Chapter 2. Functional Neuroanatomy: The Nervous System and Behavior
Follow us on Facebook and Twitter, or subscribe to our mailing list, to receive news updates. Learn more.
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
Mo Costandi A team of neuroscientists in America say they have rediscovered an important neural pathway that was first described in the late nineteenth century but then mysteriously disappeared from the scientific literature until very recently. In a study published today in Proceedings of the National Academy of Sciences, they confirm that the prominent white matter tract is present in the human brain, and argue that it plays an important and unique role in the processing of visual information. The vertical occipital fasciculus (VOF) is a large flat bundle of nerve fibres that forms long-range connections between sub-regions of the visual system at the back of the brain. It was originally discovered by the German neurologist Carl Wernicke, who had by then published his classic studies of stroke patients with language deficits, and was studying neuroanatomy in Theodor Maynert’s laboratory at the University of Vienna. Wernicke saw the VOF in slices of monkey brain, and included it in his 1881 brain atlas, naming it the senkrechte occipitalbündel, or ‘vertical occipital bundle’. Maynert - himself a pioneering neuroanatomist and psychiatrist, whose other students included Sigmund Freud and Sergei Korsakov - refused to accept Wernicke’s discovery, however. He had already described the brain’s white matter tracts, and had arrived at the general principle that they are oriented horizontally, running mostly from front to back within each hemisphere. But the pathway Wernicke had described ran vertically. Another of Maynert’s students, Heinrich Obersteiner, identified the VOF in the human brain, and mentioned it in his 1888 textbook, calling it the senkrechte occipitalbündel in one illustration, and the fasciculus occipitalis perpendicularis in another. So, too, did Heinrich Sachs, a student of Wernicke’s, who labeled it the stratum profundum convexitatis in his 1892 white matter atlas. © 2014 Guardian News and Media Limited
Link ID: 20333 - Posted: 11.20.2014
By Neuroskeptic An attempt to replicate the results of some recent neuroscience papers that claimed to find correlations between human brain structure and behavior has drawn a blank. The new paper is by University of Amsterdam researchers Wouter Boekel and colleagues and it’s in press now at Cortex. You can download it here from the webpage of one of the authors, Eric-Jan Wagenmakers. Neuroskeptic readers will know Wagenmakers as a critic of statistical fallacies in psychology and a leading advocate of preregistration, which is something I never tire of promoting either. Boekel et al. attempted to replicate five different papers which, together, reported 17 distinct positive results in the form of structural brain-behavior (‘SBB’) correlations. An SBB correlation is an association between the size (usually) of a particular brain area and a particular behavioral trait. For instance, one of the claims was that the amount of grey matter in the amygdala is correlated with the number of Facebook friends you have. To attempt to reproduce these 17 findings, Boekel et al. took 36 students whose brains were scanned with two methods, structural MRI and DWI. The students then completed a set of questionnaires and psychological tests, identical to ones used in the five papers that were up for replication. The methods and statistical analyses were fully preregistered (back in June 2012); Boekel et al. therefore had no scope for ‘fishing’ for positive (or negative) results by tinkering with the methodology. So what did they find? Nothing much. None of the 17 brain-behavior correlations were significant in the replication sample.
Keyword: Brain imaging
Link ID: 20330 - Posted: 11.20.2014
By David Shultz WASHINGTON, D.C.—Reciting the days of the week is a trivial task for most of us, but then, most of us don’t have cooling probes in our brains. Scientists have discovered that by applying a small electrical cooling device to the brain during surgery they could slow down and distort speech patterns in patients. When the probe was activated in some regions of the brain associated with language and talking—like the premotor cortex—the patients’ speech became garbled and distorted, the team reported here yesterday at the Society for Neuroscience’s annual meeting. As scientists moved the probe to other speech regions, such as the pars opercularis, the distortion lessened, but speech patterns slowed. (These zones and their effects are displayed graphically above.) “What emerged was this orderly map,” says team leader Michael Long, a neuroscientist at the New York University School of Medicine in New York City. The results suggest that one region of the brain organizes the rhythm and flow of language while another is responsible for the actual articulation of the words. The team was even able to map which word sounds were most likely to be elongated when the cooling probe was applied. “People preferentially stretched out their vowels,” Long says. “Instead of Tttuesssday, you get Tuuuesdaaay.” The technique is similar to the electrical probe stimulation that researchers have been using to identify the function of various brain regions, but the shocks often trigger epileptic seizures in sensitive patients. Long contends that the cooling probe is completely safe, and that in the future it may help neurosurgeons decide where to cut and where not to cut during surgery. © 2014 American Association for the Advancement of Science.
