Two new Earth-like planets discovered near Teegarden's Star

Exoplanets illustration.

An international research team led by the University of Göttingen has discovered two new Earth-like planets near one of our closest neighboring stars. "Teegarden's star" is only about 12.5 light years away from Earth and is one of the smallest known stars. It is only about 2,700 °C warm and about ten times lighter than the Sun. Although it is so close to us, the star wasn't discovered until 2003. The scientists observed the star for about three years. The results were published in the journal Astronomy and Astrophysics.

Their data clearly show the existence of two planets. "The two planets resemble the inner planets of our solar system," explains lead author Mathias Zechmeister of the Institute for Astrophysics at the University of Göttingen. "They are only slightly heavier than Earth and are located in the so-called habitable zone, where water can be present in liquid form."

The astronomers suspect that the two planets could be part of a larger system. "Many stars are apparently surrounded by systems with several planets," explains co-author Professor Stefan Dreizler of the University of Göttingen. Teegarden's star is the smallest star where researchers have so far been able to measure the weight of a planet directly. "This is a great success for the Carmenes project, which was specifically designed to search for planets around the lightest stars," says Professor Ansgar Reiners of the University of Göttingen, one of the scientific directors of the project.

Although planetary systems around similar stars are known, they have always been detected using the "transit method" -- the planets have to pass visibly in front of the star and darken it for a moment, which only happens in a very small fraction of all planetary systems. Such transits have not yet been found for the new planets. But the system is located at a special place in the sky: from Teegarden's star you can see the planets of the solar system passing in front of the Sun.

"An inhabitant of the new planets would therefore have the opportunity to view the Earth using the transit method," says Reiners. The new planets are the tenth and eleventh discovered by the team.

Carmenes is carried out by the universities of Göttingen, Hamburg, Heidelberg, and Madrid, the Max-Planck-Institut für Astronomie Heidelberg, Institutes Consejo Superior de Investigaciones Científicas in Barcelona, Granada, and Madrid, Thüringer Landessternwarte, Instituto de Astrofísica de Canarias, and Calar-Alto Observatory.

From Science Daily

The brain consumes half of a child's energy -- and that could matter for weight gain

Children at school.

Weight gain occurs when an individual's energy intake exceeds their energy expenditure -- in other words, when calories in exceed calories out. What is less well understood is the fact that, on average, nearly half of the body's energy is used by the brain during early childhood.

In a new paper published in the journal Proceedings of the National Academy of Sciences (PNAS), "A hypothesis linking the energy demand of the brain to obesity risk," co-authors Christopher Kuzawa of Northwestern University and Clancy Blair of New York University School of Medicine, propose that variation in the energy needs of brain development across kids -- in terms of the timing, intensity and duration of energy use -- could influence patterns of energy expenditure and weight gain.

"We all know that how much energy our bodies burn is an important influence on weight gain," said Kuzawa, professor of anthropology in the Weinberg College of Arts and Sciences and a faculty fellow with the Institute for Policy Research at Northwestern. "When kids are 5, their brains use almost half of their bodies' energy. And yet, we have no idea how much the brain's energy expenditure varies between kids. This is a huge hole in our understanding of energy expenditure."

"A major aim of our paper is to bring attention to this gap in understanding and to encourage researchers to measure the brain's energy use in future studies of child development, especially those focused on understanding weight gain and obesity risk."

According to the authors, another important unknown is whether programs designed to stimulate brain development through enrichment, such as preschool programs like Head Start, might influence the brain's pattern of energy use.

"We believe it plausible that increased energy expenditure by the brain could be an unanticipated benefit to early child development programs, which, of course, have many other demonstrated benefits," Kuzawa said. "That would be a great win-win."

This new hypothesis was inspired by Kuzawa and his colleagues' 2014 study showing that the brain consumes a lifetime peak of two-thirds of the body's resting energy expenditure, and almost half of total expenditure, when kids are five years old. This study also showed that ages when the brain's energy needs increase during early childhood are also ages of declining weight gain. As the energy needed for brain development declines in older children and adolescents, the rate of weight gain increases in parallel.

