FILE under: strange consequences of having sex. The sedentary Audubon’s warbler is starting to migrate – possibly because it is mating with a cousin that flies south in the winter.

Audubon’s warbler () lives in western US and Canada. Some head south for the winter while others don’t. of the University of British Columbia in Vancouver, Canada, and his team decided to investigate why.

When the team looked at the bird’s mitochondria – the energy-producing structures within cells – it found that those in northern birds were unusually energy efficient. This is normally only seen in the myrtle warbler (), a closely related migratory bird whose range overlaps with the Audubon’s in the north. They also found that northern Audubon’s warblers were more likely to migrate.

This suggests that interbreeding between the two subspecies has seen more energy-efficient mitochondria pass into some of the Audubon’s northern population, giving them a boost that allowed them to become migratory (Evolution, ).

This article appeared in print under the headline “Interbreeding birds begin to migrate”

Brain training might keep you mentally young after all, but only if you exercise one skill at a time.

Older people who hone their multitasking skills in a 3D video game can improve their performance in cognitive tasks. Players continue to show improvements six months later, suggesting that the right kind of games might help stave off cognitive decline.

Video games that claim to up your smarts are popular, but whether any of these games actually work has been a subject of debate. In 2010, a study of 11,000 people showed that brain-training games improved cognitive ability only by the same amount as surfing the internet did.

The volunteers in that study trained using games that targeted several skills at the same time. of the University of California in San Francisco (UCSF) wondered whether this could explain their limited benefits. “It’s like doing bicep curls and then going to run a marathon – it doesn’t work that way,” Anguera says.

Anguera and , also at UCSF, and their colleagues reasoned that training just one ability at a time might tease apart the benefits of these games. To test this, they created NeuroRacer – a video game that trains players’ multitasking skills by having them drive a car with a joystick, while reacting to the signs that appear on a screen.

Lasting benefits

Anguera, Gazzaley and their colleagues asked 16 people aged between 60 and 85 to play the video game three times a week for four weeks. At the same time, the team gave a separate, age-matched group of 15 people a simpler version of the game that only involved driving, without the signs.

A month later, the group that played the multitasking game was significantly better not only at the game itself, which you would expect, but also in tests that gauged the ability to concentrate and juggle several tasks at once. The people that played the simpler game showed no improvement.

The results also seem to last. The players were still showing improvements in cognitive tests six months later.

of Imperial College London, who co-authored the study comparing brain training games to surfing the net, says he is still “planted quite firmly on the fence”. The experiment needs to be repeated with more people in order to show strong evidence for the game’s usefulness, he says. “But I could be persuaded,” he adds.

of the University of South Florida in Tampa is more enthusiastic. “It’s an exciting study,” she says. While it is clear that some brain training games don’t work as intended, well-designed games such as this one might, she says. “We shouldn’t throw the baby out with the bathwater.” The next step, she says, would be to test whether the older adults’ actual driving skills improve after training.

Gazzaley’s team are now developing a number of video games designed to improve other specific skills such as long-term memory and attention.

Journal reference: Nature, DOI:

SIX mustangs race across the horizon, terrified, through billows of dust. A helicopter buzzes just 10 metres above their heads, harrying them, driving them out of the pink and cream-coloured Nevada desert and towards the first holding pen they’ve ever known.

It seems harsh, but this is the best chance these horses have got. Here in south-east Nevada, near Tonopah – an area that has been in near-constant drought for six years – grazing is limited, and cattle ranchers want the horses off the range. Meanwhile, the US Bureau of Land Management (BLM), which is organising today’s round-up, is struggling just to keep their number in check.

Since the 1970s, the BLM has gathered thousands of horses each year, trying to prevent them from dying of starvation due to overpopulation. The costs have skyrocketed to $74 million a year, 60 per cent of which is spent on holding facilities that now keep some 49,000 horses and donkeys penned up. Congress is unlikely to increase the BLM budget any further, so this year it is only rounding up horses from the regions experiencing the most dire conditions. But the drought is unlikely to end before , expected before the end of 2014. Crunch time looms.

