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31
EEE / Why animals have evolved to favor one side of the brain
« on: April 20, 2017, 02:09:51 PM »
Most left-handers can rattle off a list of their eminent comrades-in-arms: Oprah Winfrey, Albert Einstein, and Barack Obama, just to name three, but they may want to add on cockatoos, "southpaw" squirrels, and some house cats. "Handed-ness" or left-right asymmetry is prevalent throughout the animal kingdom, including in pigeons and zebrafish. But why do people and animals naturally favor one side over the other, and what does it teach us about the brain's inner workings? Researchers explore these questions in a Review published April 19 in Neuron.

"Studying asymmetry can provide the most basic blueprints for how the brain is organized," says lead author Onur Güntürkün, of the Institute of Cognitive Neuroscience at Ruhr-University Bochum, in Germany. "It gives us an unprecedented window into the wiring of the early, developing brain that ultimately determines the fate of the adult brain." Because asymmetry is not limited to human brains, a number of animal models have emerged that can help unravel both the genetic and epigenetic foundations for the phenomenon of lateralization.

Güntürkün says that brain lateralization serves three purposes. The first of those is perceptual specialization: the more complex a task, the more it helps to have a specialized area for performing that task. For example, in most people, the right side of the brain focuses on recognizing faces, while the left side is responsible for identifying letters and words.

The next area is motor specialization, which brings us to the southpaw. "What you do with your hands is a miracle of biological evolution," he says. "We are the master of our hands, and by funneling this training to one hemisphere of our brains, we can become more proficient at that kind of dexterity." Natural selection likely provided an advantage that resulted in a proportion of the population -- about 10% -- favoring the opposite hand. The thing that connects the two is parallel processing, which enables us to do two things that use different parts of the brain at the same time.

Brain asymmetry is present in many vertebrates and invertebrates. "It is, in fact, an invention of nature, which evolved because many animals have the same needs for specialization that we do," says Güntürkün, who is also currently a visiting fellow at the Stellenbosch Institute for Advanced Study in South Africa. Studies have shown that birds, like chickens, use one eye to distinguish grain from pebbles on the ground while at the same time using the other eye to keep watch for predators overhead.

Research on pigeons has shown that this specialization often is a function of environmental influences. When a pigeon chick develops in the shell, its right eye turns toward the outside, leaving its left eye to face its body. When the right eye is exposed to light coming through the shell, it triggers a series of neuronal changes that allow the two eyes to ultimately have different jobs.

A zebrafish model of lateralization, meanwhile, has enabled researchers to delve into the genetic aspects of asymmetrical development. Studies of important developmental pathways, including the Nodal signaling pathway, are uncovering details about how, very early in an embryo's development, the cilia act to shuffle gene products to one side of the brain or the other. By manipulating the genes in Nodal and other pathways, researchers can study the effects of these developmental changes on zebrafish behaviors.

Güntürkün says that this research can provide insight into the effects of asymmetry on brain conditions in humans. "There are almost no disorders of the human brain that are not linked to brain asymmetries," he says. "If we understand the ontogeny of lateralization, we can make a great leap to see how brain wiring early in the developmental process may go wrong in these pathological cases."

Story Source:

Materials provided by Cell Press. Note: Content may be edited for style and length.

Journal Reference:

Sebastian Ocklenburg et al. Ontogenesis of Lateralization. Neuron, April 2017 DOI: 10.1016/j.neuron.2017.02.045
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Cell Press. "Why animals have evolved to favor one side of the brain." ScienceDaily. ScienceDaily, 19 April 2017. <www.sciencedaily.com/releases/2017/04/170419131801.htm>.

32
The newly discovered super-Earth LHS 1140b orbits in the habitable zone around a faint red dwarf star named LHS 1140, in the constellation of Cetus (The Sea Monster)[1]. Red dwarfs are much smaller and cooler than the Sun and, although LHS 1140b is ten times closer to its star than the Earth is to the Sun, it only receives about half as much sunlight from its star as the Earth and lies in the middle of the habitable zone. The orbit is seen almost edge-on from Earth and as the exoplanet passes in front of the star once per orbit it blocks a little of its light every 25 days.

"This is the most exciting exoplanet I've seen in the past decade," said lead author Jason Dittmann of the Harvard-Smithsonian Center for Astrophysics (Cambridge, USA). "We could hardly hope for a better target to perform one of the biggest quests in science -- searching for evidence of life beyond Earth."

"The present conditions of the red dwarf are particularly favourable -- LHS 1140 spins more slowly and emits less high-energy radiation than other similar low-mass stars," explains team member Nicola Astudillo-Defru from Geneva Observatory, Switzerland [2].

