From within the dark confines of the skull, the brain builds its own version of reality. By weaving together expectations and information gleaned from the senses, the brain creates a story about the outside world. For most of us, the brain is a skilled storyteller, but to spin a sensible yarn, it has to fill in some details itself.

“The brain is a guessing machine, trying at each moment of time to guess what is out there,” says computational neuroscientist Peggy Seriès.
Guesses just slightly off — like mistaking a smile for a smirk — rarely cause harm. But guessing gone seriously awry may play a part in mental illnesses such as schizophrenia, autism and even anxiety disorders, Seriès and other neuroscientists suspect. They say that a mathematical expression known as Bayes’ theorem — which quantifies how prior expectations can be combined with current evidence — may provide novel insights into pernicious mental problems that have so far defied explanation.
Bayes’ theorem “offers a new vocabulary, new tools and a new way to look at things,” says Seriès, of the University of Edinburgh.

Experiments guided by Bayesian math reveal that the guessing process differs in people with some disorders. People with schizophrenia, for instance, can have trouble tying together their expectations with what their senses detect. And people with autism and high anxiety don’t flexibly update their expectations about the world, some lab experiments suggest. That missed step can muddy their decision-making abilities.
Given the complexity of mental disorders such as schizophrenia and autism, it is no surprise that many theories of how the brain works have fallen short, says psychiatrist and neuroscientist Rick Adams of University College London. Current explanations for the disorders are often vague and untestable. Against that frustrating backdrop, Adams sees great promise in a strong mathematical theory, one that can be used to make predictions and actually test them.

“It’s really a step up from the old-style cognitive psychology approach, where you had flowcharts with boxes and labels on them with things like ‘attention’ or ‘reading,’ but nobody having any idea about what was going on in [any] box,” Adams says.

Applying math to mental disorders “is a very young field,” he adds, pointing to Computational Psychiatry, which plans to publish its first issue this summer. “You know a field is young when it gets its first journal.”

A mind for math
Bayesian reasoning may be new to the mental illness scene, but the math itself has been around for centuries. First described by the Rev. Thomas Bayes in the 18th century, this computational approach truly embraces history: Evidence based on previous experience, known as a “prior,” is essential to arriving at a good answer, Bayes argued. He may have been surprised to see his math meticulously applied to people with mental illness, but the logic holds. To make a solid guess about what’s happening in the world, the brain must not rely just on current input from occasionally unreliable senses. The brain must also use its knowledge about what has happened before. Merging these two streams of information correctly is at the heart of perceiving the world as accurately as possible.

Bayes figured out a way to put numbers to this process. By combining probabilities that come from prior evidence and current observations, Bayes’ formula can be used to calculate an overall estimate of the likelihood that a given suspicion is true. A properly functioning brain seems to do this calculation intuitively, behaving in many cases like a skilled Bayesian statistician, some studies show (SN: 10/8/11, p. 18).

This reckoning requires the brain to give the right amount of weight to prior expectations and current information. Depending on the circumstances, those weights change. When the senses falter, for instance, the brain should lean more heavily on prior expectations. Say the mail carrier comes each day at 4 p.m. On a stormy afternoon when visual cues are bad, we rely less on sight and more on prior knowledge to guess that the late-afternoon noise on the front porch is probably the mail carrier delivering letters. In certain mental illnesses, this flexible balancing act may falter.

People with schizophrenia often suffer from hallucinations and delusions, debilitating symptoms that arise when lines between reality and imagination blur. That confusion can lead to hearing voices that aren’t there and believing things that can’t possibly be true. These departures from reality could arise from differences in how people integrate new evidence with previous beliefs.
There’s evidence for such distorted calculations. People with schizophrenia don’t fall for certain visual illusions that trick most people, for instance. When shown a picture of the inside of a hollowed-out face mask, most people’s brains mistakenly convert the image to a face that pops outward off the page. People with schizophrenia, however, are more likely to see the face as it actually is — a concave mask. In that instance, people with schizophrenia give more weight to information that’s coming from their eyes than to their expectation that noses protrude from the rest of the face.
To complicate matters, the opposite can be true, too, says neuropsychologist Chris Frith of the Wellcome Trust Centre for Neuroimaging at University College London. “In this case, their prior is too weak, but in other cases, their prior is too strong,” he says.

