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By Jonathan Webb Science reporter, BBC News, San Antonio Physicists have pinned down precisely how pipe-shaped cells in our retina filter the incoming colours. These cells, which sit in front of the ones that actually sense light, play a major role in our colour vision that was only recently confirmed. They funnel crucial red and green light into cone cells, leaving blue to spill over and be sensed by rod cells - which are responsible for our night vision. Key to this process, researchers now say, is the exact shape of the pipes. The long, thin cells are known as "Muller glia" and they were originally thought to play more of a supporting role in the retina. They clear debris, store energy and generally keep the conditions right for other cells - like the rods and cones behind them - to turn light into electrical signals for the brain. But a study published last year confirmed the idea, proposed in earlier simulations, that Muller cells also function rather like optical fibres. 3D scans revealed the pipe-like structure of the Muller cells (in red) sitting above the photoreceptor cells (in blue) 3D scans revealed the pipe-like structure of the Muller cells (in red) sitting above the photoreceptor cells (in blue) And more than just piping light to the back of the retina, where the rods and cones sit, they selectively send red and green light - the most important for human colour vision - to the cone cells, which handle colour. Meanwhile, they leave 85% of blue light to spill over and reach nearby rod cells, which specialise in those wavelengths and give us the mostly black-and-white vision that gets us by in dim conditions. © 2015 BBC.
|By Dina Fine Maron Obesity stems primarily from the overconsumption of food paired with insufficient exercise. But this elementary formula cannot explain how quickly the obesity epidemic has spread globally in the past several decades nor why more than one third of adults in the U.S. are now obese. Many researchers believe that a more complex mix of environmental exposures, lifestyle, genetics and the microbiome’s makeup help explain that phenomenon. And a growing body of work suggests that exposure to certain chemicals—found in nature as well as industry—may play an essential role by driving the body to produce and store surplus fat in its tissues. Evidence of that cause-and-effect relationship in humans is still limited, but in laboratory animals and in petri dishes data linking the chemicals to problematic weight gain are mounting. Moreover, the effects in animals appear to be passed on not just to immediate offspring but also grandchildren and great-grandchildren—potentially accounting for some multigenerational obesity. The murkier picture for humans may become clearer in the next five years, says Jerry Heindel, a health science administrator at the National Institute of Environmental Health Sciences. His agency is now funding 57 grants related to obesity and diabetes, he said on March 2 at a meeting of the Institute of Medicine (IOM). The studies look at how chemicals, including those that appear to alter hormone regulation (such as the plasticizer bisphenol A and the antibacterial chemical triclosan), affect weight gain or insulin resistance. Thirty-two of the ongoing studies are in humans. And 20 of those will help assess the longer-term risks to children by tracking the youngsters' chemical levels in utero or as newborns and beyond. © 2015 Scientific American
Link ID: 20660 - Posted: 03.07.2015
Dr. Lisa Sanders. On Thursday we challenged Well readers to solve the case of a middle-aged woman with arthritis who developed a wasting illness after what looked like a simple cold. Her rheumatologist was worried that the immune suppressing medications the patient took to treat her joint disease had caused the new illness. More than 300 of you took on the challenge, and 17 of you correctly identified this rarity. The correct diagnosis is … Whipple’s disease The first reader to make the diagnosis was Mike Natter, a second-year medical student at the Sidney Kimmel Medical College at Thomas Jefferson University in Philadelphia. Mike said it was an easy case for him because he had been studying for an exam the next day and had just read about the disease. He is a frequent contributor to this column and says that he got the right diagnosis twice before but this was the first time he got it in first. Well done, Mike! The Diagnosis Whipple’s was first identified in 1907 by Dr. George Whipple, who was caring for a fellow physician who had “gradual loss of weight and strength, stools consisting chiefly of neutral fat and fatty acids, indefinite abdominal signs, and a peculiar multiple arthritis.” The patient eventually died. Dr. Whipple suspected an infectious cause because he found bacteria in many of the patient’s affected tissues, but the organism itself wasn’t identified for nearly 80 years. The bug, Tropheryma whipplei, is common and found mostly in soil. And yet the infection is rare. There have been only about 1,000 reported cases of Whipple’s disease in the more than one hundred years since it was first described. Over two-thirds of those were in middle-aged white men. Many of them were farmers or others who had occupational exposure to soil. © 2015 The New York Times Company
