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Great apes make sophisticated decisions

Chimpanzees, orangutans, gorillas and bonobos make more sophisticated decisions than was previously thought. Great apes weigh their chances of success, based on what they know and the likelihood to succeed when guessing, according to a study of MPI researcher Daniel Haun, published on December 21 in the online journal PLoS ONE. The findings may provide insight into human decision-making as well.

The authors of the study, led by Daniel Haun of the Max Planck Institutes for Psycholinguistics (Nijmegen) and Evolutionary Anthropology (Leipzig), investigated the behaviour of all four non-human great ape species. The apes were presented with two banana pieces: a smaller one, which was always reliably in the same place, and a larger one, which was hidden under one of multiple cups, and therefore the riskier choice.

The researchers found that the apes’ choices were regulated by their uncertainty and the probability of success for the risky choice, suggesting sophisticated decision-making. Apes chose the small piece more often when they where uncertain where the large piece was hidden. The lower their chances to guess correctly, the more often they chose the small piece.

Risky choices

The researchers also found that the apes went for the larger piece – and risked getting nothing at all – no less than 50% of the time. This risky decision-making increased to nearly 100% when the size difference between the two banana pieces was largest. While all four species demonstrated sophisticated decision making strategies, chimpanzees and orangutans were overall more likely to make risky choices relative to gorillas and bonobos. The precise reason for this discrepancy remains unknown.

Haun concludes: “Our study adds to the growing evidence that the mental life of the other great apes is much more sophisticated than is often assumed.”

Contact: Daniel Haun
daniel.haun@mpi.nl
49-341-355-0815
Max-Planck-Gesellschaft

How skin is wired for touch

Compared to our other senses, scientists don’t know much about how our skin is wired for the sensation of touch. Now, research reported in the December 23rd issue of the journal Cell, a Cell Press publication, provides the first picture of how specialized neurons feel light touches, like a brush of movement or a vibration, are organized in hairy skin.

Looking at these neurons in the hairy skin of mice, the researchers observed remarkably orderly patterns, suggesting that each type of hair follicle works like a distinct sensory organ, each tuned to register different types of touches. Each hair follicle sends out one wire-like projection that joins with others in the spinal cord, where the information they carry can be integrated into impulses sent to the brain. This network of neurons in our own skin allows us to perceive important differences in our surroundings: a raindrop versus a mosquito, a soft fingertip versus a hard stick.

“We can now begin to appreciate how these hair follicles and associated neurons are organized relative to one another and that organization enables us to think about how mechanosensory information is integrated and processed for the perception of touch,” says David Ginty of The Johns Hopkins University School of Medicine.

Mice have several types of hair follicles with three in particular that make up their coats. Ginty’s team made a technical breakthrough by coming up with a way to label distinct populations of known low-threshold mechanoreceptors (LTMRs). Before this study, there was no way to visualize LTMRs in their natural state. The neurons are tricky to study in part because they extend from the spinal cord all the way out to the skin. The feeling in the tips of our toes depends on cells that are more than one meter long.

The images show something unexpected and fascinating, Ginty says. Each hair follicle type includes a distinct combination of mechanosensory endings. Those sensory follicles are also organized in a repeating and stereotypical pattern in mouse skin.

The neurons found in adjacent hair follicles stretch to a part of the spinal cord that receives sensory inputs, forming narrow columns. Ginty says there are probably thousands of those columns in the spinal cord, each gathering inputs from a particular region of the skin and its patch of 100 or so hairs.

Of course, we don’t have hair like a mouse, and it’s not yet clear whether some of these mechanosensory neurons depend on the hairs themselves to pick up on sensations and whether others are primarily important as scaffolds for the underlying neural structures. They don’t know either how these inputs are integrated in the spinal cord and brain to give rise to perceptions, but now they have the genetic access they need to tinker with each LTMR subtype one by one, turning them on or off at will and seeing what happens to the brain and to behavior. Intriguingly, one of the LTMR types under study is implicated as “pleasure neurons” in people, Ginty notes.

At this point, he says they have no clue how these neurons manage to set themselves up in this way during development. The neurons that form this sensory network are born at different times, controlled by different growth factors, and “yet they assemble in these remarkable patterns.” And for Ginty that leads to a simple if daunting question to answer: “How does one end of the sensory neuron know what the other end is doing?”

Contact: Lisa Lyons
elyons@cell.com
617-386-2121
Cell Press

Skeletons point to Columbus voyage for syphilis origins

Skeletons don’t lie. But sometimes they may mislead, as in the case of bones that reputedly showed evidence of syphilis in Europe and other parts of the Old World before Christopher Columbus made his historic voyage in 1492.

None of this skeletal evidence, including 54 published reports, holds up when subjected to standardized analyses for both diagnosis and dating, according to an appraisal in the current Yearbook of Physical Anthropology. In fact, the skeletal data bolsters the case that syphilis did not exist in Europe before Columbus set sail.

“This is the first time that all 54 of these cases have been evaluated systematically,” says George Armelagos, an anthropologist at Emory University and co-author of the appraisal. “The evidence keeps accumulating that a progenitor of syphilis came from the New World with Columbus’ crew and rapidly evolved into the venereal disease that remains with us today.”

