Posts tagged learning
Articles and news from the latest research reports.
Fear study reveals mental processes
July 25, 2012
A University study has shown how our minds unconsciously respond to threats.
Researchers studying how our minds develop fears in response to danger found that people can quickly learn to recognise a threat even when they are unaware of it.
However, they also found that this learning is swiftly forgotten. In contrast, when people are aware of the threat, they take longer to learn to be afraid of it, but retain the fear in the long term.
Scientists from the University of Edinburgh and New York University, who carried out the study, say the finding may be a key insight into the differences between conscious and nonconscious mental processes.
Fear study
Researchers measured physiological fear responses - the amount of sweat on the fingertips - in groups of people who looked at pictures and were given mild electric shocks whenever one of these pictures was shown.
All the people who participated in the study saw the pictures with just one eye. But whereas some of them were allowed to see the pictures clearly, the researchers suppressed the pictures from other subjects’ awareness by showing colourful, dynamic images to the other eye.
The study found that subjects who were prevented from consciously seeing the pictures learned to be afraid of the image associated with a shock more quickly than those who were allowed to see them without suppression.
However, these subjects quickly forgot this association between the images and the electric shocks as the experiment continued.
In contrast, those subjects who were allowed to see the image clearly formed a stronger association over time.
How the brain reacts to threats is key to understanding how human beings function. This study shows that we are capable of learning very rapidly that something is a threat even when we don’t perceive it consciously. Such learning, however, is fleeting.
-David Carmel, Researcher, Department of Psychology
Source: The University of Edinburgh
Piglets substitute for human babies in cognitive science maze test
A team from the Beckman Institute at the University of Illinois is using piglets instead of human babies to try and model the cognitive development of infants.
Human infants cannot be used as laboratory subjects. The idea to use piglets came when one of neuroscientist Rodney Johnson’s former students, who was working for an infant formula company, asked him about finding ways to monitor the differences in cognitive development between breast-fed and formula-fed children.
As a result he and his colleague Ryan Dilger became interested in using the neonatal piglet as a model for human brain development. The growth and development of the piglet brain is similar to that of the human brain — at birth the human brain is 25 percent of adult size. In the first two years of life, it reaches 85 to 90 percent of adult size. The piglet brain grows in a similar way in a shorter time.
They wanted to see whether they could develop tests to look at learning and memory development using these pigs. First of all they developed MRI techniques to quantify the size of the brain, taking measurements at regular intervals.
They then developed a test using a maze to assess piglets’ learning and memory. This turned out to be much more complicated than expected. Johnson said: “When we first started these studies, we used things like Skittles and apple slices as a reward because that’s what people using older pigs had done.”
However, the piglets were used to being fed on infant formula and so had no interest in solid food, nor were they motivated to perform tasks if the reward was the same as their regular food. The solution was to use Nesquik chocolate milk as a reward.
Tests took place in a plus-sign-shaped maze with one arm blocked off to leave a T shape. Piglets were trained to locate the milk reward using visual cues from outside the maze. When they learned how to do this and the reward location was moved, and the pigs were retested to assess learning and working memory.
Having established that the tests can be used to measure cognitive abilities, the team will examine how nutrient deficiencies (such as iron) and infections (such as pneumonia) affect the human brain during this time of early brain growth.
Johnson said: “There is a lot of interest in the concept of programming, the notion that things that occur early in life set that individual up for problems that occur many years later. Because the pig brain grows so much like a human brain, we thought this could be a very attractive model.”
In order to measure changes in the brain they look at neuroinflammation, neuron growth and changes, as well as biochemical in the brain.
The team hopes to receive funding to look at maternal viral infections, where pregnant pigs will be infected with diseases to see how it affects the brain development of their offspring.
Triangles guide the way for live neural circuits in a dish
July 19, 2012
Korean scientists have used tiny stars, squares and triangles as a toolkit to create live neural circuits in a dish.
They hope the shapes can be used to create a reproducible neural circuit model that could be used for learning and memory studies as well as drug screening applications; the shapes could also be integrated into the latest neural tissue scaffolds to aid the regeneration of neurons at injured sites in the body, such as the spinal cord.
