Chapter 17. Learning and Memory
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Keyword: Learning & Memory
Link ID: 21933 - Posted: 02.27.2016
The dodo is an extinct flightless bird whose name has become synonymous with stupidity. But it turns out that the dodo was no bird brain, but instead a reasonably brainy bird. Scientists said on Wednesday they figured out the dodo's brain size and structure based on an analysis of a well-preserved skull from a museum collection. They determined its brain was not unusually small but rather completely in proportion to its body size. They also found the dodo may have had a better sense of smell than most birds, with an enlarged olfactory region of the brain. This trait, unusual for birds, probably let it sniff out ripe fruit to eat. The research suggests the dodo, rather than being stupid, boasted at least the same intelligence as its fellow members of the pigeon and dove family. Mauritius Dodo bird A skeleton of a Mauritius Dodo bird stands at an exhibition in the Mauritius Institute Museum in Port Louis in this Dec. 27, 2005 file photo. (Reuters) "If we take brain size — or rather, volume, as we measured here — as a proxy for intelligence, then the dodo was as smart as a common pigeon," paleontologist Eugenia Gold of Stony Brook University in New York state said. "Common pigeons are actually smarter than they get credit for, as they were trained as message carriers during the world wars." ©2016 CBC/Radio-Canada.
by Giuseppe Gangarossa When we think about sex hormones, notably estrogens and androgens, we usually associate them with sex, gender and body development. Like all hormones, they are chemical messengers, substances produced in one part of the body that go on to tell other parts what to do. However, we often have the tendency to forget the enormous impact that these steroid hormones have on brain functions. From animal studies, it has become clear that during early development, exposure of the brain to testosterone and estradiol, hormones present in both males and females, leads to irreversible changes in the nervous system (McCarthy et al., 2012). A growing and very appealing body of science suggests that sex hormones play a neuromodulatory role in cognitive brain function (Janowsky, 2006). Moreover, testosterone dysfunctions (hypogonadism, chemical castration, etc.) have shown to be associated with memory defects. However, in spite of these advances, it still remains an enigma how sex hormones affect the brain. In an interesting paper published in PLOS ONE, Picot and colleagues tried to fill in one piece of the puzzle. They investigated the neurobiological effects of cerebral androgen receptor (AR) ablation on hippocampal plasticity and cognitive performance in male rodents (Picot et al., 2016). Although several reports have already highlighted a link between sex hormones and cognitive function (Galea et al., 2008; Janowsky, 2006), much more needs to be done to fully elucidate the “non-sexual” functions of androgens.
Meghan Rosen The people of Flint, Mich., are drinking bottled water now, if they can get it. Volunteers deliver it door-to-door and to local fire stations. The goal is to keep the city’s residents from ingesting so much lead. Success – or lack thereof – could have consequences not just now, but for generations to come. Late last year, scientists raised alarms over a link between the city’s lead-tainted water and the growing number of children with high lead levels in their blood. It’s a serious problem. Lead is toxic to the brain, something scientists have long known. “Lead is probably the most well-known neurotoxin to man,” says Mona Hanna-Attisha, the pediatrician who first connected lead in Flint’s water to lead exposure in kids. And as scientists are beginning to find out, the damage that lead inflicts on children may be long-lasting. In addition to harming kids during youth, lead could contribute to disorders that develop later in life, such as Alzheimer’s disease or schizophrenia. Lead’s reach could extend even further, too — beyond those who drank the contaminated water to their children and grandchildren. Flint’s kids “will have to be followed throughout their whole life, and maybe into the next generation or two,” says Douglas Ruden, a neural toxicologist at Wayne State University in Detroit. A few months of drinking clean water will help bring the kids’ lead levels back down, he says. “But the damage is done.” And it’s permanent. In the United States, lead is everywhere. Decades of burning leaded gasoline spewed lead into the air, and the element settled in the upper layer of soil, clinging to particles of dirt. © Society for Science & the Public 2000 - 2016.
