By MARY PILON and KEN BELSON The former N.F.L. linebacker Junior Seau had a degenerative brain disease linked to repeated head trauma when he committed suicide in the spring, the National Institutes of Health said Thursday. The findings were consistent with chronic traumatic encephalopathy, a degenerative brain disease widely connected to athletes who have absorbed frequent blows to the head, the N.I.H. said in a statement. Seau is the latest and most prominent player to be associated with the disease, which has bedeviled football in recent years as a proliferation of studies has exposed the possible long-term cognitive impact of head injuries sustained on the field. “The type of findings seen in Mr. Seau’s brain have been recently reported in autopsies of individuals with exposure to repetitive head injury,” the N.I.H. said, “including professional and amateur athletes who played contact sports, individuals with multiple concussions, and veterans exposed to blast injury and other trauma.” Since C.T.E. was diagnosed in the brain of the former Eagles defensive back Andre Waters after his suicide in 2006, the disease has been found in nearly every former player whose brain was examined posthumously. (C.T.E. can be diagnosed only posthumously.) Researchers at Boston University, who pioneered the study of C.T.E., have found it in 33 of the 34 brains of former N.F.L. players they have examined. The N.I.H. began its examination of Seau’s brain tissue in July. In addition to being reviewed by two federal neuropathologists, Seau’s brain was reviewed by three outside neuropathology experts who did not have knowledge of the source of the tissue. Upon initial examination “the brain looked normal,” according to the N.I.H. It was not until doctors looked under the microscope and used staining techniques that the C.T.E. abnormalities were seen. © 2013 The New York Times Company

Keyword: Brain Injury/Concussion
Link ID: 17668 - Posted: 01.12.2013

Elderly people with dementia should be prescribed antipsychotics carefully, say Ontario doctors who found men are at higher risk of hospitalization and death than women when the treatment begins. Researchers focused on new prescriptions of a class of drugs called atypical antipsychotics that are used to manage behaviour problems associated with dementia. "It tells us a little bit more about drug therapy and perhaps what might be affecting women and men differently," said Dr. Paula Rochon, a senior scientist at Toronto's Women College Hospital. In Wednesday's issue of the Journal of the American Geriatric Society, Rochon and her co-authors said of 21,526 older adults with dementia in Ontario who started taking the medications, about seven per cent of the women and nearly 11 per cent of the men died or were hospitalized during the 30 days after the treatment started. Little is known about how drugs may affect men and women differently after the age of 85, says Dr. Paula Rochon. "While younger women may be more likely than younger men to experience an adverse drug event, our results suggest that the incidence of serious events in the elderly is reversed and that older men are more likely than older women to experience a serious event related to atypical antipsychotic initiation," the study's authors concluded. © CBC 2013

Keyword: Alzheimers; Schizophrenia
Link ID: 17667 - Posted: 01.10.2013

Ewen Callaway In the mid-1980s, Paul Moorcraft, then a war correspondent, journeyed with a film crew into Afghanistan to produce a documentary about the fifth anniversary of the Soviet invasion. The trip took them behind Soviet lines. “We were attacked every fucking day by the Russians,” says the colourful Welshman. But the real trouble started later, when Moorcraft tried to tally his expenses, such as horses and local garb for his crew. Even with a calculator, the simple sums took him ten times longer than they should have. “It was an absolute nightmare. I spent days and days and days.” When he finally sent the bill to an accountant, he had not realized that after adding a zero he was claiming millions of pounds for a trip that had cost a couple of hundred thousand. “He knew I was an honest guy and assumed that it was just a typo.” Such mistakes were part of a lifelong pattern for Moorcraft, now director of the Centre for Foreign Policy Analysis in London and the author of more than a dozen books. He hasn't changed his phone number or PIN in years for fear that he would never remember new ones, and when working for Britain's Ministry of Defence he put subordinates in charge of remembering safe codes. In 2003, a mistaken phone number — one of hundreds before it — lost him a girlfriend who was convinced he was out gallivanting. That finally convinced him to seek an explanation. At the suggestion of a friend who teaches children with learning disabilities, Moorcraft contacted Brian Butterworth, a cognitive neuroscientist at University College London who studies numerical cognition. After conducting some tests, Butterworth concluded that Moorcraft was “a disaster at arithmetic” and diagnosed him with dyscalculia, a little-known learning disability sometimes called number blindness and likened to dyslexia for maths. Researchers estimate that as much as 7% of the population has dyscalculia, which is marked by severe difficulties in dealing with numbers despite otherwise normal (or, in Moorcraft's case, probably well above normal) intelligence. © 2013 Nature Publishing Group

