Chapter 19. Language and Hemispheric Asymmetry
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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 BILL PENNINGTON It happens dozens of times in every N.F.L. game. There is a fierce collision, or perhaps a running back is slammed to the ground. Most of the time, all the players rise to their feet uneventfully. Other times, as the pileup unravels, a player gets up slowly. His gait may be unsteady. For decades in the N.F.L., the operative term for the situation was that someone “got dinged.” It was a cute, almost harmless-sounding description of what was often a concussion or a worrying subconcussive blow to the head. But with the N.F.L. agreeing to pay hundreds of millions of dollars to settle a lawsuit brought by about 5,000 former players who said the league hid from them the dangers of repeated hits to the head, a backpedaling league has corrected its lingo and hastily amended its methodology. The N.F.L. now has a concussion management protocol, outlined in an inches-thick document that commands teams to institute a specific, detailed game-day and postconcussion course of action. Once, the treatment of players with head injuries varied from team to team and could be haphazard. Beginning last season, all players suspected of having a head injury — should they lose consciousness from a collision or experience symptoms like a headache, dizziness or disorientation — were required to go through the concussion protocol system. It features a broad cast: a head-injury spotter in the press box, athletic trainers on the bench, doctors and neuro-trauma specialists on the sideline and experts in neuro-cognitive testing in the locker room. The system is far from foolproof — players with serious symptoms remain in games. But as the N.F.L. grapples with a sobering threat to the welfare of its work force, not to mention a public-relations nightmare, the new concussion protocol is meant to establish a systemic, itemized policy on how potential brain injuries should be handled. © 2014 The New York Times Company
Keyword: Brain Injury/Concussion
Link ID: 20372 - Posted: 12.01.2014
By John Edward Terrell We will certainly hear it said many times between now and the 2016 elections that the country’s two main political parties have “fundamental philosophical differences.” But what exactly does that mean? At least part of the schism between Republicans and Democrats is based in differing conceptions of the role of the individual. We find these differences expressed in the frequent heated arguments about crucial issues like health care and immigration. In a broad sense, Democrats, particularly the more liberal among them, are more likely to embrace the communal nature of individual lives and to strive for policies that emphasize that understanding. Republicans, especially libertarians and Tea Party members on the ideological fringe, however, often trace their ideas about freedom and liberty back to Enlightenment thinkers of the 17th and 18th centuries, who argued that the individual is the true measure of human value, and each of us is naturally entitled to act in our own best interests free of interference by others. Self-described libertarians generally also pride themselves on their high valuation of logic and reasoning over emotion. The basic unit of human social life is not and never has been the selfish and self-serving individual. Philosophers from Aristotle to Hegel have emphasized that human beings are essentially social creatures, that the idea of an isolated individual is a misleading abstraction. So it is not just ironic but instructive that modern evolutionary research, anthropology, cognitive psychology and neuroscience have come down on the side of the philosophers who have argued that the basic unit of human social life is not and never has been the selfish, self-serving individual. Contrary to libertarian and Tea Party rhetoric, evolution has made us a powerfully social species, so much so that the essential precondition of human survival is and always has been the individual plus his or her relationships with others. © 2014 The New York Times Company
Link ID: 20371 - Posted: 12.01.2014
|By Jason G. Goldman A sharp cry pierces the air. Soon a worried mother deer approaches the source of the sound, expecting to find her fawn. But the sound is coming from a speaker system, and the call isn't that of a baby deer at all. It's an infant fur seal's. Because deer and seals do not live in the same habitats, mother deer should not know how baby seal screams sound, reasoned biologists Susan Lingle of the University of Winnipeg and Tobias Riede of Midwestern University, who were running the acoustic experiment. So why did a mother deer react with concern? Over two summers, the researchers treated herds of mule deer and white-tailed deer on a Canadian farm to modified recording of the cries of a wide variety of infant mammals—elands, marmots, bats, fur seals, sea lions, domestic cats, dogs and humans. By observing how mother deer responded, Lingle and Riede discovered that as