Amygdala central nucleus lesions disrupt increments, but not decrements, in conditioned stimulus processing.

The effects of neurotoxic lesions of the amygdala central nucleus (CN) on changes in the associability of a conditioned stimulus (CS) in appetitive Pavlovian conditioning were examined in 2 experiments with rats. In Experiment 1, CN lesions had no effect on the reduction in the associability of a CS produced by preexposure to that cue (latent inhibition). In Experiment 2, CN lesions prevented the enhancement of the associability of a CS that is normally observed when an inconsistent predictive relation is arranged between that CS and another cue. The results support previous claims that the amygdala CN is involved in broad-based incremental, but not decremental, changes in the processing of CSs in Pavlovian conditioning.