Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania 19129, USA.
Learn Mem. 2020 Jul 15;27(8):310-318. doi: 10.1101/lm.051797.120. Print 2020 Aug.
Learning and memory involves a large neural network of many brain regions, including the notable hippocampus along with the retrosplenial cortex (RSC) and lateral septum (LS). Previous studies have established that the dorsal hippocampus (dHPC) plays a critical role during the acquisition and retrieval/expression of episodic memories. However, the role of downstream circuitry from the dHPC, including the dHPC-to-RSC and dHPC-to-LS pathways, has come under scrutiny only recently. Here, we used an optogenetic approach with contextual fear conditioning in mice to determine whether the above two pathways are involved in acquisition and expression of contextual fear memory. We found that a selective inhibition of the dHPC neuronal terminals in either the RSC or LS during acquisition impaired subsequent memory performance, suggesting that both the dHPC-to-RSC and dHPC-to-LS pathways play a critical role in memory acquisition. We also selectively inhibited the two dHPC efferent pathways during memory retrieval and found a differential effect on memory performance. These results indicate the intricacies of memory processing and that hippocampal efferents to cortical and subcortical regions may be differentially involved in aspects of physiological and cognitive memory processes.
学习和记忆涉及到许多大脑区域的大型神经网络，包括显著的海马体以及后隔区（RSC）和外侧隔核（LS）。先前的研究已经确定，背侧海马体（dHPC）在情景记忆的获取和检索/表达过程中起着关键作用。然而，dHPC 下游的电路，包括 dHPC 到 RSC 和 dHPC 到 LS 的途径，最近才受到关注。在这里，我们使用光遗传学方法结合小鼠的情景恐惧条件反射来确定上述两条途径是否参与了情景恐惧记忆的获取和表达。我们发现，在获取过程中选择性地抑制 RSC 或 LS 中的 dHPC 神经元末梢会损害随后的记忆表现，这表明 dHPC 到 RSC 和 dHPC 到 LS 的途径都在记忆获取中起着关键作用。我们还在记忆检索过程中选择性地抑制了这两条 dHPC 传出途径，发现它们对记忆表现有不同的影响。这些结果表明了记忆处理的复杂性，并且海马体传出到皮质和皮质下区域的可能在生理和认知记忆过程的各个方面都有不同的参与。
