Chapter 8. General Principles of Sensory Processing, Touch, and Pain
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By Arlene Karidis Several years ago, Peggy Chenoweth began having excruciating cramping in her ankle. It felt severely sprained and as if her toe were twisting to the point where it was being ripped off her foot. “The pain is right here,” she told an orthopedic surgeon, “in my ankle and foot.” But the 41-year-old Gainesville, Va., resident no longer had that ankle and foot. Her leg had been amputated below the knee after a large piece of computer equipment fell off a cart, crushed her foot and caused nerve damage. Further, she insisted that since the amputation, she could feel her missing toes move. Chenoweth’s surgeon knew exactly what was going on: phantom pain. Lynn Webster, an anesthesiologist and past president of the American Academy of Pain Medicine, explains the phenomenon: “With ‘phantom pain,’ nerves that transmitted information from the brain to the now-missing body part continue to send impulses, which relay the message of pain.” It feels as if the removed part is still there and hurting, but pain is actually in the brain. The sensation ranges from annoying itching to red-hot burning. Physicians wrote about phantom pain as early as the 1860s, but U.S. research on this condition has increased recently, spurred by the surge of amputees returning from warfare in Iraq and Afghanistan and by increasing rates of diabetes. (Since 2003, nearly 1,650 service members have lost limbs, according to the Congressional Research Service. In 2010, about 73,000 amputations were performed on diabetics in the United States, according to the Centers for Disease Control and Prevention.)
Keyword: Pain & Touch
Link ID: 21620 - Posted: 11.10.2015
By Jason G. Goldman When a monkey has the sniffles or a headache, it doesn't have the luxury of popping a few painkillers from the medicine cabinet. So how does it deal with the common colds and coughs of the wildlife world? University of Georgia ecologist Ria R. Ghai and her colleagues observed a troop of more than 100 red colobus monkeys in Uganda's Kibale National Park for four years to figure out whether the rain forest provides a Tylenol equivalent. Monkeys infected with a whipworm parasite were found to spend more time resting and less time moving, grooming and having sex. The infected monkeys also ate twice as much tree bark as their healthy counterparts even though they kept the same feeding schedules. The findings were published in September in the journal Proceedings of the Royal Society B. The fibrous snack could help literally sweep the intestinal intruder out of the simians' gastrointestinal tracts, but Ghai suspects a more convincing reason. Seven of the nine species of trees and shrubs preferred by sick monkeys have known pharmacological properties, such as antisepsis and analgesia. Thus, the monkeys could have been self-medicating, although she cannot rule out other possibilities. The sick individuals were, however, using the very same plants that local people use to treat illnesses, including infection by whipworm parasites. And that “just doesn't seem like a coincidence,” Ghai says. © 2015 Scientific American,
by Laura Sanders Babies’ minds are mysterious. Thoughts might be totally different in a brain that lacks words, and sensations might feel alien in a body so new. Are babies’ perceptions like ours, or are they completely different? Even if babies could talk, words would surely fail to convey what it’s like to experience, oh, every single thing for the first time. A recent paper offers a sliver of insight into young babies’ inner lives. The study, published October 19 in Current Biology, finds an example in which 4-month-old babies are happily oblivious to the external world. The research focuses on a perceptual trick that suckers adults and 6-month-old babies alike. When the hands are crossed, people often mistake which hand feels a touch. Let’s say your left hand (now crossed over to the right side of your body) gets a tickle. Your eyes would see a hand on the right side of your body get touched — a place usually claimed by your right hand, but now occupied by your left. Those mismatches between sight, touch and expectation can thwart you from quickly and correctly saying which hand was touched. Here’s the twist: 4-month-old babies don’t fall for this trick, Andrew Bremner of Goldsmiths, University of London and his colleagues found. In the experiment, a researcher would hold infants’ legs in either a crossed position or straight, while one of two remote-controlled buzzers taped to their feet tickled one foot. The researchers then watched which foot or leg wiggled as a result. If the buzzed foot moved, that meant that the baby got it right. © Society for Science & the Public 2000 - 2015.
