齿状回中的Fos神经元群被认为编码情景记忆，另外，许多研究表明齿状回参与情景区分，那么齿状回中的Fos神经元群对情景区分有什么作用呢？本课题利用Fos基因的表达使情景恐惧记忆形成过程中被激活的齿状回神经元表达hM3Dq或hM4Di，然后在不同的情景中通过注射CNO来激活或抑制该群神经元。结果发现激活Fos神经元群使小鼠在相似情景和中性情景中的恐惧僵立水平提高，小鼠对相似情景和中性情景的区分能力下降，而抑制Fos神经元群使小鼠对相似情景的区分能力提高，这表明在情景恐惧记忆学习过程中被激活的齿状回Fos神经元群调控情景区分。另外，电生理的实验结果表明，齿状回Fos神经元接收更多的兴奋性输入，这可能与Fos神经元群参与情景区分相关。

The ensemble of Fos positive cells activated during fear conditioning in dentate gyrus is thought to encode contextual fear memory. Moreover, dentate gyrus mediates pattern separation. A question remains: can the ensemble of Fos positive cells mediate pattern separation? Here we labeled an ensemble of Fos positive cells activated during fear conditioning in dentate gyrus with hM3Dq or hM4Di, latterly reactivated or inhibited these cells with CNO in different contexts. When these cells were activated, the mice showed increased freezing in both similar context and neutral context, and the discrimination of similar context and neutral context is decreased. When these cells were inhibited, the discrimination of similar context was improved. These results suggested that the ensemble of Fos positive cells activated during fear conditioning in dentate gyrus mediated pattern separation. In addition，Fos positive cells receive more excitatory inputs, which may contributes to the pattern separation.