No dream: Electric brain stimulation during sleep can boost memory

When you sleep, your brain is busy storing and consolidating things you learned that day, stuff you'll need in your memory toolkit tomorrow, next week, or next year. For many people, especially those with neurological conditions, memory impairment can be a debilitating symptom that affects every-day life in profound ways. For the first time, UNC School of Medicine scientists report using transcranial alternating current stimulation, or tACS, to target a specific kind of brain activity during sleep and strengthen memory in healthy people.

The findings, published in the journal Current Biology, offer a non-invasive method to potentially help millions of people with conditions such as autism, Alzheimer's disease, schizophrenia, and major depressive disorder.

For years, researchers have recorded electrical brain activity that oscillates or alternates during sleep; they present as waves on an electroencephalogram (EEG). These waves are called sleep spindles, and scientists have suspected their involvement in cataloging and storing memories as we sleep.

"But we didn't know if sleep spindles enable or even cause memories to be stored and consolidated," said senior author Flavio Frohlich, PhD, assistant professor of psychiatry and member of the UNC Neuroscience Center. "They could've been merely byproducts of other brain processes that enabled what we learn to be stored as a memory. But our study shows that, indeed, the spindles are crucial for the process of creating memories we need for every-day life. And we can target them to enhance memory."

This marks the first time a research group has reported selectively targeting sleep spindles without also increasing other natural electrical brain activity during sleep. This has never been accomplished with tDCS -- transcranial direct current stimulation -- the much more popular cousin of tACS in which a constant stream of weak electrical current is applied to the scalp.

During Frohlich's study, 16 male participants underwent a screening night of sleep before completing two nights of sleep for the study.

Before going to sleep each night, all participants performed two common memory exercises -- associative word-pairing tests and motor sequence tapping tasks, which involved repeatedly finger-tapping a specific sequence. During both study nights, each participant had electrodes placed at specific spots on their scalps. During sleep one of the nights, each person received tACS -- an alternating current of weak electricity synchronized with the brain's natural sleep spindles. During sleep the other night, each person received sham stimulation as placebo.

Each morning, researchers had participants perform the same standard memory tests. Frohlich's team found no improvement in test scores for associative word-pairing but a significant improvement in the motor tasks when comparing the results between the stimulation and placebo night.

"This demonstrated a direct causal link between the electric activity pattern of sleep spindles and the process of motor memory consolidation." Frohlich said.

Caroline Lustenberger, PhD, first author and postdoctoral fellow in the Frohlich lab, said, "We're excited about this because we know sleep spindles, along with memory formation, are impaired in a number of disorders, such as schizophrenia and Alzheimer's. We hope that targeting these sleep spindles could be a new type of treatment for memory impairment and cognitive deficits."

Frohlich said, "The next step is to try the same intervention, the same type of non-invasive brain stimulation, in patients that have known deficits in these spindle activity patterns."

Frohlich's team previously used tACS to target the brain's natural alpha oscillations to boost creativity. This was a proof of concept. It showed it was possible to target these particular brain waves, which are prominent as we create ideas, daydream, or meditate. These waves are impaired in people with neurological and psychiatric illnesses, including depression.

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The above post is reprinted from materials provided by University of North Carolina Health Care. Note: Materials may be edited for content and length.

Astronomers discover dizzying spin of the Milky Way galaxy's 'halo'

Astronomers at the University of Michigan's College of Literature, Science, and the Arts (LSA) discovered for the first time that the hot gas in the halo of the Milky Way galaxy is spinning in the same direction and at comparable speed as the galaxy's disk, which contains our stars, planets, gas, and dust. This new knowledge sheds light on how individual atoms have assembled into stars, planets, and galaxies like our own, and what the future holds for these galaxies.

"This flies in the face of expectations," says Edmund Hodges-Kluck, assistant research scientist. "People just assumed that the disk of the Milky Way spins while this enormous reservoir of hot gas is stationary -- but that is wrong. This hot gas reservoir is rotating as well, just not quite as fast as the disk."

The new NASA-funded research using the archival data obtained by XMM-Newton, a European Space Agency telescope, was recently published in theAstrophysical Journal. The study focuses on our galaxy's hot gaseous halo, which is several times larger than the Milky Way disk and composed of ionized plasma.

Because motion produces a shift in the wavelength of light, the U-M researchers measured such shifts around the sky using lines of very hot oxygen. What they found was groundbreaking: The line shifts measured by the researchers show that the galaxy's halo spins in the same direction as the disk of the Milky Way and at a similar speed -- about 400,000 mph for the halo versus 540,000 mph for the disk.

"The rotation of the hot halo is an incredible clue to how the Milky Way formed," said Hodges Kluck. "It tells us that this hot atmosphere is the original source of a lot of the matter in the disk."

Scientists have long puzzled over why almost all galaxies, including the Milky Way, seem to lack most of the matter that they otherwise would expect to find. Astronomers believe that about 80% of the matter in the universe is the mysterious "dark matter" that, so far, can only be detected by its gravitational pull. But even most of the remaining 20% of "normal" matter is missing from galaxy disks. More recently, some of the "missing" matter has been discovered in the halo. The U-M researchers say that learning about the direction and speed of the spinning halo can help us learn both how the material got there in the first place, and the rate at which we expect the matter to settle into the galaxy.

"Now that we know about the rotation, theorists will begin to use this to learn how our Milky Way galaxy formed -- and its eventual destiny," says Joel Bregman, a U-M LSA professor of astronomy.

"We can use this discovery to learn so much more -- the rotation of this hot halo will be a big topic of future X-ray spectrographs," Bregman says.

