Friday, November 12, 2010

COLLECTING YOUR THOUGHTS: YOU CAN DO IT IN YOUR SLEEP!

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It is one thing to learn a new piece of information, such as a new phone number or a new word, but quite another to get your brain to file it away so it is available when you need it.

A new study published in the Journal of Neuroscience by researchers at the University of York and Harvard Medical School suggests that sleep may help to do both.

The scientists found that sleep helps people to remember a newly learned word and incorporate new vocabulary into their "mental lexicon".

During the study, which was funded by the Economic and Social Research Council, researchers taught volunteers new words in the evening, followed by an immediate test. The volunteers slept overnight in the laboratory while their brain activity was recorded using an electroencephalogram, or EEG. A test the following morning revealed that they could remember more words than they did immediately after learning them, and they could recognise them faster demonstrating that sleep had strengthened the new memories.

This did not occur in a control group of volunteers who were trained in the morning and re-tested in the evening, with no sleep in between. An examination of the sleep volunteers' brainwaves showed that deep sleep (slow-wave sleep) rather than rapid eye movement (REM) sleep or light sleep helped in strengthening the new memories.

When the researchers examined whether the new words had been integrated with existing knowledge in the mental lexicon, they discovered the involvement of a different type of activity in the sleeping brain. Sleep spindles are brief but intense bursts of brain activity that reflect information transfer between different memory stores in the brain -- the hippocampus deep in the brain and the neocortex, the surface of the brain.

Memories in the hippocampus are stored separately from other memories, while memories in the neocortex are connected to other knowledge. Volunteers who experienced more sleep spindles overnight were more successful in connecting the new words to the rest of the words in their mental lexicon, suggesting that the new words were communicated from the hippocampus to the neocortex during sleep.

Co-author of the paper, Professor Gareth Gaskell, of the University of York's Department of Psychology, said: "We suspected from previous work that sleep had a role to play in the reorganisation of new memories, but this is the first time we've really been able to observe it in action, and understand the importance of spindle activity in the process."

These results highlight the importance of sleep and the underlying brain processes for expanding vocabulary. But the same principles are likely to apply to other types of learning.

Lead author, Dr Jakke Tamminen, said: "New memories are only really useful if you can connect them to information you already know. Imagine a game of chess, and being told that the rule governing the movement of a specific piece has just changed. That new information is only useful to you once you can modify your game strategy, the knowledge of how the other pieces move, and how to respond to your opponent's moves. Our study identifies the brain activity during sleep that organizes new memories and makes those vital connections with existing knowledge."

University of York

EARTH'S FIRST GREAT PREDATOR WASN'T

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The meters-long, carnivorous "shrimp" from hell that once ruled the seas of Earth a half billion years ago may have been a real softy, it turns out. A new 3-D modeling of the mouth parts of the Anomalocaris, along with evidence that these parts were not hard like teeth, but flexible, shows that the famed predator could not have been munching on the hard shells of trilobites and other such creatures of the early seas.

What's more, there is no evidence from fossilized stomach contents or feces that Anomalocaris ate anything hard enough to leave a fossilized trace. In fact it was this lack of fossil evidence backing any dietary preference — right alongside other animals that do show fragments of what they ate in their gullets — which inspired the investigation, said paleontologist James "Whitey" Hagadorn of the Denver Museum of Nature & Science.

"It was supposed to roam around the Cambrian seas gobbling up trilobites and everything else," said Hagadorn. But the pineapple-like whorl of mouth parts and the associated whisker-like appendages of Anomalocaris all appear to have been bendable, in the fossil remains, he said. They are not mineralized like the exoskeletons of the trilobites they were supposedly eating.

His suspicions prompted Hagadorn to develop a 3-D, finite element analysis model of the Anomalocaris mouth. This allowed for testing just how the mouth worked and how much force it could create – in other words, how strong a bite it had. The model turned up some surprises.

"It couldn't even close its mouth," said Hagadorn. And there was no practical way these mouth parts could create the force needed to break open a modern lobster shell nor a shrimp shell, which were used as analogues for a trilobite carapace in the model.

Another interesting discovery made along the way came from studying more than 400 Anomalocaris mouths. In none of them did Hagadorn find any signs of wear. That's strange because if they were genuine teeth there would be chips, scratches and other signs they were being used to munch on hard-shelled animals.

The model, gut contents, feces, and wear all suggest Anomalocaris was not a trilobite eater. But they fail to help explain what this impressive beast from the Cambrian was eating.

"Maybe it ingested things and then spit them out," Hagadorn speculated. Another possibility is that it somehow broke down the food it was eating into very fine particles before ingesting it. At this point the only thing that appears certain is that the famed biggest predator of the early Cambrian is more mysterious than ever.

The Geological Society of America

TIME FOR A RAIN DANCE?

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In many areas of the world, including California's Mojave Desert, rain is a precious and rare resource. To encourage rainfall, scientists use "cloud seeding," a weather modification process designed to increase precipitation amounts by dispersing chemicals into the clouds.

But research now reveals that the common practice of cloud seeding with materials such as silver iodide and frozen carbon dioxide may not be as effective as it had been hoped. In the most comprehensive reassessment of the effects of cloud seeding over the past fifty years, new findings from Prof. Pinhas Alpert, Prof. Zev Levin and Dr. Noam Halfon of Tel Aviv University's Department of Geophysics and Planetary Sciences have dispelled the myth that seeding is an effective mechanism for precipitation enhancement.

The findings were recently reported in Atmospheric Research.

During the course of his study, Prof. Alpert and his colleagues looked over fifty years' worth of data on cloud seeding, with an emphasis on the effects of seeding on rainfall amounts in a target area over the Sea of Galilee in the north of Israel. The research team used a comprehensive rainfall database and compared statistics from periods of seeding and non-seeding, as well as the amounts of precipitation in adjacent non-seeded areas.

"By comparing rainfall statistics with periods of seeding, we were able to show that increments of rainfall happened by chance," says Prof. Alpert. "For the first time, we were able to explain the increases in rainfall through changing weather patterns" instead of the use of cloud seeding.

Most notable was a six year period of increased rainfall, originally thought to be a product of successful cloud seeding. Prof. Alpert and his fellow researchers showed that this increase corresponded with a specific type of cyclones which are consistent with increased rainfall over the mountainous regions. They observed that a similarly significant rain enhancement over the Judean Mountains, an area which was not the subject of seeding.

The researchers concluded that changing weather patterns were responsible for the higher amount of precipitation during these years. Their research method may be useful in the investigation of cloud seeding in the U.S. and other regions.

Despite being relatively expensive, there are more than 80 cloud seeding projects around the world, according to a recent World Meteorological Organization report. In Beijing, China, for example, Prof. Alpert notes, a large amount of chemical particles were introduced to the clouds to inhibit precipitation — a process called "overseeding" — to limit rainfall during the 2008 Olympics. Seeding is also used in the Sierra Mountains of California and in Wyoming to try to increase precipitation in the mountains, thus increasing water levels in reservoirs. However, he says, there is no proof that this method is successful.

The only probable place where cloud seeding could be successful, Alpert says, is when seeding is performed on orographic clouds, which develop over mountains and have a short lifespan. In this type of cloud, seeding could serve to accelerate the formation of precipitation.

(Photo: TAU)

Tel Aviv University

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