Chapter 13. Memory, Learning, and Development
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Zoë Corbyn Jesper Noehr, 30, reels off the ingredients in the chemical cocktail he’s been taking every day before work for the past six months. It’s a mixture of exotic dietary supplements and research chemicals that he says gives him an edge in his job without ill effects: better memory, more clarity and focus and enhanced problem-solving abilities. “I can keep a lot of things on my mind at once,” says Noehr, who is chief technology officer for a San Francisco startup. The chemicals he takes, dubbed nootropics from the Greek “noos” for “mind”, are intended to safely improve cognitive functioning. They must not be harmful, have significant side-effects or be addictive. That means well-known “smart drugs” such as the prescription-only stimulants Adderall and Ritalin, popular with swotting university students, are out. What’s left under the nootropic umbrella is a dizzying array of over-the-counter supplements, prescription drugs and unclassified research chemicals, some of which are being trialled in older people with fading cognition. There is no official data on their usage, but nootropics as well as other smart drugs appear popular in the Silicon Valley. “I would say that most tech companies will have at least one person on something,” says Noehr. It is a hotbed of interest because it is a mentally competitive environment, says Jesse Lawler, a LA based software developer and nootropics enthusiast who produces the podcast Smart Drug Smarts. “They really see this as translating into dollars.” But Silicon Valley types also do care about safely enhancing their most prized asset – their brains – which can give nootropics an added appeal, he says. © 2015 Guardian News and Media Limited
Patricia Neighmond Some antidepressants may increase the risk of birth defects if taken early in pregnancy, while others don't seem to pose the same risks, a study finds. The question of whether antidepressants can cause birth defects has been debated for years, and studies have been all over the map. That makes it hard for women and their doctors to make decisions on managing depression during pregnancy. To try to untangle the question, researchers at the Centers for Disease Control and Prevention analyzed federal data on more than 38,000 women who gave birth between 1997 and 2009. They looked at the number of birth defects among babies and asked women whether they took any antidepressants in the month before getting pregnant or during the first three months of pregnancy. The study, published Wednesday in The BMJ, found no association between the most commonly used antidepressant, sertraline (Zoloft), and birth defects. Forty percent of the women who took antidepressants took sertraline. They also found no increased risk of birth defects with the antidepressants citalopram (Celexa) and escitalopram (Lexapro). But the analysis did find an association between birth defects and the antidepressants fluoxetine (Prozac) or paroxetine (Paxil). That included heart defects, abdominal wall defects, and missing brain and skull defects with paroxetine, and heart wall defects and irregular skull shape with fluoxetine. The relative risk increased 2 to 3.5 times, depending on the defect and the medication. That may sound like a lot, but Jennita Reefhuis, an epidemiologist and lead researcher in the study, says "the overall risk is still small." © 2015 NPR
By Sarah C. P. Williams The next time you forget where you left your car keys, you might be able blame an immune protein that builds up in your blood as you age. The protein impairs the formation of new brain cells and contributes to age-related memory loss—at least in mice, according to a new study. Blocking it could help prevent run-of-the-mill memory decline or treat cognitive disorders, the researchers say. “The findings are really exciting,” says neurologist Dena Dubal of the University of California, San Francisco (UCSF), who was not involved in the study. “The importance of this work cannot be underestimated as the world’s population is aging rapidly.” Multiple groups of scientists have shown that adding the blood of older mice to younger animals’ bodies makes them sluggish, weaker, and more forgetful. Likewise, young blood can restore the memory and energy of older mice. Neuroscientist Saul Villeda of UCSF homed in on one actor he thought might be responsible for some of that effect: β2 microglobulin (B2M), an immune protein normally involved in distinguishing one’s own cells from invading pathogens. B2M has also been found at increased levels in patients with Alzheimer’s disease and other cognitive disorders. Villeda and his colleagues first measured B2M levels in the blood of both people and mice of different ages; they found that those levels increased with age. When the researchers injected B2M into 3-month-old mice, the young animals suddenly had trouble remembering how to complete a water maze, making more than twice as many errors after they’d already been trained to navigate the maze. Moreover, their brains had fewer new neurons than other mice. Thirty days later, however, when the protein had been cleared from their bodies, the animals' memory troubles were gone as well, and the number of newly formed brain cells was back to normal. © 2015 American Association for the Advancement of Science
