Consolidation is the transition from a labile to a consolidated memory. Although it was previously thought that this consolidation occurs just once, there is growing evidence that memory retrieval is a dynamic process that either reinforces or alters memory. Once a memory is stabilized, its reactivation renders it transiently malleable (Suzuki et al. 2004). Retrieving a consolidated memory—by exposing an animal to the learned stimulus but not to the associated reinforcement—leads to two opposing processes: one that weakens the old memory as a result of extinction learning, and another that strengthens the old, already-consolidated memory referred to as reconsolidation. Although the behavioral phenomena of the two antagonizing forms of learning are well documented, the mechanisms behind the corresponding processes of memory formation are still quite controversial. Reconsolidation and extinction seem to play a central role in animal cognition but have only recently received attention. In nature, individual do not always face the same information (for example if the quality of a resource changes with space and time) and have to make a decision concerning their future choice. The induction of one or the other process appears to depend on the experimental conditions: under weak reactivation reconsolidation occurs whereas under strong reactivation extinction occurs. The mechanism and the nature of these processes are still under debate: is reconsolidation a repetition of consolidation? Are reconsolidation and extinction two competing processes?
These processes have never been investigated in Drosophila despite the importance of this model in neurobiological studies. Taking advantage of the existence of two distinct consolidated memory phases in drosophila, we have recently demonstrated that Drosophila show reconsolidation or extinction depending on the amount of reactivation (Lagasse and Mery, submitted). These memories are both consolidated and protein dependent. Interestingly, reconsolidation and extinction can be equally well built after ARM or LTM consolidation which would suggest that reconsolidation is not a repetition of consolidation (ARM is not protein dependent and its reconsolidation leads to protein dependent memory). This study opens new perspectives on the question of variation in memory phases. I propose to expand the study of memory consolidation to reconsolidation and extinction and (1) to address the question of the relationship between consolidation, reconsolidation and extinction, (2) to address the genetic basis of reconsolidation and extinction.