Department of Clinical Neurophysiology, VU University Medical Center, Amsterdam, The Netherlands.
Hum Brain Mapp. 2011 Mar;32(3):413-25. doi: 10.1002/hbm.21030.
During childhood, brain structure and function changes substantially. Recently, graph theory has been introduced to model connectivity in the brain. Small-world networks, such as the brain, combine optimal properties of both ordered and random networks, i.e., high clustering and short path lengths. We used graph theoretical concepts to examine changes in functional brain networks during normal development in young children. Resting-state eyes-closed electroencephalography (EEG) was recorded (14 channels) from 227 children twice at 5 and 7 years of age. Synchronization likelihood (SL) was calculated in three different frequency bands and between each pair of electrodes to obtain SL-weighted graphs. Mean normalized clustering index, average path length and weight dispersion were calculated to characterize network organization. Repeated measures analysis of variance tested for time and gender effects. For all frequency bands mean SL decreased from 5 to 7 years. Clustering coefficient increased in the alpha band. Path length increased in all frequency bands. Mean normalized weight dispersion decreased in beta band. Girls showed higher synchronization for all frequency bands and a higher mean clustering in alpha and beta bands. The overall decrease in functional connectivity (SL) might reflect pruning of unused synapses and preservation of strong connections resulting in more cost-effective networks. Accordingly, we found increases in average clustering and path length and decreased weight dispersion indicating that normal brain maturation is characterized by a shift from random to more organized small-world functional networks. This developmental process is influenced by gender differences early in development.
在儿童时期，大脑结构和功能会发生重大变化。最近，图论已被引入到大脑连接的建模中。像大脑这样的小世界网络结合了有序和随机网络的最佳特性，即高聚类和短路径长度。我们使用图论概念来研究正常发育过程中儿童大脑功能网络的变化。对 227 名儿童在 5 岁和 7 岁时两次进行了闭眼静息态脑电图（EEG）（14 个通道）记录。在三个不同的频带和每个电极对之间计算了同步似然（SL），以获得 SL 加权图。计算平均归一化聚类指数、平均路径长度和权重分散度来表征网络组织。重复测量方差分析测试了时间和性别效应。对于所有频带，从 5 岁到 7 岁，平均 SL 降低。α 频带的聚类系数增加。所有频带的路径长度都增加。β 频带的平均归一化权重分散度降低。所有频带的女孩同步性更高，α 和 β 频带的平均聚类更高。功能连接（SL）的整体下降可能反映了未使用突触的修剪和强连接的保留，从而导致更具成本效益的网络。因此，我们发现平均聚类和路径长度增加，权重分散度降低，表明正常大脑成熟的特征是从随机到更有组织的小世界功能网络的转变。这个发育过程受到发育早期性别差异的影响。
