“More Complex than a Galaxy” –New Insights into the Human Brain

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“Consider the human brain,” says the physicist Sir Roger Penrose. “If you look at the entire physical cosmos, our brains are a tiny, tiny part of it. But they’re the most perfectly organized part. Compared to the complexity of a brain, a galaxy is just an inert lump.”

In a new study, scientists argue that many of our high-level abilities are carried out by more extensive brain networks linking many different areas of the brain. They suggest it may be the structure of these extended networks more than the size of any isolated brain region that is critical for cognitive functioning. The frontal lobes in humans vs. other species are not — as previously thought — disproportionately enlarged relative to other areas of the brain, according to a study by Durham and Reading universities.

It concludes that the size of our frontal lobes — an area in the brain of mammals located at the front of each cerebral hemisphere — cannot solely account for humans’ superior cognitive abilities.

The study also suggest that supposedly more “primitive” areas, such as the cerebellum, were equally important in the expansion of the human brain. These areas may therefore play unexpectedly important roles in human cognition and its disorders, such as autism and dyslexia, say the researchers.

The Durham and Reading researchers, funded by The Leverhulme Trust, analyzed data sets from previous animal and human studies using phylogenetic (“evolutionary family tree”) methods, and found consistent results across all their data. They used a new method to look at the speed with which evolutionary change occurred, concluding that the frontal lobes did not evolve especially fast along the human lineage after it split from the chimpanzee lineage.

Human brains share a consistent genetic blueprint and possess enormous biochemical complexity. The same basic functional elements are used throughout the cortex and understanding how one area works in detail will uncover fundamentals that apply to the other areas as well, according to an earlier study completed by scientists at the Allen Institute for Brain Science.

Human brains share a consistent genetic blueprint, and possess enormous biochemical complexity, they said, based on the first deep and large-scale analysis of the vast data set publicly available in the Allen Human Brain Atlas. Among other findings, these data show that 84% of all genes are expressed somewhere in the human brain and in patterns that are substantially similar from one brain to the next.

“More Complex Than a Galaxy” –New Insights Into the Enormous Biochemical Complexity of the Human Brain

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“Consider the human brain,” says physicist Sir Roger Penrose. “If you look at the entire physical cosmos, our brains are a tiny, tiny part of it. But they’re the most perfectly organized part. Compared to the complexity of a brain, a galaxy is just an inert lump.”

Human brains share a consistent genetic blueprint and possess enormous biochemical complexity. The same basic functional elements are used throughout the cortex and understanding how one area works in detail will uncover fundamentals that apply to the other areas as well, scientists at the Allen Institute for Brain Science reported in the latest issue of the journal Nature. Human brains share a consistent genetic blueprint, and possess enormous biochemical complexity, they said, based on the first deep and large-scale analysis of the vast data set publicly available in the Allen Human Brain Atlas. Among other findings, these data show that 84% of all genes are expressed somewhere in the human brain and in patterns that are substantially similar from one brain to the next.The results of this study are based on extensive analysis of the Allen Human Brain Atlas, specifically, the detailed all-genes, all-structures survey of genes at work throughout the human brain. This dataset profiles 400 to 500 distinct brain areas per hemisphere using microarray technology and comprises more than 100 million gene expression measurements covering three individual human brains to date.

“This study demonstrates the value of a global analysis of gene expression throughout the entire brain and has implications for understanding brain function, development, evolution and disease,” said Ed Lein, Ph.D., Associate Investigator at the Allen Institute for Brain Science and co-lead author on the paper. “These results only scratch the surface of what can be learned from this immense data set. We look forward to seeing what others will discover.”

 

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The results of this study show that, despite the myriad personalities and cognitive talents seen across the human population, our brains are more similar to one another than different. Individual human brains share the same basic molecular blueprint, and deeper analysis of this shared architecture reveals several further findings:

Neighboring regions of the brain’s cortex are more biochemically similar to one another than to more distant brain regions, which has implications for understanding the development of the human brain, both during the lifespan and throughout evolution. The right and left hemispheres show no significant differences in molecular architecture. This suggests that functions such as language, which are generally handled by one side of the brain, likely result from more subtle differences between hemispheres or structural variation in size or circuitry, but not from a deeper molecular basis.

Despite controlling a diversity of functions, ranging from visual perception to planning and problem-solving, the cortex is highly homogeneous relative to other brain regions. This suggests that the same basic functional elements are used throughout the cortex and that understanding how one area works in detail will uncover fundamentals that apply to the other areas, as well.*In addition to such global findings, the study provides new insights into the detailed inner workings of the brain at the molecular level – the level at which diseases unfold and therapeutic drugs take action.