In a recent study, healthy people and those who recently began experiencing psychosis, a symptom of schizophrenia, were shown confusing shadowy black-and-white images. Participants then saw color versions of the images that were easier to interpret. When shown the black-and-white images again, people with early psychosis were better at identifying the images, suggesting that they used their prior knowledge — the color pictures — to truly “see” the images. For people without psychosis, the color images weren’t as much help. That difference suggests that the way people with schizophrenia balance past knowledge and present observations is distinct from the behavior of people without the disorder. Sometimes the balance tips too far — in either direction.

In a talk at the annual Computational and Systems Neuroscience meeting in February in Salt Lake City, Seriès described the results of a different visual test: A small group of people with schizophrenia had to describe which way a series of dots were moving on a screen. The dots moved in some directions more frequently than others — a statistical feature that let the scientists see how well people could learn to predict the dots’ directions. The 11 people with schizophrenia seemed just as good at learning which way the dots were likely to move as the 10 people without, Seriès said. In this situation, people with schizophrenia seemed able to learn priors just fine.

But when another trick was added, a split between the two groups emerged. Sometimes, the dots were almost impossible to see, and sometimes, there were no dots at all. People with schizophrenia were less likely to claim that they saw dots when the screen was blank. Perhaps they didn’t hallucinate dots because of the medication they were on, Seriès says. In fact, very early results from unmedicated people with schizophrenia suggest that they actually see dots that aren’t there more than healthy volunteers.
Preliminary results so far on schizophrenia are sparse and occasionally conflicting, Seriès admits. “It’s the beginning,” she says. “We don’t understand much.”

The research is so early that no straightforward story exists yet. But that’s not unexpected. “If 100 years of schizophrenia research have taught us anything, it’s that there’s not going to be a nice, simple explanation,” Adams says. But using math to describe how people perceive the world may lead to new hunches about how that process goes wrong in mental illnesses, he argues.

“You can instill expectations in subjects in many different ways, and you can control what evidence they see,” Adams says. Bayesian theory “tells you what they should conclude from those prior beliefs and that evidence.” If their conclusions diverge from predictions, scientists can take the next step. Brain scans, for instance, may reveal how the wrong answers arise. With a clear description of these differences, he says, “we might be able to measure people’s cognition in a new way, and diagnose their disorders in a new way.”

Now vs. then
The way the brain combines incoming sensory information with existing knowledge may also be different in autism, some researchers argue. In some cases, people with autism might put excess weight on what their senses take in about the world and rely less on their expectations. Old observations fit with this idea. In the 1960s, psychologists had discovered that children with autism were just as good at remembering nonsense sentences (“By is go tree stroke lets”) as meaningful ones (“The fish swims in the pond”). Children without autism struggled to remember the non sequiturs. But the children with autism weren’t thrown by the random string of words, suggesting that their expectations of sentence meaning weren’t as strong as their ability to home in on each word in the series.

Another study supports the notion that sensory information takes priority in people with autism. People with and without autism were asked to judge whether a sight and a sound happened at the same time. They saw a white ring on a screen, and a tone played before, after or at the same time. Adults without autism were influenced by previous trials in which the ring and tone were slightly off. But adults with autism were not swayed by earlier trials, researchers reported in February in Scientific Reports.

This literal perception might get in the way of speech perception, Marco Turi of the University of Pisa in Italy and colleagues suggest. Comprehending speech requires a listener to mentally stitch together sights and sounds that may not arrive at the eyes and ears at the same time. Losing that flexibility could make speech harder to understand.

A different study found that children with autism perceive moving dots more clearly than children without autism (SN Online: 5/5/15). The brains of people with autism seem to prioritize incoming sensory information over expectations about how things ought to work. Elizabeth Pellicano of University College London and David Burr of the University of Western Australia in Perth described the concept in 2012 in an opinion paper in Trends in Cognitive Sciences. Intensely attuned to information streaming in from the senses, people with autism experience the world as “too real,” Pellicano and Perth wrote.