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The evolution of puppy dog eyes

Dog with raised eyebrows.

Dogs have evolved new muscles around the eyes to better communicate with humans.

New research comparing the anatomy and behavior of dogs and wolves suggests dogs' facial anatomy has changed over thousands of years specifically to allow them to better communicate with humans.

In the first detailed analysis comparing the anatomy and behavior of dogs and wolves, researchers found that the facial musculature of both species was similar, except above the eyes. Dogs have a small muscle, which allows them to intensely raise their inner eyebrow, which wolves do not.

The authors suggest that the inner eyebrow raising movement triggers a nurturing response in humans because it makes the dogs' eyes appear larger, more infant like and also resembles a movement humans produce when they are sad.

The research team, led by comparative psychologist Dr Juliane Kaminski, at the University of Portsmouth, included a team of behavioural and anatomical experts in the UK and USA.

It is published in the journal Proceedings of the National Academy of Sciences (PNAS).

Dr Kaminski said: "The evidence is compelling that dogs developed a muscle to raise the inner eyebrow after they were domesticated from wolves.

"We also studied dogs' and wolves' behavior, and when exposed to a human for two minutes, dogs raised their inner eyebrows more and at higher intensities than wolves.

"The findings suggest that expressive eyebrows in dogs may be a result of humans unconscious preferences that influenced selection during domestication. When dogs make the movement, it seems to elicit a strong desire in humans to look after them. This would give dogs, that move their eyebrows more, a selection advantage over others and reinforce the 'puppy dog eyes' trait for future generations."

Dr Kaminski's previous research showed dogs moved their eyebrows significantly more when humans were looking at them compared to when they were not looking at them.

She said: "The AU101 movement is significant in the human-dog bond because it might elicit a caring response from humans but also might create the illusion of human-like communication."

Lead anatomist Professor Anne Burrows, at Duquesne University, Pittsburgh, USA, co-author of the paper, said: "To determine whether this eyebrow movement is a result of evolution, we compared the facial anatomy and behaviour of these two species and found the muscle that allows for the eyebrow raise in dogs was, in wolves, a scant, irregular cluster of fibres.

"The raised inner eyebrow movement in dogs is driven by a muscle which doesn't consistently exist in their closest living relative, the wolf.

"This is a striking difference for species separated only 33,000 years ago and we think that the remarkably fast facial muscular changes can be directly linked to dogs' enhanced social interaction with humans."

Dr Kaminski and co-author, evolutionary psychologist Professor Bridget Waller, also at the University of Portsmouth, previously mapped the facial muscular structure of dogs, naming the movement responsible for a raised inner eyebrow the Action Unit (AU) 101.

Professor Waller said: "This movement makes a dogs' eyes appear larger, giving them a childlike appearance. It could also mimic the facial movement humans make when they're sad.

"Our findings show how important faces can be in capturing our attention, and how powerful facial expression can be in social interaction."

Co-author and anatomist Adam Hartstone-Rose, at North Carolina State University, USA, said: "These muscles are so thin that you can literally see through them -- and yet the movement that they allow seems to have such a powerful effect that it appears to have been under substantial evolutionary pressure. It is really remarkable that these simple differences in facial expression may have helped define the relationship between early dogs and humans."

Co-author Rui Diogo, an anatomist at Howard University, Washington DC, USA, said: "I must admit that I was surprised to see the results myself because the gross anatomy of muscles is normally very slow to change in evolution, and this happened very fast indeed, in just some dozens of thousands of years."

Soft tissue, including muscle, doesn't tend to survive in the fossil record, making the study of this type of evolution harder.

The only dog species in the study that did not have the muscle was the Siberian husky, which is among more ancient dog breeds.

An alternative reason for the human-dog bond could be that humans have a preference for other individuals which have whites in the eye and that intense AU 101 movements exposes the white part of the dogs eyes.

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NASA's Cassini reveals New Sculpting in Saturn Rings

A false-color image mosaic shows Daphnis, one of Saturn's ring-embedded moons, and the waves it kicks up in the Keeler gap. Images collected by Cassini's close orbits in 2017 are offering new insight into the complex workings of the rings.

