Slow wave sleep and REM sleep awakenings do not affect sleep dependent memory consolidation

Background: There is growing amount of evidence, that declarative as well as non-declarative memory consolidation is connected to normal sleep. But there is still an intense discussion, which sleep phases or EEG-activities are relevant for different learning tasks. Methods: Effects of REM sleep and slow wave sleep (SWS) deprivation on declarative and procedural memory consolidation were investigated in 12 healthy adults, ages 22–30 years. REM sleep and SWS deprivation was achieved by awakenings at the onset of respective sleep phase and compared to a control night without awakenings. Memory performance was tested by a verbal paired associate task and a finger tapping task at 9 pm on the study night and 60 hours later. Results: Although REM sleep and SWS awakenings led to a significant reduction of the respective sleep phase, memory consolidation remained unaffected. Conclusions: Considering our results and other recent research, we suggest that stage 2 sleep, rather than REM sleep is the important stage of sleep for efficient memory processing of a simple motor task, while declarative tasks rely on very little amounts of SWS.