David Cyranoski A Chinese neuroscientist has been sacked after reporting he had used magnetic fields to control neurons and muscle cells in nematode worms (pictured), using a protein that senses magnetism. Tsinghua University in Beijing has sacked a neuroscientist embroiled in a dispute over work on a long-sought protein that can sense magnetic fields. The university has not given a specific reason for its dismissal, however, and the scientist involved, Zhang Sheng-jia, says that he will contest their action. In September, Zhang reported in the journal Science Bulletin1 that he could manipulate neurons in worms by applying a magnetic field — a process that uses a magnetic-sensing protein. But a biophysicist at neighbouring Peking University, Xie Can, who claims to have discovered the protein’s magnetic-sensing capacity and to have a paper detailing his research under review, complained that Zhang should not have published his paper before Xie’s own work appeared. Xie said that by publishing, Zhang violated an agreement that the pair had reached — although the two scientists tell different versions about the terms of their agreement, and have different explanations of how Zhang came to be working with the protein. © 2015 Nature Publishing Group
Keyword: Animal Migration
Link ID: 21608 - Posted: 11.06.2015
By SINDYA N. BHANOO Some kinds of itching can be caused by the lightest of touches, a barely felt graze that rustles tiny hairs on the skin’s surface. This type of itch is created via a dedicated neural pathway, a new study suggests. The finding, which appears in the journal Science, could help researchers better understand chronic itchiness in conditions like eczema, diabetic neuropathy, multiple sclerosis and some cancers. The study also may help researchers determine why certain patients do not respond well to antihistamine drugs. “In the future, we may have some way to manipulate neuron activity to inhibit itching,” said Quifu Ma, a neurobiologist at Harvard University and one of the study’s authors. In the study, Dr. Ma and his colleagues inhibited neurons that express a neuropeptide known as Y or NPY in mice. When these neurons were suppressed and the mice were poked with a tiny filament, they fell into scratching fits. Normally, mice would not even respond to this sort of stimuli. “We start to see skin lesions — they don’t stop scratching,” Dr. Ma said. “It’s pretty traumatic.” The neurons only seem related to itches prompted by light touching, known as mechanically induced itches. Chemical itches, like those caused by a mosquito bite or an allergic reaction, are not transmitted by the same neurons. © 2015 The New York Times Company
Keyword: Pain & Touch
Link ID: 21593 - Posted: 11.03.2015
By Hanae Armitage Fake fingerprints might sound like just another ploy to fool the feds. But the world’s first artificial prints—reported today—have even cooler applications. The electronic material, which mimics the swirling designs imprinted on every finger, can sense pressure, temperature, and even sound. Though the technology has yet to be tested outside the lab, researchers say it could be key to adding sensation to artificial limbs or even enhancing the senses we already have. “It’s an interesting piece of work,” says John Rogers, materials scientist at the University of Illinois, Urbana-Champaign, who was not involved in the study. “It really adds to the toolbox of sensor types that can be integrated with the skin.” Electronic skins, known as e-skins, have been in development for years. There are several technologies used to mimic the sensations of real human skin, including sensors that can monitor health factors like pulse or temperature. But previous e-skins have been able to “feel” only two sensations: temperature and pressure. And there are additional challenges when it comes to replicating fingertips, especially when it comes to mimicking their ability to sense even miniscule changes in texture, says Hyunhyub Ko, a chemical engineer at Ulsan National Institute of Science and Technology in South Korea. So in the new study, Ko and colleagues started with a thin, flexible material with ridges and grooves much like natural fingerprints. This allowed them to create what they call a “microstructured ferroelectric skin” The e-skin’s perception of pressure, texture, and temperature all come from a highly sensitive structure called an interlocked microdome array—the tiny domes sandwiched in the bottom two layers of the e-skin, also shown in the figure below. © 2015 American Association for the Advancement of Science
