Structural and Functional Connectivity of Default Mode Network underlying the Cognitive Impairment in Late-onset Depression.

Yingying Yin,Yuqun Zhang,Yingying Yue,Xiaofu He,Yijun Liu,Zhenghua Hou,Mingze Xu,Yuxiu Sui,Wenhao Jiang,Yonggui Yuan,Zhi Liu,Xiaopeng Song

doi:10.1038/srep37617

Abstract

To identify the association between the functional and structural changes of default mode network (DMN) underlying the cognitive impairment in Late-onset depression (LOD), 32 LOD patients and 39 normal controls were recruited and underwent resting-state fMRI, DTI scans, and cognitive assessments. Seed-based correlation analysis was conducted to explore the functional connectivity (FC) of the DMN. Deterministic tractography between FC-impaired regions was performed to examine the structural connectivity (SC). Partial correlation analyses were employed to evaluate the cognitive association of those altered FC and SC. Compared with controls, LOD patients showed decreased FC between DMN and the cingulo-opercular network (CON), as well as the thalamus. Decreased FA and increased RD of these fiber tracts connecting DMN with CON were found in LOD patient. The DMN-CON FC and the FA, RD of the fiber tracts were both significantly correlated with the cognitive performance. Therefore, the cognitive impairment in LOD might be associated with the decreased FC between the DMN and the CON, which probably resulted from the demyelination of the white matter.

Highlights

Since the functional magnetic resonance imaging was applied to human brain research, the sophisticated functions of various brain regions have been fully studied
The most important finding of this work is that Late-onset depression (LOD) patients showed decreased functional connectivity (FC), fractional anisotropy (FA) and increased radial diffusivity (RD) between posterior cingulate cortex (PCC)/Pcu and dACC but no significant change of axial diffusivity (AD) and fiber number (FN), indicating that the posterior cingulate cortex/precuneus (PCC/Pcu)-dACC FC disruption may be resulted from the demyelination rather than degeneration or necrosis of the white matter
The FC and fasciculi’s FA between PCC/Pcu and dACC were both positively correlated with the working memory as well as executive speed, while negative correlation was found between these two cognitive scores and the RD of PCC/Pcu-dACC white matter tracts, which further provided evidences for the pathomechanism of the cognitive impairment in LOD

Summary

Materials and Methods

It was chosen because it could reliably predict the location of areas exhibiting reduced activity in the human brain, as measured with either PET or fMRI, during the performance of a variety of cognitive tasks It has been widely used as the ROI in the DMN-analyzing studies[37,38]. The FA, MD, AD, RD and FN of the white matter tracts between the LOD patients and the NCs were compared through a general linear model by SPSS 18.0 software, taking age, education and grey matter volume of the ROIs as the covariates. Partial correlation analyses using SPSS 18.0 software were employed to examine relationships between FC, FA, MD, AD, RD, FN and cognitive scores, controlling the effects of age and education

Results

Discussion

Conclusion

Limitations