Link ID: 20659 - Posted: 03.07.2015
By David Masci Potential Republican presidential candidate Dr. Ben Carson made news earlier this week when he said that being gay is a “choice,” but when it comes to public opinion, polls show that Americans remain divided over whether “nature” or “nurture” is ultimately responsible for sexual orientation. Four-in-ten Americans (42%) said that being gay or lesbian is “just the way some choose to live,” while a similar share (41%) said that “people are born gay or lesbian,” according to the most recent Pew Research Center poll on the issue, conducted in 2013. Fewer U.S. adults (8%) said that people are gay or lesbian due to their upbringing, while another one-in-ten (9%) said they didn’t know or declined to give a response. People with the most education are the most likely to say that gays and lesbians were born that way. Indeed, 58% of Americans with a postgraduate degree say that people are born gay or lesbian, compared with just 35% of those with a high school diploma or less. The percentage of all Americans who believe that people are born gay or lesbian has roughly doubled (from 20% to 41%) since 1985, when the question was asked in a Los Angeles Times survey. More than three decades of Gallup polls also show a considerable rise in the view that being gay or lesbian is a product of “nature” rather than “nurture.” But the most recent survey, in 2014, still finds that the nation remains split in its feelings on the origins of sexual orientation. Copyright 2015 Pew Research Center
Keyword: Sexual Behavior
Link ID: 20658 - Posted: 03.07.2015
In Archaeology it is very rare to find any soft tissue remains: no skin, no flesh, no hair and definitely no brains. However, in 2009, archaeologists from York Archaeological Trust found something very surprising at a site in Heslington, York. During the excavation of an Iron-age landscape at the University of York, a skull, with the jaw and two vertebrae still attached, was discovered face down in a pit, without any evidence of what had happened to the rest of its body. At first it looked like a normal skull but it was not until it was being cleaned, that Collection Projects Officer, Rachel Cubitt, discovered something loose inside. “I peered though the hole at the base of the skull to investigate and to my surprise saw a quantity of bright yellow spongy material. It was unlike anything I had seen before.” says Rachel. Sonia O’Connor, from Archaeological Sciences, University of Bradford, was able to confirm that this was brain. With the help of York Hospital’s Mortuary they were able to remove the top of the skull in order to get their first look at this astonishingly well-preserved human brain. Since the discovery, a team of 34 specialists have been working on this brain to study and conserve it as much as possible. By radiocarbon dating a sample of jaw bone, it was determined that this person probably lived in the 6th Century BC, which makes this brain about 2,600 years old. By looking at the teeth and the shape of the skull it is likely this person was a man between 26 and 45 years old. An examination of the vertebrae in the neck tells us that he was first hit hard on the neck, and then the neck was severed with a small sharp knife, for reasons we can only guess. © Copyright York Archaeological Trust 2013-2015.
Keyword: Brain imaging
Link ID: 20657 - Posted: 03.07.2015
Hannah Devlin, science correspondent Psychedelic drugs could prove to be highly effective treatments for depression and alcoholism, according to a study which has obtained the first brain scans of people under the influence of LSD. Early results from the trial, involving 20 people, are said to be “very promising” and add to existing evidence that psychoactive drugs could help reverse entrenched patterns of addictive or negative thinking. However, Prof David Nutt, who led the study, warned that patients are missing out on the potential benefits of such treatments due to prohibitive regulations on research into recreational drugs. Speaking at a briefing in London, the government’s former chief drugs adviser, said the restrictions amounted to “the worst censorship in the history of science”. After failing to secure conventional funding to complete the analysis of the latest study on LSD, Nutt and colleagues at Imperial College London, are now attempting to raise £25,000 through the crowd-funding site Walacea.com. “These drugs offer the greatest opportunity we have in mental health,” he said. “There’s little else on the horizon.” There has been a resurgence of medical interest in LSD and psilocybin, the active ingredient in magic mushrooms, after several recent trials produced encouraging results for conditions ranging from depression in cancer patients to post-traumatic stress disorder. © 2015 Guardian News and Media Limited
