RT Journal Article SR Electronic T1 Within-trial persistence of learned behavior as a dissociable behavioral component in hippocampus-dependent memory tasks: a potential post-learning role of immature neurons in the adult dentate gyrus JF eneuro JO eNeuro FD Society for Neuroscience SP ENEURO.0195-21.2021 DO 10.1523/ENEURO.0195-21.2021 A1 Alessandro Luchetti A1 Takuma Yamaguchi (山口拓馬) A1 Masato Uemura A1 Glen Yovianto A1 Luka Čulig A1 Ming Yang A1 Wei Zhou A1 Franziska Oschmann A1 MinFeng Lua A1 Ayumu Tashiro (田代歩 YR 2021 UL http://www.eneuro.org/content/early/2021/07/19/ENEURO.0195-21.2021.abstract AB The term “memory strength” generally refers to how well one remembers something but more precisely it contains multiple modalities, such as how easily, how accurately, how confidently and how vividly we remember it. In human, these modalities of memory strength are dissociable. In this study, we asked whether we can isolate a behavioral component that is dissociable from others in hippocampus-dependent memory tasks in mice, which potentially reflect a modality of memory strength. Using a virus-mediated inducible method, we ablated immature neurons in the dentate gyrus in mice after we trained the mice with hippocampus-dependent memory tasks normally. In memory retrieval tests, these ablated mice initially show intact performance. However, the ablated mice ceased learned behavior prematurely within a trial compared with control mice. In addition, the ablated mice showed shorter duration of individual episodes of learned behavior. Both affected behavioral measurements point to persistence of learned behavior. Thus, the effect of the post-learning manipulation showed dissociation between initial performance and persistence of learned behavior. These two behavioral components are likely to reflect different brain functions and be mediated by separate mechanisms, which might represent different modalities of memory strength. These simple dissociable measurements in widely used behavioral paradigms would be useful to understand detailed mechanisms underlying the expression of learned behavior and potentially different modalities of memory strength in mice. We also discuss a potential role that immature neurons in the dentate gyrus may play in persistence of learned behavior.Significance statementWe use the term “memory strength” both in everyday life and research settings. Memory strength generally means how well we remember something. However, depending on context, its meaning is varied; it can mean how easily, accurately, vividly and/or confidently we remember it. These different modalities of memory strength are generally correlated but is known to be partly independent. In this study, we asked whether such independent or dissociable behavioral components exist in hippocampus-dependent memory tasks in mice. We provide evidence that initial performance and persistence of learned behavior during memory retrieval tests are dissociable in three memory tasks. Such dissociable components would be helpful to study different modalities of memory strength and their underlying mechanisms in mice in future studies.