The Studies On Brain Functional Features Of Mild Cognitive Impairment Based On RS-fMRI

Alzheimer’s disease(AD)is the most common dementia disease that characterized by cognitive deficits and behavioral disorders.AD severely disrupt the patient’s memory,reasoning,judgment and daily activities.Mild cognitive impairment(MCI)is a disease that have similar symptoms of AD,such as memory and other cognitive impairment,but not as serious as AD,and MCI has many different subtypes.One type of MCI(deteriorative MCI,MCI_D)will be converted to AD with a noticeable probability in the next 3-5 years.there are also some longitudinal data show that there is a certain proportion of MCI patients will become better(reversed MCI,MCI_R)in the next few years,or remain in the MCI state and the condition will not deteriorate further(stable MCI,MCI_S).The main purpose of this thesis is to study the brain activity patterns of MCI_D,MCI_R and MCI_S about the three groups of MCI patients,and then hope to further clarify the brain functional characteristics of MCI disease for the early diagnosis of MCI and prediction of the conversion from MCI to AD.In the first part of this thesis,based on the resting state-functional magnetic resonance imaging(RS-f MRI),the regional brain functional characteristics of three different types of MCI patients were analyzed by regional homogeneity(Re Ho)method.Compared with the normal control(NC),the results showed that the three groups of MCI sufferer showed significant difference of the regional coherence activities in the left inferior parietal lobule,right insula and right precuneus,furthermore,there existed significant difference among three MCI groups.The results suggest that there is a differentiation in these progressive MCI,which may provide reference for clinical researchers to manipulate active but distinctive interventions for MCI patients.In the second part of this thesis,the functional data of MCI patients with different types of MCI_D,MCI_R and MCI_S were analyzed by using the method of amplitude low-frequency fluctuation(ALFF)method and then respectively started statistical comparison with the NC.The results showed that there were significant difference of the ALFF imaging results in these different types of MCI patients.In the third part of this thesis,the RS-f MRI brain image analysis method of voxel-mirrored homotopic connectivity(VMHC)was used to study the cerebral hemisphere function connectivity of these progressive MCI patients,and explored whether there was an abnormality in the hemispheres functional coordination of the brain.Compared to the NC group,the results showed that: 1)MCI_R group presented decreased VMHC index in the middle temporal gyrus(MTG),middle frontal gyrus and inferior temporal gyrus(ITG);2)MCI_D group displayed less values in the precentral gyrus,fusiform gyrus,putamen and ITG;3)MCI_S group showed decreased connectivity in the ITG,MTG,precentral gyrus and rolandic operculum.It was speculates that the weaken connections may be related to the different conversion types of the MCI subjects.In the last part of the thesis,the degree centrality(DC)method based on voxel level was used to explore the changes of functional network connection properties of the whole brain and to observe the difference of different functional connections between different outcomes of MCI.DC findings suggest that there are significant differences in brain network connectivity between MCI patients with different outcomes.DC study of MCI provides a new perspective to understand the pathogenesis of MCI disease and to predict the transformation of MCI to AD.This thesis investigated the characteristics of functional activities of three progressive MCI groups from four different perspectives.The neural mechanism of MCI has been further understood by combining the different functional characteristics of brain regions presented by different methods.Simultaneously it also provides more reference for the doctor’s diagnosis.