Chapter 15. Language and Our Divided Brain
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Helen Shen Repeated head injuries in American football have been linked to a degenerative brain disorder later in life. Dave Duerson suspected that something was wrong with his brain. By 2011, 18 years after the former American football player had retired from the Phoenix Cardinals, he experienced frequent headaches, memory problems and an increasingly short temper. Before he killed himself, he asked that his brain be donated for study. Researchers who examined it found signs of chronic traumatic encephalopathy (CTE), a degenerative condition linked to repeated head injuries. At least 69 cases have been reported in the literature since 2000, many in former boxers and American football players (P. H. Montenigro et al. Alz. Res. Ther. 6, 68; 2014) — heightening public concern about concussions during contact sports. Yet much about CTE is unknown, from its frequency to its precise risk factors and even whether its pathology is unique. Researchers now hope to take a major step towards answering those questions. At Boston University in Massachusetts on 25–27 February, neuroscientists will convene to examine the characteristics of CTE in brain tissue from post-mortem examinations. They hope to agree on a set of diagnostic criteria for the disease, and to assess whether it is distinct from other brain disorders, such as Alzheimer’s disease. The effort is sorely needed, says Walter Koroshetz, acting director of the US National Institute of Neurological Disorders and Stroke in Bethesda, Maryland, which is organizing the meeting. “The definition is the important piece that lets you do the rest of the research,” he says. And the stakes are high. CTE is associated with memory loss, irritability, depression and explosive anger, which are thought to appear and worsen years after repeated head trauma. © 2015 Nature Publishing Group
Keyword: Brain Injury/Concussion
Link ID: 20613 - Posted: 02.25.2015
By Tia Ghose A woman who had persistent headaches found there was a strange culprit for her pain: a Pilates class that caused her brain fluid to leak, according to a new case report. The brain fluid leak led to a persistent, worsening headache that was only alleviated when the 42-year-old British woman laid down, according to the report that was published in December in the Journal of Medical Case Reports. Though doctors never identified the exact location of the leak, the patient improved after a few weeks of bed rest and pain relievers. [The 16 Oddest Medical Cases] Cerebrospinal fluid is a clear liquid that flows between the brain and its outer covering, and between the spinal cord and its outer covering. Both of these structures' outer coverings are called the dura. This fluid cushions the brain and spinal cord and helps clear metabolic waste from the brain. However, sometimes holes can emerge in the dura, said Dr. Amber Luong, an otolaryngologist at the University of Texas Health Sciences Center in Houston. "The most common cause [of such leaks is] trauma, like a car accident," Luong told Live Science. Often, cerebrospinal fluid leaks out of a person's nose because there is a crack in the base of the skull and a tear in the dura lining the brain. One telltale sign of a cerebrospinal leak is that there is clear, metallic-tasting fluid coming out of just one nostril, Luong said. (The woman in this case did not experience this symptom because her tear was around the spinal cord, not the brain.)
Keyword: Brain Injury/Concussion
Link ID: 20579 - Posted: 02.16.2015
Ewen Callaway A mysterious group of humans from the east stormed western Europe 4,500 years ago — bringing with them technologies such as the wheel, as well as a language that is the forebear of many modern tongues, suggests one of the largest studies of ancient DNA yet conducted. Vestiges of these eastern émigrés exist in the genomes of nearly all contemporary Europeans, according to the authors, who analysed genome data from nearly 100 ancient Europeans1. The first Homo sapiens to colonize Europe were hunter-gatherers who arrived from Africa, by way of the Middle East, around 45,000 years ago. (Neanderthals and other archaic human species had begun roaming the continent much earlier.) Archaeology and ancient DNA suggest that farmers from the Middle East started streaming in around 8,000 years ago, replacing the hunter-gatherers in some areas and mixing with them in others. But last year, a study of the genomes of ancient and contemporary Europeans found echoes not only of these two waves from the Middle East, but also of an enigmatic third group that they said could be from farther east2 (see 'Ancient European genomes reveal jumbled ancestry'). Ancient genes To further pin down the origins of this ghost lineage, a team led by David Reich, an evolutionary and population geneticist at Harvard Medical School in Boston, Massachusetts, analysed nuclear DNA from the bodies of 69 individuals who lived across Europe between 8,000 and 3,000 years ago. They also examined previously published genome data from another 25 ancient Europeans, including Ötzi, the 5,300-year-old 'ice man' who was discovered on the Italian-Austrian border. © 2015 Nature Publishing Group
Link ID: 20571 - Posted: 02.13.2015
by Andy Coghlan Apple's the word. Chimpanzees can learn to grunt "apple" in two chimp languages – a finding that questions how unique our own language abilities are. Researchers have kept records of vocalisations of a group of adult chimps from the Netherlands before and after the move to Edinburgh zoo. Three years later, recordings show, the Dutch chimps had picked up the pronunciation of their Scottish hosts. The finding challenges the prevailing theory that chimp words for objects are fixed because they result from excited, involuntary outbursts. Humans can easily learn foreign words that refer to a specific object, and it was assumed that chimps and other animals could not, perhaps owing to their different brain structure. This has long been argued to be one of the talents making humans unique. The assumption has been that animals do not have control over the sounds they make, whereas we socially learn the labels for things – which is what separates us from animals, says Katie Slocombe of the University of York, UK. But this may be wrong, it seems. "The important thing we've now shown is that with the food calls, they changed the structure to fit in with their new group members, so the Dutch calls for 'apple' changed to the Edinburgh ones," says Slocombe. "It's the first time call structure has been dissociated from emotional outbursts." © Copyright Reed Business Information Ltd.