|By Bret Stetka The brain is protected by formidable defenses. In addition to the skull, the cells that make up the blood-brain barrier keep pathogens and toxic substances from reaching the central nervous system. The protection is a boon, except when we need to deliver drugs to treat illnesses. Now researchers are testing a way to penetrate these bastions: sound waves. Kullervo Hynynen, a medical physicist at Sunnybrook Research Institute in Toronto, and a team of physicians are trying out a technique that involves giving patients a drug followed by an injection of microscopic gas-filled bubbles. Next patients don a cap that directs sound waves to specific brain locations, an approach called high-intensity focused ultrasound. The waves cause the bubbles to vibrate, temporarily forcing apart the cells of the blood-brain barrier and allowing the medication to infiltrate the brain. Hynynen and his colleagues are currently testing whether they can use the method to deliver chemotherapy to patients with brain tumors. They and other groups are planning similar trials for patients with other brain disorders, including Alzheimer's disease. Physicians are also considering high-intensity focused ultrasound as an alternative to brain surgery. Patients with movement disorders such as Parkinson's disease and dystonia are increasingly being treated with implanted electrodes, which can interrupt problematic brain activity. A team at the University of Virginia hopes to use focused ultrasound to deliver thermal lesions deep into the brain without having patients go under the knife. © 2014 Scientific American
By JAMES GORMAN Research on the brain is surging. The United States and the European Union have launched new programs to better understand the brain. Scientists are mapping parts of mouse, fly and human brains at different levels of magnification. Technology for recording brain activity has been improving at a revolutionary pace. The National Institutes of Health, which already spends $4.5 billion a year on brain research, consulted the top neuroscientists in the country to frame its role in an initiative announced by President Obama last year to concentrate on developing a fundamental understanding of the brain. Scientists have puzzled out profoundly important insights about how the brain works, like the way the mammalian brain navigates and remembers places, work that won the 2014 Nobel Prize in Physiology or Medicine for a British-American and two Norwegians. So many large and small questions remain unanswered. How is information encoded and transferred from cell to cell or from network to network of cells? Science found a genetic code but there is no brain-wide neural code; no electrical or chemical alphabet exists that can be recombined to say “red” or “fear” or “wink” or “run.” And no one knows whether information is encoded differently in various parts of the brain. Brain scientists may speculate on a grand scale, but they work on a small scale. Sebastian Seung at Princeton, author of “Connectome: How the Brain’s Wiring Makes Us Who We Are,” speaks in sweeping terms of how identity, personality, memory — all the things that define a human being — grow out of the way brain cells and regions are connected to each other. But in the lab, his most recent work involves the connections and structure of motion-detecting neurons in the retinas of mice. Larry Abbott, 64, a former theoretical physicist who is now co-director, with Kenneth Miller, of the Center for Theoretical Neuroscience at Columbia University, is one of the field’s most prominent theorists, and the person whose name invariably comes up when discussions turn to brain theory. © 2014 The New York Times Company
Keyword: Brain imaging
Link ID: 20302 - Posted: 11.11.2014
Mo Costandi The father of modern neuroscience had a sharp eye and an even sharper mind, but he evidently overlooked something rather significant about the basic structure of brain cells. Santiago Ramón y Cajal spent his entire career examining and comparing nervous tissue from different species. He observed the intricate branches we now call dendrites, and the thicker axonal fibres. He also recognised them as distinct components of the neuron, and convinced others that neurons are fundamental components of the nervous system. For Cajal, these cells were “the mysterious butterflies of the soul… whose beating of wings may one day reveal to us the secrets of the mind.” He hunted for them in “the gardens of the grey matter” and, being an accomplished artist, meticulously catalogued the many “delicate and elaborate forms” that they take. As his beautiful drawings show, all neurons have a single axon emanating from one area of the cell body, and one or more dendrites arising from another. This basic structure has been enshrined in textbooks ever since. But there appear to be unusual varieties of soul butterflies that Cajal failed to spot – neuroscientists in Germany have identified neurons that have axons growing from their dendrites, a discovery that challenges our century-old assumption about the form and function of these cells. Cajal stated that information flows through neurons in only one direction – from the dendrites, which receive electrical impulses from other neurons, to the cell body, which processes the information and conveys it to the initial segment of the axon, which then produces its own impulses that travel down it to the nerve terminal. (He indicated this with small arrows in some of his diagrams, such as the one above.) © 2014 Guardian News and Media Limited
