Culture

New York City -- An international team of astronomers has discovered an ancient and dramatic head-on collision between the Milky Way and a smaller object, dubbed the "Sausage" galaxy. The cosmic crash was a defining event in the early history of the Milky Way and reshaped the structure of our galaxy, fashioning both its inner bulge and its outer halo, the astronomers report in a series of new papers.

The astronomers propose that around 8 billion to 10 billion years ago, an unknown dwarf galaxy smashed into our own Milky Way. The dwarf did not survive the impact: It quickly fell apart, and the wreckage is now all around us.

"The collision ripped the dwarf to shreds, leaving its stars moving in very radial orbits" that are long and narrow like needles, said Vasily Belokurov of the University of Cambridge and the Center for Computational Astrophysics at the Flatiron Institute in New York City. The stars' paths take them "very close to the centre of our galaxy. This is a telltale sign that the dwarf galaxy came in on a really eccentric orbit and its fate was sealed."

The new papers in the Monthly Notices of the Royal Astronomical Society, The Astrophysical Journal Letters and arXiv.org outline the salient features of this extraordinary event. Several of the papers were led by Cambridge graduate student GyuChul Myeong. He and colleagues used data from the European Space Agency's Gaia satellite. This spacecraft has been mapping the stellar content of our galaxy, recording the journeys of stars as they travel through the Milky Way. Thanks to Gaia, astronomers now know the positions and trajectories of our celestial neighbours with unprecedented accuracy.

The paths of the stars from the galactic merger earned them the moniker "the Gaia Sausage," explained Wyn Evans of Cambridge. "We plotted the velocities of the stars, and the sausage shape just jumped out at us. As the smaller galaxy broke up, its stars were thrown onto very radial orbits. These Sausage stars are what's left of the last major merger of the Milky Way."

The Milky Way continues to collide with other galaxies, such as the puny Sagittarius dwarf galaxy. However, the Sausage galaxy was much more massive. Its total mass in gas, stars and dark matter was more than 10 billion times the mass of our sun. When the Sausage crashed into the young Milky Way, its piercing trajectory caused a lot of mayhem. The Milky Way's disk was probably puffed up or even fractured following the impact and would have needed to regrow. And Sausage debris was scattered all around the inner parts of the Milky Way, creating the 'bulge' at the galaxy's centre and the surrounding 'stellar halo.'

Numerical simulations of the galactic mashup can reproduce these features, said Denis Erkal of the University of Surrey. In simulations run by Erkal and colleagues, stars from the Sausage galaxy enter stretched-out orbits. The orbits are further elongated by the growing Milky Way disk, which swells and becomes thicker following the collision.

Evidence of this galactic remodelling is seen in the paths of stars inherited from the dwarf galaxy, said Alis Deason of Durham University. "The Sausage stars are all turning around at about the same distance from the centre of the galaxy." These U-turns cause the density in the Milky Way's stellar halo to decrease dramatically where the stars flip directions. This discovery was especially pleasing for Deason, who predicted this orbital pileup almost five years ago. The new work explains how the stars fell into such narrow orbits in the first place.

The new research also identified at least eight large, spherical clumps of stars called globular clusters that were brought into the Milky Way by the Sausage galaxy. Small galaxies generally do not have globular clusters of their own, so the Sausage galaxy must have been big enough to host a collection of clusters.

"While there have been many dwarf satellites falling onto the Milky Way over its life, this was the largest of them all," said Sergey Koposov of Carnegie Mellon University, who has studied the kinematics of the Sausage stars and globular clusters in detail.

A study from The Auk: Ornithological Advances presents citizen science data which supports that American Crows and Northwestern Crows almost exclusively (97% of the time) instigate any aggressive interactions with Common Ravens no matter where in North America. The data showed that aggression by crows was most frequent during the breeding season, most likely due to nest predation by ravens. This study not only gives insight into interspecies dynamics, but also how citizen science data can aid behavioral studies at large geographic scales.

Cornell University's Ben Freeman and colleagues used more than 2,000 publicly collected and submitted observations from across North America via eBird to analyze the interspecific aggression between crows (American and Northwestern) and Common Ravens. From these records, it was determined that crows were the predominant aggressor. Crows primarily attacked in small groups rather than one-on-one confrontations with ravens. The breeding season was when most of the attack observations were made, suggesting that nest predation by ravens influences this behavior. Aggression during the winter is potentially explained by crows preemptively deterring nest predation and defending resources needed for nesting later in the year. This study was made possible by citizen scientists who were not even asked to submit such observations. Given this was passively collected data that aided in a behavioral study on a large geographic area, it could act as a model for other research and potential studies conducted.

Lead author Ben Freeman comments, "There are two take-home messages. First, we show that bigger birds do not always dominate smaller birds in aggressive interactions, and that social behavior may allow smaller birds to chase off larger birds. Second, this is a case example of the power of citizen science. It would be next to impossible for even the most dedicated researcher to gather this data across North America. But because there are thousands of people with expertise in bird identification and an interest in bird behavior, we can use data from eBird to study behavioral interactions on a continental scale."

"Given that aggression between crows and ravens can be quite conspicuous, birders and the general public are often the observers of such interactions," adds Kaeli Swift, who was not involved with the research, "yet despite the ease and frequency of witnessing these events, there was little scientific information for curious minds to turn to for explanation. It's quite rewarding then, that the citizen scientists that may have wished for this information are the very people whose observations made this publication possible.

Obstructive sleep apnoea (OSA) is associated with changes to the structure of the brain that are also seen in the early stages of dementia, according to a study published in the European Respiratory Journal [1].

OSA, where the walls of the throat relax and narrow during sleep stopping breathing, is known to reduce levels of oxygen in the blood. The new study suggests that this drop in oxygen may be linked to a shrinking of the brain's temporal lobes and a corresponding decline in memory.

The researchers say the study provides evidence that screening older people for OSA and giving treatment where needed could help prevent dementia in this population.

