By MATT RICHTEL SAN FRANCISCO — When one of the most important e-mail messages of his life landed in his in-box a few years ago, Kord Campbell overlooked it. Not just for a day or two, but 12 days. He finally saw it while sifting through old messages: a big company wanted to buy his Internet start-up. “I stood up from my desk and said, ‘Oh my God, oh my God, oh my God,’ ” Mr. Campbell said. “It’s kind of hard to miss an e-mail like that, but I did.” The message had slipped by him amid an electronic flood: two computer screens alive with e-mail, instant messages, online chats, a Web browser and the computer code he was writing. While he managed to salvage the $1.3 million deal after apologizing to his suitor, Mr. Campbell continues to struggle with the effects of the deluge of data. Even after he unplugs, he craves the stimulation he gets from his electronic gadgets. He forgets things like dinner plans, and he has trouble focusing on his family. His wife, Brenda, complains, “It seems like he can no longer be fully in the moment.” This is your brain on computers. Scientists say juggling e-mail, phone calls and other incoming information can change how people think and behave. They say our ability to focus is being undermined by bursts of information. Copyright 2010 The New York Times Company

Keyword: Attention
Link ID: 14153 - Posted: 06.24.2010

By PAUL BLOOM It is one of the most famous psychological demos ever. Subjects are shown a video, about a minute long, of two teams, one in white shirts, the other in black shirts, moving around and passing basketballs to one another. They are asked to count the number of aerial and bounce passes made by the team wearing white, a seemingly simple task. Halfway through the video, a woman wearing a full-body gorilla suit walks slowly to the middle of the screen, pounds her chest, and then walks out of the frame. If you are just watching the video, it’s the most obvious thing in the world. But when asked to count the passes, about half the people miss it. This experiment, published in 1999 by Christopher Chabris and Daniel Simons, is a striking demonstration of the zero-sum nature of attention. When you direct your mental spotlight to the basketball passes, it leaves the rest of the world in darkness. Even when you are looking straight at the gorilla (and other experiments find that people who miss it often have their eyes fully on it) you frequently don’t see it, because it’s not what you’re looking for. In “The Invisible Gorilla,” Chabris and Simons begin by talking about their study and its implications for everyday life. It is a mistake, they argue, to see it as revealing a bug in our software, rather than an inherent limitation. Our brains are physical systems and hence have finite ­resources. The real problem here — what Chabris and Simons call “the illusion of attention” ­— is that we are often unaware of these limitations; we think that we see the world as it really is, but “our vivid visual experience belies a striking mental blindness.” They go on to explore a series of related illusions having to do with perception, memory, knowledge and ability, providing vivid examples of the real-world problems these illusions cause. Copyright 2010 The New York Times Company

Keyword: Attention
Link ID: 14152 - Posted: 06.24.2010

By William Saletan Elizabeth Loftus warmed to the idea of memory tampering for the best of reasons. She wanted to help people. In her official career, as she described it in books, she studied the art of mental manipulation only to dissect, expose, and defeat it. Occasionally, she lent her psychological expertise to lawyers or advertisers for their self-interested purposes. But these purposes weren't hers, so she never turned them into a career. To embrace memory tampering, she needed a purpose of her own. Something she could believe in and care about. Something that could put her skills to good use. The story of how Loftus found that purpose—the story of her shadow career—began 30 years ago with a metaphor. "Imagine a world in which people could go to a special kind of psychologist or psychiatrist—a memory doctor—and have their memories modified," she mused in her 1980 book, Memory. This was no fantasy, she argued. The doctor was memory itself. "Every day, we do this to ourselves and others," she explained. "Our memories of past events change in helpful ways, leading us to be happier than we might otherwise be." Indeed, this was nature's design: Why should we cling tightly to those memories that disturb us and spoil our lives? Life might become so much more pleasant if it is not marred by our memory of past ills, sufferings, and grievances. … We seem to have been purposely constructed with a mechanism for erasing the tape of our memory, or at least bending the memory tape, so that we can live and function without being haunted by the past. Accurate memory, in some instances, would simply get in the way. © Copyright 2010 Washington Post.Newsweek Interactive Co. LLC

