Chapter 10. Vision: From Eye to Brain
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By Gretchen Vogel BERLIN—A German neuroscientist who has been the target of animal rights activists says he is giving up on primate research. Nikos Logothetis, a director at the Max Planck Institute for Biological Cybernetics in Tübingen, Germany, says he will conclude his current experiments on macaques “as quickly as possible” and then shift his research to rodent neural networks. In a letter last week to fellow primate researchers, Logothetis cites a lack of support from colleagues and the wider scientific community as key factors in his decision. In particular, he says the Max Planck Society—and other organizations—should pursue criminal charges against the activists who target researchers. Logothetis’s research on the neural mechanisms of perception and object recognition has used rhesus macaques with electrode probes implanted in their brains. The work was the subject of a broadcast on German national television in September that showed footage filmed by an undercover animal rights activist working at the institute. The video purported to show animals being mistreated. Logothetis has said the footage is inaccurate, presenting a rare emergency situation following surgery as typical and showing stress behaviors deliberately prompted by the undercover caregiver. (His written rebuttal is here.) The broadcast triggered protests, however, and it prompted several investigations of animal care practices at the institute. Investigations by the Max Planck Society and animal protection authorities in the state of Baden-Württemberg found no serious violations of animal care rules. A third investigation by local Tübingen authorities that led to a police raid at the institute in late January is still ongoing. © 2015 American Association for the Advancement of Science.
by Andy Coghlan These neon cells may be blinding, but targeting them could also help preserve sight. In this close-up image of blood vessels – shown in blue – that supply blood to the retina of a one-week-old mouse, the nuclei of cells lining their walls appear in fluorescent colours. The bright-yellow cells are the ones of interest: they could be targeted to help prevent blindness in ageing eyes. Age-related macular degeneration, or AMD, often strikes in middle age, causing a person's vision to deteriorate. A key driver of the disease is excessive growth of obtrusive blood vessels in the retina. A team led by Alain Chédotal of the Institute of Vision in Paris has now discovered that a protein called Slit2 contributes to the rapid increase in offending blood vessels. The yellow cells in the picture are the ones that are dividing. When this activity occurs in middle age, it triggers the excessive increase in blood vessels that results in AMD. By blocking Slit2, it might be possible to reduce this effect, says Chédotal. When the team genetically altered mice so that they couldn't produce Slit2, the animals no longer overproduced the blood vessels that lead to blindness. The researchers think that drugs targeting Slit2 could generate new treatments for AMD. © Copyright Reed Business Information Ltd
Link ID: 20839 - Posted: 04.23.2015
By LISA FELDMAN BARRETT and JOLIE WORMWOOD THE Justice Department recently analyzed eight years of shootings by Philadelphia police officers. Its report contained two sobering statistics: Fifteen percent of those shot were unarmed; and in half of these cases, an officer reportedly misidentified a “nonthreatening object (e.g., a cellphone) or movement (e.g., tugging at the waistband)” as a weapon. Many factors presumably contribute to such shootings, ranging from carelessness to unconscious bias to explicit racism, all of which have received considerable attention of late, and deservedly so. But there is a lesser-known psychological phenomenon that might also explain some of these shootings. It’s called “affective realism”: the tendency of your feelings to influence what you see — not what you think you see, but the actual content of your perceptual experience. Affective realism illustrates a common misconception about the working of the human brain. In everyday life, your brain seems to be a reactive organ. You stroll past a round red object in the produce section of a supermarket and react by reaching for an apple. A police officer sees a weapon and reacts by raising his gun. Stimulus is followed by response. But the brain doesn’t really work this way. The brain is a predictive organ. A majority of your brain activity consists of predictions about the world — thousands of them at a time — based on your past experience. These predictions are not deliberate prognostications like “the Red Sox will win the World Series,” but unconscious anticipations of every sight, sound and other sensation you might encounter in every instant. These neural “guesses” largely shape what you see, hear and otherwise perceive. © 2015 The New York Times Company