Keyword: Brain imaging
Link ID: 20301 - Posted: 11.11.2014
Sara Reardon Delivering medications to the brain could become easier, thanks to molecules that can escort drugs through the notoriously impervious sheath that separates blood vessels from neurons. In a proof-of-concept study in monkeys, biologists used the system to reduce levels of the protein amyloid-β, which accumulates in the brain plaques associated with Alzheimer's disease1. The blood–brain barrier is a layer of cells lining the inner surface of the capillaries that feed the central nervous system. It is nature's way of protecting the delicate brain from infectious agents and toxic compounds, while letting nutrients and oxygen in and waste products out. Because the barrier strictly regulates the passage of larger molecules and often prevents drug molecules from entering the brain, it has long posed one of the most difficult challenges in developing treatments for brain disorders. Several approaches to bypassing the barrier are being tested, including nanoparticles that are small enough to pass through the barrier's cellular membranes and deliver their payload; catheters that carry a drug directly into the brain; and ultrasound pulses that push microbubbles through the barrier. But no approach has yet found broad therapeutic application. Neurobiologist Ryan Watts and his colleagues at the biotechnology company Genentech in South San Francisco have sought to break through the barrier by exploiting transferrin, a protein that sits on the surface of blood vessels and carries iron into the brain. The team created an antibody with two ends. One end binds loosely to transferrin and uses the protein to transport itself into the brain. And once the antibody is inside, its other end targets an enzyme called β-secretase 1 (BACE1), which produces amyloid-β. Crucially, the antibody binds more tightly to BACE1 than to transferrin, and this pulls it off the blood vessel and into the brain. It locks BACE1 shut and prevents it from making amyloid-β. © 2014 Nature Publishing Group,
Link ID: 20286 - Posted: 11.06.2014
James Gorman Here is something to keep arachnophobes up at night. The inside of a spider is under pressure, like the air in a balloon, because spiders move by pushing fluid through valves. They are hydraulic. This works well for the spiders, but less so for those who want to study what goes on in the brain of a jumping spider, an aristocrat of arachnids that, according to Ronald R. Hoy, a professor of neurobiology and behavior at Cornell University, is one of the smartest of all invertebrates. If you insert an electrode into the spider’s brain, what’s inside might squirt out, and while that is not the kind of thing that most people want to think about, it is something that the researchers at Cornell had to consider. Dr. Hoy and his colleagues wanted to study jumping spiders because they are very different from most of their kind. They do not wait in a sticky web for lunch to fall into a trap. They search out prey, stalk it and pounce. “They’ve essentially become cats,” Dr. Hoy said. And they do all this with a brain the size of a poppy seed and a visual system that is completely different from that of a mammal: two big eyes dedicated to high-resolution vision and six smaller eyes that pick up motion. Dr. Hoy gathered four graduate students in various disciplines to solve the problem of recording activity in a jumping spider’s brain when it spots something interesting — a feat nobody had accomplished before. In the end, they not only managed to record from the brain, but discovered that one neuron seemed to be integrating the information from the spider’s two independent sets of eyes, a computation that might be expected to involve a network of brain cells. © 2014 The New York Times Company
by Helen Thomson As you read this, your neurons are firing – that brain activity can now be decoded to reveal the silent words in your head TALKING to yourself used to be a strictly private pastime. That's no longer the case – researchers have eavesdropped on our internal monologue for the first time. The achievement is a step towards helping people who cannot physically speak communicate with the outside world. "If you're reading text in a newspaper or a book, you hear a voice in your own head," says Brian Pasley at the University of California, Berkeley. "We're trying to decode the brain activity related to that voice to create a medical prosthesis that can allow someone who is paralysed or locked in to speak." When you hear someone speak, sound waves activate sensory neurons in your inner ear. These neurons pass information to areas of the brain where different aspects of the sound are extracted and interpreted as words. In a previous study, Pasley and his colleagues recorded brain activity in people who already had electrodes implanted in their brain to treat epilepsy, while they listened to speech. The team found that certain neurons in the brain's temporal lobe were only active in response to certain aspects of sound, such as a specific frequency. One set of neurons might only react to sound waves that had a frequency of 1000 hertz, for example, while another set only cares about those at 2000 hertz. Armed with this knowledge, the team built an algorithm that could decode the words heard based on neural activity aloneMovie Camera (PLoS Biology, doi.org/fzv269). © Copyright Reed Business Information Ltd.
