Asif Ghazanfar Picture someone washing their hands. The water running down the drain is a deep red. How you interpret this scene depends on its setting, and your history. If the person is in a gas station bathroom, and you just saw the latest true-crime series, these are the ablutions of a serial killer. If the person is at a kitchen sink, then perhaps they cut themselves while preparing a meal. If the person is in an art studio, you might find resonance with the struggle to get paint off your hands. If you are naive to crime story tropes, cooking or painting, you would have a different interpretation. If you are present, watching someone wash deep red off their hands into a sink, your response depends on even more variables. How we act in the world is also specific to our species; we all live in an ‘umwelt’, or self-centred world, in the words of the philosopher-biologist Jakob von Uexküll (1864-1944). It’s not as simple as just taking in all the sensory information and then making a decision. First, our particular eyes, ears, nose, tongue and skin already filter what we can see, hear, smell, taste and feel. We don’t take in everything. We don’t see ultraviolet light like a bird, we don’t hear infrasound like elephants and baleen whales do. Second, the size and shape of our bodies determine what possible actions we can take. Parkour athletes – those who run, vault, climb and jump in complex urban environments – are remarkable in their skills and daring, but sustain injuries that a cat doing the exact same thing would not. Every animal comes with a unique bag of tricks to exploit their environment; these tricks are also limitations under different conditions. Third, the world, our environment, changes. Seasons change, what animals can eat therefore also changes. If it’s the rainy season, grass will be abundant. The amount of grass determines who is around to eat it and therefore who is around to eat the grass-eaters. Ultimately, the challenge for each of us animals is how to act in this unstable world that we do not fully apprehend with our senses and our body’s limited degrees of freedom. There is a fourth constraint, one that isn’t typically recognised. Most of the time, our intuition tells us that what we are seeing (or hearing or feeling) is an accurate representation of what is out there, and that anyone else would see (or hear or feel) it the same way. But we all know that’s not true and yet are continually surprised by it. It is even more fundamental than that: you know that seemingly basic sensory information that we are able to take in with our eyes and ears? It’s inaccurate. How we perceive elementary colours, ‘red’ for example, always depends on the amount of light, surrounding colours and other factors. In low lighting, the deep red washing down the sink might appear black. A yellow sink will make it look more orange; a blue sink may make it look violet. © Aeon Media Group Ltd. 2012-2025.

Keyword: Vision; Attention
Link ID: 29961 - Posted: 10.08.2025

By Kenneth Chang After decades of brain research, scientists still aren’t sure whether most people see the same way, more or less — especially with colors. Is what I call red also red for you? Or could my red be your blue? Or maybe neon pink? If it were possible to project what I see directly into your mind, would the view be the same, or would it instead resemble a crazy-hued Andy Warhol painting? “That’s an age-old question, isn’t it?” said Andreas Bartels, a professor of visual neuroscience at the University of Tübingen in Germany. But scientists do have a good understanding of which parts of the brain handle vision. They have even figured out where various vision-processing tasks are performed, like recognizing what is moving, identifying colors and adjusting to different lighting conditions. Amazingly, it is even possible to deduce what you’re seeing by looking at an M.R.I. scan showing which parts of your brain are lighting up. “That comes out of the world of science fiction, or one would think, right?” Dr. Bartels said. “It’s amazing that this is possible, but this always has happened in individual brains.” That is, researchers pulled off this sleight of science with individuals. They would first show a subject lying in the M.R.I. machine a series of images, mapping out how that person’s brain responded. After that initial training, the researchers could randomly show one of the images and, based on just the brain activity, make a good guess at what the image was. In new research, Dr. Bartels and Michael Bannert, a postdoctoral researcher in Dr. Bartels’ laboratory, used that technique to provide a partial answer to the question of whether most of us have a shared sense of colors. They put 15 people, all with standard color vision, in an M.R.I. machine. The volunteers viewed expanding concentric rings that were red, green or yellow. © 2025 The New York Times Company