Laura Sanders A fly tickling your arm hair can spark a maddening itch. Now, scientists have spotted nerve cells in mice that curb this light twiddling sensation. If humans possess similar itch-busters, the results, published in the Oct. 30 Science, could lead to treatments for the millions of people who suffer from intractable, chronic itch. For many of these people, there are currently no good options. “This is a major problem,” says clinician Gil Yosipovitch of Temple University School of Medicine in Philadelphia and director of the Temple Itch Center. The new study shows that mice handle an itch caused by a fluttery touch differently than other kinds of itch. This distinction “seems to have clinical applications that clearly open our field,” Yosipovitch says. In recent years, scientists have made progress teasing apart the pathways that carry itchy signals from skin to spinal cord to brain (SN: 11/22/2008, p. 16). But those itch signals often originate from chemicals, such as those delivered by mosquitoes. All that’s needed to spark a different sort of itch, called mechanical itch, is a light touch on the skin. The existence of this kind of itch is no surprise, Yosipovitch says. Mechanical itch may help explain why clothes or even dry, scaly skin can be itchy. The new finding came from itchy mice engineered to lack a type of nerve cell in their spinal cords. Without prompting, these mice scratched so often that they developed sore bald patches on their skin. © Society for Science & the Public 2000 - 2015
Keyword: Pain & Touch
Link ID: 21587 - Posted: 10.31.2015
Adam Cole Watch a scary movie and your skin crawls. Goose bumps have become so associated with fear that the word is synonymous with thrills and chills. But what on earth does scary have do to with chicken-skin bumps? For a long time, it wasn't well understood. Physiologically, it's fairly simple. Adrenaline stimulates tiny muscles to pull on the roots of our hairs, making them stand out from our skin. That distorts the skin, causing bumps to form. Call it horripilation, and you'll be right — bristling from cold or fear. Charles Darwin once investigated goose bumps by scaring zoo animals with a stuffed snake. He argued for the now accepted theory that goose bumps are a vestige of humanity's ancient past. Our ancestors were hairy. Goose bumps would have fluffed up their hair. When they were scared, that would have made them look bigger — and more intimidating to attackers. When they were cold, that would have trapped an insulating layer of air to keep them warm. We modern humans still get goose bumps when we're scared or cold, even though we've lost the advantage of looking scarier or staying warmer ourselves. And researchers have found that listening to classical music (or Phil Collins), seeing pictures of children or drinking a sour drink can also inspire goose bumps. There's clearly a link with emotion and reward, too. © 2015 npr
by Helen Thompson Five, six, seven, eight! All together now, let's spread those jazz hands and get moving, because synchronized dancing improves our tolerance of pain and helps us bond as humans, researchers suggest October 28 in Biology Letters. A team of psychologists at the University of Oxford taught high school students varied dance routines — each requiring different levels of exertion and synchronized movement — and then tested their pain tolerance with the sharp squeeze of a blood pressure cuff. Statistically, routines with more coordinated choreography and full body movement produced higher pain thresholds and sunny attitudes toward others in the group. Coordinated dancing with a group and exerting more energy may independently promote the release of pain-blocking endorphins as well as increase social bonding, the team writes. |© Society for Science & the Public 2000 - 2015
Keyword: Pain & Touch
Link ID: 21575 - Posted: 10.28.2015
Mr Tickle can’t bamboozle a baby. Unlike grown-ups, young infants don’t let the positioning of their bodies confuse their sense of touch. If adults who can see are touched on each hand in quick succession while their hands are crossed, they can find it hard to name which hand was touched first. Adults who have been blind from birth don’t have this difficulty, but people who become blind later in life have the same trouble as those who can still see. “That suggests that early on in life, something to do with visual experience is crucial in setting up a typical way of perceiving touch,” says Andrew Bremner at Goldsmiths, University of London. To investigate how this develops in infancy, Bremner and his colleagues compared how babies reacted to having one foot tickled. With their legs crossed over, babies aged 6 months moved the foot being tickled half of the time. But 4-month-olds did better, moving the tickled foot 70 per cent of the time – as often as they did with their legs uncrossed. The team concludes that at 4 months, babies haven’t yet learned to relate what they touch to the physical space that their body occupies. For many adults, the concept might be difficult to envision. “It’s like imagining that you feel a touch on your body, but not really knowing how that’s related to what you’re looking at,” says Bremner. “It’s almost like you have multiple sensory worlds: a visual world, an auditory world and a tactile world, which are separate and not combined in space.” © Copyright Reed Business Information Ltd.
