Business School, University of Shanghai for Science and Technology, Shanghai, China.
Laboratory for Neurophysiology, Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, the Netherlands.
J Biol Rhythms. 2019 Oct;34(5):515-524. doi: 10.1177/0748730419861765. Epub 2019 Jul 18.
In mammals, an endogenous clock located in the suprachiasmatic nucleus (SCN) of the brain regulates the circadian rhythms of physiological and behavioral activities. The SCN is composed of about 20,000 neurons that are autonomous oscillators with nonidentical intrinsic periods ranging from 22 h to 28 h. These neurons are coupled through neurotransmitters and synchronized to form a network, which produces a robust circadian rhythm of a uniform period. The neurons, which are the nodes in the network, are known to be heterogeneous in their characteristics, which is reflected in different phenotypes and different functionality. This heterogeneous nature of the nodes of the network leads to the question as to whether the structure of the SCN network is assortative or disassortative. Thus far, the disassortativity of the SCN network has not been assessed and neither have its effects on the collective behaviors of the SCN neurons. In the present study, we build a directed SCN network composed of hundreds of neurons for a single slice using the method of transfer entropy, based on the experimental data. Then, we measured the synchronization degree as well as the disassortativity coefficient of the network structure (calculated by either the out-degrees or the in-degrees of the nodes) and found that the network of the SCN is a disassortative network. Furthermore, a positive relationship is observed between the synchronization degree and disassortativity of the network, which is confirmed by simulations of our modeling. Our finding suggests that the disassortativity of the network structure plays a role in the synchronization between SCN neurons; that is, the synchronization degree increases with the increase of the disassortativity, which implies that a more heterogeneous coupling in the network of the SCN is important for proper function of the SCN.
在哺乳动物中，位于大脑视交叉上核（SCN）的内源性时钟调节生理和行为活动的昼夜节律。SCN 由大约 20000 个神经元组成，这些神经元是具有非相同固有周期（范围从 22 小时到 28 小时）的自主振荡器。这些神经元通过神经递质耦合并同步形成网络，从而产生具有统一周期的强大昼夜节律。这些神经元是网络的节点，其特征具有异质性，这反映在不同的表型和不同的功能上。网络节点的这种异质性导致了一个问题，即 SCN 网络的结构是聚类的还是去聚类的。到目前为止，还没有评估 SCN 网络的去聚类性，也没有评估其对 SCN 神经元集体行为的影响。在本研究中，我们使用转移熵的方法，根据实验数据，为单个切片构建了一个由数百个神经元组成的有向 SCN 网络。然后，我们测量了网络结构的同步程度和去聚类系数（通过节点的出度或入度计算），发现 SCN 网络是一个去聚类网络。此外，我们观察到网络的同步程度与去聚类性之间存在正相关关系，这通过我们的建模模拟得到了证实。我们的发现表明，网络结构的去聚类性在 SCN 神经元之间的同步中起着作用；即，随着去聚类性的增加，同步程度增加，这意味着 SCN 网络中更异质的耦合对于 SCN 的正常功能很重要。
