Chapter 10. Vision: From Eye to Brain

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Scientists studied the brain activity of school-aged children during development and found that regions that activated upon seeing limbs (hands, legs, etc.) subsequently activated upon seeing faces or words when the children grew older. The research, by scientists at Stanford University, Palo Alto, California, reveals new insights about vision development in the brain and could help inform prevention and treatment strategies for learning disorders. The study was funded by the National Eye Institute and is published in Nature Human Behaviour. “Our study addresses how experiences, such as learning to read, shape the developing brain,” said Kalanit Grill-Spector, Ph.D., a professor at Stanford University’s Wu Tsai Neurosciences Institute. “Further, it sheds light on the initial functional role of brain regions that later in development process written words, before they support this important skill of reading.” Grill-Spector’s team used functional MRI to study areas in the ventral temporal cortex (VTC) that are stimulated by the recognition of images. About 30 children, ages 5 to 12 at their first MRI, participated in the study. While in the MRI scanner, the children viewed images from 10 different categories, including words, body parts, faces, objects, and places. The researchers mapped areas of VTC that exhibited stimulation and measured how they changed in intensity and volume on the children’s subsequent MRI tests over the next one to five years. Results showed that VTC regions corresponding to face and word recognition increased with age. Compared to the 5-9-year-olds, teenagers had twice the volume of the word-selective region in VTC. Notably, as word-selective VTC volume doubled, limb-selective volume in the same region halved. According to the investigators, the decrease in limb-selectivity is directly linked to the increase in word- and face-selectivity, providing the first evidence for cortical recycling during childhood development.

Keyword: Vision; Development of the Brain
Link ID: 27860 - Posted: 06.19.2021

Dr Rocio Camacho Morales A transparent metallic film allowing a viewer to see in the dark could one day turn regular spectacles into night vision googles. The ultra-thin film, made of a semiconductor called gallium arsenide, could also be used to develop compact and flexible infrared sensors, scientists say. Though still a proof of concept, the researchers believe it could eventually be turned into a cheap and lightweight replacement for bulky night-vision goggles, which are used in military, police and security settings. The film was developed by a team of Australian and European researchers, with details published in the journal Advanced Photonics. It works by converting infrared light – which is normally invisible to humans – into light visible to the human eye. The study’s first author, Dr Rocio Camacho Morales of the Australian National University, said the material was hundreds of times thinner than a strand of human hair. The gallium arsenide is arranged in a crystalline structure only several hundred nanometres thick, which allows visible light to pass through it. The film has certain similarities to night vision goggles. Blind man has sight partly restored after pioneering treatment Read more “The way these night vision goggles work [is] they also pick up infrared light,” said Camacho Morales. “This infrared light is converted to electrons and displayed [digitally]. In our case, we’re not doing this.” Instead, the film, which does not require any power source, changes the energy of photons of light passing through it, in what is known as a nonlinear optical process. One likely advantage of this film over existing technologies is weight: bulky helmet-mounted night vision goggles have previously been associated with neck pain in airforce pilots, for example. Photons of infrared light have very low energy, Camacho Morales said, which means that electronic night vision devices can be affected by random fluctuations in signal. To minimise these fluctuations, many infrared imaging devices use cooling systems, sometimes requiring cryogenic temperatures. © 2021 Guardian News & Media Limited

Keyword: Vision
Link ID: 27854 - Posted: 06.16.2021

By Carl Zimmer Dr. Adam Zeman didn’t give much thought to the mind’s eye until he met someone who didn’t have one. In 2005, the British neurologist saw a patient who said that a minor surgical procedure had taken away his ability to conjure images. Over the 16 years since that first patient, Dr. Zeman and his colleagues have heard from more than 12,000 people who say they don’t have any such mental camera. The scientists estimate that tens of millions of people share the condition, which they’ve named aphantasia, and millions more experience extraordinarily strong mental imagery, called hyperphantasia. In their latest research, Dr. Zeman and his colleagues are gathering clues about how these two conditions arise through changes in the wiring of the brain that join the visual centers to other regions. And they’re beginning to explore how some of that circuitry may conjure other senses, such as sound, in the mind. Eventually, that research might even make it possible to strengthen the mind’s eye — or ear — with magnetic pulses. “This is not a disorder as far as I can see,” said Dr. Zeman, a cognitive scientist at the University of Exeter in Britain. “It’s an intriguing variation in human experience.” The patient who first made Dr. Zeman aware of aphantasia was a retired building surveyor who lost his mind’s eye after minor heart surgery. To protect the patient’s privacy, Dr. Zeman refers to him as M.X. When M.X. thought of people or objects, he did not see them. And yet his visual memories were intact. M.X. could answer factual questions such as whether former Prime Minister Tony Blair has light-colored eyes. (He does.) M.X. could even solve problems that required mentally rotating shapes, even though he could not see them. I came across M.X.’s case study in 2010 and wrote a column about it for Discover magazine. Afterward, I got emails from readers who had the same experience but who differed from M.X. in a remarkable way: They had never had a mind’s eye to begin with. © 2021 The New York Times Company

