Songbirds need so-called “human language gene” to learn new tunes

The nasal screech of Chris Tucker sound worlds apart from the song of a nightingale but both human speech and birdsong actually have a lot in common. Both infants and chicks learn their respective tongues by imitating others. They pick up new material most easily during specific periods of time as they grow up, they need practice to improve and they pick up local dialects. And as infants unite words to form sentences, so do songbirds learn to combine separate riffs into a full song.

Because of these similarities, songbirds make a good model for inquisitive neuroscientists looking to understand the intricacies of human speech. Zebra finches are a particularly enlightening species and they have just shown Sebastian Haesler that the so-called human ‘language gene’ FOXP2 also controls an songbird’s ability to pick up new material.

FOXP2 has a long and sordid history of fascinating science and shoddy science writing. It has been consistently mislabelled as “the language gene” and after the discovery that the human and chimp versions differed by just two small changes, it was also held responsible for the evolution of human language. Even though these claims are far-fetched (for reasons I’ll delve into later), there is no doubt that faults in FOXP2 can spell disaster for a person’s ability to speak.

Mutated versions cause a speech impairment called developmental verbal dyspraxia (DVD), where people are unable to coordinate the positions of their jaws, lips, tongues and faces, even though their minds and relevant muscles are in reasonable working order. They’re like an orchestra that plays a cacophony despite having a decent conductor and tuned instruments.

Brain scans of people with DVD have revealed abnormalities in the basal ganglia, an group of neurons at the heart of the brain with several connections to other areas. Normal people show strong activation of FOXP2 here and fascinatingly, so do songbirds. Haesler reasoned that studying the role of this gene in birds could tell him more about its human counterpart.

Brain of the beholder – the neuroscience of beauty in sculpture

Is beauty simply in the eye of the beholder, or do all the beholders’ brains have something in common? Is there an objective side to beauty? Plato certainly seemed to think so. His view was that beauty was an inherent property that all beautiful objects possess, irrespective of whether someone likes it or not.

To him, beauty in the world stemmed from an ideal version of Beauty that real objects can only aspire to. A biologist might instead suggest that the objective side of beauty stems from built-in predispositions for certain features, colours, shapes or proportions.

The opposing view is that art is a fully subjective enterprise and our preferences are shaped by our values and experiences. The real answer is likely to lie somewhere in the middle – after all, art students learn basic common skills such as proportion, perspective and symmetry before embarking on their own stylistic journeys.

Artists, critics and gallery visitors can argue about this question all they like, but some clearer answers have now emerged from three researchers in Italy, arguably the home of the some of the world’s most beautiful art. Cinzia Di Dio, Emiliano Macaluso and Giacomo Rizzolatti from the University of Parma have brought the tools of the modern neuroscientist into the debate.

Delay not deviance: brains of children with ADHD mature later than others

Attention-deficit hyperactivity disorder is the most common developmental disorder in children, affecting anywhere between 3-5% of the world’s school-going population. As the name suggests, kids with ADHD are hyperactive and easily distracted; they are also forgetful and find it difficult to control their own impulses.

While some evidence has suggested that ADHD brains develop in fundamentally different ways to typical ones, other results have argued that they are just the result of a delay in the normal timetable for development.

Now, Philip Shaw, Judith Rapaport and others from the National Institute of Mental Health have found new evidence to support the second theory. When some parts of the brain stick to their normal timetable for development, while others lag behind, ADHD is the result.

The idea isn’t new; earlier studies have found that children with ADHD have similar brain activity to slightly younger children without the condition. Rapaport’s own group had previously found that the brain’s four lobes developed in very much the same way, regardless of whether children had ADHD or not.

But looking at the size of entire lobes is a blunt measure that, at best, provides a rough overview. To get an sharper picture, they used magnetic resonance imaging to measure the brains of 447 children of different ages, often at more than one point in time.

Metabolic gene and breastfeeding unite to boost a child’s IQ

The nature-nurture debate is one of the most famous in biology, but its own nature has shifted substantially in recent years. We now know that genes and environment are not opposing agents that shape our lives separately, but partners walking hand-in-hand. More often than not, genes affect our bodies and behaviour by altering the ways in which we react to our environment.

Now, an international team of researchers have discovered a stark example of this gene-environment partnership. They found that breastfed children have higher IQ scores, but only if they have a certain version of a gene called FADS2.

