Chapter 10. Vision: From Eye to Brain
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By Anna Azvolinsky Hummingbirds are efficient hoverers, suspending their bodies midair using rapid forward and backward strokes. Aside from their unique ability to hover, the tiny avians are also the only known birds that can fly in any direction, including sideways. Hummingbird brains appear to be adapted for this flying ability, researchers have now shown. According to a study published today (January 5) in Current Biology, a highly conserved area of the brain—the lentiformis mesencephali (LM), which receives panoramic visual motion information directly from the retina—processes the movement of objects from all directions. In contrast, the LMs of other bird species and all other four-limbed vertebrates studied to date predominantly sense back-to-front motion. While the authors had predicted the neurons of this hummingbird brain region would be tuned to slow motion, they in fact found the opposite: LM neurons were sensitive to quick visual motion, most likely because hummingbirds must process and respond to their environments quickly to avoid collisions, both during hovering and in other modes of flight. “This ancient part of the brain the authors studied has one job: to detect the motion of the image in front of the eyes,” explained Michael Ibbotson, a neuroscientist at the University of Melbourne who penned an accompanying editorial but was not involved in the research. The results of this study suggest that “hummingbirds evolved this area of the brain to have fine motor control to be able to hover and push in every direction possible,” Ibbotson said. © 1986-2017 The Scientist
Link ID: 23064 - Posted: 01.07.2017
By Susana Martinez-Conde Our perceptual and cognitive systems like to keep things simple. We describe the line drawings below as a circle and a square, even though their imagined contours consist—in reality—of discontinuous line segments. The Gestalt psychologists of the 19th and early 20th century branded this perceptual legerdemain as the Principle of Closure, by which we tend to recognize shapes and concepts as complete, even in the face of fragmentary information. Now at the end of the year, it is tempting to seek a cognitive kind of closure: we want to close the lid on 2016, wrap it with a bow and start a fresh new year from a blank slate. Of course, it’s just an illusion, the Principle of Closure in one of its many incarnations. The end of the year is just as arbitrary as the end of the month, or the end of the week, or any other date we choose to highlight in the earth’s recurrent journey around the sun. But it feels quite different. That’s why we have lists of New Year’s resolutions, or why we start new diets or exercise regimes on Mondays rather than Thursdays. Researchers have also found that, even though we measure time in a continuous scale, we assign special meaning to idiosyncratic milestones such as entering a new decade. What should we do about our brain’s oversimplification tendencies concerning the New Year—if anything? One strategy would be to fight our feelings of closure and rebirth as we (in truth) seamlessly move from the last day of 2016 to the first day of 2017. But that approach is likely to fail. Try as we might, the Principle of Closure is just too ingrained in our perceptual and cognitive systems. In fact, if you already have the feeling that the beginning of the year is somewhat special (hey, it only happens once a year!), you might as well decide that resistance is futile, and not just embrace the illusion, but do your best to channel it. © 2017 Scientific American
By Stephen L. Macknik Masashi Atarashi, a physics high school teacher from Japan, submitted this wonderful winter illusion to the 2015 Best Illusion of the Year Contest, where it competed as a finalist. Atarashi discovered this effect serendipitously, while watching the snow fall through the venetian window blinds of his school’s faculty lounge—just like his students must sometimes do in the classroom during a lecture! Notice that as the blinds occupy more area on the screen, the speed of the snowfall seems to accelerate. A great illusion to ponder during our white holiday season. Nobody knows how Atarashi’s effect works, but our working hypothesis is that each time the snow disappears behind a blind, or reappears below it, it triggers transient increases in the activity of your visual system’s motion-sensitive neurons. Such transient surges in neural activity are perhaps misinterpreted by your brain as faster motion speed. © 2016 Scientific American,
Link ID: 23022 - Posted: 12.27.2016
