Segregation of the brain into gray and white matter: a design minimizing conduction delays.
Segregation of the brain into gray and white matter: a design minimizing conduction delays.
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DOI：
10.1371/journal.pcbi.0010078
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发表时间：
2005-12
影响因子：
4.3
通讯作者：
Chklovskii, Dmitri B
中科院分区：
文献类型：
--
作者：
Wen, Quan;Chklovskii, Dmitri B
脊椎动物解剖学的一个普遍特征是大脑分为白色和灰质。假设进化使大脑功能最大化，那么这种隔离的原因是什么呢？为了回答这个问题，我们认为大脑功能需要高互连性和短传导延迟。基于这一假设，我们通过比较不同的候选设计来寻找最佳的大脑结构。我们发现，最佳设计取决于神经元的数量，神经元间的连接，和轴突直径。特别是，连接神经元和许多快速轴突的需要驱使大脑分离成白色和灰质。这些结果为脊椎动物脑的不同区域的结构提供了可能的解释，例如哺乳动物的新皮层和新纹状体，鸟类的端脑和脊髓。脊椎动物的大脑通常包含两种组织：灰质和白色物质。灰质包含由树突和大多数无髓鞘的局部轴突连接的局部神经元网络。白色物质包含长距离轴突，这些轴突通常通过有髓鞘的轴突实现全球通信。将大脑分为白色和灰质而不是将它们混合在一起，这在进化上有什么好处？在这项研究中，作者假设大脑功能受益于高突触连接和短传导延迟信号从一个神经元索马到达另一个所需的时间。利用这一假设，他们定量地表明，许多快速、长距离轴突的存在促使大脑分离成灰色和白色物质。该理论不仅为大脑皮层、新纹状体和脊髓等脑区的结构提供了可能的解释，而且还做出了一些可检验的预测，如皮层厚度的尺度估计。
A ubiquitous feature of the vertebrate anatomy is the segregation of the brain into white and gray matter. Assuming that evolution maximized brain functionality, what is the reason for such segregation? To answer this question, we posit that brain functionality requires high interconnectivity and short conduction delays. Based on this assumption we searched for the optimal brain architecture by comparing different candidate designs. We found that the optimal design depends on the number of neurons, interneuronal connectivity, and axon diameter. In particular, the requirement to connect neurons with many fast axons drives the segregation of the brain into white and gray matter. These results provide a possible explanation for the structure of various regions of the vertebrate brain, such as the mammalian neocortex and neostriatum, the avian telencephalon, and the spinal cord. Vertebrate brains generally contain two kinds of tissue: gray matter and white matter. Gray matter contains local networks of neurons that are wired by dendrites and mostly nonmyelinated local axons. White matter contains long-range axons that implement global communication via often myelinated axons. What is the evolutionary advantage of segregating the brain into white and gray matter rather than intermixing them? In this study, the authors postulate that brain functionality benefits from high synaptic connectivity and short conduction delays—the time required for a signal from one neuron soma to reach another. Using this postulate, they show quantitatively that the existence of many fast, long-range axons drives the segregation of the brain into gray and white matter. The theory not only provides a possible explanation for the structure of various brain regions such as cerebral cortex, neostriatum, and spinal cord, but also makes several testable predictions such as the scaling estimate of the cortical thickness.