By Gary Stix Our current understanding of how the brain works often borrows from observations of the anomalous patient. The iron rod that penetrated Phineas Gage’s head made the once emotionally balanced railroad foreman impulsive and profane. But it gave neurologists clues as to the role of the brain’s frontal lobes in exercising self-control. The epilepsy surgery that removed Henry Molaison’s hippocampus opened a whole new line of research about memory. Still, conclusions about mental processes from single patients arrive freighted with unavoidable risk. Neuroscientists can’t replicate what they find in neurologically damaged patients by removing a frontal lobe or hippocampus from other research subjects without planning for significant downtime in a state or federal prison. That means that what we think we learn from an initial examination of a Gage or a Molaison may be less than meets the eye. The cautionary lessons of single-case neuroscience were underlined in a recent paper in Neuropsychologia by Marc Himmelbach and two colleagues at the Hertie-Institute for Clinical Brain Research, part of Eberhard Karls University in Tübingen, Germany. The team took another look at the well-known case of D.F., a woman who suffered brain damage more than 20 years ago from carbon monoxide. D.F.’s entry into the case history annals came about because, as a result of her injuries, she could not recognize everyday objects, a condition called visual agnosia, yet she was still able to grasp them. © 2012 Scientific American

Related chapters from BP6e: Chapter 10: Vision: From Eye to Brain; Chapter 17: Learning and Memory
Related chapters from MM:Chapter 7: Vision: From Eye to Brain; Chapter 13: Memory, Learning, and Development
Link ID: 16597 - Posted: 03.31.2012

Sandrine Ceurstemont, editor, New Scientist TV Don't worry, the mesmerising swirls in this video won't hypnotise you. But once the moving pattern disappears, you may be surprised when a ghostly spinning spiral appears before your eyes. The illusion was accidentally discovered by game designer Hjalmar Snoep while he was creating an animation late at night. "I realised that the after-image that appeared wasn't part of the animation," he says. "I've never come across a moving after-image even though I have collected lots of optical illusions, so it piqued my interest." After-image effects are caused by the overstimulation of photoreceptors in the eyes after staring at an image for a long time. Typically, they take on the original shape, often appearing in its complementary colours. But a recent study by Hiroyuki Ito from Kyushu University in Japan showed for the first time how an after-image can vary in shape as well as hue. Ito is now studying moving after-image illusions, since they aren't easy to explain with existing theories. After viewing Snoep's animation, he suggests that the averaged or accumulated retinal exposure to light over the clip's duration could cause the spiral after-image. "The hypothesis could be tested by calculating the averaged luminance for each pixel during the viewing period," he says. "It's a splendid demonstration as entertainment, as well as from a scientific point of view." © Copyright Reed Business Information Ltd.

Related chapters from BP6e: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 16595 - Posted: 03.31.2012

By Rebecca Cheung Some larval sponges search for a shady place to settle down, but they don’t have optic nerves or the genes that are important for vision in most animals. Now biologists have new insight into how sponges might see light. Larvae of the sponge Amphimedon queenslandica have unique eyes made up of cells that contain pigment, a chemical that absorbs certain wavelengths of light, and cilia, which look like tiny hairs. Right next to these pigmented cells are cells with high levels of activated cry2, a gene that makes light-sensitive proteins, Todd Oakley of the University of California, Santa Barbara and others report in the April 15 Journal of Experimental Biology. These light-sensitive proteins could be involved in directing movement in cilia and steering these sponges.The finding could provide clues in how vision developed in these simple animals, Oakley says. © Society for Science & the Public 2000 - 2012

Related chapters from BP6e: Chapter 10: Vision: From Eye to Brain; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 16568 - Posted: 03.24.2012