The appraisal was led by two of Armelagos’ former graduate students at Emory: Molly Zuckerman, who is now an assistant professor at Mississippi State University, and Kristin Harper, currently a post-doctoral fellow at Columbia University. Additional authors include Emory anthropologist John Kingston and Megan Harper from the University of Missouri.

“Syphilis has been around for 500 years,” Zuckerman says. “People started debating where it came from shortly afterwards, and they haven’t stopped since. It was one of the first global diseases, and understanding where it came from and how it spread may help us combat diseases today.”

‘The natural selection of a disease’

The treponemal family of bacteria causes syphilis and related diseases that share some symptoms but spread differently. Syphilis is sexually transmitted. Yaws and bejel, which occurred in early New World populations, are tropical diseases that are transmitted through skin-to-skin contact or oral contact.

The first recorded epidemic of venereal syphilis occurred in Europe in 1495. One hypothesis is that a subspecies of Treponema from the warm, moist climate of the tropical New World mutated into the venereal subspecies to survive in the cooler and relatively more hygienic European environment.

The fact that syphilis is a stigmatized, sexual disease has added to the controversy over its origins, Zuckerman says.

“In reality, it appears that venereal syphilis was the by-product of two different populations meeting and exchanging a pathogen,” she says. “It was an adaptive event, the natural selection of a disease, independent of morality or blame.”

An early doubter

Armelagos, a pioneer of the field of bioarcheology, was one of the doubters decades ago, when he first heard the Columbus theory for syphilis. “I laughed at the idea that a small group of sailors brought back this disease that caused this major European epidemic,” he recalls.

While teaching at the University of Massachusetts, he and graduate student Brenda Baker decided to investigate the matter and got a shock: All of the available evidence at the time actually supported the Columbus theory. “It was a paradigm shift,” Armelagos says. The pair published their results in 1988.

In 2008, Harper and Armelagos published the most comprehensive comparative genetic analysis ever conducted on syphilis’s family of bacteria. The results again supported the hypothesis that syphilis, or some progenitor, came from the New World.

A second, closer look

But reports of pre-Columbian skeletons showing the lesions of chronic syphilis have kept cropping up in the Old World. For this latest appraisal of the skeletal evidence, the researchers gathered all of the published reports.

They found that most of the skeletal material did not meet at least one of the standardized, diagnostic criteria for chronic syphilis, including pitting on the skull known as caries sicca and pitting and swelling of the long bones.

The few published cases that did meet the criteria tended to come from coastal regions where seafood was a big part of the diet. The so-called “marine reservoir effect,” caused by eating seafood which contains “old carbon” from upwelling, deep ocean waters, can throw off radiocarbon dating of a skeleton by hundreds, or even thousands, of years. Analyzing the collagen levels of the skeletal material enabled the researchers to estimate the seafood consumption and factor that result into the radiocarbon dating.

“Once we adjusted for the marine signature, all of the skeletons that showed definite signs of treponemal disease appeared to be dated to after Columbus returned to Europe,” Harper says.

“The origin of syphilis is a fascinating, compelling question,” Zuckerman says. “The current evidence is pretty definitive, but we shouldn’t close the book and say we’re done with the subject. The great thing about science is constantly being able to understand things in a new light.”

Emory University is known for its demanding academics, outstanding undergraduate experience, highly ranked professional schools and state-of-the-art research facilities. Emory encompasses nine academic divisions as well as the Carlos Museum, The Carter Center, the Yerkes National Primate Research Center and Emory Healthcare, Georgia’s largest and most comprehensive health care system.

Contact: Beverly Clark
beverly.clark@emory.com
404-712-8780
Emory University

First Earth-sized planets found

Astronomers using NASA’s Kepler mission have detected two Earth-sized planets orbiting a distant star. This discovery marks a milestone in the hunt for alien worlds, since it brings scientists one step closer to their ultimate goal of finding a twin Earth.

“The goal of Kepler is to find Earth-sized planets in the habitable zone. Proving the existence of Earth-sized exoplanets is a major step toward achieving that goal,” said Francois Fressin of the Harvard-Smithsonian Center for Astrophysics (CfA).

The paper describing the finding will be published in the journal Nature.

The two planets, dubbed Kepler-20e and 20f, are the smallest planets found to date. They have diameters of 6,900 miles and 8,200 miles – equivalent to 0.87 times Earth (slightly smaller than Venus) and 1.03 times Earth. These worlds are expected to have rocky compositions, so their masses should be less than 1.7 and 3 times Earth’s.

Both worlds circle Kepler-20: a G-type star slightly cooler than the Sun and located 950 light-years from Earth. (It would take the space shuttle 36 million years to travel to Kepler-20.)

Kepler-20e orbits every 6.1 days at a distance of 4.7 million miles. Kepler-20f orbits every 19.6 days at a distance of 10.3 million miles. Due to their tight orbits, they are heated to temperatures of 1,400 degrees Fahrenheit and 800 degrees F.

In addition to the two Earth-sized worlds, the Kepler-20 system contains three larger planets. All five have orbits closer than Mercury in our solar system.

They also show an unexpected arrangement. In our solar system small, rocky worlds orbit close to the Sun and large, gas giant worlds orbit farther out. In contrast, the planets of Kepler-20 are organized in alternating size: big, little, big, little, big.

