When Columbus discovered America, European culture hadn’t yet grasped the concept of discovery. Various languages had verbs that could be translated as discover, but only in the sense of discovering things like a worm under a rock. Scholars operated within a worldview that all knowledge had been articulated by the ancients, such as Ptolemy, the astronomer who compiled the mathematical details of the Earth-centered universe. As it happened, Ptolemy was also the greatest of ancient geographers. So when Columbus showed that Ptolemy’s grasp on geography was flawed, it opened the way for Copernicus to challenge Ptolemy on his picture of the cosmos as well. Deep thinkers who were paying attention then realized that nature possessed secrets for humankind to “discover.”
“The existence of the idea of discovery is a necessary precondition for science,” writes historian David Wootton. “The discovery of America in 1492 created a new enterprise that intellectuals could engage in: the discovery of new knowledge.”

Appreciating the concept of discovery was not enough to instigate the invention of science. The arrival of the printing press in the mid-15th century was also especially essential. It standardized and magnified the ability of scholars to disseminate knowledge, enabling the growth of communities, cooperation and competition. Late medieval artists’ development of geometrical principles underlying perspective in paintings also provided important mathematical insights. Other key concepts (like discovery) required labeling and clarifying, among them the idea of “evidence.”

And modern science’s birth required a trigger, a good candidate being the supernova observed by Tycho Brahe in 1572. Suddenly, the heavens became changeable, contradicting the Aristotelian dogma of eternal changeless perfection in the sky. Tycho’s exploding star did not cause the scientific revolution, Wootton avers, but it did announce the revolution’s beginning.

In The Invention of Science, Wootton incorporates these insights into an idiosyncratic but deeply thoughtful account of the rise of science, disagreeing frequently with mainstream science historians and philosophers. He especially scorns the relativists who contend that different scientific views are all mere social constructions such that no one is better than any other. Wootton agrees that approaches to science may be socially influenced in their construction, but nevertheless the real world constrains the success of any given approach.

Wootton’s book offers a fresh approach to the history of science with details not usually encountered in the standard accounts. It might not be the last or even best word in understanding modern science’s origins or practice, but it certainly has identified aspects that, if ignored, would leave an inadequate picture, lacking important perspective.

Using flashes of blue light, scientists have pulled forgotten memories out of the foggy brains of mice engineered to have signs of early Alzheimer’s disease. This memory rehab feat, described online March 16 in Nature, offers new clues about how the brain handles memories, and how that process can go awry.

The result “provides a theoretical mechanism for reviving old, forgotten memories,” says Yale School of Medicine neurologist Arash Salardini. Memory manipulations, such as the retrieval of lost memories and the creation of false memories, were “once the realm of science fiction,” he says. But this experiment and other recent work have now accomplished these feats, at least in rodents (SN: 12/27/14, p. 19), he says.
To recover a lost memory, scientists first had to mark it. Neuroscientist Susumu Tonegawa of MIT and colleagues devised a system that tagged the specific nerve cells that stored a memory — in this case, an association between a particular cage and a shock. A virus delivered a gene for a protein that allowed researchers to control this collection of memory-holding nerve cells. The genetic tweak caused these cells to fire off signals in response to blue laser light, letting Tonegawa and colleagues call up the memory with light delivered by an optic fiber implanted in the brain.

A day after receiving a shock in a particular cage, mice carrying two genes associated with Alzheimer’s seemed to have forgotten their ordeal; when put back in that cage, these mice didn’t seem as frightened as mice without the Alzheimer’s-related genes. But when the researchers used light to restore this frightening memory, it caused the mice to freeze in place in a different cage. (Freezing in a new venue showed that laser activation of the memory cells, and not environmental cues, caused the fear reaction.)

The fact that this memory could be pulled out with light helps clarify the source of memory trouble for people with Alzheimer’s, Tonegawa says. In this experiment, the mice appeared able to form and store a memory but not call it up. “It’s a retrieval problem, not a storage problem,” Tonegawa says.

