An Aging-related Study On The Characteristics Of The Dynamic Functional Network Based On Resting State FMRI

The brain cognitive function will decline with age,which will easily lead to various neurological disorders.Currently,the resting state functional magnetic resonance imaging(RS-fMRI)technology has been widely used to study the brain aging problem.Increasing evidence suggests that brain’s cognitive decline is associated with the change in the intensity of functional connectivity between different brain regions.However,previous researches were mostly conducted under the assumption that functional connectivity among brain regions is constant in time and space.In recent years,many studies have proved that functional connectivity(FC)is dynamic over time.No study has been reported about the abnormity of dynamic functional connectivity network with brain aging.Datasets of 36 young subjects and 32 elderly subjects were selected from the RS-fMRI public database.This study constructed the dynamic functional connectivity network using sliding window and extracted the characteristics of dynamic functional connectivity.From the perspective of the dynamic functional connectivity,aging-related dynamic functional connectivity network anomalies were studied.In the study,firstly,by comparing dynamic functional connectivity variability and spectral characteristics in different window length,the network with 24 TR time window was selected.The surrogate data were then constructed using the phase randomization method.By comparing the time-domain characteristic of the surrogate data and the raw data,the nonlinear nature of the dynamic functional connectivity within network was proved.The functional connectivity variability were compared between the younger and the elderly groups.Results showed that functional connectivity variability between networks in elderly group was significantly less than that in the younger group.It suggests that the fluctuation of connectivity between networks in the elder group is reduced.Result also showed that functional connectivity within networks has no significant difference.The within group analysis also showed that the connectivity variability of superior cognitive function networks was significantly higher than that of inferior cognitive networks.Finally,normalized energy of two groups was extracted based on wavelet packet decomposition method.The between-group difference analysis showed that there was a significant difference of normalized energy in each frequency band between young and elderly groups.In lower frequency band,normalized energy between networks in the young group was significantly less than that in the elderly group;in the high band,however,normalized energy between networks in the young group was significantly greater than that in the elderly group.This indicates that the spontaneous fluctuation energy of functional connectivity in the elderly is transferred to the low frequency.The results of this study indicate that brain aging will affect the intra-network and inter-network features of time and frequency domains in resting state brain.The dynamic characteristics of functional connectivity as the low frequency oscillation signal are closely related to neural activity status.In conclusion,the study provides new methods and ideas for age-related changes in functional connectivity and provides some theoretical basis for further research to understand the physiological significance of the dynamic functional connectivity.