Links for Keyword: Laterality

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By Eric Haseltine Grab a pen or pencil and quickly make a list of things you couldn't do if you suddenly lost your right hand (or left hand if, like one in 10 people, you're a southpaw). Next, taking the same amount of time, write down what you couldn't do if you still had the use of your dominant hand but your other hand abruptly vanished. In all likelihood, your first list is longer than the second. Conventional wisdom would suggest that your dominant hand does all the really important stuff (like preparing lists of what it couldn't accomplish without itself), leaving your nondominant hand to watch helplessly from the sidelines. But conventional wisdom doesn't take into account the subtle role your brain plays in completing manual tasks, as you'll soon discover. Experiment 1 With the same pen or pencil you just used, make a note of whatever random thoughts pop into your head. If you've got writer's block, perhaps you could start by describing how you'd feel if the world lost the IRS or telemarketers. As your pencil flies across the page, notice what your nondominant hand is doing. Odds are it's holding down the page and occasionally repositioning it to keep your dominant hand from having to wander too far from its comfort zone. To appreciate fully the contribution of your nondominant appendage, keep it in your lap as you continue to write. Awkward, isn't it? © Copyright 2002 The Walt Disney Company

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry
Related chapters from MM:Chapter 15: Language and Our Divided Brain
Link ID: 3122 - Posted: 06.24.2010

Bruce Bower Plenty of evidence indicates that the recognition of familiar faces depends largely on structures on the right side of the brain's outer layer, or cortex. However, the brain appears to take a sharp left turn in fostering the ability to identify one's own face. That, at least, is the implication of experiments conducted with a so-called split-brain patient. To curb the spread of severe epileptic seizures at age 25, the now-48-year-old man had submitted to a surgical severing of nerve fibers connecting one side of his cortex to the other. If confirmed in studies of people with intact brains, the new investigation indicates that left-brain networks assume primary responsibility for memories and knowledge about oneself, including the key visual distinction between "me" and "others," says a team of neuroscientists led by David J. Turk of Dartmouth College in Hanover, N.H. Personal recognition allows for other types of complex thought, such as empathy and introspection, the scientists note. From Science News, Vol. 162, No. 8, Aug. 24, 2002, p. 118. Copyright ©2002 Science Service. All rights reserved.

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: 2519 - Posted: 06.24.2010

Our bodies may look symmetric from the outside, but inside, organs such as the heart or the liver are tucked or oriented to the left or right. New research suggests that fluid driven by tiny swirling hairs called cilia may activate certain genes in the growing embryo that lay the groundwork for this asymmetry. Based on experiments with mice, some scientists had speculated that cilia nestled in a dimple at the top of the embryo called the node might push fluid down the left side of the embryo, carrying a signal that somehow triggers certain genes to activate. Other scientists doubted the idea. The new experiments suggest that the cilia-driven flow is indeed important. Researchers led by developmental biologist Hiroshi Hamada at the University of Osaka used a pump to reverse the normal leftward flow of fluid over mouse embryos. This caused two key genes normally activated solely on the left side of the body to be expressed on the right side, the team reports in the 4 July issue of Nature. Copyright © 2002 by the American Association for the Advancement of Science.

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry
Related chapters from MM:Chapter 15: Language and Our Divided Brain
Link ID: 2284 - Posted: 06.24.2010

Ravel's last music bears the mark of his deteriorating brain. JOHN WHITFIELD Brain disease influenced Ravel's last compositions including his Boléro , say researchers. Orchestral timbres came to dominate his late music at the expense of melodic complexity because the left half of his brain deteriorated, they suggest1. Timbre is mainly the province of the brain's right hemisphere. French composer Maurice Ravel suffered from a mysterious progressive dementia from about 1927 when he was 52 years old. He gradually lost the ability to speak, write and play the piano. He composed his last work in 1932, and gave his last performance in 1933. He died in December 1937. Neurologists have puzzled over his illness ever since. Many have suggested Alzheimer's disease. But François Boller, of the Paul Broca Research Centre in Paris, believes the symptoms began too young, and that too much of Ravel's memory, self-awareness and social skills were preserved for this diagnosis to be correct. * Amaducci, L., Grassi, E. & Boller, F. Maurice Ravel and right-hemisphere musical creativity: influence of disease on his last musical works?. European Journal of Neurology, 9, 75 - 82, (2002). © Nature News Service / Macmillan Magazines Ltd 2002

Related chapters from BP7e: Chapter 9: Hearing, Vestibular Perception, Taste, and Smell; Chapter 19: Language and Hemispheric Asymmetry
Related chapters from MM:Chapter 6: Hearing, Balance, Taste, and Smell; Chapter 15: Language and Our Divided Brain
Link ID: 1389 - Posted: 06.24.2010