“We’re very concerned,” Shawna Richardson of the BLM’s Tonopah office says, as the jittery horses are corralled. “I don’t know what will happen.” The mustangs clatter past us into a metal chute that holds them while handlers check their physical condition and sort them by sex. Many have ribs showing and Richardson says it is likely that some of the mares have lost their foals. The surrounding desert contains only sage grass, so many hungry horses take to the road, where they are a threat to cars, to eat alfalfa hay that has blown from farm trucks.

The best solution to the overpopulation problem, says Cheryl Asa of the St. Louis Zoo in Missouri, would be to round up the horses, treat them with contraceptives, and release them. The most promising contraceptive is porcine zona pellucida (PZP), which causes a mare’s immune system to attack fertilised eggs. PZP appears highly effective in wild horses, but needs to be followed up with a second dose, requiring another round-up. And it is only effective for two years.

Perhaps because of this, the BLM’s contraception efforts to date have been meagre. According to a report by the National Academy of Sciences (NAS), released in June, only about 500 to 1000 of the estimated 40,000 animals on the range are treated and released each year. “It’s essentially a token effort,” says NAS study co-author, Robert Garrott of Montana State University in Bozeman.

The report blasted the BLM for its poor contraception programme and, here on the ground, the Stetson-wearing biologists charged with looking after the horses hope that changes will come soon. “Some things needed to be blasted [by the NAS],” agrees Dustin Hollowell of the BLM, as he circles the corral to look at the 24 horses collected today. He and Richardson believe that, imperfect as it is, using PZP in the most overpopulated regions would help greatly. BLM spokesman Tom Gorey says the agency does plan to expand the programme and will be releasing a response to the report this year.

But after decades of rounding up horses rather than treating them, the agency may have painted itself into a corner. There is overpopulation in most areas of the 10 western states across which the horses roam, Richardson says. And as the NAS report pointed out, uncertainties in counting the animals over such a vast area mean estimates could be far too low.

To free up holding space, the most economical option would be to kill the horses that do not get adopted. But although US law permits this, the BLM itself refuses to consider such action, largely because of public opposition. “We wouldn’t have 50,000 horses in holding if euthanasia was an option,” Hollowell says.

“We would not have 50,000 horses living in holding if euthanasia was an option”

After a time, the newest guests of the BLM settle down, with only an occasional whinny floating up from behind the corral’s fence. Next week, they’ll be shipped to holding pens in California, branded, gelded and offered for adoption online. Their chances aren’t good: only 2600 animals were adopted last year while 5700 were added to holding pens for the rest of their lives. “One has to ask: is that what a wild horse should be?” says Garrott.

To investigate, of Indiana University in Indianapolis and colleagues collected blood from the cadavers of nine men who had bipolar disorder and suicidal tendencies, and nine with bipolar but no suicidal thoughts, and compared levels of all the genes expressed in their blood.

Four genes were expressed at significantly higher levels in the blood of people who had been suicidal. Some proteins that these genes code for are known to be involved in stress and cell death.

The team then measured levels of these proteins in 42 people with bipolar disorder who had been hospitalised for attempting suicide. People who had been hospitalised more often tended to have higher levels of the proteins.

Finally, the team collected blood from the cadavers of a further nine men who had committed suicide without bipolar, and found elevated levels of some of the proteins.

at the University of Chicago says that the study is unique in that it compares bipolar suicide victims with non-suicidal people with the same condition. But the test will need to be performed on many more patients, he says, as well as on suicidal people who have other disorders such as depression or schizophrenia.

Niculescu’s team is now looking for the proteins in more people with a range of underlying conditions, and in women, with the hope of developing a blood test to identify people at risk of suicide.

Journal reference: Molecular Psychiatry, DOI: 10.1038/mp.2013.95

It can be nearly impossible to know what is happening in the mind of someone who has experienced a severe brain injury, but two new methods could offer some clues. Together, they provide not only a better indication of consciousness but also a more effective way to communicate with some vegetative people.

The way that a seemingly unconscious person behaves does not always reflect their mental state. Someone in a completely vegetative state may still be able to smile simply through reflex, while a perfectly alert person may be left unable to do so if a brain injury has affected their ability to move.

So a different way to assess mental state is needed. at the University of Milan in Italy and his colleagues have developed a possible solution by stimulating brains with an electromagnetic pulse and then measuring the response. The pulse acts like striking a bell, they say, and neurons across the entire brain continue to “ring” in a specific wave pattern, depending on how active the connections between individual brain cells are.

