White matter microstructure underlying default mode network connectivity in the human brain

Resting state functional connectivity in the default mode network (DMN) of the human brain is linked to underlying white matter microstructure. Combining diffusion tensor imaging and resting state fMRI in 20 healthy elderly adults aged 56 to 83, the authors found that functional connectivity between the posterior cingulate and hippocampus was associated with white matter integrity in the cingulate bundle and related fiber tracts. A data-driven analysis confirmed a pattern of white matter tracts resembling the hypothesis-driven findings and linked to DMN connectivity. The results support the idea that DMN functional connectivity is grounded in distinct anatomical connections within cerebral white matter.

Study at a glance

Abstract

Resting state functional magnetic resonance imaging (fMRI) reveals a distinct network of correlated brain function representing a default mode state of the human brain. The underlying structural basis of this functional connectivity pattern is still widely unexplored. We combined fractional anisotropy measures of fiber tract integrity derived from diffusion tensor imaging (DTI) and resting state fMRI data obtained at 3 Tesla from 20 healthy elderly subjects (56 to 83 years of age) to determine white matter microstructure underlying default mode connectivity. We hypothesized that the functional connectivity between the posterior cingulate and hippocampus from resting state fMRI data would be associated with the white matter microstructure in the cingulate bundle and fiber tracts connecting posterior cingulate gyrus with lateral temporal lobes, medial temporal lobes, and precuneus. This was demonstrated at the p<0.001 level using a voxel-based multivariate analysis of covariance (MANCOVA) approach. In addition, we used a data-driven technique of joint independent component analysis (ICA) that uncovers spatial pattern that are linked across modalities. It revealed a pattern of white matter tracts including cingulate bundle and associated fiber tracts resembling the findings from the hypothesis-driven analysis and was linked to the pattern of default mode network (DMN) connectivity in the resting state fMRI data. Our findings support the notion that the functional connectivity between the posterior cingulate and hippocampus and the functional connectivity across the entire DMN is based on distinct pattern of anatomical connectivity within the cerebral white matter.