| Part I: Altered Fractional Amplitude of Low-Frequency Fluctuation in Patients with VCI Based on Resting-state Functional MRIObjective: To investigate the baseline brain activity in patients with vascular cognitive impairment(VCI) by fractional amplitude of low-frequency fluctuation(f ALFF) based on resting-state functional MRI(rs-f MRI).Methods: Forty-nine patients with subcortical ischemic vascular diseases(SIVD) were included in this study. The whole brain f ALFF values of patients with SIVD with no cognition impairment(NCI), SIVD with cognition impairment no dementia(VCIND) and vascular dementia(VD)were collected and compared. The correlations between the whole brain f ALFF values with the scores of Montreal Cognitive Assessment(Mo CA)of VCI patients were assessed.Results: In resting-state, when compared to NCI group, VCI group showed decreased f ALFF in the left angle gyrus(AG), right middle frontal gyrus(MFG), right parahippocampal gyrus(PHG), right lingualis gyrus(LG) and right lenticular nucleus(LN), but increased in the bilateral superior frontal gyrus(SFG). Compared with NCI group,the f ALFF values decreased in the left orbitofrontal gyrus(OFG) but increased in the bilateral MFG in VCIND group. f ALFF values in the left putamen, left MFG, left inferior parietal lobule(IPL) and right MFG/precentral gyrus(PRG) of VD group were lower than those of VCIND group.The VD patients showed lower f ALFF values in the left OFG, left putamen, left transverse temporal gyrus(TTG) and right thalamus than those of NCI patients. In addition, the f ALFF values in the left putamen and left thalamus of VCI patients had significantly positive correlations with the scores of Mo CA.Conclusions: f ALFF values of VCI patients had significantly changed.And the decreased f ALFF values in the left putamen and thalamus may associate with cognitive disfunction. The increased f ALFF in the bilateral MFG may be seemed as a transient compensatory mechanism and can be disappeared with the severity of the disease.Part II: Changed Amplitude of Low-Frequency Fluctuation in Patients with VCI Based on Resting-state Functional MRI in Different Frequency Bands.Objective: To investigate the amplitude of low-frequency fluctuations(ALFF) in multiple frequency bands of patients with VCI during rest.Methods: The ALFF in 20 patients of SIVD with clinical cognitive impairment(VCI) and 20 age-, sex- and education level-matched patients with SIVD but without cognitive impairment(NCI) in five different frequency bands(slow-6: 0-0.01 Hz, slow-5: 0.01-0.027 Hz, slow-4:0.027-0.073 Hz, slow-3: 0.073-0.198 Hz and slow-2: 0.198-0.25Hz) were measured. Comparisons were performed between VCI and NCI in slow-4and slow-5, respectively. After correction for age, gender and education level, spearman correlations between the mean ALFF in the ROIs(at the peak MNI with a radius of 4mm) in the brain areas showing main effect for group and interaction between frequency band and group(G×F) with the scores of MMSE 、 Mo CA 、 MEMORY-Z 、 LANGUAGE-Z 、ATT-EXE-Z、Visual Spacial-Z(VS-Z) and Z-score of VCI patients were performed in slow-4 and slow-5(p<0.05).Results: Main effect for frequency bands were significantly found almost around the whole brain. Significant main effect for group were found in the right cerebellum posterior lobule, right inferior frontal gyrus(IFG),left parahippocampal gyrus(PHG), left insular and right inferior parietal lobule(IPL). G×F were found in the right cerebellum posterior lobule,left PHG, right IFG, bilateral inferior temporal gyrus(ITG), left supply motor area(SMA), left precentral gyrus(PRG) and postcentral gyrus(POG), left orbit frontal gyrus(OFG). Some brain areas not only showed significant main effect for group but also G×F such as the right cerebellum posterior lobule and the left PHG, that is the ALFF of VCI was constantly lower than that of controls in the right cerebellum posterior lobule, while higher than that of controls in the left PHG in the five frequency bands. When compared to NCI group, VCI showed a reduction of ALFF in the