Sniffing out Danger: Fearful Memories Can Trigger Heightened Sense of Smell

Dec. 12, 2013 — Most people -- including scientists -- assumed we can't just sniff out danger.

It was thought that we become afraid of an odor -- such as leaking gas -- only after information about a scary scent is processed by our brain.

But neuroscientists at Rutgers University studying the olfactory -- sense of smell -- system in mice have discovered that this fear reaction can occur at the sensory level, even before the brain has the opportunity to interpret that the odor could mean trouble.

In a new study published today in Science, John McGann, associate professor of behavioral and systems neuroscience in the Department of Psychology, and his colleagues, report that neurons in the noses of laboratory animals reacted more strongly to threatening odors before the odor message was sent to the brain.

"What is surprising is that we tend to think of learning as something that only happens deep in the brain after conscious awareness," says McGann. "But now we see how the nervous system can become especially sensitive to threatening stimuli and that fear-learning can affect the signals passing from sensory organs to the brain."

McGann and students Marley Kass and Michelle Rosenthal made this discovery by using light to observe activity in the brains of genetically engineered mice through a window in the mouse's skull. They found that those mice that received an electric shock simultaneously with a specific odor showed an enhanced response to the smell in the cells in the nose, before the message was delivered to the neurons in the brain.

This new research -- which indicates that fearful memories can influence the senses -- could help to better understand conditions like Post Traumatic Stress Disorder, in which feelings of anxiety and fear exist even though an individual is no longer in danger.

"We know that anxiety disorders like PTSD can sometimes be triggered by smell, like the smell of diesel exhaust for a soldier," says McGann who received funding from the National Institute of Mental Health and the National Institute on Deafness and Other Communication Disorders for this research. "What this study does is gives us a new way of thinking about how this might happen."

In their study, the scientists also discovered a heightened sensitivity to odors in the mice traumatized by shock. When these mice smelled the odor associated with the electrical shocks, the amount of neurotransmitter -- chemicals that carry communications between nerve cells -- released from the olfactory nerve into the brain was as big as if the odor were four times stronger than it actually was.

This created mice whose brains were hypersensitive to the fear-associated odors. Before now, scientists did not think that reward or punishment could influence how the sensory organs process information.

The next step in the continuing research, McGann says, is to determine whether the hypersensitivity to threatening odors can be reversed by using exposure therapy to teach the mice that the electrical shock is no longer associated with a specific odor. This could help develop a better understanding of fear learning that might someday lead to new therapeutic treatments for anxiety disorders in humans, he says.

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Noble Gas Molecule Discovered in Space

Dec. 12, 2013 — A molecule containing a noble gas has been discovered in space by a team including astronomers from Cardiff University.

The find was made using a Cardiff-led instrument aboard Europe's Herschel Space Observatory. The molecule, argon hydride, was seen in the Crab Nebula, the remains of a star that exploded 1,000 years ago. Before the discovery, molecules of this kind have only been studied in laboratories on Earth.

The noble gases, which include helium, argon, radon and krypton, usually do not react easily with other chemical elements, and are often found on their own. In the right circumstances, however, they can form molecules with other elements. Such chemical compounds have only ever been studied in laboratories on Earth, leading astronomers to assume the right conditions simply do not occur in space.

"The Crab Nebula was only formed 1000 years ago when a massive star exploded," said Dr Haley Gomez of Cardiff University's School of Physics and Astronomy. "Not only is it very young in astronomical terms, but also relatively close, at just 6,500 light years away, providing an excellent way to study what happens in these stellar explosions. Last year, we used the European Space Agency's Herschel Space Observatory to study the intricate network of gas filaments to show how exploding stars are creating huge amounts of space dust."

Further measurements of the Crab Nebula were made using Herschel's SPIRE instrument. Its development and operation was led by Professor Matt Griffin, from the School of Physics and Astronomy. As molecules spin in space, they emit light of very specific wavelengths, or colours, called "emission lines." The precise wavelength is dictated by the composition and structure of the molecule. Studying the emission lines observed by the SPIRE instrument allows astronomers to study the chemistry of outer space.

