Multiscale Neurodynamic Alterations in Major Depressive Disorder Revealed by Lempel–Ziv Complexity of Multi-Paradigm Resting-State EEG

Background: Electroencephalography (EEG) abnormalities in major depressive disorder (MDD) have predominantly been examined through single-frequency band analyses or single-scale nonlinear measures, and largely within a single resting-state paradigm, which limits the characterization of regulatory interactions across temporal scales. In this study, we investigated dynamic transitions and integrative patterns of multiscale EEG activity in MDD across multiple resting-state paradigms, with a focus on characterizing alterations in multiscale neural dynamic organization. Methods: Based on multiscale Lempel–Ziv Complexity (LZC), we derived two classes of features quantifying the Scale-Dependent Variation Slope and the Cross-Scale Correlation Coefficient. Resting-state EEG from the MDD Patients and Healthy Controls EEG Data (MPHC) was analyzed under eyes-open and eyes-closed conditions to compare multiscale regulatory dynamics between patients with MDD and healthy controls. Results: Patients with MDD showed impaired complexity transitions from low to high frequencies and disrupted delta-centered cross-scale integration. Distinct coupling reconfiguration patterns emerged across resting states, indicating a systemic imbalance in multiscale integrative organization. Classification models built from statistically selected features performed consistently across Support Vector Machine, K-Nearest Neighbor, and Decision Tree algorithms, reaching a maximum accuracy of 85.71% with a balanced sensitivity–specificity profile. Convergent results across models further suggested the preliminary discriminative value of the proposed features within the present dataset. Conclusions: These findings provide a preliminary multiscale neurodynamic framework for EEG characterization in MDD and suggest that cross-scale integration differences may provide a quantitative basis for characterizing multiscale EEG dynamics in depression.