大脑老化对大规模皮层网络拓扑结构的影响

Influence of Brain Ageing on Topological Patterns of Large-Scale Cortical Networks

随着世界范围内老年人口寿命的增加，人口老龄化已成为越来越严重的社会问题。大脑老化会导致记忆、执行功能、注意力、运动及感觉器官等功能的衰退，但不同个体和不同脑区间的网络变化规律和机制还不是特别清楚。在这里，我们通过对75个健康受试者（50~70岁）的T1磁共振影像进行皮层厚度测量，来构建大规模的脑结构网络。大脑网络通过对68个脑区的皮层厚度的相关矩阵阈值化来进行构建，并运用图论方法进行分析。结果显示，大脑结构网络的小世界特性与hub节点在不同年龄段存在一定差异，并且这种变化规律并不是一个线性关系。这些网络特性随年龄而变化的基本机制目前尚不清楚，但我们认为这可能是认知储备对大脑萎缩所造成的网络效率下降的一种补偿。对于大脑皮层网络拓扑结构的研究可以帮助我们更好地认识大脑的老化规律及认知储备对认知衰退的补偿作用。

As life span increases worldwide, ageing population has become more of a social strain. Aging causes declining in memory, executive function, attention, motor function, vision, hearingetc. However, how brain networks differ among individuals and across brain regions remain unclear. In this paper, cortical thickness measurement was used in T1 weighted MRI （Magnetic Resonance Imaging） of 75 healthy volunteers to investigate the large-scale structural brain networks. Brain networks were constructed by thresholding cortical thickness correlation matrices of 68 regions and analyzed using graph theoretical approaches. All age groups fully preserved the small-world architecture and organization. For different age groups, the characteristics of small-world networks exhibited different patterns, and distribution of network hubs altered, suggesting a reorganization of cortical thickness correlation networks. The underlying mechanisms of changing network properties are still unclear. However, authors thought that it might be caused by neural network compensation from cognitive reserve. Study of the cortical network topology can help us to have a better understanding of the brain aging and how cognitive reserve compensates the declining cognition.