Chapter 17. Learning and Memory
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by Emily Underwood If you are one of the 20% of healthy adults who struggle with basic arithmetic, simple tasks like splitting the dinner bill can be excruciating. Now, a new study suggests that a gentle, painless electrical current applied to the brain can boost math performance for up to 6 months. Researchers don't fully understand how it works, however, and there could be side effects. The idea of using electrical current to alter brain activity is nothing new—electroshock therapy, which induces seizures for therapeutic effect, is probably the best known and most dramatic example. In recent years, however, a slew of studies has shown that much milder electrical stimulation applied to targeted regions of the brain can dramatically accelerate learning in a wide range of tasks, from marksmanship to speech rehabilitation after stroke. In 2010, cognitive neuroscientist Roi Cohen Kadosh of the University of Oxford in the United Kingdom showed that, when combined with training, electrical brain stimulation can make people better at very basic numerical tasks, such as judging which of two quantities is larger. However, it wasn't clear how those basic numerical skills would translate to real-world math ability. © 2010 American Association for the Advancement of Science
Keyword: Learning & Memory
Link ID: 18168 - Posted: 05.18.2013
by Douglas Heaven Got a memory like a fish? The first study to visualise live memory retrieval in the whole brain has not only debunked the "three-second memory" myth, but also sheds light on the brain processes involved in forming long-term memories. Even the haziest recollections have a physical basis in the brain, but the mechanisms behind the formation and retrieval of memories are not well understood. By working with zebrafish, which are small and partially transparent, Hitoshi Okamoto at the RIKEN Brain Science Institute in Wako, Japan, and colleagues were able to study the whole brain at once. This allowed them to observe the roles played by different brain regions as a memory was retrieved. The team used fish with a genetically engineered fluorescent protein in the brain that glows less brightly when calcium levels increase – which occurs when neurons fire. They were able to study the activity of these proteins under a microscope. First, the team trained a group of fish to respond to a visual cue to avoid a small electric shock. Each fish was placed in a tank containing two compartments. When a red light shone in one compartment the fish had to swim to the other to avoid the shock. The researchers then selected the fish that had learned to perform the avoidance task successfully at least 80 per cent of the time and looked at the activity in their brains while a red light was switched on and off. © Copyright Reed Business Information Ltd.
Keyword: Learning & Memory
Link ID: 18167 - Posted: 05.18.2013
By Jason G. Goldman There is a rich tradition in psychology and neuroscience of using animals as models for understanding humans. Humans, after all, are enormously complicated creatures to begin even from a strictly biological perspective. Tacking on the messiness that comes with culture makes the study of the human mind tricky, at best. So, just as biomedical scientists have relied upon the humble mouse, psychological and cognitive scientists have too turned to our evolutionary cousins in the animal kingdom as a means of better understanding ourselves. In her new book Animal Wise, journalist Virginia Morrell recounts a conversation with one researcher who pointed out that decades of research were built upon “rats, pigeons, and college sophomores, preferably male.” The college undergrads stood in for all of humanity, the rats served as representatives of all other mammals, and pigeons served as a model for the rest of the animal kingdom. The silly part isn’t that non-human animals can be used effectively as a means of understanding more about our own species. The idea is simple: understand how a simple system works, and you can make careful inferences about the way that complex systems work. That is (or should be) obvious. In his interview with CNN today, memory research pioneer and Nobel Prize winner Eric Kandel said as much: “Rather than studying the most complex form of memory in a very complicated animal, we had to take the most simple form — an implicit form of memory — in a very simple animal.” © 2013 Scientific American
By Ian Chant Most people make good decisions most of the time. But when drug addiction, disease or brain injury enters the picture, rational thinking can go awry. What if the damaged brain just needed a little reminder of how it feels to choose wisely? Enter the MIMO neural prosthesis, an array of electrodes implanted in the brain that make contact with eight neuron circuits in the prefrontal cor-tex, the brain's command center for decision making. The device can both record the brain activity associated with good choices and stimulate the relevant neurons to get the brain back on track. Although the implant can listen in only on a tiny subset of the neurons in this region, the scientists who developed it, based at Wake Forest Baptist Medical Center, were surprised to discover that they could still pick up signature patterns associated with correct choices, at least in the context of a simple task. The researchers tested the neural prosthesis on monkeys that were trained to move a cursor over a picture on a computer screen to get a food reward. The implant first recorded the brain activity associated with choosing the correct picture. Then the monkeys were given cocaine, and their performance plummeted. But when the implant was switched on to send electric current to the neurons that had earlier been associated with the correct answers, the monkeys immediately started selecting the right pictures again. Some of them did an even better job than they had before receiving cocaine. © 2013 Scientific American,
