Chapter 13. Memory, Learning, and Development
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The mystery is starting to untangle. It has long been known that twisted fibres of a protein called tau collect in the brain cells of people with Alzheimer’s, but their exact role in the disease is unclear. Now a study in mice has shown how tau interferes with the strengthening of connections between neurons – the key mechanism by which we form memories. In healthy cells, the tau protein helps to stabilise microtubules that act as rails for transporting materials around the cell. In people with Alzheimer’s, these proteins become toxic, but an important unanswered question is what forms of tau are toxic: the tangles may not be the whole story. In the new study, Li Gan and her colleagues at the Gladstone Institute of Neurological Disease in San Francisco found that the brains of those with Alzheimer’s have high levels of tau with a particular modification, called acetylated tau. They then looked at what acetylated tau does in a mouse model of Alzheimer’s, finding that it accumulates at synapses – the connections between neurons. When we form memories, synapses become strengthened through extra receptors inserted into the cell membranes, and this heightens their response. But acetylated tau depletes another protein called KIBRA, which is essential for this synapse-strengthening mechanism. “We’re excited because we think we now have a handle on the link between tau and memory,” says Gan. “We’re also cautious because we know this may not be the only link. It’s still early days in understanding the mechanism.” © Copyright Reed Business Information Ltd.
By Emily Underwood More than 99% of clinical trials for Alzheimer’s drugs have failed, leading many to wonder whether pharmaceutical companies have gone after the wrong targets. Now, research in mice points to a potential new target: a developmental process gone awry, which causes some immune cells to feast on the connections between neurons. “It is beautiful new work,” which “brings into light what’s happening in the early stage of the disease,” says Jonathan Kipnis, a neuroscientist at the University of Virginia School of Medicine in Charlottesville. Most new Alzheimer’s drugs aim to eliminate β amyloid, a protein that forms telltale sticky plaques around neurons in people with the disease. Those with Alzheimer’s tend to have more of these deposits in their brains than do healthy people, yet more plaques don’t always mean more severe symptoms such as memory loss or poor attention, says Beth Stevens of Boston Children’s Hospital, who led the new work. What does track well with the cognitive decline seen in Alzheimer’s disease—at least in mice that carry genes that confer high risk for the condition in people—is a marked loss of synapses, particularly in brain regions key to memory, Stevens says. These junctions between nerve cells are where neurotransmitters are released to spark the brain’s electrical activity. Stevens has spent much of her career studying a normal immune mechanism that prunes weak or unnecessary synapses as the brain matures from the womb through adolescence, allowing more important connections to become stronger. In this process, a protein called C1q sets off a series of chemical reactions that ultimately mark a synapse for destruction. After a synapse has been “tagged,” immune cells called microglia—the brain’s trash disposal service—know to “eat” it, Stevens says. © 2016 American Association for the Advancement of Science
By Nicholas Bakalar Stress in childhood may be linked to hardening of the arteries in adulthood, new research suggests. Finnish researchers studied 311 children 12 to 18 years old, scoring their levels of stress according to a variety of components, including the family’s economic circumstances, the emotional environment in the home, whether parents engaged in healthy behaviors, stressful events (such as divorce, moves or death of a family member) and parental concerns about the child’s social adjustment. Using these criteria, they calculated a stress score. When the members of the group were 40 to 46 years old, they used computed tomography to measure coronary artery calcification, a marker of atherosclerosis and a risk factor for cardiovascular disease. The study, in JAMA Pediatrics, controlled for sex, cholesterol, body mass index and other factors, but still found that the higher the childhood stress score, the greater the risk for coronary artery calcification. The study is observational, and the data is based largely on parental reports, which can be biased. Still, its long follow-up time and careful control of other variables gives it considerable strength. There are plausible mechanisms for the connection, including stress-induced increases in inflammation, which in animal models have been linked to a variety of ailments. “I think that economic conditions are important here,” said the lead author, Dr. Markus Juonala, a professor of internal medicine at the University of Turku in Finland. “Public health interventions should focus on how to intervene in better ways with people with higher stress and lower socioeconomic status.” © 2016 The New York Times Company
By Matthew Hutson Earlier this month, a computer program called AlphaGo defeated a (human) world champion of the board game Go, years before most experts expected computers to rival the best flesh-and-bone players. But then last week, Microsoft was forced to silence its millennial-imitating chatbot Tay for blithely parroting Nazi propaganda and misogynistic attacks after just one day online, her failure a testimony to the often underestimated role of human sensibility in intelligent behavior. Why are we so compelled to pit human against machine, and why are we so bad at predicting the outcome? As the number of jobs susceptible to automation rises, and as Stephen Hawking, Elon Musk, and Bill Gates warn that artificial intelligence poses an existential threat to humanity, it’s natural to wonder how humans measure up to our future robot overlords. But even those tracking technology’s progress in taking on human skills have a hard time setting an accurate date for the uprising. That’s in part because one prediction strategy popular among both scientists and journalists—benchmarking the human brain with digital metrics such as bits, hertz, and million instructions per section, or MIPS—is severely misguided. And doing so could warp our expectations of what technology can do for us and to us. Since their development, digital computers have become a standard metaphor for the mind and brain. The comparison makes sense, in that brains and computers both transform input into output. Most human brains, like computers, can also manipulate abstract symbols. (Think arithmetic or language processing.) But like any metaphor, this one has limitations.