The team used this method to assess 20 people with brain injuries who were either in a vegetative state, in a minimally conscious state, or in the process of emerging from a coma. The team compared the patterns from these people with the patterns recorded from 32 healthy people who were awake, asleep or under anaesthesia. In each of the distinct states of consciousness, the researchers found, the neurons “shook” in a distinctive pattern in response to the electromagnetic pulse.

Massimini’s team proposes that each of these different patterns is a signature of a particular state of consciousness. Eventually, a doctor could use this scale, or index, to assess whether a patient is aware of their surroundings – and treat them accordingly.

Big step forward

“This is a big step forward,” says of Harvard Medical School, who was not involved in the study. He says the technique needs to be replicated with more patients and will need to be corroborated with other methods, but it may provide a starting point for developing a much-needed gold standard for assessing consciousness.

A consciousness index could be used in other ways too. For instance, it might help to improve our broader understanding of exactly what consciousness is and how it can be measured, says at the University of Michigan in Ann Arbor.

Giacino says that an index could eventually help identify which seemingly unconscious people with brain injuries are in fact sufficiently conscious to communicate with medical staff and friends or family members.

at the University of Western Ontario in London, Canada, has previously shown that such communication is possible. In 2010, he asked people in a vegetative state a series of questions with yes/no answers, and asked them to imagine performing a complex task, such as playing tennis, whenever the answer was yes. A scanner picked up a unique pattern of brain activity that indicated whether the person is visualising this task.

However, this method is very inexact. In fact, only about three-quarters of healthy conscious people can perform the task in a way that the scanner can interpret. So when someone in a vegetative state shows little brain activity, doctors are left to wonder whether the patients are actually unconscious or simply not performing the task in a way the scanner can pick up on.

Locked-in but alert

Owen and , also at the University of Western Ontario, have now developed a simpler method of determining the answers to yes/no questions given by people in a vegetative state.

After asking a yes/no question, the researchers repeated the word “yes” a number of times, interspersing the yesses with distracting, random numbers. They then did the same with “no”. The patients had been told to indicate their answer by paying close attention to how many times their desired answer was repeated. The researchers scanned the participants’ brains during this exercise to help recognise when the brain was concentrating. The task was so difficult that it was easy for the participants to ignore the answer that they didn’t want to give, Naci says.

They tested this on three people, two of whom were minimally conscious and one who had been in a persistent vegetative state for 12 years. All three patients were able to correctly answer questions about their names, for instance, or whether they were in a hospital.

Naci suspects this relatively straightforward method may reveal consciousness in more patients than had been previously thought to have it – 100 per cent of healthy, conscious people can communicate in this way. “We realise we really have to work hard to treat every patient as if they can understand and process what’s around them,” she says.

of Weill Cornell Medical College in New York City says the study is a great start, although the technique is far from ready for general use in the clinic. But in future, an extensive suite of such tools may be available to give each individual their best chance to communicate – especially as each brain injury has its own unique characteristics. “[Treating] brain injury is the ultimate in personalised medicine,” he says.

Journal references: Massimi et al paper ; Owen and Naci paper

Update: Since this article was first published, we have clarified the description of the method used by Owen and Naci to determine their patients’ yes/no answers

Thank climate change for our daily bread. High levels of carbon dioxide in the atmosphere after the last ice age drove us to cultivate wheat.

Farming arose in the Fertile Crescent in the Middle East 10,000 years ago. Over the next two millennia, people all over the world took up the practice. This suggests that some global event triggered this simultaneous development.

A has been put forward as the culprit – the gas was released from the ocean in abundance when ocean circulation patterns changed as the ice sheets started to melt.

But if that’s the case, why did we domesticate some grain species and not others? To find out, Georg Frenck at the University of Sheffield, UK, and colleagues went back to the roots of our modern food crops. They tracked down ancient species of wild barley and wheat that are known to be precursors to today’s modern crops.

The seeds of these species have been found alongside human remains in a 23,000-year-old archaeological site in Israel, suggesting that hunter-gatherers were collecting and eating these species in the Fertile Crescent during the last ice age.