That’s in line with what many clinicians now believe to be happening in early Alzheimer’s, says Salardini. People in the early stages of the disease seem able to create new memories, but then rapidly forget them, he says. Memories can sometimes be strengthened with reminders and clues from the environment, suggesting that they are “somewhere in there,” but not retrievable, he says.

Further experiments with the mice showed that the fear memory could be strengthened by forcing it to appear multiple times. This memory boot camp worked because it boosted the number of docking sites on memory-holding nerve cells in the mice with Alzheimer’s-related genes. Usually, these docking sites — knobs called dendritic spines that receive messages from other nerve cells — become scarcer with age. To counter that, Tonegawa and colleagues used light to repeatedly activate nerve cells that in turn activate the memory-holding cells. Compared with mice that didn’t get this strengthening treatment, mice with the Alzheimer’s genes that underwent this process were more fearful of the cage where they had received a shock, even six days later.
Tonegawa cautions that the results are experimental. “We have not done anything to cure human Alzheimer’s patients,” he says. And the methods, which rely on viruses to genetically engineer brain cells and optic fibers implanted in the brain, are not currently feasible for people.

But insights gained from this experiment, and others like it, do help clarify how memory works in people, says neuroscientist Christine Denny of Columbia University. “If we can understand how the process of memory retrieval is compromised and where it is impaired, then we can begin to develop treatments to target those processes or circuits.”

Monitoring the innards of Yellowstone’s gurgling geysers, scientists report in two new studies that carbonation helps the geysers erupt like shaken cans of soda.

During the buildup to an eruption of Yellowstone’s Spouter Geyser, carbon dioxide accumulates in the geyser water, researchers report online March 7 in Geology. The dissolved gas lowers the water’s boiling point and triggers an eruption. This phenomenon may occur elsewhere in Yellowstone. Several of the park’s other geysers, including Old Faithful, also contain abundant CO2 and other dissolved gases, a separate research team reports in the March Geology.
The findings overturn the 150-year-old explanation that hot water alone fuels geyser eruptions, says Jacob Lowenstern, a volcanologist at the U.S. Geological Survey in Menlo Park, Calif., who was not involved in either study. “People always assumed that water was the end of the story,” he says. “If CO2 was completely absent, many of these geysers would still erupt. But they erupt more regularly and frequently because of the dissolved CO2 gas.”

Geysers can spew thousands of liters of water tens of meters into the air. For geysers in Yellowstone National Park in the western United States, the heat from underground magma fuels these spritzers (SN: 5/16/15, p. 16). Measurements in the 1970s, however, revealed that many Yellowstone geysers, including Old Faithful, aren’t hot enough to boil pure water.

Uncovering what’s going on inside Yellowstone’s geysers is challenging. The geyser water is scorching hot and often acidic. Hydrogeologists Bethany Ladd and Cathryn Ryan of the University of Calgary in Canada, authors of the March 7 study, lost equipment to these harsh conditions while attempting to monitor several of Yellowstone’s geysers. At the nonacidic Spouter Geyser, the researchers had better luck. Using special glass jars, the researchers sampled the geyser’s water every 10 to 20 minutes from a side vent that branches off the geyser’s main channel. The measurements allowed the researchers to track the amount of dissolved CO2 in the geyser over the course of several eruptions.
The abundance of CO2 in the geyser starts low, the researchers found. During the one- to two-hour interval between eruptions, however, CO2 levels steadily increase as gases from Yellowstone’s magma enter the geyser water through permeable rocks. As CO2 increases, the gas lowers the water’s boiling point. Eventually the boiling point drops below the water’s actual temperature and bubbles of steam and CO2 form. As these bubbles climb the geyser column toward the surface, they expand, displacing water and lowering the pressure inside the geyser. That pressure drop lowers the boiling point even further, causing a runaway reaction that triggers a full-blown eruption similar to that of a shaken soda can. These eruptions can last for hours. When the eruption finally fizzles, CO2 levels have dropped to about half their peak value just before eruption and the cycle begins anew.