Keyword: Vision; Consciousness
Link ID: 29925 - Posted: 09.10.2025

By Nora Bradford During her training in anthropology, Dorsa Amir, now at Duke University, became fascinated with the Müller-Lyer illusion. The illusion is simple: one long horizontal line is flanked by arrowheads on either side. Whether the arrowheads are pointing inward or outward dramatically changes the perceived length of the line—people tend to see it as longer when the arrowheads point in and as shorter when they point out. Graphic shows how the Müller-Lyer illusion makes two equal-length lines seem to have different lengths because of arrowlike tips pointing inward or outward. Most intriguingly, psychologists in the 1960s had apparently discovered something remarkable about the illusion: only European and American urbanites fell for the trick. The illusion worked less well, or didn’t work at all, on groups surveyed across Africa and the Philippines. The idea that this simple illusion supposedly only worked in some cultures but not others compelled Amir, who now studies how culture shapes the mind. “I always thought it was so cool, right, that this basic thing that you think is just so obvious is the type of thing that might vary across cultures,” Amir says. But this foundational research—and the hypothesis that arose to explain it, called the “carpentered-world” hypothesis—is now widely disputed, including by Amir herself. This has left researchers like her questioning what we can truly know about how culture shapes how we see the world. When researcher Marshall Segall and his colleagues conducted the cross-cultural experiment on the Müller-Lyer illusion in the 1960s, they came up with a hypothesis to explain the strange results: difference in building styles. The researchers theorized that the prevalence of carpentry features, such as rectangular spaces and right angles, trained the visual systems of people in more wealthy, industrialized cultures to perceive these angles in a way that make them more prone to the Müller-Lyer illusion. © 2025 SCIENTIFIC AMERICAN

Keyword: Vision; Attention
Link ID: 29899 - Posted: 08.23.2025

By Tim Vernimmen Mexican tetras are a most peculiar fish species. They occur in many rivers and lakes across Mexico and southern Texas, where they look perfectly ordinary. But unlike most other fishes, tetras also live in caves. And there, in the absence of light, they look dramatically different: They’re very pale and, remarkably, they lack eyes. Time and again, whenever a population was swept into a cave and survived long enough for natural selection to have its way, the eyes disappeared. “But it’s not that everything has been lost in cavefish,” says geneticist Jaya Krishnan of the Oklahoma Medical Research Foundation. “Many enhancements have also happened.” Though the demise of their eyes continues to fascinate biologists, in recent years attention has shifted to other intriguing aspects of cavefish biology. It has become increasingly clear that they haven’t just lost sight, but also gained many adaptations that help them to thrive in their cave environment, including some that may hold clues to treatments for obesity and diabetes in people. It has long been debated why the eyes were lost. Some biologists used to argue that they just withered away over generations because cave-dwelling animals with faulty eyes experienced no disadvantage. But another explanation is now considered more likely, says evolutionary physiologist Nicolas Rohner of the University of Münster in Germany: “Eyes are very expensive in terms of resources and energy. Most people now agree that there must be some advantage to losing them, if you don’t need them.” Scientists have observed that mutations in different genes involved in eye formation have led to eye loss. In other words, says Krishnan, “different cavefish populations have lost their eyes in different ways.”

Keyword: Evolution; Vision
Link ID: 29885 - Posted: 08.13.2025

By Tina Hesman Saey A snail may hold the key to restoring vision for people with some eye diseases. Golden apple snails (Pomacea canaliculata) are freshwater snails from South America. Alice Accorsi became familiar with the species as a graduate student in Italy. “You could literally buy them in a pet store as snails that clean the bottom of the fish tanks,” she recalls. Turns out, the snails are among the most invasive species in the world. And that got Accorsi thinking: Why are they so resilient and able to thrive in new environments? She began studying the snails’ immune systems and has now found they are not the only parts of the animals able to bounce back from adversity. These snails can completely regrow a functional eye within months of having one amputated, Accorsi and colleagues report August 6 in Nature Communications. Side-by-side images of snail eyes. On the left is a normal, intact snail eye. On the right is an eye that has regrown two months after it was surgically removed. The eyes look similar. They are both round with a black spot in the middle. A snail’s eye was surgically removed, but it grew a new one. Two months after amputation the new eye (right) looks much like the uninjured one (left).Alice Accorsi Scientists have known for centuries that some snails can regrow their heads, and research has revealed other animals can regenerate bodies, tails or limbs. But this finding is exciting because apple snails have camera-like eyes similar to those of humans. Understanding how the snails re-create or repair their eyes might lead to therapies to heal people’s eye injuries or reverse diseases such as macular degeneration. Accorsi, now a developmental biologist at the University of California, Davis, used the molecular scissors called CRISPR/Cas9 to genetically disable certain key genes involved in eye development and established lineages of snails carrying those mutations. © Society for Science & the Public 2000–2025.