By BENEDICT CAREY Over the past few decades, cognitive scientists have found that small alterations in how people study can accelerate and deepen learning, improving retention and comprehension in a range of subjects, including math, science and foreign languages. The findings come almost entirely from controlled laboratory experiments of individual students, but they are reliable enough that software developers, government-backed researchers and various other innovators are racing to bring them to classrooms, boardrooms, academies — every real-world constituency, it seems, except one that could benefit most: people with learning disabilities. Now, two new studies explore the effectiveness of one common cognitive science technique — the so-called testing effect — for people with attention-deficit problems, one of the most commonly diagnosed learning disabilities. The results were mixed. They hint at the promise of outfoxing learning deficits with cognitive science, experts said, but they also point to the difficulties involved. The learning techniques developed by cognitive psychologists seem, in some respects, an easy fit for people with attention deficits: breaking up study time into chunks, mixing related material in a session, varying study environments. Each can produce improvements in retention or comprehension, and taken together capture the more scattered spirit of those with attention deficit hyperactivity disorder, especially children. The testing effect has proved especially reliable for other students, and it is a natural first choice to measure the potential application to A.D.H.D. The principle is straightforward: Once a student is familiar with a topic, testing himself on it deepens the recall of the material more efficiently than restudying. © 2016 The New York Times Company
By SINDYA N. BHANOO The human brain is attracted to things that were once pleasing even if they no longer are, researchers report. Study participants were asked to find red and green objects on a computer screen filled with different colored objects. They received small rewards for finding the objects: $1.50 for the red ones and 25 cents for the green ones. The next day, while brain scans were conducted, participants were asked to find certain shapes on the screen. There was no reward, and color was irrelevant. Still, when a red object appeared, participants focused on it, and scans showed dopamine was released in their brains. “They are not getting a reward for that, yet part of the brain is saying, ‘Oh, there’s a reward — pay attention to it,’” said Susan M. Courtney, a cognitive neuroscientist at Johns Hopkins University and a co-author of the study in Current Biology. The findings may help researchers develop pharmaceutical treatments for problems like food or drug addiction. © 2016 The New York Times Company
Mo Costandi Tell me where dwell the thoughts, forgotten till thou call them forth? Tell me where dwell the joys of old, and where the ancient loves, And when will they renew again, and the night of oblivion past, That I might traverse times and spaces far remote, and bring Comforts into a present sorrow and a night of pain? Where goest thou, O thought? To what remote land is thy flight? If thou returnest to the present moment of affliction, Wilt thou bring comforts on thy wings, and dews and honey and balm, Or poison from the desert wilds, from the eyes of the envier? In his epic poem, Visions of the Daughters of Albion, William Blake wonders about the nature of memory, its ability to mentally transport us to distant times and places, and the powerful emotions, both positive and negative, that our recollections can evoke. The poem contains questions that remain highly pertinent today, such as what happens to our long-lost memories, and how do we retrieve them? More than two centuries later, the mechanisms of memory storage and retrieval are the most intensively studied phenomena in the brain sciences. It’s widely believed that memory formation involves the strengthening of connections between sparsely distributed networks of neurons in a brain structure called the hippocampus, and that subsequent retrieval involves reactivation of the same neuronal ensembles. And yet, neuroscientists still struggle to answer Blake’s questions definitely. Now, a team of researchers at the University of Geneva have made another important advance in our understanding of the neural mechanisms underlying memory formation. Using a state-of-the-art method called optogenetics, they show how the neuronal ensembles that encode memories emerge, revealing that ensembles containing too many neurons – or too few – impair memory retrieval. © 2016 Guardian News and Media Limited
Keyword: Learning & Memory
Link ID: 21893 - Posted: 02.13.2016