Many previously uncharacterized genes are turned on in specific brain regions and localize with known functional groups of genes, suggesting they play roles in particular brain functions. Synapse-associated genes—those related to cell-to-cell communication machinery in the brain—are deployed in complex combinations throughout the brain, revealing a great diversity of synapse types and remarkable regional variation that likely underlies functional distinctions between brain regions.

“The tremendous variety of synapses we see in the human brain is quite striking,” said Seth Grant, FRSE, Professor of Molecular Neuroscience at the University of Edinburgh and collaborating author on the study. “Mutations in synaptic genes are associated with numerous brain-related disorders, and thus understanding synapse diversity and organization in the brain is a key step toward understanding these diseases and developing specific and effective therapeutics to treat them.”

Fully integrating several different kinds of data across different scales of brain exploration, the Allen Human Brain Atlas is an open, public online resource that details genes at work throughout the human brain. Data incorporated into the Atlas include magnetic resonance imaging (MRI),diffusion tensor imaging (DTI), as well as histology and gene expression data derived from both microarray and in situ hybridization (ISH) approaches.

Users of the Allen Human Brain Atlas comprise a diverse array of biomedical researchers — primarily neuroscientists — throughout the world. They include scientists who study the human brain itself, as well as those working in model systems, providing a rare and important opportunity for them to probe the relevance of the findings to humans. Currently, more than 5,000 unique visitors access the Atlas each month.

The Allen Human Brain Atlas is available via the Allen Brain Atlas data portal at http://www.brain-map.org.

 

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Allen Institute for Brain Science

NASA Researchers Discover the Origin of a Major Aspect of Creation of Life

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Researchers analyzing meteorite fragments that fell on a frozen lake in Canada have developed an explanation for the origin of life‘s “handedness” – why living things only use molecules with specific orientations. The work also gave the strongest evidence to date that liquid water inside an asteroid leads to a strong preference of left-handed over right-handed forms of some common protein amino acids in meteorites. The result makes the search for extraterrestrial life more challenging.

“Our analysis of the amino acids in meteorite fragments from Tagish Lake gave us one possible explanation for why all known life uses only left-handed versions of amino acids to build proteins,” said Dr. Daniel Glavin of NASA‘s Goddard Space Flight Center in Greenbelt, Md. Glavin is lead author of a paper on this research to be published in the journal Meteoritics and Planetary Science.In January, 2000, a large meteoroid exploded in the atmosphere over northern British Columbia, Canada, and rained fragments across the frozen surface of Tagish Lake. Because many people witnessed the fireball, pieces were collected within days and kept preserved in their frozen state. This ensured that there was very little contamination from terrestrial life.

“The Tagish Lake meteorite continues to reveal more secrets about the early Solar System the more we investigate it,” said Dr. Christopher Herd of the University of Alberta, Edmonton, Canada, a co-author on the paper who provided samples of the Tagish Lake meteorite for the team to analyze. “This latest study gives us a glimpse into the role that water percolating through asteroids must have played in making the left-handed amino acids that are so characteristic of all life on Earth.”

 

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Proteins are the workhorse molecules of life, used in everything from structures like hair to enzymes, the catalysts that speed up or regulate chemical reactions. Just as the 26 letters of the alphabet are arranged in limitless combinations to make words, life uses 20 different amino acids in a huge variety of arrangements to build millions of different proteins. Amino acid molecules can be built in two ways that are mirror images of each other, like your hands. Although life based on right-handed amino acids would presumably work fine, they can’t be mixed.

“Synthetic proteins created using a mix of left- and right-handed amino acids just don’t work,” says Dr. Jason Dworkin of NASA Goddard, co-author of the study and head of the Goddard Astrobiology Analytical Laboratory, where the analysis was performed. *Since life can’t function with a mix of left- and right-handed amino acids, researchers want to know how life – at least, life on Earth — got set up with the left-handed ones. “The handedness observed in biological molecules – left-handed amino acids and right-handed sugars – is a property important for molecular recognition processes and is thought to be a prerequisite for life,” said Dworkin.

All ordinary methods of synthetically creating amino acids result in equal mixtures of left- and right-handed amino acids. Therefore, how the nearly exclusive production of one hand of such molecules arose from what were presumably equal mixtures of left and right molecules in a prebiotic world has been an area of intensive research.

Theteam ground up samples of the Tagish Lake meteorites, mixed them into a hot-water solution, then separated and identified the molecules in them using a liquid chromatograph mass spectrometer.