The study was led by Professor Sharon Naismith from the University of Sydney, Australia. She said: "Between 30 and 50% of the risk for dementia is due to modifiable factors, such as depression, high blood pressure, obesity and smoking. In recent years, researchers have recognised that various sleep disturbances are also risk factors for dementia. We wanted to look specifically at obstructive sleep apnoea and its effects on the brain and cognitive abilities."

The researchers worked with a group of 83 people, aged between 51 and 88 years, who had visited their doctor with concerns over their memory or mood but had no OSA diagnosis. Each participant was assessed for their memory skills and symptoms of depression, and each was given an MRI scan to measure the dimensions of different areas of the brain.

Participants also attended a sleep clinic where they were monitored overnight for signs of OSA using polysomnography. This technique records brain activity, levels of oxygen in the blood, heart rate, breathing and movements.

The researchers found that patients who had low levels of oxygen in their blood while they were sleeping tended to have reduced thickness in the left and right temporal lobes of the brain. These are regions known to be important in memory and affected in dementia.

They also found that this alteration in the brain was linked with participant's poorer ability to learn new information. The researchers say this is the first time a direct link of this kind has been shown.

Conversely, patients with signs of OSA were also more likely to have increased thickness in other regions of the brain, which the researchers say could be signs of the brain reacting to lower levels of oxygen with swelling and inflammation.

OSA is more common in older people and has already been linked with heart disease, stroke and cancer, but it can be treated with a continuous positive airway pressure (CPAP) device, which prevents the airway closing during sleep.

Professor Naismith added: "We chose to study this group because they are older and considered at risk of dementia. Our results suggest that we should be screening for OSA in older people. We should also be asking older patients attending sleep clinics about their memory and thinking skills, and carrying out tests where necessary.

"There is no cure for dementia so early intervention is key. On the other hand, we do have an effective treatment for OSA. This research shows that diagnosing and treating OSA could be an opportunity to prevent cognitive decline before it's too late."

Professor Naismith and her team are now working on research to find out whether CPAP treatment can prevent further cognitive decline and improve brain connectivity in patients with mild cognitive impairment.

Andrea Aliverti, Professor of Bioengineering at Politecnico di Milano, Italy, is Head of the European Respiratory Society's Assembly on Clinical Physiology and Sleep and was not involved in the research. He said: "We already know that as well as disrupting sleep, OSA can increase the risk of high blood pressure, type 2 diabetes, heart attack and stroke. This research adds to evidence that OSA is also linked to dementia and suggests a likely mechanism for the link. However, we can treat OSA and measures such as stopping smoking and losing weight can reduce the risk of developing the condition."

New research provides insights into the extinction of Britain's largest native carnivore.

The study - 'The Presence of the brown bear in Holocene Britain: a review of the evidence' published in Mammal Review - is the first of its kind to collate and evaluate the evidence for the brown bear in post-Ice Age Britain.

Previous research has failed to establish when the brown bear became extinct, and whether or not remains that have been found are of wild native bears or of bears that have been imported from overseas. There is also little evidence to determine why the bear became extinct on British shores.

The author of the paper, Dr Hannah O'Regan from the Department of Classics and Archaeology at the University of Nottingham, says: "The brown bear was Britain's largest carnivore, yet we know surprisingly little about its history, both as a wild animal and in its relation to humans.

"There has never been a comprehensive review of the evidence of brown bears in Britain, and I believe what we are looking at could show that they were sadly killed off earlier than we previously thought."

Dr O'Regan has examined the location of the sites where materials have previously been found, the dating evidence and the body parts present, to determine when the bear became extinct and where it was imported from other countries.

"Previous extinction evidence is unclear and I would suggest two scenarios should be considered - that they became extinct in the late Neolithic or Bronze Age, or, in the early medieval period.

"Most of the remains that have been discovered from the Iron Age and Anglo-Saxon (early medieval) periods relate to skins that were included in burials," says Dr O'Regan.

"Whilst there were live animals present during the Roman, medieval and post-medieval periods (when they were used for entertainment), these were most certainly imported, rather than native animals."

Interpretations of where animals were living can be affected by the use of data from archaeological sites where their remains may have come from several different sources.

For example, determining when wild animals were present in the past is not straight forward, particularly when dealing with the brown bear where furs and live animals were moved and traded over huge distance and over long periods.

The remains of bears in Britain range from full skeletons to isolated toes or claws, and the sites range from caves to human cremations.

"At present the question of when and why the brown bear became extinct is impossible to answer, as there is still much that we don't know about its distribution. There are 57 sites across Britain where clear dates have been determined, but there are an additional 25 that are thought to be Holocene, but have no further information.

"There is also a gap in radiocarbon dates of some 4000 years from the Mesolithic to the Bronze Age. Some of this gap is filled with specimens from archaeological sites, but further research is needed to establish bear distribution in the past.

"Whilst we can speculate on when the bear became extinct based on existing evidence, more research, particularly on the many undated specimens from caves and fens is needed before a clearer patterns of where brown bear distribution and extinction in Britain emerges,"

Researchers have discovered that stabilizing dysfunctional endothelial cells with approved drugs reverses cellular dysfunction in a rat model of cerebral small vessel disease (SVD), hinting towards a new therapeutic approach for the treatment of vascular dementia. As life expectancies climb around the world and society ages, dementia - a group of symptoms characterized by declining memory and cognitive ability - has become a chief concern for scientists and caretakers. One of the most common causes of vascular dementia in the elderly is SVD, which occurs when small blood vessels in the brain are unable to nourish white matter tissue. SVD also contributes to the symptoms of Alzheimer's disease and triples the risk of stroke, rendering it a major cause of cognitive disability in the elderly. However, there are still no dependable therapies for the condition, partially due to a lack of understanding of the mechanisms underlying the changes in blood vessels. Here, Rikesh Rajani and colleagues zeroed in on the role of endothelial cells (ECs), which help prevent unwanted substances and cells from entering the brain. The research team studied brains from humans with SVD and observed they harbored dysfunctional ECs, and found a mutation that could be responsible for the dysfunction. Further analysis showed these ECs secreted a protein called HSP90α that impaired proper functioning of isolated connective tissue cells found in the brain. Approved drugs that stabilize ECs such as simvastatin (a cholesterol-lowering medication) reversed abnormalities in a rat model of SVD after seven weeks of treatment. The authors say that future studies should assess whether EC dysfunction can be reversed at a later stage of SVD, as well as test their findings in other animal models.

