Chapter 17. Learning and Memory
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By Michael M. Torrice, We learn from experience: It sounds like a trite sentiment posted by a friend on Facebook, but neuroscientists would agree. Our interactions with the world around us strengthen and weaken the connections between our neurons, a process that neuroscientists consider to be the cellular mechanism of learning. Now researchers report that boosting signaling of a certain receptor in the brain with a small molecule can enhance these cellular changes and improve learning in people. The findings could lead to new treatments for patients with disorders associated with deficits in learning, such as Alzheimer’s disease and schizophrenia. Through decades of research on how synapses change in animal brains, scientists have found that the N-methyl-d-aspartate receptor (NMDAR) plays a critical role in strengthening synapses during learning. Compounds that increase NMDAR signaling can drive such changes and, as a result, help animals learn new tasks. Robert F. Asarnow at UCLA and colleagues wanted to test whether one such compound, d-cycloserine, would act similarly in people. But neuroscientists measure synapse changes in animals by sticking electrodes into slices of brain tissue to record electrical signals. “Obviously, we don’t do that to our friends,” Asarnow says. So his team used electroencephalography (EEG) to record electrical activity through electrodes stuck to the scalps of its subjects. The team monitored this activity as the subjects watched a certain pattern flash on a screen at high frequency for a couple minutes. Afterward, the subjects showed a spike in EEG activity in their visual cortex when they viewed the pattern at a later time. This suggested a population of neurons had wired themselves together by strengthening their synapses. © 2015 Scientific American
Keyword: Learning & Memory
Link ID: 21684 - Posted: 12.09.2015
by Laura Sanders There’s only so much brainpower to go around, and when the eyes hog it all, the ears suffer. When challenged with a tough visual task, people are less likely to perceive a tone, scientists report in the Dec. 9 Journal of Neuroscience. The results help explain what parents of screen-obsessed teenagers already know. For the study, people heard a tone while searching for a letter on a computer screen. When the letter was easy to find, participants were pretty good at identifying a tone. But when the search got harder, people were less likely to report hearing the sound, a phenomenon called inattentional deafness. Neural responses to the tone were blunted when people worked on a hard visual task, but not when the visual task was easy, researchers found. By showing that a demanding visual job can siphon resources away from hearing, the results suggest that perceptual overload can jump between senses. © Society for Science & the Public 2000 - 2015
By Nicholas Bakalar Watching television may be bad for your brain, a new study suggests. Researchers followed 3,274 people whose average age was 25 at the start of the study for 25 years, using questionnaires every five years to collect data on their physical activity and TV watching habits. At year 25, they administered three tests that measured various aspects of mental acuity. The highest level of TV watching — more than three hours a day most days — was associated with poor performance on all three tests. Compared with those who watched TV the least, those who watched the most had between one-and-a-half and two times the odds of poor performance on the tests, even after adjusting for age, sex, race, educational level, body mass index, smoking, alcohol use, hypertension and diabetes. Those with the lowest levels of physical activity and the highest levels of TV watching were the most likely to have poor test results. The authors acknowledge that their findings, published in JAMA Psychiatry, depend on self-reports, and that they had no baseline tests of cognitive function for comparison. “We can’t separate out what is going on with the TV watching,” said the lead author, Dr. Kristine Yaffe, a professor of psychiatry and neurology at the University of California, San Francisco. “Is it just the inactivity, or is there something about watching TV that’s the opposite of cognitive stimulation?” © 2015 The New York Times Company
Link ID: 21675 - Posted: 12.05.2015
By Nala Rogers If you travel with a group of friends, you might delegate navigation to the person with the best sense of direction. But among homing pigeons, the leader is whoever flies the fastest—even if that pigeon has to pick up navigation skills on the job, according to a new study. To find out how the skills of individual pigeons influence flock direction, researchers tested four flocks on journeys from three different locations, each about 5 kilometers from their home loft near Oxford, U.K. At each site, the researchers tracked the pigeons during solo flights before releasing them together for several group journeys. The fastest birds surged to the front during group flights and determined when the flock turned, despite the fact that these leaders were often poor navigators during their initial solo expeditions. But on a final set of solo flights—made after the group journeys—these same leaders chose straighter routes than followers, the researchers report today in Current Biology. Apparently, being responsible for group decisions helped pigeons learn the route, say scientists, raising questions about the two-way interplay between skills and leadership. © 2015 American Association for the Advancement of Science