Sandrine Ceurstemont, editor, New Scientist TV Your eyes and ears can sometimes join forces to trick you. A new illusion, created by Wataru Teramoto from Tohoku University in Japan and colleagues, shows for the first time how the direction of a sound can affect how you perceive motion. The animation above should be viewed up close, while fixing your eyes on the red dot. A white square moves up and down in the periphery as a sound pans back and forth between your left and right ears. How does the square appear to move? The team found that the motion of the square either appeared to be consistent with the changing direction of the sound, in this case horizontally, or it seemed to move diagonally, lying in between the real motion and the motion of the sound. According to Teramoto, this occurs because we use auditory spatial information to help us make sense of what we see. "Sound is especially useful when the reliability of visual information is low, for example in your peripheral vision," he says. Previous studies probing whether sound can modulate motion didn't find an effect but they always considered stimuli central to a scene. Our visual system can clearly interpret detail in this region but it's much less effective when considering information even slightly off centre. In another recent study, Teramoto and his team have shown another example of how our brain links visual and audio information. After being exposed to a sound accompanied by moving visuals for three minutes, the same audio made a static object appear to move. "This indicates that even a very short observation period is enough to associate sound sequences with visual motion in the adult brain," says Teramoto. © Copyright Reed Business Information Ltd.

Related chapters from BP6e: Chapter 10: Vision: From Eye to Brain; Chapter 9: Hearing, Vestibular Perception, Taste, and Smell
Related chapters from MM:Chapter 7: Vision: From Eye to Brain; Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 16566 - Posted: 03.24.2012

Sandrine Ceurstemont, editor, New Scientist TV No, it's not science fiction: a new illusion that looks like a flight through space simultaneously tricks your brain in three different ways. Watch the moving white dots and their shadows as they move forwards and backwards. They should appear to change in contrast, grow and shrink in size and vary in depth, since the distance between the dots and their shadows seems to change. But none of these factors are actually changing: the pairs of dots are only moving to a different position on the screen. Aptly named the Star Trek illusion by researcher Yury Petrov and his team from Northeastern University in Boston, who developed the effect, the trick occurs since our brain perceives the motion as a change in viewing distance. Normally, when you move closer or further away from a scene, colour contrast, depth cues and object size are altered to account for the new viewpoint. So the strong flow in the animation tricks our brain and causes it to infer the new cues it's expecting. In their recent paper, Petrov and his colleague found that our brain first rescales the size of the dots and then adjusts contrast. Although the depth effect was predicted, it was only observed when they produced the new version of the illusion, shown above, containing shadows. The illusion has been submitted to this year's Best Visual Illusion of the Year Contest. © Copyright Reed Business Information Ltd.

Related chapters from BP6e: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 16531 - Posted: 03.17.2012

By Katherine Harmon Giant and colossal squid can grow to be some 12 meters long. But that alone doesn’t explain why they have the biggest eyeballs on the planet. At 280 millimeters in diameter, colossal squid eyes are much bigger than those of the swordfish, which at 90 millimeters, measure in as the next biggest peepers. “It doesn’t make sense a giant squid and swordfish are similar in size but the squid’s eyes are proportionally much larger, three times the diameter and 27 times the volume,” Sönke Johnsen, a biologists at Duke University, said in a prepared statement. Why would these cephalopods evolve soccer-ball-size eyes? The better to see you with, of course. Well, not you, exactly—unless you happen to be a hungry sperm whale. Scientists have found that having these extreme eyeballs likely allows these squid to spot whales when they’re still far enough away to escape the huge predators. The findings were described online March 15 in Current Biology. Bigger eyes might seem an obvious solution for acquiring better vision. “For seeing in dim light, a large eye is better than a small eye, simply because it picks up more light,” co-author Dan-Eric Nilsson of Lund University said in a prepared statement. But the low-light, low-contrast world of the pelagic oceans, where these squids and whales live and die, is much murkier than our airy environment here on land. “We have found that for animals living in water, it does not pay to make eyes much bigger than an orange,” Nilsson said. © 2012 Scientific American

Related chapters from BP6e: Chapter 10: Vision: From Eye to Brain; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 16530 - Posted: 03.17.2012

By Laura Sanders The eyes are a window to the soul, but also to the brain. The health of easy-to-check blood vessels in the retina reflects the health of blood vessels deep inside the head, findings that raise the possibility of a simple eye exam catching early signs of brain trouble, scientists report in the March 27 Neurology. “The potential is very great — to use the eye to diagnose what’s going on elsewhere in the body, particularly in the brain,” says neuroscientist Alistair Barber of Penn State College of Medicine in Hershey. “The retina is relatively easy to see. The brain is not.” The findings add to the growing number of studies focusing on blood vessels that link eye and brain health. The Neurology study was conducted as part of the Women’s Health Initiative, which tracks the health of postmenopausal women. Over 10 years, researchers led by epidemiologist and biostatistician Mary Haan of the University of California, San Francisco looked for a link between eye disease and brain performance in 511 women who were at least 65 years old. In the study, participants had their pupils dilated as researchers took pictures of their retinas. After careful examinations, 39 women, or 7.6 percent of the total, were found to have diseased blood vessels in the retina, a condition called retinopathy in which the vessels can become swollen, leaky or grow abnormally. Usually, retinopathy is a symptom of diabetes or high blood pressure, two disorders that if left untreated are known to affect brain functioning. © Society for Science & the Public 2000 - 2012

