SLEEP AND MEMORY .2. INVESTIGATIONS ON HUMANS

The positive effect of delta-sleep on retention depends on REM sleep, which facilitates this positive effect, but at the same time has its own inhibitory effect on retention. The nature of this double influence of REM sleep on retention is discussed in the context of the restoration of search activity being the main REM sleep function. Such restoration can explain the indirect positive effect of REM sleep on retention, especially on retention of the unusual and emotionally meaningful information that can cause distress. Psychic activity in REM sleep (dreams) has a direct negative effect on retention, which may be due to the interference between dream images and learned material.