Chapter 10. Vision: From Eye to Brain
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By ANAHAD O'CONNOR THE FACTS Certain regions of the human brain are dedicated to the various senses. The visual cortex handles vision, for example, while the auditory cortex processes sound. But what happens if one of the senses is lost? Do the neurons in the auditory cortex of a deaf person atrophy and go to waste, for instance, or are they put to work processing vision and other senses? In studies, scientists have shown that when one sense is lost, the corresponding brain region can be recruited for other tasks. Researchers learned this primarily by studying the blind. Brain imaging studies have found that blind subjects can locate sounds using both the auditory cortex and the occipital lobe, the brain’s visual processing center. But recently a similar phenomenon was discovered in the deaf. In a study financed by the National Institutes of Health and published in The Journal of Neuroscience, researchers recruited 13 deaf volunteers and a dozen volunteers with normal hearing and looked at what happened in their brains when touch and vision responses were stimulated. They found that both senses were processed in Heschl’s gyrus, where the auditory cortex is situated, suggesting that this part of the brain had been dedicated to other senses. Other studies have shown that structural changes in the auditory cortex are noticeable in the brains of deaf children from a very early age. THE BOTTOM LINE Losing one sense can cause the brain to become rewired. Copyright 2012 The New York Times Company
By Alyssa A. Botelho, Melanie Brunson, who has been blind since birth, suddenly awoke and found herself standing at 15th and K streets in Northwest Washington. She had stopped at the corner on her way home from work to await a safe time to cross and had dozed off. Even on awakening, she was so groggy she couldn’t focus well enough to hear passing cars and judge when it was safe to cross. The incident was a startling reminder of the sleep problems that had plagued her since birth. “Who knows how long I had been standing there,” she said. “I realized then that my safety was in jeopardy, and I began searching for remedies with a vengeance.” But years after that 2005 traffic scare and many subsequent visits to doctors and sleep clinics, Brunson still lies awake in bed night after night and then is desperately sleepy during the day. Although doctors have not definitively identified her disorder, researchers believe she suffers from non-24-hour sleep-wake disorder, or “non-24.” The chronic and little-known sleep condition is characterized by a body clock that is not aligned with a 24-hour day. Though non-24 can affect those with normal vision, it is especially prevalent among blind people who cannot sense light, the strongest environmental signal that synchronizes the brain’s internal sleep-wake pattern to the 24-hour cycle of the Earth day. © 1996-2012 The Washington Post
By RONI CARYN RABIN Older people who have eye surgery to remove cataracts and improve their vision also significantly reduce their risk of breaking a hip in a fall, with the sickest among them and those in their early 80s experiencing nearly 30 percent fewer hip fractures in the first year, a large study reports. The study adds to findings from earlier papers indicating that the benefits of cataract surgery, a relatively safe outpatient procedure with a high success rate, may significantly enhance the quality of life for the elderly, improving sleep, enabling them to be more engaged and mentally alert and curbing depression. “This is elective surgery, and sometimes people think, ‘I’m too sick to have my cataracts out,’ or ‘I’m too old,’ ” said Dr. Anne L. Coleman, the study’s lead author and a professor of ophthalmology at the Jules Stein Eye Institute at the University of California, Los Angeles. “But the take-home message from this study is that if you’re starting to have vision problems and the doctor says you have cataracts, you should probably think of having them removed.” Hip fractures, which become more common with age, are serious injuries for elderly people, with complications that can be life-threatening. The new study, published on Tuesday in The Journal of the American Medical Association, examined the incidence of hip fractures within a year of cataract surgery in a random sample of 1.1 million Medicare beneficiaries age 65 and older who were given a cataract diagnosis from 2002 to 2009. © 2012 The New York Times Company
The cause of a type of hereditary blindness has been traced to a genetic mutation, a discovery that potentially opens a new treatment approach, Canadian and international researchers say. The inherited eye disease, called Leber congenital amaurosis, usually shows its first signs at birth or in the months following. It affects about one in 80,000 newborns. About 1,000 Canadians live with the effects. The researchers' genetic discovery helps provide families with a firm diagnosis, Robert Koenenkoop says.The researchers' genetic discovery helps provide families with a firm diagnosis, Robert Koenenkoop says. (CBC) Scientists at Montreal's McGill University and their co-authors have identified that a gene called NMNAT1 can cause LCA. "We're getting closer to finding 100 per cent of the genes causing Leber congenital amaurosis," said Dr. Robert Koenekoop, director of the McGill Ocular Genetics Laboratory, who led the research team. "That gives an immediate relief to the families, because it confirms the diagnosis [and] gives you a treatment avenue." The disease was considered untreatable, but that is no longer the case for some subtypes, Koenekoop said. For the study in this week's issue of Nature Genetics, scientists analyzed the genomes of 60 infants with LCA of unknown cause. They discovered a mutation on the NMNAT1 gene, which is found in all human cells. It produces a coenzyme called NAD that is involved in hundreds of reactions. © CBC 2012
