Anaesthetists have been putting people to sleep for years, but how the drugs they use send you into a slumber is still largely a mystery. New research suggests it involves the obliteration of long distance communication in the brain.

A team led by , at the Massachusetts Institute of Technology, and , at Harvard Medical School, were given a window into the brain during three operations for epilepsy. Each patient already had electrodes implanted into their temporal cortex, which meant that the team could measure neuronal activity as they were given propofol, a common general anaesthetic.

The team asked each patient to respond to a sound as they drifted off. At the moment they stopped responding, Lewis and Purdon saw a dramatic change in neuronal activity across the cortex. Slow wave oscillations – the brainwaves that occur in deep, non-dreaming sleep – grew almost immediately.

Stop firing

Locally, these slow waves were in sync and neurons near each other coordinated their activity to correspond with the peaks and troughs of the waves they encountered, meaning continued communication. However, the slow waves were not in sync across the entire cortex.

While conscious, different regions of the cortex fire at the same time, so neurons can communicate over long distances if necessary. The peak of each slow wave represents a moment in which that area of the brain has gone silent – and all of its neurons stop firing. A silent region cannot receive a signal from a region that is awake, so out-of sync slow waves make long distance communication near impossible.

In-sync areas were roughly four millimetres square, within which neurons continued to communicate as they did before the patient lost consciousness.

Time zones

“It’s like different brain areas are in different time zones,” says Lewis, though in this case the time zones represent fractions of a second. “When one area is awake the other is asleep.”

Clinically speaking, the more we know about how anaesthesia works in the brain, the more we can make absolutely sure patients do not wake up with memories of their operations, says , a clinical anaesthetist at the University of California, San Francisco, who was not involved in the research.

To that end, Lin hopes to see the same research applied to other general anaesthetics, including inhaled forms, to see whether there are differences in how the drugs cause loss of consciousness, and whether that loss of consciousness looks the same in the brain.

Journal reference: PNAS, DOI: 10.1073/pnas.1210907109

ANCIENT flying fish could make waves in our picture of prehistoric oceans. Fossils recently found in southern China suggest that these winged wonders evolved millions of years earlier than previously thought.

Marine predators often try to trap their prey against the ocean’s surface. Flying fish have a clever escape strategy: they can leap out of the water altogether, and so elude some of the biggest hunters.

Now of the Chinese Academy of Sciences in Beijing and his team have found fossils of a new flying fish species from the Middle Triassic period, which began 247 million years ago (). Previously the oldest flying fish fossils were from the Late Triassic, which began around 230 million years ago, and were unearthed in Austria and Italy.

Modern flying fish have either two or four “wings” – rigid fins that let them glide – which afford them different talents for dodging predators. The Chinese fossils are four-winged, suggesting these fish evolved to make long-distance glides and sophisticated mid-air manoeuvres. This might give clues to what type of ancient predators, such as marine reptiles, they were facing.

This week, the released incident reports describing several deaths that may have occurred following the consumption of Monster Energy drinks. Much of the concern over energy-drink consumption is down to the high caffeine content of such beverages, which at present is not regulated as they are classed as nutritional supplements. żìĂš¶ÌÊÓÆ” takes a closer look.

How did these deaths come to light?

Fourteen-year-old Anais Fournier of Maryland died suddenly in December last year from a heart arrhythmia that resulted in cardiac arrest. She had . Last week, Fournier’s mother, Wendy Crossland, filed a lawsuit against Monster Beverage, based in Corona, California, claiming that the company did not make clear the risks that come with drinking the highly caffeinated energy drink.

As part of a Freedom of Information request by Crossland, the FDA released details of the other four cases, plus one non-fatal heart attack, all of which are alleged to be associated with drinking Monster Energy. The reports certainly do not prove that Monster Energy drinks caused the deaths, and the company maintains that its drinks are safe.

How much caffeine is in energy drinks like Monster Energy?

Actually not a huge amount. A 24-fluid-ounce (682-millilitre) can of Monster Energy contains . A typical 8-oz (225-ml) cup of brewed coffee contains anything from 90 to 200 mg of caffeine.

How much caffeine could kill me?

The lethal dose of caffeine is about 5 grams for adults, so it would take over 25 cups of coffee to reach that point. Part of the reason it is easy to avoid death by caffeine is because the symptoms that come with the early stages of caffeine toxicity – light-headedness, nausea and headache – are quite unpleasant, says , a forensic toxicologist at Sam Houston State University in Texas.

