Thanks to better brain imaging and biological insights, we're closing in on the neurons of consciousness and the subtleties of our mental machinery

Cognitive control

Towards the seat of consciousness

The question "what is consciousness?" represents one of the great frontiers of contemporary science. Thanks to studies of humans and animals, we now know that it is a subtly nuanced state whose nature and intensity varies according to the brain's intrinsic level of activity, its chemical microclimate and the information it receives from outside.

By exploiting the normal vicissitudes of waking, sleeping and dreaming states, we are now beginning to explore how consciousness is expressed and controlled. For example, I have been involved in studies comparing brain activation in REM sleep with that in lucid-dreaming states, in which we retain much executive brain function. They seem to confirm the central importance of one specific area of the frontal brain - the dorsolateral prefrontal cortex - in regulating many key aspects of consciousness, including attention, decision-making and voluntary action.

A combination of imaging techniques, judicious measures of subjective experience and detailed cellular and molecular-level studies will continue to deepen our understanding of our cognitive command centres in the coming years. With them we hope to crack the puzzle of consciousness, and perhaps correct the dysfunctional states of the brain we now call mental illness. Allan Hobson

Allan Hobson is emeritus professor of psychiatry at Harvard Medical School in Cambridge, Massachusetts

The connectome

Mental maps              

Understanding the routes by which populations of brain cells share information would be a major step towards understanding how our brains function. But although we can infer individual connections, we have no basic wiring diagram of the human brain.

This is hardly surprising. The brain contains approximately 100 billion neurons, and a single neuron may connect to 10,000 others. Yet emerging techniques mean we are now making headway in this daunting task.

Using electron microscopes, for example, we can probe animal brains neuron-by-neuron, connection-by-connection, in the hope of discovering characteristic circuits that repeat themselves throughout the brain. From a wider perspective, brain imaging technologies can map the brain's highways - large "cables" consisting of many thousands of connections between distinct brain regions.

The US National Institutes of Health has begun to fund a major effort, theHuman Connectome Project, to generate a comprehensive map of large-scale brain connections in humans. Following its directions, we might arrive at a better understanding of how the brain's regions interact to produce behaviour.Tim Behrens

Tim Behrens is a neuroscientist at the University of Oxford 

The key to how we learn and think - possibly...

The saying "monkey see, monkey do" couldn't be more true. Thanks to "mirror" neurons that fire not only when we perform an action ourselves but also when we see others perform it, our primate brains subconsciously mimic every behaviour they ever witness.

That's the theory, at least. Mirror neurons were first discovered in macaques in the 1990s, and brain scans using functional MRI had hinted that they exist in humans too. But it wasn't until May this year that researchers measured the firing of mirror neurons in humans directly, using electrodes implanted in the brains of epileptic patients awaiting surgery (Current Biology, vol 20, p 750).

While proponents of the power of mirror neurons claim they explain everything from empathy and compassion to a penchant for porn, their exact significance remains controversial. The next few years will see us homing in on what exactly they can and cannot explain about human cognition.

Top-down processing

Our past determines our present           

The human eye is a camera that faithfully records everything in front of us, passing the information through the brain's visual processor before it pops out as a conscious experience.

This "bottom-up" process represents the textbook view. In truth, we are realising that our experience is closer to a form of augmented reality, in which our brain redraws what it sees to best fit our expectations and memories.

The same goes for our other senses, and the growing suspicion is that kinks in this system of "top-down processing" might shed light on neurological disorders such as schizophrenia, autism and dyslexia. Whether or not that turns out to be the case, this idea is radically changing our view of how our past influences our here and now.

Neuronal recycling

Culture is a parasite           

The architecture of our brains far predates writing, religion and art. So how come we acquire these cultural traits and abilities with such ease?