Sara Reardon Mice are sensitive to minor changes in food, bedding and light exposure. It’s no secret that therapies that look promising in mice rarely work in people. But too often, experimental treatments that succeed in one mouse population do not even work in other mice, suggesting that many rodent studies may be flawed from the start. “We say mice are simpler, but I think the problem is deeper than that,” says Caroline Zeiss, a veterinary neuropathologist at Yale University in New Haven, Connecticut. Researchers rarely report on subtle environmental factors such as their mice’s food, bedding or exposure to light; as a result, conditions vary widely across labs despite an enormous body of research showing that these factors can significantly affect the animals’ biology. “It’s sort of surprising how many people are surprised by the extent of the variation” between mice that receive different care, says Cory Brayton, a pathologist at Johns Hopkins University in Baltimore, Maryland. At a meeting on mouse models at the Wellcome Genome Campus in Hinxton, UK, on 9–11 February, she and others explored the many biological factors that prevent mouse studies from being reproduced. Christopher Colwell, a neuroscientist at the University of California, Los Angeles, has first-hand experience with these issues. He and a colleague studied autism in the same genetically modified mouse line, but obtained different results on the same behaviour tests. Eventually they worked out why: Colwell, who studies circadian rhythms, keeps his mice dark in the daytime to trick their body clocks into thinking day is night, so that the nocturnal animals are more alert when tested during the day. His colleague does not. © 2016 Nature Publishing Group
By Uri Bram Early-life exposure to pathogenic bacteria can induce a lifelong imprinted olfactory memory in C. elegans through two distinct neural circuits, according to a study published today (February 11) in Cell. Researchers from Rockefeller University in New York City have shown that early-life pathogen exposure leads the nematode to have a lifelong aversion to the specific associated bacterial odors, whereas later-in-life exposure spurs only transient aversion. “This study is very exciting,” said Yun Zhang of Harvard who studies learning in C. elegans but was not involved in the present work. “Imprinting is a form of learning widely observed in many animals [but] finding this in C. elegans is very meaningful because this nematode is genetically tractable, and its small nervous system is well described.” A classic example of imprinting is how geese form attachments to the first moving object they see after birth; Nobel laureate Konrad Lorenz famously showed that the “moving object” could be himself instead of a mother goose. During the critical period at the start of life, animals often have unusual abilities to create and maintain long-term memories. For the present study, Rockefeller’s Xin Jin and colleagues described a form of aversive imprinting in their C. elegans: newly hatched nematodes exposed to Pseudomonas aeruginosa PA14 or toxin-emitting Escherichia coli BL21 established a long-term olfactory aversion to it. Animals that experienced the pathogen immediately after hatching were able to synthesize and maintain the aversive memory for the whole of their four-day lifespans, while animals trained in adulthood only retained the aversive memory for up to 24 hours. © 1986-2016 The Scientist
By Julia Shaw The approach to Valentine's Day is a reminder that we humans are so intrigued by the idea of love that we have made it into something to celebrate in it’s own right. Love is something amazing. Love is something special. But what are the implications of love for our memories? Remember those “your brain on drugs” awareness posters? You can essentially substitute “love” for “drugs” and the same warnings apply. Scientists have found that being in love actually makes you activate some of the same brain regions as when you take addictive drugs, like ecstasy or cocaine. Neuroscientist Kayo Takahashi and his team have described passionate love as an “all-encompassing experience” which has “disorienting effects” and is generally considered “highly pleasurable”. While you probably don’t need a bunch of scientists to tell you that, you probably do need them to explain what that actually means in the brain. In 2015 Kayo and his team were keen on exploring the role of one particular culprit of the feel-good effects of love, the neurotransmitter dopamine. Among many other effects, dopamine generally makes us feel pleasure. Kayo and his team looked into the brains of people who were in the early stages of romantic relationships, and they found that when shown pictures of their romantic partners, participants experienced a flood of dopamine to parts of their brains. As it turns out, brains need to release dopamine in order to store long-term memories. © 2016 Scientific American
