Brain Network Research Of Mild Cognitive Impairment Based On FMRI

Mild cognitive impairment(MCI)is considered to be a state between dementia and healthy state of aged people.It is characterized by impairments of memory and cognitive,but the patients who suffer with MCI can take care of themselves in daily life.In recent years,the physiological mechanism of MCI has been studied by the neuroimaging technology,but it is still need further study.We used functional MRI(f MRI)to study the MCI patients from the perspective of brain network in order to better understand the pathological mechanism of MCI.The first part of the present research we used resting-state functional MRI(RS-f MRI)to study the abnormal function of resting state networks(RSNs)in amnestic MCI(a MCI)patients.We utilized the amplitude of low-frequency fluctuation(ALFF)to find the abnormal RSNs of a MCI patients,and we explored the functional connectivity within RSNs and between RSNs.The results suggested that 1)the abnormal RSNs included the default mode network(DMN),sensorimotor network(SMN),visual network(VN)and limbic system;2)the abnormal functional connectivity existed in the intra-networks and internetworks.These finding showed the functional networks involved in cognition such as episodic memory,visual cognition and sensorimotor in a MCI patients were altered,and provided a new perspective in understanding the important subtype of a MCI.The second part we explored the changes in topology attributes in the gray matter networks of MCI(including subtypes)based on functional MRI and structural MRI.The subtypes of MCI were reversed MCI(r MCI),stable MCI(s MCI)and worsening MCI(w MCI).We used graph theory to explore the topological property in the gray matter networks of MCI(functional networks and structural networks),including small world properties and node centrality.The results suggested that 1)the grey matter networks(functional network and structural network)of all the groups have small world properties and the topological changes occurred in the network of the patients with MCI(including their subtypes);2)the network efficiency of MCI patients decreased significantly when compared with normal control;3)there was no regularity among the network properties of the three MCI subtypes;4)the node centrality of hippocampus,cingulate cortex and superior temporal gyrus occurred abnormal in MCI patients.These results indicated that the grey matter networks(including functional network and structural network)of patients with MCI have small world property,and the network efficiency were decreased significantly,but the network efficiency of the subtypes of MCI were not consistent with the clinical information,therefore it is necessary to further study the physiological mechanism of MCI subtypes.The third part we explored the changes in topology attributes in the white matter networks of MCI(including subtypes)based on diffusion tensor imaging(DTI).The white matter network of brain was constructed by fiber tracking imaging technology,and the topological properties of networks were analyzed by graph theory,including small world and network efficiency.The results suggested that 1)the white matter networks of all the groups have small world properties and the network efficiency of patients with MCI(including their subtypes)patients was changed when compared with control group;2)the network efficiency of MCI patients decreased significantly;3)there was also no regularity among the network properties of the three MCI subtypes.These results indicated that the white matter networks also have small world property,and the network efficiency of MCI patients were decreased significantly,but the network efficiency of the subtypes of MCI were not consistent with the clinical information.In this paper,we explored the changes of MCI brain network from local and global networks.We found that the networks and brain regions of MCI patients involved in cognition and memory were altered,and the efficiency of gray matter and white matter network was significantly decreased.However,there was no regularity among the network properties of the three MCI subtypes,and it is necessary to further study the physiological mechanism of MCI subtypes.