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|By Erez Ribak and The Conversation UK The human eye is optimised to have good colour vision at day and high sensitivity at night. But until recently it seemed as if the cells in the retina were wired the wrong way round, with light travelling through a mass of neurons before it reaches the light-detecting rod and cone cells. New research presented at a meeting of the American Physical Society has uncovered a remarkable vision-enhancing function for this puzzling structure. About a century ago, the fine structure of the retina was discovered. The retina is the light-sensitive part of the eye, lining the inside of the eyeball. The back of the retina contains cones to sense the colours red, green and blue. Spread among the cones are rods, which are much more light-sensitive than cones, but which are colour-blind. Before arriving at the cones and rods, light must traverse the full thickness of the retina, with its layers of neurons and cell nuclei. These neurons process the image information and transmit it to the brain, but until recently it has not been clear why these cells lie in front of the cones and rods, not behind them. This is a long-standing puzzle, even more so since the same structure, of neurons before light detectors, exists in all vertebrates, showing evolutionary stability. Researchers in Leipzig found that glial cells, which also span the retinal depth and connect to the cones, have an interesting attribute. These cells are essential for metabolism, but they are also denser than other cells in the retina. In the transparent retina, this higher density (and corresponding refractive index) means that glial cells can guide light, just like fibre-optic cables. © 2015 Scientific American
By Nicholas Weiler Where did the thief go? You might get a more accurate answer if you ask the question in German. How did she get away? Now you might want to switch to English. Speakers of the two languages put different emphasis on actions and their consequences, influencing the way they think about the world, according to a new study. The work also finds that bilinguals may get the best of both worldviews, as their thinking can be more flexible. Cognitive scientists have debated whether your native language shapes how you think since the 1940s. The idea has seen a revival in recent decades, as a growing number of studies suggested that language can prompt speakers to pay attention to certain features of the world. Russian speakers are faster to distinguish shades of blue than English speakers, for example. And Japanese speakers tend to group objects by material rather than shape, whereas Koreans focus on how tightly objects fit together. Still, skeptics argue that such results are laboratory artifacts, or at best reflect cultural differences between speakers that are unrelated to language. In the new study, researchers turned to people who speak multiple languages. By studying bilinguals, “we’re taking that classic debate and turning it on its head,” says psycholinguist Panos Athanasopoulos of Lancaster University in the United Kingdom. Rather than ask whether speakers of different languages have different minds, he says, “we ask, ‘Can two different minds exist within one person?’ ” Athanasopoulos and colleagues were interested in a particular difference in how English and German speakers treat events. © 2015 American Association for the Advancement of Science
A long-term study has pointed to a link between breastfeeding and intelligence. The research in Brazil traced nearly 3,500 babies, from all walks of life, and found those who had been breastfed for longer went on to score higher on IQ tests as adults. Experts say the results, while not conclusive, appear to back current advice that babies should be exclusively breastfed for six months. But they say mothers should still have a choice about whether or not to do it. Regarding the findings - published in The Lancet Global Health - they stress there are many different factors other than breastfeeding that could have an impact on intelligence, although the researchers did try to rule out the main confounders, such as mother's education, family income and birth weight. Dr Bernardo Lessa Horta, from the Federal University of Pelotas in Brazil, said his study offers a unique insight because in the population he studied, breastfeeding was evenly distributed across social class - not something just practised by the rich and educated. Most of the babies, irrespective of social class, were breastfed - some for less than a month and others for more than a year. Those who were breastfed for longer scored higher on measures of intelligence as adults. They were also more likely to earn a higher wage and to have completed more schooling. Dr Horta believes breast milk may offer an advantage because it is a good source of long-chain saturated fatty acids which are essential for brain development. But experts say the study findings cannot confirm this and that much more research is needed to explore any possible link between breastfeeding and intelligence. © 2015 BBC.
