Electrophysiological correlates of functional brain abnormities in major depressive disorder: microstate analysis on high-density EEG in resting conditions

Objective : The aim of the study was to identify electrophysiological biomarkers of major depressive disorder (MDD) through high-density EEG technique. Methods: Seven patients suffering from MDD and eight healthy controls underwent EEG recording using 128 or 256 scalp electrodes during eyes closed resting-state conditions. Microstate analysis was performed at individual and group levels. Microstate variants were identified and their parameters such as mean correlation, mean duration, time coverage, and segment count density were evaluated. Results: Cross-validation criterion used to determine the most dominant topographies revealed six (A-F) microstates. The six microstates across subjects in each group explained more than 80% of global variance. Results of two-way repeated measures ANOVA revealed significant group x microstate interaction for segment count density. Post-hoc test revealed significant group difference for class A microstate, which showed decreased value in MDD patients. Conclusion: Parameters revealed by microstate analysis are suggested to be possible electrophysiological biomarkers of functional brain abnormities in MDD patients. The study has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 739939