Scientists have uncovered a potential approach to treat one of the commonest causes of dementia and stroke in older people.

Studies with rats found the treatment can reverse changes in blood vessels in the brain associated with the condition, called cerebral small vessel disease.

Treatment also prevents damage to brain cells caused by these blood vessel changes, raising hope that it could offer a therapy for dementia.

Small vessel disease, or SVD, is a major cause of dementia and can also worsen the symptoms of Alzheimer's disease. It is responsible for almost half of all dementia cases in the UK and is a major cause of stroke, accounting for around one in five cases.

Patients with SVD are diagnosed from brain scans, which detect damage to white matter - a key component of the brain's wiring.

Until now, it was not known how changes in small blood vessels in the brain associated with SVD can cause damage to brain cells.

A team led by the University of Edinburgh found that SVD occurs when cells that line the small blood vessels in the brain become dysfunctional. This causes them to secrete a molecule into the brain.

The molecule stops production of the protective layer that surrounds brain cells - called myelin - which leads to brain damage.

Treating rats with drugs that stop blood vessel cells from becoming dysfunctional reversed the symptoms of SVD and prevented brain damage, tests found.

Researchers say that further studies will need to test whether the treatment also works when the disease is firmly established. They will also need to check if the treatment can reverse the symptoms of dementia.

Dementia is one of the biggest problems facing society, as people live longer and the population ages. Estimates indicate there are almost 47 million people living with dementia worldwide and the numbers affected are expected to double every 20 years, rising to more than 115 million by 2050.

The research, published in Science Translational Medicine, was carried out at the Medical Research Council Centre for Regenerative Medicine and the UK Dementia Research Institute at the University of Edinburgh. It was funded by the MRC, Alzheimer's Research UK and Fondation Leducq.

Professor Anna Williams, Group Leader at the University of Edinburgh's MRC Centre for Regenerative Medicine, said: "This important research helps us understand why small vessel disease happens, providing a direct link between small blood vessels and changes in the brain that are linked to dementia. It also shows that these changes may be reversible, which paves the way for potential treatments."

Dr Sara Imarisio, Head of Research at Alzheimer's Research UK said: "Changes to the blood supply in the brain play an important role in Alzheimer's disease as well as being a direct cause of vascular dementia. This pioneering research highlights a molecular link between changes to small blood vessels in the brain and damage to the insulating 'white matter' that helps nerve cells to send signals around the brain.

"The findings highlight a promising direction for research into treatments that could limit the damaging effects of blood vessel changes and help keep nerve cells functioning for longer. There are currently no drugs that slow down or stop Alzheimer's disease and no treatments to help people living with vascular dementia. Alzheimer's Research UK is very pleased to have helped fund this innovative research, which is only possible thanks to the work of our dedicated supporters."

Dr Nathan Richardson, the MRC's Head of Molecular and Cellular Medicine, commented: "This study is a great example of how innovative discovery science into regenerative mechanisms can be applied to improve our understanding of how vascular changes contribute to dementia. This research in rats opens up new possibilities for developing therapies for cerebral small vessel disease."

A rare juvenile foot fossil of our early hominin ancestor, Australopithecus afarensis, exhibits several ape-like foot characteristics that could have aided in foot grasping for climbing trees, a new study shows. This finding challenges the long-held assumption that A. afarensis was exclusively bipedal (using only two legs for walking) and only occasionally climbed into trees. Juvenile hominin fossils provide unique insights into how traits (like foot grasping) become less apparent as the individual grows into adulthood. However, juvenile specimens of most human hominin ancestors are scarce, and thus, it has been difficult to trace how important traits are selected in animals, over time. In 2002, archeologists discovered a well-preserved, partial skeleton of an infant A. afarensis, thought to be around 3-years-old at the time of death. Although this 3.32-million-year-old fossil from Dikika, Ethiopia, was announced in a previous 2006 study, many of the skeleton's elements, including the partial foot known as DIK-1-1f, were encased in sediment and therefore had to be carefully uncovered. Many of these structures have now been exposed after additional preparatory work through 2013, and here, Jeremy M. DeSilva and colleagues report on this juvenile hominin's foot features. They discovered that this infant possessed many of the structures necessary to walk on two legs that have been found in adult specimens, but it also retained a convexity of the medial cuneiform - a bone important for joint movement, such as that involved in climbing - into adulthood, they say. This evidence of increased mobility of the toe is an ape-like pattern that DeSilva et al. say is suggestive of a selective advantage of this trait and which offers new insights into the evolution of bipedality.

A mother's diet during pregnancy may have an effect on the composition of her baby's gut microbiome - the community of bacteria living in the gut - and the effect may vary by delivery mode, according to study published in the open access journal Microbiome.

Sara Lundgren, lead author of the study said: "Our study demonstrates an association of a readily modifiable factor, maternal diet, with the infant gut microbiome. This knowledge may be key for developing evidence-based dietary recommendations for pregnant and lactating women."

Lundgren and colleagues at Dartmouth-Hitchcock medical Center, USA found that the gut microbiome in infants six weeks after delivery was composed mostly of Enterobactericeae (~20%), Bifidobacterium (18.6%), Bacteroides (10.44%) and Streptococcus (8.10%).

