Chapter 19. Language and Hemispheric Asymmetry
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By Sara Chodosh There has long been debate about a link between serious blows to the head and the development of neurodegenerative diseases later in life. Research has made cases for and against a relationship between traumatic brain injuries and neurological ailments such as Alzheimer’s, Parkinson’s and general dementia. Now the question is drawing ever more scrutiny as the alarming extent of these injuries becomes better known—and new research is finally casting some light on this murky and often quietly terrifying topic. A large-scale analysis of three separate studies published this week in JAMA Neurology found no association between unconsciousness-causing traumatic brain injuries (TBI) and Alzheimer’s disease or general dementia—but it did find a strong association between TBI and Parkinson’s disease. “I can’t decide if the positive or negative findings are more surprising,” says one of the study’s investigators, physician and Alzheimer’s researcher Paul Crane at the University of Washington. The positive association his team found between Parkinson’s and TBI was not entirely novel, but Crane says the magnitude of the link was unexpected. The researchers found the risk of Parkinson’s rose threefold for people whose head injuries had caused them to go unconscious for more than an hour. The more contentious finding is the lack of an association between TBI and Alzheimer’s. Prior research has been divided on whether there is a link, but many of the previous studies have been smaller in scale and conducted less-comprehensive analyses. “Although early studies suggested a clear link between TBI and an increased risk for Alzheimer’s disease, this has not been replicated,” explains Frances Corrigan at the University of Adelaide, who studies how TBI influences neurodegeneration. © 2016 Scientific American,
Rachel Ehrenberg When mice have a stroke, their gut reaction can amp up brain damage. A series of new experiments reveals a surprising back-and-forth between the brain and the gut in the aftermath of a stroke. In mice, this dickering includes changes to the gut microbial population that ultimately lead to even more inflammation in the brain. There is much work to be done to determine whether the results apply to humans. But the research, published in the July 13 Journal of Neuroscience, hints that poop pills laden with healthy microbes could one day be part of post-stroke therapy. The work also highlights a connection between gut microbes and brain function that scientists are only just beginning to understand,says Ted Dinan of the Microbiome Institute at the University College Cork, Ireland. There’s growing evidence that gut microbes can influence how people experience stress or depression, for example (SN: 4/2/16, p. 23). “It’s a fascinating study” says Dinan, who was not involved with the work. “It raises almost as many questions as it answers, which is what good studies do.” Following a stroke, the mouse gut becomes temporarily paralyzed, leading to a shift in the microbial community, neurologist Arthur Liesz of the Institute for Stroke and Dementia Research in Munich and colleagues found. This altered, less diverse microbial ecosystem appears to interact with immune system cells called T cells that reside in the gut. These T cells can either dampen inflammation or dial it up, leading to more damage, says Liesz. Whether the T cells further damage the brain after a stroke rather than soothe it seems to be determined by the immune system cells’ interaction with the gut microbes. © Society for Science & the Public 2000 - 2016.
Link ID: 22431 - Posted: 07.13.2016
DAVID GREENE, HOST: Nearly one-quarter of all Americans reach for a bottle of acetaminophen every single week. Many of you might know this drug as Tylenol. It's a pain killer that can take the edge off a headache or treat you when you have a fever. It also might have another effect. And let's talk about this with NPR social science correspondent Shankar Vedantam. And, Shankar, straight out, is this going to make me not want to take Tylenol, what you're about to tell me? VEDANTAM: It might make you not want to take Tylenol when you're talking with me, David. GREENE: Oh, even more interesting. VEDANTAM: (Laughter) I was speaking with Dominik Mischkowski. He's currently a researcher at the National Institutes of Health. He recently conducted a couple of double blind experiments. These are experiments where the volunteers are given either sugar pills or Tylenol, but neither the volunteers nor the researchers know which volunteers are getting which pill. Mischkowski and his advisers at Ohio State University, Jennifer Crocker and Baldwin Way, they played loud noises for the volunteers. Not surprisingly, volunteers given Tylenol experienced less physical discomfort than volunteers given the placebo. © 2016 npr
Keyword: Pain & Touch
Link ID: 22403 - Posted: 07.07.2016
By Anthea Rowan The neurologist does not cushion his words. He tells us how it is: “She won’t read again.” I am standing behind my mother. I feel her stiffen. We do not talk of this revelation for days — and when we do, we do it in the garden of the rehab facility where she is recovering from a stroke. The stroke has scattered her memory, but she has not forgotten she will apparently not read again. I was shocked by what the doctor said, she confides. Me, too. Do you believe him? she asks. No — I am emphatic, for her and for me — I don’t. Mum smiles: “Me neither.” The damage wreaked by Mum’s stroke leaked across her brain, set up roadblocks so that the cerebral circuit board fizzes and pops uselessly, with messages no longer neatly passing from “A” to “B.” I tell the neuro: “I thought they’d learn to go via ‘D’ or ‘W.’ Isn’t that what’s supposed to happen — messages reroute?” “Unlikely,” he responds. “In your mother’s case.” Alexia — the loss of the ability to read — is common after strokes, especially, as in my mother’s case, when damage is wrought in the brain’s occipital lobe, which processes visual information. Pure alexia, which is Mum’s diagnosis, is much more rare: She can still write and touch-type, but bizarrely, she cannot read.
