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Friday, 17 April 2009

Brain bussiness-memory and sleep revealed! 03.2009

Today:

  1. Regions of the brain can rewire themselves
  2. Neuroscientists map intelligence in the brain
  3. Ants on the brain
  4. Workhorse immune molecules lead secret lives in the brain
  5. Sleep: Spring cleaning for the brain?
The last one is the most practical, but each of them is quite interesting if you're interested in brain's bussiness.

Regions of the brain can rewire themselves

March 9th, 2009

(PhysOrg.com) -- Scientists at the Max Planck Institute for Biological Cybernetics in Tübingen have succeeded in demonstrating for the first time that the activities of large parts of the brain can be altered in the long term.

The breakthrough was achieved through the experimental stimulation of in the hippocampus. Using a combination of functional magnetic resonance tomography, microstimulation and electrophysiology, the scientists were able to trace how large populations of nerve cells in the forebrain reorganize. This area of the is active when we remember something or orient ourselves spatially. The insights gained here represent the first experimental proof that large parts of the brain change when learning processes take place.

Scientists refer to the characteristic whereby synapses, nerve cells or entire areas of the brain change depending on their use as neuronal plasticity. It is a fundamental mechanism for learning and . When a nerve cell A permanently and repeatedly stimulates another nerve cell B, the synapse is altered in such a way that the signal transmission becomes more efficient. This learning process, whose duration can range from a few minutes to an entire lifetime, was intensively researched in the hippocampus.

The scientists working with Nikos Logothetis, Director at the for , have researched this phenomenon systematically for the first time. It emerged from the experiments that the reinforcement of the stimulation transmission generated in this way was maintained following experimental stimulation.

"We succeeded in demonstrating long-term reorganization in nerve networks based on altered activity in the synapses," explains Dr. Santiago Canals. The changes were reflected in better communication between the brain hemispheres and the strengthening of networks in the limbic system and cortex. While the cortex is responsible for, among other things, sensory perception and movement, the limbic system processes emotions and is partly responsible for the emergence of instinctive behavior. source

My comment: I find the way the brain work simple awesome. If you think about it-the more you use something, the better the connection between neurons becomes, thus, you can think more efficiently about it. Here, however it's interesting that obviously, the process of learning involve some type of emotion-not only your thought flow better after you have learnt something, you feel better doing it. And all this, while changing the very structure of the brain! This is sooo cool!

Neuroscientists map intelligence in the brain

March 11th, 2009

(PhysOrg.com) -- Neuroscientists at the California Institute of Technology (Caltech) have conducted the most comprehensive brain mapping to date of the cognitive abilities measured by the Wechsler Adult Intelligence Scale (WAIS), the most widely used intelligence test in the world. The results offer new insight into how the various factors that comprise an "intelligence quotient" (IQ) score depend on particular regions of the brain.

All of the (241 test-subjects) patients had some degree of cognitive impairment from events such as strokes, tumor resection, and traumatic brain injury, as assessed by testing using the WAIS. The WAIS test is composed of four indices of , each consisting of several subtests, which together produce a full-scale IQ score. The four indices are the index, which represents the ability to understand and to produce speech and use language; the perceptual organization index, which involves visual and spatial processing, such as the ability to perceive complex figures; the index, which represents the ability to hold information temporarily in mind; and the processing speed index.

The researchers first transferred the brain scans of all 241 patients to a common reference frame, an approach pioneered by neuroscientist Hanna Damasio of the University of Southern California, a coauthor of the study. Using a technique called voxel-based symptom-lesion mapping (a voxel is the three-dimensional analog of a pixel), Adolphs and his colleagues then correlated the location of brain injuries with scores on each of the four WAIS indices.

With the exception of processing speed, which appears scattered throughout the brain, the lesion mapping showed that the other three cognitive indices really do depend on specific brain regions.

For example, lesions in the left frontal cortex were associated with lower scores on the verbal comprehension index; lesions in the left frontal and parietal cortex were associated with lower scores on the working memory index; and lesions in the right parietal cortex were associated with lower scores on the perceptual organization index.

Somewhat surprisingly, the study revealed a large amount of overlap in the brain regions responsible for verbal comprehension and working memory, which suggests that these two now-separate measures of cognitive ability may actually represent the same type of intelligence, at least as assessed using the WAIS.