The team, led by Professor Mike Barlow from University College London, did not set out to make the discovery, but stumbled upon it almost by accident. "We were really concentrating on studying the dust in the filaments with SPIRE, and out pops these two bright emission lines exactly where we see the dust shining," says Dr Gomez. "The team had a hard time figuring out what these lines were from, as no-one had seen them before."

Professor Barlow said, "At first, the discovery of argon seemed bizarre. With hot gas still expanding at high speeds after the explosion, a supernova remnant is a harsh, hot and hostile environment, and one of the places where we least expected to find a noble-gas based molecule."

It now seems the Crab Nebula provides exactly the right conditions to form such molecules. The argon was produced in the initial stellar explosion, and then ionised, or energised, with electrons stripped from the atoms in resulting intense radiation as shockwaves. These shockwaves led to the formation of the network of cool filaments containing cold molecular hydrogen, made of two hydrogen atoms. The ionised argon then mixed with the cool gas to provide perfect conditions for noble gas compounds to form.

The measurements allowed the team to gauge other properties in argon molecules. "Finding this kind of molecule allowed us to evaluate the type (or isotope) of argon we discovered in the Crab Nebula," said Dr Gomez. "We now know that it is different from argon we see in rocks on the Earth. Future measurements will allow us to probe what exactly took place in the explosion 1000 years ago."

"What a great detective story," added Prof Matt Griffin, from Cardiff University, and lead scientist of the team behind the SPIRE instrument. "Here we see the excellent performance of the Herschel-SPIRE spectrometer, the expertise of the instrument team in producing the highest quality data, and the tenacity and vision of the scientists analysing it, all coming together to make an intriguing new discovery.
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Rapid Evolution of Novel Forms: Environmental Change Triggers Inborn Capacity for Adaptation

Dec. 12, 2013 — In the classical view of evolution, species experience spontaneous genetic mutations that produce various novel traits -- some helpful, some detrimental. Nature then selects for those most beneficial, passing them along to subsequent generations.

It's an elegant model. It's also an extremely time-consuming process likely to fail organisms needing to cope with sudden, potentially life-threatening changes in their environments. Surely some other mechanism could enable more rapid adaptive response. In this week's edition of the journal Science, a team of researchers from Harvard Medical School and Whitehead Institute report that, at least in the case of one variety of cavefish, that other agent of change is the heat shock protein known as HSP90.

"It's a very cool story in terms of the speed of evolution," says Nicolas Rohner, lead author of the Science paper and a postdoctoral researcher in the lab of Harvard Medical School Genetics Professor Clifford Tabin.

Rohner notes that at some point many thousands of years ago, a population of Astyanax mexicanus (a fish indigenous to northeastern Mexico) was swept from its hospitable river home into the unfriendly confines of underwater caves. Facing a dramatically different environment, the fish were forced to adapt. Living in near total darkness, the fish did away with their pigmentation, developed heightened sensory systems to detect changes in water pressure and the presence of prey and, perhaps most strikingly, they lost their eyes. Although seemingly counterintuitive, the loss of eyes is thought to be an "adaptive" or beneficial trait, as the maintenance of a complex but now useless organ would come at a high metabolic cost. Thus, the fish could reallocate their finite physiological resources to biological functions more helpful in the cave setting.

Eye loss in these fish is considered to be a demonstration of an evolutionary concept known as "standing genetic variation," which argues that pools of genetic mutations -- some potentially helpful -- exist in a given population but are normally kept silent. The manifestations of these mutations, that is, their impact on observable phenotypes, don't emerge until the population encounters stressful conditions. But what exactly keeps those mutations at bay?

