Figure 6

Electric Field Focality Results. In this figure, we analyzed the focality of stimulation as a function of the volume stimulated (mm³) that was greater than or equal to the 50th percentile E-field. A higher volume stimulated represented less focal stimulation whereas lower volume stimulated represents more focal, on-target stimulation. Subfigures a-d represent Rounds 1–4 of E-field modeling respectively. Across all rounds of modeling, HD-tDCS was the most focal type of tDCS, stimulating a volume of only 1.07 × 10⁴ mm³ (SD = 2.93 × 10³ mm³). The second most focal stimulation type was optimized APPS-tDCS in Round 4 modeling, stimulating a volume of 2.14 × 10⁴ mm³ (SD = 3.73 × 10³ mm³). Round 2 modeling demonstrated that the smaller 1 × 1 cm electrodes stimulated the most focal volume, and Round 3 modeling showed that the volume stimulated linearly increased with the inter-electrode distance. See Table 2 for details. ****p < 0.0001 (Tukey corrected).