Moody red lighting in a lab is helping researchers figure out what fruit flies like best about sex.

The question has arisen as scientists try to tease out the neurobiological steps in how the brain’s natural reward system can get hijacked in alcoholism, says neuroscientist Galit Shohat-Ophir of Bar-Ilan University in Ramat Gan, Israel.

Male fruit flies (Drosophila melanogaster) were genetically engineered to ejaculate when exposed to a red light. Ejaculation increased signs in the insects’ brains of a rewarding experience and decreased the lure of alcohol, researchers found. After several days in this red-light district, the flies tended to prefer a plain sugary beverage over one spiked with ethanol. Males not exposed to the red light went for the boozier drink, Shohat-Ophir and colleagues report April 19 in Current Biology.
Earlier lab research has shown that male flies repeatedly rejected by females are more likely to get drunk. Those with happy fly sex lives don’t show much interest in alcohol. Shohat-Ophir wondered what aspect of sex, or lack thereof, had such a profound effect on the brain’s reward system.

The answer wasn’t that obvious. In rats, for instance, the brains of first-timer males light up with intense biochemical signs of reward just from rodent intercourse, regardless of whether ejaculation occurs. In female rats, copulation needs the right circumstances to evoke reward chemistry.

The red-light system let researchers remove the possibly confounding factor of female presence and see that male flies find ejaculation itself rewarding. (Among the evidence: pairing the red light with an odor cue, which males eagerly sought out afterward.) The red light triggers what are called Crz nerve cells in the abdomen, which cause sperm release and a surge of neuropeptide F, a cousin of a human brain reward compound called neuropeptide Y.
Male flies’ bedazzlement with the right light or drinking binges after rejection may be easy for humans to understand. Shohat-Ophir says that’s because brain reward chemistry is so ancient that parts of it have been inherited by creatures with six legs as well as two.

Two major groups of plants have shown a surprising reversal of fortunes in the face of rising levels of carbon dioxide in the atmosphere.

During a 20-year field experiment in Minnesota, a widespread group of plants that initially grew faster when fed more CO2 stopped doing so after 12 years, researchers report in the April 20 Science. Meanwhile, the extra CO2 began to stimulate the growth of a less common group of plants that includes many grasses. This switcheroo, if it holds true elsewhere, suggests that in the future the majority of Earth’s plants might not soak up as much of the greenhouse gas as previously expected, while some grasslands might take up more.
“We need to be less sure about what land ecosystems will do and what we expect in the future,” says ecosystem ecologist Peter Reich of the University of Minnesota in St. Paul, who led the study. Today, land plants scrub about a third of the CO2 that humans emit into the air. “We need to be more worried,” he says, about whether that trend continues.

The two kinds of plants in the study respond differently to CO2 because they use different types of photosynthesis. About 97 percent of plant species, including all trees, use a method called C3, which gets its name from the three-carbon molecules it produces. Most plants using the other method, called C4, are grasses.
Both processes ultimately feed plants by pulling carbon dioxide from the air. But C4 plants use CO2 more efficiently, so they’re less hungry for it. As a result, it has long been dogma that when CO2 increases in the air, C3 plants gobble up more of it — and thus grow faster — while C4 plants ignore it.
And that’s what experiments on plants grown in elevated CO2 have always shown — until now. For 20 years, scientists at the Cedar Creek Ecosystem Science Reserve in Minnesota have grown both C3 and C4 grasses in 88 plots, pumping extra CO2 into half of them to increase concentrations by 180 parts per million. That amounts to about 50 percent more CO2 than was in ambient air at the experiment’s beginning, and double preindustrial levels.

For the first 12 years, the plants hummed along as expected, with C3 plants responding more strongly to extra CO2 — a 20 percent boost in growth compared with plants grown in ambient air — and C4 plants largely ignoring the difference. But then something unexpected happened: The pattern reversed. Over the next eight years, C3 plants grew on average 2 percent less plant material if they received extra CO2, while C4 plants grew 24 percent more.