Enter Whitehead Member Susan Lindquist, whose research has shown that HSP90 silences such genetic variation in a variety of organisms, from fruit flies, to yeast, to plants. Lindquist's work found that the normally robust cellular reservoir of HSP90 becomes depleted during periods of physiological stress. The loss of HSP90 activity allowed phenotypic changes to emerge quite rapidly. Although some emergent traits found in her lab were not adaptive, some clearly were.

"The delicate balance of protein folding -- especially that controlled by HSP90 -- holds the key," says Lindquist, who is also a professor of biology at MIT and an investigator of the Howard Hughes Medical Institute. "Moderate changes in the environment create stresses on protein folding, causing minor changes in the genome to have much larger effects. Because HSP90 governs the folding of the key regulators of growth and development it produces a fulcrum point for evolutionary change."

Having seen Tabin's work on the genetics of eye loss in cavefish, she proposed a research collaboration to determine whether HSP90 had been an evolutionary role-player in this vertebrate. The Tabin and Lindquist labs devised a complex set of experiments with cavefish and surface fish of the same species. Surface fish raised in the presence of a drug that blocks HSP90 activity (thereby mimicking a stressful environment) displayed significant variation in eye size -- clearly implicating HSP90's effects on this trait. Conversely, cavefish raised in the same conditions showed no increase in variation in the size of their eye orbits (although the cave fish have no eyes, their skulls retain the orbital cavity where their eyes once were). Intriguingly, however, these fish emerged with small orbits, showing that the genetics governing eye size remains responsive to HSP90.

Although impressive, these findings were chemically induced, leaving open the question of whether such HSP90-related effects would have been seen in nature. To answer this, researchers examined a host of conditions -- ranging from pH to oxygen content to temperature -- found in the surface and cave waters that are home to these fish. They discovered a considerable difference in conductivity, as measured by salinity, between cave and surface. Because low conductivity, a condition found in the caves, can trigger a heat shock response, they raised surface fish in water whose conductivity equaled that of native caves.

The results were essentially the same: fish raised in conditions of low conductivity showed significant variation in eye size. The scientists had shown that an environmental stressor could have the same effects as the chemical inhibition of HSP90.

"This is the first time that we can see in a natural setting where the stress came from and observe the variation that results," says Tabin.

Adds Rohner: "This is the first study showing that this HSP90-mediated mechanism can be applied to vertebrates for real morphological adaptive traits."

For Dan Jarosz, a former postdoctoral researcher in Lindquist's lab, the study is an important validation of Lindquist's work on evolution. Jarosz, now Assistant Professor of Chemical and Systems Biology and of Developmental Biology at Stanford University, had been involved in much of Lindquist's work on HSP90 as a driver of evolution in yeast. He believes this latest work should help quiet those who are skeptical of the impact of this mechanism throughout the plant and animal kingdoms.

"We now have enough evidence to say that large, rapid environmental change can reveal new variation and change the outcomes of real evolution in nature," he says.

This work is supported by the National Institutes of Health and the Damon Runyon Cancer Research Foundation
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Mach 1000 Shock Wave Lights Supernova Remnant

Nov. 25, 2013 — When a star explodes as a supernova, it shines brightly for a few weeks or months before fading away. Yet the material blasted outward from the explosion still glows hundreds or thousands of years later, forming a picturesque supernova remnant. What powers such long-lived brilliance?

In the case of Tycho's supernova remnant, astronomers have discovered that a reverse shock wave racing inward at Mach 1000 (1000 times the speed of sound) is heating the remnant and causing it to emit X-ray light.

"We wouldn't be able to study ancient supernova remnants without a reverse shock to light them up," says Hiroya Yamaguchi, who conducted this research at the Harvard-Smithsonian Center for Astrophysics (CfA).

Tycho's supernova was witnessed by astronomer Tycho Brahe in 1572. The appearance of this "new star" stunned those who thought the heavens were constant and unchanging. At its brightest, the supernova rivaled Venus before fading from sight a year later.

Modern astronomers know that the event Tycho and others observed was a Type Ia supernova, caused by the explosion of a white dwarf star. The explosion spewed elements like silicon and iron into space at speeds of more than 11 million miles per hour (5,000 km/s).

