Memory Trace for Fear Extinction: Fragile yet Reinforceable

Fear extinction is a biological process in which learned fear behavior diminishes without anticipated reinforcement, allowing the organism to re-adapt to ever-changing situations. Based on the behavioral hypothesis that extinction is new learning and forms an extinction memory, this new memory is more readily forgettable than the original fear memory. The brain's cellular and synaptic traces underpinning this inherently fragile yet reinforceable extinction memory remain unclear. Intriguing questions are about the whereabouts of the engram neurons that emerged during extinction learning and how they constitute a dynamically evolving functional construct that works in concert to store and express the extinction memory. In this review, we discuss recent advances in the engram circuits and their neural connectivity plasticity for fear extinction, aiming to establish a conceptual framework for understanding the dynamic competition between fear and extinction memories in adaptive control of conditioned fear responses.

Automated summary

Fear extinction is a biological process that reduces learned fear behavior without reinforcement, allowing organisms to adapt to changing situations. Recent research has shown that extinction memory is more forgettable than the original fear memory, but the cellular and synaptic traces of this extinction memory in the brain are still unclear. This review discusses the latest advances in engram circuits and neural connectivity plasticity for fear extinction, aiming to provide a conceptual framework for understanding the dynamic competition between fear and extinction memories in the control of conditioned fear responses.