Chapter 17. Learning and Memory

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Sophie Fessl Mice raised in an enriched environment are better able to adapt and change than mice raised in standard cages, but why they show this higher brain plasticity has not been known. Now, a study published January 11 in Cell Reports finds that the environment could act indirectly: living in enriched environments changes the animals’ gut microbiota, which appears to modulate plasticity. The study “provides very interesting new insights into possible beneficial effects of environmental enrichment on the brain that might act via the gut,” writes Anthony Hannan, a neuroscientist at the Florey Institute of Neuroscience and Mental Health in Australia who was not involved in the study, in an email to The Scientist. “This new study has implications for how we might understand the beneficial effects of environmental enrichment, and its relevance to cognitive training and physical activity interventions in humans.” In previous studies, mice raised in what scientists call an enriched environment—one in which they have more opportunities to explore, interact with others, and receive sensory stimulation than they would in standard laboratory enclosures—have been better able to modify their neuronal circuits in response to external stimuli than mice raised in smaller, plainer cages. Paola Tognini, a neuroscientist at the University of Pisa and lead author of the new study, writes in an email to The Scientist that she “wondered if endogenous factors (signals coming from inside our body instead of the external world), such as the signals coming from the intestine, could also influence brain plasticity.” © 1986–2022 The Scientist.

Keyword: Learning & Memory; Obesity
Link ID: 28159 - Posted: 01.19.2022

Melinda Wenner Moyer Like many paediatricians, Dani Dumitriu braced herself for the impact of the SARS-CoV-2 coronavirus when it first surged in her wards. She was relieved when most newborn babies at her hospital who had been exposed to COVID-19 seemed to do just fine. Knowledge of the effects of Zika and other viruses that can cause birth defects meant that doctors were looking out for problems. But hints of a more subtle and insidious trend followed close behind. Dumitriu and her team at the NewYork–Presbyterian Morgan Stanley Children’s Hospital in New York City had more than two years of data on infant development — since late 2017, they had been analysing the communication and motor skills of babies up to six months old. Dumitriu thought it would be interesting to compare the results from babies born before and during the pandemic. She asked her colleague Morgan Firestein, a postdoctoral researcher at Columbia University in New York City, to assess whether there were neurodevelopmental differences between the two groups. A few days later, Firestein called Dumitriu in a panic. “She was like, ‘We’re in a crisis, I don’t know what to do, because we not only have an effect of a pandemic, but it’s a significant one,’” Dumitriu recalled. She was up most of that night, poring over the data. The infants born during the pandemic scored lower, on average, on tests of gross motor, fine motor and communication skills compared with those born before it (both groups were assessed by their parents using an established questionnaire)1. It didn’t matter whether their birth parent had been infected with the virus or not; there seemed to be something about the environment of the pandemic itself. Dumitriu was stunned. “We were like, oh, my God,” she recalled. “We’re talking about hundreds of millions of babies.” Although children have generally fared well when infected with SARS-CoV-2, preliminary research suggests that pandemic-related stress during pregnancy could be negatively affecting fetal brain development in some children. Moreover, frazzled parents and carers might be interacting differently or less with their young children in ways that could affect a child’s physical and mental abilities.

Keyword: Development of the Brain; Learning & Memory
Link ID: 28152 - Posted: 01.12.2022

