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By C. CLAIBORNE RAY A. “In both humans and other mammals, as the body became more complex and reacted to environmental stressors, the brain developed in response to that,” said Dr. Philip E. Stieg, chief of neurosurgery at NewYork-Presbyterian Hospital/Weill Cornell. “We do not know what specific stimulus changed or caused a species that has a single brain lobe to evolve to have two hemispheres. It was probably a series of stimuli.” All animals that show complex responses have two hemispheres, Dr. Stieg said. A worm, for example, reacts to simple sensory input with a simple set of motor responses, he said. But the human brain deals with not just complex sensory input, but more diverse and complex motor responses mixed with an array of emotional and cognitive interplays. The result, he said, is that parts of the different hemispheres of the cerebral cortex, the top part of the brain, developed specialties. For just a few examples, he said, “the dominant side of the temporal lobes (the left in 97 percent of us) have speech and visual pathways; the parietal lobes, straight up from the ear, are intermixed on the dominant side, with the left handling speech; and the sensory function of one side of the body is handled by the other side, so that if the brain is bruised on the right side of the parietal lobe, and I hit you on the left side of the body, you might not pay attention to it.” Patients can have half their brain cut out to treat severe seizures and still function, but not at the same cognitive level, Dr. Stieg said. Copyright 2008 The New York Times Company
Nora Schultz Who ever heard of a fish being in two minds about something? Yet it seems that like humans, fish process information - and perhaps emotions - on different sides of the brain. Fish growing up in the wild among predators use their left eye to look at novel objects, while their offspring raised in captivity use the right eye. This suggests that life experiences can affect which side of the brain fish use, and even, says Victoria Braithwaite of the University of Edinburgh, UK, that they have emotional mindsets, since different sides of the brain may correspond to a curious or suspicious attitude. "The lab-reared fish could process information about novel objects in the left brain [which means they are looking at things with their right eye] because they feel more comfortable, whereas their parents are more cautious." “Lab-reared fish could process information about novel objects in the left brain because they feel more comfortable”Humans use their left and right brain lobes differently, the most well-known consequence being handedness. Brain lateralisation has been found in an increasing number of other species in recent years. "Especially for animals that have to cope with many predators, it is an advantage if they can use one hemisphere to keep an eye on predators while they use the other hemisphere to do other things," says Culum Brown, now at Macquarie University in Sydney, Australia. © Copyright Reed Business Information Ltd
Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 15: Language and Our Divided Brain; Chapter 11: Emotions, Aggression, and Stress
Link ID: 10469 - Posted: 06.24.2010
by Nora Schultz HANDICRAFTS were never my strong point at school. For each project I attempted, I'd struggle with tools and techniques that didn't suit a left-hander like me, which often made me wonder why humans are wired to prefer using one side of the body over the other. Apart from a few wrist aches, though, my handedness hasn't been too much of a burden. Contrast this with the bad luck of a toad that fails to jump away from a snake approaching from its right, just because its right eye is much worse at spotting the danger than its left. Clearly, such asymmetry can have fatal consequences. All the more perplexing, then, that creatures across the animal kingdom - including mammals, birds, fish and invertebrates - prefer to use one paw, eye or even antenna for certain tasks, even though they may then be let down in crucial situations by their weaker side. The cause of this trait, called lateralisation, is fairly simple: one side of the brain, which generally controls the opposite side of the body, is more dominant than the other when processing certain tasks. Why would animal brains ever have evolved a characteristic that seems to put them in harm's way? Armed with a spate of ingenious cognitive tests, a group of animal psychologists think they've finally found the answer, in the shape of some previously overlooked benefits to a lopsided brain-body connection. Not before time. Up until the not-too-distant past, it had been broadly assumed that handedness was a uniquely human trait that evolved as a by-product of our amazing capacity for language. © Copyright Reed Business Information Ltd
by Linda Geddes IF HYPNOSIS leaves you unmoved, blame the wiring in your brain. It seems those who find it easier to fall into a trance are more likely to have an imbalance in the efficiency of their brain's two hemispheres. The finding backs hotly disputed claims of a biological basis for hypnosis. Around 15 per cent of people are thought to be extremely susceptibleMovie Camera to hypnosis, while another 10 per cent are almost impossible to hypnotise. The rest of us fall somewhere in between. Sceptics argue that rather than being in a genuine trance, some of us are simply more suggestible and therefore more likely to act the part. However, recent studies have hinted that during hypnosis, there is less connectivity between different regions, and less activity in the rational, left side of the brain, and more in the artistic right side. Such findings suggest hypnosis is more than acting. To see if there are also differences between the brains of susceptible and unresponsive volunteers when they were awake, Peter Naish of the Open University in Milton Keynes, UK, used a standard test of hypnotic susceptibility, that combines motor and cognitive tasks, to identify 10 volunteers of each type. He then gave each volunteer a pair of spectacles with an LED mounted on the left and right side of the frame. The two LEDs flashed in quick succession, and the volunteers had to say which flashed first. Naish repeated the task until the gap between the flashes was so short that the volunteers could no longer judge the correct order. © Copyright Reed Business Information Ltd.
