Fukushima Yasuhiro, Yamaguti Yutaka, Kuroda Shigeru, Aihara Takeshi, Tsuda Ichiro, Tsukada Minoru
Comprehensive Education Center, Kawasaki University of Medical Welfare, 288 Matsushima, Kurashiki, Okayama 700-0193 Japan.
Tamagawa University Brain Science Institute, 6-1-1 Tamagawagakuen, Machida, Tokyo 194-8610 Japan.
Cogn Neurodyn. 2021 Aug;15(4):733-740. doi: 10.1007/s11571-020-09648-9. Epub 2020 Oct 29.
Cantor coding provides an information coding scheme for temporal sequences of events. In the hippocampal CA3-CA1 network, Cantor coding-like mechanism was observed in pyramidal neurons and the relationship between input pattern and recorded responses could be described as an iterated function system. However, detailed physiological properties of the system in CA1 remain unclear. Here, we performed a detailed analysis of the properties of the system related to the physiological basis of learning and memory. First, we investigated whether the system could be simply based on a series of on-off responses of excitatory postsynaptic potential (EPSP) amplitudes. We applied a series of three spatially distinct input patterns with similar EPSP peak amplitudes. The membrane responses showed significant differences in spatial clustering properties related to the iterated function system. These results suggest that existence of some factors, which do not simply depend on a series of on-off responses but on spatial patterns in the system. Second, to confirm whether the system is dependent on the interval of sequential input, we applied spatiotemporal sequential inputs at several intervals. The optimal interval was 30 ms, similar to the physiological input from CA3 to CA1. Third, we analyzed the inhibitory network dependency of the system. After GABA receptor blocker (gabazine) application, quality of code discrimination in the system was lower under subthreshold conditions and higher under suprathreshold conditions. These results suggest that the inhibitory network increase the difference between the responses under sub- and suprathreshold conditions. In summary, Cantor coding-like iterated function system appears to be suitable for information expression in relation to learning and memory in CA1 network.
康托编码为事件的时间序列提供了一种信息编码方案。在海马CA3-CA1网络中，在锥体神经元中观察到了类似康托编码的机制，并且输入模式与记录的反应之间的关系可以描述为一个迭代函数系统。然而，CA1中该系统的详细生理特性仍不清楚。在这里，我们对与学习和记忆的生理基础相关的系统特性进行了详细分析。首先，我们研究了该系统是否可能简单地基于兴奋性突触后电位（EPSP）幅度的一系列开-关反应。我们应用了一系列具有相似EPSP峰值幅度的三个空间上不同的输入模式。膜反应在与迭代函数系统相关的空间聚类特性上表现出显著差异。这些结果表明存在一些因素，这些因素不仅仅取决于一系列的开-关反应，还取决于系统中的空间模式。其次，为了确认该系统是否依赖于顺序输入的间隔，我们在几个间隔下应用了时空顺序输入。最佳间隔为30毫秒，类似于从CA3到CA1的生理输入。第三，我们分析了该系统对抑制性网络的依赖性。应用GABA受体阻断剂（gabazine）后，在阈下条件下系统中编码辨别质量较低，而在阈上条件下较高。这些结果表明抑制性网络增加了阈下和阈上条件下反应之间的差异。总之，类似康托编码的迭代函数系统似乎适合于CA1网络中与学习和记忆相关的信息表达。