“I’m not at all surprised that an experiment like this would produce the unexpected,” says forest ecologist Rich Norby of Oak Ridge National Laboratory in Tennessee. Norby led a different project that tested a forest’s response to elevated CO2 for 12 years, and says the new results highlight the importance of such long-term experiments.

In particular, Norby says, soil fertility can affect how plants respond to CO2 in the long run.

In fact, soil nutrients may have been key to the flip-flop in Minnesota. Without the nitrogen they need, plants can’t take advantage of extra CO2 no matter how much there is. Over the course of the experiment, nitrogen grew to be in shorter supply for C3 plants, but in greater supply for C4 plants. The team suspects that differences in decomposing plant material might have led to changes over time in the community of microbes that process nitrogen in the soil and make it available to plants.

Since grasslands cover 30 to 40 percent of Earth’s land area, Reich says it’s important to learn how they could store carbon in the future. If grasslands worldwide behave as in the experiment, C4 grasslands — found in warm, dry regions — may absorb more CO2 than thought, while more abundant C3 plants could soak up less. As for crops, which can be either C3 like wheat or C4 like corn, the future is even less clear since farmlands are highly managed and often fertilized with nitrogen.

More studies are needed to figure out whether, and how, the world’s plants could shift in their response to increasing CO2. In the meantime, says Reich, “this means we shouldn’t be as confident we’re right about the ability of … ecosystems to save our hides.”

Uranus’ upper clouds are made of hydrogen sulfide — the same molecule that gives rotten eggs their noxious odor.

“At the risk of schoolboy sniggers, if you were there, flying through the clouds of Uranus, yes, you’d get this pungent, rather disastrous smell,” says planetary scientist Leigh Fletcher of the University of Leicester in England.

Using a spectrograph on the Gemini North telescope in Hawaii, Fletcher and his colleagues detected the chemical fingerprint of hydrogen sulfide at the top of the planet’s clouds, the team reports April 23 in Nature Astronomy.

That wasn’t a complete surprise: Observations from the 1990s showed hints of hydrogen sulfide lurking deeper in Uranus’ atmosphere. But the gas hadn’t been conclusively detected before.
The clouds aren’t just smelly — they can help nail down details of the early solar system. Uranus’ hydrogen sulfide clouds set it apart from the gas giant planets, Jupiter and Saturn, whose cloud tops are mostly ammonia.

Hydrogen sulfide freezes at colder temperatures than ammonia. So it’s more likely that frozen hydrogen sulfide ice crystals would have been abundant in the further reaches of the early solar system, where the crystals could have glommed onto newly forming planets. That suggests that ice giants Uranus and Neptune were born farther from the sun than Jupiter and Saturn.

“This tells you the gas giants and the ice giants formed in a slightly different way,” Fletcher says. “They had access to different reservoirs of material back in the forming days of the solar system.”

Fletcher is far from repelled by the malodorous clouds. He and other planetary scientists want to send a spacecraft to the ice giants — the first since the Voyager spacecraft visited in the 1980s — to find out more (SN: 2/20/16, p. 24).

I am not the first person who has considered composing poetry to the placenta. One writer begins: “Oh Lady Placenta! What a life you lived in magenta.” Another almost coos to the “constant companion, womb pillow friend.” It might sound like odd inspiration for verse, but it’s entirely justified.

This vital organ, which is fully formed by about 12 weeks, nurtures a growing fetus throughout pregnancy, offering oxygen, nutrients and antibodies and eliminating waste. The placental cells forge a deep connection between mom and baby, a symbolic early step in a lifelong bond.
Recent research suggests a placenta that works properly might be even more important than previously thought. Myriam Hemberger of the Babraham Institute and the University of Cambridge, along with colleagues in England and Austria, looked at more than 100 genes in mice that are known to be necessary for an embryo to survive. More than two-thirds of those mouse genes were linked to problems with the placenta. And death of the embryo around days 10 to 15 —when, in mice, the placenta takes over from the yolk sac to supply nutrients — was almost always tied to these placental problems.