Related chapters from BP6e: Chapter 10: Vision: From Eye to Brain; Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 7: Vision: From Eye to Brain; Chapter 13: Memory, Learning, and Development
Link ID: 16521 - Posted: 03.17.2012

Sandrine Ceurstemont, editor, New Scientist TV It seems like it would be hard to miss the face of an actress morphing into another. But a new animation by psychologist Sebastiaan Mathôt from VU University in Amsterdam shows that Natalie Portman can turn into Leighton Meester right before your eyes and you won't notice when there's motion in the scene. In the first clip, fix your eyes on the cross in the centre of the video. As the changing faces rotate, you probably won't notice that they're morphing. But when they stop turning, the transformation becomes apparent. A second example shows that the faces themselves don't need to move to trick your brain. As you stare at a green dot in the centre, a rapidly-changing background makes you blind to the shifting face. When the motion stops, the creepy metamorphosis is obvious once again. The illusion is a version of a novel brain trick, devised last year by Jordan Suchow and George Alvarez from Harvard University, which won first place at the Best Illusion of the Year contest. It occurs due to a phenomenon called change blindness, where you can completely miss an obvious change when looking at a busy scene. When nothing much is happening, your visual system is more sensitive to change, but as the action increases, a transformation needs to be more dramatic to be detected. "In a sense, we protect ourselves from being overwhelmed by too much change," says Mathôt. © Copyright Reed Business Information Ltd.

Related chapters from BP6e: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 16493 - Posted: 03.10.2012

By Lena Groeger Our five senses–sight, hearing, touch, taste and smell–seem to operate independently, as five distinct modes of perceiving the world. In reality, however, they collaborate closely to enable the mind to better understand its surroundings. We can become aware of this collaboration under special circumstances. In some cases, a sense may covertly influence the one we think is dominant. When visual information clashes with that from sound, sensory crosstalk can cause what we see to alter what we hear. When one sense drops out, another can pick up the slack. For instance, people who are blind can train their hearing to play double duty. Those who are both blind and deaf can make touch step in—to say, help them interpret speech. For a few individuals with a condition called synesthesia, the senses collide dramatically to form a kaleidoscope world in which chicken tastes like triangles, a symphony smells of baked bread or words bask in a halo of red, green or purple. (For more on how the senses can cross each other and into unusual territory, see “Edges of Perception,” by Ariel Bleicher, Scientific American Mind, March/April 2012.) Our senses must also regularly meet and greet in the brain to provide accurate impressions of the world. Our ability to perceive the emotions of others relies on combinations of cues from sounds, sights and even smells (see “I Know How You Feel,” by Janina Seubert and Christina Regenbogen, Scientific American Mind, March/April 2012). Perceptual systems, particularly smell, connect with memory and emotion centers to enable sensory cues to trigger feelings and recollections, and to be incorporated within them. © 2012 Scientific American

Related chapters from BP6e: Chapter 8: General Principles of Sensory Processing, Touch, and Pain; Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 5: The Sensorimotor System; Chapter 7: Vision: From Eye to Brain
Link ID: 16454 - Posted: 03.01.2012

Caitlin Stier, video intern If you know where to fix your gaze, you can make a dull diamond sparkle using the power of your mind. In this animation, a striped diamond seems to twinkle when you track a circle moving back and forth within the shape. Created by psychology researcher Sebastiaan Mathôt of VU University in Amsterdam, the trick seems to be caused by poor estimation of what's happening in our peripheral vision. While focusing on the moving object, our brain only perceives a small part of the diamond shape. According to Mathôt, we expect to see the diamond's outline move perpendicular to the line due to a bias of our visual system. But when we move our gaze to the right, it confuses our brain, perhaps causing a compromise between the conflicting directions of motion that results in a sparkling effect along the line. The animation is a variation of the boogie-woogie illusion devised by psychologists Patrick Cavanagh and Stuart Anstis from Harvard University. © Copyright Reed Business Information Ltd.

