Chapter 2. Cells and Structures: The Anatomy of the Nervous System
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By Christian Jarrett Imagine a politician from your party is in trouble for alleged misdemeanors. He’s been assessed by an expert who says he likely has early-stage Alzheimer’s. If this diagnosis is correct, your politician will have to resign, and he’ll be replaced by a candidate from an opposing party. This was the scenario presented to participants in a new study by Geoffrey Munro and Cynthia Munro. A vital twist was that half of the 106 student participants read a version of the story in which the dementia expert based his diagnosis on detailed cognitive tests; the other half read a version in which he used a structural MRI brain scan. All other story details were matched, such as the expert’s years of experience in the field, and the detail provided for the different techniques he used. Overall, the students found the MRI evidence more convincing than the cognitive tests. For example, 69.8 percent of those given the MRI scenario said the evidence the politician had Alzheimer’s was strong and convincing, whereas only 39.6 percent of students given the cognitive tests scenario said the same. MRI data was also seen to be more objective, valid and reliable. Focusing on just those students in both conditions who showed skepticism, over 15 percent who read the cognitive tests scenario mentioned the unreliability of the evidence; none of the students given the MRI scenario cited this reason. In reality, a diagnosis of probable Alzheimer’s will always be made with cognitive tests, with brain scans used to rule out other explanations for any observed test impairments. The researchers said their results are indicative of naive faith in the trustworthiness of brain imaging data. “When one contrasts the very detailed manuals accompanying cognitive tests to the absences of formalized operational criteria to guide the clinical interpretation of structural brain MRI in diagnosing disease, the perception that brain MRI is somehow immune to problems of reliability becomes even more perplexing,” they said. WIRED.com © 2015 Condé Nast.
By Francis Shen and Dena Gromet Neuroscience is appearing everywhere. And the legal system is taking notice. The past few years have seen the emergence of “neurolaw.” A spread in the NYT Magazine, a best-selling NYT book, a primetime PBS documentary, the first Law and Neuroscience casebook, and a multimillion-dollar investment from the MacArthur Foundation to fund a Research Network on Law and Neuroscience have all fueled interest in how neuroscience might revolutionize the law. The potential implications of neurolaw are broad. For example, future developments in brain science might allow: criminal law to better identify recidivists; tort law to better differentiate between those in real pain and those who are faking; insurance law to more accurately and adequately compensate those with mental illness; and end-of-life law to more ethically treat patients who might be able to communicate only through their thoughts. Increasingly courts, including the U.S. Supreme Court, and legislatures are citing brain evidence. But despite the media coverage, and much enthusiasm from science and legal elites, our new research shows that Americans know very little about neurolaw, and that Republicans and independents may diverge from Democrats in their support for neuroscience based legal reforms. In our study, we conducted an experiment within a national survey of Americans (more details about the survey are in our article). Everyone in the survey was told that, “Recently developed neuroscientific techniques allow researchers to see inside the human brain as never before.”
