RETROGRADE ABOLITION OF CONDITIONAL FEAR AFTER EXCITOTOXIC LESIONS INTHE BASOLATERAL AMYGDALA OF RATS - ABSENCE OF A TEMPORAL GRADIENT

The role of the basolateral amygdala (BLA) in the acquisition and expr ession of Pavlovian fear conditioning was examined in 80 rats. Excitot oxic lesions were made in the BLA using N-methyl-D-aspartate 7 days be fore or 1, 14, or 28 days after Pavlovian fear conditioning. Condition ing consisted of three pairings of a tone with an aversive footshock i n a novel chamber, and freezing behavior served as an index of conditi onal fear. BLA lesions abolished conditional freezing to both the cont extual and acoustic conditional stimuli at all training-to-lesion inte rvals, and the magnitude of the impairment did not vary as a function of the training-to-lesion interval. Reacquisition training elevated le vels of freezing in rats with BLA lesions but did not reduce the magni tude of their deficit in relation to that of controls. These results r eveal that neurons in the BLA have an enduring role in the expression of conditional fear.