Related chapters from BP6e: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 16430 - Posted: 02.25.2012

By LAURIE TARKAN For decades, scientists have looked for explanations as to why certain conditions occur with age, among them memory loss, slower reaction time, insomnia and even depression. They have scrupulously investigated such suspects as high cholesterol, obesity, heart disease and an inactive lifestyle. Now a fascinating body of research supports a largely unrecognized culprit: the aging of the eye. The gradual yellowing of the lens and the narrowing of the pupil that occur with age disturb the body’s circadian rhythm, contributing to a range of health problems, these studies suggest. As the eyes age, less and less sunlight gets through the lens to reach key cells in the retina that regulate the body’s circadian rhythm, its internal clock. “We believe the effect is huge and that it’s just beginning to be recognized as a problem,” said Dr. Patricia Turner, an ophthalmologist in Leawood, Kan., who with her husband, Dr. Martin Mainster, a professor of ophthalmology at the University of Kansas Medical School, has written extensively about the effects of the aging eye on health. Circadian rhythms are the cyclical hormonal and physiological processes that rally the body in the morning to tackle the day’s demands and slow it down at night, allowing the body to rest and repair. This internal clock relies on light to function properly, and studies have found that people whose circadian rhythms are out of sync, like shift workers, are at greater risk for a number of ailments, including insomnia, heart disease and cancer. © 2012 The New York Times Company

Related chapters from BP6e: Chapter 10: Vision: From Eye to Brain; Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 7: Vision: From Eye to Brain; Chapter 13: Memory, Learning, and Development
Link ID: 16406 - Posted: 02.21.2012

Caitlin Stier, video intern In this video game clip, it looks like Mario is jumping vertically while an enemy tortoise slides by underneath him. But keep watching when the background stops moving and you'll see that their movement is not quite what it seems. The animation, developed by cognitive psychologist Sebastiaan Mathôt from VU University in Amsterdam, is a variation of a common illusion where our perception of an object's motion is affected by a moving background. In a previous Friday Illusion post, we shared a video that exploits the same brain trick. Can you identify it? Let us know your choice by posting the headline in the Comments section below and the first correct answer will receive a New Scientist goodie bag. Good luck! © Copyright Reed Business Information Ltd.

Related chapters from BP6e: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 16392 - Posted: 02.18.2012

by Carl Zimmer There was no way the blind mice could see, yet somehow, they could. The year was 1923, and a Harvard grad student named Clyde Keeler had set out to compare eyes from different animals, starting with mice that he bred in his dorm room. Keeler cut open one mouse’s eye and put it under a microscope. Immediately he realized something was wrong. Missing from the eye was the layer of rods and cones, the photoreceptors that catch light. Turning back to his colony, Keeler realized that half of his animals were blind. Somehow a mutation had arisen, wiping out their rods and cones. The mutation had blinded those mice with surgical precision, yet for reasons lost to history, Keeler got the strange idea to shine a light in their eyes anyway. Based on everything that scientists knew about mammalian eyes, nothing should have happened. After all, the mice had no way to capture light and relay it to the retinal ganglion cells, the neurons that normally pass visual signals on to the brain. And yet something did happen: The mouse pupils shrank. Keeler struggled to find an explanation. “We may suppose that a rodless mouse will not see in the ordinary sense,” he wrote in one journal article. But for pupils to shrink, such mice had to have some kind of cell besides rods and cones—one that scientists knew nothing about—that could also capture light and send a signal to the brain. Most vision experts scoffed at the notion that the eyes contained hidden sensory cells and ignored Keeler’s findings. It took nearly eight decades for scientists to investigate his claim and prove him right: The eye really does contain a third type of photoreceptor cells that sense light intensity without detecting images. Kalmbach Publishing Co. Copyright © 2012,

