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.
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.
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.
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.
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.
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.
Kentucky, 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.
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.
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.