The averaged evoked TF representation for each group at electrode Pz for the target stimulus is shown in Figure 1. For illustration purposes, in order to accentuate the evoked theta activity analyzed in the present study, the TF representations were filtered in the theta band (3–8 Hz). Based on visual inspection of the grand-averaged evoked TF surfaces, a theta band TFROI was selected that spanned a time range of 325–450 msec and a frequency range of 3–6 Hz (indicated by a box overlaid on the evoked TF surfaces). Figure 1 also shows topographic maps for the mean activity within the TFROI for each group. The grand-averaged ERPs for each group, that is, the evoked data submitted to TF analyses, are also shown at the top of Figure 1.