New data, however, caution against a too-simple explanation. In an experiment presented in New York City in April at the annual meeting of the Cognitive Neuroscience Society, 20 adults with and without autism had to quickly hit a certain key on a keyboard when they saw its associated target on a screen. Their job was made easier because the targets came in a certain sequence. All of the participants improved as they learned which keys to expect. But when the sequence changed to a new one, people with autism faltered. This result suggests that they learned prior expectations just fine, but had trouble updating them as conditions changed, said cognitive neuroscientist Owen Parsons of the University of Cambridge.
Distorted calculations — and the altered versions of the world they create — may also play a role in depression and anxiety, some researchers think. While suffering from depression, people may hold on to distorted priors — believing that good things are out of reach, for instance. And people with high anxiety can have trouble making good choices in a volatile environment, neuroscientist Sonia Bishop of the University of California, Berkeley and colleagues reported in 2015 in Nature Neuroscience.

In their experiment, people had to choose a shape, which sometimes  came with a shock. People with low anxiety quickly learned to avoid the shock, even when the relationship between shape and shock changed. But people with high anxiety performed worse when those relationships changed, the researchers found. “High-anxious individuals didn’t seem able to adjust their learning to handle how volatile or how stable the environment was,” Bishop says.
Scientists can’t yet say what causes this difficulty adjusting to a new environment in anxious people and in people with autism. It could be that once some rule is learned (a sequence of computer keys, or the link between a shape and a shock), these two groups struggle to update that prior with newer information.

This rigidity might actually contribute to anxiety in the first place, Bishop speculates. “When something unexpected happens that is bad, you wouldn’t know how to respond,” and that floundering “is likely to be a huge source of anxiety and stress.”

Recalculating
“There’s been a lot of frustration with a failure to make progress” on psychiatric disorders, Bishop says. Fitting mathematical theories to the brain may be a way to move forward. Researchers “are very excited about computational psychiatry in general,” she says.

Computational psychiatrist Quentin Huys of the University of Zurich is one of those people. Math can help clarify mental illnesses in a way that existing approaches can’t, he says. In the March issue of Nature Neuroscience, Huys and colleagues argued that math can demystify psychiatric disorders, and that thinking of the brain as a Bayesian number cruncher might lead to a more rigorous understanding of mental illness. Huys says that a computational approach is essential. “We can’t get away without it.” If people with high anxiety perform differently on a perceptual test, then that test could be used to both diagnose people and monitor how well a treatment works, for instance.

Scientists hope that a deeper description of mental illnesses may lead to clearer ways to identify a disorder, chart how well treatments work and even improve therapies. Bishop raises the possibility of developing apps to help people with high anxiety evaluate situations  — outsourcing the decision making for people who have trouble. Frith points out that cognitive behavioral therapy could help depressed people recalculate their experiences by putting less weight on negative experiences and perhaps breaking out of cycles of despondence.

Beyond these potential interventions, simply explaining to people how their brains are working might ease distress, Adams says. “If you can give people an explanation that makes sense of some of the experiences they’ve had, that can be a profoundly helpful thing,” he says. “It destigmatizes the experience.”

Our home planet is young at heart. According to new calculations, Earth’s center is more than two years younger than its surface.

In Einstein’s general theory of relativity, massive objects warp the fabric of spacetime, creating a gravitational pull and slowing time nearby. So a clock placed at Earth’s center will tick ever-so-slightly slower than a clock at its surface. Such time shifts are determined by the gravitational potential, a measure of the amount of work it would take to move an object from one place to another. Since climbing up from Earth’s center would be a struggle against gravity, clocks down deep would run slow relative to surface timepieces.
Over the 4.5 billion years of Earth’s history, the gradual shaving off of fractions of a second adds up to a core that’s 2.5 years younger than the planet’s crust, researchers estimate in the May European Journal of Physics. Theoretical physicist Richard Feynman had suggested in the 1960s that the core was younger, but only by a few days.
The new calculation neglects geological processes, which have a larger impact on the planet’s age. For example, Earth’s core probably formed earlier than its crust. Instead, says study author Ulrik Uggerhøj of Aarhus University in Denmark, the calculation serves as an illustration of gravity’s influence on time — very close to home.