By Chris Cesare The beautiful color of a sunset might be more than just a pretty picture. It could be a signal to our bodies that it’s time to reset our internal clock, the biological ticktock that governs everything from sleep patterns to digestion. That’s the implication of a new study in mice that shows these small rodents use light’s changing color to set their own clocks, a finding that researchers expect will hold for humans, too. “I think this work opens up how we're just starting to scratch the surface and look at the environmental adaptations of clocks,” says Carrie Partch, a biochemist at the University of California, Santa Cruz, who was not involved in the new study. Scientists have long known about the role light plays in governing circadian rhythms, which synchronize life’s ebb and flow with the 24-hour day. But they weren’t sure how different properties of light, such as color and brightness, contributed to winding up that clock. “As a sort of common sense notion people have assumed that the clock somehow measures the amount of light in the outside world,” says Tim Brown, a neuroscientist at the University of Manchester in the United Kingdom and an author of the new study. “Our idea was that it might be doing something more sophisticated than that.” To find out, Brown and his colleagues targeted an area in the brain called the suprachiasmatic nucleus, or SCN, a region common to all vertebrates. It’s where the body keeps time using chemical and electrical rhythms that last, on average, 24 hours. The team wanted to know if color signals sent from the eyes reached the SCN and whether that information affected the timing of the clock. © 2015 American Association for the Advancement of Science
By Jonathan Webb Science reporter, BBC News Living in total darkness, the animals' eyes have disappeared over millions of years A study of blind crustaceans living in deep, dark caves has revealed that evolution is rapidly withering the visual parts of their brain. The findings catch evolution in the act of making this adjustment - as none of the critters have eyes, but some of them still have stumpy eye-stalks. Three different species were studied, each representing a different subgroup within the same class of crustaceans. The research is published in the journal BMC Neuroscience. The class of "malocostracans" also includes much better-known animals like lobsters, shrimps and wood lice, but this study focussed on three tiny and obscure examples that were only discovered in the 20th Century. It is the first investigation of these mysterious animals' brains. "We studied three species. All of them live in caves, and all of them are very rare or hardly accessible," said lead author Dr Martin Stegner, from the University of Rostock in Germany. Specifically, his colleagues retrieved the specimens from the coast of Bermuda, from Table Mountain in South Africa, and from Monte Argentario in Italy. One of the species was retrieved from caves on the coast of Bermuda The animals were preserved rather than living, so the team could not observe their tiny brains in action. But by looking at the physical shape of the brain, and making comparisons with what we know about how the brain works in their evolutionary relatives, the researchers were able to assign jobs to the various lobes, lumps and spindly structures they could see under the microscope. © 2015 BBC.
By Kate Galbraith Most evenings, before watching late-night comedy or reading emails on his phone, Matt Nicoletti puts on a pair of orange-colored glasses that he bought for $8 off the Internet. “My girlfriend thinks I look ridiculous in them,” he said. But Mr. Nicoletti, a 30-year-old hospitality consultant in Denver, insists that the glasses, which can block certain wavelengths of light emitted by electronic screens, make it easier to sleep. Studies have shown that such light, especially from the blue part of the spectrum, inhibits the body’s production of melatonin, a hormone that helps people fall asleep. Options are growing for blocking blue light, though experts caution that few have been adequately tested for effectiveness and the best solution remains avoiding brightly lit electronics at night. A Swiss study of 13 teenage boys, published in August in The Journal of Adolescent Health, showed that when the boys donned orange-tinted glasses, also known as blue blockers and shown to prevent melatonin suppression, in the evening for a week, they felt “significantly more sleepy” than when they wore clear glasses. The boys looked at their screens, as teenagers tend to do, for at least a few hours on average before going to bed, and were monitored in the lab. Older adults may be less affected by blue light, experts say, since the yellowing of the lens and other changes in the aging eye filter out increasing amounts of blue light. But blue light remains a problem for most people, and an earlier study of 20 adults ages 18 to 68 found that those who wore amber-tinted glasses for three hours before bed improved their sleep quality considerably relative to a control group that wore yellow-tinted lenses, which blocked only ultraviolet light. Devices such as smartphones and tablets are often illuminated by light-emitting diodes, or LEDs, that tend to emit more blue light than incandescent products. Televisions with LED backlighting are another source of blue light, though because they are typically viewed from much farther away than small screens like phones, they may have less of an effect, said Debra Skene, a professor of neuroendocrinology at the University of Surrey in England. © 2015 The New York Times Company
