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The brain is full of Manhattan-like grids

London’s streets are a mess. Roads bend sharply, end abruptly, and meet each other at unlikely angles. Intuitively, you might think that the cells of our brain are arranged in a similarly haphazard pattern, forming connections in random places and angles. But a new study suggests that our mental circuitry is more like Manhattan’s organised grid than London’s chaotic tangle. It consists of sheets of fibres that intersect at right angles, with no diagonals anywhere to be seen.

Van Wedeen from Massachusetts General Hospital, who led the study, says that his results came as a complete shock. “I was expecting it to be a pure mess,” he says. Instead, he found a regular criss-cross pattern like the interlocking fibres of a piece of cloth.


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New neurons buffer the brains of mice against stress and depressive symptoms

For large swathes of the brain, the neurons we’re born with are the ones we’re stuck with. But a few small areas, such as the hippocampus, create new neurons throughout our lives, through a process known as neurogenesis. This production line may be important for learning and memory. But it has particularly piqued the interest of scientists because of the seductive but controversial idea that it could protect against depression, anxiety and other mood disorders.

Now, by studying mice, Jason Snyder from the National Institute of Mental Health has found some of the strongest evidence yet for a connection between neurogenesis and depression (or, at least, mouse behaviours that resemble depression). He found that the new neurons help to buffer the brains of mice against stress. Without them, the rodents become more susceptible to stress hormones and they behave in unusual ways that are reminiscent of depressive symptoms in humans.


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Memory improves when neurons fire in youthful surroundings

As we get older, our memories start to fail us. The symptoms of this decline are clear, from losing track of house keys to getting easily muddled and confused. Many of these problems stem from a failure of working memory – the ability to hold pieces of information in mind, block out distractions and stay focused on our goals. Now, a team of American scientists has discovered one of the reasons behind this decline, and a way of potentially reversing it.

Our working memory depends on an area known as the prefrontal cortex or PFC, right at the front of the brain. The PFC contains a network of nerve cells called pyramidal neurons that are all connected to one another and constantly keep each other buzzing and excited – like a neural version of Twitter. This mutual stimulation is the key to our working memory. As we age, the buzz of the pyramidal neurons gets weaker, and information falls more readily from our mental grasp.

But this decline isn’t the fault of the neurons themselves. By studying monkeys, Min Wang from the Yale University School of Medicine has found that the environment around the neurons also changes with age. And by restoring that environment to a more youthful state, he managed to ease some of the age-related decline in working memory.


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Beauty is in the brain of the beholder

What happens when I stare at Portrait of Madame X or listen to Air on a G String? Both at intensely beautiful to me, but they are different experiences that involve different senses. Nonetheless, the sight of Sargent’s pigments and the sound of Bach’s notes trigger something in common – a part of the brain that lights up when we experience feelings of beauty, no matter how we experience them.

Tomohiro Ishizu and Semir Zeki from University College London watched the brains of 21 volunteers as they looked at 30 paintings and listened to 30 musical excerpts. All the while, they were lying inside an fMRI scanner, a machine that measures blood flow to different parts of the brain and shows which are most active. The recruits rated each piece as “beautiful”, “indifferent” or “ugly”.

The scans showed that one part of their brains lit up more strongly when they experienced beautiful images or music than when they experienced ugly or indifferent ones – the medial orbitofrontal cortex or mOFC.

Several studies have linked the mOFC to beauty, but this is a sizeable part of the brain with many roles. It’s also involved in our emotions, our feelings of reward and pleasure, and our ability to make decisions. Nonetheless, Ishizu and Zeki found that one specific area, which they call “field A1” consistently lit up when people experienced beauty.


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The brain on sonar – how blind people find their way around with echoes

Daniel Kish has no eyes. He lost them to cancer at just 13 months of age, but you wouldn’t be able to tell from watching him. The 44-year-old happily walks round cities, goes for hikes, rides mountain bikes, plays basketball, and teaches other blind youngsters to do the same. Brian Bushway helps him. Now 28 years old, Bushway lost his vision at 14, when his optic nerves wasted away. But, like Kish, he finds his way around with an ease that belies his disability.

Both Kish and Bushway have learned to use sonar. By making clicks with their tongue and listening to the rebounding echoes, they can “see” the world in sound, in the same way that dolphins and bats can. They are not alone. A small but growing number of people can also “echolocate”. Some develop the skill late in life, like Bushway; others come to it early, like Kish. Some use props like canes to produce the echoes; others, just click with their tongues.