By Robert F. Service Prosthetic limbs may work wonders for restoring lost function in some amputees, but one thing they can’t do is restore an accurate sense of touch. Now, researchers report that one day in the not too distant future, those artificial arms and legs may have a sense of touch closely resembling the real thing. Using a two-ply of flexible, thin plastic, scientists have created novel electronic sensors that send signals to the brain tissue of mice that closely mimic the nerve messages of touch sensors in human skin. Multiple research teams have long worked on restoring touch to people with prosthetic limbs. 2 years ago, for example, a group at Case Western Reserve University in Cleveland, Ohio, reported giving people with prosthetic hands a sense of touch by wiring pressure sensors on the hands to peripheral nerves in their arms. Yet although these advances have restored a rudimentary sense of touch, the sensors and signals are very different from those sent by mechanoreceptors, natural touch sensors in the skin. For starters, natural mechanoreceptors put out what amounts to a digital signal. When they sense pressure, they fire a stream of nerve impulses; the more pressure, the higher the frequency of pulses. But previous tactile sensors have been analogue devices, where more pressure produces a stronger electrical signal, rather than a more frequent stream of pulses. The electrical signals must then be sent to another processing chip that converts the strength of the signals to a digital stream of pulses that is only then sent on to peripheral nerves or brain tissue. © 2015 American Association for the Advancement of Science.
By Nicholas Bakalar Physical therapy may provide little relief for recent-onset low back pain, a small randomized trial has found. The study, published in JAMA, included 207 men and women, average age 37, with a score of 20 or higher on a widely used 100-point scale that quantifies disability from low back pain. The study included people with recent-onset pain who were assigned to one of two groups. The first received four sessions of exercise and manipulation under the guidance of a trained physical therapist. Those in the other group were told that low back pain usually gets better, and were advised to be as active as possible. There were no significant differences at any time in pain intensity, quality of life or the number of visits to health care providers. Compared with the usual care group, the physical therapy group did show significant improvement on the disability scale after three months. But after one year, there was no difference between the two groups in this measure either. “Most treatments that are effective have only modest effects,” said the lead author, Julie M. Fritz, a professor in the department of physical therapy at the University of Utah. “The pattern of low back pain is one of recurrence and remission, and changing that pattern is a real challenge. There are no magic answers.” © 2015 The New York Times Company
Keyword: Pain & Touch
Link ID: 21513 - Posted: 10.15.2015
By Gretchen Reynolds Can a shot of salt water make you a faster runner? The answer appears to be a resounding yes, if you believe that the salt water contains something that should make you a faster runner, according to a new study of the power of placebos in athletic performance. Anyone who exercises knows from experience that our minds and mental attitudes affect physical performance. Who hasn’t faced a moment when, tiring at the end of a strenuous workout or race, we are about to quit before suddenly being passed on the path or shown up in the gym by someone we know we should outperform, and somehow we find an extra, unexploited gear and spurt on? This phenomenon is familiar to physiologists, many of whom believe that our brains, in order to protect our bodies, send out signals telling those bodies to quit before every single resource in our muscles and other tissues is exhausted. We think we are at the outer limits of our endurance or strength, when, in reality, we may still have a physical reserve available to us, if we can find a way to tap it. Past studies have shown that lying to people is one way to exploit that reserve. Telling athletes that they are moving slower than in fact they are, for instance, often results in their speeding up past the pace that they thought they could maintain. Or give them a sugar pill that they think contains caffeine or steroids and they will run more swiftly or lift more weight than before. But none of these studies tested the effects of placebos and deception in relatively real-world competitive situations, which have their own effects on mental responses. People are almost always faster during competitive races than in training, studies show, even when they are trying to replicate race pace. © 2015 The New York Times Company
Keyword: Pain & Touch
Link ID: 21509 - Posted: 10.14.2015
