Study On Abnormal Functional Connections Of White Matter In Alzheimer’s Disease Based On Magnetic Resonance Imaging

Functional magnetic resonance imaging can use blood oxygenation-level-dependent signal to measure cerebral hemodynamic changes,so as to evaluate the neural activity between different brain regions.However,most of the functional magnetic resonance imaging studies focused on the level dependent signal of blood oxygen in gray matter,and rarely study reported the blood oxygenation-level-dependent signal in white matter.However,recent studies have shown that the blood oxygenation-level-dependent signal in white matter is not only noise,but also reflects the neural activity of brain.Alzheimer’s disease is a progressive neurodegenerative disease characterized by memory loss and cognitive impairment,with slow onset and mild early symptoms.And very mild cognitive impairment and mild cognitive impairment are two important disease states between normal aging and Alzheimer’s disease.Although very mild cognitive impairment and mild cognitive impairment do not seriously affect an individual’s ability to live independently,they may be a risk factor for cognitive impairment in older adults,and therefore need to be evaluated.The first study used the public OASIS-3 data set,using bilateral hippocampus as seed points,and obtained the functional connection between hippocampus and whole brain voxel of each subject.Perform a nonparametric one-way anova analysis to investigate abnormal functional connectivity in healthy controls,very mild cognitive impairment,and mild cognitive impairment groups.Further,fiber bundle tracing was performed to estimate whether abnormal functional connections corresponded to structural connection interruptions.The research results show that compared with the healthy controls,the functional connectivity of very mild cognitive impairment and mild cognitive impairment between the left hippocampus and left cerebellum Crus I,left inferior temporary gyrus,right cerebellum Crus II,right middle temporary gyrus is reduced,in the gray matter.And the functional connectivity between the right hippocampus and left cerebellum Ⅶb,right cerebellum Crus II are reduced.In the white matter,the functional connectivity between the left hippocampus and left insula WM,right temporary pole WM,right inferior frontal gyrus WM is reduced,and the functional connectivity between the right hippocampus and right frontal gyrus is reduced.In addition,the fiber bundles connecting the left hippocampus and the right temporal pole in the white matter showed an abnormal increase in the mean diffusion of mild cognitive impairment.This study proposes a new direction to explore the mechanisms of memory decline and pathophysiological mechanisms in the early stages of Alzheimer’s disease.In addition,the second study aims to analyze the topological properties of the white matter network in the early stages of Alzheimer’s disease using the methods of graph theory.Using public OASIS-3 data,the white matter functional network in the early stage of Alzheimer’s disease was constructed,and the topological properties of the functional network were explored using GRETNA 2.0 tool.The research results provide evidence from the perspective of the white matter functional network,indicating that the early stages of Alzheimer’s disease exhibit abnormal network topology characteristics,including reduced small world and assortativity,clustering coefficients and node local efficiency.The results indicate that the brain network connections in the early stages of Alzheimer’s disease are more dispersed,and the efficiency of network information transmission is also lower,with lower clustering coefficients and node local efficiency.These findings provide clues for the early diagnosis and treatment in Alzheimer’s disease.