By Virginia Morell To prevent their hives from being attacked by invaders, wasps must quickly distinguish friend from foe. They typically do this by sniffing out foreigners, as outsiders tend to have a different scent than the home colony. Now researchers have discovered that, like a few other wasp species, a tiny social wasp (Liostenogaster flavolineata) from Malaysia employs an additional security measure: facial recognition. The wasps’ nests are typically found in large aggregations with as many as 150 built close together, and each colony faces persistent landing attempts by outsiders from these other nests. To find out why and how these wasps employ both vision and scent to determine if an incoming wasp is a comrade, scientists carried out a series of experiments on 50 colonies (see photo above) in the wild. Close to the nests, the researchers dangled lures made of captured and killed wasps. The lures had been given different treatments. For instance, some lures made from nest mates were coated with a foe’s scent, whereas outsiders were painted with the colony’s odor. The wasps, it turns out, pay more attention to facial markings than to scent when faced with a possible intruder, the team reports online today in the Proceedings of the Royal Society B. Indeed, in tests where the wasps could assess both an intruder’s face and scent, they relied solely on facial recognition and immediately attacked those whose faces they didn’t know, ignoring their odor. That’s the safest strategy, the scientists note, because the wasps can recognize another’s face at a distance, but need to actually touch another wasp to detect her scent—not a bad ploy for a tiny-brained insect. © 2015 American Association for the Advancement of Science
Link ID: 20547 - Posted: 02.05.2015
By ERICA GOODE A study suggests that newborn chicks map numbers spatially, associating low numerical values with space to their left. Credit Rosa Rugani/University of Padova Asked to picture the numbers from one to 10, most people will imagine a straight line with one at the left end and 10 at the right. This “mental number line,” as researchers have termed it, is so pervasive that some scientists have argued that the spatial representation of numbers is hard-wired into the brain, part of a primitive number system that underlies humans’ capacity for higher mathematics. Now a team of Italian researchers has found that newborn chicks, like humans, appear to map numbers spatially, associating smaller amounts with the left side and larger amounts with the right side. The chicks, trained to seek out mealworms behind white plastic panels printed with varying numbers of identical red squares, repeatedly demonstrated a preference for the left when the number of squares was small and for the right when the number was larger. The research, led by Rosa Rugani, a psychologist who at the time was at the University of Padova, will appear in Friday’s issue of the journal Science. Researchers demonstrated that chickens naturally order numbers left to right. When the number five is in the middle, chickens naturally go left for lower numbers and to the right for higher numbers. Publish Date January 29, 2015. In their report, the researchers said the findings supported the idea that the left-right orientation for numbers is innate rather than determined by culture or education — a possibility that was raised by some studies that found that in Arabic-speaking countries where letters and numbers are read right to left, the mental number scale was reversed. But the new research, Dr. Rugani and her colleagues wrote, indicates that orienting numbers in space may represent “a universal cognitive strategy available soon after birth.” Tyler Marghetis, a doctoral candidate in psychology at the University of California, San Diego, who has published research on the spatial association of numbers, called the researcher’s studies “very cool.” © 2015 The New York Times Company
