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PARIS, March 12 (AFP) - US researchers are poised to carry out the first tests of a silicon chip designed to replace a damaged part of the brain, New Scientist says.

The implant aims to stand in for the hippocampus, part of the forebrain that is vital for storing long-term memories, it says.

It will shortly be tested on tissue from rats' brains, then on live rats and laboratory monkeys, and if all goes well could one day be used for people who face memory loss due to Alzheimer's disease, epilepsy or a stroke.

The prosthesis mimics the way the hippocampus encodes experiences before sending them to be stored elsewhere in the brain as long-term memories, according to the report, published in next Saturday's issue of the British science weekly.

To make the chip, the team first sliced up sections of rat hippocampus, and stimulated these slices with electrical signals.

They did this millions of times over until they could be sure which electrical input produced a corresponding output.

By putting together the information from the various slices, they built up a mathematical model of the entire hippocampus, perceiving it as an array of neural circuits that work in parallel to process data.

The model was then transferred onto a chip, which communicates with the brain through two arrays of electrodes, placed on either side of the damaged area.

One set of electrodes detects the electrical activity coming in from the rest of the brain, while the other sends appropriate electrical instructions back out to the brain.

The chip is the result of a 10-year effort by a team led by Theodore Berger of the University of Southern California in Los Angeles. They are scheduled to tell a conference in Capri, Italy next week that they will now put it to the test, using slices of rat brain that have been kept alive in cerebrospinal fluid.

If it works, the team will test the prosthesis in live rats within six months, and then in monkeys trained to carry out memory tasks.

The researchers will stop part of the monkey's hippocampus from working and bypass it with the programmed chip.

If the invention works and -- ultimately -- is proved safe for humans, it would sit on the top of the skull, rather than inside the brain, in order to reduce damage to cerebral tissue.

The device would not be without drawbacks or ethical controversies. Installing the electrodes would entail bypassing some healthy brain tissue, and the programming of the chip would have to reflect the patient's fundamental identity.

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