By PAM BELLUCK The risk of developing dementia is decreasing for people with at least a high school education, according to an important new study that suggests that changes in lifestyle and improvements in physical health can help prevent or delay cognitive decline. The study, published Wednesday in The New England Journal of Medicine, provides the strongest evidence to date that a more educated population and better cardiovascular health are contributing to a decline in new dementia cases over time, or at least helping more people stave off dementia for longer. The findings have implications for health policy and research funding, and they suggest that the long-term cost of dementia care may not be as devastatingly expensive as policy makers had predicted, because more people will be able to live independently longer. There are wild cards that could dampen some of the optimism. The study participants were largely white and suburban, so results may not apply to all races and ethnicities. Still, a recent study showed a similar trend among African-Americans in Indianapolis, finding that new cases of dementia declined from 1992 to 2001. The 2001 participants had more education, and although they had more cardiovascular problems than the 1992 participants, those problems were receiving more medical treatment. Another question mark is whether obesity and diabetes, which increase dementia risk, will cause a surge in dementia cases when the large number of overweight or diabetic 40- and 50-year-olds become old enough to develop dementia. © 2016 The New York Times Company
It’s well known that some people report that their mood is influenced by the seasons. But can the time of year affect other cognitive functions? To find out, Gilles Vandewalle and colleagues at the University of Liege in Belgium scanned the brains of 28 volunteers while they performed attention and working memory tests at different times of the year. To ensure the results were influenced by the seasons rather than the environmental conditions on the test day, the participants were confined to a lab for 4.5 days prior to the test, exposed to a constant light level and temperature. Although their test scores didn’t change with the seasons, activity in some brain areas showed a consistent seasonal pattern among the volunteers: brain activity peaked in the summer on the attention task and in the autumn on the memory task. Many seasonally changing factors could regulate such a pattern, including day length (known as photoperiod), temperature, humidity, social interaction and physical activity. Since these weren’t all controlled for in the study, it’s impossible to say what is responsible for the seasonal changes seen. “In our data it seems that photoperiod, or the rate of change of photoperiod, was more likely to explain what we were seeing. But we can’t exclude all the others,” says Vandewalle. The results suggest that over the course of a year, the brain might work in different ways to compensate for seasonal factors that could affect its function, enabling it to maintain a stable performance. Vandewalle speculates that these mechanisms might not work as well in some people, for example, those vulnerable to the winter blues. © Copyright Reed Business Information Ltd.
By Jeneen Interlandi The human brain’s memory-storage capacity is an order of magnitude greater than previously thought, researchers at the Salk Institute for Biological Studies reported last week. The findings, recently detailed in eLife, are significant not only for what they say about storage space but more importantly because they nudge us toward a better understanding of how, exactly, information is encoded in our brains. The question of just how much information our brains can hold is a longstanding one. We know that the human brain is made up of about 100 billion neurons, and that each one makes 1,000 or more connections to other neurons, adding up to some 100 trillion in total. We also know that the strengths of these connections, or synapses, are regulated by experience. When two neurons on either side of a synapse are active simultaneously, that synapse becomes more robust; the dendritic spine (the antenna on the receiving neuron) also becomes larger to support the increased signal strength. These changes in strength and size are believed to be the molecular correlates of memory. The different antenna sizes are often compared with bits of computer code, only instead of 1s and 0s they can assume a range of values. Until last week scientists had no idea how many values, exactly. Based on crude measurements, they had identified just three: small, medium and large. But a curious observation led the Salk team to refine those measurements. In the course of reconstructing a rat hippocampus, an area of the mammalian brain involved in memory storage, they noticed some neurons would form two connections with each other: the axon (or sending cable) of one neuron would connect with two dendritic spines (or receiving antennas) on the same neighboring neuron, suggesting that duplicate messages were being passed from sender to receiver. © 2016 Scientific American
Keyword: Learning & Memory
Link ID: 21866 - Posted: 02.06.2016
