Chapter 7. Vision: From Eye to Brain

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By Elizabeth Pennisi One man’s trash is another man’s treasure, even at the level of the cell. That’s where—according to new research—a waste product of the retina fuels part of the eye that powers the rods and cones that help us sense light. Without this waste, that part of the eye “steals” glucose from the retina, leading to the death of retinal cells and likely vision loss. The finding could help explain why eyesight degenerates with age—and in diseases such as macular degeneration and diabetes. “It’s almost a revolutionary concept” that there is such a tight coupling between the two parts of the eye, says Stephen Tsang, a retina specialist at Columbia University who was not involved in the work. Rods and cones are very active, and they need a lot of energy to do their jobs. Exactly how they get this energy has long been a mystery. In previous studies, researchers showed that a layer of cells beneath the retina, the retinal pigment epithelium (RPE), ferries glucose from the blood to the retina. But it was unclear why the RPE didn’t keep the glucose for itself. After a decade of study, biochemist James Hurley at the University of Washington in Seattle and his colleagues have now shown that the retina’s rods and cones burn the glucose, convert leftovers into a fuel called lactate, and then feed that back to the RPE. “There is a growing consensus that no cell exists on its own in complex tissues like the retina,” says Martin Friedlander, an ophthalmologist at The Scripps Research Institute in San Diego, California, who was not involved with the new work. © 2017 American Association for the Advancement of Science.

Keyword: Vision
Link ID: 24194 - Posted: 10.14.2017

Heidi Ledford The US government is considering whether to approve a gene therapy to prevent the degradation of cells in the retina (shown here in an image from a scanning electron microscope). Advisers to the US Food and Drug Administration (FDA) have paved the way for the agency’s first approval of a gene therapy to treat a disease caused by a genetic mutation. On 12 October, a panel of external experts unanimously voted that the benefits of the therapy, which treats a form of hereditary blindness, outweigh its risks. The FDA is not required to follow the guidance of its advisers, but it often does. A final decision on the treatment, called voretigene neparvovec (Luxturna), is expected by 12 January. An approval in the lucrative US drug market would be a validation that gene-therapy researchers have awaited for decades. “It’s the first of its kind,” says geneticist Mark Kay of Stanford University in California, of the treatment. “Things are beginning to look more promising for gene therapy.” Luxturna is made by Spark Therapeutics of Philadelphia, Pennsylvania, and is designed to treat individuals who have two mutated copies of a gene called RPE65. The mutations impair the eye’s ability to respond to light, and ultimately lead to the destruction of photoreceptors in the retina. The treatment consists of a virus loaded with a normal copy of the RPE65 gene. The virus is injected into the eye, where the gene is expressed and supplies a normal copy of the RPE65 protein. © 2017 Macmillan Publishers Limited

Keyword: Vision; Genes & Behavior
Link ID: 24192 - Posted: 10.14.2017

By Toni Clarke, (Reuters) - Spark Therapeutics Inc’s experimental gene therapy for a rare inherited form of blindness is effective, though it is unclear whether the benefit lasts over time, according to a preliminary review by the U.S. Food and Drug Administration. The therapy, Luxturna, or voretigene neparvovec, would be the first-ever gene therapy for any inherited disease to be approved in the United States. The FDA’s review, posted on Tuesday on the agency’s website, comes two days ahead of a meeting of outside advisers who will discuss the treatment and recommend whether it should be approved. Advertisement Michael Yee, an analyst at Jefferies, said the FDA documents “look fairly benign and as expected,” and said he expects the advisory panel is likely to vote in favor of approval. The FDA noted there is no available long-term data to show whether the effectiveness of the therapy is maintained after a year, so the clinical benefit beyond that “is unclear.” Inherited retinal diseases are a group of rare conditions caused by mutations in one or more than 220 different genes, including one known as RPE65, which tells cells how to produce a crucial enzyme needed for normal vision. Spark studied Luxturna in people with one of these conditions, Leber congenital aumaurosis, whose disease was mediated by defects in the RPE65 gene. Clinical trial results showed 93 percent of participants experienced some improvement in their functional vision as measured by their ability to navigate obstacles in poor light. © 2017 Scientific American,

