Toward reliable characterization of functional homogeneity in the human brain: Preprocessing, scan duration, imaging resolution and computational space

Abstract

While researchers have extensively characterized functional connectivity between brain regions, the characterization of functional homogeneity within a region of the brain connectome is in early stages of development. Several functional homogeneity measures were proposed previously, among which regional homogeneity (ReHo) was most widely used as a measure to characterize functional homogeneity of resting state fMRI (R-fMRI) signals within a small region (Zang et al., 2004). Despite a burgeoning literature on ReHo in the field of neuroimaging brain disorders, its test–retest (TRT) reliability remains unestablished. Using two sets of public R-fMRI TRT data, we systematically evaluated the ReHo’s TRT reliability and further investigated the various factors influencing its reliability and found: 1) nuisance (head motion, white matter, and cerebrospinal fluid) correction of R-fMRI time series can significantly improve the TRT reliability of ReHo while additional removal of global brain signal reduces its reliability, 2) spatial smoothing of R-fMRI time series artificially enhances ReHo intensity and influences its reliability, 3) surface-based R-fMRI computation largely improves the TRT reliability of ReHo, 4) a scan duration of 5 min can achieve reliable estimates of ReHo, and 5) fast sampling rates of R-fMRI dramatically increase the reliability of ReHo. Inspired by these findings and seeking a highly reliable approach to exploratory analysis of the human functional connectome, we established an R-fMRI pipeline to conduct ReHo computations in both 3-dimensions (volume) and 2-dimensions (surface).

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

“…Further in a voxel-wise fashion, similar to the significance test of ICC, we compared ICC values between two imaging contrasts using Z test as the following Zuo et al, 2013).…”

Effects of long-term acupuncture treatment on resting-state brain activity in migraine patients: A randomized controlled trial on active acupoints and inactive acupoints

“…ReHo is based on a data-driven approach and thus requires no prior knowledge and has good test-retest reliability [17]. It was originally proposed for measuring the degree of regional synchronization of functional magnetic resonance imaging (fMRI) time courses and focused on the similarities or coherence of the intraregional spontaneous lowfrequency (,0.08 Hz) BOLD signal, which enables a novel perspective to understand the functional regulation in particular brain regions.…”

Breaking down the genetics of depression using brain endophenotypes

“…Studies have reported that test-retest reliability of ReHo measurements increases with scan duration [18,22]. We could expect a moderate to high test retest (mean ICC=0.8) after 10minutes RS-fMRI [18], while 50 minutes scans may be required to ensure an ICC greater than 0.7 for all voxels [22].…”

“…Brain MRI phenotypes represent ideal candidate endophenotypes for mental health disorders, as they do not rely on self-report [16] and are more and more reliably measured thanks to methodological and technological improvement [18][19][20][21][22][23][24][25]. In addition, the heritability of many MRI brain phenotypes has been established: from structural [26][27][28][29][30], to resting state and task fMRI [31][32][33][34].…”