Fig. 2

Overall analytic workflow of the study. (A) Multiple eyes-closed awake interictal epochs from each EEG recording are identified for data analysis. The average power spectral density (PSD) and phase-based connectivity (PC) between each channel pair are computed and stacked across recordings to obtain 3-d PSD and PC tensors (recordings x channels or channel pairs x frequencies). (B) PSD and PC population tensors are decomposed separately in an unsupervised fashion to obtain multiple interpretable spatio-spectral patterns (i.e., factors). (C) Normal interictal EEG data from focal epilepsy patients are projected on each population-level factor to obtain patient-specific factor loadings. Differences in drug-resistant and non-lesional MRI focal epilepsy are investigated by using these loadings in statistical group/sub-group comparisons and predictive analyses.