Chapter 7. Vision: From Eye to Brain

Follow us on Facebook and Twitter, or subscribe to our mailing list, to receive news updates. Learn more.


Links 1 - 20 of 1341

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

By Jessica Wapner We are living through an inarguably challenging time. The U.S. has been facing its highest daily COVID-19 case counts yet. Uncertainty and division continue to dog the aftermath of the presidential election. And we are heading into a long, cold winter, when socializing outdoors will be less of an option. We are a nation and a world under stress. But Andrew Huberman, a neuroscientist at Stanford University who studies the visual system, sees matters a bit differently. Stress, he says, is not just about the content of what we are reading or the images we are seeing. It is about how our eyes and breathing change in response to the world and the cascades of events that follow. And both of these bodily processes also offer us easy and accessible releases from stress. Huberman’s assertions are based on both established and emerging science. He has spent the past 20 years unraveling the inner workings of the visual system. In 2018, for example, his lab reported its discovery of brain pathways connected with fear and paralysis that respond specifically to visual threats. And a small but growing body of research makes the case that altering our breathing can alter our brain. In 2017 Mark Krasnow of Stanford University, Jack Feldman of the University of California, Los Angeles, and their colleagues identified a tight link between neurons responsible for controlling breathing and the region of the brain responsible for arousal and panic. This growing understanding of how vision and breathing directly affect the brain—rather than the more nebulous categories of the mind and feelings—can come in handy as we continue to face mounting challenges around the globe, across the U.S. and in our own lives. Scientific American spoke with Huberman about how it all works. © 2020 Scientific American

Keyword: Stress; Vision
Link ID: 27584 - Posted: 11.18.2020

By Elizabeth Pennisi When Ian Ausprey outfitted dozens of birds with photosensor-containing backpacks, the University of Florida graduate student was hoping to learn how light affected their behavior. The unusual study, which tracked 15 species in Peru’s cloud forest, has now found that eye size can help predict where birds breed and feed—the bigger the eye, the smaller the prey or the darker the environment. The study also suggests birds with big eyes are especially at risk as humans convert forests into farmland. The study reveals a “fascinating new area of sensory biology,” says Richard Prum, an evolutionary biologist at Yale University who was not involved in the new work. It also shows the size of a bird’s eye says a lot about its owner, adds Matthew Walsh, an evolutionary ecologist at the University of Texas, Arlington, also not involved with the work. Light matters—not just for plants, but also for animals. Large eyes have long been associated with the need to see in dim conditions, but very little research has looked in depth at light’s impact on behavior. Recently, scientists have shown that the relative size of frogs’ eyes corresponds to where they live, hunt, and breed. And several studies published in the past 3 years suggest the eyes of killifish and water fleas vary in size depending on the presence of predators. With no predators, even slightly larger eyes offer a potential survival advantage. To find out how eye size might matter for birds, Ausprey and his adviser, Scott Robinson, an ecologist at the Florida Museum of Natural History, turned to the 240 species they had identified in one of Peru’s many cloud forests. The study area included a range of habitats—dense stands of trees, farms with fencerows, shrubby areas, and open ground. Because light can vary considerably by height—for example, in the tropics, the forest floor can have just 1% of the light at the tops of the trees—they included species living from the ground to the treetops. © 2020 American Association for the Advancement of Science.

