It seems obvious that thinking about something will help you to remember it better, but it might be more surprising to know that this process works even more efficiently when we’re asleep. Erin Wamsley from Harvard Medical School has shown that people who are trained to navigate a virtual maze learn the best route through it more quickly if they dream about their experiences.

The last decade of research has clearly shown that sleep is one of the best aide memoires that we have. During this nightly time-out, our brain can rehearse information that it has picked up during the day and consolidate them into lasting memories. Wamsley’s new study supports that idea but it also shows that dreaming while you nap can strengthen our memories even further.

She asked 99 volunteers to learn the layout of a complex virtual maze so that they could reach a specific landmark after being dropped at a random starting point. Five hours later, they were tested again. Those who had stayed awake in the intervening time beat their previous times by 26 seconds, but those who had had a 90-minute nap improved by a whopping 188 seconds.

But those who dreamt about the task fared even better. Wamsley either asked her recruits directly about whether they dreamt about the labyrinth, or asked them to give an open-ended report of everything that was going through their mind while they were asleep. Either way, those who had thought about the maze during their short nap improved far more than those who didn’t. They also beat those who mentally replayed their training again while awake. These striking results suggest that there’s something special about the mental rehearsals that happen during dreaming sleep.

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For some animals, sex involves the ultimate sacrifice. Some species of spider, for example, redefine the concept of a dangerous liaison when the female turns around and devours her mate in a post-coital attack of the munchies. For males, it’s important that this act of sexual cannibalism isn’t in vain and that they die while impregnating the best possible mate. And for the wasp spider Argiope bruennichi, that means no sisters allowed.

Klaas Welke and Jutta Schneider from Hamburg’s Zoological Institute found that male wasp spiders are more likely to succumb to their grisly fate if they have just mated with an unrelated female than a sibling. Doing so allows them to avoid the heavy costs of inbreeding, where two copies of the same harmful or faulty genes have a high chance of ending up in the same individual. That’s bad news and both sexes do their best to avoid it, but for these spiders, the female holds all the cards.

She can mate with multiple partners and she can even control whose sperm actually fertilises her eggs. So the male must do everything he can in order to ensure that his genes pass on to the next generation. His job is even more difficult because he can only ever mate twice in his life. He has a pair of sexual organs – pedipalps – and each has only one use.  And of course, his mate invariably attacks him after sex with murderous intent. Around 80% of sexual encounters end with the male becoming a meal and even if he survives his first time, the second time will kill him.

The male’s chances of living to mate again depend entirely on how long he lasts during his virgin encounter. If he jumps off the female within the first five seconds, he has a shot at survival. If he hangs around for more than ten seconds, he will almost certainly die. The trouble is that the longer he sticks around, the more sperm he can pump into the female and the greater his odds of fathering the next generation. It’s a tricky dilemma – with only two chances at mating, he should only make the choice to stay, inseminate and die if his mate is worth the trouble.

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You don’t have to look very far to find a multi-million pound industry supported by the scantiest of scientific evidence. Take “brain-training”, for example. This fledgling market purports to improve the brain’s abilities through the medium of number problems, Sudoku, anagrams and the like. The idea seems plausible and it has certainly made bestsellers out of games like Dr Kawashima’s Brain Training and Big Brain Academy. But a new study by Adrian Owen from Cambridge University casts doubt on the claims that these games can boost general mental abilities.

Owen recruited 11,430 volunteers through a popular science programme on the BBC called “Bang Goes the Theory”. He asked them to play several online games intended to improve an individual skill, be it reasoning, memory, planning, attention or spatial awareness. After six weeks, with each player training their brains on the games several times per week, Owen found that the games improved performance in the specific task, but not in any others.

That may seem like a victory but it’s a very shallow one. You would naturally expect people who repeatedly practice the same types of tests to eventually become whizzes at them. Indeed, previous studies have found that such improvements do happen. But becoming the Yoda of Sudoku doesn’t necessarily translate into better all-round mental agility and that’s exactly the sort of boost that the brain-training industry purports to provide. According to Owen’s research, it fails.

All of his recruits sat through a quartet of “benchmarking” tests to assess their overall mental skills before the experiment began. The recruits were then split into three groups who spent the next six weeks doing different brain-training tests on the BBC Lab UK website, for at least 10 minutes a day, three times a week. For any UK readers, the results of this study will be shown on BBC One tomorrow night (21 April) on Can You Train Your Brain?