The standard answer is that our big, plastic brains have a uniquely flexible and generalised learning capacity. But is that true? The human brain is not homogeneous, after all, but organised into specialised areas. Moreover, brain imaging reveals that abilities such as reading and mathematics have distinct "neuronal niches"; they too are confined to specific brain circuits

That is compelling evidence for an idea known as neuronal recycling: that our cultural abilities invaded and parasitised brain circuits originally dedicated to evolutionarily older, but related functions. Reading, for example, seems to occupy circuits sensitive to complex shapes and with good connections to areas dealing with language (Reading in the Brain, Viking, 2009). If correct, it is our brains shape our culture, rather than our culture our brains. Human ingenuity is not unlimited, but fundamentally constrained by neural architecture.

Nootropics

Food for thought           

You've got a big report to file, and the clock is ticking. If only you could concentrate harder, recall facts and figures more effectively, or just shake off that feeling of fatigue after yesterday's late night.

Soon a brain boost might follow a visit to your local pharmacy. Psychostimulant drugs such as Ritalin and Adderall, prescribed to treat attention-deficit hyperactivity disorder, and Aricept, used as a treatment for Alzheimer's disease, have been shown to improve concentration and recall in healthy people, too.

Such drugs are not currently available without a prescription, but some researchers say they should be. Multiply that extra brain power by the 7 billion members of the human race, they say, and the benefits to society and the pursuit of knowledge would soon start to add up. But is a race of drugged-up super-brains what we really want to be? Food for thought indeed.

Humans know less than they 

think...

Shock!

IF NEW satellite data can be trusted, changes in solar activity warmed the Earth when they should have cooled it.

Joanna Haigh of Imperial College London studied satellite measurements of solar radiation between 2004 and 2007, when overall solar activity was in decline. The sun puts out less energy when its activity is low, but different types of radiation vary to different degrees. Until now, this had been poorly studied.

Haigh's measurements showed that visible radiation increased between 2004 and 2007, when it was expected to decrease, and ultraviolet radiation dropped four times as much as predicted.

Haigh then plugged her data into an atmospheric model to calculate how the patterns affected energy filtering through the atmosphere. Previous studies have shown that Earth is normally cooler during solar minima.Yet the model suggested that more solar energy reached the planet's surface during the period, warming it by about 0.05 °C (Nature, DOI: 10.1038/nature09426).

The effect is slight, but it could call into question our understanding of the sun's subtle effects on climate. Or could it? Stefan Brönnimann of the University of Bern in Switzerland says Haigh's study shows the importance of looking at radiation changes in detail but cautions that the results could be a one-off. He points out that the sun's most recent cycle is known to have been atypical

First frictionless superfluid molecules created

CHILL them enough and some atoms creep up walls or stay still while the bowl they sit in rotates, thanks to a quantum effect called superfluidity. Now molecules have got in on the act.

Superfluidity is a bizarre consequence of quantum mechanics. Cool helium atoms close to absolute zero and they start behaving as a single quantum object rather than a group of individual atoms. At this temperature, the friction that normally exists between atoms, and between atoms and other objects, vanishes, creating what is known as a superfluid.

To see if molecules could be made superfluid, Robert McKellar of the National Research Council of Canada in Ottawa and colleagues turned to hydrogen, which exists as pairs of atoms. The team created a compressed mixture of hydrogen and carbon dioxide gas and shot it through a nozzle at supersonic speeds. Once released, the molecules spread apart, cooling and arranging themselves so that each CO₂ molecule sat at the centre of a cluster of up to 20 hydrogens.

To test for superfluidity, the team shone an infrared laser at the clusters at wavelengths that CO₂, but not hydrogen, can absorb. This set only the CO₂molecules vibrating. Under normal conditions this movement would be slowed down due to friction between the moving CO₂ molecules and the surrounding hydrogen. But the researchers found that for clusters of 12 hydrogen molecules, the hydrogen barely impeded the motion of the CO₂.

They conclude that these hydrogen clusters are 85 per cent superfluid (Physical Review Letters, DOI: 10.1103/PhysRevLett.105.133401).