When that ejecta rammed into surrounding interstellar gas, it created a shock wave -- the equivalent of a cosmic "sonic boom." That shock wave continues to move outward today at about Mach 300. The interaction also created a violent "backwash" -- a reverse shock wave that speeds inward at Mach 1000.

"It's like the wave of brake lights that marches up a line of traffic after a fender-bender on a busy highway," explains CfA co-author Randall Smith.

The reverse shock wave heats gases inside the supernova remnant and causes them to fluoresce. The process is similar to what lights household fluorescent bulbs, except that the supernova remnant glows in X-rays rather than visible light. The reverse shock wave is what allows us to see supernova remnants and study them, hundreds of years after the supernova occurred.

"Thanks to the reverse shock, Tycho's supernova keeps on giving," says Smith.

The team studied the X-ray spectrum of Tycho's supernova remnant with the Suzaku spacecraft. They found that electrons crossing the reverse shock wave are rapidly heated by a still-uncertain process. Their observations represent the first clear evidence for such efficient, "collisionless" electron heating at the reverse shock of Tycho's supernova remnant.

The team plans to look for evidence of similar reverse shock waves in other young supernova remnants
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Archaeological Discoveries Confirm Early Date of Buddha's Life

Nov. 25, 2013 — Archaeologists working in Nepal have uncovered evidence of a structure at the birthplace of the Buddha dating to the sixth century B.C. This is the first archaeological material linking the life of the Buddha -- and thus the first flowering of Buddhism -- to a specific century.

Pioneering excavations within the sacred Maya Devi Temple at Lumbini, Nepal, a UNESCO World Heritage site long identified as the birthplace of the Buddha, uncovered the remains of a previously unknown sixth-century B.C. timber structure under a series of brick temples. Laid out on the same design as those above it, the timber structure contains an open space in the center that links to the nativity story of the Buddha himself.

Until now, the earliest archaeological evidence of Buddhist structures at Lumbini dated no earlier than the third century B.C., the time of the patronage of the Emperor Asoka, who promoted the spread of Buddhism from present-day Afghanistan to Bangladesh.

"Very little is known about the life of the Buddha, except through textual sources and oral tradition," said archaeologist Professor Robin Coningham of Durham University, U.K., who co-led the investigation. Some scholars, he said, have maintained that the Buddha was born in the third century B.C. "We thought 'why not go back to archaeology to try to answer some of the questions about his birth?' Now, for the first time, we have an archaeological sequence at Lumbini that shows a building there as early as the sixth century B.C."

Early Buddhism revealed

The international team of archaeologists, led by Coningham and Kosh Prasad Acharya of the Pashupati Area Development Trust in Nepal, say the discovery contributes to a greater understanding of the early development of Buddhism as well as the spiritual importance of Lumbini. Their peer-reviewed findings are reported in the December 2013 issue of the international journal Antiquity. The research is partly supported by the National Geographic Society.

To determine the dates of the timber shrine and a previously unknown early brick structure above it, fragments of charcoal and grains of sand were tested using a combination of radiocarbon and optically stimulated luminescence techniques. Geoarchaeological research also confirmed the presence of ancient tree roots within the temple's central void.

"UNESCO is very proud to be associated with this important discovery at one of the most holy places for one of the world's oldest religions," said UNESCO Director-General Irina Bokova, who urged "more archaeological research, intensified conservation work and strengthened site management" to ensure Lumbini's protection.

"These discoveries are very important to better understand the birthplace of the Buddha," said Ram Kumar Shrestha, Nepal's minister of culture, tourism and civil aviation. "The government of Nepal will spare no effort to preserve this significant site."

Buddhist tradition records that Queen Maya Devi, the mother of the Buddha, gave birth to him while holding on to the branch of a tree within the Lumbini Garden, midway between the kingdoms of her husband and parents. Coningham and his colleagues postulate that the open space in the center of the most ancient, timber shrine may have accommodated a tree. Brick temples built later above the timber shrine also were arranged around the central space, which was unroofed.