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This is a quick announcement to say that you might experience a slightly reduced service on this blog in terms of not responding to comments or fixing errors. I am currently in Perth and stranded by the continued eruption of Eyshsknaahskkehallyffelejokull. I have a roof and somewhere to work during the day, but everything’s a bit surreal and disjointed with no real word as to when the homeward flight will happen.

There’ll still be posts though. Probably.

E

When whales die, their massive bodies slowly sink to the ocean deaths where they provide a feast of riches for bottom-dwelling scavengers. These “whalefalls” are ecosystems unto themselves with thriving communities of living things all eking out an existence on the giant carcasses. These scavengers even include a group of worms called Osedax or “bone-eaters” that live and feed solely on the bones of fallen animals. They were discovered by humans in 2002, but their relationship with whales is an ancient one. Two new 30-million-year-old fossils suggest that as long as there have been whales, there have been Osedax worms feeding off their bones.

Osedax worms have neither stomach nor mouth. They feed by sending a system of “roots” into the bones of its fallen meals. These roots are full of bacterial partners that digest whale fat and collagen proteins, releasing nutrients that the worms can then absorb. At the centre of these roots is the worm itself, which sticks feathery gills out of a hole in the bone. Take out the worm and you’d see a central hole with a connected tangle of thin tunnels. And that’s exactly what Steffen Kiel from Christian-Albrechts University found in a pair of new fossils.

Kiel unearthed the specimens in Washington State, USA. They were small, toothed whales, no more than 4 metres in length. Time hasn’t been kind to the remains. Not only did Osedax worms corrode them but sharks clearly had a go at the carcasses too, as evidenced by small teeth that are still lodged there today.

But among the fragments that have been reasonably preserved, Kiel found the tell-tale signs of Osedax activity. The bones contain boreholes at their surface, each leading to an excavated inner chamber with a network of finer tubes branching off it that are distinct from the channels carved by the whales’ own blood vessels.

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• Jonah Lehrer has a great piece about classroom creativity. “The traits mostly closely aligned with creative thinking were also closely associated with their “least favorite” students.” Great comments too.
• At Neuron Culture, David Dobbs has his own take on the news that Williams syndrome children show no racial bias; it’s interesting and ties in nicely with a comment on my own post, written by the father of a child with Williams syndrome
• ScienceBlogs has scored multiple home runs with their latest recruits – Alex Wild of Myrmecos, whose blog contains some of the most stunning photos of insect life you’ll ever see, and Jason Goldman of The Thoughtful Animal, author of some great posts on peer-reviewed research.
• Alex immediately knocks it out of the park with these photos of the turtle ant, a species that plugs the entrances to its burrows using the incredible head-shields that some workers have.
• “The bit where the doctors test the gorilla’s eye-tracking by waving a date around in front of it is pure joy.” Vaughan Bell talks about efforts of a couple of psychiatrists to diagnose a strangely behaving gorilla
• According to Chris Mooney, a new book suggests that nearly half of scientists are religious
• Wired has the story of a project that’s trying to map every one of the 100,000 neurons in the fly brain. If you squint really hard, you can see a sailboat.
• Wired also has a piece about scrubbing out irrelevant personal info from medical records when they’re used for genetics studies, a rare case of people actually wanting less personal data…
• Ars Technica discusses the use of non-obvious organisms to study human genetic diseases
• SciCurious discusses the curious “photic sneeze reflex” or the “sunny sneeze” – the strange phenomenon where people sneeze when they see bright light.
• In a major victory for science, free speech and critical thinking, The British Chiropractic Association has (happily?) dropped its (bogus?) lawsuit against Simon Singh. I’m sorry, BCA, is that our collective foot in your face? What’s that you say? “MMMMFMFGMGMGFFH”? You’re going to have to speak up…
• Vaughan at Mind Hacks says you’re more likely to die from a heart attack when having sex while having an affair, than during sex with your regular partner. This is screaming out for an RCT
• “Researchers… fed two captive leopards eight complete baboon carcasses each in order catalog the most useful ways to identify the victim of a big cat kill.” Tell us more, Brian Switek
• Brian again, with an absolutely beautiful fossil that preserves an ancient tug of war
• Heidi Ledford at Nature has more on the tantalising link between prion proteins and Alzheimer’s disease, which I’ve covered before
• The sandcastle worm uses bio-glue to create its own shelter; scientists are using it as the inspiration for man-made adhesives, says Henry Fountain at the NYT
• Dr Petra is rightly outraged that sex education in the UK is unlikely to be statutory.
• Australian conservationists have taught quolls (a local cat-sized predator) to avoid toxic cane toads (an invasive super-pest). I’m sure Australians would be happier if they were taught to hit cane toads with golf clubs or run them over in a 4WD.
• Putting up a sign next to lifts encouraging physical activity and pointing to the nearest stairs significantly increases physical activity in a workplace. Easiest intervention ever, say the Obesity Panacea lads.
• The FakeAPStylebook produced one of my favourite tweets ever about Twitter’s place in the newsroom
• And finally, I have started a Posterous account for the purpose of taking the piss out of things in a way that would (a) dilute the quality of this blog and (b) be too long for Twitter. Note my coverage of the vitally important bowls versus ice-cream debate

