Laboratory of Behavioural Neurobiology, Swiss Federal Institute of Technology Zurich, Schwerzenbach, Switzerland.
Laboratorio de Neurociencias y Psicología Experimental, Instituto de Medicina y Biología Experimental de Cuyo (IMBECU), Facultad de Ciencias Médicas, Universidad Nacional de Cuyo, Mendoza, Argentina.
Hippocampus. 2020 Sep;30(9):938-957. doi: 10.1002/hipo.23207. Epub 2020 Apr 14.
The importance of the hippocampus in spatial learning is well established, but the precise relative contributions by the dorsal (septal) and ventral (temporal) subregions remain unresolved. One debate revolves around the extent to which the ventral hippocampus contributes to spatial navigation and learning. Here, separate small subtotal lesions of dorsal hippocampus or ventral hippocampus alone (destroying 18.9 and 28.5% of total hippocampal volume, respectively) spared reference memory acquisition in the water maze. By contrast, combining the two subtotal lesions significantly reduced the rate of acquisition across days. This constitutes evidence for synergistic integration between dorsal and ventral hippocampus in mice. Evidence that ventral hippocampus contributes to spatial/navigation learning also emerged early on during the retention probe test as search preference was reduced in mice with ventral lesions alone or combined lesions. The small ventral lesions also led to anxiolysis in the elevated plus maze and over-generalization of the conditioned freezing response to a neutral context. Similar effects of comparable magnitudes were seen in mice with combined lesions, suggesting that they were largely due to the small ventral damage. By contrast, small dorsal lesions were uniquely associated with a severe spatial working memory deficit in the water maze. Taken together, both dorsal and ventral poles of the hippocampus contribute to efficient spatial navigation in mice: While the integrity of dorsal hippocampus is necessary for spatial working memory, the acquisition and retrieval of spatial reference memory are modulated by the ventral hippocampus. Although the impairments following ventral damage (alone or in combination with dorsal damage) were less substantial, a wider spectrum of spatial learning, including context conditioning, was implicated. Our results encourage the search for integrative mechanism between dorsal and ventral hippocampus in spatial learning. Candidate neural substrates may include dorsoventral longitudinal connections and reciprocal modulation via overlapping polysynaptic networks beyond hippocampus.
海马体在空间学习中的重要性已得到充分证实，但背侧（隔区）和腹侧（颞叶）亚区的确切相对贡献仍未解决。一个争论围绕着腹侧海马体在多大程度上有助于空间导航和学习。在这里，单独的背侧海马体或腹侧海马体的小部分切除（分别破坏总海马体体积的 18.9%和 28.5%）在水迷宫中保留了参考记忆的获得。相比之下，将这两个部分切除结合起来显著降低了每天的获得速度。这为背侧和腹侧海马体在小鼠中的协同整合提供了证据。单独的腹侧损伤或联合损伤的小鼠在保留探针测试中，搜索偏好减少，这也表明腹侧海马体有助于空间/导航学习。腹侧海马体损伤的小型损伤还导致高架十字迷宫中的焦虑缓解以及条件性冻结反应对中性环境的过度泛化。具有联合损伤的小鼠也出现了类似的、相当大的影响，这表明它们主要是由于腹侧损伤所致。相比之下，小型背侧损伤与水迷宫中严重的空间工作记忆缺陷有关。综上所述，海马体的背侧和腹侧极都有助于小鼠高效的空间导航：虽然背侧海马体的完整性对于空间工作记忆是必要的，但空间参考记忆的获得和检索受到腹侧海马体的调节。虽然腹侧损伤（单独或与背侧损伤结合）后的损伤程度较小，但涉及更广泛的空间学习，包括上下文条件作用。我们的结果鼓励在空间学习中寻找背侧和腹侧海马体之间的整合机制。候选神经基质可能包括背腹向纵向连接和通过海马体以外的重叠多突触网络进行的相互调节。
