 Two-photon excitation microscopy has shown that microstimulation activates neurons sparsely around the electrode even at low currents (as low as 10 μA) up to distances as far as four millimeters away.This happens without particularly selecting other neurons much nearer the electrode's tip.This is due to activation of neurons being determined by whether they do or do not have axons or dendrites that pass within a radius of 15 μm near the tip of the electrode.