By KEN BELSON A new study of N.F.L. retirees found that those who began playing tackle football when they were younger than 12 years old had a higher risk of developing memory and thinking problems later in life. The study, published in the medical journal Neurology by researchers at the Boston University School of Medicine, was based on tests given to 42 former N.F.L. players, ages 41 to 65, who had experienced cognitive problems for at least six months. Half the players started playing tackle football before age 12, and the other half began at 12 or older. Those former N.F.L. players who started playing before 12 years old performed “significantly worse” on every test measure after accounting for the total number of years played and the age of the players when they took the tests. Those players recalled fewer words from a list they had learned 15 minutes earlier, and their mental flexibility was diminished compared with players who began playing tackle football at 12 or older. The age of 12 was chosen as a benchmark because it is roughly the point by which brains in young boys are thought to have already undergone key periods of development. Research has shown that boys younger than 12 who injure their brains can take longer to recover and have poor cognition in childhood. The findings are likely to fuel an already fierce debate about when it is safe to allow children to begin playing tackle football and other contact sports. Youth leagues are under scrutiny for putting children at risk with head injuries. Pop Warner and many other youth leagues have added training protocols, have limited contact in practice and have adjusted weight and age limits to try to reduce head injuries and the risks associated with them. But some leagues continue to allow children as young as 5 to play tackle football. © 2015 The New York Times Company
By Ling Xin For many, the hardest part of learning to speak Chinese is mastering its complex tonal variations. Now, new research suggests a surprising explanation for how those tones arose: a humid climate. By examining the correlation between humidity and the role of tone in more than 3700 languages, scientists found that tonal languages are remarkably rare in arid regions like Central Europe, whereas languages with complex tone pitches are prevalent in relatively humid regions such as the tropics, subtropical Asia, and Central Africa. Humidity keeps the voice box moist and elastic, allowing it to produce correct and complex tones, the scientists explain online this month in the Proceedings of the National Academy of Sciences. “If the United Kingdom had been a humid jungle, English may also have developed into a tonal language,” they claim. So, next time you go to your Chinese class, don’t forget to wet your whistle! © 2015 American Association for the Advancement of Science.
Link ID: 20517 - Posted: 01.26.2015
By Amy Ellis Nutt Scientists have discovered what a traumatic brain injury, or TBI, suffered by a quarter-million combat veterans of Iraq and Afghanistan looks like, and it’s unlike anything they’ve seen before: a honeycomb pattern of broken connections, primarily in the frontal lobes, our emotional control center and the seat of our personality. “In some ways it’s a 100-year-old problem,” said Vassilis Koliatsos, a Johns Hopkins pathologist and neuropsychiatrist. He was referring to the shell-shock victims of World War I, tens of thousands of soldiers who returned home physically sound but mentally wounded, haunted by their experiences and unable to fully resume their lives. “When we started shelling each other on the Western Front of World War I, it created a lot of sick people . . . . [In a way,] we’ve gone back to the Western Front and created veterans who come back and do poorly, and we’re back to the Battle of the Somme,” he said. “They have mood changes, commit suicide, substance abuse, just like in World War I, and they really do poorly and can’t function. It’s a huge problem.” Many of the lingering symptoms of shell shock, or what today is known as neurotrauma, are the same as they were a century ago. Only the nature of the blast has changed, from artillery to improvised explosive devices. Koliatsos and colleagues, who published their findings in the journal Acta Neuropathologica Communications in November, examined the brains of five recent U.S. combat veterans, all of whom suffered a traumatic brain injury from an IED but died of unrelated causes back home. Their controls included the brains of people with a history of auto accidents and of those with no history of auto accidents or TBI. Koliatsos says he was prompted to do this study because he is both a pathologist and a neuropsychiatrist, and he sees many TBI cases, both in veterans and in young people with sports concussions.