By Christopher Intagliata If you're lost, you need a map and a compass. The map pinpoints where you are, and the compass orients you in the right direction. Migratory birds, on the other hand, can traverse entire hemispheres and end up just a couple miles from where they bred last year, using their senses alone. Their compass is the Sun, the stars and the Earth's magnetic field. But their map is a little more mysterious. One theory goes that they use olfactory cues—how a place smells. Another is that they rely on their sense of magnetism. Researchers in Russia investigated the map issue in a past study by capturing Eurasian reed warblers on the Baltic Sea as they flew northeast towards their breeding grounds near Saint Petersburg. They moved the birds 600 miles east, near Moscow. And the birds just reoriented themselves to the northwest—correctly determining their new position. Now the same scientists have repeated that experiment—only this time, they didn't move the birds at all. They just put them in cages that simulated the magnetic field of Moscow, while still allowing the birds to experience the sun, stars and smells of the Baltic. Once again, the birds re-oriented themselves to the northwest—suggesting that the magnetic field alone—regardless of smells or other cues, is enough to alter the birds' mental map. The study is in the journal Current Biology. [Dmitry Kishkinev et al, Eurasian reed warblers compensate for virtual magnetic displacement] And if you're envious of that sixth sense—keep in mind that since the Earth's magnetic field fluctuates, the researchers say magnetic route-finding is best for crude navigation. Meaning for door-to-door directions—you’re still better off with your GPS. © 2015 Scientific American,
Keyword: Animal Migration
Link ID: 21508 - Posted: 10.14.2015
By Nancy Szokan Sensory deprivation is Sushma Subramanian’s topic in the October issue of Women’s Health magazine, and she offers a couple of extreme examples. Julie Malloy, 33, from York, Pa., describes living without the sense of touch: “I was born with a rare sensory illness that leaves me unable to feel pain, temperature, deep pressure, or vibrations in my arms, legs, and the majority of my chest and back. I use vision to compensate as much as I can. . . . “I always wash my face with cold water; I once burned myself without realizing it. . . . When I drive, I can’t really tell how hard I’m pushing on the pedals. I watch others really enjoy it when someone kisses their arm or get tingly when someone hugs them, but I can’t even feel anything during sex.” Erin Napoleone, 31, from Havre de Grace, Md., describes losing her sense of smell: “As a teen, I was in a car accident. A few days later, I watched my father make homemade tomato sauce — but I didn’t smell a thing. Then I couldn’t detect my mom’s familiar perfume. A head CT scan confirmed my sense of smell was gone for good.” The magazine points out that some senses naturally deteriorate with age and that taking care of your skin — say, by keeping it moisturized and protecting it from damage — can help preserve the sense of touch. But olfactory nerves facing “prolonged exposure to rank odors (think freeway fumes or curbside trash)” can be permanently damaged.
It can start with flashing lights, a tingling sensation and a feeling of unease, followed by excruciating pain. Migraines can be triggered by lack of food or too much stress but their underlying cause has remained a mystery. Now researchers have found that a migraine may be triggered by a protein deep in the brain that stimulates the neurons controlling facial sensations. The discovery creates a potential new target for safer migraine medicines and adds weight to the theory that neurons, not blood vessels, are responsible for migraine attacks. “Where a migraine starts is a key question,” says Debbie Hay at the University of Auckland in New Zealand. “There has been a great deal of debate around the mechanisms of migraine. If we can pin this down, we may have better chances of preventing it.” To investigate, Simon Akerman at New York University and Peter Goadsby at Kings College London, UK, studied two neuropeptides released by neurons thought to play a role in the pain associated with migraine. These protein-like molecules, called VIP and PACAP, first raised suspicion after they were found to be elevated in blood drained from the brains of people having a migraine attack. When researchers administered these peptides to volunteers, they found that they could cause a headache or migraine about two hours later. Both peptides widen blood vessels, which was thought to be significant in migraine. In fact, the only drugs specifically developed for migraine that are in use today – triptans – were designed to shrink blood vessels in the brain. As a result, they cannot be used by people with cardiovascular disorders. © Copyright Reed Business Information Ltd.
