I haven’t fallen off a cliff. I promise.

I know it’s been a while (again) since I posted. The night after my last post, my computer mysteriously broke. I say “mysteriously” because I have no clue how it happened. It’s got a giant crack running through it and is useless. So, I have no way to get online. Or do anything, really. The good news is that with DH’s new job, I *should* be able to buy a new one before too terribly much longer. But first I have to pay for my puppy…….

That’s right, I’ve found my new service dog candidate! ^___^ It’s a Doberman, of course, and from a breeder who does both show and working dogs. (And I’m having this tremendous feeling of déjà vu, so if I posted this already and just forgot… Um. Sorry?) The pregnancy has been confirmed and is due within a couple of weeks, so I should be able to bring my pup home the beginning of April. Hopefully I’ll have my computer replaced before then, so stay tuned for puppy pics. ^.^


neurosciencestuff:

Muting the Mozart effect
Children get plenty of benefits from music lessons. Learning to play instruments can fuel their creativity, and practicing can teach much-needed focus and discipline. And the payoff, whether in learning a new song or just mastering a chord, often boosts self-esteem.
But Harvard researchers now say that one oft-cited benefit — that studying music improves intelligence — is a myth.
Though it has been embraced by everyone from advocates for arts education to parents hoping to encourage their kids to stick with piano lessons, a pair of studies conducted by Samuel Mehr, a Harvard Graduate School of Education (HGSE) doctoral student working in the lab of Elizabeth Spelke, the Marshall L. Berkman Professor of Psychology, found that music training had no effect on the cognitive abilities of young children. The studies are described in a Dec. 11 paper published in the open-access journal PLoS One.
“More than 80 percent of American adults think that music improves children’s grades or intelligence,” Mehr said. “Even in the scientific community, there’s a general belief that music is important for these extrinsic reasons. But there is very little evidence supporting the idea that music classes enhance children’s cognitive development.”
The notion that music training can make someone smarter, Mehr said, can largely be traced to a single study published in Nature. In it, researchers identified what they called the “Mozart effect.” After listening to music, test subjects performed better on spatial tasks.
Though the study was later debunked, the notion that simply listening to music could make someone smarter became firmly embedded in the public imagination, and spurred a host of follow-up studies, including several that focused on the cognitive benefits of music lessons.
Though dozens of studies have explored whether and how music and cognitive skills might be connected, when Mehr and colleagues reviewed the literature they found only five studies that used randomized trials, the gold standard for determining causal effects of educational interventions on child development. Of the five, only one showed an unambiguously positive effect, and it was so small — just a 2.7 point increase in IQ after a year of music lessons — that it was barely enough to be statistically significant.
“The experimental work on this question is very much in its infancy, but the few published studies on the topic show little evidence for ‘music makes you smarter,’” Mehr said.
To explore the connection between music and cognition, Mehr and his colleagues recruited 29 parents and 4-year-old children from the Cambridge area. After initial vocabulary tests for the children and music aptitude tests for the parents, each was randomly assigned to one of two classes, one that had music training, or another that focused on visual arts.
“We wanted to test the effects of the type of music education that actually happens in the real world, and we wanted to study the effect in young children, so we implemented a parent-child music enrichment program with preschoolers,” Mehr said. “The goal is to encourage musical play between parents and children in a classroom environment, which gives parents a strong repertoire of musical activities they can continue to use at home with their kids.”
Among the key changes Mehr and his colleagues made from earlier studies were controlling for the effect of different teachers — Mehr taught both the music and visual arts classes — and using assessment tools designed to test areas of cognition, vocabulary, mathematics, and two spatial tasks.
“Instead of using something general, like an IQ test, we tested four specific domains of cognition,” Mehr said. “If there really is an effect of music training on children’s cognition, we should be able to better detect it here than in previous studies, because these tests are more sensitive than tests of general intelligence.”
The study’s results, however, showed no evidence for cognitive benefits of music training.
While the groups performed comparably on vocabulary and number-estimation tasks, the assessments showed that children who received music training performed slightly better at one spatial task, while those who received visual arts training performed better at the other.
“Study One was very small. We only had 15 children in the music group, and 14 in the visual arts,” Mehr said. “The effects were tiny, and their statistical significance was marginal at best. So we attempted to replicate the study, something that hasn’t been done in any of the previous work.”
To replicate the effect, Mehr and colleagues designed a second study that recruited 45 parents and children, half of whom received music training, and half of whom received no training.
Just as in the first study, Mehr said, there was no evidence that music training offered any cognitive benefit. Even when the results of both studies were pooled to allow researchers to compare the effect of music training, visual arts training, and no training, there was no sign that any group outperformed the others.
“There were slight differences in performance between the groups, but none were large enough to be statistically significant,” Mehr said. “Even when we used the finest-grained statistical analyses available to us, the effects just weren’t there.”
While the results suggest studying music may not be a shortcut to educational success, Mehr said there is still substantial value in music education.
“There’s a compelling case to be made for teaching music that has nothing to do with extrinsic benefits,” he said. “We don’t teach kids Shakespeare because we think it will help them do better on the SATs. We do it because we believe Shakespeare is important.
“Music is an ancient, uniquely human activity. The oldest flutes that have been dug up are 40,000 years old, and human song long preceded that,” he said. “Every single culture in the world has music, including music for children. Music says something about what it means to be human, and it would be crazy not to teach this to our children.”

