Time-averaged dendrograms and clusters on a topographical map when the clustering threshold is 0.48 Clustering results with the time-averaged PLV matrix from 750 ms before key press to 750 ms afterwards. In the dendrograms on the left, the y-axis indicates “distance” between electrodes defined as 1-PLV. The topographical maps on the right are obtained when the clustering threshold is set at 0.48 in the dendrograms on the left. PLV links that are greater than 0.52 are superimposed as gray lines for reference. In (a), the colour of the electrodes in the dendrograms on the left corresponds to the colour of the phase-locked cluster on the right. For comparison among conditions, the same cortical regions are kept roughly the same colours.