By Lisa Sanders, M.D. The mother stood in the baggage-claim area of the Buffalo Niagara International Airport, waiting for her 37-year-old son, who had just flown in from North Carolina. The carousel was nearly empty by the time she caught sight of him. She was shocked by how sick he looked. His face was pale and thin, his hair and clothes rumpled as if he felt too awful to care. Most surprising of all: He was being rolled toward her in a wheelchair. “I had some trouble with the stairs,” he explained. He thanked the attendant and then struggled to get to his feet. He didn’t make it. Before he got more than a few inches off the seat, his arms and then his legs began to shake and wobble, and he fell heavily back into the chair. His mother collected his bag and pushed him out to where her husband was waiting in the car. On the drive home, the young man struggled to explain what was going on. He had always considered himself to be pretty strong and healthy, but these past few weeks had been rough. It started in his legs. He felt wobbly. When he walked, his hips, legs and especially his feet felt as if they might not be able to hold him up. He saw his physician assistant about it — he worried that it was caused by the cholesterol-lowering medication he had started taking — but the P.A. assured him it wasn’t. He was running a few times a week, but he had to stop because his legs were done well before the run was. And he didn’t feel as sharp as he used to be. His brain seemed foggy and slow. Then this morning he had trouble climbing the stairs to the plane. That was scary. The guy behind him helped by holding up his backpack, but his feet felt like dead weights. He had to use his arms to help get his body up high enough to take each step. Once on the plane, he supported himself on the headrests to get to his assigned seat. They offered the wheelchair when he arrived in Buffalo, and he gratefully accepted. His mother tentatively asked if he thought he should see a doctor. She knew he hated it when she tried to tell him what to do. He had flown up to see a football game with her ex-husband, his father, and a hockey game with his stepbrother. If he didn’t feel any better after that, he conceded, it would be time to see a doctor. © 2022 The New York Times Company

Keyword: Movement Disorders; Drug Abuse
Link ID: 28150 - Posted: 01.12.2022

Don Arnold All memory storage devices, from your brain to the RAM in your computer, store information by changing their physical qualities. Over 130 years ago, pioneering neuroscientist Santiago Ramón y Cajal first suggested that the brain stores information by rearranging the connections, or synapses, between neurons. Since then, neuroscientists have attempted to understand the physical changes associated with memory formation. But visualizing and mapping synapses is challenging to do. For one, synapses are very small and tightly packed together. They’re roughly 10 billion times smaller than the smallest object a standard clinical MRI can visualize. Furthermore, there are approximately 1 billion synapses in the mouse brains researchers often use to study brain function, and they’re all the same opaque to translucent color as the tissue surrounding them. A new imaging technique my colleagues and I developed, however, has allowed us to map synapses during memory formation. We found that the process of forming new memories changes how brain cells are connected to one another. While some areas of the brain create more connections, others lose them. Mapping new memories in fish Previously, researchers focused on recording the electrical signals produced by neurons. While these studies have confirmed that neurons change their response to particular stimuli after a memory is formed, they couldn’t pinpoint what drives those changes. © 2010–2022, The Conversation US, Inc.

Keyword: Learning & Memory
Link ID: 28149 - Posted: 01.12.2022

By Maria Temming It might seem like a fish needs a car like — well, like a fish needs a bicycle. But a new experiment suggests that fish actually make pretty good drivers. In the experiment, several goldfish learned to drive what is essentially the opposite of a submarine — a tank of water on wheels — to destinations in a room. That these fish could maneuver on land suggests that fishes’ understanding of space and navigation is not limited to their natural environment — and perhaps has something in common with landlubber animals’ internal sense of direction, researchers report in the Feb. 15 Behavioural Brain Research. Researchers at Ben-Gurion University of the Negev in Beer-Sheva, Israel taught six goldfish to steer a motorized water tank. The fishmobile was equipped with a camera that continually tracked a fish driver’s position and orientation inside the tank. Whenever the fish swam near one of the tank’s walls, facing outward, the vehicle trundled off in that direction. This goldfish knows how to use its wheels. Successfully navigating in a tank on land suggests that the animals understand space and direction in a way that lets them explore even in unfamiliar habitats. Fish were schooled on how to drive during about a dozen 30-minute sessions. The researchers trained each fish to drive from the center of a small room toward a pink board on one wall by giving the fish a treat whenever it reached the wall. During their first sessions, the fish averaged about 2.5 successful trips to the target. During their final sessions, fish averaged about 17.5 successful trips. By the end of driver’s ed, the animals also took faster, more direct routes to their goal. © Society for Science & the Public 2000–2022.