“People typically think of geysers as hot-water features that only emit water and steam,” Ladd says. “But there are other things in the water such as CO2 that have huge implications for geyser eruptions.”

In the other study, Shaul Hurwitz, a hydrogeologist at the U.S. Geological Survey in Menlo Park, and colleagues discovered CO2 and other dissolved gases such as nitrogen in many of Yellowstone’s other geysers. Understanding the role gas plays in steam eruptions is also important, Hurwitz says, because geysers aren’t the only way water erupts. The rapid boiling of an enclosed underground water reservoir can generate an explosive blast. In September 2014, a steam eruption rocked Japan’s Mount Ontake volcano without warning and killed 57 people. If CO2 helps fuel steam eruptions, then monitoring gas levels in groundwater could provide early warning, Hurwitz says.

As the weather warms, watch for falling rocks. While monitoring a cracked cliff in Yosemite National Park, researchers watched the fissure widen as temperatures rose. The risk of rockfalls could increase as climate change cranks the thermostat, one scientist predicts.

For three and a half years, geologists Brian Collins of the U.S. Geological Survey in Menlo Park, Calif., and Greg Stock of the National Park Service in Yosemite monitored a 19-meter-long crack in one of the park’s cliffs. The crack had a maximum width of about 12 centimeters. A measuring device anchored to both sides of the crack recorded changes in its size. The gap grew and shrank by as much as a centimeter daily as temperature changes caused the rock to expand and contract, the researchers report online March 28 in Nature Geoscience. Some effects lingered, however: The gap widened over the course of several summers and the constant size fluctuations further weakened the rock, the researchers say.

Around 25,000 tons of rocks and debris slipped down Yosemite’s slopes in 2015 — enough to fill more than three Olympic-sized swimming pools. About 15 percent of rockfalls from Yosemite’s granite cliffs occur during summer and at the hottest times of day. The rockfall risk could grow along with the cracks as the climate warms, geoscientist Valentin Gischig of ETH Zurich in Switzerland proposes in a perspective piece on the new finding.

Multiple sclerosis clue significant — A possible link between environment and multiple sclerosis (MS) could be a valuable tool in searching for the cause and cure of the disease…. Cases of MS seem to appear in clusters, and there is apparently some as yet unknown environmental factor that is distributed in the same way, reported Dr. John F. Kurtzke.… The highest frequency of MS is found in northern United States, southern Canada and northern Europe, where there are 30 to 60 cases per 100,000 population. — Science News, April 16, 1966

Update
Researchers still aren’t sure what causes MS, a debilitating disease in which the body’s immune system attacks the insulation around nerve cell fibers. But research suggests that people who grow up farther from the equator, with reduced sun exposure, may have increased disease risk. The human body produces vitamin D in response to sunlight, and studies show that lower levels of vitamin D lead to higher MS risk (SN Online: 9/10/15). But other factors, including genetics and infections, may also play a role in disease development. Today, an estimated 90 MS cases occur for every 100,000 people in the United States.

The pale arch of light from the plane of our galaxy can be a humbling sight on a clear, dark night. But it’s just a sliver of all the treasures lurking in the Milky Way. Dense clouds of interstellar dust block visible light from remote regions of the galaxy but allow longer wavelengths to pass through. In February, astronomers completed a new map of our galaxy as seen in submillimeter light, which is shorter than radio waves but longer than infrared waves.

Submillimeter light can penetrate dust clouds, revealing details at the center of the galaxy and in stellar nurseries not visible at other wavelengths. The map was produced by ATLASGAL, a project using the APEX telescope in northern Chile to map part of the Milky Way. The project charted one-third of the band of galactic light that encircles our solar system; the images below show a narrow slice toward the constellation Sagittarius.
Combined with images from the Spitzer and Planck satellites, the ATLASGAL map (top row) creates a detailed atlas of some of the cold structures in our galaxy. Dust clouds in places like the Trifid and Lagoon nebulas (circled, left), both a few thousand light-years away, glow faintly, as do filaments of detritus in the center of the galaxy (circled, right), 28,000 light-years from Earth. At near-infrared wave-lengths (center row), these regions nearly vanish behind obscuring curtains of dust. The galactic center remains hidden in visible light (bottom row) as well, though hot stars in Trifid and Lagoon radiate pools of hydrogen gas, making them glow.