As NASA's Cassini dove close to Saturn in its final year, the spacecraft provided intricate detail on the workings of Saturn's complex rings, new analysis shows.

Although the mission ended in 2017, science continues to flow from the data collected. A new paper published June 13 in Science describes results from four Cassini instruments taking their closest-ever observations of the main rings.

Findings include fine details of features sculpted by masses embedded within the rings. Textures and patterns, from clumpy to strawlike, pop out of the images, raising questions about the interactions that shaped them. New maps reveal how colors, chemistry and temperature change across the rings.

Like a planet under construction inside a disk of protoplanetary material, tiny moons embedded in Saturn's rings (named A through G, in order of their discovery) interact with the particles around them. In that way, the paper provides further evidence that the rings are a window into the astrophysical disk processes that shape our solar system.

The observations also deepen scientists' understanding of the complex Saturn system. Scientists conclude that at the outer edge of the main rings, a series of similar impact-generated streaks in the F ring have the same length and orientation, showing that they were likely caused by a flock of impactors that all struck the ring at the same time. This shows that the ring is shaped by streams of material that orbit Saturn itself rather than, for instance, by cometary debris (moving around the Sun) that happens to crash into the rings.

"These new details of how the moons are sculpting the rings in various ways provide a window into solar system formation, where you also have disks evolving under the influence of masses embedded within them," said lead author and Cassini scientist Matt Tiscareno of the SETI Institute in Mountain View, California.

Enduring Mysteries

At the same time, new puzzles have arisen and old mysteries have deepened with the latest research. The close-up ring images brought into focus three distinct textures -- clumpy, smooth and streaky -- and made it clear that these textures occur in belts with sharp boundaries. But why? In many places the belts aren't connected to any ring characteristics that scientists have yet identified.

"This tells us the way the rings look is not just a function of how much material there is," Tiscareno said. "There has to be something different about the characteristics of the particles, perhaps affecting what happens when two ring particles collide and bounce off each other. And we don't yet know what it is."

The data analyzed were gathered during the Ring Grazing Orbits (December 2016 to April 2017) and the Grand Finale (April to September 2017), when Cassini flew just above Saturn's cloud tops. As the spacecraft was running out of fuel, the mission team deliberately plunged it into the planet's atmosphere in September 2017.

Cassini's Visible and Infrared Mapping Spectrometer (VIMS) uncovered another mystery. The spectrometer, which imaged the rings in visible and near-infrared light, identified unusually weak water-ice bands in the outermost part of the A ring. That was a surprise, because the area is known to be highly reflective, which usually is a sign of less-contaminated ice and thus stronger water ice bands.

The new spectral map also sheds light on the composition of the rings. And while scientists already knew that water ice is the main component, the spectral map ruled out detectable ammonia ice and methane ice as ingredients. But it also doesn't see organic compounds -- a surprise, given the organic material Cassini has discovered flowing from the D ring into Saturn's atmosphere.

"If organics were there in large amounts -- at least in the main A, B and C rings -- we'd see them," said Phil Nicholson, Cassini VIMS scientist of Cornell University in Ithaca, New York. "I'm not convinced yet that they are a major component of the main rings."

The research signals the start of the next era of Cassini science, said NASA's Ames Research Center's Jeff Cuzzi, who's been studying Saturn's rings since the 1970s and is the interdisciplinary scientist for rings on the Cassini mission.

"We see so much more, and closer up, and we're getting new and more interesting puzzles," Cuzzi said. "We are just settling into the next phase, which is building new, detailed models of ring evolution -- including the new revelation from Cassini data that the rings are much younger than Saturn."

The new observations give scientists an even more intimate view of the rings than they had before, and each examination reveals new complexities, said Cassini Project Scientist Linda Spilker, based at NASA's Jet Propulsion Laboratory in Pasadena, California.

"It's like turning the power up one more notch on what we could see in the rings. Everyone just got a clearer view of what's going on," Spilker said. "Getting that extra resolution answered many questions, but so many tantalizing ones remain."