Sara Reardon Annie is lying down when she answers the phone; she is trying to recover from a rare trip out of the house. Moving around for an extended period leaves the 56-year-old exhausted and with excruciating pain shooting up her back to her shoulders. “It's really awful,” she says. “You never get comfortable.” In 2011, Annie, whose name has been changed at the request of her lawyer, slipped and fell on a wet floor in a restaurant, injuring her back and head. The pain has never eased, and forced her to leave her job in retail. Annie sued the restaurant, which has denied liability, for several hundred thousand dollars to cover medical bills and lost income. To bolster her case that she is in pain and not just malingering, Annie's lawyer suggested that she enlist the services of Millennium Magnetic Technologies (MMT), a Connecticut-based neuroimaging company that has a centre in Birmingham, Alabama, where Annie lives. MMT says that it can detect pain's signature using functional magnetic resonance imaging (fMRI), which measures and maps blood flow in the brain as a proxy for neural activity. The scan is not cheap — about US$4,500 — but Steven Levy, MMT's chief executive, says that it is a worthwhile investment: the company has had ten or so customers since it began offering the service in 2013, and all have settled out of court, he says. If the scans are admitted to Annie's trial, which is expected to take place early this year, it could establish a legal precedent in Alabama. Most personal-injury cases settle out of court, so it is impossible to document how often brain scans for pain are being used in civil law. But the practice seems to be getting more common, at least in the United States, where health care is not covered by the government and personal-injury cases are frequent. Several companies have cropped up, and at least one university has offered the service. © 2015 Nature Publishing Group
By Kate Baggaley Stem cells can help heal long-term brain damage suffered by rats blasted with radiation, researchers report in the Feb. 5 Cell Stem Cell. The treatment allows the brain to rebuild the insulation on its nerve cells so they can start carrying messages again. The researchers directed human stem cells to become a type of brain cell that is destroyed by radiation, a common cancer treatment, then grafted the cells into the brains of irradiated rats. Within a few months, the rats’ performance on learning and memory tests improved. “This technique, translated to humans, could be a major step forward for the treatment of radiation-induced brain … injury,” says Jonathan Glass, a neurologist at Emory University in Atlanta. Steve Goldman, a neurologist at the University of Rochester in New York, agrees that the treatment could repair a lot of the damage caused by radiation. “Radiation therapy … is very effective, but the problem is patients end up with severe disability,” he says. “Fuzzy thinking, a loss in higher intellectual functions, decreases in memory — all those are part and parcel of radiation therapy to the brain.” For children, the damage can be profound. “Those kids have really significant detriments in their adult IQs,” Goldman says. Radiation obliterates cells that mature into oligodendrocytes, a type of cell that coats the message-carrying part of nerve cells with insulation. Without that cover, known as the myelin sheath, nerve cells can’t transmit information, leading to memory and other brain problems. © Society for Science & the Public 2000 - 2015
by Clare Wilson Once only possible in an MRI scanner, vibrating pads and electrode caps could soon help locked-in people communicate on a day-to-day basis YOU wake up in hospital unable to move, to speak, to twitch so much as an eyelid. You hear doctors telling your relatives you are in a vegetative state – unaware of everything around you – and you have no way of letting anyone know this is not the case. Years go by, until one day, you're connected to a machine that allows you to communicate through your brain waves. It only allows yes or no answers, but it makes all the difference – now you can tell your carers if you are thirsty, if you'd like to sit up, even which TV programmes you want to watch. In recent years, breakthroughs in mind-reading technology have brought this story close to reality for a handful of people who may have a severe type of locked-in syndrome, previously diagnosed as being in a vegetative state. So far, most work has required a lab and a giant fMRI scanner. Now two teams are developing devices that are portable enough to be taken out to homes, to help people communicate on a day-to-day basis. The technology might also be able to identify people who have been misdiagnosed. People with "classic" locked-in syndrome are fully conscious but completely paralysed apart from eye movements. Adrian Owen of Western University in London, Canada, fears that there is another form of the condition where the paralysis is total. He thinks that a proportion of people diagnosed as being in a vegetative state – in which people are thought to have no mental awareness at all – are actually aware but unable to let anyone know. "The possibility is that we are missing people with some sort of complete locked-in syndrome," he says. © Copyright Reed Business Information Ltd.