Keyword: Learning & Memory; Depression
Link ID: 14151 - Posted: 06.24.2010

By Katherine Harmon When your stomach growls and you have the urge to reach for the nearest snack, it is, in a way, your tummy talking. Those signals are in part sparked by the gut-based hunger hormone ghrelin, which blocks certain receptors in the brain, telling your body when it is time to eat. But a team of researchers thinks this hormone might be doing more than just urging you to pile on some calories. It might also be helping to regulate the levels of cholesterol in your bloodstream. The new research was published online June 6 in Nature Neuroscience (Scientific American is part of Nature Publishing Group). Although so-called bad cholesterol (low-density lipoprotein, or LDL) can result in clogged arteries and cardiovascular disease, good cholesterol (high-density lipoprotein, or HDL) is thought to actually prevent plaque build-up in the arteries by helping to transport lipids more smoothly through the bloodstream. Cholesterol levels have long been thought to be mainly a factor of diet and liver function. But new research in mouse models shows that changes in ghrelin and in a ghrelin-inhibited receptor in the hypothalamus altered how much HDL went to the liver for processing and how much remained in the blood stream. "Our study shows for the first time that cholesterol is also under direct 'remote control' by specific neurocircuitry in the central nervous system," Matthias Tschöp, a professor of endocrinology at the University of Cincinnati and coauthor of the paper, said in a prepared statement. © 2010 Scientific American,

Keyword: Obesity
Link ID: 14150 - Posted: 06.24.2010

A biological factor may play an essential part in the development of eating disorders in girls during puberty, a new study finds. The research, led by Michigan State University (MSU) scientists, finds that the genes of girls who have higher levels of estradiol at puberty can act as a catalyst for the development of eating disorders. Estradiol is the primary form of estrogen in women's bodies. It plays a key role in the development of secondary sex characteristics and bone development. "The reason we see an increase in genetic influences during puberty is that the genes for disordered eating are essentially getting switched on during that time," said Kelly Klump, MSU associate professor of psychology, in a release. "What we found is that increases in estradiol apparently are activating genetic risk for eating disorders." The genes responsible for activating eating disorders have yet to be identified. The researchers also believe that environmental factors and a genetic link (having a family history of eating disorders) play a part in the development of the condition. The researchers measured the amount of estradiol in the bloodstreams of 200 sets of twin girls between the ages of 10 and 15. The study is published in the journal Psychological Medicine. © CBC 2010

Keyword: Anorexia & Bulimia; Hormones & Behavior
Link ID: 14149 - Posted: 06.24.2010

By OLIVIA JUDSON A few weeks ago, I was walking through a wood in the English countryside when I heard the unmistakable call of the cuckoo. For some reason, it caused me to fall into a reverie, and as I walked, I began to meditate on that iconic bird and what it represents. The European cuckoo (Cuculus canorus) is, famously, a “brood parasite”: the female lays her eggs in other birds’ nests. Typical victims are small birds like reed warblers and wagtails. When the young cuckoo hatches, its first act is to dispose of any other eggs: it heaves them out of the nest, leaving itself as the sole occupant. What happens next is peculiar. The foster parents don’t appear to notice they are rearing a monster. Instead, they work hard to satisfy the demands of the chick, even though it sometimes becomes so large that it no longer fits inside the nest, and has to sit on top. It’s one of the oddest sights in nature. The cuckoo habit has evolved several times. It’s found in species as diverse as cowbirds, indigobirds, honeyguides and even a species of South American duck. (Actually, brood parasitism can also occur within a species — geese sometimes slip an egg into a neighbor’s nest, as do coots and starlings. Nor is it restricted to birds — fish and insects sometimes foist the rearing of their offspring onto others. But for the rest of this article, I want to focus on the birds that are “professional” brood parasites — the ones that, like the cuckoo, never build nests, and always palm their offspring onto another species.) Copyright 2010 The New York Times Company

Keyword: Sexual Behavior; Vision
Link ID: 14148 - Posted: 06.24.2010

By Nathan Seppa In science’s struggle to keep up with life on the streets, smoking cannabis for medical purposes stands as Exhibit A. Medical use of cannabis has taken on momentum of its own, surging ahead of scientists’ ability to measure the drug’s benefits. The pace has been a little too quick for some, who see medicinal joints as a punch line, a ruse to free up access to a recreational drug. But while the medical marijuana movement has been generating political news, some researchers have been quietly moving in new directions — testing cannabis and its derivatives against a host of diseases. The scientific literature now brims with potential uses for cannabis that extend beyond its well-known abilities to fend off nausea and block pain in people with cancer and AIDS. Cannabis derivatives may combat multiple sclerosis, Crohn’s disease and other inflammatory conditions, the new research finds. Cannabis may even kill cancerous tumors. Many in the scientific community are now keen to see if this potential will be fulfilled, but they haven’t always been. Pharmacologist Roger Pertwee of the University of Aberdeen in Scotland recalls attending scientific conferences 30 years ago, eager to present his latest findings on the therapeutic effects of cannabis. It was a hard sell. © Society for Science & the Public 2000 - 2010

