2 March 2013 | NewScientist | 19

Earth’s mantle in hunt for new force

HEY CERN, think you’ve got a big particle detector? Try using the entire Earth to hunt for a new fundamental force of nature.

The hypothetical force can be thought of as an extension of magnetism. A magnetic field is transmitted when two nearby particles exchange so-called virtual photons. But virtual versions of other particles could similarly be exchanged. This could produce a longer-range force that has never been detected.

Attempts to determine whether the spins of a set of nearby particles can affect the spins of neutrons in the lab via this new force have come up empty. So Larry Hunter of Amherst College in Massachusetts and colleagues searched for evidence that the spins of electrons in the minerals of Earth’s mantle – a much bigger sample – were affecting the spins of the lab neutrons (Science, doi.org/kkv).

Again the team found nothing, but Hunter says that just shows that the new force is weaker than expected. If it is found, it could be used to reveal electron spins, and thus the chemistry, of minerals in rocks deep inside the Earth via the force’s effect on surface particles.

Electrodes reset the brain to block obsessive behaviourSOME people with obsessive-compulsive disorder benefit from deep brain stimulation, carried out using electrical impulses. How this worked was unclear, but now it seems the process puts a stop to abnormal signalling in the brain.

A handful of people with difficult-to-treat OCD have had electrodes implanted deep within their brain. When signals are sent down the wires, their symptoms reduce. To work out why, Martijn Figee at the Academic Medical Center in Amsterdam, the

Netherlands, and colleagues recorded neural activity in people receiving deep brain stimulation (DBS) into the nucleus accumbens. This region conveys motivational and emotional information to the frontal cortex, guiding decisions on what actions to take next. In some people with OCD, feedback loops between these two brain areas get jammed.

It was thought that the treatment would have little effect outside the nucleus accumbens. But the team’s fMRI scans and electroencephalograms showed

YOU can’t make a fetus hold still for the camera. So it’s remarkable that the first scans have now been made of the fetal brain at different stages of pregnancy, giving a glimpse into how the brain’s neural connections form in the womb. The work could one day lead to prenatal diagnosis and treatment of conditions thought to have a developmental component, such as autism and schizophrenia.

Moriah Thomason of Wayne State University in Detroit, Michigan, and colleagues made a series of fMRI scans of the brains of 25 fetuses between 24 and 38 weeks. By

keeping only those scans for which the fetus was relatively still, they found that, as expected, the two halves of the brain formed denser and more numerous connections with each other as the weeks passed. The connections tended to begin in the middle of the brain and spread outward as the brain developed (Science Translational Medicine, doi.org/kmp).

Thomason says that the team is now scanning up to 100 fetuses of different ages. The scans might allow them to track variations in brain wiring between individuals.

Watch as baby’s brain gets wired up

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that the signals help return activity throughout the frontal cortex to what is seen in people who do not have OCD (Nature Neuroscience, doi.org/kmn). “It resets and normalises these circuits,” says Figee.

Thomas Schlaepfer at the University of Bonn, Germany, says that such techniques may allow researchers to use DBS to learn about the causes of OCD as they treat it. “It will serve as a research platform informing us about the underlying neurobiology,” he says.

Earth-like storms – on icy moon Titan

DESPITE highs of only -180 °C, Saturn’s moon Titan may boast tropical cyclones. Only glimpsed on Earth before, such storms would add to the list of features Titan shares with our planet, from lakes, and sand dunes to haze and rain.

Cyclones do occur on Mars and Saturn, but a tropical cyclone is one driven by evaporation from a sea and involves rain as well as gale-force winds: on Earth, the biggest ones are hurricanes. Now Tetsuya Tokano of the University of Cologne in Germany says that as Titan has lakes and seas, it could have mini-hurricanes too.

The key requirement is that the liquid on Titan’s surface should contain methane, which evaporates readily. “We know ethane is present and methane probably is,” says Tokano. He calculates that storms there would have winds of up to 72 kilometres per hour, equivalent to a midsize tropical storm on Earth and two-thirds of the threshold for a hurricane (Icarus, doi.org/kkx).

In contrast to Earth, Tokano says the only seas large enough to drive such a storm are near Titan’s north pole: the 1200-kilometer-long Kraken Mare, and the smaller Ligeia and Punga mares. But Titan should have its own “hurricane season”, too – and the orbiting Cassini spacecraft will be watching in 2015, when the next one kicks off.

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