The study makes you wonder: How many birth defects in humans might have their roots in the placenta? “You cannot just look at the embryo,” says Susan Fisher of the University of California, San Francisco, who studies how placental cells invade the uterus early in pregnancy. “You should work backward from the placenta.”

Both Hemberger and Fisher believe the placenta is underappreciated. I certainly thought much more about my little embryo turned fetus, growing from sesame seed to grape-sized, grapefruit and beyond, than I did about the disk of tissue supporting my baby-to-be. Fisher calls the placenta “the forgotten organ.”

In 2013, Tina Hesman Saey wrote a feature in Science News about new and growing efforts to understand the placenta. The New York Times published a story the following year, headlined “The Mysterious Tree of a Newborn’s Life.”
Then came the launch of the Human Placenta Project, an initiative of the Eunice Kennedy Shriver National Institute of Child Health and Human Development. Since 2015, the project has invested more than $65 million in the development of technologies that can study the placenta in its natural environment, while a woman is pregnant.

“There is a long history of research involving the placenta, for many, many years,” says neonatal geneticist Diana Bianchi, director of the NICHD, who calls the placenta the Rodney Dangerfield of organs. Like the comedian, it gets no respect. “But the research had pretty much exclusively been after delivery.”

Shortly after a baby is born and his umbilical cord is cut, the placenta is expelled from the mother. At that point, it’s straightforward to inspect its size and blood vessels, and to see if scarring or calcium deposits provide clues to poor function. But it’s much too late to predict a fetus in trouble or to intervene in any way that might ultimately protect mom or baby.

Through the Human Placenta Project, researchers are, for example, using ultrasound to investigate placental blood vessels and blood flow in 3-D during the middle trimester and using magnetic resonance imaging to study oxygen distribution in twins who share a placenta but have separate amniotic sacs. How and when such work might make it to the clinic to affect current and future mommies isn’t yet clear.

Bianchi predicts that a deeper appreciation of the role of the placenta, encouraged through Hemberger’s work and similar studies, could change how pregnant women are monitored in the United States. There’s currently very little monitoring for women in the earliest weeks of pregnancy, the window when the placenta is becoming established. Doctor visits then ramp up as the pregnancy progresses. More attention in the first trimester, including attention to the placenta, could identify women who might be at a high risk for stillbirth or premature delivery, even if they are young and healthy by other standards. “That is a very conceivable, no pun intended, but very likely outcome of this research,” Bianchi says.

After identifying so many genes that affect the placenta, Hemberger’s team went on to show that many of those genes are associated in mice with blood vessel, heart and brain problems in a developing fetus. In other words, problems in the heart may have begun elsewhere, in the placenta. Among three of the mouse genes studied in much more detail, the researchers identified one for which the placenta problem was solely responsible for the death of the embryo at around 10 days. Even if the gene was absent from the embryo, restoring it to the placenta could prolong the embryo’s survival.

If the work holds for humans, it might mean that a fix to the placenta could change the course for a dramatic number of babies who would otherwise be born too small or with birth defects. That’s powerful stuff for would-be moms.

And there’s much more work to be done. “You need to understand normal development before you can address anything that goes wrong,” Hemberger says. A lot of pregnancy complications, including those related to the placenta, originate in the first two to eight weeks, which is still “the black box,” she says.

Recent research out of Japan may help. In January, a team there announced deriving and growing human trophoblast stem cells, the cells that form a large part of the placenta. Though such cells have been studied from mice, this could mark the beginning of more fruitful, detailed efforts to understand placenta formation in people. “Approaches like this,” Hemberger says, “can open up what happens in these early stages.”

Once more is known about how it all begins, it may feel perfectly natural for every person born to sing the praises of the placenta, “The tree of life, the mother-child link, Nourishing baby before it can drink.”

Stephen Nicol is here to change your mind about krill: They’re not microscopic and they’re far from boring. The biologist is so sick of people misunderstanding his study subjects that he’s even gotten a (slightly botched) krill tattooed on his arm to help enlighten strangers.