Zoe Cormier Data from population surveys in the United States challenge public fears that psychedelic drugs such as LSD can lead to psychosis and other mental-health conditions and to increased risk of suicide, two studies have found1, 2. In the first study, clinical psychologists Pål-Ørjan Johansen and Teri Suzanne Krebs, both at the Norwegian University of Science and Technology in Trondheim, scoured data from the US National Survey on Drug Use and Health (NSDUH), an annual random sample of the general population, and analysed answers from more than 135,000 people who took part in surveys from 2008 to 2011. Of those, 14% described themselves as having used at any point in their lives any of the three ‘classic’ psychedelics: LSD, psilocybin (the active ingredient in so-called magic mushrooms) and mescaline (found in the peyote and San Pedro cacti). The researchers found that individuals in this group were not at increased risk of developing 11 indicators of mental-health problems such as schizophrenia, psychosis, depression, anxiety disorders and suicide attempts. Their paper appears in the March issue of the Journal of Psychopharmacology1. The findings are likely to raise eyebrows. Fears that psychedelics can lead to psychosis date to the 1960s, with widespread reports of “acid casualties” in the mainstream news. But Krebs says that because psychotic disorders are relatively prevalent, affecting about one in 50 people, correlations can often be mistaken for causations. “Psychedelics are psychologically intense, and many people will blame anything that happens for the rest of their lives on a psychedelic experience.” © 2015 Nature Publishing Group,
by Jan Piotrowski It's not the most charismatic fossil ever found, but it may reveal secrets of our earliest evolution. Unearthed in Ethiopia, the broken jaw with greying teeth suggests that the Homo lineage – of which modern humans are the only surviving member – existed up to 400,000 years earlier than previously thought. The fragment dates from around 2.8 million years ago, and is by far the most ancient specimen to bear the Homo signature. The earliest such fossil was one thought to be up to 2.4 million years ages old. Showing a mixture of traits, the new find pinpoints the time when humans began their transition from primitive, apelike Australopithecus to the big-brained conquerer of the world, says Brian Villmoare from the University of Nevada, Las Vegas, whose student made the find. Geological evidence from the same area, also reported this week in a study led by Erin DiMaggio from Pennsylvania State University, shows that the jaw's owner lived just after a major climate shift in the region: forests and waterways rapidly gave way to arid savannah, leaving only the occasional crocodile-filled lake. Except for the sabre-toothed big cat that once roamed these parts, the environment ended up looking much like it does today. It was probably the pressure to adapt to this new world that jump-started our evolution into what we see looking back at us in the mirror today, according to Villmoare. © Copyright Reed Business Information Ltd.
Link ID: 20654 - Posted: 03.05.2015
Loss of sensation in the eye that gradually leads to blindness has been prevented with an innovative technique, Canadian surgeons say. Abby Messner, 18, of Stouffville, Ont., lost feeling in her left eye after a brain tumour was removed, along with a nerve wrapped around it, when she was 11. Messner said she didn’t notice the loss of feeling until she scratched the eye. Messner wasn’t able to feel pain in the eye, a condition called corneal anaesthesia. Despite her meticulous care, the eye wouldn’t blink to protect itself when confronted by dust. A scar formed on her cornea, burrowed through, and formed a scar doctors feared would eventually obliterate her vision. "Everyone was like, 'Wow, she had a brain tumour and she’s fine," Messner recalled. "You don't really think that everything that is holding me back is my eye." Messner had to give up competitive swimming because of irritation from the chlorine, playing hockey, spending time outdoors where wind was a hazard or inside dry shopping malls. Over time, ophthalmology surgeon Dr. Asam Ali at SickKids introduced the idea of a nerve graft to restore feeling in the eye. "She started getting feeling back at about the two, three-month mark and that was a real surprise to her and we were very happy at that point because that was a lot faster than anything that had been reported before," Ali said. ©2015 CBC/Radio-Canada.