Keyword: Attention; Vision
Link ID: 27851 - Posted: 06.11.2021

Linda Geddes Science correspondent A blind man has had his sight partly restored after a form of gene therapy that uses pulses of light to control the activity of nerve cells – the first successful demonstration of so-called optogenetic therapy in humans. The 58-year-old man, from Brittany in northern France, was said to be “very excited” after regaining the ability to recognise, count, locate and touch different objects with the treated eye while wearing a pair of light-stimulating goggles, having lost his sight after being diagnosed with retinitis pigmentosa almost 40 years ago. The breakthrough marks an important step towards the more widespread use of optogenetics as a clinical treatment. It involves modifying nerve cells (neurons) so that they fire electrical signals when they’re exposed to certain wavelengths of light, equipping neuroscientists with the power to precisely control neuronal signalling within the brain and elsewhere. Christopher Petkov, a professor of comparative neuropsychology at Newcastle University medical school, said: “This is a tremendous development to restore vision using an innovative approach. The goal now is to see how well this might work in other patients with retinitis pigmentosa.” This group of rare, genetic disorders, which involves the loss of light-sensitive cells in the retina, affects more than 2 million people worldwide, and can lead to complete blindness. © 2021 Guardian News & Media Limited

Keyword: Vision
Link ID: 27831 - Posted: 05.27.2021

Rob Stein Carlene Knight would love to do things that most people take for granted, such as read books, drive a car, ride a bike, gaze at animals in a zoo and watch movies. She also longs to see expressions on people's faces. "To be able to see my granddaughter especially — my granddaughter's face," said Knight, 54, who lives outside Portland, Ore. "It would be huge." Michael Kalberer yearns to be able to read a computer screen so he could get back to work as a social worker. He also hopes to one day watch his nieces and nephews play soccer instead of just listening to them, and move around in the world without help. But that's not all. "Maybe be able to — as romantically poetic as this sounds — see a sunset again, see a smile on somebody's face again. It's the little things that I miss," said Kalberer, 43, who lives on Long Island in New York. Kalberer and Knight are two of the first patients treated in a landmark study designed to try to restore vision to patients such as them, who suffer from a rare genetic disease. The study involves the revolutionary gene-editing technique called CRISPR, which allows scientists to make precise changes in DNA. Doctors think CRISPR could help patients fighting many diseases. It's already showing promise for blood disorders such as sickle cell disease and is being tested for several forms of cancer. But in those experiments, doctors take cells out of the body, edit them in the lab and then infuse the genetically edited cells back into patients. © 2021 npr

Keyword: Vision; Genes & Behavior
Link ID: 27815 - Posted: 05.12.2021

By Jane E. Brody Look and you shall see: A generation of the real-life nearsighted Mr. Magoos is growing up before your eyes. A largely unrecognized epidemic of nearsightedness, or myopia, is afflicting the eyes of children. People with myopia can see close-up objects clearly, like the words on a page. But their distance vision is blurry, and correction with glasses or contact lenses is likely to be needed for activities like seeing the blackboard clearly, cycling, driving or recognizing faces down the block. The growing incidence of myopia is related to changes in children’s behavior, especially how little time they spend outdoors, often staring at screens indoors instead of enjoying activities illuminated by daylight. Gone are the days when most children played outside between the end of the school day and suppertime. And the devastating pandemic of the past year may be making matters worse. Susceptibility to myopia is determined by genetics and environment. Children with one or both nearsighted parents are more likely to become myopic. However, while genes take many centuries to change, the prevalence of myopia in the United States increased from 25 percent in the early 1970s to nearly 42 percent just three decades later. And the rise in myopia is not limited to highly developed countries. The World Health Organization estimates that half the world’s population may be myopic by 2050. Given that genes don’t change that quickly, environmental factors, especially children’s decreased exposure to outdoor light, are the likely cause of this rise in myopia, experts believe. Consider, for example, factors that keep modern children indoors: an emphasis on academic studies and their accompanying homework, the irresistible attraction of electronic devices and safety concerns that demand adult supervision during outdoor play. All of these things drastically limit the time youngsters now spend outside in daylight, to the likely detriment of the clarity of their distance vision. © 2021 The New York Times Company