Keyword: Attention
Link ID: 17666 - Posted: 01.10.2013

By BENEDICT CAREY Most adolescents who plan or attempt suicide have already received at least some mental health treatment, raising questions about the effectiveness of current approaches to helping troubled youths, according to the largest in-depth analysis to date of suicidal behaviors in American teenagers. Matt Nock, a professor of psychology at Harvard and the lead author of a study on the mental health treatment of troubled young people, said his research showed that “we’ve got a long way to go to do this right.” The study found that 55 percent of adolescents who plan or attempt suicide have already received some therapy. The study, in the journal JAMA Psychiatry, found that 55 percent of suicidal teenagers had received some therapy before they thought about suicide, planned it or tried to kill themselves, contradicting the widely held belief that suicide is due in part to a lack of access to treatment. The findings, based on interviews with a nationwide sample of more than 6,000 teenagers and at least one parent of each, linked suicidal behavior to complex combinations of mood disorders like depression and behavior problems like attention-deficit and eating disorders, as well as alcohol and drug abuse. The study found that about one in eight teenagers had persistent suicidal thoughts at some point, and that about a third of those who had suicidal thoughts had made an attempt, usually within a year of having the idea. © 2013 The New York Times Company

Keyword: Depression; Development of the Brain
Link ID: 17665 - Posted: 01.10.2013

By Susan Milius Male European blackbirds monitored in a lab under simulated city lighting started secreting increased levels of testosterone and growing their sexual organs up to a month earlier in the spring than birds kept in country-style darkness, Davide Dominoni of the Max Planck Institute for Ornithology in Radolfzell, Germany, reported January 6 at the annual meeting of the Society for Integrative and Comparative Biology. Dominoni’s colleagues have found that, outside the lab, male blackbirds flying around Munich undergo this growth surge about three weeks earlier than counterparts in a forest just 40 kilometers out of town. Beginning in December 2010, the researchers exposed captive blackbirds to night light levels typical of urban settings. They estimated those levels by outfitting free-flying blackbirds with light-sensitive devices and averaging the urban light exposure. A winter of lab night light sped up the males’ molting and boosted testosterone levels as well as organ development in spring. Continuing the night light treatment through the next winter left the males reproductively shut down in the spring of 2012. The lab night lights probably kept the birds’ seasonal reproductive clocks from resetting at the end of the first breeding season, Dominoni says. That second-year suppression may not be common in the real world, where birds fly around and experience more variety in night lighting, he says. But he sees the lab breeding shutdown as a sign of how big of an impact artificial light might have. © Society for Science & the Public 2000 - 2013

Keyword: Biological Rhythms; Sexual Behavior
Link ID: 17664 - Posted: 01.10.2013

by Gretchen Vogel All you graying, half-deaf Def Leppard fans, listen up. A drug applied to the ears of mice deafened by noise can restore some hearing in the animals. By blocking a key protein, the drug allows sound-sensing cells that are damaged by noise to regrow. The treatment isn't anywhere near ready for use in humans, but the advance at least raises the prospect of restoring hearing to some deafened people. When it comes to hearing, hair cells in the inner ear, so named for their bristlelike appearance, keep the process humming along, converting mechanical vibrations caused by sound waves into nerve impulses. Unfortunately for people, loud noises can overwork and destroy the cells. And once they're gone, they're gone: Birds and fish can regenerate the inner ear hair cells, but mammals cannot. Researchers have been looking for ways to reactivate the regenerative potential that other species enjoy. In 2005, scientists used gene therapy to prompt the growth of hair cells in the inner ears of adult guinea pigs, which restored some hearing. However, the drug approach would potentially be much easier to use in the clinic, says Albert Edge, a stem cell biologist at the Massachusetts Eye and Ear Infirmary in Boston. He and his colleagues had previously found that a class of drugs called gamma-secretase inhibitors could prompt the growth of hair cells from inner ear stem cells growing in the lab. The lab also showed that the drugs worked by blocking the signaling of the Notch protein, which helps determine which cells become hair cells and which become support cells during ear development. © 2010 American Association for the Advancement of Science