By Will Boggs MD NEW YORK (Reuters Health) - Adolescents with a history of childhood trauma show different neural responses to subjective anxiety and craving, researchers report. "I think the finding of increased activation of insula, anterior cingulate, and prefrontal cortex in response to stress cues in the high- relative to low-trauma group, while arguably not necessarily unexpected, is important as it suggests that youth exposed to higher levels of trauma may experience different brain responses to similar stressors," Dr. Marc N. Potenza from Yale University, New Haven, Connecticut told Reuters Health by email. Childhood trauma has been associated with anxiety and depression, as well as obesity, risky sexual behavior, and substance use. Previous imaging studies have not investigated neural responses to personalized stimuli, Dr. Potenza and his colleagues write in Neuropsychopharmacology, online January 8. The team used functional MRI to assess regional brain activations to personalized appetitive (favorite food), aversive (stress), and neutral/relaxing cues in 64 adolescents, including 33 in the low-trauma group and 31 in the high-trauma group. Two-thirds of the adolescents had been exposed to cocaine prenatally, with prenatal cocaine exposure being significantly over-represented in the high-trauma group. Compared with the low-trauma group, the high-trauma group showed increased responsivity in several cortical regions in response to stress, as well as decreased activation in the cerebellar vermis and right cerebellum in response to neutral/relaxing cues. But the two groups did not differ significantly in their responses to favorite-food cues, the researchers found. © 2015 Scientific American
Alison Abbott Europe’s ambitious but contentious €1-billion Human Brain Project (HBP) has announced changes to its organization in a response to criticisms of its management and scientific trajectory by many high-ranking neuroscientists. On 26 February, the HBP's Board of Directors voted narrowly to disband the three-person executive committee that had run the project, which launched in October 2013 and is intended to boost digital technologies such as supercomputing through collaboration with neuroscience. That decision is expected to be endorsed by HBP’s 85 or so partner universities and research institutes by the end of this week. The revamp comes seven months after 150 top neuroscientists signed a protest letter to the European Commission, charging, among other things, that the committee was acting autocratically and running the project's scientific plans off course. Led by the charismatic but divisive figure of Henry Markram, a neuroscientist at the Swiss Federal Institute of Technology in Lausanne (EPFL) which coordinates the HBP, the committee had stirred up anger last spring when it revealed plans to cut cognitive neuroscience from the initiative. The neuroscientists vowed to boycott the HBP's future phases if their concerns were ignored. An independent mediation committee was established to look into the charges and make recommendations. Its report, which is expected to further shake up the HBP's management, will be published in the next few weeks. In the meantime, the three-person committee's responsibilities will be taken on by the HBP's Board of Directors (currently a 22-strong team of scientists that includes the disbanded executive committee, although they do not have voting rights). © 2015 Nature Publishing Group
Keyword: Brain imaging
Link ID: 20651 - Posted: 03.05.2015
Children who attend school in heavy traffic areas may show slower cognitive development and lower memory test scores, Spanish researchers have found. About 21,000 premature deaths are attributed to air pollution in Canada each year, according to the Canadian Medical Association. The detrimental effects of air pollution on cardiovascular health and on the lungs are well documented and now researchers are looking at its effects on the brain. To that end, Dr. Jordi Sunyer and his colleagues from the Centre for Research in Environmental Epidemiology in Barcelona measured three aspects of memory and attentiveness in more than 2,700 primary school children every three months over 12 months. "What was surprising for us is among our children, we see very robust, consistent effects," Sunyer said Tuesday from Rome. The associations between slower cognitive development and higher levels of air pollutants remained after the researchers took factors such as parents’ education, commuting time, smoking in the home and green spaces at school into account. The researchers measured air pollutants from traffic twice, in the school courtyard and inside the classroom for schools with high and low traffic-related air pollution. Pollutants from burning fossil fuels, carbon, nitrogen dioxide and ultrafine particles were measured. For example, working memory improved 7.4 per cent among children in highly polluted schools compared with 11.5 per cent among those in less polluted schools. ©2015 CBC/Radio-Canada.
Lights, sound, action: we are constantly learning how to incorporate outside sensations into our reactions in specific situations. In a new study, brain scientists have mapped changes in communication between nerve cells as rats learned to make specific decisions in response to particular sounds. The team then used this map to accurately predict the rats’ reactions. These results add to our understanding of how the brain processes sensations and forms memories to inform behavior. “We’re reading the memories in the brain,” said Anthony Zador, M.D., Ph.D., professor at Cold Spring Harbor Laboratory, New York, and senior author of the study, published in Nature. The work was funded by the National Institutes of Health and led by Qiaojie Xiong, Ph.D., a former postdoctoral researcher in Dr. Zador’s laboratory. “For decades scientists have been trying to map memories in the brain,” said James Gnadt, Ph.D., a program director at the National Institute of Neurological Disorders and Stroke (NINDS), one of the NIH institutes that funded the study. “This study shows that scientists can begin to pinpoint the precise synapses where certain memories form and learning occurs.” The communication points, or synapses, that Dr. Zador’s lab studied were in the striatum, an integrating center located deep inside the brain that is known to play an important role in coordinating the translation of thoughts and sensations into actions. Problems with striatal function are associated with certain neurological disorders such as Huntington’s disease in which affected individuals have severely impaired skill learning.