Keyword: Vision; Development of the Brain
Link ID: 27802 - Posted: 05.05.2021

: Peter Campochiaro, M.D. A 72-year-old lawyer who is pursuing his passion for photography in retirement was suddenly unable to take sharp, well-focused photographs. An examination of each eye revealed yellow spots in the macula, the central area of the retina responsible for sharp vision. The macula in the right eye was thickened and raised in height, substantially reducing and distorting his vision. A test called a fluorescein angiogram, in which fluorescent dye is injected into an arm vein that travels to blood vessels in the retina for imaging, revealed a spot of intense fluorescence that enlarged over time, indicating the presence of abnormal blood vessels leaking plasma into surrounding tissue. An optical coherence tomography scan provided a two-dimensional optical cross section showing fluid beneath and within the right eye’s macula. The patient had a condition known as age-related macular degeneration (AMD), common to about 200 million individuals globally and referred to as “age-related” because it is rarely seen in individuals younger than 60 years old. With people living longer and longer, it is estimated that by 2040, there will be 300 million individuals with AMD throughout the world. And besides the blurred vision that this patient was experiencing, other patients often complain about difficulty recognizing familiar faces; straight lines that appear wavy; dark, empty areas or blind spots; and a general loss of central vision, which is necessary for driving, reading, and recognizing faces. Besides age, smoking is a universally agreed upon risk factor for AMD; hypertension and high blood lipids have been identified in some studies but not others. © 2021 The Dana Foundation.

Keyword: Vision
Link ID: 27774 - Posted: 04.17.2021

By Meagan Cantwell In order to see the world as clearly as we do, we process vision from each eyeball on both sides of our brain—a capability known as bilateral visual projection. For a long time, researchers thought this feature developed after fish transitioned to land, more than 375 million years ago. But does this theory hold water today? In a new study, scientists injected fluorescent tracers into the eyes of 11 fish species to illuminate their visual systems. After examining their brains under a specialized 3D fluorescence microscope, they found ancient fish with genomes more similar to mammals can project vision on both the same and opposite side of their brain (see video, above). This suggests bilateral vision did not coincide with the transition from water to land, researchers report this week in Science. In the future, scientists plan to uncover the genes that drive same-sided visual projection to better understand how vision evolved. © 2021 American Association for the Advancement of Science.

Keyword: Vision; Evolution
Link ID: 27764 - Posted: 04.10.2021

By Veronique Greenwood Sign up for Science Times: Get stories that capture the wonders of nature, the cosmos and the human body. In the warm, fetid environs of a compost heap, tiny roundworms feast on bacteria. But some of these microbes produce toxins, and the worms avoid them. In the lab, scientists curious about how the roundworms can tell what’s dinner and what’s dangerous often put them on top of mats of various bacteria to see if they wriggle away. One microbe species, Pseudomonas aeruginosa, reliably sends them scurrying. But how do the worms, common lab animals of the species Caenorhabditis elegans, know to do this? Dipon Ghosh, then a graduate student in cellular and molecular physiology at Yale University, wondered if it was because they could sense the toxins produced by the bacteria. Or might it have something to do with the fact that mats of P. aeruginosa are a brilliant shade of blue? Given that roundworms do not have eyes, cells that obviously detect light or even any of the known genes for light-sensitive proteins, this seemed a bit far-fetched. It wasn’t difficult to set up an experiment to test the hypothesis, though: Dr. Ghosh, who is now a postdoctoral researcher at the Massachusetts Institute of Technology, put some worms on patches of P. aeruginosa. Then he turned the lights off. To the surprise of his adviser, Michael Nitabach, the worms’ flight from the bacteria was significantly slower in the dark, as though not being able to see kept the roundworms from realizing they were in danger. “When he showed me the results of the first experiments, I was shocked,” said Dr. Nitabach, who studies the molecular basis of neural circuits that guide behavior at Yale School of Medicine. In a series of follow-up experiments detailed in a paper published Thursday in Science, Dr. Ghosh, Dr. Nitabach and their colleagues establish that some roundworms respond clearly to that distinctive pigment, perceiving it — and fleeing from it — without the benefit of any known visual system. © 2021 The New York Times Company