Four main Buddhist sites

Lumbini is one of the key sites associated with the life of the Buddha; others are Bodh Gaya, where he became a Buddha or enlightened one; Sarnath, where he first preached; and Kusinagara, where he passed away. At his passing at the age of 80, the Buddha is recorded as having recommended that all Buddhists visit "Lumbini." The shrine was still popular in the middle of the first millennium A.D. and was recorded by Chinese pilgrims as having a shrine beside a tree.

The Maya Devi Temple at Lumbini remains a living shrine; the archaeologists worked alongside meditating monks, nuns and pilgrims.

In the scientific paper in Antiquity, the authors write: "The sequence (of archaeological remains) at Lumbini is a microcosm for the development of Buddhism from a localized cult to a global religion."

Lost and overgrown in the jungles of Nepal in the medieval period, ancient Lumbini was rediscovered in 1896 and identified as the birthplace of the Buddha on account of the presence of a third-century B.C. sandstone pillar. The pillar, which still stands, bears an inscription documenting a visit by Emperor Asoka to the site of the Buddha's birth as well as the site's name -- Lumbini.

Despite the rediscovery of the key Buddhist sites, their earliest levels were buried deep or destroyed by later construction, leaving evidence of the very earliest stages of Buddhism inaccessible to archaeological investigation, until now.

Half a billion people around the world are Buddhists, and many hundreds of thousands make a pilgrimage to Lumbini each year. The archaeological investigation there was funded by the government of Japan in partnership with the government of Nepal, under a UNESCO project aimed at strengthening the conservation and management of Lumbini. Along with the National Geographic Society, the research also was supported by Durham University and Stirling University.

Coningham and Acharya were joined on the Antiquity paper by coauthors K.M. Strickland, C.E. Davis, M.J. Manuel, I. A. Simpson, K. Gilliland, J. Tremblay, T.C. Kinnaird and D.C.W. Sanderson.

A documentary on Coningham's exploration of the Buddha's life, "Buried Secrets of the Buddha," will premiere in February internationally on National Geographic Channel.

For a National Geographic news video about the findings, see:http://video.nationalgeographic.com/video/news/history-archaeology-news/buddha-birth-vin
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Scientists Find Brain Region That Helps You Make Up Your Mind

Nov. 24, 2013 — One of the smallest parts of the brain is getting a second look after new research suggests it plays a crucial role in decision making.

A University of British Columbia study published in Nature Neuroscience says the lateral habenula, a region of the brain linked to depression and avoidance behaviours, has been largely misunderstood and may be integral in cost-benefit decisions.

"These findings clarify the brain processes involved in the important decisions that we make on a daily basis, from choosing between job offers to deciding which house or car to buy," says Prof. Stan Floresco of UBC's Dept. of Psychology and Brain Research Centre (BRC). "It also suggests that the scientific community has misunderstood the true functioning of this mysterious, but important, region of the brain."

In the study, scientists trained lab rats to choose between a consistent small reward (one food pellet) or a potentially larger reward (four food pellets) that appeared sporadically. Like humans, the rats tended to choose larger rewards when costs -- in this case, the amount of time they had to wait before receiving food-were low and preferred smaller rewards when such risks were higher.

Previous studies suggest that turning off the lateral habenula would cause rats to choose the larger, riskier reward more often, but that was not the case. Instead, the rats selected either option at random, no longer showing the ability to choose the best option for them.

The findings have important implications for depression treatment. "Deep brain stimulation -- which is thought to inactivate the lateral habenula -- has been reported to improve depressive symptoms in humans," Floresco says. "But our findings suggest these improvements may not be because patients feel happier. They may simply no longer care as much about what is making them feel depressed."

Background

Floresco, who conducted the study with PhD candidate Colin Stopper, says more investigation is needed to understand the complete brain functions involved in cost-benefit decision processes and related behaviour. A greater understanding of decision-making processes is also crucial, they say, because many psychiatric disorders, such as schizophrenia, stimulant abuse and depression, are associated with impairments in these processes.

