News & Current Affairs

September 14, 2008

Taxi drivers ‘have brain sat-nav’

Taxi drivers ‘have brain sat-nav’

Sid James in a London cab (BBC)

The knowledge: London cabbies are famous for knowing their way around

Scientists have uncovered evidence for an inbuilt “sat-nav” system in the brains of London taxi drivers.

They used magnetic scanners to explore the brain activity of taxi drivers as they navigated their way through a virtual simulation of London’s streets.

Different brain regions were activated as they considered route options, spotted familiar landmarks or thought about their customers.

The research was presented at this week’s BA Science Festival.

Earlier studies had shown that taxi drivers have a larger hippocampus – a region of the brain that plays an important role in navigation.

Their brains even “grow on the job” as they build up detailed information needed to find their way around London’s labyrinth of streets – information famously referred to as “The Knowledge”.

“We were keen to go beyond brain structure – and see what activity is going on inside the brains of taxi drivers while they are doing their job,” said Dr Hugo Spiers from University College London.

Taxi driver's brain

The scientists used functional magnetic resonance imaging (fMRI) to obtain “minute by minute” brain images from 20 taxi drivers as they delivered customers to destinations on “virtual jobs”.

The scientists adapted the Playstation2 game “Getaway” to bring the streets of London into the scanner.

After the scan – and without prior warning – the drivers watched a replay of their performance and reported what they had been thinking at each stage.

“We tried to peel out the common thoughts that taxi drivers tend to have as they drive through the city, and then tie them down to a particular time and place,” said Dr Spiers.

The series of scans revealed a complex choreography of brain activity as the taxi drivers responded to different scenarios.

The hippocampus was only active when the taxi drivers initially planned their route, or if they had to completely change their destination during the course of the journey.

The scientists saw activity in a different brain region when the drivers came across an unexpected situation – for example, a blocked-off junction.

Another part of the brain helped taxi drivers to track how close they were to the endpoint of their journey; like a metal detector, its activity increased when they were closer to their goal.

Changes also occurred in brain regions that are important in social behaviour.

Taxi driving is not just about navigation: “Drivers do obsess occasionally about what their customers are thinking,” said Dr Spiers.

Animals use a number of different mechanisms to navigate – the Sun’s polarized light rays, the Earth’s magnetic fields and the position of the stars.

This research provides new information about the specific roles of areas within the brains of expert human navigators.

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September 3, 2008

Major ice-shelf loss for Canada

Major ice-shelf loss for Canada

Ice drifts away from the Ward Hunt ice shelf in northern Canada

Ward Hunt is the largest of the remnant ice shelves

The ice shelves in Canada’s High Arctic have lost a colossal area this year, scientists report.

The floating tongues of ice attached to Ellesmere Island, which have lasted for thousands of years, have seen almost a quarter of their cover break away.

One of them, the 50 sq km (20 sq miles) Markham shelf, has completely broken off to become floating sea-ice.

Researchers say warm air temperatures and reduced sea-ice conditions in the region have assisted the break-up.

“These substantial calving events underscore the rapidity of changes taking place in the Arctic,” said Trent University’s Dr Derek Mueller.

“These changes are irreversible under the present climate.”

Satellite images of ice loss

Satellite images show the loss of the Markham Ice Shelf over the last year

Scientists reported in July that substantial slabs of ice had calved from Ward Hunt Ice Shelf, the largest of the Ellesmere shelves.

Similar changes have been seen in the other four shelves.

As well as the complete breakaway of the Markham, the Serson shelf lost two sections totaling an estimated 122 sq km (47 sq miles), and the break-up of the Ward Hunt has continued.

Cold remnants

The shelves themselves are merely remnants of a much larger feature that was once bounded to Ellesmere Island and covered almost 10,000 sq km (3,500 sq miles).

Over the past 100 years, this expanse of ice has retreated by 90%, and at the start of this summer season covered just under 1,000 sq km (400 sq miles).

Much of the area was lost during a warm period in the 1930s and 1940s.