By Jan Hoffman As adults age, vision deteriorates. One common type of decline is in contrast sensitivity, the ability to distinguish gradations of light to dark, making it possible to discern where one object ends and another begins. When an older adult descends a flight of stairs, for example, she may not tell the edge of one step from the next, so she stumbles. At night, an older driver may squint to see the edge of white road stripes on blacktop. Caught in the glare of headlights, he swerves. But new research suggests that contrast sensitivity can be improved with brain-training exercises. In a study published last month in Psychological Science, researchers at the University of California, Riverside, and Brown University showed that after just five sessions of behavioral exercises, the vision of 16 people in their 60s and 70s significantly improved. After the training, the adults could make out edges far better. And when given a standard eye chart, a task that differed from the one they were trained on, they could correctly identify more letters. “There’s an idea out there that everything falls apart as we get older, but even older brains are growing new cells,” said Allison B. Sekuler, a professor of psychology, neuroscience and behavior at McMaster University in Ontario, who was not involved in the new study. “You can teach an older brain new tricks.” The training improved contrast sensitivity in 16 young adults in the study as well, although the older subjects showed greater gains. That is partly because the younger ones, college students, already had reasonably healthy vision and there was not as much room for improvement. Before the training, the vision of each adult, young and older, was assessed. The exercises were fine-tuned at the beginning for each individual so researchers could measure improvements, said Dr.G. John Andersen, the project’s senior adviser and a psychology professor at the University of California, Riverside. © 2015 The New York Times Company
by Andy Coghlan Who needs sight to get around when you've got a digital compass in your head? A neuroprosthesis that feeds geomagnetic signals into the brains of blind rats has enabled them to navigate around a maze. The results demonstrate that the rats could rapidly learn to deploy a completely unnatural "sense". It raises the possibility that humans could do the same, potentially opening up new ways to treat blindness, or even to provide healthy people with extra senses. "I'm dreaming that humans can expand their senses through artificial sensors for geomagnetism, ultraviolet, radio waves, ultrasonic waves and so on," says Yuji Ikegaya of the University of Tokyo in Japan, head of the team that installed and tested the 2.5-gram implant. "Ultrasonic and radio-wave sensors may enable the next generation of human-to-human communicationMovie Camera," he says. The neuroprosthesis consists of a geomagnetic compass – a version of the microchip found in smartphones – and two electrodes that fit into the animals' visual cortices, the areas of the brain that process visual information. Whenever the rat positioned its head within 20 degrees either side of north, the electrodes sent pulses of electricity into its right visual cortex. When the rat aligned its head in a southerly direction, the left visual cortex was stimulated. The stimulation allowed blind rats to build up a mental map of their surroundings without any visual cues. During training, blind rats equipped with digital compasses improved at finding food rewards in a five-pronged maze, despite being released from one of three different arms of the maze at random each time. © Copyright Reed Business Information Ltd
