Comparative Studies On Cerebral Cortical Structural In Patients With Major Depressive Disorder

Purposes: Previous structural neuroimaging studies have reported cortical structural abnormalities in widespread brain regions,with regard to different cortical indices(including cortical thickness,surface area and gyrification etc.).With the fact that the description of human cerebral cortex structure has become more detailed and in-depth,studies have found that different cortical indices provide distinct information about the cortical architecture as they appear to capture distinct evolutionary and cellular processes,and are differently affected by the genetic architecture and developmental trajectory.Considering these differences of each cortical index shown in both cellular processes and developmental trajectory,this study will be conducted in two levels: 1)at the regional level,the regional cortical folding abnormalities and corresponding alterations in resting-state functional connectivity in patients with major depressive disorder(MDD)was explored.2)at network level,the cortical structure covariance network was constructed by using multiple cortical indices at the same time.On one hand,the differences in topological properties of the structure covariance network between patients with MDD and healthy controls were explored,and on the other hand,in the patient group,the similarities and differences of structural covariance networks constructed from different cortical measurements will also be discussed,given that each cortical index has different features,we might be able to explore how the abnormal cortical structure is involved in the occurrence and development of depressive disorder.Methods: The alterations of cerebral cortical structural of patients with MDD were explored at the regional level and network level: 1)T1weighted structural imaging data and resting-state functional imaging data of 62 depressed patients and 61 healthy controls were collected.Firstly,the local gyrification index was calculated,and the differences in cortical folding of the whole cerebral cortex between the patients with MDD and healthy controls were explored.Secondly,the seed-based resting-state functional connectivity analysis was conducted to explore the corresponding functional connectivity alterations in brain regions with abnormal LGI;2)Structural image data of 76 first-episode patients with MDD and 66 healthy controls were collected.The cortical indices including cortical thickness,surface area and local gyrification index(LGI)were calculated.The morphological covariance networks were constructed by using the three cortical indices separately,and the topological properties of these group-level morphological covariance networks were analyzed using graph theoretical approaches.The results were mutual confirmed using two different atlantes(i.e.Destrieux Atlas and Desikan-Killiany Atlas).Besides,we also further explored whether patients with different clinical characteristics(including childhood trauma experiences,severity of depression,sex)would show differences in the topological characteristics of the cortical morphology covariance network.Results: 1)Comparing with healthy controls,patients with MDD showed significantly decreased LGI in the right fusiform gyrus(p<0.05,Monte Carlo Simulation Corrected).In the seed-based functional connectivity analysis,we found that compared with healthy controls,patients with MDD showed decreased functional connections between the right fusiform gyrus with sensorimotor areas(precentral and postcentral gyrus)(p<0.05,FDR corrected)and right superior temporal gyrus(p<0.05,FDR corrected).However,the association between depression severity and the structural and functional abnormalities was not detected;2)Topological differences between MDD group and healthy controls were restricted to the thickness-based network,with a significant decrease in global efficiency((p<0.05))but an increase in local efficiency of the left superior frontal gyrus(SFG)(p<0.005)and right paracentral lobule(p<0.005)in first-episode MDD.When we simulated targeted lesions affecting the most highly connected nodes,the thickness-based networks in first-episode MDD more rapidly disintegrated than those in HCs(p<0.05).Besides,MDD patients with severe childhood trauma experiences show a decreased global efficiency(p<0.05)in thicknessbased structural covariance network comparing to MDD patients with mild childhood trauma experiences.Conclusion: In conclusion,both regional-level and network-level abnormalities were observed in cerebral cortical structures of patients with MDD.At the regional level,the abnormalities in cerebral cortical folding were also accompanied by disruptions in resting-state functional connectivity.At the network level,the abnormalities were detected in both global and nodal level,and abnormalities at the global level of the covariance network are correlated with childhood traumatic experiences.The two studies discussed above provide a multi-perspectives description of the abnormalities in cortical structure in patients with MDD,these findings also promote our understanding of how the abnormal cortical structure is involved in the occurrence and development of MDD.