Playing simple card games, such as snap, can help stroke patients with their recovery, say Canadian researchers. The scientists found it improved patients' motor skills. Playing Jenga, bingo or a games consol like Wii worked equally well. They told the Lancet Neurology that the type of task used for motor rehabilitation might be less relevant, as long as it is intensive, repetitive and gets the hands and arms moving. The researchers designed their study to test whether virtual reality gaming, which is increasingly being employed as a rehab therapy for stroke patients, is any better than more traditional games for honing upper limb motor skills. The Canadian team recruited 141 patients who had recently suffered a stroke, and now had some impaired movement in one or both of their hands and arms. Approximately half of the patients, at random, were then allocated to the Wii rehab, while the rest were asked to do other recreational activities, such as playing cards. All of the patients continued to receive usual stroke rehabilitation care and support on top of the 10, one-hour sessions of gaming or card playing for a fortnight. Both groups showed significant improvement in their motor skills at the end of the two weeks and four weeks later. Importantly, both groups fared equally well, say the researchers. While it's not clear from this study how much of the improvement was from the regular stroke care the participants received, other research suggests adding in more therapy is beneficial. Investigator Dr Gustavo Saposnik, from St Michael's Hospital in Toronto, said: "We all like technology and have the tendency to think that new technology is better than old-fashioned strategies, but sometimes that's not the case. In this study, we found that simple recreational activities that can be implemented anywhere may be as effective as technology." © 2016 BBC.
Link ID: 22367 - Posted: 06.28.2016
by Helen Thompson Young zebra finches (Taeniopygia guttata) learn to sing from a teacher, usually dad. Remembering dad’s tunes may even be hardwired into the birds’ brains. Researchers at the Okinawa Institute of Science and Technology in Japan measured activity in the brains of male juvenile birds listening to recordings of singing adult males, including their fathers. The team focused its efforts on neurons in a part of the brain called the caudomedial nidopallium that’s thought to influence song learning and memory. A subset of neurons in the caudomedial nidopallium lit up in response to songs performed by dad but not those of strangers, the team reports June 21 in Nature Communications. The more baby birds heard songs, the more their neurons responded and the clearer their own songs became. Sleep and a neurotransmitter called GABA influenced this selectivity. The researchers suggest that this particular region of the brain stores song memories as finches learn to sing, and GABA may drive the storage of dad’s songs over others. Researchers played a variety of sounds for young zebra finches: their own song, dad’s song and songs and calls from other adult finches. Over time, their songs became more and more similar to that of their father. |© Society for Science & the Public 2000 - 2016
In a study of stroke patients, investigators confirmed through MRI brain scans that there was an association between the extent of disruption to the brain’s protective blood-brain barrier and the severity of bleeding following invasive stroke therapy. The results of the National Institutes of Health-funded study were published in Neurology. These findings are part of the Diffusion and Perfusion Imaging Evaluation for Understanding Stroke Evolution (DEFUSE)-2 Study, which was designed to see how MRIs can help determine which patients undergo endovascular therapy following ischemic stroke caused by a clot blocking blood flow to the brain. Endovascular treatment targets the ischemic clot itself, either removing it or breaking it up with a stent. The blood-brain barrier is a layer of cells that protects the brain from harmful molecules passing through the bloodstream. After stroke, the barrier is disrupted, becoming permeable and losing control over what gets into the brain. “The biggest impact of this research is that information from MRI scans routinely collected at a number of research hospitals and stroke centers can inform treating physicians on the risk of bleeding,” said Richard Leigh, M.D., a scientist at NIH’s National Institute of Neurological Disorders and Stroke (NINDS) and an author on the study. In this study, brain scans were collected from more than 100 patients before they underwent endovascular therapy, within 12 hours of stroke onset. Dr. Leigh and his team obtained the images from DEFUSE-2 investigators.