by Andy Coghlan Treating disease by stimulating brain cells with light is a step closer to reality following the first demonstration that the technique can improve mental performance in monkeys. Two monkeys performed better on simple computer tasks after light was used to boost the activity of brain cells necessary for the task. "For the first time, we were able to change behaviour in primates with our technique," says Wim Vanduffel of Massachusetts General Hospital in Charlestown, who is head of the group that performed the experiment. Known as optogenetics, the method has the potential to treat conditions such as epilepsy, where the light could temporarily deactivate the brain cells that cause seizures, or Parkinson's disease, where it can activate cells that make dopamine, the neurotransmitter vital for controlling mobility that those with Parkinson's lack. Previously, it has been used in nematode worms to trigger them to lay eggs, and mice to relieve depression and paralysis. Researchers have also used it in monkeys, but only on single, isolated neurons. Vanduffel and his colleagues wanted to see if they could extend this to entire networks of cells, boosting a monkey's ability to perform a simple computer-based task. Natural performance enhancers First, Vanduffel's team scanned the two monkeys' brains using functional magnetic resonance imaging while they followed a green dot on a computer screen. From the scans, the researchers could tell that the monkeys relied on an area of the brain called the arcuate sulcus to do the task. © Copyright Reed Business Information Ltd.
Link ID: 17098 - Posted: 07.28.2012
By Stephen L. Macknik and Susana Martinez-Conde As both the midget in the country of Brobdingnag and the giant on the island of Lilliput, Lemuel Gulliver—the protagonist of Jonathan Swift's Gulliver's Travels—experienced firsthand that size is relative. As we cast a neuroscientific light on this classic book, it seems clear to us that Swift, a satirist, essayist and poet, knew a few things about the mind, too. Absolute size is meaningless to our brain: we gauge size by context. The same medium-sized circle will appear smaller when surrounded by large circles and bigger when surrounded by tiny ones, a phenomenon discovered by German psychologist Hermann Ebbinghaus. Social and psychological context also causes us to misperceive size. Recent research shows that spiders appear larger to people who suffer from arachnophobia than to those who are unafraid of bugs and that men holding weapons seem taller and stronger than men who are holding tools. In this article, we present a collection of illusions that will expand your horizons and shrink your confidence in what is real. Try them out for size! Do you see tiny objects photographed with a macro lens? Look again. This remarkable illusion combines tilt-shift photography—in which the photographer uses selective focus and a special lens or tilted shot angle to make regular objects look toy-sized—with the strategic placement of a giant coin. Art designers Theo Tveterås and Lars Marcus Vedeler, from the Skrekkøgle group, created the enormous 50-cent euro coin from painted and lacquered wood at a 20:1 scale. At first sight, they look like real-life scenes from the television show Hoarders, precleanup. © 2012 Scientific American
Link ID: 17080 - Posted: 07.24.2012
by Kat McGowan When she’s looking for a mate, how does a female know what she likes? Macho mating displays—turkeys strutting, lions roaring, bighorn sheep colliding—quickly tell her who is biggest and burliest. But some females prefer a more subtle approach. Evolutionary ecologist John Endler of Deakin University in Australia discovered that among great bowerbirds, pigeon-size birds native to northern Australia, females are dazzled by craftsmanship. In nearly every species of bowerbird, males impress females by building elaborate structures called bowers: long, twiggy corridors that open to a courtyard decorated with small objects. Great bowerbirds go one step further, creating optical illusions to intrigue the ladies and make them more likely to mate. Endler realized the wooer uses a trick called forced perspective. The birds arrange objects by size, so the smallest are closest to the entrance and larger pieces farther away. From the female’s point of view inside the corridor, the bigger, more distant items look about the same size as the nearby smaller ones. The courtyard may appear smaller, potentially making the male seem larger to deliberating females. Photographers regularly use the same trick. If you stand some distance from the Leaning Tower of Pisa, a friend can take a picture that looks as if you are propping up the tower. Creating this illusion is a priority for great bowerbirds. When Endler rearranged their objects, they put their courtyards back in order within three days. © 2012, Kalmbach Publishing Co.