Keyword: Vision
Link ID: 24171 - Posted: 10.11.2017

By Frances Stead Sellers October 8 at 9:00 AM One late-summer day last year, my surroundings started playing tricks with me. The letters I typed on my computer screen looked fuzzy. Objects on my desk seemed to slip sideways, escaping their own outlines. My colleagues, viewed across the room, appeared to have shifted slightly so that now they stood or sat as ghostly silhouettes beside themselves. I put it down to fatigue or lack of food. The next morning, neither sleep nor sustenance had cured me. I squinted my way out of my apartment and reached for the handrail that runs alongside the front steps. As my left arm extended, my forearm divided somewhere between my elbow and my wrist, so that now I had two left hands and 10 fingers, groping for two railings that ran not parallel to one another but diverged into the distance. Below my four feet, the neat brick geometry of a Capitol Hill sidewalk had become a muddled mosaic. I looked up to see two identically dressed men, swinging their arms in unison as they marched, lockstep, toward me. I closed one eye and then the other. Both worked well. In fact, each restored reassuring order to the world: One man. One left hand. One railing. But when I tried to walk with only my right eye open, I keeled over to the side. I lost my balance — and a little confidence. “Not good,” the ophthalmologist murmured later that morning as he tracked the movement of my eyes from left to right and back again. Diplopia was his diagnosis. Greek for double vision. How did I feel? he asked. Had I had a virus? I needn’t go to the ER, he said, unless I developed a splitting headache or started vomiting. But I should see a neuro-ophthalmologist. Soon. © 1996-2017 The Washington Post

Keyword: Vision; Movement Disorders
Link ID: 24166 - Posted: 10.09.2017

Medical professionals and body artists say the practice of tattooing the eyeball, which recently left an Ottawa woman facing the prospect of vision loss, is on the rise despite its many risks. Ophthalmologists and tattoo studios decry the practice, saying it's very difficult to engage in it safely. Nonetheless, they say they hear of increasing demand for the extreme form of body modification which involves injecting ink into the whites of the eyes. A 24-year-old woman says she has learned the hard way about the risks of the procedure. Catt Gallinger says she recently allowed someone to dye the white of her right eye purple, but has since developed major complications. Gallinger does alternative modelling, a branch of modelling that features models who do not conform to mainstream beauty ideals and who often have body modifications. She has currently lost part of the vision in her swollen, misshapen eye and is facing the prospect of living with irreversible damage. "This is a very big toll on the mental health," she said in a telephone interview. "At this point, every day is different. Some days I feel a bit better, other days I kind of want to give up." ​Gallinger said she has long had an interest in body modification, and especially in tattooing the white of her eye, technically known as the sclera. But she said she took the plunge without doing adequate research on the procedure. Had she done so, medical and tattoo professionals say she could have found a plethora of evidence discouraging the practice, which has gained traction among body modification enthusiasts in recent years. ©2017 CBC/Radio-Canada.

Keyword: Vision
Link ID: 24125 - Posted: 09.30.2017

By JANE E. BRODY Now and then I hear someone (myself included) proclaim “my brain is on overload.” This is not surprising given the myriad complex tasks the brain performs, among them enabling you to learn, plan, remember, communicate, see, hear and smell. Perhaps also not surprising, a growing number of studies have linked compromised sensory functions like poor vision and hearing to a decline in cognitive abilities. The brain, it seems, can do only so much, and when it must struggle to make sense of the world – from reading the words on a page to understanding the spoken word – it may be less able to perform other important tasks. While a cause-and-effect relationship has yet to be established, evidence is gradually increasing to suggest that uncorrected deficits in vision and hearing can accelerate cognitive decline. National statistics demonstrate the importance of this relationship. The number of Americans with poor vision, often undetected among older adults, is expected to double by 2050; hearing loss – mostly untreated or undertreated – afflicts nearly two-thirds of adults over 70; both vision and hearing impairment occur in one person in nine age 80 and older (fewer than one in five have neither), and the prevalence of dementia is now doubling every 20 years. The latest study, published in August in JAMA Ophthalmology, found that among a representative sample of nearly 3,000 older Americans and a second sample of 30,000 Medicare beneficiaries, poor vision was associated with poor cognition. The two data sets used different measurements of cognitive abilities like memory, orientation and planning, and the consistency of their findings suggests that the association between vision impairment and compromised brain function is real, the researchers concluded. © 2017 The New York Times Company