By David Z. Hambrick Nearly a century after James Truslow Adams coined the phrase, the “American dream” has become a staple of presidential campaign speeches. Kicking off her 2016 campaign, Hillary Clinton told supporters that “we need to do a better job of getting our economy growing again and producing results and renewing the American dream.” Marco Rubio lamented that “too many Americans are starting to doubt” that it is still possible to achieve the American dream, and Ted Cruz asked his supporters to “imagine a legal immigration system that welcomes and celebrates those who come to achieve the American dream.” Donald Trump claimed that “the American dream is dead” and Bernie Sanders quipped that for many “the American dream has become a nightmare.” But the American dream is not just a pie-in-the-sky notion—it’s a scientifically testable proposition. The American dream, Adams wrote, “is not a dream of motor cars and high wages merely, but a dream of social order in which each man and each woman shall be able to attain to the fullest stature of which they are innately capable…regardless of the fortuitous circumstances of birth or position.” In the parlance of behavioral genetics—the scientific study of genetic influences on individual differences in behavior—Adams’ idea was that all Americans should have an equal opportunity to realize their genetic potential. A study just published in Psychological Science by psychologists Elliot Tucker-Drob and Timothy Bates reveals that this version of the American dream is in serious trouble. Tucker-Drob and Bates set out to evaluate evidence for the influence of genetic factors on IQ-type measures (aptitude and achievement) that predict success in school, work, and everyday life. Their specific question was how the contribution of genes to these measures would compare at low versus high levels of socioeconomic status (or SES), and whether the results would differ across countries. The results reveal, ironically, that the American dream is more of a reality for other countries than it is for America: genetic influences on IQ were uniform across levels of SES in Western Europe and Australia, but, in the United States, were much higher for the rich than for the poor. © 2016 Scientific American
Chris French The fallibility of human memory is one of the most well established findings in psychology. There have been thousands of demonstrations of the unreliability of eyewitness testimony under well-controlled conditions dating back to the very earliest years of the discipline. Relatively recently, it was discovered that some apparent memories are not just distorted memories of witnessed events: they are false memories for events that simply never took place at all. Psychologists have developed several reliable methods for implanting false memories in a sizeable proportion of experimental participants. It is only in the last few years, however, that scientists have begun to systematically investigate the phenomenon of non-believed memories. These are subjectively vivid memories of personal experiences that an individual once believed were accurate but now accepts are not based upon real events. Prior to this, there were occasional anecdotal reports of non-believed memories. One of the most famous was provided by the influential developmental psychologist Jean Piaget. He had a clear memory of almost being kidnapped at about the age of two and of his brave nurse beating off the attacker. His grateful family were so impressed with the nurse that they gave her a watch as a reward. Years later, the nurse confessed that she had made the whole story up. Even after he no longer believed that the event had taken place, Piaget still retained his vivid and detailed memory of it. © 2016 Guardian News and Media Limited
Keyword: Learning & Memory
Link ID: 22050 - Posted: 03.30.2016
Brendan Maher It took less than a minute of playing League of Legends for a homophobic slur to pop up on my screen. Actually, I hadn't even started playing. It was my first attempt to join what many agree to be the world's leading online game, and I was slow to pick a character. The messages started to pour in. “Pick one, kidd,” one nudged. Then, “Choose FA GO TT.” It was an unusual spelling, and the spaces may have been added to ease the word past the game's default vulgarity filter, but the message was clear. Online gamers have a reputation for hostility. In a largely consequence-free environment inhabited mostly by anonymous and competitive young men, the antics can be downright nasty. Players harass one another for not performing well and can cheat, sabotage games and do any number of things to intentionally ruin the experience for others — a practice that gamers refer to as griefing. Racist, sexist and homophobic language is rampant; aggressors often threaten violence or urge a player to commit suicide; and from time to time, the vitriol spills beyond the confines of the game. In the notorious 'gamergate' controversy that erupted in late 2014, several women involved in the gaming industry were subjected to a campaign of harassment, including invasions of privacy and threats of death and rape. League of Legends has 67 million players and grossed an estimated US$1.25 billion in revenue last year. But it also has a reputation for toxic in-game behaviour, which its parent company, Riot Games in Los Angeles, California, sees as an obstacle to attracting and retaining players. © 2016 Nature Publishing Group
