Hippocampal mossy fibers have long been proposed to impose new patterns to learn onto CA3 neurons during new memory formation. However, inconsistent with this theory, we found in our previous study that mossy fiber stimulation induces only transient changes in CA3 spatial firing in a familiar environment. Here, we tested whether mossy fiber stimulation affects CA3 spatial firing differently between familiar and novel environments. We compared spatial firing of CA3 neurons before and after optogenetic stimulation of mossy fibers in freely behaving mice in a familiar and three sets of novel environments. We found that CA3 neurons are more responsive to mossy fiber stimulation in the novel than familiar environments. However, we failed to obtain evidence for long‐lasting effect of mossy fiber stimulation on spatial firing of CA3 neurons in both the familiar and novel environments. Our results provide further evidence against the view that mossy fibers carry teaching signals.

中文翻译：

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苔藓纤维刺激对熟悉和新环境中 CA3 神经元空间放电的瞬时影响。

长期以来，人们一直建议海马苔藓纤维在新的记忆形成过程中施加新的学习模式到 CA3 神经元上。然而，与这一理论不一致的是，我们在之前的研究中发现，苔藓纤维刺激只会在熟悉的环境中诱导 CA3 空间发射的瞬时变化。在这里，我们测试了苔藓纤维刺激是否会在熟悉和新环境之间以不同的方式影响 CA3 空间发射。我们比较了在熟悉的和三组新环境中自由行为的小鼠在苔藓纤维光遗传学刺激之前和之后 CA3 神经元的空间放电。我们发现，与熟悉的环境相比，CA3 神经元对小说中苔藓纤维刺激的反应更灵敏。然而，我们未能获得苔藓纤维刺激对熟悉和新环境中 CA3 神经元空间放电的长期影响的证据。我们的结果为反对苔藓纤维携带教学信号的观点提供了进一步的证据。