Heidi Ledford Difficulty with concentration, memory and other cognitive tasks is often associated with depression. In the past quarter of a century, a wave of drugs has transformed the treatment of depression. But the advances have struggled to come to grips with symptoms that often linger long after people start to feel better: cognitive problems such as memory loss and trouble concentrating. On 3 February, the US Food and Drug Administration (FDA) will convene a meeting of its scientific advisers to discuss whether such cognitive impairments are components of the disorder that drugs might be able to target — or just a result of depressed mood. The discussion will help the agency to decide whether two companies that sell the antidepressant vortioxetine should be allowed to label it as a treatment for the cognitive effects. A ‘yes’ could spur drug developers to invest in ways to test cognitive function during their antidepressant trials. Psychiatrists have long noted that some people with depression also struggle to concentrate and to make decisions. The question has been whether such difficulties are merely an offshoot of altered mood and would thus clear up without specific treatment, says Diego Pizzagalli, a neuroscientist at McLean Hospital, an affiliate of Harvard Medical School in Belmont, Massachusetts. But some patients who report improved mood after treatment still struggle with cognitive deficits — so psychiatrists sometimes prescribe concentration-enhancing drugs that are approved to treat attention deficit hyperactivity disorder to people with depression. © 2016 Nature Publishing Group
Fears over surveillance seem to figure large in the bird world, too. Ravens hide their food more quickly if they think they are being watched, even when no other bird is in sight. It’s the strongest evidence yet that ravens have a “theory of mind” – that they can attribute mental states such as knowledge to others. Many studies have shown that certain primates and birds behave differently in the presence of peers who might want to steal their food. While some researchers think this shows a theory of mind, others say they might just be reacting to visual cues, rather than having a mental representation of what others can see and know. Through the peephole Thomas Bugnyar and colleagues at the University of Vienna, Austria, devised an experiment to rule out the possibility that birds are responding to another’s cues. The setup involved two rooms separated by a wooden wall, with windows and peepholes that could be covered. First, a raven was given food with another raven in the next room, with the window open or covered, to see how quickly it caches its prize. With the window open, the birds hid their food more quickly and avoided going back to conceal it further. Then individual ravens were then trained to use the peephole to see where humans were putting food in the other room. The idea here was to allow the bird to realise it could be seen through the peephole. © Copyright Reed Business Information Ltd.
Nell Greenfieldboyce The state of New Jersey has been trying to help jurors better assess the reliability of eyewitness testimony, but a recent study suggests that the effort may be having unintended consequences. That's because a new set of instructions read to jurors by a judge seems to make them skeptical of all eyewitness testimony — even testimony that should be considered reasonably reliable. Back in 2012, New Jersey's Supreme Court did something groundbreaking. It said that in cases that involve eyewitness testimony, judges must give jurors a special set of instructions. The instructions are basically a tutorial on what scientific research has learned about eyewitness testimony and the factors that can make it more dependable or less so. "The hope with this was that jurors would then be able to tell what eyewitness testimony was trustworthy, what sort wasn't, and at the end of the day it would lead to better decisions, better court outcomes, better justice," says psychologist David Yokum. Yokum was a graduate student at the University of Arizona, doing research on decision-making, when he and two colleagues, Athan Papailiou and Christopher Robertson, decided to test the effect of these new jury instructions, using videos of a mock trial that they showed to volunteers. © 2016 npr
Keyword: Learning & Memory
Link ID: 21828 - Posted: 01.27.2016
James Gorman Spotted hyenas are the animals that got Sarah Benson-Amram thinking about how smart carnivores are and in what ways. Dr. Benson-Amram, a researcher at the University of Wyoming in Laramie, did research for her dissertation on hyenas in the wild under Kay E. Holekamp of Michigan State University. Hyenas have very complicated social structures and they require intelligence to function in their clans, or groups. But the researchers also tested the animals on a kind of intelligence very different from figuring out who ranks the highest: They put out metal boxes that the animals had to open by sliding a bolt in order to get at meat inside. Only 15 percent of the hyenas solved the problem in the wild, but in captivity, the animals showed a success rate of 80 percent. Dr. Benson-Amram and Dr. Holekamp decided to test other carnivores, comparing species and families. They and other researchers presented animals in several different zoos with a metal puzzle box with a treat inside and recorded the animals’ efforts. They tested 140 animals in 39 species that were part of nine families. They reported their findings on Monday in the Proceedings of the National Academy of Sciences. They compared the success rates of different families with absolute brain size, relative brain size, and the size of the social groups that the species form in the wild. Just having a bigger brain did not make difference, but the relative size of the brain, compared with the size of the body, was the best indication of which animals were able to solve the problem of opening the box. © 2016 The New York Times Company
