Resting-State Functional Connectivity Reflects Structural Connectivity in the Default Mode Network

TLDR

Resting‑state fMRI detects spontaneous BOLD correlations during quiet rest, and while many networks have been identified, it remains debated whether these functional maps reflect true neural connectivity or merely non‑neural artifacts. The study tests whether resting‑state functional connectivity mirrors structural connectivity by combining DTI tractography with fcMRI. The authors examined default‑mode network connectivity among MPFC, MTLs, PCC, and RSC using simultaneous DTI tractography and resting‑state fcMRI. DTI revealed strong structural links between MTLs and retrosplenial cortex and between MPFC and PCC, confirming that resting‑state functional connectivity reflects underlying structural connectivity and that multimodal imaging enhances insight into canonical brain networks.

Abstract

Resting-state functional connectivity magnetic resonance imaging (fcMRI) studies constitute a growing proportion of functional brain imaging publications. This approach detects temporal correlations in spontaneous blood oxygen level-dependent (BOLD) signal oscillations while subjects rest quietly in the scanner. Although distinct resting-state networks related to vision, language, executive processing, and other sensory and cognitive domains have been identified, considerable skepticism remains as to whether resting-state functional connectivity maps reflect neural connectivity or simply track BOLD signal correlations driven by nonneural artifact. Here we combine diffusion tensor imaging (DTI) tractography with resting-state fcMRI to test the hypothesis that resting-state functional connectivity reflects structural connectivity. These 2 modalities were used to investigate connectivity within the default mode network, a set of brain regions--including medial prefrontal cortex (MPFC), medial temporal lobes (MTLs), and posterior cingulate cortex (PCC)/retropslenial cortex (RSC)--implicated in episodic memory processing. Using seed regions from the functional connectivity maps, the DTI analysis revealed robust structural connections between the MTLs and the retrosplenial cortex whereas tracts from the MPFC contacted the PCC (just rostral to the RSC). The results demonstrate that resting-state functional connectivity reflects structural connectivity and that combining modalities can enrich our understanding of these canonical brain networks.