The echoes are loaded with information, not just about the position of objects, but about their distance, size, shape and texture. By working with these remarkable people, scientists have worked out a lot about the scope and limits of their abilities. But until now, no one had looked at how their brains deal with their super-sense.


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Shedding light on sex and violence in the brain

With a pulse of light, Dayu Lin from New York University can turn docile mice into violent fighters – it’s Dr Jekyll’s potion, delivered via fibre optic cable. The light activates a group of neurons in the mouse’s brain that are involved in aggressive behaviour. As a result, the mouse attacks other males, females, and even inanimate objects.

Lin focused on a primitive part of the brain called the hypothalamus that keeps our basic bodily functions ticking over. It lords over body temperature, hunger, thirst, sleep and more. In particular, Lin found that a small part of this area – the ventrolateral ventromedial hypothalamus (VMHvl) – acts as a hub for both sex and violence.

Many of the neurons in the VMHvl fire only when male mice act belligerently, while others fire during sex. The two groups of neurons even compete with one another – some of the violence cells are suppressed while the sexual ones are busy.


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Can electrical jolts to the brain produce Eureka moments?

Finding those Eureka moments that allow us to solve difficult problems can be an electrifying experience, but rarely like this. Richard Chi and Allan Snyder managed to trigger moments of insight in volunteers, by using focused electric pulses to block the activity in a small part of their brains. After the pulses, people were better at solving a tricky puzzle by thinking outside the box.

This is the latest episode in Snyder’s quest to induce extraordinary mental skills in ordinary people. A relentless eccentric, Snyder has a long-lasting fascination with savants – people like Dustin Hoffman’s character in Rain Man, who are remarkably gifted at tasks like counting objects, drawing in fine detail, or memorising vast sequences of information.

Snyder thinks that everyone has these skills but they’re typically blocked by a layer of conscious thought. By stripping away that layer, using electric pulses or magnetic fields, we could theoretically release the hidden savant in all of us. Snyder has been doggedly pursuing this idea for many years, with the goal of producing a literal “thinking cap”. He has had some success across several studies, but typically involving small numbers of people.


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Meet the woman without fear

SMKentucky, USA. A woman known only as SM is walking through Waverly Hills Sanatorium, reputedly one of the “most haunted” places in the world. Now a tourist attraction, the building transforms into a haunted house every Halloween, complete with elaborate decorations, spooky noises and actors dressed in monstrous costumes. The experience is silly but still unnerving and the ‘monsters’ often manage to score frights from the visitors by leaping out of hidden corners.

But not SM. While others show trepidation before walking down empty corridors, she leads the way and beckons her companions to follow. When monsters leap out, she never screams in fright; instead, she laughs, approaches and talks to them. She even scares one of the monsters by poking it in the head.

SM is a woman without fear. She doesn’t feel it. She has been held at knifepoint without a tinge of panic. She’ll happily handle live snakes and spiders, even though she claims not to like them. She can sit through reels of upsetting footage without a single start. And all because a pair of almond-shaped structures in her brain – amygdalae – have been destroyed.


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The size of your brain’s visual centre affects how you see the world


Look at the image above. Which of the central orange circles looks bigger? Most people would say the one on the right – the one surrounded by the smaller ‘petals’. In truth, the central circles are exactly the same size. This is the Ebbinghaus illusion, named after the German psychologist Hermann Ebbinghaus. It has been around for over a century, but it still continues to expand our understanding of the brain.

Samuel Schwarzkopf from University College London has just discovered that the size of one particular part of the brain, known as primary visual cortex or V1, predicts how likely we are to fall for the illusion. V1 sits at the very back of our brains and processes the visual information that we get from our eyes. It’s extremely variable; one person’s V1 might have three times the surface area of another person’s. While many scientific studies try to average out those differences, Schwarzkopf wanted to explore them.


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The signature of the bluffing brain


The best poker players are masters of deception. They’re good at manipulating the actions of other players, while masking their own so that their lies become undetectable. But even the best deceivers have tells, and Meghana Bhatt from Baylor University has found some fascinating ones. By scanning the brains and studying the behaviour of volunteers playing a simple bargaining game, she has found different patterns of brain activity that correspond to different playing styles. These “neural signatures” separate the players who are adept at strategic deception from those who play more straightforwardly.