Keyword: Vision; Evolution
Link ID: 27718 - Posted: 03.06.2021

By Richard Sima Sign up for Science Times: Get stories that capture the wonders of nature, the cosmos and the human body. Though it is well-known for its many arms, the octopus does not seem to know where those eight appendages are most of the time. “In the octopus, you have no bones and no joints, and every point in its arm can go to every direction that you can think about,” said Nir Nesher, a senior lecturer in marine sciences at the Ruppin Academic Center in Israel. “So even one arm, it’s something like endless degrees of freedom.” So how does the octopus keep all those wiggly, sucker-covered limbs out of trouble? According to a study published this month in The Journal of Experimental Biology by Dr. Nesher and his colleagues, the octopus’s arms can sense and respond to light — even when the octopus cannot see it with the eyes on its head. This light-sensing ability may help the cephalopods keep their arms concealed from other animals that could mistake the tip of an arm for a marine worm or some other kind of meal. Itamar Katz, one of the study’s authors, first noticed the light-detecting powers while studying a different phenomenon: how light causes the octopus’s skin to change color. With Dr. Nesher and Tal Shomrat, another author, Mr. Katz saw that shining light on an arm caused the octopus to withdraw it, even when the creature was sleeping. Further experiments showed that the arms would avoid the light in situations when the octopus could not see it with its eyes. Even when the octopuses reached an arm out of a small opening on an opaque, covered aquarium for food, the arm would quickly retract when light was shined on it 84 percent of the time. This was a surprise, as though the octopus “can see the light through the arm, it can feel the light through the arm,” Dr. Nesher said. “They don’t need the eye for that.” ImageScientists suspect octopuses keep their arms concealed from other animals that could mistake the tip of an arm for a meal. Scientists suspect octopuses keep their arms concealed from other animals that could © 2021 The New York Times Company

Keyword: Vision; Evolution
Link ID: 27704 - Posted: 02.23.2021

By Valeriya Safronova Jennifer Lopez is wearing them, Kylie Jenner and Rashida Jones are promoting them, and Drew Barrymore is selling them. Blue-light glasses are shaping up to be the accessory of our prolonged screen-mediated moment. But do we need them? Blue-light glasses are fitted with lenses that filter out certain light waves that are emitted by the sun and, to a lesser extent, by digital devices like phones, laptops and tablets. Blue light is not inherently bad; it boosts attention and wakefulness during the day. But it suppresses the natural production of melatonin at night. By limiting exposure to blue light by as little as 20 percent, companies say, a customer could sleep better, experience less eye strain and prevent potential retinal damage. Scientists, however, are not convinced that the glasses are a worthy investment. “Whichever aspect you look at, it’s very hard to justify spending the extra money,” said Dr. John Lawrenson, a professor of clinical visual science at City, University of London. (Prices vary but start at around $20.) After reviewing several studies that tested the effectiveness of blue-light-blocking lenses, he and his colleagues concluded that the glasses are not necessary. Digital eye strain is real, but it’s impossible to say with certainty that the culprit is blue light. “No one has established an independent causal association between blue light coming from the computer and visual symptoms,” Dr. Lawrenson said. He recommended going to an eye doctor for a checkup instead of rushing to buy nonprescription glasses. Regardless, the blue-light category is booming. A quick Google search pulls up several brands that almost exclusively sell “computer glasses” (like Felix Gray, which raised more than $1.7 million in funding in 2020, bringing its total funding to $7.8 million as of September, according to PitchBook), as well as prescription-eyewear companies like Zenni (which sold two million pairs of its Blokz lenses in 2020, according to the company) and Jins (which noted an uptick in online orders last year). If you’ve shopped at Warby Parker recently, you were probably asked if you’d like a blue-light filter added to your lenses. © 2021 The New York Times Company