An Ontario study of two drugs — one approved to treat wet age-related macular degeneration, and the other used off-label to fight the eye disease —suggests neither increases the risk of stroke or heart attack, adding to the debate over why both treatments from the same company aren't covered under provincial drug plans when used for AMD. AMD, which affects about one million Canadians mostly over age 65, is a progressive condition that damages the macula in the eye, and is a leading cause of blindness. Researchers from Toronto, Hamilton and Kingston, Ont., followed 91,378 older adults with a history of retinal disease between April 1, 2006 and March 31, 2011, to determine if injections of bevacizumab (trade name Avastin) or ranibizumab (Lucentis) could be linked to increased vascular risks including stroke, heart attack or congestive heart failure. Avastin and Lucentis, both manufactured by Roche, are vascular endothelial growth factor (VEGF) inhibiting drugs, and both have the potential to cause vascular side-effects. However, the research done at Ontario's Institute for Clinical Evaluative Sciences (ICES), and published in Wednesday's edition of BMJ (British Medical Joural) concludes injections of these drugs into the eyes of patients with retinal disease did not increase such risks. © CBC 2012
Link ID: 17000 - Posted: 07.05.2012
by Michael Marshall Step from a sunlit hillside into the darkness of a cave, and you immediately have a problem: you can't see. It's best to stand still for a few minutes until your eyes adjust to the dimness, otherwise you might blunder into a hibernating bear that doesn't appreciate your presence. The same thing will happen when you leave again: the brightness of the sun will dazzle you at first. That's because your eyes have two types of receptor: one set works in bright light and the other in dim light. Barring a few minutes around sunset, only one set of receptors is ever working at any given time. Peters' elephantnose fish has no such limitations. Its peculiar eyes allow it to use the two types of receptor at the same time. That could help it to spot predators as they approach through the murky water it calls home. It's electric Peters' elephantnose fish belongs to a large family called the elephantfish, all of which live in Africa. They get their name from the trunk-like protrusions on the front of their heads. But whereas the trunks of elephants are extensions of their noses, the trunks of elephantfish are extensions of their mouths. To find a Peters' elephantnose fish, you must lurk in muddy, slow-moving water. Look closely, because the fish is brown and so is the background. © Copyright Reed Business Information Ltd.