For life as we know it to exist, a planet must have liquid surface water and retain an atmosphere. When red dwarf stars are young, they are known to emit radiation that can be damaging for the atmospheres of the planets that orbit them. In this case, the planet's large size means that a magma ocean could have existed on its surface for millions of years. This seething ocean of lava could feed steam into the atmosphere long after the star has calmed to its current, steady glow, replenishing the planet with water.

The discovery was initially made with the MEarth facility, which detected the first telltale, characteristic dips in light as the exoplanet passed in front of the star. ESO's HARPS instrument, the High Accuracy Radial velocity Planet Searcher, then made crucial follow-up observations which confirmed the presence of the super-Earth. HARPS also helped pin down the orbital period and allowed the exoplanet's mass and density to be deduced [3].

The astronomers estimate the age of the planet to be at least five billion years. They also deduced that it has a diameter 1.4 times larger than the Earth -- almost 18,000 kilometres. But with a mass around seven times greater than the Earth, and hence a much higher density, it implies that the exoplanet is probably made of rock with a dense iron core.

This super-Earth may be the best candidate yet for future observations to study and characterise its atmosphere, if one exists. Two of the European members of the team, Xavier Delfosse and Xavier Bonfils both at the CNRS and IPAG in Grenoble, France, conclude: "The LHS 1140 system might prove to be an even more important target for the future characterisation of planets in the habitable zone than Proxima b or TRAPPIST-1. This has been a remarkable year for exoplanet discoveries!" [4,5].

In particular, observations coming up soon with the NASA/ESA Hubble Space Telescope will be able to assess exactly how much high-energy radiation is showered upon LHS 1140b, so that its capacity to support life can be further constrained.

Further into the future -- when new telescopes like ESO's Extremely Large Telescope are operating -- it is likely that we will be able to make detailed observations of the atmospheres of exoplanets, and LHS 1140b is an exceptional candidate for such studies.

Notes

[1] The habitable zone is defined by the range of orbits around a star, for which a planet possesses the appropriate temperature needed for liquid water to exist on the planet's surface.

[2] Although the planet is located in the zone in which life as we know it could potentially exist, it probably did not enter this region until approximately forty million years after the formation of the red dwarf star. During this phase, the exoplanet would have been subjected to the active and volatile past of its host star. A young red dwarf can easily strip away the water from the atmosphere of a planet forming within its vicinity, leading to a runaway similar to that on Venus.

[3] This effort enabled other transit events to be detected by MEarth so that the astronomers could nail down the detection of the exoplanet once and for all.

[4] The planet around Proxima Centauri is much closer to Earth, but it probably does not transit its star, making it very difficult to determine whether it holds an atmosphere.

[5] Unlike the TRAPPIST-1 system, no other exoplanets around LHS 1140 have been found. Multi-planet systems are thought to be common around red dwarfs, so it is possible that additional exoplanets have gone undetected so far because they are too small.

Story Source:

Materials provided by ESO. Note: Content may be edited for style and length.

Journal Reference:

Jason A. Dittmann, Jonathan M. Irwin, David Charbonneau, Xavier Bonfils, Nicola Astudillo-Defru, Raphaëlle D. Haywood, Zachory K. Berta-Thompson, Elisabeth R. Newton, Joseph E. Rodriguez, Jennifer G. Winters, Thiam-Guan Tan, Jose-Manuel Almenara, François Bouchy, Xavier Delfosse, Thierry Forveille, Christophe Lovis, Felipe Murgas, Francesco Pepe, Nuno C. Santos, Stephane Udry, Anaël Wünsche, Gilbert A. Esquerdo, David W. Latham, Courtney D. Dressing. A temperate rocky super-Earth transiting a nearby cool star. Nature, 2017; 544 (7650): 333 DOI: 10.1038/nature22055
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ESO. "Newly discovered exoplanet may be best candidate in search for signs of life: Transiting rocky super-Earth found in habitable zone of quiet red dwarf star." ScienceDaily. ScienceDaily, 19 April 2017. <www.sciencedaily.com/releases/2017/04/170419131727.htm>.

33
Homing pigeons may share the human capacity to build on the knowledge of others, improving their navigational efficiency over time, a new Oxford University study has found.

The ability to gather, pass on and improve on knowledge over generations is known as cumulative culture. Until now humans and, arguably some other primates, were the only species thought to be capable of it.

Takao Sasaki and Dora Biro, Research Associates in the Department of Zoology at Oxford University, conducted a study testing whether homing pigeons can gradually improve their flight paths, over time. They removed and replaced individuals in pairs of birds that were given a specific navigational task. Ten chains of birds were released from the same site and generational succession was simulated with the continuous replacement of birds familiar with the route with inexperienced birds who had never flown the course before. The idea was that these individuals could then pass their experience of the route down to the next pair generation, and also enable the collective intelligence of the group to continuously improve the route's efficiency.