Keyword: Sleep; Vision
Link ID: 27698 - Posted: 02.19.2021

By Cara Giaimo Platypuses do it. Opossums do it. Even three species of North American flying squirrel do it. Tasmanian devils, echidnas and wombats may also do it, although the evidence is not quite so robust. And, breaking news: Two species of rabbit-size rodents called springhares do it. That is, they glow under black light, that perplexing quirk of certain mammals that is baffling biologists and delighting animal lovers all over the world. Springhares, which hop around the savannas of southern and eastern Africa, weren’t on anyone’s fluorescence bingo card. Like the other glowing mammals, they are nocturnal. But unlike the other creatures, they are Old World placental mammals, an evolutionary group not previously represented. Their glow, a unique pinkish-orange the authors call “funky and vivid,” forms surprisingly variable patterns, generally concentrated on the head, legs, rear and tail. Fluorescence is a material property rather than a biological one. Certain pigments can absorb ultraviolet light and re-emit it as a vibrant, visible color. These pigments have been found in amphibians and some birds, and are added to things like white T-shirts and party supplies. But mammals, it seems, don’t tend to have these pigments. A group of researchers, many associated with Northland College in Ashland, Wis., has been chasing down exceptions for the past few years — ever since one member, the biologist Jonathan Martin, happened to wave a UV flashlight at a flying squirrel in his backyard. It glowed eraser pink. © 2021 The New York Times Company

Keyword: Vision; Evolution
Link ID: 27697 - Posted: 02.19.2021

Bevil R. Conway Danny Garside Is the red I see the same as the red you see? At first, the question seems confusing. Color is an inherent part of visual experience, as fundamental as gravity. So how could anyone see color differently than you do? To dispense with the seemingly silly question, you can point to different objects and ask, “What color is that?” The initial consensus apparently settles the issue. But then you might uncover troubling variability. A rug that some people call green, others call blue. A photo of a dress that some people call blue and black, others say is white and gold. You’re confronted with an unsettling possibility. Even if we agree on the label, maybe your experience of red is different from mine and – shudder – could it correspond to my experience of green? How would we know? Neuroscientists, including us, have tackled this age-old puzzle and are starting to come up with some answers to these questions. One thing that is becoming clear is the reason individual differences in color are so disconcerting in the first place. Scientists often explain why people have color vision in cold, analytic terms: Color is for object recognition. And this is certainly true, but it’s not the whole story. The color statistics of objects are not arbitrary. The parts of scenes that people choose to label (“ball,” “apple,” “tiger”) are not any random color: They are more likely to be warm colors (oranges, yellows, reds), and less likely to be cool colors (blues, greens). This is true even for artificial objects that could have been made any color. © 2010–2021, The Conversation US, Inc.

Keyword: Vision; Attention
Link ID: 27682 - Posted: 02.08.2021

By Jason Castro Pursued by poets and artists alike, beauty is ever elusive. We seek it in nature, art and philosophy but also in our phones and furniture. We value it beyond reason, look to surround ourselves with it and will even lose ourselves in pursuit of it. Our world is defined by it, and yet we struggle to ever define it. As philosopher George Santayana observed in his 1896 book The Sense of Beauty, there is within us “a very radical and wide-spread tendency to observe beauty, and to value it.” Philosophers such as Santayana have tried for centuries to understand beauty, but perhaps scientists are now ready to try their hand as well. And while science cannot yet tell us what beauty is, perhaps it can tell us where it is—or where it isn’t. In a recent study, a team of researchers from Tsinghua University in Beijing and their colleagues examined the origin of beauty and argued that it is as enigmatic in our brain as it is in the real world. There is no shortage of theories about what makes an object aesthetically pleasing. Ideas about proportion, harmony, symmetry, order, complexity and balance have all been studied by psychologists in great depth. The theories go as far back as 1876—in the early days of experimental psychology—when German psychologist Gustav Fechner provided evidence that people prefer rectangles with sides in proportion to the golden ratio (if you’re curious, that ratio is about 1.6:1). © 2021 Scientific American

