Functional connectivity in BOLD and CBF data: Similarity and reliability of resting brain networks

Abstract

Resting-state functional connectivity (FC) fMRI (rs-fcMRI) offers an appealing approach to mapping the brain’s intrinsic functional organization. Blood oxygen level dependent (BOLD) and arterial spin labeling (ASL) are the two main rs-fcMRI approaches to assess alterations in brain networks associated with individual differences, behavior and psychopathology. While the BOLD signal is stronger with a higher temporal resolution, ASL provides quantitative, direct measures of the physiology and metabolism of specific networks. This study systematically investigated the similarity and reliability of resting brain networks (RBNs) in BOLD and ASL. A 2 × 2 × 2 factorial design was employed where each subject underwent repeated BOLD and ASL rs-fcMRI scans on two occasions on two MRI scanners respectively. Both independent and joint FC analyses revealed common RBNs in ASL and BOLD rs-fcMRI with a moderate to high level of spatial overlap, verified by Dice Similarity Coefficients. Test–retest analyses indicated more reliable spatial network patterns in BOLD (average modal Intraclass Correlation Coefficients: 0.905 ± 0.033 between-sessions; 0.885 ± 0.052 between-scanners) than ASL (0.545 ± 0.048; 0.575 ± 0.059). Nevertheless, ASL provided highly reproducible (0.955 ± 0.021; 0.970 ± 0.011) network-specific CBF measurements. Moreover, we observed positive correlations between regional CBF and FC in core areas of all RBNs indicating a relationship between network connectivity and its baseline metabolism. Taken together, the combination of ASL and BOLD rs-fcMRI provides a powerful tool for characterizing the spatiotemporal and quantitative properties of RBNs. These findings pave the way for future BOLD and ASL rs-fcMRI studies in clinical populations that are carried out across time and scanners.

Reliability comparison of spontaneous brain activities between BOLD and CBF contrasts in eyes-open and eyes-closed resting states

“…Test-retest reliability of CBF-mean, BOLD-and CBF-ALFF, and BOLD-and CBF-FC For CBF-mean, consistent with previous voxel-wise test-retest studies (Hodkinson et al, 2013;Jahng et al, 2005;Jann et al, 2014), we showed that both short-and long-term ICC were excellent (ICC N 0.6) for almost the entire brain volume, especially in the gray matter in both EO and EC states (Figs. 2, 3 and S1).…”

“…Similar results were observed by separate studies investigating test-retest reliability of average CBF (Hodkinson et al, 2013;Jahng et al, 2005;Jann et al, 2015). One recent study compared shortterm test-retest reliability of CBF-mean, functional connectivity based on BOLD and CBF time series, which showed generally more reliable spatial patterns of functional connectivity of BOLD than that of CBF, while the highest reproducibility was yielded by CBF-mean (Jann et al, 2015). However, functional connectivity provides measures of inter-regional relationship, i.e., relational characteristics between brain regions, while mean CBF reflects static characteristics of a region, i.e., regional characteristics at single voxel level (Zuo and Xing, 2014).…”

“…Previous investigations on test-retest reliability of spontaneous BOLD signal oscillations (Kublbock et al, 2014;Zuo et al, 2010a) showed that regions with high reliability were mainly located in the gray matter. Similar results were observed by separate studies investigating test-retest reliability of average CBF (Hodkinson et al, 2013;Jahng et al, 2005;Jann et al, 2015). One recent study compared shortterm test-retest reliability of CBF-mean, functional connectivity based on BOLD and CBF time series, which showed generally more reliable spatial patterns of functional connectivity of BOLD than that of CBF, while the highest reproducibility was yielded by CBF-mean (Jann et al, 2015).…”

“…Interleaved control and label images were acquired using a single-shot 3D GRASE sequence with the following parameters: TR/TE = 3000/23.38 ms, slice thickness = 5 mm without gap, 24 slices, FOV = 220 × 220 mm 2 with in-plane resolution of 3.44 × 3.44 mm 2 , GRAPPA factor = 2, partial Fourier = 6/8, labeling duration = 1104ms, label offset = 90 mm, postlabeling delay = 1000 ms and global inversion pulses for background suppression (Jann et al, 2014). The duration of the resting-state pCASL scan was 8 min, and it included 80 pairs of control and label images.…”

“…Thus they are of crucial importance to evaluate the test-retest reliability of brain activity measures (Hodkinson et al, 2013;Jahng et al, 2005;Jann et al, 2014;Kublbock et al, 2014;Patriat et al, 2013;Shehzad et al, 2009;Zhu et al, 2014;Zuo et al, 2010aZuo et al, ,b,c, 2013Zuo and Xing, 2014). Resting-state fMRI, including blood oxygenation level dependent (BOLD) and arterial spin labeling (ASL), has become a powerful tool in mapping human brain functions (Biswal et al, 2010;Smith et al, 2013).…”