Chapter 17. Learning and Memory
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By Emilie Reas Think back to your first childhood beach vacation. Can you recall the color of your bathing suit, the softness of the sand, or the excitement of your first swim in the ocean? Early memories such as this often arise as faded snapshots, remarkably distinct from newer memories that can feel as real as the present moment. With time, memories not only lose their rich vividness, but they can also become distorted, as our true experiences tango with a fictional past. The brain’s ability to preserve or alter memories lies at the heart of our basic human experience. The you of today is molded not only by your personal history, but also by your mental visits to that past, prompting you to laugh over a joke heard yesterday, reminisce about an old friend or cringe at the thought of your awkward adolescence. When we lose those pieces of the past we lose pieces of our identity. But just where in the brain do those old memories go? Despite decades studying how the brain transforms memories over time, neuroscientists remain surprisingly divided over the answer. Some of the best clues as to how the brain processes memories have come from patients who can’t remember. If damage to a particular brain area results in memory loss, researchers can be confident that the region is important for making or recalling memories. Such studies have reliably shown that damage to the hippocampus, a region nestled deep inside the brain, prevents people from creating new memories. But a key question, still open to debate, is what happens to a memory after it’s made. Does it stay in the hippocampus or move out to other areas of the brain? To answer this, scientists have studied old memories formed before brain damage, only to discover a mix of inconsistent findings that have given rise to competing theories. © 2013 Scientific American
Keyword: Learning & Memory
Link ID: 18792 - Posted: 10.16.2013
By Scott Barry Kaufman Brain training: yay or nay? It’s not so simple. As we all know, people differ quite a bit from one another in how much information they can maintain, manipulate, and transform in their heads at one time. Crucially, these differences relate to important outcomes, such as abstract reasoning, academic performance, reading comprehension, and the acquisition of new skills. The most consistent and least controversial finding in the literature is that working memory training programs produce reliable short-term improvements in both verbal and visuospatial working memory skills. On average, the effect sizes range from moderate to large, although the long-term sustainability of these effects is much more ambiguous. These effects are called near transfer effects, because they don’t transfer very far beyond the trained domain of cognitive functioning. What are far more controversial (and far more interesting) are far transfer effects. One particular class of far transfer effects that cognitive psychologists are particularly interested in are those that show increases in fluid intelligence: the deliberate but flexible control of attention to solve novel “on the spot” problems that cannot be perfomed by relying exclusively on previously learned habits, schemas, and scripts. Here is where we enter the swamp. Some studies have reported absolutely no effect of working memory training on fluid intelligence, whereas others have found an effect. The results are mixed and inconclusive. Various critics have rightfully listed a number of methodological flaws and alternative explanations that could explain the far transfer effects. © 2013 Scientific American
Keyword: Learning & Memory
Link ID: 18773 - Posted: 10.10.2013
By Scicurious When most of us hear birds twittering away in the trees, we hear it as background noise. It’s often hard to separate out one bird from another. But when you can, you begin to hear just how complex birdsong can be, a complex way of male signaling to a female how THEY are the best, and THEY are the one they should clearly pick. You hear ups and downs and trills and repeating themes. We used to think that birdsong was a relatively simple gene by environment interaction. The big males with the big songs get the best females, and then it’s a matter of also getting the best food, and the then healthy bird teaches its offspring to sing, and the health offspring goes on to display the best song. The song is therefore an “honest signal” of the bird’s fitness, it’s got good genes and good food and it is ready to MATE, baby! But how much of it is really training and how much is genetic? To find out, we go to what may possibly be the cutest of research subjects…the zebra finch. To look at the relationship between genes and environment in song learning, the authors turned to the zebra finch. Many other studies have also looked at the zebra finch and how it learns song, and how environmental pressures (like say, not enough food) change the way the song is displayed. But those experiments usually bred the birds and looked at the environment…they didn’t look at the teachers. The father birds, who were “teaching” their offspring to sing. © 2013 Scientific American
