Posts tagged learning
Articles and news from the latest research reports.
Babies Learn the Smell of Mum
Researchers show for the first time that a mammal begins to suckle its mother’s milk through a learned response built on learning her unique combination of smells. When it is born, the newborn is exposed to the smell of its mother’s amniotic fluid and the baby then responds to those smells to feed.
Prevailing thought has been that pheromones –chemicals that trigger an innate behavior – drove the suckling response as an automatic behavior. The new work determines that, in mice, the smells must be learned before the behavior can occur.
Suckling is a critical step for survival in mammals, which are defined by giving birth to offspring that need to feed from their mother’s milk. The newborn must begin to feed soon after birth or it will die. It is a crucial, defining behavior in mammals and offers researchers an opportunity to investigate the biology of instinct.
Specific regions of the hippocampus connected to discrete steps of task mastery, study finds
In a study published in Nature Neuroscience, neurobiologists from the Friedrich Miescher Institute for Biomedical Research have been linking synapse formation in the hippocampus to distinct learning steps. They show how different regions of the hippocampus have specific and sequential functions in the mastery of a complex task.
The setup is natural. The mouse finds herself in the water and is looking for a dry place. But how does she solve this task? And what happens if she finds herself in the same situation again? Here is what the scientists observed: At the beginning, the mouse swims all around the little pool, randomly searching for the platform. After two days, there is a change in search approach: The mouse has learned where about the platform is and will start to search right away in the area of the platform. Finally, after another five days, the mouse knows exactly where the platform is and swims directly for it. What is astonishing is that every mouse behaves same way and all the mice learn to find the platform in about the same time, through the same trial and error search strategy stages.
Pico Caroni, senior group leader at the Friedrich Miescher Institute for Biomedical Research, and his team not only described for the first time how mice learn to master such a complex task step by step, but they have also been able to show how one region of the brain, the hippocampus, is engaged in these learning processes. The hippocampus is the region of the brain that is the relay station for a lot of sensory information. In this function, the hippocampus is extremely important for learning and the consolidation of memory. The hippocampus can be divided into three areas termed ventral (vH), intermediate (iH) and dorsal hippocampus (dH). Even though the composition of the neuronal networks in each area is comparable, they differ in gene expression, connectivity, tuning and function.
Caroni and his team could now show that this difference has functional implications in learning. It has been known that during learning new synapses are formed in the hippocampus by so called mossy fibers. In their study published in Nature Neuroscience the scientists show that each search strategy, each level of learning, is associated with a different region of the hippocampus. First, mossy fiber synapses are formed in vH. With the first change in search strategy, mossy fiber formation moves to iH. The mice now have a clear understanding of the relative position of the platform, e.g. distance from the pool wall. Finally, synapse formation moves to dH. By now the mouse has a clear map of the pool, the platform and her position in these surroundings. From now on the mouse will always know where the platform is and will directly head for it.
"We believe that many complex learning tasks are achieved through sub-tasks and that the three areas of the hippocampus are involved in similar ways," comments Caroni. "Our experiments indicate further that this approach is innate, which indicates that similar processes may play as we learn to bike or become proficient in playing tennis."
(Source: medicalxpress.com)
New research methods reveal that babies and young children learn by rationally testing hypotheses, analyzing statistics and doing experiments much as scientists do
Very young children’s learning and thinking is strikingly similar to much learning and thinking in science, according to Alison Gopnik, professor of psychology and affiliate professor of philosophy at the University of California, Berkeley. Gopnik’s findings are described in the Sept 28 issue of the journal Science. She spoke about her work in a video briefing with NSF.
Learning requires rhythmical activity of neurons
The hippocampus represents an important brain structure for learning. Scientists at the Max Planck Institute of Psychiatry in Munich discovered how it filters electrical neuronal signals through an input and output control, thus regulating learning and memory processes. Accordingly, effective signal transmission needs so-called theta-frequency impulses of the cerebral cortex. With a frequency of three to eight hertz, these impulses generate waves of electrical activity that propagate through the hippocampus. Impulses of a different frequency evoke no transmission, or only a much weaker one. Moreover, signal transmission in other areas of the brain through long-term potentiation (LTP), which is essential for learning, occurs only when the activity waves take place for a certain while. The scientists even have an explanation for why we are mentally more productive after drinking a cup of coffee or in an acute stress situation: in their experiments, caffeine and the stress hormone corticosterone boosted the activity flow.
White matter, old dogs, and new tricks at Dartmouth
Most people equate “gray matter” with the brain and its higher functions, such as sensation and perception, but this is only one part of the anatomical puzzle inside our heads. Another cerebral component is the white matter, which makes up about half the brain by volume and serves as the communications network.
The gray matter, with its densely packed nerve cell bodies, does the thinking, the computing, the decision-making. But projecting from these cell bodies are the axons—the network cables. They constitute the white matter. Its color derives from myelin—a fat that wraps around the axons, acting like insulation.
