ROI analysis
As the cluster-based permutation statistics indicated an interaction of pre-cue condition by experimental phase in source clusters covering various ROIs as defined by the co-registered brain atlas (see above), mean relative ssVEF power across sources that intersected with significant source clusters and ROI regions were analyzed with a repeated measures ANOVA with within-subject factors of pre-cue baseline, experimental phase and ROI collapsed across hemispheres for homologous left and right source clusters if both ROIs indicated an interaction in the previous cluster based permutation statistics. For ROIs that only indicated an interaction in the right hemisphere, only right hemisphere relative ssVEF power values were considered. Greenhouse-Geisser corrections were applied when necessary.
As this analysis revealed a significant pre-cue baseline by experimental phase by ROI interaction, a repeated measure ANOVA with within-subject factors of pre-cue baseline and experimental phase was fitted to the data for each ROI, separately. In order to detangle the observed interactions at each ROI, modulation differences between conditions were compared using paired t-tests (testing the difference of condition differences). Finally, mean relative ssVEF power within each ROI were contrasted between the two pre-cue baseline conditions (attend central fixation cross vs. attend both peripheral rings) using paired t-tests.