Hippocampal Granule Cells Opt for Early Retirement
Hippocampal Granule Cells Opt for Early Retirement
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DOI：
10.1002/hipo.20810
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发表时间：
2010-10-01
期刊：
影响因子：
3.5
通讯作者：
Barnes, C. A.
中科院分区：
文献类型：
--
作者：
Alme, C. B.;Buzzetti, R. A.;Barnes, C. A.
在关键时期，成年海马颗粒细胞的兴奋性和可塑性增加，表明它们可能根据时间“正交化”记忆。这种“时间标签”假说的一个版本表明，年轻的颗粒细胞在其发生后的特定时间段内特别敏感，使它们在塑造CA 3表征中发挥重要作用，之后它们对任何输入的反应都变得不那么敏感。另一种可能性是，颗粒细胞在可塑性和兴奋性增加的窗口期内活跃，并选择性地调整到这段时间内发生的事件，并参与这些经历的后期恢复，排除其他细胞。为了区分这些可能性，大鼠在不同时间暴露于不同的环境中，持续数周，随后在一次会议期间评估细胞活化，其中所有环境都被重新访问。分散的初始经验的时间并没有导致增加总招聘在恢复时间预测的选择性调整假说。数据表明，在给定的时间范围内，只有极少数颗粒细胞参与许多体验，大多数颗粒细胞没有显著参与任何体验。基于这些和以前的数据，颗粒细胞的小兴奋人口可能对应于最近产生的细胞。看来，大多数颗粒细胞（可能是90- 95%）实际上是“退休”了，而不是有助于回忆很久以前的事件。“如果颗粒细胞确实塑造了CA 3的表征（这还有待证明），那么当旧记忆恢复时，有一组新的颗粒细胞参与的可能结果是，这些经验的新表征可能会在CA 3中产生。无论如何，目前的数据可能会被解释为破坏标准的“正交化”理论的齿状回在记忆中的作用。(C)2010 Wiley-Liss，Inc.
Increased excitability and plasticity of adult-generated hippocampal granule cells during a critical period suggests that they may "orthogonalize" memories according to time. One version of this "temporal tag" hypothesis suggests that young granule cells are particularly responsive during a specific time period after their genesis, allowing them to play a significant role in sculpting CA3 representations, after which they become much less responsive to any input. An alternative possibility is that the granule cells active during their window of increased plasticity, and excitability become selectively tuned to events that occurred during that time and participate in later reinstatement of those experiences, to the exclusion of other cells. To discriminate between these possibilities, rats were exposed to different environments at different times over many weeks, and cell activation was subsequently assessed during a single session in which all environments were revisited. Dispersing the initial experiences in time did not lead to the increase in total recruitment at reinstatement time predicted by the selective tuning hypothesis. The data indicate that, during a given time frame, only a very small number of granule cells participate in many experiences, with most not participating significantly in any. Based on these and previous data, the small excitable population of granule cells probably correspond to the most recently generated cells. It appears that, rather than contributing to the recollection of long past events, most granule cells, possibly 90-95%, are effectively "retired." If granule cells indeed sculpt CA3 representations (which remains to be shown), then a possible consequence of having a new set of granule cells participate when old memories are reinstated is that new representations of these experiences might be generated in CA3. Whatever the case, the present data may be interpreted to undermine the standard "orthogonalizer" theory of the role of the dentate gyrus in memory. (C) 2010 Wiley-Liss, Inc.