Keyword: Vision; Regeneration
Link ID: 29879 - Posted: 08.06.2025

Emily Kwong A grayscale ballerina who appears to be moving. A human who can fit in a doll box. A black-and-white prism which appear to change shape when viewed from three different directions. Those are the top winners of the 2024 Best Illusion of the Year Contest, open to illusion makers around the world. The contest was co-created by neuroscientist and science writer Susana Martinez-Conde. After 20 years, Martinez-Conde is still amazed that novel illusions keep coming in — submitted by artists, magicians, vision scientists and illusion makers all over the world. "Illusions are fundamental to the way that we perceive the world — the way that, frankly, we exist as human beings. Illusions are a feature and not a bug," she told All illusions are perceptual experiences that do not match physical reality. Aristotle was one of the first to document an illusion in nature, the so-called "waterfall illusion," or motion aftereffect. When someone watches a moving stimulus, such as a river, a nearby stationary object, like a rock, may also appear to move. Other famous illusions include "Rotating Snakes," which Martinez-Conde has studied as part of her research into peripheral drift. As a scientist, Martinez-Conde sees as illusions as an opportunity to study how the human brain constructs perceptions of the world. "We can analyze the neurons and the brain circuits that support neural activity that matches perception, and those could be part of the neural basis of consciousness." Voting for the 2025 Best Illusion of the Year will take place next year. The online contest is run by the non-profit Neural Correlate Society. © 2025 npr

Keyword: Vision
Link ID: 29871 - Posted: 08.02.2025

By Katrina Miller Take a look at this video of a waiting room. Do you see anything strange? Perhaps you saw the rug disappear, or the couch pillows transform, or a few ceiling panels evaporate. Or maybe you didn’t. In fact, dozens of objects change in this video, which won second place in the Best Illusion of the Year Contest in 2021. Voting for the latest version of the contest opened on Monday. Illusions “are the phenomena in which the physical reality is divorced from perception,” said Stephen Macknik, a neuroscientist at SUNY Downstate Health Sciences University in Brooklyn. He runs the contest with his colleague and spouse, Susana Martinez-Conde. By studying the disconnect between perception and reality, scientists can better understand which brain regions and processes help us interpret the world around us. The illusion above highlights change blindness, the brain’s failure to notice shifts in the environment, especially when they occur gradually. To some extent, all sensory experience is illusory, Dr. Martinez-Conde asserts. “We are always constructing a simulation of reality,” she said. “We don’t have direct access to that reality. We live inside the simulation that we create.” She and Dr. Macknik have run the illusion contest since 2005. What began as a public outreach event at an academic conference has since blossomed into an annual competition open to anyone in the world. They initially worried that people would run out of illusions to submit. “But that actually never happened,” Dr. Martinez-Conde said. “What ended up happening instead is that people started developing illusions, actually, with an eye to competing in the contest.” © 2025 The New York Times Company

Keyword: Vision; Attention
Link ID: 29843 - Posted: 06.28.2025

By Nala Rogers Coffer illusion What do you see when you stare at this grid of line segments: a series of rectangles, or a series of circles? The way you perceive this optical illusion, known as the Coffer illusion, may tie back to the visual environment that surrounds you, a recent preprint suggests.Anthony Norcia/Smith-Kettlewell Eye Research Institute Himba people from rural Namibia can see right through optical illusions that trick people from the United States and United Kingdom. Even when there’s no “right” or “wrong” way to interpret an image, what Himba people see is often vastly different from what people see in industrialized societies, a new preprint suggests. That could mean people’s vision is fundamentally shaped by the environments they’re raised in—an old but controversial idea that runs counter to the way human perception is often studied. For example, when presented with a grid of line segments that can be seen as either rectangles or circles—an optical illusion known as the Coffer illusion—people from the U.S. and U.K. almost always see rectangles first, and they often struggle to see circles. The researchers suspect this is because they are surrounded by rectangular architecture, an idea known as the carpentered world hypothesis. In contrast, the traditional villages of Himba people are composed of round huts surrounding a circular livestock corral. People from these villages almost always see circles first, and about half don’t see rectangles even when prompted. “I’m surprised that you can’t see the round ones,” says Uapwanawa Muhenije, a Himba woman from a village in northern Namibia, speaking through an interpreter over a Zoom interview. “I wonder how you can’t see them.” Muhenije didn’t participate in the research because her village is less remote than those in the study, and it includes rectangular as well as circular buildings. She sees both shapes in the Coffer illusion easily. Although the study found dramatic differences in how people see four illusions, “the one experiment that’s going to overwhelm people is this Coffer,” says Jules Davidoff, a psychologist at the University of London who was not involved in the study. “There are other striking cultural differences in perception, but the one that they’ve produced here is a real humdinger.” The findings were published as a preprint on the PsyArXiv in February and updated this week. © 2025 American Association for the Advancement of Science.