A sugar that freshens air in rooms may also clean cholesterol out of hardened arteries.

The sugar, cyclodextrin, removed cholesterol that had built up in the arteries of mice fed a high-fat diet, researchers report April 6 in Science Translational Medicine. The sugar enhances a natural cholesterol-removal process and persuades immune cells to soothe inflammation instead of provoking it, say immunologist Eicke Latz and colleagues.

Cyclodextrin, more formally known as 2-hydroxypropyl-beta-cyclodextrin, is the active ingredient in the air freshener Febreze. It is also used in a wide variety of drugs; it helps make hormones, antifungal chemicals, steroids and other compounds soluble. If the new results hold up in human studies, the sugar may also one day be used to liquefy cholesterol that clogs arteries.
Other researchers say the approach is promising, but must be tested in clinical trials. The sweet molecule is generally considered safe, but injecting it may raise the risk of liver damage or hearing loss, says Elena Aikawa, a vascular biologist at Brigham and Women’s Hospital in Boston.

Mice taking cyclodextrin in the study did not exhibit side effects from the treatment, but previous work has indicated that the sugar may damage hearing in mice and cats. The molecule shunts cholesterol through the liver, so large cholesterol influxes might cause fat to build up in the liver, impairing its function. “Overall, cyclodextrin seems worth exploring as a therapeutic, although caution should be taken,” Aikawa says.

Cyclodextrin works by flipping a master switch, a gene called LXR, Latz and colleagues found. LXR’s protein turns on other genes involved in processing cholesterol and ushering it out of the body. The sugar also activated the LXR genes in human arteries examined in the lab and turned on inflammation-calming processes, Latz’s team discovered.

Latz, of the University Hospital Bonn in Germany, credits Nevada businesswoman Chris Hempel with the idea to use cyclodextrin to treat atherosclerosis. In people with the condition, cholesterol, calcium, immune cells and other substances form plaques inside arteries, hardening them. Plaques block blood flow and can break away and cause heart attacks and strokes (SN: 2/20/16, p. 32).

Hempel has twin daughters with a rare genetic disease known as Niemann-Pick Type C, in which cholesterol crystals clog organs, especially the brain. In 2009, the girls got special permission from the Food and Drug Administration for their doctor to give them infusions of cyclodextrin to dissolve the cholesterol crystals.
Hempel later read a paper by Latz and colleagues in which the researchers described how cholesterol crystals irritate macrophages and provoke them to cause inflammation and heart disease. Macrophages normally patrol the body and help kill invading bacteria, viruses and other pathogens. The immune cells also gobble up cholesterol and deliver it to the liver where it can be made into bile and escorted out of the body in feces.

Hempel e-mailed Latz and suggested that cyclodextrin might melt the cholesterol crystals in arteries. Latz and his colleagues tested the idea by feeding mice genetically prone to atherosclerosis a high-fat diet and giving the animals regular injections of cyclodextrin under the skin. The sugar kept cholesterol plaques from building up in the rodents’ arteries. The scientists also found that cyclodextrin reduced already established plaques in mice by about 45 percent, even though the animals were still eating a high-fat diet.

Cyclodextrin could be used in combination with other drugs, such as statins, says Eran Elinav, an immunologist at the Weizmann Institute of Science in Rehovot, Israel. Statins and other drugs inhibit cholesterol production. “Potentially, combining cholesterol lowering with dissolution of preformed cholesterol in plaques could be additive,” Elinav says, “but this option needs to be explored in clinical trials.”

