Large-scale EEG neural network changes in response to therapeutic TMS

Area of Science:

• Neuroscience
• Psychiatry
• Biomedical Engineering

Background:

• Transcranial magnetic stimulation (TMS) is a recognized treatment for resistant depression, likely modulating brain circuits.
• Electroencephalography (EEG) microstates represent large-scale brain networks and are potential biomarkers for major depressive disorder (MDD).
• The impact of TMS on EEG microstates in MDD patients remains largely unexplored.

Purpose of the Study:

• To investigate changes in EEG microstates following TMS treatment in patients with MDD.
• To determine if these microstate changes correlate with clinical response to TMS therapy.

Main Methods:

• Resting-state EEG data were collected from 49 MDD patients before and after six weeks of daily TMS.
• EEG data were segmented into microstates using modified k-means clustering and localized with sLORETA.
• Statistical analyses, including mixed-effects models and t-tests, were used to compare microstate features over time and between responder/non-responder groups.

Main Results:

• Six distinct microstates (MS-1 to MS-6) were identified across all EEG data.
• Clinical responders exhibited increased features of MS-2 and decreased metrics of MS-3, while non-responders showed no significant microstate alterations.
• Changes in MS-2 occurrence/coverage (increase) and MS-3 occurrence/coverage (decrease) correlated with the magnitude of symptom improvement.

Conclusions:

• EEG microstates are modulated by TMS therapy and are associated with clinical improvement in MDD.
• These findings highlight the potential of EEG microstates as accessible biomarkers for tracking treatment response to TMS.
• The study suggests that TMS selectively alters resting-state brain networks detectable via EEG.