Is Your Brain Sleeping While You're Awake?

If you think you can function on minimal sleep, here's a wake-up call: Parts of yourbrainmay doze off even if you're totally awake, according to a new study in rats.

Scientists observed the electrical activity of brains in rats forced to stay up longer than usual. Problem-solving brain regions fell into a kind of"local sleep"—a condition likely in sleep-deprived humans too, the study authors say.

Surprisingly, when sections of the rats' brains entered these sleeplike states,"you couldn't tell that {the rats} are in any way in a different state of wakefulness,"said study co-authorGiulio Tononi, a neuroscientist at the University of Wisconsin, Madison.

Despite these periods of local sleep, overall brain activity—and the rats’ behaviors—suggested the animals were fully awake.

This phenomenon of local sleep is"not just an interesting observation of unknown significance,"Tononi said. It"actually affects behavior—you make a mistake."

For example, when the scientists had the rats perform a challenging task—using their paws to reach sugar pellets—the sleep-deprived animals had trouble completing it.

(See"Secrets of Sleeping Soundly Uncovered.")

Sleep Allows Neurons to Reset?

Tononi and colleagues recorded the electrical activity of lab rats via electroencephalogram (EEG) sensors connected to the rodents' heads.
As predicted, when the rats were awake, their neurons—nerve cells that collect and transmit signals in the brain—fired frequently and irregularly.

When the animals slept, their neurons fired less often, usually in a regular up-and-down pattern that manifests on the EEG as a"slow wave."Called non-rapid eye movement, this sleep stage accounts for about 80 percent of all sleep in both rats and people.

The researchers used toys to distract the rats into staying awake for a few hours—normally"rats take lots of siestas,"Tononi noted.

The team discovered that neurons in two sections of these overtired rats' cerebral cortexes entered a slow-wave stage that is essentially sleep.

Why Do We Sleep?

It's unknown why parts of an awake brain nod off, though it may have something to do with why mammals sleep—still an open question, said Tononi, whose study appears tomorrow in the journalNature.(Read aboutmysteries of why we sleep inNational Geographicmagazine.)

According to one leading theory, since neurons are constantly"recording"new information, at some point the neurons need to"turn off"in order to reset themselves and prepare to learn again.

"If this hypothesis is correct, that means that at some point {if you're putting off sleep} you're beginning to overwhelm your neurons—you are reaching the limit of how much input they can get."

(See"Sleep Cherry-picks Memories, Boosts Cleverness.")

So the neurons"take the rest, even if they shouldn't"—and there's a price to pay in terms of making"stupid"errors, he said.

(Seebrain pictures.)

Even"Alert"People Make Mistakes

Sleep deprivation may have dangerous consequences, Tononi said—and those mistakes may become more common.

For one, many people are getting fewer z's. In 2008 about 29 percent of U.S. adults reported sleeping fewer than seven hours per night, and 50 to 70 million had chronic sleep and wakefulness disorders, according to theU.S. Centers for Disease Control and Prevention. Adults generally need about seven to nine hours of sleep a day,according to the National Sleep Foundation.

(TakeNational Geographicmagazine's sleep quiz.)

What's more, you don't need to feel sleepy to screw up, Tononi emphasized.

"Even if you may feel that you're fit and fine and are holding up well,"he said,"some parts of your brain may not {be} ... and those are the ones that make judgments and decisions."

National Geographic News

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Pictures: Fire Ant Swarms Form Living Life Rafts

When a city floods, humans stack sandbags and raise levees. When a fire ant colony floods, the ants link up to form a literal life raft, such as the one pictured. Now, new research shows exactly how the ants manage this feat.

Engineering professor David Hu and graduate student Nathan J. Mlot atGeorgia Institute of Technologyhad heard reports of ant rafts in the wild that last for weeks. (Watch a fire ant video.)

"They'll gather up all the eggs in the colony and will make their way up through the underground network of tunnels, and when the flood waters rise above the ground, they'll link up together in these massive rafts,"Mlot said. Together with Georgia Tech systems-engineering professor Craig Tovey, the scientists collected fire ants and dunked clumps of them in water to see what would happen.

In less than two minutes the ants had linked"hands"to form a floating structure that kept all the insects safe. Even the ants down below can survive this way, thanks to tiny hairs on the ants' bodies that trap a thin layer of air.

