Multisensory integration processing during olfactory‐visual stimulation—An fMRI graph theoretical network analysis

In this study, we aimed to understand how whole‐brain neural networks compute sensory information integration based on the olfactory and visual system. Task‐related functional magnetic resonance imaging (fMRI) data was obtained during unimodal and bimodal sensory stimulation. Based on the identification of multisensory integration processing (MIP) specific hub‐like network nodes analyzed with network‐based statistics using region‐of‐interest based connectivity matrices, we conclude the following brain areas to be important for processing the presented bimodal sensory information: right precuneus connected contralaterally to the supramarginal gyrus for memory‐related imagery and phonology retrieval, and the left middle occipital gyrus connected ipsilaterally to the inferior frontal gyrus via the inferior fronto‐occipital fasciculus including functional aspects of working memory. Applied graph theory for quantification of the resulting complex network topologies indicates a significantly increased global efficiency and clustering coefficient in networks including aspects of MIP reflecting a simultaneous better integration and segregation. Graph theoretical analysis of positive and negative network correlations allowing for inferences about excitatory and inhibitory network architectures revealed—not significant, but very consistent—that MIP‐specific neural networks are dominated by inhibitory relationships between brain regions involved in stimulus processing.