Keyword: Vision; Development of the Brain
Link ID: 29838 - Posted: 06.21.2025

Anna Bawden Health and social affairs correspondent Weight loss drugs could at least double the risk of diabetic patients developing age-related macular degeneration, a large-scale study has found. Originally developed for diabetes patients, glucagon-like peptide-1 receptor agonist (GLP-1 RA) medicines have transformed how obesity is treated and there is growing evidence of wider health benefits. They help reduce blood sugar levels, slow digestion and reduce appetite. But a study by Canadian scientists published in Jama Ophthalmology has found that after six months of use GLP-1 RAs are associated with double the risk of older people with diabetes developing neovascular age-related macular degeneration compared with similar patients not taking the drugs. Academics at the University of Toronto examined medical data for more than 1 million Ontario residents with a diagnosis of diabetes and identified 46,334 patients with an average age of 66 who were prescribed GLP-1 RAs. Nearly all (97.5%) were taking semaglutide, while 2.5% were on lixisenatide. The study did not exclude any specific brand of drugs, but since Wegovy was only approved in Canada in November 2021, primarily for weight loss, it is likely the bulk of semaglutide users in the study were taking Ozempic, which is prescribed for diabetes. Each patient on semaglutide or lixisenatide was matched with two patients who also had diabetes but were not taking the drugs, who shared similar characteristics such as age, gender and health conditions. The researchers then compared how many patients developed neovascular age-related macular degeneration over three years. © 2025 Guardian News & Media Limited

Keyword: Vision; Obesity
Link ID: 29822 - Posted: 06.07.2025

Ian Sample Science editor Researchers have given people a taste of superhuman vision after creating contact lenses that allow them to see infrared light, a band of the electromagnetic spectrum that is invisible to the naked eye. Unlike night vision goggles, the contact lenses need no power source, and because they are transparent, wearers can see infrared and all the normal visible colours of light at the same time. Prof Tian Xue, a neuroscientist at the University of Science and Technology of China, said the work paved the way for a range of contact lenses, glasses and other wearable devices that give people “super-vision”. The technology could also help people with colour blindness, he added. The lenses are the latest breakthrough driven by the team’s desire to extend human vision beyond its natural, narrow range. The wavelengths of light that humans can see make up less than one hundredth of a per cent of the electromagnetic spectrum. Dr Yuqian Ma, a researcher on the project, said: “Over half of the solar radiation energy, existing as infrared light, remains imperceptible to humans.” The rainbow of colours visible to humans spans wavelengths from 400 to 700 nanometres (a nanometre is a millionth of a millimetre). But many other animals sense the world differently. Birds, bees, reindeer and mice can see ultraviolet light, wavelengths too short for humans to perceive. Meanwhile, some snakes and vampire bats have organs that detect far-infrared, or thermal radiation, which helps them hunt for prey. To extend humans’ range of vision and enhance our experience of the world, the scientists developed what are called upconversion nanoparticles. The particles absorb infrared light and re-emit it as visible light. For the study, the scientists chose particles that absorb near-infrared light, comprising wavelengths that are just too long for humans to perceive, and converted it into visible red, green or blue light. © 2025 Guardian News & Media Limited