The authors identified three distinct clusters of microbes in the guts of the 97 babies included in this study that had been vaginally delivered. Cluster 1 was characterized by a high abundance of Bifidobacterium, cluster 2 showed a high abundance of Streptococcus and Clostridium, while cluster 3 had a high abundance of Bacteroides. These clusters were different for the 48 babies delivered by caesarian section, where cluster 1 showed a high abundance of Bifidobacterium, cluster 2 was characterized by high Clostridium but low Streptococcus abundance, and cluster 3 showed a higher abundance of Enterobactericeae.

The authors also observed what appear to be effects of certain aspects of the mothers' diets on the babies' gut microbiome. In babies delivered vaginally, the odds of being in cluster 2 were 2.73 times higher for each additional serving of fruit consumed by the mothers per day. Bifidobacterium was found to be decreased in vaginally born infants if mothers ate more fruit, but increased in babies born by caesarian in relation to the mothers' consumption of red and processed meat. In babies delivered by caesarian section, the odds of being in cluster 2 were 2.36 higher for each additional maternal serving of dairy per day.

Lundgren said: "We analyzed infants delivered vaginally and by cesarean section in separate groups due to our previous knowledge of the transfer of maternal microbiota to the infant that occurs during vaginal delivery, but not with cesarean section delivery. We expected results to differ based on delivery mode, but we were surprised to find that the abundances of some microbes were increased in association with maternal intake of a food group in one delivery mode group, but decreased in the other delivery mode group."

To shed further light on the mechanisms by which maternal diet may affects children's health via the gut microbiome the authors used stool samples from 145 infants enrolled in the New Hampshire Birth Cohort Study, a research project that investigates how various factors affect the health of pregnant women and their children. Most infants whose data was used in this study were born vaginally (66.9%) and exclusively breast fed (70.3%) at six weeks of age. Information on the mothers' diets during pregnancy at 24 to 28 weeks gestation was obtained via food frequency questionnaires.

The authors caution that as their sample only included mothers and infants from Northern New England which has a relatively homogenous population, the generalizability of the findings may be limited. The authors also point out that the effects observed in this study may be due in part to maternal diet during lactation. The observational nature of the study does not allow for conclusions about cause and effect or the directionality of the observed association between maternal diet and the baby gut microbiome.

A new study in The Condor: Ornithological Applications presents negative associations between anthropogenic disturbance (human recreational use of beaches, coastal modifications) and Piping Plovers on their non-breeding grounds. Shorebirds are one of the most threatened bird families in the world. Numerous studies have shown the negative impacts of humans on these birds, whether it be large-scale (e.g., habitat loss, climate change) or small-scale (e.g., ATV use, running with pets, flying kites). This research indicates that there are direct consequences of disturbance. Most Piping Plover research has focused on the breeding season in an attempt to directly influence population numbers, however this study argues that efforts are required throughout the year in all locations to assist Piping Plover conservation.

Virginia Polytechnic Institute and State University's Dan Gibson and colleagues monitored Piping Plovers year-round to determine the health and behavior of individuals. Body condition, survival, and site fidelity were of most interest. Plovers in disturbed areas proved to be significantly lighter in mass, due to the birds not procuring enough food. Given poorer body condition, it should be no surprise that birds in these disturbed areas also had lower survival rates. Piping plovers have strong site fidelity on the breeding grounds and this study supports that fidelity continues on the non-breeding grounds. While physically capable of changing location, it was not common for individuals to do so even if there was a high level of disturbance. The lack of movement by disturbed individuals suggests that aspects of the species' life history (i.e. fidelity) constrained individuals to make seemingly adaptive habitat-use decisions. Some of the strategies used on the breeding grounds (reduced human recreation, roped-off areas, no dogs on beaches) may be beneficial to also do on the non-breeding grounds to ensure year-round conservation and oversight on this threatened shorebird species.

Lead author Dan Gibson comments, "We have a lot of of opportunity to engage with the public in what exactly our research is about. We often try to stress that the impact an individual recreationist has on a shorebird is practically non-existent. However, if every person who uses a beach in a given day influences how these shorebirds feed or rest, those minute impacts can begin to add up over the course of a season that can manifest itself as reductions in individual body condition and ultimately their ability to withstand bad weather conditions or successfully migrate and find a mate. We try to stress that small changes in how we use a beach (e.g., keep dogs on leash, avoid running through groups of birds) can really add up to substantial improvements in the overall quality of coastal habitat for shorebirds."

"This study availed itself of a unique resource that range-wide banding efforts have provided for the study of the demographics of the endangered piping plover," adds College of Environmental Science and Forestry Associate Professor Jonathan Cohen, a shorebird expert who was not involved with the research, "and successfully attempted the difficult task of teasing out the sometimes subtle effect of disturbance in nonbreeding areas on annual vital rates. The finding that this endangered species may not readily abandon habitat that is detrimental for fitness was surprising, and warrants immediate attention from the conservation community."

Failure to meet the United Nations' 2ºC warming limits will lead to sea level rise and dire global economic consequences, new research has warned.

Published today in Environmental Research Letters, a study led by the UK National Oceanographic Centre (NOC) found flooding from rising sea levels could cost $14 trillion worldwide annually by 2100, if the target of holding global temperatures below 2ºC above pre-industrial levels is missed.

The researchers also found that upper-middle income countries such as China would see the largest increase in flood costs, whereas the highest income countries would suffer the least, thanks to existing high levels of protection infrastructure.

Dr Svetlana Jevrejeva, from the NOC, is the study's lead author. She said: "More than 600 million people live in low-elevation coastal areas, less than 10 meters above sea level. In a warming climate, global sea level will rise due to melting of land-based glaciers and ice sheets, and from the thermal expansion of ocean waters. So, sea level rise is one of the most damaging aspects of our warming climate."

Sea level projections exist for emissions scenarios and socio-economic scenarios. However, there are no scenarios covering limiting warming below the 2°C and 1.5°C targets during the entire 21st century and beyond.

