Based on the scree plot, five principal components, accounting for 77.3% of the variance, were retained (see Figure 1). Components are ordered based on the amount of variance for which they account (highest to lowest) in the varimax-rotated solution. Principal Component 1 (PC1), with peak energy centered between 2 and 2.5 Hz, contains activity at the front edge of P3. Component 2 (PC2) contains activity around 1.5 Hz and is closest in time to the peak of P3. Component 3 (PC3; centered around 1 Hz) is a low-frequency delta component spanning the time-range of the P2-N2-P3 ERP complex. Component 4 (PC4) is the longest duration, lowest frequency component (centered between 0.5 and 1 Hz), and is consistent with the slow-wave after the P3. Finally, Component 5 (PC5) contains activity centered around 2.5 Hz, similar to Component 1; however, it occurs slightly earlier, beginning nearer in time to the N2 and lasting up to the peak of P3.