Keyword: Vision; Evolution
Link ID: 27554 - Posted: 10.28.2020

By Lisa Sanders, M.D. The 61-year-old woman put on her reading glasses to try to decipher the tiny black squiggles on the back of the package of instant pudding. Was it two cups of milk? Or three? The glasses didn’t seem to help. The fuzzy, faded marks refused to become letters. The right side of her head throbbed — as it had for weeks. The constant aggravation of the headache made everything harder, and it certainly wasn’t helping her read this label. She rubbed her forehead, then brought her hand down to cover her right eye. The box disappeared into darkness. She could see only the upper-left corner of the instructions. Everything else was black. She quickly moved her hand to cover her left eye. The tiny letters sprang into focus. She moved back to the right: blackness. Over to the left: light and letters. That scared her. For the past few months, she’d had one of the worst headaches she had ever experienced in her lifetime of headaches. One that wouldn’t go away no matter how much ibuprofen she took. One that persisted through all the different medications she was given for her migraines. Was this terrible headache now affecting her vision? The neurologists she saw over the years always asked her about visual changes. She’d never had them, until now. “Should I take you to the hospital?” her husband asked anxiously when she told him about her nearly sightless left eye. “This could be serious.” She thought for a moment. No, tomorrow was Monday; her neurologist’s office would be open, and the doctor would see her right away. She was always reliable that way. The patient had bad headaches for most of her adult life. They were always on the right side. They were always throbbing. They could last for days, or weeks, or sometimes months. Loud noises were always bothersome. With really bad headaches, her eye would water and her nose would run, just on that side. Bending over was agony. For the past few weeks, her headache had been so severe that if she dropped something on the floor, she had to leave it there. When she bent down, the pounding was excruciating. © 2020 The New York Times Company

Keyword: Pain & Touch; Vision
Link ID: 27553 - Posted: 10.28.2020

By Macarena Carrizosa, Sophie Bushwick A new system called PiVR creates working artificial environments for small animals such as zebra fish larvae and fruit flies. Developers say the system’s affordability could help expand research into animal behavior. © 2020 Scientific American

Keyword: Development of the Brain; Vision
Link ID: 27505 - Posted: 10.07.2020

Neuroskeptic Why do particular brain areas tend to adopt particular roles? Is the brain "wired" by genetics to organize itself in a certain way, or does brain organization emerge from experience? One part of the brain has been the focus of a great deal of nature-vs-nurture debate. It's called the fusiform face area (FFA) and, as the name suggests, it seems to be most active during perception of faces. It's broadly accepted that the FFA responds most strongly to faces in most people, but there's controversy over why this is. Is the FFA somehow innately devoted to faces, or does its face specialization arise through experience? In the latest contribution to this debate, a new study argues that the FFA doesn't need any kind of visual experience to be face selective. The researchers, N. Apurva Ratan Murty et al., show that the FFA activates in response to touching faces, even in people who were born blind and have never seen a face. Murty et al. designed an experiment in which participants — 15 sighted and 15 congenitally blind people — could touch objects while their brain activity was recorded with fMRI. A 3D printer was used to create models of faces and other objects, and the participants could explore these with their hands, thanks to a rotating turntable. The key result was that touching the faces produced a similar pattern of activity in both the blind and sighted people, and this activity was also similar to when sighted people viewed faces visually: In a follow-up experiment with n=7 of the congenitally blind participants, Murty et al. found that the same face-selective areas in these individuals also responded to "face-related" sounds, such as laughing or chewing sounds, more than other sounds. (This replicates earlier work.) © 2020 Kalmbach Media Co.

Keyword: Attention; Vision
Link ID: 27459 - Posted: 09.07.2020

By Moises Velasquez-Manoff Jack Gallant never set out to create a mind-reading machine. His focus was more prosaic. A computational neuroscientist at the University of California, Berkeley, Dr. Gallant worked for years to improve our understanding of how brains encode information — what regions become active, for example, when a person sees a plane or an apple or a dog — and how that activity represents the object being viewed. By the late 2000s, scientists could determine what kind of thing a person might be looking at from the way the brain lit up — a human face, say, or a cat. But Dr. Gallant and his colleagues went further. They figured out how to use machine learning to decipher not just the class of thing, but which exact image a subject was viewing. (Which photo of a cat, out of three options, for instance.) One day, Dr. Gallant and his postdocs got to talking. In the same way that you can turn a speaker into a microphone by hooking it up backward, they wondered if they could reverse engineer the algorithm they’d developed so they could visualize, solely from brain activity, what a person was seeing. The first phase of the project was to train the AI. For hours, Dr. Gallant and his colleagues showed volunteers in fMRI machines movie clips. By matching patterns of brain activation prompted by the moving images, the AI built a model of how the volunteers’ visual cortex, which parses information from the eyes, worked. Then came the next phase: translation. As they showed the volunteers movie clips, they asked the model what, given everything it now knew about their brains, it thought they might be looking at. The experiment focused just on a subsection of the visual cortex. It didn’t capture what was happening elsewhere in the brain — how a person might feel about what she was seeing, for example, or what she might be fantasizing about as she watched. The endeavor was, in Dr. Gallant’s words, a primitive proof of concept. And yet the results, published in 2011, are remarkable. The reconstructed images move with a dreamlike fluidity. In their imperfection, they evoke expressionist art. (And a few reconstructed images seem downright wrong.) But where they succeed, they represent an astonishing achievement: a machine translating patterns of brain activity into a moving image understandable by other people — a machine that can read the brain. © 2020 The New York Times Company