Keyword: Vision; Robotics
Link ID: 29804 - Posted: 05.24.2025

By Jacek Krywko edited by Allison Parshall There are only so many colors that the typical human eye can see; estimates put the number just below 10 million. But now, for the first time, scientists say they’ve broken out of that familiar spectrum and into a new world of color. In a paper published on Friday in Science Advances, researchers detail how they used a precise laser setup to stimulate the retinas of five participants, making them the first humans to see a color beyond our visual range: an impossibly saturated bluish green. Our retinas contain three types of cone cells, photoreceptors that detect the wavelengths of light. S cones pick up relatively short wavelengths, which we see as blue. M cones react to medium wavelengths, which we see as green. And L cones are triggered by long wavelengths, which we see as red. These red, green and blue signals travel to the brain, where they’re combined into the full-color vision we experience. But these three cone types handle overlapping ranges of light: the light that activates M cones will also activate either S cones or L cones. “There’s no light in the world that can activate only the M cone cells because, if they are being activated, for sure one or both other types get activated as well,” says Ren Ng, a professor of electrical engineering and computer science at the University of California, Berkeley. Ng and his research team wanted to try getting around that fundamental limitation, so they developed a technicolor technique they call “Oz.” “The name comes from the Wizard of Oz, where there’s a journey to the Emerald City, where things look the most dazzling green you’ve ever seen,” Ng explains. On their own expedition, the researchers used lasers to precisely deliver tiny doses of light to select cone cells in the human eye. First, they mapped a portion of the retina to identify each cone cell as either an S, M or L cone. Then, using the laser, they delivered light only to M cone cells. © 2025 SCIENTIFIC AMERICAN,

Keyword: Vision
Link ID: 29752 - Posted: 04.19.2025

By Catherine Offord Scientists say they have found a long–sought-after population of stem cells in the retina of human fetuses that could be used to develop therapies for one of the leading causes of blindness. The use of fetal tissue, a source of ethical debate and controversy in some countries, likely wouldn’t be necessary for an eventual therapy: Transplanting similar human cells generated in the lab into the eyes of mice with retinal disease protected the animals’ vision, the team reported this week in Science Translational Medicine. “I see this as potentially a very interesting advancement of this field, where we are really in need of a regenerative treatment for retinal diseases,” says Anders Kvanta, a retinal specialist at the Karolinska Institute who was not involved in the work. He and others note that more evidence is needed to show the therapeutic usefulness of the newly described cells. The retina, a layer of light-sensing tissue at the back of the eye, can degenerate with age or because of an inherited condition such as retinitis pigmentosa, a rare disease that causes gradual breakdown of retinal cells. Hundreds of millions of people worldwide are affected by retinal degeneration, and many suffer vision loss or blindness as a result. Most forms can’t be treated. Scientists have long seen a potential solution in stem cells, which can regenerate and repair injured tissue. Several early-stage clinical trials are already evaluating the safety and efficacy of transplanting stem cells derived from cell lines established from human embryos, for example, or adult human cells that have been reprogrammed to a stem-like state. Other approaches include transplanting so-called retinal progenitor cells (RPCs)—immature cells that give rise to photoreceptors and other sorts of retinal cells—from aborted human fetuses. Some researchers have argued that another type of cell, sometimes referred to as retinal stem cells (RSCs), could also treat retinal degeneration. These cells’ long lifespans and ability to undergo numerous cells divisions could make them better candidates to regenerate damaged tissue than RPCs. RSCs have been found in the eyes of zebrafish and some other vertebrates, but evidence for their existence in mammals has been controversial. Reports announcing their discovery in adult mice in the early 2000s were later discounted.