Keyword: Drug Abuse; Pain & Touch
Link ID: 14147 - Posted: 06.24.2010

By Katherine Harmon NEW YORK—When ancient denizens of central France painted leaping horses on the cave walls at Lascaux, they might not have had the late Renaissance understanding of how to illustrate perspective and three dimensions. But they did, with simple black lines, give the implication of depth, showing the far pair of limbs behind the closer pair. That seemingly simple detail reveals a world of information about the human brain, concluded various scientists and artists at a World Science Festival panel held June 3 at New York University. In the world itself, lines do not define objects. "You cannot find objects that have lines around them," rather most people make sense of their surroundings using shapes, color, shading and subtleties of depth, explained Patrick Cavanagh, of the Vision Sciences Lab at Harvard University. By that measure, line drawings are "not something we've evolved to be able to understand," he said, but rather, people in all cultures—and even babies and monkeys—can understand a simple line drawing. The effectiveness of simple line-based representations "wasn't invented; it was discovered by artists," he noted. Cavanagh called this discovery "a backdoor to the brain," through which scientists can learn more about how the brain makes sense of the visual world: for instance, why we all understand that a straight line that ends at a square's edge and then continues on the same plane on the other side is probably "behind" the square—and why our brain has so much trouble sorting out even simple optical illusions. © 2010 Scientific American,

Keyword: Vision
Link ID: 14146 - Posted: 06.24.2010

by Gisela Telis The select club of brainy critters known for carrying traditions—among them humans, primates, whales, and dolphins—has an unlikely new member: the banded mongoose. Researchers have found that the furry African carnivore learns by imitation as well and carries what it learns well into adulthood. Experts say the discovery offers the first direct observation of animals passing down traditions in the wild. The mongoose is better known for its unique social system than for its brainpower. When mongoose pups emerge from the den, they try out and eventually choose one adult—usually an older sibling, cousin, or uncle, not a parent—who becomes their "escort" or chaperone during infancy. The escort protects, feeds, and plays with the pup as it grows, and the pair spends almost all its time together until the pup reaches adulthood. The relationship made Corsin Müller, an animal cognition expert at the University of Vienna, wonder if the escort teaches the pup any behaviors; that is, whether the escort is passing down "culture" or tradition to the pup. To find out, Müller and a colleague at the University of Exeter in the United Kingdom took advantage of another mongoose quirk. When eating hard-shelled prey, such as eggs or rhinoceros beetles, some mongooses bite into the item, others hurl it against a hard surface to smash it open, and still others switch between the techniques. Each mongoose sticks to its preferred behavior, even if other members of the same group choose a different tactic. Watch and learn. A mongoose escort smashes (top) or bites (bottom) a food-filled plastic egg as his pup looks on. As an adult, the pup will adopt its escort's preferred foraging technique or "tradition" during its own encounters with the egg. © 2010 American Association for the Advancement of Science.

Keyword: Learning & Memory; Sexual Behavior
Link ID: 14145 - Posted: 06.24.2010

by Sarah Reed A new movie set for general release today follows the lives of sexually liberated females. No, its stars are not the glamorous gals from Sex and the City. The film instead throws the spotlight on crickets, offering unprecedented video footage of the insect's mating behavior in the wild and confirming lab studies that have suggested female crickets have just as many different mates as males. Most studies of insect behavior have been confined to the laboratory, due to the technical challenges faced in monitoring these small creatures in the wild. Although laboratory-based studies have revealed much about the behavior and physiology of insects, it wasn't known how much the controlled environment influenced these findings. To address this issue, a team of European scientists monitored a population of flightless field crickets (Gryllus campestris) at the bottom of a river valley in northern Spain from the spring of 2006 through to the autumn of 2007. The crickets were under surveillance 24 hours a day, with a network of 64 motion-sensitive, infrared-equipped video cameras capturing a total of 250,000 hours of footage. Tags featuring a highly visible code were glued onto the backs of the crickets as soon as they emerged from their burrows so that they could be individually identified in the footage. Parentage was then assigned by extracting DNA from the tip of a hind leg. Caught on tape. In this video, Tom Tregenza of the University of Exeter narrates several scenes from the crickets' lives. © 2010 American Association for the Advancement of Science.