“We discovered that the samples had about four times as many left-handed versions of aspartic acid as the opposite hand,” says Glavin. Aspartic acid is an amino acid used in every enzyme in the human body. It is also used to make the sugar substitute Aspartame. “Interestingly, the same meteorite sample showed only a slight left-hand excess (no more than eight percent) for alanine, another amino acid used by life.”

“At first, this made no sense, because if these amino acids came from contamination by terrestrial life, both amino acids should have large left-handed excesses, because both are common in biology,” says Glavin. “However, a large left-hand excess in one and not the other tells us that they were not created by life but instead were made inside the Tagish Lake asteroid.”

The team confirmed that the amino acids were probably created in space using isotope analysis.  Isotopes are versions of an element with different masses; for example, carbon 13 is a heavier, and less common, variety of carbon. Since the chemistry of life prefers lighter isotopes, amino acids enriched in the heavier carbon 13 were likely created in space.

“We found that the aspartic acid and alanine in our Tagish Lake samples were highly enriched in carbon 13, indicating they were probably created by non-biological processes in the parent asteroid,” said Dr. Jamie Elsila of NASA Goddard, a co-author on the paper who performed the isotopic analysis.

This is the first time that carbon isotope measurements have been reported for these amino acids in Tagish Lake. The carbon 13 enrichment, combined with the large left-hand excess in aspartic acid but not in alanine, provides very strong evidence that some left-handed proteinogenic amino acids — ones used by life to make proteins — can be produced in excess in asteroids, according to the team.

Some have argued that left-handed amino acid excesses in meteorites were formed by exposure to polarized radiation in the solar nebula – the cloud of gas and dust from which asteroids, and eventually the Solar System, were formed. However, in this case, the left-hand aspartic acid excesses are so large that they cannot be explained by polarized radiation alone. The team believes that another process is required.

Additionally, the large left-hand excess in aspartic acid but not in alanine gave the team a critical clue as to how these amino acids could have been made inside the asteroid, and therefore how a large left-hand excess could arise before life originated on Earth.

“One thing that jumped out at me was that alanine and aspartic acid can crystallize differently when you have mixtures of both left-handed and right-handed molecules,” said Dr. Aaron Burton, a NASA Postdoctoral Program Fellow at NASA Goddard and a co-author on the study. “This led us to find several studies where researchers have exploited the crystallization behavior of molecules like aspartic acid to get left-handed or right-handed excesses. Because alanine forms different kinds of crystals, these same processes would produce equal amounts of left- and right-handed alanine. We need to do some more experiments, but this explanation has the potential to explain what we see in the Tagish Lake meteorite and other meteorites.”

The team believes a small initial left-hand excess could get amplified by crystallization and dissolution from a saturated solution with liquid water. Some amino acids, like aspartic acid, have a shape that lets them fit together in a pure crystal – one comprised of just left-handed or right-handed molecules. For these amino acids, a small initial left- or right-hand excess could become greatly amplified at the expense of the opposite-handed crystals, similar to the way a large snowball gathers more snow and gets bigger more rapidly when rolled downhill than a small one.

Other amino acids, like alanine, have a shape that prefers to join together with their mirror image to make a crystal, so these crystals are comprised of equal numbers of left- and right-handed molecules. As these “hybrid” crystals grow, any small initial excess would tend to be washed out for these amino acids. A requirement for both of these processes is a way to convert left-handed to right-handed molecules, and vice-versa, while they are dissolved in the solution.

This process only amplifies a small excess that already exists. Perhaps a tiny initial left-hand excess was created by conditions in the solar nebula. For example, polarized ultraviolet light or other types of radiation from nearby stars might favor the creation of left-handed amino acids or the destruction of right-handed ones, according to the team.

This initial left-hand excess could then get amplified in asteroids by processes like crystallization. Impacts from asteroids and meteorites could deliver this material to Earth, and left-handed amino acids might have been incorporated into emerging life due to their greater abundance, according to the team. Also, similar enrichments of left-handed amino acids by crystallization could have occurred on Earth in ancient sediments that had water flowing through them, such as the bottoms of rivers, lakes, or seas, according to the team.

The result complicates the search for extraterrestrial life – like microbial life hypothesized to dwell beneath the surface of Mars, for example. “Since it appears a non-biological process can create a left-hand excess in some kinds of amino acids, we can’t use such an excess alone as proof of biological activity,” says Glavin.

Astronomers Discover Impossible Binary Systems

This artist’s impression shows the tightest of the new record breaking binary systems.

