20 April 2013 | NewScientist | 17

Anyone can have a phantom limb

MANY people who have had a limb amputated say they can feel sensations from their missing arm or leg. Now it seems anyone can experience what it is like to have a phantom limb.

Arvid Guterstam at the Karolinska Institute in Stockholm, Sweden, and his colleagues had volunteers sit at a table with their right arm hidden from view behind a screen. An experimenter then applied brush strokes to the concealed hand and, simultaneously, to a portion of empty space in full view of each volunteer. “We discovered that most participants, within less than a minute, transfer the sensation of touch to the empty space where they see the paintbrush move, and experience an invisible hand in that position,” says Guterstam.

Brain areas that are active when a real hand is being touched were also active when the volunteers watched their phantom hand being touched, a scan showed.

During a mock stabbing of the invisible hand, stress levels, measured using a sweat test, went up in about 75 per cent of the 234 participants (Journal of Cognitive Neuroscience, doi.org/k6q).

Memory drug tested in people with Down’s syndromeTHE first drug specifically designed to lessen cognitive impairment in Down’s syndrome is now being tested in humans.

David Nutt, former drug policy adviser to the UK government, told delegates at the British Neuroscience Association conference in London last week that he is collaborating with pharmaceutical company Roche in trials of a drug it has developed, called RG1662.

Memory and learning problems experienced by people with Down’s may stem from the effects

of GABA, a chemical messenger that dampens brain activity. The drug could help by reversing GABA’s effects at a receptor found mostly in the hippocampus, a part of the brain involved in memory. The hope is that this will boost activity in the hippocampus and so improve cognitive abilities.

The study is assessing the drug’s safety and tolerability in 33 adults with Down’s, but researchers will also measure its effect on motor skills, reaction time and memory, and compare the results with those of people on a placebo.

YOU can almost set your watch by it. Every 90 minutes, on average, the Old Faithful geyser in Yellowstone national park erupts. Now a secret chamber has been found in the rocks beneath the geyser, changing our understanding of how it erupts.

Jean Vandemeulebrouck of the University of Savoie in Le Bourget du Lac, France, and colleagues have analysed data collected from Old Faithful in the 1990s. Using seismic audio analysis – more commonly used to locate whales or submarines – they discovered a 60-cubic-metre cavern 15 metres down, and off to the

geyser’s side. This side cavity acts as a reservoir, making the water in the smaller main vent bob up and down like a spring. The oscillations affect the water pressure and help the geyser to boil in the early stages of eruption (Geophysical Research Letters, doi.org/k63).

The side cavern “totally changes our perspective of the physics of how geysers work”, says Shaul Hurwitz, a hydrologist with the US Geological Survey, who hopes the innovative acoustic technique can be applied to visualising the insides of volcanoes as well as geysers.

Chamber of secrets under Old Faithful

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Nutt studied a similar drug in 2007 and found that it prevented memory problems in people who had just drunk a lot of alcohol. “It didn’t have any impact on whether you could stand straight, but they could remember everything,” he says.

Dai Stephens at the University of Sussex, UK, who helped pioneer this class of drug for treating memory problems in old age, says the drug may improve some aspects of memory at the expense of others. “But it is good that someone is testing it,” he says.

How ozone takes our breath away

WE KNOW ozone is bad for lungs – the increased risk of developing diseases such as asthma was one of the reasons people wore face masks during January’s record-breaking smog in China . But exactly what it did to the lungs was unclear.

To investigate, Katherine Thompson from Birkbeck College in London and colleagues scattered neutrons off an oily surface. It was designed to mimic the fluid films on lung tissues which make the exchange of oxygen and carbon dioxide more efficient. By looking at where the neutrons ended up, the researchers were able to deduce the chemical changes involved. They found that ozone reacts with the oil at concentrations matching those in polluted town centres, prompting it to bead up rather than spread out. In the lungs, this would reduce the exchange of gases – that’s “bad news both for people with respiratory problems and healthy people”, says Thompson (Langmuir, doi.org/k66).

Thompson says the finding should back calls for tighter limits on ozone pollution from cars and factories. In the US, it is estimated that stricter emission standards could prevent more than 1000 premature deaths each year and 3 million cases of respiratory disease. Thompson plans to repeat the work using surfaces that mimic the lungs of people with respiratory diseases.

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