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Learning and Long-term Memory

開催日 2014/9/11
時間 11:00 - 12:00
会場 Poster / Exhibition(Event Hall B)

Dynamic convergence of two distinct memory traces through their repetitive retrieval

  • P1-273
  • 横瀬 淳 / Jun Yokose:1 野本 真順 / Masanori Nomoto:1,2 鈴木(大久保) 玲子 / Reiko Okubo-Suzuki:1,2 鈴木 章円 / Akinobu Suzuki:1,2 井ノ口 馨 / Kaoru Inokuchi:1,2 
  • 1:富山大院医薬・医・生化学 / Department of Biochemistry, Faculty of Medicine, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan 2:戦略的創造研究推進事業 科学技術振興機構 / CREST, JST 

Distinct units of information that have been stored in the brain sometimes interact to generate a new associative memory. In considering the processes of the associative memory, higher-order conditioning paradigms (sensory preconditioning and second-order conditioning) might help us reveal the neural substrates on it. Previous studies suggested that retrieval-induced reactivation of memory plays a potential role for the interaction with pre-existing memory. However, it remains unclear at the level of neural ensemble how two distinct memories are integrated to generate an associative memory. Here, to address this issue, we conceived of the combination of two amygdala-dependent behavioral paradigms, conditioned taste aversion task (CTA) and auditory cued fear conditioning (AFC). Mice were trained in CTA and AFC independently, where animals did not associate these two paradigms. After each memory was formed by pairing of the conditioned stimulus (CS) with the unconditioned stimulus (US) respectively, animals received synchronous and repetitive presentations of the CS for CTA and AFC, which retrieved both memories at the same time in the reactivation session. We found that presenting the CS of CTA triggered responses to the US of AFC paradigm such as freezing-like behavior, suggesting that the reactivation session leads to the interaction between CTA and AFC memories. Interestingly, in animals which had already generated interaction between CTA and AFC memories, original AFC memory was impaired by the disruption of CTA memory by blocking protein synthesis in basolateral amygdala (BLA) immediately after the CTA memory retrieval without AFC memory retrieval. Finally, Arc/Homer1a catFISH analysis elucidated an increase in the ratio of co-sharing neural subpopulation in the BLA undergoing both CTA and AFC retrievals during the reactivation session. These findings suggest that two distinct cell ensembles corresponding to each memory converge to generate an interaction of two distinct memories when both memories are synchronously and repeatedly retrieved.

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