By Patrick Monahan Yesterday, mountaineer Richard Parks set out for Kathmandu to begin some highly unusual data-gathering. As part of Project Everest Cynllun, he will climb Mount Everest without supplemental oxygen and perform—on himself—a series of blood draws, muscle biopsies, and cognitive tests. If he makes it to the summit, these will be the highest-elevation blood and tissue samples ever collected. Damian Bailey, a physiologist at the University of South Wales, Pontypridd, in the United Kingdom and the project’s lead scientist, hopes the risky experiment will yield new information about how the human body responds to low-oxygen conditions, and how similar mechanisms might drive cognitive decline with aging. As Parks began the acclimatization process with warm-up climbs on two smaller peaks, Bailey told ScienceInsider about his ambitions for the project. This interview has been edited for clarity and brevity. Q: Parks is an extreme athlete who has climbed Everest before. What can his performance tell us about regular people? A: What we’re trying to understand is, what is it about Richard’s brain that is potentially different from other people’s brains, and can that provide us with some clues to accelerated cognitive decline, which occurs with aging [and] dementia. We know that sedentary aging is associated with a progressive decline in blood flow to the brain. … And the main challenge for sedentary aging is we have to wait so long to see the changes occurring. So this is almost a snapshot, a day in the life of a patient with cognitive decline. © 2016 American Association for the Advancement of Science.
By Esther Hsieh Spinal implants have suffered similar problems as those in the brain—they tend to abrade tissue, causing inflammation and ultimately rejection by the body. Now an interdisciplinary research collaboration based in Switzerland has made a stretchable implant that appears to solve this problem. Like Lieber's new brain implant, it matches the physical qualities of the tissue where it is embedded. The “e-dura” implant is made from a silicone rubber that has the same elasticity as dura mater, the protective skin that surrounds the spinal cord and brain, explains Stéphanie Lacour, a professor at the school of engineering at the Swiss Federal Institute of Technology in Lausanne. This feature allows the implant to mimic the movement of the surrounding tissues. Embedded in the e-dura are electrodes for stimulation and microchannels for drug therapy. Ultrathin gold wires are made with microscopic cracks that allow them to stretch. Also, the electrodes are coated with a special platinum-silicone mixture that is stretchable. In an experiment that lasted two months, the scientists found that healthy rats with an e-dura spinal implant could walk across a ladder as well as a control group with no implant. Yet rats with a traditional plastic implant (which is flexible but not stretchable) started stumbling and missing rungs a few weeks after surgery. The researchers removed the implants and found that rats with a traditional implant had flattened, damaged spinal cords—but the e-dura implants had left spinal cords intact. Cellular testing also showed a strong immune response to the traditional implant, which was minimal in rats with the e-dura implant. © 2016 Scientific American
New York's Tribeca Film Festival will not show Vaxxed, a controversial film about the MMR vaccine, its founder Robert De Niro says. As recently as Friday, Mr De Niro stood by his decision to include the film by anti-vaccination activist Andrew Wakefield in next month's festival. The link the film makes between the measles, mumps and rubella vaccine and autism has been widely discredited. "We have concerns with certain things in this film," said Mr De Niro. Mr De Niro, who has a child with autism, said he had hoped the film would provide the opportunity for discussion of the issue. But after reviewing the film with festival organisers and scientists, he said: "We do not believe it contributes to or furthers the discussion I had hoped for." Image caption Wakefield published his controversial study in 1998 Vaxxed was directed and co-written by Mr Wakefield, who described it as a "whistle-blower documentary". In a statement issued following the Tribeca Film Festival's decision, he and the film's producer Del Bigtree said that "we have just witnessed yet another example of the power of corporate interests censoring free speech, art and truth". The British doctor was the lead author of a controversial study published in 1998, which argued there might be a link between MMR and autism and bowel disease. Mr Wakefield suggested that parents should opt for single jabs against mumps, measles and rubella instead of the three-in-one vaccine. His comments and the subsequent media furore led to a sharp drop in the number of children being vaccinated against these diseases. But the study, first published in The Lancet, was later retracted by the medical journal. Mr Wakefield's research methods were subsequently investigated by the General Medical Council and he was struck off the medical register.