By John Bohannon It may sound like a bird-brained idea, but scientists have trained pigeons to spot cancer in images of biopsied tissue. Individually, the avian analysts can't quite match the accuracy of professional pathologists. But as a flock, they did as well as trained humans, according to a new study appearing this week in PLOS ONE. Cancer diagnosis often begins as a visual challenge: Does this lumpy spot in a mammogram image justify a biopsy? And do cells in biopsy slides look malignant or benign? Training doctors and medical technicians to tell the difference is expensive and time-consuming, and computers aren't yet up to the task. To see whether a different type of trainee could do better, a team led by Richard Levenson, a pathologist and technologist at the University of California, Davis, and Edward Wasserman, a psychologist at the University of Iowa, in Iowa City, turned to pigeons. In spite of their limited intellect, the bobble-headed birds have certain advantages. They have excellent visual systems, similar to, if not better than, a human's. They sense five different colors as opposed to our three, and they don’t “fill in” the gaps like we do when expected shapes are missing. However, training animals to do a sophisticated task is tricky. Animals can pick up on unintentional cues from their trainers and other humans that may help them correctly solve problems. For example, a famous 20th century horse named Clever Hans was purportedly able to do simple arithmetic, but was later shown to be observing the reactions of his human audience. And although animals can perform extremely well on tasks that are confined to limited circumstances, overtraining on one set of materials can lead to total inaccuracy when the same information is conveyed slightly differently. © 2015 American Association for the Advancement of Science
By Emilie Reas What makes for a long-lasting memory? Research has shown that emotional or important events take root deeply, whereas neutral or mundane happenings create weak impressions that easily fade. But what about an experience that initially seemed forgettable but was later shown to be important? Animal research suggested that these types of older memories could be strengthened, but scientists had not been able to replicate this finding in humans—until now. New evidence suggests that our initially weak memories are maintained by the brain for a period, during which they can be enhanced. In the recent study published in Nature, psychologists at New York University showed 119 participants a series of images of tools and animals. A few minutes later the subjects saw a new set of images, with an electric shock paired with either the tools or the animals, to increase the salience of just one of those categories. The participants' memories for both sets of images were then tested either immediately, six hours later or the next day. Participants remembered images from the first neutral series better if they belonged to the same category (tool or animal) that was later paired with the shock. The findings suggest that even if an event does not seem meaningful when it occurs, a later cue that the experience was important can enhance the old memory. Although research has not yet demonstrated this effect outside the laboratory, the scientists speculate it happens often in daily life. For example, imagine you meet several new people at a networking event. During a job interview days later, you discover that one of those acquaintances is on the hiring committee, and suddenly the details of your conversation at the networking event become vivid and memorable—whereas the conversations you had with others at the event fade with time. © 2015 Scientific American
Keyword: Learning & Memory
Link ID: 21629 - Posted: 11.12.2015
By Erika Beras From the backseat of a cab, the moves a driver makes may at times seem, let’s say, daring. In fact, cabbies may actually be better, more agile drivers than the rest of us. Because they know their streets so well. Previous research found that the hippocampus in the brain of a typical cab driver is enlarged. That’s the part of the brain used in navigation. But now a study confirms that learning detailed navigation information does indeed cause that part of the brain to grow. The findings are in the journal NeuroImage. Researchers had young adults who were not regular gamers play a driving simulation game. Some practiced maneuvering the same route 20 times, while other players were confronted with 20 different routes. The participants’ brains were scanned before they performed the simulated driving and again after. Researchers found that subjects who kept repeating the same route increased their speed more than those driving multiple routes. The single-route drivers were also much better able to put in order a sequence of random pictures taken along the way and to draw a map of the route. The investigators also found increases in the single-route drivers in the functional connectivity between the hippocampus and other parts of the brain involved with navigation. And the amount of change was directly related to the amount of improvement each participant displayed. © 2015 Scientific American
Keyword: Learning & Memory
Link ID: 21612 - Posted: 11.07.2015
Laura Sanders Specialized cells that make up the brain’s GPS system have an expanding job description. In addition to mapping locations, these cells can keep track of distance and time, too, scientists report in the Nov. 4 Neuron. Those specialized cells, called grid cells, were thought to have a very specific job, says neuroscientist Loren Frank of the University of California, San Francisco. But, he says, the new study says, “not so fast, everybody.” These cells’ ability to detect time and distance is unexpected. “And I think it’s important,” Frank says. The growing to-do list of grid cells shows that the brain’s navigational system is surprisingly flexible. The discovery of grid cells, found in a part of the brain called the entorhinal cortex, was recognized with the Nobel Prize last year (SN Online: 10/6/14). These brain cells fire off regular signals as animals move around in space, partially forming an internal map of the environment. Neuroscientist Howard Eichenbaum of Boston University and colleagues wondered what those cells do when an animal stays put. By training rats to run on a treadmill, the researchers had a way to study grid cells as time and distance marched forward, but location remained the same. Unlike recently discovered “speed cells” (SN: 8/8/15, p. 8), these grid cells don’t change their firing rates to correspond to changes in the rats’ swiftness, the researchers found. Instead, these cells stay tuned to distance or time, or both. © Society for Science & the Public 2000 - 2015.