Keyword: Vision; Stem Cells
Link ID: 29719 - Posted: 03.27.2025

By Bill Newsome What paper changed your life?: Activity of superior colliculus in behaving monkey. II. Effect of attention on neuronal responses. M.E. Goldberg and R.H. Wurtz Journal of Neurophysiology (1972) In 1972, Mickey Goldberg and Bob Wurtz published a quadrilogy of papers in the Journal of Neurophysiology—yes, you could do that in those days—on the physiological activity of single superior colliculus neurons in alert monkeys trained to perform simple eye fixation and eye movement tasks. The experiments revealed a rich variety of sensory and motor signals: Some neurons fired at the onset of a visual stimulus; others showed bursts of activity immediately prior to the eye movement. The researchers found that visually evoked activity differed depending on whether the monkey ultimately used the stimulus as a target for a saccadic eye movement. The neural response to the visual stimulus was stronger and continued until the time of the eye movement, forming a sort of temporal bridge between stimulus and evoked behavioral response. This bridge was alluring because it hinted at intermediate processes—perhaps the stuff of cognition—between sensory input and behavioral output. But it was also mysterious, in that no models existed for how such activity might be initiated and maintained until the behavioral response. These papers were revelatory to me because they pointed toward a mechanistic physiological understanding of such complex cognitive functions as attention. I was particularly fascinated by the second paper in the series of four, which dug into that mystery. Goldberg and Wurtz explicitly made a suggestive leap from physiology to psychology: “[Because] we can infer that the monkey attended to the stimulus when he made a saccade to it, the enhancement can be viewed as a neurophysiological event related to the psychological phenomenon of attention.” They also issued appropriate caveats, noting that “the unitary behavioral concept” of attention “may not have a single physiological mechanism.” h. © 2025 Simons Foundation

Keyword: Vision; Attention
Link ID: 29679 - Posted: 02.22.2025

By Kristel Tjandra Close your eyes and picture an apple—what do you see? Most people will conjure up a vivid image of the fruit, but for the roughly one in 100 individuals with aphantasia, nothing will appear in the mind’s eye at all. Now, scientists have discovered that in people with this inability to form mental images, visual processing areas of the brain still light up when they try to do so. The study, published today in Current Biology, suggests aphantasia is not caused by a complete deficit in visual processing, as researchers have previously proposed. Visual brain areas are still active when aphantasic people are asked to imagine—but that activity doesn’t translate into conscious experience. The work offers new clues about the neurological differences underlying this little-explored condition. The study authors “take a very strong, mechanistic approach,” says Sarah Shomstein, a vision scientist at George Washington University who was not involved in the study. “It was asking the right questions and using the right methods.” Some scientists suspect aphantasia may be caused by a malfunction in the primary visual cortex, the first area in the brain to process images. “Typically, primary cortex is thought to be the engine of visual perception,” says Joel Pearson, a neuroscientist at the University of New South Wales Sydney who co-led the study. “If you don’t have activity there, you’re not going to have perceptual consciousness.” To see what was going on in this region in aphantasics, the team used functional magnetic resonance imaging to measure the brain activity of 14 people with aphantasia and 18 neurotypical controls as they repeatedly saw two simple patterns, made up of either green vertical lines or red horizontal lines. They then repeated the experiment, this time asking participants to simply imagine the two images.

Keyword: Attention; Vision
Link ID: 29624 - Posted: 01.11.2025

By Ann Gibbons As the parent of any teenager knows, humans need a long time to grow up: We take about twice as long as chimpanzees to reach adulthood. Anthropologists theorize that our long childhood and adolescence allow us to build comparatively bigger brains or learn skills that help us survive and reproduce. Now, a study of an ancient youth’s teeth suggests a slow pattern of growth appeared at least 1.8 million years ago, half a million years earlier than any previous evidence for delayed dental development. Researchers used state-of-the art x-ray imaging methods to count growth lines in the molars of a member of our genus, Homo, who lived 1.77 million years ago in what today is Dmanisi, Georgia. Although the youth developed much faster than children today, its molars grew as slowly as a modern human’s during the first 5 years of life, the researchers report today in Nature. The finding, in a group whose brains are hardly larger than chimpanzees, could provide clues to why humans evolved such long childhoods. “One of the main questions in paleoanthropology is to understand when this pattern of slow development evolves in [our genus] Homo,” says Alessia Nava, a bioarchaeologist at the Sapienza University of Rome who is not part of the study. “Now, we have an important hint.” Others caution that although the teeth of this youngster grew slowly, other individuals, including our direct ancestors, might have developed faster. Researchers have known since the 1930s that humans stay immature longer than other apes. Some posit our ancestors evolved slow growth to allow more time and energy to build bigger brains, or to learn how to adapt to complex social interactions and environments before they had children. To pin down when this slow pattern of growth arose, researchers often turn to teeth, especially permanent molars, because they persist in the fossil record and contain growth lines like tree rings. What’s more, the dental growth rate in humans and other primates correlates with the development of the brain and body.