By Nicholas Bakalar Gout, a form of arthritis, is extremely painful and associated with an increased risk for cardiovascular problems. But there is a bright side: It may be linked to a reduced risk for Alzheimer’s disease. Researchers compared 59,204 British men and women with gout to 238,805 without the ailment, with an average age of 65. Patients were matched for sex, B.M.I., smoking, alcohol consumption and other characteristics. The study, in The Annals of the Rheumatic Diseases, followed the patients for five years. They found 309 cases of Alzheimer’s among those with gout and 1,942 among those without. Those with gout, whether they were being treated for the condition or not, had a 24 percent lower risk of Alzheimer’s disease. The reason for the connection is unclear. But gout is caused by excessive levels of uric acid in the blood, and previous studies have suggested that uric acid protects against oxidative stress. This may play a role in limiting neuron degeneration. “This is a dilemma, because uric acid is thought to be bad, associated with heart disease and stroke,” said the senior author, Dr. Hyon K. Choi, a professor of medicine at Harvard. “This is the first piece of data suggesting that uric acid isn’t all bad. Maybe there is some benefit. It has to be confirmed in randomized trials, but that’s the interesting twist in this story.” © 2015 The New York Times Company
By Abby Phillip Jan Scheuermann, who has quadriplegia, brings a chocolate bar to her mouth using a robot arm guided by her thoughts. Research assistant Elke Brown watches in the background. (University of Pittsburgh Medical Center) Over at the Defense Advanced Research Projects Agency, also known as DARPA, there are some pretty amazing (and often top-secret) things going on. But one notable component of a DARPA project was revealed by a Defense Department official at a recent forum, and it is the stuff of science fiction movies. According to DARPA Director Arati Prabhakar, a paralyzed woman was successfully able use her thoughts to control an F-35 and a single-engine Cessna in a flight simulator. It's just the latest advance for one woman, 55-year-old Jan Scheuermann, who has been the subject of two years of groundbreaking neurosignaling research. First, Scheuermann began by controlling a robotic arm and accomplishing tasks such as feeding herself a bar of chocolate and giving high fives and thumbs ups. Then, researchers learned that -- surprisingly -- Scheuermann was able to control both right-hand and left-hand prosthetic arms with just the left motor cortex, which is typically responsible for controlling the right-hand side. After that, Scheuermann decided she was up for a new challenge, according to Prabhakar.
Link ID: 20647 - Posted: 03.04.2015
Tristram Wyatt This Valentine’s Day, like every year, there was a rash of stories in the news about sexy smells and pheromones. You could be forgiven for thinking that human ‘sex pheromones’, in particular the ‘male molecule’ androstadienone, were well established: countless ‘human pheromones’ websites sell it and there are tens of apparently scientific studies on androstadienone published in science journals. These studies are cited hundreds of times and have ended up being treated as fact in books on sexual medicine and even commentary on legislation. The birth place of the pheromone myth was a 1991 conference in Paris sponsored by a US corporation, EROX, which had an interest in patenting androstadienone and another molecule - estratetraenol, from women - as ‘human pheromones’. Unwittingly, leading mammalian olfaction scientists lent the conference credibility. Slotted into the programme and conference proceedings was the short ‘study-zero’ paper on the ‘Effect of putative pheromones on the electrical activity of the human vomeronasal organ and olfactory epithelium’. To my surprise, the authors gave no details at all of how these molecules had been extracted, identified, and tested in bioassays - all routinely required steps in the exhaustive process before any molecule can be shown to be a species-wide chemical signal, a pheromone. Instead there was just a footnote: ‘These putative pheromones were supplied by EROX Corporation’. The missing, essential details were never published. (The claim by EROX-sponsored scientists that adult humans have a functioning vomeronasal organ, against all the evidence, is a story for another day). © 2015 Guardian News and Media Limited
by Catherine de Lange You won't believe you do it, but you do. After shaking hands with someone, you'll lift your hands to your face and take a deep sniff. This newly discovered behaviour – revealed by covert filming – suggests that much like other mammals, humans use bodily smells to convey information. We know that women's tears transmit chemosensory signals - their scent lowers testosterone levels and dampens arousal in men - and that human sweat can transmit fear. But unlike other mammals, humans don't tend to go around sniffing each other. Wondering how these kinds of signals might be exchanged, Noam Sobel and his colleagues at the Weizmann Institute of Science in Rehovot, Israel turned to one of the most common ways in which people touch each other - shaking hands. "We started looking at people and noticed that afterwards, the hand somehow inadvertently reached the face," says Sobel. To find out if people really were smelling their hands, as opposed to scratching their nose, for example, his team surreptitiously filmed 153 volunteers. Some were wired up to a variety of physiological instruments so that airflow to the nose could be measured without them realising this was the intention. The volunteers were filmed as they greeted a member of the team, either with or without a handshake. The researchers recorded how often the volunteers lifted their hands close to their nose, and how long they kept them there, the minute before and after the greeting. © Copyright Reed Business Information Ltd.