by Graham McDougall, Jr., behavioral scientist at U. of Alabama Chemo brain is a mental cloudiness reported by about 30 percent of cancer patients who receive chemotherapy. Symptoms typically include impairments in attention, concentration, executive function, memory and visuospatial skills. Since the 1990s researchers have tried to understand this phenomenon, particularly in breast cancer patients. But the exact cause of chemo brain remains unclear. Some studies indicate that chemotherapy may trigger a variety of related neurological symptoms. One study, which examined the effects of chemotherapy in 42 breast cancer patients who underwent a neuropsychological evaluation before and after treatment, found that almost three times more patients displayed signs of cognitive dysfunction after treatment as compared with before (21 versus 61 percent). A 2012 review of 17 studies considering 807 breast cancer patients found that cognitive changes after chemotherapy were pervasive. Other research indicates that the degree of mental fogginess that a patient experiences may be directly related to how much chemotherapy that person receives: higher doses lead to greater dysfunction. There are several possible mechanisms to explain the cognitive changes associated with chemotherapy treatments. The drugs may have direct neurotoxic effects on the brain or may indirectly trigger immunological responses that may cause an inflammatory reaction in the brain. Chemotherapy, however, is not the only possible culprit. Research also shows that cancer itself may cause changes to the brain. In addition, it is possible that the observed cognitive decline may simply be part of the natural aging process, especially considering that many cancer patients are older than 50 years. © 2016 Scientific American,
By Emily Underwood Roughly half of Americans use marijuana at some point in their lives, and many start as teenagers. Although some studies suggest the drug could harm the maturing adolescent brain, the true risk is controversial. Now, in the first study of its kind, scientists have analyzed long-term marijuana use in teens, comparing IQ changes in twin siblings who either used or abstained from marijuana for 10 years. After taking environmental factors into account, the scientists found no measurable link between marijuana use and lower IQ. “This is a very well-conducted study … and a welcome addition to the literature,” says Valerie Curran, a psychopharmacologist at the University College London. She and her colleagues reached “broadly the same conclusions” in a separate, nontwin study of more than2000 British teenagers, published earlier this month in the Journal of Psychopharmacology, she says. But, warning that the study has important limitations, George Patton, a psychiatric epidemiologist at the University of Melbourne in Australia, adds that it in no way proves that marijuana—particularly heavy, or chronic use —is safe for teenagers. Most studies that linked marijuana to cognitive deficits, such as memory loss and low IQ, looked at a single “snapshot” in time, says statistician Nicholas Jackson of the University of Southern California in Los Angeles, lead author of the new work. That makes it impossible to tell which came first: drug use or poor cognitive performance. “It's a classic chicken-egg scenario,” he says. © 2016 American Association for the Advancement of Science.
Laura Sanders Pain can sear memories into the brain, a new study finds. A full year after viewing a picture of a random, neutral object, people could remember it better if they had been feeling painful heat when they first saw it. “The results are fun, they are interesting and they are provocative,” says neuroscientist A. Vania Apkarian of Northwestern University in Chicago. The findings “speak to the idea that pain really engages memory.” Neuroscientists G. Elliott Wimmer and Christian Büchel of University Medical Center Hamburg-Eppendorf in Germany reported the results in a paper online at BioRxiv.org first posted December 24 and revised January 6. The findings are under review at a journal, and Wimmer declined to comment on the study until it is accepted for publication. Wimmer and Büchel recruited 31 brave souls who agreed to feel pain delivered by a heat-delivering thermode on their left forearms. Each person’s pain sensitivity was used to calibrate the amount of heat they received in the experiment, which was either not painful (a 2 on an 8-point scale) or the highest a person could endure multiple times (a full 8). While undergoing a functional MRI scan, participants looked at a series of pictures of unremarkable household objects, such as a camera, sometimes feeling pain and sometimes not. Right after seeing the images, the people took a pop quiz in which they answered whether an object was familiar. Pain didn’t influence memory right away. Right after their ordeal, participants remembered about three-quarters of the previously seen objects, regardless of whether pain was present, the researchers found. © Society for Science & the Public 2000 - 2015.