The paraventricular nucleus of the thalamus (PVT), which serves as a hub, receives dense projections from the medial prefrontal cortex (mPFC) and projects to the lateral division of central amygdala (CeL). The infralimbic (IL) cortex plays a crucial role in encoding and recalling fear extinction memory. Here, we found that neurons in the PVT and IL were strongly activated during fear extinction retrieval. Silencing PVT neurons inhibited extinction retrieval at recent time point (24 h after extinction), while activating them promoted extinction retrieval at remote time point (7 d after extinction), suggesting a critical role of the PVT in extinction retrieval. In the mPFC-PVT circuit, projections from IL rather than prelimbic cortex to the PVT were dominant, and disrupting the IL-PVT projection suppressed extinction retrieval. Moreover, the axons of PVT neurons preferentially projected to the CeL. Silencing the PVT-CeL circuit also suppressed extinction retrieval. Together, our findings reveal a new neural circuit for fear extinction retrieval outside the classical IL-amygdala circuit.

作为中枢的丘脑室旁核 (PVT) 接收来自内侧前额叶皮层 (mPFC) 的密集投射并投射到中央杏仁核 (CeL) 的外侧分裂。下边缘 (IL) 皮层在编码和回忆恐惧消退记忆方面起着至关重要的作用。在这里，我们发现 PVT 和 IL 中的神经元在恐惧消退恢复过程中被强烈激活。沉默 PVT 神经元抑制最近时间点（灭绝后 24 小时）的灭绝恢复，而激活它们促进远程时间点（灭绝后 7 天）的灭绝恢复，表明 PVT 在灭绝恢复中的关键作用。在 mPFC-PVT 电路中，从 IL 而不是前肢皮层到 PVT 的投射占主导地位，并且破坏 IL-PVT 投射抑制了消光恢复。而且，PVT 神经元的轴突优先投射到 CeL。使 PVT-CeL 电路静音也抑制了消光恢复。总之，我们的研究结果揭示了一种新的神经回路，用于在经典的 IL-杏仁核回路之外进行恐惧消退检索。