Keyword: Learning & Memory
Link ID: 28148 - Posted: 01.12.2022

Leonard Mlodinow Charles Darwin created the most successful theory in the history of biology: the theory of evolution. He was also responsible for another grand theory: the theory of emotion, which dominated his field for more than a century. That theory was dead wrong. The most important tenet of his theory was that the mind consists of two competing forces, the rational and the emotional. He believed emotions played a constructive role in the lives of non-human animals, but in humans emotions were a vestige whose usefulness had been largely superseded by the evolution of reason. We now know that, on the contrary, emotions enhance our process of reasoning and aid our decision-making. In fact, we can’t make decisions, or even think, without being influenced by our emotions. Consider a pioneering 2010 study in which researchers analysed the work of 118 professional traders in stocks, bonds and derivatives at four investment banks. Some were highly successful, but many were not. The researchers’ goal was to understand what differentiated the two groups. Their conclusion? They had different attitudes toward the role of emotion in their job. The relatively less successful traders for the most part denied that emotion played a significant role. They tried to suppress their emotions, while at the same time denying that emotions had an effect on their decision-making. The most successful traders, in contrast, had a different attitude. They showed a great willingness to reflect on their emotion-driven behaviour. They recognised that emotion and good decision-making were inextricably linked. Accepting that emotions were necessary for high performance, they “tended to reflect critically about the origin of their intuitions and the role of emotion”. © 2021 Guardian News & Media Limited

Keyword: Emotions; Learning & Memory
Link ID: 28136 - Posted: 01.05.2022

By Abdulrahman Olagunju How does our brain know that “this” follows “that”? Two people meet, fall in love and live happily ever after—or sometimes not. The sequencing of events that takes place in our head—with one thing coming after another—may have something to do with so-called time cells recently discovered in the human hippocampus. The research provides evidence for how our brain knows the start and end of memories despite time gaps in the middle. As these studies continue, the work could lead to strategies for memory restoration or enhancement. The research has focused on “episodic memory,” the ability to remember the “what, where and when” of a past experience, such as the recollection of what you did when you woke up today. It is part of an ongoing effort to identify how the organ creates such memories. A team led by Leila Reddy, a neuroscience researcher at the French National Center for Scientific Research, sought to understand how human neurons in the hippocampus represent temporal information during a sequence of learning steps to demystify the functioning of time cells in the brain. In a study published this summer in the Journal of Neuroscience, Reddy and her colleagues found that, to organize distinct moments of experience, human time cells fire at successive moments during each task. The study provided further confirmation that time cells reside in the hippocampus, a key memory processing center. They switch on as events unfold, providing a record of the flow of time in an experience. “These neurons could play an important role in how memories are represented in the brain,” Reddy says. “Understanding the mechanisms for encoding time and memory will be an important area of research.” © 2021 Scientific American

Keyword: Learning & Memory; Attention
Link ID: 28133 - Posted: 12.31.2021

Sofia Moutinho When Thomas Edison hit a wall with his inventions, he would nap in an armchair while holding a steel ball. As he started to fall asleep and his muscles relaxed, the ball would strike the floor, waking him with insights into his problems. Or so the story goes. Now, more than 100 years later, scientists have repeated the trick in a lab, revealing that the famous inventor was on to something. People following his recipe tripled their chances of solving a math problem. The trick was to wake up in the transition between sleep and wakefulness, just before deep sleep. “It is a wonderful study,” says Ken Paller, a cognitive neuroscientist at Northwestern University who was not part of the research. Prior work has shown that passing through deep sleep stages helps with creativity, he notes, but this is the first to explore in detail the sleep-onset period and its role in problem-solving. In this transitional period, we are not quite awake, but also not deeply asleep. It can be as short as a minute and occurs right when we start to doze off. Our muscles relax, and we have dreamlike visions or thoughts called hypnagogia, generally related to recent experiences. This phase slips by unnoticed most of the time unless it is interrupted by waking. Like Edison, surrealist painter Salvador Dalí believed interrupting sleep’s onset could boost creativity. (He used a heavy key instead of a metal ball.) To see whether Dalí and Edison were right, researchers recruited more than 100 easy sleepers. The team gave them a math test that required them to convert strings of eight digits into new strings of seven by using specific rules in a stepwise manner, such as “repeat the number if the previous and next digit are identical.” The volunteers weren’t told that there was an easier way to get the right answers by following a hidden rule: The second number in their final string was always the same as the last number in the same string. © 2021 American Association for the Advancement of Science.

