Abstract：
When neurons are recruited to form the memory engram, they are driven to activate the expression of a series of immediate-early genes (IEGs). While these IEGs have been used relatively indiscriminately to identify the so-called engram neurons, recent research has demonstrated that different IEG ensembles can be physically and functionally distinct within the memory engram. This inherent heterogeneity of the memory engram is driven by the diversity in the functions and distributions of different IEGs. This process, which we call molecular sorting, is analogous to sorting the entire population of engram neurons into different sub-engrams molecularly defined by different IEGs. In this chapter, we will describe the molecular sorting process by systematically reviewing published work on engram ensemble cells defined by the following four major IEGs: Fos, Npas4, Arc, and Egr1. By comparing and contrasting these likely different components of the memory engram, we hope to gain a better understanding of the logic and significance behind the molecular sorting process for memory functions.
摘要：
当神经元被招募形成记忆印迹时，它们被驱动激活一系列立即早期基因（IEG）的表达。虽然这些IEG被相对不加区别地用于识别所谓的engram神经元，最近的研究表明，不同的IEG集合可以在内存印迹中物理和功能上不同。内存印迹的这种固有异质性是由不同IEG的功能和分布的多样性驱动的。这个过程,我们称之为分子分选，类似于将整个Engram神经元群体分类为由不同IEG分子定义的不同子图。在这一章中,我们将通过系统地回顾由以下四个主要IEG定义的Engram集成细胞的已发表工作来描述分子分选过程：Fos，Npas4，弧形，和Egr1。通过比较和对比内存印迹的这些可能不同的组件，我们希望能更好地理解记忆功能的分子排序过程背后的逻辑和意义。