Keyword: Sexual Behavior; Evolution
Link ID: 14144 - Posted: 06.24.2010

Researchers have found a way to pharmacologically induce a memory of safety in the brain of rats, mimicking the effect of training. The finding suggests possibilities for new treatments for individuals suffering from anxiety disorders (http://www.nimh.nih.gov/health/topics/anxiety-disorders/index.shtml). Rats normally freeze when they hear a tone they have been conditioned to associate with an electric shock. The reaction can be extinguished by repeatedly exposing the rats to the tone with no shock. In this work, administering a protein directly into the brain of rats achieved the same effect as extinction training. The protein, brain-derived neurotrophic factor or BDNF, is one of a class of proteins that support the growth and survival of neurons. Prior work has shown that extinction training does not erase a previously conditioned fear memory, but creates a new memory associating the tone with safety. "The surprising finding here is that the drug substituted for extinction training, suggesting that it induced such a memory," said Dr. Gregory Quirk at the University of Puerto Rico School of Medicine, who led the investigation with support from the National Institute of Mental Health. The work is reported in the June 4 issue of Science. Memory formation involves changes in the connections, or synapses, between neurons, a process known as synaptic plasticity. One brain structure critical for extinction memory in rats is the infralimbic prefrontal cortex (ILC). Drugs that block synaptic plasticity impair the formation of extinction memory when injected into the ILC, causing rats to continue freezing at high levels after extinction training.

Keyword: Learning & Memory; Emotions
Link ID: 14143 - Posted: 06.05.2010

In a major study, investigators have compared how individuals with Parkinson's disease respond to deep brain stimulation (DBS) at two different sites in the brain. Contrary to current belief, patients who received DBS at either site in the brain experienced comparable benefits for the motor symptoms of Parkinson's. The results appear in the June 3, 2010 issue of the New England Journal of Medicine. This is the latest report from a study that has followed nearly 300 patients at 13 clinical sites for two years. The study was funded by the Department of Veterans Affairs (VA) and the National Institute of Neurological Disorders and Stroke (NINDS), part of the National Institutes of Health. Additional support was provided by Minneapolis-based Medtronic, Inc., the makers of the DBS systems used in the study. "These results establish that DBS delivered to these two brain areas linked to key motor control pathways can have equivalent effects on tremor, stiffness and other motor symptoms of Parkinson’s disease," said Walter Koroshetz, M.D., deputy director at NINDS. "The important question now becomes how stimulation at each site affects some of the other important, non-motor symptoms and how to best individualize DBS therapy." Motor control problems such as shaking, rigidity, slowed movement and poor balance are often the first and most troubling symptoms of Parkinson’s disease. In later stages, patients tend to develop a variety of cognitive and mood problems, including depression, apathy, slowed thinking, confusion, impaired memory and trouble sleeping.

Keyword: Parkinsons
Link ID: 14142 - Posted: 06.24.2010

by Zahra Hirji Dieting is a royal pain. No matter how many carrots or grapes you eat, you still feel hungry. But what if you could go days, weeks even, without eating and not feel hungry? For yellow-bellied marmots, cat-size rodents, this miraculous ability is part of a normal routine. In a new study, scientists identified a molecule that makes marmots hungry during their hibernation phase. This molecule, nicknamed AICAR (5-aminoimidazole-4-carboxamide 1 B-D-ribofuranoside if you really want to know), is found in creatures from yeast to humans. Knowing how to manipulate it could open the door for people struggling with obesity and eating disorders. Marmots (Marmota flaviventris) spend up to seven months out of the year, October to March, hibernating. Unlike other hibernating animals such as ground squirrels and some bats, these furry critters do not store excess food within a paw’s reach for a mid-hibernation snack, Greg Florant of Colorado State University and head author of the study explained to Discovery News. Rather, they eat to the point of obesity during the summer. Impressively, they are not plagued by health problems like diabetes, Florant noted. “Even if they aren’t hibernating, marmots can go for days on end without food,” Florant said. © 2010 Discovery Communications, LLC