Keyword: Hearing; Regeneration
Link ID: 17663 - Posted: 01.10.2013

By Bruce Bower Babies may start to learn their mother tongues even before seeing their mothers’ faces. Newborns react differently to native and foreign vowel sounds, suggesting that language learning begins in the womb, researchers say. Infants tested seven to 75 hours after birth treated spoken variants of a vowel sound in their home language as similar, evidence that newborns regard these sounds as members of a common category, say psychologist Christine Moon of Pacific Lutheran University in Tacoma, Wash., and her colleagues. Newborns deemed different versions of a foreign vowel sound to be dissimilar and unfamiliar, the scientists report in an upcoming Acta Paediatrica. “It seems that there is some prenatal learning of speech sounds, but we do not yet know how much,” Moon says. Fetuses can hear outside sounds by about 10 weeks before birth. Until now, evidence suggested that prenatal learning was restricted to the melody, rhythm and loudness of voices (SN: 12/5/09, p. 14). Earlier investigations established that 6-month-olds group native but not foreign vowel sounds into categories. Moon and colleagues propose that, in the last couple months of gestation, babies monitor at least some vowels — the loudest and most expressive speech sounds — uttered by their mothers. © Society for Science & the Public 2000 - 2013

Keyword: Language; Development of the Brain
Link ID: 17662 - Posted: 01.08.2013

Taking beta-blocker drugs may cut the risk of dementia, a trial in 774 men suggests. The medication is used to treat high blood pressure, a known risk factor for dementia. In the study, which will be presented at the American Academy of Neurology's annual meeting in March, men on beta-blockers were less likely to have brain changes suggestive of dementia. Experts say it is too early to recommend beta-blockers for dementia. The findings are preliminary and larger studies in men and women from different ethnicities are needed to see what benefit beta-blockers might offer. People with high blood pressure are advised to see their doctor and get their condition under control to prevent associated complications like heart disease, stroke and vascular dementia. Having high blood pressure may damage the small vessels that supply the brain with blood. Blood carries essential oxygen and nourishment to the brain and without it, brain cells can die. Vascular dementia is the second most common cause of dementia after Alzheimer's disease and can occur if blood flow to the brain is reduced. Other research in a much larger sample of men - 800,000 in all - suggests another type of blood pressure drug known as an angiotensin receptor blocker (ARB) may cut dementia risk, including Alzheimer's disease, by as much as 50%. BBC © 2013

Keyword: Alzheimers
Link ID: 17661 - Posted: 01.08.2013

By KENNETH CHANG Mosquito bite? Poison ivy? Dry skin? Fuzzy sweater? Everyone has an itch to scratch. Why we and other animals itch remains something of a mystery. But now researchers at Johns Hopkins and Yale in the United States and several universities in China have found a key piece of the puzzle, identifying sensory neurons in mice that are dedicated to relaying itchy sensations from the top layers of skin to the spinal cord. “Our study, for the first time, shows the existence of itch-specific nerves,” said Xinzhong Dong, a professor of neuroscience at the Johns Hopkins University School of Medicine and the senior author of a paper about the findings in the journal Nature Neuroscience. Scientists have debated for decades whether separate circuitry existed for itchiness or whether its signals passed through the same nerves used to transmit pain. Earlier data — suppressing pain with morphine can cause chronic itching, for example — indicated some overlap between the two sensations. But the fact that evolution also produced dedicated itch nerves in mice — and almost certainly in people as well — suggests that itching serves an important role in survival and is not just a byproduct of the pain nerves. © 2013 The New York Times Company

Keyword: Pain & Touch
Link ID: 17660 - Posted: 01.08.2013

By Cheryl Murphy Enhancing your level of vision on demand sounds like something out of a comic book. Superman, if you recall, had the power to turn his x-ray vision on and off like a light switch. So is x-ray vision possible? I’m sorry to say: no. The ability of our naked eyes to see through layers of objects remains an idea conjured up in the minds of science fiction writers. However, the possibility of training your brain to flip to a heightened level of visual discrimination and detection whenever you want may in fact be a reality. Last month, researchers in Switzerland found that participants who were successfully trained to consciously up-regulate the level of activity in their early visual cortex as seen by neurofeedback on fMRI in real time were also able to voluntarily give their level of visual discrimination and detection a boost. This study may sound like science fiction but it is not. Here is how it was done. Sixteen, young healthy participants with normal or corrected-to-normal vision were told to focus on a central fixation light while they imagined high resolution pictures of changing color, shape and intensity in a particular part of their visual field which the researchers called the target region of interest. They visualized such things as writing their name in the air, a boat sailing on the ocean, patterns of spinning wheels and spirals, a model walking down the runway or their pet. They received on-the-spot visual feedback indicating how well their visualizations were boosting their brain activity to aid in their brain training. By imagining these detailed objects, seven out of the sixteen participants were able to train themselves to consciously up-regulate activity in areas of their early visual cortex over the course of a series of separate training sessions. In essence what the participants did was learn how to jump-start their visual cortex. Once their visual cortex was held at a higher state of activity, it was more sensitive and could better detect other stimuli in the target region of interest where they projected their visualizations. © 2013 Scientific American