Neuroscience students at the University of Lethbridge are stepping into a maze of memory functions, hoping to help people with dementia or brain injuries through new research that tests people’s memory in the field. That is, the field outside Markin Hall on the U of L’s campus, where neuroscience PhD student Erin Zelinski has set up a life-sized version of a navigation experiment that until now has only been done locally with rats. In it, participants walk around the field until they reach an invisible target spot. When they do, they’ll hear a whistle letting them know they’re in the right place. Then, while researchers time their progress, following their every move with GPS and an overhead remote-controlled camera, participants must find their way back to the same spot two days later. The idea is to first study the brain functions of people without memory impairments so that researchers can later compare that data to a future study of people with memory loss. “We’re trying to describe what normal performance on this test looks like, so if you take a person who’s healthy and you have them perform the task, what we’ll see is that there will probably be commonalities that are going to emerge,” Zelinski said. “And then if you start to look at people that have memory impairments or a brain injury, when they perform the task there might be some things that are different. The better we are at characterizing it in normal people, the better we’re going to be at identifying where the impairments are in those individuals that are having memory problems.” © 1996-2013 The Lethbridge Herald
Keyword: Learning & Memory
Link ID: 18719 - Posted: 09.30.2013
Few features of child-rearing occupy as much parental brain space as sleep, and with it the timeless question: Is my child getting enough? Despite the craving among many parents for more sleep in their offspring (and, by extension, themselves), the purpose that sleep serves in young kids remains something of a mystery—especially when it comes to daytime naps. Do they help children retain information, as overnight sleep has been found to do in adults? A study published today in the Proceedings of the National Academy of Sciences provides the first evidence that daytime sleep is critical for effective learning in young children. Psychologist Rebecca Spencer of the University of Massachusetts (UMass), Amherst, had more than a passing interest in the subject: Her daughters were 3 and 5 when she began chasing answers to these questions. She also wondered about growing enthusiasm for universal public preschool, where teachers don’t necessarily place much emphasis on naps. “There is a lot of science” about the best curriculum for preschool classrooms, “but nothing to protect the nap,” Spencer says. Still, data to support a nap’s usefulness were scarce: Studies in adults have found that sleep helps consolidate memories and learning, but whether the same is true of brief naps in the preschool set was unknown. So Spencer approached the first preschool she could think of that might help her find out: her daughters’. She later added other local preschools to her sample, for a total of 40 children ranging from nearly 3 to less than 6 years old. The goal of Spencer, her graduate student Laura Kurdziel, and undergraduate Kasey Duclos of Commonwealth Honors College at UMass, was to compare each child against him or herself: How well did a child learn when she napped, and what happened when she didn’t? © 2012 American Association for the Advancement of Science
By Laura Sanders A nap can ease the burden of a painful memory. While fast asleep, people learned that a previously scary situation was no longer threatening, scientists report September 22 in Nature Neuroscience. The results are the latest to show that sleep is a special state in which many sorts of learning can happen. And the particular sort of learning in the new study blunted a fear memory, a goal of treatments for disorders such as phobias and post-traumatic stress disorder. “It’s a remarkable finding,” says sleep neuroscientist Edward Pace-Schott of Harvard Medical School and Massachusetts General Hospital. Researchers led by Katherina Hauner of Northwestern University’s Feinberg School of Medicine first taught 15 (awake) volunteers to fear the combination of a face and odor. Participants saw a picture of a certain man’s face and at the same time smelled a distinctive scent, such as lemon. This face-odor combo was paired with a nasty shock, so that the volunteers quickly learned to expect something bad when they saw that particular face and smelled the associated odor. Then the volunteers tucked in for a nap in the laboratory. When the participants hit the deepest stage of sleep, called slow-wave sleep, Hauner and her colleagues redelivered the smell that had earlier come with a shock. During the nap, some participants had learned that the smell was safe. The volunteers sweated less (a measure of fear) when the face-odor combination appeared after the nap, the scientists found. When the odor wasn’t presented during sleep, volunteers’ responses to the associated face were unchanged. © Society for Science & the Public 2000 - 2013