Sarah Boseley Health editor The NHS is to pay for 10 people to be implanted with a “bionic eye”, a pioneering technology that can restore some sight to those who have been blind for years. Only a handful of people have undergone surgery in trials so far to equip them to use Argus II, which employs a camera mounted in a pair of glasses and a tiny computer to relay signals directly to the nerves controlling sight. The decision to fund the first 10 NHS patients to be given the bionic eye could pave the way for the life-changing technology to enter the mainstream. Those who will get the equipment can currently see nothing more than the difference between daylight and darkness. The system allows the brain to decode flashes of light, so that they can learn to see movement. One of three patients to have had the implant into the retina in trials at Manchester Royal Eye hospital is Keith Hayman, 68, from Lancashire, who has five grandchildren. He was diagnosed with retinitis pigmentosa in his 20s. The disease causes cells in the retina gradually to stop working and eventually die. Hayman, who was originally a butcher, was registered blind in 1981, and forced to give up all work. “Having spent half my life in darkness, I can now tell when my grandchildren run towards me and make out lights twinkling on Christmas trees,” he said. “I would be talking to a friend, who might have walked off and I couldn’t tell and kept talking to myself. This doesn’t happen anymore, because I can tell when they have gone.” They may seem like little things, he said, but “they make all the difference to me”. © 2016 Guardian News and Media Limited
Betsy Mason With virtual reality finally hitting the consumer market this year, VR headsets are bound to make their way onto a lot of holiday shopping lists. But new research suggests these gifts could also give some of their recipients motion sickness — especially if they’re women. In a test of people playing one virtual reality game using an Oculus Rift headset, more than half felt sick within 15 minutes, a team of scientists at the University of Minnesota in Minneapolis reports online December 3 in Experimental Brain Research. Among women, nearly four out of five felt sick. So-called VR sickness, also known as simulator sickness or cybersickness, has been recognized since the 1980s, when the U.S. military noticed that flight simulators were nauseating its pilots. In recent years, anecdotal reports began trickling in about the new generation of head-mounted virtual reality displays making people sick. Now, with VR making its way into people’s homes, there’s a steady stream of claims of VR sickness. “It's a high rate of people that you put in [VR headsets] that are going to experience some level of symptoms,” says Eric Muth, an experimental psychologist at Clemson University in South Carolina with expertise in motion sickness. “It’s going to mute the ‘Wheee!’ factor.” Oculus, which Facebook bought for $2 billion in 2014, released its Rift headset in March. The company declined to comment on the new research but says it has made progress in making the virtual reality experience comfortable for most people, and that developers are getting better at creating VR content. All approved games and apps get a comfort rating based on things like the type of movements involved, and Oculus recommends starting slow and taking breaks. But still some users report getting sick. © Society for Science & the Public 2000 - 2016.
Link ID: 22962 - Posted: 12.07.2016
.By JOANNA KLEIN A honey bee gathering pollen on a white flower. Dagmar Sporck/EyeEm, via Getty Images Set your meetings, phone calls and emails aside, at least for the next several minutes. That’s because today you’re a bee. It's time to leave your hive, or your underground burrow, and forage for pollen. Pollen is the stuff that flowers use to reproduce. But it’s also essential grub for you, other bees in your hive and your larvae. Once you’ve gathered pollen to take home, you or another bee will mix it with water and flower nectar that other bees have gathered and stored in the hive. But how do you decide which flowers to approach? What draws you in? In a review published last week in the journal Functional Ecology, researchers asked: What is a flower like from a bee’s perspective, and what does the pollinator experience as it gathers pollen? And that's why we're talking to you in the second person: to help you understand how bees like you, while hunting for pollen, use all of your senses — taste, touch, smell and more — to decide what to pick up and bring home. Maybe you're ready to go find some pollen. But do you even know where to look? © 2016 The New York Times Company
Hannah Devlin Science Correspondent Blind animals have had their vision partially restored using a revolutionary DNA editing technique that scientists say could in future be applied to a range of devastating genetic diseases. The study is the first to demonstrate that a gene editing tool, called Crispr, can be used to replace faulty genes with working versions in the cells of adults - in this case adult rats. Previously, the powerful procedure, in which strands of DNA are snipped out and replaced, had been used only in dividing cells - such as those in an embryo - and scientists had struggled to apply it to non-dividing cells that make up most adult tissue, including the brain, heart, kidneys and liver. The latest advance paves the way for Crispr to be used to treat a range of incurable illnesses, such as muscular dystrophy, haemophilia and cystic fibrosis, by overwriting aberrant genes with a healthy working version. Professor Juan Carlos Izpisua Belmonte, who led the work at the Salk Institute in California, said: “For the first time, we can enter into cells that do not divide and modify the DNA at will. The possible applications of this discovery are vast.” The technique could be trialled in humans in as little as one or two years, he predicted, adding that the team were already working on developing therapies for muscular dystrophy. Crispr, a tool sometimes referred to as “molecular scissors”, has already been hailed as a game-changer in genetics because it allows scientists to cut precise sections of DNA and replace them with synthetic, healthy replacements. © 2016 Guardian News and Media Limited