Keyword: Vision; Learning & Memory
Link ID: 17659 - Posted: 01.08.2013

By Laura Sanders Astronauts on a months-long mission to Mars and back will have more to contend with than boredom and a lack of gourmet cuisine: Disrupted sleep may be a serious side effect of extended space flight, potentially changing crew dynamics and affecting performance on high-pressure tasks. In an epic feat of playacting, a crew of six men lived for 520 days inside a hermetically sealed 550-cubic-meter capsule in Moscow. As the grueling experiment wore on, the crew drifted into torpor, moving less and sleeping more. Four men experienced sleep problems, scientists report online January 7 in the Proceedings of the National Academy of Sciences. Developed by the Russian Academy of Sciences, the “Mars 500” project was designed to test the feasibility of sending people on a journey to Mars and back. The simulation was realistic: The chamber was sealed, mission control was on standby 24 hours a day with built-in communications delays during parts of the mission, and the crew had specific jobs to do during transit and on a simulated landing on Mars. “If we at some point really want to go to Mars and we want to send humans, then we need to know how they will cope with this long period of confinement,” says study coauthor Mathias Basner, of the University of Pennsylvania’s Perelman School of Medicine in Philadelphia. Basner’s team was one of many that conducted studies on the six men during the long simulation. © Society for Science & the Public 2000 - 2013

Keyword: Sleep
Link ID: 17658 - Posted: 01.08.2013

A strong family history of seizures could increase the chances of having severe migraines, says a study in Epilepsia journal. Scientists from Columbia University, New York, analysed 500 families containing two or more close relatives with epilepsy. Their findings could mean that genes exist that cause both epilepsy and migraine. Epilepsy Action said it could lead to targeted treatments. Previous studies have shown that people with epilepsy are substantially more likely than the general population to have migraine headaches, but it was not clear whether that was due to a shared genetic cause. The researchers found that people with three or more close relatives with a seizure disorder were more than twice as likely to experience 'migraine with aura' than patients from families with fewer individuals with seizures. Migraine with aura is a severe headache preceded by symptoms such as seeing flashing lights, temporary visual loss, speech problems or numbness of the face. Dr Melodie Winawer, lead author of the study from Columbia University Medical Centre, said the findings had implications for epilepsy patients. "Our study demonstrates a strong genetic basis for migraine and epilepsy, because the rate of migraine is increased only in people who have close (rather than distant) relatives with epilepsy." BBC © 2013

Keyword: Epilepsy; Pain & Touch
Link ID: 17657 - Posted: 01.07.2013

By Diane Mapes The video touched millions: An 8-month old boy smiles with unabashed adoration at his mother as he hears her voice, seemingly for the first time, thanks to a new cochlear implant. Posted on YouTube in April of 2008, the video of "Jonathan's Cochlear Implant Activation" has received more than 3.6 million hits and thousands of comments from viewers, many clamoring for an update. Five-year-old Jonathan is “doing great,” according to his parents, Brigette and Mark Breaux of Houston, Texas. "He's in kindergarten and we're working on speech," Brigette, his 35-year-old stay-at-home mom, told TODAY.com. "He can hear everything that we say to him. It's of course artificial hearing but he can hear and understand what we're saying." After a bout with bacterial meningitis left him deaf, Jonathan Breaux regained hearing with the help of a cochlear implant, and is now a happy 5-year-old. "He's a flirt," adds Mark, a 36-year-old corporate controller. "He was chasing girls around the playground when Brigette went to see him for his class party. He's a handful." © 2013 NBCNews.com

Keyword: Hearing; Robotics
Link ID: 17656 - Posted: 01.07.2013

By James Gallagher Health and science reporter, BBC News Totally blind mice have had their sight restored by injections of light-sensing cells into the eye, UK researchers report. The team in Oxford said their studies closely resemble the treatments that would be needed in people with degenerative eye disease. Similar results have already been achieved with night-blind mice. Experts said the field was advancing rapidly, but there were still questions about the quality of vision restored. Patients with retinitis pigmentosa gradually lose light-sensing cells from the retina and can become blind. The research team, at the University of Oxford, used mice with a complete lack of light-sensing photoreceptor cells in their retinas. The mice were unable to tell the difference between light and dark. Reconstruction They injected "precursor" cells which will develop into the building blocks of a retina once inside the eye. Two weeks after the injections a retina had formed, according to the findings presented in the Proceedings of the National Academy of Sciences journal. Prof Robert MacLaren said: "We have recreated the whole structure, basically it's the first proof that you can take a completely blind mouse, put the cells in and reconstruct the entire light-sensitive layer." BBC © 2013