// by Jennifer Viegas Researchers eavesdropping on wild chimpanzees determined that the primates communicate about at least two things: their favorite yummy fruits, and the trees where these fruits can be found. Of particular interest to the chimps is the size of trees bearing the fruits that they relish most, such that the chimps yell out that information, according to a new study published in the journal Animal Behaviour. The study is the first to find that information about tree size and available fruit amounts are included in chimp calls, in addition to assessments about food quality. "Chimpanzees definitely have a very complex communication system that includes a variety of vocalizations, but also facial expressions and gestures," project leader Ammie Kalan of the Max Planck Institute for Evolutionary Anthropology told Discovery News. "How much it resembles human language is still a matter of debate," she added, "but at the very least, research shows that chimpanzees use vocalizations in a sophisticated manner, taking into account their social and environmental surroundings." Kalan and colleagues Roger Mundry and Christophe Boesch spent over 750 hours observing chimps and analyzing their food calls in the Ivory Coast's Taï Forest. The Wild Chimpanzee Foundation in West Africa is working hard to try and protect this population of chimps, which is one of the last wild populations of our primate cousins. © 2015 Discovery Communications, LLC
by Ashley Yeager The brain's got its own set of pipes for flushing waste. The plumbing is delicate, however — a finding that may complicate scientists' attempts to create a blood test to diagnose traumatic brain injuries. Bumps to the head can knock proteins out of brain cells. The brain's plumbing system is supposed to wash these proteins away from the damaged area and eventually into the blood. But new research in mice shows that slight alterations to the brain's self-cleaning system, even from treating head injuries, can change the levels of proteins flushed into the blood. As a result, the proteins are unreliable markers of injury, researchers report January 14 in the Journal of Neuroscience. © Society for Science & the Public 2000 - 2015.
By Michael Balter If there’s one thing that distinguishes humans from other animals, it’s our ability to use language. But when and why did this trait evolve? A new study concludes that the art of conversation may have arisen early in human evolution, because it made it easier for our ancestors to teach each other how to make stone tools—a skill that was crucial for the spectacular success of our lineage. Researchers have long debated when humans starting talking to each other. Estimates range wildly, from as late as 50,000 years ago to as early as the beginning of the human genus more than 2 million years ago. But words leave no traces in the archaeological record. So researchers have used proxy indicators for symbolic abilities, such as early art or sophisticated toolmaking skills. Yet these indirect approaches have failed to resolve arguments about language origins. Now, a team led by Thomas Morgan, a psychologist at the University of California, Berkeley, has attacked the problem in a very different way. Rather than considering toolmaking as a proxy for language ability, he and his colleagues explored the way that language may helps modern humans learn to make such tools. The researchers recruited 184 students from the University of St. Andrews in the United Kingdom, where some members of the team were based, and organized them into five groups. The first person in each group was taught by archaeologists how to make artifacts called Oldowan tools, which include fairly simple stone flakes that were manufactured by early humans beginning about 2.5 million years ago. This technology, named after the famous Olduvai Gorge in Tanzania where archaeologists Louis and Mary Leakey discovered the implements in the 1930s, consists of hitting a stone “core” with a stone “hammer” in such a way that a flake sharp enough to butcher an animal is struck off. Producing a useful flake requires hitting the core at just the right place and angle. © 2015 American Association for the Advancement of Science.
|By Matthew H. Schneps Many of the etchings by artist M. C. Escher appeal because they depict scenes that defy logic. His famous “Waterfall” shows a waterwheel powered by a cascade pouring down from a brick flume. Water turns the wheel and is redirected uphill back to the mouth of the flume, where it can once again pour over the wheel in an endless cycle. The drawing shows us an impossible situation that violates nearly every law of physics. In 2003 a team of psychologists led by Catya von Károlyi of the University of Wisconsin–Eau Claire made a discovery using such images. When the researchers asked people to pick out impossible figures from similarly drawn illustrations, they found that participants with dyslexia were among the fastest at this task. Dyslexia is often called a learning disability. And it can indeed present learning challenges. Although its effects vary widely, some children with dyslexia read so slowly that it would typically take them months to read the same number of words that their peers read in a day. Therefore, the fact that people with this difficulty were so adept at rapidly picking out the impossible figures puzzled von Károlyi. The researchers had stumbled on a potential upside to dyslexia, one that investigators have just begun to understand. Scientists had long suspected dyslexia might be linked to creativity, but laboratory evidence for this was rare. In the years to follow, sociologist Julie Logan of Cass Business School in London showed that there is a higher incidence of dyslexia among entrepreneurs than in the general population. Meanwhile cognitive scientist Gadi Geiger of the Massachusetts Institute of Technology found that people with dyslexia could attend to multiple auditory inputs at once. © 2015 Scientific American
by Clare Wilson Could a lopsided gap help set us apart from our primate cousins? Our brains and chimps' are built differently in the areas that give us our social skills and language. The human brain has a 4.5-centimetre-long groove running deeper along the right side than the left. Chimp brains lack this asymmetry, as François Leroy of the French National Institute of Health and Medical Research in Saclay, and colleagues, have discovered. The groove's function is unknown, but its location suggests it played a role in the evolution of our communication abilities. "One day this will help us understand what makes us tick," says Colin Renfrew of the University of Cambridge, who was not involved in the study. Although our brain is about three times the size of a chimp's, anatomical features that only the human brain possesses are surprisingly hard to find. One known difference is in a region called Broca's area, which is also involved in speech and is larger in humans than chimps. The asymmetrical groove in humans was also known, but the new study, in which 177 people and 73 chimps had brain scans, revealed it is almost completely absent in the other primates. In humans, the deeper groove in the right brain lies in the region that controls voice and face recognition and working out what other people are thinking – our so-called theory of mind. The shallower groove on the left is at the heart of the areas associated with language. The lack of symmetry could signify that tissue layers in the right brain have been reorganised, says Leroy. © Copyright Reed Business Information Ltd.
