a clinical setting. This early success potentially opens the door to better treatments for many other diseases involving the bone marrow and blood cells, such as leukaemia, thalassemia and sickle-cell disease, the researchers say. The results, from two 7-year-old Spanish children with ALD, were announced on Sunday 28 October at the fifteenth Congress of the European Society of Gene and Cell Therapy in Rotterdam, the Netherlands ALD is caused by a mutation on the X chromosome. This mutation causes degradation of the insulating sheaths that surround neurons and allow them to signal properly. The condition was made famous by Lorenzo's Oil , the Hollywood film outlining one family’s fight to help their son. The most severe, cerebral form of ALD affects one in 17,000 people, with two-thirds of sufferers being children. It progresses slowly at first, but if no bone-marrow transplant is available it can quickly progress to cause brain damage and death. © 2007 Nature Publishing Group

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 4: Development of the Brain
Link ID: 10905 - Posted: 06.24.2010

Electrical impulses foster myelination, the insulation process that speeds communication among brain cells, report researchers at two institutes of the National Institutes of Health. “This finding provides important information that may lead to a greater understanding of disorders such as multiple sclerosis that affect myelin, as well as a greater understanding of the learning process,” said Duane Alexander, M.D., Director of the NICHD. The study appears in the March 16 Neuron and was conducted by researchers at the National Institute of Child Health and Human Development and the National Cancer Institute. Neurons — specialized cells of the brain and nervous system — communicate via a relay system of electrical impulses and specialized molecules called neurotransmitters, explained the study’s senior author, R. Douglas Fields, Ph.D., Head of NICHD’s Nervous System Development and Plasticity Section. A neuron generates an electrical impulse, causing the cell to release its neurotransmitters, he said. The neurotransmitters, in turn, bind to nearby neurons. The recipient neurons then generate their own electrical impulses and release their own neurotransmitters, triggering the process in still more neurons, and so on. Neurons conduct electrical impulses more efficiently if they are covered with an insulating material known as myelin, Dr. Fields added. Layers of myelin are wrapped around the fiber-like projections of neurons like electrical tape wrapped spiral-fashion around an electrical cable. Human beings are born with comparatively little myelin, and neurons become coated with the material as they develop. Moreover, mental activity appears to influence myelination, Dr Fields said. For example, neglected children have less myelin in certain brain regions than do other children.

Related chapters from BN: Chapter 3: Neurophysiology: The Generation, Transmission, and Integration of Neural Signals; Chapter 2: Functional Neuroanatomy: The Cells and Structure of the Nervous System
Related chapters from MM:Chapter 2: Neurophysiology: The Generation, Transmission, and Integration of Neural Signals; Chapter 1: Cells and Structures: The Anatomy of the Nervous System
Link ID: 8664 - Posted: 06.24.2010

— Researchers have discovered that astrocytes — brain cells once thought to be little more than a component of the supportive scaffold for neurons — may actually play a starring role in triggering the maturation and proliferation of adult neural stem cells. The studies also suggest that growth factors produced by astrocytes may be critical in regenerating brain or spinal tissue that has been damaged by trauma or disease. The discovery that astrocytes are important for neuronal maturation, or neurogenesis, was reported in the May 2, 2002, issue of the journal Nature by Howard Hughes Medical Institute investigator Charles F. Stevens and colleagues Fred H. Gage and HHMI research associate Hong-jun Song at The Salk Institute. Neurons are the key information-carrying cells in the central nervous system. All neurons, as well as other types of brain cells, arise from immature neural stem cells, which have the potential to develop into any kind of cell in the central nervous system. ©2002 Howard Hughes Medical Institute

Related chapters from BN: Chapter 2: Functional Neuroanatomy: The Cells and Structure of the Nervous System; Chapter 19: Language and Lateralization
Related chapters from MM:Chapter 1: Cells and Structures: The Anatomy of the Nervous System; Chapter 15: Language and Lateralization
Link ID: 2005 - Posted: 06.24.2010

Tampa, FL — Researchers at the University of South Florida's Roskamp Institute have identified an immune molecule, CD40, on the surface of neurons that appears to promote both neuron development and protection. The finding is a first step in defining the role of CD40 in the brain at different stages of life and evaluating its usefulness in helping neurons survive. The study is published in the latest March issue of the journal European Molecular Biology Organization. In the bloodstream, the interaction between the protein receptor CD40 and another protein, CD40 ligand (CD40L), allows white cells to trigger antibody production and to activate cellular immunity. This immune response helps neutralize foreign invaders, such as bacteria and viruses. However, in an earlier study, the USF reseachers found that when this same CD40-CD40L signaling system is triggered in the brain, the immune response can cause microglia damage to neurons.

Related chapters from BN: Chapter 15: Emotions, Aggression, and Stress; Chapter 2: Functional Neuroanatomy: The Cells and Structure of the Nervous System
Related chapters from MM:Chapter 11: Emotions, Aggression, and Stress; Chapter 1: Cells and Structures: The Anatomy of the Nervous System
Link ID: 1796 - Posted: 06.24.2010

By Tina Hesman Saey Scientists have discovered the true identity of a contagious form of cancer that is killing Tasmanian devils. The cancer, called devil facial tumor disease, stems from cells that normally insulate nerve fibers, a new study shows. Genetic analysis of tumors taken from infected devils in different parts of Tasmania reveals that these insulating cells, known as Schwann cells, became cancerous in a single Tasmanian devil and have since passed to other devils, an international group of researchers reports in the Jan. 1 Science. Previously, scientists had suspected that a virus might be the source of the infection, but the new study confirms that cancer cells themselves are transmitted from devil to devil. Knowing the origin of the contagious tumors could help conservationists diagnose the disease more accurately and may eventually lead to a vaccine that would target tumor proteins, says Katherine Belov, a geneticist at the University of Sydney who was not involved with the project. A vaccine against the facial tumor disease, “while now pie in the sky, in 10 years might not be,” says Gregory Hannon, a Howard Hughes Medical Institute investigator at Cold Spring Harbor Laboratory on Long Island, N.Y. “Ten years might be enough time” to save the devils from extinction, he says. © Society for Science & the Public 2000 - 2010

