Enhanced conditioning produced by surprising increases in reinforcer value are unaffected by lesions of the amygdala central nucleus.

In many experimental settings, lesions of the central nucleus of the amygdala (CN) interfere with surprise-induced enhancement of event processing. In those settings, surprise was produced by omitting an expected event. This experiment examined the effects of CN lesions on enhanced learning after surprise was induced by presenting an unexpected event. After extensive light-food pellet pairings, a light-noise compound was paired with food pellets, and a sucrose solution was unexpectedly delivered after the food. Relative to a control condition, this manipulation enhanced the formation of associations between the auditory conditioned stimulus and food, in both sham- and CN-lesioned rats. These results indicate that CN circuitry implicated in surprise-induced increases in event processing is preferentially engaged when expected events are omitted, and not when unexpected events are presented.