By DOUGLAS QUENQUA A sparrow’s song may sound simple, consisting of little more than whistles and trills. But to the sparrows, those few noises can take on vastly different meanings depending on small variations in context and repetition, researchers have found. In humans, the ability to extract nearly endless meanings from a finite number of sounds, known as partial phonemic overlapping, was key to the development of language. To see whether sparrows shared this ability, researchers at Duke University recorded and analyzed the songs of more than 200 Pennsylvania swamp sparrows. They found that the sparrows’ whistles could be divided into three lengths: short, intermediate and long. The researchers then played the sparrows two versions of the songs — the original and a slightly altered one. They found that replacing a single short whistle with an intermediate one, for example, could significantly alter a bird’s reaction, but only if it came at the right moment in the song. “Identical sounds seemed to belong to a different category depending on the context,” said Robert F. Lachlan, a biologist now with Queen Mary University of London and the lead author of the study. The findings, which were published in Proceedings of the National Academy of Sciences, are part of a larger effort to better understand how human language evolved. If even birds rely on phonemic overlapping to communicate, Dr. Lachlan said, it could indicate that such features “developed independently of higher aspects of language.” © 2015 The New York Times Company
Christopher Dean Hopkins If you've ever listened to karaoke at a bar, you know that drinking can affect how well someone can sing. Christopher Olson and his colleagues at Oregon Health and Science University recently set out to find if the same was true for birds, specifically zebra finches. "We just showed up in the morning and mixed a little bit of juice with 6 percent alcohol, and put it in their water bottles and put it in the cages," Olson told All Things Considered's Arun Rath. "At first we were thinking that they wouldn't drink on their own because, you know, a lot of animals just won't touch the stuff. But they seem to tolerate it pretty well and be somewhat willing to consume it." The finches long have been used as a model to study human vocal learning, or how people learn to communicate using language, Olson said. Obviously, alcohol affects human speech, so Olson and his team checked for similar problems with the birds. The blood alcohol levels achieved — .05 to .08 percent — would be laughed off by many college students, but because birds metabolize alcohol differently it was plenty to produce the effects the scientists were looking for. Listen to the audio, and you'll hear that the finches' song gets a bit quieter and just a little slurred, or as Olson puts it, "a bit less organized in their sound production" — like a roommate calling from a bar to get a ride home. © 2014 NPR
by Lisa Seachrist Chiu Just before winter break, my fifth grader came home from school, opened her mouth and produced what sounded to me like a stuttering mess of gibberish. After complaining that when she spends the entire day immersed in Chinese, she sometimes can’t figure out what language to use, she carried on speaking flawless English to me and Chinese to a friend while they did their homework. Quite honestly, I had been eagerly anticipating this very day for a long time. Having worked several years to establish the Chinese language immersion elementary school my daughter attends, I could barely contain my excitement at this demonstration that she truly grasps a second language. Early language programs are hot, in no small part because, when it comes to language, kids under the age of 7 are geniuses. Like many parents, I wanted my child to be fluent in as many languages as possible so she can communicate with more people and because it gives her a prime tool to explore different cultures. Turns out, it may also benefit her brain. With the help of advanced imaging tools that reveal neural processes in specific brain structures, researchers are coalescing around the idea that fluency in more than one language heightens executive function — the ability to regulate and control cognitive processes. It’s a radical shift from just a few decades ago when psychologists routinely warned against raising children who speak two languages, lest they become confused and suffer delays in learning. © Society for Science & the Public 2000 - 2014
Link ID: 20448 - Posted: 01.01.2015