Keyword: Sleep; Attention
Link ID: 28106 - Posted: 12.11.2021

By Elizabeth Preston A person trying to learn the way around a new neighborhood might spend time studying a map. You would probably not benefit from being carried rapidly through the air, upside-down in the dark. Yet that’s how some baby bats learn to navigate, according to a study published last month in Current Biology. As their mothers tote them on nightly trips between caves and certain trees, the bat pups gain the skills they need to get around when they grow up. Mothers of many bat species carry their young while flying, said Aya Goldshtein, a behavioral ecologist at the Max Planck Institute of Animal Behavior in Konstanz, Germany. Egyptian fruit bats, for example, are attached to their mothers continuously for the first three weeks of life. While a mother searches for food, her pup clings to her body with two feet and its jaw, latching its teeth around her nipple. Mothers can still be seen flying with older pups that weigh 40 percent of what they do. It hadn’t been clear why the moms go to this length, instead of leaving pups in the cave where they roost, as some other species do. Dr. Goldshtein worked with Lee Harten, a behavioral ecologist at Tel Aviv University in Israel, where both she and Dr. Goldshtein were graduate students at the time in the lab of Yossi Yovel, a study co-author, to make sense of this maternal mystery. The researchers captured Egyptian fruit bat mothers and pups from a cave just outside Tel Aviv. They attached a tag holding a radio transmitter and miniature GPS device to each bat’s fur that would drop off after a couple of weeks. Then, the researchers brought the bats back to their cave. To track the bats, Dr. Harten held an antenna while standing on the roof of a 10-story building with a view of the cave. She directed Dr. Goldshtein, who was on foot or in a car with her own antenna, to follow the radio signals of bat pairs as they flew out at night. But again and again, there was a problem: The pup’s movement would suddenly stop, while the mother’s signal disappeared. “At the beginning we thought that we were doing our job wrong, and just losing the bats,” Dr. Harten said. © 2021 The New York Times Company

Keyword: Learning & Memory; Animal Migration
Link ID: 28102 - Posted: 12.08.2021

Alison Abbott There Is Life After the Nobel Prize Eric Kandel Columbia Univ. Press (2021) In 1996, Denise Kandel warned her husband that were he to win the Nobel prize for his pioneering work on memory, then it should be later rather than sooner. Laureates too often turn into socialites, she warned, and stop contributing to the intellectual life of science. Just four years later, Eric Kandel shared the 2000 Nobel Prize in Physiology or Medicine. He was then 71, an age when he could legitimately have rested on his laurels. But resting is not among Kandel’s many strengths. His new book, There Is Life After the Nobel Prize, outlines his achievements of the past couple of decades — numerous enough to dispel Denise’s fears, he writes. It is hard to disagree. The volume adds to Kandel’s respected literary oeuvre, which ranges from neuroscience textbooks to highly original popular science. But it is slight, and feels like a coda. In it, he summarises his post-Nobel research (on learning and memory deficits in addiction, schizophrenia and ageing), writing and public outreach. And he acknowledges colleagues and sponsors of his long career, particularly the Howard Hughes Medical Institute in Chevy Chase, Maryland, and Columbia University in New York City, where he remains a professor and institute director. A fuller and more poignant autobiography can be found in Kandel’s 2006 book In Search of Memory. There, he explains why his traumatic childhood in Austria drew him to study the mechanisms of memory. That book also presents a marvellous history of neuroscience. Making sense Kandel was born in 1929 in Vienna. His family was Jewish and owned a toy shop. When Hitler annexed Austria in 1938, his parents began their year-long effort to emigrate. They finally arrived in New York shortly before the outbreak of World War II, physically unharmed but psychologically traumatized. © 2021 Springer Nature Limited