by Laura Sanders Any parent trying to hustle a school-bound kid out the door in the morning knows that her child’s skull possesses a strange and powerful form of black magic: It can repel parents’ voices. Important messages like “find your shoes” bounce off the impenetrable fortress and drift unheeded to the floor. But when this perplexing force field is off, it turns out that mothers’ voices actually have profound effects on kids. Children’s brains practically buzz when they hear their moms’ voices, scientists report in the May 31 Proceedings of the National Academy of Sciences. (Fun and not surprising side note: Babies’ voices get into moms’ brains, too.) The parts of kids’ brains that handle emotions, face recognition and reward were prodded into action by mothers’ voices, brain scans of 24 children ages 7 to 12 revealed. And words were not required to get this big reaction. In the study, children listened to nonsense words said by either their mother or one of two unfamiliar women. Even when the words were fake, mothers’ voices still prompted lots of neural action. The study was done in older kids, but children are known to tune into their mothers’ voices early. Really early, in fact. One study found that fetuses’ heart rates change when they hear their moms read a story. For a fetus crammed into a dark, muffled cabin, voices may take on outsized importance. |© Society for Science & the Public 2000 - 2016.
By Amina Zafar, When Susan Robertson's fingers and left arm felt funny while she was Christmas shopping, they were signs of a stroke she experienced at age 36. The stroke survivor is now concerned about her increased risk of dementia. The link between stroke and dementia is stronger than many Canadians realize, the Heart and Stroke Foundation says. The group's annual report, released Thursday, is titled "Mind the connection: preventing stroke and dementia." Stroke happens when blood stops flowing to parts of the brain. Robertson, 41, of Windsor, Ont., said her short-term memory, word-finding and organizational skills were impaired after her 2011 stroke. She's extremely grateful to have recovered the ability to speak and walk after doctors found clots had damaged her brain's left parietal lobe. "I knew what was happening, but I couldn't say it," the occupational nurse recalled. Dementia risk A stroke more than doubles the risk of dementia, said Dr. Rick Swartz, a spokesman for the foundation and a stroke neurologist in Toronto. Raising awareness about the link is not to scare people, but to show how controlling blood pressure, not smoking or quitting if you do, eating a balanced diet and being physically active reduce the risk to individuals and could make a difference at a society level, Swartz said. While aging is a common risk factor in stroke and dementia, evidence in Canada and other developed countries shows younger people are also increasingly affected. ©2016 CBC/Radio-Canada.
By Karin Brulliard Think about how most people talk to babies: Slowly, simply, repetitively, and with an exaggerated tone. It’s one way children learn the uses and meanings of language. Now scientists have found that some adult birds do that when singing to chicks — and it helps the baby birds better learn their song. The subjects of the new study, published last week in the journal Proceedings of the National Academy of Sciences, were zebra finches. They’re good for this because they breed well in a lab environment, and “they’re just really great singers. They sing all the time,” said McGill University biologist and co-author Jon Sakata. The males, he means — they’re the singers, and they do it for fun and when courting ladies, as well as around baby birds. Never mind that their melody is more “tinny,” according to Sakata, than pretty. Birds in general are helpful for vocal acquisition studies because they, like humans, are among the few species that actually have to learn how to make their sounds, Sakata said. Cats, for example, are born knowing how to meow. But just as people pick up speech and bats learn their calls, birds also have to figure out how to sing their special songs. Sakata and his colleagues were interested in how social interactions between adult zebra finches and chicks influences that learning process. Is face-to-face — or, as it may be, beak-to-beak — learning better? Does simply hearing an adult sing work as well as watching it do so? Do daydreaming baby birds learn as well as their more focused peers? © 1996-2016 The Washington Post