Keyword: Evolution; Sexual Behavior
Link ID: 29562 - Posted: 11.16.2024

By Elena Renken Small may be mightier than we think when it comes to brains. This is what neuroscientist Marcella Noorman is learning from her neuroscientific research into tiny animals like fruit flies, whose brains hold around 140,000 neurons each, compared to the roughly 86 billion in the human brain. Nautilus Members enjoy an ad-free experience. Log in or Join now . In work published earlier this month in Nature Neuroscience, Noorman and colleagues showed that a small network of cells in the fruit fly brain was capable of completing a highly complex task with impressive accuracy: maintaining a consistent sense of direction. Smaller networks were thought to be capable of only discrete internal mental representations, not continuous ones. These networks can “perform more complex computations than we previously thought,” says Noorman, an associate at the Howard Hughes Medical Institute. The scientists monitored the brains of fruit flies as they walked on tiny rotating foam balls in the dark, and recorded the activity of a network of cells responsible for keeping track of head direction. This kind of brain network is called a ring attractor network, and it is present in both insects and in humans. Ring attractor networks maintain variables like orientation or angular velocity—the rate at which an object rotates—over time as we navigate, integrating new information from the senses and making sure we don’t lose track of the original signal, even when there are no updates. You know which way you’re facing even if you close your eyes and stand still, for example. After finding that this small circuit in fruit fly brains—which contains only about 50 neurons in the core of the network—could accurately represent head direction, Noorman and her colleagues built models to identify the minimum size of a network that could still theoretically perform this task. Smaller networks, they found, required more precise signaling between neurons. But hundreds or thousands of cells weren’t necessary for this basic task. As few as four cells could form a ring attractor, they found. © 2024 NautilusNext Inc.,

Keyword: Development of the Brain; Vision
Link ID: 29560 - Posted: 11.16.2024

By Phil Plait I remember watching the full moon rise one early evening a while back. It was when I still lived in Colorado, and I was standing outside in my yard. I first noticed a glow to the east lighting up the flat horizon in the darkening sky, and within moments the moon was cresting above it, yellow and swollen—like, really swollen As it cleared the horizon, the moon looked huge! It also seemed so close that I could reach out and touch it; it was so “in my face” that I felt I could fall in. I gawped at it for a moment and then smiled. I knew what I was actually seeing: the moon illusion. Anyone who is capable of seeing the moon (or the sun) near the horizon has experienced this effect. The moon looks enormous there, far larger than it does when it’s overhead. I’m an astronomer, and I know the moon is no bigger on the horizon than at the zenith, yet I can’t not see it that way. It’s an overwhelming effect. But it’s not real. Simple measurements of the moon show it’s essentially the same size on the horizon as when it’s overhead. This really is an illusion. It’s been around awhile, too: the illusion is shown in cuneiform on a clay tablet from the ancient Assyrian city Nineveh that has been dated to the seventh century B.C.E. Attempts to explain it are as old as the illusion itself, and most come up short. Aristotle wrote about it, for example, attributing it to the effects of mist. This isn’t correct, obviously; the illusion manifests even in perfectly clear weather. A related idea, still common today, is that Earth’s air acts like a lens, refracting (bending) the light from the moon and magnifying it. But we know that’s not right because the moon is measurably the same size no matter where it is in the sky. Also, examining the physics of that explanation shows that it falls short as well. In fact, while the air near the horizon does indeed act like a lens, its actual effect is to make the sun and moon look squished, like flat ovals, not to simply magnify them. So that can’t be the cause either.

