Chapter 10. Vision: From Eye to Brain
Follow us on Facebook and Twitter, or subscribe to our mailing list, to receive news updates. Learn more.
by Kat Arney Feeling dopey? Refresh your "circadian eye" with a burst of orange light. Light is a powerful wake-up call, enhancing alertness and activity. Its effect is controlled by a group of photoreceptor cells in the eyeball that make the light-sensing pigment melanopsin. These cells, which work separately to the rods and cones needed for vision, are thought to help reset animals' body clocks - or circadian rhythms. Studies with people who are blind suggest this also happens in humans, although the evidence isn't conclusive. To find out how melanopsin wakes up the brain, Gilles Vandewalle at the University of Liege, Belgium, and his team gave 16 people a 10-minute blast of blue or orange light while they performed a memory test in an fMRI scanner. They were then blindfolded for 70 minutes, before being retested under a green light. People initially exposed to orange light had greater brain activity in several regions related to alertness and cognition when they were retested, compared with those pre-exposed to blue light. Light switch Vandewalle thinks that melanopsin is acting as a kind of switch, sending different signals to the brain depending on its state. Orange light, which has the longer wavelength, is known to make the pigment more light-sensitive, but blue light has the opposite effect. Green light lies somewhere in the middle. The findings suggest that pre-exposure to orange light pushes the balance towards the more light-sensitive form of melanopsin, enhancing the response in the brain. © Copyright Reed Business Information Ltd.
|By Jason G. Goldman Most people don't spend much time pondering the diameter of their pupils. The fact is that we don't have much control over our pupils, the openings in the center of the irises that allow light into the eyes. Short of chemical interventions—such as the eyedrops ophthalmologists use to widen their patients' pupils for eye exams—the only way to dilate or shrink the pupils is by changing the amount of available light. Switch off the lamp, and your pupils will widen to take in more light. Step out into the sun, and your pupils will narrow. Mechanical though they may be, the workings of pupils are allowing researchers to explore the parallels between imagination and perception. In a recent series of experiments, University of Oslo cognitive neuroscientists Bruno Laeng and Unni Sulutvedt began by displaying triangles of varying brightness on a computer screen while monitoring the pupils of the study volunteers. The subjects' pupils widened for dark shapes and narrowed for bright ones, as expected. Next, participants were instructed to simply imagine the same triangles. Remarkably, their pupils constricted or dilated as if they had been staring at the actual shapes. Laeng and Sulutvedt saw the same pattern when they asked subjects to imagine more complex scenes, such as a sunny sky or a dark room. Imagination is usually thought of as “a private and subjective experience, which is not accompanied by strongly felt or visible physiological changes,” Laeng says. But the new findings, published in Psychological Science, challenge that idea. The study suggests that imagination and perception may rely on a similar set of neural processes: when you picture a dimly lit restaurant, your brain and body respond, at least to some degree, as if you were in that restaurant. © 2014 Scientific American
A man blind since birth is taking up a surprising new hobby: photography. His newfound passion is thanks to a system that turns images into sequences of sound. The technology not only gives “sight” to the blind, but also challenges the way neurologists think the brain is organized. In 1992, Dutch engineer Peter Meijer created vOICe, an algorithm that converts simple grayscale images into musical soundscapes. (The capitalized middle letters sound out “Oh, I see!”). The system scans images from left to right, converting shapes in the image into sound as it sweeps, with higher positions in the image corresponding to higher sound frequencies. For instance, a diagonal line stretching upward from left to right becomes a series of ascending musical notes. While more complicated images, such as a person sitting on a lawn chair, at first seem like garbled noise, with enough training users can learn to “hear” everyday scenes. In 2007, neuroscientist Amir Amedi and his colleagues at the Hebrew University of Jerusalem began training subjects who were born blind to use vOICe. Despite having no visual reference points, after just 70 hours of training, the individuals went from “hearing” simple dots and lines to “seeing” whole images such as faces and street corners composed of 4500 pixels. (For comparison, Nintendo’s Mario was made up of just 192 pixels in his first video game appearance.) By attaching a head-mounted camera to a computer and headphones, the blind users were even able to navigate around a room by the sound cues alone. Every few steps the system snaps a photo and converts it into sound, giving the users their bearings as they traverse tables and trashcans. One patient even took up photography, using the head-mounted system to frame his snapshots. © 2014 American Association for the Advancement of Science.