Keyword: Emotions; Vision
Link ID: 27675 - Posted: 02.03.2021

The earliest eye damage from prion disease takes place in the cone photoreceptor cells, specifically in the cilia and the ribbon synapses, according to a new study of prion protein accumulation in the eye by National Institutes of Health scientists. Prion diseases originate when normally harmless prion protein molecules become abnormal and gather in clusters and filaments in the human body and brain. Understanding how prion diseases develop, particularly in the eye because of its diagnostic accessibility to clinicians, can help scientists identify ways to slow the spread of prion diseases. The scientists say their findings, published in the journal Acta Neuropathologica Communications, may help inform research on human retinitis pigmentosa, an inherited disease with similar photoreceptor degeneration leading to blindness. Prion diseases are slow, degenerative and usually fatal diseases of the central nervous system that occur in people and some other mammals. Prion diseases primarily involve the brain, but also can affect the eyes and other organs. Within the eye, the main cells infected by prions are the light-detecting photoreceptors known as cones and rods, both located in the retina. In their study, the scientists, from NIH’s National Institute of Allergy and Infectious Diseases at Rocky Mountain Laboratories in Hamilton, Montana, used laboratory mice infected with scrapie, a prion disease common to sheep and goats. Scrapie is closely related to human prion diseases, such as variant, familial and sporadic Creutzfeldt-Jakob disease (CJD). The most common form, sporadic CJD, affects an estimated one in one million people annually worldwide. Other prion diseases include chronic wasting disease in deer, elk and moose, and bovine spongiform encephalopathy in cattle.

Keyword: Prions; Vision
Link ID: 27674 - Posted: 02.03.2021

Jessica Koehler Ph.D. The only true voyage of discovery...would be not to visit strange lands, but to possess other eyes, to behold the universe through the eyes of another, of a hundred others, to behold the hundred universes that each of them beholds, that each of them is. Marcel Proust Perception is everything—and it is flawed. Most of us navigate our daily lives believing we see the world as it is. Our brains are perceiving an objective reality, right? Well, not quite. Everything we bring in through our senses is interpreted through the filter of our past experiences. Sensation is physical energy detection by our sensory organs. Our eyes, mouth, tongue, nose, and skin relay raw data via a process of transduction, which is akin to translation of physical energy—such as sound waves—into the electrochemical energy the brain understands. At this point, the information is the same from person to person—it is unbiased. To understand human perception, you must first understand that all information in and of itself is meaningless. Beau Lotto While Dr. Lotto's statement is bold, from the perspective of neuroscience, it is true. Meaning is applied to everything, from the simplest to the most complex sensory input. Our brain's interpretation of the raw sensory information is known as perception. Everything from our senses is filtered through our unique system of past experiences in the world. Usually, the meaning we apply is functional and adequate—if not fully accurate, but sometimes our inaccurate perceptions create real-world difficulty.

Keyword: Vision; Attention
Link ID: 27666 - Posted: 01.27.2021

Daniel Osorio The neuroscientist Michael Land, who has died aged 78 from respiratory disease, was the Marco Polo of the visual sciences. He visited exotic parts of the animal kingdom, and showed that almost every way humans have discovered to bend, reflect, shape and image light with mirrors and lenses is also used by some creature’s eye. His research revealed the many different ways in which animals see their own versions of reality, often to find members of the opposite sex. His 1976 discovery that prawns focus light not by lenses, but with a structure of mirror-lined boxes, helped lead to the discovery of a method to focus X-rays, and in the 1990s he developed a simple device to track humans’ gaze as they move their eyes while doing everyday tasks. Land’s PhD thesis at University College London in the early 1960s, on how scallops evade the attacks of predatory starfish, turned out to be a serendipitous choice. He was supposed to investigate what passes for the brain of this shellfish, but found its eyes far more interesting. Scallops have many pinhead-sized eyes, just inside the lip of the shell. Rather than focusing light with a lens as people do, they use a concave mirror in the manner of a Newtonian telescope. Moving from UCL, with his first wife, Judith (nee Drinkwater), to the University of California, Berkeley, in 1968, he turned his attention to jumping spiders. These arachnids do not build webs but are visual hunters. Each of their four pairs of eyes has a different task, and Land showed how the most acute of these eyes moves to detect prey and mates. © 2021 Guardian News & Media Limited