How Magic Mushrooms Rearrange Your Brain By Brandon Keim A new way of looking at brain activity may give insight into how psychedelic drugs produce their consciousness-altering effects. In recent years, a focus on brain structures and regions has given way to an emphasis on neurological networks: how cells and regions interact, with consciousness shaped not by any given set of brain regions, but by their interplay. Understanding the networks, however, is no easy task, and researchers are developing ever more sophisticated ways of characterizing them. One such approach, described in a new Proceedings of the Royal Society Interface study, involves not simply networks but networks of networks. Perhaps some aspects of consciousness arise from these meta-networks—and to investigate the proposition, the researchers analyzed fMRI scans of 15 people after being injected with psilocybin, the active ingredient in magic mushrooms, and compared them to scans of their brain activity after receiving a placebo. Investigating psychedelia wasn’t the direct purpose of the experiment, said study co-author Giovanni Petri, a mathematician at Italy’s Institute for Scientific Interchange. Rather, psilocybin makes for an ideal test system: It’s a sure-fire way of altering consciousness. “In a normal brain, many things are happening. You don’t know what is going on, or what is responsible for that,” said Petri. “So you try to perturb the state of consciousness a bit, and see what happens.” A representation of that is seen in the image above. Each circle depicts relationships between networks—the dots and colors correspond not to brain regions, but to especially connection-rich networks—with normal-state brains at left, and psilocybin-influenced brains at right. © 2014 Condé Nast.
By Neuroskeptic A new paper threatens to turn the world of autism neuroscience upside down. Its title is Anatomical Abnormalities in Autism?, and it claims that, well, there aren’t very many. Published in Cerebral Cortex by Israeli researchers Shlomi Haar and colleagues, the new research reports that there are virtually no differences in brain anatomy between people with autism and those without. What makes Haar et al.’s essentially negative claims so powerful is that their study had a huge sample size: they included structural MRI scans from 539 people diagnosed with high-functioning autism spectrum disorder (ASD) and 573 controls. This makes the paper an order of magnitude bigger than a typical structural MRI anatomy study in this field. The age range was 6 to 35. The scans came from the public Autism Brain Imaging Data Exchange (ABIDE) database, a data sharing initiative which pools scans from 18 different neuroimaging centers. Haar et al. examined the neuroanatomy of the cases and controls using the popular FreeSurfer software package. What did they find? Well… not much. First off, the ASD group had no differences in overall brain size (intracranial volume). Nor were there any group differences in the volumes of most brain areas; the only significant finding here was an increased ventricle volume in the ASD group, but even this had a small effect size (d = 0.34). Enlarged ventricles is not specific to ASD by any means – the same thing has been reported in schizophrenia, dementia, and many other brain disorders.