Published today in the Journal of Neural Engineering, the study, by researchers at the Korea Advanced Institute of Science and Technology (KAIST), found that triangles were the most effective shape for helping to facilitate the growth of axons and guide them onto specific paths to form a complete circuit.
Co-author of the study, Professor Yoonkey Nam, said: “Eventually, we want to know if we can design a neural tissue model that biologically mimics some neural circuits in our brain.”
A neuron is an electrically excitable cell that processes and transmits information around the body. The neuron is composed of three main parts: a cell body, or soma, dendrites and an axon, which extends from the soma and links to other cells, creating a network.
When axons grow they are usually guided by proteins. Many researchers have been trying to re-create this key process in a dish by manipulating nerve cells from rat brains.
As nerve cells are usually just a few tens of micrometres in size, the challenge associated with creating a live neural network is firstly positioning cells in desired locations and, secondly, making connections between these cells by guiding the axons in designated directions.
The researchers investigated whether two star shapes, five regular shapes (square, circle, triangle, pentagon and hexagon) and three different sizes of isosceles triangles could guide axons in designated directions. Each shape was the size of a single cell and was replicated to form an array which was printed onto a glass surface.
Each of the arrays had an overall size of 1cm-by-1cm with a gap of 10 micrometres between each shape. Hippocampal neurons were taken from rats and plated onto the patterned surfaces. The neurons were fluorescently labelled with dyes so that images could be taken of their growth.
The researchers found that triangles were the most efficient shape to encourage the growth and guidance of an axon. The key to this was the angles at the points where two of the triangle’s lines meet, also known as the vertices. It was shown that the smaller the vertices, the higher chance the triangle had of inducing growth.
"Based on our results, we are suggesting a new design principle for guiding axons in a dish. We can control the axonal growth in a certain direction by putting a sharp triangle pointing to a certain direction. Then, a neuron that adhered to the triangle will have an axon in the sharp vertex direction.
"Overall, we integrated microtechnology with neurobiology to find a new engineering solution" continued Professor Nam.
Provided by Institute of Physics
Source: medicalxpress.com
Synapses are modified through learning. Up until now, scientists believed that a particular form of synaptic plasticity in the brain’s hippocampus was responsible for learning spatial relations. This was based on a receptor type for the neurotransmitter glutamate: the NMDA receptor. Researchers at the Max Planck Institute for Medical Research in Heidelberg and Oxford University have now observed that mice develop a spatial memory, even when the NMDA receptor-transmitted plasticity is switched off in parts of their hippocampus. However, if these mice have to resolve a conflict while getting their bearings, they are not successful in resolving it; the hippocampal NMDA receptors are clearly needed to detect or resolve the conflict. This has led the researchers involved in this experiment to refute a central tenet of neuroscience regarding the function of hippocampal NMDA receptor-transmitted plasticity in spatial learning.
Memories Serve as Tools for Learning and Decision-Making
ScienceDaily (July 11, 2012) — When humans learn, their brains relate new information with past experiences to derive new knowledge, according to psychology research from The University of Texas at Austin.
The study, led by Alison Preston, assistant professor of psychology and neurobiology, shows this memory-binding process allows people to better understand new concepts and make future decisions. The findings could lead to better teaching methods, as well as treatment of degenerative neurological disorders, such as dementia, Preston says.
"Memories are not just for reflecting on the past; they help us make the best decisions for the future," says Preston, a research affiliate in the Center for Learning and Memory, which is part of the university’s College of Natural Sciences. "Here, we provide a direct link between these derived memories and the ability to make novel inferences."
The paper was published online in July in the journal Neuron. The authors include University of Texas at Austin researchers Dagmar Zeithamova and April Dominick.
In the study, 34 subjects were shown a series of paired images composed of different elements (for example, an object and an outdoor scene). Each of the paired images would then reappear in more presentations. A backpack, paired with a horse in the first presentation, would appear alongside a field in a later presentation. The overlap between the backpack and outdoor scenery (horse and field) would cause the viewer to associate the backpack with the horse and field. The researchers used this strategy to see how respondents would delve back to a recent memory while processing new information.