Read more at Science Daily

The complex fate of Antarctic species in the face of a changing climate

Oxygen concentrations in both the open ocean and coastal waters have declined by 2-5% since at least the middle of the 20th century.

This is one of the most important changes occurring in an ocean becoming increasingly modified by human activities, with raised water temperatures, carbon dioxide content and nutrient inputs.

Through this, humans are altering the abundances and distributions of marine species but the decline in oxygen could pose a new set of threats to marine life.

Writing in Philosophical Transactions of the Royal Society B, scientists present support for the theory that marine invertebrates with larger body size are generally more sensitive to reductions in oxygen than smaller animals, and so will be more sensitive to future global climate change.

It is widely believed that the occurrence of gigantic species in polar waters is made possible by the fact that there is more oxygen dissolved in ice cold water than in the warmer waters of temperate and tropic regions.

So as our ocean warms and oxygen decreases, it has been suggested that such oxygen limitation will have a greater effect on larger than smaller marine invertebrates and fish.

The study was conducted by John Spicer, Professor of Marine Zoology at the University of Plymouth, and Dr Simon Morley, an Ecophysiologist with the British Antarctic Survey (BAS).

They investigated how a number of different sized amphipod species -- found in abundance in Antarctic waters and relatives of the sandhoppers on temperate beaches) -- performed when the oxygen in the water they were in was reduced.

Overall, there was a reduction in performance with body size supporting the theory that larger species may well be more vulnerable because of oxygen limitation.

However, the picture is a little more complex than this with evolutionary innovation -- such as the presence of oxygen binding pigments in their body fluids to enhance oxygen transport, and novel gas exchange structures in some, but not all, species -- to some extent offsetting any respiratory disadvantages of large body size.

Professor Spicer, who has spent more than 30 years examining the effect of climate change on marine organisms, said: "Over the last 50 years, the oxygen in our oceans has decreased by around 2-5% and this is already having an effect on species' ability to function. Unless they adapt, many larger marine invertebrates will either shrink in size of face extinction, which would have a profoundly negative impact on the ecosystems of which they are a part. This is obviously a major cause for concern.

"Our research also shows that some species have evolved mechanisms to compensate for reductions in oxygen, and so it is not always as simple as drawing a link between size and future survival. But it would be foolhardy to pin our hopes on such 'evolutionary rescue'. Many large species will almost certainly be the first casualties of our warming, oxygen-poor ocean."

Read more at Science Daily

100-year-old physics model replicates modern Arctic ice melt

The Arctic is melting faster than we thought it would. In fact, Arctic ice extent is at a record low. When that happens -- when a natural system behaves differently than scientists expect -- it's time to take another look at how we understand the system. University of Utah mathematician Ken Golden and atmospheric scientist Court Strong study the patterns formed by ponds of melting water atop the ice. The ponds are dark, while the ice is bright, meaning that the bigger the ponds, the darker the surface and the more solar energy it absorbs.

So, it's more than a little important to know how the ice's reflectivity, also called albedo, is changing. That's a key component in understanding the balance between solar energy coming in and energy reflected out of the Arctic. Earlier work showed that the presence or absence of melt ponds in global climate models can have a dramatic effect on long term predictions of Arctic sea ice volume.

To model the melt ponds' growth, Golden, Strong and their colleagues tweaked a nearly 100-year-old physics model, called the Ising model, that explains how a material may gain or lose magnetism by accounting for how atoms interact with each other and an applied magnetic field. In their model, they replaced the property of an atom's magnetic spin (either up or down) with the property of frozen (white) or melted (blue) sea ice.

"The model captures the essential mechanism of pattern formation of Arctic melt ponds," the researchers write, and replicates important characteristics of the variation in pond size and geometry. This work is the first to account for the basic physics of melt ponds and to produce realistic patterns that accurately demonstrate how melt water is distributed over the sea ice surface. The geometry of the melt water patterns determines both sea ice albedo and the amount of light that penetrates the ice, which significantly impacts the ecology of the upper ocean.

Unfortunately, a model like this can't halt the ice from melting. But it can help us make better estimates of how quickly Arctic ice or permafrost is disappearing -- and better climate models help us prepare for the warmer future ahead.

