Abstract
Previous studies have demonstrated that functional connectivity (FC) of different brain regions in resting state function MRI were abnormal in patients suffering from mild cognitive impairment (MCI) and Alzheimer’s disease (AD) when comparing to healthy controls (HC) using seed based, independent component analysis (ICA) or small world network techniques. A new technique called voxel-mirrored homotopic connectivity (VMHC) was used in the current study to evaluate the value of interhemispheric functional connectivity (IFC) as a diagnostic tool to differentiate vascular dementia (VD) from other Alzheimer’s related neurodegenerative diseases. Eighty-three participants were recruited from the university hospital memory clinic. A multidisciplinary panel formed by a neuroradiologist and two geriatricians classified the participants into VD (13), AD (16), MCI (29), and HC (25) based on clinical history, Montreal Cognitive Assessment Hong Kong version (HK-MoCA) neuropsychological score, structural MRI, MR perfusion, and 18-F Flutametamol (amyloid) PET-CT findings of individual subjects. We adopted the calculation method used by Kelly et al. (2011) and Zuo et al. (2010) in obtaining VMHC maps. Specific patterns of VMHC maps were obtained for VD, AD, and MCI to HC comparison. VD showed significant reduction in VMHC in frontal orbital gyrus and gyrus rectus. Increased VMHC was observed in default mode network (DMN), executive control network (ECN), and the remaining salient network (SN) regions. AD showed a reduction of IFC in all DMN, ECN, and SN regions; whereas MCI showed VMHC reduction in vSN, and increased VMHC in DMN and ECN. When combining VMHC values of relevant brain regions, the accuracy was improved to 87%, 92%, and 83% for VD, AD, and MCI from HC, respectively, in receiver operating characteristic (ROC) analysis. Through studying the VMHC maps and using VMHC values in relevant brain regions, VMHC can be considered as a reliable diagnostic tool for VD, AD, and MCI from HC.
Highlights
With the aging of the world population, dementia cases increase rapidly due to neurodegenerative diseases
To investigate whether the interhemispheric functional connectivity (IFC) was affected by the volume, we studied the relationship between the voxel-mirrored homotopic connectivity (VMHC) values and their corresponding brain regional volumes using partial correlation analysis, with age and sex as covariates
Our result showed that IFC decreased in frontal orbital gyrus and gyrus rectus, but increased IFC in default mode network (DMN) including superior frontal gyrus, inferior frontal gyrus triangular, anterior and posterior cingulate gyrus; in precentral gyrus of executive control network (ECN); in other parts of salient network (SN)
Summary
With the aging of the world population, dementia cases increase rapidly due to neurodegenerative diseases. Different VMHC patterns have been found in Alzheimer’s disease (AD) and mild cognitive impairment (MCI) when compared to normal healthy controls (HC) [23,24]. Many studies have demonstrated aberrant functional connectivity of different brain regions in terms of brain networks, including default mode network (DMN), salient network (SN), and executive control network (ECN) in patients that suffered from dementia. These networks are thought to provide a general framework of human normal functioning. We compared the interhemispheric resting-state functional connectivity (IFC) of cognitively impaired subjects and healthy controls (HC) using VMHC analysis. * p < 0.05 ANOVA on ranks with Bonferroni post hoc test. *#@ p < 0.05 ANOVA on ranks with Bonferroni post hoc test. ˆ% p < 0.001 ANOVA on ranks with Bonferroni post hoc test
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