Melt water on ice shelf

“Long meltwater lakes” were imaged on the Markham shelf in 2005

Temperatures in the Arctic are now even higher than they were then, and a period of renewed ice shelf break-up has ensued since 2002.

Unlike much of the floating sea-ice which comes and goes, the shelves contain ice that is up to 4,500 years old.

A rapid sea-ice retreat is being experienced across the Arctic again this year, affecting both the ice attached to the coast and floating in the open ocean.

The floating sea-ice, which would normally keep the shelves hemmed in, has shrunk to just under five million sq km, the second lowest extent recorded since the era of satellite measurement began about 30 years ago.

“Reduced sea-ice conditions and unusually high air temperatures have facilitated the ice shelf losses this summer,” said Dr Luke Copland from the University of Ottawa.

“And extensive new cracks across remaining parts of the Ward Hunt Ice Shelf mean that it will continue to disintegrate in the coming years.”

Loss of ice in the Arctic, and in particular the extensive sea-ice, has global implications. The “white parasol” at the top of the planet reflects energy from the Sun straight back out into space, helping to cool the Earth.

Further loss of Arctic ice will see radiation absorbed by darker seawater and snow-free land, potentially warming the Earth’s climate at an even faster rate than current observational data indicates.

September 1, 2008

Experts poised for rare frog hunt

Experts poised for rare frog hunt

Golden toads mating

The golden toad has vanished from Costa Rica’s rainforests

Scientists are set to begin a hunt for the some of the world’s rarest frogs in Costa Rica, including the iconic golden toad, last seen some 20 years ago.

A team from Manchester University and Chester Zoo are in Costa Rica to track down the highly endangered creatures.

News will follow their trek deep into the cloud forests of Monteverde.

Amphibians numbers around the world have crashed, in part because of a deadly fungus. Costa Rica has been particularly badly hit.

Expedition leader Andrew Gray, from the University of Manchester’s Manchester Museum, said: “Costa Rica’s highlands used to be major biodiversity hotspots – but in many areas amphibian populations have been completely decimated.”

Killer fungus

Yellow-eyed leaf frog

The killer fungus

In the late 1980s, herpetologists around the world found that amphibian populations were suffering unprecedented declines, but they struggled to understand exactly why.

A decade later, researchers isolated a previously unknown fungus, Batrachochytrium dendrobatidis, which was infecting amphibians, effectively suffocating them by making it impossible for them to breathe across their skin.

Recently, the scientists working on the Global Amphibian Assessment estimated that one-third of all amphibians were threatened by extinction and about 120 species had already become extinct since the 1980s.

Many believe the disease caused by the chytrid fungus is a key factor for this crash. Other causes are thought to include habitat destruction and changes in climate.

Frog rediscovery

Countries in Central America have been particularly badly affected by the deadly chytrid fungus, which is now widespread there. A great deal of effort is now being put into place to safeguard any remaining species.

Ithsmohyla rivularis
To find this species last year that was thought to be extinct at the same times as the golden toad was incredible
Andrew Gray

Andrew Gray said: “For the last 10 years, I’ve been working with others to ensure the future for frogs that have so far escaped extinction.

“One of the main things I have been doing is establishing breeding populations in Manchester Museum for a number of very, very rare species – including the splendid leaf frog (Cruziohyla calcarifer), the yellow-eyed leaf frog (Agalychnas annae) and the lemur leaf frog (Hylomantis lemur).

“I’ve also been working with the Costa Rican authorities and scientists to put conservation measures into place at the sites where any rare frogs are found.”

Last year, Mr Gray caught a glimpse of the Ithsmohyla rivularis in the cloud forests of Monteverde – a frog that was thought to have gone extinct about 20 years ago.

Splendid Leaf frog

Manchester Museum has a splendid leaf captive breeding population

He said: “To find this species last year that was thought to have become extinct at the same time as the golden toad was incredible – it is the rarest tree frog in the world.”

He has now been given special permission by the Costa Rican authorities to collect some of the frogs to take back to Manchester.