Jon Hamilton A biotech company and two scientists hope to change that. On Wednesday, Avalanche Biotechnologies in Menlo Park and the University of Washington in Seattle announced a licensing agreement to develop the first treatment for colorblindness. The deal brings together a gene therapy technique developed by Avalanche with the expertise of vision researchers at the University of Washington. "Our goal is to be treating colorblindness in clinical trials in patients in the next one to two years," says Thomas Chalberg, the founder and CEO of Avalanche. Dalton the squirrel monkey during the color vision test. i Dalton the squirrel monkey during the color vision test. Courtesy of Neitz Laboratory The agreement has its roots in a scientific breakthrough that occurred six years ago. That's when two vision researchers at the University of Washington used gene therapy to cure a common form of colorblindness in squirrel monkeys. "This opened the possibility of ultimately getting this to cure colorblindness in humans," says Jay Neitz, who runs the Color Vision Lab at UW along with his wife, Maureen Neitz. The couple knew that transferring their success from monkey to man would be a challenge. But they were determined, says Maureen Neitz. "We've spent our entire careers writing NIH grants where we say our goal is to improve human health." © 2015 NPR
Link ID: 20725 - Posted: 03.26.2015
By Rachel Feltman I'm not usually one for heartstring-tugging ads, but this collaboration between Valspar Paint and EnChroma, a company that makes color-boosting sunglasses for the color-blind, is pretty cool. And the coolest thing about the glasses in the above video is that they weren't designed to help the color-blind at all. Smithsonian Magazine reports that EnChroma Labs founder Don McPherson (a materials scientist) had originally engineered the glasses with surgeons in mind. The lenses contained rare earth iron and absorbed a ton of light to protect surgeons performing laser eye surgery. The boosted absorption also made colors pop more vibrantly, allowing them to more easily distinguish among different tissues during surgery. But the stellar eye protection and vibrant colors meant that many surgeons wanted to wear them outside the operating room. McPherson himself started using them as regular sunglasses. And when a color-blind friend tried them on, he was amazed: He could distinguish orange traffic cones from the grass and pavement around them. He was perceiving color in a way he never had before. Now EnChroma sells the glasses (which have been specifically tailored for color blindness since the accidental discovery) for a few hundred bucks a pop. McPherson explains that all people have three photopigments in the eye, also known as cones, which are sensitive to blue, green and red. Blue operates fairly independently, while the red and green cones, in most humans, overlap, affecting the perception of certain colors. For example, if 10 photons landed on the red cone and 100 landed on the green cone, the object viewed would appear more green. Whereas if an equal number of photons landed on the red and green cones, the color perceived would be yellow.
Link ID: 20720 - Posted: 03.25.2015
|By Susana Martinez-Conde and Stephen L. Macknik All visual art is illusory in that it involves a departure from reality, a filtering through the mind of the artist. This subjectivity applies not only to abstract works but also to representational art, in which the artist translates his or her perception into a physical object capable of inducing a similar perception in the viewer. Painters render the three-dimensional world on a flat surface. These representations are enough to suspend our visual system's disbelief and trigger barrages of neuronal firing that become visions of bathers, bridges and water lilies. It is never about reality but about how the artist sees and wants to portray it. This artistic vision is a mishmash of expectations, memories, assumptions, imagination and intent. It is also, in a sense, a reflection of neural shortcuts and basic visual processes. The picture becomes even more complicated when painters suffer from pathologies of the eyes or brain that force them to see their surroundings in ways that diverge from standard experience. The artwork produced by such artists allows us to participate in their perception—and misperception—of the world. For example, failing vision can translate into an eerie loss of precision and detail in paintings. The pictures of American artist Georgia O'Keeffe became flatter and less intricate as she developed bilateral age-related macular degeneration, a retinal disease that affects central, high-resolution vision. The later works of American painter Mary Cassatt similarly show an uncharacteristic absence of delicacy in faces as she developed cataracts. French impressionist Claude Monet also had cataracts, which rendered his paintings imprecise and muted in color. After he underwent successful cataract surgery, his paintings regained definition and vibrancy. As the examples in this column attest, the effects of vision or brain diseases can sometimes be traced in great works of art. © 2015 Scientific American
Link ID: 20710 - Posted: 03.24.2015