As hydrogen is only the second element known to form a superfluid, McKellar says the experiment could be useful for disentangling general qualities of superfluids.

Superfluid molecules might also be used as "nano-fridges", which surround and cool individual protein molecules. Superfluid helium atoms are already used for this but, unlike atoms, molecules can bend and stretch, which might present new ways to manipulate the cooled proteins.

Thank mothers for large ape brains

20:00 06 September 2010 by Michael Marshall

Humans, apes and monkeys have their mothers to thank for their large brains.

It takes a lot of energy to make and run a brain, so large ones should only have developed in animals with fast metabolisms. But according to Vera Weisbecker of the University of Cambridge and Anjali Goswami of University College London, that's only part of the story.

The pair looked at the brains of 197 marsupials and 457 placental mammals, and could find a link between metabolic rate and brain size only in placental mammals. This suggests that parenting strategies play a key role.

"Placental babies are connected to their mothers via the placenta for a long time," says Weisbecker. "So if she has a high metabolic rate, the baby is more likely to benefit." By contrast, marsupial babies are born while they are still very small, then spend a long time feeding off their mothers' milk – a slower way to grow a large brain. Placentas offer a continuous supply of rich nutrients.

However, the pair found no difference in the average brain sizes of marsupials and placental mammals – as long as they excluded primates. These, it seem, got their disproportionately large brains from a double maternal boost. They are supplied with large amounts of energy by their mothers during gestation, and then receive additional months or even years of care after birth.

Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0906486107

The natural selection of leaders

• 07 September 2010 by Anjana Ahuja

Are leaders born or made? Evolution may be throwing us a curve ball when it comes to picking them in the modern world, says Anjana Ahuja

IMAGINE this. You and your colleagues are gathered round a conference table, with coffee and biscuits. You open the door and greet the first sharp-suited candidate of the day. Before evening falls, one lucky applicant will hear the unlikely phrase: "We would like to offer you the job of being our boss."

The idea of subordinates selecting their superiors might seem fantastical, but not to our ancestors. In our new book, Mark van Vugt at VU University in Amsterdam, the Netherlands, and I propose that leadership and followership behaviours can be traced to the earliest days of our species. Given that all human groupings - be they nations, gangs or cults - have leaders and followers, and that these behaviours appear spontaneous, our thesis is that leadership and followership are adaptive behaviours.

In other words, they are behaviours that evolved to give our ancestors a survival advantage (our book's title, Selected, reflects the role natural selection plays in leadership). In fact, this arrangement proves so beneficial that other species, from fish to birds to chimpanzees, also show forms of leadership and followership, rudimentary in the cases of fish and birds, but surprisingly sophisticated in the case of our coalition-building cousins.

But what's the link between our theory that leadership and followership are evolved behaviours and you and your colleagues picking your own line manager? Studies of some hunter-gatherer communities show that gifted individuals are picked in a bottom-up, not top-down, way. Leadership is fluid rather than fixed, and assigned by peers to whoever is recognised as adept in a specific domain, from herbalism to hunting. We argue that some modern companies are unwittingly still practising this ancestral style of promotion, with great success. For example, the CEO of W. L. Gore & Associates, which makes Gore-Tex, is chosen by the rank and file of the company, not shoehorned in by management. The firm has an unusually high retention rate for "associates" (never called "employees").

Studies of hunter-gatherer societies also show that hierarchies are relatively flat and wealth disparities minimal. One tribe is documented as having no concept of personal property and, correspondingly, theft, an outlook which led its members into persistent conflict with sheep-owning incomers. A Martian alighting upon one of these societies and asking to be taken to their leader would be met with bewilderment. There are no presidential elections or prime ministerial hustings in those isolated communities: overly domineering characters are more likely to be assassinated than obeyed. Unlike in the glass-and-steel corporate empires of the developed world, there are strong norms against pushy individuals who thrust themselves forward, or whose self-interest is too clearly displayed.