For children and for the elderly, the dose that causes serious effects may be significantly lower than 5 grams, but the amount has not been firmly established.

How common is death by caffeine?

Not common at all. Only a handful of cases pop up in the scientific literature, although it is possible that such deaths are under-reported. However, non-fatal emergency-room visits are on the rise. The big question is how much of the blame for going to hospital can be attributed to energy drinks alone. Between 2005 and 2009, ER visits related to energy drinks in the US. But at least 44 per cent of these ER visits were due to mixing energy drinks and another substance, such as alcohol.

So what could have caused the five reported deaths?

Since the amount of caffeine in a can of Monster Energy would, at worst, probably only cause a case of the jitters in most healthy adults, the deaths are likely due to pre-existing medical conditions, or because the drink was combined with something else. Fournier suffered from , a genetic disorder that causes loose skin and joints, and easily damaged blood vessels. Since caffeine dilates blood vessels, Fournier’s underlying condition could have made her much more sensitive to the effects of caffeine.

What other conditions could make someone vulnerable to caffeine?

Just about anything that makes the heart muscle weaker can increase the sensitivity to caffeine’s cardiovascular impacts, says , a cardiologist at the University of California, San Francisco. Conditions like obesity and diabetes, which we do not normally associate with arrhythmia, can weaken the heart and open the door for caffeine to cause dangerous palpitations.

But caffeine sensitivity is also a highly individual trait, points out , a cardioelectrophysiologist at Northwestern University in Chicago. A 2011 showed that it is nearly impossible to pinpoint consistent disease factors that link large doses of caffeine to arrhythmia in the general population. Labels on Monster Energy drinks says they are not recommended for children under 12 or for people sensitive to caffeine.

Why aren’t energy drinks regulated?

The FDA can only regulate food and drugs. By positioning themselves as nutritional supplements, energy drinks escape the kinds of requirements placed on foods that contain caffeine. Fizzy soft drinks, for instance, are limited in the US to 71 milligrams of caffeine in a 12-oz (340-millilitre) drink, a concentration about one-third lower than is found in Monster Energy. Energy drinks in the US are not required to specify how much caffeine they contain on their labels.

What else is in energy drinks?

Taurine and guarana are often included as stimulants, along with other substances. Many of these ingredients have not been studied, says Kerrigan, and “certainly not to the extent that you’d study a new drug if you were going to start prescribing it or selling it over the counter”.

Zoologger is our weekly column highlighting extraordinary animals – and occasionally other organisms – from around the world

Species: and
Habitat: Southern Brazil, Uruguay and northern Argentina, with a tricky population overlap in Rio Grande do Sul, Brazil

Mistake another lady for your mate and you’re liable to get slapped. For males of two closely related species of spider, the mistake can be their last. Court the wrong female, and they risk being devoured.

The Paratrechalea azul spider lives on boulders on the edges of streams in South America. Trouble is, so does its close relation, Paratrechalea ornata. Though they occupy many of the same habitats and look nearly identical to the human eye, the two species cannot mate successfully with each another.

at the National University of Córdoba in Argentina has spent years studying these spiders in the wild. Even so, he is only sometimes able to tell them apart just by looking – P. azul has an average body length of 4.7 mm, which is roughly half a millimetre longer than P. ornata.

And scientists are not the only ones who struggle to tell the two species apart. The spiders themselves don’t do so well either.

During courtship, males of both species offer their larger female counterparts a gift: a tasty morsel of prey wrapped in silk. The males find a potentially receptive mate by sniffing out the pheromones that female spiders leave on their silky threads.

Wasted presents

But in the lab, Costa-Schmidt found that males struggled to identify females of their own species. They frequently wasted their gifts on an incompatible mate.

The cost of these mistakes is often dangerously high, particularly for P. ornata males. They are significantly smaller than P. azul females, and often lose both their gifts and their lives in their failed courtships. The size difference is more likely to work in favour of P. azul males, though, since the P. ornata females see them as bigger and more impressive mates than males of their own species. Consequently, they are less likely to wind up dead after courtship confusion.

The difference probably explains why P. ornata males are somewhat better than P. azul males at pinpointing which female is which.

Costa-Schmidt points out that, in addition to pheromones, male spiders in the wild probably make use of other signals to identify potential mates, so they may fare better than those in the lab. But if the lab results are representative, the males of both species would do well to keep their many appendages crossed when they feel the urge to mate.