The green hairstreak butterfly (Callophrys rubi) gets its blue-green hue from complex nanoscale structures on its wings. The structures, called gyroids, are repeating patterns of spiral-shaped curls. Light waves bouncing off the patterned surface (top inset above) interfere with one another, amplifying green colors while washing out other shades (SN: 6/7/08, p. 26).

Scientists led by Min Gu of the Royal Melbourne Institute of Technology in Australia have now painstakingly re-created the gyroid structure by sculpting the shapes out of a special resin that solidifies when hit with laser light. The technique, called optical two-beam lithography, uses a pair of lasers to set the material in just the right pattern. Afterward, the remaining resin can be washed away, leaving only the gyroid structure. The fabricated version repeats its pattern every 360 nanometers, or billionths of a meter.

The gyroid structures determine more than just color. They also divvy up light that is circularly polarized — its electric fields spiral either clockwise or counterclockwise. In the butterfly, this effect is weak because of irregularities in the structure. But the artificial version sorts the light according to polarization, reflecting one type much more than the other, the researchers report May 13 in Science Advances.

The ability to control circular polarization of light with structures like these could allow scientists to increase the bandwidth of optical communications, the researchers say. The two polarizations of light could each carry different information, which could then be separated and decoded down the line.

Everyone ages. Growing old is a fundamental feature of human existence.

Though we might not always be aware of aging, it looms in all of our futures. As Science News editor in chief Eva Emerson writes, “Aging happens to each of us, everywhere, all the time. It is so ever-present and slow that we tend to take little notice of it. Until we do.”

But, our scientific understanding of aging pales in comparison to its significance in our lives. While new studies reveal exciting prospects for slowing the effects of aging, its causes and extensive effects remain enigmatic.
Scientists are still divided on some fundamentals of aging, and that’s why aging research raises some interesting questions. For example, how does it change the brain? How did different life histories evolve? How old is the oldest blue whale? This special report addresses those questions and more.

In Colorado’s Rocky Mountains, male and female valerian plants have responded differently to hotter, drier conditions, a new study shows. Rapidly changing ratios of the sexes could be a quick sign of climate change, the researchers say.

Valerian (Valeriana edulis) plants range from hot, scrubby lowlands to cold alpine slopes. In each patch of plants, some are male and some are female. The exact proportion of each sex varies with elevation. High on the mountain, females are much more common than males; they can make up 80 percent of some populations.
Four decades ago, in patches of valerian growing in the middle of the plant’s elevation range, 33.4 percent of the plants were males. Those patches grew in the Rockies at elevations around 3,000 meters. Today, you would have to hike considerably higher to find the same proportion of male plants. Males, now 5.5 percent more common on average, are reaching higher elevations than in the past, researchers report in the July 1 Science.

“We think climate is acting almost like a filter on males and females,” says Will Petry of ETH Zurich, who led the study while at the University of California, Irvine. “The settings on this filter are controlling the sex ratio.” Those settings are sweeping up the mountainside like a rising tide at a rate of 175 meters per decade, Petry and colleagues found.
Ecologists already knew that the ratio of male to female plants can vary with altitude or water availability, says ecologist Spencer Barrett of the University of Toronto, who was not involved in this study. But “the idea that a sex ratio is moving upslope — nobody’s ever done that before.”

Those moving sex ratios have kept pace with climate change since the late 1970s. Today, winter snows are melting earlier and summers are hotter, with less rain. As a result, the same amount of precipitation that would have fallen at one elevation in 1978 now falls at higher elevations instead; it has moved upslope by 133 meters per decade. Soil moisture has moved up the mountain, too, by 195 meters per decade.

The parallel shifts mean that changing sex ratios could be a marker of climate change, says population biologist Tom Miller of Rice University in Houston, a coauthor of the study. Today, movements of whole species — often up in latitude or altitude — are a hallmark of climate change. But proportions of males and females are changing “substantially faster than species are moving,” Miller says. They “might be a much more rapid fingerprint of climate change than where species are migrating to.”
Petry’s team found that fingerprint while hiking around the Rocky Mountain Biological Laboratory in Crested Butte, Colo. As the scientists walked through the mountains in Chaffee and Gunnison counties, they counted flowering males and females at 31 sites in 2011, then compared their modern data with historical counts from nine of the same populations, made by coauthor Judy Soule from 1978 to 1980. When Petry saw that the percentage of males and females had changed, “we also started thinking about the consequences,” he says.

