The influence of prior knowledge on memory consolidation

Current research indicates that the process of memory consolidation, particularly during periods of sleep, can benefit memory in a variety of ways. Many of these behavioural changes are thought to arise from the integration of new information into pre-existing semantic memory. Despite this contention, it is not presently well understood how the relationship between new memories and prior knowledge will influence the behavioural outcomes of consolidation. To explore this issue the present thesis contains a number of experiments designed to measure the effects of consolidation on new memories that are either semantically compatible (congruent) or incompatible (incongruent) with prior knowledge. Measures of sleep physiology were also obtained in Experiments 2-5 to elucidate the potential mechanistic contributions of this state on memory consolidation. Using an adapted transitive inference paradigm Experiment 1 revealed evidence for the rapid assimilation of both congruent and incongruent information over 24 hours. However in Experiment 2, which featured congruent information only, these effects were not replicated, suggesting that consolidation may be more beneficial for the integration of more weakly encoded information. To explore this matter further Experiments 3-5 examined how semantic congruency may influence the recovery of new memories weakened by retroactive interference (RI) using a modified A-B, A-C list learning paradigm. Over the course of these investigations sleep was found to facilitate the recovery of semantically congruent memories from RI, thus negating the detrimental impact of both specific and non-specific forms of waking interference on memory. Incongruent information, however, was simultaneously forgotten suggesting a selective component to this consolidation-associated recovery. The sleep measures obtained across Experiments 2-5 were largely inconclusive although there was provisional evidence that sleep physiology may support the flexible expression of declarative memory (Experiment 2) and that rapid eye movement (REM) sleep may facilitate RI recovery (Experiment 3). These findings are interpreted in light of existing models of sleep-associated memory consolidation, integration and RI recovery.