Figure 1. Schematic of distant return and local return stimulation.

A: Anodic-first triphasic pulse passed through the central electrode. B: Center and neighbor electrodes (circles), and current waveform passed through the center electrode C: Electrodes and waveforms for local return stimulation. Current with ⅙ the amplitude of the central electrode current and opposite sign is passed through each of the 6 surrounding electrodes to create a local return. For B and C, the center stimulating electrode is outlined in red, active local return electrodes in blue, and inactive neighbor electrodes in black.