The converse--using brain-scan results to predict the IQ of patients as measured by the Weschler test--may also be possible. source

My comment: That experiment is so cool! Seriously, it shows something very important-first, it localise each type of intelligence with specific brain region and that lesions can hamper their manifestation. Though, it would be even better to see the extent to which different lesions prevent this type of intelligence. The other cool thing is that the processing speed is equally well spread in the brain, which might not be surprising but still, it's good to see it measured. And that means that the speed of thinking shouldn't depend of the brain architecture, probably only on the neural pathways already existing in the brain. And as we saw in the previous article, brain architecture can be easily altered. Which is to say that our brains are much more universal than some people want us to believe.

Ants on the brain

February 25th, 2009

(PhysOrg.com) -- Colonies of social insects such as ants and bees could collectively make decisions using mechanisms similar to those used in primate brains, according to new research from the University of Bristol.

Animals constantly make decisions, such as whether a predator is approaching or where they should establish a new home. These kinds of problems require a trade-off between speed and accuracy when making such decisions, and confront organisms at all levels of biological complexity.

By analysing models from neuroscience and insect socio-biology, Dr James Marshall from the University of Bristol and colleagues show how colonies of house-hunting social insects could collectively compromise between the speed and accuracy of decision-making, using mechanisms similar to those used by neurons in the primate brain.

The results, published in the Journal of the Royal Society Interface, draw the first formal parallels between decision-making circuits in the primate visual cortex and social insect colonies. Both ‘systems’ make choices that reflect an optimal compromise between speed and accuracy of decision-making, by assessing competing streams of evidence. source

My comment: I have some problems understanding decision-making. From personal experience, I find this almost a mystical process. For example, recently I was lied with the bill for something. At first, I decided "ok, let it go, it's not a big deal". And in the next moment I just went and took my money back. And I have no idea when exactly I decided-it was like an internal push to make something, but it wasn't concious because I had the same information all the time, I reached a conclusion in my mind and then I did totally opposing it. So, I have no idea how one decides anything. Not that this article help me understands it, but colectivism is always fun.

Workhorse immune molecules lead secret lives in the brain

March 30th, 2009

Molecules assumed to be in the exclusive employ of the immune system have been caught moonlighting in the brain - with a job description apparently quite distinct from their role in immunity.

Carla Shatz, PhD, professor of neurobiology and of biology, and her colleagues at the Stanford University School of Medicine have shown that members of a large family of proteins critical to immune function (collectively known as HLA in humans and MHC molecules in mice) also play a role in the brain. "We think that this family of molecules has an important role in and ," Shatz said. Surprisingly, the absence of one or another of them in the brain can trigger improved motor learning, although perhaps at the expense of other learning ability.

The proteins in question sit like jewel cases on the outer surfaces of most cells in the body, displaying fragments of the cell's innards, called peptides, to best advantage for window-shopping by roving inspectors called T-cells. When a T-cell "sees" a peptide with an aberrant chemical sequence - a sign of possible infection or cancer - it can attack the aberrant cell directly or alert the , which responds with a vengeance.

It was long thought that MHC molecules are found on the surfaces of only when the brain suffers injury or infection. But that picture was altered several years ago when a group led by Shatz compared gene expression in normally reared mice and another group that had been deprived of . In particular, they looked at a region of the brain that processes visual input. "Completely unexpectedly, we found that one of the genes needing input from the eye in order to be expressed encodes an MHC molecule," said Shatz.

She and her colleagues then showed that knocking out the expression of most MHC molecules in a brain region that processes visual stimuli caused developmental abnormalities in the circuitry of the mouse's visual system. "That implied indirectly that at least some MHC molecules were needed" for normal tuning up of brain circuits needed for vision, Shatz said, "but which ones?" There are about 60 in the mouse genome - and even more in the human genome.

The researchers found that two of those molecules in particular - called "K" and "D" - were expressed in the cerebellum, a brain structure critical to motor learning. It's believed that by detecting and reporting differences between intended and executed acts, cerebellar circuitry guides the body toward ever better piano recitals or tennis games. Practice makes perfect.