The concept of IQ has been central to the nature-nurture debate for years, ever since studies in twins suggested that a large part of the variation in IQ scores could be explained through inherited genetic factors. Avshalom Caspi and Terrie Moffitt from King’s College London wanted to kill this tiresome debate finding a gene that affected IQ via the environment.

They chose to look at breastfeeding, as studies have mostly found that babies who drink their mothers’ milk have higher IQ scores, among other benefits. These higher scores persist into adulthood and across social classes. We also have a reasonable idea of how breastfeeding could affect brain development at a molecular level, and it involves fatty acids.

Broken chains and faulty mirrors cause problems for autistic children

Your brain has an amazing ability to predict the future. For example, if you see someone reach for a chocolate, you can guess that they’re likely to pick it up, put it in their mouths and eat it. Like most people, you have a talent for understanding the goal of an action while you see it being performed – in this case, you know that reaching for the chocolate is only a step towards eating it.

That may not sound very impressive, but as with many mental skills, it’s only apparent how complicated it is when you see people who can’t do it.

Autistic people, for example, find it incredibly difficult to relate to other people and this may, in part, be because they can’t understand the why of someone else’s actions. While a typical child would understand that a mother holding her hands out is readying for a hug, an autistic child might be baffled by the gesture.

Now, a new study by Luigi Cattaneo, Giacomo Rizzolatti and colleagues suggests that autistic people find it difficult to understand the purpose of an act because they cannot string together different actions into a coherent whole. And underlying this problem is a special group of nerve cells called mirror neurons.

The neuroscience of optimism – how the brain creates a rosy outlook

In 1979, a crucified Eric Idle advised movie-goers to always look on the bright side of life. It seems that he needn’t have bothered. Psychological experiments have consistently shown that as a species, our minds are awash with a pervasive optimism.

We expect our future successes to overpower our past ones. Compared to an imaginary Joe Bloggs, we deem ourselves likely to live longer, more likely to have a successful career and less likely to suffer divorce or ill health. Even the most cynical of minds had a tendency for making similar, overconfident predictions.

Now, Tali Sharot and colleagues form New York University have pinpointed a neural circuit in the brain that generates this glass-half-full outlook.

Doctors repress their responses to their patients’ pain

A new study shows that experienced doctors learn to control the part of their brain that allows them to empathise with a patient’s pain, and switch on another area that allows them to control their emotions.

Many patients would like their doctors to be more sensitive to their needs. That may be a reasonable request but at a neurological level, we should be glad of a certain amount of detachment.

Humans are programmed, quite literally, to feel each others’ pain. The neural circuit in our brains that registers pain also fires when we see someone else getting hurt; it’s why we automatically wince.

This empathy makes evolutionary sense – it teaches us to avoid potential dangers that our peers have helpfully pointed out to us. But it can be liability for people like doctors, who see pain on a daily basis and are sometimes forced to inflict it in order to help their patients.

Clearly, not all doctors are wincing wrecks, so they must develop some means of keeping this automatic response at bay. That’s exactly what Yawei Chang from Taipei City Hospital and Jean Decety from University of Chicago found when they compared the brains of 14 acupuncturists with at least 2 years of experience to control group of 14 people with none at all.

Virtual reality illusions produce out-of-body experiences in the lab

Using virtual reality illusions, two groups of scientists have managed to simulate out-of-body experiences in the lab – by convincing volunteers that they were actually sitting or standing outside of their own bodies, watching themselves from behind. These studies can tell us a lot about our own self-consciousness.

The idea of an out-of-body experiences seems strange and hokey – certainly not one that would grace one of the world’s top scientific journals. So it may seem surprising it cropped up in not one, but two papers in Science this week.

Out-of-body experiences are rare and can be caused by epileptic fits, neurological conditions such as strokes and heavy drug abuse. Clearly, they are triggered when something goes wrong in our brains. And as usual for the brain, something going wrong can tell us a lot about what happens the rest of the time.

Simply put, if we very rarely have an out-of-body experience, why is it that for the most part we have ‘in-body’ experiences? It’s such a fundamental part of our lives that we often take it for granted, but there must be some mental process that ensures that our perceptions of ‘self’ are confined to our own bodies. What is it?