Alex Schelgel, first author on a paper in the August 2012 Journal of Cognitive Neuroscience, has been using the white matter as a landscape on which to study brain function. An important result of the research is showing that you can indeed “teach old dogs new tricks.” The brain you have as an adult is not necessarily the brain you are always going to have. It can still change, even for the better.
"This work is contributing to a new understanding that the brain stays this plastic organ throughout your life, capable of change," Schlegel says. "Knowing what actually happens in the organization of the brain when you are learning has implications for the development of new models of learning as well as potential interventions in cases of stroke and brain damage."
Schlegel is a graduate student working under Peter Tse, an associate professor of psychological and brain sciences and a coauthor on the paper. “This study was Peter’s idea,” Schlegel says. “He wanted to know if we could see white matter change as a result of a long-term learning process. Chinese seemed to him like the most intensive learning experience he could think of.”
Twenty-seven Dartmouth students were enrolled in a nine-month Chinese language course between 2007 and 2009, enabling Schlegel to study their white matter in action. While many neuroscientists use magnetic resonance imaging (MRI) in brain studies, Schlegel turned to a new MRI technology, called diffusion tensor imaging (DTI). He used DTI to measure the diffusion of water in axons, tracking the communication pathways in the brain. Restrictions in this diffusion can indicate that more myelin has wrapped around an axon.
"An increase in myelination tells us that axons are being used more, transmitting messages between processing areas," Schlegel says. "It means there is an active process under way."
Their data suggest that white matter myelination is precisely what was seen among the language students. There is a structural change that goes along with this learning process. While some studies have shown that changes in white matter occurred with learning, these observations were made in simple skill learning and strictly on a “before and after” basis.
"This was the first study looking at a really complex, long-term learning process over time, actually looking at changes in individuals as they learn a task," says Schlegel. "You have a much stronger causal argument when you can do that."
The work demonstrates that significant changes are occurring in adults who are learning. The structure of their brains undergoes change.
"This flies in the face of all these traditional views that all structural development happens in infancy, early in childhood," Schlegel says. "Now that we actually do have tools to watch a brain change, we are discovering that in many cases the brain can be just as malleable as an adult as it is when you are a child or an adolescent."
(Source: eurekalert.org)
Bumblebees are anything but bumbling: The insects quickly figure out the optimal route for visiting five far-flung flowers, a computational task that even human brains find challenging.
That result suggests that an elaborate mental map isn’t necessary to travel efficiently in unknown territory. Finding a way to mimic the bumblebee’s navigation system may allow programmers to develop robots that adeptly maneuver through unfamiliar places.
The new study, published online September 20 in PLOS Biology, pulls together several lines of previous research into one grand experiment. After training bumblebees to associate artificial flowers with a reward, scientists from the University of Sydney, Rothamsted Research in Harpenden, England and Queen Mary University of London arranged five flowers in a pentagon with sides 50 meters long. One at a time, bumblebees outfitted with a little radar antenna were released from the nest. The bees’ movements were tracked by radar, and motion-sensing cameras on the flowers recorded each visiting bee.
A computer analysis of the bees’ movements suggested that the insects were doing some quick comparing. If a bee went from flower A to B and later went from flower A to C, it would compare those routes, adding the one that was shorter to its itinerary and abandoning longer paths. The bees also made adjustments when a flower was moved to a different location. These results suggest that bees don’t need a big-picture map to search their surroundings, says team member Mathieu Lihoreau, a behavioral ecologist at the University of Sydney.
“It’s amazing that these little creatures are as flexible as they are and have evolved these solutions that make maximum use of these little brains they are carrying around,” says behavioral biologist Fred Dyer of Michigan State University in East Lansing.
CAMH illuminates roles of novel epigenetic chemical in the brain
Researchers from the Centre for Addiction and Mental Health (CAMH) have identified a new role of a chemical involved in controlling the genes underlying memory and learning.
"The brain is a plastic tissue, and we know that learning and memory require various genes to be expressed,” says CAMH Senior Scientist Dr. Art Petronis, who is a senior author on the new study. “Our research has identified how the chemical 5-hmC may be involved in the epigenetic processes allowing this plasticity.” Dr. Petronis is head of the Krembil Family Epigenetics Laboratory in CAMH’s Campbell Family Mental Health Research Institute.
5-hmC is an epigenetic modification of DNA, and was discovered in humans and mice in 2009. DNA modifications are chemical changes to DNA. They flag genes to be turned “on” - signalling the genome to make a protein - or turned “off.” As the overwhelming majority of cells in an individual contain the same genetic code, this pattern of flags is what allows a neuron to use the same genome as a blood or liver cell, but create a completely different and specialized cellular environment.
The research, published online in Nature Structural & Molecular Biology, sheds light on the role of 5-hmC. Intriguingly, it is more abundant in the brain than in other tissues in the body, for reasons not clear to date.
The CAMH team of scientists examined DNA from a variety of tissues, including the mouse and human brain, and looked at where 5-hmC was found in the genome. They detected that 5-hmC had a unique distribution in the brain: it was highly enriched in genes related to the synapse, the dynamic tips of brain cells. Growth and change in the synapse allow different brain cells to “wire” together, which allows learning and memory.