Keyword: Vision; Attention
Link ID: 29522 - Posted: 10.19.2024

By Yasemin Saplakoglu Two years ago, Sarah Shomstein realized she didn’t have a mind’s eye. The vision scientist was sitting in a seminar room, listening to a scientific talk, when the presenter asked the audience to imagine an apple. Shomstein closed her eyes and did so. Then, the presenter asked the crowd to open their eyes and rate how vividly they saw the apple in their mind. Saw the apple? Shomstein was confused. She didn’t actually see an apple. She could think about an apple: its taste, its shape, its color, the way light might hit it. But she didn’t see it. Behind her eyes, “it was completely black,” Shomstein recalled. And yet, “I imagined an apple.” Most of her colleagues reacted differently. They reported actually seeing an apple, some vividly and some faintly, floating like a hologram in front of them. In that moment, Shomstein, who’s spent years researching perception at George Washington University, realized she experienced the world differently than others. She is part of a subset of people — thought to be about 1% to 4% of the general population — who lack mental imagery, a phenomenon known as aphantasia. Though it was described more than 140 years ago, the term “aphantasia” was coined only in 2015. It immediately drew the attention of anyone interested in how the imagination works. That included neuroscientists. So far, they’re finding that aphantasia is not a disorder — it’s a different way of experiencing the world. Early studies have suggested that differences in the connections between brain regions involved in vision, memory and decision-making could explain variations in people’s ability to form mental images. Because many people with aphantasia dream in images and can recognize objects and faces, it seems likely that their minds store visual information — they just can’t access it voluntarily or can’t use it to generate the experience of imagery. That’s just one explanation for aphantasia. In reality, people’s subjective experiences vary dramatically, and it’s possible that different subsets of aphantasics have their own neural explanations. Aphantasia and hyperphantasia, the opposite phenomenon in which people report mental imagery as vivid as reality, are in fact two ends of a spectrum, sandwiching an infinite range of internal experiences between them. © 2024 the Simons Foundation.

Keyword: Attention; Vision
Link ID: 29417 - Posted: 08.02.2024

By Abdullahi Tsanni Time takes its toll on the eyes. Now a funky, Hitchcockian video of 64 eyeballs, all rolling and blinking in different directions, is providing a novel visual of one way in which eyes age. A video display of 64 eyeballs, captured using eye trackers, helped researchers compare the size of younger and older study participants’ pupils under differing light conditions, confirming aging affects our eyes. Lab studies have previously shown that the eye’s pupil size shrinks as people get older, making the pupil less responsive to light. A new study that rigged volunteers up with eye-trackers and GoPro videos and sent them traipsing around a university campus has confirmed what happens in the lab happens in real life, too. While pupils remain sensitive to changing light conditions, pupil size can decrease up to about 0.4 millimeters per decade, researchers report June 19 in Royal Society Open Science. “We see a big age effect,” says Manuel Spitschan, a neuroscientist at Max Planck Institute for Biological Cybernetics in Tubingen, Germany. The change helps explain why it can be increasingly harder for people to see in dim light as they age. Light travels through the dark pupil in the center of the eye to the retina, a layer of cells in the back of the eyes that converts the light into images. The pupil’s size can vary from 2 to 8 millimeters in diameter depending on light conditions, getting smaller in bright light and larger in dim light. “With a small pupil, less light enters the eye,” Spitschan says. © Society for Science & the Public 2000–2024.

Keyword: Vision; Development of the Brain
Link ID: 29375 - Posted: 07.03.2024

By Elie Dolgin The COVID-19 pandemic didn’t just reshape how children learn and see the world. It transformed the shape of their eyeballs. As real-life classrooms and playgrounds gave way to virtual meetings and digital devices, the time that children spent focusing on screens and other nearby objects surged — and the time they spent outdoors dropped precipitously. This shift led to a notable change in children’s anatomy: their eyeballs lengthened to better accommodate short-vision tasks. Study after study, in regions ranging from Europe to Asia, documented this change. One analysis from Hong Kong even reported a near doubling in the incidence of pathologically stretched eyeballs among six-year-olds compared with pre-pandemic levels1. This elongation improves the clarity of close-up images on the retina, the light-sensitive layer at the back of the eye. But it also makes far-away objects appear blurry, leading to a condition known as myopia, or short-sightedness. And although corrective eyewear can usually address the issue — allowing children to, for example, see a blackboard or read from a distance — severe myopia can lead to more-serious complications, such as retinal detachment, macular degeneration, glaucoma and even permanent blindness. Rates of myopia were booming well before the COVID-19 pandemic. Widely cited projections in the mid-2010s suggested that myopia would affect half of the world’s population by mid-century (see ‘Rising prevalence’), which would effectively double the incidence rate in less than four decades2 (see ‘Affecting every age’). Now, those alarming predictions seem much too modest, says Neelam Pawar, a paediatric ophthalmologist at the Aravind Eye Hospital in Tirunelveli, India. “I don’t think it will double,” she says. “It will triple.” © 2024 Springer Nature Limited

Keyword: Vision; Development of the Brain
Link ID: 29329 - Posted: 05.29.2024