By Arielle Duhaime-Ross The flatworms known as planarians are neuroscience darlings. Their centralized brain, complex sensory abilities and rapid regenerative capacities make these nonparasitic worms ideal for studying the mechanisms that regulate stem cell function, neuronal development and limb regrowth. To this repertoire, scientists have now added a new trick: these invertebrates can store memories outside their brain and retrieve them after losing their head and growing a new one. Researchers at Tufts University tested the worms' recall by leveraging a quirk of planarian behavior: worms that recognize a familiar locale will settle in to feed more quickly than planarians that find themselves in a new environment. Such newcomers typically need time to explore their surroundings to ensure their safety before they eat. So the researchers introduced planarians to a textured petri dish and allowed them to get acquainted with their environs. Next they decapitated the worms and waited two weeks for their heads to grow back. The scientists then jogged the worms' memory by briefly returning them to the dish and feeding them. The idea was to revive the dormant memory from the body through a short exposure to familiar turf. “For the worm, automatically imprinting the new brain tissue with an old memory that could end up being completely irrelevant would be a waste,” says study co-author Michael Levin, a Tufts developmental biologist. “So the brief exposure tells the brain that the memory is indeed relevant.” When the researchers returned the trained flatworms to the same dish, the planarians initiated feeding much more quickly than worms that had gone through the same routine but had not explored the dish prior to decapitation. © 2013 Scientific American
Keyword: Learning & Memory
Link ID: 18688 - Posted: 09.23.2013
Drugs to treat Alzheimer's disease don't help patients with mild cognitive impairment and are linked to greater risk of harm, a Canadian review concludes. People with mild cognitive impairment show symptoms of memory problems that are not severe enough to be considered dementia or to interfere with day-to-day functioning. Each year, three to 17 per cent of people with mild cognitive impairment deteriorate to dementia, research suggests. It was hoped that "cognitive enhancers" used to treat dementia might delay progression to dementia. Dr. Sharon Straus of the department of geriatric medicine at the University of Toronto and her team reviewed clinical trials and reports on the effects of four cognitive enhancers. "Cognitive enhancers did not improve cognition or function among patients with mild cognitive impairment and were associated with a greater risk of gastrointestinal harms," the reviewers concluded in Monday's issue of the Canadian Medical Association Journal. "Our findings do not support the use of cognitive enhancers for mild cognitive impairment." The medications act on different neurotransmitters in the brain, such as acetylcholine. © CBC 2013
By Melanie Tannenbaum I can remember exactly where I was twelve years ago when I learned why the sky was starting to fill with smoke about 30 miles to the west. Though I live in Illinois now, I’m originally from Long Island. In September 2001, I was just beginning the 9th grade at Friends Academy, my new high school in Locust Valley. I had just started getting to know the people who would become my closest friends over the next four years. I was on my way to Computer Programming when I ran into Molly, a girl on my bus. “Hey, did you hear?” Molly asked, somewhat casually. “No, what’s up? Oh, is Maggie taking the bus today?!” I asked excitedly. Maggie was Molly’s adorable baby sister, whose expeditions onto our bus were rare (but exciting) events. “No…apparently something really big just happened in the city. They’re canceling class right now and calling an all-school assembly in the Dolan Center. You didn’t hear?” “Oh, no, but thank God. I didn’t finish my math homework last night and I didn’t have time to do it on the bus, this is awesome,” I said with a smile. “Do you have any idea why they’re canceling class, though?!” I had no idea at the time how much I would cringe for the rest of my life whenever I looked back and thought about my first reaction to hearing that “something big” was going on in the city. © 2013 Scientific American,
Keyword: Learning & Memory
Link ID: 18636 - Posted: 09.12.2013
By Dwayne Godwin and Jorge Cham Dwayne Godwin is a neuroscientist at the Wake Forest University School of Medicine. Jorge Cham draws the comic strip Piled Higher and Deeper at www.phdcomics.com. © 2013 Scientific American
