New research reveals that structure of the human brain has an almost ideal network of connections
Date: July 7, 2015 Source: Northeastern University
Have you ever wondered why the human brain evolved the way it did?
A new study by Northeastern physicist Dmitri Krioukov and his colleagues suggests an answer: to expedite the transfer of information from one brain region to another, enabling us to operate at peak capacity.
The paper, published in the July 3 issue of Nature Communications, reveals that the structure of the human brain has an almost ideal network of connections--the links that permit information to travel from, say, the auditory cortex (responsible for hearing) to the motor cortex (responsible for movement) so we can do everything from raise our hand in class in response to a question to rock out to the beat of The 1975.
The findings represent more than a confirmation of our evolutionary progress. They could have important implications for pinpointing the cause of neurological disorders and eventually developing therapies to treat them.
"An optimal network in the brain would have the smallest number of connections possible, to minimize cost, and at the same time it would have maximum navigability--that is, the most direct pathways for routing signals from any possible source to any possible destination," says Krioukov. It's a balance, he explains, raising and lowering his hands to indicate a scale. The study presents a new strategy to find the connections that achieve that balance or, as he puts it, "the sweet spot."
Krioukov, an associate professor in the Department of Physics, studies networks, from those related to massive Internet datasets to those defining our brains. In the new research, he and his co-authors used sophisticated statistical analyses based on Nobel laureate John Nash's contributions to game theory to construct a map of an idealized brain network--one that optimized the transfer of information. They then compared the idealized map of the brain to a map of the brain's real network and asked the question "How close are the two?"
Remarkably so. They were surprised to learn that 89 percent of the connections in the idealized brain network showed up in the real brain network as well. "That means the brain was evolutionarily designed to be very, very close to what our algorithm shows," says Krioukov.
The scientists' strategy bucks tradition: It lets function--in this case, navigability--drive the structure of the idealized network, thereby showing which links are essential for optimal navigation. Most researchers in the field, says Krioukov, build models of the real network first, and only then address function, an approach that does not highlight the most crucial links.
The new strategy is also transferable to a variety of disciplines. The study, whose co-authors are at the Budapest University of Technology and Economics, mapped six diverse navigable networks in total, including that of the Internet, U.S. air¬ports, and Hungarian roads. The Hungarian road network, for example, gave travelers the "luxury to go on a road trip without a map," the authors wrote.
Future applications of the research cross disciplines, too. Knowing what links in a network are the most critical for navigation tells you where to focus protective measures, whether the site is the Internet, roadways, train routes, or flight patterns.
"Conversely, if you're a good guy facing a terrorist network, you know what links to attack first," says Krioukov. A systems designer could locate the missing connections necessary to maximize the navigability of a computer network and add them.
In the brain, the links existing in the idealized network are likely those required for normal brain function, says Krioukov. He points to a maze of magenta and turquoise tangles coursing through a brain illustration in his paper and traces the magenta trail, which is present in both the ideal and real brains.
"So we suspect that they are the primary candidates to look at if some disease develops--to see if they are dam-aged or broken."
Looking to the future, he speculates that once such links are identified, new drugs or surgical techniques could perhaps be developed to target them and repair, or circumvent, the damage.
"At the end of the day, what we are trying to do is to fix the diseased network so that it can resume its normal function," says Krioukov.
First of its kind robot is inspired by nature, capable of multiple jumps Engineers at Harvard University and the University of California, San Diego, have created the first robot with a 3D-printed body that transitions from a rigid core to a soft exterior. The robot is capable of more than 30 untethered jumps and is powered by a mix of butane and oxygen. Researchers describe the robot’s design, manufacturing and testing in the July 10 issue of Science magazine.
Absurd Creature of the Week: The World’s Tiniest Bird Weighs Less Than a Dime
There’s a lot to be jazzed about in the rekindling of relations between the US and Cuba. It seems like a pretty nice island, after all. As travel restrictions lift, American beach types will get nice beaches, cigar types get nice cigars, and people who like both will get the opportunity to piss off fellow beachgoers. Almost everyone wins! Especially fans of biodiversity, for Cuba is an absolute gem, a place where conservation—not to mention the lack of ecosystem-ravaging capitalism—has preserved all manner of majestic creatures to gawk at.
Among these island wonders is the smallest bird in the world: the bee hummingbird. It weighs a mere 1/15 of an ounce—less than a dime—and builds nests the size of a quarter (sorry, all this talk of capitalism is getting to me). It hunts mosquitoes like a hawk would hunt a pigeon. And its eggs? They’re the size of coffee beans. The bee hummingbird is so tiny, it actually competes with insects for resources, as opposed to other birds. Oh, and it’s somewhat hyperactive, beating its wings up to 200 times per second.