Keyword: Learning & Memory
Link ID: 28100 - Posted: 12.08.2021

By Pam Belluck AURORA, Ill. — There is sobering evidence of Samantha Lewis’s struggle with long Covid on her bathroom mirror. Above the sink, she has posted a neon pink index card scrawled with nine steps (4. Wet brush 5. Toothpaste) reminding her how to brush and floss her teeth. It is one of many strategies Ms. Lewis, 34, has learned from “cognitive rehab,” an intensive therapy program for Covid-19 survivors whose lives have been upended by problems like brain fog, memory lapses, dizziness and debilitating fatigue. Nearly two years into the pandemic, advances have been made in treating Covid itself, but long Covid — a constellation of lingering health problems that some patients experience — remains little understood. Post-Covid clinics around the country are trying different approaches to help patients desperate for answers, but there is little data on outcomes so far, and doctors say it is too soon to know what might work, and for which patients. While some physical symptoms of long Covid, like shortness of breath or nausea, can be addressed with medication, cognitive issues are more challenging. Few drugs exist, and while some deficits can rebound with time, they can also be exacerbated by resuming activities too soon or intensively. Over several months, The New York Times visited Ms. Lewis, interviewed her doctors, attended her therapy sessions and read her medical records. Before she was infected with the coronavirus in October 2020, experiencing a modest initial illness that did not require hospitalization, she was successfully juggling a demanding, detail-oriented job while raising a child with autism and attention deficit hyperactivity disorder. But this summer, she scored 25 on a 30-point assessment, placing her in a pre-dementia category called mild cognitive impairment. © 2021 The New York Times Company

Keyword: Learning & Memory
Link ID: 28098 - Posted: 12.04.2021

by Charles Q. Choi One injection of a potential new gene therapy for Angelman syndrome forestalls many of the neurodevelopmental condition’s key traits, according to early tests in mice. “While additional pharmacology and safety studies are needed, our viral vector can potentially provide transformative therapeutic relief with a single dose,” says lead investigator Benjamin Philpot, professor of neuroscience at the University of North Carolina at Chapel Hill. Angelman syndrome, which affects about one in 20,000 children, is associated with significant developmental delays and, often, autism. It arises from mutations or deletions in the maternal copy of the UBE3A gene, which encodes a protein that helps regulate the levels of other important proteins. There are no treatments specifically for Angelman syndrome, but several gene therapies are under development. One in clinical trials requires repeat injections in the spine and has shown serious side effects at high doses. These therapies all aim to restore UBE3A function in neurons. One challenge, though, is that neurons produce several variants, or ‘isoforms,’ of the UBE3A protein that vary slightly in length; in mice, for example, neurons make two isoforms in a ratio of about four short forms for every long one. In contrast to other gene therapies, the new one generates short and long forms of the UBE3A protein at nearly the same ratio as is seen in mouse neurons. Such proportions “may be important for therapeutic efficacy,” says Eric Levine, professor of neuroscience at the University of Connecticut in Farmington, who was not involved in this study. © 2021 Simons Foundation