By RONI JACOBSON We have seven deadly sins, seven days of the week, seven seas, seven dwarfs. The recurrence of the number seven so impressed the cognitive psychologist George A. Miller that, in an oft-cited paper in 1956, he wrote, “My problem is that I have been persecuted by an integer.” Miller went on to describe several experiments where seven pieces of information — plus or minus two — appeared to be the limit of what our minds could retain in the short term. Since then, Miller’s theory — that our short-term memory can hold about seven items before we start to forget them — has been refined. It is now understood that the capacity of short-term memory depends on several factors, including age, attention and the type of information presented. For instance, long words like “onomatopoeia” and “reciprocate” take up more memory span than short words like “cat” and “ball.” Grouping smaller bits of information into a meaningful unit, like a word of many syllables or an abstract concept, is called “chunking,” and our ability to retain information decreases as the chunk becomes more complex. Psychologists now believe that we can recall about four chunks of information at a time, which works out to approximately six letters, five one-syllable words and seven digits. As for the ubiquity of the number seven, Miller came to suspect that that is just a coincidence. © 2013 The New York Times Company
Keyword: Learning & Memory
Link ID: 18624 - Posted: 09.10.2013
by Jon White Ever tried beetroot custard? Probably not, but your brain can imagine how it might taste by reactivating old memories in a new pattern. Helen Barron and her colleagues at University College London and Oxford University wondered if our brains combine existing memories to help us decide whether to try something new. So the team used an fMRI scanner to look at the brains of 19 volunteers who were asked to remember specific foods they had tried. Each volunteer was then given a menu of 13 unusual food combinations – including beetroot custard, tea jelly, and coffee yoghurt – and asked to imagine how good or bad they would taste, and whether or not they would eat them. "Tea jelly was popular," says Barron. "Beetroot custard not so much." When each volunteer imagined a new combination, they showed brain activity associated with each of the known ingredients at the same time. It is the first evidence to suggest that we use memory combination to make decisions, says Barron. Journal reference: Nature Neuroscience, doi: 10.1038/nn.3515 © Copyright Reed Business Information Ltd.
Kelly Servick If keeping the brain spry were as simple as pumping iron, everyone would want to own the ultimate piece of cognitive exercise equipment. But designing activities to reverse the mental effects of aging is tricky. A new video game created by neuroscientists shows promise in reversing some signs of decline. Now, the researchers behind it aim to prove that video game training can be more than the latest workout craze. Games designed to keep the brain healthy as it ages have found an eager audience. “Many, many people have gotten into the business,” says neuropsychologist Glenn Smith of the Mayo Clinic in Rochester, Minnesota. The brain does appear to be capable of changing its structure and developing new skills over the course of a lifetime. But not all the products on the market are designed using scientific knowledge of the aging brain, and their ability to make meaningful, lasting changes hasn’t been proven, says Smith, who studies games as treatment for early signs of dementia. “There’s an awful lot of skepticism out there,” he says. The heart of the issue is whether practicing a video game can strengthen skills that are useful away from a computer. Early research showed that people could improve on computerized memory and speed tasks in the lab, Smith says. But it’s not clear whether these gains translate to everyday life. A recent trend puts more value in games that target the underlying problem—the decline in ability to remember and react as people age. © 2012 American Association for the Advancement of Science.
by Jennifer Viegas Goldfish not only listen to music, but they also can distinguish one composer from another, a new study finds. The paper adds to the growing body of evidence that many different animals understand music. For the study, published in the journal Behavioural Processes, Shinozuka and colleagues Haruka Ono and Shigeru Watanabe played two pieces of classical music near goldfish in a tank. The pieces were Toccata and Fugue in D minor by Johann Sebastian Bach and The Rite of Spring by Igor Stravinsky. The scientists trained the fish to gnaw on a little bead hanging on a filament in the water. Half of the fish were trained with food to gnaw whenever Bach played and the other half were taught to gnaw whenever Stravinsky music was on. The goldfish aced the test, easily distinguishing the two composers and getting a belly full of food in the process. The fish were more interested in the vittles than the music, but earlier studies on pigeons and songbirds suggest that Bach is the preferred choice, at least for birds. “These pieces can be classified as classical (Bach) and modern (Stravinsky) music,” Shinozuka explained. “Previously we demonstrated that Java sparrows preferred classical over modern music. Also, we demonstrated Java sparrows could discriminate between consonance and dissonance.” © 2013 Discovery Communications, LLC.