Keyword: Learning & Memory
Link ID: 21606 - Posted: 11.05.2015
Sara Reardon Military-service members can suffer brain injury and memory loss when exposed to explosions in enclosed spaces, even if they do not sustain overt physical injury. A strategy designed to improve memory by delivering brain stimulation through implanted electrodes is undergoing trials in humans. The US military, which is funding the research, hopes that the approach might help many of the thousands of soldiers who have developed deficits to their long-term memory as a result of head trauma. At the Society for Neuroscience meeting in Chicago, Illinois, on 17–21 October, two teams funded by the Defense Advanced Research Projects Agency presented evidence that such implanted devices can improve a person’s ability to retain memories. By mimicking the electrical patterns that create and store memories, the researchers found that gaps caused by brain injury can be bridged. The findings raise hopes that a ‘neuroprosthetic’ that automatically enhances flagging memory could aid not only brain-injured soldiers, but also people who have had strokes — or even those who have lost some power of recall through normal ageing. Because of the risks associated with surgically placing devices in the brain, both groups are studying people with epilepsy who already have implanted electrodes. The researchers can use these electrodes both to record brain activity and to stimulate specific groups of neurons. Although the ultimate goal is to treat traumatic brain injury, these people might benefit as well, says biological engineer Theodore Berger at the University of Southern California (USC) in Los Angeles. That is because repeated seizures can destroy the brain tissue needed for long-term-memory formation. © 2015 Nature Publishing Group
By Michelle Roberts Health editor, BBC News online Brain training - playing online games that give memory and reasoning skills a workout - is beneficial for older people, a large-scale study has concluded. Researchers at King's College London found the mental exercises kept minds sharp and helped people with everyday skills such as shopping and cooking. Nearly 7,000 people aged 50 and over signed up for the six-month experiment, launched by BBC TV's Bang Goes The Theory. Longer studies are now beginning. The volunteers were recruited from the general population by a partnership between the BBC, the Alzheimer's Society and the Medical Research Council. As far as the investigators were aware, none had any problems with memory or cognition when they signed up to the experiment. Some of the volunteers were encouraged to play online brain training games for 10 minutes at a time, as often as they wished. The others - the control group - were asked to do simple internet searches. The researchers tested the subjects on a series of medically recognised cognitive tests at baseline and then again at three months and six months to see if there was any detectable difference between the groups. The researchers found after six months, those who played "brain training" games for reasoning and problem-solving kept their broader cognitive skills better than those who did not. The benefit appeared to kick in when people played the games at least five times a week. And people over 60 who played these games reported better scores for carrying out essential everyday tasks, the Journal of Post-acute and Long Term Care Medicine reports. © 2015 BBC
When we hear speech, electrical waves in our brain synchronise to the rhythm of the syllables, helping us to understand what’s being said. This happens when we listen to music too, and now we know some brains are better at syncing to the beat than others. Keith Doelling at New York University and his team recorded the brain waves of musicians and non-musicians while listening to music, and found that both groups synchronised two types of low-frequency brain waves, known as delta and theta, to the rhythm of the music. Synchronising our brain waves to music helps us decode it, says Doelling. The electrical waves collect the information from continuous music and break it into smaller chunks that we can process. But for particularly slow music, the non-musicians were less able to synchronise, with some volunteers saying they couldn’t keep track of these slower rhythms. Rather than natural talent, Doelling thinks musicians are more comfortable with slower tempos because of their musical training. As part of his own musical education, he remembers being taught to break down tempo into smaller subdivisions. He suggests that grouping shorter beats together in this way is what helps musicians to process slow music better. One theory is that musicians have heard and played much more music, allowing them to acquire “meta-knowledge”, such as a better understanding of how composers structure pieces. This could help them detect a broader range of tempos, says Usha Goswami of the University of Cambridge. © Copyright Reed Business Information Ltd.