"Even when they're on the bottom of the raft, they never technically become submerged,"Mlot said.

The fire ant life raft research is described in the April 25 issue of the Proceedings of the National Academy of Sciences.

—Rachel Kaufman

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Odd Animal Deaths, Deformities Linked to Gulf Oil Spill?

On the first anniversary of theGulf oil spill, scientists are observing strange deaths and deformities in animals that could be related to the disaster, experts say.

In the past six months, the numbers of dolphin and sea turtle deaths in theGulf of Mexico (map)have risen, and some fish that inhabit the Gulf'scoral reefshave developed abnormalities. (Read more about the Gulf oil spill anniversary.)

Yet projects to document and measure the oil's effects on Gulf marine life are still in the very early stages, scientists caution. Preliminary results may not be available for months, and it may be several years before any kind of scientific consensus is reached.

(See an interactive of the Gulf's layers of life inNational Geographicmagazine.)

Such uncertainty is not unusual for oil-spill studies, notedWilliam Patterson, a marine biologist at the University of West Florida (UWF) in Pensacola.

"If you look at the literature surrounding theExxon Valdezoil spill {in 1989}, there are still some unknowns associated with that,"Patterson said.

"What we know {in the case ofExxon Valdez} is that there was an insult to the system, that there were effects on the food web and ecosystem, and that some species have not recovered to the levels they were at before."(Related:"Exxon ValdezAnniversary: 20 Years Later, Oil Remains.")

Some of theExxon Valdezoil's effects are circumstantial evidence, he added,"but it's pretty compelling evidence."

Mysterious Spike in Dolphin, Turtle Deaths

This winter, an alarmingly high number ofbottlenose dolphins—113 at last count—washed up dead on U.S. shores, according to theNational Oceanic and Atmospheric Administration (NOAA). The agency confirmed in early April that six of the bodies hadDeepwater Horizonoil on them.

(Read more:"Dolphin-Baby Die-Off in Gulf Puzzles Scientists.")

"What's important to note, however, is that even though they have this oil on them, it may not be the cause of death,"Blair Mase, NOAA's marine-mammal investigations coordinator, told reporters at a news briefing April 7.

"That's something the investigative team and our working groups are looking into."

So far this year scientists have also seen a rise in deaths of various species of Gulf sea turtle hatchlings. But NOAA researchers say the culprits may be contact with boats and fishing gear and possibly poisoning by toxins in algal blooms, which naturally appear in the Gulf each spring.

"The carcasses that we have looked at . . . had no visible oil on them,"said Barbara Schroeder, national sea turtle coordinator for NOAA.

(Relatedpictures:"Baby Gulf Turtles Released Into Atlantic.")

Fish Found With Deformed Ovaries, Missing Fins

Meanwhile, other researchers are looking for effects of the oil on other marine species, such asfish, crustaceans, andcorals.

UWF's Patterson has recently observed an increase in physical abnormalities consistent with oil exposure in red snappers that live in Gulf coral reefs.

"There are parasites showing up on the fish. They're always present, but this fall and winter we're seeing them in what appears to be higher abundances,"Patterson said.

Some of the fish are suffering so severely from a disease called fin rot that entire fins are missing—something Patterson said he has never seen before. Some female red snappers also have been discovered with hardened or deformed ovaries.

(Also see"Sex-Changing Chemicals Can Wipe Out Fish, Study Shows.")

Other red snappers have strange pigmentation issues, Patterson said."We have some images of red snappers sent to us by commercial fishermen that have black bands across the sides of the fish that is discolored skin."

These symptoms are not unusual in themselves, Patterson said, but the fact that they're appearing at what looks to be increased rates at the same time concerns him.

"Some of these things that we're seeing are classic symptoms of hydrocarbon exposure that have been documented in lab studies."

For example, the odd pigmentation could be caused by the fish's kidney or bile duct being affected or clogged by oil components.

"So it does seem to be pointing in one direction, but we don't have anything definitive yet to tell the full story."

Chuck Jagoe, an environmental toxicologist at Florida A&M University in Tallahassee, is working with Patterson to test Gulf red snappers for telltale enzymes that are produced when the fish flush toxic oil components from their bodies.

"These enzymes are associated with the detoxification process,"Jagoe said.