By TOM FIELDS-MEYER I was looking in my closet, choosing a shirt, when I lost my mind. Four hours later, I’m in the E.R., and I don’t know how I got here. My wife, Shawn, stands at my bedside, her expression alternating between reassuring and dismayed. Next to her, a doctor in his mid-50s calmly tells me he’s going to name three objects. “I want you to hold these in your mind,” he says. “Apple, table, penny.” I nod, noticing a semicircle of young interns behind him, listening intently. Then the doctor asks me to multiply 17 times 3. “I’m not very good at math,” I say. He waits. “Let’s see. Twenty times 3 is 60, minus 6.” I pause, correcting myself. “No, minus 9. Fifty-one?” “Good.” He smiles. “Now, what were those three objects I named?” I can’t recall the objects. I barely remember that he listed them. Flustered, I purse my lips and slowly shake my head, looking at Shawn. She fills in the blanks for me: I woke up, took a shower, and when I stepped out, I seemed disoriented. I sat down on the bed. “Wait, remind me, what are we doing today?” I asked her. “Do I need to remind you again? We’re having lunch at the Swerdlows’.” I didn’t remember that. I put a hand on my forehead, then lay on my back. “What day is it?” I asked her. Concerned by my blank stare, Shawn shot me questions: Do you know who came over last night? (I didn’t.) Do you remember what we argued about yesterday morning? (I couldn’t.) © 2013 The New York Times Company
Keyword: Learning & Memory
Link ID: 18596 - Posted: 09.02.2013
Alison Abbott Like humans, Drosophila fruitflies become forgetful with age. But at least their memory deficits can be reversed by eating a diet rich in polyamines, according to a study published online today1 in Nature Neuroscience. “There’s a great need for cognitive enhancers to keep us healthy into old age — now polyamines are offering a new approach,” says learning and memory specialist Ronald Davis at the Scripps Research Institute Florida in Jupiter, who was not involved in the study. “There are reasons for optimism that this fly work will translate into human.” Polyamines — which include the graphically named putrescine, cadaverine and spermidine — are small molecules that are essential for cells to survive and grow. But their cellular levels decline with age. Some foods that are popularly considered to have health benefits — such as wheatgerm and fermented soya beans — contain high levels of polyamines. Japanese scientists have shown that natto, a fermented soya-bean product, raises the level of polyamines in the blood in humans2. But there is a long way to go before anyone can say that polyamines can help to stave off memory decline in ageing people, cautions Stephan Sigrist of the Free University of Berlin, one of the study's principal investigators. “Still, the polyamine system does offer a new target for those interested in developing therapies.” © 2013 Nature Publishing Group
by Bob Holmes It's the cruel cycle of poverty. The many challenges that come with being poor can sap people's ability to think clearly, according to a new study. The findings suggest that governments should think twice before tying up social-assistance programmes in confusing red tape. Sociologists have long known that poor people are less likely to take medications, keep appointments, or be attentive parents. "Poor people make poorer decisions. They do. The question is why," says Timothy Smeeding, director of the Institute for Research on Poverty at the University of Wisconsin-Madison. But does bad decision-making help cause poverty, or does poverty interfere with decision-making? To explore this question, psychologist Eldar Shafir at Princeton University and his colleagues took advantage of a natural experiment. Small-scale sugar-cane farmers in Tamil Nadu in southern India receive most of their year's income all at once, shortly after the annual harvest. As a result, the same farmer can be poor before harvest and relatively rich after. And indeed, Shafir's team found that farmers had more loans, pawned more belongings, and reported more difficulty paying bills before the harvest than after. The researchers visited 464 farmers in 54 villages both before and after harvest. At each visit, they gave the farmers two tests of their cognitive ability: a multiple-choice pattern-matching test, and one in which they had to declare the number of digits shown rather then their value: seeing "5 5 5" but saying "three", for example. © Copyright Reed Business Information Ltd.