In The Curious Life of Krill, Nicol is taking his mission to an even bigger audience. The book is an ode to Antarctic krill (Euphausia superba), which are among the most abundant animals in the world by mass. Each several centimeters long, krill cloud the ocean in swarms that can span 20 kilometers. They’re a linchpin of ocean ecosystems — a key food source for whales, penguins and other marine life. And yet, Nicol points out, few people would be able to identify these translucent, red-and-green-speckled creatures with feathery appendages.
Anyone who has ever nurtured an affection for a species that others find odd or distasteful or unremarkable will understand Nicol’s devotion. His wry and earnest way of describing krill and their ecology will probably draw in those interested in biology or environmental science.
As one of the world’s leading experts on krill, Nicol offers an insider’s view of the political negotiations over krill fishing in the Southern Ocean. And yet the book’s conversational (sometimes slightly rambling) style makes you feel as if you’re part of an engaging dinnertime conversation. Nicol chronicles the challenges of estimating krill populations and of studying the complex behavior of an animal too small to tag or track. And he shares plenty of delightful anecdotes. At one point, for instance, his lab amassed the world’s largest collection of whale poop to study whether the cetaceans could fertilize the surface ocean by recycling the nutrient iron picked up through the krill they ate. The answer: probably yes.
The book tackles tougher subjects, too. Nicol delves into the threats that Antarctic krill face from fishing — the animals are gathered up for aquaculture feed and also ground into extracts and powders for dietary supplements and medical research — and describes efforts to regulate the industry. He ponders how krill may fare in warming oceans. The critters are resilient, he says, but it’s not clear how quickly these animals, which are known to live as long as about a decade, will adapt to rapidly changing sea temperatures.

Like millions of parents, I post pictures of my kid on Instagram. When she was born, her father and I had a brief conversation about whether it was “dangerous” in a very nebulous sense. Comforted by the fact that I use a fake name on my account, we agreed to not post nudie pics and then didn’t give it much more thought. Until recently.

As she gets older, and privacy on social media dominates the news, I’m revisiting this conversation. Am I invading my daughter’s privacy by sharing her kooky dance moves or epic Nick Nolte hair? Will she feel violated when she’s older? My generation had to contend with mom showing an embarrassing baby photo to our prom date. Is an awkward Instagram picture just today’s equivalent, or does the fact that that the photo can be revisited again and again, by potentially hundreds or even millions of eyes, change things?
There’s a growing amount of scholarship on this issue and the results are somewhat comforting: Most kids aren’t opposed to parents sharing pictures of them, but like most human beings, they would like their feelings to be considered. “Ask your kids’ permission, at least sometimes,” says Sarita Schoenebeck, an expert on how families use technology at the University of Michigan in Ann Arbor. “Pay attention to what they do and don’t like and respect that.”

Schoenebeck and her colleagues recently surveyed 331 parent-child pairs to examine both parents’ and children’s preferences about what’s fair game to share on social media. Overall, the kids, who ranged in age from 10 to 17, didn’t mind when parents posted “positive” content, Schoenebeck’s team reported. Kid-approved posts included pictures showing them engaged in hobbies like sports, or depicting a happy family moment. Embarrassing pictures, on the other hand, were not appreciated. (No “naked butt baby pictures,” said one kid). The team reported its findings in 2017 at the Association for Computing Machinery’s Conference on Human Factors in Computing Systems in Denver.

Kids also expressed being aware of their own privacy in ways adults often don’t give them credit for. Photos with potential boyfriends or girlfriends were not acceptable. Content deemed too candid (such as “what they are really like at home” and “private stuff”) was also off-limits.

This self-awareness was reassuring to me. Much of being a kid is playing literal and figurative dress-up; it’s figuring out what’s OK and not OK, personally, as a family member and as a citizen of the world. I’ve worried that today’s online ecosystem might quash the freedom to do this important experimentation. Kids seem to be tuned into this dilemma too.
Most parents thought they should probably ask their kid’s permission before posting more often. Indeed, they were right: The kids thought parents should ask for permission more often than they do. Previous work by Schoenebeck is in line with that sentiment: Children were twice as likely as parents to report that adults shouldn’t “overshare” by posting about children online without permission.

