Figure 3.

Activation thresholds of straight unmyelinated HH-model axon for a range of vertical and lateral axon-coil distances. Rows show results for the monophasic and half-sine stimulation waveforms grouped by the three coil configurations. For the aligned figure-8 coil, the left region (negative x) is not fully shown because of the symmetry of the threshold distributions. The left and center columns show threshold values obtained with the conventional and modified CEs, respectively. The right column shows the threshold difference comparing modified and conventional CEs; any unmarked contour lines are spaced 10 and 5% apart for monophasic and half-sine waveforms, respectively. The outlines of the coils are illustrated as gray boxes, with the idealized windings located in the horizontal plane of y = 0. Color scales are the same within each column and shown at the bottom. To see this figure in color, go online.