By Bruce Bower Provocative evidence that certain memory exercises make people smarter has sparked the rise of online brain-training programs such as Lumosity. But at least one type of brain training may not work as advertised, a new study finds. As expected, practicing improved volunteers’ performance on tests of memory and the ability to locate items quickly in busy scenes, say psychologist Thomas Redick of Indiana University Purdue University Columbus and his colleagues. That improvement did not, however, translate into higher scores on tests of intelligence and multitasking, the researchers report in the May Journal of Experimental Psychology: General. Redick’s investigation is part of a growing scientific debate about brain training, which is promoted by some companies as having a variety of mental benefits. Some researchers say that extensive instruction and training on memory tasks can indeed fortify reasoning and problem solving. Others are skeptical that vigorous memory sessions produce such wide-ranging effects. The dispute feeds into a longstanding scientific controversy about whether enriched environments can increase intelligence, as measured on IQ tests. What’s not up for debate is that many people feel smarter after brain training. In the new study, 10 of 23 individuals who completed memory sessions said that the program helped them to think, multitask and focus better in daily life. But the scientists say that even if some participants performed daily tasks better after memory training, they may simply have tried harder or felt better about their efforts due to a belief that training had strengthened their minds. © Society for Science & the Public 2000 - 2013
Keyword: Learning & Memory
Link ID: 18140 - Posted: 05.11.2013
By John McCarthy Into brains of newborn mice, researchers implanted human “progenitor cells.” These mature into a type of brain cell called astrocytes (see below). They grew into human astrocytes, crowding out mouse astrocytes. The mouse brains became chimeras of human and mouse, with the workhorse mouse brain cells – neurons – nurtured by billions of human astrocytes. Neuroscience is only beginning to discover what astrocytes do in brains. One job that is known is that they help neurons build connections (synapses) with other neurons. (Firing neurotransmitter molecules across synapses is how neurons communicate.) Human astrocytes are larger and more complex than those of other mammals. Humans’ unique brain capabilities may depend on this complexity. Human astrocytes certainly inspired the mice. Their neurons did indeed build stronger synapses. (Perhaps this was because human astrocytes signal three times faster than mouse astrocytes do.) Mouse learning sharpened, too. On the first try, for instance, altered mice perceived the connection between a noise and an electric shock (a standard learning test in mouse research). Normal mice need a few repetitions to get the idea. Memories of the doctored mice were better too: they remembered mazes, object locations, and the shock lessons longer. The reciprocal pulsing of billions of human and mouse brain cells inside a mouse skull is a little creepy. Imagine one of these hybrid mice exploring your living room. Would you feel like a Stone Age tribesman observing a toy robot? Does the thing think? © 2013 Scientific American
Alla Katsnelson People who use a ‘brain-workout’ program for just 10 hours have a mental edge over their peers even a year later, researchers report today in PLoS ONE1. The search for a regimen of mental callisthenics to stave off age-related cognitive decline is a booming area of research — and a multimillion-dollar business. But critics argue that even though such computer programs can improve performance on specific mental tasks, there is scant proof that they have broader cognitive benefits. For the study, adults aged 50 and older played a computer game designed to boost the speed at which players process visual stimuli. Processing speed is thought to be “the first domino that falls in cognitive decline”, says Fredric Wolinsky, a public-health researcher at the University of Iowa in Iowa City, who led the research. The game was developed by academic researchers but is now sold under the name Double Decision by Posit Science, based in San Francisco, California. (Posit did not fund the study.) Players are timed on how fast they click on an image in the centre of the screen and on others that appear around the periphery. The program ratchets up the difficulty as a player’s performance improves. Participants played the training game for 10 hours on site, some with an extra 4-hour ‘booster’ session later, or for 10 hours at home. A control group worked on computerized crossword puzzles for 10 hours on site. Researchers measured the mental agility of all 621 subjects before the brain training began, and again one year later, using eight well-established tests of cognitive performance. © 2013 Nature Publishing Group
