EPICURUS: E-field-based spatial filtering procedure for an accurate estimation of local EEG activity evoked by Transcranial Magnetic Stimulation

BackgroundThe concurrent use of Transcranial magnetic stimulation and electroencephalography (TMS-EEG) is increasingly integrated into research and clinical protocols. However, a reliable isolation of EEG responses that are locally evoked by TMS at the targeted cortical sites independent from contaminating sources, remains challenging. MethodsHere we introduce EPICURUS, a novel spatial filtering approach for TMS-EEG that uses individualized MRI-based simulations of the TMS-induced electric field (E-field) to define the spatial extent of locally evoked activity. This method guides the reconstruction of EEG signals originating from the direct stimulation site while minimizing crosstalk from distant, non-targeted sources. ResultsIn synthetic simulations and a human TMS-EEG dataset, EPICURUS preserved early-latency TMS-evoked local activity while substantially attenuating later components, consistent with suppression of non-local activity. ConclusionBy leveraging the spatial precision of individualized E-field modeling, EPICURUS may enhance the specificity of EEG signal reconstruction, offering a promising tool for improving the spatiotemporal resolution of local early and late cortical local responses directly elicited by TMS.