By Ben Thomas The past several years have brought two parallel revolutions in neuroscience. Researchers have begun using genetically encoded sensors to monitor the behavior of individual neurons, and they’ve been using brief pulses of light to trigger certain types of neurons to activate. These two techniques are known collectively as optogenetics—the science of using light to read and activate genetically specified neurons—but until recently, most researchers have used them separately. Though many had tried, no one had succeeded in combining optogenetic readout and stimulation into one unified system that worked in the brains of living animals. But now, a team led by Michael Hausser, a neuroscientist at University College London’s Wolfson Institute for Biomedical Research, has succeeded in creating just such a unified optogenetic input/output system. In a paper published this January in the journal Nature Methods [Scientific American is part of the Nature Publishing Group], the team explain how they’ve used the system to record complex signaling codes used by specific sets of neurons and to “play” those codes back by reactivating the same neural firing patterns they recorded, paving the way to get neural networks in the brains of living animals to recognize and respond to the codes they send. “This is going to be a game-changer,” Hausser says. Conventional optogenetics starts with genes. Certain genes encode instructions for producing light-sensitive proteins. By introducing these genes into brain cells, researchers are able to trick specific populations of those cells—all the neurons in a given brain region that respond to dopamine, for example—to fire their signals in response to tiny pulses of light. © 2015 Scientific American
Keyword: Brain imaging
Link ID: 20514 - Posted: 01.23.2015
By JOHN MARKOFF A new laboratory technique enables researchers to see minuscule biological features, such as individual neurons and synapses, at a nearly molecular scale through conventional optical microscopes. In a paper published last week in the journal Science, researchers at M.I.T. said they were able to increase the physical size of cultured cells and tissue by as much as five times while still preserving their structure. The scientists call the new technique expansion microscopy. The idea of making objects larger to make them more visible is a radical solution to a vexing challenge. By extending the resolving power of conventional microscopes, scientists are able to glimpse such biological mysteries as the protein structures that form ion channels and the outline of the membrane that holds the genome within a cell. The researchers have examined minute neural circuits, gaining new insights into local connections in the brain and a better understanding of larger networks. The maximum resolving power of conventional optical microscopes is about 200 nanometers, about half the wavelength of visible light. (By contrast, a human hair is about 500 times wider.) In recent decades, scientists have struggled to push past these limits. Last year, three scientists received a Nobel Prize for a technique in which fluorescent molecules are used to extend the resolving power of optical microscopes. But the technique requires specialized equipment and is costly. With expansion microscopy, Edward S. Boyden, a co-director of the M.I.T. Center for Neurobiological Engineering, and his colleagues were able to observe objects originally measuring just 70 nanometers in cultured cells and brain tissue through an optical microscope. © 2015 The New York Times Company
Keyword: Brain imaging
Link ID: 20499 - Posted: 01.20.2015
Vernon Mountcastle, one of Johns Hopkins Medicine's giants of the 20th century, died peacefully at his North Baltimore home on Sunday, with Nancy, his wife of seven decades, and family at his bedside. He was 96. Mountcastle was universally acknowledged as the "father of neuroscience" and served Johns Hopkins with extraordinary dedication for nearly 65 years. A 1942 graduate of the School of Medicine and a member of the faculty since 1948, Mountcastle served as director of the Department of Physiology and head of the Philip Bard Laboratories of Neurophysiology at Johns Hopkins from 1964 to 1980. He later became one of the founding members of Johns Hopkins' Zanvyl Krieger Mind/Brain Institute, where he continued to work until his retirement at 87. Colleagues remember his dedication to the professional development of neuroscientists, fiercely focused work ethic, and devotion to collaborative research. Also see: Mind/Brain's Mountcastle wins NAS award for lifetime of groundbreaking work (Gazette, April 1998) Mountcastle once was dubbed the "Jacques Cousteau of the cortex" for his revolutionary research delving into the unknown depths of the brain and establishing the basis for modern neuroscience. In 1957, he made the breakthrough discovery that revolutionized the concept of how the brain is built. He found that the cells of the cerebral cortex are organized in vertical columns, extending from the surface of the brain down through six layers of the cortex, each column processing a specific kind of information.