“We were surprised to find this system of flip-flopping planets,” said co-author David Charbonneau of the CfA. “It’s very different than our solar system.”

The three largest planets are designated Kepler-20b, 20c, and 20d. They have diameters of 15,000, 24,600, and 22,000 miles and orbit once every 3.7, 10.9, and 77.6 days, respectively. Kepler-20b has 8.7 times the mass of Earth; Kepler-20c has 16.1 times Earth’s mass. Kepler-20d weighs less than 20 times Earth.

The planets of Kepler-20 could not have formed in their current locations. Instead, they must have formed farther from their star and then migrated inward, probably through interactions with the disk of material from which they all formed. This allowed the worlds to maintain their regular spacing despite alternating sizes.

Kepler identifies “objects of interest” by looking for stars that dim slightly, which can occur when a planet crosses the star’s face. To confirm a transiting planet, astronomers look for the star to wobble as it is gravitationally tugged by its orbiting companion (a method known as radial velocity).

The radial velocity signal for planets weighing one to a few Earth masses is too small to detect with current technology. Therefore, other techniques must be used to validate that an object of interest is truly a planet.

A variety of situations could mimic the dimming from a transiting planet. For example, an eclipsing binary-star system whose light blends with the star Kepler-20 would create a similar signal. To rule out such imposters, the team simulated millions of possible scenarios with Blender – custom software developed by Fressin and Willie Torres of CfA. They concluded that the odds are strongly in favor of Kepler-20e and 20f being planets.

Fressin and Torres also used Blender to confirm the existence of Kepler-22b, a planet in the habitable zone of its star that was announced by NASA earlier this month. However, that world was much larger than Earth.

“These new planets are significantly smaller than any planet found up till now orbiting a Sun-like star,” added Fressin.

Contact: Christine Pulliam
cpulliam@cfa.harvard.edu
617-495-7463
Harvard-Smithsonian Center for Astrophysics

Strange new ‘species’ of ultra-red galaxy discovered

In the distant reaches of the universe, almost 13 billion light-years from Earth, a strange species of galaxy lay hidden. Cloaked in dust and dimmed by the intervening distance, even the Hubble Space Telescope couldn’t spy it. It took the revealing power of NASA’s Spitzer Space Telescope to uncover not one, but four remarkably red galaxies. And while astronomers can describe the members of this new “species,” they can’t explain what makes them so ruddy.

“We’ve had to go to extremes to get the models to match our observations,” said Jiasheng Huang of the Harvard-Smithsonian Center for Astrophysics (CfA). Huang is lead author on the paper announcing the find, which was published online by the Astrophysical Journal.

Spitzer succeeded where Hubble failed because Spitzer is sensitive to infrared light – light so red that it lies beyond the visible part of the spectrum. The newfound galaxies are more than 60 times brighter in the infrared than they are at the reddest colors Hubble can detect.

Galaxies can be very red for several reasons. They might be very dusty. They might contain many old, red stars. Or they might be very distant, in which case the expansion of the universe stretches their light to longer wavelengths and hence redder colors (a process known as redshifting). All three reasons seem to apply to the newfound galaxies.

All four galaxies are grouped near each other and appear to be physically associated, rather than being a chance line-up. Due to their great distance, we see them as they were only a billion years after the Big Bang – an era when the first galaxies formed.

“Hubble has shown us some of the first protogalaxies that formed, but nothing that looks like this. In a sense, these galaxies might be a ‘missing link’ in galactic evolution” said co-author Giovanni Fazio of the CfA.

Next, researchers hope to measure an accurate redshift for the galaxies, which will require more powerful instruments like the Large Millimeter Telescope or Atacama Large Millimeter Array. They also plan to search for more examples of this new “species” of extremely red galaxies.

“There’s evidence for others in other regions of the sky. We’ll analyze more Spitzer and Hubble observations to track them down,” said Fazio.

Contact: Christine Pulliam
cpulliam@cfa.harvard.edu
617-495-7463
Harvard-Smithsonian Center for Astrophysics

How the brain strings words into sentences

While it has long been recognized that certain areas in the brain’s left hemisphere enable us to understand and produce language, scientists are still figuring out exactly how those areas divvy up the highly complex processes necessary to comprehend and produce language.

Advances in brain imaging made within the last 10 years have revealed that highly complex cognitive tasks such as language processing rely not only on particular regions of the cerebral cortex, but also on the white matter fiber pathways that connect them.

“With this new technology, scientists started to realize that in the language network, there are a lot more connecting pathways than we originally thought,” said Stephen Wilson, who recently joined the University of Arizona’s department of speech, language and hearing sciences as an assistant professor. “They are likely to have different functions because the brain is not just a homogeneous conglomerate of cells, but there hasn’t been a lot of evidence as to what kind of information is carried on the different pathways.”

Working in collaboration with his colleagues at the UA, the department of neurology at the University of California, San Francisco and the Scientific Institute and University Hospital San Raffaele in Milan, Italy, Wilson discovered that not only are the connecting pathways important for language processing, but they specialize in different tasks.