long as the fundamental frequency was similar to that of their own infants' calls, those mothers approached the speaker as if they were looking for their offspring. Such a reaction suggests deep commonalities among the cries of most young mammals. (The mother deer did not show concern for white noise, birdcalls or coyote barks.) Lingle and Riede published their findings in October in the American Naturalist. Researchers had previously proposed that sounds made by different animals during similar experiences—when they were in pain, for example—would share acoustic traits. “As humans, we often ‘feel’ for the cry of young animals,” Lingle says. That empathy may arise because emotions are expressed in vocally similar ways among mammals. © 2014 Scientific American
by Aviva Rutkin THERE is only one real rule to conversing with a baby: talking is better than not talking. But that one rule can make a lifetime of difference. That's the message that the US state of Georgia hopes to send with Talk With Me Baby, a public health programme devoted to the art of baby talk. Starting in January, nurses will be trained in the best way to speak to babies to help them learn language, based on what the latest neuroscience says. Then they, along with teachers and nutritionists, will model this good behaviour for the parents they meet. Georgia hopes to expose every child born in 2015 in the Atlanta area to this speaking style; by 2018, the hope is to reach all 130,000 or so newborns across the state. Talk With Me Baby is the latest and largest attempt to provide "language nutrition" to infants in the US – a rich quantity and variety of words supplied at a critical time in the brain's development. Similar initiatives have popped up in Providence, Rhode Island, where children have been wearing high-tech vests that track every word they hear, and Hollywood, where the Clinton Foundation has encouraged television shows like Parenthood and Orange is the New Black to feature scenes demonstrating good baby talk. "The idea is that language is as important to the brain as food is to physical growth," says Arianne Weldon, director of Get Georgia Reading, one of several partner organisations involved in Talk With Me Baby. © Copyright Reed Business Information Ltd.
By Virginia Morell When we listen to someone talking, we hear some sounds that combine to make words and other sounds that convey such things as the speaker’s emotions and gender. The left hemisphere of our brain manages the first task, while the right hemisphere specializes in the second. Dogs also have this kind of hemispheric bias when listening to the sounds of other dogs. But do they have it with human sounds? To find out, two scientists had dogs sit facing two speakers. The researchers then played a recorded short sentence—“Come on, then”—and watched which way the dogs turned. When the animals heard recordings in which individual words were strongly emphasized, they turned to the right—indicating that their left hemispheres were engaged. But when they listened to recordings that had exaggerated intonations, they turned to the left—a sign that the right hemisphere was responding. Thus, dogs seem to process the elements of speech very similarly to the way humans do, the scientists report online today in Current Biology. According to the researchers, the findings support the idea that our canine pals are indeed paying close attention not only to who we are and how we say things, but also to what we say. © 2014 American Association for the Advancement of Science.
By Amy Ellis Nutt Debbie Hall undergoes external brain stimulation at Ohio State's Wexner Medical Center. Hall was partially paralyzed on her left side after a stroke. Doctors are conducting a study to see if a device known as NexStim can `prep` a stroke victim's brain immediately prior to physical therapy so that the therapy will be more effective. (The Ohio State University Wexner Medical Center) Using non-invasive transcranial magnetic stimulation, or TMS, researchers at Ohio State Wexner Medical Center may have found a way to help prep a stroke victim's brain prior to physical therapy to aid a more complete recovery. When one side of the brain is damaged by a stroke, the corresponding healthy part goes into overdrive in order to compensate, said Dr. Marcie Bockbrader, principle investigator of the study. She believes the hyperactivity in the healthy side may actually slow recovery in the injured side. The technology, called NexStim, employs TMS to prepare a stroke patient's brain for physical therapy by sending low-frequency magnetic pulses painlessly through a victim's scalp to suppress activity in the healthy part of the motor cortex. This allows the injured side to make use of more energy during physical therapy, which immediately follows the transcranial magnetic stimulation. "This device targets the overactive side, quieting it down enough, so that through therapies the injured side can learn to express itself again," said Bockbrader, an assistant professor of physical medicine and rehabilitation, in a new release.