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The above post is reprinted from materials provided by NASA/Goddard Space Flight Center. Note: Materials may be edited for content and length.

Before animals, evolution waited eons to inhale

A couple of times in four billion years, evolution has slowed to a crawl. And an eon or so has passed before more complex life forms, such as simple animals, could arise.

Evolution may have been waiting for a decent breath of oxygen, said researcher Chris Reinhard. And that was hard to come by. His research team is tracking down O2 concentrations in oceans, where earliest animals evolved.

By doing so, they have jumped into the middle of a heated scientific debate on what rising oxygen did, if anything, to charge up evolutionary eras. Reinhard, a geochemist from the Georgia Institute of Technology, is shaking up conventional thinking with the help of computer modeling.

Smash the beaker

That thinking goes like this: "Atmospheric oxygen had a value of 'x' back then, and so we just assume that the whole ocean is a beaker that equilibrates with that value," Reinhard said. Then all evolving animals everywhere had the selfsame concentration of oxygen to live on.

But oceans are expansive and asymmetrical; deep here, shallower there, frosty at the poles, soupy at the girth. Turbulences, streams and temperatures distribute sediment, algae, salt -- and gases like oxygen -- into lopsided stores.

Oceans leave some areas teeming and others vacuous. Then they reshuffle their loads. Even today, concentrations of dissolved oxygen vary widely from ocean region to ocean region.

Equating the global ocean to a placid lab beaker? "This is an okay thought experiment to start with, but I think everybody would acknowledge over a beer that it's simplistic," said Reinhard, an assistant professor at Georgia Tech's School of Earth and Atmospheric Sciences.

Create a stir

So, he and his team modeled how oxygen entered oceans from the atmosphere and from aquatic sources, and how oceans might have shuffled it around during the mid to late Proterozoic Eon. That was 0.6 to 1.8 billion years ago, when Earth's atmosphere had only fraction of the breathable oxygen it does today.

In the model, the ocean didn't share and share alike, but instead pushed dissolved O2 into areas of concentration that shifted starkly as corresponding concentrations in the atmosphere rose.

That has implications for the way scientists think about the timeframe for animal evolution on Earth and for future estimates for the probability of complex life on exoplanets.

The results and detailed modeling parameters appear in the Proceedings of the National Academy of Sciences. The research was funded by the National Science Foundation and the NASA Astrobiology Institute.

Be unreliable

Humans and today's large animals would quickly suffocate in a Proterozoic-like world. And according to Reinhard's research, its oceans may not have been as conducive to evolution as previously thought.

"What really matters for the early evolution of animals is ocean oxygen. To a certain degree, it's really shallow sea floor oxygen that matters," Reinhard said.

Those ocean shallows are called benthic regions, and in the Proterozoic Eon, they received plenty of sunlight and nutrients key to evolution. Even today, they're teeming with life, which makes them popular places for snorkeling and fishing.

But the new model shows oxygen levels there may have been unreliable during the mid to late Proterozoic Eon.

Rob the rich

Earliest metazoans, the term for multicellular beings that are animals, may have done alright with scarce amounts and survived O2 droughts -- periods of anoxia. But they also evolved into a world of rising breathable oxygen.

Reinhard's computational model accounted for scenarios from atmospheric oxygen concentrations of 0.5 to 10 percent of today's levels.

At low concentrations, the simulation showed oceanic oxygen building up around the equator, where hot spots in the water produced higher amounts of it. Then -- as the atmosphere began filling with oxygen -- in the oceans, it shifted toward the poles, where cold water was able to hold on to more of it.

Formerly oxygen-rich regions were robbed of conditions friendly to animal evolution.

In the beaker way of thinking, higher atmospheric oxygen should have meant evenly rising levels of oceanic oxygen for animals evolving everywhere, even in those depleted regions. "In reality, the ecology they would have been facing would have been pretty severe," Reinhart said.

Follow dead animals

Reinhard's team could have framed the study around other organisms but chose metazoans. "We focused on animals principally because that's where we have the best empirical constraints for the oxygen levels that the organisms need," he said.

Their evolution also left behind a calendar convenient to scientific study -- a progressive fossil record that became more complex as oxygen levels rose.

In Earth's roughly 3.7-billion-year history of life, animals turned up in about the most recent third. Furry, feathery and even scaly animals have only appeared in the last few hundred million years.

As oxygen became plentiful, critters got bigger, smarter, faster, and became predators and prey. Pursuit and flight accelerated as gasping lungs and gills pulled in more of the powerful oxidant to exponentially boost metabolism.

Evolution went into overdrive, diversifying the fossil record over time. But dive back down into it a billion or so years, to the mid to late Proterozoic, and animal fossils get smaller and simpler. You find little, squishy sponges and jellyfish.

Think (eco)logically

Their stony imprints mark the beginnings of that very complex evolution, and they may point to oxygen concentrations at the time.

"We were focusing on changes in atmospheric oxygen during the time period in which animals appear in the fossil record and trying to link that quantitatively to the oxygen levels early animals would have needed," Reinhard said.

His computational oxygen distribution model was based on the current constellation of Earth's continents -- vastly different from that of the Proterozoic Eon.

But Reinhard said that difference would not change the conclusions. And the concepts they support should also apply to predictions about life on exoplanets with differing continental structures.

"The basic take-home -- that we need to be thinking ecologically rather than just in terms of a single oxygen level -- is going to prove to be pretty robust," he said.

That beaker? May have just flown out the window.

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The above post is reprinted from materials provided by Georgia Institute of Technology. Note: Materials may be edited for content and length.