Richard A. Friedman YOU can increase the size of your muscles by pumping iron and improve your stamina with aerobic training. Can you get smarter by exercising — or altering — your brain? Stories from Our Advertisers This is hardly an idle question considering that cognitive decline is a nearly universal feature of aging. Starting at age 55, our hippocampus, a brain region critical to memory, shrinks 1 to 2 percent every year, to say nothing of the fact that one in nine people age 65 and older has Alzheimer’s disease. The number afflicted is expected to grow rapidly as the baby boom generation ages. Given these grim statistics, it’s no wonder that Americans are a captive market for anything, from supposed smart drugs and supplements to brain training, that promises to boost normal mental functioning or to stem its all-too-common decline. The very notion of cognitive enhancement is seductive and plausible. After all, the brain is capable of change and learning at all ages. Our brain has remarkable neuroplasticity; that is, it can remodel and change itself in response to various experiences and injuries. So can it be trained to enhance its own cognitive prowess? The multibillion-dollar brain training industry certainly thinks so and claims that you can increase your memory, attention and reasoning just by playing various mental games. In other words, use your brain in the right way and you’ll get smarter. A few years back, a joint study by BBC and Cambridge University neuroscientists put brain training to the test. Their question was this: Do brain gymnastics actually make you smarter, or do they just make you better at doing a specific task? For example, playing the math puzzle KenKen will obviously make you better at KenKen. But does the effect transfer to another task you haven’t practiced, like a crossword puzzle? © 2015 The New York Times Company
Claire Cain Miller Boys are falling behind. They graduate from high school and attend college at lower rates than girls and are more likely to get in trouble, which can hurt them when they enter the job market. This gender gap exists across the United States, but it is far bigger for poor people and for black people. As society becomes more unequal, it seems, it hurts boys more. New research from social scientists offers one explanation: Boys are more sensitive than girls to disadvantage. Any disadvantage, like growing up in poverty, in a bad neighborhood or without a father, takes more of a toll on boys than on their sisters. That realization could be a starting point for educators, parents and policy makers who are trying to figure out how to help boys — particularly those from black, Latino and immigrant families. “It’s something about family disadvantage itself,” said David Figlio, a Northwestern University economist and co-author of a new paper, presented publicly for the first time on Thursday. “Black people in America are more disadvantaged than white people in America, and if we were to reduce the disadvantage, we may see a reduction in the relative gender gap as well.” Marianne Bertrand, an economist at University of Chicago who with Jessica Pan has studied the gender gap, also found that boys fare worse than girls in disadvantaged homes, and are more responsive than girls to parental time and resources. “Their findings were very consistent: Families that invest more in children are protective for boys,” she said. The reasons that boys react more negatively to disadvantage are varied and hard to pinpoint. Even in utero, boys are more sensitive to extreme stress than girls, and tend to have more unruly temperaments. Society discourages boys from showing vulnerability. Low-income families are often led by single mothers, which has been found to affect boys differently than girls. © 2015 The New York Times Company
Alzheimer's disease can be detected decades before onset, using a virtual reality test, a study suggests. People aged 18 to 30 were asked to navigate through a virtual maze to test the function of certain brain cells. Those with a high genetic risk of Alzheimer's could be identified by their performance, according to German neuroscientists. The findings could help future research, diagnosis and treatment, they report in the journal Science. The scientists, led by Lukas Kunz of the German Centre for Neurodegenerative Diseases in Bonn, say the high risk group navigated the maze differently and had reduced functioning of a type of brain cell involved in spatial navigation. The findings could give an insight into why people with dementia can find navigating the world around them challenging, they say. "Our results could provide a new basic framework for preclinical research on Alzheimer's disease and may provide a neurocognitive explanation of spatial disorientation in Alzheimer's disease," they report in Science. Although genes play a role in dementia, their effects are complex with many unknowns. Dr Laura Phipps of Alzheimer's Research, said the latest study focused on healthy younger people at higher genetic risk of Alzheimer's, suggesting they may already show alterations in spatial navigation several decades before the disease could start. © 2015 BBC.