He told : “We are returning to thoroughly search the site in the hope of finding more specimens.

“It’s not going to be easy – they live deep in the Monteverde rainforest, they are only a couple of centimetres in size and they only come out in the dead of night – and while the males do call, the females don’t make a sound.”

‘Never say never’

The rediscovery of Ithsmohyla rivularis has spurred the team on to also try to seek out a golden toad (Bufo pereglines).

This colourful amphibian, which scientists only discovered in 1966, became the iconic symbol of amphibian decline. In 1987 there were approximately 1,500 of the toads, but just two years later it had vanished from the face of the rainforest.

Mr Gray said: “We are going to be trekking through an area where the golden toad used to thrive. It is very unlikely we will find one – but as last year’s discovery showed us, never say never.”

While in the rainforest, the team will also trying to track down the miniature red-eyed tree frog (Duellmanohyla uranochroa) – a species on the brink of extinction – to investigate how some frogs may be able to prevent the chytrid fungus from taking hold.

This is a unique opportunity to study the frogs in their natural habitat
Mark Dickinson

Previous research has shown that some species of tree frog have a special pigment in their skin that enables them to reflect light, allowing them to “sunbathe” without drying out.

Physicist Mark Dickinson, from Photon Science Institute at the University of Manchester, will be taking a spectrometer into the field to investigate how different frog species reflect light.

He said: “So far, I’ve only been able to investigate captive frogs in the lab. This is a unique opportunity to study the frogs in their natural habitat.”

The team believes that the ability to sit out in the Sun may allow the frogs’ skin to heat up just enough to kill off chytrid – preventing the disease from taking its grip.

Some of the team will also be heading to the last known breeding site of the green-eyed frog (Lithobates vibicarius) where Chester Zoo is helping to support a conservation programme.

August 23, 2008

Black hole star mystery ‘solved’

Black hole star mystery ‘solved’

Computer simulation of a molecular cloud falling into a black hole (Science/AAAS)

The researchers modelled how molecular clouds are sucked into black holes

Astronomers have shed light on how stars can form around a massive black hole, defying conventional wisdom.

Scientists have long wondered how stars develop in such extreme conditions.

Molecular clouds – the normal birth places of stars – would be ripped apart by the immense gravity, a team explains in Science magazine.

But the researchers say stars can form from elliptical discs – the relics of giant gas clouds torn apart by encounters with black holes.

They made the discovery after developing computer simulations of giant gas clouds being sucked into black holes like water spiralling down a plughole.

“These simulations show that young stars can form in the neighbourhood of supermassive black holes as long as there is a reasonable supply of massive clouds of gas from further out in the galaxy,” said co-author Ian Bonnell from St Andrews University, UK.

Ripped apart

Their findings are in accordance with actual observations in our Milky Way galaxy that indicate the presence of a massive black hole, surrounded by huge stars with eccentric orbits.

The simulations, performed on a supercomputer – and taking over a year of computing time – followed the evolution of two separate giant gas clouds up to 100,000 times the mass of the Sun, as they fell towards the supermassive black hole.

The simulations show how the clouds are pulled apart by the immense gravitational pull of the black hole.

The disrupted clouds form into spiral patterns as they orbit the black hole; the spiral patterns remove motion energy from gas that passes close to the black hole and transfers it to gas that passes further out.

This allows part of the cloud to be captured by the black hole while the rest escapes.

In these conditions, only high mass stars are able to form and these stars inherit the eccentric orbits from the elliptical disc.

These results match the two primary properties of the young stars in the center of our galaxy: their high mass and their eccentric orbits around the supermassive black hole.

“That the stars currently present around the galaxy’s supermassive black hole have relatively short lifetimes of [about] 10 million years, which suggests that this process is likely to be repetitive,” Professor Bonnell explained.

“Such a steady supply of stars into the vicinity of the black hole, and a diet of gas directly accreted by the black hole, may help us understand the origin of supermassive black holes in our and other galaxies in the Universe.”

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