A study of within-subject reliability of the brain's default-mode network

Abstract

Objective: Resting-state functional magnetic resonance imaging (fMRI) is promising for Alzheimer's disease (AD). This study aimed to examine short-term reliability of the default-mode network (DMN), one of the main haemodynamic patterns of the brain.

Materials and methods: Using a 1.5 T Philips Achieva scanner, two consecutive resting-state fMRI runs were acquired on 69 healthy adults, 62 patients with mild cognitive impairment (MCI) due to AD, and 28 patients with AD dementia. The anterior and posterior DMN and, as control, the visual-processing network (VPN) were computed using two different methodologies: connectivity of predetermined seeds (theory-driven) and dual regression (data-driven). Divergence and convergence in network strength and topography were calculated with paired t tests, global correlation coefficients, voxel-based correlation maps, and indices of reliability.

Results: No topographical differences were found in any of the networks. High correlations and reliability were found in the posterior DMN of healthy adults and MCI patients. Lower reliability was found in the anterior DMN and in the VPN, and in the posterior DMN of dementia patients.

Discussion: Strength and topography of the posterior DMN appear relatively stable and reliable over a short-term period of acquisition but with some degree of variability across clinical samples.

Keywords: Brain imaging; Hemodynamics; Reproducibility of results; fMRI.

Fig. 1

Three ROIs devised as part of the theory-driven section of the study methodology. These were constructed based on an anatomical atlas as main seed of the anterior DMN (medial prefrontal cortex, red), posterior DMN (posterior cingulate cortex, blue), and VPN (calcarine cortex, green)

Fig. 2

Maps of the anterior and posterior DMN and the VPN, as calculated from seed-based models via one-sample t tests. The strength of the haemodynamic connectivity which constitutes this network is illustrated separately for each diagnostic group: during Run 1 (yellow) and Run 2 (blue). The conjunction analysis is illustrated in gold. MNI coordinates: x = − 4; y = − 62; z = 22. Colours indicate the statistical strength of the z statistics. A legend is included on the right-hand side, CONJ conjunction

Fig. 3

Maps of the anterior and posterior DMN and the VPN, as calculated based on the dual-regression procedure via one-sample t tests. The strength of the haemodynamic connectivity which constitutes this network is illustrated separately for each diagnostic group: during Run 1 (yellow) and Run 2 (blue). The conjunction analysis is illustrated in gold. MNI coordinates: x = − 4; y = − 56; z = 22. Colours indicate the statistical strength of the z statistics. A legend is included on the right-hand side. CONJ conjunction

Fig. 4

Correlation graph of mean functional activity in the central ROIs of each network (shown in Fig. 1) as emerged from seed-based models: anterior default-mode network (aDMN), posterior default-mode network (pDMN), and visual-processing network (VPN). Pearson’s correlation coefficients and corresponding p values are also included

Fig. 5

Group distribution of individual coefficients of correlation calculated over the entire network maps. Boxplots indicate medians and interquartile ranges

Fig. 6

Voxel-based correlational maps between Run 1 and Run 2 for each brain network computed with dual regression. Maps were thresholded at r > 0.6