Double Dissociation of Basolateral and Central Amygdala Lesions on the General and Outcome-Specific Forms of Pavlovian-Instrumental Transfer

This series of experiments compared the effects of lesions of the basolateral complex (BLA) and the central nucleus (CN) of the amygdala on a number of tests of instrumental learning and performance and particularly on the contribution of these structures to the specific and general forms of pavlovian-instrumental transfer (PIT). In experiment 1, groups of BLA-, CN-, and sham-lesioned rats were first trained to press two levers, each earning a unique food outcome (pellets or sucrose), after which they were given training in which two auditory stimuli (tone and white noise) were paired with these same outcomes. Tests of specific satiety induced outcome devaluation, and tests of PIT revealed that, although the rats in all of the groups performed similarly during both the instrumental and pavlovian acquisition phases, BLA, but not CN, lesions abolished selective sensitivity to a change in the reward value of the instrumental outcome as well as to the selective excitatory effects of reward-related cues in PIT. In experiment 2, we developed a procedure in which both the general motivational and the specific excitatory effects of pavlovian cues could be assessed in the same animal and found that BLA lesions abolished the outcome-specific but spared the general motivational effects of pavlovian cues. In contrast, lesions of CN abolished the general motivational but spared the specific effects of these cues. Together, these results suggest that the BLA mediates outcome-specific incentive processes, whereas CN is involved in controlling the general motivational influence of reward-related events.