A biotech company, Tensor Biosciences of Irvine, California, has developed a method to keep pieces of living brain tissue alive for weeks, which will allow research on entire neural networks rather individual cells.

"We are building stripped-down mini-brains, if you will, directly on a chip," says Miro Pastrnak, business development director of Tensor.

"Behaviour is the result of the electrical activity of billions of brain cells connected in complex circuits, not the activity of a cell or a receptor acting in isolation," says Pastrnak. Currently, drugs are only tested on individual nerve cells because larger pieces of brain tissue couldn't be kept alive for more than a few hours.

The mini-brain consists of a glass chip containing thousands of living brain cells taken from rats or mice and suspended in a artificial cerebral fluid. Electrodes on the chip's surface monitors the overall electrical activity of the brain tissue, just like an electroencephalogram (EEG), to show the effect that drugs have on the tissue.

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