We are inside a human brain.  A pack of neurons FIRE OFF to the left,
            and rocket their way across synapses to the optic nerve.  Passing the
            eye socket, they speed toward a silky, curvilinear membrane (the
            retina) on which we see an image projected:

            AN UPSIDE DOWN COMPUTER SCREEN

            Neurons PING into the membrane: the picture suddenly FLIPS RIGHT SIDE
            UP and we follow the light, flashing in a blur through the iris and