Figure 4.

Increased detection sensitivity Δd′ with multi-electrode stimulation in four different sessions. The small colored bars in each panel indicate the d′ score for each individual electrode when stimulated with a subliminal current. Horizontal blue lines indicate the theoretical score under combined stimulation, d′_c, computed under the independence assumption as per Eq. 8. Large black bars indicate the actual effect of simultaneous stimulation, which exceeded d′_c in 9 out of 10 cases. Insets indicate the location of individual electrodes.