A Resting-state Functional Magnetic Resonance Imaging Research On Amnestic Mild Cognitive Impairment

Background and Objective:Mild cognitive impairment(MCI) is referred to a declining stage of cognition which have the abnormality related to one's age and education but cannot be diagnosed by the criteria of dementia.It is now recognized as an intermediate stage between the normal aging and dementia, which has a high risk to develop into dementia.Early diagnosis and treatment of MCI offers possibilities for the aim of delaying or preventing the onset of dementia.Therefore,MCI has become a focus of the research for dementia. Resting-state fMRI refers to the functional MRI scan during the resting state in which the subject keep consciousness,closing one's eyes and without any systematic thinking.It is very suitable for the clinical research and has showed notable advantage for the diagnosis of MCI because it does not need the participant perform any task.Regional homogeneity(ReHo) combined with functional connectivity is a new method for the analysis of resting state data, which can avoid subjective bias of researcher oneself and exhibiting great predominance in application.In this dissertation,we examined male amnestic MCI and normal control using neuropsychological scales and resting state fMRI intending to find the differences of brain functional activity between them in resting state and to study the relationship between these differences with cognition.In addition,an approach of ReHo combined with functional connectivity was applied.We expect to provide some evidences for the earlier diagnosis of dementia.Material and Methods:Sixteen retired army officers in Beijing with normal cognitive function together with fifteen aMCI Patients were included by neuropsychological test.The resting-state fMRI was scanned by the GE-Hc-3.0T MRI.All the data were used for the regional homogeneity and functional connectivity analysis,and the differences of activity and functional connectivity in the resting state was compared.Results:Compared with NC,the episodic and semantic memory both were impaired in aMCI.Moreover,aMCI also showed significant decrease of ReHo in some regions of left temporal lobe,hippocampus,occipital lobe and increase in some regions of right frontal lobe,occipital lobe and left occipital lobe,temporal lobe,frontal lobe,which are relevant to the scores of cognitive assessments.We also found reduced functional connectivity between the left Parahippocampal gyrus and bilateral temporal lobe,PCC/PCu in aMCI patients whereas increased connectivity between the left hippocampus and left frontal lobe,parietal lobe and medial cingulate gyrus.Analysis of the whole brain showed decreased connectivity between the frontal-parietal,temporal-insula and temporal-occipital whereas increased connectivity within the left frontal lobe and between the temporal-occipital,thalamus-temporal.Conclusions:In contrast with NC,aMCI may have abnormality of function and functional connectivity in the brain at resting state,which may be relevant to cognitive decline.The impairment of MTL could be a characteristic marker to distinguish aMCI from healthy aging in the resting-state.Moreover,the increased ReHo and functional connectivity changes would be some type of compensation for damage to the medial temporal regions and limbic structures.Resting-state fMRI combined with neuropsychological assessments are worth considering for application in the general clinical practice and may provide important evidence for the earlier diagnosis of dementia.