Elie Dolgin The southern city of Guangzhou has long held the largest eye hospital in China. But about five years ago, it became clear that the Zhongshan Ophthalmic Center needed to expand. More and more children were arriving with the blurry distance vision caused by myopia, and with so many needing eye tests and glasses, the hospital was bursting at the seams. So the centre began adding new testing rooms — and to make space, it relocated some of its doctors and researchers to a local shopping mall. Now during the summer and winter school holidays, when most diagnoses are made, “thousands and thousands of children” pour in every day, says ophthalmologist Nathan Congdon, who was one of those uprooted. “You literally can't walk through the halls because of all the children.” East Asia has been gripped by an unprecedented rise in myopia, also known as short-sightedness. Sixty years ago, 10–20% of the Chinese population was short-sighted. Today, up to 90% of teenagers and young adults are. In Seoul, a whopping 96.5% of 19-year-old men are short-sighted. Other parts of the world have also seen a dramatic increase in the condition, which now affects around half of young adults in the United States and Europe — double the prevalence of half a century ago. By some estimates, one-third of the world's population — 2.5 billion people — could be affected by short-sightedness by the end of this decade. “We are going down the path of having a myopia epidemic,” says Padmaja Sankaridurg, head of the myopia programme at the Brien Holden Vision Institute in Sydney, Australia. The condition is more than an inconvenience. Glasses, contact lenses and surgery can help to correct it, but they do not address the underlying defect: a slightly elongated eyeball, which means that the lens focuses light from far objects slightly in front of the retina, rather than directly on it. © 2015 Nature Publishing Group
|By Erez Ribak and The Conversation UK The human eye is optimised to have good colour vision at day and high sensitivity at night. But until recently it seemed as if the cells in the retina were wired the wrong way round, with light travelling through a mass of neurons before it reaches the light-detecting rod and cone cells. New research presented at a meeting of the American Physical Society has uncovered a remarkable vision-enhancing function for this puzzling structure. About a century ago, the fine structure of the retina was discovered. The retina is the light-sensitive part of the eye, lining the inside of the eyeball. The back of the retina contains cones to sense the colours red, green and blue. Spread among the cones are rods, which are much more light-sensitive than cones, but which are colour-blind. Before arriving at the cones and rods, light must traverse the full thickness of the retina, with its layers of neurons and cell nuclei. These neurons process the image information and transmit it to the brain, but until recently it has not been clear why these cells lie in front of the cones and rods, not behind them. This is a long-standing puzzle, even more so since the same structure, of neurons before light detectors, exists in all vertebrates, showing evolutionary stability. Researchers in Leipzig found that glial cells, which also span the retinal depth and connect to the cones, have an interesting attribute. These cells are essential for metabolism, but they are also denser than other cells in the retina. In the transparent retina, this higher density (and corresponding refractive index) means that glial cells can guide light, just like fibre-optic cables. © 2015 Scientific American
By Lily Hay Newman When I was growing up, I had a lazy eye. I had to wear a patch over my stronger eye for many years so that good-for-nothing, freeloading, lazy eye could learn some responsibility and toughen up. Wearing a patch was really lousy, though, because people would ask me about it all the time and say things like, "What's wrong with you?" Always fun to hear. I would have much preferred to treat my condition, which is also called amblyopia, by playing video games. Who wouldn't? And it seems like that dream may become a possibility. On Tuesday, developer Ubisoft announced Dig Rush, a game that uses stereoscopic glasses and blue and red figures in varying contrasts to attempt to treat amblyopia. Working in collaboration with McGill University and the eye treatment startup Amblyotech, Ubisoft created a world where controlling a mole character to mine precious metals is really training patients' brains to coordinate their eyes. When patients wear a patch, they may force their lazy eye to toughen up, but they aren't doing anything to teach their eyes how to work together. This lack of coordination, called strabismus, is another important factor that the game makers hope can be addressed better by Dig Rush than by "patching" alone. Amblyotech CEO Joseph Koziak said in a statement, “[This] electronic therapy has been tested clinically to significantly increase the visual acuity of both children and adults who suffer from this condition without the use of an eye patch.” One advantage of Dig Rush, he noted, is that it's easier to measure compliance with video games.