Keyword: Vision; Development of the Brain
Link ID: 17655 - Posted: 01.07.2013

By DAN FROSCH ALBUQUERQUE — It has been almost four decades since Betty Jo Lopez started using heroin. Her face gray and wizened well beyond her 59 years, Ms. Lopez would almost certainly still be addicted, if not for the fact that she is locked away in jail, not to mention the cup of pinkish liquid she downs every morning. “It’s the only thing that allows me to live a normal life,” Ms. Lopez said of the concoction, which contains methadone, a drug used to treat opiate dependence. “These nurses that give it to me, they’re like my guardian angels.” For the last six years, the Metropolitan Detention Center, New Mexico’s largest jail, has been administering methadone to inmates with drug addictions, one of a small number of jails and prisons around the country that do so. At this vast complex, sprawled out among the mesas west of downtown Albuquerque, any inmate who was enrolled at a methadone clinic just before being arrested can get the drug behind bars. Pregnant inmates addicted to heroin are also eligible. Here in New Mexico, which has long been plagued by one of the nation’s worst heroin scourges, there is no shortage of participants — hundreds each year — who have gone through the program. © 2013 The New York Times Company

Keyword: Drug Abuse
Link ID: 17654 - Posted: 01.07.2013

Ed Yong For years, a particular protein has been cast as a lynchpin of long-term memory. Inhibiting this enzyme could erase old memories, whereas adding it could strengthen faded ones1–3. But two independent groups of US scientists have now seriously challenged the role of this 'memory molecule' by developing mice that completely lack it — and showing that these mice have no detectable memory problems. Their results are published today in Nature4, 5. The excitement around the enzyme, called protein kinase M-ζ (PKM-ζ), started building in 2006, when Todd Sacktor at the SUNY Downstate Medical Center in New York City wiped out established spatial memories in rats. He did so by injecting their brains with ZIP, a small peptide that is meant to block the enzyme1. Other teams obtained similar results, erasing different types of memory by injecting ZIP into various brain regions in rodents, flies and sea slugs. And in 2011, Sacktor did the opposite: he strengthened rats' memory of unpleasant tastes by injecting their brains with viruses carrying extra copies of PKM-ζ3. These fascinating studies suggested that long-term memory, rather than being static and stable, is surprisingly fragile, and depends on the continuous activity of a single enzyme. Richard Huganir of Johns Hopkins University in Baltimore, Maryland, was intrigued by these results, but was concerned that much of the data depended on the actions of ZIP. He and his collaborators took a different route, by deleting two genes — one for PKM-ζ and one for a related protein called PKC-ζ — in embryonic mice4. Working independently, Robert Messing and colleagues at the University of California, San Francisco, created similar mice5. © 2013 Nature Publishing Group

Keyword: Learning & Memory
Link ID: 17653 - Posted: 01.05.2013

By Rita Levi-Montalcini and Pietro Calissano The human nervous system is a vast network of several billion neurons, or nerve cells, endowed with the remarkable ability to receive, store and transmit information. In order to communicate with one another and with non-neuronal cells the neurons rely on the long extensions called axons, which are somewhat analogous to electrically conducting wires. Unlike wires, however, the axons are fluid-filled cylindrical structures that not only transmit electrical signals but also ferry nutrients and other essential substances to and from the cell body. Many basic questions remain to be answered about the mechanisms governing the formation of this intricate cellular network. How do the nerve cells differentiate into thousands of different types? How do their axons establish specific connections (synapses) with other neurons and non-neuronal cells? And what is the nature of the chemical messages neurons send and receive once the synaptic connections are made? This article will describe some major characteristics and effects of a protein called the nerve-growth factor (NGF), which has made it possible to induce and analyze under highly favorable conditions some crucial steps in the differentiation of neurons, such as the growth and maturation of axons and the synthesis and release of neurotransmitters: the bearers of the chemical messages. The discovery of NGF has also promoted an intensive search for other specific growth factors, leading to the isolation and characterization of a number of proteins with the ability to enhance the growth of different cell lines. © 2013 Scientific American,

