Researchers have looked into the stage of sleep that is responsible for the consolidation of emotional memories in a paper that was uploaded to the bioRxiv* preprint server.
It is unclear how different sleep stages affect the consolidation of memories. Rapid-eye movement (REM) sleep has traditionally been blamed for helping the brain consolidate emotional memories. This idea was backed by research that demonstrated a correlation between REM measurements and greater emotional content recall. This gave rise to the theory that REM provides a special environment for the consolidation of emotional events.
However, a number of investigations found no such links, casting doubt on the theory. Recent research suggests that the consolidation of emotional memories occurs during non-REM (NREM) sleep. Studies have also shown links between the duration of NREM sleep and the benefits to emotional memory. Studies on targeted memory reactivation give additional support for the contribution of NREM sleep to the storage of emotional memories (TMR).
Researchers used TMR in the current work to pinpoint the sleep stage or stages important in the consolidation of emotional memories. They sought out young, healthy people with typical sleep patterns and no history of neurologic or mental illnesses. Before the trial, participants were told to maintain a normal sleep schedule for three nights, abstain from using coffee in the morning and alcohol or recreational drugs for 48 hours.
Emotional slow-wave sleep (E-SWS), emotional REM sleep (E-REM), and neutral slow-wave sleep (N-SWS) groups were assigned at random to the participants. Participants in the E-SWS and E-REM studies acquired emotional information and experienced reactivation during SWS and REM sleep, respectively. N-SWSS groups, in contrast, learnt neutral items and then reactivated them in SWS.