Although cyclodextrin is already approved by the FDA for use in people, it may be years before it’s known whether injecting the sugar will soften people’s hardened arteries. The sugar is not patentable, so no pharmaceutical companies have come forward to sponsor expensive clinical trials needed to get approval for this specific use, Latz says.

SALT LAKE CITY — A new map of the sky charts the origins of some of the highest energy photons ever detected. Researchers from the High-Altitude Water Cherenkov Observatory released their first year of observations of gamma rays, ultrahigh-energy light particles blasted in our direction from some of the most extreme environments in the universe.

The researchers found 40 gamma-ray sources, a quarter of which hadn’t previously been identified, they reported April 18 at an American Physical Society meeting. The map is “revealing new information about nature’s particle accelerators,” said Brenda Dingus, a leader of the HAWC collaboration. These accelerators include the relics of dead stars, such as supernova remnants, and active galaxies that shoot out blasts of particles, known as blazars.
From its perch on the edge of a dormant volcano in Mexico, HAWC detects gamma rays using 300 tanks of water, which cover an area the size of four football fields and register faint light signals from showers of particles produced when gamma rays slam into Earth’s atmosphere.

The team found new sources in areas that had already been searched by other high-energy gamma-ray telescopes. “That’s a little perplexing,” said Dingus. The discrepancy could be due to the fact that HAWC observes higher energy gamma rays, or that the sources are too spread out for the other telescopes to find.

In a region near a previously known gamma-ray source, the scientists found two other potential sources. They nicknamed the group “the executioner” — the bright gamma ray hot spots in the map bore some resemblance to a sinister human figure. If the name sticks, Dingus said, “it would be the first gamma-ray constellation.”

In the brain, language pops up everywhere.

All across the wrinkly expanse of the brain’s outer layer, a constellation of different regions handle the meaning of language, scientists report online April 27 in Nature.

One region that responds to “family,” “home” and “mother,” for example, rests in a tiny chunk of tissue on the right side of the brain, above and behind the ear. That region and others were revealed by an intricate new map that charts the location of hundreds of areas that respond to words with related meanings.
Such a detailed map hints that humans comprehend language in a way that’s much more complicated — and involves many more brain areas — than scientists previously thought, says Stanford University neuroscientist Russell Poldrack, who was not involved in the work.

In fact, he says, “these data suggest we need to rethink how the brain organizes meaning.”

Scientists knew that different concepts roused action in different parts of the brain, says study coauthor Jack Gallant, a computational neuroscientist at the University of California, Berkeley. But people generally thought that big hunks of the brain each dealt with different concepts separately: one region for concepts related to vision, for example, another for concepts related to emotion. And conventional wisdom said the left hemisphere was most important.

Previous studies, though, tested just single words or sentences, and made only rough estimates of where meaning showed up in the brain, Gallant says. That’s like looking at the world’s countries in Google maps, instead of zooming in to the street view.

So he and colleagues mapped the activity of some 60,000 to 80,000 pea-sized regions across the brain’s outer layer, or cerebral cortex, as people lay in a functional MRI machine and listened to stories from The Moth Radio Hour. (The program features people telling personal, narrative tales to a live audience.)
“People actually love this experiment,” Gallant says.

It stands out from others because the authors use “real life, complicated stories,” says Princeton University neuroscientist Uri Hasson. “That’s really meaningful to see how the brain operates.”

Gallant’s team used a computer program to decipher the meaning of every 1- to 2-second snippet of the stories and then cataloged where 985 concepts showed up in the brain. Meanings conveyed by different words didn’t just engage the left hemisphere, the team found, but instead switched on groups of nerve cells spread broadly across the brain’s surface. After mapping where meaning, or semantic content, was represented in the brain, the researchers figured out where individual words might show up. Often, the same word appeared in different locations. For instance, the word “top” turned up in a spot with clothing words, as well as in an area related to numbers and measurements.