Keyword: Vision; Hearing
Link ID: 24114 - Posted: 09.26.2017

By Jessica Hamzelou People who are blind use parts of their brain that normally handle for vision to process language, as well as sounds – highlighting the brain’s extraordinary ability to requisition unused real estate for new functions. Neurons in the part of the brain normally responsible for vision synchronise their activity to the sounds of speech in blind people, says Olivier Collignon at the Catholic University of Louvain (UCL) in Belgium. “It’s a strong argument that the organisation of the language system… is not constrained by our genetic blueprint alone,” he says. The finding builds on previous research showing that the parts of the brain responsible for vision can learn to process other kinds of information, including touch and sound, in people who are blind. Collignon and his colleagues made the discovery using magnetoencephalography (MEG), which measures electrical activity in the brain. Read more: How some blind people are able to echolocate like bats While they were being scanned, groups of sighted and blind volunteers were played three clips from an audio book. One recording was clear and easy to understand; another was distorted but still intelligible; and the third was modified so as to be completely incomprehensible. Both groups showed activity in the brain’s auditory cortex, a region that processes sounds, while listening to the clips. But the volunteers who were blind showed activity in the visual cortex, too. © Copyright New Scientist Ltd.

Keyword: Vision; Language
Link ID: 24075 - Posted: 09.19.2017

By Emily Chung, CBC News If you were blind and walked into a coffee shop, how would you find the counter so you could order? That's easy for Susan Vaile at 9 Bars Coffee in Toronto — she just needs to listen to her smartphone: "Walk forward six metres to carpet. Service counter at 9 o' clock." Sure enough, there it is, and within minutes, Vaile has ordered and received a small coffee with double cream and double sugar. Similar verbal directions are already available to customers like Vaile at several other businesses in the Yonge and St. Clair neighbourhood, thanks to a pilot project called ShopTalk launched by the CNIB, a charity that provides community-based support for people who are blind or partially sighted. The project installs and programs palm-sized Apple iBeacons that use Bluetooth wireless signals to connect with nearby users' phones via an iPhone app called BlindSquare. It provides directions to help them navigate through doors and vestibules, to service counters, washrooms, and other important parts of buildings such as stores and restaurants. Vaile says the beacons make it possible for customers like herself to find their way independently. ©2017 CBC/Radio-Canada.

Keyword: Vision
Link ID: 24074 - Posted: 09.19.2017

By Catherine Offord | On August 21, the moon will pass between the Earth and the sun, resulting in a total solar eclipse visible across a large strip of the United States. Self-proclaimed eclipse-chaser Ralph Chou, an emeritus professor of optometry at the University of Waterloo, has been working to spread awareness about eye-safety during eclipses for around 30 years. Last year, he put together the American Astronomical Society’s technical guide to eye safety, aimed at everyone from astronomers to educators to medical professionals. The Scientist spoke to Chou to find out what happens to the eye when exposed to too much sunlight, and how to watch next week’s solar eclipse safely. Ralph Chou: Light comes into the eye and goes through all the various layers of cells until it reaches the photoreceptors—essentially, the bottom of a stack of cells. The photoreceptors themselves guide the light towards a specialized structure [of the cells] called the outer segment, where there is a stack of discs that contain the visual pigment. Under normal circumstances, the light would interact with the pigment, which generates an electrical signal that then starts the process of sending an impulse through the optic nerve to the brain. In looking at the sun, you have a very large volume of photons—light energy—coming in and hitting these pigment discs, and it’s more than they can really handle. In addition to generating the electrical signal, [the cell] also starts generating photo-oxidative compounds. So you’re getting oxidative species like hydroxyl radicals and peroxides that will go on to attack the cell’s organelles. © 1986-2017 The Scientist