by Megan Gannon, Live Science News Editor Never before seen in biology, a state of matter called "disordered hyperuniformity" has been discovered in the eye of a chicken. This arrangement of particles appears disorganized over small distances but has a hidden order that allows material to behave like both a crystal and a liquid. The discovery came as researchers were studying cones, tiny light-sensitive cells that allow for the perception of color, in the eyes of chickens. For chickens and other birds that are most active during the daytime, these photoreceptors come in four different color varieties — violet, blue, green and red — and a fifth type for detecting light levels, researchers say. Each type of cone is a different size. These cells are crammed into a single tissue layer on the retina. Many animals have cones arranged in an obvious pattern. Insect cones, for example, are laid out in a hexagonal scheme. The cones in chicken eyes, meanwhile, appear to be in disarray. But researchers who created a computer model to mimic the arrangement of chicken cones discovered a surprisingly tidy configuration. Around each cone is a so-called exclusion region that bars other cones of the same variety from getting too close. This means each cone type has its own uniform arrangement, but the five different patterns of the five different cone types are layered on top of each other in a disorderly way, the researchers say. © 2014 Discovery Communications, LLC.
A brain-training video game that improved the vision of college baseball players by as much as two lines on an eye chart has been developed by U.S. researchers. "This is something which I think could help almost anybody," said Aaron Seitz, a neuroscientist at the University of California, Riverside, who the led the research. Players on the university's baseball team improved their visual acuity by 31 per cent after training with the app. And that translated into better performance on the baseball field, where better vision improves the odds of hitting a ball travelling well over 100 km/h. "What we found is they had fewer strikeouts, they were able to create more runs," Seitz told CBC's Quirks & Quarks in an interview that airs Saturday. The players had more runs than predicted even after taking into account the natural improvement that would be expected over the course of the season. Further calculations suggest the improved performance helped the team to win four or five additional games. Following 30 sessions of training with the app, players had better vision, fewer strikeouts, more runs and more wins. But Seitz thinks the app has even more potential to help people with eye conditions such as lazy eye, glaucoma, or age-related macular degeneration. There are 100 million people around the world who have such low vision that glasses don't help, he added. "All that they have to gain is the brain training element.… For these people, there's just really big real-world benefits that could be achieved if we're able to improve their vision."
By JAMES GORMAN SEATTLE — When Clay Reid decided to leave his job as a professor at Harvard Medical School to become a senior investigator at the Allen Institute for Brain Science in Seattle in 2012, some of his colleagues congratulated him warmly and understood right away why he was making the move. Others shook their heads. He was, after all, leaving one of the world’s great universities to go to the academic equivalent of an Internet start-up, albeit an extremely well- financed, very ambitious one, created in 2003 by Paul Allen, a founder of Microsoft. Still, “it wasn’t a remotely hard decision,” Dr. Reid said. He wanted to mount an all-out investigation of a part of the mouse brain. And although he was happy at Harvard, the Allen Institute offered not only great colleagues and deep pockets, but also an approach to science different from the classic university environment. The institute was already mapping the mouse brain in fantastic detail, and specialized in the large-scale accumulation of information in atlases and databases available to all of science. Now, it was expanding, and trying to merge its semi-industrial approach to data gathering with more traditional science driven by individual investigators, by hiring scientists like Christof Koch from the California Institute of Technology as chief scientific officer in 2011 and Dr. Reid. As a senior investigator, he would lead a group of about 100, and work with scientists, engineers and technicians in other groups. Without the need to apply regularly for federal grants, Dr. Reid could concentrate on one piece of the puzzle of how the brain works. He would try to decode the workings of one part of the mouse brain, the million neurons in the visual cortex, from, as he puts it, “molecules to behavior.” © 2014 The New York Times Company
