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

Resting-state functional connectivity MRI, which measures correlated brain activity while a person lies quietly in a scanner, has been questioned as possibly reflecting noise rather than true neural connections. By combining diffusion tensor imaging tractography with resting-state functional connectivity MRI, this work tested whether the functional correlations correspond to actual structural pathways. Focusing on the default mode network—a set of brain regions involved in memory, including the medial prefrontal cortex, medial temporal lobes, and posterior cingulate/retrosplenial cortex—the analysis found that structural connections matched the functional connectivity maps. Medial temporal lobes connected to retrosplenial cortex, while medial prefrontal cortex connected to posterior cingulate cortex. The results demonstrate that resting-state functional connectivity reflects structural connectivity, and combining methods can deepen understanding of brain networks.

Study at a glance

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.