Jane Brody The Holy Grail in any progressive disease is to find it early enough to start effective treatment before irreversible damage has occurred. For Parkinson’s disease, which afflicts 1.5 million Americans and growing, a new study has brought this goal a little closer. The study, conducted among more than 54,000 British men and women, identified a slew of symptoms that were more likely to be present in people who years later were diagnosed with Parkinson’s. The findings underscore the prevailing view among neurologists that the damage caused by this disease begins long before classic symptoms like tremors, rigidity and an unsteady gait develop and a definite diagnosis can be made. The study, by Dr. Anette Schrag and fellow neurologists at the University College London, was published in The Lancet in January. As many as five years before a diagnosis of Parkinson’s, those who developed it were more likely to have experienced tremor, balance problems, constipation, low blood pressure, dizziness, erectile and urinary dysfunction, fatigue, depression and anxiety. In addition, Dr. Claire Henchcliffe, director of the Parkinson’s Disease and Movement Disorders Institute at Weill Cornell Medical Center, said that REM sleep behavior disorder, characterized by a tendency to act out one’s dreams while asleep, is one of the strongest prediagnostic symptoms, along with a lost sense of smell and subtle changes in cognition. Dr. Melissa J. Nirenberg, a Parkinson’s disease specialist at New York University Medical Center, said, “Up to 80 percent of people with the sleep disorder get Parkinson’s or a similar neurodegenerative disease.” © 2015 The New York Times Company
Jon Hamilton Since his birth 33 years ago, Jonathan Keleher has been living without a cerebellum, a structure that usually contains about half the brain's neurons. This exceedingly rare condition has left Jonathan with a distinctive way of speaking and a walk that is slightly awkward. He also lacks the balance to ride a bicycle. But all that hasn't kept him from living on his own, holding down an office job and charming pretty much every person he meets. "I've always been more into people than anything else," Jonathan tells me when I meet him at his parents' house in Concord, Mass., a suburb of Boston. "Why read a book or why do anything when you can be social and talk to people?" Jonathan is also making an important contribution to neuroscience. By allowing scientists to study him and his brain, he is helping to change some long-held misconceptions about what the cerebellum does. And that, in turn, could help the hundreds of thousands of people whose cerebellums have been damaged by a stroke, infection or disease. For decades, the cerebellum has been the "Rodney Dangerfield of the brain," says Dr. Jeremy Schmahmann, a professor of neurology at Harvard and Massachusetts General Hospital. It gets no respect because most scientists only know about its role in balance and fine motor control. © 2015 NPR
Jon Hamilton A new understanding of the brain's cerebellum could lead to new treatments for people with problems caused by some strokes, autism and even schizophrenia. That's because there's growing evidence that symptoms ranging from difficulty with abstract thinking to emotional instability to psychosis all have links to the cerebellum, says Jeremy Schmahmann, a professor of neurology at Harvard and Massachusetts General Hospital. "The cerebellum has all these functions we were previously unaware of," Schmahmann says. Scientists once thought the cerebellum's role was limited to balance and coordinating physical movements. In the past couple of decades, though, there has been growing evidence that it also plays a role in thinking and emotions. As described in an earlier post, some of the most compelling evidence has come from people like Jonathan Keleher, people born without a cerebellum. "I'm good at routine (activities) and (meeting) people," says Keleher, who is 33. He also has good long-term memory. What he's not good at is strategizing and abstract thinking. But remarkably, Keleher's abilities in these areas have improved dramatically over time. "I'm always working on how to better myself," he says. "And it's a continuous struggle." © 2015 NPR
By PAM BELLUCK What happens to forgotten memories — old computer passwords, friends’ previous phone numbers? Scientists have long held two different theories. One is that memories do not diminish but simply get overshadowed by new memories. The other is that older memories become weaker, that pulling to mind new passwords or phone numbers degrades old recollections so they do not interfere. The difference could be significant. If old memories stay strong and are merely papered over by new ones, they may be easier to recover. That could be positive for someone trying to remember an acquaintance’s name, but difficult for someone trying to lessen memories of abuse. It could suggest different strategies for easing traumatic memories, evaluating witness testimony about crimes, or helping students study for tests. Now, a study claims to provide evidence of memory’s weakening by showing that people’s ability to remember something and the pattern of brain activity that thing generates both appear to diminish when a competing memory gets stronger. Demonstrating sophisticated use of brain scans in memory research, authors of the study, published Monday in the journal Nature Neuroscience, appear to have identified neural fingerprints of specific memories, distinguishing brain activity patterns produced when viewing a picture of a necklace, say, from a picture of binoculars or other objects. The experiment, conducted by scientists in Birmingham and Cambridge, England, involved several stages with 24 participants first trained to associate words to two unrelated black and white pictures from lists of famous people, ordinary objects or scenes. © 2015 The New York Times Company