Link ID: 21555 - Posted: 10.23.2015
Keikantse Matlhagela Susumu Tonegawa unlocked the genetic secrets behind antibodies' diverse structures, which earned him the Nobel Prize in Physiology or Medicine in 1987. Having since moved fields, he tells Keikantse Matlhagela about his latest work on the neuroscience of happy and sad memories. You started as a chemist, then you moved into molecular biology and now you are a neuroscientist. Why change fields? Strangely, the only people to ask me about this are journalists — my students never ask. I see myself as a scientist who is interested in what's going on inside of us. It doesn't matter whether it is chemistry or immunology or neuroscience, I just do research on what I find interesting. The switch from chemistry to immunology did not seem like a big shift when I was young, but immunology to neuroscience was. After about 15 years spent researching immunology I wanted to explore an area of science where there are still big, unresolved questions. The brain is probably the most mysterious subject there is. Do you keep up to date with the field in which you won your Nobel prize? I am sorry to say that I haven't been paying a lot of attention to immunology in recent years because I am preoccupied with my work on memory. I have friends, of course, from that time — very close friends. But my friends are not young. Even though they are experts, they are also retired. We tend not to talk about immunology a whole lot. © 2015 Macmillan Publishers Limited
Keyword: Learning & Memory
Link ID: 21542 - Posted: 10.22.2015
By Emily Underwood CHICAGO—In 1898, Italian biologist Camillo Golgi found something odd as he examined slices of brain tissue under his microscope. Weblike lattices, now known as "perineuronal nets," surrounded many neurons, but he could not discern their purpose. Many dismissed the nets as an artifact of Golgi's staining technique; for the next century, they remained largely obscure. Today, here at the annual meeting of the Society for Neuroscience, researchers offered tantalizing new evidence that holes in these nets could be where long-term memories are stored. Scientists now know that perineuronal nets (PNNS) are scaffolds of linked proteins and sugars that resemble cartilage, says neuroscientist Sakina Palida, a graduate student in Roger Tsien's lab at the University of California,San Diego, and co-investigator on the study. Although it's still unclear precisely what the nets do, a growing body of research suggests that PNNs may control the formation and function of synapses, the microscopic junctions between neurons that allow cells to communicate, and that may play a role in learning and memory, Palida says. One of the most pressing questions in neuroscience is how memories—particularly long-term ones—are stored in the brain, given that most of the proteins inside neurons are constantly being replaced, refreshing themselves anywhere from every few days to every few hours. To last a lifetime, Palida says, some scientists believe that memories must somehow be encoded in a persistent, stable molecular structure. Inspired in part by evidence that destroying the nets in some brain regions can reverse deeply ingrained behaviors, Palida’s adviser Tsien, a Nobel-prize-winning chemist, recently began to explore whether PNNs could be that structure. Adding to the evidence were a number of recent studies linking abnormal PNNs to brain disorders including schizophrenia and Costello syndrome, a form of intellectual disability. © 2015 American Association for the Advancement of Science.
