It’s a movie cliche: the moment when the lost traveler intersects a set of footprints, only to realize that the prints where made by his very own boot soles. The hero then realizes, with plunging heart, that he’s been walking in circles while trying to walk a straight course through the featureless expanse. Now a small study has shown that the cliche is true. Without the sun, a compass or a landmark, people trying to follow a straight course through a forest or a desert ended up back where they started [HealthDay News].
In the first experiment, six participants tried to follow a straight course through a forest in Germany, in an area where the land is flat and the trees quickly begin to look alike. The two subjects who walked on a sunny day stayed on a fairly straight course (as tracked by a GPS device), except for the first 15 minutes when the sun was behind the clouds. But the four who walked on an overcast day repeatedly traveled in circles, sometimes crossing their own paths after only 10 minutes. Says lead researcher Jan Souman: “They didn’t really believe when we showed them afterwards…. I think that’s certainly a point to take away, people may feel very confident about the direction where they’re going but it’s not certain” [ABC News].
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Three patients with severe damage to the corneas of their eyes have achieved dramatic improvements in their vision thanks to contact lenses coated with their own stem cells. While the study was extremely small and the results are quite preliminary, the unequivocal improvement seen in the three patients has given doctors hope that the treatment may work for many patients with damaged corneas. Two of the three patients were legally blind in the treated eye; they can now read big letters on the eye chart. The third could read the top few rows of the chart but is now able to pass the vision test for a driving license [The Australian].
The cornea is the transparent layer that covers the eye – but it can lose transparency, damaging sight. In the most serious cases, people can need cornea grafts or transplants. Corneal disease can be caused by genetic disorders, surgery, burns, infections or chemotherapy. In this study, all three patients had damage to the epithelium – the layer of cells covering the front of the cornea [BBC News].
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Specialized cells found only on flower petals have the same basic function as nonslip mats that prevent people from slipping in the shower, a new study has determined. The bumpy cells, called conical cells, help bees come in for a landing on the flower petals and find their footing, so they can get down to the important business of pollination.
Conical cells had been something of a botanical mystery, with most researchers assuming they played a visual role. One hypothesis held that by modifying the spectral properties of the petal, the cells enabled the plant to appear brighter to pollinators [The Scientist]. In the study, will be published in a forthcoming issue of Current Biology, researchers showed that the conical cells’ main function is to provide friction, and that bees can detect them by touch. The first experiment used two kinds white snapdragons that looked identical to both human and bee eyes, but one was a mutant with flat cells instead of conical. The bees initially went to both flower types, but after 20 visits they chose the blossoms with conical cells more than 80 percent of the time.
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A group of geneticists has peered into the eyes of nocturnal animals, and say they may have found the secret to these animals’ keen night vision: light-sensing cells with unusually structured DNA that turns each cell’s nucleus into a tiny lens.
The researchers were examining mice’s rod cells, the cells in the retina of the eye that operate under low light. Usually, they say, active genes are clustered in the center of each cell’s nucleus for convenient access to cellular machinery. But rod cells in the mouse retina shove active genes to the outside of the nucleus, the researchers found. The center of the nucleus is instead occupied by densely-packed inactive DNA called heterochromatin. Mice put this type of DNA front and center in their rod cells. “Everything that must be inside is outside, and everything that should be outside is inside,” [lead researcher Boris] Joffe says. “It was an absolutely heretic finding” [Science News].
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Scientists have found that manipulating a person’s sense of touch can confuse their sense of sight, an intriguing finding that suggests that touch and vision are integrated in the human brain…. For decades, instructors in medical schools have taught students that the senses —including vision, touch and sound — are interpreted in different, discrete parts of the brain, says Michael Beauchamp of the University of Texas Medical School at Houston. “Now it turns out what we’re teaching them is wrong,” he says. “There’s a lot more cross talk between the modalities” [Science News].
In the experiment, which will be published in an upcoming Current Biology, researchers used a postage stamp-sized device that used tiny pins to stroke the test subject’s finger in either an upward or downward direction. When subjects watched a stationary stripe on a computer screen after a machine stroked their fingertips, the motion of the stroking created the illusion that the stripe was moving [ScienceNOW Daily News].
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Stroke patients with damaged vision may be able to restore their sight with the help of computer exercises based on the phenomenon known as blindsight–when a person with vision loss senses something they cannot actually see [Reuters]. Lead researcher Krystel Huxlin explains that people with blindsight may not be able to consciously perceive a visual stimulus, yet when they’re forced to answer questions about it their answers are often correct.