Keyword: Learning & Memory
Link ID: 20695 - Posted: 03.17.2015
Brian Owens Our choice between two moral options might be swayed by tracking our gaze, and asking for a decision at the right moment. People asked to choose between two written moral statements tend to glance more often towards the option they favour, experimental psychologists say. More surprisingly, the scientists also claim it’s possible to influence a moral choice: asking for an immediate decision as soon as someone happens to gaze at one statement primes them to choose that option. It’s well known that people tend to look more towards the option they are going to choose when they are choosing food from a menu, says Philip Pärnamets, a cognitive scientist from Lund University in Sweden. He wanted to see if that applied to moral reasoning as well. “Moral decisions have long been considered separately from general decision-making,” he says. “I wanted to integrate them.” In a paper published today in the Proceedings of the National Academy of Sciences1, Pärnamets and his colleagues explain how they presented volunteers with a series of moral statements, such as 'murder is sometimes justified,' 'masturbating with the aid of a willing animal is acceptable' and 'paying taxes is a good thing.' Then the psychologists tracked the volunteers’ gaze as two options appeared on a screen. Once the tracker had determined that a person had spent at least 750 milliseconds looking at one answer and 250 milliseconds at the other, the screen changed to prompt them to make a decision. Almost 60% of the time, they chose the most viewed option — indicating, says Pärnamets, that eye gaze tracks an unfolding moral decision. © 2015 Nature Publishing Group,
By BENEDICT CAREY Behind all those canned compliments for older adults — spry! wily! wise! — is an appreciation for something that scientists have had a hard time characterizing: mental faculties that improve with age. Knowledge is a large part of the equation, of course. People who are middle-aged and older tend to know more than young adults, by virtue of having been around longer, and score higher on vocabulary tests, crossword puzzles and other measures of so-called crystallized intelligence. Still, young adults who consult their elders (mostly when desperate) don’t do so just to gather facts, solve crosswords or borrow a credit card. Nor, generally, are they looking for help with short-term memory or puzzle solving. Those abilities, called fluid intelligence, peak in the 20s. No, the older brain offers something more, according to a new paper in the journal Psychological Science. Elements of social judgment and short-term memory, important pieces of the cognitive puzzle, may peak later in life than previously thought. The postdoctoral fellows Joshua Hartshorne of M.I.T. and Laura Germine of Harvard and Massachusetts General Hospital analyzed a huge trove of scores on cognitive tests taken by people of all ages. The researchers found that the broad split in age-related cognition — fluid in the young, crystallized in the old — masked several important nuances. “This dichotomy between early peaks and later peaks is way too coarse,” Dr. Hartshorne said. “There are a lot more patterns going on, and we need to take those into account to fully understand the effects of age on cognition.” The new paper is hardly the first challenge to the scientific literature on age-related decline, and it won’t be the last. A year ago, German scientists argued that cognitive “deficits” in aging were caused largely by the accumulation of knowledge — that is, the brain slows down because it has to search a larger mental library of facts. That idea has stirred some debate among scientists. Experts said the new analysis raised a different question: Are there distinct, independent elements of memory and cognition that peak at varying times of life? © 2015 The New York Times Company
By Camilla Turner It is one of life’s most enduring mysteries. A question that music, poetry, myth and legend has, for thousands of years, tried but failed to answer. However, we may now be a step closer to discovering what love is, thanks to a scientific study that has obtained the first empirical evidence of love-related alterations in the brain. A team of researchers from universities in China and New York used MRI scans to track the physical effects of love on the brain and has pieced together a “love map” of the human mind. The study found that several areas of the brain showed increased activity in those who were in love, including in the parts of the brain linked to reward and motivation. The researchers said their results shed light on the “underlying mechanisms of romantic love” and would pave the way for a brain scan that could act as a “love test”. Scientists recruited 100 students from Southwest University in Chongqing, China, who were divided into three groups according to their relationship status: an “in-love” group, comprised of those who were in love at the time; an “ended-love” group, who had recently ended loving relationships; and a “single” group, who had never been in love. Participants were told not to think of anything while their brains were scanned, so that researchers could monitor the differences between the brains of students in all three groups. © Copyright of Telegraph Media Group Limited 2015
Keyword: Sexual Behavior
Link ID: 20692 - Posted: 03.17.2015
