Extinction learning, reconsolidation and the internal reinforcement hypothesis

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 as a result of some less well-understood form of learning. This latter process of memory strengthening is often referred to as reconsolidation, since protein synthesis can inhibit this form of memory formation. 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. Referring to results of extinction/reconsolidation experiments in honeybees, we argue that two opposing learning processes-with their respective consolidation phases and memories-are initiated by retrieval trials: extinction learning and reminder learning, the latter leading to the phenomenon of spontaneous recovery from extinction, a process that can be blocked with protein synthesis inhibition. (c) 2006 Elsevier Inc. All rights reserved.