Link ID: 22037 - Posted: 03.28.2016
John Consentino After multiple doctors had conflicted about ADHD, I decided to move away from psychiatry and seek a neuropsychologist. I thought that autism made sense, but what ultimately led me to seek help was my focus problem. When I was 8 years old, it would take me HOURS to do homework. On Wednesdays, we got out of school at noon, and I wouldn't finish homework until about 8 p.m. No one understood why this was happening, and with all of the screaming and punishments I withstood, nothing improved. I still had GPAs near the high 90s, so all was OK, supposedly. I struggled with eye contact during that time, and this is very much apparent now. I struggled speaking to waiters/waitresses, to teachers, to family members. Speaking to members of the opposite sex was a near-impossible task. I never understood social groups. I went through all of high school in the same fashion. However, my family felt that everything was OK. I still had a mid-90 GPA, and I had made numerous friends. Unfortunately, my GPA had dropped by about 15-plus points by my senior year. I struggled badly during my first two years of college. I was constantly unhappy, and I made little to no friends. My GPA was horrid, and my time at the university was dwindling. I dropped out of school twice, and my future felt bleak. After transferring schools, I did great. So, everything was OK yet again. © 2016 npr
Link ID: 22036 - Posted: 03.28.2016
Kristin Gourlay Swaddled in soft hospital blankets, Lexi is 2 weeks old and weighs 6 pounds. She's been at Women and Infants Hospital in Providence, R.I., since she was born, and is experiencing symptoms of opioid withdrawal. Her mother took methadone to wean herself from heroin when she got pregnant, just as doctors advised. But now the hospital team has to wean newborn Lexi from the methadone. As rates of opioid addiction have continued to climb in the U.S., the number of babies born with neonatal abstinence syndrome has gone up, too — by five-fold from 2000 to 2012, according to the National Institute of Drug Abuse. It can be a painful way to enter the world, abruptly cut off from the powerful drug in the mother's system. The baby is usually born with some level of circulating opioids. As drug levels decline in the first 72 hours, various withdrawal symptoms may appear — such as trembling, vomiting, diarrhea or seizures. At some point, if symptoms mount in number or severity, doctors will begin giving medication to help ease them. The idea is to give the baby just enough opioid to reduce those symptoms, and then slowly, over days or weeks, decrease that dose to zero. A doctor comes to check on Lexi and her mother, Carrie. To protect her family's privacy, Carrie asked us not to use the family name. "So, hi, Peanut!" the doctor says to the baby. "Any concerns?" she asks Carrie. "Coming down has been catching up with her," says Carrie. © 2016 npr
Healthy body, healthy mind. Elderly people who are physically active seem to be able to stave off memory loss – but only if they start exercising before symptoms appear. At the end of a five-year period, the brains of non-exercisers look 10 years older than those who did moderate exercise. That’s what Clinton Wright at the University of Miami in Florida and his colleagues found when they followed 876 people, starting at an average age of 71, for five years. At the start of the study, each participant underwent a number of memory and cognition tests, and had the health of their brain assessed during an MRI scan. Each person was also asked how much exercise they had done in recent weeks, ranging from “no/light”, such as walking or gardening, to “moderate/heavy”, which included running and swimming. Five years later, the volunteers were called back to repeat all the tests. The participants generally performed less well than they had five years earlier. But their scores were linked to their level of exercise – those who reported no or low levels of exercise scored lower in all tests, the team found. The 10 per cent of people who said they had been engaged in moderate-to-heavy exercise not only started with higher scores in the first round of tests, but showed less of a decline five years later . Those who did little or no exercise also seemed to have worse vascular health – they had higher blood pressure, and their MRI scans showed evidence of undetected strokes. © Copyright Reed Business Information Ltd.