"They can give us an indication that the animal has not only been exposed to {oil} compounds, but that the compound is having some kind of biological effect."

Jagoe has just begun testing the fish, and the first results won't be available until at least early summer.

One Species Not Enough Evidence

UWF's Patterson said he also plans to investigate whether other Gulf species are exhibiting symptoms similar to those of the snappers.

Even nearly a year after the disaster, oil could still be lurking in the Gulf's waters, he added.

"Oil is not one thing,"Patterson said."It's thousands of organic compounds. Some of them are fairly {unstable} and microbes break them down very quickly, while others could persist for a long time."

(See"Why the Gulf Oil Spill Isn't Going Away.")

Finding other affected species will be crucial to making a case that the oil spill is having a systemic effect on Gulf fish species, saidProsanta Chakrabarty, a fish biologist at Louisiana State University in Baton Rouge who was not involved in the snapper project.

"With one species, we can't really tell,"Chakrabarty said.

He also noted that red snappers are already a vulnerable species due tooverfishing, and that it's possible the symptoms that Patterson is seeing are due to inbreeding caused by a decreased population.

Whatever the cause of the deformities, though,"the oil spill didn't help any,"he said.

Fish Populations Measured via GPS

Chakrabarty is involved in another project calledDepthmap, which aims to use fish-population data collected using GPS technology before and after the spill to investigate the Gulf oil spill's impact on marine life. Museum records are also used to fill out pre-spill data.

"If, for example, 80 percent of Gulf pancake batfishes were found off the coast of Louisiana and they're not there anymore,"then that could be an indication the spill negatively affected the species, he said.

(See"Two New 'Walking' Batfish Species Found.")

And if this pattern is repeated for many fish species, it would indicate the spill has had a pervasive impact on Gulf marine life.

Chakrabarty's team hopes to gather pre- and post-spill population data for 600 fish species in the northern Gulf, but has only begun analysis for a fraction of that number due to limited funding.

His early results suggest that of the 53 species examined so far, 43 had major populations that lived in regions that were in the path of the spill.

Deep-Sea Effects Leave Scientists in the Dark

Even if Depthmap's goals were met, however, scientists would still know only about the impact the spill had on fish that live in relatively shallow water. But the spill's largest potential damage is to deep-sea creatures, Chakrabarty said. (See pictures of deep-sea animals.)

The broken wellhead blew at 5,000 feet (1,500 meters) underwater, and plumes of gushing oil floated nearly 1 mile (1.6 kilometers) up from the seafloor, polluting different layers of water as they rose.

"We knew that the oil wouldn't last at the surface for very long, but what happened at the deep sea?"Chakrabarty said.

Of particular concern, he added, are the effects of the oil dispersants piped into the waters near the wellhead in a desperate bid to break apart the oil before it reached the surface.

"The deep sea is such a stable environment. . . . It isn't used to perturbations like this influx of {dispersants},"Chakrabarty said.

"So what the impact {is} of having {dispersants} enter that area, even momentarily, is difficult to understand."

(See"Gulf Spill Dispersants Surprisingly Long-lasting.")

Despite his concerns about the deformed fish, UWF's Patterson added that it's important for scientists not to jump to conclusions.

"As scientists, we shouldn't be unwilling to say we're not quite sure,"he said.

"Instead of going out on a limb and making grand announcements, I think it's a safer approach to say, Well, these are issues that we're seeing that we're not able to attribute to any one thing, but we're concerned about them.

"And that's where we are."

*The photographer, a commercial fisher in the Gulf, requested to remain anonymous.

forNational Geographic News

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Gulf Spill Photos: 9 Animal Victims—Plus 2 Survivors

Abottlenose dolphinbreaks the oily surface ofChandeleur Sound, Louisiana (see map), on May 6, 2010, two weeks after an explosion at theDeepwater Horizonoil rig sent crude gushing into the Gulf of Mexico.

Oil, gas, and chemical dispersants contaminated thousands of square miles of marine and coastal habitat. Many animals were killed or sickened outright, but on the one-year anniversary of theGulf oil spill, scientists still don't know the extent of the spill's effects on most species.

(See:"Gulf Oil Spill Pictures: Ten Animals at Risk {May 2010.}")

Bottlenose dolphins have been dying in unusually high numbers in northern Gulf waterssince February 2010, two months before the oil spill began, and the trend continues today. Since January, 68 premature, stillborn, or newborn calves have washed ashore.

