Differential involvement of amygdala subsystems in appetitive conditioning and drug addiction

It is suggested that the basolateral amygdala is required for a conditioned stimulus to gain access to the current value of its specific unconditioned stimulus, while the central nucleus is responsible for conditioned motivational responses using a simpler stimulus-response representation.

Abstract

Abstract We review data from appetitive conditioning studies using measures of Pavlovian approach behaviour and measures of the effects of Pavlovian conditioned stimuli on instrumental behaviour, including the Pavlovian-to-instrumental transfer effect and conditioned reinforcement. These studies consistently demonstrate double dissociations of function between the basolateral area and the central nucleus of the amygdala. Moreover, these data show marked parallels with data derived from studies of aversive (fear) conditioning, and are consistent with the idea that these subsystems of the amygdala use different associative representations fonned during conditioning, as part of a larger limbic corticostriatal circuit. We suggest that the basolateral amygdala is required for a conditioned stimulus to gain access to the current value of the specific unconditioned stimulus with which it has been paired, while the central nucleus is responsible for conditioned motivational responses using a simpler stimulusresponse representation. Though these systems normally operate together, they modulate ongoing behaviour in distinct ways. We illustrate this by considering the contributions of both systems to the process of drug addiction, using second-order schedules of intravenous drug self-administration.