Modular realignment of entorhinal grid cell activity as a basis for hippocampal remapping.
Modular realignment of entorhinal grid cell activity as a basis for hippocampal remapping.
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DOI：
10.1523/jneurosci.1433-11.2011
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发表时间：
2011-06-22
期刊：
影响因子：
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通讯作者：
Abbott LF
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文献类型：
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作者：
Monaco JD;Abbott LF
海马位置场是啮齿类动物定位细胞记录的局部活动区域，在重映射过程中，其相对位置会发生很大的变化。这个过程似乎需要某种形式的调制全局输入。从大鼠内侧内嗅皮层第二层记录的网格细胞反应已被观察到与海马重映射同时重新对齐，使其成为候选输入源。然而，这种重新排列是在网格细胞的共定位集合中连贯地发生的。假设的内嗅对重新映射的贡献取决于这种一致性是否延伸到所有网格细胞，这是目前未知的。我们研究是否将网格细胞分成少量的独立重新排列的模块既可以解释这种本地化的一致性，并允许海马重新映射。为此，我们构建了一个模型，在该模型中，位置细胞的反应来自于由全局抑制介导的网络竞争。我们表明，这些模拟的反应近似的稀疏性和空间特异性的海马活动，同时充分代表了一个虚拟的环境，而无需学习。一个环境中的位置字段位置和活动位置单元集可以通过改变底层网格单元输入来独立地重新排列。我们引入新的措施重新映射网格单元模块化的有效性进行评估，并与其他几何变换的网格单元响应比较移位重排。完整的海马重新映射是可能的，有少量的移动网格模块，这表明内嗅重排可能能够产生位置场随机化，尽管大量的一致性。
Hippocampal place fields, the local regions of activity recorded from place cells in exploring rodents, can undergo large changes in relative location during remapping. This process would appear to require some form of modulated global input. Grid-cell responses recorded from layer II of medial entorhinal cortex in rats have been observed to realign concurrently with hippocampal remapping, making them a candidate input source. However, this realignment occurs coherently across colocalized ensembles of grid cells. The hypothesized entorhinal contribution to remapping depends on whether this coherence extends to all grid cells, which is currently unknown. We study whether dividing grid cells into small numbers of independently realigning modules can both account for this localized coherence and allow for hippocampal remapping. To do this, we construct a model in which place-cell responses arise from network competition mediated by global inhibition. We show that these simulated responses approximate the sparsity and spatial specificity of hippocampal activity while fully representing a virtual environment without learning. Place field locations and the set of active place cells in one environment can be independently rearranged by changes to the underlying grid-cell inputs. We introduce new measures of remapping to assess the effectiveness of grid-cell modularity and to compare shift realignments with other geometric transformations of grid-cell responses. Complete hippocampal remapping is possible with a small number of shifting grid modules, indicating that entorhinal realignment may be able to generate place-field randomization despite substantial coherence.