Owen Flanagan, contributor I use the term "neuro-enthusiasta" for those given to excessive excitement over what brain science teaches. I have been warning, often in these pages, of its mostly amusing excesses and its tendency to produce newspaper headlines exclaiming that the brain "lights up" when people think and feel various things. Still, I did not foresee "neuro-" becoming a universal prefix. We have neuro-economics, neuro-theology, neuro-aesthetics and now, if Iain McGilchrist is to be believed, neuro-history. Plato, long before neuroscience, spoke of the struggle in the soul between Reason, Appetite and Temperament. This, neurologically speaking, has turned out to be the struggle between the brain's upper and lower regions. It's so last century. master_emissary_cover.jpgThe new story is the battle between the brain's hemispheres. "The left hemisphere is competitive, and its concern, its prime motivation is power," McGilchrist writes. The right, in contrast, is personal, empathetic and "primary", experiencing things in the lovey-dovey way we did in the old days when we sat around campfires singing Kumbaya. (Music, predictably, is so right brain). If the left hemisphere has its way, McGilchrist warns, the world will seem "relatively mechanical, an assemblage of more or less disconnected 'parts'... utilitarian in ethic; overconfident of its own take on reality, and lacking insight to its problems". © Copyright Reed Business Information Ltd.
By Michael Torrice For many animals, it pays to have a split mind. A brain with multiple lobes helps humans make more efficient decisions, and it allows birds to spot predators quickly. But a new study in fish uncovers possible hidden costs to a divided brain. Scientists once thought that only humans had a split in brain functions, called lateralization, with some tasks performed on the left side and others on the right. More recently, studies in primates, birds, and fish have suggested that asymmetric brains are common in many vertebrates and that more lateralized brains are more efficient. In a recent experiment, for example, parrots with more brain lateralization were more successful at finding seeds hidden among pebbles. But despite this cognitive boost, scientists have observed a great range of brain lateralization among fish and birds. Some of these animals can have almost completely symmetrical brains. So are there disadvantages to lateralization? To find out, Marco Dadda, a psychobiologist at the University of Padova in Italy, and his colleagues focused on goldbelly topminnows (Girardinus falcatus), a species known for its lateralized brain. For 4 years, the scientists bred three minnow groups to have different dominant sides of their brains. They determined the stronger half by watching which way the fish turned to avoid a predator: Turning right 80% of the time meant the right eye--and thus the left brain hemisphere--was dominant, whereas showing no turn preference pointed to a nonlateralized brain. © 2009 American Association for the Advancement of Science.
By Constance Holden The two sides of the brain are responsible for different tasks in many animals. In people, for example, the left side is usually the language center, whereas the right side handles more visual and spatial chores. Now, research on parrots shows that this separation increases brainpower. For many years, researchers thought that the division of labor in the brain, known as cerebral lateralization, was unique to humans. But recent research has shown that such lateralization is actually pervasive in vertebrates. A leading theory suggests that the attribute leads to faster, more accurate problem-solving. The theory holds true for minnows--the ones whose brains are lateralized are better at catching shrimp while simultaneously keeping an eye out for predators--but many other species haven't been tested. Among birds, parrots and crows are renowned for their cleverness. So behavioral ecologist Culum Brown and biologist Maria Magat of Macquarie University in Sydney, Australia, tested 40 parrots from eight different Australian species. Just as right-handedness indicates left-brain dominance in most humans, brain laterality was determined in birds by observing which eye each bird used to fixate on a piece of food and which foot grabbed it. Each bird received a laterality score ranging from 0 (no preference) to 5 (strongly lateralized). The parrots were then given two tests. One involved picking out seeds from a background of similar-looking pebbles; their performance was evaluated by dividing the number of seeds consumed by the number of pecks. The more challenging task required birds to obtain food hanging below their perch on a 50-centimeter-long string. Hauling up the prize is a problem requiring a lot of beak, foot, and eye coordination. © 2009 American Association for the Advancement of Science.
