Unmasking the CA1 ensemble place code by exposures to small and large environments: more place cells and multiple, irregularly arranged, and expanded place fields in the larger space.
Unmasking the CA1 ensemble place code by exposures to small and large environments: more place cells and multiple, irregularly arranged, and expanded place fields in the larger space.
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DOI：
10.1523/jneurosci.2862-08.2008
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发表时间：
2008-10-29
期刊：
影响因子：
--
通讯作者：
Ludvig N
中科院分区：
文献类型：
--
作者：
Fenton AA;Kao HY;Neymotin SA;Olypher A;Vayntrub Y;Lytton WW;Ludvig N
在标准的实验环境中，CA1主细胞的恒定比例是位置细胞，每个细胞都有一个称为位置场的空间感受野。虽然位置细胞的特性是理解哺乳动物对空间知识的表征的基础，但对于两个基本的神经编码假设中的哪一个正确地解释了位置细胞如何编码空间信息，还没有达成共识。在专用编码假说中，每个细胞的当前活动是相对于其位置域对位置的独立估计。多个单元格的位置估计平均值代表当前位置，因此如果单个单元格具有多个位置字段，则专用的位置代码将降级。在另一种集合编码假说中，多个位置细胞的同时放电是代表当前位置的一个矢量。如果单个电池具有多个位置场，则只要每个位置处的放电向量是唯一的，则集合位置码不会降级。在更自然的环境中，可能需要具有多个位置字段的放置单元格来表示大得多的空间。为了区分专用编码假说和系综编码假说，我们比较了标准圆柱体和~6倍大的腔室中CA1位场的特征。与圆柱体相比，在小室中，更多的CA1神经元是定位细胞，每个细胞都有多个不规则排列的定位野，并且扩大了定位野。结果表明，多个位置场是CA1位置细胞活动的一个基本特征，因此，CA1放电需要一个集合的位置代码来准确地发出信号。
In standard experimental environments, a constant proportion of CA1 principal cells are place cells, each with a spatial receptive field called a place field. Although the properties of place cells are a basis for understanding the mammalian representation of spatial knowledge, there is no consensus on which of the two fundamental neural-coding hypotheses correctly accounts for how place cells encode spatial information. Within the dedicated-coding hypothesis, each cell’s current activity is an independent estimate of the location with respect to its place field. The average of the location estimates from many cells represents current location, so a dedicated place code would degrade if single cells had multiple place fields. Within the alternative, ensemble-coding hypothesis, the concurrent discharge of many place cells is a vector that represents current location. An ensemble place code is not degraded if single cells have multiple place fields as long as the discharge vector at each location is unique. Place cells with multiple place fields might be required to represent the substantially larger space in more natural environments. To distinguish between the dedicated-coding and ensemble-coding hypotheses, we compared the characteristics of CA1 place fields in a standard cylinder and a ~6-times larger chamber. Compared to the cylinder, in the chamber, more CA1 neurons were place cells, each with multiple, irregularly-arranged, and enlarged place fields. The results indicate that multiple place fields is a fundamental feature of CA1 place cell activity and that, consequently, an ensemble place code is required for CA1 discharge to accurately signal location.