Chapter 2. Cells and Structures: The Anatomy of the Nervous System
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When anticonvulsant drugs fail to control epilepsy, surgery can be used as a last resort: removing the part of the brain thought to be the source of someone’s seizures. Unfortunately, this doesn’t always work. A computer model of brain activity could change things for the better by allowing surgeons to more precisely tailor the procedure to the individual. Seizures are caused by sudden surges in electrical activity in the brain. EEG scans made during a seizure can capture what is going on, providing a clue to the part of the brain that needs to be cut out. Even so, the surgery still fails to prevent seizures in 30 per cent of cases. There are other ways to track down the source of someone’s seizures, however. For example, the connectivity of the brain’s neurons and the surface area of affected regions is different in people with epilepsy compared with those who do not have the condition. Frances Hutchings at Newcastle University, UK and her colleagues have shown that these differences can be picked up using a combination of fMRI scans and diffusion tensor imaging (DTI). They used this data to model the brains of 22 people with epilepsy. By simulating the brain’s electrical activity, they were able to see where it went awry and identify the region where seizures were most likely to originate in each individual. © Copyright Reed Business Information Ltd.
The road map of conscious awareness has been deciphered. Now that we know which brain pathways control whether someone is awake or unconscious, we may be able to rouse people from a vegetative or minimally conscious state. In 2007, researchers used deep brain stimulation to wake a man from a minimally conscious state. It was quite remarkable, says Jin Lee at Stanford University in California. The 38-year-old had suffered a severe brain injury in a street mugging six years earlier. Before his treatment he was unable to communicate and had no voluntary control over his limbs. When doctors stimulated his thalamus – a central hub that sends signals all around the brain – his speech and movement gradually returned. However, attempts to treat other people in a similar way have failed. The problem lies with the crudeness of the technique. “Deep brain stimulation is done without much knowledge of how it actually alters the circuits in the brain,” says Lin. The technique involves attaching electrodes to the brain and using them to stimulate the tissue beneath. Unfortunately, the electrodes can also stimulate unintended areas, which means it is hard to work out exactly what is happening in people’s brains. “There are a lot of fibres and different cells in the thalamus and working out what was going on in the brain was very difficult,” says Lin. “So we wanted to figure it out.” © Copyright Reed Business Information Ltd.
Laura Sanders You can thank your parents for your funny-looking hippocampus. Genes influence the three-dimensional shape of certain brain structures, scientists report in a paper posted online December 1 at bioRxiv.org. Showing a new way that genes help sculpt the brain opens up more ways to explore how the brain develops and operates. Earlier work linked genes to simple measurements of brain structures, such as overall volume or length. The new work goes beyond that by mathematically analyzing complex 3-D shapes and tying those shapes to a particular genetic makeup. A team led by researchers at Massachusetts General Hospital and Harvard Medical School analyzed MRI brain scans and genome data from 1,317 healthy young adults. Particular genetic profiles influenced the 3-D shape of structures including the hippocampus, caudate and cerebellum, the scientists found. In some brains, for instance, genes played a role in making the seahorse-shaped right hippocampus skinnier on the top and wider on the bottom. Genes also influenced whether the tail of the caudate was short or long. Quirks of brain structure shapes might play a role in disorders such as schizophrenia, autism spectrum disorder and bipolar disorder, which are known to be influenced by genes, the authors write. Citations T. Ge et al. Heritability of neuroanatomical shape. bioRxiv.org. Posted December 1, 2015. doi: 10.1101/033407. © Society for Science & the Public 2000 - 2015