By Michael T. Ullman and Mariel Y. Pullman The human brain possesses an incredible capacity to adapt to new conditions. This plasticity enables us not only to constantly learn but also to overcome brain injury and loss of function. Take away one capability, and little by little we often compensate for these deficits. Our brain may be especially well suited to overcome limitations in the case of psychiatric or neurological conditions that originate early in life, what clinicians call neurodevelopmental disorders. Given the brain's considerable plasticity during early years, children with these disorders may have particular advantages in learning compensatory strategies. It now appears that a single brain system—declarative memory—can pick up slack for many kinds of problems across multiple neurodevelopmental disorders. This system, rooted in the brain's hippocampus, is what we typically refer to when we think of learning and memory. It allows us to memorize facts and names or recall a first grade teacher or a shopping list. Whereas other memory systems are more specialized—helping us learn movements or recall emotional events, for instance—declarative memory absorbs and retains a much broader range of knowledge. In fact, it may allow us to learn just about anything. Given declarative memory's powerful role in learning, one might expect it to help individuals acquire all kinds of compensatory strategies—as long as it remains functional. Indeed, research suggests that it not only remains largely intact but also compensates for diverse impairments in five common conditions that are rarely studied in conjunction: autism spectrum disorder, obsessive-compulsive disorder (OCD), Tourette's syndrome, dyslexia and developmental language disorder (which is often referred to as specific language impairment, or SLI). © 2015 Scientific American
Keyword: Learning & Memory
Link ID: 21143 - Posted: 07.07.2015
By David Robson William’s internal clock is eternally jammed at 13:40 on 14 March 2005 – right in the middle of a dentist appointment. A member of the British Armed Forces, he had returned to his post in Germany the night before after attending his grandfather’s funeral. He had gym in the morning, where he played volleyball for 45 minutes. He then entered his office to clear a backlog of emails, before heading to the dentist’s for root-canal surgery. “I remember getting into the chair and the dentist inserting the local anaesthetic,” he tells me. After that? A complete blank. It is as if all new memories are being written in invisible ink that slowly disappears. Since then, he has been unable to remember almost anything for longer than 90 minutes. So while he can still tell me about the first time he met the Duke of York for a briefing at the Ministry of Defence, he can’t even remember where he’s living now; he wakes up every morning believing he is still in Germany in 2005, waiting to visit the dentist. Without a record of new experiences, the passing of time means nothing to him. Today, he only knows that there is a problem because he and his wife have written detailed notes on his smartphone, in a file labelled “First thing – read this”. It is as if all new memories are being written in invisible ink that slowly disappears. How could minor dental work have affected his brain in such a profound way? This real-life medical mystery offers a rare glimpse at the hidden depths of the brain’s workings. © 2015 BBC.
Keyword: Learning & Memory
Link ID: 21137 - Posted: 07.06.2015
By Adrian Cho Whether they're from humans, whales, or elephants, the brains of many mammals are covered with elaborate folds. Now, a new study shows that the degree of this folding follows a simple mathematical relationship—called a scaling law—that also explains the crumpling of paper. That observation suggests that the myriad forms of mammalian brains arise not from subtle developmental processes that vary from species to species, but rather from the same simple physical process. In biology, it rare to find a mathematical relationship that so tightly fits all the data, say Georg Striedter, a neuroscientist at the University of California, Irvine. "They've captured something," he says. Still, Striedter argues that the scaling law describes a pattern among fully developed brains and doesn't explain how the folding in a developing brain happens. The folding in the mammalian brain serves to increase the total area of the cortex, the outer layer of gray matter where the neurons reside. Not all mammals have folded cortices. For example, mice and rats have smooth-surfaced brains and are "lissencephalic." In contrast, primates, whales, dogs, and cats have folded brains and are "gyrencephalic." For decades, scientists have struggled to relate the amount of folding in a species' brain to some other characteristic. For example, although animals with tiny brains tend to have smooth ones, there is no clean relationship between the amount of folding—measured by the ratio of the total area of the cortex to the exposed outer surface of the brain—and brain mass. Make a plot of folding versus brain mass for various species and the data points fall all over and not on a unified curve. Similarly, there is no clean relationship between the amount of folding and the number of neurons, the total area of the cortex, or the thickness of the cortex. © 2015 American Association for the Advancement of Science
