The Hippocampal Engram as a Memory Index
The Hippocampal Engram as a Memory Index
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DOI：
10.1177/1179069518815942
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发表时间：
2018-12
影响因子：
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通讯作者：
Kazumasa Z. Tanaka;T. McHugh
中科院分区：
文献类型：
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作者：
Kazumasa Z. Tanaka;T. McHugh
海马体对过去事件的记忆进行编码，但海马体代码辅助这一功能的性质尚不清楚。一个得到海马体生理学有力支持的流行观点是认知地图理论。在这个观点中，情节记忆被固定在经验的空间域或同位中心性框架上，而海马体提供了外部空间的稳定表征。另一方面，最近的研究使用即刻早期基因(IEGs)作为神经元激活的代理，支持记忆指数理论。这一想法假设，海马体的记忆痕迹作为记忆的皮质表征(内部表征的映射)的索引，并假设海马体的主要功能是恢复编码过程中出现的皮质活动模式。我们最近的发现对这两种根本不同的理论提供了统一的观点。在海马区CA1区，表达锥体神经元的c-Fos的活动以类似指数的方式可靠地反映了动物所经历的背景的身份，而来自其他活跃的锥体细胞的棘波则提供了在很长一段时间内稳定的空间信息。这两个不同的海马神经元集合表明，海马神经元的亚群在记忆中扮演着不同的角色。
The hippocampus encodes memories for past events, but the nature of the hippocampal code subserving this function remains unclear. A prevailing idea, strongly supported by hippocampal physiology, is the Cognitive Map Theory. In this view, episodic memories are anchored to spatial domains, or allocentric frameworks, of experiences, with the hippocampus providing a stable representation of external space. On the other hand, recent studies using Immediate Early Genes (IEGs) as a proxy of neuronal activation support the Memory Index Theory. This idea posits that the hippocampal memory trace serves as an index for a cortical representation of memory (a map for internal representation) and hypothesizes the primary hippocampal function is to reinstate the pattern of cortical activity present during encoding. Our recent findings provide a unitary view on these two fundamentally different theories. In the hippocampal CA1 region the activity of c-Fos expressing pyramidal neurons reliably reflects the identity of the context the animal is experiencing in an index-like fashion, while spikes from other active pyramidal cells provide spatial information that is stable over a long period of time. These two distinct ensembles of hippocampal neurons suggest heterogeneous roles for subsets of hippocampus neurons in memory.