By Susan Milius Here’s a lesson on road trips from whooping cranes: For efficient migration, what matters is the age of the oldest crane in the group. These more experienced fliers nudge youngsters away from going off course on long flights. “The older birds get, the closer they stick to the straight line,” says ecologist Thomas Mueller of the University of Maryland in College Park, who crunched data from 73 Grus americana migrating between Wisconsin and Florida. One-year-olds traveling with other birds of the same age, the analysis says, tend to deviate about 76 kilometers from a direct route. But if they fly in a group with an 8-year-old crane, they stray 38 percent less, or about 47 kilometers, Mueller and his colleagues report in the August 30 Science. Eight years of data on these endangered cranes summering in Wisconsin’s Necedah National Wildlife Refuge offered a rare chance to parse how birds find their way. Conservationists have been rebuilding this eastern migratory population of the once widespread birds. Researchers release captive-bred cranes in Wisconsin and lead each class of newbies, just once, with an ultralight aircraft to Florida’s Chassahowitzka National Wildlife Refuge for the winter. Cranes navigate back to Wisconsin on their own. © Society for Science & the Public 2000 - 2013
Amanda Mascarelli It’s an inconvenient truth of aging: In our 30s and up, it gets increasingly harder for most of us to recall names, faces, and details from the past. Scientists have long debated whether this gradual decline is an early form of Alzheimer’s disease—a neurodegenerative condition that leads to severe dementia—or a distinct neurological process. Now, researchers have found a protein that distinguishes typical forgetfulness from Alzheimer’s and could lead to potential treatments for age-related memory loss. Previous studies have shown that Alzheimer’s disease and age-related memory loss involve different neural circuits in the hippocampus, a seahorse-shaped structure in the brain where memories are formed and organized. The hallmark signs of Alzheimer’s disease are well established—tangled proteins and plaques accumulate over time, and brain tissue atrophies. But little is known about what occurs when memory declines during normal aging, except that brain cells begin to malfunction, says Scott Small, a neurologist at Columbia University and senior author to the study. “At the molecular level, there’s been a lot of uncertainty about what is actually going wrong, and that’s what this paper isolates.” To tease apart the biological processes involved in memory loss in normal aging, Scott and other researchers from Columbia University in New York examined postmortem brain tissue from eight healthy people ranging in age from 33 to 86. They looked for differences in gene expression—the proteins or other products that a gene makes—between younger and older people. They also looked for age-related changes in the brains of mice. © 2012 American Association for the Advancement of Science
By Clayton Aldern We’ve been here before. Two or three times a year, a team of neuroscientists comes along and tightropes over the chasm that is dystopian research. Across the valley lies some pinnacle of human achievement; below flows the dirty, coursing river of mind control and government-sponsored brainwashing and all things Nineteen Eighty-Four. Cliffside, maybe clutching our tinfoil caps, we bite our nails and try to keep our faith in the scientists. This time is no different. On July 26, a research team took its first step onto the tightrope. Working under Nobel laureate Susumu Tonegawa, the MIT group reported that they had created a false memory in the brain of a mouse. “Our data,” wrote the authors in Science, “demonstrate that it is possible to generate an internally represented and behaviorally expressed fear memory via artificial means.” While the sterility reserved for scientific research abstracts tends to diffuse the élan of the work, the gravity here is apparent. Which brings us to the cliff and the chasm. That devil-klaxon of a sound effect from Inception always seems appropriate for heralding reports with sci-fi undertones. In the case of the closest thing we have to an actual inception, it seems particularly apt. But the group’s work is not Inception per se, and it’s certainly not Total Recall. That’s not to say it isn’t unnerving. It’s also not to say the study isn’t remarkable. More than anything, the Science paper’s publication is a reminder that neuroscience is inching over some dangerous ethical waters, and from here, it is important to tread carefully. © 2013 Scientific American
Keyword: Learning & Memory
Link ID: 18567 - Posted: 08.27.2013