Dynamic Connectivity And Evolution Of Functional Networks In Early Parkinson’s Disease With Mild Cognitive Impairment

Clinically,early Parkinson’s disease with mild cognitive impairment(ePD-MCI)cannot be accurately judged by cognitive assessment scale.Similarly,neuroimaging is difficult to directly reflect mild cognitive deterioration in early Parkinson’s disease(ePD)patients,but brain function has changed at this stage.Studies have confirmed that the change of brain functional networks’ characteristics in time domain is related to cognitive level,and the energy of EEG signal in certain rhythm also reflects the cognitive decline in ePD patients.However,it is not clear whether there are representative abnormalities in the ePD-MCI functional network dynamic of different rhythms and the potential factors causing corresponding abnormalities.In this thesis,we construct the dynamic brain functional networks,characterize the dynamic functional networks’ characteristics of different rhythms in ePD-MCI and early Parkinson’s disease without mild cognitive impairment patients,establish its relationship with the cognitive level in ePD patients,and identify the bands with obvious abnormalities.At the same time,the brain networks in the specific band are decomposed to analyze the reconstruction process of functional networks,and to characterize the dynamic characteristics of inherent patterns in the reconstruction process,so as to reveal the potential factors of network dynamic anomalies.Firstly,dynamic brain functional networks are constructed based on adaptive sliding windows,and the stability of functional networks in the process of dynamic evolution is described by calculating the fluctuation of functional connectivity and the similarity between dynamic networks.It is found that there is a significant negative correlation between the stability and cognitive level in the dynamic evolution of the brain functional networks of the alpha band,and a significant positive correlation between the stability and cognitive level in the gamma band,and the abnormal dynamic characteristics of the functional network in ePD-MCI patients are more significant in these two bands.Secondly,in quest of the potential factors for significant abnormalities of the dynamic characteristics of the functional network in the alpha and gamma bands,the inherent patterns of the functional network in ePD patients are extracted,and the dynamic characteristics of the expression intensity of the inherent patterns during the reconstruction process are analyzed.The results show that there is a significant negative correlation between the fluctuation of the inherent patterns’ expression intensity and the stability of network state transition,suggesting that the change of expression intensity in ePD-MCI patients during the reconstruction is a potential factor leading to the abnormal network state transition.Finally,by analyzing the expression intensity of inherent patterns of functional network in ePD-MCI patients during reconstruction,it is found that in the alpha and gamma bands,the parietal-temporal lobe interaction with occipital lobe is generally reduced,while the interaction with frontal lobe is increased.These results confirm that the altered interaction pattern between brain regions is one of the reasons for abnormal brain network reconstruction in ePD-MCI patients.In this thesis,we find the dynamics characteristics of brain networks that can indicate the cognitive level of ePD patients,and reveal the potential factors leading to the abnormal dynamics process of brain network in ePD-MCI patients,which provide the auxiliary information for clinical exploration of the brain pathological mechanism in ePD-MCI and the discrimination of this disease.