An Electric Brain

Don't expect one any time soon:

At present, we still know too little about how individual neurons work to know how to put them together into viable networks. For more than twenty-five years, scientists have known the exact wiring diagram of the three hundred and two neurons in the C. Elegans roundworm, but in at least half a dozen attempts nobody has yet succeeded in building a computer simulation that can accurately capture the complexities of the simple worm’s nervous system. As the N.Y.U. neuroscientist Tony Movshon notes, "Merely knowing the connectional architecture of a nervous system is not enough to deduce its function." One also needs to know the signals flowing among the elements of neural circuits, because the same circuit can perform many different functions under different circumstances. By extension, building a device whose wiring diagram mimics the brain (e.g. Markram’s Blue Brain) does not guarantee that such a device can simulate the brain in any useful way.