By SINDYA N. BHANOO It may be possible to diagnose autism by giving children a sniff test, a new study suggests. Most people instinctively take a big whiff when they encounter a pleasant smell and limit their breathing when they encounter a foul smell. Children with autism spectrum disorder don’t make this natural adjustment, said Liron Rozenkrantz, a neuroscientist at the Weizmann Institute of Science in Israel and one of the researchers involved with the study. She and her colleagues report their findings in the journal Current Biology. They presented 18 children who had an autism diagnosis and 18 typically developing children with pleasant and unpleasant odors and measured their sniff responses. The pleasant smells were rose and soap, and the unpleasant smells were sour milk and rotten fish. Typically developing children adjusted their sniffing almost immediately — within about 305 milliseconds. Children with autism did not respond as rapidly. As they were exposed to the smells, the children were watching a cartoon or playing a video game. “It’s a semi-automated response,” Ms. Rozenkrantz said. “It does not require the subject’s attention.” Using the sniff test alone, the researchers, who had not been told which children had autism, were able to correctly identify those with autism 81 percent of the time. They also found that the farther removed an autistic child’s sniff response was from the average for typically developing children, the more severe the child’s social impairments were. © 2015 The New York Times Company
By SINDYA N. BHANOO Learning can be traced back to individual neurons in the brain, according to a new study. “What we wanted to do was see if we could actually create a new association — a memory — and see if we would be able to see actual change in the neurons,” said Matias Ison, a neuroscientist at the University of Leicester in England and one of the study’s authors. He and his colleagues were able to monitor the brain activity of neurosurgical patients at UCLA Medical Center. The patients already had electrodes implanted in their medial temporal lobes for clinical reasons. The patients were first presented with images of notable people — like Jennifer Aniston, Clint Eastwood and Halle Berry. Then, they were shown images of the same people against different backdrops — like the Eiffel Tower, the Leaning Tower of Pisa and the Sydney Opera House. The same neurons that fired for the images of each of the actors also fired when patients were shown the associated landmark images. In other words, the researchers were able to watch as the patients’ neurons recorded a new memory — not just of a particular person, but of the person at a particular place. © 2015 The New York Times Company
Keyword: Learning & Memory
Link ID: 21126 - Posted: 07.02.2015
Jon Hamilton If you run into an old friend at the train station, your brain will probably form a memory of the experience. And that memory will forever link the person you saw with the place where you saw them. For the first time, researchers have been able to see that sort of link being created in people's brains, according to a study published Wednesday in the journal Neuron. The process involves neurons in one area of the brain that change their behavior as soon as someone associates a particular person with a specific place. "This type of study helps us understand the neural code that serves memory," says Itzhak Fried, an author of the paper and head of the Cognitive Neurophysiology Laboratory at UCLA. It also could help explain how diseases like Alzheimer's make it harder for people to form new memories, Fried says. The research is an extension of work that began more than a decade ago. That's when scientists discovered special neurons in the medial temporal lobe that respond only to a specific place, or a particular person, like the actress Jennifer Aniston. The experiment used a fake photo of actor Clint Eastwood and Pisa's leaning tower to test how the brain links person and place. More recently, researchers realized that some of these special neurons would respond to two people, but only if the people were connected somehow. For example, "a neuron that was responding to Jennifer Aniston was also responding to pictures of Lisa Kudrow," [another actress on the TV series Friends], says Matias Ison of the University of Leicester in the U.K. © 2015 NPR
Nancy Shute Powerful antipsychotic medications are being used to treat children and teenagers with ADHD, aggression and behavior problems, a study finds, even though safer treatments are available and should be used first. "There's been concern that these medications have been overused, particularly in young children," says Mark Olfson, a professor of psychiatry at Columbia University who led the study. It was published Wednesday in JAMA Psychiatry. "Guidelines and clinical wisdom suggest that you really should be using a high degree of caution and only using them when other treatments have failed, as a last resort." Olfson and his colleagues looked at prescription data from about 60 percent of the retail pharmacies in the United States in 2006, 2008 and 2010. That included almost 852,000 children, teenagers and young adults. Teens were most likely to be prescribed antipsychotics, with 1.19 percent getting the drugs in 2010, compared to 0.11 percent in younger children. Boys were more likely to be given the medications. Antipsychotic medications like clozapine and olanzapine are used to treat schizophrenia, bipolar disorder and some symptoms of autism. They have not been approved by the Food and Drug Administration to treat aggression and ADHD, but are prescribed off label to reduce disruptive behavior. FDA Debates Safety Of Antipsychotic Drugs In Kids Use of antipsychotics in children has been questioned because the drugs can have serious side effects, including tremors, weight gain, increased diabetes risk and elevated cholesterol. © 2015 NPR
