REM and NREM Differences in Simulation of Social Interactions
We (McNamara et al., 2005) recently hypothesized that representations of pleasant versus unpleasant emotional interactions in REM and NREM would reflect differing regional brain activation patterns associated with the two sleep states, with higher levels of aggressive interactions in REM vs. NREM. One-hundred REM, 100 NREM and 100 wake reports were collected in the home from 8 men and 7 women using the ‘Nightcap’ sleep/wake mentation monitoring system, and scored for number and variety of social interactions. They found that 1) social interactions were more likely to be depicted in dream than in wake reports; 2) aggressive social interactions were more characteristic of REM than NREM or wake reports and 3) dreamer initiated friendliness was more characteristic of NREM than REM. It is important to note that dreamer- initiated aggressive interactions were reduced to zero in NREM dreams, while dreamer-initiated friendly interactions were twice as common in NREM as in REM. It is therefore apparent that the lack of aggression in NREM was not due simply to fewer social interactions occurring in NREM relative to REM as friendly interactions in NREM were more likely to be dreamer-initiated than in REM (90% vs. 54% respectively, p<.05). This fact, along with the total absence of dreamer-initiated aggression in NREM, suggests an active process in NREM that inhibits unpleasant and aggressive social impulses while promoting the emergence of pleasant cooperative social impulses. Conversely, REM appears to facilitate emergence of unpleasant aggressive impulses. These data suggest that REM and NREM may exhibit specializations in processing routines for emotional material with NREM preferring pleasant emotional material and REM preferring unpleasant material.
