Both medial prefrontal and amygdala central nucleus lesions abolish heart rate classical conditioning, but only prefrontal lesions impair reversal of eyeblink differential conditioning.

Rabbits with lesions of either medial prefrontal cortex (mPFC) or amygdala central nucleus (ACN) were compared with sham-lesioned animals during differential and reversal classical conditioning of the eyeblink (EB) and heart rate (HR) response. Lesions of the mPFC, but not ACN, produced a severe impairment in EB reversal conditioning, but neither lesion affected original discrimination. However, both mPFC and ACN lesions produced a severe attenuation of accompanying HR decelerations during both initial differentiation and reversal. These results suggest that mPFC processing of Pavlovian conditioning contingencies affects not only the autonomic component of learning but preservative somatomotor conditioning as well, whereas ACN processing affects only the autonomic component.