by Clare Wilson Call them the neuron whisperers. Researchers are eavesdropping on conversations going on between brain cells in a dish. Rather than hearing the chatter, they watch neurons that have been genetically modified so that the electrical impulses moving along their branched tendrils cause sparkles of red light (see video). Filming these cells at up to 100,000 frames a second is allowing researchers to analyse their firing in unprecedented detail. Until recently, a neuron's electrical activity could only be measured with tiny electrodes. As well as being technically difficult, such "patch clamping" only reveals the voltage at those specific points. The new approach makes the neuron's entire surface fluoresce as the impulse passes by. "Now we see the whole thing sweep through," says Adam Cohen of Harvard University. "We get much more information - like how fast and where does it start and what happens at a branch." The idea is a reverse form of optogenetics – where neurons are given a gene from bacteria that make a light-sensitive protein, so the cells fire when illuminated. The new approach uses genes that make the neurons do the opposite - glow when they fire. "It's pretty cool," says Dimitri Kullmann of University College London. "It's amazing that you can dispense with electrodes." Cohen's team is using the technique to compare cells from typical brains with those from people with disorders such as motor neuron disease or amyotrophic lateral sclerosis. Rather than taking a brain sample, they remove some of the person's skin cells and grow them alongside chemicals that rewind the cells into an embryonic-like state. Another set of chemicals is used to turn these stem cells into neurons. "You can recreate something reminiscent of the person's brain in the dish," says Cohen. © Copyright Reed Business Information Ltd.
Keyword: Brain imaging
Link ID: 20241 - Posted: 10.25.2014
by Helen Thomson For the first time, doctors have opened and closed the brain's protector – the blood-brain barrier – on demand. The breakthrough will allow drugs to reach diseased areas of the brain that are otherwise out of bounds. Ultimately, it could make it easier to treat conditions such as Alzheimer's and brain cancer. The blood-brain barrier (BBB) is a sheath of cells that wraps around blood vessels (in black) throughout the brain. It protects precious brain tissue from toxins in the bloodstream, but it is a major obstacle for treating brain disorders because it also blocks the passage of drugs. Several teams have opened the barrier in animals to sneak drugs through. Now Michael Canney at Paris-based medical start-up CarThera, and his colleagues have managed it in people using an ultrasound brain implant and an injection of microbubbles. When ultrasound waves meet microbubbles in the blood, they make the bubbles vibrate. This pushes apart the cells of the BBB. With surgeon Alexandre Carpentier at Pitié-Salpêtrière Hospital in Paris, Canney tested the approach in people with a recurrence of glioblastoma, the most aggressive type of brain tumour. People with this cancer have surgery to remove the tumours and then chemotherapy drugs, such as Carboplatin, are used to try to kill any remaining tumour cells. Tumours make the BBB leaky, allowing in a tiny amount of chemo drugs: if more could get through, their impact would be greater, says Canney. © Copyright Reed Business Information Ltd.
Keyword: Brain imaging
Link ID: 20235 - Posted: 10.23.2014
By Erin Allday When the United States’ top public health and political leaders declared the 1990s the “decade of the brain,” Dr. Pratik Mukherjee couldn’t help but feel a little dubious. “I was kind of laughing, because I didn’t think we’d make much progress in just a decade,” said Mukherjee, a neuro-radiologist at UCSF. Twenty-four years later, Mukherjee said he and his peers around the country are primed to plunge into what he’d like to call the century of the brain — a deep dive into the basic biology and mechanics of the impossibly complex organ that controls our every thought, action, behavior and mood. The National Institutes of Health last week announced $47 million in grants as part of President Obama’s Brain Initiative, a project announced 18 months ago to, in the simplest language, reverse-engineer the human brain. The grants were among the first in a roughly 11-year plan that could cost more than $3 billion. Most of the projects are in developing new technologies to help map the brain and study its mechanics — how cells communicate, what makes them turn on and off, and how large regions of the brain interact, for example. Ultimately, scientists hope these tools will help the next generation of neuroscientists solve the brain-centric disorders — from autism and Alzheimer’s to depression and schizophrenia — that have confounded doctors for centuries.