The findings, published in Nature Communications, suggest that over time, the student does indeed become the teacher. The pairs' homing performance improved consistently over generations -- they streamlined their route to be more direct. Later generation groups eventually outperformed individuals that flew solo or in groups that never changed membership. Homing routes were also found to be more similar in consecutive generations of the same chain of pigeon pairs than across them, showing cross-generational knowledge transfer, or a "culture" of homing routes.

Takao Sasaki, co-author and Research Fellow in the Department of Zoology said: 'At one stage scientists thought that only humans had the cognitive capacity to accumulate knowledge as a society. Our study shows that pigeons share these abilities with humans, at least to the extent that they are capable of improving on a behavioural solution progressively over time. Nonetheless, we do not claim that they achieve this through the same processes.'

When people share and pass knowledge down through generations, our culture tends to become more complex over time, There are many good examples of this from manufacturing and engineering. By contrast, when the process occurs between homing pigeons, the end result is an increase in the efficiency, (in this case navigational), but not necessarily the complexity, of the behaviour.

Takao Sasaki added: 'Although they have different processes, our findings demonstrate that pigeons can accumulate knowledge and progressively improve their performance, satisfying the criteria for cumulative culture. Our results further suggest that cumulative culture does not require sophisticated cognitive abilities as previously thought.'

This study shows that collective intelligence, which typically focuses on one-time performance, can emerge from accumulation of knowledge over time.

Dora Biro, co-author and Associate Professor of Animal Behaviour concludes: 'One key novelty, we think, is that the gradual improvement we see is not due to new 'ideas' about how to improve the route being introduced by individual birds. Instead, the necessary innovations in each generation come from a form of collective intelligence that arises through pairs of birds having to solve the problem together -- in other words through 'two heads being better than one'.'

Moving forward, the team intend to build on the study by investigating if a similar style of knowledge sharing and accumulation occurs in other multi-generational species' social groups. Many animal groups have to solve the same problems repeatedly in the natural world, and if they use feedback from past outcomes of these tasks or events, this has the potential to influence, and potentially improve, the decisions the groups make in the future.

Story Source:

Materials provided by University of Oxford. Note: Content may be edited for style and length.

Journal Reference:

Takao Sasaki, Dora Biro. Cumulative culture can emerge from collective intelligence in animal groups. Nature Communications, 2017; 8: 15049 DOI: 10.1038/ncomms15049
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University of Oxford. "Homing pigeons share our human ability to build knowledge across generations." ScienceDaily. ScienceDaily, 18 April 2017. <www.sciencedaily.com/releases/2017/04/170418094512.htm>.
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35
EEE / Water is streaming across Antarctica
« on: April 20, 2017, 12:54:52 PM »
In the first such continent-wide survey, scientists have found extensive drainages of meltwater flowing over parts of Antarctica's ice during the brief summer. Researchers already knew such features existed, but assumed they were confined mainly to Antarctica's fastest-warming, most northerly reaches. Many of the newly mapped drainages are not new, but the fact they exist at all is significant; they appear to proliferate with small upswings in temperature, so warming projected for this century could quickly magnify their influence on sea level. An accompanying study looks at how such systems might influence the great ice shelves ringing the continent, which some researchers fear could collapse, bringing catastrophic sea-level rises. Both studies appear this week in the leading scientific journal Nature.

Explorers and scientists have documented a few Antarctic melt streams starting in the early 20th century, but no one knew how extensive they were. The authors found out by systematically cataloging images of surface water in photos taken from military aircraft from 1947 onward, and satellite imagery from 1973 on. They found nearly 700 seasonal systems of interconnected ponds, channels and braided streams fringing the continent on all sides. Some run as far as 75 miles, with ponds up to several miles wide. They start as close as 375 miles from the South Pole, and at 4,300 feet above sea level, where liquid water was generally thought to be rare to impossible.

"This is not in the future -- this is widespread now, and has been for decades," said lead author Jonathan Kingslake, a glaciologist at Columbia University's Lamont-Doherty Earth Observatory. "I think most polar scientists have considered water moving across the surface of Antarctica to be extremely rare. But we found a lot of it, over very large areas." The data are too sparse in many locations for the researchers to tell whether the extent or number of drainages have increased over the seven decades covered by the study. "We have no reason to think they have," said Kingslake. "But without further work, we can't tell. Now, looking forward, it will be really important to work out how these systems will change in response to warming, and how this will affect the ice sheets."

Many of the newly mapped drainages start near mountains poking through glaciers, or in areas where powerful winds have scoured snow off underlying bluish ice. These features are darker than the mostly snow-covered ice sheet, and so absorb more solar energy. This causes melting, and on a slope, liquid water then melts a path downhill through overlying snow. If the continent warms this century as projected, this process will occur on a much larger scale, say the authors. "This study tells us there's already a lot more melting going on than we thought," said coauthor Robin Bell, a Lamont-Doherty polar scientist. "When you turn up the temperature, it's only going to increase."