Keyword: Chemical Senses (Smell & Taste)
Link ID: 20645 - Posted: 03.04.2015
|By Charles Schmidt The notion that the state of our gut governs our state of mind dates back more than 100 years. Many 19th- and early 20th-century scientists believed that accumulating wastes in the colon triggered a state of “auto-intoxication,” whereby poisons emanating from the gut produced infections that were in turn linked with depression, anxiety and psychosis. Patients were treated with colonic purges and even bowel surgeries until these practices were dismissed as quackery. The ongoing exploration of the human microbiome promises to bring the link between the gut and the brain into clearer focus. Scientists are increasingly convinced that the vast assemblage of microfauna in our intestines may have a major impact on our state of mind. The gut-brain axis seems to be bidirectional—the brain acts on gastrointestinal and immune functions that help to shape the gut's microbial makeup, and gut microbes make neuroactive compounds, including neurotransmitters and metabolites that also act on the brain. These interactions could occur in various ways: microbial compounds communicate via the vagus nerve, which connects the brain and the digestive tract, and microbially derived metabolites interact with the immune system, which maintains its own communication with the brain. Sven Pettersson, a microbiologist at the Karolinska Institute in Stockholm, has recently shown that gut microbes help to control leakage through both the intestinal lining and the blood-brain barrier, which ordinarily protects the brain from potentially harmful agents. Microbes may have their own evolutionary reasons for communicating with the brain. They need us to be social, says John Cryan, a neuroscientist at University College Cork in Ireland, so that they can spread through the human population. © 2015 Scientific American
By Roni Caryn Rabin When my mother, Pauline, was 70, she lost her sense of balance. She started walking with an odd shuffling gait, taking short steps and barely lifting her feet off the ground. She often took my hand, holding it and squeezing my fingers. Her decline was precipitous. She fell repeatedly. She stopped driving, and she could no longer ride her bike in a straight line along the C&O Canal. The woman who taught me the sidestroke couldn’t even stand in the shallow end of the pool. “I feel like I’m drowning,” she’d say. A retired psychiatrist, my mother had numerous advantages — education, resources and insurance — but, still, getting the right diagnosis took nearly 10 years. Each expert saw the problem through the narrow prism of a single specialty. Surgeons recommended surgery. Neurologists screened for common incurable conditions. The answer was under their noses, in my mother’s hunches and her family history. But it took a long time before someone connected the dots. My mother was using a walker by the time she was told she had a rare condition that causes gait problems and cognitive loss, and is one of the few treatable forms of dementia. The bad news was that it had taken so long to get the diagnosis that some of the damage might not be reversible. “This should be one of the first things physicians look for in an older person,” my mother said recently. “You can actually do something about it.”
Link ID: 20643 - Posted: 03.03.2015
By Felicity Muth Visual illusions are fun: we know with our rational mind that, for example, these lines are parallel to each other, yet they don’t appear that way. Similarly, I could swear that squares A and B are different colours. But they are not. This becomes clearer when a connecting block is drawn between the two squares (see the image below). Illusions aren’t just fun tricks for us to play with, they can also tell us something about our minds. Things in the world look to us a certain way, but that doesn’t mean that they are that way in reality. Rather, our brain represents the world to us in a particular way; one that has been selected over evolutionary time. Having such a system means that, for example, we can see some animals running but not others; we couldn’t see a mouse moving from a mile away like a hawk could. This is because there hasn’t been the evolutionary selective pressures on our visual system to be able to do such a thing, whereas there has on the hawk’s. We can also see a range of wavelengths of light, represented as particular colours in our brain, while not being able to see other wavelengths (that, for example, bees and birds can see). Having a system limited by what evolution has given us means that there are many things we are essentially blind to (and wouldn’t know about if it weren’t for technology). It also means that sometimes our brain misrepresents physical properties of the external world in a way that can be confusing once our rational mind realises it. Of course, all animals have their own representation of the world. How a dog visually perceives the world will be different to how we perceive it. But how can we know how other animals perceive the world? What is their reality? One way we can try to get this is through visual illusions. © 2015 Scientific American