Sara Reardon Manipulating brain circuits with light and drugs can cause ripple effects that could muddy experimental results. In the tightly woven networks of the brain, tugging one neuronal thread can unravel numerous circuits. Because of that, the authors of a paper1 published in Nature on 9 December caution that techniques such as optogenetics — activating neurons with light to control brain circuits — and manipulation with drugs could lead researchers to jump to unwarranted conclusions. In work with rats and zebra finches, neuroscientist Bence Ölveczky of Harvard University in Cambridge, Massachusetts, and his team found that stimulating one part of the brain to induce certain behaviours might cause other, unrelated parts to fire simultaneously, and so make it seem as if these circuits are also involved in the behaviour. According to Ölveczky, the experiments suggest that although techniques such as optogenetics may show that a circuit can perform a function, they do not necessarily show that it normally performs that function. “I don’t want to say other studies have been wrong, but there is a danger to overinterpreting,” he says. Ölveczky and his colleagues discovered these discrepancies by chance while studying rats that they had trained to press a lever in a certain pattern. They injected a drug called muscimol, which temporarilty shuts off neurons, into a part of the motor cortex that is involved in paw movement. The animals were no longer able to perform the task, which might be taken as evidence that neurons in this brain region were necessary to its performance. © 2015 Nature Publishing Group
Keyword: Brain imaging
Link ID: 21690 - Posted: 12.10.2015
Laura Sanders People who use especially potent pot show signs of damage in a key part of their brain. The results, reported online November 27 in Psychological Medicine, are limited, though: The small brain scanning study doesn’t show that marijuana caused the brain abnormality — only that the two go hand-in-hand. But the findings suggest that potency matters, says study coauthor Tiago Reis Marques, a psychiatrist at King’s College London. “We are no longer talking about smoking cannabis or not smoking cannabis,” Reis Marques says. Just as vodka packs more of a punch than beer, a high-potency toke delivers much more of the psychoactive substance tetrahydrocannabinol, or THC. A bigger dose of THC may have stronger effects on the brain, Reis Marques says. That’s important because as marijuana plant breeders perfect their products, THC levels have soared. Samples sold in Colorado, for instance, now have about three times as much THC as plants grown 30 years ago, a recent survey found (SN Online: 3/24/15). Reis Marques and his colleagues scanned the brains of 43 healthy people, about half of whom use cannabis. The researchers used a method called diffusion tensor imaging to study the structure of the brain’s white matter, neural highways that carry messages between brain areas. Participants gave a detailed history of their past drug use, including information about how potent their marijuana was. POT HEAD The corpus callosum — white matter that links the left brain to the right — is weaker in people who smoke high-potency cannabis, a new study suggests. © Society for Science & the Public 2000 - 2015.
A new, open-source software that can help track the embryonic development and movement of neuronal cells throughout the body of the worm, is now available to scientists. The software is described in a paper published in the open access journal, eLife on December 3rd by researchers at the National Institute of Biomedical Imaging and Bioengineering (NIBIB) and the Center for Information Technology (CIT); along with Memorial Sloan-Kettering Institute, New York City; Yale University, New Haven, Connecticut; Zhejiang University, China; and the University of Connecticut Health Center, Farmington. NIBIB is part of the National Institutes of Health. As far as biologists have come in understanding the brain, much remains to be revealed. One significant challenge is determining the formation of complex neuronal structures made up of billions of cells in the human brain. As with many biological challenges, researchers are first examining this question in simpler organisms, such as worms. Although scientists have identified a number of important proteins that determine how neurons navigate during brain formation, it’s largely unknown how all of these proteins interact in a living organism. Model animals, despite their differences from humans, have already revealed much about human physiology because they are much simpler and easier to understand. In this case, researchers chose Caenorhabditis elegans (C. elegans), because it has only 302 neurons, 222 of which form while the worm is still an embryo. While some of these neurons go to the worm nerve ring (brain) they also spread along the ventral nerve cord, which is broadly analogous to the spinal cord in humans. The worm even has its own versions of many of the same proteins used to direct brain formation in more complex organisms such as flies, mice, or humans.