The issue of kid privacy extends beyond posting pictures, notes computer security and privacy expert Franziska Roesner. “Until what age do you track location on their phone, or even use the camera function on a baby monitor?” says Roesner, of the University of Washington in Seattle. “It’s an evolving space without clear answers.”

It’s too early to say how kids growing up in the current technology climate will feel about their parents’ sharing in hindsight. But a small study by Schoenebeck offers some insight. The researchers asked college students to reflect on their own potentially embarrassing teenage Facebook posts. The students valued the authenticity of their own historical content even if it was potentially embarrassing, Schoenebeck says. As one study participant put it: “When I look at [my old content], it’s kind of like ugh, like ‘yikes!’ [But] if someone finds it I’ll just be like, ‘yeah, I had a thing with song lyrics as my status when I was 15 years old. Get over it.’”

But just because kids didn’t mind their teenage posts surviving online, that doesn’t mean they won’t mind what you post about them. My daughter isn’t old enough yet to say, “You’re not the boss of me.” But I know that time is coming. Before that happens, I plan to start asking her permission about what I post about her and give her the option of deleting old posts.

Given the myriad other concerns parents have about kids and social media — from bullying to body image issues to what potential employers or colleges might see — asking our kids’ permission about what we share seems like an easy, thoughtful step to take.

Laura Sanders is away on maternity leave. Rachel Ehrenberg is a Boston-based science journalist and former reporter at Science News, with degrees in botany and evolutionary biology. She has raised many plants and is now trying to raise a human being.

Cracks open in the ground. Lava creeps across roads, swallowing cars and homes. Fountains of molten rock shoot up to 70 meters high, catching treetops on fire.

After a month of rumbling warning signs, Kilauea, Hawaii’s most active volcano, began a new phase of eruption last week. The volcano spewed clouds of steam and ash into the air on May 3, and lava gushed through several new rifts on the volcano’s eastern slope. Threatened by clouds of toxic sulfur dioxide–laden gas that also burst from the rifts, about 1,700 residents of a housing subdivision called Leilani Estates were forced to flee their homes, which sat directly in the path of the encroaching lava.
The event marks the 62nd eruption episode along Kilauea’s eastern flank, which is really part of an ongoing volcanic eruption that started in 1983. The volcano is one of six that formed Hawaii’s Big Island over the past million years. Mauna Loa is the largest and most central; Kilauea, Mauna Kea, Hualalai and Kohala occupy the island’s edges. Mahukona is currently submerged. All six are shield volcanoes, with broad flanks composed of hardened lava flows.

Kilauea’s activity has now shifted to its southeast flank, which continues to steam. No new rifts have opened since May 7, but the eruption may be far from over, says Victoria Avery, a volcanologist and associate program coordinator for the U.S. Geological Survey’s Volcano Hazards Program, based in Reston, Va.
Science News talked with Avery about Kilauea’s fury, the quakes and what to expect next from the volcano. Her responses were edited for brevity and clarity.
Q: Is there anything unusual about this eruption?

A: Not to scientists; it’s typical of what Kilauea volcano can do.

Q: Were there any warning signs?

A: We saw shallow earthquake activity under [the eastern flank of Kilauea] for several days. That tells us that molten rock is moving underground. We also saw that the lava lake at the summit of Kilauea was lowering; there’s a vent called Pu’u ‘O’o [which has erupted nearly continuously since 1983], and the floor [beneath its magma reservoir] collapsed on April 30. That told us that magma is being withdrawn and moved elsewhere. That collapse, plus the new seismicity, told us something was going to happen.
Q. On May 4, two large earthquakes measuring magnitude 5.4 and magnitude 6.9 shook the Big Island in quick succession. How are they related to the eruption?