Researchers studied patients whose strokes had damaged their primary visual cortex, and whose impaired vision limits some everyday activities like reading and driving. “This is a type of brain damage that clinicians and scientists have long believed you simply can’t recover from. It’s devastating, and patients are usually sent home to somehow deal with it the best they can” [CBC], says Huxlin. The primary visual cortex is the gateway to the rest of the brain for most of the visual information that comes through the eyes, Huxlin said. That area passes visual information along to dozens of other parts of the brain, which then makes sense of the information, allowing people to see [Bloomberg].
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Who says shoot-’em-up video games are a waste of time? A new study has found that playing action video games dramatically increases the players’ ability to detect subtle shades of gray. Says lead Daphne Bavelier: “Normally, improving contrast sensitivity means getting glasses or eye surgery — somehow changing the optics of the eye…. [But when] people play action games, they’re changing the brain’s pathway responsible for visual processing. These games push the human visual system to the limits and the brain adapts to it,” Bavelier said [Reuters]. The study also found that more sedate games that don’t require precisely aimed actions, like The Sims 2, do not confer a similar benefit.
The researchers say that eye doctors could one day write prescriptions for Nintendo: The finding raises the prospect that people with amblyopia, which affects contrast perception, could be treated with games. A trial has begun to test that theory. Amblyopia, sometimes known as “lazy eye”, affects around 3 per cent of people in western populations and happens when the brain fails to correctly register signals from one eye [New Scientist]. Contrast sensitivity, which is crucial for activities such as night driving, is also one of the first elements of vision to be affected by aging.
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While that headline may overstate the case slightly for comic effect, researchers say the gist of it is true: Stroke patients with impaired vision who listened to their favorite music showed vastly improved visual processing. Says lead researcher David Soto: “One of the patients chose Kenny Rogers, another Frank Sinatra and the third a country rock band. It’s not a particular kind of music that’s important, as long as the patient enjoys it” [Daily Mail].
Participants in Soto’s study had suffered lesions to their brains’ parietal cortex, a region central to visual and spatial processing. This left them with a condition called visual neglect, in which people lose half their spatial awareness. Victims will sometimes eat food from only one side of their plate, shave one side of their faces, or — as tested in the study — fail to perceive visual prompts on one side of a computer screen [Wired].
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Beauty is in the eye of the beholder, and whether that beholding eye belongs to a man or a woman may determine how beauty is processed and understood in the brain, according to a small, preliminary study. Researchers asked 10 men and 10 women to decide which paintings and photographs they found beautiful, while brain scans revealed which parts of their brains were active while they examined each image. The results suggested that while both sexes use parts of the brain associated with spacial awareness to process beauty, men use an area associated with big-picture thinking, while women also use a region linked to local details.
All the volunteers showed increased activity in the parietal lobe when gazing at a landscape or urban scene that they found beautiful, but men used only the right lobe, while women used the lobes on both the left and right sides of the brain. The researchers suggest that this is because women are contextualising the information and thinking more about the details of what they are seeing, assessing the position of objects according broad categories, such as “above” or “below”, or “left” or “right”. The men, they say, are focussing on the overall image using a more precise form of mental mapping [BBC News]. Study coauthor Camilo Cela-Conde hypothesizes that these differences may be linked to the different roles played by men and women throughout our evolution.
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When researcher Julian Asher goes to the symphony, he gets a sensory extravaganza. “When I hear a violin, I see something like a rich red wine,” says Asher…. “A cello is more like honey” [New Scientist]. Asher has a condition called synesthesia in which sensory information gets mixed in the brain; in Asher’s particular form, auditory-visual synesthesia, sounds cause him to see colors. Now, a study led by Asher may have uncovered the genetic source of the condition, which synesthetes say can be both a blessing and a curse.
The researchers collected DNA samples from 196 people who had auditory-visual synesthesia running in their families, they explain in the American Journal of Human Genetics [subscription required]. Asher expected to find a single gene associated with the condition, but scanning the genomes revealed that it was linked to four distinct regions, on chromosomes 2, 5, 6, and 12.
The region that was most strongly linked to synesthesia was an area on chromosome 2 that has also been strongly linked to autism. That doesn’t mean that the two conditions are related, per se, explained Ed Hubbard, a cognitive neuroscientist…. Instead, the common gene or genes are likely “more generally involved in how the brain gets built.” The study also pulled out a region on chromosome 6 that contains genes linked to dyslexia — especially interesting, “seeing as phonemes [the units of sound in language] and letters are two of the strongest synesthetic triggers,” Asher said [The Scientist].
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When you need to brainstorm ideas for a big project, get yourself to a room that’s painted blue. But when it’s time to proofread the final product, find a red room. Those are the implications of a fascinating new study that measured the effect that colors have on cognition. Researchers found that red can make people’s work more accurate, and blue can make people more creative [The New York Times]. Since people associate red with danger, it primes them to proceed with more caution and diligence, Zhu reasons, while blue’s oceanic connotations put them in a more adventurous mood.