By Meghan Rosen A child who is good at learning math may literally have a head for numbers. Kids’ brain structures and wiring are associated with how much their math skills improve after tutoring, researchers report April 29 in the Proceedings of the National Academy of Sciences. Certain measures of brain anatomy were even better at judging learning potential than traditional measures of ability such as IQ and standardized test results, says study author Kaustubh Supekar of Stanford University. These signatures include the size of the hippocampus — a string bean–shaped structure involved in making memories — and how connected the area was with other parts of the brain. The findings suggest that kids struggling with their math homework aren’t necessarily slacking off, says cognitive scientist David Geary of the University of Missouri in Columbia. “They just may not have as much brain region devoted to memory formation as other kids.” The study could give scientists clues about where to look for sources of learning disabilities, he says. Scientists have spent years studying brain regions related to math performance in adults, but how kids learn is still “a huge question,” says Supekar. He and colleagues tested IQ and math and reading performance in 24 8- and 9-year-olds, then scanned their brains in an MRI machine. The scans measured the sizes of different brain structures and the connections among them. “It’s like creating a circuit diagram,” says study leader Vinod Menon, also of Stanford. © Society for Science & the Public 2000 - 2013
Keyword: Learning & Memory
Link ID: 18094 - Posted: 04.30.2013
By VATSAL G. THAKKAR IN the spring of 2010, a new patient came to see me to find out if he had attention-deficit hyperactivity disorder. He had all the classic symptoms: procrastination, forgetfulness, a propensity to lose things and, of course, the inability to pay attention consistently. But one thing was unusual. His symptoms had started only two years earlier, when he was 31. Though I treat a lot of adults for attention-deficit hyperactivity disorder, the presentation of this case was a violation of an important diagnostic criterion: symptoms must date back to childhood. It turned out he first started having these problems the month he began his most recent job, one that required him to rise at 5 a.m., despite the fact that he was a night owl. The patient didn’t have A.D.H.D., I realized, but a chronic sleep deficit. I suggested some techniques to help him fall asleep at night, like relaxing for 90 minutes before getting in bed at 10 p.m. If necessary, he could take a small amount of melatonin. When he returned to see me two weeks later, his symptoms were almost gone. I suggested he call if they recurred. I never heard from him again. Many theories are thrown around to explain the rise in the diagnosis and treatment of A.D.H.D. in children and adults. According to the Centers for Disease Control and Prevention, 11 percent of school-age children have now received a diagnosis of the condition. I don’t doubt that many people do, in fact, have A.D.H.D.; I regularly diagnose and treat it in adults. But what if a substantial proportion of cases are really sleep disorders in disguise? © 2013 The New York Times Company
Karen Ravn Birds of a feather may flock together, but do birds that flock together develop distinct cultures? Two studies published today in Science1, 2 find strong evidence that, at the very least, monkeys that troop together and whales that pod together do just that. And they manage it in the same way that humans do: by copying and learning from each other. A team led by Erica van de Waal, a primate psychologist at the University of St Andrews, UK, created two distinct cultures — 'blue' and 'pink' — among groups of wild vervet monkeys (Chlorocebus aethiops) in South Africa1. The researchers trained two sets of monkeys to eat maize (corn) dyed one of those two colours but eschew maize dyed the other colour. The scientists then waited to see how the groups behaved when newcomers — babies and migrating males — arrived. Both sets of newcomers seemed to follow social cues when selecting their snacks. Baby monkeys ate the same colour maize as their mothers. Seven of the ten males that migrated from one colour culture to another adopted the local colour preference the first time that they ate any maize. The trend was even stronger when they first fed with no higher-ranking monkey around, with nine of the ten males choosing the locally preferred variety. The only immigrant to buck this trend was a monkey who assumed the top rank in his new group as soon as he got there — and he may not have given a fig what anyone else ate. “The take-home message is that social learning — learning from others rather than through individual trial and error — is a more potent force in shaping wild animals’ behaviour than has been recognized so far,” says Andrew Whiten, an evolutionary and developmental psychologist at St Andrews and co-author of the paper. © 2013 Nature Publishing Group
