Increased training in an aversively motivated task attenuates the memory-impairing effects of posttraining N-methyl-D-aspartate-induced amygdala lesions.

Abstract

This study was designed to examine the effect of variations in the amount of preoperative training on the retention deficit produced by posttraining lesions of the amygdaloid complex (AC). Rats received 1, 10, or 20 training trials in a footshock-motivated escape task 7 days before receiving N-methyl-D-aspartate lesions of the AC. Inhibitory avoidance retention performance, which was measured 4 days postoperatively, indicated that increased training improved retention in AC-lesioned animals as well as in control animals. The retention performance of AC-lesioned animals was impaired when compared with that of controls; however, the impairment was partially attenuated by increased preoperative training. The finding that AC-lesioned animals displayed greater locomotor activity on the retention test compared with nonlesioned controls suggests that the increased activity may have contributed to the impaired inhibitory avoidance retention performance. Two days after the retention test, some of the AC-lesioned animals were subsequently trained on a continuous multiple-trial inhibitory avoidance response in the same apparatus. AC lesions did not block acquisition or retention of the task. These findings suggest that the amygdala may not be a critical site for the permanent changes mediating stimulus-affect associations based on extensive training.