Keyword: Brain imaging
Link ID: 20183 - Posted: 10.09.2014
David Cyranoski Unlike its Western counterparts, Japan’s effort will be based on a rare resource — a large population of marmosets that its scientists have developed over the past decade — and on new genetic techniques that might be used to modify these highly social animals. The goal of the ten-year Brain/MINDS (Brain Mapping by Integrated Neurotechnologies for Disease Studies) project is to map the primate brain to accelerate understanding of human disorders such as Alzheimer’s disease and schizophrenia. On 11 September, the Japanese science ministry announced the names of the group leaders — and how the project would be organized. Funded at ¥3 billion (US$27 million) for the first year, probably rising to about ¥4 billion for the second, Brain/MINDS is a fraction of the size of the European Union’s Human Brain Project and the United States’ BRAIN (Brain Research through Advancing Innovative Neurotechnologies) Initiative, both of which are projected to receive at least US$1 billion over the next decade. But researchers involved in those efforts say that Brain/MINDS fills a crucial gap between disease models in smaller animals that too often fail to mimic human brain disorders, and models of the human brain that need validating data. “It is essential that we have a genetic primate model to study cognition and cognitive brain disorders such as schizophrenia and depression, for which we do not have good mouse models,” says neuroscientist Terry Sejnowski at the Salk Institute in La Jolla, California, who is a member of the National Institutes of Health BRAIN Initiative Working Group. “Other groups in the United States and China have started transgenic-primate projects, but none is as large or as well organized as the Japanese effort.” © 2014 Nature Publishing Group,
|By Nathan Collins Step aside, huge magnets and radioactive tracers—soon some brain activity will be revealed by simply training dozens of red lights on the scalp. A new study in Nature Photonics finds this optical technique can replicate functional MRI experiments, and it is more comfortable, more portable and less expensive. The method is an enhancement of diffuse optical tomography (DOT), in which a device shines tiny points of red light at a subject's scalp and analyzes the light that bounces back. The red light reflects off red hemoglobin in the blood but does not interact as much with tissues of other colors, which allows researchers to recover an fMRI-like image of changing blood flow in the brain at work. For years researchers attempting to use DOT have been limited by the difficulty of packing many heavy light sources and detectors into the small area around the head. They also needed better techniques for analyzing the flood of data that the detectors collected. Now researchers at Washington University in St. Louis and the University of Birmingham in England report they have solved those problems and made the first high-density DOT (HD-DOT) brain scans. The team first engineered a “double halo” structure to support the weight of 96 lights and 92 detectors, more than double the number in earlier arrays. The investigators also dealt with the computing challenges associated with that many lights—for example, they figured out how to filter out interference from blood flow in the scalp and other tissues. The team then used HD-DOT to successfully replicate fMRI studies of vision and language processing—a task impossible for other fMRI alternatives, such as functional near-infrared spectroscopy or electroencephalography, which do not cover a large enough swath of the brain or have sufficient resolution to pinpoint active brain areas. Finally, the team scanned the brains of people who have implanted electrodes for Parkinson's disease—something fMRI can never do because the machine generates electromagnetic waves that can destroy electronic devices such as pacemakers. © 2014 Scientific American
Keyword: Brain imaging
Link ID: 20151 - Posted: 10.02.2014
Michael Häusser Use light to read out and control neural activity! This idea, so easily expressed and understood, has fired the imagination of neuroscientists for decades. The advantages of using light as an effector are obvious1: it is noninvasive, can be precisely targeted with exquisite spatial and temporal precision, can be used simultaneously at multiple wavelengths and locations, and can report the presence or activity of specific molecules. However, despite early progress2 and encouragement3, it is only recently that widely usable approaches for optical readout and manipulation of specific neurons have become available. These new approaches rely on genetically encoded proteins that can be targeted to specific neuronal subtypes, giving birth to the term 'optogenetics' to signal the combination of genetic targeting and optical interrogation4. On the readout side, highly sensitive probes have been developed for imaging synaptic release, intracellular calcium (a proxy for neural activity) and membrane voltage. On the manipulation side, a palette of proteins for both activation and inactivation of neurons with millisecond precision using different wavelengths of light have been identified and optimized. The extraordinary versatility and power of these new optogenetic tools are spurring a revolution in neuroscience research, and they have rapidly become part of the standard toolkit of thousands of research labs around the world. Although optogenetics may not yet be a household word (though try it on your mother; she may surprise you), there can be no better proof that optogenetics has become part of the scientific mainstream than the 2013 Brain Prize being awarded to the sextet that pioneered optogenetic manipulation (http://www.thebrainprize.org/flx/prize_winners/prize_winners_2013/) and the incorporation of optogenetics as a central plank in the US National Institutes of Health BRAIN Initiative5. Moreover, there is growing optimism about the prospect of using optogenetic probes not only to understand mechanisms of disease in animal models but also to treat disease in humans, particularly in more accessible parts of the brain such as the retina6. © 2014 Macmillan Publishers Limited
Keyword: Brain imaging
Link ID: 20142 - Posted: 10.01.2014