By Meghan Holohan Need to remember some important facts for that big presentation at work? Clench your right hand while preparing to remember. When giving that talk, ball up your left hand and you’ll call to mind those details, no problem. That’s the finding from a new study authored by Ruth Propper, an associate professor and director of the cerebral lateralization laboratory at Montclair State University. Propper has long been intrigued by how body movements impact how the brain works. While most people realize that the brain influences the body (the brain tells your arm there is an itch, and you feel it), less is understood about how the body sways the brain. Past research suggests that clenching our hands can evoke emotions. When people ball up their right hands, for example, the left sides of their brains become more active, causing what’s known as “approach emotions,” feelings such as happiness or excitement. By squeezing the left hand, people engage the right side of the brain, which controls “withdrawal emotions” such as introversion, fear, or anxiety. (It probably seems like these might be less useful, but they come in handy in dangerous situations.) Propper theorized that if clenching hands impacted feelings, these gestures might influence the brain in other ways. © 2013 NBCNews.com
by Simon Makin The first drug specifically designed to improve cognitive impairment in Down's syndrome is being tested in humans. David Nutt, former drug policy adviser to the UK government, told delegates at the Festival of Neuroscience in London yesterday that he is collaborating with pharmaceutical company Roche in trials of a substance it developed, called RG1662. RG1662 reverses the effects of a chemical messenger in the brain called GABA – a neurotransmitter that inhibits brain activity. The drug acts on a specific type of brain receptor found mostly in the hippocampus, a part of the brain involved in memory. It is thought that it will reduce excessive inhibition in the hippocampus, thought to underlie memory and learning problems commonly seen in people with Down's. The study is currently assessing safety and tolerability of the drug in 33 adults with Down's, but researchers will also measure motor skills, reaction time and memory, and compare the results with those of people taking a placebo. The aim is to find appropriate doses to use in a full clinical trial, which Nutt says should happen this year. Roche said in a statement that RG1662 may help people with Down's as it has "a unique pharmacology that enables the targeting of GABA over-activity mainly in brain systems important for cognition, learning and memory". © Copyright Reed Business Information Ltd
Keyword: Learning & Memory
Link ID: 18026 - Posted: 04.13.2013
By GRETCHEN REYNOLDS Two new experiments, one involving people and the other animals, suggest that regular exercise can substantially improve memory, although different types of exercise seem to affect the brain quite differently. The news may offer consolation for the growing numbers of us who are entering age groups most at risk for cognitive decline. It was back in the 1990s that scientists at the Salk Institute for Biological Studies in La Jolla, Calif., first discovered that exercise bulks up the brain. In groundbreaking experiments, they showed that mice given access to running wheels produced far more cells in an area of the brain controlling memory creation than animals that didn’t run. The exercised animals then performed better on memory tests than their sedentary labmates. Since then, scientists have been working to understand precisely how, at a molecular level, exercise improves memory, as well as whether all types of exercise, including weight training, are beneficial. The new studies provide some additional and inspiring clarity on those issues, as well as, incidentally, on how you can get lab rats to weight train. For the human study, published in The Journal of Aging Research, scientists at the University of British Columbia recruited dozens of women ages 70 to 80 who had been found to have mild cognitive impairment, a condition that makes a person’s memory and thinking more muddled than would be expected at a given age. Mild cognitive impairment is also a recognized risk factor for increasing dementia. Seniors with the condition develop Alzheimer’s disease at much higher rates than those of the same age with sharper memories. Copyright 2013 The New York Times Company
Keyword: Learning & Memory
Link ID: 18015 - Posted: 04.10.2013
A lack of a protein in Down's syndrome brains could be the cause of learning and memory problems, says a US study. Writing in Nature Medicine, Californian researchers found that the extra copy of chromosome 21 in people with the condition triggered the protein loss. Their study found restoring the protein in Down's syndrome mice improved cognitive function and behaviour. The Down's Syndrome Association said the study was interesting but the causes of Down's were very complex. Prof Huaxi Xu, senior author of the study from the Sanford-Burnham Medical Research Institute, said that in experiments on mice they discovered that the SNX27 protein was important for brain function and memory formation. Mice with less SNX27 had fewer active glutamate receptors and therefore had impaired learning and memory. The SNX27-deficient mice shared some characteristics with Down's syndrome, so the researchers looked at human brains with the condition. This confirmed their findings in the lab - that people with Down's syndrome also have significantly lower levels of SNX27. BBC © 2013