Link ID: 19291 - Posted: 02.25.2014
by Colin Barras If it's beyond repair, you find something else to do its job. This could soon apply to rods and cones, the light-sensitive cells in our eyes that can wither with age, causing blindness. A drug has been found that coaxes neighbours of ailing cells to do their work for them. In 2012, Richard Kramer at the University of California, Berkeley, discovered that injecting a certain chemical into the eyes of blind mice made normally light-insensitive ganglion cells respond to light. These cells ferry optical signals from the rods and cones to the brain, so the mice regained some ability to see light. But it only worked with ultraviolet light. Now, Kramer's team has found a different drug that does the same with visible light. Just 6 hours after they were injected, blind mice could learn to respond to light in the same way as sighted mice – although Kramer says he doesn't know whether they regained vision or just light sensitivity. When the researchers studied the drug's impact on retinal cells in more detail, they realised it had had no effect on healthy cells. "That's what's particularly remarkable and hopeful about this," says Kramer. "It's possible that if you put this drug in a partially damaged eye it would restore vision to the damaged regions and leave the healthy areas unaffected – although we haven't done the experiments to test that." Gene therapy and stem cell treatments are also being explored as ways to restore sight, but a drug would be simpler and any side effects should be reversible, says Kramer. © Copyright Reed Business Information Ltd
Link ID: 19273 - Posted: 02.20.2014
James Hamblin Brain training is becoming big business. Everywhere you look, someone is talking about neuroplasticity and trying to train your brain. Soon there will be no wild brains left. At the same time, everyone who spends more than two continuous hours using a computer is, according to the American Optometric Association, ruining their eyes with Computer Vision Syndrome. So, Dr. Aaron Seitz might be onto something with his new brain-training program that promises better vision. UltimEyes is a game-based app that's sold as "fun and rewarding" as it improves your vision and "reverse[s] the effects of aging eyes." It doesn't claim to work on the eyes themselves, but on the brain cortex that processes vision—the part that takes blurry puzzle pieces from the eyes and arranges them into a sweet puzzle. (Brain training for memory, the kind we hear about the most on TV, would be the part that lacquers the finished puzzle, frames it, and hangs it on the wall.) A standard 25-minute session using UltimEyes forces your eyes to work in ways they probably don't in everyday life, and its website warns that after the first use, "just like the first time that you go to the gym, your eyes may feel a bit tired. This experience typically goes away by your third session as your visual system adjusts to its new work-out routine." Seitz is a neuroscientist at the University of California, Riverside. To test out his vision-training game, he had players on the university's baseball team use the app. Half the team trained for 30 sessions. For comparison, the other half did no training. © 2014 by The Atlantic Monthly Group
by Clare Wilson SOMETIMES you find out more about how something works by turning it off. That seems to be true for mirror neurons, the brain cells implicated in traits ranging from empathy and learning to language acquisition. Mirror neurons are said to help us interpret other people's behaviour, but this has yet to be shown convincingly in experiments. Now a study that briefly disabled these cells might give a better idea of what they do. Mirror neurons were discovered in the 1990s when an Italian team was measuring electrical activity in the brains of monkeys. In the region that controls movement, some of the neurons that fire to carry out a particular action – such as grasping an apple – also fired when the monkey saw another animal do the same thing. The tempting conclusion was that these neurons help interpret others' behaviour. Further work suggested that people also have this system, and some researchers claimed that conditions where empathy is lacking, such as autism or psychopathy, could arise from defective mirror neurons. Yet there has been little evidence to back this up and critics argued that mirror neuron activity could just be some sort of side effect of witnessing action. Powerful magnetic fields are known to temporarily disrupt brain cell activity, and a technique called transcranial magnetic stimulation (TMS) is increasingly used in the lab to dampen specific areas of the brain. © Copyright Reed Business Information Ltd.