Keyword: Vision
Link ID: 23969 - Posted: 08.17.2017

Thomas Cronin We humans are uncommonly visual creatures. And those of us endowed with normal sight are used to thinking of our eyes as vital to how we experience the world. Vision is an advanced form of photoreception – that is, light sensing. But we also experience other more rudimentary forms of photoreception in our daily lives. We all know, for instance, the delight of perceiving the warm sun on our skin, in this case using heat as a substitute for light. No eyes or even special photoreceptor cells are necessary. But scientists have discovered in recent decades that many animals – including human beings – do have specialized light-detecting molecules in unexpected places, outside of the eyes. These “extraocular photoreceptors” are usually found in the central nervous system or in the skin, but also frequently in internal organs. What are light-sensing molecules doing in places beyond the eyes? Vision depends on detecting light All the visual cells identified in animals detect light using a single family of proteins, called the opsins. These proteins grab a light-sensitive molecule – derived from vitamin A – that changes its structure when exposed to light. The opsin in turn changes its own shape and turns on signaling pathways in photoreceptor cells that ultimately send a message to the brain that light has been detected. © 2010–2017, The Conversation US, Inc.

Keyword: Biological Rhythms; Vision
Link ID: 23947 - Posted: 08.11.2017

By Kai Sinclair It’s hard to see underwater, and not just because of the chlorine. The image-producing light rays that enter our eyes have trouble bending and focusing when the water’s density is almost same as that of eye fluid. Sea creatures experience the same problem, but squid use a type of lens notorious for blurry images to correct that, researchers report today in Science. Spherical lenses, like the squids’, usually can’t focus the incoming light to one point as it passes through the curved surface, which causes an unclear image. The only way to correct this is by bending each ray of light differently as it falls on each location of the lens’s surface. S-crystallin, the main protein in squid lenses, evolved the ability to do this by behaving as patchy colloids—small molecules that have spots of molecular glue that they use to stick together in clusters. The S-crystallins feature a pair of loops that act as the proteins’ sticky patches and attract the loops of other S-crystallins. Globs of six proteins link together during the squid’s larval stage and form a gel that eventually becomes the center of the lens. As the gel becomes too dense with protein clumps, smaller particles struggle to diffuse through, and a new layer of protein packages forms with just under six S-crystallins in each clump. The process continues until the outer edge of the lens is formed with pairs of S-crystallins. This allows light rays to bend a little differently in each region of the lens, which yields a clearer image. Some fish eyes are nearly identical to squids’, but it’s unknown whether their eye proteins exhibit patchy colloidlike behavior. Other cephalopods, like octopuses and nautiluses, lack S-crystallin lens proteins. So they, unlike squid, likely have blurry vision. © 2017 American Association for the Advancement of Science