Michael Corballis, professor of cognitive neuroscience and psychology at the University of Auckland in New Zealand, responds: Although teaching people to become ambidextrous has been popular for centuries, this practice does not appear to improve brain function, and it may even harm our neural development. Calls for ambidexterity were especially prominent in the late 19th and early 20th centuries. For instance, in the early 20th century English propagandist John Jackson established the Ambidextral Culture Society in pursuit of universal ambidexterity and “two-brainedness” for the betterment of society. This hype died down in the mid-20th century as benefits of being ambidextrous failed to materialize. Given that handedness is apparent early in life and the vast majority of people are right-handed, we are almost certainly dextral by nature. Recent evidence even associated being ambidextrous from birth with developmental problems, including reading disability and stuttering. A study of 11-year-olds in England showed that those who are naturally ambidextrous are slightly more prone to academic difficulties than either left- or right-handers. Research in Sweden found ambidextrous children to be at a greater risk for developmental conditions such as attention-deficit hyperactivity disorder. Another study, which my colleagues and I conducted, revealed that ambidextrous children and adults both performed worse than left- or right-handers on a range of skills, especially in math, memory retrieval and logical reasoning. © 2013 Scientific American
By Felicity Muth This move from my old site to the Scientific American network has also coincided with my own physical move from the UK to the USA to start some new research. Given this is the closing of a chapter of my life (or rather, my PhD thesis, which will now no doubt sit on a dusty shelf somewhere until a grad student picks it up in 10 years time to use as a door stop), I felt now might be an appropriate time to write a little bit about what I have been doing for the past three years. In the past I have only written about other people’s research, but given that I am now a few months beyond the shock (I will resist using the word ‘trauma’ here) of it ‘all being over’, I feel like it might be time now to share a bit of what I did over my PhD. In one of my first meetings with my PhD supervisor, she said to me, ‘The way that I see it, you can either spend three months reading the limited amount of literature in your subject area, or you can go to Africa and get some data for yourself.’ This may have been the point where I realised I had chosen a good topic to study. Not only did not having much ‘literature’ to read due to the dearth of previous work done on this topic mean that I could kid myself that I was an ‘expert’ in the field after a few weeks, it was also liberating to know that most experiments that I carried out would be finding out new things. So, even before moving my books into my new PhD office, I was on a plane to Botswana to collect data on the nest building behaviour of the Southern masked weaverbird. When I tell people that the aim of my research is to work out how birds learn how to build nests, I usually get one of two responses. The first is, ‘they don’t learn anything of course, nest building in birds is innate.’ The other response is ‘surely that’s been done already?’ But actually, both of these (perfectly reasonable) assumptions are incorrect. © 2013 Scientific American,
Keyword: Learning & Memory
Link ID: 17939 - Posted: 03.23.2013
When the mind is at rest, the electrical signals by which brain cells communicate appear to travel in reverse, wiping out unimportant information in the process, but sensitizing the cells for future sensory learning, according to a study of rats conducted by researchers at the National Institutes of Health. The finding has implications not only for studies seeking to help people learn more efficiently, but also for attempts to understand and treat post-traumatic stress disorder — in which the mind has difficulty moving beyond a disturbing experience. During waking hours, electrical signals travel from dendrites — antenna-like projections at one end of the cell — through the cell body. From the cell body, they then travel the length of the axon, a single long projection at the other end of the cell. This electrical signal stimulates the release of chemicals at the end of the axon, which bind to dendrites on adjacent cells, stimulating these recipient cells to fire electrical signals, and so on. When groups of cells repeatedly fire in this way, the electrical signals increase in intensity. Dr. Bukalo and her team examined electrical signals that traveled in reverse?from the cell’s axon, to the cell body, and out its many dendrites. The reverse firing, depicted in this diagram, happens during sleep and at rest, appearing to reset the cell and priming it to learn new information. It was previously known that, during sleep, these impulses were reversed, arising from waves of electrical activity originating deep within the brain. In the current study, the researchers found that these reverse signals weakened circuits formed during waking hours, apparently so that unimportant information could be erased from the brain. But the reverse signals also appeared to prime the brain to relearn at least some of the forgotten information. If the animals encountered the same information upon awakening, the circuits re-formed much more rapidly than when they originally encountered the information.