Related chapters from BP6e: Chapter 10: Vision: From Eye to Brain; Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 7: Vision: From Eye to Brain; Chapter 10: Biological Rhythms and Sleep
Link ID: 16386 - Posted: 02.16.2012

by Catherine de Lange In an unlikely marriage of quantum physics and neuroscience, tiny particles called quantum dots have been used to control brain cells for the first time. Having such control over the brain could one day provide a non-invasive treatment for conditions such as Alzheimer's disease, depression and epilepsy. In the nearer term, quantum dots could be used to treat blindness by reactivating damaged retinal cells. "Many brain disorders are caused by imbalanced neural activity," says Lih Lin at the University of Washington, Seattle. "Manipulation of specific neurons could permit the restoration of normal activity levels." Methods to stimulate the brain artificially already exist, though each has its drawbacks. Deep brain stimulation is used in Parkinson's disease to trigger brain cell activity and prevent the abnormal signalling that causes debilitating tremors, but placing the electrodes required is highly invasive. Transcranial magnetic stimulation can stimulate brain cells from outside the head, but is not highly targeted and so affects large areas of the brain at once. Researchers in optogenetics can control genetically modified brain cells using light but because of these modifications, the technique is not yet deemed safe to use in humans. Lin's team has now come up with an alternative using quantum dots – light-sensitive, semiconducting particles just a few nanometres in diameter. © Copyright Reed Business Information Ltd.

Related chapters from BP6e: Chapter 3: Neurophysiology: The Generation, Transmission, and Integration of Neural Signals; Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 3: Neurophysiology: The Generation, Transmission, and Integration of Neural Signals; Chapter 7: Vision: From Eye to Brain
Link ID: 16382 - Posted: 02.16.2012

Caitlin Stier, video intern You may want to get your rulers out: although this oversized chessboard seems to slant when animated, its rows and columns are always perfectly parallel. The animation, developed by Sinji Nonaka, tricks your brain when alternating rows are shifted horizontally or vertically, skewing the grid pattern. The unusual effect was discovered by a member of vision researcher Richard Gregory's team as he looked at the brick tiling of a Bristol café in the 1970s. Gregory was inspired to recreate the design for a party organised by the BBC TV programme Tomorrow's World. But during the process he made a key discovery: the illusion was dependent on the shade of the mortar between the rows. To test the effect, Gregory worked with Priscilla Heard, now at the University of the West of England, to develop a customisable version of the wall using reflective surfaces, adjustable lights and moving tiles. By varying the brightness of the mortar, they found that it had to fall in between the contrast of the black and white tiles for the effect to occur. A thinner lining also produced steeper slopes. But in addition to the brightness of gaps between rows, the offset of the chessboard is also responsible for the effect. The shift causes like-shaded squares to overlap which affects the perceived brightness of the tiny space in between. The gap appears to be lighter for two dark squares and darker where white ones meet, causing a striation that's processed by our brain as a single line indicating slope. © Copyright Reed Business Information Ltd.

Related chapters from BP6e: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 16370 - Posted: 02.11.2012

Caitlin Stier, video intern The animation, created by Douglas Reedy of Dublin, Ohio, is based on a static illusion developed by Baingio Pinna from the University of Sassari in Italy and Lothar Spillmann from University Hospital Freiberg in Germany. The illusion is created due to the tilt of tiny squares that make up the outline of each circle. When they lean in opposite directions in alternating rings, a spiral is perceived. Tweaking their angle of inclination creates a spiral with a different orientation. The squares in a circle also alternate in colour, which seems to intensify the effect compared to the same pattern in a uniform colour. When the squares are shifted upright, the illusion vanishes. The effect is stronger at the edges of your gaze compared to the center, which gives insight into how it works. Alvin Raj from the Perceptual Science Group at MIT and his team have been investigating the phenomenon by testing a denser version of the illusion with more squares and rings. Raj suggests that the way we size up the image in our peripheral vision causes a calculation error that accounts for the perceived swirl. "Some of the strange things you see might be a by-product of your visual system losing some information and trying to make the best of it," explains collaborator Benjamin Balas of North Dakota State University. © Copyright Reed Business Information Ltd.

