AMYGDALA MODULATES MEMORY FOR CHANGES IN REWARD MAGNITUDE - REVERSIBLE POST-TRAINING INACTIVATION WITH LIDOCAINE ATTENUATES THE RESPONSE TOA REDUCTION IN REWARD

The present study used a reward reduction paradigm to examine the role of the amygdala in memory for reduction in reward magnitude. Male Spr ague-Dawley rats were implanted with bilateral amygdala cannulae and t rained to run a straight alley (6 trials/day) for either ten or one 45 -mg food pellets. On Day 10 of training, half the animals in the 10 pe llet reward group were shifted to a one pellet reward. Immediately fol lowing shifted trials, the animals received an intra-amygdala injectio n of either a 2% lidocaine solution or phosphate buffer (0.5 mu l/side ). Shifted training continued for 2 more days and no further injection s were given. Shifted animals that received a buffer injection display ed a sharp increase in response latencies compared to unshifted contro ls on the second day of shifted training. In contrast, shifted animals that received intra-amygdala injections of lidocaine exhibited signif icantly lower latencies compared to the shifted vehicle group on the s econd day of shifted training. The findings indicate that post-trainin g inactivation of the amygdala attenuates the response to reward reduc tion, suggesting that the amygdala modulates the storage of memory for a reduction in reward magnitude.