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bioRxiv · 10.64898/2026.01.31.703060

Symmetric Fusion of fMRI and EEG for Spectrally Resolved Functional Neuroimaging

Kim, J.-H.·Liu, Z.
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Abstract

Simultaneous electroencephalography (EEG) and functional MRI (fMRI) offers complementary sensitivity to fast electrophysiological dynamics of EEG and spatially resolved hemodynamics of fMRI, yet previous joint-analysis approaches are confined to fixed task paradigms and struggle with continuous or naturalistic brain states. We FSINC (Fusing Source Imaging based on a Neurovascular Coupling) model, a unified EEG-fMRI source imaging framework that reconstructs cortical activity to simultaneously explain both modalities. FSINC integrates frequency-resolved EEG source activity with fMRI via a data-driven neurovascular coupling model that estimates band-specific coupling coefficients ({beta}) and accommodates a tunable spatial-temporal trade-off through hyperparameters ({lambda}2,{lambda} 3). In realistic simulations, FSINC outperformed conventional methods (wMNE, LORETA) in both spatial and temporal accuracy across EEG SNRs (-10 to 10dB) and numbers of concurrent sources (up to five), with optimal performance at{lambda} 2 = 102 and{lambda} 3=1 (e.g., LE: 0.51{+/-}0.24mm; SDI: 0.03{+/-}0.37mm; temporal accuracy: 0.95 {+/-} 0.05). Applied to simultaneous EEG-fMRI during contrast-reversing visual stimulation (=5.95Hz), FSINC revealed stimulus-locked responses localized to early visual cortex and stimulus-induced modulation of intrinsic alpha oscillations extending into visual and attention networks, patterns that conventional methods failed to capture. Estimated {beta}-weights were broadly consistent with prior reports of negative (theta/alpha) and positive (gamma) BOLD-electrophysiology associations. These findings demonstrate that FSINC enables high-spatiotemporal-resolution source imaging from EEG-fMRI recordings via data-driven hemodynamic modelling, and is expected to be well-suited for continuous and naturalistic brain states (e.g., resting state, natural moving-watching, and narrative listening) that are difficult to interrogate with either modality alone.

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Kim, J.-H., Liu, Z.. 2026-02-03. Symmetric Fusion of fMRI and EEG for Spectrally Resolved Functional Neuroimaging. https://doi.org/10.64898/2026.01.31.703060

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