Finding tumour cells in the blood indicates a cancer has metastasised – but the molecular markers that are used to identify the cells can modify them and make them unsuitable for studying how treatment is proceeding and for performing basic cancer research.

So Itziar González at the Institute for Acoustics in Madrid, Spain, and colleagues developed an alternative: a tiny vibrating plastic chamber through which a blood sample flows. The vibrations create a standing wave that deflects cells in the blood to a different degree depending on their size. Tumour cells are often larger than blood cells and so collect in a different region of the device. The process does not alter the cells.

The prototype can reliably differentiate cancer cells 70 per cent of the time, and a modified version that exposes the blood to the acoustic waves for a longer amount of time should be able to differentiate a cancer cell from a normal cell 95 per cent of the time.

That’s important, because identifying just two or three tumour cells in a typical 7-millilitre sample of blood is enough to determine that a cancer is metastasising, González says. Miss that small number of cells because of problems with the sensitivity of a device and “we won’t be able to make that diagnosis”, says González.

at the University of Wisconsin, Madison, thinks the technique has potential. “Not labelling the cells is an advantage” for cultivating and studying them, he says.

González presented the work at the in Lucerne, Switzerland, last month.

Video: Follow my eyes

They may seem a little unsettling but the staring eyes of this female avatar were designed to grab your gaze and hold it, and also to obligingly follow where you look. By performing these actions with people placed inside a brain scanner, she has helped to demonstrate that guiding the gazes of others activates different brain areas than following.

This could help unravel the brain activity underlying the process of “joint attention”, thought to be key to complex, human social interactions. It could also offer insights into why social interactions can break down for people with autism.

Joint attention – the ability and motivation to both guide and follow someone else’s gaze – develops early in infants. It is considered necessary for complex social interactions, the learning of language and co-operation. For example, an eye signal from one person to another can indicate a potential meal, mate or menace.

In people with autism, , which may underpin some of the social difficulties they experience. Previously researchers have studied brain activity in people watching a . The new study is the first to separate out the processes of following and initiating joint attention.

Watch me watch her

Psychiatrist at the University of Cologne in Germany and his colleagues developed an avatar that can hold someone’s gaze and an infrared camera that tracks the eye movement of someone watching the avatar. The system was set up inside an MRI scanner.

Then the team asked 21 healthy volunteers to use their eyes to guide the avatar’s gaze towards a grey box projected on a computer screen, or to follow the avatar’s gaze, while inside the scanner. The camera allows the researchers to determine when the volunteers are following the avatar’s gaze and when the avatar is following theirs.

The real-time fMRI scans revealed that when the volunteers successfully got the avatar to follow their gaze, brain areas involved in reward and motivation were activated. When they followed the avatar’s gaze, a different area of the brain, known to be involved in imagining what other people are thinking, was active. “It’s kind of surprising that sharing something as basic as a grey square is something we enjoy,” says Schilbach.

Get engaged

The finding is novel, says autism researcher at the University of California, Davis, because previous studies of joint attention have not distinguished between initiating and responding.

It points to the possibility that differences in motivation to initiate joint attention “may be involved in the early social impairments of autism”, he says.

Mundy adds that interactive avatars will be helpful in other areas of social psychology by allowing us to simulate social interactions and observe the neural systems they involve. “Our method is progress in the direction of studying things which stem from being engaged with another person,” agrees Schilbach.

His team now plans to study the brains of people with autism as they interact with the avatar.

Journal reference: Journal of Cognitive Neuroscience, DOI: 10.1162/jocn.2009.21401