FIGURE 6.

Synaptic plasticity models for fear conditioning and extinction. Left: long-term potentiation (LTP) in axons conveying conditioned stimulus (CS) information to the basolateral amygdala (BLA) principal neurons (PN) results in the expression of a fear conditioned response. Right: extinction may be supported by several different synaptic changes including depotentiation of the LTP induced during conditioning, recruitment of LTP at CS afferents on amygdala inhibitory interneurons (IN), or LTP at inhibitory interneuron synapses on amygdala PNs (LTPi). All three forms of plasticity would be expected to reduce conditional responding, but only LTP (interneuron) and inhibitory LTP would allow for recovery of the fear CR after extinction.