Pre-sleep acute stress modulates sleep-dependent emotional memory.

Objectives

Acute stress prior to bedtime significantly alters the subsequent sleep. Although sleep is crucial for consolidating newly acquired memories, the impact of pre-sleep stress remains unclear. This experimental study examined how acute stress induction before bedtime influences overnight consolidation of emotional and neutral memories.

Methods

34 healthy adults (65% females, Mage = 25.76 years, SD = 3.35) were randomly assigned to stress (SC) or control (CC) conditions, using a virtual reality stress or control paradigm. Prior to manipulation, participants encoded emotional and neutral images, followed by recognition tasks immediately and the next morning. High-density overnight electroencephalogram (EEG) assessed sleep and salivary cortisol indexed pre-sleep stress responses.

Results

Pre-sleep stress was associated with longer slow-wave sleep duration, elevated high frequency EEG power during both rapid (REMS) and non-rapid eye movement sleep (NREMS), and lower slow oscillation spindle coupling. Memory retention was comparable between groups, but stress exposure interacted with EEG power in predicting memory outcomes. In the CC, greater low-frequency power during NREMS was associated with enhanced memory retention, whereas this association was absent in the SC. Effects were most pronounced over the central EEG derivations and were driven by the emotional material. Higher evening cortisol was independently associated with enhanced emotional memory retention.

Conclusions

Acute pre-sleep stress modifies sleep oscillatory dynamics and alters sleep-dependent memory consolidation, particularly for emotional content. These findings suggest that pre-sleep situational context shapes overnight memory processing, challenging the premise that memory consolidation mechanisms operate independently of prior waking experiences.