by Ewen Callaway It may not be obvious from the scratch marks cats dish out, but domestic felines favour one paw over the other. More often than not, females tend to be righties, while toms are lefties, say Deborah Wells and Sarah Millsopp, psychologists at Queen's University Belfast in Northern Ireland. However, these preferences only manifest when cats perform particularly dexterous feats. That's for the same reason we can open a door with either arm, yet struggle to write legibly with our non-dominant hand. "The more complex and challenging [the task], the more likely we're going to see true handedness," Wells says. She and Millsopp tasked 42 domestic cats to ferret out a bit of tuna in a jar too small for their heads. Among 21 females, all but one favoured the right paw across dozens of trials, while 20 out of 21 males preferentially used the left. One male proved ambidextrous. Not so for two simpler activities: pawing at a toy mouse suspended in the air or dragged on ground from a string. No matter their sex, all of the cats wielded their right and left paws about equally on these less demanding tasks. Hormone levels could explain sex differences in paw choice, Wells says. Previous research has linked prenatal testosterone exposure to left-handedness. While studies of two other domestic animals, dogs and horses, revealed similar sex biases. Journal reference: Animal Behaviour (DOI: 10.1016/j.anbehav.2009.06.010) © Copyright Reed Business Information Ltd
By Belle Elving I can't tell right from left. It hasn't been a serious problem. Except that night on a freeway heading into San Francisco when, befuddled by an "Exit Left" sign, I hit the brakes and got totaled by a really fast sports car. Or the day I directed a footsore family of tourists 180 degrees away from the White House. Or the time I assembled an Ikea bookcase with the dowel holes for the shelves on the outside. Or the countless times I've annoyed my husband by telling him "Turn, um, left. No wait, I'm sorry . . ." It's a mild disability that has not seriously limited my options in life. Of course, a career in air traffic control would have been unwise. Synchronized swimming and ballroom dancing were not in the cards. (Playing cards is a bit of a problem, actually. I'm never sure which way to pass them.) But I'm usually fine driving alone. I know which way I want to turn; I just don't know what to call it. On the upside, it's delightful to discover others who share this condition, including, as it happens, the editor of the Health section and the editor who wrote the accompanying medical misadventure story. And we are not that small a group. John R. Clarke, a professor of surgery at Drexel University in Philadelphia, estimates that about 15 percent of the population faces some degree of left/right challenge. Eric Chudler, a neuroscientist at the University of Washington in Seattle, puts the figure a bit higher, having found that more than 26 percent of college students and 19 percent of college professors acknowledge having difficulty telling left from right -- occasionally, frequently or always. © 2008 The Washington Post Company
John Whitfield Dogs wag their tails to the right when they see something they want to approach, and to the left when confronted with something they want to back away from, say researchers in Italy. The finding provides another example of how the right and left halves of the brain do different jobs in controlling emotions. Unfortunately, because dogs move about so much, the bias can only be detected using video analysis. It's not obvious enough for you to tell whether the next dog you encounter is going to lick your face or turn tail. "After discovering this, I look at every dog I meet, but my impression is that this is difficult to check outside the lab," says psychologist Giorgio Vallortigara of the University of Trieste. But it could be used in animal welfare, he suggests, to help gauge an animal's state of mind. Vallortigara and his colleagues tested 30 pet dogs of varying breeds, recruited through an obedience school at the University of Bari's veterinary faculty. Over a series of trials, they videoed each dog's response to being shown either their owner, a human stranger, a cat, or a Belgian shepherd malinois, a large dog breed similar to a German shepherd. ©2007 Nature Publishing Group
By Roger Dobson A word in your ear, Tom. The Hollywood star's problems with women - he's divorced from two and broken up with several - may be solely down to his tendency to whisper sweet nothings to the wrong side of the head. According to new research, the key to capturing the attentions of a lover could be boosted massively by whispering into the left ear. Men and women are able to accurately identify and recall more than 70 per cent of emotional words like love, kiss and passion with their left ear, compared to only 58 per cent with the right. This is because the left ear is controlled by the right side of the brain, the so-called emotional side, and triggers much better responses from prospective lovers. The findings may also help to explain why mothers mostly cradle babies on their left side, closer to the left ear, and why some research shows that listening to music with the left ear can be more stimulating. In the studies, to be published by Sam Houston State University in the US, 100 men and women wore earphones to listen to a number of emotional and neutral words being read in each ear separately. The words were read without any emotion. Some time later, the volunteers were asked to write down the words they had heard in each ear. The results show that the test accuracy for emotional words was 70 per cent in the left ear, and 58 per cent in the right. © 2007 Independent News and Media Limited
Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry; Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 15: Language and Our Divided Brain; Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 9971 - Posted: 06.24.2010