bilateral cerebellum posterior lobe in both slow-5 and slow-4 bands, and a elevation of ALFF in the right PCu and right supramaginal gyrus(SMG) in slow-4 and slow-5 respectively. There was significant positive correlation between the ALFF values in the left insular and the scores of MEMORY-Z(r=0.505, p=0.027). There were negative correlations between the scores of VS-Z and the ALFF values in the PHG(r=-0.521, p=0.022), and ALFF in the OFG(r=-0.469, p=0.043).The ALFF values in the IPL correlated negatively with the scores of ATT-EXE-Z(r=-0.526, p=0.021). There was on correlation between the ALFF values of the above ROIs with the cognitive performance of VCI patients in slow-4. Negative correlation suggested a reduction in ALFF with higher scores of the corresponding scale, and positive correlation meant a elevation in ALFF with higher scores of the corresponding scale.Conclusions: ALFF of VCI or NCI was found changed widely in the five frequency bands. The ALFF of the corresponding brain regions changed not only due to the diseases but also the different frequent bands.However, the unchanged ALFF in the right cerebellum posterior lobule and left PHG may be as a new biological characteristic of VCI. Our results imply that the left OFG and right IPL in the slow-5 could be more sensitive in detecting the abnormalities of spontaneous brain activity of VCI patients than in slow-4 and may help contribute to the understanding of the pathogenesis of VCI.Part III: Altered FC and VMHC in Patients with VCI Based on rs-f MRI.Objective: In the present study, the ROI-based posterior cingulate cortex(PCC) functional connectivity(FC) analysis and a newly developed voxel-mirrored homotopic connectivity(VMHC) method were performed to investigate the cortical and interhemispheric functional correlation of the whole brain in patients with VCI.Methods: Twenty-nine SIVD with cognitive impairment(VCI) patients and 23 age-, gender-, and education level-matched SIVD with no cognition impairment(NCI) underwent rs-f MRI scans. An automated FC and VMHC approaches were used to analyze the differences between the two groups. Spearman correlations of mean FC or VMHC of the ROIs(at the peak MNI with a radius of 4mm) in the brain areas survived differently between the two groups with the scores of MMSE、Mo CA、MEMORY-Z、LANGUAGE-Z、ATT-EXE-Z、VS-Z and Z-score of VCI patients were performed respectively, with age, gender and educational level as covariations(p<0.05).Results: VCI group showed increased FC in the left middle temporal gyrus(MTG) and bilateral inferior frontal gyrus(IFG), meanwhile decreased FC in the left thalamus and right middle cingulate cortex(MCC) when compared to NCI group. There was no significont correlations between the mean FC of the above ROIs and the scores of the nuropsychological tests of VCI patients. VCI patients exhibited lower VMHC than controls in bilateral thalamus and putamen, bilateral PRG/POG, cerebral cortex of calcarine sulcus/LG, PCu/superior occipital gyrus(SOG). No regions showed greater VMHC in the patient group than control group. The VMHC in the putamen correlated with the scores of MEMORY-Z(r=0.569, p=0.002) and scores of ATT-EXE-Z(r=0.385,p=0.047). The VMHC in the PRG correlated with the scores of MEMORY-Z(r=0.410, p=0.034), the VMHC in the POG correlated with the scores of ATT-EXE-Z(r=0.389, p=0.045), and the VMHC in the cerebral cortex of calcarine sulcus/LG correlated with Z-score(r=0.458,p=0.014). Positive correlation meant a reduction of VMHC with higher scores of the corresponding scales.Conclusions: The FC and VMHC of VCI patients had changed abnormally. Subcortical white matter lesions with directly and indirectly interrupt connectivity of fiber tracts across the cerebral white matter not only influenced the cortical FC but also the VMHC, which may one of the pathogenesises of VCI. And the decreased VMHC in the putamen,PRG/POG and the cerebral cortex of calcarine sulcus/LG may help contribute to the understanding of the pathogenesis of VCI. |
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