 

Astronomers working with the United Kingdom Infrared Telescope on Hawaii have discovered four pairs of stars that orbit each other in less than 4 hours.

Until now it was thought that such close-in binary stars could not exist.

About half of the stars in our Milky Way galaxy are, unlike our Sun, part of a binary system in which two stars orbit each other. Most likely, the stars in these systems were formed close together and have been in orbit around each other from birth onwards. It was always thought that if binary stars form too close to each other, they would quickly merge into one single, bigger star. This was in line with many observations taken over the last three decades showing the abundant population of stellar binaries, but none with orbital periods shorter than 5 hours.

For the first time, the team has investigated binaries of red dwarfs, stars up to ten times smaller and a thousand times less luminous than the Sun. Although they form the most common type of star in the Milky Way, red dwarfs do not show up in normal surveys because of their dimness in visible light.

“To our complete surprise, we found several red dwarf binaries with orbital periods significantly shorter than the 5 hour cut-off found for Sun-like stars, something previously thought to be impossible”, said Dr Bas Nefs of Leiden Observatory in the Netherlands, lead author of a paper accepted for publication in the journal Monthly Notices of the Royal Astronomical Society. “It means that we have to rethink how these close-in binaries form and evolve.”

Since stars shrink in size early in their lifetime, the fact that these very tight binaries exist means that their orbits must also have shrunk as well since their birth, otherwise the stars would have been in contact early on and have merged. However, it is not at all clear how these orbits could have shrunk by so much.

One possible answer to this riddle is that cool stars in binary systems are much more active and violent than previously thought.

It is possible that the magnetic field lines radiating out from the cool star companions get twisted and deformed as they spiral in towards each other, generating the extra activity through stellar wind, explosive flaring and star spots. Powerful magnetic activity could apply the brakes to these spinning stars, slowing them down so that they move closer together.

“Without UKIRT’s superb sensitivity, it wouldn’t have been possible to find these extraordinary pairs of red dwarfs,” said co-author Dr David Pinfield of the University of Hertfordshire. “The active nature of these stars and their apparently powerful magnetic fields has profound implications for the environments around red dwarfs throughout our Galaxy.”

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Bibliographic information: Nefs SV et al. 2012. Four ultra-short period eclipsing M-dwarf binaries in the WFCAM Transit Survey. Accepted for publication in Mon. Not. R. Astron. Soc.; arXiv:1206.1200v1

Mystery Wave in Milky Way Galaxy Suggests Recent Crash

The Milky Way is seen in all its glory, as well as, in the lower right, the Large Magellanic Cloud.

A mysterious wave discovered in the Milky Way suggests our galaxy is still ringing like a bell from a galactic collision, a crash that possibly occurred within the last 100 million years, scientists say. Astronomers discovered that stars north and south of the midplane of the galaxy are distributed differently, suggesting that some recent event perturbed them. The most likely explanation is that a small satellite galaxy or clump of invisible dark matter plowed through the Milky Way, leaving behind the echoes that we see.

“Our part of the Milky Way is ringing like a bell,” Brian Yanny, of the Fermi National Accelerator Laboratory (Fermilab) in Batavia, Ill., said in a statement. “But we have not been able to identify the celestial object that passed through the Milky Way. It could have been one of the small satellite galaxies that move around the center of our galaxy, or an invisible structure such as a dark matter halo.”

The wave was discovered in data from the Sloan Digital Sky Survey, which has observed roughly 300,000 nearby Milky Way stars.

An illustration of our Milky Way galaxy noting its mass distribution. Scientists suspect a recent collision with a dwarf galaxy possibly as recent as 100 million years ago, created a mysterious wave in our galaxy. Image posted July 9, 2012.

“We have found evidence that our Milky Way had an encounter with a small galaxy or massive dark matter structure perhaps as recently as 100 million years ago,” said Larry Widrow, a professor at Queen’s University in Canada. “We clearly observe unexpected differences in the Milky Way’s stellar distribution above and below the Galaxy’s midplane that have the appearance of a vertical wave – something that nobody has seen before.”

About 60 miniature “dwarf galaxies” have been discovered orbiting the Milky Way. Theory suggests that many invisible dark matter satellites also circle our galaxy, though these would only be detectable by their gravitational pull.

It’s likely that one of these may have slammed into the Milky Way, though even that is not certain.

“The perturbation need not have been a single isolated event in the past, and it may even be ongoing,” said Susan Gardner of the University of Kentucky. “Additional observations may well clarify its origin.”

The research is detailed in a recent edition of the Astrophysical Journal Letters.