By Katherine Unger A symmetrical face is often thought a sign of beauty, but symmetry may be a disadvantage when it comes to the brain. "Left-brained" or "right-brained" fish are more adept at handling multiple activities than fish with no hemispheric preference, according to a new study. Their ability to multitask could help explain why vertebrate brains evolved to function asymmetrically. Scientists used to think that only humans had lateralized, or asymmetric, brains. We generally use the left side of our brain to interpret language and the right to appreciate music, for example. Recently, though, researchers have come to believe that lateralized brains are universal among vertebrates. Some think the condition may allow animals to focus on multiple stimuli at once, with each hemisphere dealing with particular cues. Psychologists Marco Dadda and Angelo Bisazza of the University of Padova in Italy decided to test the theory in fish. They first assembled groups of the minnow Girardinus falcatus that had been bred to be either lateralized or nonlateralized. A right-lateralized fish tends to look at a companion out of its left eye and vice versa, because hemispheres process vision on the opposite side of the body. A nonlateralized fish does not favor either eye. When the researchers placed each type of fish in a glass tank and gave it shrimp to eat, they found that lateralized and nonlateralized fish took about the same time to catch 10 shrimp. In addition, both groups caught the shrimp at equal rates on both sides of their bodies, indicating that they weren't favoring either eye while scoping out their prey. © 2006 American Association for the Advancement of Science.
By Philip E. Ross New findings in neurology always seem to come with the caveat that there are subtleties that need to be explained. It is therefore refreshing to consider a big, fat unsubtlety: the size of our brains. At first glance, a big brain's function seems simple: to think big thoughts. And indeed, brain size does loosely correlate with intelligence, between species and, as recent MRI studies confirm, within our own. Yet some people who are missing brain parts remain just fine with what little they've got. The cases have multiplied since brain scans became routine. Take the 50-something lawyer who, fearing Alzheimer's, came in for an MRI and got good news and bad news. He was fine, but his brain lacked a corpus callosum, the wrist-thick stalk that normally connects the brain's hemispheres. Still, he enjoyed a successful practice and had a verbal IQ of around 130 and a nonverbal IQ above 90. The patient exhibited subtle signs of abnormal behavior, says Warren S. Brown, a neuropsychologist who studies mind-body questions at the Fuller Theological Seminary in Pasadena, Calif.: "He just seemed odd--not remarkable, but he missed the point of social interaction." Brown adds that patients without a corpus callosum often do not get the point of jokes or understand pictures. Of course, most brain abnormalities are found because neurologists had reason to look for them. To get around such bias, Elliott Sherr, a neurologist at the University of San Francisco, decided to study all the MRIs his university's hospital had taken. One in several thousand turned out to lack the corpus callosum. © 1996-2006 Scientific American, Inc.
Related chapters from BP7e: Chapter 1: Biological Psychology: Scope and Outlook; Chapter 19: Language and Hemispheric Asymmetry
Related chapters from MM:Chapter 1: An Introduction to Brain and Behavior; Chapter 15: Language and Our Divided Brain
Link ID: 8432 - Posted: 06.24.2010
By Rob Stein Are left-handed women at increased risk for breast cancer? A new study suggests that might be the case. Cuno Uiterwaal of the University Medical Center in the Netherlands and colleagues examined the relationship between handedness and breast cancer in 12,178 healthy, middle-age women from Utrecht participating in a breast cancer screening study. Between 1982 and 2000, the left-handed women in the study were more than twice as likely as right-handed women to develop breast cancer before going through menopause, the researchers found. The association held up even after the researchers took into account other factors, such as social and economic status, smoking habits, family history of breast cancer, and reproductive history. Much more research is needed to explore whether the relationship is real and what may explain it. But the researchers speculated that left-handed women may be at risk for breast cancer because they were exposed to higher levels of certain hormones in the womb. © Copyright 1996-2005 The Washington
Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry; Chapter 5: Hormones and the Brain
Related chapters from MM:Chapter 15: Language and Our Divided Brain; Chapter 8: Hormones and Sex
Link ID: 7949 - Posted: 06.24.2010
The hand you favour as a 10-week-old fetus is the hand you will favour for the rest of your life, suggests a new study. The finding comes as a surprise because it had been thought that lifelong hand preferences did not develop until a child was three or four years old. A team led by Peter Hepper of the Fetal Behaviour Research Centre at Queen's University, Belfast in the UK reached this conclusion after studying ultrasound scans of 1000 fetuses. In one study, nine out of 10 fetuses at 15 weeks' gestation preferred to suck their right thumbs. Hepper's team followed 75 of those fetuses after birth, and found that at 10 to 12 years old all 60 of the right thumb-suckers were right-handed, while 10 of the 15 left thumb-suckers were left-handed and the rest right-handed. At 10 weeks old, even before they suck their thumbs, fetuses wave their arms about. A second study found that most prefer to wave their right arm, a preference that persisted until 24 weeks, after which the fetus is too cramped to move. Hepper reported the findings at the Forum of European Neuroscience in Lisbon, Portugal, earlier in July. © Copyright Reed Business Information Ltd.
