Hippocampal Functional Organization in Fear Memory

众所周知，内嗅皮层（EC）是情节记忆形成所必需的海马输入的主要来源之一。然而，情景记忆中的多模态因素是如何在EC中加工的还不清楚。在本研究中，我们调查了个别EC次区域的贡献，情节记忆，以确定可能的功能分离EC次区域。我们害怕条件动物在一个加号迷宫与两种不同类型的刺激-空间或对象，这是在MEC和LEC处理，而光遗传学抑制MEC/LEC。在弱电击（0.3mA）条件下，LEC抑制组动物（n=6）对电击物的回避反应明显低于对照组动物（n=7; p < 0.005）。MEC抑制动物（n=8）对电击臂的回避也相对低于对照组（n=7; p = 0.06）。在1 mA强电击条件下，LEC抑制组（n=6）和对照组（n=8）动物对电击物的回避率均超过90%，但LEC抑制组动物对电击物和非电击物的回避时间均显著长于对照组（p < 0.05）。在适当的恐惧条件反射中，MEC抑制动物（n=7）倾向于避免与电击臂相邻的非电击臂，比对照动物（n=4; p = 0.07）更长。这些结果表明，EC亚区加工特定的地方/对象的信息，以及与恐惧记忆的信息。

It is well known that the entorhinal cortex (EC) is one of the main sources of inputs to the hippocampus necessary for the formation of episodic memory. However, how multimodal factors in episodic memory are processed in the EC is not well understood. In the present study, we investigated individual EC sub-regional contributions in episodic memory to determine a possible functional dissociation of EC sub-regions. We fear conditioned animals on a plus maze with two different types of stimuli - spatial or object, which is processed in MEC and LEC, while optogenetically inhibiting MEC/LEC. I finished behavioral experiments and statistically analyzed behavioral and histological data.In weak foot-shock condition (0.3mA), LEC inhibited animals (n=6) showed significantly lower avoidance toward shocked object than control animals (n=7; p < 0.005). Avoidance toward the shocked arm of MEC inhibited animals (n=8) was also comparatively lower than controls (n=7; p = 0.06). In strong foot-shock condition (1mA), LEC inhibited (n=6) as well as control (n=8) animals showed over 90% avoidance toward shock object, however, LEC inhibited animals avoided not only the shocked but also no-shocked object significantly longer than controls (p < 0.05). In place fear conditioning, MEC inhibited animals (n=7) tended to avoid the no-shocked arm, which is adjacent to the shocked arm, longer than control animals (n=4; p = 0.07). These results suggest that EC sub-regions process information about specific place/object as well as associate the information with fear memory.