In the digital age, many of us are compulsive multi-taskers. As I type this, I’m listening to some gentle music and my laptop has several programs open including Adobe Reader, Word, Firefox and Tweetdeck. I’ve always wondered what goes on in my brain as I flit between these multiple tasks, and I now have some answers thanks to a new study by Parisian scientists Sylvain Charron and Etienne Koechlin.

They have found that the part of our brain that controls out motivation to pursue our goals can divide its attention between two tasks. The left half devotes itself to one task and the right half to the other. This division of labour allows us to multi-task, but it also puts an upper limit on our abilities.

Koechlin has previously suggested that the frontopolar cortex, an area at the very front of our brains, drives our ability to do more than one thing at a time. It allows us to simultaneously pursue two different goals, holding one in the ready while we work on the other. Just behind the frontopolar cortex lies the medial frontal cortex (MFC), an area that’s involved in motivation. It drives our pursuit of multiple goals, according to the rewards we expect from them. Koechlin wanted to understand how these two areas cope with multi-tasking.

To do that, he used a brain-scanning technique called functional magnetic resonance imaging (fMRI) to study the brain activity of 32 volunteers, as they carried out a challenging task. They saw a steady stream of letters, all from the word “tablet”. For every block of three letters, they had to say if the first one was a “t” and if the other two appeared in the same order that they would in “tablet” (e.g. TAB rather than TEB). If the letters were red, they would get a sizeable cash reward but if they were green, the reward would be smaller.

Based on this same set-up, they had to cope with two slightly different tests. In the “branching” tests, they had to deal with two separate streams of triplets, a primary one indicated by normal letters and a secondary one indicated by italics. The primary stream was continuous and the volunteers had to revert back to it every time they finished a secondary triplet. They had to hold the primary stream in mind so that they could return to it after their interruption. In the simpler “switching” tests, they started afresh with every new triplet, so they only had to cope with a single stream of information.

Charron and Koechlin found that in the switching tests, when the volunteers were only faced with a single task, both halves of their MFC were active, particularly the dorsal anterior cingulated cortex (dACC) and the presupplementary motor area (PMA). The more money was at stake, the stronger the activity in these regions.

In the branching tests, both halves of the MFC were also active, but they were split between the two tasks. The right dACC took control of the secondary task; when the volunteers could earn more money from these triplets, only the right dACC became more active. The left half took control of the primary task; its activity matched the rewards associated with the primary triplets but not the secondary ones.

The frontopolar part of the brain also became active during the branching tests, which fits with its established role in multi-tasking. However, its attentions weren’t divided by the two tasks and it only became more active when both the primary and secondary rewards were higher. This suggests that the frontopolar cortex plays the role of coordinator. While each half of the MFC encodes the incentives of pursuing each separate goal, the frontopolar cortex encodes the incentives of pursuing both goals together.

It also suggests that we might not be able to cope with more than two tasks at the same time. Charron and Koechlin tested this with an even more fiendish “double branching” test, where the two streams of triplets in their original experiment were interrupted by a third stream. To succeed in this task, they had to retain three separate lanes of information at the same time. They couldn’t. When they tried to return to the first stream from the second, or the second from the third, their answers were no better than guesswork.

Despite what some psychologists have suggested, it seems that the human brain is capable of multi-tasking although to a far lesser extent than a computer can. While my laptop is running several different programs at once with nary a hint of discomfort, Charron and Koechkin’s work suggests that my brain can’t handle any more than two tasks at once.

