Objective. 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.Approach.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.Main results.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° (3.85μV) stimulation was significantly higher than that of 270° (1.87μV) 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.Significance.Our experimental results provided support for the dependence of EEG reactivity on cortical oscillation phase under TMS stimulation.
Keywords: TEP; closed-loop TMS-EEG; inter trial phase coherence; natural frequency.
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