Two brain areas called Broca’s region and Wernicke’s region serve as the main computing hubs underlying language processing, with dense bundles of nerve fibers linking the two, much like fiber optic cables connecting computer servers. But while it was known that Broca’s and Wernicke’s region are connected by upper and a lower white matter pathways, most research had focused on the nerve cells clustered inside the two language-processing regions themselves.

Working with patients suffering from language impairments because of a variety of neurodegenerative diseases, Wilsons’ team used brain imaging and language tests to disentangle the roles played by the two pathways. Their findings are published in a recent issue of the scientific journal Neuron.

“If you have damage to the lower pathway, you have damage to the lexicon and semantics,” Wilson said. “You forget the name of things, you forget the meaning of words. But surprisingly, you’re extremely good at constructing sentences.”

“With damage to the upper pathway, the opposite is true; patients name things quite well, they know the words, they can understand them, they can remember them, but when it comes to figuring out the meaning of a complex sentence, they are going to fail.”

The study marks the first time it has been shown that upper and lower tracts play distinct functional roles in language processing, the authors write. Only the upper pathway plays a critical role in syntactic processing.

Wilson collected the data while he was a postdoctoral fellow working with patients with neurodegenerative diseases of varying severity, recruited through the Memory and Aging Center at UCSF. The study included 15 men and 12 women around the age of 66.

Unlike many other studies investigating acquired language disorders, which are called aphasias and usually caused by damage to the brain, Wilson’s team had a unique opportunity to study patients with very specific and variable degrees of brain damage.

“Most aphasias are caused by strokes, and most of the strokes that affect language regions probably would affect both pathways,” Wilson said. “In contrast, the patients with progressive aphasias who we worked with had very rare and very specific neurodegenerative diseases that selectively target different brain regions, allowing us to tease apart the contributions of the two pathways.”

To find out which of the two nerve fiber bundles does what in language processing, the team combined magnetic resonance brain imaging technology to visualize damaged areas and language assessment tasks testing the participants’ ability to comprehend and produce sentences.

“We would give the study participants a brief scenario and ask them to complete it with what comes naturally,” Wilson said. “For example, if I said to you, ‘A man was walking along the railway tracks. He didn’t hear the train coming. What happened to the man?’ Usually, you would say, ‘He was hit by the train,’ or something along those lines.”

“But a patient with damage to the upper pathway might say something like ‘train, man, hit.’ We found that the lower pathway has a completely different function, which is in the meaning of single words.”

To test for comprehension of the meaning of a sentence, the researchers presented the patient with a sentence like, “The girl who is pushing the boy is green,” and then ask which of the two pictures depicted that scenario accurately.

“One picture would show a green girl pushing a boy, and the other would show a girl pushing a green boy,” Wilson said. “The colors will be the same, the agents will be the same, and the action is the same. The only difference is, which actor does the color apply to?”

“Those who have only lower pathway damage do really well on this, which shows that damage to that pathway doesn’t interfere with your ability to use the little function words or the functional endings on words to figure out the relationships between the words in a sentence.”

Wilson said that most previous studies linking neurodegeneration of specific regions with cognitive deficits have focused on damage to gray matter, rather than the white matter that connects regions to one another.

“Our study shows that the deficits in the ability to process sentences are above and beyond anything that could be explained by gray matter loss alone,” Wilson added. “It is the first study to show that damage to one major pathway more than then other major pathway is associated with a specific deficit in one aspect of language.”

The study was primarily funded by grants from the National Institutes of Health and included the following co-authors: Sebastian Galantucci, Maria Carmela Tartaglia, Kindle Rising, Dianne Patterson (both at the UA’s department of speech, language and hearing sciences), Maya Henry, Jennifer Ogar, Jessica DeLeon, Bruce Miller and Maria Luisa Gorno-Tempini.

Contact: Daniel Stolte
stolte@email.arizona.edu
520-626-4402
University of Arizona

Rebuilding the brain’s circuitry

Neuron transplants have repaired brain circuitry and substantially normalized function in mice with a brain disorder, an advance indicating that key areas of the mammalian brain are more reparable than was widely believed.

Collaborators from Harvard University, Massachusetts General Hospital, Beth Israel Deaconess Medical Center (BIDMC) and Harvard Medical School (HMS) transplanted normally functioning embryonic neurons at a carefully selected stage of their development into the hypothalamus of mice unable to respond to leptin, a hormone that regulates metabolism and controls body weight. These mutant mice usually become morbidly obese, but the neuron transplants repaired defective brain circuits, enabling them to respond to leptin and thus experience substantially less weight gain.

Repair at the cellular-level of the hypothalamus — a critical and complex region of the brain that regulates phenomena such as hunger, metabolism, body temperature, and basic behaviors such as sex and aggression — indicates the possibility of new therapeutic approaches to even higher level conditions such as spinal cord injury, autism, epilepsy, ALS (Lou Gehrig’s disease), Parkinson’s disease, and Huntington’s disease.

“There are only two areas of the brain that are known to normally undergo ongoing large-scale neuronal replacement during adulthood on a cellular level — so-called ‘neurogenesis,’ or the birth of new neurons — the olfactory bulb and the subregion of the hippocampus called the dentate gyrus, with emerging evidence of lower level ongoing neurogenesis in the hypothalamus,” said Jeffrey Macklis, Harvard University professor of stem cell and regenerative biology and HMS professor of neurology at Massachusetts General Hospital, and one of three corresponding authors on the paper. “The neurons that are added during adulthood in both regions are generally smallish and are thought to act a bit like volume controls over specific signaling. Here we’ve rewired a high-level system of brain circuitry that does not naturally experience neurogenesis, and this restored substantially normal function.”

