There is mounting evidence that the cerebellum impacts hippocampal functioning, but the impact of the cerebellum on hippocampal interneurons remains obscure. Using miniscopes in freely behaving male and female mice, we found optogenetic stimulation of Purkinje cells alters the calcium activity of a large percentage of CA1 interneurons. This includes both increases and decreases in activity. Remarkably, this bidirectional impact occurs in a coordinated fashion, in line with interneurons’ functional properties. Specifically, CA1 interneurons activated by cerebellar stimulation are commonly locomotion-active, while those inhibited by cerebellar stimulation are commonly rest-active interneurons. We additionally found that subsets of CA1 interneurons show altered activity during object investigations. Importantly, these interneurons also show coordinated modulation by cerebellar stimulation: CA1 interneurons that are activated by cerebellar stimulation are more likely to be activated, rather than inhibited, during object investigations, while interneurons that show decreased activity during cerebellar stimulation show the opposite profile. We examined two different stimulation locations (IV/V vermis or simplex) and two different stimulation approaches (7 Hz or a single 1 s light pulse)—in all cases, the cerebellum induces similar coordinated CA1 interneuron changes congruent with an explorative state. Overall, our data show that CA1 interneurons are impacted by cerebellar manipulation in a bidirectional and coordinated fashion and are therefore likely to play an important role in cerebello–hippocampal communication.

越来越多的证据表明小脑会影响海马功能，但小脑对海马中间神经元的影响仍然不清楚。使用行为不自由的雄性和雌性小鼠的微型显微镜，我们发现浦肯野细胞的光遗传学刺激会改变很大一部分 CA1 中间神经元的钙活性。这包括活动的增加和减少。值得注意的是，这种双向影响以协调的方式发生，与中间神经元的功能特性一致。具体来说，由小脑刺激激活的 CA1 中间神经元通常是运动活跃的，而那些被小脑刺激抑制的中间神经元通常是静息活跃的中间神经元。我们还发现 CA1 中间神经元的子集在对象调查期间显示出改变的活动。重要的是，这些中间神经元还显示出小脑刺激的协调调节：被小脑刺激激活的 CA1 中间神经元在物体研究期间更有可能被激活，而不是被抑制，而在小脑刺激期间表现出活性降低的中间神经元则显示出相反的特征。我们检查了两种不同的刺激位置（IV/V 蚓部或单纯体）和两种不同的刺激方法（7 Hz 或单个 1 s 光脉冲）——在所有情况下，小脑诱导类似的协调 CA1 中间神经元变化，与探索状态一致。总体而言，我们的数据表明，CA1 中间神经元以双向和协调的方式受到小脑操作的影响，因此可能在小脑-海马通讯中发挥重要作用。