Link ID: 22882 - Posted: 11.17.2016
By ARNAUD COLINART, AMAURY LA BURTHE, PETER MIDDLETON and JAMES SPINNEY “What is the world of sound?” So begins a diary entry from April 1984, recorded on audiocassette, about the nature of acoustic experience. The voice on the tape is that of the writer and theologian John Hull, who at the time of the recording had been totally blind for almost two years. After losing his sight in his mid-40s, Dr. Hull, a newlywed with a young family, had decided that blindness would destroy him if he didn’t learn to understand it. For three years he recorded his experiences of sight loss, documenting “a world beyond sight.” We first met Dr. Hull in 2011, having read his acclaimed 1991 book “Touching The Rock: An Experience of Blindness,” which was transcribed from his audio diaries. We began collaborating with him on a series of films using his original recordings. These included an Emmy-winning Op-Doc in 2014 and culminated in the feature-length documentary “Notes on Blindness.” But we were also interested in how interactive forms of storytelling might further explore Dr. Hull’s vast and detailed account — in particular how new mediums like virtual reality could illuminate his investigations into auditory experience. The diaries describe his evolving appreciation of “the breadth and depth of three-dimensional world that is revealed by sound,” the awakening of an acoustic perception of space. The sound of falling rain, he said, “brings out the contours of what is around you”; wind brings leaves and trees to life; thunder “puts a roof over your head.” This interactive experience is narrated by Dr. Hull, using extracts from his diary recordings to consider the nature of acoustic space. Binaural techniques map the myriad details of everyday life (in this case, the noises that surround Dr. Hull in a park) within a 3-D sound environment, a “panorama of music and information,” rich in color and texture. The real-time animation visualizes this multilayered soundscape in which, Dr. Hull says, “every sound is a point of activity.” © 2016 The New York Times Company
By Simon Oxenham Isy Suttie has felt “head squeezing” since she was young. The comedian, best known for playing Dobbie in the BBC sitcom Peep Show, is one of many people who experience autonomous sensory meridian response (ASMR) – a tingly feeling often elicited by certain videos or particular mundane interactions. Growing up, Suttie says she had always assumed everyone felt it too. Not everyone feels it, but Suttie is by no means alone. On Reddit, a community of more than 100,000 members share videos designed to elicit the pleasurable sensation. The videos, often described as “whisper porn”, typically consist of people role-playing routine tasks, whispering softly into a microphone or making noises by crinkling objects such as crisp packets. The most popular ASMR YouTuber, “Gentle Whispering”, has over 250 million views. To most of us, the videos might seem strange or boring, but the clips frequently garner hundreds of thousands of views. These videos often mimic real-life situations that provoke ASMR in susceptible people. Suttie says her strongest real-world triggers occur during innocuous interactions with strangers, like talking about the weather – “it’s almost as if the more superficial the subject the better,” Suttie says. She feels the sensation particularly strongly when someone brushes past her. For Suttie, the feelings are so powerful that she often feels floored by them, and they even overcome pain and emotional distress. During a trip to the dentist, she still experiences the pleasurable tingles when the assistant brushes past her, she says. © Copyright Reed Business Information Ltd.
By Jessica Boddy Glasses may be trendy now, but for centuries they were the stodgy accessories of the elderly worn only for failing eyes. Now, new research suggests that aging bonobos might also benefit from a pair of specs—not for reading, but for grooming. Many older bonobos groom their partners at arm’s length instead of just centimeters away, in the same way that older humans often hold newspapers farther out to read. This made researchers think the apes might also be losing their close-up vision as they age. To see whether their hypothesis held, the researchers took photos of 14 different bonobos of varying ages as they groomed one another (above) and measured the distance between their hands and faces. By analyzing how this so-called grooming distance varied from ape to ape, the researchers found that grooming distance increased exponentially with age, they report today in Current Biology. And because both humans and bonobos shows signs of farsightedness around age 40, deterioration in human eyes might not be the mere result of staring at screens and small text, the scientists say. Rather, it might be a deep-rooted natural trait reaching back to a common ancestor. © 2016 American Association for the Advancement of Science.
