Static and Dynamic Resting-State fMRI Connectivity Show Frequency-Resolved Associations With Intracranial EEG Connectivity.

Resting-state functional connectivity (FC) derived from functional MRI (fMRI) is widely used to characterize brain functional organization, yet its electrophysiological basis remains incompletely understood. Here, we investigated how electrophysiological connectivity relates to both static and dynamic fMRI connectivity using simultaneous intracranial EEG (icEEG)-fMRI recordings from 48 adults with focal epilepsy. Linear mixed-effects models were applied to sampled electrode-pair connections to examine frequency-resolved associations between band-limited icEEG connectivity and corresponding fMRI FC within non-epileptogenic brain regions. Time-averaged icEEG connectivity was robustly associated with spatial variation in static fMRI connectivity across sampled connections and frequency bands, with strongest effects in the beta and low-gamma ranges. At the window level, dynamic fMRI connectivity showed significant positive associations with window-specific icEEG FC deviations in the alpha, beta, and low-gamma bands. Exploratory spatial stratification suggested that cross-modal coupling varied across clinically sampled frontal, temporal, and insular region pairs, and the main findings remained robust after motion-control analyses. Together, these findings indicate that resting-state fMRI connectivity is associated with both average electrophysiological coupling across sampled connections and window-level fluctuations in electrophysiological connectivity, with the strongest primary band-wise evidence observed in the alpha, beta, and low-gamma ranges.