ReviewOut with the old and in with the new: Synaptic mechanisms of extinction in the amygdala

- Synaptic plasticity in the amygdala is involved in extinction of conditioned fear.
- Conditioning requires LTP at excitatory synapses on amygdala principal neurons.
- Depotentiation is a candidate mechanism of extinction that erases fear memory.
- Inhibitory plasticity in the amygdala encodes extinction while sparing fear memory.

Considerable research indicates that long-term synaptic plasticity in the amygdala underlies the acquisition of emotional memories, including those learned during Pavlovian fear conditioning. Much less is known about the synaptic mechanisms involved in other forms of associative learning, including extinction, that update fear memories. Extinction learning might reverse conditioning-related changes (e.g., depotentiation) or induce plasticity at inhibitory synapses (e.g., long-term potentiation) to suppress conditioned fear responses. Either mechanism must account for fear recovery phenomena after extinction, as well as savings of extinction after fear recovery.This article is part of a Special Issue entitled SI: Brain and Memory.