Keyword: Vision; Evolution
Link ID: 27651 - Posted: 01.20.2021

By Elizabeth Preston When Jessica Yorzinski chased great-tailed grackles across a field, it wasn’t a contest to see who blinked first. But she did want the birds to blink. Dr. Yorzinski had outfitted the grackles, which look a bit like crows but are in another family of birds, with head-mounted cameras pointing back at their faces. Like other birds, grackles blink sideways, flicking a semitransparent membrane across the eye. Recordings showed that the birds spent less time blinking during the riskiest parts of a flight. The finding was published Wednesday in Biology Letters. Dr. Yorzinski, a sensory ecologist at Texas A&M University, had been wondering how animals balance their need to blink with their need to get visual information about their environments. Humans, she said, “blink quite often, but when we do so we lose access to the world around us. It got me thinking about what might be happening in other species.” She worked with a company that builds eye-tracking equipment to make a custom bird-size headpiece. Because a bird’s eyes are on the sides of its head, the contraption held one video camera pointed at the left eye and one at the right, making the bird resemble a sports fan in a beer helmet. The headpiece was connected to a backpack holding a battery and transmitter. Dr. Yorzinski captured 10 wild great-tailed grackles, which are common in Texas, to wear this get-up. She used only male birds, which are big enough to carry the equipment without trouble. Each bird wore the camera helmet and backpack while Dr. Yorzinski encouraged it to fly by chasing it across an outdoor enclosure. © 2020 The New York Times Company

Keyword: Vision; Evolution
Link ID: 27636 - Posted: 12.22.2020

By Kelly Servick Do old and damaged cells remember what it was like to be young? That’s the suggestion of new study, in which scientists reprogrammed neurons in mouse eyes to make them more resistant to damage and able to regrow after injury—like the cells of younger mice. The study suggests that hallmarks of aging, and possibly the keys to reversing it, lie in the epigenome, the proteins and other compounds that decorate DNA and influence what genes are turned on or off. The idea that aging cells hold a memory of their young epigenome “is very provocative,” says Maximina Yun, a regenerative biologist at the Dresden University of Technology who was not involved in the work. The new study “supports that [idea], but by no means proves it,” she adds. If researchers can replicate these results in other animals and explain their mechanism, she says, the work could lead to treatments in humans for age-related disease in the eye and beyond. Epigenetic factors influence our metabolism, our susceptibility to various diseases, and even the way emotional trauma is passed through generations. Molecular biologist David Sinclair of Harvard Medical School, who has long been on the hunt for antiaging strategies, has also looked for signs of aging in the epigenome. “The big question was, is there a reset button?” he says. “Would cells know how to become younger and healthier?” In the new study, Sinclair and his collaborators aimed to rejuvenate cells by inserting genes that encode “reprogramming factors,” which regulate gene expression—the reading of DNA to make proteins. The team chose three of the four factors scientists have used for more than 10 years to turn adult cells into induced pluripotent stem cells, which resemble the cells of an early embryo. (Exposing animals to all four factors can cause tumors.) © 2020 American Association for the Advancement of Science.

Keyword: Vision
Link ID: 27608 - Posted: 12.05.2020

Researchers at the National Eye Institute (NEI) have decoded brain maps of human color perception. The findings, published today in Current Biology, open a window into how color processing is organized in the brain, and how the brain recognizes and groups colors in the environment. The study may have implications for the development of machine-brain interfaces for visual prosthetics. NEI is part of the National Institutes of Health. “This is one of the first studies to determine what color a person is seeing based on direct measurements of brain activity,” said Bevil Conway, Ph.D., chief of NEI’s Unit on Sensation, Cognition and Action, who led the study. “The approach lets us get at fundamental questions of how we perceive, categorize, and understand color.” The brain uses light signals detected by the retina’s cone photoreceptors as the building blocks for color perception. Three types of cone photoreceptors detect light over a range of wavelengths. The brain mixes and categorizes these signals to perceive color in a process that is not well understood. To examine this process, Isabelle Rosenthal, Katherine Hermann, and Shridhar Singh, post-baccalaureate fellows in Conway’s lab and co-first authors on the study, used magnetoencephalography or “MEG,” a 50-year-old technology that noninvasively records the tiny magnetic fields that accompany brain activity. The technique provides a direct measurement of brain cell activity using an array of sensors around the head. It reveals the millisecond-by-millisecond changes that happen in the brain to enable vision. The researchers recorded patterns of activity as volunteers viewed specially designed color images and reported the colors they saw.

Keyword: Vision; Brain imaging
Link ID: 27588 - Posted: 11.21.2020