When it comes to making tools, crows on the Pacific island of New Caledonia are mostly right-handed--or perhaps "right-billed" is the term. Researchers studying how these birds fashion tools for foraging have found that most of them prefer using their right eye and the left part of their brain--just like most humans do. The vast majority of humans use their right hands for tasks demanding strength or precision. Only recently have researchers started to discover consistent handedness, or laterality, in many other creatures--from chimps and toads to chicks and pigeons. Last year, ecologist Gavin Hunt of the University of Auckland in New Zealand was the first to show that handedness also plays a role in animal toolmaking. Hunt studied New Caledonian crows, a species that snips carefully tapered strips off leaves from the pandanus tree and uses them to retrieve beetle grubs from crevices. Some crows tend to snip tools from the left sides of leaves, using their right eye to guide their behavior, while others prefer to work from the other side, Hunt found. Copyright © 2001 by the American Association for the Advancement of Science.

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 15: Language and Our Divided Brain
Link ID: 1178 - Posted: 06.24.2010

Scientists have discovered the first gene which appears to increase the odds of being left-handed. The Oxford University-led team believe carrying the gene may also slightly raise the risk of developing psychotic mental illness such as schizophrenia. The gene, LRRTM1, appears to play a key role in controlling which parts of the brain take control of specific functions, such as speech and emotion. The study appears in the journal Molecular Psychiatry. The brain is set up in an asymmetrical way. In right-handed people the left side of the brain usually controls speech and language, and the right side controls emotions. However, in left-handed people the opposite is often true, and the researchers believe the LRRTM1 gene is responsible for this flip. They also believe people with the LRRTM1 gene may have a raised risk of schizophrenia, a condition often linked to unusual balances of brain function. Lead researcher Dr Clyde Francks, from Oxford University's Wellcome Trust Centre for Human Genetics, said the next step would be to probe the impact on the development of the brain further. He said: "We hope this study's findings will help us understand the development of asymmetry in the brain. Asymmetry is a fundamental feature of the human brain that is disrupted in many psychiatric conditions." However, Dr Francks said left-handed people should not be worried by the links between handedness and schizophrenia. (C)BBC

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry
Related chapters from MM:Chapter 15: Language and Our Divided Brain
Link ID: 10552 - Posted: 07.31.2007

Left-handed people can think quicker when carrying out tasks such as playing computer games or playing sport, say Australian researchers. Connections between the left and right hand sides or hemispheres of the brain are faster in left-handed people, a study in Neuropsychology shows. The fast transfer of information in the brain makes left-handers more efficient when dealing with multiple stimuli. Experts said left-handers tended to use both sides of the brain more easily. Study leader Dr Nick Cherbuin from the Australian National University measured transfer time between the two sides of the brain by measuring reaction times to white dots flashed to the left and right of a fixed cross. He then compared this with how good participants were at carrying out a task to spot matching letters in the left and right visual fields, which would require them to use both sides of the brain at the same time. Tests in 80 right-handed volunteers showed there was a strong correlation between how quickly information was transferred across the left and right hemispheres and how quickly people spotted matching letters. But when the tests were repeated in 20 left-handed volunteers, the researchers found that the more left-handed people were, the better they were at processing information across the two sides of the brain. Extreme left-handed individuals were 43 milliseconds faster at spotting matching letters across the right and left visual fields than right-handed people. Dr Cherbuin, research fellow at the University concluded: "These findings confirm our prediction of increasing efficiency of hemispheric interactions with increasing left-handedness." But he added that it wasn't a clear-cut pattern as there were subtle differences between strongly and mildly left-handed or right-handed individuals. (C)BBC

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry
Related chapters from MM:Chapter 15: Language and Our Divided Brain
Link ID: 9712 - Posted: 12.07.2006

Contrary to traditional wisdom, being a leftie promotes survival from attacks, at least in the world of snails and crabs, according to a report by researchers at Yale and Cornell in the Biology Letters of the Royal Society, UK. While rare in nature, many organisms including humans have some, but few, members that are lefties. Author Gregory P. Dietl, post-doctoral fellow in geology and geophysics at Yale has studied the survival advantages or disadvantages of being a "leftie" by working with snails and their predatory crabs. "One of the conclusions we draw from the interaction between crabs and these snails is that in the adversarial mode, lefties have a competitive advantage as long as they remain rare," said Dietl. This parallels some social interactions in human cultures, such as sporting competitions in which left-handed players enjoy an advantage over their right-handed opponents. The functional advantage of this rare reversal in shell-coiling direction, while a topic of fascination for scientists and laypersons alike, has evaded explanation. Persistence of handedness in snails is most often associated with a mating advantage. In this case, snails mate most effectively with snails whose shells coil in the same direction. The overwhelming majority of snail species are right-handed -- their shells coil clockwise. Dietl studied a species of snail that are lefties, and have shells that coil counterclockwise.