By Diana Kwon The human brain is unique: Our remarkable cognitive capacity has allowed us to invent the wheel, build the pyramids and land on the moon. In fact, scientists sometimes refer to the human brain as the “crowning achievement of evolution.” But what, exactly, makes our brains so special? Some leading arguments have been that our brains have more neurons and expend more energy than would be expected for our size, and that our cerebral cortex, which is responsible for higher cognition, is disproportionately large—accounting for over 80 percent of our total brain mass. Suzana Herculano-Houzel, a neuroscientist at the Institute of Biomedical Science in Rio de Janeiro, debunked these well-established beliefs in recent years when she discovered a novel way of counting neurons—dissolving brains into a homogenous mixture, or “brain soup.” Using this technique she found the number of neurons relative to brain size to be consistent with other primates, and that the cerebral cortex, the region responsible for higher cognition, only holds around 20 percent of all our brain’s neurons, a similar proportion found in other mammals. In light of these findings, she argues that the human brain is actually just a linearly scaled-up primate brain that grew in size as we started to consume more calories, thanks to the advent of cooked food. Other researchers have found that traits once believed to belong solely to humans also exist in other members of the animal kingdom. Monkeys have a sense of fairness. Chimps engage in war. Rats show altruism and exhibit empathy. In a study published last week in Nature Communications, neuroscientist Christopher Petkov and his group at Newcastle University found that macaques and humans share brain areas responsible for processing the basic structures of language. © 2015 Scientific American
Ian Sample Science editor High-strength cannabis may damage nerve fibres that handle the flow of messages across the two halves of the brain, scientists claim. Brain scans of people who regularly smoked strong skunk-like cannabis revealed subtle differences in the white matter that connects the left and right hemispheres and carries signals from one side of the brain to the other. The changes were not seen in those who never used cannabis or smoked only the less potent forms of the drug, the researchers found. The study is thought to be the first to look at the effects of cannabis potency on brain structure, and suggests that greater use of skunk may cause more damage to the corpus callosum, making communications across the brain’s hemispheres less efficient. Paola Dazzan, a neurobiologist at the Institute of Psychiatry at King’s College London, said the effects appeared to be linked to the level of active ingredient, tetrahydrocannabinol (THC), in cannabis. While traditional forms of cannabis contain 2 to 4 % THC, the more potent varieties (of which there are about 100), can contain 10 to 14% THC, according to the DrugScope charity. “If you look at the corpus callosum, what we’re seeing is a significant difference in the white matter between those who use high potency cannabis and those who never use the drug, or use the low-potency drug,” said Dazzan. The corpus callosum is rich in cannabinoid receptors, on which the THC chemical acts. © 2015 Guardian News and Media Limited
Sara Reardon Suicide is a puzzle. Fewer than 10% of people with depression attempt suicide, and about 10% of those who kill themselves were never diagnosed with any mental-health condition. Now, a study is trying to determine what happens in the brain when a person attempts suicide, and what sets such people apart. The results could help researchers to understand whether suicide is driven by certain brain biology — and is not just a symptom of a recognized mental disorder. The project, which launched this month, will recruit 50 people who have attempted suicide in the two weeks before enrolling in the study. Carlos Zarate, a psychiatrist at the US National Institute of Mental Health in Bethesda, Maryland, and his colleagues will compare these people's brain structure and function to that of 40 people who attempted suicide more than a year ago, 40 people with depression or anxiety who have never attempted suicide and a control group of 40 healthy people. In doing so, the researchers hope to elucidate the brain mechanisms associated with the impulse to kill oneself. Zarate's team will also give ketamine, a psychoactive ‘party drug’, to the group that has recently attempted suicide. Ketamine, which is sometimes used to treat depression, can quickly arrest suicidal thoughts and behaviour — even in cases when it does not affect other symptoms of depression1. The effect is known to last for about a week. © 2015 Nature Publishing Group,
Sara Reardon Panzee the chimpanzee was a skilled communicator that could tell untrained humans where to find hidden food by using gestures and vocalizations. Austin the chimp was particularly adept with a computer, and scientists have been scanning its genome for clues to its unusual cognitive abilities. Both apes lived at a language-research centre at Georgia State University in Atlanta, and both died several years ago — but they will live on in an online database of brain scans and behavioural data from nearly 250 chimpanzees. Researchers hope to combine this trove, now in development, with a biobank of chimpanzee brains to enable scientists anywhere in the world to study the animals’ neurobiology. This push to repurpose old data is especially timely now that the US National Institutes of Health (NIH) has decided to retire its remaining research chimpanzees. The agency decommissioned more than 300 animals in 2013, but kept 50 available for research in case of a public-health emergency. Following an 18 November decision, this remaining population will also be sent to sanctuaries in the coming years. The NIH also hopes to retire another 82 chimps that it supports but does not own, says director Francis Collins. “We were on a trajectory toward zero, and today’s the day we’re at zero,” says Jeffrey Kahn, a bioethicist at Johns Hopkins University in Baltimore, Maryland, who led a 2011 study on the NIH chimp colony for the Institute of Medicine. © 2015 Nature Publishing Group