neurosciencestuff:

Muting the Mozart effect

Children get plenty of benefits from music lessons. Learning to play instruments can fuel their creativity, and practicing can teach much-needed focus and discipline. And the payoff, whether in learning a new song or just mastering a chord, often boosts self-esteem.

But Harvard researchers now say that one oft-cited benefit — that studying music improves intelligence — is a myth.

Though it has been embraced by everyone from advocates for arts education to parents hoping to encourage their kids to stick with piano lessons, a pair of studies conducted by Samuel Mehr, a Harvard Graduate School of Education (HGSE) doctoral student working in the lab of Elizabeth Spelke, the Marshall L. Berkman Professor of Psychology, found that music training had no effect on the cognitive abilities of young children. The studies are described in a Dec. 11 paper published in the open-access journal PLoS One.

“More than 80 percent of American adults think that music improves children’s grades or intelligence,” Mehr said. “Even in the scientific community, there’s a general belief that music is important for these extrinsic reasons. But there is very little evidence supporting the idea that music classes enhance children’s cognitive development.”

The notion that music training can make someone smarter, Mehr said, can largely be traced to a single study published in Nature. In it, researchers identified what they called the “Mozart effect.” After listening to music, test subjects performed better on spatial tasks.

Though the study was later debunked, the notion that simply listening to music could make someone smarter became firmly embedded in the public imagination, and spurred a host of follow-up studies, including several that focused on the cognitive benefits of music lessons.

Though dozens of studies have explored whether and how music and cognitive skills might be connected, when Mehr and colleagues reviewed the literature they found only five studies that used randomized trials, the gold standard for determining causal effects of educational interventions on child development. Of the five, only one showed an unambiguously positive effect, and it was so small — just a 2.7 point increase in IQ after a year of music lessons — that it was barely enough to be statistically significant.

“The experimental work on this question is very much in its infancy, but the few published studies on the topic show little evidence for ‘music makes you smarter,’” Mehr said.

To explore the connection between music and cognition, Mehr and his colleagues recruited 29 parents and 4-year-old children from the Cambridge area. After initial vocabulary tests for the children and music aptitude tests for the parents, each was randomly assigned to one of two classes, one that had music training, or another that focused on visual arts.

“We wanted to test the effects of the type of music education that actually happens in the real world, and we wanted to study the effect in young children, so we implemented a parent-child music enrichment program with preschoolers,” Mehr said. “The goal is to encourage musical play between parents and children in a classroom environment, which gives parents a strong repertoire of musical activities they can continue to use at home with their kids.”

Among the key changes Mehr and his colleagues made from earlier studies were controlling for the effect of different teachers — Mehr taught both the music and visual arts classes — and using assessment tools designed to test areas of cognition, vocabulary, mathematics, and two spatial tasks.

“Instead of using something general, like an IQ test, we tested four specific domains of cognition,” Mehr said. “If there really is an effect of music training on children’s cognition, we should be able to better detect it here than in previous studies, because these tests are more sensitive than tests of general intelligence.”

The study’s results, however, showed no evidence for cognitive benefits of music training.

While the groups performed comparably on vocabulary and number-estimation tasks, the assessments showed that children who received music training performed slightly better at one spatial task, while those who received visual arts training performed better at the other.

“Study One was very small. We only had 15 children in the music group, and 14 in the visual arts,” Mehr said. “The effects were tiny, and their statistical significance was marginal at best. So we attempted to replicate the study, something that hasn’t been done in any of the previous work.”