The two other senior authors on the paper are Jeffrey Flier, dean of Harvard Medical School, and Matthew Anderson, HMS professor of pathology at BIDMC.

The findings are to appear Nov. 25 in Science.

In 2005, Jeffrey Flier, then the George C. Reisman professor of medicine at BIDMC, published a landmark study, also in Science, showing that an experimental drug spurred the addition of new neurons in the hypothalamus and offered a potential treatment for obesity. But while the finding was striking, the researchers were unsure whether the new cells functioned like natural neurons.

Macklis’s laboratory had for several years developed approaches to successfully transplanting developing neurons into circuitry of the cerebral cortex of mice with neurodegeneration or neuronal injury. In a landmark 2000 Nature study, the researchers demonstrated induction of neurogenesis in the cerebral cortex of adult mice, where it does not normally occur. While these and follow-up experiments appeared to rebuild brain circuitry anatomically, the new neurons’ level of function remained uncertain.

To learn more, Flier, an expert in the biology of obesity, teamed up with Macklis, an expert in central nervous system development and repair, and Anderson, an expert in neuronal circuitries and mouse neurological disease models.

The groups used a mouse model in which the brain lacks the ability to respond to leptin. Flier and his lab have long studied this hormone, which is mediated by the hypothalamus. Deaf to leptin’s signaling, these mice become dangerously overweight.

Prior research had suggested that four main classes of neurons enabled the brain to process leptin signaling. Postdocs Artur Czupryn and Maggie Chen, from Macklis’s and Flier’s labs, respectively, transplanted and studied the cellular development and integration of progenitor cells and very immature neurons from normal embryos into the hypothalamus of the mutant mice using multiple types of cellular and molecular analysis. To place the transplanted cells in exactly the correct and microscopic region of the recipient hypothalamus, they used a technique called high-resolution ultrasound microscopy, creating what Macklis called a “chimeric hypothalamus” — like the animals with mixed features from Greek mythology.

Postdoc Yu-Dong Zhou, from Anderson’s lab, performed in-depth electrophysiological analysis of the transplanted neurons and their function in the recipient circuitry, taking advantage of the neurons’ glowing green from a fluorescent jellyfish protein carried as a marker.

These nascent neurons survived the transplantation process and developed structurally, molecularly, and electrophysiologically into the four cardinal types of neurons central to leptin signaling. The new neurons integrated functionally into the circuitry, responding to leptin, insulin, and glucose. Treated mice matured and weighed approximately 30 percent less than their untreated siblings or siblings treated in multiple alternate ways.

The researchers then investigated the precise extent to which these new neurons had become wired into the brain’s circuitry using molecular assays, electron microscopy for visualizing the finest details of circuits, and patch-clamp electrophysiology, a technique in which researchers use small electrodes to investigate the characteristics of individual neurons and pairs of neurons in fine detail. Because the new cells were labeled with fluorescent tags, postdocs Czupryn, Zhou, and Chen could easily locate them.

The Zhou and Anderson team found that the newly developed neurons communicated to recipient neurons through normal synaptic contacts, and that the brain, in turn, signaled back. Responding to leptin, insulin and glucose, these neurons had effectively joined the brain’s network and rewired the damaged circuitry.

“It’s interesting to note that these embryonic neurons were wired in with less precision than one might think,” Flier said. “But that didn’t seem to matter. In a sense, these neurons are like antennas that were immediately able to pick up the leptin signal. From an energy-balance perspective, I’m struck that a relatively small number of genetically normal neurons can so efficiently repair the circuitry.”

“The finding that these embryonic cells are so efficient at integrating with the native neuronal circuitry makes us quite excited about the possibility of applying similar techniques to other neurological and psychiatric diseases of particular interest to our laboratory,” said Anderson.

The researchers call their findings a proof of concept for the broader idea that new neurons can integrate specifically to modify complex circuits that are defective in a mammalian brain.

The researchers are interested in further investigating controlled neurogenesis — directing growth of new neurons in the brain from within — the subject of much of Macklis’s research as well as Flier’s 2005 paper, and a potential route to new therapies.

“The next step for us is to ask parallel questions of other parts of the brain and spinal cord, those involved in ALS and with spinal cord injuries,” Macklis said. “In these cases, can we rebuild circuitry in the mammalian brain? I suspect that we can.”

This study was funded by the National Institutes of Health, the Jane and Lee Seidman Fund for Central Nervous System Research, the Emily and Robert Pearlstein Fund for Nervous System Repair, the Picower Foundation, the National Institute of Neurological Disorders and Stroke, Autism Speaks, and the Nancy Lurie Marks Family Foundation.

- David Cameron

Citation:

Science, Vol. 334 (6059), November 25, 2011

“Transplanted Hypothalamic Neurons Restore Leptin Signaling and Ameliorate Obesity in db/db Mice” by Czupryn et al.