Keyword: Brain imaging
Link ID: 20478 - Posted: 01.14.2015
By GARETH COOK In 2005, Sebastian Seung suffered the academic equivalent of an existential crisis. More than a decade earlier, with a Ph.D. in theoretical physics from Harvard, Seung made a dramatic career switch into neuroscience, a gamble that seemed to be paying off. He had earned tenure from the Massachusetts Institute of Technology a year faster than the norm and was immediately named a full professor, an unusual move that reflected the sense that Seung was something of a superstar. His lab was underwritten with generous funding by the elite Howard Hughes Medical Institute. He was a popular teacher who traveled the world — Zurich; Seoul, South Korea; Palo Alto, Calif. — delivering lectures on his mathematical theories of how neurons might be wired together to form the engines of thought. And yet Seung, a man so naturally exuberant that he was known for staging ad hoc dance performances with Harvard Square’s street musicians, was growing increasingly depressed. He and his colleagues spent their days arguing over how the brain might function, but science offered no way to scan it for the answers. “It seemed like decades could go by,” Seung told me recently, “and you would never know one way or another whether any of the theories were correct.” That November, Seung sought the advice of David Tank, a mentor he met at Bell Laboratories who was attending the annual meeting of the Society for Neuroscience, in Washington. Over lunch in the dowdy dining room of a nearby hotel, Tank advised a radical cure. A former colleague in Heidelberg, Germany, had just built a device that imaged brain tissue with enough resolution to make out the connections between individual neurons. But drawing even a tiny wiring diagram required herculean efforts, as people traced the course of neurons through thousands of blurry black-and-white images. What the field needed, Tank said, was a computer program that could trace them automatically — a way to map the brain’s connections by the millions, opening a new area of scientific discovery. For Seung to tackle the problem, though, it would mean abandoning the work that had propelled him to the top of his discipline in favor of a highly speculative engineering project. © 2015 The New York Times Company
Keyword: Brain imaging
Link ID: 20470 - Posted: 01.10.2015
Ewen Callaway Microscopes make living cells and tissues appear bigger. But what if we could actually make the things bigger? It might sound like the fantasy of a scientist who has read Alice’s Adventures in Wonderland too many times, but the concept is the basis for a new method that could enable biologists to image an entire brain in exquisite molecular detail using an ordinary microscope, and to resolve features that would normally be beyond the limits of optics. The technique, called expansion microscopy, involves physically inflating biological tissues using a material more commonly found in baby nappies (diapers). Edward Boyden, a neuroengineer at the Massachusetts Institute of Technology (MIT) in Cambridge, discussed the technique, which he developed with his MIT colleagues Fei Chen and Paul Tillberg, at a conference last month. Prizewinning roots Expansion microscopy is a twist on super-resolution microscopy, which earned three scientists the 2014 Nobel Prize in Chemistry. Both techniques attempt to circumvent a limitation posed by the laws of physics. In 1873, German physicist Ernst Abbe deduced that conventional optical microscopes cannot distinguish objects that are closer together than about 200 nanometres — roughly half the shortest wavelength of visible light. Anything closer than this 'diffraction limit' appears as a blur. © 2015 Nature Publishing Group
Keyword: Brain imaging
Link ID: 20464 - Posted: 01.10.2015
Mo Costandi A team of neuroscientists at University College London has developed a new way of simultaneously recording and manipulating the activity of multiple cells in the brains of live animals using pulses of light. The technique, described today in the journal Nature Methods, combines two existing state-of-the-art neurotechnologies. It may eventually allow researchers to do away with the cumbersome microelectrodes they traditionally used to probe neuronal activity, and to interrogate the brain’s workings at the cellular level in real time and with unprecedented detail. One of them is optogenetics. This involves creating genetically engineered mice expressing algal proteins called Channelrhodopsins in specified groups of neurons. This renders the cells sensitive to light, allowing researchers to switch the cells on or off, depending on which Channelrhodopsin protein they express, and which wavelength of light is used. This can be done on a millisecond-by-millisecond timescale, using pulses of laser light delivered into the animals’ brains via an optical fibre. The other is calcium imaging. Calcium signals are crucial for just about every aspect of neuronal function, and nerve cells exhibit a sudden increase in calcium ion concentration when they begin to fire off nervous impulses. Using dyes that give off green fluorescence in response to increases in calcium concentration, combined with two-photon microscopy, researchers can detect this signature to see which cells are activated. In this way, they can effectively ‘read’ the activity of entire cell populations in brain tissue slices or live brains. Calcium-sensitive dyes are injectable, so targeting them with precision is difficult, and more recently, researchers have developed genetically-encoded calcium sensors to overcome this limitation. Mice can be genetically engineered to express these calcium-sensitive proteins in specific groups of cells; like the dyes before them, they, too, fluoresce in response to increases in calcium ion concentrations in the cells expressing them.
