Sleep before and after learning promotes the consolidation of both neutral and emotional information regardless of REM presence

Sleep may play a role in consolidating emotional memories. However, studies on the effects of REM sleep on negative vs. neutral memories have produced inconsistent evidence. Here, we assess the role of NREM and REM sleep before and after learning in promoting the consolidation of neutral and arousing pleasant and unpleasant memories. Forty-six (32 F) healthy university students were exposed to a set of pictures at 1:00 PM (Session 1) and to an equivalent set at 4:45 PM (Session 2). All the pictures in Session 1 and Session 2 were presented again, intermixed with new similar pictures at 5:15 PM in a memory recognition task. Following Session 1, participants took a 90/120-min nap (NAP group), while 16 participants remained awake (WAKE group). Via polysomnographic recording, the NAP group was segregated into REM (N = 14) and NoREM groups (N = 16). Indices of memory consolidation for both stimuli presented before (discriminability of Session 1 pictures in Session 3) and after sleep (discriminability of Session 2 pictures in Session 3) were calculated. Memory consolidation for pictures presented both before and after the sleep period was higher in the NAP group as compared to the WAKE group, but no differential role of REM sleep emerged. A memory consolidation advantage was evident for neutral over pleasant (but not unpleasant) pictures. Taken together, these results indicate that a daytime nap (with or without REM sleep) facilitates consolidation of declarative memories presented before and after sleep irrespective of their valence. (C) 2016 Elsevier Inc. All rights reserved.