Reference: Science http://dx.doi.org/10.1126/science.1183614

More on multi-tasking: Information overload? Heavy multimedia users are more easily distracted by irrelevant information

In 1978, Bulgarian dissident Georgi Markov was walking across Waterloo Bridge in London when he felt a sharp stinging pain in his leg. A passer-by had jabbed him with the tip of an umbrella and, having apologised, the two parted ways. Three days later, Markov was dead. The umbrella had fired a small poisoned pellet into his leg, turning Markov into the most famous victim of one of the world’s deadliest poisons – ricin.

Ricin is a great example to cite to people who think that “natural” equates to “healthy”. It’s a protein that comes from the castor bean, which is easy to grow, used in a wide variety of products, and delivers large amounts of its lethal chemical payload. One milligram can be lethal, and there is no known antidote. All of these qualities make it a potential bioterror weapon, and they have galvanised the quest for an antidote. That quest has just taken a big step forward, for Bahne Stechmann at the Curie Institute has discovered the first small molecule that protects mice against ricin.

Stechmann’s drug, known as Retro-2, not only saves mice from death by ricin, it also defends them against a related class of poisons called Shiga-like toxins. These are produced by disease-causing strains of the gut bacterium Escherichia coli and while less toxic than ricin, they can also be fatal. So Stechmann’s new discovery is a two-for-one defensive deal.

Both ricin and Shiga-like toxins have similar structures. One half of each protein – the A subunit – does the killing. It irreversibly breaks ribosomes, the factories that cells use to produce new proteins. A single ricin protein can knock out 1,500 of these factories every minute and without the ability to create new proteins, our cells perish. But a weapon is useless if it can’t be fired in the right place.

Getting the A subunit into range of the ribosomes is the job of the other half of the protein – the B subunit. It’s a backstage pass that sticks to docking molecules on the surface of our cells and allows the entire protein to be smuggled inside. Once there, it gets shuttled from one structure to another until it reaches the endoplasmic reticulum, where ribosomes live. If you block this chain of transport, you neutralise ricin and Shiga-like toxins; after all, the proteins cannot destroy what they cannot reach. And that’s exactly what Stechmann’s team has managed to do.

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Not Exactly Pocket Science is a set of shorter write-ups on new stories with, where possible, links to more detailed takes elsewhere. It is meant to complement the usual fare of detailed pieces that are typical for this blog.

Tyrant leech king – a new T.rex found in the nose of a Peruvian girl

Three years ago, a nine-year-old girl was admitted to La Merced hospital in Peru with a headache that had lasted for two weeks and a strange “sliding sensation” in her nose. Her parents quickly discovered the source of the problem – a sizeable black worm lodged up her right nostril. They quickly sought medical help and it came in the form of Dr Renzo Arauco-Brown, who “with some effort” removed a seven-centimetre leech from the girl’s nose. Brown sent the animal to leech guru Mark Siddall from the American Museum of Natural History, who immediately recognised it as a new species. Uniquely among leeches, the bloodsucker had a single jaw (most have three) but it was lined with eight enormous sharp teeth. For this reason, the Siddall gave it the fanciful name of Tyrannobdella rex, or “tyrant leech king”. A new T.rex had arrived.

It turns out that T.rex has a history of feeding on humans. After describing the new species, Siddall found two other specimens. Both had been removed from the nostrils of young boys in 1997. Like the most recent case, these children had also been bathing in local lakes and streams, which is almost certainly how they picked up their tyrant vampire.

While most leeches are found on the skin, Tyrannobdella is a member of the praobdellid group, which have a disturbing propensity for entering human orifices. They have specialised at feeding on mucous membranes, such as those found in the nose, eye, vagina, anus and urethra (don’t click on these links if you’re squeamish). These bloodsuckers can stay inside for days or weeks on end. They lead to a condition called “orificial hirudiniasis” and they could be potentially life-threatening, especially if secondary infections kick in. It’s likely that many more members of this group are awaiting discovery, although finding them may be a tricky business. As Siddall slyly writes, “Our standard methods of attracting leeches to our exposed selves may prove awkward given their established propensity for particular anatomical feeding sites.”

Reference: PLoS ONE http://dx.doi.org/10.1371/journal.pone.0010057

Why losers ejaculate more

Not every male is a fighter and, as a result, many don’t become lovers either. But for these losers, there’s another option for passing on their genes to the next generation – make sure that you ejaculate copiously when you get the chance.

