"s are the way in which, even now, you are thinking and paying attention, because the signals that travel between neurons, down the s, are controlled by the flow of s across the membranes of the axons... [T]hey are, in effect, little demons that sense the incoming signal and open and close the gates; and the ions flow. ...[T]his is so incredibly energy efficient that ...your brain, which is like a megawatt supercomputer, operates with the energy equivalent of a small light bulb."