Keyword: Brain imaging
Link ID: 20441 - Posted: 12.23.2014
by Helen Thomson Zapping your brain might make you better at maths tests – or worse. It depends how anxious you are about taking the test in the first place. A recent surge of studies has shown that brain stimulation can make people more creative and better at maths, and can even improve memory, but these studies tend to neglect individual differences. Now, Roi Cohen Kadosh at the University of Oxford and his colleagues have shown that brain stimulation can have completely opposite effects depending on your personality. Previous research has shown that a type of non-invasive brain stimulation called transcranial direct current stimulation (tDCS) – which enhances brain activity using an electric current – can improve mathematical ability when applied to the dorsolateral prefrontal cortex, an area involved in regulating emotion. To test whether personality traits might affect this result, Kadosh's team tried the technique on 25 people who find mental arithmetic highly stressful, and 20 people who do not. They found that participants with high maths anxiety made correct responses more quickly and, after the test, showed lower levels of cortisol, an indicator of stress. On the other hand, individuals with low maths anxiety performed worse after tDCS. "It is hard to believe that all people would benefit similarly [from] brain stimulation," says Cohen Kadosh. He says that further research could shed light on how to optimise the technology and help to discover who is most likely to benefit from stimulation. © Copyright Reed Business Information Ltd.
Ian Sample, science editor Electrical brain stimulation equipment – which can boost cognitive performance and is easy to buy online – can have bad effects, impairing brain functioning, research from scientists at Oxford University has shown. A steady stream of reports of stimulators being able to boost brain performance, coupled with the simplicity of the devices, has led to a rise in DIY enthusiasts who cobble the equipment together themselves, or buy it assembled on the web, then zap themselves at home. In science laboratories brain stimulators have long been used to explore cognition. The equipment uses electrodes to pass gentle electric pulses through the brain, to stimulate activity in specific regions of the organ. Roi Cohen Kadosh, who led the study, published in the Journal of Neuroscience, said: “It’s not something people should be doing at home at this stage. I do not recommend people buy this equipment. At the moment it’s not therapy, it’s an experimental tool.” The Oxford scientists used a technique called transcranial direct current stimulation (tDCS) to stimulate the dorsolateral prefrontal cortex in students as they did simple sums. The results of the test were surprising. Students who became anxious when confronted with sums became calmer and solved the problems faster than when they had sham stimulation (the stimulation itself lasted only 30 seconds of the half hour study). The shock was that the students who did not fear maths performed worse with the same stimulation.
| By Carolyn Gregoire When reading about Harry Potter's adventures fighting Lord Voldemort or flying around the Quidditch field on his broomstick, we can become so absorbed in the story that the characters and events start to feel real. And according to neuroscientists, there's a good reason for this. Researchers in the Machine Learning Department at Carnegie Mellon University scanned the brains of Harry Potter readers, and found that reading about Harry's adventures activates the same brain regions used to perceive people's intentions and actions in the real world. The researchers performed fMRI scans on a group of eight study participants while they read chapter nine of Harry Potter and the Sorcerer's Stone, which describes Harry's first flying lesson. Then, they analyzed the scans, one cubic millimeter at a time, for four-word segments of the chapter in order to build the first integrated computational model of reading. The researchers created a technique such that for each two-second fMRI scan, the readers would see four words. And for each word, the researchers identified 195 detailed features that the brain would process. Then, an algorithm was applied to analyze the activation of each millimeter of the brain for each two-second scan, associating various word features with different regions of the brain. Using the model, the researchers were able to predict which of two passages the subjects were reading with a 74 percent accuracy rate. ©2014 TheHuffingtonPost.com, Inc