In the new study, the Shatz laboratory looked at mice's ability to learn how to keep from falling off a rotating rod called a rotarod. First author Mike McConnell, a postdoctoral researcher now at the Salk Institute in La Jolla, Calif., put two batches of mice - normal ones, and bioengineered mice that lacked the "K" and "D" proteins - through their paces on the rotarod without knowing which batch was which. He noticed that one batch was consistently superior at learning the task. A week later he retested them, with the same results. After another three-month rest, the early winners continued to excel while the slower group had to relearn the rotarod routine pretty much from scratch.

When the identity of the two mouse groups was revealed, it turned out that the good learners were the mutant mice.

Shatz said. "It implies that, normally, these molecules are putting a brake on the nervous system's ability to alter its circuitry in response to changing experiences. When you take the MHC molecules away, you remove the brake."

In the wild state, motor performance - running from predators, chasing down meat - is a nice thing to have. "Several other forms of learning besides motor learning - cognitive learning, spatial learning, recognition - don't take place in the cerebellum. There may be tradeoffs between one kind of learning and another - you're better able to escape but don't know exactly what to do in the next environment you encounter after running away - as well as between learning ability and circuit stability. More-easily altered circuitry might also be more prone to epilepsy."

The Stanford researchers have found other MHC molecules expressed in other types of neurons in other parts of the brain. "These molecules keep showing themselves to be important in limiting how much circuits can change by strengthening or weakening connections between nerve cells. We think they're going to figure as important players in many neurological disorders," Shatz said, noting a tantalizing if still controversial link between immune function and developmental brain disorders such as autism and schizophrenia. source

My comment:Hmmm. I don't have much to say, the article says it all. But I find it quite fascinating how the brain is such a magnificent machine. And everything makes sense, we just don't know it yet.

Sleep: Spring cleaning for the brain?

April 2nd, 2009
(PhysOrg.com) -- If you've ever been sleep-deprived, you know the feeling that your brain is full of wool.

Now, a study published in the April 3 edition of the journal Science has molecular and structural evidence of that woolly feeling — proteins that build up in the brains of sleep-deprived and drop to lower levels in the brains of the well-rested. The proteins are located in the , those specialized parts of neurons that allow cells to communicate with other neurons.

researchers at the University of Wisconsin-Madison School of Medicine and Public Health believe it is more evidence for their theory of "synaptic homeostasis." This is the idea that synapses grow stronger when we're awake as we learn and adapt to an ever-changing the environment, that sleep refreshes the brain by bringing synapses back to a lower level of strength. This is important because larger synapses consume a lot of energy, occupy more space and require more supplies, including the proteins examined in this study.

Sleep — by allowing synaptic downscaling — saves energy, space and material, and clears away unnecessary "noise" from the previous day, the researchers believe. The fresh brain is then ready to learn again in the morning.

The researchers — Giorgio Gilestro, Giulio Tononi and Chiara Cirelli, of the Center for Sleep and Consciousness — found that levels of proteins that carry messages in the synapses (or junctions) between neurons drop by 30 to 40 percent during sleep.

"We know that sleep is necessary for our brain to function properly, to learn new things every day, and also, in some cases, to consolidate the memory of what we learned during the day," says Cirelli, associate professor of psychiatry. "During sleep, we think that most, if not all, synapses are downscaled: at the end of sleep, the strongest synapses shrink, while the weakest synapses may even disappear."

The confocal microscope views show this happening in all three major areas of the fruit-fly brain, which are known to be very plastic (involved in learning).

Because sleep performs the same function in the brains of species as diverse as fruit flies and rats, Cirelli says it was likely conserved by evolution because it is so important to an animal's health and survival.

The Wisconsin laboratory has pioneered ways of studying sleep in different species, including fruit flies.

Flies were deprived of sleep for as long as 24 hours. Researchers then dissected their brains and measured the levels of four pre-synaptic proteins and one post-synaptic protein. All levels rose progressively during periods of wakefulness and fell after sleep. Other experiments confirmed that the changes in protein levels were not caused by exposure to light and darkness or by the stimulation itself, but by sleep and waking. They also used confocal microscopy and an antibody that specifically recognizes BRP to measure the expression of this protein in many fly-brain areas.source

My comment: This one is the coolest! Because it goes so well with my own experience. It makes great sense that the brain gets over-filled (overflow error, lol) and sleep helps it dissipate the tension and the impressions. And it only shows how IMPORTANT sleep actually is. Which everyone who had the bad luck to get insomnia will tell you.

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