Keyword: Autism; Genes & Behavior
Link ID: 28093 - Posted: 12.01.2021

Anil Ananthaswamy How our brain, a three-pound mass of tissue encased within a bony skull, creates perceptions from sensations is a long-standing mystery. Abundant evidence and decades of sustained research suggest that the brain cannot simply be assembling sensory information, as though it were putting together a jigsaw puzzle, to perceive its surroundings. This is borne out by the fact that the brain can construct a scene based on the light entering our eyes, even when the incoming information is noisy and ambiguous. Consequently, many neuroscientists are pivoting to a view of the brain as a “prediction machine.” Through predictive processing, the brain uses its prior knowledge of the world to make inferences or generate hypotheses about the causes of incoming sensory information. Those hypotheses — and not the sensory inputs themselves — give rise to perceptions in our mind’s eye. The more ambiguous the input, the greater the reliance on prior knowledge. “The beauty of the predictive processing framework [is] that it has a really large — sometimes critics might say too large — capacity to explain a lot of different phenomena in many different systems,” said Floris de Lange, a neuroscientist at the Predictive Brain Lab of Radboud University in the Netherlands. However, the growing neuroscientific evidence for this idea has been mainly circumstantial and is open to alternative explanations. “If you look into cognitive neuroscience and neuro-imaging in humans, [there’s] a lot of evidence — but super-implicit, indirect evidence,” said Tim Kietzmann of Radboud University, whose research lies in the interdisciplinary area of machine learning and neuroscience. All Rights Reserved © 2021

Keyword: Attention; Vision
Link ID: 28080 - Posted: 11.17.2021

Allison Whitten Every time a human or machine learns how to get better at a task, a trail of evidence is left behind. A sequence of physical changes — to cells in a brain or to numerical values in an algorithm — underlie the improved performance. But how the system figures out exactly what changes to make is no small feat. It’s called the credit assignment problem, in which a brain or artificial intelligence system must pinpoint which pieces in its pipeline are responsible for errors and then make the necessary changes. Put more simply: It’s a blame game to find who’s at fault. AI engineers solved the credit assignment problem for machines with a powerful algorithm called backpropagation, popularized in 1986 with the work of Geoffrey Hinton, David Rumelhart and Ronald Williams. It’s now the workhorse that powers learning in the most successful AI systems, known as deep neural networks, which have hidden layers of artificial “neurons” between their input and output layers. And now, in a paper published in Nature Neuroscience in May, scientists may finally have found an equivalent for living brains that could work in real time. A team of researchers led by Richard Naud of the University of Ottawa and Blake Richards of McGill University and the Mila AI Institute in Quebec revealed a new model of the brain’s learning algorithm that can mimic the backpropagation process. It appears so realistic that experimental neuroscientists have taken notice and are now interested in studying real neurons to find out whether the brain is actually doing it. Simons Foundation All Rights Reserved © 2021

Keyword: Learning & Memory
Link ID: 28044 - Posted: 10.20.2021

Jordana Cepelewicz Leaping, scurrying, flying and swimming through their natural habitats, animals compile a mental map of the world around them — one that they use to navigate home, find food and locate other points of vital interest. Neuroscientists have chiseled away at the problem of how animals do this for decades. A crucial piece of the solution is an elegant neural code that researchers uncovered by monitoring the brains of rats in laboratory settings. That landmark discovery was awarded a Nobel Prize in 2014, and many scientists think the code could be a key component of how the brain handles other abstract forms of information. Yet lab animals in a box with a flat floor only need to navigate through two dimensions, and researchers are now finding that extending the lessons of that situation to the real world is full of challenges and pitfalls. In a pair of studies recently published in Nature and Nature Neuroscience, scientists working with bats and rats showed — to their surprise — that the brain encodes 3D spaces very differently from 2D ones, employing a mechanism that they are still struggling to describe and understand. “We expected something else entirely,” said Nachum Ulanovsky, a neurobiologist at the Weizmann Institute of Science in Israel who led the work in Nature and has studied neural representations of 3D spaces for more than 10 years. “We had to reboot our thinking.” The findings suggest that neuroscientists might need to reconsider what they thought they knew about how the brain encodes natural environments and how animals navigate those spaces. The work also hints at the possibility that other cognitive processes, including memory, might operate very differently than researchers have come to believe. Simons Foundation All Rights Reserved © 2021