Keyword: Vision; Evolution
Link ID: 23945 - Posted: 08.11.2017

By Philip Jaekl In 1959, two French scientists, Michel Jouvet and François Michel, recorded strange patterns of neural activity in the brainstem of sleeping cats. The brain waves seemed remarkably synced to rapid eye movement (REM) sleep, which University of Chicago researchers had connected with dreaming six years earlier. These new brain activity patterns seemed as though they might also correspond with dreaming. In the 1960s, Jouvet and collaborators showed that cats with a lesion introduced into that same brainstem area—the pons—exhibited odd behavior. Cats displayed REMs as though they were asleep, while reacting to nonexistent prey or predators, pouncing, or hiding. Humans can also experience REMs while dreaming, hallucinating, or even recalling deeply emotional memories while awake. But do humans also exhibit the same patterns of neural activity—dubbed PGO waves? The waves are so named because they are generated in a part of the brain stem called the pons, and propagate to the lateral geniculate nuclei of the brain—relay stations in the thalamus for incoming visual information—and then to the occipital lobe, where most visual processing takes place. Studies have suggested that this neural pathway is crucial for functions ranging from basic ones such as the control of eye muscle movements to more-complex phenomena, including visual experiences during dreams and in hallucinations, memory consolidation, and even psychotic behavior. Researchers have recently proposed that a common thread shared by these phenomena is the overriding of retinal visual input by internally created visual experiences (Front Hum Neuro, doi.org/10.3389/fnhum.2017.00089, 2017). © 1986-2017 The Scientist

Keyword: Sleep; Vision
Link ID: 23940 - Posted: 08.10.2017

By JANE E. BRODY Putting carboxymethylcellulose sodium in one’s eyes two, three or more times a day may not sound like a great experience. But I can assure you that it can be. Drops of this chemical, called a topical lubricant, help to keep my eyes from burning, avoiding bright lights, becoming red and itchy, and generally feeling miserable. Like tens of millions of Americans, especially women older than 50, I have dry eye disease, medically known as keratoconjunctivitis sicca. Fortunately, my problem is not severe, certainly not as bad as that of an elderly woman I know who has to use a nightly ointment of mineral oil and Vaseline, which minimizes the dryness but temporarily blurs her vision. The drops I use, an over-the-counter preservative-free product called Refresh Plus (also sold as generic store brands) that I carry with me at all times, are a crucial measure I take to keep my eyes from becoming overly dry and chronically irritated — but not the only one. To minimize the drying effect of wind when driving, cycling or sitting in a room cooled by a fan or air-conditioning, I wear wraparound glasses even when I don’t need them to see clearly. Watertight goggles are de rigueur when swimming, even in fresh water. And I refresh my eyes with drops when I watch a movie, work long hours at the computer, or do any activity that depresses the frequency of blinking, which moistens the eyes. Dry eye is sometimes referred to as “a nuisance complaint — it’s not the sexiest of eye problems,” Dr. Rachel Bishop, chief consulting ophthalmologist at the National Eye Institute, told me. Nonetheless, she said, “Dry eye disease deserves serious professional — and personal — attention. It can be very debilitating and seriously diminish a person’s quality of life.” Tears serve a variety of functions, which accounts for the kinds of complications their deficiency can cause. They lubricate the eye, supply it with nutrients and oxygen, and help to focus images and clear the eye of debris. © 2017 The New York Times Company

Keyword: Vision
Link ID: 23900 - Posted: 08.01.2017

Cells within an injured mouse eye can be coaxed into regenerating neurons and those new neurons appear to integrate themselves into the eye’s circuitry, new research shows. The findings potentially open the door to new treatments for eye trauma and retinal disease. The study appears in the July 26 issue of Nature, and was funded in part by the National Eye Institute (NEI), part of the National Institutes of Health. “The findings are significant because they suggest the feasibility of a novel approach for encouraging regeneration in the mammalian retina, the light sensitive tissue at the back of the eye that dies in many blinding diseases,” said Tom Greenwell, Ph.D., program director at NEI. “Importantly, the investigation also demonstrates that newly generated cells in the mouse retina not only look and behave like neurons, they also wire correctly to the existing neural circuitry at the back of the eye.” The study’s lead investigator, Tom Reh, Ph.D., and his team at UW Medicine in Seattle, looked to the zebrafish for clues about how to encourage regeneration in the mouse eye. When a zebrafish injures its eye, cells within the eye naturally regenerate, allowing the fish to maintain vision. Mammals lack this regenerative ability. In studying zebrafish the research team homed in on Müller glia, a type of retinal cell that supports the health and functioning of neighboring neurons, and that also exhibits an innate regenerative ability. Sometimes referred to as the stem cells of the zebrafish eye, Müller glia are the cells from which all other types of retinal cells are regenerated in the fish.