The brain maps of the seven participants in the study looked remarkably similar, Gallant says. That could be due to common life experiences: All seven were raised and educated in Western societies. With so few people, the researchers can’t pick out any gender differences, he says, but ideally he’d like to repeat the experiment with 50 or 100 people.

For now, Gallant hopes the map can serve as a resource for other researchers. One day, the work could potentially help those with ALS or locked-in syndrome communicate ­— by decoding the words in a person’s thoughts. But that’s just one piece of the puzzle, Gallant says. Researchers would also need to devise a method for measuring brain activity that’s portable, unlike MRI machines.

Surgery has some surprisingly ritual roots.

Between around 6,000 and 4,000 years ago, skilled surgeons in southwestern Russia cut holes the size of silver dollars, or larger, out of the backs of people’s skulls. But the risky procedure wasn’t performed for medical reasons: These skull surgeries fulfilled purely ritual needs, a new study suggests. And those on the cutting end of the procedure usually lived.

Skulls of 13 people previously excavated at seven ancient sites in this region contain surgical holes in the same spot, in the middle of the back of the head, say archaeologist Julia Gresky of the German Archaeological Institute in Berlin and her colleagues. That’s a particularly dangerous location for this kind of skull surgery, also known as trepanation, the scientists report online April 21 in the American Journal of Physical Anthropology. It’s not an area of the skull typically targeted in ancient trepanations, which go back roughly 11,000 years in West Asia.
“There may have been an original medical purpose for these trepanations, which over time changed to a symbolic treatment,” Gresky says.

Archaeologist Maria Mednikova of the Russian Academy of Sciences in Moscow agrees that skulls in Gresky’s new study probably represent cases of ritual trepanation. She previously examined some of the same skulls. Trepanation may have been used in some ancient cultures as part of a rite of passage for people taking on new social roles, Mednikova speculates.

Carving a center hole in the back of peoples’ heads was a potentially fatal procedure. Surgeons would have needed to know precisely how deep to scrape or grind bone to avoid penetrating a blood-drainage cavity for the brain. They also had to know how to stop potentially fatal bleeding of veins nicked during surgery. The procedure must have been performed as fast as possible to minimize bleeding, the researchers suspect.

Yet 11 of 13 skull openings show signs of healing and bone regrowth, indicating that these individuals survived the operation and often lived for years after. The researchers identify six males and six females in the skull sample. One specimen’s sex couldn’t be determined from skull features.

Most individuals died between ages 20 and 40. One female with a layer of bone that had regrown from the inside border of a trepanation hole died between ages 14 and 16, suggesting her skull surgery had occurred as young as age 10, the researchers estimate.

CT scans, X-rays and analyses of bone surfaces produced no evidence of injuries or brain tumors that could have motivated surgery. Ancient skull surgery intended as a medical treatment often involved holes on the side of the head, near fractures from some type of blow to the head (SN Online: 4/25/08). It’s impossible to determine from bones whether trepanations were aimed at treating chronic headaches, epilepsy, psychological problems or difficulties attributed to evil spirits.

Other evidence, in addition to the risky and unusual location of trepanation holes, points to ritual skull surgeries in southern Russia, Gresky says. Many of these individuals were interred according to special customs, suggesting they ranked high in their societies. For instance, the skulls of seven people buried in a pit at one site had been grouped together near bundled fragments of limb bones in a special display. Incisions on the limb bones indicate that bodies had been dismembered after death before being ritually buried. Of the seven skulls, five display surgical openings at the back of the head. Another contains scrapes from a partial trepanation. Partial trepanations were probably intentional rather than unfinished, with their own cultural significance, Mednikova says.

Trepanation holes on the sides of another six skulls found at the same southern Russian sites were probably made to treat medical conditions, Gresky says. Surgical openings on several of these skulls are located near bone fractures.

Rituals and meanings attached to ancient trepanations in southern Russia will remain mysterious, Mednikova predicts. “We don’t know the myths and religions of tribes that lived there 6,000 years ago.”