PT  - JOURNAL ARTICLE
AU  - Wally, Maha E.
AU  - Nomoto, Masanori
AU  - Abdou, Kareem
AU  - Inokuchi, Kaoru
TI  - Uncovering long-term existence of a silent short-term memory trace
AID  - 10.1101/2021.05.08.443276
DP  - 2021 Jan 01
TA  - bioRxiv
PG  - 2021.05.08.443276
4099  - http://biorxiv.org/content/early/2021/05/10/2021.05.08.443276.short
4100  - http://biorxiv.org/content/early/2021/05/10/2021.05.08.443276.full
AB  - Active recall of short-term memory (STM) is known to last for a few hours, but whether STM has long-term functions is unknown. Here we show that, STM can be optogenetically retrieved at a time point during which natural recall is not possible, uncovering the long-term existence of a silent STM engram. Moreover, re-training within 3 days led to natural long-term recall, indicating facilitated consolidation. Calcium imaging revealed hippocampal CA1 reactivations of the STM trace during post-learning sleep. Inhibiting offline CA1 activity, N-methyl-D-aspartate receptor activity, or protein synthesis after first exposure to the STM-forming event impaired the future re-exposure-facilitated consolidation, which highlights a role of protein synthesis and sleep in storing a silent STM trace. These results provide evidence that STM is not completely lost within hours and demonstrates a possible two-step STM consolidation, first storage as a silent engram, then transformation into an active state by recurrence within 3 days.Competing Interest StatementThe authors have declared no competing interest.