By RENEE ENGELN ON Tuesday, in the wake of an online petition signed by thousands of people, Facebook announced that it was removing “feeling fat” from its list of status update emoticons. The petition argued that the offending emoticon, with its chubby cheeks and double chin, reinforced negative body images, and Facebook seemed to agree. Is it really such a big deal if you tell everyone how fat you feel? After all, a simple “I’m so fat!” can result in a chorus of empathetic voices, saying, “Me, too!” or “You’re beautiful just the way you are!” And that will help you feel better, and help others feel better, too — right? Wrong. As someone who studies this type of public body self-disparagement, known as “fat talk,” I can say that it probably will make you feel worse. And it may drag down other people with you. Conversational shaming of the body has become practically a ritual of womanhood (though men also engage in it). In a survey that a colleague and I reported in 2011 in the Psychology of Women Quarterly, we found that more than 90 percent of college women reported engaging in fat talk — despite the fact that only 9 percent were actually overweight. In another survey, which we published in December in the Journal of Health Psychology, we canvassed thousands of women ranging in age from 16 to 70. Contrary to the stereotype of fat talk as a young woman’s practice, we found that fat talk was common across all ages and all body sizes. Most important, fat talk is not a harmless social-bonding ritual. According to an analysis of several studies that my colleagues and I published in 2012 in the Psychology of Women Quarterly, fat talk was linked with body shame, body dissatisfaction and eating-disordered behavior. Fat talk does not motivate women to make healthier choices or take care of their bodies; in fact, the feelings of shame it brings about tend to encourage the opposite. © 2015 The New York Times Company
Keyword: Anorexia & Bulimia
Link ID: 20691 - Posted: 03.17.2015
By Emily Underwood Deep brain stimulation, which now involves surgically inserting electrodes several inches into a person's brain and connecting them to a power source outside the skull, can be an extremely effective treatment for disorders such as Parkinson's disease, obsessive compulsive disorder, and depression. The expensive, invasive procedure doesn't always work, however, and can be risky. Now, a study in mice points to a less invasive way to massage neuronal activity, by injecting metal nanoparticles into the brain and controlling them with magnetic fields. Major technical challenges must be overcome before the approach can be tested in humans, but the technique could eventually provide a wireless, nonsurgical alternative to traditional deep brain stimulation surgery, researchers say. "The approach is very innovative and clever," says Antonio Sastre, a program director in the Division of Applied Science & Technology at the National Institute of Biomedical Imaging and Bioengineering in Bethesda, Maryland. The new work provides "a proof of principle." The inspiration to use magnets to control brain activity in mice first struck materials scientist Polina Anikeeva while working in the lab of neuroscientist-engineer Karl Deisseroth at Stanford University in Palo Alto, California. At the time, Deisseroth and colleagues were refining optogenetics, a tool that can switch specific ensembles of neurons on and off in animals with beams of light. © 2015 American Association for the Advancement of Science.
Keyword: Brain imaging
Link ID: 20690 - Posted: 03.14.2015
By John Horgan In 1990 The New York Times published a front-page article by Lawrence Altman, a reporter with a medical degree, announcing that scientists had discovered “a link between alcoholism and a specific gene.” The evidence for the "feel-good gene," which supposedly reduces anxiety, is flimsy, just like the evidence linking specific genes to high intelligence, violent aggression, homosexuality, bipolar disorder and countless other complex human traits and ailments. That was merely one in a string of reports in which the Times and other major media hyped what turned out to be erroneous claims linking complex traits and disorders—from homosexuality and high intelligence to schizophrenia and bipolar disorder—to specific genes. I thought those days were over, and that scientists and the media have learned to doubt extremely reductionist genetic accounts of complex traits and behaviors. I was wrong. Last Sunday, the “Opinion” section of the Times published an essay, “The Feel-Good Gene,” which states: “For the first time, scientists have demonstrated that a genetic variation in the brain makes some people inherently less anxious, and more able to forget fearful and unpleasant experiences. This lucky genetic mutation produces higher levels of anandamide–the so-called bliss molecule and our natural marijuana–in our brains. In short, some people are prone to be less anxious simply because they won the genetic sweepstakes and randomly got a genetic mutation that has nothing at all to do with strength of character.” This article, like the one touting the alcoholism gene 25 years ago, was written by a physician, Richard Friedman, professor of psychiatry at Weill Cornell Medical College. I emphasize this fact because scientific hype is often blamed on supposedly ignorant journalists like me rather than on physicians and other so-called experts. © 2015 Scientific American
