Localized potentiation of sleep slow-wave activity induced by prefrontal repetitive transcranial magnetic stimulation in patients with a major depressive episode.

Background: The effects of repetitive transcranial magnetic stimulation (rTMS) on sleep structure in major depression are currently unknown.

Objective: To determine the effects of prefrontal rTMS on sleep electroencephalography (EEG) in major depression.

Methods: In this open-label pilot study, twelve male patients with relatively mild depression, who had been medication-resistant, underwent 10 daily rTMS sessions over the left dorsolateral prefrontal cortex (DLPFC). Polysomnographic (PSG) data were recorded over four nights: Adaptation, Baseline, Post-1 (after the fifth rTMS session), and Post-2 (after the tenth rTMS session). Discrete Fourier Transform (DFT) band power analyses were performed to quantify delta and sigma band activities during Stages II-IV, and determine time courses of these activities between Baseline and Post-1 (first five sessions) and between Post-1 and Post-2 (last five sessions).

Results: Post-hoc tests based on a three-way ANOVA model indicated significant delta power increase at F3 (t11 = -2.762, P = 0.018) during the first five sessions; however, sigma power was unchanged. No significant band power changes were observed during the second half. Stages II-IV (percent total sleep time) increased significantly during the first half (t12 = -2.43, P = 0.033). No other significant changes in sleep parameters or clinical correlations were observed.

Conclusions: The first five sessions of high frequency rTMS to the left DLPFC increase slow-wave activity (SWA) at F3, possibly reflecting locally enhanced synaptic plasticity induced by rTMS. This increased activity was not observed during the last half, possibly due to a homeostatic regulation mechanism intrinsic to SWA.