SOURCE
Clinical Neurophysiology. 132(9):2306-2316, 2021 09.
AUTHORS
Voineskos D; Blumberger DM; Rogasch NC; Zomorrodi R; Farzan F; Foussias G; Rajji TK; Daskalakis ZJ
OBJECTIVE
Repetitive transcranial magnetic stimulation (rTMS) is effective for treatment resistant depression (TRD), but little is known about rTMS’ effects on neurophysiological markers. We previously identified neurophysiological markers in depression (N45 and N100) of GABA receptor mediated inhibition. Here, we indexed TMS-electroencephalographic (TMS-EEG) effects of rTMS.
METHODS
TMS-EEG data was analyzed from a double blind 2:1 randomized active (10Hz left/bilateral):sham rTMS TRD trial. Participants underwent TMS-EEG over left dorsolateral prefrontal cortex (DLPFC) before and after 6weeks of rTMS. 30 had useable datasets. TMS-evoked potentials (TEP) and components (N45, N100, P60) were examined with global mean field analysis (GMFA) and locally in DLPFC regions of interest.
RESULTS
The N45 amplitude differed between active and sham groups over time, N100 amplitude did not. N45 (t=2.975, p=0.007) and N100 amplitudes (t=2.177, p=0.042) decreased after active rTMS, demonstrating alterations in cortical inhibition. TEP amplitudes decreased after active rTMS in left (t=4.887, p<0.001) and right DLPFC (t=4.403, p<0.001) not sham rTMS, demonstrating alterations in cortical excitability.
CONCLUSIONS
Our results provide important new knowledge regarding rTMS effects on TMS-EEG measures in TRD, suggesting rTMS reduces neurophysiological markers of inhibition and excitability.
SIGNIFICANCE
These findings uncover potentially important neurophysiological mechanisms of rTMS action.
