3.3 Flash brightness rating
ANOVA test indicated significant main effects of polarity
(F (1.5,36.9) = 5.111, p = 0.017,
ηp2 = 0.176), and intensity
(F (1,24) = 18.038, p < 0.001,
ηp2 =0.429), but not AM conditions
(F (1,24) = 1.954, p = 0.175,
ηp2 = 0.075). The flash brightness
ratings were, in general, higher for the suprathreshold (3.00 ± 0.71)
than threshold (2.52 ± 0.68) intensity. Paired comparison of the three
polarities, however, only revealed marginal results that brightness
ratings were higher for anodal otDCS (3.07 ± 0.82) than for cathodal
otDCS (2.54 ± 0.63) and tACS (2.67 ± 0.69). The test did not yield any
significant 2-way or 3-way interactions (polarity × AM: F (2,48) =
1.336, p = 0.272, ηp2 = 0.053;
AM × intensity: F (1,24) = 1.567, p = 0.223,
ηp2 = 0.061; polarity × intensity:F (2,48) = 2.278, p = 0.113,
ηp2 = 0.087; polarity × AM ×
intensity: F (2,48) =0.992, p = 0.378,
ηp2 = 0.040 (Figure 2C).