Keyword: Pain & Touch
Link ID: 21489 - Posted: 10.08.2015
Jo Marchant Most new painkiller drugs fail in clinical trials — but a growing placebo response may be to blame. Drug companies have a problem: they are finding it ever harder to get painkillers through clinical trials. But this isn't necessarily because the drugs are getting worse. An extensive analysis of trial data1 has found that responses to sham treatments have become stronger over time, making it harder to prove a drug’s advantage over placebo. The change in reponse to placebo treatments for pain, discovered by researchers in Canada, holds true only for US clinical trials. “We were absolutely floored when we found out,” says Jeffrey Mogil, who directs the pain-genetics lab at McGill University in Montreal and led the analysis. Simply being in a US trial and receiving sham treatment now seems to relieve pain almost as effectively as many promising new drugs. Mogil thinks that as US trials get longer, larger and more expensive, they may be enhancing participants’ expectations of their effectiveness. Stronger placebo responses have already been reported for trials of antidepressants and antipsychotics2, 3, triggering debate over whether growing placebo effects are seen in pain trials too. To find out, Mogil and his colleagues examined 84 clinical trials of drugs for the treatment of chronic neuropathic pain (pain which affects the nervous system) published between 1990 and 2013. © 2015 Nature Publishing Group,
Keyword: Pain & Touch
Link ID: 21484 - Posted: 10.07.2015
By Sarah C. P. Williams Looking at photos of starving refugees or earthquake victims can trigger a visceral sense of empathy. But how, exactly, do we feel others’ agony as our own? A new study suggests that seeing others in pain engages some of the same neural pathways as when we ourselves are in pain. Moreover, both pain and empathy can be reduced by a placebo effect that acts on the same pathways as opioid painkillers, the researchers found. “This study provides one of the most direct demonstrations to date that first-hand pain and pain empathy are functionally related,” says neurobiologist Bernadette Fitzgibbon of Monash University in Melbourne, Australia, who was not involved in the new research. “It’s very exciting.” Previous studies have used functional magnetic resonance imaging (fMRI) scans to show that similar areas of the brain are activated when someone is in pain and when they see another person in pain. But overlaps on a brain scan don’t necessarily mean the two function through identical pathways—the shared brain areas could relate to attention or emotional arousal, among other things, rather than pain itself. Social neuroscientist Claus Lamm and colleagues at the University of Vienna took a different approach to test whether pain and empathy are driven by the same pathways. The researchers first divided about 100 people into control or placebo groups. They gave the placebo group a pill they claimed to be an expensive, over-the-counter painkiller, when in fact it was inactive. This well-established placebo protocol is known to function similarly to opioid painkillers, while avoiding the drugs’ side effects. © 2015 American Association for the Advancement of Science.
By Jane E. Brody Mark Hammel’s hearing was damaged in his 20s by machine gun fire when he served in the Israeli Army. But not until decades later, at 57, did he receive his first hearing aids. “It was very joyful, but also very sad, when I contemplated how much I had missed all those years,” Dr. Hammel, a psychologist in Kingston, N.Y., said in an interview. “I could hear well enough sitting face to face with someone in a quiet room, but in public, with background noise, I knew people were talking, but I had no idea what they were saying. I just stood there nodding my head and smiling. “Eventually, I stopped going to social gatherings. Even driving, I couldn’t hear what my daughter was saying in the back seat. I live in the country, and I couldn’t hear the birds singing. “People with hearing loss often don’t realize what they’re missing,” he said. “So much of what makes us human is social contact, interaction with other human beings. When that’s cut off, it comes with a very high cost.” And the price people pay is much more than social. As Dr. Hammel now realizes, “the capacity to hear is so essential to overall health.” Hearing loss is one of the most common conditions affecting adults, and the most common among older adults. An estimated 30 million to 48 million Americans have hearing loss that significantly diminishes the quality of their lives — academically, professionally and medically as well as socially. One person in three older than 60 has life-diminishing hearing loss, but most older adults wait five to 15 years before they seek help, according to a 2012 report in Healthy Hearing magazine. And the longer the delay, the more one misses of life and the harder it can be to adjust to hearing aids. © 2015 The New York Times Company
By Simon Makin Most people associate the term “subliminal conditioning” with dystopian sci-fi tales, but a recent study has used the technique to alter responses to pain. The findings suggest that information that does not register consciously teaches our brain more than scientists previously suspected. The results also offer a novel way to think about the placebo effect. Our perception of pain can depend on expectations, which explains placebo pain relief—and placebo's evil twin, the nocebo effect (if we think something will really hurt, it can hurt more than it should). Researchers have studied these expectation effects using conditioning techniques: they train people to associate specific stimuli, such as certain images, with different levels of pain. The subjects' perception of pain can then be reduced or increased by seeing the images during something painful. Most researchers assumed these pain-modifying effects required conscious expectations, but the new study, from a team at Harvard Medical School and the Karolinska Institute in Stockholm, led by Karin Jensen, shows that even subliminal input can modify pain—a more cognitively complex process than most that have previously been discovered to be susceptible to subliminal effects (timeline below). The scientists conditioned 47 people to associate two faces with either high or low pain levels from heat applied to their forearm. Some participants saw the faces normally, whereas others were exposed subliminally—the images were flashed so briefly, the participants were not aware of seeing them, as verified by recognition tests. © 2015 Scientific American