Harvard Medical School (http://hms.harvard.edu) has more than 7,500 full-time faculty working in 11 academic departments located at the School’s Boston campus or in one of 47 hospital-based clinical departments at 17 Harvard-affiliated teaching hospitals and research institutes. Those affiliates include Beth Israel Deaconess Medical Center, Brigham and Women¹s Hospital, Cambridge Health Alliance, Children¹s Hospital Boston, Dana-Farber Cancer Institute, Forsyth Institute, Harvard Pilgrim Health Care, Hebrew SeniorLife, Joslin Diabetes Center, Judge Baker Children¹s Center, Massachusetts Eye and Ear Infirmary, Massachusetts General Hospital, McLean Hospital, Mount Auburn Hospital, Schepens Eye Research Institute, Spaulding Rehabilitation Hospital, and VA Boston Healthcare System.

Celebrating the 200th anniversary of its founding in 1811, Massachusetts General Hospital (http://www.massgeneral.org) is the original and largest teaching hospital of Harvard Medical School. MGH conducts the largest hospital-based research program in the United States, with an annual research budget of nearly $700 million and major research centers in AIDS, cardiovascular research, cancer, computational and integrative biology, cutaneous biology, human genetics, medical imaging, neurodegenerative disorders, regenerative medicine, reproductive biology, systems biology, transplantation biology and photomedicine.

Beth Israel Deaconess Medical Center is a patient care, teaching and research affiliate of Harvard Medical School and consistently ranks in the top four in National Institutes of Health funding among independent hospitals nationwide. BIDMC is a clinical partner of the Joslin Diabetes Center and a research partner of the Harvard/Dana-Farber Cancer Center. BIDMC is the official hospital of the Boston Red Sox. For more information, visit http://www.bidmc.org.

Contact: David Cameron
david_cameron@hms.harvard.edu
617-960-7221
Harvard Medical School

Dreaming takes the sting out of painful memories

They say time heals all wounds, and new research from the University of California, Berkeley, indicates that time spent in dream sleep can help.

UC Berkeley researchers have found that during the dream phase of sleep, also known as REM sleep, our stress chemistry shuts down and the brain processes emotional experiences and takes the painful edge off difficult memories.

The findings offer a compelling explanation for why people with post-traumatic stress disorder (PTSD), such as war veterans, have a hard time recovering from painful experiences and suffer reoccurring nightmares.They also offer clues into why we dream.

“The dream stage of sleep, based on its unique neurochemical composition, provides us with a form of overnight therapy, a soothing balm that removes the sharp edges from the prior day’s emotional experiences,” said Matthew Walker, associate professor of psychology and neuroscience at UC Berkeley and senior author of the study to be published this Wednesday, Nov. 23, in the journal Current Biology.

For people with PTSD, Walker said, this overnight therapy may not be working effectively, so when a “flashback is triggered by, say, a car backfiring, they relive the whole visceral experience once again because the emotion has not been properly stripped away from the memory during sleep.”

The results offer some of the first insights into the emotional function of Rapid Eye Movement (REM) sleep, which typically takes up 20 percent of a healthy human’s sleeping hours. Previous brain studies indicate that sleep patterns are disrupted in people with mood disorders such as PTSD and depression.

While humans spend one-third of their lives sleeping, there is no scientific consensus on the function of sleep. However, Walker and his research team have unlocked many of these mysteries linking sleep to learning, memory and mood regulation. The latest study shows the importance of the REM dream state.

“During REM sleep, memories are being reactivated, put in perspective and connected and integrated, but in a state where stress neurochemicals are beneficially suppressed,” said Els van der Helm, a doctoral student in psychology at UC Berkeley and lead author of the study.

Thirty – five healthy young adults participated in the study. They were divided into two groups, each of whose members viewed 150 emotional images, twice and 12 hours apart, while an MRI scanner measured their brain activity.

Half of the participants viewed the images in the morning and again in the evening, staying awake between the two viewings. The remaining half viewed the images in the evening and again the next morning after a full night of sleep.

Those who slept in between image viewings reported a significant decrease in their emotional reaction to the images. In addition, MRI scans showed a dramatic reduction in reactivity in the amygdala, a part of the brain that processes emotions, allowing the brain’s “rational” prefrontal cortex to regain control of the participants’ emotional reactions.

In addition, the researchers recorded the electrical brain activity of the participants while they slept, using electroencephalograms. They found that during REM dream sleep, certain electrical activity patterns decreased, showing that reduced levels of stress neurochemicals in the brain soothed emotional reactions to the previous day’s experiences.

“We know that during REM sleep there is a sharp decrease in levels of norepinephrine, a brain chemical associated with stress,” Walker said. “By reprocessing previous emotional experiences in this neuro-chemically safe environment of low norepinephrine during REM sleep, we wake up the next day, and those experiences have been softened in their emotional strength. We feel better about them, we feel we can cope.”

Walker said he was tipped off to the possible beneficial effects of REM sleep on PTSD patients when a physician at a U.S. Department of Veterans Affairs hospital in the Seattle area told him of a blood pressure drug that was inadvertently preventing reoccurring nightmares in PTSD patients.

It turns out that the generic blood pressure drug had a side effect of suppressing norepinephrine in the brain, thereby creating a more stress-free brain during REM, reducing nightmares and promoting a better quality of sleep. This suggested a link between PTSD and REM sleep, Walker said.

