The memory for a new episode is formed immediately upon experience and can last up to a lifetime. It has been shown that the hippocampal network plays a fundamental role in the rapid acquisition of a memory of a one-time experience, in which the novelty component of the experience promotes the prompt formation of the memory. However, it remains unclear which neural circuits convey the novelty signal to the hippocampus for the single-trial learning. Here, we show that during encoding neuromodulatory input from locus coeruleus (LC) to CA3, but not CA1 or to the dentate gyrus, is necessary to facilitate novel contextual learning. Silencing LC activity during exposure to a novel context reduced subsequent reactivation of the engram cell ensembles in CA3 neurons and in downstream CA1 upon reexposure to the same context. Calcium imaging of the cells reactivated in both novel and familiar contexts revealed that suppression of LC inputs at the time of encoding resulted in more variable place fields in CA3 neurons. These results suggest that neuromodulatory input from LC to CA3 is crucial for the formation of a persistent memory in the hippocampus.

中文翻译：

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输入海马CA3的蓝斑基因驱动了新情况的单次试验学习

对新情节的记忆会在经历后立即形成，并且可以持续一生。已经表明，海马网络在一次获得一次经历的记忆的快速获取中起着基本作用，其中一次经历的新颖性促进了记忆的迅速形成。但是，尚不清楚哪个神经回路将新奇信号传递到海马进行单次试验学习。在这里，我们显示了在编码从蓝斑轨迹（LC）到CA3而不是CA1或齿状回的神经调节输入过程中，对促进新型的情境学习是必要的。在暴露于新环境中时，沉默LC活性会降低CA3神经元和下游CA1中再暴露于相同环境后的Engram细胞团簇的后续再激活。在新颖和熟悉的环境中重新激活的细胞的钙成像显示，在编码时抑制LC输入会导致CA3神经元中更多的可变位置场。这些结果表明，从LC到CA3的神经调节输入对于在海马中形成持久性记忆至关重要。