The lateral habenula is considered one of the oldest regions of the brain, evolution-wise, the researchers say
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Even If Emissions Stop, Carbon Dioxide Could Warm Earth for Centuries

Nov. 24, 2013 — Even if carbon dioxide emissions came to a sudden halt, the carbon dioxide already in Earth's atmosphere could continue to warm our planet for hundreds of years, according to Princeton University-led research published in the journalNature Climate Change. The study suggests that it might take a lot less carbon than previously thought to reach the global temperature scientists deem unsafe.

The researchers simulated an Earth on which, after 1,800 billion tons of carbon entered the atmosphere, all carbon dioxide emissions suddenly stopped. Scientists commonly use the scenario of emissions screeching to a stop to gauge the heat-trapping staying power of carbon dioxide. Within a millennium of this simulated shutoff, the carbon itself faded steadily with 40 percent absorbed by Earth's oceans and landmasses within 20 years and 80 percent soaked up at the end of the 1,000 years.

By itself, such a decrease of atmospheric carbon dioxide should lead to cooling. But the heat trapped by the carbon dioxide took a divergent track.

After a century of cooling, the planet warmed by 0.37 degrees Celsius (0.66 Fahrenheit) during the next 400 years as the ocean absorbed less and less heat. While the resulting temperature spike seems slight, a little heat goes a long way here. Earth has warmed by only 0.85 degrees Celsius (1.5 degrees Fahrenheit) since pre-industrial times.

The Intergovernmental Panel on Climate Change estimates that global temperatures a mere 2 degrees Celsius (3.6 degrees Fahrenheit) higher than pre-industrial levels would dangerously interfere with the climate system. To avoid that point would mean humans have to keep cumulative carbon dioxide emissions below 1,000 billion tons of carbon, about half of which has already been put into the atmosphere since the dawn of industry.

The lingering warming effect the researchers found, however, suggests that the 2-degree point may be reached with much less carbon, said first author Thomas Frölicher, who conducted the work as a postdoctoral researcher in Princeton's Program in Atmospheric and Oceanic Sciences under co-author Jorge Sarmiento, the George J. Magee Professor of Geoscience and Geological Engineering.

"If our results are correct, the total carbon emissions required to stay below 2 degrees of warming would have to be three-quarters of previous estimates, only 750 billion tons instead of 1,000 billion tons of carbon," said Frölicher, now a researcher at the Swiss Federal Institute of Technology in Zurich. "Thus, limiting the warming to 2 degrees would require keeping future cumulative carbon emissions below 250 billion tons, only half of the already emitted amount of 500 billion tons."

The researchers' work contradicts a scientific consensus that the global temperature would remain constant or decline if emissions were suddenly cut to zero. But previous research did not account for a gradual reduction in the oceans' ability to absorb heat from the atmosphere, particularly the polar oceans, Frölicher said. Although carbon dioxide steadily dissipates, Frölicher and his co-authors were able to see that the oceans that remove heat from the atmosphere gradually take up less. Eventually, the residual heat offsets the cooling that occurred due to dwindling amounts of carbon dioxide.

Frölicher and his co-authors showed that the change in ocean heat uptake in the polar regions has a larger effect on global mean temperature than a change in low-latitude oceans, a mechanism known as "ocean-heat uptake efficacy." This mechanism was first explored in a 2010 paper by Frölicher's co-author, Michael Winton, a researcher at the National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory (GFDL) on Princeton's Forrestal Campus.

"The regional uptake of heat plays a central role. Previous models have not really represented that very well," Frölicher said.

"Scientists have thought that the temperature stays constant or declines once emissions stop, but now we show that the possibility of a temperature increase can not be excluded," Frölicher said. "This is illustrative of how difficult it may be to reverse climate change -- we stop the emissions, but still get an increase in the global mean temperature.
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