Hummingbirds in general aren’t exactly known for their towering stature, but the shrinkage of the bee hummingbird is stunning. So why has this species gotten so much smaller than its peers? “You have in all communities on the Caribbean islands always two or three hummingbirds,” says ecologist Bo Dalsgaard of the University of Copenhagen. “If you go to the lowlands, there will be two hummingbirds, and if you go to the highlands there will be two hummingbirds. Always you find one large and one small hummingbird.”
The bee hummingbird’s larger counterpart in Cuba is the emerald hummingbird, which grows to more than twice its size (though it’s still quite small for a “large” hummingbird). Dalsgaard reckons the emerald got to the island first and set up shop, assuming the typical hummingbird niche of a nectar-feeding pollinator. “Later, the ancestor of the bee hummingbird arrived on Cuba and took up the role as the smaller of the two hummingbirds,” says Dalsgaard. “To avoid feeding competition with the Cuban emerald, it had to evolve to be an even smaller hummingbird, competing more with insects for nectar.”
So it shrank and shrank and shrank over evolutionary time to avoid running out of grub, targeting smaller flowers that the emerald hummingbird wouldn’t waste energy visiting. Even better, it’s never had much competition from insects, since pollinating bugs have a tough time traveling over water to colonize new island environments. The insect biodiversity just ain’t like it is on the mainland.
Yet the bee hummingbird is not alone in its teeniness. In fact, insular dwarfism, as it’s known, is pretty common. Over on Barbados, for instance, there’s an adorable snake that’s so small it can curl up on a quarter (sorry again), and its evolutionary story is much the same as the hummingbird’s. When the so-called threadsnake arrived on Barbados, it likely found an open niche that would typically go to something like a centipede. And perhaps the snake’s typical prey on the mainland never made it to the island. So like the bee hummingbird shrank down to exploit smaller flowers, the snake shrank down to exploit the larvae and eggs of social insects like ants and termites.
Dwarfism happens time and time again on islands, but being so tiny comes at a price, especially for a hummingbird, which already has quite the appetite to fuel its child-on-Red-Bull lifestyle. “It costs a lot of energy to be a small organism, because the metabolic rate and heat loss is relatively larger,” says Dalsgaard. “Hummingbirds must therefore feed very frequently, or go into torpor, a form of deep sleep, to save energy.”
While there haven’t been any good studies on bee hummingbird torpor, this trick is consistent across hummingbird species, so scientists can infer how it works in this little marvel. The bee hummingbird is likely liberal with its use of torpor given that hummingbirds burn a whole lot of energy to begin with, and this is the smallest and most energy-starved among them: Remember that it can beat its wings 200 times per second.
So like a functioning narcoleptic, the bee hummingbird is probably slipping into torpor whenever it gets the chance. “For instance, at night when they cannot feed, they would need to consume substantial amounts of energy to keep their body temperature,” says ecologist Ana Martín González at the University of California, Berkeley. There are even “records of hummingbirds in torpor during heavy rains, when they cannot feed (they do feed during light rain) and they are not likely to get preyed upon.”
On top of all that, the bee hummingbird has to worry about finding someone for sexy time at some point. When the mating season rolls around, the males’ plumage transforms from a beautiful bluish-green into an even more beautiful sort of red-pink helmet … veil … thing, shown at the top of this story. They form groups known as leks and sing their hearts out, with the females sometimes choosing several males to mate with.
When she lays two coffee-bean-sized eggs in her nest, she doesn’t want the father(s) anywhere near them, for the males’ shiny new outfits are wildly obvious to predators. And she herself is quite cautious around the eggs. “She doesn’t fly straight into the nest,” says González. “She perches close to it, then waits there for some time, until nothing is around and then goes to the nest.” The eggs hatch after about three weeks, and she feeds the chicks for three more weeks on nectar, supplemented with mosquitoes. And then they’re off into the world.
Thonis-Heracleion (the Egyptian and Greek names of the city) is a city lost between legend and reality. Before the foundation of Alexandria in 331 BC, the city knew glorious times as the obligatory port of entry to Egypt for all ships coming from the Greek world.
The Greek historian Herodotus (5th century BC) tells us of a great temple that was built where the famous hero Herakles first set foot on to Egypt.
More than four centuries after Herodotus’ visit to Egypt, the geographer Strabo observed that the city of Heracleion, which possessed the temple of Herakles, is located straight to the east of Canopus at the mouth of the Canopic branch of the River Nile.
GREAT SPIRITS ALWAYS ENCOUNTER THE MOST VIOLENT OPPOSITION FROM MEDIOCRE MINDS E=MC2