Using functional Magnetic Resonance Imaging (fMRI) equipment, the researchers were able to look at the subjects’ brain activity as they looked at image presentations. Using this technique, Preston and her team were able to see how the respondents thought about past images while looking at overlapping images. For example, they studied how the respondents thought about a past image (a horse) when looking at the backpack and the field. The researchers found the subjects who reactivated related memories while looking at overlapping image pairs were able to make associations between individual items (i.e. the horse and the field) despite the fact that they had never studied those images together.
To illustrate the ways in which this cognitive process works, Preston describes an everyday scenario.
Imagine you see a new neighbor walking a Great Dane down the street. At a different time and place, you may see a woman walking the same dog in the park. When experiencing the woman walking her dog, the brain conjures images of the recent memory of the neighbor and his Great Dane, causing an association between the dog walkers to be formed in memory. The derived relationship between the dog walkers would then allow you to infer the woman is also a new neighbor even though you have never seen her in your neighborhood.
"This is just a simple example of how our brains store information that goes beyond the exact events we experience," Preston says. "By combining past events with new information, we’re able to derive new knowledge and better anticipate what to expect in the future."
During the learning tasks, the researchers were able to pinpoint the brain regions that work in concert during the memory-binding process. They found the hippocampal-ventromedial prefrontal cortex (VMPFC) circuit is essential for binding reactivated memories with current experience.
Source: Science Daily
Learn That Tune While Fast Asleep: Stimulation During Sleep Can Enhance Skill Learning
ScienceDaily (June 24, 2012) — Want to nail that tune that you’ve practiced and practiced? Maybe you should take a nap with the same melody playing during your sleep, new provocative Northwestern University research suggests.
Want to nail that tune that you’ve practiced and practiced? Maybe you should take a nap with the same melody playing during your sleep. (Credit: © Anton Maltsev / Fotolia)
The research grows out of exciting existing evidence that suggests that memories can be reactivated during sleep and storage of them can be strengthened in the process.
In the Northwestern study, research participants learned how to play two artificially generated musical tunes with well-timed key presses. Then while the participants took a 90-minute nap, the researchers presented one of the tunes that had been practiced, but not the other.
"Our results extend prior research by showing that external stimulation during sleep can influence a complex skill," said Ken A. Paller, professor of psychology in the Weinberg College of Arts and Sciences at Northwestern and senior author of the study.
By using EEG methods to record the brain’s electrical activity, the researchers ensured that the soft musical “cues” were presented during slow-wave sleep, a stage of sleep previously linked to cementing memories. Participants made fewer errors when pressing the keys to produce the melody that had been presented while they slept, compared to the melody not presented.
"We also found that electrophysiological signals during sleep correlated with the extent to which memory improved," said lead author James Antony of the Interdepartmental Neuroscience Program at Northwestern. "These signals may thus be measuring the brain events that produce memory improvement during sleep."
The age-old myth that you can learn a foreign language while you sleep is sure to come to mind, said Paul J. Reber, associate professor of psychology at Northwestern and a co-author of the study.
"The critical difference is that our research shows that memory is strengthened for something you’ve already learned," Reber said. "Rather than learning something new in your sleep, we’re talking about enhancing an existing memory by re-activating information recently acquired."
The researchers, he said, are now thinking about how their findings could apply to many other types of learning.
"If you were learning how to speak in a foreign language during the day, for example, and then tried to reactivate those memories during sleep, perhaps you might enhance your learning."
Paller said he hopes the study will help them learn more about the basic brain mechanisms that transpire during sleep to help preserve memory storage.
"These same mechanisms may not only allow an abundance of memories to be maintained throughout a lifetime, but they may also allow memory storage to be enriched through the generation of novel connections among memories," he said.
The study opens the door for future studies of sleep-based memory processing for many different types of motor skills, habits and behavioral dispositions, Paller said.
Source: Science Daily
Confusion Can Be Beneficial for Learning
ScienceDaily (June 20, 2012) — Most of us assume that confidence and certainty are preferred over uncertainty and bewilderment when it comes to learning complex information. But a new study led by Sidney D’Mello of the University of Notre Dame shows that confusion when learning can be beneficial if it is properly induced, effectively regulated and ultimately resolved.