|By Ryan Bradley Five years ago Viviana Gradinaru was slicing thin pieces of mouse brain in a neurobiology lab, slowly compiling images of the two-dimensional slivers for a three-dimensional computer rendering. In her spare time, she would go to see the Body Worlds exhibit. She was especially fascinated by the “plasticized” remains of the human circulatory system on display. It struck her that much of what she was doing in the lab could be done more efficiently with a similar process. “Tissue clearing” has been around for more than a century, but existing methods involve soaking tissue samples in solvents, which is slow and usually destroys the fluorescent proteins necessary for marking certain cells of interest. To create a better approach, Gradinaru, at the time a graduate student, and her colleagues in neuroscientist Karl Deisseroth's lab focused on replacing the tissue's lipid molecules, which make it opaque.* To keep the tissue from collapsing, however, the replacement would need to give it structure, as lipids do. The first step was to euthanize a rodent and pump formaldehyde into its body, through its heart. Next they removed the skin and filled its blood vessels with acrylamide monomers, white, odorless, crystalline compounds. The monomers created a supportive hydrogel mesh, replacing the lipids and clearing the tissue. Before long, they could render an entire mouse body transparent in two weeks. Soon they were using transparent mice to map complete mouse nervous systems. The transparency made it possible for them to identify peripheral nerves—tiny bundles of nerves that are poorly understood—and to map the spread of viruses across the mouse's blood-brain barrier, which they did by marking the virus with a fluorescent agent, injecting it into the mouse's tail and watching it spread into the brain. © 2014 Scientific American
Keyword: Brain imaging
Link ID: 20382 - Posted: 12.03.2014
Some teenagers appear to show changes in their brains after one season of playing American football, a small study suggests. Even though players were not concussed during the season, researchers found abnormalities similar to the effects of mild traumatic brain injury. Twenty-four players aged between 16 and 18 were studied and devices on their helmets measured head impacts. The study was presented to the Radiological Society of North America. In recent years, a number of reports have expressed concern about the potential effects on young, developing brains of playing contact sports. These studies have tended to focus on brain changes as a result of concussion. But this study focused on the effects of head impacts on the brain, even when players did not suffer concussion at any point during the season. Using detailed scans of the players' brains before the season began and then again after it ended, the researchers were able to identify slight changes to the white matter of the brain. White matter contains millions of nerve fibres which act as communication cables between the brain's regions. Those players who were hit harder and hit more often were more likely to show these changes in post-season brain scans. Dr Alex Powers, co-author and paediatric neurosurgeon at Wake Forest Baptist Medical Centre in North Carolina, said the changes were a direct result of the hits received by the young players during their football season. BBC © 2014
By David Tuller Patients with chronic fatigue syndrome are accustomed to disappointment. The cause of the disorder remains unknown; it can be difficult to diagnose, and treatment options are few. Research suggesting that an infection from a mouse virus may cause it raised hopes among patients a few years ago, but the evidence fell apart under closer scrutiny. Many patients are still told to seek psychiatric help. But two recent studies — one from investigators at Stanford a few weeks ago and another from a Japanese research team published earlier this year — have found that the brains of people with chronic fatigue syndrome differ from those of healthy people, strengthening the argument that serious physiological dysfunctions are at the root of the condition. “You’ve got two different groups that have independently said, ‘There’s something going on in the brain that is aberrant,’ ” said Leonard Jason, a psychologist at DePaul University in Chicago who studies the condition, also called myalgic encephalomyelitis and widely known as M.E./C.F.S. “I think you have a growing sense that this illness should be taken seriously.” Both studies were small, however, and their results must be replicated before firm conclusions can be drawn. Still, other studies presented at scientific conferences this year also have demonstrated physiological dysfunctions in these patients. In the most recent study, published by the journal Radiology, researchers at Stanford University compared brain images of 15 patients with the condition to those of 14 healthy people. The scientists found differences in both the white matter, the long, cablelike nerve structures that transmit signals between parts of the brain, and the gray matter, the regions where these signals are processed and interpreted. The most striking finding was that in people with the disorder, one neural tract in the white matter of the right hemisphere appeared to be abnormally shaped, as if the cablelike nerve structures had crisscrossed or changed in some other way. Furthermore, the most seriously ill patients exhibited the greatest levels of this abnormality. © 2014 The New York Times Company