“This study can help explain the mysteries of why these medications help some PTSD patients and their symptoms as well as their sleep,” Walker said. “It may also unlock new treatment avenues regarding sleep and mental illness.”

Other co-authors of the study are UC Berkeley sleep researchers Justin Yao, Shubir Dutt, Vikram Rao and Jared Saletin.

Contact: Yasmin Anwar
yanwar@berkeley.edu
510-643-7944
University of California – Berkeley

New NASA missions to investigate how Mars turned hostile

Maybe because it appears as a speck of blood in the sky, the planet Mars was named after the Roman god of war. From the point of view of life as we know it, that’s appropriate. The Martian surface is incredibly hostile for life. The Red Planet’s thin atmosphere does little to shield the ground against radiation from the Sun and space. Harsh chemicals, like hydrogen peroxide, permeate the soil. Liquid water, a necessity for life, can’t exist for very long here –any that does not quickly evaporate in the diffuse air will soon freeze out in subzero temperatures common over much of the planet.

It wasn’t always this way. There are signs that in the distant past, billions of years ago, Mars was a much more inviting place. Martian terrain is carved with channels that resemble dry riverbeds. Spacecraft sent to orbit Mars have identified patches of minerals that form only in the presence of liquid water. It appears that in its youth, Mars was a place that could have harbored life, with a thicker atmosphere warm enough for rain that formed lakes or even seas.

Two new NASA missions, one that will roam the surface and another that will orbit the planet and dip briefly into its upper atmosphere, will try to discover what transformed Mars. “The ultimate driver for these missions is the question, did Mars ever have life?” says Paul Mahaffy of NASA’s Goddard Space Flight Center in Greenbelt, Md. “Did microbial life ever originate on Mars, and what happened to it as the planet changed? Did it just go extinct, or did it go underground, where it would be protected from space radiation and temperatures might be warm enough for liquid water?”

The Mars Science Laboratory (MSL) mission features Curiosity, the largest and most advanced rover ever sent to the Red Planet. The Curiosity rover bristles with multiple cameras and instruments, including Goddard’s Sample Analysis at Mars (SAM) instrument suite. By looking for evidence of water, carbon, and other important building blocks of life in the Martian soil and atmosphere, SAM will help discover whether Mars ever had the potential to support life. Scheduled to launch in late November or December 2011, Curiosity will be delivered to Gale crater, a 96-mile-wide crater that contains a record of environmental changes in its sedimentary rock, in August 2012.

The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, scheduled to launch in late 2013, will orbit Mars and is devoted to understanding the Red Planet’s upper atmosphere. It will help determine what caused the Martian atmosphere — and water — to be lost to space, making the climate increasingly inhospitable for life.

“Both MAVEN and Curiosity/SAM will determine the history of the Martian climate and atmosphere using multiple approaches,” said MAVEN Principal Investigator Bruce Jakosky of the University of Colorado’s Laboratory for Atmospheric and Space Physics. “Measurements of isotope ratios are an approach shared by both missions.”

Isotopes are heavier versions of an element. For example, deuterium is a heavy version of hydrogen. Normally, two atoms of hydrogen join to an oxygen atom to make a water molecule, but sometimes the heavy (and rare) deuterium takes a hydrogen atom’s place.

When water gets lofted into Mars’ upper atmosphere, solar radiation can break it apart into hydrogen (or deuterium) and oxygen. Hydrogen escapes faster because it is lighter than deuterium. Since the lighter version escapes more often, over time, the Martian atmosphere has less and less hydrogen compared to the amount of deuterium remaining. The Martian atmosphere therefore becomes richer and richer in deuterium.

The MAVEN team will measure the amount of deuterium compared to the amount of hydrogen in Mars’ upper atmosphere, which is the planet’s present-day deuterium to hydrogen (D/H) ratio. They will compare it to the ratio Mars had when it was young — the early D/H ratio. (The early ratio can be measured from the D/H ratio in ancient Martian minerals and estimated from observations of the D/H ratio in comets and asteroids, which are believed to be pristine, “fossil” remnants of our solar system’s formation.)

Comparing the present and early D/H ratios will allow the team to calculate how much hydrogen (and, therefore, water) has been lost over Mars’ lifetime. MAVEN will also determine how much Martian atmosphere has been lost over time by measuring the isotope ratios of other elements in the very high atmosphere, such as nitrogen, oxygen, carbon, and noble gases like argon.

MAVEN is expected to reach Mars in 2014. By then, SAM on board the Curiosity rover will have made similar measurements from Gale crater, which will help guide the interpretation of MAVEN’s upper atmosphere measurements.

Measuring isotopes in the atmosphere will reveal its present state. To find out what the Martian atmosphere was like in the past, scientists will use what they discover with MAVEN about the various ways the atmosphere is being removed. With that data, they will build computer simulations, or models, to estimate the condition of the Red Planet’s atmosphere billions of years ago.

Scientists estimate Gale crater may have formed more than three billion years ago. Curiosity will grind up Gale crater minerals and deliver them to SAM so the isotope ratios can be measured, giving a glimpse at the Martian atmosphere from long ago, perhaps when it could have supported life. “SAM’s inputs from the surface of past Martian history will help the MAVEN team work backwards to discover how the Martian atmosphere evolved,” said Joseph Grebowsky of NASA Goddard, MAVEN Project Scientist.