The Gulf oil spill is certainly on the list of suspects in the recent dolphin deaths, but it's too early to say for sure, Blair Mase, coordinator of the Southeast Marine Mammal Stranding Network of theNational Atmospheric and Oceanic Administration, told National Geographic News in March.

Only a handful of obviously oiled dolphins have been recovered. But a recent study from theUniversity of British Columbiaestimated that the actual number of dolphins and whales killed by the spill could be 50 times higher than official tallies suggest, putting the death toll in the thousands.

—Rebecca Kessler

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Migrating Birds Escaped Worst of Gulf Oil Spill

A year aftertheGulf oil spill, predictions of massbirddie-offs and disrupted migrations have not come true—but oil is still oozing into some bird habitats, experts say.

The timing of the disaster had especially worried scientists and bird-watchers, since it came amid the annual spring migration of tens of millions of birds through the Gulf of Mexico.

(Watchvideo:"Gulf Spill Still Threatens Millions of Migrating Birds.")

"There is still the potential for impacts, but nothing like last year,"said Michael Carloss of theLouisiana Department of Wildlife& Fisheries.

Carloss, who directed the agency's rescue response, hasn't seen any"obvious"changes in migratory patterns or the numbers of birds arriving or passing throughLouisiana—a major bird habitat.

But he describes the damage assessment to wildlife as a"long, arduous process."

(Get more Gulf oil spill anniversary news.)

Breeding Birds May Get Oiled

In the short term, birds in Louisiana may still get oiled by tar balls that are still washing up on beaches and oozing in marsh grasses.

(Read more about Louisiana's embattled wetlands inNational Geographicmagazine.)

Melanie Driscoll, Gulf Coast director of bird conservation for the National Audubon Society, said she's"incredibly dismayed"that oil remains in areas where birds nest and feed in the ongoing breeding season.

Birds can get oil on their feathers and transfer it to eggs or hatchlings, which are especially vulnerable to the oil's toxicity.

With cleanup efforts still under way, the simple act of trying to repair the damage from the oil can actually do more harm.

The small shorebird Wilson's plover is especially susceptible to disruptions, Driscoll said. Cleanup crews have fenced off roads through the grasses that often lie between the birds' nests and their main food sources. Though the birds can squeeze through the fencing, it adds more stress to a bird population that's been declining for decades. (Seevideo:"Citizen 'Scientists' Track Birds in BP-Spill Zone.")

Audubon scientists have also found marine worms burrowing into tar balls in Grand Terre, Louisiana. Lab tests found concentrations of toxic hydrocarbons in the tar balls that could enter the food chain and pose long-term health risks to adult birds or harm developing bird embryos.

Habitat Loss Could Push Birds Over the Edge?

Possibly the most worrying legacy of the spill is the acceleration of habitat loss, scientists say.

For example, some Louisiana bays were hit with heavy oil last summer. The marsh grass that holds the marsh together is dying in many areas—which means that storms, waves, and ship wakes will simply wash away more of the wetlands.

(Seepictures:"Heavy Oil Seeping Into Louisiana Marshes {May 2010}.")

Wildlife& Fisheries' Carloss said it will be difficult to tease out how much habitat loss can be attributed to the spill or the long-standing yearly loss of wetlands from erosion and subsidence. But he says the combination of oiling and cleanup operations in critical marsh habitat clearly must have some effect.

For instance, inLouisiana's Barataria Bay (see map), submerged mats of oily material still send oil ashore nearly every day into many bird species' nesting habitats, Audubon's Driscoll said. (See waterbird pictures.)

For birds flying thousands of miles from wintering spots in the south to nesting sites as far as the Arctic, any loss of shelter, food, and fresh water could leave them too weak to make the journey or diminish their reproductive success when they reach nesting sites.

"A lot of these birds live right on the edge, with an incredibly physically demanding journey,” said David Ringer, Audubon's communications coordinator for the Mississippi River and Gulf of Mexico.

"Anything that goes wrong on the way can push them over the edge."

forNational Geographic News

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Pictures: 20 Surprising Species of the Past 20 Years

Back for an encore after a round of Web stardom as"Yoda bat"last fall,Papua New Guinea's tube-nosed fruit bat has now been named one of the top20 new or rarely seen species encountered during the first 20 years of Conservation International's Rapid Assessment Program(RAP), which launched in 1990.