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Drunken monkeys reveal how binge-drinking harms the adolescent brain


Most of us will be all too familiar with the consequences of night of heavy drinking. But alcohol’s effects on our heads go well beyond a mere hangover. The brain suffers too. A penchant for incoherent slurring aside, alcohol abusers tend to show problems with their spatial skills, short-term memory, impulse control and ability to make decisions or prioritise tasks. Many of these skills are heavily influenced by a part of the brain called the hippocampus. Now, Michael Taffe and researchers from the Scripps Research Institute have shown how binge-drinking during adolescence can cause lasting damage to this vital area.


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Study raises questions about the role of brain scans in courtrooms

Brain_scanA murder suspect sits in a quiet room with electrodes placed on her head. The prosecution reads out its narrative of the crime and the suspect’s alleged role in it. As she listens, the machines record her brain activity and reveal that she experienced aspects of the crime that only the murderer could have. Her own memories, teased out by technology, have betrayed her. The verdict is guilty.

This scenario might seem far-fetched, but it actually happened in an Indian trial that took place in 2008. The judge took a brain scan as proof that the suspect had “experiential knowledge” about the crime that only the killer could have possessed. She was sentenced to life in prison. There has been a smattering of attempts to use brain-scanning technology in this way, accompanied by an uproar about the technology’s readiness.

Now, a new study by Jesse Rissman from Stanford University confirms that promises about the social implications of brain scans are overplayed. Together with Henry Greely and Anthony Wagner, Rissman has shown that brain scans can accurately decode whether people think they remember something, but not whether they actually remember something. And that gap between subjective and objective memory is a vast chasm as far as the legal system is concerned.

Our memories are stored within networks of neurons so it’s reasonable to think that by studying the patterns of activity within these networks, we should be able to decipher individual memories. Studies have already started to show that this is possible with our existing brain-scanning techniques, and with every positive result, the temptation to use such advances in a practical setting grows.

The courtroom is an obvious candidate, especially because our brains respond differently when it experiences something new compared to something old. You could use brain scans to tell if someone has actually seen a place, person or thing, reliably corroborating the accounts of witnesses and suspects without having to rely on the vagaries of accurate recall and moral fortitude. For this reason, techniques like functional magnetic resonance imaging (fMRI) have been enticingly billed as the ultimate in lie detection technology. Claims of “mind-reading machines” and “psychic computers” have abounded in the press.


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A single genetic fault makes one hand mirror the other’s movements

FistsClench your left hand into a fist. What happened to your right hand when you did it?

If you’re like most people, the answer is nothing. But, surprisingly, not everyone can do this. Some people make “mirror movements”, where moving one side of the body, particularly the hands, causes the other to move unintentionally. Clench the left fist, and the right one closes too. Doing things like playing the piano or typing are very difficult. In 2002, a Chinese man with the disorder failed to get into the military because he couldn’t use the monkey bars.

Young children sometimes make mirror movements but they almost always grow out of it by the age of 10. The only exceptions tend to be people with rare genetic disorders of the nervous system, like Klippel-Feil and Kallmann syndromes. Now, Myriam Srour from the University of Montreal has found that a single faulty gene can cause the condition.


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When multi-tasking, each half of the brain focuses on different goals

MultitaskingIn 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.

Multitasking-experimentCharron 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


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When is attempted murder more acceptable than harming someone by accident?

Attempted_murderDan, a scientist working on dangerous viruses, is giving a visitor a tour of his lab. Before this happens, all test tubes containing disease-causing agents must be sealed in a chamber with a flick of a switch. Unfortunately, the switch broke recently and it hasn’t been repaired yet. Entering the room means certain death. Dan knows this but still, he bids the visitor to enter. The inevitable happens; they become sick and they die.

Would you consider Dan’s actions to be immoral? What if, in a parallel universe, the visitor miraculously survived? Does that change your views of Dan’s deeds? What if Dan didn’t know about the broken switch? For most of us, the answers are clear. If Dan knew about the broken switch, he was wrong to send in the visitor to potential death, regardless of whether they actually perished. But bizarrely, not everyone would see it that way.

Liane Young from MIT found that people with brain damage in an area called the ventromedial prefrontal cortex (VMPC) are unusually likely to brush off failed attempts at harming other people. They frowned upon actual murder with the usual severity but compared to normal people, they were twice as likely to think that attempted murder was morally permissible. Young thinks that the VMPC is vital for our ability to deduce respond emotionally to the intentions of other people, an important skill when it comes to making moral judgments.