By NATALIE ANGIER Juan F. Masello never intended to study wild parrots. Twenty years ago, as a graduate student visiting the northernmost province of Patagonia in Argentina, he planned to write his dissertation on colony formation among seabirds. But when he asked around for flocks of, say, cormorants or storm petrels, a park warden told him he was out of luck. “He said, ‘This is the only part of Patagonia with no seabird colonies,’” recalled Dr. Masello, a principal investigator in animal ecology and systematics at Justus Liebig University in Germany. Might the young scientist be interested in seeing a large colony of parrots instead? The sight that greeted Dr. Masello was “amazing” and “incredible,” he said. “It was almost beyond words.” On a 160-foot-high sandstone cliff that stretched some seven miles along the Atlantic coast, tens of thousands of pairs of burrowing parrots had used their powerful bills to dig holes — their nests — deep into the rock face. And when breeding season began not long afterward, the sky around the cliffs erupted into a raucous carnival of parrot: 150,000 crow-size, polychromed aeronauts with olive backsides, turquoise wings, white epaulets and bright red belly patches ringed in gold. Dr. Masello was hooked. Today, Dr. Masello’s hands are covered with bite scars. He has had four operations to repair a broken knee, a broken nose — “the little accidents you get from working with parrots,” he said. Still, he has no regrets. “Their astonishing beauty and intelligence,” Dr. Masello said, “are inspirational.” © 2016 The New York Times Company
Nicola Davis The same genes involved in predisposing people to autism appear to influence social skills in the wider population, suggesting that the autism spectrum has no clear cut-off point, scientists have discovered. Researchers have previously shown that autism is linked not just to one or two powerful genes, but to the combined effect of many small genetic changes. The latest findings, published in Nature Genetics, suggest that social charm, empathy and the ability to make friends is about more than just practice and upbringing, but is also affected by how many of these autism risk gene variants we possess. Dr Elise Robinson, from Harvard University and a lead author on the paper, said: “This is the first study that specifically shows that ... factors that we have unambiguously associated with autism are also very clearly associated with social communication differences in the general population.” Rather than viewing a person as either having or not having such a disorder, Robinson believes our social skills are better viewed as sitting on a sliding scale across the whole population. “The primary implication is that the line at which we say people are affected or unaffected is arbitrary,” said Robinson. “There is no clear objective point either in terms of genetic risk or in terms of behavioural traits, where you can say quite simply or categorically that you’re affected or unaffected. It’s like trying to pick a point where you say someone is tall or not.” © 2016 Guardian News and Media Limited
Link ID: 22014 - Posted: 03.22.2016
By Manuel Valdes For nearly every step of his almost 12-mile walks around Seattle, Darryl Dyer has company. Flocks of crows follow him, signaling each other, because they all know that he’s the guy with the peanuts. “They know your body type. The way you walk,” Dyer said. “They’ll take their young down and say: ‘You want to get to know this guy. He’s got the food.’ ” Scientists have known for years that crows have great memories, that they can recognize a human face and behavior, that they can pass that information on to their offspring. Researchers are trying to understand more about the crow’s brain and behavior, specifically what the birds do when they see one of their own dead. They react loudly, but the reasons aren’t entirely known. Among the guesses is that they are mourning; given that crows mate for life, losing a partner could be a significant moment for the social animals. There are anecdotes of crows placing sticks and other objects on dead birds — a funeral of sorts. Using masks with dark-haired wigs that looked creepily nonhuman, researchers showed up at Seattle parks carrying a stuffed crow and recorded the reactions. One crow signals an alarm, then dozens show up. They surround the dead crow, looking at it as they perch on trees or fly above it, a behavior called mobbing. “Crows have evolved to have these complex social relationships, and they have a big brain,” said Kaeli Swift, a University of Washington graduate student who led the study.
By Emily Underwood When pharmaceutical company Eli Lilly in Indianapolis last week announced a major change to its closely watched clinical trial for the Alzheimer’s drug solanezumab, some in the scientific community and drug development industry cried foul. To critics, the company’s decision to eliminate changes in a person’s daily ability to function as a primary measure of solanezumab’s efficacy and focus solely on a cognitive test seemed like a last-ditch attempt to keep a doomed drug from failing its third trial. Lilly’s stock plunged by nearly 5%, apparently reflecting that sentiment. Largely lost in the online “chatter,” however, was that Lilly’s move reflects a growing scientific consensus about how the early stages of Alzheimer’s disease progress, says Dennis Selkoe, a neurologist at Brigham and Women’s Hospital in Boston, who is not involved in the Lilly trial. “From the point of view of a neurologist who’s seen hundreds of patients, [Lilly’s decision] makes clinical sense,” he says. Solanezumab is an antibody designed to bind to and promote the clearance of the β-amyloid protein, which forms plaques around the neurons of people with Alzheimer’s. Not everyone agrees that these plaques are at the root of the disease—a concept called the amyloid hypothesis, of which Selkoe is a major proponent—but fighting them is the foundation of nearly all current efforts in Alzheimer’s drug development. By helping destroy the plaques in people with early stages of Alzheimer’s, Lilly hopes solanezumab can slow the disease’s progression. © 2016 American Association for the Advancement of Science.