A: It’s not frequent but not unusual for Hawaii to have earthquake[s] like that, because a volcano is a very dynamic place. The [surface swelling] associated with the eruption probably triggered the quake[s]: The magma pushed on the volcano from inside. The whole south flank of Kilauea is an area that has a history of large earthquakes. We didn’t directly anticipate it, but we weren’t that surprised when it happened.

Q: Did the people who live there know they were in a hazardous zone?

A: The eruption is right on one of the rift zones of the volcano. The fact that there was a subdivision right on top of it, I can’t comment on. But those houses are right where we know it can erupt. Right now, [emergency managers] are allowing people back in briefly to check on their homes, but not allowing them to stay.
Q: How dangerous is the gas that’s also erupting with the lava?

A: The gas is chiefly carbon dioxide and sulfur dioxide. The gas is actually what propels the [lava] to come out of the ground. Carbon dioxide in enough quantity can suffocate people. Sulfur dioxide can react with the atmosphere to create sulfuric acid. It forms “vog,” or volcanic fog, that can exacerbate asthma. That’s why they’re putting gas masks on people who go in to check on their homes.

Q: How are researchers monitoring this eruption?

A: We’re using the classic tools: instruments measuring seismicity and deformation, visual observations on the ground or flying over in helicopters, and thermal and deformation imagery from satellites. Using remote sensing, you can take [high-resolution images of ground elevation using] synthetic-aperture radar, or SAR, measurements at two different points in time to see the deformation.
Hawaii is a supersite, which means we get a lot of free SAR imagery over it, at about every two or three days. That may not be enough time for frequent eruption warnings, but it’s useful to monitor precursor activity and know what to look for. In the future, we’d like to use drones as well to monitor the eruptions.

Q: Nearby Mauna Loa is on yellow alert (to inform the aviation sector of potential ash hazards), because the volcano is showing signs of unrest. Is it at risk of erupting, too?

A: Mauna Loa really scares us. It is the largest volcano on the planet; it’s the big monster volcano of Hawaii. Kilauea has been erupting continuously since 1983, but Mauna Loa last erupted in 1984. But Mauna Loa can pump out much larger volumes and much faster. It has been yellow since September 2015, when there was elevated seismicity and deformation. It’s still a yellow, but it has quieted a bit.

Q: What’s next? Does the lull in activity at Kilauea mean the eruption is almost over?

A: It’s likely only a pause. The seismicity and deformation can wane and then build up again. The best we can do is watch precursor phenomena 24/7. [These include] the seismic data, the height of the lava lake and the deformation of the volcano along the rift zone. Where it swells, the magma is underneath it; where it goes down, the magma is withdrawing.

Q: The lava lake appears to be sinking again (as of May 6). Does that suggest more eruption is imminent?

A: It generally means that the lava is traveling down the rift zone. There’s likely more to come.

An asteroid that flouts the norms of the solar system might not be from around here.

The renegade asteroid travels around the sun in reverse — in the opposite direction of the planets and most other asteroids (SN: 5/13/17, p. 5). Now two scientists suggest that’s because the space rock originated from outside the solar system, according to a paper published May 21 in Monthly Notices of the Royal Astronomical Society Letters.

Astronomers Fathi Namouni of the Côte d’Azur Observatory in Nice, France, and Helena Morais of Universidade Estadual Paulista in Rio Claro, Brazil, used computer simulations to show that the asteroid, which shares its orbit with Jupiter, could have been traveling in reverse ever since the solar system’s youth. Because asteroids in the infant solar system formed from one swirling cloud, they should have all been traveling in the same direction. So the best explanation, the duo suggests, is that the rock, known as 2015 BZ509, migrated here from another star’s planetary system.
In 2017 astronomers spotted the first interstellar asteroid, dubbed ‘Oumuamua, which cruised through the solar system and back out again (SN Online: 12/1/17). Asteroid 2015 BZ509, however, appears to be a long-term inhabitant.
“It’s certainly an interesting possibility,” says astronomer Martin Connors of Athabasca University in Canada. But, he says, the study doesn’t nail down whether the asteroid actually came from outside the solar system.

