Regional homogeneity changes in patients with neuromyelitis optica revealed by resting-state functional MRI
Introduction
Neuromyelitis optica (NMO) is an inflammatory, demyelinating syndrome of the central nervous system that is characterised by severe attacks of optic neuritis and myelitis (Wingerchuk et al., 2006, Wingerchuk et al., 2007). Although the brain was traditionally regarded as healthy (Lennon et al., 2004, Pittock et al., 2006), cognitive impairment in NMO patients was reported only recently (Blanc et al., 2008). Some functional magnetic resonance imaging (fMRI) studies have been performed to examine the differences between NMO patients and normal controls (Rocca et al., 2004). Resting-state fMRI, as a new branch of functional imaging, can reflect the baseline brain activity. The low-frequency fluctuations of the resting-state fMRI signal were suggested to be of physiological importance and reflect spontaneous neuronal activity (Biswal et al., 1995, Zang et al., 2007). However, baseline brain activity of NMO patients is still less explored using resting-state fMRI.
Recently, a new method, regional homogeneity (ReHo), has been developed to analyse the blood-oxygen-level dependent (BOLD) signal of the brain (Zang et al., 2004). ReHo assumes that within a functional cluster, the haemodynamic characteristics of every voxel would be similar or synchronous with that of each other; and such similarity could be changed or modulated by different conditions (Zang et al., 2004). ReHo has been successfully used to investigate the functional modulations in the resting state in patients with Alzheimer’s disease (AD) (He et al., 2007), schizophrenia (Liu et al., 2006) and Parkinson’s disease (Wu et al., 2009). In the current study, we used this method to investigate NMO-related brain neural activity in the resting state.
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Subjects
We studied 17 patients with NMO (two males, 15 females; mean age 37.2 years, SD 12.1, age range 19–59 years), and 17 age- and sex-balanced healthy subjects (mean age 36.9 years, SD 11.2, age range 19–59 years). The subjects were all right-handed as measured by the Edinburgh Inventory (Oldfield, 1971). The diagnosis of NMO was according to the recently revised diagnostic criteria (optic neuritis, acute myelitis, contiguous spinal cord MRI lesion extending over ⩾3 vertebral segments, brain MRI not
Results
T1WI, T2WI and FLAIR images of each subject were evaluated by two experienced neuroradiologists, Yunyun Duan and Yaou Liu, and no brain lesions were detected for all subjects (including NMO patients and healthy controls). To evaluate grey matter atrophy in NMO patients, T1-weighted three-dimensional (3D) MRI data of NMO patients and healthy controls were analysed using a voxel-based morphometry (VBM) method (as shown in Appendix A).
Discussion
The physiological background of the ReHo measures (using KCC) is that a given voxel is temporally similar to that of its neighbours in rest/task conditions (Lu et al., 2003, Zang et al., 2004). ReHo has been used in the purification of the activated clusters (Baumgartner et al., 1999), which is not well dealt with in both data-driven and model-driven methods (Baumgartner et al., 1999, Goutte et al., 1999). In the current study, ReHo was used as an independent method in the analysis of
Acknowledgements
This work was supported by the State Key Program of National Natural Science of China (NO. 30930029) and the National Natural Science Foundation of China (NO. 30770620, NO. 60775039). Dr. Yaou Liu was supported by the McDonald Fellowship from the Multiple Sclerosis International Federation (MSIF).
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2016, Neuroscience LettersCitation Excerpt :Regional homogeneity (ReHo) measures the local coherence of spontaneous brain activity, and is sensitive to detect aberrant local functional connectivity of brain regions. It has been used in the studies of neurological and psychiatric diseases, including migraine [9], stroke [10], epilepsy [11], neuromyelitis optica [12], Parkinson’s Disease [13], attention-deficit hyperactivity disorder [14], AD [4,15], aMCI [3], social anxiety disorder [16], panic disorder [17], blindness [18], depression [19] and schizophrenia [20]. Bai et al. [5] found significant regional coherence decreases in most areas of the default mode network (DMN), especially in the PCC/PCu.
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2015, NeuroImageCitation Excerpt :Higher ReHo in the insula and ACC in low-resilient individuals, as well as PTSD patients, can be interpreted as the temporal synchronization of the neural activity in these regions. The increased ReHo has been considered as a compensatory mechanism to offset functional decrease or impairments in previous studies (e.g., Chen et al., 2012; Dai et al., 2012; Guo et al., 2012; Liang et al., 2011; Song et al., 2014; Zhang et al., 2012). This seems to fit well with the dysfunction of the insula and ACC in major depression disorder (Horn et al., 2010; Sprengelmeyer et al., 2011; van Tol et al., 2010), PTSD (Chen et al., 2006; Liberzon and Martis, 2006; Karl et al., 2006), and other anxiety disorders (Paulus and Stein, 2006; van Tol et al., 2010), all of which have been associated with impairments in psychological resilience (Hjemdal et al., 2011; Skrove et al., 2013).
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2014, Clinical NeurophysiologyCitation Excerpt :The mean ReHo maps within each group are shown in Fig. 1 (one-sample t-test; P < 0.01, FDR corrected). The voxels with greater ReHo values than the global mean ReHo value were bilaterally distributed within a few of the medial and lateral brain structures, including the medial prefrontal cortex (mPFC), anterior cingulate cortex (ACC), posterior cingulate cortex (PCC)/precuneus and inferior prefrontal cortex (iPFC) in both controls (Fig. 1A) and TIA patients (Fig. 1B), whose patterns were consistent with those in previous studies (Liang et al., 2011; Wu et al., 2009; Yu et al., 2012). The differences in the ReHo values between the TIA patients and the controls are shown in Table 3.
- 1
The first two authors wish to be regarded as joint first authors.