Dinsa Sachan Could being visually impaired have had a role in the musical genius of Stevie Wonder and Ray Charles? A study provides some clues by showing that adult mice kept in the dark quickly develop sharper hearing and become better at distinguishing pitch and frequency. The improvements were correlated with adaptations in the brain — such as strengthening of connections between neurons — that normally happen only early in life. For their study, published today in Neuron1, Hey-Kyoung Lee, a neuroscientist at Johns Hopkins University in Baltimore, Maryland, and her collaborators selected two sets of healthy adult mice. They kept the first group in a darkened environment for a week, while the other was exposed to natural light. The team used electrodes to measure activity in neurons in the animals' primary auditory cortex — the part of the brain that processes what a sound is, how loud it is and where it comes from. The researchers played sounds of different frequencies and intensities to the mice, and watched how their brain cells reacted. The results “showed that neurons in visually deprived animals can 'hear' much softer sounds” than in control animals, says Lee. “They also have much finer discrimination ability as far as identifying pitch goes.” Previous studies have found that changes in the auditory cortex take a long time, and that people who become blind early in life adapt better than those who lose their sight later. The team's findings, however, show that some modifications can occur rapidly in the adult brain, she says. “Moreover,” she adds, “the changes in the auditory cortex were achieved by changes in the strength of synaptic connections. These were believed to be unchangeable in adults.” © 2014 Nature Publishing Group
By Molly Sharlach Reader, be proud. You’re a perceptual expert. As you read, your eyes alternately focus and move along each line of text in a seamless sequence honed over years of practice. Reading, recognizing faces and distinguishing colors or musical tones are all forms of perceptual expertise. To appreciate the visual skill involved in reading, turn a text upside down. You’ll stumble along in fits and starts, your eyes pausing longer and more often, each movement bringing less information to your brain. To assess how such neuro-ocular blundering might be improved, researchers at the University of British Columbia asked seven volunteers to practice reading novels upside down. After 30 half-hour sessions over a period of 10 weeks, they gained an average of 35 words per minute in reading speed on inverted text. This could be promising news for people with right hemianopia (hemi-uh-NOH-pee-uh), a condition that erases part of the right field of vision in both eyes. Any damage to the left occipital lobe of the brain, or the pathways connecting it to the eyes, can cause this disorder. Hemianopia, from the Greek for “half sight,” most often results from a stroke, but can also befall patients with multiple sclerosis, brain tumors or traumatic injuries. When we read, we see only three or four letters to the left of our eyes’ fixation point, but we pick up information 10 to 15 letters to the right. So in a society that reads from left to right, left hemianopia has little effect on reading ability, but right hemianopia can be devastating. Brain injury patients rank the inability to read among the most significant effects on their quality of life. © 2014 Scientific America
By James Gallagher Health and science reporter, BBC News Cells taken from the donated eyes of dead people may be able to give sight to the blind, researchers suggest. Tests in rats, reported in Stem Cells Translational Medicine, showed the human cells could restore some vision to completely blind rats. The team at University College London said similar results in humans would improve quality of life, but would not give enough vision to read. Human trials should begin within three years. Donated corneas are already used to improve some people's sight, but the team at the Institute for Ophthalmology, at UCL, extracted a special kind of cell from the back of the eye. These Muller glia cells are a type of adult stem cell capable of transforming into the specialised cells in the back of the eye and may be useful for treating a wide range of sight disorders. In the laboratory, these cells were chemically charmed into becoming rod cells which detect light in the retina. Injecting the rods into the backs of the eyes of completely blind rats partially restored their vision. Brain scans showed that 50% of the electrical signals between the eye and the brain were recovered by the treatment. One of the researchers, Prof Astrid Limb, told the BBC what such a change would mean in people: "They probably wouldn't be able to read, but they could move around and detect a table in a room. BBC © 2014