The study team explored the pace and consequences of global and regional sea level rise with restricted warming of 1.5 ºC and 2 ºC, and compared them to sea level projections with unmitigated warming following emissions scenario Representative Concentration Pathway (RCP) 8.5.

Using World Bank income groups (high, upper middle, lower middle and low income countries), they then assessed the impact of sea level rise in coastal areas from a global perspective, and for some individual countries using the Dynamic Interactive Vulnerability Assessment modelling framework.

Dr Jevrejeva said: "We found that with a temperature rise trajectory of 1.5°C, by 2100 the median sea level will have risen by 0.52m (1.7ft). But, if the 2°C target is missed, we will see a median sea level rise of 0.86m (2.8ft), and a worst-case rise of 1.8m (5.9ft).

"If warming is not mitigated and follows the RCP8.5 sea level rise projections, the global annual flood costs without adaptation will increase to $14 trillion per year for a median sea level rise of 0.86m, and up to $27 trillion per year for 1.8m. This would account for 2.8 per cent of global GDP in 2100."

The projected difference in coastal sea levels is also likely to mean tropical areas will see extreme sea levels more often.

"These extreme sea levels will have a negative effect on the economies of developing coastal nations, and the habitability of low-lying coastlines," said Dr Jevrejeva. "Small, low-lying island nations such as the Maldives will be very easily affected, and the pressures on their natural resources and environmental will become even greater.

"These results place further emphasis on putting even greater efforts into mitigating rising global temperatures."

You see the flour in the pantry, so you reach for it. You see the traffic light change to green, so you step on the gas. While the link between seeing and then moving in response is simple and essential to everyday existence, neuroscientists haven't been able to get beyond debating where the link is and how it's made. But in a new study in Nature Communications, a team at MIT's Picower Institute for Learning and Memory provides evidence that one crucial brain region called the posterior parietal cortex (PPC) plays an important role in converting vision into action.

"Vision in the service of action begins with the eyes, but then that information has to be transformed into motor commands," said senior author Mriganka Sur, Paul E. and Lilah Newton Professor of Neuroscience in the Department of Brain and Cognitive Sciences. "This is the place where that planning begins."

Sur said the study may help to explain a particular problem in some people who have suffered brain injuries or stroke, called "hemispatial neglect." In such cases, people are not able to act upon or even perceive objects on one side of their visual field. Their eyes and bodies are fine, but the brain just doesn't produce the notion that there is something there to trigger action. Some studies have implicated damage to the PPC in such cases.

In the new study, the research team pinpointed the exact role of the PPC in mice and showed that it contains a mix of neurons attuned to visual processing, decision-making and action.

"This makes the PPC an ideal conduit for flexible mapping of sensory signals onto motor actions," said Gerald Pho, a former graduate student in the Sur lab who is now at Harvard University. Pho is co-lead author with Michael Goard, a former MIT postdoctoral fellow now at UC Santa Barbara.

Mouse see, mouse do

To do the research, the team trained mice on a simple task: if they saw a striped pattern on the screen drift upward, they could lick a nozzle for a liquid reward but if they saw the stripes moving to the side, they should not lick, lest they get a bitter liquid instead. In some cases they would be exposed to the same visual patterns, but the nozzle wouldn't emerge. In this way, the researchers could compare the neurons' responses to the visual pattern with or without the potential for motor action.

As the mice were viewing the visual patterns and making decisions whether to lick, the researchers were recording the activity of hundreds of neurons in each of two regions of their brain: the visual cortex, which processes sight, and the PPC, which receives input from the visual cortex, but also input from many other sensory and motor regions. The cells in each region were engineered to glow more brightly when they became active, giving the scientists a clear indication of exactly when they became engaged by the task.

Visual cortex neurons, as expected, principally lit up when the pattern appeared and moved, though they were split about evenly between responding to one visual pattern or the other.

Neurons in the PPC showed more varied responses. Some acted like the visual cortex neurons but most (about 70 percent) were active based on whether the pattern was moving the right way for licking (upward) and only if the nozzle was available. In other words, most PPC neurons were selectively responsive not merely to seeing something, but to the rules of the task and the opportunity to act on the correct visual cue.

"Many neurons in the PPC seemed to be active only during particular combinations of visual input and motor action," Goard said. "This suggests that rather than playing a specified role in sensory or motor processing, they can flexibly link sensory and motor information to help the mouse respond to their environment appropriately."

But even the occasional error was instructive. Consider the case when the nozzle was available and the stripes were moving sideways. In that case, a mouse should not lick even though it could. Visual cortex neurons behaved the same way regardless of the mouse's decision, but PPC neurons were more active just before a mouse licked by mistake, than just before a mouse didn't lick. This suggested that many PPC neurons are oriented toward acting.

Rule reversal

Not yet fully convinced that the PPC encoded the decision to lick based on seeing the correct stripe movement, the researchers switched the rules of the task. Now, the nozzle would drip out the reward upon licking to the sideways stripe pattern and emit the bitter liquid when the stripes moved up. In other words, the mouse still saw the same things, but what they meant for action had reversed.

With the same mice re-trained, the researchers then looked again at the same neurons in the same regions. Visual cortex neurons didn't change their activity at all. Those that followed the upward pattern or sideways pattern still did as before. What the mice were seeing, after all, hadn't changed.

However, the neural responses in PPC changed along with the rules for action. Neurons that had been activated selectively for upward visual patterns now responded instead to sideways patterns. In other words, learning of the new rules was directly evident in the changed activity of neurons in the PPC. The researchers therefore observed a direct correlate of learning at the cellular level, strongly implicating the PPC as a critical node for where seeing meets acting on that information.

"If you flipped the rules of traffic lights so that red means go, the visual input would still be driven by the colors, but the linkage to motor output neurons would switch, and that happens in the PPC," Sur said.

The findings extend earlier results made by other researchers in primates, the researchers wrote, suggesting that mice bear the needed similarity to aid further studies of the PPC.