By JOHN MARKOFF MOUNTAIN VIEW, Calif. — Inside Google’s secretive X laboratory, known for inventing self-driving cars and augmented reality glasses, a small group of researchers began working several years ago on a simulation of the human brain. There Google scientists created one of the largest neural networks for machine learning by connecting 16,000 computer processors, which they turned loose on the Internet to learn on its own. Presented with 10 million digital images found in YouTube videos, what did Google’s brain do? What millions of humans do with YouTube: looked for cats. The neural network taught itself to recognize cats, which is actually no frivolous activity. This week the researchers will present the results of their work at a conference in Edinburgh, Scotland. The Google scientists and programmers will note that while it is hardly news that the Internet is full of cat videos, the simulation nevertheless surprised them. It performed far better than any previous effort by roughly doubling its accuracy in recognizing objects in a challenging list of 20,000 distinct items. The research is representative of a new generation of computer science that is exploiting the falling cost of computing and the availability of huge clusters of computers in giant data centers. It is leading to significant advances in areas as diverse as machine vision and perception, speech recognition and language translation. © 2012 The New York Times Company
by Andy Coghlan Newborn babies have revealed to the world when they start seeing in three dimensions. Babies were thought to begin seeing in stereo at about four months after their due date. They actually learn to do it four months after they are exposed to light, even if they are born early. Ilona Kovács at Budapest University of Technology and Economics in Hungary and her colleagues gave 15 premature and 15 full-term babies goggles that filtered out red or green light. Once a month for eight months, the team sat the babies in a dark room and got them to stare at patterns of dots on a screen. The goggles made the dots invisible unless viewed in 3D. Sensors placed on each baby's head picked up electrical signals that revealed whether they could see the dots. If they could, the sensor registered pulses of 1.875 hertz; if not, there was only a background signal. The babies began to see stereo images about four months after they were born, whether they were premature or full term, showing that the environment, not an internal clock, is the likely trigger for the development of this ability in the brain Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1203096109 © Copyright Reed Business Information Ltd.
by Veronique Greenwood An average human, utterly unremarkable in every way, can perceive a million different colors. Vermilion, puce, cerulean, periwinkle, chartreuse—we have thousands of words for them, but mere language can never capture our extraordinary range of hues. Our powers of color vision derive from cells in our eyes called cones, three types in all, each triggered by different wavelengths of light. Every moment our eyes are open, those three flavors of cone fire off messages to the brain. The brain then combines the signals to produce the sensation we call color. Vision is complex, but the calculus of color is strangely simple: Each cone confers the ability to distinguish around a hundred shades, so the total number of combinations is at least 1003, or a million. Take one cone away—go from being what scientists call a trichromat to a dichromat—and the number of possible combinations drops a factor of 100, to 10,000. Almost all other mammals, including dogs and New World monkeys, are dichromats. The richness of the world we see is rivaled only by that of birds and some insects, which also perceive the ultraviolet part of the spectrum. Researchers suspect, though, that some people see even more. Living among us are people with four cones, who might experience a range of colors invisible to the rest. It’s possible these so-called tetrachromats see a hundred million colors, with each familiar hue fracturing into a hundred more subtle shades for which there are no names, no paint swatches. And because perceiving color is a personal experience, they would have no way of knowing they see far beyond what we consider the limits of human vision. © 2012, Kalmbach Publishing Co.
Link ID: 16928 - Posted: 06.19.2012
David Cyranoski A stem-cell biologist has had an eye-opening success in his latest effort to mimic mammalian organ development in vitro. Yoshiki Sasai of the RIKEN Center for Developmental Biology (CBD) in Kobe, Japan, has grown the precursor of a human eye in the lab. The structure, called an optic cup, is 550 micrometres in diameter and contains multiple layers of retinal cells including photoreceptors. The achievement has raised hopes that doctors may one day be able to repair damaged eyes in the clinic. But for researchers at the annual meeting of the International Society for Stem Cell Research in Yokohama, Japan, where Sasai presented the findings this week, the most exciting thing is that the optic cup developed its structure without guidance from Sasai and his team. “The morphology is the truly extraordinary thing,” says Austin Smith, director of the Centre for Stem Cell Research at the University of Cambridge, UK. Until recently, stem-cell biologists had been able to grow embryonic stem-cells only into two-dimensional sheets. But over the past four years, Sasai has used mouse embryonic stem cells to grow well-organized, three-dimensional cerebral-cortex1, pituitary-gland2 and optic-cup3 tissue. His latest result marks the first time that anyone has managed a similar feat using human cells. The various parts of the human optic cup grew in mostly the same order as those in the mouse optic cup. This reconfirms a biological lesson: the cues for this complex formation come from inside the cell, rather than relying on external triggers. © 2012 Nature Publishing Group,
