Closed-loop TMS-EEG reactivity with occipital alpha-phase synchronized.

Abstract

<i>Objective</i>. Transcranial magnetic stimulation-electroencephalogram (TMS-EEG) technology has played an increasingly important role in the field of neuroscience, and closed loop TMS has also been gradually concerned. However, the characteristics of closed-loop TMS-EEG were few discussed. To study the dependence of EEG reactivity on cortical oscillation phase under TMS stimulation, we explored in detail the TMS-EEG characteristics induced by closed-loop TMS contingent on occipital alpha phase.<i>Approach.</i>By collecting 30 healthy volunteers' closed-loop TMS-EEG data, we verified the real-time accuracy of our closed-loop system and analyzed the inter-trial phase coherence (ITPC) value, the TMS-induced natural frequency, the N100 TMS-evoked potential and the spatial characteristics of TMS-EEG data.<i>Main results.</i>The ITPC value of closed-loop TMS-EEG was higher than that of open loop TMS-EEG, suggesting that our research improves the repeatability of TMS-EEG experiments; the alpha power induced by 0° TMS was higher than that induced by 180° stimulation in the central region and parietal/occipital lobe; the N100 amplitude of 90° (3.85<i>μ</i>V) stimulation was significantly higher than that of 270° (1.87<i>μ</i>V) stimulation, and the latency of the N100 of the 90° stimulation (mean 95.01 ms) was significantly less than that of the 270° stimulation (mean 113.94 ms); the topographical distributions of the N45-P70-N100 potential were significantly affected by the O1 alpha phase at the moment of TMS.<i>Significance.</i>Our experimental results provided support for the dependence of EEG reactivity on cortical oscillation phase under TMS stimulation.