| Abstract [eng] |
Major depressive disorder is a common mental health condition associated with emotional, cognitive, and neurophysiological changes. In recent years, more attention has been given to studying brain activity and the effects of different depression treatments. EEG is one of the methods used to study brain function. One of the latest methods is repetitive transcranial magnetic stimulation (rTMS), which is widely used in the treatment of depression. However, the effects of rTMS are not yet fully understood, so a promising direction is the analysis of EEG microstates, which allows researchers to examine short-term states of brain activity and their dynamics. EEG microstate changes after rTMS therapy, however, are still not well understood. The aim of this study was to evaluate EEG microstate changes after rTMS therapy in patients with depression during eyes-open (EO) and eyes-closed (EC) resting-state conditions. EEG data recorded before and after therapy were analyzed. Changes in microstate duration, coverage, occurrence frequency, and global field power (GFP) were evaluated together with microstate transition dynamics and relationships between different parameters. After evaluating the classical A - D microstates and their standard parameters (duration, occurrence frequency, coverage, and GFP), we demonstrated that significant changes following rTMS therapy are observed only in the EC state. A tendency was observed toward an increase in the duration of microstate B, transitions between microstates B and D and from C to D, and an increase in GFP values for all microstates. Meanwhile, the recurrence frequency of the C microstate and transitions between the A and C microstates decreased. Correlation network analysis revealed stronger interrelationships among microstate parameters in the EC state, particularly those related to the D microstate and the C - D transition. The results suggest that spontaneous brain activity in individuals with depression changes after rTMS therapy. This change is the most prominent when the eyes are closed. These results confirm that EEG microstate analysis may be a promising method for assessing neurophysiological changes following rTMS therapy. |