Two groups of scientists have taken steps to answering these questions using illusion and deception. They managed to experimentally induce mild out-of-body experiences in healthy volunteers, by using virtual reality headsets to fool people into projecting themselves into a virtual body.

Scientists watch free will give way to instinct as danger approaches

You are being hunted, chased through a labyrinth by a relentless predator. Do you consider your options and plan the best possible escape, or do you switch off and rely solely on instinct? A new study provides the answer – you do both, flicking from one to the other depending on how far away the threat is.

Earlier studies have found that different parts of a rodent’s brain are activated in the face of danger, depending on how imminent that danger is. Now, a study by scientists at University College London has found the same thing in human brains.

Flexible defences

It would be a poor strategy to stick to the same defensive behaviours in all situations. Simply put, there are threats and there are threats, and we need different kinds of behaviour to cope with different scales of danger.

When a predator is fifty feet away, we have the time and space to consider our options and plan an escape. But when it’s five feet away, such luxuries are ill-afforded and behaviour needs to be fast and reflexive. In the millisecond between life and death, free will takes a back seat in the light of three simple options – fight, flight or freeze.

This sounds fairly obvious, but Dean Mobbs and colleagues actually watched the switch taking place by scanning the brains of several volunteers as they were being chased by a predator.

Molecule’s constant efforts keep our memories intact

Our memories are more fragile than we thought. New research suggests that they need the constant action of a key protein to remain stored in our minds – block the protein and erase the memories.

Our mind often seems like a gigantic library, where memories are written on parchment and stored away on shelves. Once filed, they remain steadfast and inviolate over time, although some may eventually become dusty and forgotten.

Now, Reut Shema, Yadin Dudai and colleagues from the Weizmann Institute of Science have found evidence that challenges this analogy. According to their work, our memory is more like a dynamic machine – it requires a constant energy supply to work. Cut the power and memories are lost.

Bats create spatial memories without making new brain cells

In an earlier post, I wrote about a study which used carbon-dating to show that our brains are mostly stuck with the same neurons they are born with. After birth, neurogenesis – the manufacture of new neurons – is completely absent in most of the brain.

There are only two exceptions, where new neurons are made. The first is the olfactory bulb, which governs our sense of smell. The second, the hippocampus, is involved in spatial awareness and memory. Why these regions alone should produce fresh neurons is unclear.

For the hippocampus at least, scientists thought they had an answer – the fresh neurons play a role in spatial learning and memory. They could allow mammals to learn about new places, routes and directions.

But Imgard Amrein and colleagues from the University of Zurich have found evidence that disputes this idea. When he looked at the hippocampuses of some of the most accomplished mammal navigators, the bats, he found a startling lack of neurogenesis.

Bat-brains

Bats need superb spatial awareness to effortlessly fly in three dimensions. Those that feed on fruit and nectar need especially good spatial memories, and indeed, their hippocampuses are relatively large compared to other mammals.

Their memories allow them to remember where the tastiest or ripest food sources are. And they also remember the locations of plants they have recently visited so that they don’t arrive at restaurants with no stock.

Amrein searched for signs of new neurons in 12 species of bats using special antibodies. Some detected proteins that only appear when new cells are born. Others homed in on proteins used by newborn neurons when they migrate to new places.

As expected, these molecular trackers picked up new neurons in the olfactory bulb. But they found no neurogenesis at all in the hippocampus of 9 species, and only the faintest traces in the other three. Clearly, the bats don’t need new hippocampal neurons to learn where things are or to remember how to find them.

Flexibility vs consistency

While Amrein’s bats were few in number, they were also a diverse bunch. They hailed form different evolutionary groups and had diverse diets, territory sizes and ages. This makes it unlikely that these variations in these factors were secretly responsible the trends that Amrein saw.

Instead, he believes that the dearth of new neurons in bats reflects their relatively long lifespans. Humans, apes and monkeys are similarly long-lived, and we too have low levels of neurogenesis as adults.

In contrast, rats and other rodents have short and brutal lives. In order to avoid becoming food for a predator, their behaviour must be as flexible as possible. When threatened, their stream of new hippocampal neurons could allow them to rapidly plan an escape route or find new hiding places.

Bats, and certainly humans, have far fewer predators, and can afford to take things easier. In our long lives, fixed long-term mental maps are very useful and to produce them, we can sacrifice some flexibility in our spatial memories.

