Figure 7 shows the time-frequency matrices of factor loadings and corresponding factor score topographies for three extracted CSD factors (i.e., factors 1, 2 and 6; 51.4% explained variance after rotation) that reflected meaningful alpha ERSP (for additional beta ERSP factors, see supplementary Fig. S2; for the loadings of 15 factors explaining at least 1% variance, see supplementary Fig. S3).7 In close analogy to the tPCA, factor labels were chosen to jointly reflect peak latency and frequency of the factor loadings. Similarly, the associated neuronal activation is inferred from the corresponding database, the time-frequency plots (Figs. 5 and 6), but the ERSP direction (i.e., ERS/ERD) is directly reflected by the sign of the factor scores. Note that, unlike Figure 4B, the topographies of the tfPCA factors do not directly reflect sinks and sources but rather ERS and ERD activity derived from sink and source oscillations. The positive (red-purple) areas in the factor loadings plots (Fig. 7A) indicate the time-frequency range for a given factor, for example, spanning alpha to delta frequencies (spectral peak at 9 Hz) between 400 and 800 ms