Journal reference: , DOI: 10.1016/j.anbehav.2012.08.026

Is DNA fingerprinting unconstitutional? A US Court of Appeals may be about to rule that it is, on the back of recent science.

DNA fingerprinting is a routine part of data collection on those charged with felonies in the US. The “fingerprint” comprises markers – known as – that do not code for proteins but help to distinguish individuals from one another.

Some of those fingerprinted say that recording the CODIS markers breaches their privacy, and they have .

The results of the Encyclopedia of DNA Elements (ENCODE) project – revealed last month – may play an important role in the case. The , a digital-rights advocacy group, has . It says the project’s results confirm that non-functioning DNA plays a role in cell behaviour.

Many researchers disagree with the EFF’s assessment of the science. It is unusual for single CODIS markers to give any privacy-breaching information, says at the University of Guelph in Ontario, Canada.

Nevertheless, there is a distinct possibility that the courts will take the EFF’s brief seriously, according to of Penn State law school in University Park. “I think there might well be a judge, and maybe more than one, who would refer to it as showing we cannot be secure in assurances that today the CODIS profile has value only in establishing individual identity,” he says.

Transcripts from the hearings so far make it hard to tell which way the judges are leaning, Kaye says, because the judges so often play devil’s advocate during questioning. But the courts have a history of citing current science in the results, making it likely that the ENCODE results will be discussed in the decision.

“The genetic tests [help] exonerate people,” says Gregory, “I would hate to see a backlash because of a misinterpretation of one study.”

While most vampires prefer their prey alive, vampire squid are rather less demanding. They munch on any dead plankton, crustacean remains and faecal matter that happens to pass by, making them the only cephalopod not to hunt living prey.

– literally the “vampire squid from hell” – has a pair of thin, retractable filaments. It uses them like a fishing line, letting them drift and collect bits of waste. Wiping the filaments across its arms, the squid combines the waste with mucus secreted from its suckers to form balls of food, which it gobbles up.

This diet, unique among cephalopods, allows the squid to live in environments that are too difficult for most predators to survive in, says at the Monterey Bay Aquarium Research Institute in California. He studied the squid’s eating habits using a 20-year-long record of observations captured by deep-diving remotely operated vehicles in Monterey Bay.

Other squid and octopuses use their suckers and strong arms to capture prey, but the vampire squid’s passive approach to finding food means it does not have to spend energy building muscles and chasing down live animals. This allows it to live in low-oxygen zones, where water doesn’t circulate much and most predators cannot venture for long.

Journal reference: , DOI: 10.1098/rspb.2012.1357

THE regenerated tail of a lizard is not a perfect replica of the original, but a poor knock-off with a different anatomy. This finding raises the question of whether it will ever be possible to fully regenerate injured human limbs – despite optimistic claims to the contrary.

of the University of Arizona College of Medicine in Phoenix and her colleagues discovered key anatomical differences when they looked at original and fully regenerated tails in the green anole lizard (Anolis carolinensis), which can “drop” its tail when caught by a predator and later grow another. Running through the new tail, for example, was a single long tube of cartilage rather than the chain link of vertebrae found in the original.

The muscles were different too. In place of shorter, variegated muscle fibres were long muscles stretching from tip to stump ().

Both differences suggest that the regenerated tail would be less flexible, says Fisher, because neither the cartilage tube nor the long muscle fibres are capable of the fine control that comes with shorter muscles and lots of small joints between bones. Further functional studies should show what changes these might make to the lizard’s agility.

Most intriguing to Fisher were the pores she noticed throughout the cartilage. A tail made of vertebrae has regular gaps that allow blood vessels and nerves to pass through. But the replacement cartilage, perhaps because it is all one piece, is peppered with small holes, which increase in number towards the tip of the tail. The pores only let blood vessels through – not nerves. New nerves either remain trapped within the cartilage tube or spread a short distance from the stump and don’t seem to reach the muscles and skin except right at the base of the tail ().

Whether the findings will put a dampener on hopes of eventually regenerating human limbs remains to be seen. Jason Pomerantz, a regenerative medicine researcher at the University of California, San Francisco, says there are big implications in the differences between the regenerated structure and original. “Even in a context that we think of as a ‘good’ example of regeneration, the regenerated structure is not perfect and functioning as well as the original,” he says. It highlights the challenge of regenerating a complicated structure, he adds.

, a mammalian tissue regeneration specialist at the Wistar Institute in Philadelphia, Pennsylvania, is more optimistic. A range of animals can regenerate limbs or tails, and one lizard species may not reflect the capabilities of mammals, she says.