Jon Hamilton A look at the brain's wiring can often reveal whether a person has trouble staying focused, and even whether they have attention deficit hyperactivity disorder, known as ADHD. A team led by researchers at Yale University reports that they were able to identify many children and adolescents with ADHD by studying data on the strength of certain connections in their brains. "There's an intrinsic signature," says Monica Rosenberg, a graduate student and lead author of the study in Nature Neuroscience. But the approach isn't ready for use as a diagnostic tool yet, she says. The finding adds to the evidence that people with ADHD have a true brain disorder, not just a behavioral problem, says Mark Mahone, director of neuropsychology at the Kennedy Krieger institute in Baltimore. "There are measurable ways that their brains are different," he says. The latest finding came from an effort to learn more about brain connections associated with attention. Initially, the Yale team used functional MRI, a form of magnetic resonance imaging, to monitor the brains of 25 typical people while they did something really boring. Their task was to watch a screen that showed black-and-white images of cities or mountains and press a button only when they saw a city. © 2015 npr
Jon Hamilton Patterns of gene expression in human and mouse brains suggest that cells known as glial cells may have helped us evolve brains that can acquire language and solve complex problems. Scientists have been dissecting human brains for centuries. But nobody can explain precisely what allows people to use language, solve problems or tell jokes, says Ed Lein, an investigator at the Allen Institute for Brain Science in Seattle. "Clearly we have a much bigger behavioral repertoire and cognitive abilities that are not seen in other animals," he says. "But it's really not clear what elements of the brain are responsible for these differences." Research by Lein and others provides a hint though. The difference may involve brain cells known as glial cells, once dismissed as mere support cells for neurons, which send and receive electrical signals in the brain. Lein and a team of researchers made that finding after studying which genes are expressed, or switched on, in different areas of the brain. The effort analyzed the expression of 20,000 genes in 132 structures in brains from six typical people. Usually this sort of study is asking whether there are genetic differences among brains, Lein says. "And we sort of flipped this question on its head and we asked instead, 'What's really common across all individuals and what elements of this seem to be unique to the human brain?' " he says. It turned out the six brains had a lot in common. © 2015
Sarah Schwartz With outposts in nearly every organ and a direct line into the brain stem, the vagus nerve is the nervous system’s superhighway. About 80 percent of its nerve fibers — or four of its five “lanes” — drive information from the body to the brain. Its fifth lane runs in the opposite direction, shuttling signals from the brain throughout the body. Doctors have long exploited the nerve’s influence on the brain to combat epilepsy and depression. Electrical stimulation of the vagus through a surgically implanted device has already been approved by the U.S. Food and Drug Administration as a therapy for patients who don’t get relief from existing treatments. Now, researchers are taking a closer look at the nerve to see if stimulating its fibers can improve treatments for rheumatoid arthritis,heart failure, diabetes and even intractable hiccups. In one recent study, vagus stimulation made damaged hearts beat more regularly and pump blood more efficiently. Researchers are now testing new tools to replace implants with external zappers that stimulate the nerve through the skin. But there’s a lot left to learn. While studies continue to explore its broad potential, much about the vagus remains a mystery. In some cases, it’s not yet clear exactly how the nerve exerts its influence. And researchers are still figuring out where and how to best apply electricity. © Society for Science & the Public 2000 - 2015.
Link ID: 21633 - Posted: 11.14.2015
For the first time, the barrier that protects the brain has been opened without damaging it, to deliver chemotherapy drugs to a tumour. The breakthrough could be used to treat pernicious brain diseases such as cancer, Parkinson’s and Alzheimer’s, by allowing drugs to pass into the brain. The blood-brain barrier keeps toxins in the bloodstream away from the brain. It consists of a tightly packed layer of endothelial cells that wrap around every blood vessel throughout the brain. It prevents the passage of viruses, bacteria and other toxins, while ushering in vital molecules such as glucose via specialised transport mechanisms. The downside of this is that the blood-brain barrier also blocks the vast majority of drugs. There are a few exceptions, but those drugs that are able to sneak through can also penetrate every cell in the body, which makes for major side effects. Now researchers at Sunnybrook Health Sciences Centre in Toronto, Canada, say they have successfully used ultrasound to temporarily open the blood-brain barrier, with the ultimate aim of treating a brain tumour. The procedure took place on 4 November. Ultrasound prises open brain's protective barrier for first time The team, led by neurosurgeon Todd Mainprize and physicist Kullervo Hynynen, injected the chemotherapy drug doxorubicin along with tiny gas-filled microbubbles, into the blood of a patient with a brain tumour. The microbubbles and the drug spread throughout their body, including into the blood vessels that serve the brain. © Copyright Reed Business Information Ltd.
