Moses Sandra N, Winocur Gordon, Ryan Jennifer D, Moscovitch Morris
Rotman Research Institute, Baycrest Centre, Toronto, Canada.
Hippocampus. 2007;17(5):333-7. doi: 10.1002/hipo.20275.
Contextual fear conditioning has become a benchmark measure for hippocampal function, even though several studies report successful acquisition in hippocampal-damaged rodents. The current study examined whether environmental complexity may account for these discrepancies. We directly compared single-session contextual fear conditioning in rats in a simple vs. complex environment. Hippocampal lesions led to reduced fear conditioning in both contexts, as measured by freezing, but the effect was significantly greater in the complex context. As well, lesions led to generalized fear when the complex context was paired with shock, but not when the simple context was paired. We suggest that the representation of the simple context formed by rats with hippocampal lesions was adequate to support associative learning, but the representation of the complex context, which depended to a greater extent on relational learning, was not. The results were interpreted as consistent with theories of hippocampal function that emphasize its role in integrating multiple stimulus elements in a memory trace.
情境恐惧条件反射已成为衡量海马体功能的一项基准指标，尽管有多项研究报告称海马体受损的啮齿动物也能成功习得该反射。本研究探讨了环境复杂性是否可以解释这些差异。我们直接比较了大鼠在简单环境与复杂环境中的单节段情境恐惧条件反射。通过僵立反应测量发现，海马体损伤在两种环境中均导致恐惧条件反射减弱，但在复杂环境中的影响显著更大。此外，当复杂环境与电击配对时，损伤会导致泛化性恐惧，而简单环境与电击配对时则不会。我们认为，海马体损伤的大鼠形成的简单环境表征足以支持联想学习，但更依赖关系学习的复杂环境表征则不然。这些结果被解释为与强调海马体在整合记忆痕迹中多个刺激元素方面作用的海马体功能理论一致。
