Figure 1.
Targeted remote stimulation by superposition of two bipolar nanosecond pulses into a unipolar stimulus. The approach is illustrated for a rectangular (A) and linear (B) arrays of stimulating electrodes. In (A), two pairs of independent, ground-isolated electrodes (a-a′ and b-b′) deliver two synchronized bipolar electric pulses such as shown in the right panel. Each of the bipolar pulses is inherently inefficient for electrostimulation due to bipolar cancellation (see text), but their superposition in c-c′ area forms locally a biologically-effective unipolar pulse. In (B), the formation of a unipolar pulse in the c-c′ area is accomplished by bringing the electrode b to the same electric potential as electrode a during the 2nd and the 3rd phases of the pulse. See text and Fig. 2 for more detail.