Boys are more likely than girls to receive a prescription for antipsychotic medication regardless of age, researchers have found. Approximately 1.5 percent of boys ages 10-18 received an antipsychotic prescription in 2010, although the percentage falls by nearly half after age 19. Among antipsychotic users with mental disorder diagnoses, attention deficit hyperactivity disorder (ADHD) was the most common among youth ages 1-18, while depression was the most common diagnosis among young adults ages 19-24 receiving antipsychotics. Despite concerns over the rising use of antipsychotic drugs to treat young people, little has been known about trends and usage patterns in the United States before this latest research, which was funded by the National Institute of Mental Health (NIMH), part of the National Institutes of Health. Mark OlfsonExternal Web Site Policy, M.D., M.P.H., of the Department of Psychiatry, College of Physicians and Surgeons and Columbia University and New York State Psychiatric Institute, New York City, and colleagues Marissa King, Ph.D., Yale, New Haven, Connecticut, and Michael Schoenbaum, Ph.D., NIMH, report their findings on July 1 in JAMA Psychiatry. “No prior study has had the data to look at age patterns in antipsychotic use among children the way we do here,” said co-author Michael Schoenbaum, Ph.D., senior advisor for mental health services, epidemiology and economics at NIMH. “What’s especially important is the finding that around 1.5 percent of boys aged 10-18 are on antipsychotics, and then this rate abruptly falls by half, as adolescents become young adults.” “Antipsychotics should be prescribed with care,” says Schoenbaum. “They can adversely affect both physical and neurological function and some of their adverse effects can persist even after the medication is stopped.”
By Erika Beras Marijuana is the drug of choice for people who drink alcohol. And people who use both are twice as likely to do so at the same time than to indulge in just one or the other. That’s according to a study in the journal Alcoholism: Clinical and Experimental Research. [Meenakshi S. Subbaraman and William C. Kerr, Simultaneous Versus Concurrent Use of Alcohol and Cannabis in the National Alcohol Survey The data came from self-reported answers that more than 8,600 people provided to what’s called the National Alcohol Surveys, done by phone in 2005 and 2010. People who used pot and alcohol were about twice as likely to drive drunk than those who just drank. And they doubled their chances of what are referred to as negative social consequences, such as arrests, fights and job problems. Meanwhile, another new study finds that if you’re chronically stoned, you’re more likely to remember things differently from how they happened, or not at all. Researchers showed a series of words to people who do not use marijuana and to regular pot users who had not partaken in a month. A few minutes later, all participants were shown the same list of words along with other words. The volunteers were then asked to identify only the original words. The pot smokers thought more of the new words were in the original list than did the nonusers. And brain scans revealed that the regular pot users showed less activity in brain regions associated with memory and cognitive resources than did the nonusers. The study is in the journal Molecular Psychiatry. [J. Riba et al, Telling true from false: cannabis users show increased susceptibility to false memories] © 2015 Scientific American
By Dina Fine Maron The game is a contemporary of the original Nintendo but it still appeals to today’s teens and lab monkeys alike—which is a boon for neuroscientists. It offers no lifelike graphics. Nor does it boast a screen. Primate players—whether human or not—are simply required to pull levers and replicate patterns of flashing lights. Monkeys get a banana-flavored treat as a reward for good performance whereas kids get nickels. But the game's creators are not really in it for fun. It was created by toxicologists at the U.S. Food and Drug Administration in the 1980s to study how chronic exposure to marijuana smoke affects the brain. Players with trouble responding quickly and correctly to the game’s commands may have problems with short-term memory, attention or other cognitive issues. The game has since been adapted to address a different question: whether anesthetics used to knock pediatric patients unconscious during surgery and diagnostic tests could affect a youngster's long-term neural development and cognition. Despite 20 years’ worth of experiments in young rodents and monkeys, there have been few definitive answers. To date, numerous studies suggest that being put under with anesthesia early in life seems somehow related to future cognitive problems. But whether this association is causal or merely coincidence is unclear. Researchers do know that the young human brain is exceptionally sensitive. When kids are exposed to certain harmful chemicals in their formative years, that experience can fundamentally alter the brain’s architecture by misdirecting the physical connections between neurons or causing cell deaths. But unraveling whether anesthetics may fuel such long-term damage in humans remains a challenge. © 2015 Scientific American