"Our understanding of how decisions are computed and visuomotor transformations are made, will be greatly aided by future circuit-level analyses of PPC function in this powerful model system," they concluded.

Barcelona, 4 July 2018: Despite dramatic uptake in the numbers of women electing to freeze their eggs as insurance against an anticipated age-related fertility decline, there is still little that clinics can predict about outcome based on real-life experience. Indeed, at one of Europe's biggest fertility centres - the Brussels Centre for Reproductive Medicine in Belgium - only 7.6% of women have returned to thaw their eggs and try for a pregnancy. And only one-third of those have been successful.

Details of the follow-up, which recorded the experience of 563 women freezing their eggs between January 2009 and November 2017, are presented as a poster here at the 34th Annual Meeting of ESHRE in Barcelona. Such details, said investigator Michel De Vos from the Brussels group, "are needed for a comprehensive appraisal of social freezing". Otherwise, he added, "little is known about these 'social freezers' and their reproductive outcomes."

The review of data showed that the 563 women in the series had 902 assisted reproduction treatments to collect eggs. And that:

the mean age of those freezing their eggs was 36.5 years

a mean number of 8.5 eggs per patient were collected and frozen (by the rapid freezing technique of vitrification) at each treatment cycle

so far, just 12.8% (72 of 563) have returned to the clinic for reproduction treatment; of these, no more than 43 had their eggs thawed, fertilised and transferred

of these social freezers 43% had fertilisation with donor sperm either by intrauterine insemination or ICSI

the overall survival rate of thawed eggs was 73.4%, reflecting the high efficiency of the vitrification technology

in total the ongoing pregnancy after embryo transfer was 32.6% (14/43)

De Vos also noted that the majority of the social freezers who did return had found a suitable partner to pursue motherhood. But from the data he was unable to clarify "whether their previous decision to undergo oocyte cryopreservation has enhanced the probability of a live birth".

De Vos reported that these results in Brussels are in line with others from large fertility centres, of which one (in Valencia) recorded an ongoing pregnancy rate of 21%, and reflect the limitations of social egg freezing for women freezing eggs after the age of 35. He added that the average number of eggs retrieved in social freezers who did have an ongoing pregnancy was 9.2 eggs per patient.

While social egg freezing in Brussels reflects an upward trend in popularity apparent in many other large European and US fertility centres, De Vos urged women considering uptake after the age of 35 "not to have unrealistic expectations". "Our results show that one in three women who return to the clinic do achieve an ongoing pregnancy with their vitrified oocytes," said De Vos. "They returned at a mean age of 42 years after having their oocytes vitrified at a mean age of 36 years." But he warned that - as with any fertility treatment - egg quality declines markedly with age, and success rates will be lower than 33% in women freezing their eggs beyond this age.

Poster 523

Follow-up of elective oocyte cryopreservation for age-related reasons: utilisation of vitrified oocytes and reproductive outcomes of women who return.

Researchers think they have a better understanding for how ancient North Americans thrived for centuries in northwestern New Mexico's arid desert.

A multidisciplinary team of experts from the University of Cincinnati determined that the sandy soils of Chaco Canyon were not too salty to grow crops such as maize, beans and squash for the more than 1,200 people who occupied this beautiful but harsh landscape during its most prolific years.

Researchers have long debated whether the people who lived here between 800 and 1300 AD were self-sufficient or relied partially or entirely on imported food to survive. These ancestral Puebloans built elaborate adobe structures, some of them four stories tall and recessed among cliff faces under the hot New Mexico sun.

Some previous research suggested that the desert soils simply were too saline for agriculture. The implication was that Chaco Canyon could not support a large resident population without lots of outside help. Alternately, researchers speculated that Chaco Canyon, a place of religious importance, maintained a small resident population that served and benefited from a larger population of visitors making pilgrimages.

But UC's soil analysis suggests that the most significant challenge for growing crops was irrigation. That's where ancestral Puebloans demonstrated particularly adroit farming skills and perceptive land management, said Jon-Paul McCool, a UC graduate and lead author of the study.

"The major limitation is water. You couldn't rely on rain for field agriculture," McCool said. "You'd have to gather and control water, which we know people in the region did."

McCool earned PhD and master's degrees in geography and museum studies at UC and now teaches at Valparaiso University.

Chaco Canyon has evidence of constructed canals -- water-diversion channels designed to direct rainfall to farm fields.

"If you have a population of 1,200 people, how did they survive?" McCool asked. "The part I'm interested in is the interrelationships between people and their environment and how each of them influences the other."

The study was published in June in the journal PLOS ONE.

One prevailing theory is that residents of Chaco Canyon depended heavily on outside assistance for sustenance. But the most likely resource for imported agriculture was in the Chuska Mountains on the Arizona border, more than 50 miles from Chaco Canyon.

Traveling great distances in a dry environment is commonplace in other parts of the world. But what makes travel in the ancient Southwest especially taxing is that every step was taken on foot -- human foot.

Ancient North Americans had no camels, horses, mules, llamas, alpacas, oxen or sled dogs to carry supplies. There were precious few navigable waterways. So if you wanted to bring something on such a trip, you were carrying it every step, said Nicholas Dunning, a professor of geography in UC's McMicken College of Arts and Science.

"You have to go to the Andes before you find a native beast of burden in the New World," Dunning said. "So if you're using human porters, you quickly reach a point of diminishing returns."

Dunning said the study was able to determine that the soils could support agriculture in Chaco Canyon and that irrigation canals found at the site were built at least as early as the eighth century.

"The evidence is compelling that they produced most of the food that they consumed in Chaco Canyon and devised sophisticated irrigation strategies to do it," Dunning said.

Today, Chaco Canyon sees about 9 inches of rain per year, four times less than the breadbasket of the American Midwest. To make the most of this precious resource, ancestral Puebloans built elaborate canals to divert rainfall to their farm fields.

