20 March 2010 | NewScientist | 17

Psychopathy is its own reward

A LACK of emotion isn’t the only thing driving psychopaths: the brains of people with some psychopathic traits may overvalue the reward associated with getting what they want. In extreme cases, this may result in callous and manipulative acts.

Psychopathy is a spectrum of traits including fearlessness, callousness and narcissism; people in whom a number of these traits are strong are classed as psychopaths. Brain areas involved in emotion are less active in such people, but this can’t explain other behaviour common to psychopaths, such as drug abuse.

Now Joshua Buckholtz of Vanderbilt University in Nashville, Tennessee, has discovered that people who are unusually willing to manipulate others for their own ends – another psychopathic trait – have brains that are unusually rich in dopamine, a “reward” chemical that makes us seek pleasure, be it from drugs or getting what we want (Nature

Neuroscience, DOI: 10.1038/nn.2510). Buckholtz suggests that this extra reward urge could drive psychopaths to act without considering the costs of their actions – such as hurting others.

Levitate cells to produce 3D tissue samples

IRON-RICH cells that grow into balls when “levitated” by magnets could provide a new way to study cancer in the lab – and to produce replacement tissue for grafts. The magnets can sculpt balls into shapes that resemble tumours and tissues growing in the body.

Glauco Souza of Nano3D Biosciences in Houston, Texas, and his colleagues incubated human glioblastoma cells from brain tumours with iron oxide and bacteriophages – viruses that infect bacteria and can bind to, but not harm, mammalian cells.

The phages gobbled up the iron oxide, attached themselves to the cells and then injected the cells with their magnetic cargo.

Next the team placed the cells in a Petri dish half filled with a gel and covered it with a magnetic lid. The cells rose from the bottom of the dish in response to the magnet and clumped together at the interface between the gel and the air . After 72 hours, a sphere of cells 1 millimetre in diameter had formed. Protein expression in these glioblastoma cells more closely mimicked that

OCTOPUSES make for discerning TV

viewers: they respond to high-

definition images but not traditional

cathode ray images. What’s more, in

the first study to trick octopuses into

believing video images are real

scenes, the cephalopods turn out

to lack “personality” or consistent

behaviour.

It wasn’t possible to study octopus

behaviour using video before

because their eyes were not fooled

by slow cathode ray images. But

in this study, 31 gloomy octopuses

(Octopus tetricus) reacted to

3-minute films on high-definition

TV as if they were real. They lunged

forward as if to attack crabs, and

cowered from other octopuses,

according to Renata Pronk at

Macquarie University in Sydney,

Australia, and colleagues ( The

Journal of Experimental Biology ,

DOI: 10.1242/jeb.040675).

The team found that the octopuses

did not behave consistently from day

to day – they might be bold one day

and shy the next, for instance. The

team say this suggests Octopus

tetricus do not have personality – a

trait which may allow it to adapt to

its changing environment.

Brainy octopus lacks personality

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in real cancer cells than in 2D cultures of cells, indicating that this method could be used to study cancer (Nature

Nanotechnology, DOI: 10.1038/nnano.2010.23). Exposed to both air and fluid, the cells might also be used to model the lungs and test drugs for lung disease.

The researchers also found they could create cell balls of different shapes by moving the lid, changing its shape and the strength of the magnet. This might allow skin and long, thin nerve grafts to be grown in the lab.

‘Bug’ prints can put you at crime scene

YOU might call it “CSI: Microbe”.

Our fingers are home to a unique

collection of bacteria that get left

on surfaces we touch. By comparing

bugs found on a person’s hand to

those recovered at a crime scene,

you might be able to identify

the perpetrator.

“There are certain situations

where human DNA analysis or

standard fingerprinting doesn’t

work,” says Noah Fierer, a

microbiologist at the University of

Colorado in Boulder. His team knew

that microbial communities on skin

tend to be unique to the individual

and change little over time.

To see if these qualities could

be applied to forensics, his team

swabbed several computer

keyboards and the fingertips of

their users, then identified about

1400 different kinds of bacteria

living on each, using DNA

sequencing. The keyboard bacteria

closely matched their owner’s

fingertips (Proceedings of the

National Academy of Sciences,

DOI: 10.1073/pnas.1000162107).

In another test, Fierer’s team

were able to correctly match nine

computer mice with their owners.

The “microbeprint” seems to be

long-lasting: swabs left at room

temperature for two weeks could

be matched to owners. But accuracy

issues mean you won’t see them

used in court just yet, Fierer says.

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