By Matthew J.X. Malady One hour and seven minutes into the decidedly hit-or-miss 1996 comedy Black Sheep, the wiseass sidekick character played by David Spade finds himself at an unusually pronounced loss for words. While riding in a car driven by Chris Farley’s character, he glances at a fold-up map and realizes he somehow has become unfamiliar with the name for paved driving surfaces. “Robes? Rouges? Rudes?” Nothing seems right. Even when informed by Farley that the word he’s looking for is roads, Spade’s character continues to struggle: “Rowds. Row-ads.” By this point, he’s become transfixed. “That’s a total weird word,” he says, “isn’t it?” Now, it’s perhaps necessary to mention that, in the context of the film, Spade’s character is high off nitrous oxide that has leaked from the car’s engine boosters. But never mind that. Row-ad-type word wig outs similar to the one portrayed in that movie are things that actually happen, in real life, to people with full and total control over their mental capacities. These wordnesias sneak up on us at odd times when we’re writing or reading text. I was in a full-on wordnesiac state. On one of my spelling attempts, I think I even threw a K into the mix. It was bad. Here’s how they work: Every now and again, for no good or apparent reason, you peer at a standard, uncomplicated word in a section of text and, well, go all row-ads on it. If you’re typing, that means inexplicably blanking on how to spell something easy like cake or design. The reading version of wordnesia occurs when a common, correctly spelled word either seems as though it can’t possibly be spelled correctly, or like it’s some bizarre combination of letters you’ve never before seen—a grouping that, in some cases, you can’t even imagine being the proper way to compose the relevant term. © 2014 The Slate Group LLC.
Link ID: 20688 - Posted: 03.14.2015
By Maggie Fox Teenagers who use marijuana heavily grow up to have poor memories and also have brain abnormalities, a new study shows. The study cannot say which came first — the brain structure differences or the pot use. But it suggests there could be long-term effects of heavy marijuana use. A team at Northwestern University looked at 97 volunteers with and without mental illness. The dope smokers said they'd used marijuana daily starting at age 16 or 17, and said they had not used other drugs. The daily marijuana users had an abnormally shaped hippocampus and performed about 18 percent more poorly on long-term memory tasks, the researchers reported in the journal Hippocampus. The hippocampus is a part of the brain used in storing long-term memory. "The memory processes that appear to be affected by cannabis are ones that we use every day to solve common problems and to sustain our relationships with friends and family," said Dr. John Csernansky, who worked on the study. Previous research by the same Northwestern team showed heavy pot smokers had poor short-term and working memory and abnormally shaped brain structures including the striatum, globus pallidus and thalamus. "It is possible that the abnormal brain structures reveal a pre-existing vulnerability to marijuana abuse," Matthew Smith, who led the study, said in a statement.
When it comes to fight or flight for brawling crickets, a chemical in the brain is in charge. Being roughed up in a skirmish can trigger nerve cells in Mediterranean field crickets (Gryllus bimaculatus) to release nitric oxide, making the losing cricket run away, scientists report online March 13 in Science Advances. Watch in this video as two crickets face off. When the loser hits its limit, it flees the fight. In a second bout, the loser then tries to avoid the winner. Nitric oxide prompts this continued submissive behavior, which lasts several hours before a cricket’s will to fight returns. “If you block nitric oxide they recover quickly, and if you give them nitric oxide they don’t,” says Paul Stevenson, a coauthor of the new research and behavioral neurobiologist at Leipzig University in Germany. “It’s a very simple algorithm for controlling a very complicated social situation.” P. Stevenson and J. Rillich. Adding up the odds—Nitric oxide signaling underlies the decision to flee and post-conflict depression of aggression. Science Advances. Published online March 13, 2015.doi: 10.1126/sciadv.1500060. © Society for Science & the Public 2000 - 2015.
Link ID: 20686 - Posted: 03.14.2015
By Emily Underwood From imaging babies to blasting apart kidney stones, ultrasound has proved to be a versatile tool for physicians. Now, several research teams aim to unleash the technology on some of the most feared brain diseases. The blood-brain barrier, a tightly packed layer of cells that lines the brain's blood vessels, protects it from infections, toxins, and other threats but makes the organ frustratingly hard to treat. A strategy that combines ultrasound with microscopic blood-borne bubbles can briefly open the barrier, in theory giving drugs or the immune system access to the brain. In the clinic and the lab, that promise is being evaluated. This month, in one of the first clinical tests, Todd Mainprize, a neurosurgeon at the University of Toronto in Canada, hopes to use ultrasound to deliver a dose of chemotherapy to a malignant brain tumor. And in some of the most dramatic evidence of the technique's potential, a research team reports this week in Science Translational Medicine that they used it to rid mice of abnormal brain clumps similar to those in Alzheimer's disease, restoring lost memory and cognitive functions. If such findings can be translated from mice to humans, “it will revolutionize the way we treat brain disease,” says biophysicist Kullervo Hynynen of the Sunnybrook Research Institute in Toronto, who originated the ultrasound method. Some scientists stress that rodent findings can be hard to translate to humans and caution that there are safety concerns about zapping the brain with even the low-intensity ultrasound used in the new study, which is similar to that used in diagnostic scans. © 2015 American Association for the Advancement of Science.