From Science Daily

Cold weather increases the risk of fatal opioid overdoses

Cold weather snaps are followed by a marked increase in fatal opioid overdoses, a new study finds.

A research team led by Brandon Marshall, an associate professor of epidemiology at Brown University's School of Public Health, found a 25 percent increase in fatal opioid overdoses after periods of freezing temperatures compared to days with an average temperature of 52 degrees.

And while the researchers continue to investigate the reasons for this pattern, Marshall suggests some interventions that could reduce overdose risk regardless of the cause. These include cold weather-triggered public health messages that remind people to check on neighbors and loved ones who use opioids, or those that warn individuals who use drugs not to use alone, especially during cold weather.

"It is well known that opioids induce respiratory depression, and that's what causes a fatal overdose," Marshall said. "However, there may be a host of other risk factors that contribute to opioid overdose deaths, which could be avenues for effective interventions. Regardless of what is causing the correlation between cold weather and fatal overdoses, our findings suggest that agencies and organizations should consider scaling up harm-reduction efforts after a period of cold weather."

The findings were published in the journal Epidemiology.

The research involved a partnership between opioid researchers at Brown and the Rhode Island Department of Health (RIDOH), as well as Brown experts who study how the environment impacts human health. Marshall serves also as scientific director for Prevent Overdose R.I., an overdose-surveillance dashboard operated with RIDOH, which provided the data on overdose deaths in Rhode Island.

The research team looked at more than 3,000 opioid-related deaths in Connecticut and Rhode Island from 2014 to 2017. They compared the average temperature on the day of each death -- and up to two weeks before -- to the average temperature of three reference days in the same month. They found that an average temperature of 32 degrees three to seven days prior to day of death was associated with a 25 percent increase in the risk of fatal overdose compared to periods with an average temperature of 52 degrees.

Cold snaps may contribute to increased risk of a fatal opioid overdose in several ways, the study said.

One possibility is that opioid use and exposure to cold weather could combine to create a negative biological effect, said William Goedel, a doctoral student at the School of Public Health, who spearheaded the analysis. Opioids are known to reduce breathing, and even without the effect of drugs, it is already harder to breathe in cold air. Some opioids also reduce the temperature at which the body starts to shiver, which makes it harder to regulate one's body temperature, he added.

Cold weather also changes people's behavior, which could increase the risk of overdose, Marshall said. For example, people may be more likely to use opioids alone when the weather is cold, without someone present who can administer the overdose-reversal drug naloxone. Additionally, cold weather may impact the opioid distribution network. This could potentially increase the risk of using drugs containing illicit fentanyl, or the risk of using drugs more potent than a person is accustomed to, Goedel added.

Despite the increase in overdoses in days following cold snaps, Marshall said the team was surprised to find no direct link between low temperatures on the day of death and the risk of fatal overdose.

"One possibility is that the same-day temperature is based around the recorded day of death, which in some cases is an estimate, especially when a body isn't found for a couple of days," Goedel said. "The lack of a strong correlation with temperature on the day of death could be due to the uncertainty of when people actually died."

The findings might also reflect the cumulative effect of low temperatures on overdose risk, Goedel added.

"Thirty-two degrees on just one day is cold, but to maintain an average of 32 degrees for three or four days means there was a long time where it was quite cold."

Most of the fatal overdoses during the study occurred indoors, Marshall noted. This suggests that providing support for home heating costs or providing warm locations for people to go to during cold spells could also reduce opioid overdoses, he said, although more research is needed.

Marshall would also like to see if the linkage between cold weather and increased risk of overdose deaths is due to major storms or if lower-than-average temperatures alone increase the risk of a fatal overdose.

The researchers also examined above-average temperatures, but did not detect any clear pattern.

Read more at Science Daily

Global commodities trade and consumption place the world's primates at risk of extinction

Orangutan.

A recent study published in the peer-reviewed journal PeerJ -- the Journal of Life and Environmental Sciences highlights the fact that the economic benefits of commodity export for primate habitat countries has been limited relative to the extreme environmental costs of pollution, habitat degradation, loss of biodiversity, continued food insecurity and the threat of emerging diseases.

