Gallery: Art on a chip: Accidental beauty at the nanoscale

Spend enough time with your eyes glued to a microscope and you will happen upon some beautiful structure, cell or circuit. żěè¶ĚĘÓƵs who work at the nanoscale often create and manipulate their experiments to make them even more appealing to the eye. It is in this vein that the journal has created a Flickr page, . Here are a few of our favourites.

Gallery: Art on a chip: Accidental beauty at the nanoscale

We may have underestimated whales – not their size, but their senses. Dissections of bowhead whale brains point to a fully developed olfactory system, questioning assumptions that the largest animals on Earth have a lousy sense of smell.

Toothed whales, such as killer whales, lack the nerves needed for smell. That suggests that filter-feeding mysticetes or baleen whales should have a poor sense of smell at best, because they derive from a common ancestor, says at Northeastern Ohio Universities Colleges of Medicine and Pharmacy in Rootstown. It also made sense that a mammal that spends most of its life underwater would have little use for detecting airborne odours.

But Thewissen had heard from colleagues that native Alaskan Inupiat people, who hunt the baleen bowhead whale () for food, know that fires on land will drive the whales out of coastal waters. So his team went along on Inupiat whale hunts and removed the brains of four bowheads in such a way as to leave intact any olfactory nerves there might be. Laboratory dissection revealed such a nerve running from the nostrils to the brain, where it links to a specialised brain structure, the olfactory bulb, that sends odour signals to the rest of the brain.

In other mammals, the size of the olfactory bulb relative to the rest of the brain indicates roughly how well an animal smells. Thewissen’s team found that the bowhead olfactory bulb makes up 0.13 per cent of total brain weight. “It’s similar to macaques and baboons. Those are animals that have a good sense of smell, certainly better than apes and humans,” he says.

To make the case for whale sense of smell even stronger, a colleague looked for genes in bowhead DNA that code for smell sensors. Half of the genes found seemed to produce proteins, compared with fewer than 25 per cent of smell-sensor genes in toothed whales. “I could not see how you can still doubt that bowhead whales can smell,” Thewissen says.

The whales wouldn’t be able to smell underwater, but Thewissen thinks a sense of smell could help them track down krill: the crustaceans give off a strong odour that some birds and seals are attracted to.

“One might expect a krill specialist, such as the bowhead whale, to have a better developed olfaction than a species such as the minke whale that also eats other kinds of prey such as fish,” says Henry Pihlström at the University of Helsinki, Finland.

And at Emory University in Atlanta, Georgia, notes that feeding might not be the only use for a sense of smell. It could also help bowheads find mates or avoid predators.

The new work also helps to fill a gap in our understanding of the brains and behaviour of these whales. “The mysticete brain is still a land of mystery,” Marino says.

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A baby’s first peas are a life-changing event, at least as far as the microbes in its gut are concerned.

Ruth Ley at Cornell University in Ithaca, New York, and colleagues analysed the bacteria in stool samples from a baby boy from birth to the age of 2½ – the first time this has been done while the baby’s diet was recorded.

Predictably, his gut microbes grew more numerous and diverse as he aged, but profound shifts occurred when he was sampling new foods. Besides a course of antibiotics to treat an ear infection, it was the introduction of peas and formula milk that caused the greatest upheavals, Ley says.

While the baby was breastfeeding, the bacteria in his stomach contained numerous genes useful for breaking down milk sugars. When he moved to a diet of solid foods, there were more bacteria with genes that influence starch digestion. Ley says early childhood could be a good time to manipulate gut bacteria to influence future health, since the bacteria appear to respond readily to changes in diet at this age.

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This was the strategy used by Uri Nili and , at the Weizmann Institute in Rehovot, Israel, and it showed that courage does not come when we completely banish fear, but through overcoming it enough to act. “A firefighter having to go into a burning building should display courage, but that firefighter is not fearless,” Dudai says.

Their observations suggest an area of the brain that could be targeted in efforts to rid people of their phobias.

The researchers examined the brain activity of 39 people with an abnormally strong fear of snakes as they lay on their backs in a functional MRI (fMRI) brain scanner. They were given the option to move a venomless 1.5-metre-long corn snake further away from their heads along a conveyer belt, or to bring it closer, to within a distance as small as 20 centimetres.

Decision time

One participant panicked so much that they had to withdraw from the study, and all said they were scared when they had to choose which way to move the snake. The nearer the snake was, the more scared volunteers said they felt.

However, their bodies told a different story. Dudai and Nili measured tiny changes in sweat, an uncontrollable measure of the arousal generated by fear. Participants sweated least when they showed courage.

The MRI scans showed that numerous brain areas became active when the volunteers had to decide whether to advance the snake or move it away.

Active area

One area previously linked to emotion, the subgenual anterior cingulate cortex (sgACC), was particularly active when participants brought the snakes closer, but not when they gave in to their fears. The more scared participants said they felt before drawing the snake closer, the busier their sgACCs were.

