Long-term effects of left frontal rTMS on EEG and ERPs in patients with depression

Repetitive transcranial magnetic stimulation (rTMS) treatment for depression has been under investigation in many controlled studies over the last 20 years. Little is known about the neurobiological action of rTMS in patients. We therefore investigated pre- and post-treatment effects on QEEG, ERP's and behavior (BDI and NEO-FFI). rTMS treatment was applied in 8 subjects for an average of 21 sessions to the left Dorsolateral Prefrontal Cortex (left DLPFC). Clients were assessed on a QEEG and Oddball ERP evaluation pre- and post-treatment. Clients were stimulated over the left DLPFC with 10 Hz rTMS (100% MT). Furthermore, rTMS treatment was complimented by psychotherapy. All subjects showed full remission within 20 sessions and there was a significant reduction in depressive symptomatology (BDI score) after 10 and 15 sessions and a clear decrease in the Neuroticism and an increase on the extraversion scale of the NEO-FFI personality questionnaire. Pre- and post-QEEG measurements did not reveal treatment specific effects, but only an indirect right frontal increase in delta power. On the other hand, ERP measures did reveal treatment specific effects by showing an increased positivity in the post-treatment ERP's specifically left frontal. The P2 amplitude demonstrated a significant left frontal increase in amplitude, whereas for the negative N1 and N2 a significant decrease in amplitude was observed. The results of this pilot study demonstrate that rTMS can be a safe and efficacious treatment modality for depression. Furthermore, a specific left frontal increase in positivity for the ERP's was found (increased P2 and decreased N1 and N2 components) most likely related to the rTMS over the left DLPFC. Furthermore, there was no change in the alpha asymmetry lending support to the fact that frontal alpha asymmetry can be considered a trait marker for depression. The findings from this pilot study require future replication with larger sample sizes.