About the Cover

Vol. 96 No. 3 (2020)

  In this issue, Kida (pp. 95–106) reports the functional and mechanistic relevance of memory consolidation, destabilization, reconsolidation and extinction in the process of fear memory on the basis of a series of experiments of contextual fear memory (A) and inhibitory avoidance memory (B). Following fear conditioning, short-term memory (STM) is consolidated as long-term memory (LTM) (consolidation). When the consolidated memory is retrieved, the retrieved memory becomes labile (destabilization) and requires memory reconsolidation to re-stabilize the memory. The labile memory also results in memory extinction, when memory is retrieved without any appropriate conditioning stimuli. Memory retrieval thus induces two opposing processes (reconsolidation and extinction). In this alternate process, a boundary state exists between memory destabilization and reconsolidation, and the opposing memory responses are determined by several factors such as the duration, strength and age of memory retrieval. Memory reconsolidation and memory extinction are thus not independent, rather interacting with each other at two distinct levels, namely, cellular and system (network) levels. Memory destabilization and reconsolidation both require induction of overlapping but distinct gene expression and protein phosphorylation in specified brain networks. Thus, reconsolidation and extinction of a retrieved memory are active processes, similar to consolidation of an initial memory. Importantly, memory reconsolidation following memory retrieval is required for the enhancement and updating of an original memory. The author discusses that memory destabilization following memory retrieval contributes to modifying, weakening and strengthening of an original memory and memory reconsolidation then plays a pivotal role in stabilizing the updated memory.

Shigetada Nakanishi
Member of the Japan Academy