TREATING waste water is energy intensive. In the US, it sucks up the equivalent output of four of the country’s biggest power plants every year. But it needn’t be such a drain on resources – soon it might be able to earn its keep.

A team led by Hong Liu from Oregon State University in Corvallis has plans for microbial fuel cells that will reclaim energy from waste water and produce around 2.87 watts per litre of waste water. That is almost double the amount of electrical power usual for such a cell.

And its by-products could be harnessed to create cheap, biodegradable plastics.

Waste water holds huge amounts of energy, bound up in organic molecules, but it can be difficult to access. The Oregon fuel cells run on microbes that would normally digest organic matter to produce water. In a fuel cell, though, isolated from oxygen, that conversion stalls and electrons, which are bundled with protons and oxygen to form water, are pulled away from the microbes by the potential between a cathode and an anode, creating an electrical current.

As well as tweaking the mixture of microbes on the electrodes, the Oregon design has also managed to squash far more electrodes into the fuel cell than on previous versions. Liu says her lab aims to scale up the device within the next five years and make it cheaper ().

The by-products of waste water treatment can be harnessed too. Engineers are working on a way to convert methane into biodegradable plastics.

The dream plastic would be biodegradable, made from organic materials, and break down easily. At the moment, polyhydroxyalkanoate (PHA) seems like the best bet. But PHA plastics are manufactured by genetically modified bacteria fed on sugars in a process that is both expensive and complex, making it hard for them to compete with conventional plastics. In the past, researchers have used the by-products of waste water treatment to generate fuel and sometimes even to create plastics, but nearly all these attempts have focused on the “sludge” of sediment, solid waste and chemicals. Because the sludge is made of many diverse components, it produces a less stable plastic.

“The dream plastic would be biodegradable, made from organic materials, and break down easily”

So Molly Morse of in California and colleagues are now using methane, another major by-product of treating waste water. Methanotrophs, simple organisms that feed on methane, are much better at converting it into polymers than typical bacteria are at converting sugar into plastics. Methane is pumped into a vat of methanotrophs – harvested from the waste water treatment plant itself – along with a bubbling stream of oxygen and a few other nutrients. The end result is a polymer powder that can be separated from the mass of bacteria and turned into pellets for shaping into commercial plastic products.

Morse envisions that their waste water plastic could be used for all kinds of temporary or disposable applications, ranging from packaging materials to beauty products.

Craig Criddle at Stanford University in California, who is on the firm’s advisory board, says when methane itself is sold as fuel it first needs to be cleaned up. Then it will bank about 60 to 80 cents for 3 to 4 kilograms, whereas the same amount of methane could yield a kilogram of plastic, bringing in 4 to 5 dollars. “There’s huge value added in going from biogas to plastic,” he says.

The downside to cannabis use has been made clearer. The most detailed study yet of the drug’s long-term effects shows that those who start a weed habit as teens enter middle age with an 8-point deficit in IQ compared to non-users.

Evidence is growing that cannabis-based drugs can benefit health, but suspicions remain that persistent cannabis use from an early age can have a detrimental effect on cognition. Confirming those suspicions is tricky, though, since cognitive impairment observed later in life could have been present before the drug was first used.

To get around the problem at Duke University in Durham, North Carolina, and her colleagues have taken the long view. They used a detailed health study which followed 1000 people in Dunedin, New Zealand, from birth until age 38. The data allowed them to compare IQ tests taken by the participants at age 13 – before any of them began using cannabis – with the same participants’ IQ scores as adults, in some cases after years of cannabis use.

The study showed that those who developed the most persistent dependence on the drug showed the greatest subsequent decline in IQ, losing 6 points on average regardless of how early the habit began. Within that group, those who began taking the drug before their 18th birthday saw a subsequent decline in IQ of 8 points, on average.

Furthermore, friends and relatives close to the persistent cannabis users reported that these users had more everyday memory and attention problems, including forgetting to pay bills and misplacing common items like keys and wallets.

The bad news is that the damage does not appear to be reversed after dropping the habit. But the good news is that people who picked up their drug habit after their 18th birthday did not suffer such severe cognitive decline. Although previous research has hinted at the potential impacts of cannabis on the adolescent brain, this study is the first to provide evidence that cannabis does in fact have neurotoxic effects on young brains, says Meier.

Journal reference: , DOI: 10.1073/pnas.1206820109