Keyword: Vision; Brain imaging
Link ID: 27448 - Posted: 09.02.2020

Georgina Ferry The lightning flick of the tongue that secures a frog its next meal depends on a rapid response to a small black object moving through its field of view. During the 1950s the British neuroscientist Horace Barlow established that neurons in the frog’s retina were tuned to produce just such a response, not only detecting but also predicting the future position of a passing fly. This discovery raised the curtain on decades of research by Barlow and others, establishing that individual neurons of the billions that make up the visual system contribute to the efficient processing of movement, colour, position and orientation of objects in the visual world. Barlow, who has died aged 98, combined three approaches to the question of how the brain enables us to see. He looked at how people perceive, for example measuring the smallest and faintest spot of light they could reliably detect; he studied the responses of single neurons in the retina and brain to different visual stimuli; and he developed theories to account for the relationship between what neurons are doing and the corresponding visual experience. All his work started from the principle – apparently obvious but not often stated – that a deep, mathematical understanding of what is involved in the psychological process of seeing is an essential basis for exploring how the physiological elements of the visual system serve that end. In a vivid analogy, he wrote: “A wing would be a most mystifying structure if one did not know that birds flew.” He is best known for demanding answers to the question of how such a complex system could work most efficiently. He was influenced by early computer scientists, and was a pioneer in seeing visual signals as information to be processed. His concept of “efficient coding” predicted that of all the information presented to the eye, the brain would transmit the minimum necessary, wasting no energy on redundant signals. © 2020 Guardian News & Media Limite

Keyword: Vision
Link ID: 27433 - Posted: 08.26.2020

By Katherine J. Wu Dr. Arianne Pontes Oriá stands firm: She does not make animals cry for a living. Technically, only humans can cry, or weep in response to an emotional state, said Dr. Oriá, a veterinarian at the Federal University of Bahia in Brazil. For humans, crying is a way to physically manifest feelings, which are difficult to study and confirm in other creatures. But Dr. Oriá does collect animal tears — the liquid that keeps eyes clean and nourished. In vertebrates, or animals with backbones, tears are vital for vision, Dr. Oriá said. And yet, these captivating fluids have been paid little to no attention, except in a select few mammals. “A lot of vision, we’re not aware of until it’s a problem,” said Sebastian Echeverri, a biologist who studies animal vision but doesn’t work with Dr. Oriá’s team. “We notice when tears are missing.” That’s a bit of a shame, Dr. Oriá said. Because whether it hails from dogs, parrots or tortoises, the stuff that seeps out of animals’ eyes is simply “fascinating,” she said. As she and her colleagues have reported in a series of recent papers, including one published on Thursday in the journal Frontiers in Veterinary Science, tears can be great equalizers: Across several branches of the tree of life, vertebrates seem to swaddle their eyes with fluid in much the same way. But to help them cope with the challenges of various environments, evolution has tinkered with the tears of the world’s creatures in ways that scientists are only beginning to explore. Research like Dr. Oriá’s could offer a glimpse into the myriad paths that eyes have taken to maximize their health and the well-being of the organisms that use them. © 2020 The New York Times Company

Keyword: Vision
Link ID: 27418 - Posted: 08.15.2020