Madhusree Mukerjee By displaying images on an iPad, researchers tested patients' ability to detect contrast after their vision was restored by cataract surgery. In a study of congenitally blind children who underwent surgery to restore vision, researchers have found that the brain can still learn to use the newly acquired sense much later in life than previously thought. Healthy infants start learning to discern objects, typically by their form and colour, from the moment they open their eyes. By the time a baby is a year old vision development is more or less complete, although refinements continue through childhood. But as the brain grows older, it becomes less adaptable, neuroscientists generally believe. "The dogma is that after a certain age the brain is unable to process visual inputs it has never received before," explains cognitive scientist Amy Kalia of the Massachusetts Institute of Technology (MIT) in Cambridge. Consequently, eye surgeons in India often refuse to treat children blinded by cataracts since infancy if they are over the age of seven. Such children are not usually found in wealthier countries such as the United States — where cataracts are treated as early as possible — but are tragically plentiful in India. In the study, which was published last week in Proceedings of the National Academy of Sciences1, Kalia and her collaborators followed 11 children enrolled in Project Prakash2, a humanitarian and scientific effort in India that provides corrective surgery to children with treatable cataracts and subsequently studies their visual abilities. ('Prakash' is Sanskrit for light.) © 2014 Nature Publishing Group
Mantis shrimp's super colour vision debunked Jessica Morrison Mantis shrimp don’t see colour like we do. Although the crustaceans have many more types of light-detecting cell than humans, their ability to discriminate between colours is limited, says a report published today in Science1. Researchers found that the mantis shrimp’s colour vision relies on a simple, efficient and previously unknown mechanism that operates at the level of individual photoreceptors. The results upend scientists' suspicions that the shrimp, with 12 different types of colour photoreceptors, could see hues that humans, with just 3, could not, says study co-author Justin Marshall, a marine neuroscientist at the University of Queensland in Brisbane, Australia. When the human eye sees a yellow leaf, photoreceptors send signals to the brain announcing relative levels of stimuli: receptors sensitive to red and green light report a lot of activity, whereas receptors sensitive to blue light report little. The brain compares the information from each type of receptor to come up with yellow. Using this system, the human eye can distinguish between millions of different colours. To test whether the mantis shrimp, with its 12 receptors, can distinguish many more, Marshall's team trained shrimp of the species Haptosquilla trispinosa to recognize one of ten specific colour wavelengths, ranging from 400 to 650 nanometres, by showing them two colours and giving them a frozen prawn or mussel when they picked the right one. In subsequent testing, the shrimp could discriminate between their trained wavelengths and another colour 50–100 nanometres up or down the spectrum. But when the difference between the trained and test wavelengths was reduced to 12–25 nanometres, the shrimp could no longer tell them apart. © 2014 Nature Publishing Group
Want to read someone’s mind? Look at their pupils. A person about to answer “yes” to a question, especially if they are more used to answering “no,” will have more enlarged pupils than someone about to answer “no,” according to a new study. Normally, pupils dilate when a person is in a darkened environment to let more light into the eye and allow better vision. But pupil size can also be altered by levels of signaling chemicals naturally produced by the brain. In the study, published online this week in the Proceedings of the National Academy of Sciences, scientists observed the pupils of 29 people as they pressed a “yes” or “no” button to indicate whether they’d seen a difficult-to-detect visual cue on a screen in front of them. When a person was deciding how to answer—in the seconds before pressing a button—their pupils grew larger. And if a person was normally biased toward answering “no” when they weren’t sure on the visual cue, then the pupil change was even more profound in the decision-making seconds before a “yes” answer. The finding could lead to new ways to detect people’s intrinsic biases and how confident they are in an answer given, important variables in many sociological and psychological studies. © 2014 American Association for the Advancement of Science.
|By Stephanie Pappas The justices of the Supreme Court may be among the best legal minds in the country, but they have no eye for distances — and new research may help explain why. During oral arguments Wednesday (Jan. 15) in a case about the constitutionality of laws prohibiting protestors from gathering close to abortion clinic entrances, the justices were stumped at the size of the 35-foot-long (10.6 meters) buffer zone in question. "It's pretty much this courtroom, kind of," ABC News quoted Associate Justice Elena Kagan as saying. In fact, the courtroom is more than 90 feet (30 m) long. After a back-and-forth discussion, the deputy solicitor arguing the case clarified that the no-go zone is the size of the 3-point zone on an NBA basketball court. But judging distances and depth may be trickier than it seems. A recent study, published Oct. 23 in the Journal of Neuroscience, finds that people's depth perception depends on their perception of their arm's length. Trick someone into thinking their arm is shorter or longer, and you can influence how they perceive distances between two objects. Depth perception, the ability to judge the distances of objects from one another, is an important ability; without it, one would have no way of knowing that a marble in their hand and a basketball 6 feet away were actually two different sizes. © 2014 Scientific American
Link ID: 19165 - Posted: 01.25.2014
