Erasing fear memories — key receptor and essential timeframe discovered

It is clinically important to suppress or inhibit traumatic memories, which are formed after fearful experiences. In animal models, fear memory is formed by repetitive presentation of a tone paired with an electrical foot-shock¹. It is well known that an extinction protocol, in which the tone is repeatedly presented without the foot-shock, gradually decreases the pre-acquired fear response to the tone. However, this fear extinction protocol is not sufficient to erase the fear memory; fear responses may recover spontaneously or relapse under some conditions. If the fear memory is retrieved or reactivated by a single presentation of the tone without the shock 1 h before the extinction session, the fear responses are permanently removed by this retrieval–extinction protocol². This suggests that a critical brain state is caused by the retrieval procedure, in which the fear memory becomes labile and can be destroyed by the subsequent extinction procedure. Clem and Huganir³ have found a critical receptor for the permanent erasure of fear memories by this retrieval–extinction protocol. They focused on the Ca²⁺-permeable type of α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate receptor (Ca²⁺-permeable-AMPAR) located in the lateral amygdala, an essential region of the brain for learning. They suggested that removal of Ca²⁺-permeable-AMPARs, the content of which in the synapses is elevated for a few days after fear conditioning, is responsible for the permanent erasure of the fear memory by that protocol.