Keyword: Obesity
Link ID: 14141 - Posted: 06.24.2010

Daniel Cressey Long derided by much of the mainstream medical community, acupuncture seems to have just got a little bit less alternative. Despite anecdotal evidence claiming benefits in treating ailments from allergies to pain, acupuncture faces two big challenges to acceptance in mainstream medicine. Many reviews of clinical trials have concluded that there is no evidence of efficacy for most conditions beyond the placebo effect1, and there is no scientifically accepted mechanism for how the treatment works. Research in mice has now provided a biochemical explanation that some experts are finding more persuasive2, although it might account for only some of the treatment's supposed benefits. "Our study shows there is a clear biological mechanism behind acupuncture," says Maiken Nedergaard, a neuroscientist at the University of Rochester in New York, who led the research. Nedergaard's team wanted to find out whether the neuromodulator adenosine, which is produced when tissue is injured and has pain-dulling effects, was involved in the purported pain-relieving effects of acupuncture. After inducing pain in the right hind paws of their mice, the researchers inserted and rotated an acupuncture needle just below the 'knee', at a place known in humans as the 'Zusanli point'. For about an hour after the treatment the mice took longer to respond to touch or heat on the paw, indicating that their pain had been dulled. The team found that adenosine levels had increased at the acupuncture site, and that mice lacking a key cell receptor for adenosine did not show the same response. © 2010 Nature Publishing Group,

Keyword: Pain & Touch
Link ID: 14140 - Posted: 06.24.2010

By PAM BELLUCK YARUMAL, Colombia — Tucked away on a steep street in this rough-hewn mountain town, an old woman found herself diapering her middle-age children. At frighteningly young ages, in their 40s, four of Laura Cuartas’s children began forgetting and falling apart, assaulted by what people here have long called La Bobera, the foolishness. It is a condition attributed, in hushed rumors, to everything from touching a mysterious tree to the revenge of a wronged priest. It is Alzheimer’s disease, and at 82, Mrs. Cuartas, her gray raisin of a face grave, takes care of three of her afflicted children. One son, Darío, 55, babbles incoherently, shreds his socks and diapers, and squirms so vigorously he is sometimes tied to a chair with baggy blue shorts. A daughter, María Elsy, 61, a nurse who at 48 started forgetting patients’ medications, and whose rages made her attack a sister who bathed her, is a human shell, mute, fed by nose tube. Another son, Oderis, 50, denies that his memory is dying, that he remembers to buy only one thing at a time: milk, not milk and plantains. If he gets Alzheimer’s, he says, he will poison himself. “To see your children like this ... ,” Mrs. Cuartas said. “It’s horrible, horrible. I wouldn’t wish this on a rabid dog. It is the most terrifying illness on the face of the earth.” Copyright 2010 The New York Times Company

Keyword: Alzheimers; Genes & Behavior
Link ID: 14139 - Posted: 06.24.2010

by Jennifer Couzin-Frankel In the first decision of its kind, a federal magistrate judge has ruled that functional magnetic resonance imaging shouldn't be permitted in the courtroom as a new type of lie detector. U.S. Magistrate Judge Tu Pham yesterday released a 39-page opinion asserting that the technology is unreliable and has not been accepted by the scientific community. Scientists who felt fMRIs weren't ready to be used in court as lie detectors are relieved by the ruling which, while not binding on other jurisdictions, is likely to have an impact. Lorne Semrau was seeking to include the results of scans as part of his defense in a Medicare and Medicaid fraud case being heard in a federal court in Tennessee. But while Judge Pham agreed that the technique had been subject to testing and peer review, it flunked on the other two points suggested by the Supreme Court to weigh cases like this one: the test of proven accuracy and general acceptance by scientists. Pham noted, for example, that "there are no known error rates for fMRI-based lie detection outside the laboratory setting." The distinction between lying in a controlled experiment and the real world is an important one, says Owen Jones, a law professor at Vanderbilt University Law School in Nashville. "You have much greater stakes in the lie" when you're really trying to deceive, he says. Those brain scans might not look like the scans of people told to lie, for instance, about whether they'd taken a watch off a lab table. © 2010 American Association for the Advancement of Science.

Keyword: Stress; Brain imaging
Link ID: 14138 - Posted: 06.24.2010

by Andy Coghlan Post-mortems of binge-drinking adolescent monkeys have produced the best evidence yet that heavy drinking at an early age can do lasting damage to the brain. The worst damage was to stem cells destined to become neurons in the hippocampus, the brain area responsible for memory and spatial awareness. Monkey and human brains develop in the same way, so the finding suggests that similar effects may occur in human teenagers. It thus reinforces the rationale for anti-alcohol policies in the US and elsewhere which aim to raise the age at with people start to drink. Chitra Mandyam of the Scripps Research Institute in La Jolla, California, and colleagues gave four rhesus macaque monkeys citrus-flavoured alcoholic drinks for an hour a day over a period of 11 months. Two months later the animals were killed, and their brains were compared with those of monkeys that had not consumed alcohol. The bingeing monkeys had 50 to 90 per cent fewer stem cells in their hippocampus compared with the controls. "We saw a profound decrease in vital cells," Mandyam says. "What is important for the public to know is that this type of drinking can kill off stem cells." This loss could result in damage to memory and spatial skills, she adds. Lasting effects Mandyam thinks that this degeneration could have long-term effects and provide a mechanism for why bingeing teens are more likely to develop alcohol dependence as adults. © Copyright Reed Business Information Ltd.