Link ID: 22841 - Posted: 11.08.2016
By Diana Kwon Can you feel your heart beating? Most people cannot, unless they are agitated or afraid. The brain masks the sensation of the heart in a delicate balancing act—we need to be able to feel our pulse racing occasionally as an important signal of fear or excitement, but most of the time the constant rhythm would be distracting or maddening. A growing body of research suggests that because of the way the brain compensates for our heartbeat, it may be vulnerable to perceptual illusions—if they are timed just right. In a study published in May in the Journal of Neuroscience, a team at the Swiss Federal Institute of Technology in Lausanne conducted a series of studies on 143 participants and found that subjects took longer to identify a flashing object when it appeared in sync with the rhythm of their heartbeats. Using functional MRI, they also found that activity in the insula, a brain area associated with self-awareness, was suppressed when people viewed these synchronized images. The authors suggest that the flashing object was suppressed by the brain because it got lumped in with all the other bodily changes that occur with each heartbeat—the eyes make tiny movements, eye pressure changes slightly, the chest expands and contracts. “The brain knows that the heartbeat is coming from the self, so it doesn't want to be bothered by the sensory consequences of these signals,” says Roy Salomon, one of the study's co-authors. © 2016 Scientific American
By peering into the eyes of mice and tracking their ocular movements, researchers made an unexpected discovery: the visual cortex — a region of the brain known to process sensory information — plays a key role in promoting the plasticity of innate, spontaneous eye movements. The study, published in Nature, was led by researchers at the University of California, San Diego (UCSD) and the University of California, San Francisco (UCSF) and funded by the National Eye Institute (NEI), part of the National Institutes of Health. “This study elegantly shows how analysis of eye movement sheds more light on brain plasticity — an ability that is at the core of the brain’s capacity to adapt and function. More specifically, it shows how the visual cortex continues to surprise and to awe,” said Houmam Araj, Ph.D., a program director at NEI. Without our being aware of it, our eyes are in constant motion. As we rotate our heads and as the world around us moves, two ocular reflexes kick in to offset this movement and stabilize images projected onto our retinas, the light-sensitive tissue at the back of our eyes. The optokinetic reflex causes eyes to drift horizontally from side-to-side — for example, as we watch the scenery through a window of a moving train. The vestibulo-ocular reflex adjusts our eye position to offset head movements. Both reflexes are crucial to survival. These mechanisms allow us to see traffic while driving down a bumpy road, or a hawk in flight to see a mouse scurrying for cover.
Link ID: 22750 - Posted: 10.13.2016
By Dwayne Godwin, Jorge Cham The brain processes a wealth of visual information in parallel so that we perceive the world around us in the blink of an eye Dwayne Godwin is a neuroscientist at the Wake Forest University School of Medicine. Jorge Cham draws the comic strip Piled Higher and Deeper at www.phdcomics.com. © 2016 Scientific American
Link ID: 22689 - Posted: 09.24.2016
Alva Noë Eaters and cooks know that flavor, in the jargon of neuroscientists, is multi-modal. Taste is all important, to be sure. But so is the look of food and its feel in the mouth — not to mention its odor and the noisy crunch, or juicy squelch, that it may or may not make as we bite into it. The perception of flavor demands that we exercise a suite of not only gustatory, but also visual, olfactory, tactile and auditory sensitivities. Neuroscientists are now beginning to grasp some of the ways the brain enables our impressive perceptual power when it comes to food. Traditionally, scientists represent the brain's sensory function in a map where distinct cortical areas are thought of as serving the different senses. But it is increasingly appreciated that brain activity can't quite be segregated in this way. Cells in visual cortex may be activated by tactile stimuli. This is the case, for example, when Braille readers use their fingers to read. These blind readers aren't seeing with their fingers, rather, they are deploying their visual brains to perceive with their hands. And, in a famous series of studies that had a great influence on my thinking on these matters, Miriganka Sur at MIT showed that animals whose retinas were re-wired surgically to feed directly into auditory cortex do not hear lights and other visible objects presented to the eyes, rather, they see with their auditory brains. The brain is plastic, and different sensory modalities compete continuously for control over populations of cells. An exciting new paper on the gustatory cortex from the laboratory of Alfredo Fontanini at Stony Brook University shows that there are visual-, auditory-, olfactory- and touch-sensitive cells in the gustatory cortex of rats. There are even some cells that respond to stimuli in more than one modality. But what is more remarkable is that when rats learn to associate non-taste qualities — tones, flashes of lights, etc. — with food (sucrose in their study), there is a marked transformation in the gustatory cortex. © 2016 npr