By LISA SANDERS, M.D. The middle-aged couple knocked at the door of the townhouse. When no one answered, the woman took her key and let them in. She called her daughter’s name as she hurried through the rooms. They had been trying to reach their 27-year-old daughter by phone all day, and she hadn’t answered. They found her upstairs, lying in bed and mumbling incoherently. The mother rushed over, but her daughter showed no signs of recognition. She and her husband quickly carried her to the car. Four months before, the mother told the emergency-room doctor at SSM Health St. Mary’s Hospital in St. Louis, her daughter had a procedure called gastric-sleeve surgery to help her lose weight. She came home after just a couple of days and felt great. She looked bright and eager. Once she started to eat, though, nausea and vomiting set in. After almost every meal, she would throw up. It’s an unusual but well-known complication of this kind of surgery. The cause is not clearly understood, but the phenomenon is sometimes linked to reflux. The surgeon tried different medications to stop the nausea and vomiting and to reduce the acid in her stomach, but they didn’t help. She had the surgery in order to lose weight, but now she was losing weight too quickly. After a month of vomiting, her doctors thought maybe she had developed gallstones — a common problem after rapid weight loss. But even after her gallbladder was removed, the young woman continued to vomit after eating. © 2015 The New York Times Company
Susan Gaidos CHICAGO — Eating a high-fat diet as a youngster can affect learning and memory during adulthood, studies have shown. But new findings suggest such diets may not have long-lasting effects. Rats fed a high-fat diet for nearly a year recovered their ability to navigate their surroundings. University of Texas at Dallas neuroscientist Erica Underwood tested spatial memory for rats fed a high-fat diet for either 12 weeks or 52 weeks, immediately after weaning. After rats placed in a chamber-filled box containing Lego-like toys became familiar with the box, the researchers moved the toys to new chambers. Later, when placed in the box, rats who ate high-fat foods for 12 weeks appeared confused and had difficulty finding the toys. But rats that ate high-fat foods for nearly a year performed as well as those fed a normal diet. Underwood repeated the experiment, posing additional spatial memory tests to new groups of rats. The findings were the same: Over the long-term, rats on high-fat diets recovered their ability to learn and remember. Studies of brain cells revealed that rats on the long-term high-fat diet showed reduced excitability in nerve cells from the hippocampus, the same detrimental effects seen in rats on the short-term high-fat diet. “The physiology that should create a dumber animal is there, but not the behavior,” said Lucien Thompson of UT Dallas, who oversaw the study. Underwood and Thompson speculate that some other part of the brain may be compensating for this reduction in neural response. © Society for Science & the Public 2000 - 2015.
By Martin Enserink Researchers who conduct animal studies often don't use simple safeguards against biases that have become standard in human clinical trials—or at least they don't report doing so in their scientific papers, making it impossible for readers to ascertain the quality of the work, an analysis of more than 2500 journal articles shows. Such biases, conscious or unconscious, can make candidate medical treatments look better than they actually are, the authors of the analysis warn, and lead to eye-catching results that can't be replicated in larger or more rigorous animal studies—or in human trials. Neurologist Malcolm MacLeod of the Centre for Clinical Brain Sciences at the University of Edinburgh and his colleagues combed through papers reporting the efficacy of drugs in eight animal disease models and checked whether the authors reported four measures that are widely acknowledged to reduce the risk of bias. First, if there was an experimental group and a control group, were animals randomly assigned to either one? (This makes it impossible for scientists to, say, assign the healthiest mice or rats to a treatment group, which could make a drug look better than it is.) Second, were the researchers who assessed the outcomes of a trial—for instance, the effect of a treatment on an animal's health—blinded to which animal underwent what procedure? Third, did the researchers calculate in advance the sample size needed to show that they didn't just accumulate data until they found something significant? And finally, did they make a statement about their conflicts of interest? © 2015 American Association for the Advancement of Science
By Hanae Armitage Schools of fish clump together for a very simple reason: safety in numbers. But for some, banding together offers more than just protection. It’s a way of getting to the head of the class. Schooling fish learn from each other, and new research shows that when they’re taken out of their normal social group, individuals struggle to learn on their own. Scientists have long known that schooling fish observe and learn from each other’s failures and successes, behaviors that stimulate neural development, especially in the part of the brain responsible for memory and learning. But this is the first time they have found evidence of that link in spatial learning. To test their theory, scientists divided a school of social cichlid fish into two categories: 14 social fish and 15 loners. Researchers kept the social fish grouped together while they partitioned the loners into single-fish isolation tanks. They ran both groups through a simple T-shaped maze, color coding the side that harbored food—a yellow mark for food, a green mark for no food. Seven of the 14 socialized fish learned to associate yellow with food (high marks for the cichlids, which are not the brightest fish in the animal kingdom), whereas only three of the 15 isolated fish successfully made the same association. Writing in this month’s issue of Applied Animal Behaviour Science, the researchers say this suggests fish in group settings are able to learn better and faster than their singled out counterparts. The moral? Simple: Fish should stay in school. © 2015 American Association for the Advancement of Science