Hannah Devlin Science correspondent Two licensed drugs have been shown to halt brain degeneration in mice, raising the prospect of a rapid acceleration in the search for a medicine to beat Alzheimer’s disease. The results, presented on Tuesday at the Alzheimer’s Society annual research conference in Manchester, have been hailed as “hugely promising” because they involve medicines that are already known to be safe and well-tolerated in people – potentially cutting years from the timeline for drugs to reach patients. Speaking ahead of her presentation, Giovanna Mallucci, professor of clinical neuroscience at the University of Cambridge, said: “It’s really exciting. They’re licensed drugs. This means you’d do a straightforward basic clinical trial on a small group of patients because these are not new compounds, they’re known drugs.” The scientists have chosen not to name the two drugs, which are currently used for conditions unrelated to dementia, to avoid the possibility of patients seeking to use them ahead of any clinical trial to prove their efficacy. The findings build on a landmark study two years ago, showing that brain cell death could be halted in mice by switching off a faulty signal in the brain that stops new proteins being produced. However, the breakthrough relied on a compound that had severe physical side-effects including weight loss and diabetes, making it unsuitable for use in humans. The two drugs were identified after Mallucci’s team screened hundreds of licensed compounds in search for something safe that had the same protective effects on the brain. Clare Walton, research manager at the Alzheimer’s Society, said: “The new results are hugely promising because the drugs are already given to people and we know they’re safe.” © 2015 Guardian News and Media Limited
Link ID: 21114 - Posted: 07.01.2015
By Jan Hoffman Guinea pigs do not judge. They do not bully. They are characteristically amiable, social and oh-so-tactile. They tuck comfortably into child-size laps and err on the side of the seriously cute. When playing with guinea pigs at school, children with autism spectrum disorders are more eager to attend, display more interactive social behavior and become less anxious, according to a series of studies, the most recent of which was just published in Developmental Psychobiology. In previous studies, researchers in Australia captured these results by surveying parents and teachers or asking independent observers to analyze videotapes of the children playing. In the new report, however, the researchers analyzed physiological data pointing to the animals’ calming effect on the children. The children played with two guinea pigs in groups of three — one child who was on the spectrum and two typically developing peers. All 99 children in the study, ages 5 to 12, wore wrist bands that monitored their arousal levels, measuring electric charges that race through the skin. Arousal levels can suggest whether a subject is feeling anxious or excited. The first time that typically developing children played with the guinea pigs, they reported feeling happy and registered higher levels of arousal. The researchers speculate that the children were excited by the novelty of the animals. Children with autism spectrum disorders also reported feeling elated, but the wrist band measurements suggested their arousal levels had declined. The animals seem to have lowered the children’s stress, the researchers concluded. © 2015 The New York Times Company
Link ID: 21111 - Posted: 06.30.2015
By Ariana Eunjung Cha One of the most heartbreaking things about Alzheimer's is that it has been impossible for doctors to predict who will get it before symptoms begin. And without early detection, researchers say, a treatment or cure may be impossible. Governments, drug companies and private foundations have poured huge amounts of money into trying to come up with novel ways to detect risk through cutting-edge technologies ranging from brain imaging, protein analysis of cerebrospinal fluid and DNA profiling. Now a new study, published in the journal Neurology, shows that perhaps something more old-fashioned could be the answer: a memory test. The researchers tracked 2,125 participants in four Chicago neighborhoods for 18 years, giving them tests of memory and thinking every three years. They found that those who scored lowest on the tests during the first year were 10 times more likely to be diagnosed with Alzheimer's down the road -- indicating that cognitive impairment may be affecting the brain "substantially earlier than previously established," the researchers wrote.
By Sunnie Huang, CBC News The story of a Newfoundland man who was struck by a moose but doesn't remember it is not just a curious tale of luck. It also highlights the complex underpinnings of human memory, a neuroscience expert says. Stephen Bromley, from Conche, N.L., struck a moose with his car on Monday, but said he had no recollection it, even days after the collision. It's not the first time that something was amiss about human memory after a moose encounter. hi-moose-car-2012 Michelle Higgins said the roof of her car was peeled back "like a sardine can" after she struck a moose. Another Newfoundlander drove about 40 kilometres with her car's roof peeled back "like a sardine can" after crashing into a moose in 2012. Three years later, she said she still can't recall the incident. The blackout doesn't surprise Scott Watter, a McMaster University professor who specializes in neuroscience, psychology and behaviour. "They are lucky in that sense, but it doesn't seem like a thing that breaks the rules of everything we know about how brains work," he told CBC News. People who sustain head trauma often have poor memory of the event, especially when tested on specific details, Watter said. Also, the more severe the injury gets, the further back the memory loss extends, Watter said. The system at the heart of our memory is a seahorse-shaped section of the brain called the hippocampus, Watter explained. It's responsible for linking different parts of human experience to form a coherent memory. In the most severe — but rare — cases of hippocampus damage, the person can no longer create or retain new memory, as seen in Christopher Nolan's 2000 box office hit Memento. ©2015 CBC/Radio-Canada.