Keyword: Vision; Stem Cells
Link ID: 23882 - Posted: 07.27.2017

By Erin Blakemore What do you see? That question is so complex it may be impossible to answer. But when Vanessa Potter lost her sight because of a rare condition, she became obsessed with describing the experience of both literal and inner vision. Patient H69: The Story of My Second Sight Book by Vanessa Potter Her new book, “Patient H69,” tracks Potter’s progression from advertising producer to patient. But her memoir shows how a medical ordeal also turned her into a scientific detective, advocate and artist. In 2012, Potter suddenly lost her sight. The first half of her book tracks her terrifying loss of vision and illustrates the psychological toll that accompanies the transition from healthy person to patient. Potter’s ailment turned out to be neuromyelitis optica, a disorder also known as Devic’s disease. People with the autoimmune disorder experience inflammation of the optic nerve, temporary blindness and spinal cord inflammation that can cause pain and sensory loss. Determined to regain her sight and understand her illness, Potter collaborated with scientists as her optical nerve healed.Along the way, she documented her experience. Her descriptive powers serve her well as she illustrates what it’s like to experience the development of sight in real time — a progression that, for Potter, included synesthesia (a blending of the senses in which a word may be seen as a certain color, for example), self-hypnosis and plenty of emotion. © 1996-2017 The Washington Post

Keyword: Vision; Neuroimmunology
Link ID: 23867 - Posted: 07.24.2017

By Aylin Woodward See, hear. Our eardrums appear to move to shift our hearing in the same direction as our eyes are looking. Why this happens is unclear, but it may help us work out which objects we see are responsible for the sounds we can hear. Jennifer Groh at Duke University in Durham, North Carolina, and her team have been using microphones inserted into people’s ears to study how their eardrums change during saccades – the movement that occurs when we shift visual focus from one place to another. You won’t notice it, but our eyes go through several saccades a second to take in our surroundings. Examining 16 people, the team detected changes in ear canal pressure that were probably caused by middle-ear muscles tugging on the eardrum. These pressure changes indicate that when we look left, for example, the drum of our left ear gets pulled further into the ear and that of our right ear pushed out, before they both swing back and forth a few times. These changes to the eardrums began as early as 10 milliseconds before the eyes even started to move, and continued for a few tens of milliseconds after the eyes stopped. Making sense “We think that before actual eye movement occurs, the brain sends a signal to the ear to say ‘I have commanded the eyes to move 12 degrees to the right’,” says Groh. The eardrum movements that follow the change in focus may prepare our ears to hear sounds from a particular direction. © Copyright New Scientist Ltd.

Keyword: Hearing; Vision
Link ID: 23860 - Posted: 07.22.2017

By Jane C. Hu In English the sky is blue, and the grass is green. But in Vietnamese there is just one color category for both sky and grass: xanh. For decades cognitive scientists have pointed to such examples as evidence that language largely determines how we see color. But new research with four- to six-month-old infants indicates that long before we learn language, we see up to five basic categories of hue—a finding that suggests a stronger biological component to color perception than previously thought. The study, published recently in the Proceedings of the National Academy of Sciences USA, tested the color-discrimination abilities of more than 170 British infants. Researchers at the University of Sussex in England measured how long babies spent gazing at color swatches, a metric known as looking time. First the team showed infants one swatch repeatedly until their looking time decreased—a sign they had grown bored with it. Then the researchers showed them a different swatch and noted their reaction. Longer looking times were interpreted to mean the babies considered the second swatch to be a new hue. Their cumulative responses showed that they distinguished among five colors: red, green, blue, purple and yellow. The finding “suggests we’re all working from the same template,” explains lead author Alice Skelton, a doctoral student at Sussex. “You come prepackaged to make [color] distinctions, but given your culture and language, certain distinctions may or may not be used.” For instance, infants learning Vietnamese most likely see green and blue, even if their native language does not use distinct words for the two colors. © 2017 Scientific American

