• Molecular, cellular, and network mechanisms underlying memory update system

  • Formation of knowledge is one of the bases of a human mental activity. Knowledge is not simply formed by the accurate storage of information as memory. New information is usually compared with previously stored old memories. Old memories are sometimes re-written if new information is related to the old ones (memory update). For instance, memories about an already-known person are usually modified by a new episode with that person. "Update mechanism" is necessary for the flexible adjustment to changes in environment, and becomes basic of the mental activity through the formation of knowledge. We aim to clarify the memory update mechanisms.

    Update by the association of distinct memory episodes: We analyze molecular and cellular mechanisms underlying memory association per se, including Pavlovian conditioning and behavioral tag.
    Update by memory reconsolidation: Memories change its quality even after consolidated in the brain through dynamic processes including destabilization, reconsolidation, association, and so on. Many memories become labile state upon retrieval, and then consolidated again via reconsolidation process. Memory reconsolidation is assumed to be a key process through which new information, if related to the existing ones, would be integrated into the old memories. We investigate (1) mechanisms underlying synaptic level reconsolidation in the hippocampal LTP in vivo, and (2) mechanisms underlying memory reconsolidation, specifically focusing on the involvement of autophagy.
    Neural circuit mechanisms underlying memory update processes are being studied through the analyses on the dynamism of cell assembly and on mathematical circuit models. Furthermore, a novel technique will be developed in which memory formation and retrieval will be artificially controlled.

    Memory update is one of the strategies that constructs advanced information by relating a lot of information, and an indispensable for survival of animals. In human beings, the memory update system is extremely important for the formation of knowledge. Understanding the whole image of memory update system leads not only to the understanding of the memory mechanisms but also to an approach to a philosophical proposition, for example the formation of one’s character, from a natural science.