To replicate the effect, Mehr and colleagues designed a second study that recruited 45 parents and children, half of whom received music training, and half of whom received no training.

Just as in the first study, Mehr said, there was no evidence that music training offered any cognitive benefit. Even when the results of both studies were pooled to allow researchers to compare the effect of music training, visual arts training, and no training, there was no sign that any group outperformed the others.

“There were slight differences in performance between the groups, but none were large enough to be statistically significant,” Mehr said. “Even when we used the finest-grained statistical analyses available to us, the effects just weren’t there.”

While the results suggest studying music may not be a shortcut to educational success, Mehr said there is still substantial value in music education.

“There’s a compelling case to be made for teaching music that has nothing to do with extrinsic benefits,” he said. “We don’t teach kids Shakespeare because we think it will help them do better on the SATs. We do it because we believe Shakespeare is important.

“Music is an ancient, uniquely human activity. The oldest flutes that have been dug up are 40,000 years old, and human song long preceded that,” he said. “Every single culture in the world has music, including music for children. Music says something about what it means to be human, and it would be crazy not to teach this to our children.”



neurosciencestuff:

Repairing mitochondria in neurodegenerative disease
The relationship between fine-scale structure and function in the brain is perhaps best explored today by the study of neurodegenerative disease. Disorders like Rett syndrome may be considered developmental in origin—and defined by exotic mechanisms including X-linked inactivation, DNA methylation, and genomic imprinting—but even here, its larger physical pathology evolves through the course of life and continues to be revealed in almost any place that researchers look. When diseases directly involve inputs to the brain like vitamin or diet, and can also be controlled by them, things get even more interesting. More often than not, these disorders have a clear genetic component, are frequently linked to the mitochondria, and lead to progressive and often perplexing deficits of movement. One such enigma is known as pantothenate kinase-associated neurodegeneration, or PKAN syndrome, in its the most frequent form. A recent open paper in the journal Brain explains.
This particular syndrome can be caused by any number of a hundred or so mutations in the PANK2 gene, which codes for the mitochondrial enzyme pantothenate kinase 2. Of the four nuclear-coded PANK genes, only PANK2 is targeted to the mitochondria. Its protein product is involved in co-enzyme A biosynthesis and catalyzes the phosphorylation of pantothenate (vitamin B5). The hallmark pathology, as defined by T2-weighted MRI, can be seen in the globus pallidus and even has its own unique name— the Eye-of-the-Tiger sign.

The researchers used a mouse model of the disease with a Pank2 double gene knockout. On a standard diet, the mice showed growth issues, azoospermia (lack of sperm) and minor mitochondrial dysfunction, but not some of the other typical issues like iron accumulation in the brain or retinal degeneration. Since co-enzyme A is crucial to several metabolic pathways, the researchers also tested the mice on a high fat ketogenic diet. Under these conditions, ketone bodies produced through fatty acid oxidation bypass the normal glycolytic pathways and proceed directly to the citric acid acid.

On the ketogenic diet, the mitochondria, which were already ailing with abnormal, swollen cristae, fared much worse, losing some cristae entirely. Extensive lipofuschin deposits were also found in these mice, and movement issues were amplified. It had previously been established in other organisms like flies, that panthethine (a dimeric form of vitamin B5 linked by cysteamine bridging groups) could counteract these issues. When the mice were given panthethine, the general pathology was resolved. In particular, the mitochondria were completely rescued, presumably restored to health, or otherwise replaced in the natural course of events.

The researchers also evaluated mitochondrial membrane potential using dye staining methods. In the knockout mice, membrane potential was compromised, however it was completely restored by the panthethine. At present there is no definitive way to predict functional variables, like membrane potential, from the morphology as it is seen on processed EM tissue. In a recent review of new brain mapping techniques, we discussed this issue, and also pointed to new technologies which may permit closer examinations.
On EM images, one of the most striking features in the interior of mitochondria is the crista junction. This protein structure functionally divides the inner and intermembrane spaces, and controls exchanges between them. While mitochondria come in a variety of forms, the junctions generally converge on a preferred shape and size. Efforts to thermodynamically characterize them in terms of shape entropy have been initiated, as have conceptions of how they evolve as conditions in the mitochondria change mechanically. The so-called “baffle model” of mitochondrial has been entirely replaced by the new cristae junction model which aims to relate structure to function for these organelles, just as we seek it on larger scales for the brain.