Link ID: 20667 - Posted: 03.09.2015
by Sarah Zielinski Before they grow wings and fly, young praying mantises have to rely on leaps to move around. But these little mantises are really good at jumping. Unlike most insects, which tend to spin uncontrollably and sometimes crash land, juvenile praying mantises make precision leaps with perfect landings. But how do they do that? To find out, Malcolm Burrows of the University of Cambridge in England and colleagues filmed 58 juvenile Stagmomantis theophila praying mantises making 381 targeted jumps. The results of their study appear March 5 in Current Biology. For each test leap, the researchers put a young insect on a ledge with a black rod placed one to two body lengths away. A jump to the rod was fast — only 80 milliseconds, faster than a blink of an eye — but high-speed video captured every move at 1,000 frames per second. That let the scientists see what was happening: First, the insect shook its head from side to side, scanning its path. Then it rocked backwards and curled up its abdomen, readying itself to take a leap. With a push of its legs, the mantis was off. In the air, it rotated its abdomen, hind legs and front legs, but its body stayed level until it hit the target and landed on all four limbs. “The abdomen, front legs and hind legs performed a series of clockwise and anticlockwise rotations during which they exchanged angular momentum at different times and in different combinations,” the researchers write. “The net result … was that the trunk of the mantis spun by 50˚relative to the horizontal with a near-constant angular momentum, aligning itself perfectly for landing with the front and hind legs ready to grasp the target.” © Society for Science & the Public 2000 - 2015
Link ID: 20663 - Posted: 03.07.2015
By Jonathan Webb Science reporter, BBC News, San Antonio Physicists have pinned down precisely how pipe-shaped cells in our retina filter the incoming colours. These cells, which sit in front of the ones that actually sense light, play a major role in our colour vision that was only recently confirmed. They funnel crucial red and green light into cone cells, leaving blue to spill over and be sensed by rod cells - which are responsible for our night vision. Key to this process, researchers now say, is the exact shape of the pipes. The long, thin cells are known as "Muller glia" and they were originally thought to play more of a supporting role in the retina. They clear debris, store energy and generally keep the conditions right for other cells - like the rods and cones behind them - to turn light into electrical signals for the brain. But a study published last year confirmed the idea, proposed in earlier simulations, that Muller cells also function rather like optical fibres. 3D scans revealed the pipe-like structure of the Muller cells (in red) sitting above the photoreceptor cells (in blue) 3D scans revealed the pipe-like structure of the Muller cells (in red) sitting above the photoreceptor cells (in blue) And more than just piping light to the back of the retina, where the rods and cones sit, they selectively send red and green light - the most important for human colour vision - to the cone cells, which handle colour. Meanwhile, they leave 85% of blue light to spill over and reach nearby rod cells, which specialise in those wavelengths and give us the mostly black-and-white vision that gets us by in dim conditions. © 2015 BBC.
By Felicity Muth Visual illusions are fun: we know with our rational mind that, for example, these lines are parallel to each other, yet they don’t appear that way. Similarly, I could swear that squares A and B are different colours. But they are not. This becomes clearer when a connecting block is drawn between the two squares (see the image below). Illusions aren’t just fun tricks for us to play with, they can also tell us something about our minds. Things in the world look to us a certain way, but that doesn’t mean that they are that way in reality. Rather, our brain represents the world to us in a particular way; one that has been selected over evolutionary time. Having such a system means that, for example, we can see some animals running but not others; we couldn’t see a mouse moving from a mile away like a hawk could. This is because there hasn’t been the evolutionary selective pressures on our visual system to be able to do such a thing, whereas there has on the hawk’s. We can also see a range of wavelengths of light, represented as particular colours in our brain, while not being able to see other wavelengths (that, for example, bees and birds can see). Having a system limited by what evolution has given us means that there are many things we are essentially blind to (and wouldn’t know about if it weren’t for technology). It also means that sometimes our brain misrepresents physical properties of the external world in a way that can be confusing once our rational mind realises it. Of course, all animals have their own representation of the world. How a dog visually perceives the world will be different to how we perceive it. But how can we know how other animals perceive the world? What is their reality? One way we can try to get this is through visual illusions. © 2015 Scientific American