by Linda Geddes A tapeworm that usually infects dogs, frogs and cats has made its home inside a man's brain. Sequencing its genome showed that it contains around 10 times more DNA than any other tapeworm sequenced so far, which could explain its ability to invade many different species. When a 50-year-old Chinese man was admitted to a UK hospital complaining of headaches, seizures, an altered sense of smell and memory flashbacks, his doctors were stumped. Tests for tuberculosis, syphilis, HIV and Lyme disease were negative, and although an MRI scan showed an abnormal region in the right side of his brain, a biopsy found inflammation, but no tumour. Over the next four years, further MRIs recorded the abnormal region moving across the man's brain (see animation), until finally his doctors decided to operate. To their immense surprise, they pulled out a 1 centimetre-long ribbon-shaped worm. It looked like a tapeworm, but was unlike any seen before in the UK, so a sample of its tissue was sent to Hayley Bennett and her colleagues at the Wellcome Trust Sanger Institute in Cambridge, UK. Genetic sequencing identified it as Spirometra erinaceieuropaei, a rare species of tapeworm found in China, South Korea, Japan and Thailand. Just 300 human infections have been reported since 1953, and not all of them in the brain. © Copyright Reed Business Information Ltd.
Keyword: Brain imaging
Link ID: 20344 - Posted: 11.21.2014
By Elizabeth Pennisi The microbes that live in your body outnumber your cells 10 to one. Recent studies suggest these tiny organisms help us digest food and maintain our immune system. Now, researchers have discovered yet another way microbes keep us healthy: They are needed for closing the blood-brain barrier, a molecular fence that shuts out pathogens and molecules that could harm the brain. The findings suggest that a woman's diet or exposure to antibiotics during pregnancy may influence the development of this barrier. The work could also lead to a better understanding of multiple sclerosis, in which a leaky blood-brain barrier may set the stage for a decline in brain function. The first evidence that bacteria may help fortify the body’s biological barriers came in 2001. Researchers discovered that microbes in the gut activate genes that code for gap junction proteins, which are critical to building the gut wall. Without these proteins, gut pathogens can enter the bloodstream and cause disease. In the new study, intestinal biologist Sven Pettersson and his postdoc Viorica Braniste of the Karolinska Institute in Stockholm decided to look at the blood-brain barrier, which also has gap junction proteins. They tested how leaky the blood-brain barrier was in developing and adult mice. Some of the rodents were brought up in a sterile environment and thus were germ-free, with no detectable microbes in their bodies. Braniste then injected antibodies—which are too big to get through the blood-brain barrier—into embryos developing within either germ-free moms or moms with the typical microbes, or microbiota. © 2014 American Association for the Advancement of Science
Link ID: 20338 - Posted: 11.20.2014
Sara Reardon A technique that makes mouse brains transparent shows how the entire brain responds to cocaine addiction and fear. The findings could uncover new brain circuits involved in drug response. In the technique, known as CLARITY, brains are infused with acrylamide, which forms a matrix in the cells and preserves their structure along with the DNA and proteins inside them. The organs are then treated with a detergent that dissolves opaque lipids, leaving the cells completely clear. To test whether CLARITY could be used to show how brains react to stimuli, neuroscientists Li Ye and Karl Deisseroth of Stanford University in California engineered mice so that their neurons would make a fluorescent protein when they fired. (The system is activated by the injection of a drug.) The researchers then trained four of these mice to expect a painful foot shock when placed in a particular box; another set of mice placed in the box received cocaine, rather than shocks. Once the mice had learned to associate the box with either pain or an addictive reward, the researchers tested how the animals' brains responded to the stimuli. They injected the mice with the drug that activated the fluorescent protein system, placed them in the box and waited for one hour to give their neurons time to fire. The next step was to remove the animals' brains, treat them with CLARITY, and image them using a system that could count each fluorescent cell across the entire brain (see video). A computer combined these images into a model of a three-dimensional brain, which showed the pathways that lit up when mice were afraid or were anticipating cocaine. © 2014 Nature Publishing Group