By Andy Coghlan People once dependent on wheelchairs after having a stroke are walking again since receiving injections of stem cells into their brains. Participants in the small trial also saw improvements in their speech and arm movements. “One 71-year-old woman could only move her left thumb at the start of the trial,” says Gary Steinberg, a neurosurgeon at Stanford University who performed the procedure on some of the 18 participants. “She can now walk and lift her arm above her head.” Run by SanBio of Mountain View, California, this trial is the second to test whether stem cell injections into patients’ brains can help ease disabilities resulting from stroke. Patients in the first, carried out by UK company ReNeuron, also showed measurable reductions in disability a year after receiving their injections and beyond. All patients in the latest trial showed improvements. Their scores on a 100-point scale for evaluating mobility – with 100 being completely mobile – improved on average by 11.4 points, a margin considered to be clinically meaningful for patients. “The most dramatic improvements were in strength, coordination, ability to walk, the ability to use hands and the ability to communicate, especially in those whose speech had been damaged by the stroke,” says Steinberg. In both trials, improvements in patients’ mobility had plateaued since having had strokes between six months and three years previously. © Copyright Reed Business Information Ltd
Meghan Rosen SALT LAKE CITY — In the Indian Ocean off the coast of Sri Lanka, pygmy blue whales are changing their tune — and they might be doing it on purpose. From 2002 to 2012, the frequency of one part of the whales’ calls steadily fell, marine bioacoustician Jennifer Miksis-Olds reported May 25 at a meeting of the Acoustical Society of America. But unexpectedly, another part of the whales’ call stayed the same, she found. “I’ve never seen results like this before,” says marine bioacoustician Leanna Matthews of Syracuse University in New York, who was not involved with the work. Miksis-Olds’ findings add a new twist to current theories about blue whale vocalizations and spark all sorts of questions about what the animals are doing, Matthews said. “It’s a huge mystery.” Over the last 40 to 50 years, the calls of blue whales around the world have been getting deeper. Researchers have reported frequency drops in blue whale populations from the Arctic Ocean to the North Pacific. Some researchers think that blue whales are just getting bigger, said Miksis-Olds, of the University of New Hampshire in Durham. Whaling isn’t as common as it used to be, so whales have been able to grow larger — and larger whales have deeper calls. Another theory blames whales’ changing calls on an increasingly noisy ocean. Whales could be automatically adjusting their calls to be heard better, kind of like a person raising their voice to speak at a party, she said. If the whales were just getting bigger, you’d expect all components of the calls to be deeper, said acoustics researcher Pasquale Bottalico at Michigan State University in East Lansing. But the new data don’t support that, he said. © Society for Science & the Public 2000 - 2016. A
By RUSSELL GOLDMAN There’s an elephant at a zoo outside Seoul that speaks Korean. — You mean, it understands some Korean commands, the way a dog can be trained to understand “sit” or “stay”? No, I mean it can actually say Korean words out loud. — Pics or it didn’t happen. Here, watch the video. To be fair, the elephant, a 26-year-old Asian male named Koshik, doesn’t really speak Korean, any more than a parrot can speak Korean (or English or Klingon). But parrots are supposed to, well, parrot — and elephants are not. And Koshik knows how to say at least five Korean words, which are about five more than I do. The really amazing part is how he does it. Koshik places his trunk inside his mouth and uses it to modulate the tone and pitch of the sounds his voice makes, a bit like a person putting his fingers in his mouth to whistle. In this way, Koshik is able to emulate human speech “in such detail that Korean native speakers can readily understand and transcribe the imitations,” according to the journal Current Biology. What’s in his vocabulary? Things he hears all the time from his keepers: the Korean words for hello, sit down, lie down, good and no. Elephant Speaks Korean | Video Video by LiveScienceVideos Lest you think this is just another circus trick that any Jumbo, Dumbo or Babar could pull off, the team of international scientists who wrote the journal article say Koshik’s skills represent “a wholly novel method of vocal production and formant control in this or any other species.” Like many innovations, Koshik’s may have been born of sad necessity. Researchers say he started to imitate his keepers’s sounds only after he was separated from other elephants at the age of 5 — and that his desire to speak like a human arose from sheer loneliness. © 2016 The New York Times Company