Most of us assume that confidence and certainty are preferred over uncertainty and bewilderment when it comes to learning complex information. But a new study shows that confusion when learning can be beneficial if it is properly induced, effectively regulated and ultimately resolved. (Credit: © Ana Blazic Pavlovic / Fotolia)
The study will be published in a forthcoming issue of the journal Learning and Instruction.
Notre Dame psychologist and computer scientist D’Mello, whose research areas include artificial intelligence, human-computer interaction and the learning sciences, together with Art Graesser of the University of Memphis, collaborated on the study, which was funded by the National Science Foundation.
They found that by strategically inducing confusion in a learning session on difficult conceptual topics, people actually learned more effectively and were able to apply their knowledge to new problems.
In a series of experiments, subjects learned scientific reasoning concepts through interactions with computer-animated agents playing the roles of a tutor and a peer learner. The animated agents and the subject engaged in interactive conversations where they collaboratively discussed the merits of sample research studies that were flawed in one critical aspect. For example, one hypothetical case study touted the merits of a diet pill, but was flawed because it did not include an appropriate control group. Confusion was induced by manipulating the information the subjects received so that the animated agents sometimes disagreed with each other and expressed contradictory or incorrect information. The agents then asked subjects to decide which opinion had more scientific merit, thereby putting the subject in the hot spot of having to make a decision with incomplete and sometimes contradictory information.
In addition to the confusion and uncertainty triggered by the contradictions, subjects who were confused scored higher on a difficult post-test and could more successfully identify flaws in new case studies.
"We have been investigating links between emotions and learning for almost a decade, and find that confusion can be beneficial to learning if appropriately regulated because it can cause learners to process the material more deeply in order to resolve their confusion," D’Mello says.
According to D’Mello, it is not advisable to intentionally confuse students who are struggling or induce confusion during high-stakes learning activities. Confusion interventions are best for higher-level learners who want to be challenged with difficult tasks, are willing to risk failure, and who manage negative emotions when they occur.
"It is also important that the students are productively instead of hopelessly confused. By productive confusion, we mean that the source of the confusion is closely linked to the content of the learning session, the student attempts to resolve their confusion, and the learning environment provides help when the student struggles. Furthermore, any misleading information in the form of confusion-induction techniques should be corrected over the course of the learning session, as was done in the present experiments."
According to D’Mello, the next step in this body of research is to apply these methods to some of the more traditional domains such as physics, where misconceptions are common.
Source: Science Daily
A mechanism to improve learning and memory
February 21, 2012
There are a number of drugs and experimental conditions that can block cognitive function and impair learning and memory. However, scientists have recently shown that some drugs can actually improve cognitive function, which may have implications for our understanding of cognitive disorders such as Alzheimer’s disease. The new research is reported 21 February in the open-access journal PLoS Biology.
The study, led by Drs. Jose A. Esteban, Shira Knafo and Cesar Venero, is the result of collaboration between researchers from The Centro de Biología Molecular Severo Ochoa and UNED (Spain), the Brain Mind Institute (EPFL, Switzerland) and the Department of Neuroscience and Pharmacology (Faculty of Health Sciences, Denmark).
The human brain contains trillions of neuronal connections, called synapses, whose pattern of activity controls all our cognitive functions. These synaptic connections are dynamic and constantly changing in their strength and properties. This process, known as synaptic plasticity, has been proposed as the cellular basis for learning and memory. Indeed, alterations in synaptic plasticity mechanisms are thought to be responsible for multiple cognitive deficits, such as autism, Alzheimer’s disease and several forms of mental retardation.
The study by Knafo et al. provides new information on the molecular mechanisms of synaptic plasticity, and how this process may be manipulated to improve cognitive performance. They find that synapses can be made more plastic by using a small protein fragment (peptide) derived from a neuronal protein involved in cell-to-cell communication. This peptide (called FGL) initiates a cascade of events inside the neuron that results in the facilitation of synaptic plasticity. Specifically, the authors found that FGL triggers the insertion of new neurotransmitter receptors into synapses in a region of the brain called the hippocampus, which is known to be involved in multiple forms of learning and memory. Importantly, when this peptide was administered to rats, their ability to learn and retain spatial information was enhanced.