Sandrine Ceurstemont, editor, New Scientist TV Be careful if you're walking in the jungle: what may seem like moving spots could actually be a cheetah. Now new animations by Stuart Anstis and his team from the University of California in San Diego illustrate the effect by showing how our brain can interpret a moving scene in different ways. The video starts with couples gazing into each others' eyes. As they rotate, you are likely to keep seeing four distinct couples as we are primed to recognise male-female pairs. However, in the next clip, where faces are replaced with dots in a similar arrangement, what initially appear to be groups of rotating dots will probably soon turn into two floating squares. A third animation demonstrates that by adding more pairs of dots, the motion of the whole takes over as most people will see two pulsing octagons. A final clip shows that linking the pairs of dots makes the smaller groupings stick out from the overall formation. These animations demonstrate that our brain can favour either the overall shape or its components depending on the arrangement. In many cases, we can perceive a scene in different ways and alternate between the configurations. However, Anstis and his team showed that over time, our brain usually favours one arrangement over the other by remembering how it has previously processed information in the scene. Typically, we see the motion of the smaller groupings first before perceiving an overarching shape. "In our view, the grouping of moving spots into local motion clusters is an early, fast, pre-attentive event, while grouping them into global motion clusters is a slower, high-level process," write Anstis and colleagues. "Reverting to the cheetah example, it is a modest visual achievement to group some of the moving spots locally into legs or a tail, but a prey's actions and survival will ultimately depend on organizing them globally into a whole cheetah." © Copyright Reed Business Information Ltd.
Link ID: 16920 - Posted: 06.16.2012
By Meghan Holohan You’re staring at your blank computer screen when dots drift into your line of vision. They resemble specks of dust or perhaps clouds or cobwebs. Don’t panic -- you’re not seeing things. You’re witnessing eye floaters, not tricks of the eye or mind. “Floaters are a part of the normal aging process,” says Dr. Pravin Dugel, managing partner at Retinal Consultants of Arizona in Phoenix. Eye floaters are fibers that detach from the eye. A hollow cavity filled with a vitreous jelly, composed of 99 percent water and 1 percent collagen, lies in the center of the eye. This gel helps give eyes their round shape and aids in seeing. As we age, the vitreous liquefies and pieces of it begin to release from the back wall of the eye. The debris floats across the field of vision, causing people to see dots, flies, cobwebs, or clouds. “You can think of [floaters] as UFOs floating in the eye,” explains Dr. Abdhish R. Bhavsar, director of clinical research at the Retina Center of Minnesota. He explains that unlike UFOs, physicians know what floaters are, but like UFOs they often appear differently based on who sees them. While it seems that floaters glide across the front of the eye, they’re actually drifting through the eye. It’s the shadow of the fibers reflecting on the retina that people see. © 2012 msnbc.com
Link ID: 16907 - Posted: 06.13.2012
Sandrine Ceurstemont, editor, New Scientist TV Watching a moving car can sometimes be mind-bending. At certain speeds, the wheels of a forward-moving vehicle can appear to turn backwards due to a common brain trick called the wagon wheel effect. But to confuse your brain even more, a new variation by Arthur Shapiro and his team from the American University in Washington DC shows how adding colour to a wheel can further alter the motion perceived. In the first example in the video, some of the dots in the wheel are coloured, allowing us to perceive the actual clockwise motion as well as the reverse at the same time. The effect is maintained when all of the dots are coloured using hues of the same brightness. However, by changing the brightness of the background, only one type of motion is perceived once again. When the animation is made up of both bright and dark colours, two types of motion are perceived simultaneously once again. But by applying a bright background, the animation appears to flash as both types of motion seem to cancel each other out. The classic monochrome wagon wheel effect occurs since our brain doesn't perceive motion continuously, but instead breaks it down into a series of snapshots, just like a video camera. When a wheel rotates clockwise, anti-clockwise information is sometimes generated after each step, causing our brain to misinterpret the direction of motion. © Copyright Reed Business Information Ltd.
