Bramati Giulia, Stauffer Pia, Nigri Martina, Wolfer David P, Amrein Irmgard
Division Functional Neuroanatomy, Institute of Anatomy, University Zurich, Zürich, Switzerland.
Department of Health Sciences and Technology, ETH, Zürich, Switzerland.
Front Behav Neurosci. 2023 Sep 18;17:1256744. doi: 10.3389/fnbeh.2023.1256744. eCollection 2023.
The IntelliCage is an automated home-cage system that allows researchers to investigate the spontaneous behavior and learning abilities of group-housed mice. The IntelliCage enables us to increase the standardization and reproducibility of behavioral outcomes by the omission of experimenter-mouse interactions. Although the IntelliCage provides a less stressful environment for animals, standard IntelliCage protocols use controlled water access as the motivational driver for learning. To overcome possible water restrictions in slow learners, we developed a series of novel protocols based on appetitive learning, in which mice had permanent access to plain water but were additionally rewarded with sweetened water upon solving the task. C57BL/6NCrl female mice were used to assess the efficacy of these sweet reward-based protocols in a series of learning tasks. Compared to control mice tested with standard protocols, mice motivated with a sweet reward did equal to or better in operant performance and place learning tasks. Learning of temporal rules was slower than that in controls. When faced with a combined temporal x spatial working memory task, sweet-rewarded mice learned little and chose plain water. In a second set of experiments, the impact of environmental enrichment on appetitive learning was tested. Mice kept under enriched environment (EE) or standard housing (SH) conditions prior to the IntelliCage experiments performed similarly in the sweet-rewarded place learning task. EE mice performed better in the hippocampus-dependent spatial working memory task. The improved performance of EE mice in the hippocampus-dependent spatial working memory task might be explained by the observed larger volume of their mossy fibers. Our results confirm that environmental enrichment increases complex spatial learning abilities and leads to long-lasting morphological changes in the hippocampus. Furthermore, simple standard IntelliCage protocols could easily be adapted to sweet rewards, which improve animal welfare by removing the possibility of water restriction. However, complex behavioral tasks motivated by sweet reward-based learning need further adjustments to reach the same efficacy as standard protocols.
智能笼是一种自动化的饲养笼系统，可让研究人员研究群居小鼠的自发行为和学习能力。智能笼使我们能够通过消除实验人员与小鼠的互动来提高行为结果的标准化和可重复性。尽管智能笼为动物提供了压力较小的环境，但标准的智能笼实验方案将控制饮水作为学习的动机驱动因素。为了克服学习较慢的小鼠可能出现的饮水限制问题，我们基于食欲学习开发了一系列新方案，在这些方案中，小鼠可以随时获取普通水，但在完成任务后还会额外获得糖水奖励。我们使用C57BL/6NCrl雌性小鼠在一系列学习任务中评估这些基于甜味奖励方案的效果。与使用标准方案测试的对照小鼠相比，受甜味奖励驱动的小鼠在操作性任务和位置学习任务中的表现相当或更好。时间规则的学习比对照组慢。当面对时间x空间组合的工作记忆任务时，受甜味奖励的小鼠几乎没有学习，而是选择了普通水。在第二组实验中，测试了环境丰富化对食欲学习的影响。在智能笼实验之前饲养在丰富环境（EE）或标准饲养（SH）条件下的小鼠在甜味奖励的位置学习任务中的表现相似。EE小鼠在依赖海马体的空间工作记忆任务中表现更好。EE小鼠在依赖海马体的空间工作记忆任务中的表现改善可能是由于观察到它们的苔藓纤维体积更大。我们的结果证实，环境丰富化可提高复杂的空间学习能力，并导致海马体发生持久的形态变化。此外，简单的标准智能笼实验方案可以很容易地适应甜味奖励，通过消除饮水限制的可能性来提高动物福利。然而，基于甜味奖励学习驱动的复杂行为任务需要进一步调整，以达到与标准方案相同的效果。