“For example, MAVEN will focus primarily on how solar activity erodes the Martian atmosphere,” adds Mahaffy. Things like the solar wind, a tenuous stream of electrically conducting gas blown from the surface of the Sun, and explosions in the Sun’s atmosphere called solar flares, and eruptions of solar material called coronal mass ejections can all strip away the upper atmosphere of Mars in various ways. “If we figure out how much atmosphere is removed by changes in solar activity, we can extrapolate back to estimate what the isotope ratios should have been billions of years ago. However, if the measurements of the ancient ratios from SAM don’t match up, this suggests that we may have to look at other ways the atmosphere could have been lost, such as giant impacts from asteroids,” says Mahaffy, who is Principal Investigator for SAM and Instrument Lead for the Neutral Gas and Ion Mass Spectrometer instrument on MAVEN. Some scientists believe giant impacts could have blasted significant amounts of the Martian atmosphere into space.

Also, Curiosity will carry a weather station, which will help the MAVEN team understand how changes in the upper atmosphere are related to changes at the surface. “For example, if the rover detects a dust storm, it may have an effect higher up because of the winds and the gravity waves (the bobbing up and down of a parcel of air) it sets up,” says Grebowsky.

“Curiosity will focus on geology and minerals to determine if the environment on Mars in the distant past had the potential to support life,” said Mahaffy. “It will be digging in the dirt trying to understand the habitability issue in a place where water may have flowed, where there could have been a lake. Habitability is also the basic theme of MAVEN — it will be trying to understand from the top down how the atmosphere evolved over time and how it was lost, which ties back to how clement it was early on.”

MAVEN is part of NASA’s Mars Scout program, funded by NASA Headquarters, Washington, D.C. The project is led out of the University of Colorado and managed by NASA Goddard. The Mars Science Laboratory is managed for NASA’s Science Mission Directorate, Washington, D.C., by NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena.

nancy.n.jones@nasa.gov
301-286-0039
NASA/Goddard Space Flight Center

Scientists find evidence for ‘great lake’ on Europa and potential new habitat for life

In a significant finding in the search for life beyond Earth, scientists from The University of Texas at Austin and elsewhere have discovered what appears to be a body of liquid water the volume of the North American Great Lakes locked inside the icy shell of Jupiter’s moon Europa.

The water could represent a potential habitat for life, and many more such lakes might exist throughout the shallow regions of Europa’s shell, lead author Britney Schmidt, a postdoctoral fellow at The University of Texas at Austin’s Institute for Geophysics, writes in the journal Nature.

Further increasing the potential for life, the newly discovered lake is covered by floating ice shelves that seem to be collapsing, providing a mechanism for transferring nutrients and energy between the surface and a vast ocean already inferred to exist below the thick ice shell.

“One opinion in the scientific community has been, ‘If the ice shell is thick, that’s bad for biology – that it might mean the surface isn’t communicating with the underlying ocean,’ ” said Schmidt. “Now we see evidence that even though the ice shell is thick, it can mix vigorously. That could make Europa and its ocean more habitable.”

The scientists focused on Galileo spacecraft images of two roughly circular, bumpy features on Europa’s surface called chaos terrains. Based on similar processes seen here on Earth – on ice shelves and under glaciers overlaying volcanoes – the researchers developed a four-step model to explain how the features form on Europa. It resolves several conflicting observations, some of which seemed to suggest that the ice shell is thick and others that it is thin.

“I read the paper and immediately thought, yes, that’s it, that makes sense,” said Robert Pappalardo, senior research scientist at NASA’s Planetary Science Section who did not participate in the study. “It’s the only convincing model that fits the full range of observations. To me, that says yes, that’s the right answer.”

The scientists have good reason to believe their model is correct, based on observations of Europa from the Galileo spacecraft and of Earth. Still, because the inferred lakes are several kilometers below the surface, the only true confirmation of their presence would come from a future spacecraft mission designed to probe the ice shell. Such a mission was rated as the second-highest priority flagship mission by the National Research Council’s recent Planetary Science Decadal Survey and is currently being studied by NASA. On Earth, radar instruments are used to image similar features within the ice, and are among the instruments being considered for a future Europa mission.

“This new understanding of processes on Europa would not have been possible without the foundation of the last 20 years of observations over Earth’s ice sheets and floating ice shelves,” said Don Blankenship, a co-author and senior research scientist at the Institute for Geophysics, where he leads airborne radar studies of Earth’s ice sheets.

Schmidt and Blankenship’s co-authors are Wes Patterson, planetary scientist at the Johns Hopkins University Applied Physics Laboratory, and Paul Schenk, planetary scientist at the Lunar and Planetary Institute in Houston.

The research was funded by the Institute for Geophysics at The University of Texas at Austin’s Jackson School of Geosciences, the Vetlesen Foundation and NASA.

The paper, “Active formation of ‘chaos terrain’ over shallow subsurface water on Europa,” will appear as an advance online publication of the journal Nature on Nov. 16.

Contact: Marc Airhart
mairhart@jsg.utexas.edu
512-471-2241
University of Texas at Austin

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