Link ID: 16865 - Posted: 06.02.2012
By Jason G. Goldman Getting around is complicated business. Every year, animals traverse miles of sky and sea (and land), chasing warmth or food or mates as the planet rotates and the seasons change. And with such precision! Some animals rely on visual landmarks, others on subtle changes in magnetic fields, and yet others match their internal clocks with the movement of the sun and stars across the sky. One researcher, Jennifer A. Mather, wondered: how do octopuses navigate? Do they rely on chemotactile sensory information, or do they orient towards visual landmarks? Octopuses occupy “homes” for several days or in some instances for several weeks, and when they go out looking for food, they are sometimes gone for several hours at a time. Therefore, they must use some sort of memory to find their way back home. Many molluscs use trail-following, and follow their own mucus trails, or the trails of others. You might expect that octopuses use trail-following as well, since they forage by using chemotactile exploration – at least four different types of receptors on their suckers gather chemical and tactile information as they move along the rocky seafloor. However, many other species use visual scene recognition to aid in navigation: ants, bees, gerbils, hamsters, pigeons, and even humans, use visual landmarks to navigate around their environments. Since octopuses use visual information to distinguish among different objects, they could use visual landmarks to get home as well. © 2012 Scientific American
Sandrine Ceurstemont, editor, New Scientist TV It's the closest any of us are likely to get to telekinesis. New animations created by Stuart Anstis from the University of California, San Diego, are showing how changing your gaze can alter the direction in which objects are moving. If you watch this video normally, the moving circles in the first animation rotate while the shifting dots in the second clip follow a horizontal path. But if you look away and watch the movie out of the corner of your eye, the direction of motion will appear to change. In both cases, the moving objects seem to follow the direction of the background stripes. The illusion proves that we perceive motion very differently when it's in the periphery compared with when it's picked up by the fovea, a tiny area at the back of the eye responsible for central vision. Looking at a scene directly results in the sharpest vision, whereas our peripheral vision is good at picking up motion but poor at making out the details of shapes. "That's why when you wave at someone in a crowded airport, your peripheral motion detectors pick up the motion and an eye movement steers the target onto the fovea for more detailed analysis," says Anstis. The animation was a finalist in the 2012 Best Illusion of the Year Contest and was presented earlier this month at the event gala in Naples, Florida. © Copyright Reed Business Information Ltd
Link ID: 16842 - Posted: 05.26.2012
Sandrine Ceurstemont, editor, New Scientist TV Think this animated man is running to the left? Switch your point of view and you may change your mind. Created by Steven Thurman and Hongjing Lu from the University of California, Los Angeles, the animation is most commonly seen as a man running to the left when viewed directly. But by fixing your eyes on the red cross so that it appears in your peripheral vision, the man seems to move to the right. According to the researchers, they manipulated the animation to induce the switch by adjusting features of the discs making up the man's body. Their orientation and drifting speed represent what our brain would expect from a person walking to the right. The illusion was one of the finalists in this year's Best Illusion of the Year Contest. © Copyright Reed Business Information Ltd.
Link ID: 16815 - Posted: 05.19.2012
Sandrine Ceurstemont, editor, New Scientist TV Brad Pitt may look attractive when seen head on. But an illusion that presents photos viewed in your peripheral vision shows how pretty faces can quickly look ugly. The effect was discovered accidentally by psychology student Sean Murphy from the University of Queensland in Australia while looking at photos for another experiment. He went on to study the illusion with colleagues who discovered that the distortion occurs when the eyes of a series of photos are aligned and presented quickly in succession. The transformation is caused by differences between faces that follow each other, for example big eyes will seem to bulge if preceded by squinting eyes. The illusion was published last year but now the team has created this new video that shows the effect more dramatically. The illusion has won second prize in this year's Best Illusion of the Year contest. © Copyright Reed Business Information Ltd.
Link ID: 16806 - Posted: 05.17.2012