Keyword: Development of the Brain; Trophic Factors
Link ID: 17652 - Posted: 01.05.2013

By ANAHAD O'CONNOR A new study of driving behavior across the country found that slightly more than 4 percent of adults admit to having fallen asleep at the wheel. Certain people were particularly likely to report drowsiness while driving, including those who slept less than six hours daily and those who snored at night, a potential sign of a sleep disorder. Though only 4.2 percent of adults said they had actually fallen asleep while driving in the past 30 days, the researchers said they believed the true number was probably several times that, since people who doze or nod off for a moment at the wheel may not realize it at the time or recall it later on. Drowsy driving has a widespread impact on the nation’s highways, experts say. In 2009, an estimated 730 deadly motor vehicle accidents involved a driver who was either sleepy or dozing off, and an additional 30,000 crashes that were nonfatal involved a drowsy driver. Accidents involving sleepy drivers are more likely to be deadly or cause injuries, in part because people who fall asleep at the wheel either fail to hit their brakes or veer off the road before crashing. To get a sense of just how prevalent the phenomenon is, Anne G. Wheaton, an epidemiologist at the Centers for Disease Control and Prevention, led a study looking at 147,000 adults in 19 states and the District of Columbia. The subjects were asked detailed questions about their daily activities, including their driving, sleep and work habits. Dr. Wheaton and her colleagues found that men were more likely to report drowsy driving than women, and that the behavior increased with age. About 1.7 percent of adults between 18 and 44 admitted to it, compared to 5 percent or more of those age 65 or older. The findings were published in the latest issue of Morbidity and Mortality Weekly Report. Copyright 2013 The New York Times Company

Keyword: Sleep; Attention
Link ID: 17651 - Posted: 01.05.2013

By Alexandra Witze Quietly, on the top floor of a nondescript commercial building overlooking Boston Harbor, the future is being born. Rows of young scientists tap intently in front of computer monitors, their concentration unbroken even as the occasional plane from Logan Airport buzzes by. State-of-the-art lab equipment hums away in the background. This office, in Boston’s Marine Industrial Park, is what California’s Silicon Valley was four decades ago — the vanguard of an industry that will change your life. Just as researchers from Stanford provided the brains behind the semiconductor revolution, so are MIT and Harvard fueling the next big transformation. Students and faculty cross the Charles River not to build computer chips, but to re-engineer life itself. Take Reshma Shetty, one of the young minds at work in the eighth-floor biological production facility. After receiving her doctorate at MIT in 2008, she, like many new graduates, decided she wanted to make her mark on the world. She got together with four colleagues, including her Ph.D. adviser Tom Knight, to establish a company that aims “to make biology easy to engineer.” Place an order with Ginkgo BioWorks and its researchers will make an organism to do whatever you want. Need to suck carbon dioxide out of the atmosphere? They can engineer the insides of a bacterium to do just that. Want clean, biologically based fuels to replace petroleum taken from the ground? Company scientists will design a microbe to poop those out. © Society for Science & the Public 2000 - 2013

Keyword: Robotics
Link ID: 17650 - Posted: 01.05.2013

By Christie Wilcox There’s a lot to be said for smarts—at least we humans, with some of the biggest brains in relation to our bodies in the animal kingdom, certainly seem to think so. The size of animal brains is extravagantly well-studied, as scientists have long sought to understand why our ancestors developed such complex and energetically costly neural circuitry. One of the most interesting evolutionary hypotheses about brain size is The Expensive Tissue Hypothesis. Back in the early 1990s, scientists were looking to explain how brain size evolves. Brains are exceedingly useful organs; more brain cells allows for more behavioral flexibility, better control of larger bodies, and, of course, intelligence. But if bigger brains were always better, every animal would have them. Thus, scientists reasoned, there must be a downside. The hypothesis suggests that while brains are great and all, their extreme energetic cost limits their size and tempers their growth. When it comes to humans, for example, though our brains are only 2% of our bodies, they take up a whopping 20% of our energy requirements. And you have to wonder: with all that energy being used by our brains, what body parts have paid the price? The hypothesis suggested our guts took the hit, but that intelligence made for more efficient foraging and hunting, thus overcoming the obstacle. This makes sense, but despite over a century of research on the evolution of brain size, there is still controversy, largely stemming from the fact that evidence for the expensive tissue hypothesis is based entirely on between species comparisons and correlations, with no empirical tests. © 2013 Scientific American

Keyword: Evolution; Obesity
Link ID: 17649 - Posted: 01.05.2013