(Readmore about the tube-nosed fruit bat.)

The RAP expeditions typically send large teams of scientists into remote habitats for intense, monthlong surveys.

"We go out and explore so that we can bring a wide range of new species—1,300 so far—and thousands of other rare and really interesting species to the public and policy makers,"explained RAP director
Leeanne Alonso.

"Showing people what's there helps us make the best decisions about how to manage areas to keep these species around, while continuing the benefits that humans get from these places."

In other words: Help us, they will.

—Brian Handwerk

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Eyes Made of Rock Really Can See, Study Says

When it comes to hard stares and stony gazes, no animal can match the chiton, a small mollusk with eyes made of rock crystal. Now a new study shows just what these strange eyes are capable of.

Scientists had long known that chitons have hundreds of beadlike structures resembling eyes on the backs of their shells. The lenses"are like big, clear pieces of rock,"said study leaderDan Speiser, a marine biologist at the University of California, Santa Barbara. (Related:"Coral Algae Have 'Eyes,' Study Says.")

What's been unclear, however, is if the creatures could actually see using these organs or whether the eyes were good only for sensing changes in light intensity.

"It's been known for over a hundred years that these eyes exist, but no one's really tested what sort of vision they provide,"Speiser said.

His latest research—conducted while he was a graduate student at Duke University in North Carolina—revealed that the sea creatures' eyes are the first known to be made of the mineral aragonite, the same material chitons use to make their shells.

What's more, these stony eyes likely have unique advantages over the squishy eyeballs of other animals.

(Related:"Eyeless Urchins 'See' With Spines.")

Mollusks in Lockdown

To test the chiton's vision, Speiser and his team collected Indian fuzzy chitons(Acanthopleura granulate)from the Caribbean.

When left alone, a chiton will lift part of its oval-shaped body to breathe. But when threatened, the animal will clamp down tightly on the seafloor to protect its soft underbelly.

In the lab, the scientists placed individual animals on a stone slab beneath a white screen, which could change colors. Once the chitons seemed relaxed, the team either placed a black disk directly above the mollusks or changed the color of the background screen from white to gray.

The black disk was designed to simulate a suddenly appearing predator, while the dimming screen mimicked subtle changes in natural light that chitons might experience in the wild—for example, when a cloud passes in front of the sun.

In the experiment, the chitons went into lockdown mode when shown the black disk, but the animals remained at ease when the screen dimmed. This suggests the chiton's eyes are able to distinguish shapes, a prerequisite for true vision.

"The eyes allow the chitons to see objects—not with much detail—but they can distinguish between approaching objects and just decreases in light,"Speiser said.

Speiser estimates chiton vision is about a thousand times courser than human vision, and it's likely they see only in black-and-white. (Related:"Sharks Are Color-Blind, Retina Study Suggests.")

"Even compared to other animals with small eyes, chitons don't see particularly well,"Speiser said.

Rock Eyes Better for Tidal Creatures

Chitons' rock eyes do appear to have some specific advantages. For one thing, the hard aragonite is extremely resilient, an important trait for chitons, which are constantly being pummeled by waves in their natural habitats, shallow tidal pools.

"If their eyes were made of protein"—which is the case for humans and most other animals—"they would get worn right away,"Speiser said. (See"Hammerhead Sharks Have 'Human' Vision.")

For another thing, the experiments suggest aragonite allows the chitons to see equally well in air or underwater, something that's probably useful as tides ebb around the mollusks.

"Behaviorally, the chitons react the same"in both mediums, Speiser said.

That's probably because aragonite has two refractive indices, the extent to which a particular material focuses incoming light. With an aragonite eye, one index creates an image on the eye in water while the other works in air.

Meanwhile, a few mysteries remain about chiton eyes. For instance, it's still not known why only some chiton species have eyes, or how the creatures are able to use the same material to make both their eyes and their shells.

"It's going to be interesting to see how they're shaping these lenses,” Speiser said."How do they make them the right size and shape and keep them translucent? They're exerting some very fine control."

The chiton-eyes research will be detailed in the April 26 issue of the journalCurrent Biology.

forNational Geographic News

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