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: 8701 - Posted: 03.24.2006

When it comes to the world laid before us, our mind's eye has a bias. For reasons that are not entirely clear, during some tasks humans have a tendency to devote more visual attention to the left side of the visual world than the right side, a phenomenon known as pseudoneglect. Researchers now report that pseudoneglect is not restricted to humans but is shared by birds, suggesting not only that brain structures thought to play a requisite role in pseudoneglect may not actually be essential for this phenomenon, but also that pseudoneglect may reflect evolutionary adaptations that allow animals to devote attention to multiple aspects of their environment. The findings are reported in the May 24 issue of Current Biology by Bettina Diekamp (now at Johns Hopkins University) and colleagues at Ruhr University, Bochum, Germany; the University of Padova, Italy; and The University of Trieste, Italy. It has been known for some time that human patients who have suffered injury to the brain's right hemisphere can experience a much more severe bias in their spatial attention--spatial hemineglect--in which the entire left side of the visual world seems nonexistent as the brain performs spatial tasks. In a classic example, a patient asked to draw a daisy can only manage to put petals on the right side of her drawing. The more subtle leftward bias in attention present in healthy humans likely has to do with asymmetries in the wiring of the brain's attention in the two hemispheres; the new finding in birds offers some insight into how and why this might be.

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry
Related chapters from MM:Chapter 15: Language and Our Divided Brain
Link ID: 7390 - Posted: 05.25.2005

WASHINGTON -- New MRI-based studies present more evidence that the brains of chimpanzees are human-like in terms of the relationships among brain asymmetry, handedness and language, according to research undertaken at the Yerkes National Primate Research Center in Atlanta. Understanding our evolutionary cousins helps us to understand what makes us human. Two related reports appear in the December issue of Behavioral Neuroscience, which is published by the American Psychological Association (APA). In the first study, Hani Freeman, BA, Claudio Catalupo, PhD (also with Georgia State University), and William Hopkins, PhD (also with Berry College), took magnetic resonance images of 60 chimpanzees to measure the anatomy of two key structures in their brains' limbic systems, an early-evolving central region that includes the hippocampus and amygdala. In the MRI pictures, the hippocampus (which regulates learning and consolidation of spatial memory, mood, appetite and sleep) was asymmetrical, its right half significantly larger than its left. This asymmetry was bigger in males. These findings are consistent with studies of human hippocampi, which are also asymmetrical. At the same time, just as in humans, the amygdalas of the chimps were symmetrical. Studies such as this confirm that human and chimp brains are not only asymmetrical, but asymmetrical in the same way. The findings echo previous looks at the non-limbic parts of chimpanzee brains, which also appear human-like in their patterns of asymmetry. This fact, especially if studied in the context of functional behaviors that reflect asymmetries, may help scientists get a better fix on the evolution of the limbic system in all primates, including humans.

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry
Related chapters from MM:Chapter 15: Language and Our Divided Brain
Link ID: 6532 - Posted: 12.06.2004

By Dr David Whitehouse, BBC News Online science editor The fraction of left-handed people today is about the same as it was during the Ice Age, according to data from prehistoric handprints. They were found in caves painted during the Upper Palaeolithic period, between 30,000 and 10,000 years ago. Left-handedness may have conferred prehistoric man advantages, such as in combat, say the researchers. The research is published in the February issue of the journal Biology Letters. When Stone Age man produced their remarkable cave paintings they often left handprints on the walls produced by blowing pigments from one hand through a tube held by the other hand. Charlotte Faurie and Michel Raymond at the University of Montpellier, France, deduced the prehistoric cave painters' handedness by spraying paint against cave walls to see which hand they pressed against the wall, and therefore did not use for drawing. (C)BBC

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry
Related chapters from MM:Chapter 15: Language and Our Divided Brain
Link ID: 4971 - Posted: 02.14.2004

Walruses are 'right-flippered', according to research published this week in BMC Ecology. The first study of walrus feeding behaviour in the wild showed that the animals preferentially use their right flipper to remove sediment from buried food. This is the first time that any aquatic animal has been shown to prefer using one flipper to the other when foraging. Direct observations of the underwater behaviour of free-living marine mammals are rare, especially if the animals are dangerous, like the walrus. This means that our understanding of these creatures is remarkably limited. The scuba-diving researchers from Denmark, Greenland and Sweden went to Northeast Greenland to film male Atlantic walruses while they ate. Walruses eat invertebrate animals that live on the seabed. They are particularly fond of clams. Walruses suck out the soft part of the clam, and discard the empty shells. As clams can be buried up to 40 cm deep, the walruses must remove sediment to find them.