UC researchers re-examined soil samples taken from sites in and around Chaco Canyon. While some of these sites indeed did have saline levels too high to support agriculture, that was the exception, researchers found.

Instead, researchers found that the desert soils were not much different from soils in other parts of the Southwest where agriculture was practiced.

"The evidence is persuasive that they grew their own food," Dunning said.

"My experience in traditional societies is farmers and agricultural populations are very risk averse," Dunning said. "So you tend to think in ways of making sure you have enough to eat yourself each year along with seed for next year."

UC's team consisted of geologists, archaeologists and biologists. They spent weeks each summer studying different aspects of Chaco Canyon. Many of the study sites are accessible only by foot so researchers would hike in at dawn before the afternoon heat became too oppressive. A collapsible tent shelter provided some relief from the sun.

Researchers could drink as much as four liters of water each workday, packing in provisions and packing out soil samples. Dunning said New Mexico's evening sky was full of stars.

"The skies were extraordinary. We were there for the Perseid meteor shower," Dunning said. "The environment is quite amazing. We would set off for work before dawn. We wanted to be at the excavation sites before the sun came up because the morning was the only decent time to work."

UC's research is adding to what scientists already know about ancestral Puebloans in New Mexico. These former occupants of Chaco Canyon left behind evidence of having traded goods with people from distant places. Archaeologists have found seashells from California and macaw feathers and cacao from Mexico.

Co-author and UC research associate Samantha Fladd thinks it is improbable that residents would rely on regular deliveries of staple goods from places so far away, especially if they could grow food themselves.

"It seems highly unlikely that this would be a sustainable system," Fladd said.

"It makes more sense to me that there would be trade relationships where populations would help each other in bad years. To rely on one location for most of your food would not be the most sustainable system," she said. "I would be skeptical you would see that much patronage."

Fladd said a round trip between Chaco Canyon and the Chuska Mountains would take as long as a week, depending on how many supplies were carried.

The people of Chaco Canyon left behind petroglyphs carved into the rock -- drawings of animals, people and symbols. These included the famed "Sun Dagger," a notch in a slot canyon that casts a dagger-shaped beam of light onto a shaded rock face upon which is a carved petroglyph spiral that marks the sun dagger's path across the wall over the four seasons.

They also were known for their turquoise carvings, including a famous frog figure among the collection of the National Park Service.

UC professor emeritus Vernon Scarborough, one of the paper's co-authors, spent his career studying ancient land-use strategies around the world. Chaco Canyon demonstrates how people were able to engineer their landscape in a resourceful and sustainable way, he said.

"Chaco Canyon captures the ingenuity and creativity of the human spirit like few other places," Scarborough said.

"Our work and that of other colleagues is beginning to show the significance of low-tech adaptations in attempting to accommodate life on Earth," Scarborough said. "A greater understanding of just how these ancient, 'primitive' systems adapted and function merits a thoughtful assessment given the social and environmental stress we face globally today."

Scientists still aren't sure why the population of Chaco Canyon declined over the centuries. Chaco Canyon continued to be occupied intermittently after 1300.

"Every civilization comes to an end. But they went through a lot," McCool said. "What strategies allowed that civilization to continue? You're dealing with people who lived in a place for hundreds of years. What adaptations did they make to deal with changing circumstances?"

Fladd said when she goes to Chaco Canyon, she likes to hike up the Pueblo Alto trail. From the top of the mesa, she can survey all of Pueblo Bonito below her.

"I don't want to pretend I can understand their concerns 800 years ago," Fladd said. "But I am in awe of what they were able to do. It's a testament to how adaptable and creative they were."

Chaco Canyon has a long history of generating academic debates, in part because it's such a fascinating place. Chaco Canyon has been studied or referenced in thousands of research papers.

"Archaeology is a fun science because it requires a lot of imagination," Dunning said. "You're never dealing with complete data sets, so one has to fill in the holes. That's where the controversy comes in."

A new sugar tax introduced on soft drinks in Chile has been effective in reducing consumption of sugary drinks, new research carried out in the country has revealed.

However, the international research team, led by academics from the University of York, say although consumption may have dropped, it may not be enough to reduce socioeconomic inequalities in diet-related health.

A growing number of cities and countries have adopted taxes on sugary drinks to help combat sugar consumption, which is blamed for rising obesity levels. The tax was introduced in Chile in 2014.

The team analysed household grocery purchasing data from Chile for three years before the tax was introduced and for one year afterwards.

The policy targeted any non-alcoholic beverages to which colourants, flavourings or sweeteners have been added. For beverages with an added sugar concentration of 6.25 grams per 100ml or more, the existing tax was increased from 13% to 18%; while for those below this threshold, the tax was decreased from 13% to 10%, producing an 8% tax difference.

For example, the tax change, if fully transmitted to the consumer, would increase the prices of a 500ml sugary beverage from 500 pesos (£0.60) to 525 pesos (£0.62), and it would drop the price of an equally priced non-sugary beverage to 485 pesos (£0.57).

The authors of the report conclude that despite the tax incentive being comparatively small, there are signs that purchasing of beverages with higher sugar content declined, particularly among high socioeconomic groups.

The study revealed an overall 21.6% decrease in the monthly purchased volume of the higher taxed, sugary soft drinks. Among middle and high socioeconomic groups, the monthly purchased volume fell by 16% and 31%, respectively. There was a 12% reduction in purchase volume for the low socioeconomic group.

However, this was statistically insignificant. By contrast, the volume of non-sugary soft drinks, for which the tax rate had been decreased, showed no increase in purchased volume for any socioeconomic groups.

Marc Suhrcke, Professor of Global Health Economics at the University of York said: "The results suggest that the Chilean tax policy may have been effective in reducing consumption of sugary drinks, though not necessarily to reduce socioeconomic inequalities in diet-related health." "Further evaluations are needed to analyse the policy effect on purchasing of soft drinks in the long run as well as to evaluate the impact on health outcomes."

