Bill Ditto: "They will not get up and attack anyone"

At the moment, the device can perform simple sums - the team calls the novel calculator the "leech-ulator".

But their aim is to devise a new generation of fast and flexible computers that can work out for themselves how to solve a problem, rather than having to be told exactly what to do.

Professor Bill Ditto, at the Georgia Institute of Technology, is leading the project and says he is amazed that today's computers are still so dumb.

Bill Ditto views his computer wetware

"Ordinary computers need absolutely correct information every time to come to the right answer," he says. "We hope a biological computer will come to the correct answer based on partial information, by filling in the gaps itself."

Well connected

The device the team has built can "think for itself" because the leech neurons are able to form their own connections from one to another. Normal silicon computers only make the connections they are told to by the programmer.

This flexibility means the biological computer works out it own way of solving the problem. "With the neurons, we only have to direct them towards the answer and they get it themselves," says Professor Ditto.

This approach to computing is particularly suited to pattern recognition tasks like reading handwriting, which would take enormous amounts of power to do well on a conventional computer.

Each neuron's electrical activity corresponds to a number

The neurons are harnessed in a petri dish by inserting micro-electrodes into them. Each neuron has its own electrical activity and responds in its own way to an electrical stimulus.

These features can be used to make each neuron represent a number. Calculations are then performed by linking up the individual neurons.

Leech neurons are used because they have been extensively studied and are well understood.

Though much simpler, the neuron computer works in a similar way to the human brain. Professor Ditto says a robot brain is his long-term aim, noting that conventional supercomputers are far too big for a robot to carry around.

Bill Ditto: "We want to make a robot brain"

"We want to be able to integrate robotics, electronics and these type of computers so that we can create more sentient robots," he says.

However, in the immediate future, the team from Georgia Tech and Emory University are working on enabling their computer to do multiplication.