Several issues in PNAK style neurodegeneration still stand out like a sore thumb. The iron accumulation is still unexplained, but may be related to another unexplained issue: namely, not only does panthethine fail to cross the BBB, it does not even appear to be working through a vitamin B5 function. When panthethine is metabolized into two pantothenic acid molecules, it also forms two cysteamines. While cysteamine is associated with various side effects, and it can bind and inactivate certain liver enzymes, it also can cross the BBB, perhaps as seen here, to great effect.
The doses necessary for vitamin B5 function are far below those needed here for restorative function. More work is needed to constrain the range of possible mechanisms at play here, but in addition to finding cures for the disease, it will also help cure our ignorance as far as structure-function relations.

neurosciencestuff:

Repairing mitochondria in neurodegenerative disease

The relationship between fine-scale structure and function in the brain is perhaps best explored today by the study of neurodegenerative disease. Disorders like Rett syndrome may be considered developmental in origin—and defined by exotic mechanisms including X-linked inactivation, DNA methylation, and genomic imprinting—but even here, its larger physical pathology evolves through the course of life and continues to be revealed in almost any place that researchers look. When diseases directly involve inputs to the brain like vitamin or diet, and can also be controlled by them, things get even more interesting. More often than not, these disorders have a clear genetic component, are frequently linked to the mitochondria, and lead to progressive and often perplexing deficits of movement. One such enigma is known as pantothenate kinase-associated neurodegeneration, or PKAN syndrome, in its the most frequent form. A recent open paper in the journal Brain explains.

This particular syndrome can be caused by any number of a hundred or so mutations in the PANK2 gene, which codes for the mitochondrial enzyme pantothenate kinase 2. Of the four nuclear-coded PANK genes, only PANK2 is targeted to the mitochondria. Its protein product is involved in co-enzyme A biosynthesis and catalyzes the phosphorylation of pantothenate (vitamin B5). The hallmark pathology, as defined by T2-weighted MRI, can be seen in the globus pallidus and even has its own unique name— the Eye-of-the-Tiger sign.

The researchers used a mouse model of the disease with a Pank2 double gene knockout. On a standard diet, the mice showed growth issues, azoospermia (lack of sperm) and minor mitochondrial dysfunction, but not some of the other typical issues like iron accumulation in the brain or retinal degeneration. Since co-enzyme A is crucial to several metabolic pathways, the researchers also tested the mice on a high fat ketogenic diet. Under these conditions, ketone bodies produced through fatty acid oxidation bypass the normal glycolytic pathways and proceed directly to the citric acid acid.

On the ketogenic diet, the mitochondria, which were already ailing with abnormal, swollen cristae, fared much worse, losing some cristae entirely. Extensive lipofuschin deposits were also found in these mice, and movement issues were amplified. It had previously been established in other organisms like flies, that panthethine (a dimeric form of vitamin B5 linked by cysteamine bridging groups) could counteract these issues. When the mice were given panthethine, the general pathology was resolved. In particular, the mitochondria were completely rescued, presumably restored to health, or otherwise replaced in the natural course of events.

The researchers also evaluated mitochondrial membrane potential using dye staining methods. In the knockout mice, membrane potential was compromised, however it was completely restored by the panthethine. At present there is no definitive way to predict functional variables, like membrane potential, from the morphology as it is seen on processed EM tissue. In a recent review of new brain mapping techniques, we discussed this issue, and also pointed to new technologies which may permit closer examinations.

On EM images, one of the most striking features in the interior of mitochondria is the crista junction. This protein structure functionally divides the inner and intermembrane spaces, and controls exchanges between them. While mitochondria come in a variety of forms, the junctions generally converge on a preferred shape and size. Efforts to thermodynamically characterize them in terms of shape entropy have been initiated, as have conceptions of how they evolve as conditions in the mitochondria change mechanically. The so-called “baffle model” of mitochondrial has been entirely replaced by the new cristae junction model which aims to relate structure to function for these organelles, just as we seek it on larger scales for the brain.

Several issues in PNAK style neurodegeneration still stand out like a sore thumb. The iron accumulation is still unexplained, but may be related to another unexplained issue: namely, not only does panthethine fail to cross the BBB, it does not even appear to be working through a vitamin B5 function. When panthethine is metabolized into two pantothenic acid molecules, it also forms two cysteamines. While cysteamine is associated with various side effects, and it can bind and inactivate certain liver enzymes, it also can cross the BBB, perhaps as seen here, to great effect.

