Targeted memory reactivation has a sleep stage-specific delayed effect on dream content.

Auditory cues played during specific sleep stages can shift the timing of when a newly learned virtual reality flying task reappears in dreams. Cues presented during REM sleep led to more task-related dreams 1-2 days later, while cues presented during slow-wave sleep led to more such dreams 5-6 days later, compared to no cueing. This delayed effect helps explain the day-residue effect (dreams about new learning the next day) and the dream-lag effect (dreams about new learning 5-7 days later), suggesting that memory reactivation during sleep influences the temporal pattern of dream content.

Study at a glance

Abstract

Although new learning is known to reappear in later dream scenarios, the timing of such reappearances remains unclear. Sometimes, references to new learning occur relatively quickly, 1 day post-learning (day-residue effect); at other times there may be a substantive delay, 5-7 days, before such references appear (dream-lag effect). We studied temporal delays in dream reactivation following the learning of a virtual reality (VR) flying task using 10-day home sleep/dream logs, and how these might be influenced by targeted memory reactivation (TMR). Participants were exposed twice to a VR task in the sleep laboratory; once before and once after a 2-hr opportunity to nap (n = 65) or to read (n = 32). Auditory cues associated with the VR task were replayed in either wake, rapid eye movement (REM) sleep, slow-wave sleep (SWS) or were not replayed. Although we previously showed that TMR cueing did not have an immediate effect on dream content, in the present study we extend these results by showing that TMR in sleep has instead a delayed effect on task-dream reactivations: participants dreamed more about the task 1-2 days later when TMR was applied in REM sleep and 5-6 days later when it was applied in SWS sleep, compared to participants with no cueing. Findings may help explain the temporal relationships between dream and memory reactivations and clarify the occurrence of day-residue and dream-lag phenomena.