Hippocampal representations as a function of time, subregion, and brain state
Hippocampal representations as a function of time, subregion, and brain state
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DOI：
10.1016/j.nlm.2018.03.006
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发表时间：
2018-09-01
影响因子：
2.7
通讯作者：
Schlichting, Margaret L.
中科院分区：
文献类型：
--
作者：
Duncan, Katherine D.;Schlichting, Margaret L.
海马体如何代表记忆中相互关联的经历？我们回顾突出但似乎矛盾的理论观点，这表明海马扭曲的经验表示，要么强调其独特性或突出共同的元素。这些从根本上不同的记忆表征可以在大脑中通过合取分离码和自适应差分码或集成关系码来实例化。在回顾这些不同的编码方案在海马的实证支持，我们概述了两个组织原则，可以解释在文献中的相互矛盾的结果。首先集中在记忆的形成和存储，我们认为，不同的海马区代表的经验，在多个层次的抽象，并可能将它们传输到不同的皮层网络。然后集中在记忆形成的时候，我们确定了几个可以打开和维持特定时间窗口的因素，在此期间，同一个海马网络偏向于一个编码方案。具体来说，我们讨论了以下证据：（1）兴奋性介导的整合窗口，通过特定记忆编码后持续升高的CREB水平维持;（2）短暂的胆碱能介导的窗口有利于记忆分离;（3）持续的多巴胺能介导的窗口有利于记忆整合。通过对不同物种的海马编码方案进行广泛的概述，我们希望激发未来的实证和建模研究，以考虑记忆形成周围的因素如何塑造它们存储的表征。
How does the hippocampus represent interrelated experiences in memory? We review prominent yet seemingly contradictory theoretical perspectives, which propose that the hippocampus distorts experiential representations to either emphasize their distinctiveness or highlight common elements. These fundamentally different kinds of memory representations may be instantiated in the brain via conjunctive separated codes and adaptively differentiated codes on the one hand, or integrated relational codes on the other. After reviewing empirical support for these different coding schemes within the hippocampus, we outline two organizing principles which may explain the conflicting findings in the literature. First focusing on where the memories are formed and stored, we argue that distinct hippocampal regions represent experiences at multiple levels of abstraction and may transmit them to distinct cortical networks. Then focusing on when memories are formed, we identify several factors that can open and maintain specialized time windows, during which the very same hippocampal network is biased toward one coding scheme over the others. Specifically, we discuss evidence for (1) excitability-mediated integration windows, maintained by persistently elevated CREB levels following encoding of a specific memory, (2) fleeting cholinergically-mediated windows favoring memory separation, and (3) sustained dopaminergically-mediated windows favoring memory integration. By presenting a broad overview of different hippocampal coding schemes across species, we hope to inspire future empirical and modeling research to consider how factors surrounding memory formation shape the representations in which they are stored.