The doses necessary for vitamin B5 function are far below those needed here for restorative function. More work is needed to constrain the range of possible mechanisms at play here, but in addition to finding cures for the disease, it will also help cure our ignorance as far as structure-function relations.



what disabled people consider accessibility: wheelchair ramps, elevators, stairs that aren't steep & contain breaks, braille, seeing eye dogs/assistant dogs, ergonomic workspaces, easy to grip tools, closed captions, resources in close proximity to each other, class note-takers, recording devices for lectures, medication, level ground, assisted learning, larger bathroom stalls with bars, quiet spaces (for sensory overload), lower workloads, being allowed time off work or school, just to name very very few
what able-bodied people consider accessibility: "just put wheelchair ramps everywhere!!!"



dogsontrains:

Sleepy guide dog seen by clarachang on the BART in San Francisco, USA.

dogsontrains:

Sleepy guide dog seen by clarachang on the BART in San Francisco, USA.


neurosciencestuff:

Balancing old and new skills
To learn new motor skills, the brain must be plastic: able to rapidly change the strengths of connections between neurons, forming new patterns that accomplish a particular task. However, if the brain were too plastic, previously learned skills would be lost too easily.
A new computational model developed by MIT neuroscientists explains how the brain maintains the balance between plasticity and stability, and how it can learn very similar tasks without interference between them.
The key, the researchers say, is that neurons are constantly changing their connections with other neurons. However, not all of the changes are functionally relevant — they simply allow the brain to explore many possible ways to execute a certain skill, such as a new tennis stroke.
“Your brain is always trying to find the configurations that balance everything so you can do two tasks, or three tasks, or however many you’re learning,” says Robert Ajemian, a research scientist in MIT’s McGovern Institute for Brain Research and lead author of a paper describing the findings in the Proceeding of the National Academy of Sciences the week of Dec. 9. “There are many ways to solve a task, and you’re exploring all the different ways.”
As the brain explores different solutions, neurons can become specialized for specific tasks, according to this theory.
Noisy circuits
As the brain learns a new motor skill, neurons form circuits that can produce the desired output — a command that will activate the body’s muscles to perform a task such as swinging a tennis racket. Perfection is usually not achieved on the first try, so feedback from each effort helps the brain to find better solutions.
This works well for learning one skill, but complications arise when the brain is trying to learn many different skills at once.  Because the same distributed network controls related motor tasks, new modifications to existing patterns can interfere with previously learned skills.
“This is particularly tricky when you’re learning very similar things,” such as two different tennis strokes, says Institute Professor Emilio Bizzi, the paper’s senior author and a member of the McGovern Institute.
In a serial network such as a computer chip, this would be no problem — instructions for each task would be stored in a different location on the chip. However, the brain is not organized like a computer chip. Instead, it is massively parallel and highly connected — each neuron connects to, on average, about 10,000 other neurons.
That connectivity offers an advantage, however, because it allows the brain to test out so many possible solutions to achieve combinations of tasks. The constant changes in these connections, which the researchers call hyperplasticity, is balanced by another inherent trait of neurons — they have a very low signal to noise ratio, meaning that they receive about as much useless information as useful input from their neighbors.
Most models of neural activity don’t include noise, but the MIT team says noise is a critical element of the brain’s learning ability. “Most people don’t want to deal with noise because it’s a nuisance,” Ajemian says. “We set out to try to determine if noise can be used in a beneficial way, and we found that it allows the brain to explore many solutions, but it can only be utilized if the network is hyperplastic.”
This model helps to explain how the brain can learn new things without unlearning previously acquired skills, says Ferdinando Mussa-Ivaldi, a professor of physiology at Northwestern University.
“What the paper shows is that, counterintuitively, if you have neural networks and they have a high level of random noise, that actually helps instead of hindering the stability problem,” says Mussa-Ivaldi, who was not part of the research team.
Without noise, the brain’s hyperplasticity would overwrite existing memories too easily. Conversely, low plasticity would not allow any new skills to be learned, because the tiny changes in connectivity would be drowned out by all of the inherent noise.
The model is supported by anatomical evidence showing that neurons exhibit a great deal of plasticity even when learning is not taking place, as measured by the growth and formation of connections of dendrites — the tiny extensions that neurons use to communicate with each other.
Like riding a bike
The constantly changing connections explain why skills can be forgotten unless they are practiced often, especially if they overlap with other routinely performed tasks.
“That’s why an expert tennis player has to warm up for an hour before a match,” Ajemian says. The warm-up is not for their muscles, instead, the players need to recalibrate the neural networks that control different tennis strokes that are stored in the brain’s motor cortex.
However, skills such as riding a bicycle, which is not very similar to other common skills, are retained more easily. “Once you’ve learned something, if it doesn’t overlap or intersect with other skills, you will forget it but so slowly that it’s essentially permanent,” Ajemian says.
The researchers are now investigating whether this type of model could also explain how the brain forms memories of events, as well as motor skills.