“If you manage to maintain activity in this area at a high level, you will be able to overcome your fear,” Nili says.

He speculates that the sgACC helps stymie natural physiological responses to fear. When volunteers moved the snakes away, low sgACC activity was accompanied by an increase in activity in the amygdalae, parts of the brain linked to the physical arousal that accompanies fear.

The researchers did not detect these fMRI signals when they replaced the snake with a teddy bear, or performed the experiments with snake owners and other people unafraid of snakes.

, a neuroscientist at New York University who studies fear and memory, agrees that dealing with this component of fear is the key to conquering it. “You need to shut down this system in order to act,” she says.

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A bloody 10-year dispute in the Ugandan jungle ended in mid-2009 with the victors seizing territory held by the vanquished. The episode represents the first solid evidence that chimpanzees kill their rivals to acquire land, and could help explain the evolutionary origins of some aspects of belligerent as well as cooperative behaviour in humans.

, a primatologist at the University of Michigan in Ann Arbor, and his team have observed the Ngogo chimpanzee troop in Uganda’s Kibale National Park for over a decade. Between 1999 and 2009, they witnessed 18 lethal attacks led by Ngogo males on another, smaller group of chimps. They also found indirect evidence of another three lethal attacks, making the Ngogo troop one of the most violent groups of chimpanzees so far studied.

With more than 150 individuals, the troop is two or three times as large as other well-studied groups. Superiority in numbers allows it to patrol its territory’s hinterlands, where members are likely to encounter smaller, neighbouring troops. “Attacks are made when there’s more of us than them,” says Mitani.

In mid-2009, his team noticed that the Ngogo chimps had finally seized part of the home range of their rivals, so increasing the size of their territory by 6.4 square kilometres, or 22 per cent. Where only adult males on patrol had previously visited this area, now the team saw them “going in there with females and children and acting and shouting like they would if they were in the middle of their territory”, Mitani says. The Ngogo chimps were probably drawn by food: black mulberry trees had begun fruiting in the area around the time of the takeover.

The territorial gain is likely to bring about other advantages. Chimps belonging to troops with large home ranges tend to weigh more than those with less land and their females tend to have more offspring. What’s more, territorial gains could draw in females from neighbouring troops, offering more mating opportunities to the males.

Similar changes have been seen in human hunter-gatherer communities, but Mitani cautions against drawing too many parallels between our own battles and those of chimps. Humans go to war for a variety of reasons ranging from disputes over resources to religion, and such conflicts can often be settled by negotiation. “We might be comparing apples and oranges,” he says.

In fact, rather than explaining the evolutionary origins of war, chimpanzee disputes could help explain the evolution of human cooperation. Samuel Bowles at the Santa Fe Institute in New Mexico has used evolutionary models and archaeological evidence to argue that altruism emerged in humans as a result of violent conflicts between groups of people who were willing to die for their comrades and more selfish, individualistic populations – with the altruistic warriors winning out.

Likewise, says Mitani, the Ngogo chimps worked as tightly knit coalitions to kill their opponents, with benefits for the victorious troop.

“There’s definitely an interesting relationship between cooperation and competition in both chimpanzees and in humans,” says , a primatologist at the University of Minnesota in St Paul, who was not involved in the study.

Journal reference: Current Biology, DOI: 10.1016/j.cub.2010.04.021

Rats, and possibly humans too, rely on three kinds of neuron to navigate: direction cells fire when an animal faces a specific direction; place cells fire in a specific location and only that location; and grid cells fire at regular intervals as the animal moves trough space, creating something like an internal grid for their world.

These cells have been studied in older rodents – and observed in adult humans – but researchers know little about how such cells come to guide navigation, says , a neuroscientist at the Norwegian University of Science and Technology in Trondheim.

First sight

To find out how and when these cells develop, Moser and his colleagues implanted microelectrodes into the brains of 2-week-old rat pups. They then recorded the electrical activity of the cells as the animals opened their eyes for the first time and began to explore their cage. Another group led by and at University College London performed similar tests.

Without any real exposure to the world through movement or sight, the pups seemed to have direction and place cells that worked nearly as well as those of adults, both Moser and Wills found. Moser’s team found the grid cells working right away, while Wills’s suggest these cells start firing a few days later.

Either way, both studies show that the brain cells required for navigation don’t need experience to work properly, but are ready for immediate action. “A lot of people might have predicted that a system like this would involve some sort of learning,” Wills says.

Kant argue with that

That conclusion is reminiscent of the work of the 18th-century European philosopher , who argued that knowledge about space is present in humans without any prior experience. So note philosopher and neuroscientist at the University of California, Irvine, in an that accompanies both papers.

A similar navigational system seems to be present in humans, which suggests that these cells may work without prior experience in humans, too, says Moser. Yet unlike rat pups, which might get lost exploring beyond their nest, human babies have little need for this system, says , a cognitive scientist at University London College who was not involved in either study but has collaborated with one of Wills’s co-authors in the past.

Journal references: Science, ; Wills,