Antarctica is already losing ice, but the direct effects of meltwater, which generally refreezes in winter, are probably negligible for now. The concern among glaciologists is that this could change in the future. Most loss right now is taking place near the edges, where giant, floating shelves of ice attached to the land are being eroded from underneath by warming ocean currents. The shelves, which ring three-quarters of Antarctica, help hold back the land-bound glaciers behind them, and as they lose mass, glaciers appear to be accelerating their march to the sea.

The most dramatic example is the Antarctic Peninsula, which juts far north from the main ice sheet, and where average temperatures have soared 7 degrees Fahrenheit in the last 50 years. In 1995 and 2002, large chunks of the peninsula's Larsen Ice Shelf suddenly disintegrated into the ocean within days. Scientists now suspect that pooling water was at work; liquid tends to burrow down, fracturing the ice with heat or pressure, or both, until a shattering point is reached. Today, another giant piece of the Larsen is cracking, and could come apart at any time.

Further south, temperatures have remained more or less stable, but many of the newly spotted streams there already make their way from the interior out onto ice shelves, or originate on the shelves themselves. That raises the specter that such collapses could happen across much vaster reaches of Antarctica this century, should warming proceed as expected, said Kingslake.

On the other hand, an accompanying study led by Bell found that a longtime drainage on West Antarctica's Nansen Ice Shelf may actually be helping keep the shelf together. The elaborate river-like system on the 30-mile-long shelf was first observed in 1909, by a team from the expedition led by British explorer Ernest Shackleton. Aerial imagery and remote sensing since then shows it has remained remarkably stable, efficiently draining excess meltwater during summer through a series of deep sinkholes and a roaring 400-foot-wide waterfall into the ocean. "It could develop this way in other places, or things could just devolve into giant slush puddles," said Bell. "Ice is dynamic and complex, and we don't have the data yet."

Near the other pole, seasonal melt streams and ponds are far more common on the fast-warming Greenland ice sheet, and their growing influence may hold lessons. In recent years as much as 90 percent of Greenland's ice surface has undergone some degree of seasonal melting. Much of the water probably stays at or near the surface and refreezes in winter. But in some areas, it is plunging through deep holes to underlying rock, lubricating glaciers' slide to the sea. In others, water may be refreezing near the surface into solid sheets that can more easily channel surface melt to the sea in succeeding seasons. Until recently, icebergs discharged from glaciers were Greenland's main contributor to sea-level rise. But between 2011 and 2014, 70 percent of the 269 million tons of Greenland's ice and snow lost to the ocean came directly from meltwater, not icebergs.

Antarctica's visible drainages may be the tip of the proverbial iceberg. Another study by a separate team published in January revealed that East Antarctica's Roi Baudouin Ice Shelf harbors a largely invisible liquid drainage just under the snow. The team, led by Utrecht University polar scientist Jan Lenaerts, detected it using radar images and drilling. They suspect that such features lurk in many places. And unlike surface streams, these ones are insulated, so may stay liquid year-round.

Helen Fricker, a glaciologist at Scripps Institution of Oceanography who was not involved the new studies, said of the continent-wide survey, "We knew there were other [melt] zones, but we didn't know exactly how extensive they are. This is a really nice study, as it does just that." Douglas MacAyeal, a glaciologist at the University of Chicago also not involved in the studies, said that until recently, "nobody's been that interested in melting," because most scientists thought it was relatively rare. Now, he said, "We're working hard to figure out if this stuff is relevant to sea-level predictions."

Video:


Story Source:

Materials provided by Lamont-Doherty Earth Observatory, Columbia University. Original written by Kevin Krajick. Note: Content may be edited for style and length.

Journal References:

Jonathan Kingslake, Jeremy C. Ely, Indrani Das, Robin E. Bell. Widespread movement of meltwater onto and across Antarctic ice shelves. Nature, 2017; 544 (7650): 349 DOI: 10.1038/nature22049
Robin E. Bell, Winnie Chu, Jonathan Kingslake, Indrani Das, Marco Tedesco, Kirsty J. Tinto, Christopher J. Zappa, Massimo Frezzotti, Alexandra Boghosian, Won Sang Lee. Antarctic ice shelf potentially stabilized by export of meltwater in surface river. Nature, 2017; 544 (7650): 344 DOI: 10.1038/nature22048
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Lamont-Doherty Earth Observatory, Columbia University. "Water is streaming across Antarctica: New survey finds liquid flow more widespread than thought." ScienceDaily. ScienceDaily, 19 April 2017.

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