Researcher Juliet Zhu decided to tackle the topic because previous studies had come up with inconsistent findings. Some studies had found that red enhances cognition, for example, while other studies suggest the opposite. Zhu suspected this might be because the work didn’t pay enough attention to which types of cognition were being affected. Red might enhance performance on some tasks, she reasoned, while impairing performance on others [ScienceNOW Daily News].
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The odd-looking spookfish is the only vertebrate known to have mirrors in its eyes, according to a new report. The mirrors gather and focus light better than lenses, which spookfish also have, and appear to be an adaptation for living in the murky depths of the Pacific Ocean. Scientists discovered the spookfish’s unusual anatomy after examining the first specimen of the fish ever caught alive. Researcher Ron Douglas found the rare specimen last year in the deep waters between Samoa and New Zealand, but no one on the research boat knew what it was. “It caught my attention because it looked like it had four eyes, and vertebrates with four eyes don’t exist,” says Douglas [New Scientist].
In fact, the spookfish only has two. Spookfish, also known as barreleyes, are a family of deep-sea fish with tubular eyes, rather like telescopes, that point upwards to capture the minimal sunlight that filters down from above. Each eye also has a part that points downward, forming what looks like a second pair of eyes. When researcher Julian Partridge looked at sections of the spookfish eye under the microscope, he discovered that the downward-pointing parts contain mirrors, made of tiny plates of guanine crystals, that help direct light onto the retina. Partridge explains that the mirrored “diverticular” eyes help capture light emitted by other animals: “At these depths it is flashes of bioluminescent light from other animals that the spookfish are largely looking for. The diverticular eyes image these flashes, warning the spookfish of other animals that are active, and otherwise unseen, below its vulnerable belly” [BBC News].
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In a remarkable experiment, researchers found that a man who was rendered completely blind by several strokes could deftly navigate an obstacle course unaided, easily avoiding boxes and sidling around pieces of office equipment. The patient, known only as TN, was left blind after damage to the visual (striate) cortex in both hemispheres of the brain following consecutive strokes. His eyes are normal but his brain cannot process the information they send in, rendering him totally blind [BBC News]. Researchers say TN’s successful performance was an example of the phenomenon “blindsight,” and say it suggests that some small amount of information is being transmitted from his undamaged eyes to a more primitive part of his brain, which operates beneath the level of consciousness.
TN usually walks with a cane, but researcher Beatrice de Gelder convinced him to put it aside and to try to navigate the obstacle course without its help. He was able to do so flawlessly, despite being unable to consciously see any of the obstacles. Head down and hands loose by his side, he twisted his body to slalom slowly but surely between a camera tripod and a swingbin, and neatly stepped around a random series of smaller items. “At first he was nervous,” says de Gelder. “He said he wouldn’t be able to do it because he was blind.” The scientists broke into spontaneous cheers when he succeeded [Nature News].
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Researchers have determined the mechanism by which the world’s simplest vision system works. A team of biologists spent a decade studying the larvae of the marine rag-worm Platynereis, a tiny creature with just two cells that respond to light and direct the worm to swim towards it. The rag-worm and other zooplankton like krill drift in the ocean‘s water columns, swimming up from the depths towards the light in order to graze on marine plants called phytoplankton near the surface. This movement, called phototaxis, is the biggest biomass displacement in the world [AFP].
The rag-worm has two cells that work together as “proto-eyes”: one pigment cell and one light-sensitive cell. First, the pigment cell absorbs light and casts a shadow over the photoreceptor cell. The shape of the shadow varies according to the position of the light source. The photoreceptor cell then converts this light signal into electricity, sending it in a signal along a nerve that connects to a band of cells endowed with thin hairs, called cilia, that beat to displace water [AFP]. So although the worm sees no images, it can sense the difference between light and dark and swim in the right direction.
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Tennis referees are far more likely to make wrong “out” calls than wrong “in” calls, according to a new study. A quirk of our visual perception system, which helps us anticipate the motion of an object, seems to bias our perception of where a speeding tennis ball stops moving. “This is not a problem with referees,” says study co-author David Whitney…. “It’s a consequence of human visual processing … a visual illusion caused by a mechanism that allows the system to localize a moving object” [Scientific American].
The idea to study this visual illusion in a real-world context came to Whitney during a Wimbledon match as he watched a player challenge and overturn a referee’s call. For the study, published in Current Biology [subscription required], the researchers used Hawk-Eye technology, a system of high-speed cameras that is often used for contested calls in tennis matches. Three scientists independently reviewed video and instant replay of 4,457 randomly selected points from the 2007 Wimbledon championships. Of the 83 calls that the video and instant replay showed were wrong, 70 were “out” calls [Scientific American]. Without the visual bias, there should have been the same number of wrong “out” calls as “in” calls.
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