If one sex vastly outnumbers the other, populations could die out. “Imagine if it became an Amazonia situation,” says Kailen Mooney, whose lab at UC Irvine led the new study. A 100 percent female population wouldn’t be pollinated, and would disappear once the mature females died, he says.

If those female-only populations grew above a certain altitude and died out because males couldn’t reach them, then male plants would set the upper boundary for the whole species. Sex ratios “add nuance” to the way scientists think about climate-driven migration, Mooney says, because one sex could determine geographic limits for whole species.

A new book on aging starts with what sounds like a promise: “It is a common belief that aging is inevitable and universal. Nothing could be further from the truth.” From this, you might expect the final pages to offer a list of options for fending off the ravages of time. But this is less a how-to guide and more of a dive into why aging happens.
The authors, theoretical biologist Josh Mitteldorf and writer Dorion Sagan, take an extensive stroll through evolutionary theory and aging research in support of an off-center view. After pointing out problems with several theories of why aging evolved, the authors present the controversial premise that aging is a programmed march toward oblivion that evolved as a form of population control. “Aging in animals enforces a common, predictable life span, helping to prevent the dominance of any one individual or one gene type. Diversity is preserved for the health of the community.” Other researchers have been skeptical of that idea.

Aging, however, is unyielding. The authors describe how certain hardships — starvation, exertion, even small amounts of poison — can paradoxically lead to life extension in lab animals. From these findings, Mitteldorf and Sagan make antiaging recommendations that start with familiar medical advice: exercise, lose weight and take a daily aspirin or ibuprofen. But then they jump to suggestions that have not yet been proven, including supplementation with “huge doses of vitamin D” and melatonin, plus metformin (a diabetes drug) and selegiline (a drug used to treat early Parkinson’s and depression). Next comes a list of herbs that could restore telomeres, the protective tips of chromosomes. The book spends much less real estate describing the research behind all of these recommendations, perhaps because the human studies haven’t been done yet.

The crystal ball section of the book is an optimistic look at very preliminary research on the benefits of lengthening telomeres, removing senescent cells from the body and regrowing the shrinking thymus, the organ that produces immune system T cells. The authors may be onto something. But none of these ideas have yet had a chance to mature.

Buy Cracking the Aging Code from Amazon.com. Sales generated through the links to Amazon.com contribute to Society for Science & the Public’s programs.

NASA’s Juno spacecraft has sent back its first picture of Jupiter since arriving at the planet July 4 (SN: 7/23/16, p. 14). The image, taken July 10 when the spacecraft was 4.3 million kilometers from Jupiter, shows off the planet’s clouds, its Great Red Spot (a storm a bit wider than Earth) and three of its moons (Io, Europa and Ganymede).

Juno is on the outbound leg of its first of two 53.5-day orbits of the gas giant (Juno will then settle into 14-day orbits). During orbit insertion, all of Juno’s scientific instruments were turned off while the spacecraft made its first dive through the harsh radiation belts that encircle the planet. This first image indicates that Juno is in good health and ready to study the largest planet in the solar system.

The probe is the ninth to visit Jupiter and the second to stay in orbit (SN: 6/25/2016, p. 32). For the next 20 months, Juno will investigate what lurks beneath the opaque clouds that enshroud the planet (SN: 6/25/2016, p. 16). The spacecraft won’t take its first intimate pictures of Jupiter until August 27, when it flies within 5,000 kilometers of the cloud tops.

Standoffish electrons typically keep one another at arm’s length, repelling their neighbors. But surprisingly, under certain circumstances, this repulsion can cause pairs of electrons to soften their stance toward one another and attract instead, new research shows. The effect may be the key to someday producing a new type of high-temperature superconductor, scientists report in the July 21 Nature.

Though the effect was first predicted over 50 years ago, previous attempts to coerce electrons to behave in this chummy way have failed. Like charges repel, so negatively charged electrons ordinarily rebuff one another. But now researchers have validated the counterintuitive idea that an attraction between electrons can emerge. “Somehow, you have [this] magic that out of all this repulsion you can create attraction,” says study coauthor Shahal Ilani, a physicist at the Weizmann Institute of Science in Rehovot, Israel.
Ilani and colleagues produced the effect in a bare-bones system of electrons in carbon nanotubes. Operating at temperatures just above absolute zero, the system is made up of two perpendicular carbon nanotubes — hollow cylinders of carbon atoms — about 1 nanometer in diameter.