neurosciencestuff:

Balancing old and new skills

To learn new motor skills, the brain must be plastic: able to rapidly change the strengths of connections between neurons, forming new patterns that accomplish a particular task. However, if the brain were too plastic, previously learned skills would be lost too easily.

A new computational model developed by MIT neuroscientists explains how the brain maintains the balance between plasticity and stability, and how it can learn very similar tasks without interference between them.

The key, the researchers say, is that neurons are constantly changing their connections with other neurons. However, not all of the changes are functionally relevant — they simply allow the brain to explore many possible ways to execute a certain skill, such as a new tennis stroke.

“Your brain is always trying to find the configurations that balance everything so you can do two tasks, or three tasks, or however many you’re learning,” says Robert Ajemian, a research scientist in MIT’s McGovern Institute for Brain Research and lead author of a paper describing the findings in the Proceeding of the National Academy of Sciences the week of Dec. 9. “There are many ways to solve a task, and you’re exploring all the different ways.”

As the brain explores different solutions, neurons can become specialized for specific tasks, according to this theory.

Noisy circuits

As the brain learns a new motor skill, neurons form circuits that can produce the desired output — a command that will activate the body’s muscles to perform a task such as swinging a tennis racket. Perfection is usually not achieved on the first try, so feedback from each effort helps the brain to find better solutions.

This works well for learning one skill, but complications arise when the brain is trying to learn many different skills at once.  Because the same distributed network controls related motor tasks, new modifications to existing patterns can interfere with previously learned skills.

“This is particularly tricky when you’re learning very similar things,” such as two different tennis strokes, says Institute Professor Emilio Bizzi, the paper’s senior author and a member of the McGovern Institute.

In a serial network such as a computer chip, this would be no problem — instructions for each task would be stored in a different location on the chip. However, the brain is not organized like a computer chip. Instead, it is massively parallel and highly connected — each neuron connects to, on average, about 10,000 other neurons.

That connectivity offers an advantage, however, because it allows the brain to test out so many possible solutions to achieve combinations of tasks. The constant changes in these connections, which the researchers call hyperplasticity, is balanced by another inherent trait of neurons — they have a very low signal to noise ratio, meaning that they receive about as much useless information as useful input from their neighbors.

Most models of neural activity don’t include noise, but the MIT team says noise is a critical element of the brain’s learning ability. “Most people don’t want to deal with noise because it’s a nuisance,” Ajemian says. “We set out to try to determine if noise can be used in a beneficial way, and we found that it allows the brain to explore many solutions, but it can only be utilized if the network is hyperplastic.”

This model helps to explain how the brain can learn new things without unlearning previously acquired skills, says Ferdinando Mussa-Ivaldi, a professor of physiology at Northwestern University.

“What the paper shows is that, counterintuitively, if you have neural networks and they have a high level of random noise, that actually helps instead of hindering the stability problem,” says Mussa-Ivaldi, who was not part of the research team.

Without noise, the brain’s hyperplasticity would overwrite existing memories too easily. Conversely, low plasticity would not allow any new skills to be learned, because the tiny changes in connectivity would be drowned out by all of the inherent noise.

The model is supported by anatomical evidence showing that neurons exhibit a great deal of plasticity even when learning is not taking place, as measured by the growth and formation of connections of dendrites — the tiny extensions that neurons use to communicate with each other.

Like riding a bike

The constantly changing connections explain why skills can be forgotten unless they are practiced often, especially if they overlap with other routinely performed tasks.

“That’s why an expert tennis player has to warm up for an hour before a match,” Ajemian says. The warm-up is not for their muscles, instead, the players need to recalibrate the neural networks that control different tennis strokes that are stored in the brain’s motor cortex.

However, skills such as riding a bicycle, which is not very similar to other common skills, are retained more easily. “Once you’ve learned something, if it doesn’t overlap or intersect with other skills, you will forget it but so slowly that it’s essentially permanent,” Ajemian says.

The researchers are now investigating whether this type of model could also explain how the brain forms memories of events, as well as motor skills.