By JONATHAN MAHLER The mother of the bride wore white and gold. Or was it blue and black? From a photograph of the dress the bride posted online, there was broad disagreement. A few days after the wedding last weekend on the Scottish island of Colonsay, a member of the wedding band was so frustrated by the lack of consensus that she posted a picture of the dress on Tumblr, and asked her followers for feedback. “I was just looking for an answer because it was messing with my head,” said Caitlin McNeill, a 21-year-old singer and guitarist. Within a half-hour, her post attracted some 500 likes and shares. The photo soon migrated to Buzzfeed and Facebook and Twitter, setting off a social media conflagration that few were able to resist. As the debate caught fire across the Internet — even scientists could not agree on what was causing the discrepancy — media companies rushed to get articles online. Less than a half-hour after Ms. McNeil’s original Tumblr post, Buzzfeed posted a poll: “What Colors Are This Dress?” As of Friday afternoon, it had been viewed more than 28 million times. (White and gold was winning handily.) At its peak, more than 670,000 people were simultaneously viewing Buzzfeed’s post. Between that and the rest of Buzzfeed’s blanket coverage of the dress Thursday night, the site easily smashed its previous records for traffic. So did Tumblr. Everyone, it seems, had an opinion. And everyone was convinced that he, or she, was right. “I don’t understand this odd dress debate and I feel like it’s a trick somehow,” Taylor Swift wrote on Twitter. “PS it’s OBVIOUSLY BLUE AND BLACK.” “IT’S A BLUE AND BLACK DRESS!” wrote Mindy Kaling. “ARE YOU KIDDING ME,” she continued, including an unprintable modifier for emphasis. © 2015 The New York Times Company
Link ID: 20635 - Posted: 02.28.2015
By Pascal Wallisch If you are just encountering The Dress for the first time, you might first want to click here to see what all the fuss was about. The brain lives in a bony shell. The completely light-tight nature of the skull renders this home a place of complete darkness. So the brain relies on the eyes to supply an image of the outside world, but there are many processing steps between the translation of light energy into electrical impulses that happens in the eye and the neural activity that corresponds to a conscious perception of the outside world. In other words, the brain is playing a game of telephone and—contrary to popular belief—our perception corresponds to the brain’s best guess of what is going on in the outside world, not necessarily to the way things actually are. This has been recognized for at least 150 years, since the time of Hermann von Helmholtz. This week, it was recognized by masses of people on the Internet, who have been debating furiously over what should be a simple question: What color is this dress? Many parts of the brain contribute to any given perception, and it should not be surprising that different people can reconstruct the outside world in different ways. This is true for many perceptual qualities, including form and motion. While this guessing game is going on all the time, it is possible to demonstrate it clearly by generating impoverished stimulus displays that are consistent with different, mutually exclusive interpretations. That means the brain will not necessarily commit to one interpretation, but will switch back and forth. These are known as ambiguous or bi-stable stimuli, and they illustrate the point that the brain is ultimately only guessing when perceiving the world. It usually just has more information to disambiguate the interpretation. © 2014 The Slate Group LLC. All
Link ID: 20634 - Posted: 02.28.2015
Carmen Fishwick It’s not every day that fashion and science come together to polarise the world. Tumblr blogger Caitlin posted a photograph of what is now known as #TheDress – a layered lace dress and jacket that was causing much distress among her friends. The distress spread rapidly across social media, with Taylor Swift admitting she was “confused and scared”. The internet is now made up by people firmly in two camps: the white and gold, and the blue and black – with each thinking the other is completely wrong. But Ron Chrisley, director of the Centre for Research in Cognitive Science at the University of Sussex, believes that the problem mainly lies in the fact that everyone has forgotten we are dealing with a colour illusion. Chrisley said: “The first step in reaching a truce in the dress war is to construct a demonstration that can show to the white-and-gold crowd how the very same dress can also look blue and black under different conditions.” The image below, tweeted by @namin3485, demonstrates that even though the right-hand side of each image is the same, in the context of the two different left halves, the right is interpreted as being either white and gold, or blue and black. So does this mean people who are less self-confident are more likely to be able to see both, at least eventually? Chrisley said: “My guess is it’s not to do with self-confidence. It’s a perceptual issue. I could imagine someone that’s open minded could still see it only one way. This is below the level of us trying to understand other peoples views. It’s more physiological than that.” © 2015 Guardian News and Media Limited
Link ID: 20633 - Posted: 02.28.2015