When you view leadership and followership through the prism of evolutionary psychology, many peculiarities about the way we choose our leaders look less odd. For example, political scientists have no convincing rational explanation of why taller candidates almost always beat shorter rivals. But hundreds of thousands of years ago, when tribal conflicts were resolved physically, lofty tribesmen would have enjoyed an edge over opponents of modest stature. Our societies continue to insist leaders should look "statesmanlike" without spelling out what this means, which suggests that we have some innate concept of what a leader should look like. Such an internal template of a good leader would have been reinforced over evolutionary history - though the template would vary in different circumstances, letting us opt for a different kind of leader in war or peacetime.

The modern vestiges of these templates can be detected by psychologists today. Take the startling finding that people can distinguish high-ranking CEOs from their lower-ranked peers purely on facial appearance (the key is in the squareness of the jawline). Tallness is also overrepresented in both CEOs and politicians. In another study, naive children shown photographs of election candidates typically pick the same winner as the electorate.

These studies back up our theory that many leaders owe their position not to calculated, rational decisions on the part of the electorate or interview board, but to their ability to push a "leader button" in the human psyche. Whether it's Barack Obama hitting the gym or a bare-chested Vladimir Putin posing in Siberia, politicians like us to know that they're tough guys, as if we still need musclemen to protect us in an age when governing tends to be a cerebral, rather than an aerobic, activity

In fact we know from experiments in the laboratory that the way we pick our leaders often defies easy, conscious explanation. In one experiment using university students, van Vugt showed that groups entrusted with performing task X were more likely to select leader A, who had previously failed at that task, instead of leader B, who had previously succeeded. The reason? Leader A came from the same university as the rest of the group, while leader B was from another institution. So the deeply ingrained idea of "us" and "them" lingers, even in cosmopolitan university students. Evolutionarily, there is much to be said for sticking to the fiercely loyal devil you know rather than the potentially disloyal angel you don't

That is not to say that workplaces should become havens of primitivism. Evolution might have bestowed on us an instinctive suspicion of leaders who are short, female or who belong to a different tribe (skin colour is an obvious badge of belonging), but we need to ask whether such prejudices belong in today's interconnected world, in which citizens of all colours and religions need to rub along. The election of America's first black president offers encouraging evidence that we can overcome these ancestral biases, although Obama's success was undoubtedly aided by his physical stature.

Perhaps the most important take-home message in our book is that there is a mismatch between the way we lead and follow today, and the way our ancestors operated. Where our forebears clustered in small groups on the African savannah, half of the world's population now lives in cities. Where leadership was dispersed among the many, it is now concentrated in the hands of a corporate and political elite. Could this be why we feel disconnected from our leaders?

The good news is that insights into our recent past may help improve things. People in small companies (think small tribe) are happier than those in big ones. Good bosses and adept politicians know that the personal touch goes a long way (think extended family, or at least the feeling of one) - as does roughing it sometimes on the shopfloor to show solidarity with subordinates and to earn their endorsement (think nights hunting in the forest). These working practices feel right for a reason: your ancestors thrived on them. So, the next time your line manager announces that it's time for your performance review, just smile and ask them to bring examples of their work along to it.

Profile

This article is based on Selected (Profile Books) by Mark van Vugt, professor of psychology at VU University in Amsterdam, the Netherlands, and research fellow at the University of Oxford, and Anjana Ahuja, writer and former science columnist for The Times of London

CAKE ALERT

Junkie food:

• 08 September 2010 by Bijal Trivedi
• Magazine issue 2776. Subscribe and save

Is that cupcake an innocent indulgence? Or your next hit? We're finding that a sweet tooth makes you just as much an addict as snorting cocaine

SETTLED on the sofa watching the usual rubbish on TV, I notice that predictable, uncontrollable, nightly craving. At first I sit there, fighting it. But the longer I fight, the worse it gets. After 20 minutes, I can't concentrate on anything, I feel anxious, and start fidgeting like crazy. Finally, admitting my addiction, I break. I go to the freezer - to my stash of white stuff - and take a hit. Almost instantly, I relax, my brain in a state of bliss as the chemical courses through my veins. Isn't it amazing what a few scoops of ice cream can do?

