Slices of rat hippocampus were stimulated with electrical signals millions of times, until scientists could be sure which input produced a corresponding output.

BBC: Scientists develop 'brain chip'

One way this can be successfully accomplished is by "multiplexing" the electrodes normally used to relay touch input -- that is, using the same electrodes to handle the signals for both touch control and the pixels of the LCD, according to a 2010 IHS report on touch-screen displays.

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