Resting State Functional Magnetic Resonance Imaging Study In Remitted Late-life Depression With Mild Cognitive Impairment

Background:There were emotional disorder and cognitive impairment in a substantial proportion of late life depression(LLD).The comorbidity of depression and cognitive impairment has contributed to the acceleration of memory impairment.There may be an interactive relationship between remitted depression and cognitive impairment in the remitted LLD with mild cognitive impairment(MCI),which result in dysfunction of the whole brain-network and decline of cognitive function.However,little is known about the neural correlation of interaction between remitted depression and cognitive impairment and the effect of this interaction on the topological architecture of the whole-brain functional networks in remitted LLD with MCI.Objectives:To investigate topology of the whole-brain functional networks and interactive effects of remitted depression and MCI on whole brain function in remitted LLD.Furthermore,we assessed whether remitted depression-MCI interactions were associated with the changes in the topological organization of the whole-brain network and cognitive performance in remitted LLD.Methods:85 elderly participants(remitted LLD+MCI(n=13),remitted LLD(n=19),MCI(n=26),normal controls(n=27))were completed neuropsychological tests and resting-state functional magnetic resonance scanning.The whole-brain function network was constructed by thresholding correlation matrices of brain regions and brain network topological properties were analysed using graph theoretical methods.The main and interactive relationships of remitted depression and MCI were determined using fractional amplitude of low-frequence fluctuation(fALFF)as the metric of brain activity.Topological properties of brain network were compared by analysis of covariance(ANCOVA)after controlling for grey matter volume.To examine the group difference of fALFF map across of all subjects,2(remitted depression)× 2(MCI)ANCOVA was performed after controlling for grey matter volume.Pearson correlations and multiple linear regression were utilized to explore the relationship between the change in brain function and cognitive performance in remitted LLD.Results:Both remitted LLD showed disruption in functional segregation(decreased clustering coefficient and local efficiency)and integration measures(increased path length and decreased global efficiency),with remitted LLD and MCI comorbidity exhibited the greatest degree of changes in topological properties(P<0.05).While the main effects of remitted depression on brain activity were seen in left orbital frontal cortex,left putamen and left insula cortex,the main effects of MCI on brain activity were seen in the default mode network regions.The interactive effects of remitted depression and MCI on the fALFF value were seen in the left superior frontal gyrus,left middle frontal gyrus,left inferior parietal gyrus,left superior parietal gyrus,right parahippocampus(P<0.05,corrected with GRF).In brain regions with interactive effects,increased activity in right parahippocampus was associated with increased path length,decreased global and local efficiency and poor memory performance in remitted LLD(P<0.05).Conclusions:There were interactive effects of remitted depression-MCI on brain activity of frontal-parietal-limbic system in remitted LLD and MCI comorbidity who showed the greatest degree disruption in topological of brain function network.In brain regions with interactive effects,the abnormal activity of right parahippocampus associated with the change in topological properties and memory performance,suggesting that the remitted depression-MCI interaction contributed to dysfunction of the whole brain network and decline of cognition by the impact on activity of right parahippocampus.