The male flour beetle has to battle other males over the right to mate with a female. Kensuke Okada from Okayama University found that males who lose these fights become less aggressive and avoid fighting again. However, they make up for avoiding combat by doubling the amount of sperm they produce when they ejaculate. This extra investment is a temporary one; after five days, things were back to normal.

These results show that males can fine-tune their sexual strategies according to the competition they face. Males who triumphed in combat didn’t feel the need to produce more sperm. They are strong enough to guard females they mate with and can stop other males from displacing his sperm with their own. Losers have to move about into new territories and when they do get to mate, they run the risk that a stronger male will just flush their sperm out with his own afterwards. For those who lose physical fights, contributing to the next generation means winning the sperm wars, and doing that means producing more sperm.

Reference: Biology Letters http://dx.doi.org/10.1098/rsbl.2010.0225

More on sperm competition: sperm wars of ants and bees, glowing sperm races, spiky penises, traumatic insemination and frigid echidnas

Could cuttlefish “see” with their skin?

Cuttlefish and their cephalopod relatives, squid and octopuses, are capable of nature’s most spectacular acts of camouflage. They can change the colour of their skin on a whim, send moving waves of stripes down their body, and send messages to one another in shifting hues. This ability is even more incredible when you consider that, according to all evidence to date, cuttlefish are colour-blind. If they can’t actually see colour, how can they mimic it so accurately?

Now, cephalopod specialists Lydia Mäthger and Roger Hanlon have made an intriguing discovery that could potentially answer this question. They found that a gene called opsin is active all over a cuttlefish’s skin; opsin proteins are sensitive to light and an essential part of the visual system. It’s possible that these animals can sense light using their entire skin, and that their colour-changing skill is based on this distributed “sight”.

The idea isn’t without precedent. Some squid have organs on their skin that double as an extra pair of “eyes”. But so far, Mäthger and Hanlon’s idea is still a hypothesis. The skin opsins may have no significance at all and the duo has some work ahead to them to show that they actually play an important role. For a start, there’s some evidence that opsin-like genes are active in the skin of humans, and we certainly change colour without a significant amount of make-up. And the opsins in a cuttlefish’s fin, underside and retina are all the same, so it’s unlikely that they could discriminate between different colours.

However, Mäthger and Hanlon suggest that the opsins may be useful in matching brightness and contrast. They could also interact with chromatophores – the tiny, expandable sacs of pigment that underlie a cuttlefish’s colour-changing ability. Chromatophores come in different colours and they could act as filters for the opsins. Light passing through these sacs could provide information on different wavelengths of light coming in from the environment.

Reference: Biology Letters http://dx.doi.org/10.1098/rsbl.2010.0223

More on cephalopods: the squid with living, seeing flashlights, coconut-armoured octopuses, the mimic octopus, clever cuttlefish, and the secret signals of squid

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In October 2009, a man and two women walked into a renowned Los Angeles restaurant called The Hump and ordered some sushi. This seemingly innocuous act was the start of a fascinating chain of events that would involve hidden cameras, genetic sequencing, a few arrests, and the first solid proof of an illegal international trade in whale meat.

The man in question was Charles Hambleton, a keen diver and assistant director of The Cove, an Oscar-winning documentary that exposed the annual killing of Japanese dolphins. Hambleton had heard that The Hump was serving whale meat and decided to investigate.

He and his companions ordered an “omakase meal”, a challenging assortment of different meats chosen by the chef, only offered to the “adventurous”, and priced at a hefty $800. Sure enough, the platter included four strips of whale sashimi. The receipt said as much, but Hambleton wanted proof. When the waiters and chef weren’t looking, he slipped a sample of the meat into a plastic bag and sent it to Scott Baker from Oregon State University.

By sequencing the meat’s DNA, Baker confirmed that it came from an endangered sei whale. In fact, the meat was an exact genetic match to products bought in Japan in September 2007. The whale in question must have been killed in those years during one of Japan’s controversial “scientific hunts”. From there, its meat had been illegally exported to the US, flouting a strict ban on the international trade of whale meat.

Together with Cove director Louis Psihoyos, Hambleton took his evidence to officials from the National Oceanic and Atmospheric Administration (NOAA). When the duo returned to California to attend the Academy Awards, they conducted their final stings. Psihoyos says, “Charles and I did two more operations to buy whale meat from the same restaurant with federal officials watching so we could establish a chain of custody.” The Hump was forced to close its doors a few weeks later. On 10 March 2010, federal prosecutors filed criminal charges against both the restaurant and its chef.

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