The formation and retention of hippocampus-dependent memories is impacted by neurogenesis, a process that involves the production of new neurons in the dentate gyrus of the hippocampus. Recent studies demonstrate that increasing neurogenesis after memory formation induces forgetting of previously acquired memories. Neurogenesis-induced forgetting was originally demonstrated in mice, but a recent report suggests that the same effect may be absent in rats. Although a general species difference is possible, other potential explanations for these incongruent findings are that memories which are more strongly reinforced become resilient to forgetting or that perhaps only certain types of memories are affected. Here, we investigated whether neurogenesis-induced forgetting occurs in rats using several hippocampus-dependent tasks including contextual fear conditioning (CFC), the Morris Water Task (MWT), and touchscreen paired associates learning (PAL). Neurogenesis was increased following training using voluntary exercise for 4 weeks before recall of the previous memory was assessed. We show that voluntary running causes forgetting of context fear memories in a neurogenesis-dependent manner, and that neurogenesis-induced forgetting is present in rats across behavioral tasks despite differences in complexity or reliance on spatial, context, or object memories. In addition, we asked whether stronger memories are less susceptible to forgetting by varying the strength of training. Even with a very strong training protocol in the CFC task, we still observed enhanced forgetting related to increased neurogenesis. These results suggest that forgetting due to neurogenesis is a conserved mechanism that aids in the clearance of memories.

中文翻译：

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成年神经发生介导大鼠多种类型记忆的遗忘


海马依赖性记忆的形成和保留受到神经发生的影响，神经发生是一个涉及海马齿状回产生新神经元的过程。最近的研究表明，记忆形成后神经发生的增加会导致先前获得的记忆的遗忘。神经发生引起的遗忘最初是在小鼠中得到证实的，但最近的一份报告表明，在大鼠中可能不存在相同的效果。尽管普遍的物种差异是可能的，但对这些不一致的发现的其他潜在解释是，强化程度更高的记忆对遗忘具有弹性，或者也许只有某些类型的记忆受到影响。在这里，我们研究了神经发生诱导的遗忘是否发生在使用几种海马依赖性任务的大鼠中，这些任务包括情境恐惧调节（CFC）、莫里斯水任务（MWT）和触摸屏配对联想学习（PAL）。在评估先前记忆的回忆之前，进行 4 周的自愿运动训练后，神经发生有所增加。我们发现，自愿跑步会以神经发生依赖性方式导致情境恐惧记忆的遗忘，并且神经发生诱导的遗忘存在于大鼠的跨行为任务中，尽管复杂性或对空间、情境或物体记忆的依赖程度存在差异。此外，我们还询问是否通过改变训练强度，更强的记忆力更不容易被遗忘。即使在 CFC 任务中采用非常强大的训练方案，我们仍然观察到与神经发生增加相关的遗忘增强。这些结果表明，神经发生引起的遗忘是一种保守的机制，有助于清除记忆。