By Simon Makin Optogenetics is probably the biggest buzzword in neuroscience today. It refers to techniques that use genetic modification of cells so they can be manipulated with light. The net result is a switch that can turn brain cells off and on like a bedside lamp. The technique has enabled neuroscientists to achieve previously unimagined feats and two of its inventors—Karl Deisseroth of Stanford University and the Howard Hughes Medical Institute and Ed Boyden of Massachusetts Institute of Technology—received a Breakthrough Prize in the life sciences on November 8 in recognition of their efforts. The technology is able to remotely control motor circuits—one example is having an animal run in circles at the flick of a switch. It can even label and alter memories that form as a mouse explores different environments. These types of studies allow researchers to firmly establish a cause-and-effect relationship between electrical activity in specific neural circuits and various aspects of behavior and cognition, making optogenetics one of the most widely used methods in neuroscience today. As its popularity soars, new tricks are continually added to the optogenetic arsenal. The latest breakthroughs, promise to deliver the biggest step forward for the technology since its inception. Researchers have devised ways of broadening optogenetics to enter into a dynamic dialogue with the signals moving about inside functioning brains. © 2015 Scientific American
Keyword: Brain imaging
Link ID: 21621 - Posted: 11.10.2015
Laura Sanders Blood tells a story about the body it inhabits. As it pumps through vessels, delivering nutrients and oxygen, the ruby red liquid picks up information. Hormones carried by blood can hint at how hungry a person is, or how scared, or how sleepy. Other messages in the blood can warn of heart disease or announce a pregnancy. When it comes to the brain, blood also seems to be more than a traveling storyteller. In some cases, the blood may be writing the script. A well-fed brain is crucial to survival. Blood ebbs and flows within the brain, moving into active areas in response to the brain’s demands for fuel. Now scientists have found clues that blood may have an even more direct and powerful influence. Early experiments suggest that, instead of being at the beck and call of nerve cells, blood can actually control them. This role reversal hints at an underappreciated layer of complexity — a layer that may turn out to be vital to how the brain works. The give-and-take between brain and blood appears to change with age and with illness, researchers are finding. Just as babies aren’t born walking, their developing brain cells have to learn how to call for blood. And a range of age-related disorders, including Alzheimer’s disease, have been linked to dropped calls between blood and brain, a silence that may leave patches of brain unable to do their jobs. © Society for Science & the Public 2000 - 2015
Keyword: Brain imaging
Link ID: 21604 - Posted: 11.05.2015
Alison Abbott Europe’s troubled Human Brain Project (HBP) has secured guarantees of European Commission financing until at least 2019 — but some scientists are still not sure that they want to take part in the mega-project, which has been fraught with controversy since its launch two years ago. On 30 October, the commission signed an agreement formally committing to fund the HBP past April 2016, when its preliminary 30-month ‘ramp-up’ phase ends. The deal also starts a process to change the project’s legal status so as to spread responsibility across many participating institutions. The commission hopes that this agreement will restore lost confidence in the HBP, which aims to better understand the brain using information and computing technologies, primarily through simulation. Last year, hundreds of scientists signed a petition claiming that the project was being mismanaged and was running off its scientific course; they pledged to boycott it if their concerns were ignored. Since then, the HBP has been substantially reformed along lines recommended by a mediation committee. It has dissolved its three-person executive board, which had assumed most of the management power. And it has committed to including studies on cognitive neuroscience (which the triumvirate had wanted to eliminate). It also opened up for general competition some €8.9 million ($US10 million) of cash previously allocated only to project insiders, and in September selected four major projects in systems and cognitive neuroscience proposed by different groups around Europe. © 2015 Nature Publishing Group
Keyword: Brain imaging
Link ID: 21596 - Posted: 11.03.2015