"This enrichment of 5-hmC in synapse-related genes suggests a role for this epigenetic modification in learning and memory," says Dr. Petronis.
The team further showed that 5-hmC had a special distribution even within the gene. The code for one gene can be edited and “spliced” to create several different proteins. Dr. Petronis found that 5-hmC is located at “splice junctions,” the points where the gene is cut before splicing.
"5-hmC may signal the cell’s splicing machinery to generate the diverse proteins that, in turn, give rise to the unprecedented complexity of the brain," he says.
The research team is continuing to investigate the role of 5-hmC in more detail, and to determine whether 5-hmC function is different in people with bipolar disorder and schizophrenia compared to people without these diagnoses.
This research was funded by the U.S National Institutes of Health, the Canadian Institutes of Health Research, and the Tapscott Chair in Schizophrenia Studies at the University of Toronto.
The Centre for Addiction and Mental Health (CAMH) is Canada’s largest mental health and addiction teaching hospital, as well as one of the world’s leading research centres in the area of addiction and mental health. CAMH combines clinical care, research, education, policy development and health promotion to help transform the lives of people affected by mental health and addiction issues.
(Source: Yahoo!)
By studying how birds master songs used in courtship, scientists at Duke University have found that regions of the brain involved in planning and controlling complex vocal sequences may also be necessary for memorizing sounds that serve as models for vocal imitation.
In a paper appearing in the September 2012 issue of the journal Nature Neuroscience, researchers at Duke and Harvard universities observed the imitative vocal learning habits of male zebra finches to pinpoint which circuits in the birds’ brains are necessary for learning their songs.
Knowing which brain circuits are involved in learning by imitation could have broader implications for diagnosing and treating human developmental disorders, the researchers said. The finding shows that the same circuitry used for vocal control also participates in auditory learning, raising the possibility that vocal circuits in our own brain also help encode auditory experience important to speech and language learning.
Learning faster with neurodegenerative disease
People who bear the genetic mutation for Huntington’s disease learn faster than healthy people. The more pronounced the mutation was, the more quickly they learned. This is reported by researchers from the Ruhr-Universität Bochum and from Dortmund in the journal Current Biology. The team has thus demonstrated for the first time that neurodegenerative diseases can go hand in hand with increased learning efficiency. “It is possible that the same mechanisms that lead to the degenerative changes in the central nervous system also cause the considerably better learning efficiency” says Dr. Christian Beste, head of the Emmy Noether Junior Research Group “Neuronal Mechanisms of Action Control” at the RUB.
Passive learning through repeated stimulus presentation
In a previous study, the Bochum psychologists reported that the human sense of vision can be changed in the long term by repeatedly exposing subjects to certain visual stimuli for short periods (we reported in May 2011). The task of the participants was to detect changes in the brightness of stimuli. They performed better if they had viewed the stimuli passively for a while first. In the current study, the researchers presented the same task to 29 subjects with the genetic mutation for Huntington’s disease, who, however, did not yet show any symptoms. They also tested 45 control subjects without such mutations in the genome. In both groups, the learning efficiency was better after passive stimulus presentation than without the passive training. Subjects with the Huntington’s mutation, however, increased their performance twice as fast as those without the mutation.
Glutamate may have paradoxical effect
Degenerative diseases of the nervous system are based on complex changes. A key mechanism is an increased release of the neurotransmitter glutamate. However, since glutamate is also important for learning, in some cases it could lead to the paradoxical effect: better learning efficiency despite degeneration of the nerve cells.
Detecting differences in brightness under aggravated conditions
In each experimental run, the subjects saw two consecutive small bars on a computer screen that either had the same or different brightness. Sometimes, however, not only the brightness changed from bar one to bar two, but also the orientation of the bar (vertical or horizontal). “Normally, the distraction stimulus, i.e. the change in orientation, draws all the attention” Christian Beste explains. “But after the passive training with the visual stimuli, the distraction stimulus has no effect at all.” The shift of attention from the non-relevant to the relevant properties of the stimulus was also visible in the electroencephalogram (EEG) in brain areas for early visual processing.
Better performance with stronger mutation
In Huntington’s disease, a short segment of a gene is repeated. The number of repetitions determines when the disease breaks out. In the present study, a greater number of repetitions was, however, also associated with higher learning efficiency. “This shows that neurodegenerative changes can cause paradoxical effects” says Christian Beste. “The everyday view that neurodegenerative changes fundamentally entail deterioration of various functions can no longer be maintained in this dogmatic form.”
(Source: aktuell.ruhr-uni-bochum.de)
Babies’ ability to detect complex rules in language outshines that of adults
New research examining auditory mechanisms of language learning in babies has revealed that infants as young as three months of age are able to automatically detect and learn complex dependencies between syllables in spoken language. By contrast, adults only recognized the same dependencies when asked to actively search for them. The study by scientists at the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig also highlights the important role of basic pitch discrimination abilities for early language development.