Related chapters from BP6e: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 16338 - Posted: 02.04.2012

by Michael Marshall For most of us, blurry vision is a bad thing, if only because it means we're going to have to spend a lot of money on a new pair of glasses. For one jumping spider, though, it's how it catches dinner. Adanson's house jumper, as the name implies, is a jumping spider. It springs on unsuspecting prey insects from several centimetres away and swiftly dispatches them. To pull off these leaps, it has to be an excellent judge of distance. And for that, paradoxically, it has part of its visual field permanently out of focus. It's the only animal known to judge distance in this way. Stalk, jump and bite The Adanson's house jumper is a cosmopolitan species – meaning it lives all over the place. It hunts during the day, pouncing on insects and other prey, although like many jumping spiders it may also take the occasional drink of nectar. To cope with its agile lifestyle, it must have excellent eyesight. How it works is not obvious, though. Lab tests have shown that it has top-class colour vision, but that doesn't help it judge distance. Other animals have all sorts of ways to work out how far away an object is, the most obvious being simply to have two eyes with overlapping fields of vision and compare what they see. © Copyright Reed Business Information Ltd.

Related chapters from BP6e: Chapter 10: Vision: From Eye to Brain; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 16308 - Posted: 01.28.2012

By ANDREW POLLACK LOS ANGELES — A treatment for eye diseases that is derived from human embryonic stem cells might have improved the vision of two patients, bolstering the beleaguered field, researchers reported Monday. The report, published online in the medical journal The Lancet, is the first to describe the effect on patients of a therapy involving human embryonic stem cells. The paper comes two months after the Geron Corporation cast a pall over the field by abruptly halting the world’s first clinical trial based on embryonic stem cells — one aimed at treating spinal cord injury. Geron, which has not published results from the aborted trial, also said it would abandon the entire stem cell field. The results reported Monday could help lift some of that pall. They come from the second clinical trial involving the stem cells, using a therapy developed by Advanced Cell Technology to treat macular degeneration, a leading cause of blindness. “It’s a big step forward for regenerative medicine,” said Dr. Steven D. Schwartz, a retina specialist at the University of California, Los Angeles, who treated the two patients. Both patients, who were legally blind, said in interviews that they had gains in eyesight that were meaningful for them. One said she could see colors better and was able to thread a needle and sew on a button for the first time in years. The other said she was able to navigate a shopping mall by herself. © 2012 The New York Times Company

Related chapters from BP6e: Chapter 10: Vision: From Eye to Brain; Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 7: Vision: From Eye to Brain; Chapter 13: Memory, Learning, and Development
Link ID: 16292 - Posted: 01.24.2012

by Andy Coghlan It is the light we think we see that counts. Optical illusions designed to seem brighter than they are make your pupils constrict a little more. This suggests that we have evolved systems for anticipating dazzling light to protect our eyes. Our pupils' fast response to light appears to occur even without input from the brain. For example, it is seen in people with damage to the visual cortex. Appearances can be deceptive, though. Bruno Laeng of the University of Oslo in Norway measured tiny changes in pupil size as volunteers viewed various illusions that were all identical in brightness, though did not look so. If light levels alone dictated pupil size, they would have reacted identically whichever image a person viewed. Instead, people's pupils constricted more when they viewed the illusions designed to appear brightest. "What's surprising is that even something as simple as how bright we think our environment is will be affected by our expectations," says Stuart Peirson of the University of Oxford, who was not involved in the study. Previous studies show that the brain controls pupil size in other situations: our pupils dilate when we make decisions, for instance. Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1118298109 © Copyright Reed Business Information Ltd.

Related chapters from BP6e: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 16291 - Posted: 01.24.2012

Caitlin Stier, video intern Want to freeze an object using the power of your mind? Watch the spinning objects in this video and they will suddenly appear to stop moving. However, they never actually freeze and are constantly turning at a steady rate. The illusion, created by researcher Max Dürsteler from University Hospital Zurich, uses a swaying background to trick our perception. When it rotates faster than the object in the foreground, and in the same direction, the object seems to slow down. But when the background moves in the opposite direction, the figure in the middle appears to speed up. In the first two examples, the background is distinct from the image on top of it. But in a third clip, the rotating figure blends in with the background, making the illusion more pronounced. In a final example, where background and foreground are contrasting once again, the backdrop rotates at a constant rate while the central figure sways back and forth. With this role reversal, the illusion is lost. While researchers are still investigating how this illusion works, Dürsteler suspects that our brain has a bias towards seeing objects as stationary. Motion is usually perceived in one of three states: either in or out of sync with its surroundings or stationary in relation to the observer The brain trick won the Best Illusion of the Year contest in 2006. © Copyright Reed Business Information Ltd.

Related chapters from BP6e: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 16275 - Posted: 01.21.2012