Link ID: 20349 - Posted: 11.24.2014
By Bethany Brookshire WASHINGTON — Estrogen can protect the brain from harmful inflammation following traumatic injury, a new study in zebra finches suggests. Boosting levels of the sex hormone in the brain might help prevent the cell loss that occurs following damage from injuries such as stroke. Estrogen levels quadrupled around the damaged area in both male and female zebra finches after researchers gave them experimental brain injuries, Colin Saldanha and colleagues at American University in Washington, D.C., reported November 17 at the annual meeting of the Society for Neuroscience. When the scientists prevented finch brains from making estrogen, inflammatory proteins at damaged sites increased. The helpful estrogen didn’t come from gonads. It’s made within the brain by support cells called astrocytes close to the injury. Injury inflames the brain. Initially, this inflammation recruits helpful cells to the damaged area and aids in recovery. But the long-term presence of inflammatory proteins can cause harm, killing off brain cells and reducing functions such as movement and memory. The researchers hope that by understanding how estrogen reduces inflammatory proteins, therapies might boost this natural estrogen production to keep harmful inflammation at bay. © Society for Science & the Public 2000 - 2014.
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 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 Laura Geggel A major pathway of the human brain involved in visual perception, attention and movement — and overlooked by many researchers for more than a century — is finally getting its moment in the sun. In 2012, researchers made note of a pathway in a region of the brain associated with reading, but "we couldn't find it in any atlas," said Jason Yeatman, a research scientist at the University of Washington's Institute for Learning and Brain Sciences. "We'd thought we had discovered a new pathway that no one else had noticed before." A quick investigation showed that the pathway, known as the vertical occipital fasciculus (VOF), was not actually unknown. Famed neuroscientist Carl Wernicke discovered the pathway in 1881, during the dissection of a monkey brain that was most likely a macaque. [10 Things You Didn't Know About the Brain] But besides Wernicke's discovery, and a few other mentions throughout the years, the VOF is largely absent from studies of the human brain. This made Yeatman and his colleagues wonder, "How did a whole piece of brain anatomy get forgotten?" he said. The researchers immersed themselves in century-old brain atlases and studies, trying to decipher when and why the VOF went missing from mainstream scientific literature. They also scanned the brains of 37 individuals, and found an algorithm that can help present-day researchers pinpoint the elusive pathway.
By Kate Baggaley WASHINGTON, D.C. — Adding magnets to football helmets could reduce the risk of concussions, new research suggests. When two players collide, the magnets in their helmets would repel each other, reducing the force of the collision. “All helmet design companies and manufacturers have the same approach, which is to try to disperse the impact energy after the impact’s already occurred,” neuroscientist Raymond Colello said November 15 at the annual meeting of the Society for Neuroscience. The magnets, he says, would put a brake on the impact before it happens. The idea hasn’t been tested yet in helmets with real players, said Judy Cameron, a neuroscientist at the University of Pittsburgh. “But a lot of thought has gone into it, and the data that was shown about the ability of the magnets to actually repel each other looked extremely promising.” On the field, football players can run at nearly 20 miles per hour and can experience up to 150 g’s of force upon impact. Concussions readily occur at impacts greater than 100 g’s. Every year there are 100,000 concussions at all levels of play among the nearly 1.2 million people who play football in the United States. Colello, of Virginia Commonwealth University in Richmond, is testing magnets made in China from the rare-earth element neodymium. They are the most powerful commercially available magnets and weigh about one-third of a pound each (football helmets weigh from 3.5 to 5.5 pounds). When placed one-fourth of an inch away from each other, two magnets with their same poles face-to-face exert nearly 100 pounds of repulsive force. © Society for Science & the Public 2000 - 2014
Keyword: Brain Injury/Concussion
Link ID: 20317 - Posted: 11.17.2014
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.