The world's primate fauna, distributed in the Neotropics, Africa and in South and Southeast Asia, represents an important global component of the Earth´s land-based biodiversity. The presence and activities of primates support a range of tropical community-wide ecological functions and services that provide vital resources to natural ecosystems, including local human populations.

Alarmingly, around 60% of primate species are now threatened with extinction and ~75% have declining populations as a result of escalating anthropogenic pressures resulting in deforestation, habitat degradation, and increased spatial conflict between an expanding human population and the natural range of primates.

The study finds that growing market demands for food and nonfood commodities from high-income nations and the global community at large are significant drivers of rapid and widespread primate habitat loss and degradation.

The global consumption of food and natural resources, along with an increasingly globalized economy has created an expanding international market for agricultural products. Such growth is also reflected in the growth of the area of deforestation that is commodity driven. Available evidence indicates that between 2001 to 2015, 160 million hectares of forest were lost in the tropics due to human activities and that 50% or more of this loss was commodity driven. That is, forests were converted to agricultural fields, cattle pastures, mines to extract minerals and metals, fossil fuel exploration, and urbanization.

Given that global commodity resource extraction is predicted to more than double, from 85bn tonnes today to 186bn by the year 2050, reversing the current trend of primate population decline and extinction due to habitat loss and degradation will require a stronger global resolve to reduce the world's per capita demand for forest-risk food and nonfood commodities from primate-range regions, while at the same time implementing sustainable land use practices that improve the standard of living for local human communities, protect local biodiversity, and mitigate climate change.

In order to avoid the impending extinction of the world´s primates, the researchers suggest a number of measures to be implemented including changing global consumer habits (e.g., using less oil seed, eating less meat), the creation of an international environmental improvement fund to mitigate the negative effects of forest-risk commodities trade, and assigning responsibility for environmental damage to those international corporations that control production, export, and supply chains.

Authors Alejandro Estrada, Paul A. Garber and Abhishek Chaudhary write, "Growing global consumer demands for food and non-food commodities from primate range regions are placing primate populations at risk of extinction. These increasing demands have resulted in an accelerated global expansion of agriculture and of extractive industries and in the growth of infrastructure to support these activities leading to widespread primate habitat loss and degradation."

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Exercise may have different effects in the morning and evening

Researchers from the University of Copenhagen have learned that the effect of exercise may differ depending on the time of day it is performed. In mice they demonstrate that exercise in the morning results in an increased metabolic response in skeletal muscle, while exercise later in the day increases energy expenditure for an extended period of time.

We probably all know how important a healthy circadian rhythm is. Too little sleep can have severe health consequences. But researchers are still making new discoveries confirming that the body's circadian clock affects our health.

Now, researchers from University of Copenhagen -- in collaboration with researchers from University of California, Irvine -- have learned that the effect of exercise may differ depending on the time of day it is performed. Studies in mice reveal that the effect of exercise performed in the beginning of the mouse' dark/active phase, corresponding to our morning, differs from the effect of exercise performed in the beginning of the light/resting phase, corresponding to our evening.

'There appears to be rather significant differences between the effect of exercise performed in the morning and evening, and these differences are probably controlled by the body's circadian clock. Morning exercise initiates gene programs in the muscle cells, making them more effective and better capable of metabolising sugar and fat. Evening exercise, on the other hand, increases whole body energy expenditure for an extended period of time', says one of the researchers behind the study, Associate Professor Jonas Thue Treebak from the Novo Nordisk Foundation Center for Basic Metabolic Research.

Morning Exercise Is Not Necessarily Better than Evening Exercise

The researchers have measured a number of effects in the muscle cells, including the transcriptional response and effects on the metabolites. The results show that responses are far stronger in both areas following exercise in the morning and that this is likely to be controlled by a central mechanism involving the protein HIF1-alfa, which directly regulates the body's circadian clock.

Morning exercise appears to increase the ability of muscle cells to metabolise sugar and fat, and this type of effect interests the researchers in relation to people with severe overweight and type 2 diabetes.

