當記憶無法儲存在細胞時，會導致動物無法對後續出現的線索做出反應。雖然越來越多文獻指出重新活化記憶痕跡細胞，可以將細胞從不可存取的狀態切換到可存取的狀態，但其中的細胞和分子機制仍不得其解。我們以果蠅作為動物模型來證明單次厭惡性嗅覺制約的記憶存儲在KCαβ中，即便在學習後的幾個小時內逐漸淡忘，但重新活化後仍然可以提取出記憶。此外，單次厭惡性嗅覺制約也會刺激蛋白質的生合成，利用creb在KCαβ中形成長達20天的記憶痕跡，及orb在MBON-α3中形成約1天的記憶痕跡；而PPL1-α3雖然沒有形成蛋白質，但以負向調節的方式參與在記憶提取的神經迴路中。我們的成果說明KCαβ、PPL1-α3和MBON-α3共同調節單次厭惡性嗅覺制約的記憶形成和記憶提取，又KCαβ與MBON-α3分別在不同的時間點形成活化狀態和沈默狀態的記憶痕跡細胞。
另外，我們也發現學習後未固化的記憶仍然保留在大腦中，藉由刺激與再次活化相關的神經迴路，便可以讀取這些未固化的記憶轉換而來的記憶。關於遺忘的機制，我們證實主動遺忘和被動遺忘皆具有可提取的性質，在時間自然遞進的過程記憶痕跡會在20天後消失，倘若制約的記憶被干擾，記憶痕跡則會在短時間內抹滅。我們的發現解釋了記憶的形成與遺忘的機制，也有助於理解病理性遺忘如自閉症與阿茲海默症。

Forgetting, fail to recall the previous learned experience, is the nature behavior to the animal that helps brain to reorganize the memory storage by removing outdated or unnecessary information. Although recent studies have shown that it is possible to retrieve previous un-recalled memory, the detailed cellular and molecular mechanism remains elusive. The current study showed that the memory of one-cycle of olfactory aversive conditioning is recallable after a second mild training even 8 days after first training. Previous learned experience during forgetting is not permanently removed but hided in the brain and is retrievable upon certain stimulation. Our data also showed that one-cycle of olfactory aversive conditioning induces protein synthesis to form memory trace in mushroom body α/β neurons and downstream MBON-α3. Further study showed that reduced PPL1-α3 neurons activity facilitate the forgotten memory retrieval. The formed tripartite synapse connection among MBNs, PPL1 neurons and MBONs regulates memory formation and forgetting. Furthermore, we found that passive forgetting and active forgetting possess similar way to decline the memory but with different decay rate. Together, our results indicate that the information of one-cycle of olfactory aversive conditioning forms a retrievable long lasting memory trace in the brain with a neural circuit similar to the formation of long-term memory

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