2006). Normalized pre-stimulus ERO energy values for each ROI was determined by calculating a normalized baseline, defined as: V1 − (Hb × A1), where V1 is the volume energy of ROI1, Hb is the average height of the baseline for ROI1, and A1 is area of ROI1. The area of ROI1 (A1) is calculated as the frequency range of ROI1 × the total duration of ROI1. Hb is defined as: Vb ÷ Ab, where Vb is the volume of the baseline for ROI1, and Ab is the area of the baseline for ROI1. The ROI frequencies were: delta (1–4 Hz), theta (4–8 Hz), alpha/beta (8–32 Hz). The ROI time intervals correspond to the P3 component (250–325 ms) and are consistent with our previous ERP studies (Ehlers et al., 1999).
