The Structural And Functional Magnetic Resonance Imaging Study Of Alzheimer's Disease

Objective:To study the abnormal change of hippocampal structure and functional connectivity in patients with Alzheimer's disease,we employed the structural and functional magnetic resonance imaging technique(sMRI and fMRI).Through comparing the differences in hippocampal volume and resting state brain functional connectivity between the subjects of cognitively normal elderly and AD patients,so as to provide the evidences for the early diagnosis of AD.Methods:Data used in this paper were randomly selected from the Alzheimer's disease Neuroimaging Initiative(ADNI)database.The total number of the subjects is 47.Then MoCA,MMSE,and CDR scores,high resolution sagittal T1-MPRAGE structural MRI images and resting state functional MRI images were obtained.According to the diagnostic criteria of AD,the subjects are divided into two groups: cognitively normal elderly group(CN)with 21 subjects(12 males and 9females),AD group with 26 subjects(13 males and 13 females).The TrackVis software was used to measure and process the structual MRI images obtained,then the hippocampal volume of every subject in the two groups was obtained.The functional connectivity technology based on seeds was used to process the rs-fMRI images obtained,then the whole brain functional connection map based on the hippocampus were obtained,including the functional connection map between the right hippocampus and the same side posterior cingulate cortex,and the functional connection map between the left hippocampus and the same side posterior cingulate cortex.Statistical analysis and correlation analysis were performed for the above parameters.Results:1.Eliminating the patients having poor image quality and serious motion artifacts,23 AD patients(11 males and 12 females)and 16 age-and sex-matched CN subjects(7 males and 9 females)were finally enrolled.Compared with CN group,there was no statistical difference between AD and CN group in general condition(P>0.05).There was remarkable statistical difference between AD group and CN group in score of clinical scale(P<0.05): the score of MMSE and MoCA in AD group was significantly lower than that in CN group,and the CDR score in AD group was significantly greater than that in CN group.2.There was remarkable statistical difference between AD and CN group in hippocampal volume(P<0.01),the hippocampal volume of AD group was significantly smaller than CN group.There was positively correlation between hippocampal volume and MMSE and MoCA score in AD group.3.Compared with CN group,in resting state,the functional connections between the hippocampus cortex and several cerebral areas was decreased in AD group,the difference was significant(P < 0.001).The functional connection between the right hippocampus and the same side posterior cingulate cortex is different in AD and CN group,there was remarkable statistical difference in two groups(P < 0.001).While there was no statistical difference for the functional connections between the left hippocampus and the same side posterior cingulate cortex in AD and CN group.Conclusions:1.The AD patients have dysfunction in memory and cognitive function.2.The hippocampal volume of the AD patients was decreased,and the structural abnormality may be related to cognitive dysfunction.3.In resting state,the functional connection between the hippocampus cortex and several cerebral areas(including the functional connection between hippocampus and posterior cingulate cortex)was abnormal in AD patients,and the connection strength is decreased,especially the functional connection between right hippocampus and MPFC?vACC?PCC was decreased,which showed right asymmetry,the abnormity may be associated with cognitive decline.We employed sMRI and fMRI to study the abnormal change of hippocampal anatomical structure and function in AD patients.It was expected to provide a reliable imaging basis for early diagnosis of AD.