By Colin Barras Subtract 8 from 52. Did you see the calculation in your head? While a leading theory suggests our visual experiences are linked to our understanding of numbers, a study of people who have been blind from birth suggests the opposite. The link between vision and number processing is strong. Sighted people can estimate the number of people in a crowd just by looking, for instance, while children who can mentally rotate an object and correctly imagine how it might look from a different angle often develop better mathematical skills. “It’s actually hard to think of a situation when you might process numbers through any modality other than vision,” says Shipra Kanjlia at Johns Hopkins University in Baltimore, Maryland. But blind people can do maths too. To understand how they might compensate for their lack of visual experience, Kanjlia and her colleagues asked 36 volunteers – 17 of whom had been blind at birth – to do simple mental arithmetic inside an fMRI scanner. To level the playing field, the sighted participants wore blindfolds. We know that a region of the brain called the intraparietal sulcus (IPS) is, and brain scans revealed that the same area is similarly active in blind people too. “It’s really surprising,” says Kanjlia. “It turns out brain activity is remarkably similar, at least in terms of classic number processing.” This may mean we have a deep understanding of how to handle numbers that is entirely independent of visual experience. This suggests we are all born with a natural understanding of numbers – an idea many researchers find difficult to accept. © Copyright Reed Business Information Ltd.
Tina Hesman Saey Color vision may actually work like a colorized version of a black-and-white movie, a new study suggests. Cone cells, which sense red, green or blue light, detect white more often than colors, researchers report September 14 in Science Advances. The textbook-rewriting discovery could change scientists’ thinking about how color vision works. For decades, researchers have known that three types of cone cells in the retina are responsible for color vision. Those cone cells were thought to send “red,” “green” and “blue” signals to the brain. The brain supposedly combines the colors, much the way a color printer does, to create a rainbow-hued picture of the world (including black and white). But the new findings indicate that “the retina is doing more of the work, and it’s doing it in a more simpleminded way,” says Jay Neitz, a color vision scientist at the University of Washington in Seattle who was not involved in the study. Red and green cone cells each come in two types: One type signals “white”; another signals color, vision researcher Ramkumar Sabesan and colleagues at the University of California, Berkeley, discovered. The large number of cells that detect white (and black — the absence of white) create a high-resolution black-and-white picture of a person’s surroundings, picking out edges and fine details. Red- and green-signaling cells fill in low-resolution color information. The process works much like filling in a coloring book or adding color to a black-and-white film, says Sabesan, who is now at the University of Washington. |© Society for Science & the Public 2000 - 2016
Link ID: 22660 - Posted: 09.15.2016
By Rachel Becker Optical illusions have a way of breaking the internet, and the latest visual trick looks like it’s well on its way. On Sunday afternoon, game developer Will Kerslake tweeted a picture of intersecting gray lines on a white background. Twelve black dots blink in and out of existence where the gray lines meet. In the six hours since he posted the photo to Twitter, it’s been shared more than 6,000 times, with commenters demanding to know why they can’t see all 12 dots at the same time. The optical illusion was first posted to Facebook about a day ago by Japanese psychology professor Akiyoshi Kitaoka, and it has been shared more than 4,600 times so far. But the origin of this bit of visual trickery is a scientific paper published in the journal Perception in 2000. To be clear, there really are 12 black dots in the image. But (most) people can’t see all 12 dots at the same time, which is driving people nuts. "They think, 'It’s an existential crisis,'" says Derek Arnold, a vision scientist at the University of Queensland in Australia. "'How can I ever know what the truth is?'" But, he adds, scientists who study the visual system know that perception doesn’t always equal reality. In this optical illusion, the black dot in the center of your vision should always appear. But the black dots around it seem to appear and disappear. That’s because humans have pretty bad peripheral vision. If you focus on a word in the center of this line you’ll probably see it clearly. But if you try to read the words at either end without moving your eyes, they most likely look blurry. As a result, the brain has to make its best guess about what’s most likely to be going on in the fuzzy periphery — and fill in the mental image accordingly. © 2016 Vox Media, Inc.