Ian Sample, science correspondent Two men with progressive blindness have regained some of their vision after taking part in the first clinical trial of a gene therapy for the condition. The men were among six patients to have experimental treatment for a rare, inherited, disorder called choroideremia, which steadily destroys eyesight and leaves people blind in middle age. After therapy to correct a faulty gene, the men could read two to four more lines on an optician's sight chart, a dramatic improvement that has held since the doctors treated them. One man was treated more than two years ago. The other four patients, who had less advanced disease and good eyesight before the trial, had better night vision after the therapy. Poor sight in dim light is one of the first signs of the condition. Writing in The Lancet , doctors describe the progress of the patients six months after the therapy. If further trials are as effective, the team could apply for approval for the therapy in the next five years. Some other forms of blindness could be treated in a similar way. Toby Stroh, 56, a solicitor from London, was in his early 20s when a consultant told him he would be blind by the age of 50. "I said 'what do you mean?' and he said, 'you won't be able to see me'. It was a long way away, but still a bit of a shock." Stroh was told later that his vision had deteriorated so much he would have to stop driving. Then, when he joined a solicitors' firm he told a partner his eyesight was not expected to last. The response was: "We'll be sorry to see you go." © 2014 Guardian News and Media Limited
Link ID: 19143 - Posted: 01.16.2014
by Anil Ananthaswamy Next time you happen to be snorkelling near a coral reef, keep an eye out for mantis shrimp. In all likelihood, these crustaceans, which resemble small lobsters, will have spotted you: they scan their surroundings with rapid eye movements just like those of primates. Justin Marshall of the University of Queensland in Brisbane, Australia, and colleagues have been studying mantis shrimp for years, and it is how they use their eyes that interests Marshall. Their eyes are on stalks and can dart around. Humans use similar rapid eye movements, called saccades, to "acquire" or lock on to new objects, and to track them as they move. "It was not clear whether the shrimp eye movements were anything to do with acquiring objects, or just repositioning the eyes," Marshall says. To find out, the team placed mantis shrimp in a perspex tube inside an aquarium, and suddenly introduced a small coloured disc into their line of sight. A camera outside the aquarium filmed their eyes. The team found that the mantis shrimp's fovea – the part of the eye with the highest resolution – was using saccades to home in on the coloured disc. This sort of behaviour is normally found in animals like primates, says Marshall. The saccadic eye movements are extremely rapid. Human saccades can sweep through a field of view at a rate of 200-300 degrees per second. "[Mantis shrimp] are actually going up to twice that amount," says Marshall. © Copyright Reed Business Information Ltd.
Link ID: 19113 - Posted: 01.09.2014
By Susana Martinez-Conde If you’re a bit lax with your post-holiday brushing, this little-known illusion may give you the incentive you need to keep those candy canes in check, or at least brush and floss afterwards. Vision scientist Robert O’Shea and his colleagues published a recent study in PLoS One showing that dentists can fall prey to a visual illusion of size and make larger holes in teeth than needed. The illusion fooling the dentists is a variant of a classical perceptual phenomenon known as the Delboeuf illusion, named after its creator, the Belgian natural philosopher, experimentalist, mathematician and hypnotist Joseph Remi Leopold Delboeuf. The scientists supplied 8 specialist dentists and endodontists, who served as experimental subjects, with a large pool of extracted teeth. The teeth contained holes, and the task of the dentists was to cut cavities in preparation for filling. Unknown to the dentists, each tooth presented a more or less powerful version of the Delboeuf illusion, making the holes appear smaller than their actual size. The results showed that the smaller the holes looked, the larger the cavities that the dentists made for later filling. The researchers recommend that dentists and other health practitioners receive training in “illusion awareness” (my words, not theirs), so that they may counteract these and related perceptual effects. © 2013 Scientific American,
Link ID: 19073 - Posted: 12.28.2013
By Michelle Roberts Health editor, BBC News online Scientists say they have been able to successfully print new eye cells that could be used to treat sight loss. The proof-of-principle work in the journal Biofabrication was carried out using animal cells. The Cambridge University team says it paves the way for grow-your-own therapies for people with damage to the light-sensitive layer of tissue at back of the eye - the retina. More tests are needed before human trials can begin. At the moment the results are preliminary and show that an inkjet printer can be used to print two types of cells from the retina of adult rats―ganglion cells and glial cells. These are the cells that transmit information from the eye to certain parts of the brain, and provide support and protection for neurons. The printed cells remained healthy and retained their ability to survive and grow in culture. Co-authors of the study Prof Keith Martin and Dr Barbara Lorber, from the John van Geest Centre for Brain Repair at the University of Cambridge, said: "The loss of nerve cells in the retina is a feature of many blinding eye diseases. The retina is an exquisitely organised structure where the precise arrangement of cells in relation to one another is critical for effective visual function. Human eye The retina sits at the back of the eye BBC © 2013