A novel approach for multiscale source analysis and modeling of epileptic spikes

Multiscale recordings of brain electrical activity are often performed for presurgical evaluation in patients with focal epilepsy to facilitate the identification and precise delineation of the epileptogenic zone. However, data regarding the concordance of source models derived from recordings on different scales and their reciprocal validation against clinical outcomes remains scarce. This study aims to define a common source model that accurately depicts both scalp EEG and subdural EEG (ECoG) interictal spikes. To this purpose, the sLORETA method was applied to averaged spikes and source reconstruction results were implemented to outline the location and extent of an epileptic cortical patch. This estimated patch served as the basis for the spatiotemporal source model in a generative model of EEG. Spike activity was simulated on both scalp EEG and ECoG signal scales, with simulated traces resembling measured traces regarding their spatial distribution and amplitude compared to background. Simulated spikes served for the evaluation of source reconstruction with a known generator topography. The described setup allows for the validation and, ultimately, for the refinement of source reconstruction methods. It provides novel insights towards a thorough understanding of physiological and pathological brain processes and their representation in neuroelectric measurements.