Dr. Esteban remarks: “We have known for three decades that synaptic connections are not fixed from birth, but they respond to neuronal activity modifying their strength. Thus, outside stimuli will lead to the potentiation of some synapses and the weakening of others. It is precisely this code of ups and downs what allows the brain to store information and form memories during learning”.
Within this framework, these new findings demonstrate that synaptic plasticity mechanisms mechanisms can be manipulated pharmacologically in adult animals, with the aim of enhancing cognitive ability. Dr. Knafo adds: “These are basic studies on the molecular and cellular processes that control our cognitive function. Nevertheless, they shed light into potential therapeutic avenues for mental disorders where these mechanisms go awry”.
Source: medicalxpress.com
New Brain Connections Form in Clusters During Learning
ScienceDaily (Feb. 19, 2012) — New connections between brain cells emerge in clusters in the brain as animals learn to perform a new task, according to a study published in Nature on February 19 (advance online publication). Led by researchers at the University of California, Santa Cruz, the study reveals details of how brain circuits are rewired during the formation of new motor memories.
Rendering of neural network. New connections between brain cells emerge in clusters in the brain as animals learn to perform a new task, according to a study. (Credit: © nobeastsofierce / Fotolia)
The researchers studied mice as they learned new behaviors, such as reaching through a slot to get a seed. They observed changes in the motor cortex, the brain layer that controls muscle movements, during the learning process. Specifically, they followed the growth of new “dendritic spines,” structures that form the connections (synapses) between nerve cells.
"For the first time we are able to observe the spatial distribution of new synapses related to the encoding of memory," said Yi Zuo, assistant professor of molecular, cell and developmental biology at UC Santa Cruz and corresponding author of the paper.
In a previous study, Zuo and others documented the rapid growth of new dendritic spines on pyramidal neurons in the motor cortex during the learning process. These spines form synapses where the pyramidal neurons receive input from other brain regions involved in motor memories and muscle movements. In the new study, first author Min Fu, a postdoctoral researcher in Zuo’s lab, analyzed the spatial distribution of the newly formed synapses.
Initial results of the spatial analysis showed that one third of the newly formed synapses were located next to another new synapse. These clustered synapses tended to form over the course of a few days during the learning period, when the mouse was repeatedly performing the new behavior. Compared to non-clustered counterparts, the clustered synapses were more likely to persist through the learning sessions and after training stopped.
In addition, the researchers found that after formation of the second spine in a cluster, the first spine grew larger. The size of the spine head correlates with the strength of the synapse. “We found that formation of a second connection is correlated with a strengthening of the first connection, which suggests that they are likely to be involved in the same circuitry,” Zuo said. “The clustering of synapses may serve to magnify the strength of the connections.”
Another part of the study also supported the idea that the clustered synapses are involved in neural circuits specific to the task being learned. The researchers studied mice trained first in one task and then in a different task. Instead of grabbing a seed, the mice had to learn how to handle a piece of capellini pasta. Both tasks induced the formation of clustered spines, but spines formed during the learning of different tasks did not cluster together.
The researchers also looked at mice that were challenged with new motor tasks every day, but did not repeat the same task over and over like the ones trained in seed-grabbing or capellini-handling. These mice also grew lots of new dendritic spines, but few of the new spines were clustered.
"Repetitive activation of the same cortical circuit is really important in learning a new task," Zuo said. "But what is the optimal frequency of repetition? Ultimately, by studying the relationship between synapse formation and learning, we want to find out the best way to induce new memories."
The study used mice that had been genetically altered to make a fluorescent protein within certain neurons in the motor cortex. The researchers used a special microscopy technique (two-photon microscopy) to obtain images of those neurons near the surface of the brain. The noninvasive imaging technique enabled them to view changes in individual brain cells of the mice before, during, and after learning a new behavior.
Source: Science Daily