Inference of Whole Brain Electrophysiological Networks Through Multimodal Integration of Simultaneous Scalp and Intracranial EEG

In the past decades, brain imaging research underwent a shift from mapping tasked evoked brain regions of activations towards identifying and characterizing the dynamic brain networks of multiple coordinating brain regions. Electrophysiological signals are the direct manifestation of brain activities, thus, characterizing the whole brain electrophysiological networks (WBEN) can serve as a fundamental tool for neuroscience studies and clinical applications. In this work, we introduce the first framework for the integration of scalp EEG and intracranial EEG (iEEG) for the WBEN estimation with a principled estimation framework based on state-space models, where an Expectation-Maximization (EM) algorithm is designed to infer the state variables and brain connectivity simultaneously. We validated the proposed method on synthetic data, and the results revealed improved performance compared to traditional two-step methods using scalp EEG only, demonstrating the importance of including iEEG signal for WBEN estimation. For real data with simultaneous EEG and iEEG, we applied the developed framework to understand the information flows of the encoding and maintenance phases during the working memory task. The information flows between the subcortical and cortical regions are delineated, highlighting more significant information flows from cortical to subcortical regions than maintenance phases. The results are consistent with previous research findings but with the view of the whole brain scope, which underscores the unique utility of the proposed framework.