On the other hand, the results also show that exercise in the evening increases energy expenditure in the hours after exercise. Therefore, the researchers cannot necessarily conclude that exercise in the morning is better than exercise in the evening, Jonas Thue Treebak stresses.

Read more at Science Daily

Phantom sensations: When the sense of touch deceives

Without being aware of it, people sometimes wrongly perceive tactile sensations. A new study in the scientific journal "Current Biology" shows how healthy people can sometimes misattribute touch to the wrong side of their body, or even to a completely wrong part of the body. The study was conducted by researchers at Bielefeld University's Cluster of Excellence CITEC, the University of Hamburg, and New York University.

"The limitations of the previous explanations for how and where our brain processes touch become apparent when it comes to individuals who have had parts of their bodies amputated or suffer from neurological diseases," says Professor Dr. Tobias Heed, one of the authors of the study. His research group "Biopsychology and Cognitive Neuroscience" is part of CITEC and the Department of Psychology at Bielefeld University. "People who have had a hand or a leg amputated often report phantom sensations in these limbs. But where exactly does this false perception come from?"

To begin answering this question, Heed, working together with Dr. Stephanie Badde (New York University, USA) and Professor Dr. Brigitte Röder (University of Hamburg), studied whether phantom sensations could also be found in healthy people. "In doing so, we showed that healthy adults actually did systematically misattribute touch on the hands to the feet, and vice versa," says Heed.

The Starting Point

In the brain, neighboring neurons respond to corresponding parts of the skin. "Previously, scientists thought that our conscious perception of where a touch occurred stems from a topographical map in the brain. Following this assumption, parts of the body such as the hands, feet, or the face are represented on this map. Our new findings, however, demonstrate that other characteristics of touch are also used to attribute a touch to parts of the body," says Heed. He refers to the presumed "map" as an anatomical system of reference. Previously, it was also believed that spatial perception had an influence on the processing of touch, meaning where a touch takes place in spatial terms, such as to the left, in front of, or below, as Heed explains. Many previous findings were interpreted such that the brain was probably using this other map, which is referred to as an external reference system.

"When parts of the body are positioned on the other side of the body than they usually are -- for example, when crossing your legs -- the two coordinate systems come into conflict." The external coordinate system then locates, for instance, the left leg as being on the right side -- and this does not conform what is stored in the brain about the side of the body that the leg belongs to. "In our study, our initial goal was to sort out the role of the brain's anatomical perception as well as the impact of spatial perception," says Heed.

The Study
For the experiments, tactile stimulators were affixed to each of the study participants' hands and feet. These stimulators could generate a sensation on the skin. Using this impulse generator, the researchers then quickly touched the test subjects successively on two different parts of the body, such as on the left foot and the left hand. In the next step, the participants said or showed where they felt the first touch. This process was then repeated several hundred times on each test subject. In some instances, the study participants had to cross their feet or their hands, while at other times their limbs remained in their normal positions. "Remarkably, in 8% of all cases, subjects attributed the first touch to a part of the body that had not even been touched -- this is a kind of phantom sensation," explains Stephanie Badde, the study's lead author.

The Reasons Why

The previous conception -- that the attributed location of touch on the body depends on "maps" of the body -- cannot explain these new findings. We show that phantom sensations depend on three characteristics," says Tobias Heed. "The most important is the identity of the limb -- whether we're dealing with a hand or a foot. This is why a touch on one hand is often perceived on the other hand."

The second most-important factor is the side of the body where the touched limb belongs to, which explains why a touch on the left foot can sometimes erroneously be felt on the left hand.

Another factor is the canonical anatomical position of the part of the body in question -- where in space the hands or the feet are usually located. This was demonstrated by the researchers in their experiment with crossed body parts: the left hand was positioned on the right side in the experiment. If the left hand were to be touched, the brain sometimes misattributes this touch to the right foot -- to another part of the body that belongs neither to the same side of the body nor the same external spatial position as the part of the body that was actually touched. "Decisive is the normal position of the part of the body that was touched: here, the left hand results in a response from a part of the body that is now positioned where the hand that was touched would normally be located," says Stephanie Badde.

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