Double Dissociation of PKC and AC Manipulations on Operant and Classical Learning in Drosophila

Learning about relationships between stimuli (i.e., classical conditioning [1]) and learning about consequences of one's own behavior (i.e., operant conditioning [2]) constitute the major part of our predictive understanding of the world. Since these forms of learning were recognized as two separate types 80 years ago [3], a recurrent concern has been the issue of whether one biological process can account for both of them [4, 5, 6, 7, 8, 9]. Today, we know the anatomical structures required for successful learning in several different paradigms, e.g., operant and classical processes can be localized to different brain regions in rodents [9] and an identified neuron in Aplysia shows opposite biophysical changes after operant and classical training, respectively [5]. We also know to some detail the molecular mechanisms underlying some forms of learning and memory consolidation. However, it is not known whether operant and classical learning can be distinguished at the molecular level. Therefore, we investigated whether genetic manipulations could differentiate between operant and classical learning in Drosophila. We found a double dissociation of protein kinase C and adenylyl cyclase on operant and classical learning. Moreover, the two learning systems interacted hierarchically such that classical predictors were learned preferentially over operant predictors.