By JOHN BRANCH When the N.F.L. agreed in 2012 to donate tens of millions of dollars to concussion research overseen by the National Institutes of Health, it was widely seen as a positive turning point in football’s long history of playing down the long-term effects of brain injuries on players. At the time, the league said that it would have no influence over how the money was used. But the league and its head, neck and spine committee worked to improperly influence the government research, trying to steer the study toward a doctor with ties to the league, according to a study conducted by a congressional committee and released on Monday. “Our investigation has shown that while the N.F.L. had been publicly proclaiming its role as funder and accelerator of important research, it was privately attempting to influence that research,” the study concluded. “The N.F.L. attempted to use its ‘unrestricted gift’ as leverage to steer funding away from one of its critics.” The N.F.L., in a statement, said it rejected the accusations laid out in the study, which was conducted by Democratic members of the House Committee on Energy and Commerce. “There is no dispute that there were concerns raised about both the nature of the study in question and possible conflicts of interest,” the league said. “These concerns were raised for review and consideration through the appropriate channels.” It is the latest in a long history of instances in which the N.F.L. has been found to mismanage concussion research, dating to the league’s first exploration of the crisis when it used deeply flawed data to produce a series of studies. In this case, some of the characters are the same, including Dr. Elliot Pellman, who led the league’s concussion committee for years before he was discredited for his questionable credentials and his role as a longtime denier of the effects of concussions on players. © 2016 The New York Times Company
Keyword: Brain Injury/Concussion
Link ID: 22241 - Posted: 05.24.2016
By Christie Aschwanden When concussions make the news, it’s usually about football. But head injuries happen in other sports too, and not just to men. During a congressional hearing on concussions in youth sports on Friday, Dawn Comstock, an epidemiologist who studies sports injuries, told a House Energy and Commerce subcommittee that in sports like soccer and basketball in which girls and boys play by the same rules, with the same equipment and the same facilities, “girls have higher concussion rates than boys.” Comstock, a researcher at the Colorado School of Public Health, is the first author of a 2015 study published in JAMA Pediatrics that quantified concussions in high school soccer and found that they were about one and a half times more common in girls than in boys. When U.S. Rep. Diana DeGette, D-Colo., asked whether more data was needed to show that girls have higher concussion rates, Comstock replied, “We already have the data that’s consistently shown this gender difference.” What we don’t have, she said, is a proven explanation for the discrepancy. Some researchers have wondered whether women and girls are simply more likely to report their symptoms than men and boys are. “It’s a sexist way to say that they’re not as tough,” said Katherine Price Snedaker, executive director of Pink Concussions,1 an organization that is seeking answers to how concussions affect women and girls. The group recently held a summit on female concussion and traumatic brain injuries at Georgetown University, and one of the speakers was Shannon Bauman, a sports physician who presented data from 207 athletes — both male and female — who’d been evaluated at her specialty concussion clinic in Barrie, Ontario, between September 2014 and January 2016.
By Matthew Hutson Last week, Nature, the world’s most prestigious science journal, published a beautiful picture of a brain on its cover. The computer-generated image, taken from a paper in the issue, showed the organ’s outer layer almost completely covered with sprinkles of colorful words. The paper presents a “semantic map” revealing which parts of the brain’s cortex—meaning its outer layer, the one responsible for higher thought—respond to various spoken words. The study has generated widespread interest, receiving coverage from newspapers and websites around the world. The paper was also accompanied by an online interactive model that allowed users to explore exactly how words are mapped in our brains. The combination yielded a popular frenzy, one prompting the question: Why are millions of people suddenly so interested in the neuroanatomical distribution of linguistic representations? Have they run out of cat videos? The answer, I think, is largely the same as the answer to why “This Is Your Brain on X” (where X = food, politics, sex, podcasts, whatever) is a staple of news headlines, often residing above an fMRI image of a brain lit up in fascinating, mysterious patterns: People have a fundamental misunderstanding of the field of neuroscience and what it can tell us. But before explaining why people shouldn’t be excited about this research, let’s look at what the research tells us and why we should be excited. Different parts of the brain process different elements of thought, and some regions of the cortex are organized into “maps” such that the distance between different locations corresponds to the physical and/or conceptual distance between what it represents.