Two electrons sit at sites inside the first nanotube. Left to their own devices, those two electrons repel one another. A second nanotube, known as the “polarizer,” acts as the “glue” that allows the two electrons to attract. When the scientists brought the two nanotubes close together, says Ilani, “the electrons in the first nanotube changed their nature; they became attractive instead of repulsive.”

This flip is due to the nature of the polarizer. It contains one electron, which is located at one of two sites in the carbon nanotube — either between the first nanotube’s pair of electrons or farther away. The pair of electrons in the first nanotube repels the polarizer’s electron, kicking it from the near to the far site. And the electron’s absence leaves behind a positively charged vacancy, which attracts the pair of electrons toward it — and toward each other.
It’s a “tour de force,” says Takis Kontos, a physicist at the École Normale Supérieure in Paris, who wrote a commentary on the paper in the same issue of Nature. Although the system the scientists created is very simple, he says, “the whole experiment built around it is extremely complex.”
Electrons are known to attract in certain situations. In conventional superconductors, electrons pair up due to their interactions with ions in the material. This buddy system allows superconductors to conduct electricity without resistance. But such superconductors must be cooled to very low temperatures for this effect to occur.

But in 1964, physicist William Little of Stanford University theorized that electron pairs could likewise attract due to their interactions with other electrons, instead of ions. Such pairs should stay linked at higher temperatures. This realization sparked hopes that a material with these attracting electrons could be a room-temperature superconductor, which would open up a wealth of technological possibilities for efficiently transmitting and storing energy.

It’s yet to be seen whether the effect can produce a superconductor, and whether such a superconductor might work at higher temperatures — the new discovery shows only that the attraction can occur due to electrons’ repulsion. It’s “the first important step,” says Ilani. Now, scientists can start thinking of how to build “interesting new materials that are very different than what you can find in nature.”

U.S. drivers love to hit the road. The problem is doing so safely.

In 2013, 32,894 people in the United States died in motor vehicle crashes. Although down since 2000, the overall death rate — 10.3 per 100,000 people — tops 19 other high-income countries, the U.S. Centers for Disease Control and Prevention reported July 8. Belgium is a distant second with 6.5 deaths per 100,000. Researchers reviewed World Health Organization and other data on vehicle crash deaths, seat belt use and alcohol-impaired driving in 2000 and 2013.
Canada had the highest percentage of fatal crashes caused by drunk drivers: 33.6 percent. New Zealand and the United States tied for second at 31 percent. But Canada and 16 other countries outperformed the United States on seat belt use — even though, in 2013, 87 percent of people in the United States reported wearing safety belts while riding in the front seat.

Spain saw the biggest drop — 75 percent — in its crash death rate. That country improved nearly all aspects of road safety, including decreasing alcohol-impaired driving and increasing seat belt use, the researchers say.

The newest and thorniest members of a diverse ant family may have extra help holding their heads high.

Found in the rainforests of Papua New Guinea, Pheidole drogon and Pheidole viserion worker ants have spines protruding from their thoraxes. For many ant species, the spiky growths are a defense against birds and other predators. But Eli Sarnat and colleagues suggest the spines might instead be a muscular support for the ants’ oversized heads, which the insects use to crush seeds. The heads “are so big that it looks like it would be difficult to walk,” says Sarnat, an entomologist at the Okinawa Institute of Science & Technology Graduate University in Japan.
Micro‒CT scans of worker ants with larger heads revealed bundles of thoracic muscle fibers within spines just behind their heads. Worker ants with smaller heads did not have muscles in their spines, the researchers report online July 27 in PLOS One. More research is needed to establish the spines’ function and understand why they evolved, Sarnat says. While buff spines may support big heads, hollow spines probably keep predators at bay, the researchers suspect.
Researchers named the ants after two fearsome dragons, Drogon and Viserion, in the popular book and TV series Game of Thrones.