|By Joshua A. Krisch There is a mystery on Tiwai Island. A large wildlife sanctuary in Sierra Leone, the island is home to pygmy hippopotamuses, hundreds of bird species and several species of primates, including Campbell’s monkeys. These monkeys communicate via an advanced language that primatologists and linguists have been studying for decades. Over time, experts nearly cracked the code behind monkey vocabulary. And then came krak. In the Ivory Coast’s Tai Forest Campbell’s monkeys (Cercopithecus campbelli) use the term krak to indicate that a leopard is nearby and the term hok to warn of an eagle circling overheard. Primatologists indexed their monkey lexicon accordingly. But on Tiwai Island they found that those same monkeys used krak as a general alarm call—one that, occasionally, even referred to eagles. “Why on Earth were they producing krak when they heard an eagle,” asks co-author Philippe Schlenker, a linguist at France’s National Center for Scientific Research and professor at New York University. “For some reason krak, which is a leopard in the Tai Forest, seems to be recycled as a general alarm call on Tiwai Island.” In a paper published in the November 28 Linguistics and Philosophy Schlenker and his team applied logic and human linguistics to crack the krak code. Their findings imply that some monkey dialects can be just as sophisticated as human language. In 2009 a team of scientists travelled to Tai Forest with one mission—to terrify Campbell’s monkeys. Prior studies had collected monkey calls and then parsed vague meanings based on events that were already happening on the forest floor. But these primatologists set up realistic model leopards and played recordings of eagle screeches over loudspeakers. Their field experiments resulted in some of the best data available about how monkeys verbally respond to predators. © 2014 Scientific American
By GINA KOLATA After three decades of failure, researchers have found a treatment that greatly improves the prognosis for people having the most severe and disabling strokes. By directly removing large blood clots blocking blood vessels in the brain, they can save brain tissue that would have otherwise died, enabling many to return to an independent life. The study, published online Wednesday in The New England Journal of Medicine and conducted by researchers in the Netherlands, is being met with an outpouring of excitement. One reason the treatment worked, researchers suspect, is that doctors used a new type of snare to grab the clots. It is a stent, basically a small wire cage, on the end of a catheter that is inserted in the groin and threaded through an artery to the brain. When the tip of the catheter reaches the clot, the stent is opened and pushed into the clot. It snags the clot, allowing the doctor to withdraw the catheter and pull out the stent with the clot attached. About 630,000 Americans each year have strokes caused by clots blocking blood vessels in the brain. In about a third to half, the clot is in a large vessel, which has potentially devastating consequences. People with smaller clots are helped by the lifesaving drug tPA, which dissolves them. But for those with big clots, tPA often does not help. Until now, no other treatments had been shown to work. One in five patients who had tPA alone recovered enough to return to living independently. But one in three who also had their clot removed directly were able to take care of themselves after their stroke. And that, said Dr. Larry B. Goldstein, director of the Duke Stroke Center, is “a significant and meaningful improvement in what people are able to do.” © 2014 The New York Times Company
Link ID: 20429 - Posted: 12.18.2014
Jason G Goldman We humans don’t typically agree on all that much, but there is at least one thing that an impressive amount of us accept: which hand is easiest to control. If you use one hand for writing, you probably use the same one for eating as well, and most of us – around 85% of our species – prefer our right hands. In fact, "there has never been any report of a human population in which left-handed individuals predominate", according to archaeologist Natalie Uomini at the University of Liverpool in the UK. Lateralisation of limb use – that is, a bias towards one side or the other – usually begins in the brain. We know that some tasks are largely controlled by brain activity in the left hemisphere, while the right hemisphere governs other tasks. Confusingly, there is some crossing of nerves between the body and the brain, which means it’s actually the left side of the brain that has more control over the right side of the body and vice versa. In other words, the brain’s left hemisphere helps control the operation of the right hand, eye, leg and so on. Some argue that this division of neurological labour has been a feature of animals for half a billion years. Perhaps it evolved because it is more efficient to allow the two hemispheres to carry out different computations at the same time. The left side of the brain, for instance, might have evolved to carry out routine operations – things like foraging for food – while the right side was kept free to detect and react rapidly to unexpected challenges in the environment – an approaching predator, for instance. This can be seen in various fish, toads and birds, which are all more likely to attack prey seen in the right eye. © 2014 BBC.