GrrlScientist Since today is caturday, that wonderful day when the blogosphere takes a breather from hell-raising to celebrate pets, I thought some of my favourite animals: corvids. I ran across this lovely video created by Cornell University’s Laboratory of Ornithology (more fondly referred to as the “Lab of O”) that discusses the differences between and potential meanings of the sounds made by crows and ravens. If you watch birds, even casually, you might be confused by trying to distinguish these two large black corvid species. However, both species are quite chatty, and these birds’ sounds provide important identifying information. In this video, narrated by Kevin McGowan, an ornithologist at the Cornell Lab of O, you’ll learn how to distinguish crows and ravens on the basis of their voices alone. Both crows and ravens make loud raspy signature calls, described as “caw” and “kraa” respectively, but American crows and common ravens have large repertoires of sounds in addition to these calls. They also can learn to imitate the calls of other birds. As you’ll learn in this video, crows often make a “rattle” sound along with their territorial “caw”. They also communicate using a wide variety of other sounds including clicks and bell-like notes. Ravens, on the other hand, produce deep, throaty kraa calls.
Keyword: Animal Communication
Link ID: 20255 - Posted: 10.29.2014
By Virginia Morell Human fetuses are clever students, able to distinguish male from female voices and the voices of their mothers from those of strangers between 32 and 39 weeks after conception. Now, researchers have demonstrated that the embryos of the superb fairy-wren (Malurus cyaneus, pictured), an Australian songbird, also learn to discriminate among the calls they hear. The scientists played 1-minute recordings to 43 fairy-wren eggs collected from nests in the wild. The eggs were between days 9 and 13 of a 13- to 14-day incubation period. The sounds included white noise, a contact call of a winter wren, or a female fairy-wren’s incubation call. Those embryos that listened to the fairy-wrens’ incubation calls and the contact calls of the winter wrens lowered their heart rates, a sign that they were learning to discriminate between the calls of a different species and those of their own kind, the researchers report online today in the Proceedings of the Royal Society B. (None showed this response to the white noise.) Thus, even before hatching, these small birds’ brains are engaged in tasks requiring attention, learning, and possibly memory—the first time embryonic learning has been seen outside humans, the scientists say. The behavior is key because fairy-wren embryos must learn a password from their mothers’ incubation calls; otherwise, they’re less successful at soliciting food from their parents after hatching. © 2014 American Association for the Advancement of Science.
With the passing away of Professor Allison Doupe on Friday, October 24, of cancer, UCSF and biomedical science have lost a scholar of extraordinary intelligence and erudition and a campus leader. Allison Doupe was a psychiatrist and systems neuroscientist who became a leader of her field, the study of sensorimotor learning and its neural control. Allison was recruited to the Departments of Psychiatry and Physiology and the Neuroscience Graduate Program in 1993, rising to Professor in 2000. Her academic career has been outstanding at every stage, including First Class Honors at McGill, an MD and PhD in Neurobiology from Harvard, and a prestigious Junior Fellowship from the Harvard University Society of Fellows. Her PhD work with Professor Paul Patterson definitively established the role of particular environmental factors in the development of autonomic neurons and was important in the molecular and cellular investigations of the roles of hormones and growth factors in that system. After internship at the Massachusetts General Hospital and residency in psychiatry at UCLA, she chose to pursue a postdoctoral fellowship at Caltech, studying song learning in birds with Professor Mark Konishi as a way of combining her clinical interests in behavior and development with research in cognitive neuroscience. The development of birdsong is in many important respects similar to language development in humans. The pioneering work of Peter Marler, on song sparrows in Golden Gate Park, showed that each baby songbird learns its father’s dialect but could readily learn the dialect of any singing bird of the same species placed in the role of tutor. Many birds, including the ones studied by Allison Doupe, learn their song by listening to their father sing during a period of life in which they are not themselves singing, and they later practice and perfect their own song by comparison with their memory of the father’s (or tutor’s) song.