Peter Fimrite Scientists at Stanford University have tapped into the mind of the mouse and are now circulating information about how the pesky rodents think. A team of Stanford researchers planted tiny probes inside the brains of mice to detect what were essentially mouse memories, according to a study published last month in the online edition of Nature Neuroscience. The experiment involved the insertion of a needlelike microscope into the hippocampus - a part of the brain associated with spatial and episodic memory. The microscope detected cellular activity and broadcast digital images through a cell phone camera sensor that fit like a hat over the heads of the critters as they scampered around an enclosure. "We're not really reading their minds," said the lead researcher, Mark Schnitzer, who is an associate professor of biology and applied physics at Stanford. "What is the mind of a mouse, anyway? I don't know. What we're doing is reading a spatial map in the brain. It is one little component of many, many processes that are going on inside." Over the course of a month, the scientists were able to document patterns of activity in some 700 neurons and pinpoint areas of the brain where mice store long-term information. It is important, Schnitzer said, because long-term memory is an area of the brain that researchers are struggling to understand as they attempt to develop new therapies for neurodegenerative diseases, including Alzheimer's disease. "Those are clearly diseases in which information storage has been impaired," Schnitzer said. "Now that we can look at the neural code for how the spatial information is stored, it opens the door directly to subsequent experiments. That's the logical next step." © 2013 Hearst Communications Inc.
Keyword: Learning & Memory
Link ID: 17908 - Posted: 03.18.2013
By Christie Aschwanden, A lawyer contacted Beatrice Golomb, a physician at the VA San Diego Healthcare Center, because he could no longer follow a normal conversation with his clients. A radiologist told Golomb that he found himself suddenly unable to distinguish left from right. A third person told her he had grown so forgetful that his doctor assumed he had Alzheimer’s. All three had developed their memory problems after taking a cholesterol-lowering statin drug, and the symptoms improved after they stopped the medication. The statin revolution began in 1987, when lovastatin was approved by the Food and Drug Administration. Since then, this class of drugs has transformed cardiac medicine, says Allen Taylor, chief of cardiology at MedStar Georgetown University Hospital. “Cardiovascular disease affects one in two people. This is the one drug that works.” But these drugs are not without risks. Golomb has amassed thousands of reports at her Web site Statineffects.com, detailing adverse reactions from statins. She says that cognitive problems are the second-most-common side effect reported in her database, after muscle pain. In a 2009 report in the journal Pharmacotherapy, Golomb described 171 patients who’d reported cognitive problems after taking statins. The idea that a cholesterol-lowering drug could make your brain fuzzy might sound crazy, and Golomb says the notion was greeted with suspicion at first. But eventually the FDA received enough such reports that last February it ordered drug companies to add a new warning label about possible memory problems. © 1996-2013 The Washington Post
Keyword: Learning & Memory
Link ID: 17905 - Posted: 03.15.2013
by Moheb Costandi Mice transplanted with a once-discounted class of human brain cells have better memories and learning abilities than normal counterparts, according to a new study. Far from a way to engineer smarter rodents, the work suggests that human brain evolution involved a major upgrade to cells called astrocytes. Astrocytes are one of several types of glia, the other cells found alongside neurons in the nervous system. Although long thought to merely provide support and nourishment for neurons, it's now clear that astrocytes are vital for proper brain function. They are produced during development from stem cells called glial progenitors. In 2009, Steven Goldman of the University of Rochester Medical Center in New York and his colleagues reported that human astrocytes are bigger, and have about 10 times as many fingerlike projections that contact other brain cells and blood vessels, than those of mice. To further investigate these differences, they have more recently grafted fluorescently labeled human glial progenitors into the brains of newborn mice and examined the animals when they reached adulthood. Most of the grafted cells remained as progenitors, but some matured into typical human-looking astrocytes. They connected to their mouse counterparts to form astrocyte networks that transmitted electrical signals. Furthermore, they propagated internal signals about three times faster than the mouse astrocytes and improved the strengthening of connections between neurons in the hippocampus, a process thought to be critical for learning and memory. © 2010 American Association for the Advancement of Science.