Link ID: 22011 - Posted: 03.22.2016
By Emily Underwood People with autism spectrum disorder (ASD) die on average 18 years before the general population, according to a report released today by Autistica, a philanthropic group based in the United Kingdom. People with both ASD and an intellectual disability die even younger, on average 30 years earlier than those without the conditions. Fatal accidents—often by drowning, when a child or adult with ASD wanders away from caregivers—are one of the classic causes of premature death in people who have both ASD and an intellectual disability, says Sven Bölte, a clinical psychologist at the Karolinksa Institute in Stockholm, whose research is cited in the Autistica report. Epilepsy, along with several other neurological disorders, is another common cause of death among people with both ASD and learning difficulties, suggesting that early disruption of neurodevelopment is to blame. These “classic” causes of premature death in autism, however, do not fully account for a decades-long life span gap between autistic and nonautistic people, or the difference in mortality between autistic people with and without an intellectual disability, Bölte says. To explore these gaps, in 2015 Bölte’s group published a large epidemiological study of more than 27,000 Swedish people with ASD, 6500 of whom had an intellectual disability. They found that risk of premature death was about 2.5 times higher for the entire group, a gap largely due to increased prevalence of common health problems such as diabetes and respiratory disease. Patients may be being diagnosed too late because they do not know how to express health concerns to their doctors, Bölte says, making it “extremely important” for general practitioners to thoroughly explore autistic patients’ symptoms and histories. © 2016 American Association for the Advancement of Scienc
Link ID: 22010 - Posted: 03.19.2016
By John Elder Robison What happens to your relationships when your emotional perception changes overnight? Because I’m autistic, I have always been oblivious to unspoken cues from other people. My wife, my son and my friends liked my unflappable demeanor and my predictable behavior. They told me I was great the way I was, but I never really agreed. For 50 years I made the best of how I was, because there was nothing else I could do. Then I was offered a chance to participate in a study at Beth Israel Deaconess Medical Center, a teaching hospital of Harvard Medical School. Investigators at the Berenson-Allen Center there were studying transcranial magnetic stimulation, or T.M.S., a noninvasive procedure that applies magnetic pulses to stimulate the brain. It offers promise for many brain disorders. Several T.M.S. devices have been approved by the Food and Drug Administration for the treatment of severe depression, and others are under study for different conditions. (It’s still in the experimental phase for autism.) The doctors wondered if changing activity in a particular part of the autistic brain could change the way we sense emotions. That sounded exciting. I hoped it would help me read people a little better. They say, be careful what you wish for. The intervention succeeded beyond my wildest dreams — and it turned my life upside down. After one of my first T.M.S. sessions, in 2008, I thought nothing had happened. But when I got home and closed my eyes, I felt as if I were on a ship at sea. And there were dreams — so real they felt like hallucinations. It sounds like a fairy tale, but the next morning when I went to work, everything was different. Emotions came at me from all directions, so fast that I didn’t have a moment to process them. © 2016 The New York Times Company
By Daisy Yuhas Something was wrong with Brayson Thibodeaux. At 15 months old, he still was not walking; his parents and grandparents were certain that his development was slower than normal. After pushing doctors for answers they finally got him to a neurologist who recommended a genetic test. Brayson had fragile X syndrome, the leading heritable cause of intellectual disability and of autism. The discovery sent ripples through the extended family, who live outside New Orleans. Brayson’s great-grandmother, Cheryl, recalled having heard of fragile X and discovered a cousin whose grandson had the same condition. She soon learned that many members of her family were confirmed carriers of a genetic condition—the fragile X pre-mutation—that put them at risk of having children with this syndrome. “Fragile X” refers to a mutation that alters the X chromosome in such a way that, viewed under a microscope, it would look like a piece was about to break off. That is because one gene contains multiple repetitions of noncoding DNA—specifically CGG (cytosine, guanine, guanine). The exact number of CGG repetitions is variable, but when it reaches more than 200, it is considered to be the full mutation, which causes the syndrome. People with between 55 and 200 repeats are said to have a partial or pre-mutation, an unstable gene that can expand into the full mutation in future generations. © 2016 Scientific American,