Eight-limbed creatures have a favourite. MICHAEL HOPKIN Most octopuses have a favourite arm, zoologists have discovered. This is the first time they have been found to show any bias when choosing which of their eight limbs is right for the job. The creatures use their trusty first-choice appendage when exploring a new nook or cranny, says Ruth Byrne of the University of Vienna in Austria. She presented the discovery on Sunday at the annual meeting of the Animal Behavior Society in Oaxaca, Mexico. In terms of skill, octopus arms are created pretty much equal. "All eight arms are capable of the same tasks," Byrne told the meeting. "There's hardly any specialization." This had prompted experts to suspect that the creatures simply use whichever arm is handiest. Indeed, one of their preferred hunting strategies is to jump on top of a rock and curl all of their arms underneath, grabbing whatever they find. © Nature News Service / Macmillan Magazines Ltd 2004
Study suggests brain differences between making and using tools. LAURA NELSON Crows use different sides of their beaks to make and use tools, researchers have found. This suggests that different parts of the brain may control making and using tools, and that the biology of handedness - or beakedness - may be more complex than we thought. Just like humans, New Caledonian crows are usually right 'handed' when it comes to tasks such as making tools. But it turns out the birds use their tools with left and right sides equally, although individual crows prefer one side or the other. "This has opened up Pandora's box," says William McGrew, who studies chimpanzees' tool use at Miami University. "People always assumed handedness would be the same for using and making tools." Scientists will now be more wary of making this assumption, he adds. © Nature News Service / Macmillan Magazines Ltd 2004
Reviewed by Carl T. Hall, Chronicle Science Writer It's been said that anybody who claims to understand consciousness clearly doesn't. Undaunted, neuroscientists have been offering at least partial solutions to the consciousness "problem," building machines that can learn and maybe even "think," analyzing what's different about brain-damaged patients, designing clever brain-imaging experiments that explain at least a little something about the "neural correlates of consciousness" without ever resorting to introspection. Introspection, after all, is what philosophers do. They may do it in formal ways, with impressively technical results, but lately the experimentalists seem to be taking the lead, tackling the age-old questions of mind and self-awareness with remarkable gusto. ©2003 San Francisco Chronicle
Related chapters from BP7e: Chapter 1: Biological Psychology: Scope and Outlook; Chapter 19: Language and Hemispheric Asymmetry
Related chapters from MM:Chapter 1: An Introduction to Brain and Behavior; Chapter 15: Language and Our Divided Brain
Link ID: 4250 - Posted: 06.24.2010
One gene might control both - and explain the divided brain. HELEN PEARSON Right-handed people tend to have hair that swirls clockwise, a US researcher has discovered1. Amar Klar of the National Cancer Institute in Frederick, Maryland, surreptitiously inspected people's pates by spying on them in airports and shopping malls - ignoring the long-haired and the bald. More than 95% of right-handers' hair whorls clockwise on the scalp, he found. The locks of lefties and the ambidextrous are equally likely to coil either way. © Nature News Service / Macmillan Magazines Ltd 2003
Author Chris McManus wins £10,000 Aventis award for exploration of asymmetry. PHILIP BALL This year's winner of the world's most prestigious science book competition was announced in London last night. Psychologist Chris McManus was awarded the £10,000 Aventis Prize for his work Right Hand, Left Hand: The Origins of Asymmetry in Brains, Bodies, Atoms and Cultures. A panel chaired by British novelist Margaret Drabble picked Right Hand, Left Hand, published by Weidenfeld & Nicolson, from a shortlist of six entries on topics ranging from cosmology to risk perception. In it, McManus who works at University College in London, explores the phenomenon of handedness from the human to the subatomic level. He discusses why we are predominantly right-handed, why there is an imbalance in other animals too - parrots are southpaws, he reveals - and why amino acids, the building blocks of proteins and DNA exist in mirror image forms. © Nature News Service / Macmillan Magazines Ltd 2003