Keyword: Learning & Memory
Link ID: 21106 - Posted: 06.29.2015
Amy Standen A doctor I interviewed for this story told me something that stuck with me. He said for every person with dementia he treats, he finds himself caring for two patients. That's how hard it can be to be a caregiver for someone with dementia. The doctor is Bruce Miller. He directs the Memory and Aging Center at the University of California, San Francisco. According to Miller, 50 percent of caregivers develop a major depressive illness because of the caregiving. "The caregiver is so overburdened that they don't know what to do next," he says. "This adds a huge burden to the medical system." This burden is going increase dramatically in the coming decade. By 2025, 7 million Americans will have Alzheimer's disease, according to one recent estimate. Millions more will suffer from other types of dementia. Together these diseases may become the most expensive segment of the so-called "silver tsunami" — 80 million baby boomers who are getting older and needing more medical care. The cost of caring for Alzheimer's patients alone is expected to triple by 2050, to more than $1 trillion a year. So UCSF, along with the University of Nebraska Medical Center, is beginning a $10 million study funded by the federal Centers for Medicare & Medicaid Innovation. Researchers plan to develop a dementia "ecosystem," which aims to reduce the cost of caring for the growing number of dementia patients and to ease the strain on caregivers. © 2015 NPR
Link ID: 21104 - Posted: 06.29.2015
Sharon Darwish Bottlenose dolphins have an average brain mass of 1.6 kg, slightly greater than that of humans, and about four times the size of chimpanzee brains. Although you couldn’t really imagine a dolphin writing poetry, dolphins demonstrate high levels of intelligence and social behaviour. For example, they display mirror self-recognition, as well as an understanding of symbol-based communication systems. Research into the differing brain sizes and intellectual capabilities within the animal kingdom is fascinating. Why have some species evolved to be more intelligent than others? Does brain size affect cognitive ability? Some studies say yes, but some insist otherwise. It really depends which species we are talking about. In humans, for example, larger brains do not indicate higher intelligence – otherwise Einstein, who had an average-sized brain, may have not been quite as successful in his career. (Yes, that link was to a 23-pager on the analysis of Einstein’s brain. It makes for great bedtime reading.) Most neuroscientists now believe that it is the structure of the brain on a cellular and molecular level that determines its computational capacity. Within certain animal species however, a larger brain offers evolutionary advantage. For example, large-brained female guppies are better survivors and demonstrate greater cognitive strengths than their smaller-brained counterparts. © 2015 Guardian News and Media Limited
By Nicholas Bakalar Exposure to air pollution may hasten brain aging, a new study has found. Researchers studied 1,403 women without dementia who were initially enrolled in a large health study from 1996 to 1998. They measured their brain volume with M.R.I. scans in 2005 and 2006, when the women were 71 to 89 years old. Using residential histories and air pollution data, they estimated their exposure to air pollution from 1999 to 2006. They used data recorded at monitoring sites on exposure to PM 2.5 — tiny particulate matter that easily penetrates the lungs. Each increase of 3.49 micrograms per cubic centimeter cumulative exposure to pollutants was associated with a 6.23 cubic centimeter decrease in white matter, the equivalent of one to two years of brain aging. The association remained after adjusting for many variables, including age, smoking, physical activity, blood pressure, body mass index, education and income. Previous studies have shown that air pollution can cause inflammation and damage to the vascular system, but this study, in The Annals of Neurology, showed damage to the brain itself. “This tells us that the damage air pollution can impart goes beyond the circulatory system,” said the lead author, Dr. Jiu-Chiuan Chen, an associate professor of preventive medicine at the Keck School of Medicine at the University of Southern California. “Particles in the ambient air are an environmental neurotoxin to the aging brain.” © 2015 The New York Times Company