Fujii Masashi, Ohashi Kaoru, Karasawa Yasuaki, Hikichi Minori, Kuroda Shinya
Department of Biological Sciences, University of Tokyo, Bukyo-ku, Tokyo, Japan; Molecular Genetics Research Laboratory, Graduate School of Sciences, University of Tokyo, Bukyo-ku, Tokyo, Japan.
Department of Biological Sciences, University of Tokyo, Bukyo-ku, Tokyo, Japan.
Biophys J. 2017 Feb 28;112(4):813-826. doi: 10.1016/j.bpj.2016.12.043.
Why is the spine of a neuron so small that it can contain only small numbers of molecules and reactions inevitably become stochastic? We previously showed that, despite such noisy conditions, the spine exhibits robust, sensitive, and efficient features of information transfer using the probability of Ca increase; however, the mechanisms are unknown. In this study, we show that the small volume effect enables robust, sensitive, and efficient information transfer in the spine volume, but not in the cell volume. In the spine volume, the intrinsic noise in reactions becomes larger than the extrinsic noise of input, resulting in robust information transfer despite input fluctuation. In the spine volume, stochasticity makes the Ca increase occur with a lower intensity of input, causing higher sensitivity to lower intensity of input. The volume-dependency of information transfer increases its efficiency in the spine volume. Thus, we propose that the small-volume effect is the functional reason why the spine has to be so small.
为什么神经元的树突棘如此之小，以至于只能容纳少量分子，且反应不可避免地变得具有随机性？我们之前表明，尽管存在这种噪声条件，但树突棘利用钙离子增加的概率展现出强大、敏感且高效的信息传递特征；然而，其机制尚不清楚。在本研究中，我们表明小体积效应使树突棘体积内能够实现强大、敏感且高效的信息传递，但在细胞体积内则不然。在树突棘体积中，反应的内在噪声变得大于输入的外在噪声，尽管存在输入波动，仍能实现强大的信息传递。在树突棘体积中，随机性使得钙离子增加在较低的输入强度下发生，从而对较低强度的输入具有更高的敏感性。信息传递的体积依赖性提高了其在树突棘体积中的效率。因此，我们提出小体积效应是树突棘必须如此之小的功能原因。
