Rapid eye movement and non-rapid eye movement sleep contributions in memory consolidation and resistance to retroactive interference for verbal material.

STUDY OBJECTIVES

To test the hypothesis that rapid eye movement (REM) sleep contributes to the consolidation of new memories, whereas non-rapid eye movement (NREM) sleep contributes to the prevention of retroactive interference.

DESIGN

Randomized, crossover study.

SETTING

Two sessions of either a morning nap or wakefulness.

PARTICIPANTS

Twenty-five healthy young adults.

INTERVENTIONS

Declarative learning of word pairs followed by a nap or a wake interval, then learning of interfering word pairs and delayed recall of list A.

MEASUREMENTS AND RESULTS

After a restricted night (24:00-06:00), participants learned a list of word pairs (list A). They were then required to either take a nap or stay awake during 45 min, after which they learned a second list of word pairs (list B) and then had to recall list A. Fifty percent of word pairs in list B shared the first word with list A, resulting in interference. Ten subjects exhibited REM sleep whereas 13 subjects exhibited NREM stage 3 (N3) sleep. An interference effect was observed in the nap but not in the wake condition. In post-learning naps, N3 sleep was associated with a reduced interference effect, which was not the case for REM sleep. Moreover, participants exhibiting N3 sleep in the post-learning nap condition also showed a reduced interference effect in the wake condition, suggesting a higher protection ability against interference.

CONCLUSION

Our results partly support the hypothesis that non-rapid eye movement sleep contributes in protecting novel memories against interference. However, rapid eye movement sleep-related consolidation is not evidenced.