By Diana Kwon Microglia, the immune cells of the brain, have long been the underdogs of the glia world, passed over for other, flashier cousins, such as astrocytes. Although microglia are best known for being the brain’s primary defenders, scientists now realize that they play a role in the developing brain and may also be implicated in developmental and neurodegenerative disorders. The change in attitude is clear, as evidenced by the buzz around this topic at this year’s Society for Neuroscience (SfN) conference, which took place from October 17 to 21 in Chicago, where scientists discussed their role in both health and disease. Activated in the diseased brain, microglia find injured neurons and strip away the synapses, the connections between them. These cells make up around 10 percent of all the cells in the brain and appear during early development. For decades scientists focused on them as immune cells and thought that they were quiet and passive in the absence of an outside invader. That all changed in 2005, when experimenters found that microglia were actually the fastest-moving structures in a healthy adult brain. Later discoveries revealed that their branches were reaching out to surrounding neurons and contacting synapses. These findings suggested that these cellular scavengers were involved in functions beyond disease. The discovery that microglia were active in the healthy brain jump-started the exploration into their underlying mechanisms: Why do these cells hang around synapses? And what are they doing? © 2015 Scientific American
By Emily Underwood CHICAGO—In 1898, Italian biologist Camillo Golgi found something odd as he examined slices of brain tissue under his microscope. Weblike lattices, now known as "perineuronal nets," surrounded many neurons, but he could not discern their purpose. Many dismissed the nets as an artifact of Golgi's staining technique; for the next century, they remained largely obscure. Today, here at the annual meeting of the Society for Neuroscience, researchers offered tantalizing new evidence that holes in these nets could be where long-term memories are stored. Scientists now know that perineuronal nets (PNNS) are scaffolds of linked proteins and sugars that resemble cartilage, says neuroscientist Sakina Palida, a graduate student in Roger Tsien's lab at the University of California,San Diego, and co-investigator on the study. Although it's still unclear precisely what the nets do, a growing body of research suggests that PNNs may control the formation and function of synapses, the microscopic junctions between neurons that allow cells to communicate, and that may play a role in learning and memory, Palida says. One of the most pressing questions in neuroscience is how memories—particularly long-term ones—are stored in the brain, given that most of the proteins inside neurons are constantly being replaced, refreshing themselves anywhere from every few days to every few hours. To last a lifetime, Palida says, some scientists believe that memories must somehow be encoded in a persistent, stable molecular structure. Inspired in part by evidence that destroying the nets in some brain regions can reverse deeply ingrained behaviors, Palida’s adviser Tsien, a Nobel-prize-winning chemist, recently began to explore whether PNNs could be that structure. Adding to the evidence were a number of recent studies linking abnormal PNNs to brain disorders including schizophrenia and Costello syndrome, a form of intellectual disability. © 2015 American Association for the Advancement of Science.
Jon Hamilton Babies born prematurely are much more likely than other children to develop autism, ADHD and emotional disorders. Now researchers think they may have an idea about how that could happen. There's evidence that preemies are born with weak connections in some critical brain networks, including those involved in focus, social interactions, and emotional processing, researchers reported at the Society for Neuroscience meeting in Chicago. A study comparing MRI scans of the brains of 58 full-term babies with those of 76 babies born at least 10 weeks early found that "preterm infants indeed have abnormal structural brain connections," says Cynthia Rogers, an assistant professor of psychiatry at Washington University School of Medicine in St. Louis. "We were really interested that the tracts that we know connect areas that are involved in attention and emotional networks were heavily affected," Rogers says. That would make it harder for these brain areas to work together to focus on a goal or read social cues or regulate emotions, she says. The team used two different types of MRI to study the nerve fibers that carry signals from one part of the brain to another and measure how well different areas of the brain are communicating. Full-term infants were scanned shortly after they were born, while premature infants were scanned near their expected due date. The researchers are continuing to monitor the brains of the children in their study to see which ones actually develop disorders. © 2015 NPR