Such asteroids are faint and hard to get information from, Connors says. “There isn’t really a blazing sign saying, ‘Hey, I’m not from here.’ ”

A space ravioli. A planetary baguette. A cosmic Kaiser roll. Some of Saturn’s moons have shapes that are strangely reminiscent of culinary concoctions.

Images of the oddball moons, mostly from the now-defunct Cassini spacecraft (SN Online: 9/15/17), got planetary scientists wondering how these satellites ended up with such strange shapes. Now, researchers suggest that collisions between young moonlets could have done the job, according to a study published online May 21 in Nature Astronomy.

Adrien Leleu , a planetary scientist at the University of Bern in Switzerland, and colleagues developed computer simulations that let the scientists virtually smack together similar-sized moonlets at various speeds and angles. The team found that, at low angles and relative speeds of tens of meters per second (roughly equal to a car on country roads), impacts can create offbeat shapes that look like the misfits around Saturn.
Head-on collisions result in a flattened moon like Pan, which resembles an empanada (SN Online: 3/10/17). An impact angle of just a few degrees leads to an elongated satellite such as Prometheus, which looks like a French loaf.
Not all run-ins create a weird looking moon. At higher angles, for example, moonlets might hit and run. Or they could form highly elongated rotating moons that subsequently break apart.
Leleu and collaborators focused on the smaller moons of Saturn that orbit within the planet’s rings. But the team also found that a similar collision between two larger moonlets could also account for the odd shape of Iapetus (SN Online: 4/21/14), a more distant walnut-shaped moon with a pronounced ridge along its equator that has puzzled scientists since the belt’s discovery. Other speculative origins for the ridge include volcanoes, plate tectonics or ring debris that rained down on the moon.

An account of another alleged “sonic attack” has surfaced, this time from a U.S. government employee in China. The employee reported “subtle and vague, but abnormal, sensations of sound and pressure,” according to a U.S. Embassy health alert. The episode mirrors reports from American diplomats in Cuba in late 2016, and fuels the debate among scientists about what, if anything, is actually happening.

Last year, 24 of the diplomats who reported sonic attacks in Cuba were tested to gauge whether lasting harm had occurred. In March, researchers from the University of Pennsylvania Perelman School of Medicine in Philadelphia reported in JAMA that the people had balance and thinking problems, sleep disturbances and headaches, and that some had widespread injury to brain networks.
But some scientists and engineers have been questioning whether such attacks are possible, and if the diplomats’ symptoms could have been caused by a sonic attack.

The attacks were supposedly committed with sounds outside the range of human hearing. But generating enough acoustical energy to cause hearing loss and brain damage from those types of sound waves would be no easy feat, says Andrew Oxenham, a hearing researcher at the University of Minnesota in Minneapolis. The intensity of very low frequency infrasound or very high frequency ultrasound drops rapidly over distance, so attackers would need enormous loud speakers to have enough intensity to do neurological harm.

“Even to get across the street and into a building, you’d have to have a loud speaker the size of a building,” Oxenham says.

It might be possible to focus ultrasound into a tight beam to stage a high-intensity ultrasound attack. But even with such a beam it would be difficult to make a device small enough to be used as a handheld weapon, says Tyrone Porter, a biomedical engineer at Boston University. And that device would be more likely to lead to disorientation than brain damage, he says.
Very little data exist on whether and how ultrasound in the air affects human health. One of the few people to tackle the question is Timothy Leighton, a professor of ultrasonics and underwater acoustics at the University of Southampton in England. He has investigated previous claims of people who complained that they had been victims of sonic attacks.
Some reported incidents were false alarms. But in other cases, Leighton recorded evidence of ultrasound in air at railway stations, museums and swimming pools where people had reported attacks, although the exposure was shown to be accidental, not an attack. He doesn’t know for sure how ultrasound causes symptoms such as the headaches and nausea described by the diplomats. But he suspects subaudible noise makes people anxious, which leads to the reported symptoms. The U.S. government employees in Cuba and China may be experiencing similar anxiety if exposed to ultrasound, he says.