This may explain why people tend to rely on the same routes more and more as they age. Fortunately for us, bats show a similar trend. Their reliance on the same flight paths allows canny researchers to catch them in well-placed nets and study how their brains work.

More about bats: 
Moths mimic each others’ sounds to fool hungry bats
Bats: internal compasses and record-breaking tongues

More about neurogenesis:
No new brain cells for you – settling the neurogenesis debate

More about neurons:
Simple sponges provide clues to origin of nervous systems
Monkeys (and their neurons) are calculating statisticians
Non-coding DNA drove brain evolution by making nerve cells stickier
Maternal hormone shuts down babies’ brain cells during birth

 

Reference: Amrein, Dechmann, Winter & Lipp. 2007. Absent or Low Rate of Adult Neurogenesis in the Hippocampus of Bats (Chiroptera) PLoS ONE.

Technorati Tags: bats, hippocampus, neurogenesis, navigation, spatial memory, science,

• Digg this
• Del.icio.us
• Reddit

Experience tunes a part of the brain to the shapes of words

A new brain imaging study has found a part of the brain specifically attuned to the shape of written words. And unlike other similar areas, this one develops its abilities through learning and experience.

Over the course of evolution, certain parts of our brain have been specifically tuned to faces, human bodies and landscapes. These structures turn up in the same places in very different people. Their roles are so fundamental to the way we (and our ancestors) experience the world, that they have been long since hardwired into our genetic plans.

Words on the brain

But not everything we see is like this. Words, for example, are an exception. Even though reading and writing are such central parts of our lives now, they have only been around for a few millennia. And for most of that time, they were skills available only to a learned elite.

The entire history of writing is a mere blip in evolutionary time, certainly not long enough to evolve a specialised, genetically determined brain region dedicated to processing written words. Nonetheless, one such region exists.

Chris Baker and colleagues from the National Institute of Mental Health, Bethesda, have found that a small part of the brain specifically recognises written words. And unlike the areas that recognise faces and bodies, its origins lie in learning and experience.

Where words are recognised

Baker examined the brain activity of several English speakers using functional magnetic resonance imaging (fMRI), a technique that measures the flow of blood and oxygen in the brain. He found that a small region at the back of the brain – no bigger than a piece of sweet corn – responds strongly and specifically to English words.

Strings of consonants worked just as well but strings of numbers or Hebrew words (right), which use unfamiliar characters, triggered much weaker responses. And the region responded even more weakly to line drawings of common objects or Chinese characters, which obviously perform the same function as English words but are very different in appearance.

Baker gave the region the slightly unwieldy name of ‘candidate letter string-selective region’ or cLSSR for short. He had its location, but it was still unclear if its properties are innate of the product of experience. Indeed, the cLSSR lies very close to the fusiform gyrus, a part of the brain genetically programmed to recognise faces and numbers.

Things got interesting when Baker repeated his experiments in people who were fluent speakers and readers of both Hebrew and English. Their cLSSRs responded equally strongly to both English and Hebrew words. But in all other ways, they behaved identically to the cLSSRs of those who just spoke English.

Nature and nurture

These results provide powerful evidence that experience shapes the abilities of this part of the brain. It’s obvious that experience breeds familiarity. But this is the first time that someone has shown that a part of the brain becomes specifically attuned to a type of visual through experience and learning alone.

Obviously, a genetic influence on the cLSSR cannot be ruled out. After all, genes control the structure of the developing brain, and in different people, the cLSSR is consistently found in the same place. This is most often in the left hemisphere. If it is damaged in adults, the right hemisphere can’t pick up the slack, and people suffer form problems in reading.

All this suggest that this particular bundle of neurons may develop its taste for words, but it is somehow predisposed to do so. Baker speculates that the cLSSR’s lies along the route that nervous signals take from visual areas to language areas, and gradually learns from the signals it carries.

The discovery of the cLSSR is just the beginning, and the questions practically ask themselves. Is it more diffuse or less responsive in dyslexic children? And how does it grow and develop over time? More research and new methods even more accurate than fMRI will help to provide the answers.

Reference: Baker, Liu, Wald, Kwong, Benner & Kanwisher. 2007. Visual word processing and experiential origins of functional selectivity in human extrastriate cortex. PNAS 104: 9087-9092.

Technorati Tags: Brain, language, reading, word recognition, science

• Digg this
• Del.icio.us
• Reddit