|By Steve Mirsky People have been leaving messages on bathroom walls for thousands of years. Just google “ancient Roman bathroom graffiti.” But we’re not the only ones to use latrines for information exchange—as two German researchers have confirmed after hundreds of hours watching lemurs pee and poop. For science. Primatologists Iris Dröscher and Peter Kappeler concentrated on seven sets of pair-bonded members of a species called white-footed sportive lemurs, at a nature reserve in southern Madagascar. Their report is in the journal Behavioral Ecology and Sociobiology. [Iris Dröscher & Peter M. Kappeler Maintenance of familiarity and social bonding via communal latrine use in a solitary primate (Lepilemur leucopus)] Many animals use the same spots repeatedly to do their business, primates in particular. For these lemurs, a specific tree becomes the urine and feces focal point. And because chemical compounds in their waste transmit information, the so-called latrine tree becomes like a bulletin board to post messages for the rest of the community. Based on their 1,097 hours of observations, the researchers conclude that urine and glandular secretions left on the tree trunk are the primary message vehicles. Feces mostly just collects on the ground. Some urine telegrams are probably signals from a particular lemur to the neighbors that he or she is around. But male lemurs upped their latrine visits when potential competitors for females came into their home area. So the frequent chemical messages left on the tree probably say in that case, “Buzz off, buddy, she’s with me.” In lemur. © 2014 Scientific American,
by Colin Barras LOCKED in but not shut out: for the first time people who have lost the ability to move or talk because of a stroke may be able to communicate with their loved ones using a brain-computer interface. Brain injuries can leave people aware but almost completely paralysed, a condition called locked-in syndrome. Brain-computer interfaces (BCIs) can help some people communicate by passing signals from electrodes attuned to their brain activity as they watch a screen displaying letters. Subtle changes in neural activity let researchers know when a person wishes to select a particular on-screen item, allowing them to spell out messages by thought alone. Until now, BCIs have only been tested on healthy volunteers and people with amyotrophic lateral sclerosis, a neurodegenerative disease that leads to muscle wasting. But no one had tested whether the technology could help people locked in after a brain stem stroke. Now Eric Sellers and his colleagues at East Tennessee State University in Johnson City have tested the technique on a 68-year-old man. After more than a year of training he learned to communicate reliably via the BCI. He took the opportunity to thank his wife for her hard work, and to give his thoughts on gift purchases for his children (Science Translational Medicine, DOI: 10.1126/scitranslmed.3007801). © Copyright Reed Business Information Ltd.
By Virginia Morell Two years ago, scientists showed that dolphins imitate the sounds of whales. Now, it seems, whales have returned the favor. Researchers analyzed the vocal repertoires of 10 captive orcas (Orcinus orca), three of which lived with bottlenose dolphins (Tursiops truncatus) and the rest with their own kind. Of the 1551 vocalizations these seven latter orcas made, more than 95% were the typical pulsed calls of killer whales. In contrast, the three orcas that had only dolphins as pals busily whistled and emitted dolphinlike click trains and terminal buzzes, the scientists report in the October issue of The Journal of the Acoustical Society of America. (Watch a video as bioacoustician and co-author Ann Bowles describes the difference between killer whale and orca whistles.) The findings make orcas one of the few species of animals that, like humans, is capable of vocal learning—a talent considered a key underpinning of language. © 2014 American Association for the Advancement of Science.
|By Tori Rodriguez The safety of football continues to be a heated topic for players and parents, with mixed evidence regarding the effect of head injuries on mental illness. Past studies on the connection have often been methodologically flawed or yielded ambiguous results. Now a paper in April in the American Journal of Psychiatry, the largest study yet to investigate the link, finds that even a single head injury indeed increases the risk of later mental illness, especially if the injury occurs during adolescence. Using Danish medical registries, researchers led by physician Sonja Orlovska of the University of Copenhagen studied 113,906 people who had been hospitalized for head injuries over a 23-year period. They discovered that in addition to cognitive symptoms caused by structural damage to the brain (such as delirium), these people were subsequently more likely than the general population to develop several psychiatric illnesses. Risk increased by 65 percent for schizophrenia and 59 percent for depression. Risk was highest in the first year postinjury but remained significantly elevated throughout the next 15 years. After the team controlled for several potential confounders, such as accident proneness and a family history of psychiatric problems, they found the strongest injury-related predictor for later onset of schizophrenia, depression and bipolar disorder was a head trauma experienced between the ages of 11 and 15. “Previous studies have shown that head injury induces inflammation in the brain, which causes several changes—for example, an increased permeability of the blood-brain barrier,” Orlovska says. Normally the barrier protects the brain from potentially harmful contents in the bloodstream, but injury-induced inflammation may allow these substances access to the brain. “For some individuals, this might initiate damaging processes in the brain,” she says. © 2014 Scientific American,