Keyword: Learning & Memory
Link ID: 28041 - Posted: 10.16.2021

ByRachel Fritts Across North America, hundreds of bird species waste time and energy raising chicks that aren’t their own. They’re the victims of a “brood parasite” called the cowbird, which adds its own egg to their clutch, tricking another species into raising its offspring. One target, the yellow warbler, has a special call to warn egg-warming females when cowbirds are casing the area. Now, researchers have found the females act on that warning 1 day later—suggesting their long-term memories might be much better than thought. “It’s a very sophisticated and subtle behavioral response,” says Erick Greene, a behavioral ecologist at the University of Montana, Missoula, who was not involved in the study. “Am I surprised? I guess I’m more in awe. It’s pretty dang cool.” Birds have been dazzling scientists with their intellects for decades. Western scrub jays, for instance, can remember where they’ve stored food for the winter—and can even keep track of when it will spoil. There’s evidence that other birds might have a similarly impressive ability to remember certain meaningful calls. “Animals are smart in the context in which they need to be smart,” says Mark Hauber, an animal behavior researcher at the University of Illinois, Urbana-Champaign (UIUC), and the Institute of Advanced Studies in Berlin, who co-authored the new study. He wanted to see whether yellow warblers had the capacity to remember their own important warning call known as a seet. Shelby Lawson The birds make the staccato sound of this call only when a cowbird is near. When yellow warbler females hear it, they go back to their nests and sit tight. (It could just as well be called a “seat” call.) But it’s been unclear whether they still remember the warning in the morning. © 2021 American Association for the Advancement of Science.

Keyword: Animal Communication; Learning & Memory
Link ID: 28039 - Posted: 10.16.2021

by Charles Q. Choi Chronic electrical stimulation of the fornix, a bundle of nerve fibers deep in the brain, rescues learning and memory deficits in mice with mutations of the autism-linked gene CDKL5, according to new research. The results support previous work in mice suggesting that electrical jolts to this fiber tract, which links brain regions involved in memory, could help address cognitive problems in multiple models of neurodevelopmental conditions. These animal studies all use deep brain stimulation (DBS), in which electrodes are placed chronically or, in some cases, permanently in specific neuroanatomical regions. In people, severe cognitive impairment, including memory and learning deficits, is a central feature of cyclin-dependent kinase-like 5 (CDKL5) deficiency disorder, which results from mutations that impair production of the CDKL5 protein. Other characteristics include autism traits and epileptic seizures. “Our hope is to help CDKL5 deficiency patients with at least some aspects of their problems — for example, intellectual disability,” says lead investigator Jianrong Tang, associate professor of pediatrics at the Baylor College of Medicine in Houston, Texas. Little is known about how the loss of CDKL5 affects brain circuitry. In the new study, Tang and his colleagues analyzed the brain’s memory center, the hippocampus, in mice with CDKL5 mutations. The connections between neurons there were less flexible, they found, which likely contributed to the animals’ deficits in learning and memory. The mutations also strengthened inhibitory signals in the dentate gyrus, a part of the hippocampus that helps form new memories. © 2021 Simons Foundation

Keyword: Learning & Memory
Link ID: 28038 - Posted: 10.16.2021

Jon Hamilton People who have had a stroke appear to regain more hand and arm function if intensive rehabilitation starts two to three months after the injury to their brain. A study of 72 stroke patients suggests this is a "critical period," when the brain has the greatest capacity to rewire, a team reports in this week's journal PNAS. The finding challenges the current practice of beginning rehabilitation as soon as possible after a stroke and suggests intensive rehabilitation should go on longer than most insurance coverage allows, says Elissa Newport, a co-author of the study and director of the Center for Brain Plasticity and Recovery at Georgetown University Medical Center. Newport was speaking in place of the study's lead author, Dr. Alexander Dromerick, who died after the study was accepted but before it was published. If the results are confirmed with other larger studies, "the clinical protocol for the timing of stroke rehabilitation would be changed," says Li-Ru Zhao, a professor of neurosurgery at Upstate Medical University in Syracuse, N.Y., who was not involved in the research. The study involved patients treated at Medstar National Rehabilitation Hospital in Washington, D.C., most in their 50s and 60s. One of the study participants was Anthony McEachern, who was 45 when he had a stroke in 2017. Just a few hours earlier, McEachern had been imitating Michael Jackson dance moves with his kids. But at home that night he found himself unable stand up. © 2021 npr