Professor Cuadrado from the University of Chile said: "Our results suggest an overall reduction of sugar consumption after the implementation of the tax in Chile. From a public health perspective, even a small reduction in sugar intake at the population level could lead to significant health gains."

He added: "Other countries may take heart from our findings, in that it indicates that the tax incentive may not need to be huge to have impact. It also shows that there may be more than one way in which an SSB tax can be implemented with some success."

The authors of the report say the latest findings from Chile could have implications for the UK, which introduced a sugar tax on soft drinks in April 2018.

For more than a century, scientists have understood that natural selection have profound effects on how an animal looks - Anolis lizards that spend more time on the ground, for example, might need longer legs for running, while species that remain in the trees usually have shorter legs better suited for climbing.

But can different behaviors be favored by natural selection under different environments?

Scientists have long believed the answer was yes, but empirical data to support this idea was lacking, but a new paper authored by Oriol Lapiedra, a post-doctoral fellow working in the lab of former Harvard faculty members Jonathan Losos, have provided experimental evidence to support it.

Working with Losos, now the William H. Danforth Distinguished University Professor at Washington University at Saint Louis and Director of the Living Earth Collaborative, while both were still at Harvard, Lapiedra is the lead author of a recent study that demonstrated a link between individual variation in risk-taking behavior and survival of animals in changing environments.

Along with Lapiedra and Losos, researchers from the University of Rhode Island, UC at Davis and the University of Missouri also co-authored the study.

The first-of-its-kind study released small populations of lizards onto tiny, uninhabited islands in the Bahamas, and found that specific personality types - the very bold or the very shy - survived longer depending on whether predators were present. The study was described in a paper published earlier this year in Science.

"As biologists, when we describe animals, we have the genetic part - what we call genotypes - and we have what we can see about the animal - what we call phenotypes," Lapiedra said. "Traditionally, when we think of phenotypes, we focus on morphology and physiology, but another important dimension of phenotype is behavior. Because behavior actually determines how animals interact with their environment, we expected it to be an important factor for animals to survive new ecological challenges. For instance, one would expect that behavior will play a relevant role in determining the survival of animals in the current context of global climate change."

Surprisingly, however, no experimental studies had been able to actually conduct an experiment in wild animal populations and test the idea in nature.

To pull it off, Lapiedra got some help from tiny lizards called anoles that are native to islands throughout the Caribbean.

Widely studied by biologists, including Losos, the lizards prefer to perch on low vegetation, but must forage for food on the ground, which exposes them to other, predatory lizard species.

"As you can imagine, there's a tradeoff here," Lapiedra said. "They need to go to the ground to get food, but that's where the predators are. So you could make a prediction that, if ground predators aren't present, the animals that are more bold, or willing to take risks, might go to the ground more often. They would get more food, have more offspring and pass on their genes.

"But what happens when there are predators on the ground?" he continued. "Then you would expect the opposite to happen - the bold lizards would be killed more frequently. This is a very simple idea, but up until now, we didn't have evidence from nature that natural selection acted on individual variation in behavior."

To test it, Lapiedra identified a number of tiny - only a few hundred square feet - islands in the Bahamas that had been scoured clean of lizards by recent hurricanes.

Lapiedra and colleagues trapped hundreds of lizards from the surrounding area and subjected each to a type of lizard "personality test" to evaluate their risk-taking behavior.

The lizards were placed in small experimental enclosures and researchers measured their willingness to explore their surroundings by tracking how long they waited before leaving their refuges. The team also tracked how much time each lizard spent on the ground before jumping to a perch. Based on those results, each lizard was assigned a score on a spectrum from very bold to very shy, and were implanted with unique "alpha tags," similar to those used to identify pets.

"What we did was to simulate the process of natural colonization on these islands," Lapiedra said. "On eight islands, we released lizards that ranged from very bold to very shy. On four of the islands, we went back one week later and also released native ground predators, namely curly tailed lizards, so what we have are two scenarios - on four islands, the lizards can get as much food as they want, and they don't need to worry about predators on the ground. On those islands we expected the lizards who were more willing to take risks to survive and produce more offspring.

"On the islands with predators, however, we expected that lizards with bolder 'personalities' would spend a lot of time on the ground, and would be more vulnerable to predation," he continued. "After a few months, when we went back to the islands, that's exactly what we found."

The authors of this study also found selection for different morphological traits that occurred in parallel to natural selection on behavior. This result is particularly exciting because it shows that natural selection is a complex process that can simultaneously shape different phenotypic dimensions such as behavior and morphology at the same time.

Besides upending the common view that natural selection and evolution can drive physical, but not behavioral changes, the study points to the need for further research.

"Traditionally, people have assumed an animal might be bold or shy depending on the situation, but as we are doing more research in this field, we are realizing that is not the case," Lapiedra said. "Researchers are increasingly finding that there are individuals that are always shy or others that are always bold." Unraveling how these behavioral traits emerge and change through time will help us understand how animals deal with changes in their environments--an idea of major importance in our rapidly changing Planet.

And though the study demonstrated that those traits can face pressure from natural selection, it's not yet clear whether they can be inherited by later generations.

"Natural selection is crucial for adaptation to new environmental challenges," Lapiedra said. "But the presence of natural selection per se does not imply evolution. What we have shown is that there is consistent variation in behavior. If there is heritability in behavior...lizards that are more bold would have more bold offspring. But so far, we don't have evidence for this. We can say that some phenotypes survive better than others in certain conditions...but that does not necessarily imply evolution."

That evidence, however, may be on the way. Lapiedra and colleagues have been collecting genetic samples from the offspring born on the islands and are using genetic tools to identify whether they inherit their bold or shy nature from their parents.

"We have two years of data already," he said. "From that we hope to be able to say if behavior is heritable or not, and if it's changing in one direction or not. So that would provide actual evidence for evolution in behavior - that would be a big step to unravel the role behavior plays in evolution."