Related chapters from BN: Chapter 2: Functional Neuroanatomy: The Cells and Structure of the Nervous System
Related chapters from MM:Chapter 1: Cells and Structures: The Anatomy of the Nervous System
Link ID: 13620 - Posted: 06.24.2010

By Cassandra Willyard Think back to high school biology. Remember the long, stringy neurons that make up your nervous system? You probably learned that these cells communicate by sending a chemical message across the small gap between them, called a synapse. That's still true, but new research shows that certain brain cells bypass the synapse altogether. Instead, they communicate by spraying a cloud of neurotransmitters into the spaces between cells, blanketing nearby neurons. A team of Hungarian researchers at the University of Szeged made the discovery by examining a type of neuron called a neurogliaform cell. These cells are common in the brain's cortex, a region that plays a key role in many functions, including memory, attention, awareness, and language. Studies have shown that neurogliaform cells can inhibit the firing of other brain cells by releasing a neurotransmitter called GABA (gamma-aminobutyric acid), which typically transmits messages across synapses. But some studies have suggested that GABA can diffuse into the extracellular space as well, where it carries messages between neurons not connected via synapses. To create enough ambient GABA for this to happen, however, scientists speculated that many neurons would have to fire at once. The researchers set out to test this idea. The output end, or axon, of a normal neuron is typically long and stringy. But when the Hungarian team used electron and light microscopes to examine brain tissue from rats and humans, they found that neurogliaform cells have bushy axons with many branches. These bushy axons are densely populated with sites where GABA can be released into the extracellular space, the team found. Elsewhere in the brain this occurs mainly at synapses, but only 11 of the 50 release sites examined in neurogliaform cells corresponded to a synapse, the researchers report today in Nature. © 2009 American Association for the Advancement of Science.

Related chapters from BN: Chapter 2: Functional Neuroanatomy: The Cells and Structure of the Nervous System; Chapter 4: The Chemistry of Behavior: Neurotransmitters and Neuropharmacology
Related chapters from MM:Chapter 1: Cells and Structures: The Anatomy of the Nervous System; Chapter 3: The Chemistry of Behavior: Neurotransmitters and Neuropharmacology
Link ID: 13417 - Posted: 06.24.2010

By Andrew Koob Andrew Koob received his Ph.D. in neuroscience from Purdue University in 2005, and has held research positions at Dartmouth College, the University of California, San Diego, and the University of Munich, Germany. He's also the author of The Root of Thought, which explores the purpose and function of glial cells, the most abundant cell type in the brain. Mind Matters editor Jonah Lehrer chats with Koob about why glia have been overlooked for centuries, and how new experiments with glial cells shed light on some of the most mysterious aspects of the mind. LEHRER: Your new book, The Root of Thought, is all about the power of glial cells, which actually make up nearly 90 percent of cells in the brain. What do glial cells do? And why do we have so many inside our head? KOOB: Originally, scientists didn't think they did anything. Until the last 20 years, brain scientists believed neurons communicated to each other, represented our thoughts, and that glia were kind of like stucco and mortar holding the house together. They were considered simple insulators for neuron communication. There are a few types of glial cells, but recently scientists have begun to focus on a particular type of glial cell called the 'astrocyte,' as they are abundant in the cortex. Interestingly, as you go up the evolutionary ladder, astrocytes in the cortex increase in size and number, with humans having the most astrocytes and also the biggest. Scientists have also discovered that astrocytes communicate to themselves in the cortex and are also capable of sending information to neurons. Finally, astrocytes are also the adult stem cell in the brain and control blood flow to regions of brain activity. Because of all these important properties, and since the cortex is believed responsible for higher thought, scientists have started to realize that astrocytes must contribute to thought. © 1996-2009 Scientific American Inc.

Related chapters from BN: Chapter 2: Functional Neuroanatomy: The Cells and Structure of the Nervous System; Chapter 19: Language and Lateralization
Related chapters from MM:Chapter 1: Cells and Structures: The Anatomy of the Nervous System; Chapter 15: Language and Lateralization
Link ID: 13412 - Posted: 06.24.2010

ROCHESTER, N.Y., (UPI) -- U.S. researchers say they've discovered brain cells called astrocytes are what distinguish the human brain from that of other animals. "Studies in rodents show that non-neuronal cells are part of information processing," said Dr. Maiken Nedergaard of the University of Rochester Medical Center, who led the research team. "And our study suggests that astrocytes are part of the higher cognitive functioning that defines who we are as humans." The scientists noted there are 10 times as many astrocytes in the brain than the neurons that send electrical signals. Medical student Nancy Ann Oberheim, first author of the study, said human astrocytes signals are faster, bigger and more complex than those found in mice and rats. The researchers discovered new types of astrocytes, and also determined astrocytes use calcium, rather than electrical signals, to communicate with neurons. The research team reported astrocytes send much slower signals that do neurons, but are just as important in the basic working of the brain. The study that included scientists from New York Medical College and the University of Washington appears in the Journal of Neuroscience. © 2009 United Press International, Inc.

Related chapters from BN: Chapter 2: Functional Neuroanatomy: The Cells and Structure of the Nervous System; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 1: Cells and Structures: The Anatomy of the Nervous System
Link ID: 12695 - Posted: 06.24.2010