Link ID: 22652 - Posted: 09.15.2016
Chris Chambers One of the most compelling impressions in everyday life is that wherever we look, we “see” everything that is happening in front of us – much like a camera. But this impression is deceiving. In reality our senses are bombarded by continual waves of stimuli, triggering an avalanche of sensations that far exceed the brain’s capacity. To make sense of the world, the brain needs to determine which sensations are the most important for our current goals, focusing resources on the ones that matter and throwing away the rest. These computations are astonishingly complex, and what makes attention even more remarkable is just how effortless it is. The mammalian attention system is perhaps the most efficient and precisely tuned junk filter we know of, refined through millions of years of annoying siblings (and some evolution). Attention is amazing but no system is ever perfect. Our brain’s computational reserves are large but not infinite, and under the right conditions we can “break it” and peek behind the curtain. This isn’t just a fun trick – understanding these limits can yield important insights into psychology and neurobiology, helping us to diagnose and treat impairments that follow brain injury and disease. Thanks to over a hundred years of psychology research, it’s relatively easy to reveal attention in action. One way is through the phenomenon of change blindness. Try it yourself by following the instructions in the short video below (no sound). When we think of the term “blindness” we tend to assume a loss of vision caused by damage to the eye or optic nerves. But as you saw in the video, change blindness is completely normal and is caused by maxing out your attentional capacity. © 2016 Guardian News and Media Limited
A new study by investigators at Brigham and Women's Hospital in collaboration with researchers at the University of York and Leeds in the UK and MD Andersen Cancer Center in Texas puts to the test anecdotes about experienced radiologists' ability to sense when a mammogram is abnormal. In a paper published August 29 in the Proceedings of the National Academy of Sciences, visual attention researchers showed radiologists mammograms for half a second and found that they could identify abnormal mammograms at better than chance levels. They further tested this ability through a series of experiments to explore what signal may alert radiologists to the presence of a possible abnormality, in the hopes of using these insights to improve breast cancer screening and early detection. "Radiologists can have 'hunches' after a first look at a mammogram. We found that these hunches are based on something real in the images. It's really striking that in the blink of an eye, an expert can pick up on something about that mammogram that indicates abnormality," said Jeremy Wolfe, PhD, senior author of the study and director of the Visual Attention Laboratory at BWH. "Not only that, but they can detect something abnormal in the other breast, the breast that does not contain a lesion." In the clinic, radiologists carefully evaluate mammograms and may use computer automated systems to help screen the images. Although they would never assess an image in half a second in the clinic, the ability of experts to extract the "gist" of an image quickly suggests that there may be a detectable signs of breast cancer that radiologists are rapidly picking up. Copyright 2016 ScienceDaily
Laura Sanders Despite its name, the newly identified GluMI cell (pronounced “gloomy”) is no downer. It’s a nerve cell, spied in a mouse retina, that looks like one type of cell but behaves like another. Like neighboring retina nerve cells that subdue, or deaden, activity of other nerve cells, GluMI cells have a single arm extending from their body. But unlike those cells, GluMI cells actually seem to ramp up activity of nearby cells in a way that could aid vision. GLuMIs don’t seem to detect light firsthand, but they respond to it, Luca Della Santina of the University of Washington in Seattle and colleagues found. GluMIs are among a growing list of unexpected and mysterious cells found in the retinas of vertebrates, the researchers write August 8 in Current Biology. Citations L. Della Santina et al. Glutamatergic monopolar interneurons provide a novel pathway of excitation in the mouse retina. Current Biology. Vol. 26, August 8, 2016. doi:10.1016/j.cub.2016.06.016. |© Society for Science & the Public 2000 - 2016
Link ID: 22610 - Posted: 08.30.2016