By BENEDICT CAREY Listening to music may make the daily commute tolerable, but streaming a story through the headphones can make it disappear. You were home; now you’re at your desk: What happened? Storytelling happened, and now scientists have mapped the experience of listening to podcasts, specifically “The Moth Radio Hour,” using a scanner to track brain activity. In a paper published Wednesday by the journal Nature, a research team from the University of California, Berkeley, laid out a detailed map of the brain as it absorbed and responded to a story. Widely dispersed sensory, emotional and memory networks were humming, across both hemispheres of the brain; no story was “contained” in any one part of the brain, as some textbooks have suggested. The team, led by Alexander Huth, a postdoctoral researcher in neuroscience, and Jack Gallant, a professor of psychology, had seven volunteers listen to episodes of “The Moth” — first-person stories of love, loss, betrayal, flight from an abusive husband, and more — while recording brain activity with an M.R.I. machine. Sign Up for the Science Times Newsletter Every week, we'll bring you stories that capture the wonders of the human body, nature and the cosmos. Using novel computational methods, the group broke down the stories into units of meaning: social elements, for example, like friends and parties, as well as locations and emotions . They found that these concepts fell into 12 categories that tended to cause activation in the same parts of people’s brains at the same points throughout the stories. They then retested that model by seeing how it predicted M.R.I. activity while the volunteers listened to another Moth story. Would related words like mother and father, or times, dates and numbers trigger the same parts of people’s brains? The answer was yes. © 2016 The New York Times Company
By Andy Coghlan “I’ve become resigned to speaking like this,” he says. The 17-year old boy’s mother tongue is Dutch, but for his whole life he has spoken with what sounds like a French accent. “This is who I am and it’s part of my personality,” says the boy, who lives in Belgium – where Dutch is an official language – and prefers to remain anonymous. “It has made me stand out as a person.” No matter how hard he tries, his speech sounds French. About 140 cases of foreign accent syndrome (FAS) have been described in scientific studies, but most of these people developed the condition after having a stroke. In the UK, for example, a woman in Newcastle who’d had a stroke in 2006 woke up with a Jamaican accent. Other British cases include a woman who developed a Chinese accent, and another who acquired a pronounced French-like accent overnight following a bout of cerebral vasculitis. But the teenager has had the condition from birth, sparking the interest of Jo Verhoeven of City University London and his team. Scans revealed that, compared with controls, the flow of blood to two parts of the boy’s brain were significantly reduced. One of these was the prefrontal cortex of the left hemisphere – a finding unsurprising to the team, as it is known to be associated with planning actions including speech. © Copyright Reed Business Information Ltd.
Link ID: 22161 - Posted: 04.30.2016
Ian Sample Science editor Scientists have created an “atlas of the brain” that reveals how the meanings of words are arranged across different regions of the organ. Like a colourful quilt laid over the cortex, the atlas displays in rainbow hues how individual words and the concepts they convey can be grouped together in clumps of white matter. “Our goal was to build a giant atlas that shows how one specific aspect of language is represented in the brain, in this case semantics, or the meanings of words,” said Jack Gallant, a neuroscientist at the University of California, Berkeley. No single brain region holds one word or concept. A single brain spot is associated with a number of related words. And each single word lights up many different brain spots. Together they make up networks that represent the meanings of each word we use: life and love; death and taxes; clouds, Florida and bra. All light up their own networks. Described as a “tour de force” by one researcher who was not involved in the study, the atlas demonstrates how modern imaging can transform our knowledge of how the brain performs some of its most important tasks. With further advances, the technology could have a profound impact on medicine and other fields. “It is possible that this approach could be used to decode information about what words a person is hearing, reading, or possibly even thinking,” said Alexander Huth, the first author on the study. One potential use would be a language decoder that could allow people silenced by motor neurone disease or locked-in syndrome to speak through a computer. © 2016 Guardian News and Media Limited
Jon Hamilton People who sustain a concussion or a more severe traumatic brain injury are likely to have sleep problems that continue for at least a year and a half. A study of 31 patients with this sort of brain injury found that 18 months afterward, they were still getting, on average, an hour more sleep each night than similar healthy people were getting. And despite the extra sleep, 67 percent showed signs of excessive daytime sleepiness. Only 19 percent of healthy people had that problem. Surprisingly, most of these concussed patients had no idea that their sleep patterns had changed. "If you ask them, they say they are fine," says Dr. Lukas Imbach, the study's first author and a senior physician at the University Hospital Zurich in Zurich. When Imbach confronts patients with their test results, "they are surprised," he says. The results, published Thursday in the online edition of the journal Neurology, suggest there could be a quiet epidemic of sleep disorders among people with traumatic brain injuries. The injuries are diagnosed in more than 2 million people a year in the United States. Common causes include falls, motor vehicle incidents and assaults. Previous studies have found that about half of all people who sustain sudden trauma to the brain experience sleep problems. But it has been unclear how long those problems persist. "Nobody actually had looked into that in detail," Imbach says. A sleep disorder detected 18 months after an injury will linger for at least two years, and probably much longer, the researchers say. © 2016 npr