Before you dismiss my agitation as mere weakness, consider this: to my brain, sugar is akin to cocaine. There is now compelling evidence that foods high in sugar, fat and salt - as most junk foods are - can alter your brain chemistry in the same way as highly addictive drugs such as cocaine and heroin.

The idea, considered fringe just five years ago, is fast becoming a mainstream view among researchers as new studies in humans confirm initial animal findings, and the biological mechanisms that lead to "junk-food addiction" are being revealed. Some say there is now enough data to warrant government regulation of the fast food industry and public health warnings on products that have harmful levels of sugar and fat. One campaigning lawyer claims there could even be enough evidence to mount a legal fight against the fast food industry for knowingly peddling food that is harmful to our health, echoing the lawsuits against the tobacco industry in the 1980s and 90s.

"We have to educate people about how their brains get hijacked by fat, sugar and salt," says David Kessler, former commissioner of the US Food and Drug Administration and now a director of the Center for Science in the Public Interest, based in Washington DC. With obesity levels rocketing across the world, it is clear that I am not alone in my love of sweet things, but can it really be as bad as drug addiction?

We have to educate people about how their brains get hijacked by fat, sugar and salt

Arguably, it was the weight-loss industry that first introduced the idea to the public, long before there was any scientific evidence for it. For example, in her book Lick the Sugar Habit, published in 1988, the self-confessed "sugarholic" Nancy Appleton offered a checklist to determine whether you, too, are addicted to sugar. Since then, the notion has become commonplace.

In 2001, intrigued by this nascent cultural phenomenon, neuroscientists Nicole Avena, now at the University of Florida in Gainesville, and Bartley Hoebel at Princeton University, together began exploring whether the idea had a biological basis. They started by looking for signs of addiction in animals that had been eating junk food.

Hooked on sugar

Sugar is a key ingredient in most junk food, so they offered rats sugar syrup, similar to the sugar concentration in a typical soda beverage, for about 12 hours each day, alongside regular rat feed and water. After just a month on this diet, the rats developed behaviour and brain changes that Avena and Hoebel claimed were chemically identical to morphine-addicted rats. They binged on the syrup and showed anxious behaviour when it was removed - a sign of withdrawal. There were also changes in the neurotransmitters in the nucleus accumbens, a region associated with reward.

Crucially, the researchers noticed that the rats' brains released the neurotransmitter dopamine each time they binged on the sugar solution, even after having eaten it for weeks (Neuroscience & Biobehavioral Reviews, vol 32, p 20). That's not normal.

Dopamine drives the pursuit of pleasure - whether it is food, drugs or sex. It is a brain chemical vital for learning, memory, decision-making and sculpting the reward circuitry. You would expect it to be released when they eat a new food, says Avena, but not with one they are habituated to. "That's one of the hallmarks of drug addiction," she says. This was the first hard evidence of a biological basis for sugar addiction, and sparked a slew of animal studies.

Those results were among the most exciting news in obesity research in the last 20 years, says Mark Gold, an international authority on addiction research and chairman of the psychiatry department at the University of Florida College of Medicine.

Since Avena and Hoebel's landmark study, scores of other animal studies have confirmed the findings. But it is recent human studies that have finally tipped the balance of evidence in favour of labelling a love of junk food as a proper addiction.

Addicted brains

Addiction is commonly described as a dulling of the "reward circuits" triggered by the overuse of some drug. This is exactly what happens in the brains of obese individuals, says Gene-Jack Wang, chairman of the medical department at the US Department of Energy's Brookhaven National Laboratory in Upton, New York. In another landmark study published in 2001, he discovered a dopamine deficiency in the striatum of the brains of obese individuals that was virtually identical to those of drug addicts