Department of Psychology, Durham University, Durham, DH1 3LE, United Kingdom.
Department of Psychology, Durham University, Durham, DH1 3LE, United Kingdom.
Behav Brain Res. 2019 Sep 2;369:111936. doi: 10.1016/j.bbr.2019.111936. Epub 2019 May 2.
The precise role played by the hippocampus in spatial learning tasks, such as the Morris Water Maze (MWM), is not fully understood. One theory is that the hippocampus is not required for 'knowing where' but rather is crucial in 'getting there'. To explore this idea in the MWM, we manipulated 'getting there' variables, such as passive transport or active swimming towards the hidden platform, in rats with and without hippocampal lesions. Our results suggested that for intact rats, self-motion cues enroute to the hidden goal were a necessary component for 'place learning' to progress. Specifically, intact rats could not learn the hidden goal location, when passively transported to it, despite extensive training. However, when rats were either given hippocampal lesions, or placed in a light-tight box during transportation to the hidden goal, passive-placement spatial learning was facilitated. In a subsequent experiment, the 'getting there' component of place navigation was simplified, via the placement of two overhead landmarks, one of which served as a beacon. When 'getting there' was made easier in this way, hippocampal lesions did not induce deficits in 'knowing where' the goal was. In fact, similar to the facilitation observed in passive-placement spatial learning, hippocampal lesions improved landmark learning relative to controls. Finally, demonstrating that our lesions were sufficiently deleterious, hippocampal-lesioned rats were impaired, as predicted, in an environmental-boundary based learning task. We interpret these results in terms of competition between multiple memory systems, and the importance of self-generated motion cues in hippocampal spatial mapping.
海马体在空间学习任务（如 Morris 水迷宫（MWM））中的精确作用尚未完全理解。一种理论认为，海马体对于“知道在哪里”并不重要，而对于“到达那里”至关重要。为了在 MWM 中探索这一想法，我们在有海马体损伤和无海马体损伤的大鼠中操纵了“到达那里”的变量，例如被动运输或主动游向隐藏平台。我们的结果表明，对于完整的大鼠，沿途的自我运动线索是“位置学习”进展的必要组成部分。具体来说，尽管经过了广泛的训练，完整的大鼠在被动运输到隐藏目标时无法学习隐藏目标的位置。然而，当大鼠被给予海马体损伤或在运输到隐藏目标时被放置在不透光的盒子中时，被动放置的空间学习得到了促进。在随后的实验中，通过放置两个 overhead 地标，简化了位置导航的“到达那里”部分，其中一个地标作为信标。以这种方式简化“到达那里”的过程后，海马体损伤不会导致“知道目标在哪里”的能力缺陷。事实上，与被动放置空间学习中观察到的促进作用类似，海马体损伤相对于对照组提高了地标学习能力。最后，证明我们的损伤足够严重，如预测的那样，海马体损伤的大鼠在基于环境边界的学习任务中受损。我们根据多个记忆系统之间的竞争以及海马体空间映射中自我产生的运动线索的重要性来解释这些结果。