Link ID: 20685 - Posted: 03.12.2015
|By Daisy Yuhas The brain is a hotbed of electrical activity. Scientists have long known that brain cells communicate via electrical missives, created by charged atoms and molecules called ions as they travel across the membranes of those cells. But a new study suggests that in the days and weeks that lead up to a brain forming in an embryo or fetus, altering the electrical properties of these cells can dramatically change how the ensuing brain develops. Researchers at Tufts University and the University of Minnesota have investigated how the difference in charge on either side of a resting cell’s membrane—its electrical potential—helps build the brain. In previous work Tufts University developmental biologist Michael Levin found that patterns of electrical potentials in the earliest stages of an embryo’s development can direct how an animal’s body grows, and that manipulating those potentials can cause a creature to sprout extra limbs, tails or functioning eyes. Now, Levin’s group has investigated how these potentials shape the brain. Working with frog embryos the researchers first used dyes to see the patterns of electrical potentials that precede brain development. They noticed that before the development of a normal brain the cells lining the neural tube, a structure that eventually becomes the brain and spinal cord, have extreme differences in ionic charge within and outside the membrane that houses the cells. In other words, these cells are extremely polarized. © 2015 Scientific American
Keyword: Development of the Brain
Link ID: 20684 - Posted: 03.12.2015
Older people could improve or maintain their mental function through heart healthy lifestyle changes, a large randomized trial for dementia prevention shows. Researchers in Finland and Sweden designed a trial to tackle risk factors for Alzheimer's disease. The 1,260 Finns aged 60 to 77 participating in the study were all considered at risk of dementia based on standard test scores. Half were randomly assigned to receive advice from health professionals on maintaining a healthy diet, aerobic and muscle training exercises, brain training exercises and regular checks of blood pressure, height and weight for body mass index and physical exams for two years or regular health advice. Participants in the Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability or FINGER study had their cognitive function measured in a battery of mental tests. "The main hypothesis was that simultaneous changes in several risk factors (even of smaller magnitude) would lead to a protective effect on cognition," Miia Kivipelto from the Karolinska Institute in Stockholm and her co-authors said in Wednesday's issue of The Lancet. Overall, test scores were 25 per cent in the diet and training group than the control group. There was no effect on memory. ©2015 CBC/Radio-Canada.
Link ID: 20683 - Posted: 03.12.2015
Mutations in the presenilin-1 gene are the most common cause of inherited, early-onset forms of Alzheimer’s disease. In a new study, published in Neuron, scientists replaced the normal mouse presenilin-1 gene with Alzheimer’s-causing forms of the human gene to discover how these genetic changes may lead to the disorder. Their surprising results may transform the way scientists design drugs that target these mutations to treat inherited or familial Alzheimer’s, a rare form of the disease that affects approximately 1 percent of people with the disorder. The study was partially funded by the National Institute of Neurological Disorders and Stroke (NINDS), part of the National Institutes of Health. For decades, it has been unclear exactly how the presenilin mutations cause Alzheimer’s disease. Presenilin is a component of an important enzyme, gamma secretase, which cuts up amyloid precursor protein into two protein fragments, Abeta40 and Abeta42. Abeta42 is found in plaques, the abnormal accumulations of protein in the brain which are a hallmark of Alzheimer’s. Numerous studies suggested that presenilin-1 mutations increased activity of gamma-secretase. Investigators have developed drugs that block gamma-secretase, but they have so far failed in clinical trials to halt the disease. The study led by Raymond Kelleher, M.D., Ph.D. and Jie Shen, Ph.D., professors of neurology at Harvard Medical School, Boston, provides a plot twist in the association of presenilin-1 mutations and inherited Alzheimer’s disease. Using mice with altered forms of the presenilin gene, Drs. Kelleher and Shen discovered that the mutations may cause the disease by decreasing, rather than increasing, the activity of gamma-secretase.