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry
Related chapters from MM:Chapter 15: Language and Our Divided Brain
Link ID: 4411 - Posted: 10.23.2003

Psychologists have come up with an explanation for why most mothers instinctively cradle their babies in their left arms. Research shows that if a woman is given a baby or a doll to hold she is twice as likely to hold it on her left, rather than her right hand side. Brenda Todd and Victoria Bourne, psychologists at the University of Sussex, believe the reason is that the right side of the female brain is specialised for interpreting faces and emotions. They tested 32 right handed volunteers, of whom 12 were male, on their cradling bias. The volunteers also took a test to determine which side of the brain they used for face processing. The researchers found that females who cradled on the left showed signs that the right side of their brain controlled the way they processed information about faces. No such relationship was found for males. (C) BBC

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: 2608 - Posted: 09.08.2002

Science prompts a shift in cultural attitude toward which hand we favor in life By Marcia Mattson Times-Union staff writer Not so long ago, left-handers had it rough. Considered evil, awkward, unhygienic or mentally retarded, children who showed signs of left-handedness were beaten. Their left hands were tied behind their backs or slapped with rulers so they would have to use their right hand. Today, scientists are coming closer to explaining the biological reasons for left-handedness. And society is shedding its biases and growing more accommodating of left-handers, who make up about 10 percent of the U.S. population. But it's still a right-hander's world, says Jane M. Healey, a child neuropsychologist, professor and left-hander. So parents can take simple steps from the moment their toddler grips a spoon in his pudgy left fingers to help him succeed. © The Florida Times-Union

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry
Related chapters from MM:Chapter 15: Language and Our Divided Brain
Link ID: 1092 - Posted: 12.03.2001

WASHINGTON - Does coming from a family full of "lefties" tend to make a person better at remembering events? The data from two recent experiments answer in the affirmative. What's more, psychologists may finally be able to explain why kids don't remember events until they are about four years old. This recent research is reported in the October issue of Neuropsychology, published by the American Psychological Association (APA). Stephen D. Christman, Ph.D., and Ruth E. Propper, Ph.D., of the University of Toledo in Ohio, studied memory as a function of family handedness. Interestingly, people don't have to be personally left-handed to share a unique trait: There is evidence that the two brain hemispheres of even right-handers with left-handed relatives share functions more equally, interact more and are connected by a larger corpus callosum (the bundle of mediating fibers) than the hemispheres of people with right-handed relatives. Although it is not well understood, there is a hereditary component to handedness. "Superior Episodic Memory is Associated with Interhemispheric Processing," Stephen D. Christman, Ph.D., and Ruth E. Propper, Ph.D., Neuropsychology, Vol. 15, No 4. © PsycNET 2001 American Psychological Association

Related chapters from BP7e: Chapter 17: Learning and Memory; Chapter 19: Language and Hemispheric Asymmetry
Related chapters from MM:Chapter 13: Memory, Learning, and Development; Chapter 15: Language and Our Divided Brain
Link ID: 820 - Posted: 10.20.2001

Virtual injury catches the brain's halves competing for attention.
JOHN WHITFIELD Knocking out one half of the brain can boost the performance of the other, researchers creating virtual brain injuries have found1. The finding supports the idea that mental activity is a tussle between the brain's many different areas. It also illustrates how virtual brain injuries might allow neurologists to study a whole variety of disorders without relying on the haphazard effects of accidents or strokes. Still in its infancy, the technique also offers new ways to investigate healthy minds. Claus Hilgetag, of Boston University, and his colleagues fired focused magnetic pulses through healthy subjects' skulls for 10 minutes to induce 'hemispatial neglect'. This condition, involving damage to one side of the brain, leaves patients unaware of objects in the opposite half of their visual field (which sends messages to the damaged half of the brain). 1.Hilgetag, C. C. Theoret, H. & Pascual-Leone, A Enhanced visual spatial attention ipsilateral to rTMS-induced 'virtual lesions' of human parietal cortex. Nature Neuroscience, 4, 953 - 957, (2001). © Nature News Service / Macmillan Magazines Ltd 2001

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry
Related chapters from MM:Chapter 15: Language and Our Divided Brain
Link ID: 486 - Posted: 10.20.2001

On Left-Handedness, Its Causes and Costs
By DAVID E. ROSENBAUM REDERICK, Md. -- In medieval times, right-handed warriors had a distinct advantage in swordfights. They held their shield with their left hand -- over their heart -- and thus lived to fight another day, and to reproduce, even after they had been stabbed. That, suggested Thomas Carlyle, the 19th century British writer, is why so many more people are right-handed. The lefties never lived to have offspring

Related chapters from BP7e: Chapter 19: Language and Hemispheric Asymmetry
Related chapters from MM:Chapter 15: Language and Our Divided Brain
Link ID: 384 - Posted: 10.20.2001