An Resting-state FMRI Study Of Dynamic Functional Networks In Normal Aging

More and more evidence indicated that healthy aging is accompanied by declined cognitive function.Now,the studies of functional magnetic resonance imaging(fMRI)have been illustrated age-related cognitive decline is associated with the functional connectivity(FC)strength.Based on resting-state fMRI,studies showed the aging has an influence on the default mode network(DMN)and dorsal attention network(DAN),which are linked with the attention,memory and executive functions.In addition,the abnormalities had been found in salience network and motor network in the older adults.Although many FC studies supposed that the relationships between the signals of brain regions are constant throughout the scanning,recent studies suggested that the brain doesn't keep at only one state,and thus the potential effect of temporal variability should be considered.However,the related research in dynamic FC with aging is lacking.Therefore,exploring the differences in dynamic FC between the older adults and younger controls can provide a new direction for understanding the aging mechanism.In the present study,we used the sliding-windows method to investigate the dynamic FC in healthy aging.Thirty-four healthy older adults were recruited in the current study.The fMRI data and cognitive scales scores were collected at baseline and after two years(baseline group and follow-up group).In addition,thirty-four younger adults were also recruited as the control group.Firstly,an FC analysis was used to calculate the stable and dynamic FC for all participates within three core network(default mode network,salience network,central executive network).Statistical analysis was used to compare differences among the groups.Results showed that the older adults had abnormal stable FC on some brain regions related to attention and motor compared with the younger controls.And older adults exhibited higher dynamic FC variability in some brain regions related to attention,motor and visual.The follow-up group has no differences with the baseline group.These results indicated the aging might alter the FC,and increased variability within networks of older adults may be due to the out of coupling in older adults.Furthermore,to explore the functional connectivity of networks,the independent components analysis(ICA)was carried out to extract resting-state networks,and then sliding-window correlation approach was employed to obtain the dynamic functional network pattern.To study the abnormality of dynamic functional network connectivity,the properties of dynamic functional connectivity and functional state connectivity also be calculated.In our study,the abnormal stable connectivity was found in the elderly group,and we also discovered the variability of older adults in dynamic functional network connectivity was significantly lower than the younger controls,indicating the lower flexibility of internetwork connectivity in the older group.When during the high variability state,the differences between elderly and young people were mainly on the interactions between the senior network and other networks,and there are significant differences between the primary network and other networks in the low variability state.This may be a manifestation of the functional reorganization of the elderly group.This study used two methods to investigate the aging-related FC.Results suggested that the aging might affect the dynamic characteristics.In summary,this study provided a new direction for exploring degenerative brain diseases and made us to further understand the physiological mechanism of aging.