Keyword: Stroke; Learning & Memory
Link ID: 28002 - Posted: 09.22.2021

David Kleinfeld My colleagues and I recently found that we were able to train mice to voluntarily increase the size and frequency of seemingly random dopamine impulses in their brains. Conventional wisdom in neuroscience has held that dopamine levels change solely in response to cues from the world outside of the brain. Our new research shows that increases in dopamine can also be driven by internally mediated changes within the brain. Dopamine is a small molecule found in the brains of mammals and is associated with feelings of reward and happiness. In 2014, my colleagues and I invented a new method to measure dopamine in real time in different parts of the brains of mice. Using this new tool, my former thesis student, Conrad Foo, found that neurons in the brains of mice release large bursts of dopamine – called impulses – for no easily apparent reason. This occurs at random times, but on average about once a minute. Pavlov was famously able to train his dogs to salivate at the sound of a bell, not the sight of food. Today, scientists believe that the bell sound caused a release of dopamine to predict the forthcoming reward. If Pavlov’s dogs could control their cue-based dopamine responses with a little training, we wondered if our mice could control their spontaneous dopamine impulses. To test this, our team designed an experiment that rewarded mice if they increased the strength of their spontaneous dopamine impulses. The mice were able to not only increase how strong these dopamine releases were, but also how often they occurred. When we removed the possibility of a reward, the dopamine impulses returned to their original levels. In the 1990s, neuroscientist Wolfram Schultz discovered that an animal’s brain will release dopamine if the animal expects a reward, not just when receiving a reward. This showed that dopamine can be produced in response to the expectation of a reward, not just the reward itself – the aforementioned modern version of Pavlov’s dog. © 2010–2021, The Conversation US, Inc.

Keyword: Drug Abuse; Learning & Memory
Link ID: 27993 - Posted: 09.15.2021

Sophie Fessl The hormone irisin is necessary for the cognitive benefits of exercise in healthy mice and can rescue cognitive decline associated with Alzheimer’s disease, according to a study published August 20 in Nature Metabolism. According to the authors, these results support the hypothesis that irisin undergirds the cognitive benefits of exercise—a link that has been long debated. In addition, this study has “paved the way for thinking whether irisin could be a therapeutic agent against Alzheimer’s disease,” says biologist Steffen Maak with the Leibniz Institute for Farm Animal Biology in Germany, who has been critical of the methods used to study irisin in the past and was not involved in the study. Many studies have found that exercise is good for the brain, but the molecular mechanisms responsible for the cognitive boost have remained elusive. During her postdoctoral studies, neuroscientist Christiane Wrann found that the gene that codes for irisin becomes highly expressed in the brain during exercise—one of the first studies linking irisin with the brain. See “Irisin Skepticism Goes Way Back” When she joined the faculties at Massachusetts General Hospital and Harvard Medical School, she decided to investigate the hormone further. Wrann, who holds a patent related to irisin and is academic cofounder and consultant for Aevum Therapeutics, a company developing drugs that harness the protective molecular mechanisms of exercise to treat neurodegenerative and neuromuscular disorders, began to investigate whether irisin mediates the positive effects of exercise on the brain. © 1986–2021 The Scientist.

Keyword: Learning & Memory; Hormones & Behavior
Link ID: 27985 - Posted: 09.13.2021