Multimodal analysis of hemodynamic and electrocortical causal interactions during auditory processing

Objective. Electrocortical and hemodynamic signals measured by electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS) can be used to provide complementary information about neural activity underpinning auditory processing. However, the causal interactions between these signals remain underexplored, partly due to several factors, including the complexity of disentangling cortical and systemic physiological components captured in fNIRS modality. Recent developments in the ability to estimate the influence of non-cortical sources on fNIRS signals provide new opportunities to address these confounds. In this study, we investigated causal interactions between vascular-hemodynamic and electrocortical dynamics through simultaneous recording of fNIRS and EEG during auditory processing.Approach. We employed multimodal multivariate Granger causal analysis to investigate causal interactions between EEG and fNIRS signals. To explore the role of systemic physiology on the obtained causal interactions, a temporally-embedded canonical correlation analysis-general linear model-based preprocessing approach was applied to fNIRS signals to correct for potential systemic physiology confounds.Main results. Our results showed significantly stronger causal interactions originating from fNIRS in the right auditory cortex to frontocentral EEG in the 38-42 Hz frequency range during the auditory task relative to rest before correction. We additionally observed broad connectivity in the direction originating from fNIRS variables to EEG across frequency bands within participants throughout the dataset. These results suggest complex relationships between cortical vascular-hemodynamics, electrocortical oscillations, and systemic physiological components with roles in both task-related and spontaneous neural activity.Significance. This study highlights the complex causal interplay between electrical, cerebral hemodynamic, and systemic physiology components underpinning spontaneous electro-vascular dynamics associated with auditory processing.