Keyword: Vision; Development of the Brain
Link ID: 23830 - Posted: 07.13.2017

by Laura Sanders Lots of newborn decorations come in black and white, so that young babies can better see the shapes. But just because it’s easier for babies to see bold blacks and whites doesn’t mean they can’t see color. Very few studies of color vision in newborns exist, says Anna Franklin, a color researcher at the University of Sussex in England. “But those that have been conducted suggest that newborns can see some color, even if their color vision is limited,” she says. Newborns may not be great at distinguishing maroon from scarlet, but they can certainly see a vivid red. But as babies get a little older, they get remarkably adept at discerning the world’s palette, new research shows. Babies ages 4 months to 6 months old are able to sort colors into five categories, researchers report in the May 23 Proceedings of the National Academy of Sciences. These preverbal color capabilities offer insight into something scientists have long wondered: Without words for individual colors, how do babies divvy up the hues across the color wheel, telling when blue turns to green, for instance? Along with Franklin and colleagues, psychologist Alice Skelton, also of the University of Sussex, bravely approached this question. The team coaxed 179 4- to 6-month-old babies to calmly and repeatedly look at two squares, each 1 of 14 various colors. |© Society for Science & the Public 2000 - 2017. All rights reserved.

Keyword: Vision; Development of the Brain
Link ID: 23702 - Posted: 06.03.2017

By Clare Wilson Seeing shouldn’t always be believing. We all have blind spots in our vision, but we don’t notice them because our brains fill the gaps with made-up information. Now subtle tests show that we trust this “fake vision” more than the real thing. If the brain works like this in other ways, it suggests we should be less trusting of the evidence from our senses, says Christoph Teufel of Cardiff University, who wasn’t involved in the study. “Perception is not providing us with a [true] representation of the world,” he says. “It is contaminated by what we already know.” The blind spot is caused by a patch at the back of each eye where there are no light-sensitive cells, just a gap where neurons exit the eye on their way to the brain. We normally don’t notice blind spots because our two eyes can fill in for each other. When vision is obscured in one eye, the brain makes up what’s in the missing area by assuming that whatever is in the regions around the spot continues inwards. But do we subconsciously know that this filled-in vision is less trustworthy than real visual information? Benedikt Ehinger of the University of Osnabrück in Germany and his colleagues set out to answer this question by asking 100 people to look at a picture of a circle of vertical stripes, which contained a small patch of horizontal stripes. The circle was positioned so that with one eye obscured, the patch of horizontal stripes fell within the other eye’s blind spot. As a result, the circle appeared as though there was no patch and the vertical stripes were continuous. © Copyright New Scientist Ltd.

Keyword: Vision; Attention
Link ID: 23640 - Posted: 05.20.2017

By Susana Martinez-Conde There is something deeply disconcerting about mirrors. The myriad reflecting surfaces that surround us in our everyday lives help us conduct many necessary tasks, such as applying makeup, shaving, or driving a car. But despite our constant use of mirrors, our nervous systems remain surprisingly ill-equipped to grasp the mechanics of refraction and reflection. Some magic tricks take advantage of such perceptual limitations, and are the origin of phrases such as “it’s all smoke and mirrors,” or “it’s all done with mirrors.” Kokichi Sugihara, a mathematical engineer at Meiji University in Japan, has exploited our poor understanding of mirrors to create new and spectacular varieties of perceptual magic. Our May/June Illusions column features mirror-based illusions by Sugihara and others. How can you use a mirror to vanish half an object? To make your own half-disappearing hexagon, follow the diagram above (you can print it from this template). Part A is the upper half of the object, which you will need to fold along the two edges, forming 120-degree angles. Part B, or the lower half of the object, is a flat structure and should not be folded. Glue both parts together matching the “a” and “b” letters. For the strongest effect, tilt the mirror slightly downward. © 2017 Scientific American

Keyword: Vision
Link ID: 23612 - Posted: 05.15.2017