Using coherence to measure regional homogeneity of resting-state fMRI signal

Dongqiang Liu

doi:10.3389/fnsys.2010.00024

Abstract

In this study, we applied coherence to voxel-wise measurement of regional homogeneity of resting-state functional magnetic resonance imaging (RS-fMRI) signal. We compared the current method, regional homogeneity based on coherence (Cohe-ReHo), with previously proposed method, ReHo based on Kendall's coefficient of concordance (KCC-ReHo), in terms of correlation and paired t-test in a large sample of healthy participants. We found the two measurements differed mainly in some brain regions where physiological noise is dominant. We also compared the sensitivity of these methods in detecting difference between resting-state conditions [eyes open (EO) vs. eyes closed (EC)] and in detecting abnormal local synchronization between two groups [attention deficit hyperactivity disorder (ADHD) patients vs. normal controls]. Our results indicated that Cohe-ReHo is more sensitive than KCC-ReHo to the difference between two conditions (EO vs. EC) as well as that between ADHD and normal controls. These preliminary results suggest that Cohe-ReHo is superior to KCC-ReHo. A possible reason is that coherence is not susceptible to random noise induced by phase delay among the time courses to be measured. However, further investigation is still needed to elucidate the sensitivity and specificity of these methods.

Highlights

Biswal et al (1995) found that during rest, low-frequency (0.01– 0.08 Hz) fluctuations in blood oxygenation level-dependent (BOLD) signal are highly synchronous throughout the sensorimotor cortex
Our results indicated that Cohe-regional homogeneity (ReHo) is more sensitive than Kendall’s coefficient of concordance (KCC)-ReHo to the difference between two conditions (EO vs. eyes closed (EC)) as well as that between attention deficit hyperactivity disorder (ADHD) and normal controls
The DMN is of particular interest because it was found that regions in DMN have significantly higher glucose metabolism than other brain regions (Raichle et al, 2001) and these regions show task-independent or task-unspecific deactivation in the goal directed tasks (Shulman et al, 1997; Binder et al, 1999; Mazoyer et al, 2001; McKiernan et al, 2003), suggesting these regions may have important function during resting state

Summary

Introduction

Biswal et al (1995) found that during rest, low-frequency (0.01– 0.08 Hz) fluctuations in blood oxygenation level-dependent (BOLD) signal are highly synchronous throughout the sensorimotor cortex. The vast majority of RS-fMRI studies have adopted functional connectivity to examine their data, i.e. investigating temporal relationships between fluctuations observed in spatially distinct brain regions. Functional connectivity provides little information about local features of spontaneous brain activity observed in individual regions, as the methods employed are typically relational. It has been shown that the major regions of DMN have higher ReHo than other brain regions during resting state (Long et al, 2008). ReHo method has been applied to the detection of local abnormality in some brain disorders, e.g., attention deficit hyperactivity disorder (ADHD) (Cao et al, 2006), Alzheimer’s disease (He et al, 2007), depression (Yuan et al, 2008), Parkinson disease (Wu et al, 2009), and autism (Paakki et al, 2010)

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