Sensitive seeds

The team grew the wheat and barley precursors under varying conditions. One set was exposed to levels of CO₂ seen during the last ice age and one to the elevated levels seen when farming first arose. Four wild grass species that aren’t eaten today, but were also known to grow in the region at that time, were also grown under the same conditions.

All the plants grew larger under high levels of CO₂, but the relatives of wheat and barley grew twice as large and produced double the seeds. This suggests the species are especially sensitive to high levels of CO₂, Frenck says, making them the best choice for cultivation after the last ice age.

Frenck says the group intends to look at whether other food staples around the world are similarly affected by elevated CO₂ levels. For instance, people in Asia began cultivating millet around this time, and people in North America started domesticating maize into the corn we grow today. They also plan to compare the effects of CO₂ on legumes such as peas.

, a palaeoecologist at the University of California, Merced, says that the work ties in nicely with previous findings that suggest the rise in CO₂ after the last ice age affected more than just the climate. However, she points out that because the experiment only ran for the duration of the plants’ lives rather than over successive generations, the findings might not accurately reflect what happened thousands of years ago as different plant species probably evolved different ways of adapting to the new CO₂ system.

The work was presented at a in Minneapolis.

Luciano Soares at the Polytechnic School of the University of SĂŁo Paulo in Brazil and his students created a set of virtual people with artificial intelligence and placed them inside a virtual building. Their job was simple: get away from a threat and to an exit as quickly as possible. By varying the types of threat, the number of people and their emotion level, the team simulated how crowds might react in different situations. For instance, people evacuated faster when there was a fire than when there was flooding. This is probably because fire originates at a single point that people can run from and because they recognise fire as more deadly.

“People evacuate faster when there is a fire than a flood, probably because it is seen as more deadly”

Another version of the program runs on a tablet computer and can be used as emergency planners walk through existing buildings. It uses the tablet’s built-in camera to film a room or hallway, then superimposes virtual people on the space in real time, giving planners an idea of how a crowd will behave.

Soares hopes the software will reveal problematic aspects of a building’s layout. For example, pointing the tablet at a door and watching virtual people race toward it could show if it is too narrow and could become a bottleneck in an emergency.

The system was presented at the Symposium on Virtual and Augmented Reality in Cuiabá, Brazil, in May.

It’s a case of hear no object, see no object. Hearing the name of an object appears to influence whether or not we see it, suggesting that hearing and vision might be even more intertwined than previously thought.

Studies of how the brain files away concepts suggest that words and images are tightly coupled. What is not clear, says of the University of Wisconsin in Madison, is whether language and vision work together to help you interpret what you’re seeing, or whether words can actually change what you see.

Lupyan and of Yale University used a technique called continuous flash suppression (CFS) on 20 volunteers to test whether a spoken prompt could make them detect an image that they were not consciously aware they were seeing.

CFS works by displaying different images to the right and left eyes: one eye might be shown a simple shape or an animal, for example, while the other is shown visual “noise” in the form of bright, randomly flickering shapes. The noise monopolises the brain, leaving so little processing power for the other image that the person does not consciously register it, making it effectively invisible.

Wheels of perception

In a series of CFS experiments, the researchers asked volunteers whether or not they could see a specific object, such as a dog. Sometimes it was displayed, sometimes not. When it was not displayed or when the image was of another animal such as a zebra or kangaroo, the volunteers typically reported seeing nothing. But when a dog was displayed and the question mentioned a dog, the volunteers were significantly more likely to become aware of it. “If you hear a word, that greases the wheels of perception,” says Lupyan: the visual system becomes primed for anything to do with dogs.

In a similar experiment, the team found that volunteers were more likely to detect specific shapes if asked about them. For example, asking “Do you see a square?” made it more likely than that they would see a hidden square but not a hidden circle.

of Stanford University in California, who was not involved in the work, thinks it is an important study. It suggests that sight and language are intertwined, he says.

Lupyan now wants to study how the language we speak influences the ability of certain terms to help us spot images. For instance, breeds might be categorised differently in different languages and might not all become visible when volunteers hear their language’s word for “dog”. He also thinks textures or smells linked to an image might have a similar effect on whether we perceive it as words.

Journal reference: