These effects are illustrated by Figure 1 containing time-frequency plots of PLI averaged across subjects and across frontal (F7, F3, Fz, F4, F8), central (T7, C3, Cz, C4, T8), and parietal (P7, P3, Pz, P4, P8) sites as well as corresponding ERPs under the Go/NoGo conditions. In addition, Figure 1 depicts scalp topography of PLI averaged within the two consecutive 300-ms time intervals (T1 and T2) separately for delta and theta frequency bands as well as difference maps between the two conditions. Time-frequency plots and scalp topographies for the other two conditions, Warning and Neutral, can be found in supplementary material available online (Figure S1); both figures have the same scaling and are, therefore, directly comparable. Comparison of Warning and Neutral conditions (Figure S1) showed that phase synchronization across Warning trials was consistently higher than across Neutral trials, especially in the delta frequency band. It can also be seen that phase synchronization in Go and NoGo conditions was higher than in both Warning and Neutral conditions. In general, as predicted, the Neutral condition showed the lowest phase synchronization across trials as compared with other conditions.
