The neurons in the brain are highly adaptable, and form hundreds of connections with other cells via large extensions known as axons. The axon carries the signal to a particular cell and, if it is strong enough, this cell passes it on. It is thanks to the complexity of neurons that we are able to carry out processes such as thinking and remembering.

Neurons can be grown in special conditions in a laboratory, but unlike those in the brain, these don't form 'thinking' networks'.

Professor Elisha Moses and his team, from the Physics of Complex Systems Department, in Israel, recently investigated whether or not they could create artificial nerves that functioned more like those in the brain.

First they grew a nerve network in one dimension only - by getting the neurons to grow along a groove etched in a glass plate. Using a magnetic field they tested to see if these neurons could be stimulated to send signals, and found that this was indeed possible.

In the brain, nerve cells must receive a minimum number of signals before they become active themselves and pass the signal on. The researchers, therefore, created neuron 'stripes' by grouping nerves together via their axons, and then investigated whether the width of the stripe (number of axons) would affect how well it could pass signals on.

They discovered a threshold thickness of approximately 100 axons. Below this number, it was unlikely that the nerves would respond, whilst just a few over this number, the chance of the signal being passed on was greatly increased.

The scientists then took two stripes of around 100 axons each, and created a logic gate similar to one in an electronic computer. Both of these stripes were then connected to a small number of nerve cells.

When the cells received a signal along just one of the stripes, the outcome was uncertain. However, when a signal was sent along both stripes at the same time, a response was guaranteed.

The next structure the team created was slightly more advanced. Triangles fashioned from the neuron stripes were lined up in a row, point to rib, in a way that forced the axons to develop and send signals in one direction only. Several of these segmented shapes were then attached together in a loop to create a closed circuit.

They found that nerve signals were continuously relayed around the circuit, turning it into a kind of biological clock or pacemaker.

The scientists are now trying to find out what artificial nerves need before they can carry out the complex processes of 'natural' neurons. If they find the answers to this, the possibility of an artificial 'thinking' network could become a reality. This would have exciting implications for many neurological conditions, including epilepsy, where nerve function is often lost.

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