Keyword: Drug Abuse; Development of the Brain
Link ID: 14137 - Posted: 06.24.2010

by Linda Geddes The first indication that something might be up came when I caught myself asking my friend how she was feeling twice in the space of 30 seconds. Then I got into my car and couldn't find my keys, until a helpful passer-by pointed out that they were sitting in the lock outside. Since then, I've caught myself losing track of what I'm saying mid-sentence, and walking upstairs only to realise that I have no recollection of what I've gone up there for. It seems that "mumnesia", the forgetfulness that is said to beset pregnant women, may finally be taking hold. There have been plenty of studies supporting the idea that mumnesia exists – although some others have contradicted them. But a new study casts fresh light on exactly how pregnancy might interfere with memory in women, as well as exploring how long the effects last. It is also one of the largest studies looking into pregnancy and memory to have been conducted so far. Laura Glynn at the University of California, Irvine, asked 254 pregnant women to perform a series of memory tests at different stages of their pregnancy, as well as 12 to 14 weeks after the birth. She also measured levels of the hormones oestrogen and cortisol in their blood, and repeated these tests on 48 non-pregnant women. © Copyright Reed Business Information Ltd.

Keyword: Hormones & Behavior; Learning & Memory
Link ID: 14136 - Posted: 06.24.2010

By CLAUDIA DREIFUS Three years ago, when Oxford University Press published “Music, Language, and the Brain,” Oliver Sacks described it as “a major synthesis that will be indispensable to neuroscientists.” The author of that volume, Aniruddh D. Patel, a 44-year-old senior fellow at the Neurosciences Institute in San Diego, was in New York City in May. We spoke over coffee for more than an hour and later by telephone. An edited and condensed version of the conversations follows. Q. YOU DESCRIBE YOURSELF AS A NEUROSCIENTIST OF MUSIC. THIS HAS TO BE A NEW PROFESSION. HOW DID YOU COME TO IT? A. I’ve been passionate about two things since childhood — science and music. At graduate school, Harvard, I hoped to combine the two. But studying with E.O. Wilson, I quite naturally got caught up with ants. In 1990, I found myself in Australia doing fieldwork on ants for a Ph.D. thesis. And there, I had this epiphany: the only thing I really wanted to do was study the biology of how humans make and process music. I wondered if the drive to make it was innate, a product of our evolution, as Darwin had speculated. Did we have a special neurobiological capacity for music, as we do for language and grammar? So from Australia, I wrote Wilson that there was no way I could continue with ants. Amazingly, he wrote: “You must follow your passion. Come back to Harvard, and we’ll give it a shot.” Copyright 2010 The New York Times Company

Keyword: Hearing
Link ID: 14135 - Posted: 06.24.2010

By SINDYA N. BHANOO The iguanas on the Galápagos Islands enjoy a pleasant life with few predators and ample marine algae to feast on. But every few years El Niño, a tropical Pacific weather pattern, disrupts this, warming the ocean waters and causing the algae to die. Iguanas sometimes go without food for up to several months. While some iguanas starve, others seem to make it until new algae grow. This survivability may be connected to the iguana’s ability to control stress levels, according to a study in the May 26 issue of the Proceedings of the Royal Society B. In a stress-inducing situation like that caused by El Niño, iguanas release a hormone called corticosterone. In the short term, this helps the iguanas tap into their own protein reserves. And, for example, when an iguana faces an attack by a predatory hawk, the hormone provokes a response to move faster. But in the long term, iguanas that cannot turn off the stress hormone expend too much energy too quickly, which is fatal, the researchers found in their survey of 98 iguanas. “Their ability to turn off their response was what seemed to predict who lived and who died,” said L. Michael Romero, a professor of biology at Tufts University and the paper’s lead author. Copyright 2010 The New York Times Company

Keyword: Stress
Link ID: 14134 - Posted: 06.24.2010