Detected damage?
Leighton and other scientists have questioned whether the JAMA paper actually measured harm caused by a sonic attack. One symptom investigated in the study, white matter changes in the brain, made headlines. White matter is composed of axons, the long extensions of nerve cells that connect different parts of the brain.

“As a result, people got the impression this was some sort of ultrasonic death rifle,” Leighton says. But only three people in the study had white matter abnormalities, and the researchers couldn’t attribute those changes to a sonic attack. They may just have been physical differences that those people’s brains had all along.

What’s more, in the JAMA study, scores that classified diplomats as having a deficit in brain function fall into humans’ normal variation, says Sergio Della Sala, a cognitive neuroscientist at the University of Edinburgh.

The University of Pennsylvania researchers gave diplomats a failing grade on the brain tests if their score on at least one test was below the 40th percentile (meaning that 40 percent of people who take the tests have scores that fall at the low end of the scale), an impairment threshold that Della Sala argues is too high. That’s because, statistically speaking, people would get failing marks on at least one of these tests 40 percent of the time, even without an attack.

Only six of the 24 diplomats took all 37 tests, for 222 tests total. At the 40th percentile cutoff, 89 of the 222 tests would be false positives. That means a test-taker would flunk, but the result would be mistakenly chalked up to a sonic attack when it was really just a natural variation in the way people’s brains work.

In an experiment, Della Sala and University of Edinburgh colleague Robert McIntosh substituted random numbers for diplomats’ test scores and ran a simulation of possible outcomes, using the standards from the JAMA study. The result? “Everybody tested would result affected, everybody. To make sure, we repeated the simulation 1,000 times,” Della Sala wrote in an email.

He doesn’t dispute that some of the diplomats may have experienced symptoms from the incident. But the JAMA paper’s methods would make it impossible for anyone to test normal, he says. “The tests as they have been used and presented are spurious,” he wrote. (Della Sala, along with Roberto Cubelli of the University of Trento in Italy, also published a scathing review of the JAMA study in Cortex on April 5.)

One of the JAMA paper’s coauthors, Douglas Smith, says he and his colleagues have more data than were included in the study. “We note that interpretation of neuropsychological test results is somewhat more nuanced than a simple counting of scores that are lower than a conventional percentile cutoff point,” Smith wrote in an email. Instead, the researchers considered how much each person’s performance on a particular test differed from what is normal for the individual. In some cases, test scores in one aspect of brain function fell far below that person’s normal — down to the bottom 10 percent of the person’s average brain function. That low level of function counts as impairment, says Smith, who directs the Center for Brain Injury and Repair at the University of Pennsylvania’s medical school.

The researchers are currently trying to determine if the people felled by the attacks have changes in the structure of their brains that could account for the symptoms, Smith says.

Reverse engineering a ‘sonic weapon’
The sonic attacks may not have been attacks at all, but eavesdropping gone awry, says Kevin Fu, an electrical engineer and computer scientist at the University of Michigan in Ann Arbor. Fu, who studies how malicious sounds might be used to attack computers, has some of the only experimental evidence to suggest what might have happened in Cuba.

Fu’s attention was drawn to the attacks when the Associated Press released an audio clip of the sound some diplomats in Cuba heard during the incidents. He and colleagues Chen Yan and Wenyuan Xu, both of Zhejiang University in Hangzhou, China, tried to re-create the sound and surmised that an ultrasonic listening device could have developed interference that caused it to produce the unusual noise. “This seems like bad engineering rather than a deliberate attack,” Fu says.

Fu and colleagues described their experiment in a technical paper published online March 1. The researchers did not test whether such a device could have produced health and hearing problems for the diplomats.

For now, what actually happened in Cuba and China to produce the diplomats’ symptoms remains a mystery. And it’s possible we may never know. After all, Fu says, it’s unlikely that if foreign governments did have sonic weapons that they’d allow U.S. scientists to run experiments with the devices.